WO1990001727A1 - Compositions photodurcissables et procede de coulee de precision - Google Patents

Compositions photodurcissables et procede de coulee de precision Download PDF

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Publication number
WO1990001727A1
WO1990001727A1 PCT/US1989/003303 US8903303W WO9001727A1 WO 1990001727 A1 WO1990001727 A1 WO 1990001727A1 US 8903303 W US8903303 W US 8903303W WO 9001727 A1 WO9001727 A1 WO 9001727A1
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WO
WIPO (PCT)
Prior art keywords
radiation
pattern
ethylenically unsaturated
range
present
Prior art date
Application number
PCT/US1989/003303
Other languages
English (en)
Inventor
Edward J. Murphy
Robert E. Ansel
John J. Krajewski
Original Assignee
Desoto, Inc.
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
Priority claimed from US07/229,476 external-priority patent/US4844144A/en
Application filed by Desoto, Inc. filed Critical Desoto, Inc.
Publication of WO1990001727A1 publication Critical patent/WO1990001727A1/fr

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/0037—Production of three-dimensional images
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C7/00—Patterns; Manufacture thereof so far as not provided for in other classes
    • B22C7/02—Lost patterns
    • B22C7/023—Patterns made from expanded plastic materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/02—Sand moulds or like moulds for shaped castings
    • B22C9/04—Use of lost patterns
    • 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
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/10—Processes of additive manufacturing
    • B29C64/106—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material
    • B29C64/124—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using layers of liquid which are selectively solidified
    • B29C64/129—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using layers of liquid which are selectively solidified characterised by the energy source therefor, e.g. by global irradiation combined with a mask
    • B29C64/135—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using layers of liquid which are selectively solidified characterised by the energy source therefor, e.g. by global irradiation combined with a mask the energy source being concentrated, e.g. scanning lasers or focused light sources
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Definitions

  • This invention relates to photocurable liquid compositions and a method of investment casting utilizing stereolithography to produce a three-dimensional object from these photocurable compositions.
  • the compositions include a thermoplastic material.
  • Investment casting is a conventional industrial process which employs a disposable pattern that is used to produce a ceramic mold in which a part can be cast.
  • the pattern is conventionally made by injecting a liquid pattern material, e.g., wax, a heat-softenable plastic and the like, into a pattern die.
  • the pattern die is typically manufactured from a durable material, e-g-, aluminum, steel, and the like, by conventional machining processes. The pattern is removed from the die after the pattern material solidifies.
  • a refractory material e.g., an aqueous ceramic slurry
  • a mold is produced by heating the refractory material having the pattern invested therein to remove the pattern and fuse the refractory material.
  • the details of investment casting process vary depending upon the type of metal to be cast in the mold. The casting of ferrous alloys will be used to illustrate a conventional investment casting process.
  • the pattern is coated with successive layers of refractory material. Each layer is coated with fine ceramic sand and dried before the next layer is applied. Usually about 10 to 20 layers are utilized to invest the pattern in the refractory material.
  • the invested pattern is then placed in an open ended metal container which is filled with a coarse slurry of ceramic back-up material which hardens.
  • the container is then placed into a furnace or autoclave. The temperature of the furnace or autoclave is elevated to cause the refractory material to dry and then fuse.
  • the pattern is removed, as by melting or burning out the material constituting the same, during the heating step.
  • the resulting fused ceramic structure is the desired mold. Removal of the pattern leaves a cavity in the container corresponding in shape and dimension to the final part.
  • the cavity (and therefore the pattern) can be slightly larger than the final part to compensate for the shrinkage which takes place in the subsequent casting operation, or to allow for machining when desired.
  • the mold is sometimes fired to burn out the last traces of pattern material and to fuse the refractory material before the cavity is filled with molten metal. This firing process proceeds slowly in a controlled cycle which can be in a time range of 12 to 18 hours to avoid cracking the mold.
  • the molten metal is introduced into the cavity of the mold and solidified by cooling to form a casting. After solidification, the mold is broken away to release the part.
  • the process described above is relatively slow and expensive because of the time and cost of the machining required to make the dies used in forming the pattern. Consequently, the prior art process is impractical for use when only a few parts are desired. Even when a larger number of parts is desired, the prior art process is expensive because it may be necessary to prepare several sets of pattern dies having varying dimensions. This is because the size of the pattern (and thus of the pattern die) that is necessary to compensate for shrinkage of the pattern or shrinkage and machining of the cast part must be determined empirically. A number of patterns of varying sizes are typically produced until the proper size is determined to achieve the desired dimensions of the cast part. The problem of shrinkage is particularly severe in connection with casting materials such as powdered metal where shrinkage may amount to 35 volume percent or more of the cast part. 'Elimination of expensively machined pattern dies would be beneficial for economic and production reasons.
  • Thick, solid walls can be produced by filling the honeycomb structure of the hollow-walled object with ethylenically unsaturated material and curing it therein. Other methods can also produce objects having a wall thickness up to 1/8 of an inch or even up to 1/4 of an inch. These thick-walled objects retain their strength better as the heat expands them. Thus, solid objects and objects having thick, solid walls are more likely to cause the mold to crack or distort than are the thin-walled object. If the mold is cracked or distorted it is useless.
