DE60012796T2 - POLISHING PROCESS FOR SOFT ACRYLIC OBJECTS - Google Patents

Abstract

A method for polishing articles comprising soft acrylic materials is disclosed. The method includes a polishing step and a cleaning step. In the polishing step, a receptacle is charged with polishing beads of various sizes, alumina, a swelling agent and the articles to be polished, and agitated for a period of time and at a speed sufficient to remove surface irregularities. Following the polishing step, the polished articles are cleaned by agitating them with a cleaning slurry comprising cleaning beads of various sizes, alumina, a solvent and a surfactant for a period of time and at a speed sufficient to clean the surface of the polished articles. Agitation is preferably accomplished by a tumbling machine.

Description

1. Field of the invention

The present invention relates to a method of polishing soft acrylic articles according to the preamble of claim 1. An example of such a method is disclosed in U.S. Pat US 6 010 391 A disclosed.

2. Description of the related State of the art

switch Acrylic materials are used to make a variety of products used. Since soft acrylic materials generally with biological tissues and fluids are compatible, they are particularly useful for Production of products for biomedical Applications. examples for Such soft acrylic products include soft contact lenses and soft prosthetic implants, such as intracorneal and intraocular lenses, Corneal inlays that during of refractive surgery, and intracapsule rings, which are used to the natural Lens capsule during to support an eye surgery, one.

A highly polished surface, free from sharp edges or surface irregularities is, is for many biomedical applications are required. Implantable products, like intraocular lenses are in direct contact with body tissues and a tearing or ablation of tissue through rough surfaces could lead to a rupture of blood vessels, a Irritation or other trauma to the tissue. Even tiny irregularities can in body tissues cause irritation. This is a particularly serious problem in contact lenses and parts of intraocular lenses associated with the Eye are in contact where the tissue is extremely sensitive.

The Use of soft acrylic materials for intraocular lenses is one relatively new development. Intraocular lenses are made of soft acrylic material advantageous as they can be folded and through smaller incisions can be used in the cornea, as it was possible earlier resulting in fewer complications after surgery. rough Edges caused by the cutting of lens blanks or one during the Forming generated burrs can cause intraocular irritation cause.

Also require soft contact lenses have a highly polished surface to stimulate the interior eyelid and corneal epithelium. The eye is across from Errors in contact lenses extremely sensitive and even small burrs that caused by the molding process can cause irritation and discomfort cause. Expensive molding or individual manual grinding techniques can used to give these lenses the desired surface.

mechanical Devices using a smooth, smooth movement also require highly polished smooth surfaces on soft acrylic products. Such a highly polished, smooth-worked soft acrylic object is often difficult to obtain because these products are made by hardening acrylic material into molds, even the most precise Tools for a certain burr formation and / or irregular edges to lead. The products can be cut and polished, but these surface treatment methods Generally done by hand and are both time consuming and expensive as well as inaccurate, so they do not become completely smooth or regular surface, the is required lead. Many of these items, especially for biomedical applications are still relatively small and / or irregularly shaped, what difficulties with the desired surface finish and / or clarity causes.

For silicone materials, Like silicone rubber and silicone elastomers, barrel polishing processes are known. See, e.g. U.S. Patent No. 5,133,159 for out However, silicone-fabricated articles are known not equally applicable to articles of soft acrylic materials. The removal of defects of small and irregular shaped soft acrylic products is an unsolved problem in the prior art. It would be of great Benefits, a simple, economical and effective method for polishing and / or clarifying soft acrylic articles for industrial, to provide medical and mechanical purposes.

The communicated U.S. Patent Application Serial No. 08 / 962,604 discloses methods for Drum polishing of soft acrylic objects. The methods include a cryogenic polishing stage and a cleaning stage.

Summary of the invention

The The present invention provides a method of polishing articles which soft acrylic materials available, having the characteristics of Claim 1. Examples of objects polished by the method according to the invention can be shut down one-piece Intraocular lenses, intraocular lens haptics, intraocular lens optics, Intracapsular rings, corneal inlays, intracorneal lenses and contact lenses one.

