CA1132739A - Self-bonding silicone rubber compositions - Google Patents
Self-bonding silicone rubber compositionsInfo
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- CA1132739A CA1132739A CA325,063A CA325063A CA1132739A CA 1132739 A CA1132739 A CA 1132739A CA 325063 A CA325063 A CA 325063A CA 1132739 A CA1132739 A CA 1132739A
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Abstract
ABSTRACT OF THE DISCLOSURE
A self-bonding silicone rubber composition comprising a vinyl-terminated polysiloxane polymer, a hydride siloxane cross-linking agent, a platinum catalyst and as the self-bonding additive, the partial hydrolysis product of an aliphatically unsturated hydrolyzable alkoxy silane.
Compositions of the present invetion are particularly suited for use as electrical potting compounds or encapsulants, and do not require the use of a primer when employed to these ends.
A self-bonding silicone rubber composition comprising a vinyl-terminated polysiloxane polymer, a hydride siloxane cross-linking agent, a platinum catalyst and as the self-bonding additive, the partial hydrolysis product of an aliphatically unsturated hydrolyzable alkoxy silane.
Compositions of the present invetion are particularly suited for use as electrical potting compounds or encapsulants, and do not require the use of a primer when employed to these ends.
Description
60S~
The present inven-tion relates to self-bonding silicone rubber compositions and more particularly the present invention relates to SiH-olefin platinum catalyzed self-bonding silicone rubber compositions in which the self-bonding additive is the partial hydrolysis product of an aliphatically unsaturated hydrolyzable alkoxy silane.
SiH-olefin platinum catalyzed compositions are well known. Such compositions generally comprise a vinyl-containing polysiloxane polymer as the base polymer, a filler which may be a reinforcing filler such as fumed silica or precipitated silica, or an extending filler such as fused quartz incorporated into the base vinyl containing polymer. Also, a vinyl containing silicone resin may be used with or in place of reinforcing fillers.
Such a mixture is generally stored separately. The cross-linking portion of the composition comprises a hydride siloxane which may either be a hydride-containing polysiloxane or hydride containing silicone resin. A platinum catalyst is used to promote the cure.
Various other ingredients may be added to the composition so as to enhance its cured physical properties such as, for instance, there may be added to the composition low viscosity vinyl-containing polymers. The platinum catalysts may either be incorporated with the base vinyl-containing polymer and filler or it may be packaged with the hydride siloxane cross-linking agent. When it is desired to cure the composition, the two packages or two components are mixed together and the composition is applied in the desired manner and cures at room temperature or at higher temperatures to orm a silicone elastomer.
There may also be incorporated into such composi-tions well known inhibitors such as, for instance, acetylenic X'~39 compounds and other types of compounds which inhibit the cure of the composition at room temperature. When such an inhibited composition is heated at elevated tem-peratures, that is temperatures above 100C, the effect of the inhibitor is destrayed and the composition cures rapidly in a number of minutes to produce a silicone elastomer. Such inhibitors are used in these SiH-olefin platinum catalyzed compositions so as to enhance their pot life or working life after the two pac~ages are mixed and prior to cure.
There also has been developed a one-component SiH-olefin platinum catalyzed silicone rubber compo-sition in which the inhibitor is a hydroperoxy compound which is so effective that the composition can be pack-aged as a one package system for prolonged periods of time and yet when e~posed to elevated temperatures can cure to form a silicone elastomer in a matter of minutes. Such a composition is, for instance, disclosed in the Canadian application of William J. Bobear, ?0 entitled "Inhibitor for Platinum Catalyzed Silicone Rubber Compositions", Serial No. 276,318 dated April 7, 1977.
Such SiH-olefin platinum catalyzed compositions find great use as for the preparation of silicone molds, for paper release coatings and as encapsulants. However, while such compositions are very suitable for paper release applications and for silicone molds because of their good release properties, such silicone rubber compositions are utilized with some difficulty as encapsulants and for potting applications because of poor adherence to required bonding surfaces. For potting applications, it is often desired to pot Gr enclose electric circuitry with a silicone ~3~"~3~ 60SI-112 " .t ~.J ~
composition to protect the electric circuitry from dirt, mois-ture and mechanical shock. There has even been developed a clear SiH-olefin platinum catalyzed com-position for such potting and encapsulating applications so that if there is a malfunction in the electric circuitry, the technician can view the circuitry through the clear potting composition to determine the corrective action to be taken.
Other relevant properties of such SiH-olefin platinum catalyzed compositions for potting and encapsulating electric circuitry are that they are non-conductive of electricity, resistant to ozone and weathering, and water repellent. These properties make such compositions ideal encapsulant and potting materials. However, such SiH-olefin platinum catalyzed compositions still had difficulty with respect to potting and encapsulating applications. Because of their good release properties these SiH-olefin platinum catalyzed silicone rubber compositions would not adhere very well to the electric circuitry and circuitry board substrates such that a very poor bond was formed between the silicone elastomeric composition and the substrates. Accordingly, because of the formation of such poor bonds between the silicone elastomeric composition and the encapsulated substrate, the silicone elastomeric encapsulant or potting compound had a tendency to come loose from the substrate and thus not fully protect the electric circuitry from moisture, dirt and mechanical shock.
To solve this problem, primers were developed for 1 30 such SiH-olefin platinum catalyzed compositions to apply them to metal substrates and specifically, electric circuitry substrates and the electric circuitry itself '73~
so that the cured silicone elastomer would adhere with good bond strength to the encapsulated and potted sub-state. Such primer compositions are generally com-binations of active ingredients dissolved in a volatile solvent or solvent mixture. The primer is applied to the substrate to be encapsulated or potted, say by wiping or spraying. The solvent is allowed to evapora-te, leaving a surface coating more suited to bonding. The silicone rubber potting composition is applied there-over and allowed to cure to produce a silicone elastomer with a good bond between the silicone elastomer and the electric circuitry that is to be potted or encapsulated.
Unfortunately, clear silicone potting compounds that employ vinyl containing silicone resins rather than fillers for reinforcement still did not adhere satis-factorily even when such primers were employed. Examples of materials there are desired for electric circuitry substrates that are to be bonded to by SiH-olefin platinum catalyzed compositions are for instance, glass, aluminum, steel, copper and stainless steel which, of course, includes the metals of the electric circuitry itself. Accordingly, the use of such primers sometimes operated with effectiveness to bind such SiH-olefin platinum catalyzed compositions with good bond strengths to the foregoing metal substrates. However, even when they worked well there were various problems associated with primers.
First and foremost of all, it required an additional step in the preparation of the encapsulated or potted electric circuitry apparatus, that is, the application of the primer to the substrate. In addition it increased the cost of the total operation both in the labor in-3~ 6 0 S ~ 2 volved to apply the primer composition to the electric circuitry substrate and also in the cost of manufacture and distribution of the primer composition itself.
Fur-ther, such use of primer compositions made it necessary to set for~h more detailed instructions than was usual in the preparation of the encapsulated apparatus.
Accordingly, for such encapsulated and potting applications it is highly desirable to have an SiH-olefin platinum catalyzed composition which has a self-bonding additive in it such that a primer is not needed for the application of the composition to encapsulate or pot electric circuitry.
It is especially highly desirable to have a clear SiH-olefin platinum catalyzed composition which has a self-bonding additive in it, such that satisfactory adherence is obtained without the use of a primer. Various attempts have been made to accomplish this but failed for one reason or another. One of the reasons why many of the additives that were added to the SiH-olefin platinum catalyzed composition did not operate properly was ~0 that the additive would poison or deactivate the platinum catalyst such that the composition would not cure upon application. Other supposed self-bonding additives were simply not effective in establishing a good bond between the cured elastomer and the substrates of interest.
Silyltriallylisocyanurates were, for instance, tried I as self-bonding additives for room temperature compositions but such additives did not perform as well as would be desired. Such use of the silyltriallylisocyanurates in traditional room temperature vulcanizable compositions are, for instance, set forth in Hardman and Berger, U.S. Patent No. 3,882,083 dated May 6, 1975. Another example of such an SiH-olefin platinum catalyzed com-position is to be found in sallard U.S. Pat. #3,527,655 dated September 8, 1970. The adhesive component of this composition was the reaction product of a vinyltrieh-lorosilane and a vinyl trialkoxy silane. Accordingly, it was highly desirable to find a self-bonding additive for SiH-olefin platinum catalyzed compositions whieh would ~dhere sueh eompositions with good bond strength and in the absence of a primer to such diverse substrates as glass, aluminum, steel, copper, stainless steel, so that such compositions would be desirable compositions for the encapsulation and potting of electrieal circuitry.
It is one subject of the present invention to pro-vide for a self-bonding additive for SiH-olefin platinum eatalyzed compositions. It is another object of the present invention to provide for a process for producing a self-bonding SiH-olefin platinum catalyzed eomposition.
It is an additional object of the present invention to provide for a process for adhering SiH-olefin platinum eatalyzed eompositions to eleetrieal circuitrv substrates ~0 without the use of a primer.
It is still an additional objeet of the present invention to provide for an inexpensive self-bonding additive for SiH-olefin platinum eatalyzed compositions.
It is still a further objeet of the present in-vention to provide for a preferred process for produeing a partial hydrolysis produet of an aliphatieally un-saturated hydrolyzable alkoxy silane, which can be utilized as a self-bonding additive for SiH-olefin platinum eatalyzed eompositions.
These and other objeets of the present invention are aeeomplished by means of the diselosure set forth hereinbelow.
7~ 60S~ l2 There is provided by the present invention and in accordance with the above objects, a self-bonding silicone rubber composition comprising (A) 100 parts by ~eight of a base polymer of the formula, R R R
(1) Vi - Si - ~ -SiO --Si - Vi l l R R xR
where R is selected from the class consisting of monovalent hydrocarbon radicals and halogenated monovalent hydro-carbon radicals and x is such that the viscosity of the base polymer varies from 100 to 200,000,000 centipoise at 25C; (B) from 0.5 to S0 parts by weight of a hydride siloxane cross-linking agent; (C) from 1 to 500 parts per million of a platinum catalyst; and (D) from 0.1 to 5 parts by weight of a self-bonding additive which is the partial hydrolysis product of an aliphatically unsaturated hydrolyzable alkoxy silane. The partial ~0 hydrolysis product is most preferably that of vinyl-triethoxysilane. There can also be incorporated from 10 to 100 parts of a vinvl-containing silicone reinforc-ing resin in addition to or in place of reinforcing filler composed of R6SiOo. 5 units and SiO2 units in which from about 2.5 to 10 mole percent of the silicon atoms contain silicon-bonded vinyl groups, where R6 is a monovalent hydrocarbon radical.
It should be noted that the pure vinyltriethoxy-silane will not function as a self-bonding additive in SiH-olefin platinum catalyzed compositions. On the other hand, the completely hydrolyzed vinyltriethoxysilane cannot be used as a ~elf-bonding - additive in SiH-olefin ~3~33 platinum catalyzed compositions since it is in -the form of a resinous gel and is not miscible with the composi-tion and thus will not perform a self-bonding function.
Further, such a gel cannot be beneficially incorporated into SiH-olefin platinum catalyzed compositions since its presence would seriously detract from their cured physical properties. It is the advantage of the self-bonding additive of the instant case that when properly used in the appropriate concentrations that it will not detract significantly from the final cured physical properties of the silicone elastomer that is formed.
To produce the proper partial hydrolysis product of the aliphatically unsaturated silane, it is desirable that 16 to 49~ of the available hydrocarbonoxy groups of said alkoxy silane be hydrolyzed in the process for produeing the partial hydrolyzate. If less than 16% is hydrolyzed then too large an amount of the vinyltrie-thoxysilane which does not aet as a self-bonding additive and which further dilutes the effectiveness of the partial hydrolysis product may remain in the hydrolyzate mixture.
If more than 49~ of the available hydrocarbonoxy groups in the silane is hydrolyzed, then you encounter the aforementioned problems of the formation of gels which is undesirable in the final product.
The hydride cross-linking agent may be either a hydride-containing linear polysiloxane polymer or it may be a hydride containing silicone resin compound of monofunctional and tetrafunctional siloxy units or a hydride-containing silicone resin composed of mono-funetional, tetrafunctional and/or difunctional siloxy units.
It should also be noted that with the self-bonding additive ~.s3~ ~3~ 60 SI-112 of the present invention, -the composition must be cured at elevated temperatures since the self-bonding additive acts as an inhibitor and it does not permit the com-position to cure a-t room temperatures for prolonged periods of ~ime such as, -two weeks after the two com-ponents are mixed~ In addition, in the proposed use of the self-bonding additive in the instant invention it is desirable that the self-bonding additive not be incorporated into the component of the two component SiH-olefin platinum catalyzed compositions of the instant case which contain the plat.inum catalyst, since it may deactivate the platinum catalyst. ~owever, if the self-bonding additive of the instant case is incorporated into the component that does not contain the platinum catalyst, then the composition as two separate components can be stored as long as desirable without any deleterious effects.
When it is desired to cure the composition, the two I components are simply mixed together and applied and ~0 cured at elevated temperatures, that is temperatures above 100C, within a two week period of time after mixing to form the desired self-bonding silicone elastomer of the instant invention.
