TWI735717B - Bubble porous body and manufacturing method thereof - Google Patents

Abstract

The present invention provides a new bubble porous body that can be used as a heat dissipation member and the manufacturing method. The present invention is a cellular porous body that contains a matrix resin and a thermally conductive material dispersed in the matrix resin, and at least spherical graphite is contained as the thermally conductive material; and a method for manufacturing a cellular porous body, characterized by In order to include a foaming step, the foaming step is to mechanically foam a liquid composition containing a resin having a functional group in the side chain, a foaming agent, and spherical graphite, and a hardening step to make the aforementioned The functional groups of the resin react with each other, and/or the functional groups of the polyfunctional crosslinking agent are reacted with each other, and/or the functional groups of the resin are reacted with the functions of the aforementioned polyfunctional crosslinking agent The base reaction hardens the liquid composition; the foaming step and the hardening step are performed at the same time, and/or the hardening step is performed after the foaming step.

Description

Bubble porous body and manufacturing method thereof

The present invention relates to electronic and electrical equipment products (electronic products), and is particularly useful as a heat dissipation member for thin, high-performance smartphones, computers, televisions, etc. whose internal structures are complex electronic and electrical equipment products. Bubble porous body and its manufacturing method.

Electronics and electrical machinery products (electronic products), especially smart phones, computers, televisions and other products are gradually becoming thinner and higher performance year by year. On the other hand, because the data processing speed increases, the heat generation increases, and because the internal structure is complicated, it becomes easy to accumulate heat. Due to the generated heat, there is a possibility of problems such as shortening the life of electronic parts, deformation of the frame due to thermal expansion, and low-temperature burns. Therefore, a member containing a thermally conductive substance for the purpose of heat dissipation is arranged inside the electronic and electrical equipment product. Heretofore, as the member, a member composed of a gel containing a thermally conductive substance such as silicone, acrylic, or the like has been used. However, the member system composed of the aforementioned gel has high thermal conductivity, but it has high hardness and lacks flexibility because of the high stress during compression. Therefore, it is difficult to arrange the aforementioned gel in accordance with the internal structure in electronic and electrical equipment with complicated internal structures in recent years.

Patent Document 1 discloses a foamable composition that can be used in the production of heat sinks for electronic devices and the like. However, Patent Document 1 does not describe the problem of the above-mentioned shape followability, that is, the viewpoint of flexibility, and the solution. In addition, this foamable composition contains a silicone-based surfactant as an essential component. Therefore, when the heat sink made of the composition is exposed to high temperatures, the low-molecular-weight siloxane component may be released and deteriorated. Problem, lack of heat resistance. Prior Art Documents Patent Documents

Patent Document 1: Japanese Patent Application Publication No. 2016-65196

[The problem to be solved by the invention]

The present invention was made in view of the above problems, and its subject is to provide a new bubble porous body that can be used as a heat dissipation member and the manufacturing method.　　, another subject of the present invention is to provide a bubble porous body and the manufacturing method thereof, the bubble porous system does not impair heat dissipation, has moderate flexibility, and has followability to the shape of other components. [Means to solve the problem]

The inventors of the present invention have conducted studies in order to solve the aforementioned problems, and found that the use of spherical graphite as a thermally conductive material can solve the aforementioned problems and completed the present invention. The means to solve the above-mentioned problems are as follows.　　[1] A cellular porous body characterized by containing a matrix resin and a thermally conductive material dispersed in the matrix resin, and containing at least spherical graphite as the thermally conductive material.　　[2] The bubble porous body as in [1], wherein the spherical graphite has a structure in which the basal plane is bent.　　[3] The cellular porous body as in [1] or [2], wherein the aforementioned matrix resin is an acrylic resin.　　[4] The cellular porous body according to any one of [1] to [3], wherein the thermally conductive material further contains a metal oxide.　　[5] The cellular porous body according to any one of [1] to [4], wherein the thermally conductive material is contained at 40-60% by mass based on the total mass of the cellular porous body. [6] The cellular porous body according to any one of [1] to [5], wherein the thermally conductive material contains metal oxide and spherical graphite at a blending ratio (mass ratio) of 0:10 to 5:5 .　　[7] The bubble porous body as in any one of [1] to [6], which is an open-cell porous body. [8] The cellular porous body of any one of [1] to [7], wherein the 25% compression load measured in accordance with JIS K 6254:2016 (ISO 7743:2011) is 20kPa or less, using Kyoto Electronics Industry Co., Ltd. The thermal conductivity of QTM-500 measured by the probe method is 0.3W/(m·K) or more.　　[9] The bubble porous body as in any one of [1] to [8], which is used as a heat dissipation member for electronic products. [10] A method for producing a cellular porous body, comprising a foaming step of mechanically foaming a liquid composition containing a resin having a functional group in the side chain, a foaming agent, and spherical graphite, and a The curing step is to make the functional groups of the aforementioned resin react with each other and/or the functional groups of the polyfunctional crosslinking agent to react with each other, and/or make the functional groups of the aforementioned resin react with the aforementioned The functional groups of the multifunctional crosslinking agent react to harden the liquid composition; 　　 perform the foaming step and the hardening step at the same time, and/or perform the hardening step after the foaming step.　　[11] The production method as in [10], wherein the pH of the liquid composition ranges from neutral to alkaline, and the liquid composition is an anionic surfactant containing at least one type of foaming agent.　　[12] The manufacturing method as in [10] or [11], wherein the aforementioned bubble porous body is the bubble porous body as described in any one of [1] to [9]. [Effects of Invention]

According to the present invention, a new bubble porous body that can be used as a heat dissipation member and the manufacturing method can be provided.　　In addition, the present invention can provide a bubble porous body and the manufacturing method thereof. The bubble porous system does not impair heat dissipation, has moderate flexibility, and can follow the shape of other components.

Hereinafter, the cellular porous body of the present invention and its manufacturing method will be described in detail. In this specification, "~" means a range that includes the numerical values before and after that.

