UV-curable silicone composition for stereolithography, cured product thereof, and curing method

Abstract

Provided is a UV-curable silicone composition for stereolithography, the UV-curable silicone composition containing: (A) an organopolysiloxane having, per molecule, two or more radically polymerizable group-containing groups each bonded to a silicon atom via an oxygen atom directly bonded to the silicon atom (excluding those containing a heteroatom other than an oxygen atom); (B) hydrophobic silica particles having an average particle size of 10-1,000 nm and having a hydrophobicity of 60% or more as measured by a methanol titration method; and (C) a photopolymerization initiator, wherein when the composition is irradiated with ultraviolet light having a wavelength of 405 nm at 25°C at a dose of 8,000 mJ / cm2, and then cured for 24 hours in an environment of 85°C and 85% RH to obtain a cured product having a thickness of 2.0 mm, the cured product has a tensile strength of 4.5 MPa or more and an elongation at break of 300% or more.

Description

UV-curable silicone composition for stereolithography, cured product thereof, and curing method

[0001] The present invention relates to an ultraviolet-curable silicone composition for stereolithography, a cured product thereof, and a method for curing the ultraviolet-curable silicone composition for stereolithography.

[0002] In recent years, the development of molding materials for use in 3D printers has been thriving, and a variety of molding materials, from metals to resins, are being used. In the field of resins, for example, acrylate-based photocurable resin compositions and urethane acrylate-based photocurable resin compositions can be cited, but the cured products of these resin compositions are very hard and cannot be bent freely (Patent Document 1).

[0003] In addition, a UV-curable, low-viscosity silicone material has been proposed for inkjet 3D printers (Patent Document 2). This material has the advantage of curing with short UV irradiation and achieving very good modeling accuracy, but has issues with poor mechanical strength and heat resistance compared to conventional silicone materials. Therefore, new UV-curable silicone compositions have been developed for stereolithography, which has been rapidly increasing in recent years (Patent Documents 3 and 4). However, compared to the mechanical strength of thermosetting silicone compositions, they can be brittle due to their low elongation. Furthermore, in recent years, stereolithography has become possible even with higher viscosities than before.

[0004] Patent No. 5890990 Patent No. 6687111 Patent No. 6962290 Patent No. 7342910

[0005] The present invention has been made in view of the above circumstances, and aims to provide an ultraviolet-curable silicone composition and a cured product thereof that have a viscosity that is suitable for use in stereolithography methods such as laser methods and Digital Light Processing (DLP) methods, that can be shaped with a low dose of ultraviolet light, and that, upon post-processing, gives a cured product that exhibits excellent rubber physical properties.

[0006] As a result of extensive research conducted by the present inventors in order to achieve the above object, they discovered that by adding a photopolymerization initiator to an organopolysiloxane having a specific radically polymerizable group-containing group bonded to a silicon atom via an oxygen atom directly bonded to the silicon atom, and to hydrophobic silica particles having an average particle size in the range of 10 nm to 1,000 nm and a hydrophobicity of 60% or more as measured by the methanol titration method, it is possible to obtain an ultraviolet-curable silicone composition that is also applicable to stereolithography and that, by carrying out a primary cure by ultraviolet irradiation followed by a secondary cure by condensation, gives a cured product with good rubber physical properties, thereby completing the present invention.

[0007] That is, the present invention provides: 1. A silicone composition for stereolithography comprising: (A) an organopolysiloxane having, per molecule, two or more radically polymerizable group-containing groups (excluding those containing heteroatoms other than oxygen atoms) bonded to silicon atoms via oxygen atoms directly bonded to the silicon atoms; (B) hydrophobic silica particles having an average particle size of 10 nm to 1,000 nm and a hydrophobicity of 60% or more as determined by a methanol titration method; and (C) a photopolymerization initiator, wherein the composition is irradiated with ultraviolet light having a wavelength of 405 nm at 25°C at 8,000 mJ / cm. 2 and then curing for 24 hours in an environment of 85°C and 85% RH, resulting in a 2.0 mm thick cured product having a tensile strength of 4.5 MPa or more and an elongation at break of 300% or more; 2. The ultraviolet-curable silicone composition for stereolithography according to 1, wherein component (A) is an organopolysiloxane having 2 to 6 acryloyloxyalkyloxy groups or methacryloyloxyalkyloxy groups bonded to silicon atoms per molecule; 3. The ultraviolet-curable silicone composition for stereolithography according to 1, wherein component (A) is an organopolysiloxane represented by the following formula (1): (In the formula, n is a number satisfying 1≦n≦1,000, m is a number satisfying 1≦m≦1,000, and the siloxane units to which n and m are attached may be arranged in any order. Ar are each independently an aryl group having 6 to 20 carbon atoms, and R 1are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms, and A is a group represented by the following formula (2): (In the formula, R 1 is the same as above, and R 2 is an oxygen atom or an alkylene group having 1 to 20 carbon atoms, and R 3 are each independently an acryloyloxyalkyloxy group or a methacryloyloxyalkyloxy group, a is a number that satisfies 1≦a≦3, and the dashed line represents a bond.) 4. The ultraviolet-curable silicone composition for stereolithography according to any one of 1 to 3, which contains 10 to 500 parts by mass of component (B) and 0.01 to 20 parts by mass of component (C) per 100 parts by mass of component (A); 5. The ultraviolet-curable silicone composition for stereolithography according to any one of 1 to 4, which has a viscosity at 23°C of 500 Pa·s or less; 6. 6. A cured product of an ultraviolet-curable silicone composition for stereolithography, comprising: (A) an organopolysiloxane having two or more radically polymerizable group-containing groups (excluding those containing heteroatoms other than oxygen atoms) per molecule, the radically polymerizable group-containing groups being bonded to silicon atoms via oxygen atoms directly bonded to the silicon atoms; (B) hydrophobic silica particles having an average particle size of 10 nm to 1,000 nm and a hydrophobicity of 60% or more as measured by methanol titration; and (C) a photopolymerization initiator, the cured product having a tensile strength of 4.5 MPa or more at a thickness of 2.0 mm and an elongation at break of 300% or more; 7. A method for curing the ultraviolet-curable silicone composition for stereolithography described in any one of items 1 to 5, comprising: (i) a step of irradiating the ultraviolet-curable silicone composition for stereolithography described in any one of items 1 to 5 with ultraviolet light to radically cure the composition and obtain a primary cured product; and (ii) a step of further condensation-curing the primary cured product to obtain a secondary cured product. 8. The curing method described in item 7, wherein the condensation-curing in step (ii) is curing by moisture.

