JPH09157302A - Manufacture of acetylcellulose with high degree of polymerization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an acetyl cellulose (hereinafter AC) with a high degree of polymerization by acetylating solid cellulose directly with acetic anhydride by means of a dissolution method in pyridine without subjecting the cellulose to pretreatment. SOLUTION: Though there are no specific limitation for a cellulose to be used, a cellulose with a degree of polymerization as high as possible is used. For example, a cellulose derived from an ascidian and a valonia has a high degree of polymerization and AC obtained therefrom also has a high degree of polymerization. A bacterial cellulose with a high degree of polymerization can also be used. This is produced by cellulose-producing bacteria. An aerated stirred culture yields a cellulose with a weight-average degree of polymerization (in terms of polystyrene) of not less than 1.6×10<4> and a stationary culture yields a cellulose with a weight-average degree of polymerization of not less than 2.0×10<4> . As an example of acetylation by a dissolution method, 3-20 pts.wt. acetic anhydride and 3-40 pts.wt. pyridine is added to a solid cellulose and this mixture is kept at 20-30 deg.C for 4-24hrs for acetylation.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing acetyl cellulose having a high degree of polymerization, and more specifically, to the acetylation reaction of acetic anhydride in pyridine immediately by a dissolution method without pretreatment of solid-state cellulose. The present invention relates to a method for producing acetyl cellulose having a high degree of polymerization.

[0002]

2. Description of the Related Art Various methods are known for synthesizing acetyl cellulose by acetylating cellulose.
For example, for cellulose to be acetylated,
A method of acetylating this in a state of being dissolved in a solvent such as chloral or dimethylformamide (DMF), a method of soaking in acetic acid (pretreatment) and a method of acetylating in a state of being swollen with acetic acid, There is a method of performing acetylation in the solid state as it is without performing it. As the acetylating agent, a method of acetylating using acetyl chloride, a method of acetylating using acetic anhydride and the like are known. Regarding the catalyst, there are a acetylation method using a catalyst such as sulfuric acid, an alkali metal salt of acetic acid such as potassium acetate and sodium acetate, and a acetylation method without using a catalyst. Regarding the solvent, a method of acetylating using a solvent such as acetic acid and methylene chloride, a method of acetylating without solvent, and the like are known.

In particular, when attention is paid to the behavior during the acetylation reaction when solid-state cellulose is used as the acetylation product, the synthetic methods of acetylcellulose are roughly classified into the following three. (A) Solid cellulose (starting material) is dissolved in a pretreatment step, and acetylation This reaction is carried out in a solution state of cellulose (acetylation by dissolution method (1)), (b) solid cellulose is also used as a starting material. However, it is subjected to an acetylation (main) reaction using a solvent immediately without being subjected to a pretreatment such as a solubilization treatment. In this case, cellulose is dissolved as the acetylation reaction proceeds. (Acetylation by dissolution method (2)), and (c) Acetylation in liquid phase or gas phase, which also uses solid cellulose as a starting material but remains solid (for example, acetic anhydride and pyridine). It is subjected to an acetylation (main) reaction by an agent, in which case acetylation proceeds on the surface of cellulose (fibrous acetylation method).

As is clear from the following description, the method for producing a high degree of polymerization acetyl cellulose of the present invention belongs to the category (b).

As is well known, acetyl cellulose is used in various molding materials such as fibers and films, tobacco filters, various composite separation membranes (hemodialysis membranes, ultrafiltration membranes, reverse osmosis membranes, etc.), sound absorbing materials, etc. It is widely used in building materials, paints, etc.

However, there is a great expectation that the properties and performance of cellulose for these applications will be further improved by increasing the mechanical strength.

[0007]

Under the background of the prior art described in the preceding paragraph, an object of the present invention is to provide a molded product of acetyl cellulose having a high degree of polymerization and, in turn, excellent mechanical strength. It is in.

