2 ~ 2
NOVEL COMPOSmON FOR CONTACT IENSES
Background of ~e Invention
This invention relates to contact lenses, and
in particular to pliable or "soft" contact lens having
- an exceptional combination of oxygen permeability,
strength, and resistance to protein and mucus deposits.
There is a great need for a contact lens that has high
oxygen permeability and wettability and resistance to
protein and mucus deposits. These properties all
contribute to an extension of the time during which a
contact lens can be continuously worn by a wearer.
High oxygen permeability is needed because the pupil of
the eye has no blood circulation and extracts the
oxygen needed by its cells directly from the
atmosphere. Wettability is essential for wearer
comfort. Resistance to protein and mucus deposits from
-. fluids that bathe the outer surface of the eye is
~ essential since without this feature the lens pores
¦ become clogged and both visual acuity and the oxygen
permeability of the lens suffer.
Many types of contact lens compositions have
been proposed. There are two general categories of
contact lenses--rigid and hydrogel. For example,
U.S. Patent Nos. 3,808,178 and 4,120,570 to Gaylord,
4,139,692 to Tanaka et al; 4,686,276 to Ellis et al;
u~
.','.,'. - '
-2- 210~82
4,743,106 to Novicky et al, and 4,812,598 to Chen
propose the use of various copolymer compositions
including silicon in contact lenses. The lenses are
reasonably permeable to oxygen but are not of hydrogel
or "soft" construction.
U.S. Patent No. 4,130,706 to Plambeck, Jr.
proposes a methacrylate-type fluoropolymer ("FMA") for
making contact lenses. While the lenses are described
as hydrophilic and oxygen permeable, it is believed
that they are not wettable enough to be truly
comfortable to persons wearing the lenses and are not
sufficiently permeable to oxygen to be worn safely and
continuously for extended periods.
U.S. Patent No. 3,940,207 to Barkdoll
proposes contact lenses constructed of fluorine-
containing polymers that are soft and have a low
refractive index. It is believed that these contact
lenses are not sufficiently oxygen permeable to be worn
safely for extended periods.
s 20 U.S. Patent Nos. 4,954,587 and 5,011,275 to
Mueller propose soft, extended wear contact lenses
based on N,N-dimethylacrylamide ("DMA"). While the
lenses have a high oxygen permeability, the use of
higher amounts of the relatively soft polymer of N,N-
dimethylacrylamide is limited in that the lenses could
` become too soft to be fabricated.
; It would be highly desirable to provide a
hydrogel copolymer which can be used to form an easily
fabricated pliable contact lens having the combination
of oxygen permeability, wettability and resistance to
protein and mucus deposits.
SummarY of the Invention
The present invention relates to a hydrogel
copolymer for making contact lenses, the copolymer
comprising, by weight, about 10 percent to about 85
percent o~ ~-methylene-N-methylpyrrolidone or glycerdyl
~ - ~ . . - ,.. .. .
.'' . , , ~ ''
',- ' ' , ~ ' . .
,., , ' ' ',' ' ~ ~ -
-3- 2 1 a ~ ~ ~ 2
methacryla~e and mixtures thereof, from about 5 to
about 25 percent of N,N-dimethylacrylamide, about 5
percent to about 80 percent of a polymerizable
fluoromonomer, and about 1 percent to about 15 percent
of a polymerizable hydrophophic, non-hydrolyzable
- silicone monomer. Optionally, an initiator and a
crosslinker are employed under circumstances disclosed
below.
In one embodiment of the invention, the
copolymer comprises, by weight, from about 10 to 85
percent a-methylene-N-methylpyrrolidone, from about 5
to about 85 percent of glycerdyl methacrylate, from
about 5 to about 60 percent of a polymerizable
fluoromonomer, and from about 1 to about 15 percent of
a polymerizable hydrophobic non-hydrolyzable silicone
monomer.
In another embodiment, the copolymer
comprises, by weight, from about 40 to about 90 percent
of ~-methylene-N-methylpyrrolidone and from about 10 to
about 60 percent of a polymerizable fluoromonomer such
as fluoroacyrlates, styryl fluoromonomers and vinyl
- fluoromonomers.
Detailed Descriotion of the Preferred Embodiments
The present invention will now be described
more fully hereinafter. This invention may, however,
be embodied in many different forms and should not be
construed as limited to the embodiment set forth
herein; rather, this embodiment is provided so that
this disclosure will be thorough and complete, and will
fully convey the scope of the invention to those
; skilled in the art.
