Curable composition for producing a transparent dental orthodontic attachment

Abstract

The present invention relates to a curable composition comprising a (meth)acrylate not containing a urethane moiety, a urethane (meth)acrylate, a photoinitiator, and discrete filler particles surface-treated with a silane surface treatment agent selected from a silane surface treatment agent having an average particle size in the range of 10 to 40 nm and containing a (meth)acrylate moiety, a silane surface treatment agent not containing a (meth)acrylate moiety, and a mixture of both, wherein the discrete filler particles are present in an amount of 20% by weight or more, the curable composition further contains an additive, and the curable composition does not contain, either alone or in combination, aggregates of nano-sized particles, agglomerates of nano-sized particles, and fumed silica, each in an amount of 2% by weight or more, and the weight % is based on the curable composition.

Description

Technical Field

[0001] The present invention relates to a curable composition that can be processed in a layered manufacturing process and can be used to produce a highly transparent dental orthodontic attachment for use in dental aligner therapy.

Background Art

[0002] In today's dental aligner therapy, dental orthodontic attachments are used to support tooth movement.

[0003] Currently, photocurable composite materials are used to fabricate these dental orthodontic attachments.

[0004] Based on existing color tones and formulations, dental orthodontic attachments are typically visible on the tooth surface and may detract from the overall aesthetics of aligner therapy.

[0005] Furthermore, since dental orthodontic attachments must fit the surface of the patient's individual teeth, the dental orthodontic attachments need to be custom manufactured. This is often very cumbersome.

[0006] WO 2021 / 130624 (A1) (3M), for example, describes articles, systems, and techniques for manufacturing dental orthodontic attachments by a layered manufacturing process and positioning the attachments on the tooth surface using a transfer tray.

[0007] WO 2019 / 048963 (A1) (3M) relates to a radiation curable composition comprising a radiation curable component, a photoinitiator, and a filler material having a particulate population in an amount of 50 wt% or more of the printable composition. The particulate population exhibits a median diameter (D50) of 0.3 micrometers or more on a volume average basis.

[0008] WO 2019 / 104072 (A1) (3M) describes a dental orthodontic article comprising a curable composition comprising a reaction product of a free-radically polymerizable resin comprising at least one monomer, oligomer and / or polymer comprising at least two (meth)acrylate moieties, a monofunctional reactive diluent, and a polymer comprising a free-radical photoinitiator group.

[0009] US 9,795,541 (B2) (Fontein et al.) relates to the use of a free-radically curable composition comprising a chain and / or cyclic and / or cage polysiloxane substituted by free-radically polymerizable groups and having at least three silicon atoms and / or their mixed forms, a disiloxane substituted by free-radically polymerizable groups, optionally one, two, three or more free-radically curable monomers having no silicon atoms, a filler, an initiator and / or a catalyst for free-radical polymerization, and also further customary additives, in a stereolithography (SL) and digital light processing (DLP) process, preferably in a laminated manufacturing method. SUMMARY OF THE INVENTION

[0010] Accordingly, there is a need for a curable composition that can be processed using a laminated manufacturing process and is suitable, for example, for manufacturing customized dental orthodontic attachments for use in dental aligner therapy.

[0011] It is desirable that the curable composition has a pleasant aesthetics in the patient's oral cavity.

[0012] Ideally, the curable composition should not be milky white and should have appropriate physical-mechanical properties.

[0013] Furthermore, if possible, the curable composition should also have sufficient wearing comfort and be easy to clean.

[0014] One or more of these objects can be achieved by the invention described in this specification and the claims.

[0015] In one embodiment, the invention features a curable composition as described in the claims and this specification, the curable composition including a (meth)acrylate without a urethane moiety, a urethane (meth)acrylate, a photoinitiator, an additive, and discrete nano-sized filler particles surface-treated with a silane surface treatment agent selected from a silane surface treatment agent having an average particle size in the range of 10 to 40 nm and including a (meth)acrylate moiety, a silane surface treatment agent not including a (meth)acrylate moiety, and a mixture of both, the discrete nano-sized filler particles being present in an amount of 20 wt% or more, and the curable composition not including, in an amount of 2 wt% or more each, aggregates of the nano-sized filler particles, agglomerates of the nano-sized filler particles, and fumed silica, the amounts in wt% being relative to the entire composition.

[0016] In particular, the curable composition described in this specification does not include a polymerizable component including only one (meth)acrylate moiety in an amount of 1 wt% or more in wt% relative to the curable composition, and does not include filler particles other than those described above in an amount of 2 wt% or more each.

[0017] In another embodiment, the invention relates to a cured composition obtainable by curing the curable composition described in the claims and this specification, preferably by processing the curable composition in a stereolithography process.

[0018] Another embodiment of the present invention relates to a curable composition for use in a method of aligning teeth, the method comprising attaching the curable composition described in the claims and this specification to the surface of the teeth located in the patient's oral cavity with the aid of a dental positioning tray, removing the dental positioning tray, and inserting a dental aligner tray into the patient's oral cavity, the dental aligner tray engaging with the curable composition attached to the surface of the teeth, the curable composition having the shape of a dental orthodontic attachment, the dental orthodontic attachment having a transparency measured in the range of 60 - 85% by light having a wavelength in the range of 400 - 700 nm in a 1 mm thick sample, a flexural strength measured to be in the range of 50 - 200 MPa according to ISO 4049 (2019), and comprising (meth)acrylate without a urethane moiety, urethane (meth)acrylate, and surface-treated discrete filler particles in an amount of 20 - 50% by weight.

[0019] In a further embodiment, the present invention relates to a process for manufacturing a dental orthodontic attachment, the process comprising processing the curable composition described in the claims and this specification by a stereolithography process.

[0020] Yet another embodiment of the present invention is directed to a kit of parts comprising a dental positioning tray, at least one curable composition described in the claims and this specification, or at least one cured composition described in the claims and this specification, and optionally a dental aligner tray.

[0021] Unless otherwise defined, for the purposes of this specification, the following terms shall have the meanings described below.

[0022] The term "compound" or "component" refers to a chemical substance having a specific molecular identity or a mixture of such substances, for example a polymeric substance.

[0023] The "hardenable or curable or polymerizable component" is any component that can be cured or solidified by radiation-induced polymerization in the presence of a photoinitiator. The curable component may contain only one, two, or three or more polymerizable groups. Typical examples of polymerizable groups include, among others, unsaturated carbon groups such as vinyl groups present in (methyl) acrylate groups.

[0024] As used herein, "(meth)acryl" is an abbreviation that refers to "acryl" and / or "methacryl". For example, the "(meth)acryloxy" group is an abbreviation that refers to either an acryloxy group (i.e., CH2=CH-C(O)-O-) and / or a methacryloxy group (i.e., CH2=C(CH3)-C(O)-O-).

[0025] The "urethane group" is a group having the structure "-NH-CO-O-".

[0026] As used herein, "curing" or "hardening" of a composition is used interchangeably and refers to a polymerization and / or crosslinking reaction that includes, for example, a photopolymerization reaction and chemical polymerization techniques (e.g., an ionic reaction or chemical reaction that forms radicals effective for polymerizing ethylenically unsaturated compounds) in which one or more materials contained in the composition are involved.

[0027] "Radiation curable" shall mean that a component (or in some cases, a composition) can be cured by the application of radiation, preferably electromagnetic radiation having a wavelength in the optical spectrum of 350 - 500 nm, under ambient conditions and within an appropriate time frame (e.g., within about 15, 10, or 5 minutes).

[0028] "Dental article" means an article used in the field of dentistry or orthodontics. Dental articles typically have an outer surface and an inner surface, which are two different surface portions. The outer surface is typically a surface that does not permanently contact the tooth surface. In contrast, the inner surface is the surface used to attach or fix the dental article to the tooth. When the dental article has the shape of a dental crown, the inner surface typically has a concave shape, while the outer surface typically has a convex shape. Dental articles shall not contain components that are harmful to the health of the patient and thus shall not contain harmful and toxic components that can leak from dental or orthodontic articles.

[0029] Examples of "orthodontic articles" include orthodontic brackets, orthodontic attachments, buccal tubes, lingual retainers, orthodontic bands, bite openers, buttons, and cleats, particularly orthodontic brackets and orthodontic attachments.

[0030] "Particle" means a substance that is a solid having a geometrically determinable shape. The shape may be regular or irregular. Particles can typically be analyzed, for example, with respect to particle size and particle size distribution.

