JP2007291344A - Acrylic resin composition and sheet-like molded product using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acrylic resin composition excellent in processibility, having high grade flexibility and excellent in adhesion to electric components and the like, and to provide sheet-like molded products obtained by using the composition. <P>SOLUTION: The acrylic resin composition comprises (A) an acrylic copolymer having a reactive functional group on a molecular chain and having 800-20,000 number-average molecular weight expressed in terms of polystyrene, (B) a compound having a functional group reactive with the acrylic copolymer and (C) an acrylic polymer having no reactive functional group on the molecular chain and having 800-6,000 number-average molecular weight expressed in terms of polystyrene. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an acrylic resin composition and a sheet-like molded body using the same.

  Electronic equipment parts, especially electronic devices, personal computers, etc., generally generate heat during operation, so a metal heat sink or the like is installed in the electronic equipment device to prevent damage to the parts due to heat and to ensure stable operation. Yes. Further, if necessary, the heat sink is forcibly cooled by a fan or the like. Furthermore, forced cooling by water circulation or forced cooling using a Peltier element, which is a kind of semiconductor element, is employed for components that generate large heat.

  When such a cooling device is attached to the heating element, a material called a heat conduction material is used to close the contact between the cooling device and the heating element and to transfer heat to the cooling device effectively. Yes. That is, such a heat conductive material is interposed between the cooling device and the heating element to improve heat transfer between them. As such a heat conductive material, silicone grease, a silicone rubber sheet with increased thermal conductivity, a silicone gel sheet, or the like is generally used from the viewpoints of thermal decomposition stability, flame retardancy, and the like.

  However, silicone grease is difficult to handle because it is a high-viscosity liquid, and it is difficult to control the application amount when applied to heat-generating parts, and the fluidity increases and flows out (pumps out) as the temperature rises. There was a problem. In addition, there is a problem that it is difficult to use substantially because the adhesiveness is not so good on a large uneven surface of a heat generating component. Furthermore, since it is a silicone-based material, a slight amount of siloxane gas is generated, and this siloxane gas adheres to electrode contacts and the like to generate silicon dioxide, which may cause contact failure. There was sex.

  In addition, silicone rubber sheets with higher thermal conductivity and silicone gel sheets with lower hardness cannot be easily manufactured because the silicone resin itself is expensive and may require a vulcanization step in the manufacturing process. There was a problem. Further, since siloxane gas is generated in the same manner as the above-mentioned silicone-based grease, there is a possibility that a contact failure may occur in such a silicone rubber sheet or silicone gel sheet. Moreover, when a heat conductive filler such as a metal oxide is contained in such a silicone rubber sheet in a high ratio, it becomes difficult to form a sheet, and the obtained sheet becomes a brittle sheet.

  In order to solve such problems as silicone grease, silicone rubber sheet, silicone gel sheet, etc., heat conduction such as rubber, urethane, acrylic, etc. containing a heat conductive filler such as alumina, boron nitride, etc. Materials (resin compositions) have been proposed.

  For example, Patent Document 1 discloses a heat conductive sheet including an acrylic polyurethane resin and a heat conductive filler dispersed in the acrylic polyurethane resin. However, since this sheet uses prepolymerized so-called acrylic polyurethane as a resin acrylic resin composition, the processability is low at the time of production, making it difficult to form a sheet, and the flexibility of the resulting sheet is low. There was a problem of being low.

  In Patent Document 2, an acrylic copolymer containing a carboxyl group as a functional group and a compound containing two or more glycidyl groups in one molecule are used as an acrylic resin composition, and nitride, metal Disclosed is a composition comprising a thermally conductive filler selected from the group consisting of oxides or metal powders. However, even with the composition described in Patent Document 2, the processability is not always sufficient, and the flexibility of the obtained sheet is not always sufficient.

On the other hand, in the acrylic resin composition, for example, a heat storage agent, an electromagnetic wave absorber, or an additive made of an inorganic substance or an organic substance such as a dielectric is increased, and the heat storage property, electromagnetic wave absorption property, or dielectric property is excellent. Sheet can be obtained. However, since these sheets have a high content of, for example, a heat storage material, an electromagnetic wave absorber, or a dielectric in the acrylic resin composition, the processability when producing the sheet is low and it is difficult to form a sheet. In addition, there is a problem that the flexibility of the obtained sheet is low.
JP 2002-30212 A JP 2004-161856 A

  In other words, it is possible to improve each physical property by increasing the content of a thermally conductive filler, a heat storage material, or an additive made of an inorganic substance or an organic substance such as an electromagnetic wave absorber or a dielectric, but the workability is low. It became difficult to form a sheet and the flexibility was lowered. As a result, for example, when used as a heat conductive sheet, the adhesion to electronic components and heat sinks is reduced and the contact area is reduced, so that there is a problem that substantial heat conductivity cannot be secured. It was. In addition, in the heat storage sheet, the electromagnetic wave absorbing sheet, or the dielectric sheet, if the flexibility is low, the adhesion with the sticking body is lowered, and in some cases, these sheets may be peeled off from the sticking body, It was difficult to exert excellent physical properties. The present invention has been made in view of the above-described problems of the prior art, has good workability, has high flexibility, and has good adhesion to an adhesive body such as an electrical component, for example. An object of the present invention is to provide a composition and a sheet-like molded article obtained by using the composition.

