JP2013014716A - Inorganic particle-containing foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new inorganic particle-containing foam in which at least a part of an inner wall surface in the foam is a surface of a layer where an inorganic particle is unevenly distributed, the layer containing inorganic particles.SOLUTION: This inorganic particle-containing foam includes a plurality of air bubbles in a continuous resin phase, in which at least a part of the inner wall surface in the foam is a surface of the layer where the inorganic particle is unevenly distributed, the layer containing inorganic particles.

Description

  The present invention relates to a foam containing inorganic particles. More specifically, the present invention is a foam having a plurality of bubbles in a continuous resin phase, and at least a part of the inner wall surface in the foam is a surface of an inorganic particle uneven distribution layer containing inorganic particles. The present invention relates to a foam containing inorganic particles.

  The W / O type emulsion is particularly known as a W / O type HIPE (highly discontinuous phase emulsion) (for example, see Patent Document 1).

  The formation of a W / O type HIPE containing a polymerizable monomer in an external oil phase and polymerizing it has been conducted to study the geometrical arrangement of the oil phase and aqueous phase of the emulsion. For example, by polymerizing after preparing a W / O type HIPE containing 90% aqueous phase component and using styrene monomer in the oil phase component, the geometry of the oil phase and aqueous phase of the emulsion can be reduced. It is reported to consider (for example, refer nonpatent literature 1). In Non-Patent Document 1, a W / O type HIPE is prepared by stirring an oil phase and an aqueous phase using a lipophilic emulsifier, and then the polymerization is performed, and the phase relationship of the precursor of the W / O type HIPE is determined. It has been reported that a rigid porous body having a determined bubble shape is formed.

  In forming a porous body using a W / O type emulsion, a W / O type emulsion having good emulsifiability and stationary storage stability is suitable. In order to obtain such a W / O type emulsion, it is generally essential to add an emulsifier or an emulsifier substitute material. As the lipophilic emulsifier, sorbitan monooleate, inorganic fine particles subjected to surface hydrophobization treatment, layered clay mineral, and the like are used. For example, a method for preparing a surfactant-free W / O emulsion containing fine solid spherical particles of polyalkylsilesquioxane has been reported (for example, see Patent Document 2).

  As described above, in order to prepare a W / O type emulsion having good emulsifiability and stationary storage stability, it is essential to add an emulsifier or an emulsifier substitute material. In this case, the amount of emulsifier or emulsifier substitute material is generally used in the range of up to 30 parts by weight of the oil phase component. However, even if an emulsifier or an emulsifier substitute material is blended and a W / O emulsion having good emulsifiability and stationary storage stability can be prepared, the emulsifier or the emulsifier substitute material present as a low molecular weight component is a contaminant. There is a problem that the physical properties of the porous polymer material finally obtained by polymerization are significantly affected.

  In order to avoid the above problems, a reactive emulsifier that can be introduced into the continuous phase constituting the porous polymer material has been studied. For example, functionalized metal oxide nanoparticles have been reported as reactive emulsifiers that can be introduced into the continuous phase constituting the porous polymer material (see, for example, Patent Document 3).

  However, on an industrial or pilot plant scale, a continuous process produces W / O type emulsions as described above, in particular polymerizable W / O type HIPEs, and commercializes porous polymeric materials. When the production of the porous polymer material is necessary, the physical properties of the porous polymer material are affected by the problem that the stability of the W / O emulsion to be prepared is not sufficient, and the influence of the emulsifier, the emulsifier substitute material and the reactive emulsifier. There is a problem that it is very different from physical properties. Thus, the inorganic particle used in the manufacturing method of the porous body using a W / O type emulsion is a surface-treated inorganic particle, and is used as an emulsifier or an emulsifier substitute material.

US Pat. No. 3,565,817 Japanese Patent No. 2656226 JP-T-2004-504461

"Medium and high discontinuous phase ratio water / polymer emulsion" (Lissant and Mahan, Journal of Colloid and Interfacescience, Vol. 42, No. 1, January 1973, pages 201-208)

  The present invention has been made in order to solve the above-described conventional problems, and an object of the present invention is a foam having a plurality of bubbles in a continuous resin phase, and at least an inner wall surface in the foam. An object of the present invention is to provide an inorganic particle-containing foam which is the surface of an inorganic particle unevenly distributed layer partly containing inorganic particles.

  The inorganic particle-containing foam of the present invention is a foam having a plurality of bubbles in a continuous resin phase, and at least a part of the inner wall surface in the foam is the surface of an inorganic particle uneven distribution layer containing inorganic particles. .

  In preferable embodiment, the said inorganic particle uneven distribution layer contains the component which comprises the said continuous resin phase.

  In preferable embodiment, the average particle diameter of the said inorganic particle is 5 nm-500 nm.

  In preferable embodiment, the average pore diameter of the spherical cell of the said foam is 50 micrometers or less.

In another aspect of the present invention, a method for producing the above-mentioned inorganic particle-containing foam is provided. The method for producing the inorganic particle foam includes the following steps (I) to (IV):
(I) a step of preparing a W / O emulsion using a continuous oil phase component and an aqueous phase component containing inorganic particles;
(II) a step of shaping the obtained W / O emulsion,
(III) polymerizing the shaped W / O emulsion to obtain a water-containing polymer;
(IV) A step of dehydrating the water-containing polymer and forming a foam in which at least a part of the inner wall surface in the resulting foam is an inorganic particle unevenly distributed layer.

  According to the present invention, a novel inorganic particle which is a foam having a plurality of bubbles in a continuous resin phase, wherein at least a part of the inner wall surface in the foam is the surface of an inorganic particle uneven distribution layer containing inorganic particles A containing foam can be obtained. This novel inorganic particle-containing foam can be applied to various applications.

It is a photograph figure of the cross-sectional SEM photograph which image | photographed the cross section of the inorganic particle containing foam produced in Example 1 by 250 time. It is a photograph figure of the cross-sectional SEM photograph which image | photographed the cross section of the inorganic particle containing foam produced in Example 1 by 2000 time. It is a photograph figure of the cross-sectional SEM photograph which image | photographed the cross section of the inorganic particle containing foam produced in Example 1 by 10000 times. It is a photograph figure of the cross-sectional SEM photograph which image | photographed the cross section of the inorganic particle containing foam produced in Example 2 by 250 time. It is a photograph figure of the cross-sectional SEM photograph which image | photographed the cross section of the inorganic particle containing foam produced in Example 2 2000 times. It is a photograph figure of the cross-sectional SEM photograph which image | photographed the cross section of the inorganic particle containing foam produced in Example 2 by 10000 times. It is a photograph figure of the cross-sectional SEM photograph which image | photographed the cross section of the inorganic particle containing foam produced in Example 3 by 250 time. It is a photograph figure of the cross-sectional SEM photograph which image | photographed the cross section of the inorganic particle containing foam produced in Example 3 by 2000 time. It is a photograph figure of the cross-sectional SEM photograph which image | photographed the cross section of the inorganic particle containing foam produced in Example 3 by 10000 times. It is a photograph figure of the cross-sectional SEM photograph which image | photographed the cross section of the inorganic particle containing foam produced in Example 4 by 250 time. It is a photograph figure of the cross-sectional SEM photograph which image | photographed the cross section of the inorganic particle containing foam produced in Example 4 by 2000 time. It is a photograph figure of the cross-sectional SEM photograph which image | photographed the cross section of the inorganic particle containing foam produced in Example 4 by 10000 times. It is a photograph figure of the cross-sectional SEM photograph which image | photographed the cross section of the foam produced in the comparative example 1 by 800 time. It is a photograph figure of the cross-sectional SEM photograph which image | photographed the cross section of the foam produced in the comparative example 1 by 10,000 times.

