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EP-4741074-A1 - METHOD FOR PRODUCING THERMALLY CONDUCTIVE FILLER AND METHOD FOR PRODUCING THERMALLY CONDUCTIVE COMPOSITION

EP4741074A1EP 4741074 A1EP4741074 A1EP 4741074A1EP-4741074-A1

Abstract

Provided is a method for producing a recycled thermally conductive filler from a thermally conductive scrap material containing a thermosetting resin and a thermally conductive filler, the method including: a thermal decomposition step of thermally decomposing the thermally conductive scrap material by heating the thermally conductive scrap material in a low-oxygen atmosphere with an oxygen concentration of 10 vol.% or less; and a crushing step of crushing s residue formed after the thermal decomposition, wherein in the crushing step, the residue is crushed to produce particles having a median particle size in a range from 0.1 to 300 µm. The obtained recycled thermally conductive filler is mixed with a thermosetting resin to obtain a thermally conductive resin composition. As a result, a thermally conductive filler is collected from the scrap of a thermally conductive composition that has previously been discarded, and the collected filler can be reused.

Inventors

  • YOSHIDA, YUJI

Assignees

  • Fuji Polymer Industries Co., Ltd.

Dates

Publication Date
20260513
Application Date
20241015

Claims (15)

  1. A method for producing a recycled thermally conductive filler from a thermally conductive scrap material containing a thermosetting resin and a thermally conductive filler, the method comprising: a thermal decomposition step of thermally decomposing the thermally conductive scrap material by heating the thermally conductive scrap material in a low-oxygen atmosphere with an oxygen concentration of 10 vol.% or less; and a crushing step of crushing a residue formed after the thermal decomposition, wherein in the crushing step, the residue is crushed to produce particles having a median particle size in a range from 0.1 to 300 µm.
  2. The method for producing a recycled thermally conductive filler according to claim 1, wherein in the thermal decomposition step, the thermally conductive scrap material is heated to a temperature in a range from 400°C to 1600°C.
  3. The method for producing a recycled thermally conductive filler according to claim 1 or 2, wherein the low-oxygen atmosphere is at least one atmosphere selected from the group consisting of an inert gas flow, a gas mixture flow of 51 to 100 vol.% inert gas and 0 to 49 vol.% air, an atmosphere under a reduced pressure, and a superheated steam.
  4. The method for producing a recycled thermally conductive filler according to any one of claims 1 to 3, wherein the crushing step is at least one step selected from the group consisting of ball milling, pin milling, cutter milling, jet milling, bead milling, hammer milling, and griding with an automatic mortar mixer.
  5. The method for producing a recycled thermally conductive filler according to any one of claims 1 to 4, further comprising a classification step after the crushing step.
  6. The method for producing a recycled thermally conductive filler according to claim 5, wherein the classification step is sieving through a mesh.
  7. The method for producing a recycled thermally conductive filler according to any one of claims 1 to 6, wherein the thermosetting resin is a silicone polymer.
  8. The method for producing a recycled thermally conductive filler according to any one of claims 1 to 7, wherein a Si atomic concentration of the recycled thermally conductive filler is 1 at% or less, where the Si atomic concentration is determined through SEM-EDX analysis (scanning electron microscope-energy dispersive X-ray spectroscopy).
  9. The method for producing a recycled thermally conductive filler according to any one of claims 1 to 8, wherein the recycled thermally conductive filler is at least one selected from the group consisting of alumina and aluminum nitride.
  10. The method for producing a recycled thermally conductive filler according to any one of claims 1 to 9, wherein the thermally conductive scrap material contains the thermally conductive filler in an amount in a range from 100 to 4000 parts by mass, relative to 100 parts by mass of the thermosetting resin.
  11. The method for producing a recycled thermally conductive filler according to any one of claims 1 to 10, wherein the thermally conductive scrap material is selected from the group consisting of process scrap, waste scrap, a collected product, an expired stock article, and a prototype.
  12. The method for producing a recycled thermally conductive filler according to any one of claims 1 to 11, wherein the recycled thermally conductive filler is further surface-treated with RaSi(OR') 4-a (where R represents an unsubstituted or substituted organic group having 8 to 12 carbon atoms, R' represents an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1).
  13. A method for producing a thermally conductive resin composition, comprising obtaining a thermally conductive resin composition by mixing, with a thermosetting resin, the recycled thermally conductive filler obtained using the method for producing a recycled thermally conductive filler according to any one of claims 1 to 12.
  14. The method for producing a thermally conductive resin composition according to claim 13, wherein the thermosetting resin is a silicone resin.
  15. The method for producing a thermally conductive resin composition according to claim 13 or 14, wherein the thermally conductive resin composition contains the recycled thermally conductive filler in an amount in a range from 100 to 4000 parts by mass, relative to 100 parts by mass of the thermosetting resin.

