METHOD FOR THE PREPARATION OF METHACRYLOXY AND ACRYLOXY CONTAINING ORGANOSILANES AND ORGANOSILICONES

METHODE POUR LA PREPARATION D'ORGANOSILANES ET D'ORGANOSILICONES CONTENANT DES GROUPES METHACRYLOXY ET ACRYLOXY

English Abstract

ABSTRACT
This invention relates to an improved
process for preparing, purifying and/or storing
methacryloxy or acryloxy containing organosilicon
compounds without the undesirable polymerization
normally associated with the methacrylate bonds. In
an alternative embodiment, the process is even
further improved with the addition of certain
stabilizers, and in particular diketone or ketoester
sabilizers.

Claims

-26-
The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. A process for preparing methacryloxy or
acryloxy containing organosilicon compounds which
eliminates undesirable polymerization which process
comprises:
(a) charging a first reservoir with
(i) 2-10% molar excess of a
methacryloxy or acryloxy functional
containing compound over a stoichiometric
amount of alkoxysilane which would be needed
to form a complete reaction between said
functional containing compound and said
organosilane and
(ii) 0.2 to 5.0% of an inhibitor
by weight based on the amount of
methacryloxy or acryloxy used;
(b) charging a second reservoir with
(i) a stoichiometric amount of
alkoxysilane needed to form a complete
reaction with the methacryloxy or acryloxy
containing compound employed in (a); and
(ii) a catalystic amount of
platinum-containing hydrosilation catalyst;
(c) combining the contents of the two
reservoirs in a reactor vessel at 80-120° centigrade;
(d) post treating the crude reaction
product with 1-5% alcohol by weight based on weight
of product or post heating the reaction product for
5-40 minutes at 100-140°C; and
(e) vacuum distilling the post-treated
product in the presence of inhibitors and under
reduced pressure.
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-27-
2. The process of Claim 1 wherein the
alkoxysilane is represented by the general formula:
<IMG>
wherein R and R' are lower alkyl moiety containing
1-20 carbon atoms and n is 0-1.
3. The process of Claim 2 where the lower
alkyl moiety contains 1-4 carbon atom.
4. The process of Claim 1 wherein the
methacryloxy or acryloxy functional containing
compound is represented by the general formula:
<IMG>
wherein R2 is hydrogen, a lower alkyl group having 2
to 8 carbons or an aryl group having 6 to 10 carbons,
X is a CH2 group, and m equals 0 to 10.
5. The process of Claim 4 wherein m equals
0 to 5.
6. The process of Claim 1 wherein the
inhibitor is selected from the group consisting of
phenolic inhibitors, aromatic amines, aromatic sulfur
compounds and combinations thereof.
7. The process of Claim 6 wherein the
phenolic inhibitor is monomethyl ether of
hydroquinone, Isonox? 129 or Ionol?.
8. The process of Claim 6 wherein the
aromatic amine is diphenyl-p-phenylenediamine.
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9. The process of Claim 6 wherein the
aromatic sulfur compound is phenothiazine.
10. The process of Claim 1 wherein the
platinum-containing hydrosilation catalyst is
selected from the group consisting of supported
platinum catalysts and homogeneous soluble platinum
complexes.
11. The process of Claim 10 wherein the
supported platinum catalyst is platinum on .gamma.-alumina
or charcoal.
12. The process of Claim 10 wherein the
homogenous soluble platinum complex is selected from
the group consisting of chloroplatinic acid,
bis(ethylene platinous)chloride,
dichlorobis(acetonitrile)platinum (II),
cis-dichlorobis(triphenylphosphine) platinum (II) and
tetrakis(tetraphenylphosphine)platinum (O).
13. The process of Claim 12 wherein the
soluble platinum complexes are used as solution in
solvents.
14. The process of Claim 13 wherein the
solvents are isopropanol, acetonitrile or 1,2
dimethoxyethane.
15. A process for preparing methacryloxy or
acryloxy containing organosilicon compounds which
eliminates undesirable polymerization which process
comprises:
D-14908-C-1

