WO1995011789A1 - Method of releasing contact lenses from the mold - Google Patents

Method of releasing contact lenses from the mold Download PDF

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Publication number
WO1995011789A1
WO1995011789A1 PCT/US1994/012144 US9412144W WO9511789A1 WO 1995011789 A1 WO1995011789 A1 WO 1995011789A1 US 9412144 W US9412144 W US 9412144W WO 9511789 A1 WO9511789 A1 WO 9511789A1
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WO
WIPO (PCT)
Prior art keywords
mold
contact lens
lens
isopropanol
release
Prior art date
Application number
PCT/US1994/012144
Other languages
French (fr)
Inventor
Mahendra P. Nandu
Richard J. Wrue
Original Assignee
Bausch & Lomb Incorporated
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bausch & Lomb Incorporated filed Critical Bausch & Lomb Incorporated
Priority to AU80877/94A priority Critical patent/AU8087794A/en
Publication of WO1995011789A1 publication Critical patent/WO1995011789A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D11/00—Producing optical elements, e.g. lenses or prisms
    • B29D11/00009—Production of simple or compound lenses
    • B29D11/00038—Production of contact lenses
    • B29D11/00125—Auxiliary operations, e.g. removing oxygen from the mould, conveying moulds from a storage to the production line in an inert atmosphere
    • B29D11/00192—Demoulding, e.g. separating lenses from mould halves
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/56—Coatings, e.g. enameled or galvanised; Releasing, lubricating or separating agents
    • B29C33/60—Releasing, lubricating or separating agents

Definitions

  • This invention relates to improved methods of processing contact lenses, especially releasing a contact lens from the mold in which the lens was cast.
  • Soft contact lenses are produced by several methods including spincasting, static cast molding, and combinations of casting and lathing.
  • the lens In production methods using molds, the lens is generally retained on the mold following casting, and it is necessary to release the lens from the mold without damaging the lens.
  • One way to release lenses is to place the mold with the lens in water, usually at elevated temperature, wherein the lens is hydrated and released from the mold. This conventional method is discussed in U.S. Serial No. 07/755,201 (filed September 5, 1991) along with a modification wherein a surfactant is included in the hydration bath.
  • the invention provides a method of releasing a contact lens from a mold in which the contact lens was cast which comprises contacting the contact lens and the mold with a release solution comprising isopropanol, whereby the contact lens is released from the mold.
  • the invention provides a method comprising: casting a contact lens from a polymerizable mixture in a mold, wherein the contact lens is retained in the mold; releasing the contact lens from the mold by contacting the contact lens and the mold with a release solution comprising isopropanol; and subsequently hydrating the contact lens.
  • the methods provide release of lenses with good surface properties, clarity and image quality, and improved consistency in the quality of the lenses.
  • the release solution of this invention comprises isopropanol. Either pure isopropanol or an aqueous solution of isopropanol may be used. Preferably, the isopropanol content in the solution is at least 25 volume percent, with at least 40 volume percent being especially preferred.
  • the release solution may include other components if desired, such as the surfactants disc] sed in U.S. Serial No. 07/755,201 (filed
  • Suitable contact lenses include: "hard” lenses such as rigid gas permeable (RGP) contact lenses, formed of silicone acrylate or fluorosilicone acrylate copolymers; and "soft" hydrogel contact lenses. Preferred are the soft hydrogel contact lenses.
  • Lenses in this class are generally formed of a copolymer of at least one hydrophilic monomer and a crosslinking monomer.
  • Hydrophilic monomers include: unsaturated carboxylic acids, such as methacrylic acid and acrylic acid; (meth)acrylic substituted alcohols or glycols, such as 2-hydroxyethylmethacrylate, 2- hydroxyethylacrylate, glyceryl methacrylate, and polyethyleneglycol methacrylate; vinyl lactams, such as N-vinyl-2-pyrrolidone; and acrylamides, such as methacrylamide and N,N-dimethylacrylamide.
  • the crosslinking monomer is a material having multiple polymerizable functionalities, preferably vinyl functionalities.
  • crosslinking monomers include: divinylbenzene; allyl methacrylate; ethyleneglycol di(meth)aery] " * te, tetraethyleneglycol di(meth)acrylate, polyethyleneglycol di(meth)acrylate; and vinylcarbonate derivatives of the glycol di(meth)acrylates.
  • the copolymeric material further includes a ⁇ ilicone-containing monomer.
  • the method can be used for releasing lenses cast by various known methods. These casting methods include spincasting wherein the lens is retained in the spincast mold. Another method is static casting wherein the lens is cast between two mold parts. The release solution may be used to release the lens from both mold parts, however, it is preferred that the casting method results in the lens being selectively retained on one mold part wherein the release solution is used to release the lens from this mold part. A further method is spincasting an excess of monomer by spincasting in a spincasting mold and lathing the posterior surface while the lens is retained in the mold. Following the lathing operation, the lens is released from the mold with the release solution.
  • Contact lenses are released by contacting the lens and mold with the release solution, preferably by immersing the mold and lens assembly in the solution.
  • the release step may be accomplished at room temperature, although in some cases it may be advantageous to conduct the release at other temperatures, for example, at an elevated temperature up to about 125°C.
  • the lens is hydrated with water or buffered saline. Subsequently, the lens is sterilized such as by autoclaving in water or saline. These steps also effect removal of any residual isopropanol from the lens.
  • EXAMPLE Contact lenses were obtained as follows. Monomeric mixtures, containing 2-hydroxyethyl methacrylate and a crosslinking monomer, were cured by spincasting in polyvinyl chloride (PVC) molds, followed by lathing the posterior surfaces to obtain contact lenses. The lenses, still retained in the molds, were released by one of the following three conditions: (1) immersion in water at 50°C; (2) immersion in an isopropanol/water mixture (50/50 v/v) at ambient temperature; and (3) immersion in an isopropanol/water mixture (50/50 v/v) at 55°C.
  • PVC polyvinyl chloride
  • RI refractive index

