Note: Descriptions are shown in the official language in which they were submitted.
8~0~31
- 1 - 60SI-352
PROD~CTION OF ALKOXY S`ILYL ALKYL DIEST~RS
BACKGROUND OF THE INVENTI ON
The present invention relates to the production of
the silyl maleates and more particularly the present
invention relates to a novel process for maximizing
the yield of the production of silyl maleates, furmarates,
succinates and phthalates.
Silyl maleates are well-known, for instance, see
-the disclosure of U.S. Patent No. 3,759,968 dated
September 18, 1973 to Berger et al w:ith respect to silyL
maleates also seen in the disclosure of U.S. Patent No.
3,179,612 dated April 20, 1965 to Plueddemann. When
such silyl maleates were first developed, they were
disclosed as being utilized as sel-f-bonding additives
Eor heat curable silicone rubber compositions. In a
later patent application which is still pending, silyl
malea-tes, fumarates, and succinates are disclosed
as self-bonding additives for incorporation into one
component room temperature vulcanizable silicone rubber
compositions. Silyl phthalates were not disclosed in
Canadian application, which is Serial No. 359,263
Smith et al, entitled "Self-Stable One Part Room
Temperature Vulcanizable Silicone Rubber Compositions"
-filed August 29, 1980. Although silyl phthalates were
2S not disclosed in that patent application for use as
self-bonding additives r they do have some utility as
o~
60SI-352
-- 2 --
self-bonding additives for heat vulcanizable silicone
rubber compositions. However, there was some difficulty
with the process for the production of such silyl maleates,
fumarates, succinates and phthalates (hereinafter, while
reference is made to silyl maleates, it is understood
that the same process conditions apply to the fumarates,
succinates, and phthalates).
Accordingly, the process that were clisclosed int for
instance, U.S. Patent No 3,773,817 to Berger dated
November 20, 1973, and related patents on the production
of silyl maleates, fumarates, and other related compounds
were not altogether advantageous. The difficulties of
such process will be disclosed below but to state matters
simply the overally yield from such a process did not
exceed 60 percent most of the time ancl many times the
overall yield was considerably lower. There were two
alternate processes of the prior art such as disclos~d
in the foregoing Berger et al. U.S. Patent 3,773,8:L7
which was disclosed for the production of silyl maleates.
One process was the taking of trimethoxyhydrogenosilane
and reacting with the olefinic maleate. The disadvantage
of this process was that hydrogenotrimethoxysilane is
very hard to handle since it is dangerous material that
can cause eye damage. In addition, the reaction is
exothermic and difficult to control. In another aspect,
the trimethoxyhydrogenosilane is the product of alkoxyla-
ting hydrogenotrichlorosilane which in itself is a
difficult process for the reason that will be set forth
below. Accordingly, a more acceptable process from the
material handling point of view to react the olefin
maleate with trichlorosilane in the presence of a
platinum catalyst to produce trichlorosilylpropylmaleate.
The resulting maleate was alkoxylated by reacting the
trichlorosilylmaleate with methanol in the presence of an
aromatic solvent at the temperature of 25 to 75C as
disclosed in the foregoing U.S. Patent 3,773,817.
~ ~ ~9~
60SI-352
-- 3 --
The difficulty with such a reaction was that the
methanol reacts with hydrogen chloride that is formed
to produce methyl chloride and water. This is a com-
peting reaction which tends to predominate and accordingly,
the desired yield of a methoxylated product would be quite
small. An undesirable side reaction woulcl be that if
the methyloxylation of the trichlorosilylpropylmaleate
continues, the alcohol would react with a methoxysilyl-
propyl maleate in the presence of hydrogen chloride to
cleave the trimethoxysilylpropyl ester group and yield a
methoxy maleate ester. Both of these reactions, as can be
appreciated, would not give the desired yield of a
methoxylated silylpropylmaleate compound. Accordingly,
this methoxylation was hard to control, and hiyh yields
were difficult to obtain utilizing the technique set eorth
in U.S. Patent 3,773,817 and elsewhere.
