U.S. patent application number 11/612520 was filed with the patent office on 2007-08-09 for methods and systems for processing complex shaped hydrogel devices.
Invention is credited to Dhannesh K. Dubey, James D. Ford, Frank F. JR. Molock, Douglas G. Vanderlaan.
Application Number | 20070182039 11/612520 |
Document ID | / |
Family ID | 38218501 |
Filed Date | 2007-08-09 |
United States Patent
Application |
20070182039 |
Kind Code |
A1 |
Vanderlaan; Douglas G. ; et
al. |
August 9, 2007 |
METHODS AND SYSTEMS FOR PROCESSING COMPLEX SHAPED HYDROGEL
DEVICES
Abstract
The present invention provides methods and apparatus useful for
facilitating one or more of the removal of unreacted components and
diluents from an article fashioned from silicone hydrogel and
release of the article from a mold part to which the article is
adhered.
Inventors: |
Vanderlaan; Douglas G.;
(Jacksonville, FL) ; Dubey; Dhannesh K.;
(Jacksonville, FL) ; Ford; James D.; (Orange Park,
FL) ; Molock; Frank F. JR.; (Orange Park,
FL) |
Correspondence
Address: |
PHILIP S. JOHNSON;JOHNSON & JOHNSON
ONE JOHNSON & JOHNSON PLAZA
NEW BRUNSWICK
NJ
08933-7003
US
|
Family ID: |
38218501 |
Appl. No.: |
11/612520 |
Filed: |
December 19, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60751783 |
Dec 20, 2005 |
|
|
|
Current U.S.
Class: |
264/2.6 |
Current CPC
Class: |
B29L 2011/0041 20130101;
B29C 71/0009 20130101; B29D 11/00923 20130101; B29D 11/0025
20130101; G02B 1/043 20130101; B29D 11/00125 20130101 |
Class at
Publication: |
264/002.6 |
International
Class: |
B29D 11/00 20060101
B29D011/00 |
Claims
1. A method for removing unreacted components and diluents from an
ophthalmic lens comprising silicone, the method comprising:
exposing said ophthalmic lens to a first aqueous solution
comprising about 15% or more of a leaching agent comprising
ethoxylated nonylphenol; heating said first aqueous solution to
which the ophthalmic lens is exposed; and rinsing said ophthalmic
lens through contact with a second aqueous solution until said lens
comprises a level of unreacted components and diluents that is
below a predetermined threshold.
2. The method according to claim 1, wherein the first aqueous
solution comprises essentially 100% ethoxylated nonylphenol.
3. The method according to claim 1, wherein said second liquid
comprises deionized water.
4. The method according to claim 1, wherein said first liquid, said
second liquid, or both comprise a buffered aqueous solution.
5. The method according to claim 4, wherein said first liquid, said
second liquid, or both comprise sodium chloride, boric acid, sodium
borate, dihydrogen sodium phosphate, sodium citrate, sodium
acetate, sodium bicarbonate or any combination thereof.
6. The method according to claim 1, wherein the predetermined
threshold comprises a threshold of detection of unreacted
components and diluents.
7. The method according to claim 1, wherein said ophthalmic lens
comprises a contact lens comprising from 0 to about 90 percent
water.
8. The method according to claim 1, wherein said ophthalmic lens
further comprises a diluent and said method further comprises
removing said diluent from said ophthalmic lens.
9. The method according to claim 8, wherein said ophthalmic lens
has a functional size and swells during said diluent removal.
10. The method according to claim 1, wherein said ophthalmic lens
is tinted.
11. The method according to claim 1, wherein said ophthalmic lens
comprises a pattern of colorant.
12. The method of claim 1 wherein the exposing of the ophthalmic
lens to the first aqueous solution comprises immersing the
ophthalmic lens in the first aqueous solution and the first aqueous
solution is heated to its boiling point with the ophthalmic lens
immersed in it.
