Liquid hybrid UV / vis ray curable resin composition for additive manufacturing

Abstract

To provide liquid radiation curable compositions which are suitable for hybrid polymerization when processed via additive fabrication equipment utilizing chemical radiation sources with peak spectral intensity in the UV / vis region, and methods of creating three-dimensional parts via the additive fabrication processes using the compositions, and the parts cured therefrom.SOLUTION: A liquid UV / vis radiation curable composition for additive fabrication comprises: a cationically curable constituent which undergoes cationic polymerization, the cationically curable constituent further comprising a cycloaliphatic epoxy component and an oxetane component; a free-radically curable constituent that undergoes free-radical polymerization; and a photoinitiating package further comprising a cationic photoinitiator, a vinyl ether diluent monomer, and a free-radical photoinitiator.SELECTED DRAWING: Figure 11

Description

Detailed Description of the Invention

[0001] [Technical field] The present invention relates to liquid compositions for additive manufacturing processes that are hybrid curable in the UV or visible spectral range.

[0002] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims priority to U.S. Provisional Patent Application No. 62 / 172,489, filed June 8, 2015, which is hereby incorporated by reference in its entirety as if fully set forth herein.

[0003] [background]

[0001] Additive manufacturing processes for producing three-dimensional objects are well known. Additive manufacturing processes utilize computer-aided design (CAD) data of an object to build a three-dimensional part, which may be formed from liquid resin, powder, or other materials.

[0004] A well-known, but not limiting, example of an additive manufacturing process is stereolithography (SL). Stereolithography is a process for the rapid production of models, prototypes, patterns, and production parts for certain applications. SL uses CAD data of an object and converts this data into a thin cross-section of a three-dimensional object. The data is loaded into a computer, which controls a laser that traces the pattern of the cross-section through a liquid radiation-curable resin composition contained in a vat, solidifying a thin layer of resin corresponding to the cross-section. The solidified layer is recoated with resin, and another cross-section is traced by the laser to cure another layer of resin on top of the previous layer. This process is repeated, layer by layer, until the three-dimensional object is complete. When initially formed, the three-dimensional object is generally not fully cured and is called a "green model." Although not required, the green model may be subjected to a post-cure to improve the mechanical properties of the finished part. An example of the SL process is described, for example, in U.S. Pat. No. 4,575,330.

[0005] Lasers have traditionally served as the radiation source of choice for additive manufacturing processes such as stereolithography. The use of gas lasers to cure liquid radiation curable resin compositions is well known. The delivery of laser energy in stereolithography systems can be continuous wave (CW) or Q-switched pulsed. CW lasers provide continuous laser energy and can be used in fast scanning processes. Historically, several types of lasers have been used for stereolithography, traditionally with peak spectral output in the wavelength range of 193 nm to 355 nm, although other wavelengths exist. The light emitted from lasers is monochromatic; that is, a significant percentage of the total spectral output is within a very narrow wavelength range. Laser-based additive manufacturing systems in the industry have become most prevalent, operating with a peak spectral output of 355 nm.

[0006]

[0004] However, laser-based systems, especially those operating with peak spectral output at or near 355 nm, are not without drawbacks. The significant power output of such laser-based systems can generate excessive heat at the point of irradiation, which can damage the resin. Furthermore, the use of lasers of any wavelength requires point-by-point scanning over the resin surface, a process that can be time-consuming, especially when the cross-sectional pattern to be cured is large or intricate. Additionally, 355 nm laser-based systems are expensive and involve high maintenance costs and energy consumption.

[0007]

[0005] To eliminate some of the drawbacks associated with laser-based systems, other additive manufacturing systems have begun to utilize image projection technology as the source of actinic radiation. One example of this is the liquid crystal display (LCD), a technology well known in other industries such as the manufacture of televisions and computer monitors. Another, but not limiting, example was developed by Texas Instruments and is called Digital Light Processing (DLP®). DLP systems use pixel-equivalent micromirrors known as digital micromirror devices (DMDs) controlled by and affixed to microchips to selectively transmit light from an input source and project that light in a desired output pattern or mask. DLP technology was developed for use in image projection systems as an alternative display system to LCD-based technology. The exceptional image sharpness, brightness, and uniformity associated with DLP systems are extremely useful in additive manufacturing where image resolution and precision are critical, since the boundaries of the three-dimensional object that is cured and produced are ultimately defined by the boundaries of the projected light. Furthermore, image projection systems such as LCDs and DLPs offer a theoretical speed advantage in that an entire cross-sectional layer can be exposed and cured simultaneously. Moreover, in that respect, while the curing time required in laser-based systems is directly proportional to the complexity of the cross-section being scanned, image projection systems are said to be cross-section independent, i.e., the exposure time of a given layer does not change as the shape complexity of any given layer increases. This makes them particularly suitable for parts produced by additive manufacturing that have complex and detailed geometries.

[0008]

[0006] DLPs and LCDs do not provide an alternative way to generate light itself, but rather a way to process the light emitted from an existing light source into a more desirable pattern. Therefore, a combined input light source is still needed. The light input to an image projection system can come from any source, including traditional lamps and even lasers, but more commonly the input light is collimated from one or more light emitting diodes (LEDs).

[0009]

[0007] LEDs are semiconductor devices that utilize the phenomenon of electroluminescence to generate light. Currently, LED light sources for additive manufacturing systems generally emit at wavelengths between 300 and 475 nm, with typical peak spectral outputs at 365 nm, 375 nm, 395 nm, 401 nm, 405 nm, and 420 nm. For a more detailed discussion of LED light sources, see the textbook "Light-Emitting Diodes," by E. Fred Schubert, 2nd Edition, (Copyright) E. Fred Schubert 2006, published by Cambridge University Press. LEDs offer the advantage of theoretically operating near their peak efficiency for longer durations than other light sources. In addition, they are typically more energy efficient and less expensive to maintain, thus reducing initial and ongoing costs of ownership over laser-based optical systems.

[0010]

[0008] Thus, various additive manufacturing systems utilize one of the following example optical configurations, including but not limited to: (1) laser only, (2) laser / DLP, (3) LED only, (4) LED / DLP, or (5) LED / LCD. Systems that do not utilize DLP technology may also incorporate other collimating or focusing lenses / mirrors to selectively direct light onto the liquid resin.

[0011]

[0009] Recently, newer additive manufacturing systems, regardless of optical configuration, have started to frequently utilize light sources that emit radiation at wavelengths longer than the traditional 355 nm output. Other systems have shifted away from monochromatic light sources in favor of light sources that emit light with a broader spectral power distribution. Thus, such newer systems incorporating laser / DLP, LED, LED / DLP, or LED / LCD based optical configurations have started to operate with peak spectral outputs at longer wavelengths and with broader spectral distributions than was previously common. The wavelengths utilized therein have shifted away from 355 nm toward the visible spectrum, and some even have peak spectral outputs within the visible range. These longer wavelengths (i.e., 375 nm to 500 nm) are traditionally referred to as "UV / vis".

[0012]

[0010] Some of the reasons usually cited for the current trend towards increasing use of optics in the UV / vis region include, but are not limited to, (1) the reduction in the cost (both initial and maintenance costs) of light sources operating in the UV / vis range, and (2) the fact that UV / vis light sources emit lower energy radiation and, all else being equal, are less damaging to human tissue than sources that operate deeper into the UV region. Thus, they are less harmful in the event of accidental exposure than those that operate deeper into the UV region. As additive manufacturing continues to grow in popularity in consumer, "production consumer," and industrial market segments, the need for additive modeling systems that utilize lower cost, less hazardous sources of actinic radiation to cure liquid photopolymers will become increasingly important.

[0013]

[0011] However, the benefits gained from the use of UV / vis light source / optical systems are not without significant trade-offs. To date, the biggest drawback has been the relatively large challenges associated with developing photopolymers suitable for systems utilizing UV / vis optics. One of the main reasons for this is the natural phenomenon that longer wavelengths of light have less energy, as well as the fact that the intensity of commercial light sources typically decreases with increasing wavelength of peak spectral output. Thus, a traditional 355 nm laser-based optical system can deliver 1500 W / cm2 to a resin surface. 2 While a laser can deliver a fluence of 1 W / cm2, commercial systems operating at about 400 nm are known to deliver a fluence to the resin surface that is roughly only about 1 / 1000th of that value. In fact, the fluence delivered to the resin surface by the UV / vis optics in existing 365 nm or 405 nm DLP-based commercial additive manufacturing systems is typically as low as 0.1 W / cm2 in some of the more economical desktop units. 2 Furthermore, 0.0002W / cm 2 Sometimes only slightly. This relatively reduced radiation energy / intensity makes it more difficult to photopolymerize radiation curable resins with such UV / vis optics unless the exposure time is prohibitively long. This in turn significantly increases part build times, thereby negating the theoretical speed advantage of photomask display systems. Furthermore, there are fewer photoinitiation systems, especially cationic photoinitiation systems, on the market to promote photopolymerization at these longer UV / vis wavelengths.

[0014]

[0012] Due to the challenges outlined above, the number of photopolymers available for modern optical systems operating in the UV / vis region is limited, whereas a wide range of options is available for systems operating deeper into the UV region, such as 355 nm laser-based systems.

[0015]

[0013] It is known that radically polymerizable resins exist for systems utilizing UV / vis optics. Such resins generally consist of one or more (meth)acrylate compounds (or other free radically polymerizable organic compounds) along with a free radical photoinitiator for radical generation. One such radically curable system is described in US Pat. No. 5,418,112. Although radically polymerizable resins will cure easily even under the relatively lower energy and intensity provided by UV / vis optics, they are not suitable for all additive manufacturing applications. First, (meth)acrylate-based resins that are considered suitable for additive manufacturing processes have traditionally produced cured parts with insufficient mechanical properties to be incorporated into many end uses. Thus, parts are typically produced that are not robust enough for non-prototyping applications. Also, such resins exhibit deformation issues, such as residual strain due to shrinkage differences upon curing, typically producing warped or misshapen parts. Such issues are exacerbated with larger platform additive manufacturing machines. In this case, as the cured object grows, the cumulative differential shrinkage effects amplify the warpage or misshapen of the part. These distortion problems can be partially corrected through software that compensates for the known shrinkage rates by modifying the CAD files that generate the solid three-dimensional parts. However, software corrections are insufficient to fully compensate for distortions in parts that have intricate, complex shapes or require tight dimensional tolerances over long distances.

[0016]

[0014] Another well-known type of resin suitable for use in additive manufacturing systems is a "hybrid" curable resin, i.e., one that includes (1) an epoxy, oxetane, or other type of cationically polymerizable compound, (2) one or more cationic photoinitiators, (3) an acrylate resin or other type of free radically polymerizable compound, and (4) one or more free radical photoinitiators. Examples of such hybrid curable systems are described, for example, in U.S. Pat. No. 5,434,196. Such resins have long been known to provide cured parts produced by additive manufacturing processes with superior mechanical properties compared to all-acrylate-based resins. In addition, hybrid curable systems are superior to all-acrylate systems in that they are less susceptible to the differential shrinkage problems that have long plagued all-acrylate systems.

[0017]

[0015] However, since the ring-opening process of cationic polymerization generally occurs slower and requires more activation energy than free radical polymerization, it is inherently more difficult to ensure proper curing of such formulations for additive manufacturing applications or satisfactory "building" of three-dimensional objects. Also, even if the hybrid curable resin is at least partially cured after exposure to actinic radiation, the green models produced therefrom have insufficient mechanical strength (or "green strength") for use in many additive manufacturing applications, as measured, for example, by elastic modulus or fracture strength. Such problems are significantly more severe with UV / vis optics that emit lower energy and intensity radiation than with conventional systems.

[0018]

[0016] Due to limitations of cationic polymerization, there are no known hybrid liquid radiation curable resins for additive manufacturing that are commercially suitable for use in more modern additive manufacturing systems that utilize UV / vis optics. Furthermore, there are no known liquid radiation curable resins for additive manufacturing (such as hybrid curable ones) that are suitable for additive manufacturing systems that utilize UV / vis optics and that simultaneously have both (1) a sufficiently fast curing rate and (2) the ability to impart sufficient mechanical strength and shrinkage deformation resistance to the cured three-dimensional parts.

