GB2138013A

GB2138013A - Cure accelerator for RTV composition

Info

Publication number: GB2138013A
Application number: GB08405909A
Authority: GB
Inventors: Gary Morgan Lucas
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1983-04-01
Filing date: 1984-03-07
Publication date: 1984-10-17
Also published as: FR2543559A1; GB8405909D0; DE3411691A1; JPH0521940B2; JPS59213764A; BE899276A

Abstract

One-component RTV silicone rubber composition comprises an aminoalkoxysilane crosslinker/scavenger which reacts with the silanol terminated diorganopolysiloxane base polymer to produce, in situ, an amine cure accelerator.

Description

SPECIFICATION A method of forming, in-situ, a cure accelerator for a one-package RTV composition The present invention relates to alkoxy-functional one-component RTV silicone rubber compositions and more particularly, the present invention relates to alkoxy-functional one-component RTV silicone rubber compositions in which there is formed, in-situ, a cure accelerator.

One-component RTV silicone rubber compositions have been known for a long time. The earliest such compositions were acyloxy-functional; that is, the cross-linking agent was acyloxyfunctional. Such a composition would be packaged in a substantially anhydrous state in a onepackage or a one-component container. When it was desired to cure the composition, the seal on the package would be broken. Upon the composition being exposed to atmospheric moisture, it would cure to a silicone elastomer. More recently, there have been developed alkoxy-functional one-component RTV or one-package RTV silicone rubber compositions; that is, the cross-linking agent is an alkoxy-functional silane such as methyltrimethoxysilane. An example of such a composition which was commercialized is to be found disclosed in BEERS, U.S. Patent 4,100,129.Such a composition comprises a silanol-terminated diorganopolysiloxane polymer, a trialkoxysilane cross-linking agent, a titanium chelate catalyst as a condensation catalyst, a filler, and various other additives.

While the composition of the foregoing patent was commercialized and had a shelf-life of one year or more, and a commercial curing rate, nevertheless, there were problems with these compositions. In some batches of such compositions, the shelf-life was found to be affected such that it drastically deteriorated after one or two months of storage. As a matter of fact, it was found that in most cases, the shelf-life of such compositions was affected even after two weeks of storage. Further, it was found that in some batches in such compositions, the cure rate would not be commercially acceptable. Various improvements were made to the above compositions and while these difficulties were decreased to some extent, they were not completely eliminated.

An improved commercialized alkoxy-functional one-component RTV silicone rubber composition is to be found in WHITE, et al, Serial No. 277,524. As the disclosure of this case hypothesized, it is suggested that unbonded hydroxy gorups in the RTV composition causes degradation of the alkoxy groups on the terminal silicon atoms of the base diorganopolysiloxane polymer. It is further postulated that such degradation of the alkoxy groups results in the progressive deterioration in the cure rate and shelf-stability of the RTV composition during storage.

Accordingly, an improved RTV alkoxy-functional one-component RTV silicone rubber composition is disclosed in the above WHITE, et al, Serial No. 277,524; that is, of improved shelfstability and cure rate by utilizing in such compositions certain silane scavengers having certain functional groups thereon. Such silane scavengers function to react with the unbonded hydroxy groups in the RTV mixture so as to tie them up and prevent them from degrading the terminal alkoxy groups on the base diorganopolysiloxane polymer. Accordingly, the shelf-life and the cure rate of the composition is preserved even after prolonged storage.The shelf-life of an acceptable commercialized RTV silicone rubber composition must be such that after storage of periods of time of 6 to 1 2 months after manufacture, it will have a tack-free time of 1 20 minutes or less. A more preferable composition is an alkoxy-functional one-component RTV silicone rubber composition which after storage anhydrously in its container for a period of time of 1 year or more will have a tack-free time of 60 minutes or less. Such compositions were developed as disclosed in WHITE, et al, Serial No. 277,524. It is disclosed in WHITE, et al, Serial No. 277, 524, that the functional group in the silane scavenger can be an amino group. It is also disclosed in that patent application that there be present, optionally, a cure accelerator which may be selected from amines and guanidines.

It is also important to note the patent application of MITCHELL, Serial No. 462,949, which discloses the use of certain alkoxy-functional amine-functional siloxane scavengers or integrated cross-linker, scavengers for alkoxy-functional one-component RTV silicone rubber compositions similar to the ones disclosed in the WHITE, et al, Serial No. 277,524, patent application.

In WHITE, et al, Serial No. 277,524, it is disclosed that the cure accelerator may be present in a concentration of .1 to 5 parts and preferably, from .1 to 1 part, and more preferably from .3 to 1 part per 100 parts of the silanol-terminated diorganopolysiloxane polymer. It is further disclosed with such concentrations of the cure accelerator, that the composition has a tack-free time of less than 60 minutes after the uncured composition has been accelerated shelf-aged. It is also disclosed in that patent application, that preferably the integrated cross-linker, scavenger or scavenger is utilized up to 3% excess based on the weight of the base polymer; over and above the amount needed to end-cap the base silanol-terminated diorganopolysiloxane polymer.

In accordance with the WHITE, et al, Serial No. 277,524, case, it is desirable to add up to 0.5 parts of the integrated cross-linker, scavenger for the purpose of end-capping the base polymer; to that to add as a maximum, an additional 3 parts by weight of the integrated cross-linker, scavenger for scavenging purposes; and to that to add generally from .1 to 5 parts, and more preferably from .3 to 1 part of one of the amine cure accelerators per 100 parts by weight of the silanol-terminated diorganopolysiloxane base polymer.

It has now unexpectedly been found that instead of adding a separate integrated cross-linker, scavenger and a separate cure accelerator, that when the integrated cross-linker, scavenger is amine functional, that is all that need be added and a primary or secondary amine will be liberated in sufficient quantities to act as a cure accelerator.

