JP2017183615A - Foamed material and manufacturing method of foamed material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foamed material having excellent in a balance between magnetic field shielding characteristics and a weight saving.SOLUTION: In a foamable sheet-formed material 10, a binder resin A, a filler B, and a thermal-expansion microcapsule C are randomly aggregated in a surface direction, and the foamable sheet-formed material has a sheet-formed structure so that such a surface structure is overlapped in a thickness direction. In the sheet-formed material in which the thermal-expansion microcapsule C is distributed as mentioned above, the magnetic filler B is distributed in a matrix resin having a three-dimensional structure, and thereby excellent magnetic field shielding characteristics can be obtained, and a weight saving of a magnetic field shield member can be achieved.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a foam and a method for producing the foam.

  2. Description of the Related Art Conventionally, electronic devices have been improved in performance by increasing the speed of information processing / transmission capability, increasing recording capacity, and the like, and leakage of electromagnetic waves from electronic devices and intrusion of electromagnetic waves from outside tend to increase. Therefore, various countermeasures against electromagnetic wave shielding are taken so as not to cause a malfunction or malfunction of the electronic device.

  On the other hand, a magnetic sheet using magnetic powder is used. For example, Patent Document 1 discloses a sheet in which spherical magnetic powder and a thermosetting resin are mixed from the viewpoint of increasing the real part permeability.

JP 2012-23261 A

  In light of the recent miniaturization of products and product cost reduction, there has been a demand for weight reduction of materials having magnetic field shielding characteristics. For this reason, it has been difficult to achieve weight reduction with a sheet in which spherical magnetic powder and thermosetting resin or the like as disclosed in Patent Document 1 are mixed.

  As a result of intensive studies on the weight reduction of materials having magnetic field shielding characteristics, the present inventors have focused on the foam structure. As a result of investigations on this point of view, it was found that good magnetic field characteristics can be obtained by dispersing the magnetic filler in the foam structure, and the present invention has been completed.

According to the present invention,
A foam in which a magnetic filler is dispersed in a matrix resin having a three-dimensional structure is provided.

Also according to the invention,
Preparing a slurry in which the binder resin forming the matrix resin, the magnetic particles, and the thermally expandable microcapsules are mixed, and obtaining the foamable papermaking by making the slurry; and
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.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the foam and the foam excellent in the balance of a magnetic field shield characteristic and weight reduction are 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 figure which shows the measurement result of the magnetic field shielding property of Example 1. FIG. It is a figure which shows the measurement result of the magnetic field shielding property of a reference example. It is a figure which shows the measurement result of the electric field shielding property of Example 1. FIG. It is a figure which shows the measurement result of the electric field shielding property of a reference 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 outline of the foam of this embodiment will be described.
The foam of this embodiment is a foam in which a magnetic filler is dispersed in a matrix resin having a three-dimensional structure.

  As a result of investigation by the present inventor, it has been found that by dispersing the magnetic filler, good magnetic field characteristics can be exhibited in the foam structure. Although details of such factors are not clear, it is considered that excellent magnetic field shielding properties can be obtained when the magnetic filler is well dispersed in the foam structure.

  Hereinafter, the foam of this embodiment will be described in detail.

  The foam of this embodiment has a structure in which a magnetic filler is dispersed in a matrix resin having a three-dimensional structure. In the present embodiment, the matrix resin having a three-dimensional structure may be composed of, for example, a cured resin having a three-dimensional network structure. Examples of the cured resin include a cured product of a thermosetting resin.

  In the present embodiment, the magnetic filler is not particularly limited as long as it is a particle. For example, the magnetic filler may have a fiber shape or a spherical shape. In addition, the magnetic filler may be partially or entirely made of a magnetic material having a magnetic field shielding property. From the viewpoint of a balance between magnetic field shielding characteristics and strength, the magnetic filler preferably contains a fiber filler. Moreover, the dispersibility of the magnetic filler in the foam structure can be improved by using the magnetic filler having such a fiber shape and molding the foam using a papermaking method.