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Ophthalmology & Optometry (AREA)
  • Eyeglasses (AREA)

Abstract

A method of releasing a contact lens from a mold in which the contact lens was cast comprises contacting the contact lens and the mold with a release solution comprising isopropanol.

Description

METHOD OF RELEASING CONTACT LENSES FROM THE MOLD
BACKGROUND OF THE INVENTION This invention relates to improved methods of processing contact lenses, especially releasing a contact lens from the mold in which the lens was cast.
Soft contact lenses are produced by several methods including spincasting, static cast molding, and combinations of casting and lathing. In production methods using molds, the lens is generally retained on the mold following casting, and it is necessary to release the lens from the mold without damaging the lens. One way to release lenses is to place the mold with the lens in water, usually at elevated temperature, wherein the lens is hydrated and released from the mold. This conventional method is discussed in U.S. Serial No. 07/755,201 (filed September 5, 1991) along with a modification wherein a surfactant is included in the hydration bath.
Applicants have found, however, that these methods may affect the clarity or image quality of the lenses, i.e., the clarit- and/or imaσe quality of lenses released by the prior methods is sometimes inconsistent. It would be desirable to obtain a release method which improves consistency in lens quality.
SUMMARY OF THE INVENTION
In a first aspect, the invention provides a method of releasing a contact lens from a mold in which the contact lens was cast which comprises contacting the contact lens and the mold with a release solution comprising isopropanol, whereby the contact lens is released from the mold.
In another aspect, the invention provides a method comprising: casting a contact lens from a polymerizable mixture in a mold, wherein the contact lens is retained in the mold; releasing the contact lens from the mold by contacting the contact lens and the mold with a release solution comprising isopropanol; and subsequently hydrating the contact lens.
The methods provide release of lenses with good surface properties, clarity and image quality, and improved consistency in the quality of the lenses.
DETAILED DESCRIPTION OF THE INVENTION The release solution of this invention comprises isopropanol. Either pure isopropanol or an aqueous solution of isopropanol may be used. Preferably, the isopropanol content in the solution is at least 25 volume percent, with at least 40 volume percent being especially preferred. The release solution may include other components if desired, such as the surfactants disc] sed in U.S. Serial No. 07/755,201 (filed
Figure imgf000005_0001
The method may be used to release any type of contact lens from the mold in which it was cast. Suitable contact lenses include: "hard" lenses such as rigid gas permeable (RGP) contact lenses, formed of silicone acrylate or fluorosilicone acrylate copolymers; and "soft" hydrogel contact lenses. Preferred are the soft hydrogel contact lenses. . Lenses in this class are generally formed of a copolymer of at least one hydrophilic monomer and a crosslinking monomer. Hydrophilic monomers include: unsaturated carboxylic acids, such as methacrylic acid and acrylic acid; (meth)acrylic substituted alcohols or glycols, such as 2-hydroxyethylmethacrylate, 2- hydroxyethylacrylate, glyceryl methacrylate, and polyethyleneglycol methacrylate; vinyl lactams, such as N-vinyl-2-pyrrolidone; and acrylamides, such as methacrylamide and N,N-dimethylacrylamide. The crosslinking monomer is a material having multiple polymerizable functionalities, preferably vinyl functionalities. Representative crosslinking monomers include: divinylbenzene; allyl methacrylate; ethyleneglycol di(meth)aery] "*te, tetraethyleneglycol di(meth)acrylate, polyethyleneglycol di(meth)acrylate; and vinylcarbonate derivatives of the glycol di(meth)acrylates. In the case of silicone hydrogel contact lenses, the copolymeric material further includes a εilicone-containing monomer.