[0019]

[0017] From the above, it is apparent that a heretofore unmet need exists to provide a hybrid curable liquid radiation resin composition suitable for use in additive manufacturing systems utilizing UV / vis optics that are capable of producing three-dimensional parts having mechanical properties at least comparable to existing hybrid curable materials designed for traditional laser-based 355 nm systems.

[0020] [Brief Overview] A first aspect of the present invention is a method for producing a photopolymerizable composition comprising: a cationically curable component further comprising a cycloaliphatic epoxy component that undergoes cationic polymerization; at least one free radically curable component that undergoes free radical polymerization; a cationic photoinitiator; and a free radical photoinitiator; a UV / vis optic that emits radiation having a peak spectral output at 400 nm; and a UV / vis optic that emits radiation having a peak spectral output of at least 2 mW / cm for at least 10 seconds. 2 After the liquid UV / vis ray curable composition is exposed to the liquid UV / vis ray curable composition surface at an irradiation dose of 1000 μg / cm2, the cycloaliphatic epoxy component has a T of about 70 seconds or less. 95 The present invention relates to a liquid UV / vis radiation curable composition for additive manufacturing that achieves a plateau conversion of at least about 20%.

[0021] A first aspect of the present invention is a method for producing a photoinitiator comprising: a cationically curable component that undergoes cationic polymerization, the cationically curable component further comprising a cycloaliphatic epoxy component and an oxetane component; a free radically curable component that undergoes free radical polymerization; and a photoinitiator package further comprising a cationic photoinitiator, a vinyl ether diluent monomer, and a free radical photoinitiator; and a UV / vis optic emitting radiation having a peak spectral output at 400 nm and a photoinitiator output of 2 mW / cm for 10 seconds. 2 When the liquid UV / vis ray curable composition is exposed to light with a dose of about 70 seconds or less, more preferably about 55 seconds or less, more preferably about 53 seconds or less, and more preferably about 50 seconds or less, the cycloaliphatic epoxy component exhibits the following properties: (i) a T 95 and (ii) a plateau conversion of at least about 20%, more preferably at least about 30%, more preferably at least about 36%, more preferably at least about 43%, and the oxetane component has the following properties: (i) a T of less than or equal to about 50 seconds, more preferably less than about 42 seconds, more preferably less than about 34 seconds, more preferably less than about 23 seconds. 95 and (ii) a plateau conversion of at least about 29%, more preferably at least about 34%, more preferably at least about 50%, more preferably at least about 59%.

[0022] A second aspect of the present invention is a method for producing a photopolymerizable composition comprising: (a) a cationically polymerizable component; (b) an iodonium salt cationic photoinitiator; (c) a photosensitizer for photosensitizing component (b); (d) a reducing agent for reducing component (b); (e) a free radically polymerizable component; and optionally (f) a free radical photoinitiator; and 2 and emitting radiation with a peak spectral intensity of about 375 nm to about 500 nm, more preferably about 380 nm to about 450 nm, more preferably about 390 nm to about 425 nm, and more preferably about 395 nm to about 410 nm.

[0023] A second aspect of the present invention is a method for producing a cationically polymerizable polymerizable composition comprising: a cationically polymerizable component; an iodonium salt cationic photoinitiator; a photosensitizer for photosensitizing the iodonium salt cationic photoinitiator; a first reducing agent for reducing the iodonium salt cationic photoinitiator; a free radically polymerizable component; and optionally a free radical photoinitiator and a second reducing agent for reducing the iodonium salt cationic photoinitiator, the second reducing agent having an electron donating substituent attached to a vinyl group; 2 and emitting radiation with a peak spectral intensity of about 375 nm to about 500 nm, more preferably about 380 nm to about 450 nm, more preferably about 390 nm to about 425 nm, and more preferably about 395 nm to about 410 nm.

[0024] A third aspect of the present invention is a polymerizable composition comprising from about 30 wt.% to about 80 wt.% of at least one cationically polymerizable component further comprising a cycloaliphatic epoxide and an oxetane, from about 1 wt.% to about 8 wt.% of a sulfonium salt cationic photoinitiator having an absorbance of less than 0.01 at 400 nm, and a compound represented by the following formula (V): [ka] (Wherein, R is C1 to C 20 (containing aliphatic chains) % to about 3 wt. % of a compound represented by the formula: 2 and emitting radiation with a peak spectral intensity from about 375 nm to about 500 nm, more preferably from about 380 nm to about 450 nm, and more preferably from about 390 nm to about 425 nm.

[0025]

[0023] A fourth aspect of the present invention is a method for forming a three-dimensional article with an additive manufacturing system utilizing UV / vis optics, the method comprising the steps of: (1) providing a liquid radiation curable composition for additive manufacturing of any of the first, second, or third aspects of the present invention; (2) providing a first liquid layer of liquid radiation curable resin; (3) forming a first cured layer by imagewise exposing the first liquid layer to actinic radiation using a UV / vis optics arrangement to form an imaged cross-section; (4) forming a new layer of liquid radiation curable resin in contact with the first cured layer; (5) imagewise exposing the new layer to actinic radiation to form an additional imaged cross-section; and (6) repeating steps (4) and (5) a sufficient number of times to build up the three-dimensional article, wherein the UV / vis optics emit radiation with a peak spectral intensity between about 375 nm and about 500 nm, more preferably between about 380 nm and about 450 nm, and more preferably between about 395 nm and about 410 nm.

[0026]

[0024] A fifth aspect of the present invention is a three-dimensional part formed by a process according to the fourth aspect of the present invention using a liquid radiation curable composition of any of the first, second or third aspects of the present invention. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 is a plot showing RT-FTIR (under 365 nm cure conditions) conversion of cycloaliphatic epoxide for Plastcure ABS3650, a commercial liquid hybrid radiation curable additive manufacturing composition designed to be suitable for additive manufacturing machines operating at a peak spectral intensity of 365 nm. [Diagram 2] FIG. 2 is a plot showing RT-FTIR (under 365 nm cure conditions) conversion of oxetanes in Plastcure ABS3650. [Diagram 3] FIG. 3 is a plot showing RT-FTIR (under 400 nm cure conditions) conversion of cycloaliphatic epoxides of liquid hybrid radiation curable compositions for additive manufacturing utilizing a photoinitiator package that uses a photoinitiator purported to be useful at 400 nm wavelength. [Figure 4] FIG. 4 is a plot showing RT-FTIR (under 400 nm cure conditions) conversion of oxetanes in a liquid hybrid radiation curable composition for additive manufacturing utilizing a photoinitiator package that uses a photoinitiator purported to be useful at 400 nm wavelength. [Diagram 5] FIG. 5 is a plot showing RT-FTIR (under 365 nm cure conditions) conversion of cycloaliphatic epoxides of liquid hybrid radiation curable compositions for additive manufacturing utilizing a photoinitiation package designed to be suitable for additive manufacturing machines operating at a peak spectral intensity of 365 nm. [Figure 6] FIG. 6 is a plot showing RT-FTIR (under 365 nm cure conditions) conversion of oxetanes in a liquid hybrid radiation curable composition for additive manufacturing utilizing a photoinitiation package designed to be suitable for an additive manufacturing machine operating at a peak spectral intensity of 365 nm. [Figure 7] FIG. 7 is a plot showing RT-FTIR (under 400 nm cure conditions) conversion of cycloaliphatic epoxide for a liquid hybrid radiation curable composition for additive manufacturing according to the present invention. [Figure 8] FIG. 8 is a plot showing RT-FTIR (under 400 nm cure conditions) conversion of oxetanes for a liquid hybrid radiation curable composition for additive manufacturing according to the present invention. [Figure 9] FIG. 9 is a plot showing RT-FTIR (under 400 nm cure conditions) conversion of cycloaliphatic epoxide for a liquid hybrid radiation curable composition for additive manufacturing according to the present invention. [Figure 10] FIG. 10 is a plot showing RT-FTIR (under 400 nm cure conditions) conversion of oxetanes for a liquid hybrid radiation curable composition for additive manufacturing according to the present invention. [Figure 11] FIG. 11 is a plot showing RT-FTIR (under 400 nm cure conditions) conversion of cycloaliphatic epoxide for a liquid hybrid radiation curable composition for additive manufacturing according to the present invention. [Figure 12]FIG. 12 is a plot showing RT-FTIR (under 400 nm cure conditions) conversion of oxetanes for a liquid hybrid radiation curable composition for additive manufacturing according to the present invention. [Figure 13] FIG. 13 is a plot showing RT-FTIR (under 400 nm cure conditions) conversion of cycloaliphatic epoxide for a liquid hybrid radiation curable composition for additive manufacturing according to the present invention. [Figure 14] FIG. 14 is a plot showing RT-FTIR (under 400 nm cure conditions) conversion of oxetanes for a liquid hybrid radiation curable composition for additive manufacturing according to the present invention.

[0028] [Detailed Description]

[0033] Throughout this document, "UV / vis" is defined as the region of the electromagnetic spectrum between 375 nanometers (nm) and 500 nanometers (nm).

[0029]

[0034] Thus, throughout this document, "UV / vis optics" is defined as any electrical, mechanical, or electromechanical system that generates and directs / displays actinic radiation operating with a peak spectral intensity between 375 nm and 500 nm. Non-limiting examples of UV / vis optics include lasers, LEDs, one or more LEDs coupled to a DLP display system, one or more LEDs coupled to an LCD display system, a laser coupled to a DLP display system, and a laser coupled to an LCD display system.

[0030]

[0035] The first embodiment of the present invention is a cationically curable component that undergoes cationic polymerization, the cationically curable component further comprising a cycloaliphatic epoxy component and an oxetane component; a free radically curable component that undergoes free radical polymerization; The following: a cationic photoinitiator; a vinyl ether diluent monomer; a free radical photoinitiator; a light initiation package further comprising: Including, UV / vis optics emitting radiation with a peak spectral output at 400 nm and 2 mW / cm for 10 seconds 2 When the liquid UV / vis ray curable composition is exposed to light with an irradiation amount on the surface of the liquid UV / vis ray curable composition of The cycloaliphatic epoxy component has the following properties: i. A T of about 70 seconds or less, more preferably about 55 seconds or less, more preferably about 53 seconds or less, more preferably about 50 seconds or less. 95 Value, ii. a plateau conversion of at least about 20%, more preferably at least about 30%, more preferably at least about 36%, more preferably at least about 43%; Achieve and The oxetane moiety has the following properties: i. A T of about 50 seconds or less, more preferably less than about 42 seconds, more preferably less than about 34 seconds, more preferably less than about 23 seconds. 95 Value, ii. a plateau conversion of at least about 29%, more preferably at least about 34%, more preferably at least about 50%, more preferably at least about 59%; To achieve It is a liquid UV / vis ray curable composition for additive manufacturing.

[0031] [Cationically curable component]

[0036] According to one embodiment, the liquid radiation curable resin for additive manufacturing of the present invention comprises at least one cationically polymerizable component, which is a component that undergoes cationically or in the presence of an acid generator initiated polymerization. The cationically polymerizable component may be a monomer, oligomer, and / or polymer and may contain an aliphatic moiety, an aromatic moiety, a cycloaliphatic moiety, an arylaliphatic moiety, a heterocyclic moiety, and any combination thereof. Preferably, the cationically polymerizable component comprises at least one cycloaliphatic compound. Suitable cyclic ether compounds may contain cyclic ether groups as side groups or as groups that form part of an alicyclic or heterocyclic ring system.

[0032]

[0037] The cationically polymerizable component is selected from the group consisting of a cyclic ether compound, a cyclic acetal compound, a cyclic thioether compound, a spiroorthoester compound, a cyclic lactone compound, and any combination thereof.