- 29 -
(a) charging a first reservoir with
(i) 2-10% molar excess of a
methacryloxy or acryloxy functional
containing compound
<IMG>
wherein R2 is hydrogen, a lower alkyl group
having 2 to 8 carbons or an aryl group
having 6 to 10 carbons, X is a CH2 group,
and m is equal to 0 to 10, which excess is
over a stoichiometric amount of alkoxysilane
which would be needed to form a complete
reaction between said functional containing
compound and said organosilane and
(ii) 0.2 to 5.0% monomethyl ether
of hydroquinone, Isonox? 129 or Ionol? by
weight based on the amount of methacryloxy
or acryloxy compound used;
(b) charging a second reservoir with
(i) a stoichiometric amount of an
alkoxysilane
<IMG>
wherein R and R' are lower alkyl moiety
containing 1 to 20 carbon atoms and n is 0,
which alkoxysilane is needed to form a
complete reaction with the methacryloxy or
acryloxy containing compound employed in
(a); and
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- 30 -
(ii) a catalytic amount of
platinum-containing hydrosilation catalyst
selected from the group consisting of
supported platinum catalysts and soluble
platinum complexes;
(c) combining the contents of the two
reservoirs in a reactor vessel at 80-120° centrigrade;
(d) post treating the crude reaction
product with 1-5% alcohol by weight based on weight
of product or post heating the reaction product for
5-40 minutes at 100-140°C; and
(e) vacuum distilling the post-treated
product in the presence of phenolic or nonphenolic
inhibitors under reduced pressure.
16. A process for preparing methacryloxy or
acryloxy containing organosilicon compounds which
eliminates undesirable polymerization which process
comprises:
(a) charging a first reservoir with
(i) 3-5% molar excess of a
methacryloxy or acryloxy functional
containing compound
<IMG>
wherein R" is hydrogen, a lower alkyl group
having 2 to 8 carbons or an aryl group
having 6 to 10 carbons, X is a CH2 group,
over a stoichiometric amount of alkoxysilane
which would be needed to form a complete
reaction between said functional containing
compound and said organosilane; and
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(ii) 0.5 to 2.0% monomethyl ether
of hydroquinone, phenothiazine, or
diphenylenediamine inhibitor by weight based
on the amount of methacryloxy or acryloxy
used;
(b) charging a second reservoir with
(i) a stoichiometric amount of
alkoxysilane
<IMG>
wherein R and R' are lower alkyl moiety
containing 1 to 4 carbons and n is 0 to 1
which alkoxysilane is needed to form a
complete reaction with a given methacryloxy
or acryloxy containing compound and
(ii) 2 to 20 parts per
million of platinum on .gamma.-alumina or
charcoal;
(c) combining the contents of the two
reservoirs in a reactor vessel at 80-120° centigrade;
(d) post treating the crude reaction
product with 1-3% alcohol by weight based on weight
of product or post heating the reaction product for
20-30 minutes at 100-140°C; and
(e) vacuum distilling the post-treated
product in the presence of phenolic or nonphenolic
inhibitors or diphenylenediamine and under reduced
pressure.
17. A process for preparing methacryloxy or
acryloxy containing organosilicon compounds which
D-14908-C-1

- 32 -
eliminates undesirable polymerization which process
comprises:
(a) charging a first reservoir with
(i) 3-5% molar excess of a
methacryloxy or acryloxy functional
containing compound
<IMG>
wherein R" is hydrogen, a lower alkyl group
having 2 to 8 carbons or an aryl group
having 6 to 10 carbons, X is a CH2 group,
over a stoichiometric amount of alkoxysilane
which would be needed to form a complete
reaction between said functional containing
compound and said organosilane; and
(ii) 0.5 to 2.0% monomethyl ether
of hydroquinone, Isonox? 129 or Ionol?
inhibitor by weight based on the amount of
methacryloxy or acryloxy used;
(b) charging a second reservoir with
(i) a stoichiometric amount of
alkoxysilane
<IMG>
wherein R and R' are lower alkyl moiety
containing 1 to 4 carbons and n is 0 to 1
which alkoxysilane is needed to form a
complete reactlon with the methacryloxy or
acryloxy containing compound employed in
(a); and
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- 33 -
(ii) 2 to 100 parts per million of
homogeneous soluble platinum complex
selected from the group consisting of
chloroplatinic acid,
bis-(ethylene-platinous)chloride,
dichlorobis(acetonitrile)platinum (II),
cis-dichlorobis(triphenylphosphine) platinum
(II) and tetrakis(tetraphenyl
phosphine)platinum (O);
(c) combining the contents of the two
reservoirs in a reactor vessel at 90-120° centigrade;
(d) post treating the crude reaction
product with 1-3% alcohol by weight based on weight
of product or post heating the reaction product for
20-30 minutes at 110-130°C; and
(e) vacuum distilling the post treated
product in the presence of phenolic or nonphenolic
inhibitors under reduced pressure.
18. The process of Claim 17 wherein the
homogeneous soluble platinum complex is used as
solution in solvents.
19. The process of Claim 18 wherein the
solvent is isopropanol, acetonitrile or 1,2
dimethoxyethane.
20. A process for preparing, purifying
and/or storing methacryloxy or acryloxy containing
organosilicon compounds which eliminates undesirable
polymerization which process comprises:
(a) charging a first reservoir with
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- 34 -
(i) 3-5% molar excess of a
methacryloxy or acryloxy functional
containing compound
<IMG>
wherein R" is hydrogen, a lower alkyl group
having 2 to 8 carbons or an aryl group
having 6 to 10 carbons, X is a CH2 group,
(ii) 0.5 to 2.0% monomethyl ether
of hydroquinone, Isonox? 129 or Ionol?
inhibitor by weight based on the amount of
methacryloxy or acryloxy used; and
(b) charging a second reservoir with
(i) a stoichiometric amount of
alkoxysilane
<IMG>
wherein R and R' are lower alkyl moiety
containing 1 to 4 carbons and n is 0 to 1
which alkoxysilane is needed to form a
complete reaction with the methacryloxy or
acryloxy containing compound employed in
(a); and
(ii) 2 to 100 parts per million of
homogeneous soluble platinum complex
selected from the group consisting of
chloroplatinic acid,
bis-(ethylene platinous)chloride,
dichlorobis (acetonitrile)platinum (II),
cis-dichlo:robis(triphenylphosphine) platinum
D-14908-C-1

