Compositions and methods for high temperature jetting of viscous thermoset materials to create solid articles via additive manufacturing
阅读说明：本技术 用于高温喷射粘性热固性材料以经由增材制造创建固体制品的组合物和方法 (Compositions and methods for high temperature jetting of viscous thermoset materials to create solid articles via additive manufacturing ) 是由 保卢斯·安东尼厄斯·玛丽亚·斯蒂曼 阿德里亚努斯·科内利斯·巴斯蒂安·博格尔兹 马尔科·马库斯· 于 2018-12-14 设计创作，主要内容包括：本文描述了用于经由材料喷射工艺形成三维物体的方法和组合物,所述方法包括以下重复步骤：在第一指定方向上将液体热固性材料从至少一个喷射头的喷嘴选择性地沉积到表面上；以及使所述液体热固性材料的至少一部分暴露于光化辐射源以便由固化的热固性材料形成三维物体,其中所述喷射头被配置为在规定的升高工作温度下从所述喷嘴射出所述液体热固性材料的液滴,并且其中所述液体热固性材料被选择以便具有规定的粘度和流变特性。(Described herein are methods and compositions for forming three-dimensional objects via a material jetting process, the method comprising the repeated steps of: selectively depositing liquid thermoset material from nozzles of at least one spray head onto a surface in a first specified direction; and exposing at least a portion of the liquid thermoset material to a source of actinic radiation to form a three-dimensional object from the cured thermoset material, wherein the spray head is configured to emit droplets of the liquid thermoset material from the nozzle at a prescribed elevated operating temperature, and wherein the liquid thermoset material is selected so as to have a prescribed viscosity and rheological properties.)
1. A method for forming a three-dimensional object, the method comprising:
selectively depositing liquid thermoset material from nozzles of at least one jetting head of a printing system onto a surface in a first jetting direction according to a predetermined pattern;
exposing at least a portion of the liquid thermoset to a source of actinic radiation to form a portion of a cured thermoset; and
repeating the selectively depositing and exposing steps a plurality of times to form a three-dimensional object from the cured thermoset material;
wherein the spray head is configured to emit droplets of the liquid thermoset material from the nozzle at an operating temperature of up to about 180 ℃, or from about 30 ℃ to about 160 ℃, or from about 40 ℃ to about 150 ℃, or from about 45 ℃ to about 140 ℃, or from about 50 ℃ to about 135 ℃, or from about 65 ℃ to about 130 ℃;
wherein the liquid thermoset material has a viscosity of up to about 60cPs, or from about 2cPs to about 60cPs, or from about 5cPs to about 55cPs, or from about 8cPs to about 50cPs, or from about 10cPs to about 50cPs, or from greater than 20cPs to about 60cPs, or from greater than 30cPs to about 60cPs at the operating temperature; and is
Wherein the liquid thermoset material, when tested by the CaBER extensional rheology method, satisfies the following equation:
wherein t isFracture ofIs the actual rupture time and tViscosity ofIs a viscous break time, and X is less than 1, or less than 0.8, or less than 0.7, preferably less than 0.5, or less than 0.4, or less than 0.3, or less than 0.2, or less than 0.1, or about 0.0.
2. A method for forming a three-dimensional object, the method comprising:
selectively depositing liquid thermoset material from nozzles of at least one jetting head of a printing system onto a surface in a first jetting direction according to a predetermined pattern;
exposing at least a portion of the liquid thermoset to a source of actinic radiation to form a portion of a cured thermoset; and
repeating the selectively depositing and exposing steps a plurality of times to form a three-dimensional object from the cured thermoset material;
wherein the spray head is configured to emit droplets of the liquid thermoset material from the nozzle at an operating temperature of up to about 180 ℃, or from about 30 ℃ to about 160 ℃, or from about 40 ℃ to about 150 ℃, or from about 45 ℃ to about 140 ℃, or from about 50 ℃ to about 135 ℃, or from about 65 ℃ to about 130 ℃;
wherein the liquid thermoset material has a viscosity of up to about 60cPs, or from about 2cPs to about 60cPs, or from about 5cPs to about 55cPs, or from about 8cPs to about 50cPs, or from about 10cPs to about 50cPs, or from greater than 20cPs to about 60cPs, or from greater than 30cPs to about 60cPs at the operating temperature; and is
Wherein the liquid thermoset material has a maximum relaxation time λ of less than 25 milliseconds when tested by the CaBER extensional rheology method according to the following equation:
3. the method for forming a three-dimensional object according to any of the preceding claims, wherein the jetting head comprises a jetting head
At least one nozzle plate having an aperture forming the nozzle;
and at least one transducer operatively connected to the nozzle plate, wherein the transducer is energizable to move the nozzle plate in a direction substantially parallel or anti-parallel to the first ejection direction such that at least one droplet of the liquid thermoset material is ejected from the nozzle; and is
Wherein the liquid thermoset material has a viscosity at 25 ℃ of from about 100cPs to about 3000cPs, or from about 150cPs to about 2500cPs, or from about 250cPs to about 2250cPs, or from greater than 500cPs to about 2000cPs, or from about 650cPs to about 1750cPs, or from about 750cPs to about 1500 cPs.
4. The method for forming a three-dimensional object according to any of the preceding claims, wherein the liquid thermoset material has a viscosity ratio of from 15 to 1000, or from 20 to 800, or from 30 to 500, or from 50 to 500, or from 60 to 500, or from 100 to 300, or from 60 to 200, or from 100 to 200, wherein the viscosity ratio is the ratio of the viscosity of the liquid thermoset material at 25 ℃ divided by its viscosity at 100 ℃.
5. The method for forming a three-dimensional object according to any of the preceding claims, wherein the liquid thermoset material comprises a first network-forming component having at least one free radical polymerizable compound and a second network-forming component having at least one cationic polymerizable compound.
6. The method for forming a three-dimensional object according to any of the preceding claims, wherein the liquid thermosetting material further comprises at least one free radical photoinitiator, at least one cationic photoinitiator, and optionally one or more additives.
7. The method for forming a three-dimensional object according to claim 5 or 6, wherein
The free radical photoinitiator is present in an amount of 0.1 wt% to 8 wt%;
the cationic photoinitiator is present in an amount of 0.1 wt% to 15 wt%;
the first network-forming component and the second network-forming component are each present in an amount of from about 5 wt% to about 80 wt% or from 5 wt% to 40 wt%;
the one or more additives are present in an amount of 0 wt% to 60 wt%;
wherein all weight percents are listed relative to the total weight of the composition and the weight of each component does not exceed 100 weight percent.
8. The method for forming a three-dimensional object according to any one of claims 5-7, wherein the first network-forming component comprises a multifunctional acrylate monomer.
9. The method for forming three-dimensional objects of any one of claims 5-8, wherein the second network-forming component comprises a compound having epoxy functional groups.
10. The method for forming a three-dimensional object according to any one of claims 5-9, wherein the second network forming component comprises a compound having an oxetane functionality.
11. The method for forming a three-dimensional object according to any of the preceding claims, wherein the one or more additives comprise a filler.
12. The method for forming a three-dimensional object according to the preceding claim, wherein the filler comprises a plurality of silica particles.
13. The method for forming a three-dimensional object according to any of the preceding claims, wherein silica particles further comprise a plurality of microparticles and a plurality of nanoparticles.
14. The method for forming a three-dimensional object of any one of claims 11-13, wherein the filler comprises a plurality of microparticles having an average particle size as measured by ISO 3320:2009 of: from greater than 5 microns to about 50 microns, or from greater than 5 microns to about 25 microns, or from about 10 microns to about 25 microns, or from 15 microns to about 20 microns.
15. The method for forming a three-dimensional object of any one of claims 11-14, wherein the liquid thermoset material comprises filler in an amount from about 20 wt% to about 60 wt%, or from about 30 wt% to about 50 wt%, or from about 35 wt% to about 50 wt%, relative to the weight of the total liquid thermoset material.
16. The method for forming a three-dimensional object according to any of the preceding claims, wherein the one or more additives comprise an impact modifier.
17. The method for forming a three-dimensional object according to the preceding claim, wherein the impact modifier comprises a block copolymer.
18. The method for forming a three-dimensional object of claim 16 or 17, wherein the impact modifier comprises a plurality of elastomeric core-shell particles.
19. The method for forming a three-dimensional object of any one of claims 16-18, wherein the impact modifier is present in an amount from about 3 wt% to about 40 wt%, or from about 4 wt% to about 30 wt%, or from about 5 wt% to about 20 wt%, relative to the weight of the total liquid thermoset material.
20. The method for forming a three-dimensional object according to any of the preceding claims, wherein the liquid thermoset material comprises a terephthalic acid-based polyester comprising at least two polymerizable groups.
21. The method for forming a three-dimensional object according to any of the preceding claims, wherein the printing system further comprises at least one reservoir in fluid connection with the ejection head for storing a portion of the liquid thermoset material.
22. The method for forming a three-dimensional object according to any of the preceding claims, wherein the printing system further comprises a heating element operably connected to a temperature controller, wherein the heating element is controlled to heat the liquid thermoset material in the reservoir up to about 180 ℃, or from about 30 ℃ to about 160 ℃, or from about 40 ℃ to about 150 ℃, or from about 45 ℃ to about 140 ℃, or from about 50 ℃ to about 135 ℃, or from about 65 ℃ to about 130 ℃.
23. The method for forming a three-dimensional object according to any of the preceding claims, wherein the printing system comprises an array of jetting heads, wherein each jetting head has at least one nozzle.
24. The method for forming a three-dimensional object according to the preceding claim, wherein the array of jetting heads is configured to provide a flow-through configuration.
25. The method for forming a three-dimensional object according to any of the preceding claims, wherein the array of jetting heads is configured such that the liquid thermoset material is free flowable between a plurality of nozzles.
26. The method for forming a three-dimensional object as in any one of the preceding claims, wherein the array is configured to provide fluid communication between successive jetting heads.
27. The method for forming a three-dimensional object according to the preceding claim, wherein the array is configured to provide fluid communication between successive nozzles.
28. The method for forming a three-dimensional object according to any of the preceding claims, wherein the array of jetting heads is fixedly secured, and wherein successive nozzles are separated by a barrier.
29. The method for forming a three-dimensional object according to any of the preceding claims, wherein the nozzle plate is nickel-plated.
30. The method for forming a three-dimensional object according to any of the preceding claims, wherein the transducer is piezoelectric.
31. A method for forming a three-dimensional object according to any of the preceding claims, wherein means are provided for selectively exciting transducers as required to project liquid as jets or droplets from respective external faces by moving the liquid through the nozzle in response to movement of the nozzle.
32. The method for forming a three-dimensional object according to any of the preceding claims, wherein one or more pressure absorbing regions are provided at a predetermined distance from the nozzle in a direction perpendicular to the substantially planar transducer array.
33. The method for forming a three-dimensional object of any of the preceding claims, wherein the source of actinic radiation comprises a plurality of Light Emitting Diodes (LEDs), lasers, or broadband lamps.
34. The method for forming a three-dimensional object according to any of the preceding claims, wherein the three-dimensional object has an elastic modulus of at least 1500Mpa or between 2000Mpa and 3000 Mpa.
