Resin composition for photomolding

Abstract

An object of the present invention is to provide a resin composition for photomolding that suppresses color unevenness and achieves excellent formability. The present invention solves the aforementioned problems by providing a resin composition for photomolding. The resin composition for photomolding is characterized by comprising a UV-curable resin (A) and an inorganic pigment (B), wherein the inorganic pigment (B) has a specific gravity satisfying 2.0 ≤ ρ and a particle size distribution with a particle size D50 ≤ 5 μm and D90 ≤ 20 μm. Furthermore, the resin composition for photomolding has a viscosity of 100 mPa·s or greater at 25°C.

Description

Technical Field

[0001] The present invention relates to a resin composition for photoforming for forming a three-dimensional object. Background Art

[0002] In recent years, various shapes have been created using optical stereolithography and are being used in a wide range of applications. These shapes, such as dental materials and prosthetics, are being manufactured in large quantities for personal use, tailored to the characteristics required by individual users.

[0003] As a photoforming resin used in such an optical three-dimensional forming method, a photocurable resin and a coloring material such as a pigment and a fine particle component are added for the purpose of improving working efficiency (see Patent Document 1).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application No. 2016-505525 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] However, when forming by optical three-dimensional forming, there are problems such as sedimentation of added fine particles, which causes color unevenness in the formed object, and excessive light blocking by fine particles, which reduces formability.

[0009] An object of the present invention is to provide a resin composition for photomolding that suppresses the occurrence of color unevenness and can provide good moldability.

[0010] Means for solving problems

[0011] The present invention solves the above-mentioned problems through a resin composition for photoforming. The resin composition for photoforming is characterized in that it is formed by combining a UV-curable resin (A) and an inorganic pigment (B), the specific gravity of the above-mentioned inorganic pigment (B) satisfies 2.0≤ρ, and has a particle size distribution with a particle size D50≤5μm and D90≤20μm, and the viscosity of the resin composition for photoforming at 25°C is greater than 100mPa·s.

[0012] Furthermore, the present invention may be characterized in that the ultraviolet curable resin (A) contains modified bisphenol A dimethacrylate, and the modified bisphenol A dimethacrylate is represented by the following formula (I):

[0013]

[0014] Indicates that R 1 Represents a hydrogen atom or a methyl group. Multiple R in the same molecule 1They may be the same or different, m and n each independently represent an integer greater than or equal to 1, and m+n is 4 to 40.

[0015] Furthermore, the resin composition for photoforming of the present invention may contain a long-wavelength photopolymerization initiator.

[0016] The present invention also relates to a resin molded product formed by photocuring the above-mentioned resin composition for photomolding.

[0017] Furthermore, the resin article formed by photocuring the above-mentioned resin composition for photoforming may be characterized in that the total light transmittance measured using a sample slice having a thickness of 1 mm in the direction of light irradiation is less than 60%.

[0018] Effects of the Invention

[0019] According to the present invention, it is possible to provide a resin composition for photoforming that suppresses the occurrence of color unevenness and can provide good formability. DETAILED DESCRIPTION

[0020] Several embodiments of the present invention will be described in detail below, but the present invention is not limited to the following embodiments.

[0021] The present invention relates to a resin composition for photoforming, characterized in that it is formed by combining a UV-curable resin (A) and an inorganic pigment (B), the inorganic pigment (B) having a specific gravity satisfying 2.0≤ρ, a particle size distribution with a particle size D50≤5μm and D90≤20μm, and a viscosity of the resin composition for photoforming of not less than 100mPa·s at 25°C.

[0022] The ultraviolet curable resin (A) of the present invention is not particularly limited within the scope of achieving the effects of the present invention, and photo-radical polymerizable compounds such as monofunctional and polyfunctional acryl-containing polymerizable compounds, and photo-cationic polymerizable compounds such as epoxy compounds and oxetane compounds can be used. As described above, various ultraviolet curable resins can be used, but from the perspective of suppressing warping of the resin formed object after photoforming and obtaining sufficient toughness and mechanical properties, photo-radical polymerizable compounds are preferably used.

