Source: http://www.google.es/patents/US5114632
Timestamp: 2017-11-18 08:44:50
Document Index: 578712502

Matched Legal Cases: ['arts 12', 'art 14', 'art 14', 'art 14', 'art 14', 'art 14', 'art 12', 'art 12', 'art 112', 'art 114', 'art 114', 'art 12', 'art 14', 'art 14', 'art 12', 'art 14', 'art 14', 'art 12', 'art 14', 'art 14', 'art 14', 'art 14', 'art 14', 'art 14']

Patente US5114632 - Controlled casting of a shrinkable material - Google Patentes
A method and a device are disclosed wherein a shrinkable polymer material is formed in situ in a mold without defects and with no internal stresses. A monomer or polymer solution is injected into the mold and solidified sequentially through the mold by exposure to an agent such as ultraviolet radiation,...http://www.google.es/patents/US5114632?utm_source=gb-gplus-sharePatente US5114632 - Controlled casting of a shrinkable material
Número de publicación US5114632 A
Número de solicitud US 07/608,123
Fecha de presentación 1 Nov 1990
Número de publicación 07608123, 608123, US 5114632 A, US 5114632A, US-A-5114632, US5114632 A, US5114632A
Citas de patentes (4), Citada por (43), Clasificaciones (33), Eventos legales (10)
US 5114632 A
1. A method of forming an article of precise dimensions by in situ solidification in a precisely dimensioned mold of a liquified material comprising at least one monomer, prepolymer or polymer, that, upon exposure to a solidifier polymerizes the liquified material, shrinks; the method comprising the steps of:
a. providing a mold body having a first part and a second part, said first and second part defining an internal cavity therebetween, the cavity corresponding to the precise dimensions of the finished article and having a closed end and an open end, at least one of the first or the second part formed to permit exposure of the liquefied material to the solidifier in the internal cavity in a differential and sequential manner, including a non-polymer substrate as a part of the mold, wherein the substrate is treated with a chemical coupling agent enhancing adhesion of a polymer formed from the liquified material to the substrate material;
b. providing a source of the solidifier for imposition upon the surface of the liquefied material in a differential and sequential manner;
e. differentially exposing said liquefied material to said solidifier starting at said closed end and proceeding to said open end while continuously supplying liquefied material to said open end so that polymerization takes place at a steady rate from the closed end to the open end as a function of exposure of the liquified material to the solidifier; and
2. The method of claim 1 wherein the solidifier is a slit of light moving sequentially from one end of the mold to the other end.
This is a continuation-in-part of U.S. Ser. No. 07/345,718 filed May 1, 1989, by David S. Soane, entitled "Controlled Casting of a Shrinkable Material".
This invention relates to controlled solidification of a pre-polymer mixture in a precisely dimensioned confined space.
In the third example, a liquefied polymer sheet, when cast onto a flat or curved support will warp or crack if allowed to devolatilize or coaqulate over the entire surface simultaneously. Such warping or cracking is caused by shrinkage due to solvent loss.
This invention discloses an apparatus and a method for in situ formation of precisely dimensioned precision parts made of polymers either by in situ polymerization or differential devolatilization or coagulation.
It is an object of this invention to provide a method and apparatus that permits in situ molding of parts formed of polymers without internal stresses.
It is also an object of this invention to provide a method and an apparatus that permits differential polymerization in a precision mold thereby eliminating voids caused by shrinkage.
It is also an object of this invention to provide a method and an apparatus that permits in situ polymerization of relatively thick and large precision parts without internal bubbles.
It is still another object of this invention to provide an apparatus that permits casting of precision polymer parts with widely varying thicknesses.
It is an object of this invention to provide an apparatus and method for differential polymerization of variable thickness precision parts.
This invention is a method and a device for forming an article of precise dimensions by in situ solidification in a precisely dimensioned mold of a liquefied material that upon exposure to a solidifier shrinks.
