JP7150295B2 - Photocurable slurry - Google Patents

Description

The present invention relates to photocurable slurries.

In recent years, in order to expand the use of members made of inorganic particles such as ceramics (hereinafter referred to as "inorganic molded bodies"), members having complex shapes (hereinafter referred to as "complex shaped members") have become popular as inorganic molded bodies. ) are being considered. In the manufacture of complicated-shaped members, the demand for near-net shaping is increasing in order to reduce manufacturing costs such as cutting costs for forming complicated shapes. In order to meet such demands, a wet molding method using a slurry containing inorganic particles at a high concentration is generally used. Among the wet molding methods, stereolithography, which has a particularly high degree of freedom in shaping, is attracting attention.

For example, the following methods are used in ceramic molding by conventional stereolithography. A coating film A is formed from a slurry containing inorganic particles as raw materials of ceramics and an ultraviolet curable resin (binder), and the coating film A is position-selectively irradiated with an ultraviolet laser to form a two-dimensional ceramic molded body A. to form Furthermore, the slurry is applied to a predetermined thickness on the two-dimensional ceramic molded body A to form a coating film B, and the coating film B is position-selectively irradiated with an ultraviolet laser to form a two-dimensional ceramic molding. Form body B. By repeating these operations, a three-dimensional ceramic molded body in which many two-dimensional ceramic molded bodies are laminated is obtained (see, for example, Non-Patent Documents 1 to 3).

C. Hinczewski et al., J. Eur. Ceram. Soc. 18 (1998), pp. 583-590. T. Chartier et al., J. Ceram. Sci. Tech. 06 (2015) pp. 95-104. J. W. Halloran et al., J. Eur. Ceram. Soc. 31 (2011) 2613-2619.

However, in the above-described molding method, the interface affinity between the dispersion medium containing a large amount of binder and the inorganic particles is low, so there is a problem that the inorganic particles aggregate in the slurry and are difficult to disperse uniformly. In addition, since the above molding method requires a large amount of binder, a large amount of gas is generated in the degreasing step for removing the binder. When a large amount of gas is generated in the degreasing process, there is a problem that cracks occur in the ceramic compact. Moreover, in order to remove the binder in the degreasing process, a heat treatment for a long time is required, which raises the problem of high cost. Furthermore, there is a problem that the ceramic compact after removing a large amount of binder has low mechanical strength.

The present invention has been made in view of the above circumstances, and is an inorganic material having excellent dispersion stability of inorganic particles in a slurry containing inorganic particles at a high concentration, and in which inorganic particles are strongly crosslinked by a simple operation. An object of the present invention is to provide a photocurable slurry that can be molded into a molded article.

[1] Contains inorganic particles, an association of polyalkyleneimine and fatty acid, a polyfunctional acrylate, a photopolymerization initiator, and a non-aqueous solvent, and the surfaces of the inorganic particles are modified with the association A photocurable slurry characterized by:

[2] The photocurable slurry according to [1], wherein the polyalkyleneimine has a weight average molecular weight of 300 to 30,000.

[3] The light according to [1] or [2], wherein the associated body is an association of 15 mol% to 40 mol% of the fatty acid with respect to all the alkyleneimine units of the polyalkyleneimine. Hardening slurry.

[4] The photocurable slurry according to any one of [1] to [3], wherein the content of the inorganic particles is 10% by volume to 65% by volume.

[5] The light according to any one of [1] to [4], wherein the content of the polyfunctional acrylate is 1.5% by mass to 10.0% by mass with respect to the inorganic particles. Hardening slurry.

According to the present invention, the inorganic particles are excellent in dispersion stability in a slurry containing inorganic particles at a high concentration, and an inorganic molded article in which the inorganic particles are strongly crosslinked by a simple operation can be formed by photocuring. can provide a liquid slurry.

1 is an optical photograph showing the appearance of solution AA after ultraviolet irradiation in Experimental Example 1. FIG. 4 is an optical photograph showing the appearance of solution BB after ultraviolet irradiation in Experimental Example 1. FIG. FIG. 10 is a diagram showing the relationship between the added amount and the adsorption amount of an aggregate of polyethyleneimine and oleic acid in Experimental Example 2. FIG. 3 is an optical photograph showing the appearance of a photocurable slurry immediately after preparation of the photocurable slurry in Experimental Example 3. FIG. 10 is an optical photograph showing the appearance of the photocurable slurry after standing for 12 hours without UV irradiation in Experimental Example 3. FIG. 2 is an optical photograph showing the appearance of a photocurable slurry immediately after being irradiated with ultraviolet rays immediately after preparation of the photocurable slurry in Experimental Example 3. FIG. FIG. 10 is a diagram showing flow characteristics of photocurable slurries using associations of polyethyleneimine and oleic acid with different degrees of association before and after UV irradiation in Experimental Example 3. FIG. FIG. 10 is a diagram showing the flow characteristics of photocurable slurries with different polyfunctional acrylate contents before and after UV irradiation in Experimental Example 3. FIG. 10 is an optical photograph showing the appearance of a wet molded body produced by 3D writing of a photocurable slurry in Experimental Example 4. FIG.

