JP7015682B2 - Resin composition for stereolithography - Google Patents

Description

The present invention relates to a stereolithography resin composition for producing a two-dimensional or three-dimensional model by curing by light irradiation.

Stereolithography is expected to be applied to various applications, and a resin composition for stereolithography for forming a cured product having rubber elasticity is also being studied. In such a resin composition for stereolithography, rubber elasticity is imparted to the cured product by lowering the glass transition point (Tg).

Patent Document 1 proposes a resin composition used for an optical three-dimensional modeling method in which the Tg of a cured product is 10 ° C. or lower. Patent Document 2 proposes an ink composition for three-dimensional modeling using a (meth) acrylate having a homopolymer Tg of −18 ° C. or lower.

Japanese Unexamined Patent Publication No. 2000-290328 Japanese Unexamined Patent Publication No. 2015-78255

However, the elongation rate of the cured product obtained by using the conventional stereolithography resin composition is only about 100%, and the elongation at break is low. The cured product of such a resin composition is brittle, and it is difficult to ensure sufficient quality.

One aspect of the present invention is a stereolithographic resin composition containing a photocurable compound and a photoreaction initiator.
The photocurable compound includes a first compound having a functional site capable of forming a pseudo-crosslink point and one first reactive functional group capable of forming a chemical cross-linking point, and two or more compounds capable of forming a chemical cross-linking point. Containing a second compound having a second reactive functional group,
The ratio of the first compound to the photocurable compound is 40% by mass or more, and is
The ratio of the second compound to the photocurable compound is 5% by mass or more, and is
The present invention relates to a stereolithography resin composition in which the loss tangent tan δ of the cured product of the stereolithography resin composition at 23 ° C. is 0.3 or more.

According to the above aspect of the present invention, it is possible to provide a resin composition for stereolithography capable of obtaining a cured product having a high elongation at break.

It is a schematic diagram for demonstrating the process of forming a 3D model using the resin composition for stereolithography which concerns on one Embodiment of this invention.

[Resin composition for stereolithography]
The stereolithography resin composition according to one aspect of the present invention contains a photocurable compound and a photoreaction initiator. The photocurable compound includes a compound (first compound) having a functional site capable of forming a pseudo-crosslink point and one reactive functional group (first reactive functional group) capable of forming a chemical cross-linking point, and a chemical cross-linking point. Includes a compound (second compound) having two or more reactive functional groups (second reactive functional groups) capable of forming the above. The ratio of the first compound to the photocurable compound is 40% by mass or more, and the ratio of the second compound to the photocurable compound is 5% by mass or more. The loss tangent tan δ of the cured product of the stereolithography resin composition at 23 ° C. is 0.3 or more.

The stereolithography resin composition is generally composed of a photocurable resin composition. The photocurable resin composition is converted into a stereolithographic product which is a cured product by advancing a curing reaction including polymerization and cross-linking of the photocurable resin by irradiation with light. In such a general conventional stereolithography resin composition, the polymer chains are crosslinked by strong chemical cross-linking, so that the flexibility of the cured product is low and the breaking elongation of the cured product cannot be increased. Can not. If the polymer chains are not crosslinked, the cured product will be deformed but will not return to its original shape. Further, as in the conventional case, when the Tg of the cured product is lowered, the viscosity of the cured product is increased but the elasticity is decreased. Is difficult to increase.

According to the above aspect of the present invention, by using 40% by mass or more of the first compound, the proportion of the second compound chemically crosslinked can be relatively reduced, and the functional moiety of the first compound in the cured product can be relatively reduced. Can form a pseudo-crosslink point. Further, by using a second compound of 5% by mass or more, a certain degree of chemical cross-linking point can be secured. Further, by setting tan δ to 0.3 or more, it becomes easy to adjust the balance between the viscosity and elasticity of the cured product by pseudo-crosslinking and chemical cross-linking. Therefore, the cured product can be stretched like rubber with high elongation, and after the cured product is stretched, it can be restored to its original size and shape with a high recovery rate. Therefore, high breaking elongation can be obtained.

The pseudo-crosslink point refers to a non-shared interaction. Non-shared interactions include hydrogen bonds, London dispersion forces (π-π interactions, etc.), cation-π interactions, and the like. On the other hand, the chemical cross-linking point refers to a covalent-bonding or ionic-bonding interaction, and more specifically, a cross-linking point due to a covalent bond or an ionic bond.

