JP2017181375A - Foam and method for producing foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation-blocking foam having high strength while being light in weight, and a method for producing such a foam.SOLUTION: A radiation-blocking foam has metal particles D dispersed in a matrix resin having a three-dimensional structure, the metal particles D comprising at least one selected from the group consisting of tungsten, stainless, iron, tantalum, barium and barium sulfate.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a foam and a method for producing the foam. In more detail, it is related with the foam which has radiation shielding property, and its manufacturing method.

  Radiation in nuclear power plant reactors and related facilities, radiation generating equipment such as medical facilities and research facilities that handle high-energy radiation, and containers used for transporting, storing, and storing radioactive waste A shielding material is used. Among these, radiation shielding materials based on cement mortar and concrete are often used.

  As a radiation shielding material for buildings, for example, there is a material described in Patent Document 1. In this document, it is described that a tungsten-containing elastic filler is filled in a joint portion of a building material.

JP 2013-195416 A

  However, the present inventor has found that the conventional radiation shielding material needs a sufficient thickness to effectively shield the radiation, so it is heavy and has room for improvement in terms of handling at the time of use. I found.

  The present invention provides a radiation shielding foam having a high strength while being lightweight, and a method for producing such a foam.

  According to the present invention, a foam having radiation shielding properties in which metal particles are dispersed in a matrix resin having a three-dimensional structure, wherein the metal particles are made of tungsten, stainless steel, iron, tantalum, barium, and barium sulfate. A foam is provided that is one or more selected from the group consisting of:

  Further, according to the present invention, there is provided a method for producing the above foam, which is a metal containing at least one selected from the group consisting of a matrix resin and tungsten, stainless steel, iron, tantalum, barium and barium sulfate. Preparing a slurry in which particles and heat-expandable microcapsules are mixed, and obtaining the foamable papermaking by making the slurry, and placing the foamable papermaking in part of the mold, And expanding the thermally expandable microcapsule to expand the foamable paper product to the entire inside of the mold, thereby obtaining a foam made of the foamable paper product. A method for producing a foam is provided.

  ADVANTAGE OF THE INVENTION According to this invention, it has a radiation shielding ability, is lightweight, and a foam provided with the outstanding intensity | strength is provided. Moreover, according to this invention, the manufacturing method of such a foam is provided.

It is a perspective schematic diagram which shows an example of the foamable papermaking concerning this embodiment. It is a cross-sectional schematic diagram which shows an example of the manufacturing method of the foamable papermaking concerning this embodiment. It is a cross-sectional schematic diagram which shows an example of the manufacturing method of the foam which concerns on this embodiment. It is a CT image in the X-ray transmittance measurement of the foam concerning an example and a comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

  The foam according to the present embodiment is a foam having radiation shielding properties in which metal particles are dispersed in a matrix resin having a three-dimensional structure, and the metal particles are tungsten, stainless steel, iron, tantalum, barium, and sulfuric acid. One or more selected from the group consisting of barium. The foam of this embodiment is a resin foam in which metal particles are dispersed, and has a radiation shielding ability. The present inventors have found that when the above metal particles are used as a material having radiation shielding ability, these metal particles are uniformly dispersed without being settled or unevenly distributed in the foam. Moreover, even if it was a case where the said metal particle exists in a foam, it discovered that the radiation shielding ability was exhibited. Thus, the foam in which the metal particles are dispersed has radiation shielding ability and is excellent in the balance between lightness and strength, and thus is useful as a radiation shielding material.

In one embodiment, the foam has a density of 0.1 g / cm ³ or more and 10.0 g / cm ³ or less. Preferably, the lower limit of the density of the foam is 0.5 g / cm ³ or more, and more preferably 1.0 g / cm ³ or more. Further, the upper limit value of the density of the foam is preferably 8.0 g / cm ³ or less, more preferably 6.0 g / cm ³ or less. A foam having a density within the above range is useful as a radiation shielding material because it is lightweight and excellent in mechanical strength while maintaining the radiation shielding ability.

  In one embodiment, the volume porosity of the foam is 5% or more and 90% or less. Preferably, the lower limit value of the volume porosity is 10% or more, and more preferably 15% or more. Further, the upper limit value of the volume porosity is preferably 80% or less, and more preferably 70% or less. A foam having a volume porosity within the above range is useful as a radiation shielding material because it has a good balance between strength and light weight while maintaining the radiation shielding ability.

  The volume porosity of the foam can be calculated by, for example, an image analysis method. Specifically, first, the vicinity of the center of the foam is cut out, the image of the cross section of the cut out foam is binarized, and the area of the matrix phase made of thermosetting resin and the area of the bubble phase made of bubbles are measured. . Thereafter, the ratio of the measured areas is calculated as the volume porosity.

  In one embodiment, the foam has a closed cell structure or an open cell structure. In a preferred embodiment, the foam has only a closed cell structure or a mixed structure of closed cell structure and open cell structure. The foam having such a cell structure is excellent in balance between lightness and strength while maintaining the radiation shielding ability.

  In the present embodiment, the closed cell structure means a structure having a plurality of spaces (bubbles) isolated from the outside by a matrix resin having a three-dimensional structure. In such a closed cell structure, since gas is suppressed from passing between adjacent spaces, a structure excellent in airtightness can be realized.