It should be noted that with respect to the sélf-bonding additive that it should not be present in tne total composition for a period of time of more than two weeks prior to cure of the composition, that is the self-bonding additive will act as an inhibitor and as such after the two components of the composition are mixed, they should be cured at elevated temperatures within a two week period. If more than a two week period lapses until the composition is applied to be cured at ~ OSI-112 elevated temperatures, then the compositlon may not cure in a totally satisfactory fashion.
It should be also noted that within the invention of the instant case, there is described a preferred process for producing an aliphatically unsaturated hydrolyzable aloky silane hydrolysis product in which the hydrolysis of the silane monomer is a partial hydrolysis of the silane monomer. The partial hydrolysis readily and properly takes place in the presence of a dipolar aprotic solvent where there is sufficient quantities of the solvent such that there is a homogeneous reaction medium. With such a homogeneous hydrolysis medium the reaction can take place with rapidity and also efficiently so as to produce the desired partial hydrolysis product in the most efficient manner.
It is well known that acids, and specifically strong acids, will operate as catalysts for such hydrolyses of aliphatically unsaturated hydrolyzable alkoxy silanes and in accordance with the instant invention are used to advantage.
The aliphatically unsaturated hydrolyzable silane preferably has the formula, B ~ J Rla si (OR )4 a where Rl is an aliphatically unsaturated radical selected from the class consisting of alkenyl and alkynyl radicals of 2 to 8 carbon atoms, R3 is selected from the class consisting of alkyl radicals and cycloalkyl radicals of l to 8 carbon atoms, and a is a whole number that varies from l to 2. Although Rl can be an alkynyl radical it is preferably an alkenyl radical since the acetylenic radical or the alkynyl radicals are more efficient in-hibitors than the alkenyl radicals which may be undesir-'7 3~ 60SI-lI2 ~ ,~ .
able in -the composi~ion. Accordingly, it is desirable and preferable tha-t the Rl radical be se]ected from alkenyl radicals of 2 to 8 carbon atoms such as, vinyl, allyl and etc., the most preferred raclical being vinyl.
With respect to the hydrolyzable radical, it is preferably selected from alkyl radicals or cycloalkyl radicals of 1 to 8 carbon atoms such as, methyl, ethyl, cyclohexyl, cycloheptyl and etc. It should be noted that many other hydrolyzable radicals will not perform in the self-bonding additive of the instant case, that is, additives having radicals such as, hydroxy, ketoximino, aminoxy, acetoxy, are undesirable for use as self-bonding additives in the instant composition since irrespective of their self-bonding properties it has been found that compounds with such hydrolyzable radicals may deactivate the platinum catalyst in the SiH-olefin platinum catalyzed compositions. Most preferably, R3 is selected from alkyl radicals of 1 to 5 carbon atoms such as, methyl, ethyl and propyl.
~0 In addition, while a may vary from 1 to 2, it is more preferable that a have a value of 1, since if there is too much unsaturation in the self-bonding additive then the unsaturation may unduly inhibit the cure of the composition and/or alter the physical properties of the cured elastomer. The most preferred radical for R3 is ethyl or methyl. Accordingly, the most preferred compounds of formula (2~ above for use as self-bonding additives in the instant invention is the partial hydrolysis products of the compounds of formula (2) where R is vinyl such as, vinyltrimethoxy silane or vinyltriethoxy silane. Vinyltriethoxy silane is more preferred since the alcohol that is given off during the 3'3 hydrolysis is not toxic and can be tolerated at high levels.
It should be noted that the compounds of formula (2) above by themselves cannot be used as self-bonding additives, that is, they have little or no capability as self-bonding additives. What must be utilized as a self-bonding additive in the compositions of the instant case is the partial hydrolysis product of the compounds of formula (2), such that the compound of formula (2) is hydrolyzed such that 16 to 49% mole percent of the oR3 groups are hydrolyzed.
Of course, this is the average number of hydrolyzed oR3 groups that would be in a particular composition noting that in a particular molecule of the silane one or more of the oR3 groups would be hydrolyzed. If more that 49% on the average of oR3 groups is hydrolyæed then the partial hy~rolyzate of compounds of formula (2) tends to approach the gel stage and thus is undesirable in SiH-olefin platinum catalyzed compositions for two reasons.
First of all the composition does not have good self-bonding properties, and secondly, the gel form of the compound ~0 of formula (2) tends to seriously detract from the physical properties of the SiH olefin platinum catalyzed composition.
If less than 16% of the oR3 groups are hydrolyzed then the partial hydrolyzate may contain too much of the monomer of formula (2) which does not impart any self-bonding properties of the composition and dilutes the effects of the partial hydrolyzate.
More preferably the average num~er of OR groups hydrolyzed in the monomer of formula (2) varies anywhere from 25 mole percent to 40 mole percent and is most pre-3~ ferably 33 mole percent. The optimum value for the amount of hydrolyzed oR3 groups in the monomer silane of formula
The present inven-tion relates to self-bonding silicone rubber compositions and more particularly the present invention relates to SiH-olefin platinum catalyzed self-bonding silicone rubber compositions in which the self-bonding additive is the partial hydrolysis product of an aliphatically unsaturated hydrolyzable alkoxy silane.
SiH-olefin platinum catalyzed compositions are well known. Such compositions generally comprise a vinyl-containing polysiloxane polymer as the base polymer, a filler which may be a reinforcing filler such as fumed silica or precipitated silica, or an extending filler such as fused quartz incorporated into the base vinyl containing polymer. Also, a vinyl containing silicone resin may be used with or in place of reinforcing fillers.
Such a mixture is generally stored separately. The cross-linking portion of the composition comprises a hydride siloxane which may either be a hydride-containing polysiloxane or hydride containing silicone resin. A platinum catalyst is used to promote the cure.
Various other ingredients may be added to the composition so as to enhance its cured physical properties such as, for instance, there may be added to the composition low viscosity vinyl-containing polymers. The platinum catalysts may either be incorporated with the base vinyl-containing polymer and filler or it may be packaged with the hydride siloxane cross-linking agent. When it is desired to cure the composition, the two packages or two components are mixed together and the composition is applied in the desired manner and cures at room temperature or at higher temperatures to orm a silicone elastomer.
There may also be incorporated into such composi-tions well known inhibitors such as, for instance, acetylenic X'~39 compounds and other types of compounds which inhibit the cure of the composition at room temperature. When such an inhibited composition is heated at elevated tem-peratures, that is temperatures above 100C, the effect of the inhibitor is destrayed and the composition cures rapidly in a number of minutes to produce a silicone elastomer. Such inhibitors are used in these SiH-olefin platinum catalyzed compositions so as to enhance their pot life or working life after the two pac~ages are mixed and prior to cure.
There also has been developed a one-component SiH-olefin platinum catalyzed silicone rubber compo-sition in which the inhibitor is a hydroperoxy compound which is so effective that the composition can be pack-aged as a one package system for prolonged periods of time and yet when e~posed to elevated temperatures can cure to form a silicone elastomer in a matter of minutes. Such a composition is, for instance, disclosed in the Canadian application of William J. Bobear, ?0 entitled "Inhibitor for Platinum Catalyzed Silicone Rubber Compositions", Serial No. 276,318 dated April 7, 1977.
Such SiH-olefin platinum catalyzed compositions find great use as for the preparation of silicone molds, for paper release coatings and as encapsulants. However, while such compositions are very suitable for paper release applications and for silicone molds because of their good release properties, such silicone rubber compositions are utilized with some difficulty as encapsulants and for potting applications because of poor adherence to required bonding surfaces. For potting applications, it is often desired to pot Gr enclose electric circuitry with a silicone ~3~"~3~ 60SI-112 " .t ~.J ~
composition to protect the electric circuitry from dirt, mois-ture and mechanical shock. There has even been developed a clear SiH-olefin platinum catalyzed com-position for such potting and encapsulating applications so that if there is a malfunction in the electric circuitry, the technician can view the circuitry through the clear potting composition to determine the corrective action to be taken.
Other relevant properties of such SiH-olefin platinum catalyzed compositions for potting and encapsulating electric circuitry are that they are non-conductive of electricity, resistant to ozone and weathering, and water repellent. These properties make such compositions ideal encapsulant and potting materials. However, such SiH-olefin platinum catalyzed compositions still had difficulty with respect to potting and encapsulating applications. Because of their good release properties these SiH-olefin platinum catalyzed silicone rubber compositions would not adhere very well to the electric circuitry and circuitry board substrates such that a very poor bond was formed between the silicone elastomeric composition and the substrates. Accordingly, because of the formation of such poor bonds between the silicone elastomeric composition and the encapsulated substrate, the silicone elastomeric encapsulant or potting compound had a tendency to come loose from the substrate and thus not fully protect the electric circuitry from moisture, dirt and mechanical shock.
To solve this problem, primers were developed for 1 30 such SiH-olefin platinum catalyzed compositions to apply them to metal substrates and specifically, electric circuitry substrates and the electric circuitry itself '73~
so that the cured silicone elastomer would adhere with good bond strength to the encapsulated and potted sub-state. Such primer compositions are generally com-binations of active ingredients dissolved in a volatile solvent or solvent mixture. The primer is applied to the substrate to be encapsulated or potted, say by wiping or spraying. The solvent is allowed to evapora-te, leaving a surface coating more suited to bonding. The silicone rubber potting composition is applied there-over and allowed to cure to produce a silicone elastomer with a good bond between the silicone elastomer and the electric circuitry that is to be potted or encapsulated.
Unfortunately, clear silicone potting compounds that employ vinyl containing silicone resins rather than fillers for reinforcement still did not adhere satis-factorily even when such primers were employed. Examples of materials there are desired for electric circuitry substrates that are to be bonded to by SiH-olefin platinum catalyzed compositions are for instance, glass, aluminum, steel, copper and stainless steel which, of course, includes the metals of the electric circuitry itself. Accordingly, the use of such primers sometimes operated with effectiveness to bind such SiH-olefin platinum catalyzed compositions with good bond strengths to the foregoing metal substrates. However, even when they worked well there were various problems associated with primers.
First and foremost of all, it required an additional step in the preparation of the encapsulated or potted electric circuitry apparatus, that is, the application of the primer to the substrate. In addition it increased the cost of the total operation both in the labor in-3~ 6 0 S ~ 2 volved to apply the primer composition to the electric circuitry substrate and also in the cost of manufacture and distribution of the primer composition itself.
Fur-ther, such use of primer compositions made it necessary to set for~h more detailed instructions than was usual in the preparation of the encapsulated apparatus.
Accordingly, for such encapsulated and potting applications it is highly desirable to have an SiH-olefin platinum catalyzed composition which has a self-bonding additive in it such that a primer is not needed for the application of the composition to encapsulate or pot electric circuitry.
It is especially highly desirable to have a clear SiH-olefin platinum catalyzed composition which has a self-bonding additive in it, such that satisfactory adherence is obtained without the use of a primer. Various attempts have been made to accomplish this but failed for one reason or another. One of the reasons why many of the additives that were added to the SiH-olefin platinum catalyzed composition did not operate properly was ~0 that the additive would poison or deactivate the platinum catalyst such that the composition would not cure upon application. Other supposed self-bonding additives were simply not effective in establishing a good bond between the cured elastomer and the substrates of interest.
Silyltriallylisocyanurates were, for instance, tried I as self-bonding additives for room temperature compositions but such additives did not perform as well as would be desired. Such use of the silyltriallylisocyanurates in traditional room temperature vulcanizable compositions are, for instance, set forth in Hardman and Berger, U.S. Patent No. 3,882,083 dated May 6, 1975. Another example of such an SiH-olefin platinum catalyzed com-position is to be found in sallard U.S. Pat. #3,527,655 dated September 8, 1970. The adhesive component of this composition was the reaction product of a vinyltrieh-lorosilane and a vinyl trialkoxy silane. Accordingly, it was highly desirable to find a self-bonding additive for SiH-olefin platinum catalyzed compositions whieh would ~dhere sueh eompositions with good bond strength and in the absence of a primer to such diverse substrates as glass, aluminum, steel, copper, stainless steel, so that such compositions would be desirable compositions for the encapsulation and potting of electrieal circuitry.
It is one subject of the present invention to pro-vide for a self-bonding additive for SiH-olefin platinum eatalyzed compositions. It is another object of the present invention to provide for a process for producing a self-bonding SiH-olefin platinum catalyzed eomposition.
It is an additional object of the present invention to provide for a process for adhering SiH-olefin platinum eatalyzed eompositions to eleetrieal circuitrv substrates ~0 without the use of a primer.
It is still an additional objeet of the present invention to provide for an inexpensive self-bonding additive for SiH-olefin platinum eatalyzed compositions.
It is still a further objeet of the present in-vention to provide for a preferred process for produeing a partial hydrolysis produet of an aliphatieally un-saturated hydrolyzable alkoxy silane, which can be utilized as a self-bonding additive for SiH-olefin platinum eatalyzed eompositions.
These and other objeets of the present invention are aeeomplished by means of the diselosure set forth hereinbelow.
