CA1044247A - Process for the production of silanol-stopped diorganopolysiloxanes - Google Patents
Process for the production of silanol-stopped diorganopolysiloxanesInfo
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- CA1044247A CA1044247A CA209,871A CA209871A CA1044247A CA 1044247 A CA1044247 A CA 1044247A CA 209871 A CA209871 A CA 209871A CA 1044247 A CA1044247 A CA 1044247A
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
- C08G77/04—Polysiloxanes
- C08G77/06—Preparatory processes
- C08G77/08—Preparatory processes characterised by the catalysts used
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
- C08G77/04—Polysiloxanes
- C08G77/14—Polysiloxanes containing silicon bound to oxygen-containing groups
- C08G77/16—Polysiloxanes containing silicon bound to oxygen-containing groups to hydroxyl groups
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- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Silicon Polymers (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A process for producing a silanol chain-stopped diorganopolysiloxane having a viscosity of from 1,000 to 10,000,000 centerpiece at 25°C comprises contacting a cyclic polysiloxane with 100 parts per million to less than 2% by weight of water in the presence of an acidic solid catalyst such as an acid activated clay or an ion exchange resin at a temperature of about 50°C to 200°C.
A process for producing a silanol chain-stopped diorganopolysiloxane having a viscosity of from 1,000 to 10,000,000 centerpiece at 25°C comprises contacting a cyclic polysiloxane with 100 parts per million to less than 2% by weight of water in the presence of an acidic solid catalyst such as an acid activated clay or an ion exchange resin at a temperature of about 50°C to 200°C.
Description
.
~ f~ 8SI-1563 The present lnven~ion relates to a process for producing a silanol chain-stopped diorganopolysiloxane and, more particularly, to producing a silanol chain-stopped di-organopolysiloxane having a viscosity of in excess of l,ooo and up to lO,000,000 centipoise at 25C by reacting a silanol chaln-stopp~d diorganopolysiloxane of low viscosity with a cyc~ic polysiloxane or a mixture of cycli~ polysiloxanes, or an alternate process by reacting a cyclic polysiloxane with from lO0 parts per million to less than 2% by weight of wa-ter.
As is known from the prior art, such silanol chain-stopped polydiorganosiloxanes are utilized in producing room temperature vulcanizable silicone rubber compositions. Such silanol chain-stopped diorganopolysiloxanes are the main ingredient in both one-package and two-package room temperature vulcanizable silicone rubber compositions.
It was contemplated in the past that such silanol chain-stopped diorganopolysiloxanes can be produced by hydrolyzing a mixture of pure diorganodichlorosilanes with water and then adding a strong base to the hydrolyzate and heating it to above 150C for 2 to 6 hours. During this time there would be formed in the equilibration reaction a large amount of cyclic polysiloxanes. If the reaction mixture was continuously heated after that point, say for another 2 to 6 hours, the cyclic polysiloxanes polymerize further to form a diorganopolysiloxane gum of a very high viscosity. Then water could be added to such a gum or steam could be passed through the gum so as to result in rupture of the siloxane chains in the gum and the formation of silanol groups in the terminal portion of the chain, such that a large proportion of the final product was a silanol-stopped diorganopolysiloxane which could be used as an inyredient in room temperature vulcanizable silicone rubber compositions. Although this .... . . .
J,.6~ L~ ~ Z L~7~ 8S I ~ 15 6 3 procedure could be carried out in the laborato~ to produce silanol chain-stoppea diorganopolysiloxanes of the desired viscosity, such a procedure was not very feasible in the manufacturing plant. The reason that ~his procedure could be used in the laboratory was that it was possible to obtain by laboratory procedures a mixture of aiorganodichlorosilanes which were essentially pure. Under normal manufacturing pro-cedures, the diorganodichlorosilanes that were produced had -a certain amount of impurities in them. More particularly, there was present in such diorganodichlorosilanes up to as much as 0.7% or more, such as up to 1.0% by weight, of tri-functional chlorosilanes present along wlth the diorganodi-chlorosilane, which amount of trifunctional silane could not be removed by ordinary manufacturing puri~ication procedures.
In addition, in the diorganodichlorosilanes which were pro-duced by the usual manufacturing procedures, there was present up to 0.3% by weight of monofunctional chlorosilanes, which again were undesirable reactants for producing silanol chain-stopped diorganopolysiloxanes. Such monofunctional silanes acted as chain-stoppers, thus, terminating the length of the chain with a trimethylsiloxy group rather than a silanol group as is desired in a silanol chain-stopped diorganopolysiloxane.
However, the presence of the trifunctional chlorosilane was even more undesirable. A catalyzed hydrolyzate mixture, when heated at elevated temperatures such as 150C to 200C, would rosult in the formation of cyclics. These cyclics would react with such trifunctional silanes so as to extensively cross-link such that a gel would be formed. In addition, the re-action mixture~ was not a useful polymer for producing a silanol chain-stopped diorganopolysiloxane, particularly for one-package and two-package room temperature vulcanizable silicone rubber compositions.
.. .... ~ .. ... ... ,....... . .. , ~ .
~44Z~7 8SI-1563 In order to cure -this deficiency, an alternative procedure was developed by which most of the trifunc-tional chlorosilane could be removed from the basic diorganodi-chlorosilane reactant. ~hus, as in the previous procedure, such diorganodichlorosilane was hydrolyzed to produce a certain amount of silanol chain-stopped diorganopolysiloxane of a low molecular weight and also certain quantities of cyclic polysiloxanes To this hyarolyzate, as in the prior procedure, potassium hydroxide was addea and the mixture was heated in a temperature range-of 100C to 200C for 2 to 6 hours. During such heating procedure, the cyclics that were already present in the hydrolyzate, as well as the cyclics that were formed due to the presence of the potassium hydroxide catalyst, were stripped o~f from the hydrolyzate. Thus, by this procedure, there was obtained an essentially pure mixture of diorgano cyclic polysiloxanes where there may be from 3 to lO silicon atoms in the cyclic polysiloxane. The cyclic polysiloxanes which are essentially free of the monofunctional silanes, and the trifunctional silanes were then taken and equilibrated in the presence of a strong base catalyst, such as sodium hydroxide or potassium hydroxide, for a period of
~ f~ 8SI-1563 The present lnven~ion relates to a process for producing a silanol chain-stopped diorganopolysiloxane and, more particularly, to producing a silanol chain-stopped di-organopolysiloxane having a viscosity of in excess of l,ooo and up to lO,000,000 centipoise at 25C by reacting a silanol chaln-stopp~d diorganopolysiloxane of low viscosity with a cyc~ic polysiloxane or a mixture of cycli~ polysiloxanes, or an alternate process by reacting a cyclic polysiloxane with from lO0 parts per million to less than 2% by weight of wa-ter.
As is known from the prior art, such silanol chain-stopped polydiorganosiloxanes are utilized in producing room temperature vulcanizable silicone rubber compositions. Such silanol chain-stopped diorganopolysiloxanes are the main ingredient in both one-package and two-package room temperature vulcanizable silicone rubber compositions.
It was contemplated in the past that such silanol chain-stopped diorganopolysiloxanes can be produced by hydrolyzing a mixture of pure diorganodichlorosilanes with water and then adding a strong base to the hydrolyzate and heating it to above 150C for 2 to 6 hours. During this time there would be formed in the equilibration reaction a large amount of cyclic polysiloxanes. If the reaction mixture was continuously heated after that point, say for another 2 to 6 hours, the cyclic polysiloxanes polymerize further to form a diorganopolysiloxane gum of a very high viscosity. Then water could be added to such a gum or steam could be passed through the gum so as to result in rupture of the siloxane chains in the gum and the formation of silanol groups in the terminal portion of the chain, such that a large proportion of the final product was a silanol-stopped diorganopolysiloxane which could be used as an inyredient in room temperature vulcanizable silicone rubber compositions. Although this .... . . .