It is one object of the present invention to attempt to provide for a process for forming an amine cure accelerator in-situ in an alkoxy-functional one-component RTV silicon rubber composition.

It is an additional object of the present invention to attempt to provide a process for producing, in-situ, an amine-functional cure accelerator by reacting an amino-functional integrated cross-linker, scavenger with a silanol-terminated diorganopolysiloxane polymer.

It is yet an additional object of the present invention to attempt to provide a process for producing an amine-functional cure accelerator, in-situ, in an alkoxy-functional one-component RTV silicone rubber composition by reacting a primary and secondary amine-functional integrated cross-linker, scavenger with a silanol-terminated diorganopolysiloxane polymer.

It is an additional object of the present invention to attempt to provide a process for producing alkoxy-functional one-component RTV silicone rubber composition by producing, insitu, an amine-functional cure accelerator which results in the final uncured composition having a tack-free time of 60 minutes or less after periods of storage of one year or more.

There is provided by the present invention, a method of making a one-package, substantially acid-free silicone rubber composition in which a cure accelerator is produced, in-situ; immediately upon mixing the ingredients, comprising, mixing (A) 100 parts by weight of a silanol-terminated polydiorganosiloxane consisting essentially of chemically combined units of the formula

(B) at least 5 parts of a silane scavenger for hydroxy-functional groups of the formula

(C) O to 10 parts of a cross-linking silane of the formula and

(D) an effective amount of a condensation catalyst, where R is selected from Cut 13 monovalent substituted or unsubstituted hydrocarbon radicals, R1 is a C18 aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano radicals, or a C713 aralkyl radical, R2 is a C113 monovalent substituted or unsubstituted hydrocarbon radical, X is an amino hydrolyzable leaving group and a is an integer equal to 1 or 3, b is a whole number equal to O or 1, and the sum of a + b is equal to 1 or 3.

The compound of Formula (1) is an integrated cross-linker, scavenger in which X is a primary or secondary amine and is more preferably a secondary amine. The secondary amines, when they are released upon the integrated cross-linker, scavenger of Formula (1), reacting and endcapping the silanol-terminated diorganopolysiloxane polymer, act as end-coupling catalysts and further act as cure accelerators. The released primary amines will also function in that capacity.

Optionally, the excess cross-linking agent of Formula (2) is added to the composition so as to further end-couple the base silanol-terminated diorganopolysiloxane polymer as much as possible with terminal alkoxy groups.

The integrated cross-linker, scavenger, whether silane or siloxane when reacted with the silanol groups on the diorganopolysiloxane polymer will release primary or secondary amines as stated above which will function as end-coupling catalysts for catalyzing the end-coupling of the silanol-terminated diorganopolysiloxane base polymer with the integrated, cross-linker, scavenger and will also function as cure accelerators to maintain the tack-free time of the composition to preferably below 30 minutes after storage of the composition for periods of time as long as one year or more. The preferred cross-linking agent is methyltrimethoxysilane and the preferred silane scavenger is methyldimethoxy(di-N-hexylamino)silane.

Further, for the composition to cure to properties associated with RTV silicone rubber compositions, (RTV in this application refers to room temperature vulcanizable) it is necessary that the composition have a condensation catalyst and more preferably, a tin condensation catalyst, such as, for instance, dibutyltindilaurate and dibutyltindiacetate.

As stated above, per 100 parts of the silanol-terminated diorganopolysiloxane polymer, there must be about at least 4 parts of the integrated cross-linker, scavenger in order to produce a commercial product; that is, one having a shelf-stability of about 6 to 1 2 months with a tackfree time after that period of storage of 1 20 minutes or less. The preferred shelf-stability of an alkoxy-functional one-component RTV composition, is a composition having a shelf-stability in which it can be stored for periods of 1 year or more and whereupon after that period of storage it will have a tack-free time of 60 minutes or less. To obtain such shelf-stability, it is necessary to have from about 5 parts to 7 parts of integrated cross-linker, scavenger per 100 parts of the silanol-terminated diorganopolysiloxane base polymer.More than 7 parts of the integrated crosslinker, scavenger can be utilized, but without any useful results. It should be noted that the minimum range of 4 parts is the minimum range that was determined in accordance with the experiments with the integrated cross-linker of Example I. This minimum level will change to some extent with different types of amine-functional integrated cross-linker, scavengers. Accordingly, for that reason, there is utilized in the specification and in the Examples, the language of about at least 4 parts of the integrated cross-linker, scavenger in the composition. Di-Nhexylamine is a secondary amine which is one of the more effective and preferred cure accelerators. It should also be noted that the di-N-hexylamine that is liberated in Example I as an in-situ cure accelerator is a more effective cure accelerator as compared to a primary amine.

Accordingly, the results of Example I reflect the minimum range at which an integrated, crosslinker is effective to produce an alkoxy-functional RTV silicone rubber composition which forms, in-situ, a cure accelerator so as to result in a composition with a proper shelf-stability and tackfree time. Other liberated amines from the cross-linker, scavengers may be slightly more effective and accordingly, the language is used of about at least 4 parts as the minimum level of the integrated cross-linker, scavenger which is necessary in the composition to produce in-situ a cure accelerator that will result in the composition curing at the appropriate rate.It should be noted that this effect is not cumulative, since a minimum of about 4 parts of the integrated cross-linker, scavenger would not be expected from the use of individual additives to the composition as disclosed on Page 1 3 of WHITE, et al, Serial No. 277,524. In that application, it is disclosed that the cure accelerator is a separate compound that is not one formed in-situ which is added subsequently to the composition as it is being mixed or formed. On Page 10 of that application, it is disclosed that up to 3% by weight of excess scavenger may be utilized in the composition.

