ELASTOMERIC COMPOSITIONS AND THEIR APPLICATIONS

Abstract

The present disclosure relates to self-sealing silicone sealant and/or gel compositions cured via a condensation cure chemistry and to their use subsequent to cure as puncture-resistant layers in any type of inflatable article, i.e. articles which take their functional shape after inflation with a suitable gas such as air. The present disclosure also relates to silicone materials, e.g. elastomers and/or gels obtained subsequent to curing said compositions designed to function as self-sealing tire puncture material, i.e. to seal puncture holes in the tread region of tires if/when punctured by a foreign body.

Claims

1. A multi-part self-sealing moisture curing silicone sealant composition comprising: (i) at least one condensation curable silyl terminated polymer having at least one, optionally at least 2 hydroxyl functional groups per molecule; (ii) a cross-linker selected from the group consisting of; silanes having at least 2 hydrolysable groups, optionally at least 3 hydrolysable groups per molecule, and/or silyl functional molecules having at least 2 silyl groups, each silyl group containing at least one hydrolysable group; (iii) a condensation catalyst selected from the group consisting of titanates and/or zirconates; and (iv) a filler; wherein polymer (i), cross-linker (ii) and condensation catalyst (iii) are not stored together in a single part; and wherein the molar ratio of total silicon-bonded hydroxyl groups to total hydrolysable groups is between 0.5:1 and 2:1 using a silane containing cross-linker (ii) or 0.5:1 to 10:1 using a silyl functional molecule containing cross-linker (ii) and the molar ratio of condensation catalyst (iii) M-OR functions to the sum of moisture present in the composition, as determined in accordance with ISO 787-2:1981, and total silicon-bonded hydroxyl groups is between 0.01:1 and 0.6:1, where M is titanium or zirconium.

2. The multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 1, wherein the polymer (i) and the cross-linker (ii) viscosity when mixed at 23 C. is at least 40,000 mPa.Math.s.

3. The multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 1, wherein the filler (iv) is selected from the group consisting of fumed and precipitated silicas, calcium carbonate, carbon black, hollow glass beads and/or carbon nanotubes.

4. The multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 3, wherein the filler (iv) is multiwall carbon nanotubes and/or is carbon black.

5. The multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 1, wherein the molar ratio of total silicon-bonded hydroxyl groups to total hydrolysable groups is between 1:1 and 2:1.

6. The multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 1, wherein the composition is stored in two parts, a base part comprising polymer (i) and filler (iv), and a curing part comprising cross-linker (ii) and condensation catalyst (iii).

7. A moisture cured self-sealing silicone sealant for an inflatable article which is the condensation reaction product of the multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 1.

8. A self-sealing inflatable article comprising the moisture cured self-sealing silicone sealant in accordance with claim 7.

9. The self-sealing inflatable article in accordance with claim 8, which is in the form of a tire.

10. The self-sealing inflatable article in accordance with claim 9 comprising: a) a tire body that is made of flexible and airtight material and is adapted to be assembled with a rim; and b) the moisture cured self-sealing silicone sealant adapted to seal a puncture in the tire body.

11. The self-sealing inflatable article in accordance with claim 8, having a puncture-resistant layer, wherein the puncture-resistant layer is a layer of the moisture cured self-sealing silicone sealant.

12. The self-sealing inflatable article according to claim 11, wherein the puncture-resistant layer has a thickness of greater than 0.3 mm.

13. The self-sealing inflatable article according to claim 12, wherein the puncture-resistant layer has a thickness of between 0.5 mm and 10 mm.

14. The self-sealing inflatable article according to claim 11, wherein the puncture-resistant layer is positioned on an internal wall of the inflatable article.

15. (canceled)

16. (canceled)

17. A self-sealing tire produced with the multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 1.

18. The multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 1, wherein polymer (i) has at least 2 hydroxyl functional groups per molecule.

19. The multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 1, wherein cross-linker (ii) is selected from the group consisting of silanes having at least 3 hydrolysable groups per molecule.

Description

EXAMPLES

[0099] All viscosity measurements were made Brookfield cone plate viscometer RV DIII using the most appropriate cone plate at 23 C. unless otherwise indicated.

[0100] For the benefit of the examples the following commercially available tires were purchased and utilized: [0101] Bridgestone Turanza ER300 205/55/16 91 H, [0102] Continental Conti Premium Contact 5 205/55/16 91W, [0103] Goodyear Efficient Grip 205/55/16 91H, [0104] Michelin Energy Saver 205/55/16 91V, and [0105] Pirelli Cinturato P7 205/55/16 91V.

