Vulcanizable HNBR composition with high thermal conductivity

Abstract

The present invention relates to vulcanizable compositions comprising hydrogenated nitrile rubber, synthetic graphite and/or aluminium oxide and a crosslinking agent, to vulcanizates thereof and to the use thereof as component.

Claims

1. A vulcanizable composition comprising: (a) 100 parts by weight of at least one hydrogenated nitrile rubber, (b) 150 to 300 parts by weight of at least one aluminium oxide and (c) at least one crosslinking agent.

2. The vulcanizable composition according to claim 1, which further comprises: 20 to 100 parts by weight of at least one synthetic graphite.

3. The vulcanizable composition according to claim 1, wherein the at least one hydrogenated nitrile rubber is (a) a co- or terpolymer containing at least one conjugated diene and at least one ,-unsaturated nitrile monomer and optionally further copolymerizable monomers, in which the copolymerized diene units have been wholly or partly hydrogenated.

4. The vulcanizable composition according to according to claim 2, wherein the synthetic graphite (b) has a D.sub.90 according to DIN 51938 of 70 m or more, preferably 80 m or more and more preferably 81 m.

5. The vulcanizable composition according to claim 2, wherein the synthetic graphite (b) has an ash content to ASTM C561-16 of <0.5%, preferably <0.3%.

6. The vulcanizable composition according to claim 2, wherein the synthetic graphite (b) has a density (Scott density measured as bulk density by means of a Scott volumeter) of 0.01 to 1 g/cm.sup.3.

7. The vulcanizable composition according to claim 2, wherein the synthetic graphite (b) has a D.sub.90 to DIN 51938 of 81 m, an ash content to ASTM C561-16 of <0.3% and a (bulk) density of 0.15 g/cm.sup.3.

8. The vulcanizable composition according to claim 1, wherein the aluminium oxide (b) is coated or uncoated and has a purity of >95%, a BET content of 0.8 to 1.6 m.sup.2/g (measured to DIN ISO 9277:2003-05) and a tamped density of 1 to 3 g/cm.sup.3.

9. The vulcanizable composition according to claim 1, wherein the aluminium oxide (b) is coated.

10. The vulcanizable composition according to claim 15, wherein the at least one crosslinking agent (c) is an organic peroxide selected from: dicumyl peroxide, t-butyl cumyl peroxide, bis(t-butylperoxyisopropyl)benzene, di-t-butyl peroxide, 2,5-dimethylhexane 2,5-dihydroperoxide, 2,5-dimethylhex-3-yne 2,5-dihydroperoxide, dibenzoyl peroxide, bis(2,4-dichlorobenzoyl) peroxide, t-butyl perbenzoate, butyl 4,4-di(t-butylperoxy)valerate and 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane.

11. The vulcanizable composition according to claim 1, wherein the amount of crosslinking agent (c) is 1 to 20 parts by weight, based on 100 parts by weight of the rubbers (a).

12. The vulcanizable composition of claim 2, which comprises: (c) 1 to 20 parts by weight, of at least one crosslinking agent, (d) 0 to 100 parts by weight, of one or more rubber additives, based on 100 parts by weight of the hydrogenated nitrile rubber (a).

13. A vulcanizate formed by the input of energy to a vulcanizable composition of claim 1.

14. A vulcanizate according to claim 13.

15. The vulcanizable composition of claim 1, wherein the crosslinking agent is selected from: a peroxide compound, an aminic crosslinking agent or a sulfur-containing crosslinking agent.

16. The vulcanizable composition of claim 9, wherein the aluminum oxide is coated with an alkylsilane.

17. The vulcanizable composition of claim 12, which comprises 1 to 80 parts by weight of one or more rubber additives.

18. The vulcanizable composition of claim 12, wherein the rubber additives are selected from preferably one or more fillers, one or more filler-activators, one or more ageing stabilizers, and/or one or more mould release agents or processing aids.

19. The vulcanizate according to claim 14, selected from: gaskets, belts and hoses.

Description

EXAMPLES

[0156] Production, Vulcanization and Characterization of the Compositions

[0157] Examples C to H are inventive examples. Examples A* and B* and I* to K* which follow are non-inventive comparative examples. The comparative examples are identified in the tables which follow by an * after the example number.

[0158] The primary mixing unit used was an internal mixer of the GK 1.5 E type (manufacturer: HF Mixing Group). The speed was 40 min.sup.1, the cooling water inlet temperature 40 C. This involved masticating the initial charge of the hydrogenated nitrile rubber (a) for 1 minute, then adding all further components apart from the vulcanization chemicals (peroxide compound and coagent). 3 minutes after commencement of mixing, the plunger was pulled out and brushed. After a mixing time of 250 seconds, the mixture was discharged.

[0159] The peroxide compound and the coagent were mixed in in a second step at about 30 C. on a roll (manufacturer: Trster, roll diameter 20 cm). The friction was 1:1.11. The speed of the roll was controlled here such that stable skins were obtained. Subsequently, vulcanization of these skins was undertaken in slab presses at 180 C. for 15 min.

