Thermally conductive polyorganosiloxane composition

Abstract

The present invention relates to a thermally conductive polysiloxane composition that provides a cured product having excellent tackiness and flexibility in which the composition contains (A) a thermally conductive filler, (B) a siloxane compound having an alkoxysilyl group and a linear siloxane structure, (C) a polyorganosiloxane having at least two alkenyl groups bonded to silicon atoms per molecule, (D1) a linear polyorganohydrogensiloxane represented by the general formula (4), (D2) a polyorganohydrogensiloxane having per molecule at least three units represented by the general formula (5), and (E) a platinum catalyst.

Claims

1. A thermally conductive polysiloxane composition comprising: (A) a thermally conductive filler; (B) a siloxane compound having an alkoxysilyl group and a linear siloxane structure; (C) a polyorganosiloxane having at least two alkenyl groups bonded to silicon atoms per molecule; (D1) a linear polyorganohydrogensiloxane represented by the following general formula (4): ##STR00017## wherein: R.sup.7 is a hydrogen atom, R.sup.8 is each independently a monovalent hydrocarbon group having no aliphatic unsaturated bond and having 1 to 12 carbon atoms, and f is 1 to 200; (D2) a polyorganohydrogensiloxane having per molecule at least three units represented by the following general formula (5):
R.sup.9.sub.gR.sup.10.sub.hSiO.sub.({4−(g+h)}/2)  (5) wherein: R.sup.9 is each independently a monovalent hydrocarbon group having no aliphatic unsaturated bond and having 1 to 12 carbon atoms, R.sup.10 is a hydrogen atom, g is an integer of 0 to 2, h is an integer of 1 or 2, and g+h is an integer of 1 to 3, with the proviso that a case in which g is 1 and h is 1 is excluded; and (E) a platinum catalyst, wherein (D2) is a polyorganohydrogensiloxane comprising a R.sup.11.sub.2HSiO.sub.1/2 unit, wherein R.sup.11 is synonymous with R.sup.9, and a SiO.sub.4/2 unit, and having at least three hydrogen atoms bonded to silicon atoms per molecule, wherein a ratio ((H.sub.D1+H.sub.D2)/Vi.sub.C) of a sum (H.sub.D1+H.sub.D2) of a number H.sub.D1 of hydrogen atoms bonded to silicon atoms of (D1) and a number H.sub.D2 of hydrogen atoms bonded to silicon atoms of (D2) to a number Vi.sub.C of the alkenyl groups of (C) is 0.85 or less, and wherein a ratio of H.sub.D1:H.sub.D2 is in a range of from 9:1 to 8:2.

2. The thermally conductive polysiloxane composition according to claim 1, wherein (B) is a siloxane compound represented by the following general formula (1): ##STR00018## wherein: R.sup.1 is a group having an alkoxysilyl group having 1 to 4 carbon atoms, R.sup.2 is a linear organosiloxy group represented by the following general formula (2): ##STR00019## wherein: R.sup.4 is each independently a monovalent hydrocarbon group having 1 to 12 carbon atoms, Y is a group selected from the group consisting of a methyl group, a vinyl group, and R.sup.1, and d is an integer of 2 to 500; X is each independently a divalent hydrocarbon group having 2 to 10 carbon atoms, a and b are each independently an integer of 1 or more, c is an integer of 0 or more, a+b+c is an integer of 4 or more, and R.sup.3 is each independently a monovalent hydrocarbon group having 1 to 6 carbon atoms or a hydrogen atom.

3. The thermally conductive polysiloxane composition according to claim 1, wherein (C) is a linear polyorganosiloxane represented by the following general formula (3): ##STR00020## wherein: R.sup.5 is each independently an alkenyl group having 2 to 6 carbon atoms, R.sup.6 is each independently a monovalent hydrocarbon group having 1 to 12 carbon atoms, and e is a number such that the viscosity of 0.01 to 50 Pa.Math.s at 23° C.

