JP5190277B2 - Method for producing fine fibers of cellulose and chitin - Google Patents

Description

  The present invention relates to a method for producing high-quality cellulose or chitin fine fibers easily and efficiently without requiring any special pretreatment. The cellulose or chitin fine fibers obtained by the present invention can be used in the fields of clothing, medical materials, composite materials and the like.

  Resources and environmental problems such as fossil resource depletion and global warming are the most serious problems in the 21st century. In order to solve these problems, it is necessary to establish alternative resources that are environmentally friendly, abundant and durable. Cellulose and chitin are the most abundant and renewable organic resources on earth.

  It is well known that about 400 billion tons of cellulose is synthesized on the earth every year and is the most abundant biomass. Most of the cellulose is produced by higher plants such as trees, but in addition to plants, there are also microorganisms that produce cellulose fibers. In plant cellulose, cellulose molecular chains are oriented and converged in the process of biosynthesis. First, very thin highly crystalline fibers called microfibrils are formed. These microfibrils are further bundled to form a higher-order structure in stages with fibrils, lamellae, and fiber cells. Microfibrils usually have a diameter of several nanometers to several tens of nanometers, depending on the production method. The length is several hundred nanometers to several tens of microns. Cellulose molecular chains that make up this microfibril are extended chain crystals, so properties such as elastic modulus, strength, and thermal expansion coefficient are comparable to magnesium alloys, while low specific gravity, high aspect, large surface area, etc. In recent years, it has attracted attention as a resin reinforcing material. In addition, there are great expectations for further application development that takes advantage of environmentally friendly characteristics and the use of recycled resources.

  However, lignin, hemicellulose, and amorphous cellulose strongly bind fine fibers as binders between the fine fibers that make up the plant fiber cells, such as fibrils and lamellae, from the smallest microfibrils of plant fibers. Therefore, it is very difficult to separate and extract fine fibers.

  Chitin is a polysaccharide contained in the outer shells of insects, shrimps and crabs. About 100 billion tons are synthesized annually on earth after cellulose. Furthermore, chitin is decomposed in vivo, has good biocompatibility, and has wound healing effect, so it attracts attention in the medical field, and is expected to be applied to hemostatic agents, artificial skin, artificial bones, bioabsorbable sutures, etc. Has been. Because it has antibacterial and deodorizing effects, it is also used in the textile field.

  On the other hand, chitin has an enormous hydrogen bond structure like cellulose, so it exhibits insoluble and infusible properties, and its application development is difficult, and only a small amount is used.

  Since chitin fine fibers have the above-mentioned additional functions while having mechanical performance equivalent to that of cellulose fine fibers, the application can be expected more than cellulose.

  Many proposals have been made and put into practical use for the production of cellulose fine fibers. As a conventional method, there is a method of fibrillation of cellulose fiber raw material by beating treatment or homogenizing treatment (Patent Document 1, Patent Document 2). However, in order to obtain a fine fiber having a small fiber diameter, it is necessary to sufficiently perform the beating process. As a result, the fiber is greatly damaged, and the strength and aspect ratio of the obtained fine fiber are lowered. When the beating treatment is reduced to suppress fiber damage, the obtained fiber has a large fiber diameter and a small aspect ratio, and thus fine fibers having good reinforcing properties cannot be obtained.

  In addition, the conventional method has a problem that the production efficiency is poor. For example, the preliminary beating method of Patent Document 1 requires 7 to 15 treatments with a double disc refiner. Further, as proposed in Patent Document 2, when the pre-beaten pulp is made into fine fiber fibrils by grinding with a grindstone plate and further subjected to high-pressure homogenizer treatment, ultrafine fiber fibrillated cellulose is obtained. There is a problem that production efficiency is low.

  Furthermore, a method for obtaining fine fibrous cellulose with a media agitation pulverizer has also been proposed (Patent Document 3). However, in order to perform pulverization by directly putting a fibrous cellulose suspension into a pulverizer. As with the above-described beating process, there are problems of damaging the fine fibers, and the time required for making the fine fibers is very long and the productivity is low.

  Also proposed is a method comprising a step of hydrolyzing in a hydrochloric acid solution at 120 to 130 ° C., followed by neutralization, washing, and grinding with a disc refiner (Patent Document 4). Since this method makes it easy to separate fine fibers by acid treatment, finer fibers can be obtained. However, the acid treatment has a problem that the fine fibers are damaged and the physical properties of the fine fibers are lowered.