[Bubble porous body] "The porous body of the present invention is characterized by containing a matrix resin and a thermally conductive material dispersed in the matrix resin, and at least spherical graphite is contained as the thermally conductive material. (1) Spherical graphite 　　 spherical graphite has high thermal conductivity, which contributes to the appearance and/or improvement of the heat dissipation of the porous porous body of the present invention. The graphite used in the present invention can be spherical. In the present invention, the term "spherical" does not only mean a true spherical shape. The true spherical shape is a shape that is deformed into a disc-like shape, the surface is not the same, and the surface has a cabbage-like appearance with overlapping layers, etc. Generally speaking, it also includes those who have not grasped the shape of a real ball. However, the crystalline system of natural graphite is a hexagonal system. Generally speaking, the untreated graphite system is distinguished from this system because it is scaly. That is, in the present invention, it is required to use at least spheroidizing graphite. The spheroidization treatment system also includes simple treatment methods such as pulverizing natural graphite in the form of flakes, but it is desirable to adopt a treatment method that applies a uniform pressure to the graphite. This treatment can be carried out by using a pressurized medium such as gas (inert gas such as argon), liquid (for example, water), etc., to uniformly apply pressure to graphite. Depending on the presence or absence of heating, the difference is heat equalization treatment and cold equalization treatment. Either one can also be used. By applying this treatment, the shape is spherical, and the internal voids (between the scale layers) are reduced, and high thermal conductivity spherical graphite can be obtained.

The above-mentioned spheroidized spheroidal graphite system is specified as spheroidal graphite having a structure in which other side surfaces are bent at a bottom surface (basal plane). Here, the so-called "basal plane" refers to a plane orthogonal to the C axis of the graphite crystal (hexagonal system). That is, it is ideal that the spherical graphite of the present invention is strained in the crystal system of natural graphite. This strain system can measure the X-ray diffraction pattern. Compared with natural graphite, whether the wave crest is broadened or the 2θ value is shifted can be grasped. In addition, the confirmation of whether the bubble porous body contains spheroidal graphite is not only confirmed by measuring the X-ray diffraction pattern of the raw material graphite, but also the cross section of any 2 or more of the bubble porous body can be observed under a microscope. Confirm whether the shape is round. Specifically, using a microscope to observe the mutually orthogonal surfaces of the bubble porous body, such as the shape of a corresponding part of graphite in any image, the ratio of the minor axis to the major axis is a round shape with 1/2 or more, It can be said that the pores of the bubbles contain spherical graphite.

Examples of the spherical graphite that can be used in the present invention include the spheroidization of non-spherical graphite powder such as flake graphite by the high-speed air impact method using a hybridization system. Treaters; and spherical carbon particles that crystallize petroleum-based or petroleum-based pitch or harden thermosetting resin to obtain a powder, which can be obtained by graphitizing the powder, etc. From the viewpoint of thermal conductivity, the former is ideal.

As the spheroidal graphite, commercially available products can also be suitably used, and as the specific example, spheroidized graphite manufactured by Japan Graphite Industry Co., Ltd. can be cited. The average particle diameter (median diameter) of the spherical graphite used in the present invention is about 1 to 100 μm. Ensuring heat dissipation and ensuring flexibility tends to improve one side, while the other tends to decrease. However, if spherical graphite with a smaller average particle size is used, the properties of both can be improved in a balanced manner, so it is ideal. The range of the ideal average particle size varies depending on the final shape of the bubble porous body, but the shape of a flake with a thickness of about 0.1 to 1.0 mm is preferably about 5 to 30 μm, and 5 μm to 15 μm is more desirable.

If graphite of anisotropic shape (rectangular, flake (flaky) shape) other than spherical shape is used, the heat dissipation of the bubble porous body is also anisotropic, and the improvement of heat dissipation by adding graphite becomes insufficient. However, graphite of an anisotropic shape as an impurity has a small proportion to the extent that at least the effect of the present invention can be obtained, and is a form that is included inevitably or arbitrarily, and is not excluded by the present invention. Spherical graphite is preferably 90% by mass or more of all graphite, preferably 95% by mass or more, and more preferably 99% by mass or more.

(2) Matrix resin "" The cellular porous system of the present invention contains a matrix resin. The matrix resin is the main component of the cellular porous body of the present invention. One aspect of the matrix resin is that a plurality of linear polymer chains is a resin having a three-dimensional structure crosslinked by a crosslinking agent or a functional group possessed by the polymer chain itself.

The type of matrix resin is not particularly limited, and any resin that can form a cellular porous structure, more specifically, a resin that can form a porous structure by foaming treatment, can be used. Examples of usable resins include acrylic resins; urethane resins; polyolefin resins such as polyethylene and polypropylene; polyvinyl chloride resins; polystyrene resins; melamine resins, urea resins, and other amino-based resins ;Phenolic Resin. In the above aspect, the matrix resin has a crosslinked structure formed by a crosslinking agent added separately and/or a functional group possessed by itself. Since a stable porous structure can be formed, a flexible porous body can be formed by using it in combination with graphite. Acrylic resin and urethane resin are ideal. In addition, depending on the application, the resin may be exposed to high temperatures, so a resin with high heat resistance is preferable, and from this viewpoint, an acrylic resin is preferable. In the case where the matrix resin is acrylic resin, even if exposed to a high temperature of 150°C, the heat dissipation is maintained without significant thermal deterioration.

