JP4185581B2 - Method for producing cellulose ester - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a cellulose ester useful for producing a cellulose ester used for cigarette smoke filters, fibers, photographic films, artificial kidneys and the like, and more particularly to a method for producing a fibrillar cellulose ester.
[0002]
[Prior art]
As a typical method for industrially producing cellulose acetate, raw material cellulose is treated with an acid anhydride such as acetic anhydride in the presence of an acidic catalyst such as sulfuric acid, and further hydrolyzed as necessary. There is known a method of precipitation in an aqueous solution such as an aqueous solution, washing with water, and drying if necessary. However, in cellulose ester slurries, particularly fibrillar cellulose ester slurries, it is not easy to efficiently remove impregnated acetic acid at an industrial level, and a large amount of water is required for washing the slurry. . Acetic acid diluted with a large amount of water can be reused as a precipitant. However, since the acetic acid concentration is low, enormous energy is required to recover acetic acid in the acetic acid recovery step. Therefore, there is a need for a method for producing cellulose acetate that can wash the precipitated cellulose acetate slurry with a small amount of water and that has good acetic acid recovery efficiency.
[0003]
In Japanese Patent Publication No. 53-15165, a fibrous cellulose acetate slurry obtained by precipitating an acetone solution of cellulose acetate has a surface area of 35 to 55 m. ² / G, and a method in which the sheared slurry is continuously deposited on a porous support, filtered, and then washed with a non-solvent of cellulose acetate to remove acetone. However, this document discloses that a fibrous cellulose acetate having the above surface area is produced using cellulose acetate that has already been prepared, and the adverse effects of acetic acid remaining in the cellulose acetate and the acetone from non-solvents are disclosed. There is no mention of recovery.
Japanese Patent Application Laid-Open No. 53-45468 proposes a method of homogenizing the precipitate in order to reduce the particle size of the precipitated cellulose ester. However, this method is a treatment after washing the cellulose ester, and does not provide a method for removing acetic acid in the fibrillar cellulose acetate by washing.
As described above, little is known about a method for efficiently washing and removing an organic acid impregnated in a fibrillated cellulose ester at an industrial level.
[0004]
Further, when the wet fibrillar cellulose ester is stored for a long period of time, the cellulose ester is hydrolyzed to generate a free acid, which causes problems of corrosion and acid odor. However, little is known about a method for suppressing the amount of generated free acid to a small amount and a method for storing a wet fibrillar cellulose ester.
[0005]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a method in which an organic acid impregnated in a fibrillated cellulose ester can be efficiently washed and removed at an industrial level using a small amount of washing liquid, and an organic acid can be easily recovered. It is in.
Another object of the present invention is to provide a method capable of suppressing the generation of liberated acid even when the fibrillated cellulose ester is stored for a long period of time in a wet state and stably storing the wet fibrillated cellulose ester for a long period of time. is there.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above-mentioned object, the present inventors have washed the fibrillar cellulose ester slurry after the disaggregation or pulverization treatment, and after treating with alkali, an organic acid impregnated in the fibrillar cellulose ester is obtained. The present invention was completed by finding that a small amount of washing liquid can be efficiently washed and removed at an industrial level, the organic acid can be easily recovered, and the fibrillated cellulose ester can be stably stored in a wet state for a long period of time. .
[0007]
That is, in the method of the present invention, a cellulose ester solution containing an organic acid is extruded from a nozzle into a precipitant, a shearing force is applied to produce a fibrillated cellulose ester, and the fibrillated cellulose ester slurry is disaggregated or disintegrated. Wash after. Further, the washed fibrillated cellulose ester is treated with an alkali. The disaggregation or crushing process may be performed using a disaggregator or a crusher having rotating teeth and fixed teeth maintained at a clearance of 10 to 1000 μm. The organic acid contained in the washing filtrate may be recovered in the acid recovery step. The alkali may be at least one selected from ammonia, alkali metals, and alkaline earth metals. By the alkali treatment, the pH of the liquid phase of the wet fibrillated cellulose ester may be adjusted to a neutral range (for example, about 5 to 9).
[0008]
Furthermore, in this invention, acetic acid in a cellulose acetate slurry is easily collect | recovered by wash | cleaning with a small amount of water after disaggregating or crushing the fibrillar cellulose acetate slurry produced | generated from the cellulose acetate melt | dissolved in the solvent containing at least acetic acid. In addition, the liquid phase of wet fibrillar cellulose acetate is alkali-treated until the pH reaches a neutral range (about pH 6 to 8), thereby suppressing the generation of free acid even when stored for a long period of time. it can.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In the method of the present invention, a cellulose ester solution is extruded from a nozzle into a precipitating agent, and a shearing force is applied to precipitate the cellulose ester into a fibril form, and the produced cellulose ester slurry is disaggregated or disintegrated. The cellulose ester is produced through a treatment step, a step of washing the disaggregated or crushed slurry, and an alkali treatment step of treating the fibrillated cellulose ester with an alkali. Moreover, you may collect | recover organic acids from a washing | cleaning filtrate through a collection process.
