Process and device for the manufacture of mouldings and mouldings manufactured in accordance with that process

• US 6,800,225 B1
• Filed: 07/14/1994
• Issued: 10/05/2004
• Est. Priority Date: 07/14/1994
• Status: Expired due to Term

• Current Assignee: Novartis Ag
• Original Assignee: Novartis Ag
• Inventors: Golby, John, Söllner, Norbert, Borghorst, Sharla, Hagmann, Peter, Seiferling, Bernhard, Herbrechtsmeier, Peter, Müller, Beat, Kretzschmar, Otto
• Primary Examiner(s): Vargot, Mathieu D.
• Application Number:
  US08/274,942
• Time in Patent Office: 3,736 Days
• Field of Search: 264/1.1, 264/1.36, 264/1.38, 264/2.2, 264/2.3, 264/298, 264/299, 264/301, 264/303, 264/102, 264/25, 264/22, 264/496, 264/233, 264/334, 264/335, 425/808, 425/174, 425/437, 425/174.4, 425/256, 425/444
• US Class Current: 264/1.36
• CPC Class Codes: B29C 2035/0827 using UV radiation
• CPC Class Codes: B29C 31/041 using filling or dispensing heads placed in closed moulds or in contact with mould walls B29C45/27 takes precedence
• CPC Class Codes: B29C 33/06 using radiation , e.g. electro-magnetic waves, induction heating
• CPC Class Codes: B29C 33/303 centering mould parts or halves, e.g. during mounting
• CPC Class Codes: B29C 35/0894 provided with masks or diaphragms
• CPC Class Codes: B29C 37/0003 Discharging moulded articles from the mould constructions for removing the articles B29C33/44
• CPC Class Codes: B29C 37/0007 using means operable from outside the mould for moving between mould parts, e.g. robots
• CPC Class Codes: B29C 37/005 Compensating volume or shape change during moulding, in general
• CPC Class Codes: B29C 37/02 Deburring or deflashing thermal deburring in general B23D79/005
• CPC Class Codes: B29C 39/24 Feeding the material into the mould
• CPC Class Codes: B29C 39/36 Removing moulded articles
• CPC Class Codes: B29C 39/42 Casting under special conditions, e.g. vacuum
• CPC Class Codes: B29D 11/00057 characterised by the shape or surface condition of the edge, e.g. flashless, burrless, smooth
• CPC Class Codes: B29D 11/00134 Curing of the contact lens material
• CPC Class Codes: B29D 11/00442 Curing the lens material
• CPC Class Codes: B29L 2011/0041 Contact lenses
• CPC Class Codes: Y10S 425/808 Lens mold

Abstract

A measured amount of a material that is crosslinkable by impingement of a suitable form of energy, especially UV light, is introduced into a two-part mould of which cavity determines the shape of a moulding to be produced. The two mould halves are held a small distance from one another so that a thin annular gap is formed between them, which gap is in communication with the mould cavity and through which gap excess material can escape. The crosslinking is triggered by impingement of the selected form of energy, the impingement being spatially restricted to the cavity by suitable masking so that material disposed outside the mould cavity is not crosslinked. In that manner mouldings are obtained that do not require subsequent mechanical processing, and the mould is reusable. The process is especially, but not, however, exclusively, suitable for the manufacture of contact lenses.

Claims

1. A process for the manufacture of mouldings that are crosslinked in a mould at least to a degree sufficient to be released from the mold, comprising the steps of:

obtaining a mould, wherein the mould comprises a first mould half having a first mould surface, a second mould half having a second mould surface, and at least one mask, wherein the first and second mould surfaces together define a mould cavity, wherein at least one of the first and second mould surfaces is permeable to an energy suitable to cause the crosslinking of a starting crosslinkable material, wherein the mask is fixed, constructed or arranged in, at or on one of the first and second mould halves having an energy-permeable mould surface and is impermeable or at least of poor permeability compared with the permeability of the energy-permeable mould surface, wherein the mask extends inwardly right up to the mould cavity and surrounds the mould cavity so as to screen all areas behind the mask with the exception of the mould cavity;

introducing the starting crosslinkable material that is in a state in which it is at least partially uncrosslinked into the mould;

providing the energy that is in the form of a substantially parallel beam; and

irradiating with the energy the mould containing the starting material from the mould half having the mask associated therewith so as to spatially restrict impingement of the energy to an energy-impinging region, wherein the energy-impinging region is defined by combination of the first and second mould surfaces and an imaginary wall extending between the first and second mould surfaces and surrounding the mould cavity, wherein the imaginary wall is formed by transferring the boundary contour with the mould cavity of the mask in a two-dimensionally parallel and downwards manner from one mould surface to the other mould surface; and

crosslinking, under the spatial restriction of the energy impingement, essentially only the starting crosslinkable material located inside the energy-impinging region to form a moulding having a first surface, an opposite second surface and a clean and burr-free moulding rim which does not require any subsequent mechanical processing, wherein the first surface is defined by the first mould surface, the second surface is defined by the second mould surface, and at least partial areas of the moulding rim are defined by the imaginary wall which is defined by the boundary contour of the mask with the mould cavity.

