U.S. patent number RE31,406 [Application Number 06/215,486] was granted by the patent office on 1983-10-04 for oxygen permeable contact lens composition, methods and article of manufacture.
This patent grant is currently assigned to Syntex (U.S.A.) Inc.. Invention is credited to Norman G. Gaylord.
United States Patent |
RE31,406 |
Gaylord |
October 4, 1983 |
**Please see images for:
( Certificate of Correction ) ** |
Oxygen permeable contact lens composition, methods and article of
manufacture
Abstract
Contact lenses are fabricated from a copolymer of a
polysiloxanylalkyl acrylic ester and an alkyl acrylic ester. The
copolymer has increased oxygen permeability.
Inventors: |
Gaylord; Norman G. (New
Providence, NJ) |
Assignee: |
Syntex (U.S.A.) Inc. (Palo
Alto, CA)
|
Family
ID: |
26910083 |
Appl.
No.: |
06/215,486 |
Filed: |
December 11, 1980 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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931355 |
Aug 7, 1978 |
|
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Reissue of: |
263541 |
Jun 16, 1972 |
03808178 |
Apr 30, 1974 |
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Current U.S.
Class: |
526/279; 204/165;
264/1.1; 264/2.7; 351/159.33; 556/444 |
Current CPC
Class: |
C08F
220/12 (20130101); C08F 230/08 (20130101); G02B
1/04 (20130101); G02B 1/043 (20130101); G02B
1/04 (20130101); C08L 43/04 (20130101); G02B
1/043 (20130101); C08L 33/06 (20130101) |
Current International
Class: |
C08F
220/12 (20060101); C08F 230/08 (20060101); C08F
220/00 (20060101); C08F 230/00 (20060101); G02B
1/04 (20060101); C08F 230/08 (); G02C 007/04 () |
Field of
Search: |
;526/279 ;351/16R,16H
;204/165 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Physicians' Desk Reference, p. 575 (1969). .
Bull. Acad. Sci. USSR, Chem., No. 4, pp. 467-472 (1957). .
R. L. Merker et al., Journal of Org. Chem., 21, pp. 1537-1539
(1956). .
R. L. Merker et al., Journal of Pol. Sci., 25, Issue No. 108, pp.
115-117 (1957)..
|
Primary Examiner: Levin; Stanford M.
Attorney, Agent or Firm: Hirsch; Joseph I. Peters; Howard M.
Krubiner; Alan M.
Parent Case Text
.Iadd.
This is a continuation of application Ser. No. 931,355, abandoned,
filed Aug. 7, 1978 which was a reissue application of Ser. No.
263,541, filed June 16, 1972, now U.S. Pat. No. 3,808,178.
.Iaddend.
Claims
Having described my invention in such manner as to enable those
skilled in the art to understand and practice it and having
identified the preferred embodiments thereof, I claim: .[.
1. A new composition of matter specially adapted for the production
of contact lenses having increased oxygen permeability, said new
composition being a solid copolymer of comonomers consisting
essentially of:
(a) about 10 to 60 parts by weight of a polysiloxanylalkyl ester of
the structure ##STR4## wherein:
(1) X and Y are selected from the class consisting of C.sub.1
-C.sub.5 alkyl groups, phenyl groups and Z groups,
(2) Z is a group of the structure ##STR5## (3) A is selected from
the class consisting of C.sub.1 -C.sub.5 alkyl groups and phenyl
groups,
(4) R is selected from the class consisting of methyl groups and
hydrogen,
(5) m is an integer from one to five, and
(6) n is an integer from one to three; and
(b) about 40 to 90 parts by weight of an ester of a C.sub.1
-C.sub.20 monohydric alkanol and an acid selected from the class
consisting of acrylic and methacrylic acids..].
