Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
- ~ ~726~g
-- 2
DESCE~IPTI ON
This invention relates to the manufacture
of alkyl silicates by the catalysed reaction of
silicon or silicides with an alcohol and is a develop-
ment o~ the invention, hereinafter called the previous
: invention, set out in EPC Application No, 79 300 542
published under the number 0,004,418 on 17th October
1979. This published specification is primarily
concerned with the production of ethyl silicate,
We have discovered that, when a metal alkoxide
correspondiny to the alcohol AOH is used as a catalytic
agent, substituted alkoxysilanes containing the group
_ SioA are produced. The present invention proposes
a method of increasing the yield of the substituted
alkoxysilanes which products have industrial applica-
tions,
~`
: Thus according to the present invention
:~ ~ there is provided a method of manufacturing alkoxy-
~ silanes of the type (Ro)nsi(oA)4 n where R is Cl - C6
:
: 20 alkyl, preferably ethyl, A is -C2H4OCH3, -C2H4OC2H5;
C H OC6H5, -C2H4oc2H4ocH3; -C2H~Oc2H4oc2Hs- 2 4 1 2
where Rl and R2 are Cl - C4 alkyl and n is 1, 2, 3 or 4,
~: ~ by reacting together the alcohol ROH and silicon or a
silicide in a catalytic solution containing a
~;
~ 1726
- 3 -
metal alkoxide corresponding to ~he alco~ol AOH,there be-
ing preferably at least 500 ml of catalytic solution
for each mole of silicon or silicide, thereby having
sufficient thermal capacity effecti~ely to maintain
a temperature to catalyse the rsaction and to dis-
char~e as a product a'~oxysilanes as vapour to-
Oether ~ith the alcohol vapour and hydro5en gas.
~he method of the invention is charac-
; terised by ~he step of mixing with the alcohol
ROH a quæntity of the alcohol AOX~ This mixinO
step si$nificantly increases the yield o~ the
s~bstituted alkoxysilane in the product which also
co~ta~ns the u~s~x~ituted~tra~o~ysi~LQ ~C~. It should
be noted that the use of 10~o AOH as the starting
; 15 alcohol would not proàuce a 10~/o yield o~ the alkox~si-
lane Si(OA)4 but a mixed product. In fact approxi-
. ~ .
matel~ 5% AOH, 95% (molar ratios) ROH provides a
! ~
notably increased yield of substituted product as
compared to a 100% ROH starting material. Up to
about 50/c AOH can in certain circumstances be
used.
.~ .
~ i 7~649
The reaction between the alcohol and sili-
con or a silicide is carried out at high tempera-
ture in a catalytic solution which has su~ficient
thermal capacity t~ maintain the reaction tem~er-
ature and to catalyse the reactio~ and to dischargethe alko~ysilæne products as a vapour to$ether,
with the alcohol va~ou~ and hydrogen ~as. The
; thermal capacity o~ ~he catalytic solution can ~e
; . maintained and indeed increased by stepwise
additions of the alcohol æ~d silicon or 2 silicide,
~ ~ then the alko~silæ~e ~ro.ucts are re~oved as
;~ vapour ænd the secuence ~epeated.
he term silicide is intended to
cover aàditionally to the ~e~allic silicides
,
carbon silicide more usually called silicon
carbide~
The necessary thermal capacity is
achieved by :
(a) :carrying out the reaction at as high
, ~
~ .
~ .
.
'
,
~726~9
. .
a temperatuxe as is practicable~ .
(b) maintaining a relatively large volume
of catalytic solution, that is metal al~oxide in a
sol~ent, a~ least 500 ml per mole of silicon,
(c) selecting an appropriQ~e solvent.
F-eferred solvents are linear oligomeTs
; of the followin~ general formula I:
.
:: I _ _ I where n lS 1 or
~ - Si - O - Si - O - Si - ~ a whole number
: ; 1 o L ~ n l greater than 1
:~ :
~0~ ~ A I
or cyclic compounds of the general formula II :
_ .
: A where n is 3 or
::~ _ O - Si- - a whole number
~; 15 ~ ~~ n greater than 3
FORMUI~ II
:
.. .
.
~ 11 72`B~l~
6 --
A is CE3; OR where R is C1 - C4 alkyl preferably
eth~l; O(G~2CX20)mD where D is meth~l, ethyl or
phen~l and m is 1 or 2. Preferably all the A
groups ære the sa~e in-each compound~ 3 is
t~e s~e as h and when ~ s C~3, 3 can also
be C6E5 when ~ is OR or O(CF2CH20)~D,
the solvent m~y also contain Sih~ and/or ~3Si-O-Si~3
s~ecies, provided that the-e lS not mo-e than 20Yo by
we~ght of SiA4 and 4~/o by ~eight of A~Si-O-Si~3.
~en A is C~3, the sol~-ent may also contain not more
than 20% by weight of Si(OR)4 and/or Si [O(C-~.2CE20)
~;~ species. When ~ is C~3 and 3 is C6H5 the solvent
may also contain no~ mc~e than 6~/o of Si(OR)4
; species, R belng preferably ethyl~
:
~he sol~et m~- also com~rise a mixture of
components having differen~ h ~roups and it may also
~ ~ be a mixture of cyclic and linear polymers.
; ~ Examples of suitable solvents are the
methyl polysiloxanes and the methyl phenyl poly-
siloxanes, which may be linear or cyclic, also the
;~ ethoxypolysiloxanes~ ~etraethoxysilane and technical
ethyl silicate are other suitable solvents, one
exa~ple of the latter being described in ~ritish
.
~ '
.
~ ~ 7~4~
Pa~ent No. 67~,137. Another suitable solvent is
the alkoxysilane reaction product.
The catalyst comprises at least one
metal alkoxide corresponding to the alcohol 4C~
in solution in a solvent defined as abo-~e. ~he pre-
ferred meval alkoxides are the alkali metal
alkoxides. A mi}~vure of the sodium alkoxide a~d
the ?otassium alkoxide is advantageous. We have
now disco~rered ~hzt the metal alko~:ide, preferred
in vhe pre-~-ious inveltion, is essent-al to pro-
;~ duce the substituted al~oxysila~es. It ~ill be
appreciated that the ~lkoxide has a reacvion func-
tion 2S We11 aS a catalytic and is consumed to a
certain extent~
15The reaction ma~ be carried out using
batches of reagents or ay be 5! arted with batches
of reagents and then ~aintained by ccntinuous addi-
tions of the alcohol ~nd silicon or silicide to a
relatively large volume of the catal~tic solution~
: ~
A pre~erred expedlent 1S to introduce the reagents
below the surface of the solution preferably near
the bottom OL the reaction vesselO When the reagents
are not preheated, on ent~y they i~itiall~ lower the
~temperavure of the solution and then commence their
:
.