[0008]

As a result of earnest studies to achieve the object described in the preceding paragraph, the present inventor has skillfully combined various elements as described above in the acetylation method of cellulose to acetylate them. It was found that the above-mentioned object can be achieved by carrying out, and the present invention was completed based on such knowledge. Incidentally, the combination of various elements according to the present invention is novel.

That is, the present invention relates to a method for producing acetyl cellulose having a high degree of polymerization by immediately acetylating solid-state cellulose with acetic anhydride in pyridine by a dissolution method without pretreatment.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

There is no particular limitation on the cellulose to be acetylated by the method of the present invention. Not only plant-derived cellulose obtained from cotton linter, wood pulp, etc. but also bacteria produced by microorganisms belonging to the genus Acetobacter, etc. Cellulose is also included. Further, regenerated cellulose and cellulose having a functional group partially introduced therein are also included. Of these celluloses, bacterial cellulose is generally preferable because it gives an acetylated product having high mechanical strength (see Examples below).

As the cellulose used as a raw material for producing acetyl cellulose in the present invention, one having a polymerization degree as high as possible, for example, cellulose derived from ascidian, valonia or the like is preferably used because the resulting acetyl cellulose has a high polymerization degree. Therefore, it is preferable. Further, among the bacterial cellulose of the present invention, the higher degree of polymerization of bacterial cellulose is
It is a suitable raw material for producing acetyl cellulose.

The high degree of polymerization of bacterial cellulose can be produced by a cellulose-producing strain capable of producing the high degree of polymerization of bacterial cellulose.

Among the cellulose-producing bacteria, bacterial culture having a high degree of polymerization, which has a polystyrene-equivalent weight average degree of polymerization of 1.6 × 10 ⁴ or more, preferably 1.7 × 10 ⁴ or more, is obtained by agitating and culturing. Do you manufacture
Alternatively, a strain that produces a highly-polymerized bacterial cellulose having a polystyrene-equivalent weight average degree of polymerization of 2.0 × 10 ⁴ or more by static culture is preferable.

Among the bacteria having a high degree of polymerization which can be used in the present invention, BPR3001A has been deposited at the Patent Microorganism Depositary Center, Institute of Biotechnology, Institute of Biotechnology, Ministry of International Trade and Industry, on June 12, 1995. And is assigned the accession number FERM P-14982.

The weight average degree of polymerization of various types of cellulose such as bacterial cellulose in the present invention is RI as a detector.
Built-in GPC system (Tosoh HLC-80
20) is used and measured as follows.

Various cellulose samples were treated with a fuming nitric acid-phosphorus pentoxide solution by W.I. J. Alexander, R.A. L. Mit
cell, Analytical chemistr
It is nitrated by the method of y21, 12, 1497-1500 (1949).

As a control, simultaneously used nitrated cotton linter is used.

The cellulose nitrate was dissolved in THF (Wako Pure Chemical Grade 1) at a concentration of 0.05% and then 1.0 μm.
Filter through a pore size filter.

THF is also used as an eluent for GPC.

The flow rate is 0.5 ml / min and the pressure is 10 to 10.
13 kg f / cm ² , and the sample injection amount is 100 μl.

The column is TSKgel GMH-HR.
(S) (7.5 ID x 300 mm x 2) and guard column (HHR (S)) (Tosoh Co., Ltd.)
At 35 ° C.

To calculate the molecular weight, standard polystyrene (Tosoh) is used to obtain the relative molecular weight in terms of polystyrene.

Using polystyrene having a molecular weight of 2 × 10 ⁷ to 2630, the elution time (t) and the logarithm of the molecular weight (log)
For M), a cubic expression: (logM = At ³ + Bt ² +
Ct + D) is approximated to create a standard curve.

For the molecular weight, the weight average molecular weight is calculated by a program installed in the Tosoh data processing dedicated machine (SC-8020).

