U.S. patent application number 12/515054 was filed with the patent office on 2010-02-25 for contact lens.
This patent application is currently assigned to SAUFLON CL LIMITED. Invention is credited to Robert Andrew Broad.
Application Number | 20100048847 12/515054 |
Document ID | / |
Family ID | 37636329 |
Filed Date | 2010-02-25 |
United States Patent
Application |
20100048847 |
Kind Code |
A1 |
Broad; Robert Andrew |
February 25, 2010 |
Contact Lens
Abstract
A contact lens formed of a composition comprising the reaction
product of: A) at least 10 weight percent, based on the total
composition weight excluding solvent, of at least one
silicone-containing monomer of the formula I: where n is from 1 to
3, m is from 9 to 15, each a independently is C.sub.1-4 alkyl, and
each b independently is C.sub.1-4 alkyl; B) at least 10 weight
percent, based on the total composition weight excluding solvent,
of 3-methacryloxypropyl tris(trimethylsiloxy) silane; C) N-vinyl
pyrrolidone; and D) at least one other non-ionic hydrophilic
monomer wherein the combined amount of A) and B) is at least 20
weight percent based on the total composition weight excluding
solvent, and wherein the N-vinyl pyrrolidone (NVP) is present in
such an amount that the reaction product comprises polyvinyl
pyrrolidone (PVP) homopolymer. ##STR00001##
Inventors: |
Broad; Robert Andrew;
(Curdridge, GB) |
Correspondence
Address: |
MCDONNELL BOEHNEN HULBERT & BERGHOFF LLP
300 S. WACKER DRIVE, 32ND FLOOR
CHICAGO
IL
60606
US
|
Assignee: |
SAUFLON CL LIMITED
Fareham, Hampshire
GB
|
Family ID: |
37636329 |
Appl. No.: |
12/515054 |
Filed: |
November 20, 2007 |
PCT Filed: |
November 20, 2007 |
PCT NO: |
PCT/EP07/62592 |
371 Date: |
August 25, 2009 |
Current U.S.
Class: |
526/263 ;
264/1.1 |
Current CPC
Class: |
C08F 290/068 20130101;
C08F 283/12 20130101; G02B 1/043 20130101; G02B 1/043 20130101;
G02B 1/043 20130101; C08L 43/04 20130101; C08L 51/085 20130101 |
Class at
Publication: |
526/263 ;
264/1.1 |
International
Class: |
C08F 226/10 20060101
C08F226/10; B29D 11/00 20060101 B29D011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 22, 2006 |
EP |
0623299.5 |
Claims
1. A contact lens formed of a composition comprising the reaction
product of: A) at least 10 weight percent, based on the total
composition weight excluding solvent, of at least one
silicone-containing monomer of the formula I: ##STR00004## where n
is from 1 to 3, m is from 9 to 15, each a independently is
C.sub.1-4 alkyl, and each b independently is C.sub.1-4 alkyl; B) at
least 10 weight percent, based on the total composition weight
excluding solvent, of 3-methacryloxypropyl tris(trimethylsiloxy)
silane; C)N-vinyl pyrrolidone; and D) at least one other non-ionic
hydrophilic monomer, wherein the combined amount of A) and B) is at
least 20 weight percent based on the total composition weight
excluding solvent, and wherein the N-vinyl pyrrolidone (NVP) is
present in such an amount that the reaction product comprises
polyvinyl pyrrolidone (PVP) homopolymer.
2. A contact lens formed of a composition comprising the reaction
product of: A) at least 10 weight percent, based on the total
composition weight excluding solvent, of at least one
silicone-containing monomer of Formula I ##STR00005## where n is
from 1 to 3, m is from 9 to 15, each a independently is C.sub.1-4
alkyl, and each b independently is C.sub.1-4 alkyl; B) at least 10
weight percent, based on the total composition weight excluding
solvent, of 3-methacryloxypropyl tris(trimethylsiloxy) silane; C)
from 20 to 60 weight percent, based on the total composition weight
excluding solvent, N-vinyl pyrrolidone; D) from 2 to 10 weight
percent, based on the total composition weight excluding solvent,
of at least one other non-ionic hydrophilic monomer; E) from 0.2 to
2 weight percent, based on the total composition weight excluding
solvent, of a free radical initiator; and F) from 0.2 to 5 weight
percent, based on the total composition weight excluding solvent,
of a cross-linking agent, wherein A) and B) are present in a
combined amount of at least 20 weight percent based on the total
composition weight excluding solvent.
3. A contact lens as claimed in claim 1 or claim 2, wherein D)
comprises at least one of 2-hydroxyethyl methacrylate and
N,N-dimethylacrylamide.
4. A contact lens as claimed in claim 1, additionally comprising up
to 3 weight percent based on the total composition weight excluding
solvent, of acrylic or methacrylic acid.
5. A contact lens as claimed in claim 1, wherein A) comprises
trimethylsilyl methacryloxypropyl (polydimethyl siloxane).
6. A contact lens as claimed in claim 2, wherein the free radical
initiator is AZBN.
7. A contact lens as claimed in claim 2, wherein the cross-linker
is tetraethyleneglycol methacrylate.