Description

EXAMPLES

(1) Hereinbelow, the present invention will be described with reference to the following Examples, which should not be construed as limiting the scope of the present invention. In the following Examples and Comparative Examples, the “part(s)” indicates part(s) by mass.

Examples 1 to 15 and Comparative Examples 1 to 3

(2) The materials used in the examples and the comparative examples are as shown below.

(3) <(A) Thermally Conductive Filler>

(4) AS-40: Alumina having the rounded shape and having the average particle diameter of 12 μm (manufactured by Showa Denko K.K.)

(5) AL43KT: Alumina having the polygonal shape and having the average particle diameter of 4.6 μm (manufactured by Showa Denko K.K.)

(6) AL160SG-4: Easily sinterable alumina having the average particle diameter of 0.55 μm (manufactured by Showa Denko K.K.)

(7) Silazane-treated silica: Silica obtained by treating aerosol silica having the average particle diameter of 200 μm (AEROSIL 200, manufacturer by Nippon Aerosil Co., Ltd.) with hexamethyldisilazane

(8) <(B) Siloxane Compound Having an Alkoxysilyl Group and a Linear Siloxane Structure>

(9) (B1) Cyclic siloxane compound having a polysiloxane chain having a polymerization degree of 70 (compound 1):

(10) ##STR00015##

(11) In a 5,000 mL flask, 1,100 g of 3-(methacryloyloxy)propyltrimethoxysilane was added to a solution of 440 g of toluene and 1,992 g of a cyclic siloxane having three Si—H bonds in the presence of a platinum catalyst. The resultant mixture was subjected to reaction at 120° C. for 3 hours. The solvent was removed from the resultant reaction mixture, followed by distillation, to obtain a colorless liquid.

(12) 1,650 g of a linear vinylpolysiloxane (polysiloxane represented by MD.sub.70M.sup.Vi; manufactured by Momentive Performance Materials Inc.) was added to 77 g of the above-obtained liquid. A platinum catalyst was further added and the resultant mixture was subjected to reaction at 120° C. for 5 hours, obtaining an intended siloxane having the viscosity of 0.20 Pa.Math.s in the form of a colorless oily material.

(13) In the FT IR measurement, disappearance of an absorption peak around 2,150 cm.sup.−1 originated from a Si—H group and presence of an absorption peak around 2,850 cm.sup.−1 originated from a methoxy group were confirmed. In the .sup.1H NMR measurement (at 500 MHz, in CDCl.sub.3), a signal originated from a methoxy group is observed around 3.56 ppm. The area ratio of the signal originated from a methoxy group and the signal appearing around 0.04 ppm originated from a methyl group adjacent to silicon has confirmed that two linear polysiloxane structures in which the number of D units is about 70 are introduced per molecule. From the results of the GPC measurement, a monomodal peak (degree of dispersion: 1.15) was confirmed, and the measured average molecular weight was consistent with the structural formula.

(14) (B2) Cyclic siloxane compound having a polysiloxane chain having a polymerization degree of 30 (compound 2):

(15) ##STR00016##

(16) In a 5,000 mL flask, 1,100 g of vinyltrimethoxysilane was added to a solution of 440 g of toluene and 1,992 g of a cyclic siloxane having two Si—H bonds in the presence of a platinum catalyst. The resultant mixture was subjected to reaction at 120° C. for 3 hours. The solvent was removed from the resultant reaction mixture, followed by distillation, to obtain a colorless liquid. 450 g of a linear vinylpolysiloxane (polysiloxane represented by MD.sub.30M.sup.Vi; manufactured by Momentive Performance Materials Inc.) was added to 77 g of the above-obtained liquid. A platinum catalyst was further added and the resultant mixture was subjected to reaction at 120° C. for 5 hours, obtaining an intended siloxane in the form of a colorless oily material.