2. As a new article of manufacture, a contact lens having increased
oxygen permeability .Iadd.in comparison with
poly(methylmethacrylate).Iaddend., said lens being fabricated from
.[.the copolymer composition of claim 1,.]. .Iadd.a solid copolymer
of comonomers consisting essentially of:
(a) about 10 to 60 parts by weight of a polysiloxanylalkyl ester of
the structure ##STR6## wherein (1) X and Y are selected from the
class consisting of C.sub.1 -C.sub.5 alkyl groups, phenyl groups
and Z groups,
(2) Z is a group of the structure ##STR7## (3) A is selected from
the class consisting of C.sub.1 -C.sub.5 alkyl groups and phenyl
groups,
(4) R is selected from the class consisting of methyl groups and
hydrogen,
(5) m is an integer from one to five, and
(6) n is an integer from one to three; and
(b) about 40 to 90 parts by weight of an ester of a C.sub.1
-C.sub.20 monohydric alkanol and an acid selected from the class
consisting of acrylic and methacrylic acids,
said lens .Iaddend.having a refractive index of from 1.35 to 1.50.
.Iadd.
3. The contact lens of claim 2 wherein said solid copolymer of
comonomers includes as a comonomer a minor amount of a crosslinking
monomer. .Iaddend. .Iadd. 4. The contact lens of claim 3 wherein
said cross-linking monomer is a polyol dimethacrylate or a polyol
diacrylate. .Iaddend..Iadd. 5. The contact lens of claim 3 wherein
said cross-linking monomer is present in an amount equal to about
0.01% to about 2% by weight of said copolymer. .Iaddend..Iadd. 6.
The contact lens of claim 5 wherein said cross-linking monomer is a
polyol dimethacrylate or a polyol diacrylate. .Iaddend. .Iadd. 7.
The contact lens of claim 3 wherein said solid copolymer of
comonomers includes as a comonomer a minor amount of a wetting
monomer. .Iaddend. .Iadd. 8. The contact lens of claim 7 wherein
said wetting monomer is methacrylic acid. .Iaddend..Iadd. 9. The
contact lens of claim 7 wherein said wetting monomer is present in
an amount equal to about 0.1% to about 10% by weight of said
copolymer. .Iaddend..Iadd. 10. The contact lens of claim 9 wherein
said wetting monomer is methacrylic acid. .Iaddend..Iadd. 11. The
contact lens of claim 2 wherein said solid copolymer of comonomers
includes as a comonomer a minor amount of a wetting monomer.
.Iaddend..Iadd. 12. The contact lens of claim 11 wherein said
wetting monomer is methacrylic acid. .Iaddend..Iadd. 13. The
contact lens of claim 11 wherein said wetting monomer is present in
an amount equal to about 0.1% to about 10% by weight of said
copolymer. .Iaddend..Iadd. 14. The contact lens of claim 13 wherein
said wetting monomer is methacrylic acid. .Iaddend. .Iadd. 15. The
contact lens of claims 2 or 3 wherein a wetting agent is applied to
the surface of said lens. .Iaddend..Iadd. 16. The contact lens of
claim 15 wherein said wetting agent is a dilute aqueous solution of
an alkyldimethylbenzylammonium chloride. .Iaddend..Iadd. 17. The
contact lens of claims 2 or 3 wherein the wettability of the
surface of said lens is improved by exposure of the surface to a
corona discharge. .Iaddend..Iadd. 18. The contact lens of claims 2
or 3 wherein the wettability of the surface of said lens is
improved by treatment of the surface with a strong oxidizing agent.
.Iaddend..Iadd. 19. The contact lens of claim 18 wherein said
strong oxidizing agent is nitric acid. .Iaddend.
Description
This invention relates to novel copolymer compositions.
In another aspect, the invention relates to methods for increasing
the oxygen permeability of polymerized acrylates and
methacrylates.
In still another respect, the invention concerns contact lenses
having increased oxygen permeability.
In yet another respect, the invention relates to wettable contact
lens materials.
In a further aspect, the invention concerns oxygen-permeable,
wettable transparent copolymers which can be cast, molded or
machined to provide improved contact lenses.
The prior art teaches the use of many different polymeric materials
in contact lenses. However, although these polymers possess the
optical clarity necessary for corrective lenses, they suffer from
other characteristics which reduce their potential utility.
Polymethylmethacrylate is rigid and durable but relatively
impermeable to oxygen. The hydrogel materials based on hydrophilic
polymers such as polyhydroxyethylmethacrylate are soft and have
poor durability. In addition, they provide an environment which is
favorable for bacterial growth and are also relatively impermeable
to oxygen.
Silicone rubber is soft and resilient and is highly permeable to
oxygen. However, due to the low strength of polysiloxanes, a filler
which increases the refractive index of the mixture, must be added
to improve the durability. Further, the precision machining and
polishing which is necessary in the fabrication of a corrective
contact lens is extremely difficult with the elastomeric silicone
rubbers.
