Polysiloxane filler treatment agents and compositions prepared therewith

Abstract

The present invention relates to a composition comprising: a) a polyorganosiloxane; b) filler particles; and c) a filler treatment agent of Formula I: wherein R1, R2, m, n, p and q are as defined herein. The composition is useful as a thermally conductive formulation. # imgabs0 #

Description

Background Art

[0001] The invention relates to a filler treating agent based on polysiloxane and application thereof in a thermally conductive preparation.

[0002] The increased demand for conductive composite materials is driving the discovery of thermally conductive formulations that provide more uniform and more efficient heat dissipation from integrated circuits, battery packs, microelectronic circuit systems, and electric motors. The main components of conventional thermally conductive formulations are matrix polymers, inorganic filler particles, and filler treatment agents (FTAs). Inorganic particles are the cheapest components in thermally conductive formulations and provide heat dissipation. Therefore, it is desirable to load and uniformly disperse high levels of filler particles into the matrix polymer; however, uniform dispersion is challenging because the filler particles are generally incompatible with the matrix polymer, resulting in phase separation. FTAs ​​having chemical functional groups that are compatible with both the matrix polymer and the filler particles promote compatibility and improve the dispersibility of the filler particles with the matrix by associating with the surface of the inorganic particles. An example of a commercially available FTA is a monotrimethoxysiloxy-terminated polydimethylsiloxane represented by the following formula:

[0003]

[0004] (See US 7,592,383 B2, column 6). Unfortunately, while this class of FTAs, as well as other structurally similar FTAs, are high performance, they are extremely 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 advantageous in the art of compatibilizing agents for thermally conductive formulations to discover relatively low-cost FTAs ​​that have acceptable performance properties, including extrusion flow, extrusion rate, and viscosity. Summary of the invention

[0005] The present invention solves the need in the art by providing a composition comprising:

[0006] a) polyorganosiloxane;

[0007] b) filler particles; and

[0008] c) filler treating agent of formula I:

[0009]

[0010] Where m is 5 to 150; n is 1 to 3; p is 0 to 3; q is 0 to 8; each R 1 are independently C1-C6-alkyl, vinyl, phenyl or benzyl; each R 1′ are independently C1-C6-alkyl;

[0011] R 2 for:

[0012]

[0013] Where r is 0 to 5; s is 0 or 1; t is 0 to 15; each R 3 are independently C1-C6-alkyl; a is an integer from 1 to 3; wherein the polyorganosiloxane has a degree of polymerization in the range of 40 to 800.

[0014] The composition of the present invention can be used as a thermally conductive preparation. DETAILED DESCRIPTION

[0015] The present invention is a composition comprising:

[0016] a) polyorganosiloxane;

[0017] b) filler particles; and

[0018] c) filler treating agent of formula I:

[0019]

[0020] Where m is 5 to 150; n is 1 to 3; p is 0 to 3; q is 0 to 8; each R 1 are independently C1-C6-alkyl, vinyl, phenyl or benzyl; each R 1′ are independently C1-C6-alkyl;

[0021] R 2 for:

[0022]

[0023] Where r is 0 to 5; s is 0 or 1; t is 0 to 15; each R 3 are independently C1-C6-alkyl; a is an integer from 1 to 3; and the dotted line represents the point of attachment to the alkylene group; wherein

[0024] The polyorganosiloxane has a degree of polymerization ranging from 40 to 800.

[0025] The FTA of formula I is a random copolymer; that is, the structural units with subscripts m, n and p are not necessarily in the order depicted 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 to 2.5 or to 2.2; p is 0 to 3 or to 2 or to 1 or to 0.5; q is 1 or 2 to 6 or to 4; each R 1 Preferably independently C1-C6-alkyl, more preferably methyl or ethyl, and most preferably methyl; R 3 It is preferably methyl or ethyl, more preferably methyl; a is preferably 2 or 3; more preferably 3.

[0026] In one aspect, R 2 Represented by the following groups:

[0027]

[0028] Where t is 0 or 1 or 2 or 3.

[0029] On the other hand, R 2 Represented by the following groups:

[0030]

[0031] wherein q+t is in the range of 0 or 1 or 3 or 5 to 20 or to 14 or to 9.

