CA1049191A - Oxygen-permeable contact lens composition, methods and article of manufacture - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A method is provided for improving the oxygen permeability of contact lenses. The method includes the essential step of fabricating the lenses from a copolymer of a polyslloxanylalkyl acrylic ester and an alkyl acrylic ester.

Description

:
491~
~ This inventio~ relates to a method for increasing the oxygen permeability of contact leffses, and to contact lenses having increased oxygen permeability. The invention also relates to wettable contact lens materials. The invention further concerns improved contact lehses made ~rom oxygen-permeable, wettable transparent copolymers.
I The prior art teaches the use of many different polymeric materials in contact lenses. HoweverJ although these polymers possess i~
the optical clarity necessary for corrective lenses they suffer from r-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, for example, polyhydroxyethylmethacrylate are soft and have poor durability. In addition, they provide an environment which is favourable for bacterial growth and are also relatively lmpermeable 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 correc~ive contact lens is extremely difficult with the elastomeric silicone rubbers.
Accordingly, it would be highly desirable to provide a poly-meric material suitable for use in fabricating contact lenses having increased oxygen permeability, improved mechanical strength, and which is sufficientb rigid to permit precision machinlng and polishing. It has now been discovered that certain copolymer materials possess these r-` properties. ¦ ~
i Such copolymers may be prepared by copolymerizing a polysilox- ~ ;
anylalkyl ester of acrylic or methacrylic acid with an alkanol ester of L ~ :
'30 acrylic or methacrylic acid. Alternatively, such copolymers may be pre-pared in the manner taught in United States Patent No. 2,922,807 issued January 26, 1960 to R.L. Merker.

, ' ~'~L ' 9~L9~ ~
Thus9 by a broad aspect of this inve~tion, a method is provided for improving the oxygen permeability of contact lenses, the method comprising the essential step of fabricating the lenses from a solid copolymer of comonomers consisting essentially of: (a) 10 to 60 parts by weight of a polysiloxanylalkyl ester of the structure ~ X 0 R .

tl si - (CH2)n ~ - C - C CH2 r wherein: (1) X and Y are selected from the class consisting of Cl - C5 alkyl groups, phenyl groups and Z groups, (2) Z is a group of the struc-ture A . ~*~
A- -Si - 0 l ~ ! ' (3) A is selected from the class consisting of Cl - C5 alkyl groups and phenyl groups9 (4) R is selected from the class consisting of methyl k . groups and hydrogen, (5) m is an integer from one to five, and (6) n is . an integer from one to three; and (b) 40 to 90 parts by weight of an ~.
ester of a Cl - C20 monohydric alkanol and an acid selected from the .
class consisting of acrylic and methacrylic acids. , By another aspect, the lens has a refractive index of from 1.35 to 1.50. : - .
By another aspect of this invention, a solid copolymer of comonomers is provided comprising: (a) 10 to 70 parts by weight of a .
polysiloxanylalkyl ester of the structure ~ A ~ - 0 ~ i - (Ch2)n - O - C ~ C = Ch2 - r wherein (1) X and Y are selected from ~he class consisting of Cl - C5 alkyl groups, phenyl groups and Z groups, (2) Z is a group of the struc- ~-ture r 1 1 :

- 2 - ~ ~

,:. . : , , .
: . . , . ' ~ ' ' ' ~ :' .

` r~ 4~9~ j

(3) A is selected from the class consisting of Cl - C5 alkyl groups and phenyl groups, ~4) R is selected'fro~ 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; (b) 30 to 90 parts by weight of an es~er of a Cl - C20 monohydric alkanol and an acid selected from the class I consisting of acrylic and methacrylic acids; and (c) 0.1 - 10~ by weight replacement of (a), or (b), or (a) + (b) of a hydrophilic monomer '';
selected from the group consisting of hydroxyalkyl acrylates and meth- r acrylates where the alkyl group constain~ 1 to 4 carbon atoms, acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, glycidyl acrylate, glycidyl methacrylate, and N-vinylpyrrolidone;-t~e copolymer being adapted to provide''a contact lens - having improved-oxygen~permeability and enhanced wettability.
By yet another aspect of this invention, the copolymer includes (d) O.Ol'to 2% by weight replacement of (a) or (b) or (a) + (b) ' of a cross-linking monomer selected from the group consisting of a polyol ~'' dimethacrylate, a polyol diacrylate, ethylene glycol dimethacrylate, ' r butylene glycol dimethacrylate, neopentyl glycol diacrylate, pentaery- I ~
thritol triacrylate, and pentaerythritol tetraacrylate; the copolymer ~ ' '- 20 being adapted to provide a contact lens having improved oxygen permeabi-lity, enhanced wettability and desired rigidity. ~ ' - .
', ~ ' ;~
- r~ -~
. . . I ~

, .~
`` 30 . , . _ :
, .
., ' . ' ~' - 2A - ' ~ , , , . ! . . ' . ' , .

