TWO-PART CONDENSATION CURABLE SILICONE COMPOSITIONS AND THEIR APPLICATIONS

Abstract

Two-part condensation curable silicone compositions and their applications are provided. Also provided is a new titanium-based reaction product, which, because of its incorporation as a catalyst, is able to provide compositions having both improved stability in the presence of water and accelerated cure processes when compared to conventional titanium catalysts. The titanium-based reaction product is obtained or obtainable from a process 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 polymer having at least two terminal silanol groups per molecule; (ii) enabling the first and second ingredients to react together by stirring under vacuum to form a reaction product; and collecting the reaction product of step (ii).

Claims

1. A two-part condensation curable silicone composition comprising: I) a first part comprising or consisting of: (a) a titanium-based reaction product obtained or obtainable from a process 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 polymer having at least two terminal silanol groups per molecule; (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); and II) a second part comprising or consisting of: (b) one or more silicon containing compounds having at least 2, optionally at least 3, hydroxyl and/or hydrolysable groups per molecule; and wherein either the first part, or the second part, or the first and second parts contains (c) a source of water comprising water, hydrated reinforcing inorganic filler, hydrated non-reinforcing inorganic filler or a mixture thereof.

2. The two-part condensation curable silicone composition in accordance with claim 1, wherein the first ingredient in the method for the preparation of component (a) 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 two-part condensation curable silicone composition in accordance with claim 1, wherein the second ingredient in the method for the preparation of component (a) is a dialkylsilanol terminated polydimethylsiloxane.

4. The two-part condensation curable silicone composition 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 two-part condensation curable silicone composition in accordance with claim 1, wherein the method for the preparation of component (a) utilises a third ingredient, a polydialkylsiloxane having one terminal silanol group per molecule, which is introduced in step (i).

6. The two-part condensation curable silicone composition in accordance with claim 1, wherein component (b) is selected from silanes having at least 2 hydrolysable groups, optionally at least 3 hydrolysable groups per molecule or an organopolysiloxane polymer having at least two hydroxyl or hydrolysable groups per molecule of the formula
X.sub.3-n′R.sup.3.sub.n′Si—(Z).sub.d—(O).sub.q—(R.sup.4.sub.ySiO.sub.(4-y)/2).sub.z—(SiR.sup.4.sub.2—Z).sub.d—Si—R.sup.3.sub.n′X.sub.3-n′  (7) in which each X is independently a hydroxyl group or a hydrolysable group, each R.sup.3 is an alkyl, alkenyl or aryl group, each R.sup.4 is an X group, alkyl group, alkenyl group or aryl group and Z is a divalent organic group; d is 0 or 1, q is 0 or 1 and (d+q)=1; n′ is 0, 1, 2 or 3, y is 0, 1 or 2, optionally y is 2, and z is an integer such that the organopolysiloxane polymer has a viscosity of from 50 to 150,000 mPa.Math.s at 25° C.

7. The two-part condensation curable silicone composition in accordance with claim 1, wherein component (c) is water.

8. The two-part condensation curable silicone composition in accordance with claim 7, wherein component (c) is present in a molar ratio of 0.3:1 to 1:1 with respect to the molar content of hydrolysable groups.

9. The two-part condensation curable silicone composition in accordance with claim 1, wherein the first part and/or second part of the composition includes one or more additives selected from the group consisting of anhydrous fillers, adhesion promoters, rheology additive, flux agents, acid acceptors, thermally or electrically conductive additives, salts, dyes, perfumes, preservatives, plasticizers, active ingredients, colorants, labeling agents, rust inhibitors, anti-microbial compounds, detergents, water phase stabilizing agents, pH controlling agents, pigments, colorants, UV absorbers, sunscreen agents, dyes, fragrances or perfume, antioxidants, soil release agents, oxidizing agents, reducing agents, propellant gases, dispersibility aids, inorganic salts, antibacterial agents, antifungal agents, bleaching agents, sequestering agents, enzymes, diluents, and mixtures thereof.

10. The two-part condensation curable silicone composition in accordance with claim 7, wherein component (c) is present in one or other or in both of the first part or second part of the composition.

11. A process for preparing the two-part condensation curable silicone composition in accordance with claim 1, said process comprising: providing the first part; and providing the second part.

12. A cured material which is the reaction product of the two-part condensation curable silicone composition in accordance with claim 1.

13. A method of making the cured material in accordance with claim 12, said method comprising mixing the first and second parts together and curing.

14. The process for preparing the two-part condensation curable silicone composition in accordance with claim 11, further comprising mixing the first and second parts together.

