Crosslinked polymers and refractive devices formed therefrom

Details Crosslinked polymers and refractive devices formed therefrom Crosslinked polymers and refractive devices formed therefrom

2001-09-20

2004-07-27

Lipman, Bernard (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S278000, C526S287000, C526S288000, C526S292100, C526S292200, C526S292300, C526S292500, C526S292600, C526S292950, C526S293000, C526S311000, C526S312000

Reexamination Certificate

active

06767979

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a polymeric composition, which is a crosslinked water swellable polymer, the hydrogel of which is transparent and has a high refractive index, rendering it useful for use in a refractive device, for instance an intraocular lens.
RELEVANT PRIOR ART
Various products have been developed for replacing or augmenting the natural lens. Replacement lenses may be used where the original lens is clouded by cataracts. Lenses which augment the natural lens and which are intended to be inserted into the eye, include intraocular contact lenses, corneal implants, corneal inlays and corneal onlays.
A method of implanting an intraocular lens in a rolled up form, to minimise the size of the incision is in widespread use. Such a device is described in U.S. Pat. Nos. 4,573,998 and 4,702,244. In these specifications, the material of the lens is described as having a shape memory. The device thus recovers its original conformation after being released from the restraining insertion device through which it is introduced. The above specifications do not describe in any detail the materials used to form the lens.
In U.S. Pat. No. 4,608,049, a foldable intraocular lens is formed of a silicone rubber or a crosslinked hydroxyethylmethacrylate:N-vinyl-2-pyrrolidone:methacrylic acid polymer, that is a water-swellable material.
Further descriptions of hydrogel intraocular lenses are by Barrett in U.S. Pat. No. 4,664,666. Barrett uses a hydrogel of hydroxyethylmethacrylate, a common component of hydrogel contact lens compositions. One problem with poly HEMA hydrogels is that the refractive index of the gel is relatively low. It is preferred for a hydrogel to have higher refractive indices, for instance at least 1.45, up to around 1.60.
Higher refractive index materials are described in EP-A0485197. The polymers must be formed of at least two aryl acrylate polymers, for instance 2-phenylethyl acrylate and 2-phenylethyl methacrylate. The crosslinker is selected from aliphatic diacrylates. The refractive indices of the material is in the range 1.553 to 1.556. The polymers are not, however, hydrogels (that is they are not water-swellable).
EP-A-0308130 describes elastic intraocular lenses formed of copolymers of methacrylate and acrylate esters which are respectively relatively hard and relatively soft at body temperature. The monomers are all aliphatic acrylates. The crosslinker is an aliphatic dimethacrylate.
In our earlier application WO-A-9207885, we describe crosslinked polymers formed of zwitterionic monomer and nonionic copolymerisable monomer, and hydrogel lenses formed therefrom. The examples all used an alkyl acrylate or hydroxyalkylacrylate comonomer. The crosslinking monomers were all aliphatic di-ethylenically unsaturated compounds.
In EP-A-0563299 a copolymer of a zwitterionic monomer and a nonionic monomer is used as a contact lens. In the worked examples, comonomers are hydroxyethylmethacrylate, N-vinylpyrollidone and methylmethacrylate. Crosslinkers are all aliphatic compounds (allyl methacrylate and diethylene glycol di-methacrylate).
In U.S. Pat. Nos. 5,391,669 and 5,270,415, hydrogels formed of balanced charge ion pairs and nonionic comonomer are used as contact lenses. The balanced charge ion pair may be a zwitterionic monomer. In the worked examples, the nonionic comonomers are selected from hydroxyethyl methacrylate, silyl group containing monomers, alkyl methacrylates, hydroxypropyl methacrylate, fluoroalkyl methacrylate and hydroxypropyl methacrylamide. Crosslinkers used in the worked examples are all aliphatic compounds.
SUMMARY OF THE INVENTION
A new crosslinked polymer according to the invention is obtainable by radical polymerisation of ethylenically unsaturated monomers including
