FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION (See section 10, rule 13)
"A PROCESS FOR MODIFYING Si-X BOND IN A COMPOUND"
NOUVEAW EXPORTS PVT. LTD. an Indian company, of A-12/13, MIDC Industrial Estate, TTC, Thane-Belapur Road, Navimumbai - 400 709, Maharashtra, India,
The following specification particularly describes the invention and the manner in which it is to be performed:

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Field of the invention:
The present invention relates to an economical process to modify Si-X bond, wherein X
is selected from a group consisting of radicals of 0, CI, Br, I and hydrolysable group.
More particularly, the present invention relates to process to incorporate desired
functional group in a compound having Si-X bond.
Background of Invention:
Siloxanes - (R1R2Si-O-SiR^4) - are modified to add various functional groups at the
Si-O-Si linkage. Since, the Si-O-Si being a stable linkage it is not very easy to
incorporate different functional groups.
The present invention reveals a process by which desired functional groups like (-NH)
- as in Hexamethyldisilazane (HMDS) and -OH as in hydroxy terminated
polydimethylsiloxane fluids can be incorporated. But the use of this method is not
limited to the addition of these functional groups and can be used to add many other
functional groups too.
Following are the conventional and widely used methodology to produce modified
siloxane. Hexamethyldisilazane (HMDS) is prepared from hexamethyldisiloxane
HMDO using the following two steps:
Process I:
a) Reacting HMDO with anhydrous HC1 in the presence of a dehydrating agent to
produce trimethylchlorosilane (TMCS). In this, the dehydration of Reaction
mixture is generally done using concentrated Sulfuric Acid which is allowed to
dilute to -70%. The spent acid, which contains some organic impurities also,
has to be disposed or concentrated using multiple stage evaporators. Anhydrous
HC1, which is needed for the reaction with HMDO is generally, produced using
one of the following processes.
i. Dehydration of aq. HC1 using CaCl2 or Concentrated Sulfuric acid, ii. Electrolysis of NaCl, or distillation of aqueous HC1.
b) Reacting Ammonia with TMCS produced in step-a, to produce HMDS and
Ammonium chloride
Process II:
HMDS from Trimethylchlorosilane (TMCS) produced in the Direct process using
Silicon metal and Methyl chloride. Trimethylchlorosilane (TMCS) is reacted with

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ammonia to produce HMDS and Ammonium Chloride. This amination results in
reduction of chlorine loop efficiency of chlorosilane plants and so regeneration of
chloride as HCI is desirable in this process too.
The drawbacks of the existing process are, in case of Process I, where anhydrous HCI is
used to replace oxygen with chloride ion.
Firstly, water is formed in the reaction so a dehydrating agent like 98% H2S04 has to be
added to absorb the water of reaction. This produces an effluent stream of dilute H2SO4.
Secondly some HMDO dissolves into the effluent stream and adds to losses. This in
turn reduces the yield of the product.
Thirdly TMCS produced being a volatile compound is prone to losses. This in turn
reduces the yield of the product.
To dehydrate commercially available aqueous HCI incurs lot of money and energy
which adds to the production cost.
Regarding the drawbacks of the Process II, The consequent amination in the reaction
chain results in reduction of chlorine loop efficiency of chlorosilane plants thus adding
to the economic losses of the reaction process. This is because the chlorine which gets
converted to ammonium salt, will have to be substituted by HCI for further chlorination
of silicon.
The present invention has the following advantages:
• Reduce the cost of incorporation of functional group in the siloxane by using a compound cheaper and easily available as compared to anhydrous HCI.
• The present invention does not produce any effluents as compared to existing processes.
• HMDS can be made from TMCS with recovery of HCI, by substituting the chloride with cheaper sulfate radical.
• The sulphonated silane/siloxane produced is non volatile as compared to their chlorinated counterparts. So losses by evaporation can be minimum.
• Even Ammonium sulphate produced as a by product during amination of sulfonated silane/siloxane is a fertilizer.
An existing process commercially used to make hydroxy terminated polydimethylsiloxane fluids is discussed below.

