JP2003525761A - Polishing method for soft acrylic material - 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

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of making a product comprising an acrylic material. In particular, the present invention relates to methods and means or processing goals for polishing soft acrylic materials to remove rough surfaces.

2. Description of Related Art Soft acrylic materials are used in the manufacture of a wide range of products. The soft acrylic material is
Soft acrylic materials may be particularly useful in making products for biomedical applications because they are generally compatible with biological tissues and fluids. Examples of such soft acrylic products include soft contact lenses and soft artificial implants (eg, intracorneal and intraocular lenses), corneal inlays used during refractive surgery, and natural lens capsules during ophthalmic surgery. An intracapsular ring used to support the.

Highly polished finishes without sharp edges or surface irregularities are necessary for many biomedical applications. Implantable products, such as intraocular lenses, directly contact body tissues, and tissue tears or abrasions due to rough surfaces can cause rupture of blood vessels, inflammation or other trauma to tissue. Even minute irregularities can cause inflammation of body tissues. This is a particularly serious problem for some contact lenses and intraocular lenses where the tissue contacts the eye where it is very sensitive.

The use of soft acrylic materials for intraocular lenses is a relatively new development. Intraocular lenses formed of soft acrylic material are advantageous in that they can be folded and inserted with smaller incisions in the cornea than previously possible, resulting in fewer post-operative complications. The rough edges resulting from the cutting of the lens blank or the flashing created during molding can cause inflammation in the eye.

In addition, soft contact lenses require a high degree of polishing finish to prevent inflammation of the inner lid and corneal epithelium. The eye is very sensitive to contact lens imperfections, and even the slight bumps that result from the molding process can cause irritation and discomfort. Expensive molding procedures or individual manual polishing techniques can be used to provide the desired finish for these lenses.

Mechanical devices that use smooth, frictionless movement also require highly polished smooth surfaces of soft acrylic products. Obtaining such highly polished, smooth-finished, soft acrylic articles is often difficult because these products are made by curing the acrylic material in the mold, where the most accurate die Even produces some flashing and / or irregular edges. Although these products can be cut and polished, these finishing procedures are generally manual, both time consuming and expensive, and inaccurate, and therefore the overall required Does not produce the desired smooth or regular surface. Moreover, many of these articles, especially those for biomedical applications, are relatively small and / or irregular in shape, causing difficulties in obtaining the desired finish and / or transparency.

Tumble polishing processes are known for silicone materials such as silicone rubber and silicone elastomers. For example, US Pat. No. 5,133,15
See No. 9. However, this known tumble-polishing method for articles made from silicone materials cannot be properly applied to articles made from soft acrylic products. Removal of imperfections from small and irregularly shaped soft acrylic materials
This is an unsolved problem in this field. It would be highly useful to provide a simple, economical and effective method for polishing and / or cleaning soft acrylic articles for industrial, medical and mechanical processes.

Co-pending US Provisional Application No. 08 / 962,604 by the same Applicant discloses a method for tumble polishing soft acrylic articles. This method includes ultra low temperature polishing and cleaning steps.

SUMMARY OF THE INVENTION The present invention provides a method for polishing an article comprising a soft acrylic material. This method involves two steps: a polishing step and a cleaning step. This polishing process
Filling the container with the polishing slurry and the article to be polished, and agitating the container for a time and at a rate sufficient to remove surface irregularities from the article. The polishing slurry contains polishing beads, alumina and a swelling agent. This polishing step can be performed under ambient conditions.

After polishing, the article may include alumina particles or surface coatings or other residues that cause a hazy appearance. Any alumina particles or other residues are removed in the washing process. The cleaning step includes contacting the abraded article with a cleaning slurry in a container and agitating the vessel for a time and at a rate sufficient to clean the surface of the abraded article. This cleaning slurry contains cleaning beads, alumina,
Includes solvent and surfactant.

