UV-curable polysiloxane compositions and their cured products for photoforming

Abstract

This invention provides a UV-curable polysiloxane composition for photoforming, comprising: (A) an organopolysiloxane having two groups of the following formula (1) in one molecule (where R1 represents a monovalent hydrocarbon group, R2 represents an oxygen atom or an alkyl group, R3 represents acryloxyalkyl, methacryloxyalkyl, acryloxyalkoxy, methacryloxyalkoxy, (acryloxyalkyl)dimethylsilyloxy or (methacryloxyalkyl)dimethylsilyloxy, p represents a number satisfying 0 ≤ p ≤ 10, and a represents a number satisfying 1 ≤ a ≤ 3), (B) hydrophobic silica particles with an average particle size of 10 to 1,000 nm and a hydrophobicity of 60% or more obtained by methanol titration, and (C) a photopolymerization initiator.

Description

[Technical Field]

[0001] This invention relates to ultraviolet-curable polysiloxane compositions for photoshaping and their cured forms. [Previous Technology]

[0002] In recent years, the development of shaping materials used in 3D printers has become increasingly popular, and various materials, from metals to resins, are used as shaping materials. In the field of resins, examples include acrylate-based photocurable resin compositions or urethane acrylate-based photocurable resin compositions, etc. The cured products of these resin compositions are very hard and cannot be bent freely (Patent Document 1).

[0003] Due to the increasing demand for flexible polysiloxane materials depending on the application, polysiloxane materials for 3D printers have been developed to suit various shaping methods. For example, as a material for photolithography, compositions containing alkenyl-containing organopolysiloxanes, mercapto-containing organopolysiloxanes, and MQ resins have been developed (Patent Document 2). Furthermore, for dispensing technology, polysiloxane compositions containing platinum catalysts activated by ultraviolet light have been proposed (Patent Document 3). Moreover, for 3D printers, thermosetting polysiloxane compositions have also been proposed (Patent Document 4).

[0004] Furthermore, for 3D printers using inkjet printing, UV-curable low-viscosity polysiloxane materials have been proposed (Patent Document 5). This material has the advantages of curing with short-term UV irradiation and excellent shaping accuracy, but compared to conventional polysiloxane materials, it lacks mechanical strength and heat resistance. Therefore, for the rapidly increasing use of photoforming in recent years, new UV-curable polysiloxane compositions have been developed (Patent Documents 6 and 7). However, compared to thermosetting polysiloxane compositions, they are brittle due to low elongation. Also, in recent years, even higher viscosities have become possible for photoforming. [Prior Art Documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent No. 5890990 [Patent Document 2] Japanese Patent No. 4788863 [Patent Document 3] Japanese Patent No. 5384656 [Patent Document 4] Japanese Patent No. 6727290 [Patent Document 5] Japanese Patent No. 6687111 [Patent Document 6] Japanese Patent No. 6962290 [Patent Document 7] Japanese Patent No. 7342910 [Summary of the Invention]

[0006] [Problem to be Solved by the Invention] The present invention has been made in view of the above-mentioned situation, and its object is to provide a UV-curable polysiloxane composition and its cured form that have a viscosity suitable for photoforming methods such as laser processing or digital light processing (DLP) and exhibit excellent rubber-like properties. [Means for Solving the Problem]

[0007] As a result of the inventors’ dedicated review in order to achieve the above-mentioned objectives, they discovered that by adding a photopolymerization initiator to an organopolysiloxane having a specific (meth)acryloxy group and hydrophobic silica particles having a specific average particle size and a specific degree of hydrophobicity, an ultraviolet-curable polysiloxane composition that can also be used in photoforming methods and imparts good rubber-like properties to the cured material can be obtained, thus completing the present invention.

[0008] That is, the present invention provides: 1. A UV-curable polysiloxane composition for photoforming, comprising: (A) an organopolysiloxane having two groups of the following formula (1) in one molecule: 100 parts by mass, (wherein, R1 independently represents a monovalent hydrocarbon group having 1 to 20 carbon atoms, R2 represents an oxygen atom or an alkyl group having 1 to 20 carbon atoms, R3 independently represents acryloxyalkyl, methacryloxyalkyl, acryloxyalkoxy, methacryloxyalkoxy, (acryloxyalkyl)dimethylsilyloxy or (methacryloxyalkyl)dimethylsilyloxy, p represents a number satisfying 0 ≤ p ≤ 10, a represents a number satisfying 1 ≤ a ≤ 3, and dashed lines represent bonded bonds), 1. (B) Hydrophobic silica particles with an average particle size of 10–1,000 nm and a hydrophobicity of 60% or more obtained by methanol titration: 10–500 parts by mass, and (C) Photopolymerization initiator: 0.01–20 parts by mass. 2. The UV-curable polysiloxane composition for photoforming as described in 1, having a viscosity of 500 Pa·s or less at 23°C. 3. The UV-curable polysiloxane composition for photoforming as described in 1 or 2, further containing 0.01–20 parts by mass of (D) a UV absorber having light absorption at wavelengths of 360–410 nm, relative to 100 parts by mass of component (A). 4. The UV-curable polysiloxane composition for photoforming as described in any one of 1–3, further containing 0.01–20 parts by mass of (E) a colorant, relative to 100 parts by mass of component (A). 5. A cured product of a UV-curable polysiloxane composition for photoforming as described in any one of claims 1 to 4. 6. The cured product as described in claim 5, having an elongation at cut of 150% or more. [Effects of the Invention]

[0009] The UV-curable polysiloxane composition for photoforming of the present invention has a viscosity suitable for photoforming methods such as laser and DLP, and the cured material exhibits good rubber properties after curing.