[0031] "Agglomerated" describes a weak association of particles that are normally held together by charge or polarity and can be broken down into smaller entities. The specific surface area of the agglomerated particles does not essentially deviate from the specific surface area of the primary particles that make up the aggregate (see DIN 53206; 1972).

[0032] Agglomerated fillers are commercially available, for example, from Degussa, Cabot Corp or Wacker under the product names Aerosil (trademark), CAB-O-SIL (trademark) and HDK.

[0033] "Non-agglomerated or discrete filler particles" means that the filler particles are present in the resin in a discrete, non-associated (i.e., non-agglomerated and non-coagulated) state. If desired, this can be demonstrated by TEM electron microscopy.

[0034] Non-aggregated nano-sized silica is commercially available, for example, from Nalco Chemical Co. (Naperville, Ill.) under the product names NALCO (trademark) COLLOIDAL SILICAS, such as NALCO (trademark) products #1040, 1042, 1050, 1060, 2327, and 2329.

[0035] For example, a non-aggregated filler is used and described in U.S. Patent No. 8,329,776 (B2) (Hecht et al.). The content of this reference is incorporated herein by reference.

[0036] As used herein, "agglomerated" describes a strong association of particles that are often bound together, for example, by residual chemical treatment or partial sintering. The specific surface area of agglomerated particles is typically smaller than that of the primary particles that make up the agglomerate (see DIN 53206; 1972).

[0037] "Additive manufacturing" or "3D printing" means a method that includes creating an object layer by layer from digital data. The article can be in almost any shape or geometry and is created from a three-dimensional model or other electronic data source.

[0038] There are many 3D printing technologies, one of which is vat polymerization that uses a radiation curing process to create three-dimensional articles. Examples of vat polymerization technologies include stereolithography (SLA) and digital light processing (DLP).

[0039] "Stereolithography" is an example of an additive manufacturing technique and typically uses two motors to aim a laser beam across the printing area, thereby hardening the printing resin. This method breaks the design down into a series of points, one layer at a time.

[0040] "Digital light processing" is another example of a stereolithography technique and typically involves the use of a digital projector screen to flash an image of each layer across the entire build platform of a stereolithography unit. The images are typically composed of square pixels, resulting in layers formed from small rectangular bricks called voxels.

[0041] If the calculated opalescence value OP meets the following conditions, the article is considered "opalescent": OP = [(ClEa T * -ClEa R * ) 2 +(ClEb T * -CIEb R * ) 2 1 / 2 = 3 to 15, wherein (CIEa T * -CIEa R * ) is the difference between the transmission mode and the reflection mode in the red-green coordinate a * , and (CIEb T * -CIEb R * ) is the difference between the transmission mode and the reflection mode in the yellow-blue coordinate b * .

[0042] The degree of opalescence can be quantified by colorimetric spectrophotometry using CIE standards (see U.S. Patent No. 6,232,367 (Kobashigawa et al.)).

[0043] "Ambient conditions" means the conditions to which the compositions described herein are normally exposed during storage and handling. The ambient conditions may be, for example, a pressure of 900 to 1,100 mbar, a temperature of 10 to 40 °C, and a relative humidity of 10 to 100%. In the laboratory, the ambient conditions are typically adjusted to 20 to 25 °C and 1,000 to 1,025 mbar (at sea level).​

[0044] As used herein, the terms "a", "an", "the", "at least one", and "one or more" are used interchangeably. Also, in this specification, the recitation of a numerical range by endpoints includes all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0045] Appending "(s)" to a term means that the term should include both the singular and plural forms. For example, the term "additive(s)" means one additive and more than one (e.g., two, three, four, etc.) additives.

[0046] Unless otherwise indicated, all numbers representing amounts of ingredients, measured values of physical properties, etc., as described below and used in this specification and the claims, should be understood to be modified in all instances by the term "about".

[0047] The terms "comprise" or "contain" and variations thereof do not have a limiting meaning when these terms are recited in this specification and the claims. "Consisting essentially of" means that certain additional ingredients, i.e., ingredients that do not substantially affect the essential properties of the article or composition, may be present. "Consisting of" means that no additional ingredients should be present. The term "comprise" shall also include the terms "consist essentially of" and "consists of".

[0048] When a composition does not contain a particular component as an essential feature, the composition is "essentially or substantially free of" the above component. Therefore, the above component is not intentionally added to the composition as such, or in combination with other components or constituents of other components. A composition that is essentially free of a particular component usually contains no amount of that component. However, for example, due to impurities contained in the raw materials used, the presence of a small amount of the above component may be unavoidable. "Essentially free of" typically means a content of less than 1, 0.5 or 0.1% by weight.

Brief Description of the Drawings

[0049]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0050] <L The compositions and methods described herein have been found to have several advantageous properties.

[0051] The curable composition can be processed in a stereolithography process, i.e., the curable composition is 3D printable.

[0052] Furthermore, since the filler particles are in a discrete stage, the curable composition and the cured composition are highly transparent. <L

[0053] The cured composition is also typically not milky white, which can further improve transparency.

[0054] This is advantageous as the composition can be more easily processed and cured in a stereolithography process and enables 3D printing of small and delicate structures such as orthodontic articles.

[0055] Accordingly, the composition can be used to manufacture orthodontic articles that can later be attached to the surface of teeth.

[0056] If desired, the orthodontic article can be inserted into a positioning tray and applied to the surface of the teeth.

[0057] Furthermore, due to its transparency or translucency and the absence of opalescence, the cured composition is very aesthetic, and the orthodontic articles produced therefrom are hardly visible on the surface of the teeth.

[0058] In addition, the article obtained or obtainable after curing of the curable composition has advantageous mechanical properties, particularly advantageous mechanical properties with respect to flexural strength, modulus of elasticity and / or deformation.

[0059] It has also been found that the curable composition enables the production of a cured composition or article having a smooth surface. When the article has the shape of an orthodontic attachment used in a patient's oral cavity, this can provide a kind of "soft touch" effect and increase the comfort of wearing.

[0060] The smooth surface is also easy to clean and thus contributes to avoiding contamination and discoloration of the dental attachment over time.

[0061] The curable composition described herein can be characterized as a one-component photocurable composition.

[0062] The curable composition has the following characteristics: viscosity: <50 Pa·s at a shear rate of 1 s⁻¹ at 23 °C; or 1 - 50 Pa·s at a shear rate of 1 s⁻¹ at 23 °C -1 at a shear rate of <50 Pa * s; or 23 °C, 1 s -1 at a shear rate of 1 - 50 Pa* within the range of less than s; curable by radiation having a wavelength in the range of 350 to 500 nm or 350 to 420 nm, and can be further characterized alone or in combination.

[0063] It has been found that the viscosity of the curable composition within the above range is particularly suitable for processing the curable composition in the additive manufacturing process.

[0064] Due to high transparency, there is little light scattering, enabling the easy manufacture of highly delicate articles.

[0065] The curable composition contains one or more (meth)acrylate components that do not contain a urethane moiety.

[0066] The urethane-free (meth)acrylate(s) is / are different from urethane (meth)acrylate, for example, with respect to functionality, chemical moiety, molecular weight, or a combination thereof.

[0067] The urethane-free (meth)acrylate component can typically be characterized by the following properties: containing at least two (meth)acrylate moieties; molecular weight (Mw): 170 to 1,000 g / mol, alone or in combination.

[0068] Examples include di- or poly-acrylates and methacrylates such as glycerol diacrylate, glycerol triacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, 1,3-propanediol diacrylate, 1,3-propanediol dimethacrylate, trimethylolpropane triacrylate, 1,2,4-butanetriol trimethacrylate, 1,4-cyclohexanediol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, sorbitol hexaacrylate, bis[1-(2-acryloxy)]-p-ethoxyphenyldimethylmethane, bis[1-(3-acryloxy-2-hydroxy)]-p-propoxyphenyl-dimethylmethane; copolymerizable mixtures of acrylic monomers such as bis-acrylates and bis-methacrylates of polyethylene glycol with a molecular weight of 200 to 500 g / mol, such as those described in U.S. Patent No. 4,652,274, and acrylic oligomers such as those described in U.S. Patent No. 4,642,126; and vinyl compounds such as diallyl phthalate, divinyl succinate, divinyl adipate, and divinyl phthalate.