~ ' .
~ ,726~g
catalysed reaction As the reagents rise through the
catalytic solution the reaction proceeds until the
mixture of alcohol and products is vapourised with
a considerable loss of heat. The large thermal
capacity of the volume of the catalytic solution at
elevated temperature readily provides that heat. The
rate of reaction can be monitored by measuring the
rate of evolution of hydrogen. Alternatively, the
- alcohol (or mixture of alcohols) can be introduced
as a vapour
The product of the process is an alkoxy-
silane (a silicon ester) of the formula (Ro)nSi(oA)4 n
where n is 1, 2, 3 or 4. The unsubstituted tetra
alkoxysilane Si(oR)4 which inevitably forms part of
the reaction product is, of course, the case when
~; n = ~ The present invention also proposes converting
the product to a mixture of alkoxypolysiloxanes by con--
trolled hydrolysis and condensation-pol~merisation,
thereby increasing the silica equivalent~ Thus
when the product is tetraethoxysilane it can be
converted by controlled hydrolysis and condensation-
polymerisation to technical ethyl silicate, which
is a mixture of tetraethoxysilane and ethoxypoly-
; siloxane oligomers. The preferred technical ethyl
~ ~72049
silicate contains silicon equivalent to approxi-
mately 4~o by weight SiO2o
The substituted alkoxysilane products which
characterise the present inventlon can be used in
the binding of refractory powders and paint pig-
ments. On hydrolysis, the p-oducts form a hydrolysate
whivh gels, usually with the aid of a catalyst, to
provide a rigid and coherent gel. Slurries of re-
fractory powder and a gellable hydrolysate can thus
be formed to the recuired shape either by cavity or
pattern ~oulding and 'hereafter set in this shape
by gelllng of the hydroIysateO A paint for anti-
corrosion applications can be made by dispersing
zinc dust in the hyàrolysate. ~or this use the
hydrolysate is preferably prepared from an alko~-
silane pro~uct rich in the (RO)n Si(Oh)4 n
species according to the in~Tenvion ~Jhere n is 1,
:
2 or 3, ~he reason for this is that the hydrol~sis
products are less volatile due to their higher
molecular weight.
The invention will now be described by way
of the following speci~ic examples:-
~; .
~' ' . .
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~ r,
i i~2649
- 10 -
General Notes to Examples
Moisture must be rigorously excluded.
Reactions are commenced in an atmosphere of dry
nitrogen. Dry alcohol must be used, the procedures
for drying are given in Example 1. The rate of
reaction may be followed by measuring the rate of
hydrogen evolution, This is used to control the
rate of addition of reactants to maintain optimum
reaction rate, Usually silicon (or silicide) is
added in batches and alcohol added dropwise, or
a silicon/alcohol slurry added, when the observed
rate of hydrogen evolution diminishes to a low
value, The reaction temperature is maintained
as constant as possible,
A - Metal alkoxide preparation
METHOD 1
2-Ethoxyethanol (290 ml, 2.9~ mole) was
introduced into a flask fitted with a reflux conden-
: ser and nitrogen inlet. The vessel was flushed with
nitrogen and potassium (19g, 0.5 mole) was slowlyadded over a 3 hour period, followed by sodiu~
(11.5g, 0.5 mole). The mixture was refluxed for 4
::
-,~
:
'~
` g ~ 7~4g
_ 11
.
hours until hydrogen evolution ceased. ~he initial
solution was pale yellow but turned deep red after
2 hours~
METHOD 2
Using the apparatus and proceaure of
Method 1, to 2-etho~ethænol (180 ~l, 1.75 mole)
sodium (5.58g, 0.254 mole) was slowly added, fol-
lowed by potassium (9.42g, 0.242 mole) and the re-
sulting mixture refluxed for two hours.
.
,: 10 rrF~mHOD 3 ~
Sodium (7.4g, 0.311 mole) was slowly
added to 2 ethoxyeth~nol (170 ml, 1.75 mole) and
~: :
the resulti~g mixture reflu~ed for 1 hour. In a
separate vessel, potassiu~ (13g, 0.33 mole) was
slowly added to 2-ethoxyethanol (160 ml, 1.65 mole)
ard the resulting mixture ref1uxed for 1 hour. The
two solut1ons ma~ be combi~ed for use, or used
individuall~.
METHOD 4
Toluene (40-50 ml) was placed in a flask
- 12 -
fitted with a reflux condenser, nitrogen inlet and
dropping funnel, whose lower end was under the
toluene. The flask was flushed with dry nitrogen
which was passed through the flask -throughout the
course of the reaction. Potassium (19g, 0.5 mole)
was added, then 2-ethoxyethanol (160 ml, 1~7 mole)
was slowly added dropwise When the potassium had
reacted, sodium (11,5g, 0 5 mole) was added, then
further 2-ethoxyethanol added dropwise until a
total volume of 300 ml was added. The solution was
warmed and toluene distilled off at 121C, ~he
remaining solution was refluxed for 4 hours. The
2-ethoxyethanol can also be added to sodium and
potassium metals concurrently.
~ 15 METHOD 5
- Using the apparatus and procedure of
Method 1, dry ethanol (100 ml, 1.77 mole) was
:
~used to dissolve sodium (4.75g, 0.207 mole) and
;~ potassium (9,29g, 0,238 mole) which were slowly
~; 20 added in the order given. The mixture was refluxed
for two hours, then used immediately, Sodium and
potassium may be dieeolved in ethanol individually.
;
~ 37~6~
- 13
: ME~OD 6
A 2 litre, 5 necked flas~, fitted with
a partial take-off head, mechanieal stirrer,
dropping funnel, the~mometer and nitrogen inlet
was ~lushed ~ th nitrogen after introducing a
solutio~ comprising technical eth~l silicate (4~b
SiO2 w/w - 110 ~l) ~nà dry ethanol (46g - 1 ~ole).
To this solution was added ~otass um(5.5g, 0.14
~; mole), then sodiu~ (,.2g, G~16 ~ole). ~he mixture
~0 was war~ed fcr 3 hours to give the ca..alytic
solution.
ME~HOD 7
: . ~ Using ~he procedure of Method 1, methyl-
digol (200 ml, 1.70 mole) was used as solvent for
sodium (5~67g, 0.247 mole), then for po~assiu~
(9.65g, 0.247 mole)~
ME~HOD 8
~: Using the procedure Or Method 1~ 2-phenoxy- -
~ ethanol (250 ml, 1.99 mole) was used as sol~rent for
:~: 20 sodium (5~66g, 0.246 mole) and for potassium
~ (9.82g, 0.252 mole).
~ ', , .
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~ ! 726~9
- 14 -
METHOD 9
Using a flask fitted with a reflux con-
denser and dropping funnel, sodium ethoxide
solid (NaOEt . 2EtOH, 83~6g 0.54 mole) was
dissolved in 2-ethoxyethanol t250 ml, 2.58 mole),
which was added dropwise over a period of 2 hours.
