MXPA99009164A

MXPA99009164A - Procedure for obturing components exposed to aggressive functional fluids and rtv silicone compositions suitable for use in e

Info

Publication number: MXPA99009164A
Application number: MXPA/A/1999/009164A
Authority: MX
Inventors: d davis Timothy
Original assignee: Wacker Silicones Corporation
Priority date: 1998-10-07
Filing date: 1999-10-06
Publication date: 2000-10-01

Abstract

The present invention relates to: RTV-1 silicone-based sealing materials resistant to deterioration in the presence of aggressive functional fluids are prepared from an organopolysiloxane component comprising a major amount of an organopolysiloxane with a silanol functionality, an agent crosslinker, with primary or secondary amine functionality and with iron oxide and magnesium oxide, optionally together with auxiliary fillers, adhesion promoters, catalysts, and customary additives, sealing gasket materials are particularly useful in gas tight closures. shafts and transmission shafts exposed to aggressive lubricants that activate fuel efficiency

Description

PROCEDURE TO OBTURE COMPONENTS EXPOSED TO AGRESSIVE FUNCTIONAL FLUIDS AND SILICONE COMPOSITIONS RTV SUITABLE FOR USE IN THIS TECHNOLOGICAL FIELD The present invention relates to sealant materials (sealants) based on polyorganosiloxanes, vulcanizable at room temperature of a single component ("RTV-1", one-component Room Temperature Vulcanizable), cured by amines, which exhibit resistance to aggressive functional fluids. , and its use to seal components containing said fluids.

BACKGROUND OF THE INVENTION Silicone-based elastomers have been used for many years in sealing applications. For high-temperature (HTV, High Temperature Vulcanizable) vulcanizable compositions are used for o-rings and other molded gaskets. Such compositions are somewhat less expensive than the RTV-2 compositions and also exhibit somewhat higher thermal stability. These compositions may include poly (dimethyl organosiloxanes), fillers and organic peroxides which act by curing the compositions by free radical induced crosslinking. Gaskets formed by casting in situ and the like can often not use HTV compositions, however, since the parts that are being sealed, the fluids sealed within them, or both elements at the same time, can not support the high temperatures that are required to cure. Examples of HTV elastomers and their components can be found in U.S. Pat. 4,782,107; 4,728,687; and 5,550,185. The two component, room temperature vulcanizable compositions ("RTV-2") have been used as elastomeric sealants. Said compositions generally contain unsaturated organopolysiloxanes with an alkenyl functionality, such as those containing γ-vinyl radicals, allyl, acryloxy, methacryloxy or alkenyl, such as γ -hexenyl radicals, in conjunction with an organopolysiloxane with a Si functionality. -H One or both of the components also contain a hydrosilylation catalyst. The use of fillers such as fumed silica, fine quartz powder, calcium carbonate and the like is relatively common. However, such elastomers do not, in general, have the thermal stability of the HTV elastomers, and are not suitable for use because of their two-part formulation. RTV-2 compositions are also known which employ other reactive systems, for example those described in U.S. Pat. 4,892,907. For many years, sealing materials based on vulcanizable silicones at room temperature of a single component ("RTV-1") have been known in the construction industry. Such sealants often include silicones with an acyloxy functionality as a component of a storage stable mixture that also generally includes a silicone with a silanol functionality, such as an α, β-dihydroxy-poly (dimethylsiloxane). The composition begins to heal when exposed to atmospheric moisture. To increase the viscosity and the "body" of the cured elastomer, large quantities of relatively inexpensive fillers, such as crushed calcium carbonate, are incorporated into the sealant composition. Such sealing materials are generally cured relatively slowly and first form a cured skin (surface film) which prevents the penetration of the moisture necessary to cure the interior. Although they are useful as waterproofing materials in the construction industry, such sealing materials have little use as sealants for other applications. Furthermore, said sealing materials do not possess exceptional thermal stability, exhibiting a more rigorous degradation than other elastomers based on silicones at elevated temperatures. In environments where a sealing material must be cast or poured in situ, the ability to use elastomers based on HTV silicones, as indicated above, is severely limited. Furthermore, said seals are frequently used to seal (close hermetically) cavities or passages containing fluids, particularly in the automotive sector in which the sealing materials can be exposed to water, antifreeze, gasolines, brake fluids, hot oils and cold, fluids for automatic transmissions, and lubricants and fluids for gears and shafts. In the U.S. patent No. 5,013,781, for example, describes compositions RTV-1 containing organopolysiloxane resins that are composed of units of M and Q or units of M, D and Q, together with an inorganic filler material, an adhesion promoter based on alkoxysilane, and a crosslinking agent based on ketoxime-silicone. The fillers used can be silica-based, reinforcing or non-reinforcing fillers, or they can be non-siliceous non-reinforcing fillers, such as calcium carbonate, zinc carbonate, magnesium oxide, aluminum hydroxide, oxide of iron, zinc oxide, titanium oxide and powdered mica. The loading materials were considered to be substantially equivalent, with the highest initial properties and maximum property retention being exhibited by a fumed silica and an iron oxide. The substantially equivalent behavior of a wide variety of non-reinforcing fillers is generally accepted in the art of organopolysiloxanes. For example, in U.S. Pat. No. 4,748,166, are cited as equivalent fillers, either alone or in mixtures, crushed quartz, diatomaceous earth, calcium carbonate, calcined clay, natural titanium dioxide (rutile), iron oxides, zinc, chromium, zirconium and magnesium, hydrated and non-hydrated aluminas, boron nitride, lithopone, barium metaborate, pulverized cork, wood sawdust, inorganic and organic fibers, and the like. Similar shopping lists of cargo materials can be found in U.S. Pat. 4,782,107 and 5,268,441, the latter of which discloses suitable treatments for rendering hydrophobic materials to fillers. When a heat resistance is required, it is generally recognized that iron oxide, zirconium oxide and barium zirconate are good candidates for fillers. The use of red iron oxide in automobile RTV-2 gaskets is described in U.S. Pat. 4,892,907. The most common non-reinforcing filler or extender is calcium carbonate, as described in the Examples of US Pat. 4,748,166; 4,962,151; 5,118,738; and 5,569,750. Recently, under the pressure of further increasing fuel economy, they have come under scrutiny by fluid car manufacturers such as those used in axles, differentials, transmissions and drive shafts. The use of viscous fluids in many of these applications results in a great loss of energy. Furthermore, since this loss of energy appears in the form of heat, the useful life of the various fluids is decreased. The current tendency in such fluids is therefore to decrease the viscosity. For example, lubricants for shafts and gears have previously been typically composed of relatively viscous oily or greasy components, such as a heavy paraffinic hydrotreated distillate, a heavy paraffinic distillate dewaxed with solvents and a dewaxed residual oil with solvents, but are currently being replaced. by lubricants with lower viscosity containing numerous synthetic additives to increase the oiliness (lubricity), which is necessary due to the lower capacity of formation of films that have such lubricants, particularly at elevated temperature. Examples of these lubricant additives for pressures from moderate to high are olefin sulfides and organic phosphate esters. Unfortunately, it has been found that the organopolysiloxane elastomers used earlier with great success, when exposed to conventional lubricants, exhibited a total failure in less than 200 hours of operation in simulated use tests, in which they were exposed to more aggressive lubricants. It would be desirable to provide sealing and sealing materials that retain the superior thermal stability of silicone-based elastomers but that could also provide durability when exposed to aggressive fluids. It would further be desirable to provide suitable RTV-1 compositions for forming such seals and sealants.