  The material constituting the magnetic filler preferably includes one selected from the group consisting of nickel, iron, chromium, cobalt, alloys thereof, and metal oxides thereof, and more preferably includes nickel.

  In the embodiment, the magnetic filler may have both magnetic field shielding properties and electric field shielding properties. In this case, the magnetic filler may be composed of a magnetic material having a magnetic field shielding property and a conductive material having an electric field shielding property. As such a magnetic field filler, for example, a filler obtained by coating a conductive material with a magnetic material may be used. The coating is not limited to a continuous one, but may be a part or a non-continuous one.

As the magnetic filler as described above, for example, a fiber filler coated with metal can be used. The metal to be coated is not particularly limited as long as it is a magnetic material, but preferably contains at least one selected from the group consisting of nickel, iron, chromium, cobalt, alloys thereof, and these metal oxides. More preferably.
The coating is not limited to a continuous one, but may be a part or a non-continuous one.
Moreover, as the fiber filler coated with metal, organic fibers such as carbon fibers and aramid fibers are preferable, and carbon fibers are more preferable from the viewpoint of a balance between magnetic field shielding characteristics and weight reduction.

  Moreover, the foam of this embodiment may further contain a conductive filler. The conductive filler is configured using a conductive material having electric field shielding properties. From the viewpoint of obtaining electromagnetic shielding properties, the material constituting the conductive filler preferably contains one or more selected from the group consisting of stainless steel, iron, silver, nickel, aluminum, copper, and carbon fibers. Especially, it is more preferable that it is a carbon fiber from a viewpoint of improving electric field shielding property.

In addition, the foam of the present embodiment has a specific strength indicating a bending strength per density (g / cm ³ ), preferably 50 MPa / (g / cm ³ ) or more, more preferably 80 MPa / (g / cm ^3). ) Or more, preferably 300 MPa / (g / cm ³ ) or less, more preferably 200 MPa / (g / cm ³ ) or less. Thereby, the electronic member excellent in the balance of a magnetic field shielding characteristic, shaping property, and weight reduction is realizable.
The specific strength is determined from the bending strength of the foam and the density (g / cm ³ ) of the foam. Further, the bending strength of the foam can be measured according to JIS K6911.

Further, the foam of the present embodiment has a specific elastic modulus indicating a flexural modulus per density (g / cm ³ ) at room temperature, preferably 1 GPa / (g / cm ³ ) or more, more preferably 4 GPa / (g / Cm ³ ) or more, preferably 20 GPa / (g / cm ³ ) or less, more preferably 18 GPa / (g / cm ³ ) or less. Thereby, the electronic member excellent in the balance of a magnetic field shielding characteristic, shaping property, and weight reduction is realizable.
The specific elastic modulus is determined from the bending elastic modulus at room temperature of the foam and the density (g / cm ³ ) of the foam. The flexural modulus of the foam can be measured according to JIS K6911 at room temperature (25 ° C.).

The lower limit of the density (g / cm ³ ) of the foam of the present embodiment is not particularly limited, but may be 0.1 g / cm ³ or more, 0.2 g / cm ³ or more, or 0.3 g / It may be cm ³ or more. Thereby, the balance between strength and weight reduction can be achieved. On the other hand, the upper limit of the density (g / cm ³ ) of the foam is preferably 2.5 g / cm ³ or less, and further 1.6 g / cm ³ or less, 1.55 g / cm ³ or less, More preferable in the order of 1.5 g / cm ³ or less. Thereby, the balance of weight reduction and a magnetic field shield characteristic can further be improved.

  The lower limit value of the volume porosity of the foam of the present embodiment is, for example, preferably 5% or more, more preferably 10% or more, and further preferably 15% or more. Thereby, a magnetic field shielding characteristic and weight reduction can be improved. On the other hand, the upper limit value of the volume porosity of the foam is not particularly limited, but may be 90% or less, 80% or less, or 70% or less, for example. Thereby, the balance between magnetic field shield characteristics and strength can be improved.

