CA1125780A - Process for making alpha-omega-diacyloxysiloxanes - Google Patents
Process for making alpha-omega-diacyloxysiloxanesInfo
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Abstract
ABSTRACT OF THE DISCLOSURE
A process for preparing alpha, omega-diacyloxysiloxanes of the formula P'COO(R2SiO)nOCR'9 in which at least 50 percent of the R groups are methyl and the remaining R groups are selected from the class consisting of vinyl and phenyl groups, R' is a hydrocarbon radical having from 1 to 3 carbon atoms, and n has an average value of from 3 to 25, is provided herein. The process includes the step of heating cy ic and/or linear siloxane with an acid anhydride in the presence of a carboxylic acid and of acid clay for at least 1 hour until equilibration occurs at a temperature of 120°C. - 150°C. The diacyloxysiloxanes are useful, since they maybe hydrolyzed to the siloxanediol by heating with an aqueous solution of a weak base having a pH of from 8 to 11 to a temperature of at least 50°C. The siloxanediols so formed are effective anti-structive agents (scftenev fluids) for silicone rubber.
A process for preparing alpha, omega-diacyloxysiloxanes of the formula P'COO(R2SiO)nOCR'9 in which at least 50 percent of the R groups are methyl and the remaining R groups are selected from the class consisting of vinyl and phenyl groups, R' is a hydrocarbon radical having from 1 to 3 carbon atoms, and n has an average value of from 3 to 25, is provided herein. The process includes the step of heating cy ic and/or linear siloxane with an acid anhydride in the presence of a carboxylic acid and of acid clay for at least 1 hour until equilibration occurs at a temperature of 120°C. - 150°C. The diacyloxysiloxanes are useful, since they maybe hydrolyzed to the siloxanediol by heating with an aqueous solution of a weak base having a pH of from 8 to 11 to a temperature of at least 50°C. The siloxanediols so formed are effective anti-structive agents (scftenev fluids) for silicone rubber.
Description
1:~A,5'1 80 This invention relates to a process for producing alpha,omega-diacyloxysiloxanes. This application is a division of copending applica-tion Serial No. 289,796 filed October 28, 1977.
It is known that linear alpha,omega-siloxanediols, hereinafter called siloxanediols, may be prepared by the hydrolysis of dimethyldi-chlorosilane. Depending on temperature, amo~mt of water, the nature of solvent, if any, and catalysts, siloxanediols of a wide range of chain length may be obtained. However, it is difficult to obtain siloxanediols of very short chain lengths by this process, because of their tendency to condense to longer chains under the influence of the by-product acid.
Normally hydrolysis produces an average chain length of over 30 dimethyl-siloxane units, corresponding to a hydroxyl content of 1.5 percent or less.
The process also produces a large amount, up to 50 percent or more, of cyclic siloxanes.
A somewhat better process involves equilibration of linear or cyclic siloxane with dimethyldîchlorosilane and an acid catalyst, to pro-duce an alpha,omega-dichlorosiloxane, followed by hydrolysis to give the siloxanedîol. By this process, the hydroxyl content may be increased to
It is known that linear alpha,omega-siloxanediols, hereinafter called siloxanediols, may be prepared by the hydrolysis of dimethyldi-chlorosilane. Depending on temperature, amo~mt of water, the nature of solvent, if any, and catalysts, siloxanediols of a wide range of chain length may be obtained. However, it is difficult to obtain siloxanediols of very short chain lengths by this process, because of their tendency to condense to longer chains under the influence of the by-product acid.
Normally hydrolysis produces an average chain length of over 30 dimethyl-siloxane units, corresponding to a hydroxyl content of 1.5 percent or less.
The process also produces a large amount, up to 50 percent or more, of cyclic siloxanes.
A somewhat better process involves equilibration of linear or cyclic siloxane with dimethyldîchlorosilane and an acid catalyst, to pro-duce an alpha,omega-dichlorosiloxane, followed by hydrolysis to give the siloxanedîol. By this process, the hydroxyl content may be increased to
2.~ percent, corresponding to a chain of 18 dimethylsiloxane units. If a solvent is used, the hydroxyl content may be increased to 3 percent (15 dimethylsiloxane units?. The problem lies in the rapid condensation of the intermed;ate alpha-chloro-omega-siloxanol during the hydrolysis step; the shorter the chain, the more rapîd the condensation.