7~ 60S~ l2 There is provided by the present invention and in accordance with the above objects, a self-bonding silicone rubber composition comprising (A) 100 parts by ~eight of a base polymer of the formula, R R R
(1) Vi - Si - ~ -SiO --Si - Vi l l R R xR
where R is selected from the class consisting of monovalent hydrocarbon radicals and halogenated monovalent hydro-carbon radicals and x is such that the viscosity of the base polymer varies from 100 to 200,000,000 centipoise at 25C; (B) from 0.5 to S0 parts by weight of a hydride siloxane cross-linking agent; (C) from 1 to 500 parts per million of a platinum catalyst; and (D) from 0.1 to 5 parts by weight of a self-bonding additive which is the partial hydrolysis product of an aliphatically unsaturated hydrolyzable alkoxy silane. The partial ~0 hydrolysis product is most preferably that of vinyl-triethoxysilane. There can also be incorporated from 10 to 100 parts of a vinvl-containing silicone reinforc-ing resin in addition to or in place of reinforcing filler composed of R6SiOo. 5 units and SiO2 units in which from about 2.5 to 10 mole percent of the silicon atoms contain silicon-bonded vinyl groups, where R6 is a monovalent hydrocarbon radical.
It should be noted that the pure vinyltriethoxy-silane will not function as a self-bonding additive in SiH-olefin platinum catalyzed compositions. On the other hand, the completely hydrolyzed vinyltriethoxysilane cannot be used as a ~elf-bonding - additive in SiH-olefin ~3~33 platinum catalyzed compositions since it is in -the form of a resinous gel and is not miscible with the composi-tion and thus will not perform a self-bonding function.
Further, such a gel cannot be beneficially incorporated into SiH-olefin platinum catalyzed compositions since its presence would seriously detract from their cured physical properties. It is the advantage of the self-bonding additive of the instant case that when properly used in the appropriate concentrations that it will not detract significantly from the final cured physical properties of the silicone elastomer that is formed.
To produce the proper partial hydrolysis product of the aliphatically unsaturated silane, it is desirable that 16 to 49~ of the available hydrocarbonoxy groups of said alkoxy silane be hydrolyzed in the process for produeing the partial hydrolyzate. If less than 16% is hydrolyzed then too large an amount of the vinyltrie-thoxysilane which does not aet as a self-bonding additive and which further dilutes the effectiveness of the partial hydrolysis product may remain in the hydrolyzate mixture.
If more than 49~ of the available hydrocarbonoxy groups in the silane is hydrolyzed, then you encounter the aforementioned problems of the formation of gels which is undesirable in the final product.
The hydride cross-linking agent may be either a hydride-containing linear polysiloxane polymer or it may be a hydride containing silicone resin compound of monofunctional and tetrafunctional siloxy units or a hydride-containing silicone resin composed of mono-funetional, tetrafunctional and/or difunctional siloxy units.
It should also be noted that with the self-bonding additive ~.s3~ ~3~ 60 SI-112 of the present invention, -the composition must be cured at elevated temperatures since the self-bonding additive acts as an inhibitor and it does not permit the com-position to cure a-t room temperatures for prolonged periods of ~ime such as, -two weeks after the two com-ponents are mixed~ In addition, in the proposed use of the self-bonding additive in the instant invention it is desirable that the self-bonding additive not be incorporated into the component of the two component SiH-olefin platinum catalyzed compositions of the instant case which contain the plat.inum catalyst, since it may deactivate the platinum catalyst. ~owever, if the self-bonding additive of the instant case is incorporated into the component that does not contain the platinum catalyst, then the composition as two separate components can be stored as long as desirable without any deleterious effects.
When it is desired to cure the composition, the two I components are simply mixed together and applied and ~0 cured at elevated temperatures, that is temperatures above 100C, within a two week period of time after mixing to form the desired self-bonding silicone elastomer of the instant invention.
It should be noted that with respect to the sélf-bonding additive that it should not be present in tne total composition for a period of time of more than two weeks prior to cure of the composition, that is the self-bonding additive will act as an inhibitor and as such after the two components of the composition are mixed, they should be cured at elevated temperatures within a two week period. If more than a two week period lapses until the composition is applied to be cured at ~ OSI-112 elevated temperatures, then the compositlon may not cure in a totally satisfactory fashion.
It should be also noted that within the invention of the instant case, there is described a preferred process for producing an aliphatically unsaturated hydrolyzable aloky silane hydrolysis product in which the hydrolysis of the silane monomer is a partial hydrolysis of the silane monomer. The partial hydrolysis readily and properly takes place in the presence of a dipolar aprotic solvent where there is sufficient quantities of the solvent such that there is a homogeneous reaction medium. With such a homogeneous hydrolysis medium the reaction can take place with rapidity and also efficiently so as to produce the desired partial hydrolysis product in the most efficient manner.
It is well known that acids, and specifically strong acids, will operate as catalysts for such hydrolyses of aliphatically unsaturated hydrolyzable alkoxy silanes and in accordance with the instant invention are used to advantage.
The aliphatically unsaturated hydrolyzable silane preferably has the formula, B ~ J Rla si (OR )4 a where Rl is an aliphatically unsaturated radical selected from the class consisting of alkenyl and alkynyl radicals of 2 to 8 carbon atoms, R3 is selected from the class consisting of alkyl radicals and cycloalkyl radicals of l to 8 carbon atoms, and a is a whole number that varies from l to 2. Although Rl can be an alkynyl radical it is preferably an alkenyl radical since the acetylenic radical or the alkynyl radicals are more efficient in-hibitors than the alkenyl radicals which may be undesir-'7 3~ 60SI-lI2 ~ ,~ .
able in -the composi~ion. Accordingly, it is desirable and preferable tha-t the Rl radical be se]ected from alkenyl radicals of 2 to 8 carbon atoms such as, vinyl, allyl and etc., the most preferred raclical being vinyl.
With respect to the hydrolyzable radical, it is preferably selected from alkyl radicals or cycloalkyl radicals of 1 to 8 carbon atoms such as, methyl, ethyl, cyclohexyl, cycloheptyl and etc. It should be noted that many other hydrolyzable radicals will not perform in the self-bonding additive of the instant case, that is, additives having radicals such as, hydroxy, ketoximino, aminoxy, acetoxy, are undesirable for use as self-bonding additives in the instant composition since irrespective of their self-bonding properties it has been found that compounds with such hydrolyzable radicals may deactivate the platinum catalyst in the SiH-olefin platinum catalyzed compositions. Most preferably, R3 is selected from alkyl radicals of 1 to 5 carbon atoms such as, methyl, ethyl and propyl.
~0 In addition, while a may vary from 1 to 2, it is more preferable that a have a value of 1, since if there is too much unsaturation in the self-bonding additive then the unsaturation may unduly inhibit the cure of the composition and/or alter the physical properties of the cured elastomer. The most preferred radical for R3 is ethyl or methyl. Accordingly, the most preferred compounds of formula (2~ above for use as self-bonding additives in the instant invention is the partial hydrolysis products of the compounds of formula (2) where R is vinyl such as, vinyltrimethoxy silane or vinyltriethoxy silane. Vinyltriethoxy silane is more preferred since the alcohol that is given off during the 3'3 hydrolysis is not toxic and can be tolerated at high levels.
It should be noted that the compounds of formula (2) above by themselves cannot be used as self-bonding additives, that is, they have little or no capability as self-bonding additives. What must be utilized as a self-bonding additive in the compositions of the instant case is the partial hydrolysis product of the compounds of formula (2), such that the compound of formula (2) is hydrolyzed such that 16 to 49% mole percent of the oR3 groups are hydrolyzed.
Of course, this is the average number of hydrolyzed oR3 groups that would be in a particular composition noting that in a particular molecule of the silane one or more of the oR3 groups would be hydrolyzed. If more that 49% on the average of oR3 groups is hydrolyæed then the partial hy~rolyzate of compounds of formula (2) tends to approach the gel stage and thus is undesirable in SiH-olefin platinum catalyzed compositions for two reasons.
First of all the composition does not have good self-bonding properties, and secondly, the gel form of the compound ~0 of formula (2) tends to seriously detract from the physical properties of the SiH olefin platinum catalyzed composition.
If less than 16% of the oR3 groups are hydrolyzed then the partial hydrolyzate may contain too much of the monomer of formula (2) which does not impart any self-bonding properties of the composition and dilutes the effects of the partial hydrolyzate.
More preferably the average num~er of OR groups hydrolyzed in the monomer of formula (2) varies anywhere from 25 mole percent to 40 mole percent and is most pre-3~ ferably 33 mole percent. The optimum value for the amount of hydrolyzed oR3 groups in the monomer silane of formula
(2) is 33 mole percent since it is found that the optimum
3~
self-bonding properties as well as curing proper-ties of the SiH-olefin platinum ca-talyzed composition is obtained when on the average only one of the oR3 groups in the silane of formula (2) is hydrolyzed.
It should also be noted that the self-bonding additive o the instant invention is preferably utilized at a con-centration that varies anywhere from 0.1 to 5 parts by weight based on 100 parts of the base vinyl containing polymer of formula (1), and more pre~erably varies at a concentration of 1 to 1.5 parts per 100 parts of the base vinyl-containing polymer of formula (1). If too little an amount of the partial hydrolyzate is used, then the desired degree of self-bonding is not obtained. If too much of the self-bonding additive is used, that is, more than 5 parts, then, that high concentration of the self-bonding additive can alter the stoichiometric/
structure balance of SiH and olefin and the composition may not cure properly. This balance of the SiH-olefin platinum catalyzed reaction would be altered due to the high excess of vinyl units that would be persent as a result of the addition of the self-bonding additive in more than the concentrations set forth previously.
It should also be noted that a high excess of the partial hydrolyzate above the quantities set forth previously may result in less than desirable pot life periodsO The reaction for producing the partial hydrolyzate is a simple but exacting reaction. Generally, it is desired that the hydrolysis reaction take place in a homogeneous hydrolysis medium and to this end there is utilized in the hydrolysis medium to carry out the hydrolysis reaction a dipolar aprotic solvent that is capable of dissolving the compound of formu-la (2), as well as the amount of water that is necessar~ to ~ 3~ 73~
partially hydrolyze it. Æxamples of dipolar aprotic solvent are, for instance, acetone, diethylketone, methylethyl ketone, dioxane and tetrahydrofuran. The most preferably solvent is acetone since it has the desirable solvent properties for the silane of formula (2), as well as the water that is necessary ~o partially hydrolyze it and is sufficiently volatile to permit its easy removal from the crude hydrolysis product.
In the preferred hydrolysis procedure, both the water and the compound of formula (2) are mixed with the solvent at the same time. It has been found that the best partial hydrolyzate compositions are reached in this fashion.
In another alternate hydrolysis procedure the water is dissolved in the solvent and the silane added to the solution in which the hydrolysis reaction takes place.
Yet another alternate procedure is to add the water to the silane and solvent.
Generally, in such hydrolysis reaction in accordance with the amount of partial hydrolyzate that is desired there will be added anywhere from 0.5 to 1.5 moles of water per mole of the silane of formula (2). The result-ing addition may be carried out under agitation although agitation is not strictly necessary since the reaction takes place in a homogeneous hydrolysis medium. It should be noted that enough of the solvent is utilized so that there is always a homogeneous hydrolysis during said partial hydrolysis. It can be appreciated that the reaction can take place without the presence of a solvent or with other types of solvents. However, when there are two phases present in the hydrolysis medium then the hydrolysis reaction will take place but takes place at a much slower 60S:r-ll2 ~Z'73~
rate, and not in the most preferred manner as described above.
In addition, as stated previously, anywhere from 0.5 moles to 1.5 moles of water may be utilized per mole of the silane of formula (2) so as to hydrolyze and obtain I a partial hydrolyzate with the before stated average number o~ hydrolyzed oR3 substituent groups in the compound of formula (2). Most preferably, of course, there is utilized 1 mole of water per mole of the silane of ormula (2) so as to obtain a partial hydrolyzate in which the average number of oR3 substituent groups hydrolyzed is 33 mole percent in the compound of formula (2). It would be noted further that it is preferable that the reaction take place near normal ambient temperatures although temperatures in the range of 10C to 50C can be tolerated.
The criticality in the above process for producing the partial hydrolyzate lies in the use of dipolar aprotic solvent in producing a homogeneous hydrolysis medium during the reaction. There is also a second aspect in the process for producing the partial hydrolyzate in accordance with the invention of the instant case and that is the presence of an acid catalyst during the hydrolysis.
It has been found that without an acidic catalyst in the homogeneous hydrloysis medium that the hydrolysis takes place very slowly or over a prolonged period of time.
Accordingly, in order to speed up the reaction, there should be present a catalytic amount of acid in the hydrolysis medium, that is, acetic acid or hydrochloric acid, sulfuric acid, that is, any type of mild or strong acid, ln sufficient quantities so as to raise the acidity of the hydrolysis medium of anywhere from, generally, ~,273~ 60SI-112 10 to 500 parts per million and more preferably from 10 to 50 parts per million.