≪ << A. Foam containing inorganic particles >>>>
The inorganic particle-containing foam of the present invention is a foam having a plurality of bubbles in a continuous resin phase. The bubbles of the foam may have a closed cell structure, or may have an open cell structure having through holes between adjacent spherical bubbles. In the present specification, the “spherical bubble” does not have to be a strict true spherical bubble, for example, a substantially spherical bubble having a partial strain or a bubble having a large strain. Also good.

  The average pore diameter of the spherical bubbles of the foam containing the inorganic particles of the present invention is preferably 50 μm or less, more preferably 20 μm or less, and further preferably 18 μm or less. The lower limit value of the average pore diameter of the spherical bubbles of the foam containing the inorganic particles of the present invention is not particularly limited, and is preferably 0.01 μm, more preferably 0.1 μm, and further preferably 1 μm, for example.

  When the inorganic particle-containing foam of the present invention is a foam having an open-cell structure, the average pore diameter of the through holes of the foam is preferably 5 μm or less, more preferably 4 μm or less, and even more preferably 3 μm. It is as follows. When the inorganic particle-containing foam of the present invention is a foam having an open-cell structure, the lower limit value of the average pore diameter of the through-holes possessed by the inorganic particle-containing foam of the present invention is not particularly limited. It is 001 μm, more preferably 0.01 μm.

  The inorganic particle-containing foam of the present invention is a foam having a plurality of bubbles in a continuous resin phase, and at least a part of the inner wall surface in the foam is a surface of an inorganic particle uneven distribution layer containing inorganic particles. is there. In a foam, generally, a continuous phase portion and a bubble portion are separated by a surface in contact with each bubble (gas portion) of the continuous phase (solid portion) of the foam. In the inorganic particle-containing foam of the present invention, at least a part of the portion separating the continuous phase portion and the bubble portion (that is, the inner wall surface in the foam) is the surface of the inorganic particle uneven distribution layer, and the inorganic particle uneven distribution layer The continuous resin phase and the air bubbles are separated from each other. Preferably, the inorganic particle-containing foam of the present invention is a surface of an inorganic particle uneven distribution layer in which almost the entire surface in contact with each bubble of the continuous resin phase contains inorganic particles. That is, it is preferable that almost the entire surface in contact with each bubble contained in the inorganic particle-containing foam of the present invention is the surface of the inorganic particle uneven distribution layer.

  In one preferable embodiment of the present invention, the inorganic particle uneven distribution layer is a layer containing inorganic particles and components constituting a continuous resin phase. Preferably, the content ratio of the inorganic particles in the inorganic particle uneven distribution layer is larger than the content ratio of the inorganic particles in the continuous resin phase. In this embodiment, since the inorganic particle uneven distribution layer includes a component constituting the continuous resin phase, the continuous resin phase of the foam and the inorganic particle uneven distribution layer are substantially continuous, and at least one of the inner wall surfaces in the foam. The part becomes the surface of the inorganic particle uneven distribution layer. In addition, since the inorganic particle uneven distribution layer of this invention has the content rate of an inorganic particle larger than a continuous resin phase, it can recognize as a layer clearly different from a continuous resin phase. For example, it can be confirmed from the cross-sectional SEM photograph of the inorganic particle-containing foam photographed at a magnification of 250 times or more that the inorganic particle uneven distribution layer exists as a layer clearly different from the continuous resin phase.

  In another preferred embodiment of the present invention, the inorganic particle uneven distribution layer is a layer containing only inorganic particles. The inorganic particle uneven distribution layer containing only the inorganic particles can be formed, for example, by attaching inorganic particles to the inner wall surface in the foam. The presence of the inorganic particle uneven distribution layer can be confirmed by, for example, a cross-sectional SEM photograph of the inorganic particle-containing foam taken at a magnification of 250 times or more.

  The inorganic particle-containing foam of the present invention has a plurality of bubbles in the continuous resin phase. As the bubbles, (1) at least a part of the inner wall surface in the foam is only the surface of the inorganic particle uneven distribution layer containing only inorganic particles, and (2) at least a part of the inner wall surface in the foam is A bubble that is only the surface of the inorganic particle uneven distribution layer containing the inorganic particles and the component constituting the continuous resin phase, (3) the surface of the inorganic particle uneven distribution layer in which at least a part of the inner wall surface in the foam contains only the inorganic particles And the bubble which is the surface of the inorganic particle uneven distribution layer containing the component which comprises an inorganic particle and a continuous resin phase is mentioned. The inorganic particle-containing foam of the present invention may contain at least one of the above-mentioned bubbles (1) to (3). In addition, the inorganic particle containing foam of this invention should just contain either of the said air bubbles of (1)-(3), and also may contain the bubble which does not have an inorganic particle uneven distribution layer.

  The thickness of the inorganic particle uneven distribution layer can be set to any appropriate value depending on the average particle diameter of inorganic particles to be used and / or the blending amount thereof. The thickness of the inorganic particle uneven distribution layer is preferably 0.1 μm or more, and more preferably 0.5 μm or more. When the thickness of the inorganic particle uneven distribution layer is less than 0.1 μm, the properties imparted to the foam may not be sufficiently exhibited when the inorganic particle uneven distribution layer is formed. The upper limit value of the thickness of the inorganic particle uneven distribution layer is preferably 10 μm, and more preferably 5 μm. When the thickness of the inorganic particle uneven distribution layer exceeds 10 μm, the obtained foam becomes brittle, and the workability and handling properties may be reduced. In the present specification, the thickness of the inorganic particle uneven distribution layer is measured from a cross-sectional SEM photograph taken by cutting the obtained foam in an arbitrary direction.

  Any appropriate inorganic particles can be used as the inorganic particles. Examples of the inorganic particles include conductive inorganic particles, fillers, flame retardant imparting particles, inorganic pigments, dielectric particles, heat conductive particles, and porous particles. Specifically, such inorganic particles include antimony-doped tin oxide (ATO), indium tin oxide (ITO), barium titanate, calcium carbonate, magnesium carbonate, silicic acid and its salts, clay, mica powder, Examples thereof include aluminum hydroxide, magnesium hydroxide, zinc white, bent nine, carbon black, silica (colloidal silica), alumina, aluminum silicate, acetylene black, aluminum powder, boron nitride, and zeolite. The inorganic particles are preferably inorganic particles that have not been surface-treated. Only one type of inorganic particles may be used, or two or more types may be used.