From these molecular weight values, the weight average polymerization degree is calculated in consideration of the degree of substitution after nitration.

The solid-state cellulose referred to in the present invention is
It refers to a dried product of cellulose that has been separated from various cellulose sources by an appropriate method and purified to an appropriate purity.

The reaction conditions for acetylating solid-state cellulose in pyridine with acetic anhydride by a dissolution method are not particularly limited as long as solid-state cellulose is acetylated with acetic anhydride in pyridine and gradually dissolved. There is no.
For example, 1 part by weight of cellulose in a solid state is added to 3 to 20 parts by weight of acetic anhydride and 3 to 40 parts by weight of pyridine, and this mixture is maintained at a temperature of 20 to 30 ° C. for 4 to 24 hours to perform acetylation. be able to. If the amount of acetic anhydride used is less than the above range, the acetylation reaction will not proceed as desired, and if it is more than the above range, a decomposition reaction will occur and the quality of the product will be deteriorated. Further, if the amount of pyridine used is less than the above range, the acetylation reaction does not proceed as desired, and if it is more than the above range, the acetylation reaction does not proceed as desired, either of which is not preferable. As the reaction progresses, cellulose gradually dissolves and undergoes an acetylation reaction in a dissolved state (dissolution method). Regarding the temperature, if the temperature is lower than the above range, the acetylation reaction does not proceed as desired, and if the temperature is higher than the above range, the decomposition reaction occurs and the quality of the product deteriorates.
Neither is preferred. When the time is shorter than the above range, the acetylation reaction does not proceed, and when the time is longer than the above range, a decomposition reaction occurs and the polymerization degree of the product is lowered, so that both are not preferable.

The termination of the acetylation reaction can be carried out according to a conventional method, that is, the reaction mixture is dropped into a large amount of water to stop the reaction.

There is no particular limitation in separating and obtaining the desired acetylcellulose from the reaction mixture in which the reaction has been stopped, and the conventional method can be applied. That is, for example,
A general solid-liquid separation method such as centrifugation, (suction) filtration, and concentration is appropriately adopted to obtain the target acetyl cellulose.

The acetyl cellulose thus obtained can be put into distribution as its product.

The technique for producing acetyl cellulose having a high degree of polymerization described in the present invention can be applied to the preparation of various cellulose derivatives, and a cellulose derivative having a high degree of polymerization can be obtained.

Examples of cellulose derivatives include various cellulose ethers, cellulose esters, unsaturated celluloses, anhydrous celluloses, deoxycelluloses, oxidized celluloses, alkali celluloses, cellophane, viscose rayon, cellulose graft copolymers and bioactive cellulose derivatives. And the following derivatives. Cellulose sulfate, cellulose phosphate, propionate, butyrate, valerate, caproate, heptylate,
Caprylate, laurit, myristate, palmitate, cellulose acetate butyrate, cellulose acetate propionate, acetate / methacrylate,
Acetate / malate, propionate / crotonate, acetate / N, N-diethylaminoacetate,
Propionate / morpholinobutyrate, mixed ester with unsaturated carboxylic acid, aminodeoxycellulose, sodium carboxymethylcellulose, carboxymethylhydroxyethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxyalkylmethylcellulose, ethylcellulose, ethylhydroxyethylcellulose, cyanoethylcellulose, Ethyl hydroxyethyl cellulose, hydroxypropyl methyl cellulose, diethylaminoethyl cellulose, hydroxypropyl / methyl cellulose phthalate, hydroxyethyl hydroxypropyl cellulose, cellulose carbamate, aminodeoxy cellulose, halodeoxy cellulose, cationic cellulose ether Carboxylic acid-containing oxidized cellulose,
Carboxyl group-containing oxidized cellulose, 2,4-dichloro-6- (3 ', 6', 8'-trisulfo-1'-naphthylamino) -cintriazine-containing polyacrylic acid graft cellulose, ethylferrocene cellulose, chlorononyl acrylate-containing Cellulose derivative, β-galactosidase-immobilized p-aminocarbanilate cellulose, tetracycline-bonded cellulose diazobenzoate,
2,2'-methylenebis (3,4,6-trichlorophenol) 2Na salt-containing derivative, morpholine / cellulose ether complex, ethanolamine-cellulose derivative,
Phosphorus cellulose, β-amylose-immobilized cellulose derivative, and other cellulose derivatives (CMC “Development of Functional Cellulose” p.50-111)
(Described in (1985)).

