Silane-modified polymer-based thermally conductive composition

Abstract

The present invention comprises a) a thermally conductive filler, b) a first silane-modified polymer functionalized with at least two C1-C4-alkyl-di-C1-C4-alkoxysilyl groups or tri-C1-C4-alkoxysilyl groups, c) a second silane-modified polymer functionalized with one C1-C4-alkyl-di-C1-C4-alkoxysilyl group or one tri-C1-C4-alkoxysilyl group, and d) di-C1-C 12 -Alkyl-di-C1~C4-alkoxysilanes and amino-C1~C 12 -Alkyl-C1~C 12 The present invention relates to a composition comprising at least one dialkoxysilane selected from the group consisting of alkyl-di-C1~C4-alkoxysilanes. The composition of the present invention is useful as an intermediate for a curable composition that can serve as an intermediate layer between a heat sink substrate and a heat-generating substrate.

Description

[Technical Field]

[0001] The present invention relates to silane-modified polymer-based (SMP-based) thermal conductive compositions, and more specifically, to moisture-curable SMP-based thermal conductive compositions.

[0002] Thermal interface materials (TIMs) are used at the interface between heat-generating electronic components and heat sinks to protect the electronic components from overheating. Liquid-dispersed TIMs are preferred over off-the-shelf elastomer TIMs because the liquid conforms to the complex geometry of the joint, achieving thin joint lines and low thermal resistance. Liquid-dispersed TIMs are preferably cured into an elastomer state in less than two weeks, and even more preferably in less than 24 hours. The hardness after curing is ideally low enough to achieve vibration resistance and easy delamination in non-adhesive applications. It is most desirable to achieve a thermal conductivity of 1 W / m·K or higher in the cured elastomer.

[0003] While silicone-based TIMs offer advantages such as high-temperature resistance and flexible curing elastomer properties, some TIM users (particularly automotive manufacturers) are reluctant to use silicone in their factories due to the actual or perceived risk of surface contamination that would impair other processes such as painting or adhesive assembly.

[0004] While polyurethane-based thermal interface materials (TIMs) avoid concerns about silicone surface contamination, the presence of unreacted isocyanate groups from the polyurethane precursors raises handling and toxicity concerns. Furthermore, achieving acceptable high pre-curing fluidity and low post-curing hardness often requires undesirable high concentrations of potentially toxic plasticizers. Since plasticizers are known to migrate over the lifespan of the application, the need to reduce or eliminate plasticizers is even more advantageous. Moreover, polyurethane-based TIMs are unstable under high temperature and high humidity conditions, as urethane bonds tend to dissociate under such conditions. Therefore, it would be desirable to find a thermal interface material that a) has a fast curing time to the elastomer state, b) is silicone and isocyanate-free, and c) has a low plasticizer content. [Overview of the project]

[0005] In one embodiment, the present invention comprises: a) a thermally conductive filler; b) a first silane-modified polymer functionalized with at least two C1-C4-alkyl-di-C1-C4-alkoxysilyl groups or two tri-C1-C4-alkoxysilyl groups; c) a second silane-modified polymer functionalized with one C1-C4-alkyl-di-C1-C4-alkoxysilyl group or one tri-C1-C4-alkoxysilyl group; and d) di-C1-C 12 -Alkyl-di-C1~C4-alkoxysilanes and amino-C1~C 12 -Alkyl-C1~C 12 It comprises at least one dialkoxysilane selected from the group consisting of alkyl-di-C1~C4-alkoxysilanes, The needs in the art are addressed by providing a composition in which the concentration of a thermally conductive filler is in the range of 70 to 95 weight percent based on the weight of the composition, the concentration of at least one dialkoxysilane is in the range of 0.1 to 3 weight percent based on the weight of the composition, and the weight-to-weight ratio of the second silane-modified polymer to the first silane-modified polymer is in the range of 0.8 to 3.0.