[0033]

[0038] Suitable cationic polymerizable components include cyclic ether compounds such as epoxy compounds and oxetanes, cyclic lactone compounds, cyclic acetal compounds, cyclic thioether compounds, and spiro orthoester compounds.Specific examples of cationic 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 resin, 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, 4-vinylepoxycyclohexane, vinylcyclohexene dioxide, limonene oxide, limonene dioxide, bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate , 3,4-epoxy-6-methylcyclohexyl-3',4'-epoxy-6'-methylcyclohexanecarboxylate, ε-caprolactone-modified 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, trimethylcaprolactone-modified 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, β-methyl-δ-valerolactone-modified 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexa carboxylate, methylene bis(3,4-epoxycyclohexane), bicyclohexyl-3,3'-epoxide, bis(3,4-epoxycyclohexyl) having the bonds -O-, -S-, -SO-, -SO2-, -C(CH3)2-, -CBr2-, -C(CBr3)2-, -C(CF3)2-, -C(CCl3)2-, or -CH(C6H5)-, dicyclopentadiene diepoxide, di(3,4-epoxycyclohexylmethyl)ether of ethylene glycol, ethylene bis(3,4-epoxycyclohexanecarboxylate), epoxy hexahydrodioctylphthalate, epoxy hexahydro-di-2-ethylhexylphthalate, 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 phenols, cresols, butylphenols, or polyether alcohols obtained by addition of alkylene oxides to compounds, glycidyl esters of higher fatty acids, epoxidized soybean oil, epoxy butyl stearic acid, epoxy octyl stearic 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-(meth)-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, ethyl diethylene glycol (3-ethyl-3-oxetanylmethyl) ether, dicyclopentadiene (3-ethyl-3-oxetanylmethyl) ether, dicyclopentenyloxyethyl (3-ethyl-3-oxetanylmethyl) ether, dicyclopentenyl (3-ethyl-3-oxetanylmethyl) ether, tetrahydrofurfyl (3-ethyl-3-oxetanylmethyl) ether, 2-hydroxyethyl (3-ethyl-3-oxetanylmethyl) ether, 2-hydroxypropyl (3-ethyl-3-oxetanylmethyl) ether, and any combination thereof.

[0034]

[0039] The cationically polymerizable component may also optionally contain multifunctional materials, including dendritic polymers such as dendrimers with epoxy or oxetane functional groups, linear dendritic polymers, dendrigraft polymers, hyperbranched polymers, star-branched polymers, hypergraft polymers, etc. Dendritic polymers may contain one type of polymerizable functional group or different types of polymerizable functional groups, for example, epoxy and oxetane functional groups.

[0035]

[0040] In an embodiment, the composition of the present invention also includes one or more mono- or polyglycidyl ethers of aliphatic alcohols, aliphatic polyols, polyester polyols, or polyether polyols. Examples of preferred components include 1,4-butanediol diglycidyl ether, glycidyl ethers of polyoxyethylene and polyoxypropylene glycols and triols having a molecular weight of about 200 to about 10,000, and glycidyl ethers of polytetramethylene glycol or poly(oxyethylene-oxybutylene) random or block copolymers. In a specific embodiment, the cationically polymerizable component includes a multifunctional glycidyl ether that does not have a cyclohexane ring in the molecule. In another specific embodiment, the cationically polymerizable component includes neopentyl glycol diglycidyl ether. In another specific embodiment, the cationically polymerizable component includes 1,4-cyclohexanedimethanol diglycidyl ether.

[0036]

[0041] Examples of preferred commercially available polyfunctional glycidyl ethers are Erisys™ GE22 (Erisys™ products are available from Emerald Performance Materials™), Heloxy™ 48, Heloxy™ 67, Heloxy™ 68, Heloxy™ 107 (Heloxy™ modifiers are available from Momentive Specialty Chemicals), and Grilonit® F713. Examples of preferred commercially available monofunctional glycidyl ethers are Heloxy™ 71, Heloxy™ 505, Heloxy™ 7, Heloxy™ 8, and Heloxy™ 61.

[0037]

[0042] In embodiments, the epoxide is 3,4-epoxycyclohexylmethyl-3',4-epoxycyclohexanecarboxylate (available from Daicel Chemical as CELLOXIDE™ 202IP or from Dow Chemical as CYRACURE™ UVR-6105), hydrogenated bisphenol A epichlorohydrin based epoxy resin (available from Momentive as EPON™ 1510), 1,4-cyclohexanedimethanol diglycidyl ether (available from Momentive as HELOXY™ 107), hydrogenated bisphenol A diglycidyl ether (available from Momentive as EPON™ 825), a mixture of dicyclohexyl diepoxide and nanosilica (available as NANOPOX™), and any combination thereof.

[0038]

[0043] In a specific embodiment, the cationically polymerizable component is a cycloaliphatic epoxy, for example, a cyclic epoxy represented by the following Formula I: [ka] (Wherein, R is a carbon atom, an ester-containing C1-C 10 Aliphatic chain, or C1-C 10 (It is an alkyl chain) The epoxy groups include cycloaliphatic epoxies having two or more epoxy groups, such as

[0039]

[0044] In another specific embodiment, the cationically polymerizable component comprises an epoxy having an aromatic or aliphatic glycidyl ether group having two (difunctional) or more than two (multifunctional) epoxy groups.

[0040]

[0045] The above-mentioned cationically polymerizable compounds can be used alone or in combination of two or more thereof. In an embodiment of the present invention, the cationically polymerizable component further comprises at least two different epoxy components.

[0041]

[0046] In other embodiments of the present invention, the cationically polymerizable component also includes an oxetane component. In specific embodiments, the cationically polymerizable component includes an oxetane, for example, an oxetane containing one, two, or more than two oxetane groups. In other embodiments, the oxetane utilized is monofunctional and additionally has a hydroxyl group. According to embodiments, the oxetane has the following structure: [ka] has.

[0042]

[0047] When utilized in the composition, the oxetane component is present in a preferred amount of from about 5 to about 50 wt % of the resin composition, hi other embodiments, the oxetane component is present in an amount of from about 10 to about 25 wt % of the resin composition, and in yet other embodiments, the oxetane component is present in an amount of from 20 to about 30 wt % of the resin composition.

[0043]

[0048] Thus, the radiation curable liquid resin for additive manufacturing may comprise a suitable amount of cationically polymerizable component, for example, in one particular embodiment, from about 10 to about 80 wt % of the resin composition, in a further embodiment, from about 20 to about 70 wt % of the resin composition, in a further embodiment, from about 25 to about 65 wt % of the resin composition, in a further preferred embodiment, from about 30 to about 80 wt % of the resin composition, and more preferably from about 50 to about 85 wt %.

[0044] [Free radical polymerizable compounds]

[0049] According to an embodiment of the present invention, the liquid radiation curable resin for additive manufacturing of the present invention comprises at least one free radically polymerizable component, i.e., a component that undergoes polymerization initiated by free radicals. The free radically polymerizable component can be a monomer, oligomer, and / or polymer, and can be a monofunctional or polyfunctional material, 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 can contain aliphatic, aromatic, cycloaliphatic, arylaliphatic, heterocyclic moieties, or any combination thereof. Examples of polyfunctional materials include dendritic polymers, such as dendrimers, linear dendritic polymers, dendrigraft polymers, hyperbranched polymers, star-branched polymers, hypergraft polymers, etc. See, for example, US 2009 / 0093564 A1. Dendritic polymers can contain one type of polymerizable functional group or different types of polymerizable functional groups, for example, acrylate and methacrylate functional groups.

[0045]

[0050] Examples of free radical polymerizable components include isobornyl (meth)acrylate, bornyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dicyclopentanyl (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, and the like. Acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, amyl (meth)acrylate, isobutyl (meth)acrylate, 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 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, ethoxydiethylene glycol (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, polyethylene glycol mono (meth)acrylate Acrylates and polypropylene glycols, mono(meth)acrylates, methoxyethylene glycol(meth)acrylate, ethoxyethyl(meth)acrylate, methoxypolyethylene glycol(meth)acrylate, methoxypolypropylene glycol(meth)acrylate, diacetone(meth)acrylamide, beta-carboxyethyl(meth)acrylate, phthalic acid(meth)acrylate, dimethylaminoethyl(meth)acrylate, diethylaminoethyl(meth)acrylate, butylcarbamylethyl(meth)acrylate,Examples of the acrylates and methacrylates include n-isopropyl (meth)acrylamide fluorinated (meth)acrylate and 7-amino-3,7-dimethyloctyl (meth)acrylate.

[0046]

[0051] Examples of polyfunctional free radical polymerizable components include those 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]ethyl]-5-ethyl-1,3-dioxane-5-yl]methyl acrylate, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane di(meth)acrylate. acrylate, 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, polybutanediol di(meth)acrylate, tripropylene glycol di(meth)acrylate, glycerol tri(meth)acrylate, phosphate mono- and di(meth)acrylates, C7-C 20Alkyl di(meth)acrylates, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tricyclodecanediyldimethyl di(meth)acrylate, and alkoxylated (e.g., ethoxylated and / or propoxylated) versions of any of the above monomers, and Examples of the di(meth)acrylates include diol di(meth)acrylates which are adducts of ethylene oxide or propylene oxide to bisphenol A, di(meth)acrylates of diols which are adducts of ethylene oxide or propylene oxide to hydrogenated bisphenol A, epoxy (meth)acrylates which are (meth)acrylate adducts to bisphenol A diglycidyl ether, diacrylates of polyoxyalkylated bisphenol A, and adducts of triethylene glycol divinyl ether and hydroxyethyl acrylate.

[0047]

[0052] According to an embodiment, the radically polymerizable component is a multifunctional (meth)acrylate, which may contain all methacryloyl groups, all acryloyl groups, or any combination of methacryloyl and acryloyl groups. In an embodiment, the free radically 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.

[0048]

[0053] In an embodiment, the multifunctional (meth)acrylate has a functionality of more than two. According to another embodiment, the multifunctional (meth)acrylate has a functionality of more than three. In yet another embodiment, the multifunctional (meth)acrylate has a functionality of more than four. In another preferred embodiment, the radically polymerizable component consists exclusively of a single multifunctional (meth)acrylate component. In a further embodiment, the exclusively radically polymerizable component is tetrafunctional, in a further embodiment, the exclusively radically polymerizable component is pentafunctional, and in a further embodiment, the exclusively radically polymerizable component is hexafunctional.

[0049]

[0054] In another embodiment, the free radically polymerizable component contains an aromatic (meth)acrylate. The aromatic acrylate is derived from, for example, but not limited to, bisphenol A, bisphenol S, or bisphenol F. In a particular embodiment, the aromatic 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-dioxane-5-yl]methyl acrylate, dipentaerythritol monohydroxypentaacrylate, propoxylated trimethylolpropane triacrylate, and propoxylated neopentyl glycol diacrylate, and any combination thereof. In an embodiment, the aromatic (meth)acrylate is difunctional.

[0050]

[0055] In specific embodiments, the radiation curable liquid 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, more specifically one or more of bisphenol A diglycidyl ether diacrylate, dicyclopentadiene dimethanol diacrylate, dipentaerythritol pentaacrylate, propoxylated trimethylolpropane triacrylate, and / or propoxylated neopentyl glycol diacrylate.

[0051]

[0056] The above-mentioned radical polymerizable compounds can be used alone or in combination of two or more thereof. The liquid radiation curable resin for additive manufacturing can include any suitable amount of free radical polymerizable components, for example, up to about 50 wt% of the resin composition in one particular embodiment, about 2 to about 40 wt% of the resin composition in one particular embodiment, about 5 to about 30 wt% of the resin composition in another embodiment, about 10 to about 20 wt% of the resin composition in a further embodiment, about 8 to about 50 wt% of the resin composition in another further preferred embodiment, and more preferably about 15 to about 25 wt% of the resin composition.

[0052] [Cationic photoinitiator]

[0057] According to one embodiment, the liquid radiation curable resin composition comprises a cationic photoinitiator, which upon irradiation with light initiates cationic ring-opening polymerization.

[0053]

[0058] In embodiments, any suitable iodonium-based cationic photoinitiator can be used, such as those having a cation selected from the group consisting of diaryliodonium salts, triaryliodonium salts, aromatic iodonium salts, and any combination thereof.

[0054]

[0059] In other embodiments, 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, acylsulfonium salts, and any combination thereof. In other embodiments, the cation is a polymeric sulfonium salt, such as those described in US Pat. No. 5,380,923 or US Pat. No. 5,047,568, or other aromatic heteroatom-containing cations and naphthyl-sulfonium salts, such as those described in US Pat. No. 7,611,817, US Pat. No. 7,230,122, US Pat. App. Pub. No. 2011 / 0039205, US Pat. App. Pub. No. 2009 / 0182172, US Pat. No. 7,678,528, EP Pat. No. 2,308,865, WO Pat. No. 2010046240, or EP Pat. No. 2,218,715. In other embodiments, the cationic photoinitiator is selected from the group consisting of triarylsulfonium salts, diaryliodonium salts, and metallocene-based compounds, and any combination thereof. Onium salts, such as iodonium and sulfonium salts, as well as ferrocenium salts, have the advantage that they are generally more thermally stable.

