JP5247557B2 - INORGANIC NANOPARTICLE-MATRIX MATERIAL FIBER COMPOSITE AND PROCESS FOR PRODUCING THE SAME - Google Patents

Description

  The present invention relates to an inorganic nanoparticle-matrix material fibrous composite and a method for producing the same. More specifically, the present invention relates to an inorganic nanoparticle-matrix material fibrous composite in which inorganic nanoparticles are highly dispersed, a fibrous composite having a core-sheath structure, and a method for producing the same.

  Research on the synthesis of inorganic nanoparticles has made remarkable progress. In recent years, methods for synthesizing nanoparticles having excellent monodispersibility and uniform morphology have been reported one after another.

  Inorganic nanoparticles are significantly different from bulk materials in chemical, physical, electrical, magnetic, and optical properties due to size effects and quantum effects. The remarkable size effect and quantum effect of such inorganic nanoparticles appear only when the particle size is very small, for example, when the particle size is 30 nm or less. Specifically, it is estimated that the most probable particle size is 10 nm to 20 nm with respect to the supermagnetism of the material due to the high filling rate dispersion of the magnetic nanoparticles. However, when the particle size is very small, the surface energy of the particles becomes very high, so the particles spontaneously aggregate with each other, and the excellent properties of each inorganic nanoparticle are fully exhibited as material properties I can't do that.

  Therefore, establishment of a technique for uniformly dispersing inorganic nanoparticles in a matrix material, further controlling the dispersion state, and immobilizing them was a very important issue for applied research of inorganic nanoparticles. As a matrix material for dispersing inorganic nanoparticles, a polymer is most often used because of its excellent electrical insulation and moldability.

  For example, inorganic nanoparticle-organic matrix composites (organic / inorganic nanocomposite materials) in which inorganic nanoparticles are dispersed in a polymer have already been used in the fields of electronic materials, optical materials, magnetic materials, catalyst materials, automotive materials, etc. It is being used. In addition, inorganic nanoparticle-organic matrix composites are transparent in many fields such as electronic materials, optical materials, magnetic materials, pharmaceuticals, cosmetics, pigments, environmental materials, mechanical materials, memory element materials, supermagnetic materials, etc. It is expected for various properties such as heat resistance, strength, and conductivity.

  About the manufacturing method of an inorganic nanoparticle-organic matrix composite, the following three methods are generally known.

  The first method for producing the inorganic nanoparticle-organic matrix composite material is a method of directly dispersing inorganic nanoparticles in an organic matrix (direct kneading method) (see Patent Documents 1 and 2). Moreover, the 2nd method of manufacturing an inorganic nanoparticle-organic-matrix composite material mix | blends an organic monomer with an inorganic nanoparticle, and polymerizes an organic monomer after that (in-situ polymerization method) (refer patent documents 3-7) ).

  However, in the first and second methods, it is extremely difficult to uniformly disperse the inorganic nanoparticles in the organic matrix, and in many cases, the inorganic nanoparticles are aggregated and exist in the organic matrix. . For this reason, even if small-sized inorganic nanoparticles are used, only the properties of the aggregate of inorganic nanoparticles are exhibited, making it difficult to extract various functions obtained from the inorganic nanoparticles. It was.

  Moreover, the 3rd method of manufacturing an inorganic nanoparticle-organic matrix composite material is an ion dope reduction method (refer patent document 8). This method is mainly applied to the dispersion of metal nanoparticles. Specifically, after doping a metal ion or a metal complex into an organic matrix, it is carried out in the organic matrix by a superheat reduction treatment in a reducing gas. This is a method of depositing metal nanoparticles.

  According to this ion-doped reduction method, uniform dispersion of metal nanoparticles can be achieved to some extent, but it is difficult to control the particle size and dispersibility of the nanoparticles, and the material characteristics due to residual metal ions that cannot be reduced Degradation will also occur. For this reason, it was difficult to obtain the target inorganic nanoparticle-organic matrix composite also by the ion doping reduction method.

  Patent Document 9 proposes to produce a polymer nanofiber having a core-shell (core-sheath) heterophasic structure using a double nozzle with respect to the electrospinning method. Non-Patent Document 1 shows an example of manufacturing a core-sheath nanofiber using a combination of different polymers using double nozzle electrostatic spinning. Furthermore, Non-Patent Document 2 uses nanofibers containing metal ions and confirms that nanoparticles can be deposited in the fibers in an appropriate reaction environment.

JP 2000-294441 A JP 2007-314667 A JP-A-62-84155 Japanese Patent Laid-Open No. 10-72552 JP 2002-179931 A JP 2007-56115 A Japanese Patent Laid-Open No. 2007-239022 JP-A-2005-139438 JP 2007-197859 A

Compound Core-Sell polymer Nanofibers by Co-Electrospinning, Adv. Mater. 2003, 15, no. 22, Nov 17 Preparation and charac- terization of Ag2S nanoparticulars embedded in polymer fibers by electrospinning, Nanotechnology 16 (2005) 2233

  The present invention has been made in view of the background art described above, and the object of the present invention is inorganic nanoparticles in which inorganic nanoparticles are highly dispersed by suppressing aggregation of inorganic nanoparticles- It is to provide a matrix material composite and a manufacturing method thereof.

  For inorganic nanoparticle-matrix material composites in which inorganic nanoparticles are highly dispersed, the inventors do not agglomerate the nanoparticles by confining the nanoparticles in a space that can be considered one-dimensional, It has been found that high concentration and high dispersion can be achieved. Specifically, the present inventors use a dispersion solution in which inorganic nanoparticles are uniformly dispersed, and create a fiber from the dispersion solution by an electrospinning method (electrospinning method). Has found that an inorganic nanoparticle-matrix material fibrous composite in which inorganic nanoparticles are highly dispersed can be obtained.

  Accordingly, the present invention proposes to improve such inorganic nanoparticle-matrix material fibrous composites and / or extend the application range of such inorganic nanoparticle-matrix material fibrous composites.

  As a result of diligent research in view of the above problems, the inventors of the present invention used a dispersion solution in which inorganic nanoparticles were uniformly dispersed, and used the electrospinning method (electrospinning method) to produce fibers from the dispersion solution. It has been found that the above problems can be solved by spinning the fiber so that the fiber has a core-sheath structure, and the present invention has been completed.

That is, the present invention is as follows:
<1> It is a form of a fiber having a core part and a sheath part around the core part,
The average diameter of the sheath part is 50 nm or more and 3 μm or less,
At least one of the core part and the sheath part is composed of a composite material of inorganic nanoparticles and matrix material containing inorganic nanoparticles and a matrix material, and the average primary particle diameter of the inorganic nanoparticles is 100 nm or less.
Inorganic nanoparticle-matrix material fibrous composite.
<2> The average particle size of the inorganic nanoparticles is 1 nm or more and 20 nm or less, and in the inorganic nanoparticle-matrix material composite, 70% or more of the inorganic nanoparticles are in a form of a dispersed particle size of 30 nm or less. The fibrous composite as described in <1> above, which is dispersed.
<3> The <1> or <2>, wherein the content of the inorganic nanoparticles in the inorganic nanoparticle-matrix material composite is 30% by mass or more based on the composite material of the inorganic nanoparticle-matrix material. The fibrous composite according to Item.
<4> One of the core part and the sheath part is made of a composite material of inorganic nanoparticle-matrix material containing inorganic nanoparticles and a matrix material, and the other of the core part and the sheath part is a fiber-forming organic material. The fibrous composite according to any one of <1> to <3>, which is made of a material.
<5> Any of <1> to <3> above, wherein the sheath is made of a composite material of inorganic nanoparticles and matrix material containing inorganic nanoparticles and a matrix material, and the core is hollow. A fibrous composite according to any one of the above.
<6> The above-described <1> to <3>, wherein both the core part and the sheath part are made of a composite material of inorganic nanoparticles and matrix material containing inorganic nanoparticles and a matrix material. Fibrous composite.
<7> Bulk composite including pressing the fibrous composite according to any one of <1> to <6> above under a condition for maintaining a dispersion state of the inorganic nanoparticles. Body manufacturing method.
<8> A method for producing a fibrous composite, comprising removing a portion made of an organic material for fiber formation in the core and the sheath of the fibrous composite according to <4>.
<9> Obtaining a fibrous composite by the method described in <8> above, and molding the obtained fibrous composite under pressure so as to maintain a dispersion state of the inorganic nanoparticles. A method for producing a bulk composite, comprising:
<10> Providing a dispersion solution containing the inorganic nanoparticles, the matrix material, and a solvent,
Providing a fiber forming solution containing an organic material for fiber formation and a solvent;
Spinning the dispersion solution from one of the double nozzles and spinning the fiber-forming solution from the other of the double nozzles using an electrostatic spinning device having a double nozzle;
The manufacturing method of the fibrous composite as described in said <4> item containing.
<11> In the method according to <10>, the dispersion solution is spun from the outer nozzle of the double nozzle, and the fiber-forming solution is spun from the inner nozzle of the double nozzle. Obtaining a fibrous composite having a core made of an organic material for fiber formation and a sheath made of the inorganic nanoparticle-matrix material composite, and for forming the fiber constituting the core of the fibrous composite Removing organic materials,
The manufacturing method of the fibrous composite as described in said <5> item containing.
<12> Providing two types of dispersion solutions containing the inorganic nanoparticles, the matrix material, and a solvent,
Using an electrostatic spinning device having a double nozzle, one of the dispersion solutions is spun from one of the double nozzles, and the other of the dispersion solutions is spun from the other of the double nozzles. Spinning,
The manufacturing method of the fibrous composite as described in said <6> item containing.

  In the inorganic nanoparticle-matrix material fibrous composite of the present invention, the inorganic nanoparticle-matrix material composite material constituting at least one of the core portion and the sheath portion is inorganic because aggregation of inorganic nanoparticles is suppressed. The nanoparticles are highly dispersed.

  Therefore, according to the inorganic nanoparticle-matrix material fibrous composite of the present invention, the functions unique to the contained nanoparticles can be fully utilized. According to such an inorganic nanoparticle-matrix material fibrous composite of the present invention, various materials that require functions unique to nanoparticles, such as electronic materials, optical materials, magnetic materials, pharmaceuticals, cosmetics, pigments, and environmental materials. It can be widely used as a mechanical material, a catalyst material, an automobile material, a memory element material, a supermagnetic material, and the like, and is therefore very useful as a new functional material. In addition, according to the inorganic nanoparticle-matrix material fibrous composite of the present invention, the required properties can be obtained by combining inorganic nanoparticles and a matrix material, using a plurality of inorganic nanoparticles, using two or more polymers, and the like. A composite material having various functions can be realized.

  Moreover, the inorganic nanoparticle-matrix material fibrous composite of the present invention has a core part and a sheath part around the core part, and at least one of the core part and the sheath part is composed of inorganic nanoparticles and a matrix material. By comprising the composite material of inorganic nanoparticle-matrix material containing, the core portion and the sheath portion can have different roles.

