Silicone rubber syntactic foam

Abstract

The present invention relates to a novel silicone rubber syntactic foam and the silicone precursor of said foam.

Claims

1. An addition curing type organopolysiloxane composition X, wherein the addition curing type organopolysiloxane composition X is stored before use as a multi-component RTV comprising at least two separate packages: a) the first package A1 comprising: 100 parts by weight of at least one organopolyosiloxane A of the following formula: ##STR00003## in which: R and R are chosen independently of one another from the group consisting of methyl, ethyl, propyl, trifluoropropyl, and phenyl, R is a C.sub.1 to C.sub.20 alkenyl radical, and n is an integer having a value from 5 to 1000, from 4 to 150 ppm based on metal platinum of a platinum-based hydrosilylation catalyst C, from 5 to 30 parts by weight of hollow glass beads D which are hollow borosilicate glass microspheres, and from 5 to 30 parts by weight of at least one reactive diluent E for reducing the viscosity of the composition and which reacts through hydrosilylation reaction and is chosen from the group consisting of: a silicon compound comprising a single silicon hydride group per molecule, and an organic compound containing a single ethylenically unsaturated group chosen from the group consisting of dodecene, tetradecene, hexadecene, octadecene and a combination of these and all with a terminal vinyl group, and an organopolysiloxane having a single telechelic alkenyl group chosen from the group consisting of vinyl, allyl, hexenyl, decenyl and tetradecenyl, b) the second package A2 comprising: 100 parts by weight of at least one organopolyosiloxane A of the following formula: ##STR00004## in which: R and R are chosen independently of one another from the group consisting of methyl, ethyl, propyl, trifluoropropyl, and phenyl, R is a C.sub.1 to C.sub.20 alkenyl radical, and n is an integer having a value from 5 to 1000, from 10 to 70 parts by weight of a silicon compound B1 comprising two telechelic hydrogen atoms bonded to silicon per molecule, from 5 to 25 parts by weight of a silicon compound B2 comprising at least three hydrogen atoms bonded to silicon per molecule, from 5 to 30 parts by weight of hollow glass beads D which are hollow borosilicate glass microspheres, and an effective amount of at least one cure rate controller G which slows the curing rate; wherein the hydrosilylation catalyst C is not present in the same package with silicon compound B or with reactive diluent E when it is a silicon compound comprising a single silicon hydride group per molecule.

2. The addition curing type organopolysiloxane composition X according to claim 1, wherein the hollow borosilicate glass microspheres have true density ranging from 0.10 gram per cubic centimeter to 0.65 gram per cubic centimeter.

3. The addition curing type organopolysiloxane composition X according to claim 1, wherein the at least one reactive diluent E: is chosen from the group consisting of dodecene, tetradecene, hexadecene, octadecene or a combination of these and all having a terminal vinyl group, or is a liquid organopolysiloxane with formula I ##STR00005## In which: R and R.sup.2 are chosen independently of one another from a C.sub.1 to C.sub.30 hydrocarbon radical, R is chosen from the group consisting of vinyl, allyl, hexenyl, decenyl, and tetradecenyl, and x is between 0 and 100, and is chosen so that it will lower the viscosity of addition curing type organopolysiloxane composition X compared to same composition without the reactive diluent.

4. The addition curing type organopolysiloxane composition X according to claim 1, wherein: the viscosity at 25 C. of said at least one organopolysiloxane A is between 5 mPa.Math.s and 60000 mPa.Math.s; and wherein said silicon compound B1 comprising two telechelic hydrogen atoms bonded to silicon per molecule does not comprise pendent hydrogen atoms bonded to silicon and wherein the viscosity at 25 C. of said silicon compound B1 comprising two telechelic hydrogen atoms bonded to silicon per molecule with no pendent hydrogen atoms bonded to silicon per molecule is between 5 and 100 mPa.Math.s, and wherein the viscosity at 25 C. of said silicon compound B2 comprising at least three hydrogen atoms bonded to silicon per molecule is between 5 and 2000 mPa.Math.s.

5. The addition curing type organopolysiloxane composition X according to claim 1, wherein the viscosities at 25 C. of said at least one organopolysiloxane A and said silicon compounds B1 and B2 are chosen so that the viscosity at 25 C. of the addition curing type organopolysiloxane composition X is between 500 mPa.Math.s to 5000 mPa.Math.s.

6. The addition curing type organopolysiloxane composition X according to claim 1, wherein the proportions in weight of the at least one organopolysiloxane A, the at least one reactive diluent E, and the silicon compounds B1 and B2 are such that the overall molar ratio of the hydrogen atoms bonded to the silicon to the overall alkenyl radicals bonded to the silicon is within a range from 0.35 to 10.

7. A silicone rubber syntactic foam obtained by crosslinking said addition curing type organopolysiloxane composition X as defined in claim 1.

