Process for the manufacture of moldings

Details Process for the manufacture of moldings Process for the manufacture of moldings

2000-05-15

2001-07-03

Foelak, Morton (Department: 1711)

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

Synthetic resins

Cellular products or processes of preparing a cellular...

C435S395000, C521S145000, C521S149000, C526S072000, C526S246000, C526S247000, C526S320000

Reexamination Certificate

active

06255360

ABSTRACT:

The present invention relates to a process for the manufacture of porous polymers, to moldings, especially biomedical moldings such as in particular ophthalmic moldings obtainable by the process and to specific copolymers, in both porous and non-porous form, being particularly suitable for various biomedical applications.
WO96/31548 discloses a class of materials based on perfluoroalkylpolyether macromonomers, which in both their porous and non-porous forms can act as cell growth substrates and are suitable for use as biomaterials, particularly in ocular applications. The document also discloses perfluoroalkylpolyether-containing compositions copolymerized with comonomers including minor amounts of dihydroperfluorooctyl acrylate. Although the polymers of the prior art document are suitable for biomedical applications, they suffer limitations mainly due to their pronounced hydrophobicity. For example, the permeability of the polymers to proteins, nutrients and the like is often not completely satisfactory. In particular, the permeability to high molecular weight proteins (about 600000 Daltons and higher) is difficult to achieve with the prior art materials. Moreover, the optical quality of the known materials may be affected during handling under ambient air or in contact with the biological environment. The hydrophobic prior art materials in general show a dry out effect in air which means that they lose the optical transparency when exposed to air. An extensive equilibration process in alcohol/water mixtures is then necessary to regain the transparency which means a serious restriction concerning the handling and application of the materials. Moreover, the prior art materials tend to irreversibly absorb proteins which likewise affects the optical transparency of the materials. Accordingly, there is a demand for novel polymeric materials comprising a further improved biocompatibility as well as improved optical properties.
It now has surprisingly been found that novel porous polymers with a unique combination of biocompatibility with living tissue including a suitable surface topography that enhances cell growth, oxygen permeability, permeability to proteins and nutrients and optical transparency in vivo may be obtained by the process as outlined below.
The present invention therefore in one aspect relates to a process for producing a porous polymer comprising the steps of:
(a) forming a composition comprising
(i) a polymerizable component comprising at least one free radically polymerizable unsaturated monomer of formula
Q—X—A  (1)
wherein Q is a radical of formula
(alk) is linear or branched C
2
-C
12
-alkylene, R
3
is hydrogen or C
1
-C
4
-alkyl, and t is the number 0 or 1, X is a group —O—, —S— or —NR
1
— and R
1
is hydrogen, C
1
-C
4
-alkyl or a radical A, and A is a radical of formula
wherein R
2
is hydrogen or fluorine, a is an integer from 1 to 15, b is an integer from 0 to 6, c is an integer from 1 to 19, d is an integer of 0 or 1, and z is an integer from I to 12; and
(ii) a solvent system being capable of effecting phase separation in the polymer which is obtained upon polymerizing the polymerizable component according to (i);
(b) polymerizing said composition and thereby forming a two-phase system comprising a polymer phase and a discrete solvent phase both of which are intermingled,
(c) removing the discrete solvent phase and
(d) subjecting the polymer obtained to an aftertreatment in an acidic or basic medium.
R
3
is preferably hydrogen or methyl and most preferably hydrogen.
(alk) is preferably C
2
-C
6
-alkylene, more preferably C
2
-C
4
-alkylene and in particular ethylene.
The variable t preferably denotes the number 0.
Especially preferred radicals —Q correspond to the formula
X is preferably a group —O— or —NR
1
— and most preferably —O—.