There was a very exothermic reaction, giving a
liquid mixtureO The dropping funnel and reflux
condenser were removed and replaced by a distillation
head and condenser. The mixture was heated under
reduced pressure (100 mm Hg) and 102 grams distillate
collected over 2 hours. This distillate comprised
ethanol 41 parts and 2-ethoxyethanol 59 parts. The
residue was used in the preparation of mixed alkoxy-
15 silanes (Eto)nSi(OCM2CH2OEt)4 n~; n = 4, 3, 2, 1.
METHOD 10
Using the procedure of Method 2, ethyldigol(190 ml, 1~4 mole) was used as solvent for sodium
(5,80g, 0.252 mole) and for potassium (9.83g, 0.252
-20 mole).
.~
~ l 72~9
- 15
ME~HOD 11
Using the procedure of Me~hod 2, 2-di-
methylaminoethanol (125 ml, 1.21 mole) was used as
solvent for sodium (4.84g, 0.21 mole) and for potas-
sium (9.70g~ 0.25 mole).
~ - Production oD Alkoxysilanes
-- .
.
~ EX~lPLE 1
... .. ~
A 2 litre~ 5 nec~ed flask fit~ed witn a
partial take-off heaà, mechanical stirrer, ~ropping
funnel and nitrogen gas inlet was flushed with ni-
trogen. Then 170 ml of meual alkoxide solution
prepared as described in Method 2 was adàed, to-
ge'her with 340 ml of tetraethoxysil~ne to form the
catalytic solution. 14g of siliccn powder, average
15 particle size 50 - 80 microns, composition 9~/o Si,
3% ~e, were added, i.e. 51Q ml catalytic solution/
~ mole silicon. Then 30 ml dry ethanol were added.
;~ The ethanol mus~ be dried prior to use either by
treatment with a molecular sieve (eOg. ~inde type 3~)
or by distillation o~er sodium or magnesium. ~he
mixture was heated by an electric heating mantle.
;,': .
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- 16 -
When the reactor temperature reached 120C, the
distillation head temperature rose to 90C. ~fter
80 ml distllla-te (mixture of ethanol and alkoxy-
silane) was collected, the distillation head tem-
perature fell to ambient and the reactor tempera-
ture rose to 150C, at which temperature it was
maintained for the remalnder of the reaction period.
~he reaction was monitored b~ measuring the rate of
hydrogen evolution. Fu~ther reactants were added
;lO when the rate fell to less ~han 30 ml/min. Silicon
was added in batches of 7 or 14 grams, ethanol (dr~)
belng added dropwise at a rate such that the reactor
temperature remained at 150C. The reaction was run
in this way for 26 hours. A total of 70~2~14 mole)
silicon was added, 93% belng converted to alkoxy-
` sil~e. The average rate of production of alkoxy-
silane was 18g/hour. The final reaction mixture was
distilled at atmospheric pressure to recover pure
alkoxysilane.
EX~MPLE 2
180 ml of metal alkoxide solution prepared
b~ Method 1 was added to 500 ml of technical ethyl
,
~ ~ 7 ~
17 -
'
silicate to form the catalytic solution. To
this was added 12 grams of silicon (i.e. 1587 ml cat~
alytic solution/mole silicon) and 303O5 gr~ms
(6.6 mole) dry ethanol. ~he mixture was heated for
3 houh~s at 70 - 80C then the temperature was raised
to 120C~ 580 ml of distillate (b~82-90C) being
collected. ~he temperature W2S raised to 145C
and a 4: 1 molar ra~io slurry of ethanol : silicon
addeà. The reaction ~e~perature rose ar.d vJas main-
10 tained in the temperature r~nge 165 190C by ad-
justing the rate of addition of the slurry. Distil-
~' late (b.115-130C) was collected at the rate of about
90 ml/hour during the 40 hours which the reaction
was run, a total of 3500 ml being collected. Frac-
tionation at atmospheric ~ressure gave 750g pure tetra
ethoxysilane b. 168 - 170C. ~he purity was con-
firmed by the IR spectrum.
:
EXAMP~E 3
o the catal~tic solution prepared in
` 20 ~lethod 6, silicon (6~, 0.21 mole, i.e. 798 ml catalvtic
solution/mole silicon) was added. Distilla~e was re-
moved u~til the reactor temperature reached
.
~ 172~9
- 18 -
145C, then a slurry of ethanol/silicon (molar
ratio 4 : 1) was added. The reactor temperature
rose to 165C and was maintained in the range 165 -
190C by adjusting the rate of addition of the
ethanol/silicon slurry. The reaction was carried
out for 5 hours, during which time 225 ml of dis-
tillate (b, 130 - 156C) was collected. Fractiona-
tion of this mixture gave 125g pure tetraethoxysilane,
The purity was confirmed by the IR spectrum,
EXAMPLE 4
To the metal alkoxide solution prepared
as in Method 5 was added 450 ml of the alkoxysilane
product of Example 2 to give the catalytic solution,
Then 14g silicon powder, average particle size 50 -
15 60 microns were added, i.e. 1100 ml cataIytic
solution~mole silicon. Following the procedure of
Example 1, 56g ~2.0 mole) silicon and 425 ml (7.5
mole) dry ethanol were added over a period of 22 1/2
hours, the reactor temperature being maintained
' 20 between 150 - 160C. The percentage conversion of
silicon to product was greater than 95% and the
production rate was 20.5 grams/hour. The product
~ ~728~9
- 19
was purified as described in Example 1
EYI~IP~ 5
~ o 170 ~l o~ the metal alkoxide solution
prepared as described in l~e~hod 7, 3~0 ml of tetra-
ethox~s lane were added to prepare the catalyticsolution. ~o this was added 1~ grams of sili^on
powder, average particle size 50 - 50 microns,
i.e. 893 ml catalytic solu~ion/mole silicon, t;~en
30 ml d~y ethanol. The mix~ure W2S heated to 150C
and maintained in the tem?erature range 150 ~ 160C
during 231 hours, in which time 44g (1.7 mole)
silicon a d 330 ml (5.85 mole) dry ethanol were
added. The percentage conversion of silicon to
product was greater than 95% and the production rate
-
was 16.1 grams/hour.
EX~iPLE 6 `
:
To 250 ml of the metal alkoxide solutio~
prepared as described in Method 8, 340 ml of tetra-
ethox~silane were added to prepare the catalytic solu~
tion. To this was added 16 grams of silicon powder,
average particle size 50 - 60 microns, i.e. 1033 ~l
.