Therefore it is an ob~ect of one broad aspect of this invention to provide a process for the controlled preparation of alpha,omega-diacyl-oxysiloxanes.
5'7~
By a broad aspect of this invention, a process is provided for making alpha, omega-diacyloxysiloxanes of the formula R'COO(R2SiO)nOCR', in which at least 50 percent of the R groups are methyl and the remaining R groups are selected from the class con-sisting of vinyl and phenyl groups, R' is a hydrocarbon radical having from 1 to 3 carbon atoms, and n has an average value of from
Therefore it is an ob~ect of one broad aspect of this invention to provide a process for the controlled preparation of alpha,omega-diacyl-oxysiloxanes.
5'7~
By a broad aspect of this invention, a process is provided for making alpha, omega-diacyloxysiloxanes of the formula R'COO(R2SiO)nOCR', in which at least 50 percent of the R groups are methyl and the remaining R groups are selected from the class con-sisting of vinyl and phenyl groups, R' is a hydrocarbon radical having from 1 to 3 carbon atoms, and n has an average value of from
3 to 25, which comprises: heating a siloxane selected from the class consisting of cyclic siloxanes, linear siloxanes and mixtures thereof with an acid anhydride having from 4 to 8 carbon atoms and a carboxylic acid having from 2 to 4 carbon atoms in the presence of an acid clay for at least 1 hour until equilibration occurs at a temperature of from 120C to 150C.
- la -~5~71~
By a variant thereof, the alpha,omega-diacyloxysiloxane is alpha,omega-diacetoxysiloxane.
Cyclic siloxanes used in the above-recited process generally have the formula (R2SiO) , in which x is a number of from 3 to 10, pre-ferably from 3 to 6, and R is as defined above.
Linear siloxanes used in the above-recited process generally have the formul~
HO~R2SiO) H or R'COO(R2SiO) OCR' in which y has an average value of from 2 to 300 and preferably from 2 to 50.
The siloxanes may contain a minor amount of a silane of the formula R2Si)OH)2 or R2Si(OCOR )2 Examples of suitable cyclic siloxanes include cyclic dimethyl-siloxanes of the formula [(CH3)2SiO] where x is from 3 to 6; cyclic methyl vinyl siloxanes, e.g., heptamethylvinylcyclotetrasiloxane and tetramethyltetravinylcyclotetrasiloxane; and cyclic methyl phenyl siloxanes.
Examples of suitable linear siloxanes include the hydrolysis products and cohydrolysis products of dimethyldichlorosilane, methylvinyl-dichlorosilane, methylphenyldichlorosilane, and diphenyldichlorosilane.
Examples of suitable silanes include dimethyldiacetoxysilane, methylvinyldiacetoxysilane, methylphenyldiacetoxysilane, diphenyldiacetoxy-silane and diphenylsilanediol.
The carboxylic acids used in providing the alpha,omega-siloane-diols of aspects of this inventio~ are preferably the water-soluble unsub-stituted monobasic acids having from 2 to 4 carbon atoms. Likewise the 7~
acid anhydrides are preferably those with from 4 to 8 carbon atoms.
Examples of suitable acids and anhydrides include acetic, propionic, butyric, acrylic and crotonic.
When the siloxane, i.e., a cyclic and/or linear siloxane is equilibrated with, for example, acetic anhydride, the chain length of the resulting diacetoxysiloxane is determined mainly by the mole ratio of acetic anhydride to siloxane units, the reaction being essentially:
n(R2SiO) + ~CH3C0)20 ~ CH3COO(R2SiO)nCOCH3 where n is the same as above, and the mole ratio of R2SiO to acetic anhydride may be varied between 3:1 and 25:1.
The carboxylic acid acts as a solvent and cocatalyst, but has little effect on the equilibrium chain length. The amount used is not critical, but it should be between 2 and 20 percent of the total reaction n~xture. In many cases one mole of acid per mole of anhydride is satis-factory.
The principal catalyst is an acid clay prepared by treatingclay with sulfuric acid. Suitable grades include FILTRGL 13 (fine) and FILTROL 24 (coarse), FILTROL being the Trade Mark of acid clays of Filtrol Corporation. The amount required is not critical, but good results are obtained with from 0,5 to 2 percent of the total reaction mixture.