Implementation Method

[0010] [Forms of the Invention] The present invention will now be described in detail. [1] UV-curable polysiloxane composition for photoforming The UV-curable polysiloxane composition for photoforming of the present invention contains the following components (A) to (C). (A) An organic polysiloxane having two groups of the following formula (1) in one molecule (B) Hydrophobic silica particles with an average particle size of 10 to 1,000 nm and a hydrophobicity of 60% or more obtained by methanol titration (C) Photopolymerization initiator

[0011] (A) Organic polysiloxane The component (A) used in this invention is one of the crosslinking components of this composition. It is an organic polysiloxane having two bases as shown in the following formula (1) in one molecule, and whose main chain is substantially composed of repeating two organic polysiloxane units.

[0012] (In the formula, the dashed line represents the bond).

[0013] In formula (1), R1 is a monovalent hydrocarbon group with 1 to 20 carbon atoms, preferably a monovalent hydrocarbon group with 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, excluding aliphatic unsaturated groups. R2 is an oxygen atom or an alkyl group with 1 to 20 carbon atoms, preferably an alkyl group with 1 to 10 carbon atoms, more preferably an alkyl group with 1 to 5 carbon atoms. R3 is an acryloxyalkyl group, methacryloxyalkyl group, acryloxyalkoxy group, methacryloxyalkoxy group, (acryloxyalkyl)dimethylsilyloxy group, or (methacryloxyalkyl)dimethylsilyloxy group.

[0014] In formula (1), the monovalent hydrocarbon group of R1 with 1 to 20 carbon atoms can be any of straight chain, branched, or cyclic, such as alkyl, alkenyl, aryl, aralkyl, etc. As specific examples, alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tributyl, n-hexyl, cyclohexyl, n-octyl, 2-ethylhexyl, n-decyl, etc.; alkenyl groups such as vinyl, allyl (2-propenyl), 1-propenyl, isopropenyl, butenyl, etc.; aryl groups such as phenyl, tolyl, xylyl, naphthyl, etc.; and aralkyl groups such as benzyl, phenylethyl, phenylpropyl, etc.

[0015] Furthermore, some or all of the hydrogen atoms of the carbon atoms bonded to these monovalent hydrocarbon groups may be replaced by halogen atoms such as chlorine, fluorine, and bromine, or by other substituents such as cyano. Specific examples of such substituents include halogen-substituted hydrocarbon groups such as chloromethyl, bromoethyl, and trifluoropropyl; and cyano-substituted hydrocarbon groups such as cyanoethyl. Among these, R1 is preferably an alkyl or phenyl group having 1 to 5 carbon atoms, and more preferably methyl, ethyl, or phenyl.

[0016] The alkyl group having 1 to 20 carbon atoms in R2 can be straight-chain, branched, or cyclic. Specific examples include methylene, ethyl, propyl, trimethylene, tetramethylene, isobutyl, pentamethylene, hexamethylene, heptamethylene, octamethylene, nonamethylene, and decyl. Among these, R2 is preferably an oxygen atom, methylene, ethyl, or trimethylene, and more preferably an oxygen atom or ethyl.

[0017] The number of carbon atoms in the alkyl (alkylyl) group of R3, such as acryloxyalkyl, methacryloxyalkyl, acryloxyalkoxy, methacryloxyalkoxy, (acryloxyalkyl)dimethylsilyloxy, or (methacryloxyalkyl)dimethylsilyloxy, is not particularly limited, but is preferably 1 to 10, more preferably 1 to 5. Specific examples of such alkyl groups include those exemplified in R1 with 1 to 10 carbon atoms. Specific examples of R3 include those shown in the following formulas, but are not limited to these.

[0018] (In the formula, the dashed line represents the bond).

[0019] In the above formula, b is a number satisfying 1 ≤ b ≤ 4, preferably a number satisfying 1 ≤ b ≤ 3. R4 is an alkyl group having 1 to 10 carbon atoms, preferably an alkyl group having 1 to 5 carbon atoms. As a specific example of R4, those of the groups exemplified in R2 having 1 to 10 carbon atoms can be given, among which methylene, ethylene, and trimethylene are preferred, and methylene and ethylene are even more preferred.

[0020] In formula (1), p is a number that satisfies 0≦p≦10, preferably 0≦p≦5, and even more preferably 0 or 1, and a is a number that satisfies 1≦a≦3, preferably 1 or 2.

[0021] (A) The bonding position of the base shown in the above general formula (1) in the organic polysiloxane molecule of the component can be at the end of the molecular chain (single end or two ends), or at the non-end of the molecular chain (i.e., in the middle of the molecular chain or the side chain of the molecular chain), or both, but in terms of the flexibility of the resulting hardened material, only the end is desired.

[0022] In the organopolysiloxane molecule of component (A), the groups bonded to silicon atoms other than those shown in the general formula (1) above can be, for example, the same groups as those in R1 above, preferably 1 to 12 carbon atoms excluding aliphatic unsaturated groups, and more preferably 1 to 10 monovalent hydrocarbon groups. As specific examples, the same groups as those exemplified in R1 above can be given, but for the sake of ease of synthesis, alkyl, aryl, halogenated alkyl groups are preferred, and methyl, phenyl, and trifluoropropyl groups are even more preferred.

[0023] Furthermore, the molecular structure of component (A) is basically a straight-chain or branched chain (including a straight-chain structure with branches in a portion of the main chain) formed by repeating two organosiloxane units in the main chain, preferably a straight-chain organopolysiloxane with both ends of the molecular chain capped by the base shown in the above general formula (1). Component (A) may be a single polymer having such molecular structure, a copolymer formed by such molecular structure, or a mixture of two or more such polymers.

