WO2025198914A1 - Composition for polishing ophthalmic substrate and method of polishing ophthalmic substrate - Google Patents

Abstract

Disclosed is an aqueous slurry composition for polishing an organic polymer-based ophthalmic substrate comprising: about 5 wt.% to about 40 wt.% of an abrasive particle; about 0.5 wt.% to about 4 wt.% of a polishing accelerator; about 0.01 wt.% to about 4 wt.% of a polishing additive; about 0.5 wt.% to about 4 wt.% of a polishing suspension additive; about 0.025 wt.% to about 0.30 wt.% of an anti-foaming agent; and water, wherein the polishing additive comprises a cellulose or a cellulose derivative. Also disclosed is a method of using the aqueous slurry composition for polishing an organic polymer-based ophthalmic substrate.

Description

COMPOSITION FOR POLISHING OPHTHALMIC SUBSTRATE AND

METHOD OF POLISHING OPHTHALMIC SUBSTRATE

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of filing date of U.S. Provisional Application No. 63/567,103, filed on March 19, 2024, the disclosure of which is incorporated by reference herein.

TECHNICAL FIELD

[0002] Disclosed herein are compositions for polishing ophthalmic substrate and method of using the compositions for polishing ophthalmic substrate. Specifically, the ophthalmic substrate is an organic polymer-based ophthalmic substrate.

BACKGROUND

[0003] Many of today’s modem polishing systems for polishing organic polymer-based ophthalmic substrates, also known as ophthalmic plastic lenses, are based on high-speed, soft flexible tooling systems, or better known as digital lens polishing systems. The most significant way these systems differ from traditional plastic lens polishing systems is that the newer digital lens polishing systems no longer require a perfectly matched hard tool as a template for every type of prescription to carry a finishing and/or a polishing pad to finish a lens that has been rough cut using a lens generator. Instead, these digital lens polishing systems rely on at most a very small number of flexible tools that enable the entire power curve range of prescription lenses to be produced instead of thousands of unique hard tools used in the traditional plastic lens polishing systems to provide the polished finish to make the ophthalmic lenses acceptable for vision correction.

[0004] The digital lens polishing systems involve unique challenges not encountered in the traditional plastic lens polishing systems, and thus, require different compositions to address these challenges.

BRIEF SUMMARY

[0005] The present disclosure describes compositions for polishing organic polymer-based ophthalmic substrate and method of using the compositions for polishing organic polymer-based ophthalmic substrate. [0006] One aspect of the present disclosure describes an aqueous slurry composition for polishing an organic polymer-based ophthalmic substrate comprising: about 5 wt.% to about 40 wt.% of an abrasive particle; about 0.5 wt.% to about 4 wt.% of a polishing accelerator; about 0.01 wt.% to about 4 wt.% of a polishing additive; about 0.5 wt.% to about 4 wt.% of a polishing suspension additive; about 0.025 wt.% to about 0.30 wt.% of an anti-foaming agent; and water, wherein the polishing additive comprises a cellulose or a cellulose derivative.

[0007] An aqueous slurry composition for polishing an organic polymer-based ophthalmic substrate is described herein. In one aspect, the slurry composition may be: about 5 wt.% to about 40 wt.% of an abrasive particle; about 0.5 wt.% to about 4 wt.% of a polishing accelerator; about 0.01 wt.% to about 4 wt.% of a polishing additive; about 0.5 wt.% to about 4 wt.% of a polishing suspension additive; and about 0.025 wt.% to about 0.30 wt.% of an anti-foaming agent. The slurry may also include water. The polishing additive comprises a cellulose or a cellulose derivative.

[0008] In one aspect, the abrasive particle is selected from aluminum oxide, cerium oxide, iron oxide, tin oxide, titanium oxide or combinations thereof. In a further aspect, the abrasive particle is aluminum oxide.

[0009] In a further aspect, the abrasive particle has an average particle size of about 0.01 microns to about 4 microns, or about 1.8 micron to about 2.2 microns. The aqueous slurry composition may be about 17 wt.% to about 20 wt.% of the abrasive particle.

[0010] In a further aspect, the polishing accelerator of the slurry composition is an aluminum compound selected from aluminum nitrate, polyaluminum chloride, aluminum bromide, aluminum sulfate, aluminum iodide, aluminum chloride and aluminum phosphate, and mixtures thereof. The polishing accelerator may be aluminum nitrate. The amount of polishing accelerator in the aqueous slurry composition may be about 1.5 wt.% to about 2.5 wt.%.

[0011] In a further aspect, the polishing additive of the slurry composition may be one of a cellulose derivative selected from hydroxyethyl cellulose (HEC), hydroxpropyl cellulose (HPC), methyl cellulose (MC), hydroxypropyl methyl cellulose (HPMC), hydroxybutyl methylcellulose (HBMC), or a combination of two or more thereof. In one aspect, the polishing additive is hydroxyethyl cellulose. The aqueous slurry composition may have about 0.25 wt.% to about 1 wt.% of the polishing additive and/or about 0.5 wt.% to about 4 wt.% of a polishing suspension additive. In one aspect, the polishing suspension additive may be one of ahiminum hydroxide and aluminum hydroxide oxide.

[0012] In one aspect, the aqueous slurry composition may have about 0.025 wt.% to about 0.3 wt.% of an anti-foaming agent. In a further aspect, the aqueous slurry composition may have about 0.025 wt.% to about 0.1 wt.% of the anti-foaming agent. In one aspect, the anti-foaming agent is a modified siloxane treated fumed silica.

