JP2010229563A - Method for producing particle-polymer fibrous composite - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently producing a particle-polymer composite in which particles are highly dispersed. <P>SOLUTION: The method for producing a particle-polymer fibrous composite includes: a step (32) for preparing a fiber-forming composition containing particles and a polymer; and a step of jetting the fiber-forming composition from a spinning portion (31) by an electrospinning method and spinning a fiber. In the spinning, vibration is supplied (31a) to the spinning portion (31). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a particle-polymer fibrous composite, and more particularly to a method for producing an inorganic nanoparticle-polymer fibrous composite.

  Using composites of particles and polymer materials, it has been studied to provide both properties derived from particles and properties derived from a polymer that is a matrix.

  In this regard, in particular, it has been proposed to use nanoparticles having a particle size of 30 nm or less, for example, when the particle size is very small as the particles to be dispersed in the matrix polymer. Such inorganic nanoparticles have significantly different chemical, physical, electrical, magnetic, and optical properties from bulk materials due to size effects, quantum effects, etc. Therefore, inorganic nanoparticles are incorporated into matrix materials. Establishment of a technique for uniformly dispersing and controlling the dispersion state and immobilizing it was an extremely important issue for applied research of inorganic nanoparticles.

As for the method for producing the inorganic nanoparticle-polymer composite (composite material), the following three methods are known.
(1) A method of directly dispersing inorganic nanoparticles in a polymer material (direct kneading method) (see Patent Documents 1 and 2).
(2) A method of blending an organic monomer with inorganic nanoparticles and then polymerizing the organic monomer (in-situ polymerization method) (see Patent Documents 3 to 7).
(3) An ion doping reduction method in which metal nanoparticles are precipitated in a polymer material by superheating reduction treatment in a reducing gas after the polymer material is doped with metal ions or metal complexes (see Patent Document 8).

  As a method for producing a fiber assembly made of ultrafine fibers (particularly, ultrafine fibers referred to as “nanofibers”), a method called electrostatic spinning (electrospinning) is known. For example, Patent Document 9 can be referred to for the electrostatic spinning method.

  In the electrostatic spinning method, a charged spinning solution is spun into an atmosphere in which an electrostatic field is formed, and collected as a fiber assembly, whereby a web having a fiber diameter of submicron order or micron order is obtained. In recent years, it has become possible to obtain a fibrous aggregate having a fiber diameter of nanometer order.

  Patent Document 10 examines the supply of ultrasonic waves to the spinning section in a spinning method such as an electrostatic spinning method.

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 2008-190055 A JP 2008-223208 A

  The present invention provides a method for efficiently producing a particle-polymer complex in which particles are highly dispersed.

  The present inventors use a polymer solution in which particles are uniformly dispersed to create a fiber assembly from the polymer solution by an electrostatic spinning method (electrospinning method), and in this electrostatic spinning method, The inventors have found that the above problems can be solved by applying vibration to the spinning section, and have completed the present invention described below.

<1> a step of preparing a fiber-forming composition containing particles and a polymer, and a step of spinning the fiber by ejecting the fiber-forming composition from a spinning part by an electrostatic spinning method.
And a method for producing a particle-polymer fibrous composite comprising supplying vibration to the spinning section during spinning.
<2> The method according to <1>, wherein the vibration is ultrasonic vibration.
<3> The method according to <1> or <2>, wherein the particle-polymer fibrous composite has an average fiber diameter of 50 nm to 4 μm.
<4> The method according to any one of <1> to <3>, wherein the average primary particle diameter of the particles is 100 nm or less.
<5> The method according to any one of <1> to <4>, wherein the content of the particles is 20% by mass or more based on the entire fibrous composite.
<6> Obtaining the fibrous composite by the method according to any one of <1> to <5> above, and pressurizing the fibrous composite under conditions for maintaining a dispersed state of the particles. A method for producing a particle-polymer bulk composite.
<7> The method according to <6> above, wherein the fibrous composite is pressed and molded.

