Note: Descriptions are shown in the official language in which they were submitted.
21281~8
CL/V-19623/A/CVE 42
A process and device for the nl~mlf~cture of mouldin~s and mouldin~s manuf~elu~ed
in accordance with that process
The invention relates to a process for the manufacture of mouldings, especially optical
lenses and specifically contact lenses, to a corresponding device for the manufacture of
mouldings, and to mouldings, especially optical lenses and specifically contact lenses,
manufactured or obtainable in accordance with that process or by means of that device, in
accordance with the preamble of the respective independent patent claim.
Contact lenses that are to be manufactured economically in large numbers are preferably
produced by the so-called mould or full-mould processes. In those processes, the lenses
are manufactured in their final form between two moulds, so that neither subsequent
m~hininp of the surfaces of the lenses nor machining of the rim is necessary. Mould
processes are described, for example, in PCT Patent Application publication No.
WO 87/04390 and in Eul~eall Patent Application publication No. 0 367 513.
In those known mould processes, the geometry of the contact lens that is to be produced is
determinçd by the mould cavity. The rim of the contact lens is also formed by the mould,
which usually consists of two mould halves. The geometry of the rim is determined by the
contour of the two mould halves in the region in which they are in contact with one other.
In order to produce a contact lens, first of all a determin~ amount of the flowable starting
m~teri~l is introduced into the female mould half. The mould is then closed by applying
the male mould half. Normally, the starting material is supplied in slight excess, so that
the excess amount is forced into an overflow chamber exte.rn~lly ~ ent to the mould
cavity when the mould is closed. The subsequent polym~ri~tion or crosslinking of the
starting m~teri~l is effected by irr~ tion with UV light or by thermal action or by
another, non-therm~l, method, during the course of which both the starting m~teri~l in the
mould cavity and the excess material in the overflow chamber are fully cured. The full
cure of the excess material may be delayed slightly, since it mày initially be inhibited by
atmospheric oxygen. In order to achieve fault-free separation of the contact lens from the
excess m~teri~l the excess m~tt-.ri~l must be well sealed off or expelled from the zone in
212~1~8
- 2 -
which the two mould halves are in contact with one another. Only in that manner is it
possible to obtain fault-free contact lens rims.
The materials currently used for the moulds are preferably plastics, such as, for example,
polyl,r~ylene. The moulds are produced by injection moulding and used only once
(disposable moulds). The reason for this, inter alia is that the moulds are in some cases
cont~min:lted by the excess material, are damaged when the contact lens is separated, or
are irreversibly deformed in some areas.
In the case of injection-moulded moulds, variations in the dimensions must also be
expected, as a result of variations in the manufacturing process (temperatures, pressures,
material pl~pel~ies). Shrink~ge of the moulds may also occur after injection moulding.
The dimensional variations in the mould may lead to v~ri~tion~ in the parameters of the
contact lens being produced (vertex refractive power, di~ml~to,r, base curve, middle
thickness etc.), which may have an adverse effect on the quality of the lenses and thus
result in a reduced yield. If the seal between the two mould halves is inadequate, the
excess material is not cleanly sep~t~d, which may result in the formation of so-called
flash at the contact lens rim. Where that is relatively pronounced, such a cosmetic fault at
the rim of the lens may also cause irritation to the wearer, and such lenses therefore have
to be iclentified by inspection and removed.
Particularly in view of the quality requil~,me,lts of the contact lens rim, the moulds are
also used only once, because it is not possible to rule out absolutely a certain deform~tion
of the moulds in the region in which they are in contact with one another.
A further mould process for the m~nllf~cture of, inter alia, contact lenses is described in
US-PS 4 113 224. That process uses a mould in which the cavity is not completely sealed
but is connected by a thin annular gap to an annular reservoir ch:~nnel (overflow channel)
surrounding the cavity. During the crosslinking process, material can flow back from the
reservoir through the annular gap and into the mould cavity to colllpellsate for the
relatively large shrinkage in volume which occurs with the lens m~teri~l~ customarily
used.
The material in the reservoir channel can be prevented from crosslinking by an inhibiting
gas atmosphere or by being ~hie!-led from the energy r~ ti(?n causing the cro~clinking
To ensure that m:lteri~l flows back into the mould cavity, the m~teri:~l located in the mould
'~ -
212~1S8
- 3 -
cavity is, at least to begin with, subjected to radiation only in a central region, which is
smaller than the diameter of the mould cavity, or is exposed to a stronger intensity of
radiation in that central region than in the edge region of the mould cavity surrounding
that central region. After crosslinking has commenced in the central region and has
progressed to a certain degree, the edge region too, however, together with the ~dj~ent
annular gap and the m~teri~l located in the reservoir channel, is exposed to the full
radiation and crosslinked. The burrs and flash mentioned above are inevitably formed, so
that contact lenses and other mouldings manufactured by that known process require
subsequent mechanical processing.
The aim of the present invention is to develop further and so improve a process and a
device of the generic types that the difficulties and problems described above in the
example of the manufacture of contact lenses are avoided. In particular, con~lition~ are to
be created to allow re-use of the necessary moulds or mould halves and avoid theformation of burrs and flash on the manufactured monl-lin~c, so that the mouldings will
have an extremely low reject rate and mech~ni~al or other subsequent processing of the
mouldings will be dispensed with.
The aim underlying the invention is achieved by the measures and features described in
the latter part of the independent process claim and of the independent device claim.
Especially expe lient and advantageous arr~nge.,~ and further develop~ ts of theprocess of the invention and of the device of the invention are given in the dependent
claims.
"Cros~linking", here and in the following, is to be understood as m~ning, briefly, any
kind of reaction in which the m~t~ri~l is converted by polymPrisation of a suitable
monomer, oligomer and/or prepolymer and/or a mixture thereof into a state in which it
retains the shape defined by the mould cavity. Suitable m:lteri~l~ and polymerisation/-
crosslinking reactions are known to the person skilled in the art and typical examples are
to be found, inter alia, in the mentioned US-PS 4 113 224 and the publications mentioned
therein.
According to the general underlying concept of the invention, therefore, the polymerisa-
tion or crosslinking of the starting material is restricted solely to the region of the
moulding, specifically the contact lens, being produced. Any excess m~teri~l present is not
polymerised or cros~link~cl In the process according to the invention partial areas of the
212~
- 4 -
moulding rim are formed not by a mechanical limitation of the material by mould walls
but by a spatial limitation of the impinging energy (usually UV or some other radiation)
that triggers the polymerisation or crosslinking. As a result of those two measures, contact
between the two mould halves can in a ~lc;rell~;d arrangement be avoided, so that they are
not deformed and can accordingly be used again. In addition, the known problem of
volume shrink~ge which occurs during crosslinking can also be dealt with very simply
thereby without it being necessary, as in the case, for example, of US-PS 4 113 224, for
the moulding to be mech~ni~lly processed subsequently.
Further aspects and advantages of the process of the invention and the device of the
invention are disclosed in the following description of example embodiments in
association with the drawings in which:
Fig. 1 is a section through a first example embodiment of a device
according to the invention clesi~n~d for the process of the invention
with the mould in the closed position,
Fig. 2 is a detail, int1i~t~ by II in Fig. 1, on a greatly enlarged scale,
Figures 3-5 are details analogous to Fig. 2 of three furdler example emb~i
of the device according to the invention,
Figs. 6A-C show a further example embodiment of the device according to the
invention,
Figs. 7A-C show a further example embodiment of the device according to the
invention,
Figs. 8A-C show a variant of the example embodiment of Figs. 7A-C,
Figs. 9A-C show a further example embodiment of the device according to the
invention
and
Figs. 10-11 each show a further variant of the process according to the invention
~8 11 ~8
.,~
in each of which one mould half is used as
packaging.
The device shown in Fig. 1 is designed for the
manufacture of contact lenses from a liquid starting material
that can be polymerised or crosslinked by W radiation.
According to the illustration, it comprises a mould 1, shown
in this case in the closed position, and an energy source 2a,
in this case a W light source, and also means 2b for
directing the energy supplied by the energy source in the form
of a substantially parallel beam 3 onto the mould 1. The
energy source 2a and means 2b can obviously also be combined
into a single unit.
In its general design, the device shown is identical
in construction to the devices described in the patent
specifications mentioned as prior art in the introduction, so
that the following description can be limited to the most
important points and to the differences from the prior art
that are relevant to the invention. Details on the general
construction and on questions concerning ~;m~ncions, material
and stability etc., ac well as, for example, on suitable
materials for the mouldings and on aspects concerning
processing technology, are dealt with very comprehensively in
EP-A-0 367 513 and especially in US-PS 4 113 224.
The mould 1 consists of two mould members or mould
halves 11 and 12, each of which has a curved mould face 13 and
14, respectively, which together define a mould cavity 15
which in turn determines the shape of the contact lens CL to
be produced (Fig. 2). The face 13 of the upper mould half 11
A 21489-8890
2 ~ 2 8 ~ 5 8
..
-5a-
in the drawing i8 convex and deter~;nes the rear or base face
of the contact lens with the rim area adjacent thereto; that
mould half is usually referred to as the male mould half.
Conversely, the face 14 of the other mould half, which is
referred to correspo~;ngly as the female mould half, is of
concave shape and determines the front face of the contact
lens to be produced, also together with the rim area adjacent
thereto.
Unlike the moulds known, for example, from the
documents WO 87/04390 or EP-A-0 367 513 mentioned in the
introduction, the mould cavity 15 is not completely and
tightly sealed but, in the example embodiment shown, is open
all the way round in the region of its circumferential rim,
which defines the rim of the contact lens to be produced, and
i~ in co~mlln;cation there with a relatively narrow annular gap
16, as is also the case in the moulds shown in US-PS 4 113
224. The annular gap 16 is limited or formed by a
21489-8890
2 1 ~ 8
- 6 -
flat mould wall 17 on the male mould half 11 and a flat mould wall 18 on the female
mould half 12. To prevent complete closure of the mould, spacers, for example in the form
of several spacer bolts l9a and l9b, are provided on the female mould 12 which interact
with a collar or flange 20 on the male mould 11 and so keep the two mould halves far
enough apart to form the said annular gap 16. The spacers may also be of adjustable or
resilient construction, as indicated symbolically by a thread in respect of the spacer bolts
l9b on the right in Fig. 1. In that manner the two mould halves can be moved towards one
another during the crosslinking operation by adjusting the spacers (indicated symbolically
by the direction of rotation arrow l9c) or against a resilient force to compensate for
~hrink~ge. The mould can obviously be opened and closed in the usual manner, forexample by means of a closing unit indic~ here by the arrow symbol la only. Adjust-
ment of the distance between the two mould halves to compensate for shrink~ge can be
carried out, for example, also by means of that external closing unit.
In another arrangement, not shown here, a number of segment-shaped gaps may be
provided instead of the continuous annular gap 16 and the spacers 19a and l9b, the inter-
mediate spaces between the individual segment gaps taking over the function of the
spacers. Obviously, other configurations are also possible.
The two mould halves 11 and 12 consist of a material that is as permeable as possible to
the sçlected form of energy, which in this case, as mentioned, is UV light, for example
they consist of poly~lul,ylene usually used for such purposes or of another polyolefin.
Since the irr~ tion with W light is in this case from one side only, that is from above, it
is necessary only for the upper, that is to say in this case the male, mould 11 to be
UV-permeable. Obviously, the same applies also for irradiation from below through the
female mould. According to an especially expedient and advantageous arrangement of the
invention, at least the mould half that is irradiated with UV light consists of quartz. Not
only does that material have especially good UV permeability but it is also very hard and
resistant, so that moulds made from it can very readily be reused. A prerequisite for that,
however, which is ~ closed in further detail in the following, is that the mould is closed
either without force or not fully, so that the mould halves are not damaged by contact.