~ ~ 72~
- 20 -
catalytic solution/mole silicon, then 30 ml dry
ethanol. The mixture was heated as described in
Example 1 and maintained at a temperature of 150 -
190C during 13~ hours. In this time 18g (0.64
mola) of silicon and 130 ml (2.3 mole) dry ethanol
we~e added. Tha pe~centage converslon of silicon
to product was 66% and the production rate was
6.~ grams/hour.
. , .
~X~L~ 7
To 350 ml of metal alkoYide solution
preparad as described in Method 1 was added 500 ml
technical etnyl silicate to prepa~e the catalytic
solution. ~hen 21g of ferrosilicon powder, average
particle size 50 - 60 microns was added, i.e. 850
ml catalytic solution/mole silicon, together with 50
ml dry ethanol. ~ollowing ~he procedure of rxample
1, a further 72.5g ferrosilicon (2.5 mole~ and
46~2 ml dry ethanol (1206 mole) were added over 50
hours, the temperature being maintained at 160-180C~
The percentage conversion of silicon to product was
greater than 95% and the production rate was 10 grams/
hour.
,'
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~ 1 7~
~ 21 -
EXAMPLE 8
To 290 ml of metal alkoxide solution pre-
pared as described in Method 1 was added 700 ml
tetraalkoxysilane prepared as described in Example
1, to give the catalytic solution 21 grams of
ferrosilicon (1 mole Si), average particle size
50 - 60 microns, were added i e, 990 ml catalytic
solution/mole silicon, together with 50 ml dry
ethanol. Following the procedure of Example 1, the
reaction was carried out for 34 hours at an average
temperature of 148C. The percentage conversion of
silicon to product was greater than 95% and the
production rate was 34 grams/hour,
EXAMPLE 9
_ _
A catalytic solution was prepared by
mixing 150 ml of a metal alkoxide solution prepared
according to Method 1 with 250 ml of a polymethyl-
phenyl siloxane (Dow Corning 550 fluid)o 7 grams
(0,25 mole) of silicon, average particlP size 50 -
60 microns, were added, i.e. 1600 ml catalytic
solution/mole silicon, Dry ethanol (S0 ml) was added
and the mixture was gently warmed, being maintained
~ ~7~6~
_ 22
between 90C and 130C during the reaction (10
hours). Alkoxysilane product was produced at
rates between 11 and 56 gram/hour, depending on
the reaction temperature.
EXAMPLE 10
,~
A catalytic solution was prepared by
mixing 150 ml of a metal alkoxide solution prepared
according to Method 1 with 125 ml of a polymethyl-
phenyl siloxane (Dow Corning 550 fluid) and with
125 ml tetraethoxysilaneO 7 grams (0 2S mole) of
silicon, average particle size 50 - 60 microns,
were added, i.e. 1600 ml catalytic solution/mole
silicon. Dry ethanol (50 ml) was added and the
mixture was gently warmed, being maintained between
90C and 130C during the reaction (10 hours).
Alkoxysilane was produced at rates between 11 and
112 gram5/hour, depending on the reaction tempera-
; ture,
EXAMEZLE 11
In the preceding Examples, the volume ratio
of solvent to metal alkoxide solution, giving the
~ 11 726~9
_ 23 -
catalytic solution is 2 : 1 or greater. In this
Example, the catalytic solution used has a volume
ratio of solvent to metal alkoxide solution of
1 : 2.
The procedure followed is as described in
Example 1, The metal alkoxide solution is prepared
as described in Method 1. The catalytic solution is
made by adding to 350 ml of metal alkoxide solution,
prepared as described in Method 1, 170 ml of
alkoxysilane prepared as described in Example 1.
To this catalytic solution is added 14g (0.5 mole)
silicon powder, average particle size 50 - 60 microns,
i.e. 1040 ml catalytic solution/mole silico~, together
with 30 ml dry ethanol. The mixture was heated to
15 150C and the reaction was carried out for 14 1/4
~; hours. During this time 43.75 grams (1.75 mole)
silicon and 410 ml (7.27 mole) dry ethanol were
~; added. The percentage conversion of silicon to
product was greater than 95% and the production rate
was 34 grams/hour,
EXAMPLE 12
A catalytic solution was prepared by adding
350 ml of tetraethoxysilane to 175 ml of metal
.
~: ~
7264 9
- 24
alkoxide solution prepared as described in Method
1. To this catalytic solution is added 14g
(0.5 mole) silicon powder, particle size 5 microns
or less, i.e. 1050 ml catalytic solution/mole
5 silicon, together with 30 ml dry ethanol. The
reaction was carried out as described in Example 1,
; except that the dry ethanol used contained 2% v/v
; toluene. During 19 1/2 hours 61g ~2.1 mole~ silicon
and 450 ml (9.27 mole~ ethanol were added. The per-
centage conversion of silicon was greater than 95%
and the production rate was 44 grams/hour.
EXAMPLE 13
AlkoxysilaneS were prepared following the
- procedure of Example 1, except that ethanol was
lS introduced into the reactor as a 70 : 30 mixture by
- volume of ethanol and alkoxysilane.
` The catalytic solution was prepared by
adding 350 ml of alkoxysilane prepared as described
in Example 1 to 190 ml of metal alkoxide solution
prepared as described in Method 1. To this catalytic
solution was added 14 grams (0.5 mole) silicon powder,
particle size 5 microns or less, i e. 1080 ml catalytic
~:
:;
..~
",~,.~,
~ 172~
- 25 -
solution/mole silicon, together with 30 ml dry
ethanol. The average reaction temperature w~s
137C over a 15 hour reaction period. 43,5g
(1.5 mole) silicon and 275 ml (5.88 mole) dry
ethanol (as the ethanol-alkoxysilane rnixture)
were added. The percentage conversion of silicon
was greater than 95% and the production rate was
23.6 grams/hour.
EXAMPLE 14
:
A catalytic solution was prepared by
adding to 500 ml tetraethoxysilane, 290 ml of metal
alkoxide solution prepared as described in Method 1.
To this catalytic solution was added 15 grams (0,5
mole) silicon powder (95% Si : 5% Fe + Mn, particle
size 50 - 60 microns), i.e, 1580 ml catalytic
solution/mole silicon, together with 60 ml dry
ethanol. The procedure of Example 1 was followed,
giving a percentage conversion of silicon greater
than 95% and a production rate of 35.7 grams/hour.
EXAM_ LE 15
Following the procedure of Example 1,
; silicon powder containing 0.5 - 1.5% Fe, 0.2 - 0.75%
-
.
g ~726~
_ 26 -
Ca and 0 5 - 1 5% Al was used The catalytic
solution was prepared by adding to 400 ml tetra-
ethoxysilane, 200 ml of metal alkoxide solution
prepared as described in Method 1, To this
catalytic solution was added 16 grams ~0.5 mole~
of the silicon powder particle size 50 - 60 microns,
i.e. 1200 ml catalytic solution/mole silicon,
together with 30 ml dry ethanol. The average
temperature of the reactor was 133C. The reaction
was carried out for 12 hours, 28.5 grams of the
silicon and 360 ml dry ethanol being added. The
percentage conversion of silicon to alkoxysilane
was 66% and the production rate was 22 grams/hour.
