JP6363340B2 - Emulsions containing nano-sized fibrous polysaccharides, materials and methods for producing them - Google Patents

Description

The present invention relates to an emulsion obtained by mixing nano-fine fibrous polysaccharide suspension water and a water-insoluble organic solvent, a material obtained from the emulsion, and a method for producing them.

Cellulose, a kind of fibrous polysaccharide, is a plant such as woody plants such as broad-leaved trees and coniferous trees, herbaceous plants such as bamboo and bamboo, some animals represented by sea squirts, and one represented by acetic acid bacteria. It is known that it is produced by some fungi and the like. What has the structure where this cellulose aggregated in the fiber form is called a cellulose fiber. In particular, a cellulose fiber having a fiber width of 100 nm or less and an aspect ratio of 100 or more is generally called cellulose nanofiber (CNF), and has excellent properties such as light weight, high strength, and low thermal expansion coefficient.

In nature, CNF does not exist as a single fiber except for CNF produced by some fungi represented by acetic acid bacteria. Most of CNF exists in the state which has the fiber width of the micro size tightly assembled by the interaction represented by the hydrogen bond between CNF. The fibers having the micro-sized fiber width also exist as higher order aggregates.

In the papermaking process, these fiber aggregates are pulverized to pulp with a micro-sized fiber width by pulping, represented by the kraft cooking method, which is one of chemical pulping. The paper is made from the raw material. The fiber width of this pulp varies depending on the raw material, but it is 5-20 μm for bleached kraft pulp made from hardwood, 20-80 μm for bleached kraft pulp made from softwood, and 5-20 μm for bleached kraft pulp made from bamboo. Degree.

As described above, the pulp having these micro-sized fiber widths is an aggregate of single fibers having a fibrous form in which CNF is firmly assembled by an interaction typified by hydrogen bonding, and by further defibrating. CNF, which is a single fiber having a nano-sized fiber width, can be obtained.

Many methods for preparing CNF have been reported, but there are two types of methods: chemical methods such as acid hydrolysis and TEMPO catalytic oxidation, and physical methods such as the grinder method, high-pressure homogenizer method, and underwater collision method (ACC method). Broadly divided.

The TEMPO catalytic oxidation method, which is one of the chemical preparation methods for CNF, uses a TEMPO catalyst to convert the hydroxyl group on the CNF surface of a CNF aggregate having a micro-sized fiber width represented by wood bleached kraft pulp to a carboxyl group. By converting it into Na salt, electrostatic repulsion between CNFs and osmotic pressure effect act in water, and nano dispersion of CNF is made possible by simple underwater fibrillation treatment. Therefore, the obtained CNF is chemically modified. Also in the acid hydrolysis method, which is one of the chemical preparation methods for CNF, the resulting CNF is chemically modified by the acid catalyst used.

In the grinder method and the high-pressure homogenizer method, which are physical preparation methods of CNF, cellulose undergoes damage to the molecular structure of the cellulose and a decrease in the degree of polymerization due to grinding and impact received during the nano-miniaturization process. Therefore, the obtained CNF is subjected to damage of the cellulose molecular structure that affects its properties and a degree of polymerization.

On the other hand, the ACC method, which is one of the physical methods among the CNF preparation methods, collides the suspended water of CNF aggregates having a micro-sized fiber width represented by wood bleached kraft pulp under high pressure. As a result, only the interaction between the CNFs is cleaved by using only a fluid medium such as water and the fluid energy of the pulp as a driving source, thereby performing nano-miniaturization.

As disclosed in Patent Document 1, this ACC method introduces natural cellulose fibers suspended in water into two nozzles (FIG. 5: 4a, 4b) facing each other in the chamber (FIG. 5: 3). In this method, the nozzles inject and collide toward one point (FIG. 5). According to this technique, the suspension water of natural microcrystalline cellulose fibers (e.g., funacell) is collided oppositely, the surface is nanofibrillated and peeled off, and the affinity with water as a carrier is improved. In particular, it becomes possible to reach a state close to dissolution. The device shown in FIG. 5 is a liquid circulation type, and includes a tank (FIG. 5: 1), a plunger (FIG. 5: 2), two opposing nozzles (FIG. 5: 4a, 4b), and as necessary. A heat exchanger (FIG. 5: 5) is provided, and fine particles dispersed in water are introduced into two nozzles, sprayed from opposite nozzles (FIG. 5: 4a, 4b) under high pressure, and opposed to each other in water. In this method, only water is used in addition to natural cellulose fibers, and nano-miniaturization is achieved by cleaving only the interaction between fibers using only a fluid medium such as water and the flow energy of pulp as a driving source. Therefore, there is no change in the structure of the cellulose molecule, and it becomes possible to obtain a nano-miniaturized product in a state in which the decrease in the degree of polymerization accompanying cleavage is minimized. The ACC method, which is a method for preparing CNF by physical treatment, allows CNF aggregates having micro-sized fiber widths typified by bleached wood kraft pulp to collide with each other under high pressure, thereby causing mutual interaction between CNFs. Nano-miniaturization is performed by cleaving only the action. For this reason, the obtained CNF is hardly damaged by the molecular structure of the cellulose or the degree of polymerization.