[0069] Preferred ethylenically unsaturated monomers are methacrylate and acrylate monomers, for example, di(meth)acrylates of propanediol, butanediol, hexanediol, octanediol, nonanediol, decanediol, and eicosanediol, di(meth)acrylates of ethylene glycol, polyethylene glycol, and polypropylene glycol, di(meth)acrylates of ethoxylated bisphenol A, for example, 2,2'-bis(4-(meth)acryloxy-tetraethoxyphenyl)propane, and (meth)acrylamide. The monomers used can further be esters of [alpha]-cyanoacrylic acid, crotonic acid, cinnamic acid, and sorbic acid.

[0070] Bis[3[4]-methacryloxy-methyl-8(9)-tricyclo[5.2.1.02,6 It is also possible to use methacrylic acid esters such as those mentioned in U.S. Patent No. 4,795,823 (Schmitt et al.) containing decylmethyltriglycolate. Particularly preferred are 2,2-bis-4(3-methacryloxy-2-hydroxypropoxy)phenylpropane (Bis-GMA), 2,2-bis-4(3-methacryloxypropoxy)phenylpropane, triethylene glycol dimethacrylate (TEGDMA), and bis-hydroxymethyltricyclo-(5.2.1.0 2,6 ) decane di(meth)acrylate.

[0071] The (meth)acrylate component without a urethane moiety is typically present in the following amounts: at least 20% by weight, or at least 25% by weight, or at least 30% by weight; or at most 75% by weight, or at most 70% by weight, or at most 65% by weight; or 20 - 75% by weight, or 25 - 70% by weight, or 30 - 65% by weight, where the % by weight is based on the total composition.

[0072] The curable composition contains one or more urethane (meth)acrylates. The urethane (meth)acrylate typically contains at least two (meth)acrylate moieties and at least two urethane moieties.

[0073] The molecular weight (Mw) of the urethane (meth)acrylate is at least 400 g / mol, or at least 800 g / mol, or at least 1,000 g / mol. Useful ranges include 400 - 3,000 g / mol, or 800 - 2,700 g / mol, or 1,000 - 2,500 g / mol.

[0074] The urethane (meth)acrylate used in the composition is typically obtained by reacting an NCO-terminated compound with suitable monofunctional (meth)acrylate monomers such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, preferably hydroxyethyl and hydroxypropyl methacrylate.

[0075] Urethane (meth)acrylate can be obtained by many methods known to those skilled in the art.

[0076] For example, a polyisocyanate and a polyol can be reacted to form an isocyanate-terminated urethane prepolymer, which can then be reacted with a (meth)acrylate such as 2-hydroxyethyl (meth)acrylate. These types of reactions can be carried out at room temperature or higher temperatures, optionally in the presence of a catalyst such as a tin catalyst or a tertiary amine.

[0077] The polyisocyanate that can be used to form the isocyanate-functional urethane prepolymer can be any organic isocyanate having at least two free isocyanate groups. Aliphatic, cycloaliphatic, aromatic, and cycloaliphatic (araliphatic) isocyanates are included.

[0078] Any of the known polyisocyanates such as combinations of alkyl and alkylene polyisocyanates, cycloalkyl and cycloalkylene polyisocyanates, and alkylene and cycloalkylene polyisocyanates can be used.

[0079] Preferably, a diisocyanate having the formula X(NCO)2 is used, where X represents an aliphatic hydrocarbon radical having 2 to 12 carbon atoms, a cycloaliphatic hydrocarbon radical having 5 to 18 carbon atoms, an aromatic hydrocarbon radical having 6 to 16 carbon atoms, and / or a cycloaliphatic hydrocarbon radical having 7 to 15 carbon atoms.

[0080] Examples of suitable polyisocyanates include 2,2,4-trimethylhexamethylene-1,6-diisocyanate, hexamethylene-1,6-diisocyanate (HDI), cyclohexyl-1,4-diisocyanate, 4,4'-methylene-bis(cyclohexyl isocyanate), 1,1'-methylenebis(4-isocyanato)cyclohexane, isophorone diisocyanate, 4,4'-methylenediphenyl diisocyanate, 1,4-tetramethylene diisocyanate, meta- and para-tetramethylxylylene diisocyanate, 1,4-phenylene diisocyanate, 2,6- and 2,4-toluene diisocyanate, 1,5-naphthylene diisocyanate, 2,4'- and 4,4'-diphenylmethane diisocyanate, and mixtures thereof.

[0081] It is also possible to use highly functional polyisocyanates known from polyurethane chemistry or modified polyisocyanates containing, for example, carbodiimide groups, allophanate groups, isocyanurate groups and / or biuret groups. Particularly preferred isocyanates are isophorone diisocyanate, 2,4,4-trimethyl-hexamethylene diisocyanate and highly functional polyisocyanates having an isocyanurate structure.

[0082] The isocyanate-terminated urethane compound is capped with a (meth)acrylate to produce a urethane (meth)acrylate compound. Generally, any (meth)acrylate-type capping agent having a terminal hydroxyl group and also having an acrylic moiety or a methacrylic moiety (the methacrylic moiety is preferred) can be used.

[0083] Examples of suitable capping agents include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, glycerol di(meth)acrylate and / or trimethylolpropane di(meth)acrylate. Particularly preferred are 2-hydroxyethyl methacrylate (HEMA) and / or 2-hydroxyethyl acrylate (HEA).

[0084] The equivalent ratio of the compound reactive with respect to the isocyanate group to the isocyanate group is 1.1:1 to 8:1, preferably 1.5:1 to 4:1.

[0085] The isocyanate polyaddition reaction can be carried out in the presence of a catalyst known from polyurethane chemistry, such as an organotin compound such as dibutyltin dilaurate or an amine catalyst such as diazabicyclo[2.2.2]octane. Further, the synthesis can be carried out in the melt or in a suitable solvent that can be added before or during the preparation of the prepolymer. Suitable solvents are, for example, acetone, 2-butanone, tetrahydrofuran, dioxane, dimethylformamide, N-methyl-2-pyrrolidone (NMP), ethyl acetate, alkyl ethers of ethylene and propylene glycol, and aromatic hydrocarbons. The use of ethyl acetate as the solvent is particularly preferred.

[0086] Suitable examples of urethane (meth)acrylate include 7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazhexadecane-1,16-dioxy-dimethacrylate (e.g., Plex 666-1, Rohm), urethane (meth)acrylate derived from 1,4 and 1,3-bis(1-isocyanato-1-methylethyl)benzene (e.g., those described in European Patent Application Publication No. 0934926 (A1)), and mixtures thereof.

[0087] According to one embodiment, the urethane (meth)acrylate is characterized as follows: Structure A-(-S1-U-S2-MA) n having A is a connector element containing at least one unit, S1 is a spacer group containing at least four units connected to each other, S2 is a spacer group containing at least four units connected to each other, The units of A, S1 and S2 are independently CH3-, -CH2-, -O-, -S-, -NR 1 -, -CO-, -CR 1 =,

[0088]

Chemical formula

[0089] According to one embodiment, the urethane (meth)acrylate has the following structure: A(-S1-U-S2-MA) n [wherein, A is a connector element containing at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 units, S1 consists of units connected to each other and is a spacer group containing at least 4, 5, 6, 7, 8, 9 or 10 units, S2 consists of units connected to each other and is a spacer group containing at least 4, 5, 6, 7, 8, 9, 10, 12, 15, 20 or 25 units, U is a urethane group that connects spacer groups S1 and S2, MA is an acrylate or methacrylate group, n is represented by 3 to 6 or 4 to 6 or 5 to 6.

[0090] It may be preferable if A has a cyclic structure and contains at least about 6 units.

[0091] It may be more preferable if S1 has a linear or branched structure and contains at least 4 or 6 units.

[0092] It may be more preferable if S2 has a linear or branched structure and contains at least 6 or 8 units.

[0093] Urethane (meth)acrylate in which A has a cyclic structure and contains at least 6 units, S1 has a linear structure and contains at least 4 units, S2 has a linear structure and contains at least 8 units, and U is a urethane group may also be preferable.

[0094] The atoms of the urethane group connecting S1 and S2 and the atoms of the (meth)acrylic group do not belong to the spacer group S1 or S2. Therefore, the atoms of the urethane group are not counted as units of the spacer group S1 or S2.