[0010]
[Cellulose ester solution]
Examples of the cellulose ester used in the present invention include carboxylic acid esters such as cellulose acetate, cellulose butyrate, and cellulose propionate; cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and nitrate acetate. Examples include mixed acid esters. These cellulose esters can be used alone or in admixture of two or more.
[0011]
The average degree of polymerization of the cellulose ester is, for example, 50 to 600, preferably about 100 to 500, and more preferably about 150 to 400, and the average degree of substitution of the cellulose ester is, for example, about 1 to 3.
[0012]
Preferred cellulose esters include carboxylic acid esters (for example, esters with carboxylic acids having about 2 to 4 carbon atoms), particularly cellulose acetate. The bound acetic acid (acetylation degree) of cellulose acetate can be appropriately selected in the range of about 29 to 62%, and is usually about 40 to 62%.
[0013]
The cellulose ester solution only needs to contain an organic acid (particularly a free organic acid), and the organic acid may be derived from a solvent (good solvent) that dissolves the cellulose ester prepared in advance. It may be derived from the raw material used (organic acid and / or acid anhydride).
[0014]
The cellulose ester solution can be prepared by dissolving cellulose ester in a good solvent. The good solvent can be appropriately selected according to the type of cellulose ester and the average degree of substitution. Examples thereof include ketones such as acetone and methyl ethyl ketone; ethers such as dioxane, diethyl ether and tetrahydrofuran; carboxyls such as acetic acid, propionic acid and butyric acid. Acids; Halogenated hydrocarbons such as dichloromethane and dichloroethane; Alcohols such as methanol, ethanol and isopropanol; Organic solvents such as esters such as methyl acetate and ethyl acetate, mixed solvents of these organic solvents, and these organic solvents A mixed solution of water and water can be used. As preferable good solvents, water-soluble carboxylic acids such as acetic acid, propionic acid, butyric acid, and carboxylic acid-water mixed solvents are usually used, and more preferable good solvents include acetic acid and an acetic acid content of 60% by weight or more. An acetic acid-water mixed solvent is used.
[0015]
As the cellulose ester solution, a cellulose ester solution obtained through a cellulose ester preparation step, for example, a dope obtained by esterifying raw cellulose in a solvent with an organic acid or an acid anhydride thereof and hydrolyzing as necessary. It may be used in the form.
The kind of cellulose is not particularly limited, and natural or regenerated cellulose can be used, and usually wood pulp is often used.
The dope can be prepared by pre-activating cellulose with an organic acid (such as acetic acid) and esterifying it with an organic acid or an acid anhydride (such as acetic anhydride) in the presence of an acidic catalyst (such as sulfuric acid). .
[0016]
The concentration of the cellulose ester in the cellulose ester solution is usually 2 to 50% by weight (eg 2 to 35% by weight), preferably 5 to 40% by weight (eg 5 to 30% by weight), more preferably 10 to 25% by weight. %.
[0017]
Even when the cellulose ester solution contains a large amount of organic acid (particularly acetic acid), it can be washed and removed with a small amount of washing liquid, and the organic acid can be easily recovered.
[0018]
[Fibrillation process]
The fibrillated cellulose ester can be obtained, for example, by extruding a cellulose ester solution from a nozzle into a precipitating agent (hereinafter sometimes referred to as a poor solvent) for the cellulose ester, and applying a shearing force to the cellulose ester solution. The cellulose ester solution extruded from the nozzle starts to solidify from the outer periphery due to contact with the precipitant. In this method, by applying a shearing force to the extruded cellulose ester solution, the cellulose ester is fibrillated before solidifying, so that a fibrillated cellulose ester can be obtained. In addition, when the cellulose ester is precipitated from the solution while acting a shearing force in this way, the fibrillar cellulose ester of the present invention can be obtained easily and efficiently. However, the method for producing the fibrillar cellulose ester is limited to this. However, various methods for obtaining the fibrillated cellulose ester by applying a shearing force to the cellulose ester solution by other means to solidify the cellulose ester can also be adopted.
[0019]
Hereinafter, this method will be described with reference to the drawings as necessary.
In the method of the present invention, various devices that can be fibrillated while applying a shearing force to the fibrous cellulose ester solution can be used. Such an apparatus includes a flow path through which a precipitant is supplied, a nozzle means for discharging a cellulose ester solution (hereinafter sometimes simply referred to as a spinning solution) into the flow path, and extrusion or ejection from the nozzle means. In many cases, a cutting means (shearing means) is provided for stirring the discharged fiber spinning solution and cutting it together with fibrillation.