The loss tangent tan δ is the ratio of the stored shear modulus G1 of the cured product to the loss shear modulus (G2) at 23 ° C.: G2 / G1. tan δ can be determined by dynamic viscoelasticity measurement (DMA). Specifically, first, a film having a thickness of 300 μm is prepared using a stereolithography resin composition, and the film is completely cured by irradiating the film with light to prepare a sample of the cured product. Then, using this sample, tan δ can be obtained under the conditions of 23 ° C. and a frequency of 1 Hz by DMA using a commercially available dynamic viscoelasticity measuring device.

Hereinafter, the configuration of the stereolithography resin composition will be described more specifically.
(Photocurable compound)
The photocurable compound includes a first compound and a second compound.
The first compound has a functional site capable of forming a pseudo-crosslink point, but has only one reactive functional group (first reactive functional group) capable of forming a chemical crosslink point, and is used for a curing reaction. The curable material used is generally referred to as a monofunctional compound. On the other hand, the second compound has two or more reactive functional groups (second reactive functional groups) capable of forming a chemical cross-linking point, and is generally abundant in the curable material used for the curing reaction. It is called a functional compound.

Since the first compound has one chemical cross-linking point, it is incorporated into the polymer chain by polymerization or chemical cross-linking together with the second compound when the resin composition is cured. By incorporating the first compound into the polymer chain, functional sites capable of forming pseudo-crosslink points are introduced into the polymer chain. The functional sites introduced into the polymer chain form pseudo-crosslink points in the cured product, thereby exhibiting the elasticity of the cured product. Pseudo-crosslinking points behave like pseudo-crosslinking between polymer chains, but are weaker interactions than chemical cross-linking points, which are strong bonds. Therefore, when the cured product is pulled, even if the pseudo-crosslink is once broken, a pseudo-crosslink point is formed again with a nearby functional group. Therefore, while ensuring elasticity by the pseudo-crosslinking point, breakage when the cured product is pulled is unlikely to occur. On the other hand, when the cured product has many chemical cross-links, if the polymer chain or the cross-linking point is physically broken when the cured product is pulled, it is difficult to cross-link again. It's difficult to make it bigger.

(1st compound)
As the pseudo-crosslink point of the first compound, at least one of hydrogen bond and π-π interaction is preferable. Examples of the functional site forming a hydrogen bond include a hydroxy group, a urethane bond, a urea bond, an amide bond, and an amino group. The hydroxy group is preferably a side chain hydroxy group present in the side chain rather than a terminal hydroxy group present at the end of the first compound so that pseudo-crosslink points are easily formed between the polymer chains. Examples of the functional site forming the π-π interaction include an aromatic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring (C _6-20 aromatic ring, etc.) and the like. Of the aromatic rings, the benzene ring is preferable from the viewpoint that the π-π interaction is easily formed.

Of these, a hydroxy group (particularly, a side chain hydroxy group), a urethane bond, and an aromatic ring are preferable from the viewpoint of easily forming a pseudo-crosslinked point having an appropriate bonding force. The first compound may have one of these functional sites, or may have two or more (for example, two or more and four or less). When the first compound has two or more functional sites, all functional sites may be the same or different, and some functional sites may be the same. For example, the first compound may comprise one or more functional moieties that form hydrogen bonds and one or more aromatic rings (such as a benzene ring). Further, the photocurable compound may contain one kind of first compound, or may contain two or more kinds of first compounds having different functional sites and / or first reactive functional groups.

Examples of the first reactive functional group include functional groups that can be cured or polymerized by the action of radicals, cations, anions and the like generated by light irradiation (also referred to as polymerizable functional groups). As the polymerizable functional group, a group having a polymerizable carbon-carbon unsaturated bond such as a vinyl group, an allyl group, an acryloyl group, and a methacryloyl group is preferable. Among them, as the first reactive functional group, a radically polymerizable functional group such as an acryloyl group and a methacryloyl group is preferable. The first compound having an acryloyl group and / or a methacryloyl group is called an acrylic compound.