13. The method of claim 12 wherein the ophthalic lens is immersed
in the boiling first aquesous solution for a period of time
comprising more than one hour.
14. The method of claim 12 wherein the ophthalic lens is immersed
in the boiling first aquesous solution for a period of time
comprising between one hour and five hours.
15. The method of claim 1 additionally comprising the step of
forming the ophthalmic lens by UV curing at 5000 MW a monomer
comprising .alpha.,.omega.-bismethacryloxypropyl
polydimethylsiloxane, TRIS and DMA with a diluent comprising
t-butanol.
16. The method of claim 1 wherein the step of rinsing the
ophthalmic lens comprises exposing the ophthalmic lens three times
to at least 50 ml of deionized water.
17. The method of claim 1, wherein, the first aqueous additionally
comprises one or more of: ethoxylated alcohols; ethoxylated
carboxylic acids, ethoxylated glucosides; ehtoxylated sugars;
ethoxylated carboxylic acids with attached C8 to C14 carbon chains,
ethoxylated glucosides with attached C8 to C14 carbon chains;
ehtoxylated sugars with attached C8 to C14 carbon chains;
polyalkylene oxides, sulfates, carboxylates or amine oxides of
C8-C10 compounds.
18. The method of claim 1, wherein, the first aqueous additionally
comprises, one or more of: cocoamidopropylamine oxide, C.sub.12-14
fatty alcohol ethoxylated with 10 ethylene oxides; sodium dodecyl
sulfate; polyoxyethylene-2-ethyl hexyl ether; polypropylene glycol;
polyethylene glycol monomethyl ether; ethoxylated methyl glucoside
dioleate; the sodium salt of n-octylsulfate; and sodium salt of
ethylhexyl sulfate.
19. The method of claim 1 wherein the exposing of the ophthalmic
lens to the first aqueous solution comprises flowing the first
aqueous solution over the ophthalmic lens.
20. The method of claim 1 wherein the exposing of the ophthalmic
lens to the first aqueous solution comprises immersing the
ophthalmic lens in the first aqueous solution.
Description
RELATED PATENT APPLICATIONS
[0001] This application claims priority to Provisional Patent
Application U.S. Ser. No. 60/751,783 which was filed on Dec. 20,
2005.
FIELD OF THE INVENTION
[0002] This invention relates to processing complex shaped hydrogel
devices, specifically including methods of processing ophthalmic
lenses made from silicone hydrogels in order to leach components
from the lenses and release the lenses from molds.
BACKGROUND OF THE INVENTION
[0003] It is well known that contact lenses can be used to improve
vision. Various contact lenses have been commercially produced for
many years. Early designs of contact lenses were fashioned from
hard materials. Although these lenses are still currently used in
some applications, they are not suitable for all patients due to
their poor comfort and relatively low permeability to oxygen. Later
developments in the field gave rise to soft contact lenses, based
upon hydrogels.
[0004] Hydrogel contact lenses are very popular today. These lenses
are often more comfortable to wear than contact lenses made of hard
materials. Malleable soft contact lenses can be manufactured by
forming a lens in a multi-part mold where the combined parts form a
topography consistent with the desired final lens.
[0005] Multi-part molds used to fashion hydrogels into a useful
article of a complex shape, such as an ophthalmic lens, can include
for example, a first mold portion with a convex surface that
corresponds with a back curve of an ophthalmic lens and a second
mold portion with a concave surface that corresponds with a front
curve of the ophthalmic lens. To prepare a lens using such mold
portions, an uncured hydrogel lens formulation is placed between
the concave and convex surfaces of the mold portions and
subsequently cured. The hydrogel lens formulation may be cured, for
example by exposure to either, or both, heat and light. The cured
hydrogel forms a lens according to the dimensions of the mold
portions.