[0008] The UV-curable silicone composition for stereolithography of the present invention can be used in stereolithography methods such as laser and DLP, and the cured product after UV curing exhibits good rubber physical properties when moistened.

[0009] The present invention will be described in detail below. [1] UV-curable silicone composition for stereolithography The UV-curable silicone composition for stereolithography according to the present invention contains the following components (A) to (C): (A) an organopolysiloxane having two or more radically polymerizable group-containing groups per molecule, each group being bonded to a silicon atom via an oxygen atom directly bonded to the silicon atom; (B) hydrophobic silica particles having an average particle size in the range of 10 nm to 1,000 nm and a hydrophobicity of 60% or more as measured by methanol titration; and (C) a photopolymerization initiator.

[0010] (A) Organopolysiloxane Component (A) used in the present invention is the crosslinking component of the composition and is an organopolysiloxane having two or more radically polymerizable group-containing groups per molecule that are bonded to silicon atoms via oxygen atoms directly bonded to those silicon atoms, preferably 2 to 6, and more preferably 2 to 4 such radically polymerizable group-containing groups per molecule, provided that the radically polymerizable group-containing groups do not contain heteroatoms other than oxygen atoms.

[0011] The composition of the present invention has radical curing properties and condensation curing properties due to the radically polymerizable group-containing group bonded to the silicon atom via an oxygen atom directly bonded to the silicon atom. In particular, a primary cured product obtained by irradiating the composition of the present invention with ultraviolet light (radical curing) can be further post-treated with moisture (condensation curing) to obtain a secondary cured product with even better rubber physical properties.

[0012] Specific examples of the radically polymerizable group-containing group include an acryloyloxyalkyloxy group or a methacryloyloxyalkyloxy group bonded to a silicon atom.

[0013] The improvement in rubber properties of the cured product by post-treatment with moisture is believed to be due to the hydrolysis and condensation of the (meth)acryloyloxyalkyloxy groups and other groups bonded to silicon atoms, which causes a chain extension reaction between the organopolysiloxanes of component (A) and a crosslinking reaction between the organopolysiloxanes of component (A) and the silanol groups on the surface of the silica particles of component (B), which will be described later.In the present invention, the (meth)acryloyloxyalkyloxy group represents an acryloyloxyalkyloxy group or a methacryloyloxyalkyloxy group.

[0014] The radical polymerizable group-containing group may be located at either a molecular chain terminal (one terminal or both terminals), in the middle of the molecular chain, or both terminals. However, it is preferably located at a molecular chain terminal (one terminal or both terminals), and more preferably at both molecular chain terminals.

[0015] In the organopolysiloxane molecule of component (A), groups bonded to silicon atoms other than the radically polymerizable group-containing groups include monovalent hydrocarbon groups having 1 to 20 carbon atoms, preferably monovalent hydrocarbon groups having 1 to 10 carbon atoms, and more preferably monovalent hydrocarbon groups having 1 to 8 carbon atoms, excluding aliphatic unsaturated groups. Furthermore, some or all of the hydrogen atoms bonded to carbon atoms in the monovalent hydrocarbon groups may be substituted with other substituents such as halogen atoms. The monovalent hydrocarbon groups may be linear, branched, or cyclic, and, for ease of synthesis, include alkyl, aryl, and halogenated alkyl groups. Specific examples of these groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-hexyl, cyclohexyl, n-octyl, 2-ethylhexyl, and n-decyl groups; phenyl, tolyl, xylyl, and naphthyl groups; and chloromethyl, 3-chloropropyl, and 3,3,3-trifluoropropyl groups. Among these, alkyl groups and aryl groups having 1 to 3 carbon atoms are preferred, and methyl groups, ethyl groups and phenyl groups are more preferred.

[0016] The molecular structure of component (A) is preferably a linear or branched main chain consisting of repeating diorganosiloxane units (including linear main chains having a branch at one end), and is particularly preferably a linear diorganopolysiloxane in which both molecular chain terminals are blocked with units having the above-mentioned radically polymerizable group-containing groups.

[0017] As component (A), an organopolysiloxane represented by the following formula (1) is more preferred.

[0018] In formula (1), R 1 are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, and more preferably 1 to 8 carbon atoms.

[0019] In formula (1), R 1 The monovalent hydrocarbon group having 1 to 20 carbon atoms is preferably a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms, and may be linear, branched, or cyclic. Specific examples thereof include linear, branched, or cyclic alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-hexyl, cyclohexyl, n-octyl, 2-ethylhexyl, and n-decyl; and alkenyl groups such as vinyl, allyl (2-propenyl), 1-propenyl, isopropenyl, and butenyl.

[0020] In addition, some or all of the hydrogen atoms bonded to carbon atoms of these monovalent hydrocarbon groups may be substituted with halogen atoms such as chlorine, fluorine, and bromine, or other substituents such as a cyano group, and specific examples thereof include halogen-substituted hydrocarbon groups such as chloromethyl, bromoethyl, and trifluoropropyl groups; and cyano-substituted hydrocarbon groups such as a cyanoethyl group. 1 As the alkyl group, an alkyl group having 1 to 3 carbon atoms is preferred, and a methyl group or an ethyl group is more preferred.

[0021] In formula (1), Ar are each independently an aryl group having 6 to 20 carbon atoms, preferably an aryl group having 6 to 10 carbon atoms, and specific examples thereof include aromatic hydrocarbon groups such as phenyl, biphenyl, and naphthyl groups, and aromatic groups containing a heteroatom (O, S, N) such as furanyl groups, and the aromatic groups may further have a substituent such as a halogen atom (for example, a chlorine atom, a bromine atom, or a fluorine atom). Of these, Ar is preferably an unsubstituted aryl group, and particularly preferably a phenyl group.

[0022] In formula (1), n ​​is a number that satisfies 1≦n≦1,000, and in consideration of further improving the viscosity of the composition and the mechanical properties of the cured product, it is preferably a number that satisfies 1≦n≦400, and more preferably 1≦n≦200. If n is less than 1, the composition is prone to volatilization, and if n is more than 1,000, the viscosity of the composition increases, making it difficult to mold.

[0023] In formula (1), m is a number that satisfies 1≦m≦1,000, and in consideration of further improving the viscosity of the composition and the mechanical properties of the cured product, it is preferably a number that satisfies 1≦m≦400, and more preferably 10≦m≦300. If m is less than 1, the composition is prone to volatilization, and if m is more than 1,000, the viscosity of the composition increases, making it difficult to mold.

