Suspension capable of being used for extrusion molding and preparation method and application thereof

Abstract

The invention belongs to the technical field of heat conduction materials, and discloses a suspension for extrusion molding and a preparation method and application thereof. The suspension is composed of polysiloxane, a sheet-shaped heat-conducting filler and a nanometer spherical heat-conducting filler. On the basis that the total volume of the polysiloxane, the flaky heat-conducting filler and the nano spherical heat-conducting filler is 100 parts, the flaky heat-conducting filler accounts for 5-30 parts by volume; and 5-20 parts by volume of the nano spherical heat-conducting filler. The yield viscosity value of the suspension at room temperature is not lower than 2 * 10 < 4 > Pa.s, the ratio of the yield viscosity to the viscosity when the strain rate is 100 s <-1 > is not lower than 2 * 10 < 3 >, and the strain of a linear viscoelastic region is not lower than 0.1%. The suspension provided by the invention can be stably extruded and molded to prepare a heat-conducting gel or a heat-conducting elastomer, and the prepared heat-conducting elastomer has better heat-conducting property.

Description

Technical Field

[0001] The invention relates to the technical field of heat-conducting materials, and in particular to a suspension liquid that can be used for extrusion molding, and a preparation method and application thereof. Background Art

[0002] With the development of electronic technology, the heat dissipation problem of devices has attracted widespread attention from industry and academia. Thermal interface materials are important materials that effectively transfer or remove waste heat from electronic devices to avoid device failure due to excessively high working environment temperatures. In order to obtain high thermal conductivity thermal interface materials, people usually compound large-sized anisotropic fillers (such as asphalt-based carbon fibers, graphite, and boron nitride) with elastomers and use special means to orient the fillers in a certain direction.

[0003] In practical applications, the screw extrusion process is usually accompanied by a strong shear process, which is an effective method for directional arrangement of anisotropic fillers to mass produce thermal interface materials. US patent documents US 8808607 B2 and US 9365001 B2 disclose a method for producing thermal interface materials, which can quickly and easily obtain high thermal conductivity and low hardness thermal interface materials through continuous blending / stirring, extrusion, molding and curing, slicing and other processes.

[0004] Chinese patent document CN115011126A discloses a thermally conductive gasket and a method for preparing the same, specifically a thermally conductive silicone gasket that uses carbon nanotubes and inorganic fillers for dual thermal conductivity, which has better thermal conductivity and mechanical properties. Chinese patent document CN 110194946 A discloses an organic silicon encapsulation adhesive and a method for preparing the same, specifically using vinyl-terminated polydimethylsiloxane and polymethylhydrogensiloxane as the main reaction part of the material, the filler part is obtained by coupling reaction of hydroxylated modified nano boron nitride and vinyl trimethoxysilane, and finally curing by hydrosilane addition to obtain a highly thermally conductive transparent LED organic silicon encapsulation adhesive.

[0005] However, none of the above patent documents mentions the rheological properties and subsequent processing performance of the suspension composed of polysiloxane and thermal conductive filler. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a suspension that can be used for extrusion molding and a preparation method thereof in view of the problems of poor static stability and difficult processing of thermally conductive silicone suspensions. The present invention relates the rheological properties of the silicone suspension to the extrusion molding stability and thermal conductivity of the thermally conductive silicone rubber to guide the development of thermal interface materials; the silicone elastomer prepared from the suspension can be used in the field of thermal management of electronic devices.

[0007] In order to solve the above technical problems, the first aspect of the present invention provides a suspension that can be used for extrusion molding, wherein the suspension comprises polysiloxane and a thermally conductive filler; wherein the thermally conductive filler is a mixture of a flaky thermally conductive filler and a nano-spherical thermally conductive filler; the weight average molecular weight of the polysiloxane is 10,000-30,000 g / mol, and the molecular weight distribution is not less than 3; the diameter of the flaky thermally conductive filler is 4-16 μm, and the diameter of the nano-spherical thermally conductive filler is 20-100 nm.

[0008] In the present invention, the thermally conductive filler is selected from a combination of fillers of different shapes, which makes it easier to form a continuous thermally conductive network in the suspension by filling the gaps between each other, which is beneficial to improving the thermal conductivity of the final product.

