TITANIUM-BASED COMPOUNDS AND THEIR APPLICATIONS

Abstract

A process for the preparation of a titanium-based reaction product is provided. The titanium-based reaction product comprises the reaction product of an alkoxy titanium compound and a silanol terminated polydiorganosiloxane. The polydiorganosiloxane typically has at least two silanol groups per molecule. The titanium-based reaction product is also described, as is its use as a catalyst, having improved stability in the presence of water, for condensation curable silicone compositions. The titanium-based reaction product may additionally at least partially replace the need for a separate polymer to be used in the condensation curable silicone compositions.

Claims

1. A method for the preparation of a titanium-based reaction product said method comprising the steps of: (i) mixing a first ingredient, an alkoxy titanium compound having from 2 to 4 alkoxy groups with a second ingredient, a linear or branched polydiorganosiloxane having at least two terminal silanol groups per molecule and a viscosity of from 30 to 300000 mPa.Math.s at 25 C.; (ii) enabling the first and second ingredients to react together by stirring under vacuum to form a reaction product; and (iii) collecting the reaction product of step (ii).

2. The method for the preparation of a titanium-based reaction product in accordance with claim 1, wherein the first ingredient is Ti(OR).sub.4, Ti(OR).sub.3R.sup.1, Ti(OR).sub.2R.sup.1.sub.2 or a chelated alkoxy titanium molecule where there are two alkoxy (OR) groups present and a chelate bound twice to the titanium atom; where R is a linear or branched alkyl group having from 1 to 20 carbons and each R.sup.1 may be the same or different and is selected from an alkyl group, an alkenyl group or an alkynyl group in each case having up to 10 carbons.

3. The method for the preparation of a titanium-based reaction product in accordance with claim 1, wherein the polydialkylsiloxane having at least two terminal silanol groups per molecule of the second ingredient is a dialkylsilanol terminated polydimethylsiloxane.

4. The method for the preparation of a titanium-based reaction product in accordance with claim 1, wherein the second ingredient has a viscosity of between 70 and 20,000 mPa.Math.s at 25 C.

5. The method for the preparation of a titanium-based reaction product in accordance with claim 1, wherein the reaction takes place under vacuum to remove at least 50 wt. %, of the total amount of alcoholic by-products generated during the reaction.

6. The method for the preparation of a titanium-based reaction product in accordance with claim 1, wherein the titanium-based reaction product has a viscosity of between 500 and 1,000,000 mPa.Math.s.

7. The method for the preparation of a titanium-based reaction product in accordance with claim 1, wherein a third ingredient, a polydialkylsiloxane having one terminal silanol per molecule, is introduced in step (i).

8. The method for the preparation of a titanium-based reaction product in accordance with claim 1, wherein in step (i) the first ingredient is added into the second ingredient.

9. The method for the preparation of a titanium-based reaction product in accordance with claim 1, wherein in step (i) the second ingredient is added into the first ingredient.

10. The method for the preparation of a titanium-based reaction product in accordance with claim 1, wherein the main reaction products, when the first ingredient is Ti(OR).sub.4, is a mixture of
(RO).sub.nTi(OSiR.sup.2.sub.2).sub.nOH).sub.4-n(2) where R is a linear or branched alkyl group having from 1 to 20 carbons, each R.sup.2 is independently an organic group, n is 0, 1 or 2, and m is an integer indicative of the viscosity of the second ingredient.

11. The method for the preparation of a titanium-based reaction product in accordance with claim 1, wherein the main reaction products, when the first ingredient is substantially Ti(OR).sub.3R.sup.1, is a mixture of
R.sup.1(RO).sub.aTi((OSiR.sup.2.sub.2).sub.mOH).sub.3-a(4) where R is a linear or branched alkyl group having from 1 to 20 carbons, each R.sup.1 may be the same or different and is selected from an alkyl group, an alkenyl group or an alkynyl group in each case having up to 10 carbons, each R.sup.2 is independently an organic group, a is 0 or 1, and m is an integer indicative of the viscosity of the second ingredient.