Another alternative process was to use trimethylortho-
formate to carry out methoxylation of bis-(trichloro-
silylpropyl) maleate. However, the cost of this process
is prohibitive, such as to make it disadvantageous to use
even though the process operates properly and results
in a high yield of product. It takes 6 moles of the
trimethylorthoformate for one mole of a maleate to
he desired methoxylated product. Accordingly,
in spite of the fact that this process with trimethyl-
orthoformate is desirable, in that it results in a high
yield of product with a minimum of side reaction, never-
theless it is prohibitively expensive. Accordingly, it
was highly desirable to find an inexpensive route for the
production of methoxylated silylpropyl maleates, fumarates,
succinates and phthalates. This was true whether there
was one methoxy per silicon atom in the maleate or three
methoxy groups per silicon atom in the maleate, fumarate,
succinate or phthalate.
Accordingly, it is one object of the present invention
,?
¢~
- ~.18gO~
- 4 - 60SI-352
to provide an economical process for producing alkoxylated
silyl maleates, fumarates, succinates, and phthalates.
It is an additional ob~ect of the present inven-tion
to provide an efficient and economic process for the
production of alkoxylated silyl maleates, fumarates,
succinates, and phthalates in over ~ yield.
It is an additional object of the present inven-
tion to provide a saEe process for the production of
alkoxylated silyl maleates, fumarates, succinates, and
phthalates which does not result in the handling of
hazardous or dangerous materials.
It is still an additional object of the present
invention to provide a process for the production of
alkoxylated silyl maleates, fumarates, succinates, and
ph-thalates.
The process is car.ried out such that the entire
addition reaction as well as the alkoxylation reactlon
takes place in one reaction chamber which results i.n
an economical utilization of process conditions and
process materials. These and other objects of the
present invention are accomplished by means of a disclosure
set forth herein and below.
Summary of the Invention
In accordance with the above there is provided by
the present invention a process for producing silyl
maleates comprising (a) reaction a maleate of -the
formula,
(1) R - C - C - O - R - CH = CH2
Il 'L
R - C - C - O - R` - CH = CH2
o
~,
.90~
_ 5 60SI-352
,a
with (2) H-Si X3 a in the presence of a platinum catalyst
and (b) then mixing and reacting the intermediate product
with an aliphatic alcohol of the formula R2OH where said
in-termediate product is presen-t in an organic solven-t
and where said aliphatic alcohol is added to said
intermediate product beneath and into the layer of said
intermediate product and where said intermediate product
is maintained at or near the reflux temperature of said
organic solvent during said addition to produce in at
least 70% yield a silyl maleate of the formula,
O ,a
(3) R - C - C - O - R - CH2 - CH2 - Si(oR )3 a
ll ,Ra
R - C - C - O - Rl - CH2 - CH2 - Si(OR2)3 a
where R2 and R3 are monovalent hydrocarbon radicals Oe
to 8 carbon atoms, R is selected from hydrogen and
monovalent hydrocarbon radicals of 1 to 8 carbon atoms,
a varies from 0 to 2, X is halogen and R1 is a divalent
hydrocarbon radical of 1 to 8 carbon atoms.
Similar process conditions apply for the
production of the silyl maleates, silyl fumerates, silyl
succinates, and silyl phthalates as will be disclosed below.
An important aspect of the process of the instant case is
to remove the hydrogen chloride that is formed during the
reaction as soon as or in close proximity to when it is
formed by refluxing it out as a gas and b~ trapping it
in an azeotrope of methanol, organic solvent and water
where the methanol, water and dissolved hydrogenchloride
is continually removed as the lower layer from a trap
which collects the condensed vapors from the reflux. The
upper layer is returned to the vessel. This removal of
the HCl prevents it from building up and reacting with
~3
1~ ~90~33L
- 6 - 60SI-352
methanol to produce methyl chloride and water. Another
important aspect of the methoxylation process of the
instant case is that at the point where the reaction is
close to being completed; that is, where 10,000 parts
per million or less of silyl chloride boncls (Si-Cl)
are present there is added sufficient methanol and
tertiary amine on an alkali metal alkoxide to terminate
the reaction.