  As a result of intensive studies to achieve the above object, the present inventors have (A) an acrylic copolymer having a reactive functional group in the molecular chain and a number average molecular weight of 800 to 20,000 in terms of polystyrene. In addition to the polymer and (B) the compound having a functional group that reacts with the acrylic copolymer, (C) the number average molecular weight in terms of polystyrene, which has no reactive functional group in the molecular chain, is 800 to 6, It has been found that an acrylic resin composition having good processability and high flexibility can be obtained by containing 000 acrylic polymer, and has completed the present invention.

  That is, the acrylic resin composition according to claim 1 of the present invention has (A) an acrylic copolymer having a reactive functional group in the molecular chain and a number average molecular weight of 800 to 20,000 in terms of polystyrene. (B) a compound having a functional group that reacts with the acrylic copolymer, and (C) an acrylic having no reactive functional group in the molecular chain and having a number average molecular weight in terms of polystyrene of 800 to 6,000. It contains a polymer. The acrylic resin composition according to claim 2 contains 5 to 150 parts by weight of the acrylic polymer (C) with respect to 100 parts by weight of the acrylic copolymer (A). It is characterized by. Further, the acrylic resin composition according to claim 3 is characterized by containing 150 to 500 parts by weight of a heat conductive filler with respect to 100 parts by weight of the acrylic copolymer (A). Is. Further, the sheet-like molded product according to claim 4 is formed by molding and curing the acrylic resin composition according to any one of claims 1 to 3 into a sheet shape. It is what.

  According to the present invention, an acrylic resin composition having good processability and having a high degree of flexibility and capable of obtaining a sheet-like molded article having good adhesion to an adhesive body such as an electrical component, and The sheet-like molded object obtained using it can be provided.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

  First, the acrylic resin composition of the present invention will be described. That is, the acrylic resin composition of the present invention comprises (A) an acrylic copolymer having a reactive functional group in the molecular chain and having a number average molecular weight of 800 to 20,000 in terms of polystyrene; A compound having a functional group that reacts with an acrylic copolymer, and (C) an acrylic polymer having no reactive functional group in the molecular chain and having a number average molecular weight of 800 to 6,000 in terms of polystyrene It is.

  The acrylic copolymer (A) according to the present invention has a reactive functional group in the molecular chain and has a number average molecular weight of 800 to 20,000 in terms of polystyrene. A method for producing such an acrylic copolymer is not particularly limited. For example, a vinyl monomer and a carboxyl that are copolymerizable mainly with an acrylic monomer having no functional group. A method of simultaneously polymerizing (copolymerizing) a monomer having a group, a method of copolymerizing an acrylic monomer having a functional group and another acrylic monomer, and a monomer copolymerizable with an acrylic monomer to polymerize and functionalize as a termination reaction. A method of performing a terminal termination reaction with a group-containing molecule can be employed.

  The acrylic copolymer (A) has only to have a reactive functional group in the molecular chain, and the functional group has any one of a hydroxyl group, a carboxyl group, and a glycidyl group. These functional groups may exist at the molecular chain end, may exist in the middle of the molecular chain, or may exist on the side chain. Furthermore, it is preferable that two or more reactive functional groups are present on the molecular chain on average. If the reactive functional group is less than this, the reactive functional group cannot react with the compound (B) to sufficiently extend the chain, and heat resistance is improved. It becomes difficult to obtain a molded body. These functional groups are introduced by copolymerizing monomers having functional groups at the time of copolymerization.

  The acrylic copolymer (A) may be a random copolymer or a block copolymer.

  The structure of the acrylic copolymer (A) is not limited to a single one, and a mixture of acrylic copolymers of various repeating units can be used.

  Furthermore, the acrylic copolymer (A) is a mixture of different acrylic homopolymers in addition to the acrylic copolymer obtained by copolymerizing two or more monomers obtained as described above. A mixture of an acrylic homopolymer and an acrylic copolymer, or a mixture of acrylic copolymers can be used. Further, the obtained polymer may have two or more different functional groups. In that case, (B) upon the curing reaction with the compound having a functional group that reacts with the acrylic copolymer. The reaction is not stable and control tends to be difficult.

  Examples of the acrylic monomer having no functional group include acrylic acid alkyl ester, alicyclic alkyl acrylate, methacrylic acid alkyl ester, and alicyclic alkyl methacrylate.

  Examples of alkyl acrylate esters include methyl acrylate (methyl acrylate), ethyl acrylate (ethyl acrylate), propyl acrylate (propyl acrylate), iso-propyl acrylate (acrylic acid-iso-propyl), and n-butyl acrylate (acrylic). Acid-n-butyl), iso-butyl acrylate (acrylic acid-iso-butyl), tert-butyl acrylate (acrylic acid-tert-butyl), 2-ethylhexyl acrylate (acrylic acid-2-ethylhexyl), octyl acrylate (acrylic) Octyl acid), iso-octyl acrylate (acrylic acid-iso-octyl), decyl acrylate (decyl acrylate), iso-decyl acrylate (isodecyl acrylate), iso-no Le acrylate (acrylic acid -iso- nonyl), neopentyl acrylate (neopentyl acrylate), tridecyl acrylate (tridecyl acrylate), and the like lauryl acrylate (lauryl acrylate) is.

    Examples of the alicyclic alkyl acrylate include cyclohexyl acrylate, isobornyl acrylate, tricyclodecyl acrylate, and tetrahydrofurfuryl acrylate.