[0009] According to some embodiments of the present invention, based on the total volume of polysiloxane, flaky thermally conductive filler and nano-spherical thermally conductive filler as 100 parts, the flaky thermally conductive filler is 5-30 parts by volume, preferably the flaky thermally conductive filler is 10-25 parts by volume; the nano-spherical thermally conductive filler is 5-20 parts by volume, preferably the nano-spherical thermally conductive filler is 5-15 parts by volume.

[0010] According to some embodiments of the present invention, the weight average molecular weight of the polysiloxane is 10,000-20,000 g / mol, and the molecular weight distribution is 3-5. The molecular weight and molecular weight distribution of the polysiloxane will directly affect the viscosity of the suspension. Generally, a relatively low molecular weight and a wide molecular weight distribution can make the suspension exhibit a lower viscosity during extrusion, which is conducive to processing and molding.

[0011] According to some embodiments of the present invention, the diameter of the flake thermal conductive filler is 6-12 μm, and the diameter of the nano-spherical thermal conductive filler is 40-80 nm.

[0012] According to some embodiments of the present invention, the polysiloxane includes at least one of polydimethylsiloxane, vinyl-terminated polydimethylsiloxane, and polymethylhydrogensiloxane.

[0013] According to some embodiments of the present invention, the flake-shaped thermal conductive filler is at least one of flake-shaped aluminum oxide, flake-shaped aluminum nitride and flake-shaped boron nitride.

[0014] According to some embodiments of the present invention, the nano-spherical thermal conductive filler is at least one of spherical alumina and spherical aluminum powder.

[0015] According to some embodiments of the present invention, the suspension has a yield viscosity of not less than 2×10 4 Pa·s, yield viscosity and strain rate is 100s -1 The viscosity ratio is not less than 2×10 3 , the strain in the linear viscoelastic region is not less than 0.1%.

[0016] The second aspect of the present invention provides a method for preparing a suspension that can be used for extrusion molding, comprising mixing polysiloxane, a flake-shaped thermally conductive filler and a nano-spherical thermally conductive filler to obtain the suspension that can be used for extrusion molding.

[0017] According to some embodiments of the present invention, the mixing conditions include: temperature of 25-30° C., time of 4-10 minutes, and rotation speed of 10-50 rpm; wherein the rotation speed is the rotation speed of the stirring kettle.

[0018] The third aspect of the present invention provides a thermally conductive gel, which is obtained by extruding the suspension provided by the first aspect or the second aspect above; preferably, the extrusion conditions include: a temperature of 25-30°C and a rotation speed of 50-200 rpm; wherein the rotation speed is the rotation speed of a single-screw extruder.

[0019] The fourth aspect of the present invention provides a thermally conductive elastomer, which is obtained by extruding and curing the suspension provided by the first aspect or the second aspect; preferably, the extrusion conditions include: a temperature of 25-30°C and a rotation speed of 50-200 rpm; wherein the rotation speed is the rotation speed of a single-screw extruder; the curing conditions include: a curing temperature of 95-105°C and a curing time of 0.5-1.5 hours.

[0020] The fifth aspect of the present invention provides the use of the suspension provided in the first or second aspect, the thermally conductive gel provided in the third aspect, or the thermally conductive elastomer provided in the fourth aspect in electronic devices, preferably chips, circuit boards, and power supply components.

[0021] Beneficial effects:

[0022] The polysiloxane suspension of the present invention can be used to prepare a thermally conductive gel or a thermally conductive elastomer by extrusion molding. The suspension prepared by the present invention has a higher yield viscosity and thus has higher stability in static state. The appropriate viscosity at a high shear rate can ensure the surface quality of the extruded product, and the extrusion process is stable and controllable. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a graph showing the change of storage modulus of the suspensions prepared in Example 1, Example 2, and Example 3 of the present invention with shear strain;

[0024] Figure 2 3 is a graph showing the change in storage modulus of the suspensions prepared in Comparative Examples 1, 2 and 3 of the present invention as a function of shear strain. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the embodiments, but the present invention is not limited by these embodiments.