Examples of articles that may be polished according to the methods of the present invention include one-piece intraocular lenses, intraocular lens haptics, intraocular lens optics, intracapsular rings, corneal inlays, intracorneal lenses and contact lenses.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for polishing an article comprising a soft acrylic material. As used herein, "soft acrylic material" means a material comprising a polymer or copolymer of acrylic acid, methacrylic acid, esters of these acids or acrylonitrile, where the polymer or copolymer is about Glass transition temperature (T _g ) of 35 ° C. or lower and Shore A hardness (Shore A) of about 90 or lower.
Hardness) value. Preferably, the soft acrylic material is about 25
° C. has the following _{T g} of, and most preferably about 20 ° C. below _{T g} of,. The soft acrylic material preferably has a Shore A hardness value of about 60 or less, and most preferably a Shore A hardness value of about 45 or less.

Examples of suitable soft acrylic materials for making foldable intraocular lenses include (i) about 65 wt. % 2-phenylethyl acrylate, about 30 wt.
% 2-phenylethylmethacrylate, an acrylic material made from the copolymerization of a UV absorber and a crosslinker, and (ii) about 80 wt. % 2-phenylethyl acrylate, about 15 wt. % Acrylic acid made from copolymerization of 2-phenylethylmethacrylate, UV absorber and crosslinker. These soft acrylic materials and other suitable soft acrylic materials are described in US Pat. No. 5,290.
, 892 and U.S. Provisional Application No. 08/739 by the same applicant, which is currently being continued.
245. Other examples of soft acrylic materials include US Pat.
Examples thereof include, but are not limited to, those disclosed in No. 1,073.

As used herein, “preferred acrylic material” refers to 1.
8 wt. % Perkadox 16 using about 65 wt. % 2-phenylethyl acrylate, about 30 wt. % 2-phenylethylmethacrylate, about 1.8 wt. % O-methallyl tinuvin (Tinuvin) P and 3.2 wt.
． %, A soft acrylic material obtained by copolymerization of 1,4-butanediol diacrylate.

The method includes a polishing step and a cleaning step. This polishing step can be performed,
And preferably under ambient conditions. In this polishing process, a container is filled with the polishing slurry and the article to be polished. The container can be of various sizes and shapes and can be made of glass, polycarbonate or other suitable material. This container is preferably a spherical glass container (eg 1 liter of W
heaton (registered trademark) glass bottle with a glass lid).

The polishing slurry comprises a mixture of polishing beads, alumina and one or more swelling agents. However, one of ordinary skill in the art will appreciate that the exact composition of the polishing slurry will vary depending on various factors such as the nature of the acrylic material and the size and shape of the article to be polished. Preferably, the abrasive beads are relatively inexpensive,
Glass beads are readily available and available, but can be solid or filled beads formed of any suitable material. Commercially available glass beads are available in various sizes, for example 0.3 mm, 0.5 mm, 1 mm and 2 mm. The glass beads contained in this polishing slurry are preferably preconditioned so that they are not untreated; that is, they are preferably slightly warmed or conditioned to make them less likely to scratch the surface of the lens. To be done.

One method for preparing untreated glass beads received from a commercial supplier is an acidic (eg, 2N HCl for 10 minutes) wash solution and a basic (eg, 1% NaOH for 1 hour) wash. Continuous rotation of the beads in each solution. After the rough surface is slightly warmed, the beads can be used in the polishing process.

The required number and size of abrasive beads will depend on the number and size of the articles being abraded, but the appropriate selection can be readily determined without undue experimentation. Typically,
A mixture of abrasive beads of different sizes is preferred. For example, for the preferred acrylic material, the polishing slurry contains 0.5 mm glass beads and 1.0 mm glass beads in a ratio of 1: 3. For example, this abrasive bead added to a 1 liter container has the following content: about 1000 g of abrasive beads: about 250 g of 0.5 m
m glass beads and about 750 g of 1.0 mm glass beads.

The polishing slurry also contains alumina as an abrasive. Alumina polishing powder is commercially available. Available alumina mesh sizes range from less than 0.05 microns to over 3.0 microns. The optimum amount of alumina and mesh size will depend on other process parameters, including the nature of the soft acrylic material.
However, in general, this abrasive slurry contained in a 1 liter container will achieve a satisfactory result, regardless of the size and shape of the article to be abraded, a minimum of about 0.2% relative to the swelling agent. Of alumina (w / w) is required. Increasing the amount of alumina appears to increase the efficiency of this polishing slurry, up to about 2 w / w% (alumina to solvent), especially as the number of articles to be polished increases. Higher concentrations of alumina can result in damage to the treated article and do not appear to provide any significant improvement in this polishing efficiency or results. For the preferred acrylic article, the polishing slurry contains about 1% (w / w) of 0.5 micron alumina to swelling agent.

