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

Technical Field

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

Background Art

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

[0003] Also, an ultraviolet curable low-viscosity silicone material has been proposed for 3D printers using an inkjet method (Patent Document 2). This material has the advantages of curing by short-time ultraviolet irradiation and having very good molding accuracy, but it has the problem of poor mechanical strength and heat resistance compared with ordinary silicone materials. Therefore, an ultraviolet curable silicone composition has been newly developed for optical molding, which has been rapidly increasing in recent years (Patent Documents 3 and 4). However, compared with the mechanical strength of thermosetting silicone compositions, the elongation was low and it was sometimes brittle. Also, in recent years, even with a higher viscosity than before, it has become possible to perform optical molding.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

[0005] The present invention has been made in view of the above circumstances, and aims to provide an ultraviolet-curable silicone composition and its cured product that has a viscosity applicable to stereolithography methods such as laser and digital light processing (DLP), can be fabricated even with a small amount of ultraviolet irradiation, and provides a cured product exhibiting excellent rubber properties when post-processed. [Means for solving the problem]

[0006] The present inventors conducted diligent studies to achieve the above objectives and discovered that by adding a photopolymerization initiator to an organopolysiloxane having a specific radical polymerizable group bonded to a silicon atom via an oxygen atom directly bonded to the silicon atom, and hydrophobic silica particles having an average particle size in the range of 10 nm to 1,000 nm and a degree of hydrophobicity of 60% or more as determined by methanol titration, a UV-curable silicone composition can be obtained that is also applicable to stereolithography and provides a cured product with good rubber properties by performing a second curing by condensation after primary curing by UV irradiation. Thus, the present invention was completed.

[0007] In other words, the present invention is 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. 2A UV-curable silicone composition for stereolithography is obtained by irradiating it in such a manner, and then curing it for 24 hours in an environment of 85°C and 85%RH, resulting in a cured product with a thickness of 2.0 mm having 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 photopolymerizable UV-curable silicone composition according to claim 1, wherein component (A) is an organopolysiloxane represented by the following formula (1). [ka] (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 with n and m attached is arbitrary. Ar is an aryl group 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 formula (2) below. [ka] (In the formula, R 1 This is the same as above, and 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) Per 100 parts by mass of component, (B) Component 10 to 500 parts by mass, and (C) A UV-curable silicone composition for photopolymerization according to any one of 1 to 3, containing 0.01 to 20 parts by mass of component (C). 5. A UV-curable silicone composition for photopolymerization according to any one of 1 to 4, 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 UV-curable silicone composition containing the following, 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 described in any of 1 to 5, (i) A step of irradiating a photopolymerizable UV-curable silicone composition described in any of 1 to 5 with ultraviolet light to radically cure the composition and obtain a primary cured product, and (ii) A step of further condensing and hardening the obtained primary hardened product to obtain a secondary hardened product. A curing method including 8. The curing method according to 7, wherein the condensation curing in step (ii) is curing due to moisture. To provide. [Effects of the Invention]

[0008] The UV-curable silicone composition for stereolithography of the present invention is applicable to stereolithography methods such as laser and DLP methods, and the cured product after UV curing exhibits good rubber properties when moisture is applied. [Modes for carrying out the invention]

[0009] The present invention will be described in detail below. [1] UV-curable silicone composition for stereolithography The UV-curable silicone composition for photopolymerization according to the present invention contains the following components (A) to (C). (A) Organopolysiloxane having two or more radical polymerizable groups in one molecule that are bonded to the silicon atom via an oxygen atom directly bonded to the silicon atom. (B) Hydrophobic silica particles with an average particle size in the range of 10 nm to 1,000 nm and a degree of hydrophobicity of 60% or more as determined by methanol titration. (C) Photopolymerization initiator

[0010] (A) Organopolysiloxane Component (A) used in the present invention is a crosslinking component of the composition and is an organopolysiloxane having two or more radical polymerizable group-containing groups bonded to a silicon atom via an oxygen atom directly bonded to the silicon atom in one molecule. Preferably, it is an organopolysiloxane having 2 to 6 such radical polymerizable group-containing groups, more preferably 2 to 4 such groups in one molecule. However, the radical polymerizable group-containing groups do not contain heteroatoms other than oxygen atoms.