Preparation of Base A

[0106] 73.01 g of Nanocyl NC 7000 carbon nanotubes, 3544.2 g of OH terminated polydimethylsiloxane exhibiting a viscosity of ca 50,000 mPa.Math.s and an number average molecular weight (Mn) of 63,000 g/mol and 382.8 g of Trimethoxysilyl terminated polydimethylsiloxane exhibiting a viscosity of ca 56,000 mPa.Math.s and an number average molecular weight (Mn) of 62,000 g/mol were added in a Neulinger 5 liter mixer. They were initially mixed for 2 minutes using a planetary mixer at 50 rpm, then for a further 15 minutes using the planetary mixer at 50 rpm and the disk at 700 rpm and finally for a further 30 minutes using the planetary mixer at 100 rpm and the disk at 700 rpm. The resulting base product was then unloaded into a pail.

Preparation of Base B

[0107] 1500 g of Evonik Printex A carbon black, 8825 g of OH terminated polydimethylsiloxane exhibiting a viscosity of ca 50,000 mPa.Math.s and an number average molecular weight (Mn) of 63,000 g/mol and 973 g of Trimethoxysilyl terminated polydimethylsiloxane exhibiting a viscosity of ca 56,000 mPa.Math.s and an number average molecular weight (Mn) of 62,000 g/mol were added in a 20 liter pail and was mixed 60 minutes with a Collomix Biax pail mixer.

Preparation of the Mixtures

Example 1

[0108] 24.87 g of Trimethoxysilyl terminated polydimethylsiloxane having a viscosity of ca 56,000 mPa.Math.s and an number average molecular weight (Mn) of 62,000 g/mol and 0.133 g of tetra n-butyl titanate were mixed together with a dental mixer at 2300 rpm for 30 seconds. 250 g of base A was introduced into a plastic container. The pre-mixture of trimethoxysilyl terminated polydimethylsiloxane (viscosity, 56,000 mPa.Math.s) and tetra n-butyl titanate was added into the container and mixed for four periods of 30 seconds in a speed-mixer at 2300 rpm.

Example 2

[0109] 28.85 g of Trimethoxysilyl terminated polydimethylsiloxane having a viscosity of ca 56,000 mPa.Math.s and an number average molecular weight (Mn) of 62,000 g/mol and 0.155 g of tetra n-butyl titanate were mixed together with a dental mixer at 2300 rpm for 30 seconds. 290 g of base 2 was introduced into a plastic container. The pre-mixture of trimethoxysilyl terminated polydimethylsiloxane (viscosity, 56,000 mPa.Math.s) and tetra n-butyl titanate was added into the container and mixed for four periods of 30 seconds in a speed-mixer at 2300 rpm.

Comparative Example 1

[0110] 40.85 g of trimethoxysilyl terminated polydimethylsiloxane exhibiting a viscosity of ca 56,000 mPa.Math.s and an number average molecular weight (Mn) of 62,000 g/mol was premixed with 0.133 g of tetra n-butyl titanate. 250 g of the base A was added into a plastic container. The pre-mixture of trimethoxysilyl terminated polydimethylsiloxane (viscosity, 56,000 mPa.Math.s) and tetra n-butyl titanate was added into the container and mixed for four periods of 30 seconds in a speed-mixer at 2300 rpm.

Comparative Example 2

[0111] 15.89 g of trimethoxysilyl terminated polydimethylsiloxane exhibiting a viscosity of ca 56,000 mPa.Math.s and an number average molecular weight (Mn) of 62,000 g/mol was premixed with 0.133 g of tetra n-butyl titanate. 250 g of base A was added in a plastic container. The pre-mixture of trimethoxysilyl terminated polydimethylsiloxane (viscosity, 56,000 mPa.Math.s) and tetra n-butyl titanate was added into the container and mixed for four periods of 30 seconds in a speed-mixer at 2300 rpm.

[0112] Tabulated details of the compositions of Example 1 and Comparative examples 1 and 2 tested are provided in Table 1. The results of the test on the tires as run below are depicted in Table 2.