  • the combination of stereolithography with investment casting in this invention provides a powerful production system because it enables the relatively rapid and inexpensive production of accurate patterns for use in the investment casting process.
  • the present invention has overcome the aforementioned shortcomings of both conventional investment casting and stereolithography. More particularly, the burden and expense of forming the patterns are reduced by forming them using stereolithography, and the resulting patterns do not destroy the mold when used in an investment casting process.
  • a method of investment casting which utilizes a stereolithographically formed pattern that loses structural rigidity when exposed to elevated temperatures.
  • the liquid composition comprises an ethylenically unsaturated material and a thermoplastic, low molecular weight material that is an oligomer or compound and which (1) is inert with respect to, and soluble in, the ethylenically unsaturated material, and (2) has a melting point less than about 150 * C.
  • an oligomer desirably has a melting point at a temperature below about 100° C.
  • a compound is used, it is a solid at ambient temperature, i.e., about 20°C. to about 35°C. , and has a sharp melting point at a temperature less than about 150°C. Mixtures of oligomers and compounds can also be utilized.
  • the present method which is suitable for producing a mold from a stereolithographically produced pattern, comprises the steps of: (a) investing a pattern in a refractory material, the pattern being a cross-linked polymeric matrix of a radiation-cured ethylenically unsaturated material having distributed throughout the above-described thermoplastic material, the thermoplastic material being present in an amount effective to prevent the pattern from cracking or distorting a mold during a heating step; and (b) heating the refractory material and the pattern to produce the mold.
  • a method of investing the pattern has been previously discussed in more detail.
  • the pattern is a cross-linked, thermoset polymer matrix of the radiation-cured ethylenically unsaturated material.
  • the thermoplastic material which is easily heat-softenable, is distributed throughout the matrix.
  • the thermoplastic material flows from the matrix when the pattern is heated thus weakening the matrix and inhibiting thermal expansion thereof. This weakening of the matrix also causes the pattern to have a softening point at a temperature that is sufficiently low to prohibit destruction of the mold as by cracking or distortion. Further heating can cause the pattern to decompose and be burned out of the mold.
  • solid thick-walled patterns having a thickness of up to about 1/4 of an inch and manufactured from conventional, non-thermoplastic material-containing compositions maintain a high degree of rigidity at the elevated temperature encountered in the investment casting process, destroying the mold.
  • solid, thin- and thick-walled patterns manufactured from the present liquid composition and having the thermoplastic material distributed throughout can be utilized in investment casting because the thermoplastic materials flow from the matrix of the pattern lessening the rigidity of the pattern at elevated temperatures.
  • thermoplastic compounds which are preferred, are ambient temperature solids having a sharp melting temperature of less than about 150°C. and further enhance the efficacy of stereolithographically produced objects in investment casting as compared to oligomers. These compounds have a sharp melting point and thus go from a solid state to a liquid state within a relatively small temperature range. The flowability of the compound in the liquid state results in expulsion of the compound from the pattern more readily and hence loss of structural rigidity.
  • the present invention includes a method suitable for producing a mold from a stereolithographically produced patten comprising the steps of investing a pattern in a refractory material, the pattern comprising a polymeric matrix having a thermoplastic material distributed throughout, and heating the refractory material and the pattern to remove the pattern and produce a mold.
  • the thermoplastic material is present in an amount effective to prevent the pattern from cracking or distorting the mold during heating and has a low molecular weight and is an oligomer or a compound having a meting temperature less than about 150 ⁇ C.
  • an oligomer desirably has a melting point at a temperature below about 100°C.
  • a compound is utilized it is an ambient temperature, i.e., about 20°C. to about 35°C. , solid having a sharp melting point less than about 150°C.
  • Mixtures of oligomers and compounds are also suitable for use in this invention.
  • Radiation-polymerizable liquid compositions suitable for producing the pattern are also disclosed.
  • the composition comprises an ethylenically unsaturated material and the thermoplastic material.
  • thermoplastic material is dissolved in the liquid ethylenically unsaturated material.
  • the pattern is produced by curing the composition to produce a polymeric matrix of the cured ethylenically unsaturated material having intersticial spaces containing the thermoplastic material.
  • a conventional stereolithographic process as disclosed in the aforementioned Hull Patent, can be utilized to produce the pattern.
  • the present radiation-polymerizable (photopolymerizable) liquid composition is used in the reservoir.
  • the object constituting the pattern can be utilized in a conventional investment casting process as previously discussed.
  • the thermoplastic material is substantially chemically inert, i.e., non-reactive, with the other materials, constituents and components of the composition.
  • the thermoplastic material cannot contain any reactive ethylenic functionality, e.g., an acrylate group.
  • Reactive groups such as hydroxy groups or carboxy groups, can be present in the thermoplastic material provided the ethylenically unsaturated materials do not contain groups that are reactive therewith.
  • the thermoplastic material also should not adversely effect the radiation cure of the composition from the liquid to the solid state. Thus, amine groups that can adversely effect cure, and cause the thermoplastic material to chemically bond with the polymeric matrix that is formed, are preferably excluded.