Description

EXAMPLES

[0105] 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 1s.sup.−1. All viscosities were measured at 25° C. unless otherwise indicated. All mixtures in the Tables are indicated in parts by weight.

[0106] Regarding the preparation of component (a), silanol (Si—OH)/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

[0107] A component (a) titanium-based reaction product was the first prepared. 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. 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.

[0108] The ingredients were then mixed in the Hauschild DAC 600 FVZ/VAC-P SpeedMixer™ for 2 minutes at 2350 rpm at atmospheric pressure and then 2 minutes at 2350 rpm under vacuum and then left 6 minutes under vacuum without mixing. This mixing regime was repeated.

[0109] After completion of the above mixing regime the SpeedMixer® receptacle, lid and resulting reaction product, were re-weighed to determine weight loss due to the extraction of volatile alcohols. The weight loss was determined to be=0.429 g. The resulting loss of 0.429 g in weight accounted for approximately 100% of the alcohol content extractable as a by-product of the reaction between the first and second ingredients. The calculated Si—OH/Ti molar ratio was about 10.4, assuming a number average molecular weight of the polymer of about 22,000.

[0110] The viscosity of the 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 using a 25 mm diameter rotational plate with a gap of 0.3 mm at a shear rate of 1s.sup.−1.

[0111] 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 48,856 mPa.Math.s. This was then used as the pat A composition in (Ex. 1a-1c) below.

Compositions Prepared as Described in Table 1

Mixing Method

[0112] The part B composition was separately prepared in accordance with the compositions indicated in Table 1 below and then the Part A and Part B were then mixed together, in a 1:1 weight ratio for a 30 seconds at 3500 rpm using a SpeedMixer™ DAC 150 FV from Hauschild & Co. KG Germany and subsequently the non-flow time for each sample prepared was determined using the following procedure. Comparative examples were prepared using the compositions indicated and were mixed using the same process.

Non-Flow Time

[0113] For the purpose of these examples, non-flow time was a manual assessment process at room temperature and 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 1 two-part condensation curable silicone compositions made using the reaction product of example 1 above (Ex. 1a-1c) and comparatives (C. 1a-1e) Ex. Ex. Ex. C. C. C. C. C. 1a 1b 1c 1a 1b 1c 1d 1e Part A Ex. 1 reaction product 100 100 100 100 OH terminated polydimethylsiloxane 100 100 100 100 (viscosity ca 2,163 mPa .Math. s) Water 0.12 0.19 0.42 Part B Component (b) 1 100 100 100 100 100 100 100 100 TiPT 0.25 0.25 0.25 0.25 Water 0.11 0.17 0.4 Non-flow time (min) 11 8 5 120 40 32 27 300

[0114] In the above Table and hereafter component (b) 1 is Trimethoxysilyl terminated polydimethylsiloxane (viscosity ca 2,000 mPa.Math.s) and TiPT is tetraisopropoxy titanium.

[0115] It can be seen that component (a) effectively replaces the standard polymer and catalyst in the composition. It is believed that the chains resulting from the second ingredient are chemically preventing water from hydrolyzing the attacking the titanium molecule, and consequently no additional polymer is required as component (a) the titanium-based reaction product is fully involved in the cure process. Furthermore, it was noticed that the use of component (a) resulted in Examples 1a, 1b, 1c exhibiting a very fast gel time in comparison to the comparative examples.

Example 2

[0116] An alternative component (a) titanium-based reaction product was prepared. 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. 0.592 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.

[0117] The ingredients were then mixed in a DAC 600 FVZ/VAC—P type SpeedMixer™ from Hauschild for 2 minutes at 2350 rpm at atmospheric pressure and then 2 minutes at 2350 rpm under vacuum and then left 6 minutes under vacuum without mixing. This procedure was then repeated.

[0118] 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=0.469 g. The resulting loss of 0.469 g in weight again accounts for approximately 94% 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). The calculated Si—OH/Ti molar ratio was about 8.7:1 assuming a number average molecular weight of the polymer of about 22,000.

[0119] 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 using a 25 mm diameter rotational plate with a gap of 0.3 mm at a shear rate of 1s.sup.−1.

[0120] The 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 208,190 mPa.Math.s.

Example 3

[0121] A further component (a) titanium-based reaction product was prepared. 200 g of dimethylsilanol terminated polydimethylsiloxane having a viscosity of 70 mPa.Math.s at 25° C. was introduced into a plastic receptacle of a DAC 600 FVZ/VAC—P type SpeedMixer™ from Hauschild. 3.5 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.

