CA2186564A1 - Mold material made with additives - Google Patents

Abstract

The present invention is directed to a composition comprising polystyrene or polypropylene with at least 0.05% (w/w) of an additive or wetting agent, the article of manufacture comprised thereof, such as a mold for making contact lenses and the mold assembly containing said mold, and the use of such mold so to minimize defects, such as holes, puddles, chips and tears in the lens.

Description

7~ 6~9~FeC~9~9~
MO~D l/lATT~RrAT MADE WITE ADDITIVES
The present invention relatea to a novel polymeric formulation AA,ntA~nin~ an internal mold release additive which assists in the release of one mold, ~A,n=Ant from 5 another or an internal mold wetting agent which enhances the interfacial wetting between the reactive monomer mix and the mold 3urfaces, thereby reducing the amount of defects formed in the contact lens. The present invention is also directed to the moldg made f rom such 10 polymeric formulation as well as to a method of preparing contact lenses from these molds.
An extengive array of methodg ig currently utilized in the manufacture of hydrophilic polymer articles, such as soft contact lenses. A considerable variety of 15 tecbnique8 have been employed, ,,uch as spin ca8ting, gtatic ca8t molding, lathing, and a combination of casting and lathing, and particularly through the use of two part molds. Generally, such mold parts for hydrophilic contact len8es consi8t of a curvilinear 20 (Concave/conveX) center of front curve mold part adapted to form, in cooperation with a mating base mold curve part, a two part mold for the contact lenses. These hydrophilic contact lenges are usually constituted from a ~hydrophilic polymer, preferably a HEMA-based polymer 25 (hydroxy-ethylmethacrylate), among numerous other materials .
The ~: ~ AntA of the mold within which the hydrophilic polymer contact lengeg are molded may consist of suitable pallets, each including a plurality 30 of cavlties receiving mold parts having female and/or -2- 21 8~64 male base surfaces or curvilinear mold E~ortions for the 1 formation of the curved contact lenses. The molds, as described, for instance in the molding technology, may be constituted from suitably selected conventional plastic materials, whereby the hydrophilic polymer 5 articles, i.e., the contact lenses, will be formed in the cavity therebetween, and may possibly adhere to one or both of the mold partg. In the l~ili7~;on of separable two part molds for the molding of hydrophilic contact lenses, upon completing the molding step, it is 10 of critical importance to be able to release the hydrophilic contact lenses from their surface engagement without adherence to the mold parts or at least one of the mold halves and to separate the ~ mold part without causing damage to the contact lenses which would render 15 the lenses unusable.
Unfortunately, all too frequently, damage is sustained during the preparation of contact lenses. The potential damages which generally renders the contact lenses unable to meet n~cl~Aq;lry quality and/or 20 inspection standards may consist of edge tears and chips, nicks or other surface defects formed in the contact lenses. Other causes of rejected lenses are holes, voids in center of the ca3t that are developed in the lenses during the molding process, pits, i.e. areas 25 on non-uniform thickness, and puddles.
As a result there is a need to f ind a new formulation for the mold that would reduce the risk of damage and defects.
Lens defects are major factors that causes low 30 production yield. There are two different types of -_3_ 2~86564 problems associated with contact lenses production which 1 the present invention is solving.
One such problem is the appearance of chips and tears in the lens. These are caused during the demolding step and are caused by adhesion of the mold to 5 the lenses. The present invention ~,v~ this problem by utilizing an alternative material for one of the mold parts. This new material contains an additive that is added to the mold which greatly reduces the adhesion forces between the lenses and the mold part, 10 thereby facilitating the release of the mold material and minimizing the risk of developing defects in the lens caused by and during the demolding step.
The second problem which is addressed by the present invention is the prevention of the forr~ti~n of 15 holes and puddles, which are developed in the lenses during the molding process. Eloles are usually found as voids in the center of the lens, while puddles are usually in random or in tree branch shapes, and are usually found along the lens edge and are usually 20 associated with the concave or front curve mold.
According to the inventors, they are caused mainly by poor wetting of the mold surface by the reactive monomer mix at assembly of the mold surface More specifically, the poor wettin~ usually is due to either i n~ _ ~t i hle 25 chemistry or incompatible charges across the interface of the mold and the reactive monomer mix or the combination of both. More importantly, a heterogeneous mold surface which causes uneven wetting by the reaction monomer mix, results in many local unwetted voids, and 30 therefore lead to holes or puddles in the contact lens.

According to the inventors these holes and puddles 1 would be overcome if a prior wetting agent is added to the polymer mold 80 as to increase the wettability power of the mold. In order to understand the concept of wetting, a brief digression will be made to discuss the 5 events occurring on the molecular level in a liquid. In the body of a liquid, the time-averaged force exerted on any given molecule by its neighboring molecule i8 zero.
Even though such a molecule may undergo diffusive displacements due to random collisions within the 10 liquid, for any long duration, there exists no directed forces upon it. There is equal probability to be displaced in one direction as another. However, the situation is quite different at the surface of the liquid since there exist no molecules to counteract the 15 force8 e~erted by the molecules in the interior for molecules on the surface. As a result, molecules on the surface of a liquid experience a net attraction toward the interior of a drop, thereby causing the droplet to a8sume a spherical shape, minimi~ing both free energy 20 and 8urface area- This create3 a surface tension, which from a microscopic point of view is the reversible isothermal work which must be done in bringing molecules from the interior of the liquid to the surface, and creating 1 unit of new surface thereby. The present 25 inventors believe that overcoming the surface tension would remove the potential for forming Nholes" in the liquid, i.e., would make the liquid spreadable or wettable on a solid.
In the wetting or nonwetting of solids by liquids, 30 the criteria employed is the contact angle between the ~5~ 21 g6564 ~olid and the liquid (measured through the liquid).
1 Reference i8 made to Figure 6 which illustrates the relation3hip between contact angle "a" and the interfacial ten3ions that exi8t at the surface of a liquid. As clearly shown, there are three interfaces 5 which exist when a droplet of liquid contacts a solid, and thus there are three ~uLr.~L~ n~ interfacial tensions, ~SL, ~SV and yLV, wherein ~ refers to the interfacial tension, S, L and V referg to golid, liquid and vapor, respectively. A liquid is said to wet a 10 801id if the contact angle "a"~ lies between 0 and 90, and not to wet the solid if the contact angle lies between 90 and 180. At equilibrium, a balance of interfacial tensions exist at the line of common contact, which intersects Figure 6 at point 0. For a 15 liquid wetting the solid, this equilibrium is expressed by the relation:
ySV = ~ySL + ~LV cos 0 The present inventors have modified this concept and utilized this modification to ~tf~rm~nf~ if a particular substance could be used to reduce the tendency of forming holes and puddleg in making contact lenses. Moreover, the present inventorg have found a trend and thus have found that particular, ~ when admixed with the polymeric mold material significantly reduces the amount of holes and puddles in contact lenses .
Their solution was based upon their understanding of the thf dyllamics of the situation. They calculated -6- 21 8656~
that, the theoretical estimation of wetting, which is 1 the ~h, 'yllamic parameter called the 3preading coefficient, is defined as:
s = ~ ~'Ya~

where S is the 3preading coefficient, ~, is the surface energy of the mold material, ~ is the surface tension of the reactive monomer mix ( "RMM" ) and the ~ is the interfacial tension between reaction monomer mix and thf3 10 mold material. A positive "S" indicates spreading (or wetting). Therefore, in order to spread or to wet, ~
and ~ should be made as small as possible or ~ should be made as large as possible. Practically, this means that the surface energy of the mold is increased or the 15 8urface tension of the reactive monomer mix is reduced or both is effected in order to obtain the appropriate wetting between reactive monomer mix and the mold. With respect to increasing the mold surface energy, this requires consideration of increasing not only the total 20 8urface energy, but al80 increasing the portion of high energy surface.
This can be accomplighed by various techniques for example, by coating the surface of one of the mold halveA with surfactant, or by transiently coating a the 25 mold surface with a wetting agent. Another method, which is an embodiment of the present invention is the incorporation of wetting agentg into the mold material.
Obviougly, not all wetting agents to the mold material will be effective. The present inventors have 30 developed a methodology for determining which admixtures ~7~ 21 86564 will be useful for the composition of the mold material for :the manufacture of contact lenses having a reduced number of holes or puddles. In consequence thereof, the present inventors have developed a new mold material which have the added advantage of reducing the tendency 5 to form holes or puddles.
Theref ore, the present inventors have developed new mold formulations improving the yield in and reducing the defects in contact lenses. In one embodiment, the formulation of the present invention reduces the 10 tendencies to form chips and tears. In another , the present f~ t;~n reduces the tF~n~l.on~ to form holes and puddleg in contact lenses.
Accordingly, the present invention provides for a mold for making contact lenses comprising thermoplastic 15 polymer of either polystyrene or polypropylene admixed with an internal mold release agent (additive) or wetting agent.
More specifically, the present invention is directed to a mold material constituting a mold half for 20 u~e in the pro~ t; f-n of contact lenses, said mold material comprising a thermoplastic polymer and a ;ntF.rni:l additive which is impregnated into said thermoplastic material and which is present in amounts ranging from about 0 05% to about 59~ by weight, said 25 thermoplastic material being polystyrene or polypropylene and said additive being a polyethylene or polypropylene wax having a molecular weight ranging from about 5000 to about 200,000, an amide wax of the formula RlCONEI" wherein Rl is a hydrocarbyl group, and the amide 30 wax has a molecular weight of about 200-2000, silicone .
-8- 2 1 ~6564 having a molecular weight ranging from about 2000 to about 100, 000, Montan wax, oxidized wax, fatty acid having a molecular weight of about 200 to about 2000, a complex ester or a in~tion thereof, The pre8ent invention is further directed to a mold 5 material constituting a mold half for use in the production of contact lenses, said mold material comprising polystyrene and an wetting effective amount of a wetting agent admixed therewith, the wetting force of said mold material being described by the equation:

