JP5555603B2 - Foamable resin composition, foamable resin sheet, foam and method for producing the same - Google Patents

Description

  The present invention relates to a foamable resin composition, a foamable resin sheet, a foam and a method for producing the same, and more particularly to a foamable resin composition, a foamable resin sheet, a foam and a method for producing the same used in various industrial fields.

  Conventionally, a heat-foamable resin composition contains a resin and a foaming agent. For example, the heat-foamable resin composition is foamed by generating gas by heating, and is widely used in various industrial fields by utilizing such foaming.

  For example, by placing a thermally foamable reinforcing agent composition containing polyolefin and thermally expandable microspheres on a steel plate of a vehicle body, and then putting them into a heating furnace and heating them to foam and cure the polyolefin, It has been proposed to reinforce a steel plate (see, for example, Patent Document 1).

  In the thermally foamable reinforcing agent composition of Patent Document 1 described above, the thermally expandable microspheres used as the foaming agent include a shell (shell) made of a thermoplastic resin having a gas barrier property, and a low shell included in the shell. Contains a boiling point substance (core, thermal expansion agent).

JP 2004-244508 A

  However, in the thermally foamable reinforcing agent composition of Patent Document 1, in order to foam the polyolefin, it is necessary to thermally expand the low boiling point substance (core) and to melt or soften the shell (shell) by heating. . In order to sufficiently melt or soften the shell, it is necessary to heat the thermally foamable reinforcing agent composition at a high temperature.

  Therefore, a member such as a steel plate on which such a heat-foamable reinforcing agent composition is disposed needs sufficient heat resistance, and if such member has insufficient heat resistance, such member From the viewpoint of protecting (for example, plastics), it is necessary to heat at a low temperature. In such a case, sufficient foaming of the heat-foamable resin composition and further sufficient reinforcement are to be achieved. There is a bug that cannot be done.

  An object of the present invention is to provide a foamable resin composition, a foamable resin sheet, a foam and a method for producing the same, which can be foamed by microwave irradiation.

  In order to achieve the above object, the expandable resin composition of the present invention contains a resin, expandable resin particles containing a thermally expandable substance in a solid resin matrix, and a magnetic material. It is a feature.

  Moreover, in the foamable resin composition of this invention, it is suitable that the mixture ratio of the said magnetic body is 30 mass parts or more with respect to 100 mass parts of said resins.

  In the foamable resin composition of the present invention, it is preferable that the magnetic body is ferrite.

  In the foamable resin composition of the present invention, it is preferable that the magnetic material has a Curie temperature of 300 ° C. or lower.

  The foamable resin composition of the present invention is preferably foamed by microwave irradiation.

  The foamable resin sheet of the present invention is characterized in that the foamable resin composition described above is formed into a sheet shape.

  The foam of the present invention is obtained by foaming the above-described foamable resin composition by microwave irradiation.

  In addition, the foam of the present invention is obtained by foaming the above-described foamable resin sheet by microwave irradiation.

  Moreover, the manufacturing method of the foam of this invention is characterized by making the above-mentioned foaming resin composition foam by irradiation of a microwave.

  Moreover, the manufacturing method of the foam of this invention is characterized by foaming the above-mentioned foaming resin sheet by irradiation of a microwave.

  When the foamable resin composition and the foamable resin sheet of the present invention are irradiated with microwaves, the magnetic material is heated while reliably preventing microwave sparks (creeping discharge). The thermally expandable substance in the resin particles can be expanded, and thus the resin can be surely foamed. By this, the foam of this invention can be obtained reliably.

  In particular, in the expandable resin particles, since the thermally expandable substance is contained in a solid resin matrix, even if the magnetic material is heated at a low temperature based on the irradiation of the low-power microwave, the expandable resin particles are thermally expandable. The material can be reliably expanded.

  Therefore, since the foamable resin composition and foamable resin sheet of the present invention and the member on which they are placed can be foamed by microwave irradiation without being heated in a heating furnace or the like and heated at a high temperature, The foamable resin composition and foamable resin sheet of the invention can be used in various industrial fields where low temperature foaming is required.

FIG. 1 is a schematic explanatory diagram of a foam filling property evaluation method in Examples, wherein (a) is a step of placing a foamable resin sheet made of a foamable resin composition between test plates, and (b) is foaming. The process of foaming the conductive resin sheet by microwave irradiation is shown.

  The expandable resin composition of the present invention contains a resin, expandable resin particles, and a magnetic material.

  Examples of the resin include rubber, thermoplastic resin (excluding rubber), thermosetting resin, and the like.

  The rubber is not particularly limited. For example, polyisobutylene rubber (PIB), chloroprene rubber, butyl rubber, ethylene / propylene rubber, ethylene / propylene / diene rubber, styrene rubber, nitrile rubber, urethane rubber, polyamide rubber, Synthetic rubbers such as silicone rubber, polyether rubber and polysulfide rubber, for example, natural rubber and the like can be mentioned.

