JP7463971B2 - Resin composition and method for producing three-dimensional object using same - Google Patents

Description

The present invention relates to a resin composition and a method for producing a three-dimensional object using the same.

In recent years, various methods have been developed that enable relatively easy production of three-dimensional objects with complex shapes, and rapid prototyping and rapid manufacturing that utilize these methods are attracting attention.

Traditionally, these methods for manufacturing 3D objects have been widely used in the field of modeling, but in recent years, there has been a growing movement to apply these techniques to direct manufacturing. 3D objects that are directly manufactured must not only have high modeling precision, but also high strength.

Here, laser sintering is known as a method for manufacturing a three-dimensional object. In laser sintering, resin particles are spread evenly to form a thin layer. Then, laser light is irradiated onto the thin layer in a pattern that finely divides the three-dimensional object in the thickness direction. This selectively sinters or melts and bonds (hereinafter simply referred to as "melt and bond") the resin particles in the area irradiated with the laser light. Then, resin particles are further spread on the obtained layer of the object, and laser light is irradiated in the same manner. By repeating these steps, layers of the object are piled up to obtain a three-dimensional object of the desired shape (hereinafter, this method is also referred to as the "SLS method").

Fused deposition modeling is also known as another method for manufacturing three-dimensional objects. In this method, for example, a resin composition is melt-extruded into filaments, and a three-dimensional object is finely divided in the thickness direction to form a layer of the object on a stage. Further melt extrusion is then performed on the layer of the object. Then, by repeating the melt extrusion, a three-dimensional object of the desired shape is obtained (hereinafter, this method is also referred to as the "FDM method").

Another method for producing a three-dimensional object is to spread resin particles evenly to form a thin layer, and then apply a binding fluid containing an infrared light absorber or the like only to the areas of the thin layer that are to be hardened (a pattern in which the desired three-dimensional object is finely divided in the thickness direction). Infrared light is then irradiated to heat and melt only the powder material in the areas where the binding fluid has been applied, thereby obtaining the desired three-dimensional object (hereinafter, this method is also referred to as the "MJF method").

Here, a composition containing resin and reinforcing fibers has been proposed as a resin composition for use in the above-mentioned SLS method (Patent Document 1).

JP 2007-535585 A

Three-dimensional objects are required to have high elasticity and, furthermore, high breaking elongation. However, when fillers are added to increase elasticity, the three-dimensional object tends to become brittle and the breaking elongation tends to become low. In particular, when fibrous fillers are added, as in Patent Document 1, the three-dimensional object tends to become brittle.

The present invention has been made in consideration of the above problems. The present invention aims to provide a resin composition capable of producing a three-dimensional object having high elasticity and high breaking elongation, and to provide a method for producing a three-dimensional object using the same.

The present invention provides the following resin composition.
[1] A resin composition for use in a three-dimensional modeling method, which involves forming a thin layer containing a particulate resin composition and repeatedly irradiating the thin layer with selective energy, or laminating a filament of molten resin composition, the resin composition comprising a thermoplastic resin and a water-soluble metal salt and/or metal complex, the metal salt and/or the metal complex being non-spherical, having an average minor axis of 0.1 to 10 μm, and a ratio of the average major axis to the average minor axis of 10 to 100.

[2] The resin composition according to [1], wherein the metal salt and/or the metal complex has water of hydration in the molecule.
[3] The resin composition according to [1] or [2], which is in particulate form.
[4] The resin composition according to [1] or [2], which is in a filament form.

The present invention also provides the following method for producing a three-dimensional object.
[5] A method for manufacturing a three-dimensional object, comprising: a thin layer formation step of forming a thin layer containing the particulate resin composition described in [3] above; and a laser light irradiation step of selectively irradiating the thin layer with laser light to form a modeled object layer in which a plurality of the resin compositions are melt-bonded, wherein the thin layer formation step and the laser light irradiation step are repeated a plurality of times to stack the modeled object layers to form a three-dimensional object.

[6] A method for producing a three-dimensional object, comprising: a melting step of melting the resin composition described in [4] above; and a thin layer forming step of extruding the molten resin composition into a filament shape to form a thin layer made of the resin composition, the melting step and the thin layer forming step being repeated multiple times to laminate the thin layers to form a three-dimensional object.

