Liquid Hybrid UV / VIS Radiation Curable Resin Composition for Additional Shaping

Abstract

Liquid radiation-curable compositions suitable for hybrid (i.e., cationic and free-radical) polymerization when processed by an additive manufacturing apparatus utilizing an actinic radiation source with peak spectral intensity in the UV / vis region are disclosed. According to one embodiment, the compositions have a first photoinitiator that is an iodonium salt of a non-fluorinated borate anion. According to another embodiment, the compositions are substantially devoid of Norrish Type I and / or Type II photoinitiators. Also disclosed are methods of using the liquid radiation-curable compositions suitable for hybrid polymerization to fabricate three-dimensional parts by an additive manufacturing process utilizing an actinic radiation source with peak spectral intensity in the UV / vis region, as well as parts cured therefrom.

Description

Detailed Description of the Invention

[0001] [Technical Field] The present invention relates to a liquid composition for an additive manufacturing process that is hybrid curable in the UV or visible spectrum.

[0002] [Cross - Reference to Related Applications]

[0001] This application claims priority to U.S. Provisional Patent Application No. 62 / 893,969, filed on August 30, 2019, the entire content of which is incorporated herein by reference as if fully set forth herein.

[0003] [Background]

[0002] Additive manufacturing processes for manufacturing three - dimensional objects are well - known. Additive manufacturing processes utilize computer - aided design (CAD) data of an object to construct a three - dimensional part. These three - dimensional parts can be formed from liquid resins, powders, or other materials.

[0004]

[0003] A well - known non - limiting example of an additive manufacturing process is stereolithography (SL). Stereolithography is a process for rapidly manufacturing models, prototypes, patterns, and manufactured parts in certain applications. SL uses CAD data of an object, which is converted into thin cross - sections of the three - dimensional object. The data is loaded into a computer, which controls a laser to trace 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 the laser traces another cross - section to cure another resin layer on top of the previous layer. The process is repeated layer by layer until the three - dimensional object is complete. When first formed, the three - dimensional object is generally not fully cured and is called a "green model". Optionally, the green model may be post - cured to enhance the mechanical properties of the finished part. Examples of the SL process are described, for example, in U.S. Patent No. 4,575,330.

[0005]

[0004] Traditionally, lasers have served as optimal radiation sources in 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 a stereolithography system can be in continuous wave (CW) or Q-switched pulses. CW lasers provide continuous laser energy and can be used in high-speed scanning processes. Historically, several types of lasers with peak spectral outputs in the wavelength range of 193 nm to 355 nm have been used in stereolithography, although there are also those with other wavelengths. The light emitted from a laser is monochromatic, that is, a significant proportion of the total spectral output lies within a very narrow wavelength range. Among laser-based additive manufacturing systems in the industry, those operating at a peak spectral output of 355 nm have become the most widespread.

[0006]

[0005] However, laser-based systems, especially those operating at a peak spectral output of 355 nm or in the vicinity thereof, do not come without drawbacks. The significant power output of such laser-based systems can generate excessive heat at the irradiation point, which can be harmful to the resin. Furthermore, the use of a laser at any wavelength requires scanning point by point on the resin surface, which can be a particularly time-consuming process when the cross-sectional pattern to be cured is large or complex. Also, 355 nm laser-based systems are expensive and are associated with high maintenance costs and energy consumption.

[0007]

[0006] To counter some of the drawbacks associated with laser-based systems, in other additive manufacturing systems, image projection technology has begun to be utilized as a source of actinic radiation. An 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 non-limiting example is that developed by Texas Instruments, called Digital Light Processing (DLP (registered trademark)). The DLP system uses micromirrors, known as digital micromirror devices (DMDs), which are controlled by and fixed to a microchip and represent pixels, to selectively transmit light from an input source and project that light with a desired output pattern or mask. The DLP technology was developed for use in image projection systems as an alternative display system to LCD-based technology. Since the boundaries of the 3D object to be cured and fabricated are ultimately defined by the boundaries of the projected light, the DLP system is very useful for additive manufacturing where image resolution and accuracy are important due to its exceptional image sharpness, brightness, and uniformity associated with it. Furthermore, image projection systems such as LCDs and DLP offer an advantage in theoretical speed in that they can expose and cure an entire cross-sectional layer simultaneously. Additionally, while the curing time required in a laser-based system is directly proportional to the complexity of the cross-section being scanned, image projection systems are said to be independent of the cross-section, meaning that the exposure time for a given layer does not change with an increase in the shape complexity of any given layer. This makes image projection systems particularly well-suited for the fabrication of parts with complex and detailed geometries by additive manufacturing.

[0008]

[0007] DLP and LCD do not provide an alternative way to generate light itself, but rather provide a way to process light emitted from an existing light source into a more desirable pattern. Thus, a combined input light source is still required. The light input into the image projection system can be from a traditional lamp or, more generally, from any light source including lasers, but more commonly the input light is collimated from one or more light-emitting diodes (LEDs).

[0009]

[0008] An LED is a semiconductor device that generates light by utilizing the phenomenon of electroluminescence. Currently, LED light sources for additive manufacturing systems emit light in the wavelength range of 300 - 475 nm, with 365 nm, 375 nm, 395 nm, 401 nm, 405 nm, and 420 nm being common peak spectral outputs. For a more detailed discussion of LED light sources, see the text "Light-Emitting Diodes" published by Cambridge University Press, authored by E. Fred Schubert, 2nd edition, (Copyright) E. Fred Schubert 2006. LEDs theoretically offer the advantage of operating at near-peak efficiency over a longer duration than other light sources. Additionally, LEDs are typically more energy-efficient and have lower maintenance costs than laser-based optical systems, resulting in lower initial and ongoing ownership costs.

[0010]

[0009] Accordingly, in various additive manufacturing systems, one of the following non-limiting examples of optical arrangements is used: (1) lasers only, (2) lasers / DLP, (3) LEDs only, (4) LEDs / DLP, or (5) LEDs / 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]

[0010] In recent years, in newer additive manufacturing systems (regardless of optical configuration), light sources that emit radiation at wavelengths greater than the traditional 355 nm output have begun to be used more frequently. In other systems, there has been a shift away from single-color light sources and instead towards selecting light sources that emit light with a broader spectral output distribution. Thus, such newer systems incorporating laser / DLP-based, LED-based, LED / DLP-based, or LED / LCD-based optical configurations are beginning to operate with longer wavelength peak spectral outputs and broader spectral distributions than has been typical heretofore. The wavelengths used therein are shifted away from 355 nm and towards the visible spectrum, and some even have peak spectral outputs within the visible range. Such longer wavelengths (i.e., 375 nm - 500 nm) have heretofore been referred to as "UV / vis".

[0012]

[0011] Some of the commonly cited non-limiting reasons for the current trend of increasing use of optical systems in the UV / vis region are (1) a 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, which emit radiation of lower energy than light sources that emit more deeply within the UV region, cause less damage to human tissue, all else being equal. This makes UV / vis light sources less harmful in the event of accidental exposure than those operating more deeply within the UV region. As the popularity of additive manufacturing continues to grow among consumers, "prosumer", and industrial market segments, the need for additive manufacturing systems that use lower-cost and less hazardous chemical radiation sources for curing liquid photopolymers will become increasingly important.

[0013]

[0012] However, the advantages of using a UV / vis light source / optical system are not without significant trade - offs. To date, the biggest drawback has been the relatively great difficulty in developing photopolymers suitable for systems that utilize UV / vis optics. One of the main reasons for this is that, in addition to the natural phenomenon that light of longer wavelengths has lower energy, the intensity of commercial light sources also typically decreases with an increase in the wavelength of the peak spectral output. Thus, a traditional 355 - nm laser - based optical system can impart an irradiation dose of 1500 W / cm 2 to the resin surface, while commercial systems operating at approximately 400 nm are known to impart an irradiation dose of only about 1 / 1000 of that value to the resin surface. In fact, in existing 365 - nm or 405 - nm DLP - based commercial additive manufacturing systems, the irradiation dose at the resin surface imparted by the UV / vis optics is, in some more economical desktop units, 0.1 W / cm 2 or even as low as 0.0002 W / cm 2 . Due to these relatively reduced radiation energies / intensities, it becomes more difficult to cause a photopolymerization reaction in a radiation - curable resin using such UV / vis optics, unless the exposure time is extremely long. This, in turn, significantly increases the part build time, and as a result, the theoretical speed advantage of the photomasking display system is lost. Furthermore, there are only a few photoinitiating systems available on the market for promoting photopolymerization at such longer UV / vis wavelengths, especially cationic photoinitiating systems.

[0014]

[0013] As a result of the above - mentioned problems, the number of photopolymers available for modern optical systems operating in the UV / vis region is limited compared to the various options available for systems operating deeper in the UV region, such as 355 - nm laser - based systems.

[0015] Radical polymerizable resins for systems using UV / vis optical systems are known to exist. Such resins generally consist of one or more (meth)acrylate compounds (or other free radical polymerizable organic compounds) together with a free radical photoinitiator for radical generation. U.S. Patent No. 5,418,112 describes one such radical curing system. Radical polymerizable resins can be readily cured even under the relatively lower energy and lower intensity provided by UV / vis optical systems, but these are not suitable for all additive manufacturing applications. First, (meth)acrylate-based resins that are considered suitable for the additive manufacturing process have traditionally produced cured parts with mechanical properties that are insufficient for incorporation into many end-use applications. Thus, parts that are not sufficiently robust for non-prototyping applications are typically produced. Also, such resins exhibit deformation problems such as the production of warped parts or parts with poor shape due to residual stresses resulting from shrinkage differences during curing. These problems are exacerbated in additive manufacturing machines with larger platforms, where, as the cured object grows, the warping or poor shape of the part is amplified by the effects of the cumulative shrinkage differences. These deformation problems can be partially corrected by software that accounts for known shrinkage rates by modifying the CAD file for creating solid three-dimensional parts. However, software correction is insufficient to fully compensate for the deformation of parts having intricate complex shapes or requiring tight dimensional tolerances over long distances.