[0095] The nature and structure of the connector element are not particularly limited. The connector element can contain saturated (without double bonds) or unsaturated (at least one or two double bonds) units, aromatic or heteroaromatic units (aromatic structures containing atoms including N, O, and S).

[0096] Specific examples of the connector element A having a cyclic structure include the following:

[0097]

Chemical formula

[0098] [ka] Specific examples of connector elements A that are acyclic but have a branched structure include the following:

[0099] [ka]

[0100] [ka]

[0101] [ka]

[0102] [ka]

[0103] [ka]

[0104] [ka]

[0105] [ka]

[0106] [ka]

[0107] [ka]

[0108]

Chem.

[0109] The dotted line indicates the bond to the spacer group S1.

[0110] The nature and structure of the spacer group S1 or S2 are not particularly limited either.

[0111] The spacer group is composed of units connected to each other. Typical units include CH3-, -CH2-, -O-, -S-, -NR 1 -, -CO-, -CR 1 =,

[0112]

Chem.

[0113] These units can form linear, branched or cyclic structures such as alkyl, cycloalkyl, aryl, ester, urethane or amide groups.

[0114] The structure of S1 can be the same as that of S2. However, in some embodiments, the structure of S1 is different from S2. In a specific embodiment, the number of units present in S1 is less than or equal to the number of units present in S2.

[0115] In a specific embodiment, S1 can have a saturated hydrocarbon structure.

[0116] In another specific embodiment, S2 can have a saturated hydrocarbon structure.

[0117] Typical examples of useful spacer groups for S1 include:

[0118] [ka]

[0119] [ka]

[0120] [ka]

[0121] [ka]

[0122] [ka]

[0123] [ka]

[0124] [ka]

[0125] The dotted lines indicate chemical bonds to either group A or group U.

[0126] Typical examples of useful spacer groups for S2 include:

[0127] [ka]

[0128] [ka]

[0129]

Chem.

[0130] The dotted line indicates a chemical bond to either the (meth)acrylate group or group U. The number of units counted according to the present invention is given in parentheses.

[0131] Specific examples of urethane (meth)acrylates include the following:

[0132]

Chem.

[0133] More preferred urethane (meth)acrylates can be based on alpha-omega terminal poly(meth)acrylatdiols (such as those described in European Patent No. 1242493 (B1)), or can be polyester, polyether, polybutadiene or polycarbonate urethane (meth)acrylates (such as those described in U.S. Patent No. 6,936,642 (B2)).

[0134] The urethane (meth)acrylate is typically present in the following amounts: at least 5 wt%, or at least 8 wt%, or at least 10 wt%; or at most 25 wt%, or at most 20 wt%, or at most 15 wt%; or 5 - 25 wt%, or 8 - 20 wt%, or 10 - 15 wt%, where the wt% is based on the total composition.

[0135] The (meth)acrylate that does not contain a urethane moiety is typically used in weight excess over the (meth)acrylate that contains a urethane moiety.

[0136] (Meth)acrylate not containing urethane moiety) / (Meth)acrylate containing urethane moiety) ratio is usually in the range of 10 / 1 to 2 / 1 by weight.

[0137] The curable composition contains a photoinitiator. If desired, one or more photoinitiators can be used.

[0138] In order to process the curable composition in the additive manufacturing process, the photoinitiator should have a light absorption peak in the range of 350 to 500 nm.

[0139] Suitable photoinitiators include acylphosphine oxides.

[0140] Acylphosphine oxides are represented by the following formula: (R 9 )2-P(=O)-C(=O)-R 10 [Wherein each R 9 may each independently be a hydrocarbyl group such as alkyl, cycloalkyl, aryl, and aralkyl, which may each be substituted with a halo group, an alkyl group, or an alkoxy group, or two R 9 groups may combine to form a ring with the phosphorus atom, and R 10 is a hydrocarbyl group, an S, O, or N-containing 5- or 6-membered heterocyclic group, or a -Z-C(=O)-P(=O)-(R 9 )2 group (wherein Z represents a divalent hydrocarbyl group such as alkylene or phenylene having 2 to 6 carbon atoms)] and can be characterized by.

[0141] Suitable systems are also described, for example, in U.S. Patent No. 4,737,593 (Ellrich et al.), the content of which is incorporated herein by reference.

[0142] Preferred acylphosphine oxides are R 9 and R 10The base is phenyl or lower alkyl or phenyl substituted with lower alkoxy. "Lower alkyl" and "lower alkoxy" mean such groups having 1 to 4 carbon atoms. In particular, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Lucirin™ TPO, BASF) has been found to be useful.

[0143] More specific examples include bis-(2,6-dichlorobenzoyl)phenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-4-ethoxyphenyl-phosphine oxide, bis-(2,6-dichlorobenzoyl)-4-biphenylylphosphine oxide, bis-(2,6-dichloro-benzoyl)-4-propylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-2-naphthylphosphine oxide, bis-(2,6-dichlorobenzoyl)-1-naphthylphosphine oxide, bis-(2,6-dichlorobenzoyl)-4-chlorophenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-2,4-dimethoxyphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)decylphosphine oxide, bis-(2,6-dichlorobenzoyl)-4-octylphenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-phenylphosphine oxide, bis-(2,4,6-trimethylbenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dichloro-3,4,5-trimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dichloro-3,4,5-trimethoxybenzoyl)-4-ethoxyphenylphosphine oxide, bis-(2-methyl-1-naphthoyl)-2,5-dimethyl-phenylphosphine oxide, bis-(2-methyl-1-naphthoyl)phenylphosphine oxide, bis-(2-methyl-1-naphthoyl)-4-biphenylylphosphine oxide, bis-(2-methyl-1-naphthoyl)-4-ethoxyphenylphosphine oxide, bis-(2-methyl-1-naphthoyl)-2-naphthylphosphine oxide, bis-(2-methyl-1-naphthoyl)-4-propylphenylphosphine oxide, bis-(2-methyl-1-naphthoyl)-2,Examples include 5-dimethylphosphine oxide, bis-(2-methoxy-1-naphthoyl)-4-ethoxyphenylphosphine oxide, bis-(2-methoxy-1-naphthoyl)-4-biphenylylphosphine oxide, bis-(2-methoxy-1-naphthoyl)-2-naphthylphosphine oxide, and bis-(2-chloro-1-naphthoyl)-2,5-dimethylphenylphosphine oxide.,

[0144] The acylphosphine oxide bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (formerly known as IRGACURE™ 819 from Ciba Specialty Chemicals) may be preferred in some cases.,

[0145] Suitable photoinitiators also include binary and ternary photoinitiator systems. Typical ternary photoinitiators include iodonium salts, photosensitizers, and electron donor compounds as described in U.S. Patent No. 5,545,676 (Palazzotto et al.). Suitable iodonium salts include diaryliodonium salts such as diphenyliodonium chloride, diphenyliodonium hexafluorophosphate, and diphenyliodonium tetrafluoroborate. Suitable photosensitizers are monoketones and diketones. Particularly suitable photosensitizers include alpha-diketones. Examples include camphorquinone, benzil, 3,3,6,6-tetramethyl-cyclohexanedione, 1-phenyl-1,2-propanedione, and other 1-aryl-2-alkyl-1,2-ethanediones, as well as cyclic alpha-diketones. Suitable electron donor compounds include substituted amines. In particular, tertiary amines are commonly used.,

[0146] In addition to the photoinitiator, a reducing agent may be present. The combination of a photoinitiator and a reducing agent is often referred to as a photoinitiator system. As the reducing agent or donor component, tertiary amines are commonly used.,

[0147] Suitable examples of the tertiary amine include N,N-dimethyl-p-toluidine, N,N-dimethylaminoethyl methacrylate, triethanolamine, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, methyldiphenylamine, and isoamyl 4-dimethylaminobenzoate.

[0148] The photoinitiator is typically present in the following amounts: at least 0.01 wt%, or at least 0.02 wt%, or at least 0.03 wt%; or at most 5 wt%, or at most 4 wt%, or at most 3 wt%; or 0.01 - 5 wt%, or 0.02 - 4 wt%, or 0.03 - 3 wt%, where the wt% is based on the weight of the composition.

[0149] The curable composition contains discrete nano-sized filler particles.

[0150] The average particle size of the discrete nano-sized filler particles is 40 nm or less, or 35 nm or less, or 30 nm or less. The average particle size is typically in the range of 10 - 40 nm, or 10 - 35 nm, or 10 - 30 nm.