8. A method of making a contact lens comprising the steps of:
mixing: A) at least 10 weight percent, based on the total
composition weight excluding solvent, of at least one
silicone-containing monomer of Formula I ##STR00006## where n is
from 1 to 3, m is from 9 to 15, each a independently is C.sub.1-4
alkyl, and each b independently is C.sub.1-4 alkyl; B) at least 10
weight percent, based on the total composition weight excluding
solvent, of 3-methacryloxypropyl tris(trimethylsiloxy) silane; C)
from 20 to 60 weight percent, based on the total composition weight
excluding solvent, N-vinyl pyrrolidone; D) from 2 to 10 weight
percent, based on the total composition weight excluding solvent,
of at least one other non-ionic hydrophilic monomer; E) from 0.2 to
2 weight percent, based on the total composition weight excluding
solvent, of a free radical initiator; and F) from 0.2 to 5 weight
percent, based on the total composition weight excluding solvent,
of a cross-linking agent, wherein A) and B) are present in a
combined amount of at least 20 weight percent based on the total
composition weight excluding solvent addition of a solvent in an
amount of from 15 to 30 weight percent based on the weight of
reactants, wherein the solvent comprises at least one primary
alcohol; adding the mixture into a contact lens mould; and curing
the reaction mixture to form a contact lens.
9. A method as claimed in claim 8, wherein the solvent does not
contain any secondary or tertiary alcohols.
10. A method as claimed in claim 8, wherein the solvent comprises
ethanol and/or decanol and/or propanol.
11. A method as claimed in claim 8, wherein, the solvent comprises
at least one primary alcohol and at least one additional solvent
which is more hydrophobic than the primary alcohol, and which is
present in an amount of from 20 to 50 weight percent of the
solvent.
12. A method as claimed claim 11, wherein the additional solvent is
one or more of hexanol, octanol, decanol and ethyl acetate.
13. A method as claimed in claim 12, wherein the solvent comprises
a mixture of ethanol and at least one of hexanol, octanol, decanol
and ethyl acetate.
14. A method of making a contact lens comprising the reaction
product of at least one silicone-containing monomer and at least
one hydrophilic monomer, wherein the method comprises the step of
incorporating in the reaction mixture from 15 to 30 weight percent,
based on 100 weight percent of the reactants, of a mixed solvent,
wherein the mixed solvent comprises ethanol and a co-solvent in an
amount of at least 20 weight percent based on the total amount of
solvent, wherein the co-solvent is at least one of hexanol,
octanol, decanol and ethyl acetate.
15. A contact lens formed of the reaction product of a composition
comprising trimethylsilyl methacryloxypropyl (polydimethyl
siloxane).
Description
[0001] The present invention relates to hydrogel contact lenses
made from silicone-containing monomers.
[0002] A hydrogel is a hydrated cross-linked polymeric system that
contains water in an equilibrium state. Hydrogels typically are
oxygen permeable and biocompatible, making them a preferred
material for producing biomedical devices and in particular contact
or intraocular lenses.
[0003] Conventional hydrogels are prepared from monomeric mixtures
predominantly containing hydrophilic monomers, such as
2-hydroxyethyl methacrylate (HEMA) or N-vinyl pyrrolidone (NVP).
U.S. Pat. Nos. 4,495,313; 4,889,664 and 5,039,459 disclose the
formation of conventional hydrogels.
[0004] Conventional hydrogels have poor levels of oxygen
permeability. Therefore, there has been a shift towards the
introduction of silicone-containing monomers to increase the oxygen
permeability. Silicone-containing polymers generally have higher
oxygen permeabilities than conventional hydrogels.
[0005] However, the hydrophobic nature of silicone-containing
polymers means that contact lenses made from them are difficult to
wet. The suitability of a material for use in biomedical devices
depends on the wettability of the material and its proclivity for
adhesion or reaction with biological materials such as proteins and
lipids.
[0006] One approach for dealing with the low wettability of
silicone-containing contact lenses is to coat the hydrogels with a
more hydrophilic coating. This adds an additional level of
complexity to their manufacture. Additionally, coating material
selection can be difficult as can the determination of proper
coating thickness, coating uniformity and other factors that can
affect physiological performance.
[0007] U.S. Pat. No. 5,219,965 proposes modifying the surface
properties of polymeric objects such as contact lenses by the
inclusion of macromers having a hydrophobic portion, a hydrophilic
portion, a chain transfer agent, and an unsaturated end group in
the monomer mix used to make the objects. The macromers can include
poly-N-vinyl pyrrolidone having molecular weights of 500 to 10,000
with 1,000 to 5,000 being most preferred. The macromers are
polymerized into the hydrogel and do improve wettability of the
polymers. However, the improvement is generally not to such a
degree that lenses can be made from the hydrogels without the need
for a hydrophilic coating. In any event, enhancing the wettability
of biomedical devices such as contact lenses without the need for
lens coating would be considered a significant advance in the
art.
[0008] U.S. Pat. Nos. 4,045,547 and 4,042,552 propose the
polymerization of large amounts (14.25 to 35% wt) of polyvinyl
pyrrolidone (PVP) into a poly(hydroxyethyl methacrylate) (HEMA)
based contact lens formulation. The polymerizations are conducted
without regard for the presence of water. No mention is made of the
molecular weight of the PVP.
[0009] U.S. Pat. Nos. 4,833,196; 4,791,175; and 4,678,838 are
directed to the incorporation of poly-N-vinyl lactams into polymers
used to make contact lenses. Polyvinyl pyrrolidone (PVP) is the
preferred polylactam. Low molecular weight (about 40,000 Daltons)
PVP is covalently bonded with the monomers used to form the lens by
first hydroperoxidizing the PVP by reaction with ozone and then
polymerizing the PVP with the other monomers.