  According to the method of the present invention for producing a particle-polymer fibrous composite, electrostatic repulsive force between charged particles is suppressed by electrostatic spinning while suppressing aggregation of particles within one-dimensional ultrafine fibers. Can be used to effectively prevent the particles from agglomerating, and the solvent can be instantly evaporated by the amount of fine fibers, thereby achieving uniform dispersion of the particles. Still further, according to the method of the present invention, by supplying vibration to the spinning section, the increase in the viscosity of the fiber-forming composition is suppressed to maintain or promote particle dispersibility, and the nozzle used as the spinning section is clogged. And the like can be achieved. That is, according to the method of the present invention, stable production of the particle-polymer fibrous composite, promotion of particle dispersibility, and the like can be achieved.

  In addition, according to the method of the present invention for producing a bulk composite, the functions specific to the contained particles can be utilized in the form of a shaped bulk. In the context of the present invention, “bulk” refers to a composite in which the composite has a three-dimensional extension, whereby the effect of the surface can be ignored, and the properties as a material having a specific shape can be exhibited. I mean. That is, “bulk” in the present invention is a concept used in the opposite sense to fine fibers, fine powders and the like.

It is the schematic of the electrospinning apparatus which can implement the method of this invention. It is a figure which shows the viscosity raise mechanism of a spinning part when using the inorganic nanoparticle of dielectric material as particle | grains. It is a sample preparation image for TEM observation by an inverted embedding method. 2 is a transmission electron microscope (TEM) photograph of a deposit of Fe ₃ O ₄ nanoparticle-dispersed PVB fibers obtained in Example 1. FIG. ₄ is a transmission electron microscope (TEM) photograph of a deposit of Fe ₃ O ₄ nanoparticle-dispersed PVB fibers obtained in Comparative Example 1. FIG. 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.

Details of the present invention will be described below.
<Method of the present invention for producing particle-polymer fibrous composite>
The method of the present invention includes a step of preparing a fiber-forming composition containing particles and a polymer, and a step of spinning the fiber by ejecting the fiber-forming composition from a spinning portion by an electrostatic spinning method. . Here, in the method of the present invention, at the time of spinning, by supplying vibration, particularly ultrasonic vibration, to the spinning part, an increase in the viscosity of the fiber-forming composition is suppressed, and particle dispersibility is maintained or maintained. Promotion, suppression of nozzle clogging, etc. can be achieved.

<Process for preparing fiber-forming composition>
In the method of the present invention, first, a fiber-forming composition containing particles and a polymer is prepared. This fiber-forming composition can have an arbitrary composition as long as it can be spun by an electrospinning method. In addition, a dispersion assisting device such as a bead mill can be used for dispersing the particles in the polymer. The concentration of the fiber-forming composition can be adjusted to an appropriate concentration for electrospinning by using an appropriate solvent.

<Spinning process>
Next, in the method of the present invention, the fiber forming composition is ejected from the spinning portion by an electrospinning method, and the fiber is spun. Further, in this spinning, vibration, particularly ultrasonic vibration is supplied to the spinning portion.

  Here, “electrospinning method” or “electrospinning method” means that a solution or dispersion containing a fiber-forming substrate is discharged into an electrostatic field formed between electrodes, and the solution or dispersion is discharged. In this method, a fibrous material is formed by spinning toward an electrode. The fibrous material obtained by spinning is usually laminated on an electrode that is a collection substrate.

  In addition, the fibrous substance to be formed is not only in a state where the fiber-forming solute and solvent contained in the fiber-forming composition are completely distilled off, but also remains in the fibrous substance. Including state.

<Fibrous composite>
In the method of the present invention, an arbitrary form of fibrous composite can be obtained. However, the average fiber diameter of the fibrous composite that can be obtained in the electrospinning apparatus of the present invention is usually from 50 nm to 4 μm, preferably from 50 nm to 2 μm, more preferably from 100 nm to 1 μm, and even more preferably 150 nm. The range is 800 nm or more and 500 nm or less.

  If the average fiber diameter is sufficiently small, it is considered that the space in which the particles dispersed in the fiber can be aggregated is limited from three dimensions to one dimension, and as a result, compared with a film obtained by a casting method or the like. Thus, particle aggregation can be physically prevented. In addition, as the average fiber diameter decreases, the surface area of the fiber greatly increases, and when a fiber forming composition is ejected from a nozzle by an electrostatic spinning method, a large amount of solvent is instantly evaporated by high-speed stretching. As a result, the particles can be fixed in the ultrafine fibers before aggregation occurs. That is, in the present invention, by these two synergistic effects, it is possible to significantly reduce the probability of aggregation of the particles in the polymer matrix and to highly disperse the particles almost in the state of primary particles.