F = 2~1 pc where F is the wetting force of the mold half ~l is the surface tension of distilled water 15 ~ P i8 the perimeter of the mold material at the meniscus when the mold half is partially immersed in the water and ~ is dynamic contact an~le, wherein the contact angle of said mold material is less than 100.
When these materials were used to make one of the mold halves in the mold assembly for making the contact lenses, it wa8 found that fewer lenses were formed having the defects described hereinabove. Thus, the pre3ent invention is further directed to the mold half comprised of this new formulation. This mold half is part of the mold assembly, and therefore the pre~ent invention is 8till further directed to the mold assembly comprising aaid mold half comprised of these f. 1~t;ong of the pre8ent invention.
3o _g _ More particularly, the present invention is 1 directed to a mold half Useful in the production of a contact lens by the polymerization of a polymerizable composition in a mold assembly comprised of 3aid mold half and a second mold half, said mold half comprising 5 an integral article having a central curved section defining a concave surface, a convex surface and a circumferential edge, at leagt the central portion of at least one of said concave surface and said convex surface having the dimensions of the back curve of the lO de8ired 8welled or un8welled contact lens to be produced in said mold assembly and being sufficiently smooth and contoured 80 that the surface of said contact lens formed by polymerization of said polymerizable composition in contact with said surface is optically 15 acceptable, 8aid article having an annular flange integral width and ~uLLuu~lding said circular circumferential edge and extending therefrom in a plane normal to the axis of said concave gurface, said article also having a generally triangular tab situated in a 20 plane normal to 3aid axis and ~.Yt~n~in~ from said flange, 3aid article having a thinness and rigidity effective to transmit heat therethrough and to withstand prying forces applied to separate gaid mold half from 3aid mold assembly, and said article being comprised the 25 mold material comprised of a thermoplastic polymer admixed with an additive or anti-wetting agent as described above.
The mold assembly preferentially comprise~ at least two pieces, a female concave piece (front piece) and a 30 male convex piece (back piece) forming a cavity -lo- 2 t 865~4 therebetween, and when said pieces are mated, at least 1 one piece having a flange thereabout. More particularly, in a preferred ~ 1; , the mold assembly comprises a front mold half and a back mold hal f in contact therewi th, thereby def ining and 5 enclosing a cavity therebetween, and a polymerizable composition in said cavity in contact with said mold halves, the front mold of which has a central curved section with a concave surface, a convex surface and a circular circumferential edge, wherein the portion of 10 8aid concave 8urface in contact with said polymerizable composition has the curvature of the front curve of a contact lens to be produced in said mold a~sembly and i8 sufficiently smooth that the ~3urface of a contact len3 formed by polymerization of ~aid polymerizable 15 composition in contact with said surface is optically acceptable, said front mold also having an annular f lange integral with and surrounding said circular circumferential edge and ~ctPn~;n~ therefrom in a plane normal to the axis and ~rt~onrl;ng from said flange, while 20 the back mold has a central curved section with a concave surface, convex ~iurface and circular circumferential edge, wherein the portion of said convex surface in contact with said polymerizable composition has the curvature of the back curve of a contact lens to 25 be produced in said mold assembly and is sufficiently smooth that the surface of a contact lens formed by polymerization of the polymerizable composition in contact with said surface is optically acceptable; said back curve also having an annular flange integral with 30 and ~uLL~uulding said circular circumferential edge and .

~t~n~l;n~ therefrom in a plane normal to the axis of 1 said convex structure, and a generally triangular tab situated in a plane normal to said axis and extending from said flange, wherein the convex structure of said back mold half contacts the circumferential edge of the 5 front mold half.
The inner concave surface of the front mold half defines the outer surface of the contact lens, while the outer convex surface of the base mold half defines the inner surface of the con~act lens which rests upon the lo edge.
In this assembly, either the back mold or the front mold half or both is comprised of the novel formulation of the present invention. However, ` it is the back mold half that is p~eferably comprised of the novel 15 formulation of the pre8ent invention, while the front curve mold i~ comprised of a thermoplastic material that does not contain the additive or wetting agent. Thus the present invention is also directed to the base mold comprised of said novel formulation.
More specifically, the present invention is directed to a mold assembly used in the production of a contact len3 by the polymerization of a polymerizable composition in said mold assembly, said mold assembly compri~ing a front mold half and a back mold half in contact therewith thereby def ining and f~n~ ; ng a cavity therebetween, and a polymerizable composition in said cavity in contact with both mold halves, wherein said f ront mold half compri8e8 a f irst article o thermoplastic polymer transparent to ultraviolet light, said article having a central curved section with a .

concave surface, a convex surface and a circular 1 circumferential edge, wherein the portion of said concave surface in co~tact with said polymerizable composition has the curvature of the front curve of a contact len~3 to be produced in ~aid mold assembly, and 5 i~ sufficiently smooth 80 that the surface of a contact lens formed by polymerization of said polymerizable composition in contact with said surface is optically acceptable;
f3aid f irst article having an annular f lange 10 integral with and sUrrounding said circular circumferential edge and f~Yt~n~l;n~ therefrom in a plane normal to the aYil3 of said concave surface, and generally triangular tab situated in a plane normal to said axis and extending from said flange;
said back mold comprised of an integral article having a central curved section with a concave surface, a convex surface and a circular circumferential edge, wherein the portion of said convex surface in contact with said polymerizable composition has the curvature of 20 the back curve of a contact lens to be produced in said mold assembly and is suf f iciently smooth 80 that the surface of a contact lens formed by polymerization of said polymerization composition in contact with said surface is optically acceptable;
25 ~ said second article having an annular f lange ;nt~r~l with and gurrounding ~aid circular circumferential edge with and surrounding said circular circumferential edge and extending therefrom in a plane normal to the axis of said conveY surface, and a 30 generally triangular tab situated in a plane normal to . - ~

2~ 86564 said axis and ex~nrl;n~ from said flange wherein the l convex 8urface of 8aid back mold half contacts the circumferential edge of said front mold half;
said back mold being comprised of a mold material comprised of a thermoplastic polymer admixed with an 5 additive as described above.
The mold assembly with the base curve mold made up of the poly8tyrene/additive or polypropylene/additive, polystyrene/wetting agent or polypropylene/wetting agent formulations is used in making soft contact lenses.
lO Thu8, the pre8ent invention is still further directed to the process of making soft contact lenses utilizing this mold assembly. That is, an improved process for forming a contact lens from a mold assembly comprising a front mold half and a back mold half in contact therewith 15 thereby defining and enclosing a cavity therebetween, and ~nn~;l;nin~ in said cavity a polymerizable composition in contact with said mold halves;
said front mold half comprising a first article of thermoplastic polymer transparent to ultraviolet light, 20 9aid article having a central curved section with a concave surf ace, a convex surf ace and a circular circumferential edge, wherein the portion of said Goncave surfaca in contact with said polymerizable composition has the curvature of the front curve of a 25 contact lens to be produced in said mold assembly and is sufficiently smooth 80 that the surface of a contact lens formed by polymerization of said polymerizable composition in contact with said surface is optically acceptable;

2 i 865G~

sald back mold half compri~ing a second article of l thermopla3tic polymer transparent to ultraviolet light, said article having a central curved section with a concave surface, a convex surface and a circular circumferertial edge, wherein the portion of said convex 5 surface in contact with said polymerizable composition has the curvature of the back curve of a contact ler,s to be produced in said mold assembly and i3 suf f iciently smooth 90 that the surface of a contact lens formed by polymerization of said polymerizable composition in lO contact with said surface is optically acceptable, wherein the convex surface of said back mold contacts the circumferential edge of 8aid front mold half;
and the front mold half is ciamped against the back mold half;
and the polymerizable composition undergoes polymerization under precuring and curing conditions with ultraviolet light and the back curve is separated from the front curve and the contact lens during a demolding process and the front curve is subseguently 20 ~eparated from the contact ler,s, the ; , LUV~ ---t comprining ~It;1;7ing a back curve mold that is comprised of the mold material a3 described above.
As described herein, the use of the ~ t; ons of the present invention modifies the surface chemistry of 25 the back mold by Pnh~nr; n~ its wettability . In addition, a formulation of the present invention facilitates the release of the mold from the polymerized polymer comprising the contact lens and the front mold.
Another aspect of the present invention is directed 30 to~a process of m;nim;7;n~ and/or preventing ch.ps or tears in the contact lens by utilizing a mold comprised l of poly8tyrene or polypropylene admixed with the additive de8cribed hereinabove in mold releasing effective amounts. Another aspect of the present invention i~ directed to a process of minimizing and/or 5 preventing holes or puddles in the contact lens by ll~il;7;ny a mold half compri3ed of a thermoplastic material admixed with an effective amount of a wetting agent, said thermoplastic material being polystyrene or polypropylene, and said mold half being sufficiently wet lO to have a dynamic contact angle when immersed in water of 100 or less.
The present invention may be more readily understood by one skilled in the art with reference being had to the following detailed description of 15 8everal preferred embodiments thereof, taken in conjunction with the accompanying drawings wherein like elements are designated by identical reference 1,~;
throughout tl~e several view8.
Figure 1 i8 a f low diagram of the continuous 20 proce88 for contact len8 production, including molding, treatment and h:lnrll ;n~ of the molds and contact lenses in a low oxygen environment.
Figure 2 is a top elevational planar view of the production line system constructed according to the 25 pre8ent invention.
Figures 3 and 3 (a) are re3pectively, a top or planar view and an elevation of side view of one 'lo~ of a first (~emale) or front curve mold half molded pursuant to the present invention.

-16- 2 1 865~
Figure 3 (b) is an enlarged detail of a portion of 1 Figure 3 (a) .
Figures 4 and 4 (a) are respectively a top or planar view and an elevation or side view of one ' ~rl; t of a second (male) or back curve mold half molded pursuant 5 to the present = invention .
Figure 5 is a ba~e curve frame of 8 mold halves (cavities) supported and regi8tered in a pallet comprised of various formulations, as described in Example 1 .
Figure 6 is a schematic diagram of the contact angle and the surface tension at the solid-vapor and solid-liquid; nt~rf~ of a solid immer8ed in a probe liquid .
Figure 7 is a schematic diagram of the methodology 15 of the pre8ent invention used to measure the contact angle .
Figure 8 is a schematic of the various parameters in detF~rm;n;ng the contact angle.
Figure 9 is a typical water wetting force trace As described hereinabove, the mold contains an internal additive or wetting agent. In other words, the additive or wetting agent ig thoroughly admixed with the thermoplastic polymer. This provides a substantially uniform distribution of the~e internal additives or wetting agents across the surface of the mold resin and decreases the probability that they would be retained on the lens. The polystyrene/additive, polypropylene/additive, polystyrene/wetting agent or the polypropylene/wetting agent compositions are prepared by 30 processes well known to those skilled in the art. The following procedure exemplifies the techniques u3ed to 1 make the formulation8 of the present invention, using polystyrene and an additive ag an example. However, it il3 exemplary and is equally applicable for the preparations of the other formulations of the present 5 invention.
The polystyrene and the additive are mixed together ~ :
by techniques known to one gkilled in the art. In one methodology, the polystyrene is r ,Irl~n-lP-l with the additive . In other words, a prp~l~tprm; nF-f~ amount of the 10 additive and ~oly8tyrene are mixed together, the mixture is heated to melt the polystyrene, the melted polystyrene and the additive are then again mixed together, such as with an extruder, - which further ;ntr-rm;~ q the two r,nen~q The mixture can then be 15 repelletized in a pellatizer. Alternatively, the polystyrene may first be melted to form the molten polystyrene and the additive added to the molten polystyrene in the mixer, e.g., extruder, and mixed together and then repelletized with the pelletizer.
20 Alternatively, the additive can ~e compounded with the thermoplastic material directly in the molding machine.
The amount of additive added to the thermoplalitic material is a mold releasing effective amount, while the amount of wetting agent added i~ a wetting effective 25 amount. The mold material comprised thereof is to be transparent to W transmi~sion, egpecially of from 3 to 5 nm up to wavelengths of 300 n~ .ors E~owever these amounts preferentially overlap. More qpr---;f;~11y, when pregent, the additive or wetting 30 agent i~ preferably present in an amount ranging from -18- ~ 8656~
about O . 0596 to about 5~6 (w/w) relative to the 1 thermopla3tic material, and more preferably ranging from about O .1~ to about 2 . 596 (w/w) .
These mold formulations solve two different problems; thus, the mold formulation used is dependent 5 upon the obj ective . If the obj ective is to reduce holes, the mold formulation utilized is the thermoplastic material admixed with wetting agent. If the ob~ective i8 to reduce puddles, the front curve mold is formed of the th~ tic material with wetting 10 agent, On the other hand, if the objective is to facilitate mold release from the lens, then the mold f~ t;nn utilized for at lea~3t one of the molds, preferably the back mold, is the thermoplastic material with additive.
As used herein, reference to the "wetting formulation" or "composition" refers to the mold material comprised of the thermoplastic material (e . g .
polypropylene and more preferably polygtyrene) and the wetting agent, as defined herein . Alternatively 20 reference to the "mold release formulation~ or "composition~ refers to the mold material comprised at the thermoplastic r-t~rli-l (e.g. polypropylene or polystyrene) and the mold releage agent. Reference to the "f, l;~t;r~nFI~ or "compO8ition8" of the present 25 invention or equivalent expression which does not speclfy 'ld release' or ~wetting~ referg to both f ormulations .
The mold formulations of the present invention may comprise either the backcurve mold, the front curve mold 30 or both. Because of their surface curative differences, 35 ~ = ~