UV-permeable special glasses or sapphire are possible alternatives to quartz. On account
of the reusability of the mould or mould halves, expenditure on their m~mlf~ctllre may
have to be relatively high in order to obtain moulds of t;~ ely high precision and
reproduceability. Since the mould halves do not touch in the region of the lens being
produced, that is to say in the region of the cavity or of the actual mould faces, damage by
212~ 38
contact is excluded. A high degree of durability of the moulds is thereby assured. This also
has favourable consequences in general for the reproduceability of the contact lenses or
mouldings being produced.
When energy is applied from one side, the mould half remote from the energy source can,
in principle, be made from any material that is compatible with the crosslinkable or
crosslinked material or components thereof. If metals are used, however, depending on the
nature of the energy radiation the possibility of reflections must be expected, which may
possibly result in undesired effects such as over-exposure, the formation of defects at the
edges, or the like. Absorbent m~t~ri~l~ do not have those disadvantages.
Thus far the device, and especially the mould 1, corresponds substantially to that of the
mentioned US-PS 4 113 224. The most marked and most important diL~lt;nce from the
device disclosed therein is that, according to the main underlying concept of the invention,
impingement upon the m~teri~l from which the moulding is produced of the energy form
that causes cros~linking is restricted to the mould cavity, that is to say only the cross-
linkable material located in the mould cavity is impinged upon by the suitable energy
form, in this case UV radiation, and only the material that is located in the cavity is cross-
linked. In particular, the m~teri~l located in the annular gap surrounding the mould cavity
and the material located in a possible ~se,~oir connected to that gap is not impinged upon
by energy and not cros~linkçcl "Mould cavity" denotes that cavity of the closed mould
which is dçfine-l by the complete contour of the moulding to be produced, spe~ifiç~lly,
therefore, the contact lens. The annular gap 16 opening into the mould cavity thus does not
form part of the mould cavity 15.
For the practical re~lis~tion of the main concept of the invention, in accordance with the
example embodiment of the device shown in Figures 1 and 2 there is provided on the
mould wall 17, in the region of the annular gap 16, a mask 21 that is i~ elllRable (or at
least of poor permeability compared with the permeability of the mould) to the energy
form used, in this case therefore UV light, which mask extends right up to the mould
cavity and, with the exception thereof, screens from the radiated energy all rem~ining
parts, cavities or s~ es of the mould that are in contact with or may come into contact
with the here liquid uncrosslinke~l, possibly excess, m~teri~l In the process according to
the invention partial areas of the lens rim are formed not by a limitation of the m~t~o,ri~l by
mould walls but by a spatial restriction of the radiation or other form of energy triggering
polymeri~ti~ n or crosslinking Details of this are given further below with reference to
2~ 2~1~38
- 8 -
Figures 2 to 5.
In the case of UV light, the mask may preferably be a thin chrome layer, which can be
produced according to processes as known, for example, in photo and UV lithography.
Other metals or metal oxides may also be suitable mask m~ten~l~ The mask can also be
coated with a protective layer, for example of silicon dioxide if the m~tç~ l used for the
mould or mould half is quartz. The mask does not necessarily have to be fixed but could,
for example, be constructed or arranged to be removable or exchangeable. Furthermnre, it
is also not absolutely necessary, although it is advantageous, for the mask to be arranged
as in Figures 2 to 5. It could, in principle, be provided anywhere at or on the mould as long
as it was able to fulfil the function for which it was intende-l namely the screening of all
areas of the mould carrying uncrosslinked material with the exception of the mould cavity.
In principle it is even possible to dispense with a mask or m~king in or at the mould if the
energy impingement can be restricted locally to the mould cavity by some other means,
where necessary taking into consideration the optical effect of the mould. In the case of
UV radiation this could be achieved, for example, by a spatially restricted light source, a
suitable lens arrangement optionally in combination with external masks, screens or the
like and taking into consideration the optical effect of the mould.
The individual steps for the m~nl]f~cture of a contact lens are essentially as follows:
- Measuring the liquid, uncros.slink~d starting material into the female mould half 12 with
the mould 1 open. Normally an excess amount is measured out, that is to say the measured
volume is larger than the volume of the mould cavity 15 and of the contact lens CL to be
produced.
- Closing the mould 1. As the two mould halves are closed, excess material is forced into
the annular gap 16 beLween the two mould halves 11 and 12. The annular gap 16 is made
so wide or high (~y) that contact between the two mould halves 11 and 12 in the region of
the mask 21 is avoided with absolute reliability. The guiding and positi ?ning (spacing) of
the two mould halves is effected by guide and stop elements located further out, as known
also in principle from the devices of US-PS 4 113 224, which are in this case symbolised
only by the spacer bolts l9a and l9b. For the manufacture of contact lenses, typical gap
heights ~y are in the range below al~p~uxilllately 100 ~m. Tests have shown that, at least
when parallel energy radiation is used, a clean structuring of the rim of the moulding being
produced is still possible even with gap heights of approximately 1 mm. Conversely,
21~ 1 58
g
however, the width or height of the annular gap can also readily be reduced to practically
zero, provided that the mould is closed without force, that is to say that the two mould
halves lie one on top of the other without external pressure. In that case only a film of
uncrosslink~l material a few micrometres thick remains between the two mould halves in
the region of the annular gap, which, however, because of the screening from the UV
radiation, still cannot result in the formation of flash. On account of the force-free closure
of the mould, the mould is also not damaged at least if a suitable material has been chosen.
- Polymerisation or crosslinking of the m~t~ri~l in the mould cavity 15. By irradiation with
UV light (or, generally, impingement of a suitable form of energy) polym~ris~tion or
cro~linking of the starting m~t~ri~l is effected in the region that corresponds to the
contact lens to be produced (or, generally, to the moulding to be produced).
- Opening the mould and removal of the cros~linked lens. After polymerisation or cross-
linking of the starting m~tçri~l in the mould cavity 15, the mould halves 11 and 12 are
separated from one another, for example by means of a device not shown, and the mould 1
is thereby opened. The lens CL becomes freely ~ccessihle and can be removed m~nll~lly
or by means of devices also not shown. If desired, suitable measures known per se can be
taken to ensure that the contact lens so produced preferably re~ s ~-lherin~ to one or the
other of the mould halves. Suitable measures are described, for example, in
US-PS 4 113 224.
Figure 2 shows the arrangement of the mould 1 in the transition region between the mould
cavity 15 and the annular channel i6 as an enlarged detail. The cavity 15 has here, by way
of example, a shape that corresponds to the typical rim geolllel.y of a so-called soft
contact lens CL. The cavity rim, and thus the lens rim, is formed here by two wall faces 22
and 23 which are arranged at right angles to one another and are arranged on the male and
on the female mould halves 11 and 12 respectively. The width and the height of those two
wall faces, and of the rim areas of the contact lens defined by them, are intlir~tç(1 by X and
Y respectively. Obviously, the lens rim may in practice also be slightly rounded.
As can be seen clearly, the cylin-lri~l wall face 23 of the female mould half 12 does not
extend right up to the flat wall face 22 and the wall face 17, lying se~mles~ly 2/dj~ nt
thereto, of the male mould half 11, but is lower by the amount ~y, so that the annular gap
16 already mentioned, between the wall face 17 and the wall face 18 of the two mould
halves 11 and 12, is formed or remains open.
212~
- 10-
The mask 21 provided on the wall face 17 of the male mould half 11 in this example
embodiment extends horizontally exactly up to the extension 23a of the wall face 23 of the
female mould half 12. If the UV light, in the form of a parallel beam 3 causing the cross-
linking, is incident at right angles to the wall face 22 and 17 and parallel to the cylintlri~l
wall face 23, the space located at right angles below the mask 21 is in shadow and only the
material located inside the cavity 15, that is inside the im~in~ry wall extension 23a, is
crosslinkf ~, resulting in a clean and burr-free lens rim which does not require any
subsequent mechanical processing If parallel energy r~ tion is used, therefore,
disregarding the diffraction and scattering effects, which are usually negligible in practice,
the contour of the mask 21 is transferred two-~limen~ionally parallel and (in this case)
downwards into the rim area of the contact lens. Therefore, if the two mould halves 11 and
12 are separated from one another by the annular gap 16 of height ~y, the rim is formed
towards the outside of the area resulting from that displacement by means of the spatial
restriction of the energy radiation.
In principle it is also possible to exploit the diffraction and/or sc~ttering effects in a
cont~rolled manner in order to produce a moulding with a contour that is intentionally not
sharp or has somewhat rounded edges. The same effect can also be achieved using masks
with locally variable perm.oability~ It is thus possible for sharp-edged rims of the moulding
being produced to be rounded in a controlled manner by controlled incomplete cross-
linking and by partial dissolution of the incompletely crosslinked regions with a suitable
solvent, which may also be the uncrosslinked m~teri~l itself. Iso~lopanol, for example, is a
suitable solvent in the case of HEMA (hydlo~yelhyl methacrylate).
After the moulding produced in that manner has been released from the mould, anyuncrosslink~d m:~teri~l adhering to the moulding can easily be washed away by means of a
suitable solvent which, depending on the m~t~ri~l, may possibly even be water.
In the example embodiment of the device according to the invention shown in Figure 3,
the energy causing crosslinking acts through the female mould half 12, that is to say from
below in the drawing. Accordingly the mask 21 is in this arr~ngem~nt provided on the
wall face 18 of the female mould half 12 instead of on the wall face 17 of the male mould
half 11. Otherwise there are no dirrelellces between this arrangement and that of Figures 1
and 2.
2 ~
In the example embodiment of Figure 4, the energy radiation is again at the male mould
half 11 side, and the mask 21 is again located on the wall face 17 of that mould half. The
female mould half 12, however, is not raised at the side, that is to say the cylindrical wall
face of the female mould half indicated by 23 in Fig. 2 is missing. Instead, the annular gap
16 is correspondingly wider or higher. Tests have shown that with the flim~n~ions
cuslolllal~ for the manufacture of contact lenses that configuration of the mould too
produces fault-free results.
Finally, the example embodiment according to Fig. 5 corresponds to that according to Fig.
4 except that in this case the energy again acts from below through the female mould half
12 and the mask 21 is provided on the wall face 18 of that mould half.
Obviously, the impingement upon the crosslink~hle material located in the mould cavity
of the energy c~ ing the crosslinking can be effected not only from one side but also from
both sides. Care must merely be taken that the energy enters only the cavity and is
effectively kept away from the l~ ini~g parts. This can be achieved, for e~mpl~, by
suitable arr~ngement of two or possibly even more masks. Otherwise, the mask or masks
do not necess~rily have to be arranged on the surfaces of the mould walls but may possibly
also be provided inside the mould walls. Preferably, the mask or masks is/are arranged on,
or just below, a wall surface that is in contact with the uncrosslinkfA m~teri~l, since in that
way it is possible for undesired diffraction and SC~If - ;ng effects subst~nti~lly to be
excluded.
In accordance with a further aspect of the invention, one of the two mould halves can also
later be used as p~k~ging for the contact lens. For that purpose it is possible to use either
the male mould half 11 or the female mould half 12 and the complete mould merely has to
be constructed accordingly. This is illusllaled in Fig. 10 and Fig. 11, in each of which one
mould half (in Fig. 10 the male mould half 11 and in Fig. 11 the female mould half 12) is
later used as p~ gin~ Those mould halves may advantageously be constructed as
disposable mould halves, whilst the other mould half in each case may be constructed as a
reusable mould half (for example made of quartz or sapphire). The mask 21 is provided in
each case on the reusable mould half. The energy in the form of the UV beam 3 acts in
each case through the reusable mould half (with the exception of the m~ d area) which
is readily perm.o~ble to the energy r~ ti-m For the lens moulded by the shape of the
cavity 15 to adhere to the disposable mould half after polymeri ~tion, the disposable
mould half can be a~lu~liately plcll~,aled. The excess m~teri~l that is located in the
2~2~
- 12-
region of the mask 21 after polymerisation and has not been polymerised can then be
removed from that mould half. The polymerised lens, adhering to the disposable mould
half, can be hydrated in that mould half during further processing if hydration is necessary.