Detailed description the invention

As used herein, the term "soft acrylic material" means a material that includes polymers or copolymers of acrylic acid, methacrylic acid, esters of these acids or acrylonitrile, where the polymers or copolymers have a glass transition temperature (T _g ) of about 35 ° C or less and have a value for the Shore A hardness of about 90 or less. Preferably, the soft acrylic materials have a T _g of about 25 ° C or less, and most preferably 20 ° C or less. The soft acrylic materials preferably have a Shore A hardness value of about 60 or less, and most preferably about 45 or less.

Examples for soft Acrylic materials used in the manufacture of foldable intraocular lenses are suitable, close (i) acrylic material obtained by copolymerizing about 65% by weight 2-Phenylethyl acrylate, about 30% by weight of 2-phenylethyl methacrylate, a Ultraviolet absorber and a crosslinking agent and (ii) acrylic material obtained by copolymerizing about 80% by weight of 2-phenylethyl acrylate, about 15% by weight of 2-hydroxyethyl methacrylate, an ultraviolet absorber and a crosslinking agent was prepared without being limited thereto. These and others suitable soft acrylic materials are disclosed in U.S. Patent No. 5,290 892 and co-pending, commonly assigned US patent application no. 08 / 739,245. Further examples of soft acrylic materials, shut down those disclosed in U.S. Patent No. 5,331,073, without limited to this to be.

Of the Expression "preferred Acrylic material ", like it is used here means the soft acrylic material obtained by adding about 65% by weight of 2-phenylethyl acrylate, about 30% by weight of 2-phenylethyl methacrylate, about 1.8 wt% o-methallyl-Tinuvin P and 3.2 wt% 1,4-butanediol diacrylate copolymerized using 1.8% Perkadox 16 as Initiator.

The present methods include a polishing step and a cleaning step. The polishing step can be carried out at ambient conditions and this is preferred. In the polishing step, a container is loaded with a polishing slurry and the objects to be polished. The container may be of various sizes and shapes and may be formed of glass, polycarbonate or other suitable material. The receptacle is preferably a round glass container, such as a 1-liter Wheaton ^® -Glasbehälter with glass lid.

The polishing contains a mixture of polishing beads, alumina and one or more Swelling agents. However, as one skilled in the art will appreciate, the exact one varies Composition of the polishing slurry depending on several factors, such as the particular acrylic material and the size and shape of the to be polished Object. Preferably, the polishing beads are glass beads that are relatively They are cheap and readily available in the market, but they can also solid or filled Be beads made of any suitable material. Commercially available Glass beads are available in various sizes, e.g. in a size of 0.3, 0.5, 1 and 2 mm. The glass beads contained in the polishing slurry are preferably preconditioned so they will not are in the raw state; that means they prefer to rub off easily or have been conditioned so that they are less likely to surface the Damage lenses can.

A Kind to condition raw glass beads used by commercial suppliers Consistently, the beads are acidic in succession (e.g., 2N HCl for 10 minutes) or basic (1% NaOH for 1 hour long) wash solutions to move in a drum. After the rough surfaces light have been rubbed off the beads are used in the polishing stage.

The necessary number and size distribution the polished beads hang starting from the number and size of the too polishing objects, but an appropriate choice can easily be determined without undue experimentation. In general, a mixture of polishing beads is different Sizes preferred. In the case of the preferred acrylic material, e.g. the polishing slurry glass beads with 0.5 mm and 1.0 mm in a ratio of 1: 3. For example, would the polishing beads added to a 1 liter container, about 1000 g polishing beads as follows: about 250 g glass beads with 0.5 mm and about 750 g of 1.0 mm glass beads.

