Non-silicon heat-conducting gasket as well as preparation method and application thereof

Abstract

The invention discloses a non-silicon heat-conducting gasket as well as a preparation method and application thereof, and the non-silicon heat-conducting gasket is prepared from the following components in parts by weight: 4 to 9 parts of polyol, 0.5 to 1 part of plasticizer, 0.2 to 0.5 part of coupling agent, 0.2 to 0.4 part of isocyanate, 0.005 to 0.01 part of catalyst and 90 to 93 parts of heat-conducting powder. The non-silicon heat-conducting gasket has high heat conductivity coefficient and low hardness at the same time, the preparation process is simple, and the non-silicon heat-conducting gasket is suitable for the field of silicon sensitivity.

Description

Technical Field

[0001] This invention relates to the field of thermal interface materials technology, and in particular to a non-silicon thermally conductive pad, its preparation method, and its application. Background Technology

[0002] With the development of technology, electronic components are becoming increasingly integrated and miniaturized, resulting in ever-increasing heat output. If this heat cannot be dissipated in time, it can cause a sharp rise in equipment temperature, reducing equipment lifespan and even leading to safety accidents. Studies have shown that for every 2°C increase in temperature, the lifespan of electronic components decreases by 10%. Therefore, effectively dissipating heat has become a critical issue. In the field of thermal interface materials, thermal pads are widely used due to their high thermal conductivity, high insulation, shock absorption, and double-sided adhesive properties. However, most thermal pads on the market are currently made of silicone, which is unsuitable for silicon-sensitive applications. For example, it can affect the optical performance of precision optics and easily migrate to precision connectors, switches, or electrical contacts, forming an insulating film that increases contact resistance, leading to signal instability or even complete device failure. Non-silicone thermal pads have gradually become a research focus in recent years because they can eliminate the risk of silicone oil volatilization and migration, and can significantly improve the long-term stability and yield of products while ensuring excellent thermal conductivity. However, traditional non-silicone thermal pads usually have high hardness, and thermal pads with high hardness have poor compressibility and filling capacity, making it difficult to effectively fill the air gaps between heat dissipation interfaces, which can easily lead to poor local contact, significantly increasing the actual thermal resistance. In addition, their high cost limits their large-scale production.

[0003] Therefore, there is an urgent need for a non-silicon thermal pad and its preparation method that can simultaneously take into account both thermal conductivity and hardness, in order to overcome the shortcomings of existing technologies. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a non-silicone thermal conductive pad, its preparation method, and its application.

[0005] This invention provides a non-silicone thermally conductive pad, comprising the following components by weight: 4-9 parts of polyol, such as 4, 5, 6, 7, 8, or 9 parts; 0.5-1 part of plasticizer, such as 0.5, 0.6, 0.7, 0.8, 0.9, or 1 part; 0.2-0.5 parts of coupling agent, such as 0.2, 0.3, 0.4, or 0.5 parts; 0.2-0.4 parts of isocyanate, such as 0.2, 0.3, or 0.4 parts; 0.005-0.01 parts of catalyst, such as 0.005, 0.006, 0.007, 0.008, 0.009, or 0.01 parts; and 90-93 parts of thermally conductive powder, such as 90, 91, 92, or 93 parts.

[0006] This invention utilizes a specific formulation and polyurethane system to prepare non-silicone thermal pads. The resulting thermal pads are free of silicone oil and possess high thermal conductivity and low hardness, making them suitable as thermal interface materials in silicon-sensitive applications. Starting from the polyurethane main chain, flexible polyols are used as soft segments, isocyanates as hard segments, and plasticizers are added to effectively reduce the hardness of the thermal pads. Coupling agents are used to increase the compatibility between the thermally conductive powder and polyurethane, reduce interfacial thermal resistance, and increase the thermal conductivity of the thermal pads. This invention prepares non-silicone thermal pads in a one-step process, which is simple and can effectively reduce manufacturing costs.