  The rubbers can be used alone or in combination of two or more.

  Of the rubbers, synthetic rubber is preferable, and PIB, styrene rubber, and silicone rubber are more preferable.

  PIB is a synthetic rubber obtained by polymerization of isobutylene (isobutene).

  Examples of the styrene rubber include styrene / butadiene rubber (SBR). Styrene-butadiene rubber is a synthetic rubber made of a copolymer of styrene and butadiene. The styrene content of the styrene-butadiene rubber is, for example, 10 to 50% by mass.

Silicone rubber is a synthetic rubber containing organic groups such as alkyl groups and / aryl groups in polysiloxane ((—Si—O—) _n ).

  The weight average molecular weight (GPC: standard polystyrene conversion value) of rubber is, for example, 1,000 to 1,000,000, preferably 10,000 to 100,000.

  The Mooney viscosity (JIS K 6300-1 (2001)) of rubber (styrene butadiene rubber) is, for example, 10 to 100 (ML1 + 4, at100 ° C.).

Moreover, the density of rubber | gum is 0.8-2.1 g / cm < ³ >, for example, Preferably, it is 0.85-2.0 g / cm < ³ >.

  The thermoplastic resin includes a thermoplastic elastomer, for example, styrene resin, acrylic resin, polyolefin, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyacrylonitrile, polyamide, polycarbonate, polyacetal, polyethylene terephthalate, Polyphenylene oxide, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyallylsulfone, thermoplastic polyimide resin, thermoplastic urethane resin, polyamino bismaleimide resin, polyamideimide resin, polyetherimide resin, bismaleimide triazine resin, Polymethylpentene, fluorinated resin, liquid crystal polymer, olefin-vinyl alcohol copolymer, ionomer, polyarylate, etc. That.

  The thermoplastic resins can be used alone or in combination of two or more.

  The thermosetting resin is not particularly limited. For example, epoxy resin, thermosetting polyimide resin, phenol resin, urea resin, melamine resin, unsaturated polyester resin, diallyl phthalate resin, silicone resin, thermosetting urethane resin, etc. Is mentioned.

  The thermosetting resins can be used alone or in combination of two or more.

  As the thermosetting resin, preferably, an epoxy resin is used.

  Examples of the epoxy resin include aromatic epoxy resins such as bisphenol type epoxy resins (for example, bisphenol A type epoxy resins), novolac type epoxy resins, naphthalene type epoxy resins, fluorene type epoxy resins, and triphenylmethane type epoxy resins. Examples thereof include aliphatic epoxy resins, such as alicyclic epoxy resins, such as glycidyl ether type epoxy resins.

  These epoxy resins can be used alone or in combination of two or more.

  An aromatic epoxy resin is preferable, and a bisphenol type epoxy resin is more preferable.

The epoxy equivalent of the epoxy resin is, for example, 100 to 1000 g / eqiv. The density is, for example, 0.75 to 1.25 g / cm ³ , the glass transition temperature is, for example, 30 to 180 ° C., and the weight average molecular weight (GPC: standard polystyrene conversion value) is, for example, 1,000 to 1, 000,000.

  As the above-mentioned resin, rubber and thermosetting resin are preferable.

  The blending ratio of the resin is, for example, 10 to 90% by mass, preferably 10 to 50% by mass with respect to the foamable resin composition.

  The expandable resin particles contain (impregnate) a thermally expandable substance in a solid resin matrix.

  The resin matrix can be made of a resin that can uniformly contain a heat-expandable substance and is hard to be cured by heating. Examples of such a resin include a thermoplastic resin.

  Examples of the thermoplastic resin include the same ones as described above.

  Of the thermoplastic resins, styrene resins and acrylic resins are preferable.

  An example of the styrene resin is a styrene polymer (styrene homopolymer) obtained by polymerizing a monomer containing a styrene monomer. Examples of the styrenic monomer include styrene, α-methylstyrene, ring halogenated styrene, ring alkylated styrene, 2-vinyltoluene (o-methylstyrene), 3-vinyltoluene (m-methylstyrene), 4 -Styrene derivatives such as vinyltoluene (p-methylstyrene). These styrenic monomers can be used alone or in combination of two or more. As the styrene monomer, styrene is preferably used.

  The styrenic polymer is preferably polystyrene (polystyrene homopolymer).

  Examples of the styrene resin include a styrene copolymer (styrene copolymer) of the above styrene monomer and a copolymerizable monomer copolymerizable with the styrene monomer. As the copolymerizable monomer, for example, an ester of (meth) acrylic acid (acrylic acid and / or methacrylic acid) and an alcohol having 1 to 8 carbon atoms (that is, (meth) acrylate), dimethyl fumarate, (Meth) acrylonitrile, vinyl cyanide, ethylene, butadiene, divinylbenzene, alkylene glycol dimethacrylate and the like. These copolymerizable monomers can be used alone or in combination of two or more. Preferred examples of the copolymerizable monomer include (meth) acrylate, acrylonitrile, ethylene, and butadiene.