Examples of polymerizable monomers in the aforementioned acrylic resin include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and (meth)acrylic acid Hexyl ester, heptyl (meth)acrylate, octyl (meth)acrylate, stearyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, Nonyl (meth)acrylate, dodecyl (meth)acrylate, stearate (meth)acrylate, isobornyl (meth)acrylate, dicyclopentyl (meth)acrylate, (meth) ) (Meth) acrylate monomers such as phenyl acrylate and benzyl (meth)acrylate; acrylic acid, methacrylic acid, β-carboxyethyl (meth)acrylate, 2-(meth)acrylic acid Unsaturated bond-containing monomers with carboxyl groups such as propyl propionic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, itaconic acid half ester, maleic acid half ester, maleic anhydride, itaconic anhydride, etc. ; Glycidyl (meth)acrylate, allyl glycidyl ether and other glycidyl-containing polymerizable monomers; 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate , Polyethylene glycol mono(meth)acrylate, glyceryl mono(meth)acrylate and other hydroxyl-containing polymerizable monomers; ethylene glycol di(meth)acrylate, 1,6-hexanediol Di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate Base) acrylate, diallyl terephthalate, divinylbenzene, allyl (meth)acrylate, etc.

It is preferable that the main component of the matrix resin is an acrylic resin having a cross-linked structure. An example of an acrylic resin with a cross-linked structure includes the introduction of functional side-chain-based (meth)acrylates alone or in combination with one or more other monomers that can be introduced functionally-based side chains (e.g., Ikang) (Acrylic acid, acrylonitrile) are simultaneously copolymerized together or after polymerization, the crosslinking reaction proceeds to form an acrylic resin having a crosslinked structure. Once an acrylic resin having a functional group in the side chain is obtained, it is ideal to form a crosslinked structure. The crosslinking structure can be formed by the reaction between the functional groups of the side chain part of the resin and/or by the reaction between the functional groups and the crosslinking agent added. The acrylic resin system preferably has a functional group that contributes to the formation of a crosslinked structure, and in this example, it contains a hydroxyl group, a carboxyl group, a nitrile group, a glycidyl group, a sulfo group, and the like.

In addition, as the crosslinking agent system, conventionally known crosslinking agents can be used. In this example, a polyfunctional compound having two or more functionalities can be used (in the present invention, the so-called "polyfunctional compound" means having 2 Compounds of the above functional groups. The functional groups contained in one molecule may be the same or different.). Specifically, the crude hexamethylene diisocyanate (crude HDI) of aliphatic isocyanate or the hexamethylene diisocyanate (HDI) of the aforementioned crude HDI and the HDI isocyanurate of the trimer of HDI can be used Esters, isophorone diisocyanate (IPDI), aromatic isocyanate diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI) and the isocyanate group of toluene diisocyanate (TDI) modified with a blocking agent Isocyanate-based crosslinking agents such as block polyisocyanates, epoxy-based cross-linking agents, melamine-based cross-linking agents, carbodiimide-based cross-linking agents, oxazoline-based cross-linking agents, etc., according to the resin compounding system used The type and amount of functional groups contained are used in an appropriate amount. An example of the crosslinked structure is a crosslinked structure formed by the reaction of any one or more of the above-mentioned functional groups possessed by the acrylic resin in the side chain and the diisocyanate group possessed by the crosslinking agent.

(3) Additives "The cellular porous system of the present invention may also contain other additives together with the aforementioned matrix resin and spherical graphite. An example of the additive is a thermally conductive material other than graphite. Adding other thermally conductive materials together with spheroidal graphite can further improve heat dissipation. Examples of other thermally conductive materials include metal nitrides such as boron nitride and aluminum nitride; metal oxides such as aluminum oxide and magnesium oxide; and clay minerals such as talc. It is ideal that the thermal conductivity of the thermally conductive material used in combination is 30W/(m·K) or more. In addition, among the thermally conductive materials, there are materials with high hardness, and since the softness of the cellular porous body of the present invention may be lost if used, it is desirable to use a thermally conductive material with low hardness. Specifically, it is desirable to use a material with a Mohs hardness of 9 or less, and preferably a Mohs hardness of 6 or less. From the viewpoint of heat dissipation and flexibility, an example of an ideal aspect is a aspect in which spherical graphite and a metal oxide having a Mohs hardness in the aforementioned range are contained as a thermally conductive material.

Other examples of additives include one or more types of surfactants. Surfactants contribute to the stable formation of bubbles during the foaming process. That is, it functions as a foaming agent. In addition, it also contributes to stable dispersion of spherical graphite in the matrix resin. In particular, if a surfactant having excellent wettability with respect to spherical graphite is used, it is desirable because it can ensure high dispersibility of spherical graphite with respect to the matrix resin. One type or two or more types selected from conventionally known anionic surfactants, nonionic surfactants, and amphoteric surfactants can be used. Examples of surfactants that are excellent in bubble formation stability and wettability include sulfosuccinates (for example, sodium dialkylsulfosuccinate), alkylbenzene sulfonates, and polyoxyethylene alkyl ethers Sulfate salt-based anionic surfactants containing hydrophilic sulfo groups. In addition, an example of a surfactant having excellent wettability is a nonionic surfactant having a polyoxyalkylene chain including polyoxyethylene alkyl ether and polyoxyethylene fatty acid ester. In the present invention, it is desirable to use one or more of the aforementioned anionic surfactants that are excellent in both bubble formation stability and wettability, or when using one or more of the aforementioned anionic surfactants, both of them are used. One or more nonionic surfactants with excellent wettability. In addition, one or more types of amphoteric surfactants such as amino acid type, betaine type, amine oxide type, etc. may also be used.

The present invention is also characterized in that even if a polysiloxane-based surfactant is not used as a surfactant, a bubble porous body with high heat dissipation properties can be obtained. Polysiloxane-based surfactants have excellent bubble formation stability, but there is a problem in that low-molecular-weight siloxanes are released when exposed to high temperatures. The present invention does not use a silicone-based surfactant as a surfactant, and can provide a polysilicon-free porous porous body with excellent heat resistance.