  The average particle diameter of the inorganic particles is not particularly limited, and inorganic particles having any appropriate average particle diameter can be used. The average particle diameter of the inorganic particles is preferably 5 nm to 500 nm, more preferably 10 nm to 300 nm, and still more preferably 20 nm to 200 nm. By using inorganic particles having an average particle diameter in the above range, an inorganic particle-containing foam having a more uniform inorganic particle uneven distribution layer can be obtained.

≪≪B. Method for producing foam containing inorganic particles >>
Arbitrary appropriate methods can be employ | adopted as a manufacturing method of the inorganic particle containing foam of this invention. The inorganic particle-containing foam of the present invention can be preferably produced using a W / O emulsion obtained by using a continuous oil phase component and an aqueous phase component containing inorganic particles.

  As a method for producing the foam containing inorganic particles of the present invention, for example, a continuous oil phase component and an aqueous phase component containing inorganic particles are continuously supplied to an emulsifier to obtain the foam containing inorganic particles of the present invention. A W / O type emulsion that can be used for the following, followed by polymerizing the obtained W / O type emulsion to produce a hydrous polymer, and subsequently dehydrating the obtained hydrous polymer. ". As a method for producing the foam containing inorganic particles of the present invention, for example, an aqueous phase component containing an appropriate amount of inorganic particles relative to the continuous oil phase component is charged into an emulsifier and continuously stirred while stirring. A W / O emulsion that can be used to obtain the inorganic particle-containing foam of the present invention by supplying an aqueous phase component containing particles is prepared, and the obtained W / O emulsion is polymerized to obtain a hydrous polymer. And subsequently dehydrating the obtained water-containing polymer.

  The continuous polymerization method in which the W / O emulsion is continuously polymerized is a preferable method because the production efficiency is high and the effect of shortening the polymerization time and the shortening of the polymerization apparatus can be most effectively utilized.

More specifically, the inorganic particle-containing foam of the present invention is preferably,
A step (I) of preparing a W / O type emulsion using a continuous oil phase component and an aqueous phase component containing inorganic particles;
Step (II) for shaping the obtained W / O emulsion,
Step (III) of polymerizing the shaped W / O emulsion to obtain a water-containing polymer;
Step (IV) of dehydrating the water-containing polymer and forming a foam in which at least a part of the inner wall surface in the resulting foam is an inorganic particle unevenly distributed layer
It can manufacture with the manufacturing method containing. Here, at least a part of the step (II) for shaping the obtained W / O emulsion and the step (III) for polymerizing the shaped W / O emulsion may be performed simultaneously.

<< B-1. Step (I) for preparing a W / O type emulsion using a continuous oil phase component and an aqueous phase component containing inorganic particles (I) >>
The W / O type emulsion that can be used for the production of the foam of the present invention includes a continuous oil phase component and a water phase component that is immiscible with the continuous oil phase component and contains inorganic particles. / O type emulsion. More specifically, a water phase component containing inorganic particles is dispersed in a continuous oil phase component. In the method for producing a foam of the present invention, since the aqueous phase component containing inorganic particles is used, most of the inorganic particles are contained in the aqueous phase of the W / O emulsion that can be used for producing the foam. A part of the inorganic particles contained in the water phase component can also move to the continuous oil phase component at the stage of making the emulsion state.

  In the W / O type emulsion that can be used to obtain the foam of the present invention, the ratio of the aqueous phase component containing inorganic particles to the continuous oil phase component is arbitrarily appropriate as long as the W / O type emulsion can be formed. A good ratio. The ratio of the water phase component containing inorganic particles to the continuous oil phase component in the W / O type emulsion that can be used to obtain the foam of the present invention is a porous polymer obtained by polymerization of the W / O type emulsion. It can be an important factor in determining the structural, mechanical, and performance properties of a material. Specifically, the ratio of the aqueous phase component containing inorganic particles to the continuous oil phase component in the W / O emulsion is determined by the density of the porous polymer material obtained by the polymerization of the W / O emulsion, the bubbles It can be an important factor in determining the size, the bubble structure, the dimensions of the wall forming the porous structure, and the like.

  The ratio of the aqueous phase component containing the inorganic particles in the W / O type emulsion that can be used to obtain the foam of the present invention can be any suitable ratio depending on the content of the inorganic particles and the like. . The ratio of the aqueous phase component containing inorganic particles is preferably 30% by weight, more preferably 40% by weight, and the upper limit is preferably 80% by weight, more preferably 75% by weight, as the lower limit. %, More preferably 70% by weight, particularly preferably 65% by weight. If the ratio of the aqueous phase component containing the inorganic particles in the W / O emulsion that can be used to obtain the foam of the present invention is within the above range, the effects of the present invention can be sufficiently exhibited.

  The W / O emulsion that can be used to obtain the foam of the present invention may contain any appropriate additive as long as the effects of the present invention are not impaired. Examples of such additives include tackifier resins; organic pigments; dyes. Only one kind of such an additive may be contained, or two or more kinds thereof may be contained.

  Any appropriate method can be adopted as a method for producing a W / O emulsion that can be used to obtain the foam of the present invention. As a method for producing a W / O type emulsion that can be used for obtaining the foam of the present invention, for example, a continuous oil phase component and an aqueous phase component containing inorganic particles are continuously supplied to an emulsifier. / Continuous method for forming an O-type emulsion or water phase component containing an appropriate amount of inorganic particles relative to the continuous oil phase component in an emulsifier and continuously containing water with inorganic particles while stirring Examples include a “batch method” in which a W / O emulsion is formed by supplying phase components.

  When producing a W / O emulsion that can be used to obtain the foam of the present invention, as a shearing means for obtaining an emulsion state, for example, a high shear using a rotor-stator mixer, a homogenizer, a microfluidizer, etc. Application of conditions is mentioned. In addition, as another shearing means for obtaining an emulsion state, for example, gentle mixing of continuous and dispersed phases by application of low shear conditions using a moving blade mixer or a pin mixer, low stirring conditions using a magnetic stir bar, etc. Can be mentioned.

  Examples of the apparatus for preparing the W / O emulsion by the “continuous method” include a static mixer, a rotor stator mixer, and a pin mixer. More intense agitation may be achieved by increasing the agitation speed or by using an apparatus designed to finely disperse the aqueous phase component in the W / O emulsion by a mixing method.

  Examples of the apparatus for preparing the W / O type emulsion by the “batch method” include manual mixing and shaking, a driven blade mixer, and three propeller mixing blades.