[0016] Another well-known type of resin suitable for use in an additive manufacturing system 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-radical polymerizable compound, and (4) one or more free-radical photoinitiators. Examples of such hybrid curing systems are described, for example, in U.S. Patent No. 5,434,196. Such resins have long been known to result in cured parts having superior mechanical properties compared to all-acrylate resins produced by an additive manufacturing process. Further, hybrid curing systems are superior to all-acrylate systems in that they are less affected by the shrinkage differential problems that have long plagued all-acrylate systems.

[0017]

[0016] However, the ring-opening process of cationic polymerization is generally carried out at a slower rate than free-radical polymerization and requires more activation energy, so it is inherently more difficult to ensure that such formulations for additive manufacturing applications cure properly or "build" a three-dimensional object successfully. And even if the hybrid curable resin undergoes at least partial curing after being exposed to actinic radiation, the resulting green model will have insufficient mechanical strength (or "green strength") for use in many additive manufacturing applications, as measured, for example, by modulus of elasticity or fracture strength. Such problems are significantly exacerbated by UV / vis optical systems that emit radiation of lower energy and intensity than conventional systems.

[0018]

[0017] Due to such limitations, hitherto, there has been little knowledge of hybrid liquid radiation-curable resins for additive manufacturing that are suitable for use in more modern additive manufacturing systems using UV / vis optical systems. Some are described in U.S. Patent Nos. 9,708,442 and 10,604,659 (each assigned to DSM IP Assets B.V.), but further solutions are welcome considering the wide variety of additive manufacturing systems using UV / vis optical systems.

[0019]

[0018] Therefore, it would be desirable to provide a liquid radiation-curable resin (hybrid curable or otherwise) for additive manufacturing that is suitable for use in an additive manufacturing system using a UV / vis optical system and that can also simultaneously (1) cure sufficiently rapidly and (2) impart sufficient mechanical strength and resistance to shrinkage deformation to the three-dimensional part being cured. Further or alternatively, it would be desirable to provide a hybrid curable liquid radiation resin composition suitable for use in an additive manufacturing system using a UV / vis optical system that can produce three-dimensional parts having excellent accuracy and / or mechanical properties comparable to existing hybrid curable materials designed for traditional laser-based 355 nm systems.

[0020] [Brief Summary]

[0019] Some embodiments of the present invention are described herein. According to a first aspect, the present invention includes a radiation-curable composition comprising a cationically curable component and a free-radical curable component, the composition further comprising at least a first photoinitiator that is an iodonium salt of a non-fluorinated borate anion. According to other embodiments of the first aspect, the non-fluorinated borate anion of the iodonium salt has the formula [Chemical Formula] (wherein R 1 ~R 4is independently selected from the group consisting of alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, and heteroaryl, and further, (i) one or more replaceable carbon atoms of alkyl, alkenyl, or alkynyl are optionally substituted by hydroxy, carboxy, alkoxy, alkanoyl, hydroxyalkyl, carboxyalkyl, alkoxyalkyl, or alkanoylalkyl, or (ii) one or more replaceable carbon atoms of cycloalkyl, heterocycloalkyl, aryl, or heteroaryl are optionally substituted by alkyl, hydroxy, carboxy, alkoxy, alkanoyl, hydroxyalkyl, carboxyalkyl, alkoxyalkyl, or alkanoylalkyl) has

[0021]

[0020] According to yet a further embodiment, the composition is substantially free of certain types of free radical photoinitiators such as phosphorus-containing photoinitiators, Norrish type I photoinitiators, and / or Norrish type II photoinitiators.

[0022]

[0021] According to yet a further embodiment, the composition further comprises a photosensitizer and / or a reducing agent. The reducing agent is preferably a polyfunctional vinyl ether compound containing an electron-donating substituent bonded to a vinyl group, for example, at least two vinyl groups per molecule.

[0023]

[0022] The second aspect of the claimed invention describes a method of forming a three-dimensional article by an additive manufacturing system using a UV / vis optical system, utilizing any of the compositions according to the first aspect.

[0024]

[0023] The third aspect of the claimed invention is a three-dimensional part formed according to the second aspect of the invention using the liquid radiation curable composition of the first aspect of the invention.

[0025] [Detailed Description] Throughout this specification, "UV / vis" is defined as the electromagnetic spectrum region from 375 nanometers (nm) to 500 nanometers (nm).

[0026]

[0025] Accordingly, throughout this specification, a "UV / vis optical system" is defined as any electrical, mechanical, or electromechanical system that generates and directs / dispenses actinic radiation operating at a peak spectral intensity of 375 nm to 500 nm. Specific non-limiting examples of UV / vis optical systems 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.

[0027]

[0026] Furthermore, as used herein, "substantially free of" is intended to indicate that a particular composition or component (as specified by the context) has virtually no amount by weight of a particular substance, e.g., less than 0.1 wt.%, or less than 0.05 wt.%, or preferably less than 0.01 wt%, or about 0.00 wt.% of the particular substance.

[0028]

[0027] A first embodiment of the present invention is a radiation curable composition comprising a cationically curable component and a free radical curable component, the composition further comprising at least a first photoinitiator which is an iodonium salt of a non-fluorinated borate anion.

[0029]

[0028] The composition according to the first aspect thus contains a cationically curable component, a free radical polymerizable component, and a photoinitiator. In a preferred embodiment, the composition contains both a free radical photoinitiator and a cationic photoinitiator. The composition may further contain one or more photosensitizers, reducing agents, and / or additives.

[0030] [Cationically curable component] According to an embodiment, the liquid radiation-curable resin for additive manufacturing of the present invention contains at least one cationically polymerizable component, i.e., a component that undergoes polymerization initiated by a cation or in the presence of an acid generator. The cationically polymerizable component may be a monomer, an oligomer, and / or a polymer, and may contain an aliphatic moiety, an aromatic moiety, an alicyclic moiety, an arylaliphatic moiety, a heterocyclic moiety, and any combination thereof. Preferably, the cationically polymerizable component contains at least one alicyclic compound. Suitable cyclic ether compounds can contain a cyclic ether group as a side group or as a group forming part of an alicyclic or heterocyclic ring system.

[0031]

[0030] The cationically polymerizable component is selected from the group consisting of cyclic ether compounds, cyclic acetal compounds, cyclic thioether compounds, spiro-orthoester compounds, cyclic lactone compounds, and any combination thereof.

[0032] [

[0031] ]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 the 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 novolak 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-vinyl epoxycyclohexane, 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'-epoxycyclohexanecarboxylate, methylene bis(3,4-epoxycyclohexane), bicyclohexyl-3,3'-epoxide, -O-, -S-, -SO-, -SO 2 -, -C(CH 3 ) 2 -, -CBr 2 -, -C(CBr 3 ) 2 -, -C(CF 3 ) 2 -, -C(CCl 3 )2 - or -CH(C 6 H 5)-linked bis(3,4-epoxycyclohexyl), dicyclopentadiene diepoxide, ethylene glycol bis(3,4-epoxycyclohexylmethyl) ether, ethylene bis(3,4-epoxycyclohexanecarboxylate), epoxy hexahydrodioctyl phthalate, epoxy hexahydro-di-2-ethylhexyl phthalate, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, diglycidyl esters of aliphatic long-chain dibasic acids, monoglycidyl ethers of aliphatic higher alcohols, monoglycidyl ethers of phenol, cresol, butylphenol, or polyether alcohols (obtained by the addition of alkylene oxides to these compounds), glycidyl esters of higher fatty acids, epoxidized soybean oil, epoxybutyl stearate, epoxy octyl stearate, 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, ethyldiethylene glycol(3-ethyl-3-oxetanylmethyl)ether, dicyclopentadiene(3-ethyl-3-oxetanylmethyl)ether, dicyclopentenyl oxyethyl(3-ethyl-3-oxetanylmethyl)ether, dicyclopentenyl(3-ethyl-3-oxetanylmethyl)ether, tetrahydrofurfuryl(tetrahydrofurfuyl)(3-ethyl-3-oxetanylmethyl)ether, 2-hydroxyethyl(3-ethyl-3-oxetanylmethyl)ether, 2-hydroxypropyl(3-ethyl-3-oxetanylmethyl)ether, and any combination thereof.,

[0033]

[0032] The cationic polymerizable component may optionally also contain a polyfunctional material including a dendritic polymer having an epoxy or oxetane functional group, such as a dendrimer, a linear dendritic polymer, a dendrigraft polymer, a hyperbranched polymer, a star branched polymer, and a hypergraft polymer. The dendritic polymer may contain one type of polymerizable functional group or various types of polymerizable functional groups, such as epoxy and oxetane functional groups.

[0034]

[0033] In an embodiment, the composition of the present invention also includes one or more mono- or polyglycidyl ethers of an aliphatic alcohol, an aliphatic polyol, a polyester polyol, or a polyether polyol. Examples of preferred components include 1,4-butanediol diglycidyl ether, glycidyl ethers of polyoxyethylene and polyoxypropylene glycols and triols having a molecular weight of about 200 to about 10,000; glycidyl ethers of polytetramethylene glycol or poly(oxyethylene-oxybutylene) random or block copolymers. In a particular embodiment, the cationic polymerizable component includes a polyfunctional glycidyl ether lacking a cyclohexane ring in the molecule. In another particular embodiment, the cationic polymerizable component includes neopentyl glycol diglycidyl ether. In another particular embodiment, the cationic polymerizable component includes 1,4-cyclohexanedimethanol diglycidyl ether.

[0035]

[0034] Examples of commercially available preferred polyfunctional glycidyl ethers are Erisys TM GE 22 (Erisys TM products are available from Emerald Performance Materials TM ), Heloxy TM 48, Heloxy TM 67, Heloxy TM 68, Heloxy TM 107 (Heloxy TMThe regulator is available from Momentive Specialty Chemicals) and is Grilonit® F713. Examples of commercially available preferred monofunctional glycidyl ethers are Heloxy TM 71, Heloxy TM 505, Heloxy TM 7, Heloxy TM 8, and Heloxy TM 61.