12. A titanium-based reaction product which is prepared by the method of claim 1.

13. A titanium-based reaction product obtained or obtainable by the method in accordance with claim 1.

14. A condensation curable silicone elastomer composition comprising the titanium-based reaction product of claim 12.

15. A condensation curable silicone elastomer composition comprising the titanium-based reaction product of claim 13.

Description

EXAMPLES

[0051] All viscosity measurements were made using a Modular Compact Rheometer (MCR) 302 from Anton Paar GmbH of Graz, Austria using a 25 mm diameter rotational plate with a gap of 0.3 mm at a shear rate of 1 s.sup.1. All viscosities were measured at 25 C. unless otherwise indicated. Silanol (SiOH)/Ti molar ratio values given were calculated using the method described above. When vacuum was applied during the process, a vacuum of about 160 mbar (16 kPa) was applied. Where appropriate the mixer lids were pierced with 5 small holes to help the volatile compounds to leave the mixture.

Example 1

[0052] 200 g of dimethylsilanol terminated polydimethylsiloxane having a viscosity of 2,163 mPa.Math.s at 25 C. was introduced into a plastic receptacle of a DAC 600 FVZ/VAC-P type SpeedMixer from Hauschild.

[0053] 0.497 g of tetraisopropoxy titanium was then added into the dimethylsilanol terminated polydimethylsiloxane. A lid was placed on the receptacle and the initial weight of the ingredients, the receptacle and the lid were weighed together.

[0054] The ingredients were then mixed in a DAC 600 FVZ/VAC-P type SpeedMixer from Hauschild for: [0055] 2 minutes at 2350 rpm at atmospheric pressure and then [0056] 2 minutes at 2350 rpm under vacuum and then [0057] left 6 minutes under vacuum without mixing. [0058] This procedure was repeated, i.e., the ingredients were mixed again for a further [0059] 2 minutes at 2350 rpm at atmospheric pressure and then a further 2 minutes at 2350 rpm under vacuum and finally were left for a further period of 6 minutes under vacuum without mixing.

[0060] After completion of the above mixing regime the receptacle, lid and resulting reaction product, were re-weighed to determine weight loss due to the extraction of volatile alcohols. [0061] Initial weight was 277.005 g [0062] Final weight was 276.576 g [0063] Weight loss=0.429 g [0064] The resulting loss of 0.429 g in weight accounts for approximately 100% of the alcohol content extractable as a by-product of the reaction between the tetraisopropoxy titanium (the first ingredient) and the dimethylsilanol terminated polydimethylsiloxane (second ingredient). The calculated SiOH/Ti molar ratio was about 10.4, assuming a number average molecular weight of the polymer of about 22,000 g/mol.

[0065] The viscosity of the titanium-based reaction product generated via the above process was determined to be 47,338 mPa.Math.s using a Modular Compact Rheometer (MCR) 302 from Anton Paar GmbH of Graz, Austria with a 25 mm diameter rotational plate with a gap of 0.3 mm at a shear rate of 1 s.sup.1.

[0066] The titanium-based reaction product was then stored at room temperature in a glass bottle for a period of 28 days before the viscosity was re-measured using the same testing protocol and was found to have remained pretty constant with a minor increase to 48,856 mPa.Math.s.

Example 2

[0067] 200 g of dimethylsilanol terminated polydimethylsiloxane having a viscosity of 2,163 mPa.Math.s at 25 C. was introduced into a plastic receptacle of a DAC 600 FVZ/VAC-P type SpeedMixer from Hauschild.

[0068] 0.592 g of tetraisopropoxy titanium was then added into the dimethylsilanol terminated polydimethylsiloxane. A lid was placed on the receptacle and the initial weight of the ingredients, the receptacle and the lid were weighed together.

[0069] The ingredients were then mixed in a DAC 600 FVZ/VAC-P type SpeedMixer from Hauschild for [0070] 2 minutes at 2350 rpm at atmospheric pressure and then [0071] 2 minutes at 2350 rpm under vacuum and then [0072] left 6 minutes under vacuum without mixing. [0073] This procedure was repeated, i.e., the ingredients were mixed again for a further 2 minutes at 2350 rpm at atmospheric pressure and then a further 2 minutes at 2350 rpm under vacuum and finally were left for a further period of 6 minutes under vacuum without mixing.