Various applications using the features of CNF obtained by these methods have been proposed. That is, using the characteristics of the fiber itself such as light weight, high strength, and low thermal expansion, and the morphological characteristic of the nano-sized fiber width, application to a resin reinforcing material such as plastic or a transparent film is expected.

A problem in using CNF is the compatibility of CNF. Since CNF is a hydroxyl group derived from cellulose molecules and the fiber surface has a hydrophilic characteristic, when used as a reinforcing material for a resin such as plastic, the compatibility between CNFs causes aggregation. For this reason, attempts have been actively made to improve dispersibility by chemical modification of the CNF surface (Non-Patent Documents 1 and 2).

It is known that chemically modified CNF has improved compatibility with organic solvents (Non-Patent Documents 1 and 2). Studies have been carried out for the purpose of making it hydrophobic by chemically modifying the hydroxyl group on the CNF surface to make it composite with a resin having hydrophobic properties. On the other hand, taking advantage of this feature, some studies on emulsion formation by mixing with an organic solvent have been reported (Non-Patent Documents 3 and 4). However, all of them use chemical modification to change the charge on the fiber surface, and CNF, cellulose nanocrystals, cellulose nanowhiskers, etc. used for emulsion formation are prepared by the above-mentioned chemical preparation method. Has undergone chemical modification. Having the hydrophilic property by the hydroxyl group on the CNF surface and the hydrophobic property added by chemical modification in the same fiber, an emulsion is formed in mixing with an organic solvent.

CNF obtained by chemically modifying the surface of CNF, or CNF obtained by chemical modification by a chemical preparation method is different from natural cellulose that naturally exists in nature. Therefore, the effects on safety and the environment due to long-term exposure are unknown.

In addition, CNF prepared by nano refining by a physical method other than the ACC method may be damaged in the molecular structure of the cellulose and the degree of polymerization may be reduced during the nano refining process. Properties may be different from cellulose.

JP-A-2005-270891

Gousse, C., Chanzy, H., Cerrada, M. L. and Fleury, E. (2004): Surface silylation of cellulose microfibrils: preparation and rheological properties, Polymer, 45 (5), 1569-1575. John, M. J. and Anandjiwala, R. D. (2008): Recent Developments in Chemical Modification and Characterization of Natural Fiber-Reinforced Composites, Polym. Compos., 29 (2), 187-207. Sebe.G., Pichavant.F.H. And Pecastaings.G. (2013): Dispersibility and emulsion-stabilizing effect of cellulose nanowhiskers esterified by vinyl acetate and vinyl cinnamate, Biomacromolecules, 14, 2937-2944. Kalashnikova. I., Bizot. H., Cathala. B. and Capron I. (2011): New pickering emulsions stabilized by bacterial cellulose nanocrystals, Langmuir, 27, 7471-7479.

Various uses of CNF are currently being studied, and one of these is the development of new applications using emulsion formation. However, CNF currently being studied for emulsion formation is CNF that has been intentionally chemically modified in the CNF preparation process and / or before and after the process, or that has been chemically modified with the chemicals used. CNF that does not exist.

The present invention not only causes little physical damage to cellulose, but also substantially reduces the flow energy of water and pulp without giving chemical treatment or chemical modification with an emphasis on safety and environmental conservation. One of the applications of CNF that uses CNF suspension water prepared by a nano-miniaturization method as a driving source and is currently studying various uses. Emulsions with organic solvents, materials obtained from these emulsions, and An object is to provide a manufacturing method.