  On the other hand, if the average fiber diameter is too small, it is difficult to stably produce fibers containing particles, and there is a risk of stress aggregation of the particles due to the strong 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 particles dispersed in the fiber is not greatly affected. Here, the “average fiber diameter” is an average value of the diameters of 25 fibers randomly selected from an optical micrograph using a sample of ultrafine fibers as a sample.

<Formation of bulk composite>
The fiber comprising such a particle-polymer fibrous composite can be made into a bulk form by a method including a step of pressurizing under a condition for maintaining the dispersed state of the particles. Here, in this pressurization, when the high temperature is too high or the applied pressure is too large, the mobility of the polymer chain is increased, the retention force on the particles is reduced, and the dispersed state of the particles in the fiber can be maintained. It may disappear. On the other hand, when pressurization is performed at an appropriate temperature and pressure, while maintaining the particles, the mobility of the polymer chains is increased to cause fusion between the fibers, thereby changing the dispersion state of the particles in the fibers. While maintaining, it can be made into a bulk composite, in particular a shaped bulk composite. That is, the conditions for forming a bulk composite by pressing while maintaining the dispersed state of the particles are the conditions in which the polymer maintains the dispersed state of the particles and the polymer has sufficient moldability.

  Such a condition is that, for example, when the polymer constituting the particle-polymer fibrous composite is a single amorphous polymer, such a particle-polymer fibrous composite is made of polymer glass. It can be molded by pressurizing at a temperature around the transition temperature, for example, within the range of the glass transition temperature of the polymer ± 10 ° C. Further, for example, when the polymer constituting the particle-polymer fibrous composite is substantially composed of a crystalline polymer, or when the crystalline polymer component is a main component, such particles-high The molecular fibrous composite can be molded by pressurization at a temperature in the vicinity of the softening point, for example, within the range of the softening point ± 10 ° C. Furthermore, for example, when the polymer constituting the particle-polymer fibrous composite is a blend of a crystalline polymer component and an amorphous polymer, such a particle-polymer fibrous composite is Can be molded by pressing in an appropriate temperature range between the melting point derived from the crystalline polymer and the glass transition temperature derived from the amorphous polymer.

  Here, the pressurization of the particle-polymer fibrous composite can optionally be accompanied by a reduced pressure of the atmosphere to promote the reduction of voids between the fibers. In general, the particle-polymer fibrous composite is preferably molded at a temperature lower than the melting point of the polymer. This is because particles dispersed in the polymer may reaggregate at a temperature higher than the melting point of the polymer.

<Composition for fiber formation>
The fiber-forming composition spun in the method of the present invention contains particles and a polymer.

<Fiber forming composition-particles>
(Primary particle size of particles)
The particles used in the present invention have an average primary particle size of 1 μm or less, 500 nm or less, 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 particle-polymer fibrous composite. It is preferable. Moreover, it is preferable that the average primary particle size is sufficiently small in order to stably produce the particle-polymer fibrous composite by the method of the present invention. In addition, the average primary particle size is sufficiently small, for example, 100 nm or less, the characteristic characteristic of the particles can be effectively expressed, light scattering can be suppressed, and thereby the application development to optical materials can be suppressed. It is preferable in that it can be performed.

  The “average primary particle size” before dispersing the particles in the particle-polymer fibrous composite is obtained by drying the dispersion of the particles and photographing the resulting dried product with a transmission electron microscope (TEM) (340,000). Image analysis software (NEXUS NEW QUEBE) is used for the acquired image, and image analysis is performed to determine 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.

(Particle material)
The material of the particles used in the present invention is not particularly limited. In the present invention, for example, particles of an inorganic material can be used, and can be appropriately selected and used based on functions and characteristics desired to be expressed in the composite. In addition, the particle | grains in this invention may be single 1 type, or may use multiple types simultaneously.

  When the fiber-forming composition containing particles of dielectric material is electrospun, the method of the present invention can be applied particularly effectively. This is because, when a voltage is applied to a spinning part holding such a fiber-forming composition, the particles in the spinning part are aligned by the action of an electric field, thereby making the apparent fiber-forming composition appear. By increasing the viscosity.