[0034]

The present invention will be further described with reference to the following examples.

Example 1 (Preparation of Bacterial Cellulose by Static Culture of High-Polymerization Cellulose-Producing Bacteria) BPR3001A was used as a medium 10 from glycerol stock.
Inoculation was carried out at a concentration of 1% in a 750 ml roux flask charged with 0 ml, and the mixture was allowed to stand still at 28 ° C. for 3 days. After the culture, shake the roux flask well to remove the cells from the cellulose membrane, and then add 3 ml of the bacterial solution to CSL (corn steep liquor) -F.
The cells were inoculated into a petri dish (diameter 90 mm) containing 27 ml of ru (fructose) medium, and cultured at 28 ° C. for 10 days.

After the culture was completed, the obtained cellulose membrane was washed with running water and then heated in about 500 ml of water at 80 ° C. for 20 minutes. After the heating, the cellulose membrane was further washed with running water, and then washed in about 500 ml of 0.1 N NaOH at 80 ° C.
The cells contained in the cellulose membrane were lysed by heating for 0 minutes. After lysis, the cellulose membrane was washed by heating in about 500 ml of distilled water at 80 ° C. for 20 minutes. The same washing was performed 3 to 5 times while replacing distilled water to obtain purified bacterial cellulose.

The weight average degree of polymerization of this purified bacterial cellulose was 22,500 as measured by the method described above.

Example 2 (Preparation of Bacterial Cellulose by Aeration and Stirring Culture of High-Polymerization Cellulose-Producing Bacterium) BPR3001A was prepared from CSL-containing glycerol stock.
1% of the cells were inoculated into a 750 ml roux flask charged with 100 ml of Fru medium, and statically cultured at 28 ° C. for 3 days. After culturing, shake the Roux flask well to remove the cells from the cellulose membrane, inoculate 12.5 ml of the bacterial solution into a 500 ml flask containing 112.5 ml of medium, and 180 rpm at 28 ° C.
The cells were cultured for 3 days under the condition of m. The culture was aseptically disaggregated with a blender and 60 ml of it was added to 540 ml of CSL-
Inoculate into a jar fermenter with a volume of 1 liter containing Fru medium and adjust the pH to NH ₃ gas and 1N H ₂ S.
Main culture was performed while controlling the 4.9 to 5.1 with O ₄ and automatically controlling the number of revolutions so that the dissolved oxygen content (DO) was 3.0% or more.

After completion of the culture, the obtained culture solution was diluted about 5 times with an acetate buffer and then centrifuged to collect the precipitate. After diluting the precipitate with distilled water to about 8 times the initial culture volume,
After heating at 80 ° C. for 20 minutes, the precipitate was collected by centrifugation after heating. The sediment is also occupied by 8 times the amount of 0.1 N NaO.
H, and lysed by heating at 80 ° C. for 20 minutes. After lysis, the precipitate was recovered by centrifugation. After this,
Further, the precipitate was suspended in 8 times the volume of distilled water, heated at 80 ° C. for 20 minutes, heated, centrifuged, and the precipitate was collected to wash the cellulose. The same washing was performed three times to obtain purified bacterial cellulose.

The weight average degree of polymerization of this purified bacterial cellulose was measured by the method described above, and it was 17400.

