Resin composition and three-dimensional object

#The present invention relates to a photocurable resin composition used in three dimensional photofabrication, a process for making a three-dimensional object and the resulting three-dimensional object.

#In recent years, photofabrication of three-dimensional objects made from cured resin layers integrally laminated by repeating a step of selectively irradiating a photocurable resin composition has been proposed (see Japanese Patent Application Laid-open No. 247515/1985, U.S. Pat. No. 4,576,330 (Japanese Patent Application Laid-open No. 35966/1987), Japanese Patent Application Laid-open No. 101408/1987, and Japanese Patent Application Laid-open No 24119/1993).

#A typical example of such photofabrication is as follows. The surface of a photocurable resin composition (a liquid material) in a vessel is selectively irradiated with light from an ultraviolet laser and the like based on CAD data to form a cured resin layer having a specified pattern. The equivalent of one layer of a resin composition is provided over this cured resin layer and the liquid surface is selectively irradiated to form a new cured resin layer integrally laminated over the cured resin layer. This step is repeated a certain number of times using the same or different irradiating patterns to obtain a three-dimensional object consisting of integrally laminated cured resin layers. The object preferably is washed with a washing agent to remove excess resin sticking to the surface of the object, and the object preferably is postcured by for example UV or heat to further improve the mechanical properties of the object. This photofabrication has attracted considerable attention because a three-dimensional object having a complicated shape can be easily formed in a short period of time.

#FIG. 1 is a chart showing an example of a stress-strain curve measured using a ultra-micro hardness tester.

#FIG. 2 is a perspective view showing photofabricated products in Fabrication Examples 1 and 2.

#FIGS. 3(1) and 3(2) are, respectively, a plane view and a cross-section showing the configuration and dimensions of a three-dimensional object for evaluating interlayer adhesion and fabrication accuracy. A and B in FIG. 1 represent overhanging parts.

#A 1 l reaction vessel equipped with a reflux condenser, stirrer, thermometer, and dropping funnel was charged with 75 g of n-butyl acrylate, 25 g of 2-ethylhexyl acrylate, 4 g of dodecylmercaptan, 1 g of benzoyl peroxide, and 200 g of toluene. The mixture was heated to 75-85° C. A mixture of 75 g of n-butyl acrylate, 25 g of 2-ethylhexyl acrylate, and 1 g of benzoyl peroxide was continuously dropped while stirring the mixture at this temperature to carry out the polymerization reaction for three hours. After the reaction, the solvent and low boiling point matters were removed by evaporation under reduced pressure, thereby obtaining an n-butyl acrylate/2-ethylhexyl acrylate copolymer. This copolymer is designated as “Copolymer (C-1)”.

#According to the formulations of Table 1, a vessel equipped with a stirrer was charged with 30 parts by weight of 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexanecarboxylate “UVR-6110” (manufactured by Union Carbide Corp.) as component (A), 25 parts by weight of bis(3,4-epoxycyclohexylmethyl)adipate “UVR-6199” (manufactured by Union Carbide Corp.) as component (A), 10 parts by weight of 1,6-hexanediol diglycidyl ether “Epolite 1600” (manufactured by Kyoeisha Chemical Co., Ltd.) as component (A), 2 parts by weight of triarylsulfonlumhexafluoroantimonate “UVI-6974” (manufactured by Union Carbide Corp.) as component (B), 0.1 part by weight of “Polyflow No. 90” (manufactured by Kyoeisha Chemical Co., Ltd.) as component (C), 13 parts by weight of trimethylolpropane triacrylate “Viscoat 295” (manufactured by Osaka Organic Chemical Industry Co., Ltd.) as component (D), 2 parts by weight of 1-hydroxycyclohexylphenyl ketone “Irgacure 184” (manufactured by Ciba Specialty Chemicals Co., Ltd.) as component (E), 10 parts by weight of PO-modified glycerol “Sunnix GP 400” (manufactured by Sanyo Chemical Industries, Ltd.) as component (F), and 8 parts by weight of core-shell elastomer particles (core: partially crosslinked styrene/butadiene copolymer, shell; methyl methacrylate/glycidyl methacrylate copolymer) produced by emulsion polymerization, having an average particle diameter of 200 nm, as component (G). The mixture was stirred for three hours at 60° C. to obtain a liquid composition (the resin composition of the present invention). Viscosity of the resulting composition at 25° C. measured by using a B-type viscometer was 620 cps.

#A liquid composition (the resin composition of the present invention) was prepared in the same manner as in Example 1 except for changing the amount of “Polyflow No. 90” (manufactured by Kyoeisha Chemical Co., Ltd.) used as the component (C) to 0.5 part by weight, as shown in Table 1. Viscosity of the resulting composition at 25° C. measured by using a B-type viscometer was 620 cps.