  The increase in the apparent viscosity of such a fiber-forming composition will be described with reference to FIG. Here, FIG. 2 shows that the fiber-forming composition containing the dielectric material particles 21 and the polymer 22 flows in the flow path 23 corresponding to the spinning portion in the direction indicated by the arrow 25. ing. When no voltage is applied to the flow path 23 corresponding to the spinning portion, the particles are substantially randomly distributed in the fiber-forming composition, as shown in FIG. On the other hand, when a voltage is applied to the flow path 23, as shown in FIG. 2 (b), the particles are aligned in the direction of the electric field in the fiber-forming composition, thereby forming the fiber-forming composition. Apparent viscosity increases.

(Particle coating)
The particles used in the present invention may be used as they are, but the surface thereof is protected by a surface modifying molecule having affinity, coordination and binding properties with the particles, for example, alkylamine. Is preferred. By using the particles coated with the surface modifying molecules, aggregation between the particles can be suppressed and the particles can be stably present in the state of primary particles. According to this, a higher dispersion state can be formed in the method of the present invention for producing a particle-polymer fibrous composite.

(Particle content)
The content (filling rate) of the metal particles in the particle-polymer fibrous composite is preferably a mass fraction, and is 5% by mass, 9% by mass, 10% by mass, and 15% by mass with respect to the entire complex. % Or more, 20 mass% or more, or 25 mass% or more. Further, the content (filling rate) of the particles in the particle-polymer fibrous composite is preferably a volume fraction of 0.5% by volume or more, 0.8% by volume or more, and 1. It is 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. When the content (filling rate) is sufficiently large, the function of the particles can be sufficiently exhibited, 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.

  The particle content (filling rate) in the composite is a value that can be measured by, for example, a thermogravimetric balance (TGA) (trade name: TGA8120, manufactured by Rigaku Corporation).

<Fiber forming composition-polymer>
As the polymer contained in the fiber-forming composition, any material can be used, which is based on the use of the particle-polymer fibrous composite, the affinity with the particles to be dispersed, and the like. Can be determined.

  The polymer contained in the fiber-forming composition is not particularly limited as long as it is a spinnable polymer. In addition, as such a polymer, a mixture of a plurality of polymers can be used.

  Preferred polymer materials from the viewpoint of spinnability include, for example, polyvinyl butyral, polyethylene oxide, polyvinyl alcohol, polyvinyl acetal, polyvinyl ester, polyvinyl ether, polyvinyl pyridine, polyacrylamide, ether cellulose, pectin, starch, polyvinyl chloride, poly Examples include acrylonitrile, polylactic acid, and copolymers thereof.

  In the present invention, it is preferable to use a polymer material having a functional group having a high particle coordinating property in addition to the spinnability, because the particles can be dispersed to a higher degree. Such a particle coordinating functional group is not particularly limited as long as it has a capturing ability for particles. In the present invention, a suitable functional group can be selected depending on the type of particles used, and examples include carboxylic acid groups (including acid anhydrides and carboxylates), amino groups, imide groups, amide groups, and the like. Can do.

(Polymer (molecular weight))
Needless to say, the polymer to be used must have a spinnability. However, in consideration of the self-supporting property, mechanical strength, workability, etc. of the obtained ultrafine fiber, the molecular weight may be in the range of 50,000 to 1,500,000. preferable. In addition to these, when considering the more stable dispersion of the particles, the molecular weight of the polymer is most preferably in the range of 80,000 to 500,000.

<Composition for fiber formation-other components>
The fiber-forming composition may contain additives and the like as long as the effects of the present invention are not impaired in addition to the above-described particles and polymer. That is, for example, for fiber-forming compositions, additives such as dispersion aids, antioxidants, antifreeze agents, pH adjusters, hiding agents, colorants, plasticizers, special functional agents, etc., that promote particle dispersion Or an elastomer, resin, etc. may be contained.