The method can be used for releasing lenses cast by various known methods. These casting methods include spincasting wherein the lens is retained in the spincast mold. Another method is static casting wherein the lens is cast between two mold parts. The release solution may be used to release the lens from both mold parts, however, it is preferred that the casting method results in the lens being selectively retained on one mold part wherein the release solution is used to release the lens from this mold part. A further method is spincasting an excess of monomer by spincasting in a spincasting mold and lathing the posterior surface while the lens is retained in the mold. Following the lathing operation, the lens is released from the mold with the release solution.
Contact lenses are released by contacting the lens and mold with the release solution, preferably by immersing the mold and lens assembly in the solution. The release step may be accomplished at room temperature, although in some cases it may be advantageous to conduct the release at other temperatures, for example, at an elevated temperature up to about 125°C.
Following release of the lens from the mold, the lens is hydrated with water or buffered saline. Subsequently, the lens is sterilized such as by autoclaving in water or saline. These steps also effect removal of any residual isopropanol from the lens.
The following example further illustrates various preferred embodiments of the invention.
EXAMPLE Contact lenses were obtained as follows. Monomeric mixtures, containing 2-hydroxyethyl methacrylate and a crosslinking monomer, were cured by spincasting in polyvinyl chloride (PVC) molds, followed by lathing the posterior surfaces to obtain contact lenses. The lenses, still retained in the molds, were released by one of the following three conditions: (1) immersion in water at 50°C; (2) immersion in an isopropanol/water mixture (50/50 v/v) at ambient temperature; and (3) immersion in an isopropanol/water mixture (50/50 v/v) at 55°C. Subsequently, the released lenses were hydrated in buffered saline, inspected for clarity, and then autoclaved in buffered saline. Following autoclaving, the lenses were again inspected for clarity. The clarity inspection results are summarized in Table 1.
Additionally, the refractive index (RI) of each lens surface was measured with a refractometer following autoclaving for some of the lenses. The RI values are reported in Table 1, as well as the definition of the RI line (blurry or sharp) .
TABLE 1
Claritv
Release Before After
Lens Condition Autoclave Autoclave
1 1 Blue Haze Cloudy Patches
2 1 Blue Haze Cloudy Patches
3 1 Blue Haze Cloudy Patches
4 1 Blue Haze Cloudy Patches
5 1 Blue Haze Cloudy Patches
6 1 Clear Clear
7 1 Clear Clear
8 2 Clear Clear
9 2 Clear Clear
10 2 Clear Clear
11 3 Clear Clear
12 3 Clear Clear
13 2 Clear Clear
14 2 Clear Clear
15 3 Clear Clear
16 2 Clear Clear
17 2 Clear Clear
18 3 Clear Clear
19 3 Clear Clear TABLE 2
Release Image Lens Condition Surface Ouality RI
1 1 Front Blurry 1.4335 Back Sharp 1.4370
Front Blurry 1.4365 Back Sharp 1.4385
Front Blurry 1.4345 Back Sharp 1.4375
Front Sharp 1.4440 Back Sharp 1.4440
Front Sharp 1.4440 Back Sharp 1.4440
Front Sharp 1.4375 Back Sharp 1.4375
Front Sharp 1.4370 Back Sharp 1.4370
10 Front Sharp 1.4375 Back Sharp 1.4380
11 Front Sharp 1.4375 Back Sharp 1.4375
16 Front Sharp 1.4440 Back Sharp 1.4440
17 Front Sharp 1.4440 Back Sharp 1.4395
18 Front Sharp 1.4440 Back Sharp 1.4440
19 Front Sharp 1.4440 Back Sharp 1.4440 The lenses released with the methods employing isopropanol solutions exhibited more uniform clarity and image quality.
Although certain preferred embodiments have been described, it is understood that the invention is not limited thereto and modifications and variations would be evident to a person of ordinary skill in the art.