An embodiment of the photocurable slurry of the present invention will be described.
It should be noted that the present embodiment is specifically described for better understanding of the gist of the invention, and does not limit the invention unless otherwise specified.

[Photocurable slurry]
The photocurable slurry of the present embodiment contains inorganic particles, an association of polyalkyleneimine and fatty acid, a polyfunctional acrylate, a photopolymerization initiator, and a non-aqueous solvent.

More specifically, the photocurable slurry of the present embodiment is obtained by dispersing inorganic particles whose surfaces are modified with an association of polyalkyleneimine and fatty acid in a solution containing a polyfunctional acrylate and a photopolymerization initiator. is.
The expression that the surface of the inorganic particles is modified by the association of the polyalkyleneimine and the fatty acid means that the association of the polyalkyleneimine and the fatty acid adheres to at least a part of the surface of the inorganic particles.

In the photocurable slurry of the present embodiment, the inorganic particles are not particularly limited, but examples include silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), apatite hydroxide (Ca ₁₀ (PO ₄ ) ₆ ( OH) ₂ ), aluminum oxide (Al ₂ O ₃ ), aluminum nitride (AlN), boron nitride (BN), yttrium oxide (Y ₂ O ₃ ), zinc oxide (ZnO), titanium oxide (TiO ₂ ), calcium carbonate Particles of inorganic compounds such as (CaCO ₃ ) and barium titanate (BaTiO ₃ ), particles of nickel (Ni), silicon (Si) and the like.

The specific surface area diameter of the inorganic particles is preferably 10 nm to 10 μm, more preferably 30 nm to 5 μm.
If the inorganic particles have a specific surface area diameter of 10 nm or more, they can be surface-modified with the associated body. On the other hand, if the average primary particle size of the inorganic particles is 10 μm or less, it is possible to mold a member having a complicated shape without collapsing the shape.

In addition, the "specific surface area diameter" in the photocurable slurry of the present embodiment is a numerical value obtained by the following method. That is, the specific surface area of the inorganic particles in the photocurable slurry of the present embodiment is determined by a gas adsorption method, and the diameter geometrically calculated from the specific surface area when the shape of the particles is assumed to be spherical is the specific surface area. diameter.

Examples of the polyalkyleneimine in the photocurable slurry of the present embodiment include polyethyleneimine, polypropyleneimine, and polybutadieneimine. Among these, polyethyleneimine is more preferable from the viewpoint of the dispersion stability of the inorganic particles in the slurry containing the inorganic particles at a high concentration.

The weight average molecular weight (Mw) of the polyalkyleneimine is preferably 300-30,000, more preferably 600-10,000.
If the weight average molecular weight (Mw) of the polyalkyleneimine is 300 or more, the polyalkyleneimine and the fatty acid can associate to form an aggregate. On the other hand, if the weight average molecular weight (Mw) of the polyalkyleneimine is 30000 or less, the inorganic particles modified with the association of the polyalkyleneimine and the fatty acid are uniformly and stably dispersed in the non-aqueous solvent in the photocurable slurry. .

In the photocurable slurry of the present embodiment, fatty acids include saturated fatty acids and unsaturated fatty acids.
As saturated fatty acids and unsaturated fatty acids, those having 4 to 30 carbon atoms are used.
Examples of saturated fatty acids include lauric acid, myristic acid, palmitic acid, and stearic acid. Examples of unsaturated fatty acids include oleic acid, linoleic acid, and eleostearic acid. Among these, oleic acid is more preferable from the viewpoint of the dispersion stability of the inorganic particles in the slurry containing the inorganic particles at a high concentration.
Moreover, as a saturated fatty acid and an unsaturated fatty acid, the said thing can be used individually by 1 type or in mixture of 2 or more types.

The association of polyalkyleneimine and fatty acid is preferably associated with 15 mol% to 40 mol% of fatty acid, more preferably 15 mol% to 30 mol% of fatty acid, with respect to all alkyleneimine units of polyalkyleneimine. is more preferable.
As long as 15 mol % or more of fatty acid is associated with the associated body, the associated body can modify the surface of the inorganic particles as described above. On the other hand, if the associated body contains 40 mol % or less of fatty acid, the inorganic particles modified with the associated body of polyalkyleneimine and fatty acid are uniformly and stably dispersed in the non-aqueous solvent in the photocurable slurry.