- 35 -
(II) and tetrakis(tetraphenyl phosphine)
platinum (0);
(c) combining the contents of the two
reservoirs in a reactor vessel at 90-120° centigrade;
and
(d) vacuum distilling the product in
the presence of phenolic and nonphenolic inhibitors
and under reduced pressure.
D-14908-C-1

Description

~L3~ ~3~ -
IMPROVED METHOD ~OR PREPARING METHAC~YLOXY
~ND ACRY~OXY CONTAINING ORG~NOSILANES
~ ~ ORGANOSILICO~ES
BACXGROUND OF THE INVENTION
Field of the Invention
Thi~ invention r~latQs generally to a ~ovel
method for impro~i~g yields in hydrosilation
rea~tio~s. More par~icularly, this invention
relat~s to a~ improv~d method for preparing
me~hacryloxy and acryloxy containing organosilanes
and organo~ilicones under certain conditions without
th~ u~wan~ed polymerization, i.e., gellation,
generally as~ocia~ed with the reactions in~olving
these compounds. ~he process is further improved
whe~ a stabilizer is used to obviate some of the
specific co~ditions required to ~void gellation.
This application is a division of copending
Canadian Patent Application Serial No. 526,060 filed
April 30, 1987. The claims of the parent application
are directed to a process for preparing methacryloxy or
acryloxy-containing organosilicon compounds which
requires a stabilizer but no post-treatment. The claims
of t~is applicati.on are directed to such a process but
including a post-treatment step.
Prior Art
. . _
The hydrosila~ion reaction, the addition of
silicon hydrides to unsaturated ~ompounds, is the
most common m~thod ~or the preparatio~ o~
organosilicon compound~ with func~ional groups in
~he organic position o th~ molecules. There are
numerous litera~ures which teach how to car~y ou~
hydrs~ilation r~actions with various unsa~urated
compounds suc~ as al~enes, un~aturated ethers,
amines, ~tc. 1 C. Earborn and R.W. Bott,
Organometalli~ compounds o the Grou~ IV Elemen~s
(19~8).
Th~se ~ethods, however, ar~ ~o~ suitable
~or the preparation o~ compou~ds containing

- 2 - ~ 31~
methacryloxy, CH2~C(CH3)COO-, and/or acryloxy,
CH2-CHCOO-, functional groups. This is because,
unlike the other organosili~on compounds,
methacryloxy and acryloxy cont~ining organosilicon
compounds can polymerize easily during preparation
and/or purification through reaction of the
methacrylate double bonds. Such polymerization not
only results in wastçd products, but also renders
clean up very difficult, if not impossible, because
of the gelled product inside.
U.S. Patent No. 3,258,~77 to Plueddemann et
al. teaches ~he preparation of a stable
Y-methacryloxypropyltrimethoxysilane by
simultaneously charging both trimethoxysilane and
allyl methacrylate into a toluene solution
containing 2,5-ditertiarylbutylhydro~uinone,
additional trimethoxysilane and a solution of
chloroplatinic acid all a~ 105C. The use of large
amounts of toluene as a solvent, however, makes this
process rather expensive and economically
unattractive.
In U.S. Patent No. 4,276,426 to Lindner et
al., Y-methacryloxypropyltrichlorosilane was again
prepared without gellation when trichlorosilane,
allyl methacrylate and platinum catalyst were
continuously introduced into a pipe-shaped reactor
and circulated in the reactor while the reaction
mixture was continuously being removed from the
reactor. In this reference, the improvement of the
process comprised continuously circulating the
reaction mixture in the reactor at at lesst 1000
centi~ ~ers per minute. The contents of the reactor
D-14908

will gel when the contents are no~ continually
ciroulated, i.~., this proc~ss cannot be carried out
as a batch proc~ss.
Thus, there i~ no teachinq i~ the prior art
of a process to hal~ the undesirable poly~erization
caused by methacryloxy and acryloxy containing
organosilicon compounds which process does no~
reguir~ either the use o~ large amounts of solvents
or the co~tinuous circula~ion of ~he reaction
produ~t mixture. There is a n~ed in the art for a
more economic and more expedi~n~ proc~ss for
preparing these compound~. Further, there is a need
to insure undesirable polymerizatio~ does not occur
during preparation, purification or storage of the
compounds.
This invention is directed towards the
provision of a more economic and more expedient process
for preparing methacryloxy and acryloxy containing
organosilicon compounds, wherein undesirable
polymerization does not occur during the preparation,
purification or storage of these compounds.
D-1490B

~ 3 ~
BRIEF SUMMARY OF THE INVENTION
Accordingly, this invention relates to a novel
process for eliminating undesirable polymerization
associated with the acrylate double bonds ~ound in
methacryloxy or acryloxy containing organosilico~
compounds. The process eliminates this unwanted
polymerization by ~1) combining the contents of a first
reservoir containing a methacryloxy or acryloxy
containing compound and an inhibitor or inhibitors with
a second reservoir containing alkoxy silane or an SiH
containing silicone and a platinum catalyst under
appropriate conditions, t2) pos~-treating the
reaction produc~ with alcohol and/or a heat
treatment, and (3) vacuum distilling the
post-treated product.
D-14903

