METHACRYLATED SILOXANES

SILOXANES AVEC GROUPES METHACRYLATES

English Abstract

A B S T R A C T
Methacrylated siloxanes are prepared by hydrosilation of
beta(allyloxy)ethyl methacrylate using a silicon hydride func-
tional siloxane. Propene elimination is not a significant side
reaction of the method. Methacrylated silicones prepared in
accordance with the invention are capable of anaerobic cure.

Claims

Claims:
1. An organosiloxane compound containing at least two
siloxy repeat units, at least one of which has the
formula
<IMG>
where X is a methacryloxyethyleneoxypropylene group, R
is a hydrocarbon group or a
methacryloxyethyleneoxypropylene group and a is 1 or 2.
2. A polyorganosiloxane as in Claim 1 having a molecu-
lar weight of 2500 or more.
3. A compound as in Claim 1 containing a plurality
of said methacryloxyethyleneoxypropylene groups.
4. A composition comprising a compound as in Claim
1 in combination with an anaerobic acrylate cure
system.
5. A method of preparing a methacrytated organosiloxane
compound comprising reacting a siloxane having silicon
hydride functionality and at least two repeat units,
at least one of which has the formula
<IMG>
where R is a hydrocarbon group or a methacryloxyethyl-
eneoxypropylene group and a is 1 or 2, with beta
(allyloxy)ethyl methacrylate in the presence of an
amount of hydrosilation catalyst effective for
catalyzing a hydrosilation reaction between the allyl
group on said methacylate and said silicon hydride
functional siloxane.

6. A method as in Claim 5 wherein a hydrosilation
catalyst is selected from platinum-based and
rhodium-based catalysts.
7. A method as in Claim 6 wherein said catalyst
is chloroplatinic acid.
8. A method as in Claim 5 wherein the silicon hydride
functional siloxane compound is a polyorganosiloxane
having a molecular weight of 2500 or more.
9. A compound as in Claim 1 wherein R is a hydro-
carbon group.
10. A compound as in Claim 1 wherein R is methyl.
11. A polyorganosiloxalle as in Claim 1 having a
molecular weight of at least 20,000.
12. A polyorganosiloxane as in Claim 1 further com-
prising a plurality of dimethylsiloxane repeat
units.
13. A composition as in Claim 4 wherein the anaerobic
cure system comprises a peroxy initiator.
14. A composition as in Claim 13 further comprising
a sulfimide and a tertiary aromatic amine.
15. A method as in Claim 6 wherein the hydrosilation
catalyst is selected from platinum and hydrocar-
bon platinum complexes.
16. A method as in Claim 5 wherein R is a hydro-
carbon group.

17. A method as in Claim 16 wherein R is methyl.
18. A method as in Claim 5 wherein said silicon hydride
functional siloxane is selected from tetramethyl-
disiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane
and polydimethyl silicones containing a plurality
methylhydrosiloxane repeat units.
19. A free radically cured polymeric product of a
compound as in Claim 1.
20. A cured product as in Claim 19, cured with a cure
system comprising a hydroperoxide, a sulfonimide
and a tertiary aromatic amine.
11

Description

2~2~7
~ ,
sackground of the Invention
This invention relates to polyorganosiloxane polymers
(silicones) which have methacrylate functionality thereon.
Methacrylate functional organosiloxane compounds and poly-
mers are desirable because they have fastex and more versatile
free radical cure characteristics than do the commercially
available vinyl silicones. As described in U.S. Patents
2,956,044 and 4,035,355, methacrylate functional silicones can
be formulated with other unsaturated monomers to give monomer
compositions or cured polymers with unique and desirable proper- ¦
ties. U.S. Patent 4,035,355 describes anaerobically curing
compositions of methacrylate functional siloxane polymers. U.S.
Patent 3,577,26~ describes radiation curable film-forming paint
binders utilizing acrylate or methacrylate functional siloxanes.
Other patents describing methods of preparation or uses for
methacrylate functional siloxanes include U.S. Patents 2,793,223;
2,898,361; 2,922,806; and 2,922,807, and 4,348,454 and U.K.
Patents 1384898 and 1323869.
In U.K. Patent 949,126 there are described hydrolyzable
silane compounds used as adhesion promoters for glass fiber
reinforcing materials, some o~ which are prepared by hydro-
silation of allyl-functional methacrylates such as allyl-
methacrylate and beta(allyloxy)ethyl methacrylate. ~owever,
hydrosilation of allyl-substituted compounds has elsewhere been
observed can be complicated by competing side reactions such as
propene elimination unless the reacting silicon hydride contains
strong electron withdrawing groups such as chlorine or carboxyl.
.~