[0006] Following cure, traditional practice dictates that the mold
portions are separated and the lens remains adhered to one of the
mold portions. A release process detaches the lens from the
remaining mold part. The extraction step removes unreacted
components and diluents (hereinafter referred to as "UCDs") from
the lens and affect clinical viability of the lens. If the UCDs are
not extracted from the lens, they may make the lens uncomfortable
to wear.
[0007] According to prior art, release of the lens from the mold
can be facilitated by exposure of the lens to aqueous or saline
solutions which act to swell the lens and loosen adhesion of the
lens to the mold. Exposure to the aqueous or saline solution can
additionally serve to extract UCDs and thereby make the lens more
comfortable to wear and clinically acceptable.
[0008] New developments in the field have led to contact lenses
that are made from silicone hydrogels. Known hydration processes
using aqueous solutions to effect release and extraction have not
been efficient with silicone hydrogel lenses. Consequently,
attempts have been made to release silicone lenses and remove UCDs
using organic solvents. Processes have been described in which a
lens is immersed in an alcohol (ROH), ketone (RCOR'), aldehyde
(RCHO), ester (RCOOR'), amide (RCONR'R'') or N-alkyl pyrrolidone
for 20 hours-40 hours and in the absence of water, or in an
admixture with water as a minor component (see e.g., U.S. Pat. No.
5,258,490).
[0009] However, although some success has been realized with the
known processes, the use of highly concentrated organic solutions
can present drawbacks, including, for example: safety hazards;
increased risk of down time to a manufacturing line; high cost of
release solution; and the possibility of collateral damage, due to
explosion.
[0010] Therefore, it would be advantageous to find a method of
producing a silicone hydrogel contact lens which requires the use
of little or no organic solvent, avoids the use of flammable
agents, that effectively releases lenses from the molds in which
they were formed, and which removes UCDs from the lens.
SUMMARY OF THE INVENTION
[0011] Accordingly, the present invention provides methods of
releasing a silicone hydrogel contact lens from a mold and leaching
the lens of UCDs without soaking the lens in organic solvents.
According to the present invention, release of a silicone hydrogel
lens from a mold in which the lens is formed is facilitated by
exposing the lens to an aqueous solution of an effective amount of
a release aid. In addition, leaching of UCDs from the lens is also
facilitated by exposing the lens to an aqueous solution of an
effective amount of a leach aid
[0012] The present invention further relates to a contact lens
produced using a method which comprises treating the cured lens in
an aqueous solution of an effective amount of a release aid and to
ophthalmic lenses produced using a method comprising treating the
cured lens in an aqueous solution of an effective amount of a
leaching aid.
DETAILED DESCRIPTION OF THE INVENTION
[0013] It has been found that a silicone hydrogel ophthalmic lens
can be released from a mold in which it was cured by exposing the
cured lens to an aqueous solution of an effective amount of a
release aid. It has also been found that adequate removal of
Leachable Materials from the silicone hydrogel ophthalmic lens can
be realized by exposing the cured lens to an aqueous solution of an
effective amount of a leach aid.
[0014] Definitions
[0015] As used herein, "adequate removal of Leachable Materials"
means that at least 50%, of the Leachable Materials have been
removed from a lens after treating the lens.
[0016] As used herein, "Leachable Material" includes UCD's and
other material which is not bound to the polymer and may be
extracted from the polymer matrix, for example, by leaching with
water or an organic solvent.
[0017] As used herein, a "Leaching Aid" is any compound that if
used in an effective amount in an aqueous solution to treat a
ophthalmic lens can yield a lens with an adequate amount of removal
of Leachable Materials.
[0018] As used herein the term "monomer" is a compound containing
at least one polymerizable group and an average molecular weight of
about less than 2000 Daltons, as measured via gel permeation
chromatography refractive index detection. Thus, monomers can
include dimers and in some cases oligomers, including oligomers
made from more than one monomeric unit.