The finished lens is later packed in the disposable mould half by, for example, closing and
sealing the disposable mould half with a lidding foil.
A further problem arising during manufacture according to hitherto known processes is
that air inclusions may occur when the mould is closed. Air inclusions in the lenses result,
however, in the lenses being identified as rejects in the subsequent inspection (quality
control). The mould has hitherto been closed correspondingly slowly, so as to enable the
air to escape as fully as possible from the mould cavity. The comparatively slow closure
of the mould, however, takes up a relatively large amount of time.
According to a further aspect of the invention it is therefore desirable to provide a process
and a device of the kind mentioned in which the degree of efficiency is high, that is to say
the mould can be used efficiently, and in which expenditure is comparatively low, but
always with the proviso that the moulding (e.g. contact lens) produced is free from air
inclusions.
This is solved in accordance with the process by carrying out the filling of the mould
cavity in the starting m~teri~l that is still at least partially in the uncrosslink~d state. As a
result, right from the beginning, when the mould is being filled, there can be no air in the
mould, so that air inclusions are completely avoided. Consequently, the mould can be
closed more quickly, and as a result can be used more efficiently, while at the same time
expenditure is comparatively very low. Furthermore, in that manner an exact mea~ulcmellt
of the required amount of starting material is provided ~l~tom~tic~lly, since the filling
takes place in the starting m~t~,ri~h
In one variant of the process, for the purpose of filling the mould cavity, the cavity can be
connected to a rcsel voi~ which surrounds it, in which the starting m~teri~l iS stored and
from which the mould cavity is flooded. This is a process variant that is especially
uncomplicated technologically.
In a fur~her process variant, the mould is also closed in the starting m~t~,ri~l SO as to
e~hl-le the risk of air in any way getting into the mould cavity during the closing
operation.
2 t 2 ,3 ~ ~3 ~
In a further variant, a mould is used that comprises a container and a mould member
displaceable in the manner of a piston in that container. The mould member can be moved
away from and towards the container wall lying opposite it for the purpose of opening and
closing the mould. Starting material is fed in between the container wall and the mould
member as the mould is opened and conveyed away again as the mould is closed. As a
result of the movement of the displaceable mould member away from the opposite-lying
container wall the space between the displaceable mould member and the container wall is
filled with starting material without air being able to penetrate into that space.
Subsequently, as a result of the movement of the displaceable mould member towards the
container wall, the starting m~t~ri~l disposed between the mould member and the
container wall is conveyed away again, the m:~teri~l located in the mould cavity naturally
rem~ining there. It is also impossible for any air to enter the mould cavity as the mould
member moves towards the container wall, as a result of which mouldings that are free
from air inclusions can be produced in a simple and efficient manner.
For example, a mould having two mould halves may be used in which one mould half is
provided on the cont~iner wall and the other mould half is provided on the displaceable
mould member. In that arrangement a mould having a male mould half and a female
mould half may be used, the male mould half being provided on the con~ wall and the
female mould half on the displaceable mould member. Pumps may advantageously be
used to feed in and convey away the starting material. In a further advantageous process
variant, the piston may be driven in order to feed in and convey away the starting m~teri~l
The crosslinked moulding can be removed from the mould in an especially simple manner
by flllching out the mould with starting material. This can be effected, for example, by the
moulding being separated from the mould by the flow of starting m~teri~l as the mould is
opened and being flushed out of the mould by the flow of starting material as the mould is
closed.
In one variant of the process, in a first cycle the mould is opened and closed again.
Subsequently, at least the cros~linking nf~cess~ry for it to be possible for the moulding to
be released from the mould is effected by the action of energy. In a second cycle the
mould is opened again, the moulding being separated from the mould. The piston-like
mould member is then moved towards the opposite-lying container wall again and the
mould is thus closed again, the crosslinked moulding being flushed out of the mould. This
212~ 3 8
- 14-
"two-cycle" variant of the process is distinguished by the fact that the moulding is
produced in the first cycle and then flushed out of the mould in a second cycle. The mould
can sim~llt~neously be cleaned in the "flushing cycle".
The process variant just described can be carried out either by providing first a
"production cycle" (first cycle) and then a sep~ale "flushing cycle" (second cycle, for
example using a flushing liquid), or ~ltP.rn~tively the flushing can be arranged to coincide
with the production cycle of a new moulding, that is to say as new starting m~teri~l is
introduced into the mould cavity the moulding produced in the prece ling cycle is flushed
out of the mould. The "two-cycle" variant of the process then becomes a "single-cycle"
variant.
The crosslink~d moulding can, however, also be removed from the mould by means of a
gripping device. This can be effected by depositing the moulding removed from the mould
by the gripping device on the displaceable mould member outside the space between the
displaceable mould member and the opposile-lying cont~ er wall. The moulding
deposited on the displaceable mould member can be held fast thereto by negative pressure
and then released from it again by positive ~rt;S~ulc;.
In a further process variant, the mould is not completely closed after the starting m~teri~l
has been introduced into the mould cavity, so that an annular gap co~ g unclosslink~
starting m~teri~l, which suIrounds the mould cavity and is in co,--...~-ic~tion with that
mould cavity, remains open. By this means on the one hand a shrink~e in volume
occurring during crosslinking can be compensated by starting m~tPri~l flowing back
through the annular gap into the mould cavity, and on the other hand the mould halves are
~revenled from being pressed hard against one another during m~nnf~Gtllre of themoulding. Especially in view of the risk of the mould halves being illGvel~ibly deformed
by mechanical stress, mould halves have hitherto been used only once, as exrl~in~l in the
intr~llctinn In accordance with this process variant, the mould halves can be used
repeatedly.
It is also conceivable for the mould to be closed further following crosslinking ~hrink~ge
as crosslinking of the m~t~.ri~l progresses.
It is however, in any event, important to use a starting material that is of at least viscous
flowability prior to the cr~s~linking, so that starting m~teri~l can flow back through the
~ 2~2~ 8
- 15-
annular gap into the mould cavity to compensate for shrinkage.
The problem of possible air inclusions is solved in the device according to the invention
by arranging the mould cavity, during filling, in starting material that is at least partially
still in the uncros~linked state. As a result, from the start air cannot enter the mould during
filling, and so air inclusions are completely avoided. The mould can consequently be
closed more quickly and thus used more efficiently, while at the same time expenditure is
comparatively very low.
In one example embodiment the device comprises a reservoir for supplying the starting
material that surrounds the mould cavity. The reservoir can be connected to the mould
cavity. When the mould cavity is being filled, the reservoir is connected to the mould
cavity and floods that cavity. This allows several structurally especially simple further
developments, which will be explained in more precise detail.
In a further example embodiment, the device comprises means for closing the mould
which is arranged in the starting m~tFri~l, the mould, in this case too, always being closed
in the starting m~teri~l so that no air can enter the mould cavity.
In an advantageous example embodiment, the mould comrrises a cont~in-or and a mould
member displaceable in the ll.almer of a piston in that container, which mould member can
be moved away from and towards the container wall lying opposite it for the purpose of
opening and closing the mould. Provided in the container is an inlet through which starting
m~teri~l flows in between the container wall and the mould member as the mould is
opened. Also provided in the container is an outlet through which starting m~tt-ri~l flows
out again as the mould is closed. This example embodiment is structurally comparatively
simple, that is to say very uncomplicated, and is therefore well suited to practical use.
The mould in that arrangement preferably has two mould halves, one mould half being
provided on the cont~inPr wall and the other on the displaceable mould member. The
mould has (especially in the manufacture of contact lenses) a male mould half and a
female mould half. Preferably, the male mould half is provided on the container wall and
the female mould half on the displaceable mould member. In that arrangement the
moulding (contact lens) can later be released from the mould especially simply.
Pumps are preferably provided for feeding in and/or conveying away starting material
212~158
- 16-
which, as the mould is opened, feed in starting material through the inlet and between the
container wall and the mould member and, as the mould is closed, convey it back through
the outlet. Such pumps operate reliably and therefore do not represent any special
expenditure.
In a further example embodiment, means are provided for driving the mould memberwhich is displaceable in the manner of a piston. Those means may be provided, both in a
device that works without and in a device that works with pumps, for the purpose of
moving the mould member displaceable in the manner of a piston in the direction towards
the opposite-lying con~il~er wall and thus forcing starting m~teT i~l disposed belween the
mould halves out again.
In a further example embodiment of the device, means are provided for producing a flow.
That flow sep~les the moulding from the mould when the mould is opened and flushes
the moulding out of the mould when the mould is closed. Those means may be in the form
of jets or simil~rly acting means. It is important that they produce a flow or a turbulence in
the starting m~teri~l disposed between the mould halves so that the moulding (contact
lens) is lifted off the mould half by means of the flow or turbulence.
In a further e~rPmrle embodiment of the device, in a first cycle ("pr~lllr-tion cycle")
starting m~teri~l first of all flows in through the inlet and between the conl;-;nf ~ wall and
the displaceable mould member and then flows back out through the outlet. The source for
the energy then acts upon the mould with an amount of energy n~es~ for it to be
possible for the moulding to be released from the mould, so that crosslinking occurs.
Then, in a second cycle, for example starting mptrri~l again flows in through the inlet and
between the container waU and the displaceable mould member, sep~tes the moulding
from the mould and flushes it out through the outlet.
That "two-cycle" device is distinguished by the fact that in the first cycle the moulding is
produced, and then in the second cycle (fl~shing cycle, clç~ning cycle) the molllding is
flushed out of the mould and the mould is also cimlllt~neously cle-~nrd
That device may either be so constructed that, as described, there is first of all a
"prod~lction cycle" (first cycle) and then a sep~u~le "flllching cycle" (second cycle), or
~ltern~tively it may be so constructed that the flllching out coinrides with the pro~ rtion
cycle of a new moulding, that is to say, as new starting material is introduced into the
212~1a~
mould cavity, the moulding produced in the preceding cycle is flushed out of the mould.
The "two-cycle" device then becomes a "single-cycle" device. In the "single-cycle"
device, however, starting material must be used for flushing, whereas in the "two-cycle"
device the use of a special cleaning liquid in the flushing cycle is also possible.
To remove the moulding, a gripping device may be provided which removes the
crosslinked moulding from the mould. For that purpose the container preferably has on a
container wall other than the shape-giving face a hollow or recess that extends substan-
tially in the direction of mu~elllellt of the displaceable mould member. The gripping
device is arranged in that hollow or recess. The displaceable mould member comprises, on
an outer wall that does not lie opposite the shape-giving cont:~in~or wall, an indent~tion in
which the gripping device deposits the removed moulding. This is a structurally especially
advantageous and simple arrangement of the device.
In a possible further development of that device the displaceable mould member
compri~es a channel that leads to the indent~tion and can be connected to a negative
pressure or positive pressure source. The channel is connected to the negative ~l~S~iUlC
source when the gripping device deposits the removed moulding in the inflent~tion of the
mould member. In order to release the lens it is then connected to the positive pressure
source. By this means the lens can be produced during one cycle and, during the next
cycle, removed, deposited on the mould member and then removed from the mould
member. This is possible both in a device constructed as a "two-cycle" device and in a
device constructed as a "single- cycle" device.