a) a zwitterionic monomer of the general formula I
YBX  I
wherein
B is a straight or branched alkylene, oxaalkylene or oligo-oxaalkylene chain optionally containing one or more fluorine atoms up to and including perfluorinated chains or, if X or Y contains a terminal carbon atom bonded to B, a valence bond;
X is a zwitterionic group; and
Y is an ethylenically unsaturated polymerisable group selected from
CH
2
═C(R)—CH
2
—O—, CH
2
═C(R)—CH
2
OC(O)—, CH
2
═C(R)OC(O)—, CH
2
═C(R)—O—, CH
2
═C(R)CH
2
OC(O)N(R
1
)—, R
2
OOCCR═CRC(O)—O—, RCH═CHC(O)O—, RCH═C(COOR
2
)CH
2
—C(O)—O—,
wherein:
R is hydrogen or a C
1
-C
4
alkyl group;
R
1
is hydrogen or a C
1
-C
4
alkyl group or R
1
is —B—X where B and X are as defined above; and
R
2
is hydrogen or a C
1-4
alkyl group or BX where B and X are as defined above;
A is —O— or —NR
1
—;
K is a group —(CH
2
)
p
OC(O)—, —(CH
2
)
p
C(O)O—, —(CH
2
)
p
OC(O)O—, —(CH
2
)
p
NR
3
—, —(CH
2
)
p
NR
3
C(O)—, —(CH
2
)
p
C(O)NR
3
—, —(CH
2
)
p
NR
3
C(O)O—, —(CH
2
)
p
OC(O)NR
3
—, —(CH
2
)
p
NR
3
C(O)NR
3
— (in which the groups R
3
are the same or different), —(CH
2
)
p
O—, —(CH
2
)
p
SO
3
—, or, optionally in combination with B, a valence bond and p is from 1 to 12 and R
3
is hydrogen or a C
1
-C
4
4
group.
b) an aromatic group containing monomer of the general formula II
Y
1
R
4
  II
wherein Y
1
is selected from
CH
2
═C(R
5
)—CH
2
—O—, CH
2
═C(R
5
)—CH
2
OC(O)—, CH
2
═C(R
5
)OC(O)—, CH
2
═C(R
5
)—O—, CH
2
═C(R
5
)CH
2
OC(O)N(R
6
)—, R
7
OOCCR
5
═CR
5
C(O)—O—, R
5
CH═CHC(O)O—, R
5
CH═C(COOR
7
)CH
2
—C(O)—O—,
wherein:
R
5
is hydrogen or a C
1
-C
4
alkyl group,
R
6
is hydrogen or a C
1
-C
4
alkyl group or R
5
is R
3
;
R
7
is hydrogen or a C
1-4
alkyl group or R
3
;
A
1
is —O— or —NR
5
—; and
K
1
is a group —(CH
2
)
q
OC(O)—, —(CH
2
)
q
C(O)O—, —(CH
2
)
q
OC(O)O—, —(CH
2
)
q
NR
8
—, —(CH
2
)
q
NR
8
C(O)—, —(CH
2
)
q
C(O)NR
8
—, —(CH
2
)
q
NR
8
C(O)O—, —(CH
2
)
q
OC(O)NR
8
—, —(CH
2
)
q
NR
8
C(O)NR
8
— (in which the groups R
8
are the same or different), —CH
2
)
q
O—, —(CH
2
)
q
SO
3
—, or a valence bond and p is from 1 to 12 and R
8
is hydrogen or a C
1
-C
4
alkyl group;
and R
4
is an aromatic group; and
c) a cross-linking monomer of the general formula III
(Y
2
)
n
R
9
  III
in which n is an integer of at least 2, each Y
2
is selected from
CH
2
═C(R
10
)—CH
2
—O—, CH
2
═C(R
10
)—CH
2
OC(O)—, CH
2
═C(R
10
)OC(O)—, CH
2
═C(R
10
)—O—, CH
2
═C(R
10
)CH
2
OC(O)N(R
11
)—, R
12
OOCCR
10
═CR
10
C(O)—O—, R
10
CH═CHC(O)O—, R
10
CH═C(COOR
12
)CH
2
—C(O)—O—,
wherein:
R
10
is hydrogen or a C
1
-C
4
alkyl group;
R
11
is hydrogen or a C
1
-C
4
alkyl group or R
11
is R
3
;
R
12
is hydrogen or a C
1-4
alkyl group or R
3
;
A
2
is —O— or —NR
11
—;
K
2
is a group —(CH
2
)
r
OC(O)—, —(CH
2
)
r
C(O)O—, —(CH
2
)
r
OC(O)O—, —(CH
2
)
r
NR
12
—, —(CH
2
)
r
NR
13
C(O)—, —(CH
2
)
r
C(O)NR
13
—, —(CH
2
)
r
NR
13
C(O)O—, —(CH
2
)
r
OC(O)NR
13
—, —(CH
2
)
r
NR
13
C(O)NR
13
— (in which the groups R
13
are the same or different), —(CH
2
)
r
O—, —(CH
2
)
r
SO
3
— or a valence bond and r is from 1 to 12 and R
13
is hydrogen or a C
1
-C
4
alkyl group;
and R
9
is an n-functional organic group.
Suitable examples of aromatic groups R
4
are optionally substituted aralkyl and alkaryl groups. Most preferably, a group R
4
is an unsubstituted aryl or aralkyl group, in which the alkyl group has 1 to 4 carbon atoms, for instance benzyl, 2-phenylethyl or phenyl.
For optimum copolymerisability, the groups Y, Y
1
and Y
2
have the same general definition. Most preferably each such group is an (alk)acrylic or a styrenic group. An acrylic group, H
2
C═C(H or Me)CO—(O or NH) are particularly preferred. Preferably all such groups are either methacrylic R=R
5
=R
10
=Me) or acrylic (R, R
5
, R
10
=hydrogen), and are preferably all ester or amide derivatives thereof. Most conveniently, the monomers are all acrylic esters, generally either methacrylate esters or acrylate esters.
In the invention, it is found that optimum crosslinking of the aromatic and zwitterionic monomers is achieved where a crosslinking monomer of the formula III in which the group R
9
is a

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