In addition to polishing beads and alumina, the polishing slurry also contains one or more swelling agents. The swelling agent component slightly swells the article to be polished, making its surface more brittle, thereby promoting and improving this polishing result. In addition to slightly swelling the article to be polished, this swelling agent also acts as a medium for the alumina and abrasive beads. Any agent capable of swelling the article to be polished without irreversibly damaging is suitable.

Suitable swelling agents include, but are not limited to, solvents such as alcohols, aliphatic hydrocarbons, chlorinated solvents, and aromatic hydrocarbons. Examples of suitable alcohol solvents include short chain alcohols (up to about 10 total carbon atoms), such as methanol, ethanol and isopropanol. Examples of suitable aliphatic hydrocarbon solvents include pentane, hexane, heptane and mineral spirits. Examples of suitable chlorinated solvents include methylene chloride and trichloromethane. Examples of suitable aromatic hydrocarbon solvents include benzene and toluene. Preferred solvents include mineral spirits having a flash point of about 90-145 degrees Fahrenheit, such as the mineral spirit fraction known as Stoddard solvent.

As in the case of determining the optimum amount of alumina contained in this polishing slurry,
The nature and amount of swelling agent to be included in the polishing slurry depends on the nature of the soft acrylic material selected. For certain acrylic materials and polishing conditions, swelling agents with a certain boiling range or glass transition temperature perform better than others contained in this polishing slurry. In the case of the preferred acrylic materials, this preferred swelling agent is the commercially available mineral spirits fraction known as "Stoddard solvent". Other mineral spirits fractions or other swelling agents may be more suitable for soft acrylic materials other than this preferred acrylic material. Generally, a suitable amount of swelling agent is sufficient to cover the standard volume of polishing beads contained in the polishing slurry. Thus, in a 1 liter container containing about 1000 g of glass polishing beads, the preferred polishing slurry for the preferred acrylic material contains about 250 mL of Stoddard solvent as the mineral spirit component.

The polishing slurry is preferably formulated in a container that is free of the acrylic article to be polished. For example, first the alumina and selected swelling agent components are added to a vessel containing abrasive beads. The polishing slurry is then mixed before adding the article to be polished. For example, in the case of a 1 liter container and polishing slurry for the preferred acrylic material, the complete polishing slurry is spun at room temperature for a short time (about 30 minutes) before adding the article to be polished.

Once the article to be polished is added to the mixed polishing slurry, the container is sufficient to remove any rough spots, sharp edges, and any tools or machined marks from the surface of the article. Stir for different time and speed. The agitation is preferably carried out on a commercially available rotary machine (eg Topline Mfg. Co., Ful.
This is accomplished by placing the container in a rotating device such as a Model 3BAR from Lerton, CA. The optimum time and speed of rotation will depend on the batch size, the nature of the soft acrylic material, the size and shape of the article to be polished, and so on. When the method of the present invention is used to polish intraocular lenses, typical batch sizes are on the order of 50-100 lenses per liter container. In the case of the preferred acrylic material, the article is about 3 to 3 at a container rotation speed of about 80 rpm.
Excellent polishing results are obtained when tumbled for 10 days.

After the polishing step, the article is separated from the abrasive beads by pouring the contents of the polishing bottle into a sieve stack to drain the swelling agent. Then
To separate the lens from the beads, the article can be rinsed by flushing with either fresh solvent or deionized water. The abraded article may look very smooth, but may contain alumina particles on its surface, and / or may appear hazy or hazy, such as when residues are present on the surface of the abraded article. . Any alumina particles and any surface residue are removed in the washing step.