4~9~
1 The polysiloxanylalkyl ester monomer has the 2 structural formula . - r 51 A ~ si- ~ si-(CH2)n-- --C--C= CU2 ~ wherein X and ~ are selected from the class consisting of ¦ :
9 Cl - C5 alkyl groups, phenyl groups and Z groups; Z is a .
group of the structure . . .....

2 ~ ~ ; ~ r 14 . ` : ~
A is selected from the class consisting of Cl - C5 alkyl P.
16 groups and phenyl groups; R is selected from the class ~... .
17 consisting of methyl groups and hydrogen; m is an integer 18 from one to five; and n is an integer from one to three. ¦.
19 ! `::
In the alkanol ester comonomers, the alkyl group , .
22~ contains from l to 20 carbon atoms. . . ¦

23 ¦ . Repres~ntative polysiloxanylalkyl ester comonomers 24 which may be employed $n preparing the copolvner used in the practice i~
of aspects of this invention include: . r-26 pentamethy1~isiloxanylmethyl methacrylate 27 CH3 1113 ~ 13 . .
28 CH3- i-o-Si-CH2-o-C-C-CH2 29 CH3 C~13 .
: . .
31 ~
32 . . 3 ~ .
~3.,w. ' ; ' , I . ,~ .. . .~

--4g~91 . ` .:
heptamet}lyltrislloxanylethyl acrylatc, 3IH3 Cl}l3 CH3 0 IH

~: C~l -si~o-si-o-si-c~2c~l2-c-c=cH2 5C}13 C113 CH3 6 .
7 tris~t~imethylsiloxy)- ~-methacryloxypropylsilane, ~ C}13 10CH3-Si-CH3 ~3-Si-O-Si-CH2C112CH2-o_c_c_cH2 . :

1~CH3-1i-CH3 ~:
1.5 CH3 . :
16 phenyltetramethyldisiloxanylethyl acrylate, 17CH3 C}13 0 Hl .
1~. ~6}~5 ~i 0-1i C112CH2-o-c-c=cH2 : .~.
19C~13 CH3 .
21phenyltetracthyldisiloxanyletllyl methacrylate, ::
22~2~15 C16H5 B 7 :~
23C2~15 li o-fi-c}l2cl~2 o c c=cH2 :: :
24C~15 C2~15 , ~ : .
25. .~ . ~ . ~ :
2G triphenyldimethyldisiloxanylmethyl acrylate, . 27C6}~5 C}13 0 ~1 ~ ~:
2~c6~15- li-o- li c112_o-c-c=c~2 31 ~IC6115c1~3 3~

4 . : ~ :
. ' " ' ' ' . .. .
~ ... . . .
: . . .
. : . : . .

919~
1 isobutylhexame~hyltrisiloxanylmethyl methacrylate, .
2 C113 C1~13 f H 3 o CH3 . C4~19 ~i 0 1i_0_7i_0_CH2_o-~-C=CH2 , ~
~ ,C}13 C~13 C113 1 5 . . .
6 methyldi(trimethylsiloxy)-methacryloxymethylsilane, 7 fH3 8CH3-Si-CH3 .
9 o 0 fH3 10C113-Si-CH2-0-C-c=cH2 :
11 . ' I ' ............................................. :
12CH3-Si-CH3 .
13 C~3 ~:
14 . ' . .
n-propyloctamethyltetrasiloxanylpropyl methacrylate, ' 16 CH3 fH3 CIH3 l~3 0 CH3 , 17 C3ll7-si-o-si-o-si-o-7l-cll2c~l2cll2 C C 2 .:
18 . CH3 CH3 C1~3 CH3 19 . , ' . , pentam~thyldi(trimeth,ylsiloxy~-acryloxymethylsilane, :
21 . CH3 ' : .
22 . , , CH3-Si-CH3 :, 23 1}13 1l13 1 1l ~1 .
24 C113-Si-0-Si-0-Si-CH2-0-C-C=CH2 .
I , ' :' .
26 CH3-Sl-CN3 , 28 ' ~ : ' , 29 , ~ ,' ' ' ' . .
' ~ ' . ' 31 ; ' . ~
32 : ~ ~ . '.
. . ..
' ' ~ ~ ~:

.
, . .
, ::. . .;: , . . .

`~ 1049191 - ~
t-butyltctramethyldisiloxanylethyl acrylate, 2 ! .
3 ;1~13 fH3 fH3 H .
~ C~3 - f - Si O - fi_c}l2c}l2 o_C_C=CH2 ~

6 C}13 C~3 CH3 7 .. .
8 n-pentylhexamethyltrisiloxanylmethyl methacrylate, 9 . . ~:
CH3 CIH3 CIH3 1I C1~13 11 C5Hll-li-O~Ii-O-si-cH2-o-c-c=cH2 !2 CH3 CH3 CH3 13 . .
14 . . ... ~:
tri-i-propyltetramethyltrisiloxanylethyl acrylate~
16 . .
17CH3 CIH3 13H7 H ::
18C3H7-si-o-si-o-si-c~i2cH2-o-c-c-c~2 19 CE13 CE13 C3H7 :
2~ . . .
q! ~ : `
22 . :
23 . ; . ~:
24 .