SUMMARY OF THE INVENTION It has now been discovered with surprise that compositions based on organopolysiloxane elastomers RTV-1 comprising organopolysiloxanes cured by amines carrying a silanol functionality, and including fillers of both iron oxide and magnesium oxide, can be used to produce sealing materials whose physical properties, when exposed to aggressive functional fluids, are vastly greater than those of otherwise similar compositions, which contain iron oxide in combination with other fillers such as calcium carbonate. The RTV-1 compositions can be used for gaskets and sealing materials cast by casting and cast in situ as well as for other traditional and sealing applications.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a graphical representation of the hardness of the durometer as a function of time for two RTV-1 sealing materials exposed to an aggressive axle lubricant; Figure 2 is a graphic representation of the tensile strength as a function of time for two RTV-1 sealants exposed to an aggressive axle lubricant; Figure 3 is a graphic representation of the elongation as a function of time for two RTV-1 sealing materials exposed to an aggressive axle lubricant; and Figure 4 is a graphical representation of the shear strength with overlapping as a function of time for two RTV-1 sealants exposed to an aggressive axle lubricant.

DESCRIPTION OF PREFERRED EMBODIMENTS The compositions of the present invention include, as necessary ingredients, (A) an organopolysiloxane component containing one or more organosiloxanes with a silanol functionality; (B) an amine curing agent; (C) iron oxide; and (D) magnesium oxide. Other optional ingredients include adhesion promoters, viscosifying and thixotropy additives, antioxidants, thermal stabilizers and reinforcing fillers as well as non-reinforcing fillers other than iron oxide and magnesium oxide. The compositions may also include reactive and non-reactive diluents as well as other organopolysiloxanes. The organopolysiloxanes with a silanol functionality are composed predominantly of units of M and D having the formulas: RaR1bR2cXdSiO1 / 2 (M) and RaR ^ R ^ SiO ^ (D), and preferably those having the formulas: RaR1bSiO1 / 2 (M ') and RaR1bSi? 2O'), wherein R is a Ci.-substituted or unsubstituted alkyl, preferably an optionally substituted C-? -4 alkyl and more preferably a methyl group or a phenyl group or substituted or unsubstituted naphthyl; R1 is a hydroxyl group; and R 2 is a substituted or unsubstituted alkynyl, alkenyl or cycloalkenyl group, preferably an alkenyl group C-MS that is preferably unsaturated in α, containing both R and R 2 optionally intermixed groups O -o-c- • C-0, -0-C-0, -O-C-NH-, and similar, in that in the units of (M), the sum of a + b + c is = 3, and in the units of (D), the sum of a + b + c is 2, in which a, b and c they may be from 0 to 3. Preferably, few R2 groups are present or none of them. R1 is a silicon-bonded hydroxyl group, of which at least one per molecule must be present, on average, and preferably, on average, 2 or more hydroxyl groups per molecule of the organopolysiloxane with a silanol functionality. The hydroxyl groups are preferably terminal, ie they are located in units of M or M ', but may also be pendant hydroxyl groups. Suitable substituents for the R and R2 groups include halogen, preferably chloro and fluoro radicals, cyano groups, alkoxy groups, hydroxyalkylenoxy groups and other substituents, which are preferably not reactive under storage conditions such that an RTV- formulation can be prepared. 1 stable. X is an alkoxy d.sup.-ts group optionally containing hetero-mixed groups such as -O-, -S-, -NH- and the like, and d is 0, 1 or 2. Preferably, few, if any, alkoxy X groups are present in the organopolysiloxane with a silanol functionality. The organopolysiloxanes with a silanol functionality can also contain units of T corresponding to the formula RaR1 bR2cXdS03 / 2 (T), and preferably RaR1bSi? 3/2 (T), and more preferably RaR1bXdSiO3 / 2 (T ") wherein R, R1, R2 and X as well as a, b, c and d are defined as above, but the sum of a, b, c and d is 1, in other words only one of the R, R1, R2 or X is present. Organopolysiloxanes with a silanol functionality may also contain units of S¡O 2 (Q) Preferably, the majority, in percent by weight, of all organopolysiloxanes with a silanol functionality are substantially linear, consisting of units of (M) and (D) and less than 10 mole percent of units of T and Q, preferably units of (M) and (D) which are terminated in a, β-silanol, are used with the greatest preference, due both to their lower cost as to the behavioral advantages, the a,? - dihydroxy-poly (dimethylsiloxanes) having a viscosities (at 25 ° C) from 100 to 1,000,000 mm2-s "1, more preferably from 2,000 to 350,000 mm2-s ~ 1. Other examples of organopolysiloxanes with a silanol functionality can be found with reference to U.S. Pat. 4,748,166; 5,550,185; and 4,892,407. In general, a single organopolysiloxane with a silanol functionality, or a mixture of two or more organopolysiloxanes with a silanol functionality are useful. In addition to the hydroxyl terminated organopolysiloxanes, which are preferably substantially linear, organopolysiloxane resins may be used. In