[0074] After completion of the above mixing regime, the receptacle, lid and resulting reaction product, were re-weighed to determine weight loss due to the extraction of volatile alcohols. [0075] Initial weight was 277.058 g [0076] Final weight was 276.589 g [0077] Weight loss=0.469 g

[0078] The resulting loss of 0.469 g in weight accounts for approximately 94% of the alcohol content extractable as a by-product of the reaction between the tetraisopropoxy titanium (the first ingredient) and the dimethylsilanol terminated polydimethylsiloxane (second ingredient). The calculated SiOH/Ti molar ratio was about 8.7:1 assuming a number average molecular weight of the polymer of about 22,000.

[0079] The viscosity of the titanium-based reaction product generated via the above process was determined to be 211,700 mPa.Math.s using a Modular Compact Rheometer (MCR) 302 from Anton Paar GmbH of Graz, Austria with a 25 mm diameter rotational plate with a gap of 0.3 mm at a shear rate of 1 s.sup.1.

[0080] The titanium-based reaction product was then stored at room temperature in a glass bottle for a period of 28 days before the viscosity was re-measured using the same testing protocol is and was found to have remained pretty constant with a minor increase to 208,190 mPa.Math.s.

[0081] Example 2 is showing that at a SiOH/Ti ratio below 10, the viscosity of the mixture is greater but there is no problem preparing the titanium-based reaction product.

Example 3

[0082] 200 g of dimethylsilanol terminated polydimethylsiloxane having a viscosity of 70 mPa.Math.s at was introduced into a plastic receptacle of a DAC 600 FVZ/VAC-P type SpeedMixer from Hauschild.

[0083] 3.5 g of tetraisopropoxy titanium was then added into the dimethylsilanol terminated polydimethylsiloxane. A lid was placed on the receptacle and the initial weight of the ingredients, the receptacle and the lid were weighed together.

[0084] The ingredients were then mixed in a DAC 600 FVZ/VAC-P type SpeedMixer from Hauschild for 10 minutes at 2350 rpm under vacuum and then this mixing step was undertaken a further seven times.

[0085] After completion of the above mixing regime the resulting reaction product, receptacle and lid were re-weighed to determine weight loss due to the extraction of volatile alcohols. [0086] Initial weight was 280.082 g [0087] Final weight was 277.481 g. [0088] Weight loss=2.601 g [0089] The resulting loss of 2.601 g in weight again accounts for approximately 88% of the alcohol content extractable as a by-product of the reaction between the tetraisopropoxy titanium (the first ingredient) and the dimethylsilanol terminated polydimethylsiloxane (second ingredient). The calculated SiOH/Ti molar ratio is about 10.3:1, assuming a number average molecular weight of the polymer of about 3,168.

[0090] The viscosity of the titanium-based reaction product generated via the above process was determined to be 617 mPa.Math.s using a Modular Compact Rheometer (MCR) 302 from Anton Paar GmbH of Graz, Austria with a 25 mm diameter rotational plate with a gap of 0.3 mm at a shear rate of 1 s.sup.1.

[0091] The titanium-based reaction product was then stored at room temperature in a glass bottle for a period of 28 days before the viscosity was re-measured using the same testing protocol is and was found to have remained pretty constant at 597 mPa.Math.s.

[0092] Example 3 is showing that a lower viscosity second ingredient can be used successfully and will lead to a lower viscosity reaction product, which can be useful for easy dispensing.

Example 4

[0093] 200 g of dimethylsilanol terminated polydimethylsiloxane having an average viscosity of 803 mPa.Math.s at 25 C. was introduced into a plastic receptacle of a DAC 600 FVZ/VAC-P type SpeedMixer from Hauschild. [0094] 0.8 g of tetraisopropoxy titanium were then added into the dimethylsilanol terminated polydimethylsiloxane. A lid was placed on the receptacle and the initial weight of the ingredients, the receptacle and the lid were weighed together.