On the other hand, there are still few technical proposals regarding a method for producing natural chitin fine fibers (microfibril chitin).
Reference 1 reports that chitin nanofibers remain as rod-like chitin nanofibers by removing the amorphous phase of commercially available chitin by repeated hydrolysis. According to this method, it is necessary to repeat the hydrolysis reaction several times at 90 ° C. In addition, since an acid is used in the hydrolysis, the molecular structure of chitin may be destroyed.
Japanese Patent Laid-Open No. 2 00 0-1 7 5 9 2 Japanese Laid-Open Patent Publication No. 8-284090 Japanese Patent Laid-Open No. 6-2 1 2 5 8 7 Japanese Examined Patent Publication No. 6 2-30 0 2 Biomacromolecules 2007, 8, 252-257

  The present invention solves the above-mentioned conventional problems, and uses a solvent containing an ionic liquid in order to enable easy and efficient production of cellulose and chitin fine fibers with less damage. It is an object of the present invention to provide a method for producing cellulose or chitin fine fibers, which is characterized by swelling or / and partially dissolving and defibrating cellulose-based materials such as wood pulp and chitin materials.

    As a result of earnest research to solve the above problems, the present inventors have swelled cellulose and / or chitin using a production method that can achieve the object of the present invention, that is, a solvent containing a specific ionic liquid. By partially dissolving and defibrating, a method for producing cellulose and chitin fine fibers could be found and the present invention was completed.

  This method is a method for efficiently producing cellulose or chitin fine fibers with little damage, and the cellulose or chitin fiber raw material is swollen or partially dissolved using a solvent containing an ionic liquid represented by the chemical structural formula of Chemical Formula 1, A fine fiber of cellulose or chitin is obtained by defibration.

式中、Ｒ_１は炭素数１〜４のアルキル基であり、Ｒ_２は炭素１〜４のアルキル基またはアリル基である。Xはハロゲン又は擬ハロゲンである。

In the formula, R ₁ is an alkyl group having 1 to 4 carbon atoms, and R ₂ is an alkyl group having 1 to 4 carbon atoms or an allyl group. X is halogen or pseudohalogen.

  Here, swelling cellulose or chitin means that the fine fibers constituting cellulose or chitin are slightly relaxed and are easily cleaved by an external force. Partial dissolution means dissolving a substance present as a binder between highly crystalline fine fibers. These substances include lignin, hemicellulose and amorphous cellulose in the case of cellulosic materials, proteins, minerals, and amorphous chitin in the case of chitin. Further, defibration refers to a change from the original orientation state of the fine fibers constituting cellulose or chitin to a disordered state.

  Further, the solvent containing the ionic liquid preferably has a weight content of the ionic liquid of 20 to 100%. When the content of the ionic liquid is adjusted within this range, rapid penetration and swelling of the solvent cellulose or chitin between the fine fibers occurs, and both extraction efficiency and reduction of damage to the fine fibers can be achieved.

  The solvent containing the ionic liquid is at least one selected from N, N-dimethylacetamide, N, N-dimethylformamide, 1-methyl-2-pyrrolidone, dimethyl sulfoxide, acetonitrile, methanol, and ethanol. It is preferable to contain the above solvent. By containing these components, the penetration rate of the solvent can be improved, and damage to the fine fibers can be further reduced.

  Further, it is preferable that the cellulose or chitin raw material is swollen with a solvent containing an ionic liquid and then further defibrated by mechanical treatment or ultrasonic treatment. Since the cellulose or chitin raw material that has been subjected to the swelling treatment with the solvent containing the ionic liquid has weak bonds between the fine fibers, the fine fibers are easily defibrated by the action of external force.

  Wood pulp, cellulosic fiber, recycled paper recycled pulp, or the like can be used as the cellulose fiber raw material.

  The chitin raw material is not particularly limited, and chitin obtained from plants such as crab, shrimp and insect shells and mushrooms can be used.

    The cellulose or chitin fine fiber is preferably used as a non-woven fabric, film, clothing, or resin reinforcing material.

  In the present invention, high-quality cellulose or chitin fine fibers can be efficiently produced from a substance containing fine fibers such as woody cellulose and chitin without requiring any special pretreatment. The cellulose and chitin fine fibers obtained by the production method of the present invention can be used as a reinforcing material for nonwoven fabrics, films, clothing, and resins having excellent performance.

  The present invention is described in further detail below. In the present invention, a cellulose or chitin fine fiber is produced by swelling or partially dissolving a cellulose or chitin raw material containing fine fibers using a solvent containing an ionic liquid represented by the chemical structural formula of Chemical Formula 1 To do.