[0026] In the following examples and comparative examples of the present invention, unless otherwise specified, all raw materials used are commercially available.

[0027] In the Examples and Comparative Examples:

[0028] The polysiloxane used is polymethyl hydrogen siloxane, which was purchased from Ningbo Runhe High-tech Materials Technology Co., Ltd.; the weight average molecular weight of the polymethyl hydrogen siloxane is 18100 g / mol, and the molecular weight distribution is 3.13;

[0029] Flaky boron nitride was purchased from Merck, Germany, with the trade name RonaFlair Boroneige SF-3.

[0030] Flake aluminum nitride and flake aluminum oxide were purchased from Henan Kesheng Abrasive Materials Co., Ltd.;

[0031] The micron-sized spherical aluminum powder and alumina used were purchased from Angang Industrial Fine Aluminum Powder Co., Ltd.

[0032] The nano-scale spherical aluminum powder and alumina used were purchased from Hongwu New Materials Co., Ltd.

[0033] The analytical characterization instruments used in the present invention are as follows:

[0034] The yield viscosity and shear rate of the suspension obtained in the test examples and comparative examples are 100s -1 Viscosity and storage modulus-shear strain curves (such as Figure 1 and Figure 2 ), using the Anton Paar MCR302 instrument with 25 mm parallel plates, a temperature of 25 ° C, and a gap of 0.5 mm. In order to avoid the sedimentation and aggregation effects of the filler during storage, all rheological measurements were performed 10 minutes after sample preparation. For steady-state scanning measurements, the strain rate range tested was 10 -2 Up to 10 4 s -1 For dynamic strain amplitude sweeps, all measurements were performed in the range of 0.01% to 104% with a constant frequency of 10 s. -1 .

[0035] The extruder used for extrusion molding in the examples and comparative examples is a single screw extruder purchased from HAKKE.

[0036] The thermal conductivity in the examples and comparative examples was measured using a KEM rapid thermal conductivity meter QTM-500 manufactured by Kyoto Electronics of Japan.

[0037] Example 1

[0038] This example is used to illustrate the suspension that can be used for extrusion molding and the preparation method thereof according to the present invention.

[0039] 75 parts by volume of polysiloxane, 20 parts by volume of flaky boron nitride with an average diameter of 10 μm, and 5 parts by volume of spherical aluminum powder with an average diameter of 50 nm were measured and placed in a stirring kettle and mixed for 5 minutes under vacuum conditions at a temperature of 30° C. to obtain the suspension that can be used for extrusion molding, which is recorded as Sample 1; wherein the rotation speed of the stirring kettle is 50 rpm.

[0040] The sample 1 was subjected to rheological test and extrusion test using a single screw extruder (the extrusion temperature of the single screw extruder was 30° C. and the speed of the single screw extruder was 100 rpm). The test results are shown in Table 1 and Figure 1 shown.

[0041] Example 2

[0042] This example is used to illustrate the suspension that can be used for extrusion molding and the preparation method thereof according to the present invention.

[0043] 75 parts by volume of polysiloxane, 15 parts by volume of flaky aluminum nitride with an average diameter of 16 μm, and 10 parts by volume of spherical aluminum powder with an average diameter of 80 nm were measured and placed in a stirring kettle and mixed for 5 minutes under vacuum at a temperature of 30° C. to obtain the suspension that can be used for extrusion molding, which is recorded as Sample 2; wherein the rotation speed of the stirring kettle is 50 rpm.

[0044] The sample 2 was subjected to rheological tests and extrusion tests using a single screw extruder (the extrusion temperature of the single screw extruder was 30° C. and the speed of the single screw extruder was 100 rpm). The test results are shown in Tables 1 and Figure 1 shown.

[0045] Example 3

[0046] This example is used to illustrate the suspension that can be used for extrusion molding and the preparation method thereof according to the present invention.

[0047] 65 parts by volume of polysiloxane, 20 parts by volume of flaky alumina with an average diameter of 4 μm, and 15 parts by volume of spherical alumina with an average diameter of 20 nm were measured and placed in a stirring kettle and mixed under vacuum conditions at a temperature of 30°C for 5 minutes to obtain the suspension that can be used for extrusion molding, which is recorded as Sample 3; wherein the rotation speed of the stirring kettle is 50 rpm.