  • thermoplastic material is sufficiently soluble in the ethylenically unsaturated material to provide uniform distribution of the thermoplastic material in the cross-linked, thermoset polymer matrix that is produced.
  • a non-soluble thermoplastic material can cause scattering of the radiation used to cure the composition thus resulting in loss of dimensional accuracy of the pattern.
  • thermoplastic material suitable for use in the present application must flow (flow may result from depolymerization as well as softening) at a temperature less than the temperature at which the degree of thermal expansion of the pattern cracks or deforms the mold.
  • the temperature at which the pattern destroys the mold is partially dependent upon the size, thickness and composition of the mold, the thickness of the pattern, and the like.
  • the presence of the thermoplastic material reduces the softening temperature of the pattern.
  • depolymerize means a reduction in molecular weight. Such reduction can cause the thermoplastic material to flow by making the material softer, or by lowering its melting point, or even by vaporizing a portion of it.
  • the objective is to weaken the polymeric matrix of the pattern so that it yields instead of destroying the mold.
  • the thermoplastic material should not significantly add to the viscosity of the overall composition which preferably is less than about 10,000 centipoise (cp) . More preferably, the viscosity is in the range of about 200 to about 2000 cp. Most preferably, the viscosity is in the range of about 300 to about 800 cp. The viscosity is measured at a temperature of 25°C. using a conventional Brookfield viscometer operated in accordance with the instructions provided therewith. Low viscosity helps in the formation of thin layers in the stereolithographic process, and it also helps in draining away excess liquid composition when the specimen is removed from the bath of liquid composition in which it was formed.
  • cp centipoise
  • thermoplastic oligomers can be a liquid at ambient temperature. However, patterns (specimens) formed by the present composition are solid at about ambient temperature, the liquid oligomer being held within the cross-linked polymeric matrix that is formed. 27
  • the thermoplastic oligomer desirably has a number average molecular weight in the range of about 200 to about 5000, preferably 250 to 1500 daltons, and preferably is a liquid or waxy solid at room temperature which is soluble in the ethylenically unsaturated liquid.
  • the oligomer preferably has a melting point at a temperature below about 100°C. , most preferably about 10°C. to about 40°C. , since this permits adequate weakening of the polymeric matrix on heating while retaining maximum strength (as measured by tensile modulus) at room temperature.
  • the oligomers typically have a relatively higher molecular weight (as compared to the thermoplastic compounds) or melt over a relatively broad temperature range of greater than about + 10°C. Such oligomers desirably have a melting point below about 100°C. to inhibit expansion of the pattern.
  • Illustrative oligomers suitable for use in the present composition include natural waxes, e.g., animal waxes (beeswax) , vegetable waxes (carnauba) , mineral waxes (olibraryrite, paraffin, and microcrystalline petroleum), synthetic waxes (ethylenic polymers, ethylenic polyol ether-esters, and chlorinated naphthalenes) , plasticizers (phthalate, adipate and sebacate esters of alcohols containing about 4 to about 22 carbon atoms and of polyols such as ethylene glycol, glycerol, and pentaerythritol) .
  • natural waxes e.g., animal waxes (beeswax) , vegetable waxes (carnauba) , mineral waxes (olibraryrite, paraffin, and microcrystalline petroleum), synthetic waxes (ethylenic polymers, ethylenic polyol ether-est
  • Low molecular weight polyesters formed by reacting a large excess of a diol with a polycarboxylic acid, such as adipic acid or trimellitic acid are also useful. Combinations of the foregoing are also useful.
  • Preferred thermoplastic oligomers are low molecular weight polyesters, e.g., epsilon caprolactone polyester polyols. These are made by polyesterifying a polyol, such as ethylene glycol, propylene glycol or butylene glycol, with the lactone. Polyols with more than two hydroxy groups are also useful, such as trimethylol propane and pentaerythritol. Control of the proportion of lactone and the selection of the polyol permits selection of a polyester having the desired number average molecular weight. Triols, such as trimethylol propane, are particularly useful in this process and are preferred oligomers.
  • Tone 0301 and Tone 0310 Two thermoplastic oligomers that are epsilon caprolactone polyesters of a polyhydric alcohol and that are useful herein are the commercial products Tone 0301 and Tone 0310. These are available from Union Carbide Corp. of New York, NY.
  • Tone 0301 is a polyester formed by esterifying ethylene glycol with the caprolactone to provide a number average molecular weight of about 300 daltons. This product is a liquid at room temperature.
  • Tone 0310 is a polyester formed by esterifying trimethylol propane with the caprolactone to provide a number average molecular weight of about 900 daltons. This product is a waxy solid at room temperature, melting at about 32°C.
  • thermoplastic compounds are solid at ambient temperature, and are easily heat softenable.
  • the melting point of the thermoplastic compound is at a temperature less than about 150°C. , preferably less than about 125°C.
  • the compound has a sharp melting point and preferably goes from a solid state to a liquid state over a temperature range of preferably ⁇ about 5°C, more preferably + about 3°C. , of the melting point.
  • these compounds are relatively pure, i.e., commercial technical grade purity. Patterns formed from 727
  • the present composition are solid at about ambient temperature.
  • the preferred thermoplastic compounds have a number average molecular weight of less than about 250 daltons, preferably about 120 to about 210 daltons.