In the experiment reported in Example I of the present application, there was utilized about at least 4 parts of integrated cross-linker, scavenger to obtain a commercially practical composition per 100 parts of the silanol-terminated diorganopolysiloxane polymer. There was needed only .33 parts of the integrated cross-linker, scavenger to completely chain-stop the silanolterminated diorganopolysiloxane polymer. This is the theoretical value. Such amount of integrated cross-linker, scavenger liberates about .12 parts of the di-N-hexylamine as a cure accelerator.Accordingly, in accordance with the disclosure of the WHITE, et al, patent application, Serial No. 277,524, when the cure accelerator is added as a separate ingredient and the integrated cross-linker, scavenger is added as a separate ingredient to the composition, it would appear that as a maximum there can be 3.5 parts of the integrated cross-linker, scavenger in the composition. However, as the experimental results of Example I indicate, it was necessary to have at least about 4 parts of the integrated cross-linker, scavenger in the composition as a minimum, in order to produce a commercially practical RTV composition; that is, one having a commercially practical shelf-life and tack-free time.

Accordingly, what is meant to be pointed out in the above discussion is that the effect when the in-situ cure accelerator is formed is not comulative as would be expected from the disclosure in WHITE, et al, Serial No. 277,524, but has to be determined by experimental procedure.

There is nowhere disclosed in WHITE, et al, Serial No. 277,524, or any of the other patents, the in-situ formation of a cure accelerator and the compositions of the instant case. In that application as well as in any of the other patent applications, the cure accelerator is a separate compound and a separate ingredient which is added to the composition during the mixing procedure. One of the advantages and the basic advantage of the present composition is that it allows the composition to be formed more easily in a continuous manner; that is, one ingredient need be added, not two separate ingredients; thus facilitating the production of the composition by the continuous mixing of the ingredients in a devolatilizing extruder as disclosed in CHUNG, et al, Serial No. 437,895 (all the patents and patent applications are hereby incorporated by reference).This is true, even though more of the integrated cross-linker, scavenger is utilized in the composition than would be normally utilized if a separate cure accelerator was added to the composition. Accordingly, the basic advantage of the instant process is facilitating the production of the alkoxy-functional RTV composition, and more particularly, the continuous formation or manufacture of such a composition.

Proceeding now to the compount of Formula (1), such a compound is well-known as disclosed in WHITE, et al, Serial No. 277,524. This compound, unlike to some extent, the compounds disclosed in WHITE, et al, Serial No. 277,524, is not only an integrated cross-linker, scavenger, but is an integrated cross-linker scavenger compound which may have a single alkoxy group appendent to the silicon atom. Thus, it is possible to form from such integrated cross-linker compositions, diorganopolysiloxane base polymers having only a single alkoxy group on the terminal silicon atom and also one or two amine groups on the terminal silicon atom in the polymer chain. Such compositions are within the scope of the instant invention and will cure in accordance with the disclosure of the instant invention. The formation of such base polymers is also disclosed in LUCAS, Serial No. 449,105.The compounds of Formula (1) are disclosed in LUCAS, Serial No. 449,105, more fully than was the case with respect to the disclosure of WHITE, et al, Serial No. 277,524, which discloses that integrated cross-linker, scavengers must have at least two alkoxy groups thereon. Accordingly, irrespective of whether the integrated cross-linker, scavengers of WHITE, et al, Serial No. 277,524, are utilized or that of LUCAS, Serial No. 449,105, there will be formed an end-stopped polymer in which the terminal silicon atoms have one, two or three alkoxy groups which, in accordance with the disclosure in the instant invention, will form a cure accelerator in-situ and result in the composition having the desirable shelf-stability and cure rate.

It should also be noted that as the integrated cross-linker, scavenger of Formula (1) chainstops the silanol-terminated diorganopolysiloxane polymer, the amines that are liberated, which may be either primary or secondary amines, will also function as end-coupling catalysts in accordance with the disclosure of WHITE, et al, Serial No. 277,524. Additional end-coupling catalysts may be utilized as disclosed in CHUNG, et al, Serial No. 427,930.

Further, there is disclosed above that the cross-linking silane of Formula (2) may be utilized in the composition as an optional cross-linking agent to insure the maximum amount of chainstopping of the silanol-terminated diorganopolysiloxane polymer takes place and also to result in high cross-link density in the composition.

Alternatively, or in combination or in place of the silane integrated cross-linker, scavenger silane of Formula (1), there may be utilized an integrated cross-linker, scavenger of the formula

where R', R2 are as defined below and A is a radical consisting of simple amine radicals of the formula,

where R10, R11 are individually selected from hydrogen, and C18 monovalent hydrocarbon radicals, x varies in the range of 0.05 to 2.50; y varies in the range of 0.00 to 2.50; w varies in the range of 0.05 to 1.5; and the sum x + y + w varies in the range of 2.10 to 3.00.

The compounds of Formula (3) differ from the compounds of Formula (1) in that they are siloxanes, but are nevertheless, integrated cross-linker, scavengers. Such compounds have at least one alkoxy group and have from 2 to 20 silicon atoms. The amine functional group in such siloxanes of Formula (3) is either a simple primary or secondary amine.

A more preferred amine-functional siloxane integrated cross-linker, scavenger compound is one of formula

where R', R2 are as previously defined and A is a simple amine radical of the formula,

where R10, R11 are individually selected from hydrogen, and C18 monovalent hydrocarbon radicals; m varies in the range of 0.15 to 2.50; n varies in the range of 0.1 to 1.9; and ovaries in the range of 0.05 to 2.00; and the sum of m + n + o varies in the range of 2.10 to 3.00.