35. A method for forming a three-dimensional object, the method comprising:
selectively depositing liquid thermoset material from nozzles of at least one jetting head of a printing system onto a surface in a first jetting direction according to a predetermined pattern;
exposing at least a portion of the liquid thermoset to a source of actinic radiation to form a portion of a cured thermoset; and
repeating the selectively depositing and exposing steps a plurality of times to form a three-dimensional object from the cured thermoset material;
wherein the spray head is configured to emit droplets of the liquid thermoset material from the nozzle at an operating temperature of up to about 180 ℃, or from about 30 ℃ to about 160 ℃, or from about 40 ℃ to about 150 ℃, or from about 45 ℃ to about 140 ℃, or from about 50 ℃ to about 135 ℃, or from about 65 ℃ to about 130 ℃;
wherein the liquid thermoset material has a viscosity of up to about 60cPs, or from about 2cPs to about 60cPs, or from about 5cPs to about 55cPs, or from about 8cPs to about 50cPs, or from about 10cPs to about 50cPs, or from greater than 20cPs to about 60cPs, or from greater than 30cPs to about 60cPs at the operating temperature; and is
Wherein the liquid thermosetting material comprises:
a. 30 to 100 wt% of a first network-forming component, based on the total weight of the liquid thermoset material, the first network-forming component consisting of
i. 19.95 to 80 weight percent of a TPA based polyester or first oligomer based on the total weight of the first network forming component, wherein the TPA based polyester or the first oligomer comprises a backbone and at least 2 polymerizable groups, wherein the polymerizable groups comprise an acrylate, a methacrylate, an itaconate, a vinyl ether, an allyl ether, a maleate or a fumarate, and wherein the TPA based polyester or the first oligomer has a number average molecular weight of from 800 to 10000g/mol and a T of at least 25 ℃ or at least 40 ℃g；
19.95 to 80 wt. -%, based on the total weight of the network forming components, of one or more first network monomers having an average number of 0.95-1.1 of polymerizable groups capable of (co) polymerizing with the polymerizable groups of the TPA based polyester or the first oligomer, wherein the linear polymer formed from the one or more first network monomers has a T of at least 25 ℃ or at least 40 ℃g；
From 0.05 wt% to 5 wt%, based on the total weight of the first network-forming components, of one or more first network initiators capable of initiating polymerization of the TPA-based polyester and the first network monomer or the first oligomer and the first network monomer; and
optionally, up to 15 weight percent of one or more additional first network monomers, oligomers, or polymers having an average of 2 or more numbers of polymerizable groups capable of (co) polymerizing with the polymerizable groups of the TPA-based polyester, the first oligomer, or the one or more first network monomers;
b optionally, a second network forming component comprising one or more second network compounds comprising a polymerizable group that is not (co) polymerized with the polymerizable group of the TPA-based polyester or the first oligomer, and a second network initiator for initiating polymerization of the one or more second network compounds; and
c optionally, a particulate filler comprising polymerizable groups capable of (co) polymerizing with the polymerizable groups of the TPA-based polyester or the first oligomer.
36. The process according to the preceding claim, wherein the backbone of the TPA-based polyester comprises the reaction product of terephthalic acid and a polyol.
37. The process according to any of the preceding claims, wherein at least 50 mol%, or at least 75 mol%, or from 50 mol% to about 90 mol% of the backbone of the TPA-based polyester comprises the reaction product of a polyacid and a polyol, wherein at least 50 mol% of the polyacid content is terephthalic acid.
38. The method of any preceding claim, wherein the backbone of the first oligomer comprises a polyepoxide based on bisphenol A, F or S, a polyepoxide based on hydrogenated bisphenol A, F or S, a polycarbonate, or a polyimide.
39. The method of any one of the preceding claims, wherein at least 50 mol%, or at least 75 mol%, or from 50 mol% to about 90 mol% of the backbone of the first oligomer comprises a polyepoxide based on bisphenol A, F or S, a polyepoxide based on hydrogenated bisphenol A, F or S, a polycarbonate, or a polyimide.
40. The process according to any of the preceding claims, wherein the TPA-based polyester or the first oligomer has a number average molecular weight of from 800 to 8000 g/mol.
41. The method of any preceding claim, wherein the one or more first network monomers have a molecular weight of 300g/mol or less, and wherein the T of the linear polymer formed from the one or more first network monomersgIs 60 ℃ or higher.
42. The method of any one of the preceding claims, wherein the one or more first network monomers comprise methyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, or isobutyl (meth) acrylate.
43. The method of any one of the preceding claims, wherein the one or more first network monomers comprise cyclohexene oxide, t-butyl glycidyl ether, 4-chlorophenyl glycidyl ether, cyclopentene oxide, exo-2, 3-alkylenenorbornane, 1, 2-epoxy-3-phenoxypropane, (2, 3-epoxypropyl) benzene, N- (2, 3-epoxypropyl) phthalimide, exo-3, 6-epoxy-1, 2,3, 6-tetrahydrophthalic anhydride, 3, 4-epoxytetrahydrothiophene-1, 1-dioxide, furfuryl glycidyl ether, glycidyl 4-methoxyphenyl ether, glycidyl 2-methylphenyl ether, isophorone oxide, isophorone diisocyanate, and mixtures thereof, Alpha-pinene oxide, cis-stilbene oxide, styrene oxide, methyl 7-oxabicyclo [4.1.0] heptane-3-carboxylate, 7-oxabicyclo (4.1.0) heptane-3-carboxylic acid 2-ethylhexyl ester, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3- (3-hydroxypropyl) oxymethyloxetane or 3-ethyl-3- (4-hydroxybutyl) oxymethyloxetane.
44. A composition as disclosed in any one of the preceding claims as used in a method as claimed in any one of the preceding claims.
45. A three-dimensional article formed by the method of any of the preceding claims.
Technical Field
The present invention relates to methods and compositions for forming three-dimensional articles via additive manufacturing jetting processes using viscous thermoset compositions and three-dimensional articles created thereby.
Cross Reference to Related Applications
Priority of the present application for U.S. provisional application No. 62/599245 filed on 12/15/2017 and U.S. provisional application No. 62/610303 filed on 12/26/2017, the entire contents of each of which are hereby incorporated by reference in their entirety as if fully set forth herein.
Background
Additive manufacturing processes for producing three-dimensional objects are well known. Additive manufacturing processes utilize computer data of an object to build a three-dimensional object from various materials, which may take the form of liquid resins, solid powders, molten filaments, or pastes/slurries, in a layer-by-layer or batch-wise manner. Seven such non-limiting additive manufacturing techniques, also known as additive manufacturing or 3D printing, are currently defined under ISO/ASTM52900-15, including: adhesive jetting, directed energy deposition, material extrusion, material jetting, powder bed fusing, sheet lamination, and photopolymerization (vat photopolymerization).
Material jetting is a well-known, non-limiting form of additive manufacturing that has recently become commercially increasingly popular. Material jetting for additive manufacturing involves selectively ejecting one or more materials from a prescribed number of jetting heads. In such processes, droplets of the material to be deposited are transferred onto the surface in a predefined pattern, rapidly and continuously. In a material-jet additive manufacturing process, the deposition process is repeated until a three-dimensional object is formed. In a material-jet additive manufacturing process, the surface onto which the material is jetted may include, but is not limited to, a rigid build platform, a flexible foil, a previously hardened portion of the jetted material, or a powder bed of a different material.
A wide variety of different materials may be employed in the additive manufacturing process. Thermoplastic materials are commonly used in sheet lamination and material extrusion processes such as fuse fabrication (FFF). Thermoplastics are also commonly used in directed energy deposition processes such as Selective Laser Sintering (SLS), but metals and other inorganic materials may also be used in SLS processes. Photopolymerization techniques such as stereolithography typically employ a single liquid thermoset material, thereby curing the three-dimensional article.
Material injection processes are advantageous because they enable the simultaneous use of multiple different materials or material types in the same build process. For example, a jet print head in an additive manufacturing process may dispense a wax or thermoplastic material that hardens upon cooling after selective deposition on a surface to be covered. Such materials are often used as scaffold materials to provide support for the desired object to be formed in order to prevent deformation during the build process. On the other hand, other inkjet printheads may be designed to emit a photopolymer that responds to the application of actinic radiation to form an irreversible thermoset bond at a specified wavelength and/or intensity.
Electromagnetic radiation is used to promote rapid curing of thermoset materials. The radiation may be emitted in the UV, visible, UV/vis or infrared portions of the electromagnetic spectrum and may be applied, for example, by a laser, lamp or LED. The electromagnetic or actinic radiation may be selectively applied in a laser-drawn specific pattern, for example by using a Digital Micromirror Device (DMD) or a mask, or non-selectively applied across the entire surface, for example by a lamp. To achieve the desired properties of three-dimensional objects formed from the thermosetting composition, post-treatment by applying additional temperature or light to the newly formed three-dimensional object may be required.
Thermoset materials designed for additive manufacturing processes are generally known. It is known that there are low viscosity, typically low molecular weight, free radical polymerizable resins present in material jet additive manufacturing processes. Such resins typically consist of one or more (meth) acrylate compounds (or other free radical polymerizable organic compounds) and a free radical photoinitiator for free radical generation. One such free radical curable system is described in U.S. patent No. 5,418,112. While such free radical polymerizable resins generally have low viscosities and will readily cure at even relatively low energies and/or strengths, they are not always capable of producing solid objects sufficient for many end use applications. First, several (meth) acrylate-containing resins that are considered suitable for material jet additive manufacturing processes have traditionally produced cured parts that are too brittle or have other undesirable mechanical properties. Thus, they can produce parts that are typically not robust enough for non-prototype applications. In addition, such resins may exhibit deformation problems, such as production of warped or misshapen parts, due to residual strain resulting from differential shrinkage during curing. Such problems are more severe on larger platform additive manufacturing machines, where cumulative differential shrinkage effects amplify part warpage or deformity as the solidified object becomes larger. These deformation problems can be partially corrected by software that calculates the known shrinkage by modifying the CAD file used to create the solid three-dimensional part. However, software corrections are not sufficient to fully compensate for distortion in parts having intricate shapes or requiring tight dimensional tolerances across longer distances.
Another well-known type of thermoset material suitable for use in additive manufacturing systems is a "hybrid" curable resin, or a thermoset material comprising: (1) epoxy resins, oxetanes or other types of cationically polymerizable compounds; (2) one or more cationic photoinitiators; (3) acrylate resins or other types of free radical polymerizable compounds; and (4) one or more free radical photoinitiators. Examples of such hybrid curable systems are described, for example, in U.S. patent No. 5,434,196. Such materials have long been known to provide for the creation of cured parts produced via additive manufacturing processes that can have superior mechanical properties relative to low molecular weight all-acrylate systems. Furthermore, it is believed that the hybrid curable systems are preferred over the all-acrylate systems because they are less subject to differential shrinkage problems that have plagued all-acrylate systems for a long time.
Various hybrid curable photopolymer compositions for use in additive manufacturing processes are further described, for example, in U.S. patent No. 7,183,040. Such compositions, which are optimized in particular for stereolithography processes, comprise specified amounts of a cationically curable component having cross-linking aliphatic ester groups, an additional epoxy-containing component, an oxetane-containing component, a multifunctional acrylate, a free-radical photoinitiator and a cationic photoinitiator. The resulting part has a desirable combination of stiffness, toughness, heat resistance, and water absorption resistance.
Additional thermoset materials capable of producing three-dimensional parts with superior toughness have been described in U.S. patent No. 9,676,899. Among other things, radiation curable resin compositions are disclosed that comprise a cationically polymerizable component and various types of impact modifiers that impart high tensile modulus and high toughness to parts cured thereby, as measured by high impact strength and/or high crack propagation resistance.