  In the present embodiment, the method for measuring the volume porosity of the foam is not particularly limited, but can be calculated by, for example, image analysis. Specifically, the following measuring method can be used. That is, first, the vicinity of the center of the foam is cut out. The image of the cross-section of the cut foam was binarized, and the area ratio between the matrix phase composed of a matrix resin such as a thermosetting resin and the cellular phase composed of bubbles was expressed as volume porosity (foam material volume after foam molding). Fraction (volume%)).

The foam structure of the foam of this embodiment may have a closed cell structure or an open cell structure. In the foam of this embodiment, the whole may have a closed cell structure from the viewpoint of the balance between strength and magnetic field shielding characteristics, and from the viewpoint of the balance between weight reduction and magnetic field shielding characteristics, together with the closed cell structure Some may have an open-cell structure.
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 having excellent airtightness can be realized.

  When the foam of this embodiment has a closed cell structure, the lower limit of the size of the bubble in the closed cell structure is not particularly limited, but 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.

  The lower limit value of the glass transition temperature (Tg) of the foam of the present embodiment may be, for example, 100 ° C. or higher, preferably 120 ° C. or higher, and more preferably 150 ° C. or higher. Thereby, heat resistance can be improved and it can be used for the place where heat history, such as a heat-generating member, arises, for example. On the other hand, the upper limit value of the glass transition temperature (Tg) of the foam is not particularly limited, but may be, for example, 350 ° C. or less. The glass transition temperature (Tg) can be measured by, for example, a differential scanning calorimeter (DSC-2920, manufactured by TA Instruments).

  Moreover, the foam of this embodiment may be comprised entirely or partially by the molded object of a foamable papermaking body. In the present embodiment, from the viewpoint of production stability, it is preferable that the entire foam is composed of a foamed paper product (foamed product).

  According to the foam of this embodiment, the magnetic filler is dispersed in the matrix resin having a three-dimensional structure, so that good magnetic field shielding characteristics can be obtained and the magnetic field shielding material can be reduced in weight. . In addition, the magnetic field shielding characteristic by the foam of the present embodiment uses a loss due to an overcurrent generated when electromagnetic waves pass through the inside of the foam, and has an excellent magnetic shielding rate. In addition, the foam of the present embodiment can exhibit good magnetic field shielding properties particularly in a low frequency region.

Hereinafter, the foamable papermaking product and the foamed molded product of this embodiment will be described.
<Foaming paper 10>
FIG. 1 is a schematic perspective view showing an example of the foamable papermaking product 10 of the present embodiment.
The foamable papermaking body 10 of the present embodiment is a papermaking body in which the thermally expandable microcapsules C are dispersed.

  Here, in the present specification, the term “papermaking” is generally used as a technical term indicating the state of an object obtained by using a method of spreading a fiber material. Regarding the state of this thing, it describes in the patent gazette 1 (patent 4675276) and the patent gazette 2 (patent 5426399), for example. According to the document, the papermaking product is described as a wet solid content remaining on a filter after a liquid component is dehydrated from a raw material slurry in which raw materials such as fibers and resins are dispersed in a dispersion medium. ing. The said wet state here means the uncured state before performing heat processing, ie, the uncured state before post-cure.

  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) can be obtained by performing foam molding, such as heat processing, with respect to this foamable papermaking body 10. FIG. The foamed molded body 50 is a cured product of the foamable papermaking body 10.

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.
(Characteristic 1) In the planar view of the surface of the foamable papermaking body 10, the filler B and the thermally expandable microcapsule C are randomly oriented.
(Feature 2) In the cross-sectional view in the thickness direction of the foamable papermaking product 10, the orientation state of the filler B is highly controlled, and the filler B is oriented in a specific direction. In other words, the filler B is in a laminated state in the thickness direction of the foamable papermaking product 10.
(Characteristic 3) Fillers B are bound together by binder resin A.
As described above, in the foamable papermaking product 10 shown in FIG. 1, the binder resin A, the filler B, and the thermally expandable microcapsule C are randomly entangled in the plane direction, and such a plane structure is overlapped in the thickness direction. It has a papermaking structure.