The resin composition of the present invention makes it possible to produce three-dimensional objects with high elasticity and high breaking elongation.

1. Resin Composition The resin composition of the present invention is used in a method for producing a three-dimensional object by repeatedly forming a thin layer containing a particulate resin composition and selectively irradiating the thin layer with energy (e.g., SLS method or MJF method), or a method for producing a three-dimensional object by laminating a molten filament-like resin composition (FDM method), etc. The shape of the resin composition is not particularly limited, but it can usually be particulate or filament-like.

As mentioned above, three-dimensional objects are required to have a high elastic modulus and high breaking elongation. However, it is difficult to achieve a high elastic modulus when making a three-dimensional object from thermoplastic resin alone. On the other hand, when a typical filler is added to a thermoplastic resin, the elastic modulus of the resulting three-dimensional object increases, but it tends to become brittle and the breaking elongation tends to be low. In other words, there is a trade-off between the elastic modulus and the breaking elongation, and it is difficult to achieve both.

In contrast, the resin composition of the present invention contains a thermoplastic resin and a metal salt and/or metal complex that has a specific shape and is soluble in water. When the resin composition contains such a metal salt and/or metal complex, the breaking elongation is less likely to decrease.

The reason is unclear, but it is thought to be as follows. In general, when a three-dimensional object containing a filler is subjected to, for example, tensile stress, the stress tends to concentrate on the thermoplastic resin around the filler, and the thermoplastic resin generates heat at that location. The thermoplastic resin then melts or softens locally, causing cracks or breakage around the filler. In contrast, the metal salt and/or metal complex contained in the resin composition of the present invention attracts moisture in the air to its surroundings or has hydration water inside. Therefore, even if a three-dimensional object is subjected to tensile stress, the moisture inside or near the metal salt and/or metal complex suppresses the heat generation of the thermoplastic resin. As a result, it is thought that the melting or softening of the thermoplastic resin does not progress, making it difficult for breakage to occur.

In addition, when the resin composition contains a metal salt and/or a metal complex, the elastic modulus of the resulting three-dimensional object is also increased. Therefore, the resin composition of the present invention can produce a three-dimensional object having a high elastic modulus and also a high breaking elongation.

Below, we will explain in detail each component contained in the resin composition of the present invention and its physical properties.

(Thermoplastic resin)
The thermoplastic resin is appropriately selected depending on the application of the three-dimensional object to be produced. The thermoplastic resin may be a resin contained in a resin composition for a general SLS method or MJF method, or a resin contained in a resin composition for an FDM method. The resin composition may contain only one type of thermoplastic resin, or may contain two or more types of thermoplastic resin.

However, if the melting temperature of the thermoplastic resin is too high, the amount of energy required to melt the resin composition (thermoplastic resin) during the production of the three-dimensional object increases. As a result, it takes time to melt the resin composition, and the efficiency of producing the three-dimensional object decreases. Therefore, the melting temperature of the thermoplastic resin is preferably 300°C or lower, and more preferably 230°C or lower. On the other hand, from the viewpoint of the heat resistance of the resulting three-dimensional object, the melting temperature of the thermoplastic resin is preferably 100°C or higher, and more preferably 150°C or higher. The melting temperature can be adjusted depending on the type of thermoplastic resin, etc.

Examples of thermoplastic resins include crystalline resins such as polyethylene, polypropylene, polyamide (such as nylon 6 and nylon 12), polyacetal, polyethylene terephthalate (PET), polyphenylsulfide (PPS), polyetheretherketone (PEEK), and crystalline polyester; and non-crystalline resins such as polystyrene, polyurethane, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer (ABS), acrylic polymer, polycarbonate, ethylene-vinyl acetate copolymer (EVA), styrene-acrylonitrile copolymer (SAN), polyarylate, polyphenylene ether, and polycaprolactone. As the thermoplastic resin, polypropylene, polyethylene, and polyamide are preferred, and polypropylene and nylon 12 are particularly preferred.

The thermoplastic resin is preferably contained in the resin composition at 40 to 95% by mass, and more preferably at 60 to 92% by mass. When the resin composition contains 40% or more by mass of the thermoplastic resin, the strength of the resulting three-dimensional object is likely to be increased and the breaking elongation is unlikely to decrease. On the other hand, by making the amount of thermoplastic resin in the resin composition 95% by mass or less, the amount of metal salt and/or metal complex can be relatively sufficient, and the strength of the three-dimensional object, such as the elastic modulus of the resulting three-dimensional object, can be increased.