Even further thermosets capable of producing three-dimensional parts with superior levels of stiffness and heat resistance are described in U.S. patent No. 9,228,073. Therein, compositions are disclosed and claimed that utilize a defined matrix of filler particles to facilitate achieving such desired properties into resins containing a cationically curable component and a free radically curable component.
Thermosets capable of producing three-dimensional parts from hybrid curable photopolymer compositions in an additive manufacturing process employing a radiation source operating in the UV/vis region of the electromagnetic spectrum are described and claimed in U.S. patent No. 9,708,442. Such compositions have a photoinitiating package comprising a Norrish type I photoinitiator with a defined ionization potential, a compound having an electron donating substituent attached to the vinyl group, a cationically curable component, a cationic photoinitiator, and a free radical curable component.
The compositions described in the above thermosetting compositions give excellent properties in the cured objects they create, but the chemical action required to do so often results in highly viscous liquid compositions. In some cases, the compositions are specified to have a viscosity of up to and well above 1000 centipoise (cPs) at 25 ℃.
Advances purportedly enabling the use of slightly higher viscosity materials (relative to conventional "inks" of low viscosity) in contemporary material jet additive manufacturing processes are described, inter alia, in US2002/008333 and US 2010/0092691. These references indicate that jet deposition can occur at elevated temperatures, thereby enabling the materials employed to have viscosities of 50-500cPs at 25 degrees celsius. However, a trade-off is still necessary: these references teach that such compositions must still have very low viscosity (e.g., less than 20cPs) at printing temperatures in order to function properly in the jetting process. These references recognize that the initial viscosity of many curable compositions that can provide the desired final properties makes them difficult to spray.
Despite the foregoing, the amount of material that is in fact suitable for use with known material injection systems for additive manufacturing systems remains extremely limited. In particular, there is an unmet need for material injection systems and processes that utilize a wider range of highly viscous thermoset materials capable of producing three-dimensional articles with excellent mechanical properties.
Disclosure of Invention
Described herein are several embodiments of the present invention that address this unmet need. A first embodiment is a method for forming a three-dimensional object, the method comprising the steps of: selectively depositing liquid thermoset material from nozzles of at least one jetting head of a printing system onto a surface in a first jetting direction according to a predetermined pattern; exposing at least a portion of the liquid thermoset to a source of actinic radiation to form a portion of a cured thermoset; and repeating the selectively depositing and exposing steps a plurality of times to form a three-dimensional object from the cured thermoset material, wherein the jet head is configured to eject droplets of the liquid thermoset material from the nozzle at an operating temperature of up to about 180 ℃, or from about 30 ℃ to about 160 ℃, or from about 40 ℃ to about 150 ℃, or from about 45 ℃ to about 140 ℃, or from about 50 ℃ to about 135 ℃, or from about 65 ℃ to about 130 ℃, further wherein the liquid thermoset material has a viscosity of up to about 60cPs, or from about 2cPs to about 60cPs, or from about 5cPs to about 55cPs, or from about 8cPs to about 50cPs, or from about 10cPs to about 50cPs, or from greater than 20cPs to about 60cPs, or from greater than 30cPs to about 60cPs at the operating temperature;
wherein the liquid thermoset material, when tested by the CaBER extensional rheology method, satisfies the following formula:
wherein t isFracture ofIs the actual rupture time and tViscosity ofIs a tack rupture time, and X is less than 1, or less than 0.8, orLess than 0.7, preferably less than 0.5, or less than 0.4, or less than 0.3, or less than 0.2, or less than 0.1, or about 0.0.
A second embodiment is a three-dimensional article formed via the method according to the first embodiment using the composition according to the first embodiment. Further embodiments of the invention are described below.
Drawings
FIG. 1 depicts a cross-section of a nozzle plate and nozzles of an ejection head used in various embodiments of the current invention.
FIG. 2 depicts a cross section of a non-limiting example of a jetting head of a printing system as used in an embodiment of the present invention.
Fig. 3 shows a time-delayed plot of a material subjected to CaBER extensional rheology testing.
FIG. 4 is a graph of the diameter as a function of time for several different materials according to the CaBER extensional rheology test. The actual and viscous break times of at least one material are depicted in the line graph.
Fig. 5 is a line graph of data points that may be used to fit
FIG. 6 depicts a simplified diagram of a high speed camera and suitable light source as used herein.
Detailed Description
The method according to the first embodiment of the present invention comprises the steps of: selectively depositing liquid thermoset material from nozzles of at least one jetting head of a printing system onto a surface in a first jetting direction according to a predetermined pattern; exposing at least a portion of the liquid thermoset to a source of actinic radiation to form a portion of a cured thermoset; and repeating the selectively depositing and exposing steps a plurality of times to form a three-dimensional object from the cured thermoset material, wherein the jet head is configured to eject droplets of the liquid thermoset material from the nozzle at an operating temperature of up to about 180 ℃, or from about 30 ℃ to about 160 ℃, or from about 40 ℃ to about 150 ℃, or from about 45 ℃ to about 140 ℃, or from about 50 ℃ to about 135 ℃, or from about 65 ℃ to about 130 ℃, further wherein the liquid thermoset material has a viscosity of up to about 60cPs, or from about 2cPs to about 60cPs, or from about 5cPs to about 55cPs, or from about 8cPs to about 50cPs, or from about 10cPs to about 50cPs, or from greater than 20cPs to about 60cPs, or from greater than 30cPs to about 60cPs at the operating temperature;
wherein the liquid thermoset material, when tested by the CaBER extensional rheology method, satisfies the following formula:
wherein t isFracture ofIs the actual rupture time and tViscosity ofIs a viscous break time, and X is less than 1, or less than 0.8, or less than 0.7, preferably less than 0.5, or less than 0.4, or less than 0.3, or less than 0.2, or less than 0.1, or about 0.0.
In one embodiment, a material ejection process according to the present invention involves selectively depositing liquid thermoset material onto a surface from nozzles of at least one ejection head of a printing system in a first ejection direction according to a predetermined pattern according to methods known in the art. The jetting material is deposited from the nozzles of the jetting head by means of several types of actuators. One such type that has traditionally incorporated so-called bubble jet technology utilizes electromechanical actuation means. Actuation may also be accomplished via piezoelectric and/or piezoresistive means. Such methods and devices incorporating electro-acoustic and magneto-acoustic actuators are described in WO 1993010910.
In one embodiment, the material injection process according to the present invention additionally involves exposing at least a portion of the liquid thermoset material to a source of actinic radiation sufficient to form a portion of the cured thermoset material. Exposure as referred to herein refers to irradiation with actinic radiation. The exposure or irradiation may occur at any suitable time with respect to deposition, but it is preferred that a radiation dose sufficient to fully cure the liquid thermoset material is performed after the droplet has reached its intended destination on the surface. Full curing prior to deposition will result in a failure of the continuous droplets or layers of the three-dimensional part to have sufficient adhesion or cohesion to enable the production of a single solid article having the desired mechanical properties. Similarly, it is preferred that exposure to electromagnetic radiation does not occur too late after the material has been deposited, as the droplets may move from their original predetermined positions, or the material may change certain properties if exposed to environmental conditions for too long.
The source of actinic radiation or light source may be one or more of any of the sources described elsewhere herein. In various embodiments, the radiation may be emitted in the UV, visible, UV/vis, or infrared portions of the electromagnetic spectrum, but the light source should be selected so that its emission spectrum matches the optimal absorption range of the liquid thermoset being utilized.
The light source may be disposed in any suitable position relative to the surface. In one embodiment, the source of actinic radiation is fixed in a position parallel to and above the build surface such that the ejected droplets travel normal to and away from the source of actinic radiation. However, in other embodiments, the light source may be located below the light source, particularly where the material ejection process is building the part upside down. In this case, the light source may be disposed below the transparent film on which the most recently deposited material layer has been deposited. In still other embodiments, the light source can be disposed in other locations, or even movable so as to travel along the surface to be cured.
In one embodiment, the previous steps are repeated multiple times in order to build the three-dimensional article to be created. Build time and number of iterations depend on droplet size, size and geometry of the article to be created, desired detail and accuracy of part features, amount of energy required to fully cure the liquid thermoset material, and speed of the material ejection system.
While most known material jetting systems for use in additive manufacturing processes incorporating thermoset materials are capable of performing a repetitive sequence of selective deposition and curing in some manner, there remains a need for jetting systems and methods that enable the use of an extended library of materials, particularly highly viscous thermoset materials capable of producing three-dimensional articles with superior properties. Thus, in particular, as a minimum premise, such injection systems must be configured to satisfy the following two conditions: (1) may be operated at an elevated temperature and simultaneously (2) shooting material having an elevated viscosity at the elevated temperature.
Thus, in various embodiments, the ejection head is configured to eject droplets of the liquid thermoset material from the nozzle at an elevated operating temperature of up to about 180 ℃, or from about 30 ℃ to about 160 ℃, or from about 40 ℃ to about 150 ℃, or from about 45 ℃ to about 140 ℃, or from about 50 ℃ to about 135 ℃, or from about 65 ℃ to about 130 ℃, or from greater than 80 ℃ to about 140 ℃, or from greater than 80 ℃ to about 130 ℃.
Similarly, in various embodiments, the ejection head must also be configured to eject viscous droplets of liquid thermoset material from the nozzles at such elevated temperatures. Thus, in various embodiments, at elevated operating temperatures, the ejection head is configured to successfully eject droplets of liquid thermoset material having a viscosity of up to about 60cPs, or from about 2cPs to about 60cPs, or from about 5cPs to about 55cPs, or from about 8cPs to about 50cPs, or from about 10cPs to about 50cPs, or from greater than 20cPs to about 60cPs, or from greater than 30cPs to about 60 cPs.
In one embodiment, the method involves the use of a material ejection system capable of dispensing droplets at temperatures up to 150 degrees celsius at maximum viscosities of up to 50 cPs. In another embodiment, the method involves the use of a material ejection system capable of ejecting droplets having filler with a size of up to 50 microns.
A non-limiting embodiment of a material ejection system that can meet the above-described temperature and high viscosity ejection requirements is shown in fig. 1 and 2. Turning to fig. 1, a cross-section of a
Turning to fig. 2, a jettable material reservoir module is shown. In this embodiment, the reservoir module is disposed above the nozzle plate 7 and allows for storage, fluid circulation, and heating of the
A non-limiting example of a known material jetting system for additive manufacturing processes suitable for use in the processes described and claimed herein is the Vista array printhead jetting system developed by Technology Partnership plc of melbourne, england.
Indeed, the inventors have found that certain highly viscous liquid thermoset materials are suitable for use in additive manufacturing processes incorporating ejection heads that operate at elevated temperatures and are capable of dispensing materials at elevated temperatures, including those that remain viscous (i.e. greater than 20cPs or 30cPs) even after heating to the highest temperatures currently achievable on known ejection systems (or to the highest temperatures to which the liquid thermoset material itself can withstand before degradation). However, the inventors have surprisingly found that highly viscous liquid thermoset materials are compatible in such material ejection systems only if formulated or selected to have certain rheological properties, as will be described in more detail elsewhere herein.
The liquid thermosetting material used in the process according to the invention has at least one initiator and one or more polymerizable compounds. The initiator and polymerizable compound may be ejected simultaneously from the same fluid reservoir or nozzle, but they may also be ejected separately from two or more independent ejection heads, such that they mix or combine only at the location where curing is desired. Such a multiple jet head process is particularly desirable in otherwise unstable compositions, where the initiator and polymerizable components are likely to react prematurely in the jet head or reservoir. This may occur, for example, due to chemical reactions between components that cause the composition to slowly polymerize over time, or because undesirable initiation begins to occur at the elevated temperatures at which the spray heads of the present invention are intended to operate.
