Polysiloxane filler treating agent and compositions prepared therewith

Abstract

The present invention provides a filler treating agent comprising: a) a polyorganosiloxane; b) filler particles; and c) a filler treating agent of formula (I): [Case 1] JPEG2025526622000017.jpg42170 In the formula, R 1 , R 1’ , R 2 , R 2’ and a filler treating agent of formula (I), wherein m, n, p, and q are as defined herein. The composition is useful as a thermally conductive formulation.

Description

[Technical Field]

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

[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 0.1 to 5, p is 0 to 5, q is 1 to 6, and X is S or NR 6 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] R 2 ' is the following formula,

[0008] [ka] In the formula, R 3 is H or methyl, and each R 4 are independently C1-C6-alkyl, a is an integer from 1 to 3, and R 5 However, C1~C 12 -alkyl, and R 6 is H or C1-C6 alkyl and the dashed line represents the point of attachment to X; and a filler treating agent of formula I, The present invention addresses a need in the art by providing a composition wherein the polyorganosiloxane has a degree of polymerization in the range of 40-800.

[0009] The compositions of the present invention are useful as thermally conductive formulations. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention provides a composition comprising: a) a polyorganosiloxane; b) filler particles; c) a filler treating agent of formula I,

[0011] [ka] In the formula, m is 5 to 150, n is 0.1 to 5, p is 0 to 5, q is 1 to 6, and X is S or NR 6 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:

[0012] [ka] R 2 ' is the following formula,

[0013] [ka] In the formula, R 3 is H or methyl, and each R 4 are independently C1-C6-alkyl, a is an integer from 1 to 3, and R 5 However, C1~C 12 -alkyl, and R 6 is H or C1-C6 alkyl and the dashed line represents the point of attachment to X; and a filler treating agent of formula I, The composition contains polyorganosiloxane having a degree of polymerization in the range of 40 to 800.

[0014] 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 0.5 or 1 or 1.2 or 1.5 to 5 or 3 or 2, p is 0 or 0.3 or 0.5 to 5 or 3 or 2 or 1, 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 H, and R 4 is preferably methyl or ethyl, more preferably methyl, and a is preferably 2 or 3. Suitable R 5 Examples of groups include methyl, ethyl, n-butyl, t-butyl, n-hexyl, 2-ethylhexyl, and n-octyl groups. 6 is preferably H or ethyl, more preferably H.

[0015] The filler treating agent used in the compositions of the present invention comprises a compound of formula Ia:

[0016] [ka] an acrylate or methacrylate of formula Ib,

[0017] [ka] It can be prepared by contacting in the presence of a coupling catalyst such as dimethylphenylphosphine to prepare a compound of formula I (wherein p is 0 and n' is 0.1 to 10).

[0018] Alternatively, a compound of formula Ia is contacted under the same conditions with a compound of formula Ib and a compound of formula Ic to form

[0019] [ka] A compound of formula I, where p is >0, can be formed.

[0020] 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.

[0021] 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.

[0022] The polyorganosiloxane concentration is preferably in the range of 1.9 or 5% to 15 or 10% by weight based on the weight of the composition, the FTA concentration is preferably in the range of 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 is preferably in the range of 70 or 80 or 85 or 90% to 98 or 94% by weight based on the weight of the composition.

[0023] The formulated compositions of the present invention have been found to have favorable squeeze flow rates, viscosities, extrusion rates, and thermal conductivities. [Example]

[0024] 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).

[0025] 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).

[0026] Example A - General Method for Preparing Sulfide-Linked FTAs GP-71-SS mercapto-functional silicone fluid (15.0 g, 4.5 mmol SH functionality, MW = 6600 g / mol, dp = 83 for Comparative Example 1 and Examples 1-5), 3-(trimethoxysilyl)propyl acrylate (TMSiPA) for Example 1 only, or a mixture of TMPSiPA and butyl acrylate (BA) or octyl acrylate (OA) for Examples 2-5 (4.5 mmol total acrylate functionality in all cases), and dimethylphenylphosphine (6.2 mg, 0.045 mmol) were weighed into a capped glass vial, and the headspace was purged with nitrogen. The reaction mixture was mixed on a vortex mixer for 30 minutes and then held at room temperature for 24 hours. The reaction mixture was then purified by gravity filtration through a plug of neutral alumina (2 g). The product was characterized by SEC and proton NMR spectroscopy. For Examples 6 and 7, GP-800 mercapto-functional silicone fluid (15.0 g, 9.1 mmol SH functionality, MW=8400 g / mol, dp=108) and an acrylate or a mixture of acrylates (9.1 mmol acrylate functionality), and dimethylphenylphosphine (0.091 mmol) were used.

