Curable resin composition and gap filler

Abstract

An object of the present invention is to provide a curable resin composition which contributes to reducing the abrasion resistance of a gap filler and which has both low viscosity and high thermal conductivity. [Solution] A curable resin composition is provided which contains a polyol, a polyisocyanate, and an inorganic filler, the inorganic filler including at least an inorganic filler (first inorganic filler) surface-coated with zinc molybdate.

Description

[Technical field]

[0001] The present invention relates to a curable resin composition and a gap filler. [Background technology]

[0002] In recent years, as electronic devices become smaller and more powerful, the issue of how to deal with heat dissipation from electronic devices has become an issue, and the development of various thermally conductive materials is progressing. Thermally conductive materials that are being developed can be broadly divided into fillers and resins, with alumina and magnesium oxide being known as fillers, and silicone-based resins and urethane-based resins being known as resins.

[0003] For example, Patent Document 1 reports an isocyanate-containing composition containing an isocyanate group-containing urethane polymer, an inorganic filler, a plasticizer, and at least one compound selected from the group consisting of phosphoric acid esters, sulfuric acid esters, sulfonic acids, and carboxylic acids. It is disclosed that the inorganic filler is a metal oxide such as alumina or magnesium oxide, a metal hydroxide such as aluminum hydroxide or magnesium hydroxide, or a metal nitride such as aluminum nitride or boron nitride.

[0004] Patent Document 2 reports a curable composition containing a polyol (A), a polyisocyanate (B), at least one inorganic filler dispersant (C) selected from the group consisting of a phosphoric acid ester (C1), a fatty acid having 12 to 24 carbon atoms (C2), a sucrose fatty acid ester (C3), a sorbitan fatty acid ester (C4), and a glycerin fatty acid ester (C5), and an inorganic filler (D). It is disclosed that the inorganic filler (D) is titanium oxide, alumina, magnesium oxide, a metal nitride, a metal hydroxide, or the like. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2022-176868 A [Patent Document 2] International Publication No. 2021 / 261519 Summary of the Invention [Problem to be solved by the invention]

[0006] Thermally conductive materials can be used for a variety of purposes, such as sheets, potting, adhesives, greases, and gap fillers. Demand is increasing for gap fillers with excellent performance and reliability, especially with the shift to electric vehicles.

[0007] Generally, gap fillers are applied through a dispenser, but because they contain a large amount of abrasive thermally conductive inorganic fillers, the equipment wears out quickly and parts need to be replaced periodically. Therefore, in order to reduce running costs, there is a demand for gap fillers with low abrasive properties.

[0008] However, in all of these patent documents, the main inventions are related to the structures and physical properties of dispersants for inorganic fillers and resins, and the inorganic fillers used are generally metal oxides such as alumina and titanium oxide, and there has been no sufficient consideration given to reducing the abrasion properties of the gap filler.

[0009] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a curable resin composition that contributes to reducing the abrasion of a gap filler and has both low viscosity and high thermal conductivity. [Means for solving the problem]

[0010] As a result of intensive research, the present inventors have found that the above-mentioned problems can be solved by a resin composition containing an inorganic filler whose surface is coated with a specific substance.

[0011] (1) A curable resin composition comprising a polyol, a polyisocyanate, and an inorganic filler, the inorganic filler including at least an inorganic filler surface-coated with zinc molybdate (first inorganic filler). (2) The curable resin composition according to the above (1), further comprising a plasticizer, the plasticizer including at least a phosphoric acid ester. (3) The curable resin composition according to (1) or (2) above, wherein the inorganic filler further comprises one or more inorganic fillers (second inorganic fillers) selected from the group consisting of metals, metal oxides, metal nitrides, metal hydroxides, and metal carbonates. (4) The curable resin composition according to (3) above, wherein the second inorganic filler is magnesium carbonate. (5) The curable resin composition according to any one of the above (1) to (4), wherein the first inorganic filler is talc. (6) The curable resin composition according to any one of the above (1) to (5), wherein the inorganic filler has a porosity of 15 to 28%. Porosity = total pore volume (Vp) x compressed bulk density x 100 (7) A gap filler comprising the curable resin composition according to any one of (1) to (6) above. (8) The gap filler according to (7) above, having a thermal conductivity of 2 to 5 W / m·K. Effect of the Invention

[0012] According to the present invention, it is possible to provide a curable resin composition and a gap filler that have reduced abrasion, low viscosity, and high thermal conductivity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described in detail.