[0013] In one aspect, the water in the aqueous slurry composition may be de-ionized water. The aqueous slurry composition may have about 0.1 wt.% to about 10 wt.% of at least one of (a) of a polyvinyl alcohol compound, (b) a tertiary amide compound, or (c) combinations thereof. In a further aspect, the aqueous slurry composition may have the polyvinyl alcohol compound and the tertiary amide compound. The polyvinyl alcohol compound may be one of polyvinyl formate, polyvinyl benzoate, polyvinyl stearate, polyvinyl chloroacetate, polyvinyl fluoroacetate, and polyvinyl propionate. The tertiary amide compound may be one or more of poly 2-ethyloxazoline, poly (N,N-dimethylacrylamide), poly (N-methyl N-vinyl acetamide), N-methylcaprolactam, and N-methyl-2-piperidone.

[0014] In a further aspect, a method of polishing an organic polymer-based ophthalmic substrate is described. According to the method: an aqueous slurry composition is provided that may have: about 5 wt.% to about 40 wt.% of an abrasive particle; about 0.5 wt.% to about 4 wt.% of a polishing accelerator; about 0.01 wt.% to about 4 wt.% of a polishing additive; about 0.5 wt.% to about 4 wt.% of a polishing suspension additive; about 0.025 wt.% to about 0.30 wt.% of an anti-foaming agent; and water. In one aspect, the polishing additive may have a cellulose or a cellulose derivative. The aqueous slurry composition is disposed between a polishing pad and the organic polymer-based ophthalmic substrate; and the organic polymer-based ophthalmic substrate with the polishing pad and the aqueous slurry composition to remove a surface portion of the organic polymer-based ophthalmic substrate.

[0015] In one aspect the abrasive particle of the slurry composition may be one of aluminum oxide, cerium oxide, iron oxide, tin oxide, titanium oxide or combinations thereof. In a further aspect, the abrasive particle may be aluminum oxide. The abrasive particle may have an average particle size of about 0.01 microns to about 4 microns. In a further aspect, the abrasive particle may have an average particle size of about 1.8 micron to about 2.2 microns. The aqueous slurry composition may have about 17 wt.% to about 20 wt.% of the abrasive particle.

[0016] In a further aspect, the polishing accelerator of the slurry composition may be an aluminum compound selected from aluminum nitrate, polyaluminum chloride, aluminum bromide, aluminum sulfate, aluminum iodide, aluminum chloride and aluminum phosphate, and mixtures thereof. In one aspect, the polishing accelerator may be aluminum nitrate. In one aspect, the aqueous slurry composition used in the method may have about 1.5 wt.% to about 2.5 wt.% of the polishing accelerator.

[0017] In a further aspect, the polishing additive used in the method is a cellulose derivative that may be hydroxy ethyl cellulose (HEC), hydroxpropyl cellulose (HPC), methyl cellulose (MC), hydroxypropyl methyl cellulose (HPMC), hydroxybutyl methylcellulose (HBMC), or a combination of two or more thereof. In a further aspect, the polishing additive may be hydroxyethyl cellulose. In a further aspect, the aqueous slurry composition in the method may be about 0.25 wt.% to about 1 wt.% of the polishing additive.

[0018] In a further aspect, the aqueous slurry composition used in the method may be about 0.5 wt.% to about 4 wt.% of a polishing suspension additive. The polishing suspension additive may be one of aluminum hydroxide and aluminum hydroxide oxide.

[0019] In a further aspect, the aqueous slurry composition used in the method may be about 0.025 wt.% to about 0.3 wt.% of an anti-foaming agent. In a further aspect, the aqueous slurry composition may be about 0.025 wt.% to about 0.1 wt.% of the anti-foaming agent. In a further aspect, the anti-foaming agent may be a modified siloxane treated fumed silica. The aqueous slimy composition used in the method may have de-ionized water.

[0020] In a further aspect, the aqueous slurry composition used in the method may have about 0.1 wt.% to about 10 wt.% of at least one of (a) of a polyvinyl alcohol compound, (b) a tertiary amide compound, and (c) combinations thereof. In a further aspect, the aqueous slurry composition may have one of the polyvinyl alcohol compound and the tertiary amide compound. In a further aspect, the polyvinyl alcohol compound may be polyvinyl formate, polyvinyl benzoate, polyvinyl stearate, polyvinyl chloroacetate, polyvinyl fluoroacetate, or polyvinyl propionate. In a further aspect, the tertiary amide compound may be one of poly 2-ethyloxazoline, poly (N,N- dimethylacrylamide), poly (N-methyl N-vinyl acetamide), N-methylcaprolactam, or N-methyl-2- piperidone.

[0021] In one aspect of the method, the organic polymer-based ophthalmic substrate may be a high index organic polymer-based ophthalmic substrate. In a further aspect, the organic polymer- based ophthalmic substrate may be a part of a digital lens polishing system.

[0022] Another aspect of the present disclosure describes a method of using the aqueous slurry composition of the present disclosure for polishing an organic polymer-based ophthalmic substrate.

DETAILED DESCRIPTION

[0023] Embodiments of the present disclosure are described in detail with reference to the drawing figures wherein like reference numerals identify similar or identical elements. It is to be understood that the disclosed embodiments are merely examples of the disclosure, which may be embodied in various forms. Well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure in virtually any appropriately detailed structure.

Polishing Theory:

[0024] One skilled in the art is aware that polishing lens blanks requires the removal of surface substances in an environment and under conditions that will provide an acceptable lens that provides clear vision and a target vision correction. Removal rates can be characterized using Preston’s equation. Preston’s equation states r=k *pv. In this equation, p is the pressure or force per unit area, v is the velocity of the lap relative to the stone, and r is the rate of material removed (cutting depth per unit time). The constant, k, is known as the Preston coefficient. This coefficient reflects the type of lap, the type of material, the type of grit, etc. This simple relation means that the rate of surface removal (or weight loss) increases as the downward force on the stone increases or if the velocity of the lap increases. It has been found that for the most part, the rate of surface removal is independent of polishing particle size.