The compounds of Formula (4) are preferred integrated cross-linker, scavenger siloxane compounds within the scope of the compounds of Formula (3) which have at least 3 alkoxy groups in the polymer species. Again, such compounds have from 2 to 20 silicon atoms in the polymer chain. With respect to amine functional groups, the compounds of Formula (4) must have at least the same amount; that is, one amine group in the polymer species, but as a maximum may have more amine groups in the polymer species than is possible with the compound of Formula (3). Accordingly, such compounds of Formula (4) are the more preferred integrated cross-linker, scavengers.For more information as to the formation of the compounds of Formulas (3) and (4) and their use in producing alkoxy-functional one-component RTV silicone rubber compositions, one is referred to the disclosure of MITCHELL, Docket No. 60SI-660.

Serial No. 462,949. The same compounds as disclosed in that patent application are disclosed in this case with the additional purpose of adding the foregoing quantities of integrated crosslinker, scavenger in the composition, so as to produce an in-situ cure accelerator in the composition. The only caveat is that with such compounds, especially ones of high molecular weight and a small number of amine groups, it will be necessary to use a considerably greater amount of such compounds as integrated cross-linker, scavengers in the composition than in the case with the minimum level of about 4 parts as is indicated above for the more simple amines of Formula (1).

The compounds of Formula (1), (3) and (4) can be found in the foregoing patent application of WHITE, et al, Serial No. 277,524, LUCAS, Docket No. 60Si-584, Serial No.449,105 and MITCHELL, Docket No. 60Si-660, Serial No. 462,949, and their utilization as integrated crosslinker, scavengers is fully explained in those applications. It is only necessary that these ingredients be mixed into the composition in the foregoing quantities indicated above in order for them to function not only as integrated cross-linker, scavengers, but also as pure scavenging compounds, so as to produce in-situ primary, secondary amine cure accelerators which will improve the cure rate of the composition.

The silanol-terminated diorganopolysiloxane polymer preferrably has the formula,

where R is individually selected from a C 13 monovalent substituted or unsubstituted hydrocarbon radicals which are preferably methyl or a mixture of a major amount of methyl and a minor amount of phenyl, cyanoethyl, trifluoropropyl vinyl and mixtures thereof; and n is an integer having a value of from about 50 to about 2500. Preferably, the polymer has a viscosity in the range of 100 to about 400,000 centipoise and more preferably has a viscosity in the range of about 1,000 to about 250,000 centipoise when measured at about 25"C. Preferably, the n in Formula (5) varies from 500 to 2,000.

Radicals included with R of Formulas (1), (2) and (5) are, for example, aryl radicals and halogenated aryl radicals, such as phenyl, tolyl, chlorophenyl, naphthyl; aliphatic and cycloaliphatic radicals, for example, cyclohexyl, cyclobutyl; alkyl and alkenyl radicals, such as methyl, ethyl, propyl, chloropropyl, vinyl, allyl, trifluoropropyl; and cyanoalkyl radicals, for example cyanoethyl, cyanopropyl, cyanobutyl. Radicals preferably included within R1 are, for example, Ct 8 alkyl radicals, for example, methyl, ethyl, propyl, butyl, pentyl; C7 t3 aralkyl radicals, for example, benzyl; phenethyl; alkylether radicals such as 2-methoxyethyl; alkylester radicals, for example 2-acetoxyethyl; alkylketone radicals, for example 1-butan-3onyl; alkylcyano radicals, for example 2-cyanoethyl.Radicals included within R2 are the same as radicals included within the R radicals.

The radicals R, R1 and R2 are as defined in the above Formulas; that is, Formulas (1), (2), (3), (4) and (5) may be any of the radicals defined above and in the compound or polymer species may be the same of different.

A preferred polyalkoxy-terminated polydiorganosiloxane produced by the above reaction of the silanol-terminated diorganopolysiloxane polymer of Formula (5) with the integrated cross-linker, scavengers of Formula (1), are the ones having the formula

where R, Rt, R2 are as previously defined, X is a hydrolyzable amino leaving group; e is an integer equal to O or 2; b is a whole number equal to O or 1; and the sum of b + e is equal to O or 2; and n is an integer having a value of about 50 to abut 2,500, inclusive. Such a preferred polyalkoxyterminated diorganopolysiloxane of Formula (6) is desirably formed in the RTV compositions of the present case and may be mixed with the other ingredients of the instant composition in various ways to form various types of mixtures.

One preferred such mixture is, for instance, a room temperature vulcanizable material selected from (i) a mixture comprising (a) 100 parts of a silanol-terminated polydiorganosiloxane consisting essentially of chemically combined units of the formula

(c) O to 10 parts of a cross-linking silane of the formula

(d) an effective amount of a condensation catalyst, and (ii) a mixture comprising (a) 100 parts of a polyalkoxy-terminated polydiorganosiloxane of the formula

(b) O to 10 parts of a cross-linking silane of the formula,

(c) an effective amount of a condensation catalyst where R, R1, R2 and X are as previously defined; a is an integer equal to 1 to 3; b is a whole number equal to O or 1; and the sum of a + b is equal to 1 to 3; e is a whole number equal to O or 2; the sum of b + e is equal to O or 2; n is an integer having a value of about 50 to 2500, inclusive. Such a composition can also be produced utilizing an integrated cross-linker, scavenger of Formulas (3) and (4) in the mixture of the above method. In all cases there is formed a cure accelerator which will function to result in an RTV composition having the appropriate shelf-stability and cure rate. The preferred crosslinking agent in the instant invention of Formula (2) is methyltrimethoxysilane. Preferably R, R' and R2 are selected from methyl.

Further, it is necessary that the composition have a condensation catalyst if it is to cure to cross-link to the density anthave the properties normally associated with silicone rubber compositions. The preferred condensation catalyst is a tin condensation catalyst.