According to the present invention, there is provided an emulsion of nano-fine fibrous polysaccharide suspension in which a thin layer of nano-fine fibrous polysaccharide exists in the form of individual spherical hollow bodies and a water-insoluble organic solvent. Is done.
Furthermore, according to the present invention, the nano-fine fibrous polysaccharide is composed of a suspension of nano-fine fibrous polysaccharide that exists in the form of a network having a large number of spherical voids and a water-insoluble organic solvent. An emulsion is provided.
Moreover, the spherical hollow material which consists of a thin layer of the nano refined | miniaturized fibrous polysaccharide is provided.
Furthermore, a material comprising a network of nano-sized fibrous polysaccharides having a large number of spherical voids is provided.
In these emulsions and materials, it is preferable that the nano-sized fibrous polysaccharide is a cellulose nanofiber, and the cellulose nanofiber is not chemically modified.
In these emulsions and materials, it is preferable that the nano-sized fibrous polysaccharide is a cellulose nanofiber, and that the cellulose nanofiber is not damaged by the cellulose molecular structure or the degree of polymerization.
According to another aspect of the present invention, there is provided a method for producing an emulsion comprising mixing a nano-miniaturized fibrous polysaccharide suspension with a water-insoluble organic solvent. In this emulsion, a thin layer of nano-fine fibrous polysaccharide exists in the form of individual spherical hollow bodies, or a nano-fine fibrous polysaccharide exists in the form of a network with many spherical voids. Furthermore, according to the present invention, there is provided a method for producing a material comprising preparing an emulsion by mixing nano-fine fibrous polysaccharide suspension with a water-insoluble organic solvent and drying the emulsion. Is done. This material is a spherical hollow material composed of a thin layer of nano-fine fibrous polysaccharide, or a nano-fine fibrous polysaccharide network having a number of spherical voids.
In these production methods, it is preferable that the nanosized fibrous polysaccharide is cellulose nanofiber, and the cellulose nanofiber is not chemically modified.
In these production methods, it is preferable that the nano-sized fibrous polysaccharide is a cellulose nanofiber, and the cellulose nanofiber is not damaged by the cellulose molecular structure or the degree of polymerization.
Furthermore, in these production methods, the water-insoluble organic solvent is preferably an alkane.

  The water-insoluble organic solvent is not particularly limited as long as it does not react with nano-fine fibrous polysaccharides such as CNF. Examples of the fibrous polysaccharide include cellulose, glucan, fructan, chitin, chitosan, glucomannan and the like. The mixing method is not particularly limited, and may be stirring using equipment or human power, mixing using ultrasonic waves, or the like.

The mixed solution obtained by this mixing forms an emulsion. The state of the emulsion to be formed varies depending on the CNF raw material used for mixing. Specifically, when CNF suspension water using bamboo as a raw material is used, each micelle exists as a single spherical micelle having a solvent inside and outside. However, when wood-derived CNF suspension water is used, the solvent exists only inside the micelle and the cellulose nanofiber exists outside. Therefore, cellulose nanofibers form independent spherical hollow particles when the raw material is bamboo. On the other hand, when derived from wood, a sponge-like structure having a large number of spherical voids is formed.

The emulsion formed is very stable and is maintained over a long period of time.

According to the present invention, it is possible to easily obtain an emulsion simply by mixing with a water-insoluble organic solvent using CNF suspension water that is not subjected to complicated treatment such as chemical modification. It has the potential as a new use of CNF as well as its application.

The observation photograph of the time-dependent change of the emulsion of this invention. The state observation photograph of the emulsion of the present invention. The state when the container containing the sample is tilted 5 days after the emulsion preparation. The optical microscope observation image of the emulsion of this invention. An image obtained by magnifying a cloudy spot 100 times. The scanning electron microscope image of the emulsion of this invention. An observation image of a sample obtained by freezing a white cloudy portion and then cleaving and freeze-drying. (A), (c) When using CNF suspension water prepared from bleached kraft pulp derived from wood, (b), (d) CNF suspension water prepared from bleached kraft pulp derived from bamboo If used. (A) and (b) are 300 times observation images, (c) is 1000 times observation images, (d) is 1500 times observation images. Illustration of ACC method In addition to the ACC method, an explanatory diagram of a nano-miniaturization method that performs nano-miniaturization by cleaving only the interaction between fibers using only the flow energy of a fluid medium such as water as a driving source.

Below, the preparation method of the emulsion obtained by mixing the CNF suspension water of this invention and a water-insoluble organic solvent, and the characteristic of the obtained emulsion are demonstrated in detail.

The raw material of the CNF suspension water is not particularly limited as long as it contains cellulose, and examples thereof include various wood pulp, non-wood pulp, bacterial cellulose, waste paper pulp, cotton, valonia cellulose, and squirt cellulose. Various cellulose powders that are commercially available can also be used.

