Thermally conductive silicone composition

Abstract

The present invention relates to a composition comprising alumina trihydrate, an ester-functionalized trialkoxysilane, and a polysiloxane. The composition of the present invention is useful as a thermally conductive composite material having desirable viscosity and thermal conductivity.

Description

[Technical Field]

[0001] The present invention relates to thermally conductive silicone composites, and in particular to composites containing ester-functionalized trialkoxysilanes. [Background technology]

[0002] Thermally conductive silicone composites are widely used as thermal interface materials to transfer heat from heat-generating electronic components to heat sinks. High loadings of one or more thermally conductive fillers, such as zinc oxide and alumina trihydrate (Al2O3·3H2O, ATH), are necessary to achieve the desired thermal conductivity. ATH is particularly attractive because it is non-toxic, halogen-free, chemically inert, and inexpensive. ATH also has the added benefits of being abrasion resistant and flame retardant.

[0003] A continuing challenge with highly filled silicone composites is the concomitant increase in viscosity of the composite, which makes it difficult to dispense. Therefore, finding a way to reduce the viscosity of ATH-containing composites without adversely affecting other desirable properties would be advantageous in the field of thermally conductive composites. Summary of the Invention

[0004] The present invention provides a composition comprising, based on the weight of the composition, a) 50 to 90 weight percent alumina trihydrate; b) up to 30 weight percent zinc oxide; and c) 0.1 to 2 weight percent of an ester-functionalized trialkoxysilane of Formula 1 or Formula 2,

[0005] [ka] Here, R is C1 to C 16 Alkyl or C2-C 16 alkenyl, and each R 1 are independently C1-C6 alkyl, and R 2is H or methyl and n is 1, 2, or 3; and d) 10 to 20 weight percent of a polysiloxane of Formula 3,

[0006] [ka] Here, each R 3 are independently C1-C6 alkyl or phenyl, and each R 4 is independently a C1-C6 alkyl or a C2-C6 alkenyl, and x is 20-300.

[0007] The compositions of the present invention are useful as thermal interface materials. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present invention provides a process for producing a silane-based emulsion of a composition comprising: a) 50 to 90 weight percent alumina trihydrate; b) up to 30 weight percent zinc oxide; and c) 0.1 to 2 weight percent of an ester-functionalized trialkoxysilane of Formula 1 or Formula 2,

[0009] [ka] Here, R is C1 to C 16 Alkyl or C2-C 16 alkyl, and each R 1 are independently C1-C6 alkyl, and R 2 is H or methyl and n is 1, 2, or 3; and d) 10 to 20 weight percent of a polysiloxane of Formula 3,

[0010] [ka] Here, each R3 are independently C1-C6 alkyl or phenyl, and each R 4 are independently C1 to C6 alkyl or C2 to C6 alkenyl, and x is 20 to 300.

[0011] The concentration of alumina trihydrate in the composition ranges from 50, or 55, or 60 weight percent to 90, or 70, or 68, or 65 weight percent based on the weight of the composition. The composition may further include ZnO at a concentration of up to 30 weight percent. Preferably, the composition includes ZnO at a concentration ranging from 5, or 15, or 18, or 20 weight percent to 30, or 27, or 24 weight percent based on the weight of the composition.

[0012] The polysiloxane of Formula 3 is preferably a polydimethylsiloxane terminated with two trimethylsilyl groups, or one trimethylsilyl group and one vinyldimethylsilyl group, or two vinyldimethylsilyl groups. Thus, in a preferred embodiment, each R 3 is methyl, and each R 4 are independently methyl or vinyl, and x (also referred to as the degree of polymerization) ranges from 20, or 50, or 100 to 300, or 200.

[0013] The concentration of polysiloxane ranges from 10, or 12, percent by weight to 20, or 18, or 16 percent by weight based on the weight of the composition.