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Process I:
Hydroxy terminated polydimethylsiloxane (reactive silicone oil) fluid is generally
manufactured by the hydrolysis of dimethyldichlorosilane (M2). This hydrolysis
generates a mixture of cyclic & linear chain silicones called hydrol. The cyclic silicones
(DMC) can be distilled out of hydrol leaving behind hydroxy terminated low molecular
weight silicones (LMS).
Process II:
A process of preparing silanol stopped siloxane by the ring opening polymerization of
hexaorganotrisiloxane in the mixture of water & a volatile polar aprotic organic solvent
in the presence of catalytic amounts of strong base, followed by neutralization, water
washes & solvent recovery by distillation, (as described in US Patent No: 6433204B)
Process III:
A process of preparing linear hydroxy end-terminated linear siloxanes by mixing
chlorosiloxanes with volatile methyl siloxanes, followed by hydrolysis preferably in
dilute HC1 solution, & recovery of hydroxy terminated linear siloxanes. (as described in
US Patent No: 6316655 Bl)
The main drawback, of manufacturing low molecular weight hydroxy terminated
silicone oil in case of process I is that the LMS so obtained can contain low levels of
impurities particularly trifunctionalities due to traces of methyltrichlorosilane (Ml) in
M2.
The main drawback, of manufacturing low molecular weight hydroxy terminated
silicone oil in case of process II is as follows:
Firstly, the need for hexaorganocyclotrisiloxane, which has to be produced and is
difficult to handle. For example hexamethylcyclotrisiloxane which is used to make
hydroxy ended polydimethylsiloxane is a solid at room temperature and has a melting
point of-70°C.
Secondly this process needs the presence of a solvent like acetone, which being highly
volatile can add to losses and/or high utility costs to prevent/reduce losses.
The main drawback, of manufacturing low molecular weight hydroxy terminated
silicone oil in case of process III is as follows:
Firstly the need for chlorosiloxanes, which has to be produced and not easily
commercially available.

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Secondly the preferable need for dilute aq. HC1, which again leads to the chlorine loop efficiency of chlorosilane plants, (the general parent plant of all these products). The present invention offers a method to conveniently manufacture pure LMS. This is because it is easy to convert even DMC into hydroxy terminated polydimethylsiloxane. The process of the present invention can work efficiently with or without hexaorganocyclotrisiloxane (generally called D3), or mixtures of D3 with other siloxanes. Further, this process can work with or without solvents. When preparing die amine modified siloxane such as Hexamediyldisilazane the methodology used in the present invention will help to recover HC1 from chlorosilanes as anhydrous or aqueous HCI without losing the reactive nature of parent chlorosilane. The present invention will also be useful in recovering HCI from waste chlorosilane mixtures. This can be done by reacting sulfuric acid with chlorosilane mixtures, The products will be anhydrous HCI and a liquid mixture of high boiling (and some water-soluble) sulfonated silanes, which can be handled with comparative ease (for disposal by neutralization). This would be useful in reducing the frequency of choking in waste chlorosilane water scrubbers that are common in Chlorosilane plants. HMDS which is extensively used as a silylating agent in the industry can be made more economically using an environment friendly process described in this invention. Similarly hydroxy terminated polydimethylsiloxane fluids (reactive silicone oil) are extensively used for manufacture of silicone rubber and special purpose silicone fluids. This invention offers a convenient method of the manufacture of these fluids which can be of better quality than the conventionally produced fluids.
Object of the present invention:
The main object of the present invention is to modify a compound having a Si-0 bond. Yet in another object of the present invention is conveniently produce hydroxy-ended polysiloxanes.
Still in another object of the present invention is to reduce the need for solvents in making hydroxy ended polysiloxanes.
Further in another object of the present invention is to substitute the halogen X in Si-X
with the cheaper sulphate radical.
Further in another object of the present invention is to recover hydrogen halide from
halogen silanes/siloxane.

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Detailed description of the Invention;
Accordingly, the present invention deals with a process of modifying a compound having Si-O bond by breaking the said bond and incorporating desired functional group.
In another embodiment of the present invention is to incorporate a sulphate group to a compound having Si-0 bond, wherein the compound is selected from silane or siloxane.
The sulphate group thus incorporated can be further used as a door to add other functional groups.
In addition to the above, the reaction of H2SO4 or Oleum with chlorosilanes also results in the replacement of chlorine with sulphate group at the SiCl bond; this liberates HCl which can be used to manufacture other products. Furthermore the sulphate group attached to the silicon can be used to attach other functional groups to the silicon atom, Further, in another embodiment of the present invention the Si-0 linkage is converted to Si-S04 then converted to the Si-NH, wherein the formation of sulphate group helped in the addition of-NH- linkage to the siloxane compound.
Alternatively, trimethylchlorosilane (TMCS) is reacted with sulfuric acid to produce anhydrous HCl and Bis (trimethylsilyl) sulfate. The Bis (trimethylsilyl) sulfate is then reacted with ammonia to produce HMDS and ammonium sulfate. The Anhydrous HCl generated can be reused to manufacture other products/chlorosilanes. In this process the substitution of costlier Chloride ions with cheaper Sulfate ion results in significant cost savings. This process is not restricted to TMCS and can be used for other chlorosilanes. Optionally, the sulphonated compound can further be modified by reacting the same with Lewis base like ammonia or water to obtain hydroxy-terminated or amine modified compound.
Still in another object of the present invention, wherein a poly-dimethylsiloxane molecule is reacted with Sulfurtrioxide (SO3) or Oleum then hydrolysed with water to form Hydroxy terminated polydimethylsiloxane fluid and dilute sulfuric acid. Still in another embodiment of the present invention is to modify Si-X bond in a compound, wherein X is selected from group consisting of O, CI, Br, I and hydrolysable group, said process comprising the steps:
1. contacting first compound containing Si-X linkage with second compound capable of producing sulphate to produce sulphonated product of the first