2~
2!) 1~

32 ~ 6 ~ . ,,' ,. , I

': . . . . .
_, ~ . . . , , ,., , . !

[)49~
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 I isopropyl acrylate and methacrylate butyl acrylate and methacrylate amyl acrylate and methacrylate r hexyl acrylate and methacrylate heptyl acrylate and methacrylate octyl acrylate and methacrylate 2-ethylhexyl acrylate and methacrylate ~ff 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 copolymers of the present invention comprise 10 - 60 parts 6y weight of one or more of the polysiloxanylalkyl ester monomers copolymerized ~ith 40 - 90 parts by weight of one or more of : the alkanol ester comonomers.
.

- . I .
~ ' ~ ' _ , :
s ~ ~ _ 7 - ' ~ I .
.t ~4g~91 1 At present it is preferred to employ polysiloxanyl 2 acrylate and methacrylate esters which have a straight or 3 ~ranched siloxane chain containing two to four silicon atoms having methyl or phenyl substituents and one to three cthylene yroups connectincJ the siloxanyl chain to the acryloxy or 6 methacryloxy group. Best results are obtained if the poly-7 siloxanyl ester content of the comonomer is ~p to 35~ by 8 weight and correspondingly less, e.g., 10-15%, as the silica 9 content of the ester is increased. If one employs a branched chain alkanol ester, e.g., 2-ethylhexyl acrylate, one preferably 11 employs a lower polysiloxanyl ester comonomer, e.g., pentamethyl 12 disiloxanylmethyl acrylate.

`

19 .

~6 .. ; ~ . ,.
. ~ . ' ': ', '., :- . . - . . . ~' , ' . ., : . .: . . :

~ ~049191 The copoIymers of the invention are prepared by ~-contacting the mixture of comonomers with a free radical 3 generating polymerization initiator o~ the type commonly 4 used in polymerizing ethylenically unsaturated compounds.
Represcntative free radical polymerization initiators include:

7 acetyl peroxide 8 lauroyl peroxide 9 decanoyl peroxide caprylyl peroxide 11 benzoyl peroxide 12 tertiarybutyl peroxypivalate 13 diisopropy1 peroxycarbonate 14 tertiarybutyl peroctoate CX~CX'~azobisisobutyronitrile 18 Conventional polymerization techniques can be 19 employed to produce the copolymers. The comonomer mixture containing betwe~n 0.05 - 2% by weight oE the 21 free radical initiator is heated to a ~emperature between 22 30C - 100C, preferably below 70C, to initiate and 23 complete the polymerization. The polymerization can be 2~ carried out directly in a contact lens mold to form a lens generally having the desired configuration. Alternatively, 26 the polymerization mixtu~e can be heated in a suitable 27 mold or container to form discs, rods or sheets which can 28 then be machined to the desired shape using conventional 29 equipment and procedures employed for fabricating lenses from polymethyl methacrylate. 1~he temperature is preferably 31 maintained below 70JC in order to minimize the formation . E~ . . .
.... 9 ' ' '. , ':
, : ' ' ', '' ' ' , ", ~ , , , , ~ , ; , ~, , . . :

:; :
... ,, - . ~ . .... . .. .
, . , `~ 1[)4~ I

1 of bubbles in the copolymer. Instead of employing the bulk .
2 polymerization techniclues described above, one can employ ~ -3 solution, emulsion or suspension polymeri~ation to- _ _, r 4 prepare the copolymers, using techniques conventionally used in the preparation of polymers from ethylenically unsaturated ¦

6 monomers. The copolymer thus produced may be extruded, j;
7 pressed or molded into rods, sheets or other convenient r 8 shapes which are then machined to produce the contact lenses.
9 . . ;~
The c-opolymers have been found to have vastly increased oxygen :
11 permeability in comparison to conventional contact lens ~ ;
12 materials. For example, a copolymer comprising 35 parts 13 pentamethyldisiloxanylmethyl methacrylate and'65 parts of 14 methyl methacrylate has an oxygen permeability of 500 cc.-mil/
lO0 in.2/ 2~ hr./atm. compared to an oxygen permeability of 16 34 for polymethyl methacrylate and 13 for polyhydroxyethyl- r 17 methacrylate. These oxygen permeability values were 18 detexmined in accordance with ASTM Dl434, using a tester which 19 has a 3 "Dow" cell pressure change detection units. Dises were cut to proper size to fit the tester, placed in the ¦
21 apparatus and conditioned a minimum of 16 hours under both 22 vacuum and oxygen. Immediately following the conditioning 23 period, the test was performed by plotting a curve of cell 24 pressure versus time. The slope of the curve was then used to calculate the oxygen transmission rate. In general, tl1e r -26 oxycJen permeability of the copolymers of the invention is at 27 least ~ times to as much as several hundred times higher than 28 that of lenses prepared from polymethylmethacrylate or the 2~ so-ealled "hydrogel" lenses prepared from polyhydroxyethyl- - ~
~30 methacrylate. ~ - ~ ;-~".,~i. . 10 i ,', , .. - , . . I ' ~