In addition, the foamable papermaking body 10 can be used as a material for obtaining a foamed molded body 50 by molding into a desired shape by foaming treatment.
The resin 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. And the foaming paper-making body 10 can obtain the foaming molding 50 by foaming and complete-hardening resin by heating at the curing temperature of binder resin A which is a thermosetting resin.

Subsequently, the component which comprises the foamable papermaking body 10 is demonstrated.
(Binder resin A)
The binder resin A functions as a binder that connects between the fillers B, and later forms a matrix resin having a three-dimensional structure in the foamed molded body 50. As the binder resin A, for example, a thermosetting resin can be used.
Examples of the thermosetting resin include phenol resin, epoxy resin, unsaturated polyester resin, melamine resin, polyurethane, and the like. 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, it is preferable to use at least one of a phenol resin and an epoxy resin. Moreover, it is preferable to use a phenol resin from a viewpoint of coexistence in the dimension in weight reduction and a high dimension of strength.

  The thermosetting resin may have a granular or powdery shape. Thereby, the intensity | strength of the foaming molding 50 obtained by foaming and hardening the foamable papermaking body 10 can be improved more effectively. Although the reason for this is not clear, when the foamable papermaking product 10 is heated and pressurized to foam, the thermosetting resin has a granular or powdery shape, so that the impregnation property of the thermosetting resin at the time of melting is improved. It is estimated that the interface between the filler B and the thermosetting resin is well formed.

As the thermosetting resin, for example, one having an average particle size of 500 μm or less and a solid state at room temperature can be used. Thereby, in the manufacturing process of the foamable papermaking body 10, it can make it easy to form the aggregation state of a thermosetting resin. 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 is more preferably 1 nm or more and 300 μm or less.
The thermosetting resin having such an average particle diameter can be obtained by performing a pulverization process using, for example, an atomizer pulverizer.
The average particle size of the thermosetting resin is determined, for example, by using a laser diffraction particle size distribution measuring device such as SALD-7000 manufactured by Shimadzu Corporation as the average particle size based on a 50% particle size. Can do.

  The thermosetting resin contained in the foamable papermaking product 10 is preferably in a semi-cured state. The semi-cured thermosetting resin is completely cured in the process of producing the foamable paper product 10 and then foaming it into a desired shape by heating and pressurizing. Thereby, the foaming molding 50 excellent in the balance of high intensity | strength and weight reduction is obtained.

(Filler B)
The filler B is obtained by cutting a fiber yarn or a long fiber bundle into a predetermined length.
The average fiber length of the filler B is preferably 0.1 mm or more from the viewpoint of obtaining a special structure by papermaking, more preferably 2 mm or more, and 2.5 mm or more from the viewpoint of obtaining mechanical strength. More preferably, it is more preferably 4 mm or more. On the other hand, from the viewpoint of obtaining good dispersibility, it is preferably 20 mm or less, more preferably 15 mm or less, and further preferably 12 mm or less.

Filler B includes at least a magnetic filler, and may further include a conductive filler. As the magnetic filler and the conductive filler, those described above can be used.
Furthermore, aramid fiber, glass fiber, wholly aromatic polyester, wholly aromatic polyester amide, wholly aromatic polyether, wholly aromatic polycarbonate, wholly aromatic polyazomethine, polyphenylene sulfide (PPS), poly (para-phenylenebenzo) Bisthiazole) (PBZT), polybenzimidazole (PBI), polyetheretherketone (PEEK), polyamideimide (PAI), polyimide, polytetrafluoroethylene (PTFE), poly (para-phenylene-2,6-benzobis) Oxazole) (PBO) and the like may be included.
These fillers B 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.