  When the foam has a closed cell structure, the lower limit of the bubble size may be, for example, 5 μm or more, or 10 μm or more. On the other hand, the upper limit value of the bubble size is not particularly limited, but may be, for example, 500 μm or less, or 400 μm or less.

  In one embodiment, the lower limit of the glass transition temperature (Tg) of the foam may be, for example, 100 ° C or higher, preferably 120 ° C or higher, and more preferably 150 ° C or higher. . Thereby, the heat resistance of a foam can be improved. A foam having such a glass transition temperature can be used, for example, in an environment exposed to high temperatures. On the other hand, the upper limit value of the glass transition temperature (Tg) of the foam may be, for example, 350 ° C. or lower. The glass transition temperature (Tg) can be measured by, for example, a differential scanning calorimeter (DSC-2920, manufactured by TA Instruments).

  In one embodiment, the X-ray shielding rate of the foam is 95% or more. Preferably, the X-ray shielding rate is 96% or more, and more preferably 98% or more. A foam having such an X-ray shielding rate is useful as a radioactive shielding material.

  In one embodiment, the foam includes a fiber filler. Preferably, the foam has a configuration in which fiber fillers are dispersed therein. By using a fiber filler, a foam in which metal particles are more uniformly dispersed can be obtained. Therefore, a foam having a radiation shielding ability and an excellent balance between strength and lightness is provided.

In one embodiment, the specific bending strength (bending strength per density) of the foam is 20 MPa / (g / cm ³ ) or more and 300 MPa / (g / cm ³ ) or less. The pressure is preferably 40 MPa / (g / cm ³ ) or more and 250 MPa / (g / cm ³ ) or less, more preferably 60 MPa / (g / cm ³ ) or more and 200 MPa / (g / cm ³ ) or less. A foam having a specific bending strength in the above range is useful as a radioactive shielding material for buildings.

In one embodiment, the specific flexural modulus at room temperature (flexural modulus per density) of the foam is 1 GPa / (g / cm ³ ) or more and 20 GPa / (g / cm ³ ) or less. Preferably, the specific flexural modulus of the foam is 2 GPa / (g / cm ³ ) or more and 18 GPa / (g / cm ³ ) or less, more preferably 4 GPa / (g / cm ³ ) or more and 16 GPa / (g / Cm ³ ) or less. A foam having a specific bending elastic modulus within the above range is useful as a heat insulating material. This bending elastic modulus can be measured according to JIS K-7171.

  In one embodiment, the matrix resin constituting the foam is a cured body of a thermosetting resin. By using a thermosetting resin, it is possible to impart properties such as mechanical properties and heat resistance to the foam. As the thermosetting resin, an epoxy resin or a phenol resin is preferably used because it has excellent moldability.

  The characteristic of said foam can be suitably adjusted by changing the kind and compounding quantity of resin to be used, a fiber filler, and a foaming agent.

  In one embodiment, the foam is composed of a foamed paper product. Preferably, the foam is a molded body obtained by thermoforming a papermaking body containing a thermosetting resin, a fiber filler, metal particles, and a foaming agent. By using a formed body of a papermaking containing a fiber filler as the foam, it is possible to obtain a foam that is uniformly dispersed without uneven distribution of metal particles. Such a foam has an excellent balance of radiation shielding ability, density and strength.

  Hereinafter, the foam of the present invention will be described by taking as an example an embodiment in which the foam is formed of a molded product of a papermaking product including a thermosetting resin, a fiber filler, metal particles, and a foam.

<Foaming paper 10>
FIG. 1 is a schematic perspective view showing an example of a foamable papermaking product 10 in the present embodiment.
As shown in FIG. 1, the foamable papermaking product 10 includes a thermosetting resin A as a matrix resin, a fiber filler B, a thermally expandable microcapsule C, and metal particles D.

Here, the “papermaking” used in this specification will be described. The papermaking body is obtained by a papermaking method from a material slurry containing materials such as a fiber filler and a resin. The papermaking method refers to a wet papermaking method, that is, a papermaking technique which is one of papermaking techniques.
The terms “papermaking method” and “papermaking body” are obtained by using a method of papermaking a fiber material as described in, for example, Patent Publication 1 (Patent No. 4675276) and Patent Publication 2 (Patent No. 5426399). Generally used as a technical term to indicate the state of a given object. According to this document, the papermaking product refers to the wet solid content remaining on the filter after passing the raw material slurry in which the raw material such as fiber or resin is dispersed in the dispersion medium through the filter. , And is described. The wet state here means an uncured state of the resin before the heat treatment, that is, an uncured state before post-curing.

  In the present embodiment, the foamable paper-making body 10 may be a sheet shape or a three-dimensional shape processed into a shape imitating a desired molded product shape (that is, a shape of an element). And the molded object (foaming molded object 50) which is a hardening body of the foamable papermaking object 10 can be obtained by performing foam molding by heat processing etc. with respect to this expandable papermaking object 10. FIG.