Accordingly, it would be highly desirable to provide a polymeric
material suitable for use in fabricating contact lenses having
increased oxygen permeability, improved mechanical strength, and
which is sufficiently rigid to permit precision machining and
polishing. I have now discovered novel copolymer materials which
possess these properties.
The novel copolymers which I have discovered are prepared by
copolymerizing a polysiloxanylalkyl ester of acrylic or methacrylic
acid with an alkanol ester of acrylic or methacrylic acid.
The polysiloxanylalkyl ester monomer has the structural formula
##STR1## wherein X and Y are selected from the class consisting of
C.sub.1 -C.sub.5 alkyl groups, phenyl groups and Z groups; Z is a
group of the structure ##STR2## A is selected from the class
consisting of C.sub.1 -C.sub.5 alkyl groups and phenyl groups; R is
selected from the class consisting of methyl groups and hydrogen; m
is an integer from one to five; and n is an integer from one to
three.
In the alkanol ester comonomers, the alkyl group contains from 1 to
20 carbon atoms.
Representative polysiloxanylalkyl ester comonomers which may be
employed in the practice of the invention include: ##STR3##
Representative alkanol ester comonomers which may be employed in
the practice of the invention include:
methyl acrylate and methacrylate
ethyl acrylate and methacrylate
propyl acrylate and methacrylate
isopropyl acrylate and methacrylate
butyl acrylate and methacrylate
amyl acrylate and methacrylate
hexyl acrylate and methacrylate
heptyl acrylate and methacrylate
octyl acrylate and methacrylate
2-ethylhexyl acrylate and methacrylate
nonyl acrylate and methacrylate
decyl acrylate and methacrylate
undecyl acrylate and methacrylate
lauryl acrylate and methacrylate
cetyl acrylate and methacrylate
octadecyl acrylate and methacrylate
The novel copolymers of the present invention comprise about 10-60
parts by weight of one or more of the polysiloxanylalkyl ester
monomers copolymerized with about 40-90 parts by weight of one or
more of the alkanol ester comonomers.
At present it is preferred to employ polysiloxanyl acrylate and
methacrylate esters which have a straight or branched siloxane
chain containing two to four silicon atoms having methyl or phenyl
substituents and one to three ethylene groups connecting the
siloxanyl chain to the acryloxy or methacryloxy group. Best results
are obtained if the polysiloxanyl ester content of the comonomer is
up to 35% by weight and correspondingly less, e.g., 10-15%, as the
silica content of the ester is increased. If one employs a branched
chain alkanol ester, e.g., 2-ethylhexyl acrylate, one preferably,
employs a lower polysiloxanyl ester comonomer, e.g.,
pentamethyldisiloxanylmethyl acrylate.
The copolymers of the invention are prepared by contacting the
mixture of comonomers with a free radical generating polymerization
initiator of the type commonly used in polymerizing ethylenically
unsaturated compounds. Representative free radical polymerization
initiators include:
acetyl peroxide
lauroyl peroxide
decanoyl peroxide
caprylyl peroxide
benzoyl peroxide
tertiarybutyl peroxypivalate
diisopropyl peroxycarbonate
tertiarybutyl peroctoate
.alpha.,.alpha.'-azobisisobutyronitrile
Conventional polymerization techniques can be employed to produce
the novel copolymers. The comonomer mixture containing between
about 0.05-2% by weight of the free radical initiator is heated to
a temperature between 30.degree. C.-100.degree. C., preferably
below 70.degree. C., to initiate and complete the polymerization.
The polymerization can be carried out directly in a contact lens
mold to form a lens generally having the desired configuration.
Alternatively, the polymerization mixture can be heated in a
suitable mold or container to form discs, rods or sheets which can
then be machined to the desired shape using conventional equipment
and procedures employed for fabricating lenses from polymethyl
methacrylate. The temperature is preferably maintained below
70.degree. C. in order to minimize the formation of bubbles in the
copolymer. Instead of employing the bulk polymerization techniques
described above, one can employ solution, emulsion or suspension
polymerization to prepare the novel copolymers, using techniques
conventionally used in the preparation of polymers from
ethylenically unsaturated monomers. The copolymer thus produced may
be extruded, pressed or molded into rods, sheets or other
convenient shapes which are then machined to produce the contact
lenses.
