JP2988717B2 - Production method of novel cellulose organic ester - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel method for producing a cellulose organic ester, and more particularly, to a method for producing a cellulose organic ester by allowing an organic esterification agent to act on a liquid mixture of cellulose and an aqueous alkali solution. About the law.

(Prior art)

Representative examples of cellulose organic esters that are currently commercially used include cellulose acetate (hereinafter abbreviated as CA) and cellulose acetate butyrate (CA).
B), cellulose propionate (CP), cellulose butyrate (CB) and the like. In particular, CA is one of useful cellulose derivatives used in a wide range of fields such as fibers, plastics, filters, and paints.

Since the production method of these cellulose organic esters is based on a solid-liquid (solid) reaction between a cellulose solid (linter, pulp, cotton) and an organic esterifying agent, it has been compared with other derivatization reactions of cellulose for a long time. It is known to be non-uniform. Therefore, to advance the reaction quickly, pre-treat cellulose with some reagent in advance,
How to increase the permeability of the organic esterifying agent into the solid is an element of the technology. For example, in the case of cellulose acetate, it takes a very long time even if cellulose and acetic acid are reacted at room temperature, and the reaction at a high temperature (180 ° C.) for 1 to 2 hours becomes a highly substituted CA only in 1865. Was discovered by Schutzenberger in
Cellulose was severely decomposed and was not a practical method. Since then, a number of studies have been made, and a method of using a catalyst (such as sulfuric acid) and a pretreatment of cellulose (immersion treatment with an aqueous solution of acetic acid or sodium acetate) in combination are the basis of the current production method.

The biggest drawback of these methods is that it is almost impossible to produce a low-substituted homogeneous derivative directly in a one-step process, and in order to increase the homogeneity of the resulting derivative, once a highly substituted derivative is obtained. , It was necessary to desubstitute to produce a low-substituted derivative. In some cases, it is currently used as it is in highly substituted derivatives.

On the other hand, in recent years, dimethyl sulfoxide / paraformaldehyde, dimethylformamide / nitrogen tetroxide, sulfur dioxide / amine, dimethylformamide / chloral, N-methylmorpholine-N-oxide, dimethylacetamide / lithium chloride, etc. Many organic solvents that dissolve cellulose have been found, and studies on derivatization of cellulose using homogeneous reactivity in these solvents have been conducted. For example, dimethyl sulfoxide /
Japanese Patent Application No. 55-166669 using methylene diacetate or ethylene diacetate as a reactant and sodium acetate as a catalyst is an example of the use of paraformaldehyde. As an example using a dimethylacetamide / lithium chloride system, Miyamoto et al. (J. Polym. Sci., Polym. Chem. Ed.,
23 , 1373 (1985)).

The above methods have problems in practicality due to the stability, toxicity, price (recoverability) and the like of the organic solvent, and are still in the stage of academic research.

[Problems to be solved by the invention]

The present inventors in view of such a situation, as a result of intensive studies, by using a mixture obtained by previously dissolving or highly swelling cellulose in an aqueous solution of an alkali metal hydroxide as a reaction base, The inventors have found that cellulose can be esterified more uniformly and quickly than the conventional method, and have reached the present invention.

The main object of the present invention is to provide a method for preparing a cellulose organic ester more uniformly and quickly than in the conventional method. Is also provided.

[Means for solving the problem]

The main constituent requirement of the method for producing a cellulose organic ester of the present invention is to dissolve cellulose in an aqueous solution containing 5 to 15% by weight of an alkali metal hydroxide at a temperature of 16 ° C. or less for preparing the cellulose organic ester. High swelling, coagulating the resulting mixture once with a non-solvent for cellulose, washing with water and then immersing in an organic esterifying agent or contacting the mixture directly with the organic esterifying agent.

Here, "highly swelled" means that when the state of cellulose in an aqueous solution of an alkali metal hydroxide is observed with a polarizing microscope (crossed Nicols), when the cellulose is fibrous, its diameter (thickness) Is three times or more of the original, and when the cellulose is in the form of powder, it means that the diameter is swollen to three times or more of the original. Further, the “dissolved” state is recognized as a dark field in the same observation with a polarizing microscope. In addition, those which do not even swell at all can clearly observe the shape as it is.

The most important feature in the constitution of the present invention is that when preparing a cellulose organic ester, 5 to 15% by weight as a reactive base is used.
A mixture obtained by dissolving or highly swelling cellulose in an aqueous solution containing an alkali metal hydroxide at a low temperature.

As described above, in the conventional method, since solid cellulose is used as a reaction base, the diffusion rate of the reaction agent into the solid is limited, or the diffusion rate between the crystalline region and the amorphous region is different. Non-uniformity due to differences is a problem. In contrast, in the method of the present invention, a mixture obtained by previously dissolving or highly swelling cellulose in an aqueous solution of an alkali metal hydroxide is used as a reaction base, so that the diffusion rate is higher than in the solid state, and There is an advantage that non-uniformity in reactivity based on the difference between the crystalline and amorphous structures is eliminated.