The foamable papermaking body 10 according to the present embodiment is obtained by a papermaking method.
As shown in FIG. 1, the foamable papermaking body 10 obtained by the papermaking method has structural features 1 to 3 in the following points.
(Feature 1) The fiber filler B, the thermally expandable microcapsule C, and the metal particles D are randomly oriented in a plan view of the surface of the foamable papermaking body 10.
(Characteristic 2) In the cross-sectional view in the thickness direction of the foamable papermaking product 10, the orientation state of the fiber filler B is highly controlled, and the fiber filler B is oriented in a specific direction. In other words, the fiber filler B is in a laminated state in the thickness direction of the foamable papermaking product 10.
(Feature 3) The fiber fillers B are bound together by the thermosetting resin A.
As described above, in the foamable papermaking product 10 shown in FIG. 1, the thermosetting resin A, the fiber filler B, the thermally expandable microcapsule C, and the metal particles D are entangled randomly in the plane direction. The papermaking structure has a structure that overlaps in the thickness direction.

Moreover, the foamable papermaking body 10 can be formed into a desired shape by foaming and curing by heat treatment.
The thermosetting resin A in the foamable papermaking product 10 is not completely cured, for example, in a B stage state. Therefore, the foamable papermaking product 10 can be deformed into another shape. Specifically, the foamable paper product 10 is heated at the curing temperature of the thermosetting resin A to completely cure the thermosetting resin A, and the thermally expandable microcapsule C contained in the foamable paper product 10. By foaming, foamed molded body 50 in which bubbles are dispersed can be obtained.

Subsequently, the component which comprises the foamable papermaking body 10 is demonstrated.
(Thermosetting resin A)
The thermosetting resin A is a resin that can be cured by heat treatment and become a foam. Moreover, the thermosetting resin A contained in the foamable papermaking body 10 functions as a binder (binder resin) that connects between the fiber fillers B.
Examples of such a thermosetting resin A include a phenol resin, an epoxy resin, an unsaturated polyester resin, a melamine resin, and a polyurethane resin. These resins can be appropriately selected and used as necessary, and one kind may be used alone, or two or more kinds may be used in combination.
From the viewpoint of mechanical properties and heat resistance of the foamed molded product 50 obtained by curing the foamable papermaking product 10, it is preferable to use a phenol resin or an epoxy resin. Moreover, it is preferable to use a phenol resin from a viewpoint of the heat resistance and intensity | strength of the foaming molding obtained.

  The thermosetting resin A may be in the form of particles or powder. Thereby, the intensity | strength of the foaming molding 50 obtained by foaming and hardening the foamable papermaking body 10 can be improved effectively. The reason for this is not clear, but when the foamable papermaking product 10 is heated and pressurized to be foamed, the thermosetting resin A has a granular or powdery form, so that the fiber filler B can be impregnated during melting. It is estimated that the interface between the fiber filler B and the thermosetting resin A is well formed.

As the thermosetting resin A, for example, it is preferable to use a resin that has an average particle diameter of 500 μm or less and is in a solid state at room temperature. Thereby, in the manufacturing process of the foamable papermaking body 10, the thermosetting resin A tends to aggregate. Moreover, in the manufacturing process of the foamable papermaking body 10, from the viewpoint of obtaining a varnish-like material composition, the average particle size of the thermosetting resin A is more preferably 1 nm or more and 300 μm or less.
The thermosetting resin A having such an average particle diameter can be obtained, for example, by pulverizing an untreated thermosetting resin using an atomizer pulverizer.
In addition, the average particle diameter of the thermosetting resin A is obtained, for example, by using a laser diffraction particle size distribution measuring apparatus such as SALD-7000 manufactured by Shimadzu Corporation as a mass-based 50% particle diameter. be able to.

  The thermosetting resin A contained in the foamable papermaking product 10 is preferably in a semi-cured state. The semi-cured thermosetting resin A is completely cured in the foamable papermaking product 10 in the foaming and molding process by heat and pressure. Thereby, the foaming molding 50 excellent in the balance of intensity | strength and lightness is obtained.

(Fiber filler B)
The fiber filler B used for the foam of the present invention is a fiber yarn having a predetermined fiber length. Examples of the fiber filler B that can be used in the present invention include carbon fiber, metal fiber, inorganic fiber, natural fiber, regenerated fiber, semi-synthetic fiber, and synthetic fiber. Among these, carbon fibers are preferably used because of their excellent strength.

Examples of the carbon fiber include PAN-based carbon fiber and pitch-based carbon fiber.
As the metal fiber, a fiber containing at least one selected from the group consisting of aluminum, silver, copper, magnesium, iron, chromium, nickel, titanium, zinc, tin, molybdenum, and tungsten can be used. Specific examples of metal fibers include, for example, stainless steel fibers manufactured by Nippon Seisen Co., Ltd. and Bekaert Japan Co., Ltd., copper fibers manufactured by Niji Gi Co., Ltd., aluminum fibers, brass fibers, steel fibers, titanium fibers, phosphor bronze. A fiber etc. are mentioned, These are available as a commercial item.
Examples of the inorganic fiber include glass fiber and ceramic fiber.
Examples of natural fibers include wood fibers, cotton, hemp, and wool.
Examples of the recycled fiber include rayon fiber.
Examples of semisynthetic fibers include polyamide fibers, aramid fibers, polyimide fibers, polyvinyl alcohol fibers, polyester fibers, acrylic fibers, polyparaphenylene benzoxazole fibers, polyethylene fibers, polypropylene fibers, polyacrylonitrile fibers, and ethylene vinyl alcohol fibers. It is done. These fiber fillers B may be used alone or in combination of two or more.