  • the compounds can be aliphatic or aromatic in nature, and linear, branched or cyclic in structure. Provided they meet the requirements of being substantially onomeric, solid at ambient temperature, soluble in the ethylenically unsaturated liquid composition, nonrea ⁇ tive with respect to the free radical reaction of the unsaturated liquid material, and possess a sharp melting point less than about 150°C.
  • Suitable thermoplastic compounds are selected from the group consisting of caprolactam, 2,2 dimethyl-3-hydroxy propyl 2,2 dimethyl-3-hydroxy propyl propionate which is commercially available from Union Carbide Corp., New York, NY, under the designation Esterdiol 204, dimethyl terephthalate, dimethyl cyclohexanol, dimethyl dioxane dione, the like and mixtures thereof.
  • the compounds are presently the preferred thermoplastic material.
  • the ethylenically unsaturated materials used in the stereolithographic process can vary considerably and are conventional. It is preferred that the ethylenically unsaturated material not include reactive groups other than the ethylenic unsaturation to ensure avoidance of reaction with the thermoplastic compound, Reactive groups other than the ethylenic unsaturation can be tolerated only if these groups do not react with the thermoplastic compound.
  • An exemplary radiation-polymerizable liquid composition that is suitable for use in the present invention can include a liquid ethylenically unsaturated material that polymerizes by a free-radical mechanism.
  • the ethylenically unsaturated material comprises a resinous (meth)acrylate copolymerizable and cross-linkable component [ (meth)acrylate component] dissolved in a liquid reactive diluent, preferably an ethylenically unsaturated liquid that can comprise a liquid mono(meth)acrylate, a liquid poly(meth)acrylate, or a mixture of these liquids, and a photoinitiator.
  • (meth)acrylate and various grammatical forms thereof, identifies esters that are the reaction product of an acrylic or a methacrylic acid with mono- or poly-hydroxy compounds, such as ethanol, butanol, ethylene glycol, trimethylol propane and the like.
  • (meth)acrylate copolymerizable and cross-linkable component and “(meth)acrylate component”, and various grammatical forms thereof, identify (meth)acrylates and poly(meth)acrylates. These terms also identify monomers and polymers that have a * radiation-polymerization mechanism similar to (meth)acrylates.
  • reactive diluent identifies a diluent capable of dissolving, and copolymerizing with, the (meth)acrylate component.
  • the resinous (meth)acrylate copolymerizable and cross-linkable component suitable for use in the present invention can contain monomers and polymers and is subject to considerable variation.
  • the (meth)acrylate component contains an average of at least about 1.2, and more preferably at least about 2.0, (meth)acrylate groups per molecule.
  • the (meth)acrylate component should have a flowable viscosity and be stable at the operating conditions and the monomers and polymers are selected to achieve these ends.
  • the resinous (meth)acrylate component can also be a poly(meth)acrylate containing an average of at least about two (meth)acrylate groups per molecule, e.g., a diacrylate of an epoxy functional resin. These diacrylates are exemplified by the commercial product
  • Novacure 3700 available from Interez, Inc., Louisville, KY, which is the diester of Epon 828 and acrylic acid.
  • Epon 828 is an epoxy functional resin that is a diglycidyl ether of bisphenol A and is commercially available from Shell Chemicals, New York, NY.
  • the number average molecular weight of Novacure 3700 is about 500 daltons and of Epon 828 is about 390 daltons.
  • Poly(meth)acrylate-modified polyurethanes are also useful as the resinous (meth)acrylate component, especially those that have a polyester base.
  • polyacrylate-terminated polyurethanes that are the urethane reaction products of a hydroxy-functional polyester, especially those having an average of about 2 to about 5 hydroxy groups per molecule, with a monoacrylate monoisocyanate.
  • poly(meth)acrylate-modified polyurethanes can be obtained from a polyester made by reacting trimethylol propane with caprolactone to a number average molecular weight of about 600 daltons followed by reaction of one mole of the polyester with three moles of the reaction product of 1 mole of 2-hydroxyethyl acrylate with 1 mole of isophorone diisocyanate.
  • the end product is a polyurethane triacrylate.
  • the urethane-forming reaction is conventionally performed at about 60°C. in the presence of about 1% by weight of dibutyltin dilaurate.
  • a commercial, polyester-based, polyacrylate-modified polyurethane that is useful herein is Uvithane 893, available from Thiokol Chemical Corp., Trenton, NJ.
  • the polyester in the Uvithane 893 product is the reaction product of adipic acid with about 1.2 molar proportions of ethylene glycol polyesterified to an acid number of less than about 5.
  • This polyester is converted as described above to a polyacrylate-modified polyurethane that is a semi-solid at ambient temperature and that has an average of about 0.15 to about 0.175 ethylenically unsaturated groups per 100 grams of resin.
  • the acid number defined as the number of milligrams of base required to neutralize one gram' of polyester, is used to monitor the progress of the reaction. The lower the acid number, the further the reaction has progressed.
  • An additional polyacrylate-modified polyurethane that is suitable as the (meth)acrylate component is the reaction product of a diisocyanate, a hydroxyalkyl acrylate and a catalyst reacted at a temperature of about 40°C. for a time period of 4 hours followed by reacting therewith a commercial hydroxy end-functional caprolactone polyester at a temperature of about 60° C. for a time period of about 2 hours.