. , . ... . ', , ; ._.. _ ~
' ' ''' ' ' . - ' ' ' ' .'-. ' '','" '' ' ' ' ".', ', ' '; ' ", "`' , ' . ," ', ' ',: .: ' ' . ' ' . : ~ . . ' , '; . ' , . ' . . : . ' : ' . : : . .

4~9~ i While some of the copolymers used in the practlce of aspects of this invention are inherently wettable by human tears, it may be ~
necessary to improve the wettability of others. This can be accom- ~-plished by several alternate methods. For example, wettability canibe r imparted to the copolymer by the addition of from 0.1% to 10% by weight I of one or more hydrophilic monomers to the copolymerization mixture. I
Sueh 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-methylol-; 10 methacrylamide, glycidyl acrylate and methacrylate, and N-vinylpyrroli-done. Alternatively, the wettability of the surface of contact lenses !~
made from the copolymers used in the practice of aspects of this inven-tion ean be improved by the application of a wetting agent such as, for example, a dilute aqueous solution of alkyldimethylbenzylammonium ehloride, by exposure of the surface to a corona discharge or by ~;
ehemical treatment of the surface wi~h a strong oxidizing agent such as, ~`
, for example, nitric acid.
The rig;dity of the contact lenses prepared from materials used in the practice of aspects of this invention may be varied by ehanging the ratio of comonomers andtor 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 ; farbrlcated into a eontact lens which is more rigid than a lens prepared from the copolymer of the corresponding aerylates. The lower the alkyl . :
I methaerylate content of the copolymer the more flexible the contact lens prepared therefrom.

: . ' ~,'.~ . ,. .' ;` ~
_. .

, ~, , , r~ I
!f ~ 49~91 The rigidity of a contac~ lens prepared from materials used -- ~ in the practice of aspects-of this invention may be increased, if l~.
desired, by the incorporation into the copolymer composition of 0.01~ il of 2~ by weight of a cross-linking monomer such as, for example, a ~ ¦
polyol dimethacrylate or diacrylate or a polyol acrylic ester of higher I functionality, for example, ethylene glycol dimethacrylate, butylene glycol dimethacrylate, neopentyl glycol diacrylate and pentaerythritol triacrylate or tetra-acrylate. r The refractive index is an important but non~critical ¦
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 ' ~`
used in the practice of aspects of this invention may be varied r between 1.35 and 1.50 by varying the ratio and nature of the comonomers.
In general, increasing the polysiloxanyi monomer content of the copolymer wlll decrease its refractive index. The nature of the sub-stituents on the silicon atoms of the polysiloxanyl monomer also importantly affects the refractive index of the copolymer. Lower straight chain alkyl substituents product 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 various aspects of the invention.
- '''' ' , .
j` ': .: '.

r:

.

, , ' I ,~ ' .

.

3LD' ~ I

... . . . . .
. ~
, .

Jl ~al49~L91 EXP.~lrLI~ 1 1 ¦ This example illustrates thc syntllesis of a 2 representativc pclysiloxanylalkyl ester comonomcr, 3 pentamethyldisiloxanylmethyl methacrylate. ~' ~ . , .
1 5 Synthcsis of Dimethylc}llorometllylchlorosilane. Distilled . --6 trimethylchlorosilane (635 ml., 5 moles), b.p. 59.9C., is 7 plaeed in a l~liter, 3-necked, round-bottom flask equipped 8 with a magnetie stirrer, a thermometer, a gas inlet tube and 9 a dry-ice cooled reflux condenser whose outlet is connected to a water scrubber. After flushing the apparatus with dry 11 nitrogen for 15 minutes, chlorine gas is introduced through 12 the gas inlet tube and the flask is irradiated by ultràviolet 13 liCJht from a General Electrie 15-watt germicidal lamp placed 14 at a distance of 6 in. from the flask. Gaseous hydrogen chloride is evolved and absorbed in tlle water scrubber which 16 eontains a caustic soda solution and a small amount of 17 phellolphthalein. The temperature is mai..tained in ~he range 18 30-40C. while chlorine is bubbled throucJh the r~action 19 mixture. After 30 hours of photochlorination, 5 moles of hydrogen chloride is evolved, as indicated by the discharge 21 of the pink color in the water scrubber. The product is 22 distilled throu~Jh a column with 18 theoretical plates and the 23 fraction distilling at 115C. is collected. The yield of 24 dimethylclllorometllylcl)lorosilane (d25 = i.o7) is 30~.
- -26 Synthesis of Pentamethylcllloromethyldisiloxalle. 134 ml.
.
27 dimethylchlorolllethylchlorosilane (1 mold) and 127 ml. (1 mole) 2~ of trimethylchlorosilane are mi~:ed and shaken thoroughly.
29 Wllen 600 ml. of distilled water is added, exothermic hydrolytic reactions occ~lr immecliately. The mixture is shaken on a 31 mechallica] sl-a~:er overniyht t~ complete hydrolysis. The ': .. ' '.
', . . ~
,. : ~ ' , :