  From the viewpoint of obtaining a papermaking structure, the average fiber length of the fiber filler B is preferably 0.1 mm or more, more preferably 2 mm or more, from the viewpoint of obtaining the mechanical strength of the resulting papermaking body or molded body. More preferably, it is 2.5 mm or more, and particularly preferably 4 mm or more. On the other hand, from the viewpoint of obtaining good dispersibility in the papermaking body, it is preferably 20 mm or less, more preferably 15 mm or less, and further preferably 12 mm or less.

  From the viewpoint of increasing strength, the content of the fiber filler B may be, for example, 10% by weight or more, or 20% by weight or more with respect to the thermosetting resin A. From the viewpoint of improving the balance between strength and lightness, the content of the fiber filler B may be, for example, 80% by weight or less or 75% by weight or less with respect to the thermosetting resin A. It may be less than or equal to 50% by weight.

(Thermal expansion microcapsule C)
The thermally expandable microcapsule C is a particle obtained by microencapsulating a volatile liquid foaming agent with a thermoplastic shell polymer having a gas barrier property. The thermally expandable microcapsule C functions as a foaming agent by the following mechanism. That is, while the outer shell of the capsule is softened by heating, the liquid foaming agent contained in the capsule is vaporized and the pressure is increased. As a result, the particles expand to form hollow spherical particles (foamed particles of the thermally expandable microcapsule C), thereby forming bubbles in the resin.

Examples of the liquid blowing agent include low boiling point hydrocarbons such as isopentane, isobutane, and isopropane.
Examples of the thermoplastic shell polymer include polyacrylonitrile, vinylidene chloride-acrylonitrile copolymer, vinylidene chloride-methyl methacrylate copolymer, vinylidene chloride-ethyl methacrylate, acrylonitrile-methyl methacrylate copolymer, acrylonitrile-ethyl methacrylate, and the like. Can be mentioned. These may be used alone or in combination of two or more.

  Examples of the thermally expandable microcapsule C include Expancel (manufactured by Nippon Philite), Microsphere F50, Microsphere F60 (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.), Advancel EM (manufactured by Sekisui Chemical Co., Ltd.), and the like. Commercial products can be used.

  The content of the thermally expandable microcapsule C is 0.05% by weight or more with respect to the thermosetting resin A from the viewpoint of reducing the density of the foamed molded product 50 without causing a decrease in the strength of the foamed molded product 50. Or 0.1% by weight or more. Further, from the viewpoint of imparting appropriate strength to the foamed molded product 50, it may be 10 wt% or less or 5 wt% or less with respect to the thermosetting resin A.

(Metal particle D)
The foam of the present invention contains one or more metal particles D selected from the group consisting of tungsten, stainless steel, iron, tantalum, barium and barium sulfate. These metal particles D are uniformly dispersed in the foamable papermaking product 10. Further, these metal particles D are uniformly dispersed without being settled or unevenly distributed in the step of heat-treating the foamable papermaking product 10 and foaming the heat-expandable microcapsules C contained therein. Therefore, a foam in which the metal particles D are uniformly dispersed can be obtained. Moreover, such a foam has a uniform radiation shielding ability throughout.

  In addition, the foamable papermaking product 10 according to the present embodiment may include other components such as pulp, aggregating agent, and various additives in addition to the above components as necessary.

(pulp)
The foamable papermaking body 10 of the present embodiment may include pulp. Pulp is a fiber having a fibril structure and refers to a fiber different from the fiber filler B. Pulp can be obtained, for example, by mechanically or chemically fibrillating the fiber material.
In the step of obtaining the foamable papermaking product 10 by the papermaking method, the binder resin A, the fiber filler B, the thermally expandable microcapsule C, and the metal particles D can be more effectively aggregated by using pulp. Therefore, it becomes possible to realize more stable production of the foamable papermaking product 10.

  Examples of the pulp include cellulose fibers such as linter pulp and wood pulp, natural fibers such as kenaf, jute and bamboo, para-type wholly aromatic polyamide fibers (aramid fibers) and copolymers thereof, aromatic polyester fibers, poly Examples include fibrillated organic fibers such as benzazole fibers, meta-type aramid fibers and copolymers thereof, acrylic fibers, acrylonitrile fibers, polyimide fibers, and polyamide fibers. Pulp may be used individually by 1 type and may use 2 or more types together.

  The content of the pulp may be 0.5% by weight or more, 1% by weight or more, or 2% by weight or more with respect to the thermosetting resin A. This makes it easier to aggregate the materials in the paper making process. On the other hand, the pulp content may be 10% by weight or less, 8% by weight or less, or 5% by weight or less with respect to the thermosetting resin A. Thereby, the target foaming molding 50 can be obtained, without impairing mechanical characteristics, such as intensity | strength.