- 5 - ~3~
The present invention may be practiced as a
batch process a~ well as a continuous process.
DETAILED DESCRIPTI02~ OE' THE INVE2tTION
In accordance with the presen~ invention,
there is provided a nov~l process for ~liminating
undesirable polymerization or gellation which occurs
in methacryloxy or acryloxy containing organosilicon
eompounds. More specifically it has been found ~hat
acryloxypropyltrialkoxysilanes such a~
Y-methacryloxypropyltrimethoxysilane or
Y-acryloxypropyltrimethoxysilane can ~e prepared
and purified without pol~merization problems when
the reactants, trialkoxysilane or SiH containing
silicone, allyl methacrylat~ or allyl acrylate and
th~ platinum catalyst, are brought together.
The process of the invention comprises the
steps of:
(1) charging a first reservoir wi~h a
methacryloxy or acryloxy func~ional containing
compound and an inhibitor or inhibitors;
(2) charging a second reservoir with an
alkoxysilane or an SiH containing silicone and a
platinum-containing hydrosilation compound;
(3~ combining the contents of the ~wo
reservoirs in a reactor vessel at the appropriate
temperature;
(4) post treating t~e crude reaction
product with alcohol or post heating the products at
the appropriate temperature and for the appropriate
time; and
(5~ vacuum distilling the pos~-treated
products in the presence of inhibitors and under
reduced pressure.
D-14908

- 6 ~ J~s ,s f3
The present inven~ion may be further
improved by addition of stabiliz~rs to the first
resexvoir containing methacryloxy and acryloxy
functional compounds.
The addition of these stabilizers obviate.s the
post-treatment step as claimed in the pare~t
applicationî the use of these stabilizers also makes th~
system less sensitive to polymerization and thus reduces
the quantity of excess methacryloxy and acryloxy
functional compound~ which are used when no stabilizers
are present to react with unreacted Si-H compounds or
unreacted alkoxysilanes and thus halt their
polymerization.
The proc~ss of this inv~n~ion can be
carried out as a batch or as a continuous process.
This has no consequenc~s with regard to ~he
parame~ers of the in~ention except as to how it
affQcts the order of combining the reactants.
For example, when the prepara~ion of
me~hacryloxy containing organosilicon ~ompound is
carried out by a continuous process, the platinum
catalyst should be mixed together with the
alkoxysilane before combining with the methacrylate
or acrylate compound and inhibitor. Thus, the
platinum-catalyst can be either dissolved in
alkoxysilane and the mixture dropped into the
methacryla~e-inhibitor mixture at reaction
temperatur~, as in the continuous process, or the
platinum catalyst can be added incrementally to the
hydrosilation mixture, as when the prepara~ion is
carrisd out batYh-wl~e. In any case, one should
avoid heating the platinum ca~alyst with the
D-14908

7 1 3 ~ J
methacrylate-inhibitor mixture to reaction
temperature and then dropping in the silane to the
platinum-methacrylate-inhibitor mix~ure, because
gellation of the reaction mixt~re often results when
this mode of addition is used. This latter scenario
will not occur if the reservoirs are kep~ separate
as indicated by ~he process steps.
It shoula be noted tha~ it is important, in
the continuous reaction, to keep the reaction
mixture moving all the time in order ~o preclude
undesired polymerization from occurring. The
continuous unit should also be washed at the end of
each preparation with an iner~ solvent such as
toluene.
The silanes which can be used in this
process may be represented by ~he general formula:
R'nSi(OR)3-n
H
wherein R and R' are lower alkyl moieties containing
1 to 20 carbons or more preferably with 1 to 4
~arbon atoms and n eguals 0 to 1.
The SiH containing silicone of this
invention is a polysiloxane polymer with the general
formula:
R3SiO[R2SiO]x[RSiO~ySiR3
H
where R is a lower alkyl group having 1 to 8 carbons
or an aryl group having 6 to 10 carbons, methyl is
the preferred R group, x can range from 0 to 100 and
y can range from 1 to 30.
Reactants containing methacryloxy or
acryloxy functional groups may be represented by the
general formula:
D-14908

- 8 - ~ J~3
CH2-CCOO(X)mCH2CH=cH2
R2
wherein R2 is hydrogen, a lower alkyl group having
2 to 8 carbons or an aryl group having 6 to 10
carbons, X is CH2CH2O or a CH2 group or a
combination of the two groups, and m equals 0 to 10
or, preferably, 0 to 5.
The amount of methacryloxy containing
compound, when no stabilizer is used, should always
be used in 2 to 10% molar excess over the
stoichiometric amount needed to react with the
silane or polysilioxane polymer or, preferably, in
3-5~ molar e~cess. As discussed above, the excess
use of methacrylate or acrylate components over the
stoichiometric required amount will prevent the
presence of significant amounts of unreacted
alkoxysilanes or Si-H containing polysiloxanes in
the crude reaction product.
Inhibitors are used during two stages of
the present process: during the hydrosilation
reaction and during the vacuum distillation of the
post-treated product.
Inhibitors which may be used in either the
hydrosilation or vacuum distillation steps of this
process include phenolic inhibitors such as
monomethyl ether of hydro~uinone ("MMHQ") or
Isonox~ 129, aromatic amines such as
diphenylendiamine, aromatic sulfur compounds such as
phenothiazine (~PTZ") or combinations thereof.
Although both these non-phenolic and phenolic
inhibitors may be used during either step, it is
preferred to use only phenolic inhibitors, e.g,
. .
D-14908