    Examples of alkyl methacrylates include methyl methacrylate (methyl methacrylate), ethyl methacrylate (ethyl methacrylate), propyl methacrylate (propyl methacrylate), iso-propyl methacrylate (methacrylic acid-iso-propyl), and n-butyl methacrylate (methacrylic acid). Acid-n-butyl), iso-butyl methacrylate (methacrylic acid-iso-butyl), tert-butyl methacrylate (methacrylic acid-tert-butyl), 2-ethylhexyl methacrylate (methacrylic acid-2-ethylhexyl), octyl methacrylate (methacrylic acid) Octyl acid), iso-octyl methacrylate (methacrylic acid-iso-octyl), decyl methacrylate (decyl methacrylate), isodecyl methacrylate Rate (isodecyl methacrylate), isononyl methacrylate (isononyl methacrylate), neopentyl methacrylate (methacrylic acid neopentyl), tridecyl methacrylate (methacrylic acid tridecyl), and the like lauryl methacrylate (lauryl methacrylate) is.

  Examples of the alicyclic alkyl methacrylate include cyclohexyl methacrylate, isobornyl methacrylate, tricyclodecyl methacrylate, and tetrahydrofurfuryl methacrylate.

  Among these, acrylic acid alkyl esters and methacrylic acid alkyl esters are preferable, and n-butyl acrylate (acrylic acid-n-butyl) and 2-ethylhexyl acrylate (acrylic acid-2-ethylhexyl) are particularly preferable.

  Examples of vinyl monomers include acrylonitrile, acrylamide, methacrylamide, N-dimethylacrylamide, N-dimethylmethacrylamide, N-dimethylaminoethyl acrylate, N-dimethylaminoethyl methacrylate, N-diethylaminoethyl acrylate, N-diethylaminoethyl methacrylate, Examples include vinyl acetate, styrene, α-methylstyrene, divinylbenzene, and allyl (meth) acrylate.

  Examples of the monomer having a functional group include a hydroxyl group-containing monomer, a carboxyl group-containing monomer, and a glycidyl group-containing monomer.

  Examples of the hydroxyl group-containing monomer include hydroxymethyl acrylate, hydroxymethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, pentaerythritol. Triacrylate, pentaerythritol methacrylate, glycerol monoacrylate, glycerol monomethacrylate, monoester of acrylic acid or methacrylic acid and polypropylene glycol or polyethylene glycol, ethylene glycol diacrylate, ethylene glycol dimethacrylate, butylene glycol diacrylate, butylene glycol dimethacrylate , La Ton compound and 2-hydroxyethyl acrylate or an adduct of 2-hydroxyethyl methacrylate, and the like.

  Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, and fumaric acid. Examples of the glycidyl group-containing monomer include glycidyl acrylate, glycidyl methacrylate, 2-ethyl glycidyl acrylate, 2-ethyl glycidyl methacrylate, and allyl glycidyl ether.

  The acrylic polymer (A) of the present invention has a polystyrene-equivalent number average molecular weight of 800 to 20,000 as measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent. If the number average molecular weight is less than 800, the resulting molded article tends to have poor heat resistance and weather resistance. Also, if the molded article is a sheet, the hardness becomes high and the desired flexibility cannot be obtained. Can't get good adhesion. On the other hand, if the number average molecular weight exceeds 20,000, the flowability of the acrylic polymer tends to be lost, and it becomes difficult not only to fill the heat conductive filler in a high ratio but also to improve the workability. Low and difficult to form into a sheet.

  The acrylic copolymer (C) according to the present invention adjusts the flexibility as the acrylic resin composition of the present invention. That is, the acrylic copolymer (C) includes (A) an acrylic copolymer having a reactive functional group in the molecular chain and having a number average molecular weight of 800 to 20,000 in terms of polystyrene, and (B) the acrylic copolymer. By including in a compound having a functional group that reacts with the copolymer, the apparent cross-linking density per unit volume in the acrylic resin composition can be reduced, and an acrylic resin composition having excellent flexibility can be obtained. Is possible. The acrylic copolymer (C) contains an acrylic polymer having no reactive functional group in the molecular chain and having a number average molecular weight of 800 to 6,000 in terms of polystyrene. A method for producing such an acrylic copolymer is not particularly limited. For example, a copolymerizable vinyl monomer is mainly copolymerized with an acrylic monomer having no functional group. Can be obtained.

  Moreover, the thing similar to what was used in order to superpose | polymerize an acrylic polymer (A) is mentioned as an acryl-type monomer and vinyl-type monomer which do not have a functional group.

  The acrylic polymer (C) preferably has a polystyrene-equivalent number average molecular weight of 800 to 6,000 as measured by gel permeation chromatography (GPC). When the number average molecular weight is less than 800, when the molded product is a sheet-like product, the hardness becomes high and desired flexibility cannot be obtained, and excellent adhesion cannot be obtained. Further, in the obtained molded body, the acrylic polymer (C) bleeds out, contaminates the heat-generating component and deteriorates the adhesion. Conversely, if the number average molecular weight exceeds 6,000, the flowability of the acrylic polymer tends to be lost, and it becomes difficult to fill the heat conductive filler at a high ratio, and the processability is low. It is difficult to make a sheet.

  The acrylic polymer (C) is preferably contained in an amount of 5 to 150 parts by weight with respect to 100 parts by weight of the acrylic copolymer (A). When the content of the acrylic polymer (C) is less than 5 parts by weight, it is difficult to ensure flexibility and the adhesion to the heat-generating component is deteriorated. In particular, when the acrylic resin composition of the present invention is formed into a sheet-like molded body, the sheet cannot be attached to the heat-generating component unless the sheet is strongly compressed to the heat-generating component, thereby damaging the heat-generating component. There is. Moreover, when there is more content of an acrylic polymer (C) than 150 weight part, since sclerosis | hardenability of a sheet | seat will deteriorate, it will become difficult to obtain a sheet | seat shape.

