Oxygen permeable hard and semi-hard contact lens compositions, methods and articles of manufacture

The invention relates to new monomers of polysiloxanyl alkyl esters of acrylic and methacrylic acids and their copolymerization with alkyl esters of acrylic, methacrylic acids and/or itaconate esters to produce highly permeable contact lens material. The copolymers preferably include a cross-linking agent and hydrophilic monomer. Contact lenses manufactured from the material are easily machined and polished into hard or semi-hard contact lenses having excellent dimensional stability.

BACKGROUND OF THE INVENTION 
The present invention relates to novel chemical compounds, polymers made 
from such compounds and novel materials and products made from such 
compounds. Important use of the materials made from the invention is the 
manufacture of corneal contact lenses. 
In recent years, corneal contact lenses have become more and more popular 
in the United States and throughout the world. 
The great popularity of contact lenses is easily understood. One important 
reason is that such lenses provide perhaps the best possible manner of 
achieving optical correction for the eyes. The lenses fit directly over 
the eye, and when properly fitted, are easily retained in place. Problems 
common with spectacles, such as interference with peripheral vision, 
moving about on the head, discomfort, and the possibility of improper 
interpupilary distance, are easily overcome. Contact lenses provide 
cosmetic advantages and afford convenience and increased safety when used 
in diverse pursuits, particularly sporting events. 
Now most commonly used contact lenses are generally subdivided into two 
types, so-called hard contact lenses, and soft contact lenses. Each type 
of lens has its own advantages, but each also includes certain 
disadvantages. 
Referring first to the advantages of hard contact lenses, these lenses 
provide dimensional stability, so that the characteristics of an optical 
prescription will remain unchanged while the lens is in use in the eye. In 
some cases, the eye will actually conform to the contour of the lens over 
a period of time so as to improve the vision of the wearer. Moreover, hard 
contact lenses are relatively durable in relation to soft lenses. 
While hard contact lenses have the above and other advantages, some 
patients find such lenses somewhat uncomfortable in use, and prefer the 
so-called soft contact lens. These lenses fall generally into three 
categories, namely lenses made from silicone rubber or like materials, 
lenses made from "HEMA" (hydroxyethylmethacrylate) or so-called "hydrogel" 
lenses, and finally, lenses of the methylmethacrylate base type, modified 
by the addition of polymers such as cellulose acetate butyrate ("CAB"). 
Soft lenses readily conform to the eye and are quite comfortable in short 
term use. They are extremely thin as well as soft and pliable. However, 
they do not provide satisfactory oxygen transmissibility through the lens. 
Referring now to the disadvantage of both soft and hard contact lenses, 
neither type of lens is able to be worn by a user over an extended period 
of time because both types of lenses are not enough permeable to the 
oxygen. As a result, the cornea is unable to "breathe" properly. 
Consequently, after a period of time, the cornea becomes irritated or 
perhaps even damaged. Moreover, the lenses sometimes tend to adhere to the 
eye of the wearer after being in place for an unduly long period of time, 
and this can cause discomfort and even damage to the eye. 
In view of the foregoing advantages of contact lenses, it would be even 
further advantageous if there were a contact lens that possessed the known 
advantages of machinability, dimensional stability, toughness and optical 
clarity, and which were also sufficiently oxygen permeable to be worn by a 
user for an extended period, such as for several days, weeks, or even 
months or more. Users of such lenses could wear them for extended periods 
and still feel comfortable; could have good vision and not risk injuring 
their eyes. Contact lense which could be worn for an extended period would 
eliminate common problems with existing lenses. 
The anticipated life of an extended duration contact lens would be 
lengthened considerably. This is because the requirement for handling 
would be very greatly reduced. More sturdy lenses, such as known types of 
hard lenses, are not susceptible to tearing or cracking, but can be 
scratched by frequent removal and insertion, and cleaning, particularly if 
they are dropped occasionally. Losing the lenses is a realistic 
possibility which could be minimized substantially by having lenses which 
are removed weekly, or monthly, or at greater intervals. 