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

[0012] Specific examples of the radical polymerizable group-containing groups mentioned above include, for example, an acryloyloxyalkyloxy group or a methacryloyloxyalkyloxy group bonded to a silicon atom.

[0013] The improvement in the rubber properties of the cured product due to post-treatment with moisture is thought to be because the (meth)acryloyloxyalkyloxy groups bonded to the silicon atoms undergo hydrolysis condensation, resulting in chain extension reactions between the organopolysiloxanes of component (A) and crosslinking reactions 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 this invention, (meth)acryloyloxyalkyloxy group represents either an acryloyloxyalkyloxy group or a methacryloyloxyalkyloxy group.

[0014] The radical polymerizable group-containing group may be located at the end of the molecular chain (one or both ends), in the middle of the molecular chain, or in both locations. However, it is preferable that it be located at the end of the molecular chain (one or both ends), and even more preferable that it be located at both ends.

[0015] In the organopolysiloxane molecule of component (A), groups bonded to silicon atoms other than the radical polymerizable group-containing group mentioned above include monovalent hydrocarbon groups having 1 to 20 carbon atoms, preferably monovalent hydrocarbon groups having 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, excluding aliphatic unsaturated groups. Furthermore, some or all of the hydrogen atoms bonded to the carbon atoms of the monovalent hydrocarbon group may be substituted with other substituents such as halogen atoms. The monovalent hydrocarbon group mentioned above may be linear, branched, or cyclic, and due to the ease of synthesis, alkyl, aryl, and alkyl halides are examples. Specific examples 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 and aryl groups having 1 to 3 carbon atoms are preferred, and methyl, ethyl, and phenyl groups are more preferred.

[0016] Furthermore, the molecular structure of component (A) is preferably linear or branched (including linear with branching in part of the main chain) consisting of repeating diorganosiloxane units in the main chain, and in particular, a linear diorganopolysiloxane sealed at both ends of the molecular chain with units having the above-mentioned radical polymerizable group-containing groups is preferred.

[0017] (A) Component is more preferably an organopolysiloxane represented by the following formula (1). [ka]

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

[0019] In equation (1), R 1 The monovalent hydrocarbon group having 1 to 20 carbon atoms is preferably a monovalent aliphatic hydrocarbon having 1 to 20 carbon atoms, and may be linear, branched, or cyclic. Specific examples 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 groups; and alkenyl groups such as vinyl, allyl (2-propenyl), 1-propenyl, isopropenyl, and butenyl groups.

[0020] Furthermore, some or all of the hydrogen atoms bonded to the carbon atoms of these monovalent hydrocarbon groups may be substituted with halogen atoms such as chlorine, fluorine, or bromine, or with other substituents such as cyano groups. Specific examples of these include halogen-substituted hydrocarbon groups such as chloromethyl, bromoethyl, and trifluoropropyl groups; and cyano-substituted hydrocarbon groups such as cyanoethyl groups. Among these, R 1 Preferably, the alkyl group has 1 to 3 carbon atoms, and more preferably, a methyl group or an ethyl group.

[0021] In formula (1), Ar is an aryl group having 6 to 20 carbon atoms, preferably having 6 to 10 carbon atoms. Specific examples include aromatic hydrocarbon groups such as phenyl, biphenyl, and naphthyl groups, and aromatic groups containing heteroatoms (O, S, N) such as furanyl groups. Furthermore, these aromatic groups may have substituents such as halogen atoms (e.g., chlorine, bromine, or fluorine atoms). Among these, Ar is preferably an unsubstituted aryl group, and particularly preferably a phenyl group.

[0022] In formula (1), n is a number satisfying 1 ≤ n ≤ 1,000, and considering the further improvement of the viscosity of the composition and the mechanical properties of the cured product, it is preferably a number satisfying 1 ≤ n ≤ 400, more preferably 1 ≤ n ≤ 200. If n is less than 1, it is likely to volatilize, and if n is greater than 1,000, the viscosity of the composition becomes high and shaping becomes difficult.

[0023] In formula (1), m is a number satisfying 1 ≤ m ≤ 1,000, and considering the further improvement of the viscosity of the composition and the mechanical properties of the cured product, it is preferably a number satisfying 1 ≤ m ≤ 400, more preferably 10 ≤ m ≤ 300. If m is less than 1, it is likely to volatilize, and if m is greater than 1,000, the viscosity of the composition becomes high and shaping becomes difficult.