' ~049~l 1 upper oily laycr is separated and i~ dried over anhydrous 2 sodium carbonate. ~fter drying, the product is distilled 3 througll a column of 13 theoretical plates and the fraction 4 which distills at 151-152C. is collected. The yield of pentamethylchloromethyldiciloxare (b.p. 151.8C., d25 = 0.910, G nD = 1.410G) is 30~. -7 .
8 Synthesis o~ Pentamethyldisiloxanylmethyl Methacrylate.
9 30 ml. pentamethylchloromethyldisiloxane ~0.14 mole), 13.8 ml.
(0.16 mole) distilled methacrylic acid, 21.0 ml. ~0.15 mole) 11 triethylamine, 30 ml. xylene and 0.8 g. hydroquinone are mixed 12 and refluxed for 16 hours. Triethylamine hydrochloride 13 precipitates and is filtered. The filtrate is mixed with 1 g.
14 of hydroquinone and l g. of copper powder. Xylene is dis-tilled from the mixture at atmospheric pressure. The 16 distillation apparatus is then connected to a vacuum line and 17 the fraction which distilles at 73-75C. under 4-5 mm. ~Ig 18 pressure is collected. The yield of pentamethyldisiloxanyl- -19 metllyl methacrylate (b.p. 73-74C./ 4 mm. ~g, d = 0.910, nD = 1.420) is 45%.
21 ' ' 22 The disiloxane monomer recovered by distillation 23 contains co-distilled hydroquinone. Purification is accom-24 pllshed by washing the monomer with aqueous alkali solution containing 25~ sodium carbonate and 1% sodium hydroxide until 26 the~aqueous layer is colorless. The oily monomer layer i5 .
27 then washecl with water until neutral and dried over anhydrous 28 sodium carbonate. The dried monomer is refrigerated until 29 used.
.

:~ ~
. ., ~ .
. .. _.. .. ~
, . ' -: .
: ., : . .

1 EX~MPLE 2 2 ' ,~ , 3 I This example illustrates the preparation of,'a 4 representati~e oxygen-permeable copolymer.

6 A mixture of 35 parts of the disiloxane monomer of 7 Example l, 65 parts of methyl methacrylate and 0.004 ml. of 8 tert-butyl peroxypivalate per-ml. of monomer mixture is placed . ' in a polypropylene Petri dish to a height of one eighth of an 1~ inc,h. The dish is covered and placed in a vacuum oven which 11 has been purged with nitrogen. The oven is closed and the 12 temperature is maintained at 45C. for 20 hours. The copolyme 13 disc is hard, colorless, transparent and rigid. The oxygen ' l~ permeability is 500,cc.-mil/lO0 in. / 24 hr./atm. , , -~
16 The oxygen permeability of a disc of polymethyl-,methacrylate is 34 cc.-mil/lO0 in.2/24 hr./atm. while that of 18 a disc of polyhydroxyethylmethacryiate is 13 cc.-mil/lO0 19 in.2/24 hr./atm. ' .~ ' ' . 20 ~ ' ' ' ' . '~ '' ' - ' " ~ ' 2l A cylindrical plu~ having dimensions of l/4 inch 22 thickness and lJ2 inch diameter is prepared by copolymerizing 23 the 35/65 disiloxane monomer/methyl methacrylate mixture in 24 a polyethylene cap at 45C. for 20 hours. The plug is, ' ;
. . :
machined, cut, polished and finished to a concavo-convex ?G lens.
2i _ , ' ' ' ' , ' , ' 2~ , '~ ,,, , , ~"~ ' ' ' ~ " "' ' ' 3G ~ , `~ , 3l ' - ~ ' '' , ' ' - , Il 15 " ' li ~ . . ',: ' '. ~

, , , ,, . : : : .

919~
¦ EXP~PLES 3-9 2 ! . . .

3 ¦ T,hese examples illustrate the preparation an~
¦ properties of copolymers containing varying proportions of

5 ¦ a siloxanyl monomer, methyl methacry'ate, and a hydrophilic

6 ¦ monomer ~hydroxyethyl methacrylate).