  • An illustrative polyacrylate-modified polyurethane can be prepared from 1 mole of isophorone diisocyanate, 1 mole of 2-hydroxyethyl acrylate, about 1 weight percent, based on the weight of the diisocyanate, acrylate and catalyst, dibutyltin dilaurate (a catalyst) and 1 mole of the caprolactone polyester.
  • a suitable caprolactone polyester is the reaction product of caprolactone and an alkylene glycol reacted at a temperature of about 60° C. for a time period of 4 hours.
  • An illustrative caprolactone polyester can be prepared from about a 2:1 mole ratio of caprolactone: ethylene glycol.
  • a commercial caprolactone polyester is available from Union Carbide Corp. , New York, NY, under the trade designation Tone M-100 which has a number average molecular weight of about 345 daltons.
  • Tone M-100 Another illustrative ethylenically unsaturated material suitable for use in the present invention is Potting Compound 363, a modified acrylate, commercially available from Locktite Corporation, Newington, CT.
  • a process for making ethylenically unsaturated material suitable for use as the present invention is described in U.S. Patent No. 4,100,141 to O 1 Sullivan.
  • the resinous (meth)acrylate component preferably includes both acrylate- and methacrylate- functional materials to minimize distortion in the stereolithographic process.
  • the (meth)acrylate component includes at least about 40 weight percent, based on the weight of the ethylenically unsaturated constituent, of acrylate-functional material (including vinyl monomers having a radiation polymerization mechanism similar to acrylates) and at least about 5 weight percent of methacrylate-functional material.
  • the resinous (meth)acrylate component is dissolved in a liquid reactive diluent that preferably includes a polyethylenically unsaturated liquid material such as a poly(meth)acrylate.
  • a liquid reactive diluent that preferably includes a polyethylenically unsaturated liquid material such as a poly(meth)acrylate.
  • Liquid tri(meth)acrylates e.g., trimethylol propane triacrylate
  • di(meth)acrylates e.g., 1,6-hexanediol di(meth)acrylate
  • Liquid tetra(meth)acrylates e.g., pentaerythritol tetraacrylate, are also useful.
  • Preferred liquid poly(meth)acrylates include Sartomer C 9003, a polypropoxylate-modified diacrylate of neopentyl glycol with an average of two propylene oxide units per molecule and having a number average molecular weight of about 330 daltons and SR 339, a 2-phenoxyethyl acrylate, both commercially available from Sartomer, West Chester, PA.
  • a triacrylate that is suitable as the liquid reactive diluent is Photomer 4094, a propoxylated glyceryl triacrylate having a number average molecular weight of 430 daltons which is commercially available from Henkel Corp., Ambler, PA.
  • the liquid reactive diluent also preferably includes a monoethylenically unsaturated liquid material such as a mono(meth)acrylate.
  • a monoethylenically unsaturated liquid material such as a mono(meth)acrylate.
  • Suitable materials include phenoxyethyl(meth)acrylate, hydroxyethyl- (meth)acrylate, hydroxypropyl(meth)acrylate, N-vinyl pyrrolidone, and the like. Mixtures of these monoethylenically unsaturated materials are also suitable.
  • the liquid reactive diluent is preferably a mixture of monoethylenically and polyethylenically unsaturated materials in a weight ratio of about 4:1 to about 1:4, respectively.
  • An optional, reactive diluent can be a liquid N-vinyl monomer that is regarded to be embraced by the term (meth)acrylate because its radiation-polymerization mechanism is similar to that of (meth)acrylates.
  • Illustrative N-vinyl monomers include N-vinyl pyrrolidone and N-vinyl caprolactam, with N-vinyl pyrrolidone being preferred.
  • a photoinitiator effective to initiate radiation-polymerization upon exposure to actinic energy such as light in or near the ultraviolet and visible ranges, e.g., light having a wavelength of about 200 to about 500 nanometers, is utilized.
  • the radiation-polymerizable liquid composition can be supplied without the photoinitiator, the photoinitiator being added prior to cure.
  • photoinitiators are themselves well known and in common use. They are usually ketonic, and frequently aromatic, such as the benzophenones.
  • Darocur 1173 is an illustrative, commercially available benzyl ketal-based photoinitiator from EM Chemicals that contains
  • 2-hydroxy-2-methyl-l-phenyl-propane-l-one as the active ingredient.
  • a commercially available aryl ketone photoinitiator, Irgacure 184, from Ciba Geigy Corp. that contains hydroxycyclohexyl phenyl ketone as the active ingredient is also suitable.
  • actinic energy as used herein in its various grammatical forms, defines a type of light radiation capable of producing chemical change in the radiation polymerizable liquid composition.
  • the resinous (meth)acrylate component is preferably present in an amount of about 15 to about 80, more preferably about 40 to about 70, weight percent of the weight of the ethylenically unsaturated material.
  • the liquid reactive diluent is preferably • present in an amount of about 20 to about 80, more preferably about 30 to about 60, weight percent of the weight of the ethylenically unsaturated material.