[0048] The sample 3 was subjected to rheological test and extrusion test using a single screw extruder (the extrusion temperature of the single screw extruder was 30° C. and the speed of the single screw extruder was 100 rpm). The test results are shown in Tables 1 and Figure 1 shown.

[0049] Example 4

[0050] This example is used to illustrate the suspension that can be used for extrusion molding and the preparation method thereof according to the present invention.

[0051] 70 parts by volume of polysiloxane, 10 parts by volume of flaky boron nitride with an average diameter of 10 μm, and 20 parts by volume of spherical aluminum powder with an average diameter of 50 nm were measured and placed in a stirring kettle and mixed under vacuum conditions at a temperature of 30°C for 4 minutes to obtain the suspension that can be used for extrusion molding, which is recorded as Sample 4; wherein the rotation speed of the stirring kettle is 50 rpm.

[0052] The sample 4 was subjected to a rheological test and an extrusion test using a single screw extruder (the extrusion temperature of the single screw extruder was 30° C. and the speed of the single screw extruder was 100 rpm). The test results are shown in Table 1.

[0053] Example 5

[0054] This example is used to illustrate the suspension that can be used for extrusion molding and the preparation method thereof according to the present invention.

[0055] 75 parts by volume of polysiloxane, 15 parts by volume of flaky aluminum nitride with an average diameter of 16 μm, and 10 parts by volume of spherical aluminum powder with an average diameter of 100 nm were measured and placed in a stirring kettle and mixed for 10 minutes under vacuum at a temperature of 30°C to obtain the suspension that can be used for extrusion molding, which is recorded as Sample 5; wherein the rotation speed of the stirring kettle is 50 rpm.

[0056] The sample 5 was subjected to a rheological test and an extrusion test using a single screw extruder (the extrusion temperature of the single screw extruder was 30° C. and the speed of the single screw extruder was 100 rpm). The test results are shown in Table 1.

[0057] Example 6

[0058] This example is used to illustrate the suspension that can be used for extrusion molding and the preparation method thereof according to the present invention.

[0059] 65 parts by volume of polysiloxane, 30 parts by volume of flaky boron nitride with an average diameter of 10 μm, and 5 parts by volume of spherical aluminum powder with an average diameter of 50 nm were measured and placed in a stirring kettle and mixed under vacuum conditions at a temperature of 30°C for 5 minutes to obtain the suspension that can be used for extrusion molding, which is recorded as Sample 6; wherein the rotation speed of the stirring kettle is 50 rpm.

[0060] The sample 6 was subjected to a rheological test and an extrusion test using a single screw extruder (the extrusion temperature of the single screw extruder was 30° C. and the speed of the single screw extruder was 100 rpm). The test results are shown in Table 1.

[0061] Comparative Example 1

[0062] This comparative example is used to illustrate the suspension that can be used for extrusion molding and the preparation method thereof of the present invention.

[0063] 55 parts by volume of polysiloxane, 20 parts by volume of flaky boron nitride with an average diameter of 10 μm, and 25 parts by volume of spherical aluminum powder with an average diameter of 50 nm were measured and placed in a stirring kettle and mixed for 5 minutes under vacuum conditions at a temperature of 30°C to obtain the suspension that can be used for extrusion molding, which is recorded as sample D1; wherein the rotation speed of the stirring kettle is 50 rpm.

[0064] The sample D1 was subjected to rheological test and extrusion test using a single screw extruder (the extrusion temperature of the single screw extruder was 30° C. and the speed of the single screw extruder was 100 rpm). The test results are shown in Table 1 and Figure 2 shown.

[0065] Comparative Example 2

[0066] This comparative example is used to illustrate the suspension that can be used for extrusion molding and the preparation method thereof of the present invention.

