GB2413332A

GB2413332A - Room temperature vulcanizable (RTV) silicone compositions having improved body

Info

Publication number: GB2413332A
Application number: GB0408804A
Authority: GB
Inventors: Sabine Springael; Andreas Thomas Franz Wolf; Andreas Stammer
Original assignee: Dow Corning Corp
Current assignee: Dow Silicones Corp
Priority date: 2004-04-21
Filing date: 2004-04-21
Publication date: 2005-10-26
Also published as: GB0408804D0

Abstract

A room temperature vulcanizable silicone composition has improved body, and contains an acetoxy sealant, an alkoxy sealant, or an oximo silicone sealant, and a high molecular weight polyether polyol. The acetoxy, alkoxy or oximo silicone sealant may consist of a hydrogen-endblocked polydiorganosiloxane, an acetoxy-, alkoxy- or oximo-silane, a catalyst and filler. The high molecular weight polyether polyol is preferably an oxypropylene adduct of sorbitol. Preferably the sealant composition contains about 0.5-5 percent by weight of the high molecular weight polyether polyol based on the total weight of the composition.

Description

24 1 3332 ROOM TEMPERATURE VULCANIZABLE (RTV! SILICONE COMPOSITIONS

HAVING IMPROVED BODY

1 l I This invention relates to room temperature vulcanizable silicone compositions such as acetoxy silicone sealants, alkoxy silicone sealants, and oximo silicone sealants; and more particularly, to an acetoxy silicone sealant having improved body imparted to it by addition of a high molecular weight polyether polyol.

100021 So called Gun-grade sealants are applied by extruding a wet material from a cartridge, sausage pack, or other container, into a joint or onto substrate(s). Additional tooling after application of the sealant may or may not occur. If no tooling occurs, the quality of the application process is even more important, since final appearance of the sealant is created during the application process. If tooling is applied, tooling may be carried out manually, or robotically, as in automated application equipment, or as in insulating glass manufacture. The speed and quality of the application and tooling processes are important, since they determine the overall application cost, and the proper functioning of the joint. A number of theological properties are important during the application and tolling process.

These are extrusion rate, stringing, non-slump, and body.

10003] The extrusion rate determines how much sealant can be applied from a container such as a cartridge within a given period of time. Ideally, a sealant should have a medium to high extrusion rate, since this allows faster application speeds. However, as a practical matter, measures taken to achieve other favourable theological properties often result in medium to low extrusion rates, which is compensated by applying higher extrusion pressures during application.

10004] Stringing occurs when the application equipment, i.e., the cartridge, is pulled away from the joint while in contact with the wet sealant. This occurs, for instance, when the applicator pulls away the cartridge from the joint after completion of sealing a section. The wet sealant between the nozzle and the joint strings out, and causes a contamination of the adjacent substrate or the application equipment. Ideally, a sealant should have zero stringing.

10oo5] Non-slump is the property that prevents the wet sealant from running out of joints under the force of gravity. It is essentially determined by the yield strength of the sealant. Ideally, a sealant should be completely non-slumping for joints up to 40-50 mm in width, over a temperature range of -20 C to +60 C. Current commercial compositions generally show limited slump of less than 2 mm in 20-25 mm joints under standard test conditions.

10006] Finally, Body is a term used by applicators to describe the resistance of the wet sealant felt during the application and tooling of the sealant. Ideally, a sealant should have a lO high body, that is, it should provide a strong resistance during application and tooling. A sealant with a low body is difficult to apply, and application without tooling typically results in an irregular and uneven surface, and therefore a poor appearance. This is because it is difficult to maintain a constant distance between the application nozzle and the joint or the substrate, if the wet sealant does not provide much resistance against the nozzle.

l 5 Furthermore, a sealant with low body is difficult to tool, since it tends to smear out below and onto the spatula. It is also more difficult to maintain a constant distance between the spatula and the joint or substrate, with a low body sealant, making it more difficult to achieve a good surface finish by tooling. The body or resistance felt during tooling is essential for effectively forcing the sealant into the depth of the joint, which in turn is important to achieve good substrate wetting and the penetration of all surface irregularities.

10oo7] Body is therefore an important property for both surface aesthetics and functioning of a sealed joint. The property of high body can be best described technically as possessing a high viscosity at a low shear rate. Sealants therefore may have high extrusion rates at high shear rates, but a high body at a low shear rate. The theological measurement which best assesses the body of a sealant involves the penetration of a needle into a wet sealant.

