JPS6321681B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing cellulose derivatives directly from wood. More specifically, the present invention is a novel method for producing cellulose derivatives in which the cellulose derivatives are obtained in high yield by chemically modifying wood and then using an organic solvent as a separating agent.

Cellulose derivatives have conventionally been prepared by derivatizing purified cotton linters and dissolving pulp from wood, and there have been few attempts to obtain cellulose derivatives directly from wood. As one of the few examples, in order to quantify the molecular weight of cellulose in the natural state in wood, wood was directly nitrated with a mixed acid nitrating agent, and the nitrated lignin, which was oxidized and degraded during nitration and had a lower molecular weight, was There is an example of first extracting with methanol and then extracting nitrocellulose with acetone.

In this reaction example, lignin is significantly decomposed during the reaction, making it possible to extract lignin with alcohol.
Therefore, it has been regarded as a unique system in which the cellulose derivative remains in a residual form. However, this method has extremely high tree species selectivity, and studies on coniferous trees, especially deciduous pine (larch), are notable.
Risks such as explosions due to careless drying operations have occurred even during the experimental stage, and this method has not become a common method for preparing nitrocellulose.

Cotton linters are more expensive than wood pulp, but a-cellulose purity is inherently high (approx.
90%), and because it yields high-quality cellulose derivatives, it is valued as a raw material for the production of cellulose derivatives. On the other hand, as a method for producing dissolving pulp from wood, the sulfite pulping-alkali refining method is more widely used, but this sulfite method has several drawbacks. Namely, 1) the types of trees that can be used are limited, and 2) it is difficult to recover chemicals and utilize wood components in the cooking waste, and discharging this will cause river pollution. 3) The manufacturing method is not suitable for mass production or automation; 4) The pulp quality, especially the strength of the paper, is inferior to that of the Kraft method. Also,
In the Kraft method, the waste liquid is concentrated, the organic matter is used as a heat source to burn it, and the remaining inorganic matter is recovered and reused as a cooking chemical, but this method also has drawbacks, such as requiring a large amount of energy to concentrate the waste liquid.

As mentioned above, in order to prepare cellulose derivatives using wood as a raw material, the conventional procedure is to separate cellulose from wood and then derivatize it, and it is difficult to use wood components other than cellulose. It has some drawbacks. The present invention provides a method for omitting these complicated pulp manufacturing steps, producing cellulose derivatives directly from wood, and separating and obtaining components in a state that can effectively utilize components other than cellulose contained in wood. .

That is, the present invention provides a method for producing cellulose derivatives, which comprises heating wood into which at least one type of organic group has been introduced into some of the hydroxyl groups, and then treating it with a lower aliphatic alcohol to separate the cellulose derivative as an insoluble component. It is.

Wood into which organic groups have been introduced in advance, preferably pulverized wood (hereinafter referred to as wood flour), used in the present invention refers to the wood that has been treated with a certain type of modifier to obtain the cellulose contained in the wood flour. It is a modified wood flour made by causing a chemical reaction in at least some of the hydroxyl groups in chemical components such as , hemicellulose, and lignin, and specifically replacing hydrogen atoms with at least one type of organic group.

There are no particular restrictions on the raw wood or tree species of the wood powder to be treated here, but in the sense that it is easy to undergo modification treatment, it is preferable to use soft materials or materials for which homogeneous powder is easily available.

Wood flour does not need to be made into a particularly fine powder20
~60 meters is sufficient.

In principle, wood flour modification treatment is carried out in the presence of a solvent or a reaction agent/solvent that swells the wood structure or causes derivatives of components in the wood to swell or dissolve within the wood structure as the reaction progresses. This is carried out by reacting a compound (modifying agent) that can react with the hydroxyl groups of wood flour, replacing the hydrogen atoms of the hydroxyl groups, and introducing the organic groups of the modifier.

It goes without saying that the type of organic group to be introduced into wood flour and the reaction used for the introduction are selected depending on the type of cellulose derivative intended, but a reaction that is relatively easily adopted is the reaction of hydroxyl groups. Esterification or etherification.

