Process for producing mouldings

Details Process for producing mouldings Process for producing mouldings

1999-01-22

2001-02-20

Seidleck, James J. (Department: 1711)

Plastic and nonmetallic article shaping or treating: processes

Direct application of electrical or wave energy to work

Polymerizing, cross-linking, or curing

C264S001380, C264S002600, C264S001700, C264S494000, C264S343000, C522S162000, C522S163000, C522S164000, C522S165000, C522S166000, C522S167000

Reexamination Certificate

active

06190603

ABSTRACT:

The invention relates to a novel process for producing mouldings, especially opthalmological mouldings, such as especially contact lenses, in which a liquid or readily meltable prepolymer containing crosslinkable groups is crosslinked in the absence of solvents, and to the further processing thereof to form ready-to-use contact lenses.
Processes for producing mouldings, especially contact lenses, by suitable crosslinking of polymers containing crosslinkable groups are known. The previously known processes are customarily carried out in the presence of a solvent and optionally with the addition of vinyl comonomers. For the production of a ready-to-use contact lens it is accordingly often necessary to replace the solvent when the crosslinking is complete and/or to extract unreacted monomers. There is therefore a need for a simplified process for producing mouldings that can be carried out without solvent and does not include an extraction step.
The present Application therefore relates to a process for producing mouldings that comprises the following steps:
a) introducing into a mould a prepolymer containing photocrosslinkable groups that is liquid at room temperature or is readily meltable and is substantially free of solvents,
b) initiating the photocrosslinking for a period of <20 minutes,
c) opening the mould, so that the moulding can be removed from the mould.
The criterion that the prepolymer be liquid or readily meltable is to be understood according to the invention as meaning that the prepolymer is liquid at room temperature or has a melting point of ≦100° C., preferably ≦75° C. and especially ≦50° C. Preferred for the process according to the invention are prepolymers that are liquid at room temperature.
The polymeric base structure of the prepolymers can belong to a wide variety of classes of polymer; examples are polyethers, polyesters, polyureas, polyurethanes, polycarbonates and polyamides. Also possible are homogeneous mixtures of two or more different polymers.
When the prepolymer is a polyether, then, for example, a polyalkylene glycol homo- or co-polymer or a polytetrahydrofuran comes into consideration. Examples of suitable polyalkylene glycol homo- or co-polymers are C
1
-C
6
polyalkylene glycol homopolymers or block copolymers and preferably polymers based on polyethylene glycol or polypropylene glycol or polyethylene glycol/polypropylene glycol block copolymers.
Preference is given to the use of a polyester, polyamide, polyamide with polyethylene glycol blocks, polyurethane, polyurea or of one of the above-mentioned polyethers as prepolymer.
The prepolymer used according to the invention must also contain photocrosslinkable groups. Photocrosslinkable groups are to be understood as being customary photocrosslinkable groups well known to the person skilled in the art, especially those such as have already been proposed for the production of contact lens materials. They include especially, but not exclusively, groups containing carbon-carbon double bonds. In order to demonstrate the wide variety of suitable crosslinkable groups, there may be mentioned here as crosslinking mechanisms, merely by way of example, radical polymerisation, 2+2-cycloaddition, Diels-Alder reaction, ROMP (Ring Opening Metathesis Polymerisation), vulcanisation, cationic crosslinking and epoxy curing. Suitable photopolymerisable groups are especially radically or cationically polymerisable groups.
Suitable radically crosslinkable groups correspond, for example, to formula
P
1
—(Y)
m
—(R—X)
p
—  (1),
wherein
P
1
is a radically crosslinkable group,
Y is the radical —CONHCOO—, —CONHCONH—, —OCONHCO—, —NHCONHCO—, —NHCO—, —CONH—, —NHCONH—, —COO—, —OCO—, —NHCOO— or —OCONH—,
m and p are each independently of the other the number 0 or 1,