[0020]
FIG. 1 is a schematic configuration diagram of an apparatus for fibrillating cellulose ester, and FIG. 2 is a schematic bottom view of the cutting means of FIG.
The apparatus shown in FIG. 1 and FIG. 2 supplies a cylindrical casing 3 whose upper part is closed, nozzle means 1 for discharging a cellulose ester solution upward from the bottom of the casing 3, and a precipitant in the lower part of the casing 3. Then, the precipitating agent supply port 4 for coagulating and precipitating the cellulose ester solution in contact with the discharged cellulose ester solution is connected to the upper side of the casing 3 and the fibrillated cellulose ester produced is precipitated. And a delivery port 5 for delivery together.
[0021]
And between the said nozzle means 1 and the delivery port 5, in the contact area | region of a cellulose-ester solution and a precipitant, while stirring the fibrous cellulose-ester solution extruded from the nozzle means 1, shear force is given. A cutting means (or shearing means) 6 is provided for acting to fibrillate the fibrous cellulose ester solution.
[0022]
The cutting means 6 includes a cutter 8 which is opposed to the nozzle means 1 and is rotatably disposed, and a perforated plate attached to the casing 3 in the vicinity of the cutter 8 on the downstream side of the cutter. 10. That is, the cutting means 6 includes a shaft 7 that extends in the axial direction in the casing 3, and a cutter 8 that is attached to an end of the shaft and has a plurality of blades that can be rotated by a rotational drive source such as a motor. The plate 10 is provided on the downstream side of the cutter and is attached to the casing 3 and has a plurality of holes 9 in the circumferential direction. In this example, the plate 10 is disposed in parallel with the cutter 8. The cutter 8 of the cutting means 4 is close to the plate 10 and close to the discharge port of the nozzle means 1.
[0023]
When such an apparatus is used, the cellulose ester solution supplied from the cellulose ester solution supply port 2 and extruded in a pressurized state from the nozzle means 1 into the casing 3 is obtained from the precipitating agent supplied from the precipitant supply port 4. It contacts and is stirred by the cutter 8 of the cutting means 6. At that time, since the cutter 8 is interposed between the nozzle 1 and the perforated plate 10 so as to face the nozzle 1, while the nozzle means 1 passes through the hole 9 of the plate 10, A shearing force acts on the cellulose ester solution by the stirring force, and the cellulose ester solution can be solidified while being fibrillated. The fibrillated cellulose ester passes through the hole 9 of the plate 10 and is delivered from the fibrillated cellulose ester delivery port 6.
[0024]
The degree of fibrillation and the fiber length are the extrusion rate of the cellulose ester solution, the distance between the discharge port and the cutting means, the distance between the cutting means and the plate, the shearing force by the cutting means (rotating speed of the cutter), the nozzle hole diameter It can be adjusted by. The shear force may be applied before the cellulose ester is completely solidified, or may be a partially solidified cellulose ester. When the cutter is used, the number of rotations of the cutter can be appropriately selected according to the distance between the nozzle 1 and the cutter 8, and can be selected from a range of about 3000 to 15000 rpm, for example.
[0025]
The distance between the tip of the nozzle and the cutter can be appropriately selected depending on the supply rate of the cellulose ester solution and the rotation speed of the cutter, but is usually about 1 to 5 mm, preferably about 1 to 3 mm (for example, about 2 mm). If the distance is shorter than this, it becomes a lump, and if it is longer, the fiber length and the fiber width tend to be large.
[0026]
The shearing force is not limited to the rotational shearing force of the cutter, but may be applied to the cellulose ester solution by utilizing, for example, an impact caused by a jet flow or a pulse wave.
[0027]
When a nozzle having a circular cross section is used, the nozzle diameter can be appropriately selected according to the desired fiber diameter and the like, but is usually 50 μm to 5 mm (for example, 1 to 5 mm), preferably 100 μm to 4 mm, more preferably 500 μm to 3 mm. Degree. The shape of the nozzle is not limited to a circular cross section, and may have an irregular cross sectional shape as long as it has a cross sectional area comparable to that of a circular nozzle. Further, the nozzle for discharging the cellulose ester solution is not limited to a single nozzle, and may be constituted by a die having a large number of holes corresponding to the nozzle hole diameter.
[0028]
The precipitant (coagulant) can be selected from a non-solvent or a poor solvent for cellulose ester according to the type of cellulose ester or a good solvent used, for example, water; alcohols such as methanol; water and the good solvent Examples thereof include an aqueous mixed solvent. The precipitating agent usually includes water, alcohol such as methanol, acetone-water mixed solvent, dioxane-water mixed solvent, acetic acid-water mixed solvent and the like. In addition, when the mixed solvent used as a precipitant contains a good solvent, the ratio of water is large compared with a good solvent.