  As the styrene copolymer, (meth) acrylate-styrene copolymer (MS), acrylonitrile-ethylene-styrene copolymer (AES), acrylonitrile-styrene copolymer (AS), acrylonitrile-butadiene-styrene are preferable. A copolymer (ABS) etc. are mentioned. More preferably, MS and AS are mentioned.

  MS is a block or random copolymer of methyl (meth) acrylate and styrene, and the methyl (meth) acrylate content is, for example, 10 to 60% by mass.

  AS is a block or random copolymer of acrylonitrile and styrene, and the acrylonitrile content is, for example, 10 to 60% by mass.

  Examples of the acrylic resin include poly (meth) methyl acrylate (that is, polymethyl acrylate and / or polymethyl methacrylate), poly (meth) ethyl acrylate, poly (meth) acrylate, and the like. Preferably, poly (meth) acrylic acid methyl is mentioned.

The resin matrix has a solid (that is, not hollow) shape, and its density is, for example, 0.9 to 2.0 g / cm ³ , and preferably 1.0 to 1.5 g / cm ³ .

  Moreover, the glass transition temperature of a resin matrix is 50-110 degreeC, for example, Preferably, it is 80-90 degreeC. The glass transition temperature is measured by the DMA method.

  A thermally expandable substance is a substance that expands when a magnetic substance is heated based on microwave irradiation, and specifically expands at a specific temperature described later, that is, vaporizes (evaporates or boils). Examples of such substances include hydrocarbons, halogenated hydrocarbons, and nonflammable gases.

  Examples of the hydrocarbon include saturated hydrocarbons and unsaturated hydrocarbons. Saturated hydrocarbon is preferable.

  Examples of saturated hydrocarbons include linear alkanes, branched alkanes, and cycloalkanes.

  Examples of the linear alkane include linear alkanes (aliphatic hydrocarbons) having 1 to 7 carbon atoms such as methane, ethane, propane, butane, pentane, hexane, and heptane.

  Examples of branched alkanes include 2-methylpropane (isobutane), 2-methylbutane (isopentane), 2,2-dimethylpropane (neopentane), 2-methylpentane, 3-methylpentane, and 2,3-dimethylbutane. And branched alkanes having 4 to 7 carbon atoms such as 2,4-dimethylpentane.

  Examples of the cycloalkane include cycloalkanes having 3 to 7 carbon atoms (alicyclic hydrocarbons) such as cyclopropane, cyclobutane, cyclopentane, cyclohexane, and cycloheptane.

  The saturated hydrocarbon is preferably a linear alkane.

Examples of the halogenated hydrocarbon include a chlorohydrocarbon such as dichloromethane (CCl ₂ H ₂ ), a fluorohydrocarbon such as difluoromethane (CF ₂ H ₂ ), such as Freon 22 (trademark, CHClF ₂ ), and Freon. And chlorofluorohydrocarbons such as 12 (trademark, CCl ₂ F ₂ ) and Freon 113 (trademark, CCl ₂ FCClF ₂ ).

  Examples of the nonflammable gas include carbon dioxide gas.

  Of these thermally expandable materials, hydrocarbons are preferable.

  The boiling point of the thermally expandable substance is, for example, −160 to 120 ° C., preferably −50 to 100 ° C., and more preferably −5 to 70 ° C.

  When the boiling point of the thermally expandable substance exceeds the above-described range, foaming of the foamable resin composition by microwave irradiation may be difficult. If the boiling point of the thermally expandable material is less than the above range, it may be difficult to uniformly contain the thermally expandable material in the resin.

  The expandable resin particles can be obtained by polymerizing the monomer of the resin matrix described above in the presence of a solvent and a thermally expandable substance. Alternatively, it can be obtained by polymerizing the monomer of the resin matrix described above in the absence of a solvent and in the presence of a thermally expandable substance.

  Preferably, the monomer of the resin matrix is polymerized in the presence of a solvent and a thermally expandable material.

  Examples of the solvent include an aqueous solvent such as water and an organic solvent such as toluene. Preferably, an aqueous solvent is used.

  Specifically, in the expandable resin particles, the monomer is subjected to suspension polymerization while being dispersed in water in an aqueous solvent in which a dispersant is blended and a thermally expandable substance is blown (inflowed). By According to the polymerization method described above, the thermally expandable substance can be uniformly contained in the resin matrix.

  The expandable resin particles thus obtained are formed into a solid spherical shape (bead shape) or a solid pellet shape, preferably a solid bead shape.

  The average value of the maximum length of the expandable resin particles (in the case of a spherical shape, the average particle diameter) is, for example, 0.2 to 4 mm, preferably 0.4 to 2.0 mm. If the average value of the maximum length of the expandable resin particles exceeds the above range, the uniformity in design and foamability may be deteriorated. If the average value of the maximum length of the expandable resin particles is less than the above range, the thermally expansible material easily volatilizes, and the storage stability may be impaired.