[0024] In formula (1), n ​​+ m is preferably a number that satisfies 2≦n + ​​m ≦ 2,000, more preferably 2 ≦n + m ≦ 1,000, and even more preferably 2 ≦n + m ≦ 800. If n + m is less than 2, the composition may be prone to volatilization, and if n + m is more than 2,000, the viscosity of the composition may be high, making shaping difficult. The order of arrangement of the siloxane units to which n and m are attached is arbitrary.

[0025] A in formula (1) is a group represented by the following formula (2). (In the formula, the dashed lines represent bonds.)

[0026] In formula (2), R 1 is the same as above.

[0027] In addition, in formula (2), R 2represents an oxygen atom or an alkylene group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, and more preferably 1 to 5 carbon atoms.

[0028] In formula (2), R 2 The alkylene group having 1 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include methylene, ethylene, propylene, trimethylene, tetramethylene, isobutylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, nonamethylene, and decylene groups. 2 As the alkyl group, an oxygen atom, a methylene group, an ethylene group, or a trimethylene group is preferred, and an oxygen atom or an ethylene group is more preferred.

[0029] R 3 are each independently an acryloyloxyalkyloxy group or a methacryloyloxyalkyloxy group.

[0030] R 3 The number of carbon atoms in the alkyl (alkylene) group in the acryloyloxyalkyloxy group or methacryloyloxyalkyloxy group is not particularly limited, but is preferably 1 to 10, and more preferably 1 to 5. Specific examples of these alkyl groups include R 1 Among the groups exemplified in R, those having 1 to 10 carbon atoms can be mentioned. 3 Specific examples of the compound include, but are not limited to, those represented by the following formulas:

[0031] (In the formula, the dashed lines represent bonds.)

[0032] In the above formula, R 4 is an alkylene group having 1 to 10 carbon atoms, preferably an alkylene group having 1 to 5 carbon atoms. 4 Specific examples of 2 Among the groups exemplified above, those having 1 to 10 carbon atoms are preferred, and among these, methylene, ethylene and trimethylene groups are preferred, with ethylene groups being more preferred.

[0033] In formula (2), a is a number that satisfies 1≦a≦3, and is preferably 1 or 2.

[0034] The component (A) may be a single polymer having these molecular structures, a copolymer having these molecular structures, or a mixture of two or more of these polymers.

[0035] Specific examples of the organopolysiloxane of component (A) include those represented by the following formulas (3) and (4), but are not limited to these.

[0036] (In the formula, Me represents a methyl group, Ph represents a phenyl group, n and m have the same meanings as above, and the siloxane units to which n and m are attached may be arranged in any order.)

[0037] Such organopolysiloxanes can be obtained, for example, by reacting 2-hydroxyethyl acrylate with the hydrosilylation reaction product of a dimethylsiloxane-diphenylsiloxane copolymer endblocked at both ends with dimethylvinylsiloxy groups and chlorodimethylsilane or dichloromethylsilane.

[0038] (B) Hydrophobic Silica Particles Component (B) is hydrophobic silica particles. By including component (B), the mechanical strength of the cured product can be increased while maintaining the fluidity of the composition.

[0039] The average particle size of component (B) is 10 to 1,000 nm, preferably 20 to 1,000 nm, more preferably 20 to 500 nm, and even more preferably 30 to 200 nm. If the average particle size is smaller than 10 nm, aggregation becomes severe and fluidity is lost. If it is larger than 1,000 nm, the effect of improving mechanical strength is small. The above average particle size is determined by measuring the volume-based median diameter (D 50 ) is the value measured.

[0040] The hydrophobicity of component (B) measured by methanol titration is 60% or more, preferably 64% or more. Silica particles with a high hydrophobicity do not aggregate even when highly loaded in the composition, and the mechanical strength of the cured product can be increased without impairing the flowability.

[0041] The degree of hydrophobicity is determined by the methanol titration method shown below. (1) A sample is suspended in a predetermined amount of ion-exchanged water, and methanol is added dropwise while stirring. (2) The amount of added methanol is read when the entire amount of the sample is suspended in ion-exchanged water. (3) The value calculated by [{amount of methanol added (mL)} / {amount of methanol added (mL)+amount of ion-exchanged water (mL)}]×100 is the degree of hydrophobicity.

[0042] The shape of the component (B) used in the present invention is not particularly limited, but a spherical shape is preferred.

[0043] The amount of component (B) blended is preferably 10 to 500 parts by mass, more preferably 20 to 300 parts by mass, and even more preferably 30 to 200 parts by mass per 100 parts by mass of component (A). When the amount is 10 parts by mass or more, the effect of improving the mechanical strength of the cured product is sufficiently obtained, and when the amount is 500 parts by mass or less, the viscosity of the composition does not become too high and excellent flowability is achieved.

[0044] In addition, component (B) is a compound having R 7 SiO 3 / 2 Unit (R 7 is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and R 9 3SiO 1 / 2 Unit (R 9 are the same or different substituted or unsubstituted monovalent hydrocarbon groups having 1 to 6 carbon atoms.

[0045] Such component (B) is, for example, a compound obtained by hydrolyzing and condensing a tetrafunctional silane compound, an alkyl silicate, or a mixture thereof to form an R group on the surface of hydrophilic silica particles. 7 SiO 3 / 2 Units, then R 9 3SiO 1 / 2 It can be obtained by introducing units by hydrolysis condensation.

[0046] [Method for synthesizing component (B)] Specifically, the component (B) used in the present invention is preferably synthesized by a method including the following three steps: Step (α): A step for synthesizing hydrophilic silica particles; Step (β): A step for subjecting the hydrophilic silica particles to surface hydrophobic treatment to obtain an intermediate for component (B); Step (γ): A step for further subjecting the intermediate for component (B) to surface hydrophobic treatment to obtain hydrophobic silica particles of component (B).

[0047] Each step will be explained below in order. Step (α): Synthesis of Hydrophilic Silica Particles Step (α) is a step of obtaining a dispersion of hydrophilic silica particles by hydrolyzing and condensing either or both of a tetrafunctional silane compound represented by the following general formula (I) and an alkyl silicate represented by the following general formula (II) in a mixed solution of a hydrophilic organic solvent and water in the presence of a basic substance. Si(OR 5 ) 4 (I) (In the formula, R 5 are the same or different monovalent hydrocarbon groups having 1 to 6 carbon atoms; and k is a number from 1 to 100.

[0048] In the above general formulas (I) and (II), R 5 are the same or different monovalent hydrocarbon groups having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, and more preferably 1 or 2 carbon atoms. 5 The monovalent hydrocarbon group represented by may be linear, branched, or cyclic, and specific examples thereof include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, and n-butyl groups; and aryl groups such as phenyl groups. Among these, R 5 is preferably a methyl, ethyl, n-propyl or n-butyl group, more preferably a methyl group or an ethyl group.