the polysiloxane technique, resins are considered as highly crosslinked, high molecular weight species, which are often solid materials that have only limited solubility in many solvents, and which contain relatively large numbers of units of (T) and / o (Q). Such resins are often soluble to a certain extent in liquid organopolysiloxanes and in solvents such as toluene and xylene. Preferably, such resins, when used, are also carriers of silanol functional groups. The resins are preferably included in less than 40 weight percent of the total organopolysiloxanes, preferably in less than 20 weight percent, and more preferably in less than 10 weight percent. Most preferably, no resins are used or substantially no resins are used (< 5 percent by weight). Also non-functional organopolysiloxanes such as poly (dimethylsiloxanes) terminated in trimethylsilyl and the like are useful as a portion of the organopolysiloxane component. Such organopolysiloxanes are useful for providing flexibility to the cured composition as well as serving to modify the viscosity of the curable formulations. The organosiloxanes which have been described above may contain other groups which do not interfere with the storage stability of the RTV-1 compositions, and which do not interfere with the ability to cure. Non-limiting examples of such groups are pendant and terminal poly (oxyalkylene) groups, and intra-chain alkylene and poly (oxyalkylene) groups, for example silicon atoms bonded by an intermixed alkylene group of 1 to 18 carbon atoms, an alkylenedioxy radical p. eg -O (CH2) nO- or a polyoxyalkylene radical. Preferably, however, the organic silicon compounds used herein in component (A) are organopolysiloxanes in which the silicon-bonded organic substituents are predominantly methyl groups. The amine (crosslinking) curing agent (B) can be any amine that is effective to activate the curing of the compositions involved after exposure to moisture. Suitable amine curing agents are well known in the art and in general are aliphatic or cycloaliphatic amino silanes. Examples of curing agents (B) are amino-substituted silicon organic compounds of the formula R3ZSi (NY2) 4-Z, or amino-silazanes of the formula: (Y2N) dR3eSiNH [R3e (Y2N) fSiNH] gSiR3e (NY2) d in which each of the R3 is a C -? - 22 alkyl radical, a C6-3o aryl radical, a C7-3 o arylaryl or alkylaryl radical, each of the Y is a hydrogen atom, a C1-22alkyl radical, a C6-3al aryl radical, a C4-12 cycloalkyl radical, a C7-30 alkylaryl radical or a C3-3 arylalkyl radical, d is 2 or 3, e is 0 or 1, f is 1 or 2, g is at least 1 and z is 0 or 1. Preferred amino-silanes contain 3 or 4 amino substituents per Si atom and 0 or 1 alkyl radical, aryl radical, alkylaryl radical or arylalkyl radical for each Si atom. Therefore, tri- or tetra-functional silanes are preferred. Tetra-functional silanes are generally more reactive than tri- or di-functional silanes, and will therefore carry out vulcanization (curing) faster than can be obtained with tri-functional silanes. In general, amino-silanes can be represented by the formulas R3Si (NY2) 3 and Si (NY2) 4, wherein R3 is an alkyl radical, preferably an alkyl radical or cycloalicylic radical Ci.-iß such as methyl, ethyl, propyl, cyclopentyl, cyclohexyl or octadecyl; an aryl radical such as phenyl, naphthyl or anthracyl; an arylalkyl radical such as benzyl or phenylethyl; or an alkylaryl radical such as the tolyl or xylyl radicals, and each Y is H, or an alkyl, aryl, cycloalkyl, alkylaryl or arylalkyl radical as defined for R3. Mixtures of these amino silanes can also be used. The amino silanes can be prepared by known methods, such as that consisting in reacting a silane containing hydrogen, a halogen or an alkoxy substituent, with a primary or secondary amine. Suitable silane reactants include SiCU, Si (OC2H5) 4, CH3SiCl3, CH3Si (OC3H7) 3, C6H5Si (OCH3) 3, C6H5SiCI3 and C6H5SiH3. Suitable amine reactants include aliphatic, cycloaliphatic, aromatic and arylaliphatic primary and secondary amines, as well as ammonia. Preferred amines include monobutyl amine, diethylamine, aniline and N-methyl aniline. The amino silazanes that can be used are prepared by known methods and are materials described and discussed in the art. Other amino-substituted organic silicon compounds which can be used are those obtained from the reaction of a halosilane and a monoalkylalkyl amine. The silane reactant can be illustrated by the formula R3SiX3 in which R3 is the same as above. The halogen atoms represented by X can be fluorine, chlorine, bromine or iodine. Low molecular weight siloxanes, which have at least three chlorine atoms per molecule, bonded to silicon, can be used in the reaction with the cycloalkyl amine. The organohalo silane or siloxane is reacted with any of the monocycloalkyl amines, preferably with monocycloalkyl amines having from 5 to 12 carbon atoms, such as cyclopentyl amine, cyclohexyl amine, cycloheptylamine, 3, 5,5-trimethyl-cyclohexyl-amine and 2,3,4-triethyl-cyclohexyl-amine. Cyclohexyl amine is the preferred cycloalkyl amine. The reactants can include mixtures of various silanes and various cycloalkyl amines and therefore the reaction is carried out between at least one silane and at least one cycloalkyl amine.