(Metal Salts and/or Metal Complexes)
As described above, the metal salt and/or metal complex is composed of a solid component that is soluble in water. The resin composition may contain only one of the metal salt and the metal complex, or may contain both. In addition, the resin composition may contain multiple types of metal salts and metal complexes.

In this specification, whether or not a metal salt and/or metal complex is soluble in water is determined by the following method. A cubic three-dimensional object is produced using a resin composition containing 90 g of thermoplastic resin and 10 g of metal salt and/or metal complex. The three-dimensional object is immersed in 1000 ml of pure water. In this state, the object is left for a day while being vibrated by an ultrasonic homogenizer (for example, trade name: US-1200, manufactured by Nippon Kikai Co., Ltd.). The amount of metal ions in the water is then detected. If the amount of metal ions detected is 0.001 mg/l or more, the metal salt and/or metal complex is determined to be soluble in water. However, the amount of metal ions detected is preferably 0.001 mg/l to 10 mg/l, and more preferably 0.01 mg/l to 8 mg/l.

The shape of the metal salt and/or metal complex is not particularly limited as long as the average minor axis is 0.1 to 10 μm and the ratio of the average major axis to the average minor axis (hereinafter, this ratio is also referred to as the "aspect ratio") is 10 to 100. For example, it may be ellipsoidal, needle-like, fibrous, flat, etc. In this specification, the major axis of the metal salt and/or metal complex refers to the length of the line connecting the most distant positions when the shape of the metal salt and/or metal complex is analyzed. On the other hand, the minor axis of the metal salt and/or metal complex refers to the shortest length of the lines connecting the surfaces of the metal salt and/or metal complex so as to be perpendicular to the major axis. When the average minor axis and aspect ratio are within the above ranges, the surface area of the metal salt and/or metal complex is large, and the effect of adding the metal salt and/or metal complex is easily obtained.

The average short diameter and the average long diameter are values calculated by measuring the short diameter and long diameter of 500 or more metal salts and/or metal complexes using a scanning electron microscope (SEM) and averaging these values.

Here, the average minor axis is more preferably 0.3 to 5 μm. The aspect ratio is preferably 2 to 100, more preferably 5 to 60.

In addition, it is preferable that the metal salt and/or metal complex contains water of hydration in the molecule. Specific examples of metal salts and metal complexes include basic magnesium sulfate, magnesium hydroxide, calcium sulfate, etc. Among these, basic magnesium sulfate or magnesium hydroxide is preferable from the viewpoint of ease of handling and availability.

The metal salt and/or metal complex is preferably contained in the resin composition in an amount of 5 to 60% by mass, more preferably 8 to 40% by mass. When the resin composition contains 5% by mass or more of the metal salt and/or metal complex, the elastic modulus of the resulting three-dimensional object is likely to increase, and the strength of the three-dimensional object is likely to increase. On the other hand, if the amount of the metal salt and/or metal complex in the resulting three-dimensional object is excessive, the amount of resin decreases, and the interface between the resin and the metal salt increases. Therefore, the breaking elongation is likely to decrease. Furthermore, the three-dimensional object may be affected by moisture in the air, and its strength may decrease. On the other hand, if the amount of the metal salt and/or metal complex is 60 parts by mass or less, such a decrease in breaking elongation or strength is unlikely to occur.

(Other materials)
The resin composition may contain components other than the above-mentioned thermoplastic resin and metal salt and/or metal complex, as long as the object of the present invention is not impaired. Examples of other materials include various additives, laser absorbers, etc.

Examples of various additives include antioxidants, acidic compounds and their derivatives, lubricants (e.g., magnesium stearate, etc.), ultraviolet absorbers, light stabilizers, nucleating agents, flame retardants, impact modifiers, foaming agents, colorants, organic peroxides, spreading agents, adhesives, etc. The resin composition may contain only one of these, or two or more of them. In addition, these may be applied to the surface of the resin composition as long as the purpose of the present invention is not impaired.

Examples of laser absorbents include carbon powder, nylon resin powder, pigments, dyes, etc. The resin composition may contain only one type of these laser absorbents, or two or more types of them.