[0049] In the above general formula (II), k is a number from 1 to 100, preferably a number from 1 to 50, and more preferably a number from 1 to 25.

[0050] Specific examples of the tetrafunctional silane compound represented by the general formula (I) include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane; and tetraaryloxysilanes such as tetraphenoxysilane. Among these, preferred are tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane, and more preferred are tetramethoxysilane and tetraethoxysilane. Specific examples of the alkyl silicate represented by the general formula (II) include methyl silicate and ethyl silicate, and preferred is methyl silicate. These may be used alone or in combination of two or more.

[0051] Specific examples of the hydrophilic organic solvent used in step (α) are not particularly limited as long as they dissolve the tetrafunctional silane compound represented by general formula (I) or the alkyl silicate represented by general formula (II) and water, and examples thereof include alcohols; cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, and cellosolve acetate; ketones such as acetone and methyl ethyl ketone; and ethers such as dioxane and tetrahydrofuran. Among these, alcohols and cellosolves are preferred, and alcohols are more preferred.

[0052] Examples of the alcohols include alcohols represented by the following general formula (VI): 6 OH (VI) (wherein, R 6 is a monovalent hydrocarbon group having 1 to 6 carbon atoms.

[0053] In the above general formula (VI), R 6 is a monovalent hydrocarbon group having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, and more preferably 1 or 2 carbon atoms. 6 Specific examples of the monovalent hydrocarbon group represented by R 5 Among them, R 6is preferably a methyl, ethyl, n-propyl, or isopropyl group, more preferably a methyl group or an ethyl group.

[0054] Specific examples of the alcohol represented by general formula (VI) include methanol, ethanol, propanol, isopropanol, butanol, etc., and among these, methanol and ethanol are preferred. As the number of carbon atoms in the alcohol increases, the particle size of the resulting silica particles increases. Therefore, methanol is preferred to obtain silica particles with a desired small particle size.

[0055] The amount of water used in the hydrolysis and condensation is preferably 0.5 to 5 moles, more preferably 0.6 to 2 moles, and even more preferably 0.7 to 1 mole, per mole of the total of the hydrocarbyloxy groups of the tetrafunctional silane compound represented by general formula (I) and / or the alkyl silicate represented by general formula (II). The ratio of water to hydrophilic organic solvent is preferably 10 to 200 parts by mass of the hydrophilic organic solvent per 100 parts by mass of water.

[0056] Specific examples of the basic substance used in step (α) include ammonia, dimethylamine, diethylamine, etc., and among these, ammonia and diethylamine are preferred, and ammonia is more preferred. These basic substances can be dissolved in a required amount in water, and then the resulting aqueous solution (basic) can be mixed with a hydrophilic organic solvent.

[0057] The amount of basic substance used is preferably 0.01 to 2 mol, more preferably 0.02 to 0.5 mol, and even more preferably 0.04 to 0.12 mol, per mol of the total hydrocarbyloxy groups of the tetrafunctional silane compound represented by general formula (I) and / or the alkyl silicate represented by general formula (II). The smaller the amount of basic substance, the more likely it is that the desired small-sized silica particles will be obtained. The basic substance may be added to a mixture of a hydrophilic organic solvent and water, and then further added to the resulting mixture together with the tetrafunctional silane compound represented by general formula (I) and / or the alkyl silicate represented by general formula (II). Alternatively, the basic substance may be added to a mixture of water and a hydrophilic organic solvent simultaneously with the addition of the tetrafunctional silane compound and / or the alkyl silicate and the hydrophilic organic solvent.

[0058] The reaction conditions for step (α) are not particularly limited, and the reaction can be carried out under conventionally known conditions, for example, at about 10 to 80° C. for about 1 to 10 hours.

[0059] The obtained mixed solvent dispersion containing hydrophilic silica particles may be used as is in step (β). However, it is preferable to convert the mixed solvent dispersion containing hydrophilic silica particles into an aqueous dispersion by adding water to the mixed solvent dispersion containing hydrophilic silica particles, evaporating off the hydrophilic organic solvent, and converting the mixture into an aqueous dispersion, since the remaining alkoxy groups are hydrolyzed by this process.

[0060] The dispersion medium of the silica particle mixed solvent dispersion can be converted to water, for example, by adding water to the dispersion and distilling off the hydrophilic organic solvent (this operation can be repeated as necessary). The amount of water added at this time is preferably 50 to 200 parts by mass, more preferably 80 to 150 parts by mass, per 100 parts by mass of the combined amount of the hydrophilic organic solvent used and the alcohol produced in the synthesis step of the hydrophilic silica particles.

[0061] Step (β): Surface Treatment Step of Hydrophilic Silica Particles Step (β) is a step of adding either one or both of a trifunctional silane compound represented by the following general formula (III) and its (partial) hydrolysis condensate to the mixed solvent dispersion of hydrophilic silica particles obtained in step (α) to treat the surfaces of the hydrophilic silica particles, thereby obtaining a dispersion of silica particles (hydrophobic silica particle intermediates) which are an intermediate of component (B). 7 Si(OR 8 )3 (III) (wherein, R 7 is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and R 8 are the same or different monovalent hydrocarbon groups having 1 to 6 carbon atoms.

[0062] In the above general formula (III), R 7 is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 3 carbon atoms, and even more preferably 1 or 2 carbon atoms. 7 The monovalent hydrocarbon group may be linear, branched, or cyclic, and specific examples thereof include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, n-hexyl, and n-decyl groups. Among these, R 7 is preferably a methyl, ethyl, n-propyl or isopropyl group, more preferably a methyl group or an ethyl group. Some or all of the hydrogen atoms of these monovalent hydrocarbon groups may be substituted with halogen atoms such as fluorine atoms, chlorine atoms or bromine atoms, and is preferably a fluorine-substituted alkyl group.

[0063] In the above general formula (III), R 8 are the same or different monovalent hydrocarbon groups having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms, and more preferably 1 or 2 carbon atoms. 8 Specific examples of 5 Among them, R 8 is preferably a methyl, ethyl or n-propyl group, more preferably a methyl group or an ethyl group.

[0064] Specific examples of the trifunctional silane compound represented by general formula (III) include unsubstituted or halogen-substituted trialkoxysilanes such as methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, hexyltrimethoxysilane, trifluoropropyltrimethoxysilane, and heptadecafluorodecyltrimethoxysilane. Among these, preferred are methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, and ethyltriethoxysilane, and more preferred are methyltrimethoxysilane and methyltriethoxysilane.