[0025] Similar to Preston’s equation above, the polishing rate may be determined by the pressure or force applied to the lens at a velocity as a function of time. The polishing rates can vary between lens materials (CR-39, Polycarbonate, Hi Index and Trivex are the main classes of lens materials; sub classes exist depending on the index of refraction where the lens material monomer may be altered slightly to accommodate for a change in index of refraction as a function of resin makeup at a given lens thickness).

[0026] Conventional polishing is defined by the final lens curvature being surfaced by fixed tools at prescribed curves limited by 2 planes, i.e., Base and Cross curve. This is also referred to as a “toric” lens. The typical process for conventional is a lens generation step where the curve is introduced into a blank followed by a fining step where an abrasive paper is affixed to a lap or tool (typically plastic or aluminum) and loaded onto a machine similar to a polisher where water is used to help wash the plastic from the abrasive paper. Conventional fining can with be with a single or 2 step process before the lens is polished. During the polishing cycle, a different machine is used where the same lap or tool now has a flocked/ velveteen pad affixed to the same tool used for fining and the polishing slurry is pumped across the surface of the tool while downward pressure is applied to the lens. Most conventional machines have an orbital/circular motion for the tool where the lens is held which sweeps from side to side ensuring the polishing action removes the fining step. It is noted here neither the lens nor the tool are spinning.

[0027] The older, traditional plastic lens polishing systems typically employed a very large surface area tool, for example, with a diameter of up to 75mm. In these systems, the lens holder was held in place under a reasonable amount of pressure, and the lens holder moved across the 180°-axis in a side-to-side motion. This sat on top of the tool holder post and this post travelled in a fixed 180°-axis position while being rotated in a small circular motion within a large circular motion or a figure-eight motion. This action provided a very large polish surfacing area, which worked very well at the lower speeds of the traditional plastic lens polishing systems.

[0028] In contrast, in the digital lens polishing system, cut to polish or free form polishing is significantly different and is not limited to having fixed curves since the lap or tool has now been replaced by a flexible tool or “cap” that has the pad integrated into the design. There is no lens fining step where the process has a lens generation step followed by polishing. The digital lens polishing system typically utilizes a single point diamond which is capable of producing very complex curvature and is no longer limited to a single base and/or cross curve. The lens is indexed axially during generation where the single point diamond is programmed to remove material as a function of all planes (X, Y and Z axis positions). Since the polishing tool will conform to the lens surface, an infinite number of curves may be done. While in the traditional lens polishing system, the fixed tool imparted the final curve to the lens, in the digital lens polishing system, the lens curvature is derived from the lens generation step and the polish step is done to remove any final surface defects from the single point diamond left behind.

[0029] Further, the digital lens polishing systems operate at a very high spindle speed on both the lens holder and the tool holder. This very high speed reduces the time taken to obtain the desired level of finish quality for the plastic lenses. These systems use tools with a very small tool diameter, for example, with a diameter of up to about 45 mm. These diameters are by way of example and not by way of limitation. Larger diameters are certainly compatible with this technology. Typically, a cut plastic lens is held in place between two posts, one post directly above the other. During operation, a polish is pumped across the surface of the lens to allow the movement of the equipment to deliver a polished/ finished surface. Either the top post or the bottom post, dependent on which manufacturer’s equipment is selected, rotates in a clockwise direction and moves side to side at the same time, while the other spindle spins in a counter-clockwise direction, but remains in a fixed position.

[0030] Moreover, the digital lens polishing system includes additional spinning action of both the lens and/or the tool, which will spin on axis (sometimes depending on the equipment and macro, the same or different directions). The directions of spinning are intermittently changed to ensure polishing uniformity. The speeds or “feed rates” in which the lens/tools will spin will depend on the size, curve and lens type. Additionally, the applied down pressure will also be predicated upon the same criteria. Specific operating conditions are selected based on the lens type, curvature and size.

[0031] Also, the digital lens polishing system uses a more wear resistant polish tool surface, which is typically made of urethane, polyethylene (PE) foam (i.e., closed cell), polyester foam (i.e., open cell), or brushed PE foam, and in some instances, tight rayon flock of varying hardness and densities. The pad surface for a digital lens polishing system can vary from a buffed polyurethane (typically a woven fabric with impregnated polyurethane with the top being buffed or abraded away yielding a unique surface to help trap polish). Other elastomers are used in creating a range of pad hardness and a combination of open and closed cells which also are critical for the polishing action. On a digital polishing system, due to the aggressive high-speed wear and tear generated, the flexible tooling would need to be changed far more if it lacked a PE or urethane top surface. The top surface materials of these digital lens polishing system tools are far more robust, but have the issue that they are more difficult to wet out. This is true of the surface of the different plastic lenses, more so with some than others, but they all suffer from this. As used herein, the term “wet out” refers to the ability of a liquid to settle on to a surface. If a product is repelled by the surface of the lenses and the surface of the tools, this can dramatically change the performance of the polish that is in use.

[0032] In a traditional lens polishing system, the polishing pads are typically made up of a flocked Reemay (typically rayon) with a greater length and with either an acrylic or oil emulsion adhesive which keeps the pad on the fixed tool for a single use, then removed and discarded. This type of design provides a polish medium that may carry a lot of polish over the surface of the lens and adds an additional flexing/ scrubbing action in a gentler fashion. This results in a medium that provides a pad that provides acceptable polishing action. The flock polishing pads may be used as a single surface use as the flock may become compacted and damaged during the time taken to polish a single plastic lens and to polish further lenses with the same pad would take more time to give the same result each time it was used. Such a tool, when used in the traditional lens polishing system, was likely needed to be used as a fining tool, which requires the polishing pad to be removed after each use. Advantages of the present disclosure are provided in both traditional and digital lens polishing technologies.