  Further, the glass transition temperature (Tg) of the acrylic polymer (C) according to the present invention is a value measured by DSC method of −10 ° C. or less, a pressure of 1013 hPa, and a temperature of 25 ° C., 5,000 mPa It is preferably s or less, more preferably 1,000 mPa · s or less. If the glass transition temperature of such a polymer is too high, the resulting acrylic resin composition tends to be hard, and if the viscosity exceeds 5,000 mPa · s, the fluidity of the polymer decreases and the thermal conductivity is reduced. Addition and dispersion of fillers are difficult and workability tends to be reduced. The viscosity is a value measured with a Brookfield BH rotational viscometer.

  The compound (B) according to the present invention reacts with the reactive functional group of the acrylic polymer (A) to form a bond. However, it is not preferable to use a byproduct during the reaction. For example, when the reactive functional group of the acrylic polymer (A) is a hydroxyl group and the functional group of the compound (B) is a carboxyl group, water is generated as a by-product by the reaction between the two. These by-products often remain in the molded body to be cured, and are particularly undesirable because they are accompanied by the generation of bubbles. Therefore, when the reactive functional group of the acrylic polymer (A) is a hydroxyl group, an isocyanate compound, an acid anhydride, or the like is selectively used as the compound (B). Among them, an isocyanate compound is particularly preferably used. As the isocyanate compound, various compounds can be used, but those which are liquid at normal temperature are preferred, and bubbles may be generated in the molded product obtained when diluted with a solvent, which is not preferred. As these isocyanate compounds, aliphatic isocyanates such as hexamethylene diisocyanate (HDI) are particularly preferably used in terms of excellent weather resistance.

  When the reactive functional group of the acrylic polymer (A) is a carboxyl group, a compound having a glycidyl group is preferably used as the compound (B), and the cured product reacts with the carboxyl group of the acrylic copolymer. Obtainable. Examples of the compound having a glycidyl group include sorbitol polyglycidyl ether (SORPGE), polyglycerol polyglycidyl ether (PPGGE), pentaerythritol polyglycidyl ether (PETGE), diglycerol polyglycidyl ether (DGPGE), and glycerol polyglycidyl ether. (GREPGE), trimethylolpropane polyglycidyl ether (TMMPGE), resorcinol diglycidyl ether (RESDGE), neopentyl glycol diglycidyl ether (NPGDGE), 1,6-hexanediol diglycidyl ether (HDDGE), ethylene glycol diglycidyl Ether (EGDGE), polyethylene glycol diglycidyl ether (PEGDGE), Lopylene glycol diglycidyl ether (PGDGE), polypropylene glycol diglycidyl ether (PPGDGE), polybutadiene diglycidyl ether (PBDGE), phthalic acid diglycidyl ether (DGEP), halogenated neopentylglycerol diglycidyl ether, bisphenol A type diglycidyl ether (DGEBA), bisphenol F-type diglycidyl ether (DGEBF) and the like, and trimethylolpropane polyglycidyl ether (TMMPGE), sorbitol polyglycidyl ether (SORGGE) and the like can be used particularly preferably.

  The epoxy equivalent (WPE) of the compound having a glycidyl group as a functional group is preferably in the range of 80 to 400. When the epoxy equivalent exceeds 400, the required performance of the sheet-like molded product obtained by adding a large amount of the compound to react with the acrylic copolymer tends to be insufficient, If the epoxy equivalent is less than 80, the reaction rate tends to be too high, and it tends to be difficult to produce a sheet-like molded product.

  Further, such a compound having a glycidyl group is preferably in a liquid state under conditions of a pressure of 1013 hPa and a temperature of 25 ° C.

    Furthermore, as such a compound having a glycidyl group, the weight loss value after heating for 10 minutes at 150 ° C. under a pressure of 1013 hPa is substantially 3% or less with respect to the weight before heating. It is preferable that the solvent does not contain a solvent. When such a weight loss value by heating exceeds 3%, the contained solvent tends to hinder the reaction, making it difficult to produce a sheet-like molded article. Furthermore, a sheet from which the contained solvent can be obtained. This is because bubbles are generated inside the shaped molded body. In addition, as a calculation method of such a heating weight reduction | decrease value, when the sample 5g was heated for 10 minutes by the temperature conditions of 150 degreeC under normal pressure (1013 hPa) using the HG53 type | mold halogen moisture meter by a METTLER TOLEDO Co., Ltd. A method is used in which the change in weight is measured and the reduction rate is calculated by comparing the weight before and after heating. Epoxy compounds (glycidyl group-containing compounds) and the like can be selectively used. Examples thereof include propylene glycol diglycidyl ether, N, N, N ′, N′-tetraglycidyl-m-xylenediamine and the like.

    When the reactive functional group of the acrylic polymer (A) is a glycidyl group, the compound (B) includes an amine compound, an isocyanate compound, a mercapto compound, a chlorosulfonyl compound, an imidazole compound, an acid anhydride, and the like. Select used. Among these, amine compounds such as diethylenetriamine, acid anhydrides such as maleic anhydride, and carboxylic acid compounds such as terephthalic acid are particularly preferably used.

    Furthermore, from the viewpoint of more reliably preventing the occurrence of voids when producing a sheet-like molded body as described below, it is preferable to use a solvent-free one as the acrylic copolymer. .