The present invention utilizes in various
combinations, as described below ~-methylene~N-
methylpyrrolidone ("~-MMP") or glycerdyl methacrylate
("GMA") and mixtures thereof, N,N-dimethyl
methacrylamide, a polymerizable fluoromonomer, a
~. - : - .. . .
t`
:.. -. , : . . ;' :~
'' ' - , ~ ~,
: - .
~4~ 210~6~2
polymerizable hydrophobic, non-hydrolyzable silicone
monomer, an initiator, and a crosslinker.
Preferably, the hydrogel copolymer comprises,
by weight, from about 5 to about 85 percent of -
S methylene-N-methylpyrrolidone ox glycerdyl methacrylate
and mixtures thereof, from about 10 to about 25
percent, and preferably from about 5 to about 20
percent of N,N-dimethylacrylamide, from about 5 to
about 85 percent, and preferably from about 20 to about
40 percent by weight of a polymerizable fluoromonomer
and from about l to about 15 percent, and preferably
from about 2 to about 4 percent of a polymerizable
hydrophobic non-hydrolyzable silicone monomer.
Preferably, from about 20 to about 30 percent of ~-
methylene-N-methylpyrrolidone or from about 5 to about
30 percent of glycerdyl methacrylate is used.
If a mixture of ~-methylene-N-pyrrolidone and
glyceridyl methacrylate is used, preferably from about
10 to about 85 percent of ~-methylene-N-pyrrolidone and
from about 5 to about 85 percent of glycerdyl
methacrylate are used.
In one embodiment of the invention, from
about 50 to about 90 percent of ~-methylene-N-
pyrrolidone can be blended with from about lO to about
50 percent of a polymerizable fluoromonomer to form the
hydrogel copolymer. In this embodiment, the hydrogel
copolymer can further include, by weight, from about 10
to about 25 percent of a polymerizable hydrophilic
monomer selected from the group consisting of
methacrylic acid ("MA"), 2-hydroxyethylmethacrylate
("HEMA"), N-vinyl-2-pyrrolidone ("NVP") and N,N-
dimethylacrylamide ("DMA").
The polymerizable fluoromonomer useful herein
can vary. An exemplary fluoromonomer is one based on a
fluoroacrylate composition which includes the following
fluorine-containing monomer:
.~ . ~... ..
.~ .
_5_ ~ 682
C= CH2
C=O
I
( CH2 ) m
( CFz ) n
CF3
where R is H or CH3, m is an integer from 0 to 9, and n
is an integer from 1 to 4. A similar monomer is
disclosed in U.S. Patent No. 4,130,706 to Plambeck,
Jr., the disclosure of which is incorporated herein by
reference.
; Another exemplary fluoromonomer can be a
fluoracrylate
~ R
.~ C= CH2
'. C=O
I -CH2 CHz C"~l F2 (m~
.
where R and m are defined as above. A similar monomer
~, is disclosed in U.S. Patent No. 3,282,905 to Fosick et
i 10 al, the disclosure of which is incorporated herein by
reference.
A particularly preferred composition is
2,2,2-trifluoroethyl methacrylate ("FMA").
CH3
CHz= Cl F
O=C-O -CH2-C-F
-6- ~ 1 08 ~ ~2
Alternatively, styryl fluoromonomers can be
employed. The general formula of these monomers is
CH-fH
~F,
where r + s = 5 and r = 1 to 5 and s = 5 to 1.
A particularly preferred styryl fluoromonomer is
pentafluorostyrene.
CH2-CH
F ~ F
F
Other examples of fluoromonomers are p-vinyl benzyl
trifluoroacetate and p-vinyl benzyl hexafluoroisopropyl
' ether.
Alternatively, vinyl fluoromonomers can be
, 10 used. They have the general formula
CH2=CH
( CH2 ) tCUF2U~l ~
where t = 1 to 4 and u = 1 to 9. A particularly ~-
preferred vinyl fluoromonomer is 3,3,3
I trifluorovinylpropane
CH2 = CH F
C8,C82-C-F
A
i
i
~, . ' ., ', ' : " ': . . : ' '
_7_ 2108~2
Alternatively, perfluorocyclohexyl acrylates
can be used having the general formula
R F F
CH~-C ~
O-C-O~F
~ I
F F
where R = ~ or CH3. A particularly preferred
pefluorocyclohexyl acrylate is perfluorocyclopentane.
It is no~ed that only ~-methylene-N-methylpyrrolidone
and the polymerizable fluoromonomer can be used.