Most preferred are tris- (aminoalkyl) silanes such as methyl-tris- (sec-butylamino) silane, methyl-tris- (n-butylamino) silane, and particularly methyl-tris- (cyclohexyl-amino) ) silane, the amine nitrogens being bound in each case directly to Si. The reaction of the silane and the cycloalkyl amine is carried out according to known procedures for reacting halosilanes with primary amines. Such procedures are described, for example, in U.S. Pat. Núms. 2,564,674, 2,579,417 and 2,579,418. The reaction of the silane with the monocycloalkyl amine to produce the desired silamines is carried out optimally in the substantial absence of water and in a solvent system. The solvent used, of course, must be inert to the reactants. Examples of suitable solvents are toluene and methylene chloride. After the reaction has been completed as indicated by the cessation of the precipitation of amine salts, the reaction product is separated from the amine salts by filtration or by other means, as desired. The solvent is removed from the reaction product preferably by distillation under reduced pressure in order to avoid or minimize the decomposition of the reaction product. The residue obtained is suitable for use as an organic compound of silicon substituted with amino. The amino-substituted organic silicon compounds are stored under essentially anhydrous conditions and added to the siloxane polymer under essentially anhydrous conditions. These amino-substituted organic silicon compounds are used in amounts which will preferably provide at least one gram equivalent of silicon atoms of the amino-substituted organic silicon compound per gram equivalent of reactive end groups in the organo-polysiloxane. Generally, 0.2 to 15 parts by weight of the amino-substituted organic silicon compound are added per 100 parts by weight of the hydroxyl-terminated organopolysiloxane polymer. The order of addition of the various ingredients is optional, but the mixture should be prepared in an atmosphere substantially free of water. In addition to the siloxane polymer and the amino-substituted silicon organic compound, the composition may contain additives such as compression-cure additives, pigments, soluble dyes, aromatic substances (essential oils), oxidation inhibitors, heat stabilizers, flame retardants and light stabilizers, plasticizers and softeners such as end-blocked dimethyl-polysiloxane fluids with trimethylsiloxy, reinforcing fillers and non-reinforcing fillers. The condensation catalysts described in US Pat. Núms. 2,843,555, 3,127,363, 3,082,527 and others. Iron oxide is a necessary ingredient of the compositions involved, and should be present in amounts of about 5% to about 50% by weight relative to the total weight of the composition, preferably 15% to 40% by weight. All types of finely ground iron oxides or small particle sizes are suitable. The average particle size should preferably be greater than 0.05 Fm, and will normally be in the range of 0.1 Fm to less than 10 Fm. Black iron oxide, yellow iron oxide and red iron oxide, as well as other pigment grade iron oxides, are among those that are appropriate. A preferred iron oxide is available from Harcross Pigments, Inc., as red iron oxide RY 2096. Without the iron oxide component or a transition metal oxide or other equivalent, the thermal stability of the sealant materials will not be appropriate. . Magnesium oxide is a necessary ingredient, and should be present in amounts of about 2% to about 50% by weight, preferably from 4% to 40% by weight, and most preferably from about 6% to 20% by weight. Magnesium oxide can have the same particle size range as iron oxide. A suitable magnesium oxide is the Magox 98 HR STI available from Premier Services Corp. Other fillers are optional ingredients. Charging materials such as crushed quartz, fumed silica, diatomaceous earth, clay materials, crushed feldspar, crushed limestone and precipitated calcium carbonate and other forms of calcium carbonate, magnesium silicate, calcium silicate and others are acceptable. inorganic fillers In general, organic fillers should be avoided. A calcium carbonate available from Zeneca Resins such as Winnofil® SPM is extremely preferred as an auxiliary filler material. The iron oxide, the magnesium oxide and the auxiliary fillers can be hydrophilic or hydrophobic. Hydrophobic fillers are prepared by treatment with organosilanes by methods that are currently well known, or by treating with wax or waxy compounds such as long chain fatty acids. For example, the preferred calcium carbonate based charging material is calcium stearate carbonate. Adhesion activators may be useful in the compositions involved in limited amounts. An adhesion promoter generally provides both alkoxy groups attached to silicon as well as amino groups. Examples of adhesion promoters include? -amino-propyl-triethoxy-silane and similar compounds and other reactive silanes which are known in the art. Also suitable are metalophilic compounds that are soluble or dispersible in the compositions involved. By "metalophilic" is meant a compound that improves the adhesion of the compositions involved in metals. A preferred adhesion promoter is KS-1 available from Wacker-Chemie, which is an oxyethylated and oxyethylated ethylenediamine. Other adhesion promoters include N, N, N ', N'-tetrakis [2-hydroxy-alkyl] alkylenediamines and their oxyethylated, oxypropylated and other oxyalkylated species. Compounds such as diethanol-amine, dipropanol-amine and its oxyalkylated analogs are also suitable, as are various compounds with a morpholino functionality. Although adhesion promoters such as the various aminoalkyl-alkoxy silanes such as α-amino-propyltrimethoxysilane are useful, the total content of silicon-linked alkoxy groups should generally be less than 5% by weight in the total composition, preferably less than 3% by weight, and most preferably less than 1% by weight. Compositions containing silicon-bonded alkoxy groups, present in excess, may not exhibit a desirable cure of deep sections. Other additives and auxiliary agents may be optionally added. These include additives such as solvents, surfactants and thixotropes which may be useful for modifying the viscosities or viscosity-shear relationships of the compositions, or other properties thereof.; pigments (other than iron oxide filler) such as carbon black, manganese dioxide, phthalocyanines and the like; catalysts such as the various tin compounds, especially organic tin compounds such as dibutyl tin diacetate, dibutyl tin dilaurate, diethyl tin diacetate, tin octoate and complexes with titanium, particularly titanium-based condensation catalysts which are described in U.S. Pat. 5,268,441; and ketoximes as well as amino-hydrocarbyl-ketoximes which can act as catalysts, crosslinking agents, and / or adhesion promoters, such as those described in U.S. Pat. 5,569,750 and 5,013,781.