[0023] As the ultraviolet curable resin (A) used in the present invention, it is particularly preferred to use the following modified bisphenol A dimethacrylate, which is represented by the following formula (I):

[0024]

[0025] Indicates that R 1Represents a hydrogen atom or a methyl group. Multiple R in the same molecule 1 They may be the same or different, m and n each independently represent an integer greater than or equal to 1, and m+n is 4 to 40.

[0026] In addition, R in the above formula (I) 1 Represents a hydrogen atom or a methyl group. Multiple R in the same molecule 1 may be the same or different, m and n each independently represent an integer greater than 1, and m+n is 4 to 40. In formula (I), R 1 When R is a hydrogen atom, the modified bisphenol A dimethacrylate is sometimes referred to as ethylene oxide modified bisphenol A dimethacrylate. 1 When the methyl group is present, the modified bisphenol A dimethacrylate may be referred to as propylene oxide-modified bisphenol A dimethacrylate.

[0027] In the modified bisphenol A dimethacrylate, m+n (modification amount) is 4 or more, thereby significantly improving the toughness and strength of the three-dimensional shape formed. From the same point of view, m+n can be 6 or more, or 10 or more. In addition, m+n can be 30 or less. In the case where the ultraviolet curable resin (A) contains a plurality of modified bisphenol A dimethacrylates of formula (1) with different m+n, their average value can be 4 to 40. Other ultraviolet curable resins can be added and used as photopolymerizable components within the range that can obtain the effect of the present invention.

[0028] As the ultraviolet curable resin (A) used in the present invention, for example, those commercially available under the names of MIRAMER M241, MIRAMER M2101, and MIRAMER M2301 (all product names, manufactured by Miwon Specialty Chemical Co., Ltd.) can be used.

[0029] The content of the ultraviolet curable resin (A) in the present invention is not particularly limited within the range that can achieve the effects of the present invention. However, from the perspective of improving the strength of the formed object, it is preferably 15% by mass or more and 70% by mass or less in the resin composition for photoforming. From the perspective of improving the elastic modulus and toughness of the formed object, it is more preferably 20% by mass or more and 60% by mass or less. From the perspective of improving the forming precision, it is particularly preferably 30% by mass or more and 50% by mass or less.

[0030] In addition, if the content of the ultraviolet curable resin (A) is set within the above range, it is easy to obtain better effects in terms of suppressing odor and warping of the shaped object. It should be noted that the mass % in this specification refers to the ratio when the total mass % of the resin composition for photoforming is set to 100%.

[0031] The inorganic pigment (B) used in the present invention is characterized by having a specific gravity satisfying 2.0 ≤ ρ and a particle size distribution with a particle size D50 ≤ 5 μm and D90 ≤ 20 μm. Including a pigment that satisfies these specific gravity and particle size conditions as an inorganic pigment effectively suppresses sedimentation over time, thereby achieving suitable formability during molding.

[0032] In the present invention, the specific gravity of the inorganic pigment is measured using the method for measuring density and specific gravity of the individual particles according to JIS Z 8807: 2012. Furthermore, the particle size distribution of the inorganic pigment is determined by measuring the particle size according to JIS Z8825 "Particle Size Analysis - Laser Diffraction / Scattering Method."

[0033] The specific gravity of the inorganic pigment (B) used in the present invention satisfies 2.0≤ρ. Furthermore, from the viewpoint of sedimentation suppression, the specific gravity preferably satisfies 2.0≤ρ≤6.0, and most preferably satisfies 2.0≤ρ≤4.0.

[0034] The inorganic pigment (B) used in the present invention has a particle size distribution with a particle size D50 ≤ 5 μm and D90 ≤ 20 μm. Furthermore, from the perspective of suppressing sedimentation and improving curing efficiency, D50 ≤ 4 μm and D90 ≤ 10 μm are more preferably used. It should be noted that D50 and D90 refer to the particle sizes at which the cumulative values ​​of particles in the particle size distribution determined above reach 50% and 90% respectively.