-19- 21 ~6564 the wettir~g or adhesion force at the RMM/backcurve 1 interface i8 different from that of the 3~MM/front curve interface It is preferred that the backcurve be comprised of the mold material of the pre3ent invention.
In the discussions that follow, reference will be 5 made to the backcurve, however, unless indicated to the contrary, these discussions are equally applicable to the front curve, and the use of the backcurve is for illustrative purposes.
To ~ PrDl~n~ the feasibility of a mold material for lO u8e in the backcurve mold to reduce the tendency to form holes in the contact lenses, the inventor3 developed a modif ied wetting method to measure the wettability of the backcurve mold. This method measures the wetting forces between the probe wetting liquid (D . I . water) and 15 the backcurve mold surface defined by the relationship.
F = 2 Yl pcos 0 20 wherein F is the wetting force (mg) of the mold half being measured;
~ 1 is the surface tersion of the probe liquid, i.e., the water;
25 ~ P i8 the perimeter of the mold half at the meniscus (cm) when the mold half is partially immersed in the water; and e is the dynamic contact angle in degrees.

-20_ 21 8g564 A schematic diagram of the experimental set-up is l given in Figure 7, while the various perimetera are schematically depicted in Pigure 8.
A aample (901), such a8 the backcurve, i8 87lflp~n~
vertically on a microbalance (902) . The probe liquid 5 (903), such as water, is slowly raised to immerse the backcurve. The wetting force between the probe liquid and the backcurve as the probe liquid is being raised is measured by the microbalance which is recorded on a recorder 905. A trace of the wetting forces as a lO function of di8tance travelled by the water meniscus (904) over the backcurve surface is obtained. A typical water (backcurve) wetting force trace is given in Figure 9. In this way, the value of p can`be measured.
The probe liquid that is used to make these tests 15 is a common liguid or solvent which has a known surface ter~sion. The preferred probe liquid is water, which has a surface tension of 72.75 dynes cm at 20~.
From these mea~uL ~, the contact angle is calculated .
The inventors have determined that a backcurve with a water dynamic contact angle less than or equal to 100 produces contact lenses with significantly less holes.
It is more preferred that the contact angle be less than or equal to 905. It is even more preferred that the 25 contact angle be less then or egual to about 75.
Thus, mixing the appropriate wetting agent with the polystyrene or polypropylene making the mold half thereof and measuring the contact angle in accordance with the above procedure i8 an ea8y te8t to d~t~rm; n~
30 the feasibility of using the mold half in the process of -21- 2 ~ 86564 making contact lenses having a decreased tendency of l forming hole8 or puddles.
The wetting agents u3ed in the present invention are surface active chemicals, such as lubricants, anti-static agents or 3urfactant3 which when mixed with the 5 mold material to form the backcurve, ef~ectively changes the mold surface chemistry and its surface properties.
Preferred wetting agents that are utilized are the wetting agents, normally used in the plastic arts that are not toxic to humans. They include the nonionic lO 9urfactant9, cationic 8urfactants and anionic surfactants. Especially preferred are salts of fatty acids cnn~;l;ninS 16-30 carbon atoms. The preferred salts are stearates.
Stearates are salts of stearic acid. They include 15 ammonium salts and metal salts thereof. "Metal stearates" as used herein are the metal saltg of stearic acid. These metals include alkali metals, alkaline earth metals, i salts, Group 13 metals, Group 14 metals and transition metals, such as Group 12.
20 Examples of the metals include zinc, sodium, calcium, lead, barium, cadmium, aluminum, lithium, and the like.
Examples include EIYTECH RSN 248D, PETRAC CP-llLS, PETRAC
CP-115G, PETRAC 22, SYN PRO CALCIUM STEARATE PG, SYN
PROTYPE 114-36, WITCO F, WITCO EXTRA DENSE G, WITCO FP, 25 COMETALS SODIUM STEARATE, SYNPRO SODIUM STEARATE ST, WITCO HEAT STABLE, INTERSTAB ZN-18-1, PETRAC ZN-4, MATHE
CALCIUM STEARATE, MILJAC CALCIUM STEARATE, WITCO CALCIUM
STEARATE, MATHE SODIUM STEARATE, WITCO SODIUM STEARATE, WITCO T-l, COAD 20, 21, 23, 26 USP, 27B, 27D, 27F, 30 HYTECH RSN lS31, MATHE ZINC ST13ARATE S, MATHE ZINC
, ~ - ~

STEARATE 25S, MILJAC ZINC STEARATE, WITCO ZINC STEARATE, 1 PLASTOIUBE, SYNPRO ACF, SYNPRO 8 (Synthetic Product Zinc Stearate ~3), WITCO 42, WITCO 11, and the like.
Other pref erred wetting agents are oxygen ,-nntA;n;n~ amines 6uch ag ethyoxylated tertiary amines, 5 hydroxyalkyl tertiary amines ( i . e ., tertiary amine tri 6ub6tituted with alkyl groups ~nn~A;n;ng 1-20 carbon atoms which at least one of the alkyl groups substituted by hydroxy) and ~lA~-~rnAry ammonium compounds, especially quaternary ammonium sulfates. Examples of 10 oxygen r~ntAin;n~ amine6 are described in Kirk-Othmer "Encyclopedia of Chemical Technology, n Vol. 22, p.379-381, (1983), the contei~ts of which are incorporated by reference. Preferred hydroxalkyl tertiary amine are of the f ormula Rl~ N R
Rlii where R~1 and R~j, are alkyl of 1-20 carbon atoms cnn~A;n;n~ a hydroxy group and Rlo is an alkyl group of 1-20 carbon atoms. Examples of quaterrary ammonium salts are described in Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 22, pp. 383-384 (1983).
Examples include ARMOSTAT 410~, manufactured by AKZO, (ethoxylated tertiary amine), ATMER 163~, manu~actured by ICI Americas (N,N-BIS- (2-hydroxyethyl)alkylamine), 5 CYASTAT ~S, manufactured by CYTEC (3-I~auramidopropyl) trimethyli ;- methylsulfate, l AROSTATE 264A, ~nl1~Ac~tllred by PPG (Soy Dimethyl Ethyl Ethosulfate), and the like.
3o ,- :

-23- 21 8656~
Other examples of pref erred wetting agents are 1 listed hereinbelow Surfactant . 5u~Plier Antistat A21750 Polyccm ~ nt Armo3tat 310 Akzo,Ampacat Armostat 41 0 Akzo ArmoYtat 475 Akzo Atmer 16 ICI America~
Chemstat 122 Chemax Chemsat 122/60DC Chemax Chemstat 182 Chemax Eurestat T22 5chering Berlin R~ ' n~ A5 6 5 0 Humko Antistatic E~N 3-V Chemical ~ Atmer~ 1002 ICI Americas InL
Cyastat 609 Am. Cyanamid Cyastat LS Am. Cyanamid Cyastat SN Am. Cyanamid Cyastat SP Am. Cyanamid Eurestat 66 Schering Bedin Larostat 96 PPG
1arostat 451, 477 PPG
Markstat AL- 12 Argus Markstat AL-26,AI,-48 Argus Neutro-Stat A (Conc. ) Simco Addaroma IN Merix Ari~tac M & 2M CDC Infl.
3o 21 8656~

Surfactant SuPplier Antffog/Antstatic MCG Morix Antistat AS, 50059 Ferro Antistat AS50098 Ferro Antistat ETA Hf tech 5 Antistabc Agent 575 Houghton Angstatic Coating 1412 Coating Systems Aritistatc Spray Price-Driscoll Atmer 1 90 ICI Americas Atmer 8505 ICI Americas Atmos 150, Atmul 124 Humko Atmul 84 Humko The additives used in the present invention are materials that are k~own or commercially available.
15 They are al80 known release agents. Preferred additives are silicones, amide waxes, fatty acids, polyethylene and propylene waxes, mineral wax, oxidized waxes and the like .
As used herein, the term llsilicones" is a term 20 applied to a range of materials based upon a silicon oxygen polymer h~ khnn~ with a carbon cnn~;l;nin~ side chain of hydrocarbyl groups -nn~;~;n;ng 1-6 carbon atoms.
More specifically, it consists of a polymer having a structure consisting of alternate silicon and oxygen 25 atoms of the formula:
R --~ R -- I
- O - Sl O - Si O - Sl R -- R --n n --25- 2 1 ~6564 wherein each R may be different, but preferably the l 8ame and are a hydrocarbyl group and n is an integer ranging from 20 to about 1500. The molecular weight of the silicone ranges from 2000 to 100,000 g/mole, inclusive. The silicone3 have very low surface tension, 5 preferably 22-24 mN/m or dyn/cm. In~ addition, the silicones contemplated for use by the present invention are physiologically inert. They are stable, heat resiRtant, chemically inert, colorless and odorless.
The term silicones includes among other things, silicone lO oil and silicone wax. Examples include ABILWAX 9800 and 9801, L-42, ~-45, NM-l, VISC-lOM, SF96, SF1080, SF18-850 DOW CORNING 200, 203, 230, K~NTSTIK 406 NOO, KANTSTIK M-55, silicone wax (steroyldimethicone), dimethyl silicone, and the like.
15 ~ As used herein, amide waxe8 are waxes having the $ormula RlCO~I, wherein Rl is a hydrocarbyl radical and RlCONEIl has a molecular weight ranging from about 200 to about 2000 g/mole. There may be complete saturation in Rl or there may be at least one carbon-carbon double bond 20 in Rl. The amide waxes preferably have up to 40 carbon atoms, although it is preferred that the amide waxes contain from 12-30 carbon atoms. The amide waxes also include higher fatty acid amides, that is, fatty acids having an even number of carbon atoms, ranging from 12-25 30 carbon atoms. Examples include CRODAMIDE ER,CRODAMIDE OR, CRODAMIDE SR, CRODAMIDE 203, CRODAMIDE
212, EIJRESLIP 58, KEMAMIDE E, PARICIN 285, PARICIN 220, PETRAC ERMIDE, PETRAC SLIP-EZE, PETRAC VIN-EZE, PETRAC
SLIP-QUICK, ACRAWAX C (1,2-30 ethanediylbiscoct~ n .1,~), ADWAX 280 , EBS WAX, ~ 1 ~6564 EOSTALU3 FA1, PARACIN 285, ROSSWAX 140, CRODAMIDE EBS, 1 ~iu~ 047, ER, OR, 203, 2I2 KEMi~MIDE B, S, U,ethylene bis (stearamide), oleamide, erucamide, and the l ike .
Examples of fatty acid are CROD ACID, stearic acid, 5 and the like.
Polyethylene and propylene waxes as used herein are waxes of low, medium or high density of polyethylene or polypropylene, respecti~rely, having a molecular weight ranging from about 5000 to 200, 000 g/mole. Examples of lO polyethylene wax include EPOLENE C-13, C-14, C-15, C-17, C-18, E-10, N-10, N-11, N-21, N-34, HOECHST WAX PE 190, STl~NWAX, and the like. Examples of propylene wax are EPOLEN N-15P, and EPOLENE E-43P, and the like.
Other waxes such as mineral was, e.g., Montan wax 15 can al80 be u8ed- Montan wax contains three portion8, the wax portion, the resin portion and the asphalt portion. The wax ~ of Montan wax is a mixture of ~ long-chain ~C2~-C30~ ester ~62-68 wt%), long chain acids (22-26 wt%), and long-chain alcohol3, ketones and 20 l~ydluuclrlJull8 ~7-15 wt9~). The resin portion is approximately 70 wt % terpenes and polyterpenes and 30 wt % resinic acid and oxyreginic acid, while the a3phalt portion is belieYed to be polymerized esters of oxyresinic acid.
25 ~ Oxidized waxes are alkane hydrocarbons ~paraffins) having a molecular weight of 100 - 2000 g/mole. They are capped at the ends with either ester, carboxylic or hydroxy groups. Examples include carnauba wax and RoE~swax, such as Rosswax 100 and 1343 and the like.