The novel copolymers have vastly increased oxygen permeability in
comparison to conventional contact lens materials. For example, a
copolymer comprising 35 parts pentamethyldisiloxanylmethyl
methacrylate and 65 parts of methyl methacrylate has an oxygen
permeability of 500 cc.-mil/100 in..sup.2 /24 hr./atm. compared to
an oxygen permeability of 34 for polymethyl methacrylate and 13 for
polyhydroxyethylmethacrylate. These oxygen permeability values were
determined in accordance with ASTM D1434, using a tester which has
a 3 "Dow" cell pressure change detection units. Discs were cut to
proper size to fit the tester, placed in the apparatus and
conditioned a minimum of 16 hours under both vacuum and oxygen.
Immediately following the conditioning period, the test was
performed by plotting a curve of cell pressure versus time. The
slope of the curve was then used to calculate the oxygen
transmission rate. In general, the oxygen permeability of the
copolymers of the invention is at least 4 times to as much as
several hundred times higher than that of lenses prepared from
polymethylmethacrylate or the so-called "hydrogel" lenses prepared
from polyhydroxyethylmethacrylate.
While some of the novel copolymers are inherently wettable by human
tears, it may be necessary to improve the wettability of others.
This can be accomplished by several alternate methods. For example,
wettability can be imparted to the copolymer by the addition of
from about 0.1% to about 10% by weight of one or more hydrophilic
monomers to the copolymerization mixture. Such monomers include
hydroxyalkyl acrylates and methacrylates wherein the alkyl group
contains 1 to 4 carbon atoms, acrylic and methacrylic acid,
acrylamide, methacrylamide, N-methylolacrylamide,
N-methylolmethacrylamide, glycidyl acrylate and methacrylate and
N-vinylpyrrolidone. Alternatively, the wettability of the surface
of contact lenses made from the novel copolymers can be improved by
the application of a wetting agent such as, for example, a dilute
aqueous solution of alkyldimethylbenzylammonium chloride, by
exposure of the surface to a corona discharge or by chemical
treatment of the surface with a strong oxidizing agent such as
nitric acid.
The rigidity of the contact lenses prepared from materials useful
in the practice of this invention may be varied by changing the
ratio of comonomers and/or their chemical composition. Thus,
contact lenses prepared from acrylate monomers are more flexible
than those prepared from methacrylate monomers. A copolymer of a
polysiloxanylalkyl methacrylate and an alkyl methacrylate may be
fabricated into a contact lens which is more rigid than a lens
prepared from the copolymer of the corresponding acrylates. The
lower the alkyl methacrylate content of the copolymer the more
flexible the contact lens prepared therefrom.
The rigidity of a contact lens prepared from the materials useful
in the practice of this invention may be increased, if desired, by
the incorporation into the copolymer composition of 0.01% to about
2% by weight of a crosslinking monomer such as a polyol
dimethacrylate or diacrylate or a polyol acrylic ester of higher
functionality, for example, ethylene glycol dimethacrylate,
butylene glycol dimethacrylate, neopentyl glycol diacrylate and
pentaerythritol triacrylate or tetra-acrylate.
The refractive index is an important but noncritical characteristic
of a contact lens. Thus, the refractive index of
polymethylmethacrylate, the polymer most widely used in the
fabrication of contact lenses, is 1.49. The refractive indices of
the copolymers useful in the practice of this invention may be
varied between 1.35 and 1.50 by varying the ratio and nature of the
comonomers. In general, increasing the polysiloxanyl monomer
content of the copolymer will decrease its refractive index. The
nature of the substituents on the silicon atoms of the
polysiloxanyl monomer also importantly affects the refractive index
of the copolymer. Lower straight chain alkyl substituents produce
copolymers of lower refractive index while polysiloxanyl monomers
having phenyl substituents on the silicon atoms yield copolymers
having a higher refractive index.
The following examples are presented to illustrate the practice of
the invention and not as an indication of the limits of the scope
thereof.
EXAMPLE 1
This example illustrates the synthesis of a representative
polysiloxanylalkyl ester comonomer, pentamethyldisiloxanylmethyl
methacrylate.