It has been found -that with the use of such acids in the hydrolysis medium and with the temperature range of 10 to 50C the reaction will proceed to yield desirable compositions in a period of anywhere from 0.5 to 12 hours and that without an acidic catalyst the reaction reaches this completion only after much longer period of time.
It should be noted with the acidic catalyst in the foregoing concentrations that the reaction is substantially complete in as little as 0.5 hours. Accordingly, with the above acid concentration in a homogeneous hydrolysis medium~ the partial hydrolysis will be complete in a period of time of as little as 0.5 hours. It should be noted that the catalyst may be any acidic catalyst;
a few of the well known acidic catalysts having been given previously. Further, it is preferred that not too much of the acidic catalyst be added so that no difficulty will be encountered in removing the excess acid after the hydrolysis reaction is completed. To utilize the self-bonding additive, that is, the partial hydrolyzate of the compound of formula (2) as a self-bonding additive in SiH-olefin platinum catalyzed compositions, its acidity has to be below 10 parts per million, otherwise, the excess acidity will affect the cure and final physical properties of the elastomer that is formed. Accordingly, to facilitate in the purification and preparation of the final partial hydrolysis product, it is desired that a lower amount of acidity be used in the homogeneous hydroly-sis reaction.
In any case, there has to be added a neutralizing agent such as, sodium bicarbonate, to the homogeneous hydrolysis 3 ~3'~73~
medium after the hydrolysis reaction is complete to sub-I stantially neutralize -the acid and then the solution i5 filtered to remove the salts formed therefrom. If the acidity is not too high-say 10 ppm or less, then the partial hydrolyzate product may be obtained in its final form by simply stripping off the solvent, the unreacted water and some unreacted silane of formula (2) still remaining in the composition, by heating the mix-ture at a temperature in the range of 100 to 125C, either at atmospheric pressure or preferably sub-atmospheric pressure. If the composition has excess acidity as noted previously, sodium bicarbonate is added to the homo-geneous hydrolysis medium after the hydrolysis reaction is complete to neutralize the excess acid and then the solution is filtered and then finally the solvent and water and some unreacted silane of formula (2) is stripped off by heating the solution at a temperature in the range of 100 to 125C, preferably at sub-atmospheric pressure until these ingredients are removed. At any rate, by this procedure there is obtained a partial hydroly-zate product which is the self-bonding additive of the instant case. ;~
To insure its optimum use in the SiH-olefin platinum catalyzed compositions it is necessary to further dry the partial hydrolyzate so as to remove substantially all residual water. Anhydrous sodium or magnesium sulfate among other dessicants may be utilized for this purpose to sufficiently dry the partial hydrolyzate product. It should be noted that even with small quantities o~ water in the partial hydrolyzate product such water will in-terfere with the SiH-olefin platinum catalyzed composition and result in the evolution of hydrogen which may cause the ~3~t~3~ 60SI-112 composition to foam or in the alternative may result in there not being enough oE the hydride cross-linking agent to cross-link with the vinyl polysiloxane polymer of ~ormula (1) which results in a soft elastomer being obtained, that is, an elastomer that does not have good physical pro-perties.
Accordingly, after the above procedure there is obtained a partial hydrolysis product of the compound of formula (2) which is the self-bonding additive of the instant case. It should be noted that such par-tial hydroly-zate product consists of some silane of formula (2) mixed with a partial hydrolyzate which generally comprises olefinically containing siloxanes which may be dimers, trimers, tetramers, and etc., that is, mainly linear siloxanes or branched chain siloxanes of low molecular weight having olefinically substituent groups as well as containing the unhydrolyzed oR3 radicals in the polymer chain. It has been found that the above partial hydrolysis product is the self-bonding additive of the instant case for SiH-olefin platinum catalyzed compositions.
The basic ingredient of the SiH-olefin platinum composition is well known in the art. Such basic in-gredient comprises 100 parts by weight of vinyl siloxanes of formula (1) above. In the above description R is given as being selected from the class of monovalent hydrocarbon radicals and halogenated monovalent hydrocarbon radicals and generally may be selected from alkyl radicals of 1 to 8 carbon atoms, such as, methyl, ethyl; cycloalkyl radicals such as, cyclohexyl of 4 to 8 carbon atoms; mononuclear aryl radicals such as phenyl, ethylphenyl; fluoroalkyl radicals such as 3,3,3-trifluoropropyl and alkenyl radicals such as vinyl, allyl 3~
and etc. In the most preferred embodiment of the instant case, it is preferred that there be no olefinically un-saturated radicals other -than at the terminal position of the polymer chain of the compounds oE formula (1).
Accordingly, most preferably the R radical is selected from alkyl radicals of l to 8 carbon atoms, mononuclear aryl radicals of 6 to 8 carbon atoms such as, phenyl and fluoroalkyl radicals of 3 ~o 8 carbon atoms such as, 3,3,3-trifluoropropyl. Generally, it is indicated that x may vary in the polymer such that the polymer has a viscosity that varies anywhere from 100 to 200,000/000 centipoise at 25C, but in the more preferred embodiment it is preferred that the vinyl-terminated polymer that is, the base polymer, have a viscosity that varies anywhere from 30G to 500,000 centipoise at 25C and more preferably has a viscosity that varies from 300 to 200,000 centipoise at 25C. Although the self-bonding additive of the present invention may be used with high viscosity i, compositions, nevertheless, it is more desirable in low ~0 viscosity compositions. The self-bonding additive of the instant case can be utilized with any two component high viscosity SiH-olefin platinum catalyzed composition, however, it is more effective as a self-bonding additive in low viscosity SiH-olefin platinum catalyzed compositions.
It is especially effective in low viscosity compositions that are clear and use vinyl containing silicone resin in place of reinforcing fillers. Accordingly, the self-bonding additive of the instant case finds wide application as a self-bonding additive for low viscosity SiH-olefin platinum catalyzed compositions. Thus, it is desired that the vinyl polysiloxane polymer of formula (l) have a viscosity that generally varies anywhere from lO0 to 60SI-1.12 ~3~'73~
200,000 centipoise at 25C.
The process for producing such vinyl-containing polymers is well known in the art, and generally comprises the equilibrating of the appropriate substituted cyclote-trasiloxanes in the presence of a basic catalyst, most preferably, potassium hydroxide. In order to obtain vinyl termination on the polymer chain and also to obtain the appropriate viscosity in the final polymer there is utilized the appropriate amount and type of chain stoppers in the equilibration reaction medium. Thus, divinylte-tramethyldisiloxane may be utilized as a chainstopper to produce the vinyl-terminated polymer of formula (1) in the desired viscosity. The chain stopper, cyclotet-rapolysiloxanes and the required amount of catalyst which may be present at a concentration of anywhere from 10 to 100 parts per million is then heated at temperatures above 150C for periods of time averaging from 1 to 8 hours to produce the linear polysiloxane and polymer of formula (1). At the equilibration point approximately 80 to 85% of the cyclotetrasiloxanes have been converted to the polymere and there is as much of the polymer as being prepared from cyclotetrasiloxanes as there is of the polymer breaking up to form the cyclotetrasiloxanes at the equilibration point.
At that point the catalyst s simply neutralized and the cyclics stripped off to give the desired liner polysiloxane polymer of formula (1). To 100 parts by weight of the base polymer of formula (1) above there is utilized from 1 to 50 parts by weight of a hydride siloxane cross-linking agent. Such a hydride siloxane cross-linking agent may be, for instance, have the formula, ~OSI-112 ~.;32'73~
R4 R7 ,R4 H - SiO - - sio - - si - Tl B R R4 Y R4 l ) where R7 iS selected from the class consisting of hydrogen, monovalent hydrocarbon radicals and halogenated monovalent hydrocarbon radicals, R4 i.s a monovalent hydrocarbon radical and is more preferably selected from the class consisting of alkyl radicals of 1 to 8 carbon atoms; cycloalkyl radicals of up to 8 carbons; mono-nuclear aryl radicals such as, phenyl, and 3-3,3-trifluoropropyl radicals.
Accordingly, R may be selected from the class con-sisting of hydrogen and any saturated monovalent hydro-carbon radicals, and halogenated monovalent hydro-carbon radicals such as, for instance, fluoroalkyl radicals of 3 to 8 carbon atoms such as, 3,3,3-trifluoro-propyl. Preferably, the R4 radical is selected from alkyl radicals of 1 to 8 carbon atoms such as, methyl, ethyl, propyl;mononuclear aryl radicals such as, phenyl ~0 and fluoroalkyl radicals of 3 to 8 carbon atoms such as 3,3,3-trifluoropropyl.
In the foregoing formula (3), y varies such that the polymer has a viscosity in the range of 5 to 500 centipoise at 25C and more preferably has a viscosity that varies from 10 to 50 centipoise at 25 C. In place of this hydride cross-linking agent there may be utilized a silicone resin cross-linking agent, that is, a hydride silicone resin cros~s-linking agent which is generally a silicone resin composed of H R2 SiOo 5 units and SiO2 units where the ratio of the H + R5 radicals to Si varies from 1.1 to 1 to 2.7 to 1 and where R5 can consist of the same radicals as those given for the R4 ~ 60SI~
radical given above.
The hydride polysiloxane of formula (3) as well as the hydride siloxane silicone resin given previously are easily obtained by simply hydrolyzing the appropriat~
chlorosilanes in water and then purifying the desired product. In the case of the resin this may involve the use of a solvent during the hydrolysis such as a water immiscible organic solvent selected from benzene, toluene, xylene and etc. At any rate such hydrolysis reactions for producing such hydride silicone resins is well known as well as the process for producing the hydrogen-containing polysiloxane polymer of formula (3) above. The polysiloxane polymer of formula (3) above may also be obtained by equilibrating a cyclotetrasiloxanes in the presence of an acid catalyst such as toluene sulfonic acid at elevated temperatures with the appropriate type of hydride chainstoppers. In such equilibration procedure, the neutralization and venting of volatiles is followed as well as the same heating step during equilibration to produce the desired hydrogen polysiloxane polymer of formula (3) above. These processes will not be going into detail since such is well known in the art.
In addition to the hydride silicone resin composed of monofunctional units and tetrafunctional units there may be utilized as a cross-linking agent a hydride silicone resin composed of HR 2 SiOo. units and SiO2 units and R 2 SiO units where the H + R5 to Si ratio varies anywhere from 1.1 to 1 to 2.7 to 1, where R5 is as defined previously. More preferably, the silicone resin composed of the hydrogen containing siloxane monofunctional uni~s and the tetrafunctional siloxy units is preferred as a cross-linking agent in the compositions of the instant case Z~
or the hydrogen siloxane o~ formula (3) above. ~he silicone resin containing the difunctional siloxy units is more difficult and expenslve to produce. However, such a resin could be utilized as a cross-linking agent with the SiH-olefin platinum catalyze~ composition of the instant case.
As a catalyst there is utilized anywhere from 1 to 500 parts per million and more preferably from 1 to 200 parts per million of a platinum catalyst.
Many types of platinum compounds for this SiH olefin addition reaction are known and such platinum catalysts may be used also for the reaction of the present case.
The preferred platinum catalysts especially when optical clarity is required are those platinum compound catalysts which are soluable in the present reaction mixture. The platinum compound can be selected from those having the formula (PtC12. Olefin)2 and H(PtC13. Ole~in) as described in U.S.Patent No. 3,159,601 dated December 1, 1964 - Ashby.
The olefin shown in the previous two formulas can be almost any type of olefin but is preferably an alkenylene having from 2 to 8 carbon atoms, a cycloalkenylene having from 5 to 7 carbon atoms or styrene. Specific olefins utilizable in the above formulas are ethylene, propylene, the various isomers of butylene, octylene, cyclopentene, cyclohexene, cycloheptene, etc.
A further platinum containing material usable in the composition of the present invention is the platinum chloride cyclopropane complex (PtC12C3H6)2 described in U.S. patent No. 3,159,662 dated December 8, ]964 Ashby.
Still, further, the patent containing material can be a complex formed from chloroplatinic acid with up to 2 moles per gram of platinum of a member selected from the ~;3~ 60SI-112 class consisting of alcohols, e-thers, aldehydes and mixtures of the above as described in U.S. Paten-t 3,220,972 da-ted November 30, 1965 - Lamoreaux.
The preferred platinum compound to be used not only as a platinum catalyst but also as a flame retardant additive is that disclosed in U~S. Patent 3,775,452 dated November 27, 1973, Karstedt. Generally spea~ing, this type of platinum complex is formed by reacting chloroplatinic acid containing 4 moles of water of hydration with tetravinyltetramethylcyclotetrasiloxane in the presence of sodium bicarbonate in an ethanol solution.
To enhance the physical properties of the composition there may be incorporated in the base vinyl-containing polymer from 10 to 200 parts by weight of a filler, based on 100 parts of the base vinyl-containing polymer of Formula (1), when the filler is selected from the class of reinforcing fillers and extending fillers. Generally, the reinforcing fillers are such fillers such as, fumed silica and precipitated silica while examples of extend-ing fillers are, for instance, fused quartz and etc. The reinforcing fillers are preferred for strength properties, however, the extending fillers are less expensive and also do not tend to increase the viscosity of the uncured composition as much.