[0067] 65 parts by volume of polysiloxane, 20 parts by volume of flaky alumina with an average diameter of 4 μm, and 15 parts by volume of spherical alumina with an average diameter of 10 μm were measured and placed in a stirring kettle and mixed under vacuum conditions at a temperature of 30°C for 5 minutes to obtain the suspension that can be used for extrusion molding, which is recorded as sample D2; wherein the rotation speed of the stirring kettle is 50 rpm.

[0068] The sample D2 was subjected to rheological tests and extrusion tests using a single screw extruder (the extrusion temperature of the single screw extruder was 30° C. and the speed of the single screw extruder was 100 rpm). The test results are shown in Tables 1 and Figure 2 shown.

[0069] Comparative Example 3

[0070] This comparative example is used to illustrate the suspension that can be used for extrusion molding and the preparation method thereof of the present invention.

[0071] 60 parts by volume of polysiloxane, 35 parts by volume of flaky boron nitride with an average diameter of 10 μm, and 5 parts by volume of spherical aluminum powder with an average diameter of 50 nm were measured and placed in a stirring kettle and mixed under vacuum conditions at a temperature of 30°C for 5 minutes to obtain the suspension that can be used for extrusion molding, which is recorded as sample D3; wherein the rotation speed of the stirring kettle is 50 rpm.

[0072] The sample D3 was subjected to rheological test and extrusion test using a single screw extruder (the extrusion temperature of the single screw extruder was 30° C. and the speed of the single screw extruder was 100 rpm). Figure 2 shown.

[0073] Comparative Example 4

[0074] This comparative example is used to illustrate the suspension that can be used for extrusion molding and the preparation method thereof of the present invention.

[0075] 80 parts by volume of polydimethylsiloxane and 20 parts by volume of flaky boron nitride with an average diameter of 10 μm were measured and placed in a stirring kettle and mixed for 5 minutes under vacuum conditions at a temperature of 30° C. to obtain the suspension that can be used for extrusion molding, which is recorded as sample D4; wherein the rotation speed of the stirring kettle is 50 rpm.

[0076] The sample D4 was subjected to a rheological test and an extrusion test using a single screw extruder (the extrusion temperature of the single screw extruder was 30° C. and the speed of the single screw extruder was 100 rpm). The test results are shown in Table 1.

[0077] Application Examples

[0078] The suspension (sample 6) prepared in Example 6 of the present invention is extruded at a temperature of 30°C and a single screw extruder speed of 100 rpm, and the obtained thermally conductive gel has a smooth outer surface. The thermally conductive gel obtained by the suspension (sample 6) prepared in Example 6 of the present invention is cured in an oven at a temperature of 100°C for 1 hour to obtain a thermally conductive elastomer that can be used as an interface filling material between electronic device components, which has good elasticity and thermal conductivity. The thermal conductivity of the thermally conductive elastomer is 2.4W / (m·K) measured according to GB / T 20671.10-2006.

[0079] The suspension (sample D3) prepared in the above comparative example 3 of the present invention was extruded at a temperature of 30°C and a single screw extruder speed of 100 rpm. However, due to the high viscosity of the suspension system at high shear rates, extrusion molding was difficult and a regular and continuous thermal conductive gel could not be obtained.

[0080] Table 1

[0081]

[0082] In Table 1, *yield viscosity is the maximum value of viscosity in the low-frequency region in the viscosity versus shear rate curve obtained by steady-state scanning during rheological testing; **stable extrusion means that the suspension can be continuously discharged during extrusion and has a relatively smooth surface; linear viscoelastic strain refers to the deformation range in which the modulus remains constant in the storage modulus versus shear strain curve measured during rheological testing.

[0083] From Table 1, Figure 1 and Figure 2 It can be seen that the suspension composed of polysiloxane and thermal conductive filler in the present invention has a yield viscosity of not less than 2×104 Pa·s, yield viscosity and strain rate is 100s -1 The viscosity ratio is not less than 2×10 3 , the strain in the linear viscoelastic region is not less than 0.1%. The suspension that meets the above rheological conditions has good extrusion processability and can be used for extrusion molding of thermal interface thermal conductive gel or thermal conductive elastomer material.