[0055]

[0060] In certain embodiments, the cationic photoinitiator is BF4 - , 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-alkyloxyphenyl)borate, tetrakis(2,3,5,6-tetrafluoro-4-alkyloxyphenyl)borate, perfluoroalkylsulfonates, tris[(perfluoroalkyl)sulfonyl]methides, bis[(perfluoroalkyl)sulfonyl]imides, perfluoroalkylphosphates, tris(perfluoroalkyl)trifluorophosphates, bis(perfluoroalkyl)tetrafluorophosphates, tris(pentafluoroethyl)trifluorophosphate, and (CHB 11 Br6) - , (CH6B 11 Cl6) - and other halogenated carborane anions.

[0056]

[0061] Reviews of other onium salt initiators and / or metallocene salts can be found in “UV Curing, Science and Technology”, edited by S.P. Pappas, Technology Marketing Corp., 642 Westover Road, Stamford, Conn., USA), “Chemistry & Technology of UV & EB Formulation for Coatings, Inks & Paints”, Vol. 3, edited by P.K. Toldring, or in “Photoinitiators for polymer synthesis” by J.P. Fouassier and J. Lavelee, Wiley 2012 ISBN978-3-527-33210-6.

[0057]

[0062] In an embodiment, the cationic photoinitiator is SbF6 - , PF6 - , B(C6F5)4 - , [B(CF3)4] -, tetrakis(3,5-difluoro-4-methoxyphenyl)borate, perfluoroalkylsulfonates, perfluoroalkylphosphates, tris[(perfluoroalkyl)sulfonyl]methides, and [(C2F5)3PF3] - and a cation selected from the group consisting of an aromatic sulfonium salt, an aromatic iodonium salt, and a metallocene-based compound.

[0058]

[0063] Examples of suitable cationic photoinitiators for other embodiments include 4-[4-(3-chlorobenzoyl)phenylthio]phenylbis(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-methyloxyphenyl)borate, 4-[4-(3-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium tetrakis(2,3-difluoro ... ,3,5,6-tetrafluoro-4-methyloxyphenyl)borate, tris(4-(4-acetylphenyl)thiophenyl)sulfonium tetrakis(pentafluorophenyl)borate (Irgacure® PAG290 from BASF), tris(4-(4-acetylphenyl)thiophenyl)sulfonium tris[(trifluoromethyl)sulfonyl]methide (Irgacure® GSID26-1 from BASF), tris(4-(4-acetylphenyl)thiophenyl)sulfonium hexafluorophosphate (Irgacure® 270 from BASF), and HS-1 available from San-Apro Ltd.

[0059]

[0064] In a preferred embodiment, the cationic photoinitiator component, either alone or in admixture, is selected from the group consisting of bis[4-diphenylsulfonium phenyl]sulfide bishexafluoroantimonate, thiophenoxyphenylsulfonium hexafluoroantimonate (available as Chivacure 1176 from Chitec), tris(4-(4-acetylphenyl)thiophenyl)sulfonium tetrakis(pentafluorophenyl)borate (Irgacure® PAG 290 from BASF), tris(4-(4-acetylphenyl)thiophenyl)sulfonium tris[(trifluoromethyl)sulfonyl]methide (available as Chivacure® 1176 ... Irgacure® GSID26-1), and tris(4-(4-acetylphenyl)thiophenyl)sulfonium hexafluorophosphate (Irgacure® 270 from BASF), [4-(1-methylethyl)phenyl](4-methylphenyl)iodonium tetrakis(pentafluorophenyl)borate (available as Rhodorsil 2074 from Rhodia), 4-[4-(2-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium hexafluoroantimonate (available as SP-172 from Adeka), SP-300 from Adeka, and (PF 6-m (C n F 2n+1 ) m ) - (wherein m is an integer of 1 to 5 and n is an integer of 1 to 4) (available from San-Apro Ltd. as monovalent sulfonium salts CPI-200K or CPI-200S, TK-1 available from San-Apro Ltd., or HS-1 available from San-Apro Ltd.).

[0060]

[0065] In an embodiment of the present 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. See US Patent Publication No. 20120251841 to DSM IP Assets, BV, and US Patent No. 6,368,769 to Asahi Denki Kogyo, which discuss aromatic triarylsulfonium salts with tetraarylborate anions, including tetrakis(pentafluorophenyl)borate, and the use of such compounds in stereolithography applications. Triarylsulfonium salts are disclosed, for example, in J Photopolymer Science & Tech (2000), 13(1), 117-118, and J Poly Science, Part A (2008), 46(11), 3820-29. Triarylsulfonium salts include BF4 - , AsF6 - , PF6 - , SbF6 - Complex metal halide anions such as Ar3S+MXn - The salts are disclosed in J Polymr Sci, Part A (1996), 34(16), 3231-3253.

[0061]

[0066] An example of a triarylsulfonium tetrakis(pentafluorophenyl)borate cationic photoinitiator is tris(4-(4-acetylphenyl)thiophenyl)sulfonium tetrakis(pentafluorophenyl)borate, commercially known as Irgacure® PAG-290, available from Ciba / BASF.

[0062]

[0067] In another embodiment, the cationic photoinitiator is SbF6 - , PF6 - , BF4 - , (CF3CF2)3PF3 -, (C6F5)4B - , ((CF3)2C6H3)4B - , (C6F5)4Ga - , ((CF3)2C6H3)4Ga - , trifluoromethanesulfonate, nonafluorobutanesulfonate, methanesulfonate, butanesulfonate, benzenesulfonate, or p-toluenesulfonate. Such photoinitiators are described, for example, in U.S. Pat. No. 8,617,787.

[0063]

[0068] Other cationic photoinitiators are aromatic triarylsulfonium cationic photoinitiators having an anion of fluoroalkyl-substituted fluorophosphate. Commercially available examples of aromatic triarylsulfonium cationic photoinitiators having an anion of fluoroalkyl-substituted fluorophosphate are the CPI200 series (e.g., CPI-200K (registered trademark) or CPI-210S (registered trademark)) or 300 series available from San-Apro Co., Ltd.

[0064]

[0069] There are also several commercially available cationic photoinitiators designed to be particularly suitable for absorbing light at UV / vis wavelengths to generate photoreactive species. The incorporation of one or more of these cationic photoinitiators into a liquid radiation curable composition for UV / vis curing may be accomplished via "direct" excitation of the photoinitiator. Some non-limiting examples of UV / vis direct excitation cationic photoinitiators include Irgacure 261, Irgacure PAG103, and Irgacure PAG121 (each commercially available from BASF), R-Gen® 262 (η5-2,4-cyclopentadien-1-yl)[(1,2,3,4,5,6-η)-(1-methylethyl)benzene]-iron(I)-hexafluoroantimonate) (commercially available from Chitec Technology Co.), and CPI400 series photoinitiators (available from San-Apro Co.).

[0065]

[0070] However, applicants have surprisingly found that the UV / vis directly excited cationic photoinitiators listed above are not suitable for achieving sufficient hybrid cure of compositions used in additive manufacturing processes utilizing UV / vis optics. Without wishing to be bound by any theory, it is speculated that because the free radical portions of the polymer network cure fairly quickly, the free radical curing portions of the resin build up viscosity and polymer structure to significantly reduce the molecular mobility of the slower curing cationic curing species, thereby significantly reducing the overall cure speed to unacceptably low rates. This problem is inherent to dual-cure hybrid resins and is exacerbated at the longer wavelengths, lower energies, and lower intensities typical of modern UV / vis optics. Applicants have therefore found that formulating hybrid-cure radiation-curable compositions suitable for UV / vis wavelengths for additive manufacturing cannot be achieved by simply changing the cationic photoinitiator of a hybrid resin suitable for UV curing with, for example, a 355 nm laser-based system. Thus, the inventors have discovered that such "direct excitation" mechanisms for achieving suitable hybrid curing are insufficient to address the processing realities of modern additive manufacturing systems that utilize UV / vis optics.

[0066]

[0071] More precisely, applicants have surprisingly discovered that a combination of one or more alternative mechanisms is instead required to achieve sufficient cure in additive modeling systems utilizing UV / vis optics. The first is via an "indirect excitation" mechanism. The second is via a free radical promoted cationic polymerization mechanism. The third is via a vinyl ether polymerization mechanism. As discussed further below, liquid radiation curable compositions for additive modeling made according to the present invention synergistically utilize one or more of these mechanisms to achieve a suitable hybrid cure in additive modeling processes incorporating UV / vis optics.

[0067]

[0072] The liquid radiation curable resin composition may include any suitable amount of cationic photoinitiator, for example, in certain embodiments up to about 15 wt% of the resin composition, in certain embodiments up to about 5 wt% of the resin composition, in further embodiments from about 2 wt% to about 10 wt% of the resin composition, and in other embodiments from about 0.1 wt% to about 5 wt% of the resin composition, in further embodiments, the amount of cationic photoinitiator is from about 0.2 wt% to about 4 wt%, and in other embodiments from about 0.5 wt% to about 3 wt% of the total resin composition.

[0068] [Free radical photoinitiators]

[0073] In an embodiment, the liquid radiation curable resin for additive manufacturing of the present invention comprises a free radical photoinitiator. According to an embodiment, the liquid radiation curable resin composition comprises a photoinitiator system containing at least one photoinitiator having a cationic initiation functional group and at least one photoinitiator having a free radical initiation functional group. Additionally, the photoinitiator system may comprise a photoinitiator containing both free radical initiation functional groups and cationic initiation functional groups on the same molecule. A photoinitiator is a compound that undergoes a chemical change under the action of light or under the action of light in combination with the electronic excitation of a sensitizing dye to produce at least one of a radical, an acid, and a base.

[0069]

[0074] Typically, free radical photoinitiators are classified into those that generate radicals by cleavage, known as "Norrish type I," and those that generate radicals by hydrogen abstraction, known as "Norrish type II." Norrish type II photoinitiators require a hydrogen donor to function as a source of free radicals. Since initiation is based on a bimolecular reaction, Norrish type II photoinitiators are generally slower than Norrish type I photoinitiators, which are based on the unimolecular generation of radicals. On the other hand, Norrish type II photoinitiators have better light absorption in the near-UV spectral region. Photolysis of aromatic ketones such as benzophenone, thioxanthone, benzil, and quinone in the presence of hydrogen donors such as alcohols, amines, and thiols produces radicals arising from carbonyl compounds (ketyl type radicals) and other radicals derived from hydrogen donors. Photopolymerization of vinyl monomers is usually initiated by radicals arising from hydrogen donors. Ketyl radicals are usually not reactive towards vinyl monomers due to steric hindrance and delocalization of the unpaired electron.

[0070]

[0075] To successfully formulate a liquid radiation curable resin for additive manufacturing, the wavelength sensitivity of the photoinitiator present in the resin composition must be examined to determine whether it will be activated by the radiation source selected to provide the curing light.

[0071]

[0076] According to embodiments, the radiation curable liquid resin for additive manufacturing comprises at least one free radical photoinitiator, such as one selected from the group consisting of benzoylphosphine oxide, aryl ketones, benzophenones, hydroxylated ketones, 1-hydroxyphenyl ketones, ketals, metallocenes, and any combination thereof.

[0072]

[0077] In an embodiment, the liquid radiation curable resin for additive manufacturing is selected from the group consisting of 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 2,4,6-trimethylbenzoylphenyl, ethoxyphosphine 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, 4,4'-bis(diethylamino)benzophenone, and 4,4'-bis(N,N'-dimethylamino)benzophenone (Michler's ketone), benzophenone, 4- The photoinitiator comprises at least one free radical photoinitiator selected from the group consisting of methylbenzophenone, 2,4,6-trimethylbenzophenone, dimethoxybenzophenone, 1-hydroxycyclohexyl phenyl ketone, 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, 4,4'-bis(diethylamino)benzophenone, benzil dimethyl ketal, bis(η5-2-4-cyclopentadien-1-yl)bis[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl]titanium, and any combination thereof.