[0010] U.S. Pat. No. 5,198,477 employs low molecular weight (about
25,000 Daltons) PVP within an interpenetrating polymer network
formed principally from macrocycles made from vinyl containing
monomers. The PVP appears to be crosslinked into the
interpenetrating network.
[0011] U.S. Pat. No. 6,367,929 discloses a wettable silicone
hydrogel made by including a high molecular weight hydrophilic
polymer into the silicone hydrogel monomer mix. The hydrophilic
polymer is entrapped in the hydrogel with little or no covalent
bonding between it and the hydrogel matrix. Typically the
hydrophilic polymer is polyvinyl pyrrolidone.
[0012] We have now found that it is possible to produce a wettable
silicone hydrogel contact lens without the need to introduce
polyvinyl pyrrolidone as a polymer into the reaction mixture.
[0013] Accordingly, in a first aspect of the present invention,
there is provided a contact lens formed of a composition comprising
the reaction product of:
A) at least 10 weight percent, based on the total composition
weight excluding solvent, of at least one silicone-containing
monomer of the formula I:
##STR00002##
where n is from 1 to 3, m is from 9 to 15, each a independently is
C.sub.1-4 alkyl, and each b independently is C.sub.1-4 alkyl; B) at
least 10 weight percent, based on the total composition weight
excluding solvent, of 3-methacryloxypropyl tris(trimethylsiloxy)
silane; C) N-vinyl pyrrolidone; D) at least one other non-ionic
hydrophilic monomer; and wherein the combined amount of A) and B)
is at least 20 weight percent based on the total composition weight
excluding solvent, and wherein the N-vinyl pyrrolidone (NVP) is
present in such an amount that the reaction product comprises
polyvinyl pyrrolidone (PVP) homopolymer. Optionally, the reaction
mixture additionally comprises up to 3 weight percent, based on the
total composition weight excluding solvent, of acrylic or
methacrylic acid.
[0014] The production of a PVP homopolymer can be tested by
measurement of residual monomers present during curing. Sample
compositions can be measured at different points of the cure, and
the residual monomeric mixture can be tested to see which monomers
remain.
[0015] One method by which the remaining monomers can be tested is
described below. Other methods will be apparent to the skilled
person. Sealed moulds filled with monomer are removed at various
points during the cure process. The part-cured monomer/polymer
mixture is removed, and a known amount of the monomer/polymer
mixture placed into a known amount of solvent. The solvent/monomer
mix is then analysed quantitatively to measure its components
parts. This may be done, for example, using gas chromatography or
high pressure liquid chromatography, although other methods may be
employed. By removing moulds at different points through the cure
process, a profile of the incorporation of the various monomers
throughout the cure profile can be established. For contact lenses
according to the present invention, the remaining monomers at some
stage of the cure will be essentially only N-vinyl pyrrolidone, so
that polymerisation of the remaining monomers will necessarily
produce PVP homopolymer.
[0016] In a second aspect of the present invention, there is
provided a contact lens formed of a composition comprising the
reaction product of:
A) at least 10 weight percent, based on the total composition
weight excluding solvent, of at least one silicone-containing
monomer of Formula I above; B) at least 10 weight percent, based on
the total composition weight excluding solvent, of
3-methacryloxypropyl tris(trimethylsiloxy) silane; C) from 20 to 60
weight percent, based on the total composition weight excluding
solvent, N-vinyl pyrrolidone; D) from 2 to 10 weight percent, based
on the total composition weight excluding solvent, of at least one
other non-ionic hydrophilic monomer; E) from 0.2 to 2 weight
percent, based on the total composition weight excluding solvent,
of a free radical initiator; and F) from 0.2 to 5 weight percent,
based on the total composition weight excluding solvent, of a
cross-linking agent, wherein A) and B) are present in a combined
amount of at least 20 weight percent based on the total composition
weight excluding solvent. Optionally, the reaction mixture
additionally comprises up to 3 weight percent, based on the total
composition weight excluding solvent, of acrylic or methacrylic
acid.
[0017] In a third aspect of the present invention, there is
provided a method of making a contact lens comprising the steps
of:
mixing A) at least 10 weight percent, based on the total
composition weight excluding solvent, of at least one
silicone-containing monomer of Formula I above; B) at least 10
weight percent, based on the total composition weight excluding
solvent, of 3-methacryloxypropyl tris(trimethylsiloxy) silane; C)
from 20 to 60 weight percent, based on the total composition weight
excluding solvent, N-vinyl pyrrolidone; D) from 2 to 10 weight
percent, based on the total composition weight excluding solvent,
of at least one other non-ionic hydrophilic monomer; E) from 0.2 to
2 weight percent, based on the total composition weight excluding
solvent, of a free radical initiator; and F) from 0.2 to 5 weight
percent, based on the total composition weight excluding solvent,
of a cross-linking agent, wherein A) and B) are present in a
combined amount of at least 20 weight percent based on the total
composition weight excluding solvent addition of a solvent in an
amount of from 15 to 30 weight percent based on the weight of
reactants, wherein the solvent comprises at least one primary
alcohol; adding the mixture into a contact lens mould; and curing
the reaction mixture to form a contact lens. Optionally, the
reaction mixture additionally comprises up to 3 weight percent,
based on the total composition weight excluding solvent, of acrylic
or methacrylic acid.