If the initial silane or siloxane has a high hydroxyl content some changes must be made in the ratio of reactaats. Bearing in mind that two hydroxyl groups generate one molecule of ~Jater~ which destroys one molecule of acid anhydride, the amount of the latter must be increased accordingly. In other words, for every mole of water formed by condensation, or which may be present as an impurity, one additional mole of acid anhydride must be employed. In some cases enough carboxylic acid is generated so that none need be added.
The equilibration times and temperatures are inversely related.
~S~7~
~o to five hours at reflux temperature, approxim~tely 140C., is generally sufficient. ~len FILTROL 13 is used, ten (10) hours is required at 130C.
and twellty (20) hours at 120C. Slightly longer times are required with FILTR01 24. Shorter times are sufficient is the equilibration is carried out at temperatures up to 150C. under slight pressure, or if the amount of catalyst is increased. The reaction may be carried out at any tempera-ture between 100 and 200C., but the preferred range is from 120C. to 150C.
The equilibrated material is coolèd to room temperature and the unreacted carboxylic acid is removed by washing several times with water.
If desired, sodium chloride or other salt may be added to facilitate phase separation by increasing the density of the water layer. Normally the acid clay is wetted by the water and is removed with the water. Alter-natively, it may be removed first by filtration.
~ le washed material still contains most of the acyloxy end groups, as well as some free carboxylic acid. At this stage, it is some-what unstable, as any prematurely formed hydroxyl groups tend to condense with residual acyloxy groups, thus producing longer-chain siloxanes. The rate is somewhat variable, but in general there is only slight loss of end groups in one hour and very considerable loss in 24 hours. Thus the washing step should be completed with deliberate speed.
In order to produce a stable siloxanediol as provided by the parent applic~tion, further hydrolysis is necessary. A siloxanediol of adequate stability is reached when the total of acyloxy groups and free carboxylic acid is reduced to less than 0.25 percent by weight of the siloxanediol.
Although hydrolys;s of acyloxy groups is slow in neutral or acid ~ solution,-it proceeds-more rapidly as the pH is increased, especially if the temperature is also raised. Very rapid hydrolysis takes place in ~5~
strongly alkaline solutions of pH 13 or more. Such a pH also causes con-densation however, and severely reduces the final hydroxyl content. On the other hand, saturated sodium bicarbonate, which has a pH of 8.3, drops oater to ~ pH of 7.5 as the acid is neutralized, and gives incomplete neutralization even after 24 hours at room temperature. Somewhat better results are obtained with sodium carbonate and potassium carbonate solu-tions at room temperature, but even so, as the pH is raised beyond 10.5 some condensation occurs. In general the pH should be in the range of 8 to 11, and preferably in the range of 8.5 to 10.5.
Best results are obtained by heating with an aqueous solution of a weak base to a temperature between 30 and 105C. Suitable weak bases include sodium bicarbonate, sodium carbonate, sodium sesquicarbonate, potassium bicarbonate, potassium carbonate and ammonium hydroxide.
The desired pH may be achieved with sodium bicarbonate by boiling the mixture. This causes evolution of carbon dioxide and the gradual con-version of bicarbonate to carbonate. Two hours of boiling with 20 percent sodium bicarbonate is sufficîent to achieve substantially complete hydroly-sis and neutralization with little condensation. There is one slight disadvantage to this process in that there is no control over the final pH.
It tends to keep rising and eventually goes beyond 10.5, with resulting loss of hydroxyl groups.
Another way to achieve the desired pH is to heat with bicarbonate at a somewhat lower temperature, preferably 50 to 90C., add a little carbonate to bring the pH to the desired level and heat a short time longer, e.g., for a half hour.
The process of aspects of the invention provided by the parent application produces a homologous mixture of silo~anediols. If desired, ~ the various siloxanediols, e.g., hexamethyltrisiloxanediol, octamethyl-tetrasiloxanediol and decamethylpentasiloxanediol can be separated from 5'7~0 the mixtule by fractional distillation.
~ le siloxanediols of aspects of the invention provided by the parent~application are particularly useful as antistructure agents in silicone rubber. They are useful as treating agents for inorganic sur-faces to make them hydrophobic. They also are useful as chemical inter-mediates in the formation of other siloxanes.