In order to get the high desired tensile strength in the compositions of the instant case and particularly when such compositions are formed to thin coatings or films, it is desirable to incorporate a filler into the com-position. Illustrative of the many fillers, which can beemployed are titanium oxide, lithopone, zinc oxide, zirconium silicate, silica aerogel, iron oxide, diatomaceous ~3'~
earth, calcium carbonate, fumed silica, silazane treated silica, precipitated silica, glass fibers, magnesium oxide, chromic oxide, zirconium oxide, aluminum oxide, alpha quartz, calcined clay, asbestos, carbon, graphite cork, cotton, synthetic fibers and etc.
Yhe preferred fillers that should be utilized in the composition of the instant case and particularly in component (A) of the lnstant case, is preferably either a fumed silica or a precipitated silica that has been treated. Thus, the silica fillers may be treated as, for example, as disclosed in U.S. Patent No. 2,938,009 dated May 24, 1960 - Lucas with cyclic polysiloxanes.
Another method for treating fillers or treated fillers that can be utilized in the invention of the instant case is that disclosed in Brown U.S. Patent No.
3,024,126 dated March 6, 1962.
More specifically, silazane treated fillers in accordance with the disclosure of Smith U.S. Patent No.
~0 3,635,743 dated January 18, 1972 and Beers, U.S. patent No. 3,837,878, issued September 24, 1974, both assigned commonly herewith, are preferred as the treated fillers to be utilized in the compositions of the present case.
For more information as to the preparation of the base vinyl containing polymer as well as the hydride polysiloxane and as to the general details as to such SiH-olefin platinum catalyzed compositions, one is referred to the U.S. Patent of Jeram, et al, U.S.
Patent No. 3,957,713 dated May 18, 1976. As noted in that patent, other ingredients well known in SiH-olefin platinum catalyzed compositions may be incorporated in the basic composition to obtain one property or another ~ 3~ 60SI-112 in the cured elastomer that results from the composition.
Thus, based on 100 parts of the base vinyl containing polymer of formula (1), there may be ad~ed to -the com-position form 1 to 30 parts by weight of a vinyl-containing polymer of the formula, Vi-S O ~ slO ~ i - R
R6 ¦ R6 ¦ R6 or vinyl containing silicone resing of formula, ~CH3)3 SiOl/2~ ¦~i o 1 ~i2 ]
where m, p, q vary such that the resin contains from 2.5 to 10 mole percent of vinyl groups, and where R6 is delected from the class consisting of alkyl radicals, cycloalkyl radicals, aryl radicals and fluoralkyl radicals of 1 to 8 carbon atoms and where z varies such that the viscosity of the polymer varies from 100 to 5,000 centi-poise at 25C, and more preferably varies from 100 to 1,000 centipoise at 25C.
Preferably, R6 is selected from radicals such as, methyl, phenyl and 3,3,3-trifluoropropyl and is most preferably selected from methyl and phenyl. The yinyl-containing polymer of Formula (4) as given above when added to the basic vinyl-containing polymer will result in a cured elastomer with higher strength properties and for instance, higher tear then when the SiH-olefin platinum catalyzed composition does not contain such an 73~
ingredients.
For the preparation of fluorosilicone substituted SiH-olefin pla-tinum catalyzed compositions, one is referred to the patent ofJeram U.S. Patent No. 4,041,010 dated August 9, 1977. Both of these patents disclose the preparation of the appxopriate base vinyl-containing polymers, the type of platinum catalyst that can be utilized and the type of hydride siloxane crosslinking agents as well as fillers and other ingredients that are tradi~ionally added to SiH-olefin platinum catalyzed compositions to produce a cured elastomer.
It should be understood that the self-bonding additive of the instant case is not disclosed to be utilized only with the composition of these patents but can be utilized generally with most SiM-olefin platinum catalyzed com-positions and that the above patents are given as being exemplary of both traditional SiH-olefin platinum cat-alyzed compositions as well as fluorosilicone SiH-olefin platinum catalyzed compositions. It is well known in addition to the above basic ingredients disclosed above for the SiH-olefin platinum catalyzed compositions to which the self-bonding additive of the instant case can be added, there may be added other ingredients as long as they do not interfere with the self-bonding properties of theingredient of the instant case such ingredients being, for instance, pigments and etc. that are traditionally added to SiH-olefin platinum catalyzed compositions as well as fluorosilicone SiH-olefin platinum catalyzed compositions. It is well known in addition to the above basic ingredients disclosed above for the SiH-olefin platinum catalyzed compositions to which the self-bonding additive of the instant case can be added, there may be 7~3~ 6os~ 2 d 1~
added other in~redients as long as they do not interfere with the self-bonding properties of the ingredient of the instant case such ingredients being, for instance, pig-ments and etc. that are traditionally added to SiH-olefin platinum catalyzed compositions. It should be noted, however, that for clear potting compounds, a pigment may not be a desirable additive for SiH-olefin platinum catalyzed potting compositions. However, various vinyl-containing fluids and/or resins that are known for addition to SiH-olefin platinum catalyzed compositions may be added to the basic ingredients disclosed above and as disclosed in the foregoing Jeram U.S. patents to enhance one or the other properties of the cured elastomer that is formed from the composition.
As noted previously, the self-bonding additive of the instant case is to be applied to two component SiH-olefin platinum catalyzed compositions and be applied to that component of two-component SiH-olefin platinum catalyzed compositions which does not contain the platinum catalyst.
Accordingly, preferably the filler or vinyl containing silicone reinforcing resin is incorporated into the base vinyl-containing polymer of Formula (1) and the platinum catalyst may be added to it and the composition is thus stored separately along with the other ingredients. To form the second component of the second package, the hydrogen siloxane cross-linking agent is then packaged by itself or with some of the filler along with it and without any of the vinyl-containing polymer if the platinum catalyst is to be incorporated along with the hydrogen polysiloxane. However, if the platinum catalyst is incorporated with the base vinyl~containing polymer 60SI~112 7~
of Formula (1) and the filler, then the vinyl-containing fluids may also be incorporated along with hydrogen siloxane cross-linking agent component. As long as the platinum catalyst is not present with the hydrogen siloxane and the low viscosity vinyl-containing polymers, then the component will not cross-link or cure. However, if the platinum catalyst is incorporated along with the hydrogen siloxane cross-linking agent, then the vinyl-containing fluids must be packaged in the other com-ponent that is with the base vinyl-containing polymer.
The self bonding additive must be packaged in that component which does not contain the platinum catalyst, otherwise, it may have a tendency to deactivate and ultimately poison the platimum catalyst upon storage.
Accordingly, the two components are packaged, shipped and stored as such and when it is desired to cure the composition the components are simply mixed in the specified amounts and formed to the desired part. It is then necessary to heat the composition to a temperature above 100C so that the composition can cure to a self-bonding silicone elastomer in periods of time varying from a few minutes to 1 or 2 hours depending on the level of heating. It should be noted that once the two components are mixed that it is necessary to cure the composition within two weeks since if the mixed com-position is not cured within such a period that it may be very difficult to cure the composition, if at all, due to deactivation of the platinum catalyst. Accordingly, once the two components are mixed it is desirable that the composition be cured within a two week period. As can be understood with the compositions of the instant case, after the two components are mixed the mixed composition ~ 9 60SI-112 has a pot life of two weeks wherein the composition will not cure at room temperature but will cure at elevated temperatures, that is, temperatures above 100C, to a silicone elastomer. The examples below are yiven for the purpose of illustrating the reduction to practice of the instant invention. They are not given for any purpose of setting limitations in the scope of the specification and claims of the instant case and they are not given for any purpose of defining the scope of the invention.
All parts in the examples are by weight.
EXAMPLE I
An adhesion promoting additive composition was prepared as follows: Into a l-quart bottle there were charged 250 parts acetone, l9l parts vinyltriethoxysilane, and 18 parts of water. The bottle was capped and shaken moderately. A mild exotherm ensured. During the exotherm the bottle was vented several times. After the exotherm waned the mixture stood overnight. A titration then showed the product mixture was lO ppn acid, no doubt ~0 owing to trace residual silyl chloride in the vinyltriethox-ysilane. The mixture was stripped to 100C at maximum vacuum (25 inches) in a rotary evaporator. The final product weighed 103 parts. It was a clear, water-white liquid. Anhydrous sodium sulphate was employed to dry the material prior to analysis and use. Analyses of the stripped product by gas chromatography showed some re-actant silane survived (up to 5%) but that more sub~
stantial vinyl silicone was present as dimer (approximately 40%) and higher mers (approximately 40%). ~ trace of ethyl alcohol was also present in the stripped product.
~3~3~ 60SI-112 EXAMPLE I I
An adhesion promoting additive composition was prepared as follows:
Into an all glass reaction apparatus fitted for reagent addition were charged 135 parts of acetone, 255 gm vinyl-triethoxysilane, and a few drops of 12 molar hydrochloric acid. While stirring gently, 24 parts of water was admitted at a rate sufficient to generate a mild exotherm, but keeping the reaction temperature below 50C. The reaction mixture was allowed to stir gently for 2 hours following water addition and then cooled to room temperature.
Approximately 5 parts of sodium bicarbonate was added to neutralize the acid. This mixture stirred an additional hour and was then filtered through celite at the pump.
The filtrate was stripped under vacuum (28") at 100C
and dried over anhydrous magnesium sulphate. Approxi-mately 100 parts of product was obtained.
The product was a clear, water-white liquid. It contained less than 10 ppm acid and contained less than 0.05% by weight of water. An infrared spectrum was in agreement with the expected composition, showing bands due to vinyl at 6.25 microns and siloxy at 9 - 10 microns, etc. Analyses by gas chromatography indicated that about 5 - 10% by weight of the mixture was unconverted vinyl-triethoxysilane, the remainder being dimer and higher mers. A small amount ( ~ 1%) of ethyl alcohol was also EXAMPLE III
There was prepared a clear resin reinforced potting/
encapsulating composition after the teaching of U.S.
Patent 3,425,967 dated February 4, 1969 to Modic. The composition consisted of two packages, A and B. Package A was comprised of 75 parts of a base polymer of the average formula, ~OSI~
7~3~
CH3 ' ~ - Si-O t Si - CH=CH~
CH3 ~ x where x was such that the polymer had a viscosity of 400 cps at 25C, 25 pts of a resin of the average formula, - CH3 - ~CH=CH~
CH3 - Si ~ 1/2 Si - O ~ Si 2]
CH3 - ~CH3 ~ 1. 0 .; 0.7 0.17 and 10 ppm Pt in the form described in U.S. Patent No.
" 3,220,972 dated November 30, 1965 - Lamoreaux. Package `~ B was comprised of 50 pts. of the above described base polymer present in Package A and 50 pts. of a resin .
crosslinker of the average formula, ~` CH3 H - Si - 1/' [ Si O2 To 100 pts. of Package A was added 1 pt. by weight of the adhesion promoting addition composition of Example I.
This mixture was then combined immediately with 10 pts.
` of Package B and mixed throughly. The mixture did not cure at ambient laboratory temperatures. The mixture ` did cure at elevated temperatures. For example, after 1 hours time at lQ0C, the mixture cured to form a clear silicone elastomer. For up to 14 days following its preparation, the mixture cured satisfactory on exposure to 100C for 1 hour. Following the 14-day period, un-satisfactory cures were obtained at this raised temperature (100C) in that the final elastomer was too soft.
~f~3~ 60SI-112 The physical properties of the compositions with and without the self-bonding additive were as follows:
Without With Tensile 920 psi 820 Elongation 150~ 160 Durometer - Shore A 35 28 Tear - 40 lbs./in 20 Thus, no significant reduction in physical proper-ties of the cured elastomer resulted from the additive being present at the level of the example.
EXAMPLE IV
To the above SiH-olefin platinum catalyzed composition of Example III there was added l part by weight of the partial hydrolysis vinyl siloxy silane of Example 1.
During the 14-day period of satisfactory elevated tem-perature cure detailed in Example III, a 60 mil thickness of RTV composition of Example III was applied to each substrate tested and cured in place by baking one hour at 300F. Again no substantial reduction in the physical properties of the cured rubber was observed.
The 60 mil thickness of RTV was applied to each substrate tested and cured in place as described. All surfaces were clean in the usual sense. The cured silicone' elastomer which was a clear SiH-olefin platinum catalyzed composition had good clarity at this thickness. The following bonds were obtained:
Substrate Bond glass excellent aluminum (bare) marginal steel (carbon) excellent copper excellent stainless steel excellent ~ 3~ 60SI-112 An excellent bond is taken to mean a cohesive failure bond was noted when attempts to remove the cured elasto-mer from the surface were made. No bonds developed without the additive present. The bond to aluminum was improved to excellent by priming the surface with a silicone primer. These same results were obtained in each of three instances when the bonding tests were repeated during the 14 day period of satisfactory raised temperature cure.
self-bonding properties as well as curing proper-ties of the SiH-olefin platinum ca-talyzed composition is obtained when on the average only one of the oR3 groups in the silane of formula (2) is hydrolyzed.