[0024] In formula (1), n + m is preferably a number satisfying 2 ≤ n + m ≤ 2,000, more preferably 2 ≤ n + m ≤ 1,000, still more preferably 2 ≤ n + m ≤ 800. If n + m is less than 2, it may be likely to volatilize, and if n + m is greater than 2,000, the viscosity of the composition becomes high and shaping may become difficult. Note that the order of arrangement of the siloxane units with n and m attached is arbitrary.

[0025] A in formula (1) is a group represented by the following formula (2).

Chemical formula

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

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

[0028] In formula (2), R 2The alkylene group, having 1 to 20 carbon atoms, can be linear, branched, or cyclic. Specific examples include methylene, ethylene, propylene, trimethylene, tetramethylene, isobutylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, nonamethylene, and desilene groups. Among these, R 2 The preferred elements are oxygen atoms, methylene, ethylene, and trimethylene groups, with oxygen atoms or ethylene groups being more preferred.

[0029] R 3 These are, independently of each other, 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 above, those with 1 to 10 carbon atoms are examples. R 3 Specific examples include, but are not limited to, those shown in the following formula.

[0031] [ka] (In the equation, dashed lines represent connections.)

[0032] In the above formula, R 4 R is an alkylene group having 1 to 10 carbon atoms, but preferably an alkylene group having 1 to 5 carbon atoms. 4 A concrete example is R 2 Among the groups exemplified above, those having 1 to 10 carbon atoms are preferred, with methylene, ethylene, and trimethylene groups being particularly preferred, and the ethylene group being more preferred.

[0033] In equation (2), a is a number that satisfies 1 ≤ a ≤ 3, but 1 or 2 is preferred.

[0034] 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 organopolysiloxanes of component (A) include, but are not limited to, those shown in formulas (3) and (4) below.

[0036] [ka] (In the formula, Me represents a methyl group, and Ph represents a phenyl group. n and m have the same meanings as above, and the order of the siloxane units with n and m attached is arbitrary.)

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

[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] Component (B) has an average particle diameter of 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 diameter 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 diameter is the median diameter (D) based on volume in particle size distribution measurement by laser diffraction. 50 This is the value measured as follows:

[0040] The degree of hydrophobicity of component (B) by methanol titration is 60% or higher, preferably 64% or higher. When silica particles have a high degree of hydrophobicity, they do not aggregate even when densely packed in the composition, and the mechanical strength of the cured product can be increased without degrading fluidity.

[0041] The degree of hydrophobicity can be determined by the methanol titration method shown below. (1) Float the sample in a predetermined amount of deionized water and add methanol dropwise while stirring. (2) Read the volume of the sample when the entire sample is suspended in deionized water. (3) The degree of hydrophobicity is calculated by [{volume of methanol added (mL)} / {volume of methanol added (mL) + volume of deionized water (mL)}] × 100.

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

[0043] The amount of component (B) 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). If the amount is 10 parts by mass or more, the effect of improving the mechanical strength of the cured product is sufficiently obtained, and if it is 500 parts by mass or less, the viscosity of the composition does not become too high and it has excellent fluidity.

[0044] Furthermore, component (B) has R on the silica surface 7 SiO 3 / 2 Unit (R 7 ) and R 9 3SiO 1 / 2 Unit (R 9 It is preferable that the group has the same or different substituted or unsubstituted monovalent hydrocarbon groups having 1 to 6 carbon atoms.

[0045] Such component (B) is, for example, obtained by hydrolysis and condensation of a tetrafunctional silane compound, alkyl silicate, or a mixture thereof, on the surface of hydrophilic silica particles R7 SiO 3 / 2 Units, followed by R 9 3SiO 1 / 2 It can be obtained by introducing units through hydrolysis and condensation.

[0046] [(B) Method of synthesis] Specifically, component (B) used in the present invention is preferably synthesized by a method comprising the following three steps. Step (α): Synthesis step of hydrophilic silica particles Step (β): A step in which hydrophilic silica particles are surface-hydrophobicated to obtain the intermediate component (B). Step (γ): Further surface hydrophobic treatment of the intermediate component (B) to obtain hydrophobic silica particles of component (B).