  For example, one of the core part and the sheath part is made of a composite material of inorganic nanoparticle-matrix material containing inorganic nanoparticles and a matrix material, and the other of the core part and the sheath part is made of an organic material for fiber formation. In this case, the core or sheath made of the fiber-forming organic material enables the stable formation of the fiber, while the core or sheath made of the composite material of the inorganic nanoparticle-matrix material is thinly formed to form the nanoparticle. By providing a quasi-one-dimensional space suitable for the dispersion of the inorganic nanoparticles, aggregation of inorganic nanoparticles can be suppressed. That is, in this case, it is possible to reduce or substantially eliminate the requirement of spinnability for the matrix material. In this case, therefore, the choice of matrix material can be expanded, for example, making this matrix material a preferred material for the dispersion of inorganic nanoparticles.

  Further, for example, when both the core and the sheath are made of a composite material of inorganic nanoparticle-matrix material containing inorganic nanoparticles and a matrix material, the inorganic nanoparticles and the matrix material different from each other in the core and the sheath Thus, the degree of freedom in material design is increased.

  The inorganic nanoparticle-matrix material fibrous composite according to the present invention is contained in a bulk form by pressurizing and molding under the conditions for maintaining the dispersed state of the inorganic nanoparticles. The unique functions of the particles can be utilized in bulk form, especially in shaped bulk form. Here, “bulk” in the context of the present invention is a composite in which the composite has a three-dimensional extension, so that the effect of the surface can be ignored and the properties as a material having a specific shape can be exhibited. Means. That is, “bulk” in the present invention is a concept used in the opposite sense to fine fibers, fine powders and the like.

FIG. 1 is an image of an electrospinning method for producing the inorganic nanoparticle-matrix material fibrous composite of the present invention. 2 is an optical micrograph (magnification 3000 times) of the inorganic nanoparticle-matrix material fibrous composite of Example 1. FIG. FIG. 3 is a TEM observation photograph (left: cross section, right: cross section in the length direction) of the inorganic nanoparticle-matrix material fibrous composite of Example 1. FIG. 4 is a TEM observation photograph of the inorganic nanoparticle-matrix material fibrous composite of Example 1. FIG. 5 is an optical micrograph (5000 times transmission) of the inorganic nanoparticle-matrix material fibrous composite of Example 2. 6 is a TEM photograph (left: cross section, right: cross section in the length direction) of the inorganic nanoparticle-matrix material fibrous composite of Example 2. FIG. FIG. 7 is a TEM photograph (left: cross section, right: cross section in length direction) of the inorganic nanoparticle-matrix material fibrous composite of Example 3. 8 is a TEM photograph (left: cross section, right: cross section in length direction) of the inorganic nanoparticle-matrix material fibrous composite of Example 4. FIG. FIG. 9 is a TEM photograph of the inorganic nanoparticle-matrix material fibrous composite of Example 4. 10 is an optical micrograph (magnification 3000 times) of the inorganic nanoparticle-matrix material fibrous composite of Example 5. FIG. FIG. 11 is a TEM photograph (cross section) of the inorganic nanoparticle-matrix material fibrous composite of Example 5. ₄ is an optical micrograph (magnification 3000 times) of a deposit of Fe ₃ O ₄ nanoparticle-dispersed PVB fibers obtained in Reference Example 1. It is a transmission electron microscope (TEM) photograph of the obtained _Fe 3 _{O 4} nanoparticles dispersed PVB fibers deposit in Reference Example 1 (360,000-fold). _{4 is} a transmission electron micrograph of a Fe ₃ O ₄ nanoparticle-dispersed PVB bulk sample obtained in Reference Example 2.

<< Inorganic nanoparticle-matrix material fibrous composite >>
The inorganic nanoparticle-matrix material fibrous composite of the present invention is in the form of a fiber having a core part and a sheath part around the core part, the average diameter of the sheath part is 50 nm or more and 3 μm or less, and the core part and At least one of the sheath parts is composed of a composite material of inorganic nanoparticles and matrix material containing inorganic nanoparticles and a matrix material, and the average primary particle size of the inorganic nanoparticles is 100 nm or less. Here, for example, the average primary particle size of the inorganic nanoparticles is 1 nm or more and 20 nm or less, and in the inorganic nanoparticle-matrix material composite, 70% or more of the inorganic nanoparticles are dispersed in the form of a dispersed particle size of 30 nm or less. You can do it. For example, the content of the inorganic nanoparticles in the inorganic nanoparticle-matrix material composite may be 30% by mass or more based on the composite material of the inorganic nanoparticle-matrix material.

(Primary particle size of inorganic nanoparticles)
The inorganic nanoparticles used in the inorganic nanoparticle-matrix material composite of the present invention are 100 nm or less, 50 nm or less, 30 nm or less, 20 nm or less, or 10 nm or less before being dispersed in the inorganic nanoparticle-matrix material composite. Average primary particle size. The average primary particle size of the inorganic nanoparticles may be 1 nm or more. It is preferable that the average primary particle size is sufficiently small in that the characteristics specific to the nanoparticles can be effectively expressed, light scattering can be suppressed, and application development to optical materials can be thereby performed.

  The “average primary particle size” before the inorganic nanoparticles are dispersed in the inorganic nanoparticle-matrix material composite is obtained by drying the dispersion of the inorganic nanoparticles and using a transmission electron microscope (TEM) to obtain the dried product. Taking an image (750,000 times), and using the image analysis software (NEXUS NEW QUABE) for the acquired image, image analysis is performed to obtain the diameter of a circle having the same area on the image for 100 primary particles. It is a value obtained as an average value of diameters.

(Dispersion state of inorganic nanoparticles in the composite (dispersed particle size distribution))
In the inorganic nanoparticle-matrix material composite of the present invention, 70% or more, 80% or more, 90% or more, or substantially all of the inorganic nanoparticles dispersed in the composite have a dispersed particle size of 30 nm or less, For example, it is dispersed in a form of 20 nm or less or 10 nm or less. In particular, the inorganic nanoparticle-matrix material composite of the present invention is substantially free of aggregated particles having a dispersed particle size of 50 nm or more.

  When inorganic nanoparticles are highly dispersed in the inorganic nanoparticle-matrix material composite of the present invention, light scattering can be suppressed, so that application to optical materials can be developed. Moreover, since the surface area of a nanoparticle becomes large, the functional characteristic which the said nanoparticle has can be expressed more clearly. Furthermore, when the inorganic nanoparticles are particularly highly dispersed, for example, when 70% or more of the inorganic nanoparticles are dispersed in a form of 30 nm or less, the function based on the quantum effect peculiar to the nanoparticles is added to the composite. Can be expressed, and the application development can be further expanded.

In addition, the ratio of the particles (that is, aggregated particles or primary particles) dispersed in a form having a predetermined dispersed particle size (for example, 30 nm) or less is determined using a transmission electron microscope (trade name: TECNAI G2 manufactured by FEI). Observation and photographing of the inorganic nanoparticle-matrix material composite were performed at an acceleration voltage of 120 kV, and then the obtained images were isolated and dispersed in the composite using image analysis software (NEXUS NEW QUEBE). For each agglomerated particle or primary particle, perform image analysis to obtain the diameter of a circle having the same area on the image, obtain a dispersed particle size distribution, and based on this distribution, obtain a value obtained by the following formula: is there:
{Number of particles dispersed in a form having a predetermined dispersed particle size (for example, 30 nm) or less} / {Number of all particles} × 100 (%)

(Content of inorganic nanoparticles)
The content (filling rate) of the metal nanoparticles in the inorganic nanoparticle-matrix material composite of the present invention is preferably 5% by mass or more, 9% by mass or more, and 10% by mass or more with respect to the composite material of the inorganic nanoparticle / matrix material. It is more than mass%, more than 15 mass%, more than 20 mass%, more than 25 mass%, more than 30 mass%, or more than 50 mass%. Further, the content (filling rate) of the inorganic nanoparticles in the inorganic nanoparticle-matrix material composite of the present invention is preferably a volume fraction of 0.5 volume with respect to the composite material of the inorganic nanoparticle-matrix material. % Or more, 0.8 volume% or more, 1.0 volume% or more, 1.5 volume% or more, 3 volume% or more, 4 volume% or more, 5 volume% or more, or 8 volume% or more.

  In addition, the content (filling rate) of the metal nanoparticles in the inorganic nanoparticle-matrix material fibrous composite of the present invention is, for example, 1 / of the above amount with respect to the entire inorganic nanoparticle-matrix material fibrous composite. It may be 5 or 1/10.

  When the content (filling ratio) is sufficiently large, the function of the nanoparticles can be sufficiently exerted, and the applicability of the resulting composite can be further expanded. For example, when the content (filling rate) is sufficiently large, macroscopic material properties such as the recording density of a high-density recording medium can be efficiently expressed.

  In addition, content (filling rate) of an inorganic nanoparticle is a value calculated from preparation amount. Therefore, the content (filling rate) of the inorganic nanoparticle-matrix material fibrous composite as a whole can be measured by thermogravimetric balance (TGA) (trade name: TGA8120, manufactured by Rigaku Corporation) of the fibrous composite. In addition, the content (filling ratio) of the inorganic nanoparticle-matrix material with respect to the composite material is determined by thermogravimetry after removing portions other than the inorganic nanoparticle-matrix material composite material containing the inorganic nanoparticles and the matrix material. It can be measured by analyzing a balance (TGA) (manufactured by Rigaku Corporation, trade name: TGA8120).

<Inorganic nanoparticles-average fiber diameter of matrix material fibrous composite>
The average fiber diameter of the inorganic nanoparticle-matrix material fibrous composite of the present invention, that is, the fiber diameter of the sheath part is 50 nm or more, 100 nm or more, or 200 nm or more, and is 3 μm or less, 1 μm or less, or 800 nm or less. It's okay. Moreover, the average fiber diameter of the core part of the inorganic nanoparticle-matrix material fibrous composite of the present invention is 30 nm or more, 50 nm or more, or 100 nm or more, and may be 800 nm or less, 500 nm or less, or 400 nm or less. . Here, the average fiber diameter of the core can be determined by dissolving the inorganic nanoparticle-matrix material fibrous composite. Thus, for example, when the sheath is made of a water-soluble polymer, the fiber composite is immersed in water, and optionally irradiated with ultrasonic waves to dissolve and remove the sheath, and then the fiber diameter is measured. By doing, the average fiber diameter of a core part can be calculated | required.