It should also be noted that the self-bonding additive o the instant invention is preferably utilized at a con-centration that varies anywhere from 0.1 to 5 parts by weight based on 100 parts of the base vinyl containing polymer of formula (1), and more pre~erably varies at a concentration of 1 to 1.5 parts per 100 parts of the base vinyl-containing polymer of formula (1). If too little an amount of the partial hydrolyzate is used, then the desired degree of self-bonding is not obtained. If too much of the self-bonding additive is used, that is, more than 5 parts, then, that high concentration of the self-bonding additive can alter the stoichiometric/
structure balance of SiH and olefin and the composition may not cure properly. This balance of the SiH-olefin platinum catalyzed reaction would be altered due to the high excess of vinyl units that would be persent as a result of the addition of the self-bonding additive in more than the concentrations set forth previously.
It should also be noted that a high excess of the partial hydrolyzate above the quantities set forth previously may result in less than desirable pot life periodsO The reaction for producing the partial hydrolyzate is a simple but exacting reaction. Generally, it is desired that the hydrolysis reaction take place in a homogeneous hydrolysis medium and to this end there is utilized in the hydrolysis medium to carry out the hydrolysis reaction a dipolar aprotic solvent that is capable of dissolving the compound of formu-la (2), as well as the amount of water that is necessar~ to ~ 3~ 73~
partially hydrolyze it. Æxamples of dipolar aprotic solvent are, for instance, acetone, diethylketone, methylethyl ketone, dioxane and tetrahydrofuran. The most preferably solvent is acetone since it has the desirable solvent properties for the silane of formula (2), as well as the water that is necessary ~o partially hydrolyze it and is sufficiently volatile to permit its easy removal from the crude hydrolysis product.
In the preferred hydrolysis procedure, both the water and the compound of formula (2) are mixed with the solvent at the same time. It has been found that the best partial hydrolyzate compositions are reached in this fashion.
In another alternate hydrolysis procedure the water is dissolved in the solvent and the silane added to the solution in which the hydrolysis reaction takes place.
Yet another alternate procedure is to add the water to the silane and solvent.
Generally, in such hydrolysis reaction in accordance with the amount of partial hydrolyzate that is desired there will be added anywhere from 0.5 to 1.5 moles of water per mole of the silane of formula (2). The result-ing addition may be carried out under agitation although agitation is not strictly necessary since the reaction takes place in a homogeneous hydrolysis medium. It should be noted that enough of the solvent is utilized so that there is always a homogeneous hydrolysis during said partial hydrolysis. It can be appreciated that the reaction can take place without the presence of a solvent or with other types of solvents. However, when there are two phases present in the hydrolysis medium then the hydrolysis reaction will take place but takes place at a much slower 60S:r-ll2 ~Z'73~
rate, and not in the most preferred manner as described above.
In addition, as stated previously, anywhere from 0.5 moles to 1.5 moles of water may be utilized per mole of the silane of formula (2) so as to hydrolyze and obtain I a partial hydrolyzate with the before stated average number o~ hydrolyzed oR3 substituent groups in the compound of formula (2). Most preferably, of course, there is utilized 1 mole of water per mole of the silane of ormula (2) so as to obtain a partial hydrolyzate in which the average number of oR3 substituent groups hydrolyzed is 33 mole percent in the compound of formula (2). It would be noted further that it is preferable that the reaction take place near normal ambient temperatures although temperatures in the range of 10C to 50C can be tolerated.
The criticality in the above process for producing the partial hydrolyzate lies in the use of dipolar aprotic solvent in producing a homogeneous hydrolysis medium during the reaction. There is also a second aspect in the process for producing the partial hydrolyzate in accordance with the invention of the instant case and that is the presence of an acid catalyst during the hydrolysis.
It has been found that without an acidic catalyst in the homogeneous hydrloysis medium that the hydrolysis takes place very slowly or over a prolonged period of time.
Accordingly, in order to speed up the reaction, there should be present a catalytic amount of acid in the hydrolysis medium, that is, acetic acid or hydrochloric acid, sulfuric acid, that is, any type of mild or strong acid, ln sufficient quantities so as to raise the acidity of the hydrolysis medium of anywhere from, generally, ~,273~ 60SI-112 10 to 500 parts per million and more preferably from 10 to 50 parts per million.
It has been found -that with the use of such acids in the hydrolysis medium and with the temperature range of 10 to 50C the reaction will proceed to yield desirable compositions in a period of anywhere from 0.5 to 12 hours and that without an acidic catalyst the reaction reaches this completion only after much longer period of time.
It should be noted with the acidic catalyst in the foregoing concentrations that the reaction is substantially complete in as little as 0.5 hours. Accordingly, with the above acid concentration in a homogeneous hydrolysis medium~ the partial hydrolysis will be complete in a period of time of as little as 0.5 hours. It should be noted that the catalyst may be any acidic catalyst;
a few of the well known acidic catalysts having been given previously. Further, it is preferred that not too much of the acidic catalyst be added so that no difficulty will be encountered in removing the excess acid after the hydrolysis reaction is completed. To utilize the self-bonding additive, that is, the partial hydrolyzate of the compound of formula (2) as a self-bonding additive in SiH-olefin platinum catalyzed compositions, its acidity has to be below 10 parts per million, otherwise, the excess acidity will affect the cure and final physical properties of the elastomer that is formed. Accordingly, to facilitate in the purification and preparation of the final partial hydrolysis product, it is desired that a lower amount of acidity be used in the homogeneous hydroly-sis reaction.
In any case, there has to be added a neutralizing agent such as, sodium bicarbonate, to the homogeneous hydrolysis 3 ~3'~73~
medium after the hydrolysis reaction is complete to sub-I stantially neutralize -the acid and then the solution i5 filtered to remove the salts formed therefrom. If the acidity is not too high-say 10 ppm or less, then the partial hydrolyzate product may be obtained in its final form by simply stripping off the solvent, the unreacted water and some unreacted silane of formula (2) still remaining in the composition, by heating the mix-ture at a temperature in the range of 100 to 125C, either at atmospheric pressure or preferably sub-atmospheric pressure. If the composition has excess acidity as noted previously, sodium bicarbonate is added to the homo-geneous hydrolysis medium after the hydrolysis reaction is complete to neutralize the excess acid and then the solution is filtered and then finally the solvent and water and some unreacted silane of formula (2) is stripped off by heating the solution at a temperature in the range of 100 to 125C, preferably at sub-atmospheric pressure until these ingredients are removed. At any rate, by this procedure there is obtained a partial hydroly-zate product which is the self-bonding additive of the instant case. ;~
To insure its optimum use in the SiH-olefin platinum catalyzed compositions it is necessary to further dry the partial hydrolyzate so as to remove substantially all residual water. Anhydrous sodium or magnesium sulfate among other dessicants may be utilized for this purpose to sufficiently dry the partial hydrolyzate product. It should be noted that even with small quantities o~ water in the partial hydrolyzate product such water will in-terfere with the SiH-olefin platinum catalyzed composition and result in the evolution of hydrogen which may cause the ~3~t~3~ 60SI-112 composition to foam or in the alternative may result in there not being enough oE the hydride cross-linking agent to cross-link with the vinyl polysiloxane polymer of ~ormula (1) which results in a soft elastomer being obtained, that is, an elastomer that does not have good physical pro-perties.
Accordingly, after the above procedure there is obtained a partial hydrolysis product of the compound of formula (2) which is the self-bonding additive of the instant case. It should be noted that such par-tial hydroly-zate product consists of some silane of formula (2) mixed with a partial hydrolyzate which generally comprises olefinically containing siloxanes which may be dimers, trimers, tetramers, and etc., that is, mainly linear siloxanes or branched chain siloxanes of low molecular weight having olefinically substituent groups as well as containing the unhydrolyzed oR3 radicals in the polymer chain. It has been found that the above partial hydrolysis product is the self-bonding additive of the instant case for SiH-olefin platinum catalyzed compositions.
The basic ingredient of the SiH-olefin platinum composition is well known in the art. Such basic in-gredient comprises 100 parts by weight of vinyl siloxanes of formula (1) above. In the above description R is given as being selected from the class of monovalent hydrocarbon radicals and halogenated monovalent hydrocarbon radicals and generally may be selected from alkyl radicals of 1 to 8 carbon atoms, such as, methyl, ethyl; cycloalkyl radicals such as, cyclohexyl of 4 to 8 carbon atoms; mononuclear aryl radicals such as phenyl, ethylphenyl; fluoroalkyl radicals such as 3,3,3-trifluoropropyl and alkenyl radicals such as vinyl, allyl 3~
and etc. In the most preferred embodiment of the instant case, it is preferred that there be no olefinically un-saturated radicals other -than at the terminal position of the polymer chain of the compounds oE formula (1).
Accordingly, most preferably the R radical is selected from alkyl radicals of l to 8 carbon atoms, mononuclear aryl radicals of 6 to 8 carbon atoms such as, phenyl and fluoroalkyl radicals of 3 ~o 8 carbon atoms such as, 3,3,3-trifluoropropyl. Generally, it is indicated that x may vary in the polymer such that the polymer has a viscosity that varies anywhere from 100 to 200,000/000 centipoise at 25C, but in the more preferred embodiment it is preferred that the vinyl-terminated polymer that is, the base polymer, have a viscosity that varies anywhere from 30G to 500,000 centipoise at 25C and more preferably has a viscosity that varies from 300 to 200,000 centipoise at 25C. Although the self-bonding additive of the present invention may be used with high viscosity i, compositions, nevertheless, it is more desirable in low ~0 viscosity compositions. The self-bonding additive of the instant case can be utilized with any two component high viscosity SiH-olefin platinum catalyzed composition, however, it is more effective as a self-bonding additive in low viscosity SiH-olefin platinum catalyzed compositions.
It is especially effective in low viscosity compositions that are clear and use vinyl containing silicone resin in place of reinforcing fillers. Accordingly, the self-bonding additive of the instant case finds wide application as a self-bonding additive for low viscosity SiH-olefin platinum catalyzed compositions. Thus, it is desired that the vinyl polysiloxane polymer of formula (l) have a viscosity that generally varies anywhere from lO0 to 60SI-1.12 ~3~'73~
200,000 centipoise at 25C.
The process for producing such vinyl-containing polymers is well known in the art, and generally comprises the equilibrating of the appropriate substituted cyclote-trasiloxanes in the presence of a basic catalyst, most preferably, potassium hydroxide. In order to obtain vinyl termination on the polymer chain and also to obtain the appropriate viscosity in the final polymer there is utilized the appropriate amount and type of chain stoppers in the equilibration reaction medium. Thus, divinylte-tramethyldisiloxane may be utilized as a chainstopper to produce the vinyl-terminated polymer of formula (1) in the desired viscosity. The chain stopper, cyclotet-rapolysiloxanes and the required amount of catalyst which may be present at a concentration of anywhere from 10 to 100 parts per million is then heated at temperatures above 150C for periods of time averaging from 1 to 8 hours to produce the linear polysiloxane and polymer of formula (1). At the equilibration point approximately 80 to 85% of the cyclotetrasiloxanes have been converted to the polymere and there is as much of the polymer as being prepared from cyclotetrasiloxanes as there is of the polymer breaking up to form the cyclotetrasiloxanes at the equilibration point.
At that point the catalyst s simply neutralized and the cyclics stripped off to give the desired liner polysiloxane polymer of formula (1). To 100 parts by weight of the base polymer of formula (1) above there is utilized from 1 to 50 parts by weight of a hydride siloxane cross-linking agent. Such a hydride siloxane cross-linking agent may be, for instance, have the formula, ~OSI-112 ~.;32'73~
R4 R7 ,R4 H - SiO - - sio - - si - Tl B R R4 Y R4 l ) where R7 iS selected from the class consisting of hydrogen, monovalent hydrocarbon radicals and halogenated monovalent hydrocarbon radicals, R4 i.s a monovalent hydrocarbon radical and is more preferably selected from the class consisting of alkyl radicals of 1 to 8 carbon atoms; cycloalkyl radicals of up to 8 carbons; mono-nuclear aryl radicals such as, phenyl, and 3-3,3-trifluoropropyl radicals.
Accordingly, R may be selected from the class con-sisting of hydrogen and any saturated monovalent hydro-carbon radicals, and halogenated monovalent hydro-carbon radicals such as, for instance, fluoroalkyl radicals of 3 to 8 carbon atoms such as, 3,3,3-trifluoro-propyl. Preferably, the R4 radical is selected from alkyl radicals of 1 to 8 carbon atoms such as, methyl, ethyl, propyl;mononuclear aryl radicals such as, phenyl ~0 and fluoroalkyl radicals of 3 to 8 carbon atoms such as 3,3,3-trifluoropropyl.
In the foregoing formula (3), y varies such that the polymer has a viscosity in the range of 5 to 500 centipoise at 25C and more preferably has a viscosity that varies from 10 to 50 centipoise at 25 C. In place of this hydride cross-linking agent there may be utilized a silicone resin cross-linking agent, that is, a hydride silicone resin cros~s-linking agent which is generally a silicone resin composed of H R2 SiOo 5 units and SiO2 units where the ratio of the H + R5 radicals to Si varies from 1.1 to 1 to 2.7 to 1 and where R5 can consist of the same radicals as those given for the R4 ~ 60SI~
radical given above.