[0047] The following explains each step in order. Step (α): Synthesis step of hydrophilic silica particles Step (α) is a step in which a dispersion of hydrophilic silica particles is obtained by hydrolyzing and condensing either or both of the tetrafunctional silane compound represented by the following general formula (I) and the alkyl silicate represented by the following general formula (II) in a mixture of a hydrophilic organic solvent and water in the presence of a basic substance. Si(OR 5 )4(I) [ka] (In the formula, R 5 (This refers to monovalent hydrocarbon groups with 1 to 6 carbon atoms, either identical or different. k is a number from 1 to 100.)

[0048] In the above general formulas (I) and (II), R 5 These are monovalent hydrocarbon groups having 1 to 6 carbon atoms, either identical or different, but preferably monovalent hydrocarbon groups having 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms. R 5The monovalent hydrocarbon group represented by can be linear, branched, or cyclic. Specific examples 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 The group is preferably a methyl, ethyl, n-propyl, or n-butyl group, and more preferably a methyl or 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 compounds represented by the above general formula (I) include, for example, tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane; and tetraaryloxysilanes such as tetraphenoxysilane. Among these, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane are preferred, and tetramethoxysilane and tetraethoxysilane are more preferred. Furthermore, specific examples of alkyl silicates represented by general formula (II) include, for example, methyl silicate and ethyl silicate, with methyl silicate being preferred among them. These can be used individually or in combination of two or more types.

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

[0052] Examples of these alcohols include those represented by the following general formula (VI). R 6 OH (VI) (In the formula, R 6 (This refers to a monovalent hydrocarbon group having 1 to 6 carbon atoms.)

[0053] In the above general formula (VI), R 6 R is a monovalent hydrocarbon group having 1 to 6 carbon atoms, preferably a monovalent hydrocarbon group having 1 to 4 carbon atoms, more preferably a monovalent hydrocarbon group having 1 or 2 carbon atoms. 6 A specific example of a monovalent hydrocarbon group represented by R is: 5 Similar to the bases exemplified above, among them, R 6 The group is preferably a methyl, ethyl, n-propyl, or isopropyl group, and more preferably a methyl or ethyl group.

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

[0055] The amount of water used in the above 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 1 mole of total 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 hydrophilic organic solvent per 100 parts by mass of water.

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

[0057] The amount of basic substance used is preferably 0.01 to 2 moles, more preferably 0.02 to 0.5 moles, and even more preferably 0.04 to 0.12 moles, per 1 mole 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). In this case, the smaller the amount of basic substance, the more desirable small-particle-sized silica particles will be formed. The basic substance may be added to a mixture of hydrophilic organic solvent and water, and then further added to the resulting mixture together with a tetrafunctional silane compound represented by general formula (I) and / or an alkyl silicate represented by general formula (II), or it may be added to the mixture of water and hydrophilic organic solvent at the same time as the addition of the tetrafunctional silane compound and / or alkyl silicate and the hydrophilic organic solvent.

[0058] The reaction conditions for step (α) are not particularly limited and can be carried out under conventionally known conditions, for example, it is preferable to use a temperature of about 10 to 80°C for about 1 to 10 hours.

[0059] The resulting mixed solvent dispersion containing hydrophilic silica particles may be used as is in step (β), but it is preferable to add water to the mixed solvent dispersion containing hydrophilic silica particles, then distill off the hydrophilic organic solvent to convert it into an aqueous dispersion, which hydrolyzes any remaining alkoxy groups.

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

[0061] • Step (β): Surface treatment step for hydrophilic silica particles Step (β) is a step in which the surface of the hydrophilic silica particles is treated by adding either or both of the 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), thereby obtaining a dispersion of silica particles (hydrophobic silica particle intermediate), which is an intermediate of component (B). R 7 Si(OR 8 )3(III) (In the formula, R 7 R is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, 8 (These are monovalent hydrocarbon groups with 1 to 6 carbon atoms, either identical or different.)

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

[0063] In the above general formula (III), R 8 R is a monovalent hydrocarbon group having 1 to 6 carbon atoms, either identical or different, preferably a monovalent hydrocarbon group having 1 to 3 carbon atoms, more preferably 1 or 2 carbon atoms. 8 A concrete example is R 5 Similar to the bases exemplified above, among them, R 8 The group is preferably a methyl, ethyl, or n-propyl group, and more preferably a methyl or ethyl group.

[0064] Specific examples of trifunctional silane compounds represented by general formula (III) include, for example, 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, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, and ethyltriethoxysilane are preferred, and methyltrimethoxysilane and methyltriethoxysilane are more preferred.