[0014] [Curable resin composition] The curable resin composition of the present invention contains a polyol, a polyisocyanate, and an inorganic filler, and is characterized in that the inorganic filler at least includes an inorganic filler (first inorganic filler) surface-coated with zinc molybdate.

[0015] The curable resin composition of the present invention relates to a two-liquid reaction type polyurethane resin composition that essentially uses a reaction product of a polyol and a polyisocyanate.

[0016] (Polyol) Examples of the polyol include polyester polyol, polyether polyol, polycarbonate polyol, polybutadiene polyol, and hydrogenated polybutadiene polyol. These polyols may be used alone or in combination of two or more kinds.

[0017] Examples of the polyester polyol that can be used include a reaction product obtained by esterifying a low-molecular-weight polyol with a polycarboxylic acid using one or more low-molecular-weight compounds having three or more active hydrogen atoms (e.g., compounds having a molecular weight of 50 or more and less than 500) as an initiator; a ring-opening polymerization product of a cyclic ester compound such as ε-caprolactone; and a copolymer of the above-mentioned esterification reaction product or ring-opening polymerization product.

[0018] Examples of low molecular weight polyols that can be esterified with polycarboxylic acids to form polyester polyols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,5-hexanediol, 1,6-hexanediol, 2,5-hexanediol, 1,7-heptanediol, and 1,8-octanediol. aliphatic polyols such as 1,5-pentanediol, 2-ethyl-1,3-hexanediol, and 2-methyl-1,8-octanediol; alicyclic polyols such as 1,4-cyclohexanedimethanol; hydroquinone, resorcinol; and aromatic polyols such as bisphenol A, bisphenol F, and 4,4'-biphenol.

[0019] Examples of the polycarboxylic acid include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and dodecanedicarboxylic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid; and anhydrides or esters thereof.

[0020] Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyoxyethylene polyoxypropylene glycol, polyoxyethylene polyoxytetramethylene glycol, and polyoxypropylene polyoxytetramethylene glycol.

[0021] Examples of the polycarbonate polyol include a reaction product obtained by reacting a carbonate ester and / or phosgene with a low molecular weight polyol using one or more low molecular weight compounds (e.g., compounds with a molecular weight of 50 to 500) having three or more active hydrogen atoms as an initiator. One or more types of the carbonate ester may be used, and examples thereof include aliphatic carbonates such as alkyl carbonates (e.g., methyl carbonate, ethyl carbonate, etc.) and dialkyl carbonates (e.g., dimethyl carbonate, diethyl carbonate, etc.); carbonates containing an alicyclic structure such as cyclocarbonate (hereinafter, "containing an alicyclic structure" may be simply referred to as "alicyclic"); and aromatic carbonates such as diphenyl carbonate.

[0022] From the viewpoint of excellent heat resistance and high temperature humidity constant, polybutadiene polyol, hydrogenated polybutadiene polyol, etc. are preferable. Examples of commercially available polyols include Hyblen (registered trademark) XLA-8054A-4 (manufactured by Mitsui Chemicals, Inc.), NISSO-PB GI-1000 (manufactured by Nippon Soda Co., Ltd.), NISSO-PB GI-2000 (manufactured by Nippon Soda Co., Ltd.), NISSO-PB GI-3000 (manufactured by Nippon Soda Co., Ltd.), Poly bd R15HT (manufactured by Idemitsu Kosan Co., Ltd.), Poly bd R45HT (manufactured by Idemitsu Kosan Co., Ltd.), and Pandex GCB41 (manufactured by DIC Corporation).

[0023] The number average molecular weight of the polyol is not particularly limited, but is preferably in the range of 700 to 10,000, and more preferably in the range of 1,000 to 10,000. Within the above range, the moldability and stability over time of the obtained resin composition are excellent. In this specification, the number average molecular weight can be calculated by gel permeation chromatography (GPC).

[0024] (Polyisocyanate) Examples of the polyisocyanate include aromatic polyisocyanates, aliphatic polyisocyanates, alicyclic polyisocyanates, etc. These may be used alone or in combination of two or more kinds.