J,.6~ L~ ~ Z L~7~ 8S I ~ 15 6 3 procedure could be carried out in the laborato~ to produce silanol chain-stoppea diorganopolysiloxanes of the desired viscosity, such a procedure was not very feasible in the manufacturing plant. The reason that ~his procedure could be used in the laboratory was that it was possible to obtain by laboratory procedures a mixture of aiorganodichlorosilanes which were essentially pure. Under normal manufacturing pro-cedures, the diorganodichlorosilanes that were produced had -a certain amount of impurities in them. More particularly, there was present in such diorganodichlorosilanes up to as much as 0.7% or more, such as up to 1.0% by weight, of tri-functional chlorosilanes present along wlth the diorganodi-chlorosilane, which amount of trifunctional silane could not be removed by ordinary manufacturing puri~ication procedures.
In addition, in the diorganodichlorosilanes which were pro-duced by the usual manufacturing procedures, there was present up to 0.3% by weight of monofunctional chlorosilanes, which again were undesirable reactants for producing silanol chain-stopped diorganopolysiloxanes. Such monofunctional silanes acted as chain-stoppers, thus, terminating the length of the chain with a trimethylsiloxy group rather than a silanol group as is desired in a silanol chain-stopped diorganopolysiloxane.
However, the presence of the trifunctional chlorosilane was even more undesirable. A catalyzed hydrolyzate mixture, when heated at elevated temperatures such as 150C to 200C, would rosult in the formation of cyclics. These cyclics would react with such trifunctional silanes so as to extensively cross-link such that a gel would be formed. In addition, the re-action mixture~ was not a useful polymer for producing a silanol chain-stopped diorganopolysiloxane, particularly for one-package and two-package room temperature vulcanizable silicone rubber compositions.
.. .... ~ .. ... ... ,....... . .. , ~ .
~44Z~7 8SI-1563 In order to cure -this deficiency, an alternative procedure was developed by which most of the trifunc-tional chlorosilane could be removed from the basic diorganodi-chlorosilane reactant. ~hus, as in the previous procedure, such diorganodichlorosilane was hydrolyzed to produce a certain amount of silanol chain-stopped diorganopolysiloxane of a low molecular weight and also certain quantities of cyclic polysiloxanes To this hyarolyzate, as in the prior procedure, potassium hydroxide was addea and the mixture was heated in a temperature range-of 100C to 200C for 2 to 6 hours. During such heating procedure, the cyclics that were already present in the hydrolyzate, as well as the cyclics that were formed due to the presence of the potassium hydroxide catalyst, were stripped o~f from the hydrolyzate. Thus, by this procedure, there was obtained an essentially pure mixture of diorgano cyclic polysiloxanes where there may be from 3 to lO silicon atoms in the cyclic polysiloxane. The cyclic polysiloxanes which are essentially free of the monofunctional silanes, and the trifunctional silanes were then taken and equilibrated in the presence of a strong base catalyst, such as sodium hydroxide or potassium hydroxide, for a period of
2 to 6 hours to produce a diorganopolysiloxane gum of high viscosity, for instance, a viscosity of from above 1,000,000 to up to 30,000,000 centipoise at 25C. This high viscosity gum was then taken and there was added to it the desired amount of water or steam such that the long molecular chains of the diorganopolysiloxane gum were broken up to form a low viscosity material chain-stopped by silanol groups. Thus, by this long drawn out procedure, it was possible to form a silanol chain-stopped diorganopolysiloxane of the desired viscosity which could be used as an ingredient in one or two~
package room temperature vulcanizable silicone rubber ... . ..
2 ~7 8 S I--15 6 3 compos itions.
One dif~iculty with this process was the formati~n of the high viscosity gum, which was very difficult to handle. It was very difficult, if not impossible, to make the production of such silanol chain-stopped diorgano-polysiloxanes by a continuous process. Several attempts were made to dissolve the diorganopolysiloxané gum in a solvent for use in a contemplated continuous proeess so as to con-serve on equipment ana labor. However, the use of a solvent complicates the process and makes it necessary to use special handling equipment and, in addition, creates a fire hazard.
Further, in addition, even in a batch process, this prior art process was undesirable since it was very difficult to control the desired and viscosity of the silanol chain-stopped di-organopolysiloxane by the use of steam or the incorporation of water therein. The reason be;ng that the addition of water to the diorganopolysiloxane gum of a high molecular weight caused an erratic drop in viscosity. Thus, it was desired to form a polysiloxane whose viscosity would increase after the initial mixing of the reaetants by a measurable and controlled amount without going through a high viscosity maximum. In addition, in the foregoing prior art process, the presence of ~ ;
water or even small amounts of water was undesirable until the final step w~en steam or water was added to the diorganopoly-siloxane gum. Since the presence of water or moisture are very readily present in a manufacturing plant, it was desired to develop a process where the presence of water which might ineidentally get mixed into the reactants, would not inhibit the process.
~owever, as was stated previously, the main deficiency in sueh prior art processes were that they could not be made ~ L~ 8SX-1563 continuous. Even with the use of solvents~ these prior art processes could not be made continuous since such solvent solutions necessitated prohibitatively expensi~e equipmen-t of large capacities and also necessitated special safety procedures because of the flammability of such solvents. It was, thus, ~ighly desirable to find a process w~ich would be continuous in the production o~ silanol chain-stopped di- -organopolysiloxanes.
It is one object of the present invention to provide a process for producing silanol chain-stopped dior~anopoly-siloxane gum which can be produced economically in a batch process.
It is another object of the present invention to provide a process for producing a silanol-stopped diorgano-polysiloxane having a viscosity from 1,000 to 10,000,000 centipoise at 25C, which process could be semi-continuous.
It is an additional object of the present invention to provide a process for the production of the aforesaid silanol chain-stopped diorganopolysiloxane polymer which polymer could be made economically by a continuous process.
It is yet another object of the present invention to provide a process for economically producing a silanol chain-stopped diorganopolysiloxane gum useful as an ingredient ~ -;
in the preparation of room temperature vulcanizable silicone rubber compositions.
It is yet another object o~ the present invention to provide an economical process ~or the production of silanol chain-stopped diorganopolysiloxane gum, which process would not be affected by the presence of water.
It is ~till another object of the present invention to provide a continuous process for the production of a silanol chain-stopped diorganopolysiloxane polymer, which process would ~ 7 8SI-1563 be bo-th economical and safe to operate.
In accordance with the above objects, -there is provided a process for producing a silanol chain-stopped di-organopolysiloxane ~aving a viscosity of 1,000 to 10,000,000 centipoise at 25C, where the organo groups are selected from the class consisting of monovalent hydrocarbon radicals, monovalen~ halogenated hydrocarbon radicals and cyanoalkyl radicals comprising equilibrating cyclic polysiloxanes having a formula (1~ (R2SiO) :' wherein the R groups are identical to the organo ~roups of the previously described diorganopolysiloxaneO and wherein it varies from 3 to 10, and desirably 3 to 5 with certain critical amounts of water, that is, 100 parts per million to less than 2% by weight of water, based on the wei~ht of the cyclic polysiloxanes, at a temperature range of 50 to 200C.
In this process there is utilized essentially pure cyclic polysiloxanes of Formula (1) which cyclic polysiloxanes can be obtained by the methods well known to a person skilled in the art and which methods are set forth in the present specification. The equilibration takes place in the presence of catalyst constituted by a solid having active protons on it. Another way of defining such a catalyst is a solid having active hydrogen atoms on it. Such catalysts are well known in the art but were not known or contemplated for the above-described process. Thus, any solid w~ich has absorbed on it or has been treated with an acid of a pH below 5 may be used as a catalyst in the present invention. It is ob-served that a liquid acid catalyst e.g. sulfonic acid or a solid pure acid catalyst e.g. toluene sulfonic acid, will not operate in the foregoing process.
The cyclopolysiloxane reactant and the controlled ~SI-1563 quantity of water are reacted in the presence of the solid catalyst until equilibrium is reached, that is, until the desired silanol chain-stopped diorganopolysiloxane is form~d;
at equilibrium about 12 to 13~ cyclic polysiloxanes are normally present in the mixture. At that point, the reaction is terminated and the solid catalyst is filtered out.
The process can be completely batch, semi-continuous or totally continuous.
