JP3281921B2 - Method for acylating cellulose - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a novel acylation method for acylating cellulose to produce a partial or complete ester of cellulose.

[0002]

2. Description of the Related Art Heretofore, the ester of cellulose and acetic acid, that is, cellulose acetate, is best known as an ester of cellulose, and is widely used as a complete photographic film, acetate rayon, lacquer and plastic material, insulating foil and the like. Have been. In addition, cellulose propionate, butyrate, mixed ester of acetic acid and butyric acid, mixed ester of propionic acid and isobutyric acid, mixed ester of propionic acid and valeric acid are also known, and lubricity and water resistance are required. It is used as a plastic composite material. Cellulose also forms an ester with an aromatic carboxylic acid, for example, cinnamate and salicylate are known.

Incidentally, these esters of cellulose, for example, cellulose acetate, are usually sulfuric acid, acetates,
It is produced by a method in which cellulose and acetic anhydride are reacted at a temperature of 35 to 60 ° C. in the presence of a catalyst such as zinc chloride. However, this method requires a long period of time to uniformly promote acetylation of cellulose. In addition to the need for treatment, there is a disadvantage that a treatment for removing the catalyst from the reaction product must be performed. In recent years, a method using a Bridgman-type high-pressure generator has been proposed as a method for producing ecological cellulose acetate [Journal
Of Applied Polymer Science (J. App
l. Polym. Sci. ), Vol. 57, p. 439 (1995)], according to this method, it is possible to omit the pretreatment and the catalyst removal treatment for uniformly proceeding the acetylation. Since a special device is required to generate the above, there are disadvantages that the cost is inevitably increased and that mass production is not possible.

[0004]

SUMMARY OF THE INVENTION Under such circumstances, the present invention can efficiently produce a cellulose ester in as short a process as possible without complicated processing, and is suitable for mass production. The purpose of the present invention is to provide a method for acylating cellulose.

[0005]

Means for Solving the Problems The present inventors have prepared cellulose in an air-dried state without using a catalyst or a special device.
In addition, as a result of intensive studies to develop a method for producing acylated cellulose or partial ester by acylating efficiently, as a result of crushing using a crushing medium with the acylating agent adsorbed on cellulose, It was found that when the grinding media collided, a pressure field was formed at about the same level as in the high-pressure generator and the temperature rose due to frictional heat, and the acylation reaction of cellulose proceeded quickly. Invented the invention.

[0006] That is, the present invention provides a method for acylating cellulose, comprising adsorbing an acylating agent to cellulose and pulverizing the adsorbent with a pulverizing medium.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Cellulose used as a raw material in the present invention includes wood-derived cellulose such as conifers such as pine, fir, spruce, hemlock and cedar, and broadleaf trees such as beech, hippo, poplar and maple. , Asa, flax, ramie, Manila Asa, leaf fiber, stem fiber derived cellulose and mitsumata, mulberry, ganpi, straw, bagasse, bamboo, etc. In addition to natural cellulose such as cellulose, any of refined pulp, semi-purified pulp, and processed cellulose derived from waste paper recycled pulp may be used, and there is no particular limitation.

[0008] The cellulose chains in these cellulose molecules are composed of β-D-glucopyranose units, and these units have a total of three secondary hydroxyl groups and one primary hydroxyl group. And some or all of them are acylated (esterified) to form a cellulose ester. In this acylation, a primary hydroxyl group generally reacts most easily.

Next, as the acylating agent used in the method of the present invention, an organic carboxylic acid or an anhydride thereof is used, and a lower fatty acid or an anhydride thereof or a mixture thereof is particularly preferable. Examples of the lower fatty acid include acetic acid, propionic acid, and butyric acid. Examples of the lower fatty acid anhydride include acetic anhydride, propionic anhydride, butyric anhydride, and a mixed anhydride of acetic acid and butyric acid. Further, depending on the purpose, an aromatic carboxylic acid such as cinnamic acid or salicylic acid or an anhydride thereof can be used.

These organic carboxylic acids or their anhydrides may be used alone or in combination of two or more. Of these, a mixture of acetic acid and acetic anhydride in a volume ratio of 30:70 to 20:80, particularly a mixture of 25:75, is preferred because it provides a high acylation ratio.

The acylation method of the present invention does not require the use of a catalyst as in conventional acylation of cellulose,
It is only necessary to adsorb the acylating agent on the cellulose and pulverize it with a pulverizing medium. To adsorb the acylating agent to the cellulose, for example, the acylating agent is brought into contact with air-dried cellulose. At this time, if necessary, the acylating agent may be diluted with a solvent, for example, alcohol, ketone, ether, ester or the like. The amount of the acylating agent adsorbed is 50 to 3 based on the absolute dry weight of the cellulose.
00% by weight, preferably in the range of 100 to 200% by weight. In this case, it is preferable to use cellulose in a state containing a little moisture.