The polishing slurry also contains alumina as a polishing agent. Alumina polishing powder is commercially available. Available grain sizes of alumina expressed as mesh size are in a range of less than 0.05 μm to 3.0 μm and more. The optimum amount and mesh size of the alumina depends on other process parameters, including the type of soft acrylic material. Generally, however, the polishing slurry contained in a one liter container requires a minimum of about 0.2% alumina based on swelling agent (w / w) to achieve satisfactory results, regardless of the size and shape of the product polishing objects. Increasing the amount of alumina appears to increase the efficiency of the polishing slurry, especially as the number of articles to be polished increases, to a maximum of about 2% (alumina: solvent G / G). Higher levels of alumina can damage the articles to be processed and do not appear to provide significant improvement in polishing efficiency or results. In the case of the preferred acrylic material, the polishing slurry contains about 1% alumina at 0.5 μm, based on swelling agent (w / w).

In addition to The polishing slurry and alumina also contain the polishing slurry or more swelling agents. The swelling agent ingredient swells the To polish the object easily, makes the surface more brittle, thereby the polishing results are facilitated and improved. In addition to The swelling agent is used for the light swelling of the article to be polished also as a medium for the alumina and the polishing beads. Any means that the is capable of swelling without damaging it inversely suitable.

suitable Close swelling agent solvent such as alcohols, aliphatic hydrocarbons, chlorinated solvents and aromatic hydrocarbons, without being limited thereto. Examples for suitable Alcohol solvent shut down short-chain alcohols (approx 10 carbon atoms in total or less), such as methanol, ethanol and isopropanol. examples for suitable aliphatic hydrocarbon solvents include pentane, Hexane, heptane and light gasoline. Examples of suitable chlorinated solvents shut down Methylene chloride and trichloromethane. Examples of suitable aromatic hydrocarbon solvents shut down Benzene and toluene. Preferred solvents include mineral spirits with a flash point of about 90-145 ° F, such as the Stoddard solvent known light benzine fraction.

As in determining the optimal amount of alumina used in the polishing slurry should be included the type and amount of swelling agent contained in the polishing slurry should be, depending on the nature of the selected soft acrylic material. For certain Acrylic materials and polishing conditions are suitable swelling agents with specific boiling point ranges or glass transition temperatures better than others in the polishing slurry. In the case of the preferred acrylic material, the preferred swelling agent is a commercially available Minor benzine fraction known as "Stoddard solvent". Other Minor benzine fractions or other swelling agents may be used for other soft acrylic materials, as the preferred acrylic material. In general a suitable amount of the swelling agent is the amount that is sufficient by the standing volume of the polishing beads contained in the polishing slurry are to cover. So, in a 1 liter container, that about Contains 1000 g of glass polishing beads, the preferred polishing slurry for the preferred acrylic material is about 250 ml of Stoddard solvent as a mineral spirit ingredient on.

The polishing is preferred in the container without acrylic objects, which are to be polished, formulated. For example, be alumina first and the selected one Swelling agent ingredient in the container containing the polishing beads contains given. The polishing slurry is then mixed before the objects to be polished are added. In the case of a 1 liter container and the polishing slurry for the preferred acrylic material is e.g. the whole polishing slurry over one short period (about 30 minutes) at room temperature, briefly mixed in a drum before the objects to be polished be added.

As soon as the objects to be polished to the polishing slurry have been added, the vessel over a period of time and with a speed sufficient to handle all the rough spots, sharp edges and any tooling or machining marks from the surface of the objects to remove. The movement is preferably achieved by placing the vessel on a Rotation device is provided, e.g. a commercially available Tumble device (e.g., Model 3BAR from Topline Mfg. Co., Fullerton, CA). The optimal time and rotation speed vary with batch size, type of soft acrylic material, size and style the objects to be polished etc. When the methods of the present invention are used, To polish intraocular lenses is a typical batch size in the range from 50 to 100 lenses per 1-liter tube. In the case of the preferred Acrylic material will get excellent polishing results, if the item is polished in the drum for about 3 to 10 days with the rotational speed of the vessel being about 80 rpm.

To the polishing stage can things are separated from the polishing beads by the contents of the polishing vessel on a stack of sieves is emptied, so that the swelling agent expires. The objects can then rinsed be either with fresh solvent or deionized water to separate the lenses from the beads. The polished objects appear very smooth, can but contain alumina particles on the surface and / or cloudy or frosty or appear dull, as if a residue on the surface of polished objects would. Any Aluminum oxide particles and any surface residues are in a cleaning step away.