[0122] 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.

[0123] 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. The weight loss was determined to be=2.601 g. 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 titanate catalyst (the first ingredient) and the polymer (the second ingredient). The calculated Si—OH/Ti molar ratio is about 10.3:1, assuming an average molecular weight of the polymer of about 3,168.

[0124] The viscosity of the 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 1s.sup.−1.

[0125] The 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 597 mPa.Math.s.

[0126] Example 3 is showing that a lower viscosity OH polymer can be used successfully and will lead to a lower viscosity reaction product (a), which can be useful for easy dispensing.

Example 4

[0127] 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. 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.

[0128] The ingredients were then mixed in a DAC 600 FVZ/VAC—P type SpeedMixer™ from Hauschild for 6 minutes at 2350 rpm under vacuum and then this mixing step was repeated a further four times.

[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=0.575 g. The resulting loss of 0.575 g in weight 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 polymer (the second ingredient). The calculated Si—OH/Ti molar ratio was about 9.6:1 assuming an average molecular weight of the polymer of about 14,800.

[0130] The viscosity of the reaction product generated via the above process was determined to be 20,237 mPa.Math.s. The viscosity may be measured using a Modular Compact Rheometer (MCR) 302 from Anton Paar GmbH of Graz, Austria a 25 mm diameter rotational plate with a gap of 0.3 mm at a shear rate of 1s.sup.−1.

[0131] 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 an increase to 24,505 mPa.Math.s.

[0132] After the viscosity of the aged reaction products was completed, water was added and mixed into the reaction product for 30 second at 3500 rpm using a SpeedMixer™ DAC 150 FV from Hauschild & Co. KG Germany in the amounts indicated in Table 2a. Comparative examples were generated using the same mixing protocol but involved the addition of a standard catalyst where indicated.

TABLE-US-00002 TABLE 2a Part A compositions of two-part condensation curable silicone compositions containing reaction product of Ex. 4 and comparatives Ex 4a Ex 4b C. 4a C. 4b C. 4c C. 4d Part A Ex. 4 reaction product 100.4 100.4 OH terminated polydimethylsiloxane 100 100 (viscosity of 803 mPa .Math. s @ 25° C.) Trimethylsiloxy terminated 100 100 polydimethylsiloxane (viscosity 1090 mPa .Math. s @ 25° C.) TiPT 0.4 0.4 0.4 0.4 Water 0 0.14 0.14* 0.14** 0 0.14* Measured viscosity initial 20237 20665 5495 1959 3806 1265 Measured viscosity after aging 24505 23360 1905 1482 1772 1873 for 28D at 25° C. & 50% RH In the above Table *indicates the water was added after TiPT and **indicates that water was added before the TiPT.

[0133] Table 2a is showing the part A compositions and variation of viscosity between immediate measurements and measurements after aging for 28 days and that the pre-reaction of the polymer with the catalyst is protecting the titanium from both hydrolysis from added water as well as aging for a period of 28 days at 50% relative humidity.

[0134] The viscosity variation after 28 days is an indication of the loss of activity of the several comparative examples which use standard titanium catalystswhich are at least partially hydrolysed with water and moisture. Comparative examples C. 4a and C. 4b are showing that the reaction between the first and second ingredients for making component (a) leads to a significant viscosity drop and will lead to a drop of activity which results in longer gel time as indicated in Table 2b below.

[0135] The mixtures/reaction products identified from Table 2a were then used in a 1:1 weight ratio with part B, which in this case was component (b) 1 (Trimethoxysilyl terminated polydimethylsiloxane (viscosity ca 2,000 mPa.Math.s)). The part A composition was introduced into one cylinder of a 1:1 mixing unit having side by side cylinders. The other cylinder was filled with Trimethoxysilyl terminated polydimethylsiloxane (viscosity ca 2,000 mPa.Math.s). The material was then extruded through a static mixer and was allowed to cure with the gel time being determined using the following procedure.

Gel Time

[0136] 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 δ and the gel point is to be understood to be when tan δ=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.

As soon as tan δ is equal to or is less than 1, the curing material is considered to have gelled. Unless otherwise indicated these tests were undertaken at a temperature of 25° C.