As the acrylic compound, for example, a (meth) acrylic acid ester of an alcohol having the above-mentioned functional moiety is used. From the viewpoint that a high reaction rate can be easily obtained and three-dimensional stereolithography can be easily performed, it is preferable to use an acrylic compound having an acryloyl group. In the present specification, acrylic acid ester and methacrylic acid ester may be collectively referred to as (meth) acrylic acid ester or (meth) acrylate.

The ratio of the first compound to the photocurable compound is 40% by mass or more. When the ratio of the first compound is less than 40% by mass, the ratio of the second compound is relatively large, so that the ratio of the chemical cross-linking points becomes too large and the elongation at break decreases. From the viewpoint of forming many pseudo-crosslink points and ensuring higher breaking elongation, the ratio of the first compound to the photocurable compound is preferably 50% by mass or more. The proportion of the first compound is preferably 95% by mass or less, and may be 90% by mass or less. These lower limit values and upper limit values can be arbitrarily combined.

(Second compound)
The second reactive functional group contained in the second compound can be selected from those exemplified for the first reactive functional group. Among them, as the second reactive functional group, a radically polymerizable functional group (acryloyl group, methacryloyl group, etc.) is preferable. The second compound having an acryloyl group and / or a methacryloyl group is called an acrylic compound.

The number of the second reactive functional groups in the second compound may be 2 or more, preferably 2 or more and 8 or less, and more preferably 2 or more and 4 or less. A second compound having two second reactive functional groups and a second compound having three or more second reactive functional groups may be used in combination.

As the acrylic compound, for example, a poly (meth) acrylic acid ester of a polyol is used. The polyol may be a polyester polyol, a polyether polyol, a polyurethane polyol, a polyester polyurethane polyol, a polyether urethane polyol, or the like, in addition to an aliphatic polyol, an alicyclic polyol, an aromatic polyol, and the like.
As the second compound, one type may be used alone, or two or more types may be used in combination.

The ratio of the second compound to the photocurable compound is 5% by mass or more. If the proportion of the second compound is less than 5% by mass, when the cured product is pulled, the effect of returning to the original state is hardly obtained. From the viewpoint of easily ensuring the restoring effect when the cured product is pulled, the ratio of the second compound to the photocurable compound is preferably 10% by mass or more. The ratio of the second compound is preferably 60% by mass or less, and preferably 50% by mass or less. These lower limit values and upper limit values can be arbitrarily combined.

(others)
The photocurable compound may further contain a third compound other than the first compound and the second compound. Examples of the third compound include compounds having one reactive functional group but no functional group capable of forming a pseudo-crosslink point (monofunctional compound). As the third compound, as the reactive functional group, a compound having a radically polymerizable functional group such as an acryloyl group and a methacryloyl group (acrylic compound) is preferable. Examples of the third compound include (meth) acrylic acid esters of monoalcohols. As the third compound, what is generally called a reactive diluent (preferably an acrylic reactive diluent) may be used.
The ratio of the third compound to the photocurable compound is preferably 10% by mass or less.

(Photoreaction initiator)
The photoreaction initiator (or photopolymerization initiator) contained in the photomodeling resin composition is activated by the action of light to initiate curing (specifically, polymerization) of the photocurable compound. Examples of the photoreaction initiator include radical polymerization initiators that generate radicals by the action of light, and agents that generate acids (or cations) by the action of light (specifically, cation generators). .. As the photoreaction initiator, one type may be used alone, or two or more types may be used in combination. The photoreaction initiator is selected depending on the type of photocurable compound, for example, whether it is radically polymerizable or cationically polymerizable. Examples of the radical polymerization initiator (radical photopolymerization initiator) include an alkylphenone-based photopolymerization initiator and an acylphosphine oxide-based photopolymerization initiator.

Examples of the alkylphenone-based photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethane-1-one (BASF, IRGACURE 651) and 1-hydroxy-cyclohexyl-phenyl-ketone (BASF, IRGACURE). 184), 2-Hydroxy-2-methyl-1-phenyl-propan-1-one (BASF, IRGACURE 1173), 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl -1-Propane-1-one (BASF, IRGACURE 2959), 2-Hirodoxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propane -1-one (BASF, IRGACURE 127), 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1-one (BASF, IRGACURE 907), 2-benzyl-2-dimethylamino -1- (4-morpholinophenyl) -butanone-1 (BASF, IRGACURE 369E), 2- (dimethylamino) -2-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) ) Phenyl] -1-butanone (BASF, IRGACURE 379EG) and the like.