After the articles have been polished, but before they are subjected to the cleaning step, it may be advantageous to reduce or remove any residual swelling agent from the surface of the articles in the event that the selected cleaning slurry contains a different solvent than that for the cleaning slurry Polishing slurry selected swelling agents. This can be achieved by briefly cleaning the articles in a commercially available ultrasonic cleaner. Cleaning solutions suitable for use in ultrasonic cleaners generally include solvents, detergents, water and mixtures thereof. The exact composition of the cleaning solution is not critical, although it may be desirable to adjust the ingredients of the composition based on the type of solvent selected. In the case where the selected swelling agent is Stoddard solvent, a suitable stock ultrasonic cleaning solution comprises a mixture of water, 2-butoxyethanol, Micr ^® -Detergenz and ammonium hydroxide.

To Ultrasonic cleaning, if done, will be polished objects in a moving container, the one cleaning slurry with cleaning beads, alumina, a solvent and a surfactant contains cleaned. The solvent is preferably the same as that used in the polishing slurry Solvent. As in the polishing step above, the movement is preferred with the help of achieved a rotating device. The container is preferably a round 1 liter glass jar with a Glass lid, although each container with a shape in which the objects to be cleaned are not attached (e.g., in corners of a rectangular vessel) or captured (e.g., in the neck area connecting the recess of the body to the lid) would be suitable. The cleaning beads can of the same type as those for use as polishing beads appropriate. As in the case of the polishing beads are the cleaning beads preferably conditioned glass beads. In general, a mixture of cleaning beads of various sizes.

The necessary number and size distribution The cleaning beads vary with the number and size of the polishing objects, but an appropriate choice can be easily determined without undue experimentation. In the case of the preferred acrylic material, e.g. the cleaning slurry, the added to a 1 liter container would, about 1000 g cleaning beads as follows: about 250 g glass beads with 0.5 mm and about 750 g 1.0 mm glass beads (larger beads become common avoided in trying to get the opportunity reduce the cleaning beads from damaging the surfaces of the objects).

The cleaning slurry contains Alumina, a surfactant and a solvent in which the alumina not soluble is. The most preferred solvents are light gasoline solvents with a flash point of about 90 to 145 ° F, such as Stoddard solvent. In a preferred embodiment contains the polishing slurry a solvent as the swelling agent, and the cleaning slurry contains the same solvent. This simplifies the polishing and cleaning process by the Necessity is avoided, the lenses between polishing and cleaning stages to win and to flush. In this preferred embodiment The cleaning stage can start just after adding a suitable one Surfactant directly to the polishing slurry in the container, the is used for polishing as soon as the polishing stage is completed is.

suitable Surfactants for use in the cleaning slurry are those that are in the selected one solvent solve and suspending the alumina particles in the solvent promote. The preferred amount of surfactant in the cleaning slurry is the amount, about a ratio of 1: 1 (w / w) to the amount of alumina in the cleaning slurry. A diminishing of the ratio from surfactant to alumina can cause the alumina particles in the surface the objects to be cleaned embedded or damage on the surface of the objects can cause. An increase the ratio of Surfactant to alumina can increase the effectiveness of the purification process Reduce. The preferred surfactant for use with Stoddard solvent is Dioctylsulfosuccinate ("DSS"), a commercially available available Surfactant.

The preferred amount and "mesh size" of the alumina for use in the cleaning slurry depends on other process parameters including, the type of soft acrylic material. In general, that requires cleaning slurry, contained in a 1 liter container is, however, a minimum of about 0.2% alumina: solvent (G / G) to achieve acceptable cleaning results regardless of the size and shape the objects to be cleaned. The heightening The amount of alumina and surfactant seems to increase the efficiency of the product cleaning slurry to increase up to a maximum of about 2% (w / w each of alumina and surfactant). higher Concentrations can the objects to be cleaned to damage and do not appear to significantly improve the cleaning results. In the case of the preferred acrylic material, the cleaning slurry contains 1% Alumina with 0.05 μm and 1% DSS based on solvent (w / w).