2. A process according to claim 1, wherein the energy employed to cause the crosslinking is a radiation energy.

3. A process according to claim 2, wherein the radiation energy is a UV light.

4. A process according to claim 1, wherein the first mould surface of the first mould half is highly permeable to the energy, and wherein the mask comprises parts of the mould that are impermeable or of poor permeability to the energy.

5. A process according to claim 1, wherein the mould is not fully closed after the introduction of the starting material into the mould cavity, so that at least a gap containing excess starting material remains open, which gap is in communication with and surrounds the mould cavity and, and wherein the gap and the excess starting material disposed in the gap is located behind the mask and screened from irradiation of the energy.

6. A process according to claim 5, wherein the mould is closed further following crosslinking shrinkage as crosslinking of the starting crosslinkable material progresses.

7. A process according to claim 5, wherein the starting crosslinkable material is a flowable liquid, and wherein a reservoir that is not impinged upon by the energy is provided from which the starting crosslinkable material can flow back through the gap into the mould cavity to compensate for shrinkage.

8. A process according to claim 1, wherein, after the moulding has been released from the mould, any uncrosslinked or only partially crosslinked material adhering to the moulding is removed by washing with a suitable solvent.

9. A process according to claim 1, wherein the mould is closed without force, so that the two mould halves lie against one another without external pressure.

10. A process according to claim 1, wherein the filling of the mould cavity is carried out with the mold at least partially immersed in the starting crosslinkable material that is at least partially still in the uncrosslinked state.

11. A process according to claim 10, wherein, for filling the mould cavity, the cavity is connected to a reservoir which surrounds it, in which the starting crosslinkable material is stored and from which the mould cavity is flooded.

12. A process according to claim 10, wherein the mould is closed in the starting crosslinkable material.

13. A process according to claim 10, wherein the mould is used that comprises a container and a mould member that is displaceable in that container and can be moved away from and towards the container wall lying opposite it for the purpose of opening and closing the mould, the starting crosslinkable material being fed in between the container wall and the mould member as the mould is opened and conveyed away again as the mould is closed.

14. A process according to claim 13, wherein one of the first and second mould halves is provided on the container wall and the other mould half is provided on the displaceable mould member.

15. A process according to claim 14, wherein the first mould half is a male mould half and the second mould half is a female mould half, the male mould half being provided on the container wall and the female mould half being provided on the displaceable mould member.

16. A process according to claim 13, wherein pumps are used to feed in and convey away the starting crosslinkable material.

17. A process according to claim 13, wherein the displaceable mould member is driven in order to feed in and convey away the starting crosslinkable material.

18. A process according to claim 10, wherein the crosslinked moulding can be released from the mould by flushing out the mould with the starting crosslinkable material.

19. A process according to claim 13, wherein the crosslinked moulding can be released from the mould by flushing out the mould with the starting crosslinkable material, and wherein the moulding is separated from the mould by the flow of the starting crosslinkable material as the mould is opened and is flushed out of the mould by the flow of the starting crosslinkable material as the mould is closed.

20. A process according to claim 18, wherein in a first cycle the mould is opened and closed again, then at least the crosslinking necessary for it to be possible for the moulding to be released from the mould is effected by the impingement of energy and, in a second cycle, the mould is opened again, the moulding being separated from the mould and the displaceable mould member then being moved back towards the opposite-lying container wall again in order to close the mould, in the course of which the crosslinked moulding is flushed out of the mould.

21. A process according to claim 10, wherein the crosslinked moulding is removed from the mould by means of a gripping device.

22. A process according to claim 13, wherein the crosslinked moulding is removed from the mould by means of a gripping device, and wherein the moulding removed from the mould by the gripping device is deposited on the displaceable mould member outside the space between the displaceable mould member and the opposite-lying wall.