EXA~LE 16
_
~ catalytic solution was prepared by
adding 1000 ml tetraethoxysilane to 400 ml of metal
alkoxide solution prepared according to Method 1,
To this catalytic solution was added 28g (1 mole~
silicon, particle size 50 - 60 microns, i.e. 1400
ml catalytic solution/mole silicon, together with 70
ml dry ethanol. Following the procedure of Example
;; 1, 156~25 grams of silicon, particle size 5 microns
, j~
, ~, .
- - ~ 17264~
_ 27 -
or less were added together with 1920 rnl dry
ethanol in the course of 45 1/2 hours. The
reactor temperature was maintained at an average
of 148C. The percentage conversion of silicon
was greater than 95% and the production rate was
53,5 grams/hour.
EXAMPLE 17
A catalytic solution was prepared by
adding 600 ml tetraethoxysilane to 300 ml of metal
alkoxide solution prepared according to Method 1.
To this catalytic solution was added 28 grams ~1
mole) silicon, particle size 50 60 microns, i,e,
900 ml catalytic solution/mole silicon together with
50 ml dry ethanol, Following the procedure of Example
16, silicon of 74 micron particle size was used.
The percentage conversion of silicon was greater
;~ than 95% and the production rate was 34 grams/hour,
EXAMPLE 18
A catalytic solution was prepared by
adding 300 ml of alkoxysilane prepared as described
in Example 1 to 175 ml o~ the metal alkoxide product
of Method 8. To this catalytic solution was added
~1
î 1 726~19
- 28 -
14 grams (0,5 mole) silicon, particle size 50
60 microns, i.e~ 950 ml catalytic solution/mole
silicon together with 30 ml dry ethanol. Follow-
ing the procedure of Example 1, the reaction was
carried out for 20 1/2 hours, the mean reaction
temperature being 158C. 28 grams silicon and 230
ml dry ethanol were added. The percentage conver-
sion of silicon was greater than 95% and the
production rate was 10,2 grams/hour.
EXAMPLE 19
A catalytic solution was prepared by adding
340 ml of alkoxysilane prepared as described in
Example 1 to 170 ml of sodium 2-ethoxyethoxide solu-
tion prepared as described in Method 3. To this
catalytic solution was added 14 grams (0,5 mole~
silicon powder, particle size 50 - 60 microns, i,e.
1020 ml catalytic solution/mole silicon, together
with 40 ml dry ethanol, Following the procedure of
Example 1, the reaction was carried out for 22 1/2
20 hours, the mean reaction temperature being 148C, 49
grams silicon and 290 ml ethanol were added, The percen-
; tage conversion of silicon to product was greater
:
,S'
:
~7
- 29 -
than 95% and the production ra~e was 15 grams/hour.
P~ 20
The procedure of ~xample 19 was followed~
except that the catal~t~c sGlu~ion was ~repared
usinO 170 ~l of potassium 2-ethoxyethoxide made as
describ~d in Method 3. ~he ~ercentage conversion of
silicon to alkoxysilans was greater th~ 9,%
anà the ~roduc~ion rate was 22 grams/hour.
: ' .
hXk~PL~ 21
h catalytic solution was prepared by addin
~; 675 ml Or tetraethoxysilane to 290 ml metal alkoxide
solution prepared as described in Ms~hod 1. In this
catalytic solution the volums ratio of solvent to me-
tal alkoxide solution is 2.25 : 1. To the catalytic
solution is added 14g (0.5 mole) silicon, i.e. 1930
ml catalytic solution/mole silicon, together with
60 ml dry ethanol. The mixture was warmed to 145C
.
and ethanol slowly added dropwise so as to maintain
tbe reaction temperature in the range 165 - 170C~
The alkoxysilane produced was removed from the re-
action system by distillation as a mixture of ethanol
~ ~72649
- 30 -
and producv. At 145C the production rate of
alkoxysilane was 24 grams/hour~ ht the end of
the reaction the production rave of alkoxysilane
was 14.6 gr2ms/hour~
~X~'~.L~ 22
n ~nis ~xa~le, the thernal capacity of the
cataly~ic solution is first increased by stepwise
adaitions o^ ethanol and silicon~ then alkoxysilane
and ethanol were r-mo~ed as V&pOU~ and the seauence
repeated.
Startin~ ~oceau~e
A clean and oLry reaction vessel is purged
, .
. with dry nitrogen for a;~out 15 minutes~ The catalytic
solution is made by charging the reaction vessel with
204 li~res of tetraethoxysilane, followed by 204
litres of metal alkoxide solutio~ prepared according
to Method 4 and then by a further 136 litres of
tetraethoxysilane~ To this catalytic solution 5 kg
silicon powder was added, i~e. 3046 ml catalytic
solution/mole silicon, followed by 10 litres ~rJ
ethanol. The mixture was heated until the reactor
temperature was 140C. At this stage the distillation
;: ' '
~ : ,:,
,: . ,
11 117~49
31
head temperature (head te,perature) was the a~bient
temperature~
Dry and preheated ethanol was added at a
rate such that the reactor temperature did not drop
below 140C. ~thanol was added at this reouired rate
until evolution Of hydrogen ceased. Then a further 5
kg silicon was added and more ethanol was added at
the r-quired rate u~til evolution of hydrogen ceased.
No ~istillate was collected in ~hi~ cycle, i.e. ~he
reactior ~as do~e u~--er total reflux condition.
; It is necessary to mainta n a ~inimum reac-
tor temperature of 140C~ Althou~h a minimum reactor
~` ~ temperature of 1'~0C is require~, t:~e te~perature is
~5 preferably in the ræ~ge 155-165C~ The ethanol
addition can be replaced by a ~ixture of ethanol and
tetraethoxysilane.
he separation of alkoxysilane from the
reacticn mi~ture was carried out by the following
, ~
procedure.
(i) The preferred reactor temperature
is 150C.
- 32 _ ~
(ii~ Dry ethanol was added to the reaction
mixture at a rate such that a constant head tempera-
ture is maintained.
(iii) It is preferable to remove the product
as a mixture of alkoxysilane and ethanol. The product
should be removed at a high head temperature (140C
or over~ to ensure that the distillate is rich in
alkoxysilane. It is important that only the amount
; of alkoxysilane produced is removed.
The ethanol-alkoxysilane mixture collected
is distilled to separate the ethanol and the alkoxy-
silane, The ethanol recovered can be re-used.