[0024] (A) The viscosity of the organopolysiloxane component at 25°C is preferably 10 to 10,000 mPa·s, more preferably 50 to 5,000 mPa·s, considering further improvement in the viscosity of the composition and the mechanical properties of the hardened product. This viscosity range is generally equivalent to about 10 to 550 in terms of number-average degree of polymerization for linear organopolysiloxanes, preferably about 50 to 450. Furthermore, in this invention, the viscosity can be measured by a rotational viscometer (e.g., BL type, BH type, BS type, cone-plate type, rheometer, etc.) (the same applies below). Also, in this invention, the degree of polymerization (or molecular weight) can be obtained, for example, by using toluene or the like as the developing solvent, as the number-average degree of polymerization (or number-average molecular weight) converted from polystyrene in gel permeation chromatography (GPC) analysis.

[0025] Specific examples of organic polysiloxanes as components (A) can be shown in the following formulas (2) to (5), but are not limited to these.

[0026] (In the formula, R4 and b represent the same definitions as above, Me represents methyl, Ph represents phenyl, q and r represent the numbers that make the viscosity of the above organopolysiloxane the above value, but q is preferably 1≦q≦400, more preferably 1≦q≦200, and even more preferably 1≦q≦100, and r is preferably 1≦r≦400, and even more preferably 10≦r≦300; the order of the siloxane units with q and r is arbitrary).

[0027] Such organopolysiloxanes can be manufactured using well-known methods. For example, the polysiloxane shown in formula (2) above can be obtained by reacting 2-hydroxyethyl acrylate with a dimethylsiloxane-diphenylsiloxane copolymer with dimethylvinylsiloxy-terminated ends in a hydrosilane reactant of dimethylchlorosilane. The organopolysiloxane shown in formula (3) above can be obtained as a hydrosilane reactant of a dimethylvinylsiloxy-terminated dimethylsiloxane-diphenylsiloxane copolymer with 3-(1,1,3,3-tetramethyldisiloxyl)propyl methacrylate (CAS No. 96474-12-3). The organopolysiloxane shown in formula (4) above can be obtained by reacting 2-hydroxyethyl acrylate with a dimethylsiloxane-diphenylsiloxane copolymer with a hydrosilane reactant of dichloromethylsilane. The organopolysiloxane shown in formula (5) above can be obtained by reacting methacrylate (hydroxydimethylsilyl) ester (CAS No. 118536-45-1) with a dimethylsiloxane-diphenylsiloxane copolymer with a hydrosilane reactant of dichloromethylsilane.

[0028] (B) Hydrophobic silicon dioxide microparticles (B) Component is hydrophobic silicon dioxide particles. By containing component (B), the fluidity of the composition can be maintained while the mechanical strength of the hardened material can be improved.

[0029] (B) The average particle size of the component is 10–1,000 nm, preferably 20–1,000 nm, more preferably 20–500 nm, and even more preferably 30–200 nm. If the average particle size is less than 10 nm, the aggregation becomes intense and the fluidity is lost. Furthermore, if it is greater than 1,000 nm, the effect of improving mechanical strength is small. Moreover, the above-mentioned average particle size is the value of the median particle size (D50) of the volume standard determined by particle size distribution measurement by laser diffraction method.

[0030] (B) The degree of hydrophobicity of the component obtained by methanol titration is 60% or more, preferably 64% or more. If the silicon dioxide particles have a high degree of hydrophobicity, they will not agglomerate even when highly filled in the composition, thus not deteriorating the fluidity and improving the mechanical strength of the hardened material.

[0031] The degree of hydrophobicity is determined by the methanol titration method shown below. (1) Float the sample in a specific amount of ion-exchanged water and add methanol dropwise while stirring. (2) Read the dropwise amount when the total volume of the sample is suspended in ion-exchanged water. (3) The degree of hydrophobicity is calculated as [{methanol dropwise amount (mL)} / {methanol dropwise amount (mL) + ion-exchanged water volume (mL)}]×100.

[0032] The shape of component (B) used in this invention is not particularly limited, but it is preferably spherical.

[0033] The amount of component (B) is 10 to 500 parts by mass relative to 100 parts by mass of component (A), preferably 20 to 300 parts by mass, and more preferably 30 to 200 parts by mass. If it is less than 10 parts by mass, the effect of improving the mechanical strength of the hardened material will be smaller, and if it is more than 500 parts by mass, the viscosity of the composition will be too high and the fluidity will be poor.

[0034] Furthermore, (B) is preferably a silicon dioxide surface having R7SiO3 / 2 units (R7 being a monovalent hydrocarbon group with 1 to 20 substituted or unsubstituted carbon atoms) and R9 3SiO1 / 2 units (R9 being a monovalent hydrocarbon group with 1 to 6 substituted or unsubstituted carbon atoms of the same or different kind).

[0035] Such component (B) can be obtained, for example, by introducing R7SiO3 / 2 units into the surface of hydrophilic silica particles obtained by hydrolysis and condensation of a 4-functional silane compound, alkyl silicate or a mixture thereof, followed by introducing R9 3SiO1 / 2 units.

[0036] [(B) Synthesis Method] Specifically, the (B) component used in this invention is preferably synthesized by a method comprising the following three steps: Step (α): Synthesis of hydrophilic silica particles; Step (β): Surface hydrophobic treatment of the hydrophilic silica particles to obtain an intermediate of (B) component; Step (γ): Further surface hydrophobic treatment of the (B) component intermediate to obtain hydrophobic silica particles of (B) component.