Effective amounts of the condensation catalysts which can be used in the practice of the present invention to facilitate the cure of the RTV compositions are, for example, 0.001 to 1 part based on the weight of 100 parts of the silanol-terminated polydiorganosiloxane of Formula (1). There are included tin compounds, for example dibutyltindilaurate; dibutyltindiacetate; dibutyltindimethoxide; carbomethoxyphenyl tin trisuberate; tin octoate; isobutyl-tin triceroate; dimethyl tin dibutyrate; dimethyl tin di-neodeconoate; triethyl tin tartrate; dibutyl tin dibenzoate; tin oleate; tin naphthenate; butyltintri-2-ethylhexoate; tinbutyrate. The preferred condensation catalysts are tin compounds and dibutyltindiacetate is particularly preferred.

Titanium compounds which can be used are, for example, 1 ,3-propanedioxytitanium bis(ethylacetoacetate); 1 , 3-propaned ioxytitanium bis(acetylacetonate); diisopropoxytitanium bis(acetylacetonate); titanium naphthenate; tetrabutyltitanate; tetra-2-ethylhexyltitanate; tetraphenyltitanate; tetraoctadecyltitanate; ethyltriethanolaminetitanate. In addition beta-dicarbonyltitaniu m compounds as shown by WEYENBERG, U. S. Patent 3,334,067 can be used as condensation catalysts in the present invention.

Zircomium compounds, for example, zirconium octoate, also can be used.

Further examples of metal condensation catalysts are, for example, lead 2-ethyloctoate; iron 2ethylhexoate; cobalt 2-ethylhexoate; manganese 2-ethylhexoate; zinc 2-ethylhexoate; antimony octoate; bismuth naphthenate; zinc naphthenate; zinc stearate.

Examples of nonmetal condensation catalysts are hexylammonium acetate and benzyltrimethylammonium acetate.

Various fillers and pigments can be incorporated in the silanol or alkoxy-terminated organopolysiloxane, such as for example, titanium dioxide, zirconium silicate, silica aerogel, iron oxide, diatomaceous earth, fumed silica, carbon black, precipitated silica, glass fibers, polyvinyl chloride, ground quartz, calcium carbonate, etc. The amounts of filler used can obviously be varied within wide limits in accordance with the intended use. For example, in some sealant applications, the curable compositions of the present invention can be used free of filler. In order applications, such as the employment of the curable compositions for making binding material on a weight basis, as much as 700 parts or more of filler, per 100 parts of organopolysiloxane can be employed.In such applications, the filler can consist of a major amount of extending materials, such as ground quartz, polyvinylchloride or mixtures thereof, preferably having an average particle size in the range of from about 1 to 10 microns.

The compositions of the present invention also can be employed as construction sealants and caulking compounds. The exact amount of filler, therefore, will depend upon such factors as the application for which the organopolysiloxane composition is intended, the type of filler utilized (that is, the density of the filler and its particle size). Preferably, a proportion of from 10 to 300 parts of filler, which can include up to about 35 parts of a reinforcing filler, such as fumed silica filler, per 100 parts of silanol-terminated organopolysiloxane is utilized.

As utilized hereinafter, the term "stable" as applied to the one-package polyalkoxy-terminated organopolysiloxane RTV's of the present invention means a moisture curable mixture capable of remaining substantially unchanged while excluded from atmospheric moisture and which cures to a tack-free elastomer after an extended shelf-period. In addition, a stable RTV also means that the tack-free time exhibited by freshly mixed RTV ingredients under atmospheric conditions will be substantially the same as that exhibited by the same mixture of ingredients exposed to atmospheric moisture after having been held in a moisture resistant and moisture-free container for an extended shelf period at ambient conditions or an equivalent period based on accelerated aging at an elevated temperature.

The expression "substantially acid-free" with respect to defining the elastomer made from the RTV composition of the present invention upon exposure to atmospheric moisture means yielding by-products having a pKa of 5.5 or greater with 6 or greater preferred and 10 or greater being particularly preferred.

Besides the above ingredients, the composition may have other ingredients such as plasticizers to make the composition low-modulus, sag control additives, adhesion promoters and so forth. Examples of such additives are to be found disclosed in BEERS, Serial No. 349,537 and LUCAS, Serial No. 349,538. The composition may be prepared in many ways, but most preferably it is prepared by mixing the integrated cross-linker, scavenger with the silanolterminated diorganopolysiloxane polymer in a substantially anhydrous manner and then there is added to it any additional end-coupling catalyst. However, the reaction mixture is autocatalytic as has been stated above. Then, in subsequent mixing steps or mixing stations there can be added other ingredients, including plasticizers, adhesion promoters, fillers and so on; as disclosed in CHUNG, et al, Serial No. 347,895.Also in additional mixing steps there may be added excess integrated cross-linker, scavenger as disclosed in the foregoing CHUNG, et al, Serial No. 347,895 application, so long as in the total mixing there is the minimum amount of integrated cross-linker, scavenger indicated above. The minimum amount of a particular integrated cross-linker, scavenger will have to be determined by experimentation as indicated above.

Once the composition is formed, it is packaged in a substantially anhydrous manner in moisture-proof packages and stored and sold as such. When it is desired to cure the composition, the seal on the package is broken and the composition is applied and exposed to atmospheric moisture whereupon it will cure to a silicone elastomer with full cure taking place in 24 to 72 hours. As noted above, this composition may be prepared continuously or semicontinuously as disclosed in CHUNG, et al, Serial No. 347,895 or may be produced or mixed batchwise as is desirable.

The examples below are given for the purpose of illustrating the present invention. They are not given for any purpose of setting limits and boundaries to the instant invention. Ali parts in the Examples are by weight.

Preferred integrated cross-linker, scavengers within the scope of Formula (1) are: methyldimethoxy(di-N-hexylamino)silane methyldimethoxy(di-N-methylamino)silane methyldimethoxyisopropylaminosilane methyldimethoxy(di-N-butylamino)silane methyldimethoxy(di-N-isobutylamino)silane methyldimethoxy(di-N-propylamino)silane methyldimethoxy(di-N-vinylamino)silane Preferred tin condensation catalysts for use in the instant invention are dibutyltindiacetate and dibutyltindilaurate.