In the event that the selected cleaning slurry comprises a different solvent than the swelling agent selected for the polishing slurry, after the article has been abraded but before the article is subjected to the cleaning step, It may be advantageous to reduce or remove any residual swelling agent from the surface of the article. This can be accomplished by briefly cleaning the article with a commercially available ultrasonic cleaner. Suitable cleaning solutions for use in ultrasonic cleaning generally include solvents, detergents, water and mixtures thereof. The exact composition of these wash solutions is not essential, but it may be desirable to tailor the components of the composition based on the nature of the solvent selected. When the swelling agent is selected to be a Stoddard solvent, a suitable stock ultrasonic cleaning solution comprises a mixture of water, 2-butoxyethanol, Micro (R) detergent, and ammonium hydroxide.

Following the ultrasonic cleaning, if any, these abraded articles are cleaned with cleaning beads,
Wash in a stirred vessel containing a wash slurry containing alumina, solvent and surfactant. This solvent is preferably the same as any solvent used in the polishing slurry. As in the polishing step above, this agitation may be accomplished, preferably by means of a rotating machine. The container may be a round glass bottle with a glass lid, preferably 1 liter, but is not shaped or scratched (eg in the corner of a square bottle) by the article to be washed (eg in the corner of a square bottle). Any container having a shape (in the area of the neck where the cavity and lid connect) is suitable. The wash beads can be of the same type as beads suitable for use as abrasive beads. As with the abrasive beads, the wash beads are preferably conditioned glass beads.
In general, a mixture of wash beads of different sizes is preferred.

The required number and size of wash beads will depend on the number and size of the articles to be polished, but the appropriate choice can be readily determined without undue experimentation. For example, for the preferred acrylic material, this wash slurry added to a 1 liter container contains about 1000 g of the following wash beads: about 250 g 0.5 mm glass beads and about 750 g 1.0 mm glass beads. (Large size beads are generally avoided as they reduce the likelihood that the cleaning beads will damage the surface of the article).

The cleaning slurry contains alumina, a surfactant, and a solvent in which the alumina is insoluble. The most preferred solvent is about 90-14 degrees Fahrenheit, such as Stoddard solvent.
It is a mineral spirit solvent with a flash point of 5 degrees. In a preferred embodiment, the polishing slurry comprises a solvent such as a swelling agent and the cleaning slurry comprises the same solvent. This simplifies the polishing and cleaning processes by eliminating the need for lens recovery and rinsing between the polishing and cleaning steps. In this preferred embodiment, the washing step, once the polishing step is complete, can be started after merely adding the appropriate surfactant directly to the polishing slurry in the vessel used for polishing.

Suitable surfactants for use in this wash slurry are those that help dissolve the selected solvent and suspend the alumina particles in the solvent.
The preferred amount of surfactant in the wash slurry is that amount which provides a ratio (w / w) of about 1: 1 with the amount of alumina in the wash slurry. Reducing the surfactant to alumina ratio may allow the alumina particles to become embedded in or cause damage to the surface of the article being cleaned. Increasing the ratio of surfactant to alumina can reduce the efficiency of this cleaning process. A preferred surfactant for use with standard solvents is the commercially available surfactant, dioctyl sulfosuccinate ("DSS").

The preferred amount of alumina and "mesh size" for use in this wash slurry depends on other process parameters, including the nature of the soft acrylic material. However, in general, this cleaning slurry contained in a 1 liter container, regardless of the size and shape of the article being cleaned, has a minimum of about 0.2 to solvent to achieve acceptable cleaning results. % (W / w) alumina is required. Increasing the amount of alumina and surfactant appears to increase the efficiency of the wash slurry, up to about 2 w / w% (of each alumina and surfactant). Higher concentrations can damage the item being cleaned and do not appear to significantly improve cleaning results. For the preferred acrylic material, the wash slurry comprises 1 w / w% 0.05 micron alumina and 1 w / w% DSS, relative to the solvent.

The volume of liquid to be included in this wash slurry depends on the volume of wash beads, the number and size of the articles to be tumble washed, etc. However, in general, in the case of a tumble wash, this wash slurry prevents the wash beads from drying out and riding along the inner surface of the wash container to the extent that the wash beads fall apart or too hard. Should contain a sufficient liquid level. Instead, the wash beads should rotate relatively smoothly. Similarly, the volume of liquid in the wash slurry should not be too large so that the article to be washed floats or stays outside the rotating stream of wash beads. For example,
For the preferred acrylic material, a 1 liter container containing 1000 g of glass cleaning beads as described above contains about 250 mL of liquid.