[0095] The ingredients were then mixed in a DAC 600 FVZ/VAC-P type SpeedMixer from Hauschild for [0096] 6 minutes at 2350 rpm under vacuum and then this mixing step was undertaken a further four times.

[0097] After completion of the above mixing regime the resulting reaction product, receptacle and lid were re-weighed to determine weight loss due to the extraction of volatile alcohols. [0098] Initial weight was 277.179 g [0099] Final weight was 276.604 g. [0100] Weight loss=0.575 g [0101] The resulting loss of 0.575 g in weight again accounts for approximately 85% of the alcohol content extractable as a by-product of the reaction between the titanate catalyst (the first ingredient) and the linear or branched polydiorganosiloxane (second ingredient). The calculated SiOH/Ti molar ratio is about 9.6:1 assuming an average molecular weight of the polymer of about 14,800.

[0102] The viscosity of the titanium-based reaction product generated via the above process was determined to be 20,237 mPa.Math.s using a Modular Compact Rheometer (MCR) 302 from Anton Paar GmbH of Graz, Austria with a 25 mm diameter rotational plate with a gap of 0.3 mm at a shear rate of 1 s.sup.1.

[0103] The titanium-based reaction product was then stored at room temperature in a glass bottle for a period of 28 days before the viscosity was re-measured using the same testing protocol is and was found to have remained pretty constant with a minor increase to 24,505 mPa.Math.s.

Example 5

[0104] 200 g of dimethylsilanol terminated polydimethylsiloxane having a viscosity of 2,163 mPa.Math.s at 25 C. was introduced into a plastic receptacle of a DAC 600 FVZ/VAC-P type SpeedMixer from Hauschild.

[0105] 0.51 g of tetra n-butoxy titanium were then added into the dimethylsilanol terminated polydimethylsiloxane. A lid was placed on the receptacle and the initial weight of the ingredients, the receptacle and the lid were weighed together.

[0106] The ingredients were then mixed in a DAC 600 FVZ/VAC-P type SpeedMixer from Hauschild for [0107] 2 minutes at 2350 rpm at atmospheric pressure and then [0108] 2 minutes at 2350 rpm under vacuum and then [0109] left 6 minutes under vacuum without mixing. [0110] This procedure was repeated 4 times, i.e., the ingredients were mixed again for a further 2 minutes at 2350 rpm at atmospheric pressure and then a further 2 minutes at 2350 rpm under vacuum and finally were left for a further period of 6 minutes under vacuum without mixing.

[0111] After completion of the above mixing regime the resulting reaction product, receptacle and lid were re-weighed to determine weight loss due to the extraction of volatile alcohols. [0112] Initial weight was 277.01 g [0113] Final weight was 276.6 g [0114] Weight loss=0.41 g [0115] The resulting loss of 0.41 g in weight accounts for approximately 95.2% of the alcohol content extractable as a by-product of the reaction between the titanate catalyst (the first ingredient) and the linear or branched polydiorganosiloxane (second ingredient).

[0116] The viscosity of the titanium-based reaction product generated via the above process was determined to be 54245 mPa.Math.s using a Modular Compact Rheometer (MCR) 302 from Anton Paar GmbH of Graz, Austria with a 25 mm diameter rotational plate with a gap of 0.3 mm at a shear rate of 1 s.sup.1.

[0117] The titanium-based reaction product was then stored at room temperature in a glass bottle for a period of 28 days before the viscosity was re-measured using the same testing protocol is and was found to have increased to 67132 mPa.Math.s.

Example 6

[0118] In this example the titanium-based reaction product was successfully prepared using the less preferred option of introducing the second ingredient into the first ingredient.

[0119] 59.088 g of tetra n butoxy titanium was introduced into a plastic receptacle of a DAC 600 FVZ/VAC-P type SpeedMixer from Hauschild. Then 267.339 g of OH terminated polydimethylsiloxane (viscosity of 70 mPa.Math.s @ 25 C.) were added and mixed for 3 times 2 minutes under vacuum at 2300 rpm.

[0120] 15 g of the here above product was mixed with 15 g Trimethoxysilyl terminated polydimethylsiloxane (viscosity ca 2,000 mPa.Math.s @ 25 C.) in a dental mixer at 3500 rpm for 30 seconds leading to a gelled material in about 30 minutes.