[0065] The amount of the trifunctional silane compound represented by general formula (III) added is preferably 0.001 to 1 mol, more preferably 0.01 to 0.4 mol, and even more preferably 0.01 to 0.2 mol per mol of Si atoms in the hydrophilic silica particles obtained in step (α). If the amount added is 0.001 mol or more, the hydrophobicity of the resulting component (B) will be increased, resulting in excellent dispersibility, while if the amount added is 1 mol or less, the risk of aggregation of component (B) can be suppressed. The treatment conditions for step (β) are not particularly limited, and are preferably, for example, about 10 to 80°C for about 1 to 10 hours.

[0066] Step (γ): Surface Treatment Step of Component (B) Intermediate In step (γ), the dispersion medium of the mixed solvent dispersion of silica particles, which is an intermediate of component (B) obtained in step (β), is converted to, for example, a ketone-based solvent to obtain a ketone-based solvent dispersion of hydrophobic silica particle intermediates, and then either one or both of a silazane compound represented by the following general formula (IV) and a monofunctional silane compound represented by the following general formula (V) are added to this ketone-based solvent dispersion to treat the surfaces of the silica particles, which are intermediates of component (B), thereby obtaining hydrophobic silica particles of component (B). In this step, silanol groups remaining on the surfaces of the hydrophobic silica particle intermediates are triorganosilylated to form R 9 3SiO 1 / 2 Units are introduced to the surface. 9 3SiNHSiR 9 3 (IV) R 9 3SiX (V) (wherein, R 9 are the same or different substituted or unsubstituted monovalent hydrocarbon groups having 1 to 6 carbon atoms, and X is an OH group or a hydrolyzable group.

[0067] In the above general formulas (IV) and (V), R 9 are the same or different substituted or unsubstituted monovalent hydrocarbon groups having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms. 9 Specific examples of 5 Among them, R 9 is preferably a methyl, ethyl or n-propyl group, more preferably a methyl group or an ethyl group. Some or all of the hydrogen atoms of these monovalent hydrocarbon groups may be substituted with halogen atoms such as fluorine atoms, chlorine atoms or bromine atoms, and is preferably a fluorine-substituted alkyl group.

[0068] X is an OH group or a hydrolyzable group. Examples of the hydrolyzable group include a chlorine atom; an alkoxy group such as a methoxy group or an ethoxy group; an amino group, an N-methylamino group, an N,N'-dimethylamino group, an N-ethylamino group, an N,N'-diethylamino group; and an acyloxy group such as an acetoxy group. Among these, an alkoxy group or an amino group is preferred, an alkoxy group is more preferred, and a methoxy group or an ethoxy group is even more preferred.

[0069] Specific examples of the silazane compound represented by general formula (IV) include hexamethyldisilazane, hexaethyldisilazane, tetramethyldivinyldisilazane, etc., with hexamethyldisilazane being preferred.Specific examples of the monofunctional silane compound represented by general formula (V) include monosilanol compounds such as trimethylsilanol and triethylsilanol; monochlorosilanes such as trimethylchlorosilane and triethylchlorosilane; monoalkoxysilanes such as trimethylmethoxysilane and trimethylethoxysilane; monoaminosilanes such as trimethylsilyldimethylamine and trimethylsilyldiethylamine; and monoacyloxysilanes such as trimethylacetoxysilane.Among these, trimethylsilanol, trimethylmethoxysilane, or trimethylsilyldiethylamine are preferred, and trimethylsilanol or trimethylmethoxysilane is more preferred.These compounds may be used alone or in combination of two or more.

[0070] The amount of the silazane compound represented by general formula (IV) and / or the monofunctional silane compound represented by general formula (V) used is preferably 0.1 to 0.5 mol, more preferably 0.2 to 0.4 mol, and even more preferably 0.25 to 0.35 mol, relative to 1 mol of Si atoms in the hydrophobic silica particle intermediate obtained in step (β). If the amount used is 0.1 mol or more, the degree of hydrophobicity of the obtained hydrophobic silica particles will be high and they will have excellent dispersibility, and taking into consideration costs and the like, an amount used of 0.5 mol or less will be sufficient.

[0071] To convert the dispersion medium of the mixed solvent dispersion of hydrophobic silica particle intermediates obtained in step (β) from a mixed solvent of water or a hydrophilic organic solvent and an alcohol generated during hydrolysis to a ketone-based solvent, a ketone-based solvent can be added to the mixed solvent dispersion of the hydrophobic silica particle intermediates and the water or hydrophilic organic solvent and alcohol mixture are distilled off (this operation can be repeated as necessary). The conditions for this conversion are preferably about 10 to 150°C for about 1 to 20 hours. The amount of ketone-based solvent added is preferably 50 to 500 parts by weight, more preferably 100 to 300 parts by weight, per 100 parts by weight of the obtained hydrophobic silica particle intermediates. Specific examples of ketone-based solvents used here include methyl ethyl ketone, methyl butyl ketone, and acetylacetone, with methyl isobutyl ketone being preferred. The surface treatment conditions for step (γ) are also not particularly limited, and are preferably, for example, about 10 to 150°C for about 1 to 20 hours.

[0072] The component (B) obtained as described above can be obtained as a powder by a conventional method such as drying at room temperature or under heat at normal pressure or drying under reduced pressure.

[0073] (C) Photopolymerization Initiator The component (C) is a photopolymerization initiator. Specific examples of photoinitiators that can be used in the present invention include 2,2-diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethan-1-one (Omnirad 651), 1-hydroxy-cyclohexyl-phenyl-ketone (Omnirad 184), 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Omnirad 1173), 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-propan-1-one (Omnirad 127), phenylglyoxylic acid methyl ester (Omnirad MBF), 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (Omnirad 907), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone (Omnirad 369), bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (Omnirad 819), 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (Omnirad TPO), ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate (Omnirad TPO-L) and the like (all manufactured by IGM Resins B.V.), and these may be used alone or in combination of two or more. Among these, from the viewpoint of compatibility with the components (A) and (B), 2,2-diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Omnirad 1173), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819), 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (Omnirad TPO H), and ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate (Omnirad TPO-L) are preferred, and liquid ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate (Omnirad TPO-L) is more preferred.

[0074] The amount of photopolymerization initiator added is preferably 0.01 to 20 parts by mass, and more preferably 0.1 to 10 parts by mass, per 100 parts by mass of component (A). When the amount is 0.01 part by mass or more, sufficient surface curing properties are achieved, and when the amount is 20 parts by mass or less, there is no risk of deterioration in deep curing properties.

[0075] (D) Ultraviolet absorber having light absorption in the wavelength range of 360 to 410 nm An ultraviolet absorber having light absorption in the wavelength range of 360 to 410 nm can be added to the composition of the present invention in order to adjust the curing properties during stereolithography using a 3D printer.