  If the average fiber diameter is sufficiently small, it is considered that the space in which the nanoparticles dispersed in the fibers can be aggregated is limited from three dimensions to one dimension, and as a result, a film obtained by a casting method or the like In comparison, aggregation of nanoparticles can be physically prevented. In addition, as the average fiber diameter decreases, the surface area of the fiber increases significantly, so when the solution is sprayed from the nozzle by the electrospinning method, a large amount of solvent can be instantly evaporated by high-speed stretching. As a result, the nanoparticles can be fixed in the ultrafine fibers before aggregation occurs. In other words, in the present invention, by these two synergistic effects, it is possible to greatly reduce the probability of aggregation of nanoparticles in the matrix material and to highly disperse the nanoparticles substantially in the state of primary particles.

  On the other hand, when the average fiber diameter is too small, it becomes difficult to stably produce fibers containing nanoparticles. Moreover, there is a risk of stress aggregation of the nanoparticles due to an intense drawing force in the fiber length direction.

  Of course, the fiber diameter of the obtained fiber may vary. However, within the above average fiber diameter range, the dispersibility of the nanoparticles dispersed in the fiber is not greatly affected. Here, the “average diameter of the sheath portion” is an average value of the diameters of 25 fibers randomly selected from an optical microscope photograph using a deposit of ultrafine fibers as a sample.

<< Preparation process of inorganic nanoparticle-matrix material fibrous composite >>
Below, the manufacturing method of the inorganic nanoparticle-matrix material fibrous composite of this invention is demonstrated. The inorganic nanoparticle-matrix material fibrous composite of the present invention uses a dispersion solution containing inorganic nanoparticles, a matrix material, and a solvent in combination with a fiber-forming solution containing an organic material for fiber formation and a solvent. It can be obtained by producing core-sheath microfibers by an electrostatic spinning method.

  Thus, for example, in the present invention, inorganic nanoparticles are highly dispersed in a dispersion solution in advance, and the dispersion solution in which the nanoparticles are dispersed and the organic material solution for fiber formation having a spinnability are respectively formed in a coaxial double nozzle. By introducing into the core side and the sheath side and applying to the electrospinning method, ultrafine fibers having a core-sheath structure are formed. In this case, by forming the core-sheath structure fiber, the dispersion space of the nanoparticles is surely suppressed to quasi-one dimension, the probability of aggregation of the nanoparticles is greatly reduced, and the dispersibility of the nanoparticles is improved. Can be made. Moreover, by having the fiber forming organic material with excellent spinnability responsible for the fiber formation, it is possible to control the dispersibility of the nanoparticles and the formation of the microfibers that provide the nanoparticle dispersion space, respectively. , Increase the degree of freedom of the combination of inorganic nanoparticles and matrix materials, and can support a wide range of functional design of nanocomposites (nanocomposites). Furthermore, due to the synergistic effect of different kinds of nanoparticles selectively dispersed in the core-sheath structure space in which the nanostructure is controlled, the microfiber itself is highly expected as a functional element.

  Specifically, for example, the method for producing an inorganic nanoparticle-matrix material fibrous composite of the present invention includes the following “preparation of dispersion solution”, “preparation of fiber-forming solution”, and “electrostatic spinning”. It is a waste.

<Preparation of dispersion solution>
In preparing the dispersion solution, for example, first, the inorganic nanoparticles are developed in the solvent A while stirring, and then surface modifying molecules are added as necessary. In this case, the solvent A is not particularly limited as long as the surface modification molecule can be dissolved. A single solvent or a mixed solvent system using a plurality of solvents may be used. Further, it is desirable that the amount of the surface modifying molecule added is excessive as compared with the amount that further covers the entire particle surface.

  Subsequently, the matrix material is dissolved in the solvent B, and a dispersion aid is simultaneously developed as necessary. The solvent B is not particularly limited as long as it can completely dissolve the matrix material even in the presence of the solvent A and does not precipitate or aggregate the inorganic nanoparticles. Absent. The solvent B may be a single solvent or a mixed solvent system using a plurality of solvents.

  Next, the prepared solvent A and solvent B are mixed, and the dispersion solution is prepared by dispersing inorganic nanoparticles in the matrix material using a known dispersion device such as stirring (for example, a mechanical vibration type tube mixer). Get. The dispersion treatment can usually be performed at room temperature in about 0.2 to 2 hours, but can be heated as necessary. Furthermore, when it is desired to realize high concentration and high dispersibility, it is preferable to perform ultrasonic irradiation or use a dispersion assist device such as a bead mill in the dispersion treatment.

  Finally, according to the viscosity of the fiber-forming solution or other dispersion solution used together, according to the stable spinning conditions, use a suitable solvent, including fine adjustment of the evaporation rate of the solvent, and adjust to the optimum spinning concentration. Is desirable.

  In particular, when used with a fiber-forming organic material having good spinnability, the matrix material for dispersing inorganic nanoparticles may be spinnable or not as long as it is dispersible with respect to inorganic nanoparticles.

<Preparation of fiber forming solution>
The fiber forming solution can be prepared, for example, as known in conventional electrospinning methods. Therefore, for example, the fiber-forming solution can be obtained as a solution that can be stably spun in electrospinning. The fiber-forming solution can be any solution that can be spun in the electrospinning method, and does not necessarily have a good spinnability. For example, a fiber composite was obtained by spinning. You may select as a material which can be removed by melt | dissolution etc. later.

<Electrostatic spinning>
In the electrospinning process, for example, in an electrospinning apparatus equipped with a double nozzle, the dispersion solution and the fiber forming solution or other dispersion solution are respectively introduced into the double nozzle, and a predetermined electric field strength is obtained. And a core-sheath structure fiber by ejecting at a discharge speed. The spinning method and spinning device in the electrostatic spinning process will be described below.

(Spinning method)
As the spinning method, an electrostatic spinning method is used. Here, the “electrostatic spinning method” means that a solution or dispersion containing a fiber-forming substrate or the like is discharged into an electrostatic field formed between the electrodes, and the solution or dispersion is directed toward the electrodes. This is a method for forming a fibrous substance. The fibrous material obtained by spinning is usually laminated on an electrode that is a collection substrate.

  Further, the fibrous composite formed is not only in a state in which the solvent and the like contained in the dispersion solution and / or the fiber forming solution are completely distilled off, but also remains in the fibrous substance. Including state.

  Note that normal electrostatic spinning is performed at room temperature. However, in the present invention, when the volatilization of the solvent or the like is insufficient, the temperature and atmosphere of the spinning environment are controlled or trapped as necessary. It is also possible to control the temperature of the collector substrate.

(Spinning equipment)
Next, an apparatus used in the spinning process will be described.

  FIG. 1 is a diagram showing an embodiment of an apparatus used for a double nozzle-mounted electrostatic spinning method. In the electrostatic spinning device shown in FIG. 1, an injection needle-like ejection nozzle 1 to which a voltage is applied by a high voltage generator 6 is installed at the tip of syringes 2 and 3, and the core for the core in syringe 2 is used. And the solution for the sheath in the syringe 3 are guided to the tip of the ejection nozzle 1. In the apparatus shown in FIG. 1, the high voltage generator 6 is used, but any appropriate means can be used.

  Next, the tip of the ejection nozzle 1 is disposed at an appropriate distance from the fiber collecting electrode 4, and the solution for the core in the syringe 2 and the solution for the sheath in the syringe 3 are ejected from the ejection nozzle 1. The fibrous substance can be formed between the distal end portion of the ejection nozzle 1 and the fiber collecting electrode 4 by ejecting from the distal end portion.

  The electrode for forming the electrostatic field may be any material such as a metal, an inorganic material, or an organic material as long as it exhibits conductivity. Alternatively, a thin film made of a metal, an inorganic material, an organic material, or the like having conductivity may be provided on an insulator.

  The electrostatic field is formed between a pair or a plurality of electrodes, and a high voltage may be applied to any electrode that forms the electrostatic field. This includes, for example, the case of using two high-voltage electrodes with different voltage values (for example, 15 kV and 10 kV) and one electrode connected to the ground, or a total of more than three electrodes. Including the case where it is used.

  Moreover, as a method for discharging the core solution and the sheath solution into the electrostatic field, any method can be adopted. In FIG. 1, the core solution and the sheath solution are used. Is supplied to a nozzle, and these solutions are spun by an electric field from the nozzle to be fiberized.

  In addition, as for the shape of the nozzle for ejecting a solution, it is preferable that the front-end | tip forms an acute angle. When the tip of the ejection nozzle forms an acute angle, it is easy to control droplet formation at the tip of the nozzle. The material of the nozzle is not particularly limited, but usually glass and metal are often used. In the case of glass, a conducting wire such as platinum is fixed in a nozzle and used as an electrode.

  The appropriate nozzle diameter of the double nozzle required for the production of the core-sheath structure fiber varies depending on the solution used, but the inner diameter of the inner nozzle for forming the core is preferably in the range of 0.05 to 1 mm. It is. When the nozzle diameter is too small, the nanoparticles may be clogged in the nozzle or the injection may be discontinuous, which makes stable spinning difficult. On the other hand, if the nozzle diameter is too large, droplets are likely to drop off from the nozzle tip, preventing stable spinning. Moreover, since the fiber diameter to be produced becomes thick, the effect of the present invention cannot be sufficiently exhibited. In consideration of securing the fineness of the fiber and operability, the thickness is more preferably 0.1 to 0.5 mm.

  The inner diameter of the outer nozzle for forming the sheath is preferably 0.5 to 2.5 mm, more preferably 1.0 to 2.0 mm for the same reason.

  The distance between the ejection nozzle and the fiber collecting electrode depends on the charge amount, the nozzle size, the ejection amount of the fiber forming solution from the nozzle, the solution concentration of the fiber forming solution, etc., but when the applied voltage is about 15 kV A range of 10 to 30 cm is preferred. If the distance is too short, the solvent will not evaporate completely, the fibers from spinning will be fused together and the shape will be lost, and there will be a lot of residual solvent in the fiber, so the aggregation of nanoparticles will be sufficiently suppressed It may not be possible. On the other hand, if the distance is too long, a sufficient drawing force cannot be obtained, so that the spinnability is deteriorated, the variation of the produced fiber diameter is increased, and the fiber recovery rate is low. May cause problems.

  The applied electrostatic potential is preferably in the range of 5 to 30 kV. If the applied voltage is too high, abnormal discharge may occur, and stable fiber production cannot be performed. On the other hand, when the applied voltage is too low, sufficient electrostatic repulsion cannot be caused, so that the fiber diameter is increased, and as a result, aggregation of nanoparticles cannot be sufficiently suppressed. Here, the desired potential may be produced by any appropriate method known in the art.

  The control accuracy of the syringe pump that adjusts the discharge amount of the fiber forming solution is preferably about 0.1 μl / min. Further, the discharge amount of the fiber forming solution varies depending on the fiber forming solution to be used, but if it is too fast, there is an adverse effect on the spinning stability and the formation of the core-sheath structure. It may be difficult to obtain a typical core-sheath fiber. A range of 10 to 100 μl / min is preferable. In addition, by precisely adjusting the discharge speed of the core sheath in accordance with the characteristics of the core-sheath forming component, the spinning parameters can be optimized and the core-sheath structure (the thickness of the core and the sheath portion) can be precisely controlled. I understood.