Synthesis of dimethylchloromethylchlorosilane
Distilled trimethylchlorosilane (635 ml., 5 moles), B.P.
59.9.degree. C., is placed in a 1-liter, 3-necked, round-bottom
flask equipped with a magnetic stirrer, a thermometer, a gas inlet
tube and a Dry-Ice cooled reflux condenser whose outlet is
connected to a water scrubber. After flushing the apparatus with
dry nitrogen for 15 minutes, chlorine gas is introduced through the
gas inlet tube and the flask is irradiated by ultraviolet light
from a General Electric 15-watt germicidal lamp placed at a
distance of 6 in. from the flask. Gaseous hydrogen chloride is
evolved and absorbed in the water scrubber which contains a caustic
soda solution and a small amount of phenolphthalein. The
temperature is maintained in the range 30.degree.-40.degree. C.
while chlorine is bubbled through the reaction mixture. After 30
hours of photochlorination, 5 moles of hydrogen chloride is
evolved, as indicated by the discharge of the pink color in the
water scrubber. The product is distilled through a column with 18
theoretic plates and the fraction distilling at 115.degree. C. is
collected. The yield of dimethylchloromethylchlorosilane (d.sup.25
=1.07) is 30%.
Synthesis of pentamethylchloromethyldisiloxane
134 ml. dimethylchloromethylchlorosilane (1 mole) and 127 ml. (1
mole) of trimethylchlorosilane are mixed and shaken thoroughly.
When 600 ml. of distilled water is added, exothermic hydrolytic
reactions occur immediately. The mixture is shaken on a mechanical
shaker overnight to complete hydrolysis. The upper oily layer is
separated and is dried over anhydrous sodium carbonate. After
drying, the product is distilled through a column of 13 theoretical
plates and the fraction which distills at 151.degree.-152.degree.
C. is collected. The yield of pentamethylchloromethyldisiloxane
(B.P. 151.8.degree. C., d.sup.25 =0.910, n.sub.D.sup.20 =1.4106) is
30%.
Synthesis of pentamethyldisiloxanylmethyl methacrylate
30 ml. pentamethylchloromethyldisiloxane (0.14 mole), 13.8 ml.
(0.16 mole) distilled methacrylic acid, 21.0 ml. (0.15 mole)
triethylamine, 30 ml. xylene and 0.8 g. hyroquinone are mixed and
refluxed for 16 hours. Triethylamine hydrochloride precipitates and
is filtered. The filtrate is mixed with 1 g. of hydroquinone and 1
g. of copper powder. Xylene is distilled from the mixture at
atmospheric pressure. The distillation apparatus is then connected
to a vacuum line and the fraction which distills at
73.degree.-75.degree. C. under 4-5 mm. Hg pressure is collected.
The yield of pentamethyldisiloxanylmethyl methacrylate (B.P.
73.degree.-74.degree. C./4 mm. Hg, d.sup.20 =0.910, n.sub.D.sup.20
=1.420) is 45%.
The disiloxane monomer recovered by distillation contains
co-distilled hydroquinone. Purification is accomplished by washing
the monomer with aqueous alkali solution containing 25% sodium
carbonate and 1% sodium hydroxide until the aqueous layer is
colorless. The oily monomer layer is then washed with water until
neutral and dried over anhydrous sodium carbonate. The dried
monomer is refrigerated until used.
EXAMPLE 2
This example illustrates the preparation of a representative
oxygen-permeable copolymer.
A mixture of 35 parts of the disiloxane monomer of Example 1, 65
parts of methyl methacrylate and 0.004 ml. of tert-butyl
peroxypivalate per ml. of monomer mixture is placed in a
polypropylene Petri dish to a height of one-eighth of an inch. The
dish is covered and placed in a vacuum oven which has been purged
with nitrogen. The oven is closed and the temperature is maintained
at 45.degree. C. for 20 hours. The copolymer disc is hard,
colorless, transparent and rigid. The oxygen permeability is 500
cc.-mil/100 in..sup.2 /24 hr./atm.
The oxygen permeability of a disc of polymethylmethacrylate is 34
cc.-mil/100 in..sup.2 /24 hr./atm. while that of a disc of
polyhydroxyethylmethacrylate is 13 cc.-mil/100 in..sup.2 /24
hr./atm.