In some cases it may be desirable to remove the cyclic polysiloxanes remaining after equilibration has been reached without first removing the solid catalyst from the equilibration mixtureO Thus, if it is desired to neutralize the solid catalyst after equilibration has been reached, there ~ `
may be added to the equilibration mixture neutralizing amounts of an additive such as, NH~OEI, R NH30H, R R520~, (R )4NOH and (R )4POH, where R and R are selected from the class consisting of alkyl radicals of 1 to 8 carbon atoms, alkenyl radicals oF 2 to 8 carbon atoms, cycloalkyl radicals of 4 to 8 carbon atoms, and mononuclear aryl radicals such as phenyl, methylphenyl, etc.
After such neutralizing agents have been added to the equilibration reaction mixture the excess cyclic poly-siloxanes can be stripped at elevated temperatures to leave behind the desired silanol chain-stopped diorganopolysiloxanes, having therein the solid catalyst which can then be filtered out or left in the desired product. This neutralization procedure is desirable when the solid catalyst is present or utilized in a loose form in the equilibration reaction ~1~3~ 7 8SI-1563 mixture rather than wherl the solid catalyst is used in a packed column, since in tha loose form the solid catalyst can only be removed from the equilibration reaction mixture by filtration.
The organic groups in the silanol chain-stopped diorganopolysiloxanes, and thus the R radicals in the cyclic polysiloxane of Formula (1), can include, for example, alkyl ;
radicals such as methyl, ethyl, propyl, butyl, octyl; aryl radicals such as, phenyl, tolyl; aralkyl radicals such as, benzyl, phenylethyl, alkenyl radicals such as, vinyl and allyl; cycloaliphatic radicals such as, cyclohexyl, cyclo-heptyl and cyclohexenyl; haloalkyl and haloaryl such as, chloromethyl, alpha-chloroethyl, beta-chloroethyl, chloro-phenyl, dibromophenyl, trifluoromethylphenyl and trifluoro-methylpropyl and cyanoalkyl radicals such as, cyanomethyl, beta-cyanoethyl, beta-cyanopropyl, gamma-cyanoprop~l, and omega-cyanobutyl. The R radicals on the same silicon atom may be the same or different. Thus, the R groups on the same silicon atom may be the same or different such as, methyl, phenyl and the silanol chain-stopped diorganopolysiloxane reaction product can have dimethyl substituents, diphenyl substituents, methylphenyl substituents, or other of the aforementioned groups bonded to the silicon atoms of the chain.
The preferred substitutent groups selected from lower a~kyl of 1 to 8 carbon atoms, such as, methyl, ethyl, mononuclear aryl radicals such as, phenyl and lower alkenyl radicals such as vinyl and alkyl. --Preparation of the cyclic polysiloxanes of Formula (1) above which contain both saturated and olefinically un-saturated hydrocarbon groups, may be carried out by any ofthe procedures well known to those skilled in the art. Such polysiloxanes can be produced by following the procedure L~L7 involving hydrolysis of one or more hydrocarbon substituted dichlorosilanes of which -the substitutents consist of saturated and/or unsaturated hydrocarbon groups. Thus, the diorganodihalogenosilanes may be added to an acid-water mix-ture slowly over a perioa of 30 minutes to 2 hours with con-stant agitation and, a-t the end of that time, the agitation is continued for 15 minutes more. If desired the diorganodi-halogenosilanes may be dissolved in a solvent and added to the acid-water mixture. The hydrolysis reaction may be 1~ carried out at any temperature between 20C to 50C. After the hydrolysis is complete, then there is present in the hydrolyzate a mixture of cyclic polysiloxanes and a silanol chain-stopped diorganopolysiloxane. To the crude hydrolyzate there is then added a strong base catalyst such as potassium hydroxide, cesium hydroxide, lithium hydroxide or sodium hydroxide. Preferably, there is added from 1 to 5 percent of the strong base to the hydrolyzate. The hydrolyzate is then heated at a temperature in the range of 125C to,175c for a period of time varying from ~ to 4 hours, during which 20 period a number of reactions occur. The silanol groups are condensed to produce siloxane linkages and water. In addition, an e~uilibration is set up w~ich proauces a mixture of the cyclic siloxanes of Formula (1) above. Thus, in the most preferred process, the hydrolyzate with the base catalyst is heated to a temperature of about 150C until equilibration is reached wherein thare is being formed a maximum amount of cyclic polysiloxanes. At the end of this period, the reaction mixture is heated to a temperature of about 200C and all of the cyclic polysiloxanes are stripped off and collected.
In particular, in the more preferable process, when the hydrolyzate is heated with a base catalyst at a tem-perature of 150 C or over, the cyclic polysiloxanes are - . . . . - . . .. ~ . . -contlnually distilled off and collected until the ~ydrol~zate has produced the maximum amount of cyclic polysiloxanes 9 which are continually collected Thi5 procedur~ of drawing off the cyclic polysiloxanes as they are formed results in the production of as much cyclic polysiloxanes as possible. Such cyclic polysiloxanes which are collected from this equilibration and stripping procedure are essentially pure and free o~ tri-functional units~
Thus, in order to depolymerize the crude hydrolyzate that is formed, there is added to the hydrolyzate a catalyst and the mixture is heated at a tempera-ture o~ over 150C to produce and recover2 by distillation a product consisting of low molecular weight cyclic polysiloxanes of Formula (1) above, comprising about 85% of a cyclic polysiloxane having three silicon atoms and five silicon atoms.
Whilst the cyclic polysiloxanes of Formula (1) above, for use in our process can be obtained by any of the methods known to those skilled in the silicone art, it is necessary that they be in essentially pure form in order to obtain hi~h yields of the desired product. The catalyst that is employed in our process can be described as a solid having active protons on it or as a solid that has active hydrogen atoms on it or as a solid that has been treated with an acid having a pH below 5. Thus, ion-exchange resins can be used -as a catalyst in the present invention. Synthetic resins, such as sulfonated polystyrenes, may also be used as a cata-lyst in the present invention. Acid-activated carbon and acid-activated clays, such as montmorillonite, can be used in the present invention. The preferred acid-activated clay is montmorillonite, an example of which is Filtrol, manufactured by Filtrol Corporation of Los Angeles, California. The particular advanta~es of Filtrol and other acid-activated ~SI-1563 solid catalysts is that they do not impart any acidity to the reactants or to the reaction product. Accordin~ly, after the reaction is completed with the use of Filtrol, the Filtrol is simply removed or separated from the reactants and there is no need for neutralizing the reaction product that is formed in this reaction.
Other examples of catalysts, which may be used in the present invention are: Florida Earth, Kambara Earth, sulfuric acid-treated carbon montmorillonites, sulfuric or hydrochloric acid treated halloysite, beidellite, illite, Filtrol-20, Filtrol-24, Filtrol-25 (trademar~s of acid treated clay manufactured by the Filtrol Corporation, Los Angeles, California); natural zeolites, natrolite, analcime, stilbite, -~
chabazite, mordenite, clinophilolite, glauconite (green sand), synthetic zeolites, Zeolon Series (tradenames of synthetic mineral cation exchange resins sold by Norton Co.), Permutit (tradename of synthetic mineral cation exchange resins -manufactured by Permutit Co.), bentonite, kaolinite (China Clay), alumino-silicates, Fuller's Earth, acidified carbon, acidified charcoal, sulfonated coal, sulfonated polystyrene acid forms of Dowex-50 (manufactured by Dow Chemical Co.), Amberlyst-15 (manufactured by Rohn & ~ass), Ionac C-242 (manufactured by Ionac Co.), Duolite C-20 (manufactured by Diamond Alkali).