    Moreover, as a polymerization method of the acrylic copolymer, a known method can be appropriately employed. For example, an emulsion polymerization method (emulsion polymerization method), a suspension polymerization method (suspension polymerization method), a bulk polymerization method ( A polymerization method such as a bulk method can be employed.

    In addition, the acrylic copolymer obtained in this way can be utilized for various uses, such as a molded object, an adhesive, a coating material, a fiber, a sealing agent.

    (A) an acrylic copolymer having a reactive functional group in the molecular chain and having a number average molecular weight of 800 to 20,000 in terms of polystyrene; and (B) a functional group that reacts with the acrylic copolymer. An acrylic resin composition comprising a compound having a group and (C) an acrylic polymer having a number average molecular weight of 800 to 6,000 in terms of polystyrene, which does not have a reactive functional group in the molecular chain, You may contain the heat conductive filler which consists of a metal hydroxide or a metal oxide in the said acrylic resin composition. Such metal hydroxides tend to have higher compatibility with the resin and higher flame retardancy than other thermally conductive fillers. In addition, metal oxides have particularly high thermal conductivity and electrical insulation. Such metal hydroxide powder and metal oxide powder are preferably metal hydroxide powder and metal oxide powder having a decomposition temperature of 250 ° C. or higher. Specifically, as metal hydroxide powder, Examples of powders such as aluminum hydroxide, magnesium hydroxide, and barium hydroxide, and metal oxide powders include alumina, magnesia, and zinc oxide. When the decomposition temperature is less than 250 ° C., it tends to be difficult to impart sufficient thermal conductivity to the obtained sheet-like molded body. In addition, the measurement method of the said decomposition temperature measured only the metal hydroxide powder (thermal conductive filler) by TGA (Thermo Gravimetric Analyzer) in the air atmosphere from room temperature to 600 ° C. at a heating rate of 10 ° C./min. And the temperature at which weight loss occurs is measured to obtain the decomposition temperature.

  The size and shape of such metal hydroxide powder and metal oxide powder are not particularly limited, but the shape is preferably spherical or pseudospherical.

  The particle size of such metal hydroxide powder and metal oxide powder is preferably about 0.5 to 30 μm. When the particle size is less than 0.5 μm, the liquid viscosity becomes too high when the metal hydroxide powder or metal oxide powder is contained in the acrylic resin composition to produce a sheet-like molded body. On the other hand, when the particle size exceeds 30 μm, the metal hydroxide powder tends to be difficult to mix in the acrylic resin composition, and thus tends to be difficult to disperse uniformly.

  Furthermore, as such metal hydroxide powder and metal oxide powder, it is possible to use a combination of powders having different particle diameters. Thus, the viscosity of the acrylic resin composition obtained can be reduced by including in the acrylic resin composition a metal hydroxide powder and a metal oxide, which are a combination of several different particle sizes. It becomes possible, and it is possible to make a higher filling than combining those having the same particle size.

  The content of the metal hydroxide and metal oxide (thermally conductive filler) in the acrylic resin composition of the present invention is 150 to 500 with respect to 100 parts by weight of the acrylic copolymer (A). It is preferable that the amount is part by weight (more preferably 250 to 500 parts by weight). By setting it as such addition amount, it exists in the tendency which the heat conductivity and flame retardance of the acrylic resin composition of this invention improve more. Further, if the content of the metal hydroxide and the metal oxide is less than 150 parts by weight, sufficient flame retardancy and thermal conductivity tend not to be ensured. On the other hand, the content of the metal hydroxide and the metal oxide When the amount exceeds 500 parts by weight, flame retardancy and thermal conductivity are improved, but the viscosity of the resulting acrylic resin composition tends to be high, and the workability when producing a sheet-like molded product tends to decrease. is there.

  Furthermore, such metal hydroxides and metal oxides can be used in combination with other thermally conductive fillers. As such other heat conductive fillers, it is possible to add nitride silicon carbide such as boron nitride and aluminum nitride, metal powder such as copper, silver and aluminum, and further, heat conductively It is also possible to add a metal carbonate such as calcium carbonate, which is not necessarily excellent, or a filler such as clay or kaolin.

  In the present invention, the graphite can be at least one selected from natural graphite, artificial graphite and expanded graphite. Natural graphite includes phosphorous, earthy, flakes, and lumps, and is not particularly limited. Among these, flake graphite is preferred from the viewpoint of performance and price.

  Further, the average particle size of such flake graphite is preferably about 5 to 300 μm, and more preferably about 30 to 200 μm. If the average particle size is less than 5 μm, it becomes difficult to contain the flake graphite in the acrylic resin composition, and a sheet-like molded product cannot be obtained. On the other hand, when the average particle diameter exceeds 300 μm, the flake graphite is mixed in the acrylic resin composition, and when a sheet-like molded body is obtained, the sheet surface is uneven and a beautiful sheet cannot be obtained. .

  Further, as such flake graphite, it is possible to use a combination of flake graphite having the same composition but different average particle diameters. Thus, it becomes possible to reduce the viscosity of the obtained acrylic resin composition by combining the flake graphite in the acrylic resin composition by combining several types having different average particle diameters. .