[0151] The discrete nano-sized filler particles typically include oxides of Si, Zr, Al and mixtures thereof, and oxides of Si and Zr may be preferred in some cases.

[0152] The specific surface area (BET) of the nano-sized filler particles is preferably 80 m 2 / g or more, or 100 m 2 / g or more, or 120 m 2 / g or more. The specific surface area (BET) is typically in the range of 80 - 500 m 2 / g, or 100 - 400 m 2 / g, or 120 - 300 m 2 / g. If desired, the specific surface area can be determined according to Brunauer, Emmet and Teller (BET) by using an apparatus (Monosorb (trademark)) available from Quantachrome.

[0153] Preferred nano-sized silica is commercially available from Nalco Chemical Co. (Naperville, IL) under the product name NALCO (trademark) COLLOIDAL SILICAS. For example, preferred silica particles can be obtained using NALCO (trademark) products 1040, 1042, 1050, 1060, 2327, and 2329. Other suitable nano-sized silica is commercially available from Covestro (Leverkusen, Germany) under the product name Dispercoll (trademark) (e.g., Dispercoll (trademark) S 3030 or Dispercoll (trademark) S 4020), from Grace GmbH & Co. KG (Worms, Germany) under the product name Ludox (trademark) (e.g., Ludox (trademark) P-X30 or Ludox (trademark) P-W30), and from Nouryon (Amsterdam, Netherlands) under the product name Levasil (trademark) (e.g., Levasil (trademark) CS50-34P).

[0154] The discrete nano-sized filler particles are surface-treated. A useful surface treatment agent is silane.

[0155] The silane surface treatment agent can contain a polymerizable moiety, particularly a (meth)acrylate moiety, or may not contain a polymerizable moiety. Only one silane surface treatment agent or a mixture of different silane treatment agents can be used.

[0156] In a specific embodiment, a mixture of a silane surface treatment agent containing a polymerizable moiety, particularly a (meth)acrylate moiety, and a silane surface treatment agent not containing a polymerizable moiety is used.

[0157] The surface treatment can enable easier dispersion of the nano-sized filler particles in the monomer matrix and prevent sedimentation of the filler from the formulation during storage.

[0158] When the surface treatment is carried out using two different silane surface treatment agents, the polymerizable silane surface treatment agent is used in a higher amount with respect to weight as compared to the non-polymerizable silane surface treatment agent.

[0159] It has been found that the ratio of the polymerizable silane surface treatment agent to the non-polymerizable silane surface treatment agent in the range of 90 / 10 to 60 / 40 or 80 / 20 to 70 / 30 with respect to weight is useful.

[0160] If desired, the surface of the treated particles can be analyzed using FT-IR or NMR techniques.

[0161] The polymerizable silane surface treatment agent is usually an alkoxysilane, preferably a trialkoxysilane containing a (meth)acrylate group.

[0162] Typical embodiments are represented by the following formula: A m BSi(R 1 ) n (OR 2 ) 3-n [wherein A contains a (meth)acrylic moiety, B contains a spacer group such as (i) a linear or branched C1-C 12 alkyl, (ii) a C6-C 12 aryl, (iii) an organic group having 2 to 20 carbon atoms bonded to each other by one or more ether, thioether, ester, thioester, thiocarbonyl, amide, urethane, carbonyl and / or sulfonyl bonds, R 1 contains an alkyl group (e.g., C1-C6) or an aryl group (e.g., C6-C 12 ), R 2 contains an alkyl group (e.g., C1-C6), m = 1, 2 or 3 and n = 0, 1 or 2].

[0163] Examples of (meth)acrylate-functionalized trialkoxysilanes include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropyltris(methoxyethoxy)silane, 3-(meth)acryloxypropenyltrimethoxysilane, (meth)acryloxyethyldimethyl(3-trimethoxysilylpropyl)ammonium chloride, N-(3-(meth)acryloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane, O-((meth)acryloxyethyl)-N-(triethoxysilylpropyl)-urethane, (meth)acryloxy-methyltrimethoxysilane, (meth)acryloxymethyltriethoxysilane, (meth)acryloxymethylmethyldimethoxysilane, (meth)acryloxymethylmethyldiethoxysilane, (meth)acryloxyoctyltrimethoxysilane, [(meth)acryloxymethyl]phenethyltrimethoxysilane, O-[(meth)acryloxyethyl]-N-(triethoxysilylpropyl)carbamate, (meth)acryloxypropyltriisopropoxysilane, (meth)acryloxypropylmethyldimethoxysilane, (meth)acryloxypropylmethyldiethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, (meth)acryloxymethyldimethyldimethoxysilane, (meth)acryloxymethyldimethyldiethoxysilane, oligomeric hydrolyzates of 3-(meth)acryloxypropyltrimethoxysilane, oligomeric hydrolyzates of 3-(meth)acryloxypropyltriethoxysilane, but are not limited thereto.

[0164] The non-polymerizable silane surface treatment agent is usually an alkoxysilane, preferably a trialkoxysilane.

[0165] A typical embodiment is the following formula: DSi(R 1 ) n (OR 2 ) 3-n [wherein, D is (i) a linear or branched unsubstituted or substituted (e.g., by one or more amino or mercapto groups) C1-C 16 alkyl, (ii) an unsubstituted or substituted (e.g., by one or more amino or mercapto groups) C6-C 12 aryl group, or (iii) an organic group having 2 to 20 carbon atoms bonded to each other by one or more ether, thioether, ester, thioester, thiocarbonyl, amide, urethane, carbonyl and / or sulfonyl bonds, R 1 is an alkyl group (e.g., C1-C6) or an aryl group (e.g., C6-C 12 ), R 2 is an alkyl group (e.g., C1-C6), n = 0, 1 or 2].

[0166] Suitable non-polymerizable silane surface treatment agents include phenyltrimethoxysilane, phenyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, hexadecyltrimethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, propyltrimethoxysilane, 3-aminopropyl-methyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-cyclohexyl-3-aminopropyltrimethoxysilane, 3-ureidopropyltrimethoxysilane, (cyclohexyl)methyldimethoxysilane, and mixtures thereof.

[0167] Polymerizable and non-polymerizable silane surface treatment agents are commercially available, for example, under the product name Geniosil (trademark) from Wacker (Munchen, Germany), or under the product name Dynasylan (trademark) from Evonik (Hanau, Germany).

[0168] A process for surface treating discrete nano-sized filler particles typically comprises the following steps: A step of mixing a sol containing nano-sized particles with a silane surface treatment agent and stirring the mixture in a solvent such as ethanol under reflux for several hours (e.g., 2 to 10 hours). After stirring for several hours (e.g., 2 to 10 hours), a step of stirring again for several hours (e.g., 2 to 10 hours) while mixing a monomer into the obtained mixture. A step of removing the solvent under vacuum is included.

[0169] A suitable process is also described in U.S. Patent No. 6,899,948 (Zhang et al.).

[0170] The curable composition does not contain filler particles other than those described herein, each in an amount of 2% by weight or more.

[0171] In particular, the following filler components: aggregates of nano-sized filler particles; agglomerates of nano-sized filler particles; fumed silica do not exist either alone or in combination, and the average particle size of the primary filler particles is in the range of 10 to 40 nm.

[0172] Therefore, the curable composition essentially does not contain fillers including clusters of nano-sized filler particles, fumed silica, and mixtures thereof.

[0173] It has been found that the presence of these filler components can have an undesirable effect on rheology, transparency and / or opacity.

[0174] The discrete nano-sized filler particles are typically present in the following amounts: at least 20% by weight, or at least 25% by weight, or at least 30% by weight; or at most 50% by weight, or at most 45% by weight, or at most 40% by weight; or 20 to 50% by weight, or 25 to 45% by weight, or 30 to 40% by weight, and the weight percentages are based on the entire composition.

[0175] Using such amounts of filler typically contributes to the physical-mechanical properties of the composition, especially in its cured state.

[0176] The curable composition typically also contains one or more additives.

[0177] Possible additives include stabilizers, fluorescent dyes, UV light absorbers, and mixtures thereof.