式中、Ｒ_１は炭素数１〜４のアルキル基であり、Ｒ_２は炭素１〜４のアルキル基またはアリル基である。Xはハロゲン又は擬ハロゲンである。

In the formula, R ₁ is an alkyl group having 1 to 4 carbon atoms, and R ₂ is an alkyl group having 1 to 4 carbon atoms or an allyl group. X is halogen or pseudohalogen.

  Examples of these ionic liquids include 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, 1-allyl-3-methylimidazolium chloride, and 1-allyl-3 bromide. -Methylimidazolium, 1-propyl-3-methylimidazolium bromide. Although the fiber raw material can be treated only with the ionic liquid, when the dissolving power is too high and there is a possibility that even fine fibers may be dissolved, it is preferable to add and use an organic solvent. The organic solvent species to be added may be appropriately selected in consideration of the compatibility with the ionic liquid, the affinity with the cellulose or chitin material, the solubility of the mixed solvent, the viscosity, etc., but N, N-dimethylacetamide, N, N It is preferable to use at least one of dimethylformamide, 1-methyl-2-pyrrolidone, dimethyl sulfoxide, acetonitrile, methanol, and ethanol. By the coexistence of these organic solvents, penetration of cellulose or chitin between fine fibers of the ionic liquid is promoted, and destruction of the crystal structure of the fine fibers by the ionic liquid can be prevented.

  What is necessary is just to adjust the addition amount of an organic solvent suitably according to the dissolving power, melt | dissolution rate, solution viscosity, etc. which are calculated | required. However, when the content of the ionic liquid in the solution is less than 20% by weight, the ability to swell and dissolve becomes insufficient, and sufficient defibration cannot be performed. The ionic liquid content is more preferably 30% or more.

  The kind of cellulose fiber raw material used for this invention is not specifically limited. Examples of usable raw materials include natural cellulosic raw materials such as wood / wood flour, cotton, hemp, and straw, chemically treated pulp such as kraft pulp and sulfite pulp, semi-chemical pulp, waste paper, and recycled pulp thereof. Among these, wood pulp is preferable from the viewpoint of cost, quality, and global environment.

  The chitin fiber raw material can be used with natural chitin or regenerated chitin, and the source is not particularly limited. For example, there can be mentioned chitin obtained from plants such as crab, shrimp and insect shells and mushrooms.

  The shape of the cellulose or chitin raw material to be used is not particularly limited, but it may be used after being appropriately pulverized for the purpose of ease of treatment and promotion of solvent penetration.

  The method for producing the fine fibrous cellulose or chitin of the present invention using the solvent containing the ionic liquid is not particularly limited, and a known processing method and apparatus can be used. For example, a cellulose or chitin raw material is dispersed in a solution containing an ionic liquid, and the raw material is swollen or partially dissolved under standing or stirring, and then further defibrated by homogenization treatment, ultrasonic treatment, or the like.

  The amount of the fiber material added to the treatment liquid is preferably in the range of 0.5 to 30% by weight. If it is lower than 0.5% by weight, the economical efficiency is low, which is not preferable. If it is higher than 30% by weight, the uniformity of fiber defibration is inferior, which is not preferable. More preferably, the fiber concentration is 1.0 to 20% by weight.

  The treatment temperature is not particularly limited, and an appropriate temperature for swelling the fiber material and softening / dissolving the bonded material between the fine fibers may be selected, but it is usually 20 to 120 ° C. When the temperature is 20 ° C. or lower, the treatment speed is low and the viscosity of the treatment liquid is high, so that the defibrating effect is low. If it is 120 ° C. or higher, the fine fibers are dissolved, and the fine fibers are damaged and the yield of the fine fibers tends to be low.

  After the treatment of the solution containing the ionic liquid, it is preferable to perform a machine or ultrasonic treatment for further promoting defibration. Examples of the method include mechanical shearing, pulverization and polishing, homogenization, and ultrasonic treatment.

  The fibrillated cellulose or chitin dispersion is separated from the solvent containing fine fibers and ionic liquid by a centrifugal separator or filtration, and then the fine fibers are washed. The solvent for washing the fine fibers is not particularly limited as long as it is a solvent that can extract a solvent containing an ionic liquid, but water and alcohol are preferable from the viewpoint of low cost and safety.

Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited thereto. In the present invention, an Ultra-Turrax T25 Basic homogenizer made in Germany was used in order to promote fibrillation of cellulose or chitin. The rotation speed is 13000 rpm.
Example 1
ADVANTEC's FilterPaper NO. 2B obtained by cutting 5B into 3mm squares with scissors is placed in a 200ml beaker, 75ml of N, N-dimethylformamide and 50g of ionic liquid 1-butyl-3-methylimidazolium chloride are added, and constant at 60 ° C by magnetic stirring After swelling and defibrating in a short time, the mixture was stirred at 13000 rpm for 5 minutes using an Ultra-Turrax homogenizer. The obtained fiber dispersion was observed with an optical microscope. The time when the form of the fiber before the treatment can no longer be seen is defined as the defibration time. The obtained photograph observation results and defibration time are shown in FIG. 1 and Table 1, respectively.

An ionic liquid was extracted from the ionic liquid dispersion of cellulose fine fibers by centrifugation, and further washed with methanol. The washed cellulose fine fibers were dispersed in distilled water and observed with an optical microscope. The results are shown in FIG.
Example 2
The same procedure as in Example 1 was performed except that 100 mL of N, N-dimethylformamide was used. The results are shown in Table 1.
Example 3
The same procedure as in Example 2 was performed except that N, N-dimethylacetamide was used instead of N, N-dimethylformamide. The results are shown in Table 1.
Example 4
The same procedure as in Example 1 was performed except that 1-methyl-2-pyrrolidone was used instead of N, N-dimethylformamide. The results are shown in Table 1.
Example 5
The same procedure as in Example 1 was performed except that dissolved pulp was used instead of cellulose filter paper 5B. The results are shown in Table 1 and FIG.
Example 6
It implemented like Example 1 except having used chitin (Nacalai Tesque Co., Ltd. product) marketed instead of cellulose filter paper 5B. The results are shown in (Table 1) and FIG.
Example 7
The same procedure as in Example 1 was performed except that dimethyl sulfoxide was used instead of N, N-dimethylformamide. The results are shown in Table 1. The defibration time is almost the same as in Example 1.
Comparative Example 1
The finely cut cellulose filter paper 5B and 2 g were added to 100 g of an amide solvent, which was stirred with the same method and time as in Example 1 and then observed with an optical microscope. The fiber shape remained almost unchanged. The results are shown in FIG.

表１から本発明によりセルロースやキチンは短時間内で解繊されることが分った。

From Table 1, it was found that cellulose and chitin were defibrated within a short time according to the present invention.

  The present invention can efficiently produce high-quality cellulose or chitin fine fibers from a substance containing fine fibers such as woody cellulose and chitin without requiring any special pretreatment. The cellulose and chitin fine fibers obtained by the production method of the present invention can be used as a reinforcing material for medical materials, clothing, nonwoven fabrics, films and resins. Furthermore, chitin nonwoven fabrics are suitable for wound covering protective materials in the medical field.

The optical microscope photograph which shows the form of the cellulose fine fiber obtained in Example 1. FIG. The optical microscope photograph which shows the form after washing | cleaning of the cellulose fine fiber obtained in Example 1. FIG. The optical microscope photograph which shows the form of the cellulose fine fiber obtained in Example 5. FIG. The optical microscope photograph which shows the form of the chitin fine fiber obtained in Example 6. FIG. The optical microscope photograph of the cellulose fiber in the comparative example 1.

Claims (2)

A method for producing fine fibers from a cellulose or chitin raw material containing fine fibers using a solvent containing an ionic liquid ,
1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, 1-allyl-3-methylimidazolium chloride, 1-allyl-3-methylimidazolium bromide and 1-butyl bromide As a solvent containing at least one ionic liquid selected from propyl-3-methylimidazolium , N, N-dimethylacetamide, N, N-dimethylformamide, 1-methyl-2-pyrrolidone, dimethylsulfate Using a solvent containing at least one solvent selected from foxside, acetonitrile, methanol, and ethanol , the cellulose or chitin raw material is used in the range of 0.5 to 30% by weight based on the solvent. was added, the treatment temperature 20 to 120 ° C. in having to cellulose or swelling and / or partially dissolve the chitin raw material, is defibrated Separating the fine fiber forming the cellulose or chitin, extraction method for producing fine fibers, which comprises. The method for producing fine fibers according to claim 1, wherein the cellulose or chitin raw material is swollen and / or partially dissolved in the solvent containing the ionic liquid and then further defibrated by mechanical treatment or ultrasonic treatment. .

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