In the following examples all parts are by weight unless other-wise specified.
Example 1 The following materials were mixed together: 740 parts of octa-methylcyclotetrasiloxane (D4), 204 parts of acetic anhydride, 120 parts of acetic acid, and 40 parts of acid clay (FILTROL 13). The mixture was heated to reflux temperature and kept under reflux at 137.5 - 139C. for
- la -~5~71~
By a variant thereof, the alpha,omega-diacyloxysiloxane is alpha,omega-diacetoxysiloxane.
Cyclic siloxanes used in the above-recited process generally have the formula (R2SiO) , in which x is a number of from 3 to 10, pre-ferably from 3 to 6, and R is as defined above.
Linear siloxanes used in the above-recited process generally have the formul~
HO~R2SiO) H or R'COO(R2SiO) OCR' in which y has an average value of from 2 to 300 and preferably from 2 to 50.
The siloxanes may contain a minor amount of a silane of the formula R2Si)OH)2 or R2Si(OCOR )2 Examples of suitable cyclic siloxanes include cyclic dimethyl-siloxanes of the formula [(CH3)2SiO] where x is from 3 to 6; cyclic methyl vinyl siloxanes, e.g., heptamethylvinylcyclotetrasiloxane and tetramethyltetravinylcyclotetrasiloxane; and cyclic methyl phenyl siloxanes.
Examples of suitable linear siloxanes include the hydrolysis products and cohydrolysis products of dimethyldichlorosilane, methylvinyl-dichlorosilane, methylphenyldichlorosilane, and diphenyldichlorosilane.
Examples of suitable silanes include dimethyldiacetoxysilane, methylvinyldiacetoxysilane, methylphenyldiacetoxysilane, diphenyldiacetoxy-silane and diphenylsilanediol.
The carboxylic acids used in providing the alpha,omega-siloane-diols of aspects of this inventio~ are preferably the water-soluble unsub-stituted monobasic acids having from 2 to 4 carbon atoms. Likewise the 7~
acid anhydrides are preferably those with from 4 to 8 carbon atoms.
Examples of suitable acids and anhydrides include acetic, propionic, butyric, acrylic and crotonic.
When the siloxane, i.e., a cyclic and/or linear siloxane is equilibrated with, for example, acetic anhydride, the chain length of the resulting diacetoxysiloxane is determined mainly by the mole ratio of acetic anhydride to siloxane units, the reaction being essentially:
n(R2SiO) + ~CH3C0)20 ~ CH3COO(R2SiO)nCOCH3 where n is the same as above, and the mole ratio of R2SiO to acetic anhydride may be varied between 3:1 and 25:1.
The carboxylic acid acts as a solvent and cocatalyst, but has little effect on the equilibrium chain length. The amount used is not critical, but it should be between 2 and 20 percent of the total reaction n~xture. In many cases one mole of acid per mole of anhydride is satis-factory.
The principal catalyst is an acid clay prepared by treatingclay with sulfuric acid. Suitable grades include FILTRGL 13 (fine) and FILTROL 24 (coarse), FILTROL being the Trade Mark of acid clays of Filtrol Corporation. The amount required is not critical, but good results are obtained with from 0,5 to 2 percent of the total reaction mixture.
If the initial silane or siloxane has a high hydroxyl content some changes must be made in the ratio of reactaats. Bearing in mind that two hydroxyl groups generate one molecule of ~Jater~ which destroys one molecule of acid anhydride, the amount of the latter must be increased accordingly. In other words, for every mole of water formed by condensation, or which may be present as an impurity, one additional mole of acid anhydride must be employed. In some cases enough carboxylic acid is generated so that none need be added.
The equilibration times and temperatures are inversely related.
~S~7~
~o to five hours at reflux temperature, approxim~tely 140C., is generally sufficient. ~len FILTROL 13 is used, ten (10) hours is required at 130C.
and twellty (20) hours at 120C. Slightly longer times are required with FILTR01 24. Shorter times are sufficient is the equilibration is carried out at temperatures up to 150C. under slight pressure, or if the amount of catalyst is increased. The reaction may be carried out at any tempera-ture between 100 and 200C., but the preferred range is from 120C. to 150C.
The equilibrated material is coolèd to room temperature and the unreacted carboxylic acid is removed by washing several times with water.