Example 7

[0121] 199.961 g of dimethylsilanol terminated polydimethylsiloxane having a viscosity of 803 mPa.Math.s at 25 C. was introduced into a plastic receptacle of a DAC 600 FVZ/VAC-P type SpeedMixer from Hauschild.

[0122] 1.290 g of tetra t-butoxy titanium were then added into the dimethylsilanol terminated polydimethylsiloxane. A lid was placed on the receptacle and the initial weight of the ingredients, the receptacle and the lid were weighed together.

[0123] The ingredients were then mixed in a DAC 600 FVZ/VAC-P type SpeedMixer from Hauschild for 2 minutes at 2350 rpm without vacuum, then 2 minutes at 2350 rpm under vacuum and 6 minutes under vacuum without stirring. This mixing regime was repeated a further four times.

[0124] After completion of the mixing receptacle, lid and resulting reaction product, were re-weighed to determine weight loss due to the extraction of volatile alcohols. [0125] Initial weight was 277.524 g [0126] Final weight was 276.470 g. [0127] Weight loss=1.054 g
The resulting loss of 1.054 g in weight again accounts for approximately 93.8% of the alcohol content extractable as a by-product of the reaction between the titanate catalyst (ingredient 1) and the polymer (ingredient 2). The calculated SiOH/Ti molar ratio was about 7.1:1 assuming an average molecular weight of the polymer of about 14,800.

Example 8: Partially Trimethylsilyl Terminated OH Terminated PDMS

[0128] In this example component (a) was prepared with the first, second and third ingredients. 200 g of a polydimethylsiloxane having 12.5 mol % trimethylsilyl and 87.5 mol % of dimethylsilanol end groups (viscosity of 12,225 mPa.Math.s @ 25 C.) and 0.217 g of tetraisopropoxy titanium was introduced into a plastic receptacle of a DAC 600 FVZ/VAC-P type SpeedMixer from Hauschild. A lid was placed on the receptacle and the initial weight of the ingredients, the receptacle and the lid were weighed together. The mixture was mixed in a speedmixer for 4 minutes at 2350 rpm under vacuum and then left for 6 minutes under vacuum without mixing. This procedure of mixing was repeated twice.

[0129] After completion of the above mixing regime the resulting reaction product, receptacle and lid were re-weighed to determine weight loss due to the extraction of volatile alcohols. The weight loss was determined to be=0.242 g. The resulting loss of 0.41 g in weight accounts for approximately 100% of the alcohol content extractable as a by-product of the reaction between the titanate catalyst (the first ingredient) and the polymer (the second ingredient).

[0130] The viscosity of the reaction product generated via the above process was determined to be 69,545 mPa.Math.s with an Anton Paar MCR 302 rheometer using a rotational 25 mm plate probe at 25 C. and a shear rate of 1 s.sup.1.

[0131] 30 g of here above prepared product was used to make part A of example 8a adding water parts as mentioned in the table here below using a dental mixer for 30 s at 3500 rpm. 15 g of the preparation was mixed with 15 g of part B in a dental mixer for 30 s at 3500 rpm. The gel time using the same method as previously described was 19 minutes which is much faster than the previously described comparatives.

Comp. Ex. 1

[0132] Usually zirconates function very similarly to titanates but in this instance unexpectedly repeating the process herein with zirconates failed to produce an analogous zirconium reaction product.

[0133] 200.13 g of dimethylsilanol terminated polydimethylsiloxane having a viscosity of 803 mPa.Math.s at was introduced into a plastic receptacle of a DAC 600 FVZ/VAC-P type SpeedMixer from Hauschild.

[0134] 1.345 g of zirconium (IV) n-butoxide 80% in butanol was then added into the dimethylsilanol terminated polydimethylsiloxane. A lid was placed on the receptacle and the initial weight of the ingredients, the receptacle and the lid were weighed together.

[0135] The ingredients were then mixed in a DAC 600 FVZ/VAC-P type SpeedMixer from Hauschild for 6 minutes at 2350 rpm under vacuum. This procedure of mixing was repeated 4 times.