Claims

CLAIMS :
1. A method of releasing a contact lens from a mold in which the contact lens was cast comprising contacting the contact lens and the mold with a release solution comprising isopropanol, whereby the contact lens is released from the mold.
2. The method of claim 1, wherein the contact lens is a soft contact lens.
3. The method of claim 2, wherein the contact lens is formed of a copolymer of 2-hydroxyethyl methacrylate.
4. The method of claim 1, wherein the release solution is an aqueous solution containing isopropanol.
5. The method of claim 4, wherein the release solution is an aqueous solution containing at least 25 percent by volume isopropanol.
6. The method of claim 1, wherein the contact lens and the mold are immersed in the release solution at ambient temperature or an elevated temperature.
7. A method comprising: casting a contact lens from a polymerizable mixture in a mold, wherein the contact lens is retained in the mold; releasing the contact lens from the mold by contacting the contact lens and the mold with a release solution comprising isopropanol; and hydrating the contact lens.
8. The method of claim 7, wherein the contact lens is cast by spincasting and retained on the spincast mold.
9. The method of claim 7, wherein the contact lens is cast by spincasting followed by lathing a posterior lens surface, and retained on the spincast mold.
10. The method of claim 7, wherein the contact lens is static cast in a mold assembly formed of first and second mold sections.
11. The method of claim 10, wherein the contact lens is retained on one of the first and second mold sections and released from the other of the first and second mold sections with the release solution.
12. The method of claim 10, wherein the contact lens is released from both the first and second mold sections with the release solution.
13. The method of claim 7, wherein the release solution is an aqueous solution containing isopropanol.
14. The method of claim 12, wherein the release solution is an aqueous solution containing at least 25 percent volume isopropanol.
15. The method of claim 7, wherein the contact lens and the mold are immersed in the release solution at ambient temperature or an elevated temperature.
16. The method of claim 7, wherein the contact lens is hydrated by immersing the lens in water or buffered saline.
PCT/US1994/012144 1993-10-28 1994-10-25 Method of releasing contact lenses from the mold WO1995011789A1 (en)

Priority Applications (1)

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Applications Claiming Priority (2)

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US14492393A 1993-10-28 1993-10-28
US08/144,923 1993-10-28

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001030559A1 (en) * 1999-10-25 2001-05-03 Hydron Limited Method for the production of opthalmic devices
WO2003082367A2 (en) * 2002-03-28 2003-10-09 Bausch & Lomb Incorporated Process for extracting biomedical devices
WO2007075558A2 (en) * 2005-12-29 2007-07-05 Johnson & Johnson Vision Care, Inc. Methods and systems for releasing silicone hydrogel ophthalmic lenses using surfactants
WO2007075760A2 (en) * 2005-12-20 2007-07-05 Johnson & Johnson Vision Care, Inc. Methods and systems for leaching and releasing silicone hydrogel ophthalmic lenses with alcohol solutions
EP1752166A3 (en) * 2005-08-09 2007-10-03 CooperVision Inc. Contact lens extration/hydration systems and methods of reprocessing fluids used therein
WO2008036795A1 (en) * 2006-09-21 2008-03-27 Novartis Ag Method of de-molding contact lenses
US7811483B2 (en) 2006-06-01 2010-10-12 Coopervision International Holding Company, Lp Delensing of ophthalmic lenses using gas
EP1752280A3 (en) * 2005-08-09 2010-11-17 CooperVision International Holding Company, LP Demolding and delensing methods and systems in the manufacture of silicone hydrogel contact lenses
US7968018B2 (en) 2007-04-18 2011-06-28 Coopervision International Holding Company, Lp Use of surfactants in extraction procedures for silicone hydrogel ophthalmic lenses
US8313675B2 (en) 2009-08-31 2012-11-20 Coopervision International Holding Company, Lp Demolding of ophthalmic lenses during the manufacture thereof