lZ~2~47
See Speier, J.L., et al., J.Am.Chem.Soc., 79 1974 (1957); and
Ryan, J.W., et al., J. Am. Chem. Soc., 82, 3601 (1960).
In U.S. Patent 3,878,263 there are described acrylate and
methacrylate functional siloxanes prepared from hydrolyzable
acrylic functional silanes. The silanes may be prepared by
hydrosilation of acrylic esters of unsaturated alcohols.
Alternatively, the silanes may be prepared by reacting an alkoxy ¦
or hydroxy chloroalkyl silane with a tertiary amine salt of
acrylic or methacrylic acid.
It is possible to prepare methacrylate functional silicones
; by hydrosilation of allyl methacrylate with silicon hydride
functional polyorganosiloxane polymers, but, consistent with
published reports on allyl hydrosilations, it has been observed
that the process consistently yields a product in which about
30% of the methacrylate groups graEted onto the polymer are
hydrolyzable. These groups are believed to have the following
structure (where the hydrosllating groups were methylhydro-
silo~ane groups).
CH3
-SiO-
O-C-C=CHz
O CH3
The presence of these hydrolyzable methacrylate groups produces
; a number of problems when the polymer is exposed to moisture,
including loss of methacrylate functionality and increase in
viscosity of the uncured polymer due to siloxy crosslinking.
The problem of propene elimination when allyl esters are
hydrosilated is also recognized in U.S. Patent 3,767,690 to
Speier where organosilicon cinnamates were prepared from allyl
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~24~7
cinnamates and organosilicon compounds which have mercapto
functionality instead of SiH functionality.
When methallyl methacrylate is substituted for allyl meth-
acrylate the propene elimination problem is eliminated but
hydrosilation occurs at both ends of the molecule.
CH3 O CH3 CH3 CH3
32 20C C CH2 ---~ R3SiCH2CHCH2oc-c=cH
methallyl methacrylate
CH3 CH3
3 iCH2CHCH2oC CHCH2SiR3
`C~H`3 CH3
+ R3SiCH2CHCoCH2C CH2
SUMMARY OF THE INVENTION
The present invention encompasses a method of preparing
methacrylate functional organosiloxanes by hydrosilation of an
allyl functional methacrylate compound with a silicon hydride
functional siloxane. The allyl functional methacrylate which
is used in the invention is beta(allyloxy)ethyl methacrylate
which has unexpectedly been found to be successfully hydro
; silated across the allyl double bond in substantially quantita-
tive yield with no observable production of hydrolyzable meth-
acrylate groups.
-- 3 --

~%~
In particular, the present invention is directed to a
method of preparing a methacrylated organosiloxane compound
comprising reacting a siloxane having silicon hydride
functionality and at least two repeat units, at least one
of which has the formula
Ra
5i~ -~/2
where R is a hydrocarbon group or a methacryloxye~hylene-
oxypropylene group and a is 1 or 2~ with beta(allyloxy)-
ethyl methacrylate in the presence of an amount of
hydrosilation catalyst effective for catalyzing a hydro-
silation reaction between the allyl group on said
methacylate and said silicon hydride functional siloxane.
The invention further emcompasses the novel methacryl-
lS oxyethyleneoxypropyleneyl silicones produced by the
inventive method and the cured products thereof.
That i5, the pre~ent invention is directed to an
organosiloxane compound containing at least two siloxy
repeat units, at least one of which has the formula
Ra
X $ i~_~2
where X is a methacryloxyethyleneoxypropylene group, R is
a hydrocarbon group or a methacryloxye~hyleneoxypropylene
group and a is 1 or 2.
- 3a -
,,~,

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BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a 60mhz NMR scan of a methacrylated polydi-
methylsiloxane prepared from allylmethacrylate.
Figure 2 is a 60mhz NMR scan of a methacrylated polydi- !-
methylsiloxane prepared from beta(allyloxy)ethyl methacrylate.
DETAILED DESCRIPTION OF THE INVENTION
The hydrosilation of beta(allyloxy)ethyl methacrylate maybe accomplished with silicon hydride functional siloxane polymers
or low molecular weight analogs such as 1,3,5,7-tetramethylcyclo-
tetrasiloxane and tetramethyldisiloxane. A noble metal hydro-
silation catalyst is used, preferably a platinum catalyst.
Reaction temperatures should be kept below about 100C in order
to prevent thermal polymerization of the methacrylate groups.
Examples 1, 2 and 3 describe synthesis with tetramethyldi-
siloxane, a commerci.ally available silicone hydride functionalsiloxane polymer and a specially synthesized SiH functional
polyorganosiloxane, respectively.
Example 1
4.0 grams tetramethyldisiloxane (0.03 moles) in 10 ml
toluene was added gradually to a moisture protected flask con-
taining 20.0 grams beta(allyloxy)ethyl methacrylate (0.12
moles), 0.50 grams 2% H2PtC16.6H2O in butyl acetate and 0.05
grams phenothiaziane in 50ml toluene.
The reaction was heated to 80C, producing an exotherm
between 85cand 89C for one hour. After the exotherm subsided,
temperature was maintained at ~0C for three additional hours
when an IR scan showed no SiH stretch at 2200c~ 1. The mixture
was cooled, stripped with a rotary evaporator to remove toluene
and deep-stripped at 80C and 0.35mm.