[0136] After completion of the above mixing regime the receptacle, lid and resulting reaction product, were re-weighed to determine weight loss due to the extraction of volatile alcohols. [0137] Initial weight was 277.744 g g [0138] Final weight was 277.567 g [0139] Weight loss=0.177 g

[0140] The resulting loss of 0.177 g is attributed to the butanol solvent from the zirconium catalyst. The initial viscosity of the material was determined to be 1050 mPa.Math.s as measured using a Modular Compact Rheometer (MCR) 302 from Anton Paar GmbH of Graz, Austria with a 25 mm diameter rotational plate with a gap of 0.3 mm at a shear rate of 1 s.sup.1.

[0141] This viscosity is only slightly more than the initial viscosity of the linear or branched polydiorganosiloxane, which is an indication that no reaction occurred.

[0142] Cured Silicone Compositions Using the Titanium-Based Reaction Product Made in Example 1 Above as Catalyst and Polymer

[0143] As previously indicated, the titanium-based reaction product described herein functions as a catalyst in or as a curing agent for curing condensation curable silicone compositions and furthermore, the titanium-based reaction product may additionally replace a proportion or even all the standard silicone polymer utilised in such compositions given the chemically available silanol groups (SiOH) on the terminal positions enabling the titanium-based reaction product herein to participate in the cure process of the silicone composition. The following Table provides the details of a series of compositions prepared using the titanium-based reaction products of the above examples as catalyst and polymer. These are provided merely as evidence of the suitability of the titanium-based reaction product disclosed herein being successful in these roles. The ability of the titanium-based reaction products of the above examples to cure the compositions in the following Tables can be seen from the gel times or non-flow times provided. The amount of each ingredient is provided in parts by weight in each example unless otherwise indicated.

Mixing Method

[0144] The mixtures were prepared using a SpeedMixer DAC 150 FV from Hauschild & Co. KG Germany. The two parts of a two-part composition herein, referred to as Part A and Part B were prepared separately in accordance with Table 1. Part A was the titanium-based reaction product prepared in Example 1 above with the respective ingredients for each part being added to reach 30 g in total at the end of the process and were then mixed for a period of 30 seconds at 3500 revolutions per minute (rpm). Part A and Part B were then mixed together, in a 1:1 weight ratio for a further 30 seconds at 3500 rpm and subsequently the non-flow time for each sample prepared was determined using the following procedure.

Non-Flow Time

[0145] For the purpose of these examples, non-flow time was a manual assessment process at room temperature between 23-25 C. and at 50% relative humidity (RH). The values identified in Table 1 were the time at which point the material stops flowing by visual inspection when the container is inclined by 90 (i.e., vertically).

TABLE-US-00001 TABLE 1a Non-flow times of Several compositions using the Example 1 titanium-based reaction product as catalyst and linear or branched polydiorganosiloxane parts by weight) Ex. 1a Ex. 1b Ex. 1c Ex. 1d Part A Example 1 reaction product 100 100 100 100 Part B Cross-linker 1 100 100 100 100 Water 0.11 0.17 0.40 Non-flow time (min) 11 8 5 300

[0146] Cross-linker 1 (in Wt. %) is trimethoxysilyl terminated polydimethylsiloxane (viscosity ca 2,000 mPa.Math.s).

[0147] In the following case, compositions were made by mixing 30 g of part A with the respective weight of part B as described in the following table. Part A and part B were mixed 30 seconds at 3500 rpm in a dental mixer and the gel time was determined as described herein.

[0148] In the formulations depicted in Table 1b there are two sources for water, the water added in the part B composition but also water present in the fillers when introduced into the composition.

