Polysiloxane filler treating agent and compositions prepared therewith

Abstract

The present invention relates to a composition comprising a) a polyorganosiloxane, b) filler particles, and c) a filler treating agent of Formula I, wherein R, R, m, n, p, and q are as defined herein. The composition is useful as a thermally conductive formulation. [Formula 1] JPEG2025526625000022.jpg49170

Description

[Technical Field]

[0001] The present invention relates to polysiloxane-based filler treatments and their application in thermally conductive formulations. [Background technology]

[0002] The increasing demand for conductive composite materials has driven the discovery of thermally conductive formulations that provide more uniform and efficient heat dissipation from integrated circuits, battery packs, microelectronic circuits, and electric motors. The main components of conventional thermally conductive formulations are a matrix polymer, inorganic filler particles, and a filler treating agent (FTA). The inorganic particles are the least expensive component in thermally conductive formulations and provide heat dissipation. Therefore, it is desirable to load and uniformly disperse high levels of filler particles in the matrix polymer. However, achieving uniform dispersion is difficult because the filler particles are generally immiscible with the matrix polymer, resulting in phase separation. FTAs, which have chemical functional groups compatible with both the matrix polymer and the filler particles, associate with the surfaces of the inorganic particles, promoting miscibility with the matrix and improving the dispersibility of the filler particles. An example of a commercially available FTA is monotrimethoxysilyloxy-terminated polydimethylsiloxane, represented by the following formula:

[0003] [ka]

[0004] (See U.S. Pat. No. 7,592,383(B2), column 6.) Unfortunately, while this class and other structurally similar FTAs are highly efficient, they are very expensive because they are prepared by multi-step synthetic procedures that require the use of toxic reagents and solvents and numerous purification steps. Therefore, it would be beneficial in the art of compatibilizers for thermally conductive formulations to find relatively low-cost FTAs with acceptable performance characteristics, including squeeze flow rate, extrusion rate, and viscosity. Summary of the Invention

[0005] The present invention provides a composition comprising: a) a polyorganosiloxane; b) filler particles; c) a filler treating agent of formula I,

[0006] [ka] In the formula, m is 5 to 150, n is 1 to 3, p is 0 to 3, q is 0 to 8, and each R 1 is independently C1-C6-alkyl, vinyl, phenyl, or benzyl, and each R 1’ are independently C1-C6-alkyl, R 2 is the following equation:

[0007] [ka] In the formula, r is 0 to 5, s is 0 or 1, t is 0 to 15, and each R 3 is independently C1-C6-alkyl and a is an integer from 1 to 3; and a filler treating agent of Formula I, wherein the polyorganosiloxane has a degree of polymerization in the range of 40 to 800.

[0008] The compositions of the present invention are useful as thermally conductive formulations. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention provides a composition comprising: a) a polyorganosiloxane; b) filler particles; c) a filler treating agent of formula I,

[0010] [ka] In the formula, m is 5 to 150, n is 1 to 3, p is 0 to 3, q is 0 to 8, and each R 1 is independently C1-C6-alkyl, vinyl, phenyl, or benzyl, and each R 1’ are independently C1-C6-alkyl, R 2 is the following equation:

[0011] [ka] In the formula, r is 0 to 5, s is 0 or 1, t is 0 to 15, and each R 3 are independently C1-C6-alkyl, a is an integer from 1 to 3, and the dashed line represents the point of attachment to the alkylene group; and a filler treating agent of Formula I, wherein the polyorganosiloxane has a degree of polymerization in the range of 40 to 800.

[0012] The FTA of Formula I is a random copolymer, i.e., the structural units having subscripts m, n, and p need not be in the order shown in Formula I. Preferably, m is 20 or 50 to preferably 125, preferably n is 1 or 1.5 or 1.8 to 3 or 2.5 or 2.2, p is 0 to 3 or 2 or 1 or 0.5, q is 1 or 2 to 6 or 4, and each R 1 are preferably independently C1-C6-alkyl, more preferably methyl or ethyl, most preferably methyl; R 3 is preferably methyl or ethyl, more preferably methyl; a is preferably 2 or 3, more preferably 3.

[0013] In one aspect, R 2 is represented by the group

[0014] [ka] In the formula, t is 0, 1, 2, or 3.

[0015] In another embodiment, R 2 is represented by the group

[0016] [ka] In the formula, q+t is in the range of 0 or 1 or 3 or 5 to 20 or 14 or 9.

[0017] The filler treating agent of the present invention is a compound of formula Ia

[0018] [ka] wherein x is n+p with a compound of formula Ib:

[0019] [ka] in the presence of a platinum catalyst at elevated temperature to produce a compound of formula I, 2 can be prepared by forming

[0020] [ka]

[0021] The filler treating agent may also be a compound of formula Ic:

[0022] [ka] wherein x is n+p, with a compound of formula Id,

[0023] [ka] in the presence of a platinum catalyst at elevated temperature to form a compound of formula I, wherein s is 0 and y is 0-25.