(Flocculant)
The foamable papermaking body 10 of the present embodiment may include a flocculant. The aggregating agent has a function of aggregating the binder resin A, the fiber filler B, the heat-expandable microcapsule C, and the metal particles D in a floc state when the foamable papermaking product 10 is manufactured. For this reason, manufacture of the more stable foamable papermaking body 10 is realizable.

  Examples of the flocculant include cationic polymer flocculants, anionic polymer flocculants, nonionic polymer flocculants, and amphoteric polymer flocculants. More specifically, for example, cationic polyacrylamide, anionic polyacrylamide, Hoffman polyacrylamide, mannic polyacrylamide, amphoteric copolymerized polyacrylamide, cationized starch, amphoteric starch, polyethylene oxide and the like can be mentioned. These flocculants may be used individually by 1 type, and may use 2 or more types together. In the flocculant, the polymer structure and molecular weight, the amount of functional groups such as hydroxyl groups and ionic groups, and the like can be adjusted according to the required characteristics.

  The content of the flocculant may be 0.01% by weight or more, 0.05% by weight or more, or 0.1% by weight or more with respect to the thermosetting resin A. Thereby, in manufacture of the foamable papermaking body 10, the improvement of a yield can be aimed at. On the other hand, the content of the flocculant may be 1.5% by weight or less, 1% by weight or less, or 0.5% by weight or less with respect to the thermosetting resin A. Thereby, in manufacture of the foamable papermaking body 10 using a papermaking method, a dehydration process etc. can be performed more easily.

  The foamable papermaking product 10 may contain other additives depending on the production conditions and desired properties. Examples of additives include thermoplastic resins, inorganic powders for improving properties, metal powders, stabilizers such as antioxidants and ultraviolet absorbers, flame retardants, mold release agents, plasticizers, resin curing catalysts, Curing accelerators, pigments, paper strength improvers such as dry paper strength improvers, wet paper strength improvers, yield improvers, drainage improvers, size fixers, rosin sizing agents for acidic papermaking, rosins for neutral papermaking Examples include sizing agents such as sizing agents, alkyl ketene dimer sizing agents, alkenyl succinic anhydride sizing agents, and specially modified rosin sizing agents, and coagulants such as sulfate bands, aluminum chloride, and polyaluminum chloride.

  Especially, it is preferable that the foamable papermaking body 10 contains an aramid microfiber as an additive. By using the aramid microfibers, it is possible to improve the handling properties of the papermaking body obtained by drying the foamable papermaking body 10.

<Method for Producing Foamable Paper 10>
FIG. 2 is a schematic cross-sectional view showing the manufacturing process of the foamable papermaking product 10.
In the production method of the foamable papermaking product 10 of the present embodiment, a binder resin (thermosetting resin) A, a fiber filler B, a thermally expandable microcapsule C, and metal particles D are mixed, and then the resulting mixture is mixed. The process includes the step of obtaining the foamable papermaking product 10 by processing by the papermaking method.

  Hereinafter, with reference to FIG. 2, the manufacturing method of the foamable papermaking body 10 by a wet papermaking method is explained in full detail.

  First, as shown to Fig.2 (a), binder resin A, the fiber filler B, the heat | fever expansible microcapsule C, and the metal particle D are added to a solvent, and it stirs, mixes, and disperses. At this time, of the above-described components, other components excluding the flocculant are added to the solvent. The varnish-like material composition (slurry) for forming the foamable papermaking body 10 can be obtained according to the said process.

  Examples of a method for dispersing each component in a solvent include a method of stirring using a disperser.

  As a solvent for preparing the material slurry, it is difficult to volatilize in the process of dispersing the above materials, it is easy to remove the solvent in order to reduce the residual in the papermaking, and the increase in energy due to the solvent removal can be suppressed. In view of the above, a solvent having a boiling point of 50 ° C. or higher and 200 ° C. or lower is preferable. Examples of such solvents include water; alcohols such as ethanol, 1-propanol, 1-butanol, and ethylene glycol; ketones such as acetone, methyl ethyl ketone, 2-heptanone, and cyclohexanone; ethyl acetate, butyl acetate, and methyl acetoacetate. And esters such as methyl acetoacetate; ethers such as tetrahydrofuran, isopropyl ether, dioxane and furfural. These solvents may be used alone or in combination of two or more. Among these, it is particularly preferable to use water because the supply amount is abundant, the cost is low, the environmental load is low, the safety is high, and the handling is easy.

  Subsequently, the above-mentioned flocculant is preferably added to the obtained slurry. Thereby, the binder resin A, the fiber filler B, the thermally expandable microcapsule C, and the metal particles D in the solvent can be more easily aggregated in a floc form to obtain an aggregate F (FIG. 2). (B)).

  Then, the foamable papermaking body 10 is obtained by papermaking the slurry which mixed the binder resin A, the fiber filler B, the thermally expansible microcapsule C, the metal particle D, etc. with a filter.