[0019] As used herein, the term "Ophthalmic Lens" refers to devices
that reside in or on the eye. These devices can provide optical
correction, wound care, drug delivery, diagnostic functionality,
cosmetic enhancement or effect or a combination of these
properties. The term lens includes but is not limited to soft
contact lenses, hard contact lenses, intraocular lenses, overlay
lenses, ocular inserts, and optical inserts.
[0020] As used herein, a "release aid" is a compound or mixture of
compounds, excluding organic solvents, which, when combined with
water, decreases the time required to release a ophthalmic lens
from a mold, as compared to the time required to release such a
lens using an aqueous solution that does not comprise the release
aid.
[0021] As used herein, "released from a mold" means that a lens is
either completely separated from the mold, or is only loosely
attached so that it can be removed with mild agitation or pushed
off with a swab.
[0022] As used herein, the term "treat" means to expose a cured
lens to an aqueous solution including at least one of: a leaching
aid and a release aid.
[0023] As used herein and also defined above, the term "UCD" means
unreacted components and diluents.
Treatment
[0024] According to the present invention, treatment can include
exposing a cured lens to an aqueous solution which includes at
least one of: a leaching aid and a release aid. In various
embodiments, treatment can be accomplished, for example, via
immersion of the lens in a solution or exposing the lens to a flow
of solution. In various embodiments, treatment can also include,
for example, one or more of: heating the solution; stirring the
solution; increasing the level of release aid in the solution to a
level sufficient to cause release of the lens; mechanical agitation
of the lens; and increasing the level of leach aid in the solution
to a level sufficient to facilitate adequate removal of UCDs from
the lens.
[0025] By way of non-limiting examples, various implementations can
include release and UCD removal that is accomplished by way of a
batch process wherein lenses are submerged in a solution contained
in a fixed tank for a specified period of time or in a vertical
process where lenses are exposed to a continuous flow of a solution
that includes at least one of a leach aid and a release aid.
[0026] In some embodiments, the solution can be heated with a heat
exchanger or other heating apparatus to further facilitate leaching
of the lens and release of the lens from a mold part. For example,
heating can include raising the temperature of an aqueous solution
to the boiling point while a hydrogel lens and mold part to which
the lens is adhered are submerged in the heated aqueous solution.
Other embodiments can include controlled cycling of the temperature
of the aqueous solution.
[0027] Some embodiments can also include the application of
physical agitation to facilitate leach and release. For example,
the lens mold part to which a lens is adhered can be vibrated or
caused to move back and forth within an aqueous solution. Other
embodiments may include ultrasonic waves through the aqueous
solution.
[0028] These and other similar processes can provide an acceptable
means of releasing the lens and removing UCDs from the lens prior
to packaging.
Release
[0029] According to the present invention, release of a silicone
hydrogel lens is facilitated by treating the lens with a solution
including one or more release aids combined with water at
concentrations effective for causing release of the lens. In some
embodiments, release can be facilitated by the release solution
causing a silicone hydrogel lens to swell by 10% or more in which
percentage of swelling is equal to 100 times the diameter of lens
in release aid solution/diameter of lens in borate-buffered
saline.
[0030] In some embodiments, the release aid can include alcohols,
such as, for example, C.sub.5 to C.sub.7 alcohols. Some embodiments
can also include alcohols that are useful as release aids and
include primary, secondary and tertiary alcohols with one to 9
carbons. Examples of such alcohols include methanol, ethanol,
n-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol,
1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, tert-amyl
alcohol, neopentyl alcohol, 1-hexanol, 2-hexanol, 3-hexanol,
2-methyl-1-pentanol, 3-methyl-1 pentanol, 4-methyl-1-pentanol,
2-methyl-2-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol,
1-heptanol, 2-heptanol, 3-heptanol, 4-heptanol, 1-octanol,
2-octanol, 1-nonanol, and 2-nonanol. IN some embodiments, phenols
may also be used.
[0031] In addition, in some embodiments of the present invention
Leach Aids, which are further discussed below, can also be combined
with alcohols to improve the rate of release. In some cases leach
aids may be used as release aids without the addition of alcohols.