The Volume of liquid, in the cleaning slurry should be included depends on the volume of cleaning beads, the number and size of in the drum to be cleaned objects, etc. from. In general should, however, for the Drum cleaning the cleaning slurry a liquid content contain sufficient to prevent the cleaning beads too become dry and on the inner surface of the cleaning container walk along to such an extent that they sporadically or fall too hard. Instead, the cleaning beads should be relative smoothly falling apart. In the same way should the volume the liquid in the cleaning slurry not too big so that the items to be cleaned float up or out of the stream of cleaning beads moving in the drum. For example, contains in the case of the preferred acrylic material, a 1 liter jar containing 1,000 contains glass cleaning beads as described above, approximately 250 ml of liquid.

The Purification stage is preferably carried out at a temperature which sufficiently over the glass transition temperature of the soft acrylic material to ensure that the article in the cleaning slurry is soft and at least slightly flexible to the removal to promote frosty or dull or cloudy residues. In the case of the preferred Acrylic material, the cleaning step is preferably carried out at about 18 ° C or more.

As in the case of the polishing step, the optimum time and rotational speed varies in the purification stage with the batch size, the type of soft acrylic material, Size and shape the objects to be cleaned, the state of the cleaning beads, etc. When using the methods of the present invention To polish intraocular lenses is a typical batch size in the area from 50 to 100 lenses per 1 liter container. In the case of the preferred Acrylic material will get excellent polishing results, if the object is about The drum is polished for 3 to 10 days, with the rotation speed of the container approximately 80 rpm. After about 1 to 3 days of drum cleaning with one rotation speed or rotational speed of the container of about 80 U / min are the intraocular lenses made of the preferred acrylic material very pure (no dull appearance) and optically clear with little or no cosmetic errors. Certain embodiments of the invention are explained in the following examples.

example 1

Drum polishing of intraocular lenses (preferred acrylic material)

One 1000 ml round glass jug was used with approximately 1,000 g of a mixture of glass polishing beads filled. The mixture contained approximately 25% glass beads with 0.5 mm and 75% glass beads with 1.0 mm. For this 2.0 g of 0.05 μm alumina polishing powder (Baikowski International Corp., Charlotte, NC) and 250 ml Stoddard solvent (EM Scientific, Gibbstown, NJ). The container and its contents were into a modified 3BAR tumbler (Topline Mfg. Co.). The tumbler unit was lowered to low speed (80 rpm) turned on and the vessel about 15 minutes Stumble at ambient temperature (21.0 ° C) for a long time the contents could mix before the addition of one-piece intraocular lenses from the preferred acrylic material. After adding 10 lenses was the container put back in the drum and treated for 5 days in the drum. After the drum treatment, the vessel was removed and the contents poured into a No. 6 sieve to remove the lenses from the glass beads separate. They were then deionized with water for 2 minutes rinsed and dried with compressed air. A trial lens was added an enlargement of 16X examined for roundness and surface quality. She appeared highly polished. All processing lines were removed and the optic and haptic edges were smooth and rounded. A very slight cloudiness, the entire surface the lens covered was also observed after the drum treatment.

Example 2

Drum cleaning of intraocular lenses, which were polished in Example 1 (cleaning slurry on Solvent-based)

A 1000 ml round-bottomed jar was filled with approximately 1,000 grams of a mixture of cleaning glass beads. The mixture contained about 25% glass beads with 0.5 mm and 75% glass beads with 1.0 mm. To this was added approximately 1.0 g of 0.05 mesh alumina polish and 1.0 g of dioctylsulfosuccinate (DSS). Finally, about 250 ml of Stoddard solvent was added to the vessel to complete the cleaning slurry mixture. The polished lenses of Example 1 were then placed in the cleaning vessel, which was capped and placed on a 3BAR tumbler (Topline Mfg. Co.). The vessel and its contents were treated at 80 rpm for about 3 days at room temperature (21.0 ° C) in the drum. At the end of the cleaning cycle, the vessel was removed from the drum pour the contents and contents into a # 6 sieve to separate the lenses from the cleaning beads. The lenses were rinsed briefly with deionized water and allowed to air dry. A trial lens was examined at 16X to determine if the surface haze had been successfully removed. The lens surface appeared pure and clear.