In one embodiment, the liquid thermoset material comprises a first network forming component having at least one free radical polymerizable compound (i.e., a compound that undergoes polymerization initiated by a free radical). The free radical polymerizable compound is a monomer, oligomer and/or polymer; they are monofunctional or multifunctional materials, i.e., having 1,2,3,4,5,6, 7, 8, 9, 10.. 20.. 30.. 40.. 50.. 100 or more functional groups that can be polymerized by free radical initiation, and may contain aliphatic, aromatic, cycloaliphatic, araliphatic, heterocyclic segments, or any combination thereof. Examples of multifunctional materials include dendrimers, such as dendrimers, linear dendrimers, dendritic graft polymers, hyperbranched polymers, star-branched polymers, and supergraft polymers; see, for example, US 2009/0093564 a 1. Dendrimers may contain one type of polymerizable functional group or different types of polymerizable functional groups, such as acrylate and methacrylate functionality.
Examples of the radical polymerizable component include acrylates and methacrylates such as isobornyl (meth) acrylate, bornyl (meth) acrylate, tricyclodecyl (meth) acrylate, dicyclopentenyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, 4-butylcyclohexyl (meth) acrylate, acryloylmorpholine, meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, isobutyl (meth) acrylate, benzyl (meth) acrylate, 4-butylcyclohexyl (meth) acrylate, acryloylmorpholine, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, methyl (, T-butyl (meth) acrylate, pentyl (meth) acrylate, caprolactone acrylate, isoamyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, tridecyl (meth) acrylate, undecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, butoxyethyl (meth) acrylate, ethoxydiethanol (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polyoxyethylene glycol mono (meth, Polypropylene glycol mono (meth) acrylate, methoxy ethylene glycol (meth) acrylate, ethoxyethyl (meth) acrylate, methoxy polyethylene glycol (meth) acrylate, methoxy polypropylene glycol (meth) acrylate, diacetone (meth) acrylamide, β -carboxyethyl (meth) acrylate, phthalate (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, butylcarbamoylethyl (meth) acrylate, n-isopropyl (meth) acrylamide fluorinated (meth) acrylate, 7-amino-3, 7-dimethyloctyl (meth) acrylate.
Examples of the polyfunctional radical polymerizable component include components having a (meth) acryloyl group such as trimethylolpropane tri (meth) acrylate, pentaerythritol (meth) acrylate, ethylene glycol di (meth) acrylate, bisphenol A diglycidyl ether di (meth) acrylate, dicyclopentadiene dimethanol di (meth) acrylate, [2- [1, 1-dimethyl-2- [ (1-oxoallyl) oxy ] acrylate]Ethyl radical]-5-ethyl-1, 3-dioxan-5-yl]Methyl esters; di (methyl) acrylic acid 3, 9-bi (1, 1-dimethyl-2-ethoxyl) -2,4,8, 10-tetraoxaspiro [5.5]Undecyl esters; dipentaerythritol monohydroxypenta (meth) acrylate, propoxylated trimethylolpropane tri (meth) acrylate, propoxylated neopentyl glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, 1, 4-butanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polybutylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, glycerol tri (meth) acrylate, phosphoric acid mono (meth) acrylate and phosphoric acid di (meth) acrylate, di (meth) acrylate C (meth) acrylate7-C20Alkyl esters, tris (2-hydroxyethyl) isocyanurate of tri (meth) acrylate, tris (2-hydroxyethyl) isocyanurate of di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tricyclodecanediyldimethyl di (meth) acrylate, and alkoxylated versions (e.g., ethoxylated and/or propoxylated) of any of the foregoing monomers, and di (meth) acrylates of diols as ethylene oxide or propylene oxide adducts of bisphenol a, di (meth) acrylates of diols as ethylene oxide or propylene oxide adducts of hydrogenated bisphenol a, epoxy (meth) acrylates of (meth) acrylate adducts of bisphenol a as diglycidyl ether, diacrylates and triethylene glycol divinyl ether of polyoxyalkylated bisphenol a, and addition of hydroxyethyl acrylate A compound (I) is provided.
According to one embodiment, the free radical polymerizable component is a multifunctional (meth) acrylate. The multifunctional (meth) acrylate may include all methacryloyl groups, all acryloyl groups, or any combination of methacryloyl and acryloyl groups. In one embodiment, the free radical polymerizable component is selected from the group consisting of: bisphenol A diglycidyl ether di (meth) acrylate, ethoxylated or propoxylated bisphenol A or bisphenol F di (meth) acrylate, dicyclopentadiene dimethanol di (meth) acrylate, 2- [1, 1-dimethyl-2- [ (1-oxoallyl) oxy ] ethyl ] -5-ethyl-1, 3-dioxan-5-yl ] methyl acrylate, dipentaerythritol monohydroxypenta (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, propoxylated trimethylolpropane tri (meth) acrylate, and propoxylated neopentyl glycol di (meth) acrylate, and any combination thereof.
In one embodiment, the multifunctional (meth) acrylate has more than 2 functional groups. According to another embodiment, the multifunctional (meth) acrylate has more than 3 functional groups. In yet another embodiment, the multifunctional (meth) acrylate has more than 4 functional groups. In another preferred embodiment, the free radical polymerizable component consists exclusively of a single multifunctional (meth) acrylate component. In further embodiments, the exclusive radical polymerizable component is tetrafunctional, in further embodiments the exclusive radical polymerizable component is pentafunctional, and in further embodiments the radical polymerizable component is hexafunctional.
In another embodiment, the free radical polymerizable component comprises an aromatic (meth) acrylate. As non-limiting examples, the aromatic acrylate may be derived from bisphenol-A, bisphenol-S, or bisphenol-F. In certain embodiments, the aromatic compound is selected from the group consisting of: bisphenol A diglycidyl ether diacrylate, dicyclopentadiene dimethanol diacrylate, [2- [1, 1-dimethyl-2- [ (1-oxoallyl) oxy ] ethyl ] -5-ethyl-1, 3-dioxan-5-yl ] methyl acrylate, dipentaerythritol monohydroxypentaacrylate, propoxylated trimethylolpropane triacrylate and propoxylated neopentyl glycol diacrylate and any combination thereof. In one embodiment, the aromatic (meth) acrylate is difunctional.
In particular embodiments, the liquid radiation curable resin for additive manufacturing of the present invention comprises one or more of: bisphenol a diglycidyl ether di (meth) acrylate, dicyclopentadiene dimethanol di (meth) acrylate, dipentaerythritol monohydroxypenta (meth) acrylate, propoxylated trimethylolpropane tri (meth) acrylate, and/or propoxylated neopentyl glycol di (meth) acrylate, and more specifically includes one or more of the following: bisphenol a diglycidyl ether diacrylate, dicyclopentadiene dimethanol diacrylate, dipentaerythritol pentaacrylate, propoxylated trimethylolpropane triacrylate and/or propoxylated neopentyl glycol diacrylate.
The first network-forming component may contain the above-described radical polymerizable compound alone or in any combination of two or more thereof. The liquid thermoset material can comprise the first network-forming component in any suitable amount, for example, in certain embodiments, the amount of the first network-forming component is up to about 50% by weight of the liquid thermoset material, in certain embodiments, from about 2% to about 40% by weight of the liquid thermoset material, in other embodiments from about 5% to about 30% by weight, and in further embodiments, from about 10% to about 20% by weight of the liquid thermoset material. In preferred embodiments, the first network forming component is present in an amount of about 5 wt% to about 80 wt%, or about 5 wt% to about 40 wt%, relative to the total weight of the liquid thermoset material ejected from a particular ejection head or nozzle. Of course, if the initiator is sprayed separately from the polymerizable compound, the weight percentage of the first network-forming component in the reservoir or spray head containing the polymerizable compound may be much higher, even up to 100 wt.%.
In various embodiments, the liquid thermoset material can further comprise a second network forming component comprising at least one cationically polymerizable compound; that is the component that undergoes polymerization initiated by the cation or in the presence of an acid generator. The cationically polymerizable compounds can be monomeric, oligomeric, and/or polymeric and can contain aliphatic, aromatic, cycloaliphatic, araliphatic, heterocyclic segments, and any combination thereof. In one embodiment, the cationically polymerizable compound comprises at least one cycloaliphatic compound. Suitable cyclic ether compounds may contain cyclic ether groups as pendant groups or groups that form part of a cycloaliphatic or heterocyclic ring system.
The cationic polymerizable compound may be one or more selected from the group consisting of: cyclic ether compounds, cyclic acetal compounds, cyclic thioether compounds, spiro orthoester compounds, cyclic lactone compounds, and vinyl ether compounds, and any combination thereof.
Suitable cationically polymerizable compounds include cyclic ether compounds (e.g., epoxy compounds and oxetanes), cyclic lactone compounds, cyclic acetal compounds, cyclic thioether compounds and spiro orthoester compounds specific examples of cationically polymerizable components include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, brominated bisphenol A diglycidyl ether, brominated bisphenol F diglycidyl ether, brominated bisphenol S diglycidyl ether, epoxy novolac resins, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol S diglycidyl ether, 3, 4-epoxycyclohexylmethyl-3 ',4' -epoxycyclohexanecarboxylate, 2- (3, 4-epoxycyclohexyl-5, 5-spiro-3, 4-epoxy) -cyclohexane-1, 4-dioxane, bis (3, 4-epoxycyclohexylmethyl) adipate, vinylcyclohexene oxide, vinylcyclohexene dioxide, limonene oxide, bis (3, 4-epoxy-6-methylcyclohexylmethyl) adipate, 3, 4-vinylcyclohexene oxide, vinylcyclohexene dioxide, limonene dioxide, bis (3, 4-epoxy-6-methylcyclohexylmethyl) adipate, 3, 4-epoxycyclohexylmethyl-3 ',4' -epoxycyclohexane carboxylate modified with 3,3' -epoxycyclohexyl lactone, 3' -epoxycyclohexyl-4 ' -epoxymethyl-3 ',4' -epoxycyclohexane carboxylate, 3' -epoxycyclohexyl-4 ' -epoxycyclohexane carboxylate, 3' -epoxymethyl-3 ', 4-epoxycyclohexane modified with 3' -epoxymethyl lactone, 3' -epoxycyclohexyl-4 ' -epoxymethyl-3 ' -epoxycyclohexane carboxylate, 3' -epoxymethyl-4-3 ' -epoxycyclohexane modified with 3' -epoxymethyl-4-epoxycyclohexane carboxylic ester, 3' -epoxycyclohexane-3, 3' -epoxymodified with a modified with a methyl-4 ' -epoxycyclohexane-methyl-4 ' -epoxylactone, 3' -epoxymethyl-methyl-42-、-C(CH3)2-、-CBr2-、-C(CBr3)2-、-C(CF3)2-、-C(CCl3)2-or-CH (C)6H5) Bis (3, 4-ethoxycyclohexyl) of (E), dicyclopentadiene diepoxide, bis (3, 4-epoxycyclohexylmethyl) ether of ethylene glycol, ethylene bis (3, 4-epoxycyclohexylcarboxylate), hexahydrodioctylphthalate, hexahydro-di-2-ethylhexyl phthalate, 1, 4-butanediol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, diglycidyl esters of aliphatic long-chain dibasic acids, monoglycidyl ethers of aliphatic higher alcohols, monoglycidyl ethers of phenol, cresol, butylphenol or polyether alcohols obtained by adding alkylene oxides to these compounds, glycidyl esters of higher fatty acids, epoxidized soybean oil, epoxybutylstearic acid, epoxyoctylstearic acid, epoxidized linseed oil, epoxidized polybutadiene, 1, 4-bis [ (3-ethyl-3-oxetanylmethoxy) methyl]Benzene, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3- (3-hydroxypropyl) oxymethyloxetane, 3-ethyl-3- (4-hydroxybutyl) oxymethyloxetane, 3-ethyl-3- (5-hydroxypentyl) oxymethyloxetane, 3-ethyl-3-phenoxymethyloxetane, bis ((1-ethyl (3-oxetanyl)) methyl) ether, 3-ethyl-3- ((2-ethylhexyloxy) methyl) oxetane, 3-ethyl- ((triethoxysilylpropoxymethyl) oxetane, 3- (methyl) -allyloxymethyl-3-ethyloxetane, 3-hydroxymethyl-3-ethyloxetane, (3-ethyl-3-oxetanylmethoxy) methylbenzene, 4-fluoro- [1- (3-ethyl-3-oxetanylmethoxy) methyl]Benzene, 4-methoxy- [1- (3-ethyl-3-oxetanylmethoxy) methyl]-benzene, [1- (3-ethyl-3-oxetanylmethoxy) ethyl]Phenyl ether, isobutoxymethyl (3-ethyl-3-oxetanylmethyl) ether, 2-ethylhexyl (3-ethyl-3-oxetanylmethyl) ether, ethyldiglycol (3-ethyl-3-oxetanylmethyl) ether, dicyclopentadiene (3-ethylcyclopentadiene)-3-oxyethynylmethyl) ether, dicyclopentenyloxyethyl (3-ethyl-3-oxetanylmethyl) ether, dicyclopentenyl (3-ethyl-3-oxetanylmethyl) ether, tetrahydrofurfuryl (3-ethyl-3-oxetanylmethyl) ether, 2-hydroxyethyl (3-ethyl-3-oxetanylmethyl) ether, 2-hydroxypropyl (3-ethyl-3-oxetanylmethyl) ether, and any combination thereof.