ll
This product had a tendency to polymerlze during the deep-
strip operation indicating that additional polymerization inhi-
bitor should be added prior to the deep-stripping step.
Example 2
5.0 grams of a commercially available 2500MW polydimethyl-
siloxane having 7 methyl hydrosiloxane units per molecule
randomly distributed, (0.128 moles SiH), 2.18 grams beta-(allyl- ¦
oxy)ethyl methacrylate (0.128 moles) and 0.5 grams of a 2%
solution of chloroplatinic acid in butyl acetate were mixed with
10 25 mls toluene and 0.3 grams hydroquinone and heated to 70C
under dry hydrogen for three hours. At the end of this time, IR j
showed no SiH stretch at 2200cm 1. The mixture was cooled,
stirred overnight with 2 grams activated basic alumina and then
filtered through Cellte, stripped to remove solvent, and deep-
stripped to give 6.50 grams product.
The ability of this product to cure with an anaerobic
acrylic cure system was demonstrated as follows. 5 grams of
product was mixed with 2 drops (about 0.2g) of cume~e hydro-
peroxide, 1 drop of a 50% solution of saccharin in dimethylsulf-
oxide and 1 drop of dimethyl-p-tolui.dine. The mixture was
applied to 6 strips of one inch wide sandblasted steel which
were overlapped at a 90 angle by six additional one inch wide
steel strips, three of which had been primed with a commercial
primer based on mercaptobenzothiazole and dimethyl-p-toluidine.
After 24 hours at room temperature, all had fixtured. There
were no gross differences between the primed and unprimed sets,
demonstrating that the methacrylated silicone products of the
invention are capable of anaerobic cure on steel.
- 5 -
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lZ'12447
Example 3
A polydimethylsiloxane polymer having a theoretical molecu- I,
lar weight of 20,000 and 6.8 methylhydrosiloxane units per
molecule was prepared by stirring at room temperature for 2 days ¦
a mixture of 50.00 grams octamethylcyclotetrasiloxane, 1.06
grams tetramethylcyclotetrasiloxane, 0.42 grams hexamethyl-
disiloxane and 0.13 grams trifluoromethane sulfonic acid. After
2 days the mixture was diluted with 150 ml ether and washed with
3 grams NaHCO3 in 50 ml water. The organic layer was washed
twice with 50 ml water portions, dried over sodium sulfate,
filtered and stripped to give 47.1 grams of product.
A methacrylated silicone in accordance with the invention
was prepared from the polymer of the previous parac3raph by
mixing 10.00 grams of polymer, 0.51 grams beta-(allyloxy~ethyl
methacrylate, 0.5 grams of a 2% chloroplatinic acid solution in
butyl acetate and 0.03 grams hydroquinone with 25ml toluene and
heating the mixture to 70C under N2 with stirring for 3 hours.
The reaction mixture was then stirred overnight at room tempera-
ture with activated basic alumina. The alumina was'filtered off
through Celite, stripped to remove solvent and then deep-stripped
as in E~amples 1 and 2 to give 8.9 grams of a light brown product.
Example 4
Allyl methacrylate and beta(allyloxy)ethyl methacrylate
were compared for propene elimination during hydrosilation as
follows. Both esters were hydrosilated with a silicon hydride
functional polydimethylsiloxane as in Example 2 except that mole
ratios of es~ers to SiH were 1.05/1 and activated alumina was
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12~2447
not used in the workup. NMR scans of the products were obtained ¦
using a 60 mhzNMR. The portions o~ those scans between about 1 ,
and 7~ are shown in Figures 1 and 2 for the allyl methacrylate
and beta(allyloxy)ethyl methacrylate products, respectively.
The hydrogen atoms were labeled as follows for the two products:
(A) CH30 (C)~D)(~)
CH2=C--C-o-cH2cH2cH2si-
(A) CH30 (F)(G) (C)(D)(E)
2 C----COCH2CH2o-cH2cH2cH2_si_
The NMR scan of the allyl methacrylate product, Figure 1,
gave a clean separation between methacrylate methylene group A
and propyl methylene group C as shown in Figure 1~ Integration
of these peaks gave a ratio of C/A=18/30. The theoretical ratio
is 1/1, indicating substantial propene elimination. The meth-
acryloxy siloxane product resulting from the propene elimination
was further evidenced by the strong methacrylic acid odor which
the product developed when exposed to atmospheric moisture
overnight.
The NMR scan of the beta(allyloxy)ethyl methacrylate product,
Figure 2, showed clean separation for the methacrylate methylene
hydrogens (A) and a complex combined peak for propyl and ethyl
methylene hydrogens (C) and (G). The theoretical ratio of C and
G to A was 2/1. The ratio found was 43/21~ demonstrating that
propene elimination did not occur.

~L2~2~47
In addition to the chloroplatinic acid used in the examples ¦
above, other hydrosilation catalysts may be used in the prepara- I
tion of the inventive siloxanes. Examples are platinum, hydro-
carbon platinum complexes and rhodium complexes. Platinum based
catalysts are preferred at levels between lOppm and 500ppm
platinum, preferably between 50ppm and 300ppm.