The method for preparing CNF suspension water may be a nano-miniaturization technique that performs nano-miniaturization by cleaving only the interaction between fibers using only the flow energy of a fluid medium such as water as a driving source, Although the ACC method corresponds to this, it is not particularly limited to the ACC method. Hereinafter, an example of the ACC method will be described with reference to FIG. Suspended water of the above raw material is prepared and charged into the tank 1, and the pressure is increased by the plunger 2 to obtain a predetermined injection pressure, and then introduced into two opposing nozzles 4 a and 4 b in the chamber 3. From these two nozzles 4 a, 4 b, the suspension water is injected and collided at a predetermined injection pressure toward one point, and then cooled by the heat exchanger 5 and returned to the tank 1. The number of cycles of this tank 1 → plunger 2 → chamber 3 → heat exchanger 5 is defined as the number of treatments (pass). Since the concentration of the raw material varies depending on the performance of the equipment used, it is not particularly limited as long as it can be processed, but it is 20 wt% or less, preferably 10 wt% or less. Since the injection pressure also varies depending on the performance of the equipment to be used, it is not particularly limited as long as it is an ejection pressure at which nano refinement of the raw material occurs, but it is usually 100 MPa or more, preferably 150 to 250 MPa. The number of treatments varies depending on the jet pressure, but is preferably 3 passes or more, more preferably 30 to 150 passes.

In addition to this ACC method, as a nano-miniaturization method for performing nano-miniaturization by cleaving only the interaction between fibers using only the flow energy of a fluid medium such as water as a driving source, as shown in FIG. The pulp slurry liquid is circulated in the first circulation system through the one chamber, and the water is circulated in the second circulation system through the one chamber, and is circulated in the first circulation system. Thus, a nano-miniaturization technique can be applied in which water circulating in the second circulation system is orifice-injected with respect to the pulp slurry liquid flowing in the one chamber. Unlike the ACC method, in the nano-miniaturization method, the collision energy of the pulp slurry liquid is not a driving source for the miniaturization, and the high-speed and high-pressure energy of the water jetted to the pulp slurry liquid causes the pulp slurry liquid to Pulp is refined.

The water-insoluble organic solvent is preferably a liquid that is liquid at room temperature and normal pressure and incompatible with water, but is not particularly limited. Examples of the water-insoluble organic solvent include alkanes having 5 or more carbon atoms, preferably alkanes having 6 to 20 carbon atoms.

The ratio of the CNF suspension water to the water-insoluble organic solvent is not particularly limited because it depends on the CNF content in the CNF suspension water and the size of micelles in the emulsion.
The temperature at the time of mixing is not particularly limited, but it must be lower than the boiling point of the organic solvent to be used. Furthermore, the lower limit of the temperature is not limited as long as it is 0 ° C. or higher, which is the temperature at which water freezes. When using a low-boiling organic solvent, it is preferably 10 ° C. or lower and 0 ° C. or higher.

The mixing of the CNF suspension water and the water-insoluble organic solvent may be performed by using a device or by human power as long as both are mixed. The technique is not particularly limited, and may be mixing by ultrasonic waves or the like in addition to mixing by stirring using an agitator or a stirrer.

It was confirmed that the emulsion obtained by mixing the CNF suspension water of the present invention and the water-insoluble organic solvent maintains the state for a long period of time as shown in FIG.

The state of the emulsion obtained by mixing the CNF suspension water of the present invention with a water-insoluble organic solvent varies depending on the raw material of the CNF suspension water used. As shown in FIG. 1, when wood pulp uses CNF suspension water as a raw material, an emulsion is generated between an aqueous layer (lower layer) and an organic solvent layer (upper layer), and bamboo pulp uses CNF suspension water as a raw material. The emulsion took up all of the organic solvent, and the organic solvent layer could not be confirmed. As can be seen from FIG. 2 which was observed by tilting the liquid 5 days after the emulsion formation, the emulsion obtained using the CNF suspension water from which bamboo pulp was a raw material showed high viscosity. Further, it was confirmed from the optical micrograph of FIG. 3 that micelles were formed in the emulsion. Furthermore, from the scanning electron micrograph of the surface that was cut after freezing the emulsion forming portion in FIG. 4, the emulsion obtained using the CNF suspension water of which the wood pulp is the raw material has a hollow inside the micelle, and the micelle and micelle It turned out that CNF was filled up. In the emulsion in which bamboo pulp was obtained using CNF suspension water as a raw material, micelles existed alone, and it was confirmed that CNF formed micelles. It seems that the amphipathic action of CNF contributes to the formation of such micelles.

From these results, the preparation of the emulsion of the present invention obtained by mixing the CNF suspension water and the water-insoluble organic solvent does not require any special treatment such as chemical modification. It can be easily prepared simply by mixing CNF suspension water with an organic solvent, and the obtained emulsion maintains its state for a long time. Furthermore, emulsions having different characteristics can be prepared by changing the raw material species of CNF suspension water to be used.