100081 The above noted theological properties, i.e., extrusion rate, stringing, non slump, and body, in silicone sealants, are generally achieved by addition of treated or untreated fumed silica. However, such silicas are expensive, and therefore alternative rheology modifiers have been sought. Due to the increased market penetration of extended silicone sealants, low cost rheology modifiers have become even more important. Extended silicone sealants are low cost silicone sealants that are obtained by replacing part or all of the silicone plasticizer, or part of the silicone polymer, with an organic plasticizer or organic polymer. Since sufficient compatibility between the organic plasticizer or organic polymer, and the silicone polymer, can typically only be achieved at low molecular weights of generally below about 400-450, these organic plasticizers and organic polymers often tend to be low viscosity materials.

100091 However, the addition of a low viscosity organic extender to a silicone sealant composition only makes the rheology profile worse in terms of body. In order to compensate for poorer rheology profiles, more silica would need to be added, offsetting most, if not all, of the cost savings gained by addition of the organic extender. Therefore, the identification of alternative, low cost rheology modifiers, is most important in the development of low cost, extended silicone sealants. Furthermore, due to the complexity of an organic extended silicone sealant, not all rheology modifiers will behave the same in extended silicone sealant compositions, as they would behave in 100 percent silicone sealant compositions.

100101 Some alternative rheology modifiers described in the prior art are themselves organic polymers that are not compatible with a silicone-based matrix, and therefore negatively affect other sealant properties, such as the transparency of clear silicone sealants.

Since these negative effects are influenced by the amount of organic rheology modifier that is added, it is desirable to identify modifiers that provide strong theological effects at low addition levels.

10011] The use of polyethers and non-ionic surfactants as rheology modifiers in non aqueous RTV silicone sealant compositions as described in the prior art, relates to their use as rheology modifier additives in order to provide beneficial effects on slump resistance, extrusion, and stringing. However, nothing in the prior art describes any beneficial effect on body. Furthermore, nothing in the prior art relates to the use of polyether additives in extended silicone sealants to improve body. While European Published Application EP 0 857 760 (August 12, 1998) in Example 3 shows that the addition of one percent by weight of a certain polyethylene glycol surfactant in an acetoxy sealant composition containing an organic plasticizer, reduces stringiness, no improvement in the body of the sealant is demonstrated.

10012] There appear to be different mechanisms by which organic rheology modifiers S function in silicone sealant compositions. The mechanism considered most important for hydroxyl-endblocked organic polyethers, is the reaction of the silane component with the hydroxyl groups on the organic polyether, the silicone polymer, and on any additional silica that is present in the composition. While the Si-O-C bond is generally not considered stable when exposed to weathering, it is sufficiently stable in wet sealant compositions to provide for structures that affect theological properties such as slump, extrusion rate, stringing and body. It therefore appears that the higher the degree of branching and OH functionality of an organic polyether, the better it functions as a theological additive. Thus, the focus of this invention is to identify highly branched, highly OH-functional commercial polyethers, which provide desired theological properties in both 100 percent silicone containing sealant compositions, as well as in extended silicone sealant compositions.

[00131 The invention is therefore directed to a room temperature vulcanizable silicone composition having improved body, comprising an acetoxy silicone sealant, an alkoxy silicone sealants, or an oximo silicone sealant, characterized in that it contains a high molecular weight polyether polyol. Acetoxy silicone sealants, in particular, generally comprise a hydroxyl-endblocked polydiorganosiloxane, an acetoxysilane, a catalyst, and filler. The acetoxy silicone sealant contains 0.5-5 percent by weight of the high molecular weight polyether polyol based on the total weight of the composition. Corresponding alkoxy silicone sealants and oximo silicone sealants contain essentially the same components as the acetoxy silicone sealant, except that in each instance, an appropriate silane is used, i.e., an alkoxysilane or an oximosilane. In each case any suitable high molecular weight polyether polyol may be utilized. These are typically produced by extending multihydroxylfunctional compounds such as sugars. Preferably the term multihydroxylfunctional compounds means a value of at least 3. Preferably the multihydroxylfunctional compounds may be sucrose and/or glycerine initiated polyethers but most preferably comprises an oxypropylene adduct of sorbitol. Examples of commercially available products which may be utilized include the VORANOL range of products marketed by Dow Chemical Inc. including VORANOL 360 which has a functionality of 4.5, VORANOL 370 which has a functionality of 7.0, VORANOL 446 which has a functionality of 4.5, VORANOL 490 which has a functionality of 4.3, VORANOL 520 which has a functionality of 5.0 and VORANOLX 550 which has a functionality of 4.9, although VORANOL(D 5055 HH is most preferred.