[0076] Specific examples of the ultraviolet absorber that can be used in the present invention include 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (Tinuvin 571, manufactured by BASF), benzenepropanoic acid 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy C7-9 side chain and linear alkyl ester (Tinuvin 384-2, manufactured by BASF), 2-(5-chloro-2-benzotriazolyl)-6-tert-butyl-p-cresol (Tinuvin 326, manufactured by BASF), and reaction products of 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-hydroxyphenyl with [(C10-C16 mainly C12-C13 alkyloxy)methyl]oxirane (Tinuvin 400, manufactured by BASF), thioxanthone, 2-isopropylthioxanthone, 2,4-diethylthioxanthone, benzophenone, camphorquinone, 1-phenyl-1,2-propanedione, diethylaminohydroxybenzoylhexylbenzoate (Uvinul A Plus, manufactured by BASF), 1-(4-tert-butylphenyl)-3-(4-methoxyphenyl)-1,3-propanedione, 2-ethylhexyl 4-methoxycinnamate, and the like. These may be used alone or in combination of two or more.

[0077] When an ultraviolet absorber is used, the amount added is preferably 0.01 to 20 parts by mass, and more preferably 0.1 to 10 parts by mass, per 100 parts by mass of component (A). When the amount is 0.01 part by mass or more, the effect of the ultraviolet absorber can be fully obtained, and when the amount is 20 parts by mass or less, there is no risk of deterioration in deep section curability.

[0078] (E) Coloring Material Various coloring materials can be added to the composition of the present invention for the purpose of adjusting the curability of the composition or coloring it. As the coloring material, general pigments (iron oxide, titanium oxide, zinc oxide, etc.), dyes, carbon black, etc. can be used. These may be used alone or in combination of two or more.

[0079] When a colorant is used, the amount added is preferably 0.01 to 20 parts by mass per 100 parts by mass of component (A). When the amount is 0.01 part by mass or more, the effect of the colorant can be fully obtained, and when the amount is 20 parts by mass or less, there is no risk of deterioration in deep section curing.

[0080] The composition of the present invention may contain additives such as a silane coupling agent, an adhesion promoter, a polymerization inhibitor, an antioxidant, an ultraviolet absorber as a light resistance stabilizer, a light stabilizer, etc., within the range that does not impair the effects of the present invention. The composition of the present invention may also be used by appropriately mixing it with other resin compositions.

[0081] [2] Method for Producing Silicone Composition The method for producing the silicone composition of the present invention is not particularly limited, and any conventionally known method can be used. That is, the silicone composition of the present invention can be obtained by mixing components (A) to (C) and, if necessary, other components.

[0082] The method for producing the silicone composition of the present invention preferably comprises the following steps (1) and (2): Step (1): Producing component (B) by a method including the following steps (α), (β), and (γ); Step (2): Mixing components (A) to (C) and, if necessary, other components.

[0083] Step (1): Step of Producing Component (B) Step (1) is a step of producing component (B) by a method including the following steps (α), (β), and (γ):

[0084] Step (α): A step of obtaining a dispersion of hydrophilic silica particles by hydrolyzing and condensing one or both of a tetrafunctional silane compound represented by the following general formula (I) and an alkyl silicate represented by the following general formula (II) in a mixed liquid of a hydrophilic organic solvent and water in the presence of a basic substance: Si(OR 5 ) 4 (I) (In the formula, R 5 and k have the same meaning as above.)

[0085] Step (β): A step of adding either one or both of a trifunctional silane compound represented by the following general formula (III) and its (partial) hydrolysis condensate to the mixed solvent dispersion of hydrophilic silica particles obtained in step (α) to treat the surfaces of the hydrophilic silica particles, thereby obtaining a dispersion of silica particles, which is an intermediate of component (B). 7 Si(OR 8 )3 (III) (wherein, R 7 and R 8 has the same meaning as above.)

[0086] Step (γ): A step of adding either a silazane compound represented by the following general formula (IV) or a monofunctional silane compound represented by the following general formula (V) to a dispersion of silica particles, which are an intermediate for component (B), obtained in step (β), to treat the surfaces of the silica particles, which are an intermediate for component (B), thereby obtaining hydrophobic silica particles for component (B). 9 3SiNHSiR 9 3 (IV) R 9 3SiX (V) (wherein, R 9 and X have the same meaning as above.

[0087] The detailed method for producing the component (B) is as described above.

[0088] Step (2): Mixing Components (A) to (C) There are no particular limitations on the step of mixing components (A) to (C). The UV-curable silicone composition for stereolithography of the present invention can be obtained by mixing the above-mentioned components (A) to (C), and, if necessary, other components, in any order, followed by stirring, etc. The equipment used for stirring, etc., is not particularly limited, but includes a crusher, a three-roll mill, a ball mill, a planetary mixer, etc. These equipment may also be used in combination as appropriate.

[0089] The silicone composition of the present invention may be in the form of a one-component type or a two-component type. A one-component type composition can be obtained, for example, by adding components (A) to (C) and, if necessary, other components, to a gate mixer (manufactured by Inoue Seisakusho Co., Ltd., product name: Planetary Mixer) and mixing them. Alternatively, components (A) and (B) are placed in a gate mixer and mixed under reduced pressure at room temperature for 1 hour. After cooling the resulting mixture, component (C) is added and the mixture is mixed at room temperature for 30 minutes.

[0090] From the viewpoint of stereolithography, the viscosity at 23°C of the ultraviolet-curable silicone composition for stereolithography of the present invention is preferably 500 Pa·s or less, more preferably 400 Pa·s or less, and even more preferably 100 Pa·s or less. If the viscosity exceeds 500 Pa·s, the shaping properties will deteriorate and the desired shaped object may not be accurately obtained. There is no particular restriction on the lower limit, but a viscosity of 1 Pa·s or more is preferred, and 2 Pa·s or more is more preferred. In the present invention, the viscosity can be measured using a rotational viscometer (e.g., BL type, BH type, BS type, cone-plate type, rheometer, etc.) (the same applies hereinafter).

[0091] [3] Cured Product The UV-curable silicone composition for stereolithography of the present invention can be used to form a cured product with excellent rubber properties by the following steps: (i) irradiating the UV-curable silicone composition for stereolithography of the present invention with UV light to radically cure the composition and obtain a primary cured product, and (ii) further condensation-curing the resulting primary cured product to obtain a secondary cured product.

[0092] Step (i): Step of Obtaining a Primary Cured Product Step (i) is a step of irradiating the ultraviolet-curable silicone composition for stereolithography of the present invention with ultraviolet light to radically cure the composition and obtain a primary cured product.