[0018] The silicone containing monomers A) are generally not fully
miscible with the other monomers. If components A) to E) are simply
mixed in the absence of solvent, the mixture generally becomes
cloudy when stirred, and separates into two distinct layers when
left to stand for a few minutes. It is therefore preferred to
utilise a suitable solvent, which will improve the mutual
compatibility of the monomer components. The weight percentages of
the reactants mentioned above are however calculated based on the
total amount of reactants excluding any solvent.
[0019] Preferably, the solvent is utilised in an amount of from 10
to 30 parts by weight, based on 100 parts by weight of the total
amount of reactants excluding solvent. It is preferred that the
solvent comprises at least one primary alcohol, preferably ethanol,
propanol or decanol. In a particularly preferred embodiment, the
solvent comprises at least one primary alcohol (for example
ethanol) and at least one additional solvent which is more
hydrophobic than the primary alcohol, and which is present in an
amount of from 20 to 50 weight percent of the solvent. The
additional solvent may also be a primary alcohol. Particularly
preferred additional solvents include propanol, hexanol, octanol,
decanol and ethyl acetate. In a most favourable embodiment, the
solvent comprises a mixture of ethanol and at least one of hexanol,
octanol, decanol and ethyl acetate. Preferably, the solvent does
not comprise any secondary or tertiary alcohols.
[0020] In a further aspect of the present invention, there is
provided a method of making a contact lens comprising the reaction
product of at least one silicone-containing monomer and at least
one hydrophilic monomer, wherein the method comprises the step of
incorporating in the reaction mixture from 10 to 30 weight percent,
based on 100 weight percent of the reactants, of a mixed solvent,
wherein the mixed solvent comprises ethanol and a co-solvent in an
amount of at least 20 weight percent based on the total amount of
solvent, wherein the co-solvent is at least one of propanol,
hexanol, octanol, decanol and ethyl acetate.
[0021] This method is particularly useful for making the contact
lens of the first aspect of the present invention. The solvent
mixture is particularly good at preventing phase separation of the
hydrophilic and hydrophobic monomers.
[0022] In situ production of PVP results in the ability to produce
PVP-containing contact lenses without the need to add
pre-polymerised PVP to the monomer mixture. If PVP is incorporated
into the monomer mixture in polymerised form, it is necessary to
employ secondary or tertiary alcohols, in order to ensure
dissolution of the PVP polymer, as is discussed, for example, in
U.S. Pat. No. 6,020,445. However, the use of secondary or tertiary
alcohols in the polymerisation mixture is undesirable, because they
are difficult to extract from the cured lens using water based
extraction systems. In general, they require the use of complex
solvent/water systems for their extraction, which leads to
increased complexity and cost in manufacturing, as disclosed in
WO01/27174. Therefore, by producing the PVP in situ, such
complexity can be avoided.
[0023] Methacrylic acid (MAA) is not usually added to
silicone-containing contact lenses. In conventional, non-silicone
containing hydrogels, ionic materials such as methacrylic acid have
been associated with increased bio-fouling, especially protein
deposition. For this reason silicone hydrogel materials do not
typically include ionic monomers.
[0024] It has now been found that, surprisingly, the addition of
relatively small amounts of MAA reduces the haze of the produced
contact lenses. Accordingly, when MAA is used in an amount of at
least 1.5 weight percent, based on the total composition weight
excluding solvent, haze is reduced in the hydrated contact lenses.
The MAA is most preferably used in an amount of less than 2 weight
percent, based on the total composition weight excluding solvent.
However, it can be used in an amount of up to 4 weight percent,
more preferably less than 3 weight percent.
[0025] Previously, it has been considered preferable to ensure that
the amounts of monomers used are "normalised" i.e. the amount of
monomers are chosen to ensure that the complete consumption of all
of the monomers present occurs at approximately the same time so
that homopolymers of one particular species are not produced. It
was believed that if the amount of the monomers were not
normalised, problems would arise with the resulting lens such as
separation of hydrophobic and hydrophilic phases and haze or even
opacity in either the dry or hydrated lens materials.
[0026] Because different monomers have different reactivity ratios,
it is difficult to normalise the amount of monomers. Typically,
monomers will polymerise at different rates, and therefore it is
not straightforward to ensure that the different monomers react to
form a single phase polymer. What the applicant has found is that
normalization is not necessary. By the use of N-vinyl pyrrolidone
with a careful choice of particular silicone monomers it is
possible to produce a lens containing a silicon-containing
copolymer and a PVP homopolymer. The resulting contact lens is
wettable and does not suffer from phase separation or haze.
[0027] It will be apparent to those skilled in the art that in free
radical initiated bulk polymerisations of this type that 100%
conversion of monomer to polymer is difficult, if not impossible to
achieve. For this reason, there are low levels of residual,
unreacted monomers in the polymer at the completion of the
reaction, which are typically removed by an aqueous or solvent
extraction process to yield a contact lens suitable for in vivo
use. It follows that some of these residual monomers will be
incorporated into the polymer at the end of the reaction. For these
reasons, it is understood that the PVP homopolymer produced at the
end of the polymerisation will necessarily include very low levels
of the other monomeric components of the formulation. Accurate
quantification of the levels of these residual monomers
incorporated into the lens polymer at the end of the reaction is
very difficult due to the nature of the polymers produced. However
it is understood that trace levels of the other components will be
incorporated into the PVP homopolymer. Therefore, according to the
present invention, PVP homopolymer is to be understood as covering
polymers which consist essentially only of polymerized NVP with
trace amounts of other monomers present.