[0033] The digital lens polishing systems have several advantages over traditional plastic lens polishing systems, such as providing flexibility of tooling any variation in the curved surfaces of the plastic lenses to be polished from a very small range of tools. However, as discussed above, these digital polishing systems also present a far more challenging operating environment. For example, in addition to the equipment in a digital lens polishing system operating at a much greater speed than in a traditional lens polishing system, the digital lens polishing system is designed to allow for a far greater degree of frictional surface contact than seen on a traditional lens polishing system, which makes up in part for the smaller size of the tooling used in a digital lens polishing system. The polishing action is typically done under higher pressure than traditional polishing (about 1.5 to 2.5 bar) so that the polishing tool’s surface remains in contact with the surface of the plastic lens to be polished.

[0034] The makeup of the tool as well as the more aggressive action of the machine is an additional reason why polishing is more challenging on a digital lens polishing system than on a traditional lens polishing system. Thus, due to the unique challenges of the equipment used in the digital lens polishing system and the conditions under which they are operated, the compositions of the plastic lens polishes used in such systems need to be modified as the traditional plastic lens polish simply do not work well enough.

[0035] One aspect of the present disclosure describes an aqueous slurry composition for polishing an organic polymer-based ophthalmic substrate in a digital polishing system. The slurry composition may have: about 5 wt.% to about 40 wt.% of an abrasive particle; about 0.5 wt.% to about 4 wt.% of a polishing accelerator; about 0.01 wt.% to about 4 wt.% of a polishing additive; about 0.5 wt.% to about 4 wt.% of a polishing suspension additive; about 0.025 wt.% to about 0.30 wt.% of an anti-foaming agent; and water, wherein the polishing additive comprises a cellulose or a cellulose derivative. Weight percent or “wt.%”, as used herein, refers to the percentage weight of the constituent relative to the weight of a unit of the slurry composition. The unit may be a unit weight (e.g., a kilogram of slurry) or a unit volume (e.g., a liter of slurry).

[0036] In some embodiments, the organic polymer-based ophthalmic substrate is a high index organic polymer-based ophthalmic substrate. In some embodiments, the organic polymer-based ophthalmic substrate is a plastic based optical (ophthalmic) lens or plastic optical (ophthalmic) lens. However, the organic polymer-based ophthalmic substrate does not include inorganic glasses and inorganic crystal based substrates. In some embodiments, the organic polymer-based ophthalmic substrate is apart of a digital lens polishing system. In some embodiments, the organic polymer-based ophthalmic substrate is a part of a traditional (non-digital) lens polishing system.

[0037] In some embodiments, the aqueous slurry composition comprises about 5 wt.% to about 40 wt.% of an abrasive particle, preferably about 15 wt.% to about 25 wt.%, even more preferably, about 17 wt.% to about 20 wt.%. hi some embodiments, the abrasive particle is selected from aluminum oxide, cerium oxide, iron oxide, tin oxide, titanium oxide or combinations thereof. In some embodiments, the abrasive particle is aluminum oxide (alumina). In some embodiments, the abrasive particle has an average particle size of about 0.5 microns to about 4 microns, preferably about 1 to about 3 microns, even more preferably, about 1.8 micron to about 2.2 microns. The average particle size is typically measured using a laser diffraction system, such as the Malvern Mastersizer (Malvern Panalytical) or Horiba LA series (Horiba Scientific). It does this by measuring the intensity of light scattered as a laser beam passes through a dispersed particulate sample. [0038] In some embodiments, the aqueous slurry composition comprises about 0.5 wt.% to about 4 wt.% of a polishing accelerator, preferably, about 1 wt.% to about 3 wt.%, even more preferably, about 1.5 wt.% to about 2.5 wt.%. The polishing accelerator is described in U.S. Patent No. 4,225,349 as being added to a polishing composition to improve the efficiency of polishing operation without the appearance of any defect on the polished surface. In some embodiments, the polishing accelerator is an aluminum compound selected from aluminum nitrate, polyaluminum chloride, aluminum bromide, aluminum sulfate, aluminum iodide, aluminum chloride and aluminum phosphate, and mixtures thereof.

[0039] In some embodiments, the aqueous slurry composition comprises about 0.01 wt.% to about 4 wt.% of a polishing additive, preferably about 0.25 wt.% to about 1 wt.%, even more preferably about 0.3 wt.% to about 0.6 wt.%. The polishing additive comprises a cellulose or a cellulose derivative. In some embodiments, the polishing additive is a cellulose derivative selected from hydroxyethyl cellulose (HEC), hydroxpropyl cellulose (HPC), methyl cellulose (MC), hydroxypropyl methyl cellulose (HPMC), hydroxybutyl methylcellulose (HBMC), Combinations of two or more additives are contemplated. Other cellulose derivatives are contemplated. Preferably, the polishing additive is hydroxyethyl cellulose. Even more preferably, the polishing additive is hydroxyethyl cellulose (HEC), for example, sold by Ashland under trade name Natrosol™ 250 GR HEC. Preferably, the hydroxyethyl cellulose has a medium viscosity of about 10 cps to about 50 cps when measured using a Brookfields viscometer at a speed of 60 rpm.