  And in this expandable resin particle, the thermally expansible substance is contained in the solid resin matrix.

  That is, in the expandable resin particles, the thermally expandable substance is permeated from the surface of the solid (not hollow) granular resin matrix to the inside.

  The content rate of a thermally expansible substance is 1-10 mass parts with respect to 100 mass parts of resin matrices, Preferably, it is 2-8 mass parts.

  Thereby, in expandable resin particles, low temperature, specifically, for example, 120 ° C. or lower (specifically, 70 to 120 ° C.), 110 ° C. or lower (specifically, 70 to 110 ° C.), Furthermore, thermal expansion starts at a temperature (thermal expansion start temperature) of 100 ° C. or lower (specifically, 70 to 120 ° C.).

Moreover, the density of the expandable resin particle after thermal expansion is 0.005-0.5 g / cm < ³ >, for example, Preferably, it is 0.01-0.1 g / cm < ³ >.

  The expansion coefficient at 100 ° C. of the expandable resin particles is, for example, 2 to 200 times, preferably 10 to 100 times, although it depends on the content ratio of the thermally expandable substance.

  As such an expandable resin, commercially available products (expandable beads) can be used. For example, “Kanepal” (expandable polystyrene beads or expandable polymethylmethacrylate beads, manufactured by Kaneka Corporation), “Styrodia” (expanded) Polystyrene beads), "heat pole" (expandable acrylonitrile / styrene resin beads, "clear pole" (expandable methyl methacrylate-styrene resin beads) (from JSP), "Eslen beads" (expandable polystyrene beads) ), “PN beads” (special expanded polystyrene beads) (manufactured by Sekisui Plastics Co., Ltd.).

  The blending ratio of the expandable resin particles is, for example, 30 to 1000 parts by mass, preferably 50 to 500 parts by mass with respect to 100 parts by mass of the resin.

  If the blending ratio of the expandable resin particles is less than the above range, the expansion ratio becomes too low, and the resin may not be sufficiently foamed. On the other hand, if the blending ratio of the expandable resin particles exceeds the above range, the expandable resin particles may fall off the resin.

  Examples of the magnetic material include a ferromagnetic material and a diamagnetic material, and a ferromagnetic material is preferable.

  A ferromagnetic material is a magnetic material that is strongly magnetized in that direction by a magnetic field and retains residual magnetization even when the magnetic field is removed. Examples of such a ferromagnetic material include a soft magnetic material and a hard magnetic material.

  Examples of the soft magnetic material include soft magnetic ferrite (soft ferrite), soft magnetic irons, and the like.

  Soft magnetic ferrite is an iron oxide represented by the following composition formula (1).

AO · Fe ₂ O ₃ (1)
(A represents a divalent transition element or a Group 12 element.)
In the composition formula (1), examples of the divalent transition element represented by A include a main transition element. Examples of such a main transition element include Sc, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. are mentioned.

  The above divalent transition elements can be used alone or in combination of two or more.

  In the composition formula (1), examples of the Group 12 element represented by A include Zn, Cd, and Hg. These Group 12 elements can be used alone or in combination of two or more.

Specific examples of the soft magnetic ferrite include Ni—Cu—Zn ferrite (NiO / CuO / ZnO.Fe ₂ O ₃ , the same applies hereinafter), Ni—Zn ferrite, Ni—Cu ferrite, and Mn—Zn ferrite. .

  Examples of soft magnetic irons include β iron and iron alloys.

  As an iron alloy, for example, an alloy containing a small amount of Si, Ni, Al, etc. in iron (for example, 10 mass% or less in the iron alloy), specifically, Fe-Si (Si-containing iron alloy, The same applies hereinafter. Silicon steel), Fe-Ni, Fe-Si-Al, and the like.

  Examples of the hard magnetic material include α iron, hard magnetic ferrite (hard ferrite), alloys (excluding hard magnetic ferrite), and the like.

  An example of the hard magnetic ferrite is an iron oxide represented by the following composition formula (2).

B.Fe ₂ O ₃ (2)
(B represents an alkaline earth metal.)
In the composition formula (2), examples of the alkaline earth metal represented by B include Be, Mg, Ca, Sr, Ba, and Ra. Preferably, Ba is mentioned.

  Specific examples of the hard magnetic ferrite include Ba ferrite.

  The alloy includes, for example, a transition element. Specifically, the alloy includes a main transition element as an essential component and an inner transition element as an optional component.

  Examples of the main transition element include the same main transition elements as described above.

  Examples of the inner transition element include La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

  Specific examples of the alloy include Fe—Al—Ni—Co (alloy of Al, Ni and Co, hereinafter the same as an alnico alloy), Sm—Co, Nd—Fe—B, and the like.

  The ferromagnetic material is preferably a hard magnetic ferrite.

  Examples of the magnetic material include Fe—Si, Fe—Ni, Fe—Al, YIG (yttrium iron garnet), and the like.

  Preferably, the magnetic material includes ferrite such as the soft magnetic ferrite and hard magnetic ferrite described above.

