Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G75/00—Macromolecular compounds obtained by reactions forming a linkage containing sulfur with or without nitrogen, oxygen, or carbon in the main chain of the macromolecule
  • C08G75/02—Polythioethers
  • C08G75/04—Polythioethers from mercapto compounds or metallic derivatives thereof
  • C08G75/045—Polythioethers from mercapto compounds or metallic derivatives thereof from mercapto compounds and unsaturated compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y70/00—Materials specially adapted for additive manufacturing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y80/00—Products made by additive manufacturing
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F283/00—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G
  • C08F283/12—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G on to polysiloxanes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L81/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing sulfur with or without nitrogen, oxygen or carbon only; Compositions of polysulfones; Compositions of derivatives of such polymers
  • C08L81/02—Polythioethers; Polythioether-ethers
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
  • A61C13/00—Dental prostheses; Making same
  • A61C13/0003—Making bridge-work, inlays, implants or the like
  • A61C13/0006—Production methods
  • A61C13/0013—Production methods using stereolithographic techniques
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
  • A61C7/00—Orthodontics, i.e. obtaining or maintaining the desired position of teeth, e.g. by straightening, evening, regulating, separating, or by correcting malocclusions
  • A61C7/08—Mouthpiece-type retainers or positioners, e.g. for both the lower and upper arch
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
  • B29C64/10—Processes of additive manufacturing
  • B29C64/106—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material
  • B29C64/124—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using layers of liquid which are selectively solidified
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y10/00—Processes of additive manufacturing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y70/00—Materials specially adapted for additive manufacturing
  • B33Y70/10—Composites of different types of material, e.g. mixtures of ceramics and polymers or mixtures of metals and biomaterials

Definitions

• the invention relates to a process of processing a radiation-curable composition with additive-manufacturing technology, in particular by 3d-printing technology.
• the radiation-curable composition is in particular useful for producing clear-tray aligners for dental and orthodontic purposes.
• Thiol-ene based formulations for dental use are generally known.
• WO 2015/069454 (Dow Corning) describes a shear-thinning UV curable composition of mercapto-functionalized silicones in combination with a silicone based and one organic vinyl component resulting in optically clear materials.
• the application also includes a method of ink-jet printing such formulations.
• US 2017/0291357 (Fong et al.) describes thiolen/ene based inks in combination with 5 to 60 wt.% oligomeric (meth)acrylates for use in stereolithography.
• US 2017/0007362 Al (Align Technology) describes a crosslinked polymer useful in orthodontic appliances.
• the crosslinked polymer comprises a first repeating unit derived from a urethane (meth)acrylate oligomer and a second repeating unit derived from a vinyl or thiol monomer.
• US 2016/0145392 Al (TODA et al.) relates to an ene-thiol based curable composition including a certain thiol compound and an ene oligomere having an acyclic or aromatic ring structure and two more ethylenically unsatureated groups in the molecule with a number average molecular weight of 500 to 20,000 in terms of polystyrene.
• the composition can be cured by photopolymerization or thermal polymerization and is said to be useful e.g. as coating material, adhesive, sealing agent.
• US 2014/0216649 Al (Woods et al.) relates to a thiol-ene curing composition, which cure upon exposure to UV light and/or heat.
• the curable composition include a vinyl polymer bearing alkenyl or thiol terminal functional groups and a crosslinking agent having the opposing functionality.
• One object of the invention is to provide a radiation-curable composition which can be used for producing dental or orthodontic appliances such as clear tray aligners in a more efficient way, in particular by applying an additive-manufacturing technique.
• the 3-dim article obtained by the processing of the radiation-curable composition with an additive-manufacturing technique has adequate mechanical and/or physical properties.
• a high surface resolution of the obtained article would also be desirable.
• the invention features a radiation-curable composition for use as construction material in an additive-manufacturing technique comprising a radiation curing step, the radiation-curable composition comprising mercapto-functional Component A comprising at least three mercapto moieties, crosslinker Component B with at least three vinyl or allyl moieties, photo-initiator(s) Component C for initiating a curing reaction between Component A and Component B, wherein the radiation-curable composition does not comprise urethane (meth)acrylate oligomers in an amount of more than 4 wt.%.
• a further embodiment of the invention is directed to a process of producing a 3- dim article by applying an additive-manufacturing technique comprising a radiation-curing step, the radiation-curable composition comprising mercapto-functional Component A comprising at least three mercapto moieties, crosslinker Component B with at least three vinyl or allyl moieties, photo-ini tiator(s) Component C for initiating a curing reaction between Component A and Component B, wherein the radiation-curable composition does not comprise urethane (meth)acrylate oligomers in an amount of more than 4 wt.% with respect to the amount of the whole composition.
• the invention relates to a 3 -dim article obtained or obtainable by the processing of the radiation-curable composition with an additive manufacturing technique.