Regarding formula (3) the term in rectangular brackets is to be understood as a statistic description of the respective radicals, that is to say, the sequence of the groups —CH
2
—, —CHF—, —CF
2
— and —CF[(CF
2
)
z
—R
2
] is not fixed in any way by said formula.
R
2
in formula (3) denotes preferably fluorine.
Variable a is preferably an integer from 1 to 4, more preferably 1 or 2 and in particular 1. Variable b is preferably an integer from 0 to 4 and in particular 0. Variable c is preferably an integer from 1 to 14, more preferably 1 to 9 and in particular 5 to 9. Variable d is preferably an integer of 0. Variable z is preferably an integer from 1 to 8, more preferably 1 to 4 and most preferably 1.
Variable A is preferably a radical of the formula
—(CH
2
)
a
—(CF
2
)
c
—(CF[CF
3
])
d
—CF
2
—R
2
  (3a),
wherein R
2
is hydrogen or fluorine, a is an integer of 1 or 2, c is an integer from 1 to 19, preferably 1 to 14 and in particular 1 to 9, and d is an integer of 0 or 1, in particular 0. In a particular preferred embodiment of the invention A is a radical of formula (3a) above, wherein R
2
is fluorine, a is an integer of 1, d is 0, and c is an integer of from 1 to 19, preferably 1 to 14, more preferably 1 to 9 and in particular 5 to 9.
The fluorine-containing moiety A advantageously contains a fluorine to hydrogen ratio of greater than 50%, preferably of greater than 80%, and most preferably of greater than 90%.
Examples of particularly preferred compounds of formula (1) are 1H,1H,2H,2H-heptadecafluorodecyl acrylate, 1H,1H,9H-hexadecafluorononyl acrylate, 1H,1H-pentadecafluorooctyl acrylate, 1H,1H,2H,2H,-tridecylfluorooctyl acrylate, 1H, 1H-heptafluorobutyl acrylate, 1H, 1H-undecylfluorohexyl acrylate, 2-(perfluoro-7-methyloctyl)ethyl acrylate, or 2-(perfluoro-9-methyldecyl)ethyl acrylate. It is preferable that the length of the perfluorinated chain be 6 to 10 carbons long to obtain a material with a refractive index similar to tear film. However, this does not preclude the use of a combination of different length perfluorinated chains, ie less than 6 and greater than 10 to result in a material that has a refractive index similar to tear film or the use of perfluorinated chains greater than 10 carbons in order to counteract the high refractive indexes of other additives in the formulation. Also in some non-ocular applications matching refractive index of the material to tear film may not be important and hence the perfluorinated chain length may be outside the preferred range.
The polymerizable component used in the process of the invention may contain one or more different monomers of formula (1), preferably at least two different monomers of formula (1), more preferably 2 to 4 different monomers of formula (1) and in particular 2 different monomers of formula (1). The amount of monomer(s) of formula (1) used in the polymerizable component is, for example, in the range of from 15 to 100%, advantageously in the range from 20 to 90%, preferably in the range of 25 to 80%, more preferably in the range of 40 to 70% and particularly preferably in the range of 40 to 60% in each case by weight of the entire polymerizable component.
In addition to one or more different monomers of formula (1), further compounds comprising one or more ethylenically unsaturated groups, for example crosslinkers or comonomers, may be incorporated into the polymerizable component which can enter into a reaction to form the polymers of the invention. It is preferred that the ethylenically unsaturated group be selected from the group consisting of acryloyl, methacryloyl, styryl, acrylamido, acrylamidoalkyl, or urethanemethacrylate, or any substituted derivatives thereof.
The polymerizable component employed in step (a) preferably comprises one or more different crosslinkers. One group of suitable crosslinkers comprises a macromonomer of formula
Q
1
—(PFPE—L)
n-1
—PFPE—Q
1
  (4),
wherein n is ≧1, each PFPE may be the same or different and is a perfluorinated polyether of formula
—OCH
2
CF
2
O(CF
2
CF
2
O)
x
(CF
2
O)
y
CF
2
CH
2
O—  (5)
wherein the CF
2
CF
2
O and CF
2
O units may be randomly distributed or distributed as blocks throughout the chain and wherein x and y may be the

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