[0006] The present invention addresses the needs in the art by providing a composition that can be used as a thermal interface material having desirable properties and low toxicity. [Modes for carrying out the invention]

[0007] The present invention comprises a) a thermally conductive filler, b) a first silane-modified polymer functionalized with at least two C1-C4-alkyl-di-C1-C4-alkoxysilyl groups or two tri-C1-C4-alkoxysilyl groups, c) a second silane-modified polymer functionalized with one C1-C4-alkyl-di-C1-C4-alkoxysilyl group or one tri-C1-C4-alkoxysilyl group, and d) di-C1-C 12 -Alkyl-di-C1~C4-alkoxysilanes and amino-C1~C 12 -Alkyl-C1~C 12 It comprises at least one dialkoxysilane selected from the group consisting of alkyl-di-C1~C4-alkoxysilanes, The composition is characterized in that the concentration of the thermally conductive filler is in the range of 70 to 95 weight percent based on the weight of the composition, the concentration of at least one dialkoxysilane is in the range of 0.1 to 3 weight percent based on the weight of the composition, and the weight-to-weight ratio of the second silane-modified polymer to the first silane-modified polymer is in the range of 0.8 to 3.0.

[0008] As used herein, “thermal conductive filler” refers to at least one thermal conductive filler. Examples of suitable thermal conductive fillers include zinc oxide; hydrates, hydroxides, and aluminum oxides such as aluminum oxide (alumina) and aluminum trihydroxide (ATH); aluminum; boron nitride; aluminum nitride; magnesium oxide; magnesium hydroxide; silver; amorphous carbon; graphite; and aluminosilicates; and combinations thereof. The concentration of the thermal conductive filler is preferably in the range of 80 to 90 weight percent based on the weight of the composition.

[0009] The first silane-modified polymer (SMP) and the second silane-modified polymer (SMP) include polyethers such as polyethylene oxide and polypropylene oxide; polybutadiene; polycarbonate; polyacrylate; polyurethane; and polyester. The first SMP is preferably functionalized with at least two C1-C4-alkyl-di-C1-C2-alkoxysilyl groups, or two C1-C2-alkyl-di-C1-C2-alkoxysilyl groups, or two terminal methyldimethoxysilyl groups. The second SMP is preferably functionalized with one C1-C4-di-C1-C2-alkoxysilyl group, or one C1-C2-alkyl-di-C1-C2-alkoxysilyl group, or one methyldimethoxysilyl group, or one tri-C1-C2-alkoxysilyl group, or one trimethoxysilyl group. The weight-to-weight ratio of the second SMP to the first SMP ranges from 0.8 or 1.0 to 3.0 or 1.9. The total concentration of the first polymer and the second polymer typically ranges from 5 weight percent to 20 or 15 weight percent based on the weight of the composition.

[0010] The composition further includes one or more dialkoxysilanes. The first dialkoxysilane is represented by the following Structure I,

[0011]

Chemical formula

[0012] The second dialkoxysilane is represented by the following Structure II,

[0013]

Chemical formula

[0014] The total concentration of at least one dialkoxysilane is in the range of 0.1 to 3 weight percent based on the weight of the composition. If the composition contains both a first dialkoxysilane and a second dialkoxysilane (which is preferred for optimal curing time), the concentration of the first dialkoxysilane is typically in the range of 0.5 to 2.0 weight percent based on the weight of the composition, and the concentration of the second dialkoxysilane is typically in the range of 0.1 or 0.2 to 1 or 0.8 or 0.6 weight percent based on the weight of the composition.

[0015] When the composition contains a first dialkoxysilane and a second dialkoxysilane, the weight-to-weight ratio of the second dialkoxysilane to the first dialkoxysilane is preferably in the range of 0.15:1, 0.20:1, 0.25:1 to 0.65:1, 0.50:1, or 0.45:1.

[0016] The composition of the present invention is useful as an intermediate for curable compositions, further comprising a plasticizer, a condensation catalyst, water, and an antioxidant. A plasticizer is a substance added to a material to reduce its viscosity and hardness. Examples of plasticizers include esters such as phthalates, terephthalates, adipates, glycols, polyalkylene glycols, glycol ether esters, and low-viscosity polyethers. The plasticizer is typically used in concentrations ranging from 0.2 or 0.5 or 1.0 or 2.0 weight percent to 10 or 8 or 6 weight percent, based on the weight of the composition.