[0024] The polyorganosiloxane may be functionalized with one or more crosslinkable groups, such as terminal vinyl groups. Examples of such functionalized polyorganosiloxanes include monovinyl-di-C1-C6-alkyl-terminated polysiloxanes and bis(vinyl-di-C1-C6-alkyl)-terminated polysiloxanes, more specifically bis(vinyl-dimethyl)-terminated polysiloxanes, which may be prepared as described in U.S. Pat. No. 4,329,273.

[0025] The filler particles are metal, metal oxide, metal hydrate, or ceramic nitride particles, such as aluminum, aluminum oxide (alumina), aluminum trihydrate, boron nitride, or zinc oxide particles. The D of the filler particles measured using a HELOS laser diffraction device 50 Particle sizes typically range from 0.5 μm to 100 μm. To increase the filler particle concentration, a multimodal (e.g., bimodal) distribution of first and second filler particles can be used in the formulation.

[0026] The polyorganosiloxane concentration preferably ranges from 1.9 or 5% to 15 or 10% by weight based on the weight of the composition, the FTA concentration preferably ranges from 0.1 or 0.2 or 0.3% to 3 or 1 or 0.7 or 0.5% by weight based on the weight of the composition, and the filler loading preferably ranges from 70 or 80 or 85 or 90% to 98 or 94% by weight based on the weight of the composition. The formulated compositions of the present invention have been found to have favorable squeeze flow rates, viscosities, extrusion rates, and thermal conductivities. [Example]

[0027] Size Exclusion Chromatography SEC separations were performed on an Agilent 1260 Infinity II liquid chromatograph equipped with an isocratic pump, a multicolumn thermostat, an integrated degasser, an autosampler, and a refractive index detector. The system was equipped with two PLgel Mixed A columns (300 × 7.5 mm i.d., 20 μm particle size) and a guard column (50 × 7.5 mm i.d.). The column oven and refractive index detector were operated at 40 °C. Sample injection volumes were 100 μL, and separations were performed at a flow rate of 1.0 mL / min using THF as the eluent. The instrument was calibrated with 10 narrow-dispersity polystyrene standards ranging from 580 to 371,000 Da. Data analysis was performed using the Agilent GPC / SEC software package, version A.02.01 (build 9.34851).

[0028] NMR spectroscopy NMR spectroscopy was performed using a Bruker Avance III HD 500 spectrometer equipped with a 5 mm Prodigy BBO CryoProbe (Billerica, MA). Proton spectra were acquired with a 10 s pulse repetition delay. Chemical shifts were determined from residual solvent protons (δ ) in CDCl3. 1 H, 7.26 ppm).

[0029] Example A - Preparation of Filler Treatment

[0030] [ka]

[0031] The copolymer of Formula Ia' and the compound of Formula Ib' were mixed at room temperature in a vinyl to Si-H molar ratio of 1:1. Karstedt's catalyst (0.1 mol % based on vinyl groups) was added to the mixture, and the temperature was raised to 120°C. After 2 hours, the mixture was cooled to room temperature, after which the reaction mixture was diluted with CHCl3 and filtered through activated carbon / Celite. The volatiles in the polymer solution were removed, and the product was characterized by SEC and NMR.

[0032] Example B - Preparation of Filler Treatment

[0033] [ka]

[0034] The copolymer of formula Ic' and the compound of formula Id' were mixed at room temperature in a 1:1 molar ratio of vinyl to Si-H groups, and the reaction, work-up, and characterization were carried out as described in Example A.

[0035] Examples C, D, E - Preparation of Filler Treatment Agents

[0036] [ka]

[0037] Examples C, D, and E were prepared by mixing compounds of Formula Ie' and Formula Ib' at room temperature in mole to mole ratios of vinyl to Si-H groups of 3:1, 3:2, and 1:1.

[0038] Examples 1-5 and Comparative Example 1 - Preparation of Formulations Containing FTA A formulation was prepared by combining FTA (0.23 g) with DOWSIL™ 2-7287 vinyldimethyl-terminated polydimethylsiloxane (5.31 g, viscosity = 80 cP, trademark of The Dow Chemical Company or its affiliates) and DOWSIL™ CV-119 vinyldimethyl-terminated polydimethylsiloxane (1.79 g, viscosity = 450 cP) in a Max-10 mixer cup and mixing at 2000 rpm for 30 seconds. This blend was then mixed with SB 36 alumina trihydrate (7.07 g, D 50 = 25 μm) in a Max-40 mixer cup and mixed at 1300 rpm for 30 seconds. Maxfil MX200 alumina trihydrate (35.57 g, D 50= 45 μm) was added to the formulation and mixed at 1300 rpm for 30 seconds. The blended material was then mixed by hand, then mixed again at 1300 rpm for 30 seconds, and then transferred to a glass jar and heated at 150°C under vacuum for 1 hour. The total filler loading of the material was 85.3% by weight and 69.7% by volume.