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compound wherein the weight % of first and second compound can vary from 1 to 99%, and 2. optionally, mixing the sulphonated compound of step (i) with a Lewis Base to incorporate a functional group in the sulphonated product of step (i) to obtain modified Si-X bond.
Further, in another embodiment of the present invention, wherein Si-X bond containing
compound is selected from a group consisting of silane and siloxane.
Yet in another embodiment of the present invention, wherein sulfate producing
compound in step (i) is selected from a group comprising SO3, sulfuric acid, sulphurous
acid and oleum.
In one more embodiment of the present invention, wherein the silicon of siloxane or
silane is attached to a halogen other than fluorine, when sulfate producing compounds
are either sulphuric or sulphurous acid.
Still in another embodiment of the present invention, wherein Lewis Base is selected
from ammonia, ethylenediamine and water.
Further in another embodiment of the present invention, wherein the modified silanes
are Bis (trimethylsilylsufate) and Hexamethyldistlazane.
Yet in another embodiment of the present invention, wherein the modified siloxanes are
hydroxy terminated polydimethylsiloxane and Bis (trimethylsilylsulfate).
EXAMPLES
The following examples are illustrative only and shall not be construed as limiting the
invention.
Example-1
500 gm mixture of 94% TMCS and rest HMDO is stirred in a 5 litre RB flask having 2 columns and reflux condenser attached to it. Column below the reflux condenser has a height of- 400 mm and diameter of-1.5". Column above the reflux condenser has a height of- 150mm and diameter of ~1". Both columns are filled with glass Raschig rings of ~ 4 to 15mm) 800 gm Hexane was added to the flask. The flask was heated to maintain a temperature between 30 to 80°C. 240 gm Sulphuric acid was added slowly into the RB flask from the top of the column above the reflux condenser, the HC1 evolved was vented to a water scrubber. At the end of sulfuric addition, the chloride content analysis of reaction mass showed 0.16% chloride. Then the reaction flask was kept half immersed in a ice bath then 600 gm of Hexane was added to the solution and

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later Ammonia vapours was passed into the system until the reaction mixture shows pH>7. Then 3 water washes were done and the organic layer was separated and collected. 13% HMDS was detected in the organic layer by gas chromatography
Example-2
50 gm mixture of pure HMDO was taken in a stirred 2 litre RB flask. The flask was kept half immersed in ice bath. 70 gm Oleum (19.53%) was added slowly over a period of 1 hour maintaining the temperature in the range of 10 to 40°C. 500 gm Hexane was added to the flask. Ammonia vapours were passed into the stirred system until the reaction mixture shows pH>7. Then 3 water washes were done and the organic layer was separated and collected. 2.8% HMDS was detected in the organic layer by gas chromatography.
Examplc-3
150 gm mixture of 100% HMDO was taken in a stirred 2 litre RB flask. The flask as kept half immersed in water bath. ~ 70 gm SO3 was added slowly over a period of 1 hour maintaining the temperature in the range of 40°C to 55 C. Part of the mixture was separately vacuum distilled and Bis (trimethylsilyl) sulphate was obtained. In rest of the solution 500 gm Hexane was added. Ammonia vapours were passed into the stirred system until the reaction mixture shows pH>7. Then 3 water washes were done and the organic layer was separated and collected. 13% HMDS was detected in the organic layer by gas chromatography.
Example-4
A 322 gm mixture of HMDO (50%) and toluene having no HMDS was taken in a stirred 2 litre RB flask. The flask was kept half immersed in water bath maintaining the temperature between 20°C to 40°C. One litre flask containing 554 gm oleum was connected to the HMDO flask through a glass connector at the top of both flasks through a vertical, water-cooled condenser to drop condensed SO3 into the HMDO flask. Oleum was then heated from 30°C to 260°C over a period of 45 minutes in the flask. Then 450 gm Hexane was added followed by, Ammonia vapours, which was passed into the stirred system until the reaction mixture shows pH>7.*This amination was followed by 3 water washes. The organic layer obtained after the third wash was separated and collected. The organic layer contained 109 gm HMDS (as analysed by gas chromatography).