[0014] The concentration of the ester-functionalized trialkoxysilane ranges from 0.1, or 0.2, or 0.4 weight percent to 2, or 1, or 0.6 weight percent based on the weight of the composition. R is a C1-C 16 Alkyl or C1-C 10 Alkyl, or C1-C6 alkyl, or C2-C 16 Alkenyl or C2-C 10 alkenyl, R is preferably methyl, and each R 1are independently C1-C6 alkyl, preferably methyl, and R 2 is preferably methyl, and n is preferably 1 or 2.

[0015] Ester-functionalized trialkoxysilanes of formula 1 can be prepared by condensation of a salt of a carboxylic acid with a trialkoxysilyl alcohol, as described, for example, in WO 2011 / 101278. Compounds of formula 1 can also be prepared by the base-catalyzed reaction of a salt of a carboxylic acid with a chloromethyltrialkoxysilane.

[0016] [ka] Alternatively, compounds of formula 1 can be prepared by hydrosilylation of allyl esters and trichlorosilane, followed by alkanol decomposition.

[0017] [ka]

[0018] Ester-functionalized trialkoxysilanes of formula 2 can be prepared by reacting trichlorosilane with an acrylate or methacrylate in the presence of a hydrosilylation catalyst, such as a platinum catalyst, followed by alkanollysis.

[0019] [ka]

[0020] The compositions of the present invention may further comprise up to 10 weight percent of a trimethylsilyl-trimethoxysilyl treating agent of Formula 4.

[0021] [ka] Here, each R 5are independently C1-C6 alkyl, preferably methyl, Y is O or CH2-CH2, preferably O, and x is 20 to 200. When used, the concentration of the composition of Formula 4 ranges from 0.2 or 1 to 10 or 8 weight percent based on the weight of the composition.

[0022] The composition may be curable or non-curable. To make the composition curable, each R 4 is a C2-C6 alkenyl group, preferably vinyl, and the composition further comprises a polysiloxane functionalized with at least two Si—H groups and having a degree of polymerization in the range of 5 to 300, or 5 to 200, or 5 to 100, or 5 to 50. For curable compositions, the mole to mole ratio of Si—H groups to alkenyl groups in the polysiloxane of Formula 3 preferably ranges from 0.2:1 to 2:1.

[0023] The compositions of the present invention exhibit lower viscosities when the alkyltrialkoxysilane treating agent is replaced with an ester-functionalized trialkoxysilane treating agent. [Example]

[0024] In the following examples, pbw refers to parts by weight and TA refers to ester-functionalized trialkoxysilane treating agent.

[0025] General preparation of composite materials Vinyl-terminated polydimethylsiloxane of Formula 3 (Vi-PDMS, 14.14 pbw, x = 130) and ester-functionalized trialkoxysilane treating agents (TA1-TA6, 0.47 pbw) were added to a MAX100 cup, followed by Zoco 102 zinc oxide (ZnO, 22.51 pbw, 0.12 μm particle size) and MX-200 alumina trihydrate (ATH, 62.88 pbw, 45 μm particle size). The mixture was placed in a Flacktek Speedmixer and mixed at 2500 rpm for 20 seconds, then mixed by hand with a spatula, and then mixed again at 2500 rpm for 20 seconds. The mixture was transferred to an aluminum pan and heated to 150 °C under vacuum (23 Torr) for 1 hour.

[0026] Table 1 summarizes the materials and amounts (pbw) used to prepare the Examples and Comparative Examples. Treating agents TA-1 to TA-6 are exemplified.

[0027] [ka]

[0028] [Table 1]

[0029] Viscosity measurement Viscosity was measured using an Ares G2 rheometer (TA Instruments) in a parallel plate configuration with a 25 mm diameter serrated steel plate. Care was taken to avoid trapping air in the sample when loading it. Excess material was trimmed from the edge of the fixture with the flat edge of a spatula. Tests were performed using a 1.0 mm gap. Measurements were performed using standard procedures with an oscillation frequency of 10 rad / s, sweeping strain amplitudes from 0.01 to 300 percent with 20 sampling points per decade. All experiments were performed at 25°C. Complex viscosity at 0.1 percent strain, η * was measured.