Referring now to prior attempts to provide polymers with increased oxygen 
permeability; normally, most or all such known polymers have either been 
too dimensionally unstable for satisfactory use, or have had other 
disadvantages. For example, it is known to add significant amounts of 
additives normally intended to increase wettability. While such materials 
are helpful in proper amounts, using excess amounts thereof has often 
tended to cause proteinaceous matter to deposit on and impair the 
transparency of the inner surface of the lens. 
While numerous attempts have been made to improve the oxygen permeability 
of both hard and soft contact lenses, the attempts have met with only 
limited success, particularly in thicker lens. Moreover, many soft lens 
material provides an environment which is highly suitable for bacterial 
growth, and this calls for sterilization procedures which in turn require 
the lenses to be handled frequently. 
The present invention, therefore, is intended from the standpoint of an end 
use product to provide contact lens materials which are sufficiently 
oxygen permeable that they may be worn by the user on a greatly extended 
basis in relation to prior art lenses, which do not have the disadvantages 
associated with known prior art lenses intended for this purpose. 
Referring now to its chemical aspects, the invention relates to the 
manufacture of copolymers of an acrylic or methacrylic material of a known 
type and novel, silicone substituted acrylic or methacrylic compounds so 
as to produce an oxygen permeable plastic material which is uniquely 
suitable for manufacturing novel corneal contact lenses as referred to 
above. The expression "copolymers" is sometimes used herein for simplicity 
in referring to a polymer which includes two principal comonomers, 
although such polymer may incidentally include one or more additional 
known monomers in minor amounts for purposes such as cross-linking, 
increasing the wettability of the final product, or otherwise. 
The copolymer compositions and products made therefrom are improved over 
counterpart prior art compositions by reason of increased dimensional 
stability and improved gas permeability. Such novel compositions also 
retain or provide improvements in desirable prior art characteristics such 
as optical clarity, the ability to be cast, molded and machined, and 
compatability with chemically bonded, hydrophilic materials adapted to 
improve the wettability of the finished product. 
Preferably, the compositions comprise high molecular weight 
polysiloxanylalkylesters of acrylic and methacrylic acids and other 
compositions as monomers, copolymerized with methacrylates or other esters 
of acrylic or methacrylic acids, vinyl carbazole, vinyl benzenes, vinyl 
pyrrolidinone and itaconate esters. 
According to the invention, one comonomer (the "first" comonomer) is an 
acrylic or methacrylic ester silane, substituted with one or more highly 
substituted siloxanyl group. One such typical comonomer is 
bis(trimethylsiloxy)methylsiloxanylbis(pentamethyldisiloxanyl)methacryloxy 
propylsilane which can be copolymerized with an alkyl acrylate or alkyl 
methacrylate, (the "second" comonomer), with this copolymer composition in 
turn being cross-linked to a slight degree by cross-linking agents, and 
preferably further modified by the addition of compounds intended to 
increase the wettability of the finished copolymer material. This basic 
polymerization of the novel comonomers with know comonomers occurs through 
a known double-bond polymerization mechanism. 
A certain proportion, such as 10% to 60% of this compound is then 
polymerized with one or more other second comonomer compounds having the 
same or similar acrylic or methacrylic ester portion, together with the 
minor amounts of cross-linking and wetting agents, referred to above. 
One more aspect of the present invention relates to the method of making 
the so-called first or novel comonomers of the invention. According to 
this method, chlorosilanes are reacted with hydroxy derivatives of 
polysiloxanyl groups, in the presence of pyridine to bond released 
hydrochloric acid in the form of precipitated salt of pyridinium 
hydrochloride at low temperatures. The details of this method are brought 
out in other portions of the specification. In still another aspect, the 
invention relates to alternate methods of preparing the above or similar 
products. One alternate method comprises reacting others, mono-, di-, or 
methacryloxypropyltrichlorosilanes with an excess of pyridine and reacting 
the resulting intermediates with polysilanols pentamethyldisiloxanol and 
heptamethylisotrisiloxanol (3-hydroxyheptamethyltrisiloxane) at about 
-50.degree. C. 