As defined herein, glycerol egterg are hydrocarbyl 1 esters of glycerol having a molecular weight of 200 to 2000 g/mole. They include monoglycerides, diglycerides and polyglycerides, including fatty acids of triglycerides. Examples include PATIONIC 900, 901, 902, 5 907, 919, 1042 and 1042 K, and the like.
Alcohol esters contain 5-2000 carbon atoms, and include such species as LU~3E 106, and the like.
Complex esters are copolymers of organic phosphate esters having a molecular weight of 200-2000 g/mole 10 which contain glyceride9, organic acid derivatives and fatty acids. Examples include KANTSTIK FX-9 and Q, and the like.
Combination of the additives ligted hereinabove or blends include MOLD EASE PCR, MOLD WIZ INT 33 PA, INT 38 15 E~,~ INT 33 T~DK, and the like. It i9 preferred that the combination have a molecular weight ranging from 200 to 200,000 g/mole.
As defined herein, hydrocarbyl is an aliphatic, cy~lA1 iph~tic, or aromatic moiety ~nnt~in;ng carbon and 20 hydrogen atoms, having 1 to 2 0 0 carbon atom~ . The hydrocarbyl moiety may be straight chain, or hr~nt h~ or cyclic. If cyclic, the rings are preferably fused. The hydrocarbyl group may be completely saturated or partially saturated or completely aromatic or 25 conjugated. The hydrocarbyl moiety may contain at least one double bond . It is pref erred that the hydrocarbyl group contains 1-100 carbon atoms.
The most preferred additives are SF 1080 Silicone Oil, Int 38E~ Ester Complex, Kantstick Q Ester Complex, 30 FC 430 Ester Complex, A~3IL(9 Wax 9801, Silicone Wax (stearyl dimethicone), SF 96-5 Silicone Oil, L-42, 1 Acrawax~D C (1,2 ethanediylbis-O--tA-i~r~
polystyrene 202, FC 4331 Ester Complex, SF 18-350 gilicone Oil, L-45 (dimethyl silicone), A13IL~ wax 9801 (cetyl dimethicone), VSC-lOM, Carnauba Wax and Ross Wax 5 100. The more preferred additives are SF 1080 Silicone Oil, Int. 38H Ester Complex, Rantstick Q Ester Complex, FC 430 Ester Complex and Abilwax 9801 Silicone Oil.
Exemplary formulations include polystyrene with the following additives or wetting agents in the indicated 10 amount8, ADDITIVE AMOUNT BY WEIGHT
ABILWAX 9801 0.25%
ABILWAX 9801 1. 00%
FC 430 0.25%
KI~NTSTICK Q 0.25%
KANTSTICK Q 1. 50%
SF 1080 5%
SF 1080 0 . 25%
AXEL 33 P/A O . 25%
AXEL 33 P/A 2 . 50%
AXEL 33-H 0.25%
AXEL 38-H 2 . 5%
GE 1080 0 . 5%
GE 1080 0.25%
CYASTAT LS O . 05%
CYASTAT LS O . 50%
CYASTAT LS 1 . O 0 96 ATMER 163 - 50%

The composition of the pregent invention i9 1 utilized to replace articles of ~-n1lf~rtl-re wherein polystyrene or polypropylene i8 normally utilized. In one such application, the compo~3ition of the present invention is employed to comprise a mold half of 5 aeparable two part mold assembly u~; 1 i 7~.1 in the preparation of soft contact lense3. The mold is comprised of at least two piece!3, a female, concave piece and a male convex piece, forming a cavity therebetween, when ~uch pieceg are mated, with at least 10 one f lange thereabout . At least one of the pieces is comprised of the compogition of the present invention.
In other words, both mold halves or one mold half i8 comprised of the composition of the present invention.
When only one mold half i3 compriged of the compoE;ition 15 of the pre8ent invention, the other mold half is comprised of a thermoplastic polymer that is normally u~ed to make mold halves for contact lenses, as described hereinbelow. It is preferred that the base mold half be comprised of the compo~ition of the present 20 invention.
A preferred mold assembly is depicted in Figures 3 and 3a, which illustrate regpectively top elevational and side views of one embodiment of a front mold half lO
useful in the production of a contact lens by the 25 polymerization of a polymerizable composition in a mold assembly comprised of two complementary front and base mold halves. Ag indicated, the mold halves are useful in the production of contact lenses in that lenses can be made which are; '; ;1~l y ready to wear, and in that 3o _30_ 21 86564 unswelled ler~eA can be made which need to be swelled l lhydrated) to be ready to wear.
Although as indicated above, the front mold half 10 may be comprised of the present formulation, it i~
preferred that the front mold half 10 is formed of a 5 suitable thermoplastic polymer which is sufficiently transparent to ultraviolet light to allow irradiation therethrough with light to promote the subsequent polymerization of a soft contact lens. ~xamples of suitable materials include polyolefins such as low, lO medium, and high den8ity polyethylene, polypropylene, including copolymers thereof; poly-4-methylpentene; and polystyrene. Other suitable materials are polyacetal resins, polyacrylethers, polyarylether sulfones, nylon 6, nylon 66 and nylon~11_ Thermoplastic polyesters and 15 variou8 fluorinated materials ~uch as the fluorinated ethylene propylene copolymers and ethylene fluoroethylene copolymers may also be utilized. Other materials that can be ~ .1 for the front mold half are described in U. S . Patent No . 4, 565, 348 . The most 20 preferred material for the front mold ha~f i8 polystyrene or polypropylene.
The front mold half 10 defines a central curved section with an optical quality concave surface 15, which has a circular circumferential parting edge 14 25 extending therearound. The parting edge 14, shown in enlarged detail in Figure 3 (b), is desirable to form a sharp and uniform plastic radius parting line (edge) for the subsequently molded soft contact lens. A generally parallel convex ~3urface 16 is spaced from the concave 30 surface 15, and an annular essentially uniplanar flange 2 ~ 86564 18 is formed .o~ n~; n~ radially outwardly from the l 8urface8 15 and 16 in a plane normal (perpendicular) to the axis (of rotation) of the concave surface 15. The concave surface lS has the dimension3 o the front curve (power curve) of a contact lens to be produced by the 5 front mold half, and is sufficiently smooth such that the surface of a contact lens formed by polymerization of a polymerizable composition in contact with the surface is of optically acceptable quality. The front mold half is designed with a thinness (typically 0 . 8 mm) lO and rigidity effective to transmit heat therethrough rapidly and to withstand prying forces applied to separate the mold half from the mold assembly during demolding .
Figures 4 and 4 (a) illustrate respectively top, 15 elerational and side views of one: ~ '; of a second, or back curve mold half 30. The back curve mold half is designed with all of the same design considerations mentioned hereinabove with respect to the front curve mold half 10.
The back curve mold half 30 i~ preferably formed of the composition of the present invention. The back curve mold half 30 defines a central curved section with an optical quality convex surface 33, a generally parallel concave surface 34 spaced from the convex sUrface 33, and~an annular essentially uniplanar flange 36 formed PY~nrl;ng radially outwardly from the surfaces 33 and 34 in a plane normal to the axis (of rotation) of . -concave surface 34. The convex surface 33 has the .1; qinnF- of the rear curve (which rests upon the cornea of the eye) of a contact lens to be produced by 2 1 8656~