The method comprises the steps of providing a mold body having a first closed end and a second open end and defining an internal cavity corresponding to the precise dimensions of the finished article. The mold body is so formed that it may be differentially exposed to a solidifier starting at the first closed end and moving in a controlled manner to the second open end. The method also includes the step of providing a source of the solidifier for imposition upon the liquefied material within the mold body. It also includes the step of providing a constant source of liquefied material at the open end of the mold body. Finally, it includes the step of differentially exposing the liquefied material to the solidifier starting at the closed end and proceeding to the open end while continuously supplying liquefied material to the open end. The invention also includes a device for forming an article of a material that upon exposure to a solidifier shrinks. The device comprises a mold body defining an internal cavity having a portion of the mold body so formed that the internal cavity is differentially exposeable to a solidifier, the mold body having a first end and a second end with the internal cavity conforming to the desired outer dimensions of the article, the mold body further includes a gate at the second end of the cavity, the gate communicating with the cavity. The device also includes a source for the solidifier and means for focusing the solidifier upon a selected area of the material such that it is imposed differentially upon the material in the internal cavity. Means are also provided for moving the solidifier imposed upon the material in the internal cavity relative the internal cavity from the first end to the second end at a controlled velocity.
FIG. 9 is a mold with a glass substrate for use in a modification of the method.
Referring to FIG. 1 a mold body 10 is shown in cross-section. The mold body as shown in FIG. 1 is designed specifically for a lens shaped precision article such as a projection lens for a televison receiver. The device 10 shown in FIG. 1 is formed of at least two parts 12 and 14, brought together to form a cavity 16. Cavity 16 is formed having the shape of the precision body that is desired to be molded. As is usual with a mold, a gate 18 provides access to the mold body 10 when the first and second part are engaged. Communicating with gate 18 is a reservoir 20 which is utilized to feed raw material to cavity 16 through gate 18. Reservoir 20 is represented in FIG. 1 as a hopper-like device. A vent 21 (see FIG. 2) may also be included to facilitate the filling of cavity 16. It should be understood that other means for providing raw material to cavity 16 through gate 18 may be advantageously used. For example, it may be appropriate to provide raw material to cavity 16 under pressure.
Mold body 10, as can be seen in FIG. 1, necessarily has one part, in the case illustrated, part 14, that is transparent to a source of energy. A source of energy 22 is movable relative to mold body 10 and includes a focusing means such as gate 24. The source of energy 22 may be drawn across the second part 14 by means of a two-way motor 26. Source of energy 22 is selected according to the material to be molded. For example, if the monomers (sometimes referred to as the reaction mixture or polymer precusor) provided to the mold cavity 16 from reservoir 20 are to be polymerized by heat, then source of energy 22 is appropriately a heat source which is focused through an opening 23 in focusing gate 24. Opening 23 is preferably designed to focus a plane of energy on second part 14. The plane of energy is substantially normal to the movement of focusing gate 24. Alternatively if the monomers utilized in cavity 16 are polymerized by an ultra violet source or other light source, then source of energy 22 may be a light of the proper wave length. Again, second part 14 is of necessity transparent to the wave length of light utilized in source of energy 22 in the event polymerization takes place under the imposition of a light source. In the event that polymerization takes place as a result of the imposition of heat, second part 14 is appropriately thin and made of material that has little or no insulative qualitites. It may also include passages 34 for cooling. These passages, as will be seen, may be selectively used so that a time-dependent temperature gradient will be maintained. Similar passages may be symmetrically located in part 12 (not shown).
Returning now to FIG. 1, movement of focusing gate 24 relative to mold body 10 is controlled so that source of energy 22 scans across the mold body 10 starting at the closed end 26 of cavity 16 and moving toward gate 18. Should cavity 16 be exposed to a source of energy 22 across the entire surface, which is the normal process in polymerization, there would be severe shrinkage in the mold body and a strong likelihood that bubbles would form in the formed polymer especially in highly stressed portions. Reference is made to FIG. 4 wherein an example is shown of what would occur with simultaneous polymerization within the mold body. It is to be understood that second part 12 has been removed in FIG. 4 and the molded form 28 is shown with a void 30 at its upper and adjacent to gate 18. Additionally, bubbles 32 formed by cavitation during polymerization also may very likely occur in the molded body 28. The voids 30 and bubbles 32 are attributable to the chemical linkage formation during polymerization. In order to avoid these problems, it has been found that providing a continuous source of monomer or reaction mixture to be polymerized at reservior 20 and in turn to gate 18 will avoid the formation of unacceptable bubbles and voids. Since monomers generally have a relatively low viscosity, they will flow easily through gate 18 into cavity 16 to fill the volume lost to shrinkage of the reacting mixture.