[0093] In step (i), examples of the light source of the ultraviolet light to be irradiated include a UV-LED lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, a carbon arc lamp, a xenon lamp, etc. The ultraviolet light irradiation is preferably carried out, for example, at around room temperature (25° C.) under an inert gas atmosphere such as nitrogen or argon.

[0094] To form a primary cured product by irradiation with ultraviolet light, the irradiation dose (integrated light amount) of ultraviolet light is preferably 1 to 10,000 mJ / cm for a sheet formed from the composition of the present invention to a thickness of about 2.0 mm. 2 and more preferably 10 to 8,000 mJ / cm 2 That is, the illuminance is 100 mW / cm 2 When ultraviolet light is used, the ultraviolet light may be irradiated for about 0.01 to 100 seconds.

[0095] The tensile strength of the primary cured product obtained in step (i) is preferably 2.0 MPa or more, more preferably 3.0 MPa or more. The elongation at break is preferably 150% or more, more preferably 200% or more. These values ​​are measured in accordance with JIS-K6249 (the same applies hereinafter).

[0096] Step (ii): Obtaining a Secondary Cured Product Step (ii) is a step in which the obtained primary cured product is further condensed and cured to obtain a secondary cured product. In the condensation curing of step (ii), the hydrolysis and condensation of component (A) and / or component (B) can be accelerated by applying moisture. Specifically, condensation curing is preferably carried out in an environment of 50% RH to 85% RH and 20°C to 85°C for 12 to 36 hours, and particularly 18 to 24 hours.

[0097] The secondary cured product obtained in step (ii) has a tensile strength of 4.5 MPa or more, preferably 5.0 MPa or more. The elongation at break is 300% or more, preferably 250% or more. In the present invention, the secondary cured product is particularly cured by irradiating the product with ultraviolet light having a wavelength of 405 nm at 25° C. at 8,000 mJ / cm 2 After irradiating the resin so as to satisfy the above condition, the resin is further cured for 24 hours in an environment of 85°C and 85% RH, whereby the tensile strength and elongation at break of the resulting cured product having a thickness of 2.0 mm can be set within the above ranges.

[0098] The present invention will be described in more detail below with reference to Synthesis Examples, Comparative Synthesis Examples, Examples, and Comparative Examples, but the present invention is not limited to these Examples. The compounds of the respective components used in the Examples are as follows. In the following formulas, Me represents a methyl group, and Ph represents a phenyl group.

[0099] [1] Ingredients (A) Component (In the formula, the siloxane units in parentheses may be arranged in any order.)

[0100] Component (B) (B-1) Hydrophobic silica particles obtained in Synthesis Example 1 (B-2) Hydrophobic silica particles obtained in Synthesis Example 2 (B-3) Hydrophobic silica particles obtained in Synthesis Example 3 (Comparative to B-1) Hydrophobic silica particles obtained in Comparative Synthesis Example 1

[0101] Component (C) (C-1) Ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate (Omnirad TPO-L, manufactured by IGM Resins B.V.)

[0102] [2] Synthesis of Hydrophobic Silica Microparticles [Synthesis Example 1] Step (α): Synthesis of Hydrophilic Silica Particles 623.7 g of methanol, 41.4 g of water, and 49.8 g of 28% by weight aqueous ammonia were mixed in a 3-liter glass reactor equipped with a stirrer, a dropping funnel, and a thermometer. The solution was adjusted to 35°C, and while stirring, 1,163.7 g of tetramethoxysilane and 418.4 g of 5.4% by weight aqueous ammonia were simultaneously added dropwise over 5 hours. After the dropwise addition was completed, stirring was continued for another 0.5 hours to carry out hydrolysis, thereby obtaining a suspension of hydrophilic spherical silica particles. An ester adapter and a condenser were attached to the glass reactor, and the reactor was heated to 60-70°C to distill off 649 g of methanol, at which point 1,600 g of water was added. The reactor was then further heated to 70-90°C to distill off 160 g of methanol, obtaining an aqueous suspension of hydrophilic silica particles.

[0103] Step (β): Surface treatment step of hydrophilic silica particles 115.8 g of methyltrimethoxysilane (0.1 equivalents relative to SiO) and 46.6 g of 5.4 mass % aqueous ammonia were added dropwise to this aqueous suspension at 25° C. over 0.5 hours, and after the addition, the suspension was heated to 50° C. and aged for 1 hour. After completing the reaction, the suspension was cooled to 25° C. and the surfaces of the hydrophilic silica particles were treated to obtain a dispersion of a hydrophobic silica particle intermediate, which is an intermediate for component (B).

[0104] Step (γ): Surface Treatment Step of Component (B) Intermediate After adding 1,000 g of methyl isobutyl ketone to the dispersion thus obtained, the dispersion was heated to 80-115°C while maintaining the intense wave motion of the liquid interface, and 1,336 g of a mixture of methanol and water was distilled off over 11 hours. 357.4 g of hexamethyldisilazane was added to the resulting dispersion at 25°C, and the dispersion was heated to 120°C and reacted for 3 hours, resulting in trimethylsilylation of the silica particles and the production of hydrophobic silica particles. The solvent was then distilled off under heating using an evaporator, yielding 477 g of hydrophobic silica particles (B-1).

[0105] Synthesis Example 2 470 g of hydrophobic silica particles (B-2) were obtained in the same manner as in Step (α) of Synthesis Example 1, except that 1,163.7 g of tetramethoxysilane was changed to 901.9 g of methyl silicate (Methyl Silicate 51 manufactured by Colcoat Co., Ltd.).

[0106] Synthesis Example 3 360 g of hydrophobic silica particles (B-3) were obtained in the same manner as in Step (β) of Synthesis Example 1, except that the amount of methyltrimethoxysilane used was changed to 11.6 g (0.01 equivalents relative to SiO 2 ).

[0107] Comparative Synthesis Example 1 60 g of isopropanol and 100 g of Snowtex OL (a type of colloidal silica, manufactured by Nissan Chemical Industries, Ltd., average particle size 50 nm, dispersed in water, solids concentration 20% by mass) silica particles were added to a 3-liter glass reactor equipped with a stirrer, a dropping funnel, and a thermometer, and mixed. 0.48 g of methyltrimethoxysilane was added dropwise to this solution over 0.5 hours, and after the addition, the solution was heated to 50°C and aged for 1 hour. After the reaction was completed, the solution was cooled to 25°C, and the silica particle surfaces were treated.