  Furthermore, from the viewpoint of achieving a balance between weight reduction and strength, inorganic fibers may be used, and glass fibers may be preferably used. Moreover, when using glass fiber, you may use what gave the aminosilane process. The aminosilane treatment is performed by impregnating glass fibers with an amino group-containing silane coupling agent solution, or by applying an amino group-containing silane coupling agent solution to glass fibers.

  Examples of amino group-containing silane coupling agents include N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, and γ-aminopropyl. Methyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, N- (β An amino group-containing alkoxysilane such as (aminoethyl) -γ-aminopropylmethyldiethoxysilane, and hydrolysates thereof. These amino group-containing silane coupling agents may be used alone or in combination of two or more.

The content of the filler B is preferably 10% by weight or more and more preferably 20% by weight or more with respect to the binder resin A (thermosetting resin) from the viewpoint of increasing the strength. Further, from the viewpoint of balancing strength and weight reduction, it is preferably 80% by weight or less, more preferably 75% by weight or less, and more preferably 70% by weight with respect to the binder resin A (thermosetting resin). More preferably, it is more preferably 50% by weight or less.
Moreover, it is preferable that it is 10 weight% or more with respect to binder resin A (thermosetting resin), and, as for content of a magnetic filler, it is more preferable that it is 20 weight% or more. Further, from the viewpoint of balancing strength and weight reduction, it is preferably 80% by weight or less, more preferably 75% by weight or less, and more preferably 70% by weight with respect to the binder resin A (thermosetting resin). More preferably, it is more preferably 50% by weight or less.
The content of the magnetic filler in the filler B is preferably 10% by weight or more, more preferably 20% by weight or more, further preferably 50% by weight or more, and even 100% by weight. Good.

(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 and hollow spherical particles (foamed particles of the thermally expandable microcapsule C) are formed.

Examples of the liquid blowing agent include low-boiling 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 commercially available products such as EXPANSEL (manufactured by Nippon Fillite), Microsphere F50, Microsphere F60 (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.), Advancel EM (manufactured by Sekisui Chemical Co., Ltd.). Product can be used.

  The content of the heat-expandable microcapsule C may be 0.05% by weight or more with respect to the binder resin A (thermosetting resin) from the viewpoint of lowering the specific gravity of the foamed molded body 50, and 0.1% by weight. % Or more. Further, from the viewpoint of expressing an appropriate strength of the foamed molded product 50, it may be 10% by weight or less or 5% by weight or less with respect to the binder resin A (thermosetting resin).

  In addition, the foamable papermaking body 10 in this embodiment can contain components, such as a pulp, a flocculant, and various additives other than the said component.

(pulp)
The foamable papermaking body 10 of the present embodiment may include pulp. Pulp is a fiber material having a fibril structure, and is different from the filler B. Pulp can be obtained, for example, by mechanically or chemically fibrillating the fiber material.
Since the pulp can be made together with the binder resin A, the filler B, and the thermally expandable microcapsule C at the time of manufacturing the foamable papermaking product 10, these can be more effectively aggregated, so that more stable foaming properties can be obtained. Production of the papermaking body 10 can be realized.

  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 is preferably 0.5% by weight or more, more preferably 1% by weight or more, and more preferably 2% by weight or more based on the binder resin A (thermosetting resin). Further preferred. Thereby, aggregation of the thermosetting resin at the time of papermaking can be generated more effectively, and further stable production of the foamable papermaking body 10 can be realized. On the other hand, the pulp content is preferably 10% by weight or less, more preferably 8% by weight or less, and more preferably 5% by weight or less based on the binder resin A (thermosetting resin). Further preferred. Thereby, it becomes possible to improve the mechanical characteristic and thermal characteristic of the foaming molding 50 more effectively.

(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 filler B, and the thermally expandable microcapsule C in a floc state at the time of manufacturing the foamable papermaking product 10. 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 is preferably 0.01% by weight or more, more preferably 0.05% by weight or more, and 0.1% by weight with respect to the binder resin A (thermosetting resin). It is still more preferable that it is above. 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 is preferably 1.5% by weight or less, more preferably 1% by weight or less, and more preferably 0.5% by weight with respect to the binder resin A (thermosetting resin). More preferably, it is as follows. Thereby, in manufacture of the foamable papermaking body 10 using a papermaking method, it becomes possible to perform a dehydration process etc. more easily and stably.