In the photocurable slurry of the present embodiment, the content of the inorganic particles is preferably 10% by volume to 65% by volume, more preferably 40% by volume to 50% by volume.
If the content of the inorganic particles is 10% by volume or more, it is possible to suppress a significant decrease in the mechanical strength of the inorganic molded article imparted with a complicated shape. On the other hand, when the content of the inorganic particles is 65% by volume or less, the inorganic particles modified with the association of polyalkyleneimine and fatty acid are uniformly and stably dispersed in the non-aqueous solvent.

In the photocurable slurry of the present embodiment, the association amount of oleic acid with respect to all alkyleneimine units of polyalkyleneimine can be confirmed by, for example, CHN analysis using an organic elemental analyzer.

In the photocurable slurry of the present embodiment, the content of the aggregate is preferably 0.6 mg/m ² to 3.0 mg/m ² based on the surface area of the inorganic particles, more preferably 0.8 mg/m ² More preferably ˜2.0 mg/m ² .
If the content of the aggregate is 0.6 mg/m ² or more, almost the entire surface of the inorganic particles can be modified. On the other hand, when the content of the association is in the range of 0.8 mg/m ² to 3.0 mg/m ² , the inorganic particles modified with the association of polyalkyleneimine and fatty acid are non-toxic in the photocurable slurry. Disperses uniformly and stably in aqueous solvents.

In the photocurable slurry of the present embodiment, the polyfunctional acrylate preferably has two or more acryloyl groups (CH ₂ =CH-C(=O)-), preferably four to six. It is more preferable to have

Examples of polyfunctional acrylates include bisphenol F ethylene oxide-modified diacrylate (formula (1) below), bisphenol A ethylene oxide-modified diacrylate (formula (2) below), ethylene oxide isocyanurate-modified diacrylate (formula (3) below), Polypropylene glycol diacrylate (formula (4) below), polyethylene glycol diacrylate (formula (5) below), trimethylolpropane acrylate (formula (6) below), trimethylolpropane propylene oxide-modified triacrylate (formula (7) below ), trimethylolpropane ethylene oxide-modified triacrylate (formula (8) below), ethylene oxide isocyanurate-modified diacrylate or ethylene oxide isocyanurate-modified triacrylate (formula (9) below), pentaerythritol triacrylate and pentaerythritol tetraacrylate (formula below (10)), ditrimethylolpropane tetraacrylate (formula (11) below), dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (formula (12) below), diglycerin ethylene oxide-modified acrylate (formula (13) below), A compound represented by the following formula (14), a compound represented by the following formula (15), a compound represented by the following formula (16), and the like are included. One of these polyfunctional acrylates may be used alone, or two or more thereof may be used in combination. Among these polyfunctional acrylates, dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (formula (12) below) are preferred in terms of solubility in non-aqueous solvents and high acryloyl group density per molecule.

（但し、ｎ≒２である。）

(However, n≈2.)

（但し、ｎ≒２である。）

(However, n≈2.)

（但し、ｎ≒４である。）

(However, n≈4.)

（但し、Ｒ＝ＨまたはＣＯＣＨ＝ＣＨ_２である。）

(with the proviso that R=H or COCH= _CH2 ).

（但し、Ｒ＝ＨまたはＣＨ_２＝ＣＨＣＯである。）

(However, it is R=H or _CH2 =CHCO.)

（但し、Ａはアクリル酸、Ｍは二価アルコール、Ｎは二塩基酸である。）

(However, A is acrylic acid, M is dihydric alcohol, and N is dibasic acid.)

（但し、Ａはアクリル酸、Ｍは二価アルコール、Ｎは二塩基酸である。）

(However, A is acrylic acid, M is dihydric alcohol, and N is dibasic acid.)

In the photocurable slurry of the present embodiment, the content of the polyfunctional acrylate is preferably 1.5% by mass to 10.0% by mass with respect to the inorganic particles, and 1.5% by mass to 5.0% by mass. % is more preferred.
When the content of the polyfunctional acrylate is 1.5% by mass or more relative to the inorganic particles, the photocurable slurry is solidified, and complex shapes can be molded without collapsing the molded body. On the other hand, if the content of the polyfunctional acrylate is 10.0% by mass or less relative to the inorganic particles, cracking in the degreasing step can be effectively suppressed.