In FIG. 3, the mold body 110 with its first part 112 and second part 114 transparent to source of energy 122, is moved relative to source of energy 122 with polymerization occuring first at the closed end 126 and moving across cavity 116 to gate 118 by the relative movement of the source of energy and the mold body. Here again, second part 114 is transparent to the source of energy be it heat or a particular type of light. In situ polymerization in this instance may be more adaptable to heat triggered reaction as the control of the incidence of heat upon the cavity 116 where the molded body 136 is of a uniform thickness is more readily controlled. Here again the unreacted mixture contained in reservoir 120 communicates with cavity 116 through gate 118 to fill the volume lost due to reaction shrinkage thereby compensating for any shrinkage in the disc. The final product is a perfectly shaped disc with all portions in a stress free state and free of any internal voids. It lacks birefringence and residual distortion and is dimensionally exact to the degree provided in cavity 116.
Referring now to FIG. 5 a device for solidification of a liquefied polymer mixture by the application of a solidifier is shown. As in the embodiment just discussed a mold structure 10' is utilized in this embodiment. Mold structure 10' has a first part 12' and a second part 14' with second part 14' being slidably removable from the first part 12'. In this embodiment a liquefied polymer mixture, that consists of a solid polymer and perhaps other fillers that have been dissolved in a solvent is contained in reservoir 20' which is in communication with cavity 16'. Cavity 16' is filled with the liquefied polymer when second part 14' fully closes cavity 16'. In the mold structure shown in FIG. 5 a flat plate like structure or sheet will be the result of the casting process. Should drying or devolatilization take place simultaneously over the entire flat plate or sheet, the sheet will warp or crack as shrinkage occurs due to solvent evaporation. Equivalently, when a nonsolvent extractant is used to leach out the solvent as in coagulation, a certain degree of shrinkage will result depending on the relative rates of solvent leaving the mixture and nonsolvent entering the mixture. If, however, second part 14' is withdrawn slowly from the mold body 10' so that devolatilization and/or coagulation can occur in a differential manner such as described above with the polymerization process, then the dissolved polymer feed contained in reservoir 20 can flow into the mold cavity 16' to fill the spaces that occur because of the shrinkage. While shrinkage may not be as great in the devolatilization or coagulation of a liquefied polymer as in polymerization, it is sufficiently significant that cracking will occur in the finished sheet. Should it be necessary to evacuate the space above mold cavity 16' or to use some atmosphere other than ambient air or to use a liquid nonsolvent or nonsolvent vapor, a vacuum pump or source of solidifier 22' may be affixed to a chamber that surrounds the mold body 10'.
Referring now to FIG. 7, a schematic is shown for a device used for devolatilization of a liquid polymer to form a curved part. In particular mold body 10" is formed with a first part 12" and second part 14" (see FIG. 8) forming a curved cavity 16". In this particular embodiment second part 14" swings from an axle or pivot point 52 to differentially expose mold cavity 16" to an evaporating atmosphere. The resrvoir 20" is filled with a liquefied polymer and communicates through a conduit 54 with a gate 56 to ensure that mold cavity 16" is continuously filled with liquefied polymer. The liquefied polymer may be subsequently devolatilized by the withdrawal of second part 14" in a sequential or differential manner as described above.
In the devolatilization or coagulation differential casting process shown in FIGS. 5, 6, 7, and 8, the liquefied polymer mixture contained in reservoir 20' or 20" is allowed to flow into the mold space 16' or 16" as appropriate and completely fill the mold cavity. Once the mold cavity is completely filled, then withdrawal of the second part 14' to expose the liquefied polymer differentially to the solidifying atmosphere or nonsolvent may be accomplished. The rate of removal of the second part 14' is dependent upon the liquefied polymer to be solidified. This of course will vary with the different materials utilized and in part may be dependent upon the thickness of the material. In FIGS. 7 and 8, the same procedure is followed except that the second part 14' is swung away sequentially to form a curved shape as indicated.
In a modification of the method described herein, and polymer lenses produced thereby, a glass or other non-polymer substrate may form a part of the polymer lens. The end product is a polymer-glass lens, formed by casting the polymer onto a glass substrate within the mold and sequentially polymerizing the polymer in the same manner as in the absence of the glass substrate. This modification is depicted in FIG. 9, wherein the process shown in FIG. 1 is modified by the insertion in the mold half 14 (or 12) of a glass substrate 140. The monomer solution 20 is poured into the cavity 16, adjacent the glass substrate 140, and polymerized. In the most preferred embodiment, the substrate 140 is first coated with a coupling agent 142 that increases the adhesion of the polymer to the substrate.