[0108] Subsequently, 0.78 g of hexamethyldisilazane was added, and the dispersion was heated to 105°C and reacted for 2 hours. Finally, 2.6 parts by mass of a 35% by mass aqueous hydrochloric acid solution was added to precipitate silica particles. Thereafter, the solvent was distilled off under heating using an evaporator to obtain hydrophobic silica particles (comparison B-1).

[0109] [Measurement Method] The obtained hydrophobic silica particles were measured according to the following measurement methods 1 and 2. The obtained results are shown in Table 1.

[0110] 1. Particle size measurement of hydrophobic silica particles (1) 0.1 g of sample was placed in a glass bottle, and 20 g of methanol was added and stirred. (2) The sample was dispersed for 10 minutes using an ultrasonic disperser to prepare a measurement sample. (3) The sample (2) was measured using a laser analysis scattering particle size distribution measuring device (Nikkiso Co., Ltd., Nanotrac 150), and the volume-based median diameter (the particle diameter corresponding to 50% of the cumulative distribution when the particle size distribution is expressed as a cumulative distribution) was determined as the particle size.

[0111] 2. Measurement of hydrophobicity of hydrophobic silica particles (methanol titration method) (1) 0.2 mg of sample was weighed into a 500 mL Erlenmeyer flask. (2) 50 mL of ion-exchanged water was added to (1) and stirred with a stirrer. (3) Methanol was added dropwise from a burette while stirring, and the amount added when the entire amount of the sample was suspended in ion-exchanged water was read. (4) The hydrophobicity was calculated using the following formula: Hydrophobicity (%) = [{amount of methanol added (mL)} / {amount of methanol added (mL) + amount of ion-exchanged water (mL)}] x 100

[0112]

[0113] [3] Production and evaluation of silicone compositions, production and evaluation of cured products [Examples 1 to 5 and Comparative Examples 1 and 2] Silicone compositions were prepared by mixing the components (A) to (C) described above in the formulations shown in Table 2. The viscosity of the compositions shown in Table 2 was measured at 23°C using a rotational viscometer. The prepared silicone compositions were cured in a UV curing device manufactured by CCS Inc. under a nitrogen atmosphere at room temperature (25°C) with ultraviolet light of 405 nm wavelength at an irradiation dose of 8,000 mJ / cm. 2 The resulting composition was cured by irradiating it with ultraviolet light so that the temperature reached 85°C and the temperature reached 85% RH for 24 hours to obtain a primary cured product. Sheets (2.0 mm thick) of the resulting primary cured product and secondary cured product were measured for hardness, elongation at break, and tensile strength in accordance with JIS K 6249:2003.

[0114]

[0115] As shown in Table 2, the UV-curable silicone compositions prepared in Examples 1 to 5 had low viscosities suitable for use in stereolithography, and the cured products obtained after UV irradiation and moisture treatment had good mechanical properties. On the other hand, Comparative Example 1, in which the radically polymerizable group-containing group in component (A) was changed to one in which an oxygen atom directly bonded to the silicon atom and a dimethylsilyl group were bonded to the silicon atom, exhibited low condensation reactivity with moisture, resulting in poor physical properties for the secondary cured product. Furthermore, Comparative Example 2, in which silica particles with insufficient hydrophobicity were used, exhibited a significant increase in viscosity of the composition, and curability was also insufficient.

Claims

1. (A) Organopolysiloxanes having two or more radical polymerizable group-containing groups (excluding those containing heteroatoms other than oxygen atoms) bonded to a silicon atom via an oxygen atom directly bonded to the silicon atom in one molecule. (B) Hydrophobic silica particles having an average particle size of 10 nm to 1,000 nm and a degree of hydrophobicity of 60% or more as determined by methanol titration, and (C) Photopolymerization initiator A silicone composition for photopolymerization containing, The composition was subjected to ultraviolet light at a wavelength of 405 nm at 25°C at a rate of 8,000 mJ / cm². 2 A UV-curable silicone composition for stereolithography, obtained by irradiating it in such a manner and then curing it for 24 hours in an environment of 85°C and 85% RH, having a cured product with a thickness of 2.0 mm that has a tensile strength of 4.5 MPa or more and an elongation at break of 300% or more.

2. The UV-curable silicone composition for photopolymerization according to claim 1, wherein component (A) is an organopolysiloxane having 2 to 6 acryloyloxyalkyloxy groups or methacryloyloxyalkyloxy groups bonded to silicon atoms in one molecule.

3. The UV-curable silicone composition for photopolymerization according to claim 1, wherein component (A) is an organopolysiloxane represented by the following formula (1). 【Chemistry 1】 (In the formula, n is a number satisfying 1 ≤ n ≤ 1,000, m is a number satisfying 1 ≤ m ≤ 1,000, and the order of the siloxane units to which n and m are attached is arbitrary. Ar are aryl groups having 6 to 20 carbon atoms, R 1 These are monovalent hydrocarbon groups with 1 to 20 carbon atoms, and A is the group represented by the following formula (2). 【Chemistry 2】 (In the formula, R 1 This is the same as above, R 2 R is an oxygen atom or an alkylene group having 1 to 20 carbon atoms. 3 (Each of the groups is independently an acryloyloxyalkyloxy group or a methacryloyloxyalkyloxy group, a is a number satisfying 1 ≤ a ≤ 3, and the dashed line represents a bond.)

4. (A) 100 parts by mass of component (B) Component in 10 to 500 parts by mass, and (C) The UV-curable silicone composition for photopolymerization according to claim 1, comprising 0.01 to 20 parts by mass of component C.

5. The UV-curable silicone composition for photopolymerization according to claim 1, wherein the viscosity at 23°C is 500 Pa·s or less.

6. (A) Organopolysiloxanes having two or more radical polymerizable group-containing groups (excluding those containing heteroatoms other than oxygen atoms) bonded to a silicon atom via an oxygen atom directly bonded to the silicon atom in one molecule. (B) Hydrophobic silica particles having an average particle size of 10 nm to 1,000 nm and a degree of hydrophobicity of 60% or more as determined by methanol titration, and (C) Photopolymerization initiator A cured product of a photopolymerizable ultraviolet-curable silicone composition containing the above, wherein the cured product has a tensile strength of 4.5 MPa or more and an elongation at break of 300% or more when the thickness is 2.0 mm.

7. A method for curing a photopolymerizable ultraviolet-curable silicone composition according to any one of claims 1 to 5, (i) A step of irradiating a photopolymerizable UV-curable silicone composition according to any one of claims 1 to 5 with ultraviolet light to radically cure the composition and obtain a primary cured product, and (ii) A step to obtain a secondary cured product by further condensation curing of the obtained primary cured product. A curing method that includes [a specific component].

8. The curing method according to claim 7, wherein the condensation curing in step (ii) is curing by moisture.