In a further example embodiment of the device, the mould is provided with spacers which
hold the two mould halves a small distance apart from one another when the mould is in
the closed position, so that an annular gap that surrounds the mould cavity and is in
commllnic~tion therewith is formed.
By that means volume shrink~ge occurring during crosslinking can on the one hand be
compe~tçd. since starting m~t~.ri~l can flow back into the mould cavity through the
annular gap. On the other hand the spacers prevent the mould halves from being pressed
hard against one another during production of the moulding. Particularly in view of the
risk of the mould halves being illc;vel~ibly deformed as a result of mPch~nic~l stress,
mould halves have hitherto been used only once, as explained in the introduction Using
this example embodiment of the device it is possible for the mould halves to be used
2~ 2Sl~
- 18-
repeatedly. It is furthermore possible in a further development of the device for the mould
to be provided with resilient means or displacement means that allow the two mould
halves to move closer together following crosslinking ~hrink~e.
In particular, mouldings, especially optical lenses and specifically contact lenses, ean be
produced in accordance with the process and with the deseribed device.
The example embodiment of the device according to the invention shown in Figs. 6A-C is
designed for the manufacture of contact lenses from a liquid starting material that can be
polymerised or cros~link~A, for example, by UV r~ tion Fig. 6A shows the mould 1 in
the closed position. The mould 1 is arranged in a cont~iner 10, which has been filled with
uncrosslinked liquid starting m~teri~l M. The device further comprises an energy source in
the form of a UV light source 2a and also means 2b which direet the energy, supplied by
the UV light source 2a, in the form of a parallel beam 3 onto the mould 1. Those means 2a
may in particular also comprise a screen arranged between the UV light source 2a and the
container 10. Obviously, the UV light source 2a and the means 2b may be combined to
form a single unit.
The mould 1 comprises two mould halves 11 and 12, each of which has a curved mould
face 13 and 14, respectively, which together define a mould cavity 15, which in turn
determines the shape of the contact lens CL to be produced. The mould face 13 of the
upper mould half 11 is concave and determint-s the front face with the rim area ~rlj~ent
thereto. That mould half 11 is usually referred to as the female mould half. The mould
face 14 of the lower mould half 12 is convex and d~t~,lmilles the rear or base faee of the
contact lens CL and the rim area adjacent thereto. That mould half 12 is usually referred to
as the male mould half.
The space between the two mould halves 11 and 12 and thus also the mould cavity lS is
arranged in the uncrosslinked starting m~teri~l M for the entire production proeess. In
accordance with the general concept of the invention, in any event at least the mould
cavity is arranged completely in the starting material in its uncrosslink~cl state during
filling. Fig. 6B shows that the upper mould half 11, even in the opened position, is not
completely clear of the starting m~tPri~l M, the space between the mould halves 11 and 12
always rem~ining below the liquid surface of the starting m~teri~l M disposed in the
container 10. Consequently, the space between the two mould halves, and especially also
the mould cavity, are always in co~ tion with the starting m~t~ri~l M disposed in
~ 212~17S8
- 19 -
the container 10. As a result air can at no time enter the space between the two mould
halves 11 and 12.
When the mould cavity is full and the mould is closed (Fig. 6A), the mould is impinged
upon by UV rays 3 and the moulding is thus cros~link~l
After crosslinking, the mould is opened and the moulding in the form of the contact lens
CL is released from the mould, that is to say taken off and removed from the mould. There
is shown symbolically in Fig. 6 for that purpose a gripping device 4 which, when the
upper mould half has been raised, takes the contact lens CL off the male mould half 12
(Fig. 6B) and removes it from the mould (Fig. 6C). The release and removal of the contact
lens or moulding from the mould may, however, also be carried out by other means, as
will be explained by way of the other example embodiments. After removal of the contact
lens or moulding, the mould can be closed again and a new contact lens CL produced.
Since the entire production process according to Pigs. 6A-C takes place below the liquid
surface of the starting m~teri~l M in the container 10, no air can enter the space between
the two mould halves 11 and 12 or in particular into the mould cavity 15. Since the mould
is opened and closed below the liquid surface, the mould can also be closed comparatively
quickly, which was not possible with the processes and devices according to the state of
the art. It is thus possible for contact lenses that are free from any air inclusions to be
produced efficiently and with low expenditure.
In the example embodiment shown in Figs. 6A-C, in addition impingement upon the
mould by UV rays is restricted to the m~teri~l in the mould cavity lS, that is to say only
the m~teri~l disposed in the mould cavity lS is crosslinked. In particular, the starting
material in the annular gap 16, which surrounds the mould cavity lS, and the rem~in~.or Of
the starting m:~tf.ri~l M disposed in the container 10 are not impinged upon by energy and
are not crosslinkecl "Mould cavity" therefore here denotes that cavity of the closed mould
which is defined by the complete contour of the moulding to be produced, specifically
therefore the contact lens CL. The annular gap 16 opening into the mould cavity does not,
therefore, form part of the mould cavity lS here.
For re~ tion in practice, according to Figs. 6A-C there is provided on the mould wall 17,
in the region of the annular gap 16, a mask 21 that is il~e~ eable (or at least of poor
permeability compared with the permeability of the mould) to the energy used, in this case
212~
- 20 -
therefore UV light, which mask extends right up to the mould cavity and, with the
exception of the mould cavity, screens from the radiated energy all remaining parts,
cavities or surfaces of the mould that are in contact with or may come into contact with
the here liquid uncrosilinke~l, possibly excess, material. Partial areas of the lens rim are
formed not by a limitation of the m~teri~31 by mould walls but by a spatial restriction of the
radiation or other energy triggering polymerisation or crosslinking The side walls of the
upper mould half are also provided with the mask 21 so as to prevent the starting m~t~ri~31
M that surrounds the mould in the container 10 from being cros~linkt-(l
A further example embodiment of the device according to the invention is shown in Figs.
7A-C. In that example embodiment one mould half, in this case the male mould half, is
formed by one wall of a container 10a, in this case the cnnt~inPr base 100a. The male
mould half is thus formed directly on the Cont~in~r base 100a. Also provided in the
container 10a is a mould member 1 la displaceable in the manner of a piston, which can be
moved away from the container wall lying opposite it, in this case the container base 100a,
and back towards the container base, while m~int~ining a seal along the side walls of the
container. The mould can therefore be opened and closed in that manner. The mould
member 1 la is correspondingly formed as the female mould half on its face 17a that faces
the container base. Container base 100a and mould face 17a define the mould cavity 15a
when the mould is in the closed position (Fig. 7A). Naturally, the mould member does not
necessarily have to be constructed in the form of a piston and it would equally be possible
for a diaphragm to be provided to which the mould half was attached. Other methods of
altering the volume are also possible.
Provided in the container 10a, in this case the con~inel base 100a, is an inlet 101a through
which starting material can flow into the space between the mould member 1 la and the
container base 100a. The space between the mould member 1 la and the con~incr base
100a is for that purpose continuously in col-""ll~ tion with a reservoir R. By means of
pumps Pl and P2 at the inlet 101a and outlet 102a respectively, starting m~teri~l can be
conveyed to and from the space between mould member 1 la and container base 100a, it
being important for the space between mould member 1 la and cl nt~iner base 100a always
to be filled with staTting m~teri~l M so that no air can penetrate into that space. The pumps
Pl and P2 are represented with an integrated non-return valve, but it is also possible to use
pumps without an integrated non-return valve and to connect the valve separately between
pump and container or, depending on the type of pump, to dispense with such a non-return
valve completely.
~ 2123~S~
When the mould is in the closed position (Fig. 7A), it is impinged upon by energy, in this
case again UV radiation 3. In this case, too, the impingement upon the mould by energy is,
for example, from above. Crosclinking is caused thereby. The crosslink~l moulding CL is
then lifted from the mould and removed from the mould. For that purpose, first of all
liquid starting material M is fed by means of the pump Pl through the inlet 101a into the
space between the container base 100a and the mould member 1 la, and the piston-like
mould member 1 la is moved upwards (Fig. 7B). The moulding, in this case in the form of
the contact lens CL, can then be separated from the mould and removed. That can be
effected, for example, by means of a special gripping device, as already described with
reference to Fig. 1. The contact lens CL can, however, equally be flushed out of the
mould, as will be explained in more detail in the following.
The mould member 1 la displaceable in the manner of a piston is then moved downwards
again and the material disposed between the mould member 1 la and the con~aille~ base
100a is conveyed away through the outlet 102a (Fig. 7C). The material can be conveyed
away by means of the pump P2 provided at the outlet.
It is, in principle, possible here for the mould member 1 la displaceable in the manner of a
piston to be driven solely by the liquid starting material fed in and conveyed away from
between mould member 1 la and container base 100a, so that the pumps Pl and P2 supply
the driving energy necessary therefor. It is also possible for there to be no pumps at all and
for the mould member 1 la displaceable in the manner of a piston to be driven m~ch~nic-
ally, that is to say for starting material to be sucked in during the upward movement and
forced back out again during the dowllwald movwllellt. Obviously combinations with
pumps and a mech~niç~l drive are also possible.
A mask 21a is provided on the mould member 1 la. In a similar manner to that described
for the upper mould half 11 in Pigs. 6A-C, it extends over the annular gap 16a up to the
mould cavity lSa, and also optionally along the side walls of the mould m~ml~,r 1 la
displaceable in the manner of a piston. If the mould is then impinged upon by UVradiation 3, crosslinking occurs in the region of the mould cavity lSa only, with
consequent formation of the moulding. The m~teri~l in the re.l~i"i"g areas, espe~i~lly in
the annular gap 16a, and also other starting m~tqri~l in the container 10a, is not
crosslink~d In principle, the same considerations in respect of the m~t~ri~l~ and the
pro~ ction and mounting of such masks as those already made in the expl~n~tions of Figs.
2~8 15~
6A-C apply here too.
Figs. 8A-C show an example embodiment of the device that in principle is very similar to
the example embodiment of Figs. 7A-C. One dirrGlGllce, however, is that no pump P2 is
provided at the outlet 102a in the example embodiment according to Figs. 8A-C, but the
outlet 102a is constructed as a deformable flap or plate or as a trap door. In the expl~n~tion
of Figs. 8A-C, especially the release from the mould of the moulding, in this case
the,erolG of the contact lens CL, will be described in detail in the following. The filling of
the mould cavity lSa is carried out analogously to the example embodiment according to
Figs. 7A-C by means of the pump Pl. When the mould is in the closed position (Fig. 8A),
the contact lens CL is produced by crosslinking by impingement upon the mould of UV
r~ tiQn 3.
As the piston-like mould member 1 la (Fig. 8B) moves upwards, liquid starting m~te.ri~l
flows into the cont~inçr 10a between the ct)nt~iner base 100a and the mould member 1 la
displaceable in the manner of a piston. The inlet 101a may be constructed as a jet or
similarly acting flow-prod~lcing means. As the liquid starting m~teri~l is fed through the
inlet, the crosslink~A contact lens CL is lifted from the mould by the flow produced and,
with ~ iate arrangement of the jet, is flushed towards the outlet 102a, which in this
case is constructed as a deformable flap or plate. During the dowllw~.l lllove~ of the
piston-like mould member 1 la (Fig. 8C), the flap is deformed d~w~lw~ds by the ~ UlC
generated and opens the outlet 102a, so that the liquid starting m~tçri~l together with the
contact lens CL can be flushed out through the outlet 102a. The contact lens can be
collected in a sieve S that is permeable to the liquid starting m~teri~l The starting m~tt-.ri~l
may, for example, be recycled and reused, where n~cess~. ~ after it has been cle~n~
While the contact lens is being flushed out~ the mould cavity 15a is filled with new
starting m~t.ori~l, so that a new contact lens CL can immediately be crosslink~d by the
impingement of UV r~di~til n 3.