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

[0066] • Step (γ): Surface treatment step for the (B) component intermediate. Step (γ) is a step in which 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 the hydrophobic silica particle intermediate. Then, one or both of the silazane compound represented by the following general formula (IV) and the monofunctional silane compound represented by the following general formula (V) are added to this ketone-based solvent dispersion to treat the surface of the silica particles, which are an intermediate of component (B), thereby obtaining hydrophobic silica particles of component (B). This step causes the silanol groups remaining on the surface of the hydrophobic silica particle intermediate to be triorganosilylated in the form of R 9 3SiO 1 / 2 The unit is introduced to the surface. R 9 3SiNHSiR 9 3(IV) R 9 3SiX (V) (In the formula, R 9 (wherein X is an identical or different substituted or unsubstituted monovalent hydrocarbon group 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 R is a monovalent hydrocarbon group having 1 to 6 carbon atoms, either identical or different substituted or unsubstituted, preferably having 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms. 9A concrete example is R 5 Similar to the bases exemplified above, among them, R 9 The group is preferably a methyl, ethyl, or n-propyl group, and more preferably a methyl or ethyl group. Furthermore, some or all of the hydrogen atoms of these monovalent hydrocarbon groups may be substituted with halogen atoms such as fluorine, chlorine, or bromine atoms, and is preferably a fluorine-substituted alkyl group.

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

[0069] Specific examples of silazane compounds represented by general formula (IV) include, for example, hexamethyldisilazane, hexaethyldisilazane, and tetramethyldivinyldisilazane, with hexamethyldisilazane being preferred. Specific examples of monofunctional silane compounds represented by general formula (V) include, for example, 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 are preferred. These can be used individually or in combination of two or more types.

[0070] The amount of silazane compound represented by general formula (IV) and / or monofunctional silane compound represented by general formula (V) used is preferably 0.1 to 0.5 moles, more preferably 0.2 to 0.4 moles, and even more preferably 0.25 to 0.35 moles, per mole of Si atoms of the hydrophobic silica particle intermediate obtained in step (β). If the amount used is 0.1 mole or more, the degree of hydrophobicity of the resulting hydrophobic silica particles will be high and will have excellent dispersibility, and considering cost and other factors, an amount of 0.5 moles or less is sufficient.

[0071] To convert the dispersion medium of the mixed solvent dispersion of the hydrophobic silica particle intermediate obtained in step (β) from a mixed solvent of water or a hydrophilic organic solvent and an alcohol produced during hydrolysis to a ketone-based solvent, this can be done by adding the ketone-based solvent to the mixed solvent dispersion of the hydrophobic silica particle intermediate and distilling off the water or hydrophilic organic solvent and alcohol mixture (repeating this operation as needed). The conditions for this operation are preferably around 10 to 150°C for 1 to 20 hours. The amount of ketone solvent added at this time is preferably 50 to 500 parts by mass, more preferably 100 to 300 parts by mass, per 100 parts by mass of the obtained hydrophobic silica particle intermediate. Specific examples of ketone solvents used here include methyl ethyl ketone, methyl butyl ketone, and acetylacetone, with methyl isobutyl ketone being preferred. Furthermore, the surface treatment conditions for step (γ) are not particularly limited; for example, a temperature of approximately 10 to 150°C for approximately 1 to 20 hours is preferred.

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

[0073] (C) Photopolymerization initiator (C) Component is a photopolymerization initiator. Specific examples of photopolymerization initiators usable in this invention include 2,2-diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethane-1-one (Omnirad 651), 1-hydroxycyclohexylphenyl ketone (Omnirad 184), 2-hydroxy-2-methyl-1-phenylpropan-1-one (Omnirad 1173), 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)-benzyl]-phenyl}-2-methylpropan-1-one (Omnirad 127), phenylglyoxylic acid methyl ester (Omnirad MBF), and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (Omnirad Examples include 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), phenyl(2,4,6-trimethylbenzoyl) ethyl phosphinate (Omnirad TPO-L), etc. (all manufactured by IGM Resins BV), which may be used individually or in combination of two or more. Among these, 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 from the viewpoint of compatibility with components (A) and (B), 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). If the amount is 0.01 parts by mass or more, sufficient surface curability will be achieved, and if it is 20 parts by mass or less, there is no risk of deterioration of deep curability.