8 ¦ Mixtures of the dis-loxane monomer of Example 1 9 ¦ (DSM), methyl methacrylate (~), hydroxyethyl methacrylate 10 ~ Er~) and tert-butyl peroxypivalate (0.004 ml. per ml. of 11 ¦ monomer mixture) is polymerized in polyethylene caps under 12 ¦ the conditions shown in the following table:
18 ¦ Composition, wt.% Temp. Time 1~ I Example DSM MMA HEMA , _C. hr. Properties*
15 ¦ 3 20 75 5 50 6.5 T, H, R
16 4 35 60 5 45 20 T, H, R
17 ¦ 5 44 50 6 50 48 T, H! SR
18 ¦ 6 45 50 5 45 20 T, H. SR
19 ¦ 7 45 49 6 70 1 T, B, SR -21 ¦ 8 51 40 9 7$ 2.5 T, H. SR
~22 ¦ 9 65 30 5 ! 60 4 NT, S, E
23 ¦ *T = transparent; H = hard; R = Rigid; SR = Semi-rigid;
NT = hazy; S = soft; E = elas,tomeric `

25 I ~
26 ¦ The polymeriæed plugs are machined and finished in 27 ¦ the usual manner to lenses with a concave sur~ace on one side 28 I and a convex sur~ace on the opposite side. The lenses are 29 ¦ easily wetted by water an~ an aqueous saline solution.

31 ~ -32 ll 16 :` ' ~ ' . ' ~C~491~ ' 1 I EXA~lPLE lO
2 I .
3 This example illustrates the preparation an~
4 properties of a wetta~le oxycJen-permeable terpolymer.
.
6 A disc is prepared in the manner described in

7 Example 2 from a mixture of 45 parts of the disiloxane

8 monomer of E~ample l, 50 parts of methyl methacrylate and 5

9 parts of hydroxyethylmethacrylate using tert-butyl peroxypivalate as catalyst. The polymerization is carried 11 out at 45C. for 20 hours. The resultant disc is colorless, 12 transparent, hard and semi-rigïd. The surface of the disc 13 is readily wetted by wate~ ~nd salire solution. The oxygen 14 permeability of the terpoLymer is 76~ cc.-mil/lO0 in.2/24 hr./

16 atm.
17 ;

i9 2~

3~
:` 1! 17 ~
. . ' . ', . : ~, :, I ',' ''~ ' . ':~

` ~ 1049191 1 . EXAMPLE 1 1 2 . ~ . .
3 ~his`example illustrates the preparation and properties of a ~tettable oxygen-permeable terpolymer.

G A disc prepared in ~he same manner described in 7 Example 2 by polymerizing a mixture of 20 parts of the 8 disilo~ane monomer of Example 1, 75 parts of methyl 9 methacrylate, 5 parts of hydroxyethyl methacrylate and 0.004 ml. of tert-butyl peroxypivalate per ml. of monomer mixture, 11 at 50C. has an oxy~en permeability of 135 cc.-mil/100 in.2/
12 24 hr./atm. Lenses cut and machined from the disc are trans-13 ~ par , hard and rigid. ¦

6 , 18 ~ ~-19 . ' ' ' . ' - ' .
~0 . ~ . . ..

22 :
~3 -24 `

27 .
28 .
29 .

31 ~ ~`~
321' ` 11 i 1~ ' ' ' ' ' -. .
.

,~ ~ 491g~ . .
I EXAMPI.~S 1~-14 :
2 I . - . . :
3 ¦ These.e~amples illustrate the preparation an~
¦ properties of copolymers of a siloxanyl monomer with various 5 ¦ proportions of other methacrylate ester comonomers. .
.1~ I . ` , . :

7 ¦ Cylindrical plugs are prepared in the manner ..
8 ¦ described in Example 3 from mixtures of the disiloxane monomer ¦ (DSM) of Example 1, methyl methacrylate (~), octadecyl

10 1 methacrylate (ODMA), hydroxyethyl methacrylate (HE~) and

11 ¦ ethylene glycol dimethacrylate (EGD~) by polymerization at

12 ¦ 70C. for 2.5 hours using tert-butyl peroxypivalate as

13 ¦ catalyst. The properties of lenses prepared from the plugs

14 ¦ are shown in the following table; .:

15 I . .
. Composition, wt.% ............... .... .. ..

16 I Example DSM MMA OD~A HEMA EGDMA Pro~er~ies . ~ .

17 ¦ 12 . 35 30 30 5 O T, H, E :..... .

18 ¦ 13 45 30 20 5 0 T, S, E
1~ ¦ 14 . 45 38 10 . 5 2 T, S, R
20 ~ : . .
21` I : .
22 ~
2a ¦ ~ :
24 ~

26 ~ : . :
27 I ;
28 I ~ ~ :
29 I ~ . . .~ ~:
30 I : . ~::
3~ ~
32 11' . ' ' ' '. ' ~i . ' 19 ' . :: . :

. . . . . . . ~ ... . .. ~

.. ~: . . , ~: . : : , . : : .:

:
4919~ :
E~MPL lS

3 ~his example illustrates the synthesis o~
tris(~rimethylsiloxy)methacrylatopropylsilane.