[0028] It is preferred that the amount of N-vinyl pyrrolidone is
present in an amount of from 20 to 60 weight percent. More
preferably, N-vinyl pyrrolidone is present in an amount of at least
30 weight percent, and most preferably at least 40 weight percent.
If the N-vinyl pyrrolidone is present in an amount greater than 60
weight percent, the resultant lens will not contain enough
silicone-based material to have sufficient oxygen permeability.
[0029] As well as N-vinyl pyrrolidone, at least one other non-ionic
hydrophilic monomer is used. A hydrophilic monomer is one which can
combine with other monomers to form a polymer that has hydrophilic
properties or can impart such properties to the final polymer.
Molecules with hydrophilic properties have an affinity to water and
are typically charged or have polar side groups to their structure
that will attract water.
[0030] Examples of suitable hydrophilic monomers include hydroxyl
substituted C.sub.1-6 alkyl acrylates and methacrylates, for
example 2-hydroxyethyl methacrylate (HEMA), (meth)acrylamide,
(C.sub.1-6 alkyl)-acrylamides and -methacrylamides, for example
N,N-dimethylacrylamide (DMA), ethoxylated acrylates and
methacrylates, hydroxyl substituted (C.sub.1-6 alkyl)acrylamides
and -methacrylamides, hydroxyl-substituted C.sub.1-6 alkyl vinyl
ethers, sodium vinylsulfonate, sodium styrenesulfonate,
N-vinylpyrrole, 2-vinyloxazoline,
2-vinyl-4,4'-dialkyloxazolin-5-one, 2- and 4-vinylpyridine,
amino(C.sub.1-6 alkyl)- (where the term "amino" also includes
quaternary ammonium), mono(C.sub.1-6 alkylamino)(C.sub.1-6 alkyl)
and di(C.sub.1-6 alkylamino)(C.sub.1-6 alkyl)acrylates and
methacrylates and allyl alcohol.
[0031] It is preferred that the additional hydrophilic monomer is
selected from hydroxyl-substituted C.sub.1-6 alkyl acrylates and
methacrylates, most preferably 2-hydroxyethyl methacrylate
(HEMA).
[0032] In a particularly preferred embodiment, the additional
hydrophilic monomers are present in an amount of from 2 to 10
weight percent. It is yet further preferred that the hydrophilic
monomers are present in an amount of from 2 to 6 weight
percent.
[0033] When HPMA is used, it is used in an amount of from 2 to 10
weight percent. Preferably, it is used in an amount of from 4 to 6
weight percent.
[0034] Monomer Component A is at least one silicone-containing
monomer having the formula:
##STR00003##
where n is from 1 to 3, m is from 9 to 15, each a independently is
C.sub.1-4 alkyl, and each b independently is C.sub.1-4 alkyl.
[0035] It is particularly preferred that at least one of the
silicone-containing monomers present is
methacryloxypropyl(polydimethyl siloxane). Preferably the
methacryl-oxypropyl(polydimethyl siloxane) has an average molecular
weight of approximately 1000. A particularly preferred silicone
monomer is methacryloxypropyl(polydimethyl siloxane) which is
terminated with a trimethyl silyl group.
[0036] In a further aspect of the present invention, there is
provided a contact lens formed of the reaction product of a
composition comprising trimethylsilyl methacryl-oxypropyl
(polydimethyl siloxane).
[0037] It is possible to include other silicone-containing monomers
other than those of the Component A) or B). Examples of other
silicone monomers may include, but are not limited to,
3-methacryloxy propylpentamethyldisiloxane,
bis(methacryloxypropyl)-tetramethyldisiloxane,
N[tris(trimethylsiloxy)silylpropyl]methacrylamide (TSMAA),
N[tris(trimethylsiloxy)silylpropyl]acrylamide,
[tris(trimethylsiloxy)silylpropyl]-methacryloxyethylcarbamate,
N[tris(dimethylpropylsiloxy)silylpropyl]methacrylamide,
N[tris(dimethylphenylsiloxy)silylpropyl]methacrylamide,
N[tris(trimethylsiloxy)-silylpropyl]methacryloxyglycerylcarbamate,
N[tris(dimethylethylsiloxy)silylpropyl]-methacrylamide,
N[tris(trimethylsiloxy)silylpropyl]methacryloxyacetamide, and
N[tris(trimethylsiloxy)silylpropyl]methacryloxymethyl
dimethylacetamide. Additional silicone-containing monomers may be
used up to a maximum amount of 10 weight percent, based on the
total composition weight excluding solvent, preferably less than 5
weight percent, and more preferably no other silicone-containing
monomers are included.
[0038] Preferably, an initiator is used, such as a free-radical
initiator. Examples of suitable polymerisation initiators or
catalysts which are well understood in the art include peroxide or
azo containing compounds such as benzoyl peroxide, lauroyl
peroxide, di-isopropyl-peroxy dicarbonate, azo bis(2,4-dimethyl
valeronitrile), azo bis (isobutyronitrile), redox systems, for
example ammonium persulphate, and photoinitiators for example
benzoin methyl ether. Particularly preferred is
2,2'-azobisisobutyronitrile, (AZBN).
[0039] The composition also preferably comprises a cross-linker.