[0032] The filler treating agent of the present invention can be prepared by making the compound of formula Ia:

[0033]

[0034] wherein x is n+p; and the compound of the following formula Ib:

[0035]

[0036] in the presence of a platinum catalyst and at an elevated temperature to form a compound of formula I, wherein R 2 for:

[0037]

[0038] The filler treating agent can also be prepared by making a compound of formula Ic:

[0039]

[0040] wherein x is n+p; and a compound of formula Id:

[0041]

[0042] In the presence of a platinum catalyst and at an elevated temperature, to form a compound of formula I wherein s is 0 and y is 0 to 25.

[0043] The polyorganosiloxanes can be functionalized, for example, 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 particularly bis(vinyl-dimethyl)-terminated polysiloxanes, which can be prepared as described in US 4,329,273.

[0044] 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 is determined using a HELOS laser diffraction device. 50 The particle size is typically in the range of 0.5 μm to 100 μm.A multimodal (eg, bimodal) distribution of the first filler particles and the second filler particles may be used in the formulation to increase the filler particle concentration.

[0045] The polyorganosiloxane concentration is preferably in the range of 1.9 wt % or 5 wt % to 15 wt % or to 10 wt % based on the weight of the composition; the FTA concentration is preferably in the range of 0.1 wt % or 0.2 wt % or 0.3 wt % to 3 wt % or to 1 wt % or to 0.7 wt % or to 0.5 wt % based on the weight of the composition; and the filler loading is preferably in the range of 70 wt % or 80 wt % or 85 wt % or 90 wt % to 98 wt % or to 94 wt % based on the weight of the composition. The formulated compositions of the present invention have been found to have advantageous extrusion flow rates, viscosities, extrusion rates and thermal conductivity.

[0046] Example

[0047] Size Exclusion Chromatography

[0048] SEC separation was performed on a liquid chromatograph with an Agilent 1260 Infinity II isocratic pump, multicolumn thermostat, integrated degasser, autosampler and refractive index detector. The system was equipped with two PLgel mixed A columns (300 mm × 7.5 mm id, particle size = 20 μm) and a guard column (50 mm × 7.5 mm id). Column oven and refractive index detector were operated at 40 ° C. The sample injection volume was 100 μL, and THF was used as an eluent to perform separation at a flow rate of 1.0 mL / min. The instrument was calibrated with ten narrow dispersity polystyrene standards of 580 Da to 371000 Da. Data analysis was performed using Agilent GPC / SEC software package version A.02.01 (Build 9.34851).

[0049] NMR spectroscopy

[0050] 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 pulse repetition delay of 10 s. Chemical shifts (δ 1H, 7.26 ppm).

[0051] Example A - Preparation of filler treatment agent

[0052]

[0053] The copolymer of formula Ia' and the compound of formula Ib' were mixed at room temperature in a 1:1 molar ratio of vinyl to Si-H groups. Karstedt's catalyst (0.1 mol%, based on vinyl) 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 time the reaction mixture was diluted with CHCl3 and filtered through activated carbon / diatomaceous earth. Volatile substances were removed from the polymer solution, and the product was characterized by SEC and NMR.

[0054] Example B - Preparation of filler treatment agent

[0055]

[0056] 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 reacted, worked up and characterized as described in Example A.

[0057] Example C, Example D, Example E-Preparation of filler treatment agent

[0058]

[0059] Compounds of Formula Ie' and Formula Ib' were mixed at room temperature in 3:1, 3:2 and 1:1 mole to mole ratios of vinyl to Si-H groups to prepare Example C, Example D and Example E.

[0060] Examples 1 to 5 and Comparative Example 1 - Preparation of Formulations Containing FTA

[0061] By mixing FTA (0.23 g) with DOWSIL TM 2-7287 vinyl dimethyl terminated polydimethylsiloxane (5.31 g, viscosity = 80 cP, a trademark of The Dow Chemical Company or its affiliates) and DOWSIL TM CV-119 vinyl dimethyl terminated polydimethylsiloxane (1.79 g, viscosity = 450 cP) was combined in a Max-10 mixing cup and mixed at 2000 rpm for 30 seconds to prepare a formulation. This blend was then mixed with SB 36 alumina trihydrate (7.07 g, D 50=25 μm) were combined in a Max-40 mixing 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 formulated material was then hand-mixed and then mixed again at 1300 rpm for 30 seconds before being transferred to a glass jar and heated at 150° C. for 1 hour under vacuum. The total filler loading of the material was 85.3 wt % and 69.7 vol %.