[0040] The molecular weight of the cellulose derivative is about 90,000 to 1,300,00 Daltons. One skilled in the art is aware that if the molecular weight of the cellulose is too low, the amount of polishing additive required becomes too large. If the molecular weight is too hight, it becomes difficult to add the precise amount needed to yield the best properties. In one aspect, the molecular weight range of the cellulose derivative is in the range of about 200,00 to about 500,000. In another advantageous aspect, the molecular weight range of the cellulose derivative in in the range of about 275,00 Daltons to about 325,000 Daltons. One skilled in the art is able to select a polishing additive with a molecular weight most suited to their products.

[0041] In some embodiments, the aqueous slurry composition comprises about 0.5 wt.% to about 4 wt.% of a polishing suspension additive, preferably, about 1 wt.% to about 3 wt.%, even more preferably, about 2 wt.%. In some embodiments, the polishing suspension additive is a submicron particle size metal oxide or metal hydroxide. Non-limiting examples of the polishing suspension additive include, for example, submicron particle size aluminum hydroxide (e.g., boehmite and gibbsite) or submicron particle size products made from aluminum hydroxide, such as aluminum hydroxide oxide. For example, boehmite is sold by Sasol under trade name DISPAL™ 23N4-80 and by Nyacol under trade name Nyacol™ AL20SD (manufacturer refers to it as aluminum hydroxide oxide). It is known that boehmite or gibbsite based suspension agents and other similar product or products made from them such as, aluminum hydroxide oxide (e.g., Nyacol™ AL20SD) can be used to help keep a polish formulation in a suspended state. The polishing suspension additive has a submicron particle size or nano sized particles. One skilled in the art is aware that the particle size of the suspension additive is such that it will not provide significant abrasive effect.

[0042] In some embodiments, the aqueous slurry composition comprises about 0.025 wt.% to about 0.30 wt.% of an anti-foaming agent, preferably, about 0.25 wt.% to about 0.1 wt.%. For example, U.S. Patent No. 7,294,044 describes modified siloxane treated fumed silica as an antifoaming agent. The anti-foaming agent may also be referred to as a defoamer or defoaming agent. [0043] The aqueous slurry composition comprises water, preferably deionized water. The amount of water is the remainder of the composition that will yield a composition with the constituents present in the specified weight percents.

[0044] Another aspect of the present disclosure describes a method of using an aqueous slurry composition for polishing an organic polymer-based ophthalmic substrate. The aqueous slurry composition is as described herein. The method comprises the steps of providing an aqueous slurry composition described herein; disposing the aqueous slurry composition between a polishing pad and the organic polymer-based ophthalmic substrate; and polishing the organic polymer-based ophthalmic substrate with the polishing pad and the aqueous slurry composition to remove a surface portion of the organic polymer-based ophthalmic substrate.

[0045] As used herein, the term “stock removal rate” refers to the amount of material removed from a lens during polishing as a function of polishing time [. For example, if a CR-39 lens is polished for 5 minutes and its weight loss is 232 mg, the stock removal rate would be 232 mg per 5 minutes as measured by the weight of the lens before and after polishing. Since each lens material may require a change in machine/macro setting, it should be noted as a generalization that CR-39 and Hi Index lens typically process easier or faster and require shorter time cycles than Trivex or Polycarbonate lenses. For example, using the same machine, the stock removal rate of a typical polycarbonate lens might be 96 mg for 6 minutes. As confusing as this can be, since time cycles vary from lab to lab, most will report stock removal rate as just a total stock removal of a lens material regardless of a time function. In other words, using the same example, a lab might refer to the stock removal rate of CR-39 as 232 mg and for comparison reasons, competitive testing used for reference would be reported as a percent of standard. If the reference standard is 232 mg and the subject material is 180 mg, then that would be reported as 76% (should be 77.5% = 180/232) of standard.

EXAMPLES

[0046] The following examples are given as specific illustrations of the aqueous slurry compositions of the present disclosure. It should be understood, however, that the aqueous slurry compositions of the present disclosure are not limited to the specific details set forth in the examples.

EXAMPLE 1

[0047] In the following examples, the amounts in the tables of the various components in a slurry composition are their weight percents of these components in the total formulation.

[0048] TABLE 1 shows illustrative embodiments of the aqueous slurry compositions of the present disclosure along with comparative aqueous slurry compositions. The comparative aqueous slurry compositions were based on certain U.S. patents as noted below. All the compositions comprised alumina (aluminum oxide), aluminum nitrate, aluminum hydroxide, antifoam and deionized water. Some of the formulations had additional components are shown in TABLE 1. In these examples, the “Alumina” used was calcined aluminum oxide. “Aluminum nitrate” was also used The “Aluminum hydroxide” that was used was boehmite-based Nyacol™ AL20SD, which the manufacturer describes as aluminum hydroxide oxide. The particle sizes were as described previously herein. The “Antifoam” used in the examples are described previously herein.

[0049] Aluminum hydroxide was added to all the slurries tested as a suspension aid. Without such a suspension agent, the formulation would simply drop out of solution and not be able to be processed in a polishing machine to gain any meaningful stock removal readings to judge against. Adding this suspension agent will not affect the stock removal rate; it simply acts to keep the solution in a state where it can be run though the polishing process.

TABLE 1

[0050] Control Slurry 1 : The formulation for Slurry 1 was based on a formulation described in U.S. Patent No. 4,225,349. Slurry 1 was used as the control for the comparative studies shown in the Examples. Even though it was not in the formulations of U.S. Patent No. 4,225,349, aluminum hydroxide was added to this control slurry (and all the slurries of TABLE 1) as a suspension aid in order to keep the solution in a state where it can be run though the polishing process during testing. As noted above, adding this suspension agent will not affect the stock removal rate.