Specifically, as shown in FIG. 2B, the above slurry is introduced into a container having a sheet-like mesh 30 (filter) on the bottom surface. Then, the solvent in the slurry is passed through the mesh 30 and discharged out of the container, and the aggregate F in the slurry is left on the mesh 30 (filter). Thereby, the aggregate F and the solvent can be separated from each other.
Here, it is possible to adjust the shape of the foamable papermaking body 10 obtained by selecting the shape of the mesh 30 suitably.
Thereafter, the agglomerate F obtained on the filter (mesh 30) may be subjected to a drying treatment, for example, in a drying furnace to further remove the solvent remaining in the agglomerate F.
As described above, the foamable papermaking product 10 shown in FIG. 2C is manufactured.

By using a papermaking method as shown in FIG. 2 (b), the foamable papermaking body 10 is formed along the surface of the filter. As described above with reference to FIG. 1, the foamable paper product 10 has a structure in which the fiber filler B is laminated in the thickness direction of the foamable paper product 10 and is randomly entangled in the surface direction. .
Moreover, the dispersibility of the thermally expansible microcapsule C and the metal particle D in the foamable papermaking body 10 can be improved by using a papermaking method.

<Foamed molded product 50>
The foamed molded product 50 of this embodiment is a molded product of the foamable papermaking product 10 and has a cell structure in which bubbles E formed by foaming the thermally expandable microcapsules C are dispersed in the molded product.

<Method for Manufacturing Foam Molded Body 50>
The manufacturing method of the foaming molding 50 of this embodiment prepares the slurry which mixed the thermosetting resin A, the filler (fiber filler B), and the thermally expansible microcapsule C, and foams by making this slurry into paper. Obtaining the papermaking body 10;
The foamable papermaking body 10 is arranged in a part of the inside of the molds 40 and 41, the thermally expandable microcapsule C is expanded, and the foamable papermaking body 10 is expanded to the whole inside of the molds 40 and 41. The process of obtaining the foam (foaming molding 50) which consists of a molding of the foamable papermaking body 10 by this can be included.

FIG. 3 is a schematic cross-sectional view showing an example of a method for producing a foam according to the present embodiment.
Hereinafter, with reference to FIG. 3, the manufacturing method of the foaming molding 50 is explained in full detail.

  First, as shown to Fig.3 (a), the foamable papermaking body 10 is arrange | positioned inside the metal mold | dies 40 and 41 (metal mold cavity). At this time, the volume of the mold cavity including the mold 40 and the mold 41 is assumed to be larger than the volume of the foamable papermaking product 10. Thereby, the foamable papermaking body 10 can be arrange | positioned by the state in which the inside of metal mold | die 40,41 is not completely filled, so-called short shot.

Next, foam molding is performed on the foamable papermaking product 10. For example, as shown in FIG. 3B, the heat-expandable microcapsule C is expanded by the heat treatment, and the foamable papermaking product 10 is expanded. The expanded foamed paper product 10 is filled in the entire mold cavity. At this time, the foamable papermaking product 10 is molded by the internal pressure (stress from the molds 40 and 41) due to the foaming of the thermally expandable microcapsule C, and the foamed molded product 50 is obtained. Thereby, it can shape | mold to the foaming molding 50 which has a predetermined shape.
In the foam molding step described above, the curing reaction of the thermosetting resin A proceeds, and a cured resin body having a three-dimensional network structure is formed in the foam molded body 50. Further, the thermally expandable microcapsule C expands by the above heat treatment, and bubbles E (hollow spherical particles) are formed.
Thus, the foaming molding 50 of this embodiment can be manufactured by the short shot method. By using the short shot method, the foamable papermaking product 10 can be formed using the foaming pressure generated by the expansion of the bubbles of the thermally expandable microcapsule C.

  Although the said heat processing is not specifically limited, For example, it is good also as about 160-250 degreeC and about 10 to 30 minutes. In the manufacturing method of the foam molded body 50 of the present embodiment, the molding pressure is not applied from the outside, but the internal pressure in the molds 40 and 41 is, for example, about 1.5 to 5 MPa.

Here, as a method of applying molding pressure from the outside, there is an injection molding method or the like. However, in the injection molding method, the thermally expandable microcapsule does not foam or the bubbles are destroyed due to the filling pressure or holding pressure.
On the other hand, in the manufacturing method of the foam molded body 50 of the present embodiment, since no molding pressure is applied from the outside, unexpanded of the thermally expandable microcapsule C and destruction of the bubbles E can be sufficiently suppressed. .

  The radiation shielding ability, density, and mechanical properties of the foam of the present embodiment are the types of components such as the thermosetting resin A, the fiber filler B, the thermally expandable microcapsule C, and the metal particles D used for the foamable papermaking product 10. It can be adjusted to a desired value by changing the amount or by changing the manufacturing conditions of the foamable papermaking product 10 and the foamed molded product 50. Among these, for example, the use of tungsten particles as the metal particles D, the use of carbon fibers as the fiber filler B, and the dispersibility of the fiber filler B, the thermally expandable microcapsule C, and the metal particles D are improved by a papermaking method. For example, a method of appropriately controlling the bubble magnification and size by the short shot method is an effective method for bringing the above characteristics into a desired range.

  The foam of this embodiment can be used as a heat insulating material used for, for example, building materials, electronic devices, vehicle-mounted components, and the like.

  As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail with reference to an Example, this invention is not limited to description of these Examples at all.