The content of the flake graphite (thermally conductive filler) in the acrylic resin composition of the present invention is 5 to 180 parts by weight (more than 100 parts by weight of the acrylic copolymer (A)). It is preferably 10 to 150 parts by weight. By setting it as such addition amount, it exists in the tendency which the heat conductivity and workability of the acrylic resin composition of this invention improve more. Further, if the content of the flake graphite is less than 5 parts by weight, sufficient thermal conductivity tends to be not ensured. On the other hand, if the content of the flake graphite exceeds 180 parts by weight, the thermal conductivity However, since the volume resistance of the obtained sheet-like molded product is 10 ¹⁰ Ω or less, there is a tendency that a short circuit occurs in a circuit such as an electronic device component, and further, the smoothness of the sheet surface tends to decrease. It is in.

  Further, in the acrylic resin composition of the present invention, from the viewpoint of further improving the flame retardancy, the red phosphorus flame retardant is added in an amount of 5 to 50 parts by weight with respect to 100 parts by weight of the acrylic copolymer (A). It is preferable to add. If the amount of red phosphorus added is less than 5 parts by weight, sufficient flame retardancy cannot be ensured. On the other hand, even if the amount of red phosphorus added exceeds 50 parts by weight, the level of flame retardancy does not change.

  The acrylic resin composition of the present invention may further contain a wetting and dispersing agent. The wet dispersing agent has a functional group capable of improving compatibility with the acrylic copolymer and a wet functional group capable of adsorbing to the thermally conductive filler (filler). A dispersant can be suitably used. In a system not containing such a wetting and dispersing agent, the metal hydroxide powder and metal oxide powder particles collide with each other and aggregate. And in the system which caused such agglomeration, since the apparent particle diameter becomes large, sedimentation (or levitation) separation occurs at an early stage.

  In the present invention, a wet dispersant is added to the acrylic resin composition so as to contain the metal hydroxide powder and the metal oxide powder in a high ratio. Therefore, the wet dispersant is added to the metal water. It is possible to have the oxide powder adsorbed on the powder surface to have a larger charge, thereby increasing the electrostatic repulsion between the powder particles and aggregating the metal hydroxide powder and metal oxide powder. Can be prevented. In the present invention, aggregation of the metal hydroxide powder can also be prevented by the steric repulsion force between the wetting and dispersing agents adsorbed on the surface of the powder particles.

  The acrylic resin composition of the present invention contains graphite as the heat filler in the acrylic resin composition. The wetting and dispersing agent makes it possible to highly fill graphite. As a result, a desired thermal conductivity can be achieved. In a system that does not contain such a wetting and dispersing agent, the graphite cannot be highly filled. As a result, the desired thermal conductivity cannot be achieved.

  Such wet dispersants include saturated polyester copolymers having boric acid groups and / or phosphoric acid groups, polyhydric alcohol organic acid esters, special alcohol organic acid esters, urethane-modified acrylic copolymers, high molecular weight polyesters, polycarboxylic acid copolymer Polymer, grafted product of allyl alcohol, maleic anhydride, styrene copolymer and polyoxyalkylene monoalkyl ether, polyacrylic acid ammonium salt, acrylic copolymer ammonium salt, silicon-based polymer ethylene oxide and / or propylene oxide adduct Etc. Among such wetting and dispersing agents, it is preferable to use a saturated polyester copolymer having a boric acid group and / or a phosphoric acid group. The reason is that when the acrylic resin composition is filled with a predetermined amount of a saturated polyester copolymer having boric acid groups and / or phosphoric acid groups, the boric acid groups and / or phosphoric acid groups are dissociated and negative charges are generated. It is presumed that the negative and charged electric charge can be adsorbed on the metal hydroxide, metal oxide, and graphite to increase the electrostatic repulsion force, and as a result, it is difficult to aggregate.

  The amount of the wetting dispersant added to 100 parts by weight of the acrylic copolymer (A) in the acrylic resin composition of the present invention is 0.05 to 3.0 parts by weight. If the addition amount of the wetting and dispersing agent is less than 0.05 parts by weight, the compatibility between the acrylic resin composition and the metal hydroxide powder becomes low and kneading becomes difficult. When the amount exceeds 3.0 parts by weight, thickening and gelation of the resulting acrylic resin composition occur, and the curability of the composition decreases, making it difficult to produce a sheet-like molded product.

  Moreover, you may add another flame retardant to the acrylic resin composition of this invention from a viewpoint of improving a flame retardance more. Examples of such a flame retardant include ammonium polyphosphate, phosphate ester, ammonium phosphate, ammonium carbonate, zinc stannate, triazine compound, melamine compound, guanidine compound, boric acid, zinc borate, zinc carbonate, hydrotalcite and the like. .

  Furthermore, in the acrylic resin composition of the present invention, a catalyst, a flame retardant, a wetting and dispersing agent, an antioxidant, a weather stabilizer, a heat stabilizer, etc. are appropriately added according to the required performance of the molded product obtained by molding. It is possible to add.

  The acrylic resin composition of the present invention can be produced by measuring and blending each component so as to have the aforementioned content, and mixing and stirring. The method of mixing and stirring is not particularly limited, and can be appropriately selected depending on the composition of the polymer, the viscosity, and the amount of each component added. Specifically, a stirrer such as a dissolver mixer or a homomixer is used. The method to use is mentioned.

  Moreover, you may filter what was mixed and stirred in this way as needed, for example in order to remove the lump of an undispersed component. By performing such filtration, a homogeneous acrylic resin composition can be obtained, and it becomes possible to efficiently produce a sheet-like molded body. Moreover, it is preferable that bubbles generated in the liquid during such mixing and stirring are defoamed under reduced pressure. By performing such defoaming, it is possible to prevent bubbles from being generated in the sheet-like molded body produced using the resulting acrylic resin composition.