[0039] Measurement of squeeze flow rate A squeeze flow test was used to characterize the flow properties of test formulations containing FTA samples as follows: Thermal conductivity test formulation (0.6 g) was sandwiched between two glass slides (25 × 75 × 1.0 mm, obtained from Thermofisher) and separated by two 1 mm shims to control thickness. The top glass slide was pressed down by hand to ensure uniform spreading of the material, and the initial diameter of the material was recorded as D1. The 1 mm spacer was then removed from the test sample, and a 350 g mass was placed on the top glass and allowed to sit for 1 minute. The post-squeezing diameter was recorded as D2, and the squeeze flow rate was calculated as ΔR = (D2 - D1) / 2 (mm).

[0040] Viscosity measurement at 0.1% strain To characterize formulation viscosity and shear thinning behavior, oscillatory shear strain amplitude sweeps were performed on test formulation samples. Test formulation samples were loaded onto an Anton Paar High Throughput Rheometer (AP HT Rheometer) using a 25 mm parallel plate geometry. Trimming was performed at 1.0 mm intervals using an automated trimming robot. After a 300 s pre-test soak time, measurements were performed using a standard procedure with an oscillatory frequency of 10 rad / s, sweeping strain amplitudes from 0.01 to 300% with 20 sampling points per decade. Viscosity at 0.1% strain (low shear rate viscosity) was reported.

[0041] Extrusion speed measurement The extrusion rate was measured by loading the gel formulation into a 30 mL EFD syringe. The syringe was then attached to an EFD dispenser and the material was dispensed under nitrogen at 55 psi for 5 seconds. The extrusion rate was recorded as the mass dispensed during the 5 second dispense period, as determined using an analytical balance.

[0042] Thermal Conductivity Measurement Thermal conductivity was measured using a Hot Disk transient planar source tool (TPS 2500S) and a Kapton-coated thermal probe. Isotropic bulk measurements were performed in a 6 mm diameter vessel.

[0043] Table 1 shows the squeeze flow rate (SF, in mm), viscosity at 0.1% strain (Visc., in Pa·s), and extrusion rate (ER, in g / 5 sec) at 55 psi for the thermogel samples. RMS-759 refers to DOWSIL™ RMS-759 mono-trimethoxysiloxy-dimethylsiloxane polymer (a trademark of The Dow Chemical Company or its affiliates), which is the FTA used in Comparative Example 1. The thermal conductivity of all formulations was measured at 2.3 W / m·K.

[0044] [Table 1]

[0045] The formulations of Examples 1-5 exhibited acceptable squeeze flow rates, viscosities at 0.1% strain, extrusion rates, and thermal conductivities. The extrusion rates were significantly improved compared to the commercially available formulation (C1). The formulations of the present invention also benefit from the ease of preparation of FTAs.

Claims

1. 1. A composition comprising: a) a polyorganosiloxane; b) filler particles; and c) a filler treating agent of formula I, 【Chemical 1】 In the formula, m is 5 to 150, n is 1 to 3, p is 0 to 3, q is 0 to 8, and each R １ But independently, C １ ~C ６ - alkyl, vinyl, phenyl, or benzyl, and each R １’ But independently, C １ ~C ６ - alkyl, R ２ is the following equation: 【Chemistry 2】 In the formula, r is 0 to 5, s is 0 or 1, t is 0 to 15, and each R ３ But independently, C １ ~C ６ a filler treating agent of Formula I, wherein a is -alkyl and a is an integer from 1 to 3, and said polyorganosiloxane has a degree of polymerization in the range of 40 to 800.

2. 10. The composition of claim 1, wherein the concentration of the polyorganosiloxane is in the range of 1.9 to 15 wt. %, the concentration of the filler particles is in the range of 70 to 98 wt. %, the concentration of the filler treating agent of Formula I is in the range of 0.1 to 3 wt. %, and the filler particles are aluminum, alumina, aluminum trihydrate, boron nitride, or zinc oxide particles, based on the weight of the composition.

3. Each R １ But independently, C １ ~C ６ -alkyl, p is 0 to 2, q is 2 to 4, and each R １ But independently, C １ ~C ６ -alkyl, a is 2 or 3, and the filler particles are alumina particles at a concentration ranging from 85 to 94 weight percent based on the weight of the composition.

4. Each R １ The composition of claim 3 , wherein is independently methyl or ethyl and p is 0 or 1.

5. Each R １ is methyl, m is 50 to 125, n is 1.8 to 2.2, and each R ３ 5. The composition of claim 4, wherein: is methyl; p is from 0 to 0.5; and the alumina filler particles are present as a bimodal distribution of first alumina filler particles and second alumina filler particles.

6. n is 2, and R ２ is expressed by the following equation: 【Chemistry 3】 The composition according to any one of claims 1 to 5, wherein t is 0 or 1 or 2 or 3 and p is 0.

7. t is 0, and each R ３ The composition of claim 6 wherein is methyl.

8. n is 2, and R ２ is expressed by the following equation: 【Chemistry 4】 6. The composition of claim 1, wherein q+t ranges from 0 to 20 and p is 0.

9. 9. The composition of claim 8, wherein q+t is in the range of 3 to 14.

10. 9. The composition of claim 8, wherein q+t is in the range of 5 to 9.

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