[0075] (D) UV absorber with light absorption in the 360-410 nm range The composition of the present invention may contain an ultraviolet absorber that absorbs light at wavelengths of 360 to 410 nm in order to adjust the curability during stereolithography using a 3D printer.

[0076] Specific examples of UV absorbers usable in the present invention include 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (Tinuvin 571, manufactured by BASF), 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxyC7-9 side chain and linear alkyl ester of benzenepropanoate (Tinuvin 384-2, manufactured by BASF), 2-(5-chloro-2-benzotriazol)-6-tert-butyl-p-cresol (Tinuvin 326, manufactured by BASF), and the reaction product of 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl)-5-hydroxyphenyl and [(C10-C16 mainly C12-C13 alkyloxy)methyl]oxirane (Tinuvin Examples include 400 (manufactured by BASF), thioxanthone, 2-isopropylthioxanthone, 2,4-diethylthioxanthone, benzophenone, camphorquinone, 1-phenyl-1,2-propanedione, diethylaminohydroxybenzoyl hexyl benzoate (Uvinul A Plus, manufactured by BASF), 1-(4-tert-butylphenyl)-3-(4-methoxyphenyl)-1,3-propanedione, 2-ethylhexyl 4-methoxycinnamate, etc., which may be used individually or in combination of two or more.

[0077] When using an ultraviolet absorber, 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). If the amount is 0.01 parts by mass or more, the effect of the ultraviolet absorber is sufficiently obtained, and if it is 20 parts by mass or less, there is no risk of deterioration of deep curing properties.

[0078] (E) Color material Various colorants may be added to the composition of the present invention for the purpose of adjusting the curability of the composition or adding color. As colorants, general pigments (iron oxide, titanium dioxide, zinc oxide, etc.), dyes, carbon black, etc. can be used. These may be used individually or in combination of two or more.

[0079] When using a colorant, the amount added is preferably 0.01 to 20 parts by mass per 100 parts by mass of component (A). If the amount is 0.01 parts by mass or more, the effect of the colorant can be obtained sufficiently, and if it is 20 parts by mass or less, there is no risk of deterioration of deep hardening properties.

[0080] Furthermore, the composition of the present invention may contain additives such as silane coupling agents, adhesion aids, polymerization inhibitors, antioxidants, and light-resistant stabilizers such as ultraviolet absorbers and light stabilizers, to the extent that they do not impair the effects of the present invention. Furthermore, the composition of the present invention can be used in appropriate mixtures with other resin compositions.

[0081] [2] Method for producing a silicone composition The method for producing the silicone composition of the present invention is not particularly limited, and conventionally known methods can be used. That is, the silicone composition of the present invention is 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 includes the following steps (1) and (2). Step (1): A process for producing component (B) by a method comprising the following steps (α), (β), and (γ). Step (2): A step of mixing components (A) to (C) and other components as needed.

[0083] • Process (1): Process for manufacturing component (B) Step (1) is a step of producing component (B) by a method comprising the following steps (α), (β), and (γ).

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

[0085] Step (β): To obtain a dispersion of silica particles, which is an intermediate for component (B), the surface of the hydrophilic silica particles is treated by adding either or both of the 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). R 7 Si(OR 8 )3(III) (In the formula, R 7 and R 8 (This expresses the same meaning as above.)

[0086] Step (γ): To obtain hydrophobic silica particles of component (B), the surface of the silica particles, which are an intermediate of component (B), is treated by adding either or both of the silazane compound represented by the following general formula (IV) and the monofunctional silane compound represented by the following general formula (V) to the dispersion of silica particles, which are an intermediate of component (B), obtained in step (β). R 93SiNHSiR 9 3(IV) R 9 3SiX (V) (In the formula, R 9 And X has the same meaning as above.

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

[0088] • Step (2): The process of mixing components (A) to (C). The process of mixing components (A) to (C) is not particularly limited. The UV-curable silicone composition for photopolymerization of the present invention can be obtained by mixing components (A) to (C) above, and other components as needed, in any order and stirring. The apparatus used for stirring and other operations is not particularly limited, but a grinder, a three-roll grinder, a ball mill, a planetary mixer, etc., can be used. These apparatuses may also be combined as appropriate.