[0030] Thermal Conductivity Measurement Thermal conductivity was measured using a Hot Disk Instrument TPS 2500 S Hot Disk Instrument and a C5501 sensor according to ISO 22007-2:2015 (Test Method for Determining Thermal Conductivity). Each sample was placed in two cups, with a flat sensor held between the cups. Analysis conditions: fine-tuned analysis, temperature drift compensation and time correction, and calculations selected between 50 and 150 points.

[0031] Table 2 shows the effect of the treatment agent on thermal conductivity (TC) and viscosity at 0.1 percent strain (viscosity).

[0032] [Table 2]

[0033] The example compositions containing the ester-functionalized trimethoxysilane treating agent exhibited lower viscosities than the comparative compositions containing n-dodecyl-trimethoxysilane as the treating agent. In all cases, the example compositions exhibited comparable or superior thermal conductivity.

Claims

1. 1. A composition comprising, based on the weight of the composition, a) 50 to 70 weight percent alumina trihydrate; b) up to 30 weight percent zinc oxide; and c) 0.1 to 2 weight percent of an ester-functionalized trialkoxysilane of Formula 1 or Formula 2; 【Chemistry 1】 where R is C １ ~C １６ Alkyl or C ２ ~C １６ alkenyl, and each R １ are independently １ ~C ６ alkyl, and R ２ is H or methyl and n is 1, 2, or 3; and d) 10 to 20 weight percent of a polysiloxane of Formula 3, 【Chemistry 2】 Here, each R ３ are independently １ ~C ６ alkyl or phenyl, and each R ４ are independently １ ~C ６ Alkyl or C ２ ~C ６ and a polysiloxane, wherein x is 20 to 300.

2. Each R ４ is independently vinyl or methyl, and each R ３ The composition of claim 1, wherein is methyl and x is 50 to 200.

3. 3. The composition of claim 1, wherein the concentration of the alumina trihydrate is in the range of 55 to 68 weight percent, the concentration of the zinc oxide is in the range of 5 to 30 weight percent, the concentration of the vinyl-terminated polydimethylsiloxane is in the range of 12 to 18 weight percent, the concentration of the ester-functionalized trialkoxysilane is in the range of 0.2 to 1 weight percent, and x is 50 to 200, based on the weight of the composition.

4. 4. The composition of claim 3, wherein the concentration of the alumina trihydrate is in the range of 60 to 68 weight percent, the concentration of the zinc oxide is in the range of 20 to 24 weight percent, the concentration of the vinyl-terminated polydimethylsiloxane is in the range of 12 to 16 weight percent, and the concentration of the ester-functionalized trialkoxysilane is in the range of 0.2 to 0.6 weight percent, and x is 100 to 200, based on the weight of the composition.

5. R is C １ ~C １０ Alkyl or C ２ ~C １０ alkenyl, and R １ is methyl, and R ２ The composition of claim 4 , wherein is H and n is 1 or 2.

6. 6. The composition of claim 5, wherein the ester-functionalized trialkoxysilane is represented by a compound selected from the group consisting of: 【Transformation 3】

7. further comprising 0.2 to 10 weight percent of a trimethylsilyl-trimethoxysilyl treating agent of Formula 4, based on the weight of the composition; 【Chemistry 4】 Here, each R ５ are independently １ ~C ６ alkyl, and Y is O or CH ２ -CH ２ and x is 20 to 200, and each R ４ The composition of any one of claims 1 to 6, wherein is vinyl.

8. 8. The composition of claim 7, further comprising a polysiloxane functionalized with at least two Si—H groups and having a degree of polymerization in the range of 5 to 300, wherein the mole to mole ratio of Si—H groups to vinyl groups in said polysiloxane of Formula 3 ranges from 0.2:1 to 2:1.

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