[0036]

[0035] In an embodiment, the epoxide is 3,4-epoxycyclohexylmethyl-3’,4-epoxycyclohexanecarboxylate (available from Daicel Chemical as CELLOXIDE TM 2021P, or from Dow Chemical as CYRACURE TM UVR-6105), a hydrogenated bisphenol A-epichlorohydrin based epoxy resin (available from Momentive as EPON TM 1510), 1,4-cyclohexanedimethanol diglycidyl ether (available from Momentive as HELOXY TM 107), hydrogenated bisphenol A diglycidyl ether (available from Momentive as EPON TM 825), a mixture of dicyclohexyl diepoxide and nanosilica (available as NANOPOX TM ), and any combination thereof.

[0037]

[0036] In a particular embodiment, the cationically polymerizable component is an alicyclic epoxy, such as the following formula I:

Chemical formula

[0038]

[0037] In another specific embodiment, the cationically polymerizable component includes an epoxy having an aromatic or aliphatic glycidyl ether group having two (bifunctional) or three or more (polyfunctional) epoxy groups.

[0039]

[0038] The above-described 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 includes at least two different epoxy components.

[0040]

[0039] In another embodiment of the present invention, the cationically polymerizable component also includes an oxetane component. In a specific embodiment, the cationically polymerizable component includes an oxetane, for example, an oxetane containing one, two or three or more oxetane groups. In another embodiment, the oxetane used is monofunctional and further has a hydroxyl group. According to an embodiment, the oxetane has the following structure:

Chemical formula

[0041]

[0040] When used in the composition, the oxetane component is present in an appropriate amount of about 5 to about 50 wt% of the resin composition. In another embodiment, the oxetane component is present in an amount of about 10 to about 25 wt% of the resin composition, and in yet another embodiment, the oxetane component is present in an amount of 20 to about 30 wt% of the resin composition.

[0042]

[0041] The liquid radiation-curable resin for additive manufacturing thus can include a cationically curable component in an appropriate amount, for example, in a specific embodiment, in an amount of about 10 to about 80% by weight of the resin composition, in a further embodiment about 20 to about 70 wt% of the resin composition, in a further embodiment about 25 to about 65 wt% of the resin composition, in a more preferred embodiment about 30 to about 80 wt% of the resin composition, more preferably about 50 to about 85 wt%.

[0043] [Free radical curable component]

[0042] According to an embodiment of the present invention, the liquid radiation curable resin for additive manufacturing of the present invention contains at least one free radical curable component, i.e., a component that undergoes polymerization initiated by free radicals. The free radical polymerizable component is a monomer, oligomer, and / or polymer, which are monofunctional or polyfunctional materials, i.e., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10... 20... 30... 40... 50... 100, or more functional groups that can be polymerized by free radical initiation, and may contain an aliphatic moiety, an aromatic moiety, an alicyclic moiety, an arylaliphatic moiety, a heterocyclic moiety, or any combination thereof. Examples of polyfunctional materials include dendritic polymers such as dendrimers, linear dendritic polymers, dendrigraft polymers, hyperbranched polymers, star-branched polymers, and hypergraft polymers. See, for example, U.S. Patent Application Publication No. 2009 / 0093564A1. The dendritic polymer may contain one type of polymerizable functional group or various types of polymerizable functional groups, such as acrylate and methacrylate functional groups.

[0044]

[0043] Examples of free radical curable or polymerizable components include acrylates and methacrylates, such as 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, 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, 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, polypropylene glycol mono (meth)acrylate, 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,Examples include butylcarbamoylethyl (meth)acrylate, n-isopropyl (meth)acrylamide fluorinated (meth)acrylate, 7-amino-3,7-dimethyloctyl (meth)acrylate.

[0045]

[0044] Examples of the polyfunctional free-radical polymerizable component 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-dioxan-5-yl]methyl acrylate; 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane di(meth)acrylate; dipentaerythritol monohydroxy penta(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, monophosphoric and diphosphoric (meth)acrylate, C 7 ~C 20Alkyl di(meth)acrylate, 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, tricyclodecanediyl dimethyl di(meth)acrylate, and alkoxylates of any of the foregoing monomers (e.g., ethoxylated and / or propoxylated products), further including di(meth)acrylates of diols that are ethylene oxide or propylene oxide addition products to bisphenol A, di(meth)acrylates of diols that are ethylene oxide or propylene oxide addition products to hydrogenated bisphenol A, epoxy (meth)acrylates that are (meth)acrylate addition products of diglycidyl ether to bisphenol A, diacrylates of polyoxyalkylated bisphenol A, and triethylene glycol divinyl ether, and addition products of hydroxyethyl acrylate are included.

[0046] According to an embodiment, the radically polymerizable component is a polyfunctional (meth)acrylate. The polyfunctional (meth)acrylate may include all methacryloyl groups, all acryloyl groups, or any combination of methacryloyl and acryloyl groups. In an embodiment, the free radical polymerizable component is 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, selected from the group consisting of.

[0047] In an embodiment, the polyfunctional (meth)acrylate has three or more functional groups. According to another embodiment, the polyfunctional (meth)acrylate has four or more functional groups. In yet another embodiment, the polyfunctional (meth)acrylate has five or more functional groups. In another preferred embodiment, the radically polymerizable component consists exclusively of a single polyfunctional (meth)acrylate component. In a further embodiment, the exclusive radically polymerizable component is tetrafunctional, in a further embodiment, the exclusive radically polymerizable component is pentafunctional, and in a further embodiment, the exclusive radically polymerizable component is hexafunctional.

[0048]

[0047] In another embodiment, the free-radical polymerizable component contains an aromatic (meth)acrylate. The aromatic acrylate can be derived from, as non-limiting examples, bisphenol A, bisphenol S, or bisphenol F. In certain embodiments, 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-dioxan-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 bifunctional.

[0049]

[0048] In a particular embodiment, the liquid radiation-curable resin for additive manufacturing of the present invention comprises one or more of bisphenol A diglycidyl ether di(meth)acrylate, dicyclopentadiene dimethanol di(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, and / or propoxylated neopentyl glycol di(meth)acrylate, 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.

[0050]

[0049] The above radical polymerizable compounds can be used alone or in combination of two or more thereof. The liquid radiation curable resin for additive manufacturing can be in any suitable amount, for example, in certain embodiments, up to about 50 wt% of the resin composition, in certain embodiments, about 2 to about 40 wt% of the resin composition, in other embodiments, about 5 to about 30 wt%, in further embodiments, about 10 to about 20 wt% of the resin composition, and in even more preferred embodiments, about 8 to about 50 wt%, more preferably about 15 to about 25 wt% of the resin composition, of a free radical polymerizable component.

[0051] [Photoinitiator]

[0050] In embodiments according to the present invention, the composition comprises at least one photoinitiator. A photoinitiator is a compound that chemically changes upon the action of light (or a synergistic effect between the action of light and the electronic excitation of a sensitizing dye) to produce at least one of a radical, an acid, and a base, and then that radical, acid, and / or base causes a polymerization reaction in one or more of the polymerizable substances present in the corresponding composition. According to embodiments of the first aspect of the present invention, the composition comprises a photoinitiator useful for causing polymerization in a free radical curable component, a cationic curable component, or both such components.

[0052]

[0051] A photoinitiator capable of causing polymerization of a free radical curable component (when exposed to light of a suitable wavelength and / or intensity) is a free radical photoinitiator. A photoinitiator capable of causing polymerization of a cationic curable component (when exposed to light of a suitable wavelength and / or intensity) is a cationic photoinitiator. Certain photoinitiators can function as both a free radical photoinitiator and a cationic photoinitiator, but usually at least two different photoinitiators are used for this purpose. According to embodiments, the liquid radiation curable resin composition comprises a photoinitiator system containing at least one photoinitiator having a cationic initiating functional group and at least one photoinitiator having a free radical initiating functional group. In another embodiment, the photoinitiator system can comprise a photoinitiator containing both a free radical initiating functional group and a cationic initiating functional group on the same molecule.

[0053]

[0052] In an embodiment, the liquid radiation curable resin for additional shaping of the present invention contains a free radical photoinitiator. Usually, the free radical photoinitiator includes those that form radicals by either Norrish type I or II mechanism. Such mechanisms are well known in the technical field to which the present invention is applied and are described, for example, in Parikh, A., Parikh, H., & Parikh, K. (2006). Norrish Type I and II Reaction (Cleavage). In Name Reactions in Organic Synthesis (pp. 325 - 329). Foundation Books. Such photoinitiators include those that form radicals by cleavage known as "Norrish type I" and those that form radicals by hydrogen abstraction known as "Norrish type II". Norrish type II photoinitiators require a hydrogen donor that functions as a free radical source. Since the initiation is based on a bimolecular reaction, Norrish type II photoinitiators are generally slower than Norrish type I photoinitiators based on unimolecular formation of radicals. On the other hand, Norrish type II photoinitiators have better light absorption characteristics in the near UV spectral region. The photolysis of aromatic ketones such as benzophenone, thioxanthone, benzyl, and quinone in the presence of a hydrogen donor such as alcohol, amine, or thiol results in the formation of radicals (ketyl type radicals) from the carbonyl compound and another radical derived from the hydrogen donor. The photopolymerization of vinyl monomers is usually initiated by radicals generated from the hydrogen donor. Ketyl radicals are usually not reactive towards vinyl monomers due to steric hindrance and delocalization of the unpaired electrons.

[0054]

[0053] The inventors of the present invention have now found that not all compounds suitable for use in promoting free radical polymerization, particularly in promoting the polymerization of radiation curable compositions in additive manufacturing processes utilizing UV / vis light sources, can be characterized in either of the two classifications described above. To the inventors' surprise, some photoinitiators are effective in promoting free radical polymerization (and potentially cationic polymerization as well) without utilizing a Norrish type I or II mechanism. Specific examples of such include certain iodonium salts, preferably iodonium salts of non-fluorinated borate anions. As used herein, "non-fluorinated" means containing no fluorine atoms. In addition to being non-fluorinated, the anion of the iodonium salt compound is preferably also non-halogenated. As used herein, "non-halogenated" means containing no atoms of any halogen group.