The polymerizable hydrophobic non-
hydrolyzable silicone monomer useful herein can vary.
An exemplary silicone has the formula
AtSI-O~SI-l CH2 )~ C=CH2
A a Y
where a is an integer from 1 to 5 and b is an integer
from 0 to 6, A is selected from the group consisting Of
¦ Cl-C5 alkyl groups and phenyl groups, R is selected from
the group consisting of a methyl group (CH~) and
hydrogen, X and Y are selected from the group
consisting of Cl to C5 alkyl groups, phenyl groups and Z
groups wherein Z is a group of the structure
:~ A-¦~i - -¦
A a
where a and A are as defined previously, and ~ is a
3 phenyl group. In the alkanol ester co-monomers, the
~ alkyl group contains from 1 to 20 carbon atoms.
20 Exemplary silicon-containing monomers are disclosed in
J U.S. Patent Nos. 3,808,178 and 4,120,570 to Gaylord,
~;
i
-8- 2 ~ ~ ~r;~ 2
the disclosures of which are incorporated herein by
reference.
Alternatively, vinyl silicone monomers can be
employed. The general formula can be represented as
CH2=CH (I)
Rl-s i -R
or ~1
(II)
CH2 = CH R
(CH2)X- si -Rl
where X = 1 to 6 and Rl is selected from the class
consisting of Cl to C6 alkyl groups and phenyl groups or
a mixture of alkyl and phenyl groups.
Particularly preferred examples of Class (I) ;
are
CH2 = CH CH2 = CH : :
CH3 - si - CH3 CH3 -Si - CH3
CH3CH2 = CH <P
~-fi-
C~3
where "~" represents a phenyl group.
Particularly preferred examples of Class (II) are
., :
.1 ,
J, ~ ,:
J .~ . . -:. . ~ , ' ' . ' . . , `.'. . :
. . .
~',: " ' ' , ' ' , , , . ' ',' ' :' - .
,: ' '' ~ . ' ' . ~ .' ' ' ' . - , ' , . '''
'' ' '',' ' ' . " ,. ' ' ' ' .. '. ' . ,' . " ' '~: " ';. ' .
",' ' ,~ ' '. . '' .. ' ', ' , ~ '"." . ' ', ' ' ' ", . ,. '' ' ',
2 1 ~
- 9 -
CH2= I H CIH3 CH2=CH CH,
CH2 cH2 -si - CH3 Cf~z Cf~2 -SI-~>
CH3 CH,
.
CH2 = CH
CH2 CH2 -Si -~
CH3
In both classes of vinyl silicone monomers,
any methyl group (CH3 group) can be replaced by a
benzene ring, as the preceding examples suggest.
Generally, vinyl silicone monomers are less
reactive than acrylate silicone monomers. When vinyl
silicone monomers are used, cobalt-60 ("Co-60"),
radiation may be used as a source of polymerization
energy. Co-60 may optionally be used as a source of
polymerization energy even when vinyl silicone monomers
are not employed.
. Exemplary non-hydrolyzable silicones include
~; methyldi(trimethylsiloxy)silylpropylglycerol
methacrylate, methylidi(trimethylsiloxy)silylpropyl-
glycerolethyl methacrylate, m,p-styrlethyltrimethyl-
silane, m,p-styrylethyltris(trimethylisiloxy)silane,
methylacryloxypropyltris(trimethylsiloxy)silane and 4-
(3-trimethylsilylpropyl)benzylstyrene sulfonate.
Preferably a crosslinker is used. The
crosslinker can constitute, by weight, about 0.01
percent to about 5 percent and more preferably about
0.5 percent to about 2 percent of the weight of the
hydrogel copolymer. The crosslinker is preferably one
of a mixture of ethyleneglycoldimethacrylate ("EGDMA"),
' a fluorine-containing compound, or a silicon-containing
:~ .
~ .
~ -
~.', . ' . ~ , '. ' ,' '- ' : " ' ' ' " :' :' .
-lo- 2 1 ~ 2
compound such as 1,3-bis[(p-acryloxymethyl)
- phenethyl]tetramethyldisiloxane or bis(3-
methacryloxypropyl)tetramethyldisiloxane.