If desired, sodium chloride or other salt may be added to facilitate phase separation by increasing the density of the water layer. Normally the acid clay is wetted by the water and is removed with the water. Alter-natively, it may be removed first by filtration.
~ le washed material still contains most of the acyloxy end groups, as well as some free carboxylic acid. At this stage, it is some-what unstable, as any prematurely formed hydroxyl groups tend to condense with residual acyloxy groups, thus producing longer-chain siloxanes. The rate is somewhat variable, but in general there is only slight loss of end groups in one hour and very considerable loss in 24 hours. Thus the washing step should be completed with deliberate speed.
In order to produce a stable siloxanediol as provided by the parent applic~tion, further hydrolysis is necessary. A siloxanediol of adequate stability is reached when the total of acyloxy groups and free carboxylic acid is reduced to less than 0.25 percent by weight of the siloxanediol.
Although hydrolys;s of acyloxy groups is slow in neutral or acid ~ solution,-it proceeds-more rapidly as the pH is increased, especially if the temperature is also raised. Very rapid hydrolysis takes place in ~5~
strongly alkaline solutions of pH 13 or more. Such a pH also causes con-densation however, and severely reduces the final hydroxyl content. On the other hand, saturated sodium bicarbonate, which has a pH of 8.3, drops oater to ~ pH of 7.5 as the acid is neutralized, and gives incomplete neutralization even after 24 hours at room temperature. Somewhat better results are obtained with sodium carbonate and potassium carbonate solu-tions at room temperature, but even so, as the pH is raised beyond 10.5 some condensation occurs. In general the pH should be in the range of 8 to 11, and preferably in the range of 8.5 to 10.5.
Best results are obtained by heating with an aqueous solution of a weak base to a temperature between 30 and 105C. Suitable weak bases include sodium bicarbonate, sodium carbonate, sodium sesquicarbonate, potassium bicarbonate, potassium carbonate and ammonium hydroxide.
The desired pH may be achieved with sodium bicarbonate by boiling the mixture. This causes evolution of carbon dioxide and the gradual con-version of bicarbonate to carbonate. Two hours of boiling with 20 percent sodium bicarbonate is sufficîent to achieve substantially complete hydroly-sis and neutralization with little condensation. There is one slight disadvantage to this process in that there is no control over the final pH.
It tends to keep rising and eventually goes beyond 10.5, with resulting loss of hydroxyl groups.
Another way to achieve the desired pH is to heat with bicarbonate at a somewhat lower temperature, preferably 50 to 90C., add a little carbonate to bring the pH to the desired level and heat a short time longer, e.g., for a half hour.
The process of aspects of the invention provided by the parent application produces a homologous mixture of silo~anediols. If desired, ~ the various siloxanediols, e.g., hexamethyltrisiloxanediol, octamethyl-tetrasiloxanediol and decamethylpentasiloxanediol can be separated from 5'7~0 the mixtule by fractional distillation.
~ le siloxanediols of aspects of the invention provided by the parent~application are particularly useful as antistructure agents in silicone rubber. They are useful as treating agents for inorganic sur-faces to make them hydrophobic. They also are useful as chemical inter-mediates in the formation of other siloxanes.
In the following examples all parts are by weight unless other-wise specified.
Example 1 The following materials were mixed together: 740 parts of octa-methylcyclotetrasiloxane (D4), 204 parts of acetic anhydride, 120 parts of acetic acid, and 40 parts of acid clay (FILTROL 13). The mixture was heated to reflux temperature and kept under reflux at 137.5 - 139C. for
4 hours. It was then cooled, filtered, and analyzed by gel permeation chromatography~ which showed that 80 percent of the D4 had been converted to a mixture of short, lînear siloxanes averaging 6 to 7 siloxane units.
Similar results were obtained from a sample taken after 2.5 hours. This material was washed with 1000 parts of 10 percent aqueous sodium chloride, then with a slurry of 900 parts of water and 100 parts of sodium bicar-bonate, and finally with 1000 parts of aqueous sodium bicarbonate, at which point a strong odor of acetic acid was still present.