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

[0090] The viscosity of the UV-curable silicone composition for photopolymerization of the present invention at 23°C is preferably 500 Pa·s or less, more preferably 400 Pa·s or less, and even more preferably 100 Pa·s or less, from the viewpoint of photopolymerization properties. If it exceeds 500 Pa·s, the moldability deteriorates, and it may not be possible to accurately obtain the desired molded object. The lower limit is not particularly limited, but it is preferably 1 Pa·s or more, and more preferably 2 Pa·s or more. In this invention, 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 form a cured product having excellent rubber properties through the following process. (i) A step of irradiating the photopolymerizable UV-curable silicone composition of the present invention with ultraviolet light to radically cure the composition and obtain a primary cured product, and (ii) A step of further condensing and hardening the obtained primary hardened product to obtain a secondary hardened product.

[0092] • Process (i): Process for obtaining the first cured product Step (i) is a step of irradiating the photopolymerizable ultraviolet-curable silicone composition of the present invention with ultraviolet light to radically cure the composition and obtain a primary cured product.

[0093] Examples of ultraviolet light sources used in process (i) include UV-LED lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, carbon arc lamps, and xenon lamps. Ultraviolet irradiation is preferably carried out, for example, at room temperature (around 25°C) under an inert gas atmosphere such as nitrogen or argon.

[0094] The amount of ultraviolet radiation (cumulative light dose) required to form a primary cured product by ultraviolet radiation is preferably 1 to 10,000 mJ / cm² for a sheet formed from the composition of the present invention to a thickness of about 2.0 mm. 2 More preferably, 10 to 8,000 mJ / cm² 2 That is, an illuminance of 100 mW / cm². 2 When using ultraviolet light, irradiation for approximately 0.01 to 100 seconds is sufficient.

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

[0096] • Process (ii): Process for obtaining the 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 condensation of component (A) and / or component (B) can be accelerated by applying moisture. Specifically, it is preferable to carry out the condensation curing in an environment of 50%RH to 85%RH and 20°C to 85°C for 12 to 36 hours, particularly 18 to 24 hours.

[0097] The tensile strength of the secondary hardened product obtained in step (ii) is 4.5 MPa or higher, preferably 5.0 MPa or higher. The elongation at break is 25 It is 0% or more, 30 0% or more is preferable. In this invention, in particular, ultraviolet light with a wavelength of 405 nm at 25°C is used at a rate of 8,000 mJ / cm². 2 After irradiation to achieve this state, the tensile strength and elongation at break of the 2.0 mm thick cured material obtained by further curing in an environment of 85°C and 85%RH for 24 hours can be within the above range. [Examples]

[0098] The present invention will be described more specifically 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 each component used in the examples are as follows. In the formula below, Me represents a methyl group and Ph represents a phenyl group.

[0099] [1] Ingredients (A) component [ka] (In the formula, the order of siloxane units enclosed in parentheses is arbitrary.)

[0100] (B) Component (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 (B-1 ratio) Hydrophobic silica particles obtained in comparative synthesis example 1

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

[0102] [2] Synthesis of hydrophobic silica nanoparticles [Synthesis Example 1] Step (α): Synthesis step of hydrophilic silica particles In a 3-liter glass reactor equipped with a stirrer, dropping funnel, and thermometer, 623.7 g of methanol, 41.4 g of water, and 49.8 g of 28% by mass aqueous ammonia were added and mixed. The temperature of this solution was adjusted to 35°C, and while stirring, 1,163.7 g of tetramethoxysilane and 418.4 g of 5.4% by mass aqueous ammonia were simultaneously added dropwise over 5 hours. After the dropwise addition was complete, stirring was continued for another 0.5 hours to carry out hydrolysis and obtain a suspension of hydrophilic spherical silica particles. An ester adapter and condenser were attached to the glass reactor, and the mixture was heated to 60-70°C to remove 649 g of methanol by distillation. Then, 1,600 g of water was added, and the mixture was further heated to 70-90°C to remove 160 g of methanol by distillation to obtain an aqueous suspension of hydrophilic silica particles.

[0103] • Step (β): Surface treatment step for hydrophilic silica particles To this aqueous suspension, 115.8 g of methyltrimethoxysilane (0.1 equivalent relative to SiO2) and 46.6 g of 5.4% by mass aqueous ammonia were added dropwise over 0.5 hours at 25°C. After addition, the mixture was heated to 50°C and aged for 1 hour. After completing the reaction, the mixture was cooled to 25°C, and the hydrophilic silica particle surface was treated to obtain a dispersion of hydrophobic silica particle intermediate, which is an intermediate of component (B).