  The foamable paper product of the present embodiment can further use various additives for the purpose of adjusting production conditions and expressing required physical properties. For example, thermoplastic resins, inorganic powders for improving properties, metal powders, stabilizers such as antioxidants and UV absorbers, flame retardants, mold release agents, plasticizers, resin curing catalysts and accelerators, pigments , Dry paper strength improver, wet strength strength improver, yield improver, drainage improver, size fixer, rosin sizing agent for acidic papermaking, rosin sizing agent for neutral papermaking, alkyl Examples thereof include sizing agents such as ketene dimer sizing agents, alkenyl succinic anhydride sizing agents and specially modified rosin sizing agents, and coagulants such as sulfuric acid bands, aluminum chloride and polyaluminum chloride.

  The foamable papermaking body 10 of this embodiment may have aramid microfibers as an additive. Thereby, the handleability of the papermaking body which dried the foaming papermaking body 10 can be made favorable.

<Method for Producing Foamable Paper 10>
FIG. 2 is a process cross-sectional view showing the manufacturing process of the foamable papermaking product 10.
The manufacturing method of the foamable papermaking body 10 of this embodiment is obtained by mixing the binder resin A, the filler B, and the thermally expandable microcapsule C, and then papermaking the mixture by a papermaking method to obtain the foamable papermaking body10. Process. Here, the papermaking method uses a papermaking technique which is one of papermaking techniques as shown in FIG.

  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 in FIG. 2A, a binder resin A, a filler B, and a thermally expandable microcapsule C are added to a solvent, stirred, mixed, and dispersed. At this time, you may add other components except a flocculant among the components mentioned above in a solvent. Thereby, the varnish-like material composition (slurry) for forming the foamable papermaking body 10 can be obtained.

  A method of dispersing each component in a solvent is not particularly limited, and examples thereof include a method of stirring using a disperser.

The solvent is not particularly limited, but it is difficult to volatilize in the process of dispersing the constituent materials of the material composition, and it is easy to remove the solvent in order to suppress remaining in the foamed papermaking product. From the standpoint of suppressing the increase in energy due to, the one having a boiling point of 50 ° C. or higher and 200 ° C. or lower is preferable.
Examples of the solvent include alcohols such as water, ethanol, 1-propanol, 1-butanol and ethylene glycol, ketones such as acetone, methyl ethyl ketone, 2-heptanone and cyclohexanone, ethyl acetate, butyl acetate, methyl acetoacetate, Examples thereof include esters such as methyl acetoacetate and 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 more 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, a flocculant may be further added to the obtained slurry. Thereby, it becomes easier to obtain the aggregate F formed by aggregating the binder resin A, the filler B, and the thermally expandable microcapsule C in the solvent in a floc form (FIG. 2B).

  Then, the foamable papermaking body 10 can be obtained by papermaking the slurry which mixed the binder resin A, the filler B, the thermally expansible microcapsule C, 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) provided 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, by appropriately selecting the shape of the mesh 30, it is possible to adjust the shape of the foamable paper product to be obtained.
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. Such a foamable papermaking body 10 has a structure in which fiber fillers B entangled randomly in the plane direction are laminated in the thickness direction. By having a structure in which the fiber fillers B are entangled, it is possible to obtain a foamable papermaking product 10 that is lightweight but has excellent strength.
Further, by using the papermaking method, the dispersion of the thermally expandable microcapsules C in the foamable papermaking product 10 can be increased.