[0062] Squeeze flow measurement

[0063] The flow properties of the test formulations containing the FTA samples were characterized using the squeeze flow test as follows: The thermally conductive test formulation (0.6 g) was sandwiched between two glass slides (25 mm x 7.5 mm x 1.0 mm, obtained from Thermofisher) and separated by two 1 mm spacers to control the thickness. The top glass slide was manually pressed down 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 block was placed on the top glass and allowed to stand for 1 minute. The diameter after squeezing was recorded as D2, and the squeeze flow was calculated as ΔR = (D2 - D1) / 2 (mm).

[0064] Measurement of viscosity at 0.1% strain

[0065] The test formulation samples were subjected to oscillatory shear strain amplitude sweeps to characterize formulation viscosity and shear thinning behavior. The test formulation samples were loaded onto the Anton Paar high throughput rheometer (AP HT rheometer) using a 25 mm parallel plate geometry. Dressing was performed with an automatic dressing robot with a gap of 1.0 mm. After the soak time before the 300 second test, the standard procedure of 10 rad / s oscillation frequency was used to measure, from 0.01% to 300% strain amplitude sweeps, 20 sampling points per decade. The viscosity (low shear rate viscosity) under 0.1% strain was reported.

[0066] Extrusion rate measurement

[0067] The extrusion rate was measured by loading the gel formulation into a 30 mL EFD syringe. The syringe was then connected to the EFD dispensing device and the material was dispensed for 5 seconds at 55 Psi under nitrogen. The extrusion rate was recorded as the mass dispensed during the 5 second dispensing period, as determined using an analytical balance.

[0068] Thermal conductivity measurement

[0069] Thermal conductivity was measured using a hot plate transient plane source tool (TPS2500S) and a Kapton encapsulated thermal probe. Isotropic volume measurements were performed on 6 mm diameter containers.

[0070] Table 1 shows the extrusion flow (SF, in mm), viscosity at 0.1% strain (Visc., in Pa.s) and extrusion rate at 55 psi (ER, in g / 5s) of the thermogel samples. TM 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 to be 2.3 W / m·K.

[0071] Table 1 - Properties of the Thermogel Samples

[0072] Example No. FTA SF Viscosity ER C1 RMS-759 9.6 61.9 0.46 1 Example A 8.3 88.0 2.3 2 Example B 7.8 88.5 2.4 3 Example C 8.6 108.8 2.0 4 Example D 9.4 194.8 2.9 5 Example E 9.5 243.1 2.3

[0073] The formulations of Examples 1 to 5 exhibited acceptable extrusion flow, viscosity at 0.1% strain, extrusion rate and thermal conductivity. The extrusion rate was significantly improved compared to the commercial formulation (C1). The formulations of the present invention also benefit from the ease of preparation of FTA.

Claims

1. A composition comprising: a) polyorganosiloxane; b) filler particles; and c) filler treating agent of formula I: Where m is 5 to 150; n is 1 to 3; p is 0 to 3; q is 0 to 8; each R 1 are independently C1-C6-alkyl, vinyl, phenyl or benzyl; each R 1′ are independently C1-C6-alkyl; R 2 for: Where r is 0 to 5; s is 0 or 1; t is 0 to 15; each R 3 are independently C1-C6-alkyl; a is an integer from 1 to 3; wherein the polyorganosiloxane has a degree of polymerization in the range of 40 to 800.

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

3. The composition according to claim 2, wherein each R 1 are independently C1-C6-alkyl; p is 0 to 2; q is 2 to 4; each R 1 are independently C1-C6-alkyl; and a is 2 or 3; wherein the filler particles are alumina particles at a concentration in the range of 85 wt % to 94 wt % based on the weight of the composition.

4. The composition according to claim 3, wherein each R 1 are independently methyl or ethyl; And p is 0 or 1.

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

6. A composition according to any one of claims 1 to 5, wherein n is 2 and R 2 It is represented by: wherein t is 0 or 1 or 2 or 3; and p is 0.

7. The composition according to claim 6, wherein t is 0; and each R 3 It is methyl.

8. A composition according to any one of claims 1 to 5, wherein n is 2 and R 2 It is represented by: wherein q+t is in the range of 0 to 20; and p is 0.

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

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

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