[0037] The following steps are described in sequence. • 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 the 4-functional silane compound shown in general formula (I) and the alkyl silicate shown in general formula (II) in the presence of an alkaline substance in a mixture of a hydrophilic organic solvent and water. (In the formula, R5 is a monovalent hydrocarbon group with 1 to 6 carbon atoms of the same or different kind; m is a number from 1 to 100).

[0038] In the above general formulas (I) and (II), R5 is a monovalent hydrocarbon group with 1 to 6 carbon atoms, either the same or different, preferably a monovalent hydrocarbon group with 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms. As a monovalent hydrocarbon group represented by R5, it can be any of straight-chain, branched, or cyclic. Specific examples include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, and n-butyl; aryl groups such as phenyl, etc., wherein R5 is preferably methyl, ethyl, n-propyl, or n-butyl, more preferably methyl or ethyl.

[0039] In the above general formula (II), m is a number from 1 to 100, preferably from 1 to 50, and even more preferably from 1 to 25.

[0040] Specific examples of the tetrafunctional silane compounds represented by general formula (I) above include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane; and tetraaryloxysilanes such as tetraphenoxysilane, with tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane being preferred, and tetramethoxysilane and tetraethoxysilane being even more preferred. Furthermore, specific examples of alkyl silicates represented by general formula (II) include methyl silicate and ethyl silicate, with methyl silicate being preferred. These compounds can be used alone or in mixtures of two or more.

[0041] As a specific example of the hydrophilic organic solvent used in step (α), there are no particular limitations as long as it can dissolve the 4-functional silane compound represented by general formula (I) or the alkyl silicate represented by general formula (II) and water. Examples include alcohols; ceroxyls such as methyl ceroxyls, ethyl ceroxyls, butyl ceroxyls, and acetic acid ceroxyls; ketones such as acetone and methyl ethyl ketone; and ethers such as dialkyl and tetrahydrofuran. Alcohols and ceroxyls are preferred, and alcohols are even more preferred.

[0042] As such alcohols, alcohols represented by the following general formula (VI) can be cited. (In the formula, R6 is a monovalent hydrocarbon group having 1 to 6 carbon atoms).

[0043] In the above general formula (VI), R6 is a monovalent hydrocarbon group having 1 to 6 carbon atoms, preferably having 1 to 4 carbon atoms, and more preferably having 1 or 2 carbon atoms. As a specific example of the monovalent hydrocarbon group represented by R6, the same group as that exemplified in R5 can be given, but R6 is preferably methyl, ethyl, n-propyl and isopropyl, and more preferably methyl and ethyl.

[0044] Specific examples of alcohols represented by general formula (VI) include methanol, ethanol, propanol, isopropanol, butanol, etc., with methanol and ethanol being preferred. If the number of carbon atoms in the alcohol increases, the particle size of the resulting silicon dioxide particles becomes larger. Therefore, methanol is preferred for obtaining silicon dioxide particles with the desired small particle size.

[0045] The amount of water used in the above hydrolysis and condensation is preferably 0.5 to 5 mol, more preferably 0.6 to 2 mol, and even more preferably 0.7 to 1 mol, relative to 1 mol of the total alkyl groups of the 4-functional silane compound represented by general formula (I) and / or the alkyl silicate represented by general formula (II). Furthermore, the ratio of water to hydrophilic organic solvent is preferably 10 to 200 parts by mass of hydrophilic organic solvent relative to 100 parts by mass of water.

[0046] Furthermore, specific examples of the alkaline substance used in step (α) include ammonia, dimethylamine, and diethylamine, with ammonia and diethylamine being preferred, and ammonia being even more preferred. These alkaline substances can be dissolved in water in the required amount, and the resulting aqueous solution (alkaline) can be mixed with a hydrophilic organic solvent.

[0047] Relative to 1 mole of the total hydroxyl groups of the 4-functional silane compound shown in general formula (I) and / or the alkyl silicate shown in general formula (II), 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. In this case, the less basic substance used, the more desirable the small-diameter silica particles become.

[0048] The alkaline substance may be added to the mixture of water and water after being added to the mixture of the hydrophilic organic solvent, and may be further added together with the 4-functional silane compound of general formula (I) and / or the alkyl silicate of general formula (II), or may be added to the mixture of water and hydrophilic organic solvent at the same time as the addition of the 4-functional silane compound and / or the alkyl silicate and the hydrophilic organic solvent.

[0049] The reaction conditions in step (α) are not particularly limited and can be carried out under known conditions, such as preferably at around 10 to 80°C for about 1 to 10 hours.

[0050] The resulting mixed solvent dispersion containing hydrophilic silica particles can be used directly in step (β), but it is preferable to add water to the mixed solvent dispersion containing hydrophilic silica particles, distill off the hydrophilic organic solvent, convert it into an aqueous dispersion, and the remaining alkoxy groups are hydrolyzed, thus converting it into an aqueous dispersion containing hydrophilic silica particles.

[0051] 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 (repeated as needed). The amount of water added is preferably 50 to 200 parts by mass, more preferably 80 to 150 parts by mass, relative to 100 parts by mass of the total amount of hydrophilic organic solvent and alcohol generated in the synthesis step of the hydrophilic silica particles.

[0052] ・Step (β): Surface treatment step of hydrophilic silica particles Step (β) is a step in which the surface of the aforementioned hydrophilic silica particles is treated by adding one or both of the following general formula (III) trifunctional silane compound 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) of component (B). (In the formula, R7 is a monovalent hydrocarbon group with 1 to 20 carbon atoms, substituted or unsubstituted, and R8 is a monovalent hydrocarbon group with 1 to 6 carbon atoms, the same or different).