23. A process according to claim 22, wherein the moulding deposited on the displaceable mould member is held fast thereto by negative pressure and then released from it by positive pressure.

24. A process according to claim 10, wherein the mould is not fully closed after the introduction of the starting crosslinkable material into the mould cavity, so that an annular gap containing excess starting crosslinkable material remains open, which gap surrounds the mould cavity and is in communication with that mould cavity.

25. A process according to claim 24, wherein the mould is closed further following crosslinking shrinkage as crosslinking of the starting crosslinkable material progresses.

26. A process according to claim 25, wherein the starting crosslinkable material is a flowable liquid, and wherein the excess starting crosslinkable material can flow back through the annular gap into the mould cavity to compensate for shrinkage.

27. A process according to claim 1, wherein the starting crosslinkable material is a prepolymer that is a derivative of a polyvinyl alcohol having a molecular weight of at least about 2000 that, based on the number of hydroxy groups of the polyvinyl alcohol, comprises from approximately 0.5 to approximately 80% of units of formula I

wherein

R is lower alkylene having up to 8 carbon atoms,

R¹ is hydrogen or lower alkyl and

R² is an olefinically unsaturated, electron-withdrawing, copolymerisable radical preferably having up to 25 carbon atoms.

28. A process according to claim 27, wherein the starting crosslinkable material is a prepolymer wherein R² is an olefinically unsaturated acyl radical of formula R³—

CO—

, in which R³ is an olefinically unsaturated copolymerisable radical having from 2 to 24 carbon atoms.

29. A process according to claim 28, wherein the starting crosslinkable material is a prepolymer wherein R³ is alkenyl having from 2 to 8 carbon atoms.

30. A process according to claim 27, wherein the starting crosslinkable material is a prepolymer wherein the radical R2 is a radical of formula II

31. A process according to claim 27 wherein the prepolymer is a derivative of a polyvinyl alcohol having a molecular weight of at least about 2000 that, based on the number of hydroxy groups of the polyvinyl alcohol, comprises from approximately 0.5 to approximately 80% of units of formula III

wherein

R is lower alkylene,

R¹ is hydrogen or lower alkyl,

p is zero or one,

q is zero or one,

R³ is an olefinically unsaturated copolymerisable radical having from 2 to 8 carbon atoms and

R⁴ and R⁵ are each independently lower alkylene having from 2 to 8 carbon atoms, arylene having from 6 to 12 carbon atoms, a saturated divalent cycloaliphatic group having from 6 to 10 carbon atoms, arylenealkylene or alkylenearylene having from 7 to 14 carbon atoms or arylenealkylenearylene having from 13 to 16 carbon atoms.

32. A process according to claim 31, wherein the starting crosslinkable material is a prepolymer wherein

R is lower alkylene having up to 6 carbon atoms,

p is zero and

R³ is alkenyl having from 2 to 8 carbon atoms.

33. A process according to claim 31, wherein the starting crosslinkable material is a prepolymer wherein

R is lower alkylene having up to 6 carbon atoms, p is one,

q is zero,

R⁵ is lower alkylene having from 2 to 6 carbon atoms and

R³ is alkenyl having from 2 to 8 carbon atoms.

34. A process according to claim 31, wherein the starting crosslinkable material is a prepolymer wherein R is lower alkylene having up to 6 carbon atoms,

p is one,

q is one,

R⁴ is lower alkylene having from 2 to 6 carbon atoms, phenylene, unsubstituted or substituted by lower alkyl, cyclohexylene or cyclohexylene-lower alkylene, unsubstituted or substituted by lower alkyl, phenylene-lower alkylene, lower alkylene-phenylene or phenylene-lower alkylene-phenylene,

R⁵ is lower alkylene having from 2 to 6 carbon atoms and

R³ is alkenyl having from 2 to 8 carbon atoms.

35. A process according to claim 27, wherein the starting material is a prepolymer that is a derivative of a polyvinyl alcohol having a molecular weight of at least about 2000 that, based on the number of hydroxy groups of the polyvinyl alcohol, comprises from approximately 1 to approximately 15% of units of formula I.

36. A process according to claim 1, wherein one half of the mould is used as packaging for the moulding.

58. A process of claim 1, wherein said molding is an optical lens.

59. A process of claim 1, wherein said molding is a contact lens.

60. A process of claim 2, wherein the radiation energy is gamma radiation.

61. A process of claim 2, wherein the radiation energy is electron radiation.

62. A process of claim 2, wherein the radiation energy is thermal radiation.

63. A process of claim 3, wherein the mask is provided on or in the mould but outside the mould cavity.

64. A process of claim 63, wherein the mould comprises different mould members and the mask is arranged in the region of separating planes or separating faces of different mould members.