8. The addition curing type organopolysiloxane composition X according to claim 1, wherein the at least one organopolyosiloxane A is at least one organosiloxane A of the following formula: ##STR00006## in which: R and R are each methyl groups, R is a vinyl radical, and n is an integer having a value from 5 to 100.

9. The addition curing type organopolysiloxane composition X according to claim 1, further comprising at least one additive H.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1 and 2 provide a schematic representation of two preferred embodiments of a method for producing an addition curing type organopolysiloxane composition X wherein the inhibitor master batch MI and catalyst master batch MC are separately fed into other components so as to control the curing rate.

(2) FIG. 1 shows a method for producing an addition curing type organopolysiloxane composition X according to one embodiment of the invention wherein said liquid silicone base MS1 is stored in a storage tank 1, said catalyst master batch MC is stored in a storage tank 20, said inhibitor master batch MI is stored in a storage tank 50 and said additive masterbatch MA is stored in a storage tank 65 and are fed separately into their respective feed lines 200, 210, 220 and 230 respectively. The storage tank 1 of the liquid silicone base MS2 is connected to the stirring tank 80 via a feed pump 10, which can be any large displacement pump, and via an optional feed rate adjuster 15. The storage tank 20 of the catalyst master batch MC is connected to the stirring tank 80 via a feed pump 25, which can be any small piston displacement pump, gear pump, micro motion injector pump, or other positive displacement pump, and via an optional feed rate adjuster 30. The storage tank 50 of the inhibitor master batch MI is connected to the stirring tank 80 via a feed pump 55, which can be any small piston displacement pump, gear pump, micro motion injector pump, or other positive displacement pump, and via an optional feed rate adjuster 60. The storage tank 65 of the additive masterbatch MA is connected to the stirring tank 80 via a feed pump 70, which can be any small piston displacement pump, gear pump, micro motion injector pump, or other positive displacement pump, and via an optional feed rate adjuster 75. When said liquid silicone base MS2, said catalyst master batch MC and said inhibitor master batch MI and optionally said additive masterbatch MA are directed into said stirring tank 80; the resulting mixture is mixed preferably by using a high flow, low-shear mixer to yield the addition curing type organopolysiloxane composition X according to the invention. Said composition is now available to be introduced into for example a battery module casing of an electric battery by mean 100 which could be either via an injection apparatus or via a pump to allow free flow to fill the free spaces of said battery module casing and cures via crosslinking.

(3) FIG. 2 shows a method for producing an addition curing type organopolysiloxane composition X according to another embodiment of the invention wherein said liquid silicone base MS2 is stored in a storage tank 1, said catalyst master batch MC is stored in a storage tank 20, said inhibitor master batch MI is stored in a storage tank 50 and said additive masterbatch MA is stored in a storage tank 65 and are fed separately into their respective feed lines 200, 210, 220 and 230 respectively. The storage tank 1 of the liquid silicone base MS2 is connected to the stirring tank 80 via a feed pump 10, which can be any large displacement pump, and via an optional feed rate adjuster 15. The storage tank 20 of the catalyst master batch MC is connected to the stirring tank 80 via a feed pump 25, which can be any small piston displacement pump, gear pump, micro motion injector pump, or other positive displacement pump, and via an optional feed rate adjuster 30. The storage tank 50 of the inhibitor master batch MI is connected to the stirring tank 80 via a feed pump 55, which can be any small piston displacement pump, gear pump, micro motion injector pump, or other positive displacement pump, and via an optional feed rate adjuster 60. The storage tank 65 of the additive masterbatch MA is connected to the stirring tank 80 via a feed pump 70, which can be any small piston displacement pump, gear pump, micro motion injector pump, or other positive displacement pump, and via an optional feed rate adjuster 75. When said liquid silicone base MS2, said catalyst master batch MC and said inhibitor master batch MI and optionally said additive masterbatch MA are directed into said stirring tank 80; the resulting mixture is mixed preferably by using a high flow, low-shear mixer. To said resulting mixture, hollow glass beads D and preferably hollow borosilicate glass microspheres D1 which are stored in storage tank 90, which is preferably a hopper, are transferred into said stirring tank 80 either directly by gravity discharge or via screw feeder 95 to yield addition curing type organopolysiloxane composition X according to the invention. Said composition is now available to be introduced into for example a battery module casing of an electric battery by mean 100 which could be either via an injection apparatus or via a pump to allow free flow to fill the free spaces of said battery module casing and cures via crosslinking.

(4) Other advantages provided by the present invention will become apparent from the following illustrative examples.