  Arbitrary appropriate methods can be employ | adopted as a method of preparing the aqueous phase component containing an inorganic particle. Examples of the method for preparing the aqueous phase component containing inorganic particles include a method in which a continuous oil phase component, an immiscible aqueous fluid, and inorganic particles are mixed using any means. In addition, a dispersion or slurry of commercially available inorganic particles in an aqueous fluid (for example, Ishihara Sangyo Co., Ltd., trade name: SN-100D, Nissan Chemical Industries, Ltd., trade name: Snowtex 50, Sakai Chemical Industry) The above-mentioned aqueous fluid may be added to a product of trade name: high-purity perovskite BT-02, etc., and the desired inorganic particle content may be used as an aqueous phase component. The dispersion or slurry may be used as an aqueous phase component.

  Arbitrary appropriate methods can be employ | adopted as a method of preparing a continuous oil phase component. As a method for preparing a continuous oil phase component, typically, for example, a mixed syrup containing an ethylenically unsaturated monomer, an acrylic polymer, and a polar monomer copolymerizable with any ethylenically unsaturated monomer is used. It is preferable to prepare a continuous oil phase component by preparing and subsequently blending the mixed syrup with a polymerization initiator, a crosslinking agent, and any other appropriate components.

  Arbitrary appropriate methods can be employ | adopted as a method of preparing the said acrylic polymer. Typically, it is obtained by polymerizing the monomer component by an arbitrary polymerization method (for example, a partial polymerization method and a solution polymerization method) in the presence of a polymerization initiator.

<B-1-1. Water phase component>
The aqueous phase component contains an aqueous fluid that is substantially immiscible with the continuous oil phase component and inorganic particles.

(B-1-1-1. Aqueous fluid that is immiscible with the continuous oil phase component)
The aqueous fluid may be any aqueous fluid that is substantially immiscible with the continuous oil phase component. From the viewpoint of ease of handling and low cost, water such as ion-exchanged water is preferable.

(B-1-1-2. Inorganic particles)
Any appropriate inorganic particles can be used as the inorganic particles. Examples of the inorganic particles include conductive inorganic particles, fillers, flame retardant imparting particles, inorganic pigments, dielectric particles, heat conductive particles, and porous particles. Specifically, such inorganic particles include antimony-doped tin oxide (ATO), indium tin oxide (ITO), barium titanate, calcium carbonate, magnesium carbonate, silicic acid and its salts, clay, mica powder, Examples thereof include aluminum hydroxide, magnesium hydroxide, zinc white, bent nine, carbon black, silica (colloidal silica), alumina, aluminum silicate, acetylene black, aluminum powder, boron nitride, and zeolite. Only one type of inorganic particles may be used, or two or more types may be used. Water-dispersible inorganic particles can be suitably used as the inorganic particles.

  The average particle diameter of the inorganic particles is not particularly limited, and inorganic particles having any appropriate average particle diameter can be used. The average particle diameter of the inorganic particles is preferably 5 nm to 500 nm, more preferably 10 nm to 300 nm, and still more preferably 20 nm to 200 nm. By using inorganic particles having an average particle diameter in the above range, a water phase component and / or a W / O emulsion containing more stable inorganic particles can be prepared. Furthermore, by using inorganic particles having an average particle diameter in the above range, it becomes easy to form a foam having an inorganic particle uneven distribution layer having a uniform thickness.

  The content (solid content) of the inorganic particles in the aqueous phase component is preferably 5% by weight to 70% by weight, more preferably 10% by weight to 60% by weight, and even more preferably 15% by weight to 50% by weight. %. When the content of the inorganic particles is less than 5% by weight, the inorganic particle uneven distribution layer may not be formed in the obtained foam containing inorganic particles. If the content of the inorganic particles exceeds 70% by weight, the stability of the W / O emulsion may be lowered.

(B-1-1-3. Other components in the aqueous phase component)
In order to improve the dispersibility of the inorganic particles, the water phase component may contain any appropriate dispersant as long as the effects of the present invention are not impaired. Examples of such a dispersing agent include polycarboxylic acid ammonium salts (for example, product name: SN Dispersant manufactured by San Nopco).

  The content of the dispersant in the aqueous phase component may be any appropriate content depending on the average particle size of the inorganic particles used and / or the content of the inorganic particles in the aqueous phase component. The content of the dispersant in the aqueous phase component is preferably 0.3 wt% to 2 wt%, more preferably 0.3 wt% to 1 wt%. When the content of the dispersant in the aqueous phase component is less than 0.3% by weight, the dispersibility of the inorganic particles in the aqueous phase component is lowered, and the inorganic particles may be aggregated and / or precipitated. Moreover, there exists a possibility that the emulsification stability of a W / O type emulsion may fall. If the content of the dispersant in the aqueous phase component exceeds 2% by weight, phase inversion is likely to occur in the process of preparing the W / O emulsion, and the target W / O emulsion may not be prepared.

  Any appropriate additive may be contained in the aqueous phase component as long as the effects of the present invention are not impaired. Examples of such additives include polymerization initiators and water-soluble salts. The water-soluble salt can be an effective additive for further stabilizing the W / O emulsion used in the present invention. Examples of such water-soluble salts include sodium carbonate, calcium carbonate, potassium carbonate, sodium phosphate, calcium phosphate, potassium phosphate, sodium chloride, potassium chloride and the like. Only one kind of such an additive may be contained, or two or more kinds thereof may be contained. The additive that can be contained in the aqueous phase component may be only one kind or two or more kinds.

<B-1-2. Continuous oil phase component>
The continuous oil phase component preferably contains an ethylenically unsaturated monomer and an acrylic polymer. The content ratio of the ethylenically unsaturated monomer and the acrylic polymer in the continuous oil phase component may take any appropriate content ratio as long as the effects of the present invention are not impaired.

(B-1-2-1. Ethylenically unsaturated monomer)
As the ethylenically unsaturated monomer, any appropriate monomer can be adopted as long as it is a monomer having an ethylenically unsaturated double bond. Only one type of ethylenically unsaturated monomer may be used, or two or more types may be used.

  The ethylenically unsaturated monomer preferably comprises a (meth) acrylic ester. The content ratio of the (meth) acrylic acid ester in the ethylenically unsaturated monomer is preferably 70% by weight, more preferably 75% by weight, even more preferably 80% by weight, as the lower limit, and the upper limit. Is preferably 98% by weight, more preferably 96% by weight, and still more preferably 95% by weight. Only one (meth) acrylic acid ester may be used, or two or more may be used.

  The (meth) acrylic acid ester is preferably an alkyl (meth) acrylate having an alkyl group having 1 to 20 carbon atoms (a concept including a cycloalkyl group, an alkyl (cycloalkyl) group, and a (cycloalkyl) alkyl group). It is. Preferably the carbon number of the said alkyl group is 4-18. In addition, (meth) acryl means acryl and / or methacryl, and (meth) acrylate means acrylate and / or methacrylate.