<Foamed molded product 50>
The foamed molded product 50 of the present embodiment is a molded product of the foamable papermaking product 10 and has a cell structure in which bubbles D 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 (binder resin A), the filler B, and the thermally expansible microcapsule C, and makes foamability by making this slurry. Obtaining the papermaking body 10;
The foamable papermaking body 10 is disposed 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 | die 40,41 (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 which is a raw material can be arrange | positioned in the state which the inside of metal mold | die 40,41 is not completely filled, ie, what is called a 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 formed 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 above-described foam molding step, the curing reaction of the binder resin A proceeds, and a matrix resin having a three-dimensional structure (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 D (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, an injection molding method etc. are mentioned as a method of applying a molding pressure from the outside. In this method, the thermally expandable microcapsule cannot be foamed due to the filling pressure or holding pressure, and the bubbles are destroyed.
On the other hand, in the manufacturing method of the foamed molded product 50 of this embodiment, since no molding pressure is applied from the outside, unexpanded of the thermally expandable microcapsule C and destruction of the bubbles D can be sufficiently suppressed. .

  In the present embodiment, the magnetic field shielding characteristics can be controlled by appropriately selecting the type and content of the compounding component in the foamable papermaking product 10, the manufacturing method of the foamable papermaking product 10 and the foamed molded product 50, and the like. Is possible. Among these, for example, a specific magnetic filler is used as the filler B, the dispersibility of the filler B and the thermally expandable microcapsule C is improved by a papermaking method, and the expansion ratio and the bubble size are appropriately set by a short shot method. The control method and the like are listed as elements for achieving both magnetic shielding characteristics and weight reduction. Further, as a method of increasing the expansion ratio by the short shot method, for example, the number of thermally expandable microcapsules C is increased, and the content of the matrix resin (binder resin A) and the content of the filler B are decreased by the expansion ratio. Can be mentioned.

  The foam of this embodiment can be used, for example, for a housing such as an electronic device or an industrial machine that generates electromagnetic waves.

  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 the examples and comparative examples are as follows.
(Binder resin)
Thermosetting resin 1: phenol resin (phenol resin, “PR51723”, manufactured by Sumitomo Bakelite Co., Ltd.)
(Filler)
Filler 1: Nickel-coated carbon fiber (magnetic filler), “Tenax HT C923”, manufactured by Toho Tenac Co., Ltd.)
Filler 2: Stainless steel fiber (conductive filler), “Naslon CHOP6 / 5CMC”, manufactured by Nippon Seisen Co., Ltd.)
Filler 3: Aramid fiber, “Technola T32PNW”, manufactured by Teijin Limited)
(Foaming agent)
Foaming agent 1: Thermally expandable microcapsule ("Advancel (registered trademark) EM-304", manufactured by Sekisui Chemical Co., Ltd.)
(Other additives)
Aramid microfiber 1: Aramid microfiber ("Tiara", manufactured by Daicel FineChem Co., Ltd.)

<Example 1, Comparative Example 2>
(Manufacture of foamable paper products)
With the blending ratios shown in Table 1 (raw material volume fraction [Vol%] after foaming), foamable paper products were produced as follows.
First, a binder resin, a filler, a foaming agent, and an additive pulverized to an average particle size of 100 μm (50% particle size based on mass) with an atomizer pulverizer are added to water and stirred with a disperser for 30 minutes. To obtain 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 binder resin, a filler, 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 Example 1 and Comparative Example 2, the obtained foamable papermaking product was placed in a 4 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. In Example 1 and Comparative Example 2, foam molding was performed by the short shot method.
The following evaluation 1 was performed about the obtained foam. The results are shown in Table 1. In addition, the raw material volume fraction after shaping | molding of the foaming agent in Table 1 shows the volume porosity of a foam.

<Comparative example 1, reference example>
(Manufacture of papermaking)
In Comparative Example 1 and Reference Example, 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 binder resin pulverized to an average particle diameter of 100 μm (50% particle diameter based on mass) with an atomizer pulverizer, a filler, and an additive are added to water, and stirred for 30 minutes with a disperser to obtain a mixture. It was. 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 binder 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 1 and Reference Example, the obtained paper product was placed in a 4 mm-thick mold, subjected to heat treatment at 180 ° C. for 10 minutes, and subjected to compression molding to form a non-foamed product made of the paper product. Manufactured. At this time, the following evaluation 1 was performed about the obtained non-foamed body whose internal pressure in a metal mold | die was 2 MPa. The results are shown in Table 1.