Regarding the use of the above mixture as a reaction base, a person having ordinary chemical knowledge can cause a violent neutralization reaction when an alkali is applied to a water-inhibited substance such as an acid anhydride or an acid chloride. Although it is common to think that a practical reaction cannot be expected, the present inventors have experimentally found that these systems respond relatively mildly, and at present, the mechanism of action is not clear. Although not available, the possibility of an alkali metal hydroxide having a function of dissolving or highly swelling cellulose acting as a catalyst at the time of the reaction was identified, thereby realizing development to a practical production method.

As the alkali metal hydroxide used in the present invention,
Sodium hydroxide, lithium hydroxide, potassium hydroxide,
Cesium hydroxide and the like can be mentioned. The alkali concentration of the aqueous alkali solution is 5 to 15% by weight. In particular, a 7 to 10% by weight solution of sodium hydroxide is preferably used.

The cellulose that can be used in the present invention dissolves or swells highly in an aqueous solution of 5 to 15% by weight of an alkali hydroxide, and is not limited by crystal type, degree of polymerization, plant species, etc., but is preferably used. Cellulose having a high degree of breaking intramolecular hydrogen bonds described in Japanese Patent Application No. 58-149149 is used.

The concentration of cellulose in a mixture with an aqueous alkali solution is a problem to be determined depending on the degree of polymerization of cellulose, but should be contained at least 3% by weight from an economic viewpoint. Degree of polymerization
Cellulose at position 400 can dissolve 5 to 7% by weight, and can swell uniformly up to about 9% by weight. Melting at 16 ° C
It is carried out under the following low temperature, preferably at a low temperature of −10 ° C. or more and 10 ° C. or less.

The second feature in the constitution of the present invention is that when the organic esterifying agent is acted on, the mixture is once coagulated with a non-solvent of cellulose and washed with water, and then immersed in the organic esterifying agent, or the mixture is mixed. In direct contact with the organic esterifying agent.

In this case, when the mixture is once coagulated with a non-solvent of cellulose, or when it is directly contacted with an organic esterifying agent, a film, a yarn, and a reaction molded body can be obtained in one step simultaneously with the reaction if molded into a powder. . That is, when the above mixture is a solution in which cellulose is uniformly dissolved, by using an acid anhydride or an acid chloride for a coagulation bath, it is possible to simultaneously form an organic ester while forming a film, a thread, a powder, or the like. Has the advantage that molding and derivatization are achieved in one step. On the other hand, when the mixture is a highly swollen mixture, a powdery derivative can be prepared by adding an acid anhydride or an acid chloride thereto, mixing and treating them,
By controlling the amount of the esterifying agent added, a derivative having a low degree of substitution can be prepared in one step. These features are not found in conventional methods.

Examples of the organic esterifying agent that can be used in the present invention include acid anhydrides of fatty acids having 4 or less carbon atoms, such as acetic anhydride, propionic anhydride, and butyric anhydride; valeric acid, caproic acid, caprylic acid, palmitic acid, stearic acid, and the like. Acid halides of fatty acids having 5 or more carbon atoms; dibasic acid anhydrides such as maleic anhydride, succinic anhydride, and phthalic anhydride; unsaturated fatty acids such as crotonic acid, undecylenic acid, and oleic acid; Halogenated acetic acid; aromatic compounds such as benzoyl chloride, benzoic anhydride, and paratoluenesulfonic acid chloride; and carbamic acid. At least one or more selected from these are used,
When the esterifying agent itself is solid, it may be dissolved in the solvent before use.

Specific embodiments are described in Examples below, but when acting on an organic esterifying agent while being formed into a film, a yarn, and a powder, by using a film forming apparatus or a spinning apparatus, The organic esterifying agent may be used as a coagulation bath, or once coagulated with a non-solvent of cellulose, washed with water, and then used as a secondary bath with an organic esterifying agent. In the case where an organic esterifying agent is added, mixed and treated, the reaction can be achieved by allowing a predetermined amount of the organic esterifying agent to drop and mix with the mixture under stirring.

The degree of substitution of the obtained cellulose can be calculated by ¹³ C-NMR spectrum measurement, which is an absolute method, for a solvent in which the obtained cellulose organic ester is uniformly dissolved. FT-
Absorbance ratio calculated from IR (absorption based on ester group (around 1720 Kaiser) and absorption as internal standard (2911
The ratio can be calculated from a calibration curve of the ratio obtained from the ratio of K. Kaiser) to the value obtained by ¹³ C-NMR spectrum analysis.

〔The invention's effect〕

In the method of the present invention, a mixture obtained by dissolving or highly swelling cellulose in an aqueous solution of an alkali metal hydroxide as a reaction base, that is, a liquid mixture, is used. In addition, the reaction can proceed uniformly.
(2) A derivative with a low degree of substitution can be easily prepared. (3) It has the advantage that an organic esterified molded product can be prepared in one step at the time of molding.