  Examples of the alkyl (meth) acrylate having an alkyl group having 1 to 20 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, and s-butyl. (Meth) acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate, n-pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, isoamyl (meth) Acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isode Ru (meth) acrylate, n-dodecyl (meth) acrylate, isomyristyl (meth) acrylate, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, pentadecyl (Meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, eicosyl (meth) acrylate, isostearyl (meth) acrylate, isobornyl (meth) acrylate, etc. It is done. Among these, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and isobornyl (meth) acrylate are preferable. Only 1 type may be sufficient as the alkyl (meth) acrylate which has a C1-C20 alkyl group, and 2 or more types may be sufficient as it.

  The ethylenically unsaturated monomer preferably further comprises a polar monomer copolymerizable with the (meth) acrylic acid ester. The content of the polar monomer in the ethylenically unsaturated monomer is preferably 2% by weight, more preferably 4% by weight, even more preferably 5% by weight as the lower limit, and the upper limit is preferably It is 30% by weight, more preferably 25% by weight, and still more preferably 20% by weight. Only one type of polar monomer may be used, or two or more types may be used.

  Examples of polar monomers include (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, ω-carboxy-polycaprolactone monoacrylate, phthalic acid monohydroxyethyl acrylate, itaconic acid, maleic acid, and fumaric acid. Carboxyl group-containing monomers such as acid and crotonic acid; acid anhydride monomers such as maleic anhydride and itaconic anhydride; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and (meth) acrylic acid 4-hydroxybutyl, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethyl) Hydroxyl group-containing monomers such as cyclohexyl) methyl (meth) acrylate; N, N- dimethyl (meth) acrylamide, N, amide group-containing monomers such as N- diethyl (meth) acrylamide; and the like.

(B-1-2. Acrylic polymer)
The acrylic polymer is preferably a polymer obtained by polymerizing an ethylenically unsaturated monomer. The acrylic polymer is preferably compatible with the ethylenically unsaturated monomer contained in the continuous oil phase component. As the ethylenically unsaturated monomer used for the polymerization of the acrylic polymer, an alkyl (meth) acrylate having a C 1-20 alkyl group and a polar monomer can be suitably used. Specifically, alkyl (meth) acrylates and polar monomers having an alkyl group having 1 to 20 carbon atoms exemplified in the above section B-2-1-1. Each of the alkyl (meth) acrylate and polar monomer having an alkyl group having 1 to 20 carbon atoms may be one kind or two or more kinds. The alkyl (meth) acrylate having an alkyl group having 1 to 20 carbon atoms and the polar monomer used as the monomer component of the acrylic polymer may be the same as the ethylenically unsaturated monomer contained in the continuous oil phase component. It may be good or different.

  The weight average molecular weight of the acrylic polymer is preferably 10,000 to 500,000, more preferably 30,000 to 300,000, and further preferably 50,000 to 200,000. When the weight average molecular weight of the acrylic polymer is within the above range, a W / O emulsion in which the aqueous phase component containing inorganic particles is more stably dispersed can be obtained.

  The acrylic polymer is obtained by charging an ethylenically unsaturated monomer and a polymerization initiator and polymerizing monomer components by any appropriate polymerization method. For example, the acrylic polymer can be obtained by a solution polymerization method.

  When obtaining an acrylic polymer by solution polymerization, any appropriate solution polymerization method can be used. For example, an ethylenically unsaturated monomer, a chain transfer agent, and a polymerization initiator are charged in an arbitrary solvent, and a monomer component Next, the desired acrylic polymer can be obtained by washing with a poor solvent in which the monomer component, chain transfer agent and polymerization initiator are dissolved but the resulting acrylic polymer is not dissolved.

  As a solvent used for the solution polymerization of the acrylic polymer, any appropriate solvent can be used, for example, ester solvents such as ethyl acetate and methyl acetate; ketone solvents such as acetone and methyl ethyl ketone; methanol, ethanol, Alcohol solvents such as butanol; hydrocarbon solvents such as cyclohexane, hexane and heptane; aromatic solvents such as toluene and xylene can be used. Only 1 type may be used for the solvent used for solution polymerization, and 2 or more types may be used for it.

  The polymerization initiator used for solution polymerization of the acrylic polymer may be any polymerization initiator that is soluble in a solvent, and any appropriate polymerization initiator can be used. Examples of the polymerization initiator include azo compounds and peroxides. Only one type of polymerization initiator may be used, or two or more types may be used. The content ratio of the polymerization initiator at the time of solution polymerization of the acrylic polymer can be appropriately set according to the target acrylic polymer, for example, 0.03% by weight to 1% by weight of the total amount of the monomer components. % Can be set.

  Any appropriate chain transfer agent can be used as the chain transfer agent used for the solution polymerization of the acrylic polymer. Examples of the chain transfer agent include lauryl mercaptan, glycidyl mercaptan, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol. Only one type of chain transfer agent may be used, or two or more types may be used. The content ratio of the chain transfer agent used at the time of solution polymerization of the acrylic polymer can be appropriately set according to the target acrylic polymer, and can be set to 0.2% by weight or less of the total amount of the monomer components. .

  As a poor solvent used for washing after solution polymerization, a polymerization initiator and a chain transfer agent can be dissolved, but any solvent that does not dissolve the obtained acrylic polymer can be used, and any appropriate solvent can be used. Examples thereof include alcohol solvents such as methanol, ethanol and isopropanol; aliphatic hydrocarbon solvents such as hexane, heptane and octane. Of these, methanol can be preferably used.

  The content of the acrylic polymer is preferably 5% by weight, more preferably 7% by weight as the lower limit with respect to the total amount of the ethylenically unsaturated monomer and acrylic polymer contained in the continuous oil phase component. More preferably, it is 10% by weight, and the upper limit is preferably 50% by weight, more preferably 40% by weight, still more preferably 30% by weight. By setting the content of the acrylic polymer to 5% by weight or more, a W / O emulsion containing fine water droplets can be obtained, and the stationary stability of the obtained W / O emulsion is improved.

(B-1-2-3. Polymerization initiator)
The continuous oil phase component preferably contains a polymerization initiator.

  As a polymerization initiator, a radical polymerization initiator, an anionic polymerization initiator, a cationic polymerization initiator, a redox polymerization initiator etc. are mentioned, for example. Examples of the radical polymerization initiator include a thermal polymerization initiator and a photopolymerization initiator.

  Examples of the thermal polymerization initiator include azo compounds, peroxides, peroxycarbonic acid, peroxycarboxylic acid, potassium persulfate, t-butylperoxyisobutyrate, and 2,2′-azobisisobutyronitrile. .