The hydride polysiloxane of formula (3) as well as the hydride siloxane silicone resin given previously are easily obtained by simply hydrolyzing the appropriat~
chlorosilanes in water and then purifying the desired product. In the case of the resin this may involve the use of a solvent during the hydrolysis such as a water immiscible organic solvent selected from benzene, toluene, xylene and etc. At any rate such hydrolysis reactions for producing such hydride silicone resins is well known as well as the process for producing the hydrogen-containing polysiloxane polymer of formula (3) above. The polysiloxane polymer of formula (3) above may also be obtained by equilibrating a cyclotetrasiloxanes in the presence of an acid catalyst such as toluene sulfonic acid at elevated temperatures with the appropriate type of hydride chainstoppers. In such equilibration procedure, the neutralization and venting of volatiles is followed as well as the same heating step during equilibration to produce the desired hydrogen polysiloxane polymer of formula (3) above. These processes will not be going into detail since such is well known in the art.
In addition to the hydride silicone resin composed of monofunctional units and tetrafunctional units there may be utilized as a cross-linking agent a hydride silicone resin composed of HR 2 SiOo. units and SiO2 units and R 2 SiO units where the H + R5 to Si ratio varies anywhere from 1.1 to 1 to 2.7 to 1, where R5 is as defined previously. More preferably, the silicone resin composed of the hydrogen containing siloxane monofunctional uni~s and the tetrafunctional siloxy units is preferred as a cross-linking agent in the compositions of the instant case Z~
or the hydrogen siloxane o~ formula (3) above. ~he silicone resin containing the difunctional siloxy units is more difficult and expenslve to produce. However, such a resin could be utilized as a cross-linking agent with the SiH-olefin platinum catalyze~ composition of the instant case.
As a catalyst there is utilized anywhere from 1 to 500 parts per million and more preferably from 1 to 200 parts per million of a platinum catalyst.
Many types of platinum compounds for this SiH olefin addition reaction are known and such platinum catalysts may be used also for the reaction of the present case.
The preferred platinum catalysts especially when optical clarity is required are those platinum compound catalysts which are soluable in the present reaction mixture. The platinum compound can be selected from those having the formula (PtC12. Olefin)2 and H(PtC13. Ole~in) as described in U.S.Patent No. 3,159,601 dated December 1, 1964 - Ashby.
The olefin shown in the previous two formulas can be almost any type of olefin but is preferably an alkenylene having from 2 to 8 carbon atoms, a cycloalkenylene having from 5 to 7 carbon atoms or styrene. Specific olefins utilizable in the above formulas are ethylene, propylene, the various isomers of butylene, octylene, cyclopentene, cyclohexene, cycloheptene, etc.
A further platinum containing material usable in the composition of the present invention is the platinum chloride cyclopropane complex (PtC12C3H6)2 described in U.S. patent No. 3,159,662 dated December 8, ]964 Ashby.
Still, further, the patent containing material can be a complex formed from chloroplatinic acid with up to 2 moles per gram of platinum of a member selected from the ~;3~ 60SI-112 class consisting of alcohols, e-thers, aldehydes and mixtures of the above as described in U.S. Paten-t 3,220,972 da-ted November 30, 1965 - Lamoreaux.
The preferred platinum compound to be used not only as a platinum catalyst but also as a flame retardant additive is that disclosed in U~S. Patent 3,775,452 dated November 27, 1973, Karstedt. Generally spea~ing, this type of platinum complex is formed by reacting chloroplatinic acid containing 4 moles of water of hydration with tetravinyltetramethylcyclotetrasiloxane in the presence of sodium bicarbonate in an ethanol solution.
To enhance the physical properties of the composition there may be incorporated in the base vinyl-containing polymer from 10 to 200 parts by weight of a filler, based on 100 parts of the base vinyl-containing polymer of Formula (1), when the filler is selected from the class of reinforcing fillers and extending fillers. Generally, the reinforcing fillers are such fillers such as, fumed silica and precipitated silica while examples of extend-ing fillers are, for instance, fused quartz and etc. The reinforcing fillers are preferred for strength properties, however, the extending fillers are less expensive and also do not tend to increase the viscosity of the uncured composition as much.
In order to get the high desired tensile strength in the compositions of the instant case and particularly when such compositions are formed to thin coatings or films, it is desirable to incorporate a filler into the com-position. Illustrative of the many fillers, which can beemployed are titanium oxide, lithopone, zinc oxide, zirconium silicate, silica aerogel, iron oxide, diatomaceous ~3'~
earth, calcium carbonate, fumed silica, silazane treated silica, precipitated silica, glass fibers, magnesium oxide, chromic oxide, zirconium oxide, aluminum oxide, alpha quartz, calcined clay, asbestos, carbon, graphite cork, cotton, synthetic fibers and etc.
Yhe preferred fillers that should be utilized in the composition of the instant case and particularly in component (A) of the lnstant case, is preferably either a fumed silica or a precipitated silica that has been treated. Thus, the silica fillers may be treated as, for example, as disclosed in U.S. Patent No. 2,938,009 dated May 24, 1960 - Lucas with cyclic polysiloxanes.
Another method for treating fillers or treated fillers that can be utilized in the invention of the instant case is that disclosed in Brown U.S. Patent No.
3,024,126 dated March 6, 1962.
More specifically, silazane treated fillers in accordance with the disclosure of Smith U.S. Patent No.
~0 3,635,743 dated January 18, 1972 and Beers, U.S. patent No. 3,837,878, issued September 24, 1974, both assigned commonly herewith, are preferred as the treated fillers to be utilized in the compositions of the present case.
For more information as to the preparation of the base vinyl containing polymer as well as the hydride polysiloxane and as to the general details as to such SiH-olefin platinum catalyzed compositions, one is referred to the U.S. Patent of Jeram, et al, U.S.
Patent No. 3,957,713 dated May 18, 1976. As noted in that patent, other ingredients well known in SiH-olefin platinum catalyzed compositions may be incorporated in the basic composition to obtain one property or another ~ 3~ 60SI-112 in the cured elastomer that results from the composition.
Thus, based on 100 parts of the base vinyl containing polymer of formula (1), there may be ad~ed to -the com-position form 1 to 30 parts by weight of a vinyl-containing polymer of the formula, Vi-S O ~ slO ~ i - R
R6 ¦ R6 ¦ R6 or vinyl containing silicone resing of formula, ~CH3)3 SiOl/2~ ¦~i o 1 ~i2 ]
where m, p, q vary such that the resin contains from 2.5 to 10 mole percent of vinyl groups, and where R6 is delected from the class consisting of alkyl radicals, cycloalkyl radicals, aryl radicals and fluoralkyl radicals of 1 to 8 carbon atoms and where z varies such that the viscosity of the polymer varies from 100 to 5,000 centi-poise at 25C, and more preferably varies from 100 to 1,000 centipoise at 25C.
Preferably, R6 is selected from radicals such as, methyl, phenyl and 3,3,3-trifluoropropyl and is most preferably selected from methyl and phenyl. The yinyl-containing polymer of Formula (4) as given above when added to the basic vinyl-containing polymer will result in a cured elastomer with higher strength properties and for instance, higher tear then when the SiH-olefin platinum catalyzed composition does not contain such an 73~
ingredients.
For the preparation of fluorosilicone substituted SiH-olefin pla-tinum catalyzed compositions, one is referred to the patent ofJeram U.S. Patent No. 4,041,010 dated August 9, 1977. Both of these patents disclose the preparation of the appxopriate base vinyl-containing polymers, the type of platinum catalyst that can be utilized and the type of hydride siloxane crosslinking agents as well as fillers and other ingredients that are tradi~ionally added to SiH-olefin platinum catalyzed compositions to produce a cured elastomer.
It should be understood that the self-bonding additive of the instant case is not disclosed to be utilized only with the composition of these patents but can be utilized generally with most SiM-olefin platinum catalyzed com-positions and that the above patents are given as being exemplary of both traditional SiH-olefin platinum cat-alyzed compositions as well as fluorosilicone SiH-olefin platinum catalyzed compositions. It is well known in addition to the above basic ingredients disclosed above for the SiH-olefin platinum catalyzed compositions to which the self-bonding additive of the instant case can be added, there may be added other ingredients as long as they do not interfere with the self-bonding properties of theingredient of the instant case such ingredients being, for instance, pigments and etc. that are traditionally added to SiH-olefin platinum catalyzed compositions as well as fluorosilicone SiH-olefin platinum catalyzed compositions. It is well known in addition to the above basic ingredients disclosed above for the SiH-olefin platinum catalyzed compositions to which the self-bonding additive of the instant case can be added, there may be 7~3~ 6os~ 2 d 1~
added other in~redients as long as they do not interfere with the self-bonding properties of the ingredient of the instant case such ingredients being, for instance, pig-ments and etc. that are traditionally added to SiH-olefin platinum catalyzed compositions. It should be noted, however, that for clear potting compounds, a pigment may not be a desirable additive for SiH-olefin platinum catalyzed potting compositions. However, various vinyl-containing fluids and/or resins that are known for addition to SiH-olefin platinum catalyzed compositions may be added to the basic ingredients disclosed above and as disclosed in the foregoing Jeram U.S. patents to enhance one or the other properties of the cured elastomer that is formed from the composition.
As noted previously, the self-bonding additive of the instant case is to be applied to two component SiH-olefin platinum catalyzed compositions and be applied to that component of two-component SiH-olefin platinum catalyzed compositions which does not contain the platinum catalyst.
Accordingly, preferably the filler or vinyl containing silicone reinforcing resin is incorporated into the base vinyl-containing polymer of Formula (1) and the platinum catalyst may be added to it and the composition is thus stored separately along with the other ingredients. To form the second component of the second package, the hydrogen siloxane cross-linking agent is then packaged by itself or with some of the filler along with it and without any of the vinyl-containing polymer if the platinum catalyst is to be incorporated along with the hydrogen polysiloxane. However, if the platinum catalyst is incorporated with the base vinyl~containing polymer 60SI~112 7~
of Formula (1) and the filler, then the vinyl-containing fluids may also be incorporated along with hydrogen siloxane cross-linking agent component. As long as the platinum catalyst is not present with the hydrogen siloxane and the low viscosity vinyl-containing polymers, then the component will not cross-link or cure. However, if the platinum catalyst is incorporated along with the hydrogen siloxane cross-linking agent, then the vinyl-containing fluids must be packaged in the other com-ponent that is with the base vinyl-containing polymer.
The self bonding additive must be packaged in that component which does not contain the platinum catalyst, otherwise, it may have a tendency to deactivate and ultimately poison the platimum catalyst upon storage.
Accordingly, the two components are packaged, shipped and stored as such and when it is desired to cure the composition the components are simply mixed in the specified amounts and formed to the desired part. It is then necessary to heat the composition to a temperature above 100C so that the composition can cure to a self-bonding silicone elastomer in periods of time varying from a few minutes to 1 or 2 hours depending on the level of heating. It should be noted that once the two components are mixed that it is necessary to cure the composition within two weeks since if the mixed com-position is not cured within such a period that it may be very difficult to cure the composition, if at all, due to deactivation of the platinum catalyst. Accordingly, once the two components are mixed it is desirable that the composition be cured within a two week period. As can be understood with the compositions of the instant case, after the two components are mixed the mixed composition ~ 9 60SI-112 has a pot life of two weeks wherein the composition will not cure at room temperature but will cure at elevated temperatures, that is, temperatures above 100C, to a silicone elastomer. The examples below are yiven for the purpose of illustrating the reduction to practice of the instant invention. They are not given for any purpose of setting limitations in the scope of the specification and claims of the instant case and they are not given for any purpose of defining the scope of the invention.
All parts in the examples are by weight.
EXAMPLE I
An adhesion promoting additive composition was prepared as follows: Into a l-quart bottle there were charged 250 parts acetone, l9l parts vinyltriethoxysilane, and 18 parts of water. The bottle was capped and shaken moderately. A mild exotherm ensured. During the exotherm the bottle was vented several times. After the exotherm waned the mixture stood overnight. A titration then showed the product mixture was lO ppn acid, no doubt ~0 owing to trace residual silyl chloride in the vinyltriethox-ysilane. The mixture was stripped to 100C at maximum vacuum (25 inches) in a rotary evaporator. The final product weighed 103 parts. It was a clear, water-white liquid. Anhydrous sodium sulphate was employed to dry the material prior to analysis and use. Analyses of the stripped product by gas chromatography showed some re-actant silane survived (up to 5%) but that more sub~
stantial vinyl silicone was present as dimer (approximately 40%) and higher mers (approximately 40%). ~ trace of ethyl alcohol was also present in the stripped product.
~3~3~ 60SI-112 EXAMPLE I I
An adhesion promoting additive composition was prepared as follows:
Into an all glass reaction apparatus fitted for reagent addition were charged 135 parts of acetone, 255 gm vinyl-triethoxysilane, and a few drops of 12 molar hydrochloric acid. While stirring gently, 24 parts of water was admitted at a rate sufficient to generate a mild exotherm, but keeping the reaction temperature below 50C. The reaction mixture was allowed to stir gently for 2 hours following water addition and then cooled to room temperature.