[0084] Furthermore, by comparing Example 1 of the present invention with Comparative Example 1, and Example 6 with Comparative Example 3, it can be seen that if too much flaky thermally conductive filler or spherical thermally conductive filler is added, the linear viscoelastic region of the suspension will become narrower, and stable extrusion cannot be achieved; by comparing Example 3 of the present invention with Comparative Example 2, it can be seen that the combination of nano-scale spherical thermally conductive fillers and micron-scale flaky thermally conductive fillers is beneficial to the improvement of the yield viscosity of the system and the widening of the linear viscoelastic region, thereby ensuring the static stability and extrusion stability of the suspension; while in Comparative Example 4, only flaky thermally conductive fillers are added, and the yield viscosity of the prepared suspension system is low, the suspension is prone to flow when static, and the stability is poor.

[0085] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A suspension that can be used for extrusion molding, characterized in that: The suspension comprises polysiloxane and a thermally conductive filler; wherein the thermally conductive filler is a mixture of a flaky thermally conductive filler and a nano-spherical thermally conductive filler; the weight average molecular weight of the polysiloxane is 10,000-30,000 g / mol, and the molecular weight distribution is not less than 3; the diameter of the flaky thermally conductive filler is 4-16 μm, and the diameter of the nano-spherical thermally conductive filler is 20-100 nm.

2. The suspension according to claim 1, characterized in that Based on 100 parts by total volume of polysiloxane, flaky thermal conductive filler and nano-spherical thermal conductive filler, the flaky thermal conductive filler is 5-30 parts by volume, preferably 10-25 parts by volume of the flaky thermal conductive filler; the nano-spherical thermal conductive filler is 5-20 parts by volume, preferably 5-15 parts by volume of the nano-spherical thermal conductive filler.

3. The suspension according to claim 1 or 2, characterized in that The polysiloxane includes at least one of polydimethylsiloxane, vinyl-terminated polydimethylsiloxane, and polymethylhydrogensiloxane; And / or, the flaky thermally conductive filler is at least one of flaky aluminum oxide, flaky aluminum nitride and flaky boron nitride; And / or, the nano-spherical thermal conductive filler is at least one of spherical alumina and spherical aluminum powder.

4. The suspension according to any one of claims 1 to 3, characterized in that The weight average molecular weight of the polysiloxane is 10,000-20,000 g / mol, and the molecular weight distribution is 3-5; And / or, the diameter of the flake thermal conductive filler is 6-12 μm, and the diameter of the nano-spherical thermal conductive filler is 40-80 nm.

5. The suspension according to any one of claims 1 to 4, characterized in that The suspension has a yield viscosity of not less than 2×10 4 Pa·s, yield viscosity and strain rate is 100s -1 The viscosity ratio is not less than 2×10 3 , the strain in the linear viscoelastic region is not less than 0.1%.

6. A method for preparing a suspension that can be used for extrusion molding according to any one of claims 1 to 5, characterized in that: The method comprises mixing polysiloxane, a flake-shaped heat-conducting filler and a nano-spherical heat-conducting filler to obtain the suspension that can be used for extrusion molding.

7. The preparation method according to claim 6, characterized in that: The mixing conditions include: temperature of 25-30° C., time of 4-10 minutes, and rotation speed of 10-50 rpm.

8. A thermally conductive gel, characterized in that: The thermally conductive gel is obtained by extruding the suspension according to any one of claims 1 to 5 or the suspension obtained by the preparation method according to claim 6 or 7; preferably, the extrusion conditions include: a temperature of 25-30° C. and a rotation speed of 50-200 rpm.

9. A thermally conductive elastomer, characterized in that: The thermally conductive elastomer is obtained by extruding and curing the suspension according to any one of claims 1 to 5 or the suspension obtained by the preparation method according to claim 6 or 7; preferably, the extrusion conditions include: a temperature of 25-30°C and a rotation speed of 50-200 rpm; and / or, the curing conditions include: a curing temperature of 95-105°C and a curing time of 0.5-1.5 hours.

10. Use of the suspension according to any one of claims 1 to 5 or the suspension obtained by the preparation method according to claim 6 or 7 or the thermally conductive gel according to claim 8 or the thermally conductive elastomer according to claim 9 in electronic devices, preferably chips, circuit boards, and power supply components.

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