10014] These and other features of the invention will become apparent from a

consideration of the detailed description.

10015] Organopolysiloxane compositions having a source of silicon-bonded acetoxy radicals in particular, are known in the art. These acetoxycontaining organopolysiloxane compositions typically comprise a product obtained by mixing a hydroxyl-endblocked polydiorganosiloxane with an acetoxysilane. The hydroxyl (silanol) functional polydiorganosiloxane component preferably has a viscosity of less than about 100 Pals at 25 C., and an average degree of polymerization (DP) from 50-700. Preferred hydroxyl endblocked polydiorganosiloxanes are hydroxyl-endblocked polydimethylsiloxanes, and polydimethylsiloxanes endblocked on one terminal end by a triorganosiloxy group, i.e., (CH3)3Si-, and on the other end by a hydroxyl group. The polydiorganosiloxane which have both hydroxyl end groups and triorganosilyl end groups, should have more than 50 percent, preferably more than 75 percent, of the total end groups as hydroxyl groups. The amount of triorganosilyl group in the polymer can be used to regulate the modulus of the resulting cured sealant. Higher concentrations of triorganosilyl end groups provide a lower modulus in cured sealants.

10016] The acetoxysilane used in the sealant composition can comprise a tetraacetoxysilane, an organotriacetoxysilane, a diorganodiacetoxysilane, or a mixture thereof. In certain compositions, the acetoxysilane can be a diorganodiacetoxysilane used as a chain extender. The acetoxysilane may contain lower alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, and tertiary butyl; alkenyl groups such as vinyl, allyl, or hexenyl; aryl groups such as phenyl, tolyl, or xylyl; aralkyl groups such as benzyl or 2-phenylethyl; and fluorinated lower alkyl groups such as 3, 3,3-trifluoropropyl.

l0017l Preferred acetoxysilanes are organotriacetoxysilane, especially mixtures containing methyltriacetoxysilane and ethyltriacetoxysilane, which are shown below. The amount ofthe acetoxysilane that is used in the sealant composition is typically from 0.5-15 parts by weight per l 00 parts by weight of the silanol functional polydiorganosiloxane; preferably from 3-10 parts by weight of acetoxysilane per 100 parts by weight of the silanol functional polydiorganosiloxane.

O O

11 11 f c CH3 1 l f C CH3 1 l H. C Si o C CH3 CH CH Si O C CH3 O ICI CH3 0 ICI CH3

O O

8] The acetoxy-containing organopolysiloxane composition can also contain other additives such as cure-accelerating catalysts, fillers, rheology control additives, pigments, and other additives generally used in room temperature vulcanizable silicone compositions. The additive should be selected with the proviso that it will not add a significant amount of volatile material to the sealant composition, such as to become volatile during the curing process, or during use of the cured compositions.

9] It is often desirable to accelerate the cure of these types of compositions by the use of catalysts such as the carboxylic acid salts of metals, ranging from lead to manganese inclusive, in the electromotive series of metals. Other silanol condensation catalysts can also be used, however, including stannous carboxylates such as stannous octoate; and titanates such as tetrabutyltitanate, tetraisopropyltitanate, and bis(ethoxyacetoacetonate)diisopropoxy titanium (IV). Preferred curing catalysts are dibutyltin diacetate, dibutyltin dilaurate, tetrabutyl titanate, tetraisopropyl titanate, bis-(ethoxyacetoacetonate)diisopropoxy titanium (IV), and stannous octoate.

[00201 Fillers can be used in the room temperature vulcanizable silicone compositions of the invention. These fillers include treated and untreated reinforcing silica fillers such as Dime silica, silica aerogel, silica zerogel, and precipitated silica; and extending fillers such as crushed quartz, aluminium oxide, magnesium oxide, calcium carbonate, zinc oxide, talc, diatomaceous earth, iron oxide, clays, titanium dioxide, zirconia, sand, carbon black, and graphite. The preferred fillers are reinforcing silica, treated reinforcing silica, calcium carbonate, and carbon black.

100211 These RTV silicone compositions are stable when stored in containers that protect them from exposure to moisture, but the compositions cure rapidly when exposed to moisture. The cure is very rapid. For example, at room temperature and 44 percent relative humidity, the cure can be considered instantaneous. At a relative humidity of about 2 percent, the cure will generally occur in about 30 seconds.