Evaluation of Hardness and Storage Modulus

[0113] A TA XT plus texture analyzer was used to monitor the hardness of the cured elastomer. The probe used is a polycarbonate cylinder terminated by a spherical end. The diameter of the probe and sphere is inch (1.27 cm). A return to start program was used. The pretest speed is 5 mm/s and the trigger force is 0.1 g. The test speed is 1 mm/s. the probe is inserted to a distance of 5 mm in the product and then removed to a distance where no significant force is measured. The maximum positive and negative force is measured and reported here. A higher positive force is representative of a harder elastomer. A higher negative force is representative of a more tacky elastomer

Evaluation of Sealing Efficiency

[0114] Holes of 3 mm diameter were cut on the rolling band of the tires with the help of a press and a cutting cylinder. The resulting product of Example 1, 2 and Comparative examples 1 and 2 were respectively filled into 310 ml cartridges and applied onto the inside of the tires and smoothed with a ruler at the designed thickness.

[0115] The products of Example 1, 2 and Comparative examples 1 and 2 were applied at the desired thickness to cover 3 holes in the tire without filling them. After 7 days of cure at 23 C. and 50% relative humidity the tires were mounted on wheels and pressurized at 1 bar (0.1 MPa). Nails of 5 mm diameter were pushed in the 3 mm holes to a distance of 40 mm inside the tire. The pressure was then increased to 2.7 bars (0.27 MPa) and the holes were removed from the tire.

[0116] In the following hours and days the leaking holes were filled with string repair plugs without cement, until no more leaks were observed, using optionally water to track leaks. The tires were kept for two weeks after repair. Results after 14 days without a loss of more than 0.1 bar (0.01 MPa) are reported in table 2. A 3/3 means that no leakage were observed on any of the 3 holes. 0/3 means that all three holes had to be repaired since they leaked.

TABLE-US-00001 TABLE 1 Compositions Compar- Compar- ative ative Exam- Exam- exam- exam- Weight parts ple 1 ple 2 ple 1 ple 2 Part 1 - Base OH terminated 100 100 100 100 polydimethylsiloxane (viscosity ca 50,000 mPa .Math. s) Nanocyl NC 7000 2.06 2.06 2.06 carbon nanotubes Printex A carbon black 17 Trimethoxysilyl terminated 10.8 10.8 10.8 10.8 polydimethylsiloxane (viscosity ca 56,000 mPa .Math. s) Part 2 - Crosslinker and catalyst Trimethoxysilyl terminated 11.2 11.2 18.36 7.2 polydimethylsiloxane (viscosity ca 56,000 mPa .Math. s) tetra n-butyl titanate 0.06 0.06 0.06 0.06 SiOH/SiOR mol content 1.46 1.37 1.10 1.79 Xlinker content (mmol/100 g) 0.29 0.26 0.36 0.24

TABLE-US-00002 TABLE 2 Evaluation results Comparative Comparative Example 1 Example 2 example 1 example 2 Tire (5 mm Tightness of punctures after 2 weeks at thick coating) 2.7 bars (0.27 MPa) Bridgestone 3/3 3/3 3/3 2/3 Continental 3/3 3/3 0/3 0/3 Goodyear 3/3 3/3 1/3 1/3 Michelin 3/3 3/3 2/3 2/3 Pirelli 3/3 3/3 3/3 3/3 Tire (3 mm Tightness of punctures after 2 weeks at thick coating) 2.7 bars (0.27 MPa) Bridgestone 2/3 3/3 2/3 1/3 Continental 3/3 3/3 0/3 0/3 Goodyear 3/3 3/3 2/3 0/3 Michelin 3/3 0/3 0/3 1/3 Pirelli 2/3 3/3 1/3 0/3 Texture analyzer F+ (g) 210 217 290 138 F (g) 100 93 33 77

[0117] Example 1 is showing excellent results for tightness, while Comparative examples 1 and 2 are showing numerous failures in the test. This shows that an appropriate crosslink density is required to obtain a product that will seal tires.

[0118] Texture analyzer results of the examples indicate that a compromise in hardness and tackiness has to be achieved for an appropriate performance in the tire. A too rigid material (Comparative example 1) will not exhibit enough tackiness to be able to close the gap definitely, while a too soft material (Comparative example 2) will not exhibit enough hardness to prevent creep of the material out of the hole. Example 1 and 2 exhibit an appropriate balance of hardness and tackiness to close the gap caused by the nail without exhibiting creep.

[0119] Rheology measurements on Example 1 and Comparative examples 1 and 2 indicate that a temperature range of from 20 to 80 C. has a very limited impact on the storage modulus of the product. This range of temperature is typical of temperature extremes a tire may need to endure during its lifetime in use. This highlights the potential advantage of the silicone technology as a tire sealant over other organic alternatives, which exhibit typically a much higher variation in rheology measurements over this temperature range.