EXAMPLE I A 5-liter, 3-neck flask fitted with a mechanical stirrer, pot thermometer, water reflux condenser with N2 inlet port, and two 250 ml pressure equalizing addition funnels, was purged with dry N2 and charged with 2 liters of hexane and 2 moles (280 parts) of Et3N. After stirring and purging with N2, the additiqn funnel was charged with 1.00 mole (140 parts) CH3Si(OCH3)2CI. The second addition funnel was charged with 1.25 moles (231.8 parts) di-Nhexylamine. While stirring at room temperature, under an N2 atmosphere, the CH3Si(OCH3)2CI was rapidly added to the pot mixture. The di-N-hexylamine was added dropwise to the rapidly stirring pot mixture over over a 2 hour period.A slight exotherm was observed, causing the pot temperature to rise from 22"C to 35"C. Copious amounts of solid, white, triethylamine hydrochloride formed during the course of the reaction. After stirring at room temperature for 1 5 hours, the solids were removed by vacuum filtration and liquid volatiles were removed via rotary flash evaporation under reduced pressure. Vacuum filtration yielded the desired product, methyldimethoxy(di-N-hexylamino)silane, b.p. 113-115 C/5 mm. Hg., 92% purity by gas chromotography analysis.

The CH3-Si(OCH3)2-N(hexyl)2 was then compounded with polymer, filler and Sn+4 catalyst, under anhydrous conditions, using a Semkit(E) mixer. Two step catalyzations were used as follows.

In the first step which comprised 1 5 minute mixing time, at room temperature, there was mixed 85 parts by weight of a silanol-terminated dimethylpolysiloxane polymer of 3,000 centipoise viscosity at 25"C, 1 5 parts by weight of an octamethylcyclotetrasiloxane fumed silica filler and 2 to 6 parts as indicated in Table I below of methyldimethoxydihexylaminosilane.This mixture was taken and in a second catalyzation step in the Semkit(E) mixer there was mixed in to it over a 1 5 minute period mixing time at room temperature, 0.23 parts of dibutyltindiacetate and 21 parts by weight of a trimethylsiloxy-end-stopped dimethylpolysiloxane polymer of 100 centipoise viscosity at 25"C having a silanol content in the range of 500 to 1 500 parts per million.

After mixing, the RTV compositions were packaged into sealed aluminum tubes and stored 24 hr RT, 24 hr 100"C and 48 hr 1 00'C prior to exposure to a room temperature, 50% R.H.

curing environment. Speed and degree of cure was determined by Tack Free Time and 24 hr Durometer measurements. An acceptable cure is defined by TFT c 30 min. and 24 hr Durometer L 28. The results are given in Table I.

TABLE I CH3Si(OCH3)2-N(hexyl)2 Results Shelf Age 24 Hr CH3Si(OCH3)2-N(hexyl)2 Age Temp. T.F.T. Durolevel (parts) (days) "C (min.) meter 2.0 0 25 35 - 1 25" gelled in tube 2.5 0 25 25 - 1 25" gelled in tube 3.0 0 25 20 - 1 25" 25 28 1 100" gelled in tube 3.5 0 25 40 - 1 25" 55 27 1 100" 50 25 2 100" gelled in tube 4.0* 0 25 20 - 1 25" 20 26 1 100" 20 31 2. 100" 15 30 5.0 2 100 15 29 6.0 2 100" 20 28 Minimum CH3Si(OCH3)2-N(hexyl)2 level to achieve shelf stability and fast cure.

EXAMPLE II

A 5-liter, 3-neck flask fitted with mechanical stirrer, pot thermometer, water reflux condenser with N2 inlet port, and two 250 ml pressure equalizing addition funnels, was purged with dry N2 and charged with 2-liters hexane and 2 moles (280 ml) Et3N. After stirring and purging with N2, the addition funnel was charged with 1.00 mole (140 parts) CH3Si(COH3)2CI. The second addition funnel was charged with 1.25 moles (161.6 parts) di-N-butylamine While stirring at room temperature, under an N2 atmosphere, the CH3Si(OCH3)2CI was rapidly added to the pot mixture. The di-N-butylamine was added dropwise to the rapidly stirring pot mixture over a 2 hour period.A slight exotherm was observed, causing the pot temperature to rise from 22"C to 35"C. Copious amounts of solid, white, triethylamine hydrochloride formed during the course of the reaction. After stirring at room temperature for 1 5 hours, the solids were removed by vacuum filtration and liquid volatiles were removed via rotary flash evaporation under reduced pressure. Vacuum filtration yielded the desired product, methyldimethoxy (di-N-butylamino)silane, b.p. 60 /7 mm. Hg., 88% purity by gas chromotography analysis.

The aminosilane was then compounded with a polymer filler and tin catalyst under anhydrous conditions using a SemkitB mixer. Step catalyzation was used as follows: To 85 parts of the same silanol-terminated dimethylpolysiloxane polymer of Example I, there was added 1 5 parts of the same treated fumed silica filler of Example I, 2 to 5 parts of the amino silane which varied in concentration from 2 to 5 parts in the mixture. This mixture was mixed in a first mixing step for 1 5 minutes at room temperature.

In a catalyzation 1 5 minute mixing step at room temperature in a SemkitX mixer, there was added or mixed into this first mixture .23 parts of dibutyltindiacetate and 1.0 parts of a trimethylsiloxy-end-stopped dimethylpolysiloxane polymer of 100 centipoise viscosity at 25"C having a silanol content in the range of 500 to 1 500 parts per million. The cure data obtained from such compositions including accelerated aging, where applicable and tack-free time is given in Table II below.