[0025] Examples of the aromatic polyisocyanate include phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenylether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, and xylylene diisocyanate.

[0026] Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

[0027] Examples of the alicyclic polyisocyanate include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated tetramethylxylylene diisocyanate.

[0028] Further examples of the aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates include carbodiimide-modified polyisocyanates, castor oil-modified polyisocyanates, biuret-modified polyisocyanates, allophanate-modified polyisocyanates, polymethylene polyphenyl polyisocyanates (polymeric MDI), and isocyanurate-modified polyisocyanates.

[0029] From the viewpoint of suppressing viscosity, hexamethylene diisocyanate is preferred, and from the viewpoint of heat resistance, isophorone diisocyanate is preferred. Commercially available products of such polyisocyanates include Hyblen (registered trademark) XLA-8054A-5 (manufactured by Mitsui Chemicals, Inc.) and Pandex GCA11 (manufactured by DIC Corporation).

[0030] In the resin composition of the present invention, the blending ratio of polyol to polyisocyanate is preferably such that the polyisocyanate is in excess. The blending ratio may be determined based on the ratio (molar ratio) of isocyanate groups to hydroxyl groups, and is preferably isocyanate groups:hydroxyl groups=1.5 to 2.5:1, and more preferably 1.7 to 2.3:1. When it is within the above range, the reaction can be efficiently carried out to form a polyurethane resin.

[0031] In this specification, the isocyanate group content can be measured by potentiometric titration in accordance with JIS K1603-1:2007.

[0032] In the resin composition of the present invention, the total mass of the polyol and polyisocyanate is preferably 5 to 30 mass%, and more preferably 7 to 15 mass%, when the total mass of the resin composition is 100 mass%.

[0033] In this embodiment, a commercially available gel urethane in which a polyol component and a polyisocyanate component are mixed in advance can also be used. Examples of gel urethane include Pandex GC (manufactured by DIC Corporation), SU-4500A / B (manufactured by Sanyu Rec Co., Ltd.), and MU-120A / MU-120B (manufactured by Bellnox Co., Ltd.).

[0034] (First inorganic filler) The first inorganic filler of the present invention is not particularly limited, but is characterized by containing at least an inorganic filler whose surface is coated with zinc molybdate.

[0035] In this specification, the term "surface coating" means, more specifically, that zinc molybdate is supported on the particle surface. The state of support may be that the zinc molybdate is supported on the entire particle without gaps, or may be that the zinc molybdate is supported partially.

[0036] Examples of inorganic fillers to be surface-coated with zinc molybdate include metals such as gold, silver, copper, and alloys thereof; metal oxides such as alumina, titanium oxide, magnesium oxide, and silica; metal hydroxides such as aluminum hydroxide, magnesium hydroxide, and calcium hydroxide; metal carbonates such as calcium carbonate and magnesium carbonate; metal nitrides such as aluminum nitride, boron nitride, and silicon nitride; and silicates such as talc, mica, and glass. From the viewpoints of high thermal conductivity and low Mohs hardness, zinc oxide, aluminum hydroxide, magnesium hydroxide, and talc are preferred, and talc is particularly preferred.

[0037] (Second inorganic filler) In the present invention, the second inorganic filler may further include an inorganic filler that is not surface-coated with zinc molybdate.

[0038] The second inorganic filler is not particularly limited, and may be the same as the first inorganic filler, but from the viewpoints of chemical stability, high thermal conductivity, and low Mohs hardness, alumina and magnesium carbonate are preferred.

[0039] The second inorganic filler may be used alone or in combination of two or more. When using two or more, different filler types can be used so that characteristics according to the application can be obtained. For example, if the thermal conductivity is to be improved, aluminum hydroxide or alumina can be blended, and if the abrasion resistance is to be improved, it is preferable to use only magnesium carbonate.

[0040] Even when the filler type is the same, it is preferable to mix and use multiple fillers with different average particle sizes (D50) as described below. By mixing multiple fillers with different average particle sizes (D50), the fillers can have a close-packed structure, which is preferable because it results in improved thermal conductivity.

[0041] The shape of the inorganic filler is not particularly limited, and examples thereof include plate-like, spherical, polyhedral, and card house shapes (aggregations of multiple plate-like particles). From the viewpoint of further improving thermal conductivity, however, polyhedral shapes are preferred.