  Next, the sheet-like molded body of the present invention will be described. That is, the sheet-like molded body of the present invention is obtained by molding and curing the above-mentioned acrylic resin composition of the present invention into a sheet shape.

  The method for forming such an acrylic resin composition into a sheet and curing it is not particularly limited, and a known method can be appropriately employed. As such a method, for example, the acrylic resin composition is coated on a base film (polyester film or the like), and cured by heating at a temperature of 100 to 200 ° C. for 5 to 15 minutes. Can be mentioned.

  The thickness of the sheet-like molded body of the present invention is preferably 0.5 mm to 3 mm, and more preferably 1.0 mm to 2.0 mm. When the thickness is less than 0.5 mm, sufficient flame retardancy tends not to be achieved. On the other hand, when the thickness exceeds 3 mm, flame retardancy is facilitated, but for use purposes such as electronic device parts. There is a tendency to become unsuitable products.

  Such a sheet-like molded body can be cut as necessary, and can be easily attached to a portion requiring heat dissipation by making it into an arbitrary shape.

  In addition, the hardness of such a sheet-like molded body is preferably 5 to 40 when measured with an ASKER-C hardness meter. When the hardness is less than 5, when the acrylic resin composition of the present invention is coated on, for example, a polyester film that has been subjected to a silicone release treatment at the time of producing a sheet-like molded body, the resin is cured by heating and then cured for a predetermined period of time. Although it peels from a film, in the process made to peel from this polyester film, it exists in the tendency for the said acrylic resin composition to stick to the said polyester film, and to peel. On the other hand, when the hardness exceeds 40, the flexibility of the sheet-like molded body is reduced, and for example, air is easily mixed between the electronic device and the sheet-like molded body when being attached to an electronic device or the like. Since the adhesiveness with the electronic device is reduced and the contact area is reduced, the substantial thermal conductivity tends to be unable to be ensured.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

  Table 8 shows the acrylic copolymer shown in Table 1, the acrylic copolymer shown in Table 3, the plasticizer shown in Table 4, the thermally conductive filler shown in Table 5, the graphite shown in Table 6, and the flame retardant shown in Table 7. And blended at the ratios shown in Table 9 and sufficiently defoamed after mixing and stirring, and the compounds shown in Table 2 were mixed and stirred at the ratios shown in Tables 8 and 9 to obtain an acrylic resin composition.

  Next, the acrylic resin composition thus obtained is coated on a polyester film whose surface has been subjected to silicone release treatment, and then cured by heating in an oven. The sheet-shaped molded body was obtained by curing by allowing to stand for a period of time.

  The following evaluation was performed on the sheet-like molded body thus obtained.

<Processability>
The processability of the sheet-like molded bodies of the present invention obtained in Examples 1 to 8 and the comparative sheet-like molded bodies obtained in Comparative Examples 1 to 7 was judged. The evaluation criteria are as follows. The results are shown in Table 8 and Table 9.

〔Evaluation criteria〕
A: Completely cured as a sheet.
○: There is a portion that is not hardened at 5% or less of the sheet volume.
Δ: Not hardened at 6% to 50% of the sheet volume.
X: 51% or more is not cured.

<Hardness measurement>
Using an ASKER-C hardness meter, the hardness of the sheet-like molded bodies of the present invention obtained in Examples 1 to 8 and the comparative sheet-like molded bodies obtained in Comparative Examples 1 to 7 were measured. The results are shown in Table 8 and Table 9.

<Adhesion>
First, using the sheet-like molded product of the present invention obtained in Examples 1 to 8 and the comparative sheet-like molded product obtained in Comparative Examples 1 to 7, the length was 4 cm, the width was 4 cm, and the thickness was 1.0 mm. Each sample was manufactured. Thereafter, each sample (4 cm × 4 cm) obtained as described above is sandwiched between two glass plates (6 cm long and 6 cm wide), and heated for 100 hours at a temperature of 100 ° C. under a load of 1 kg. Then, the mixed state of the air layer between the sample and the glass plate was observed. The evaluation criteria are as follows. The results are shown in Table 8 and Table 9.

〔Evaluation criteria〕
A: No air layer is mixed. O: The air layer is mixed in a very small part. Δ: The air layer is partially mixed. X: The air layer is mixed in almost the entire surface.

<Bleed-out>
First, using the sheet-like molded product of the present invention obtained in Examples 1 to 8 and the comparative sheet-like molded product obtained in Comparative Examples 1 to 7, the length was 4 cm, the width was 4 cm, and the thickness was 1.0 mm. Each sample was manufactured. Thereafter, each sample (4 cm × 4 cm) obtained as described above was heated for 100 hours under a temperature condition of 100 ° C., and the bleed-out of the sample surface was observed. The evaluation criteria are as follows. The results are shown in Table 8 and Table 9.

〔Evaluation criteria〕
○: No bleed out ×: Bleed out on the entire surface

<Thermal conductivity>
Using a rapid thermal conductivity meter QTM-500 (manufactured by Kyoto Denshi Kogyo Co., Ltd.), the sheet-like molded body of the present invention obtained in Examples 1 to 8 and the sheet form as a comparison obtained in Comparative Examples 1 to 8 The thermal conductivity (unit: W / mK) of the molded body was measured. The results are shown in Table 8 and Table 9.