Example 3

Barrel polishing / cleaning of intraocular lenses (preferred acrylic material)

One 1000 ml round glass drum vessel was with approximately 1,000 g of a mixture of glass polishing beads filled. The mixture contained approximately 25% glass beads with 0.5 mm and 75% glass beads with 1.0 mm. For this 1.5 g of alumina polishing powder (Baikowski International Corp., Charlotte, NC) at 0.05 μm and 250 ml of Stoddard solvent (EM Scientific, Gibbstown, NJ). The vessel and his Content was transferred to a modified 3BAR tumbler (Topline Mfg. Co.). The tumbler unit was lowered to low speed (80 Rpm) and the vessel became about 15 Treated for minutes at ambient temperature (21.0 ° C) in the drum and the contents allowed to mix before adding one-piece intraocular lenses from the preferred acrylic material. After adding 10 lenses was the vessel back in given the drum and treated in the drum for 9 days. After this an acceptable degree of polishing of the lens samples had been achieved, was the vessel from the Drum removed and opened. 1.0 g of dioctylsulfosuccinate (DSS) was added, containing the polishing slurry in the Substantially converted to a cleaning slurry. The vessel was then closed again and returned to the drum and at lower Speed (80 rpm) for a further 3 days in the drum. Upon completion of the cleaning cycle, the vessel became again taken from the drum and the contents poured into a sieve No. 6, to separate the lenses from the glass beads. They were then with deionized water for 2 minutes and purged with compressed air dried. A trial lens was examined for roundness and surface quality at 16X. All processing lines had been removed and the optics and haptics edges were smooth and rounded. The lens surface appeared pure and highly polished without a trace of surface haze.

The The invention has been described with reference to certain preferred embodiments described; It is understood, however, that they are specific in others Shapes or variations can be made within the scope of the claims. The embodiments described above become therefore as explanatory in every respect and not restrictive The scope of the invention is limited to the appended claims.

Claims (10)

A method of polishing an article comprising a soft acrylic material, the method comprising a) polishing the article by loading a container with a polishing slurry and the article to be polished, and moving the container over such time and at such a speed; sufficient to remove surface irregularities from the article; and b) cleaning the polished article by contacting it with a cleaning slurry in a container and agitating the container for a time and at a rate sufficient to cause the cleaning article Cleaning surface of the article, wherein the cleaning slurry contains cleaning beads, alumina, a solvent and a surfactant, characterized in that the polishing slurry contains polishing beads, alumina and a swelling agent. The method of claim 1, wherein the polishing beads and the cleaning beads are glass beads. The method of claim 2, wherein the polishing beads Glass beads of 0.5 mm and 1 mm in a ratio of 1: 3 have. The method of claim 2, wherein the cleaning beads Having glass beads of 0.5 mm and 1 mm in a ratio of 1: 3 and the amount of alumina in the cleaning slurry about 0.2 to 2% (alumina to solvent G / G) is. The method of claim 1, wherein the amount of alumina in the polishing slurry at least 0.2% (alumina to swelling agent G / G). The method of claim 1, wherein the swelling agent a solvent is selected from the group consisting of alcohols; aliphatic hydrocarbons; chlorinated solvents and aromatic hydrocarbons. The method of claim 6, wherein the solvent a light gasoline solvent with a flash point of about 90 to 145 ° F. The process of claim 1, wherein the surfactant in the cleaning slurry is present in a ratio of about 1: 1 (w / w) based on the amount of alumi nium oxide is present in the cleaning slurry. The method of claim 1, wherein the cleaning slurry is prepared is added by adding a surfactant to the polishing slurry and wherein the container used for cleaning the same as the container used for polishing. The method of claim 1, wherein the article selected is from the group consisting of one-piece intraocular lenses, intraocular lens haptics, Intraocular lens optics, intracapsular rings, corneal inlays, intracorneal lenses and contact lenses.