A monomer is removed from these reaction mixtures by purification following 
removal of the low molecular weight materials, with the reaction products 
being purified by washing with weak alkalies or like materials. 
The novel comonomer compounds of the present invention can be represented 
by the following formulas: 
##STR1## 
where n is an integer 1, 2 or 3. 
and by: 
##STR2## 
where n is an integer 1, 2 or 3. 
and by: 
##STR3## 
where n is an integer 1, 2 or 3. 
In the alkyl or phenyl ester second principal comonomer, the alkyl group 
contains 1 to about 10 carbon atoms, (typically one to six carbon atoms). 
One compound which may be used as the first principal comonomer of the 
present invention is 
bis(pentamethyldisiloxanyl)bis(trimethylsiloxy)methylsiloxanylmethacryloxy 
propylsilane: 
##STR4## 
another compound is 
bis[bis(trimethylsiloxy)methylsiloxanyl]pentamethyldisiloxanylmethacryloxy 
propylsilane: 
##STR5## 
One more suitable compound is 
tris[bis(trimethylsiloxy)methylsiloxanyl]methacryloxypropylsilane: 
##STR6## 
Representative known or second comonomers which may be employed in the 
practice of the invention include the following: 
methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, 
propyl acrylate, propyl methacrylate, isopropyl acrylate, isopropyl 
methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, cyclohexyl 
acrylate, cyclohexyl methacrylate, benzyl acrylate, benzyl methacrylate, 
phenyl acrylate, phenyl methacrylate, n-vinyl carbazole, n-vinyl 
pyrrolidinone, 3-hydroxy 2-naphtyl methacrylate, ethyl vinyl benzene, 
divinyl benzenes, dimethyl itaconate, dibutyl itaconate. 
Cross-linking monomers include difunctional compounds such as: 
ethyleneglycoldimethacrylate 
diethyleneglycoldimethacrylate 
triethyleneglycoldimethacrylate 
tetraethyleneglycoldimethacrylate 
polyethyleneglycoldimethacrylate 
divinyl benzene 
tetramethyldisiloxanyldi(methylmethacrylate) 
and mixtures thereof. 
The wetting agents include, but are not limited to: 
acrylic acid 
methacrylic acid 
N-vinyl 2-pyrrolidine, and 
hydroxyalkyl esters of acrylic and methacrylic acids, 
and mixtures thereof. 
In view of the shortcomings of prior art contact lenses and the compounds 
and compositions used in making them, it is an object of the present 
invention to provide novel monomers useful in making improved lens 
materials, improved polymer compositions made from such novel monomers, 
and improved lenses made from such polymers. 
Another object of the invention is to provide novel silicone compounds used 
as components of polymerizable monomers. 
A still further object is to provide a method of making starting or 
intermediate materials for making novel silicone compounds, and to provide 
starting and intermediate materials for other uses as well. 
Yet another object is to provide highly branched or substituted silane, 
silanol and siloxane materials for a variety of uses, including the 
manufacture of copolymers, terpolymers or other polymer incorporating such 
materials. 
A still further object is to provide one or more compounds containing alkyl 
esters of acrylic or methacrylic acids, and incorporating three 
polysiloxanylalkyl groups. 
A still further object is to provide an optically useful, novel polymeric 
material of increased oxygen permeability with respect to prior art 
compounds. 
Still another object is to provide a material of the foregoing type which 
may be formulated or synthesized so as to have a desirably high refractive 
index, and which can therefore be used in the manufacture of bifocal 
contact lenses, particularly fused bifocal contact lenses. 
A still further object is to provide a composition which will make possible 
the manufacture of corneal contact lenses which can be worn for an 
extended time period while providing greatly increased comfort to the 
wearer. 