(17) In the FT IR measurement, an absorption peak appearing around 2,850 cm.sup.−1 originated from a methoxy group was confirmed. In the .sup.1H NMR measurement (at 500 MHz, in CDCl.sub.3), a signal appearing at 3.56 ppm originated from a methoxy group was observed. The area ratio of the signal originated from a methoxy group and the signal appearing around 0.04 ppm originated from a methyl group adjacent to silicon has confirmed that one linear polysiloxane structure in which the number of D units is about 30 is introduced per molecule. From the results of the GPC measurement, a monomodal peak (degree of dispersion: 1.15) was confirmed, and the measured average molecular weight was consistent with the structural formula.

(18) <(C) Polyorganosiloxane Having at least Two Alkenyl Groups Bonded to Silicon Atoms per Molecule>

(19) (C1) M.sup.ViD.sub.nM.sup.Vi 0.5 Pa.Math.s: α,ω-divinylpolydimethylsiloxane; viscosity 0.5 Pa.Math.s

(20) (C2) M.sup.ViD.sub.nM.sup.Vi 0.1 Pa.Math.s: α,ω-divinylpolydimethylsiloxane; viscosity 0.1 Pa.Math.s

(21) (C3) M.sup.ViD.sub.nM.sup.Vi 1.0 Pa.Math.s: α,ω-divinylpolydimethylsiloxane; viscosity 1.0 Pa.Math.

(22) <(D1) Polyorganohydrogensiloxane>

(23) M.sup.HD.sub.20M.sup.H 0.02 Pa.Math.s: viscosity 0.02 Pa.Math.s

(24) <(D2) Polyorganohydrogensiloxane>

(25) M.sup.H.sub.mQ 0.02 Pa.Math.s: polymethylhydrogen siloxane represented by the average compositional formula M.sup.H.sub.mQ (polymethylhydrogensiloxane consisting of the M.sup.H unit and the Q unit, and having at least three hydrogen atoms bonded to silicon atoms per molecule) (content of the hydrogen atoms bonded to silicon atoms: 1.0 wt. %; number average molecular weight in terms of polystyrene: 800); viscosity 0.02 Pa.Math.s

(26) <Other (D)>

(27) MD.sub.20D.sup.H.sub.20M

(28) <(E) Platinum Catalyst>

(29) Pt-M.sup.ViM.sup.Vi: 1,2-divinyltetramethyldisiloxane complex of platinum

(30) <(F) Reaction Inhibitor>

(31) Surfynol 61 (manufactured by Nissin Chemical Co., Ltd.)

(32) [Preparation of Thermally Conductive Polysiloxane Composition]

(33) (A), (B), and (C) were kneaded in the blended amounts shown in Tables 1 to 3 (part by mass) by a predetermined method using a planetary mixer to obtain a mixture. Then, (D1), (D2), (E), and (F) were added and kneaded by a predetermined method using a planetary mixer to obtain a composition. Note that, in Comparative Example 1, (D2) was not added. In Comparative Example 2, (D1) was not added. In Comparative Example 3, the other (D) was added in place of (D2).

(34) [Properties]

(35) For the composition and the cured product of the composition, the following properties were measured. (1) Viscosity

(36) The viscosity of the composition was measured in accordance with JIS K 6249 by using a B-type rotational viscometer (Vismetron VDH) (manufactured by Shibaura System K.K.) and using No. 7 rotor at 10 rpm, at 23° C. for 1 minute. (2) Hardness

(37) The composition was charged in a mold having the thickness of 6 mm and subjected to heat curing at 70° C. for 30 minutes. The hardness of the cured product of the composition (type E hardness) was measured in accordance with JIS K 6249. (3) Elongation

(38) The composition was charged in a mold having the thickness of 2 mm and subjected to heat curing at 70° C. for 30 minutes. By using the obtained thermally conductive silicone rubber sheet having the thickness of 2 mm, the elongation of the cured product of the composition B was measured in accordance with JIS K 6249. (4) Thermal conductivity