Within the range that does not harm the effects of the present invention, other tackifiers, bubble nucleating agents, plasticizers, lubricants, colorants, antioxidants, fillers, reinforcing agents, flame retardants, and antistatic agents can also be used , Surface treatment agent and other well-known additives. "As a result, it is ideal that the glass transition temperature (Tg) of the available bubble porous body is -80～0℃. Preferably, it is -60 to -10°C. This glass transition temperature can be used as an index of the hardness of the bubble porous body. If the Tg is excessively lower than -80°C, the air-cell porous body becomes soft, and the sheet, etc., is not stiff, and if the Tg is higher than 0°C, the air-cell porous body becomes hard and loses flexibility.

(4) The ratio of the aforementioned thermally conductive material contained in the cellular porous body of the present invention is based on the total mass of the cellular porous body, 30 to 70% by mass is ideal, 35 to 65% by mass is more desirable, and 40 ～60% by mass is more desirable. As the thermally conductive material, the ratio of the spherical graphite in the aspect containing only the spherical graphite is preferably within the aforementioned range. In addition, according to the above, in the present invention, as a thermally conductive material, materials other than spherical graphite may also be included, such as metal oxides, but the mass ratio of metal oxide to spherical graphite is 0:10-2:3. Ideal, 0:10～5:5 is more ideal.

(5) Form and properties 　　 There are no particular restrictions on the form of the bubbles in the cellular porous body of the present invention, but from the viewpoint of heat dissipation and flexibility, continuous cells are preferable. The term "interconnected bubbles" means that the resin film separating adjacent bubbles has through holes, and the adjacent bubbles are in a three-dimensional communication state. In addition, if it has a "continuous bubble" structure, it has the property that external air can pass through to the inside of the foam. In the present invention, it is not strictly required that all the pores are in communication, and even if a part of the closed pores exists inside, as a whole, if there is a property that the outside air can pass through, it is set to a "continuous bubble" structure. The shape of the bubbles can be confirmed by observation with an electron microscope.

If the density of the cellular porous body of the present invention is 250 to 600 kg/m ³ , it is ideal because it is excellent in both heat dissipation and flexibility, and it is more preferably 300 to 500 kg/m ³ . If the density is lower than the aforementioned range, the heat dissipation property becomes low, and it becomes inappropriate depending on the application system (for example, the application system of the heat sink arranged inside the precision electronic and electrical equipment). If the density exceeds the aforementioned range, the flexibility will decrease and the hardness will increase. As a result, the shape followability to complex structures will deteriorate. Depending on the application system (for example, the use of heat sinks arranged inside precision electronic and electrical equipment) Department) becomes inappropriate.

According to the present invention, a cellular porous body exhibiting high heat dissipation and high flexibility can be provided. Specifically, it is possible to provide a cellular porous body, which is a 25% compression load measured in accordance with JLS K 6254:2016 (ISO 7743:2011) (meaning the pressure necessary to compress 25% of the thickness. 25% compression load) It may be abbreviated as ("25%CLD (Compression-Load-Deflection)".) It is 20kPa or less, and the thermal conductivity measured by the probe method using QTM-500 manufactured by Kyoto Electronics Industry Co., Ltd. is 0.3W/(m.K) ) Above. From the viewpoint of flexibility, the lower the 25% compression load is, the better, but from the viewpoint of operability, generally speaking, the lower limit of the 25% compression load is about 3kPa. From the viewpoint of performance, it is considered that the higher the thermal conductivity, the better, but in general, the upper limit is about 0.7W/(m·K).

One embodiment of the bubble porous body of the present invention is a sheet-like bubble porous body with a thickness of about 0.1 to 1 mm. The bubble porous system of the present invention fully exhibits high heat dissipation even if it is a thin flake. At the same time, by taking advantage of the flexibility, it can be easily deployed in precision electronics and electrical appliances with complicated internal structures. Machine products. The foregoing embodiment removes heat that is easily filled inside precision electronic and electrical equipment, and can be used as a heat sink that reduces deterioration due to heat of precision electronic and electrical equipment.

(6) Molding method "In order to form the cellular porous body of the present invention into a desired shape, molding can be performed by various methods generally known in the past. The appropriate forming method can be selected according to the desired final shape. The casting method can be used in the case of manufacturing a thin bubble porous body. It is ideal that the bubble introduction process (foaming process) is performed before the forming process. In addition, in the case where the matrix resin has a cross-linked structure, the formation of the cross-linked structure, that is, the progress of the cross-linking reaction may also be performed simultaneously with the molding process.

(7) Application 　　 The bubble porous system of the present invention is suitable for use as a heat dissipation member for electronic and electrical equipment products. In addition, it is also useful as a packing material. In particular, it is suitable for heat dissipation components of precision electronic and electrical machinery products whose internal structure is complicated. Among the heat dissipating members, there are also those that have poor heat resistance and are arranged without contact with electronic parts that become a heat source. The cellular porous body of the present invention, especially the aspect in which the matrix resin is acrylic resin, is excellent in heat resistance, so it can also be used as a contact type heat dissipation member that can contact electronic parts that become a heat source.

[Method for manufacturing cellular porous body] 　　 The present invention also relates to a manufacturing method for cellular porous body, including: a foaming step of making a liquid composition containing a resin having a functional group in the side chain, a foaming agent, and spherical graphite Carry out a mechanical foaming and hardening step, which is to make the functional groups of the aforementioned resin react with each other, and/or make the functional groups of the polyfunctional crosslinking agent react with each other, and/or make the aforementioned resin's functional groups react with each other. The functional group possessed reacts with the functional group of the aforementioned multifunctional crosslinking agent to harden the aforementioned liquid composition; 　　 perform the aforementioned foaming step and the aforementioned curing step at the same time, and/or implement the aforementioned curing step after the aforementioned foaming step. "By this method, the bubble porous body of the present invention can be produced stably.

(1) Each component of the liquid composition The liquid composition used in the production method of the present invention contains at least a resin having a functional group in the side chain, a foaming agent, and spherical graphite. Furthermore, it may also contain a multifunctional compound which helps the hardening of the aforementioned resin, that is, a crosslinking agent. The ideal examples of each of the resin having a functional group in the side chain, the foaming agent, the spherical graphite, and the crosslinking agent are the same as the ideal examples of the respective components described in the above-mentioned [bubble porous body].