In the compositions of the present invention, the organopolysiloxane component (A) generally constitutes from about 10% to about 90% by weight of the total sealant material, preferably from about 15% to about 85% by weight, more preferably about 20% by weight. % to about 50% by weight, and most preferably from about 20% to 45% by weight. Of the total organopolysiloxane in component (A), it is preferable that organic silicon compounds with a silanol functionality constitute the major part of component (A), preferably about 60 weight percent or more, and most preferably about 70-90 percent by weight. Of the organopolysiloxane without silanol functionality, it is preferable that a poly (dimethylsiloxane) blocked at the end with trimethylsilyl or another group without functionality be used. The crosslinking agent (B) is used in an effective amount such that curing can be obtained, preferably in amounts of from about 0.2 percent to about 15 percent by weight, more preferably from about 3 to about 10 percent by weight. weight, and most preferably from about 4 to about 8 weight percent. The percentages by weight of iron oxide and magnesium oxide have been given previously. An auxiliary filler material is preferably used in amounts of 15% to 50% by weight, preferably 20% to 40% by weight, and more preferably 25% to 30% by weight. The total weight of the filler, including iron oxide, magnesium oxide, and auxiliary fillers, can range from about 5% by weight to about 70% by weight, more preferably between 15% and about 65% by weight, and most preferably between 25% and about 55% by weight. The total content of filler material is generally greater when considerable quantities of auxiliary fillers are used. The mixing order of the ingredients is not too critical. In general, the organopolysiloxane components are added and homogenized in a mixer or malaxer followed by addition of the filler. Generally, crosslinking agents, adhesion promoters, etc. are added last. The mixing operation typically takes place under vacuum or under protection with dry nitrogen, such that moisture is excluded. Having generally described this invention, further understanding can be obtained by reference to certain specific examples that are provided in the present context for purposes of illustration only and are not intended to be limiting, unless otherwise specified.