(39) The thermal conductivity of the composition was measured by using a thermal conductivity meter (TPS 1500, manufactured by Kyoto Electronics Manufacturing Co., Ltd.). The composition was charged in a metal container that was made from aluminum and coated with Teflon (registered trademark) and that had the inner diameter of 30 mm and the depth of 6 mm, and subject to heat-curing at 70° C. for 30 minutes. The sensor of the thermal conductivity meter was sandwiched by two produced samples to measure the thermal conductivity (unit: W/(m.Math.K)) of the cured product of the composition. (5) Probe Tack Test

(40) The composition was charged in a metal container that was made from aluminum and coated with Teflon (registered trademark) and that had the size of 60 mm×30 mm and the depth of 6 mm, and heat-cured at 70° C. for 30 minutes. The tackiness of the cured product of the composition B was measured in accordance with JIS Z 0237.

(41) The results are shown in Tables 1 to 3. Each amount of the platinum catalyst in the tables is expressed in terms of a platinum element amount.

(42) TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 6 7 8 (A) AS-40 25 25 25 25 25 25 25 25 AL43KT 50 50 50 50 50 50 50 50 AL160SG-4 25 25 25 25 25 25 25 25 Silazane-treated silica 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 (B) (B1) Compound 1 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 (B2) Compound 2 (C) (C1) M.sup.ViD.sub.nM.sup.Vi 0.5 Pa .Math. s 10.6 10.6 10.6 10.6 10.6 10.6 10.6 10.6 (C2) M.sup.ViD.sub.nM.sup.Vi 0.1 Pa .Math. s (C3) M.sup.ViD.sub.nM.sup.Vi 1.0 Pa .Math. s (D1) M.sup.HD.sub.nM.sup.Vi 0.02 Pa .Math. s 0.96 0.80 0.85 1.00 1.10 0.70 0.74 0.53 (D2) M.sup.H.sub.mQ 0.02 Pa .Math. s 0.015 0.028 0.030 0.035 0.039 0.042 0.045 0.075 Other (D) MD.sub.20D.sup.H.sub.20M (E) Pt-M.sup.ViM.sup.Vi 2 ppm 2 ppm 2 ppm 2 ppm 2 ppm 2 ppm 2 ppm 2 ppm (F) Surfynol 61 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 (H.sub.D1 + H.sub.D2)/Vi.sub.c 0.85 0.80 0.85 1.00 1.10 0.80 0.85 0.85 H.sub.D1:H.sub.D2 9:1 8:2 8:2 8:2 8:2 7:3 7:3 5:5 Viscosity (No. 7 × 10 rpm, type B) 122 124 120 121 119 129 127 130 Hardness (cured at 70° C. for 30 minutes) type E 15 25 45 67 72 51 63 68 Elongation (%) 130 120 60 50 40 60 40 40 Thermal conductivity (W/mK) 2.40 2.39 2.35 2.42 Probe tack test (N) 1.4 1.3 1.6 0.7 0.7 1.0 0.8 0.9