The photopolymerization initiator is not particularly limited as long as it generates radicals for initiating radical polymerization of the polyfunctional acrylate by irradiating the photocurable slurry with light. Photopolymerization initiators include, for example, benzyl dimethyl ketal, benzophenone, methyl 2-benzoylbenzoate, 4,4'-bis(diethylamino) benzophenone, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl -1-phenyl-1-propanone, 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4, 6-trimethylbenzoyl)-phenylphosphine oxide and the like.

In the photocurable slurry of the present embodiment, the content of the photopolymerization initiator is preferably 0.5% by mass to 8.0% by mass, and 1.0% by mass to 5.0% by mass with respect to the polyfunctional acrylate. It is more preferably 0% by mass.
If the content of the photopolymerization initiator is 0.5% by mass or more with respect to the polyfunctional acrylate, the photocurable slurry can be solidified in a short time to form a complicated shape. On the other hand, when the content of the photopolymerization initiator is 8.0% by mass or less with respect to the polyfunctional acrylate, it is possible to suppress the decrease in the solidification speed of the photocurable slurry when molding a complicated shape.

The non-aqueous solvent is not particularly limited as long as it can dissolve the association of polyalkyleneimine and fatty acid, and includes α-terpineol, toluene, xylene, tetrahydrofuran and the like.

In the photocurable slurry of the present embodiment, the content of the non-aqueous solvent is preferably 35% to 90% by volume, more preferably 50% to 60% by volume.
If the content of the non-aqueous solvent is 35% by volume or more, the inorganic particles can be uniformly dispersed in the photocurable slurry. On the other hand, when the content of the non-aqueous solvent is 90% by volume or less, a complex shape can be molded without causing the collapse of the molded body.

The photocurable slurry of this embodiment may contain a polymerization inhibitor for inhibiting polymerization of the polyfunctional acrylate.

The polymerization inhibitor is not particularly limited, and a general radical polymerization inhibitor is used according to the type of polyfunctional acrylate.

In the photocurable slurry of the present embodiment, the content of the polymerization inhibitor is not particularly limited, and is appropriately adjusted according to the type of polyfunctional acrylate, the content in the photocurable slurry, and the like.

The reaction mechanism (curing mechanism) of the photocurable slurry of this embodiment will be described.
When the photocurable slurry of the present embodiment is irradiated with light, the photopolymerization initiator first generates radicals. Then, the polyfunctional acrylate initiates radical polymerization to form a polyfunctional acrylate polymer.
Moreover, since radical polymerization is an exothermic reaction, heat is generated with the initiation of radical polymerization.
The heat (reaction heat) resulting from this radical polymerization adds the amino group of the polyalkyleneimine that forms the aggregate attached to the surface of the inorganic particles to the double bond that forms the polyfunctional acrylate and its polymer. A Michael addition reaction occurs. That is, the photocurable slurry of the present embodiment first initiates radical polymerization of a polyfunctional acrylate by irradiating light, and the heat resulting from the radical polymerization forms a polyfunctional acrylate and a polymer thereof. A Michael addition reaction occurs between the double bond and the amino group of the polyalkyleneimine. Therefore, the photocurable slurry of the present embodiment does not need to apply heat from the outside in order to cause the Michael addition reaction, and can cause the radical polymerization reaction and the Michael addition reaction only by irradiating light. As a result, the photocurable slurry of the present embodiment can be used to form an inorganic molded article with a simple operation.

This Michael addition reaction causes cross-linking between the inorganic particles. A bond resulting from a Michael addition reaction is formed by a chemical reaction as shown in formula (17) below.

That is, in the above formula (17), (a) the amino group of the polyalkyleneimine undergoes a Michael addition reaction with the double bond that constitutes the (b) polyfunctional acrylate, resulting in (c) or (d) form a bond.

A bond formed by such a Michael addition reaction can be confirmed, for example, by measuring an infrared absorption spectrum with infrared spectroscopy (IR). A Fourier Transform Infrared Spectrometer (FT-IR) is used to measure the infrared absorption spectrum.

According to the photocurable slurry of the present embodiment, the inorganic particles are contained at a high concentration, and the dispersion stability of the inorganic particles in the slurry is excellent. Further, according to the photocurable slurry of the present embodiment, the reaction heat generated by the radical polymerization reaction of the polyfunctional acrylate is used to bond the inorganic particles to the double bonds that constitute the polyfunctional acrylate and its polymer. Since the Michael addition reaction that adds the amino group of the polyalkyleneimine that forms the association of the polyalkyleneimine and the fatty acid attached to the surface of the polyalkyleneimine occurs, a simple operation forms an inorganic molded product in which the inorganic particles are strongly crosslinked. can do.