the base mold half, and is suf f iciently smooth such that l the 8urface of a contact lens formed by polymerization of a polymerizable composition in contact with the surface is of optically acceptable quality. ~he base mold half is designed with a thinness (typically 0 . 6 mm) 5 to transmit heat therethrough rapidly and rigidity effective to withstand prying forces applied to separate the mold half from the mold assembly during demolding.
The mold halves 10,30 defi~le generally triangular tabs 26,37 integral with the flange which pro~ect from 10 one 8ide of the flange. The tab 37 extends to the inj ection hot tip which supplies molten thermoplastic to the mold, and also defines therein angled (e.g., 45) web sections 22,38 for smoothing the flow of the polymer wave front and thus to avoid jetting, sink marks, weld 15 line8 and other undesirable flows which would impair the optical quality of the mold half. ~he mold halves 10,30 also define small circular projections 25,35 which serve aY traps in the molding process to; ,h; 1; 7e small plugs of colder polymers that may form at the injection 20 hot tip between cycles.
The reactive monomer mixtures (polymerizable - -composition) which are polymerized in the mold assembly comprised of the two mold halves include copolymers based on 2 -hydroxyethylmethacrylate ( ~HEMA" ) and one or 25 more . ~ rg 8uch ag 2-hydroxyethyl acrylate, methyl acrylate, methyl methacrylate, vinyl pyrrolidone, N-vinyl acrylamide, 11YdLU~Y~LU~Y1 methacrylate, isobutyl methacrylate, styrene, ethoxyethyl methacrylate, methoxy triethylene/glycol methacrylate, glycidyl methacrylate, 30 diacetone acrylamide, vinyl acetate, acrylamide, hydroxytrimethylene aerylate, methoxyethyl methacrylate, 1 acrylic aeid, methaerylic aeid, glycerol methacrylate, and dimethylamino ethyl acrylate.
Preferred polymerizable compositions are diselo8ed in U.S. Patent No. 4,495,313 to Larsen, J.S. Patent No.
5 5,039,459 to Larsen et al. and U.S. Patent No. 4,680,336 to Larsen et al., whieh inelude anhydrous mixtures of a polymerizable hydrophilie hydroxy ester of aerylie aeid or methaerylie aeid and a polyhydrie aleohol, and a water displaceable ester of boric acid and a 10 polyhydroxyl compound having preferably at least 3 hydroxyl groups. Polymerization of such eompositions, followed by displaeement of t~e boric acid ester with water, yields a hydrophilic contact lens. The mold assembly of the present invention described herein may 15 be u8ed to make hydrophobie or rigid eontaet lenses, but the manufaeture of hydrophilie le~ses is preferred.
The polymerizable eompositions preferably contain a small amount of a cross-linking agent, ugually from 0 . 05 to 29~ and most frequently from 0.05 to 1.096, of a 20 diester or trieste~. Bxamples of representative cross linking agents include: ethylene glycol diaerylate, ethylene glycol dimethacrylate, 1,2-butylene dimethacrylate, 1,3-butylene rlll ~h~rrylate, 1,4-butylene dimethacrylate, propylene glycol diacrylate, 25 propylene glycol dimethacrylate, diethylglycol dimethacrylate, dipropylene glycol dimethacrylate, diethylene glyeol diacrylate, dipropylene glyeol diaerylate, glyeerine trimethaerylate, trimethylol propane triaerylate, trimethylol propane 30 trimethaerylate, and the like. Typieal eross-linking _34_ 2 t ~6564 agentu usually, but not necessarily, have at least two l ethylenically unsaturated double bonds.
The polymerizable compo3itions generally also include a catalyst, usually from about 0 . 05 to 1% (w/w) of a free radical catalyst. Typical exampleu of such 5 catalysts include lauroyl peroxide, benzoyl peroxide, isopropyl percarbonate, azobisi80butyronitrile and known redox uyntems such au the ammonium persulfate-sodium metabisulf ite combination and the like . Irr~ n by visible light, ultraviolet light, electron beam or a lO radioactive uource may al50 be employed to catalyze the polymerization reaction, optionally with the addition of a polymerization initiator. Representative initiatoru include camphorquinone, ethyl-4- (N,N-dimethyl-amino) benzoate, and 4- (2-hydroxyethoxy) phenyl-2-15 hydroxyl-2-propyl ketone Polymerization of the monomer or monomer mixture in the mold as3embly i~ pre~erably carried out by expouing the composition to polymerization initiating conditions.
The pref erred technique is to include in the 20 compo8itiOn, initiatoru which work upon exposure to ultraviolet radiation; and exposing the composition to ultraviolet radiation of an intensity and duration effective to initiate polymerization and to allow it to proceed For this reason, the mold halves are 25 pref erably tranuparent to ultraviolet radiation . Af ter the procure utep, the monomer is again exposed to ultraviolet radiation in a cure step in which the polymerization iu permitted to proceed to completion.
The required duration of the l~ ; n~ r of the reaction 3o 2 1 ~6564 can readily be ascertained experimentally for any l polymerizable composition As indicated at step 108 in Figure 1, the monomer or monomer mixture ig degasged prior to the filling of the front curve mold half in order tD remove dissolved 5 gases. l is removed because of its deleterious effect on polymerization. Other gages, including N" are removed to avoid the formation of gas bubble3 when the monomer is erpelled from the relatively high pre3sure of the pump line which suppliea the fill nozzle, to 10 encounter the atmospheric or 8-1hA ~rh~ric N, pressure of the filling and assellLbly chambers.
The contact lens are prepared by variou~ techniques known to be skilled arti~an, except at least one mold half iB compri~ed of a formulation of the present 15 invention- For example, they may be prepared by the direct molding of hydrogel contact lenseg, which is disclosed in U.S. Patent No~. 4,495,313 to Larsen, 4, 565, 348 to Larsen, 4, 640, 489 to Larsen et al ., 4,680,336 to Lar~en et al., 4,889,664 to Larsen, et al.
20 and 5,039,459 to Larsen et al. Another method is schematically depicted in Figures 1 and 2 aE; will be hereinafter described in detail. Also see U.S. Patent No. 5,540,410 to Lust et al.
In the description hereinbelow, the procedure is 25 described in which the ~ackcurve mold i~ comprised of the fULI lA~ n of the pregent invention. Thig is just exemplary ag the front curve mold or both the backcurve mold and the front curve mold may be comprised of the instant formulation.

-36- 2~ 86564 For efficlency, ea3e of operation and cycle times, 1 the front curve mold and back curve mold are made using injection molding devices. It is preferred that the thermoplastic material for the front lens and the composition of the present invention for the back mold 5 i8 provided in the form of pellets or particles of relatively high surface area which have e~uilibrated fully with available oxygen available in the atmosphere.
In this nethodology the mold ig degigned to produce fully formed lens mold parts directly, that is without 10 a880ciated 8upport 8tructure such as a frame; there is in consequence no need to dissociate the part from llnn~Prlf~fl polymer material on fl 1~1in~, and the lens mold parts may be directly collected by automated robotic means for delivery to the transport means. In 15 any given cycle, any number of mold parts may be prapared but for convenience of handling, typically 8 lens mold parts of concave or convex conf iguration are prepared in a given cycle and transf erred by automated robotic means to a pallet of aluminum or stainless steel 20 in which they are received and supported in a regular spatial array adapted for further operations.
It should be understood that at most stages of the t~7nt; n~ R proce88, ingpection meang are operational to effect rejection of parts against reference criteria;
25 hence, following injection molding, inspection, generally visual, employing photoelectric means, for example, for such defectg as haze, mold defect as in configuration due to;, u~eL material feed and the like may lead to rejection of a part and thus disposal. To 30 m~int~1n the continuity and consistency in line 2~ 86564 operations generally a whole mold cycle or pallet of 1 len8 mold part8 will be expelled from the line following diacovery of a defect in any one lens mold part. 13ach of the pallets contain a unique bar code number for use in pallet tracking and guality control procedures 5 1~til;7ing bar code scanners.
The apparatus ~or removing and transporting lens mold parts from the mold to the transport means includes hand means for receiving the mold parts and a support subassembly capable of sliding and pivotable I v~ t 10 required for tran8fer of the mold parts to the horizontally operating transport means.
As illustrated in Figures 1 and 2 inj ection molds #1 and #2, shown at steps 101 and 102 in the f low diagram of Figure 1, mold respectively front curve and 15 back curve len8 mold parts or sections; they may be located in tandem as shown in Figure 2 or to shorten exposure to the atmosphere still further, they may be located in a common plane intersecting a bifurcated transport line, even perpendicularly oriented thereto in 20 the 8ame plane.
Robotic means 103 ,104 are provided adj acent the mold registry and ~ . t station for receiving concave-and convex lens molds, respectively and transferring said mold part to a low oxygen environment 25 at a high production cycle rate, as noted at step 105.
In the course of or following complete degassing of the lens mold sections as indicated at 106 in Figure 1, the pallets c"ntAin;n~ concave and convex lens mold sections are ordered into interleaved relation and 30 degassed when enclosed in feed conveyor such that -38- ~l 86564 t~ t~ q,l l t may effect their operative 1 int~L~llycl~ into molding relation.
The sequencing conveyor 32 including the interleaving station 40 i8 enclosed and pressurized over its entire length with an inert gas, conveniently 5 nitrogen. The amount of nitrogen i8 not critical, it being suitable to use just enough nitrogen pressure to ef f ectively exclude the atmosphere under the operating conditions experienced. In the nitrogen tunnel surrounding sequencing conveyor 32 the freshly prepared lO len8 mold blanks are degassed as indicated at step 106 in Figure 1.
The concave lens molds are filled with the reactive monomer composition at step 107 and the concave and convex lens molds are placed into registry and urged 15 into complementary molding relation. The filling and assembly zone 50 surrounds a portion of the conveying or transport means 32, which deliverg to the zone pallets concave and convex le~s mold sections, respectively, and at the terminus of the zone carries pallets of paired 20 and filled molds to the procure zone. The filling and assembly zone illustrated in Figure 2 at 50 is defined by a geometrically appropriate, trangparent enclosure, generally of rectangular cross-section, formed of any suitable thermoplastic or metal and thermoplastic 25 con8truction.
As illustrated at 107 in Figure 1, the concave lens mold section3 are filled with degassed monomer composition from step 108, and then tran8ported to an a~sembly module optionally having a vacuum chamber 30 formed intermittently within the nitrogen tunnel in _39_ 21 8~5~
which filled concave lens molds are engaged with convex 1 mold 9ection8 in vertical alignment and in mating relation, such that the reactive monomer composition is trapped between the optical surfaces of the respective mold sections and at least partially sealed by the 5 F'n~5 ~ of the parting edge formed peripherally in each of the lens mold gections. If pregent, the vacuum is released. Then, the mated mold is passed through nitrogen to the precure station, an integral part of the nitrogen tunnel.
Following assembly of the mold parts, the incipient lens monomer is precured at step 109 in the precure module 60 of the present invention. The process of the procure involves clamping the mold h~lves in registration and then precuring the monomer or monomer 15 mixture to a gel like state.
Following precure, the polymerization of the monomer or monomer mixture is completed in curing tunnel 75 as indicated at step 110 with irradiation.
In the cure zone (75), the monomer/diluent mixture 20 i8 then cured in a W oven whereby polymerization is completed in the monomer ~8) . This irradiation with actinic visible or ultraviolet radiation produces a polymer/solvent mixture in the shape of the f inal desired hydrogel. In addition, the cure zone alE;o has a 25 source of heat which is effective to raise the temperature of the polymerizable composition to a temperature suf f icient to aggist the propagation of the polymerization and to counteract the tendency of the polymerizable composition to shrink during the period 30 that it is exposed to the ultraviolet radiation.
~ ~