<Electrostatic spinning device>
A spinning device for carrying out the method of the present invention is, for example, as shown in FIG. In the electrostatic spinning device 30 shown in FIG. 1, a syringe 32 is used as a fiber-forming composition supply unit for supplying a fiber-forming composition 33, and a spinning nozzle 31 is used as a spinning unit. A fiber collecting electrode 35 is used as a collecting portion facing the 31. Further, a voltage is applied between the spinning nozzle 31 and the collecting electrode 35 by a voltage generator 34. Furthermore, a vibration supply unit 31 a that supplies vibration to the spinning nozzle 31 is disposed at the tip of the spinning nozzle 31. The fibrous composite spun from the spinning nozzle 31 is indicated by a dotted line in FIG.

  Here, as the spinning section for the electrostatic spinning apparatus, any spinning section capable of spinning the particle-polymer fibrous composite, for example, a spinning nozzle can be used.

  In addition, as for the shape of the nozzle for ejecting the composition for fiber formation, 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 varies depending on the fiber-forming composition used, but is preferably in the range of 0.05 to 1 mm. When the nozzle diameter is too small, the particles may be clogged in the nozzle or the injection may be discontinuous, making it difficult to produce stable fibers. On the other hand, when the nozzle diameter is too large, the fiber diameter to be manufactured becomes large, and thus 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.

  Further, as the spinning section for the electrostatic spinning device of the present invention, a spinning section having a tapered protrusion as shown in Patent Document 9 can also be used.

  Further, here, the strength and frequency of vibration supplied to the spinning section achieves suppression of increase in viscosity of the fiber-forming composition, maintenance or promotion of particle dispersibility in the composite, suppression of clogging of the spinning section, and the like. Can be selected. Further, it is preferable to select the intensity and frequency of the vibration so as not to cause resonance of the spinning section, heat storage, and the like. Therefore, for example, the vibration supplied by the vibration supply unit can be ultrasonic vibration, that is, vibration of, for example, 20 kHz or more, for example, 30 to 200 kHz.

  Further, this vibration is preferably supplied so as to reach the tip portion of the spinning portion. Therefore, for example, the vibration can be supplied from the spinning portion toward the direction in which the fibrous composite is spun.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

<Measuring method>
In the following examples and reference examples, the following items were measured and evaluated by the following methods.

(1) Average fiber diameter of fiber An ultrafine fiber deposit was collected, and a transmission photograph (5000 times) was taken with DIGITALMICROSCOCOPY (manufactured by KEYENCE, trade name: VHX-200). 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.

(2) Dispersion state of metal particles in composite fiber A deposit of ultrafine fibers was collected, and a transmission electron microscope (TEM) observation sample by an inverted embedding method shown in FIG. 3 was produced. In FIG. 3, symbol 6 indicates a fiber deposit, symbol 7 indicates Pt, symbol 8 indicates an uncured resin, symbol 9 indicates a slide glass, and symbol 10 indicates a cured resin.

  Subsequently, a 90-nm thin piece was formed using a microtome (Leica, trade name: ULTRACUT-S), and TEM observation and photographing were performed with a transmission electron microscope (FEI, trade name: TECNAI G2) at an acceleration voltage of 120 kV. Carried out.

  In addition, the specific compounding ratio of the embedding resin (epoxy resin: Nisshin EM Co.) used for manufacture 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) Particle content in fibers (filling rate evaluation)
Using a thermogravimetric balance (trade name: TGA8120, manufactured by Rigaku Denki Co., Ltd.), thermal analysis was performed at 900 ° C. in an air stream, and the residue amount was evaluated. In the evaluation, the average value of three samples was adopted.

<Example 1>
PVB2400 / Ag (50wt%)
1 g of polyvinyl butyral (hereinafter referred to as “PVB”) dried at 70 ° C. for 1 week (trade name: polyvinyl butyral first grade, average polymerization degree: 2400) manufactured by Wako Pure Chemical Industries, completely dissolved in 19 g of dichloromethane, A PVB solution was obtained.

  To 10 g of the PVB solution obtained above, 0.06 g of gamma-mercaptopropyltrimethoxysilane (hereinafter referred to as “MPTMS”) (manufactured by Chisso, trade name: Silaace S810) was added dropwise and stirred sufficiently. An MPTMS coupling PVB (hereinafter referred to as “MPTMS-PVB”) solution was obtained by carrying out the coupling reaction.