  The Curie temperature (temperature at which magnetism disappears by heating) of the magnetic material is, for example, 300 ° C. or less, preferably 70 to 250 ° C., and more preferably 80 to 150 ° C.

  If the Curie temperature of the magnetic material exceeds the above range, the foamable resin composition may be overheated (for example, 150 ° C. or more), and shrinkage may occur due to outgassing of the foamable resin particles, and foaming may not be possible. .

  On the other hand, if the Curie temperature of the magnetic material is within the above range, the upper limit of the temperature at which the magnetic material is heated by the microwave irradiation is within the above range, so that the foamable resin composition can be foamed at a low temperature. .

  The magnetic permeability (μ ″ at a wavelength of 2.45 GHz) of the magnetic material is, for example, 0.1 or more, preferably 0.1-10. The magnetic permeability is calculated by the coaxial tube method.

  The magnetic permeability is a ratio between the magnitude of the magnetic flux density and the strength of the magnetic field, and specifically indicates the ease of heating by microwave irradiation. If the magnetic permeability of the magnetic material is within the above-described range, the magnetic material can be efficiently heated by microwave irradiation.

Note that the complex permeability μ, which is a complex representation of the permeability, is represented by the following formula (3):
μ = μ'-jμ '' (3)
(In the formula, μ ′ represents a real component of complex permeability, j represents (−1) ^1/2 , and μ ″ represents an imaginary component of complex permeability.)
Moreover, the retention strength of a magnetic body is 1-20 A / m (Oe), for example, Preferably, it is 2-10 A / m.

The saturation magnetization of the magnetic material is, for example, 1 to 200 A · m ² / kg (emu / g), preferably ^{2 to} 100 A · m ² / kg (emu / g).

The remanent magnetization of the magnetic substance is, for example, 0.01 to 2.0 A · m ² / kg (emu / g), preferably 0.1 to 1.0 A · m ² / kg.

  The magnetic substance is usually solid at room temperature, and the shape thereof is not particularly limited. For example, the magnetic substance is particulate. Further, the magnetic body may be porous.

  When the magnetic material is in the form of particles, the d50, that is, the particle size (d50) when the mass percentage in the particle size accumulation curve is 50% is, for example, 0.1 to 100 μm, preferably 1 ~ 50 μm.

  When the particle size (d50) exceeds the above range, the appearance of the foamable resin composition may be poor, and when it is less than the above range, it may be difficult to fill (blend) the resin.

  In addition, d10 of a magnetic body is 0.05-50 micrometers, for example, and d90 is 0.5-100 micrometers, for example.

  The particle size accumulation curve is measured by, for example, a laser diffraction method.

The specific surface area of the magnetic body, for example, 0.001~1m ² / g, preferably from 0.01~0.1m ² / g. The specific surface area is calculated by, for example, the BET method.

The true specific gravity of the magnetic material is, for example, 0.5 to 50, preferably 1 to 10, and the bulk density is, for example, 0.2 to 20 g / cm ³ , preferably 0.5 to ⁵ g / cm ^3. It is.

  The blending ratio of the magnetic substance is, for example, 30 parts by mass or more, preferably 35 to 350 parts by mass, and more preferably 40 to 250 parts by mass with respect to 100 parts by mass of the resin.

  When the blending ratio of the magnetic material is less than the above range, when the microwave is irradiated, the degree to which the magnetic material is heated in the foamable resin composition becomes insufficient, and the resin cannot be foamed. There is.

  Moreover, when the mixture ratio of a magnetic body exceeds the said range, the foaming resin composition may not be reduced in weight.

  On the other hand, when the blending ratio of the magnetic material is within the above range, when the microwave is irradiated, the magnetic material is sufficiently heated in the foamable resin composition, and the resin can be efficiently foamed. .

  The foamable resin composition is prepared, for example, by blending the above-described resin, foamable resin particles, and magnetic material, and stirring and mixing them.

  Specifically, the foamable resin composition is prepared as a kneaded product by kneading the above-described resin, foamable resin particles, and magnetic body with, for example, a mixing roll, a pressure kneader, an extruder, or the like.

  In this kneading, for example, the resin and the expandable resin are used at a temperature lower than the thermal expansion start temperature of the expandable resin particles, specifically at a temperature of room temperature (20 ° C.) to less than 70 ° C., preferably 20 to 55 ° C. The particles and the magnetic material are heated.

  Thereby, the foamable resin composition of this invention can be obtained.

  In addition, the foamable resin composition of the present invention includes, for example, a filler (such as zinc oxide; excluding a magnetic substance), a curing agent (such as an amine compound such as ethylenediamine), curing, and the like within a range that does not impair the effects of the present invention. Accelerators (such as imidazole compounds), cross-linking agents, vulcanizing agents, other foaming agents (foaming agents excluding foamable resin particles), foaming accelerators, cross-linking accelerators, vulcanization accelerators, thixotropic agents, Known additives such as lubricants, pigments, anti-scorch agents, stabilizers, softeners, plasticizers, anti-aging agents, antioxidants, UV absorbers, colorants, anti-mold agents, flame retardants, tackifiers, It can also be added at an appropriate ratio.