[0104] • Step (γ): Surface treatment step for the (B) component intermediate. To the dispersion obtained in this way, 1,000 g of methyl isobutyl ketone was added, and the dispersion was heated to 80-115°C while the liquid interface remained in a highly turbulent state, and 1,336 g of a methanol and water mixture was removed by distillation over 11 hours. To the obtained dispersion, 357.4 g of hexamethyldisilazane was added at 25°C, and the dispersion was heated to 120°C and reacted for 3 hours to trimethylsilylate the silica particles and obtain hydrophobic silica particles. Subsequently, the solvent was removed by heating and distillation using an evaporator to obtain 477 g of hydrophobic silica particles (B-1).

[0105] [Synthesis Example 2] In step (α) of Synthesis Example 1, 470 g of hydrophobic silica particles (B-2) were obtained by following the same procedure except that 1,163.7 g of tetramethoxysilane was replaced with 901.9 g of methyl silicate (methyl silicate 51, manufactured by Colcoat).

[0106] [Synthesis Example 3] Except for changing the amount of methyltrimethoxysilane used in step (β) of Synthesis Example 1 to 11.6 g (0.01 equivalents relative to SiO2), 360 g of hydrophobic silica particles (B-3) were obtained in the same manner.

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

[0108] Next, 0.78 g of hexamethyldisilazane was added, and the dispersion was heated to 105°C and reacted for 2 hours. Finally, 2.6 g of 35% hydrochloric acid aqueous solution was added. g The silica particles were precipitated by adding [a certain substance]. Then, the solvent was removed by heating and distillation using an evaporator to obtain hydrophobic silica particles (B-1 ratio).

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

[0110] 1. Measurement of particle size of hydrophobic silica particles (1) 0.1 g of the sample was placed in a glass bottle, 20 g of methanol was added, and the mixture was stirred. (2) The sample was dispersed for 10 minutes using an ultrasonic dispersion device and used as the measurement sample. (3) The sample from (2) was measured using a laser scattering particle size distribution analyzer (Nikkiso Co., Ltd., Nanotrac150), and the volume-based median diameter (the particle size corresponding to 50% of the cumulative distribution when the particle size distribution is expressed as a cumulative distribution) was defined as the particle size.

[0111] 2. Measurement of the degree of hydrophobicity of hydrophobic silica particles (methanol titration method) (1) 0.2 mg of the sample was weighed into a 500 mL Erlenmeyer flask. (2) Add 50 mL of deionized water to (1) and stir with a stirrer. (3) Methanol was added dropwise from the burette while stirring, and the volume added was read when the entire sample was suspended in deionized water. (4) The degree of hydrophobicity was determined by the following equation. Degree of hydrophobicity (%) = [{Amount of methanol added (mL)} / [{Amount of methanol added (mL) + Amount of deionized water (mL)}] × 100

[0112] [Table 1]

[0113] [3] Manufacturing and evaluation of silicone compositions, manufacturing and evaluation of cured products [Examples 1-5 and Comparative Examples 1,2] The components (A) to (C) above were mixed in the compositions shown in Table 2 to prepare a silicone composition. The viscosity of the compositions in Table 2 was measured at 23°C using a rotational viscometer. The prepared silicone composition was cured using a UV curing device manufactured by CCS Corporation under a nitrogen atmosphere at room temperature (25°C) with ultraviolet light at a wavelength of 405 nm, at a dose of 8,000 mJ / cm². 2 The material was cured by irradiating it with ultraviolet light to obtain a primary cured product. Subsequently, the obtained primary cured product was treated at 85°C and 85%RH for 24 hours to obtain a secondary cured product. The hardness, elongation at break, and tensile strength of the obtained primary and secondary cured sheets (2.0 mm thick) were measured in accordance with JIS K 6249:2003.

[0114] [Table 2]

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

Claims

1. (A) Organopolysiloxanes having two or more acryloyloxyalkyloxy groups or methacryloyloxyalkyloxy groups directly bonded to a 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 directly bonded to a silicon atom 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 acryloyloxyalkyloxy groups or methacryloyloxyalkyloxy groups directly bonded to a 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.

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