<Post-treatment of core-sheath fiber>
For example, an inorganic nanoparticle-matrix material that achieves high filling and high dispersion of inorganic nanoparticles by dissolving or decomposing and removing only one side of the core or sheath of the core-sheath structure fiber produced by the above method A fibrous composite can be obtained. For example, by utilizing the difference in heat resistance between the core portion and the sheath portion and removing one side by firing, a nanoparticle-dispersed sintered body effective for applications such as a catalyst and a carrier can be obtained. Also, by utilizing the difference in solubility between the core and the sheath, immersing in a solvent that can be dissolved only on one side, and removing one side is useful for ultrafine fibers that cannot be produced in one step or structural control and functional design Hollow type microfibers can be produced. Here, any method can be used as long as the core portion or the sheath portion can be selectively removed without adversely affecting the dispersion of the nanoparticles. Naturally, the inorganic nanoparticle-matrix material fibrous composite from which one side is removed is scraped and post-treatment such as vacuum hot press can be used to produce a bulk material that can express the excellent properties of nanoparticles as material properties. It is.

<< Use of inorganic nanoparticle-matrix material composite >>
The inorganic nanoparticle-matrix material fibrous composite of the present invention utilizes the excellent properties of light, electricity, magnetism, etc. of nanoparticles dispersed at high concentration and uniformity, and the core-sheath microfiber itself is a functional element. Is expected to work as a combination of functional nanoparticles and matrix materials, the use of multiple inorganic nanoparticles, the use of two or more matrix materials, and various functionalities for precisely controlled nanostructures. Creation of a composite material having desired material characteristics can be expected due to the advanced organization of the composite.

  Moreover, the inorganic nanoparticle-matrix material fibrous composite of the present invention can be made into a bulk form by a method including pressurizing and molding under the condition of maintaining the dispersed state of the inorganic nanoparticles. Here, in this molding, when the high temperature is too high or the applied pressure is too large, the mobility of the molecular chain of the matrix material becomes high, the holding power to the nanoparticles decreases, and the dispersed state of the nanoparticles in the fiber May not be maintained. On the other hand, when molding is performed at an appropriate temperature and pressure, while maintaining the nanoparticles, the mobility of the molecular chains of the matrix material is increased to cause fusion between the fibers, thereby causing inorganic nanoparticles in the fibers. Thus, it can be formed into a bulk functional material while maintaining the dispersion state. That is, the conditions under which pressure can be formed while maintaining the dispersed state of the inorganic nanoparticles are the conditions in which the matrix material maintains the dispersed state of the inorganic nanoparticles and the matrix material has sufficient formability.

  For example, if the fibrous matrix material is a single non-crystalline polymer, such fibrous inorganic nanoparticle-matrix material composites may have a temperature near the glass transition temperature of the matrix material, such as the glass of the matrix material. It can be molded by pressurization in the range of transition temperature ± 10 ° C. In addition, for example, when the fibrous matrix material of the present invention is substantially composed of a crystalline polymer, or has a crystalline polymer component as a main component, such a fibrous inorganic nanoparticle-matrix The material composite can be molded by pressing at a temperature near the softening point, for example, within the range of the softening point ± 10 ° C. Furthermore, for example, when the fibrous matrix material of the present invention is a blend of a crystalline polymer component and an amorphous polymer, such a fibrous inorganic nanoparticle-matrix material composite has a high crystalline property. Molding can be performed by applying pressure in an appropriate temperature range between the melting point derived from the molecule and the glass transition temperature derived from the amorphous polymer in the polymer constituent. Here, the pressurization of the fibrous inorganic nanoparticle-matrix material composite can be optionally accompanied by a reduced pressure of the atmosphere to promote the reduction of voids between the fibers. In general, it is preferable to form the fibrous inorganic nanoparticle-matrix material composite at a temperature lower than the melting point of the polymer. This is because the nanoparticles dispersed in the matrix material may reaggregate at a temperature higher than the melting point of the matrix material.

  Thus, for example, the fiber comprising the inorganic nanoparticle-matrix material composite of the present invention is coated on the surface using the obtained fiber deposit, or the gap between the fibers is reduced by vacuum suction to form a thin film. The obtained thin films are overlapped and can be developed into a bulk material by hot pressing at a temperature below the glass transition point (Tg) of the polymer used. In this case, the functional characteristics of the nanoparticles can be expressed as bulk material characteristics.

  In addition, in the inorganic nanoparticle-matrix material fibrous composite of the present invention having a core and a sheath, after removing either the sheath or the core, a bulk material is formed from the fibrous composite by the above method. You can also In this case, for example, either the core portion or the sheath portion is formed of a water-soluble material to obtain an inorganic nanoparticle-matrix material fibrous composite, and the resulting fibrous composite is washed with water and centrifuged. And drying to remove either the core or the sheath formed of the water soluble material, after which a bulk material can be made from the fibrous composite.

<Inorganic nanoparticles>
The “inorganic nanoparticles” described in the present invention are not particularly limited to certain types.

  Specifically, examples of the “inorganic nanoparticles” include conductor nanoparticles, semiconductor nanoparticles, insulator nanoparticles, magnetic nanoparticles, phosphor nanoparticles, light absorbing nanoparticles, light transmitting nanoparticles, and pigment nanoparticles. . Some “organic-inorganic hybrid nanoparticles” can also be applied to drug fine particles for DDS (Drug Delivery System), cosmetic fine particles, organic-inorganic hybrid pigment fine particles, and the like.

The inorganic nanoparticles used in the present invention are appropriately selected according to the use of the obtained inorganic nanoparticle-matrix material fibrous composite or bulk composite material. Specifically, antireflection, infrared reflection, etc. Examples of optical applications include SiO ₂ , TiO ₂ , Ta ₂ O ₅ , ZrO ₂ , SnO ₂ , and In ₂ O ₃ . For high-density memory applications, various magnetic materials, for example, simple metals selected from iron group elements or transition metal elements such as Fe, Co, Ni, or alloys or intermetallic compounds containing at least one of these elements or metal oxides, _{specifically, Fe, Fe 3 O 4,} γ-Fe 2 O 3, CrO 2, Co-γ-Fe 2 O 3, Co-Ni, Co-Ni-P, Co-Cr, Ba Examples thereof include ferrite.

Furthermore, as applications for high-density memories and light-emitting displays, various fluorescent materials such as inorganic oxides and halides, or compounds in which rare earth elements and the like are introduced using these as base materials, specifically, the following materials are used. (Hereinafter, the left side of: represents the base material and the right side represents the introduced element): BaSi ₂ O ₅ : Pb, Sr ₂ P ₂ O ₇ : Eu, BaMa ₂ Al ₁₆ O ₂₇ : Eu, MgWO ₄ 3Ca ₃ (PO ₄ ) ₂ Ca (F, Cl) ₂ : Sb, Mn, MgGa ₂ O ₄ : Mn, Zn ₂ SiO ₄ , (Ce, Tb) MgAl ₁₁ O ₁₉ , Y ₂ SiO ₅ : Ce, Tb _{, Y 2 SiO 5: Ce,} Y 2 SiO 5: Eu, Y 2 O 3: Eu, YVO 4: Eu, (Sr, Mg, Ba) 3 (PO 4) 2: Sn, 3.5MgO · 5MgF _{· GeO 2: Mn, ZnS:} Cu, ZnS: Mn, ZnS: TbF 3, ZnS: Ag, ZnS: Cu, Al, ZnS: Cu, Au, Al, ZnO: Zn.

  In addition, the inorganic nanoparticle used for this invention may be single 1 type, or may use multiple types simultaneously, as long as the dispersibility in a matrix material is good. From the viewpoint of the composition of the nanoparticles, it may be homogeneous, core-shell type, or hollow type.

  The inorganic nanoparticles used in the present invention may be the inorganic nanoparticles as they are, but in order to achieve uniform dispersion of the nanoparticles and to maintain the dispersion state stably, the affinity for the inorganic nanoparticles on the nanoparticle surface is sufficient. It is preferably protected by a surface modifying molecule having a property, a coordination property, a binding property and the like. By using the inorganic nanoparticles coated with the surface modifying molecules, aggregation between the nanoparticles can be suppressed, and the nanoparticles can stably exist in a state of almost primary particles in the dispersion solvent. As a result, it finally leads to production of inorganic nanoparticle-matrix material fibrous composite that realizes high concentration and high dispersion of nanoparticles.

Examples of functional groups that can be adsorbed on the nanoparticle surface include those containing sulfur such as organic sulfur groups (—S═O, —SH), and nitrogen atoms such as amide groups and amino groups (—NH ₂ ). Thing, a hydroxyl group, a carboxyl group, a cationic group, for example, an ammonium group (which may be substituted by a hydroxy group or a linear or branched alkyl group having 1 to 6 carbon atoms), a pyridinium group and a phosphonium group, anionic Examples thereof include a carboxyl group, a sulfonic acid group, a phosphoric acid group, and a phosphonic acid group and a salt compound thereof.

  As long as the effects of the present invention are not impaired, the surface modifying molecule may be used alone or in combination of two or more kinds. Moreover, it is desirable that the amount of the surface-modifying molecule added is excessive as compared with the amount that further covers the entire surface of the inorganic nanoparticles.

  Finally, the inorganic nanoparticles described in the present invention are used as a form stably dispersed in a dispersion solvent. The dispersion solvent is not particularly limited. Depending on the dispersion matrix, both nanoparticles dispersed in water or organic solvents can be used. In some cases, water-dispersed nanoparticles and organic solvent-dispersed nanoparticles can be used simultaneously for the core and sheath forming components, respectively. When selecting a solvent, it is premised that stable concentration of nanoparticles can be dispersed at a high concentration, but the evaporation rate is one of the important parameters according to the spinning environment and stable spinning conditions.

《Matrix material》
The matrix material, that is, the material used as the dispersion matrix for the inorganic nanoparticles is not particularly limited as long as a stable high concentration dispersion state can be achieved for the selected inorganic nanoparticles, for example, a polymer or an oligomer. It may be. In view of dispersion stability, morphology control and processability, a compound that can be applied to a sol-gel method, which is one of methods for producing polymers, reactive oligomers, and nanoparticles, is desirable. Here, the polymer or oligomer used as the matrix material is an organic matrix material such as an alkyl polymer, an inorganic matrix material such as polysiloxane, or an organic-inorganic hybrid matrix material such as polysilsesquioxane. Good.

  When a polymer or oligomer is used as the matrix material, a polymer or oligomer having a capturing functional group for inorganic nanoparticles is preferable because the nanoparticles can be dispersed at a higher concentration. Such an inorganic nanoparticle-capturing functional group is not particularly limited as long as it has a capturing ability for inorganic nanoparticles. In the present invention, a suitable capturing functional group can be selected depending on the type of inorganic nanoparticles used.