[0007] Furthermore, the polyol is one or both of polyether polyol or polyester polyol, preferably polyether polyol, where the ether bonds in the main chain of polyether polyol have better flexibility.

[0008] Furthermore, the plasticizer is one or more of the following: fatty acid ester-based environmentally friendly plasticizers and benzoic acid ester-based environmentally friendly plasticizers.

[0009] Furthermore, the fatty acid ester-based environmentally friendly plasticizer is either tributyl citrate or trioctyl trimellitate.

[0010] Furthermore, the coupling agent is one or more of titanate coupling agents, aluminate coupling agents, or zirconate aluminate coupling agents.

[0011] Furthermore, the isocyanate is one or a mixture of hexamethylene diisocyanate, isophorone diisocyanate, or diphenylmethane diisocyanate, preferably hexamethylene diisocyanate. Hexamethylene diisocyanate has isocyanate groups at both ends and a methylene group in the middle. Combined with a polyol, it can reduce the hardness of the material. This invention uses a preferred highly flexible polyether polyol combined with a specific isocyanate as a crosslinking agent, and adds a specific plasticizer to the system. The plasticizer inserts into the crosslinking points of the polyurethane, promoting polyurethane chain movement, which further reduces the hardness of the material.

[0012] Furthermore, the catalyst is one or both of dibutyltin dilaurate or stannous octoate.

[0013] Furthermore, the mass ratio of the polyol to the plasticizer is (5-11):1. If too much plasticizer is added, it will destroy the cross-linking structure of the polyurethane in the system, causing problems such as precipitation. If too little plasticizer is added, it will result in a higher viscosity of the system during mixing, poor operability, and a higher hardness of the finished sheet.

[0014] Furthermore, the thermally conductive powder is one or more of spherical alumina, spherical aluminum hydroxide, or angular aluminum hydroxide. This invention effectively improves thermal conductivity while reducing the cost of thermally conductive pads by using a mixture of alumina and aluminum hydroxide with different particle sizes and / or shapes as the thermally conductive powder.

[0015] Further, the thermally conductive powder is a mixture of alumina with different particle sizes and / or aluminum hydroxide with different particle sizes and shapes; preferably, it is a mixture of spherical alumina with a D50 of 5 μm, spherical alumina with a D50 of 40 μm, spherical alumina with a D50 of 70 μm, and spherical alumina with a D50 of 120 μm in a 3:2:3:4 ratio, and a mixture of spherical alumina with a D50 of 5 μm, angular aluminum hydroxide with a D50 of 5 μm, spherical alumina with a D50 of 40 μm, and spherical alumina with a D50 of 120 μm in a 3:1:2:6 ratio, more preferably the latter. When the same proportion of thermally conductive powder is added, the thermal conductivity of the thermally conductive pad prepared using the latter will be better than that of the former, mainly because the latter contains a large amount of 120 μm aluminum hydroxide. Large-diameter spherical alumina with a particle size of μm can serve as a framework, while small and medium-diameter thermally conductive powders can fill the gaps. The combination of various thermally conductive powders with different particle sizes can increase the thermal conductivity chain and the thermal conductivity coefficient. Furthermore, using low-cost alumina as the thermally conductive powder can greatly reduce the cost of thermal pads, and the preparation process is simple.

[0016] Furthermore, the hardness of the non-silicone thermal pad is 55-60 (Shore00).

[0017] The present invention also provides a method for preparing the aforementioned non-silicone thermal pad, comprising the following steps: Weigh out the polyol, plasticizer and coupling agent by weight and mix them evenly. Then weigh out the thermally conductive powder by weight and mix it evenly. After dehydration and cooling, weigh out the isocyanate and catalyst by weight and mix them evenly. After vacuuming, calender and bake to obtain the non-silicone thermally conductive pad.

[0018] Furthermore, the dehydration process is carried out at a temperature of 100-110℃, with a vacuuming time of 0.1-1 h, and the baking temperature is 80-100℃ for 7-10 h.