  Then, the foamable resin composition (kneaded material) obtained as described above is formed into a predetermined shape such as a sheet by a molding method such as calendar molding, extrusion molding, injection molding, or press molding.

  In the molding of the kneaded product, the kneaded product is heated at a temperature lower than the thermal expansion start temperature of the expandable resin particles, specifically at a normal temperature (20 ° C.) or a temperature of less than 70 ° C., preferably 20 to 55 ° C. .

  Moreover, when forming in a sheet form, the thickness of the sheet | seat is 0.2-10 mm, for example.

  Thereby, a foamable resin composition can be obtained as the foamable resin sheet of the present invention.

  The foamable resin sheet thus obtained is used as a microwave foamed resin sheet that foams by microwave irradiation.

  That is, when the foaming resin sheet is irradiated with microwaves, the microwaves are absorbed by the magnetic material, thereby heating the magnetic material. Then, the heat-expandable substance in the expandable resin particles expands due to the heating, so that the resin can be reliably foamed. Thereby, a foam can be obtained reliably.

  At the same time, in the foamable resin sheet, it is possible to effectively prevent the reflection of microwaves and the occurrence of sparks (creeping discharge) due to the microwaves while the magnetic material appropriately absorbs the microwaves. Therefore, it is possible to prevent the microwave generator from being damaged due to the spark while efficiently foaming the foamable resin sheet.

  In particular, in this expandable resin particle, since the thermally expandable substance is contained in a solid resin matrix, the magnetic material is irradiated to the microwave with a low irradiation output (for example, 260 W or less), and the magnetic material is cooled to a low temperature. Even when heated at (for example, 140 ° C. or lower, more specifically 80 to 130 ° C.), the thermally expandable substance can be reliably expanded.

  Moreover, since the magnetic body is heated by the microwave magnetic field, when the magnetic body is heated to the Curie temperature, the magnetism disappears and the heating by the magnetic field is stopped. Thereafter, when the temperature falls below the Curie temperature, it is heated again. And the stop and restart of heating are repeated. With such a principle, it is possible to perform low-temperature heating near the Curie temperature, and temperature control to prevent overheating is possible.

  Therefore, since the magnetic body having a relatively low Curie temperature of Curie temperature of 300 ° C. or less is not heated exceeding that, the blending ratio of the magnetic body to the foamable resin composition is, for example, By adjusting to the range of 5-50 mass%, it is possible to adjust the temperature of a foamable resin sheet to the range of less than 150 degreeC and also less than 130 degreeC, for example.

  However, when the blending ratio of the magnetic material exceeds 50% by mass with respect to the foamable resin composition, heating by an electric field is performed due to the influence of the metal component contained in the magnetic material, and the temperature rises exceeding the Curie temperature. It is presumed that there is a case of doing so.

  On the other hand, in the case of foaming below the Curie temperature without using the disappearance of the magnetism of the magnetic material at the Curie temperature, by adding a conductive substance to the foamable resin composition at the desired blending ratio described above. The wavelength of the microwave is, for example, 100 μm to 1 m, the frequency is, for example, 300 MHz to 3 THz, the irradiation output of the microwave is, for example, 100 to 2,000 W, and the irradiation time is, for example, 0.2 to 30 minutes ( Preferably, the foamable resin sheet foams in 0.5 to 10 minutes.

  In addition, when the microwave irradiation conditions described above are made constant, the temperature of the foamable resin sheet and further the foaming of the resin can be controlled by adjusting the blending ratio of the magnetic substance in the foamable resin composition. Can do.

  As a result, the foamable resin sheet of the present invention can be foamed by microwave irradiation without being heated in a heating furnace or the like together with the member in which the foamed resin sheet is disposed. And the like can be used in various industrial fields that require low-temperature foaming.

  For example, the foam obtained by foaming the above-described foamable resin sheet can be used as a filler for industrial products in various industrial fields that are filled between various members or in the internal space of the hollow member.

  In order to fill the space between the various members or the internal space of the hollow member, for example, a foamable resin sheet is installed between the various members or in the internal space of the hollow member, and then the foamable resin sheet installed In addition, the foam is formed by foaming the foamable resin sheet by irradiating with microwaves. Thus, the formed foam fills the space between the members or the internal space of the hollow member.

  And the above-mentioned filler can give various effects, such as reinforcement, vibration suppression (vibration-proof), soundproofing, dustproofing, heat insulation, buffering, watertightness and airtightness, or adhesion to the above-mentioned member or hollow member. it can. Therefore, for example, a reinforcing material, a damping material (vibration-proofing material), a soundproofing material, a dustproofing material, a heat-insulating material, a shock-absorbing material, a water-stopping material, or a sealing material is filled between various members or inside the hollow member. Alternatively, it can be suitably used as a filler for various industrial products such as adhesives.