-40- 21 8~564 After the polymerization process is completed, the 1 two halve8 of the mold are separated during a demolding step leaving the contact lens in the fir3t or front curve mold half 10, from which it is subsequently removed. It should be mentioned that the front and back 5 curve mold halves are used for a single molding and then discarded or disposed of.
Heating the back curve len8 mold creates differential expansion of the heated mold polymer relative to the cooler lens polymer which shif ts one 10 8urface with re8pect to the other. The resultant shear force breaks the polymerized lens/polymer mold adhesion and assists in the separation of mold portions. The greater the temperature gradient between the surfaces of the mold portions, the greater the shearing force and 15 the easier the mold portions separate. This effect is greatest when there i3 maximum thermal gradient. As time t-f~nt~n~l.oq, heat is lost through c~nfl~ t;~)n from the back mold portion into the lens polymer and the f ront mold portion, and then collectively into the surrounding 20 environment. The heated back mold portion is, therefore, promptly removed 80 that very little energy is transferred to the polymer lens, avoiding the possibility of thermal decomposition of the lens. The heating may be accomplished by techni~ues known to one 25 skilled in the art such as by steam, laser and the like.
The process of laser fl lfl;n~ is described in U.S.
Patent No. 5,294,379 to Ross et al.
If the heating step is hot air or steam, af ter the heating step, the back curve is pried from the front 30 curve and mold in the mold assembly, as indicated at .
2 ~ 86564 Step 111. If on the other hand, the heating is by laser l or infrared, no prying is Used and the back curve 3eparates spontaneou31y from the front curve.
The ~ lin~ a3semblies of the mold separation apparatua 90 each physically pry the back curve mold 5 half 30 from the front curve half 10 of each contact lens mold to physically expose each contact lens situated in the lens mold for conveyance to a hydration station for hydration of the lenses. The prying process occurs under carefully controlled conditions, 80 that lO the back curve half 30 will be separated from the front curve half 10 without destroying the integrity of the lens f ormed in the lens mold .
After the mold assemblies have been separated in the demold apparatus 90, each pallet r~ntAinin~ the 15 front curve mold halve8 with an exposed polymerized contact lens therein, ig subsequently transported to a hydration station for hydration and demolding from the front curve lens mold, inspection and packaging, as indicated at Step 112.
In the processes described hereinabove, when the base mold does not contain the additive or wetting agent therein, many lenses that were formed were unusable because they ~ ntA;n~d defects, such as chips or edge tears or holes, i . e ., voids in the center of the cast lenses. Without wishing to be bound, these defects are caused by two different mechanigms. The chips are caused during the demolding process and were noticed when the base curve was separated frorn the front curve using the prying I ~hAni ~ described hereinabove.
30 However, when the appropriate additive is present in the back curve, demolding is facilitated and the back curve 1 i9 more ea9ily removed. As a result, there are greatly reduced instances of lens damage during the demolding step, in which the back curve is separated from the front curve and the lens, which stays in the front 5- curve. Without wishing to be bound, it is believed that the additive in the back curve modifies the adhesion forces between the lens and the base curve. For example, when polystyrene alone is used, it adheres very strongly to the polymeric material of the lens; however, lO when the additive is added to the polystyrene, the presence of the additive weakens the friction forces between the polystyrene and the lens material, making it easier to separate the back curve f~om the lens and the front curve mold. Thus, there is less stress on the 15 len8 8urface during demolding, making it easier to separate Thus in a prying action betweeIl the lens mold halves, as occurs during ~ ing, the lens will slip more easily from the convex mold half. Consequently, when the back curve is made up of the mold relea8ing 20 f' lA~ n of the pregent invention, separating the back curve from the front curve and the leng hag become facile. Consequently, less stringent conditions are required for. demolding than that used heretofore. In fact, in certain embodiments guch ag with A13IL WAX 9801, 25 demolding occurs without the temperature gradient thus f~l;min~t;ng the necegsity of heat in the rl lrl;n~ step.
Thus, using the compositions of the present invention to separate the back curve from the mold a88embly, len8e8 can be ~ 1 tif~d in good yields right af ter the demold 30 tunnel at lower temperature, such as about 60 to 70C, 2 ~ 865~4 The additives that are added to the mold material that 1 effectuate those changes are the mold release agents the oils, soaps, waxes, and the like, describe herein.
Wetting agents, when added to the lens mold increase the wetting of the mold material. These 5 wetting agents include the anti-static compounds, i.e., the alkoxylated amineg and the ~~ rn~ry complexes and the stearic salt8, described herein.
Without wishin~ to be bound, it i8 believed that the original polystyrene or polypropylene mold (i.e., 10 the mold without additional wetting agents) was a low energy heterogeneous surface having a small portion of high energy area. For example, the mold surface when composed of polystyrene has a mold surface free energy of 42 dynes/cm. A heterogeneous polystyrene or 15 polypropylene mold surface with small portions of high energy surface area caused local non-wetting and voids, which in turn led to lens holes. The lens hole problem was a problem of prior wetting between the reactive monomer mix and the mold surface.
20 - ~ Nhen the wetting agent is added to the mold surface, it significantly improved its wettability. The surface became more homogenous and the high energy surface area was significantly increased. As a result, using the mold material wetting formulation of the 25 present invention instead of the typical formulation, lens holes were reduced significantly. For example, using zinc stearate, as the additive in a polystyrene back curve mold, the lens holes were reduced from the typical 10 to 15~ to lesg than 29~.
3o .
_44_ 21 86564 However, in many cases, even when the thermoplastic 1 material i9 admixed with either a wetting agent or additive, the resulting contact lenses have not only a minimum of holes or tears, respectively but concomitantly therewith, the contact lenses have 5 improved yields. For example, when the contact lenses were ~l!"L':d utilizing a backcurve comprised of polystyrene and 196 zinc stearate as the wetting agent, as described hereinabove, the resulting contact lenses had significantly less hole3. Lens puddles are also 10 8ignif icantly reduced. Concomitant therewith, however, the amount of chips and tears were decreased, with lens yield improving 7 to 99~. Although such result may indicate that zinc stearate may also act as a mold releasing agent, further experiments show t~lat the zinc 15 8tearate i8 not acting in that capacity. In a study measuring demold forces at various temperatures between contact lens and the polystyrene mold, the results show that there was little or no effect when zinc stearate was used. The major e~ect on lens demold (or lens 20 release) was due to the higher temperature.
Observations of lens demold operation during production did not show any de-mold difference between molds with and without zinc stearate addition.
8imilarly, a backcurve comprised of Abilwax, was 25 not wettable in accordance with the wetting test as described hereinabove. It produced, as expected based upon the tF~ hin~q herein, contact lenses having significantly less chips and tears. However, as shown in Example 8, under the conditions therewith, 3o 2~ 86564 concomitantly, contact lenses where produced having less 1 holes~
Unless indicated to the contrary, the molecular weights are in units of grams per mole. Moreover, unless indicated to the contrary, the percentages are 5 given in weight percentage3.
The pre8ent invention is more specifically described by the following illustrative examples.
However, it is to be understood that these examples are only described to illustrate the invention, but not to 10 limit 8cope o~ the present invention.

~

~ ~ :

2~ 86564 Frame8 were molded on a 60 -ton Nestal from the candidate formulations listed hereinbelow in Table 2, in accordance with the procedure described herein. As described herein, and shown in Figure 5, the pallet 5 c~nt;l;n~d 8 base mold halves (cavities) arranged as depicted therein. The mold halves were comprised of the various f~.L, ls~t;~nq described hereinbelow and contact lens were prepared in accordance with the procedure described herein.
0 .t The frame parameters are presented in the following Table .

-4~ 6564 TABI,E 1 FRA7.1E A~tALYSlS
c. I C-~ C:6 C-~
liU~tTS~lAlJ 202 5 ~ (Poly~t~lene~
FF~AME ~I RA171~5 1.~-7 I.U7 ~.~61 S.~.IJ
p/V 0.~57 ~.576 1.361 I.U~
FRA~IE 12 MDIUS 1.~4~ 57 ~.~J7 ~.~.19 rrv 0.191 ].7-1 ~.5t 1 0.916 FR~IE 1~ F~ADIUS 1.~19 t.46~ 1.-1~ .-02 plV 0.95~ ~.250 2.
~IUNT5MAN 201/PvDF I Po I ys t y r ene ~
tF~lE.II Rl~DIUS 1.172 8.8B1 1.119 1~75 PIV 0.651 0.557 0.595 0.65~

tRN~lE 12 RADIUS t 179 I.B~ 87 1.117 prV 0.121 0.631 0.549 0.552 FRAI.IE /~ F~ADIUS ~.159 a.at6 1.179 ~.172 PIV 0.5~5 2.7Y6 1.1l~ 2.297 IIUNTS~IAN 20V0.2225~ SF1080 I sl L icone oi I ~
FF~IIE 11 RADIUS 7.155 7.161 7.~7t 7.-5-PIV 0.561 0.677 0.~96 0.~5~
t~l-lE n P~ADIUS 7.~57 7.~62 7.~69 7.~5-25 : Plv 0.156 0.~50 0 57~ 0.69~
tPJ~E 13 RADIUS 7.15~ 7.161 7.170 7.-5-PIV 0.579 0.72- 0.l1~ 0.9C0 3o -48- 2 ~ 86~64 FlNAL ~ALYSIS
C3 C6 C-l IIUI-lSMAN102~0.~5F1080 ~Sil~cone ol11 5 FI~ IE ~I RA171US 7.~ 7.~7 7.~6~ 7.~3 p~V 0.~26 0.~7 0.~2 O.~tO
.IE ~2 RJ~DIUS 7.156 7.~9 7.t67 7,1~1 Irlv 0.611 0.-l~ 0.~1~ o.--g ~1E ~ RADIUS 7.~56 7.~62 7.~67 7.~SI
PIV o.~ o.~ o.~ o.~l 15 ~ =

l.EGEND:
C-1 cavity ONE of the pallet : C-3 cavity THREE of the pallet C-6 cavity SIX of the pallet C-8 cavity EIGHT of the pallet P/V peak to valley roughness, an inter~erometric measurement PVDF polyvinylidene fluoride _49_ 2 1 86564 In table 1, P/V is a roughnegg measurement, wherein l a lower number is a better result. The C-legend refers to the cavity in a frame BO that the data as pre~ented PliTn;ni~ cavity variations.
As can readily be seen from the data in Table l, in 5 all cases, when the additive, such as SF 1080 was preaent in the mold, the P/V valve were signif icantly lower than in its absence. Thug, the data clearly show that the frames using a mold rnn~;n;n~ the additive rr~lllr~ smoother lenses.

-50_ 21 86~64 EX~MPLE 2 Frames manufactured from sample candidate f,~ lAti~nR plug a control, indicated in the key to Table 2, were prepared on the Acuvue Pilot lens to ~-nllf;~t~lre lengeg in accordance with the procedure 5 described in the present 3pecification. The re3ult3 are presented in Table 2.

4 of Edg~ D~f~ctll TOTAL
SET t CHIPS
CHIP TI~AR AND TEARS
44 . 50 1. 90 46 . 40 II 20.40 1.10 21.50 III 17.40 2.20 19.60 IV 13 . ~0 0 . 00 13 . 80 V 14.10 2.20 16.30 VI 11.50 6.30 17.~0 VII Z2.50 15.00 37.50 VIII 32.50 5.00 37.50 IX 5 . 00 15 . 00 20 . 00 X 10 . 00 10 . 00 20 . 00 XI 21.60 5.40 27.00 XII 27.50 10.00 37.50 3o 35~ -2~ ~656~

TAI~LE 2 (CONT. ) KeY
HUNTSMAN 202 p~
5 II 0.5% GE SF1080 III 0.25~ GE SF1080 IV 1. 0i ABILWAX 9801 V 4.0~ A~3ILWAX 9801 VI 0.25% 3M FC430 VI I 2 . 5 % AXEL 3 3 VIII 0.25% AXEL 33 IX 2 . 5~ AXEL 33 ' X 0.25~ AXEL 38 XI 1. 50% KiWTSTIK Q
xrl 0.25t I~ANTSTII~ Q
As can be readlly seen by the data in Table 2, the total amount of edge defects (chips and tears) i~ lower in all cases and signif icantly lower in many cases when the additives i~ present.

21 8656~

In thi8 8et of experiments, a study was ~ n~ rtpf~
to evaluate the ~ l~;n~ of different compounds plus a standard polystyrene as base curve8.
The lenses (14.0 Acuvue formulation) were processed 5 on the WK Maximize lab line in accordance with the procedure described herein using vacuum deposition and 30 sec W pre-cure under weight. They had additional four minutes of W cure without weight at 60 in the R; 1 ;lt~l tunnel. The frameg were kept thermostated in 10 an oven with hot air circulation i 1. 5C prior to demold, transferred to an aluminum pallet kept at the same temperature and demolded immediately af ter the WK
lab demolder mark 1 which simulates the i ,v, ~ of the mark 1 demolder at pre~ent installed in the Maximize 15 pllot line at Vistakon.
No steam was applied.
t: 3 . 5 deg O . 5 sec fast 6. o deg 3 . 0 sec slow 15 deg 4.4 sec slow (end ~ast) One side was preyed apart. The frames were ;nRrect~rl in a gtereomicrogcope at 10 x immediately after demold. Broken BC flanges, lens lift, missing 25 lenses and tears were recorded. Results from this demold inspection are shown in Table 3.
All lenses, except thoge with broken f langes, were hydrated in simulated Maximize process: 5 mins at 70(, O . 0596 Tween 80 in D1-water, followed by 3 mins in D1-3o water + storage overnight in bufered saline.