2] While the following examples are specifically directed to the preparation of acetoxy silicone sealants according to the invention, as noted above, the features of the invention are applicable to the corresponding alkoxy silicone sealants and oximo silicone sealants.

3] The following examples are set forth in order to illustrate the invention in more detail.

Example 1

4] In this example, the benefits obtained according to the invention are shown, wherein the addition of a particular high molecular weight polyether polyol, to an acetoxy silicone sealant, improves its theological properties; and decreases its extrusion values, penetration values, and stringing. For example, as little as one percent of the high molecular weight polyether polyol additive, allows a decrease simultaneously of all three properties.

The composition shown in Table I is representative of typical commercially available acetoxy silicone sealant compositions for which improvements of rheology can be obtained according to the invention by addition of high molecular weight polyether polyols.

Table 1 - Acetoxy Silicone Sealant Composition Component Component Name Chemical Function Parts by Weight Polymer 80000 cSt PDMS OH end capped PDMS 52.8 Plasticizer PDMS fluid, 1000 (CH3)3Si endcapped 30.4 cSt PDMS Crosslinkers ETA Ethyltriacetoxysilane 0.64 MTA Methyltriacetoxysilane ETS 900 50:50 MTA/ETA 3.56 DBDAc Dibutoxydiacetoxysilane 0.27 Catalyst DBTDa Dibutyltindiacetate 0. 01 Filler LM 150 Fumed Undensified 11.92 Silica 10025] The theological properties obtained for a Comparison Sealant I containing no additive, and a Sealant II according to the invention and to which had been added one percent by weight of VORANOL(D 5055 HH polyol, based on the weight of the composition, are shown in Table 2. Table 2 also shows the theological properties of a Comparison Sealant III containing one percent by weight of a silicone glycol graft copolymer, based on the weight of the composition, as an additive instead of the polyol. The three sealant samples were prepared using a twin-screw continuous compounder and the additives were added at the last barrel of the compounder.

Table 2 - Rheoloical Properties for Comparison and Improved Compositions of the Invention Property Sealant I - No Sealant II - Polyol Sealant III Silicone | Additive Additive, 1 % Glycol Additive, 1 Extrusion (gr/min) 146 96 124 Penetration (mm/10) 99 74 92 String (mm) 27 24 27 Viscosity at 0.5S-l Pa.sec 2543 3021 I Yield stress 620 752 Shear Rate extrapolated to 39.12 17.7 7000 pas-1

_

6] Standard test protocols were used for evaluating these silicone sealants.

Rheological data were obtained using a Carri-Med CSL 500 cone and plate rheometer. The rheometer was equipped with a 4 centimetre, 2 (degree), 57 121 m gap cone. The tests were carried out under flow conditions. The Carri-Med conditions included an equilibrium time of one minute; an up curve time = down curve time = 2 minute time period; and a maximum shear stress of 2,000 Pa.

7] String data, extrusion values, and penetration values, shown in Table 2, were obtained using test methods developed by the assignee corporation. These methods are the same as or the equivalent of standard industrial protocols. In Table 2, string is expressed as the length of thread formed when applying a sealant and when the nozzle is pulled away. The stringiness of the substance was determined by measuring the maximum length of a strand or string that could be pulled from the surface of a sample. A tensometer was used to provide a constant rate of pulling, and the maximum travel before the string breaks was reported in millimetre. The tensometer allowed a grip to be pulled at a constant rate, and provided a reading of the distance between the grips to the nearest millimetre. The tensometer used in the test was a Model 14445 ZWICK Tensometer, manufactured by Zwick USA LP, Atlanta, Georgia.

100281 In Table 2, extrusion is expressed as the amount of sealant coming out of a cartridge under certain conditions such as nozzle type and pressure. In this test, the rate at which a material will extrude through a standard nozzle under a specified pressure is determined, and the results are reported in grams per minute. This test method was based on MIL specification MIL-S-8802 D. A standard cartridge, gun, and nozzle are used in the test.

The nozzle is made out of a rigid material, so that its dimensions do not significantly change under pressure. In the test method, a cartridge is loaded with the sample material to be tested, and the cartridge, gun and nozzle are assembled. An air supply is connected to the assembly, and the gage is adjusted to read 90 psi (620 kPa). A small amount of material is extruded to fill the nozzle and clear any of the trapped air. The material is then extruded into suitable tared containers. The weight of the extruded material, and the time to the nearest second, is recorded. Extrusion is continued for a minimum of 15 seconds, or until about 20 gram is collected. An average of three weights is obtained, and the average value is used to calculate the extrusion rate in grams per minute, according to the relationship: Extrusion Rate (gram/minute) = Average Weight Extruded (gram) . Time (minutes).