A quantity of an initiator equal in weight to
0.05 percent to 2 about percent of the weight of the
mixture of monomers is preferably added thereto, except
when Co-60 is used as a source of polymerization
energy. The initiator may be selected from the group
consisting essentially of 2,2'-azobis(2,4-
- 10 dimethylvaleronitrile) ("VAZ0 52"), azobisisobutyro-nitrile ("AIBN"), benzoinmethylether ("BME"), di(sec-
butyl)peroxydicarbonate ("SBC"), and
isopropylperoxydicarbonate ("Ipp"). The initiator may
also be any of those disclosed in the U.S. Patent
No. 4,120,570, to Gaylord, i.e., acetyl peroxide,
lauroyl peroxide, decanoyl peroxide, caprylyl peroxide,
b~nzoyl peroxide, tertiary-butyl peroxypivalate,
diisopropyl peroxycarbonate, tertiary-butyl peroctoate,
and ~ azobisisobutyronitrile.
VAZ0 52 or AIBN may be used as an initiator
when polymerization is aided by ultraviolet or thermal
radiation, BME may be used as the initiator when
polymerization is aided by the ultraviolet radiation,
and SBC or Ipp may be used as the initiator when
polymerization is aided by thermal radiation. Co-60 or
another radioactive source may also be used to promote
polymerization, particularly when vinyl silicone
monomers or other monomers that are not highly reactive
are employed. When Co-60 or another radioactive source
is not used, polymerization energy is supplied in the
form of thermal energy or in the form of ultraviolet
radiation, as may be appropriate in view of the -
initiator employed. When Co-60 radiation is employed,
3 no initiators are needed.
After curing, the resulting polymer is formed
in any conventional or otherwise suitable process into
contact lenses. The lenses have a shore hardness (D
.
: : " . : ~ . .: . . ,
-11-
scale) within atherange of 82 to 89. Oxygen
permeability in DK units (ml cm/cm2 sec cmHg X 10-10) at
35°C is within the range of 10°-34°, light
transmission is greater than 95%, refractive index is
close to that of HEMA, and the coefficient of expansion
is within the range of 1.1 to 1.6.
The following examples set forth
representative formulas for the materials used in
making contact lenses according to the invention:
Example 1
The following are mixed at room temperature
in a 100ml beaker:
<IMG>
The initiator is added to the mixture, and
the mixture is poured into a test tube and polymerized
by thermal polymerization (i.e., application of heat)
1.alpha.-methylene-N-methylpyrrolidone
22,2,2-trifluoroethylmethacrylate available from Aldrich Chemical Company of Milwaukee,
Wisconson
3N,N-dimethylacrylamide available from Aldrich Chemical Company
4methylacryloxypropyltris(trimethylsiloxy)silane available from Huls America, Inc, of Newark, New
Jersey
5etheyleneglycoldimethacrylate available from Rohm Tech, Inc. of Marden, Massachuseets
6isopropylperoxydicarbonate available from Polyscience, Inc. of Warrington, Pennsylvania
21'~8f;82
-12-
This is accomplished by placing the test tube in a hot
water bath at a temperature of 30C. The polymerized
material is a colorless, solid, transparent polymer.
The polymer is lathe-cut into buttons of conventional
shape and size. The buttons are ground to the shape of
contact lenses having respective center thicknesses of
O.lmm to 0.2mm, and then polished. The lenses are
highly transparent (light transmission i8 greater than
95%) and have uniform optical properties. They have an
oxygen permeability of 35 DK units at 35 C (normal eye
temperature), a contact angle of less than 18-, and a
refractive index of 1.40S.
The following examples are similar to
Example 1 but illustrate variations of the materials
and quantities thereof employed and of the method of
polymerization.
ExamPle2
Percent 8y
Inaredients Weiaht
~-MMP
FMA 19.94
DMA 39.38
; MDC 29.90
EGDMA .50
BME7 0.02
25 The mixture is molded in the form of shells and
polymerized by ultraviolet radiation in accordance with
U. S. Patent No. 4,812,598 to Chen, the disclosure of
which is incorporated herein by reference. The shells ~-
are lathe-cut to form contact lenses in accordance
therewith.
. ~ .
7bcn~oinmethylefher iniliator available from Polyscience, rnc
,, .
::
. - ` : ' ' , . -
.. . : :: : : :,
.- -: ' ' . ; -.- :: . :
.: . ' ` ' ' '' . ' '`~ `' ' ' ', .,
:
:: .: ' : ' - ;
.
2~0'~2
-13-
ExamPle3
Percent By
In~redients Weiaht
~-MMP 64.74
MDC 9.96
FMA 24.90
BME
The mixture is molded in the form of shells
and polymerized by W polymerization in accordance with
Example 2. The shells are lathe-cut to form contact
lenses in accordance therewith.