  Examples of preferred functional groups possessed by the polymer or oligomer used in the present invention include carboxylic acid groups (including acid anhydrides and carboxylates), amino groups, imide groups, amide groups, pyridine groups, phosphoric acid groups, Examples include sulfonic acid groups, alcoholic hydroxyl groups, thiol groups, disulfide groups, nitrile groups, isonitrile groups, alkynes, and the like.

When the particles to be dispersed in the present invention are metal nanoparticles, the functional group of the polymer or oligomer used is selected from the group consisting of oxygen, nitrogen, sulfur, and phosphorus because it can be easily coordinated with the metal. A functional group containing at least one element is preferred. Examples of such a functional group include a hydroxyl group (—OH), a carbonyl group (—C═O), an amide group, an amino group (—NH ₂ ), an isocyanate (—CN), a pyridine group, a pyrrolidone group, and an organic system. A phosphoric acid group (-P = O), an organic sulfur group (-S = O, -SH), etc. can be mentioned. These groups may be used singly or in a state where two or more kinds are present. Of these, amino groups, organic sulfur groups, and organic phosphate groups are preferred because of their relatively strong interaction with metal nanoparticles, and organic compounds have the strongest interaction with metal nanoparticles. Most preferred is a sulfur group.

  An example of the polymer having an inorganic nanoparticle-capturing functional group is polyvinyl butyral (PVB). With polyvinyl butyral, the dispersibility of the nanoparticles can be controlled to a higher degree by controlling the vinyl structure of the main chain and the presence of two types of functional groups, the OH group and acetal group of the side chain, at a predetermined ratio. can do.

  As long as the dispersibility of the nanoparticles is good, the matrix material may be spinnable or not. However, after the fluidity of the matrix material solution in which the nanoparticles are dispersed and the molding conditions of the nanodispersed tissue after electrospinning, etc. When the matrix material is a polymer, a polymer having a molecular weight of 1 to 1.5 million is desirable. Considering the fluidity of the nanoparticle-containing matrix material solution, the dispersion stability of the nanoparticles and the stability of electrospinning, when the matrix material is a polymer, a polymer having a molecular weight of 5 to 500,000 is more preferable. .

  The purpose of making the dispersion matrix into oligomers, especially reactive oligomers, is that the nanoparticles and reactive oligomers are trapped in ultrafine fibers by electrospinning, and the highly dispersed state of the nanoparticles is grown by growing the oligomers by post-treatment such as heat. It is to solidify. Since the viscosity of the solution is lower than that of the polymer, it is considered advantageous for high concentration dispersion of the nanoparticles. The nanoparticles can be easily dispersed in the reactive oligomer, and the reactive oligomer modified on the surface of the nanoparticle suppresses the aggregation between the nanoparticles, and the post-treatment process such as heat treatment and UV irradiation causes the reactive oligomer to It is highly anticipated for the production of fibrous composites of inorganic nanoparticle-matrix materials that have grown rapidly into a network while maintaining the dispersed state of the nanoparticles, and achieved high concentration and high dispersion characteristics of the nanoparticles. The

  The oligomer used for the matrix material of the present invention is not particularly limited as long as it can achieve a stable and highly dispersed state with respect to the selected inorganic nanoparticles. (Meth) polyfunctional acrylate oligomers, polysilsesquioxanes, etc. having both thermosetting and ultraviolet curing properties are preferred. In particular, in the case of polysilsesquioxane, some are commercially available in the form of nanoparticles, are mixed with a large number of inorganic nanoparticles, exhibit excellent dispersibility, and are preferably used.

  The sol-gel method has long been known as a method for producing nanoparticles. It is considered that a dense sintered polycrystalline body can be obtained, and it can be easily applied to the matrix material used in the present invention because it can easily achieve high homogeneity. So far, the raw material of the sol-gel method is mainly a metal alkoxide, and if the functional inorganic nanoparticles to be dispersed are metal oxides, synthesis and dispersion of nanoparticles in situ can be considered. Otherwise, if the dispersion and functionality of the nanoparticles intended for dispersion are not adversely affected, it can be handled as a polycrystalline bulk body or a fixed state in a dispersed state with the dispersed nanoparticles by the sol-gel reaction. Conceivable.

  Hydroxyl group-containing polymers containing silicon, titanium and aluminum elements are obtained by suitable methods such as hydrolysis and (co) condensation of aluminum alkoxides using alkoxy and / or organoalkoxysilanes. An example of the production of such a heterocondensate is “Sol-Gel Science”, J. Org. Brinker, 1990.

  Catalysts that can be used for the hydrolysis and condensation of such monomers, oligomers and polymers are acids, bases, metal complexes and organometallic compounds. Illustrative acids are, for example, p-toluenesulfonic acid, hydrochloric acid, formic acid and acetic acid. Bases that can be used are, for example, alkali metal (Li, Na, K) and alkaline earth metal (Mg, Ca, Ba) hydroxides. In particular, it is preferable to use an acid in the form of a 0.1N to 1.5N aqueous solution.

  When a raw material applicable to the sol-gel method is used as a dispersion matrix, in order to obtain a final bulk material of the nanoparticle dispersion, it must pass through sintering. If the sintering environment is controlled to be an atmosphere of a reducing gas or other reactive gas, in some cases, a metal, alloy nanoparticle, or multi-component polycrystalline bulk state may be finally obtained.

《Organic material for fiber formation》
As an organic material for fiber formation, that is, an organic material used without being combined with inorganic nanoparticles, any organic material that can be spun by an electrostatic spinning method, particularly a polymer material can be exemplified.

<Organic material for fiber formation-spinnability>
The organic material for fiber formation can be selected, for example, as a material with good spinnability, particularly as a polymer with good spinnability.

  In this case, preferred polymers from the viewpoint of spinnability include, for example, polyethylene oxide, polyvinyl alcohol, polyvinyl acetal, polyvinyl ester, polyvinyl ether, polyvinyl pyridine, polyacrylamide, ether cellulose, pectin, starch, polyvinyl chloride, poly Acrylonitrile, polylactic acid, polyglycolic acid, polylactic acid-polyglycolic acid copolymer, polycaprolactone, polybutylene succinate, polyethylene succinate, polystyrene, polycarbonate, polyhexamethylene carbonate, polyarylate, polyvinyl isocyanate, polybutyl isocyanate, Polymethyl methacrylate, polyethyl methacrylate, polynormal propyl methacrylate, polynormal butyl methacrylate, Limethyl acrylate, polyethyl acrylate, polybutyl acrylate, polyethylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polyparaphenylene terephthalamide, polyparaphenylene terephthalamide-3,4'-oxydiphenylene terephthalamide Polymer, polymetaphenylene isophthalamide, cellulose diacetate, cellulose triacetate, methyl cellulose, propyl cellulose, benzyl cellulose, fibroin, natural rubber, polyvinyl acetate, polyvinyl methyl ether, polyvinyl ethyl ether, polyvinyl normal propyl ether, polyvinyl isopropyl ether, Polyvinyl normal butyl ether, polyvinyl isobutyl ether, polyvinyl tar Libutyl ether, polyvinylidene chloride, poly (N-vinyl pyrrolidone), poly (N-vinyl carbazole), poly (4-vinyl pyridine), polyvinyl methyl ketone, polymethyl isopropenyl ketone, polypropylene oxide, polycyclopentene oxide, polystyrene Examples include sulfone, nylon 6, nylon 66, nylon 11, nylon 12, nylon 610, nylon 612, and copolymers thereof.

<< Organic material for fiber formation-removability >>
Moreover, the organic material for fiber formation can be selected as a material that can be easily removed after the fiber is formed, for example.

  In this case, mineral oil can be selected as a material that can be easily removed after fiber formation. In particular, a material that can be easily removed after forming the fiber can be used as a material for forming the core. In this case, after the formation of the composite fiber having the core-sheath structure, the core part formed of the fiber-forming organic material is removed by immersing the composite fiber having the core-sheath structure in a solvent. be able to.

《Dispersing aid》
In order to improve the dispersibility of the nanoparticles or to disperse them at a high concentration, it is desirable to use a dispersion aid between the inorganic nanoparticles used in the present invention and the matrix material. By using a dispersion aid, it becomes possible to bond inorganic nanoparticles to the matrix material at a portion other than the inorganic nanoparticle-capturing functional group of the matrix material, or to disperse the functional group portion of the matrix material. By binding the auxiliary agent, a stronger particle capturing group can be formed, and as a result, the dispersibility of the inorganic nanoparticles can be further improved.

  The dispersion aid is not particularly limited as long as it improves the dispersibility of the inorganic nanoparticles, but at one end, affinity and coordination with a hydrophobic group or polymer having good affinity with the matrix material. And a functional group that reacts with the surface modification molecule of the nanoparticle or a functional group containing elements such as nitrogen, sulfur, and phosphorus that have nanoparticle capture properties. It is preferable that it is an amphiphilic compound.

  Examples of the dispersion aid include acids such as carboxylic acids having 6 to 22 carbon atoms, sulfonic acids, sulfinic acids, and phosphonic acids, and basic organic compounds such as amines having 6 to 22 carbon atoms. In the present invention, among these, a silane coupling agent having an alkoxy group and containing silicon in the skeleton can be preferably used. In particular, when metal nanoparticles are used as the inorganic nanoparticles in the present invention, it is preferable to use a silane coupling agent having a group having a strong interaction with a metal such as an amino group or a mercapto group.

When the inorganic nanoparticles are metal or metal oxide nanoparticles, a silane coupling agent represented by the following formula is preferably used. Here, R is OCH ₃ , OC ₂ H ₅ , Cl, CH ₃ , R ′ is SH, NH ₂ , CH ₃ , NCO, and the like.

<Other additives>
Moreover, as long as the effect of the present invention is not impaired, an additive or the like according to the purpose may be included between the inorganic nanoparticles and the matrix material. For example, inorganic organic electrolytes, antioxidants, antifreeze agents, pH adjusters, hiding agents, colorants, plasticizers, surfactants, special functional agents and other additives, or elastomers and resins are included. May be.

  The method of adding an optional additive is not particularly limited as long as the dispersion state of the nanoparticles is not adversely affected, and it is added to any of the matrix material to be used, the dispersion medium of the inorganic nanoparticles, or the dispersion solution. Also good.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example etc., this invention does not receive a restriction | limiting at all by these examples. Unless otherwise specified, the solvents used in Examples and Comparative Examples are anhydrous reagents.

"Measuring method"
In Examples and Comparative Examples, the following items were measured and evaluated by the following methods.