[0053] In the above general formula (III), R7 is a monovalent hydrocarbon group with 1 to 20 carbon atoms, either substituted or unsubstituted, preferably with 1 to 10 carbon atoms, more preferably with 1 to 3 carbon atoms, and even more preferably with 1 or 2 carbon atoms. The monovalent hydrocarbon group of R7 can be any of straight-chain, branched, or cyclic. Specific examples include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, n-hexyl, and n-decyl, wherein R7 is preferably methyl, ethyl, n-propyl, or isopropyl, and more preferably methyl or ethyl. Furthermore, some or all of the hydrogen atoms of these monovalent hydrocarbon groups can be substituted by halogen atoms such as fluorine, chlorine, or bromine atoms, preferably fluorinated alkyl groups.

[0054] In the above general formula (III), R8 is a monovalent hydrocarbon group with 1 to 6 carbon atoms, either the same or different, preferably a monovalent hydrocarbon group with 1 to 3 carbon atoms, more preferably 1 or 2 carbon atoms. As a specific example of R8, the same group as that exemplified in R5 can be given, wherein R8 is preferably methyl, ethyl or n-propyl, more preferably methyl or ethyl.

[0055] Specific examples of the trifunctional silane compound represented by general formula (III) include, for example, non-substituted 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 even more preferred.

[0056] The amount of the trifunctional silane compound shown in 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, relative to 1 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 obtained component (B) becomes higher, and therefore the dispersibility becomes better. If it is less than 1 mol, the possibility of aggregation of component (B) can be suppressed. The processing conditions of step (β) are not particularly limited, for example, it is preferably about 10 to 80°C for about 1 to 10 hours.

[0057] ・Step (γ): Surface treatment step of component (B) Step (γ) is a step in which the surface of the intermediate of component (B) is treated by adding either or both of the silane compound shown in general formula (IV) and the monofunctional silane compound shown in general formula (V) to the ketone solvent dispersion obtained in step (β) to obtain the intermediate of component (B) hydrophobic silica particles. By this step, R9 3SiO1 / 2 units are introduced to the surface in the form of triorganosilylation of the silanol groups remaining on the surface of the hydrophobic silica particle intermediate. (In the formula, R9 is a monovalent hydrocarbon group with 1 to 6 carbon atoms, which may be the same or different, substituted or unsubstituted, and X is an OH group or a hydrolyzable group).

[0058] In the above general formulas (IV) and (V), R9 is a monovalent hydrocarbon group with 1 to 6 carbon atoms, either substituted or unsubstituted, preferably with 1 to 4 carbon atoms, more preferably with 1 or 2 carbon atoms. Specific examples of R9 may include those similar to those exemplified in R5, wherein R9 is preferably methyl, ethyl, or n-propyl, more preferably methyl or ethyl. Furthermore, some or all of the hydrogen atoms of these monovalent hydrocarbon groups may be substituted by halogen atoms such as fluorine, chlorine, or bromine atoms, preferably fluorinated alkyl groups.

[0059] X is an OH group or a hydrolyzable group. Examples of hydrolyzable groups include chlorine atoms; alkoxy groups such as methoxy and ethoxy; amino groups, N-methylamino groups, N,N'-dimethylamino groups, N-ethylamino groups, N,N'-diethylamino groups; acetoxy groups such as acetoxy groups, etc., preferably alkoxy or amino groups, more preferably alkoxy groups, and especially preferably methoxy or ethoxy groups.

[0060] Specific examples of silazane compounds represented by general formula (IV) include hexamethyldisilazane, hexaethyldisilazane, tetramethyldivinyldisilazane, etc., with hexamethyldisilazane being preferred. Specific examples of monosilane compounds represented by general formula (V) include monosilyl alcohol compounds such as trimethylsilyl alcohol and triethylsilyl alcohol; monochlorosilanes such as trimethylchlorosilane and triethylchlorosilane; monoalkoxysilanes such as trimethylmethoxysilane and trimethylethoxysilane; monoaminosilanes such as trimethylsilyldimethylamine and trimethylsilyldiethylamine; and monoacetoxysilanes such as trimethylethoxysilane. Trimethylsilyl alcohol, trimethylmethoxysilane, or trimethylsilyldiethylamine are preferred, and trimethylsilyl alcohol or trimethylmethoxysilane is even more preferred. These compounds can be used alone or in mixtures of two or more.

[0061] The amount of the silazane compound shown in general formula (IV) and / or the monofunctional silane compound shown in 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 hydrophobicity of the obtained hydrophobic silica particles becomes higher and the dispersibility becomes better. Considering cost, etc., an amount of 0.5 mol or less is sufficient.

[0062] To convert the dispersion medium of the mixed solvent dispersion of the hydrophobic silica particle intermediate obtained in step (β) from a mixture of water or a hydrophilic organic solvent and an alcohol produced during hydrolysis into a ketone solvent, this can be done by adding a ketone 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 are preferably at approximately 10–150°C for approximately 1–20 hours. The amount of ketone solvent added is preferably 50–500 parts by mass, more preferably 100–300 parts by mass, relative to 100 parts by mass of the obtained hydrophobic silica particle intermediate. Specific examples of the ketone solvent used herein include methyl ethyl ketone, methyl butyl ketone, acetone, etc., with methyl isobutyl ketone being preferred. Furthermore, there are no particular limitations on the surface treatment conditions for step (γ), but it is preferable to treat at around 10 to 150°C for about 1 to 20 hours.

[0063] The (B) component obtained above can be obtained as a powder by common methods such as atmospheric pressure drying at room temperature or under heating, or vacuum drying.