[0042] The average particle diameter (D50) of the inorganic filler is not particularly limited, but is preferably 0.001 μm to 100 μm, more preferably 0.01 μm to 50 μm, and particularly preferably 0.1 μm to 30 μm. The average particle diameter (D50) can be measured by a laser diffraction scattering particle size distribution measurement method.

[0043] The porosity of the inorganic filler of the present invention may be 15 to 28%, and more preferably 17 to 26%. When it is within the above range, it is preferable because the viscosity of the obtained resin composition can be further reduced and the thermal conductivity can be further increased.

[0044] The porosity can be calculated by the following formula. Porosity = total pore volume Vp × compressed bulk density × 100

[0045] The total pore volume Vp can be calculated from the compressed bulk density and the true density, and the true density can be determined from the theoretical density and ratio of the inorganic filler used. Total pore volume Vp = (1 / compressed bulk density) - (1 / true density)

[0046] Compressed bulk density can be measured using a density analyzer (e.g., a GeoPyc® Model 1360 density analyzer (Micromeritics, Norcross, GA). Specifically, a sample is subjected to a compressive force of 180 N with a plunger, and the linear distance traveled by the plunger is converted to the volumetric displacement of the powder sample. The measurements are then averaged to give the calculated bulk density value (g / cm) of the sample. 3 (expressed as

[0047] In the present invention, an inorganic filler surface-coated with zinc molybdate (first inorganic filler) is essential, and an inorganic filler that is not surface-coated (second inorganic filler) can be used in combination. When two or more types of inorganic fillers are used in combination, the porosity is calculated in the mixed state.

[0048] The content of the inorganic filler may be 50 to 95% by mass, preferably 70 to 95% by mass, and particularly preferably 85 to 95% by mass, when the total solid content of the resin composition is taken as 100% by mass. If the content is within the above range, the thermal conductivity of the resulting resin composition is excellent, which is preferable.

[0049] When the first inorganic filler and the second inorganic filler are used in combination, the amount of the first inorganic filler is not particularly limited, but may be more than 0% by mass and less than 100% by mass, preferably 1% by mass or more and less than 50% by mass, and more preferably more than 1% by mass and less than 10% by mass, when the total amount of the inorganic fillers is taken as 100% by mass. If the amount is within the above range, the resin composition obtained has excellent wear properties, which is preferable. .

[0050] (Plasticizer) The resin composition of the present invention may further contain a plasticizer, which contains at least a phosphate ester. The phosphate ester is not particularly limited, but examples thereof include Disparlon DA-375 (manufactured by Kusumoto Chemical Industry Co., Ltd.), Plysurf A208N (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Phosphanol RL-210 (manufactured by Toho Chemical Industry Co., Ltd.), Phosphanol RS-710 (manufactured by Toho Chemical Industry Co., Ltd.), and Phosphanol RS-410 (manufactured by Toho Chemical Industry Co., Ltd.).

[0051] The content of the phosphate ester may be within a range that does not impair the effects of the present invention. For example, when the total solid content of the resin composition is taken as 100% by mass, the content is preferably 0.5 to 8% by mass, and more preferably 1 to 5% by mass.

[0052] Examples of plasticizers other than phosphate esters include phthalic acid-based plasticizers such as phthalic acid diesters, adipic acid diesters, diisononyl phthalate, and diisodecyl phthalate; fatty acid ester-based plasticizers such as di-(2-ethylhexyl)adipate, di-(2-ethylhexyl)azelate, and dibutyl sebacate; epoxy-based plasticizers; polyester-based plasticizers; and sulfonate-based plasticizers. From the viewpoint of heat resistance and bleedlessness during durability tests, highly compatible and highly heat-resistant plasticizers are preferred.

[0053] The content of the plasticizer may be within a range that does not impair the effects of the present invention. For example, when the total solid content of the resin composition (excluding the inorganic filler) is taken as 100 mass%, the content is preferably 50 to 90 mass%, and more preferably 55 to 85 mass%.

[0054] (others) If necessary, a urethane catalyst, a surfactant, an antioxidant, an ultraviolet absorber, etc. may be added within a range that does not impair the effects of the present invention.