Seven portions of 100 parts each were hydrolyzed in 336 parts of water with added sodium carbonate or sodium bicarbonate. The conditions and results are summarized in the following table:
~ ~ ~ St7 ~ ~
Na2CO' Temp. Time, Final OH, OAc, Example parts C. Hours pH % %
lA 26 30 6 9.7 5.55 4.70 lB 39 30 6 9.9 6.83 2.60 lC 52 30 6 10.2 6.52 2.07 lD 36 60 4 9.87 6.24 0.09 lE 31 60 4 9.75 6.20 0.13 lF 26 70 5 9.56 6.34 0.04 lG 22* 70 5 8.66 6.70 0.21 It can be seeD that hydrolysis was incomplete at 30C., even when a large excess of sodium carbonate was used and the final pH of the water solution was above 10 (Example lC). The high acetoxy (OAc) level results in a somewhat unstable material. Hydrolysis carried out at 60C.
and 70C. was much more nearly complete and gave satisfactory products, even when the final pH was as low as 8.66 ~Example lG).
Example 2 In similar fashion 444 parts of D4, 56 parts of acetic anhydride, 30 parts of acetic acid, and 10 parts of FILTROL 13 were heated at reflux, 144~C.~for 1 hour. A sample analyzed by gas chromatography showed the following (Ac=CH3CO; D=(CH3)2SiO):
AcOH 19.04%
D3 1.26%
D4 14.20%
AcOD3Ae 0.08%
D5 8.44%
AcOD4Ae 1.87%.
_ D6 2.84~
AeOD5Ae 2.69%
7 _ '57~(~
D7 0.67%
AcOD6Ac 3.25%
` . ~ D8 0.44%
~` ~ AcOD7Ac 3.77%
Dg 0.44%
AcOD8Ac 3.84%
D1o 0.16%
AcODgAc 3.96%
Dll O.09%
AcODloAc 4.11%
Other linear diacetoxysiloxanes were observed in the rar.ge of 1 to 4 per-cent up to AcODlgAc. Similar results were obtained on a sample taken after 2 hours. In this case equilibration was essentially complete in 1 hour.
Example 3 A mixture of 250 parts of D4, 17 parts of a methylvinylsiloxane (MeViSiO) , consisting of linear and cyclic siloxanes in a ratio of 6:4, and having a viscosity of 100 cP; 50 parts of acetic anhydride; 23 parts of glacial acetic acid; and 5 parts of FILTROL 13 LM (low-moisture grade) was heated to 145C. in a closed vessel for 5 hours with continuous agitation. The mixture was then cooled and washed three times with aqueous sodium bicarbonate at 40~C., whereupon most of the acid clay was found to have been removed with the water. The washed fluid was then heated to 80C. with a slurry of lOO parts of sodium bicarbonate in 460 parts of water. After 3 hours, lO parts of sodium carbonate was added and heating continued for another 2 hours. The aqueous phase was drawn off while still hot, and found to have a pH of 9.8. The final siloxandiol was analyzed, with the following results:
1~5'7~0 Hydroxyl content 4.51 percent Vinyl content 2.14 percent , pH ~ 7.87 ~` ~ Acetoxy (calculated as acetic acid) 122 ppm Viscosity 32.6 cSt Specific gravity 0.979 This siloxanediol was tested in a silica-filled silicone rubber and found to be an effective antistructure agent. On a weight basis it is much more effective than other siloxanediols having a hydroxyl content in the range of 2 - 3 percent.
Similar results were obtained from a sample taken after 2.5 hours. This material was washed with 1000 parts of 10 percent aqueous sodium chloride, then with a slurry of 900 parts of water and 100 parts of sodium bicar-bonate, and finally with 1000 parts of aqueous sodium bicarbonate, at which point a strong odor of acetic acid was still present.
Seven portions of 100 parts each were hydrolyzed in 336 parts of water with added sodium carbonate or sodium bicarbonate. The conditions and results are summarized in the following table:
~ ~ ~ St7 ~ ~
Na2CO' Temp. Time, Final OH, OAc, Example parts C. Hours pH % %
lA 26 30 6 9.7 5.55 4.70 lB 39 30 6 9.9 6.83 2.60 lC 52 30 6 10.2 6.52 2.07 lD 36 60 4 9.87 6.24 0.09 lE 31 60 4 9.75 6.20 0.13 lF 26 70 5 9.56 6.34 0.04 lG 22* 70 5 8.66 6.70 0.21 It can be seeD that hydrolysis was incomplete at 30C., even when a large excess of sodium carbonate was used and the final pH of the water solution was above 10 (Example lC). The high acetoxy (OAc) level results in a somewhat unstable material. Hydrolysis carried out at 60C.
and 70C. was much more nearly complete and gave satisfactory products, even when the final pH was as low as 8.66 ~Example lG).