Next, the cellulose on which the acylating agent is adsorbed as described above is subjected to a pulverizing treatment. This pulverizing treatment is performed by a pulverizing apparatus using a pulverizing medium without wetting with water. In this case, as a grinding device, tungsten nitride,
A vibration mill using a pulverizing medium such as a ball or a rod of tantalum nitride or stainless steel is used. As the balls and rods, those used in a normal fine grinding vibrating mill can be used as they are, but in general, better results can be obtained by using balls having a higher specific gravity.

The pulverizing conditions are not particularly limited, and the conditions used in the conventional vibrating ball mill and vibrating rod mill, for example, an amplitude of 5 to 20 mm and a rotation speed of 1000 to 300
The condition of 0 rpm can be used, but in general, the acylation proceeds faster as the amplitude and the number of rotations increase.

In the method of the present invention, at room temperature, for example, 1
The pulverization is started at 0 to 20 ° C., and the temperature gradually increases with the elapse of the pulverization time.
Or more. The pulverization time at this time, that is, the reaction time depends on the pulverization conditions, but is usually 30 minutes.
Within a range of ~ 120 minutes. By such a treatment, an acylated cellulose having a maximum acyl content of 7% can be obtained. In a normal pulverization process, the average particle size is 20 μm.
In order to obtain the following particles, it is necessary to grind them in a state of being wetted with water. However, according to the method of the present invention, even in the absence of substantially water, an acylated fine particle having an average particle size of about 10 μm is obtained. Particles can be obtained.

The acylated cellulose thus obtained is repeatedly dispersed in water and warm water and filtered to remove unreacted acylating agent and by-products produced by the reaction, and then dried. Can be purified.

[0016]

Next, the present invention will be described in more detail by way of examples. In addition, the acetylation rate of cellulose in each example was qualitatively confirmed by infrared absorption spectrum analysis of a sample collected after each pulverization time, and further quantified by an alkali saponification method.

REFERENCE EXAMPLE Vibration type ball mill (manufactured by CM Corporation, trade name "T") to which digital thermo tape (manufactured by NOF Engineering Co., Ltd.) is attached.
I-300 ", ball: stainless steel, diameter 16m
m, amplitude: 14 mm, number of revolutions: 1700 rpm), 50 g of air-dried wood cellulose (manufactured by Nippon Paper Industries Co., Ltd., trade name "KC Floc W-100") (absolute dry weight) was added, and the initial temperature was 16C and 24C. Crushed. FIG. 1 shows a graph A (16 ° C.) and a graph B (24 ° C.) of the relationship between the pulverization time and the container temperature of the pulverizer at this time. As can be seen, at any initial temperature, 6
By 0 minutes, a temperature rise of about 35 ° C. is observed due to the grinding process.

Example 1 50 g of the same wood cellulose as used in the reference example and 75 g of acetic anhydride were charged into the pulverizing apparatus used in the reference example, and pulverized under initial conditions of 16 ° C. and 24 ° C. under the same conditions as in the reference example. did. FIG. 2 shows the relationship between the pulverizing time and the container temperature at this time as a graph A (16 ° C.) and a graph B (24 ° C.). The relationship between the grinding time and the acetyl content (%) of cellulose at this time is shown in FIG.
And graph B (24 ° C.). As can be seen from these figures, even when the acetylating agent is added to the cellulose, the vessel temperature rises over time, and the rate of increase is higher than when the acetylating agent is not added. At the same time, the acetyl content of cellulose increases. The acetyl content tends to increase rapidly especially after 40 minutes. When the initial temperature is increased from 16 ° C. to 24 ° C., the acetyl content after 60 minutes of pulverization is:
It can be seen that it increases from 5.3% to 7%. On the other hand, the vessel temperature of the reaction system in which cellulose and the acetylating agent coexist is
Compared to the temperature of a blank container in which only cellulose is present, the temperature is lower up to a pulverization time of 30 minutes, but becomes higher when the pulverization time is exceeded. In addition, when only cellulose is pulverized, the acetyl content hardly increases even if it exceeds 60 minutes.

Example 2 The same amount of purified cotton linter (manufactured by Whatman, trade name "CF1") was used instead of wood cellulose in Example 1.
1)), the initial temperature was adjusted to 16 ° C., and pulverization was performed in the same manner as in Example 1. A graph showing the relationship between the grinding time and the vessel temperature at this time is shown by a solid line in FIG. 4, and a graph showing the relationship between the grinding time and the acetyl content is shown in FIG. In FIG. 4, a graph in the case where no acetylating agent is added is shown by a broken line for reference. In addition, about 60 minutes or more of the grinding | pulverization time, the measurement by a digital thermo tape was impossible. As can be seen from these figures, when the type of cellulose changes, the tendency of the container temperature to increase with time due to pulverization also changes, and the acetyl content also changes.