Approximately 5 parts of sodium bicarbonate was added to neutralize the acid. This mixture stirred an additional hour and was then filtered through celite at the pump.
The filtrate was stripped under vacuum (28") at 100C
and dried over anhydrous magnesium sulphate. Approxi-mately 100 parts of product was obtained.
The product was a clear, water-white liquid. It contained less than 10 ppm acid and contained less than 0.05% by weight of water. An infrared spectrum was in agreement with the expected composition, showing bands due to vinyl at 6.25 microns and siloxy at 9 - 10 microns, etc. Analyses by gas chromatography indicated that about 5 - 10% by weight of the mixture was unconverted vinyl-triethoxysilane, the remainder being dimer and higher mers. A small amount ( ~ 1%) of ethyl alcohol was also EXAMPLE III
There was prepared a clear resin reinforced potting/
encapsulating composition after the teaching of U.S.
Patent 3,425,967 dated February 4, 1969 to Modic. The composition consisted of two packages, A and B. Package A was comprised of 75 parts of a base polymer of the average formula, ~OSI~
7~3~
CH3 ' ~ - Si-O t Si - CH=CH~
CH3 ~ x where x was such that the polymer had a viscosity of 400 cps at 25C, 25 pts of a resin of the average formula, - CH3 - ~CH=CH~
CH3 - Si ~ 1/2 Si - O ~ Si 2]
CH3 - ~CH3 ~ 1. 0 .; 0.7 0.17 and 10 ppm Pt in the form described in U.S. Patent No.
" 3,220,972 dated November 30, 1965 - Lamoreaux. Package `~ B was comprised of 50 pts. of the above described base polymer present in Package A and 50 pts. of a resin .
crosslinker of the average formula, ~` CH3 H - Si - 1/' [ Si O2 To 100 pts. of Package A was added 1 pt. by weight of the adhesion promoting addition composition of Example I.
This mixture was then combined immediately with 10 pts.
` of Package B and mixed throughly. The mixture did not cure at ambient laboratory temperatures. The mixture ` did cure at elevated temperatures. For example, after 1 hours time at lQ0C, the mixture cured to form a clear silicone elastomer. For up to 14 days following its preparation, the mixture cured satisfactory on exposure to 100C for 1 hour. Following the 14-day period, un-satisfactory cures were obtained at this raised temperature (100C) in that the final elastomer was too soft.
~f~3~ 60SI-112 The physical properties of the compositions with and without the self-bonding additive were as follows:
Without With Tensile 920 psi 820 Elongation 150~ 160 Durometer - Shore A 35 28 Tear - 40 lbs./in 20 Thus, no significant reduction in physical proper-ties of the cured elastomer resulted from the additive being present at the level of the example.
EXAMPLE IV
To the above SiH-olefin platinum catalyzed composition of Example III there was added l part by weight of the partial hydrolysis vinyl siloxy silane of Example 1.
During the 14-day period of satisfactory elevated tem-perature cure detailed in Example III, a 60 mil thickness of RTV composition of Example III was applied to each substrate tested and cured in place by baking one hour at 300F. Again no substantial reduction in the physical properties of the cured rubber was observed.
The 60 mil thickness of RTV was applied to each substrate tested and cured in place as described. All surfaces were clean in the usual sense. The cured silicone' elastomer which was a clear SiH-olefin platinum catalyzed composition had good clarity at this thickness. The following bonds were obtained:
Substrate Bond glass excellent aluminum (bare) marginal steel (carbon) excellent copper excellent stainless steel excellent ~ 3~ 60SI-112 An excellent bond is taken to mean a cohesive failure bond was noted when attempts to remove the cured elasto-mer from the surface were made. No bonds developed without the additive present. The bond to aluminum was improved to excellent by priming the surface with a silicone primer. These same results were obtained in each of three instances when the bonding tests were repeated during the 14 day period of satisfactory raised temperature cure.
Claims (24)
1. A self-bonding silicone rubber composition comprising (A) 100 parts by weight of a base polymer of the formula, where R is selected from the class consisting of monovalent hydrocarbon radicals and halogenated monovalent hydrocarbon radicals, and x is such that the viscosity of the base polymer varies from 100 to 200,000,000 centipoise at 25°C (B) from 0.5 to 50 parts by weight of a hydride siloxane cross-linking agent;
(C) from 1 to 500 parts per million of a platinum catalyst;
and (D) from 0.1 to 5 parts by weight of a self-bonding additive which is the partial hydrolysis product of an aliphatically unsaturated hydrolyzable alkoxy silane of the formula:
wherein: R1 is an aliphatic unsaturated radical selected from the class consisting of alkenyl radicals and alkynyl radicals of 2 to 8 carbon atoms; R3 is selected from the class consisting of alkyl radicals and cycloalkyl radicals of 1 to 8 carbon atoms; "a" varies from 1 to 2; and on the average of 16 to 49%
of the hydrocarbonoxy, R3 groups are hydrolysed.
(C) from 1 to 500 parts per million of a platinum catalyst;
and (D) from 0.1 to 5 parts by weight of a self-bonding additive which is the partial hydrolysis product of an aliphatically unsaturated hydrolyzable alkoxy silane of the formula:
wherein: R1 is an aliphatic unsaturated radical selected from the class consisting of alkenyl radicals and alkynyl radicals of 2 to 8 carbon atoms; R3 is selected from the class consisting of alkyl radicals and cycloalkyl radicals of 1 to 8 carbon atoms; "a" varies from 1 to 2; and on the average of 16 to 49%
of the hydrocarbonoxy, R3 groups are hydrolysed.
2. The composition of claim 1 wherein 1 to 1.5 parts by weight of said self-bonding additive is utilized.
3. The composition of claim 1 wherein R is selected from the class consisting of alkyl radicals, cycloalkyl radicals, aryl radicals and fluoroalkyl radicals of 1 to 8 carbon atoms.
4. The composition of claim 1 wherein the hydride siloxane cross-linking agent has the formula, where R7 is selected from the class consisting of hydrogen, monovalent hydrocarbon radicals and halogenated monovalent hydrocarbon radicals, R4 is a monovalent hydrocarbon radicals and y varies such that the polymer has a viscosity in the range of 10 to 500 centipoise at 25°C.
5. The composition of claim 1 wherein the hydride siloxane cross-linking agent is a resin composed of H R? SiO 0.5 units, and SiO2 units wherein the ratio of the H + R5 radicals to Si varies from 1.0 to 1.0, to 2.7 to 1.0 wherein R5 is seleeted from the class consisting of monovalent hydrocarbon radicals and halogenated monovalent hydrocarbon radicals.
6. The composition of claim 1 wherein there is additionally present from 10 to 200 parts by weight of a compound selected from reinforcing fillers, extending fillers, and a vinyl-containing reinforcing resin eomprising R6SiO 0.5 units and SiO2 units, in whieh from about 2.5 to 10 mole percent of the silieon atoms contain silicon-bonded vinyl groups where R6 is a monovalent hydrocarbon radical.
7. The composition of claim 1 wherein the reinforcing filler is selected from the class consisting of fumed silica and precipitated silica.
8. The composition of claim 7 wherein said filler is treated with a treating agent seleeted from the class consisting of cyclosiloxanes, silazanes and mixtures thereof.
9. The composition of claim 1 wherein there is present from 1 to 30 parts by weight of a vinyl-containing polymer of the formula, wherein R6 is selected from the class consisting of alkyl radicals, cycloalkyl radicals, aryl radicals and fluoroalkyl radicals of 1 to 8 carbon atoms where z varies such that the viscosity of the polymer varies from 100 to 5,000 centipoise at 25°C.
10. A process for adhereing a self-bonding silicone rubber composition to a substrate comprising (1) mixing (A) 100 parts by weight of a base polymer of the formula, where R is selected from the class consisting of monovalent hydrocarbon radicals and halogenated monovalent hydrocarbon radicals, and x is such that the viscosity of the base polymer varies from 100 to 200,000,000 centipoise at 25°C; (B) from 0.5 to 50 parts by weight of a hydride siloxane cross-linking agent;
(C) from 1 to 500 parts per million of a platinum catalyst; and (D) from 0.1 to 5 parts by weight of a self-bonding additive which is the partial hydrolysis product of an aliphatically unsaturated hydrolyzable alkoxy silane of the formula, wherein R1 is an aliphatically unsaturated radical selected from the class consisting of alkenyl radicals and alkynyl radicals of 2 to 8 carbon atoms, R3 is selected from the class consisting of alkyl radicals and cycloalkyl radicals of 1 to 8 carbon atoms; "a" varies from 1 to 2; and, on the average of 16 to 49% of the hydrocarbonoxy groups, OR3 are hydrolysed;
(2) applying the mixture to said substrate, and (3) heating the substrate and mixture at elevated temperatures.
(C) from 1 to 500 parts per million of a platinum catalyst; and (D) from 0.1 to 5 parts by weight of a self-bonding additive which is the partial hydrolysis product of an aliphatically unsaturated hydrolyzable alkoxy silane of the formula, wherein R1 is an aliphatically unsaturated radical selected from the class consisting of alkenyl radicals and alkynyl radicals of 2 to 8 carbon atoms, R3 is selected from the class consisting of alkyl radicals and cycloalkyl radicals of 1 to 8 carbon atoms; "a" varies from 1 to 2; and, on the average of 16 to 49% of the hydrocarbonoxy groups, OR3 are hydrolysed;
(2) applying the mixture to said substrate, and (3) heating the substrate and mixture at elevated temperatures.
11. The process of claim 10 wherein 1 to 1.5 parts by weight of a self-bonding additive is utilized.
12. The process of claim 10 wherein R is selected from the class consisting of alkyl radicals, cycloalkyl radicals, aryl radicals and fluoroalkyl radicals of 1 to 8 carbon atoms.
13. The process of claim 10 wherein the hydride siloxane cross-linking agent has the formula, where R7 is selected from the class consisting of hydrogen, monovalent hydrocarbon radicals and halogenated monovalent hydrocarbon radicalsp R4 is a monovalent hydrocarbon radical and y varies such that the polymer has a viscosity in the range of 10 to 500 centipoise at 25°C.
14. The process of claim 10 wherein the hydride siloxane cross-linking agent is a resin composed of H R? SiO 0.5 units and SiO2 units wherein the ratio of the HR + R5 radicals to Si varies from 1.1 to 1.0 to 2.7 to 1.0 wherein R5 is selected from the class consisting of monovalent hydrocarbon radicals and halogenated monovalent hydrocarbon radicals.
15. The process of claim 10 wherein there is additionally present from 10 to 200 parts by weight of a filler selected from reinforcing fillers and extending fillers.
16. The process of claim 10 wherein the reinforcing filler is selected from the class consisting of fumed silica and precipitated silica.
17. The process of claim 16 wherein said filler is treated with a treating agent selected from the class consisting of cyclicsiloxanes, silazanes and mixtures thereof.
18. The process of claim 10 wherein there is present from 1 to 30 parts by weight of a vinyl containing polymer of the formula, wherein R6 is selected from the class consisting of alkyl radicals, cycloalkyl radicals, aryl radicals and fluoroalkyl radcials of 1 to 8 carbon atoms where z varies such that the viscosity of the polymer varies from 100 to 5,000 centipoise at 25°C.
19. The composition of claim 1 wherein said hydrocarbonoxy groups of said hydrolyzable silane are hydrolysed in solution with a dipolar aprotic solvent and water equivalent to from 0.5 to 1.5 moles of water per mole of hydrolysable silane.
20. The composition of claim 19 wherein said dipolar aprotic solvent is selected from the class consisting of acetone, methylethylketone, dioxane, and tetrahydrofuran.
21. The composition of claim 20 wherein said solution is homogeneous and there is present an acidic catalyst such that the solution has an acidity of 10 to 500 parts per million during hydrolysis of said hydrolysable silane.
22. The composition of claim 21 wherein following partial hydrolysis of said hydrolysable silane there is added to said solution a neutralizing amount of a mild base.
23. The composition of claim 1 wherein said hydrolyz-able silane is vinyl-triethoxysilane.
24. The process of claim 10 wherein said hydrolyzable silane is vinyl-triethoxysilane.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA325,063A CA1132739A (en) | 1979-04-06 | 1979-04-06 | Self-bonding silicone rubber compositions |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA325,063A CA1132739A (en) | 1979-04-06 | 1979-04-06 | Self-bonding silicone rubber compositions |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1132739A true CA1132739A (en) | 1982-09-28 |
Family
ID=4113930
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA325,063A Expired CA1132739A (en) | 1979-04-06 | 1979-04-06 | Self-bonding silicone rubber compositions |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1132739A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116333498A (en) * | 2022-11-23 | 2023-06-27 | 四川天邑康和通信股份有限公司 | High-heat-conductivity wave-absorbing gasket and preparation method thereof |
-
1979
- 1979-04-06 CA CA325,063A patent/CA1132739A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116333498A (en) * | 2022-11-23 | 2023-06-27 | 四川天邑康和通信股份有限公司 | High-heat-conductivity wave-absorbing gasket and preparation method thereof |
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