[0027] Example B - General Method for Preparing Amine-Linked FTAs For Example 8, GP-6 amino-functional silicone fluid (15.0 g, 7.5 mmol NH functionality, MW=7900 g / mol, dp=100), TMSiPA (1.8 g, 7.5 mmol), or for Example 9, a mixture of TMSiPA (0.88 g, 0.375 mmol) and OA (0.69 g, 0.375 mmol) was weighed into a capped glass vial and the headspace was purged with nitrogen. For Example 10, a mixture of GP-4 amino-functional silicone fluid (15.0 g, 12.8 mmol NH functionality, MW=4800 g / mol, dp=58), TMSiPA (1.5 g, 6.4 mmol), and OA (1.2 g, 6.4 mmol) was weighed into a capped glass vial and the headspace was purged with nitrogen. The reaction mixture was vortexed for 30 minutes and then held at 100°C for 2 hours. The reaction mixture was then purified by gravity filtration through a plug of neutral alumina (2g). The product was characterized by SEC and proton NMR spectroscopy.

[0028] Table 1 provides a summary of the starting materials and the molar:molar ratios of TMPSiPA:BA or TMPSiPA:OA, where applicable, for Comparative Example 1 and Examples 1-10.

[0029] [Table 1]

[0030] Examples 1-10 - General Procedure for Preparation of Formulations with Alumina Filler The FTA sample (0.16 g) and bis-vinyl terminated polysiloxane (2.80 g, viscosity = 60 mPa.s) were first high speed mixed in a Max-40 mixer cup at 2000 rpm for 30 seconds. This premix fluid (2.96 g) was then mixed with Al-43-BE alumina particles (17.02 g, D 50 CB-A20S alumina particles (17.02 g, D 50= 50 μm) was then added to the formulation and speed mixed at 1300 rpm for 30 seconds. The resulting fully formulated thermogel was then mixed by hand, speed mixed again at 1300 rpm for 30 seconds, transferred to a glass jar, and heated at 150°C under vacuum for 1 hour.

[0031] 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).

[0032] 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.

[0033] 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.

[0034] 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.

[0035] Table 2 shows the squeeze flow rate (SF, Squeeze flow, in mm), viscosity at 0.1% strain (Visc., Viscosity, in Pa·s), and extrusion rate (ER, Extrusion rate, in g / 5 s) at 55 psi for the thermogel samples.

[0036] All FTAs were prepared essentially as described in Examples A and B, except for varying the molar ratio of TMSiPA to BA or TMSiPA to OA. M R refers to the relative moles of TMPSiPA to the moles of BA or OA used to prepare the sample. 5 is either octyl or butyl as shown. DP refers to the degree of polymerization of the FTA.

[0037] 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 2. The thermal conductivity of the comparative gel formulation containing RMS-759 was measured at 3.02 W / m·K, while the thermal conductivity of the example formulations ranged from 2.8 to 3.0 W / m·K. SF, Visc., and ER could not be measured for C1(NM) because a flowable formulation was not obtained.

[0038] [Table 2]

[0039] All of the formulations in Examples 1-10 exhibited acceptable squeeze flow rates, viscosities at 0.1% strain, extrusion rates, and thermal conductivities. The extrusion rates were significantly improved compared to the commercial formulation (C2), as was the viscosity at 0.1% strain. Higher viscosities are advantageous in mitigating filler settling in the composition. The formulations of the present invention also benefit from the ease of preparation of FTAs and the flexibility in tailoring desired properties.

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 0.1 to 5, p is 0 to 5, q is 1 to 6, and X is S or NR ６ 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】 R ２ ' is the following formula, 【Chemistry 3】 In the formula, R ３ is H or methyl, and each R ４ But independently, C １ ~C ６ -alkyl, a is an integer from 1 to 3, and R ５ But C １ ~C １２ -alkyl, and R ６ is H or C １ ~C ６ and a filler treating agent of formula I, wherein X is alkyl and the dashed line represents the point of attachment to X; The composition, wherein the 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, n is 1 to 3, p is 0 to 2, and 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 at a concentration ranging from 85 to 94 weight percent based on the weight of the composition.

4. Each R １ is independently methyl or ethyl, R ５ is methyl, ethyl, n-butyl, t-butyl, n-hexyl, 2-ethylhexyl, or n-octyl, and R ３ The composition of claim 3 wherein is H and q is 2.

5. Each R １ is methyl, and R ５ is methyl, ethyl, n-butyl, t-butyl, n-hexyl, 2-ethylhexyl, or n-octyl, and the polyorganosiloxane is bis(vinyl-di-C １ ~C ６ 5. The composition of claim 4, wherein the polysiloxane is a (-alkyl)-terminated polysiloxane.

6. R ５ 6. The composition of claim 5, wherein n is n-butyl or n-octyl, n is 2, p is 0, the vinyl functionalized polyorganosiloxane is a bis(vinyl-dimethyl) terminated polysiloxane, and the alumina filler particles have a bimodal distribution.

7. The composition of any one of claims 1 to 6, wherein X is S.

8. X is N and R ６ The composition of any one of claims 1 to 6, wherein is H.

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