In order to prepare it as a liquid composition, it is preferable to further include a solvent. Examples of solvents that can be used include water, organic solvents (for example, methanol, ethanol, isopropanol, ethyl carbitol, ethyl cellosolve, butyl cellosolve, and other alcohols, N-methylpyrrolidone One or two or more of such polar solvents), but in the present invention, it is desirable to use only water. If an organic solvent is used, the viscosity of the liquid composition becomes higher compared to the case of using water, and the bubble formation stability and moldability deteriorate. It is desirable not to include an organic solvent, but it may also be included in a ratio to a degree that does not affect the moldability (for example, the viscosity is not increased to a degree that is harmful to moldability).

(2) Preparation method of liquid composition The above-mentioned liquid composition is prepared separately from the aqueous emulsion of the resin and the aqueous dispersion of spheroidal graphite. If these are mixed and prepared, it can be prepared without causing aggregation of spheroidal graphite. Therefore, a liquid composition is ideal. There are no particular restrictions on the solid content concentration of the resin in the aqueous emulsion of the resin and the solid content concentration of the spherical graphite in the aqueous dispersion of the spherical graphite, but generally it is about 50% by mass to 90% by mass . It is ideal to mix the surfactant as a foaming agent in the aqueous dispersion of spherical graphite in advance because the dispersion stability to the spherical graphite in the resin is improved when it is mixed with the aqueous emulsion of the resin. In particular, as a foaming agent, if at least one surfactant with good wettability is used, it is desirable because the dispersion stability of spherical graphite into the resin is improved. Among them, it is desirable to use at least one selected from the above-mentioned anionic surfactants with good bubble formation stability and wettability, and further to use at least one selected from the above-mentioned nonionic surfactants with good wettability. Ideal. For example, an aqueous dispersion of spherical graphite can be prepared by mixing spherical graphite with an aqueous solution or suspension of a surfactant (foaming agent) with a solid content of about 20-60% by mass. Furthermore, it is desirable to add other additives to the aqueous dispersion of spherical graphite in the form of using crosslinking agents, other thermally conductive materials, etc., and to mix with the aqueous emulsion of resin to prepare a liquid composition.

(3) Composition and properties of the liquid composition 　　 The total solid content of the aforementioned liquid composition is about 50 to 90% by mass, preferably 65 to 85% by mass. Generally speaking, in the total solid content of a liquid composition, the total mass of resin (and crosslinking agent added as desired) and spherical graphite (other thermally conductive materials added as desired) becomes 95% or more. The total mass of other additives such as a foaming agent (specifically, a surfactant) is 5% or less. However, the ideal mass ratio of each material in the solid form varies according to the type of material used. In addition, the pH of the liquid composition is to form bubbles stably, so it is preferably in the neutral to alkaline range. Specifically, the pH is 7 or higher, and 7-11 is ideal. Preferably it is 7-9. The pH of the liquid composition is adjusted to adjust the type or amount of the foaming agent, and it can be set to the aforementioned ideal range. In addition, the viscosity of the liquid composition is due to the stable formation of bubbles in the following foaming step, so the viscosity of about 10,000 to 200,000 mPa·s is appropriate.

(4) Foaming step "In the foaming step, mechanical foaming is performed by stirring the aforementioned liquid composition to generate bubbles. The mechanical froth method is a method in which a liquid composition is stirred with a stirring blade or the like, and gas such as air in the atmosphere is mixed into the emulsion composition to make it foam. The stirring device is not particularly limited in the mechanical foaming method, and a generally used stirring device can be used. For example, a homogenizer, a dissolver, a mechanical froth foaming machine, etc. can be used. In the present invention, the foaming step is implemented by a mechanical foaming method to suppress the formation of closed cells, form continuous cells predominantly, prevent the density of the porous body after hardening from increasing, and obtain a porous body with high flexibility.

There are no particular restrictions on the stirring conditions, but the stirring time is usually 1 to 10 minutes, preferably 2 to 6 minutes. In addition, the stirring speed of the above-mentioned mixing is to make the bubbles fine, so 200rpm or more is ideal (500rpm or more is ideal). In order to smooth the discharge of the foam from the foaming machine, 2000rpm or less is ideal (800rpm The following is more ideal). Regarding the temperature condition of the foaming step, there is no particular limitation, but it is usually normal temperature. When the curing step described later is carried out at the same time as the foaming, heating may also be used in order to advance the reaction of the functional group.

(5) Hardening step In the hardening step, the functional groups of the aforementioned resin are reacted with each other, and/or the functional groups of the polyfunctional crosslinking agent are reacted with each other, and/or the functional groups of the aforementioned resin are reacted with each other. Reacts with the functional groups of the aforementioned multifunctional crosslinking agent to harden the liquid composition. Through this step, the aforementioned liquid composition becomes a structure of a bubble porous body. It is ideal to implement the curing step after the foaming step. In order to evaporate the solvent (water) in the liquid composition and to advance the crosslinking reaction, heating is ideal. The heating temperature and heating time may be the temperature and time for crosslinking (hardening) the raw material, for example, it may be set to about 1 hour at 80 to 150°C (especially, about 120°C is suitable).