[0055]

[0054] In order to successfully formulate a liquid radiation curable resin for additive manufacturing, it is of course necessary to reexamine the wavelength sensitivity of the photoinitiator present in the resin composition to determine whether it will be activated by a radiation source selected to provide the curing light.

[0056]

[0055] However, in an embodiment, the composition has the following structure:

Chemical formula

[0056] (wherein R 1 ~R 4is independently selected from the group consisting of alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, and heteroaryl, and further, (i) one or more replaceable carbon atoms of alkyl, alkenyl, or alkynyl are optionally substituted by hydroxy, carboxy, alkoxy, alkanoyl, hydroxyalkyl, carboxyalkyl, alkoxyalkyl, or alkanoylalkyl, or (ii) one or more replaceable carbon atoms of cycloalkyl, heterocycloalkyl, aryl, or heteroaryl are optionally substituted by alkyl, hydroxy, carboxy, alkoxy, alkanoyl, hydroxyalkyl, carboxyalkyl, alkoxyalkyl, or alkanoylalkyl) comprises a iodonium salt photoinitiator.

[0057]

[0057] In an embodiment, R 1 ~R 4 is independently selected from aryl radicals optionally substituted by alkyl or alkoxy at one or more replaceable carbon atoms. More specifically, R 1 ~R 4 may be a phenyl group optionally and independently substituted by an alkyl or alkoxy group, wherein the alkyl portion of the alkyl or alkoxy group contains 1 to 10 carbon atoms.

[0058]

[0058] In an embodiment, the non-fluorinated borate anion of the iodonium salt has the following structure:

Chemical formula

[0059]

[0059] The cation of the iodonium salt of the above non-fluorinated borate anion can be of any suitable type. In an embodiment, the iodonium salt has a diaryliodonium cation. In an embodiment, the cation is a diphenyliodonium salt having two phenyl radicals optionally substituted by an alkyl or alkoxy group, where the alkyl portion of the alkyl or alkoxy group has 1 to 10 carbon atoms.

[0060]

[0060] In an embodiment, the photoinitiator has the following structure:

Chemical formula

[0061]

[0061] In an embodiment, the photoinitiator includes bis(4-cumyliodonium)tetraphenylborate or bis(4-tert-butyl Phenyl iodonium)tetraphenylborate. Such compounds are commercially available from Hampford Research as FP5041 and FP5028, respectively.

[0062]

[0062] The inventors have found that when the photoinitiator comprises, consists of, or consists essentially of one or more of the above-mentioned iodonium salt photoinitiators, when the radiation curable composition is exposed to a light source using a UV / optical system, free radical and / or cationic polymerization can be maximized. The inventors have further surprisingly found that the addition of other more well-known free radical photoinitiators may not improve (and may even inhibit) the polymerization efficacy. Thus, in embodiments, the composition according to the first aspect is substantially free of any Norrish type I photoinitiator. In another embodiment, the composition additionally or alternatively lacks any Norrish type II photoinitiator. In embodiments, the composition contains a Norrish type I and / or Norrish type II photoinitiator in an amount by weight of less than about 0.1 wt%, or less than about 0.05 wt%, or less than about 0.01 wt%, or about 0.00 wt.%.

[0063]

[0063] According to an embodiment, the liquid radiation curable resin for additive manufacturing comprises at least one free radical photoinitiator selected from the group consisting of, for example, benzoylphosphine oxide, aryl ketone, benzophenone, hydroxylated ketone, 1-hydroxy phenyl ketone, ketal, metallocene, and any combination thereof.

[0064]

[0064] Nevertheless, in some embodiments, the composition may have an additional free radical photoinitiator. In embodiments, the liquid radiation curable resin for additive manufacturing further includes, for example, 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'-methyldiphenyl sulfide, 4,4'-bis(diethylamino)benzophenone, and 4,4'-bis(N,N'-dimethylamino)benzophenone (Michler's ketone), benzophenone, 4-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, or benzyl dimethyl ketal, bis(η5-2,4-cyclopentadien-1-yl)bis[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl]titanium, and combinations of any of these, but not limited to these, at least one free radical photoinitiator.

[0065]

[0065] For light sources emitting in the wavelength range of 300 to 475 nm, particularly those emitting at 365 nm, 390 nm, or 395 nm, examples of potentially suitable free radical photoinitiators that absorb 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-yl-phenyl)-butan-1-one (Irgacure 379 from Ciba), 4-benzoyl-4'-methyldiphenyl sulfide (Chivacure BMS from Chitec), 4,4'-bis(diethylamino)benzophenone (Chivacure EMK from Chitec), and 4,4'-bis(N,N'-dimethylamino)benzophenone (Michler's ketone). Mixtures of these are also suitable.

[0066]

[0066] According to an embodiment of the present invention, the free radical photoinitiator may further include an acylphosphine oxide photoinitiator. Acylphosphine oxide photoinitiators are disclosed, for example, in U.S. Patent Nos. 4,324,744, 4,737,593, 5,942,290, 5,534,559, 6,020,528, 6,486,228, and 6,486,226. Acylphosphine oxide photoinitiators include bisacylphosphine oxide (BAPO) and monoacylphosphine oxide (MAPO). Generally, acylphosphine oxide photoinitiators have good delocalization of phosphinoyl radicals upon light irradiation, so they are preferred for use with UV / vis optical systems. However, when a non-fluorinated borate anion iodonium salt photoinitiator is used, such phosphorus-containing photoinitiators are not necessarily required and may not promote curing much or at all. Thus, in an embodiment, the composition is substantially lacking in free radical phosphorus-containing photoinitiators or contains a free radical phosphorus-containing photoinitiator in an amount by weight of less than about 0.1 wt%, preferably less than about 0.05 wt%, or preferably less than about 0.01 wt%, or about 0.00 wt.%.

[0067]

[0067] The liquid radiation curable resin for additive manufacturing can include the free radical photoinitiator described herein in any suitable amount, for example, in certain embodiments, up to about 10 wt% of the resin composition, in certain embodiments, about 0.1 to about 10 wt% of the resin composition, and in further embodiments, about 1 to about 6 wt% of the resin composition.

[0068]

[0068] According to some embodiments, the liquid radiation curable resin composition includes a cationic photoinitiator. The cationic photoinitiator initiates cationic ring-opening polymerization when irradiated with light. In a preferred embodiment, the cationic photoinitiator comprises, consists of, or consists essentially of an iodonium salt-based cationic photoinitiator.

[0069]

[0069] In an embodiment, any suitable iodonium-based cationic photoinitiator, for example, those having a cation selected from the group consisting of diaryliodonium salts, triaryliodonium salts, aromatic iodonium salts, and any combination thereof can be used.

[0070]

[0070] In another embodiment, the cation of the cationic photoinitiator is selected from the group consisting of aromatic diazonium salts, aromatic sulfonium salts, aromatic iodonium salts, metallocene compounds, aromatic phosphonium salts, acylsulfonium salts, and any combination thereof. In another embodiment, the cation is a polymeric sulfonium salt such as that described in U.S. Patent No. 5,380,923 or U.S. Patent No. 5,047,568, or other aromatic heteroatom-containing cations and naphthyl-sulfonium salts such as those described in U.S. Patent No. 7,611,817, U.S. Patent No. 7,230,122, U.S. Patent Application Publication No. 2011 / 0039205, U.S. Patent Application Publication No. 2009 / 0182172, U.S. Patent No. 7,678,528, EP2308865, International Publication No. 2010046240 Pamphlet, or EP2218715. In another embodiment, the cationic photoinitiator is selected from the group consisting of triarylsulfonium salts, diaryliodonium salts, and metallocene compounds, and any combination thereof. Onium salts, such as iodonium salts and sulfonium salts, and ferrocenium salts generally have the advantage of being more thermally stable.

[0071]

[0071] In a particular embodiment, the cationic photoinitiator is BF 4 - 、AsF 6 - 、SbF 6 - 、PF 6 - 、[B(CF 3 ) 4 - 、B(C 6 F 5 ) 4 - 、B[C 6 H​3 -3,5(CF 3 ) 2 4 - 、B(C 6 H 4 CF 3 ) 4 - 、B(C 6 H 3 F 2 ) 4 - 、B[C 6 F 4 -4(CF 3 )] 4 - 、Ga(C 6 F 5 ) 4 - 、[(C 6 F 5 ) 3 B-C 3 H 3 N 2 -B(C 6 F 5 ) 3 - 、[(C 6 F 5 ) 3 B-NH 2 -B(C 6 F 5 ) 3 - 、tetrakis(3,5-difluoro-4-alkyloxyphenyl)borate, tetrakis(2,3,5,6-tetrafluoro-4-alkyloxyphenyl)borate, perfluoroalkyl sulfonate, tris[(perfluoroalkyl)sulfonyl]methide, bis[(perfluoroalkyl)sulfonyl]imide, perfluoroalkyl phosphate, tris(perfluoroalkyl)trifluorophosphate, bis(perfluoroalkyl)tetrafluorophosphate, tris(pentafluoroethyl)trifluorophosphate, and (CH 6 B 11 Br 6 ) - 、(CH 6 B 11 Cl 6 ) - ​​​and has an anion selected from the group consisting of other halogenated carborane anions.

[0072]

[0072] Investigations on 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., U.S.A.) “Chemistry & Technology of UV & EB Formulation for Coatings, Inks & Paints”, Vol.3 (edited by P.K.T.Oldring), or J.P.Fouassier, J.Lavelee, “Photoinitiators for polymer synthesis” Wiley 2012 ISBN978 - 3 - 527 - 33210 - 6.

[0073]

[0073] In an embodiment, the cationic photoinitiator is at least SbF 6 - , PF 6 - , B(C 6 F 5 ) 4 - , [B(CF 3 ) 4 - , tetrakis(3,5 - difluoro - 4 - methoxyphenyl)borate, perfluoroalkyl sulfonate, perfluoroalkyl phosphate, tris[(perfluoroalkyl)sulfonyl]methide, and [(C 2 F 5 ) 3 PF 3 - and has a cation selected from the group consisting of aromatic sulfonium salts, aromatic iodonium salts, and metallocene - based compounds, together with an anion selected from the group consisting of those mentioned above.