After the alkoxysilane produced has been
removed, the sequence of stepwise additions of silicon
and ethanol is repeated to continue the production of
, alkoxysilane. This in its turn is removed then the
sequence of stepwise additions of silicon and ethanol
is continued.
Preparation of polysilicat_
Alkoxysilane - 259 volumes
~i Anhydrous ethanol - 82.2 volumes
Water - 16.4 volumes - must be distilled
or de-ionised
~ ~ Acid solution - 1,3 volumes
::
.
~ 1726~
- 33 ~
The acid solution is 1% v/v of concentrated
sulphuric acid (9~/0 ~ S04 by weight) in anhydrous
ethanol.
The mixture of alkoxysilane, anhydrous
ethanol and acid solution is heated to reflux
temperature and water added dropwise with stirring
over a period of 30 minutes. Refluxing is carried
out for 60 minutes when the addition is completed.
The ethanol is recovered from the product by dis-
tillation under gradual lowering of pressure.
Distillation was finished when a pot temperature
of 140C at 100 mm Hg pressure was reached, The
. amount of ethanol recovered was 180 volumes, This
-: can be used again in the preparation.
Product characterisation
, ~ Density at 20C - 1.06 gm/ml
Silica content = 36,1% w/w
Acidity = 0.013% wv H2S04
- ' .
- :
~ ~ 7~49
-- 34 --
EXAMPLE 2 3
A catalytic solution was prepared by mixing
125 ml of the metal alkoxide solution prepared as
in Method 11 with 395 ml of tetraethoxysilane. To
this solution was added 14g (0.5 mole) silicon powder
average particle size 50 - 60 microns and 30 ml dry
ethanol, i,e. 1040 ml catalytic solution per mole
silicon. The procedure followed was according to
Example 1 and over 29 1i2 hours at an average reaction
temperature of 155C, the average production rate of
alkoxysilane was 18.9 grams/hour with a yield of 86~o
based on the weight of silicon used.
EXAMPLE 24
A catalytic solution was prepared by mixing
190 ml of the metal alkoxide solution prepared accord-
ing to Method 10 with 360 ml of tetraethoxysilane.
To this solution was added 14g (0.5 mole)of silicon
powder, average particle size 50 - 60 microns and 30
ml dry ethanol, i.e, 1100 ml catalytic solution per
mole silicon, Following the procedure of Example 1
~7~
- 35 -
the reaction was run for 30 hours at an average
temperature o 148C yielding 72~/o of alko~ysilane
based on the weight of silicon used, at an average
production rate of 19.2 grams/hour.
EXAMPLE 25
150 ml of metal alkoxide solution prepared
according to Method 2 was added to 300 ml of alkoxy-
silane prepared according to Example 1 and to it was
added 14g (0.5 mole) of silicon powder, average
particle size S0 - 60 microns, and 30 ml dry ethanol
(i.e, 900 ml catalytic solution per mole silicon).
The procedure followed was similar to that of
Example 1 except that the ethanol was added in the
vapour state, being boiled in a 100 ml 3-necked
round-bottomed flask fitted with a glass delivery
tube to transfer ethanol vapour to the reaction
vessel~ below the liquid surface and a 50 ml dropping
funnel to add cold ethanol dropwise to the boiling
ethanol in the flask. ~he delivery tube was wrapped
in trace heating wire in order to prevent condensa-
tion of the ethanol between the flasks. The reaction
was run for 29.8 hours under these conditions and
the average production rate of the product was
~ î7264~
- 36 -
18.9 grams/hour at an average reaction temperature
of 152Co The yield of product based on the weight
of silicon used was 86~3%~
EXAMPLE 26
A catalytic solution was prepared by mixing
300 ml of tetraethoxysilane with 150 ml of metal
alkoxide solution made according to Method 2. To
this was added 14g (0.5 mole) silicon powder,
average particle size 5 microns and 30 ml dry
ethanol, i,e, 900 ml catalytic solution per mole
silicon. The procedure of Example 1 was followed
and the reaction run for 37~8 hours at an average
temperature of 153C~ AlkoxySilane was produced at
an average rate of 29,1 grams/hour in 94,2% yield
based on the weight of silicon used.
EXAMPLE 27
.
300 ml tetraethoxysilane were added to 150 ml
of metal alkoxide solution made following Method 1
but using only sodium 111,58g, 0.504 mole), to make
' ~ 20 the catalytic solution. To this was added 14g
(0~5 mole) of silicon powder, average particle size
5 microns, and 30 ml dry ethanol, to give 900 ml
:
~ 1l726~
- 38 -
solution was added 3~0 ml tetraethoxysilane,
producing 480 ml of catalytic solution. To this
was added l~g (0.5 mole) of silicon powder, average
particle size 5 microns, i.e. 960 ml catalytic
solution per mole silicon. Following the procedure
of Example 1, the reaction was run for 32.8 hours
at an average temperature of 149C with an average
ester production rate of 19 grams/hour and in 94 1%
yield based on the weight of silicon consumed.
EXAM2LE 30
Following the procedure of Method 5, but
using only potassium metal (19.47g, 0 499 mole3 a
metal alkoxide solution was made up (110 ml) and
added to 370 ml tetraethoxysilane to produce the
catalytic solution. Silicon powder (14g 0.5 mole)
of average particle size 5 microns was added to it,
producing a system with 960 ml catalytic solution
per mold silicon The reaction was carried out
according to Example 1 and over 37 75 hours at an
average temperature of 151C produced ester at an
average rate of 22.6 grams/hour in ~6 6% yield based
~ ~ 72~19
- 37 ~
catalytic solution per mole silicon. ~ollowing
the procedure of Example 1, the reaction was run
for 2&.5 hours at an a~erage temperature of 158C
giving a 97.6~o yield Or alkox~sil~ne based on the
weight of silicon used, av an average ?roductlon
rate of 27.7 ~ra s/hour~
- EK~IPL~ 28
~ o 300ml tetraethoxysilane were added 150ml of
met21 alko~ide solution m~ce following Method 1 bui
USl~g only po'vassium metal ( 19.5g, ~.5 mol~ to
produce 450ml catalytic solution. Silicon powder
g 0.5mole) was added together with 30~1 dr,y
ethanol to the catal~tic solution, producing 900ml
catal~tic solution per mole silicon. ~ollol.~ing the
procedure of ~xample 1 the reaction was run for
3~75 hours at an average te~pera'ure o~ 152C.
he ~ield Or ~x~uct based on the weight of silicon
used was~94.1% and the ave-age production rate
28.4 grams/hour.
~X~MP~ 29
A metal alkoxide solution was made following
the procedure oI Method 5 ard to 100ml o:[ this
~ ::
.