1 ~ rJ~J~
_ g _
MMHQ, IonolT" or Isonox~ 129 for the hydrosilation
reaction step. A combination of both phenolic and
non phenolic inhibitors is preferred during vacuum
distillation. The concentration of the inhibitor
used during hydrosilation varies in the range of 0.2
to 5.0% by weight based on methacrylate or acrylate
or, preferably, in the 0.5-2.0% range. For vacuum
distillation, the concentration of non phenolic
varies in the range of 200 to 10,000 ppm while the
concentration of phenolic inhibitor varies from 500
to 15,000 ppm, based on the weight of product used.
The platinum-containing hydrosilation
catalyst us~d in the invention may be chosen from
the group of supported platinum-catalysts, such as
platinum on y-alumina or on charcoal, or from the
group of homogeneous soluble platinum complexes such
as chloroplatinic acid, bis-(ethylene
platinous)chloride,
dichlorobis~acetonitrile)platinum (II),
cis-dichlorobis(triphenylphosphine)platinum (II),
tetrakis(triphenylphosphine)platinum (O) or other
soluble platinum comple~es well known in the art.
The soluble platinum complexes are normally in
solution in solvents such as isopropanol,
acetonitrile or 1,2-dimethoxyethane. The
concentration of the platinum catalyst required
depends on reaction temperature and time but is
generally used in the range of 2 to 100 ppm and
preferably 10 to 25 ppm, based on the total weight
of the hydrosilane or Si-H containing silicone and
allyl methacrylate.
To improve the distillation stability of
the crude products in the reaction vessel, the
..
D-14908

- 10 ~
reactlon mlxture has to b~ post-treated with a small
amount of alcohol such ~s me~h~nol and/or heated at
sbout 120~C for a period of time. Otherwise, other
gellation may occur during the vscuum distillfltion
step or during storage or the yield percent of final
product may be significantly reduced. The exact
reagon why post-treatments $mprove the stability of
crude product is no~ known~ But comparison of gas
chromatograms taken before or after the
post-treatment showed thflt both treatments, alcohol
addition or heating at about 120DC, remove the
unreacted alkoxysilane or SiH containing silicone
left in the mixture AS well as small amounts of
by-product.
The smount of ~lcohol required for the
post-treatment depends upon the amount sf unreaoted
alkoxysllane or SiH containing silicone left in the
reaction mixture. Under normal conditions when the
hydro~ilation is csrried out to completion, i.e.,
the alkoxysilane or Si-H containing silicone left
unreacted is less than 1% by GC analysis, an
~ddition of 1-3~ of alcohol by weight based on
weight of product msde, is enough; although an
amount higher than 3% can also be used up until
about 5%. Any alcohol, ROH, where R is a 1 to 10
carbon ~tom alkyl group, can be used, but methanol
is the most preferred.
Post-trestment requires heating the
reaction mixture in the presence of inhibitors at
100-140C for 5 to ~0 minutes, or more preferably at
110-130~C for 20 to 30 minutes.
After the post treatment~s), crude
methacryloxy and scryloxy containing org3nosilicon
D-14908

~31~3~
compounds can be dis~illed in the presence of the
~bove defined inhibitors under reduced pressure.
Accordlng to th~ continuous process of the
invention, the meth~crylate/acrylate-inhibitor
mixture of the f~rst reservoir should be preheated
to 85 to 1~0C or preferably at 90 to 100C. The
preheatlng o~ the meth~crylAte will make the
temper~ture ~t the point where the react~nts from
the two reservoirs meet at 79 to 90C, pre~erably 75
to 85C. The oil bath temperature at which the
reactor vessel is kept is best kept at 80 to 120C
or preferably At ~0 to 110C.
When the reaction is carried out in batch,
~he ~irst reservoir can be the reactor itself, the
second reservoir sn additional funnel. The
reac~ants in the reactor sre slso preheated to
85-100C or preferably ~t 90-100C before the
reactants 1n the funnel are dropped in. The
preferred reaction temperature is at 80-120C or,
more preferably, ~t 90-110C. A reaction
tempersture lower than 80~C can slso be used, but
the reaction t~kes longer time to run and the
unreacted alkoxysilane left in the reaction mix~ure
will also be higher. The higher the amGunt of
unreacted alkoxysilane remaining in the reaction
mixture, the larger the chance the product will gel
during distillation und stor~ge if not post
treated. Gellstion during hydrosilation may occur
when the hydrosilation is carried out at rePction
temper2tures sbove 125C.
For both the continuous or the betch
process, both residence time of the re~ction mixture
.
~ D-14908