In addition, the hardening step can also be implemented as one of the steps of the molding process for making the available cellular porous body into a desired shape. For example, the hardening step can also be implemented as one of the steps of the casting method in the aspect of manufacturing the thin bubble porous body. Specifically, the liquid composition that has been subjected to the "(4) foaming step" is cast on the surface of the substrate to a desired thickness, and heated to evaporate the solvent (water), and at the same time, the crosslinking reaction proceeds and hardens. Can be made on the surface of the substrate. The base material of the casting liquid composition is not particularly limited. A resin base material (PET film with a thickness of 25-50μm, if the surface has been demolded as desired), a metal base material with a thickness of 2-100μm or cut into tapes can be used. A long metal substrate in the shape of a strip, a laminated substrate of a PET film with a thickness of 1 μm to 30 μm and an adhesive layer with a thickness of 2 μm to 100 μm, which is similarly cut into a strip shape, and is cut into The strip-shaped long film has an air-free laminated base material and the like composed of an adhesive layer with a concave-convex shape having a depth of 2 μm-100 μm and a height of the convex part of 2 μm-100 μm.

One embodiment of the manufacturing method of the present invention is a method of manufacturing a sheet-like cellular porous body, which includes a foaming step of making a resin containing a functional group in the side chain, a foaming agent, and a spherical shape The liquid composition of graphite undergoes mechanical foaming and casting steps. The casting step is followed by the foaming step. The liquid composition is cast on the surface of the substrate to a flaky shape, and a hardening step. The hardening step is the casting step After that, the functional groups of the aforementioned resin are allowed to react with each other, and/or the functional groups of the polyfunctional crosslinking agent are allowed to react with each other, and/or the functional groups of the aforementioned resin are reacted with the aforementioned polyfunctional ones. The functional groups of the crosslinking agent react to harden the aforementioned liquid composition to obtain a sheet. Example

Hereinafter, the effects of the bubble porous body of the present invention and the manufacturing method will be specifically explained by using examples.

(Material) ‧Matrix resin material As matrix resin material 1, prepare an acrylic resin emulsion of acrylonitrile-alkyl acrylate-itonic acid copolymer (Tg -40°C, pH9, solid content concentration 60% by mass, solvent is water ). "As the matrix resin material 2, an emulsion of urethane resin (pH 8, solid content 60% by mass, and water as the solvent) was prepared. ‧Foaming agent 　　As a foaming agent, prepare the following surfactants separately.　　As an anionic surfactant 1, prepare a mixture of ammonium stearate and water (pH 11, solid content 30%). "As an anionic surfactant 2, prepare a mixed solution of sodium alkylsulfosuccinate and water (pH 9.3, solid content 35%).　　As an amphoteric surfactant 1, prepare a mixture of coconut oil fatty acid amidopropyl betaine and water (pH 7.5, solid content 30%).　　As amphoteric surfactant 2, prepare a mixture of myristyl betaine and water (pH 6.5, solid content 36%).　　As a non-ionic surfactant 1, prepare a mixture of polyoxyethylene alkyl ether and water (pH 6.5, solid content 50%).

‧Crosslinking agent 　　As a crosslinking agent, prepare hydrophobic HDI isocyanurate (functional group number 3.5). ‧Thermal conductive material (graphite) 　　As graphite 1, prepare spherical graphite powder (average particle size 20μm) manufactured by Japan Graphite Industry Co., Ltd. This spherical graphite is processed by spheroidization to bend the basal plane of the graphite crystal (hexagonal system).　　As graphite 2, a powder of spherical graphite (average particle diameter 10 μm) manufactured by Nippon Graphite Industry Co., Ltd., which is different from graphite 1 only in average particle size, was prepared.　　As graphite 3, a powder of spherical graphite (average particle size 20μm) manufactured by Ito Graphite Industry Co., Ltd. was prepared. This graphite system is different from graphite 1 and graphite 2. The basal plane of the graphite crystal (hexagonal crystal system) is processed to an unbent spherical shape (scaly graphite processed to a spherical shape).　　As graphite 4, a graphite powder (average particle size 20μm) manufactured by Ito Graphite Industry Co., Ltd. was prepared. This graphite system has not been spheroidized, and the bottom surface (basal plane) of the graphite crystal (hexagonal system) is not bent (flaky graphite). ‧Heat conductive material (other than graphite) 　　As metal oxide 1, prepare powder of oxide composed of aluminum and magnesium (shape: spherical, average particle size 10μm, Mohs hardness 6). "As the metal oxide 2, a powder of an oxide composed of aluminum and magnesium (shape: spherical, average particle size 20 μm, Mohs hardness 6) was prepared.　　As the metal oxide 3, a powder of alumina (shape: spherical, average particle size 20 μm, Mohs hardness 9) was prepared.

(Examples 1 and 2) 　　 Graphite 1, anionic surfactant 1, anionic surfactant 2, amphoteric surfactant 1, amphoteric surfactant 2, and nonionic surfactant 1 were mixed in the ratio shown in the table below, Here, a crosslinking agent was added to prepare an aqueous dispersion of graphite 1, and this was added and mixed with 100 parts by mass of the above-mentioned matrix resin material 1 to prepare liquid compositions for Examples 1 and 2, respectively.　　The total solid content of the liquid composition and the solid content of the thermally conductive material are described in the following table. The pH of this liquid composition was 8.4. In addition, the viscosity is also a viscosity range that can be mechanically foamed.

Each liquid composition prepared as above is foamed by a mechanical foaming method (stirring 500 rpm, stirring time 3 minutes, temperature 23°C), and then the aforementioned liquid composition is cast on a PET film that has undergone a mold release treatment The surface of the substrate is flaky, heated to 120°C to evaporate the water, and at the same time it undergoes a cross-linking reaction to harden the acrylic resin to produce a flaky porous body. The thickness, appearance, density, thermal conductivity (the higher the heat dissipation, the better the heat dissipation), the hardness (the lower the flexibility, the better the flexibility), and the heat resistance of the obtained sheet-like cellular porous body were measured by the following methods, and the results The system is shown in the following table.

(Examples 3 and 4) "In the preparation of the above-mentioned liquid composition, except that graphite 2 was used instead of graphite 1, it was carried out in the same manner, and each of Examples 3 and 4 with the composition shown in the following table was prepared. Liquid composition. The pH of each liquid composition was 8.4 similarly to the liquid composition of Example 1. "Except for using the respective liquid compositions of Examples 3 and 4, the same procedure was performed as described above, and the flake-shaped cellular porous bodies of Examples 3 and 4 were produced and evaluated in the same manner. The results are shown in the following table.