Another object is to provide a polymeric contact lens material which is 
compatible with additives of known kinds used to provide other desirable 
end use properties. 
A still further object is to provide a method of manufacturing copolymers 
incorporating the compositions made by the novel methods referred to above 
.

These and other objects and advantages of the invention, including those 
inherent therein, may be achieved in practice by carrying out the methods, 
and making the compounds and compositions referred to herein. The 
following examples, which are set forth by way of illustration and not by 
way of limitation, illustrate preferred methods of carrying the invention 
into practice. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
EXAMPLE 1 
This example illustrates a preparation of a new and useful monomer, 
bis(pentamethyldisiloxanyl) 
bis(trimethylsiloxy)methylsiloxanylmethacryloxypropylsilane. 
Trichloromethacryloxypropylsilane (261.5 g.) is dissolved in 700 ml of dry 
diethylether and placed in a 5 liter, 3 necked, round bottom flask 
equipped with a mechanical stirrer, a thermometer and an additional 
funnel. The solution is cooled down to -50.degree. C. with a dry 
ice-isopropanol cooling bath. When the temperature has reached -50.degree. 
C., 280 grams (slight excess) of dry pyridine is added over a period of 
about 2 hours, with the temperature being held at -50.degree. C. or less 
during pyridine addition. At the same temperature, two moles of 
pentamethyldisiloxanol and one mole of heptamethylisotrisiloxanol 
(3-hydroxyheptamethyltrisiloxane), which are prepared by known methods in 
the art, is added in a diethylether solvent, forming a white precipitate 
of pyridinium hydrochloride. When all the mixtures of the silanols have 
been added, the temperature of the reaction mixture is increased rapidly 
to about +30.degree. C. and stirred for 1/2 hour. The pyridinium 
hydrochloride is isolated by filtration and the filter cake is washed with 
diethylether. 
The crude monomer bis(pentamethyldisiloxanyl) 
bis(trimethylsiloxy)methylsiloxanylmethacryloxypropylsilane in 
diethylether is washed twice with water (200 ml each). The upper (organic) 
layer is then separated and diethylether is removed by means of 
distillation. The crude monomer (I) is washed with 150 ml of distilled 
water, and thereafter twice with a dilute sodium bicarbonate solution, 
again with distilled water once, and then dried over anhydrous magnesium 
sulfate for 2 hours. The dried monomer is purified by distilling off all 
low boiling materials at 85.degree. C. and 0.1 mm Hg pressure. The 
purified monomer is refrigerated until used. Density of the monomer (I) is 
0.975 g/ml at 20.degree. C. and n.sub.D.sup.25 =1.4135.+-.0.0010. 
The monomer can also be prepared by another chemical route known in the 
art. (Ref: Alexandrov K. A., Dabagova A. K. Akad. Nauk SSSR; V-119 (1958) 
pp. 1149-1151). 
The chemical route has been adapted by N. G. Gaylord, U.S. Pat. No. 
3,808,178; however, the referenced route produces a lower yield of said 
monomer. 
EXAMPLE 2 
This example illustrates a preparation of a new and useful monomer, 
bis[bis(trimethylsiloxy)methylsiloxanyl]pentamethyldisiloxanylmethacryloxy 
propylsilane. 
Trichloromethacryloxypropylsilane (1 mole is dissolved in 1000 ml of dry 
n-hexane and placed in a 5 liter, 3 necked, round bottom flask equipped 
with a mechanical stirrer, a thermometer and an additional funnel. The 
solution is cooled down to -50.degree. C. with a dry ice-isopropanol 
cooling bath. When the temperature has reached -50.degree. C., 280 grams 
(slight excess) of dry pyridine is added over a period of about 2 hours, 
with the temperature being held at -50.degree. C. or less during pyridine 
addition. At the same temperature, two moles of 
3-hydroxyheptamethyltrisiloxane and one mole of pentamethyldisiloxanol is 
added in n-hexane solution, forming a white precipitate of pyridinium 
hydrochloride. When all the mixtures of the silanols have been added, the 
temperature of the reaction mixture is increased rapidly to about 
+30.degree. C. and stirred for 1/2 hour. The pyridinium hydrochloride is 
isolated by filtration and the filter cake is washed with n-hexane. 