R is the residue of a divalent organic compound having from 1 to 20 carbon atoms, and
X is the radical —NHCO—, —CONH—, —NHCONH—, —COO—, —OCO—, —NHCOO— or —OCONH—.
P
1
is, for example, alkenyl, which is unsubstituted or substituted, for example, by C
1
-C
4
-alkoxycarbonyl or by vinyloxycarbonyl, or alkenylaryl or alkenylarylenealkyl, the said radicals each having up to 20 carbon atoms. Examples of alkenyl are vinyl, C
1
-C
4
alkoxycarbonylvinyl, vinyloxycarbonylvinyl, allyl, 1-propen-2-yl, 1-buten-2-, -3- or -4-yl, 2-buten-3-yl and straight-chain or branched pentenyl, hexenyl, octenyl, decenyl and undecenyl. Examples of alkenylaryl are vinylphenyl, vinyinaphthyl and allylphenyl. Examples of alkenylarylenealkyl are o-, m- and p-vinylbenzyl.
P
1
is preferably alkenyl or alkenylaryl each having up to 12 carbon atoms, especially alkenyl having up to 8 carbon atoms and more especially alkenyl having up to 4 carbon atoms.
Y is preferably —COO—, —OCO—, —NHCONH—, —NHCOO—, —OCONH—, —NHCO— or —CONH—, especially —COO—, —OCO—, —NHCO— or —CONH— and more especially —COO— or —OCO—.
X is preferably —NHCONH—, —NHCOO— or —OCONH— and especially —NHCOO— or —OCONH—.
The variables m and p are preferably not both the number 0. When p is 0, m is preferably the number 1.
R is preferably alkylene, arylene, cycloalkylene having from 6 to 20 carbon atoms, arylene-alkylene, alkylenearylene, alkylenearylenealkylene or arylenealkylenearylene. R is especially a divalent radical having up to 12 carbon atoms and more especially a divalent radical having up to 8 carbon atoms. R is preferably alkylene or arylene having up to 12 carbon atoms, especially alkylene having up to 6 carbon atoms and more especially alkylene having up to 4 carbon atoms.
Preferred as radically crosslinkable groups are acryloyl, methacryloyl, maleate, vinyl ether maleate, styryl, acrylamido, methacrylamido, acrylamidoalkyl, urethane methacrylate or unsubstituted or substituted derivatives of the mentioned radicals, with special preference being given to acryloyl, methacryloyl, acrylamido and methacrylamido.
Especially preferred radically crosslinkable groups correspond to formula (1) above wherein P
1
is alkenyl having up to 4 carbon atoms, Y is —COO— or —CONH—, R is alkylene having up to 4 carbon atoms, X is —NHCOO—, and m and p are each independently of the other 0 or 1, the sum of (m+p) being ≧1.
Cationically crosslinkable groups that may be mentioned are, for example, epoxy, vinyl ether, propenyl ether, spiroorthoester and spiroorthocarbonate groups and cyclic carbonates, with epoxy or vinyl ether groups being preferred.
When the cationically crosslinkable group is an epoxy group, that epoxy group corresponds, for example, to formula
P
2
—Y
1
—  (2),
wherein
P
2
is the residue of an organic epoxy-group-containing compound and
Y
1
is the radical —NHCO—, —CONH—, —NHCONH—, —COO—, —OCO—, —NHCOO— or —OCONH—.
Examples of suitable residues P
2
correspond to the formula
wherein
R
1
and R
2
are each independently of the other C
1
-C
6
alkylene.
Y
1
is preferably —COO—, —OCO—, —NHCO— or —CONH—.
Preferred as photocrosslinkable groups are radically polymerisable groups containing carbon-carbon double bonds, especially acryloyl, methacryloyl, acrylamido or methacrylamido.
A preferred group of prepolymers used according to the invention corresponds to the formula
wherein
one of the radicals R
3
and R
4
is hydrogen and the other is methyl, R
5
is hydrogen or C
1
-C
30
-alkyl, n and q are each independently of the other a number from 0 to 100, the sum of (n+q) being ≧5, and Z is a photocrosslinkable radical, preferably one of the photocrosslinkable radicals mentioned above, with the said preferences applying. Z in formulae (4) and (5) is preferably a radical of formula (1) or (2) above and is especially acryloyl, methacryloyl, acrylamido or methacrylamido or is a radical of formula (2) above wherein Y
1
is —COO—, —OCO—, —CONH— or —NHCO— and P
2
is a residue of formula (3a)-(3d) above.
The prepolymer used according to the invention contains crosslinkable groups preferably in an amount of from approximately 0.5 to approximately 80% equivalents, based on the equivalents of monomers forming the polymeric base structure, especially approximately from 1 to 50%, more espec

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