[0035] The inorganic pigment used in the present invention is not particularly limited as long as it meets the above-mentioned conditions of specific gravity, D50 and D90 particle size, and various inorganic pigments can be used. As these inorganic pigments, titanium oxide, iron oxide, zinc white, iron oxide red, cobalt blue, ultramarine, iron black, titanium yellow, etc. can be used. Titanium oxide and iron oxide are particularly preferably used because they have good sedimentation suppression effects and good formability.

[0036] The inorganic pigment (B) used in the present invention can also be used in the form of a dispersion liquid formed by being dispersed in various solvents according to expectation. As the solvent used when making these dispersion liquids, there is no particular restriction within the scope that can obtain the effect of the present invention, and inorganic solvents such as water, alcohol, and other various organic solvents can be used. In addition, in order to make the dispersibility good, a dispersing aid can also be added.

[0037] In addition, the inorganic pigment (B) is preferably an inorganic pigment that improves the curing efficiency using active energy rays during photoforming, and can be appropriately selected according to the wavelength of the active energy rays used during curing. As a colorant that improves the curing efficiency using active energy rays, titanium oxide, iron oxide, zinc white, iron oxide red, cobalt blue, ultramarine, iron black, titanium yellow, etc. can be used.

[0038] Examples of the inorganic pigment (B) that can be used in the present invention include COD-8001, COD-8005, and COD-8008 manufactured by Sun Chemical.

[0039] In the present invention, the content of the inorganic pigment (B) is not particularly limited within a range that allows the effects of the present invention to be achieved, but is preferably from 0.005% by mass to 10% by mass. From the perspective of promoting good ultraviolet curing, it is more preferably from 0.01% by mass to 5% by mass. From the perspective of minimizing the occurrence of color unevenness, it is most preferably from 0.01% by mass to 3% by mass.

[0040] The long-wavelength photopolymerization initiator used in the present invention is not particularly limited as long as it is a polymerization initiator that promotes the start of curing for light with a wavelength of 385 nm or longer. It is a compound that can initiate photoradical polymerization of the ultraviolet curable resin (A) used in the present invention. It is preferably a long-wavelength polymerization initiator that shows a good polymerization initiation reaction for a wavelength of 385 nm or 405 nm.

[0041] As the long-wavelength photopolymerization initiator used in the present invention, for example, at least one selected from 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propane-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropane-1-one, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide can be used.

[0042] The content of the long-wavelength photopolymerization initiator is not particularly limited within a range that can achieve the effects of the present invention, and can be 0.1 to 15 parts by mass relative to 100 parts by mass of the photopolymerizable component. In terms of obtaining good formability, it is particularly preferably 0.5 to 10 parts by mass.

[0043] Examples of the long-wavelength photopolymerization initiator used in the present invention include "Omnirad 819" (product name, manufactured by IGM Resin Co., Ltd.), "Omnirad TPO" (product name, manufactured by IGM Resin Co., Ltd.), and "KAYACURE DETX-S" (product name, manufactured by Nippon Kayaku Co., Ltd.).

[0044] The photoforming resin composition of the present invention is characterized by comprising the aforementioned UV-curable resin (A) and an inorganic pigment (B), and having a viscosity of 100 mPa·s or greater at 25°C. When the conditions (A) and (B) are met and the viscosity of the photoforming resin composition is within the above range, color unevenness is preferably suppressed. As described above, the viscosity of the photoforming resin composition can be 100 mPa·s or greater, but to further suppress color unevenness, it is preferably 400 mPa·s or greater.

[0045] The photoforming resin composition of the present invention may contain various solvents for purposes such as viscosity adjustment, but may also be substantially solvent-free. For example, the proportion of solvent relative to the total amount of the photoforming resin composition may be less than 5% by mass, less than 3% by mass, or less than 1% by mass.

[0046] In addition to the components listed above, the photomolding resin composition of the present invention may further comprise other components as needed. Examples of such other components include UV stabilizers, polymerization inhibitors, antioxidants, stabilizers, leveling agents, defoaming agents, thickeners, flame retardants, sensitizers, surfactants, dyes, inorganic pigments other than component (B), organic pigments, fluorescent pigments, inorganic fillers, and organic fillers.