Example 2 In similar fashion 444 parts of D4, 56 parts of acetic anhydride, 30 parts of acetic acid, and 10 parts of FILTROL 13 were heated at reflux, 144~C.~for 1 hour. A sample analyzed by gas chromatography showed the following (Ac=CH3CO; D=(CH3)2SiO):
AcOH 19.04%
D3 1.26%
D4 14.20%
AcOD3Ae 0.08%
D5 8.44%
AcOD4Ae 1.87%.
_ D6 2.84~
AeOD5Ae 2.69%
7 _ '57~(~
D7 0.67%
AcOD6Ac 3.25%
` . ~ D8 0.44%
~` ~ AcOD7Ac 3.77%
Dg 0.44%
AcOD8Ac 3.84%
D1o 0.16%
AcODgAc 3.96%
Dll O.09%
AcODloAc 4.11%
Other linear diacetoxysiloxanes were observed in the rar.ge of 1 to 4 per-cent up to AcODlgAc. Similar results were obtained on a sample taken after 2 hours. In this case equilibration was essentially complete in 1 hour.
Example 3 A mixture of 250 parts of D4, 17 parts of a methylvinylsiloxane (MeViSiO) , consisting of linear and cyclic siloxanes in a ratio of 6:4, and having a viscosity of 100 cP; 50 parts of acetic anhydride; 23 parts of glacial acetic acid; and 5 parts of FILTROL 13 LM (low-moisture grade) was heated to 145C. in a closed vessel for 5 hours with continuous agitation. The mixture was then cooled and washed three times with aqueous sodium bicarbonate at 40~C., whereupon most of the acid clay was found to have been removed with the water. The washed fluid was then heated to 80C. with a slurry of lOO parts of sodium bicarbonate in 460 parts of water. After 3 hours, lO parts of sodium carbonate was added and heating continued for another 2 hours. The aqueous phase was drawn off while still hot, and found to have a pH of 9.8. The final siloxandiol was analyzed, with the following results:
1~5'7~0 Hydroxyl content 4.51 percent Vinyl content 2.14 percent , pH ~ 7.87 ~` ~ Acetoxy (calculated as acetic acid) 122 ppm Viscosity 32.6 cSt Specific gravity 0.979 This siloxanediol was tested in a silica-filled silicone rubber and found to be an effective antistructure agent. On a weight basis it is much more effective than other siloxanediols having a hydroxyl content in the range of 2 - 3 percent.
Claims (2)
1. A process for making alpha, omega-diacyloxysiloxanes of the formula R'COO(R2SiO)nOCR', in which at least 50 percent of the R groups are methyl and the remaining R groups are selected from the class consisting of vinyl and phenyl groups, R' is a hydrocarbon radical having from 1 to 3 carbon atoms, and n has an average value of from 3 to 25, which comprises: heating a siloxane selected from the class consisting of cyclic siloxanes, linear siloxanes and mixtures thereof with an acid anhydride having from 4 to 8 carbon atoms and a carboxylic acid having from 2 to 4 carbon atoms in the presence of an acid clay for at least 1 hour until equilibration occurs at a temperature of from 120°C to 150°C.