65. A process of claim 64, wherein the mask is provided on the separating face of one of the mould members.

66. A process of claim 64, wherein the mask is arranged such that it is in contact with the starting crosslinkable material.

67. A process according to claim 65, wherein the mould is not fully closed:

after the introduction of the starting crosslinkable material into the mould cavity, so that at least a gap containing excess starting crosslinkable material remains open, the gap being in communication with the mould cavity, and wherein the crosslinking energy is restricted from the excess starting crosslinkable material disposed in the gap by the mask.

68. A process of claim 67, wherein the mould is closed further following crosslinking shrinkage as crosslinkage of the material progresses.

37. A device for the manufacture of mouldings, comprising:

a closable and openable mould, wherein the mould comprises a first mould half having a first mould surface and a second mould half having a second mould surface, wherein the first and second mould surfaces together define a mould cavity which can be filled with a starting crosslinkable material, wherein at least one of the first and second mould surfaces is permeable to an energy suitable to cause crosslinking of a crosslinkable material to be introduced into the mould;

a source providing the energy;

at least one mask fixed, constructed or arranged in, at or on one of the first and second mould halves having an energy-permeable mould surface, wherein the mask is impermeable or at least of poor permeability compared with the permeability of the energy-permeable mould surface, wherein the mask extends inwardly right up to the mould cavity and surrounds the mould cavity so as to screen all areas behind the mask with the exception of the mould cavity, wherein the mask, under irradiation of the energy in a form of a substantially parallel beam, spatially restricts impingement of the energy to an energy-impinging region, thereby crosslinking essentially only the starting crosslinkable material located inside the energy-impinging region to form a moulding having a first surface, an opposite second surface and a clean and burr-free moulding rim which does not require any subsequent mechanical processing, wherein the energy-impinging region is defined by combination of the first and second mould surfaces and an imaginary wall extending between the first and second mould surfaces and surrounding the mould cavity, wherein the imaginary wall is formed by transferring the boundary contour with the mould cavity of the mask in a two-dimensionally parallel and downwards manner from one mould surface to the other mould surface, wherein the first surface is defined by the first mould surface, the second surface is defined by the second mould surface, and partial areas of the moulding rim are defined by the imaginary wall which is defined by the boundary contour of the mask with the mould cavity.

38. A device according to claim 37, wherein the first and second mould halves are separated along a separating face, and wherein the mask is arranged outside the mould cavity on one of the two mould halves and/or on both mould halves in the region of the separating face.

39. A device according to claim 38, wherein the source generates UV radiation and wherein at least one of the two mould halves of the mould consists of UV-permeable material.

40. A device of claim 39, wherein the mask consists of a layer of material that is impermeable to UV radiation.

41. A device according to claim 37, wherein the mould is provided with spacers which hold the two mould halves a small distance apart from one another when the mould is in the closed position, so that at least a gap is formed that surrounds the mould cavity and is in communication with that cavity, and wherein the mask is arranged in the region of the gap.

42. A device according to claim 41, wherein the mould is provided with resilient means or displacement means that allow the two mould halves to move closer together following crosslinking shrinkage.

43. A device according to claim 37, wherein during filling of the mould cavity the mould is at least partially immersed in starting crosslinkable material that is at least partially still in the uncrosslinked state.

44. A device according to claim 43 which comprises a reservoir for supplying the starting crosslinkable material, which reservoir surrounds the mould cavity and can be connected to the mould cavity, and wherein during filling of the mould cavity the reservoir is connected to the mould cavity and floods that cavity.

45. A device according to claim 43, which comprises means for closing the mould while the mould is at least partially immersed in the starting crosslinkable material.

46. A device according to claim 43, wherein the mould comprises a container and a displaceable mould member, wherein the displaceable mould member can be moved away from and towards the container wall lying opposite it for the purpose of opening and closing the mould, and wherein there is provided in the container an inlet through which the starting crosslinkable material flows in between the container wall and the displaceable mould member as the mould is opened, and wherein there is provided in the container an outlet through which the starting crosslinkable material flows out again as the mould is closed.

47. A device according to claim 46, wherein one of the two mould halves is provided on the container wall and the other on the displaceable mould member.

48. A device according to claim 47, wherein the first mould half is a male mould half and the second mould half is a female mould half, and wherein the male mould half is provided on the container wall and the female mould half is provided on the displaceable mould member.