[Method for producing photocurable slurry]
The method for producing a photocurable slurry of the present embodiment includes the step of stirring and mixing a polyalkyleneimine and a fatty acid in a non-aqueous solvent to prepare a non-aqueous solution containing an association of the polyalkyleneimine and the fatty acid ( hereinafter referred to as “step A”); and a step of dispersing inorganic particles and a photopolymerization initiator in a non-aqueous solution to prepare a dispersion of inorganic particles (hereinafter referred to as “step B”). and a step of adding a polyfunctional acrylate to the dispersion (hereinafter referred to as “step C”).

In step A, a polyalkyleneimine and a fatty acid are added to a non-aqueous solvent, and they are stirred and mixed. As a result, the polyalkyleneimine and the fatty acid are associated in the non-aqueous solvent to form an associated body of the polyalkyleneimine and the fatty acid. In step A, the obtained aggregate is dissolved in a non-aqueous solvent, so a non-aqueous solution containing the aggregate is prepared.

The time for stirring the polyalkyleneimine and the fatty acid in the non-aqueous solvent is not particularly limited, but is preferably, for example, 1 hour to 24 hours.

In step B, inorganic particles and a photopolymerization initiator are dispersed in the non-aqueous solution obtained in step A to prepare a dispersion of inorganic particles.

In step B, the method of dispersing the inorganic particles and the photopolymerization initiator in the non-aqueous solution is not particularly limited. For example, the non-aqueous solution containing the inorganic particles and the photopolymerization initiator is stirred using a stirring blade or a magnetic stirrer. and a method of applying ultrasonic waves to a non-aqueous solution containing inorganic particles and a photopolymerization initiator.

In step C, a polyfunctional acrylate is added to the dispersion liquid obtained in step B. Thereby, the photocurable slurry of the present embodiment is obtained.

In step C, the method of adding the polyfunctional acrylate to the dispersion and dispersing it is not particularly limited. Examples include a method of applying ultrasonic waves to the dispersion liquid contained.

[Inorganic molding]
The inorganic molded article of the present embodiment is an inorganic molded article obtained by curing the photocurable slurry of the present embodiment. The amino group of the polyalkylenimine having a bond formed by the Michael addition reaction.

More specifically, in the inorganic molded article of the present embodiment, the surface of the inorganic particles is modified with an association body of polyalkyleneimine and fatty acid, and the amino group of the polyalkyleneimine constituting the association body is a polyfunctional acrylate and its It has a bond formed by a Michael addition reaction to the double bond that constitutes the polymer.

Examples of the inorganic molded article of the present embodiment include an elastically deformable molded article such as rubber and a plastically deformed molded article.

In the inorganic molded article of the present embodiment, the amino group of the polyalkyleneimine that forms the aggregate attached to the surface of the inorganic particles undergoes Michael addition to the double bond that constitutes the polyfunctional acrylate and its polymer. Therefore, the inorganic particles are strongly crosslinked. Therefore, according to the inorganic molded article of this embodiment, it is possible to mold a complicated-shaped member (molded article). Further, by sintering the inorganic molded body of the present embodiment, a sintered body in which the complicated shape of the inorganic molded body is maintained can be obtained.

[Manufacturing method of inorganic molding]
The method for producing an inorganic molded article of the present embodiment comprises a step of irradiating the photocurable slurry of the present embodiment with light to cure the photocurable slurry to form an inorganic molded article made of the photocurable slurry (hereinafter referred to as , referred to as “process D”).

In step D, the photocurable slurry of the present embodiment is irradiated with light. This causes the polyfunctional acrylate to initiate radical polymerization, as described above. Then, due to the heat caused by this radical polymerization, the amino group of the polyalkyleneimine that forms the aggregate adhering to the surface of the inorganic particles is added to the double bond that forms the polyfunctional acrylate and its polymer. An addition reaction occurs. As a result, the photocurable slurry is solidified or aggregated to obtain the above inorganic molded article of the present embodiment.

In step D, for example, the photocurable slurry is put into a light-transmitting mold corresponding to the desired shape, and in that state, the photocurable slurry is irradiated with light to solidify or solidify the photocurable slurry. By agglomeration, an inorganic molded article having an outer shape according to the molding die is obtained. Further, by making the molding die have a complicated shape, the outer shape of the inorganic molded article can be made complicated.

Further, in step D, for example, the photocurable slurry is discharged from a nozzle or the like so that the photocurable slurry has a desired shape, and the photocurable slurry immediately after being discharged is irradiated with light to make the photocurable slurry By solidifying or aggregating the slurry, an inorganic molded article having a desired shape may be formed.