[0074]

[0074] Examples of known cationic photoinitiators 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-methoxyphenyl)borate, 4-[4-(3-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium tetrakis(2,3,5,6-tetrafluoro-4-methoxyphenyl)borate, tris(4-(4-acetylphenyl)thiophenyl)sulfonium tetrakis(pentafluorophenyl)borate (Irgacure® PAG 290 from BASF), tris(4-(4-acetylphenyl)thiophenyl)sulfonium tris[(trifluoromethyl)sulfonyl]methide (Irgacure® GSID 26-1 from BASF), tris(4-(4-acetylphenyl)thiophenyl)sulfonium hexafluorophosphate (Irgacure® 270 from BASF), and HS-1 available from San-Apro Ltd.

[0075] [

[0075] ]Known cationic photoinitiators include bis[4-diphenylsulfoniumphenyl]sulfide bishexafluoroantimonate; thiophenoxyphenylsulfonium hexafluoroantimonate (available from Chitec as Chivacure 1176), tris(4-(4-acetylphenyl)thiophenyl)sulfonium tetrakis(pentafluorophenyl)borate (Irgacure® PAG 290 from BASF), tris(4-(4-acetylphenyl)thiophenyl)sulfonium tris[(trifluoromethyl)sulfonyl]methide (Irgacure® GSID 26-1 from BASF), and tris(4-(4-acetylphenyl)thiophenyl)sulfonium hexafluorophosphate (Irgacure® 270 from BASF), [4-(1-methylethyl)phenyl](4-methylphenyl)iodonium tetrakis(pentafluorophenyl)borate (available from Rhodia as Rhodorsil 2074), (4-octyloxyphenyl)phenyl iodonium hexafluoroantimonate (available from Hampford as OPPI FP 5386), 4-[4-(2-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium hexafluoroantimonate (from Adeka as SP-172), SP-300 from Adeka, and an aromatic sulfonium salt (available from San-Apro Ltd. as the monovalent sulfonium salt CPI-200K or CPI-200S, TK-1 available from San-Apro Ltd., or HS-1 available from San-Apro Ltd.) with an anion of (PF 6-m (C n F 2n+1 ) m ) - (wherein m is an integer from 1 to 5 and n is an integer from 1 to 4), alone or in a mixture.

[0076] [

[0076] ]In an embodiment of the present invention, the liquid radiation-curable resin for additive modeling contains an aromatic triarylsulfonium salt cationic photoinitiator. The use of aromatic triarylsulfonium salts in additive modeling applications is known. See U.S. Patent Application Publication No. 20120251841 (DSM IP Assets, B.V.) and U.S. Patent No. 6,368,769 (Asahi Denki Kogyo), which discuss aromatic triarylsulfonium salts with tetraarylborate anions containing 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. Complex metal halide anions such as BF 4 - , AsF 6 - , PF 6 - , and SbF 6 - -accompanied triarylsulfonium salt Ar 3 S + MXn - are disclosed in J Polymr Sci, Part A (1996), 34(16), 3231-3253.

[0077] [

[0077] ]An example of a triarylsulfonium tetrakis(pentafluorophenyl)borate cationic photoinitiator is tris(4-(4-acetylphenyl)phenyl) sulfonium tetrakis(pentafluorophenyl)borate. Tris(4-(4-acetylphenyl)phenyl) sulfonium tetrakis(pentafluorophenyl)borate is commercially known as IRGACURE® PAG-290 and is available from Ciba / BASF.

[0078] [

[0078] ]In another embodiment, the cationic photoinitiator is SbF 6- , PF 6 - , BF 4 - , (CF 3 CF 2 ) 3 PF 3 - , (C 6 F 5 ) 4 B - , ((CF 3 ) 2 C 6 H 3 ) 4 B - , (C 6 F 5 ) 4 Ga - , ((CF 3 ) 2 C 6 H 3 ) 4 Ga - It is an aromatic triarylsulfonium salt having an anion represented by trifluoromethanesulfonate, nonafluorobutanesulfonate, methanesulfonate, butanesulfonate, benzenesulfonate, or p-toluenesulfonate. Such a photoinitiator is described, for example, in U.S. Patent No. 8,617,787.

[0079]

[0079] Another cationic photoinitiator is an aromatic triarylsulfonium cation photoinitiator having an anion which is a fluoroalkyl-substituted fluorophosphate. Commercially available examples of aromatic triarylsulfonium cation photoinitiators having a fluoroalkyl-substituted fluorophosphate anion are the CPI-200 series (e.g., CPI-200K (registered trademark) or CPI-210S (registered trademark)) or the 300 series available from San-Apro Limited.

[0080] The liquid radiation curable resin composition can contain a cationic photoinitiator in any suitable amount, 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, about 2 wt% to about 10 wt% of the resin composition, and in other embodiments, about 0.1 wt% to about 5 wt% of the resin composition. In further embodiments, the amount of the cationic photoinitiator is about 0.2 wt% to about 4 wt% of the total resin composition, and in other embodiments, about 0.5 wt% to about 3 wt%.

[0081] [Sensitizer]

[0081] 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 sensitizer. The term "sensitizer" is used to refer to any substance that either increases the rate of photoinitiated polymerization or shifts the wavelength at which polymerization occurs. See the text by G. Odian, Principles of Polymerization, 3rd Edition, 1991, page 222. Substances that operate by the latter definition and are used with photoinitiators that cannot absorb light of a specific wavelength in other forms are said to operate by an "indirect excitation" mechanism with their associated photoinitiators. The Applicants have utilized this mechanism to formulate the compositions of the present invention suitable for curing by UV / vis optical systems.

[0082]

[0082] A variety of compounds including complex cyclic and condensed ring aromatic hydrocarbons, organic dyes, and aromatic ketones can be used as photosensitizers. Examples of photosensitizers include those selected from the group consisting of methanone, xanthenone, pyrenemethanol, anthracene, pyrene, perylene, quinone, xanthenone, thioxanthenone, benzoyl ester, benzophenone, and any combination thereof. Specific examples of photosensitizers include [4-[(4-methylphenyl)thio]phenyl]phenyl-methanone, 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-methylanthraquinone, 2-ethylanthraquinone, 2-tert butylanthraquinone, 1-chloroanthraquinone, 2-amylanthraquinone, thioxanthenone and xanthenone, isopropylthioxanthenone, 2-chlorothioxanthenone, 2,4-diethylthioxanthenone, 1-chloro-4-propoxythioxanthenone, methyl benzoylformate (Darocur MBF from BASF), methyl-2-benzoylbenzoate (Chivacure OMB from Chitec), 4-benzoyl-4'-methyldiphenyl sulfide (Chivacure BMS from Chitec), 4,4'-bis(diethylamino)benzophenone (Chivacure EMK from Chitec), and those selected from the group consisting of any combination thereof.

[0083]

[0083] Also, the novel mixture may also contain various photoinitiators having different sensitivities to the radiation of emission lines of different wavelengths in order to obtain better utilization of the UV light source. The use of known photoinitiators having different sensitivities to the radiation of emission lines is well known in the technical field of additive manufacturing and can be selected, for example, according to radiation sources of 351 nm, 355 nm, 365 nm, 385 nm, and 405 nm. In this regard, the various photoinitiators are advantageously selected and used at such concentrations so that equal light absorption occurs by the emission lines used.

[0084]

[0084] In an embodiment, the photosensitizer is a fluorone, for example, 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

Chemical formula

[0085]

[0085] When using a photosensitizer, other photoinitiators that absorb at shorter wavelengths can be used. Examples of such photoinitiators include benzophenones such as benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, and dimethoxybenzophenone, and 1-hydroxybenzyl phenyl ketones such as 1-hydroxycyclohexyl phenyl ketone, phenyl(1-hydroxyisopropyl)ketone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, and 4-isopropylphenyl(1-hydroxyisopropyl)ketone, benzyl dimethyl ketal, and oligo-[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone] (Esacure KIP 150 from Lamberti).

[0086]

[0086] It can be noted that some cationic photoinitiators have low absorption at favorable actinic wavelengths. For example, in an embodiment, the additive manufacturing application of interest utilizes a UV / optical system having a peak intensity at about 400 nm. For example, iodonium salts such as Rhodorsil 2074 available from Rhodia Silicones, Irgacure 250 iodonium available from Ciba, (4-methylphenyl)[4-(2-methylpropyl)phenyl]-hexafluorophosphate(1-), and UV9380c available from GE Silicones have insufficient direct absorption at the favorable wavelengths and thus require either excessive concentrations or sensitizers. Thus, triplet sensitizers such as thioxanthone and Michler's ketone may be used to absorb actinic energy and then efficiently transfer that energy to the iodonium initiator. However, some thioxanthones and Michler's ketones tend to produce orange or red colors, raising concerns about safety, and while they have significant actinic absorption at 430 nm, they are not very effective at sensitizing the photoreaction at the curing light wavelength of about 400 nm.

[0087]

[0087] However, in an embodiment, chloropropylthioxanthone (CPTX) has no significant light absorption above 500 nm and forms articles with little coloring, and thus is a suitable sensitizer for iodonium initiators, particularly for use in stereolithography.

[0088]

[0088] To reduce the concentration of the photosensitizer used in the complex and prevent adverse effects on the final physical properties of the composition that may result from a relatively high concentration of the photosensitizer, it is preferable to use a photosensitizer having a high extinction coefficient at 400 nm. For example, benzophenone can act as a triplet photosensitizer in some cases, but at the laser wavelength of a frequency tripled YAG laser (Coherent AVIA model #355-1800) operating at, for example, about 355 nm, the extinction coefficient is about 108 liters / mol·cm. On the other hand, CPTX when using the same laser at the same laser wavelength of about 400 nm has an extinction coefficient of 2585 liters / mol·cm, which is approximately X times that of benzophenone. This suggests that CPTX may require a concentration of 1 / X in the formulation to provide an equivalent light absorption effect. Therefore, the photosensitizer preferably has an extinction coefficient of 300 liters / mol·cm or more, for example, more than 1000 liters / mol·cm, preferably more than 2000 liters / mol·cm at a curing light wavelength above 380 nm, but this is not necessary.