Incidentally, the CSL-Fru used in the above examples.
Is as shown in Table 1 below.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

Example 3 (a) The purified bacterial cellulose obtained in Example 2 was subjected to solvent substitution with organic solvents such as methanol, acetone and hexane in this order and dried (JP-A-6-233691).
And U.S. Geyer, Int. J. Biol. Macr
omol. , 16, 6 (1994)). This dried product is an example of solid-state (bacterial) cellulose.

2 to this solid-state bacterial cellulose
Add 0 times (weight) acetic anhydride and the same amount of pyridine,
The acetylation reaction was carried out by maintaining the temperature of the obtained mixture at 20 to 30 ° C. for 12 hours. Then, the reaction mixture was thrown into a large amount of water to obtain acetyl cellulose. This was neutralized, washed thoroughly with water, and dried. After drying,
Acetyl cellulose was dissolved in acetone, the solution was placed in a flat-bottom glass container and air-dried, and the acetyl cellulose membrane formed on the bottom of the container was recovered.

(B) An acetylcellulose membrane was recovered in exactly the same manner as in (a) above, except that a commercially available cotton linter was used in place of the solid-state bacterial cellulose dried by solvent substitution.

Comparative Example 1 (Comparison with the conventional method (acetic acid method)) (a) 20 times amount (weight) of solid state bacterial cellulose dried by solvent substitution obtained in the same manner as in (a) of Example 3 After dipping for 3 hours using glacial acetic acid in 1), adhering acetic acid was removed by suction filtration.

100 parts by weight of the pretreated bacterial cellulose from which acetic acid had been removed was mixed with 20 parts by weight (weight) of acetic anhydride, 20 parts by weight of glacial acetic acid and 15 parts by weight of concentrated sulfuric acid (acetylating agent). In addition to the temperature of 20-30
When the reaction liquid was kept at 5 ° C. for 5 hours, the cellulose was completely dissolved and the reaction liquid became transparent.

After adding water in an amount 3 times (by weight) that of bacterial cellulose and aging at 25 ° C. for 2 days, the reaction mixture was poured into a large amount of water to stop the reaction to obtain acetyl cellulose. This was neutralized, washed thoroughly with water, and dried. After drying,
This was dissolved in acetone, the solution was placed in a flat-bottomed glass container and air-dried, and the acetylcellulose membrane formed on the bottom surface of the container was recovered.

(B) An acetylcellulose membrane was recovered in exactly the same manner as in (a) above, except that a commercially available cotton linter was used in place of the bacterial cellulose dried by solvent substitution.

Inspection Example 1 (Mechanical Strength Inspection of Various Acetyl Cellulose Membranes) Regarding the cellulose membranes obtained in Example 3 and Comparative Example,
The weight average degree of polymerization (DPw) and Young's modulus were examined.

In this inspection example, DPw is measured as follows. That is, a GPC (size exclusion chromatography) system "Tosoh HLC-8020" having a built-in RI (differential refractometer) as a detector is used to perform the measurement as follows.

Acetylcellulose is 0.05% in THF (tetrahydrofuran manufactured by Wako Pure Chemical Industries, Ltd., reagent first grade).
After dissolving at a concentration, it is filtered with a filter having a pore size of 1.0 μm. THF is also used as the eluent for GPC. Flow rate is 0.5 ml / min, pressure is 10 to 13 kgf / c
m ² , and sample injection volume is 100 μl. The column is "TSKgel GMH-HR (S)" (7.5I).
D x 300 mm x 2) and guard column "HHR
(S) ”(Tosoh Co ,, Ltd.)
Measure at 5 ° C.

A standard polystyrene "Tosoh" is used to calculate the molecular weight, and the relative molecular weight in terms of polystyrene is determined. More specifically, polystyrene having a molecular weight (M) of 2 × 10 ⁷ to 2630 is used, and the elution time (t) and the logarithm of the molecular weight (log M) are expressed by a cubic expression: (log
M = At ³ + Bt ² + Ct + D) to make a standard curve. Regarding the molecular weight, the weight average molecular weight is calculated by a program installed in the Tosoh data processing computer "SC-8020".