It has been described above that, for the purpose lifting off and flllshing out, liquid starting
m~t~ri~l is fed into the cont~in~r 10a, in the same cycle the mould cavity 15a is filled
again and, with the mould in the closed position, the mould is again impinged upon by UV
radiation 3 for the purpose of cros~linking and producing the next contact lens CL. The
device thus operates, as it were, as a "single-cycle" device. In each cycle (upward and
dowllwal.l m~Jvt;~ t of the piston-like mould 111~111~l 1 la) a contact lens is produced
and flushed out of the mould.
'~ 212.~S~
- 23 -
It is, however, also possible for the production of the contact lens to be carried out in a
first cycle ("production cycle"), that is to say for the piston-like mould member 1 la to be
moved upwards, for liquid starting material to flow between the mould member 1 la and
the container base lOOa and then for the mould member 1 la to be moved downwardsagain. In the closed position the mould is then impinged upon by W radiation 3, as a
result of which crosslinking occurs and the contact lens CL is thus produced. Then, in a
separate second cycle ("flushing cycle"), the contact lens can be flushed out of the mould
without a new contact lens being produced in that second cycle, whereas in the
"single-cycle" device a new contact lens CL is again produced. For the flushing operation
in the "two-cycle" device, it is therefore possible to use liquid starting material, but it is
also possible, in particular, to use a separate çle~ning liquid. This is of advantage in as
much as the mould can be especially well cleaned on the inside during the flushing cycle
before starting material flows in again in the next cycle and the next contact lens CL is
produced. In the example embodiment according to Figs. 8A-C, therefore, both a
"single-cycle" operation (a contact lens is produced in every cycle) and a "two-cycle"
operation (a contact lens is produced in the first cycle and in the second cycle it is flushed
out and the mould cleaned without a new contact lens being produced) are possible.
A further example embodiment of the device according to the invention is shown in Figs.
9A-C. That example embodiment is in principle also similar to the example embo li~
described with reference to Figs. 7A-C and Figs. 8A-C, but differs ~ignifi~ntly from those
in that it compri ~es a somewhat dirrtilcl~tly constructed mould member 1 lb displaceable in
the manner of a piston. In addition, the con~ainel lOb is also signifi(~ntly dirrel~;ntly
constructed in the respect that there is provided in one of its side walls 103b a hollow or
recess 104b which extends in the direction of movement of the piston-like mould member
1 lb. Arranged in that recess 104b is a gripping device 4b. The mould member 1 lb has an
in(lent~tion 114b on its outer wall 113b exactly in the region in which the recess 104b is
provided in the side wall 103b of the container 1 lb. The mould ~lell,ber 1 lb furthtormore
comprises a channel 115b which can be connected to a negative pl.,s~ule source and
positive p,es~ule source P3. The gripping device 4b can also be connected to that negative
pressure and positive pressure source P3.
The manufacture of the contact lens CL by crosslinking by means of impingement upon
the mould of UV radiation 3a is carried out in the same manner as already described with
reference to Figs. 7A-C and Figs. 8A-C. The expl~n~tion of Figs. 9A-C is therefore
2 1 2 ~
- 24 -
directed mainly to the manner in which the contact lens CL is removed from the mould.
When the mould is in the closed position, the mould is impinged upon by UV radiation 3
and the contact lens CL is produced by cros~linking (Fig. 9A). Starting m~t~ l is then
pumped by means of the pump Pl between the mould member 1 lb and the container base
lOOb, and the mould member 1 lb is moved upwards (Fig. 9B). The gripping device 4b is
then pivoted out of the recess 104b and over the contact lens CL. The gripping device 4b
has a borehole in its gripper plate 40b through which negative pressure is then applied by
means of the negative pressure source P3, so that the contact lens CL is lifted and sucked
towards the gripper plate 40b. When the contact lens CL has been sucked against the
gripper plate 40b, the gripping device 4b is pivoted back into the recess 104b and the
mould member 1 lb is moved dowllwa~ds again. As that happens, the liquid starting
material disposed between mould member 1 lb and container base lOOb is sucked away by
means of the pump P2 (Fig. 9C).
The gripping device 4b disposed in the recess 104b at the same time either glides along
the outer wall 113b of the mould member 1 lb or is held in the recess 104b until the
gripper plate 40b is located opposite the indentation 114b on the outer wall of the mould
member 1 lb. At that point positive pressure is applied through the borehole in the gripper
plate 40b, so that the contact lens CL is released from the gripper plate 40b and deposited
in the in(le.nt~tion 114b. Negative pressure is applied through the channel 115b leading to
the in~lont~tion 114b at the same time as the contact lens CL is released from the gripper
plate 40b, so that the contact lens CL is simply deposited by the gripper plate 40b in the
indent~tion 114b (Fig. 9A).
When the mould member 1 lb has been moved upwards, the in~ent~tir n 114b of the mould
member 1 lb is located outside the container lOb (Fig. 9B). If positive pressure is then
applied through the ch~nnt~l 115b, the contact lens CL is released from the in(lt-.nt~tion
114b and can be con~ yt;d away for further processing. In this connection it should in
particular be noted that the side wall 103b can also be extçn-led even further upwards and
can have a further recess in which the contact lens CL can be deposited or into which it
can be flushed. By that means even better guidance of the mould member 1 lb and
preservation of its corresponding sealing faces, which glide along the co~ r wall, is
achieved.
In Figs. 9A-C the pump P3 is provided for the application of positive ~l~s~ure or negative
pressure, the positive pressure connection HP and negative ples~ult; connection NP of
~- 212~
- 25 -
which pump are connected to the channel 115b or the borehole in the gripper plate 40b
depending on the position of the mould member displaceable in the manner of a piston.
The pump P3 can suck starting material out of the reservoir R, in which the starting
material is stored, by means of which the necessary pressure is produced. Figs. 9A-C show
at the inlet lOlb and at the outlet 102b two separate reservoirs into which the pumps Pl or
P2 and P3 respectively project, but obviously it is also possible for there to be one
reservoir only.
It should be noted at this point that also the example embodiment according to Figs. 9A-C
can operate both as a "single-cycle" device and as a "two-cycle" device. It must, however,
be ensured in tbe case of the "single-cycle" device that it is always only starting m~teri~l
that flows into the container lOb. In the "two-cycle" device, on the other hand, in the
second cycle in which the contact lens CL is also removed, a cleaning liquid can be fed in.
It is also clear that the device explained with reference to the Figures may also comprise
several cavities instead of only one cavity, so that several contact lenses can be produced
simlllt~neously in one cycle. That variant is especially efficient.
Furth~rm-~re, in the variants with the piston-like mould member a throughflow control can
be effected in a controlled manner to the effect that first of all the piston-like mould
member is acted upon by force m~ch~ni~lly, and release of the starting m~t,o,ri~l into the
container as it is fed in is slightly delayed and release from the cont~iner as it is conveyed
away is slightly delayed. This applies also to the variant in which both pumps are used and
the piston is driven m~h~ni~lly. With this measure it is possible for a negative pressure
when feeding in, and a positive pressure when conveying away, to be generated in the
container in a controlled manner, or for the pressure in the container to be influenced
generally in that manner.
Also possible is a variant in which the number of cycles by which a new contact lens is
produced is variable. For example, a sensor can detect whether a contact lens has actually
been flushed out of the mould, and only when the sensor has detected such a flushed-out
contact lens is the mould fully closed and a new contact lens produced. If the sensor has
not detected a flushed-out contact lens, flushing of the mould is contin~led until the contact
lens has been flushed out of the mould.
For contact lenses there may be used as starting m~teri~l that can be crl!sslink~d by
ii~ 21~
- 26 -
irradiation with UV light, for example, the HEMA (hydroxyethyl methacrylate) or poly-
HEMA used widely for such purposes, especially in ~clmixtllre with a suitable cr~s~linkor,
such as, for example, ethylene glycol dimethacrylate. For other mouldings, depending on
the intenflefl use other crosslink~ble m~teri~l may possibly be used and, in principle, it is
also possible for other forms of energy, for example electron radiation, gamma r~ tinn,
thermal energy etc., to be used to trigger crosslir~king depending on the nature of the
crosslinkable m~t~ri~l In the m~nllf~tllre of contact lenses, starting m~tt~ri~ls that are
cros~link~kle by UV light are generally cu~Lo~ but not absolutely essenti:~l
According to a further aspect of the invention special prepolymers, especially those based
on polyvinyl alcohol, that comprise cyclic acetal groups and cros~link~ble groups are
suitable as starting material.
Contact lenses based on polyvinyl alcohol are already known. For example, contact lenses
comprising polyvinyl alcohol that has (meth)acryloyl groups bonded by way of urethane
groups are disclosed, for example, in EP 216 074. Contact lenses made of polyvinyl
alcohol crosslinked with polyepoxides are described in EP 189 375.
Also already known are some special acetals that comprise crosslink~ble groups.
Reference is made in that conn~tion, for example, to EP 201 693, EP 215 245 and
EP 211 432. EP 201 693 describes, inter alia, acetals of unbranched aldehydes having
from 2 to 11 carbon atoms that carry a termin~l amino group which has been substituted
by a C3-C24-olefinic~lly unsaturated organic radical. That organic radical has a function-
ality which removes electrons from the nitrogen atom, and also the olt~fini~lly unsatur-
ated functionality is polymeri~ble. Also cl~im~ in EP 201 693 are reaction products of
the above-characterised acetals with a 1,2-diol, a 1,3-diol, a polyvinyl alcohol or a
cellulose. Products of that kind are not, however, expressly described.
Insofar as one of the acetals according to EP 201 693 is mentioned at all in connection
with, for e~mple, polyvinyl alcohol, as is the case, inter alia, in Example 17 of that Patent
Application, then the acetal polymeri.c~ble by way of its olefinic group is first copolymer-
ised, for example, with vinyl acetate. The copolymer so obtained is then reacted with
polyvinyl alcohol, and an em~ ion with a pH of 5.43 and a viscosity of 11640 cps which
contains 37 % solids is obtained.
In contrast, the present invention is directed to prepolymers that comprise a 1,3-diol basic
. 21281~8
structure in which a certain percentage of the 1,3-diol units have been modified to a
1,3-dioxane having in the 2-position a radical that is polymerisable but not polymerised.
The polymerisable radical is especially an aminoaLkyl radical having a polymerisable
group bonded to the nitrogen atom. The present invention relates also to crosslinkrd
homo- or co-polymers of the said prepolymers, to processes for the plcpal~Lion of the
novel prepolymers and to the homo- and co-polymers obtainable thclcr~ ll, to mouldings
of the said homo- or co-polymers, especially contact lenses made from those homo- or
co-polymers, and to processes for the m~nllf~cture of contact lenses using the said homo-
or co-polymers.
The prepolymer according to the invention is preferably a derivative of a polyvinyl
alcohol having a molecular weight of at least about 2000 that, based on the number of
hydroxy groups of the polyvinyl alcohol, comprises from approxim~tely 0.5 to approx-
imately 80 % of units of formula I
\CH/CH2\CH/CH2\
\ CH / (I)
~R1
R--N~
wherein
R is lower aLcylene having up to 8 carbon atoms,
Rl is hydrogen or lower aL~yl and
R2 is an olefinic~lly unsaturated, electron-withdrawing, copolymt-ri~able radical
preferably having up to 25 carbon atoms.