Example 4
Percent By
Inqredients _ Weiqht
~-MMP 10.00
FMA 30-00
; DMA 29.50
~-~ 20 MDC 30.00
EDGMA 0.50
BME 0.02
The mixture ls molded in the form of shells
- and polymerized by W polymerization in accordance with
Example 2. The shells are lathe-cut to form contact
-~ lenses in accordance therewith.
~.
-` ExamPle 5
Percent By
Inaredients Weiqht
GMA ~10;00
MDC 11.40
FMA 25.00
DMA 53.50
EGDMA 0.10
VAZ0-52 0.20
X
.
,~ . .
-: . .
,. : - ~ . . ~ . :. :
., -: , - , . . ..
21~86~2
-14-
The mixture is molded in the form of shells
and polymerized by thermal polymerization in accordance
with Example 1. The shells are lathe-cut to form
contact lenses in accordance therewith.
The lenses are highly transparent (light
transmission is greater than 95%~ and have uniform
optical properties. They have an oxygen permeability
of 46.7 DK units at 35-C (normal eye temperature), an
expansion factor of 1.39, and a water content of about
54 percent.
ExamPle6
Percent By
Ingredients Weiaht
~-MMP
NVp8 20.00
FMA 15.00 :
MDC 7.00
EGDMA 0.
VAZ0-52 0.02 -
The mixture is molded in the form of shells
and polymerized by W polmerization in accordance with
Example 2. The shells are lathe-cut to form contact
lenses in accordance therewith.
, The lenses are highly transparent (light
transmission is greater than 95%) and have uniform
optical properties. They hav~ an oxygen permeability
of 47.4 DK units at 35-C, an expansion factor of 1.4,
and a water content of about 65 percent.
... .
~.
.
... .
:~ .
~ 8N-vinyl-2-~qrolidone
'~
,
- - - .
",
~ - . . ..
~ . .... `' .' '',' ' ' .. ~' ~ , .
.. . ., - . . : . . :
., . , . . -
-15- 21~8682
Example 7
Percent By
Ingredients Weiaht
~-MMP 75.00
FMA 24.70
EGDMA 0.30
VAZO-52 0.30
The mixture is molded in the form of shells
and polymerized by W polymerization in accordance with
Example 2. The shells are lathe-cut to form contact
lenses in accordance therewith.
The lenses are highly transparent (light
transmission is greater than 95%) and have uniform
optical properties. They have an oxygen permeability
of 25 DK units at 35 C, an expansion factor of 1.32,
and a water content of about 54.4 percent.
Example 8
Percent By
- Inqredients Weiqht
~-MMP 80.00
FMA 19.20
EGDMA 0.30
; BME 0.30
The mixture is molded in the form of shells
and polymerized by UV polymerization in accordance with
Example 2. The shells are lathe-cut to form contact
lenses in accordance therewith.
The lenses are highly transparent (light
, transmission is greater than 95%) and have uniform
optical properties. They have an oxygen permeability
of 62.7 DK units at 35-C, an expansion factor of 1.69,
and a water content of 77.3 percent.
' .
:,
,j .
'
2lQ~r;~
--16--
Example 9
Percent By
Inaredients Weiaht
~-MMP 67.95
GMA 17.00
FMA 10.00
MDC 5 0O
EGDMA o.05
VAZO-52 0.02
The mixture is molded in the form of shells
and polymerized by W polymerization in accordance with
Example 2. The shells are lathe-cut to form contact
lenses in accordance therewith.
The lenses are highly transparent (light
lS transmission is greater than 95%) and have uniform
optical properties. They have an oxygen permeability
of 45.5 DK units at 35 C, an expansion factor of 1.38,
and a water content of 62.5 percent.
Thus there is provided in accordance with the
20 invention a novel and highly-effective contact lens
that has an exceptional combination of oxygen
permeability, wettability and resistance to protein and
mucus deposits. A novel material for manufacturing the
lens is also provided, and it is noted that the
25 material may be used for other medical articles needing
the combination of oxygen permeability, wettability and
resistance to protein and mucus deposits.
Many modifications of the preferred
embodiments of the invention disclosed above will
30 readily occur to those skilled in the art upon
consideration of this disclosure. For example,
initiators other than the ones disclosed may be
employed, the contact lens may be tinted or clear, the
temperature and times of polymerization may vary, etc.
~, 35 Accordingly, the invention is not limited except by the
appended claims.
:~
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.. . ..
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