〔Example〕

 Hereinafter, the present invention will be specifically described with reference to examples.

Example 1 100 parts of softwood pulp (Alaska pulp) having a polymerization degree of 1300 was immersed in 1000 parts of water for 3 hours, and then dehydrated with a dehydrator to obtain 220 parts of hydrous cellulose. This hydrous cellulose was subjected to steam treatment at 230 ° C. for 20 seconds using an explosion treatment apparatus (manufactured by Nippon Chemical Machinery Co., Ltd.) to obtain cellulose soluble in an alkaline aqueous solution having a polymerization degree of 390.

10 g of the cellulose was dissolved in 190 g of an 8% by weight aqueous sodium hydroxide solution at 5 ° C. to obtain a homogeneous solution. This solution was cast into a glass plate using a casting applicator, and immersed in butyric anhydride for 1 minute as a coagulation bath to obtain a butyrylated cellulose film. The resulting cellulose film was dissolved in deuterated DMSO, ¹³ C
-NMR measurement. As a result of the spectrum analysis, the substitution degree (butyrylation degree) of this film was 2.3.

Example 2 10 g of alkali-soluble cellulose prepared in the same manner as in Example 1 was treated with a 6% by weight aqueous solution of lithium hydroxide 19.
Dissolved at 0 ° C. at −5 ° C. to obtain a homogeneous solution. Using a plunger-type extruder, this solution is passed through a spout with 100 holes of 0.1 mm diameter and a 20% sulfuric acid aqueous solution (10 ° C).
And then thoroughly washed on a Nelson-type roll (with a water-washing shower). Then, the running yarn is subjected to an organic esterification bath (acetic acid (80% by weight) / propionic anhydride (18% by weight) / sulfuric acid (2% by weight). )), Immersed in water, washed again and dried, and wound up at a speed of 12 m / min.

The obtained fiber was cut into small powders with scissors and subjected to FT-IR measurement by the diffuse reflection method to determine the degree of substitution, which was 0.9. Usually, when the degree of propylation is 1.0 or less, it is generally a water-soluble derivative, but the fiber obtained in this example is probably because only the surface layer portion of the fiber cross section is highly propylated, As a result, cellulose fibers having insolubility and imparting water resistance could be obtained.

Example 3 Softwood pulp (Alaska pulp) having a polymerization degree of 1300 was treated with sulfuric acid of 20% by weight at 60 ° C. for 30 minutes to obtain cellulose having a polymerization degree of 470. 9% by weight of 12 grams of this cellulose
Was dissolved in 188 g of sodium hydroxide at 10 ° C., but did not result in uniform dissolution, but a mixture in which the diameter (thickness) of the pulp fiber was swollen about four times was obtained. The mixture was stirred at 10 ° C., and reacted while gradually adding an esterifying agent in which 50 g of paratoluenesulfonic acid chloride was dissolved and dispersed in 300 g of benzene.

The reaction aggregate was purified by repeating filtration / washing sufficiently with a large amount of water. The degree of substitution of the reaction purified product determined by ¹³ C-NMR measurement was 0.8.

Example 4 According to the method of Example 1, Alaska pulp was subjected to an explosion treatment to obtain an alkali-soluble cellulose having a polymerization degree of 350.

12 g of the cellulose was dissolved in 188 g of a 9% by weight aqueous sodium hydroxide solution at 5 ° C. to obtain a homogeneous solution. While stirring 10 grams of this solution at 5 ° C,
The reaction was carried out while gradually adding acetic anhydride in an amount shown in -1.

The reaction aggregate was sufficiently washed and purified with a large amount of water or methanol. Table 1 also shows the results of the degree of substitution of the reaction product obtained by ¹³ C-NMR measurement.

FIGS. 1 and 2 show the ¹³ C-NMR spectrum and FT-IR spectrum of the product when the amount of acetic anhydride added was 4.0 g.

[Brief description of the drawings]

FIG. 1 is a FT-IR spectrum of a typical cellulose acetate obtained by the method of the present invention (Example 4),
FIG. 2 shows a ¹³ C-NMR spectrum of the acetate.

Claims (2)

(57) [Claims] 1. Cellulose is dissolved or highly swelled in an aqueous solution containing 5 to 15% by weight of an alkali metal hydroxide at 16 ° C. or lower, and the resulting mixture is once coagulated with a non-solvent of cellulose and washed with water. A process for producing a cellulose organic ester, which comprises immersing in an organic esterifying agent or directly contacting the mixture with the organic esterifying agent. 2. The organic esterifying agent is an anhydride of a fatty acid having 4 or less carbon atoms, a halide of a fatty acid having 5 or more carbon atoms,
Acid anhydride of dibasic acid, unsaturated fatty acid, halogenated acetic acid,
2. The method according to claim 1, wherein the method is selected from an aromatic compound and carbamic acid.