[0064] (C) Photopolymerization initiator (C) is a photopolymerization initiator. Specific examples of photopolymerization initiators that can be used in this invention include 2,2-diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethane-1-one (Omnirad 651), 1-hydroxy-cyclohexyl-phenyl-one (Omnirad 184), 2-hydroxy-2-methyl-1-phenyl-propane-1-one (Omnirad 1173), 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionic)-benzyl]-phenyl}-2-methyl-propane-1-one (Omnirad 127), methyl phenylglyoxylate (Omnirad MBF), 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinylpropane-1-one (Omnirad 907), and 2-benzyl-2-dimethylamino-1-(4-morpholinylphenyl)-1-butanone (Omnirad). 369), bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (Omnirad 819), 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (Omnirad TPO), bis(2,4,6-trimethylbenzoyl)ethyl hypophosphite (Omnirad TPO-L), etc. (all of the above are manufactured by IGM Resins BV). These can be used alone or in combination of two or more. Of these, from the viewpoint of compatibility with components (A) and (B), 2,2-diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one (Omnirad 1173), bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (Omnirad 819), 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (Omnirad TPO H), and bis(2,4,6-trimethylbenzoyl)ethyl hypophosphite (Omnirad TPO-L) are preferred.

[0065] The amount of photopolymerization initiator added relative to 100 parts by weight of component (A) is 0.01 to 20 parts by weight, preferably 0.1 to 10 parts by weight. If it is less than 0.01 parts by weight, the curing property is insufficient; if it is more than 20 parts by weight, the deep curing property deteriorates.

[0066] (D) In ​​order to adjust the curing properties during photoforming by a 3D printer, an ultraviolet absorber with light absorption at a wavelength of 360-410 nm may be added to the composition of the present invention.

[0067] Specific examples of ultraviolet absorbers that can be used in this 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-hydroxy C7-9 side-chain and straight-chain alkyl esters of phenylpropanoic acid (Tinuvin 384-2, manufactured by BASF), 2-(5-chloro-2-benzotriazolyl)-6-tert-butyl-p-cresol (Tinuvin 326, manufactured by BASF), and the product of the reaction of 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-tris(2-yl)-5-hydroxyphenyl with [(C10-C16, mainly C12-C13 alkoxy)methyl]ethylene oxide (Tinuvin). 400 (manufactured by BASF), thioxanthone, 2-isopropylthioxanthone, 2,4-diethylthioxanthone, benzophenone, camphorquinone, 1-phenyl-1,2-propanedione, hexyl diethylaminohydroxybenzoate (Uvinul A Plus, manufactured by BASF), 1-(4-tert-butylphenyl)-3-(4-methoxyphenyl)-1,3-propanedione, 2-ethylhexyl 4-methoxycinnamic acid, etc. These can be used alone or in combination of two or more.

[0068] When using a UV absorber, the amount added is preferably 0.01 to 20 parts by weight, and more preferably 0.1 to 10 parts by weight, relative to 100 parts by weight of component (A). If the amount is less than 0.01 parts by weight, the effect of the UV absorber may not be fully demonstrated; if the amount is more than 20 parts by weight, deep hardening may be deteriorated.

[0069] (E) Colorant: Various colorants may be added to the composition of the present invention for the purpose of adjusting or coloring the curing properties of the composition. As colorants, common pigments (iron oxide, titanium oxide, zinc oxide, etc.), dyes, carbon black, etc. may be used. One of these may be used alone, or two or more may be used in combination.

[0070] When using colorant, the amount added is preferably 0.01 to 20 parts by weight relative to 100 parts by weight of component (A). If the amount is less than 0.01 parts by weight, the effect of the colorant may not be fully realized; if the amount is more than 20 parts by weight, the deep hardening properties may be deteriorated.

[0071] Furthermore, additives such as silane coupling agents, adhesive aids, polymerization inhibitors, antioxidants, light stabilizers, ultraviolet absorbers, and light stabilizers may be incorporated into the composition of the present invention without impairing the effects of the present invention. Also, the composition of the present invention can be suitably mixed with other resin compositions for use.

[0072] [2] Method for manufacturing polysiloxane composition The method for manufacturing polysiloxane composition of the present invention is not particularly limited and conventional methods can be used. That is, the polysiloxane composition of the present invention can be obtained by mixing components (A) to (C) and other components as needed.

[0073] The method for manufacturing the polysiloxane composition of the present invention preferably includes the following steps (1) and (2). Step (1): manufacturing component (B) by means of steps (α), (β) and (γ) below. Step (2): mixing components (A) to (C) and other components as needed.

[0074] ・Step (1): Step (1) is a step of manufacturing component (B) by means of steps (α), (β) and (γ) below.

[0075] Step (α): A step of obtaining a dispersion of hydrophilic silica particles by hydrolyzing and condensing either or both of the 4-functional silane compound represented by general formula (I) and the alkyl silicate represented by general formula (II) in the presence of an alkaline substance in a mixture of a hydrophilic organic solvent and water (where R5 and m represent the same definitions as above).

[0076] Step (β): The step of treating the surface of the hydrophilic silica particles by adding one or both of the trifunctional silane compound and its (partial) hydrolytic condensate represented by the following general formula (III) to the mixed solvent dispersion of the hydrophilic silica particles obtained in step (α), thereby obtaining a dispersion of silica particles of the intermediate of component (B). (Where R7 and R8 represent the same definitions as above).

[0077] Step (γ): The step of treating the surface of the silica particles of the intermediate of component (B) with either or both of the following general formula (IV) and the following general formula (V) to the dispersion of silica particles of the intermediate of component (B) obtained in step (β) to obtain hydrophobic silica particles of component (B) (where R9 and X represent the same definitions as above).