[0178] Suitable stabilizers include free radical scavengers such as substituted and / or unsubstituted hydroxyaromatic compounds (e.g., butylated hydroxytoluene (BHT), hydroquinone, hydroquinone monomethyl ether (MEHQ), 3,5-di-tert-butyl-4-hydroxyanisole (2,6-di-tert-butyl-4-ethoxyphenol), 2,6-di-tert-butyl-4-(dimethylamino)methylphenol or 2,5-di-tert-butylhydroquinone, 2-(2'-hydroxy-5'-methylphenyl)-2H-benzotriazole, 2-(2'-hydroxy-5'-t-octylphenyl)-2H-benzotriazole, 2-hydroxy-4-methoxybenzophenone (UV-9), 2-(2'-hydroxy-4',6'-di-tert-pentylphenyl)-2H-benzotriazole, 2-hydroxy-4-n-octoxybenzophenone, 2-(2'-hydroxy-5'-methacryloxyethylphenyl)-2H-benzotriazole, phenothiazine, and HALS (hindered amine light stabilizer).

[0179] Suitable fluorescent dyes often contain an anthracene or perylene moiety.

[0180] The fluorescent dye typically has an absorption peak in the range of 350 to 450 nm.

[0181] Commercially available fluorescent dyes include, for example, Lumilux™ Blau LZ, Lumilux™ Gelb LZ, and dyes containing an anthracene moiety (e.g., 2-ethyl-9,10-dimethoxyanthracene; EDMO).

[0182] When present, the fluorescent dye is typically present in an amount of 0.001 to 0.5% by weight based on the weight of the composition.

[0183] Suitable UV light absorbers include components containing a benzotriazole moiety.

[0184] The UV absorber typically has an absorption peak in the range of 350 to 420 nm.

[0185] Commercially available UV light absorbers include Tinuvin™ 326, Tinuvin™ 328, Tinuvin™ P, and Uvinul™ M40.

[0186] When present, the UV light absorber is typically present in an amount of 0.001 to 1.0% by weight based on the weight of the composition.

[0187] The additives are typically present in the following amounts: at least 0.001% by weight, or at least 0.01% by weight, or at least 0.1% by weight; or at most 10% by weight, or 7.5% by weight, or 5% by weight; or 0.001 to 10% by weight, or 0.01 to 7.5% by weight, or 0.1 to 5% by weight, and the % by weight is based on the entire composition.

[0188] The curable composition described herein typically comprises the following components: a polymerizable component containing an acidic moiety in an amount of 1% by weight or more; a polymerizable component containing only one (meth)acrylate moiety in an amount of 1% by weight or more; and no plasticizer, either alone or in combination, where the % by weight is based on the weight of the curable composition. Thus, the curable composition essentially does not contain these components.

[0189] For example, if a polymerizable component containing only one (meth)acrylate moiety is present in an amount of 1% by weight or more, it may have an undesirable effect on mechanical properties such as the elastic modulus. A composition containing a polymerizable component containing only one (meth)acrylate moiety in an amount of 1% by weight or more may be considered to be too flexible.

[0190] The curable composition described in this specification typically contains each component in the following amounts: Methacrylate without urethane moiety: 20 - 75% by weight, Urethane (meth)acrylate: 5 - 25% by weight, Photoinitiator: 0.01 - 5% by weight, Discrete surface-treated nano-sized filler particles: 20 - 50% by weight, Additives: containing 0.001 - 10% by weight, or consisting essentially of, or consisting of, and the weight is based on the whole composition.

[0191] The curable composition also contains each component in the following amounts: Methacrylate without urethane moiety: 25 - 70% by weight, Urethane (meth)acrylate: 8 - 20% by weight, Photoinitiator: 0.02 - 4% by weight, Discrete surface-treated nano-sized filler particles: 25 - 45% by weight, Additives: containing 0.01 - 7.5% by weight, or consisting essentially of, or consisting of, and the weight percentage is based on the whole composition.

[0192] The curable composition also contains each component in the following amounts: Methacrylate without urethane moiety: 30 - 65% by weight, Urethane (meth)acrylate: 10 - 15% by weight, Photoinitiator: 0.03 - 3% by weight, Discrete surface-treated nano-sized filler particles: 30 - 40% by weight, Additives: containing 0.1 - 5% by weight, or consisting essentially of, or consisting of, and the weight percentage is based on the whole composition.

[0193] More specific embodiments of the curable composition are provided below:

[0194] Embodiment 1 A curable composition, a. (Meth)acrylate that does not contain a urethane moiety in an amount of 20 to 75% by weight, b. Urethane (meth)acrylate in an amount of 5 to 25% by weight, c. A photoinitiator, d. Discrete nano-sized filler particles, having an average particle size in the range of 10 to 40 nm, (Meth)acrylate-containing silane surface treatment agent, (Meth)acrylate-free silane surface treatment agent, and having a surface treated with a silane surface treatment agent selected from both mixtures thereof, Discrete nano-sized filler particles present in an amount of 20% to 50% by weight, e. Additives, and comprising, consisting essentially of, or consisting of the same, The curable composition is the following components: Aggregates of nano-sized filler particles, Aggregates of nano-sized filler particles, Fumed silica, Not containing each alone or in combination in an amount of 2% by weight or more, and the weight % is based on the whole composition, a curable composition.

[0195] Embodiment 2 A curable composition, a. (Meth)acrylate that does not contain a urethane moiety in an amount of 20 to 75% by weight, b. Urethane (meth)acrylate in an amount of 8 to 20% by weight, c. A photoinitiator, d. Discrete nano-sized filler particles, having an average particle size in the range of 10 to 40 nm, (Meth)acrylate-containing silane surface treatment agent, (Meth)acrylate-free silane surface treatment agent, and having a surface treated with a silane surface treatment agent selected from both mixtures thereof, Discrete nano-sized filler particles present in an amount of 25% to 45% by weight, e. containing, consisting essentially of, or consisting of an additive and a curable composition comprising the following components: an aggregate of nano-sized filler particles, an agglomerate of nano-sized filler particles, fumed silica a curable composition that does not contain each of them alone or in combination in an amount of 2% by weight or more, where the % by weight is based on the entire composition.

[0196] Embodiment 3 a curable composition, a. a (meth)acrylate that does not contain a urethane moiety in an amount of 20 to 75% by weight, and b. a urethane (meth)acrylate in an amount of 8 to 20% by weight, and c. a photoinitiator, and d. discrete nano-sized filler particles, having an average particle size in the range of 10 to 40 nm, surface-treated with a surface treatment agent containing a (meth)acrylate moiety and a surface treatment agent not containing a (meth)acrylate moiety, preferably, the surface treatment agent containing a (meth)acrylate moiety is used in a higher amount by weight compared to the surface treatment agent not containing a (meth)acrylate moiety, discrete nano-sized filler particles present in an amount of 25% to 45% by weight, and e. containing, consisting essentially of, or consisting of an additive and a curable composition comprising the following components: an aggregate of nano-sized filler particles, an agglomerate of nano-sized filler particles, fumed silica a curable composition that does not contain each of them alone or in combination in an amount of 2% by weight or more, where the % by weight is based on the entire composition.

[0197] The curable compositions described herein can be produced by mixing the respective components under light-excluding conditions. If desired, a speed mixer can be used.

[0198] During storage, the curable compositions described herein are typically stored under light - excluding conditions, particularly in a sealed container, vessel, or foil bag. The volume of the container may range from 1 mL to 1 L.

[0199] The curable composition can be processed in a stereolithography process for manufacturing 3D printed articles. 3D printing processes are generally known to those skilled in the art.

[0200] An example of this type of technology is described in U.S. Patent No. 8,003,040 (B2) (El - Siblani), which relates to a process for manufacturing three - dimensional objects by solidifying layers using electromagnetic radiation of synergistic stimuli in a pattern.

[0201] In particular, so - called SLA or DLP 3D printing processes have been found to be useful. Commercially available technical devices can be obtained, for example, from 3Shape, Rapid Shape, Formlabs, Lithoz, Prodways, Stratasys, EnvisionTec, etc.

[0202] The stereolithography apparatus typically operates at a specific radiation wavelength in the range of 350 - 500 nm.

[0203] The stereolithography apparatus can also be characterized by the achievable resolution. Suitable resolutions are typically in the range of 5 - 100 μm, or 10 - 80 μm, or 20 - 60 μm.

[0204] After performing the stereolithography process, if desired, the printed article can be post - processed.

[0205] Useful post - processing steps include washing and post - curing of the washed article.