TABLE-US-00002 TABLE 1b Non-flow times of Several compositions containing standard fillers using the Example 1 titanium-based reaction product as catalyst and linear or branched polydiorganosiloxane (parts by weight) Ingredients Ex. 1e Ex. 1f Ex. 1g Ex. 1h Part A Example 1 reaction product 100.3 100.3 100.3 100.3 Aerosil R 974 16.7 26.7 Winnofil SPM 52.18 Fumed Silica CAB-O-SIL 10 LM 150 Part B Trimethoxysilyl terminated 100 100 100 100 polydimethylsiloxane (viscosity ca 2,000 mPa .Math. s) Water 0.23 0.23 0.23 0.23 Non flow time 10 min 13 min 90 min 20 min

[0149] Aerosil R 974 is a hydrophobic fumed silica treated with dimethyldichlorosilanes based on a hydrophilic fumed silica with a specific surface area of 200 m 2/g (supplier information) commercially available from Evonik. WINNOFIL SPM is an ultrafine coated precipitated calcium carbonate commercially available from Imerys. CAB-O-SIL LM-150 is an untreated, low surface area, hydrophilic fumed silica commercially available from the Cabot Corporation.

Cured Silicone Compositions Using the Titanium-Based Reaction Product Made in Example 1 Above as Catalyst and Polymer

[0150] In these examples, the above Example 2 titanium-based reaction product was used as the catalyst/linear or branched polydiorganosiloxane and was mixed with standard silane cross-linkers and it can be seen that short gel times were achieved, irrespective of the cross-linker.

Gel Time

[0151] Gel time is defined as the time at which the storage modulus G and the loss modulus G coincide. The value of G/G is sometimes referred to as tan and the gel point is to be understood to be when tan =G/G=1. The measurements of G and G were undertaken using the aforementioned Modular Compact Rheometer (MCR) 302 from Anton Paar GmbH of Graz, Austria using a 25 mm diameter rotational plate with a gap of 0.3 mm.

[0152] As soon as tan =G/G is equal to (or less than) 1 the curing material is considered to have gelled. Unless otherwise indicated these tests were undertaken at a temperature of 25 C.

[0153] The uncured material is placed in the Modular Compact Rheometer between two plates separated by a gap of 0.3 mm. The upper plate was typically 25 mm in diameter and the excess of material is removed with a tissue or a spatula. A rotary oscillation is carried out at an angular frequency of 10 rad/s and a shear strain of 1%. A measurement is made every 30 seconds initially with a descending logarithmic ramp. For example, after 1500 points, the measurements are carried out every 17.5 min. The gel time is defined as the interval of time between when the product was mixed and when the storage modulus G and loss modulus G coincide, i.e., when tan is equal to or first less than () 1 on the rheometer. This time is roughly equivalent to the time the material under test stops flowing freely.

TABLE-US-00003 TABLE 2a Ex. 2a Ex. 2b Ex. 2c Ex. 2d Ex. 2e Part A Example 2 reaction 101.75 101.75 101.75 101.75 101.75 product water 0.8 0.8 0.8 0.8 0.8 Part B Methyltrimethoxysilane 5.5 Tetraethoxysilane 8.6 50/50 by weight mixture 10 of methyl triacetoxysilane and ethyl triacetoxysilane n-propyl orthosilicate 11 Methyltrioximinosilane 12.2 Gel time G/G at 25 9.2 26 29 69 110 C. (min)

[0154] In Table 3a the titanium-based reaction product of Example 4 above is used as the catalyst and replaces the need for polymer.

TABLE-US-00004 TABLE 3a Ex 4a Ex 4b Part A Example 4 reaction product 100.4 100.4 Water 0 0.14 Part B Trimethoxysilyl terminated polydimethylsiloxane Mixing Mixing (viscosity ca 2,000 mPa .Math. s) ratio 1:1 ratio 1:1 Gel time G/G at 25 C. (min) 30 18

[0155] Part A and part B were mixed after the Example 4 reaction product (i.e., part A) had been aged for 28 days at room temperature and 50% relative humidity (RH) exposure.

[0156] Part B was prepared by mixing stepwise ingredients of the table directly after their addition in a speedmixer for 30 seconds at 2300 rpm.

[0157] The compositions used in the following examples were made by mixing part A and part B together in a speedmixer. The part A and Part B were introduced into a speedmixer and were then mixed for four periods of 30 seconds at a speed of 2300 revolutions per minute (rpm). The resulting mixture was poured into an aluminium cup and onto a glass substrate surface and left to cure for 7 days at room temperature.