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, R1 ', R2, 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 present invention relates to a polysiloxane-based filler treating agent and its use in thermally conductive formulations.

[0002] The increased demand for conductive composites is driving the exploration 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 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, despite the high performance of such FTAs, and other structurally similar FTAs, 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 field of compatibilizers for thermally conductive formulations to explore relatively low-cost FTAs ​​with 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] wherein m is 5 to 150; n is 0.1 to 5; p is 0 to 5; q is 1 to 6; X is S or NR 6 ; Each R 1 Independently for C 1 -C 6 -alkyl, vinyl, phenyl or benzyl; each R 1′ Independently for C 1 -C6 -alkyl;

[0011] R 2 for:

[0012]

[0013] R 2 'for:

[0014]

[0015] Where R 3 is H or methyl; each R 4 Independently for C 1 -C 6 -alkyl; a is an integer from 1 to 3; R 5 It is C 1 -C 12 -alkyl, R 6 Is H or C 1 -C 6 alkyl, and the dotted line indicates the point of attachment to X;

[0016] The degree of polymerization of the polyorganosiloxane is in the range of 40 to 800.

[0017] The composition of the present invention can be used as a thermally conductive preparation. DETAILED DESCRIPTION

[0018] The present invention is a composition comprising:

[0019] a) polyorganosiloxane;

[0020] b) filler particles; and

[0021] c) filler treating agent of formula I:

[0022]

[0023] wherein m is 5 to 150; n is 0.1 to 5; p is 0 to 5; q is 1 to 6; X is S or NR 6 ; Each R 1 Independently for C 1 -C 6 -alkyl, vinyl, phenyl or benzyl; each R 1′ Independently for C 1 -C 6 -alkyl;

[0024] R 2 for:

[0025]

[0026] R2 'for:

[0027]

[0028] Where R 3 is H or methyl; each R 4 Independently for C 1 -C 6 -alkyl; a is an integer from 1 to 3; R 5 It is C 1 -C 12 -alkyl, R 6 Is H or C 1 -C 6 alkyl, and the dotted line indicates the point of attachment to X;

[0029] The degree of polymerization of the polyorganosiloxane is in the range of 40 to 800.

[0030] 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 from 20 or from 50 to preferably 125; preferably n is from 0.5 or from 1 or from 1.2 or from 1.5 to 5 or to 3 or to 2; p is from 0 or from 0.3 or from 0.5 to 5 or to 3 or to 2 or to 1; q is from 1 or from 2 to 6 or to 4; each R 1 Preferably, they are independently C 1 -C 6 - alkyl, more preferably methyl or ethyl, and most preferably methyl; R 3 Preferably H; R 4 It is preferably methyl or ethyl, more preferably methyl; a is preferably 2 or 3. Suitable R 5 Examples of radicals include methyl, ethyl, n-butyl, tert-butyl, n-hexyl, 2-ethylhexyl and n-octyl radicals. 6 Preferably it is H or methyl, more preferably H.

[0031] The filler treating agent used in the composition of the present invention can be prepared by making a compound of formula Ia:

[0032]

[0033] With an acrylate or methacrylate of formula Ib:

[0034]

[0035] The contacting is carried out in the presence of a coupling catalyst such as dimethylphenylphosphine to prepare a compound of formula I, wherein p is 0; n' is 0.1 to 10.

[0036] Alternatively, a compound of formula Ia may be contacted with a compound of formula Ib and a compound of formula Ic under the same conditions:

[0037]

[0038] To form a compound of formula I, wherein p>0.

[0039] The polyorganosiloxane can be functionalized, for example, with one or more crosslinkable groups such as terminal vinyl groups. Examples of such functionalized polyorganosiloxanes include monovinyl-di-C 1 -C 6 -alkyl-terminated polysiloxane and bis(vinyl-di-C 1 -C 6 -alkyl) terminated polysiloxanes, more particularly bis(vinyl-dimethyl) terminated polysiloxanes, which can be prepared as described in US Pat. No. 4,329,273.

[0040] 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.