  Examples of the photopolymerization initiator include 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone (for example, Ciba Japan, trade name: Darocur-2959), α-hydroxy- α, α'-dimethylacetophenone (for example, Ciba Japan, trade name: Darocur-1173), methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone (for example, Ciba Japan, trade name) Acetophenone photopolymerization initiators such as Irgacure-651) and 2-hydroxy-2-cyclohexylacetophenone (for example, Ciba Japan, trade name; Irgacure-184); Ketal photopolymerization initiator such as benzyldimethyl ketal Agents; Other halogenated ketones; Acylphosphine oxides (For example, Ciba Japan Co., Ltd., trade name: Irgacure-819); Diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (example: BASF, trade name: Lucillin TPO) Can do.

  The polymerization initiator may contain only 1 type and may contain 2 or more types.

  The content of the polymerization initiator is preferably 0.05% by weight, more preferably 0.1% by weight, more preferably 0.1%, and preferably 5.0% as a lower limit with respect to the entire continuous oil phase component. % By weight, more preferably 1.0% by weight. If the content of the polymerization initiator is less than 0.05% by weight based on the entire continuous oil phase component, the amount of unreacted monomer components increases, and the amount of residual monomers in the resulting porous material may increase. is there. When the content ratio of the polymerization initiator exceeds 5.0% by weight with respect to the entire continuous oil phase component, the mechanical properties of the resulting inorganic particle-containing foam may be lowered.

  Note that the amount of radicals generated by the photopolymerization initiator varies depending on the type and intensity of light to be irradiated, irradiation time, the amount of dissolved oxygen in the monomer and solvent mixture, and the like. And when there is much dissolved oxygen, the radical generation amount by a photoinitiator is suppressed, superposition | polymerization does not fully advance and an unreacted substance may increase. Therefore, it is preferable that an inert gas such as nitrogen is blown into the reaction system to replace oxygen with an inert gas or deaerate by a decompression process before the light irradiation.

(B-1-2-4. Crosslinking agent)
The continuous oil phase component preferably includes a cross-linking agent.

  Crosslinking agents are typically used to link polymer chains together to build a more three-dimensional molecular structure. Selection of the type and content of the cross-linking agent depends on the structural properties, mechanical properties, and fluid treatment properties desired for the resulting inorganic particle-containing foam. The selection of the specific type and content of the cross-linking agent is important in achieving the desired combination of structural properties, mechanical properties, and fluid treatment properties of the porous material.

  As a crosslinking agent, polyfunctional (meth) acrylate, polyfunctional (meth) acrylamide, and mixtures thereof are mentioned, for example. Examples of the polyfunctional (meth) acrylate include diacrylates, triacrylates, tetraacrylates, dimethacrylates, trimethacrylates, and tetramethacrylates. Examples of the polyfunctional (meth) acrylamide include diacrylamides, triacrylamides, tetraacrylamides, dimethacrylamides, trimethacrylamides, tetramethacrylamides and the like.

  The polyfunctional (meth) acrylate can be derived from, for example, diols, triols, tetraols, bisphenol A and the like. Specifically, for example, 1,10-decanediol, 1,8-octanediol, 1,6 hexane-diol, 1,4-butanediol, 1,3-butanediol, 1,4 butane-2-enedi It can be derived from all, ethylene glycol, diethylene glycol, trimethylolpropane, pentaerythritol, hydroquinone, catechol, resorcinol, triethylene glycol, polyethylene glycol, sorbitol, polypropylene glycol, polytetramethylene glycol, bisphenol A propylene oxide modified product, and the like.

  The polyfunctional (meth) acrylamide can be derived from, for example, corresponding diamines, triamines, tetraamines and the like.

  The crosslinking agent may contain only 1 type and may contain 2 or more types.

  The content of the crosslinking agent is preferably 5% by weight, more preferably 10% by weight, and more preferably 30% as the lower limit with respect to the total amount of the ethylenically unsaturated monomer and the acrylic polymer. % By weight. When the content of the cross-linking agent is less than 5% by weight with respect to the total amount of the ethylenically unsaturated monomer and the acrylic polymer, bubbles are caused by shrinkage in the step of dehydrating the high water content cross-linked polymer due to a decrease in heat resistance. There is a possibility that the structure is almost destroyed. When the content of the crosslinking agent exceeds 30% by weight with respect to the total amount of the ethylenically unsaturated monomer and the acrylic polymer, the mechanical properties of the resulting porous material may be deteriorated.

(B-1-2-5. Other components in the continuous oil phase component)

  Examples of the antioxidant include a phenol-based antioxidant, a thioether-based antioxidant, and a phosphorus-based antioxidant.

  Arbitrary appropriate content rates can be employ | adopted for the content rate of antioxidant in the range which does not impair the effect of this invention.

  Antioxidant may contain only 1 type and may contain 2 or more types.

  Any appropriate organic solvent can be adopted as the organic solvent as long as the effects of the present invention are not impaired.

  Arbitrary appropriate content rates can be employ | adopted for the content rate of an organic solvent in the range which does not impair the effect of this invention.

  The organic solvent may contain only 1 type and may contain 2 or more types.

<< B-2. Step of shaping the obtained W / O emulsion (II) >>
In the step (II), any appropriate shaping method can be adopted as a method for shaping the W / O type emulsion. For example, in the case of forming a sheet-like foam, there is a method in which a W / O emulsion is continuously supplied onto a running belt and shaped into a smooth sheet on the belt. Moreover, the method of apply | coating to one surface of a thermoplastic resin film, and shaping is mentioned.

  In the step (II), as a method of shaping the W / O type emulsion, when adopting a method of coating and shaping on one surface of a thermoplastic resin film, as a method of coating, for example, a roll coater, Examples include a method using a die coater, a knife coater, or the like.

  Even in the W / O emulsion after shaping, most of the inorganic particles are considered to be dispersed in the aqueous phase component.

<< B-3. Step (III) for polymerizing shaped W / O emulsion to obtain water-containing polymer (III) >>
In the step (III), any appropriate polymerization method can be adopted as a method for polymerizing the shaped W / O emulsion. For example, the belt surface of a belt conveyor is heated by a heating device, and a W / O type emulsion is continuously supplied onto a traveling belt and shaped into a smooth sheet on the belt by heating. A W / O emulsion is continuously supplied onto the running belt, with a method of polymerization and a structure in which the belt surface of the belt conveyor is heated by irradiation of active energy rays, and a smooth sheet is formed on the belt. The method of superposing | polymerizing by irradiation of an active energy ray is mentioned, shaping.

  When polymerizing by heating, the polymerization temperature (heating temperature) is preferably 23 ° C., more preferably 60 ° C., further preferably 70 ° C., particularly preferably 80 ° C. as the lower limit, and the upper limit. The value is preferably 150 ° C., more preferably 130 ° C., and still more preferably 100 ° C. When the polymerization temperature is less than 23 ° C., the polymerization takes a long time, and industrial productivity may be reduced. When the polymerization temperature exceeds 150 ° C., the pore size of the obtained foam may be non-uniform or the strength of the foam may be reduced. The polymerization temperature need not be constant. For example, the polymerization temperature may be varied in two stages or multiple stages during the polymerization.