R2 is, for example, an ole~lnir~lly unsaturated acyl radical of formula R3-Co-, in which
R3 is an olefinicz~lly unsaturated copolymPri~able radical having from 2 to 24 carbon
atoms, preferably from 2 to 8 carbon atoms, especially preferably from 2 to 4 carbon
atoms. In another embodiment, the radical R2 is a radical of formula II
~CO~NH~(R4~NH~CO~O)q~R5~0~CO~R3 (II)
~ 212~1~3.~
- 28 -
wherein
q lS zero or one and
R4 and Rs are each independently lower aL~ylene having from 2 to 8 carbon atoms,arylene having from 6 to 12 carbon atoms, a saturated divalent cycloaliphatic group
having from 6 to 10 carbon atoms, aryleneaLl~ylene or aL~ylenearylene having from 7 to 14
carbon atoms or aryleneaL~ylenearylene having from 13 to 16 carbon atoms, and
R3 is as defined above.
The prepolymer according to the invention is therefore especially a derivative of a poly-
vinyl alcohol having a molecular weight of at least about 2000 that, based on the number
of hydroxy groups of the polyvinyl alcohol, comprises from app~ illlately 0.5 to approx-
imately 80 % of units of formula III
\CH /CH2\cH /CH2
O O
\ CH / ~III)
R N /
\ [CO-NH-(R4-NH-CO-O)q-R5-0]p-CO-R3
wherein
R is lower aL~ylene,
Rl is hydrogen or lower aL~yl,
p is ~ro or one,
q is ~ro or one,
R3 is an olefinically unsaturated copolym~n~ble radical having from 2 to 8 carbon atoms
and
R4 and Rs are each independently lower aLl~ylene having from 2 to 8 carbon atoms,
arylene having from 6 to 12 carbon atoms, a saturated divalent cycloaliphatic group
having from 6 to 10 carbon atoms, aryleneaL~ylene or aLl~ylenearylene having from 7 to 14
carbon atoms or aryleneaL~ylenearylene having from 13 to 16 carbon atoms.
Lower aL~ylene R preferably has up to 8 carbon atoms and may be straight-chained or
branched. Suitable examples include octylene, hexylene, pentylene, butylene, propylene,
- 29 -
ethylene, methylene, 2-propylene, 2-butylene or 3-pentylene. Preferably lower aLIcylene R
has up to 6 and especially preferably up to 4 carbon atoms. The meanings methylene and
butylene are especially plerelltid.
Rl is preferably hydrogen or lower aL~yl having up to seven, especially up to four, carbon
atoms, especially hydrogen.
Lower aLl~ylene R4 or R5 preferably has from 2 to 6 carbon atoms and is especially
straight-chained. Suitable examples include propylene, butylene, hexylene, dimethyl-
ethylene and, especially preferably, ethylene.
Arylene R4 or Rs is preferably phenylene that is unsubstituted or is substituted by lower
aL~yl or lower aL~oxy, especially 1,3-phenylene or 1,4-phenylene or methyl-1,4-
phenylene.
A saturated divalent cycloaliphatic group R4 or Rs is preferably cyclohexylene or cyclo-
hexylene-lower aL~ylene, for example cyclohexylenel~lelhylene, that is unsubstituted or is
substituted by one or more methyl groups, such as, for example, Llhllelllylcyclohexylene-
methylene, for example the divalent isophorone radical.
The arylene unit of aLl~ylenearylene or aryleneaL~ylene R4 or Rs is preferably phenylene,
unsubstituted or subsliluled by lower aL~yl or lower aLkoxy, and the aL~ylene unit thereof
is preferably lower aL~ylene, such as methylene or ethylene, especially methylene. Such
radicals R4 or Rs are therefore preferably phenylenemethylene or methylenephenylene.
AryleneaL~ylenearylene R4 or Rs is preferably phenylene-lower alkylene-phenylenehaving up to 4 carbon atoms in the aLkylene unit, for example phenyleneethylene-phenylene.
The radicals R4 and Rs are each indepen~lçntly preferably lower aLl~ylene having from 2 to
6 carbon atoms, phenylene, unsubstituted or substituted by lower aLl~yl, cyclohexylene or
cyclohexylene-lower aL~ylene, unsubstituted or substituted by lower aL~cyl, phenylene-
lower aL~cylene, lower alkylene-phenylene or phenylene-lower aL~ylene-phenylene.
Within the scope of this invention, the term "lower" used in conn~ction with radicals and
colllpoullds denotes radicals or compounds having up to 7 carbon atoms, preferably up to
2 1 ~
- 30 -
4 carbon atoms, unless defined otherwise.
Lower aL~yl has especially up to 7 carbon atoms, preferably up to 4 carbon atoms, and is,
for example, methyl, ethyl, propyl, butyl or tert-butyl.
Lower aL~oxy has especially up to 7 carbon atoms, preferably up to 4 carbon atoms, and is,
for example, methoxy, ethoxy, propoxy, butoxy or tert-butoxy.
The olefinically unsaturated copolym~.ri~hle radical R3 having from 2 to 24 carbon atoms
is preferably aL~enyl having from 2 to 24 carbon atoms, especially aL~enyl having from 2
to 8 carbon atoms and especially preferably aL~enyl having from 2 to 4 carbon atoms, for
example ethenyl, 2-pl~ellyl, 3-~1~enyl, 2-butenyl, hexenyl, octenyl or dodecenyl. The
meanings ethenyl and 2-propenyl are plGrGllcd, so that the group -Co-R3 is the acyl
radical of acrylic or methacrylic acid.
The divalent group -R4-NH-Co-o- is present when q is one and absent when q is zero.
Prepolymers in which q is ~ro are plGfell~
The divalent ~roup ~CO~NH~(R4~NH~CO~O)q~Rs~O~ is present when p is one and absent
when p is zero. Prepolymers in which p is ~ro are plGf~l~d.
In prepolymers in which p is one the index q is preferably ~ro. Prepolymers in which p is
one, the index q is ~ro and Rs is lower aL~ylene are especially l~lerGllGd.
A plGre~lGd prepolymer according to the invention is th~GfolG especially a derivative of a
polyvinyl alcohol having a molecular weight of at least about 2000 that, based on the
number of hy~y groups of the polyvinyl alcohol, compri~es from app~ i-l-ately 0.5 to
o~ ately 80 % of units of formula m in which R is lower aLIcylene having up to 6carbon atoms, p is ~ro and R3 is alkenyl having from 2 to 8 carbon atoms.
A further plGrGllGd prepolymer according to the invention is thelefolG especially a
deliv~tive of a polyvinyl alcohol having a mnlPcul~r weight of at least about 2000 that,
based on the number of hydroxy groups of the polyvinyl ~l~ohol, compri~es from approx-
imately O.S to appl~i-llately 80 % of units of formula III in which R is lower aL~ylene
having up to 6 carbon atoms, p is one, q is ~ro, Rs is lower aL~ylene having from 2 to 6
carbon atoms and R3 is alkenyl having from 2 to 8 carbon atoms.
2 1 2 8
- 31 -
A further pl~rellcd prepolymer according to the invention is therefore especially a
deliva~ive of a polyvinyl alcohol having a molecular weight of at least about 2000 that,
based on the number of hydroxy groups of the polyvinyl alcohol, comrri~es from approx-
imately 0.5 to a~plùAilllaLtily 80 % of units of formula III in which R is lower aLkylene
having up to 6 carbon atoms, p is one, q is one, R4 is lower aLylene having from 2 to 6
carbon atoms, phenylene, unsubstituted or substituted by lower aLcyl, cyclohexylene or
cyclohexylene-lower aLylene, unsubstituted or subs~i~u~ed by lower aLkyl, phenylene-
lower aLylene, lower aLylene-phenylene or phenylene-lower aLylene-phenylene, Rs is
lower aL~ylene having from 2 to 6 carbon atoms and R3 is aLenyl having from 2 to 8
carbon atoms.
The prepolymers according to the invention are d~liv~ives of polyvinyl alcohol having a
molecular weight of at least about 2000 that, based on the number of hydluAy groups of
the polyvinyl alcohol, comrrises from a~luAi,llately 0.5 to a~plo,~ AIely 80 %,
especially a~lv,~ ely from 1 to 50 %, preferably a~ploAi l~ately from 1 to 25 %,preferably a~loAi",~t;ly from 2 to 15 % and especially preferably a~~ lely from 3
to 10 %, of units of formula m. Prepolymers according to the invention which areprovided for the m~nllf~ture of contact lenses comprise, based on the number of hydroxy
groups of the polyvinyl ~ ohol~ especially from a~p,~,x;.-.~lely 0.5 to a~lo,~ tely 25 %,
especially ~vx;~AIely from 1 to 15 % and especially preferably aL~lux;lll~tely from 2
to 12 %, of units of formula m.
Polyvinyl ~lCQhols that can be derivatised in accor~lce with the invention preferably
have a mol~c~ r weight of at least 10 000. As an upper limit the polyvinyl ~lcohol~ may
have a mnlP~llAr weight of up to 1 000 000. Preferably, the polyvinyl alcohols have a
molecular weight of up to 300 000, especially up to a~l loAima~ly 100 000 and especially
preferably up to al)ploxi---~lely 50 000.
Polyvinyl ~ QhO1S suitable in accor~lce with the invention usually have a poly-
(2-hydluAy)ethylene structure. The polyvinyl alcohols derivatised in accordance with the
invention, may, however, also compri~e 11Y~JAY groups in the form of 1,2-glycols, such as
copolymer units of 1,2-dihydl~JAyelllylene, as may be obtained, for eY~mple, by the
~lkAlin~. hydrolysis of vinyl acetate/vinylene carbonate copolymers.
In ~dflition, the polyvinyl alcohols derivatised in accoç~lce with the invention may also
~ 2~2~1~8
- 32 -
comprise small proportions, for example up to 20 %, preferably up to 5 %, of copolymer
units of ethylene, propylene, acrylamide, methacrylamide, dimethacrylamide, hydroxy-
ethyl methacrylate, methyl methacrylate, methyl acrylate, ethyl acrylate, vinylpyrrolidone,
hydroxyethyl acrylate, allyl alcohol, styrene or similar customarily used comonomers.
Commercially available polyvinyl alcohols may be used, such as, for example, Vinol(~
107 produced by Air Products (MW = 22 000 to 31 000, 98 - 98.8 % hydrolysed),
Polysciences 4397 (MW = 25 000, 98.5 % hydrolysed), BF 14 produced by Chan Chun,Elvanol(~) 90 - 50 produced by DuPont, UF-120 produced by Unitika, Moviol(~ 4-88,
10-98 and 20-98 produced by Hoechst. Other manufacturers are, for example, Nippon
Gohsei (Gohsenol(g'), Monsanto (Gelvatol~), Wacker (Polyviol~)) and the Japanesem~nl]f~ctnrer Kuraray, Denki and Shin-Etsu.
As already menh~nt-d, it is also possible to use copolymers of hydrolysed vinyl acetate,
which are obtainable, for example, in the form of hydrolysed ethylene/vinyl acetate
(EVA), or vinyl chloride/vinyl acetate, N-vinylpyrrolidone/vinyl acetate and rnaleic acid
anhydride/vinyl acetate.
Polyvinyl alcohol is usually prepared by hydrolysis of the corresponding homopolymeric
polyvinyl acetate. In a pl~r~lled emb~lim~.nt, the polyvinyl alcohol derivatised in
accordance with the invention comprises less than 50 % of polyvinyl acetate units,
especially less than 20 % of polyvinyl acetate units.