Examples of suitable cross-linking agents include, C.sub.2-6
alkylene glycol di(meth)acrylate, poly(C.sub.2-6 alkylene) glycol
di(meth)acrylate, C.sub.2-6 alkylene di(meth)acrylate, divinyl
ether, divinyl sulfone, di- and trivinylbenzene, trimethylolpropane
tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, bisphenol A
di(meth)acrylate, methylenebis(meth)acrylamide, triallyl phthalate
and diallyl phthalate.
[0040] Standard UV absorbers and/or colorants may be added to the
monomer mix using methods known to those skilled in the art.
[0041] Silicon-containing dimers may also be used as cross linking
agents. Examples of suitable silicon-containing dimers include
1,3-Bis(methacrylamidopropyl)-1,1,3,3-tetrakis(trimethylsiloxy)disiloxane-
, 1,3-Bis(3-methacryloxypropyl) tetramethyldisiloxane,
1,3-Bis(N-methylmethacrylamidopropyl)-1,1,3,3-tetrakis(trimethylsiloxy)
disiloxane,
1,3-Bis(methacrylamidopropyl)-1,1,3,3-tetrakis(trimethylsiloxy)disiloxane-
, Bis(methacryloxypropyl)polydimethylsiloxane,
1,3-Bis(acrylamidopropyl)-1,1,3,3-tetrakis(trimethylsiloxy)disiloxane,
and
1,3-Bis(methacryloxyethylureidopropyl)-1,1,3,3-tetrakis(trimethylsilo-
xy) disiloxane.
[0042] The preferred cross linking agent is tetraethyleneglycol
dimethacrylate.
[0043] The present invention is further illustrated by the
following Examples and also with reference to the drawings in
which:
[0044] FIG. 1 shows the contact angle of lens formulations made
using different amounts of methacrylic acid, as measured by sessile
drop;
[0045] FIG. 2 shows the contact angle of lens formulations made
using different amounts of methacrylic acid, as measured by captive
bubble.
EXAMPLES 1 TO 10
[0046] Contact lenses were made by reacting various monomer
mixtures having the compositions shown in Table 1. For all contact
lenses, a 50:50 mixture of ethanol and ethyl acetate was used as
the solvent.
[0047] The reactants and solvent were mixed at room temperature to
produce a curable mixture. The mixtures were placed in a contact
lens mould and cured using a two stage cure in a nitrogen
atmosphere. The cure involved a 1 hour purge in Nitrogen, followed
by a first temperature ramp of 45.degree. C./minute to 55.degree.
C., followed by curing at that temperature for 8.5 hours.
Thereafter, the temperature was ramped to 124.degree. C. at
45.degree. C./minute, and then cured at 124.degree. C. for 1 hour.
The O.sub.2 concentration in the oven is preferably less than 100
ppm, and more preferably less than 50 ppm.
TABLE-US-00001 TABLE 1 Total Total Methacrylic (exc. Ethyl (inc
HEMA NVP acid Tris TEGDMA MAPDMS AZBN solvent) EtOH Acetate
solvent) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) 1 4.67 52.55
0.00 20.06 2.40 19.94 0.38 100 10.00 10.00 120 2 4.67 52.53 0.00
20.05 2.02 19.93 0.79 100 10.00 10.00 120 3 4.56 51.25 2.00 19.56
2.40 19.44 0.79 100 10.00 10.00 120 4 4.59 51.68 2.00 19.72 2.02
19.61 0.38 100 10.00 10.00 120 5 4.57 51.46 2.00 19.64 2.02 19.52
0.79 100 10.00 10.00 120 6 4.58 51.47 2.00 19.65 2.40 19.53 0.38
100 10.00 10.00 120 7 4.65 52.33 0.00 19.97 2.40 19.86 0.79 100
10.00 10.00 120 8 4.69 52.75 0.00 20.14 2.02 20.02 0.38 100 10.00
10.00 120 9 4.57 51.46 2.00 19.64 2.02 19.52 0.79 100 10.00 10.00
120 10 4.57 51.46 2.00 19.64 2.02 19.52 0.79 100 10.00 10.00
120
[0048] Different lenses were made to vary the amount of methacrylic
acid, cross-linker (TEGDMA) and initiator (AZBN). The lenses were
typically tested for a number of different characteristics,
including thickness, power, haze (subjective), surface quality,
diameter, base curve (calculated from saggital height measurement),
water content, and wettability by sessile drop and captive bubble
contact angle measurement.
[0049] Prior to measurement lenses were hydrated in vials in
bicarbonate buffered saline and equilibrated for at least 4 hours
at 21.degree. C.+/-1.degree. prior to measurement. Where
appropriate, equipment was calibrated prior to use.
[0050] Dry centre thickness is measured with a Mitutoyo Digimatic
Indicator model 1D110-ME fitted to a model DGS-E stand.
[0051] Wet lens diameter and saggital height are measured on an
Optimec type B contact lens analyser SAG model, and the base curve
calculated.
[0052] Lens powers and image quality are measured using a Nikon PL2
Focimeter. Lens wet centre thickness is measured using a Rehder
ET-3 electronic thickness gauge.
[0053] Surface quality was determined subjectively by inspecting
the lens in a wet cell, with the lens image projected onto a screen
with a magnification of X17.5. Apart from the usual defects found
in moulded contact lenses, surface marks of undetermined cause
could be identified on lenses made under certain formulation and
cure conditions. These marks were scored as a percentage of marks
found, with zero being the preferred result.