The materials used in Examples and Comparative Examples are as follows.
(Thermosetting resin)
Thermosetting resin 1: phenol resin (phenol resin, “PR51723”, manufactured by Sumitomo Bakelite Co., Ltd.)
(Filler)
Fiber filler 1: Carbon fiber (Tenax “HT C110”, manufactured by Toho Tenax Co., Ltd.)
(Foaming agent)
Foaming agent 1: Thermally expandable microcapsule ("Advancel (registered trademark) EM-304", manufactured by Sekisui Chemical Co., Ltd.)
(Metal particles)
Metal particles 1: Tungsten particles (tungsten powder “W-L”, manufactured by Nippon Shin Metal Co., Ltd.)
(Other additives)
Aramid microfiber 1: Aramid microfiber ("Tiara", manufactured by Daicel FineChem Co., Ltd.)

<Examples 1 and 3>
(Manufacture of foamable paper products)
In Examples 1 and 3, foamable paper products were produced in the following manner at the blending ratios shown in Table 1 (raw material volume fraction [Vol%] after foam molding).
First, thermosetting resin, filler, foaming agent and metal particles pulverized to an average particle size of 100 μm (50% particle size based on mass) with an atomizer pulverizer are added to water, and 30 minutes with a disperser Stir to give a mixture. Here, it added to 10000 weight part of water with respect to a total of 100 weight part of the constituent material which consists of a thermosetting resin, a filler, a metal particle, a foaming agent, and an additive.
Next, a flocculant (synthetic smectite: smecton (manufactured by Kunimine Kogyo Co., Ltd.)) dissolved in water in advance was added in an amount of 0.2% by weight based on the total of the constituent materials described above, and the constituent materials were aggregated in a floc form. .
Subsequently, the obtained agglomerates were separated from water with a 30 mesh metal net. Thereafter, the agglomerates remaining on the metal net were subjected to dehydration pressing, and further placed in a drier at 70 ° C. for 3 hours for drying to obtain a foamable paper product. The yield was 97%.

(Manufacture of foam)
In Examples 1 and 3, the obtained foamed papermaking material was placed in a 1 mm-thick mold and subjected to heat treatment at 180 ° C. for 10 minutes to produce a foamed product made of a foamed molded product. At this time, the internal pressure in the mold was 2 MPa. Examples 1 and 3 were foamed by the short shot method. As a result, a foam in which the metal particles were dispersed throughout was obtained. The following evaluation was performed about the obtained foam. The results are shown in Table 1 and FIG. In addition, the raw material volume fraction after foam molding of the foaming agent in Table 1 indicates the volume porosity of the foam.

<Examples 2 and 4>
First, in the same manner as in Examples 1 and 3, an expandable paper-making body containing metal particles having a thickness of 0.5 mm after foam formation was obtained (after foam molding of metal particles in Examples 2 and 4). The raw material volume fraction is 20 Vol% and 40 Vol%, respectively). Subsequently, an expandable papermaking body containing no metal particles having a thickness of 0.25 mm after foaming was obtained in the same manner as in Examples 1 and 3 except that no metal particles were contained.

  Thereafter, sandwiching the both sides of the foamable papermaking body containing the metal particles with the foaming papermaking body not containing the metal particles, a metal particle uneven distribution sample having a sandwich structure was prepared. It was placed in a mold and subjected to heat treatment at 180 ° C. for 10 minutes to produce a foamed product made of a foamed molded product. At this time, the internal pressure in the mold was 2 MPa. Examples 2 and 4 were foamed by the short shot method. As a result, a foam in which the metal particles were unevenly distributed in the center was obtained. The results are shown in Table 2 and FIG. Table 2 shows the raw material volume fraction after foam molding in the entire foam. Among these, the raw material volume fraction after foam molding of a foaming agent shows the volume porosity of the whole foam. The foams of Examples 2 and 4 each had a higher concentration of metal particles at the center than the metal particle concentrations of Examples 1 and 3, respectively.

<Comparative Example 1>
In Comparative Example 1, a foamable papermaking product was produced in the same manner as in Examples 1 and 3 at the blending ratio shown in Table 1. Subsequently, the obtained foamable papermaking product was heat-treated in the same manner as in Examples 1 and 3 to produce a foamed product made of a foamed molded product. The following evaluation was performed about the obtained foam. The results are shown in Table 1 and FIG.

<Comparative example 2>
In Comparative Example 2, a papermaking product was produced in the following manner at the blending ratio shown in Table 1 (raw material volume fraction after compression molding [Vol%]).
First, a thermosetting resin pulverized to an average particle size of 100 μm (50% particle size based on mass) with an atomizer pulverizer, a filler, and an additive are added to water, and the mixture is stirred for 30 minutes with a disperser. Got. Here, it added to 10000 weight part of water with respect to a total of 100 weight part of the constituent material which consists of a thermosetting resin, a filler, and an additive.
Next, a flocculant (synthetic smectite: smecton (manufactured by Kunimine Kogyo Co., Ltd.)) dissolved in water in advance was added in an amount of 0.2% by weight based on the total of the constituent materials described above, and the constituent materials were aggregated in a floc form. .
Subsequently, the obtained agglomerates were separated from water with a 30 mesh metal net. Thereafter, the agglomerates remaining on the metal net were subjected to dehydration pressing, and further placed in a drier at 70 ° C. for 3 hours for drying to obtain a papermaking product. The yield was 97%.