Example 3 A pulverizing treatment was carried out by adjusting the initial temperature to 24 ° C. in the same manner as in Example 1 except that a pulverizing apparatus having an amplitude of 8 mm was used instead of the pulverizing apparatus used in Example 1. . FIG. 6 is a graph showing the relationship between the crushing time and the vessel temperature at that time, and FIG. 7 is a graph showing the relationship between the crushing time and the acetyl content. For reference, when the tendency of increasing the container temperature when only cellulose was pulverized without adding an acetylating agent was examined, the graph was completely consistent with the case where the acetylating agent was added. As can be seen from these figures, when the amplitude is reduced to 8 mm, the container temperature after 60 minutes of pulverization is 55 ° C. lower than the case of 14 mm, and the acetyl content of cellulose is 1/3 or less.

Example 4 As an acetylating agent, a mixture of acetic anhydride and acetic acid having different mixing ratios was used, the initial temperature was adjusted to 24 ° C., and wood cellulose was ground for 40 minutes under the same grinding conditions as in Example 1. FIG. 8 is a graph showing the relationship between the content (volume%) of acetic anhydride and the vessel temperature, and FIG. 9 is a graph showing the relationship between the content of acetic anhydride and the acetyl content of wood cellulose. As can be seen from these figures, as the acetic anhydride content increases, the container temperature and the acetyl content of the cellulose increase, and when the acetic anhydride content is 75% by volume, both become maximum.

Example 5 A pulverization treatment was performed under the same conditions as in Example 1 at an initial temperature of 24 ° C., and the change over time in the average particle size of the acetylated cellulose produced was examined. The result is shown as a graph in FIG. As can be seen from this graph, according to the present invention, fine particles having an average particle diameter of 20 μm or less are already obtained in a pulverization time of 20 minutes, and fine particles of approximately 10 μm are obtained in 40 minutes.

[0023]

According to the present invention, an acylated cellulose having a high acyl content can be obtained by a simple treatment without using a catalyst and in a short reaction time, and a catalyst removing step is not required. There is an advantage that the step of purifying the reaction product can be simplified.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between grinding time and container temperature in a container containing only wood cellulose.

FIG. 2 is a graph showing the relationship between the grinding time and the container temperature in a container containing wood cellulose and an acetylating agent.

FIG. 3 is a graph showing the relationship between crushing time and acetyl content when wood cellulose and an acetylating agent are crushed.

FIG. 4 is a graph showing a relationship between a grinding time and a container temperature in a container containing cotton cellulose and an acetylating agent.

FIG. 5 is a graph showing the relationship between crushing time and acetyl content when cotton cellulose and an acetylating agent are crushed.

FIG. 6 is a graph showing a relationship between a pulverization time and a container temperature when a pulverizer having a small amplitude is used.

FIG. 7 is a graph showing the relationship between the crushing time and the acetyl content of cellulose when a crusher with a small amplitude is used.

FIG. 8 is a graph showing the relationship between the acetic anhydride content and the vessel temperature when a mixture of acetic anhydride and acetic acid is used as an acetylating agent.

FIG. 9 is a graph showing the relationship between the acetic anhydride content and the acetyl content of wood cellulose when a mixture of acetic anhydride and acetic acid is used as an acetylating agent.

FIG. 10 is a graph showing the relationship between the grinding time and the average particle size of acetylated cellulose.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Ryoichi Kitagawa 2217-14 Hayashi-cho, Takamatsu-shi, Kagawa Prefectural Institute of Industrial Science Shikoku Institute of Industrial Technology (58) Field surveyed (Int. Cl. ⁷ , DB name) C08B 3 / 08 C08B 3/06 CA (STN) REGISTRY (STN) WPIDS (STN)

Claims (5)

(57) [Claims] 1. A method for acylating cellulose, comprising adsorbing an acylating agent on cellulose and pulverizing the adsorbent with a pulverizing medium. 2. The acylation method according to claim 1, wherein the acylating agent is an anhydride of a lower fatty acid. 3. The acylation method according to claim 1, wherein the acylating agent is a mixture of an anhydride of a lower fatty acid and a lower fatty acid. 4. The acylation method according to claim 3, wherein the acylating agent is a mixture of acetic acid and acetic anhydride. 5. The acylation process according to claim 4, wherein the acylating agent is a mixture of acetic acid and acetic anhydride in a volume ratio of 30:70 to 20:80.