For example, leach aids at concentrations greater than about 12%,
or when used to release lenses with water soluble diluents such as
t-amyl alcohol.
Lens Materials
[0032] Ophthalmic lenses suitable for use with the current
invention include those made from silicone hydrogels. Silicone
hydrogels offer benefits to ophthalmic lens wearers as compared to
conventional hydrogels. For example, they typically offer much
higher oxygen permeability, Dk, or oxygen oxygen/transmissibility,
Dk/1, where 1 is the thickness of the lens. Such lenses cause
reduced corneal swelling due to reduced hypoxia, and may cause less
limbal redness, improved comfort and have a reduced risk of adverse
responses such as bacterial infections. Silicone hydrogels are
typically made by combining silicone-containing monomers or
macromers with hydrophilic monomers or macromers.
[0033] Examples of silicone containing monomers include SiGMA
(2-propenoic acid,
2-methyl-,2-hydroxy-3-[3-[1,3,3,3-tetramethyl-1-[(trimethylsilyl)oxy]disi-
loxanyl]propoxy]propyl ester),
.alpha.,.omega.-bismethacryloxypropylpolydimethylsiloxane, mPDMS
(monomethacryloxypropyl terminated mono-n-butyl terminated
polydimethylsiloxane) and TRIS
(3-methacryloxypropyltris(trimethylsiloxy)silane).
[0034] Examples of hydrophilic monomers include HEMA
(2-hydroxyethylmethacrylate), DMA (N,N-dimethylacrylamide) and NVP
(N-vinylpyrrolidone).
[0035] In some embodiments, high molecular weight polymers may be
added to monomer mixes and serve the function of internal wetting
agents. Some embodiments can also include additional components or
additives, which are generally known in the art. Additives can
include, for example: ultra-violet absorbing compounds and monomer,
reactive tints, antimicrobial compounds, pigments, photochromic,
release agents, combinations thereof and the like.
[0036] The silicone monomers and macromers are blended with the
hydrophilic monomers or macromers, placed into ophthalmic lens
molds, and cured by exposing the monomer to one or more conditions
capable of causing polymerization of the monomer. Such conditions
can include, for example: heat and light, wherein the light may
include one or more of: visible, ionizing, actinic, X-ray, electron
beam or ultra violet (hereinafter "UV") light. In some embodiments,
the light utilized to cause polymerization can have a wavelength of
about 250 to about 700 nm. Suitable radiation sources include UV
lamps, fluorescent lamps, incandescent lamps, mercury vapor lamps,
and sunlight. In embodiments, where a UV absorbing compound is
included in the monomer composition (for example, as a UV block),
curing can be conducted by means other than UV irradiation (such
as, for example, by visible light or heat).
[0037] In some embodiments a radiation source, used to facilitate
curing can be selected from UVA (about 315-about 400 nm), UVB
(about 280-about 315) or visible light (about 400-about 450 nm), at
low intensity. Some embodiments can also include a reaction that
mixture includes a UV absorbing compound.
[0038] In some embodiments, wherein the lenses are cured using heat
then a thermal initiator may be added to the monomer mix. Such
initiators can include one or more of: peroxides such as benzoyl
peroxide and azo compounds such as AIBN
(azobisisobutyronirile).