  • the photoinitiator is present in an amount of about 1 to about 10 weight percent of the weight of the ethylenically unsaturated material.
  • the optional reactive diluent when utilized, is present in an amount of about 10 to about 40 weight percent of the weight of the ethylenically unsaturated material and replaces an equal amount of the
  • a stabilizer and polymerization inhibitor can also be present in an amount less than about 1 weight percent of the ethylenically unsaturated material.
  • Illustrative is methyl ether of hydroquinone.
  • the viscosity of the radiation-polymerizable liquid composition can be adjusted utilizing a diluent that is non-reactive and inert with respect to the ethylenically unsaturated material.
  • the diluent can be present in an amount up to about 5 weight percent based on the ethylenically unsaturated material. When the diluent is present, the amount of the ethylenically unsaturated material present is reduced.
  • An illustrative diluent is n-hexanol.
  • the oligomer is present in an amount in the range of about 5 to about 50, preferably about 15 to about 35 weight percent, based on the total weight of the radiation-polymerizable liquid composition.
  • the ethylenically unsaturated liquid material is present in an amount in the range of about 50 to about 95, preferably about 65 to about 85, weight percent based on the total weight of the radiation-polymerizable liquid composition.
  • the thermoplastic material is a thermoplastic compound
  • the compound is present in an amount in the range of about 5 to about 40, preferably about 15 to about 25 weight percent, based on the total weight of the radiation-polymerizable liquid composition.
  • the ethylenically unsaturated liquid material is present in an amount in the range of about 60 to about 95, preferably about 75 to about 85, weight percent based on the total weight of the radiation-polymerizable liquid composition.
  • patterns produced from the present compositions have softening temperatures of about 180°C. or less.
  • softening temperature indicates the temperature at which the cured composition and pattern produced therefrom, loses its structural rigidity.
  • the object removed from the reservoir is somewhat gelatinous.
  • the cure of this object to a rigid solid can be completed by conventional means such as further exposure to actinic energy after the object has been removed from the reservoir in which it was formed.
  • the object can be cured by heat.
  • a free-radical polymerization catalyst can be utilized to make the thermal cure more rapid or effective at lower temperature.
  • the cured object has the thermoplastic material dispersed within the interstices of the polymeric matrix and is suitable for use as a pattern.
  • Actinic energy suitable for curing the radiation-curable liquid composition can be produced by a Liconix Model 4240 N, helium-cadmium laser having an output of 15 milliwatts at 325 nanometers focused to 350 micron diameter.
  • the usual dosage is about 3.0 Joules per square centimeter of surface area which results in a polymerized layer about 20 mils thick.
  • the wavelength of the actinic energy and dosage will vary depending upon the radiation-curable liquid composition utilized. The following example is provided as an illustration, and not as a limitation, of the present invention.
  • EXAMPLE 1 Comparison of Percent Wei ⁇ ht Loss for Various Compositions Comparative tests were conducted utilizing control compositions containing no thermoplastic materials (A and B) , compositions of the present invention each containing a different thermoplastic oligomer (C, D, E, and F) , and compositions of the present invention each containing a different thermoplastic compound (G and H) .
  • the compositions were prepared by admixing the respective components of each composition in the proportions of TABLE I, below, at ambient temperature to a substantial homogeneous condition. TABLE I
  • Polyethylene glycol 8 30 Tone 0310 9 30 30 20.0 Caprolactam 10 20.0 Esterdiol 204 11 20 Irgacure 184 12 4.0 4.0 4.0 4.0 4.0 4.0
  • Epon 828 commercially available from Shell Chemicals, New York, NY, a diglycidyl ether of bisphenol A which is reacted with two moles of acrylic acid to produce the Epon 828 diacrylate.
  • Photomer 4094 commercially available from Henkel Corp. , Ambler, PA, a propoxylated glyceryl triacrylate having a number average molecular weight of 430 daltons.
  • SR 339 is 2-phenoxyethyl acrylate, commercially available from Sartomer Corp., West Chester, PA.
  • Irgacure 184 commercially available from Ciba-Geigy Corp., Oak Brook, IL, is an aryl ketone photoinitiator.
  • the object was removed from the reservoir and unreacted radiation-polymerizable liquid was drained therefrom. This object was then conventionally cured to a rigid solid in a sealed chamber utilizing ultraviolet light. The cured object having a thickness of about 20 mils was then utilized as a pattern in the tests described hereinbelow.
  • Patterns produced from Composition C exhibited about 20 to about 25 weight percent extractables in methyl ethyl ketone (MEK) .
  • Weight percent extractables was determined by placing a pattern of known weight in a MEK bath having a temperature of about 25°C. for a time period of 2 hours. The pattern was then removed from "' the bath, dried and reweighed and the percent weight loss calculated.
  • specimens obtained from a composition similar to that of Composition C but without the thermoplastic oligomer (the Tone 0301) exhibited less than 1 weight percent extractable under the same conditions. This demonstrates that the oligomer did not react to become a part of the cross-linked polymeric matrix constituting the cured specimen, so as to be able to act independently of that matrix.