21 ~6564 The lenses were inspected for visual defects in a 1 D~2 u8ing the Vistakon pilot line standards. Theconditions are indicated in Table 3.
TA~Le 3 HATÆ~IAL ~ CH + T~ t HO
PolyDtyrene 20 3 Polyntyrene/CE 1080 0 . 5~ 20 3 ~olyutyrene~ABILWAX 9801, 1~ 8 2 Polyntyrone/a8ILWAX 9801, 4~ 10 2 Avq. valv~ of 3 ruml only 1 run w~ performed l~ey CH -- chlpll HO - Hol---15 TR . T -r-As clearly shown by the data, a preferred embodiment in this run is the mold of polystyrene with A}3ILWA~3, i.e., silicone wax which produced contact lenses having significantly less chips and tears therein than when the lenses were comprised of polystyrene 25 alone.
3o ~ 1 86~64 p~E 4 1~ Zinc ~tearate (~}nst) was mixed with poly~tyrene to produce backcurve moldA. The contact lense~ were prepared in accordance with the procedureg described 5 herein. The amount of hole~ and the overall yield were measured and compared with a control wherein no additive waE; added. Three trial~3 were conducted, and the re~ult~
are indicated hereinbelow.

3o 2 t 86564 TRIAL ADDITIVE HOLES YIELD
Control 23% 67%
1% ZnSt 2% 85%
added Control 23% 58%
5 2 1% ZnSt ~2% 84%
Control 62% 35%
1% ZnSt 169~ 78%
As clearly shown, the back curve mold compri~ed of polystyrene admixed with Zinc ~tearate showed signif icant reduction of hole3 and signif icant increase in lens yields compared to those of the control EX~MPLE 5 Various Rurface active anti-gtatic agentg indicated hereinbelow were admixed with polystyrene to produce 20 backcurve molds. The contact lenses were prepared in accordance with the procedure described herein and the amount of holes meagured and compared with the control wherein no additive i~ used. The results are indicated hereinbelow:
25 : : -: _ 35 ~

-56- 2 ~ 865~4 ANTISTATrC AGENTS MANUFACTURBR COMPOUND MOLD hOLES
MATER IAL
ADDITIVE

17 . 2 LAROSTAT 264A~ PPG Soy Dimethyl 0 . 5t 53 LARSTAT
Ethyl 264A
Ammonium Etosulfate LAROSTAT 264~ PPG Soy Dimethyl Lt 2.6-LARSTAT 3 . 6;
Ethyl 264A' Ammonlum Btosulfate CYSTAT LN(~ CYTEC 3 -Lauramido- 0 . 5% 2 . 3 propyltri- LYSTAT LNa' methylul methylsulf~te 15 CYSTAT LN~ CYTEC 3-Lauramido- l~ 16.1-propyltri- CYSTAT LN~9 21.6 methylul ammonium methylsulfate ARMOSTAT 410 A!~20 Ethoxylated 0 . 5t 10 7t Tertiary ARMOSTAT
Amine 410 20 ARMOSTAT 410~ AK20 Ethoxylated lt 3 Tertiary ARMOSTAT
Amine 4 10 ATMER 163~ ICI A~SERICA N, N-Sis(2- o.s~ 1.0-hydroxyethyl) ATMER 163(D 1.3"
alkylamine ATMER 163~9 IC~ A~5ERICA N, N-Sis (2 - lt 0 . 8~i-r~ r~Ll.rl) ATMER 163~ 1.3 c~ alkylamine ZINC STERATE a'' SYNPRO ZINC STEARATE 1~ ZINC 0 . 7 -STEARATE 7 . 5t ZINC STERATE 8~' SYNPRO ZINC STEARATE 2'~ ZINC 2.~3t STEARATE
3o 21 8656~

EXAMPI,E 6 Following the procedures of Examp1 eg 4 and 5, the following materials were u8ed to make the backcurve8 and the len8es were produced in accordance with the degcription herein. The re8ult8 are indicated 5 hereinbelow.
Hole Count8 of Len8e8 Made U8ing Variou8 Backcurve Material Vioual Audi nn A ' Backcurve MaCerial used tn Tu el udlts to Produce ehe Lenses '~ 95~ CL ~ 95%
0 Holes Holes CL
HCC202HlY- (base resin; 9 8 2.4 15.7 4.5 productlon) HCC204SONb ~base regin~ 8.6 2.3 7.0 3.1 0.25% CYASTAT LS/HCC204HON 0.7 0.5 1.7 1.6 0.54 CYASTAT L8/HCC204HON 0.2 0.4 0.7 1.0 151~ ZnSt8/HCC204DON 0.3 0.5 2.0 1.7 DOW666D' ~base renin, production) 6 . 2 1. 3 6 . 5 2 .1 DOW666APRd (base resin, 4.3 1.7 5.2 2.7 production) 0 . 05% CYASTAT L9/DOW666APR 0 . 5 0 . 6 1. 7 1. 6 0 . 25~ CYA8TAT LS/DOW666APR 0 . 3 0 . 3 1. 8 1. 6 201% Zn8t8/DOW666APR 0 . 6 0 .1 1~ ZnSt8~0.05% LAROSTAT 0.7 0.7 0.3 0.7 Polystyrene base re~iin, ' ~ ed by Hunst~an Chemicals Corp Polystyrene baDe re~in manuEactured b Hun t n Ch i als Co ' Polystyrene base resin 1 ~ bY D 8Cmha em c rp.
Y ene base resin manuEactured by Dw Chem ca 8 ~ g6564 EXAMP~E 7 1% Zinc stearate wa~ mixed with poly~tyrene to produce backcurve molds. The contact lens were prepared in accordance wlth the procedures described herein, except the curing temperatures were modif ied . The %
5 yields are indicated hereinbelow.
Yi~
Cudn~ Tunnel ~3 l-C) 5~ ~ 62 I'C) 69 ('C) Zooo I TempeRlun: nomul opcRline condilion ~roduclion/Conlrol 3l% 36% 34% 30%
1~ ZnSl~ l 7l# 73~ éJ% n~.
As shown hereinabove, the lenses made u~ing 1~6 zinc stearate molds under the above wide temperature range gave about the same high yields. In addition, they gave low holes . Thus, the zinc E;tearate modif ied molds allows a wide range of variationg in curing conditions 20 and do not affect the lens yields.

3o 2~ 86564 sg EXl~pLE 8 Variou8 sof t contact lenses were prepared in accordance with the above procedures llt; l; 7; n~ a back mold half made of either polystyrene or polystyrene and additive as described hereinabove . Af ter the mold 5 halves were pried apart, the percentage of holes in the contact lens produced by that mold was determined. The results are tAh1~1 Atf'ri hereinabove.
Typo Or Hatorlal ~ O Hol~
1. Polystyrene 5 . 4 2 . Poly~ityrene 3 . 8 3 . Polystyrene 1. 8 4 . Polystyrene 3 . 2 5. Polystyrene + 1% O. l Abl lwax 9 80 l C . Polystyrene + i t S
SFlO~0 7 . Polystyrene + 3S 0 . 9 Axelwax 33 RD
8. Polystyrene + 1% 1. 2 . Poly~tyren~ + 2.0S 0.
.~xel~a~ 3 8H
As readily 3hown under these conditions, there were less hole~ in the contact len8 when the back mold ~ntA i nf~d an ; ntf~n;~1 additive.

2 t 86~64 --6û -The above preferred ~ and examples are 1 given to illustrate the acope and ~pirit of the present invention. The embodiments and example~ de~;cribed herein will make apparent to tho~e 13killed in the art other embodiment~ and examples. The~e other embodiment~
5 and examples are within the contemplation of the present invention. Therefore, the present invention should be limited only by the ~rp~n~ d claim~.

~ :

3o _

Claims (52)

1. A mold material constituting a mold half for use in the production of contact lenses, said mold material comprising a thermoplastic polymer and a internal additive which is impregnated into said thermoplastic material and which is present in amounts ranging from about 0.05% to about 5% by weight, said thermoplastic material being polystyrene or polypropylene and said additive being a polyethylene or polypropylene wax having a molecular weight ranging from about 5000 to about 200,000, an amide wax of the formula R1CONH2 wherein R1 is a hydrocarbyl group, and the amide wax has a molecular weight of about 200-2000, silicone having a molecular weight ranging from about 2000 to about 100,000, Montan wax, oxidized wax, fatty acid having a molecular weight of about 200 to about 2000, a complex ester or a combination thereof.

2. A mold material constituting a mold half for use in the production of contact lenses, said mold material comprising polystyrene and an wetting effective amount of a wetting agent admixed therewith, the wetting force of said mold material being described by the equation:
F = 2.gamma.1 pcos ?
where F is the wetting force of the mold half .gamma.1 is the surface tension of distilled water p is the perimeter of the mold material at the meniscus when the mold half is partially immersed in the water and ? is dynamic contact angle, wherein the contact angle of said mold material is less than 100°.

3. The mold material of claim 1 in which the amide wax is a fatty acid amide wax.

4. The mold material of claim 1 wherein the thermoplastic polymer is polystyrene.

5. The mold material of claim 1 wherein the thermoplastic polymer is polypropylene.

6. The mold material of claim 1 wherein the additive is present in amounts ranging from about 0.1 to about 2.5% by weight.

7. The mold material of claim 1 wherein the additive is silicone.

8. The mold material of claim 2 wherein the additive is an anti-static agent or lubricant.

9. The mold material of claim 2 in which the wetting agent is an ethoxylated amine, hydroxy alkyl tertiary amine or quaternary ammonium sulfate, stearic acid or salt thereof.

10. The mold material of claim 9 wherein the wetting agent is ethoxylated tertiary amine, N, -N-Bis (2-hydroxyethyl) alkylamine, zinc stearate, (3-Lauramidopropyl) trimethyul ammonium methyl sulfate, or soy Dimethyl Ethyl Ammonium Ethosulfate.

11 A mold half useful in the production of a contact lens by the polymerization of a polymerizable composition in a mold assembly comprised of said mold half and a second mold half, said mold half comprising an integral article having a central curved section defining a concave surface, a convex surface and a circumferential edge, at least the central portion of at least one of said concave surface and said convex surface having the dimensions of the back curve of the desired swelled or unswelled contact lens to be produced in said mold assembly and being sufficiently smooth and contoured so that the surface of said contact lens formed by polymerization of said polymerizable composition in contact with said surface is optically acceptable, said article having an annular flange integral width and surrounding said circular circumferential edge and extending therefrom in a plane normal to the axis of said concave surface, said article also having a generally triangular tab situated in a plane normal to said axis and extending from said flange, said article having a thinness and rigidity effective to transmit heat therethrough and to withstand prying forces applied to separate said mold half from said mold assembly, and said article being comprised the mold material comprised of a thermoplastic polymer admixed with an additive or anti-wetting agent in accordance with claim 1.