Comparison Example 1 Sealant compositions are prepared, one of whose formulations is compatible with the prior art practice for sealing materials useful in shafts when exposed to lubricants for conventional shafts (Comparison Example C1) and a sealing formulation in accordance with the present invention. The sealants are RTV-1 compositions which are prepared by mixing the ingredients listed in Table 1 until homogeneous, with the exclusion of water.

TABLE 1 a,? - dihydroxy-poii (dimethyl-siloxane), 20,000 cSt. Poly (dimethylsiloxane) fluid terminated in trimethylsilyl of 100 cSt Poly (dimethylsiloxane) fluid terminated in trimethylsilyl of 10,000 cSt Methyl-tris [aminocyclohexyl] silane N- [3-trimethoxy-silyl-propyl] -1,2-ethanediamine Ethylene diamine poly (oxyalkylated) 7 Calcium stearate carbonate. The compositions were placed inside hermetically sealed containers, until their use. Films having a nominal thickness of 0.080"(2.032 mm) were cast from each of the compositions and allowed to cure at room temperature and a relative humidity of about 50% for 7 days. (Hardness tester, Shore A) (ASTM-D2240), tensile strength (ASTM-D412), and elongation (ASTM-D412). In addition, a portion of each sealing material was applied between the edges of overlapping metal sheets to measure overlapping shear strength (ASTM-D1002). Samples of the Comparative Seal Material and the sealing material of the invention were immersed in an aggressive shaft lubricant, the Texaco® 2224 lubricant, maintained at 150 ° C. The samples were removed and tested periodically. The hardness (of Durometer) is illustrated in Figure 1. As noted, the hardness of the sealing material decreased rapidly. At approximately 170-180 hours of exposure, the elastomers of Comparison Example C1 had essentially dissolved and / or disintegrated. The resistance to the Traction (Figure 2); and Elongation (Figure 3) showed similar results in all cases. The most aggressive lubricant destroyed the Comparative Seal Material. On the other hand, the sealing material of the invention, in which approximately 25% of the calcium carbonate loading material had been replaced by magnesium oxide, manifested an initial loss in the properties which were then leveled substantially in plateau in the range of 200-400 hours of immersion. From this point, no substantial decrease in properties was observed. The overlapping shear test (Figure 4) shows that the Comparative Seal Material lost approximately 50% of its shear strength with overlap at 200 hours, while the obturator material of the invention lost only about 20-25% of its shear strength with overlap over the same interval. Having now fully described the invention, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made therein without departing from the spirit or scope of the invention as set forth herein. By the term "resistant to aggressive functional fluids" is meant that the physical properties of the cured sealant material exceed those of a similar sealant prepared from the same ingredients but not containing magnesium oxide when exposed to the Texaco® 2224 lubricant. or a similar aggressive lubricant or in juxtaposed tests with a particular functional fluid. The term "principal", when used, means 50% or more in weight or in moles when so indicated, while "secondary" means less than 50% on the same basis. The claimed compositions should include the necessary ingredients, organopolysiloxane with a silanol functionality, amino-curing agent, iron oxide and magnesium oxide, but can exclude any of the ingredients identified here as optional, any ingredient that is not available can be further excluded. identify here