The solid acid catalyst is preferably used in the equilibration reaction at a concentration of 0.1 to 50% by weight or more by volume. As will be explained further on, when the process is a batch process, the solid catalyst may be present at a concentration of as low as 0.1 to 5 or 10%
by volume of the reaction mixture. On the other hand, when a continuous or semi-continuous process is used where the reactants are passed through a column of Filtrol or other solid 8SI~1563 ~3~ 7 acid catalyist, then the volume of -the catalyst with respect to the volume of reactants in -the column or reaction may be as hiyh as 50% to 90% by volume or more. As stated in terms of weight percent, the concentration of the acid-activated solid catalyst may be present at a concentration of 0.1% to 75% by weight of the reaction mixture. The equilibration reaction is carried out in the presence of water. Preferably, there may be used anywhere from .05% by weight to less than 2% by weight of water based on the cyclic polysiloxanes of Formula (1~. If less than 100 parts per million of water is initially present in the equilibration reaction, then the desirable silanol chain-stopped diorganopolysiloxane is of too high a viscosity. If 2% by weight or more water is utilized in the equilibration reaction mixture the desired silanol chain-stopped diorganopolysiloxane polymer is obtained at a very poor yield, that is, at equilibration there is less than 80% of the cyclic polysiloxanes of Formula (1), converted to the desired silanol end-stopped diorganopolysiloxane polymer of a viscosity of 1,000 to 10,000,000 centipoise at 25C.
Accordingly, it is critical to our process that there be present less than 2% by weight of water based on the cyclic polysiloxanes of Formula (1) above. Thus, by con-trolling the amount of water as indicated above and equilibrating the cyclic polysiloxanes in the presence of the critical solid catalyst of the present invention which were defined previously, there can be obtained the desired silanol chain-stopped diorganopolysiloxane of Formula (4) above, which has a silanol content of anywhere from .001 to 0.5% by weight. Accordingly, in a more pref~red embodiment, there is preferred to be utilized anywhere from .05% by weight to less than 2% by weight of water in contact with the :
, , , . ~ . . ' ' . ~ . :
cyclic polysiloxanes of Formula (1~ above. The desired silanol chain-stopped diorganopolysiloxane is present at above 80 and 85% by weight in the equilibration reaction mixture after the water and cyclic polysilo~anes of Formula (1) have reached the equilibration point. The reaction is carried out at a ~emperature range of anywhere from 50 to 200C and preferably at a temperature range of 150 to 200C.
The reaction time may vary anywhere from 1-1/2 hours to 48 hours depending on the temperature of reaction and the amount of solid catalyst that is utilized in t~e reaction mixture.
The silanol chain-stopped diGrganopolysiloxane product of the present invention can be used to form one-packaye room temperature vulcanizable silicone rubber com-positions by mixing it with a cross-linking agent such as an alkyltriacyloxysilane, a filler and a catalyst such as the metal salt of a carboxyl.ic acid, such as dibutyl tin di-laurate. There may also be added various other types of in~redients to the silicone rubber composition such as a dial~oxydiacyloxysilane, so as to improve the adhesiveness of the resultant silicone rubber composition. For an example of the various types of additives that can be added to the silanol chain-stopped diorganopolysiloxane reaction product of the present invention, one is referred to the disclosure of the U.S~. Patent No. 3,701,753 dated October 31, 1972 or :
Harvey P. Shaw, entitled "Solutions of Room Temperature ~ :
Vulcanizable Silicone Rubber Compositions". Suffice hereto state that the silanol chain-stopped diorganopolysiloxane product of the present invention is useful in all types of room temperature vulcanizable silicone rubber compositions or .
other types of compositions in which a silanol fluid is necessary or desired as an inyredient. Thus, the silanol chain-stopped diorganopolysiloxane fluid of the present L~ 7 8 S I--15 6 3 reaction may be utitlized as the basic fluid in two-part room t~mperature vulcanizable silicone rubber compositions. Such compositions normally comprise a silanol chain-stopped di-organopolysiloxane f:Luid having a viscosity an~where ~rom 1,000 to 10,000,000 centipoise at 25C, to which silanol chain-stopped fluid there is adaed an alkyl silicate and a catalyst which again may be a metal salt of a carboxylic acid. Examples of such two-package room temperature vulcan-izable silicone compositions with var~ous self-bonding a~ditives and other types of additives is exemplified by the disclosure in U.S. Patent ~o. 3,696,090 dated October 3, 1972 of Warren P. Lampe entitled "Room Temperature Vulcanizable Silicone Rubber Composition".
The following examples are given to merely illus trate the scope of the invention and they should not be interpreted to limit the scope of the specification or -the claims of this case in any way or manner. All parts are by weight.
There is utilized 500 parts of a mixture of cyclic-polysiloxanes w~ich have therein 5% by weight of hexamethyl-cyclotrisiloxanes, 75O/o by weight of octamethylcyclotetra-siloxanes, and 50% by weight of decamethylcyclopentasiloxanes, whlch mixture was heated at elevat~d temperatures with various amounts of water. The various amounts of water are indicated in Table 1 below. In each reaction mixture there was also present 7.5 parts of Filtrol-20. The reactants along with the Filtrol-20 were heated in a Parr model 4521 pressure reactor at 150C for 1 hour. The pressure bomb was then cooled to 90 to 95C and the contents were removed and immediately filtered by air pressure with a Kreuger filter. The clear, stable, viscous filtrate was analyzed to determine its ~ 2'~ 8SI-1563 volatile content and bulk viscosity. The results of the analysis both in -tarms of % volatiles in the final equili-bration mixture, as well as the final viscosity of the desi~ed silanol chain-stopped dimethylpolysiloxane is shown in Table 1 below:
Final %
Experiment # Water Added, ml. viscosity, cpsa Volatilesb 1 1.0 9200 12.0 2 2~0 7920 12.0
package room temperature vulcanizable silicone rubber ... . ..
2 ~7 8 S I--15 6 3 compos itions.
One dif~iculty with this process was the formati~n of the high viscosity gum, which was very difficult to handle. It was very difficult, if not impossible, to make the production of such silanol chain-stopped diorgano-polysiloxanes by a continuous process. Several attempts were made to dissolve the diorganopolysiloxané gum in a solvent for use in a contemplated continuous proeess so as to con-serve on equipment ana labor. However, the use of a solvent complicates the process and makes it necessary to use special handling equipment and, in addition, creates a fire hazard.
Further, in addition, even in a batch process, this prior art process was undesirable since it was very difficult to control the desired and viscosity of the silanol chain-stopped di-organopolysiloxane by the use of steam or the incorporation of water therein. The reason be;ng that the addition of water to the diorganopolysiloxane gum of a high molecular weight caused an erratic drop in viscosity. Thus, it was desired to form a polysiloxane whose viscosity would increase after the initial mixing of the reaetants by a measurable and controlled amount without going through a high viscosity maximum. In addition, in the foregoing prior art process, the presence of ~ ;
water or even small amounts of water was undesirable until the final step w~en steam or water was added to the diorganopoly-siloxane gum. Since the presence of water or moisture are very readily present in a manufacturing plant, it was desired to develop a process where the presence of water which might ineidentally get mixed into the reactants, would not inhibit the process.
~owever, as was stated previously, the main deficiency in sueh prior art processes were that they could not be made ~ L~ 8SX-1563 continuous. Even with the use of solvents~ these prior art processes could not be made continuous since such solvent solutions necessitated prohibitatively expensi~e equipmen-t of large capacities and also necessitated special safety procedures because of the flammability of such solvents. It was, thus, ~ighly desirable to find a process w~ich would be continuous in the production o~ silanol chain-stopped di- -organopolysiloxanes.
It is one object of the present invention to provide a process for producing silanol chain-stopped dior~anopoly-siloxane gum which can be produced economically in a batch process.
It is another object of the present invention to provide a process for producing a silanol-stopped diorgano-polysiloxane having a viscosity from 1,000 to 10,000,000 centipoise at 25C, which process could be semi-continuous.
It is an additional object of the present invention to provide a process for the production of the aforesaid silanol chain-stopped diorganopolysiloxane polymer which polymer could be made economically by a continuous process.
It is yet another object of the present invention to provide a process for economically producing a silanol chain-stopped diorganopolysiloxane gum useful as an ingredient ~ -;
in the preparation of room temperature vulcanizable silicone rubber compositions.
It is yet another object o~ the present invention to provide an economical process ~or the production of silanol chain-stopped diorganopolysiloxane gum, which process would not be affected by the presence of water.