[0017] Suitable condensation catalysts include organotin catalysts such as dibutyltin dilaurate and dibutyltin diacetate, and bismuth catalysts such as bismuth octoate, at a concentration in the range of preferably 0.01 or 0.05 weight percent to 1.0 or 0.5 or 0.2 weight percent based on the weight of the composition.

[0018] Water is present in the curable composition at a concentration of 0.1 or 0.5 weight percent to 2.0 or 1.2 weight percent based on the weight of the composition. The antioxidant is present in the curable composition at a concentration in the range of preferably 0.05 or 0.2 weight percent to 1.0 or 0.5 weight percent based on the weight of the composition. Di-C6-C 16 -diphenylamine is an example of a suitable antioxidant, and a commercially available example thereof is Irganox 5057 antioxidant (bis(4-octylphenyl)amine).

[0019] The curable composition of the present invention is advantageously prepared by blending two pre-prepared intermediate compositions as follows. The first intermediate composition (Part A) is advantageously prepared by mixing a plasticizer and a portion of one or more heat-conductive fillers in a container and then heating the mixture under vacuum. After cooling the contents of the container, the catalyst and water are then added to the container while further mixing.

[0020] The second intermediate composition (Part B) is preferably prepared by mixing the first silane-modified polymer and the second silane-modified polymer with the antioxidant and the remainder of one or more fillers, and then heating the mixture under vacuum. Then, one or more dialkoxysilanes are added to the mixture while further mixing. Then, preferably, Part A and Part B are mixed by a static or active mixing method typically well-known in the art, preferably at a Part A:Part B w / w ratio in the range of 20:1 or 10:1 or 2:1 or 1:1 to 1:2, 1:5 or 1:10, or 1:20, and then used as a curable intermediate layer between a heat-generating substrate such as a battery or a semiconductor chip and a heat sink substrate. This multilayer article is preferably prepared by applying the mixed two-component composition to one of the substrates, then pressing the other substrate against the composition to spread the composition into a uniform layer, and then curing the composition.

[0021] Thus, in another aspect, the present invention is a multilayer article comprising a heat sink substrate, a cured or curable intermediate layer overlapping the heat sink substrate, and a heat-generating substrate overlapping the intermediate layer.

[0022] The curable composition of the present invention has been found to meet the performance criteria of sufficiently low compressive force, curing time, and curing hardness at the target thermal conductivity value.

Examples

[0023] Example 1 - Preparation of a Curable Silane-Modified Polymer Composition Part A Preparation The first component (Part A) was prepared by the following procedure: Plasthall 190 plasticizer (10.28 g) and ZOCO 104 ZnO particles (17.57 g) were added to a 100MAX Flacktek speed mixer cup and covered with a lid. The contents were mixed using a Flacktek speed mixer at 1800 rpm for 20 seconds. Next, DAM-40K alumina particles (32.98 g) were added to the cup and the contents were mixed in the speed mixer at 2000 rpm for 30 seconds. Next, MX 200 aluminum trihydrate powder (36.87 g) was added to the cup and the contents were mixed in the speed mixer at 1500 rpm for 30 seconds, and then at 2000 rpm for a further 10 seconds. The lid was removed and the cup was placed in a vacuum chamber preheated to 80°C. The chamber was evacuated to 50 Torr and the contents were held in the chamber for 1 hour. Next, the cup was removed from the chamber, covered with a lid, and then allowed to cool to room temperature.

[0024] Dibutylsulfur laurate (0.29 g) and deionized water (2.00 g) were added to a cup, and the contents were mixed in a speed mixer at 2000 rpm for 20 seconds. The contents of the cup were then stirred manually, and then mixed again in the speed mixer at 2000 rpm for a further 5 seconds.