[0051] Slurry 2: The formulation for Slurry 2 was based on a formulation described in U.S. Patent No. 7,467,988 B2. Slurry 2 included 0.5 wt.% of polyvinyl pyrrolidone (PVP) in addition to the other components of Slurry 1. The weight average molecular weight of the PVP used was 10,000, which was a preferred pyrrolidone used in U.S. Patent No. 7,467,988 B2.

[0052] Slurry 3: The formulation for Slurry 3 was based on a formulation described in U.S. Patent No. 10,508,220 B2. Slurry 3 included 0.5 wt.% of polyvinyl alcohol in addition to the other components of Slurry 1. The polyvinyl alcohol used was SELVOL™ 502.

[0053] Slurry 4: The formulation for Slurry 4 is an embodiment of the aqueous slurry formulation of the present disclosure. Slurry 4 included 0.2 wt.% of polishing additive hydroxyethyl cellulose in addition to the other components of Slurry 1. The hydroxyethyl cellulose used was Natrosol™ 250 GR HEC.

[0054] Slurry 5: The formulation for Slurry 5 is another embodiment of the aqueous slurry formulation of the present disclosure. Slurry 5 included 0.5 wt.% of polishing additive hydroxyethyl cellulose in addition to the other components of Slurry 1. The hydroxyethyl cellulose used was Natrosol™ 250 GR HEC.

[0055] Stock Removal Rates:

[0056] The slurry formulations of TABLE 1 were tested as follows to measure their stock removal rates. The lenses tested were organic polymer-based and are referred to by “RI” or their refractive index. The specific lenses used were Zeiss 70mm 6.50 base semi-finished uncuts CR39 1.498 RI and Polycarbonate 1.596 RI. Surfacing machine used was Schneider CCP Swift freeform optical polishing unit. The tools used were Flexible Red 1.50 SX one step freeform polishing tools. [0057] Test polish slurry was chilled to 13 degrees C and was run at a flow rate of 36 litres per minute. Schneider’s Poly 3 macro was used, which gave a polishing time of 180 seconds. Note this time is by way of example and not limitation. The speed of rotation and pressure used were set by the macro selection, which are proprietary to the manufacturer, Schneider, and are not known by applicant.

[0058] The lenses were weighed on a digital set of scales capable of 3 decimal places measurements and this measurement was recorded as the weight removed was very low (mg). After the lenses were polished, they were thoroughly cleaned, dried and weighed again and the difference between the two number is the amount of stock removed. Each test was repeated ten times per slurry and their average stock removal rate is shown in TABLE 2 and relative removal rates are reported for the different slurries used on the two substrates.

TABLE 2

[0059] The stock removal rates of control Slurry 1 show the performance of a polish made with the addition of aluminium nitrate, which U.S. Patent No. 4,225,349 refers to as a polishing accelerator. The results of Slurry 1 also show how this known polish will perform when used in a modem freeform lens polishing equipment, unlike the traditional polishing equipment described in U.S. Patent No. 4,225,349.

[0060] Slurry 2, which included 0.5 wt.% of polyvinyl pyrrolidone, showed a higher stock removal rate on Polycarbonate 1.586 RI lens compared to control Slurry 1 , but stock removal rate on CR39 1.498 RI lens for Slurry 2 was less when compared to control Slurry 1. The results of Slurry 2 also show how this known polish will perform when used in a modem freeform lens polishing equipment, unlike the traditional polishing equipment described in U.S. Patent No. 7,467,988 B2.

[0061] Slurry 3, which included 0.5 wt.% of polyvinyl alcohol, had a lower stock removal rate compared to control Slurry 1 and Slurry 2 on CR39 1.498 RI lens but a higher stock removal rate compared to control Slurry 1 and Slurry 2 on Polycarbonate 1.586 RI lens.

[0062] Slurry 4, which is an embodiment of the present invention and included 0.2 wt.% of polishing additive hydroxyethyl cellulose, showed a higher stock removal rate compared to control Slurry 1, Slurry 2, and Slurry 3 on both CR39 1.498 RI lens and Polycarbonate 1.586 RI lens. Slurry 5, which is also an embodiment of the present invention and included 0.5 wt.% of polishing additive hydroxyethyl cellulose, showed the effect of increasing hydroxyethyl cellulose on increasing stock removal rate on both CR39 1.498 RI lens and Polycarbonate 1.586 RI lens compared to Slurry 4 with 0.2 wt.% of hydroxyethyl cellulose. These results were achieved without any loss of quality of the surface finish of the lenses polished.

[0063] The above results demonstrate that stock removal rates increase with the addition of comparable or lesser amount of polishing additive hydroxyethyl cellulose when compared with known plastic lens polishing slurry formulations, which included the traditional polishing accelerator aluminum nitrate, or other known additives such as polyvinyl pyrrolidone or polyvinyl alcohol. Advantageously, these results were achieved without any loss of quality of the surface finish of the lenses polished.

EXAMPLE 2

[0064] Slurry 5 of the present disclosure of TABLE 1, the control Slurry 1 of TABLE 1 and commercially available plastic lens polishing slurry formulations, sold as Poly-Pro All-Format™ and Americal Plus, were each separately used to polish CR39 1.498 RI and Polycarbonate 1.586

RI lenses. The stock removal rates for each slurry were measured separately using the polishing conditions described in EXAMPLE 1. The results are shown in TABLE 3.

TABLE 3

[0065] In TABLE 3, the term “Baume” refers to the density of the polish formulation when a fixed amount is measured. The density of 100 ml of each of the slurry formulations in TABLE 3 was measured and listed as its Baume. As a skilled person would understand, Baume is not a linear scale measurement. [0066] Density is calculated by the weight divided by the volume. For example, water has a density of 1 milligram per millilitre which is the equivalent of weighing 1 milligram which will then have a volume of 1 millilitre. Baume is therefore a density unit.