The cationically polymerizable component can also optionally contain multifunctional materials, including dendrimers with epoxy or oxetane functionality, such as dendrimers, linear dendrimers, dendritic graft polymers, hyperbranched polymers, star-branched polymers, and supergraft polymers. Dendrimers may contain one type of polymerizable functional group or different types of polymerizable functional groups, such as epoxy and oxetane functionalities.
In one embodiment, the second network forming component further comprises one or more mono or polyglycidyl ethers of an aliphatic alcohol, an aliphatic polyol, a polyester polyol or a polyether polyol. Examples of preferred components include 1, 4-butanediol diglycidyl ether, polyoxyethylene glycols and triols and glycidyl ethers of polyoxypropylene glycols and triols having molecular weights of from about 200 to about 10,000; and glycidyl ethers of polytetramethylene glycol or poly (oxyethylene-oxybutylene) random or block copolymers. In one embodiment, the cationically polymerizable component comprises a multifunctional glycidyl ether lacking a cyclohexane ring in the molecule. In another embodiment, the second network forming component comprises neopentyl glycol diglycidyl ether. In another embodiment, the second network forming component comprises 1, 4-cyclohexanedimethanol diglycidyl ether.
An example of a commercially available preferred multifunctional glycidyl ether is ErisysTMGE 22(ErisysTMThe product is available from Emerald Performance MaterialsTM)、HeloxyTM48、HeloxyTM67、HeloxyTM68、HeloxyTM107(HeloxyTMModifiers available from Momentive Specialty Chemicals) and
In one embodiment, the epoxide is 3, 4-epoxycyclohexylmethyl-3', 4-epoxycyclohexane carboxylate (which can be used as CELLOXIDE)TM2021P is available from Daicel Chemical, or as CYRACURETMUVR-6105 from Dow chemical), epoxy resins based on hydrogenated bisphenol A-epichlorohydrin (available as EPON)TM1510 from Momentive), 1, 4-cyclohexanedimethanol diglycidyl ether (available as HELOXY)TM107 from Momentive), hydrogenated bisphenol A diglycidyl ether (available as EPON)TM825 from Momentive), dicyclohexyl diepoxide and nanosilica (available as NANOPOX)TMCommercially available) and any combination thereof.
In another embodiment, the cationically polymerizable component comprises an epoxy resin having aromatic or aliphatic glycidyl ether groups with 2 (difunctional) or more than 2 (polyfunctional) epoxy groups.
The above cationic polymerizable compounds may be used alone or in combination of two or more thereof. In an embodiment of the invention, the second network forming component further comprises at least two different epoxy components.
In other embodiments of the invention, the second network forming component further comprises an oxetane compound. In one embodiment, the second network forming component comprises an oxetane, for example, an oxetane containing 1,2 or more than 2 oxetanyl groups. In another embodiment, the oxetane employed is monofunctional and additionally has a hydroxyl group.
The second network-forming component may contain the above-described cationic polymerizable compound alone or in any combination of two or more thereof. The liquid thermoset material can comprise any suitable amount of the second network-forming component, for example, in certain embodiments, the amount of the second network-forming component is up to about 50% by weight of the liquid thermoset material, in certain embodiments, from about 2% to about 40% by weight of the liquid thermoset material, in other embodiments from about 5% to about 30% by weight, and in further embodiments, from about 10% to about 20% by weight of the liquid thermoset material. In preferred embodiments, the second network forming component is present in an amount of about 5 wt% to about 80 wt%, or about 5 wt% to about 40 wt%, relative to the total weight of the liquid thermoset material ejected from a particular ejection head or nozzle. Of course, if the initiator is sprayed separately from the polymerizable compound, the weight percentage of the second network forming component in the reservoir containing the polymerizable component may be much higher, even up to 100 wt.%.
In one embodiment, the liquid thermosetting material further comprises at least one free radical photoinitiator. The photoinitiator is a compound that is chemically changed to generate at least one of a radical, an acid, and a base due to the action of light or a synergistic action between the action of light and the electronic excitation of the sensitizing dye.
Generally, radical photoinitiators are divided into radical initiators which form radicals by cleavage (known as Norrish type I) and radical initiators which form radicals by hydrogen abstraction (known as Norrish type II). Norrish type II photoinitiators require a hydrogen donor, which acts as a source of free radicals.
In accordance with one embodiment, a liquid radiation curable resin for additive manufacturing includes at least one free radical photoinitiator selected from the group consisting of: benzoylphosphine oxides, aryl ketones, benzophenones, hydroxylated ketones, 1-hydroxyphenyl ketones, ketals, metallocenes, and any combination thereof.
In one embodiment, the liquid radiation curable resin for additive manufacturing comprises at least one free radical photoinitiator selected from the group consisting of: 2,4, 6-trimethylbenzoyldiphenylphosphine oxide and 2,4, 6-trimethylbenzoylphenylethoxyphosphine oxide, bis (2,4, 6-trimethylbenzoyl) -phenylphosphine oxide, 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholinopropanone-1, 2-benzyl-2- (dimethylamino) -1- [4- (4-morpholinyl) phenyl ] -1-butanone, 2-dimethylamino-2- (4-methyl-benzyl) -1- (4-morpholin-4-yl-phenyl) -butan-1-one, 4-benzoyl-4' -methyldiphenylsulfide, N-methyltetrahydromethyltetrahydromethyltetrahydromethyltetrahydromethyltetrahydromethyltetrahydromethyltetrahydromethyltetrahydromethyltetrahydromethyltetrahydromethyltetrahydromethyltetrahydromethyltetrahydromethyltetrahydromethyltetrahydromethyltetrahydromethyltetrahydromethyltetrahydromethyltetrahydromethyltetrahydromethyltetrahydromethyltetrahydromethyl, 4,4 '-bis (diethylamino) benzophenone and 4,4' -bis (N, N '-dimethylamino) benzophenone (Mildron), benzophenone, 4-methylbenzophenone, 2,4, 6-trimethylbenzophenone, dimethoxybenzophenone, 1-hydroxycyclohexylphenylketone, phenyl (1-hydroxyisopropyl) ketone, 2-hydroxy-1- [4- (2-hydroxyethoxy) phenyl ] -2-methyl-1-propanone, 4-isopropylphenyl (1-hydroxyisopropyl) ketone, oligo- [ 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl ] propanone, camphorquinone, 4' -bis (diethylamino) benzophenone, camphor, and a mixture thereof, Benzyldimethyl ketal, bis (. eta.5-2-4-cyclopentadien-1-yl) bis [2, 6-difluoro-3- (1H-pyrrol-1) -yl) phenyl ] titanium, and any combination thereof.
According to one embodiment of the invention, the radical photoinitiator is a Norrish type I variant. According to one embodiment, the radical photoinitiator is an alkyl, aryl or acyl substituted compound. In one embodiment, the alkyl, aryl or acyl substituted photoinitiator has or is centered on an atom in a carbon (group 14) group. In this case, the group 14 atoms present in the photoinitiator compound form radicals upon excitation (via absorption of radiation). Such compounds can thus produce radicals having or centered on an atom selected from the group consisting of: carbon, silicon, germanium, tin, and lead. In one embodiment, the alkyl, aryl or acyl substituted photoinitiator is an acylgermanium compound. In one embodiment, the free radical photoinitiator is an acylgermanium compound. In one embodiment, the acylgermanium is Benzoyltrimethylgermane (BTG) or bisacylgermanyl (bis acyl germanoyl).
Examples of suitable free radical photoinitiators that absorb in this region for light sources emitting in the 300-475nm wavelength range, especially light sources emitting at 365nm, 390nm or 395nm, include: benzoylphosphine oxides, for example 2,4, 6-trimethylbenzoyldiphenylphosphine oxide (Lucirin TPO from BASF) and 2,4, 6-trimethylbenzoylphenylethoxyphosphine oxide (Lucirin TPO-L from BASF), bis (2,4, 6-trimethylbenzoyl) -phenylphosphine oxide (Irgacure 819 or BAPO from Ciba), 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholinopropane-1 (Irgacure 907 from Ciba), 2-benzyl-2- (dimethylamino) -1- [4- (4-morpholino) phenyl ] -1-butanone (Irgacure 369 from Ciba), 2-dimethylamino-2- (4-methyl-benzyl) -1- (4-morpholin-4-yl-phenyl) -butan-e Alk-1-ones (Irgacure 379 from Ciba), 4-benzoyl-4 '-methylbenzophenone sulfide (Chivacure BMS from Chitec), 4' -bis (diethylamino) benzophenone (Chivacure EMK from Chitec) and 4,4 '-bis (N, N' -dimethylamino) benzophenone (mikimone). Mixtures thereof are also suitable.
In addition, a photosensitizer may be used in combination with a photoinitiator to effect curing using an LED light source emitting in this wavelength range. Examples of suitable photosensitizers include: anthraquinones, such as 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone and 2-amylanthraquinone; thioxanthone and xanthone (xanthone), such as isopropylthioxanthone, 2-chlorothioxanthone, 2, 4-diethylthioxanthone and 1-chloro-propoxythioxanthone; methyl benzoylformate (Darocur MBF from Ciba), methyl 2-benzoylbenzoate (Chivacure OMB from Chitec), 4-benzoyl-4 '-methyldiphenyl sulfide (Chivacure BMS from Chitec), 4' -bis (diethylamino) benzophenone (Chivacure EMK from Chitec).