• the invention is also related to kit of parts comprising the radiation-curable composition described in the present text and additive-manufacturing equipment.
• the invention features the use of the radiation-curable composition described in the present text as manufacturing material in an additive-build up technique for producing dental or orthodontic appliances.
• compound or“component” is a chemical substance which has a certain molecular identity or is made of a mixture of such substances, e.g., polymeric substances.
• A“hardenable component” or“polymerizable component” is any component which can be cured or solidified in the presence of a photo-initiator by radiation-induced polymerization.
• a hardenable component may contain only one, two, three or more polymerizable groups.
• Typical examples of polymerizable groups include unsaturated carbon groups, such as a vinyl group being present i.a. in a (methyl)acrylate group.
• a “derivative” or “structural analogue” is a chemical compound showing a chemical structure closely related to the corresponding reference compound and containing all featured structural elements of the corresponding reference compound but having small modifications like bearing additional chemical groups like e.g. alkyl moieties, Br, Cl, or F or not bearing chemical groups like e.g. alkyl moieties in comparison to the corresponding reference compound. That is, a derivative is a structural analogue of the reference compound.
• a derivative of a chemical compound is a compound comprising the chemical structure of said chemical compound.
• A“monomer” is any chemical substance which can be characterized by a chemical formula, bearing polymerizable groups (including (meth)acrylate groups) which can be polymerized to oligomers or polymers thereby increasing the molecular weight.
• the molecular weight of monomers can usually simply be calculated based on the chemical formula given.
• An“oligomer” is a chemical substance composed of a low number of repeating units of monomers which are connected with each other by chemical bonds.
• the number of repeating units is typically in a range of 4 to 10 or 4 to 8.
• Polymer or “polymeric material” are used interchangeably to refer to a homopolymer, copolymer, terpolymer etc, i.e. a component being composed of a large number of repeating units of monomers. The number of repeating units is typically more than 10.
• A“mercapto moiety” means an -SH moiety.
• Alkyl means an organic radical comprising 1 to 12 or 1 to 10 or 1 to 8 or 1 to 6 carbon atoms.
• (meth)acryl is a shorthand term referring to "acryl” and/or “methacryl”.
• hardening or “curing” a composition are used interchangeably and refer to polymerization and/or crosslinking reactions including, for example, photopolymerization reactions and chemical polymerization techniques (e. g., ionic reactions or chemical reactions forming radicals effective to polymerize ethylenically unsaturated compounds) involving one or more materials included in the composition.
• chemical polymerization techniques e. g., ionic reactions or chemical reactions forming radicals effective to polymerize ethylenically unsaturated compounds
• A“powder” means a dry, bulk material composed of a large number of fine particles that may flow freely when shaken or tilted.
• A“particle” means a substance being a solid having a shape which can be geometrically determined. The shape can be regular or irregular. Particles can typically be analysed with respect to e.g. particle size and particle size distribution.
• a particle can comprise one or more crystallites. Thus, a particle can comprise one or more crystal phases.
• A“photo-initiator” is a substance being able to start or initiate the curing process of a hardenable composition in the presence of radiation, in particular light (wave length from 300 to 700 nm).
• A“transparent article” is an article being transparent, if inspected with the human eye, particularly an article which has a light transmission of at least 80 % for a path length of lmm for light having a wave length of 500 nm. So, a picture can be seen through a platelet (lmm thick) of such a transparent material.
• A“solvent” means a liquid that can dissolve a solid or liquid.
• “Additive-manufacturing” or “3d-printing” means processes comprising a radiation-curing step used to make 3-dimensional articles.
• An example of an additive- manufacturing technique is stereolithography (SLA) in which successive layers of material are laid down under computer control.
• SLA stereolithography
• the articles can be of almost any shape or geometry and are produced from a 3 -dimensional model or other electronic data source.
• dental or orthodontic appliance means any article which is to be used in the dental or orthodontic field.
• Examples of dental or orthodontic appliances include tray aligners and mouth guards.
• a dental or orthodontic appliance should not contain components which are detrimental to the patient's health and thus free of hazardous and toxic components being able to migrate out of the dental or orthodontic article.
• a material or composition is “essentially or substantially free of’ a certain component within the meaning of the invention, if the material or composition does not contain said component as an essential feature. Thus, said component is not wilfully added to the composition or material either as such or in combination with other components or ingredient of other components. Ideally the composition or material does not contain the said component at all. However, sometimes the presence of a small amount of the said component is not avoidable e.g. due to impurities.
• Ambient conditions mean the conditions which the composition described in the present text is usually subjected to during storage and handling. Ambient conditions may, for example, be a pressure of 900 to 1100 mbar, a temperature of 10 to 40 °C and a relative humidity of 10 to 100 %. In the laboratory ambient conditions are typically adjusted to 20 to 25 °C and 1000 to 1025 mbar.
• Adding an“(s)” to a term means that the term should include the singular and plural form.