The methanol will react with Si-Cl bonds
remaining in the reactant maleate or the compound to produce
the desired methoxylated product where the tertiary amine
in the reaction mixture will react with HCl that is given
up to tie it up so that the HCl will not catalyze a
cleavage reaction as was discussed above. Utilizing
this procedure, it is possible to obtain as much as
75 percent yield and more likely, at least 80% of the
desired alkoxylated or methoxylatecl silyl maleate~
fumarate, succinate, or phthalate.
Des'cription of the' Pr'e'f'er;red Embo'diment
A similar method to the above is encompassed
within the instant invention process for the production of
silyl fumarates comprising reacting a fumarate of the
formula,
o
(4~ R - C - C - O - R - CH = CII2
CH2 = CH - R6 _ o - C - C - R
R3
a
with (5) H-Si-X3 a in the presence of a platinum catalyst
and (b) then reacting the intermediate product with an
aliphatic alcohol of the formula R2OH where said inter-
mediate product is present in an organic solvent and
where said aliphatic alcohol is added to said inter-
mediate product slowly over a period of at least six
~î8~
~ 7 - 60SI-352
hours wherein said intermediate product is maintained
at the reflux temperature of said organic solvent during
said addition of said alcohol to produce in at least 75%
yield a silyl fumarate of the formula, 3
,Ra
(6) lRa R5 C-C-O-R -CH2-CH2Si(OR )3-a
(R O)3 aSi CH2-CH2-R -o-C-C~R5
where R2 and R3 are monovalent hydrocarbon radicals of 1
to 8 carbon atoms, R is selected from hydrogen and mono-
valent hydrocarbon radicals of 1 -to 8 carbon atoms, a
varies from 0 to 2, X is halogen and preferably chlorine,
and R6 is a divalent hydrocarbon radical of 1 to 8 carbon
atoms.
Yet another embodiment of the instant invention
provides a process for producing s.ilyl succ:inates
comprising (a) reacting a silyl succinate o~ the formula,
o
O ~ a
R - CH - C - O - R' - CH - CH
(7)
R - CH - C - O - R - CH = CH2
o
R3
.a
with (8) H-Si-X3 a in the presence of a platinum catalyst
and (b) then reacting the intermediate silyl product with
an aliphatic alcohol of the formula R2OH where said inter-
mediate product is present in an organic solvent and
where said aliphatic is added to said intermediate product
slowly over a period of at least six hours wherein said
intermediate product is maintained at the reflux
temperature of said organic solvent during said addition
to produce in at least 75% yield a silyl succinate of
,~6~ ~
~.~,
39~
- 8 - 60SI-352
the formula,
R3
R - CH - C - O - R - CH2 - CH2Si(OR )3-a
(9)
R - CH - C - O - R - CH2 - CH2Si(oR2)3
R
a
where R2 and R3 are monovalent hydrocarbon radicals of
1 to 8 carbon atoms, R is selected from hydrogen and
monovalent hydrocarbon radicals of 1 to 8 carbon atoms,
a varies from 0 to 2, X is halogen and preferably chlorine,
and R9 is a divalent hydrocarbon radical of 1 to 8 carbon
atoms.