[0206] The washing of the 3D - printed article can be carried out by using a washing solution and / or by performing a so - called spin - washing process.

[0207] By performing a cleaning process, undesirable residues of the curable resin remaining on the surface of the 3D printed article can be removed.

[0208] Suitable cleaning solutions include alcohols such as ethanol or isopropanol, esters of carboxylic acids such as dibasic esters of carboxylic acids and / or tribasic esters of carboxylic acids, or mixtures thereof.

[0209] Suitable cleaning solutions are also described in International Publication No. WO 2018 / 222395 (A1) (3M).

[0210] The spin cleaning process includes the step of moving or rotating the three-dimensional article. By doing this, a mass inertial force is generated.

[0211] The term "mass inertial force" referred to in this specification may be specified as the force per unit mass, and thus may be specified in units of m / s 2 It may also be represented by the G force which is a factor of the acceleration due to gravity. In this specification, the acceleration due to gravity is 9.81 m / s 2 That is. Therefore, for example, a mass inertial force of 9.8I m / s 2 can be expressed as 1G.

[0212] The accelerating force or mass inertial force is induced by moving, for example rotating, an object.

[0213] The centrifugal force on the particles on the surface of the three-dimensional article typically depends on the rotational speed and the radius at which the particles are located from the axis of rotation.

[0214] By varying parameters such as the speed of movement or rotation, its duration and / or the axis of rotation, this technique enables adjustment of the amount and layer thickness of the radiation curable composition remaining on the surface of the three-dimensional article.

[0215] In one embodiment, the mass inertia force generated during the cleaning process corresponds to a g-force of at least 100 g. A mass inertia force of 100 g has proven suitable for removing medium to high viscosity radiation-curable materials. Those skilled in the art will recognize that the mass inertia force required for the cleaning process may be lower for low viscosity materials and higher for high viscosity materials. Such methods are described, for example, in WO 2019 / 023120 A1 (3M).

[0216] Post-curing typically involves applying heat or radiation to the 3D printed article. If desired, post-curing can be carried out under reduced pressure.

[0217] Performing a post-curing step typically serves to further enhance the mechanical properties of the 3d printed article.

[0218] The post-curing step can be characterized by the following features, alone or in combination: applying radiation having a wavelength of 350-500 nm; applying a heating step of 30-200°C or 40-150°C.

[0219] Equipment that can be used to post-cure three-dimensional articles obtained by additive manufacturing is commercially available, for example from Rapidshape, 3Shape, EnvisonTEC, Formlabs, etc.

[0220] The present invention also relates to cured compositions or articles obtained or obtainable by curing the curable compositions described herein.

[0221] The cured compositions can typically be characterized by the following features, either alone or in combination: a. Opalescence value OP: measured to be less than 15 for a 1.0 mm thick sample; b. Flexural strength: measured to be 50~200Mpa according to ISO4049(2019); c. Modulus of elasticity: It is measured to be 1 - 4 GPa according to DIN EN843-2:2007.

[0222] Combinations of features a) and b), or combinations of a), b) and c) may be preferred. If desired, this parameter can be determined as described in the Examples section below.

[0223] It has been found that a milky white value of less than 15% is suitable, for example, for producing a hardened composition having the shape of an orthodontic article that is hardly visible in the patient's oral cavity.

[0224] The bending strength and / or modulus of elasticity within the above ranges have been found to meet the expectations of the practitioner for articles used in the field of orthodontics with respect to mechanical properties.

[0225] The hardened composition may have different shapes and dimensions.

[0226] The hardened composition typically includes a convex surface on one side and a concave surface on the other side.

[0227] Suitable shapes include aligner attachments, orthodontic brackets, buccal tubes, Class II and Class III correction devices, buttons, cleats, and other attachment devices, especially aligner attachments.

[0228] The dimensions (x, y, z - dimensions) of the hardened composition or article are typically in the range of 0.5 - 10 mm for each dimension.

[0229] This curable composition is particularly useful for manufacturing orthodontic attachments for use in so-called dental aligner therapy, i.e., a therapy or method for aligning teeth in a patient's oral cavity.

[0230] Such a method typically includes the following steps: a. Processing the curable composition in a stereolithography process and optionally performing post-treatment steps such as washing and curing thereafter to obtain a 3D printed dental orthodontic attachment; b. Inserting the dental orthodontic attachment into the cavity of a dental positioning tray; c. Inserting the dental positioning tray into the patient's oral cavity; d. Attaching the dental orthodontic attachment to the surface of the teeth to be aligned; e. Removing the dental positioning tray from the patient's oral cavity; f. Optionally, engaging and inserting a dental aligner tray with the dental orthodontic attachment.

[0231] Attachment and / or fixation of the dental orthodontic attachment to the tooth surface can be assisted by using a dental adhesive. Suitable dental adhesives are commercially available, for example, Scotchbond (trademark) Universal (3M Oral Care). Suitable dental adhesives are described in U.S. Patent No. 11,160,733 (B2) (Thalacker et al.) or U.S. Patent No. 7,700,668 (B2) (Thalacker et al.).

[0232] Alternatively, dental cement can be used. Suitable dental cements are commercially available, for example, RelyX (trademark) Unicem (3M Oral Care) or RelyX (trademark) Universal (3M Oral Care). Suitable dental cements are also described in International Publication No. 2017 / 100231 (A1) (3M) or U.S. Patent No. 8,236,871 (B2) (Hecht et al.).

[0233] The present invention also relates to a kit of parts comprising a dental positioning tray and at least one curable composition having the shape of the dental orthodontic attachment described herein, or any of the at least one curable composition described herein, and optionally a dental aligner tray.

[0234] Dental positioning trays are typically used to place dental correction attachments on a patient's teeth. Examples of dental positioning trays are described in US Patent Application Publication No. 2015 / 0313687 (A1) (Blees et al.) and US Patent Application Publication No. 2020 / 131356 (A1) (Zech et al.).

[0235] Dental aligner trays are used to correct the tooth alignment like dental braces. They use gentle and constant force to move the teeth to the desired positions. They are typically transparent and custom-made.

[0236] The complete disclosures of the patents, patent documents, and publications cited herein are incorporated by reference in their entirety as if each were individually incorporated. Various modifications and changes to the present invention will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The above specification, examples, and data provide a description of the manufacture and use of the compositions and methods of the present invention. The present invention is not limited to the embodiments disclosed herein. Those skilled in the art will understand that many alternative embodiments of the present invention can be made without departing from the spirit and scope of the present invention.

[0237] The following examples are presented to illustrate the present invention.

Example

[0238] Unless otherwise specified, all parts and percentages are by weight, all water is deionized water, and all molecular weights are weight-average molecular weights. Further, unless otherwise specified, all experiments were conducted under ambient conditions (23 °C, 1013 mbar).

[0239] Method Viscosity If desired, the viscosity was measured with a Physica MCR 301 (Anton Paar Germany GmbH, Ostfildern-Scharnhausen) using a 25 mm plate / cone system at 0.1 s -1 ~1,000 s-1 It can be measured at 23.0 °C with a shear gradient of

[0240] Transparency If desired, the transparency can be determined using a spherical benchtop spectrophotometer Color i7800 (x-rite, Michigan, USA). To measure the transparency, a sample with a height of 1.0 mm and a diameter of 15 mm is placed between the sphere and the sensor using a specific transmission sample holder made by x-rite. Measurement parameters: measurement including specular reflection, blend aperture 10 mm, field of view area 6 mm, wavelength from 360 nm to 780 nm in 10 nm increments. The transmittance TR [%] is the average of all transmittance values at 10 nm increments between 400 nm and 700 nm through the sample relative to a measurement without the sample in the light beam.

[0241] Opalescence value (OP) If desired, the opalescence value can be determined using a spherical benchtop spectrophotometer Color i7800 (x-rite, Michigan, USA) by applying the above formula. The opalescence value was measured with a sample having a height of 1.0 mm and a diameter of 15 mm.

[0242] Particle size distribution (non-nano-sized particles) If desired, the particle size can be measured using a Malvern Mastersizer 2000 (Malvern Instruments, Malvern, Worcestershire, UK) light scattering device. The Mastersizer 2000 uses an integrated optical system to cover the range of 0.02 - 2000 μm. The mixture to be analyzed is added to a test chamber filled with isopropanol until it reaches an obscuration of about 8 - 15%. No ultrasonic waves are applied to avoid changing the particle size distribution. The raw data is processed using instrument software that applies Mie correction along with the Fraunhofer approximation, a frequently used technique known to experts, using a refractive index of 1.459.