[0019] The present invention also provides the application of the non-silicon thermal conductive pad in the field of new energy vehicles or as a thermal conductive material in the power battery pack between the cell and the liquid cooling plate / battery shell. The low hardness thermal conductive pad can provide extremely low contact stress and perfectly fill the gap.

[0020] In summary, compared with the prior art, the present invention achieves the following technical effects: (1) The non-silicone thermal pad provided by the present invention has a high thermal conductivity; (2) The non-silicone thermal pad provided by the present invention has a low and suitable hardness. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0022] Example The present invention will be further illustrated below with reference to specific embodiments and comparative embodiments. The following specific embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following embodiments, and are not in particular limited to the types of raw materials used in the following specific embodiments.

[0023] I. The sources of raw materials for the examples and comparative examples are as follows: Polyol #1: Polyether polyol, brand name VORANOL 4000LM, Dow Chemical Company, USA; Polyol #2: Polyester polyol, brand name BY3020, Beijing Baiyuan Chemical Co., Ltd.; Plasticizer #1: Citrate plasticizer, brand name WT109, Shandong Wantu Polymer Materials Co., Ltd.; Plasticizer #2: Trioctyl trimellitate, commercially available; Coupling agent: Titanate coupling agent, brand name KR-TTS, Guangzhou Jianshuang Chemical Technology Co., Ltd.; Isocyanate #1: Hexamethylene diisocyanate, Guangzhou Haoyi New Material Technology Co., Ltd.; Isocyanate #2: Isophorone diisocyanate, Guangzhou Haoyi New Material Technology Co., Ltd.; Isocyanate #3: Diphenylmethane diisocyanate, Guangzhou Haoyi New Material Technology Co., Ltd.; Catalyst: Dibutyltin dilaurate, grade T12, Guangzhou Yihua Digital Technology Co., Ltd.; Thermally conductive powder #1: A mixture of spherical alumina with a D50 of 5 μm, spherical alumina with a D50 of 40 μm, spherical alumina with a D50 of 70 μm, and spherical alumina with a D50 of 120 μm in a ratio of 3:2:3:4. Thermally conductive powder #2: A mixture of spherical alumina with a D50 of 5 μm, angular aluminum hydroxide with a D50 of 5 μm, spherical alumina with a D50 of 40 μm, and spherical alumina with a D50 of 120 μm in a ratio of 3:1:2:6.

[0024] The preparation method of the non-silicone thermal pad in the embodiments and comparative examples of the present invention includes the following steps: After weighing and adding polyol, plasticizer and coupling agent according to the weight parts, mix evenly, then weigh and add thermally conductive powder according to the weight parts and mix evenly. Heat to 100℃ to dehydrate and then cool. Continue to weigh and add isocyanate and catalyst according to the weight parts and mix evenly. After vacuuming for 0.5 h, calender and bake at 100℃ for 8 h to obtain the non-silicone thermally conductive pad.

[0025] II. Performance Testing Methods (1) Thermal conductivity test: The test was conducted using a DRL-III series thermal conductivity tester in accordance with the ASTM-D5470-2017 standard.

[0026] (2) Hardness test: The hardness test was conducted using a GS-754G Shore00 hardness tester in accordance with the ASTM-D2240-2015 standard.

[0027] Table 1. Technical solutions and effects of the embodiments and comparative examples (unit: parts by weight)

[0028] Examples 1-6 simultaneously introduced polyols, plasticizers, isocyanates, catalysts, and thermally conductive powders to prepare silicone-free thermal pads. All the resulting thermal pads maintained good thermal conductivity while exhibiting low hardness, making them suitable for use in silicon-sensitive applications. Furthermore, their suitable low hardness ensured effective filling of air gaps between heat dissipation interfaces. This invention allows for adjustment of the thermal conductivity of the thermal pad by adding different proportions and types of thermally conductive powders to the system, thereby modifying the internal thermal conductivity chain.