[0073]

[0078] For light sources emitting in the wavelength range of 300 to 475 nm, and particularly for light sources emitting at 365 nm, 390 nm, or 395 nm, examples of suitable free radical photoinitiators absorbing in this region include benzoylphosphine oxides, such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Lucirin TPO from BASF) and 2,4,6-trimethylbenzoylphenyl,ethoxyphosphine 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-morpholinopropanone-1 (Irgacure 907 from Ciba), 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone (Irgacure 369 from Ciba), 2-dimethylamino 2-(4-methyl-benzyl)-1-(4-morpholin-4-ylphenyl)-butan-1-one (Irgacure 379 from Ciba), 4-benzoyl-4'-methyldiphenyl sulfide (CibaCure BMS from Cheetech), 4,4'-bis(diethylamino)benzophenone (CibaCure EMK from Cheetech), and 4,4'-bis(N,N'-dimethylamino)benzophenone (Michler's ketone). Mixtures thereof are also suitable. These acylphosphine oxide photoinitiators are preferred because they have good delocalization of the phosphinoyl radicals upon irradiation with light.

[0074]

[0079] According to an embodiment of the present invention, the free radical photoinitiator is an acylphosphine oxide photoinitiator, as disclosed, for example, in U.S. Patents 4,324,744, 4,737,593, 5,942,290, 5,534,559, 6,020,528, 6,486,228, and 6,486,226.

[0075]

[0080] The acylphosphine oxide photoinitiator is a bisacylphosphine oxide (BAPO) or a monoacylphosphine oxide (MAPO).

[0076]

[0081] The bisacylphosphine oxide photoinitiator has the formula II: [ka] As shown in the figure.

[0082] In the above formula, R 50 is C1~C 12 alkyl, cyclohexyl, or phenyl unsubstituted or substituted with 1-4 halogen or C1-C8 alkyl; R 51 and R 52 are each independently C1-C8 alkyl or C1-C8 alkoxy; R 53 is hydrogen or C1-C8 alkyl, and R 54 is hydrogen or methyl.

[0077]

[0083] For example, R 50 is C2~C 10 alkyl, cyclohexyl, or phenyl that is unsubstituted or substituted with 1-4 C1-C4 alkyl, Cl, or Br. 50 is C3-C8 alkyl, cyclohexyl, or phenyl that is unsubstituted or substituted at the 2, 3, 4, or 2,5 positions with C1-C4 alkyl. For example, R 50 is C4~C 12 alkyl or cyclohexyl; R 51 and R 52 are each independently C1-C8 alkyl or C1-C8 alkoxy, and R 53 is hydrogen or C1-C8 alkyl. For example, R 51 and R 52 is C1-C4 alkyl or C1-C4 alkoxy, and R 53is hydrogen or C1-C4 alkyl. In another embodiment, R 51 and R 52 is methyl or methoxy, and R 53 is hydrogen or methyl. For example, R 51 , R 52 , and R 53 is methyl. In another embodiment, R 51 , R 52 , and R 53 is methyl and R 54 is hydrogen. In other embodiments, R 50 is C3-C8 alkyl. For example, R 51 and R 52 is methoxy and R 53 and R 54 is hydrogen and R 50 is isooctyl. For example, R 50 is isobutyl. For example, R 50 is phenyl. The bisacylphosphine oxide photoinitiator of the present invention is, for example, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (CAS#162881-26-7) or bis(2,4,6-trimethylbenzoyl)-(2,4-bis-pentyloxyphenyl)phosphine oxide.

[0078]

[0084] The monoacylphosphine oxide photoinitiator has formula III: [ka] In the above formula, R1 and R2 are each independently C1 to C 12alkyl, benzyl, phenyl unsubstituted or substituted 1-4 times with halogen, C1-C8 alkyl, and / or C1-C8 alkoxy, or cyclohexyl or -COR3 group, or R1 is -OR4, R3 is phenyl unsubstituted or substituted 1-4 times with C1-C8 alkyl, C1-C8 alkoxy, C1-C8 alkylthio, and / or halogen, and R4 is C1-C8 alkyl, phenyl, or benzyl. For example, R1 is -OR4. For example, R2 is phenyl unsubstituted or substituted 1-4 times with halogen, C1-C8 alkyl, and / or C1-C8 alkoxy. For example, R3 is phenyl unsubstituted or substituted 1-4 times with C1-C8 alkyl. For example, the monoacylphosphine oxide of the present invention is 2,4,6-trimethylbenzoylethoxyphenylphosphine oxide or 2,4,6-trimethylbenzoyldiphenylphosphine oxide.

[0079]

[0085] The radiation curable liquid resin for additive manufacturing can include a free radical photoinitiator as component (d) in any suitable amount, for example, in certain embodiments up to about 10 wt % of the resin composition, in certain embodiments from about 0.1 to about 10 wt % of the resin composition, and in further embodiments from about 1 to about 6 wt % of the resin composition.

[0080] [Light Start Package]

[0086] According to a particular embodiment, one or more cationic and / or free radical photoinitiators are included in the resin composition together with a diluent monomer. The cationic and free radical photoinitiators are as discussed herein, and any suitable diluent may be used. Typical liquid diluents for dispersing certain cationic photoinitiators include (poly)propylene glycol or (poly)propylene carbonate. Surprisingly, the inventors have discovered that the use of vinyl ether as a diluent monomer or dispersant in combination with at least one cationic photoinitiator results in improved photopolymerization effectiveness when subjected to curing under UV / vis optical conditions according to the present invention.

[0081]

[0087] In embodiments, the cationic photoinitiator is present in an amount of about 8 wt % to about 50 wt %, more preferably about 30 wt % to about 45 wt %, the vinyl ether diluent monomer is present in an amount of about 25 wt % to about 90 wt %, more preferably about 40 wt % to about 60 wt %, and the free radical photoinitiator is present in an amount of about 8 wt % to about 30 wt %, more preferably about 10 wt % to about 25 wt %, based on the total weight of the photoinitiator package, provided that the cationic photoinitiator is at least partially dissolved in solution with the vinyl ether diluent monomer in a ratio of 0.1:1 to 1:1.

[0082]

[0088] A second aspect of the claimed invention is (a) a cationically polymerizable component; (b) an iodonium salt cationic photoinitiator; and (c) a photosensitizer for photosensitizing component (b); and (d) a first reducing agent for reducing component (b); (e) a free radically polymerizable component; and (f) optionally a free radical photoinitiator; (g) a second reducing agent for reducing component (b), the second reducing agent having an electron donating substituent attached to the vinyl group; and Including, 20mJ / cm 2and emitting radiation with a peak spectral intensity between about 375 nm and about 500 nm, more preferably between about 380 nm and about 450 nm, more preferably between about 390 nm and about 425 nm, and more preferably between about 395 nm and about 410 nm. A liquid radiation curable composition for additive manufacturing.

[0083]

[0089] The cationically polymerizable component, the free radically polymerizable component, and the free radical photoinitiator according to the first aspect of the invention are similarly suitable for use in the second aspect of the invention. Moreover, the above description of the iodonium salt cationic photoinitiator according to the first aspect of the invention is also similarly suitable for use in the second aspect of the invention. In a preferred embodiment, the iodonium salt cationic photoinitiator is a diphenyliodonium salt. Some suitable diphenyliodonium salt photoinitiators are, for example, (4-methylphenyl)[4-(2-methylpropyl)phenyl]-, hexafluorophosphate, [4-(1-methylethyl)phenyl](4-methylphenyl)-, tetrakis(pentafluorophenyl)borate(1-) (bis(4-dodecylphenyl)iodonium hexafluoroantimonate), and (bis(4-tert-butylphenyl)iodonium hexafluorophosphate).

[0084] [Photosensitizer]

[0090] In some embodiments, depending on the wavelength of light used to cure the liquid radiation curable resin, it is desirable for the liquid radiation curable resin composition to contain a photosensitizer. The term "photosensitizer" is used to mean any substance that either increases the rate of photoinitiated polymerization or shifts the wavelength at which polymerization occurs. See textbook (G. Odian, Principles of Polymerization, 3rd Edition, 1991, p. 222). Substances that operate under the latter definition and that are used in conjunction with photoinitiators that do not otherwise absorb light of a particular wavelength are said to operate by an "indirect excitation" mechanism with their associated photoinitiator. Applicants have utilized this mechanism to formulate compositions of the present invention that are suitable for curing with UV / vis optics.

[0085]

[0091] A variety of compounds can be used as photosensitizers, including heterocyclic and fused ring aromatic hydrocarbons, organic dyes, and aromatic ketones. Examples of photosensitizers include those selected from the group consisting of methanone, xanthenone, pyrenemethanol, anthracene, pyrene, perylene, quinone, xanthone, thioxanthone, benzoyl ester, benzophenone, and any combination thereof. Specific examples of photosensitizers include [4-[(4-methylphenyl)thio]phenyl]phenylmethanone, isopropyl-9H-thioxanthen-9-one, 1-pyrenemethanol, 9-(hydroxymethyl)anthracene, 9,10-diethoxyanthracene, 9,10-dimethoxyanthracene, 9,10-dipropoxyanthracene, 9,10-dibutyloxyanthracene, 9-anthracenemethanol acetate, 2-ethyl-9,10-dimethoxyanthracene, 2-methyl-9,10-dimethoxyanthracene, 2-t-butyl-9,10-dimethoxyanthracene, 2-ethyl-9,10-diethoxyanthracene, and 2-methyl-9,10-diethoxyanthracene, anthracene, anthraquinone, 2-methylanthracene, laquinone, 2-ethyl anthraquinone, 2-tert butyl anthraquinone, 1-chloro anthraquinone, 2-amyl anthraquinone, thioxanthone and xanthone, isopropyl thioxanthone, 2-chloro thioxanthone, 2,4-diethyl thioxanthone, 1-chloro-4-propoxy thioxanthone, methyl benzoyl formate (Darocur MBF from BASF), methyl-2-benzoyl benzoate (Civacure OMB from Cheetech), 4-benzoyl-4'-methyldiphenyl sulfide (Civacure BMS from Cheetech), 4,4'-bis(diethylamino)benzophenone (Civacure EMK from Cheetech), and any combination thereof.

[0086]

[0092] The novel mixture may also contain various photoinitiators with different sensitivity to emission line radiation of different wavelengths in order to achieve better utilization of UV light sources.The use of known photoinitiators with different sensitivity to emission line radiation is well known in the additive manufacturing art and may be selected according to, for example, the radiation sources of 351 nm, 355 nm, 365 nm, 385 nm, and 405 nm.In this connection, it is advantageous to select various photoinitiators and use them in concentrations that will produce equal light absorption at the emission lines used.

[0087]

[0093] In embodiments, the photosensitizer is a fluorone, such as 5,7-diiodo-3-butoxy-6-fluorone, 5,7-diiodo-3-hydroxy-6-fluorone, 9-cyano-5,7-diiodo-3-hydroxy-6-fluorone, or the photosensitizer is [ka] and any combination thereof.

[0088]

[0094] When a photosensitizer is used, other photoinitiators that absorb at shorter wavelengths can be used. Examples of such photoinitiators include benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, and dimethoxybenzophenone, and 1-hydroxyphenyl ketones, such as 1-hydroxycyclohexylphenyl ketone, phenyl(1-hydroxyisopropyl)ketone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, and 4-isopropylphenyl(1-hydroxyisopropyl)ketone, benzil dimethyl ketal, and oligo-[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone] (Esacure KIP150 from Lamberti).

[0089]

[0095] It may be noted that some cationic photoinitiators have low absorption at the preferred actinic wavelengths. For example, in embodiments, UV / optics with peak intensity at about 400 nm are utilized in the additive manufacturing application of interest. For example, iodonium salts such as Rhodolsil 2074 available from Rhodia Silicones, Irgacure 250 Iodonium, (4-methylphenyl) [4- (2-methylpropyl) phenyl] hexafluorophosphate (1-) available from Ciba, and UV9380c available from GE Silicones have poor direct absorption at the preferred wavelengths and therefore require excess concentration or sensitizers. Therefore, triplet sensitizers such as thioxanthone and Michler's ketone may be used to absorb actinic energy and transfer it efficiently to the iodonium initiator. However, some thioxanthones and Michler's ketones tend to produce an orange or red color, pose safety concerns, and are not very effective at sensitizing the photoreaction at curing light wavelengths of about 400 nm, although they have significant actinic absorption up to 430 nm.

[0090]

[0096] However, in embodiments, chloropropylthioxanthone (CPTX) is a suitable sensitizer, particularly for iodonium initiators for use in stereolithography, because it does not have significant light absorption above 500 nm and produces articles with less coloration.