By degreasing and sintering the inorganic molded body thus obtained, a sintered body in which the complex shape of the inorganic molded body is maintained can be obtained.

According to the method for producing an inorganic molded article of the present embodiment, the amino group of the polyalkyleneimine forming the aggregate adhered to the surface of the inorganic particles is attached to the double bond forming the polyfunctional acrylate and its polymer. An inorganic molded article is obtained in which the inorganic particles are strongly crosslinked by Michael addition. Therefore, it is possible to mold a complicated-shaped member (molded body). Further, by sintering the inorganic molded body obtained by the method for manufacturing the inorganic molded body of the present embodiment, a sintered body in which the complicated shape of the inorganic molded body is maintained can be obtained.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to experimental examples, but the present invention is not limited to the following experimental examples.

[Experimental example 1]
A monofunctional acrylate (methyl methacrylate (MMA)) from which a polymerization inhibitor was removed was dissolved in α-terpineol to prepare a solution AA having a monofunctional acrylate content of 60% by mass. The content of benzyl dimethyl ketal in solution AA was 1.2% by weight (2% by weight relative to MMA).
In addition, polyfunctional acrylate (trade name: M400 (mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate), manufactured by Toagosei Co., Ltd.) and photopolymerization initiator benzyl dimethyl ketal are dissolved in α-terpineol, Solution BB was prepared with a functional acrylate content of 60% by weight. The content of benzyl dimethyl ketal in solution BB was 1.2% by mass (2% by mass relative to M400).

Solution AA and solution BB were placed in a sample bottle, and in that state, solution AA and solution BB were irradiated with ultraviolet light (wavelength: 365 nm) to evaluate the polymerization state of each acrylate. The results are shown in FIGS. 1 and 2. FIG. FIG. 1 is an optical photograph showing the appearance of solution AA after UV irradiation. FIG. 2 is an optical photograph showing the appearance of solution BB after UV irradiation.
As shown in FIG. 1, it was confirmed that even if the solution AA was irradiated with ultraviolet light for 3 minutes, the viscosity of the solution AA did not increase, that is, the monofunctional acrylate did not polymerize.
On the other hand, as shown in FIG. 2, it was confirmed that the polyfunctional acrylate was polymerized only by irradiating the solution BB with ultraviolet light for 5 seconds. In FIG. 2, it is the polyfunctional acrylate polymer that forms the turbid layer on the bottom side of the sample bottle. Further, when the solution BB was irradiated with ultraviolet rays, due to the high polymerizability of the polyfunctional acrylate, enough reaction heat was generated to volatilize α-terpineol with a boiling point of 219°C. Thus, it was found that by using a polyfunctional acrylate, radical photopolymerization accompanied by high-temperature heat of reaction is possible at normal temperature and in the air.

[Experimental example 2]
Polyethyleneimine (weight average molecular weight (Mw) = 1800) and oleic acid are added to α-terpineol, and the mixture is stirred and mixed at room temperature for 24 hours to associate polyethyleneimine and oleic acid, resulting in polyethyleneimine. and oleic acid aggregates were obtained. Here, the blending amount of oleic acid with respect to polyethyleneimine was set to 15 mol % to 40 mol % of oleic acid with respect to all ethyleneimine units of polyethyleneimine.
Next, aluminum oxide (Al ₂ O ₃ ) particles are dispersed in α-terpineol containing the above aggregate in the range of 0 mg/m ² to 3.0 mg/m ² to obtain aluminum oxide (Al ₂ O ₃ ) A dispersion of particles was prepared. The content of aluminum oxide (Al ₂ O ₃ ) particles in the resulting dispersion was 5% by mass. Here, the amount of aggregate added is a value based on the surface area of aluminum oxide (Al ₂ O ₃ ) particles.
Next, after stirring and mixing the dispersion for 24 hours, the dispersion was centrifuged (20000 G, 10 minutes) to obtain a supernatant.
Next, the conductivity of the resulting supernatant was measured to estimate the amount of association of polyethyleneimine and oleic acid adsorbed on the surface of aluminum oxide (Al ₂ O ₃ ) particles. Here, the adsorption amount of the aggregate is a value based on the surface area of the aluminum oxide (Al ₂ O ₃ ) particles.
The method for measuring the conductivity of the supernatant is as follows. 20.0 g of ethanol was added to 10.0 g of each supernatant containing an aggregate of polyethyleneimine and oleic acid, and subjected to ultrasonic bath treatment for 5 minutes. The electrical conductivity of these solutions was measured with a desk-top electrical conductivity meter (AC two-electrode method). The amount of polyethyleneimine-oleic acid association in the supernatant was determined by adding 20.0 g of ethanol to 10.0 g of a terpineol solution containing a known amount of polyethyleneimine-oleic acid association, followed by ultrasonic bath treatment for 5 minutes. was estimated from a calibration curve obtained by measuring the conductivity of the solution to which the
FIG. 3 shows the relationship between the added amount and the adsorption amount of the aggregate of polyethyleneimine and oleic acid.