9] In Table 2, penetration is expressed as a measure of the body of a sealant, and/or its resistance to deformation at low shear. The method used is a protocol for determining the firmness of soft gels. A lightweight blunt head shaft is used in the test. The results are reported in tenths of a millimetre. The test device comprises a penetrometer Model No. 73510 made by Universal, Precision Scientific, Chicago, Illinois. A rod, shaft and head are also used to perform the test. The rod is made of aluminium or magnesium, and measures about 16- 1/2 inch (42 cm) in length, and having a diameter of 3/16 inch (0.48 cm).

The weight of the rod should be about 15 gram, and it should be straight and equipped with stops. The lightweight rod is so constructed as to insure that it can fall free when the penetrometer is assembled. The shaft is also aluminium or magnesium, and measures 6 inch (15.2 cm) in length, with a diameter of 1/8 inch (0.32 cm). The weight of the shaft is adjusted to meet the total weight requirement shown under the head. The shaft must be straight and attached to the rod. The rod and shaft may be one piece, if the stops on the rod are secured with set screws to allow removal of the rod from the penetrometer. The shaft should be threaded on the bottom end to accept the head. The head is preferably brass, and measures 3/16 inch (0.48 cm) in length, and it has a diameter of 1/4 inch (0.64 cm). It is tapped to screw onto the shaft. The total weight of the shaft and the head should be about 4.30 gram. The total assembly of the head, shaft and rod should be adjusted to weigh about 19.5 gram.

0] According to this test protocol, the sample is mixed and placed into a suitable container. The sample is cured, cooled to room temperature if necessary, and then allowed to stabilize for at least 30 minutes at 25 C. The penetrometer dial is zeroed, and the rod is lowered over the sample, so that the head just touches the surface of the sample without making any indentation in the sample. While observing the sweep second hand of a clock, the release trigger is rapidly depressed, held down for 5.0 seconds, and then rapidly released.

During this time, the head and rod penetrate the sample. The depth gauge is gently depressed as far as it will travel. Penetration is read from the dial as a whole number. The Dial reads in tenths of a millimetre, and ranges from readings of zero to 620 in one revolution of the pointer. The release trigger is then gently depressed to gently raise the depth gauge and the rod as far as they will go. The trigger is released, and the zero point is observed to insure a proper reading. At least two readings are taken at different points, and the average is reported as the penetration value.

Example A and Comparative Examples B-G [0031] To about 150 gram of a commercially available acetoxy silicone sealant containing a low amount of filler, one percent of an additive was mixed using a SEMCO mixer. The material was mixed for 5 minutes, and a smooth paste was obtained. The acetoxy silicone sealant used in these examples was a medium modulus acetoxy silicone sealant, manufactured by the Dow Corning Corporation, Midland, Michigan. It is a solvent free, one part, acetic moisture curing silicone sealant, suitable for general construction sealing applications. The additives used were: (a) A high molecular weight polyether polyol sold under the trademark VORANOL 5055 HH, and covering a high molecular weight polyether polyol, manufactured and distributed by The Dow Chemical Company Europe SA, Horgen, Switzerland. Such compositions are described generally in US Patent 5,856,678 (January 5, 1999); US Patent 6,548,616 (April 15, 2003); and in US Patent 6,613,827 (September 2, 2003). The particular composition used in the examples is described generally in the '678 patent as one of a type of oxypropylene adduct of sorbitol. This particular polyol has a functionality of six, and an average molecular weight of about 12,000. It is prepared using sorbitol as the starting material, which is then polymerised with propylene oxide.

When the desired molecular weight has been obtained, ethylene oxide is added in order to form end groups. However, the amount of ethylene oxide used is very small compared to the amount of propylene oxide.

(b) A polyurethane-based thixotropic agent (PUTA) in which the polyol used in its manufacture is an ethoxylated glycerine compound. Such additives are described generally in US Patent No. 6,545,104 (April 8, 2003) assigned to Dow Corning Gmbh, Wiesbaden, Germany.

(c) EPION 303 S is tradename covering a dimethoxysilyl endcapped polyisobutylene manufactured and distributed by Kaneka Corporation, Osaka, Japan.

(d) Silicone glycol graft copolymer with secondary hydroxyl functionality, manufactured by the Dow Corning Corporation, Midland, Michigan.

(e) A trimethoxysilyl modified butadiene homopolymer sold under the tradename POLYVEST 50, and manufactured and distributed by Degussa-Huels Aktiengesellschaft, Frankfurt, Germany.