• the term“additive(s)” means one additive and more additives (e.g. 2, 3, 4, etc.).
• Fig. 1 shows a 3-dim test specimen obtained by processing the radiation-curable composition described in the present text by an additive-manufacturing process.
• the radiation-curable composition can be easily processed with an additive manufacturing technique and allows the production of 3 -dim articles with adequate surface-resolution.
• the obtained 3 -dim article is essentially colourless and highly transparent.
• the obtained 3 -dim article is a polymeric substance obtained by polymerizing mercapto-functional components with vinyl or allyl-functional components, the 3 -dim article does not have a negative olfactory impression.
• the obtained 3-dim article is essentially odourless.
• the radiation-curable composition enables the practitioner to produce 3 -dim articles having beneficial physical properties, like a sufficient tensile strength and an adequate elongation at break. Clear tray aligner products should not be too elastic. Otherwise, an adequate movement of the individual teeth during the treatment process cannot be effected.
• the 3-dim article has a low water-absorbing capacity. That is, the 3-dim article does not swell if brought in contact with water. This can be beneficial, if the 3-dim article is used as dental or orthodontic appliances, in particular as clear tray aligner which should not change its physical properties over time when brought in contact with water (e.g. saliva).
• water e.g. saliva
• the radiation-curable composition can also be processed with a high 3d- printing speed.
• uncured resin can be easier removed from the surface of a 3 -dim article obtained by an additive-manufacturing technique such as SLA.
• SLA additive-manufacturing technique
• the radiation-curable composition described in the present text facilitates in particular the production of dental or orthodontic appliances with an additive- manufacturing technique, e.g. due to a higher printing speed and/or an easier and faster post processing process.
• the radiation-curable composition described in the present text does not comprise urethane (meth)acrylate oligomers in an amount of more than 4 wt.%.
• the radiation-curable composition described in the present text does not comprise urethane (meth)acrylate in an amount of more than 4 wt.%.
• urethane (meth)acylate oligomers or urethane (meth)acylate in general often has a negative impact on the overall processing time, in particular the time needed for post-processing the 3d-printed article after the printing process.
• Urethane (meth)acrylates are typically comparably high viscous substances and are more difficult to process by using e.g. SLA technology. More importantly, these materials tend to stick or adhere to the surface of the 3d-printed article, when the 3d-printed article is removed from the printing vat of the 3d-printer. Removing these materials from the surface of the 3d-printed articles is often tedious and takes time.
• compositions as described in the present text not containing urethane (meth)acrylate oligomers or urethane (meth)acrylate in an amount of more than 4 wt.% or more than 3 wt.% or 2 wt.% or 1 wt.% in an additive manufacturing process for producing 3-dim articles such as clear tray aligners is advantageous in particular from a post processing perspective.
• the radiation-curable composition comprises one or more mercapto-functional Components A.
• the mercapto-functional Component A comprises at least 3 mercapto moieties.
• mercapto-functional Component A comprising at least 3 mercapto moieties allows the formation of a higher crosslinked network after polymerization.
• mercapto-functional components can be used, if desired.
• the mercapto-functional Component A may have the formula
• R° being an organic radical which is preferably free from ethylenically unsaturated double bonds and n being an integer from 3 to 12 or 3 to 8 or 3 to 6 or 3 to 4.
• Suitable mercapto-functional components are, for example, polyoxyalkylene triols with mercaptan end moieties.
• R denotes an aliphatic hydrocarbon radical having 1-12 C-atoms and n is an integer from 1 to 25,
• R denotes an aliphatic hydrocarbon radical having 1-12 C-atoms, n is an integer 1 or 2 and m is an integer 5 or 6.
• esters of mercaptocarboxylic acids with at least trifunctional alcohols are also useful.
• Examples of this compound class are the mercaptocarboxylic acid esters of trimethylol propane and of pentaerythrite.
• the mercaptocarboxylic acids used here have carbon skeletons having 2 to 20 C-atoms, preferably 5 to 15 C-atoms.
• Suitable mercapto-functional components can also be described by the following formulas:
• X, Y, Z, and A are each independently a linear or branched C1-C3 6 alkyl or alkylene, alkenyl or alkenylene, aryl or arylene, or heteroaryl or heteroarylene moiety;
• R 1 , R 2 , R 3 , and R 4 are each independently H or CH3;
• a, b, c, and d are each independently an integer from 0 to 100;
• n is an integer from 1 to 36.
• X, Y, Z, and A is CH2 or CH2CH2; and R 1 , R 2 , R 3 , and R 4 are each H.