The emulsion of the present invention obtained by mixing CNF suspension water with a water-insoluble organic solvent is not only applied to existing industrial products but also developed a new application using CNF because of its easy adjustment method and characteristics. It is expected to become the basis of

Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited by the following description.

The CNF suspension used for mixing with the water-insoluble organic solvent was prepared by the following procedure. A bleached kraft pulp derived from wet hardwood is suspended in water so as to have a concentration of 0.10 wt%, and treated under the conditions of an ejection pressure of 180 MPa and a treatment frequency of 90 passes using the ACC method disclosed in Patent Document 1. And 0.10 wt% CNF suspension water was obtained from bleached kraft pulp derived from hardwood. By the same procedure, 0.10 wt% CNF suspension water was obtained from bamboo-derived bleached kraft pulp.

10 ml of CNF suspension immediately after being prepared by the above method was placed in a 30 cc screw tube containing 10 ml of n-hexane (manufactured by Wako Pure Chemical Industries, Ltd.), shaken up and down, and then subjected to ultrasonic treatment. It was emulsified by performing for 2 minutes. Normally, when water and n-hexane are mixed, they are in a suspended state immediately after mixing but are separated into two layers after a few minutes. At that time, water is separated into the lower layer and n-hexane is separated into the upper layer. However, when CNF suspension water was used, the cloudy state was maintained even after 5 days, as shown in FIG.

FIG. 2 shows the state of various mixed solutions after standing still, with the screw tube container tilted. It turns out that the state of the liquid mixture obtained by the kind of raw material changes.

Further, FIG. 3 shows a clouded portion observed in FIG. 1, which is observed by magnifying it 100 times with an optical microscope (BHA: manufactured by Olympus). Both were found to form spherical micelles, suggesting that the cloudy part was an emulsion.

In order to observe the micelle state in more detail, observation with a scanning electron microscope was performed. The cloudy portion seen in FIG. 1 was dropped on a sample stage for scanning microscope observation and frozen with liquid nitrogen, and then the frozen sample was cleaved with tweezers and then subjected to lyophilization. The sample after drying was observed with a scanning electron microscope (JSM5600LV: manufactured by JEOL Ltd.).

From FIG. 4, when using CNF suspension water made from bleached kraft pulp derived from hardwood and using CNF suspension water made from bleached kraft pulp derived from bamboo, the state of the micelle obtained is different. There was found. That is, when CNF suspension water made from bleached kraft pulp derived from hardwood is used, spherical voids where n-hexane seems to have existed are observed, and the gap between the voids (between micelles) CNF was densely occupied. That is, it can be seen that an O / W type emulsion in which n-hexane is present in spherical micelles in CNF suspension water was formed. On the other hand, when CNF suspension water made from bamboo-derived bleached kraft pulp was used, it was observed that the CNFs seemed to be assembled into hollow spheres, but there was almost nothing between the micelles and micelles. It did not exist. That is, the micelle and the micelle exist independently. In addition, the emulsion type forms an O / W type emulsion as in the case of hardwood, or forms a W / O type emulsion in which the inside is water and the surroundings are n-hexane. Even if the micelle interior is an aqueous solvent, it is considered that the solvent is in an almost water state with very little CNF.

From these results, it was suggested that different emulsions were formed due to differences in the raw materials of CNF suspension water.

Claims (4)

  Bamboo-derived cellulose nanofibers obtained by cleaving only the interactions between cellulose fibers and performing nano-miniaturization, and a thin layer of cellulose nanofibers not chemically modified An emulsion of suspended water of a nano-sized fibrous polysaccharide and a water-insoluble organic solvent, characterized by existing in the form of a spherical hollow body.   Bamboo-derived cellulose nanofibers obtained by cleaving only the interactions between cellulose fibers and performing nano-refining, consisting of a thin layer of cellulose nanofibers that are not chemically modified, and spherical A material characterized by being hollow. It is a manufacturing method of the emulsion of Claim 1, Comprising: It is a cellulose nanofiber derived from bamboo obtained by cleaving only the interaction between cellulose fibers, and performing nano refinement | miniaturization, And chemical modification is carried out A method for producing an emulsion, comprising mixing a suspension of untreated cellulose nanofibers and a water-insoluble organic solvent. It is a manufacturing method of the material of Claim 2 , Comprising: It is a cellulose nanofiber derived from bamboo obtained by cleaving only the interaction between cellulose fibers, and performing nano refinement | miniaturization, And chemical modification is carried out The manufacturing method of the material characterized by mixing the suspension water of the cellulose nanofiber which has not been given, and the water-insoluble organic solvent, and preparing this emulsion and drying this emulsion.