[0067] Slurry 5 has a density of 116.2 mg per 100 ml of liquid when checked against a Baume degree converter (e.g., www.engineeringtoolbox.com/degrees-baume-hydrometer-specific- gravity-d_1615.html). According to this reference Slurry 5 has a Baume of 20. Both the commercially available products that were tested had a higher reading on the Baume scale than Slurry 5. Poly -Pro All-Format™ had a Baume of 23 (density of 118.9 grams per 100 ml this equates to 20% grit used to make it) and Americal Plus had a Baume of 25 (density of 120.8 grams per 100 ml this equates to 22% grit used to make it).

[0068] TABLE 3 shows that the stock removal rates for Slurry 5 of the present invention with polishing additive hydroxyethyl cellulose is significantly higher than both the commercially available plastic lens polishing slurry formulations for Polycarbonate 1.586 RI lens and was higher (compared to Americal Plus) or comparable (compared to Poly-Pro All-Format™) in value for CR39 1.498 RI lens, but at a much lower alumina grit than either of the commercially available products. This result was surprising as a skilled person would expect that reducing the amount of grit in a slurry formulation should reduce the effectiveness of the stock removal of the polish made with it. Advantageously, these results were achieved without any loss of quality of the surface finish of the lenses polished.

EXAMPLE 3

[0069] The effect of the addition of the polishing additive of the present disclosure on the stock removal rate of commercially available plastic lens polishing slurry formulation, sold as Poly-Pro All-Format™ was studied. To the Poly -Pro All-Format™ formulation, 0.1 wt.% polishing additive hydroxyethyl cellulose of the present invention was added and the resultant slurry was labeled “Poly-Pro All-Format™ Sample B”. The stock removal rates for Poly-Pro All-Format™ Sample B were measured using the polishing conditions described in EXAMPLE 1. The results are shown in TABLE 3 along with the results of the control Slurry 1 of EXAMPLE 1 and Poly-Pro AllFormat™ of EXAMPLE 2.

TABLE 4

[0070] The results in TABLE 4 demonstrate that adding the polishing additive hydroxy ethyl cellulose of the present disclosure to commercially available formulations resulted in a significant increase in stock removal rate when compared to both the control Slurry 1 and the commercially available formulation without the hydroxyethyl cellulose, and the significant increase was seen for both CR39 1.498 RI and Polycarbonate 1.586 RI lenses. Advantageously, these results were achieved without any loss of quality of the surface finish of the lenses polished.

[0071] From the above, it is observed that stock removal rates are improved using the slurry formulations described herein having the cellulose derivative polishing additives. Advantageously, these results were achieved without any loss of quality of the surface finish of the lenses polished. [0072] From the foregoing and with reference to the various figure drawings, those skilled in the art will appreciate that certain modifications can also be made to the present disclosure without departing from the scope of the same. While several embodiments of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.

Claims

1. An aqueous slurry composition for polishing an organic polymer-based ophthalmic substrate comprising: about 5 wt.% to about 40 wt.% of an abrasive particle; about 0.5 wt.% to about 4 wt.% of a polishing accelerator; about 0.01 wt.% to about 4 wt.% of a polishing additive; about 0.5 wt.% to about 4 wt.% of a polishing suspension additive; about 0.025 wt.% to about 0.30 wt.% of an anti-foaming agent; and water, wherein the polishing additive comprises a cellulose or a cellulose derivative.

2. The aqueous slurry composition of claim 1, wherein the abrasive particle is selected from aluminum oxide, cerium oxide, iron oxide, tin oxide, titanium oxide or combinations thereof.

3. The aqueous slurry composition of claim 1, wherein the abrasive particle is aluminum oxide.

4. The aqueous slurry composition of claim 1, wherein the abrasive particle has an average particle size of about 0.01 microns to about 4 microns.

5. The aqueous slurry composition of claim 1, wherein the abrasive particle has an average particle size of about 1.8 micron to about 2.2 microns.

6. The aqueous slurry composition of claim 1, wherein the aqueous slurry composition comprises about 17 wt.% to about 20 wt.% of the abrasive particle.

7. The aqueous slurry composition of claim 1, wherein the polishing accelerator is an aluminum compound selected from aluminum nitrate, polyaluminum chloride, aluminum bromide, aluminum sulfate, aluminum iodide, aluminum chloride and aluminum phosphate, and mixtures thereof.

8. The aqueous slurry composition of claim 1, wherein the polishing accelerator is aluminum nitrate.

9. The aqueous slurry composition of claim 1, wherein the aqueous slurry composition comprises about 1.5 wt.% to about 2.5 wt.% of the polishing accelerator.

10. The aqueous slurry composition of claim 1, wherein the polishing additive is a cellulose derivative selected from hydroxyethyl cellulose (HEC), hydroxpropyl cellulose (HPC), methyl cellulose (MC), hydroxypropyl methyl cellulose (HPMC), hydroxybutyl methylcellulose (HBMC), or a combination of two or more thereof.

11. The aqueous slurry composition of claim 1 , wherein the polishing additive is hydroxyethyl cellulose.

12. The aqueous slurry composition of claim 1, wherein the aqueous slurry composition comprises about 0.25 wt.% to about 1 wt.% of the polishing additive.

13. The aqueous slurry composition of claim 1, further comprising about 0.5 wt.% to about 4 wt.% of a polishing suspension additive.

14. The aqueous slurry composition of claim 13, wherein the polishing suspension additive is selected from aluminum hydroxide and aluminum hydroxide oxide.

15. The aqueous slurry composition of claim 1, further comprising about 0.025 wt.% to about 0.3 wt.% of an anti-foaming agent.