[0029]
Although the combination of such a good solvent and a precipitant is not particularly limited, for example, the following combinations are exemplified.
(A) Good solvent: acetone / water = 100/0 to 70/30 (% by weight)
Precipitant: Water / acetone = 100 / 0-50 / 50 (% by weight) solvent
(B) Good solvent: Dioxane
Precipitant: Water / dioxane = 100/0 to 70/30 (% by weight) solvent
(C) Good solvent: Acetic acid / water = 100 / 0-60 / 40 (wt%) solvent
Precipitant: Water / acetic acid = 100/0 to 60/40 (% by weight) solvent
In order to effectively use an organic acid as a precipitant component, it is advantageous to use an organic acid or an aqueous organic acid solution (such as an aqueous acetic acid solution) as a solvent for the cellulose ester solution. For example, in order to effectively use acetic acid as a precipitant component, water or an acetic acid-water mixed solvent having an acetic acid content of 40% by weight or less is often used as the precipitant.
[0030]
The ratio of the precipitating agent to the cellulose ester solution can be appropriately selected within a range where the cellulose ester is precipitated and fibrillation occurs. Usually, 10 parts by weight of the precipitating agent per 1 part by weight of the cellulose ester solution having a concentration of 13% by weight. Part or more, for example, 10 to 50 parts by weight (for example, 15 to 50 parts by weight), preferably 12 to 40 parts by weight (for example, 15 to 40 parts by weight), and more preferably 15 to 30 parts by weight (for example, 20 to 20 parts by weight). 30 parts by weight).
[0031]
In addition, the temperature of a cellulose ester solution and the temperature of a precipitant can be suitably selected in the range in which a cellulose ester precipitates in a fibrous form, and is usually room temperature or higher, preferably about 30 to 60 ° C. (for example, 40 to 60 ° C.). is there.
[0032]
The form of the fibrillated cellulose ester may be fibrous and may be close to an indefinite shape having a higher order branch. The average diameter of the fibrillated cellulose ester is about 1 to 200 μm, preferably about 2 to 100 μm, and more preferably about 3 to 50 μm. The average fiber length of the fibrillar cellulose ester can be appropriately selected within a range not losing the strength and formability of the material, and is usually about 0.1 to 2 mm, preferably about 0.2 to 1 mm.
[0033]
[Disaggregation or crushing process]
The fibers of the fibrillated cellulose ester obtained by the fibrillation may contain long fibers, for example, fibers of several centimeters (for example, about 1 cm). When such a fibrillar cellulose ester is filtered and washed, at a stage where the precipitated slurry is filtered and a cake layer is formed, fibrillar cellulose esters having long fibers are entangled with each other, and block aggregates are generated. For this reason, even if the cleaning liquid is uniformly poured into the cake layer, the cleaning liquid does not sufficiently permeate into the agglomerates, and a large amount of cleaning liquid is required for sufficient replacement cleaning. In order to perform this cleaning efficiently with a small amount of cleaning liquid, the slurry may be disaggregated or disintegrated (hereinafter sometimes simply referred to as disaggregation) before the cleaning.
[0034]
By disaggregating the slurry, the block-like aggregates can be dispersed, and the fibrillar cellulose ester slurry can be efficiently washed with a small amount of washing liquid.
[0035]
The disaggregation treatment may be performed by ordinary disaggregation means, for example, disaggregation by a stirrer such as a mixer, ultrasonic treatment, disaggregation having a rotating tooth and a fixed tooth maintained at a certain clearance, or disaggregation by a disintegrator. it can. When disaggregation with a stirrer such as a mixer, the fiber length distribution and / or fiber diameter distribution of the fibrillar cellulose ester becomes wide, and the block-like aggregates may be generated at the stage of washing. A preferable disaggregation process can be performed using a disaggregator or a disintegrator having rotating teeth and fixed teeth maintained at a constant clearance. When the disaggregator or crusher is used, the fiber length distribution width and fiber diameter distribution width of the fibrillated cellulose ester can be narrowed, and the generation of aggregates due to the entanglement between the fibrillated cellulose esters is reduced. Thus, the detergency of the impregnated organic acid can be improved.
[0036]
The clearance between the rotating teeth and the fixed teeth of the disintegrator or crusher can be appropriately selected within a range that can improve the detergency of the solvent, and is, for example, 10 to 1000 μm (for example, 30 to 600 μm), preferably 20 to 800 μm ( For example, it is about 40 to 400 μm), more preferably about 50 to 600 μm (for example, 60 to 200 μm).
[0037]
The number of rotations of the rotating teeth of the disintegrator or crusher can be appropriately selected according to the clearance and the like, and is, for example, about 500 to 5000 rpm, preferably about 800 to 3000 rpm. For example, it is 3000-15000 rpm, Preferably it is about 8000-13000 rpm.