• mercapto-functional components include pentaerythritol tetra(3-mercaptopropionate) (PETMP), dipentaerythritol hexa(3-mercaptopropionate) (DiPETMP), trimethylol-propane tri(3-mercaptopropionate) (TMPMP), pentaerythritol tetramercaptoacetate (PETMA), trimethylol-propane trimercaptoacetate (TMPMA), ethoxylated trimethylolpropane tri(3-mercaptopropionate) (ETTMP), propyleneglycol 3- mercaptopropionate (PPGMP), tris[2-(3-mercaptopropionyloxy)ethyl
• PPGMP propyleneglycol 3-
• the mercapto-functional component can also be a mercapto-functional polyorganosiloxane(s).
• the mercapto-functional polyorganosiloxane(s) can be characterized by the following features alone or in combination:
• Mn molecular weight
• viscosity from 10 to 1,000 mPa*s or from 20 to 750 mPa*s at 23°C.
• (mercaptoalkyl)methylsiloxane units in the range of 70 to 100 are sometimes preferred.
• mercapto-functional polyorganosiloxanes comprise a high amount of mercapto moieties (e.g. in the range of 7 to 100 mol-%).
• Examples of mercapto-functional polyorganosiloxanes include poly(mercaptobutyl)methylsiloxane, poly(mercaptopropyl)methylsiloxane, poly(mercaptoethyl)methylsiloxane, poly(mercaptomethyl)methylsiloxane, co- poly(merctaptopropyl)methylsiloxane dimethylsiloxane and mixtures thereof.
• composition can also comprise polyorgansiloxane with a low amount of mercapto moieties.
• Using a mixture of two different mercapto-functional polyorgansiloxanes may help to adjust the shore hardness of the cured composition.
• Such polyorgansiloxane with a low amount of mercapto moieties are for example mercaptopropyldimethyl siloxoy end-capped polydimethylsiloxanes or copolymers according to the following formula:
• Such a polyorganosiloxane typically comprises 2 to 3 mol-% of
• the mercapto-functional Component A can typically be characterized by the following properties alone or in combination:
• the molecular weight is typically given as number average molecular weight Mn. Methods for determining the molecular weight are known to the expert. If desired, the Mn can be determined by gel permeation chromatography (GPC) using a suitable solvent (e.g. tetrahydrofuran) and an appropriate polystyrene standard.
• GPC gel permeation chromatography
• the mercapto-functional Component A is typically present in the following amount: Lower amount: at least 20 or at least 25 wt.%;
• the radiation-curable composition described in the present text comprises one or more crosslinker Components B.
• the crosslinker Component B comprises at least 3 vinyl or allyl moieties.
• Crosslinker components comprising 3 ally moieties can be preferred, as these moieties may have a higher reactivity toward the mercapto moiety of Component A compared to vinyl moieties.
• the poly-ene may for example have the following structure:
• m is at least 3, 4, 5 or 6,
• X is selected from the group consisting of
• f is an integer from 0 to 9
• R can have the meanings H, F, Cl, furyl, thienyl, pyridyl, phenyl and substituted phenyl, benzyl and substituted benzyl, alkyl and substituted alkyl, alkoxy and substituted alkoxy as well as cycloalkyl and substituted cycloalkyl and in each case may be the same or different,
• (A) is an at least trifunctional organic radical which comprises the atoms selected from the group consisting of C, O, N, S, Si and H,
• Suitable crosslinker components also include the allyl and/or vinyl esters of at least trifunctional carboxylic acids.
• Suitable as carboxylic acids for this purpose are those with carbon chains of 2 to 20 C-atoms, preferably 5 to 15 C-atoms; also well-suited are allyl and vinyl esters of aromatic tricarboxylic acids such as citric acid, tri-mesic acid and tri-mellitic acid.
• Suitable are also the allyl ethers of polyfunctional alcohols, for example polyether poly-ols, their copolymers or also copolymers of ethylene oxide and tetrahydrofuran. Preferred are sometimes the allyl ethers of trifunctional alcohols. Examples which can be named are the allyl ethers of trimethylol propane or pentaerythritol or 2,2-bis-oxyphenyl propane-bis-(diallyl phosphate).
• triallyl-functionalized compounds of the type cyanuric acid, triazine trione and the like in particular l,3,5-Triallyl-l,3,5-triazine-2,4,6(lH,3H,5H)- trione, and mixtures thereof.
• the crosslinker Component B is typically present in the following amount:
• the ratio of mercapto moieties in Component A to vinyl or allyl moieties in Component B being in the range of 1.5 : 1 to 1 : 1.5 with respect to mol;
• Component A and Component B being present in a ratio of 1.5 : 1 to 1 :l.5 with respect to weight.
• the radiation-curable composition described in the present text comprises one or more photo- initiator(s) as Component C.
• the nature and structure of the photo-initiator is not particularly limited, unless the desired result cannot be achieved.
• the photo-initiator(s) has typically a light absorption band in a wave length range from 250 to 450 nm, preferably in the range from 300 to 450 nm or from 350 to 420 nm.
• the photo-initiator is capable of generating free radicals for polymerization upon exposure to light energy having a wavelength between 250 and 450 nm.