Still, another embodiment of the present lnvention
there is provided a process for producing silyl phthalates
comprising (a) reacting a phthalate oE the formula,
o
C - O - R - OEI = CH2
(10~ R ~
C - O - R - CH = CH2
R3
la
with (11) H~Si-X3 a in the presence of a platinum catalyst
and (b) then reacting the intermediate silyl product with
an aliphatic alcohol of the formula R2OH where sai~
intermediate product is present in an organic solvent
and where said aliphatic alcohol is added to said
intermediate product slowly over a period of at least
six hours wherein said intermediate product is maintained
at the reflux temperature of organic solvent during
said addition to produce in at least 75% yield silyl
phthalate of the formula,
- 9 - 60SI-352
O la
~ C - O - R - CH2 -- CH2 - Si(OR )3 a
(12) R ~
\ C - O - R10 - CH2 -- CH2 - I (OR )3-a
where R and R3 are monovalent hydrocarbon radicals of 1 to
8 carbon atoms, Rll is selected from hydrocarbon halogen,
nitro and hydrogen, a varies from O to 2, X is halogen, and
preferably chlorine and R10 is a divalent hydrocarbon
radical of 1 to 8 carbon atoms. The silyl maleate inter-
mediate product identified in the above reaction has the
following formula, R3
" 1 l a
(13) R - C - C - O - R - CH2 C~l2 3-a
R - C - C - O - R - CH2 - CH2 - SliX3_a
R3
The silyl fumarate intermediate product has the formula,
(14) o IRa
iRa R - C - C - O - R - CH2 - CH2 - SiX3
3-a 2 2 "
The silyl succinate intermediate product has 3the following
formula, O la
R8 _ CH - C - O - R9 - CH - CH - SiX
(15~ 1
" R - CH2 - CH2 - SiX
R3
The silyl phthalate intermediate product has the following
formula,
.......
~L~8~
- 10 - 60SI-352
(16) R3
O la
~ C - O - R - CH2 - C~I2 - Sl X3 a
R 11 _~
C - ~ - R - CH2 - CH2 - Si X3 a
O 3
Ra
In the above formulas, R~ and R3 can be any monovalent
hydrocarbon radical of 1 to 8 carbon atoms. Preferably
such radicals are selected from alkyl radicals of 1
to 8 carbon atoms such as methyl, ethyl, propyl, etc.;
cycloalkyl radical such as cyclo hexyl, cycloheptyl; mono-
nuclear aryl radicals such as phenyl, methylphenyl,
ethylphenyl, etc., haloalkyl radicals such as 3,3,3-
trifluoropropyl, etc.; and alkenyl radlcals such as
vinyl, allyl, etc. More preferably R2 and R3 are selected
from alkyl radicals oE 1 to 8 carbon atoms ancl phenyl
radicals. The radicals R and R8, R5 and can any oE the
radicals disclosed above for R2 and R3 and in addition
can be hydrogen. More preferably the R, R5 and R8
radicals are selected from alkyl radicals of 1 to 8
carbon atoms and phenyl. The R11 radical can be any
hydrogen radical preferably chlorine, nitro or hydrogen,
most preferably it is hydrogen or an alkyl radical of 1
to 8 carbon atoms. The radicals Rl, R , R and R are
any divalent hydrocarbon radicals of 1 to 8 carbon atoms
and more preferably are alkylene and arylene radicals
of 1 to 8 carbon atoms. In the above formulas, a varies
from O to 2 and is most preferably 0. Accordin~ly, in the
most preferred compounds of the instant invention there
are three alkoxy radicals per silicone atom. I-t should
be understood there can be as little as one alkoxy
radical per silicone atom in the compounds in the instant
case. In the most preferred case there are three alkoxy
radicals per silicone atom since that gives -the products
o~
60SI-352
-- 11 --
with the best self-bonding properties or the best self-
bonding properties to room temperature vulcanizable
silicone rubber compositions. In the description below,
the description refers specifically to the production
of the silyl maleates of Formula (3). However, it should
be understood that process conditions and other process
limitations defined for the silyl maleates to be disclosed
below applies to the production also of the other silyl
compounds such as silyl fumarates, silyl succinates, and
silyl phthalates. In the first reaction oE the instant
process when X is preferably chlorine, trichlorosilane
is reacted with the olefinic maleate of Formula (1) in
the presence of a plantium catalyst. Preferably the
reaction is carried out in the presence of an organic
solvent which results in more intimate contacting of
the reactants. Any organic solvent may be utilized and
preferably there are utilized aliphatic hydrocarbon
solvents, aromatic hydrocarbon solvents such as heptane,
pentane, hexane, cyclohexane, xylene, toluene. The
most preferred solvents being toluene or hexane. Bxamples
of other organic solvents that may be utilized are as
follows: ethylether, dimethoxyethylether, methylene
chloride, carbontetrachloride, chloroform, dioxane,
pentane, hexane, heptane, octane, cyclohexane, benzene,
toluene, xylene, chlorohenzene dichlorobenzene, trich-
loroethane, etc.