[0038]
Examples of the disaggregator or crusher having the rotating teeth and fixed teeth maintained at a certain clearance include a disc refiner and a mass collider.
[0039]
[Washing process]
The fibrillated cellulose ester slurry that has been subjected to the disaggregation treatment does not entangle the fibrillated cellulose esters at the stage of preparing the cake layer by filtering the slurry, so that block aggregates are not generated. Therefore, if the cleaning liquid is uniformly poured over the entire cake layer, the cleaning liquid uniformly penetrates to the inside of the cake layer, and replacement cleaning can be sufficiently performed. Since the washing solution penetrates uniformly throughout the cake, it can be washed efficiently with a small amount of washing solution.
[0040]
As the cleaning liquid, alcohols, ketones, ethers, a mixed solvent thereof or a mixed solvent thereof or an aqueous solvent thereof may be used, but water is generally used in order to suppress elution of fibrillar cellulose ester. . Further, these cleaning liquids may be alkaline. When an alkaline cleaning liquid (such as an aqueous alkali solution) is used, cleaning and alkali treatment can be performed simultaneously.
[0041]
The ratio between the washing liquid and the disaggregated fibrillated cellulose ester slurry (solid content) can be selected as long as the organic acid can be easily recovered and can be sufficiently washed. Usually, the washing liquid / fibrillar cellulose ester slurry ( Hereinafter, it may be referred to as a cleaning ratio) = 5/1 to 35/1 (weight ratio) [for example, 8/1 to 35/1 (weight ratio)], preferably 10/1 to 30/1 (weight ratio) More preferably, it is about 12/1 to 25/1 (weight ratio).
The washing can be carried out by a conventional method such as rinsing using a centrifugal filter or filtration and washing such as countercurrent multi-stage washing using a countercurrent horizontal belt filter. The washing rate can be improved by washing by any of batch, semi-batch and continuous methods.
[0042]
In addition, since it can wash | clean efficiently with a small amount of washing | cleaning liquid as mentioned above, it can suppress that the organic acid density | concentration in a washing | cleaning filtrate falls large, and a washing | cleaning filtrate can be reused as a precipitant. Moreover, since the organic acid concentration does not decrease, the organic acid can be recovered from the washing filtrate with a small amount of energy even in the organic acid recovery step. Further, since cleaning can be performed with a small amount of cleaning liquid, for example, countercurrent multi-stage cleaning can be performed without increasing the number of cleaning stages, and the apparatus can be reduced in size and energy can be saved.
[0043]
The organic acid is recovered from the washing filtrate by a conventional method, for example, a water-insoluble solvent that can be separated into water (for example, a chain hydrocarbon such as hexane, an alicyclic hydrocarbon such as cyclohexane, toluene, etc. Aromatic hydrocarbons, esters such as ethyl acetate, ketones such as methyl ethyl ketone, ethers such as diethyl ether, halogenated hydrocarbons such as carbon tetrachloride), distillation methods using a flash distillation column, etc. It can carry out by the method which combined. Since the decrease in the organic acid concentration in the washing filtrate is small, the recovery efficiency by extraction or distillation of the organic acid can be increased. Further, the organic acid can be recovered by distillation purification with a small amount of energy.
[0044]
[Alkali treatment process]
When the wet fibrillar cellulose ester is treated with an alkali, the generation of liberated acid can be suppressed to a small amount even when stored for a long time, and the wet fibrillar cellulose ester can be stored stably for a long time.
[0045]
The generation of free acid is believed to be caused by ester hydrolysis within the wet fibrillar cellulose ester. In this hydrolysis, since the hydrogen ions of the free acid serve as a catalyst for the hydrolysis reaction, the lower the initial hydrogen ion concentration, the lower the amount of free acid generated during long-term storage can be suppressed. Therefore, if the wet fibrillar cellulose ester is treated with an alkali, the initial hydrogen ion concentration can be kept low, so that the generation of free acid can be suppressed to a small amount even when stored for a long period of time.
[0046]
Examples of the alkali that can be used include ammonia, alkali metals (sodium, potassium, etc.), alkaline earth metals (magnesium, calcium, strontium, barium, etc.), and the like.
[0047]
Alkali metals and alkaline earth metals are usually used as compounds containing the alkali metal or alkaline earth metal. Examples of the compound include hydroxides; inorganic acid salts such as carbonates, hydrogen carbonates, and phosphates; hydroxycarboxylates such as malate, tartrate, and citric acid, acetates, propionates, Examples thereof include organic acid salts such as carboxylic acid salts such as oxalate.
[0048]
Examples of the alkali metal compound include hydroxides (sodium hydroxide, potassium hydroxide, etc.), carbonates (sodium carbonate, potassium carbonate, etc.), bicarbonates (sodium bicarbonate, potassium bicarbonate, etc.), phosphates. (Trisodium phosphate, tripotassium phosphate, etc.), hydroxycarboxylates (sodium malate, potassium malate, sodium tartrate, potassium tartrate, sodium citrate, potassium citrate, etc.), carboxylates (sodium acetate, acetic acid) Potassium, sodium propionate, potassium propionate, sodium oxalate, potassium oxalate, etc.).