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH04212819A (en) * 1990-10-16 1992-08-04 Seiko Epson Corp Manufacture of plastic molded form

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH04212819A (en) * 1990-10-16 1992-08-04 Seiko Epson Corp Manufacture of plastic molded form

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
DATABASE WPI Week 9237, Derwent World Patents Index; AN 92-305328, "production of plastic moulding for lenses" *

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001030559A1 (en) * 1999-10-25 2001-05-03 Hydron Limited Method for the production of opthalmic devices
WO2003082367A2 (en) * 2002-03-28 2003-10-09 Bausch & Lomb Incorporated Process for extracting biomedical devices
WO2003082367A3 (en) * 2002-03-28 2003-12-04 Bausch & Lomb Process for extracting biomedical devices
EP1752280A3 (en) * 2005-08-09 2010-11-17 CooperVision International Holding Company, LP Demolding and delensing methods and systems in the manufacture of silicone hydrogel contact lenses
US7629436B2 (en) 2005-08-09 2009-12-08 CooperVision International Holding Compound, LP Contact lens extraction/hydration systems and methods of reprocessing fluids used therein
US9102110B2 (en) 2005-08-09 2015-08-11 Coopervision International Holding Company, Lp Systems and methods for removing lenses from lens molds
EP2345429A1 (en) * 2005-08-09 2011-07-20 CooperVision International Holding Company, LP Contact lens extration/hydration systems and methods of reprocessing fluids used therein
EP1752166A3 (en) * 2005-08-09 2007-10-03 CooperVision Inc. Contact lens extration/hydration systems and methods of reprocessing fluids used therein
US7319133B2 (en) 2005-08-09 2008-01-15 Coopervision, Inc. Contact lens extraction/hydration systems and methods of reprocessing fluids used therein
WO2007075760A2 (en) * 2005-12-20 2007-07-05 Johnson & Johnson Vision Care, Inc. Methods and systems for leaching and releasing silicone hydrogel ophthalmic lenses with alcohol solutions
WO2007075760A3 (en) * 2005-12-20 2007-09-07 Johnson & Johnson Vision Care Methods and systems for leaching and releasing silicone hydrogel ophthalmic lenses with alcohol solutions
WO2007075558A2 (en) * 2005-12-29 2007-07-05 Johnson & Johnson Vision Care, Inc. Methods and systems for releasing silicone hydrogel ophthalmic lenses using surfactants
WO2007075558A3 (en) * 2005-12-29 2007-09-07 Johnson & Johnson Vision Care Methods and systems for releasing silicone hydrogel ophthalmic lenses using surfactants
US7811483B2 (en) 2006-06-01 2010-10-12 Coopervision International Holding Company, Lp Delensing of ophthalmic lenses using gas
US8197724B2 (en) 2006-06-01 2012-06-12 Coopervision International Holding Company, Lp Delensing of ophthalmic lenses using gas
WO2008036795A1 (en) * 2006-09-21 2008-03-27 Novartis Ag Method of de-molding contact lenses
US7968018B2 (en) 2007-04-18 2011-06-28 Coopervision International Holding Company, Lp Use of surfactants in extraction procedures for silicone hydrogel ophthalmic lenses
US8313675B2 (en) 2009-08-31 2012-11-20 Coopervision International Holding Company, Lp Demolding of ophthalmic lenses during the manufacture thereof

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Publication number Publication date
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