The crude monomer 
bis[bis(trimethylsiloxy)methylsiloxanyl]pentamethyldisiloxanylmethacryloxy 
propylsilane in n-hexane is washed twice with water (200 ml each). The 
upper (organic) layer is then separated and n-hexane is removed by means 
of distillation. The crude monomer (II) is washed with 150 ml of distilled 
water, and thereafter twice with a dilute sodium bicarbonate solution, 
again with distilled water once, and then dried over anhydrous magnesium 
sulfate for 2 hours. The dried monomer is purified by distilling off all 
low boiling materials at 85.degree. C. and 0.1 mm Hg pressure. The 
purified monomer is refrigerated until used. 
EXAMPLE 3 
This example illustrates the preparation of a representative oxygen 
permeable copolymer. 
A mixture of 45 parts of the comonomer (I) of Example 1, 50 parts of methyl 
methacrylate, 3 parts of methacrylic acid and 2 parts of 
triethyleneglycoldimethacrylate and 0.14% by weight of the entire mixture 
of t-butyl peroxypivalate is placed in a glass dish or tube and then 
placed in a vacuum oven which has been purged with nitrogen. The oven is 
closed and the temperature is maintained at 48.degree. C. for 24 hours. 
The monomers react to create a copolymer plastic which is hard, colorless, 
transparent and rigid. The oxygen permeability is 21.4.times.10.sup.-11 
(cm.sup.2 /sec) (ml O.sub.2 /ml.times.mm Hg). The oxygen permeability of a 
disc of polymethylmethacrylate, measured in the same way is less 
0.2.times.10.sup.-11 (same units), while that of a disc of hydrated 
polyhydroxyethylmethacrylate is 8.times.10.sup.-11 (same units). 
EXAMPLE 4 
This example illustrates the preparation of a representative oxygen 
permeable copolymer from another comonomer (II). 
A mixture of 35 parts of novel comonomer (II) of Example 2, 50 parts of 
methyl methacrylate, 10 parts of cyclohexyl methacrylate, 2 parts of 
N-vinyl pyrrolidone and 3 parts of triethyleglycoldimethacrylate and 0.25% 
by weight of the entire composition of t-butyl peroxydecanoate is 
polymerized in a polyproylene dish or tube at 50.degree. C. for 24 hours. 
The resulting copolymer plastic material is machined, cut, polished, and 
finished into a concavoconvex lens of 0.10 mm thickness. The oxygen 
permeability of this lens is 24.6.times.10.sup.-11 (cm.sup.2 /sec)(ml 
O.sub.2 /ml.times.mm Hg). (155 mm Hg is the normal partial pressure of 
oxygen in a 760 mm Hg atmosphere.) This particular measurement was made by 
a "Schema-Versatae" Model 920 gas flux meter which is known and widely 
used in the contact lens industry. 
The following Examples 5-11 illustrate the conditions of preparation and 
properties of copolymers which contain varying proportions of the novel 
comonomer of Example 2 when such comonomers are reacted with one or more 
of the following compounds: 
methyl methacrylate (MMA) 
cyclohexyl methacrylate (CHMA) 
methacrylic acid (MAA) 
N-vinyl pyrrolidone (NVP) 
triethyleneglycoldimethacrylate (Tri-EGDMA) 
tetraethyleneglycoldimethacrylate (TEGDMA) 
ethyleneglycoldimethacrylate (EGDMA) 
The siloxane comonomer used in these examples is that prepared in Example 
1, namely, bis(pentamethyldisiloxanyl) 
bis(trimethylsiloxy)methylsiloxanylmethacryloxypropylsilane and which is 
abbreviated in the table below as C(I). 