(1) Confirmation of average fiber diameter of fiber and nanoparticle aggregate in fiber A deposit of ultrafine fibers was collected, and a transmission photograph (5000 times) was taken with DIGITALMICROSCOCOPY (trade name: VHX-200, manufactured by KEYENCE). Five measurement areas were randomly selected from the obtained photographs, five fibers were randomly extracted from one area, and the fiber diameter was measured for a total of 25 fibers. An average value of all measurement results (n = 25) was obtained, and the obtained value was defined as an average fiber diameter of the fibers.

  Moreover, in the obtained transmission photograph (5000 times), the presence or absence of the aggregation spot of a nanoparticle was evaluated.

(2) Dispersion particle size of nanoparticles in fiber (dispersibility evaluation)
A deposit of ultrafine fibers was collected, and a transmission electron microscope (TEM) observation sample by an embedding method was prepared. Subsequently, a 90-nm thin piece was formed using a microtome (Leica, trade name: ULTRACUT-S), and transmission electron microscope (FEI, trade name: TECNAI G2) was used for TEM observation and photographing (acceleration voltage 120 kV). 750,000 times).

  The obtained TEM image is further magnified four times, and all particles present in the 150 nm x 150 nm area are visually marked by judging the wrinkle of the particles based on the difference in contrast and allowing the computer to recognize them. It was. Subsequently, image analysis was performed using analysis software (NEXUS NEW CUBE) to obtain an average particle size and a maximum particle size.

  At this time, when the shape (planar shape) of the particles observed in the TEM photograph is not circular, a circular shape having the same area as that of the observed inorganic nanoparticles is assumed, and the diameter of the assumed circle is determined as the particle size. It was.

  Moreover, when the independence of the nanoparticles was difficult to understand visually, the determination was made by 3D-TEM observation. In 3D-TEM observation, the ratio of isolated and dispersed particles (no overlap on a plane) to the total number of particles in an area of 150 nm × 150 nm is evaluated as one index of the degree of aggregation of nanoparticles. did.

  In addition, the specific compounding ratio of the embedding resin (epoxy resin: Nisshin EM Co.) used for preparation of the sample for TEM observation is as follows.

Main agent: Quetol 812 77.2
Soft curing agent: DDSA 60
Hard curing agent: MNA 35.6
Polymerization accelerator: DMP-30 2.6

(3) Aggregation state of inorganic nanoparticles in fiber In the photographic image taken in (2) above, from the particle size distribution obtained using image analysis software (NEXT US QUEBE), the number of particles of 20 nm or less / total particles The number x100 (%) was obtained.

Example 1 PVB / Ag (35% by mass) // PS
Here, “PVB / Ag (35% by mass) // PS” has, as a core part, a dispersion in which 35% by mass of silver nanoparticles (Ag) are dispersed in polyvinyl butyral (“PVB”). And a fibrous composite having polystyrene (“PS”) as a sheath portion. Similar expressions are used for the following examples.

<Preparation of dispersion solution (core forming solution)>
1 g of polyvinyl butyral (“PVB”) (trade name: polyvinyl butyral first grade, average degree of polymerization: 2400), which was dried at 70 ° C. for one week, was completely dissolved in 19 g of dichloromethane to obtain a PVB solution. .

  Using 10 g of the above PVB solution, a colloidal solution of Ag nanoparticles containing alkylamine as a surfactant (manufactured by Toda Kogyo Co., Ltd., trade name: nanosilver dispersion, dispersion: toluene, Ag nanoparticle content: 53 mass% , Ag nanoparticle average particle diameter: 6 to 8 nm, alkylamine content: 11 mass%) was added and stirred for 1 hour to obtain an Ag nanoparticle-PVB dispersion solution.

<Preparation of fiber forming solution (sheath forming solution)>
2 g of polystyrene (“PS”) (manufactured by Aldrich, Mw of about 280000) dried at 70 ° C. for one week was mixed with N, N′-dimethylformamide (manufactured by Wako, dehydrated solvent, “DMF”) and tetrahydrofuran (Wako). Tetrabutylammonium chloride (“TBAC”), which is an ionic surfactant, is completely dissolved in 18 g of a mixed solvent (volume ratio of 1: 1) of “THF”, which does not include a dehydrating solvent and a stabilizer. The solution was adjusted to 5 mM to obtain a PS solution.

<Electrostatic spinning using double nozzle>
The double nozzle used in the examples is a stainless steel tubular body (inner diameter 1.5 mm) used as a sheath forming nozzle and 23G (inner diameter 0.4 mm, outer diameter 0.65 mm) used as a core forming nozzle. Consisting of a needle. After finely adjusting the viscosity with each solvent, the Ag nanoparticle-PVB dispersion solution was introduced into the core forming nozzle and the PS solution was introduced into the sheath forming nozzle, and set in an electrostatic spinning apparatus. Adjusting the discharge rate of the core-forming solution and sheath-forming solution from the syringe pump to 0.5 ml / hr and 4.0 ml / hr, applying voltage of 16 kV and flight distance of 20 cm, adhesive with stainless steel collecting electrode Stable spinning was performed on the prevention PET film. From the color of the droplet at the tip of the nozzle and the color tone of the obtained electrospun fiber, it was estimated that a core-sheath structure was formed.

  Using the fiber produced on the PET film, the shape of the fiber was observed with an optical microscope, and the average fiber diameter was determined to be 0.89 μm. From a 5000 × transmission photograph (FIG. 2), it was confirmed that there was no aggregate of 200 nm or more of nanoparticles dispersed in the fiber.

  The above fibers are collected on a PET film with a window (1.0 x 0.5 mm), and after Pt deposition on both sides, embedded in epoxy resin and cured, sliced thinly from a microtome for TEM observation A sample was used.

  From the TEM observation photographs (FIGS. 3 and 4), the core-sheath structure of the prepared fiber was confirmed, there was no aggregate of Ag nanoparticles of 30 nm or more, and high concentration packing and high dispersion of nanoparticles in the microfiber were achieved. It is understood that

Example 2 PVB (MPTMS) / Ag (50% by mass) // PS
<Preparation of dispersion solution (core forming solution)>
1 g of polyvinyl butyral (referred to as “PVB”) (trade name: polyvinyl butyral first grade, average degree of polymerization: 700) dried for one week at 70 ° C. was completely dissolved in 19 g of dichloromethane, and the PVB solution was dissolved. Obtained.

  Take 10 g of the PVB solution obtained above and add 0.1 g of gamma mercaptopropyltrimethoxysilane (“MPTMS”, manufactured by Chisso Corporation) as a dispersion aid (corresponding to twice the surface modifier of Ag nanoparticles). Then, the MPTMS coupling PVB (referred to as “PVB (MPTMS)”) solution was obtained by carrying out the coupling reaction by stirring for 30 minutes.

  Subsequently, a colloidal solution of Ag nanoparticles containing alkylamine as a surfactant (trade name: Nanosilver dispersion, toluene dispersion, Ag nanoparticle content: 53, manufactured by Toda Kogyo Co., Ltd.) in the obtained coupling PVB solution. 1.0% by mass, Ag nanoparticle average particle diameter: 6 to 8 nm, alkylamine content: 11% by mass) was added and stirred for 1 hour to obtain an Ag nanoparticle-PVB dispersion solution.

<Preparation of fiber forming solution (sheath forming solution)>
2 g of polystyrene (“PS”) (manufactured by Aldrich, Mw of about 280000) dried at 70 ° C. for one week was mixed with N, N′-dimethylformamide (manufactured by Wako, dehydrated solvent, “DMF”) and tetrahydrofuran (Wako). It was completely dissolved in 18 g of a mixed solvent (volume ratio 1: 1) of “THF”, which does not include a dehydrated solvent and a stabilizer, and was prepared so that TBAc was 5 mM to obtain a PS solution.

<Electrostatic spinning using double nozzle>
The double nozzle used in the examples is a stainless steel tubular body (inner diameter 1.5 mm) used as a sheath forming nozzle and 23G (inner diameter 0.4 mm, outer diameter 0.65 mm) used as a core forming nozzle. Consisting of a needle. After finely adjusting the viscosity with each solvent, the Ag nanoparticle-PVB dispersion solution was introduced into the core forming nozzle and the PS solution was introduced into the sheath forming nozzle, and set in an electrostatic spinning apparatus. Adjust the discharge rate of the core-forming solution and sheath-forming solution from the syringe pump to 0.5 ml / hr and 3.0 ml / hr, respectively, when the applied voltage is 15 kV and the flight distance is 20 cm. Stable spinning on PET film was obtained. From the color of the droplet at the tip of the nozzle and the color tone of the obtained electrospun fiber, it was estimated that a core-sheath structure was formed.

  Using fibers prepared on a PET film, the shape of the fibers was observed with an optical microscope and the average fiber diameter (0.92 μm) was determined. From the 5000 × transmission photograph (FIG. 5), the fibers were dispersed in the fibers. It was confirmed that there was no aggregate of 200 nm or more of the nanoparticles.

  The above fiber is collected on a PET film with a window (1.0 x 0.5 mm), deposited on both sides of Pt, embedded in epoxy resin, cured and dried, sliced thinly from a microtome, and observed by TEM A sample was used.

  From the TEM observation photograph (FIG. 6), the core-sheath structure of the produced fiber was confirmed, there was no aggregate of Ag nanoparticles of 30 nm or more, and high concentration packing and high dispersion of nanoparticles in the microfiber were achieved. Is understood.

Example 3 PVB (MPTMS) / Fe ₃ O ₄ (50% by mass) // PS
<Preparation of dispersion solution (core forming solution)>
1 g of polyvinyl butyral (“PVB”) (trade name: polyvinyl butyral first grade, average degree of polymerization: 2400), which was dried at 70 ° C. for one week, was completely dissolved in 19 g of dichloromethane to obtain a PVB solution. .

  10 g of the PVB solution obtained above was taken, and 0.05 g (corresponding to 10% by mass of PVB) of gamma mercaptopropyltrimethoxysilane (“MPTMS”, manufactured by Chisso Corporation) was added as a dispersion aid, and 30 minutes An MPTMS coupling PVB solution (“PVB (MPTMS)”) solution was obtained by carrying out the coupling reaction with stirring.

Subsequently, a colloidal solution of Fe ₃ O ₄ nanoparticles not disclosed in the surfactant (trade name: magnetic nano particle dispersion, dispersion: toluene, Fe ₃ O ₄ nano, manufactured by Toda Kogyo Co., Ltd.) was not added to the obtained coupling PVB solution. Particle content: 16% by mass, Fe ₃ O ₄ nanoparticle average particle size: 15 nm, surfactant content: unknown) 3.2 g was added and kept on a tube mixer for 15 minutes, Fe ₃ O ₄ nano A particle-PVB dispersion solution was obtained.