[0025] Part B preparation The second component (Part B) was prepared by the following process. Bis-(methyldimethoxysilyl)-terminated polypropylene oxide (SMP1, 7.08 g) with a dynamic viscosity of 600 mPa·s, mono-(methyldimethoxysilyl)-terminated polypropylene oxide (SMP2, 5.66 g) with a dynamic viscosity of 1000 mPa·s, Irganox 5057 antioxidant (0.53 g), and ZOCO 104 ZnO particles (17.04 g) were added to a 100MAX Flacktek speed mixer cup and covered with a lid. The contents were mixed using a Flacktek speed mixer at 1800 rpm for 20 seconds. Then, DAM-40K alumina particles (31.98 g) were added to the cup, and the contents were mixed in the speed mixer at 2000 rpm for 30 seconds. Next, MX 200 aluminum trihydroxide powder (35.76 g) was added to the cup, and the contents were mixed in a speed mixer at 1500 rpm for 30 seconds, then at 2000 rpm for a further 10 seconds. The lid was removed, and the cup was placed in a vacuum chamber preheated to 80°C. The chamber was evacuated to 50 Tor and the contents were held inside the chamber for 1 hour. The cup was then removed from the chamber, covered with the lid, and allowed to cool to room temperature.

[0026] n-octylmethyldimethoxysilane (OMDMS, 1.45 g) and 3-aminopropyldimethoxysilane (APMDMS, 0.50 g) were added to a cup. The cup was covered and the contents were mixed in a speed mixer at 2000 rpm for 20 seconds. The contents of the cup were then stirred manually, and then mixed again in the speed mixer at 2000 rpm for a further 5 seconds.

[0027] Preparation of composition A portion of Part A (15.00g) and a portion of Part B (28.66g) were added to a speed mixer cup. The cup was covered with a lid and mixed in a speed mixer at 1800 rpm for 20 seconds. The contents of the cup were stirred manually, and then mixed again in the speed mixer at 1500 rpm for a further 5 seconds.

[0028] The blends of Part A and Part B were immediately transferred onto a square Teflon plate with a dam. The injected composition was flattened by lightly tapping the plate.

[0029] Comparative Example 1 - Preparation of a curable silane-modified polymer composition Part A was prepared as described in Example 1. Part B was prepared as described in Example 1, except that Polymer 1 (12.74 g) was the only polymer used.

[0030] Comparative Example 2 - Preparation of a curable silane-modified polymer composition Part A was prepared as described in Example 1. Part B was prepared as described in Example 1, except that Polymer 2 (12.74 g) was the only polymer used.

[0031] Examples 2-5 were prepared essentially as described in Example 1, except that the relative amounts of polymer 1 and polymer 2 were varied while keeping the total amount of polymer constant. Table 1 shows the relative amounts by weight of the components of the Part A and Part B blends at the time Part A and Part B are combined. SMP2:SMP1 refers to the w / w ratio of SMP2 to SMP1.

[0032] [Table 1]

[0033] Cured hardness measurement Fresh mixtures of Part A and Part B were poured onto a Teflon plate. The cured hardness was determined as the median of five measurements using a Shore A dual durometer. Before measurement, four pieces, each approximately 1 mm thick, were stacked. The sample was considered cured if no residue transferred to a gloved finger lightly pressing the slab, and it could be peeled from the Teflon plate with a spatula.

[0034] Thermal conductivity measurement Thermal conductivity was measured from the cured slab using a Hot Disk TPS2500 unit in accordance with the ISO 22007-2 standard.

[0035] For each sample, the curing time, curing hardness, and thermal conductivity (TC) were measured and are shown in Table 2. Curing hardness was measured in Shore A units, and cured coatings with a Shore A index of 2 to 65 passed the hardness requirement. Samples cured within two weeks passed the curing time requirement (P), and samples cured within 24 hours were particularly desirable (Hi P). Samples cured for more than two weeks failed the curing test (F).

[0036] [Table 2]

[0037] Examples 6-9 were prepared in the same manner as in Example 2, except that the ratio of dialkoxysilane OMDMS to APMDMS was varied as shown in Table 3.

[0038] [Table 3]

[0039] The data demonstrate that an acceptable curing hardness can be achieved with one or both of the dialkoxysilanes, and that the most desirable curing time was achieved using a combination of dialkoxysilanes.