• Photo-initiator(s) one component system where two radicals are generated by cleavage.
• Photo-initiators which can be used typically contain a moiety selected form benzoin ether, acetophenone, benzoyl oxime or acyl phosphine oxids, phenylglyoxate, ⁇ - hydroxyketones or ⁇ -aminoketones. In one embodiment, blends of at least two different photo-initiators are used.
• Exemplary UV initiators include 1 -hydroxy cyclohexyl benzophenone (available, for example, under the trade designation “OMNIRADTM 184” from IGM Resin B.V., Waalwijk, Netherlands), 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl) ketone (available, for example, under the trade designation“OMNIRADTM 2959” from IGM Resin B.V), 2-hydroxy -2-methylpropiophenone (available, for example, under the trade designation “OMNIRADTM 1173” from IGM Resin B.V.) and 2-benzyl-2-(N,N- dimethylamino)-l-(4-morpholinophenyl)-l-butanone (OMNIRADTM 369, IGM Resins B.V ).
• a particularly suitable class of photo-initiators include the class of acylphosphine oxides, as described e.g. in US 4,737,593 (Elrich et ah).
• acylphosphine oxides are of the general formula
• Preferred acylphosphine oxides are those in which the R 9 and R 10 groups are phenyl or lower alkyl- or lower alkoxy-substituted phenyl.
• R 9 and R 10 groups are phenyl or lower alkyl- or lower alkoxy-substituted phenyl.
• lower alkyl and“lower alkoxy” is meant such groups having from 1 to 4 carbon atoms.
• a preferred acylphosphine oxide is bis(2,4,6-trimethylbenzoyl)phenyl phosphine oxide (OMNIRADTM 819, IGM Resin B.V., Waalwijk, Netherlands).
• liquid blends of acylphosphine oxides with at least one other photo-initiator available e.g. as OMNIRADTM 1000, OMNIRADTM 2022, OMNIRADTM 2100 or OMNIRADTM 4265, IGM Resin B.V., Waalwijk, Netherlands).
• Tertiary amine reducing agents may be used in combination with an acylphosphine oxide.
• Illustrative tertiary amines include ethyl 4-(N,N-dimethylamino)benzoate and N,N- dimethylaminoethyl methacrylate.
• photo-initiators comprising an alpha, beta-triketon moiety or comprising an alpha-diketon dialkyl ketal moiety.
• the photo-initiator(s) is typically present in the following amounts:
• the radiation-curable composition described in the present text further comprises an UV radiation absorbing component.
• Adding an UV radiation absorbing component can be beneficial for reducing the risk of“over-curing” during the processing of the radiation-curable composition with an additive-manufacturing technique.
• Suitable UV radiation absorbing components often contain one of the following moieties: benzophenone, benzotriazole, triazine.
• Hindered amine light stabilizers can also be used, if desired.
• UV radiation absorbing components which can be used include products commercialized under the trade designations TinuvinTM, ChimasorbTM, IrgastabTM and mixtures thereof.
• UV radiation absorbing component is present in the following amounts:
• Range 0.01 to 2 or 0.05 to 2 wt.% or 0.1 to 0.5 wt.%;
• the radiation-curable composition described in the present text may further comprises filler(s).
• Adding a too high amount of filler is typically not intended as this may lead to an undesired light scattering during the curing process, in particular, if the 3-dim article is produced with an additive-manufacturing technique, such as SLA.
• a too high amount of filler may also have an undesired impact on the translucency of the 3 -dim article.
• the 3 -dim article should be sufficient translucent, so that the tooth structure to be aligned is still visible during the treatment process.
• the filler(s) comprises agglomerated nano-sized particles.
• Nano-filler(s) comprising agglomerated nano-sized particles are typically characterized by at the following features alone or in combination:
• Suitable agglomerated nanoparticles include fumed silicas such as products sold under the tradename AerosilTM e.g. AerosilTM OX-130, -150, and -200, AerosilTM R8200 available from Degussa AG, (Hanau, Germany), CAB-O-SILTM M5 available from Cabot Corp (Tuscola, Ill ), and HDKTM, e.g. HDK-H 2000, HDK H15; HDK H18, HDK H20 and HDK H30 available from Wacker.
• filler(s) there is no need for filler(s) to be present. However, if present, the filler(s) is typically present in the following amounts:
• Range 0.01 to 5 or 0.1 to 4 or 0.5 to 2 wt.%; wt.% with respect to the whole composition.
• the radiation-curable composition described in the present text may further comprise solvent(s).
• Solvents may be used for adjusting the viscosity of the radiation-curable composition or for dissolving individual components in the composition like photo initiators or stabilizers.
• Solvent(s) which can be used include polyethylene glycol (e.g. PEG 400), polypropylene glycol, co-polymers of polyethylene glycol and polypropylene glycol, dimethylformamide, butyl acetate, toluene, xylol, benzyl alcohol.