6 23.8 g. (13~0 ml.) of concentrated sulfuric acid 7 is added slowly with stirring to a ~ixture of 11.6 g. ~14.7 8 ml.) of absolute ethanol and 16.S ml. of water. The mixture 9 is cooled in a water bath.
10 . - . , . .':
11 ~ethacrylatopropyltrimethoxysilane ~0.1 mole, 12 24.8 g.), is mixed with 0.3 mole (39.6 g.~ of trimethyl-13 acetoxysilane in a flask equipped with a magnètic stirrer.
14 Ethylsulfuric acid (6.5 g.), prepared as described above, is -added dropwise from a dropping funnel into the stirred mixture.
16 The flas~ is cooled during the addition of the ethylsulfuric i7 ~cid catalyst solution in an ice water bath. After completion 18 of the catalyst addition, the solution is stirred at room

19 ~emperature for two days. The upper oily layer is then separated, washed with sodium bicarbonate solution, washed 21 with water and then dried over anhydrous sodium sulfate.
22 The product is distilled under vacuum to remove ethyl acetate. I -23 The distillation flask is immersed in a water bath whose 2~ temperature is maintained at ~0-45C. to prevent premature polymerization of the monomer. The yield of tris(trimethyl-26 siloxy)methacrylatopropylsilane is 86% and the density of the 27 monomer is 0.989 g./cc. at 20C. The monomer is refriger2ted 28 until used.

-1l 20 i ' ' ' :.
! . , .
. , ``-`` 1! ~0~9~9~
1 ¦I EXAMPLE 16 2 ~
3 ¦ This example illustrates the preparation of a 4 copolym~r of methyl methacrylate with the novel polysiloxanyl ester of Example 15.

7 . A cylindrical plug is prepared by polymerizin~ a 8 mixture of ~0 parts of tris(trimethylsiloxy)-~-methacryloxy- -9 propylsilane and 60 parts of methyl methacrylate in the I0 presence of tert-butyl pexoxypivalate at 50C. Lenses :
11 prepared from the plug are hard, transparent and oxygen 12 permeable.

18.
19 I ' ''' .'-'.
:
21 .

23 ; : -l ' , : ~ ' . :' . -29 . ~ .
3~ . : : .

3~ . 21. . .

'I . . .

, .......... . ... , . .. ; , . . . . ; . .

~1~ 104~191 ~ ¦ EXA~IPL~ 17-28 2 I i 3 ¦ This e~:ample illustrates the preparation of various ¦ copolymers or polysiloxanyl esters and various alXyl acrylate~
5 ¦ or methacrylates. The polysiloxanyl ester comonomers are 6 I prepared according to the ~eneral techniques of Examples 1 7 ¦ and 15. The copolymer is prepared according to the general 8 ¦ technique of Example 2. All copolymers resulting are trans-9 I parent, hard and rigid so as to be suitable for contact 10 I lens manufacture. The oxygen permeability of the copolymers 11 varies from 300-500 cc.-mil/100 in.2/24 hr./atm. as measured 13 by the technique previously descFibed.
14 I : .

16 .

18 ~ ~ ~.
19 I : ~ ' ' ''~ '.

20 I . '

21 I -

22 I

23 .

24 226 :

27 .

229 I I ::
3i~ . ~ ..

3' 11 l', 22 li . .
1'1 '' ''' , ' . .' .
,: . . : , . , ~ ~

I h ~ ~I h l h U h r1 ~ o ~ ,~ ~ ~J ~ U
3 ¦ ~ O h h ~ h 4 ¦ ~ O X ~ h ~ U O h 5 ¦ w '~ P~ ,, k ~
1 .~ , ~ ~ X
l , o I I a~ a) 0 1 7 ~ N ~ ~ ~ O O .C ,~

8 ~ h . ' ~ ~ ' :
9 _~ ~) o o ~ o o o u~ o io ~
11 . '' ~-. 12 ` $ 0 ~

~ h ~1 ,1 0 .'1 '~
1~

~ h ~ O a) ~:
a\
16 q ~ ~ h ~ t Q' 51 0 . . . . ~ ;C O ~1 17 . h ~ h U
18 td e ~ 0 5~ e ~ U ~
C~ ~ ~ X ~ a)a) ~ o X
.C~ X ~ ~ X ~ 'I e ~. e o ~ .~ o x ~ ~ x ,~
21 h ~ ,l ,1 ~1 o. ^ .
Fi X ~ $ ~ X u~ ~ ~
22 ~r; ~ ~ a 23 u~ r~ J) ~ S ~
~ h ~ e a~
, 24 ~ X ~ ~ ~ X
~
~ H ~J X ~ ~ ~
C . o ~ ~ ,4 ~ ~ ~ .,, ." ~ ~
, ~ Q) a) ", . 27 0 ~ :
2~ .C:E~i . ::
' 29 .-1 ul o o ul ~n o o o In Lt) u~ o . ¦ ol? O ('7 ~ ~ N N ~ ~ N ~ l 301 . ~0 . .. . .. :
~ ¦ 31 1 1` oo t~ o ~I N ~ ~ Il~ ~D 1` CO
1! ,32 li ~. Ii ' . . ,.
23 ~:
1~