A cylindrical plug having dimensions of 1/4 inch thickness and 1/2
inch diameter is prepared by copolymerizing the 35/65 disiloxane
monomer/methyl methacrylate mixture in a polyethylene cap at
45.degree. C. for 20 hours. The plug is machined, cut, polished and
finished to a concavo-convex lens.
EXAMPLES 3-9
These examples illustrate the preparation and properties of
copolymers containing varying proportions of a siloxanyl monomer,
methyl methacrylate, and a hydrophilic monomer (hydroxyethyl
methacrylate).
Mixtures of the disiloxane monomer of Example 1 (DSM), methyl
methacrylate (MMA), hydroxyethyl methacrylate (HEMA) and tert-butyl
peroxy pivalate (0.004 ml. per ml. of monomer mixture) is
polymerized in polyethylene caps under the conditions shown in the
following table:
______________________________________ Composition, wt. % Temp.
Time Example DSM MMA HEMA .degree.C. hr. Properties*
______________________________________ 3 20 75 5 50 6.5 T, H, R 4
35 60 5 45 20 T, H, R 5 44 50 6 50 48 T, H, SR 6 45 50 5 45 20 T,
H. SR 7 45 49 6 70 1 T, H, SR 50 16 8 51 40 9 75 2.5 T, H. SR 9 65
30 5 60 4 NT, S, E ______________________________________ *T =
transparent; H = hard; R = Rigid; SR = Semirigid; NT = hazy; S =
soft; E = elastomeric
The polymerized plugs are machined and finished in the usual manner
to lenses with a concave surface on one side and a convex surface
on the opposite side. The lenses are easily wetted by water and an
aqueous saline solution.
EXAMPLE 10
This example illustrates the preparation and properties of a
wettable oxygen-permeable terpolymer.
A disc is prepared in the manner described in Example 2 from a
mixture of 45 parts of the disiloxane monomer of Example 1, 50
parts of methyl methacrylate and 5 parts of
hydroxyethylmethacrylate using tert-butyl peroxypivalate as
catalyst. The polymerization is carried out at 45.degree. C. for 20
hours. The resultant disc is colorless, transparent, hard and
semi-rigid. The surface of the disc is readily wetted by water and
saline solution. The oxygen permeability of the terpolymer is 765
cc.-mil/100 in..sup.2 /24 hr./atm.
EXAMPLE 11
This example illustrates the preparation and properties of a
wettable oxygen-permeable terpolymer.
A disc prepared in the same manner described in Example 2 by
polymerizing a mixture of 20 parts of the disiloxane monomer of
Example 1, 75 parts of methyl methacrylate, 5 parts of hydroxyethyl
methacrylate and 0.004 ml. of tert-butyl peroxypivalate per ml. of
monomer mixture, at 50.degree. C. has an oxygen permeability of 135
cc.-mil/100 in..sup.2 /24 hr./atm. Lenses cut and machined from the
disc are transparent, hard and rigid.
EXAMPLES 12-14
These examples illustrate the preparation and properties of
copolymers of a siloxanyl monomer with various proportions of other
methacrylate ester comonomers.
Cylindrical plugs are prepared in the manner described in Example 3
from mixtures of the disiloxane monomer (DSM) of Example 1, methyl
methacrylate (MMA), octadecyl methacrylate (ODMA), hydroxyethyl
methacrylate (HEMA) and ethylene glycol dimethacrylate (EGDMA) by
polymerization at 70.degree. C. for 2.5 hours using tert-butyl
peroxypivalate as catalyst. The properties of lenses prepared from
the plugs are shown in the following table:
______________________________________ Ex- am- Composition, wt. %
Prop- ple DSM MMA ODMA HEMA EGDMA erties
______________________________________ 12 35 30 30 5 0 T, H, E 13
45 30 20 5 0 T, S, E 14 45 38 10 5 2 T, S, R
______________________________________
EXAMPLE 15
This example illustrates the synthesis of
1,1,1-tris(trimethylsiloxy)methacrylatopropylsilane.
23.8 g. (13.0 ml.) of concentrated sulfuric acid is added slowly
with stirring to a mixture of 11.6 g. (14.7 ml.) of absolute
ethanol and 16.5 ml. of water. The mixture is cooled in a water
bath.