When reference is made to an organic solvent, it is
understood that any of the above solvents may be utilized
in the process of the instant case. The platinum
i 30 c~ alyst~t~at may be utilized may be solid platinum
dssFx~t=~ in charcoal or solid platinum deposited on
gamma alumina. Most preferably the platinum is a
solubilized platinum catalyst such as that disclosed in
Lamoreaux U.S. Patent No. 3,220,972 dated November 30,
36 1965.
The reaction temperature can be anywhere from room
60SI-352
- 12
temperatu to 150C and preferably the reaction is carried
~ e ~ o
out at e~ee~ed temperature of anywhere from 50 to 100 C.
If the temperature is raised too high, the reaction is
difficul-t to control and if i-t is too low the reaction does
not go at a sufflcient rate. It should be pointed out
that the pressure can be utilized at this part of the process
but it is not necessary. Accordingly, even -though pressure
could be utilized in the first step of the process, it is
preferably not utilized since it does not serve a real
useful purpose. It does not offer any additional advantages
and necessitates the use of pressure equipment. It should
be noted that the trichlorosilane is preferably utilized
at a concentration of 10 to 30 percent in excess since that
helps to push the reaction to completion as far as the
maleate of Formula (1) is concerned and results in the highest
yield of desired product o:E silyl maleate intermediate product
of Formula (13). In this hydrosilation reaction, SiCl~ is
formed as a by-product. The product o.E SiC14 with
methanol is very toxic and can cause blindness. Accordingly,
before it is desired to carry on the alkoxylation of the
chlorine groups in the silyl maleate it is necessary to remove
all of this SiC14 foreign byproduct. To do this, an organic
solvent is added in additional amounts such as 25 to 300
percent by volume of the reaction mixture and SiC14 is
distilled out or refluxed out along with the solvent. The
preferred solvents for doing this is toluene or xylene.
Accordingly, by adding toluene and heating the mixlng in
excess of 100C there is formed an azeotrope o:E toluene and
SiC14 from the silyl maleate intermediate product o:E :Eormula
(13). It should be noted that the azeotrope is removed by
refluxing the reaction mixture in which the additional
solvent is added. It should be noted that the additional
solvent does not have to be added if there is sufficient
solvent added in the initial part oE the reaction.
However, if such solvent has not been added or if an
9~s~
60SI-352
- 13 -
insufficient amount of solvent has been added to the
reaction mixture then additional amounts of solvents can
be added as pointed out previously and the SiCl~ is
refluxed out along with the solvent. Preferably a
solvent is added to form an azeotrope with the SiC14
so that azeotrope can be refluxed out off the reaction
mixture to get rid of the SiC14. A preferred solvent
Eor this purpose is toluene; however, any other solvent
that forms an azeotrope with SiC14 may be utilized.
Reflux temperature of this azeotrope is above 100C and
is in the range of 100 to 130C. The refluxing is
preferably at atmospheric pressure to remove the SiC14
through this procedure. This refluxing out of this
SiCl~ usually takes place over a period of time from
anywhere from 1 to 6 hours. The first part of this
process, the hydrosilation reaction or addition oE th~
trichlorosilane to the silyl maleate of Formula (1) takes
place in anywhere from 1 to 3 hours. Af-ter this reaction
and removal of the SiC14 is comple-ted there is left in
the reaction mixture the intermediate of Formula (13).