Various acids such as acid halides, acid anhydrides, and fatty acids are used for esterification, and halides such as methyl chloride, ethyl chloride, and ethylene chlorohydrin, epoxy compounds such as ethylene oxide, chloroacetate, dimethyl sulfate, and sulfuric acid are used for etherification. Organometallic compounds such as diethyl and titanium alkylate are used as modifiers. In addition, in these reactions, sulfuric acid, pyridine, subchloride, etc. may be used as catalysts in the former case, and alkalis such as caustic soda may be used as catalysts in the latter case. Preferred organic groups to be introduced include fatty acid acyl groups such as acetyl, propionyl, butyl, valeroyl, caproyl, capryloyl, lauroyl, palmitoyl, and stearoyl groups, and aromatic acyl groups such as benzoyl. , short chain alkyl groups such as methyl group, ethyl group, carboxymethyl group, benzyl group, polyoxymethylene group, polyalkylene glycol group, long chain alkyl group such as pentyl group, octyl group, dodecyl group, and similar groups. It will be done. Furthermore, it is also possible to introduce two or more of these organic groups, such as an acetyl group and a butyryl group.

Swelling of wood during and prior to the reaction to facilitate the introduction of organic groups usually uses a solvent, water, or a solution thereof, but depending on the agglomeration density of the wood structure to be treated, degree of substitution, and reactive species , the type of solvent, processing conditions, etc. can be selected as appropriate.

The properties of wood flour modified by the introduction of organic groups obtained through such treatments, especially the ease with which components other than cellulose can be separated by heat treatment and elution treatment, depend on the type of organic groups and the substitution rate of hydroxyl groups. It's different. It is convenient to express the substitution rate of hydroxyl groups in wood in terms of substituent morality. i.e. wood
It is expressed by the number of moles of substituents introduced by substitution per 1000 g. For pure cellulose, if complete substitution is performed, the substituent morality is approximately 18.5, and if wood is composed of 30% lignin, 25% hemicellulose, and 45% cellulose, then 100% substitution will result. The substituent morality in the case of aging is approximately 13.0.

In the present invention, the substituent morality is preferably 8 or more in order to facilitate subsequent processing steps.

Suitable examples of the solvent and swelling agent (including the reactant if the swelling effect increases when combined with the reactant) used when introducing an organic group include N ₂ O ₄ -dimethylformamide type, trichloroacetic acid-chloroform type. , trichloroacetic acid-benzene series, SO ₂ -diethylamine-dimethylsulfoxide series, paraformaldehyde-dimethylsulfoxide series, dialkylamides such as dimethylformamide, trichloroacetic acid, glacial acetic acid, ethylene chloride, urea-ammonium sulfate series, ammonium sulfate-dimethylformamide series, Examples include potassium acetate-anhydrous acid system, potassium acetate-dimethylformamide system, and caustic soda water system. There are no particular restrictions on the conditions for modifying wood flour, but a typical method is to stir a mixture of wood flour and a solvent at room temperature or a predetermined temperature, and then add a modifier and optionally a catalyst continuously or all at once. This method involves reacting at room temperature or at a predetermined temperature of 150° C. or lower until the desired proportion of the desired organic groups is introduced, and then removing the solvent and thoroughly washing and drying the wood flour.

The modified wood flour thus obtained is modified by heat treatment so that the cellulose derivative and components other than cellulose can be easily separated. This heat treatment is usually carried out at a temperature of 100°C or higher, preferably 200°C or higher. Although this heat treatment can be carried out by directly heating the modified wood flour and possibly melting the wood flour, it is also preferable to carry out the heat treatment in a suitable organic solvent.

Modified wood flour with organic groups has improved solubility and affinity for organic solvents, so it is completely or highly resistant to organic solvents, depending on the modification method, degree, and type of solvent. dissolves in or swells. Most preferably, the heat treatment is performed in a solvent that completely dissolves the modified wood flour. In this case, the cellulose derivative can be easily separated as an insoluble component by treating the resulting solution with a lower aliphatic alcohol.

The organic solvent preferably used in the heat treatment step is preferably neutral, and may be a mixture of two or more organic solvents. For example, in the case of aliphatic acylated wood flour, benzyl ether, styrene oxide (1,2-epoxyethylbenzene), n-butyl acetate-acetone, tetrahydrofuran-acetone, benzene-acetone, and isopropyl ether-ethylene glycol are used. Particularly preferred are dimethyl sulfoxide, ethylbenzene, benzoyl chloride, epichlorohydrin, xylene-pyridine, chlorobenzene-methylcellosolve, tetrahydrofuran-pyridine, and the like.

When heating to a temperature higher than the boiling point of the solvent, it can also be carried out in a pressure-resistant container.

In some cases, it is also possible to use a lower aliphatic alcohol as the organic solvent used in the heat treatment process, transfer the non-cellulose components in the modified wood flour to the liquid phase at the same time as the heat treatment, and separate and obtain cellulose derivatives as insoluble components. be. In this case, fairly high temperatures and long heating times are required, and generally a high substitution rate of organic groups is required.