[0047] The optical 3D forming method of the present invention, which involves repeatedly photocuring the resin composition for photoforming, allows for the rapid and easy production of 3D objects. The optical 3D forming method is not particularly limited; for example, it may be a surface exposure method (DLP: Digital Light Processing). The resulting 3D object can be post-cured by irradiation with light.

[0048] The present invention can also be provided as a resin composition (hereinafter referred to as a cured resin composition) obtained by curing the above-mentioned optical shaping resin composition through various optical stereoscopic shaping. The cured resin composition of the present invention thus cured is characterized in that a total light (or UV) transmittance is less than 60% when measured using a sample slice having a thickness of 1 mm in the direction of light irradiation. By having a total light transmittance after shaping within the above range, the contrast of the surface of the cured resin composition is improved, thereby improving the appearance of the shaped object.

[0049] The curable resin composition of the present invention can be molded and used according to the desired application. Examples of such applications include dental products such as dentures, inlays, bridges, crowns, surgical guides, body assistive devices such as prostheses, and jewelry molds.

[0050] Example

[0051] The present invention will be described in more detail below with reference to the following examples. However, the present invention is not limited to these examples. (Hereinafter, "parts" indicating the amount of each component means "parts by mass").

[0052] (Example 1)

[0053] In a container equipped with a stirrer, 100 parts by mass of bisphenol A ethylene oxide-modified (4 mol addition) dimethacrylate, 2 parts by mass of a photopolymerization initiator ("Omnirad 819" manufactured by IGM; 2,4,6-trimethylbenzoyldiphenylphosphine oxide), and 0.3 parts by mass of a titanium oxide dispersion (titanium oxide content 50%. Titanium oxide specific gravity: 4.0, D50: 1.2 μm, D90: 15 μm) were added. The mixture was stirred and mixed for 1 hour while controlling the liquid temperature at 60°C to uniformly dissolve the mixture, thereby obtaining a resin composition for photoforming (1).

[0054] (Example 2)

[0055] In a container equipped with a stirrer, 100 parts by mass of bisphenol A ethylene oxide modified (4 mol addition) dimethacrylate and a photopolymerization initiator ("Omnirad" manufactured by IGM) were mixed. 819"; 2,4,6-trimethylbenzoyldiphenylphosphine oxide) 1.4 mass parts, titanium oxide dispersion (titanium oxide content 50%. Titanium oxide specific gravity: 4.0, D50: 1.2 μm, D90: 15 μm) 0.3 mass parts, iron oxide dispersion (iron oxide content 50%. Iron oxide specific gravity: 5.0, D50: 1.5 μm, D90: 20 μm) 0.11 mass parts, and lake pigment dispersion (lake pigment content 40%. Lake specific gravity: 1.6, D50: 1.0 μm, D90: 12 μm) 0.03 mass parts, while controlling the liquid temperature at 60°C, stirring and mixing for 1 hour, and uniformly dissolving, thereby obtaining a resin composition for photoforming (2).

[0056] (Example 3)

[0057] In a container equipped with a stirrer, 100 parts by mass of bisphenol A ethylene oxide-modified (4 mol addition) dimethacrylate, 1.1 parts by mass of a photopolymerization initiator ("TPO-H" manufactured by IGM; diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide), 0.3 parts by mass of a titanium oxide dispersion (titanium oxide content 50%. Titanium oxide specific gravity: 4.0, D50: 1.2 μm, D90: 15 μm), and 0.01 parts by mass of a lake pigment dispersion (lake pigment content 40%. Lake specific gravity: 1.6, D50: 1.0 μm, D90: 12 μm) were added, and the mixture was stirred and mixed for 1 hour while controlling the liquid temperature at 60°C to uniformly dissolve the mixture, thereby obtaining a resin composition for photoforming (3).