- , . .......... . : : , ,,` ' !` 1049~L91 1 ~s illustrated by Examples 17-28, it is preferred 2 to use a strai~ht chain al~anol ester monomer if the 3 polysiloxanyl ester monomer is a branched chain compound,~
4 and vice versa. Also, it is preferred to employ two acrylate or two mcthacrylate comonomers to prepare the copolymer, G rather than an acrylate monomer and a methacrylate monomer.
7 Finally, where more complex polysiloxanyl ester comonomers B are employed, the proportion of polysiloxanyl ester is 9 lower, e.g., 10-20~, than if simpler polysiloxanyl esters are employed. In general, the presence of larger, more 11 complex substituents on the interior silicon atoms tend 12 to increase the refractive index of the copolymer, all 13 other factors being equal.

-19 . ' ', , " " ' .

~1 ' . ' ': ' ' ' ' 2~

2i`

3l .

, . , . , .: .... .. : .... , . . ' ~ ~ : . . . . .

Claims (6)

?he embodiments of the invention in which an exclusive property ?r privilege is claimed are defined as follows:

1. A method for improving the oxygen permeability of contact lenses, said method comprising the essential step of fabricating said lenses from a solid copolymer of comonomers consisting essentially of:
(a) 10 to 60 parts by weight of a polysiloxanylalkyl ester of the structure wherein (1) X and Y are selected from the class consisting of C1 - C5 alkyl groups, phenyl groups and Z
groups, (2) Z is a group of the structure (3) A is selected from the class consisting of C1 - C5 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) 40 to 90 parts by weight of an ester of a C1 - C20 monohydric alkanol and an acid selected from the class consisting of acrylic and methacrylic acids.

2. The method of claim 1 which comprises the essential step of fabricating said lenses from a solid copolymer comonomers consisting essentially of:
(a) 10 to 70 parts by weight of a polysiloxanylalkyl ester of the structure wherein (1) X and Y are selected from the class consisting of C1 - C5 alkyl groups, phenyl groups and Z
groups, (2) Z is a group of the structure (3) A is selected from the class consisting of C1 - C5 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;
(b) 30 to 90 parts by weight of an ester of a C1 - C20 monohydric alkanol and an acid selected from the class consisting of acrylic and methacrylic acids;
and (c) 0.1 - 10% by weight replacement of (a), or (b), or (a) + (b) of a hydrophilic monomer selected from the group consisting of hydroxyalkyl acrylates and methyacrylates where -the alkyl group contains 1 to carbon atoms, acrylic acid, methacrylic acid, acryl-amide, methacrylamide, N-methylolacrylamide, N-methy-lolmethacrylamide, glycidyl acrylate, glycidyl methacrylate, and N-vinylpyrrolidone.

3. The method of claim 1 which comprises the essential .
step of fabricating said lenses from a solid copolymer of comonomers consisting essentially of (a) 10 to 70 parts by weight of a polysiloxanylalkyl ester of the structure wherein (1) X and Y are selected from the class consisting of C1 - C5 alkyl groups, phenyl groups and Z
groups, (2) Z is a group of the structure (3) A is selected from the class consisting of C1 - C5 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;
(b) 30 to 90 parts by weight of an ester of a C1 - C20 monohydric alkanol and an acid selected from the class consisting of acrylic and methacrylic acids, (c) 0.1 - 10% by weight replacement of (a), (b), or (a) + (b) of a hydrophilic monomer selected from the group consisting of hydroxyalkyl acrylates and methyacrylates where the alkyl group contains 1 to 4 carbon atoms, acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-methylolacryl-amide, N-methylolmethacrylamide, glycidyl acrylate, glycidyl methacrylate, and N-vinylpyrrolidone, and (d) 0.001 to 2% by weight replacement of (a) or (b) or (a) + (b) of a cross-linking monomer selected from the group consisting of a polyol dimethacrylate, a polyol diacrylate, ethylene glycol dimethacrylate, butylene glycol dimethacrylate, neopentyl glycol diacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate.

4. A contact lens having increased oxygen permeability, said lens being prepared by the method of claim 1 and having a refractive index of from 1.35 to 1.50.

5. A contact lens having increased oxygen permeability and enhanced wettability, said lens being prepared by the method of claim 2 and having a refractive index of from 1.35 to 1.50.

6. A contact lens having increased oxygen permeability, enhanced wettability and desired rigidity, said lens being prepared by the method of claim 3 and having a refractive index of from 1.35 to 1.50.