16. The aqueous slurry composition of claim 15, wherein the aqueous slurry composition comprises about 0.025 wt.% to about 0.1 wt.% of the anti-foaming agent.

17. The aqueous slurry composition of claim 1, wherein the anti-foaming agent is a modified siloxane treated fumed silica.

18. The aqueous slurry composition of claim 1, wherein the water is de-ionized water.

19. The aqueous slurry composition of claim 1, further comprising about 0.1 wt.% to about 10 wt.% of at least one selected from the group consisting of (a) of a polyvinyl alcohol compound, (b) a tertiary amide compound, and (c) combinations thereof.

20. The aqueous slurry composition of claim 19, wherein the aqueous slurry composition comprises the polyvinyl alcohol compound and the tertiary amide compound.

21. The aqueous slurry composition of claim 19, wherein the polyvinyl alcohol compound is selected from polyvinyl formate, polyvinyl benzoate, polyvinyl stearate, polyvinyl chloroacetate, polyvinyl fluoroacetate, and polyvinyl propionate.

22. The aqueous slurry composition of claim 19, wherein the tertiary amide compound is selected from poly 2-ethyloxazoline, poly (N,N-dimethylacrylamide), poly (N-methyl N-vinyl acetamide), N-methylcaprolactam, and N-methyl-2-piperidone.

23. A method of polishing an organic polymer-based ophthalmic substrate, the method comprising the steps of: providing an aqueous slurry composition comprising: about 5 wt.% to about 40 wt.% of an abrasive particle; about 0.5 wt.% to about 4 wt.% of a polishing accelerator; about 0.01 wt.% to about 4 wt.% of a polishing additive; about 0.5 wt.% to about 4 wt.% of a polishing suspension additive; about 0.025 wt.% to about 0.30 wt.% of an anti-foaming agent; and water, wherein the polishing additive comprises a cellulose or a cellulose derivative; disposing the aqueous slurry composition between a polishing pad and the organic polymer-based ophthalmic substrate; and polishing the organic polymer-based ophthalmic substrate with the polishing pad and the aqueous slurry composition to remove a surface portion of the organic polymer-based ophthalmic substrate.

24. The method of claim 23, wherein the abrasive particle is selected from aluminum oxide, cerium oxide, iron oxide, tin oxide, titanium oxide or combinations thereof.

25. The method of claim 23, wherein the abrasive particle is aluminum oxide.

26. The method of claim 23, wherein the abrasive particle has an average particle size of about 0.01 microns to about 4 microns.

27. The method of claim 23, wherein the abrasive particle has an average particle size of about 1.8 micron to about 2.2 microns.

28. The method of claim 23, wherein the aqueous slurry composition comprises about 17 wt.% to about 20 wt.% of the abrasive particle.

29. The method of claim 23, wherein the polishing accelerator is an aluminum compound selected from aluminum nitrate, polyaluminum chloride, aluminum bromide, aluminum sulfate, ahiminum iodide, aluminum chloride and aluminum phosphate, and mixtures thereof.

30. The method of claim 23, wherein the polishing accelerator is aluminum nitrate.

31. The method of claim 23, wherein the aqueous slurry composition comprises about 1.5 wt.% to about 2.5 wt.% of the polishing accelerator.

32. The method of claim 23, wherein the polishing additive is a cellulose derivative selected from hydroxyethyl cellulose (HEC), hydroxpropyl cellulose (HPC), methyl cellulose (MC), hydroxypropyl methyl cellulose (HPMC), hydroxybutyl methylcellulose (HBMC), or a combination of two or more thereof.

33. The method of claim 23, wherein the polishing additive is hydroxyethyl cellulose.

34. The method of claim 23, wherein the aqueous slurry composition comprises about 0.25 wt.% to about 1 wt.% of the polishing additive.

35. The method of claim 23, wherein the aqueous slurry composition further comprises about 0.5 wt.% to about 4 wt.% of a polishing suspension additive.

36. The method of claim 23, wherein the polishing suspension additive is selected from aluminum hydroxide and aluminum hydroxide oxide.

37. The method of claim 23, wherein the aqueous slurry composition further comprises about 0.025 wt.% to about 0.3 wt.% of an anti-foaming agent.

38. The method of claim 33, wherein the aqueous slurry composition comprises about 0.025 wt.% to about 0.1 wt.% of the anti -foaming agent.

39. The method of claim 23, wherein the anti-foaming agent is a modified siloxane treated finned silica.

40. The method of claim 23, wherein the water is de-ionized water.

41. The method of claim 23, wherein the aqueous slurry composition further comprises about 0.1 wt.% to about 10 wt.% of at least one selected from the group consisting of (a) of a polyvinyl alcohol compound, (b) a tertiary amide compound, and (c) combinations thereof.

42. The method of claim 41, wherein the aqueous slurry composition comprises the polyvinyl alcohol compound and the tertiary amide compound.

43. The method of claim 41, wherein the polyvinyl alcohol compound is selected from polyvinyl formate, polyvinyl benzoate, polyvinyl stearate, polyvinyl chloroacetate, polyvinyl fluoroacetate, and polyvinyl propionate.

44. The method of claim 41, wherein the tertiary amide compound is selected from poly 2- ethyloxazoline, poly (N,N-dimethylacrylamide), poly (N-methyl N- vinyl acetamide), N- methylcaprolactam, and N-methyl-2-piperidone.

45. The method of claim 23, wherein the organic polymer-based ophthalmic substrate is a high index organic polymer-based ophthalmic substrate.

46. The method of claim 23, wherein the organic polymer-based ophthalmic substrate is a part of a digital lens polishing system.