[0089]

[0089] CPTX can be used to improve the activity of cationic photoinitiators, but the sensitizers used in combination with the above-mentioned cationic photoinitiators are not necessarily limited thereto. Various compounds including heterocyclic and fused-ring aromatic hydrocarbons, organic dyes, and aromatic ketones can be used as photosensitizers. Examples of sensitizers include those disclosed by J.V. Crivello in Advances in Polymer Science, 62, 1 (1984), and J.V. Crivello & K. Dietliker, “Photoinitiators for Cationic Polymerization” in Chemistry & technology of UV & EB formulation for coatings, inks & paints. Volume III, Photoinitiators for free radical and cationic polymerization by K. Dietliker; [edited by P.K.T. Oldring], SITA Technology Ltd, London, 1991. Specific examples include polycyclic aromatic hydrocarbons and their derivatives, such as anthracene, pyrene, perylene and their derivatives, substituted thioxanthone, α-hydroxyalkylphenone, 4-benzoyl-4'-methyldiphenyl sulfide, acridine orange, and benzoflavin.

[0090]

[0090] In an embodiment, the liquid radiation-curable composition for additive manufacturing according to the first aspect of the present invention has the following structure:

Chemical formula

[0091]

[0091] In an embodiment, the photosensitizer used is an anthracene-based photoinitiator. Such commercially available photosensitizers include Anthracure available from Kawasaki Chemical TM UVS-1101 and UVS-1331.

[0092]

[0092] 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.%.

[0093]

[0093] The liquid radiation-curable resin for additive manufacturing can contain 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 an embodiment, the above ranges are particularly suitable for use with epoxy monomers. In another embodiment, the photosensitizer can be used in an amount from about 0.05 wt% to about 2 wt% of the total composition in which it is incorporated.

[0094] [Reducing agent]

[0094] As used herein, a reducing agent is a component that loses, i.e., "donates", one or more electrons to a cationic photoinitiator component in a redox chemical reaction during the polymerization of the liquid radiation composition for additive manufacturing according to the present invention. Such a component can still be considered a reducing agent for the purposes of the present invention even if it does not have the ability to readily donate electrons until it forms free radicals after dissociation or decomposes into free radicals, or otherwise becomes excited upon exposure to actinic radiation in the UV / vis wavelength range. Thus, these can alternatively be referred to herein as "activating reducing agents".

[0095]

[0095] The photoinitiated cationic polymerization of monomers such as epoxides and vinyl ethers plays a necessary role in hybrid curing additive manufacturing applications. Since additives are used in various applications, when targeting a specific spectral sensitivity, the wavelength flexibility of photoinitiation becomes a fundamental factor in determining the curing performance of a particular formulation. Therefore, photoinitiating systems for cationic polymerization that are sensitive to longer wavelengths, such as those emitted by modern UV / vis optical systems, are becoming increasingly important. Many of the existing photoinitiating systems for cationic polymerization are based on the use of certain onium salts such as diphenyliodonium, triphenylsulfonium, and alkoxypyridinium salts. However, these salts do not absorb much (if at all) in the UV / vis spectrum unless additional chromophores are incorporated into the salt structure. Therefore, it is important to find alternative methods to synthetically extend the sensitivity range of readily available onium salts up to UV / vis wavelengths, given the fact that commercially available photoinitiators that are already designed to absorb in the UV / vis spectrum are not suitable for incorporation into hybrid curing systems for additive manufacturing for other reasons.

[0096]

[0096] This is known to be achieved using a combination of sensitizers by a mechanism called indirect excitation. Additionally, onium salts act as electron acceptors in redox reactions, each accompanied by a free radical, an electron donor compound in a charge transfer complex, and a long-lived electronic excited state of a sensitizer. Among these approaches, so-called "free radical promoted" cationic polymerization seems to be a more effective and flexible method for generating cationic species that can initiate the cationic polymerization of monomers. The overall mechanism involves the oxidation of photochemically formed radicals by an onium salt (On+) having an appropriate reduction potential: R· + ON+ → R+ (1)

[0097]

[0097] Potential reducing agents that are said to promote free radical - promoted cationic polymerization generally include, to name a few, amines, benzoin and its derivatives, o - phthalaldehyde, polysilanes, and compounds having an electron - donating substituent bonded to a vinyl group such as vinyl ether or vinyl halide, along with some of the above - mentioned free radical photoinitiators such as acylphosphine oxide.

[0098]

[0098] Amines are considered to be efficient hydrogen donors and would readily form free radicals that can reduce the relevant cationic photoinitiator by a chain - transfer mechanism. Thus, in certain embodiments, they can act as suitable reducing agents. However, since the nitrogen atoms contained therein are known to tend to inhibit the cationic polymerization reaction in other ways, care must be taken when such compounds are included in hybrid radiation - curable compositions for additive manufacturing.

[0099]

[0099] There are several systems for generating oxidative radicals in the presence of a UV / vis light source. For example, the radicals formed by irradiation of a system containing a xanthene dye and an aromatic amine can function as a reducing agent for diphenyliodonium salts. Similarly, a combination of decacarbonyl dimanganese - organic halide is an efficient reducing agent for cationic polymerization at UV / vis wavelengths when used with onium salts. Further, commercially available titanocene - type photoinitiators such as Irgacure 784 can be used as a source of reducing agents generated by irradiation with visible light.

[0100] Preferably, the reducing agent comprises, consists of, or consists essentially of a component having an electron-donating substituent bonded to a vinyl group. Such a component can further provide a mechanism for improving the cationic curing of a liquid radiation-curable composition for an additive manufacturing system using a UV / vis optical system. Such compounds, such as vinyl ethers, are avoided in many modern commercially available hybrid curable compositions that are exposed to additive manufacturing systems using traditional UV-based radiation sources due to (1) their tendency to generate excessive heat by the exothermic reaction of their rapid polymerization; and (2) their tendency to induce copolymerization and, simultaneously, non-uniform polymers, thereby resulting in three-dimensional parts having inconsistent and low physical properties. Nevertheless, including them in a composition tailored to a system that utilizes a UV / vis optical system with lower energy / intensity is desirable when used with other required components according to the present invention. Specifically, including an additional component having an electron-donating substituent bonded to a vinyl group results in synergistically improved polymerization.

[0101]

[0101] One preferred example of a component having an electron-donating substituent bonded to a vinyl group is a vinyl ether. Vinyl ethers can be formed from various starting materials such as ethers, esters, or biscarbamates, or vinyl ether-terminated (poly)urethanes or carbonates. Some non-limiting examples of each are listed below.

[0102]

[0102] 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; and polyfunctional vinyl ethers such as trimethylolethane trivinyl ether, trimethylolpropane trivinyl ether, ditrimethylolpropane tetravinyl ether, glycerol trivinyl ether, pentaerythritol tetravinyl ether, pentaerythritol divinyl ether dipentaerythritol pentavinyl ether, dipentaerythritol hexavinyl ether, ethylene oxide adducts of trimethylolpropane trivinyl ether, propylene oxide adducts of trimethylolpropane trivinyl ether, ethylene oxide adducts of ditrimethylolpropane tetravinyl ether, propylene oxide adducts of ditrimethylolpropane tetravinyl ether, ethylene oxide adducts of pentaerythritol tetravinyl ether, propylene oxide adducts of pentaerythritol tetravinyl ether, ethylene oxide adducts of dipentaerythritol hexavinyl ether, and propylene oxide adducts of dipentaerythritol hexavinyl ether.

[0103]

[0103] Vinyl ether monomers from esters or biscarbamates: Specific examples of polyfunctional vinyl ethers such as divinyl adipate, divinyl terephthalate, divinyl cyclohexyl dicaroxylate. Bis[4-(vinyloxy)butyl] adipate (VEctomer® 4060), bis[4-(vinyloxy)butyl] succinate (VEctomer® 4030), bis[4-(vinyloxy)butyl] isophthalte (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), etc.

[0104]

[0104] Vinyl ether-terminated urethane or carbonate: Specific examples of polyfunctional vinyl ethers such as polyurethanes or polycarbonates end-capped with hydroxyvinyl ethers having at least a hydroxyl group and at least a vinyl ether group in the molecule. For example, 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-cyclohexanedimethanol 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, etc.

[0105]

[0105] In a preferred embodiment, the component having an electron-donating substituent bonded to a 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.

[0106]

[0106] In another preferred embodiment, the component having an electron-donating substituent bonded to a vinyl group is polyfunctional. As used herein, "polyfunctional" means that the vinyl ether has at least two vinyl groups per molecule.

[0107]

[0107] One or more of the above-described components having an electron-donating substituent bonded to a vinyl group can be used in the composition according to the present invention in any suitable amount and can 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 bonded 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.%, and even 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 bonded to a vinyl group is present in an amount of 1 wt.% to 15 wt.%, more preferably 1 wt.% to 10 wt%, and even more preferably 3 wt.% to about 8 wt.%.

[0108] [Additive]

[0108] Stabilizers are often added to the resin composition to further prevent viscosity increase, such as viscosity increase during use in a solid image forming process. Useful stabilizers include those described in U.S. Patent No. 5,665,792. The presence of stabilizers is optional. In a particular embodiment, the liquid radiation curable resin composition for additive shaping contains 0.1 wt% to 3% stabilizer.

[0109]

[0109] Other possible additives include organic and inorganic fillers, dyes, pigments, antioxidants, wetting agents, defoaming agents, chain transfer agents, leveling agents, antifoaming agents, surfactants, etc. Such additives are known and, as will be recognized by those skilled in the art, can generally be used as desired for a particular application.

[0110]

[0110] The liquid radiation-curable resin composition for additive manufacturing of the present invention may further include one or more additives selected from the group consisting of defoaming agents, antioxidants, surfactants, acid scavengers, pigments, dyes, thickeners, flame retardants, silane coupling agents, ultraviolet absorbers, resin particles, core-shell particle impact modifiers, soluble polymers, and block polymers.