(Manufacture of non-foamed products)
In Comparative Example 2, the obtained papermaking product was placed in a 1 mm-thick mold, subjected to heat treatment at 180 ° C. for 10 minutes, and a non-foamed product made of the papermaking product was produced by compression molding. At this time, the molding pressure was 10 MPa. The following evaluation was performed about the obtained non-foamed body. The results are shown in Table 1 and FIG.

(Measurement of radiation shielding rate)
In Examples 1 and 3, a foam in which tungsten particles were uniformly dispersed as a whole was produced, and the X-ray shielding rate was measured. Specifically, the above-mentioned foam of 100 mm square and 1 mm thickness was used as a sample plate. “Sample density after molding” shown in Table 1 indicates the density of the sample plate itself.

  In Examples 2 and 4, as described above, a foam in which tungsten particles were unevenly distributed in the center of the sandwich structure was produced, and the X-ray shielding rate was measured. Specifically, the foam of 100 mm square and 1 mm thickness was used as a sample plate. The “sample density after molding” shown in Table 2 is a density obtained from the mass of the entire sample plate thus obtained.

(Evaluation)
Density: measured by a method based on JIS K-7112 A method. The unit is g / cm ³
Radiation shielding rate: X-rays were incident on a sample plate having a size of 100 mm square and a thickness of 1 mm, and the transmittance was measured as the luminance value of the X-ray CT image. Specifically, a sample plate was placed at a position 300 mm from the X-ray source, and CT images were taken by irradiating X-rays under conditions of 50 kV and 70 μA. Luminance values (average, maximum, minimum) within the observation range of 38 mm were calculated from the obtained CT images. And the transmittance | permeability was computed from ratio of the luminance value of the sample board with respect to the luminance value in the air when there is no shielding object. Using the obtained transmittance, the shielding rate was calculated according to the formula of shielding rate (%) = [1− (transmittance)] × 100. TDM-1000H II (2K) (manufactured by Yamato Scientific Co., Ltd.) was used as the X-ray CT apparatus, and tungsten was used as the filament. Here, in Table 1, “shielding rate (average value reference) (%)” is a shielding rate calculated using the average value of the luminance values of the sample plates, and “shielding rate (maximum value reference) (%)”. "Is a shielding rate calculated using the maximum luminance value of the sample plate. The darker the CT image obtained, the higher the shielding rate, and the brighter, the lower the shielding rate, that is, the greater the amount of X-ray transmission. The obtained CT image is shown in FIG.
The above measurement was performed at room temperature (25 ° C.).

  It turned out that the foam of Examples 1-4 is excellent in the balance of radiation shielding property and lightness. Moreover, as a result of performing cross-sectional observation of the foams of Examples 1 to 4, it was found to have a closed cell structure. On the other hand, the foam of Comparative Example 1 did not have radiation shielding properties. Moreover, the non-foamed material of Comparative Example 2 had a high density.

  As described above, the present invention has been described more specifically based on the embodiments. However, these are exemplifications of the present invention, and various configurations other than the above can be adopted.

DESCRIPTION OF SYMBOLS 10 Foamable body 30 Mesh 40 Mold 41 Mold 50 Foam molded body A Binder resin (thermosetting resin)
B Fiber filler C Thermally expandable microcapsule D Metal particle E Bubble F Aggregate

Claims (10)

A foam having radiation shielding properties in which metal particles are dispersed in a matrix resin having a three-dimensional structure,
A foam in which the metal particles include one or more metals selected from the group consisting of tungsten, stainless steel, iron, tantalum, barium, and barium sulfate. The foam according to claim 1,
A foam having a density of 0.1 g / cm ³ or more and 10 g / cm ³ or less. The foam according to claim 1 or 2,
A foam having a volume porosity of 5% or more and 90% or less. The foam according to any one of claims 1 to 3,
A foam having a closed cell structure. The foam according to any one of claims 1 to 4,
A foam having an X-ray shielding rate of 95% or more. The foam according to any one of claims 1 to 5,
A foam further comprising a fiber filler. The foam according to any one of claims 1 to 6,
A foam in which the matrix resin includes a cured body of a thermosetting resin. The foam according to claim 7,
A foam in which the thermosetting resin contains an epoxy resin or a phenol resin. The foam according to any one of claims 1 to 8,
A foam comprising a foamed paper product. A method for producing a foam according to any one of claims 1 to 9, comprising:
Preparing a slurry in which a matrix resin, the metal particles containing at least one selected from the group consisting of tungsten, stainless steel, iron, tantalum, barium and barium sulfate, and thermally expandable microcapsules are mixed, A process of obtaining a foamable papermaking by papermaking,
By disposing the foamable paper product in a part of the mold, expanding the thermally expandable microcapsule, and expanding the foamable paper product to the entire interior of the mold, thereby expanding the foam. And a step of obtaining a foam composed of a molded product of the characteristic papermaking body.