Description

Technical Field The present invention relates to a method for producing a recycled thermally conductive filler useful for a thermally conductive composition suitable for being interposed between a heat generating portion of an electric or electronic component or the like and a heat sink, and a method for producing a thermally conductive composition. Background Art Thermally conductive silicone materials in which silicone is used are used as heat dissipation materials for electronic components. Conventionally, scraps generated during production and materials after use have been discarded by landfill as industrial waste without being reused from the viewpoint of ensuring quality. In particular, when a thermosetting polymer is used, the polymer and a thermally conductive filler need to be separated and reused, but an effective separation process for a heat dissipation material has not yet been put into practical use. A process has been proposed in which a polymer is thermally decomposed into monomers in a high-temperature alkaline aqueous solution, and the monomers are collected and then repolymerized, but the residue such as an inorganic reinforcing material, which remains as precipitates, are discarded. When a heat dissipation material is treated in this process, the thermally conductive filler, which will be a residue, may be reusable by cleaning the filler, but this is not practical from the viewpoint of costs and environmental impact. In recent years, there is a demand for recycling technologies suitable for heat dissipation materials in response to a growing demand for Sustainable Development Goals (SDGs). Patent Document 1 proposes that silicone rubber is thermally decomposed, and separated into volatile siloxane and silicic acid, followed by collection. Patent Document 2 proposes catalytic pyrolysis of silicone rubber with alcohol to recycle a polymer. Prior Art Documents Patent Documents [Patent Document 1] JP H5-271416A[Patent Document 2] JP 2002-187976A Disclosure of Invention Problem to be Solved by the Invention However, regarding conventional recycling methods, there have not been effective proposals for reusing thermally conductive fillers, and most of the thermally conductive fillers have been discarded by landfill. For this reason, disposal costs are currently high. In order to solve the aforementioned problem, the present invention provides a method for producing a recycled thermally conductive filler, by which a thermally conductive filler can be collected from the scrap of a thermally conductive composition that has previously been discarded and the collected filler can be reused, and a method for producing a thermally conductive composition. Means for Solving Problem An embodiment according to the present invention is a method for producing a recycled thermally conductive filler from a thermally conductive scrap material containing a thermosetting resin and a thermally conductive filler, the method including a thermal decomposition step of thermally decomposing the thermally conductive scrap material by heating the thermally conductive scrap material in a low-oxygen atmosphere with an oxygen concentration of 10 vol.% or less; and a crushing step of crushing a residue formed after the thermal decomposition, wherein in the crushing step, the residue is crushed to produce particles having a median particle size in a range from 0.1 to 300 µm. Another embodiment according to the present invention relates to a method for producing a thermally conductive resin composition, the method including: obtaining a thermally conductive resin composition by mixing, with a thermosetting resin, the recycled thermally conductive filler obtained using the method for producing a recycled thermally conductive filler. Effects of the Invention The present invention can provide a method for producing a recycled thermally conductive filler, the method including a thermal decomposition step of thermally decomposing a thermally conductive scrap material by heating the thermally conductive scrap material in a low-oxygen atmosphere with an oxygen concentration of 10 vol.% or less; and a crushing step of crushing a residue formed after the thermal decomposition, wherein in the crushing step, the residue is crushed into particles having a median particle size of 0.1 to 300 µm, and thus a recycled thermally conductive filler is produced using the scrap material of a thermally conductive composition that has conventionally been discarded, as a result of which, the scrap material can be reused. The present invention can also provide a method for producing a thermally conductive composition. Brief Description of Drawings [FIG. 1] FIG. 1 is a schematic cross-sectional view illustrating how a thermally conductive sheet according to an embodiment of the present invention is used.[FIG. 2] FIGS. 2A to 2B are schematic diagrams illustrating a method for measuring the thermal conductivity of a sample according to an example of the p