Methacrylatopropyltrimethoxysilane (0.1 mole, 24.8 g.), is mixed
with 0.3 mole (39.6 g.) of trimethylacetoxysilane in a flask
equipped with a magnetic stirrer. Ethylsulfuric acid (6.5 g.),
prepared as described above, is added dropwise from a dropping
funnel into the stirred mixture. The flask is cooled during the
addition of the ethylsulfuric acid catalyst solution in an ice
water bath. After completion of the catalyst addition, the solution
is stirred at room temperature for two days. The upper oily layer
is then separated, washed with sodium bicarbonate solution, washed
with water and then dried over anhydrous sodium sulfate. The
produce is distilled under vacuum to remove ethyl acetate. The
distillation flask is immersed in a water bath whose temperature is
maintained at 40.degree.-45.degree. C. to prevent premature
polymerization of the monomer. The yield of
tris(trimethylsiloxy)methacrylatopropylsilane is 86% and the
density of the monomer is 0.989 g./cc. at 20.degree. C. The monomer
is refrigerated until used.
EXAMPLE 16
This example illustrates the preparation of a copolymer of methyl
methacrylate with the novel polysiloxanyl ester of Example 15.
A cylindrical plug is prepared by polymerizing a mixture of 40
parts of tris(trimethylsiloxy)-.alpha.-methacryloxypropylsilane and
60 parts of methyl methacrylate in the presence of tert-butyl
peroxypivalate at 50.degree. C. Lenses prepared from the plug are
hard, transparent and oxygen permeable.
EXAMPLES 17-28
This example illustrates the preparation of various copolymers of
polysiloxanyl esters and various alkyl acrylates or methacrylates.
The polysiloxanyl ester comonomers are prepared according to the
general techniques of Examples 1 and 15. The copolymer is prepared
according to the general technique of Example 2. All copolymers
resulting are transparent, hard and rigid so as to be suitable for
contact lens manufacture. The oxygen permeability of the copolymers
varies from 300-500 cc.-mil/100 in..sup.2 /24 hr./atm. as measured
by the technique previously described.
__________________________________________________________________________
POLYSILOXANYL ESTER ALKANOL ESTER Wt. % in Wt. % in
.Iadd.Example.Iaddend. Copolymer Monomer Copolymer Monomer
__________________________________________________________________________
17 35 heptamethyltrisiloxanylethyl acrylate 65 2-ethylhexyl
acrylate 18 30 isobutylhexamethyltrisiloxanylmethyl methacrylate 70
t-butyl methacrylate 19 30 n-propyloctamethyltetrasiloxanylpropyl
methacrylate 70 decyl methacrylate 20 25
tri-i-propyltetramethyltrisiloxanylethyl acrylate 75 isopropyl
acrylate 21 25 t-butyltetramethyldisiloxanylethyl acrylate 75
methyl acrylate 22 20 n-pentylhexamethyltrisiloxanylmethyl
methacrylate 80 ethyl methacrylate 23 20
phenyltetramethyldisiloxanylethyl acrylate 80 octadecyl acrylate 24
20 phenyltetraethyldisiloxanylethyl methacrylate 80 hexyl
methacrylate 25 15 triphenyldimethylsiloxanylmethyl acrylate 85
methyl acrylate 26 15
tris(trimethylsiloxy)-.gamma.-methacryloxypropylsilane 85 methyl
methacrylate 27 15
methyldi(trimethylsiloxy)-methacryloxymethylsilane 85 n-propyl
methacrylate 28 10
pentamethyldi(trimethylsiloxy)-acryloxymethylsilane 90 ethyl
acrylate
__________________________________________________________________________
As illustrated by Examples 17-28, it is preferred to use a straight
chain alkanol ester monomer if the polysiloxanyl ester monomer is a
branched chain compound, and vice versa. Also, it is preferred to
employ two acrylate or two methacrylate comonomers to prepare the
copolymer, rather than an acrylate monomer and a methacrylate
monomer. Finally, where more complex polysiloxanyl ester comonomers
are employed, the proportion of polysiloxanyl ester is lower, e.g.,
10-20%, than if simpler polysiloxanyl esters are employed. In
general, the presence of larger, more complex substituents on the
interior silicon atoms tend to increase the refractive index of the
copolymer, all other factors being equal.
* * * * *