[0160] Components Used:

TABLE-US-00001 Therban 3627 partly hydrogenated nitrile rubber, ACN content: 36% by weight, Mooney viscosity ML 1 + 4 @100 C.: 66 MU, residual double bond content: max. 2%, available from ARLANXEO Therban 3407 hydrogenated nitrile rubber, ACN content: 34% by weight, Mooney viscosity ML 1 + 4 @100 C.: 70 MU, residual double bond content: max. 0.9%, available from ARLANXEO Therban 3443 VP partly hydrogenated nitrile rubber, ACN content: 34% by weight, Mooney viscosity ML 1 + 4 @100 C.: 39 MU, residual double bond content: max. 4%, available from ARLANXEO Therban 3668 VP partly hydrogenated nitrile rubber, ACN content: 36% by weight, Mooney viscosity ML 1 + 4 @100 C.: 80 MU, residual double bond content: max. 6%; available from ARLANXEO Therban XT VP KA 8889 hydrogenated carboxylated nitrile rubber (terpolymer), ACN content: 33% by weight, Mooney viscosity ML 1 + 4 @100 C.: 77 MU, residual double bond content: 3.5%; available from ARLANXEO Corax N 550 ASTM carbon black; available from Orion Engineered Carbon Corax N 220 ASTM carbon black; available from Orion Engineered Carbon Corax N 990 MT carbon black; available from Orion Engineered Carbon Vulkasil A1 sodium aluminium silicate, available from Rheinchemie Rheinau GmbH Silatherm 1360-8 aluminosilicate, available from HPF Quarzwerke GmbH CFA 50 boron nitride boron nitride, available from 3M Deutschland GmbH TIMREX C-Therm 001 synthetic graphite; D.sub.90 = 81 m (to DIN 51938), ash <0.3% (to ASTM C561-16), available from Imerys, CAS-Nummer: 7782-42-5 Martoxid TM-2410 alkylsilane-coated surface-coated aluminium oxide; purity >99%, BET = 1.2 m.sup.2/g, tamped density = 1.8 g/cm.sup.3; available from Martinswerk (Huber), CAS number: 1344-28-1 Martoxid TM-1410 uncoated aluminium oxide; purity >99%, BET = 1.2 m.sup.2/g, tamped density = 1.8 g/cm.sup.3; vailable from Martinswerk (Huber), CAS number: 1344-28-1 Silquest RC-1 Silane organic silanizing agent, available from Momentive Performance Materials, Inc., Dynasylan 6490 oligomeric siloxane, available from Evonik Industries Dymalink 633 zinc diacrylate, available from Cray Valley Mistron R10 C talc, available from Imerys Maglite DE magnesium oxide, available from CP Hall Vulkanox HS 2,2,4-trimethyl-1,2-dihydroquinoline, polymerized, available from Lanxess Deutschland GmbH Luvomaxx CDPA 4,4-bis(1,1-dimethylbenzyl)diphenylamine, available from Lehmann and Voss Vulkanox MB2 4- and 5-methyl-2-mercaptobenzimidazole; available from Lanxess Deutschland GmbH Aflux18 primary fatty amine, available from Rheinchemie Rheinau GmbH Rhenofit TRIM/S 70% trimethylolpropane trimethacrylate on 30% silica; coagent; available from Rhein Chemie Rheinau GmbH Perkadox 14-40 di(tert-butylperoxyisopropyl)benzene 40% supported on silica, available from Akzo Nobel Polymer Chemicals BV

[0161] The amounts in part by weight stated in the examples are based on 100 parts by weight of the hydrogenated nitrile rubber (a).

[0162] Mooney viscosity is measured according to DIN 53523/3 or ASTM D 1646 at 100 C. for the HNBR-containing mixtures.

[0163] Shore A hardness was measured in accordance with ASTM-D2240-81.

[0164] Elongation at break and tensile strength of the vulcanizates are measured on S2 specimens according to DIN 53504 at room temperature.

[0165] Thermal conductivity is measured by means of a stationary method. This involves holding a 2 mm-thick test specimen at room temperature in contact with a heat source and a temperature sensor until an equilibrium of the heat flow in the test specimen has been established. The measurement is then effected by means of a DTC 300 instrument from TA instruments. Thermal conductivity is then calculated from the calibration factor, the specimen thickness and the temperature drop above

TABLE-US-00002 TABLE 1 Vulcanizable compositions (examples with a * are non-inventive comparative tests) C* D* E* F* G H Examples [pts. by wt.] Therban AT 3443 VP 100 100 100 100 100 100 Corax N 550 5 5 5 5 5 Corax N 220 30 TIMREX C-Therm 001 40 80 120 150 Martoxid TM-2410 150 270 Dynasylan 6490 1 1 1 Maglite DE 3 3 3 3 3 3 Vulkanox HS 1.1 1.1 1.1 1.1 1.1 1.1 Vulkanox MB2 0.3 0.3 0.3 0.3 0.3 0.3 Aflux18 1 1 1 1 1 1 Rhenofit TRIM/S 2 2 2 2 2 2 Perkadox 14-40 5 5 5 5 5 5 PROPERTIES C* D* E* F* G H ML 1 + 4 MU 69.3 117.1 151.4 n.d. 58.6 97.7 Hardness [ShA] 77 87 92 93 60 72 Elongation [%] 423 100 36 23 536 528 at break Tensile [MPa] 9 10.1 16 15.7 12 8.6 strength Thermal [W/m*K] 2.06 3.68 4.44 3.84 2.0 3.32 conductivity Blistering on y y y y n n heating MU = Mooney units; n = no; y = yes; n.d. = not determined (>155.0 MU)

[0166] The tests show that the vulcanizates C to C and G to H have a high thermal conductivity of 2.00 to 4.44 W/m*K.