_ 12 ~ 3~
and charging rate of reactants depend on the size of
the reactor and the temperature of the oil bath
used. It is not critical to use specific residence
times and/or charging rates. For the continuous
process, it is important that the charging rates
have to be regulated in such a way that the contents
of the reaction mixture, after passing through the
continuous reactor, contain little or no unreacted
alkoxysilane or Si-H containing silicone and that
the mi~ture in the reactor be kept moving all the
time.
In another aspect of the invention, as claimed
in the parent application, the stability of methacryloxy
and acryloxy containing organosilicon compound may be
further improved when compounds such as diketone and
ketoester are used together with the inhibitor in the
first reaction reservoir. Compounds which may be used
include almost any compound with 2 oxygen functions such
as ketones and esters. Mono keto or ester containing
compounds such as mesityl oxide, pentan~ne-2 and
methyl propionate also show some stabilizing
effec~, but the amount required of such compounds to
stabilize the methacrylo~y containing organosilicon
compounds toward polymerization will be much higher
than those required for diketones and ketoesters.
Diketones such as pentanedione-2,4 and
he~adione-Z,5 and ketoesters such as methyl
acetoacetate are, therefore, the preferred compounds
to be used as stabilizer for the present invention
or, more preferably, only the diketones.
The amount of stabilizer used may vary from
2 to 10 per ent by weight based on the amount of
. .
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~ 3 ~ 3~
- 13 -
methacrylate or acrylate used at the start, and more
preferably from 2 to 5 percent.
EXAMPLES
The following specific exsmples ~nd
procedures are presen~ed to illustrate the
invention, but are not to be construed as 11mlting
thereon.
Definitions
percent
g gram or grams
hr hour or hours
GC gas chromotography
: platinum pl~tinum
~1 microliters
ppm p~rts per million
Insonox~ 129 a phenolic
stabilizer sold
under this
trademark name and
generally available
PTZ phenothizine
MMHQ monomethyl ethers
of hydroquinone
ExamPle 1
Using ~ l~boratory unit comprising two
reservoirs, A and B, sttached to a reaction vessel
~which was heated with an oil bath, a continuous
: preparation of ~-me~hacryloxypropyl~rimethoxy-
silane was made ~s follows:
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Be~ore the preparation, the pump used for
Reservoir A (allyl methacrylste) was preset to
deliver toulene at a r~te of about 2.5-3.0 g/mlnute
and the oil bath heated to 110C. Allyl
methacrylste, 222 g, and Isonoxm 129, 2.22 g, were
mixed ~nd charged ts Reservoir A. When the
temperature of the thermocouple reached about 95~C
(at a point where it me~sured the ~emper~ture of
allyl methsrryll~te-Isonox~ 129 before the mixture
me~ the re~ctants of the second reservoir), ~oluene
delivery was stopped ~nd the mixture of allyl
methacrylate-Isonox~ 129 was pumped through to the
reaction vessel. When most of the toluene in the
unit was replaced by allyl methacrylate,
trimethoxysilane, 10~ g, was mixed with about 15 ppm
of platinum catalyst, H2PtC16, and charged to
the unit via Reservoir B. The r~te of
trimethoxysilane pumped w~s ad~usted ~irst based on
the predetermined ~llyl methacrylate rste to ensure
that there was a 3 to 5% mol~r excess o~ the
methacrylate. It was further ad~usted when gas
chromatographic analysls of the first fraction of
product collected showed too much or not enough
trimethoxysilsne. The obJective of the adJustment
was to obtain a crude
; y-meth~cryloxypropyltrimethoxysilsne mixture
contsining no or very little unreacted
trimethoxysilane and ~bout 3 to 5% molsr excess
allyl methacrylate. The prepar~tion was continued
for about 5 hours ~nd 1087 g of crude
~-methacryloxypropyltrimethoxysilane, ldentified
~ by gRS chromotography, were collected. At the end
:
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.