The compounds comprising units of formula m may be prepared in a manner known ~
se. For example, a polyvinyl alcohol having a molecular weight of at least about 2000 that
comprises units of formula IV
-CH(OH)-CH2- (IV)
may be reacted with a~plu~illlately from 0.5 to 80 %, based on the number of hydroxy
groups of the compound of formula IV, of a compound of formula (V)
2128~ ~
- 33 -
R' R"
\ CH / (V)
~R1
R N
\ [CO-NH-(R4-NH-CO-O)q-R5-0]p-CO-R3
in which
R' and R" are each independently hydrogen, lower aLkyl or lower aL~anoyl, such as acetyl
or propionyl, and the other variables are as defined for formula m, especially in an acidic
medium.
~ltern~tively, a polyvinyl alcohol having a molP~ r weight of at least about 2000 that
comprises units of formula IV may be reacted with a compound of formula VI
R' R"
\ CH / (VI)
~R1
R N~
in which the variables are as defined for the colllpound of formula V, especially unde
acidic con-1ition~, and the cyclic acetal obtainable in that manner may then be reacted with
a compound of formula VII
OCN~(R4~NH~CO~O)q~R5~0~CO~R3 (VII)
in which the variables are as defined for the compound of foImula V.
~ltern~tively, the reaction product of a col~oulld of formula IV and a compound of
formula VI may be reacted, simil:lrly to the product obtainable as desc.ribed above, with a
compound of formula (Vm)
X-Co-R3 (VIII:)
~ 2~2~
- 34 -
in which R3 is, for example, alkenyl having from 2 to ~ carbon atoms and X is a reactive
group, for example etherified or esterified hydroxy, for example halogen, especially
chlorine.
Compounds of formula V in which p is zero are known, for example, from EP 201 693.
Compounds of formula VI are also described therein. Compounds of formula VII areknown E~r se, or can be prepared in a manner known per se. An example of a compound
of formula VII in which q is zero is isocyanatoethyl methacrylate. An example of a
compound of formula VII in which q is one is the reaction product of isophorone diiso-
cyanate with 0.5 equivalent of hydroxyethyl methacrylate. Compounds of formula VIII are
known ~ se; a typical representative is methacryloyl chloride. Compounds of formula V
in which p and/or q are 1 can be prepared in a manner known ~ se from the above-mentioned compounds, for example by reaction of a compound of formula VI with iso-
cyanatoethyl methacrylate or by reaction of a compound of formula VI with isophorone
diisocyanate which has previously been termin~t~ with 0.5 equivalent of hydroxyethyl
methacrylate.
Surprisingly the prepolymers of formnl~e I and m are extraordinarily stable. This is
unexpected for the person skilled in the art bec~ e7 for example, higher-functional
acrylates usually have to be stabilised. If such compounds are not stabilised then rapid
polymeri~tion usually occurs. Spontaneous crosslinking by homopolymerisation does not
occur, however, with the prepolymers of the invention. The prepolymers of formulae I and
III can furthermnre be purified in a manner known per se, for example by precipitation
with acetone, dialysis or ultrafiltration, ultra~lltration being especially plcfcllcd. By means
of that pnrific~tion process the prepolymers of formulae I and III can be obtained in
extremely pure form, for example in the form of concenll~tcd aqueous solutions that are
free, or at least substantially free, from reaction products, such as salts, and starting
m:~t~ri~li, such as, for example, compounds of formula V or other non-polymeric
constituent~,
The ~rercll~d purific~tir)n process for the prepolymers of the invention, ultrafiltration, can
be carried out in a manner known E~r se. It is possible for the ultrafiltration to be carried
out repeatedly, for example from two to ten times. ~ltern~tively, the ultrafiltration can be
carried out continuously until the selected degree of purity is attained. The selected degree
of purity can in principle be as high as desired. A suitable measure for the degree of purity
'~ 212~
is, for example, the sodium chloride content of the solution, which can be determined
simply in known manner.
The prepolymers of formula I and III according to the invention are on the other hand
crosslinkable in an extremely effective and controlled manner, especially by photocross-
linking.
In the case of photocros~linking, apprupliately a photoiniti~tor is added which can initiate
radical cros~linking Examples thereof are familiar to the person skilled in the art and
suitable photoiniators that may be mentioned specifically are benzoin methyl ether,
l-hydroxycyclohexylphenyl ketone, Daracure 1173 or Irgacure types. The crosslinking
can then be triggered by actinic rafli~tic)n, such as, for example, UV light, or ionising
radiation, such as, for example, gamma radiation or X-radiation.
The photopolymeri~tion is suitably carried out in a solvent. A suitable solvent is in
principle any solvent that dissolves polyvinyl alcohol and the vinylic comonomers
optionally used in addition, for example water, alcohols, such as lower aLanols, for
example ethanûl or m~t~anol, also carboxylic acid ami~les, such as (lhllcLllyl~~ . "ifle~ or
dimethyl sulfoxide, and also a ~ Lul~ of suitable solvents, such as, for example, a
ll~ix Lure of water with an alcohol, such as, for example, a water/ethanol or a water/-
methanol llli~lUl'C.
The photocros~linking is carried out preferably directly from an aqueous solution of the
prepolymers according to the invention, which can be obtained by the ~rcrell~,d purifica-
tion step, ultrafiltration, where applupliate after the addition of an acldition~l vinylic
comonomer. For example, an applu~ aLt;ly 15 to 40 % aqueous solution can be photo-
crosslinked.
The process for the preparation of the polymers of the invention may comprise, for
example, photocrosslinking a prepolymer comprising units of formula I or III, especially
in substantially pure form, that is to say, for example, after single or repeated ultra-
filtration, preferably in solution, especially in aqueous sollltion, in the absence or presence
of an additional vinylic comonomer.
The vinylic comonomer which, in accordance with the invention may be used in addition
in the photocrosslinking, may be hydrophilic or hydrophobic, or a IlliX.IUlC of a hydro-
2~2~1~38
- 36-
phobic and a hydrophilic vinylic monomer. Suitable vinylic monomers include especially
those customarily used in the manufacture of contact lenses. A hydrophilic vinylic
monomer denotes a monomer that typically yields as homopolymer a polymer that iswater-soluble or can absorb at least 10 % by weight of water. Analogously, a hydrophobic
vinylic monomer denotes a monomer that typically yields as homopolymer a polymer that
is water-insoluble and can absorb less than 10 % by weight of water.
Generally, applu~ lately from 0.01 to 80 units of a typical vinylic comonomer react per
unit of formula I or III.
If a vinylic comonomer is used, the crosslinked polymers according to the invention
preferably comprise approximately from 1 to 15 %, especially preferably approximately
from 3 to 8 %, of units of formula I or III, based on the number of hydru~y groups of the
polyvinyl alcohol, which are reacted with applo~ ately from 0.1 to 80 units of the vinylic
monomer.
The proportion of the vinylic comonomers, if used, is preferably from 0.5 to 80 units per
unit of formula I, especially from 1 to 30 units per unit of formula I, and especially
preferably from 5 to 20 units per unit of formula I.
It is also preferable to use a hydrophobic vinylic comonomer or a llli~LurG of ahydrophobic vinylic comonomer with a hydrophilic vinylic comonomer, the l~ UlG
comprising at least 50 % by weight of a hydrophobic vinylic comonomer. In that manner
the mech~nic~l ~lopGlLies of the polymer can be improved without the water content
falling substantially. In principle, however, both conventional hydrophobic vinylic
comonomers and conventional hydrophilic vinylic comonomers are suitable for the
copolymçris~tion with polyvinyl alcohol comprising groups of formula I.
Suitable hydrophobic vinylic comonomers include, without the list being exhaustive,
Cl-CI8aLLyl acrylates and m~th~rylates, C3-C~8aLcyl acryl~mi-l~.s and mPth~cryl~mi~es,
acrylonitril~, methacrylonitrile, vinyl-CI-CI8aLkanoates, C2-CI8~1kçnPs, C2-CI8halo-
aLkenes, styrene, Cl-C6aLkylstyrene, vinyl aLkyl ethers, in which the aLl~yl moiety cont~ins
from 1 to 6 carbon atoms, C2-CIOperfluoroaLLyl acrylates and mP.th~crylates or corres-
pondingly partially fl~10rin~terl acrylates and methacrylates, C3-CI2perfluoroaL~yl-ethyl-
thiocarbonylaminoethyl acrylates and methacrylates, acryloxy- and methacryloxy-aL~ylsil-
oxanes, N-vinylcarbazole, Cl-Cl2aLkyl esters of maleic acid, fumaric acid, it~onic acid,
_ 2128~ S~
- 37 -
mesaconic acid and the like. Cl-C4alkyl esters of vinylically unsaturated carboxylic acids
having from 3 to 5 carbon atoms or vinyl esters of carboxylic acids having up to 5 carbon
atoms, for example, are ~lt;rell~d.
Examples of suitable hydrophobic vinylic comonomers include methyl acrylate, ethyl
acrylate, propyl acrylate, isopropyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate,
methyl methacrylate, ethyl methacrylate, propyl methacrylate, vinyl acetate, vinyl
propionate, vinyl butyrate, vinyl valerate, styrene, chloroprene, vinyl chloride, vinylidene
chloride, acrylonitnle, l-butene, butadiene, meth~rrylonitrile, vinyltoluene, vinyl ethyl
ether, perfluorohexylethylthiocarbonylaminoethyl methacrylate, isobornyl methacrylate,
trifluoroethyl mrth:~rrylate, hexafluoroisopropyl methacrylate, hexafluorobutyl
methacrylate, tris-trimethylsilyloxy-silyl-propyl methacrylate, 3-methacryloxypropyl-
pentamethyldisiloxane and bis(methacrylo~y~lupyl)tetramethyldisiloxane.
Suitable hydrophilic vinylic comonomers include, without the list being exhaustive,
hydroxy-substituted lower alkyl acrylates and methacrylates, acrylamide, methacrylamide,
lower alkyl acryl~mir~es and meth~rryl~mi(les, ethoxylated acrylates and methacrylates,
hy(llo~y-substituted lower alkyl acrylamides and methacrylamides, hydroxy-substitutrd
lower alkyl vinyl ethers, sodium ethylenesulfonate, sodium styrenesulfonate, 2-acryl-
amido-2-1llelllylpl~anesulfonic acid, N-vinyl~yllule, N-vinylsuccinimi~lr~ N-vinyl-
pyrrolidone, 2- or 4-vinylpyridine, acrylic acid, mrth~r,rylic acid, amino- (the term
"amino" also including q ~ l y ammonium), mono-lower aL~ylamino- or di-lower
alkylamino-lower aL~yl acrylates and methacrylates, allyl alcohol and the like. Hydlu~y-
substituted C2-C4aL~cyl(meth)acrylates, five- to seven-membered N-vinyl l~cts~m~, N,N-
di-Cl-C4aL~yl(meth)acryl~mi(les and vinylically unsatul~ted carboxylic acids having a
total of from 3 to 5 carbon atoms, for example, are preferred.
Examples of suitable hydrophilic vinylic comonomers include hydroxyethyl m~th~rrylate,
hydroxyethyl acrylate, acrylamide, methacrylamide, lilllelhylacrylamide, allyl alcohol,
vinyl~ylidine, vinylpyrroli(10n~" glycerol mrth~f~rylate, N-(l,l-dil~e~hyl-3-oxobutyl)-
acrylamide, and the like.
Preferred hydrophobic vinylic comonomers are methyl methacrylate and vinyl acetate.
Preferred hydrophilic vinylic comonomers are 2-hydlu~y~;~lyl meth~rrylate, N-vinyl-
pyrrolidone and acrylamide.