[0091]

[0097] In order to reduce the concentration of sensitizer used in the formulation and to prevent possible adverse effects from relatively high concentrations of sensitizer on the final physical properties of the composition, it is preferable to use a sensitizer with a high extinction coefficient at 400 nm. For example, benzophenone can act as a triplet sensitizer in some cases, but at a laser wavelength of, for example, a frequency tripled YAG laser (Coherent AVIA model #355-1800) operating at about 355 nm, the extinction coefficient is on the order of 108 liters / mole·cm. On the other hand, CPTX has an extinction coefficient of approximately X times that of benzophenone, or 2585 liters / mole·cm, using the same laser at the same laser wavelength of about 400 nm. This suggests that CPTX may require a concentration of 1 / X in the formulation to provide an equivalent light absorption effect. It is therefore preferred, although not required, that the sensitizer has an extinction coefficient at curing light wavelengths above 380 nm of 300 Litres / mole·cm or greater, for example greater than 1000 Litres / mole·cm, preferably greater than 2000 Litres / mole·cm.

[0092]

[0098] Although it is taught that CPTX can be used to improve the activity of cationic photoinitiators, the sensitizers used in combination with the cationic photoinitiators mentioned above are not necessarily limited thereto. A variety of compounds can be used as photosensitizers, including heterocyclic and fused ring aromatic hydrocarbons, organic dyes, and aromatic ketones. Examples of sensitizers include those disclosed in JV Crivello, Advances in Polymer Science, Vol. 62, No. 1 (1984), and JV Crivello and K. Dietliker, "Photoinitiators for Cationic Polymerization", Chemistry & technology of UV & EB formulation for coatings, inks & paints, Vol. III, Photoinitiators for free radical and cationic polymerization, K. Dietliker, [P.K.T. Oldring, Ed.], SITA Technology Ltd, London, 1991. Specific examples include polycyclic aromatic hydrocarbons and their derivatives, such as anthracene, pyrene, perylene and their derivatives, substituted thioxanthones, α-hydroxyalkylphenones, 4-benzoyl-4'-methyldiphenyl sulfide, acridine orange, and benzoflavins.

[0093]

[0099] The radiation curable liquid resin for additive manufacturing may include other cationic photoinitiators or photosensitizers in any suitable amount, for example, in certain embodiments, from 0.1 to 10 wt % of the resin composition, in certain embodiments, from about 1 to about 8 wt % of the resin composition, and in further embodiments, from about 2 to about 6 wt % of the resin composition. In embodiments, the above ranges are particularly suitable for use with epoxy monomers. In other embodiments, the photosensitizers may be utilized in amounts of from about 0.05 wt % to about 2 wt % of the total composition in which they are incorporated.

[0094] [Reducing agent]

[0100] As used herein, a reducing agent refers to a component that loses one or more electrons, i.e., "donates" one or more electrons to a cationic photoinitiator component in a redox chemical reaction upon polymerization of the present invention's liquid radiation-based additive manufacturing compositions. Even if such a component does not have the ability to readily donate electrons until it generates free radicals, i.e., until it decomposes into free radicals after dissociation or is otherwise excited by exposure to UV / vis wavelength actinic radiation, it is still considered a reducing agent for the purposes of the present invention. For this reason, it may alternatively be referred to herein as an "activated reducing agent."

[0095]

[0101] Photoinitiated cationic polymerization of monomers such as epoxides and vinyl ethers plays a necessary role in hybrid-curing additive manufacturing applications. Due to the use of additives in various applications, wavelength flexibility of photoinitiation is a fundamental factor in determining the curing performance of a particular formulation when targeting a specific spectral sensitivity. Photoinitiating systems for cationic polymerization that are sensitive to longer wavelengths, especially those emitted by modern UV / vis optics, are therefore gaining importance. Many of the existing photoinitiating systems for cationic polymerization are based on the use of onium salts such as diphenyliodonium salts, triphenylsulfonium salts, and alkoxypyridinium salts. However, these salts do not absorb significantly (if at all) in the UV / vis spectrum unless additional chromophores are incorporated into the salt structure. It is therefore important to find alternative ways to synthetically extend the sensitivity range of readily available onium salts to UV / vis wavelengths, especially in light of the fact that commercially available photoinitiators already designed to absorb in the UV / vis spectral range are not suitable for incorporation into hybrid curing systems for additive manufacturing for other reasons.

[0096]

[0102] As discussed herein, applicants have achieved the objective at least in part through a mechanism called indirect excitation, utilizing a combination of sensitizers. Besides, onium salts act as electron acceptors in redox reactions in conjunction with free radicals, electron donor compounds of charge transfer complexes, and long-lived electronic excited states of sensitizers, respectively. Among these methods, the so-called "free radical promoted" cationic polymerization appears to be an additional effective and flexible way to generate cationic species capable of initiating the cationic polymerization of monomers. The overall mechanism involves the oxidation of photochemically formed radicals by onium salts (On+) with suitable reduction potentials. R·+ON+→R+ (1)

[0097]

[0103] Reducing agents suitable for promoting free radical promoted cationic polymerization generally include some of the free radical photoinitiators listed above, such as acylphosphine oxides, along with amines, benzoin and its derivatives, o-phthalaldehyde, polysilanes, and compounds having electron donating substituents attached to the vinyl group, such as vinyl ethers and vinyl halides, to name a few.

[0098]

[0104] Amines are considered to be efficient hydrogen donors and will readily form free radicals that reduce the associated cationic photoinitiator via a chain transfer mechanism. Thus, in certain embodiments, they can act as suitable reducing agents. However, care must be taken when including such compounds in hybrid radiation curable additive manufacturing compositions, since the nitrogen atoms they contain are known to tend to otherwise inhibit cationic polymerization reactions.

[0099]

[0105] There are several systems that generate oxidizing radicals in the presence of a UV / vis light source. For example, the radicals formed by irradiating a system containing a xanthene dye and an aromatic amine can act as reducing agents for diphenyliodonium salts. Similarly, the dimanganese decacarbonyl-organohalide combination is an effective reducing agent for cationic polymerization at UV / vis wavelengths when used in combination with an onium salt. Additionally, commercially available titanocene-type photoinitiators such as Irgacure 784 can be used as a source of reducing agent generated by irradiation with visible light.

[0100]

[0106] Acylphosphine oxides and acylphosphanates of various structures have been used as photoinitiators for free radical polymerization. Extensive studies on the photochemistry of acylphosphine oxides have shown that they undergo α-scission with fairly high quantum yields.

[0101]

[0107] In embodiments, acylphosphine oxides, at least when combined with a second reducing agent having an electron donating substituent attached to the vinyl group, are suitable reducing agents that contribute to facilitating cationic polymerization of suitable monomers at UV / vis wavelengths. Cationic polymerization of tetrahydrofuran and butyl vinyl ether can be readily initiated upon irradiation at UV / vis wavelengths in the presence of bisacylphosphine oxides and diphenyliodonium salts. Without wishing to be bound by theory, it is believed that the photoinitiated bisacylphosphine oxides readily abstract hydrogen from a suitable donor (e.g., solvent or monomer) to become a reducing agent when used in conjunction with a cationic photoinitiator. The resulting carbon-centered radical is converted to a carbocation by reaction with PhI+ ions to initiate cationic polymerization. As disclosed herein, it has been found that acylphosphine oxides, more preferably substituted acylphosphine oxides, when combined with suitable onium salts, such as iodonium salts and pyridinium salts, are efficient and effective reducing agents for facilitating free cationic polymerization at UV / vis curing wavelengths. The proposed initiation mechanism appears to involve the photogeneration of phosphinoyl and benzoyl radicals in a first step. The phosphinoyl radical is then oxidized by an onium salt to generate a phosphonium ion capable of initiating the polymerization of monomers. The efficiency of the latter step should be controlled by the redox potential of the onium salt and the electron delocalization (p character) of the phosphinoyl radical. Thus, one embodiment of the present invention is to maximize the redox potential between the onium salt and the acylphosphine oxide free radical photoinitiator while simultaneously searching for an acylphosphine oxide with maximum electron delocalization (p character) so that the effect of this mechanism is maximized at 400 nm wavelength light and maximum cationic cure speed is realized.

[0102]

[0108] In embodiments, the reducing agent for reducing the cationic photoinitiator has the following formula IV: [ka] In the above formula, Ar1 is a substituted or unsubstituted aromatic group, R1 is Ar1, C2 to C 20 Aliphatic chain, or C2-C 20 is an alkyl chain, and R2 is R1 or contains one or more substituted or unsubstituted acylphenyl groups.

[0103]

[0109] The liquid radiation curable resin for additive manufacturing may include a reducing agent for reducing the cationic photoinitiator, for example, in certain embodiments, in an amount of 0.01 to 30 wt %, in other preferred embodiments, in an amount of 0.01 to 10 wt % of the resin composition, in other certain embodiments, about 1 to about 8 wt % of the resin composition, and in further embodiments, about 2 to about 6 wt % of the resin composition. In embodiments, the above ranges are particularly suitable when an iodonium salt photoinitiator is used in combination. In embodiments, the same reducing agent component may function simultaneously as a free radical photoinitiator and a reducing agent, thereby promoting both free radical and cationic polymerizations simultaneously. In other embodiments, the reducing agent may be utilized in an amount of about 0.05 wt % to about 4 wt % of the total composition in which it is incorporated.

[0104] [Reducing agents having an electron-donating substituent attached to a vinyl group]

[0110] The inclusion of additional components having electron donating substituents attached to the vinyl group can further provide a mechanism for improving cationic curing of liquid radiation curable compositions for additive modeling systems utilizing UV / vis optics. Such compounds, such as vinyl ethers, are avoided in many modern commercial hybrid curable compositions for additive modeling systems utilizing traditional UV-based radiation sources because of their (1) tendency to generate excess heat due to rapid polymerization exothermic reactions, and (2) tendency to result in copolymerization and concomitant non-uniform polymers to produce three-dimensional parts with inconsistent and poor physical properties. Nevertheless, the inventors have surprisingly found that their incorporation into compositions tailored to systems utilizing UV / vis optics with lower energy / intensity becomes desirable when used in conjunction with other necessary components according to the present invention. Specifically, the inventors have further found that the inclusion of additional components having electron donating substituents attached to the vinyl group surprisingly improves polymerization synergistically with the presence of components that induce other reaction mechanisms cited herein (i.e., indirect excitation and free radical promoted cationic polymerization).

[0105]

[0111] A preferred example of a component having an electron donating substituent attached to the vinyl group is a vinyl ether. Vinyl ethers can be produced from a variety of starting materials, such as ethers, esters, or biscarbamates, or vinyl ether terminated (poly)urethanes or carbonates. Some non-limiting examples of each include:

[0106]

[0112] Vinyl ether monomers from ethers: Specific examples of polyfunctional vinyl ethers include divinyl ethers such as ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, isobutyl vinyl ether, butylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanediol divinyl ether, bisphenol A alkylene oxide divinyl ether, and bisphenol F alkylene oxide divinyl ether, as well as polyfunctional vinyl ethers such as trimethylolethane trivinyl ether, trimethylolpropane trivinyl ether, ditrimethylolpropane tetravinyl ether, divinyloxy ... nyl ether, glycerol trivinyl ether, pentaerythritol tetravinyl ether, pentaerythritol divinyl ether, dipentaerythritol pentavinyl ether, dipentaerythritol hexavinyl ether, an ethylene oxide adduct of trimethylolpropane trivinyl ether, a propylene oxide adduct of trimethylolpropane trivinyl ether, an ethylene oxide adduct of ditrimethylolpropane tetravinyl ether, a propylene oxide adduct of ditrimethylolpropane tetravinyl ether, an ethylene oxide adduct of pentaerythritol tetravinyl ether, a propylene oxide adduct of pentaerythritol tetravinyl ether, an ethylene oxide adduct of dipentaerythritol hexavinyl ether, and a propylene oxide adduct of dipentaerythritol hexavinyl ether.