  In particular, the foamable resin sheet is used, for example, for sealing automobiles, electrical products, residential products, and the like. In that case, for example, the foamable resin sheet is attached to a gap between an automobile, an electrical product, or a residential product, and then foamed by irradiation with microwaves. Thus, the gap is filled with the foam.

  That is, the foamable resin sheet is preferably used as a sealing material for sealing gaps between various members of automobiles, electrical products, residential products, etc., as automotive exterior sealing materials, electrical product sealing materials, residential sealing materials, etc. It is done. The foam is used as an anti-vibration material, sound-proof material, dust-proof material, heat-insulating material, shock-absorbing material, water-stopping material, sealing material, etc. for automobiles, electrical products or residential products. Can be watertight and airtight.

  The foamable resin sheet of the present invention is used, for example, for reinforcing automobile structural members, specifically, resin bumpers and instrument panels that require foaming at low temperatures. In that case, first, a reinforcing sheet is produced by laminating a constraining layer formed of glass cloth or the like on a foamable resin sheet. Next, the foamable resin sheet of the produced reinforcing sheet is attached to the above-described automobile structural member, and then foamed by microwave irradiation. And the structural member of a motor vehicle can be reinforced with the steel plate reinforcement sheet provided with a foam.

  In order to irradiate the foamable resin sheet with microwaves, the foamable resin sheet and the above-described automobile structural member on which the foamable resin sheet is adhered are put into a known microwave generator, and the microwave is applied to them. Irradiate. Alternatively, only the foamable resin sheet can be irradiated with microwaves.

The foam thus obtained has a density of, for example, 0.03 to 1.0 g / cm ³ , preferably 0.05 to 0.5 g / cm ³ , and more preferably 0.06 to 0. .2 g / cm ³ . In addition, the density of a foam is measured based on JISZ8807.

  If the density of the foam is out of the above range, the filling property of the foam may be lowered.

  Further, the expansion ratio (that is, the volume expansion ratio at the time of expansion of the expandable resin sheet) is, for example, 1.5 to 30 times, preferably 2 to 20 times.

  The expansion ratio is calculated as [density of foamable resin sheet (foamable resin sheet before foaming)] / [density of foam (foamable resin sheet after foaming)].

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited thereto.

Examples 1-6 and Comparative Examples 1-3
Each component was kneaded with a mixing roll at 50 ° C. for 10 minutes at a rotation speed of 10 min ⁻¹ for 10 minutes according to the formulation of Table 1 to prepare a foamable resin composition as a kneaded product. Thereafter, the prepared foamable resin composition was pressed at 50 ° C. and a pressure of 50 kg / cm ² for 5 minutes to form a foamable resin sheet having a thickness of 2 mm.

(Evaluation)
(1) Density and expansion ratio The foamable resin sheet obtained as described above was punched into a circular shape with a diameter of 19 mm to prepare a sample, and then the prepared sample was converted into a microwave irradiation device (model number CRE173-5, Investa Inc.). The sample was foamed by irradiating the sample with a microwave (wavelength: 12.2 cm, frequency: 24.5 GHz) at an output of 260 W for a predetermined time (see Table 1), and a foam was obtained. .

The densities before and after foaming (the sample before foaming and the foam after foaming) were measured in accordance with JIS Z8807, and the foaming ratio was calculated therefrom. The results are shown in Table 1.
(2) Foam filling property The foamable resin sheet obtained as described above was cut into a size of 50 mm in length and 20 mm in width to produce a sample (1). Thereafter, the produced sample (1) was obtained as shown in FIG. ) Between the plastic test plates (2) having the size shown in FIG. 2 (length: 50 mm, width: 25 mm).

  After that, by putting them into a microwave irradiation device (model number CRE173-5, manufactured by Convesta) and irradiating the sample with microwaves under the same conditions as shown above, as shown in FIG. Sample (1) was foamed to obtain foam (3).

  And the foam filling property of the foam (3) between the test plates (2) was visually evaluated according to the following criteria. The results are shown in Table 1.

(Evaluation criteria)
○: The foam filling property was good.

  X: There was a gap (unfilled portion), and the foam filling property was slightly poor.

  In Table 1, the numerical value in the column of the blending prescription of the foamable resin composition indicates the number of parts by mass of each component.