[0041] The polyorganosiloxane concentration is preferably in the range of from 1.9 wt % or from 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 from 0.1 wt % or from 0.2 wt % or from 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 from 70 wt % or from 80 wt % or from 85 wt % or from 90 wt % to 98 wt % or to 94 wt % based on the weight of the composition.

[0042] The formulated compositions of the present invention have been found to have advantageous extrusion flow rates, viscosities, extrusion rates and thermal conductivity.

[0043] Example

[0044] Size Exclusion Chromatography

[0045] SEC separation is performed on a liquid chromatograph with an Agilent 1260 Infinity II isocratic pump, multicolumn thermostat, integrated degasser, autosampler and refractive index detector. The system is equipped with two PLgel mixed A columns (300 × 7.5 mm inner diameter, particle size = 20 μm) and a guard column (50 × 7.5 mm inner diameter). Column oven and refractive index detector are operated at 40 ° C. The sample injection volume is 100 μL, and THF is used as an eluent to perform separation at a flow rate of 1.0 mL / min. The instrument is calibrated with ten narrow dispersity polystyrene standards from 580 Da to 371,000 Da. Data analysis is performed using Agilent GPC / SEC software package version A.02.01 (Build 9.34851).

[0046] NMR spectroscopy

[0047] NMR spectroscopy was performed using a Bruker Avance III HD500 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 1 H, 7.26 ppm).

[0048] Example A - General Method for Preparing Sulfide-Linked FTA

[0049] 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 to 5), 3- (trimethoxysilyl) propyl acrylate (TMSiPA) alone for Example 1 or a mixture of TMPSiPA and butyl acrylate (BA) or octyl acrylate (OA) for Examples 2 to 5 (total acrylate functionality of 4.5 mmol in all cases), and dimethylphenylphosphine (6.2 mg, 0.045 mmol) were weighed into a capped glass vial; the headspace was purged with nitrogen. The reaction mixture was mixed by a vortex mixer for 30 min and then kept at room temperature for 24 h. 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 acrylate or acrylate mixture (9.1 mmol acrylate functionality) and dimethylphenylphosphine (0.091 mmol) were used.

[0050] Example B - General Method for Preparing Amine-Linked FTAs

[0051] GP-6 amino functional silicone liquid (15.0 g, 7.5 mmol NH 2 Functionality, MW = 7900 g / mol, dp = 100), for Example 8, TMSiPA (1.8 g, 7.5 mmol) or for Example 9, TMSiPA (0.88 g, 0.375 mmol) and OA (0.69 g, 0.375 mmol) were weighed into a capped glass vial; the headspace was purged with nitrogen. GP-4 amino-functional silicone fluid (15.0 g, 12.8 mmol NH 2 Functionality, MW = 4800 g / mol, dp = 58), for Example 10 a mixture of TMSiPA (1.5 g, 6.4 mmol) and OA (1.2 g, 6.4 mmol) was weighed into a capped glass vial; the headspace was purged with nitrogen. The reaction mixture was mixed by a vortex mixer for 30 min and then kept at 100 ° C for 2 h. 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.

[0052] Table 1 provides a summary of the starting materials and the mole:mole ratios of TMPSiPA:BA or TMPSiPA:OA for Comparative Example 1 and Examples 1 to 10 (where applicable).

[0053] Table 1 - Molar ratios of starting materials for FTA samples

[0054]

[0055] Examples 1 to 10 - General Procedure for Preparing Formulations with Alumina Fillers

[0056] First, the FTA sample (0.16 g) and the bis-vinyl terminated polysiloxane (2.80 g, viscosity = 60 mP·s) were mixed in a Max-40 mixer cup at 2000 rpm for 30 s. This premixed fluid (2.96 g) was then mixed with Al-43-BE alumina particles (17.02 g; D 50 =1-2 μm) were combined and mixed at 1300 rpm for 30 s. Then CB-A20S alumina particles (17.02 g; D 50 =50 μm) was added to the formulation and mixed at 1300 rpm for 30 s. The resulting fully formulated thermogel was then mixed manually, mixed again at 1300 rpm for 30 s, and transferred to a glass jar and heated at 150° C. under vacuum for 1 h.