Examples of the acylphosphine oxide-based photopolymerization initiator include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (BASF, IRGACURE TPO) and bis (2,4,6-trimethylbenzoyl) -phenylphosphine. Examples thereof include oxides (BASF, IRGACURE 819).

(others)
The stereolithography resin composition may further contain other known curable resins and the like.
Moreover, the resin composition for stereolithography can contain a known additive.

The loss tangent tan δ of the cured product of the stereolithography resin composition at 23 ° C. may be 0.3 or more, preferably 0.4 or more. When tan δ is less than 0.3, the elongation at break is low. The tan δ is preferably 3 or less from the viewpoint of suppressing the deterioration of the property of returning to the original shape after pulling, which is peculiar to rubber, as the storage shear elastic modulus decreases.

The viscosity of the stereolithography resin composition at 25 ° C. is, for example, 50 mPa or more and 50 Pa or less. When the resin composition for stereolithography has such a viscosity, the workability of stereolithography can be enhanced.
The above viscosity can be measured, for example, using a cone plate type E-type viscometer at a rotation speed of 10 rpm.

The stereolithography resin composition is preferably liquid at room temperature (for example, 20 ° C. or higher and 35 ° C. or lower). The liquid resin composition can be easily stereolithographically formed using a 3D printer or the like. In this case, the viscosity of the stereolithography resin composition at 25 ° C. is, for example, 50 mPa or more and 5 Pa or less.

According to the above aspect of the present invention, the breaking elongation of the cured product of the stereolithography resin composition can be greatly improved. For example, the tensile elongation of the cured product can be improved to 200% or more, and the tensile elongation of 250% or more or 300% or more can be secured.

The tensile elongation of the cured product is an index of the elongation at break. The tensile elongation of the cured product is measured at a tensile speed of 50 mm / min and a distance between marked lines of 20 mm for the cured product sample in accordance with JIS K7127-1999 under the conditions of 23 ° C. and 50% RH. The maximum growth (%) of time. As a sample, a film having a thickness of 300 μm is prepared using a stereolithography resin composition, and the film is completely cured by irradiating the film with light.

The Tg of the cured product of the stereolithography resin composition is, for example, −10 ° C. or higher, preferably 10 ° C. or higher, and more preferably 10 ° C. or higher and 40 ° C. or lower. When the Tg of the cured product is in such a range, elasticity due to the pseudo-crosslinking point is likely to be developed. Tg is determined by DMA using a commercially available dynamic viscoelasticity measuring device, for example, using a sample similar to the measurement of tan δ. In DMA, tan δ is measured at a frequency of 1 Hz while changing the temperature, and the temperature at which tan δ reaches the top peak is defined as Tg.

The cured product of the photocurable resin composition exhibits a high elastic modulus. The storage tensile modulus of elasticity of the cured product at 23 ° C. is, for example, 1 Pa or more, preferably 1.7 Pa or more, more preferably 1.8 Pa or more, and may be 3 Pa or more. The storage tensile modulus is determined by DMA using a commercially available dynamic viscoelasticity measuring device using a sample similar to the measurement of tan δ under the conditions of 23 ° C. and a frequency of 1 Hz.

The cured product of the photocurable resin composition exhibits high rubber elasticity. The shore A hardness of the cured product at 23 ° C. is preferably 1 or more and 90 or less. The Shore A hardness of the cured product can be measured in accordance with JIS K6253: 2012 under the condition of using a cured product having a thickness of 6 mm or more and a load of 1 kg.

The stereolithography resin composition can be obtained by mixing the constituent components. The stereolithography resin composition may be a one-component curing type or a two-component curing type.

Further, the stereolithography resin composition is suitable for being cured by light irradiation to form a two-dimensional or three-dimensional stereolithography product (cured product).

For the three-dimensional stereolithography, for example, a step (i) of forming a liquid film of a stereolithography resin composition and curing the liquid film to form a pattern, and forming another liquid film so as to be in contact with the pattern. It can be manufactured by a manufacturing method including a step (ii) of performing the process (ii) and a step (iii) of curing another liquid film on the pattern and laminating another pattern.