• solvent(s) there is no need for solvent(s) to be present. However, if present, the solvent(s) is typically present in the following amounts:
• Range 0.1 to 15 or 0.3 to 12 or 0.5 to 10 wt.%;
• the radiation-curable composition described in the present text may further comprise stabilize ⁇ s).
• a stabilizer may extend the shelf life of the curable composition, help prevent undesired side reactions, and adjust the polymerization process of the radiation-curable component s) present in the curable composition.
• Adding one or more stabilizer(s) to the curable composition may further help to improving the accuracy or detail resolution of the surface of the 3 -dim article to be produced.
• Stabilize ⁇ s which can be used often comprise a phenol moiety or phosphonic acid moieties.
• stabilizer(s) which can be used include: p-methoxyphenol (MOP), hydroquinone monomethylether (MEHQ), 2,6-di-tert-butyl-4-methyl-phenol (BHT; Ionol), phenothiazine, 2,2,6,6-tetramethyl-piperidine-l-oxyl radical (TEMPO) Vitamin E; N,N'-di-2-butyl-l,4-phenylenediamine; N,N'-di-2-butyl-l,4-phenylenediamine;
• 2,4,6(lH,3H,5H)trione pyrogallol; N-nitroso-N-phenylhydroxylamine; 3-propenylphenol, phenothiazine, N-Phenyl-2-naphthylamine, or mixtures thereof.
• the stabilizer(s) is typically present in the following amounts:
• Range 0.001 to 1 or 0.005 to 0.1 wt.%, or 0.01 to 0.1 wt.% with respect to the weight of the curable composition.
• the radiation-curable composition described in the present text typically is characterized by the following properties alone or in combination:
• the combination of the following features is sometimes preferred: a), b) and c) or a), c) and d).
• the properties can be determined as described in the example section.
• the radiation-curable composition typically comprises the components in the following amounts:
• Crosslinker component(s) 15 to 65 wt.%
• Photo-initiator(s) 0.01 to 2 wt.%
• UV radiation absorbing component(s) 0.01 to 2 wt.%
• Solvent(s) 0 to 15 wt.%
• Stabilizer(s) 0 to 1 wt.%.
• the radiation-curable composition described in the present text does typically not comprise the following component(s) alone or in combination:
• Pt-catalyst in an amount of more than 0.00001 wt.% calculated with respect to the weight of Pt;
• organic dye(s) in an amount of more than 0.5 wt.%
• inorganic pigment(s) in an amount of more than 0.5 wt.%
• the radiation-curable composition does not comprise the following components alone or in combination:
• urethane (meth)acrylate component(s) in an amount of more than 4 wt.% or more than 2 wt.% or more than 1 wt.%;
• (meth)acylate oligomers in an amount of more than 4 wt.% or more than 2 wt.% or more than 1 wt.%;
• (meth)acylate in an amount of more than 4 wt.% or more than 2 wt% or more than 1 wt.%;
• components comprising epoxy moieties in an amount of more than 5 wt.% or more than 2 wt.% or more than 1 wt.%.
• the radiation-curable composition can be essentially free of any of these components.
• the radiation-curable composition described in the present text can be produced by mixing the respective components, particularly under save light conditions. If desired, a speed mixer can be used.
• Component A is provided first.
• the other components are added as desired.
• the radiation-curable composition described in the present text is particularly useful for producing a 3 -dim article by processing the radiation-curable composition in an additive-manufacturing process comprising a radiation-curing step, in particular an SLA process. As a result, a transparent 3-dim article is obtained.
• Such a process typically comprises the following steps:
• Such a process comprises the step of applying radiation to the surface of a radiation- curable material, wherein the radiation is applied only to those parts of the surface which will later form a part of the article to be produced.
• Radiation can be applied by using e.g. a laser beam or by mask-image projection.
• a mask-image projection based stereolithographic process MIP-SL is sometimes preferred, as it allows a more rapid manufacturing of the article.
• An MIP-SL process can be described as follows:
• a three-dimensional digital model of the article to be produced is provided.
• the three-dimensional digital model is sliced by a set of horizontal planes.
• Each thin slice is converted into a two-dimensional mask image.
• the mask image is then projected with the aid of a radiation source onto the surface of the radiation-curable material being located in a building platform (e.g. having the shape of a vat).
• the radiation-curable material is only cured in those regions which are exposed.
• the building platform containing the radiation-curable material or the layer of cured material is moved relative to the radiation source, wherein a new layer of radiation-curable material is provided being in contact with the layer of the cured material produced in the previous step.
• Steps (iv) to (vi) are repeated until the desired article is formed.
• Projecting the mask image on the radiation-curable material can be done either top- down or bottom-up with respect to the orientation of the vat.
• Using the bottom-up technique can be beneficial as less radiation-curable material is needed.
• the radiation-curable composition described in the present text is in particular useful for processing it in a mask-image projection stereolithography process using the bottom-up projection technique.