It is ~till another object of the present invention to provide a continuous process for the production of a silanol chain-stopped diorganopolysiloxane polymer, which process would ~ 7 8SI-1563 be bo-th economical and safe to operate.
In accordance with the above objects, -there is provided a process for producing a silanol chain-stopped di-organopolysiloxane ~aving a viscosity of 1,000 to 10,000,000 centipoise at 25C, where the organo groups are selected from the class consisting of monovalent hydrocarbon radicals, monovalen~ halogenated hydrocarbon radicals and cyanoalkyl radicals comprising equilibrating cyclic polysiloxanes having a formula (1~ (R2SiO) :' wherein the R groups are identical to the organo ~roups of the previously described diorganopolysiloxaneO and wherein it varies from 3 to 10, and desirably 3 to 5 with certain critical amounts of water, that is, 100 parts per million to less than 2% by weight of water, based on the wei~ht of the cyclic polysiloxanes, at a temperature range of 50 to 200C.
In this process there is utilized essentially pure cyclic polysiloxanes of Formula (1) which cyclic polysiloxanes can be obtained by the methods well known to a person skilled in the art and which methods are set forth in the present specification. The equilibration takes place in the presence of catalyst constituted by a solid having active protons on it. Another way of defining such a catalyst is a solid having active hydrogen atoms on it. Such catalysts are well known in the art but were not known or contemplated for the above-described process. Thus, any solid w~ich has absorbed on it or has been treated with an acid of a pH below 5 may be used as a catalyst in the present invention. It is ob-served that a liquid acid catalyst e.g. sulfonic acid or a solid pure acid catalyst e.g. toluene sulfonic acid, will not operate in the foregoing process.
The cyclopolysiloxane reactant and the controlled ~SI-1563 quantity of water are reacted in the presence of the solid catalyst until equilibrium is reached, that is, until the desired silanol chain-stopped diorganopolysiloxane is form~d;
at equilibrium about 12 to 13~ cyclic polysiloxanes are normally present in the mixture. At that point, the reaction is terminated and the solid catalyst is filtered out.
The process can be completely batch, semi-continuous or totally continuous.
In some cases it may be desirable to remove the cyclic polysiloxanes remaining after equilibration has been reached without first removing the solid catalyst from the equilibration mixtureO Thus, if it is desired to neutralize the solid catalyst after equilibration has been reached, there ~ `
may be added to the equilibration mixture neutralizing amounts of an additive such as, NH~OEI, R NH30H, R R520~, (R )4NOH and (R )4POH, where R and R are selected from the class consisting of alkyl radicals of 1 to 8 carbon atoms, alkenyl radicals oF 2 to 8 carbon atoms, cycloalkyl radicals of 4 to 8 carbon atoms, and mononuclear aryl radicals such as phenyl, methylphenyl, etc.
After such neutralizing agents have been added to the equilibration reaction mixture the excess cyclic poly-siloxanes can be stripped at elevated temperatures to leave behind the desired silanol chain-stopped diorganopolysiloxanes, having therein the solid catalyst which can then be filtered out or left in the desired product. This neutralization procedure is desirable when the solid catalyst is present or utilized in a loose form in the equilibration reaction ~1~3~ 7 8SI-1563 mixture rather than wherl the solid catalyst is used in a packed column, since in tha loose form the solid catalyst can only be removed from the equilibration reaction mixture by filtration.
The organic groups in the silanol chain-stopped diorganopolysiloxanes, and thus the R radicals in the cyclic polysiloxane of Formula (1), can include, for example, alkyl ;
radicals such as methyl, ethyl, propyl, butyl, octyl; aryl radicals such as, phenyl, tolyl; aralkyl radicals such as, benzyl, phenylethyl, alkenyl radicals such as, vinyl and allyl; cycloaliphatic radicals such as, cyclohexyl, cyclo-heptyl and cyclohexenyl; haloalkyl and haloaryl such as, chloromethyl, alpha-chloroethyl, beta-chloroethyl, chloro-phenyl, dibromophenyl, trifluoromethylphenyl and trifluoro-methylpropyl and cyanoalkyl radicals such as, cyanomethyl, beta-cyanoethyl, beta-cyanopropyl, gamma-cyanoprop~l, and omega-cyanobutyl. The R radicals on the same silicon atom may be the same or different. Thus, the R groups on the same silicon atom may be the same or different such as, methyl, phenyl and the silanol chain-stopped diorganopolysiloxane reaction product can have dimethyl substituents, diphenyl substituents, methylphenyl substituents, or other of the aforementioned groups bonded to the silicon atoms of the chain.
The preferred substitutent groups selected from lower a~kyl of 1 to 8 carbon atoms, such as, methyl, ethyl, mononuclear aryl radicals such as, phenyl and lower alkenyl radicals such as vinyl and alkyl. --Preparation of the cyclic polysiloxanes of Formula (1) above which contain both saturated and olefinically un-saturated hydrocarbon groups, may be carried out by any ofthe procedures well known to those skilled in the art. Such polysiloxanes can be produced by following the procedure L~L7 involving hydrolysis of one or more hydrocarbon substituted dichlorosilanes of which -the substitutents consist of saturated and/or unsaturated hydrocarbon groups. Thus, the diorganodihalogenosilanes may be added to an acid-water mix-ture slowly over a perioa of 30 minutes to 2 hours with con-stant agitation and, a-t the end of that time, the agitation is continued for 15 minutes more. If desired the diorganodi-halogenosilanes may be dissolved in a solvent and added to the acid-water mixture. The hydrolysis reaction may be 1~ carried out at any temperature between 20C to 50C. After the hydrolysis is complete, then there is present in the hydrolyzate a mixture of cyclic polysiloxanes and a silanol chain-stopped diorganopolysiloxane. To the crude hydrolyzate there is then added a strong base catalyst such as potassium hydroxide, cesium hydroxide, lithium hydroxide or sodium hydroxide. Preferably, there is added from 1 to 5 percent of the strong base to the hydrolyzate. The hydrolyzate is then heated at a temperature in the range of 125C to,175c for a period of time varying from ~ to 4 hours, during which 20 period a number of reactions occur. The silanol groups are condensed to produce siloxane linkages and water. In addition, an e~uilibration is set up w~ich proauces a mixture of the cyclic siloxanes of Formula (1) above. Thus, in the most preferred process, the hydrolyzate with the base catalyst is heated to a temperature of about 150C until equilibration is reached wherein thare is being formed a maximum amount of cyclic polysiloxanes. At the end of this period, the reaction mixture is heated to a temperature of about 200C and all of the cyclic polysiloxanes are stripped off and collected.
In particular, in the more preferable process, when the hydrolyzate is heated with a base catalyst at a tem-perature of 150 C or over, the cyclic polysiloxanes are - . . . . - . . .. ~ . . -contlnually distilled off and collected until the ~ydrol~zate has produced the maximum amount of cyclic polysiloxanes 9 which are continually collected Thi5 procedur~ of drawing off the cyclic polysiloxanes as they are formed results in the production of as much cyclic polysiloxanes as possible. Such cyclic polysiloxanes which are collected from this equilibration and stripping procedure are essentially pure and free o~ tri-functional units~
Thus, in order to depolymerize the crude hydrolyzate that is formed, there is added to the hydrolyzate a catalyst and the mixture is heated at a tempera-ture o~ over 150C to produce and recover2 by distillation a product consisting of low molecular weight cyclic polysiloxanes of Formula (1) above, comprising about 85% of a cyclic polysiloxane having three silicon atoms and five silicon atoms.