[0137] 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. 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 δ 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 2b Part B compositions of two-part condensation curable silicone compositions containing reaction product of Ex. 4, as seen in Table 2a, and comparatives Ex 4a Ex 4b C. 4a C. 4b C. 4c C. 4d Component (b) 1 100 100 100 100 100 100 (in Wt. %) Mixing Ratio (wt.) 1:1 1:1 1:1 1:1 1:1 1:1 Gel time G′/G″ 30 18 162 232 260 Not curing at 25° C. (min)

[0138] Comparative example C. 4c is showing that the use of a trimethylsiloxy terminated polydimethylsiloxane in place of a silanol terminated polydimethylsiloxane in the part A composition leads to a further loss of activity, while comparative example C. 4d is showing that the titanium catalyst gets totally deactivated if water is added to the mixture, which shows no protective effect of such polymers in comparison with examples 4a and 4b.

Example 5

[0139] A series of examples were prepared using the compositions depicted in Tables 3a (part A) and 3b (part B).

TABLE-US-00004 TABLE 3a Assorted Part A compositions of two-part condensation curable silicone compositions Ingredients Ex. 5a Ex. 5b Ex. 5c Ex. 5d Ex. 5e Ex. 5f OH terminated 100 100 100 polydimethylsiloxane (viscosity ca 2,000 mPa .Math. s @ 25° C.) OH terminated 100 100 polydimethylsiloxane (viscosity ca 13,500 mPa .Math. s @ 25° C.) OH terminated 100 polydimethylsiloxane (viscosity ca 70 mPa .Math. s @ 25° C.) TnBT 0.3 1.3 TiPT 0.075 0.075 0.3 0.3

[0140] The following process was used to make the component (a) reaction product for Ex. 5a. The same process was used to prepare the part A compositions of Ex. 5b to Ex. 5f.

[0141] 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. 0.51 g of tetra n-butyloxy 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.

[0142] The ingredients were then mixed in a in a DAC 600 FVZ/VAC—P type SpeedMixer™ from Hauschild for 2 minutes at 2350 rpm at atmospheric pressure and then 2 minutes at 2350 rpm under vacuum and then left 6 minutes under vacuum without mixing. This procedure was then repeated for a further 4 times.

[0143] 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=0.41 g. 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 polymer (the second ingredient).

[0144] The viscosity of the reaction product generated via the above process was determined to be 54245 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.

[0145] The 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 67132 mPa.Math.s.

[0146] A part B composition was then prepared as indicated in Table 3b and the resulting part A composition was then mixed and used in the weight ratio indicated in Table 3b with part B, which in this case was component (b) 1 and water added as indicated. The material was then extruded through a static mixer to measure the non-flow time as described above.

TABLE-US-00005 TABLE 3b Assorted Part B compositions of two-part condensation curable silicone compositions showing enhanced and comparatives Ingredients Ex. 5a Ex. 5b Ex. 5c Ex. 5d Ex. 5e Ex. 5f Part B Mix 5:1 5:1 10:1 1:1 5:1 10:1 ratio (weight A:B) Component (b) 100 100 100 100 100 100 1 in wt. %) Water 0.8 0.25 0.25 0.25 0.25 0.25 Non flow time 45 min 120 min 120 min 60 min 22 min 180 min

[0147] The cured materials resulting from the compositions prepared formed soft gels that typically cure over a period of 24 hours until the non flow time when cured with standard titanium catalysts such as TiPT and tetra n-butyl titanate (TnBT), but it will be seen that they cure remarkably faster when using component (a) reaction products as described herein.

Example 6

[0148] This example describes the preparation of a component (a) reaction product using the less preferred option of introducing the second ingredient into the first ingredient.

[0149] 59.088 g of tetra n butoxy titanium was added into a plastic receptacle of a DAC 600 FVZ/VAC—P type SpeedMixer™ from Hauschild. 267.339 g of an OH terminated polydimethylsiloxane (viscosity of 70 mPa.Math.s @ 25° C.) was then added and the mixture was mixed for three 2-minute periods under vacuum at 2300 rpm. 15 g of the resulting component (a) reaction product was mixed with 15 g of trimethoxysilyl terminated polydimethylsiloxane (viscosity ca 2,000 mPa.Math.s @ 25° C.) in a dental mixer at 3500 rpm for 30 seconds. The composition cured with a 30 minute non flow time.

Example 7

[0150] The following example shows two-part compositions as hereinbefore described containing fillers in the preparation of the part A composition.

TABLE-US-00006 TABLE 4a Part A compositions for two-part condensation curable silicone compositions containing fillers Ingredients Part A Ex. 7a Ex. 7b Ex. 7c Ex. 7d dimethylsilanol 100 100 100 100 terminated polydimethylsiloxane having a viscosity of 2,163 mPa .Math. s at 25° C. TiPT 0.3 0.3 0.3 0.3 Aerosil ™ R 974 16.7 26.7 Winnofil ™ SPM 52.18 CAB-O-SIL ™ LM-150 10

[0151] Component (a) was prepared as previously described using the process of Example 1 above and then the respective filler was introduced into the composition.