[0039] In some embodiments, lenses can be cured using UV or visible
light and a photoinitiator may be added to the monomer mix. Such
photoinitiators may include, for example, aromatic alpha-hydroxy
ketones, alkoxyoxybenzoins, acetophenones, acyl phosphine oxides,
and a tertiary amine plus a diketone, mixtures thereof and the
like. Illustrative examples of photoinitiators are
1-hydroxycyclohexyl phenyl ketone,
2-hydroxy-2-methyl-1-phenyl-propan-1-one, bis
(2,6-dimethoxybenzoyl)-2,4-4-trimethylpentyl phosphine oxide
(DMBAPO), bis (2,4,6-trimethylbenzoyl)-phenylphosphineoxide
(Irgacure 819), 2,4,6-trimethylbenzyldiphenyl phosphine oxide and
2,4,6-trimethylbenzyoyl diphenylphosphine oxide, benzoin methyl
ester and a combination of camphorquinone and ethyl
4-(N,N-dimethylamino)benzoate. Commercially available visible light
initiator systems include Irgacure 819, Irgacure 1700, Irgacure
1800, Irgacure 819, Irgacure 1850 (all from Ciba Specialty
Chemicals) and Lucirin TPO initiator (available from BASF).
Commercially available UV photoinitiators include Darocur 1173 and
Darocur 2959 (Ciba Specialty Chemicals).
[0040] In some embodiments, it may also be useful to include
diluents in the monomer mix, for example to improve the solubility
of the various components, or to increase the clarity or degree of
polymerization of the polymer to be formed. Embodiments can include
secondary and tertiary alcohols as diluents Various processes are
known for processing the reaction mixture in the production of
ophthalmic lenses, including known spincasting and static casting.
In some embodiments, a method for producing an ophthalmic lens from
a polymer includes molding silicone hydrogels. Silicone hydrogel
molding can be efficient and provides for precise control over the
final shape of a hydrated lens.
[0041] Molding an ophthalmic lens from a silicone hydrogel can
include placing a measured amount of monomer mix in a concave mold
part. A convex mold part is then placed on top of the monomer and
pressed to close and form a cavity that defines a contact lens
shape. The monomer mix within the mold parts is cured to form a
contact lens. As used herein, curing the monomer mix includes a
process or condition which allows or facilitates the polymerization
of the monomer mix. Examples of conditions which facilitate
polymerization include one or more of: exposure to light and
application of thermal energy.
[0042] When the mold halves are separated the lens typically
adheres to one or the other mold half. It is typically difficult to
physically remove the lens from this mold half, and it is generally
preferred to place this mold half into a solvent to release the
lens. The swelling of the lens that results when the lens absorbs
some of this solvent typically facilitates release of the lens from
the mold.
[0043] Silicone hydrogel lenses may be made using relatively
hydrophobic diluents such as 3,7-dimethyl-3-octanol. If one
attempts to release such lenses in water, such diluents prevent
absorption of water, and do not allow sufficient swelling to case
release of the lens.
[0044] Alternatively, silicone hydrogels may be made using
relatively hydrophilic and water soluble diluents such as ethanol,
t-butanol or t-amyl alcohol. When such diluents are used and the
lens and mold are placed into water, the diluent may more easily
dissolve and the lens may more easily release in water than if more
hydrophobic diluents are used.
Leachable Material
[0045] After a lens is cured the polymer formed typically contains
some amount of material that is not bound to or incorporated into
the polymer. Leachable Material not bound to the polymer may be
extracted from the polymer matrix for example by leaching with
water or an organic solvent (hereinafter "Leachable Material").
Such Leachable Material may not be favorable to the use of the
contact lens in an eye. For example, Leachable Material may slowly
be released from a contact lens when the contact lens is worn in an
eye and may cause irritation or a toxic effect in the eye of the
wearer. In some cases, Leachable Material may also bloom to the
surface of a contact lens where it may form a hydrophobic surface
and may attract debris from tears, or may interfere with wetting of
the lens.
[0046] Some material may be physically trapped in the polymer
matrix and may not be able to be removed for example by extracting
with water or an organic solvent. As used herein, trapped material
is not considered Leachable Material.
[0047] Leachable material typically includes most or all of the
material included in the monomer mix that does not have
polymerizable functionality. For example, a diluent may be a
Leachable Material. Leachable material may also include
nonpolymerizable impurities which were present in the monomer. As
polymerization approaches completion, the rate of polymerization
will typically slow and some small amount of the monomer may never
polymerize. Monomer that never polymerizes can be included in the
material that will be leached from the polymerized lens. Leachable
material may also include small polymer fragments, or oligomers.