The UV radiation source may be designed to emit light at shorter wavelengths. For light sources emitting at wavelengths between about 100nm and about 300nm, a photosensitizer may be employed with the photoinitiator. When photosensitizers such as those previously listed are present in the formulation, other photoinitiators that absorb at shorter wavelengths may be used. Examples of such photoinitiators include: benzophenones, for example benzophenone, 4-methylbenzophenone, 2,4, 6-trimethylbenzophenone, dimethoxybenzophenone, and l-hydroxyphenylmethanones, for example l-hydroxycyclohexylphenylketone, phenyl (1-hydroxyisopropyl) ketone, 2-hydroxy-1- [4- (2-hydroxyethoxy) phenyl ] -2-methyl-1-propanone and 4-isopropylphenyl (1-hydroxyisopropyl) ketone, benzyldimethyl ketal and oligo- [ 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl ] propanone ] (Esacure KIP 150 from Lamberti).
The radiation source may also be designed to emit at higher wavelengths. Examples of suitable free radical photoinitiators for radiation sources that emit light at wavelengths from about 475nm to about 900nm include: camphorquinone, 4' -bis (diethylamino) benzophenone (Chivacure EMK from Chitec), 4' -bis (N, N ' -dimethylamino) benzophenone (Mildron), bis (2,4, 6-trimethylbenzoyl) -phenylphosphine oxide ("BAPO" or Irgacure 819 from Ciba), metallocenes such as bis (. eta.5-2-4-cyclopentadien-1-yl) bis [2, 6-difluoro-3- (1H-pyrrol-1-yl) phenyl ] titanium (Irgacure 784 from Ciba) and visible light photoinitiators from Spectra Group Limited, Inc., such as H-Nu470, H-Nu-535, H-Nu-635, H-Nu-Blue-640 and H-Nu-Blue-660.
In one embodiment of the claimed invention, the light emitted by the radiation source is UVA radiation, which is radiation having a wavelength between about 320nm and about 400 nm. In one embodiment of the claimed invention, the light emitted by the radiation source is UVB radiation, which is radiation having a wavelength between about 280nm and about 320 nm. In one embodiment of the claimed invention, the light emitted by the radiation source is UVC radiation, which is radiation having a wavelength between about 100nm and about 280 nm.
The liquid thermoset may comprise any suitable amount of free radical photoinitiator, for example, in certain embodiments, the amount of free radical photoinitiator is up to about 10 wt%, or from about 0.1 wt% to about 10 wt%, or from 0.5 wt% to about 6 wt%, or from about 1 wt% to about 3 wt%, relative to the weight of the total liquid thermoset composition being sprayed. Of course, if the initiator is sprayed separately from the polymerizable compound, the weight percentage of free radical photoinitiator in the reservoir or spray head containing the initiator may be much higher, even up to 100 wt.%.
In one embodiment, the liquid thermosetting material comprises a cationic photoinitiator.
The cationic photoinitiator initiates cationic ring-opening polymerization upon irradiation with light. In one embodiment, any suitable onium salt based cationic photoinitiator may be used, but iodonium based cationic photoinitiators are preferred, for example, photoinitiators having a cation selected from the group consisting of: diaryliodonium salts, triaryliodonium salts, aromatic iodonium salts, and any combination thereof.
In another embodiment, the cation of the cationic photoinitiator is selected from the group consisting of: aromatic diazonium salts, aromatic sulfonium salts, aromatic iodonium salts, metallocene-based compounds, aromatic phosphonium salts, and any combination thereof. In another embodiment, the cation is a polymeric sulfonium salt, as in US5380923 or US5047568, or other aromatic heteroatom containing cations and naphthyl sulfonium salts, as in US7611817, US7230122, US2011/0039205, US2009/0182172, US7678528, EP2308865, WO2010046240 or EP 2218715. In another embodiment, the cationic photoinitiator is selected from the group consisting of: triarylsulfonium salts, diaryliodonium salts, and metallocene-based compounds, and any combination thereof. Onium salts (e.g., iodonium salts and sulfonium salts) and ferrocenium salts have the advantage that they are generally more thermally stable.
In a particular embodiment, the cationic photoinitiator has an anion selected from the group consisting of: BF (BF) generator4 -、AsF6 -、SbF6 -、PF6 -、[B(CF3)4]-、B(C6F5)4 -、B[C6H3-3,5(CF3)2]4 -、B(C6H4CF3)4 -、B(C6H3F2)4 -、B[C6F4-4(CF3)]4 -、Ga(C6F5)4 -、[(C6F5)3B-C3H3N2-B(C6F5)3]-、[(C6F5)3B-NH2-B(C6F5)3]-Tetrakis (3, 5-difluoro-4-alkoxyphenyl) borate, tetrakis (2,3,5, 6-tetrafluoro-4-alkoxyphenyl) borate, perfluoroalkylsulfonate, tris [ (perfluoroalkyl) sulfonyl]Methide, bis [ (perfluoroalkyl) sulfonyl group]Imide radicals, perfluoroalkyl phosphates, tris (perfluoroalkyl) trifluorophosphate, bis (perfluoroalkyl) tetrafluorophosphate, tris (pentafluoroethyl) trifluorophosphate and (CH)6B11Br6)-、(CH6B11Cl6)-And other halocarborane anions.
In one embodiment, the cationic photoinitiator has a cation selected from the group consisting of: aromatic sulfonium salts, aromatic iodonium salts, and metallocene-based compounds having an anion selected from at least the group consisting of: SbF6 -、PF6 -、B(C6F5)4 -、[B(CF3)4]-Tetrakis (3, 5-difluoro-4-methoxyphenyl) borate, perfluoroalkylsulfonate, perfluoroalkylphosphate, tris [ (perfluoroalkyl) sulfonyl group]Methide and [ (C)2F5)3PF3]-。
Examples of suitable cationic photoinitiators in other embodiments include 4- [4- (3-chlorobenzoyl) thiophenyl]Phenyl bis (4-fluorophenyl) sulfonium hexafluoroantimonate, 4- [4- (3-chlorobenzoyl) phenylthio]Phenylbis (4-fluorophenyl) sulfonium tetrakis (pentafluorophenyl) borate, 4- [4- (3-chlorobenzoyl) phenylthio]Phenylbis (4-fluorophenyl) sulfonium tetrakis (3, 5-difluoro-4-methoxyphenyl) borate, 4- [4- (3-chlorobenzoyl) phenylthio]Tetrakis (2,3,5, 6-tetrafluoro-4-methoxyphenyl) borate, tris (4- (4-acetylphenyl) thiophenyl) sulfonium tetrakis (pentafluorophenyl) borate (from BASF)PAG290), tris (4- (4-acetylphenyl) thiophenyl) sulfonium tris [ (trifluoromethyl) sulfonyl group]Methide (from BASF)
In a preferred embodiment, the cationic photoinitiator component comprises, alone or in admixture: bis [ 4-diphenylsulfonium phenyl group]Thioether bis hexafluoroantimonate; thienyloxyphenylsulfonium hexafluoroantimonate (Chivacure 1176 from Chitec corporation), tris (4- (4-acetylphenyl) thiophenyl) sulfonium tetrakis (pentafluorophenyl) borate (from BASF)
In one embodiment of the invention, the liquid radiation curable resin for additive manufacturing comprises an aromatic triarylsulfonium salt cationic photoinitiator. The use of aromatic triarylsulfonium salts in additive manufacturing applications is known. Please refer to the product of Dismann knowledgeUS 20120251841 to property limited, U.S. patent No. 6,368,769 to Asahi Denki Kogyo, discusses aromatic triarylsulfonium salts having tetraarylborate anions, including tetrakis (pentafluorophenyl) borate, and the use of these compounds in stereolithography applications. In, for example, J Photoolmer Science&Triarylsulfonium salts are disclosed in Tech (2000),13(1),117, 118and J Poly Science, Part A (2008),46(11), 3820-29. Having complex metal halide anions such as BF are disclosed in J Polymer Sci, Part A (1996),34(16),3231-4 -、AsF6 -、PF6 -And SbF6 -Of triarylsulfonium salt Ar3S+MXn -。
An example of a triarylsulfonium tetrakis (pentafluorophenyl) borate cationic photoinitiator is tris (4- (4-acetylphenyl) thiophenyl) sulfonium tetrakis (pentafluorophenyl) borate. Tris (4- (4-acetylphenyl) thiophenyl) sulfonium tetrakis (pentafluorophenyl) borate is commercially known as
In another embodiment, the cationic photoinitiator is an aromatic triarylsulfonium salt having an anion represented by: SbF6 -、PF6 -、BF4 -、(CF3CF2)3PF3 -、(C6F5)4B-、((CF3)2C6H3)4B-、(C6F5)4Ga-、((CF3)2C6H3)4Ga-Silver trifluoromethanesulfonate, nonafluorobutanesulfonate, methanesulfonate, butanesulfonate, benzenesulfonate or p-toluenesulfonate. Such photoinitiators are described, for example, in U.S. patent No. 8,617,787.
Another cationic photoinitiator is an aromatic triarylsulfonium cationic photoinitiator having an anion that is a fluoroalkyl-substituted fluorophosphate. Having fluorineA commercial example of an aromatic triarylsulfonium cationic photoinitiator with an alkyl-substituted fluorophosphate anion is the CPI-200 series available from San-Apro Limited (e.g., CPI-Or CPI-
There are also several commercially available cationic photoinitiators that are designed to be particularly suitable for absorbing light and generating photoreactive species at UV/vis wavelengths. Incorporation of one or more of these cationic photoinitiators into a liquid radiation curable composition for UV/vis curing will be achieved by "direct" excitation of the photoinitiator. Some non-limiting examples of UV/vis direct excitation cationic photoinitiators include: irgacure 261, Irgacure PAG 103, and Irgacure PAG121, each of which are available from BASF; r-262(η 5-2, 4-cyclopentadien-1-yl) [ (1,2,3,4,5,6- η) - (1-methylethyl) benzene]Iron (I) -hexafluoroantimonate, commercially available from Chitec; and a CPI-400 series photoinitiator, available from San-Apro, Inc.
The liquid thermoset material can comprise any suitable amount of cationic photoinitiator, for example, in certain embodiments, the amount of cationic photoinitiator is up to about 15 wt%, or up to about 5 wt%, and in further embodiments from about 2 wt% to about 10 wt%, or from about 0.1 wt% to about 5 wt%, or from about 0.2 wt% to about 4 wt%, or from about 0.5 wt% to about 3 wt%, relative to the weight of the total liquid thermoset material being sprayed. Of course, if the initiator is sprayed separately from the polymerizable compound, the weight percentage of cationic photoinitiator in the reservoir or spray head containing the initiator may be much higher, even up to 100 wt.%.
The liquid thermoset material may optionally comprise one or more additives. An additive is any desired component that is desired to be added to a material and that does not fall under any of the categories listed above. Possible additives include stabilizers, organic and inorganic fillers, dyes, pigments, antioxidants, wetting agents, foam breakers, chain transfer agents, leveling agents, defoamers, surfactants, and the like. Such additives are known and may generally be employed as desired for a particular application, as will be appreciated by one of ordinary skill in the art.
Stabilizers are often added to resin compositions as additives to further prevent viscosity increases, such as during use in solid imaging processes. Useful stabilizers include those described in U.S. Pat. No. 5,665,792. The presence of a stabilizer is optional. In one embodiment, the liquid thermoset material comprises from 0.1 to 3% by weight of a stabilizer. In another embodiment, the liquid thermoset material is substantially free of stabilizers.