(Examples 5 and 6) "The preparation of the above liquid composition was carried out in the same manner except that graphite 3 was used instead of graphite 1, and each of Examples 5 and 6 of the composition shown in the following table was prepared. Liquid composition. The pH and viscosity of each liquid composition are not much different from those in the above-mentioned embodiment, and there is also little difference in bubble formation obtained by the mechanical froth method. "Except for using the liquid compositions of Examples 5 and 6, respectively, it was performed in the same manner as described above, and the flaky bubble porous bodies of Examples 5 and 6 were produced, respectively, and evaluated in the same way. The results are shown in the following table.

(Comparative Examples 1 and 2) 　　 The preparation of the above-mentioned liquid composition was carried out in the same manner except that graphite 4 was used instead of graphite 1, and each of Comparative Examples 1 and 2 of the composition shown in the following table was prepared. Liquid composition. The viscosity of each liquid composition is significantly higher than that of the above-mentioned examples, and the bubble formation obtained by the mechanical froth method is inferior. "Except for using the liquid compositions of Comparative Examples 1 and 2, respectively, it was performed in the same manner as described above, and the flaky bubble porous bodies of Comparative Examples 1 and 2 were produced and evaluated in the same manner. The results are shown in the following table.

(Thickness) 　　The thickness of each sheet is measured using a thickness gauge with a contact piece of φ50mm. The measured values are shown in the following table. (Density) 　　The density of each sheet is measured in accordance with JIS K 7222:2005 (ISO 845:1988). The measured values are shown in the following table. (Appearance evaluation) 　　 The appearance evaluation of each sheet surface and bubbles (cell) was performed visually. In addition, the fact that any of the prepared sheets are continuous bubbles was confirmed with a scanning electron microscope (200 times). The case where the cells are uniform and the surface is not rough is evaluated as "○", and the case where some bubbles are rough or the surface condition is rough is evaluated as "△". The air bubbles are very rough, the air bubbles are not formed, or the surface condition is obvious. Rough conditions are evaluated as "×". The results are shown in the following table.

(Thermal conductivity) 　　The thermal conductivity of each sheet was measured by the probe method using a rapid thermal conductivity meter (QTM-500) manufactured by Kyoto Electronics Industry Co., Ltd. The case where the thermal conductivity is 0.3W/(m·K) or higher is evaluated as "○", and the case where the thermal conductivity is 0.2W/(m·K) or more but less than 0.3W/(m·K) is evaluated as "△" ", the case where the thermal conductivity is less than 0.2W/(m.K) is evaluated as "×". The evaluation results are shown in the following table. (Flexibility) 　　 The hardness of each sheet was measured in accordance with JIS K6254:2016 (ISO 7743:2011). Specifically, a sample punched with a diameter of 50mm is overlapped so that the thickness becomes 1mm or more, and an automatic plotter is used to measure the magnitude of the rebound stress when 25% of the thickness is flattened at a speed of 1mm/min. For the measurement system, AUTOGRAPH AGS-X manufactured by Shimadzu Corporation was used. The case where 25% CLD is less than 20 kPa is evaluated as "○", the case where 25% CLD is more than 20 kPa and less than 50 kPa is evaluated as "△", and the case where 25% CLD is more than 50 kPa is evaluated as "×". The results are shown in the following table. (Heat resistance) 　　 Each sheet was placed in a constant temperature bath with a temperature of 150°C for 336 hours and then taken out. After being left at room temperature and humidity for 24 hours, a sample piece was produced and the tensile strength was measured. The tensile strength is measured in accordance with JIS K6251:2017 (ISO 37:2011). For the measurement system, AUTOGRAPH AGS-X manufactured by Shimadzu Corporation was used. In addition, the tensile strength was similarly measured before the treatment at 150°C×336 hours, and the value of the tensile strength before and after the treatment was substituted into the following formula to calculate the reduction rate for evaluation. Reduction rate = (tensile strength after treatment ÷ tensile strength before treatment)×100 　　 The reduction rate is evaluated as "○" when the reduction rate is less than 20%, and the case where the reduction rate is more than 20% and less than 30% is evaluated as " △", the case of more than 30% is evaluated as "×".

From the results shown in the above table, it can be understood that the Examples 1 to 6 containing graphite 1 to 3 as spheroidal graphite are comprehensive compared to Comparative Examples 1 and 2 containing graphite 4 in the same ratio as flake graphite. The evaluation is excellent. In particular, it can be understood that if the bottom surface bent spherical graphite with a small average particle diameter (less than 20μm) is used, it will not adversely affect the appearance, and the effect of improving both thermal conductivity (heat dissipation) and flexibility can be obtained. The range of composition becomes wider.

On the other hand, it can be understood that, compared with Examples 1 to 6, Comparative Examples 1 and 2 using the scaly graphite 4 have poor thermal conductivity (poor heat dissipation) and poor appearance. The reason for this is believed to be that the liquid composition used as the raw material of each sheet has a high viscosity and cannot form bubbles stably by the mechanical foaming method. Since there is a tendency for the viscosity of the liquid to increase as the amount of flaky graphite increases, even if the amount of flaky graphite is increased to improve the heat dissipation of the comparative example, the thermal conductivity cannot be improved, that is, from the above results It can be said that the use of scaly graphite cannot achieve the high thermal conductivity (heat dissipation) and flexibility that can be obtained when spherical graphite is used. Furthermore, as shown in the following table, in the preparation of the composition used in Comparative Example 1, the metal oxide 1 was used together with graphite 4 to try to improve the thermal conductivity. However, although the thermal conductivity improvement effect can be obtained somewhat, On the other hand, poor appearance becomes obvious. That is, it can be understood that the combined use of flake graphite and metal oxide has a limit to the improvement effect of thermal conductivity, and the effect of the embodiment of the present invention using spherical graphite cannot be obtained.