• the 3d-printing process is typically followed by a post-processing treatment.
• the post-processing treatment typically comprises the steps of removing residues of uncured composition from the surface of the 3-dim article.
• the removal can be done, e.g. with the use of solvents like methanol, ethanol or iso propanol.
• a post-curing step might be applied to the 3 -dim article.
• Such a post-curing step may result in a 3-dim article with better physical and/or mechanical properties such as tensile strength and elongation at break.
• a post-curing step can be done with e.g. a light polymerization device such as OtoflashTM
• the radiation-curable composition described in the present text can be used for producing a 3 -dim article.
• the 3 -dim article obtained by curing the radiation-curable composition can typically be characterized by the following features alone or in combination:
• the 3-dim article is not rubber-elastic.
• a combination of the following features is sometimes preferred: a) and b); or a), b) and d); or a), b), and e); or e), f) and g).
• the above mechanical and/or physical properties refer to the 3-dim article obtained after a post-processing step has been conducted, which typically includes a cleaning and post-curing step.
• the 3 -dim article which can be produced by processing the radiation-curable composition described in the present text with an additive-manufacturing technique may have any desirable shape.
• the radiation-curable composition described in the present text is in particular useful for producing 3-dim articles having the shape of protection mask, shock absorber, seals or orthodontic and dental appliances.
• Dental or orthodontic appliances include clear tray aligners, night quards, mouth guards and parts thereof.
• Clear tray aligners can straighten a dental patient’s teeth without the need for using wires and brackets of traditional braces.
• the aligners typically consist of a sequence of clear, removable trays that fit over the teeth to straighten them.
• clear tray aligners are typically made by thermoforming.
• composition described in the present text is typically packaged in a suitable packaging device.
• the curable composition described in the present text is typically stored in container.
• Suitable containers include vessels, foil bags, cartridges, etc.
• the volume of the respective containers is not particularly limited, but is typically in a range of 2 to 200,000 ml or 5 to 100,000 ml or 10 to 50,000 ml.
• the invention also relates to a kit of parts comprising the radiation-curable composition described in the present text and either of the following components alone or in combination:
• additive-manufacturing equipment preferably selected from a stereolithographic printer
• Embodiment 1 is a diagrammatic representation of Embodiment 1 :
• a radiation-curable composition for use as construction material in an additive- manufacturing technique comprising a radiation-curing step for producing dental clear tray aligners as described in any of the preceding claims, the radiation-curable composition comprising
• mercapto-functional Component A comprising at least 3 mercapto moieties, crosslinker Component B with at least 3 vinyl or allyl moieties,
• photo-initiator(s) component C for initiating a curing reaction between Component A and Component B, the photo-initiator comprising a phosphine-oxide moiety,
• the radiation-curable composition not comprising urethane (meth)acrylate in an amount of more than 4 wt.%, wt.% with respect to the weight of the whole composition,
• the radiation-curable composition having a viscosity less than 100 Pa*s at 23°C.
• a radiation-curable composition for use as construction material in an additive manufacturing technique comprising a radiation-curing step, the radiation-curable composition comprising
• mercapto-functional Component A comprising at least 3 mercapto moieties, crosslinker Component B with at least 3 vinyl or allyl moieties,
• photo-initiator(s) component C for initiating a curing reaction between Component A and Component B, the photo-initiator comprising a phosphine-oxide moiety,
• the radiation-curable composition not comprising urethane (meth)acrylate in an amount of more than 4 wt.%, wt.% with respect to the weight of the whole composition,
• the ratio of mercapto moieties to vinyl or allyl moieties being in the range of 1.5 : 1 to 1 : 1.5 with respect to mol
• Embodiment 3 the radiation-curable composition having a viscosity less than 50 Pa*s at 23°C.
• a radiation-curable composition for use as construction material in an additive manufacturing technique comprising a radiation-curing step, the radiation-curable composition comprising
• mercapto-functional Component A comprising at least 3 mercapto moieties, crosslinker Component B with at least 3 vinyl or allyl moieties,
• photo-initiator(s) component C for initiating a curing reaction between Component A and Component B, the photo-initiator comprising a phosphine-oxide moiety,
• the radiation-curable composition not comprising (meth)acrylate oligomer(s) in an amount of more than 4 wt.%, wt.% with respect to the weight of the whole composition,
• the ratio of mercapto moieties to vinyl or allyl moieties being in the range of 1.5 : 1 to 1 : 1.5 with respect to mol
• the radiation-curable composition having a viscosity less than 50 Pa*s at 23°C.