[0107]

[0113] Vinyl ether monomers from esters or biscarbamates: specific examples of polyfunctional vinyl ethers such as divinyl adipate, divinyl terephthalate, divinyl cyclohexyl dicarboxylate, etc. Bis[4-(vinyloxy)butyl]adipate (VEctomer® 4060), bis[4-(vinyloxy)butyl]succinate (VEctomer® 4030), bis[4-(vinyloxy)butyl]isophthalate (VEctomer® 4010), bis[4-(vinyloxymethyl)cyclohexylmethyl]glutarate (VEctomer® 4020), tris[4-(vinyloxy)butyl] trimellitate (Vectomer® 5015), bis[4-(vinyloxymethyl)cyclohexylmethyl]isophthalate (Vectomer® 4040), bis[4-(vinyloxy)butyl](4-methyl-1,3-phenylene) biscarbamate (Vectomer® 4220), and bis[4-(vinyloxy)butyl](methylenedi-4,1-phenylene) biscarbamate (Vectomer® 4210).

[0108]

[0114] Vinyl ether-terminated urethanes or carbonates: Specific examples of polyfunctional vinyl ethers, such as polyurethanes and polycarbonates end-capped with hydroxyvinyl ethers having at least a hydroxyl group and at least a vinyl ether group in the molecule, such as 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 2-hydroxyisopropyl vinyl ether, 4-hydroxybutyl vinyl ether, 3-hydroxybutyl vinyl ether, 2-hydroxybutyl vinyl ether, 3-hydroxyisobutyl vinyl ether, 2-hydroxyisobutyl vinyl ether, 1-methyl-3-hydroxypropyl vinyl ether, 1-methyl-2-hydroxypropyl vinyl ether, 1-hydroxymethylpropyl vinyl ether, 4-hydroxycyclohexyl vinyl ether, 1,6-hexanediol monovinyl ether, 1,4-cyclohexanedimethanol monovinyl ether, 1,3-cyclohexanedimethanol monovinyl ether, 1,2-cyclo ... Methanol monovinyl ether, p-xylene glycol monovinyl ether, m-xylene glycol monovinyl ether, o-xylene glycol monovinyl ether, diethylene glycol monovinyl ether, triethylene glycol monovinyl ether, tetraethylene glycol monovinyl ether, pentaethylene glycol monovinyl ether, oligoethylene glycol monovinyl ether, polyethylene glycol monovinyl ether, dipropylene glycol monovinyl ether, tripropylene glycol monovinyl ether, tetrapropylene glycol monovinyl ether, derivatives thereof, for example, pentapropylene glycol monovinyl ether, oligopropylene glycol monovinyl ether, and polypropylene glycol monovinyl ether.

[0109]

[0115] In preferred embodiments, the component having an electron donating substituent attached to the vinyl group is one or more of the following: vinyl ether, vinyl ester, vinyl thioether, n-vinyl carbazole, n-vinyl pyrrolidone, n-vinyl caprolactam, allyl ether, and vinyl carbonate.

[0110]

[0116] In another preferred embodiment, the component having an electron donating substituent attached to the vinyl group is multifunctional.

[0111]

[0117] Any suitable amount of one or more of the above-listed components having an electron-donating substituent attached to a vinyl group may be utilized in the composition of the present invention, and may be selected alone or in combination with one or more of the types listed herein. In a preferred embodiment, the component having an electron-donating substituent attached to a vinyl group is present in an amount of about 1 wt.% to about 25 wt.%, more preferably about 5 wt.% to about 20 wt.%, more preferably about 5 wt.% to about 12 wt.%, based on the total weight of the composition. In another embodiment, the component having an electron-donating substituent attached to a vinyl group is present in an amount of 1 wt.% to 15 wt.%, more preferably 1 wt.% to 10 wt.%, more preferably 3 wt.% to about 8 wt.%.

[0112] [Other ingredients]

[0118] To further prevent viscosity increase, for example during use in a solid imaging process, stabilizers are often added to the resin composition. Useful stabilizers include those described in U.S. Pat. No. 5,665,792. The presence of a stabilizer is optional. In a specific embodiment, the liquid radiation curable resin composition for additive manufacturing comprises 0.1 wt % to 3% of a stabilizer.

[0113]

[0119] Other possible additives include organic and inorganic fillers, dyes, pigments, antioxidants, wetting agents, cell collapse agents, chain transfer agents, leveling agents, defoamers, surfactants, etc. Such additives are well known and are generally available as desired for a particular application, as would be understood by one skilled in the art.

[0114]

[0120] The radiation curable liquid resin composition for additive manufacturing of the present invention may further comprise one or more additives selected from the group consisting of a bubble disintegrant, an antioxidant, a surfactant, an acid scavenger, a pigment, a dye, a thickener, a flame retardant, a silane coupling agent, an ultraviolet absorber, a resin particle, a core-shell particle impact modifier, a soluble polymer, and a block polymer.

[0115]

[0121] In addition, many of the known liquid radiation curable resin compositions for additive manufacturing use hydroxy-functional compounds to improve the properties of parts made from the resin composition. Any hydroxy group, if present, may be used for a specific purpose. If present, the hydroxyl-containing material preferably contains one or more primary or secondary aliphatic hydroxyls. The hydroxyl groups may be present in the molecule or at the end. Monomers, oligomers, or polymers may be used. The hydroxyl equivalent, 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 resin composition preferably contains at most 10 wt%, more preferably at most 5 wt%, and most preferably at most 2 wt% of one or more non-free radically polymerizable hydroxy-functional compounds based on the total weight of the resin composition.

[0116] [ratio]

[0122] Surprisingly, the inventors have found that the compositions of the present invention can be specifically optimized for curing by certain additive manufacturing processes utilizing UV / vis optics by controlling the ratios of the various necessary components relative to one another. In a preferred embodiment, the weight ratio of the iodonium salt cationic photoinitiator, the photosensitizer, the first reducing agent, and the second reducing agent having an electron donating substituent attached to a vinyl group is about 2:2:1:2 to about 20:1:5:25, more preferably about 10:1:2:12. If the amount of iodonium salt cationic photoinitiator is too high, the radiation absorption becomes too significant and interferes with the ability to cure to a sufficient depth of the layer. If it is too low relative to the other components, cationic curing is initiated but not to the level required to produce a three-dimensional part with adequate green strength. The amount of photosensitizer should generally not exceed the amount of iodonium salt cationic photoinitiator, but should be present in an amount sufficient to allow indirect excitation of said cationic photoinitiator. The reducing agent should also generally not exceed the amount of cationic photoinitiator being reduced, but should likewise be present in an amount sufficient to promote free radical promoted cationic polymerization. Finally, the component having an electron donating substituent attached to the vinyl group can be present in a maximum amount by weight compared to the other components listed above to fully enable additional cationic polymerization mechanisms, but should not be present in a disproportionately large amount as this may accelerate the cure, resulting in uncontrolled exothermic reactions and excessive heat generation.

[0117]

[0123] In other embodiments, the ratio of iodonium salt cationic photoinitiator to photosensitizer is from 1:3 to 10:1. In embodiments, the ratio of iodonium salt cationic photoinitiator to reducing agent is from 1:5 to 10:1.

[0118]

[0124] A third aspect of the claimed invention comprises: (a) about 30 wt.% to about 80 wt.% of at least one cationically polymerizable component further comprising a cycloaliphatic epoxide and an oxetane; (b) about 1 wt.% to about 8 wt.% of a sulfonium salt cationic photoinitiator having an absorbance of less than 0.01 at 400 nm; (c) the following formula (V): [ka] (Wherein, R is C1 to C 20 (containing aliphatic chains) About 0.5 wt.% to about 3 wt.% of a compound represented by the formula: (d) a free radically polymerizable component; and (e) diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide free radical photoinitiator; and Including, 20mJ / cm 2 and emitting radiation with a peak spectral intensity between about 375 nm and about 500 nm, more preferably between about 380 nm and about 450 nm, and more preferably between about 390 nm and about 425 nm. A liquid radiation curable composition for additive manufacturing.

[0119]

[0125] According to another aspect of the invention, the cationic photoinitiator used in formulating the liquid radiation curable composition for additive manufacturing that is curable by UV / vis optics is a sulfonium salt. The above description of the sulfonium salt cationic photoinitiator according to the first aspect of the claimed invention is equally suitable for use in this third aspect of the claimed invention. In a preferred embodiment of the third aspect of the invention, the cationic photoinitiator is a triarylsulfonium salt. In a preferred embodiment, the (triaryl)sulfonium salt cationic photoinitiator has a very low direct absorbance at UV / vis wavelengths in practice. In an embodiment, the (triaryl)sulfonium salt photoinitiator used has an absorbance at 400 nm of less than 0.05, more preferably less than 0.01, more preferably less than 0.005, and most preferably less than 0.001. As described, the applicant has surprisingly found that indirect excitation of the cationic photoinitiator is a more preferred mechanism for initiating the cationic polymerization of liquid radiation curable composition for additive manufacturing using UV / vis optics than direct excitation of a cationic photoinitiator that has a significant absorbance at 400 nm.

[0120]

[0126] In embodiments, the sulfonium salt cationic photoinitiator has the following structure: [ka] It is a triarylsulfonium salt having a cation represented by the formula:

[0121]

[0127] In embodiments, the triarylsulfonium salt further has a hexafluoroantimonate or hexafluorophosphate counterion.

[0122]

[0128] In embodiments, the sulfonium salt cationic photoinitiator is present in the composition in any suitable amount from 0.01 wt % to 15 wt %, in other embodiments from 1 wt % to 8 wt %, and in other embodiments from 2 wt % to 5 wt %.

[0123]

[0129] Furthermore, the cationically polymerizable and free radically polymerizable components according to the first and second aspects of the invention are similarly suitable for use in the claimed third aspect of the invention.

[0124]

[0130] The liquid radiation curable composition for additive manufacturing according to the third aspect of the invention also contains a free radical photoinitiator. The description of the free radical photoinitiator according to the first and second aspects of the invention is generally suitable for use in the claimed third aspect of the invention as well. However, in a preferred embodiment, the free radical photoinitiator comprises diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide. Furthermore, the inventors have surprisingly found that in an embodiment, the free radical photoinitiator component can produce improved curability in combination with a sulfonium salt cationic photoinitiator when it has less than 50% of compounds containing two or more carboxyl groups, preferably less than 33% of compounds containing two or more carboxyl groups, based on the total amount of free radical photoinitiator present in the composition.

[0125]

[0131] The liquid radiation curable composition for additive manufacturing according to the third aspect of the present invention also contains a photosensitizer. In an embodiment, the photosensitizer may generally be selected according to the description of the photosensitizer according to the second aspect of the present invention. In a preferred embodiment, the photosensitizer utilized has the following formula (V): [ka] (Wherein, R is C1 to C 20 (containing aliphatic chains) It has a structure shown below.

[0126]

[0132] In a preferred embodiment of the third aspect of the invention, the photosensitizer utilized is an anthracene-based photoinitiator. Commercially available products of such photosensitizers include Anthracure™ UVS-1101 and UVS-1331 available from Kawasaki Chemical.

[0127]

[0133] The photosensitizer is present in any suitable amount from about 0.5 wt.% to about 10 wt.%, more preferably from 0.5 wt.% to 3 wt.%.

[0128]

[0134] A fourth aspect of the invention as claimed is a method of forming a three-dimensional article with an additive fabrication system utilizing UV / vis optics, comprising: (1) providing a liquid radiation curable composition for additive manufacturing according to the first, second or third aspect of the present invention; (2) providing a first liquid layer of a liquid radiation curable resin; (3) forming a first cured layer by imagewise exposing the first liquid layer to actinic radiation using a UV / vis optical configuration to form an imaged cross-section; (4) forming a new layer of liquid radiation curable resin in contact with the first cured layer; (5) imagewise exposing the new layer to actinic radiation to form an additional imageable cross-section; (6) repeating steps (4) and (5) a sufficient number of times to build a three-dimensional article; and Including, the UV / vis optical element emits radiation with a peak spectral intensity between about 375 nm and about 500 nm, more preferably between about 380 nm and about 450 nm, more preferably between about 390 nm and about 425 nm, more preferably between about 395 nm and about 410 nm; This is the method.

[0129]

[0135] The liquid radiation curable composition provided in the above-mentioned aspects of the invention must be suitable for curing by an additive manufacturing system utilizing UV / vis optics. Such compositions are particularly described in the first, second and third aspects of the invention. When providing the first liquid layer or forming a new layer of liquid radiation curable resin, the layer can be of any suitable thickness and shape and will depend on the additive manufacturing process being utilized. For example, it can be selectively dispensed by jetting or can be added by dipping an already cured layer into a vat of resin to produce a layer of substantially uniform thickness, as is common in most stereolithography processes. In other non-limiting embodiments, a cartridge or dispenser can alternatively be used to transfer a predetermined thickness through a foil, film or carrier.