Claims

1. A composition comprising: a) a thermally conductive filler; and b) at least two C １ , １ , １２ , ４ , １ , １ , ４ , ４ , １ , １ , １２ , ４ , １ , ４ , １ , ４ , １ , １ , ４ , １２ to C ４ -alkyl-di-C １ to C ４ -alkoxysilyl group or a first silane-modified polymer functionalized with two tri-C １ to C ４ -alkoxysilyl groups; and c) one C １ to C ４ -alkyl-di-C １ to C ４ -alkoxysilyl group or a second silane-modified polymer functionalized with one tri-C １ to C ４ -alkoxysilyl group; and d) at least one dialkoxysilane selected from the group consisting of di-C １ to C １２ -alkyl-di-C １ to C ４ -alkoxysilane and amino-C １ to C １２ -alkyl-C １ to C １２ -alkyl-di-C １ to C ４ -alkoxysilane, A composition in which the concentration of the thermally conductive filler is in the range of 70 to 95 weight percent based on the weight of the composition, the concentration of the at least one dialkoxysilane is in the range of 0.1 to 3 weight percent based on the weight of the composition, and the weight-to-weight ratio of the second silane-modified polymer to the first silane-modified polymer is in the range of 0.8 to 3.

0.

2. The composition according to claim 1, wherein the thermally conductive filler is one or more fillers selected from the group consisting of zinc oxide, alumina, aluminum trihydroxyoxide, aluminum, boron nitride, aluminum nitride, magnesium oxide, magnesium hydroxide, silver, amorphous carbon, graphite, and aluminosilicate, and the silane-modified polymer is selected from the group consisting of polyether, polybutadiene, polycarbonate, polyacrylate, polyurethane, and polyester.

3. The first silane-modified polymer has at least two C １ ~C ４ -Alkyl-di-C １ ~C ２ - Functionalized with an alkoxylsilyl group, the second silane-modified polymer is one C １ ~C ４ -G-C １ ~C ２ - The composition according to claim 2, which is functionalized with an alkoxylsilyl group.

4. The first silane-modified polymer has two C １ ~C ２ -Alkyl-di-C １ ~C ２ - Functionalized with an alkoxysilyl group, the second silane-modified polymer is one C １ ~C ２ -Alkyl-di-C １ ~C ２ - The composition according to claim 3, wherein the thermally conductive filler is functionalized with alkoxysilyl groups, and the thermally conductive filler is a mixture of zinc oxide, alumina, and aluminum trihydroxyoxide.

5. The aforementioned at least one dialkoxysilane is di-C １ ~C １２ -Alkyl-di-C １ ~C ４ - The first dialkoxysilane, which is an alkoxysilane, and amino-C １ ~C １２ -Alkyl-C １ ~C １２ -Alkyl-di-C １ ~C ４ - The composition according to claim 4, which is a mixture of a second dialkoxysilane, which is an alkoxysilane.

6. The aforementioned G-C １ ~C １２ -Alkyl-di-C １ ~C ４ - The alkoxysilane is n-octylmethyldimethoxysilane, and the amino-C １ ~C １２ -Alkyl-C １ ~C １２ -Alkyl-di-C １ ~C ４ The composition according to claim 5, wherein the alkoxysilane is 3-aminopropyl-methyl-dimethoxysilane, and the weight-to-weight ratio of the second dialkoxysilane to the first dialkoxysilane is in the range of 0.15:1 to 0.65:

1.

7. The composition according to claim 6, wherein the weight-to-weight ratio of the second dialkoxysilane to the first dialkoxysilane is in the range of 0.20:1 to 0.50:

1.

8. The composition according to any one of claims 1 to 7, wherein the silane-modified polymer is silane-modified polyethylene oxide or silane-modified polypropylene oxide.

9. The composition according to any one of claims 1 to 7, which is a curable composition further comprising a plasticizer, a condensation catalyst, water, and an antioxidant.

10. A multilayer article comprising a heat sink substrate, a curable intermediate layer overlapping the heat sink substrate, and a heat-generating substrate overlapping the intermediate layer.

11. The multilayer article according to claim 10, wherein the curable intermediate layer is cured.

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