EXAMPLES

(5) I) Definition of the Components

(6) Organopolysiloxane A1=polydimethylsiloxane with dimethylvinylsilyl end-units with a viscosity at 25 C. ranging from 80 mPa.Math.s to 120 mPa.Math.s;
Organopolysiloxane A2=polydimethylsiloxane with dimethylvinylsilyl end-units with a viscosity at 25 C. ranging from 500 mPa.Math.s to 650 mPa.Math.s; Organopolysiloxane B1 (CE) as chain extender=polydimethylsiloxane with dimethylsilylhydride end-units with a viscosity at 25 C. ranging from 7 mPa.Math.s to 10 mPa.Math.s and formula: MD.sub.xM In which: D is a siloxy unit of formula (CH.sub.3).sub.2SiO.sub.2/2 M is a siloxy unit of formula (CH.sub.3).sub.2(H)SiO.sub.1/2 and x is an integer ranging from 8 to 11; Organopolysiloxane B2 (XL) as crosslinker, with a viscosity at 25 C. ranging from 18 mPa.Math.s to 26 mPa.Math.s, over 10 SiH reactive groups are present (in average from 16 to 18 SiH reactive groups): poly(methylhydrogeno) (dimethyl)siloxane with SiH groups in-chain and end-chain (/), Hollow glass beads D1: 3M Glass Bubbles Series S15, sold by 3M Company, Particle Size (50%) microns by volume=55 microns, Isostatic Crush Strength: Test Pressure 300 psi (2.07 MPa.), True Density (g/cc)=0.15. Hollow glass beads D2: 3M iM16K Glass Bubbles, sold by 3M Company, (Particle Size (50%) microns by volume=20 microns, Isostatic Crush Strength Test Pressure 16,000 psi, True Density (g/cc)=0.46. Cure rate controller G1: 1,3,5,7-tetramethyl-1,3,5,7-tetravinyl-cyclotetrasiloxane. Cure rate controller G2: 1-Ethynyl-1-cyclohexanol (ECH). Cure rate controller G3-MB: 90% by weight of Organopolysiloxane A1 and 10% by weight of cure rate controller G2. Catalyst C: 10% platinum as Karstedt catalyst in 350 cS dimethylvinyldimer, sold by Johnson Matthey Company. Catalyst C-MB: 98% by weight of Organopolysiloxane A1 and 2% by weight of Catalyst C. Reactive diluent E=1-tetradecene.

(7) TABLE-US-00001 TABLE 1 Inventive two-parts formulation 1 precursor of a silicone rubber syntactic foam Parts by weight Part A Organopolysiloxane A1 81.88 Reactive diluent E 5.03 Catalyst C 0.037 hollow glass beads D1 13.05 Part B Organopolysiloxane A1 81.88 Organopolysiloxane B2 (XL) 8.6 Organopolysiloxane B1 (CE) 53.41 Cure rate controller G1 0.01 hollow glass beads D1 13.05

(8) TABLE-US-00002 TABLE 2 Inventive two-parts formulation 2 precursor of a silicone rubber syntactic foam. Parts by weight Part A Organopolysiloxane A1 78.27 Reactive diluent E 8.62 Catalyst C 0.063 hollow glass beads D1 13.05 Part B Organopolysiloxane A1 69.23 Organopolysiloxane B2 (XL) 2.46 Organopolysiloxane B1 (CE) 15.26 Cure rate controller G1 0.0029 hollow glass beads D1 13.05 For two-parts formulation 1, parts A and B were combined as a 6:1 w/w (weight ratio) to prepare the compositions I before curing For two-parts formulation 2, parts A and B were combined as a 1:1 w/w (weight ratio) to prepare the compositions II before curing

(9) Each composition 1 and 2 were cured at room temperature to yield a silicone rubber syntactic foam comprising a silicone rubber binder and hollow glass beads.

(10) Other formulations were prepared according to the invention and are described in Table 3. Each formulation was cured to yield a silicone rubber syntactic foam according to the invention. Thermal Conductivity (W/mK) and specific gravity (g/cm3) were measured. Thermal conductivity was measured using a Thermtest Hot Disk TPS (Transient Plane Source) 2500S Tester.

(11) TABLE-US-00003 TABLE 2 Inventive two-parts formulations 3, 4 & 5 precursor of a silicone rubber syntactic foam. Mix Ratio 1:1 Formulation 3 Formulation 4 Formulation 5 by weight (Invention) (Invention) (Invention) Part A Organopolysiloxane A2 89.09% 89.09% 89.09% Hollow glass beads D2 9.09% 9.09% 9.09% Catalyst C-MB 1.82% 1.82% 1.82% Total 100.00% 100.00% 100.00% Part B Organopolysiloxane A2 80.627% 78.124% 74.097% Hollow glass beads D2 9.091% 9.091% 9.091% Organopolysiloxane B1 (CE) 8.479% 9.943% 13.640% Reactive diluent E 0.909% 1.818% 1.818% Organopolysiloxane B2 (XL) 0.756% 0.886% 1.216% Cure rate controller G3-MB 0.138% 0.138% 0.138% Total 100.000% 100.000% 100.000% (H as SiH)/Vinyl Molar Ratio 0.72 0.72 1.00 Form when cured Sticky Gel Sticky Gel Gel/Elastomer Thermal Conductivity 0.17 0.18 0.18 W/mK Specific Gravity of the syntactic 0.87 0.87 0.87 foam ASTM D 792, 23 C.