The glass transition temperature of the soft acrylic material is adjusted to ensure that the article in the cleaning slurry is soft and at least slightly flexible to assist in the removal of any hazy or hazy residue. This washing step is preferably carried out at a temperature well above. For the preferred acrylic materials, this washing step is preferably carried out above about 18 ° C.

As with this polishing step, the optimal time and spin speed for this washing step depends on the batch size, the nature of the soft acrylic material, the size and shape of the article to be washed, the condition of the washing beads. It depends on When the method of the invention is used to clean an intraocular lens, a typical batch size is around 50-100 lenses per 1 liter container. With the preferred acrylic material, excellent polishing results are obtained when the article is tumble polished at a container rotation speed of about 80 rpm for about 3 to 10 days. About 1 at a container rotation speed of about 80 rpm
After three days of tumbling wash, an intraocular lens made of this preferred acrylic material
It is very clean (does not have a hazy appearance) and is optically clear with little or no cosmetic defects.

[0035]   Specific embodiments of the present invention are illustrated in the following examples.

Example 1 Tumble Polishing of Intraocular Lens Preferred Acrylic Material A 1000 ml round glass carousel was filled with about 1000 g of a mixture of glass polishing beads. This mixture contains about 25% 0.5 mm glass beads and about 75%.
% 1.0 mm glass beads. To this, 0.05 micron of alumina polishing powder (Baikowski International Corp., Ch.
Arlotte, NC) 2.0 and Stoddard solvent (EM Scient)
250 ml of ific, Gibbstown, NJ) was added. The bottle and its contents were placed on a conditioned 3BAR rotator (Topline Mgf. Co.). Switch the rotation unit to low speed (80 RPM) and
Prior to the addition of the one-piece intraocular lens made of the preferred acrylic material, the contents were stirred at ambient temperature (21.0 ° C.) for about 15 minutes to allow mixing. After adding 10 lenses, the bottle was returned to the rotator and rotated for 5 days. After spinning, the bottle was removed and the contents were No. The lens was separated from the glass beads by pouring on a No. 6 sieve. They were then washed with deionized water for 2 minutes and dried with compressed air. The sample lenses were inspected at 16x for roundness and surface finish quality. It appeared to be highly polished. All machining lines have been removed and the optical and tactile edges (opti)
The c and haptics edg) were smooth and round. A very slight haze covering the entire surface of the lens was also observed after rotation.

Example 2 Tumble Cleaning of Intraocular Lens Polished in Example 1 Solvent-based Cleaning Slurry A 1000 ml round glass bottle was filled with about 1000 g of a mixture of glass cleaning beads. The mixture contained about 25% 0.5 mm glass beads and about 75% 0.1 mm glass beads. Add about 1.0 g of 0.05 mesh size alumina abrasive, and 1.0 g of dioctyl sulfosuccinate (DSS).
Was added. Finally, about 250 ml of Stoddard's solvent was added to the bottle to complete the wash slurry mixture. The polished lens from Example 1 was then added to the wash bottle, the bottle was sealed and a 3BAR rotator (Topline M).
fg. Co. ) Installed. The bottle and contents were filled with 80 r.p.m. p. m. At room temperature (
It was rotated at 21.0 ° C. for about 3 days. At the end of the wash cycle, the bottle was removed from the rotator and the contents were No. The lens was separated from the wash beads by pouring onto a No. 6 sieve. The lenses were briefly rinsed with deionized water and air dried. The sample lenses were inspected at 16x to determine if the surface haze was successfully removed. The surface of the lens was clean and transparent.