Whilst the cyclic polysiloxanes of Formula (1) above, for use in our process can be obtained by any of the methods known to those skilled in the silicone art, it is necessary that they be in essentially pure form in order to obtain hi~h yields of the desired product. The catalyst that is employed in our process can be described as a solid having active protons on it or as a solid that has active hydrogen atoms on it or as a solid that has been treated with an acid having a pH below 5. Thus, ion-exchange resins can be used -as a catalyst in the present invention. Synthetic resins, such as sulfonated polystyrenes, may also be used as a cata-lyst in the present invention. Acid-activated carbon and acid-activated clays, such as montmorillonite, can be used in the present invention. The preferred acid-activated clay is montmorillonite, an example of which is Filtrol, manufactured by Filtrol Corporation of Los Angeles, California. The particular advanta~es of Filtrol and other acid-activated ~SI-1563 solid catalysts is that they do not impart any acidity to the reactants or to the reaction product. Accordin~ly, after the reaction is completed with the use of Filtrol, the Filtrol is simply removed or separated from the reactants and there is no need for neutralizing the reaction product that is formed in this reaction.
Other examples of catalysts, which may be used in the present invention are: Florida Earth, Kambara Earth, sulfuric acid-treated carbon montmorillonites, sulfuric or hydrochloric acid treated halloysite, beidellite, illite, Filtrol-20, Filtrol-24, Filtrol-25 (trademar~s of acid treated clay manufactured by the Filtrol Corporation, Los Angeles, California); natural zeolites, natrolite, analcime, stilbite, -~
chabazite, mordenite, clinophilolite, glauconite (green sand), synthetic zeolites, Zeolon Series (tradenames of synthetic mineral cation exchange resins sold by Norton Co.), Permutit (tradename of synthetic mineral cation exchange resins -manufactured by Permutit Co.), bentonite, kaolinite (China Clay), alumino-silicates, Fuller's Earth, acidified carbon, acidified charcoal, sulfonated coal, sulfonated polystyrene acid forms of Dowex-50 (manufactured by Dow Chemical Co.), Amberlyst-15 (manufactured by Rohn & ~ass), Ionac C-242 (manufactured by Ionac Co.), Duolite C-20 (manufactured by Diamond Alkali).
The solid acid catalyst is preferably used in the equilibration reaction at a concentration of 0.1 to 50% by weight or more by volume. As will be explained further on, when the process is a batch process, the solid catalyst may be present at a concentration of as low as 0.1 to 5 or 10%
by volume of the reaction mixture. On the other hand, when a continuous or semi-continuous process is used where the reactants are passed through a column of Filtrol or other solid 8SI~1563 ~3~ 7 acid catalyist, then the volume of -the catalyst with respect to the volume of reactants in -the column or reaction may be as hiyh as 50% to 90% by volume or more. As stated in terms of weight percent, the concentration of the acid-activated solid catalyst may be present at a concentration of 0.1% to 75% by weight of the reaction mixture. The equilibration reaction is carried out in the presence of water. Preferably, there may be used anywhere from .05% by weight to less than 2% by weight of water based on the cyclic polysiloxanes of Formula (1~. If less than 100 parts per million of water is initially present in the equilibration reaction, then the desirable silanol chain-stopped diorganopolysiloxane is of too high a viscosity. If 2% by weight or more water is utilized in the equilibration reaction mixture the desired silanol chain-stopped diorganopolysiloxane polymer is obtained at a very poor yield, that is, at equilibration there is less than 80% of the cyclic polysiloxanes of Formula (1), converted to the desired silanol end-stopped diorganopolysiloxane polymer of a viscosity of 1,000 to 10,000,000 centipoise at 25C.
Accordingly, it is critical to our process that there be present less than 2% by weight of water based on the cyclic polysiloxanes of Formula (1) above. Thus, by con-trolling the amount of water as indicated above and equilibrating the cyclic polysiloxanes in the presence of the critical solid catalyst of the present invention which were defined previously, there can be obtained the desired silanol chain-stopped diorganopolysiloxane of Formula (4) above, which has a silanol content of anywhere from .001 to 0.5% by weight. Accordingly, in a more pref~red embodiment, there is preferred to be utilized anywhere from .05% by weight to less than 2% by weight of water in contact with the :
, , , . ~ . . ' ' . ~ . :
cyclic polysiloxanes of Formula (1~ above. The desired silanol chain-stopped diorganopolysiloxane is present at above 80 and 85% by weight in the equilibration reaction mixture after the water and cyclic polysilo~anes of Formula (1) have reached the equilibration point. The reaction is carried out at a ~emperature range of anywhere from 50 to 200C and preferably at a temperature range of 150 to 200C.
The reaction time may vary anywhere from 1-1/2 hours to 48 hours depending on the temperature of reaction and the amount of solid catalyst that is utilized in t~e reaction mixture.
The silanol chain-stopped diGrganopolysiloxane product of the present invention can be used to form one-packaye room temperature vulcanizable silicone rubber com-positions by mixing it with a cross-linking agent such as an alkyltriacyloxysilane, a filler and a catalyst such as the metal salt of a carboxyl.ic acid, such as dibutyl tin di-laurate. There may also be added various other types of in~redients to the silicone rubber composition such as a dial~oxydiacyloxysilane, so as to improve the adhesiveness of the resultant silicone rubber composition. For an example of the various types of additives that can be added to the silanol chain-stopped diorganopolysiloxane reaction product of the present invention, one is referred to the disclosure of the U.S~. Patent No. 3,701,753 dated October 31, 1972 or :
Harvey P. Shaw, entitled "Solutions of Room Temperature ~ :
Vulcanizable Silicone Rubber Compositions". Suffice hereto state that the silanol chain-stopped diorganopolysiloxane product of the present invention is useful in all types of room temperature vulcanizable silicone rubber compositions or .
other types of compositions in which a silanol fluid is necessary or desired as an inyredient. Thus, the silanol chain-stopped diorganopolysiloxane fluid of the present L~ 7 8 S I--15 6 3 reaction may be utitlized as the basic fluid in two-part room t~mperature vulcanizable silicone rubber compositions. Such compositions normally comprise a silanol chain-stopped di-organopolysiloxane f:Luid having a viscosity an~where ~rom 1,000 to 10,000,000 centipoise at 25C, to which silanol chain-stopped fluid there is adaed an alkyl silicate and a catalyst which again may be a metal salt of a carboxylic acid. Examples of such two-package room temperature vulcan-izable silicone compositions with var~ous self-bonding a~ditives and other types of additives is exemplified by the disclosure in U.S. Patent ~o. 3,696,090 dated October 3, 1972 of Warren P. Lampe entitled "Room Temperature Vulcanizable Silicone Rubber Composition".
The following examples are given to merely illus trate the scope of the invention and they should not be interpreted to limit the scope of the specification or -the claims of this case in any way or manner. All parts are by weight.
There is utilized 500 parts of a mixture of cyclic-polysiloxanes w~ich have therein 5% by weight of hexamethyl-cyclotrisiloxanes, 75O/o by weight of octamethylcyclotetra-siloxanes, and 50% by weight of decamethylcyclopentasiloxanes, whlch mixture was heated at elevat~d temperatures with various amounts of water. The various amounts of water are indicated in Table 1 below. In each reaction mixture there was also present 7.5 parts of Filtrol-20. The reactants along with the Filtrol-20 were heated in a Parr model 4521 pressure reactor at 150C for 1 hour. The pressure bomb was then cooled to 90 to 95C and the contents were removed and immediately filtered by air pressure with a Kreuger filter. The clear, stable, viscous filtrate was analyzed to determine its ~ 2'~ 8SI-1563 volatile content and bulk viscosity. The results of the analysis both in -tarms of % volatiles in the final equili-bration mixture, as well as the final viscosity of the desi~ed silanol chain-stopped dimethylpolysiloxane is shown in Table 1 below:
Final %
Experiment # Water Added, ml. viscosity, cpsa Volatilesb 1 1.0 9200 12.0 2 2~0 7920 12.0
3 3.0 5040 11.8
4 4.0 3520 11~4 4.5 900 12.5 6 5.~ 79~ 12O6 7 10.0 ~504 13.2 a--measured by Brookfield viscometer at 25C.
b-- measured by heating a 1.0 + O.lg. sample in an aluminum cup at 10-20 Torr and 130-140C for 45 minutes in a vacuum oven.