Claims

NOVELTY OF THE INVENTION CLAIMS

1. - In a process for sealing components with a sealing material based on a RTV-1 siiicone, the improvement comprising: selecting as said sealing material a sealant material resistant to aggressive functional fluids, said sealant material prepared by curing a prepared sealant composition from the components: (A) from about 10 percent to about 90 percent of an organopolysiloxane component comprising, for the most part, one or more organopolysiloxanes with a silanol functionality; (B) an amount of cross-linking agent with an amine functionality, effective to cure said sealing composition in the presence of moisture; (C) from about 5 percent to about 50 percent iron oxide; and (D) from about 2 to about 50 percent magnesium oxide, wherein all the percent that are presented here are so many percent by weight relative to the total weight of the sealant composition unless otherwise specified something different

2. The process of claim 1, wherein said crosslinking agent with an amine functionality is present in an amount of about 0.2 percent to about 15 percent by weight based on the component (A).

3. - The process of claim 1, wherein said one or more organopolysiloxanes with a silanol functionality comprise 60 parts or more per 100 parts of the organopolysiloxane component (A); wherein said organopolysiloxane component (A) comprises from 20 to about 50 percent of said sealant composition; and wherein said magnesium oxide is present in an amount of 4% to about 40 percent of said sealant composition.

4. The method of claim 1, wherein said sealing composition further comprises an adhesion promoter.

5. The method of claim 1, wherein said sealing composition comprises: (A) from about 20 to about 50 percent of an organopolysiloxane component comprising, a) i) for the most part, one or more siloxanes with a silanol functionality containing residues that have the formulas: RaR1bSiO1 / 2 (M1) and RaR1bSi? 2y2 (D1), wherein each R individually is a monovalent saturated Ci.ia hydrocarbon radical, substituted or unsubstituted, optionally containing intermixed residues of O O O II -o-, -s- -NH- -C-, -C-O, -o-c-o wherein R1 is hydroxy; and in which a is 0, 1, 2 or 3 and b is 0 or 1, with the proviso that in M 'a + b = 3 and in D' a + b = 2, and in that said organopolysiloxane with a functionality of silanol contains at least one R1; (B) from about 2 percent to about 15 percent of an amino-silane or amino-silazane-based crosslinking agent that contains the Si-N-linked residue (s) of one or more aliphatic or cycloaliphatic amino groups primary or secondary; (C) from about 15 percent to about 40 percent iron oxide; and (D) from about 4 to about 40 percent magnesium oxide.

6. The process of claim 5, wherein said organopolysiloxane component further comprises one or more poly (dimethylsiloxanes) capped with trimethylsilyl.

7. The method of claim 5, wherein said sealing composition further comprises an effective amount of an adhesion promoter.

8. The process of claim 1, wherein said crosslinking agent (B) comprises: B) i) R3zSi (NY2) 4-z, B) ii) (Y2N) dR3S-NH (R3e (Y2N) fS) NH) gSR3e (NY2) d, B) iii) siloxanes or polysiloxanes having attached thereto one or more residues (NY2) Si, where d is 1, 2 or 3, or B) iv) mixtures thereof, wherein each R3 is a C -? - 22 alkyl radical, a C6-30 aryl radical. a C7-30 arylalkyl or alkylaryl radical, each Y is a hydrogen atom, a C-22 alkyl radical, a C6-30 aryl radical. a C4-12 cycloalkyl radical, a C7-30 alkylaryl radical or a C7-30 arylalkyl radical, d is 2 or 3, e is 0 or 1, f is 1 or 2, g is at least 1 and z is 0 or 1.