In Table 1, for each component, the compounds indicated by “*” and evaluation are described in detail below.
Opanol B50 ^{* 1} : Polyisobutylene rubber, weight average molecular weight (GPC: standard polystyrene conversion value) 340,000, density 0.92 g / cm ³ , OPSFOL B12 ^{* 2} manufactured by BASF Corporation: polyisobutylene rubber, weight average molecular weight (GPC: Standard polystyrene equivalent value) 51,000, density 0.92 g / cm ³ , KE-550-U ^{* 3} manufactured by BASF: silicone rubber, density 1.21 g / cm ³ , Toughden 2003 manufactured by Shin-Etsu Silicone, Inc. ^{* 4} : SBR, Mooney viscosity 33 (ML1 + 4, 100 ° C), styrene content 25% by mass
PKHM-301 ^{* 5} : bisphenol A type epoxy resin, glass transition temperature 45 ° C., weight average molecular weight 39,000, Epicoat # 834 ^{* 6} manufactured by InChem, Inc .: bisphenol A type epoxy resin, epoxy equivalent 230-270 g / eqiv. , Density 1.18 g / cm ³ , ST-01-8 ^{* 7} manufactured by JER: Ni—Cu—Zn ferrite powder, soft magnetic ferrite, Curie temperature: 230 ° C., specific surface area 0.07 m ² / g, true specific gravity 5 .25, coercive force 7.0 A / m (Oe), saturation magnetization 69 A · m ² / kg (emu / g), residual magnetization 0.6 A · m ² / kg (emu / g), permeability: complex permeability Real component μ′2.5 / imaginary component μ ″ of complex permeability μ ″ 1.2 (frequency at the time of permeability measurement: 1 GHz), d50 (laser diffraction method, the same applies hereinafter): 28 μm, d10: 18 μm, d90: 40 μm, Toda Kogyo JR11G ^{* 8} : Ni—Zn ferrite powder, soft magnetic ferrite, Curie temperature: 100 ° C. or higher, 130 ° C. or lower, bulk density 1.58 g / cm ³ , d50: 1.57 μm (laser diffraction method) ,Japan Chemical Industry Co., Ltd. Zinc oxide ^{* 9:} Zinc oxide two products, the average particle diameter 0.24～0.3Myuemu, Mitsui Mining & Smelting Co. ^{NB-7 * 10:} expandable polystyrene beads, Kaneparu NB-7, of the resin matrix Glass transition temperature 85 ° C, butane and pentane content, average particle size 0.46mm, thermal expansion start temperature 70 ° C, density (before thermal expansion) 1.00g / cm ³ , expansion ratio 45 times (100 ° C), manufactured by Kaneka Corporation HJM ^{* 11} : Expandable polystyrene beads, Kanepal HJM, glass transition temperature of resin matrix 85 ° C., hydrocarbon content, average particle diameter 0.5 mm, thermal expansion start temperature 70 ° C., density (before thermal expansion) 1.00 g / cm ^3, fold expansion ratio 45 (100 ° C.), manufactured by Kaneka Corporation ^{K-M * 12:} expandable polystyrene beads, Kaneparu K-M, the glass transition temperature of the resin matrix 85 ° C. Hydrocarbons containing an average particle diameter of 1 mm, the thermal expansion starting temperature of 70 ° C., a density (before thermal expansion) 1.00 g / cm ^3, expansion ratio 45 times (100 ° C.), manufactured by Kaneka Corporation ^{K-BS * 13:} expandable polystyrene Beads, Kanepal K-BS, glass transition temperature of resin matrix 85 ° C., hydrocarbon content, average particle diameter 0.6 mm, thermal expansion start temperature 70 ° C., density (before thermal expansion) 1.00 g / cm ³ , expansion ratio 45 Double (100 ° C.), Density manufactured by Kaneka ^{* 14} : Measured in accordance with JIS Z8807 Foaming ratio ^{* 15} : Volume foaming ratio = density of sample before foaming / density of foam after foaming ^{* 16} : microwave After foaming by foaming ^{* 17} : After foaming by microwave radiation

1 Expandable resin sheet (sample)
2 Test plate (hollow member)
3 Foam

Claims (12)

Resin,
Expandable resin particles containing a thermally expandable substance in a solid resin matrix containing a styrenic resin and having a thermal expansion start temperature of 120 ° C. or less ;
A foamable resin composition comprising a magnetic material.   The foamable resin composition according to claim 1, wherein a blending ratio of the magnetic body is 30 parts by mass or more with respect to 100 parts by mass of the resin.   The expandable resin composition according to claim 1, wherein the magnetic body is ferrite.   The expandable resin composition according to any one of claims 1 to 3, wherein the Curie temperature of the magnetic body is 300 ° C or lower.   The foamable resin composition according to any one of claims 1 to 4, wherein the foamable resin composition is foamed by microwave irradiation.   A foamable resin sheet, wherein the foamable resin composition according to any one of claims 1 to 5 is formed into a sheet shape.   A foam obtained by foaming the foamable resin composition according to any one of claims 1 to 5 by irradiation with microwaves.   A foam obtained by foaming the foamable resin sheet according to claim 6 by microwave irradiation.   A foam production method comprising foaming the foamable resin composition according to any one of claims 1 to 5 by irradiation with microwaves.   A method for producing a foam, wherein the foamable resin sheet according to claim 6 is foamed by microwave irradiation. The method for producing a foam according to claim 9, wherein the foamable resin composition is foamed at a temperature of 140 ° C. or lower. The method for producing a foam according to claim 10, wherein the foamable resin sheet is foamed at a temperature of 140 ° C. or lower.

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