[0049]
Examples of alkaline earth metal compounds include hydroxides (magnesium hydroxide, calcium hydroxide, barium hydroxide, etc.), carbonates (magnesium carbonate, etc.), bicarbonates (magnesium bicarbonate, calcium bicarbonate, etc.), Hydroxycarboxylate (magnesium malate, calcium malate, magnesium tartrate, calcium tartrate, magnesium citrate, calcium citrate, etc.), carboxylate (magnesium acetate, calcium acetate, barium acetate, magnesium propionate, calcium propionate, And barium propionate).
These alkalis can be used alone or in combination of two or more.
[0050]
Preferred alkalis include ammonia, hydroxides (such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, and calcium hydroxide), hydroxycarboxylates (such as sodium malate and potassium malate), and the like.
[0051]
In general, these alkalis are often used as an aqueous solution.
[0052]
The degree of treatment with alkali is adjusted to be, for example, 5 to 9 (for example, 7 to 9), preferably 6 to 8 (for example, 7 to 8) at the pH of the liquid phase of the wet fibrillar cellulose ester after the treatment. It is advantageous to do so. If the pH of the liquid phase is about 6 to 8, the initial hydrogen ion concentration is low, and the generation of free acid can be suppressed to a small amount even after long-term storage. Furthermore, the drainage after the alkali treatment can be reused as a cleaning liquid for the fibrillated cellulose ester slurry.
[0053]
The alkali-treated fibrillar cellulose ester is drained and dried, and can be used in a wide range of applications such as cigarette smoke filters, fibers, photographic films, and artificial kidneys.
[0054]
【The invention's effect】
In the method of the present invention, the cellulose ester slurry is washed after the disaggregation or pulverization treatment, whereby the good solvent to be impregnated can be efficiently washed at an industrial level, and the organic acid can be easily recovered. . Further, by treating the wet fibrillar cellulose ester after washing with an aqueous alkaline solution, the generation of organic acid can be suppressed to a small amount, and the wet fibrillar cellulose ester can be stored stably for a long period of time.
[0055]
【Example】
Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.
In the examples and comparative examples, the cleaning rate and storage stability were measured by the following methods.
[0056]
[Washing rate]
The fibrillated cellulose acetate slurry that has been disintegrated and disintegrated and the fibrillar cellulose acetate slurry that has not been disintegrated and disintegrated are weighed so that the solid content is 6.5 g. Suction filtration is performed at a vacuum degree of 400 Torr for 1 minute. 87 g of water is uniformly added to the obtained cake, and suction filtered at a vacuum degree of 400 Torr for 1 minute. The washing rate and washing ratio were calculated by the following methods.
[0057]
Cleaning rate (%) = (A−B) ÷ A × 100
In the formula, A represents the weight (g) of acetic acid contained in the cake before washing, and B represents the weight (g) of acetic acid contained in the cake after washing.
Wash ratio (weight ratio) = C / D
In the formula, C represents the washing water weight (g), and D represents the cake solid content weight (g).
The cake solid content weight D is determined by measuring the weight E (g) of the wet cake, then weighing about 5 g from the cake divided and mixed, and drying by an infrared moisture meter at about 130 ° C. until equilibrium is reached. Using the obtained volatile content F (% by weight), the calculation was performed according to the following formula.
D = E × (100−F) ÷ 100
The washing ratio in this washing method is preferably suppressed to a range of water / cake solid content = 25/1 (weight ratio) or less in order to maintain a high concentration of aqueous acetic acid in acetic acid recovery. In the examples and comparative examples, the cleaning ratio was set to substantially the same level [water / cake solid content = 13/1 to 14/1 (weight ratio)].
[0058]
Moreover, the one where the washing | cleaning rate in this washing | cleaning method is higher is preferable. Therefore, 60% was set as the target cleaning rate in the first stage water cleaning, and cleaning was good when 60% or more, and poor cleaning when it was lower than 60%.
[0059]
[Storage]
The fibrillated cellulose acetate slurry after the pulverization treatment was sufficiently washed with water and centrifuged to remove liquid. This wet fibrillar cellulose acetate was immersed in a 0.05 wt% acetic acid aqueous solution of 9 times its own weight for a whole day and night, followed by centrifugal drainage. Ten parts by weight of this wet fibrillar cellulose acetate is weighed, immersed in about 100 parts by weight of ion exchange water of pH 7 or an alkaline aqueous solution, measured for pH, and centrifuged to remove fibrillated cellulose acetate (hereinafter referred to as wet fibrette). In addition, a dried product was called an absolutely dry fibrette). While measuring a volatile matter using a part of the wet fibrette, 20 g of the wet fibret was taken in a 100 ml glass container and sealed. The glass container was placed in a constant temperature room at 40 ° C., and the amount of acetic acid liberated according to the number of days elapsed was measured. The amount of free sulfuric acid was very small, and all the free acid was regarded as acetic acid. In Examples and Comparative Examples, free acetic acid concentration T (ppm) was calculated by the following formula.