[0055] The resin composition in this embodiment is preferably in a liquid state with a viscosity at 25°C in the range of 50 Pa·s to 2,000 Pa·s, more preferably 100 Pa·s to 1,000 Pa·s, and particularly preferably 100 Pa·s to 350 Pa·s. When the viscosity is in the above range and a non-fluid reactant is formed after application to a substrate, the composition is suitable for application to a substrate using a dispenser or the like.

[0056] [Application] Since the resin composition of the present invention has excellent thermal conductivity, it can be widely used as a heat dissipation material in electrical and electronic components, semiconductor elements, etc., but since it has low abrasion and low viscosity, it can be particularly suitably used as a gap filler. EXAMPLES

[0057] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0058] [Examples 1 to 10, Comparative Examples 1 and 2] The polyol, the isocyanate, the first inorganic filler, and the second inorganic filler were mixed in the mixing ratios shown in Tables 1 and 2 to obtain resin compositions.

[0059] [Evaluation method] The resulting resin compositions were evaluated according to the following methods.

[0060] (Thermal Conductivity) Each of the obtained resin compositions was poured into a mold and cured at 70° C. for 3 hours to obtain a sheet cured product having a thickness of 1 mm. The thermal diffusivity and specific heat of the prepared cured sheet were measured at 25°C using a thermal conductivity measuring device (LFA467 HyperFlash, manufactured by NETZSCH). The density of the heat dissipation member was then measured by the Archimedes method. The thermal conductivity of the heat dissipation member was estimated from the product of the obtained thermal diffusivity, specific heat, and density.

[0061] (Wear resistance) Each resin composition was cured to a thickness of 1.6 mm, and 2000 holes were drilled at 150,000 rpm with a drill (drill diameter 0.3 mm). The wear rate of the drill bit after drilling was evaluated as the ratio (percentage) of the area of ​​the drill bit worn by drilling to the area of ​​the drill bit before drilling. The wear property was evaluated according to the following criteria. ○: Less than 10% △: 10% to less than 20% ×: 20% or more

[0062] (viscosity measurement) The viscosity of the resulting resin composition was measured (25° C.) using an E-type viscometer TVE-20H (manufactured by Toki Sangyo Co., Ltd.).

[0063] (Compressed bulk density) The inorganic filler obtained by the formulation in Table 1 was measured using a density analyzer (e.g., GeoPyc® Model 1360 density analyzer (Micromeritics, Norcross, GA)). Specifically, a compressive force of 180 N was applied to the inorganic filler by a plunger, and the linear distance traveled by the plunger was converted into the volumetric displacement of the inorganic filler. The average of the measured values ​​was then calculated as the bulk density value (g / cm) of the inorganic filler. 3 The calculation is performed by converting the

[0064] (porosity) Using the calculated compressed bulk density, it can be calculated according to the following formula. Porosity = total pore volume Vp × compressed bulk density × 100

[0065] [Table 1]

[0066] [Table 2]

Claims

1. Contains a polyol, a polyisocyanate, and an inorganic filler, the inorganic filler comprises an inorganic filler (first inorganic filler) surface-coated with zinc molybdate, and one or more inorganic fillers (second inorganic fillers) selected from the group consisting of metals, metal oxides, metal nitrides, metal hydroxides, and metal carbonates, which are not surface-coated with zinc molybdate; When the total solid content of the curable resin composition is taken as 100% by mass, the content of the inorganic filler is 50 to 95% by mass, and when the total amount of the inorganic fillers is taken as 100% by mass, the blending amount of the first inorganic filler is 1% by mass or more and 10% by mass or less.

2. The curable resin composition according to claim 1 , further comprising a plasticizer, the plasticizer including at least a phosphate ester.

3. The curable resin composition according to claim 1 , wherein the second inorganic filler is magnesium carbonate.

4. The curable resin composition according to claim 1 , wherein the first inorganic filler is talc.

5. A curable resin composition described in any one of claims 1 to 4, wherein the porosity of the inorganic filler, calculated by the following formula, is 15 to 28%. Porosity = total pore volume (Vp) × compressed bulk density × 100

6. A gap filler comprising the curable resin composition according to claim 5.

7. 7. The gap filler of claim 6, having a thermal conductivity of 2 to 5 W / m·K.

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