Fillers include those described in U.S. patent No. 9,228,073, which is hereby incorporated by reference in its entirety. In one embodiment, the liquid thermoset material contains a filler component. In one embodiment, the filler component comprises a plurality of silica particles. In one embodiment, the silica particles further comprise a plurality of microparticles and a plurality of nanoparticles. In yet another embodiment, the filler component comprises a plurality of microparticles having an average particle size as measured by ISO 3320:2009 of: from greater than 5 microns to about 50 microns, or from greater than 5 microns to about 25 microns, or from about 10 microns to about 25 microns, or from about 15 microns to about 20 microns.
If utilized, the fillers are present in an amount from about 10 wt.% to about 65 wt.%, or from about 20 wt.% to about 60 wt.%, or from about 30 wt.% to about 50 wt.%, or from about 35 wt.% to about 50 wt.%, relative to the weight of the total liquid thermoset material into which they are incorporated.
The liquid radiation curable resin composition for additive manufacturing of the present invention may further comprise one or more additives selected from the group consisting of: examples of suitable additives include, but are not limited to, foam breakers, antioxidants, surfactants, acid scavengers, pigments, dyes, thickeners, flame retardants, silane coupling agents, ultraviolet light absorbers, resin particles, impact modifiers, soluble polymers and block copolymers and combinations thereof.
Impact modifiers include those described in U.S. patent No. 9,676,899, which is hereby incorporated by reference in its entirety. In one embodiment, the liquid thermoset material contains an impact modifier. In one embodiment, the impact modifier comprises a block copolymer. In one embodiment, the impact modifier comprises a plurality of elastomeric core-shell particles. If utilized, the impact modifiers are present in an amount from about 3 wt.% to about 40 wt.%, or from about 4 wt.% to about 30 wt.%, or from about 5 wt.% to about 20 wt.%, relative to the weight of the total liquid thermoset material into which they are incorporated.
In addition, many known thermosets utilize hydroxy-functional compounds to enhance the properties of parts made therefrom. Any hydroxyl group, if present, may be used for a particular purpose. The hydroxyl containing material, if present, preferably contains one or more primary or secondary aliphatic hydroxyl groups. The hydroxyl group may be internal to the molecule or terminal. Monomers, oligomers or polymers may be used. The hydroxyl equivalent weight, i.e. the number average molecular weight divided by the number of hydroxyl groups, is preferably in the range of 31 to 5000. If present, the liquid thermosetting material preferably comprises up to 10 wt% of one or more non-free radical polymerizable hydroxy-functional compounds, or up to 5 wt%, or up to 2 wt%, relative to the total weight of the total material.
In one embodiment, the liquid thermoset material comprises a TPA-based polyester. The TPA-based polyester comprises a backbone and an average of at least 2 polymerizable groups per molecule. The backbone comprises the reaction product of terephthalic acid (TPA) and a polyol.
The backbone comprises a polyester formed from the polycondensation product of terephthalic acid and a polyol. The polyol is an alcohol having two or more hydroxyl groups. In one embodiment, the polyol is a diol, triol, or tetraol. In one embodiment, the polyol is a pentahydric or higher order polyol. In one embodiment, the polyol is a diol. The TPA-based polyester may comprise only a single type of polyol and TPA; it may also comprise more than one type of polyol, for example two, three, four, five or six different polyols and TPA. In one embodiment, the TPA-based polyester is linear. In one embodiment, the TPA-based polyester is branched or dendritic.
In one embodiment, the polyol is an aliphatic or cycloaliphatic polyol. In one embodiment, the polyol is an aromatic polyol. In one embodiment, the polyol has at least 2, at least 3, at least 4, at least 5, or at least 6 hydroxyl groups. In one embodiment, the polyol has at most 2, at most 3, at most 4, at most 5, at most 6, at most 8, or at most 10 hydroxyl groups. In one embodiment, the polyol is linear. In one embodiment, the polyol is branched.
The polyol is selected to impart a glass transition temperature (T) to the TPA-based polyesterg) Is 40 ℃ or higher. In one embodiment, the Tg of the TPA-based polyester is at least 40 ℃, at least 45 ℃, at least 50 ℃, at least 55 ℃, at least 60 ℃, at least 65 ℃, or at least 70 ℃. In one embodiment, T of TPA-based polyestersgIs 150 ℃ or less, 125 ℃ or less, or 120 ℃ or less.
In one embodiment, the polyol comprises a polyalkylene polyol or a polyalkylene oxide polyol. In one embodiment, the polyol comprises polyethylene glycol, polypropylene glycol, polytetramethylene oxide (PTMO) polyol, random or block polypropylene oxide-polyethylene oxide copolymer polyol, random or block polybutylene oxide-polyethylene oxide copolymer polyol, polycarbonate polyol, hydroxyl terminated siloxane, random or block siloxane-polyethylene oxide copolymer polyol, polybutadiene polyol, polyisobutylene polyol, polybutylene oxide polyol, or mixtures thereof.
In one embodiment, the polyol comprises 1, 4-butanediol, 1, 2-propanediol, 1, 3-propanediol, dipropylene glycol, tripropylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, neopentyl glycol, 1, 6-hexanediol, hydrogenated bisphenol A, ethoxylated bisphenol A, propoxylated bisphenol A, glycerol, 1,2, 6-hexanetriol, 1,1, 1-tris (hydroxymethyl) propane, pentane-1, 2, 3-triol, propane-1, 1, 1-triol, 1, 2-cyclohexanediol, 1, 4-cyclohexanediol, 1, 1-cyclohexanediol, cyclohexane-1, 2, 4-triol, Cyclopropane-1, 2, 3-triol, benzenetriol, pentane-1, 1,5, 5-tetraol, hexane-1, 2,5, 6-tetraol, 1,2,4, 5-tetrahydroxybenzene, butane-1, 2,3, 4-tetraol, [1,1' -biphenyl ] -3,3',5,5' -tetraol, trimethylolpropane, pentaerythritol, 1, 4-cyclohexanedimethanol, phenyldiethanolamine, or mixtures thereof.
In one embodiment, the TPA-based polyester comprises another polyacid other than TPA. In one embodiment, the other polyacid is an aliphatic polyacid or an aromatic polyacid. In one embodiment, the other polyacid comprises a dicarboxylic acid represented by the general formula HOOC-Z-COOH, wherein Z is an aliphatic compound containing at least 2 carbon atoms. Such dicarboxylic acids include adipic acid, sebacic acid, phthalic acid, isophthalic acid, octadecanedioic acid, pimelic acid, suberic acid, azelaic acid, tridecanoic acid, dodecanedioic acid, glutaric acid, maleic acid, fumaric acid, 6-naphthalenedicarboxylic acid, 4' -oxybis-benzoic acid, 3, 6-dichlorophthalic acid, tetrachlorophthalic acid, tetrahydrophthalic acid, hexahydroterephthalic acid, hexachloroendomethylenetetrahydrophthalic acid, endomethylenetetrahydrophthalic acid, decanedicarboxylic acid, succinic acid, and trimellitic acid. In one embodiment, the other polyacid comprises phthalic acid or isophthalic acid.
In one embodiment, at least 20 mol%, or at least 50 mol%, or at least 70 mol%, or at least 90 mol%, or at least 98 mol%, or 100 mol% of the backbone of the TPA-based polyester comprises the reaction product of a polyacid and a polyol.
The TPA based polyesters are preferably functionalized or reacted with reactive groups that participate in the polymerization reaction. In one embodiment, the TPA-based polyester comprises polymerizable groups including acrylates, methacrylates, oxetanes, hydroxyls, itaconates, vinyl ethers, allyl ethers, maleates, or fumarates. In one embodiment, the polymerizable group comprises an acrylate, methacrylate, epoxy, oxetane or itaconate. In one embodiment, the polymerizable group comprises an acrylate, a methacrylate, an epoxy, or an oxetane. In one embodiment, the polymerizable group comprises an acrylate or methacrylate. In one embodiment, the polymerizable group comprises a methacrylate. The polymerizable groups can be formed, for example, by reacting a hydroxy-functional monomer comprising the desired polymerizable group with a carboxylic acid-functional polymer comprising a TPA/polyol backbone. If the TPA-based polyester is functionalized with free radical functionality, it will be considered part of the first network forming component. If the TPA-based polyester is functionalized with cationically polymerizable functional groups, it will be considered part of the second network forming component.
In one embodiment, the polymerizable group comprises a terminal group. An end group is a group present at the end of the polymer. In one embodiment, the polymerizable groups are end groups and there are no polymerizable groups that are not end groups in the TPA-based polyester.
In one embodiment, the TPA-based polyester comprises an average number of 2.0, at least 2.1, at least 2.2, at least 2.3, at least 2.4, at least 2.5, at least 2.6, or at least 2.7 polymerizable groups per molecule. In one embodiment, the TPA-based polyester comprises an average of up to 10, up to 9, up to 8, up to 7, up to 6, up to 5, up to 4.5, up to 4, up to 3.5, or up to 3 polymerizable groups per molecule. In one embodiment, the TPA-based polyester comprises from 2.3 to 3 polymerizable groups. Generally, as the functionality of the TPA-based polyester increases, the amount of TPA-based polyester in the composition may decrease.
In one embodiment, the TPA-based polyester has a number average molecular weight of at least 800g/mol, at least 900g/mol, at least 1000g/mol, at least 1100g/mol, at least 1200g/mol, at least 1300g/mol, at least 1400g/mol, or at least 1500 g/mol. In one embodiment, the TPA-based polyester has a number average molecular weight of at most 10,000g/mol, at most 9,000g/mol, at most 8,000g/mol, at most 7000g/mol, at most 6,000g/mol, at most 5,000g/mol, at most 4,000g/mol, or at most 3,000 g/mol.
In one embodiment, the TPA-based polyester has an average number of 2 to 3 end groups, and the amount of TPA-based polyester, the number average molecular weight, and the number of end groups in the composition all satisfy the above equation, and f is the average number of end groups of the TPA-based polyester.
It is possible that the TPA-based polyester achieves an average of 2 to 3 polymerizable groups per molecule by a blend of TPA-based polyesters having different functionalities. For example, a TPA-based polyester using 70 mole% of an average of 2.3 number of polymerizable groups per molecule and 30 mole% of an average of 4.0 number of polymerizable groups per molecule is considered to be a TPA-based polyester of an average of 2.8 number of polymerizable groups per molecule. In this example, f in the above equation would be 2.8 and M calculated based on the mol% of each TPA based polyesterPolyester。
In one embodiment, the TPA-based polyester is present in an amount of at least 5 weight percent, at least 10 weight percent, at least 15 weight percent, at least 19.95 weight percent, at least 20 weight percent, at least 25 weight percent, at least 30 weight percent, at least 40 weight percent, at least 50 weight percent, at least 60 weight percent, at least 70 weight percent, or at least 80 weight percent, based on the total weight of the composition. In one embodiment, the TPA-based polyester is present in an amount of up to 80 weight percent, up to 78 weight percent, up to 75 weight percent, up to 70 weight percent, up to 60 weight percent, up to 50 weight percent, up to 40 weight percent, up to 30 weight percent, or up to 20 weight percent, based on the total weight of the composition.
In one embodiment, the TPA-based polyester is present in an amount of at least 5 weight percent, at least 10 weight percent, at least 15 weight percent, at least 19.95 weight percent, at least 20 weight percent, at least 25 weight percent, at least 30 weight percent, at least 40 weight percent, at least 50 weight percent, at least 60 weight percent, at least 70 weight percent, or at least 80 weight percent, based on the total weight of the composition excluding any solvent. In one embodiment, the TPA-based polyester is present in an amount of up to 80 weight percent, up to 78 weight percent, up to 75 weight percent, up to 70 weight percent, up to 60 weight percent, up to 50 weight percent, up to 40 weight percent, up to 30 weight percent, or up to 20 weight percent, based on the total weight of the composition excluding any solvent.