`. ~172~;4~ :
- ~8 -
solution :as added 380ml tetraethox~silane, pro-
ducing 480ml of catalytic solution. ~o this was
added 14g (0.5 mole) of silicon powder, average
~ particle slze 5 microns, i.e~ 960 ml catal~tic
; 5 solution per mole silicon. ~ollowing the proced-
ure ol Exa~ple 1, the reaction was run for 32.8
hours at a~- averG_e ~e-~erat~are of 149C wlth a~
avera~e es~er production rate o~ 19 ~ a~ns~ ~& in
9!'.13~ ield based o~ ~ne weight Or silicon
1C co~sumed.
.
~ E~LE 33
. .
~ ollo~.~n~ the procedure of Method ~, but
.
: using onl~ potassium metal (19.~7~,0.49~ole) a
metal alkoxide solution was ~ade up (110 ml) and
~: ~15 adaed to 370 ~l tetraethox~silane to produce the
catalytic solutio~O Silicon powder (1~g 0.5 mole)
o~ average particle size 5 microns was added to
it, producing a s~stem with 960ml catal~tic solu-
tio~ per mole silicon~ The reaction was carried out
~ 20 according to E~smple 1 and o~er 37.75 hours at an
: ~ ~ . average tem~eratu~e o~ 151C produced ester at an
~ ~ average rate of 22.6 ~rGms/hour in 86.~5' yield based
': ' '
, , .
~ . .
~ ~7~164
- 3~
.: ,.,
on the weight of sllicon used.
~h~PL~
A metal alkoxide solution was made up
according to Method 7 (145 ml ) ~nd mixed with 290ml
tetraethox~s~lane and 14g silicon powder (005mole~
of aver~e particle size 5 microns and 30 ml of
dr~ ethanol~ i.e. 870ml catalj~ic solution per mole
silicon. ~ollo~ing the procedure of Example 1
the reaction was ru~ for 43.1 hours at an ave~age
te~perature of 150C, giving a yield of 95.~/0 pro-
duct based on the weight of silicon used at an
average production rate of 28.1 ~ra~s/hour.
.
ollowing Method 10 195ml of metal alkoxide
solution was made and mixed with 285ml tetraethoxy-
silane, 14g (005mole)silicon po~der of average
particle size 5 microns and 30 ml of dry ethanol,
e. 960 ml catal~tic solution per mole silicon.
he reaction was run for 41.3 hours at an average
~; 20 temperature of 155C according to ~xample 1 and pro-
duced a product yield of 97.2/o based on the weight of
.
,~,
'`.
,
~ ~726~1
- 40 -
silicon used at an average production rate of 27,3
grams/hour,
EXAMPLE 33
170 ml of metal alkoxide solution was
prepared according to Method 1, but using only sodium
metal (15,48g, 0,673 mole), To this was added 340 ml
alkoxysilane produced according to Example 1 and 40 ml
dry ethanol and 14g (0.5 mole) silicon powder of
average particle size 50 - 60 microns, i.e. 1020 ml
catalytic solution per mole silicon, Following
Example 1 the reaction was run for 22,5 hours at an
average temperature of 148C yielding alkoxysilane
at an average rate of 15,0 grams/hour in 78,~/o yield
based on the weight of silicon used,
EXAMPLE 34
175 ml of metal alkoxide solution was
:~:
prepared according to Method 1 but using only potassium
metal ~26.6g, 0.68 mole). To this was added 350 ml
alkoxysilane produced according to Example 1, 30 ml
dry ethanol and 14g (0.5 mole) silicon powder of
~! average particle size 50 - 60 microns, i~e, 1050 ml
catalytic solution per mold silicon, Following
~ 172~49
- 41 -
Example 1 the reaction was run for 21,8 hours at an
average temperature of 155C, producing alkoxysilane
at an average rate of 22.7 grams/hour in 84.4% yield
based on the weight of silicon used~
EXAMPLE 35
130 ml of metal alkoxide solution was pre-
pared according to Method 5, but using only sodium
metal 511.61g, 0,528 mole), To this was added 420 ml
alkoxysilane produced according to Example 1, and
14g (0.5 mole) silicon powder of average particle
size 50 - 60 microns, i.e, 1100 ml catalytic solution
per mole silicon. Following Example 1 the reaction
was run for 23.2 hours at an average temperature of
149C, alkoxysilane was produced at an average rate
of 13 grams/hour,
EXAMPLE 36
-.-
100 ml of metal alkoxide solution was pre-
; pared according to Method 5, but using only potassium
metal (19.50g, 0,50 mole~. To this was added 450 ml
alkoxysilane produced according to Example 1 and
14g (0.5 mole) silicon powder of average particle
.... ..
_,,
~ ~7~6~9
_ 42 -
size, 50-60 microns, i.e. 1100 ml catalytic solu-
tion per mole silicon. Following Fxample 1 the
reaction was run for 23.2 hours at an average tem-
; perature of 152C. Alkoxysilane was produced at an
average rate of 16.2 grams/hour in 75.1~ yield
based on ~he weicht of silicon used.
X~ 37
- i catalytic solu~ion was ?repared by dis-
solvin~ so~iu (4.8g, 0.21 mo1~)in 75 ml 2-dimethyl-
~minoeth~nol over a two hour period. It was r.eces-
sary to h~at the mixture gently to ~acili~ate solu-
tion of the sodium when about half the quantity was
added. Potassium (9.70g, 0~25 mole) was now d~ssolved
in the mixture over a six hour period, with tne addition
of two 25 ml portions of 2-di ethyl~minoeth~nol. ~he
mixture was heated for two hours after all the metal
dissolved. To this solution was added
: :
~ 395 ml alkox~sila~e produced according to xample
; ~
1, then 14 grams silicon powder, avera~e p~rticle size
.
53 microns were added (i~e. 1040 ml catalytic solution
per molesilicon~. Then 30 ml of dry eth~nol were
~ added. The reaction was run ~or 29~ hours, the avera~e
:;:
~: :
!1 ~7~9
- 43 -
reaction temperature being 155C. The average rate
of production of alkoxysilane was 18.9 grams/hour,
the yield of alkoxysilane, based on the weight of
silicon used, was 86.0%.
Identiflcation of Components of the Reaction Product
Ester
The product collected from the various re-
actions detailed in the Examples was analysed by Gas
Liquid Chromat`ography (G.L.C.) using a Pye model 204
GCD chromatograph and with SE 30 and OV17 columns,
The carrier gas used was nitrogen, at a flow rate of
40 ml per minute and the oven temperature of the
chromatograph was 200C.
Peaks other than ethanol, alkali metal solvent
and tetraethoxysilane were found, in quantities between
1 and 20 area % depending upon the circumstances under
which the product was collected,
These peaks have been identified as mixed
esters of the type (EtO)nSi(OA)~ n where n = 1, 2, 3
by chemically equilibrating mixtures involving AOH and
Si(oEt)4 also EtOH and Si(oA)4 (A=EtOOEI2C~ ,
_ a~4 _
EtOEI2CH2OCH2CH2) and analysing them by G.L,C.