On the other hand, it is also possible to melt the modified wood flour by respectively heating it at a suitable temperature. For example, aliphatic acylated wood flour can be melted when treated for a short time (several minutes) at a temperature of 300 to 320°C for acetylated or propionylated wood flour, and about 250°C for higher acylated wood flour.

The heat-treated modified wood flour can be treated with lower aliphatic alcohols in solution, swollen state, or melt form to produce cellulose derivatives as precipitates or solids, such as lignin, hemicellulose, and others as solutions or extracts. It can be divided into mixtures of derivatives of wood components. for example,
By introducing a solution of lower acylated wood flour into methanol, about 45% of the modified wood falls into the sedimentation category and 55% into the dissolution category. It was confirmed that the former was derived from a lower acylate of cellulose, and the latter was derived from a wood component other than cellulose acylate.

Examples of lower aliphatic alcohols used here include aliphatic alcohols having about 1 to 4 carbon atoms, such as methanol, ethanol, propanol, and butanol.

The cellulose derivative obtained by the present invention has a purity of 95% or more as a derivative thereof, and can be purified by conventional methods such as fractional precipitation and liquid chromatography, if necessary. That is,
It can be said that this is a method of obtaining cellulose derivatives directly from wood, which has not been done before.

On the other hand, lignin, which is separated from cellulose derivatives and obtained dissolved in hydrocarbons or alcohol,
Hemicellulose and other wood component derivatives can be used as they are, or after being recovered by distillation of the solvent, used alone or with the addition of reactive compounds such as crosslinking agents, mixtures such as synthetic polymers, or other additives to molding materials.
In addition to being used as an adhesive, the solution itself can also be used as a liquid fuel. Currently, the pulp and cellulose derivative industries mainly use the cellulose section of wood.
Many of the other ingredients are treated as waste,
This is of great significance considering that although its use is desired, progress has not been made sufficiently.

In addition, when using dissolved lignin and hemicellulose components as a liquid fuel, the amount dissolved can be increased by increasing the heat treatment temperature, lengthening the treatment time, or adding a small amount of weak acid. It is possible to improve the stability of liquid fuel as a solution.

The method of obtaining cellulose derivatives from the modified wood of the present invention by direct physicochemical methods has never existed, and in addition, it solves the problem of using waste liquid from pulping wood, which has been a problem in the past. It is possible to find significant advantages in this. In particular, since components other than cellulose derivatives are ultimately obtained in an alcohol-dissolved state, it has the potential to turn wood into liquid fuel, and is currently significant as alcohol fuels are expected to be put into practical use as biomass technology advances in the future. be discovered.

The present invention will be explained in more detail with reference to Examples below.

Example 1 38 mmol of trifluoroacetic anhydride (5.4
ml), lauric acid 40 mmol and benzene 20 ml
Mix and leave at 30℃ for 1 hour for preliminary reaction (ripening)
After this, 1 g of bone dry wood flour (40 to 60 mesh, birch sapwood) was added, the container was tightly stoppered, and left at 30° C. for 24 hours to react.

After the reaction, add about 20ml of methanol to decompose the excess acylation reagent, and then add G-2 for Soxhlet extraction.
It was collected with a glass filter, washed several times with methanol, and then subjected to Soxhlet extraction with methanol for 24 hours. Thereafter, the mixture was air-dried and then vacuum-dried at 70°C for one day and night to obtain 2.4 g of modified wood flour.

0.1 g of the modified wood flour obtained above was placed in a test tube, 10 ml of benzyl ether was added thereto, and the mixture was heated in an oil bath at 250°C. The modified wood flour was dissolved by heating for about 30 minutes, and a pale yellow transparent solution was obtained. When this solution was poured into excess methanol, a white precipitate formed. The precipitate was collected separately and its molecular weight was estimated by gel permeation analysis. That is,
Cellulose trilaurate with an average molecular weight (weight) of 125,000 obtained by lauroylation of Whatman cellulose CF-11 was used as a standard and compared with its gel permeation curve. The molecular weight of the cellulose derivative obtained above was that of the standard. It turns out that it is almost the same.

Further, it was confirmed by infrared absorption spectrum and nuclear magnetic resonance spectrum that the precipitate obtained above was cellulose laurate (substituent morality: 11.2). The amount of components thought to be derived from lignin components was extremely small, showing minute signals at 1500 and 1600 cm ^-1 in the infrared absorption spectrum, but was not detected at all in the nuclear magnetic resonance spectrum.