(43) TABLE-US-00002 TABLE 2 Example 9 10 11 12 13 14 15 (A) AS-40 25 25 25 25 25 25 25 AL43KT 50 50 50 50 50 50 50 AL160SG-4 25 25 25 25 25 25 25 Silazane-treated silica 0.4 0.4 0.4 0.4 0.4 0.4 0.4 (B) (B1) Compound 1 1.5 1.5 1.5 1.5 1.5 1.5 1.5 (B2) Compound 2 (C) (C1) M.sup.ViD.sub.nM.sup.Vi 0.5 Pa .Math. s 10.6 (C2) M.sup.ViD.sub.nM.sup.Vi 0.1 Pa .Math. s 10.6 10.6 10.6 (C3) M.sup.ViD.sub.nM.sup.Vi 1.0 Pa .Math. s 10.6 10.6 10.6 (D1) M.sup.HD.sub.nM.sup.Vi 0.02 Pa .Math. s 0.80 1.63 1.75 1.86 0.83 0.87 0.92 (D2) M.sup.H.sub.mQ 0.02 Pa .Math. s 0.028 0.46 0.49 0.52 0.024 0.025 0.026 Other (D) MD.sub.20D.sup.H.sub.20M (E) Pt-M.sup.ViM.sup.Vi 2 ppm 2 ppm 2 ppm 2 ppm 2 ppm 2 ppm 2 ppm (F) Surfynol 61 0.02 0.02 0.02 0.02 0.02 0.02 0.02 (H.sub.D1 + H.sub.D2)/Vi.sub.c 0.80 0.70 0.75 0.80 0.85 0.90 0.95 H.sub.D1:H.sub.D2 8:2 8:2 8:2 8:2 8:2 8:2 8:2 Viscosity (No. 7 × 10 rpm, type B) 75 20 19 18 130 123 115 Hardness (cured at 70° C. for 30 minutes) type E 33 24 36 45 27 35 51 Elongation (%) 120 130 100 50 200 140 90 Thermal conductivity (W/mK) 2.43 2.31 2.30 2.30 2.45 2.44 2.41 Probe tack test (N) 1.5 1.2 1.0 0.7 1.8 1.6 1.5

(44) TABLE-US-00003 TABLE 3 Comparative Example 1 2 3 (A) AS-40 25 25 25 AL43KT 50 50 50 AL160SG-4 25 25 25 Silazane-treated silica 0.4 0.4 0.4 (B) (B1) Compound 1 1.5 1.5 1.5 (C) (C1) M.sup.ViD.sub.nM.sup.Vi 0.5 Pa .Math. s 10.6 10.6 10.6 (D1) M.sup.HD.sub.nM.sup.H 0.02 Pa .Math. s 1.06 0.9 (D2) M.sup.H.sub.mQ 0.02 Pa .Math. s 0.150 Other (D) MD.sub.20D.sup.H.sub.20M 0.13 (E) Pt-M.sup.ViM.sup.Vi 2 ppm 2 ppm 2 ppm (F) Surfynol 61 0.02 0.02 0.02 (H.sub.D1 + H.sub.D2)/Vi.sub.c 0.85 0.85 H.sub.D1:H.sub.D2 10:0 0:10 Viscosity (No. 7 × 10 rpm, type B) 121 140 135 Hardness (cured at 70° C. for 30 minutes) Not 75 50 type E cured Elongation (%) <5 30 Thermal conductivity (W/mK) 2.45 2.31 Probe tack test (N) 0.3 0.5

(45) All of the cured products of the compositions of Examples exhibited excellent flexibility due to their high elongation and exhibited excellent tackiness.

(46) From the comparison of Examples 1, 3, 7, and 8 and the comparison of Examples 6 and 2, when the value H.sub.D1 relative to the sum of H.sub.D1 and H.sub.D2 was greater, higher elongation and superior tackiness were achieved.

(47) From the comparison of Examples 2 to 5, the comparison of Examples 6 and 7, the comparison of Examples 10 to 12, and the comparison of Examples 13 to 15, when the ratio (H.sub.D1+H.sub.D2)/Vi.sub.C was smaller, higher elongation was achieved.

(48) From the comparison of Examples 2 to 5, each of Examples 2 and 3 in which the ratio (H.sub.D1+H.sub.D2)/Vi.sub.C was 0.85 or less exhibited particularly excellent tackiness.

(49) From the comparison of Examples 9 and 11, when the viscosity of (C) was increased, higher elongation and superior tackiness were achieved.

(50) On the other hand, because Comparative Example 1 was a composition containing no (D2), the composition of Comparative Example 1 was not cured. Because Comparative Example 2 was a composition containing no (D1), the elongation of the cured product of the composition of Comparative Example 2 was remarkably insufficient, and the tackiness was poor. Because Comparative Example 3 used, in place of (D2), a crosslinking agent having silicon-bonded hydrogen atoms in the middle units; however, the elongation of the cured product of the composition of Comparative Example 3 was remarkably insufficient, and the tackiness was poor.