In one embodiment, the TPA-based polyester is present in an amount of 19.95 weight percent, at least 20 weight percent, at least 25 weight percent, at least 30 weight percent, at least 40 weight percent, at least 50 weight percent, at least 60 weight percent, at least 70 weight percent, or at least 80 weight percent, based on the total weight of the first network-forming component. In one embodiment, the TPA-based polyester is present in an amount of up to 80 weight percent, up to 78 weight percent, up to 75 weight percent, up to 70 weight percent, up to 60 weight percent, up to 50 weight percent, up to 40 weight percent, up to 30 weight percent, or up to 20 weight percent, based on the total weight of the first network-forming component.
In one embodiment, the TPA-based polyester is amorphous. In one embodiment, the TPA-based polyester comprises a blend of an amorphous TPA-based polyester and a semi-crystalline TPA-based polyester. In one embodiment, the TPA-based polyester comprises a blend of an amorphous TPA-based polyester, a semicrystalline TPA-based polyester, and a crystalline TPA-based polyester.
In one embodiment, a printing system is configured such that an ejection head ejects liquid thermoset material through a nozzle at an elevated operating temperature. In another embodiment, a printing system is configured such that the ejection head ejects liquid thermoset material through the nozzles at an elevated viscosity. In a preferred embodiment, the printing system is configured such that the ejection head ejects the liquid thermoset material through the nozzle at an elevated temperature and an elevated viscosity.
To be compatible with the printing system used in the method of the current invention, the liquid thermoset material may be selected or formulated according to known methods and/or as described herein above. Such liquid thermoset materials selected to be used in practicing the methods according to the present invention described herein are highly viscous, for example at 25 degrees celsius, when compared to ink compositions known to be used in conventional material jetting processes. Thus, in one embodiment, the viscosity of the selected one or more liquid thermoset materials has a viscosity of at least 20 centipoise (cPs), or at least 30cPs, or at least 40cPs, or at least 50cPs, or at least 60cPs, or at least 70cPs, or at least 80cPs, or at least 90cPs, or at least 100cPs, or at least 150cPs, or at least 200cPs, or at least 250cPs, or at least 300cPs, or at least 350cPs, or at least 400cPs, or at least 450cPs, or at least 500cPs, or at least 550cPs, or at least 600cPs, or at least 650cPs, or at least 700cPs, or at least 750cPs, or at least 800cPs, or at least 850cPs, or at least 900cPs, or at least 950cPs, or at least 1000cPs, or at least 1100cPs, or at least 1200cPs, or at least 1300cPs at 25 degrees celsius. In one embodiment, the selected liquid thermoset material has a viscosity of less than 2000cPs, or less than 1500cPs, or less than 1400cPs, or less than 1300cPs, or less than 1200cPs, or less than 1100cPs, or less than 1000cPs, or less than 900cPs, or less than 800cPs, or less than 700cPs, or less than 600cPs, or less than 500cPs, or less than 400cPs, or less than 300cPs, or less than 200cPs at 25 degrees celsius.
In an alternative embodiment, the one or more selected liquid thermoset materials have a viscosity at 25 degrees celsius of from about 100cPs to about 3000cPs, or from about 150cPs to about 2500cPs, or from about 250cPs to about 2250cPs, or from greater than 500cPs to about 2000cPs, or from about 650cPs to about 1750cPs, or from about 750cPs to about 1500 cPs.
It has been determined that many liquid thermoset materials that are capable of imparting desired physical properties to solid parts formed from the liquid thermoset material are highly viscous, as indicated by, for example, increasing viscosity near room temperature. It is natural that many such liquid thermosets suitable for use in the processes of the current invention similarly have elevated viscosities at the temperatures at which the jetting heads of the printing systems incorporating them operate. This surprisingly includes a higher viscosity at the so-called working temperature than any material used according to the known method of material jetting for additive manufacturing applications.
However, in order to be suitable for use in the methods of various embodiments of the present invention, such highly viscous liquid thermoset materials must still be sufficiently flowable at the operating temperature of the jetting head. Thus, in one embodiment, the liquid thermoset material has a viscosity at the operating temperature of up to 60cPs, or up to 55cPs, or up to 50cPs, or up to 45cPs, or up to 40cPs, or up to 35cPs, or up to 30cPs, or up to 25cPs, or up to 20 cPs. In an alternative embodiment, the viscosity of the liquid thermoset material at the operating temperature is from about 2cPs to about 60cPs, or from about 5cPs to about 55cPs, or from about 8cPs to about 50cPs, or from about 10cPs to about 50cPs, or from greater than 20cPs to about 60cPs, or from greater than 30cPs to about 60 cPs.
In view of the foregoing, it is noted that the viscosity sensitivity of a particularly viscous liquid thermoset material due to temperature changes can play an important role in determining whether the viscous material is suitable for use in accordance with the processes described herein. That is, liquid thermosets that exhibit relatively high levels of viscosity reduction with increasing temperature would be more desirable, all other things being equal, since it follows that such highly viscous resins would be more likely to be sufficiently flowable at a given elevated operating temperature than materials without such thermal sensitivity. It follows, therefore, that in one embodiment, a liquid thermoset material selected or formulated for use in a printing system according to the method of the present invention exhibits a relatively large viscosity ratio when its relative viscosity is plotted as a function of temperature. As used herein, the viscosity ratio is a measure of the viscosity of a material at 25 ℃ divided by the viscosity of the same material at 100 ℃.
Thus, in one embodiment, the liquid thermoset has a viscosity ratio greater than 15, or greater than 20, or greater than 30, or greater than 50, or greater than 60, or greater than 100. In another embodiment, the liquid thermoset material has a viscosity ratio of less than 1000, or less than 800, or less than 500, or less than 300, or less than 200. If the viscosity ratio becomes too high, the resin may be unstable and therefore unusable in the spraying process. Thus, in an alternative embodiment, the viscosity ratio of the liquid thermoset material is from 15 to 1000, or from 20 to 800, or from 30 to 500, or from 50 to 500, or from 60 to 500, or from 100 to 300, or from 60 to 200, or from 100 to 200.
In addition to the aforementioned so-called "static" viscosity characteristics, the inventors have also determined that the liquid thermosetting material used in the method according to the invention should also have certain rheological properties. This is true at least in part due to the following well-known facts: the jetting process for additive manufacturing (e.g. the jetting process of the current invention) is optimized if the material used with it breaks into droplets upon ejection. The inventors have found that highly viscous liquid thermosetting materials are not suitable for use in the material ejection process according to the current invention if their elongational flow behaviour or elongational viscosity indicates a significant amount of elasticity. This is true even though they have the proper viscosity (both at 25 degrees celsius and at elevated operating temperatures) according to embodiments of the present invention. This is true because such materials will not form droplets, will form them inconsistently, or will form so-called satellites, resulting in accidental or inconsistent deposition of additional material.
The inventors have determined that understanding of the elongational flow behaviour of liquid thermoset materials is important in predicting their suitability under the processing conditions required by the material ejection process for additive manufacturing of the present invention. A good proxy for determining elongational flow behavior is to analyze capillary breaks in the material. For materials that exhibit viscoelastic behavior, cracking may be delayed.
Capillary breakup, determined by the elongational flow behavior and elastic tendency of the material, is measured via capillary breakup extensional rheology (CaBER). The CaBER technique requires that a liquid sample be loaded between the circular surfaces of two opposing rods or cylinders. The sample is loaded such that the space between the surfaces is completely filled. The surfaces (ends of the cylindrical rods) are then separated from each other and the sample is elongated. High speed video surveillance equipment is then used to follow the deformation, especially thinning, of the sample after rod separation.
The diameter reduction of the monofilaments or strands of material can then be determined via analysis of the recorded video. The finest diameter of the liquid column was measured during the evaluation of the recorded video. A practical depiction of a strand of any material subjected to the CaBER test is depicted in fig. 3. Figure 3 shows the geometry of the strands of material tested at 10 different time points chronologically as the rod is removed. As can be observed in fig. 3, the strands eventually split and become discontinuous (i.e., break time). This minimum diameter is plotted as a function of time to aid in the analysis of the material being tested.
The inventors have found that the physical principle underlying the CaBER method, i.e. the surface tension dominated thinning of the filaments of the polymer solution, provides an ideal proxy for the situation encountered by liquid thermoset materials ejected from the nozzles of a printhead in material ejection applications for additive manufacturing.
The CaBER test enables a given material to be evaluated in a number of ways. One such quantitative approach relies on a comparison between the actual break time and the theoretical viscous break time (which represents an estimate of the break time in the absence of elastic effects in the material). The viscous break time was determined by fitting a straight line in a minimum diameter versus time graph over a range of diameters from 0.25mm to 0.75 mm. The time at which the diameter of the formed wire intersects the x-axis is referred to as the viscous break time. The greater the gap between actual and viscous break times, the less likely the material will lack elasticity and be unable to be incorporated into the jetting process of the current invention. One expression for determining this gap is equation 1:
wherein t isFracture ofIs the actual rupture time and tViscosity ofIs the viscous break time. Thus, in one embodiment, select orThe one or more liquid thermoset materials formulated for use in the material ejection process of the current invention have an actual break time and a viscous break time such that when stretched and tested according to the CaBER method at 23 ± 2 degrees celsius, the results of
If the actual break up time is too great, especially with respect to the viscous break up time, the material will prove too elastic to be suitably used in the material ejection method according to the current invention. The relatively large elastic stress inside the jet will inhibit the droplets from separating from the nozzle and the total jet will be drawn back into the resin reservoir, rendering the process unable to reliably create a three-dimensional object from such thermoset materials.
Another CaBER related quantitative result used to predict the suitability of a material when sprayed in the process of the current invention is by determining its relaxation time according to the Entov & hindch elongational elastic behavior model. In such a method,
wherein:
D0is the strand at time tViscosity ofIs measured at the beginning of the measurement of diameter (m),
ηpis the zero shear viscosity (Pa · s) of the material,
gamma is the surface tension (N/m) of the material, and
λ is the relaxation time(s), where
Combination ofAre fitting parameters.
Thus, in one embodiment, the one or more liquid thermoset materials selected or formulated for use in the material ejection process of the current invention have a CaBER profile such that the relaxation time derived from
The second embodiment is a three-dimensional article formed by the method of any of the aspects of the first embodiment. The three-dimensional article may be formed from any of the liquid thermoset materials according to the current invention via any of the methods described herein.
The three-dimensional articles formed by the material injection method of the current invention should have excellent mechanical properties. In one embodiment, the three-dimensional article formed by the material injection method of the current invention has substantially the same properties as such material for a given liquid thermoset material when used in an alternative additive manufacturing process, such as stereolithography. In one embodiment, a part of a given geometry made of a specified liquid thermosetting material in a method according to the invention has an elastic modulus value within 80%, more preferably within 85%, more preferably within 90%, more preferably within 95%, or within 99% of a part made of the same liquid thermosetting material of the same geometry via stereolithography.
Some potential applications for the articles disclosed herein include as molded articles, shoe soles, eyewear, three-dimensional objects formed by additive manufacturing processes, coatings for optical fibers, coatings on medical devices or medical devices, other coatings, and paints.
The following examples further illustrate the invention but, of course, should not be construed as in any way limiting its scope.
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