[0152] 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.sup.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.

TABLE-US-00007 TABLE 4b Part B compositions for two-part condensation curable silicone compositions containing fillers Ingredients Ex. 7a Ex. 7b Ex. 7c Ex. 7d Part B Mix ratio 1:1 1:1 1:1 1:1 (weight A:B) Component (b) 100 100 100 100 1 in wt. % Water 0.23 0.23 0.23 0.23 Non flow time 10 min 13 min 90 min 20 min

[0153] It can be seen that the compositions cure equally well using a component (a) reaction product as catalyst and polymer in the presence of a suitable filler.

Example 8

[0154] This series of examples and comparatives relies on silane based cross-linkers as part B.

[0155] A reaction product (a) was prepared for the following examples shown in Table 5a. 3000 g of dimethylsilanol terminated polydimethylsiloxane having a viscosity of 70 mPa.Math.s at 25° C. was introduced into a Neulinger 5 litre mixer. 53 g of tetraisopropoxy titanium was then added and mixed into the OH terminated polydimethylsiloxane under vacuum using a planetary and disk for 10 minutes at room temperature. Some gelation was observed and therefore the mixture was heated to 100° C. and mixed for a further 4 hours under vacuum. The resulting example 8 reaction product was cooled and stored in a 5-litre plastic pail. It had a viscosity of 1358 mPa.Math.s measured at 25° C.

[0156] The example 8 reaction product (a) prepared was then used in the part A compositions for five examples Ex. 8a-e and five comparative examples c. 8a-e.

[0157] The part A silicone compositions for Ex. 8a-e were prepared with 101.75 parts by weight e.g., 396.88 g of the example 8 reaction product and 0.8 parts by weight e.g. 3.12 g of water which were mixed together in a DAC 600 FVZ/VAC—P type SpeedMixer™ from Hauschild for 30 seconds at 2350 rpm and stored in two 310 m1 cartridges.

[0158] The part A silicone compositions for C. 8a-e were prepared with 390.05 g of OH terminated polydimethylsiloxane having a viscosity of 70 mPa.Math.s @ 25° C. (siloxane 1 in Table 5) was mixed with 3.12 g of water for 30 seconds at 2350 rpm. Then 6.83 g of tetraisopropoxy titanium was added in the mixture and mixed for 30 seconds at 2350 rpm. The preparation was stored in two 310 m1 cartridges.

[0159] Examples and comparative examples were made by mixing 30 g of part A with the respective weight of part B as described in the following table so 102.55 parts by weight of part A with the respective part of table 5a. Part A and part B were mixed 30 seconds at 3500 rpm using a SpeedMixer™ DAC 150 FV from Hauschild & Co. KG Germany. The product gel time was determined in the same manner as previously described.

TABLE-US-00008 TABLE 5a Ex. 8a & Ex. 8b & Ex. 8c & Ex. 8d & Ex. 8e & Part B C. 8a C. 8b C. 8c C. 8d C. 8e methyltrimethoxysilane 5.5 Tetraethoxysilane 8.6 Acetoxy mix 10 n-propyl orthosilicate 11 Methyltrioximinosilane 12.2

[0160] Acetoxy mix in Table 5a is a 50/50 by weight mixture of methyl triacetoxysilane and ethyl triacetoxysilane.

[0161] The gel times of the respective examples and comparative examples are provided in Tables 5b and 5c below.

TABLE-US-00009 TABLE 5b Ex. 8a Ex. 8b Ex. 8c Ex. 8d Ex. 8e Gel time G′/G″ at 9 26 29 69 110 25° C. (min)

TABLE-US-00010 TABLE 5c C. 8a C. 8b C. 8c C. 8d C. 8e Gel time G′/G″ at 124 100 100 240 1500 25° C. (min)

[0162] As it can be seen in the above the examples using component (a) reaction products in part A compositions cause much faster cured products, typically gels in each case using silane cross-linkers.

Example 9: Partially Trimethylsilyl Terminated OH Terminated PDMS

[0163] 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 DAC 600 FVZ/VAC—P type SpeedMixer™ from Hauschild for 4 minutes at 2350 rpm under vacuum and then left 6 minutes under vacuum without mixing. This procedure of mixing was repeated twice.

[0164] 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).

[0165] 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.

[0166] 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 30s at 3500 rpm. 15 g of the preparation was mixed with 15 g of part B in a dental mixer for 30s 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.