[0167] Vulcanizates C*, D*, E* and F* comprising only synthetic graphite (Timrex C-THERM 001) as thermally conductive filler, have blistering. Vulcanizates comprising aluminium oxide (Martoxide TM-2410), by contrast, do not have any blistering and are thus preferred.

[0168] The Mooney viscosity (ML 1+4) of the vulcanizable composition increases as the amount of Timrex C-THERM 001 increases. Vulcanizable compositions comprising aluminium oxide, by contrast, have a lower Mooney viscosity than vulcanizable compositions having the same amount of Timrex C-THERM 001. A lower Mooney viscosity results in better processibility of the vulcanizable compositions. Compositions having 150 parts by weight of Timrex C-THERM 001 have an excessively high Mooney viscosity.

[0169] Elongation at break decreases as the amount of Timrex C-THERM 001 increases. Vulcanizates having high amounts of aluminium oxide, by contrast, have high and hence preferred elongation at break.

TABLE-US-00003 TABLE 2 Vulcanizable compositions (comparison) A* B* I* J* K* Examples [pts. by wt.] Therban 3443 VP 100 100 Therban 3407 100 Therban 3627 100 100 Corax N 550 5 5 15 15 Corax N 990 65 Vulkasil A1 5 5 TIMREX C-Therm 001 20 Mistron R10 C 15 CFA 50 boron nitride 80 Silatherm 1360-8 80 Silquest RC-1 Silane 0.5 1 1 Dymalink633 8 Maglite DE 3 3 4 3 3 Vulkanox HS 1.1 1.1 Luvomaxx CDPA 1.5 1.5 1.5 Vulkanox MB2 0.3 0.3 0.3 0.3 0.3 Aflux 18 1 1 Rhenofit TRIM/S 2 2 2.5 2 2 Perkadox 14-40 5 5 8 8 8 PROPERTIES A* B* I* J* K* ML 1 + 4 MU 39.1 55.5 n.d. n.d. n.d. Hardness [ShA] 47 65 78 82 69 Elongation [%] 557 541 197 305 265 at break Tensile [MPa] 24.3 15.3 18.3 14 13.5 strength Thermal [W/m*K] 0.88 1.6 0.5 1.25 0.49 conductivity Blistering on n y y y n heating MU = Mooney units; n = no; y = yes; n.d. = not determined (>155 MU)

[0170] The vulcanizable compositions from Examples A* and B* and I* to K* serve as a comparative test for inventive examples, since these contain no aluminium oxide (Martoxid TM-2410).

[0171] The comparative examples show that vulcanizates A* and B* and I* to K* have a low thermal conductivity of only 0.44 to 1.6 W/m*K.

[0172] The example series also shows that the inventive vulcanizates C to E and G to H have better processibility than comparative examples A* and B* and I* to K*.

TABLE-US-00004 TABLE 3 Vulcanizable compositions L M N O P Examples [pts. by wt. Therban 3443 VP 100 70 100 100 100 Therban XT VP KA 8889 30 Corax N 220 20 20 20 20 20 TIMREX C-Therm 001 60 60 60 60 60 Martoxid TM-2410 200 200 Martoxid TM-1410 200 200 200 Silquest RC-1 Silane 5 Vulkasil N 20 Maglite DE 3 3 3 3 Aflux 18 1 1 1 1 1 Rhenofit TRIM/S 2 2 2 2 2 Perkadox 14-40 9 9 9 9 9 PROPERTIES L M N O P ML 1 + 4 MU 120.68 117.12 137.64 115.7 139.51 Hardness [ShA] 94 94 93 94 95 Elongation [%] 72 59 51 40 51 at break Tensile [MPa] 15.4 15.5 13.9 19 13.8 strength Thermal [W/m*K] 5.0 4.8 5.3 4.7 5.3 conductivity MU = Mooney units

[0173] The examples L, M, N, O and P comprise 100 parts by weight hydrogenated nirtrile rubber (Therban 3443 VP; Therban XT VP KA 8889), 60 party by weight synthetic graphite (TIMREX C-Therm 001) and 200 parts by weight aluminium oxide (Martoxid TM-2410; Martoxid TM-1410).

[0174] The examples show, that all the inventive vulcanizates L to P have a high thermal conductivity of more than 4.5 W/m*K.

[0175] In-situ silanisation (example O) lead to an improved tensile strength.

[0176] The example N comprising non-functionalized aluminum oxide (Martoxid TM-1410) has a slightly improved thermal conductivity compared to example L with functionalized aluminium oxide (Martoxid TM-2410).