FIG. 1 is an example of a case where a three-dimensional model is formed by using a stereolithography device (patterning device) provided with a resin tank. In the illustrated example, the modeling of the suspension method is shown, but the method is not particularly limited as long as it is a method capable of three-dimensional stereolithography using a resin composition for stereolithography. Further, the method of light irradiation (exposure) is not particularly limited, and point exposure or surface exposure may be used.

The patterning apparatus 1 includes a platform 2 having a pattern forming surface 2a, a resin tank 3 containing a stereolithography resin composition 5, and a projector 4 as a surface exposure type light source.
(I) Step of forming a liquid film and curing it to form a pattern In step (i), as shown in (a), first, a platform is placed on the stereolithography resin composition 5 housed in the resin tank 3. The pattern forming surface 2a of 2 is immersed in a state of facing the projector 4 (that is, the bottom surface of the resin tank 3). At this time, the height of the pattern forming surface 2a (or platform 2) is such that the liquid film 7a (liquid film a) is formed between the pattern forming surface 2a and the projector 4 (or the bottom surface of the resin tank 3). To adjust. Next, as shown in (b), the liquid film 7a is photocured to form the pattern 8a (pattern a) by irradiating (surface exposure) light L from the projector 4 toward the liquid film 7a.

In the patterning apparatus 1, the resin tank 3 serves as a supply unit for the stereolithography resin composition 5. It is desirable that at least the portion of the resin tank (the bottom surface in the illustrated example) existing between the liquid film and the projector 4 is transparent with respect to the exposure wavelength so that the liquid film is irradiated with light from the light source. The shape, material, size, etc. of the platform 2 are not particularly limited.

After forming the liquid film a, the liquid film a is photocured by irradiating the liquid film a with light from a light source. Light irradiation can be performed by a known method. As the light source, a known light source used for photocuring can be used. In the case of the surface exposure method, it is convenient to use a projector as a light source. Examples of the projector include an LCD (transmissive liquid crystal display) method, an LCoS (reflection type liquid crystal display) method, and a DLP (registered trademark, Digital Light Processing) method. The exposure wavelength can be appropriately selected depending on the constituent components (particularly, the type of photoreactive initiator) of the stereolithography resin composition.

(Ii) Step of forming a liquid film between the pattern a and the light source In the step (ii), the stereolithography resin composition is supplied between the pattern a obtained in the step (i) and the light source. To form a liquid film (liquid film b). That is, the liquid film b is formed on the pattern a formed on the pattern forming surface. For the supply of the resin composition for stereolithography, the description of step (i) can be referred to.

For example, in step (ii), as shown in FIG. 1 (c), after forming the two-dimensional pattern 8a (two-dimensional pattern a), the pattern forming surface 2a may be raised together with the platform 2. Then, the liquid film 7b (liquid film b) can be formed by supplying the stereolithography resin composition 5 between the two-dimensional pattern 8a and the bottom surface of the resin tank 3.

(Iii) Step of laminating another pattern b on the pattern a In the step (iii), the liquid film b formed in the step (ii) is exposed from a light source to photocure the liquid film b, and the pattern is formed. Another pattern (pattern b obtained by photocuring the liquid film b) is laminated on a. By stacking the patterns in the thickness direction in this way, a three-dimensional modeling pattern can be formed.

For example, as shown in FIG. 1D, the liquid film 7b (liquid film b) formed between the pattern 8a (pattern a) and the bottom surface of the resin tank 3 is exposed from the projector 4 to liquid. The film 7b is photocured. By this photo-curing, the liquid film 7b is converted into the pattern 8b (pattern b). In this way, the pattern 8b can be laminated on the pattern 8a.
For the light source, exposure wavelength, etc., the description of step (i) can be referred to.

(Iv) Step of repeating step (ii) and step (iii) The first step can include step (iv) of repeating step (ii) and step (iii) a plurality of times. By this step (iv), a plurality of patterns b are laminated in the thickness direction, and a three-dimensional modeling pattern can be obtained. The number of repetitions can be appropriately determined according to the shape and size of the desired three-dimensional model (three-dimensional model pattern).