The weight average degree of polymerization (hereinafter, abbreviated as DPw or degree of polymerization) is calculated from these molecular weight values in consideration of the degree of substitution after acetylation.

The degree of substitution was determined from the ratio of peak intensities of acetyl groups and hydroxyl groups in FT-IR analysis using commercially available acetyl cellulose as a reference substance. FT-IR is "FTS
165 "(manufactured by Bio-Rad) was used for the measurement by the permeation method.

Young's modulus is measured as follows. That is, 5 × 30 mm from the prepared acetyl cellulose membrane
A strip-shaped sample was cut out, the thickness and weight were measured, and the dynamic viscoelasticity measuring device “DMS” manufactured by Seiko Electronic Industry Co., Ltd.
210 ”. The measurement is automatic tension measurement, initial tension 250 g / mm ² , variation amount ± 20.
A temperature rise measurement is performed under conditions of μm and a frequency of 10 Hz to obtain a tensile storage elastic modulus (Young's modulus) and an internal loss. Temperature distribution pattern of Young's modulus (temperature range 28-40
The highest value of (° C) is used as the value of Young's modulus. The specific gravity of acetyl cellulose is set to 1.36, and the value obtained by correcting the measured value of the above Young's modulus is calculated to obtain the true Young's modulus.

The inspection results are shown in Table 2 below.

[0060]

[Table 4]

From Table 2, it can be seen that the acetyl cellulose of the present invention (obtained in Example 3) has a higher degree of polymerization (DP) than the conventional acetyl cellulose (comparative example).
It can be seen that w) is generally high, and the produced acetylcellulose membrane is superior in mechanical strength to the one according to the present invention as compared with the one by the conventional method.

Further, it can be seen that even in the case of the present invention, the degree of polymerization and mechanical strength of bacterial cellulose are remarkably superior to those of conventional plant-based cellulose. This is because when the acetyl cellulose of the present invention, particularly acetyl cellulose made from bacterial cellulose is used for various composite separation membranes, the film thickness can be reduced,
By extension, it means that the substance permeability can be significantly improved.

The substitution degree of the acetyl cellulose obtained in the present invention was 2.4 in all cases.

[0064]

Industrial Applicability According to the present invention, acetyl cellulose having a high degree of polymerization (DPw) can be provided, which in turn can easily provide a molded product of acetyl cellulose having excellent mechanical strength.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Watanabe Otohiko 32-1 Sakado, Takatsu-ku, Kawasaki City, Kanagawa KSP R & D Business Park Building B-1015 Biopolymer Research Co., Ltd. (72) Inventor Yasunori Morinaga KSP R & D Business Park Building B-1015, 3-2-1 Sakado, Takatsu-ku, Kawasaki City, Kanagawa Prefecture (72) Inventor Fumitaka Horii 4-1-1 Oridai, Uji City, Kyoto Prefecture 101

Claims (4)

[Claims] 1. A process for producing acetyl cellulose having a high degree of polymerization, which comprises acetylating solid-state cellulose in acetic anhydride in pyridine immediately without subjecting it to pretreatment. 2. The method for producing a high degree of polymerization acetyl cellulose according to claim 1, wherein the cellulose is bacterial cellulose. 3. A polystyrene-based weight average degree of polymerization of bacterial cellulose obtained by aeration stirring culture is 1.6.
The method for producing a high degree of polymerization acetyl cellulose according to claim 2, wherein the bacterial cellulose has a density of × 10 ⁴ or more. 4. A weight average degree of polymerization in terms of polystyrene obtained by static culture of bacterial cellulose of 2.0 × 1.
The method for producing a high-polymerization degree acetyl cellulose according to claim 2, which is a bacterial cellulose of 0 ⁴ or more.