From the results of FIG. 3, regardless of the degree of association of oleic acid in the associated product of polyethyleneimine and oleic acid, when the amount of the associated product added is small, almost all of the added associated product is aluminum oxide ( Al ₂ O ₃ ) particles, and it was confirmed that there is a tendency to reach saturation adsorption as the amount of aggregates added increases. The saturated adsorption amount is 1.1 mg/m ^{2 when the oleic acid association degree is 15 mol%, the saturated adsorption amount is 1.1 mg/m 2 when} the oleic acid association degree is 30 mol%, and the oleic acid association degree is In the case of 40 mol%, the saturated adsorption amount was 1.4 mg/m ² , and in both cases, it was found that the association of polyethyleneimine and oleic acid functions as a dispersant and has excellent adsorption capacity. . It was also confirmed that under saturated adsorption conditions, a dispersion containing aluminum oxide (Al ₂ O ₃ ) particles is dispersed and stabilized.

[Experimental example 3]
Polyethyleneimine (weight average molecular weight (Mw) = 1800) and oleic acid are added to α-terpineol, and the mixture is stirred and mixed at room temperature for 24 hours to associate polyethyleneimine and oleic acid, resulting in polyethyleneimine. and oleic acid aggregates were obtained. Here, the blending amount of oleic acid with respect to polyethyleneimine was set to 15 mol % to 40 mol % of oleic acid with respect to all ethyleneimine units of polyethyleneimine.
Next, aluminum oxide (Al ₂ O ₃ ) particles and benzyl dimethyl ketal as a photopolymerization initiator are dispersed in α-terpineol containing the above aggregate to obtain a dispersion of aluminum oxide (Al ₂ O ₃ ) particles. prepared.
Next, a polyfunctional acrylate (trade name: M400 (a mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate), manufactured by Toagosei Co., Ltd.) is added to the above dispersion liquid and planetarily mixed to form a photocurable slurry. got The content of aluminum oxide (Al ₂ O ₃ ) particles in the resulting photocurable slurry was 40% by volume.
In Experimental Example 2, the aluminum oxide (Al ₂ O ₃ ) particles were modified with an aggregate of polyethyleneimine and oleic acid having a saturated adsorption amount determined from adsorption characteristics. Also, aluminum oxide (Al ₂ O ₃ ) particles modified with aggregates were dispersed and stabilized in α-terpineol. Thus, the polyfunctional acrylate was added so that the polyfunctional acrylate was 3.0% by mass with respect to the mass of the aluminum oxide (Al ₂ O ₃ ) particles.

The content of aluminum oxide (Al ₂ O ₃ ) particles is 40% by volume, the degree of association of oleic acid in the aggregate is 15 mol%, and the content of polyfunctional acrylate is 3.0% relative to the aluminum oxide (Al ₂ O ₃ ) particles. A photocurable slurry of 0% by mass was placed in a sample bottle, and the appearance of the photocurable slurry was observed in that state.
The results are shown in FIGS. 4-6. FIG. 4 is an optical photograph showing the appearance of the photocurable slurry immediately after preparation of the photocurable slurry. FIG. 5 is an optical photograph showing the appearance of the photocurable slurry after standing for 12 hours without UV irradiation. FIG. 6 is an optical photograph showing the appearance of the photocurable slurry after it was irradiated with ultraviolet rays immediately after the preparation of the photocurable slurry.
As shown in FIGS. 5 and 6, the Michael addition reaction causes some aluminum oxide (Al ₂ O ₃ ) particles to be crosslinked, reducing the fluidity of the photocurable slurry and increasing the viscosity of the photocurable slurry. It is thought that Further, as shown in FIG. 6, it was observed that the photocurable slurry after being irradiated with ultraviolet rays immediately after preparation of the photocurable slurry had a significantly increased viscosity.