  • Patterns produced from Composition C also exhibited significant softening and loss of structural rigidity and dimensional integrity at a temperature of about 250°C. In contrast, specimens obtained from a composition similar to that of Composition C but without the thermoplastic oligomer retained structural rigidity and dimensional integrity at this temperature. Patterns produced from Composition C were invested in a refractory slurry. The slurry was dried for a time period sufficient to cause hardening. The pattern and slurry were then heated to a temperature sufficient to remove the pattern and fuse the slurry. A mold was thereby produced.
  • thermographic analysis in which each pattern was heated at a controlled rate increase (10°C./minute) and the resulting weight loss was graphed as a function of temperature.
  • the analysis was performed utilizing a thermogravimetric analyzer Model 651 commercially available from DuPont Co., Wilmington, Delaware operated in accordance with the manual of operation. The results of the thermographic analysis are presented in TABLE II.
  • compositions D, G and H achieve this 20 weight percent loss at a temperature less than 300°C. This indicates that these compositions, which each utilize a thermoplastic material, are better suited for use in investment casting than the control Compositions A and B which did not utilize a thermoplastic material. Also, Compositions D, G and H achieved this weight percent loss at a lower temperature than Compositions E and F. However, patterns produced from Compositions E and F are suitable for use in investment casting, experiencing a significant weight loss, i.e., 56 weight percent, at 400°C.
  • Composition B had a relatively high modulus. However, patterns produced from Composition B do not exhibit sufficient softening (see TABLE II and accompanying discussion) and are not suitable for investment casting. However, both Compositions D and E are suitable and
  • Composition E is most suitable because it has a higher tensile modulus than Composition D.
  • Patterns produced from Composition A would thermally expand without softening and therefore crack or distort a mold. Patterns produced from Compositions F, G or H would not crack or distort a mold because of the relatively low coefficients of thermal expansion and softening temperatures. Furthermore, patterns produced from Compositions G and H, which each utilize a thermoplastic compound, exhibit lower softening temperatures than that of Composition F, which uses a thermoplastic oligomer, making these two compositions even more suitable for use in investment casting.

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  • Physics & Mathematics (AREA)
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  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • General Physics & Mathematics (AREA)
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  • Casting Or Compression Moulding Of Plastics Or The Like (AREA)

Abstract

On a mis au point un procédé de coulée de précision utilisant un modèle produit par stéréolithographie. Ledit modèle a une matrice polymère dans laquelle sont dispersés des espaces interstitiels. Lesdits espaces comportent une matière thermoplastique s'écoulant à partir de la matrice lors du chauffage pendant le procédé de coulée de précision, ramollissant le modèle afin d'empêcher que la dilatation thermique du modèle ne fendille ou ne déforme le moule.
PCT/US1989/003303 1988-08-08 1989-07-31 Compositions photodurcissables et procede de coulee de precision WO1990001727A1 (fr)

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US07/229,476 US4844144A (en) 1988-08-08 1988-08-08 Investment casting utilizing patterns produced by stereolithography
US229,476 1988-08-08
US37661289A 1989-07-07 1989-07-07
US376,612 1989-07-07

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Cited By (14)

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WO1992002572A1 (fr) * 1990-07-30 1992-02-20 Dsm N.V. Compositions contenant des melanges reactifs et associatifs
EP0499486A2 (fr) * 1991-02-14 1992-08-19 E.I. Du Pont De Nemours And Company Procédé de coulée de précision et composition du modèle
US5178673A (en) * 1991-04-12 1993-01-12 Union Carbide Chemicals & Plastics Technology Corporation Investment casting compositions and processes for the manufacture and use thereof
EP0536086A1 (fr) * 1991-10-03 1993-04-07 Ciba-Geigy Ag Mélange photosensible
EP0649691A1 (fr) * 1993-09-24 1995-04-26 Texas Instruments Incorporated Procédé de production d'un modèle pour moulage de précision
EP0729824A1 (fr) * 1995-03-03 1996-09-04 General Motors Corporation Procédé de fabrication rapide d'un prototype ou d'un moule en utilisant un modèle stéréolithigraphique
EP0729823A1 (fr) * 1995-03-03 1996-09-04 General Motors Corporation Procédé de fabrication d'une électrode d'usinage par décharge électrique utilisant un modèle stéréolithographique
WO1996041239A1 (fr) * 1995-06-07 1996-12-19 E.I. Du Pont De Nemours And Company Composition epoxydique photodurcissable
EP0763417A1 (fr) * 1995-09-13 1997-03-19 Toyota Jidosha Kabushiki Kaisha Procédé et dispositif pour déterminer l'épaisseur et la forme de couches laminées d'un produit