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ExampIe-5
- 180 gm S03 was added to 3000 gram DMC in a stirred 5 litre RB flask. Then the
mixture was mixed with water. The mixture was then given water washes till the oil
layer was neutral. The oil was heated to 180°C in vacuum >755 mm Hg for 2 hours.
This devolatilized silicone oil was of ~ 80 cP viscosity. For a person skilled in the art of
making silicone oils, the low viscosity in absence of any volatiles is a makes it clear the
silicones are hydroxyl ended. Hence the hydroxy terminated low molecular weight
silicone was formed. The hydroxy termination was checked by condensation
polymerization test.
Example-6
100 gm 20% Oleum was added to 100 gram DMC in a stirred 5 litre RB flask. Then the mixture was mixed with water. The mixture was then given water washes till the oil layer was neutral. This hydroxy terminated low molecular weight silicone oil was of ~ 10 cP viscosity, (hydroxy termination was checked by condensation polymerization test)
Example-7
- 180 gm S03 was added to 3000 gram DMC in a stirred 5 litre RB flask. 3000 gm
Hexane was added to the mixture. Then the mixture was mixed with water. The mixture
was then given water washes till the oil layer was neutral. The oil was heated to 200 C
for 1 hour to remove hexane. This silicone oil so obtained was of - 20 cP viscosity.
Hence the hydroxy terminated low molecular weight silicone was formed. Hydroxy
termination was checked by condensation polymerization test.

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Claims
1. A process for modifying Si-X bond in a compound, wherein X is selected from
group consisting of radicals of 0, CI, Br, I and hydrolysable group, said process
comprising the steps:
i) contacting first compound containing Si-X linkage with second compound capable of producing sulphate to produce sulphonated product of the first compound wherein the weight % of first and second compound can vary from 1 to 99% , to obtain modified Si-X bond, and
ii) if desired, mixing the sulphonated compound of step (i) with a Lewis Base to incorporate a functional group.
2. A process as claimed in Claim 1, wherein Si-X bond containing compound is selected from a group consisting of silane and siloxane.
3. A process as claimed in Claim 1, wherein sulfate producing compound in step (i) is selected from a group comprising of SO3 and oleum when the X in Si-X is 0 radical.
4. A process as claimed in Claim 1, wherein sulfate producing compound in step (i) is selected from a group comprising sulphuric acid, sulphurous acid and oleum, when X in Si-X is selected from radicals consisting of CI, Br, I and hydrolysable group.
5. A process as claimed in Claim 2, wherein the silicon of siloxane or silane is attached to a halogen radical other than fluorine radical, when sulfate producing compounds are sulphuric or sulphurous acid or oleum.
6. A process as claimed in Claim 1, wherein Lewis Base is selected from ammonia, ethylene diamine, NH2CONH2, C6H5NH2, CH3NH2 and water.
7. A process as claimed in claim 1, wherein in step (ii), the functional group is selected from a group comprising hydroxy and amino group.
8. A process as claimed in Claim 2, wherein the modified silanes are Bis(trimethylsilylsufate) and Hexamethyldisilazane.
9. A process as claimed in Claim 1, wherein the modified siloxanes are hydroxy terminated polydimethylsiloxane, Hexamethyldisilazane and Bis (trimethylsilyl sufate).
10. A process as claimed in Claim 1, wherein the hydrolysable group is selected from -OCH3, -OC2H5, -NH, -NH2, butylamino, sec-butylamino,

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cyclohexylamino, benzylmethylamino, dimethylanimoxy, dimethylaninoxy, dipropylaminoxy, acetophenoneoximo, acetone oximo, benzophenoneoximo, methylethyl ketoximo, n-propoxy, isopropoxy, butoxy, hexyloxy, heptoxy, octyloxy, formyloxy, acetoxy, propionyloxy, caproyloxy or stearoxy.
11. A process for modifying Si-X bond in a compound substantially as herein described with reference to the foregoing examples.
Dated this 6th day of December, 2005

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Abstract
The present invention relates to an economical process to modify Si-X bond, wherein X
is selected from a group consisting of radicals of 0, CI, Br, I and hydrolysable group and more particularly, the present invention relates to process to incorporate desired functional group in a compound having Si-X bond.