[0060]
Wet fibrette weight (g) = G
Volatile content (% by weight) of wet fibrette = H
Analysis value of acetic acid concentration in extracted water (ppm) = J
Ca concentration (ppm) in absolutely dry fibrette = K
Na concentration (ppm) in absolute dry fibrette = L
Absolutely dry fibrette weight M (g) = G × (100−H) ÷ 100
Absolutely dry fibrette Ca amount N (g) = M x K / 1000000
Absolutely dry fibrette Na amount P (g) = M x L / 1000000
Total acetic acid weight Q (g) = {(G × H ÷ 100) +50} × J ÷ 1000000
Amount of acetic acid in salt R (g) = (N ÷ 40.08 × 60.05 × 2) + (P ÷ 22.99 × 60.05)
Free acetic acid amount S (g) = Q−R
Free acetic acid concentration T (ppm) = (S ÷ 1000000) ÷ M
In the above formula,
In the formula, the numerical value indicated by the decimal point indicates Ca atomic weight = 40.08, Na atomic weight = 22.99, and acetic acid molecular weight = 60.05.
H represents a value of volatile matter (% by weight) obtained by weighing about 5 g of wet fibrette and drying it with an infrared moisture meter until equilibrium is reached at about 130 ° C.
J adds 50 g of ion-exchanged water to a wet fibrette in a glass container for measuring the change of free acid over time, puts the glass container in an ultrasonic cleaning tank, and extracts acetic acid into water by ultrasonic for one hour. The product is filtered, the filtrate is further filtered through a 0.22 μm filter, and the acetic acid value measured by liquid chromatography is shown. In liquid chromatography, metal acetate and free acetic acid cannot be distinguished, and this value is a combination of both.
K and L represent calcium and sodium values measured by atomic absorption spectrometry. Other metals were negligible and ignored.
In the examples, the free acid concentration may be negative, which means that the alkali is excessive.
In the alkali treatment method of the present invention, the generation of free acid is preferably low, and it is not preferable to generate it in a short time. Therefore, with a target value of 1000 ppm, the free acid concentration generated in 30 days or more is considered good if it is less than the target value, and the free acid concentration generated in a period shorter than 30 days is considered poor if it is higher than the target value. did.
[0061]
Example 1
Cellulose acetate was dissolved in a 60 wt% aqueous acetic acid solution so that the concentration of cellulose acetate (average substitution degree 2.5) was 13 wt%, and the temperature was adjusted to 50 ° C. On the other hand, a 29% by weight acetic acid aqueous solution was prepared as a precipitant and the temperature was set to 40 ° C. The apparatus provided with the cutting means 4 shown in FIG. 1 was used as a fibrillar cellulose acetate production apparatus. The cellulose acetate solution is injected from the nozzle means 1 into the precipitant while cutting with a cutter rotating at a high speed of 10,000 rpm from the precipitant supply port 2 of FIG. Extrusion was performed in the direction of the arrow at a flow rate of 1 liter / min. The cellulose acetate solution was subjected to shearing force when coming into contact with the precipitating agent, and precipitated and solidified into a fibril form to obtain a fibril-like cellulose acetate slurry.
[0062]
This fibrillar cellulose acetate slurry was crushed using a supermass colloider (MKZA6-5) manufactured by Masuko Sangyo Co., Ltd., which was adjusted to a clearance of 100 μm and a rotational speed of 1800 rpm as a crusher. The fibrillated cellulose acetate slurry was washed by the washing method.
As a result, the cleaning ratio was 13.3 / 1 (weight ratio) and the cleaning rate was 71.3%, indicating a high cleaning rate.
[0063]
Comparative Example 1
It implemented by the precipitation method similar to Example 1, and the washing | cleaning method, without performing a crushing process.
As a result, the cleaning ratio was 14.0 / 1 (weight ratio), the cleaning rate was 46.6%, indicating a low cleaning rate.
As is clear from the above examples, the cleaning rate can be improved in the example compared to the comparative example.
[0064]
Example 2
The wet fibrette was prepared using an aqueous 0.005 wt% sodium hydroxide solution as an aqueous alkaline solution. The pH of the liquid phase when immersed in the alkaline aqueous solution was 6.76. Moreover, when the free acid after 0 day, 8 days, 14 days, 29 days, and 49 days was measured by the said method by the said storage method, they were -86ppm, 202ppm, 318ppm, 433ppm, and 606ppm, respectively. The total amount of free acid generated during 49 days was 692 ppm, and generation of free acid could be suppressed.