[0130]

[0136] In the above, "exposure" means exposure to actinic radiation. As stated above, the liquid radiation compositions for additive manufacturing of the present invention described herein are particularly suitable for applying hybrid cure via UV / vis optics. In an embodiment, the UV / vis optics utilizes one or more LEDs as the light source. In an embodiment, the light source is a laser. In an embodiment, the LED or laser light source is coupled to a DLP or LCD image projection system. In an embodiment, where the image projection system includes an LCD display, the light source may be configured to emit actinic radiation exclusively above 400 nm to minimize the deleterious effects of UV wavelengths on the LCD components.

[0131]

[0137] A fifth aspect of the claimed invention is a three-dimensional part formed according to the fourth aspect of the invention using the liquid radiation curable composition of the first, second or third aspect of the invention.

[0132]

[0138] The following examples further illustrate the invention but, of course, should not be construed as in any way limiting its scope.

[0133] [Example]

[0139] These examples illustrate embodiments of the radiation curable liquid resin for additive manufacturing of the present invention. Table 1 lists the various components of the radiation curable liquid resin for additive manufacturing used in the examples of the present invention.

[0134] [Test Method]

[0140] Real-time Fourier transform infrared (FTIR) spectroscopy was used to measure the polymerization kinetics (curing speed) of each example. A mercury cadmium telluride (MCT) detector was used to increase the data acquisition frequency and therefore the resolution. Instead of transmission mode, an attenuated total reflectance (ATR) configuration was used. All polymerization kinetic measurements were performed using a Thermo Scientific Nicolet 8700 model. The experimental conditions set for the measurements are shown in the table below. Under these conditions, a total of 41 spectra were obtained for each measurement over a period of 200 seconds.

[0135] [Table 1]

[0136]

[0141] For UV / Vis light control, Digital Light Lab LED spot lamps (365 nm, 395 nm, and 400 nm) and a controller (AccuCure Photo Rheometer) were used. Calibrated continuous mode was selected. Light intensity and duration (exposure time) were selected before measurements.

[0137]

[0142] For the measurement, a few drops of the selected sample were placed in the center of the ATR crystal setup. A 3 mil (±0.4 mil) drawdown bird bar was then used to coat approximately a 3 mil film (±0.4 mil) on the ATR crystal. Immediately after application of the 3 mil coating, an LED lamp was held above the ATR setup and positioned in the hole at the center of the holding. A real-time FTIR scan was then started. After acquiring one spectrum, the light source was turned on to start the polymerization. Based on the above program inputs, each spectrum was acquired every 5 seconds for a total of 200 seconds. A total of 41 spectra were acquired for each experiment.

[0138]

[0143] Polymerization conversion versus time was calculated based on the specific IR peak changes representing each functional group. Examples of IR peak changes are shown in the images above. To calculate the conversion of each relevant functional group, the peak height or peak area was calculated according to the following table, as appropriate:

[0139] [Table 2]

[0140]

[0144] When using the raw data obtained, it was important to remove the first one or two data points because the experimental cure speed procedure has an unknown short time lag between the turn-on of the FTIR detector and the turn-on of the light source used to cure the sample. To compensate for any uncertainty associated with the amount of statistical noise generated by these preliminary data points, three curve fits were created for each data set. In each case, the model equation used to fit the data sets was Conv=a(1-e(-b*(time-c))). For this, the raw data were fitted using Microsoft Excel version 14.0.7116.5000 (32-bit) with the Data Analysis add-on.

[0141]

[0145] In the first case, the entire data set (including the first two data points) was fitted. In the second case, the entire data set minus the first data point was fitted. In the third case, the entire data set minus the first and second data points was fitted. In both cases, the curve fitting coefficient r 2 The first data point with a conversion rate greater than 1% and a combined curve fit with an r value greater than 0.90 was generated. 2 The data set that gave the curve fitting coefficient r was selected and used, and the resultant curve fitting equation was used for further calculation of the cure speed at 95% of the plateau conversion. 2 If was less than 0.90, the data was re-run again.

[0142]

[0146] As discussed above, the data was fitted to an equation of the form Conv=a(1-e(-b*(time-c))), where "Conv" is the percent conversion as measured by FTIR peak ratio, time is the duration of exposure, "a" is the plateau conversion, "b" is the derived cure speed factor used to calculate cure speed, and "c" is the derived cure induction time. After fitting the data, the software created an empirically derived equation with the numerical parameters "a", "b", and "c" determined from the experimental data and the fit. For cationically curable materials (i.e., epoxies and oxetanes), "c" has no meaning since there is no cure induction time. Thus, in such cases, "c" was ignored. The variable "a" is used as the plateau conversion under the cure conditions used and represents the overall asymptotic range to which the components have been converted. The variable "b" is used as the percent conversion in the equation T 95 = ln(.05 / b) gives the 95% plateau conversion rate of "a" (T 95 ) was used to calculate the time T 95 are listed in Tables 2, 3, and 4, as appropriate (and if available).

[0143] [Examples 1 to 8]

[0147] First, an additive modeling base resin was prepared by combining an oxetane component, a cycloaliphatic epoxide component, a polyol component, a glycidyl ether epoxide component, and an acrylate component according to methods known in the art.

[0144] [Table 3]

[0145] [Table 4]

[0146]

[0148] Irgacure PAG103 (used in Comparative Example 1) and Irgacure PAG121 (used in Comparative Example 2) are available from BASF and are specifically promoted as non-ionic cationic photoacid photoinitiators for cationically curable resins with significant absorbance in the UV / vis spectrum. CPI400 (used in Comparative Example 3) is a cationic photoinitiator available from San-Apro with significant absorbance at 400 nm. The three above-listed cationic photoinitiators would be expected to be suitable candidates for possible incorporation into liquid hybrid radiation curable compositions for additive modeling systems utilizing UV / vis optics.

[0147]

[0149] T of cycloaliphatic epoxy components 95 and plateau conversion is calculated as described in the Test Methods section above.

[0148] [Table 5]

[0149]

[0150] Comparative Example 4 utilizes a photoinitiation package shown to be suitable for curing at a wavelength of 365 nm, and is therefore useful for benchmarking against the inventive examples provided in Table 3 using the same base resin.

[0150] [Table 6]

[0151] [Discussion of results] Table 1 lists the base resins used in most of the formulations in Tables 2, 3, and 4.

[0152]

[0152] In Table 2, known commercial techniques used for 365 nm cure applications are used to establish acceptable levels of performance using the RT-FTIR methods described herein. These test results will be used to benchmark the results in Tables 3 and 4 to establish acceptance criteria.

[0153] In Table 3, cationic photoinitiators are used that are known to absorb in the UV / vis spectral range and are expected to be suitable for incorporation into liquid hybrid radiation curable compositions for additive modeling systems with a direct excitation mechanism utilizing UV / vis optics. However, as can be seen, none of these alternative methods come close to the cure performance of the benchmark in Table 2 made at 365 nm. Three different photoinitiators were identified by their suppliers as useful for curing at wavelengths of about 405 nm. Of all three tested, only CPI-400 showed any measurable cure activity. The data generated from this experiment was entered into the curve fitting software described in the Test Methods section above, but the data was statistically very insignificant in the tests, so r 2 The value never reached the acceptable level. Therefore, the actual T 95 While not statistically significant in demonstrating the rate of conversion and plateau conversion, the data in Table 3 and Figures 3 and 4 are nevertheless instructive in showing how poorly such photoinitiators utilizing a direct excitation mechanism perform.

[0154]

[0154] Table 4 shows tests based on the inventive concepts discussed herein as cured at 400 nm (at the listed intensities and durations). As can be seen, all of the examples achieve results that are comparable to and even better than the 365 nm acceptance criteria established in Table 2. The time to reach 95% of the plateau, T 95 A shorter conversion time is desirable while a higher plateau conversion is desirable.

[0155]

[0155] Unless otherwise specified, the term wt. % refers to the amount by weight of a particular component incorporated relative to the total radiation-curable liquid composition for additive manufacturing.

[0156]

[0156] The use of the terms "a," "an," and "the" and similar reference words in connection with the description of the present invention (particularly in connection with the claims which follow) should be construed to encompass both the singular and the plural, unless otherwise specified herein or clearly contradicted by context. The terms "comprising," "having," "including," and "containing" should be construed as open-ended terms (i.e., meaning "including, but not limited to") unless otherwise noted. The recitation of ranges of values ​​herein is intended to serve as a shorthand notation for individually referencing each individual value falling within the range, unless otherwise specified herein, and each individual value is incorporated herein as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise specified herein or otherwise clearly contradicted by context. The use of any examples or illustrative language provided herein (e.g., "such as") is intended merely to facilitate a better understanding of the invention and does not impose a limitation on the scope of the invention unless specifically claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0157]

[0157] Preferred embodiments of the present invention are described herein, including the best mode known to the inventor for carrying out the invention. Variations of such preferred embodiments will become apparent to those skilled in the art upon reading the foregoing description. The inventor anticipates that those skilled in the art will utilize such variations as appropriate, and it is the inventor's intention that the invention be practiced otherwise than as specifically described herein. Accordingly, the present invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the present invention unless otherwise indicated herein or otherwise clearly contradicted by context.

[0158]

[0158] Although the present invention has been described in detail with reference to specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention as claimed.

Claims

1. (a) 30 to 80% by weight of a cationically polymerizable component; (b) an iodonium salt cationic photoinitiator; and (c) 0.05 to 6 weight percent of a photosensitizer for photosensitizing component (b); (d) a reducing agent for reducing component (b), the reducing agent comprising a vinyl ether monomer produced from an ether as a starting material; (e) 8 to 25 weight percent of a free radically polymerizable component; optionally (f) a free radical photoinitiator; Including, 20 mJ / cm ２ and emitting radiation between 375 nm and 500 nm with a peak spectral intensity.

2. 2. The liquid radiation curable composition for additive manufacturing of claim 1, wherein component (d) further comprises a free radical photoinitiator configured to reduce component (b) upon exposure to UV / vis wavelength actinic radiation to generate free radicals upon dissociation.

3. 3. The radiation curable liquid composition for additive manufacturing according to claim 1 or 2, wherein component (a) additionally comprises a glycidyl ether epoxy selected from the group consisting of bisphenol A based glycidyl ethers, bisphenol S based glycidyl ethers, and bisphenol F based glycidyl ethers.

4. The radiation curable liquid composition for additive manufacturing according to any one of claims 1 to 3, wherein component (b) is a diphenyliodonium salt.

5. 5. The radiation curable liquid composition for additive manufacturing of claim 4, wherein the diphenyliodonium salt is selected from the group consisting of (4-methylphenyl)[4-(2-methylpropyl)phenyl]iodonium hexafluorophosphate, [4-(1-methylethyl)phenyl](4-methylphenyl)iodonium tetrakis(pentafluorophenyl)borate(1-), (bis(4-dodecylphenyl)iodonium hexafluoroantimonate), and (bis(4-tert-butylphenyl)iodonium hexafluorophosphate).

6. The radiation curable liquid composition for additive manufacturing according to any one of claims 1 to 5, wherein component (c) is thioxanthone.

7. 7. The radiation curable liquid composition for additive manufacturing of claim 6, wherein the thioxanthone is further selected from the group consisting of chloropropoxythioxanthone and isopropylthioxanthone.

8. The free radical photoinitiator has the following formula (IV): 【Chemistry 1】 (In the formula, Ar １ is a substituted or unsubstituted aromatic group, R １ is Ar １ Or C ２ ~C ２０ an aliphatic chain, and R ２ is R １ or containing one or more substituted or unsubstituted acylphenyl groups) The liquid radiation curable composition for additive manufacturing according to any one of claims 2 to 7, wherein

9. 9. The radiation curable liquid composition for additive manufacturing according to any one of claims 1 to 8, wherein component (f) is optionally hydroxycyclohexyl phenyl ketone.

10. 10. The radiation curable liquid composition for additive manufacturing according to any one of claims 1 to 9, wherein the vinyl ether monomer is a multifunctional vinyl ether monomer.

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