Infrared spectra confirmed the presence of silanol chain-terminated units in the equilibration polymers that were ~ormed in the above seven experiments. As enumerated in Table 1 above, from the results of the seven experiments there is obtained by the alternate process of the present case silanol chain-stopped diorganopolysiloxanes having the viscosities shown in Table 1 above, by reacting a cyclic-polysiloxane in essentially pure form with various amounts of water in the presence of the solid catalyst of the present invention.
This example is an illustrat;on of the neutralizing step that may be utilized with the process of the present case so as to eliminate the filtration step after equilibration 8sI-l563 3 ~
has been reached, imperative w~ether the preferred process is used or the alterna~e process.
There was first prepared a silanol end-stopped dime-thylpolysiloxane by heating 1500 parts of a cyclic poly-siloxane mixture ~ich cyclic polysiloxane mixture is com-posed of 4.53% by weight of hexamethylcyclotrisiloxane, 80.71%
by weight of octamethylcyclotetrasiloxane and 13.27% by wei~ht of decamethylcyclopentasiloxane and said 1500 parts of the cyclic polysiloxane mixture having therein .55% by weight of higher cyclics. To this cyclic polysiloxane mixture there is aaded 5 ml of water and the mixture is heated to 150C, then 22.5 parts of Filtrol-20 added. The mixture is ayitated for 10 minutes. At the end of that time, 50 ml of 28% ammonium hydroxide was added and the first batch was stirred while the mixture cooled. 785 parts of this reaction mixture was vacuum stripped at 3 ml. of mercury pressure and at a stripping tem-perature of 170C. The residue was a tan, opaque polymer wei~hing 678 parts, that is, there was 13.6% loss of weight from the original mixture that was stripped. The volatiles content of this polymer was 1.3% by weight and the viscosity was 1875 centipoise at 25C.
~ lere was prepared a two-part RTV system from the silanol chain-stopped dimethylpolysiloxane polymer that was obtained by the above procedure. To 100 parts of such polymer there was added ~0 parts of commercial grade calcium carbonate filler, 3 parts o~ condensed ethyl silicate, also k~own as ES-40 sold by U~ion Carbide, and 0.05% by weight of dibutyl tin dilaurate. This mixture was homogenized in a Baker-Perkins mixer. Then slabs were formed from the mixture and the slabs were allowed to cure at room temperature. The slabs from this two-part room temperature vulcanizable silicone rubber composition was allowed to cure over a 24-hour period~
: . ~
2 ~7 8 S I--15 6 3 During such curing process, the viscosity in centipoise at 25c was 7000. ThP worklife of the composition was 70 minutes. The tack-free -time was 120 minutes and the Shore A
Durometer after 24 hours was 44.
The cured slabs that were obtained from the above mixture were tested as to its physical properties which were as f ollows:
Durometer, Shore A49 Tensile, psi 150 Elongation, % 145 Tear, P.i. 9 Specific Gravity1.20 This example is to illustrate a control so as to make a comparison with the experiment of Example 2, where in the present example there is not utilized a neutralizing agent ~-after the equilibration has been reached. Accordingly, to 98.5 parts of a silanol-stopped dimethylpolysiloxane having a viscosity of 2500 cps. at 25C and a volatiles content of less than 1.0% (as measured in Example 7), there was added 1.5 parts of Filtrol-20 and the polymer and solid catalyst were stirred together at room temperature. Then after that point, 1.0536 parts of this mixture were heated in a 135C
vacuum oven for 45 minutes with 10 to 20 millimeters of Hg vacuum. As a result of this stripping procedure there was a loss in weight of the mixture amounting to .4822 parts or 45.7% by weight. This is the weight loss in comparison with the weight loss of 1.36% by weight which was incurred in the experiment of Example 8 utilizing the ammonium hydroxide treating procedure. Accordingly, as can be seen from the results of this example compared to the results of Example 2 after the equilibration point has been reached in the ~ 8SI-1563 preferred process or in the alternate process and the solid catalyst is neutralized with a neutraliziny agent such as, ammonia, the resultin~ vola-tiles that are present in the equilibration point in the reaction can be easily removed without degrading or effecting the desired silanol-terminated diorganopolysiloxane polymer that is formed by either process of the present case. On the other hand, as illustrated by the present example, if after the equilibration point is reached in either process of the present case, and the volatiles are stripped off without adding a neutralizing agent and specifically adding one of the neutralizing agents disclosed in the present case to the reaction mixture, then upon attempting to strip off the volatiles from the desired end product side reactions will occur which will lower the yield of the desired end products, that is, the high molecular weight silanol end-stopped diorganopolysiloxane which is produced by the processes of the present case.
In addition, the inno~ation of the present dis-closure, that is, utilizing the neutralizing agents of the present case, to neutralize the solid catalyst of the present case after equilibration has been reached instead of utilizing a filtration step to filter out the solid catalyst results in either of the processes of the present case being run in an inexpensive continuous fashion. On the other hand, if the filtration step is utilized in place of the neutralizing agents of the present case, then this results in the process being semi-continuous rather than continuous.
It should also be noted that the neutralizing agents for the solid cata~yst in either of the processes of the present case, that suc~ neutralizing agents are unique in the performance of this function. Other mild bases or strong bases for that matter such as, sodium bicarbonate, sodium hydroxide, 'Z~ 8SI-1563 potassium hydroxide, etc., have not been found to be effective neutralizing agents .
.:
. , - L9 ~
;
b-- measured by heating a 1.0 + O.lg. sample in an aluminum cup at 10-20 Torr and 130-140C for 45 minutes in a vacuum oven.
Infrared spectra confirmed the presence of silanol chain-terminated units in the equilibration polymers that were ~ormed in the above seven experiments. As enumerated in Table 1 above, from the results of the seven experiments there is obtained by the alternate process of the present case silanol chain-stopped diorganopolysiloxanes having the viscosities shown in Table 1 above, by reacting a cyclic-polysiloxane in essentially pure form with various amounts of water in the presence of the solid catalyst of the present invention.
This example is an illustrat;on of the neutralizing step that may be utilized with the process of the present case so as to eliminate the filtration step after equilibration 8sI-l563 3 ~
has been reached, imperative w~ether the preferred process is used or the alterna~e process.
There was first prepared a silanol end-stopped dime-thylpolysiloxane by heating 1500 parts of a cyclic poly-siloxane mixture ~ich cyclic polysiloxane mixture is com-posed of 4.53% by weight of hexamethylcyclotrisiloxane, 80.71%
by weight of octamethylcyclotetrasiloxane and 13.27% by wei~ht of decamethylcyclopentasiloxane and said 1500 parts of the cyclic polysiloxane mixture having therein .55% by weight of higher cyclics. To this cyclic polysiloxane mixture there is aaded 5 ml of water and the mixture is heated to 150C, then 22.5 parts of Filtrol-20 added. The mixture is ayitated for 10 minutes. At the end of that time, 50 ml of 28% ammonium hydroxide was added and the first batch was stirred while the mixture cooled. 785 parts of this reaction mixture was vacuum stripped at 3 ml. of mercury pressure and at a stripping tem-perature of 170C. The residue was a tan, opaque polymer wei~hing 678 parts, that is, there was 13.6% loss of weight from the original mixture that was stripped. The volatiles content of this polymer was 1.3% by weight and the viscosity was 1875 centipoise at 25C.
~ lere was prepared a two-part RTV system from the silanol chain-stopped dimethylpolysiloxane polymer that was obtained by the above procedure. To 100 parts of such polymer there was added ~0 parts of commercial grade calcium carbonate filler, 3 parts o~ condensed ethyl silicate, also k~own as ES-40 sold by U~ion Carbide, and 0.05% by weight of dibutyl tin dilaurate. This mixture was homogenized in a Baker-Perkins mixer. Then slabs were formed from the mixture and the slabs were allowed to cure at room temperature. The slabs from this two-part room temperature vulcanizable silicone rubber composition was allowed to cure over a 24-hour period~
: . ~
2 ~7 8 S I--15 6 3 During such curing process, the viscosity in centipoise at 25c was 7000. ThP worklife of the composition was 70 minutes. The tack-free -time was 120 minutes and the Shore A
Durometer after 24 hours was 44.