[0065]
Example 3
The wet fibrette was prepared using a 0.006 wt% aqueous sodium hydroxide solution as the alkaline aqueous solution. The pH of the liquid phase when immersed in the alkaline aqueous solution was 7.37. Moreover, when the free acid after 0 day, 8 days, 14 days, 29 days, and 49 days was measured by the said method by the said storage method, they were -238 ppm, 92 ppm, 272 ppm, 332 ppm, and 542 ppm, respectively. The total amount of free acid generated during 49 days was 780 ppm, and generation of free acid could be suppressed.
[0066]
Example 4
The wet fibrette was prepared by using 0.004 wt% calcium hydroxide aqueous solution as the alkaline aqueous solution. The pH of the liquid phase when immersed in the alkaline aqueous solution was 6.46. Moreover, when the free acid after 0 day, 8 days, 14 days, 29 days, and 49 days was measured by the said method by the said storage method, they were 53 ppm, 292 ppm, 322 ppm, 441 ppm, and 561 ppm, respectively. The total amount of free acid generated during 49 days was 508 ppm, and generation of free acid could be suppressed.
[0067]
Example 5
The wet fibrette was prepared by using 0.005 wt% calcium hydroxide aqueous solution as the alkaline aqueous solution. The pH of the liquid phase when immersed in the alkaline aqueous solution was 7.36. Moreover, when the free acid after 0 day, 8 days, 14 days, 29 days, and 49 days was measured by the said method by the said storage method, they were -167 ppm, 144 ppm, 144 ppm, 326 ppm, and 378 ppm, respectively. The total amount of free acid generated during 49 days was 545 ppm, and the generation of free acid could be suppressed.
[0068]
Comparative Example 2
The said wet fibrette was produced using ion-exchange water. Moreover, when the free acid after the lapse of 0 days, 7 days, 14 days and 27 days was measured by the above method by the above storage method, they were 776 ppm, 990 ppm, 1287 ppm and 2261 ppm, respectively. The total amount of free acid generated in 27 days was 1485 ppm, and a large amount of free acid was generated.
[0069]
Comparative Example 3
The said wet fibrette was produced using ion-exchange water. Moreover, when the free acid after the lapse of 0 days, 8 days, and 20 days was measured by the above method by the above storage method, they were 0 ppm, 598 ppm, and 1050 ppm, respectively. The total amount of free acid generated in 20 days was 1050 ppm, and a large amount of free acid was generated.
[0070]
As is clear from the above examples, in the examples, the generation of free acid can be effectively suppressed for a long period of time compared to the comparative examples.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an example of a fibrillation apparatus used in the production method of the present invention.
FIG. 2 is a schematic bottom view of the cutting means of the fibrillation device of FIG. 1;
[Explanation of symbols]
1 ... Nozzle means
2 ... Cellulose ester solution inlet
3 ... Casing
4 ... Precipitant supply port
5 ... Fibril cellulose ester outlet
6. Cutting means
7 ... Shaft
8 ... Cutter
9 ... hole
10 ... Plate

Claims (6)

Rotating teeth in which a cellulose ester solution containing an organic acid is extruded from a nozzle into a precipitant and a shearing force is applied to produce a fibrillar cellulose ester, and the resulting cellulose ester slurry is maintained at a clearance of 10 to 1000 μm And a disintegrator having a fixed tooth and a disintegrator or disintegrator, and then washing and then treating the fibrillated cellulose ester with an alkali. The manufacturing method of the cellulose ester of Claim 1 which wash | cleans with 1-25 weight part washing | cleaning liquid with respect to 1 weight part of cellulose ester slurry solid content, and collect | recovers organic acids from a washing | cleaning filtrate. The method for producing a cellulose ester according to claim 1, wherein the alkali comprises at least one selected from ammonia, an alkali metal, and an alkaline earth metal. The method for producing a cellulose ester according to claim 1, wherein the pH of the liquid phase of the wet fibrillated cellulose ester is adjusted to 5 to 9 by alkali treatment. A cellulose acetate solution dissolved in a solvent containing at least acetic acid is extruded from a nozzle into a precipitating agent to generate fibrillar cellulose acetate by applying a shearing force, and the resulting cellulose acetate slurry is kept at a clearance of 10 to 1000 μm. Alkaline until the pH of the liquid phase of fibrillated cellulose acetate is 6 to 8 after being disaggregated or disintegrated using a disintegrator or disintegrator having sagging rotating teeth and fixed teeth and then washed with water. The manufacturing method of the cellulose acetate processed by. The method for producing cellulose acetate according to claim 5 , wherein the precipitant is an aqueous acetic acid solution.

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