For example, as shown in FIG. 1 (e), the platform 2 in which the pattern 8a (pattern a) and the pattern 8b (pattern b) are laminated on the pattern forming surface 2a is raised. At this time, a liquid film 7b (liquid film b) is formed between the pattern 8b and the bottom surface of the resin tank 3. Then, as shown in FIG. 1 (f), the projector 4 exposes the liquid film 7b to light-curing the liquid film 7b. As a result, another pattern 8b (pattern b) is formed on the pattern 8b. Then, by alternately repeating (e) and (f), a plurality of patterns 8b (two-dimensional patterns b) can be laminated.

Since the uncured stereolithography resin composition is attached to the three-dimensional modeling pattern obtained in the step (iii) and the step (iv), it is usually subjected to a cleaning treatment with a solvent.

If necessary, the three-dimensional modeling pattern obtained in the step (iii) or the step (iv) may be post-cured. Post-curing can be performed by irradiating the pattern with light. The conditions of light irradiation can be appropriately adjusted according to the type of the stereolithography resin composition, the degree of curing of the obtained pattern, and the like. Post-curing may be performed on a part of the pattern or on the whole pattern.

[Example]
Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Examples 1 to 6, Reference Examples 1 to 2, and Comparative Examples 1 to 3.
(1) Preparation of Photopolymerization Resin Composition The photocurable compound and photoreaction initiator (photoradical polymerization initiator) shown in Tables 1 and 2 are mixed at the mass ratio shown in Table 2 and stirred at 80 ° C. A uniform liquid resin composition was prepared by heating in the same oven to dissolve the solid components.

(2) Evaluation The following evaluation was performed using the resin composition obtained in (1) above.
(A) Viscosity The viscosity of the resin composition was measured at 25 ° C. and a rotation speed of 10 rpm using an E-type viscometer (TVE-20H, Toki Sangyo Co., Ltd.).

(B) tanδ, storage modulus, and Tg
A resin composition is poured into a tray to prepare a liquid film having a thickness of 300 μm, and both main surfaces of the liquid film are irradiated with LED light having a wavelength of 405 nm to completely cure the liquid film. A sample of the cured product was prepared. As the tray, a tray that transmits the above LED light was used.
The obtained sample was heated from -100 ° C to + 100 ° C at a heating rate of 1 Hz and 5 ° C / min at a frequency of 1 Hz and 5 ° C / min using DMA (DMS6100, manufactured by Hitachi High-Tech Science Co., Ltd.), and tan δ and storage tension were applied. The elastic modulus (Pa) was measured. The tan δ and the storage tensile elastic modulus at 23 ° C., and the temperature at which tan δ reaches the top peak were determined as Tg.

(C) Fracture elongation (tensile elongation)
For the sample prepared in the same manner as in (b) above, the maximum at break was obtained under the conditions of 23 ° C. and 50% RH, a tensile speed of 50 mm / min and a distance between marked lines of 20 mm in accordance with JIS K7127-1999. Elongation (%) was measured.

(D) Shore A hardness A sample for type A of JIS K6253: 2012 (thickness 6 mm) was cured by curing the resin composition using a DLP (registered trademark) type 3D printer (ML-48 manufactured by Muto Kogyo Co., Ltd.). ) Was prepared as a sample of the cured product. For this sample, the shore A hardness was measured under the condition of a load of 1 kg according to JIS K6253: 2012 using a durometer (manufactured by TECLOCK, GS-719H).

(E) Curing rate A resin composition was poured into a tray to prepare a liquid film having a thickness of 150 μm, and the liquid film was irradiated with light to cure the liquid film. The irradiation amount until the curing was completed at this time was used as an index of the curing rate. The light irradiation was performed by fixing the illuminance to 0.2 mW / cm ² with LED light having a wavelength of 405 nm. The completion of curing was confirmed by touching the cured product of the liquid film.

(F) Curing shrinkage amount When preparing the sample in (b) above, the density d ₁ of the resin composition before curing and the density d ₂ of the obtained cured product were measured using a gas-type densitometer, respectively. The measurement was performed, and the amount of curing shrinkage (%) was determined from the following formula.
Curing shrinkage amount (%) = (d ₂ -d ₁ ) / d ₂ × 100

(G1) Stereolithography evaluation 1
Using a DLP (registered trademark) type 3D printer (ML-48 manufactured by Muto Kogyo Co., Ltd.), a 10 mm square with an irradiation time of 30 seconds per layer and a pitch of 100 μm in the z-axis (height direction). Then, a plate-shaped sample having a hole for hanging (diameter 1 mm) was prepared. The sample was suspended with a rod-shaped object passed through the hole, and the state of the sample at this time was evaluated under the following conditions.
◯: No sample is dropped or hung down.
Δ: The vertical length of the suspended sample is less than 20% of the initial length of the sample.
X: The vertical length of the suspended sample is 20% or more of the initial length of the sample.
The initial length of the sample is the length of the portion that takes the maximum length in the vertical direction immediately after the sample is suspended, before suspension.