The cured slabs that were obtained from the above mixture were tested as to its physical properties which were as f ollows:
Durometer, Shore A49 Tensile, psi 150 Elongation, % 145 Tear, P.i. 9 Specific Gravity1.20 This example is to illustrate a control so as to make a comparison with the experiment of Example 2, where in the present example there is not utilized a neutralizing agent ~-after the equilibration has been reached. Accordingly, to 98.5 parts of a silanol-stopped dimethylpolysiloxane having a viscosity of 2500 cps. at 25C and a volatiles content of less than 1.0% (as measured in Example 7), there was added 1.5 parts of Filtrol-20 and the polymer and solid catalyst were stirred together at room temperature. Then after that point, 1.0536 parts of this mixture were heated in a 135C
vacuum oven for 45 minutes with 10 to 20 millimeters of Hg vacuum. As a result of this stripping procedure there was a loss in weight of the mixture amounting to .4822 parts or 45.7% by weight. This is the weight loss in comparison with the weight loss of 1.36% by weight which was incurred in the experiment of Example 8 utilizing the ammonium hydroxide treating procedure. Accordingly, as can be seen from the results of this example compared to the results of Example 2 after the equilibration point has been reached in the ~ 8SI-1563 preferred process or in the alternate process and the solid catalyst is neutralized with a neutraliziny agent such as, ammonia, the resultin~ vola-tiles that are present in the equilibration point in the reaction can be easily removed without degrading or effecting the desired silanol-terminated diorganopolysiloxane polymer that is formed by either process of the present case. On the other hand, as illustrated by the present example, if after the equilibration point is reached in either process of the present case, and the volatiles are stripped off without adding a neutralizing agent and specifically adding one of the neutralizing agents disclosed in the present case to the reaction mixture, then upon attempting to strip off the volatiles from the desired end product side reactions will occur which will lower the yield of the desired end products, that is, the high molecular weight silanol end-stopped diorganopolysiloxane which is produced by the processes of the present case.
In addition, the inno~ation of the present dis-closure, that is, utilizing the neutralizing agents of the present case, to neutralize the solid catalyst of the present case after equilibration has been reached instead of utilizing a filtration step to filter out the solid catalyst results in either of the processes of the present case being run in an inexpensive continuous fashion. On the other hand, if the filtration step is utilized in place of the neutralizing agents of the present case, then this results in the process being semi-continuous rather than continuous.
It should also be noted that the neutralizing agents for the solid cata~yst in either of the processes of the present case, that suc~ neutralizing agents are unique in the performance of this function. Other mild bases or strong bases for that matter such as, sodium bicarbonate, sodium hydroxide, 'Z~ 8SI-1563 potassium hydroxide, etc., have not been found to be effective neutralizing agents .
.:
. , - L9 ~
;
Claims (14)
1. A process for producing a silanol chain-stopped diorganopolysiloxane having a fiscosity of 1,000 to 10,000,000 centipoise at 25°C and a silanol content ranging from 0.001 to .5% by weight where the organo groups are selected from the class consisting of monovalent hydrocarbon radicals, halogenated monovalent hydrocarbon radicals and cyanoalkyl radicals com-prising reacting cyclic polysiloxanes of the formula, (R2SiO)n with water at a concentration of 100 parts per million to lass than 2% by weight where the R radicals are selected from the class consisting of monovalent hydrocarbon radicals, halogenated monovalent hydrocarbon radicals and cyanoalkyl radicals, n varies from 3 to 10, in the presence of at least 0.1 percent by weight of the total mixture of a solid catalyst selected from the class consisting of acid activated carbon and acid activated clay in the temperature range of 50°C to 200°C.
2. The process of claim 1 wherein the formula of the cyclic polysiloxane, n varies from 3 to 5.
3. The process of claim 1 wherein after said reaction has been completed, further comprising filtering out said solid catalyst and then stripping out of the reaction mixture the remaining cyclic polysiloxanes.
4. The process of claim 1, wherein after said reaction has been completed, further comprising adding to the reaction mixture a neutralizing agent for the solid catalyst selected from the class consisting of NH4OH, R4NH3OH,, (R4)4NOH, and (R4)4POH, where R4 and R5 are selected from the class consisting of alkyl radicals of 1 to 8 carbon atoms, alkenyl radicals of 2 to 8 carbon atoms, cycloalkyl radicals of 4 to 8 carbon atoms and mononuclear aryl radicals, and then stripping off the remaining cyclic polysiloxanes from the reaction mixture.
5. The process of claim 1 wherein the water is present at a concentration of 0.05% by weight to less than 2%
by weight.
by weight.
6. The process of claim 1 wherein the reaction temperature is at 120°C to 100°C which reaction is allowed to proceed for 1 to 3 hours.
7. The process of claim 1 wherein said solid catalyst has been activated with sulfuric acid.
8. The process of claim 1 wherein said catalyst comprises from 0.1 to 90% by volume of the reaction mixture.
9. The process of claim 1 wherein the acid that is used to activate said solid catalyst has a pH below 5.
10. The process of claim 1 wherein the reactants are circulated continuously through a column containing said solid catalyst.
11. The process of Claim 1,2 or 3 wherein said acid is sulfuric acid.
12. The process of claim 1,2 or 3 wherein said solid catalyst is acid-activated montmorillonite.
13. The process of claim 1,2 or 3 wherein R is selected from the class consisting of lower alkyl, alkenyl and aryl.
14. The process of claim 1,2 or 3 wherein R is selected from methyl and phenyl, and wherein said solid catalyst is acid-activated clay.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US452940A US3903047A (en) | 1973-10-23 | 1974-03-20 | Process for the production of silanol-stopped diorgano-polysiloxanes |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1044247A true CA1044247A (en) | 1978-12-12 |
Family
ID=23798586
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA209,871A Expired CA1044247A (en) | 1974-03-20 | 1974-09-24 | Process for the production of silanol-stopped diorganopolysiloxanes |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS585928B2 (en) |
| BE (1) | BE826906A (en) |
| CA (1) | CA1044247A (en) |
| DE (1) | DE2511475A1 (en) |
| FR (1) | FR2264837B1 (en) |
| GB (1) | GB1506734A (en) |
| IT (1) | IT1034417B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1549344A (en) * | 1975-05-19 | 1979-08-08 | Gen Electric | Process for producing silanol end-stopped diorganopolysiloxane oils |
| JP2678371B2 (en) * | 1987-08-31 | 1997-11-17 | 東レ・ダウコーニング・シリコーン株式会社 | Method for producing organopolysiloxane having alkenyl group at terminal |
| JP3862007B2 (en) | 2002-05-31 | 2006-12-27 | 信越化学工業株式会社 | Method for reactivating sulfonated resin catalyst |
| DE102007055484A1 (en) | 2007-11-21 | 2009-05-28 | Evonik Goldschmidt Gmbh | Process for the preparation of polydimethylsiloxanes on sulfonic acid cation exchange resins |
| TWI742534B (en) * | 2019-02-20 | 2021-10-11 | 日商旭化成股份有限公司 | Cured product, cured product modified product and curing method |
-
1974
- 1974-09-24 CA CA209,871A patent/CA1044247A/en not_active Expired
-
1975
- 1975-03-15 DE DE19752511475 patent/DE2511475A1/en not_active Withdrawn
- 1975-03-18 IT IT2144175A patent/IT1034417B/en active
- 1975-03-18 FR FR7508339A patent/FR2264837B1/fr not_active Expired
- 1975-03-19 GB GB1144775A patent/GB1506734A/en not_active Expired
- 1975-03-19 JP JP50032482A patent/JPS585928B2/en not_active Expired
- 1975-03-20 BE BE154519A patent/BE826906A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| DE2511475A1 (en) | 1975-09-25 |
| FR2264837B1 (en) | 1981-06-19 |
| IT1034417B (en) | 1979-09-10 |
| JPS50133299A (en) | 1975-10-22 |
| FR2264837A1 (en) | 1975-10-17 |
| JPS585928B2 (en) | 1983-02-02 |
| GB1506734A (en) | 1978-04-12 |
| BE826906A (en) | 1975-07-16 |
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