Example 3 Tumble Polishing / Cleaning of Intraocular Lenses Preferred Acrylic Material A 1000 ml round glass carousel was filled with a mixture of about 1000 g of glass cleaning beads. This mixture contains about 25% 0.5 mm glass beads and about 75%.
% 0.1 mm glass beads. About 1.5 g of 0.05 micron alumina powder (Baikowski International Corp.
, Charlotte, NC) and Stoddard's solvent (EM Scienti)
fic, Gibbstown, NJ) 250 ml was added. The bottle and its contents were placed on a modified 3BAR rotator (Topline Mgf. Co.). The rotating unit was switched to low speed (80 RPM) and the bottle was allowed to circulate for about 15 minutes to allow the contents to mix prior to addition of the one-piece intraocular lens made of the preferred acrylic material. Stirred at temperature (21.0 ° C). After the addition of 10 lenses, the bottle was returned to the rotator and rotated for 9 days. After achieving an acceptable polishing level for the lens sample, the bottle was removed from the rotator and the lid opened. To this was added 1.0 g of dioctyl sulfosuccinate (DSS), which essentially converted the polishing slurry into a wash slurry. The bottle was then resealed and returned to the rotator and spun at low speed (80 rpm) for an additional 3 days. At the completion of the wash cycle, the bottle was removed from the rotator again and its contents were The lens was separated from the glass beads by pouring on a No. 6 sieve. They were then rinsed with deionized water for 2 minutes and dried with compressed air. Sample lenses were inspected for roundness and surface finish quality at 16x. All machining lines were removed and the optical and tactile edges were smooth and round. The surface of this lens was clean and highly polished and appeared to have no trace of haze on the surface.

The present invention has been described with reference to certain preferred embodiments; however, it may be embodied in other specific forms or modifications thereof without departing from the spirit or essential characteristics of the invention. Should be understood. It is therefore believed that the above embodiments are illustrative in all aspects and do not limit the scope of the invention, which is indicated by the appended claims rather than by the foregoing description.

─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Ruwellen, Kevin             United States Texas 76018, A             Lynton, Creek Valley Dry             Boot 5006 F term (reference) 3B116 AA46 AB43 BA06 BB83 BB87                 3C047 FF08 GG15                 3C058 AA02 AA07 AA18 CB01 CB03

Claims (11)

[Claims] 1. A method of polishing an article comprising a soft acrylic material, comprising: a) polishing the article by filling a container with the polishing slurry and the article to be polished, and surface from the article. Agitating the vessel for a time and at a rate sufficient to remove irregularities, wherein the polishing slurry comprises polishing beads, alumina, and a swelling agent; and b) the polished Cleaning the abraded article by contacting the article with a cleaning slurry in a vessel and agitating the vessel for a time and at a rate sufficient to clean the surface of the article, wherein , The wash slurry comprising wash beads, alumina, a solvent, and a surfactant. 2. The method of claim 1, wherein the polishing beads and the cleaning beads are glass beads. 3. The polishing beads are 0.5 mm glass beads and 1 mm.
The method according to claim 2, wherein the glass beads are included in a ratio of 1: 3. 4. The cleaning beads are 0.5 mm glass beads and 1 mm glass beads.
3. The method of claim 2, comprising the glass beads of claim 1 in a ratio of 1: 3, and the amount of alumina in the wash slurry is about 0.2-2 w / w% (alumina to solvent). 5. The amount of alumina in the polishing slurry is at least 0.2 w.
/ W% (alumina to swelling agent). 6. The swelling agent is alcohol; aliphatic hydrocarbon; chlorinated solvent;
The method of claim 1, wherein the solvent is selected from the group consisting of and aromatic hydrocarbons. 7. The method of claim 6, wherein the solvent is a mineral spirit solvent having a flash point of about 90 to 145 degrees Fahrenheit. 8. The surfactant in the wash slurry is present in a ratio (w / w) of about 1: 1 with respect to the amount of the alumina in the wash slurry.
The method described in. 9. The cleaning slurry is prepared by adding a surfactant to the polishing slurry, and the container used for cleaning is the same as the container used for polishing. The method according to claim 1. 10. The article of claim 1, wherein the article is selected from the group consisting of one-piece intraocular lenses, intraocular lens haptics, intraocular lens optics, intracapsular rings, corneal inlays, intracorneal lenses and contact lenses. The method described. 11. A soft acrylic article polished according to the method of claim 1.