Oligomers can result from the termination reactions early in the
formation of any given polymer chain. Accordingly, Leachable
Materials can include any or all of a mixture of the above
described components, which may vary one to another in their
properties such as toxicity, molecular weight or water
solubility.
Leach Aids
[0048] According to the present invention, leaching of a silicone
hydrogel lens is facilitated by exposing the lens to a solution
including one or more leaching aids combined with water at
concentrations effective to remove UCDs from the lens.
[0049] For example, in some embodiments, ophthalmic lenses can be
subjected to a treatment exposing the lenses to a leach aid and a
GC Mass Spectrometer can be used to measure the level of one or
more UCDs in the ophthalmic lenses. The GC Mass Spectrometer can
determine whether treatment with a particular leaching aid is
effective to reduce an amount of particular UCDs present in the
lenses to a maximum threshold amount.
[0050] Accordingly, in some embodiments, a GC Mass Spectrometer can
be used to check for a maximum threshold of UCDs, such as SiMMA,
mPDMS, SiMMA glycol, and epoxide, of approximately 300 ppm. A
minimum hydration treatment time period necessary to reduce the
presence of such UCDs to 300 ppm or less in specific lenses can be
determined by the periodic measurements. In additional embodiments,
other UCDs, such as, for example, D3O or other diluents, can be
measured to detect the presence of a maximum amount of
approximately 60 ppm. Embodiments can also include setting a
threshold amount of a particular UCD at the minimum detection level
ascertainable by the testing equipment.
[0051] Examples of leaching aids, according to the present
invention include: ethoxylated alcohols or ethoxylated carboxylic
acids, ethoxylated glucosides or sugars, optionally with attached
C8 to C14 carbon chains, polyalkylene oxides, sulfates,
carboxylates or amine oxides of C8-C10 compounds. Examples include
cocoamidopropylamine oxide, C.sub.12-14 fatty alcohol ethoxylated
with 10 ethylene oxides, sodium dodecyl sulfate,
polyoxyethylene-2-ethyl hexyl ether, polypropylene glycol,
polyethylene glycol monomethyl ether, ethoxylated methyl glucoside
dioleate, and the sodium salt of n-octylsulfate, sodium salt of
ethylhexyl sulfate.
[0052] In order to illustrate the invention the following examples
are included. These examples do not limit the invention. They are
meant only to suggest a method of practicing the invention. Those
knowledgeable in contact lenses, as well as other arts, may find
other methods of practicing the invention, those methods are deemed
to be within the scope of this invention.
EXAMPLES
[0053] About 1 g of polymer was formed by UV curing 5000 MW
.alpha.,.omega.-bismethacryloxypropyl polydimethylsiloxane, TRIS
and DMA with t-butanol as diluent. and soaked in 50 g of 15% (wt)
ethoxylated nonylphenol (Ethal NP-9) in water overnight at room
temperature, followed by submersion in boiling water for 5 hours.
The polymer was rinsed three times with 50 ml deionized water. The
resulting polymer was analyzed for residual PDMS, TRIS and DMA as
compared to polymer that was not leached. The results are shown in
Table 1.
[0054] In addition, a Comparative example 1 was prepared with the
same polymer used in Example 1. The Comparative Example was soaked
2 hours in 50 g IPA, one hour in 50 g fresh IPA, and one hour again
in 50 g fresh IPA. The Comparative example polymer was analyzed for
residual monomers and the results are shown in Table 1.
[0055] Table 1 also includes data from the same polymer which was
not leached. TABLE-US-00001 TABLE 1 PDMS TRIS DMA Example 1 BLD*
BLD* BLD* Comparative Example 1 BLD* BLD* BLD* Not leached 2.1%
0.034% BLD* Limit of detection 0.8% 0.017% 0.012%
* * * * *