[0054] Haze was assessed subjectively by viewing wet lenses in a
wet cell on a documator. The documator is a device which
illuminates the lenses from underneath, and allows the lenses to be
observed at approximately 45.degree. to the light source, to enable
haze to be observed. Haze was assessed subjectively with a value of
5 indicating a completely opaque lens, and a level of 0 indicating
no discernable haze. The values shown indicate the average of
several assessments.
[0055] Water content measurements are made on either an Atago CL-1
contact lens refractometer or an Index Instruments Contact Lens
Refractometer CLR12-70. The Atago refractometer is used by placing
a sample lens directly onto the prism, gently clamping the sample
with light finger pressure on the daylight plate, and focussing so
that the scale can be clearly read. The upper area of the scale
appears as a blue band, and the lower screen appears as a white
band. Water content can be directly read from the scale at the
point where the blue and white bands meet.
[0056] The Index refractometer is used by gently placing a lens on
the sample holder and closing the lid. After a few seconds the
reading stabilises and the result printed. The refractive index
reading is converted to a water content using a previously
validated equation.
[0057] Prior to measurement all lenses are equilibrated at
21.degree.+/-1.degree. C. in saline solution for a minimum of 2
hours, and gently blotted with lint free tissue to remove excess
surface water immediately prior to measurement. Bulk water content
may also be measured gravimetrically.
[0058] Sessile drop (water in air) and captive bubble (air in
water) contact angles were measured using a Dataphysics OCA15
contact angle analyzer with contact lens adaptor. Lenses were
equilibrated and measured in bicarbonate buffered saline.
[0059] Oxygen permeability can also be measured using a Rheder O2
Permeometer model 201T using the method described in the
international standard ISO 9913-1.
[0060] The results of the tests for Examples 1 to 10 are shown in
Table 2 below.
TABLE-US-00002 TABLE 2 Base- Diameter curve % Surface Sessile
Captive (mm) (mm) Water Marks % Haze Drop Bubble 1 12.81 7.96 55.3
23 2.72 65.2 38.3 2 13.20 8.30 57.7 30 3.00 53.0 31.5 3 13.23 8.30
58.2 0 1.00 75.4 38.2 4 13.26 8.11 60.7 0 0.94 82.2 45.2 5 13.06
7.87 59.1 1 0.50 85.9 37.1 6 13.08 8.04 57.3 0 0.50 87.3 45.3 7
12.80 7.97 55.8 5 1.00 56.0 28.9 8 12.83 7.89 56.8 15 1.00 64.1
32.2 9 13.18 8.12 60.0 30 0.50 54.6 36.2 10 13.17 8.12 58.7 1 0.50
86.4 42.1
[0061] It can bee seen that the inclusion of MAA decreases the
amount of haze in the lens. It can also be seen that the lenses
according to the present invention have good contact angles, water
content, clarity and surface quality.
EXAMPLES 11 TO 13
[0062] Examples 11 to 13 demonstrate the effect of methacrylic acid
on compositions where ethanol and decanol as used as co-solvents in
equal proportions.
[0063] The contact lenses were made in the same way as Examples 1
to 10 according to the compositions in Table 3.
TABLE-US-00003 TABLE 3 Total Total Methacrylic (exc. Ethyl (inc
HEMA NVP acid Tris TEGDMA MAPDMS AZBN solvent) EtOH Acetate
solvent) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) 11 4.67 52.51
0.00 20.04 2.04 19.93 0.81 100.00 10.00 10.00 120.00 12 4.62 51.99
0.99 19.84 2.02 19.73 0.80 100.00 10.00 10.00 120.00 13 4.58 51.48
1.97 19.65 2.00 19.53 0.80 100.00 10.00 10.00 120.00
[0064] Several different contact lenses of each composition were
tested to measure the contact angle as measured by sessile drop and
captive bubble as described above. The results are shown in Table 4
below and in FIGS. 1 and 2.
TABLE-US-00004 TABLE 4 Example 11 Example 12 Example 13 Sessile
Captive Sessile Captive Sessile Captive Drop Bubble Drop Bubble
Drop Bubble 48.3 23.3 59.8 27.2 73 40.5 28.6 26.4 49.6 29.6 75.9
35.2 26.4 22.9 44.6 29.5 80.1 37.8 32 26.5 49.3 25.7 80 35.6 35.2
26.3 48.1 21.7 81.2 39.2 52.3 Mean 34.1 25.1 50.6 26.7 78.0 37.7
Standard 8.61 1.81 5.15 3.26 3.47 2.28 Deviation
[0065] It can be seen that an increase in the amount of methacrylic
acid results in an increase in the contact angle as measured by
both sessile drop and captive bubble. Increased contact angle is
not favourable. However, at low levels of methacrylic acid,
formulations have a tendency to produce lenses with high levels of
haze. By carefully balancing the methacrylic acid content with the
other formulation components, lenses with both low haze and good
wettability may be obtained.
EXAMPLES 14 TO 37
[0066] Further contact lenses were made by reacting various monomer
mixtures having the compositions shown in Table 5. The contact
lenses were made using the same method as described for Examples 1
to 10 and the resultant contact lenses were tested in the same
manner. In Examples 33 to 37, the wet lens diameter and base curve
were measured on an Optimec type JCF.
TABLE-US-00005 TABLE 5 n- Ethyl Total % Total % HEMA NVP MAA DMA
TRIS TEGDMA IBoMA MAPDMS AZBN Ethanol Propanol Acetate (exc. (inc.