(Examples 7-12) 　　Instead of preparing the liquid composition of the above-mentioned Example 1 or 2, changing the concentration of graphite 1 or 2, using metal oxide (other thermally conductive materials) together with graphite 1 or 2, and changing the mixing ratio Etc., each liquid composition used in Examples 7 to 21 having the composition shown in the following table was prepared. The pH of each liquid composition was about 8.4 like the liquid composition of Example 1 or 2. "Except for using each liquid composition of the composition shown in the following table, it carried out in the same manner as the above-mentioned Example 1 etc., and each produced the sheet-like bubble porous body of Examples 7-21.

Examples 7 to 21 described in the above table are examples in which spheroidal graphite 1 or 2 and any one of metal oxides 1 to 3 are combined. Compared with Comparative Examples 1 and 2 using flake graphite, both have higher thermal conductivity. Among them, the combination of graphite 1 or 2 (especially graphite 1) and metal oxide 1 or 2 with a Mohs hardness of less than 9 are in Examples 7 to 14 and 18 to 21, compared with metals with a Mohs hardness of 9 Examples 15 to 17 of oxide 3 have excellent flexibility improving effects. If a metal oxide with a Mohs hardness of less than 9 is used, the decrease in flexibility due to the influence of the metal oxide can be suppressed, and high thermal conductivity and flexibility can be achieved in a well-balanced manner. Moreover, even embodiments with poor heat dissipation properties are useful for applications that do not require strict heat dissipation (such as filling materials). Moreover, even embodiments with poor flexibility, the internal structure is not complicated. Of electronic and electrical equipment are used as heat dissipation components.

(Examples 22 to 31) "In place of the preparation of the liquid composition of Example 1 above, the concentration of graphite 1 was changed, metal oxides (other thermally conductive materials) were used together with graphite 1, the mixing ratio was changed, and the matrix resin was changed. For the kind, etc., each liquid composition used in Examples 22 to 31 of the composition shown in the following table was prepared. The pH of each liquid composition was 8.4 like the liquid composition of Example 1, but the pH of the liquid composition used in Example 31 was 8.0. In addition, the liquid composition has a higher viscosity than the liquid composition of Example 1, and the bubble formation caused by the mechanical foaming method is also inferior. "Except for changing the liquid composition of Example 1 to each liquid composition, it carried out in the same manner as Example 1, etc., and each produced the sheet-shaped bubble porous body of Examples 22-31.

Regarding each sheet that has arrived, after the above-mentioned evaluation was performed in the same manner as in Example 1, the comprehensive evaluation was better than the comparative example, and it was a grade that can withstand practical use. From the evaluation results of the examples shown in Table 1, Table 3, and Table 4, it can be understood that, in particular, 40-60% by mass of thermally conductive materials are included, and if it is a total thermally conductive material, spherical graphite occupies If the ratio is 50% by mass or more, a sheet having high heat dissipation and flexibility in a well-balanced manner can be obtained. "Furthermore, it is understood that if an acrylic resin is used as the matrix resin, a sheet having excellent heat resistance can be obtained. In the above-mentioned examples, the effect obtained by the blending of spherical graphite is clarified, so the composition of the surfactant in each example is set to be the same. Even if the composition is changed, the same effect can be obtained. .

The present invention will be described in detail with reference to specific aspects, but it is obvious to the practitioner that various changes and modifications can be made without departing from the spirit and scope of the present invention.　　 This application is a Japanese patent application (Japanese Patent Application 2016-237524) filed on the date of December 7, 2016, and the entirety is incorporated by reference. In addition, all reference frames cited here are included as a whole.

Claims (10)

A cellular porous body characterized by containing a matrix resin and a thermally conductive material dispersed in the matrix resin. The thermally conductive material contains at least spheroidal graphite, and the spheroidal graphite has a structure in which a basal plane is bent , Based on the total mass of the bubble porous body, 30~70% by mass contains the aforementioned thermally conductive material. The cellular porous body of claim 1, wherein the aforementioned matrix resin is an acrylic resin. The cellular porous body of claim 1 or 2, wherein the thermally conductive material further contains a metal oxide. The cellular porous body of claim 1 or 2, wherein the thermally conductive material is contained at 40-60% by mass based on the total mass of the cellular porous body. The cellular porous body of claim 1 or 2, wherein, as the aforementioned thermally conductive material, metal oxide and spherical graphite are contained in a blending ratio (mass ratio) of 0:10 to 5:5. Such as the bubble porous body of claim 1 or 2, which is an open-cell porous body. Such as the bubble porous body of claim 1 or 2, in which the 25% compression load measured in accordance with JIS K 6254:2016 (ISO 7743:2011) is 20kPa or less, using QTM-500 manufactured by Kyoto Electronics Industry Co., Ltd. and the probe method The measured thermal conductivity is 0.3W/(m.K) or more. Such as the bubble porous body of claim 1 or 2, which is used as a heat dissipation member for electronic products. A method for producing a cellular porous body according to any one of claims 1 to 8, comprising a foaming step of making a liquid composition containing a resin having a functional group in the side chain, a foaming agent, and spherical graphite Carry out mechanical foaming and hardening steps by making the functional groups of the aforementioned resin react with each other, and/or making the functional groups of the polyfunctional crosslinking agent react with each other, and/or making the aforementioned resin The functional group possessed reacts with the functional group of the aforementioned polyfunctional crosslinking agent to harden the aforementioned liquid composition; wherein, the aforementioned foaming step and the aforementioned curing step are carried out at the same time, and/or the aforementioned step is carried out after the aforementioned foaming step Hardening step. The manufacturing method of claim 9, wherein the pH of the liquid composition is in a range from neutral to alkaline, and the liquid composition contains at least one anionic surfactant as the foaming agent.