  In the case of polymerization by irradiation with active energy rays, examples of the active energy rays include ultraviolet rays, visible rays, and electron beams. The active energy ray is preferably ultraviolet light or visible light, and more preferably visible to ultraviolet light having a wavelength of 200 nm to 800 nm. Since the W / O type emulsion has a strong tendency to scatter light, it is possible to penetrate the W / O type emulsion by using visible to ultraviolet light having a wavelength of 200 nm to 800 nm. Moreover, the photoinitiator which can be activated with a wavelength of 200 nm-800 nm is easy to obtain, and a light source is easy to obtain.

  The wavelength of the active energy ray is preferably 200 nm, more preferably 300 nm as the lower limit value, and preferably 800 nm, more preferably 450 nm as the upper limit value.

  As a typical apparatus used for irradiation of active energy rays, for example, an ultraviolet lamp capable of performing ultraviolet irradiation includes an apparatus having a spectral distribution in a wavelength region of 300 to 400 nm. , Black light (trade name manufactured by Toshiba Lighting & Technology Co., Ltd.), metal halide lamp and the like.

  The illuminance at the time of irradiation with active energy rays can be set to any appropriate illuminance by adjusting the distance from the irradiation device to the irradiation object and the voltage. For example, by the method disclosed in Japanese Patent Application Laid-Open No. 2003-13015, ultraviolet irradiation in each step is performed in a plurality of stages, and thereby the efficiency of the polymerization reaction can be precisely adjusted.

  In order to prevent the adverse effect of oxygen having an inhibitory action on the ultraviolet rays, for example, a W / O emulsion is applied to one surface of a substrate such as a thermoplastic resin film and then shaped under an inert gas atmosphere. UV rays such as polyethylene terephthalate coated with a release agent such as silicone after passing through a W / O emulsion on one surface of a substrate such as a thermoplastic resin film and shaping, but blocking oxygen It is preferable to carry out by covering the film.

  As the thermoplastic resin film, any appropriate thermoplastic resin film can be adopted as long as it can be formed by coating a W / O emulsion on one surface. Examples of the thermoplastic resin film include plastic films and sheets such as polyester, olefin resin, and polyvinyl chloride.

  The inert gas atmosphere refers to an atmosphere in which oxygen in the light irradiation zone is replaced with an inert gas. Therefore, in the inert gas atmosphere, it is necessary that oxygen is not present as much as possible, and the oxygen concentration is preferably 5000 ppm or less.

<< B-4. Step (IV) of dehydrating the obtained water-containing polymer and forming a foam in which at least a part of the inner wall surface in the resulting foam is the surface of the inorganic particle uneven distribution layer >>
In the step (IV), the water-containing polymer obtained in the step (III) is dehydrated to form a foam in which at least a part of the inner wall surface in the obtained foam is an inorganic particle unevenly distributed layer. In the water-containing polymer obtained in step (III), an aqueous phase component containing inorganic particles is present in a dispersed state. By removing the aqueous phase component by dehydration and drying, the inorganic particle-containing foam of the present invention is obtained. In this dewatering step, the aqueous fluid that is immiscible with the continuous oil phase component of the water phase component is removed, for example, by evaporation. At this time, the inorganic particles contained in the aqueous phase component move to the interface between the aqueous phase component and the continuous oil phase component together with the aqueous fluid, but due to the interaction with the resin component contained in the continuous oil phase component, the continuous oil phase component It stays at the interface part. Therefore, the inorganic particle-containing foam of the present invention is an inorganic particle-containing foam in which at least a part of the inner wall surface in the foam is the surface of the inorganic particle uneven distribution layer. In the inorganic particle-containing foam of the present invention, the inorganic particles contained in the water phase component are unevenly distributed in an almost uniform thickness on at least a part of the inner wall surface in the foam, and an inorganic particle unevenly distributed layer having a thickness of about several μm is formed. It is preferred that

  Arbitrary appropriate drying methods can be employ | adopted as a dehydration method in process (IV). Examples of such a drying method include vacuum drying, freeze drying, press drying, microwave drying, drying in a heat oven, drying with infrared rays, or a combination of these techniques.

  The foam of the present invention is suitable for countless applications including cushion materials, insulating materials, heat insulating materials, soundproof materials, dustproof materials, filter materials, reflective materials, and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples at all. In addition, the test and evaluation method in an Example etc. are as follows. “Parts” means “parts by weight”.

(Molecular weight measurement)
The weight average molecular weight was determined by GPC (gel permeation chromatography).
Equipment: “HLC-8020” manufactured by Tosoh Corporation
Column: “TSKgel GMH _HR- H (20)” manufactured by Tosoh Corporation
Solvent: Tetrahydrofuran Standard: Polystyrene

(Measurement of average pore diameter and thickness of each layer)
A sample for measurement was prepared by cutting the produced inorganic particle-containing foam sheet with a microtome cutter in the thickness direction. The cut surface of the sample for measurement was photographed with a low vacuum scanning electron microscope (Hitachi, S-3400N) at 250 to 10,000 times. Using the obtained image, the long axis length (pore diameter of spherical bubbles) of 20 pores from the largest for spherical bubbles in an arbitrary range was measured, and the average value of the measured values was taken as the average diameter. Moreover, it was observed whether the bubble inner wall was an inorganic particle uneven distribution layer using this image.

[Production Example] Preparation of polymerizable reaction syrup 84 parts by weight of 2-ethylhexyl acrylate (manufactured by Toa Gosei Co., Ltd., hereinafter abbreviated as “2EHA”) as an ethylenically unsaturated monomer, acrylic acid (Toa Gosei Co., Ltd.) as a polar monomer Thioglycolic acid (manufactured by Sakai Chemical Industry Co., Ltd., trade name “mercaptoacetic acid”) with respect to 100 parts by weight of the mixed monomer solution consisting of 16 parts by weight. 2 parts by weight, 2 parts of 2,2′-azobisisobutyronitrile (manufactured by Kishida Chemical Co., Ltd., trade name: AIBN) as a polymerization initiator, 0.2 part by weight, and a solution consisting of 67 parts by weight of ethyl acetate as a solvent The solution was put into a one-necked flask and heated in a hot water bath at 60 ° C. for 4 hours and further at 70 ° C. for 3 hours to obtain a polymer solution having a polymer concentration of about 60%. The obtained polymer solution was washed several times with methanol to obtain a polymer having a weight average molecular weight of 130,000. The obtained polymer is dissolved in a mixed monomer solution consisting of 66 parts by weight of 2EHA, 24 parts by weight of isobornyl acrylate (Osaka Organic Chemical Co., Ltd., trade name: IBXA), and 10 parts by weight of AA as a polar monomer. The polymer concentration was adjusted to 16% with a polymerization reactive syrup.