<Flame retardancy test>
About each sheet-like molded object obtained in Examples 1 thru | or 8 and Comparative Examples 1 thru | or 7, the flame retardance evaluation was performed as follows. In other words, each sheet-like molded body cut into a size of 13.0 mm × 127 mm is used as a sample, and conforms to UL-94V (Vertical Burning Test), which is a flame retardant standard of UL (Underwriters Laboratories Inc.) plastics. Measurements were made. The evaluation criteria for such tests are as follows. Further, the evaluation method evaluates whether or not the five items defined in the following V-0 are satisfied. If all the five items are satisfied, the evaluation is V-0. In addition, in the case where one of the five items specified in V-0 does not satisfy one item, it is next evaluated whether or not the five items specified in V-1 are satisfied. When satisfying, evaluation becomes V-1. Furthermore, in the case where one of the five items specified in V-1 does not satisfy one item, it is evaluated whether or not the five items specified in V-2 are satisfied. The evaluation is V-2, and the evaluation is rejected when one of the five items is not satisfied. The obtained results are shown in Table 8 and Table 9.

〔Evaluation criteria〕
[V-0]
1) Combustion time after the first or second flame contact of each sample is 10 seconds or less 2) The total combustion time after the flame contact of 10 times (including the second flame contact) is 50 seconds or less 3) 2 The sum of the combustion time and the ignition type time after the second flame contact is 30 seconds or less. 4) There is no combustion or fire type that reaches the 125 mm mark.
[V-1]
1) Combustion time after the first or second flame contact of each sample is 30 seconds or less 2) The total combustion time after the flame contact of 10 times (including the second flame contact) is 250 seconds or less 3) 2 The sum of the combustion time and the ignition type time after the second flame contact is 60 seconds or less. 4) There is no combustion or fire type that reaches the 125 mm mark. 5) There is no ignition of absorbent cotton by falling objects.
[V-2]
1) Combustion time after the first or second flame contact of each sample is 30 seconds or less 2) The total combustion time after the flame contact of 10 times (including the second flame contact) is 250 seconds or less 3) 2 The sum of the combustion time and the flame type time after the second flame contact is 60 seconds or less. 4) There is no combustion or fire type that reaches the 125 mm mark. 5) Absorbent cotton was ignited by falling objects.

  The acrylic copolymers 1 to 5 in Table 1 are acrylic copolymers having a reactive functional group in the molecular chain (A) and a number average molecular weight of 800 to 20,000 in terms of polystyrene.

  In addition, the compounds 1 to 4 in Table 2 are compounds having a functional group that reacts with the (B) acrylic copolymer.

  The acrylic copolymers 6 to 7 in Table 3 are (C) acrylic polymers having no reactive functional group in the molecular chain and having a number average molecular weight of 800 to 6,000 in terms of polystyrene. The acrylic copolymer 8 does not have a reactive functional group in the molecular chain, but has a number average molecular weight of 325 in terms of polystyrene.

＊表中の数値は重量部であり、空欄は０を示す。

* Numerical values in the table are parts by weight, and blanks indicate 0.

* 表中の数値は重量部であり、空欄は０を示す。
* *表中のNAはシート成形体を得ることができず、測定不能であることを示す。

* The numerical values in the table are parts by weight, and the blank indicates 0.
* * NA in the table indicates that a sheet molding cannot be obtained and measurement is impossible.

As is clear from the results shown in Tables 8 and 9, Examples 1 to 8 have good processability, and the obtained sheet-like molded bodies have a high degree of flexibility. It was excellent. Furthermore, it has high thermal conductivity and flame retardancy. On the other hand, Comparative Examples 1, 4, 5, and 7 do not use the acrylic copolymer (C). As a result, the obtained sheet-like molded body has high hardness and high flexibility. Therefore, the adhesion was not excellent. In Comparative Examples 2 and 6, a plasticizer was used instead of the acrylic copolymer (C) in order to impart flexibility as the acrylic resin composition, but the processability was low and it was difficult to form a sheet. (Comparative Example 2) In addition, the processability was low, and the plasticizer bleeded out (Comparative Example 6), and the adhesion was not excellent. Comparative Example 3 contains acrylic polymer 8 having a number average molecular weight of 325 in terms of polystyrene. As a result, after forming into a sheet-like molded product, acrylic copolymer 8 bleeds out and adheres. It was not excellent.

    As described above, according to the present invention, the acrylic resin composition is capable of obtaining a sheet-like molded body that has good workability and has high flexibility and can be attached to an electrical component or the like with good adhesion. It becomes possible to provide a product and a sheet-like molded product obtained by using the product.

    Accordingly, the sheet-like molded body of the present invention is a sheet used for transferring heat generated from parts such as electronic devices such as IC chips, CPU chips, GPU chips, etc., which generate heat locally, to a heat radiating part such as a heat sink. Useful as.

Claims (4)

  (A) A compound having a reactive functional group in the molecular chain, an acrylic copolymer having a number average molecular weight of 800 to 20,000 in terms of polystyrene, and (B) a functional group that reacts with the acrylic copolymer. And (C) an acrylic resin composition comprising an acrylic polymer having a number average molecular weight in terms of polystyrene of 800 to 6,000 and having no reactive functional group in the molecular chain.   2. The acrylic resin composition according to claim 1, comprising 5 to 150 parts by weight of the acrylic polymer of (C) with respect to 100 parts by weight of the acrylic copolymer of (A). .   The thermal conductive filler is contained in 150 to 500 parts by weight with respect to 100 parts by weight of the acrylic copolymer (A), according to any one of claims 1 to 2. Acrylic resin composition.   A sheet-like molded article, wherein the acrylic resin composition according to any one of claims 1 to 3 is molded and cured into a sheet.