TABLE II CH3Si(OCH3)2-N(Butyl)2 Results Shelf Age 24 Hr CH3Si(OCH3)2-N(Butyl)2 Age Temp T.F.T. Durolevel (parts) (days) C (min.) meter 2.0 0 25 25 - 1 25" 40 24 1 100" gelled in tube 2.7 0 25 20 - 1 30 30 1 100" gelled in tube 4.0* 0 25 55 - 1 25" 40 31 100 30 27 2 100 25 29 5.0 0 25 25 - 1 25" 30 34 1 100 15 34 2 100 25 31 * Minimum CH3Si(OCH3)2-N(Butyl)2 level to achieve shelf stability and fast cure.

Claims

1. A method of making a one-package and substantially acid-free room temperature vulcanizable silane rubber composition in which a cure accelerator is formulated in-situ immediately upon mixing the ingredients, comprising, mixing (a) 100 parts by weight of a silanol-terminated polydiorganosiloxane consisting essentially of chemically combined units of the formula

(b) at least about 4 parts of a silane scavenger for hydroxy-functional groups of the formula

(c) O to 10 parts of a cross-linking silane of the formula and

(d) an effective amount of a condensation catalyst, where R is selected from C, ,3 monovalent substituted or unsubstituted hydrocarbon radicals, R' is a C18 aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylketone and alkylcyano radicals, or a C7 13 monovalent substituted or unsubstituted hydrocarbon radical, X is an amino hydrolyzable leaving group and a is an integer equal to 1 or 3, b is a whole number equal to O or 1, and the sum of a + b is equal to 1 or 3.

2. The method of Claim 1 wherein the cross-linking agent is methyltrimethoxysilane.

3. The method of Claim 2 wherein R, R1, R2 are methyl.

4. The method of Claim 3 wherein the condensation catalyst is a tin compound.

5. The method of Claim 4 wherein the condensation catalyst is selected from the class consisting of dibutyltindilaurate and dibutyltindiacetate.

6. The method of Claim 1 wherein the silane scavenger is methyldimethoxy(di-N-hexylami- no)silane.

7. The method of Claim 1 wherein the silane scavenger is methylmethoxydi-N-methylamino silane.

8. The method of Claim 1 wherein the silane scavenger is methyldimethoxyisopropylaminosilane.

9. A method of making a substantially acid-free room-temperature vulcanizable organopolysiloxane composition under sstantially anhydrous conditions in which a cure accelerator is produced in-situ immediategupon mixing the ingredients and utilizing an effective amount of a condensation catalyst with a silanol-terminated organopolysiloxane and a polyalkoxysilane crosslinking agent, the improvement which comprises adding to 100 parts by weight of the silanolterminated organopolysiloxane at least about 4 parts by weight of a polyalkoxysilane which is both a scavenger for hydroxy-functional groups and a cross-linking agent of the formula

where R1 is a C18 aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano radicals, or a C7 r3 aralkyl radical, R2 is a C1-13 monovalent substituted or unsubstituted hydrocarbon radical, X is an amino hydrolyzable leaving group; a is an integer equal to 1 or 3; b is an integer equal to O or 1; the sum of a + b is equal to 1 or 3; and thereafter adding an effective amount of a condensation catalyst.

10. The method of Claim 9 wherein the cross-linking agent is methyltrimethoxysilane.

11. The method of Claim 10 wherein the R, R1, R2 are methyl.

1 2. The method of Claim 11 wherein the condensation catalyst is a tin compound.

1 3. The method of Claim 1 2 wherein the condensation catalyst is selected from the class consisting of dibutyltindilaurate and dibutyltindiacetate.

14. The method of Claim 9 wherein the silane scavenger is methyldimethoxy(di-N-hexylami- no)silane.

1 5. The method of Claim 9 wherein the silane scavenger is methylmethoxydi-N-methylaminosilane.

16. The method of Claim 10 wherein the silicone scavenger is methyltrimethoxyisopropylaminosilane.

1 7. A method of making a one-package and substantially acid-free room-temperature vulcanizable composition curable to the solid elastomeric state, in which a cure accelerator is produced, in-situ, immediately upon mixing the ingredients and which method comprises agitating under substantially anhydrous conditions at a temperature in the range of from O"C to 180"C, a room temperature vulcanizable material selected from (i) a mixture comprising (a) 100 parts of a silanol-terminated polydiorganosiloxane consisting essentially of chemically combined units of the formula

(c) O to 10 parts of a cross-linking silane of the formula

(b) O to 10 parts of a cross-linking silane of the formula,

(c) an effective amount of a condensation catalyst where R is selected from C, I3 monovalent substituted or unsubstituted hydrocarbon radicals, R1 is a C18 aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano radicals, or a C7 I3 alkaryl radical, R2 is a C1-13 monovalent substituted or unsubstituted hydrocarbon radical, X is a hydrolyzable amino leaving group, a is an integer equal to 1 or 3, b is a whole number equal to O or 1, and the sum of a + b is equal to 1 or 3, e is a whole number equal to O or 2 and the sum of b + e is equal to O to 2, n is an integer having a value of from about 50 to about 2500 inclusive.

1 8. A method of making a one-package and substantially acid-free room-temperature vulcanizable silicone rubber composition in which a cure accelerator is produced in-situ immediately upon mixing the ingredients, comprising, mixing (a) 100 parts of a silanol-terminated polydiorganosiloxane consisting essentially of chemically combined units of the formula

(b) at least about 4 parts of a siloxane scavenger for hydroxy-functional groups of the formula

where R1, R2 are as defined below and A is a radical consisting of simple amine radicals of the formula

where R10, R" are individually selected from hydrogen and C18 monovalent hydrocarbon radicals, x varies in the range of 0.05 to 2.50; y varies in the range of 0.00 to 2.50; w varies in the range of 0.05 to 1.5; and the sum of x + y + w varies in the range of 2.10 to 3.00, (c) O to 10 parts of a cross-linking silane of the formula, and

(d) an effective amount of a condensation catalyst and where R is selected from C"3 monovalent substituted or unsubstituted hydrocarbon radicals, R' is a C18 aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano radicals, or a C7 3 aralkyl radical, R2 is a C1-13 monovalent substituted or unsubstituted hydrocarbon radical, and b is O or 1.