[0057] Squeeze flow measurement

[0058] The squeeze flow test was used to characterize the flow properties of the test formulations containing the FTA samples as follows: The thermally conductive 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 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 D 1 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 sit for 1 min. The diameter after extrusion was recorded as D 2 , and the squeeze flow is calculated as ΔR = (D 2 –D 1 ) / 2(mm).

[0059] Measurement of viscosity at 0.1% strain

[0060] 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 300 s pre-test soak time, the standard procedure of 10 rad / s oscillation frequency was used to measure, with a strain amplitude sweep from 0.01% to 300%, 20 sampling points per decade. The viscosity (low shear rate viscosity) under 0.1% strain was reported.

[0061] Extrusion rate measurement

[0062] The extrusion rate was measured by loading the gel formulation into a 30 mL EFD syringe. The syringe was then attached to the EFD dispensing device and the material was dispensed under nitrogen at 55 Psi for 5 s. The extrusion rate was recorded as the mass dispensed during the 5 s dispensing period as determined using an analytical balance.

[0063] Thermal conductivity measurement

[0064] 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.

[0065] Table 2 shows the squeeze 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.

[0066] All FTAs ​​were prepared essentially as described in Example A and Example B except that the molar ratios of TMSiPA and BA or TMSiPA and OA were varied. M refers to the relative number of moles of TMPSiPA compared to the number of moles of BA or OA used to prepare the sample. 5 It is octyl or butyl. DP refers to the degree of polymerization of FTA.

[0067] RMS-759 refers to DOWSIL TM RMS-759 mono-trimethoxysiloxy-dimethylsiloxane polymer (trademark of 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 to be 3.02 W / m·K; the thermal conductivity of the example formulations was in the range of 2.8 W / m·K and 3.0 W / m·K. The SF, Visc., and ER of C1 could not be measured (not measured (NM)) because a flowable formulation was not obtained.

[0068] Table 2 - Properties of the Thermogel Samples

[0069]

[0070] The formulations of Examples 1 to 10 all exhibit acceptable extrusion flow, viscosity at 0.1% strain, extrusion rate, and thermal conductivity. Compared to the commercially available formulation (C2), the extrusion rate is significantly improved, and the viscosity at 0.1% strain is also significantly improved. The higher viscosity is beneficial to reduce the sedimentation of the filler in the composition. The formulations of the present invention also benefit from the ease of FTA preparation and the flexibility of tuning the properties of interest.

Claims

1. A composition comprising: a) polyorganosiloxane; b) filler particles; and c) filler treating agent of formula I: wherein m is 5 to 150; n is 0.1 to 5; p is 0 to 5; q is 1 to 6; X is S or NR 6 ; Each R 1 are independently C1-C6-alkyl, vinyl, phenyl or benzyl; each R 1′ are independently C1-C6-alkyl; R 2 for: R 2 'for: Where R 3 is H or methyl; each R 4 are independently C1-C6-alkyl; a is an integer from 1 to 3; R 5 C1-C 12 -alkyl, R 6 is H or C1-C6 alkyl, and the dotted line indicates the point of attachment to X; The degree of polymerization of the polyorganosiloxane is in the range of 40 to 800.

2. The composition according to claim 1, wherein Based on the weight of the composition, 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 treatment agent of Formula I is in the range of 0.1 wt % to 3 wt %; 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; n is 1 to 3; 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 aluminum oxide in a concentration ranging from 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; R 5 is methyl, ethyl, n-butyl, tert-butyl, n-hexyl, 2-ethylhexyl or n-octyl; R 3 is H; and q is 2.

5. The composition according to claim 4, wherein each R 1 is methyl; R 5 is methyl, ethyl, n-butyl, tert-butyl, n-hexyl, 2-ethylhexyl or n-octyl; wherein the polyorganosiloxane is a bis(vinyl-di-C1-C6-alkyl)-terminated polysiloxane.

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

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

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

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