Plastic and nonmetallic article shaping or treating: processes – Optical article shaping or treating – Utilizing plasma – electric – electromagnetic – particulate – or...
Patent
1999-01-22
2000-08-22
Vargot, Mathieu D.
Plastic and nonmetallic article shaping or treating: processes
Optical article shaping or treating
Utilizing plasma, electric, electromagnetic, particulate, or...
264 11, 264 138, 264496, 264 28, B29D 1100
Patent
active
061067466
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a novel process for producing mouldings, especially contact lenses, in which a soluble prepolymer containing crosslinkable groups is crosslinked in solution, which process is distinguished from the known metering techniques by the fact that the solution of the prepolymer is metered into a mould in the solid state.
EP-A-641 806 describes a process for producing mouldings which comprises the following steps: that contains crosslinkable groups,
The present invention is directed towards a further development of that process in which the introduction of the solution obtained into the mould has been fundamentally improved. The improvement consists essentially in that the solution is metered into the mould in the solid state. As a result, for example, the solution can be introduced into the mould without any bubble formation. Furthermore, the formation of schlieren, which may occur with the known process, can be avoided in accordance with the invention. In addition, the appearance of drying rings, which may also be observed using the known process, can be substantially avoided in accordance with the invention. A further important advantage of the process according to the invention is that the viscosity of the prepolymer solution to be used is no longer a limiting factor for the metering, since the prepolymer solution in the solid state can be metered without any problem. To summarise, the process according to the invention, as a result of resorting to metering in the solid state, has proved extremely advantageous compared with the known process, especially where prepolymer solutions of relatively high viscosity are to be processed.
The invention accordingly relates to a process for producing mouldings, especially contact lenses, which comprises the following steps: that contains crosslinkable groups, from the mould.
The decisive criteria for the use of a prepolymer in the process according to the invention are that the prepolymer be soluble in water, that it contain crosslinkable groups and that it be possible for a substantially aqueous solution of the prepolymer to be reversibly converted from the liquid state to the solid state.
A substantially aqueous solution of a water-soluble prepolymer that contains crosslinkable groups can be prepared in a manner known per se, for example by synthesising the prepolymer in a substantially aqueous solution or by isolating the prepolymer, for example in pure form, that is to say free of undesirable constituents, and dissolving it in a substantially aqueous medium.
Broadly speaking, the process is carried out in an aqueous solvent. A suitable solvent is, in principle, any solvent that dissolves the prepolymer and the vinyl comonomers possibly used in addition, and is water-miscible, for example water, an alcohol, such as a lower alkanol, for example ethanol or methanol, a carboxylic acid amide, such as dimethylformamide, or dimethyl sulfoxide. An aqueous solution is to be understood as meaning water or a mixture of a suitable solvent with water, for example a mixture of water with an alcohol, such as a water/ethanol mixture or a water/methanol mixture, in which water clearly constitutes the larger portion. A substantially aqueous solution is to be understood as meaning that water makes up at least 80% by weight of the solvent, preferably at least 90% by weight, especially at least 95% by weight, more especially at least 98.5% by weight and most especially 100% by weight.
These figures relate only to solvents other than water and do not have any bearing on any possible content of prepolymer, salts or other dissolved substances.
In accordance with the invention, the criterion that the prepolymer be soluble in water is to be understood especially as meaning that the prepolymer is soluble in a substantially aqueous solution, at 20.degree. C., in a concentration of approximately from 3 to 90% by weight, preferably of approximately from 5 to 60% by weight and especially of approximately from 10 to 60% by weight. Insofar as is possible in any individual cas
REFERENCES:
patent: 3151095 (1964-09-01), Stone et al.
patent: 3171870 (1965-03-01), Monteil et al.
patent: 3968051 (1976-07-01), Stamm et al.
patent: 4673539 (1987-06-01), Hammar et al.
patent: 4788017 (1988-11-01), Schlomer et al.
patent: 4978575 (1990-12-01), Ziess
patent: 5508317 (1996-04-01), Mueller
patent: 5804106 (1998-09-01), Yi et al.
Gorman, Jr. Robert J.
Meece R. Scott
Novartis AG
Vargot Mathieu D.
LandOfFree
Manufacture of mouldings does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Manufacture of mouldings, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Manufacture of mouldings will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-576907