It should be pointed out that the whole process may be
carried in a single reaction vessel and there is left
in the single vessel, the silyl maleate of Formula (13)
and the organic solvent. To this mixture is added an
alcohol and most preferably an aliphatic alcohol of 1
to 3 carbon atoms and most preferably the alcohol is methanol.
, ~b 50% to 300% by weight of excess methanol is added to
a reaction mixture so as to be sure to drive the meth-
oxylation or alkoxylation reaction to completion. It
should be noted here that the aliphatic alcohol of 1 to
8 carbon atoms and most preferably methanol is added to
the liquid layer of solvent and silylmaleate intermediate
product of formula (13) so that it will not come in
in contact with the hydrogen chloride by-product to yield
methyl chloride and water; a side reaction which if it
predominates will considerably reduce the yield of the
0.~
- 14 - 60SI-352
desired product of Formula (3).
Another and critical part of the instant inven-
tion is that the methanol or aliphatic alcohol of 1 to 8
carbon atoms is added slowly to -the reaction mixture
in the pot. Normally the total amount of the aliphatic
alcohol will be added over a period of at least 6 hours
and more preferably will be added over a period of from
6 to 36 hours and most preferably from 10 to 24 hours.
The aliphatic alcohol must be added slowly over this
period of time since it it is added too fast it will tend
to produce large amounts of HCl which cannot be removed
fast enough and which large amounts of HCl will react
with large amounts of aliphatic alcohol present to
produce methyl chloride and water by means of the
competing reaction. Accordingly, to keep this side
reaction a minimum it is necessary to add the aliphatic
alcohol slowly to the reaction mixture, speci~ically
to the organic solven-t and silyl maleate :intermedlate
product of Formula (13)slowly over a period of time as
stated previously of at least 6 hours and more pre~erably
from 6 to 36 hours so that a maximum amount of the
desired silyl maleate product in Formula (3) can be
obtained. Another part of the process that should be
carried, to keep the reaction of methanol with hydrogen
chloride to a minimum so that the yield of silyl maleate
intermediate product of Formula (13) ls maximized, is
that organic solvent is heated to a reflux temperature
of the mixture so as to continually distill overhead
an azeotrope of the excess aliphatic alcohol and the
organic solvent in which there is dissolved some
of the hydrogen chloride that is given off by the
alkoxylation reaction. This a~eotrope layer after it
forms in the reflux trap must be removed continually
so as to keep the hydrogen chloride and alcohol from
building up in the reaction vessel. It should be noted
~i8go~
- 15 - 60SI-352
that a minimum of alcohol is needed. The alcohol is
present at 50 to 300 mole percent in excess just as there
was from 10 to 30 mole percent in excess of trichlorosilane
in the first reaction. In ~he second reaction there
must be present at least 50 to 300 mole percent of
aliphatic alcohol so as to drive the reaction to
completion. This is done by the aliphatic alcohol
forming an azeotrope with the hydrogen chloride or
hydrohalogen gas to produce a constant boiling mixture
with the solvent which is then removed in an azeotrope.
It should be noted that the a~eotrope does not appear
usually until 40% of the total amount of methanol that
will be added has been fed to the reaction pot. However,
once the azeotrope layers appears in the reflux tray,
the lower azeotrope is continually removed so as to get
rid of the HCl gas so as to keep tht side reaction of
the aliphatic alcohol with the hyclrogen chloricle to
a minimum, to remove the hydroyen chloride gas away
from the reaction pot so that it will not remain in
the reaction pot and react with the aliphatic
alcohol.
The organic solvent in this last reaction is
preferably toluene but i-t can be any organic solvent
disclosed above and is preferably an aliphatic hydro-
carbon organic solvent and an aromatic hydrocarbonsolvent. It is most preferably hexane or toluene.