• Embodiment 4 is a diagrammatic representation of Embodiment 4:
• a radiation-curable composition for use as construction material in an additive- manufacturing technique comprising a radiation-curing step, the radiation-curable composition comprising
• mercapto-functional Component A comprising at least 3 mercapto moieties, crosslinker Component B with at least 3 vinyl or allyl moieties,
• photo-initiator(s) component C for initiating a curing reaction between Component A and Component B, the photo-initiator comprising a phosphine-oxide moiety,
• the radiation-curable composition not comprising (meth)acrylate in an amount of more than 4 wt.%, wt.% with respect to the weight of the whole composition,
• the ratio of mercapto moieties to vinyl or allyl moieties being in the range of 1.5 : 1 to 1 : 1.5 with respect to mol
• Embodiment 5 the radiation-curable composition having a viscosity less than 50 Pa*s at 23°C.
• a 3 -dim article having the shape of a dental clear tray aligner comprising a polymer obtained by polymerizing a radiation-curable composition with the aid of an additive-manufacturing technique comprising a radiation step,
• the radiation-curable composition comprising
• mercapto-functional Component A comprising at least 3 mercapto moieties, crosslinker Component B with at least 3 vinyl or allyl moieties,
• photo-initiator(s) component C for initiating a curing reaction between Component A and Component B, the photo-initiator comprising a phosphine-oxide moiety,
• UV radiation absorbing component in an amount of 0.01 to 2 wt.%
• the radiation-curable composition not comprising urethane (meth)acrylate oligomer(s) in an amount of more than 4 wt.%, wt.% with respect to the weight of the whole composition,
• the ratio of mercapto moieties to vinyl or allyl moieties being in the range of 1.5 : 1 to 1 : 1.5 with respect to mol
• the radiation-curable composition having a viscosity less than 100 Pa*s at 23°C, the 3 -dim article being characterized by the following features:
• the viscosity can be measured at 23 °C using a ThermoHaake Rotovisco 1 device with a plate/plate system (diameter 20 mm) and a slit of 0.1 mm.
• the viscosity values (Pa*s) and share stress values (Pa) can be recorded for each share rate (starting from 10 l/s to 100 l/s in 10 l/s steps. For each share rate, a delay of 5 seconds was used before collecting data.
• the above-mentioned method of measurement corresponds essentially to DIN 53018-1.
• the glass transition temperature can be determined by means of
• the water absorption can be measured according to ISO 62:2008-05. This test is modified to meet the requirements in the application of 3d-printed articles in dentistry by fully curing and not drying the specimens. Instead of drying the specimens are stored in 50% rel. humidity and 23°C for 24 hours.
• the pastes were filled into a brass mould and section-wise light-cured on both sides at 23 °C using a curing light with 395 nm LED and a power of 630 mW/cm 2 .
• the specimens were removed directly after the end of light-curing and put into an OtoflashTM device under argon atmosphere for 1000 flashes.
• the measurements were performed at a Crosshead speed of 200mm/min.
• a test specimen as shown in Fig. 1 was prepared according the following general procedure:
• Compositions are processes in a DLP/SLA 3D-printer (Rapid Shape S30) at room temperature (23°C) and 50% humidity to produce test specimen to check the detail accuracy of the resulting printed elastomers.
• the specimens are cleaned in an ultrasonic bath filled with iso-propanol for 5 min and post-processed using an OtoflashTM light polymerization chamber at 2000 flashes in argon atmosphere.
• the light exposure times are varied though the printing process of the test specimen.
• test specimen - determined by the number of sharp printed edges visible - was sufficient, a proper light exposure time can be selected for further printing of 3d articles.
• the design of the test specimen showed several edges and notches of different width and height.
• the printability of a composition in an SLA process was rated by the number of clearly visible edges of the printed test specimen according to Table 1.
• the test specimen had the dimensions 25x6mmx20mm and consisted of edges and notches of constantly reducing size and distance to each other from 2.0x2.0mm to 1.0x0.04mm. A sample of such a test specimen is shown in Fig. 1.
• the amount of liquid residue on the printed articles is measured.
• the material to be tested is filled into a round plastic mould having an inner diameter of l5mm and a thickness of l,5mm.
• the mould is covered with clear PET foils and light cured for 20 seconds from both sides using a curing light containing 395nm LED with a power of 630mW/cm 2 .
• the specimen is removed from the mold and the weight of the specimen is determined on an analytical scale ( ⁇ 0.0002g).
• the specimen is placed into the liquid material to be tested so that it is fully covered by liquid for 20sec.
• the specimen is then removed from the liquid and held vertically in an upright position for lmin ⁇ 2sec. to let the residue liquid drop of the specimen.
• the mass of the specimen including the residual liquid is measured and the amount of the residual liquid is calculated in grams.
• All Compositions can be mixed at ambient conditions on a magnetic stirrer for 30min. Afterwards the Mixtures are homogenized in a Vacuum- Speedmixer DAC600-V for 4min under Vacuum.
• Example CE3 The material in Example CE3 was too elastic to be measured according to tensile strength measurement described herein.

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• 2019
  • 2019-05-20 EP EP19735631.4A patent/EP3797128B1/en active Active
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• 2023
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