  In the MPTMS-PVB solution obtained above, an Ag colloid solution containing alkylamine as a surfactant (trade name: nano silver dispersion, Ag nanoparticle content: 53% by mass, alkylamine content, manufactured by Toda Kogyo Co., Ltd.) : 11% by mass, dispersion: toluene, Ag particle size: 6.0 nm) 1.0 g was added dropwise and stirred for 2 hours to obtain a composite dispersion.

  The composite dispersion was set in a syringe (capacity 5 ml) of an electrostatic spinning apparatus (manufactured by MEC, NF-103A), and a 22G injection needle (inner diameter 0.48 mm, outer diameter 0.70 mm) was used as a nozzle. As the spinning conditions, the discharge amount was 5.0 μl / min, the distance between the nozzle tip and the collection substrate was 20 cm, and the applied voltage was controlled to 18 kV, while the fiber-forming composite dispersion was jetted to the collection electrode. It was deposited on the affixed aluminum foil.

  In this electrostatic spinning, the output of the ultrasonic oscillator (108 kHz mounted) arranged on the nozzle was set to 5 W, and ultrasonic vibration was continuously supplied to the nozzle. According to this, a good quality fiber deposit sheet free from nozzle clogging and continuously and stably spun for 20 minutes or more and free from defects due to discontinuous jetting was obtained. A cross-sectional TEM observation was performed on the obtained fiber deposit sheet (results are shown in FIG. 4).

  In addition, instead of continuously supplying ultrasonic vibration to the nozzle, when the provision of ultrasonic waves is stopped at regular time intervals, specifically, after supplying ultrasonic waves for 4 minutes, the ultrasonic waves are applied for 1 minute. When the supply of sonic waves was repeatedly stopped, there was no nozzle clogging, and spinning was performed continuously and stably.

<Comparative example 1>
Electrospinning was performed in the same manner as in Example 1 except that ultrasonic irradiation was not performed. In this case, within 5 minutes from the start of spinning, a lump was formed from the tip of the nozzle, the injection became discontinuous, and finally the nozzle was completely clogged. A cross-sectional TEM observation was performed on the fiber deposit sheet obtained during stable spinning (the result is shown in FIG. 5).

  In addition, when using a mechanical automatic cleaning function, that is, a function in which the fixed yarn rubs off the lump of the nozzle tip at a certain spinning time and performs stable spinning, continuous prevention can be performed. However, the droplets rubbed off from the nozzle tip by the thread fell on the surface of the fiber deposit and became a defect.

<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 the electrostatic spinning device shown in FIG. 1, and the fibers are accumulated by continuously spinning, A fiber deposit was produced.

  At this time, the inner diameter of the ejection nozzle 1 is 0.4 mm (injection needle: 23 G), the capacity of the syringe 2 is 10 ml, the voltage is 16.5 kV, and the distance from the ejection nozzle 1 to the fiber collecting electrode 5 (stainless steel plate) is 20 cm. Met. 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. 6 and a transmission electron microscope (TEM) photograph ( FIG. 7 shows the observation magnification (360,000 times). The average fiber diameter of the obtained fibers 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, 13 mm in diameter) 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 disc-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. 8).

30 Electrostatic spinning device 31a Vibration supply unit 31 Spinning unit (spinning nozzle)
32 Fiber forming composition supply unit (syringe)
33 Fiber forming composition 34 Voltage generator 35 Collection part (fiber collection electrode)

Claims (7)

A step of preparing a fiber-forming composition comprising particles and a polymer, and a step of spinning the fiber by ejecting the fiber-forming composition from a spinning part by an electrostatic spinning method.
And a method for producing a particle-polymer fibrous composite comprising supplying vibration to the spinning part during spinning.   The method of claim 1, wherein the vibration is ultrasonic vibration.   The method according to claim 1 or 2, wherein an average fiber diameter of the particle-polymer fibrous composite is 50 nm or more and 4 µm or less.   The method in any one of Claims 1-3 whose average primary particle diameter of the said particle | grain is 100 nm or less.   The method in any one of Claims 1-4 whose content of the said particle | grain is 20 mass% or more with respect to the said whole fibrous composite.   A particle-polymer bulk comprising the steps of obtaining the fibrous composite by the method according to any one of claims 1 to 5 and pressurizing the fibrous composite under conditions that maintain a dispersed state of the particles. Method for producing a composite.   The method according to claim 6, wherein the fibrous composite is pressed and shaped.