[0111]

[0111] Furthermore, many known liquid radiation-curable resin compositions for additive manufacturing use hydroxy-functional compounds to improve the properties of parts produced from the resin composition. If present, any hydroxy groups can be used for specific purposes. If present, the hydroxyl-containing material preferably contains one or more primary or secondary aliphatic hydroxyls. The hydroxyl groups can be present in the molecule or at the ends. Monomers, oligomers, or polymers can be used. The hydroxyl equivalent, i.e., the value obtained by dividing the number-average molecular weight by the number of hydroxyl groups, is preferably in the range of 31 to 5000. If present, the resin composition preferably contains one or more non-free-radical polymerizable hydroxy-functional compounds up to 10 wt%, more preferably up to 5 wt%, and most preferably up to 2 wt% based on the total weight of the resin composition.

[0112]

[0112] The second aspect of the claimed invention is a method of forming a three-dimensional article by an additive manufacturing system utilizing a UV / vis optical system, the method comprising: (1) providing a liquid radiation-curable composition for additive manufacturing according to the first aspect of the present invention; (2) installing a first liquid layer of the liquid radiation-curable resin; (3) Forming a first cured layer by imagewise exposing the first liquid layer to actinic radiation with a UV / vis optical configuration to form an imaged cross-section; (4) Forming a new layer of a 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; (6) Repeating steps (4) and (5) a sufficient number of times to build a three-dimensional article comprising, wherein the UV / vis optical system emits radiation having a peak spectral intensity of from about 375 nm to about 500 nm, more preferably from about 380 nm to about 450 nm, more preferably from about 390 nm to about 425 nm, more preferably from about 395 nm to about 410 nm.

[0113]

[0113] The liquid radiation curable composition provided in the second aspect of the present invention described above must be suitable for curing by an additive manufacturing system utilizing a UV / vis optical system. Such a composition is described in the first aspect of the present invention. In the placement of the first liquid layer or the formation of a new layer of the liquid radiation curable resin, the layer may be of any suitable thickness and shape and depends on the additive manufacturing process utilized. For example, the layer may be selectively dispensed by jetting or, as is typical in most stereolithography processes, added by dipping the already cured layer into a bath of resin to yield a layer of substantially uniform thickness. In another non-limiting embodiment, alternatively, it may be transferred by a foil, film or carrier of a predetermined thickness using a cartridge or dispenser.

[0114]

[0114] In the above, "exposure" refers to irradiation by chemical radiation. As already mentioned, the liquid radiation composition for additive shaping of the present invention described in this specification is particularly suitable for providing hybrid curing by a UV / vis optical system. In an embodiment, the UV / vis optical system utilizes one or more LEDs as a light source. In an embodiment, the light source is a laser. In an embodiment, the LED or laser light source is connected to a DLP or LCD image projection system. In an embodiment where the image projection system includes an LCD display, the light source can be configured to emit only chemical radiation with a wavelength exceeding 400 nm in order to minimize the harmful effects of UV wavelengths on the LCD components.

[0115]

[0115] The third aspect of the claimed invention is a three-dimensional part formed by the second aspect of the present invention using the liquid radiation curable composition of the first aspect of the present invention.

[0116]

[0116] The following examples further illustrate the present invention, but should of course not be construed as limiting its scope in any way.

[0117] [Examples]

[0117] These examples illustrate embodiments of the liquid radiation curable resin for additive shaping of the present invention. Table 1 describes the various components of the liquid radiation curable resin for additive shaping used in this example.

[0118]

Table 1

[0119] [Test Methods]

[0118] To measure the polymerization rate (curing rate) of each example, real-time Fourier transform infrared (FTIR) spectroscopy was used. To increase the data acquisition frequency and resolution, a cadmium telluride mercury (MCT) detector was used. Instead of the transmission mode, an attenuated total reflection (ATR) setting was used. All polymerization rate measurements were carried out using a Thermo Scientific Nicolet 8700 model. The following table shows the experimental condition settings for the measurements. Under these conditions, a total of 41 spectra were obtained for each measurement over 200 seconds.

[0120]

Table 2

[0121]

[0119] For UV / Vis light control, a Digital Light Lab LED spot lamp (wavelength 385 nm, intensity 5 mW) and a controller (AccuCure Photo Rheometer) were used. The calibration continuous mode was selected. The light intensity and duration (exposure time) were selected before the measurement.

[0122]

[0120] For the measurement, 2 - 3 drops of the selected sample were placed at the center of the ATR crystal setup. Next, a film of approximately 3 mils (±0.4 mils) was coated on top of the ATR crystal using a 3 mil (±0.4 mil) draw down bird bar. Immediately after applying the 3 mil coating, an LED lamp was held above the ATR setup and a hole was placed at the center of the hold. Next, a real-time FTIR scan was started. Once one spectrum was obtained, the light source was turned on to initiate polymerization. Based on the program input above, each spectrum was obtained every 5 seconds over a total of 200 seconds. A total of 41 spectra were obtained for each experiment.

[0123] Based on specific IR peak changes representing each functional group, the polymerization conversion rate over time was calculated. Examples of IR peak changes are shown in the above description. To calculate the conversion rate of each relevant functional group, the peak height or peak area was calculated according to the following table as necessary.

[0124]

Table 3

[0125]

[0122] Regarding the obtained raw data, the experimental cure rate procedure had 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. Therefore, it was important to remove the first 1 - 2 data points. To account for any uncertainty associated with the amount of statistical noise generated by these preliminary data points, three sets of curve fits were created for each data set. In each case, the model equation that fit the data set was Conv = a(1 - e^(-b * (time - c))). For this purpose, the raw data was fit using Microsoft Excel version 14.0.7116.5000 (32-bit) with added data analysis.

[0126]

[0123] In the first case, the entire data set (including the first two data points) was fit. In the second case, the first data point was subtracted from the entire data set and then fit. In the third case, the first and second data points were subtracted from the entire data set and then fit. In each case, the curve fit coefficient r 2 was created. The data set having the first data point with a conversion rate exceeding 1% and whose combination of curve fits resulted in an r 2 exceeding 0.90 was selected and used, and the results of the obtained curve fit equation were used for further calculation of the cure rate at 95% of the plateau conversion rate. If the curve fit coefficient r 2 was less than 0.90, the data was re-run.

[0127]

[0124] As discussed above, the data was fit to the equation Conv = a(1 - e^(-b * (time - c))). Here, "Conv" is the conversion rate % as measured by the FTIR peak ratio, time is the duration of exposure, "a" is the plateau conversion rate, "b" is the cure rate coefficient used to calculate the cure rate derived as a result, and "c" is the cure induction time derived as a result. Once the data was fit, software was used to create an experimentally derived equation with the numerical parameters of "a", "b", and "c" determined from the experimental data and the fit. In the case of cation-curable materials (i.e., epoxy and oxetane), since there is no cure induction time, "c" has no meaning. Therefore, in such cases, "c" was ignored. The variable "a" was used as the plateau conversion rate under the cure conditions used and represents the entire asymptotic range over which the component was converted. The variable "b" was used to calculate the time to 95% of the plateau conversion rate (T 95 ) of "a" by the equation T 95 = ln(.05 / b). Reported in Table 3 below are the conversion rates calculated at 100 seconds for three different polymerizable components (epoxy, oxetane, and acrylate).

[0128] [Examples 1 - 13]

[0125] First, a base resin for additive manufacturing was prepared by mixing an oxetane component, an alicyclic epoxide component, a polyol component, a glycidyl ether epoxide component, and an acrylate component according to methods well known in the art. Details of the so-called "control package" are provided in Table 2 below. The full compositions of Formulations 1 - 13 are provided in Table 3 along with the conversion rate test results using a 5mW, 385 nm UV / vis light source.

[0129]

Table 4

[0130]

Table 5

[0131] [Discussion of Results]

[0126] The data in Table 3 illustrate that various embodiments according to the present invention are suitable for promoting hybrid curing under UV / vis exposure conditions. In particular, when Formulation 1 is compared with Formulations 10 - 12, the addition of Norrish type I or II photoinitiators did not show much curing performance. In fact, the presence of phosphine-containing photoinitiators (BAPO and TPO; see Examples 10 - 11) actually decreased the curing performance.

[0132] [Additional Exemplary Embodiments]

[0127] The first additional exemplary embodiment is a. A first photoacid generator having an iodonium salt cation and a borate-containing anion lacking a fluorine atom, preferably where the cation has the following structure: [Chemical formula] (bis(4-cumyl)iodonium tetraphenylborate; CAS 1158840-74-4), or [Chemical formula] (bis(4-tert-butylphenyl)iodonium tetraphenylborate CAS 131725-16-1) and preferably having a cation with the following structure: [Chemical formula] A first photoacid generator having, and b. A second photoacid generator, preferably an iodonium salt, and c. An electron-donating substituent bonded to a vinyl group, such as a vinyl ether, and d. Optionally, a photosensitizer, and e. A polymerizable component, and f. Optionally, an additive component including one or more stabilizers A radiation-curable composition containing, wherein the composition preferably substantially lacks a free radical photoinitiator having a phosphorus atom, or substantially lacks a Norrish type I photoinitiator, or substantially lacks a Norrish type II photoinitiator.

[0133]

[0128] A first aspect of a second additional exemplary embodiment is a radiation-curable composition containing a free radical polymerizable component, a cationic polymerizable component, a free radical photoinitiator component, and a cationic photoinitiator component, wherein the free radical photoinitiator component substantially lacks a Norrish type I photoinitiator, or contains less than 0.1 wt.%, or less than 0.05 wt.%, or less than 0.01 wt.% of a Norrish type I photoinitiator.

[0134]

[0129] Another aspect of the second additional exemplary embodiment is a radiation-curable composition according to the first aspect of the second additional exemplary embodiment, wherein the free radical photoinitiator component substantially lacks a Norrish type II photoinitiator, or contains less than 0.1 wt.%, or less than 0.05 wt.%, or less than 0.01 wt.% of a Norrish type II photoinitiator.

