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JP-7856221-B2 - UV-curable silicone composition for stereolithography, cured product thereof, and curing method

JP7856221B2JP 7856221 B2JP7856221 B2JP 7856221B2JP-7856221-B2

Inventors

  • 松本 展明
  • 北川 太一
  • 小材 利之
  • 松村 和之

Assignees

  • 信越化学工業株式会社

Dates

Publication Date
20260511
Application Date
20250415
Priority Date
20240426

Claims (8)

  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) a photopolymerization initiator, comprising a silicone composition for photopolymerization, A UV-curable silicone composition for photopolymerization, wherein the composition is irradiated with ultraviolet light of 405 nm wavelength at 25°C at a concentration of 8,000 mJ/cm², and then cured for 24 hours at 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 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). (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 is an aryl group having 6 to 20 carbon atoms, R1 is a monovalent hydrocarbon group having 1 to 20 carbon atoms, and A is the group shown in formula (2) below.) (In the formula, R1 is the same as above, R2 is an oxygen atom or an alkylene group having 1 to 20 carbon atoms, R3 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 The UV-curable silicone composition for photopolymerization according to claim 1, comprising 10 to 500 parts by mass of component (B) and 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) a cured product of a photopolymerization initiator containing an ultraviolet-curable silicone composition for photopolymerization, 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 ultraviolet-curable silicone composition according to any one of claims 1 to 5 with ultraviolet light to radically cure the composition to obtain a primary cured product, and (ii) a step of further condensation curing the obtained primary cured product to obtain a secondary cured product.
  8. The curing method according to claim 7, wherein the condensation curing in step (ii) is curing due to moisture.

Description

This invention relates to an ultraviolet-curable silicone composition for stereolithography, a cured product thereof, and a method for curing an ultraviolet-curable silicone composition for stereolithography. In recent years, the development of materials used in 3D printers has become increasingly active, and a wide variety of materials, from metals to resins, are being used. In the resin field, examples include acrylate-based photocurable resin compositions and urethane acrylate-based photocurable resin compositions. However, the cured products of these resin compositions are extremely hard and cannot be freely bent (Patent Document 1). Furthermore, a UV-curable, low-viscosity silicone material has been proposed for 3D printers using the inkjet method (Patent Document 2). This material has the advantage of curing with short-term UV irradiation and having very good molding accuracy, but it has the drawback of having poor mechanical strength and heat resistance compared to ordinary silicone materials. Therefore, a new UV-curable silicone composition has been developed for use in stereolithography, which has seen a rapid increase in recent years (Patent Documents 3 and 4). However, compared to the mechanical strength of thermosetting silicone compositions, they were sometimes brittle due to their low elongation. Furthermore, in recent years, stereolithography has become possible even with higher viscosities compared to the past. Patent No. 5890990Patent No. 6687111Patent No. 6962290Patent No. 7342910 The present invention will be described in detail below. [1] UV-curable silicone composition for stereolithography The UV-curable silicone composition for stereolithography according to the present invention contains the following components (A) to (C). (A) 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 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; (C) Photopolymerization initiator (A) Organopolysiloxane The 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 the silicon atom via an oxygen atom directly bonded to the silicon atom in one molecule, preferably 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. 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. 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. 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 groups represent either acryloyloxyalkyloxy groups or methacryloyloxyalkyloxy groups. 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 both ends. 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. 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 groups may be substituted with other substituents such as halogen atoms. The monovalent hydrocarbon