The polymerization is conducted in polypropylene tubes for 24 hours at the 
temperature shown in the table. The table also shows the composition of 
each form of polymer, and the temperature at which polymerization took 
place. The properties of the polymer are abbreviated in the right hand 
corner, with the meanings of the abbreviations appearing below. 
In the examples, the principal polymers are C(I) and MMA, with the 
compositions including one or more other compounds as indicated. MAA 
provides wettability, CHMA supplements the MMA to accomplish better 
rigidity, and NVP provides increased wettability, except that, where more 
than 4 or 5% NVP is present, a portion thereof serves as a third monomer. 
The TEGDMA, Tri-EGDMA, and EGDMA are cross-linking agents. 
__________________________________________________________________________ 
COMPOSITION, WT., PERCENT 
Tri- TEMP 
Example 
C(I) 
MMA CHMA MAA NVP 
EGDMA 
TEGDMA 
EGDMA 
.degree.C. 
PROP. 
__________________________________________________________________________ 
5 35 57 3 3 2 49 T,H,R 
6 40 50 10 50 T,H,R 
7 45 35 10 4 2 4 45 T,H,R 
8 60 40 45 T,H,R 
9 38 45 10 3 4 47 T,H,R 
10 37 27 27 5 4 49 T,H,R 
11 42 27 27 2 2 43 T,H,R 
__________________________________________________________________________ 
T=Transparent 
H=Hard 
R=Rigid 
Products of the invention herein described as "hard" have a hardness, 
measured on the Shore D scale of about 84-90, (ASTM 2240) while 
polymethylmethacrylate, tested the same way, has a hardness of 90-93. 
EXAMPLE 12 
This example illustrates the preparation and properties of a wettable, 
oxygen permeable polymer. A disc is prepared in the manner described in 
Example 4 from a mixture of 40 parts of the bis 
bis(trimethylsiloxy)methylsiloxanyl-pentamethyldisiloxanylmethacryloxyprop 
ylsilane (II) of Example 2, 40 parts of methyl methacrylate, 5 parts of 
N-vinyl pyrrolidone and 15 parts of dimethyl itaconate, using 
t-butylperoxypivalate as a catalyst. The polymerization is carried out at 
48.degree. C. for 24 hours. The resulting disc is colorless, transparent, 
hard and rigid. The oxygen permeability (Dk-value) of the polymer is 
16.2.times.10.sup.-11 (cm.sup.2 /sec)(ml O.sub.2 /ml mm Hg). In this 
example, no difunctional cross-linking agent was used. 
EXAMPLE 13 
This example illustrates the preparation of a copolymer of methyl 
methacrylate and the novel comonomer (II) referred to in Example 2. 
A cylindrical plug of the copolymer is prepared by polymerizing a mixture 
of 40 parts of such novel comonomer (II), 50 parts of methyl methacrylate, 
5 parts of vinyl carbazole and 5 parts of divinyl benzene, in the presence 
of t-butylperoxydecanoate at 45.degree. C. Polymer plastic is hard, rigid, 
and highly oxygen permeable in relation to prior art material. 
The previous Examples illustrate the outstanding properties of the 
resulting polymers of this invention. In great measure these properties 
are attributed to the novel comonomers. 
Other additives to the polymers of this invention as known in the art can 
be made. In all cases, the polymers are optically clear and transparent 
and meet required standards of desirable high oxygen permeability in 
semi-rigid and rigid contact lenses. 
Even though I have described specific examples of this invention, there are 
many variations possible within the scope of keeping the physical 
properties as previously described. Such variations include the use of 
mixtures of monomers within the components to comprise of the required 
parts of each. For example, two or more siloxanyl alkyl ester comonomers 
can be used instead of a single such comonomer for the component of the 
composition. Respectively, two or more cross-linking agents can be used. 
Other additives to the copolymers such as colorants, tints and like 
materials may also be employed within the scope of normal ranges of this 
invention.