(Evaluation 1)
-Density (g / cm < ³ >): It measured by the method based on JIS K-7112 A method.
-Bending strength: Measured at room temperature (25 ° C.) at a measurement frequency of 1 GHz by a method based on JIS K6911.
Specific strength: Calculated by dividing the bending strength by the density (g / cm ³ ).
-Flexural modulus: Measured at room temperature (25 ° C.) and measurement frequency 1 GHz by a method based on JIS K6911.
Specific modulus: Calculated by dividing the bending modulus by density (g / cm ³ ).

The following evaluation 2 was performed on the foam obtained in Example 1 and the sheet obtained in the reference example. The results are shown in FIGS. 4 shows the magnetic field shielding properties of Example 1, FIG. 5 shows the magnetic field shielding properties of the reference example, FIG. 6 shows the electric field shielding properties of Example 1, and FIG. 7 shows the measurement results of the electric field shielding properties of the reference example. Each is shown.
(Evaluation 2)
Magnetic field shielding property: The KEC method was used.
-Electric field shielding property: Performed using the KEC method.

It turned out that the foam of Example 1 is excellent in the balance of electromagnetic wave shielding characteristics and weight reduction. Moreover, it turned out that the foam of Example 1 can obtain the electromagnetic wave shielding characteristics similar to the non-foamed sheet of the reference example. Moreover, it was confirmed that the foam of Example 1 has a closed cell structure.
On the other hand, since Comparative Examples 1 and 2 did not contain a magnetic filler, magnetic field shielding properties were not obtained.

  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 Expandable paper-making body 30 Mesh 40 Mold 41 Mold 50 Foam molded body A Binder resin B Filler C Thermal expansion microcapsule D Bubble F Aggregate

Claims (14)

  A foam in which a magnetic filler is dispersed in a matrix resin having a three-dimensional structure. The foam according to claim 1,
The foam which the material which comprises the said magnetic filler contains 1 type selected from the group which consists of nickel, iron, chromium, cobalt, these alloys, and these metal oxides. The foam according to claim 1 or 2,
A foam containing a conductive filler. The foam according to claim 3,
The foam in which the material which comprises the said conductive filler contains 1 or more types selected from the group which consists of stainless steel, iron, silver, nickel, aluminum, copper, and a carbon fiber. The foam according to any one of claims 1 to 4,
A foam in which the magnetic filler includes a fiber filler coated with a metal. The foam according to any one of claims 1 to 5,
Density (g / cm ³⁾ specific strength indicating the bending strength per ^{are, 50MPa / (g / cm 3} ) or more 300MPa / (g / cm ³⁾ or less, foam. The foam according to any one of claims 1 to 6,
Density (g / cm ³⁾ per bend exhibits an elastic modulus ratio modulus at room ^{temperature, 1GPa / (g / cm 3} ) or more 20GPa / (g / cm ³⁾ or less, foam. The foam according to any one of claims 1 to 7,
A foam having a density (g / cm ³ ) of 0.1 g / cm ³ or more and 2.5 g / cm ³ or less. The foam according to any one of claims 1 to 8,
A foam having a volume porosity of 5% or more and 90% or less. The foam according to any one of claims 1 to 9,
A foam having a closed cell structure. The foam according to any one of claims 1 to 10,
A foam in which the matrix resin includes a cured body of a thermosetting resin. The foam according to claim 11,
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 12,
A foam comprising a foamed paper product. A method for producing a foam for producing the foam according to any one of claims 1 to 13,
Preparing a slurry in which the binder resin forming the matrix resin, the magnetic filler, and the thermally expandable microcapsule are mixed, and obtaining the foamable papermaking by making the slurry; and
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.

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