(G2) Stereolithography evaluation 2
Using a DLP (registered trademark) type 3D printer (ML-48 manufactured by Muto Kogyo Co., Ltd.), strips are used under the conditions of an irradiation time of 30 seconds per layer and a pitch of 100 μm in the z-axis (height direction). Sample (length 40 mm × width 20 mm × thickness (height) 6 mm) was prepared. This sample was bent 180 ° near the center in the vertical direction, and the state at this time was evaluated according to the following criteria.
◯: Adhesive and cracks are not seen in the parts that come into contact with each other due to bending.
X: The contacting part adheres due to bending. No cracks are seen.
Table 2 shows the evaluation results of Examples , Reference Examples, and Comparative Examples. Table 1 shows the photocurable compounds and photoreaction initiators used in Examples , Reference Examples, and Comparative Examples.

As shown in Table 2, the resin compositions of Comparative Examples 2 and 3 having a tan δ of less than 0.3 have a low elongation at break. Further, in Comparative Example 1 in which the ratio of the second compound was less than 5% by mass, when the sample of the cured product was pulled, the deformation started immediately, and the quantitative elongation at break could not be measured. On the other hand, in Examples and Reference Examples , a high elongation at break of 200% or more (preferably 250% or more) was obtained. Further, in the examples, a high elongation at break of 300% or more can be obtained.

In the examples, the shore A hardness is also 3 to 50, and it can be seen that the cured product has rubber-like elasticity. In addition, the elastic modulus is high, and Tg is relatively high as compared with the comparative example. Further, in the examples, the curing speed was high, the amount of curing shrinkage was suppressed to a low level, and excellent results were obtained in the stereolithography evaluation. As described above, the resin composition of the example is suitable for stereolithography.

The stereolithography resin composition according to the above aspect of the present invention has a high elongation at break. Therefore, it is suitable for various applications (for example, artificial organs, tissues, figures, etc.) for forming two-dimensional or three-dimensional stereolithographic objects that require high breaking elongation.

1: Optical modeling device, 2: Platform, 2a: Pattern forming surface, 3: Resin tank, 4: Projector, 5: Resin composition for optical modeling, 6: Release agent layer, 7a: Liquid film a, 7b: Liquid Film b, 8a: two-dimensional pattern a, 8b: two-dimensional pattern b, L: light

Claims (5)

A resin composition for stereolithography containing a photocurable compound and a photoreaction initiator.
The photocurable compound includes a first compound having a functional site capable of forming a pseudo-crosslink point and one first reactive functional group capable of forming a chemical cross-linking point, and two or more compounds capable of forming a chemical cross-linking point. Containing a second compound having a second reactive functional group,
The functional site is at least one selected from the group consisting of hydroxy groups, urethane bonds, and aromatic rings.
The second compound contains a poly (meth) acrylic acid ester of a polyether urethane polyol.
The ratio of the first compound to the photocurable compound is 50 % by mass or more, and is
The ratio of the second compound to the photocurable compound is 10 % by mass or more, and is
The loss tangent tan δ of the cured product of the stereolithography resin composition at 23 ° C. is 0.3 or more .
A resin composition for stereolithography, wherein the cured product of the resin composition for stereolithography has a tensile elongation of 300% or more . The resin composition for photomodeling according to claim 1 , wherein the hydroxy group is a side chain hydroxy group present in the side chain of the first compound. The stereolithography resin composition according to claim 1 or 2 , wherein the first reactive functional group and the second reactive functional group are radically polymerizable, respectively. The resin composition for stereolithography according to any one of claims 1 to 3 , wherein the first compound and the second compound are acrylic compounds, respectively. The resin composition for stereolithography according to any one of claims 1 to 4 , wherein the ratio of the second compound is 10% by mass or more and 50% by mass or less.

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