[0135]

[0130] Another aspect of the second additional exemplary embodiment is a radiation-curable composition according to any of the previous aspects of the second additional exemplary embodiment, wherein the composition substantially lacks a Norrish type I photoinitiator, or contains less than 0.1 wt.%, or less than 0.05 wt.%, or less than 0.01 wt.% of a Norrish type I photoinitiator.

[0136]

[0131] Another aspect of the second additional exemplary embodiment is a radiation-curable composition according to any of the previous aspects of the second additional exemplary embodiment, wherein the free radical photoinitiator component consists essentially of, or consists of, one or more iodonium salt-based photoinitiators.

[0137]

[0132] Another aspect of the second additional exemplary embodiment is a radiation curable composition according to the previous aspect of the second additional exemplary embodiment, wherein the iodonium salt-based photoinitiator comprises a borate-containing anion.

[0138]

[0133] Another aspect of the second additional exemplary embodiment is a radiation curable composition according to either of the previous two aspects of the second additional exemplary embodiment, wherein the iodonium salt-based photoinitiator comprises a tetraphenylborate anion.

[0139]

[0134] Another aspect of the second additional exemplary embodiment is a radiation curable composition according to any of the previous aspects of the second additional exemplary embodiment, wherein the cationic photoinitiator component consists of, consists essentially of, or comprises one or more iodonium salt-based cationic photoinitiators.

[0140]

[0135] Another aspect of the second additional exemplary embodiment is a radiation curable composition according to any of the previous aspects of the second additional exemplary embodiment, wherein the free radical polymerizable component consists of, consists essentially of, or comprises one or more (meth)acrylate functional compounds.

[0141]

[0136] Another aspect of the second additional exemplary embodiment is a radiation curable composition according to any of the previous aspects of the second additional exemplary embodiment, wherein the cationic polymerizable component consists of, consists essentially of, or comprises one or more epoxy- and / or oxetane functional compounds.

[0142]

[0137] Another aspect of the second additional exemplary embodiment is a radiation curable composition according to any of the previous aspects of the second additional exemplary embodiment, wherein the cationic polymerizable component consists of, consists essentially of, or comprises one or more alicyclic epoxides, glycidyl ether epoxides, and / or oxetanes.

[0143] Another aspect of the second additional exemplary embodiment is a radiation curable composition according to any of the aspects preceding the second additional exemplary embodiment, further comprising a photosensitizer.

[0144] Another aspect of the second additional exemplary embodiment is a radiation curable composition according to any of the aspects preceding the second additional exemplary embodiment, further comprising a polyfunctional vinyl ether compound.

[0145] Another aspect of the second additional exemplary embodiment is a radiation curable composition according to the aspects preceding the second additional exemplary embodiment, wherein the polyfunctional vinyl ether compound has at least two vinyl groups.

[0146] Another aspect of the second additional exemplary embodiment is a radiation curable composition according to any of the aspects preceding the second additional exemplary embodiment, further comprising one or more additives.

[0147] Another aspect of the second additional exemplary embodiment is a radiation curable composition according to any of the aspects preceding the second additional exemplary embodiment, wherein, based on the weight of the entire composition, the free radical polymerizable component is present at 5 wt.% to 50 wt.%, the cationic polymerizable component is present at 20 wt.% to 90 wt.%, the free radical photoinitiator component is present at 0.025 wt.% to 5 wt.%, the cationic photoinitiator component is present at 0.5 to 8 wt.%, the additives are present at 0 to 40 wt.%, and the weights of all components are equal to 100%.

[0148] Unless otherwise specified, the term wt.% means the amount by mass of the component relative to the entire liquid radiation curable composition for additive manufacturing into which the specific component is incorporated.

[0149]

[0144] In the context of the description of the present invention (in particular, in relation to the following claims), the terms "a", "an", and "the", and the use of similar referents, should be construed to include both the singular and the plural forms, unless otherwise stated herein or the context clearly dictates otherwise. 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 a range of values herein is, unless otherwise stated herein, merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, and each separate value is incorporated herein as if it were individually recited herein. All methods described herein can be performed in any suitable order, unless otherwise stated herein or the context clearly dictates otherwise. The use of any and all examples, or exemplary language (e.g., "such as") provided herein is merely intended to better illuminate the invention and does not limit the scope of the invention unless otherwise claimed. No language in this specification should be construed as indicating that any non-claimed element is essential to the practice of the invention.

[0150]

[0145] Preferred embodiments of the invention are described herein, including the best mode known to the inventor for carrying out the invention. Variations of those 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 make use of such variations as appropriate, and the inventor intends for the invention to be practiced otherwise than as specifically described herein. Accordingly, the invention includes all modifications and equivalents of the subject matter recited in the claims as permitted by applicable law. Further, any combination of the above-described elements in all possible variations thereof is included in the invention unless otherwise stated herein or the context clearly dictates otherwise.

[0151]

[0146] Although the present invention has been described in detail and with reference to its specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the claimed invention. (Appendix 1) A radiation-curable composition containing a cation-curable component and a free-radical curable component, wherein the composition further comprises at least a first photoinitiator which is an iodonium salt of a non-fluorinated borate anion, the radiation-curable composition. (Appendix 2) The radiation-curable composition according to Appendix 1, wherein the iodonium salt of the non-fluorinated borate anion is an iodonium salt of a non-halogenated borate anion. (Appendix 3) The non-fluorinated borate anion of the iodonium salt has the formula:

Chemical formula

Chemical formula

Claims

1. A radiation curable composition for additive manufacturing, comprising a cationically curable component and a free radical curable component, wherein the cationically curable component contains at least one alicyclic compound, the free radical curable component contains at least one acrylate or methacrylate, the composition further comprises a first photoinitiator which is at least an iodonium salt of a non-fluorinated borate anion, the composition further comprises a photosensitizer, the composition contains a Norrish type I and / or Norrish type II photoinitiator in an amount of less than 0 to 0.1 wt%, a radiation curable composition.

2. The radiation curable composition according to claim 1, wherein the iodonium salt of the non-fluorinated borate anion is an iodonium salt of a non-halogenated borate anion.

3. The non-fluorinated borate anion of the iodonium salt has the formula: 【Chemical 1】 (wherein R １ ~R ４ is independently selected from the group consisting of alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, and heteroaryl, and further, (i) one or more substitutable carbon atoms of said alkyl, alkenyl, or alkynyl are optionally substituted by hydroxy, carboxy, alkoxy, alkanoyl, hydroxyalkyl, carboxyalkyl, alkoxyalkyl, or alkanoylalkyl, or (ii) one or more substitutable carbon atoms of said cycloalkyl, heterocycloalkyl, aryl, or heteroaryl are optionally substituted by alkyl, hydroxy, carboxy, alkoxy, alkanoyl, hydroxyalkyl, carboxyalkyl, alkoxyalkyl, or alkanoylalkyl) The radiation curable composition according to claim 1.

4. R １ to R ４ The radiation-curable composition according to claim 3, wherein R to R are each independently selected from aryl radicals optionally substituted by alkyl or alkoxy at one or more replaceable carbon atoms.

5. R １ to R ４ each is phenyl optionally and independently substituted by alkyl or alkoxy, and the alkyl part of the alkyl or alkoxy has 1 to 10 carbon atoms, the radiation-curable composition according to claim 4.

6. The non-fluorinated borate anion of the iodonium salt has the formula: 【Chemical Formula 2】 The radiation curable composition according to claim 5, which is a tetraphenylborate anion having the formula:

7. The radiation curable composition according to any one of claims 1 to 6, wherein the iodonium salt of the non-fluorinated borate anion has a diaryliodonium cation.

8. The diaryliodonium cation of the iodonium salt is a diphenyliodonium salt having two phenyl radicals optionally substituted by alkyl or alkoxy, and the alkyl part of the alkyl or alkoxy has 1 to 10 carbon atoms. The radiation curable composition according to claim 7.

9. The diphenyliodonium cation of the iodonium salt has the structure: 【Chemical Formula 3】 The radiation curable composition according to claim 8, which is a bis(4-cumyl)iodonium cation or a bis(4-tert-butylphenyl)iodonium cation having the formula:

10. The radiation curable composition according to any one of claims 1 to 9, wherein the first photoinitiator is bis(4-cumyl)iodonium tetraphenylborate or bis(4-tert-butylphenyl)iodonium tetraphenylborate.

11. The composition is substantially free of a free radical phosphorus-containing photoinitiator, or contains a free radical phosphorus-containing photoinitiator in an amount of less than about 0.1 wt%, preferably less than about 0.05 wt%, or preferably less than about 0.01 wt%, or about 0.00 wt.%, by weight, of the radiation curable composition according to any one of claims 1 to 10.

12. The radiation curable composition according to any one of claims 1 to 11, wherein the cation curable component contains both an alicyclic epoxy compound and an oxetane compound.

13. When the composition is exposed to a UV / vis optical system emitting radiation having a peak spectral output of 375 - 405 nm and an irradiation dose on the surface of the composition of 2 mW / cm ２ for 10 seconds, the alicyclic epoxy compound achieves a conversion rate of at least about 35%, or at least about 40%, or at least about 45%, and the oxetane compound achieves a conversion rate of at least about 40%, or at least about 45%, or at least about 50%. The radiation-curable composition according to claim 12.

14. The radiation curable composition according to any one of claims 1 to 13, wherein the first photoinitiator is present in the composition in an amount of about 0.1 wt% to about 1 wt%.

15. The radiation curable composition according to any one of claims 1 to 14, further comprising a second iodonium salt cationic photoinitiator, wherein the second iodonium salt cationic photoinitiator is present in the composition in an amount of about 0.5 wt% to about 8 wt%.

16. The radiation curable composition according to any one of claims 1 to 15, further comprising a reducing agent, wherein the reducing agent has an electron donating substituent bonded to a vinyl group.

17. The radiation curable composition according to claim 16, wherein the reducing agent comprises, consists of, or consists essentially of a vinyl ether compound, and preferably, the vinyl ether compound has at least two vinyl groups.

18. The radiation curable composition according to claim 16 or 17, wherein the photosensitizer is present in the composition in an amount by weight of about 0.05 to about 0.8 wt%, and the reducing agent is present in the composition in an amount by weight of about 1 wt% to about 10 wt%.

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