<Preparation of fiber forming solution (sheath forming solution)>
2 g of polystyrene (“PS”) (manufactured by Aldrich, Mw of about 280000) dried at 70 ° C. for one week was mixed with N, N′-dimethylformamide (manufactured by Wako, dehydrated solvent, “DMF”) and tetrahydrofuran (Wako). A PS solution was obtained by completely dissolving in 18 g of a mixed solvent (volume ratio of 1: 1) of “THF” without dehydration solvent and stabilizer, and adjusting the TBAc to 5 mM.

<Electrostatic spinning using double nozzle>
The double nozzle used in the examples is a stainless steel tubular body (inner diameter 1.5 mm) used as a sheath forming nozzle and 23G (inner diameter 0.4 mm, outer diameter 0.65 mm) used as a core forming nozzle. Consisting of a needle. After finely adjusting the viscosity with each solvent, the Fe ₃ O ₄ nanoparticle-PVB dispersion solution was introduced into the core forming nozzle and the PS solution was introduced into the sheath forming nozzle, and set in the electrostatic spinning apparatus. . Adhesives spread on a stainless steel collection electrode by adjusting the discharge rates of the core-forming solution and sheath-forming solution from a syringe pump to 0.5 ml / hr and 3.0 ml / hr, respectively, with an applied voltage of 15 kV and a flight distance of 20 cm. Stable spinning was obtained on the prevention PET film. From the color of the droplet at the tip of the nozzle and the color tone of the obtained electrospun fiber, it was estimated that a core-sheath structure was formed.

  Using the fiber produced on the PET film, the shape of the fiber was observed with an optical microscope, and the average fiber diameter was determined to be 0.93 μm. From a 5000 × transmission photograph, it was confirmed that there were no aggregates of 200 nm or more of nanoparticles dispersed in the fiber.

  The above fiber is collected on a PET film with a window (1.0 x 0.5 mm), deposited on both sides of Pt, embedded in epoxy resin, cured and dried, sliced thinly from a microtome, and observed by TEM A sample was used.

From the TEM observation photograph (FIG. 7), the core-sheath structure of the prepared fiber was confirmed, there was no aggregate of Fe ₃ O ₄ nanoparticles of 30 nm or more, and high concentration packing and high dispersion of nanoparticles in the microfiber were achieved. It is understood that

Example 4 PVB (MPTMS) / Fe ₃ O ₄ (50% by mass) // PEG
<Preparation of dispersion solution (core forming solution)>
1 g of polyvinyl butyral (“PVB”) (trade name: polyvinyl butyral first grade, average degree of polymerization: 2400), which was dried at 70 ° C. for one week, was completely dissolved in 19 g of dichloromethane to obtain a PVB solution. .

  Taking 10 g of the PVB solution obtained above, 0.1 g of gamma mercaptopropyltrimethoxysilane (“MPTMS”, manufactured by Chisso Corporation) as a dispersion aid (corresponding to 10% by mass with respect to PVB) is added, and 30 minutes An MPTMS coupling PVB (“PVB (MPTMS)”) solution was obtained by carrying out the coupling reaction with stirring.

Subsequently, a colloidal solution of Fe ₃ O ₄ nanoparticles (trade name: magnetic nanoparticle dispersion, dispersion: toluene, Fe ₃ O, manufactured by Toda Kogyo Co., Ltd.), which does not disclose information on the surface modifier, was added to the obtained coupling PVB solution. ₄ nanoparticle content: 16% by mass, Fe ₃ O ₄ nanoparticle average particle diameter: 15 nm) 3.2 g was added and kept on a tube mixer (NS-80, manufactured by Inoue Seieido Co., Ltd.) for 15 minutes. An Fe ₃ O ₄ nanoparticle-PVB dispersion solution was obtained.

<Preparation of fiber forming solution (sheath forming solution)>
1.4 g of polyethylene glycol (“PEG”, manufactured by Aldrich, Mw of about 300,000 to 500,000) is mixed with ethanol (made by Wako Pure Chemical Industries, Ltd., anhydrous solvent) and pure water (ion exchange water) (volume ratio 1: 1) It completely dissolved in 18.6 g to obtain a PEG solution.

<Electrostatic spinning using double nozzle>
The double nozzle used in the examples is a stainless steel tubular body (inner diameter 1.5 mm) used as a sheath forming nozzle and 23G (inner diameter 0.4 mm, outer diameter 0.65 mm) used as a core forming nozzle. Consisting of a needle. After fine-tuning the viscosity with the respective solvent, the Fe ₃ O ₄ nanoparticle-PVB dispersion solution is introduced into the core forming nozzle and the PEG solution is introduced into the sheath forming nozzle, and the core and the sheath are generated from the syringe pump. Stable spinning on an anti-adhesive PET film with a stainless steel collection electrode when the component discharge rate is adjusted to 0.5 ml / hr and 2.5 ml / hr, the applied voltage is 12 kV and the flight distance is 18 cm. Was obtained. From the color of the droplet at the tip of the nozzle and the color tone of the obtained electrospun fiber, it was estimated that a core-sheath structure was formed.

  Using the fiber produced on the PET film, the shape of the fiber was observed with an optical microscope, and the average fiber diameter was determined to be 0.95 μm. From a 5000 × transmission photograph, it was confirmed that there were no aggregates of 200 nm or more of nanoparticles dispersed in the fiber.

  The above-prepared fibers are collected on a PET film with a window (1.0 × 0.5 mm), and after double-sided Pt deposition, embedded in an epoxy resin and cured, then sliced thinly from a microtome, TEM It was set as the sample for observation.

From the TEM observation photographs (FIGS. 8 and 9), the core-sheath structure of the produced fiber was confirmed, there was no aggregate of Fe ₃ O ₄ nanoparticles of 30 nm or more, and the nanofibers were highly packed and highly dispersed in the microfibers. It is understood that has been achieved.

Example 5 PSQ / Ag 50% by mass // PS
<Preparation of dispersion solution (core forming solution)>
Polysilsesquioxane (“PSQ”, manufactured by Konishi Chemical Co., Ltd.) SR20 (Mw about 6400) and SR23 (Mw about 910) mixture (SR20 / SR23), which is an organic-inorganic hybrid oligomer without spinnability when used alone = 1: 2 (weight ratio)) is weighed 3 g, completely dissolved in 10 g of a mixed solvent of toluene and dichloromethane (1: 1 weight ratio), and a colloidal solution of Ag nanoparticles (manufactured by Toda Kogyo Co., Ltd., trade name: Nano Silver) 5 g of dispersion, toluene dispersion, Ag nanoparticle content: 53 mass%, Ag nanoparticle average particle size: 6-8 nm, alkylamine content: 11 mass%) are added and dispersed by applying to a tube mixer for 15 minutes. , Ag nanoparticle-PSQ dispersion solution was obtained.

<Preparation of fiber forming solution (sheath forming solution)>
2 g of polystyrene (“PS”) (manufactured by Aldrich, Mw about 280000) dried for one week at 70 ° C. was added to N, N′-dimethylformamide (manufactured by Wako Pure Chemical Industries, Ltd., dehydrated solvent, “DMF”). It is completely dissolved in 18 g of a mixed solvent (DMF / THF = 1: 1, volume ratio) of tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd., dehydrated solvent, does not contain stabilizer, “THF”) so that TBAc becomes 5 mM. To obtain a PS solution.

<Electrostatic spinning using double nozzle>
The double nozzle used in the examples is a stainless steel tubular body (inner diameter 1.5 mm) used as a sheath forming nozzle and 23G (inner diameter 0.4 mm, outer diameter 0.65 mm) used as a core forming nozzle. Consisting of a needle. After fine-tuning the viscosity with each solvent, the Ag nanoparticle-PSQ dispersion solution is introduced into the core forming nozzle and the PS solution is introduced into the sheath forming nozzle, and the core and sheath generating components are discharged from the syringe pump. When the amount is adjusted to 0.4 ml / hr and 4.0 ml / hr, the applied voltage is 15 kV and the flight distance is 18 cm, stable spinning can be obtained on an anti-adhesive PET film with a stainless steel collecting electrode. It was. From the color of the droplet at the tip of the nozzle and the color tone of the obtained electrospun fiber, it was estimated that a core-sheath structure was formed.

  Using the fiber produced on the PET film, the shape of the fiber was observed with an optical micrograph (FIG. 10), and the average fiber diameter was determined to be 0.87 μm. From the transmission photograph (FIG. 11), it was confirmed that there was no aggregate of 200 nm or more of nanoparticles dispersed in the fiber.

Example 6 Oil // PVB (MPTMS) / Fe ₃ O ₄ (40% by mass)
<Preparation of dispersion solution (sheath forming solution)>
1 g of polyvinyl butyral (“PVB”) (manufactured by Wako Pure Chemical Industries, Ltd., trade name: polyvinyl butyral first grade, average degree of polymerization: 2400) dried at 70 ° C. for one week was completely dissolved in 19 g of dichloromethane to obtain a PVB solution. Got. 10 g of the PVB solution was taken, 0.05 g of gamma mercaptopropyltrimethoxysilane (“MPTMS”, manufactured by Chisso Corporation) as a dispersion aid was added and stirred for 30 minutes to MPTMS By performing the coupling reaction, an MPTMS coupled PVB (“PVB (MPTMS)”) solution was obtained.

In the obtained coupling PVB solution, a colloidal solution of Fe ₃ O ₄ nanoparticles not disclosed for the surface modifier (trade name: magnetic nanoparticle dispersion, toluene dispersion, nanoparticle content: 16 manufactured by Toda Kogyo Co., Ltd.) Add 2.5 g of mass%, nanoparticle average particle size: 15 nm), and continue to apply to a tube mixer (NS-80, manufactured by Inoue Seieido Co., Ltd.) for 15 minutes to obtain a Fe ₃ O ₄ nanoparticle-PVB dispersion solution. Got.

<Preparation of fiber forming solution (core forming solution)>
Mineral oil (manufactured by Sigma Aldrich, white heavy) was used as the core forming solution.

<Electrostatic spinning using double nozzle>
The double nozzle used in the examples is a stainless steel cylindrical body (inner diameter 2.0 mm) used as a sheath part forming nozzle and 22G (inner diameter 0.48 mm, outer diameter 0.70 mm) used as a core part forming nozzle. Consisting of a needle. Mineral oil and Fe ₃ O ₄ nanoparticle-PVB dispersion solution are set as a core forming solution and a sheath forming solution, respectively, in this electrostatic spinning device equipped with a double nozzle, and the discharge amount is 0.3 ml by a syringe pump. / Hr and 2.4 ml / hr, an applied voltage of 14 kV and a spinning distance between the nozzle and the collecting electrode of 170 mm, stable spinning was performed on the aluminum foil-coated stainless steel electrode.

  The collected fibers are immersed in octane (manufactured by Wako Pure Chemical Industries, Ltd.) overnight, extracted with oil, dried, fixed to adhesive tape, thrown into liquid nitrogen, folded tape, Pt deposited, and FE -It was set as the sample for observation of SEM (made by Hitachi, Ltd.).