49. A device according to claim 46, wherein pumps are provided which, as the mould is opened, feed in the starting crosslinkable material through the inlet and between the container wall and the displaceable mould member and, as the mould is closed, convey it back through the outlet.

50. A device according to claim 46, wherein means are provided for driving the displaceable mould member.

51. A device according to claim 43, wherein means are provided for producing a flow that separates the moulding from the mould when the mould is opened and flushes the moulding out of the mould when the mould is closed.

52. A device according to claim 46, wherein means are provided for producing a flow that separates the moulding from the mould when the mould is opened and flushes the moulding out of the mould when the mould is closed, and wherein, in a first cycle, the starting crosslinkable material first of all flows in through the inlet and between the container wall and the displaceable mould member and then flows back out through the outlet, the source for the energy then acts upon the mould with an amount of energy necessary for it to be possible for forming the moulding to be released from the mould, and then, in a second cycle, the starting crosslinkable material flows in through the inlet and between the container wall and the displaceable mould member separates the moulding from the mould and then flushes it out through the outlet.

53. A device according to claim 43, wherein a gripping device is provided which removes the crosslinked moulding from the mould.

54. A device according to claim 46, wherein a gripping device is provided which removes the crosslinked moulding from the mould, and wherein the container comprises, on a container wall other than the shape-giving face, a hollow or recess that extends substantially in the direction of movement of the displaceable mould member, the gripping device being arranged in that hollow or recess, and wherein the displaceable mould member comprises, on an outer wall that does not lie opposite the shape-giving container wall, an indentation in which the gripping device deposits the removed moulding.

55. A device according to claim 54, wherein the displaceable mould member comprises a channel that leads to the indentation and can be connected to a negative pressure or positive pressure source, which channel is connected to the negative pressure source when the gripping device deposits the removed moulding in the indentation of the displaceable mould member and then is connected to the positive pressure source In order to release the lens.

56. A device according to claim 47, wherein the mould is provided with spacers that hold the two mould halves a small distance apart from one another when the mould is in the closed position, so that an annular gap is formed that surrounds the mould cavity and is in communication with that cavity.

57. A device according to claim 56, wherein the mould is provided with resilient means or displacement means that allow the two mould halves to move closer together following crosslinking shrinkage.

69. A device of claim 37, wherein the mask is fixed at or on the mould.

70. A device of claim 39, wherein the UV-permeable material is quartz.

71. A device of claim 40, wherein the layer is a metal oxide layer.

72. A device of claim 71, wherein the layer is a chrome layer.

73. A process for the manufacture of a crosslinked moldings, comprising the steps of:

(a) introducing a starting crosslinkable material into a mold, wherein said mold comprises a first mold half having a first molding surface, a second mold half having a second molding surface, and at least one mask, wherein the first and second molding surfaces together define a mold cavity, wherein at least one of the first and second mould surfaces is permeable to a crosslinking energy suitable to cause the crosslinking of the starting crosslinkable material, wherein the mask is fixed, constructed or arranged in, at or on one of the first and second mould halves having an energy-permeable mould surface and is impermeable or at least of poor permeability compared with the permeability of the energy-permeable mould surface, wherein the mask extends inwardly right up to the mould cavity and surrounds the mould cavity so as to screen all areas behind the mask with the exception of the mould cavity;

(b) providing the crosslinking energy in a form of a substantially parallel beam; and

(c) irradiating with the enemy the mould containing the starting material from the mould half having the mask associated therewith so as to spatially restrict the crosslinking energy to be impinged to the mold cavity in an energy-impinging region, wherein the energy-impinging region is defined by combination of the first and second mould surfaces and an imaginary wall extending between the first and second mould surfaces and surrounding the mould cavity, wherein the imaginary wall is formed by transferring the boundary contour with the mould cavity of the mask in a two-dimensionally parallel and downwards manner from one mould surface to the other mould surface, thereby causing essentially only the starting crosslinkable material located inside the energy-impinging region to be crosslinked to a degree sufficient to form the molding capable of being released from said mold, wherein the produced molding comprises a first surface defined by the first molding surface, an opposite second surface defined by the second molding surface, and a clean and burr-free moulding rim which does not require any subsequent mechanical processing and at least partial areas of which are defined by the imaginary wall which is defined by the boundary contour of the mask with the mould cavity.

74. A process of claim 73, wherein said molding is an ophthalmic lens.

75. A process of claim 74, wherein said ophthalmic lens is a contact lens.