9. A sealant composition based on a curable RTV-1 organopolysiloxane resistant to aggressive functional fluids, said sealant composition comprising: (A) from about 10 percent to about 90 percent of an organopolysiloxane component comprising, for the most part , one or more organopolysiloxanes with a silanol functionality; (B) an amount of cross-linking agent with an amine functionality, effective to cure said sealing composition in the presence of moisture; (C) from about 5 percent to about 50 percent iron oxide; and (D) from about 2 to about 50 percent magnesium oxide.

10. The curable sealant composition of claim 9, wherein said crosslinking agent with an amine functionality is present in an amount of about 0.2 percent to about 15 percent by weight based on the component (A).

11. The curable sealant composition of claim 9, wherein said one or more organopolysiloxanes with a silanol functionality comprise 60 parts or more per 100 parts of the organopolysiloxane component (A); wherein said organopolysiloxane component (A) comprises from 20 to about 50 percent of said sealant composition; and wherein said magnesium oxide is present in an amount of 4 percent to about 40 percent of said sealant composition.

12. The curable sealant composition of claim 9, wherein said sealant composition further comprises an adhesion promoter.

13. The curable sealant composition of claim 9, wherein said sealant composition comprises: (A) of about 20 to about 50 percent of an organopolysiloxane component * - which comprises, a) i) for the most part, one or more siloxanes with a silanol functionality containing residues having the formulas: RaR1bS¡O1 / 2 (M1) and RaR1bS¡O2 / 2 (D ') , wherein each R individually is a substituted or unsubstituted monovalent saturated hydrocarbon radical C-MS, optionally containing 15 intermixed residues of -o- • S-, -NH-, -C- -c-o, -O-C-0 wherein R1 is hydroxy; and in which a is O, 1, 2 or 3 and b is 0 or 1, with the proviso that in M 'a + b = 3 and in D' a + b = 2, and in that said organopolysiloxane with a functionality of silanol contains at least one R1; (B) from about 2 percent to about 15 percent of an amino-silane or amino-silazane-based crosslinking agent that contains the Si-N-linked residue (s) of one or more aliphatic or cycloaliphatic amino groups primary or secondary; (C) from about 15 percent to about 40 percent iron oxide; and (D) from about 4 to about 40 percent magnesium oxide.

14. The curable sealant composition of claim 13, wherein said organopolysiloxane component further comprises one or more poly (dimethylsiloxanes) capped with trimethylsilyl.

15. The curable sealant composition of claim 13, wherein said sealant composition further comprises an effective amount of an adhesion promoter.

16. The curable sealant composition of claim 13, wherein said amino crosslinking agent comprises a silane with an aminoalkyl functionality.

17. The curable sealant composition of claim 14, wherein said crosslinking agent comprises a silane with a poly [aminoalkyl] functionality.

18. The curable sealant composition of claim 17, wherein said crosslinking agent (B) comprises: B) ¡) R3zSi (NY2) 4-z, B) ii) (Y2N) dR3SiNH (R3e (Y2N) fSiNH) gSiR3e (NY2) d, B) iii) siloxanes or polysiloxanes having attached thereto one or more residues (NY2) dSi, where d is 1, 2 or 3, or B ) iv) mixtures thereof, in which each R3 is a C? -22 alkyl radical, a C6-3 o aryl radical. a C7-3al arylalkyl or alkylaryl radical, each Y is a hydrogen atom, a C1-22 alkyl radical, a C6-3al aryl radical, a cycloalkyl radical C4.12, a C3-3 alkylaryl radical or a C7-3al arylalkyl radical, d is 2 or 3, e is 0 or 1, f is 1 or 2, g is at least 1 and z is 0 or 1. 5

19. - The curable sealant composition of claim 13, wherein said organopolysiloxane component (A) further comprises one or more residues corresponding to the formula: RaR1bR2cXdS¡O1 / 2 (M) and RaR1bR2cXdSiO2 / 2 (D), wherein R , R1, a and b have the same meanings as in claim 13; Wherein R is an unsaturated alkynyl, alkenyl or cycloalkenyl group C-MS that optionally contains heteroatoms of O, S and N; where c is 1, 2 or 3; wherein X is alkoxy C-MS, optionally intermixed with -O-; and where d is 0, 1, 2 or 3, with the proviso that in (M), a + b + c + d = 3, and in (D), a + b + c + d = 2. 20.- The curable sealing composition of Claim 13, Wherein said organopolysiloxane component (A) or an optional adhesion promoter or both also contain CMS alkoxy groups attached to silicon. 21. The curable sealant composition of claim 13, wherein said organopolysiloxane component (A) further comprises a 20 organopolysiloxane resin. 22. The curable sealant composition of claim 13, further comprising from about 20 percent to about 40 percent of an auxiliary filler material.