[0078] The detailed manufacturing method of component (B) is as described above.

[0079] ・Step (2): The step of mixing components (A) to (C) is not particularly limited. The UV-curable polysiloxane composition for photoforming of the present invention can be obtained by mixing the above-mentioned components (A) to (C) and other components as needed in any order, and stirring, etc. The apparatus used for stirring, etc. is not particularly limited, and a pounder, a three-roll mill, a ball mill, a planetary mixer, etc. can be used. Furthermore, such apparatus can be appropriately combined.

[0080] The polysiloxane composition of the present invention can be in a single-liquid or two-liquid form. The single-liquid composition can be obtained, for example, by mixing components (A) to (C) and other components as needed in a frame mixer (manufactured by Inoue Manufacturing Co., Ltd., trade name: planetary mixer). Alternatively, components (A) and (B) can be obtained in a frame mixer and mixed under reduced pressure at room temperature for 1 hour. After cooling the resulting mixture, component (C) can be added and mixed at room temperature for 30 minutes to obtain the final product.

[0081] The viscosity of the UV-curable polysiloxane composition for photoforming 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 photoforming properties. If it exceeds 500 Pa·s, the photoforming properties deteriorate, and there may be cases where the desired shape cannot be obtained correctly. Furthermore, there is no particular limitation on the lower limit value, but it is preferably 1 Pa·s or more, and more preferably 2 Pa·s or more.

[0082] [3] Cured Material The UV-curable polysiloxane composition for photoforming of the present invention is rapidly cured by irradiation with ultraviolet light. At this time, the light source for irradiation with ultraviolet light can be, for example, 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 irradiation with ultraviolet light is preferably carried out at room temperature (25°C) in an inert gas environment such as nitrogen or argon.

[0083] The amount of ultraviolet radiation (cumulative light intensity) is preferably 1 to 10,000 mJ / cm², more preferably 10 to 8,000 mJ / cm², when the component of the present invention is hardened by ultraviolet radiation alone, for example, for forming a sheet with a thickness of about 2.0 mm. That is, when using ultraviolet radiation with an illuminance of 100 mW / cm², only about 0.01 to 100 seconds of ultraviolet radiation is required.

[0084] In order for the cured product obtained from the UV-curable polysiloxane composition for photoforming of the present invention to exhibit excellent rubber properties, the tensile strength is preferably 2.0 MPa or more, more preferably 3.0 MPa or more. Furthermore, the elongation at cut is preferably 150% or more, more preferably 200% or more. Moreover, these values ​​are based on measurements according to JIS-K6249. [Example]

[0085] Hereinafter, synthetic examples, comparative synthetic examples, exemplary examples, and comparative examples will be given to illustrate the present invention in more detail, but the present invention is not limited to these examples. Furthermore, the compounds of each component used in the examples are as follows. In the following formulas, Me represents methyl and Ph represents phenyl.

[0086] [1] Blending component (A) Component (wherein, the order of the siloxane units in parentheses is arbitrary).

[0087] (B) Components (B-1) Hydrophobic silicon dioxide particles obtained in Synthesis Example 1 (B-2) Hydrophobic silicon dioxide particles obtained in Synthesis Example 2 (B-3) Hydrophobic silicon dioxide particles obtained in Synthesis Example 3 (B-1 ratio) Comparison of hydrophobic silicon dioxide particles obtained in Synthesis Example 1

[0088] (C) Ingredients (C-1) 2-hydroxy-2-methyl-1-phenyl-propane-1-one (Omnirad 1173, manufactured by IGM Resins BV) (C-2) bis(2,4,6-trimethylbenzoyl) ethyl hypophosphite (Omnirad TPO-L, manufactured by IGM Resins BV)

[0089] [2] Synthesis of hydrophobic silica microparticles [Synthesis Example 1] ・Step (α): The synthesis of hydrophilic silica particles was carried out in a 3-liter glass reactor equipped with a stirrer, a dropping funnel and a thermometer. 623.7 g of methanol, 41.4 g of water and 49.8 g of 28% by mass ammonia were placed and mixed. The solution was adjusted to 35°C, and 1,163.7 g of tetramethoxysilane and 418.4 g of 5.4% by mass ammonia were added dropwise over 5 hours while stirring. 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 adaptor and cooling pipe were installed in a glass reactor. The reactor was heated to 60-70°C and 649g of methanol was distilled off. Then, 1,600g of water was added, and the reactor was heated to 70-90°C and 160g of methanol was distilled off, resulting in an aqueous suspension of hydrophilic silica particles.

[0090] ・Step (β): Surface treatment of hydrophilic silica particles. In the aqueous suspension, 115.8 g of methyltrimethoxysilane (0.1 equivalents relative to SiO2) and 46.6 g of 5.4% ammonia water were added dropwise at 25°C at 0.5 μL. After adding the dropwise solution, the temperature was raised to 50°C and allowed to mature for 1 hour. After the reaction was completed, the temperature was cooled to 25°C, and the surface of the hydrophilic silica particles was treated to obtain a dispersion of a hydrophobic silica particle intermediate, which is the intermediate of component (B).

[0091] ・Step (γ): (B) Surface treatment step of component intermediate: After adding 1,000 g of methyl isobutyl ketone to the dispersion thus obtained, the dispersion is heated to 80-115°C under intense fluctuation at the liquid interface, and 1,336 g of the methanol and water mixture is distilled off after 11 hours. 357.4 g of hexamethyldisilazane is added to the obtained dispersion at 25°C, and the dispersion is heated to 120°C and reacted for 3 hours to trimethylsilyl alkylate the silica particles to obtain hydrophobic silica particles. Subsequently, the solvent is distilled off under heating using an evaporator to obtain 477 g of hydrophobic silica particles (B-1).