GB2307439A (en) * 1995-11-23 1997-05-28 Univ Nottingham Method of making an object having an internal lattice-type structure
US5855836A (en) * 1995-09-27 1999-01-05 3D Systems, Inc. Method for selective deposition modeling
US6305769B1 (en) 1995-09-27 2001-10-23 3D Systems, Inc. Selective deposition modeling system and method
WO2008042376A1 (fr) * 2006-09-29 2008-04-10 Dentsply International Inc. Procédé de fabrication de couronnes et de bridges dentaires provisoires et à long terme
CN113102688A (zh) * 2021-03-29 2021-07-13 上海联泰科技股份有限公司 一种改善3d打印光敏树脂模在熔模铸造中胀壳的方法

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DE4108780C2 (de) * 1991-03-18 1994-12-15 D Andres Malfaz Prieto Vorrichtung zum Zusammenlegen von dünnen Trägermaterialien
JP3127230B2 (ja) * 1994-06-21 2001-01-22 株式会社メイコー 貴金属製品の鋳造方法
JP3470207B2 (ja) * 1994-12-28 2003-11-25 株式会社メイコー 光硬化樹脂製ワックスパターンの製造方法
JP2014217490A (ja) * 2013-05-06 2014-11-20 株式会社内藤貴金属製作所 宝石用貴金属枠の製造方法

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US4203770A (en) * 1977-07-26 1980-05-20 E. I. Du Pont De Nemours And Company Negative tonable photohardenable element
SU741227A1 (ru) * 1977-12-22 1980-06-15 Ордена Трудового Красного Знамени Институт Физической Химии Им. Л.В. Писаржевского Водорастворима фотополимеризующа с композици
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US4421840A (en) * 1980-12-13 1983-12-20 Basf Aktiengesellschaft Photopolymerizable recording material containing a diisocyanate modified nylon binder
US4423135A (en) * 1981-01-28 1983-12-27 E. I. Du Pont De Nemours & Co. Preparation of photosensitive block copolymer elements
US4621044A (en) * 1981-12-10 1986-11-04 Toray Industries, Inc. Photosensitive polymer composition
EP0085472A1 (fr) * 1982-01-06 1983-08-10 Toray Industries, Inc. Composition polymère photosensible
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US4575330B1 (fr) * 1984-08-08 1989-12-19
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Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1992002572A1 (fr) * 1990-07-30 1992-02-20 Dsm N.V. Compositions contenant des melanges reactifs et associatifs
EP0499486A2 (fr) * 1991-02-14 1992-08-19 E.I. Du Pont De Nemours And Company Procédé de coulée de précision et composition du modèle
EP0499486A3 (en) * 1991-02-14 1992-10-14 E.I. Du Pont De Nemours And Company Investment casting method and pattern material
US5178673A (en) * 1991-04-12 1993-01-12 Union Carbide Chemicals & Plastics Technology Corporation Investment casting compositions and processes for the manufacture and use thereof
EP0536086A1 (fr) * 1991-10-03 1993-04-07 Ciba-Geigy Ag Mélange photosensible
EP0649691A1 (fr) * 1993-09-24 1995-04-26 Texas Instruments Incorporated Procédé de production d'un modèle pour moulage de précision
US5616293A (en) * 1995-03-03 1997-04-01 General Motors Corporation Rapid making of a prototype part or mold using stereolithography model
EP0729824A1 (fr) * 1995-03-03 1996-09-04 General Motors Corporation Procédé de fabrication rapide d'un prototype ou d'un moule en utilisant un modèle stéréolithigraphique
EP0729823A1 (fr) * 1995-03-03 1996-09-04 General Motors Corporation Procédé de fabrication d'une électrode d'usinage par décharge électrique utilisant un modèle stéréolithographique
US5728345A (en) * 1995-03-03 1998-03-17 General Motors Corporation Method for making an electrode for electrical discharge machining by use of a stereolithography model
WO1996041239A1 (fr) * 1995-06-07 1996-12-19 E.I. Du Pont De Nemours And Company Composition epoxydique photodurcissable
EP0763417A1 (fr) * 1995-09-13 1997-03-19 Toyota Jidosha Kabushiki Kaisha Procédé et dispositif pour déterminer l'épaisseur et la forme de couches laminées d'un produit
US5855836A (en) * 1995-09-27 1999-01-05 3D Systems, Inc. Method for selective deposition modeling
US6305769B1 (en) 1995-09-27 2001-10-23 3D Systems, Inc. Selective deposition modeling system and method
US6133355A (en) * 1995-09-27 2000-10-17 3D Systems, Inc. Selective deposition modeling materials and method
GB2307439A (en) * 1995-11-23 1997-05-28 Univ Nottingham Method of making an object having an internal lattice-type structure
US6110602A (en) * 1995-11-23 2000-08-29 University Of Nottingham Method of making a three-dimensional object
GB2307439B (en) * 1995-11-23 1997-12-24 Univ Nottingham Method of making a three-dimensional article
WO1997018933A1 (fr) * 1995-11-23 1997-05-29 The University Of Nottingham Procede de fabrication d'un objet tridimensionnel
WO2008042376A1 (fr) * 2006-09-29 2008-04-10 Dentsply International Inc. Procédé de fabrication de couronnes et de bridges dentaires provisoires et à long terme
WO2008042375A1 (fr) * 2006-09-29 2008-04-10 Dentsply International Inc. Enveloppe permettant de fabriquer des restaurations dentaires provisoires et à long terme
US9119692B2 (en) 2006-09-29 2015-09-01 Dentsply International Inc. Shell forms for making provisional and long-term dental restorations
CN113102688A (zh) * 2021-03-29 2021-07-13 上海联泰科技股份有限公司 一种改善3d打印光敏树脂模在熔模铸造中胀壳的方法

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JPH04500929A (ja) 1992-02-20
EP0430992A1 (fr) 1991-06-12

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