Major peaks in these mixtures, whose proportion
varies systematically with the molar ratio of
equilibrants, have similar retention times to
5 the minor product components~
EXAMPLE 3_
Tetraethoxysilane (58 66g, 0~282 mole) and
2-ethoxyethanol (25 69g, 0.285 mole) were refluxed
together in a three-necked, 100 ml round-bottomed flask
10 fitted with thermometer and reflux condenser, for
6 hours, the temperature of the mixture fell from
132C to 110C during this time. Similarly mixtures
of tetraethoxysilane and 2-ethoxyethanol ~69 75g,
0.335 mole and 85.14g, 0.409 mole with 10~06g, 0.112
mole and 102.10g, 1 138 mole respectively) of mole
ratios 3: 1 and 1: 3 were refluxed for 6 hours,
the temperatures of the mixtures falling as in the
first case.
G.L.C, analysis of these mixtures showed
20 peaks corresponding to ethanol, 2-ethoxyethanol and
tetraethoxysilane together with the three mixed esters
(EtO)nSi(oCH2CH2oEt)4 n~ n = 1, 2, 3. Samples of
~ ~ 7~6~9
-- 45 --
product from Examples 26, 27, 28 showed peaks with
similar retention times as the mixed esters
EXAMPLE 39
Using the procedure of Example 38 two
5 mixtures of ethyldigol and tetraethoxysilane were
refluxed and analysed by G.L C In the :Eirst case
tetraethoxysilane (43.12g, 0.205 mole) and ethyl-
digol (27.98g! 0 209 mole) were refluxed for 7 1/2
hours during which time the temperature of the
10 mixture fell from 164C to 104C In the second case
tetraethoxysilane (26.83g, 0.128 mole) and ethyldigol
(51.51g, 0.38 mole) were refluxed for 8 hours during
which time the temperature of the mixture fell from
170 to 127C.
G.L.C. analysis of these two mixtures
after reflux showed the presence of five components,
ethanol, ethyldigol, tetraethoxysilane and two
mixed esters (EtO~3SioCH2CH2oCH2 CH2OEt and
(Eto)2Si(oCH2cH2ocH2cH2oEt)2. Samples of product
20 from Examples 24 and 32 which were also analysed
contained components with similar retent:ion times
as the mixed esters
,
,
1 ~ 7~649
-- 46 --
EXAMPLE 40
Following Example 38 two mixtures of 2-
dimethylaminoalcohol and tetraethoxysilane were
refluxed and analysed by G,L.C. In the first case
tetraethoxysilane (42.70g, 0.205 mole) and 2-
dimethylaminoethanol (18.27g, 0.205 mole) were
reEluxed for 7 1/3 hours after which the mixture
had reached a constant temperature of 105C.
Secondly tetraethoxysilane (29 81g, 0.143 mole) and
2-dimethylaminoethanol (38.39g, 0.431 mole) were
refluxed for 6 1/2 hours a Einal, constant tempera-
ture oE 107.5~C being reached.
G.L.C. analysis of the two mixtures showed
the presence of ethanol, 2-dimethylaminoethanol,
and tetraethoxysilane together with the mixed esters
(EtO)nSi(OCH2CH2NMe2)4 n; n -- 1, 2, 3, Samples of
product from Example 23 were analysed under similar
conditions and were :eound to have peaks corresponding
to the three mixed esters,
20 ~ EXAMPLE 41
Following Example 38 two mixtures of met~yl
digol and tetraethoxysilane were refluxed and analysed
by G.L.C. ~etraethoxysilane (34,70g, 0~167 mole) and
:
methyl digol (20.01g, 0.167 mole) were refluxed for
'
1 ~72~9
- 47 -
15 1/3 hours attaining a final temperature of 115C.
A second mixture of tetraethoxysilane (20,92g,
0 100 mole) and methyl digol (36 05g, 0 300 mole)
was refluxed for 14 3¦4 hours reaching a final,
constant, temperature of 116C~
G.L.C, analysis of tne two mixtures showed
the presence of ethanol, methyl digol and tetra-
ethoxysilane plus two mixed esters (EtO)n
Si(ocH2cH2ocH2cH2oMe)4 n; n = 2, 3~ Samples of
product from Examples 5 and 31 were analysed under
similar conditions and found to contain peaks
corresponding to the two mixed esters.
EXAMPLE 42
Following Example 38 two mixtures of
15 tetraethoxysilane (20.83g, 0.100 mole and 10.42g,
:: 0.050 mole) and 2-phenoxyethanol (14 04g, 00102 mole
and 20.23g, 0.146 mole) were refluxed and analysed
- by G.L.C. The first mixture was refluxed for 14 1/2
hours reaching a final, constant, temperature of
20 115C and the second for 13 1/4 hours reaching
18C.
G.L,C. analysis of both mixtures showed
the presence of ethanol, tetraethoxysilane,
~; 2-phenoxyethanol and PhOC~ CH2OSi~OEt)3 Samples
,~
~ .
6~9
- 48 -
of pro~uct from Example 6 were analysed under
the sa e conditions ~nd found to contain
PhOCH2CH20Si(O~t)
~XAMPL~ 43 -
invention with prc~ortio~ of an zlcohol ~0.~ in
t~ ]c~hol.
A catal~,,ic solution W2S prepareà by mixing
300 ml of tetraethox~silane with 150 ml of metal
alkoxide solution ?repa~ed according to ~e~hod 2,
i.e. the catalyst was the reaction product of
otassium and 2-ethoxyethanol~ ~o this solution
was acGed 14g (0.~ ~oL~)of silicon powder of
average pzrticle size:five~micro~s znd 30 ml dry
e~hanol, i.e. 900 ~l catalytic solution per mole of
silicon. mhe procedure followed was according to
xample 1 wlth the exceptlon that the alcohol added
was not pu~e etha~ol but 95% etha~ol b~ volume and
/o 2-ethoxyethanol by volume, During a 33.5 hour
period at an average reaction te~perature of 158C
the average production rate of product was 30.5gr~ms/hour
with a ~ield of 98~o based on the weight of silicon
.
used.
.: '
:~
'
! 7 7264 ~
~9 _
G,L,C. analysis of the product collected
showed that there was an increased yield of the
substituted alkoxysilanes (Eto)nSi(oCH2CH2oEt)4 n~
n = 3, 2, 1 compared with product collected from
~ 5 a reaction carried out under the same conditions
: but with only ethanol added. The content of such
substituted product was increased, Specifically
the content of (Eto)3SioCH2CH2oEt was increased
from 12 to 2C%~ of (Eto)2Si(oCH2CH20Et)2 from 1.5%
to 3/O and of (Eto)Si(oCH2CH2oEt33 from 0 to 1%.
,~
.
:
::