12. The mold half of claim 11 wherein the additive is a fatty acid amide wax.

13. The mold half of claim 11 wherein the thermoplastic polymer is polystyrene.

14. The mold half of claim 11 wherein the thermoplastic polymer is polypropylene.

15. The mold half of claim 11 wherein the additive is present in amounts ranging from about 0.1 to about 2.5% by weight.

16. The mold half of claim 11 wherein the additive is silicone.

17. A mold half useful in the production of a contact lens by the polymerization of a polymerizable composition in a mold assembly comprised of said mold half and a second mold half, said mold half comprising an integral article having a central curved section defining a concave surface, a convex surface and a circumferential edge, at least the central portion of at least one of said concave surface and said convex surface having the dimensions of the back curve of the desired swelled or unswelled contact lens to be produced in said mold assembly and being sufficiently smooth and contoured so that the surface of said contact lens formed by polymerization of said polymerizable composition in contact with said surface is optically acceptable, said article having an annular flange integral width and surrounding said circular circumferential edge and extending therefrom in a plane normal to the axis of said concave surface, said article also having a generally triangular tab situated in a plane normal to said axis and extending from said flange, said article having a thinness and rigidity effective to transmit heat therethrough and to withstand prying forces applied to separate said mold half from said mold assembly, and said mold half being comprised of a mold material comprised of a polystyrene admixed with a wetting agent in accordance with claim 2.

18. The mold half of claim 17 wherein the contact angle of the mold material is less than or equal to 90°.

19. The mold half of claim 17 wherein the wetting agent is an ethoxylated amine, hydroxy alkyl tertiary amine, or quaternary ammonium sulfate, stearic acid or salt thereof.

20. The mold half of Claim 17 wherein the contact angle of the mold material is less than or equal to 75°.

21. The mold half of Claim 17 wherein the amount of wetting agent present from 0.05% to 5% (w/w).

22. The mold half of Claim 21 wherein the amount of wetting agent present range from 0.1% to 2.5% (w/w).

23. The mold half of claim 17 wherein the mold material is ethoxylated tertiaryamine, N,N-Bis (2-hydroxyethyl)alkylamine, zinc stearate, 3-(Lauramidopropyl) trimethylulammonium methyl sulfate, or soy dimethyl Ethyl Ammonium Ethosulfate.

24. A mold assembly used in the production of a contact lens by the polymerization of a polymerizable composition in said mold assembly, said mold assembly comprising a front mold half and a back mold half in contact therewith thereby defining and enclosing a cavity therebetween, and a polymerizable composition in said cavity in contact with both mold halves, wherein said front mold half comprises a first article of thermoplastic polymer trangparent to ultraviolet light, said article having a central curved section with a concave surface, a convex surface and a circular circumferential edge, wherein the portion of said concave surface in contact with said polymerizable composition has the curvature of the front curve of a contact lens to be produced in said mold assembly, and is sufficiently smooth so that the surface of a contact lens formed by polymerization of said polymerizable composition in contact with said surface is optically acceptable;

said first article having an annular flange integral with and surrounding said circular circumferential edge and extending therefrom in a plane normal to the axis of said concave surface, and generally triangular tab situated in a plane normal to said axis and extending from said flange;
said back mold comprised of an integral article having a central curved section with a concave surface, a convex surface and a circular circumferential edge, wherein the portion of said convex surface in contact with said polymerizable composition has the curvature of the back curve of a contact lens to be produced in said mold assembly and is sufficiently smooth so that the surface of a contact lens formed by polymerization of said polymerization composition in contact with said surface is optically acceptable;
said second article having an annular flange integral with and surrounding said circular circumferential edge with and surrounding said circular circumferential edge and extending therefrom in a plane normal to the axis of said convex surface, and a generally triangular tab situated in a plane normal to said axis and extending from said flange wherein the convex surface of said back mold half contacts the circumferential edge of said front mold half;
said back mold being comprised of a mold material comprised of a thermoplastic polymer admixed with an additive in accordance with claim 1.

25. The mold assembly of claim 24 in which the additive is a fatty acid amide wax.

26. The mold assembly of claim 24 wherein the thermoplastic polymer is polystyrene.

27. The mold assembly of claim 24 wherein the thermoplastic polymer is polypropylene.

28. The mold assembly of claim 24 wherein the additive or wetting agent is present in amounts ranging from about 0.1 to about 2.5% by weight.

29. The mold assembly of claim 24 wherein the additive is silicone.

30. A mold assembly used in the production of a contact lens by the polymerization of a polymerizable composition in said mold assembly, said mold assembly comprising a front mold half and a back mold half in contact therewith thereby defining and enclosing a cavity therebetween, and a polymerizable composition in said cavity in contact with both mold halves, wherein said front mold half comprises a first article of thermoplastic polymer transparent to ultraviolet light, said article having a central curved section with a concave surface, a convex surface and a circular circumferential edge, wherein the portion of said concave surface in contact with said polymerizable composition has the curvature of the front curve of a contact lens to be produced in said mold assembly, and is sufficiently smooth so that the surface of a contact lens formed by polymerization of said polymerizable composition in contact with said surface is optically acceptable;
said first article having an annular flange integral with and surrounding said circular circumferential edge and extending therefrom in a plane normal to the axis of said concave surface, and generally triangular tab situated in a plane normal to said axis and extending from said flange;
said back mold comprised of an integral article having a central curved section with a concave surface, a convex surface and a circular circumferential edge, wherein the portion of said convex surface in contact with said polymerizable composition has the curvature of the back curve of a contact lens to be produced in said mold assembly and is sufficiently smooth so that the surface of a contact lens formed by polymerization of said polymerization composition in contact with said surface is optically acceptable;
said second article having an annular flange integral with and surrounding said circular circumferential edge with and surrounding said circular circumferential edge and extending therefrom in a plane normal to the axis of said convex surface, and a generally triangular tab situated in a plane normal to said axis and extending from said flange wherein the convex surface of said back mold half contacts the circumferential edge of said front mold half;
said back mold being comprised of a mold material comprised of a polystyrene admixed with an wetting agent in accordance with claim 2.

31. The mold assembly of claim 30 wherein the contact angle is less than 90°.

32. The mold assembly of claim 30 wherein the wetting agent is an ethoxylated amine hydroxy alkyl tertiaryamine, quaternary ammonium sulfate, stearic acid or salt thereof.

33. The mold assembly of claim 30 wherein the wetting agent is ethoxylated tertiary amine, N,N-Bis(2-hydroxyethyl)alkylamine, zinc stearate, 3-(Lauramidopropyl) trimethylulammonium methyl sulfate, or soy dimethyl Ethyl Ammonium Ethosulfate.

34. The mold assembly of Claim 30 wherein the contact angle is less than or equal to about 75°.

35. The mold assembly of Claim 30 wherein the wetting agent is present in amounts ranging from about 0.05% to 5% (w/w).

36. The mold assembly of Claim 35 wherein the wetting agent is present in amounts ranging from about 0.1 to about 2.5% (w/w).

37. In an improved process for forming a contact lens from a mold assembly comprising a front mold half and a back mold half in contact therewith thereby defining and enclosing a cavity therebetween, and containing in said cavity a polymerizable composition in contact with said mold halves;
said front mold half comprising a first article of thermoplastic polymer transparent to ultraviolet light, said article having a central curved section with a concave surface, a convex surface and a circular circumferential edge, wherein the portion of said concave surface in contact with said polymerizable composition has the curvature of the front curve of a contact lens to be produced in said mold assembly and is sufficiently smooth so that the surface of a contact lens formed by polymerization of said polymerizable composition in contact with said surface is optically acceptable;

said back mold half comprising a second article of thermoplastic polymer transparent to ultraviolet light, said article having a central curved section with a concave surface, a convex surface and a circular circumferential edge, wherein the portion of said convex surface in contact with said polymerizable composition has the curvature of the back curve of a contact lens to be produced in said mold assembly and is sufficiently smooth so that the surface of a contact lens formed by polymerization of said polymerizable composition in contact with said surface is optically acceptable, wherein the convex surface of said back mold contacts the circumferential edge of said front mold half;
and the front mold half is clamped against the back mold half;
and the polymerizable composition undergoes polymerization under precuring and curing conditions with ultraviolet light and the back curve is separated from the front curve and the contact lens during a demolding process and the front curve is subsequently separated from the contact lens, the improvement comprising utilizing a back curve mold that is comprised of the mold material of claim 1.

38. The process of claim 37 wherein the thermoplastic polymer is polystyrene.

39. The process of claim 37 wherein the thermoplastic polymer is polypropylene.

40. The process of claim 37 wherein the additive is present in amounts ranging from 0.1 to 2.5% by weight.

41. The process of claim 37 wherein the additive is silicone.

42. In an improved process for forming a contact lens from a mold assembly comprising a front mold half and a back mold half in contact therewith thereby defining and enclosing a cavity therebetween, and containing in said cavity a polymerizable composition in contact with said mold halves;
said front mold half comprising a first article of thermoplastic polymer transparent to ultraviolet light, said article having a central curved section with a concave surface, a convex surface and a circular circumferential edge, wherein the portion of said concave surface in contact with said polymerizable composition has the curvature of the front curve of a contact lens to be produced in said mold assembly and is sufficiently smooth so that the surface of a contact lens formed by polymerization of said polymerizable composition in contact with said surface is optically acceptable;
said back mold half comprising a second article of thermoplastic polymer transparent to ultraviolet light, said article having a central curved section with a concave surface, a convex surface and a circular circumferential edge, wherein the portion of said convex surface in contact with said polymerizable composition has the curvature of the back curve of a contact lens to be produced in said mold assembly and is sufficiently smooth so that the surface of a contact lens formed by polymerization of said polymerizable composition in contact with said surface is optically acceptable, wherein the convex surface of said back mold contacts the circumferential edge of said front mold half;
and the front mold half is clamped against the back mold half;
and the polymerizable composition undergoes polymerization under precuring and curing conditions with ultraviolet light and the back curve is separated from the front curve and the contact lens during a demolding process and the front curve is subsequently separated from the contact lens, the improvement comprising utilizing a back curve mold that is comprised of the mold material of claim 2.

43. The process of Claim 42 wherein the contact angle is less than or equal to 90°.

44. The process of Claim 42 wherein the contact angle is less than or equal to 75°.

45. The process of Claim 42 wherein the wetting agent is present in amounts ranging from about 0.05% to about 5% (w/w).

46. The process of Claim 42 wherein the wetting agent is present in amounts ranging from about 0.1% to about 2.5% (w/w).

47. The process of claim 42 wherein the anti-wetting agent is an ethoxylated amine, hydroxy alkyl tertiary amine, or quaternary ammonium sulfate, or stearic acid or salt thereof.

48. The process of claim 42 wherein the mold material is ethoxylated tertiaryamine, N,N-Bis (2-hydroxyethyl) alkylamine, zinc stearate, 3-(Lauramidopropyl) trimethylulammonium methyl sulfate, or soy dimethyl Ethyl Ammonium Ethosulfate.

49. The mold material of Claim 2 in which the wetting agent is present in amounts ranging from about 0.05% to 5% (w/w).

50. The mold material of Claim 49 in which the wetting agent is present in amounts ranging from 0.1% to 2.5% (w/w).

51. The mold material of Claim 2 in which the dynamic contact angle is less than or equal to about 90°.

52. The mold material of Claim 51 in which the dynamic contact angle is less than or equal to about 75°.