(f) No additive.

2] The sealants were stored for one week at room temperature, and then the penetration values were measured with a 3 millimetre steel needle, using the same procedure that was used in Example 1.

Table 3

Sealant Penetration (mm/30s) B 253 C 350 Example G and Comparative Examples H-L 100331 To about 150 gram of an extended commercial grade acetoxy silicone sealant containing about 30 percent by weight of a paraffin oil, one percent of an additive was added, using a SEMCO mixer. The material was mixed for 5 minutes, and a smooth paste was obtained. The additives used were: (h) VORANOL 5055 HH (i) PBTA 0) Silicone Glycol Graft Copolymer (k) POLWEST 50 (1) No additive 10034] The sealants were stored for one week at room temperature, and then the penetration values were measured, using a 3 millimetre steel needle according to the same procedure as in Example 1.

Table 4

Sealant Penetration (mm/30s) l H 186 J 229 LK 22535 | Examples M-O and Comparative Example P [0035] To about 150 gram of the acetoxy silicone sealant containing a low amount of filler that was used in Example A, different amounts of VORANOL 5055 H were added, using a SEMCO mixer. The material was mixed for 5 minutes and a smooth paste was obtained.

(m) 0.5 percent VORANOL(D 5055 HH (n) 1 percent VORANOL(D 5055 HH (o) 2 percent VORANOL() 5055 HH (p) Reference, no additive [0036] The sealants were repackaged in 310 millilitre standard cartridges, and stored for one week at room temperature. Penetration values were then obtained, using a 3 millimetre steel needle, according to the same procedure used in Example 1. Extrusion values were measured with a calibrated nozzle at 6.2 atmosphere, according to the same procedure as in Example 1.

Table 5

Sealant Penetration (mm/30s) Extrusion (g/min) 281 429 N 210 387 O 241 336 P 336 532 Examples R-S and Comparative Example U 100371 To about 150 gram of a high body acetoxy silicone sealant, different amounts of VORANOL(D 5055 H polyol, were added, using a SEMCO mixer. The material was mixed for 5 minutes, and a smooth paste was obtained. The acetoxy silicone sealant used in lo these examples was a low modulus acetoxy silicone sealant manufactured by the Dow Corning Corporation, Midland, Michigan. It is a one-part, low modulus, acetic moisture curing silicone sealant, formulated so as to be suitable for sanitary or other construction sealing applications, where mildew resistance is required. It contains no solvent.

(m) 0.5 percent VORANOL(D 5055 HH (n) 1 percent VORANOLQ3) 5055 HH (o) 2 percent VORANOL(D 5055 HH (P) Reference, no additive 100381 The sealants were repackaged in 310 millilitre standard cartridges, and stored for one week at room temperature. Penetration values were measured with a 3 millimetre steel needle, according to the same procedure used in Example l. Extrusion values were measured with a calibrated nozzle at 6.2 atmosphere, using the same procedure as in Example

Table 6

Sealant Penetration (mm/30s) Extrusion (g/min) O --- 1 12419 P 106 298 [00391 Other variations may be made in compounds, compositions, and methods described herein without departing from the essential features ofthe invention. The embodiments of the invention specifically illustrated herein are exemplary only and not intended as limitations on their scope except as defined in the appended claims. i

Claims

1. A room temperature vulcanizable silicone sealant composition having improved body comprising an acetoxy silicone sealant, an alkoxy silicone sealant, or an oximo silicone sealant, characterized in that the silicone sealant contains a high molecular weight polyether polyol.

A

2. A composition according to Claim 1 in which the acetoxy silicone sealant comprises a hydroxyl-endblocked polydiorganosiloxane, an acetoxysilane, a catalyst, and a filler.

3. A composition according to Claim 1 in which the alkoxy silicone sealant comprises a hydroxyl-endblocked polydiorganosiloxane, an alkoxysilane, a catalyst, and a filler.

4. A composition according to Claim 1 in which the oximo silicone sealant comprises a hydroxyl-endblocked polydiorganosiloxane, an oximosilane, a catalyst, and a filler.

5. A composition according to any preceding claim in which the silicone sealant contains 0.5-5 percent by weight of the high molecular weight polyether polyol based on the total weight of the composition.

6. A composition according to any preceding claim in which the high molecular weight polyether polyol is an oxypropylene adduct of sorbitol.

7. A composition as hereinbefore described with reference to examples A, G. M, O. R and

S.