[0029] Comparative Example 1 was compared with Example 1, and Comparative Examples 2 and 3 were compared with Example 2. The isocyanate added in Comparative Example 1 was diphenylmethane diisocyanate, which was insufficient to reduce the hardness of the thermal pad. Comparative Example 2 did not contain a plasticizer. When no plasticizer is added, the polymer molecular chains are tightly entangled, resulting in strong intermolecular forces and a high hardness of the thermal pad. Adding a plasticizer allows the small molecule plasticizer to insert between the polymer molecular chains, weakening the intermolecular forces and making the chains easier to slide, thereby reducing the hardness of the thermal pad. Comparative Example 3, without the addition of a coupling agent, exhibits poor compatibility between polyurethane and the inorganic thermally conductive powder, resulting in poor filler dispersion. This leads to an interface between the organic phase of the polyurethane and the inorganic phase of the thermally conductive powder, which is prone to significant interfacial thermal resistance, thus reducing the thermal conductivity of the thermal pad. When a coupling agent is added, one end of the agent bonds to the surface of the inorganic powder, while the other end reacts with the polyurethane, resulting in more uniform dispersion of the filler in the system and increasing the thermal conductivity of the thermal pad. Furthermore, the filler forms a strong bridge with the polyurethane matrix, allowing for effective stress transfer between the filler and the matrix, reducing interfacial defects, and effectively lowering the hardness of the thermal pad. The silicone-free thermal pads prepared in Comparative Examples 1-3 struggle to simultaneously achieve both high thermal conductivity and low hardness.

[0030] Based on the test data of thermal conductivity and hardness of the silicone-free thermal pads in Table 1, the silicone-free thermal pads prepared by Examples 1-6 have significant advantages over the comparative examples and can effectively meet the high standards of customers and the market.

[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A non-silicone thermally conductive pad, characterized in that, By weight, it includes the following components: 4-9 parts of polyols Plasticizer 0.5-1 part 0.2-0.5 parts of coupling agent 0.2-0.4 parts isocyanate Catalyst 0.005-0.01 parts 90-93 parts of thermally conductive powder.

2. The non-silicone thermal pad according to claim 1, characterized in that, The polyol is one or both of polyether polyols or polyester polyols.

3. The non-silicone thermal pad according to claim 1, characterized in that, The plasticizer is one or more of the following: fatty acid ester-based environmentally friendly plasticizers and dibenzoic acid ester-based environmentally friendly plasticizers.

4. The non-silicone thermal pad according to claim 1, characterized in that, The coupling agent is one or more of titanate coupling agents, aluminate coupling agents, or zirconate aluminate coupling agents.

5. The non-silicone thermal pad according to claim 1, characterized in that, The isocyanate is one or a mixture of hexamethylene diisocyanate, isophorone diisocyanate, or diphenylmethane diisocyanate.

6. The non-silicone thermal pad according to claim 1, characterized in that, The catalyst is one or both of dibutyltin dilaurate or stannous octoate.

7. The non-silicone thermal pad according to claim 1, characterized in that, The mass ratio of the polyol to the plasticizer is (5-11):

1.

8. The non-silicone thermal pad according to claim 1, characterized in that, The thermally conductive powder is one or more of spherical alumina, spherical aluminum hydroxide, or angular aluminum hydroxide.

9. The method for preparing the non-silicone thermal pad according to any one of claims 1-8, characterized in that, Includes the following steps: Weigh out the polyol, plasticizer and coupling agent by weight and mix them evenly. Then weigh out the thermally conductive powder by weight and mix it evenly. After dehydration and cooling, weigh out the isocyanate and catalyst by weight and mix them evenly. After vacuuming, calender and bake to obtain the non-silicone thermally conductive pad.

10. The application of the non-silicone thermally conductive pad according to any one of claims 1-8 in the field of new energy vehicles or as a thermally conductive material applied between the cell and the liquid cooling plate / battery shell in a power battery pack.

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