[0058] (Example 4)

[0059] In a container equipped with a stirrer, 100 parts by mass of bisphenol A ethylene oxide-modified (4 mol addition) dimethacrylate, 2 parts by mass of a photopolymerization initiator ("Omnirad 819" manufactured by IGM; 2,4,6-trimethylbenzoyldiphenylphosphine oxide), 0.3 parts by mass of a titanium oxide dispersion (50% titanium oxide content. Specific gravity of titanium oxide: 4.0, D50: 1.2 μm, D90: 15 μm), and 0.11 parts by mass of an iron oxide dispersion (50% iron oxide content. Specific gravity of iron oxide: 5.0, D50: 1.5 μm, D90: 20 μm) were added, and the mixture was stirred and mixed for 1 hour while controlling the liquid temperature at 60°C to uniformly dissolve the mixture, thereby obtaining a resin composition for photoforming (4).

[0060] (Example 5)

[0061] In a container equipped with a stirrer, 100 parts by mass of bisphenol A ethylene oxide-modified (4 mol addition) dimethacrylate, 5 parts by mass of a photopolymerization initiator ("DETX" manufactured by Tokyo Chemical Industry Co., Ltd.; 2,4-diethylthioxanthen-9-one), 8 parts by mass of EPA, 0.3 parts by mass of a titanium oxide dispersion (50% titanium oxide content. Specific gravity of titanium oxide: 4.0, D50: 1.2 μm, D90: 15 μm), and 0.11 parts by mass of an iron oxide dispersion (50% iron oxide content. Specific gravity of iron oxide: 5.0, D50: 1.5 μm, D90: 20 μm) were added, and the mixture was stirred and mixed for 1 hour while controlling the liquid temperature at 60°C to uniformly dissolve the mixture, thereby obtaining a resin composition for photoforming (5).

[0062] (Example 6)

[0063] In a container equipped with a stirrer, 50 parts by mass of bisphenol A ethylene oxide-modified (4 mol addition) dimethacrylate, 40 parts by mass of PPG400-DMA (NK ESTETR 9PG), 10 parts by mass of PPG2000 (Uniol D2000), 2 parts by mass of a photopolymerization initiator ("Omnirad 819" manufactured by IGM; 2,4,6-trimethylbenzoyldiphenylphosphine oxide), and 0.2 parts by mass of a titanium oxide dispersion (titanium oxide content 50%. Titanium oxide specific gravity: 4.0, D50: 1.2 μm, D90: 15 μm) were added, and the mixture was stirred and mixed for 1 hour while controlling the liquid temperature at 60°C to uniformly dissolve the mixture, thereby obtaining a resin composition for photoforming (6).

[0064] (Comparative Example 1)

[0065] In a container equipped with a stirrer, 50 parts by mass of bisphenol A ethylene oxide-modified (4 mol addition) dimethacrylate, 40 parts by mass of PPG400-DMA (NK ESTETR 9PG), 10 parts by mass of PPG2000 (Uniol D2000), and 2 parts by mass of a photopolymerization initiator ("Omnirad 819" manufactured by IGM; 2,4,6-trimethylbenzoyldiphenylphosphine oxide) were added and stirred for 1 hour while controlling the liquid temperature at 60°C to uniformly dissolve the mixture, thereby obtaining a comparative photoforming resin composition (1).

[0066] (Comparative Example 2)

[0067] In a container equipped with a stirrer, 100 parts by mass of bisphenol A ethylene oxide-modified (4 mol addition) dimethacrylate, 2 parts by mass of a photopolymerization initiator ("Om-184" manufactured by IGM; 1-hydroxycyclohexyl-phenyl ketone), 0.3 parts by mass of a titanium oxide dispersion (titanium oxide content 50%. Titanium oxide specific gravity: 4.0, D50: 1.2 μm, D90: 15 μm), 0.11 parts by mass of an iron oxide dispersion (iron oxide content 50%. Iron oxide specific gravity: 5.0, D50: 1.5 μm, D90: 20 μm), and 0.03 parts by mass of a lake pigment dispersion (lake pigment content 40%. Lake specific gravity: 1.6, D50: 1.0 μm, D90: 12 μm) were added, and the mixture was stirred and mixed for 1 hour while controlling the liquid temperature at 60°C to uniformly dissolve the mixture, thereby obtaining a comparative photoforming resin composition (2).