In order to elucidate the curing reaction of the photocurable slurry, the rheometer was used to evaluate the flow characteristics of the photocurable slurry before and after UV irradiation.
The method for evaluating the flow characteristics of the photocurable slurry using a rheometer is as follows. 6.3 mL of slurry having an association degree of oleic acid in the aggregate of 15 mol% to 40 mol% and a polyfunctional acrylate amount of 1.5 to 3.0% by mass with respect to aluminum oxide (Al ₂ O ₃ ) particles, While being stirred at 300 rpm, it was irradiated with ultraviolet rays of 365 nm for 20 seconds. After that, the slurry was subjected to planetary mixing at 2000 rpm for 30 seconds, and then irradiated with ultraviolet rays for 20 seconds while being stirred to harden the entire slurry. A few mL of the hardened slurry was subjected to planetary mixing at 2000 rpm for 30 seconds and a flow curve was obtained with a rheometer.
FIG. 7 shows the flow characteristics of photocurable slurries using associations of polyethyleneimine and oleic acid with different association degrees of oleic acid when irradiated with ultraviolet rays.
From the results of FIG. 7, it was found that when the association degree of oleic acid was 40 mol %, the increase in viscosity of the photocurable slurry after ultraviolet irradiation was slight. On the other hand, when the association degree of oleic acid is 15 mol %, the viscosity of the photocurable slurry before UV irradiation is low, and the viscosity of the photocurable slurry after UV irradiation is significantly increased. The lower the degree of association of oleic acid, the greater the number of amino groups in the aggregate, and thus the number of reactive amino groups on the surface of aluminum oxide (Al ₂ O ₃ ) particles also increases. Therefore, it is thought that the lower the degree of association of oleic acid, the higher the density of crosslinks formed on the surface and matrix of aluminum oxide (Al ₂ O ₃ ) particles after UV irradiation, and the significantly higher viscosity of the photocurable slurry. .

FIG. 8 shows the flow characteristics of photocurable slurries with different contents of polyfunctional acrylate under UV irradiation.
From the results of FIG. 8, it was found that when the content of the polyfunctional acrylate was 1.5% by mass, the increase in viscosity of the photocurable slurry after UV irradiation was slight. On the other hand, when the content of the polyfunctional acrylate was 3.0% by mass, it was found that the viscosity of the photocurable slurry before UV irradiation was low, and the viscosity of the photocurable slurry after UV irradiation was significantly increased. . The reason why the viscosity of the photocurable slurry before ultraviolet irradiation was low is that the content of aluminum oxide (Al ₂ O ₃ ) particles in the photocurable slurry decreased as the content of the polyfunctional acrylate increased. it is conceivable that. Moreover, the reason why the viscosity of the photocurable slurry significantly increases after the ultraviolet irradiation is thought to be that the number of crosslinks between the polymers in the matrix has increased due to the radical polymerization of the polyfunctional acrylate.

[Experimental example 4]
A photocurable slurry having a content of aluminum oxide (Al ₂ O ₃ ) particles of 42% by volume, a degree of association of oleic acid in the aggregate of 15 mol%, and a content of polyfunctional acrylate of 3.0% by mass was irradiated with ultraviolet rays. 3D lighting was performed while irradiating. A 10-mL syringe shielded from light with aluminum foil was filled with the photocurable slurry, and the slurry was discharged under irradiation with ultraviolet light of 365 nm to obtain a modeled object in a simple manner.
FIG. 9 shows a wet compact produced by 3D writing of a photocurable slurry.
As shown in FIG. 9, the photocurable slurry discharged from the nozzle was formed into an arbitrary shape at high speed, and the structure could be maintained. Even after drying the resulting wet molded body at 80° C., the molded body retained its molded shape without forming defects.

From the above results, the dispersion stabilization of the photocurable slurry containing aluminum oxide (Al ₂ O ₃ ) particles at a high concentration and the intervening aluminum oxide (Al ₂ O ₃ ) particles via a small amount of binder (polyfunctional acrylate) was able to realize the formation of cross-links. That is, according to the present invention, a photocurable slurry that can form a strong inorganic molded article can be obtained.

Claims (5)

Inorganic particles, an association of polyalkyleneimine and fatty acid, a polyfunctional acrylate, a photopolymerization initiator, and a non-aqueous solvent ,
A photocurable slurry , wherein the surfaces of the inorganic particles are modified with the aggregates . 2. The photocurable slurry according to claim 1, wherein the polyalkyleneimine has a weight average molecular weight of 300-30,000. 3. The photocurable slurry according to claim 1 or 2, wherein the associated body comprises 15 mol% to 40 mol% of the fatty acid associated with all alkyleneimine units of the polyalkyleneimine. 4. The photocurable slurry according to any one of claims 1 to 3, wherein the content of the inorganic particles is 10% by volume to 65% by volume. The photocurable slurry according to any one of claims 1 to 4, wherein the content of the polyfunctional acrylate is 1.5% by mass to 10.0% by mass with respect to the inorganic particles. .

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