[0092] [Synthesis Example 2] Except that in step (α) of Synthesis Example 1, 1,163.7 g of tetramethoxysilane was replaced with 901.9 g of methyl silicate (methyl silicate 51 manufactured by COLCOAT), 470 g of hydrophobic silica particles (B-2) were obtained in the same manner.

[0093] [Synthesis Example 3] Except that in step (β) of Synthesis Example 1, the amount of methyltrimethoxysilane used was changed to 11.6 g (0.01 equivalents relative to SiO2), 360 g of hydrophobic silicon dioxide particles (B-3) were obtained in the same way.

[0094] [Comparative Synthesis Example 1] In a 3-liter glass reactor equipped with a stirrer, dropping funnel, and thermometer, 60g of isopropanol and 100g of Snowtex OL (manufactured by Nichisan Chemical Industries, Ltd., with an average particle size of 50nm, dispersed in water, and a solid content concentration of 20% by mass), a type of colloidal silica particle, were added and mixed. 0.48g of methyltrimethoxysilane was added dropwise to the solution over 0.5 hours. After the addition, the mixture was heated to 50°C and allowed to mature for 1 hour. After the reaction was completed, the mixture was cooled to 25°C, and the surface of the silica particles was treated.

[0095] Next, 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 35% hydrochloric acid aqueous solution were added to precipitate the silica particles. The solvent was removed by distillation under heating using an evaporator to obtain hydrophobic silica particles (B-1 ratio).

[0096] [Determination Method] The obtained hydrophobic silicon dioxide particles were determined according to determination methods 1 and 2 below. The results are shown in Table 1.

[0097] 1. Determination of the average particle size of hydrophobic silicon dioxide particles (1) Take 0.1g of sample in a glass bottle, add 20g of methanol and stir. (2) Disperse it for 10 minutes with an ultrasonic dispersion device as the test sample. (3) Measure the sample in (2) with a laser analytical scattering particle size distribution measuring device (Nikkiso Corporation, Nanotrac 150), and take the median particle size of the volume standard (equivalent to the cumulative 50% particle size when the particle size distribution is expressed as a cumulative distribution) as the average particle size.

[0098] 2. Determination of the hydrophobicity of hydrophobic silicon dioxide particles (methanol titration method) (1) Weigh 0.2 mg of the sample into a 500 mL Erlenmeyer flask. (2) Add 50 mL of ion-exchange water to (1) and stir with a stirrer. (3) While stirring, drip methanol from the burette and read the dripping amount when the total amount of the sample is suspended in the ion-exchange water. (4) Calculate the degree of hydrophobicity using the following formula. Degree of hydrophobicity (%) = [{methanol dripping amount (mL)} / {methanol dripping amount (mL) + ion-exchange water volume (mL)}] × 100

[0099]

[0100] [3] Manufacturing and evaluation of polysiloxane compositions, manufacturing and evaluation of cured products [Examples 1-7 and Comparative Example 1] The above-mentioned components (A) to (C) were mixed with the compositions in Table 2 to prepare the polysiloxane compositions listed in Table 2. Furthermore, the viscosity of the compositions in Table 2 was measured using a rotational viscometer at 23°C.

[0101] Using a CCS (Chemical Solid State) UV curing apparatus, the prepared polysiloxane composition was cured by irradiating it with ultraviolet light at a wavelength of 405 nm at room temperature (25°C) under a nitrogen atmosphere. The sheet thickness was set to 2.0 mm. The hardness, elongation at cut, and tensile strength of the cured material were measured according to JIS K 6249:2003.

[0102]

[0103] As shown in Table 1, it can be seen that the UV-curable polysiloxane compositions prepared in Examples 1 to 7 have low viscosity suitable for photoforming methods, and the cured products have good mechanical properties.

Claims

1. A UV-curable polysiloxane composition for photoforming, comprising: (A) 100 parts by mass of an organopolysiloxane having one group of the following formula (1) at each end of one molecule, (wherein, R1 independently represents a monovalent hydrocarbon group having 1 to 20 carbon atoms, R2 represents an oxygen atom or an alkyl group having 1 to 20 carbon atoms, R3 independently represents acryloxyalkyl, methacryloxyalkyl, acryloxyalkoxy, methacryloxyalkoxy, (acryloxyalkyl)dimethylsilyloxy or (methacryloxyalkyl)dimethylsilyloxy, p represents a number satisfying 0 ≤ p ≤ 10, a represents a number satisfying 1 ≤ a ≤ 3, and dashed lines represent bonded bonds), (B) 10 to 500 parts by mass of hydrophobic silica particles with an average particle size of 10 to 1,000 nm and a hydrophobicity of more than 60% obtained by methanol titration, and (C) 0.01 to 20 parts by mass of photopolymerization initiator.

2. The UV-curable polysiloxane composition for photoforming as claimed in claim 1, having a viscosity of 500 Pa·s or less at 23°C.

3. The UV-curable polysiloxane composition for photoforming as claimed in claim 1, further comprising 0.01 to 20 parts by mass of (D) a UV absorber having light absorption at wavelengths of 360 to 410 nm, relative to 100 parts by mass of component (A).

4. The UV-curable polysiloxane composition for photoforming as claimed in claim 1, further comprising 0.01 to 20 parts by mass of colorant (E) relative to 100 parts by mass of component (A).

5. A cured product of a UV-curable polysiloxane composition for photoshaping as claimed in any one of claims 1 to 4.

6. The hardened material as requested in item 5 has an elongation of 150% or more when cut.