~ 3 ~ ~ 3~
of the preparation, toluene was again pumped through
to wash the system free of the organosilane to
preserve the unit for the next preparatlon.
The crude products collected were combined
and stabilized with 1000 ppm of phenothiazlne and
500 ppm of monomethyl ether of hydroqulnone. The
yield of ~-methacryloxypropyltrimethoxysilane
calculAted based on distillation data was 83.9
based on G.C. analysis.
~,æa~
The procedure used for Example 1 was
repea~ed five more times. Variations in residence
time, reactlon temperature, crude product collected
~nd yield of y-methacryloxypropyl~rimethoxysilane
~re summarized in Table 1.
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TABLE I
CONTINUOUS PREPARATION OF
Y-METHAcRyLoxypRopyLTRIMETHoxysILANE
Res~dence Reactlon Grude Product Collected Yield X
No. Tlme.Sminutes) Temp. ~C) Tlme (hr) Welaht (q) ~based on GC~
2 24-28 1~0-106 5.7 1261 85.1
3 24 102-108 2.7 556 71.2
4 20.5 lOS-109 4.8 1037 83 5
17.7 105-108 4.0 1272 85.5
6 18.2 105-108 3.4 1217 ~5.3
.
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ExamPles 7 13; Comparative Exam~les A and B
The crude products collected from each
experiment were divided and post treated with
methanol and/or 120C heating for half an hour prior
to distilla~ion. They were then distilled to show
the effect of post ~reatmen~. Results obtained are
summarized in Table II.
T~BLE Il
EFEECT OF POST TREATMENT
Yield %
Post Treatment (based on
Obtained from 120C distillation
No. Experiment Heatinq MeOH Eroduct)
7 Exp. 2, Table I Yes Yes 82 . 7
8 Exp. 2, Table I Yes No 81.1
Comparative A Exp.2, Table I No No Gelled
~ Exp.2, Table I No Yes ~2.8
.
10 Exp.3, Table I Yes No 69.3
Comparative B Exp.3, Table I No No 42. 7
11 Exp.3, Table I No Yes 70.3
12 Exp. 4, Table I No Yes ~6.0
. . _
13 Exp. 5, Table I No Yes 80 . g
From the above data, it ean be seen that to
obtain a uniform distillation stabili~y, the crude
product should be post trea~ed wi~h either heat or
alcohol prior to di~tillation.
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Exæm~le 14
The same procedure o~ Example 1 was
~ollowed except that pentançdione-2,4, 3.4 percent
by weight, based on allyl mPthacrylate, was added ~o
the mixture of a~lyl methacrylate and Isonox
129. The preparation was carried out for 3.1 hours
and 977 g of crude product was col lected . The yield-
of Y-methacrylo~ypropyltrimetho~ysilane of the
reaction based on GC data was ~5.3%.
Example 15
The same procedure of Example 1 was
followed except that pentanedione 2, 4, 3 . 4 percent
by weight, based on allyl metharcylate, was added to
the mixture of allyl methacrylate-Isonox 129
~efore it was charged into the unit and the
platinum-catalyst used was dichlorobis(acetonitrile)-
platinum (II). The preparation was carried out for
3.3 hours and 1036 g of crude product were collected
during the period. Yield of reaction based on GC
analysis was 83.4%
ExamPle 16
The same procedure of Example 1 was
followed sxcept that the amount of allyl
methacrylate was reduced to an allyl
methacrylate/trimethoxysilane mole ratio of 0.98 and
that pentanedione-2,4, 3.4 percent by weight, based
on ally methacrylate, was added to ~he mixture of
allyl methacrylate-Isonox 129. The preparation
was carried ou~ for 3.5 hours. ~uring the ~irst 1.7
hours, about 15 ppm C12Pt(CH3CN)2 was used as
the platinwm catalyst. For the next 1.8 hours, the
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platinum catalyst was switched to about 15 ppm
H2PtC16. Reaction tempera~ure of the oil bath
was 109-113C. The crude product, 555 g, was
collected for the first 1.7 hours and 570 g for the
ne~ 1.8 hours. GC analysis of the crude products
collected using the two platinum catalysts indicated
the presence o~ 3.99 and 2.84 area % of unreacted
trimethoxysilane, respectively. Yield of the
reaction for the first half preparation was 84.8%
and the second half, 84.5% based on G.C. analysis
and based on the distillation product produced.
Examples 17-20
The crude products obtained from Examples
14, 15 and 16 were vacuum distilled in the presence
of 1000 ppm of PTZ and 4000 ppm of MMHQ without the
post treatment. Results obtained are listed in
Table III.
TABLE III
VACUUM DISTILLATION OF
Y-METHACRYLOXYPROPYLTRIMETHOXYSILANE
Crude Product(MeO)3SiH Left
No.Made fromIn Crude (Area %) Yield %
_ _
I7 14 0~7s 86.9
18 15 1.53 79.5
1916 (lst Half) 3.99 80.5
2017 (2nd Half) 2.84 84.7
From the above examples, i~ can be seen
that Y-methacryloxypropyltrimethoxysilane made in
~he presence of pen~anedione-2,~ is more stable than
those made in the ahsence of pentanedione-2,4. As a
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result, ~he ~rude product made in the presence of
pentanedione-2, 4 not only can be made with
stoichiometric amounts of allyl methacrylate, it can
also be distilled without post treatment prior to
distillation, ev@n when 2-4% molar excess
trimethoxysilane is present.
Example.21 and Comparative Ex~mple C
The pro~edure of Example 1 was followed
except that the trimethoxysilane pumping rate was
adjusted in such a way that the first ~wo fractions
of crude r-methacryloxypropyltrimethoxysilane
contained 7-9% molar excess of unreacted
~rimethoxy~ilane and that the remaining fractions
collected contained little or ~ra~e amounts of
unreacted trimethoxysilane. The fraetions were
allowed to stand overnight at room temperature in
the presence of 1000 ppm PTZ and S00 ppm MMHQ, based
on the weight of product used. Both fractions which
contained 7-9% excess unreacted trimethoxysilane
