Low oxygen molding of soft contact lenses

• US 5,753,150 A
• Filed: 03/06/1997
• Issued: 05/19/1998
• Est. Priority Date: 06/10/1994
• Status: Expired due to Term

• Current Assignee: Johnson & Johnson Vision Products, Inc.
• Original Assignee: Johnson & Johnson Vision Products, Inc.
• Inventors: Enns, John Benjamin, Adams, Jonathan Patrick, Kindt-Larsen, Ture, Martin, Wallace Anthony
• Primary Examiner(s): Vargot, Mathieu D.
• Application Number:
  US08/812,817
• Time in Patent Office: 439 Days
• Field of Search: 264/2.5, 264/1.1, 264/85, 425/73-75, 425/808
• US Class Current: 264/2.5
• CPC Class Codes: B29C 2791/001 Shaping in several steps
• CPC Class Codes: B29C 2791/005 Using a particular environment, e.g. sterile fluids other than air
• CPC Class Codes: B29C 33/3842 Manufacturing moulds, e.g. shaping the mould surface by machining
• CPC Class Codes: B29C 37/006 Degassing moulding material or draining off gas during moulding venting means in moulds B29C33/10
• CPC Class Codes: B29C 39/42 Casting under special conditions, e.g. vacuum
• CPC Class Codes: B29C 45/00 Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor injection blow-moulding B29C49/06
• CPC Class Codes: B29D 11/00125 Auxiliary operations, e.g. removing oxygen from the mould, conveying moulds from a storage to the production line in an inert atmosphere
• CPC Class Codes: B29K 2105/0002 monomers or prepolymers
• CPC Class Codes: B29K 2825/00 Use of polymers of vinyl-aromatic compounds or derivatives thereof as mould material
• CPC Class Codes: B29L 2011/0041 Contact lenses
• CPC Class Codes: B29L 2031/757 Moulds, cores, dies

Abstract

A process for providing degassed complementary concave and convex lens molds to filling and mold assembly stations in a continuous or semicontinuous automated soft contact lens manufacturing system. The process includes injection molding the lens molds, immediately transferring the lens molds to an inert gas atmosphere, degassing the lens molds, and filling the lens molds with a polymerizable monomer under the inert gas prior to mold assembly.

Claims

1. A process for molding contact lenses, comprising:

a. providing lens mold material that has been exposed to atmospheric oxygen;

b. injection molding, at an elevated temperature sufficient to remove substantially all of the oxygen, a lens mold from the lens mold material;

c. transferring the lens molds to an inert gas atmosphere;

d. holding the lens molds in the inert gas atmosphere for a period of time; and

e. filling the lens molds with a polymerizable monomer under the inert gas atmosphere.

2. The process of claim 1, wherein the transfer of the lens mold to the inert gas atmosphere is accomplished within about 30 seconds of completion of the injection molding step.

3. The process of claim 1, wherein the period of time in the holding step is from about 0 to about 15 minutes.

4. The process of claim 1, wherein the period of time in the holding step is from about 3 to about 5 minutes.

5. The process of claim 1, wherein in the filling step the lens molds are filled with an acrylate reactive monomer composition and at the time of filling there is an oxygen concentration at the lens mold/reactive monomer interface of not greater than 1×

10^-8 moles/cm³.

6. The process of claim 1 wherein the lens mold material is polystyrene.

7. A process for manufacturing lens molds for immediate use in a contact lens manufacturing system comprising:

a. providing lens mold material that has been exposed to atmospheric oxygen;

b. injection molding the lens molds from the lens mold material in the presence of atmospheric oxygen at a mold temperature such that substantially all of the oxygen is removed said mold temperature applied over a cycle of three to twelve seconds;

c. transferring the lens molds to an inert gas atmosphere;

d. holding the lens molds in the inert gas atmosphere for a period of time; and

e. filling the lens molds with a polymerizable monomer under the inert gas atmosphere prior to mold assembly.

8. The process of claim 7 wherein the transfer step is accomplished within about 12 to 15 seconds of completion of the injection molding step.

9. The process of claim 7 wherein the lens mold material is polystyrene.

10. The process of claim 7 wherein the holding step is at least about 3 minutes.

11. The process of claim 7, wherein said mold temperature is at least about 450°

F.