[Example 1]
100 parts by weight of the prepared polymerization reactive syrup, 10 parts by weight of trimethylol tripropane acrylate (Osaka Organic Chemical Co., Ltd., trade name: TMPTA), diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (BASF) Manufactured and trade name: Lucillin TPO) was uniformly mixed to obtain a continuous oil phase component (hereinafter referred to as “oil phase”).
As an aqueous phase component (hereinafter referred to as “aqueous phase”) with respect to 100 parts by weight of the oil phase, an ATO aqueous dispersion (manufactured by Ishihara Sangyo Co., Ltd., trade name: SN-100D (secondary particle size 85-120 nm)) The solid content was 30% by weight), and 142.8 parts by weight were continuously added dropwise at room temperature while stirring into the stirring mixer charged with the oil phase component to form a stable W / O emulsion. The weight ratio of the water phase to the oil phase was 58.8 / 41.2.
A W / O emulsion that was stored at room temperature for 1 hour after formation was applied onto a substrate that had been subjected to a release treatment so as to have a thickness of 300 μm after light irradiation, and was continuously molded. Further, a polyethylene terephthalate film having a thickness of 38 μm and subjected to a release treatment was placed thereon. This sheet was irradiated with ultraviolet light having a light illuminance of 5 mW / cm ² (measured with Topcon UVR-T1 having a peak sensitivity maximum wave of 350 nm) using black light (15 W / cm) to obtain a hydrous crosslinked polymer having a thickness of 300 μm. Next, the top film was peeled off, and the hydrous crosslinked polymer was heated at 130 ° C. for 20 minutes to obtain an ATO particle-containing foam having a thickness of about 300 μm.
A cross-sectional SEM photograph of the obtained ATO particle-containing foam is shown in FIG. 1 (FIG. 1A is 250 times, FIG. 1B is 2000 times, and FIG. 1C is 10000 times).

[Example 2]
In Example 1, colloidal silica (colloidal silica (manufactured by Nissan Chemical Industries, Ltd., trade name: Snowtex 50 (particle diameter 20-30 nm)) having a solid content of 30% by weight by adding ion-exchanged water as an aqueous phase, A solid W / O emulsion was formed in the same manner as in Example 1, except that the solid content was 50 wt%) 85.7 parts by weight, and ion-exchanged water 57.1 parts by weight) 142.8 parts by weight. It was. The weight ratio of the water phase to the oil phase was 58.8 / 41.2.
Next, a silica particle-containing foam having a thickness of about 300 μm was obtained by the same operation as in Example 1.
The cross-sectional SEM photograph of the obtained silica particle containing foam is shown in FIG. 2 (FIG. 2A is 250 times, FIG. 2B is 2000 times, and FIG. 2C is 10000 times).

Example 3
In Example 1, a barium titanate aqueous dispersion (barium titanate fine particles (manufactured by Sakai Chemical Industry Co., Ltd., trade name: high-purity perovskite BT-02) having a solid content of 30% by weight by adding ion exchange water as an aqueous phase (Particle size 200 nm)) 42.9 parts by weight, dispersant (manufactured by San Nopco, trade name: SN Dispersant 5468) 0.5 parts by weight, ion-exchanged water 99.5 parts by weight) 142.8 parts by weight were used. Except for the above, a stable W / O emulsion was formed by the same operation as in Example 1. The weight ratio of the water phase to the oil phase was 58.8 / 41.2.
Next, a barium titanate particle-containing foam having a thickness of about 300 μm was obtained by the same operation as in Example 1.
A cross-sectional SEM photograph of the obtained barium titanate particle-containing foam is shown in FIG. 3 (FIG. 3A is 250 times, FIG. 3B is 2000 times, and FIG. 3C is 10,000 times).

Example 4
In Example 3, barium titanate aqueous dispersion (added 75.7 parts by weight of barium titanate fine particles (manufactured by Sakai Chemical Industry Co., Ltd., trade name: 43% by weight of solid content by adding ion exchange water as an aqueous phase) 176.1 parts by weight of high-purity perovskite BT-02 (particle diameter 200 nm), 0.9 part by weight of a dispersant (manufactured by San Nopco, trade name: SN Dispersant 5468), 99.4 parts by weight of ion-exchanged water) A stable W / O emulsion was formed by the same operation as in Example 1 except that was used. The weight ratio of the aqueous phase to the oil phase was 63.8 / 36.2.
Next, a barium titanate particle-containing foam having a thickness of about 300 μm was obtained by the same operation as in Example 1.
A cross-sectional SEM photograph of the obtained barium titanate particle-containing foam is shown in FIG. 4 (FIG. 4A is 250 times, FIG. 4B is 2000 times, and FIG. 4C is 10000 times).

(Comparative Example 1)
In Example 1, 100 parts by weight of ion-exchanged water was used as the water phase component, and 100 parts by weight of the aqueous phase was stirred at room temperature with respect to 100 parts by weight of the oil phase. A stable W / O emulsion was formed in the same manner as in Example 1 except that a stable W / O emulsion was formed by continuously dropping it into the mixer. The weight ratio of the water phase to the oil phase was 50/50.
A foam having a thickness of about 300 μm was obtained in the same manner as in Example 1 except that the obtained W / O emulsion was used. The obtained foam did not have an inorganic particle uneven distribution layer on the bubble inner wall.
The cross-sectional SEM photograph of the obtained foam is shown in FIG. 5 (FIG. 5A is 800 times, FIG. 5B is 10,000 times).

  As apparent from FIGS. 1 to 4, in the foam of the present invention, at least a part of the inner wall surface in the foam was the surface of the inorganic particle uneven distribution layer.

  The inorganic particle-containing foam of the present invention is suitable for countless applications including cushion materials, insulation, heat insulating materials, soundproof materials, dustproof materials, filter materials, reflective materials and the like.

Claims (5)

A foam having a plurality of bubbles in a continuous resin phase,
An inorganic particle-containing foam in which at least a part of the inner wall surface in the foam is the surface of an inorganic particle uneven distribution layer containing inorganic particles.   The inorganic particle-containing foam according to claim 1, wherein the inorganic particle uneven distribution layer includes a component constituting the continuous resin phase.   The inorganic particle-containing foam according to claim 1 or 2, wherein the inorganic particles have an average particle diameter of 5 nm to 500 nm.   The inorganic particle-containing foam according to any one of claims 1 to 3, wherein an average pore diameter of spherical bubbles of the foam is 50 µm or less. A method for producing an inorganic particle-containing foam according to any one of claims 1 to 4, comprising the following steps (I) to (IV):
(I) a step of preparing a W / O emulsion using a continuous oil phase component and an aqueous phase component containing inorganic particles;
(II) a step of shaping the obtained W / O emulsion,
(III) polymerizing the shaped W / O emulsion to obtain a water-containing polymer;
(IV) A step of dehydrating the water-containing polymer and forming a foam in which at least a part of the inner wall surface in the resulting foam is an inorganic particle unevenly distributed layer.