2. The process of claim 1 wherein said alpha, omega-diacyloxysiloxane is alpha, omega-diacetoxysiloxane.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA360,251A CA1125780A (en) | 1977-10-28 | 1980-09-15 | Process for making alpha-omega-diacyloxysiloxanes |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA289,796A CA1115726A (en) | 1977-10-28 | 1977-10-28 | Process for making alpha, omega-siloxanediols |
| CA360,251A CA1125780A (en) | 1977-10-28 | 1980-09-15 | Process for making alpha-omega-diacyloxysiloxanes |
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| Publication Number | Publication Date |
|---|---|
| CA1125780A true CA1125780A (en) | 1982-06-15 |
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| Application Number | Title | Priority Date | Filing Date |
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| CA360,251A Expired CA1125780A (en) | 1977-10-28 | 1980-09-15 | Process for making alpha-omega-diacyloxysiloxanes |
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| CA (1) | CA1125780A (en) |
Cited By (8)
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|---|---|---|---|---|
| CN111690138A (en) * | 2020-07-16 | 2020-09-22 | 江西蓝星星火有机硅有限公司 | Low-viscosity vinyl hydroxyl silicone oil and preparation method thereof |
| CN112011054A (en) * | 2019-05-28 | 2020-12-01 | 赢创运营有限公司 | Acetoxy system |
| CN112010887A (en) * | 2019-05-28 | 2020-12-01 | 赢创运营有限公司 | Method for preparing siloxane with acetoxy group |
| CN112010888A (en) * | 2019-05-28 | 2020-12-01 | 赢创运营有限公司 | Method for preparing siloxane with acetoxy group |
| EP3744753A1 (en) * | 2019-05-28 | 2020-12-02 | Evonik Operations GmbH | Method for purifying acetoxy siloxanes |
| CN113754888A (en) * | 2020-06-02 | 2021-12-07 | 赢创运营有限公司 | Linear acetoxy-containing siloxanes and derivatives |
| CN114430757A (en) * | 2019-09-27 | 2022-05-03 | 赢创运营有限公司 | Silicone (meth) acrylates, method for the production thereof and use thereof in curable compositions |
| US11795275B2 (en) | 2018-12-04 | 2023-10-24 | Evonik Operations Gmbh | Reactive siloxanes |
-
1980
- 1980-09-15 CA CA360,251A patent/CA1125780A/en not_active Expired
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| US11795275B2 (en) | 2018-12-04 | 2023-10-24 | Evonik Operations Gmbh | Reactive siloxanes |
| US11066429B2 (en) | 2019-05-28 | 2021-07-20 | Evonik Operations Gmbh | Process for producing acetoxy-bearing siloxanes |
| US11286351B2 (en) | 2019-05-28 | 2022-03-29 | Evonik Operations Gmbh | Process for producing acetoxy-bearing siloxanes |
| CN112010888A (en) * | 2019-05-28 | 2020-12-01 | 赢创运营有限公司 | Method for preparing siloxane with acetoxy group |
| EP3744755A1 (en) * | 2019-05-28 | 2020-12-02 | Evonik Operations GmbH | Method for producing siloxanes bearing acetoxy groups |
| CN112011054A (en) * | 2019-05-28 | 2020-12-01 | 赢创运营有限公司 | Acetoxy system |
| EP3744753A1 (en) * | 2019-05-28 | 2020-12-02 | Evonik Operations GmbH | Method for purifying acetoxy siloxanes |
| CN112010887A (en) * | 2019-05-28 | 2020-12-01 | 赢创运营有限公司 | Method for preparing siloxane with acetoxy group |
| EP3744756A1 (en) * | 2019-05-28 | 2020-12-02 | Evonik Operations GmbH | Acetoxy systems |
| EP3744754A1 (en) * | 2019-05-28 | 2020-12-02 | Evonik Operations GmbH | Method for producing siloxanes bearing acetoxy groups |
| CN112011054B (en) * | 2019-05-28 | 2023-09-29 | 赢创运营有限公司 | Acetoxygen systems |
| US11472822B2 (en) | 2019-05-28 | 2022-10-18 | Evonik Operations Gmbh | Process for purifying acetoxysiloxanes |
| US11420985B2 (en) | 2019-05-28 | 2022-08-23 | Evonik Operations Gmbh | Acetoxy systems |
| CN114430757A (en) * | 2019-09-27 | 2022-05-03 | 赢创运营有限公司 | Silicone (meth) acrylates, method for the production thereof and use thereof in curable compositions |
| EP3919550A1 (en) * | 2020-06-02 | 2021-12-08 | Evonik Operations GmbH | Linear acetoxy group bearing siloxanes and secondary products |
| CN113754888A (en) * | 2020-06-02 | 2021-12-07 | 赢创运营有限公司 | Linear acetoxy-containing siloxanes and derivatives |
| CN111690138A (en) * | 2020-07-16 | 2020-09-22 | 江西蓝星星火有机硅有限公司 | Low-viscosity vinyl hydroxyl silicone oil and preparation method thereof |
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