From these results, the modified wood component recovered as a methanol precipitate fraction after being dissolved in benzyl ether at a temperature around 250°C is small (5%).
It can be concluded that the cellulose laurate contains the lignin derivative (below), and that the other components remain dissolved in methanol. This shows that the cellulose derivative can be easily separated from the modified wood and the other components can be used as a methanol solution.

Example 2 Bone dry wood flour (40-60 mesh, birch sapwood) 5
g, lauroyl chloride 22 ml (20.8 g; 95 mmol), pyridine 9 ml (8.8 g; 111.8 mmol)
and 70 ml of dimethylformamide were placed in an Erlenmeyer flask, a condenser was attached, and the flask was reacted at 100°C for 6 hours.

After the reaction, the reaction solution was poured into about 500 ml of methanol, and after roughly extracting the unreacted acylating agent and solvent from the modified wood flour, Soxhlet extraction with ethanol was performed for 24 hours. Thereafter, it was air-dried and then vacuum-dried at 70°C for one day and night to obtain 13.3 g of modified wood flour.

0.5 g of this modified wood flour was taken, mixed with 10 ml of acetone-benzene (1:1 volume) mixed solvent, and treated at 250°C for 90 minutes using a pressure vessel to obtain a 5% solution. Next, a very small amount of undissolved components were removed by filtration.

When this solution was poured into methanol, 0.18 g of yellowish white precipitate was produced. When this precipitate was analyzed by infrared absorption spectroscopy, nuclear magnetic resonance spectroscopy, and gel permeation analysis, it was confirmed that it was highly purified laurylcellulose with a substituent morality of 11.0 and maintained a high molecular weight.

On the other hand, as a result of UV detection gel permeation analysis, it was confirmed that the obtained methanol solution contained a large amount of lignin components with low molecular weight. This solution was stable and no phenomena such as solute precipitation or gelation were observed even when it was left at room temperature.

Example 3 1 g of wood flour (40 to 60 mesh, birch sapwood) was immersed in an aqueous solution containing 10% by weight of each of urea and ammonium sulfate, left for 24 hours, and then dried separately. 7 ml of dimethylformamide and 3.4 ml of acetic anhydride were added to the obtained pretreated wood flour, and the mixture was reacted at 85° C. for 15 minutes in an Erlenmeyer flask equipped with a cooling tube.

After the reaction, the reaction solution was poured into about 300ml of methanol to extract the acetylating agent, catalyst and solvent.
After separation, it was thoroughly washed with water. After that, air drying for another night 70
Modified wood flour (acetylated wood flour) by vacuum drying at °C
1.42g was obtained. When 15 g of benzyl ether was added to the obtained acetylated wood flour and heated at 280°C for about 30 minutes, the acetylated wood flour was completely dissolved and a pale yellow transparent solution was obtained. When this solution is left at room temperature, a gel precipitates, but when heated to about 80°C, it becomes a transparent solution again. By pouring this solution into methanol, a yellowish white solid is precipitated as a methanol-insoluble component.

This product was confirmed to be cellulose acetate with a substituent morality of 10.9 by infrared absorption spectroscopy and nuclear magnetic resonance spectroscopy.

Example 4 60.9 g (0.29 mol) of trifluoroacetic anhydride, 73 g (0.39 mol) of lauric acid and chloroform
Mix 170ml and let stand at 50℃ for 20 minutes to pre-react (ripen), then add 5g of bone dry wood flour (40-60 mesh, birch sapwood) and attach a cooling pipe.
The mixture was left to react at 50°C for 4 hours.

After the reaction, the reaction solution was poured into about 500 ml of methanol to coarsely extract the unreacted acylating agent and solvent from the modified wood flour, followed by Soxhlet extraction with ethanol for 24 hours. Thereafter, it was air-dried and then vacuum-dried at 70°C for one day and night to obtain 14.2 g of modified wood flour.

0.5 g of the modified wood flour obtained above was placed in a pressure container together with 10 ml of methanol and heat treated at 250° C. for 2 hours. 56.5% of the solid content is dissolved in methanol, approximately 0.28
g was recovered as a solid. It was confirmed by infrared absorption spectrum and nuclear magnetic resonance spectrum that the main component of the recovered solid was lauryl cellulose.

Claims (1)

[Claims] 1. A method for producing a cellulose derivative, which comprises heating wood into which at least one kind of organic group has been introduced into a portion of the hydroxyl groups, and then treating the wood with a lower aliphatic alcohol to separate the cellulose derivative as an insoluble component.