1 9. The method of Claim 18 wherein the cross-linking agent is methyltrimethoxysilane.

20. The method of Claim 1 9 wherein R, R' and R2 are methyl.

21. The method of Claim 20 wherein the condensation catalyst is a tin compound.

22. The method of Claim 21 wherein the condensating catalyst is selected from the class consisting of dibutyltindilaurate and dibutyltindiacetate.

23. The method of Claim 1 8 wherein the siloxane scavenger has the formula

where R', R2 are as previously defined and A is a simple amine radical of the formula

where R10, R" are individually selected from hydrogen, and C18 monovalent hydrocarbon radicals; m varies in the range of 0.1 5 to 2.50; n varies in the range of 0.1 to 1.9; and o varies in the range of 0.05 to 2.00; and the sum of m + n + ovaries in the range of 2.10 to 3.00.

24. In the method of making a substantially acid-free room-temperature vulcanizable organopolysiloxane composition under substantially anhydrous conditions in which a cure accelerator is produced in-situ immediately upon mixing the ingredients and utilizing an effective amount of a condensation catalyst with a silanol-terminated organopolysiloxane and a polyalkoxysilane cross-linking agent, the improvement which comprises adding to 100 parts by weight of the silanol-terminated organopolysiloxane at least about 4 parts by weight of a polyalkoxysilane which is both a scavenger for hydroxy-functional groups and a cross-linking agent of the formula

where A is a radical consisting of simple amine radicals of the formula,

where R'O, R11 are individually selected from hydrogen, and C18 monovalent hydrocarbon radicals; x varies in the range of 0.05 to 2.50; y varies in the range of 0.00 to 2.50; and w varies in the range of 0.05 to 1.5; and the sum of x + y +w varies in the range of 2.10 to 3.00; where R' is a C18 aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano radicals, or a C7 53 aralkyl radical, R2 is a C1-13 monovalent substituted or unsubstituted hydrocarbon radical, and thereafter adding an effective amount of a condensation catalyst, whereby improved stability is achieved in the resulting roomtemperature vulcanizable organopolysiloxane composition.

25. The method of Claim 24 wherein the cross-linking agent is methyltrimethoxysilane.

26. The method of Claim 25 wherein R, R1 and R2 are methyl.

27. The method of Claim 26 wherein the condensation catalyst is a tin compound.

28. The method of Claim 27 wherein the condensation catalyst is selected from the class consisting of dibutyltindiacetate and dibutyltindilaurate.

29. The method of Claim 24 wherein the siloxane scavenger has the formula

where R1, R2 are as previously defined and A is a simple amine radical of the formula,

where R'O, R" are individually selected from hydrogen and C, 8 monovalent hydrocarbon radicals, m varies in the range of 0.15 to 2.50; n varies in the range of 0.1 to 1.9; ovaries in the range of 0.05 to 2.00; and the sum of m + n + o varies in the range of 2.10 to 3.00.

30. A method of making a one-package and substantially acid-free room-temperature vulcanizable composition curable to the solid elastomeric state, in which a cure accelerator is produced in-situ immediately upon mixing the ingredients and which method comprises agitating under substantially anhydrous conditions at a temperature in the range of from O"C to 180"C, a room-temperature vulcanizable material selected from (i) a mixture comprising (a) 100 parts of a silanol-terminated polydiorganosiloxane consisting essentially of chemically combined units of the formula

(b) a stabilizing amount of a siloxane scavenger for hydroxy-functional groups of the formula

where R, R', RZ are as defined below and A is a radical consisting ot simple amine radicals ot the formula,

where R'O, R11 are individually selected from hydrogen and C, 8 monovalent hydrocarbon radicals, x varies in the range of 0.05 to 2.50; y varies in the range of 0.00 to 2.50; w varies in the range of 0.05 to 1.5; and the sum of x + y + w varies in the range of 2.10 to 3.00; (c) 0 to 10 parts of a cross-linking silane of the formula

(d) an effective amount of a condensation catalyst; and (ii) a mixture comprising (a) 100 parts of a polyalkoxy-terminated polydiorganosiloxane of the formula

(iii) O to 10 parts of a cross-linking silane of the formula, and

(iv) an effective amount of a condensation catalyst, where R is selected from C1,3 monovalent substituted or unsubstituted hydrocarbon radicals, R' is a C, 8 aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano radicals, or a C7 r3 alkaryl radical, R2 is a C1-13 monovalent substituted or unsubstituted hydrocarbon radical, X is a hydrolyzable amino leaving group; b is a whole number that is O or 1; e is a whole number equal to O or 2; the sum of b + e is equal to O to 2; and n is an integer having a value of from about 50 to 2500 inclusive.

31. The method of Claim 30 wherein the siloxane scavenger compound has the formula

where R'O, R" are individually selected from hydrogen, and C18 monovalent hydrocarbon radicals; m varies in the range of 0.15 to 2.50; n varies in the range of 0.1 to 1.0; and ovaries in the range of 0.05 to 2.00; and the sum of m + n + o varies in the range of 2.10 to 3.00.

32. A method of making a room temperature vulcanizable composition as claimed in claim 1 substantially as hereinbefore described in any one of the examples.

33. The method of making a room temperature vulcanizable composition as claimed in claim 9 substantially as hereinbefore described in any one of the examples.

34. A room temperature vulcanizable composition when produced by a method as claimed in any one of the preceding claim.