  The average diameter of the fiber produced from the SEM photograph was determined to be 2.8 μm, and the hollow structure after oil extraction was confirmed. According to this, it is understood that the diameter of the hollow portion and the thickness of the wall can be adjusted by optimizing and adjusting the discharge amount of the core forming solution and the sheath forming solution.

Example 7 PVB (MPTMS) / Fe ₃ O ₄ (40% by mass) // PVP / TiO ₂ (30% by mass)
<Preparation of dispersion solution (core forming solution)>
1 g of polyvinyl butyral (“PVB”) (manufactured by Wako Pure Chemical Industries, Ltd., trade name: polyvinyl butyral first grade, average degree of polymerization: 2400) dried at 70 ° C. for one week was completely dissolved in 19 g of dichloromethane to obtain a PVB solution. Got. Take 10 g of the PVB solution, add 0.75 g of gamma mercaptopropyltrimethoxysilane (“MPTMS”, manufactured by Chisso Corporation) as a dispersion aid (corresponding to 15% by mass with respect to PVB), and stir for 30 minutes. By carrying out the ring reaction, an MPTMS coupled PVB (“PVB (MPTMS)”) solution was obtained.

In the obtained coupling PVB solution, a colloidal solution of Fe ₃ O ₄ nanoparticles not disclosed for the surface modifier (trade name: magnetic nanoparticle dispersion, toluene dispersion, nanoparticle content: 16 masses, manufactured by Toda Kogyo Co., Ltd.) %, Average particle size of nanoparticle: 15 nm) was added, and the mixture was continuously applied to a tube mixer (NS-80, manufactured by Inoue Seieido Co., Ltd.) for 15 minutes, and the Fe ₃ O ₄ nanoparticle-PVB dispersion solution was added. Obtained.

<Preparation of dispersion solution (sheath forming solution)>
Polyvinylpyrrolidone (manufactured by Alderich, Mw about 1300000) was weighed in 1.4 g and completely dissolved in 18.6 g of a mixed solvent of ethanol and water (ethanol: water = 1: 2, weight ratio) to obtain a PVP solution.

2 g of titanium oxide slurry (manufactured by C-I Kasei Co., Ltd., TiO ₂ content 15 mass% alcohol dispersion, average particle size: less than 20 nm) was added to the 10 g PVP solution, and the mixture was applied to a tube mixer for 15 minutes, followed by TiO ₂ A particle-PVP dispersion solution was obtained.

<Electrostatic spinning using double nozzle>
The double nozzle used in the examples is a stainless steel cylindrical body (inner diameter 1.5 mm) used as a sheath part forming nozzle and 22G (inner diameter 0.48 mm, outer diameter 0.70 mm) used as a core part forming nozzle. Consisting of a needle. The Fe ₃ O ₄ nanoparticle-PVB dispersion solution and the TiO ₂ nanoparticle-PVP dispersion solution are respectively introduced into the core / sheath forming nozzle, and the discharge amount of the core forming solution and the sheath forming solution is 0.4 ml from the syringe pump. / Hr and 3.0 ml / hr, an applied voltage of 8.5 kV and a spinning distance between the nozzle and the collecting electrode of 170 mm, stable spinning was performed on the aluminum foil-coated stainless steel electrode.

  The average fiber diameter was determined to be about 1.26 μm from an optical microscope photograph.

<Reference Example 1> PVB2400 / Fe ₃ O ₄ (33.3 mass%)
1 g of polyvinyl butyral (hereinafter referred to as “PVB”) dried at 70 ° C. for one week (trade name: polyvinyl butyral first grade, average polymerization degree: 2400) manufactured by Wako Pure Chemical Industries, completely dissolved in 19 g of DCM, A solution was obtained.

To the obtained PVB solution, a colloidal solution of Fe ₃ O ₄ nanoparticles containing alkylamine as a surfactant (manufactured by Toda Kogyo Co., Ltd., trade name: magnetic nanoparticle dispersion, dispersion: toluene, Fe ₃ O ₄ nanoparticles) 3.25 g of content: 16% by mass, average particle size of nanoparticles: 15 ± 3 nm) was added, and the mixture was stirred for 15 minutes with a tube mixer to prepare a Fe ₃ O ₄ nanoparticle-PVB composite solution.

At this time, in the obtained Fe ₃ O ₄ nanoparticle-PVB composite solution, no color tone change due to aggregation of the Fe ₃ O ₄ nanoparticles is confirmed, and the Fe ₃ O ₄ nanoparticles are formed on the wall of the glass container. The precipitation of was not confirmed.

Furthermore, 10 g of the obtained Fe ₃ O ₄ nanoparticle-PVB complex solution was electrospun using a mixed solvent of dichloromethane (hereinafter referred to as “DCM”) and chloroform (70% by mass / 30% by mass). The composition for fiber formation was prepared by diluting to an appropriate concentration.

[Spinning process]
Using the fiber-forming composition (spinning solution) obtained above, the fiber-forming composition is ejected by an electrostatic spinning device, and the fibers are accumulated by continuously spinning, thereby forming a fiber deposit. Manufactured.

  The inner diameter of the ejection nozzle at this time was 0.4 mm (injection needle: 23 G), the capacity of the syringe was 10 ml, the voltage was 16.5 kV, and the distance from the ejection nozzle to the fiber collection electrode (stainless steel plate) was 20 cm. PET film in which the fiber-forming composition is jetted and attached to the collecting electrode while controlling the discharge amount of the fiber-forming composition to 50 μl / min by a syringe pump (trade name: MD-1020, manufactured by Bioanalytical Systems Inc.) Deposited on top of.

[Measurement evaluation]
The obtained Fe ₃ O ₄ nanoparticle-PVB composite fiber deposit was collected, and a transmission photograph (magnified 3000 times) taken with an optical microscope is shown in FIG. 12, and a transmission electron microscope (TEM) photograph ( FIG. 13 shows the observation magnification (360,000 times). The average fiber diameter of the obtained fiber was 3.24 μm, and Fe ₃ O ₄ nanoparticles were uniformly dispersed by TEM observation, and aggregation of 50 nm or more was not confirmed. The filling rate of Fe ₃ O ₄ was 30.7% by mass by TGA measurement.

<Reference Example 2> PVB2400 / Fe ₃ O ₄ (33.3 mass%) (bulk)
The Fe ₃ O ₄ nanoparticle-dispersed fiber deposit produced in Reference Example 1 was scraped and placed in pellets for IR measurement tablet production (made by PACAC, diameter 13 mm) that had been heat-treated at 80 ° C. for 1 hour. While pulling, molding was performed at a pressure of 300 kg / cm ² for 15 minutes. The molded disk-shaped lump (diameter 13 × 1 to 2 mm) was taken out, the surface fiber pattern was confirmed with an optical microscope, and hot pressing was performed 5 times per minute under the condition of 80 ° C. × 50 kg / cm ² . In addition, the glass transition temperature (Tg) of the polymer (PVB) constituting the fiber deposit was 70 to 80 ° C.

  The surface of the sample is checked with an optical microscope every minute, and after the fiber pattern has completely disappeared, it is heat-treated in an oven at 80 ° C. for 1 hour while being sandwiched between stainless steel plates, and bulk molding is made of nanoparticle-dispersed fiber deposits. A body sample was obtained.

  The manufactured bulk molded body sample was embedded in an epoxy resin, sliced from a microtome (ULTRACUT-S, manufactured by Leica), and a TEM observation of a cross section of the bulk sample was performed. It was confirmed that there was no void and no fiber pattern while maintaining the high dispersibility of the nanoparticles in the fiber (shown in FIG. 14).

Claims (12)

It is in the form of a fiber having a core part and a sheath part around the core part,
The average diameter of the sheath is 50 nm or more and 3 μm or less,
At least one of the core part and the sheath part is composed of a composite material of inorganic nanoparticles and matrix material containing inorganic nanoparticles and a matrix material, and the average primary particle diameter of the inorganic nanoparticles is 100 nm or less.
Inorganic nanoparticle-matrix material fibrous composite.   The average particle size of the inorganic nanoparticles is 1 nm or more and 20 nm or less, and in the inorganic nanoparticle-matrix material composite, 70% or more of the inorganic nanoparticles are dispersed in the form of a dispersed particle size of 30 nm or less. The fibrous composite according to claim 1.   The fibrous composite according to claim 1 or 2, wherein a content of the inorganic nanoparticle in the inorganic nanoparticle-matrix material composite is 30% by mass or more with respect to the composite material of the inorganic nanoparticle-matrix material. body.   One of the core part and the sheath part is made of an inorganic nanoparticle-matrix material composite material containing inorganic nanoparticles and a matrix material, and the other of the core part and the sheath part is made of a fiber-forming organic material. The fibrous composite according to any one of claims 1 to 3.   The fibrous composite according to any one of claims 1 to 3, wherein the sheath portion is composed of a composite material of inorganic nanoparticles and matrix material containing inorganic nanoparticles and a matrix material, and the core portion is a cavity. body.   The fibrous composite according to any one of claims 1 to 3, wherein both the core part and the sheath part are made of a composite material of inorganic nanoparticle-matrix material containing inorganic nanoparticles and a matrix material.   A method for producing a bulk composite, comprising pressing and molding the fibrous composite according to any one of claims 1 to 6 under conditions for maintaining the dispersed state of the inorganic nanoparticles.   The manufacturing method of a fibrous composite including removing the part which consists of the organic material for fiber formation of the said core part and sheath part of the said fibrous composite of Claim 4.   A bulk composite comprising: obtaining a fibrous composite by the method according to claim 8; and pressing and molding the obtained fibrous composite under a condition that maintains a dispersion state of the inorganic nanoparticles. A method for producing the composite. Providing a dispersion solution containing the inorganic nanoparticles, the matrix material, and a solvent;
Providing a fiber forming solution containing an organic material for fiber formation and a solvent;
Using an electrospinning apparatus having a double nozzle, spinning the dispersion solution from one of the double nozzles, and spinning the fiber-forming solution from the other of the double nozzles;
The manufacturing method of the fibrous composite of Claim 4 containing this. The method according to claim 10, wherein the dispersion forming solution is spun from an outer nozzle of the double nozzle, and a fiber forming solution is spun from the inner nozzle of the double nozzle, whereby the organic material for fiber formation is used. And a fibrous composite having a sheath made of the inorganic nanoparticle-matrix material composite, and the fiber-forming organic material constituting the core of the fibrous composite is removed. about,
The manufacturing method of the fibrous composite of Claim 5 containing this. Providing two types of dispersion solutions containing the inorganic nanoparticles, the matrix material, and a solvent;
Using an electrostatic spinning device having a double nozzle, one of the dispersion solutions is spun from one of the double nozzles, and the other of the dispersion solutions is spun from the other of the double nozzles. Spinning,
The manufacturing method of the fibrous composite of Claim 6 containing this.