During the total reaction period in the second reaction,
the reaction mixture of the silyl maleate of Formula
(13) along with the organic solvent and the added
alcohol which is preferably methanol is maintained at
the reflux temperature of the reaction mixture. Then the
reaction mixture is maintain at a reflux temperature
above 100C and more preferably at a temperature of
above 100 and up to 130C. In this second reaction,
the process is carried out at atmospheric pressure since
~. .~,..
~9~
- 16 - 60SI-352
hydrogen chloride gas and the azeotrope has -to be
removed by refluxing. It should be noted that it is
necessary to use an organic solvent in this second
reaction that will form an azeotrope with the
alcohol and preferably methanol. That is so that
an azeotrope layer can be collected in a reflux trap
and separated out from -the reaction chamber so as to
continually remove the hydrogen chloride gas that
is formed during the alkoxylation reaction. The
reaction period for this second reaction is
basically the time of addition of the methanol and
is accordingly at least six hours long and up to
36 hours and is more preferably from 10 to 24 hours
long. During the reaction the silyl maleate
intermediate of Formula 13, is continually analyzed
to determine how much of this intermed:iate is
still left in the reaction pot and specifically ho~
much silicon chloride bonds are leEt in the reaction
pot. Although the analysis is carried in terms of
hydrogen chloride it is really a measure of the amount
of Si-Cl there is still present in the reactlon vessel
as the silyl maleate of Formula (3). When it is
determined that there is 10,000 parts per million
of SiCl or less, the reaction first is cooled to room
temperature and there is added sufficient tertiary
amine on an alkali metal alkoxide along the methanol
in the reaction pot so as to completely alkoxylate
the SiCl remaining in the reaction pot and to tie
up all of the hydrogen chloride that is formed as
a result of this reaction with tertiary amine.
The tertiary amines that can be used are of the
formula R153N where R15 is alkyl radical or cycloalkyl
radical or an aryl radical of 1 to 8 carbon atoms, most
preferably R15 is an alkyl radical of 1 to 15 carbon
atoms and is most preferably triethylamine. The reason
~,f~
17 - 60SI-352
for the addition of the triethylamine with the stoichio-
metric amount of aliphatic alcohol which materials
are added at a slight access to the stoichiometric amount
necessary is to completely alkoxylate the silyl maleate to
product of Formula (3) and to use up all the HCl that is
given off as the resul-t of the alkoxylation. The tertiary
amine complexes with the hydrogen chloride as the result
of the following reactions that take place as one approaches
the complete alkoxylation of the silyl maleate intermediate
product of Formula (13) in the reaction vessel.
~aSi ~ Cl + MeOH ~ - Si - OMe + HCl
MeOH
o
C - O - ~lCH2CH2 si(oMe)3 ~
~ C -- OMe -~ HO - RlCEl2CH2Si(OMe)3
The reactions above show as one approaches the compleke
alkoxylation of a silyl maleate intermediate product of
Formula (13) the methanol, in -the presence of HCl, will react
with the trimethoxysilylpropoxy group, cleave the group and
replace it with a methoxy group. Accordingly, the addition
of a tertiary amine on alkali metal salt of an aliphatic
alcohol of 1-8 carbon atoms along with the stoichiometric
amount of methanol is to keep this cleavage reaction to a
minimum. It is preferably to keep the cost of the process as
low as possible and that the tertiary amine or alkali metal
alkoxide along with a stoichiometric amount of aliphatic
alcohol be added to the reaction mixture after it has cooled
to room temperature when there is less than 2000 parts
per million of SiCl remaining, when measured as HCl
in the reaction chamber. It should be noted that the
entire alkoxylation reaction could be carried out by
the use a tertiary amine as a hydrogen chloride accepter
which would do away with the parts of the process
~'
60SI-352
- 18 -
which require removal of HCl by the refluxing of the
azeotrope. However, the uses of large amount of tertiary
amine in the process of the instant case result in the
process in becoming very expensive. Accordingly, the
tertiary amine is added at the terminal part of the
entire react.ion so as to keep the cost of the process
to a minimum.