The use of a coupling agent has been found to significantly enhance the adhesion of the cast polymer lens onto a glass substrate. Use of such couplings is a common practice in the field of the casting of polyacrylamide gels. An additional benefit of the method described herein, however, is the simplicity of the preferred coupling procedure used. In particular, prior to filling the mold containing the glass substrate with the polymer mixture, straight (pure) or diluted 3-methacryloxy-propyl-trimethoxysilane (MAPTMS) (in acetone solution), or an equivalent coupling agent, is used to coat the substrate. The substrate is then air dried and heated in an oven for three hours at about 130° C. to effect MAPTMS binding to the substrate surfaces. The MAPTMS promotes strong adhesion to the substrate and a dense, highly cross-linked polymer adjacent to the substrate.
Although not as simple, other coupling agents and procedures may also be used. For example, another approach is to covalently bond aminopropyltrimethoxysilane or aminopropyltriethoxysilane to the substrate. N-acryloxysuccimide is then used to cause substitution addition. This is then followed by treatment with diethylacrylamide to cause crosslinking of the materials on the substrate. In all of the procedures above, the goal is to leave a substrate surface covered with double bonds directly linked to the substrate by chemical bonds. These double bonds can then react with acrylamide monomers and crosslinkers in the differential gellation process.
Once the substrate is treated, the mold cavity can then be filled with the gelling mixture, and the casting process begun.
US4798690 * 3 Nov 1986 17 Ene 1989 Electric Power Research Institute, Inc. Molding a glass-plastic composite lens
US4873029 * 30 Oct 1987 10 Oct 1989 Blum Ronald D Method for manufacturing lenses
US4919850 * 6 May 1988 24 Abr 1990 Blum Ronald D Method for curing plastic lenses
US4983335 * 29 Dic 1988 8 Ene 1991 Matsushita Electrical Industrial Co., Ltd. Method for producing transparent plastic article
US5382310 * 29 Abr 1994 17 Ene 1995 Eastman Kodak Company Packaging medical image sensors
US5706140 * 31 Ago 1994 6 Ene 1998 Kansei Corp. Optical distance measuring equipment
US20050069676 * 24 Sep 2004 31 Mar 2005 Koichiro Nakamura Etched article, mold structure using the same and method for production thereof
US20060132919 * 12 Oct 2005 22 Jun 2006 Rupert Schnell Composite for beam shaping
US20060192306 * 25 Feb 2005 31 Ago 2006 The Microoptical Corporation Manufacturing methods for embedded optical system
US20060192307 * 27 Feb 2006 31 Ago 2006 Eugene Giller Method for producing high quality optical parts by casting
US20100104855 * 28 Mar 2008 29 Abr 2010 Fujifilm Corporation Preform manufacturing method, preform manufacturing apparatus, preform and optical member
US20100214663 * 29 Ago 2008 26 Ago 2010 Fujifilm Corporation Method for molding optical member, apparatus for molding optical member and optical member
WO2002078930A1 * 22 Mar 2002 10 Oct 2002 Krauss-Maffei Kunststofftechnik Gmbh Device and method for injection moulding plastic parts having differences in thickness
WO2008123589A1 * 28 Mar 2008 16 Oct 2008 Fujifilm Corporation Manufacturing preform for an optical member
WO2009028732A1 29 Ago 2008 5 Mar 2009 Fujifilm Corporation Method and apparatus for molding optical member and optical member
Clasificación de EE.UU. 264/496, 264/1.36, 264/1.33, 264/1.7, 264/259, 264/327
Clasificación internacional B29D11/00, G02B1/04, B29C39/40, C08F283/00, B29C37/00, B29C35/08, C08F283/01
Clasificación cooperativa B29C39/40, B29D11/00163, B29D11/00413, B29C35/0894, C08F283/00, B29D11/00442, B29K2105/0002, G02B1/041, B29C2035/0827, B29C37/005, C08F283/01
Clasificación europea B29D11/00C4Y2C2, C08F283/01, G02B1/04B, B29C39/40, B29D11/00C20, B29D11/00C22B, B29C37/00D, C08F283/00, B29C35/08M2
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:SOANE, DAVID S.;REEL/FRAME:005748/0067