Example (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) EtOH) EtOH)
14 4.84 54.72 1.98 0 17.84 1.98 0 17.84 0.79 15.03 0 0 100.00
115.03 15 4.59 51.87 2.00 0 19.77 1.22 0 19.77 0.79 15.03 0 0
100.00 115.03 16 4.72 53.40 1.50 0 18.96 1.65 0 18.96 0.81 17.50 0
0 100.00 117.50 17 4.93 55.71 1.00 0 18.17 1.22 0 18.17 0.81 15.03
0 0 100.00 115.03 18 4.63 52.40 1.00 0 19.97 1.22 0 19.97 0.80
20.03 0 0 100.00 120.03 19 4.89 55.28 1.00 0 18.03 1.98 0 18.03
0.80 20.03 0 0 100.00 120.03 20 4.55 51.46 2.00 0 19.62 1.98 0
19.62 0.78 20.03 0 0 100.00 120.03 21 4.72 53.42 1.50 0 18.97 1.65
0 18.97 0.77 17.50 0 0 100.00 117.50 22 4.60 52.00 0.99 0 19.82
1.97 0 19.82 0.79 15.03 0 0 100.00 115.03 23 4.72 53.42 1.50 0
18.97 1.65 0 18.97 0.77 17.50 0 0 100.00 117.50 24 4.87 55.14 2.00
0 17.98 1.22 0 17.98 0.80 20.03 0 0 100.00 120.03 25 4.84 54.72
1.98 0 17.84 1.98 0 17.84 0.79 25.02 0 0 100.00 125.02 26 4.59
51.87 2.00 0 19.77 1.22 0 19.77 0.79 25.02 0 0 100.00 125.02 27
4.72 53.40 1.50 0 18.96 1.65 0 18.96 0.81 22.51 0 0 100.00 122.51
28 4.93 55.71 1.00 0 18.17 1.22 0 18.17 0.81 22.51 0 0 100.00
122.51 29 4.93 55.71 1.00 0 18.17 1.22 0 18.17 0.81 22.51 0 0
100.00 122.51 30 4.60 52.00 0.99 0 19.82 1.97 0 19.82 0.79 25.02 0
0 100.00 125.02 31 4.93 55.71 1.00 0 18.17 1.22 0 18.17 0.81 22.51
0 0 100.00 122.51 32 (C) 10.61 30.94 0 0 43.76 0.10 0 14.59 0.05
21.07 0 0 100.05 121.12 33 (C) 4.89 24.64 0 24.64 32.00 1.00 0
12.00 0.83 0 10.00 0 100.00 110.00 34 (C) 4.89 24.64 0 24.64 32.00
1.00 0 12.00 0.83 10.00 0 0 100.00 110.00 35 6.55 38.97 0 12.99
19.91 1.00 0 19.80 0.78 0 0 11.20 100.00 111.20 36 6.55 38.97 0
12.99 19.91 1.00 0 19.80 0.78 0 11.20 0 100.00 111.20 37 6.36 44.14
0 6.31 19.33 0.97 2.91 19.22 0.76 0 16.02 0 100.00 116.02 (C) is
comparative example. Example 37 includes 2.91% isobornyl
methacrylate (IBoMA).
[0067] The results are shown in Table 6.
TABLE-US-00006 TABLE 6 Surface Captive Example Haze Marks %
Diameter Base Curve % Water Sessile drop bubble 14 1 1.7 13.75 8.65
66.2 74.5 48.4 15 0.83 0 13.77 8.71 65.6 90.6 59.7 16 1 2 13.98
8.82 65.2 -- -- 17 1.4 6.6 13.91 8.75 67.7 54.4 38.1 18 2.8 2 13.9
8.68 66.6 42.5 37.9 19 2 35 13.88 8.89 66.3 35.3 34.6 20 1.9 11
13.46 8.59 66.6 55.0 40.0 21 1 10 13.75 8.79 65.1 44.0 43.4 22 2 15
13.53 8.63 62.5 90.2 49 23 2 4 13.81 8.81 66.6 46.2 34.3 24 3 20
13.83 8.69 65.4 42.8 32.9 25 1 1.7 13.75 8.65 66.2 74.5 48.4 26
0.83 0 13.77 8.71 65.6 90.6 59.7 27 1 2 13.98 8.82 65.2 -- -- 28
1.4 6.6 13.91 8.75 67.7 54.4 38.1 29 2.8 20 13.90 8.68 66.6 42.5
37.9 30 2 35 13.88 8.89 66.3 35.3 34.6 31 1.9 11 13.46 8.59 66.6
55.0 40.0 32 (C) 5 -- 12.24 7.28 47.8 99.4 65.4 33 (C) 1 -- 14.33*
8.88* 64.8 103.2 32.7 34 (C) 1 -- 14.50* 8.85* 64.8 108.5 26.8 35 1
-- 13.70* 8.65* 62.7 93.6 36.0 36 1 -- 13.99* 9.29* 62.6 95.6 29.3
37 2 -- 14.03* 8.87* 64.3 101.6 31.6
[0068] It can be seen from the above results that contact lenses
made according to the present invention have good properties for
haze, wettability, sessile drop and captive bubble. In addition,
the contact lenses can be produced easily and reproducibly using a
conventional cast moulding process, such as that described in
GB2004/000514. Furthermore, the lenses according to the present
invention have good mechanical properties including tensile
strength, elongation at break etc. The skilled person is aware of
the mechanical properties required by a contact lens.
* * * * *