Sufficient tertiary amine is added along with the
aliphatic alcohol and more specifically methanol and
triethylamine until in the reaction mixture there is
left less than 50 parts million of --SiCl. When this
value has been reached then for all practical purposes
most of the _Si-Cl has been converted from the silyl
maleate intermediate product of Formula (13) to the
desired product of Formula (3). Accordingly, then the
organic solvent is distilled oEf by vacuum di.stillation
and the final product is filetred so as to removed
the tertiary amine chloride salts by filtration to
yield the desired product in at least 75~ yield. This
75% yield is an overall yield. The yield in accordance
with the instant invention in the first part of the
process is 88%, the yield in the second part of the
process is at least 85% and the overall yield of the
two processes or of the two reaction is at least 75%
and more preferably at least 80%. In order that the
instant invention be applied to produce silyl furmate
of the formula as disclosed above, silyl succinates and
silyl phthalates as disclosed above, the same process
conditions as was given with respect to the production
of the silyl maleates of Formula (3) are utilized.
The only changes are those carried by the different
materials. Accordingly, the reflux temperature will
be different for the produc-tion of these other compounds
and also the reaction temperature will vary and the
reflux temperatures will vary as solvents other than
toluene are utilized. It should be noted that the
3B~
60SI-352
-- 19 --
reflux temperature of the particular reaction will vary
depending on what organic solvent is used and depending
on what the reactant or intermediate product in the
reaction is. Also, the amount of azeotrope to be
removed during the process may vary depending on the
alcohol used. It is expected that the amount of
azeotrope seen will be directly proportioned to the
reactivity of the alcohol with HCl. That is, the greater
the tendency of the alcohol to form water and alkyl halide
the more azeotrope will be observed. In other respects,
the process conditions should stay the same. The examples
given below are given for the purpose of illustrating
the present invention. They are not given for any purpose
of setting limits and boundaries to the instant invention.5 All parts in the examples are by weight.
Examples 1 - :L7
To a 5,000 mL, three~necked Elaslc was attached a
thermometer, a mechanical stirrer, a 2,000 mL dropping
funnel and a Dean-Stark azeotrope trap with a water-
cooled condenser attached. To the flask was added880 parts (2 moles) of bis(3-trichlorosilylpropyl)
maleate and 1320 parts (1524 mL) of anhydrous toluene.
To the dropping funnel was added 1029 parts (32.2 moles)
of anhydrous methanol. The dropping funnel was
adapted so that the methanol was added below the surface
of the solution. The solution in the flask was heated
to reflux and the addition of methanol was started.
After approximately 30 - 40% of the methanol was added,
the liquid in the azeotrope trap s~r ted forming two
layers. The rate of methanol addition was adjusted so
that the pot temperature did not fall below 105C.
The bot~om layer in the azeotrope tape was continuously
removed without allowing any to return to the reaction
mixture. This solu1tion contained methanol, HCl, H2O
and a small amount of toluene. The upper layer in the
trap was mostly toluene with a small amount of methanol.
~1~90~1
60-SI-352
- 20 -
When the layers in the azetrope trap become one phase,
the toluene reflux to the trap was continuously removed
while the balance of the 200% excess methanol was
added. At the end of the addi~ion, the reaction mixture
was cooled to less than 25C and analyzed by titration
for parts per million unreacted Si-Cl. Based on the
titration value, the reaction mixture was neutralized
with a 50~ solution of triethylamine in methanol.
The solvent was then removed by distillation, preferably
using vacuum to prevent the temperature from rising
above 90C. The residue obtained was cooled to room
temperature and filtered through Celite 5~5, a diato
maceous earth. The yield was 680 grams ~77%). Results
from preparation of other bis (3-trimethoxys.ilylp.ropy:L)
diesters are shown in Table 1.
Examples 2 through 17 was carrled out in the same
manner as Example 1. The results of these Examples and
the process conditions are set in Table 1.
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