(Comparative Example C) gelled overnight, while
those fractions which had only little or trace
amounts of trimethoxysilane (Example 21) remained as
nonviscous liquid. The~e results indicate the
effect of unreacted trimethoxysilane in the
stability of crude Y-methacryloxypropyl-
trimethoxysilane.
Exam~le 22
Into a 1000 ml four-nec~ed round bottom
flask, fitted with a mechanical stirrer, an addition
funnel, a thermometer and a condenser were added
Isonox 129, 2.6 g, and allyl methacrylate, 259 g,
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. - 21 ~ 13~ 3~
after the flask was flushed with dry air. To the
addition funnel was added trimetho~ysilane, 244 g.
The reaction ~ixture was heated to 85C,
trimethoxysilane was dropped in and H2PtC16
solution was added:
(MeO)3SiH H PtCl Solution
2 6
After 1~4 of total added 180 ~1
l/2 180 ~l - total = 650 ~1
(20 ppm platinum)
3/4 160 ~1
End of (MeO)3SiH
addition 130 ~1
During the addition, the mixture was kept at 85-95C
wi~h cold water bath or heating. Heating was
stopped when GC of the reaction mixture showed that
all of the trimethoxysilane added had reacted.
PTZ, 1000 ppm, and MMHQ, 500 ppm, were
added to the reaction mixture and the mixture was
heated ~o 120C and kept at that temperature for
one-half hour. The experiment was repeated for
another five times; none of them showed any
instability problems. Yield % of
Y-methacryloxypropyltrimethoxysilane all remained
in the range of 81-84~ based on G.C. analysis.
ExamPle 23
The procedure used for Example ~2 was
followed excep~ that the reaction was carried out on
a scale of 1 mole trimethoxysilane and that the
platinum catalyst was mixed with trimethoxysilane
and ~ropped into allyl methacrylate-Isonox 129 at
90-100C. Yield of Y-me~hacrylo~ypropyltri-
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methoxysilane calculated hased on GC analysis was
81.3%.
Comparative Example ~
The procedure of Example 22 was followed
except that 112.6 g of allyl methacrylate, 1.12 g of
Isonox 129, 108 g o~ trimethoxysilane and 220
~1 of a H~PtC16 solution (platinum = 15 ppm)
were used and that the platinum catalyst was mixed
with the allyl me~hacrylate-Isonox 129 mixture
and heated to 90C before trimethoxysilane was
dropped in.
The experiment was repea~ed five times. Of
the five experiments, three of them gelled when
approximately B0-85% of the required
trime~hoxysilane was added to the reaction mixture.
Yield o~ the other two experiments which did not gel
was 66-68% according to ~C analysis of the reaction
mixture.
Comparison of Examples 22 and Comparative
Example D indicates the importance of the method of
platinum-catalyst addition. The platinum catalyst
should be reacted with the alkoxysilane prior to its
addition to the methacrylate/inhibitor mixture to
significantly reduce the chances of gelling.
Example 24
- The procedure of Comparative Example D was
followed except that pentanedione-2,4, 3.B g, was
added to the allyl methacrylate-Isonox
129~platinum catalyst mixture before the mixture was
heated to 90C. The ~xperimen~ was repeated three
times but none of them gelled during the
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~3 ~ 3 ~-, 3 ~
hydrosilation. Yield of Y-metha~ryloxypropyltri-
me~hoxysilane was 65-77~. Furthermore, the three
reaction mixtures were also YacUUm dis~illed without
the post ~reatment in the pr~senc~ of lO00 ppm PTZ
and ~000 ppm of MMHQ prior to distillation. Yield
of Y-methacryloxypropyltrime*ho~silane based on
distillation data was 63-74~ ~ased on G.C. analysis.
- Therefore, the addition of pentanedione-2,4
to the reaction mixture has greatly reduced the
gellation tendency of ~he Y-methacrylo~ypropyl-
trimethoxysilane so that the compound can be made
even under those conditions which facilitate the
gellation of the said compound, i.e., wh~n the
plati~um catalyst is added before the silane or when
no alcohol or post-treatment step is used.
Examples 25-29; ComParatie Examples E-K
To test the stability ~ffect of various
compounds, a series of experiments was carried out
as follows:
Into a 50 ml three-necked round bottom
flask, fitted with a condenser, a thermometer and
dry air inlet-outlet tubing, were added lO g of
distilled Y-methacryloxypropyltrimethoxysilane,
0.0174 g of PTZ, 1.0 or 3.4 g of trimethoxysilane
and the desired amount of the tested compound. The
mixture was heated to 85C and platinum catalyst was
added. Heating was continued and the temperature of
th~ reaction mixture was kept at 95-100C. The time
when change of viscosity of the reaction mixture was
observed was recorded. Results obtained are
summarized in Table IV.
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It can be seen from the-data that diketones
are the most effective compounds to stabilize
Y-me~hacryloxypropyltrimethoxysilane against
polymerization in the presence of trimethoxysilane
and platinum catalyst, or under conditions used for
the preparation of methacryloxy-con~aining
organosilicon compo~nds. Compounds containing keto-
and~or es~er groups also show YariOUS degrees of
stabilizing effect (for example, compare Comparative
Examples E and F versus Examples 28 and 29 ~d
Comparative Examples H-~, but the amounts required
for these compounds to prevent the polymerization of
metha~ryloxy-~ontaining organosilicon compounds such
as Y-methacryloxypropyltrimethoxysilane are much
larger tha.n those required when diketone such as
pentanedione-2,4 is used.
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