2128i~8
- 38 -
The polymers according to the invention can be processed in a manner known per se into
monl(ling~, especially contact lenses, for example by carrying out the photocrosslinking of
the prepolymers according to the invention in a suitable contact lens mould. The invention
thelGrolG further relates to mouldings that consist essenti~lly of a polymer according to the
invention. Further examples of mouldings according to the invention, besides contact
lenses, are biome-licin~l or especially ophth~lmi~ monkling.~, for example intraocular
lenses, eye b~ntl~ges, mouldings that can be used in surgery, such as heart valves, artificial
arteries or the l~ke, and also films or m~mbr~n~.s, for example membranes for diffusion
control, photostructurizable films for information storage, or photoresist m~teri~ls, for
example membranes or mouldings for etch resist or screen printing resist.
A specific embodiment of the invention is directed to contact lenses that comprise a
polymer according to the invention or consist substantially or wholly of a polymer
according to the invention. Such contact lenses have a wide range of unll~u~l and
extremely advantageous pl~GlLies, which inclucle, for example, their e~ell~-nt compat-
ibility with the human cornea, which is based on a balanced rel~tion~hip of water content,
oxygen permeability and mP~h~ni~l pl~llies. The contact lenses according to the
invention furth~rmnre exhibit a high degree of (limen~ion~l stability. No changes in shape
are tletected even after autoclaving at, for example, about 120~C.
~ttention may also be drawn to the fact that the contact lenses according to the invention
can be produced in a very simple and efficient n al~ com~ ,d with the state of the art.
This is as a result of various factors. First, the starting m~teri~l~ can be obtained or
produced at a favourable cost. Secondly, there is the advantage that the prepolymers are
surprisingly stable, so that they can be subjected to a high degree of pnrifir~tion It is
therefore possible to use for the cr(!sslinking a matPri~l that requires practically no
subsequent pnrific~tion~ such as especially a complicated extraction of unpolym~ri~ed
con~ ent~. Also, the polymerisation can be carried out in aqueous sohltion, so that a
subse~luelll hydration step is not ntocess~ry. Finally, the photopol~ n occurs within
a short period, so that the process for m~nllf~cturing the contact lenses according to the
invention can be organised to be e~ ,mely economi~l from that point of view also.
All of the advantages mentioned above naturally apply not only to contact lenses but also
to other mouldings according to the invention. Taking into account all the various advant-
ageous aspects in the manllra~;lul~ of the mouldings according to the invention it can be
' -
21~81 .~
seen that the mouldings according to the invention are especially suitable as mass-
produced articles, such as, for example, contact lenses that are worn for a short time and
then replaced by new lenses.
In the following Examples, unless expressly stated otherwise amounts are amounts by
weight, and temperatures are in degrees Celsius. The Exarnples are not intended to limit
the invention in any way, for instance to the scope of the Examples.
Example la): Over a period of 4 hours, 104.5 parts of methacryloyl chloride dissolved in
105 parts of dichloromethane are added dropwise at a ma~ um of 15~C, while cooling
with ice, to 105.14 parts of aminoacetaldehyde dimethylacetal and 101.2 parts of triethyl-
amine in 200 parts of dichloromethane. When the reaction is complete, the
dichlorc,ll~ ane phase is washed with 200 parts of water then with 200 parts of lN HCl
solution, and then twice with 200 parts of water. After drying with anhydrous magnesium
sulfate, the dichlorollR~l,ane phase is concentl~l~;d by evaporation and stabilised with
0.1 % of 2,6-di-tert-butyl-p-cresol, based on the reaction product. After ~ till~tion at
90~C/10-3 mbar, 112 g of methacryt~mi to~etaldehyde dimetllylacetal are obtained in the
form of a colourless liquid, boiling point 92~C/10-3 mbar (65 % yield).
Example lb): 52.6 g of aminoacetaldehyde dimethylacetal are dissolved in 150 ml of
deionised water and cooled to 5~C with ice. Subsequently, 50 ml of methacrylic acid
chloride and 50 ml of 30 % sodium hydroxide solution are ~imlllt~neously so added over a
period of 40 minlltes that the pH value remains at 10 and the temperature does not exceed
20~C. When the ~1~1ition iS complete, the l~ i"ing content of aminoacetaldehyde
dillle~lylacetal is determined as 0.18 % by gas chromatography. The amine is reacted fully
by the further addition of 2.2 ml of methacrylic acid chloride and 2.0 ml of 30 % sodium
hydroxide solution. The solution is then neutralised with lN hydrochloric acid (pH = 7).
The aqueous phase is extracted with 50 ml of petroleum ether and washed with water. The
petroleum ether phase contains 3.4 g of secondary product. The aqueous phases are
combined and yield 402.8 g of a 20.6 % solution of methacryl~mil1o~cet~l~1ehyde
dhlle~llylacetal. According to a gas chromatogram, the product is 98.2 %.
Example 2: 10 parts of polyvinyl alcohol having a molecular weight of 22 000 and a
degree of hydrolysis of 97.5 - 99.5 % are dissolved in 90 parts of water, 2.5 parts of meth-
acryl~mi~o~cet~ hyde dillle~}lylacetal are added and the ~ ; is acidified with 10
parts of concentrated hydrochloric acid. The solution is stabilised with 0.02 parts of
' -
2 ~ 3 8
- 40 -
2,6-di-tert-butyl-p-cresol. After stirring for 20 hours at room temperature, the solution is
adjusted to pH 7 with 10 % sodium hydroxide solution and then ultrafiltered seven times
using a 3kD membrane (ratio 1:3). After concentration, an 18.8 % aqueous solution of
methacryl:~mido~çetaldehydo-1,3-acetal of polyvinyl alcohol having a viscosity of
2240 cP at 25~C is obtained.
Example 3: 10 parts of the solution of methacrylamidoacetaldehydo-1,3-acetal of
polyvinyl alcohol obtained in accordance with Example 2 are photochemically cr~s~linkPd
by adding 0.034 parts of Darocure 1173 (CIBA-GEMY) thereto. The ~lul~ is irradiated
in the form of a 100 micron t~hick layer between two glass plates with 200 pulses of a 5000
watt iIr~ tion device produced by Staub. A solid transparent film with a solids content of
31 % is obtained.
Example 4: 110 g of polyvinyl alcohol (Moviol 4-88, Hoechst) are dissolved at 90~C in
440 g of deionised water and cooled to 22~C. 100.15 g of a 20.6 % aqueous ss)llltion of
methacrylamido~et~ hyde dillle~lylacetal, 38.5 g of concen~,aled hydrochlori~ acid
(37 % p.a., Merck) and 44.7 g of deioni~ed water are added thereto. The ~ ul~ is stirred
at room lc~Gl~lulc for 22 hours and then adjusted to pH 7.0 with a 5 % NaOH solution.
The solution is diluted to 3 litres with deionise~l water, filtered and nltrafiltPrcd using a
l-KD-Omega lllcml~ e ploduced by Filtron. After the three-fold spec ,en volume has
pPrmP~tP~l, the solntion is conce~ ed. 660 g of a 17.9 % sollltion of the m.oth~ylamido-
acetaldehydo-1,3-acetal of polyvinyl alcohol having a viscosity of 210 cp are obtained.
The inherent viscosity of the polymer is 0.319. The nitrogen content is 0.96 %. According
to NMR investig~tion, 11 mol % of the OH groups have been ~ret~lise~l and 5 mol % of
the OH groups acetylated. Concentration of the aqueous polymer solution under reduced
pressure and air draft yield a 30.8 % solution having a viscosity of 3699 cp.
Example 5: 66.6 g of deionised water, 3.3 g of monom~o-ric 4-methacrylamidobutyr-
aldehyde diethylacetal and 20.0 g of concel~ cd hydrochloric acid (37 % p.a, Merck)
are added to 133.3 g of a 15 % polyvinyl alcohol solution (Moviol 4-88, ~oeçh~t) and the
u,e is sti~red at room ~c~ c for 8 hours. The solution is then adjusted to pH 7
with 5 % sodium hydroxide solution. After ultraf~tration of the solntion using a3-KD-Omega m~mbranl~ produced by Filtron, the sodium çhlorirl.o content of the polymer
solution being reduced from 2.07 % to 0.04 %, a 20 % polymer sol-l~ion of the ...~l.
amidobutyraldehydo- l ,3-acetal of polyvinyl alcohol having a viscosity of 400 cp is
obtained. The inherent viscosity of the polymer is 0.332. The nitrogen content is 0.41 %.
~ 212~:15~
- 41 -
According to NMR investigation, 7.5 mol % of the OH groups are charged with acetal
groups and 7.3 mol % of the OH groups are charged with acetate groups.
Example 6: 2.4 g (14.8 mmol) of aminobutyraldehyde diethylacetal (Fluka) and 20 g of
concentrated hydrochloric acid (37 % p.a., Merck) are added to 200 g of a 10 % polyvinyl
alcohol solution (Moviol 4-88, Hoechst). The solution is stirred at room le~ el~lult; for
48 hours and then neutralised with 10 % sodium hydroxide solution. The solution is
diluted to 400 ml. 200 ml of the solution are further processed in accordance with
Example 7. 0.85 g (8.1 mmol) of methacrylic acid chloride (Fluka) is added to the
;mai~ g 200 ml of the solution and the pH value is ~ ed at 10 with 2N sodiumhydroxide solution. After 30 minutes at room temperature, the pH is adjusted to 7.0 and
the solution is purified analogously to Example S using a 3-KD-Omega membrane
produced by Filtron. Concentration yields a 27.6 % polymer solution of the methacryl-
amidobutyraldehydo- l ,3-acetal of polyvinyl alcohol having a viscosity of 2920 cp. The
inherent viscosity of the polymer is 0.435. The nitrogen content is 0.59 %.
Example 7: 1.3 g (8.5 mmol) of 2-isocyanatoethyl methacrylate are added to 200 ml of the
polymer solution of Example 6 and the pH is m:~int~ined at 10 with 2N sodium hydroxide
solution. After 15 minutes at room temperature the solution is neutralised with 2N hydro-
chloric acid and ultrafiltered analogously to Example 6. Concentration yields a 27.1 %
polymer solution of the 4-(2-methacryloylethyl-ureido)butyraldehydo-1,3-acetal of poly-
vinyl alcohol having a viscosity of 2320 cp. The inherent viscosity of the polymer is
0.390. The nitrogen content is 1.9 %.
Example 8: 0.7 % Darocur 1173 (based on the content of polymer) is added to the 30.8 %
polymer solution according to Example 4 having a viscosity of ~p~ ately 3600 cp.The solution is introduced into a transparent contact lens mould of poly~lupylene and the
mould is closed. The solution is irrdiated for 6 seconds from a distance of 18 cm using a
200 watt Oriel W lamp. The mould is opened and the finished contact lens can be
removed. The contact lens is transparent and has a water content of 61 %. The modulus is
0.9 mPa, the flexural elongation (DIN 53 371) 50 %. The contact lens is autoclaved for 40
minutes at 121~C. No changes in shape can be detected in a contact lens treated in that
manner.
Example 9: 0.0268 g of Darocur 1173 (0.7 % based on the polymer content) and 0.922 g
of methyl methacrylate are added to 10.00 g of a 27.1 % polymer solution according to
2 ~ ~. P~
- 42 -
Example 7. After the addition of 2.3 g of methanol a clear solution is obtained. That
solution is irradiated for a period of 14 seconds analogously to Example 8, using a
200 watt Oriel lamp. A L~ s~ contact lens having a water content of 70.4 % is
obtained.
Example 10: 1.04 g of acrylamide and 0.03 g of Darocur 1173 are added to 12.82 g of a
24.16 % solution of the prepolymer of Example 4. The clear solution is then irr~ ted for
14 seconds analogously to Example 8, using a 200 watt Oriel lamp. A contact lens having
a water content of 64.4 % is obtained.