[0243] Particle size distribution (nano-sized particles) The measurement of the size of the nanoparticles is preferably based on the TEM (transmission electron microscope) method, by which the aggregates are analyzed and the average particle diameter is obtained. The preferred method for particle size measurement can be explained as follows: A sample approximately 80 nm thick is placed on a 200-mesh copper grid (SPI Supplies, a division of Structure Probe, Inc., West Chester, PA) equipped with a carbon-stabilized formvar substrate. Transmission electron micrographs (TEM) are taken using a JEOL 200CX (JEOL Ltd., Akishima City, Japan; sold by JEOL USA, Inc.) at 200 kV. The population size of about 50 - 100 particles can be measured and the average diameter is determined.

[0244] Flexural strength (FS) If desired, the measurement of the flexural strength can be carried out in accordance with ISO 4049 (2019) using a universal testing machine (Zwick Z 010, crosshead speed 1 mm / min) and test specimens of size 2 * 2 * 25 mm. The flexural strength is typically given in MPa.

[0245] Elastic modulus (EM) If desired, E-M(I) can be determined in accordance with ISO 4049 (2019) using a test bar having a dimension of 2 * 2 * 25 mm together with a sample of 6 mm width. The elastic modulus is determined in the range of 20% - 50% of the maximum force of the test specimen. The elastic modulus is given in [GPa].

[0246] Material The following materials were used:

[0247]

Table 1

[0248] General process for manufacturing a surface-treated discrete nano-sized filler Mix a sol containing nano-sized particles with a desired silane surface treatment agent and stir it under reflux in a solvent such as ethanol for several hours (e.g., 2 to 10 hours). If necessary, add the (meth)acrylate component or a part thereof and stir the mixture again for several hours. Remove the solvent under reduced pressure.

[0249] General process for producing surface-treated fumed silica Mix fumed silica, silane, and a solvent with a stirrer for about 2 hours. Dry the dispersion in an oven at ambient temperature until the solvent evaporates. Screen the dried fumed silica through a 500 μm sieve. The final condensation of silane onto the surface of the fumed silica is carried out at a temperature above 100 °C for 3 to 4 hours, followed by a final screening of the silane-treated fumed silica through a 100 μm screen.

[0250] General process for producing a curable composition Mix each component using a speed mixer under light-shielding conditions. In addition, subject the mixture to a vacuum evacuation treatment in a laboratory kneader.

[0251] The following compositions were produced.

[0252]

Table 2

[0253] General process for producing a 3D printed article Additive manufacturing process: Pour the composition into the working tray of a commercially available DLP printer (Rapidshape, Heimsheim, Germany). Load the preprocessing data (STL file; shape of a three-dimensional rectangular parallelepiped object; 25 mm * 2 mm * 2 mm) into the printer. The following printing conditions can be applied: curing light wavelength: light of 360 to 420 nm; curing light intensity: 5 to 100 W / m 2 ; exposure time: 1 to 11 seconds; layer thickness: 25 μm.

[0254] Three-dimensional article The three-dimensional article can be manufactured as follows: Place the composition in the vat of a stereolithography apparatus. Manufacture the three-dimensional article layer by layer by using the above-described parameters in the stereolithography process. The three-dimensional article had the shape of an orthodontic article. Remove the three-dimensional article from the vat of the stereolithography apparatus.

[0255] Washing process: Washing of the three-dimensional article from excess material can be carried out using the parameters described in the above text, as described in WO 2019 / 023120 (A1) (3M).

[0256] Post-curing step For final curing of the three-dimensional article, a light-curing device capable of emitting light with a wavelength of 360 nm to 420 nm at 50 to 500 mW / cm 2 can be used. Light curing until complete curing of the sample can be carried out under reduced pressure (in the range of 1 to 100 mbar), if desired.

[0257] The properties of the obtained samples were evaluated. The results are provided in Table 3.

[0258]

Table 3

[0259] Photographs of samples CE1, CE2, IE1, IE2 and CE3 (from left to right) having the shape of an orthodontic article are shown in Figure 2. The sample in the upper left corner corresponds to CE1 and the sample in the lower right corner corresponds to CE3.

[0260] Sample CE1 is opaque and contains a nanocluster filler and fumed silica.

[0261] Sample CE2 contains discrete nanofiller particles, but the average particle size is about 50 nm. This sample is milky white.

[0262] Sample CE3 is transparent and does not contain a filler.

[0263] Sample CE4 is opaque and contains fumed silica.

[0264] Samples IE1 and IE2 (the present invention) contain discrete surface-treated nanofiller particles, but the average particle size is in the range of 10 to 40 nm. This sample is transparent and not milky white.

[0265] Figure 3 shows sample IE1 attached to the surface of a tooth. Due to its transparency, the sample is hardly visible on the surface of the tooth.

[0266] By using the curable composition described herein containing discrete filler nanoparticles, it is possible to produce small articles that are highly transparent and hardly visible on the surface of a tooth.

[0267] This is in contrast to formulations containing nanoclusters (CE1) or commercially available flowable composites.

[0268] Surprisingly, the transparency of the cured composition is equivalent to that of a formulation without a filler (CE3). In addition, the cured composition exhibits beneficial mechanical properties such as flexural strength (after storage in water for 24 hours).

Claims

1. A curable composition, a. (Meth)acrylate, which does not contain urethane, present in an amount of 20-75% by weight, b. Urethane (meth)acrylate present in an amount of 5 to 25% by weight, c. A photoinitiator present in an amount of 0.01 to 5% by weight, d. Discrete nano-sized filler particles present in an amount of 20-50% by weight, When measured according to the method described in the specification, the average particle size is in the range of 10 to 40 nm. Silane surface treatment agent containing (meth)acrylate portion, Silane surface treatment agents that do not contain (meth)acrylate portions, and Discrete nano-sized filler particles having a surface treated with a silane surface treatment agent selected from a mixture of both, e. Contains additives present in an amount of 0.001 to 10% by weight, The curable composition does not contain any filler particles other than those mentioned above in an amount of 2% by weight or more, nor does it contain any polymerizable component containing only one (meth)acrylate moiety in an amount of 1% by weight or more, and the weight percentages are relative to the curable composition. A curable composition characterized by the discrete nano-sized filler particles being, individually or in combination, characterized by: containing oxides of Si, Zr, Al and mixtures thereof, and having a BET specific surface area of ​​80 m² / g or more.

2. The following features: Viscosity: 23℃, 1s －１ Shear rate < 50 Pa ＊ Being s, The curable composition according to claim 1, characterized by being curable by radiation having a wavelength in the range of 350 to 500 nm, either alone or in combination.

3. The curable composition according to claim 1 or 2, wherein the discrete nano-sized filler particles are surface-treated with a surface treatment agent containing a (meth)acrylate portion and a surface treatment agent not containing a (meth)acrylate portion, and preferably, the surface treatment agent containing a (meth)acrylate portion is used in a higher amount relative to weight than the surface treatment agent not containing a (meth)acrylate portion.

4. The following amounts of each ingredient: Methacrylate excluding urethane portion: 25-70% by weight, Urethane (meth)acrylate: 8-20% by weight, Photoinitiator: 0.02-4% by weight, Discrete surface treatment nano-sized filler particles: 25-45% by weight, The curable composition according to claim 1 or 2, comprising 0.001 to 10% by weight of an additive, wherein the weight percentage is relative to the curable composition.

5. A cured composition obtained by curing the curable composition described in claim 1, preferably by processing the curable composition in an additive manufacturing process.

6. The following features: Transparency: For a sample with a thickness of 1 mm, it should be measured to be 60-85% using light with wavelengths in the range of 400-700 nm. Milky whiteness value: Measured to be less than 15 for a sample with a thickness of 1 mm. Bending strength: To be measured to be 50-200 MPa according to ISO 4049 (2019). The cured composition according to claim 5, characterized by, alone or in combination, having an elastic modulus measured to be 1 to 4 GPa according to DIN EN 843-2:2007.

7. A curing composition according to claim 5 or 6, having the shape of an orthodontic attachment.

8. A kit of components comprising a dental positioning tray, at least one curable composition according to claim 1, or at least one curable composition according to claim 5, and optionally a dental aligner tray.

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