[0068] The following compatibility evaluation was performed on the above-prepared resin compositions for light shaping (1) to (6) and the comparative resin compositions for light shaping (1) to (2).

[0069] (Compatibility evaluation)

[0070] The photoforming resin compositions (1) to (6) and the comparative photoforming resin compositions (1) to (2) were placed in a vial and allowed to stand for 24 hours in a light-shielding environment. Three persons then visually evaluated the presence or absence of color separation.

[0071] (Evaluation Criteria)

[0072] ○ (3 people commented that there was no color separation)

[0073] ×(At least one person rated it as color separation)

[0074] The above-prepared resin compositions for light shaping (1) to (6) and comparative resin compositions for light shaping (1) to (2) were used to produce resin molded articles by the following steps, and their curability and total light transmittance were evaluated.

[0075] (Production of resin sculptures)

[0076] For the resin compositions (1) to (6) for photoforming and the comparative resin compositions (1) to (2) for photoforming, a surface exposure (DLP) photoforming system (DLP Printer manufactured by ASIGA) was used to generate resin forms of a predetermined shape using a photocurable resin composition. The stacking spacing of the photoforming was set to 0.05 to 0.1 mm, the irradiation wavelength was set to 400 to 410 nm, and the irradiation time was set to 2 to 20 seconds per layer. The formed resin forms were ultrasonically cleaned in ethanol and then a high-pressure mercury lamp was used to achieve a cumulative light intensity of 10,000 to 2,000 mJ / cm 2 The surface and back of the three-dimensional shape are illuminated in a manner to post-curing the three-dimensional shape.

[0077] (Evaluation of curability)

[0078] Curing property: Three people conducted a sensory evaluation of the stickiness of the surface of resin objects created using a 3D printer and then washed with ethanol.

[0079] (Evaluation Criteria)

[0080] ○ (3 people rated it as not sticky)

[0081] ×(At least one person rated it sticky)

[0082] (Evaluation of total light transmittance)

[0083] According to the above-described method for producing resin articles, blocks of the resin compositions for photoforming (1) to (6) and comparative resin compositions for photoforming (1) to (2) were produced, each having a thickness of 1 mm. The transmittance of each of the produced samples was measured using a haze meter in accordance with JIS K7375:2008.

[0084] The results of the above tests are shown in Tables 1 and 2.

[0085] [Table 1]

[0086]

[0087] [Table 2]

[0088]

[0089] As shown in Tables 1 and 2, the photomolding resin compositions of Examples 1 to 7 suppressed color unevenness and exhibited good moldability. On the other hand, the photomolding resin compositions of Comparative Examples 1 and 2 exhibited color unevenness due to poor curability and compatibility, and their moldability was also poorly evaluated.

Claims

1. A resin composition for photoforming, characterized in that It is made of UV curable resin (A) and inorganic pigment (B). The inorganic pigment (B) has a specific gravity of 2.0≤ρ and a particle size distribution of D50≤5μm and D90≤20μm. The viscosity of the resin composition for photoforming at 25°C is 100 mPa·s or more, and The ultraviolet curable resin (A) includes modified bisphenol A dimethacrylate, and the modified bisphenol A dimethacrylate is represented by the following formula (I): R 1 Represents a hydrogen atom or a methyl group. Multiple R in the same molecule 1 are optionally the same or different, m and n each independently represent an integer greater than 1, m+n is 4 to 40, The photopolymerization resin composition further comprises a long wavelength photopolymerization initiator. The long-wavelength photopolymerization initiator is a polymerization initiator that accelerates the start of curing in response to light having a wavelength of 385 nm or longer.

2. A resin molded object obtained by photocuring the resin composition for photomolding according to claim 1.

3. The resin molded article according to claim 2, wherein: When measured using a sample slice having a thickness of 1 mm in the light irradiation direction, the total light transmittance of the resin shape is less than 60%.

Images