(Physical Properties)
The resin composition preferably has a melting temperature of 100 to 300° C., and more preferably has a melting temperature of 150 to 230° C. When the melting temperature is within this range, it becomes possible to produce a three-dimensional object without excessive heating in the method for forming a three-dimensional object described below. The melting temperature of the resin composition can be adjusted depending on the type of thermoplastic resin, the method for producing a three-dimensional object, and the like.

On the other hand, the shape of the resin composition is appropriately selected according to the use of the resin composition, that is, the three-dimensional modeling method to be applied. For example, when the resin composition is used in the SLS method or the MJF method, the resin composition is made particulate. At this time, the shape of the particles can be a sphere, a polygonal cylinder, a cylinder, an elliptical cylinder, or an indefinite shape in which the shapes are broken down, but from the viewpoint of improving the dimensional accuracy of the three-dimensional object, it is preferable that the shape is spherical. The average particle diameter of the particulate resin composition is preferably 10 μm or more and 200 μm or less, more preferably 20 μm or more and 150 μm or less, and even more preferably 30 μm or more and 100 μm or less. When the average particle diameter of the resin composition is 10 μm or more, the resin composition is likely to have sufficient fluidity and the resin composition is easy to handle. In addition, when the average particle diameter is 10 μm or more, the particulate resin composition is easy to prepare, and the manufacturing cost of the resin composition is not high. The above average particle diameter is the volume average particle diameter measured by dynamic light scattering. The volume average particle size can be measured by a laser diffraction particle size distribution measuring device (MT3300EXII, manufactured by Microtrackbell Co., Ltd.) equipped with a wet disperser.

Furthermore, when the resin composition is used in the FDM method, the resin composition may be in the form of a filament. The average diameter of the filament-shaped resin composition is appropriately selected according to the type of three-dimensional modeling device, but is usually preferably 1.0 to 5.0 mm, and more preferably 1.3 to 3.5 mm. The filament-shaped resin composition may have fine irregularities formed on its surface as necessary so that it can be adequately held within the three-dimensional modeling device. Furthermore, the filament-shaped resin composition may be wound around a bobbin or the like.

(Production method)
The method for producing the resin composition is not particularly limited and can be appropriately selected depending on the shape of the resin composition.

For example, a particulate resin composition can be prepared by melt-kneading the above-mentioned thermoplastic resin, metal salt and/or metal complex, and, if necessary, other components, using a known device, and then mechanically pulverizing the mixture.

When the molten kneaded material is mechanically pulverized, it may be pulverized at room temperature or may be frozen and then pulverized. Mechanical pulverization can be performed using known devices such as a hammer mill, a jet mill, a ball mill, an impeller mill, a cutter mill, a pin mill, and a two-shaft crusher. When mechanical pulverization is performed, the thermoplastic resins may be fused together due to frictional heat generated by the thermoplastic resin during pulverization. Therefore, the thermoplastic resin may be cooled using liquid nitrogen or the like to be embrittled and then crushed. Mechanical pulverization makes it easy to adjust the average particle size of the resulting particulate resin composition to the desired range, but further classification, etc. may be performed as necessary.

On the other hand, when the resin composition is made into a filament, it can be produced by melt-kneading the above-mentioned thermoplastic resin, metal salt and/or metal complex, and other components as necessary, and extruding the mixture from a general extrusion molding machine. The temperature during extrusion molding is appropriately selected depending on the melting temperature of the resin composition.

2. Manufacturing method of a three-dimensional object The above-mentioned resin composition can be used in a manufacturing method of a three-dimensional object by, for example, the SLS method, the MJF method, or the FDM method. Hereinafter, a manufacturing method of a three-dimensional object will be described using the SLS method and the FDM method as examples of manufacturing a three-dimensional object, but the use of the resin composition is not limited thereto, and it may be applied to a manufacturing method of a three-dimensional object other than the SLS method and the FDM method.

2-1. Manufacturing method of a three-dimensional object by the SLS method The manufacturing method of a three-dimensional object by the SLS method can include (1) a thin layer forming step of forming a thin layer containing the above-mentioned particulate resin composition, and (2) a laser light irradiation step of selectively irradiating the thin layer containing the resin composition with a laser light to form a modeled object layer in which the particulate resin composition is melt-bonded to each other. Then, the steps (1) and (2) are repeated multiple times to laminate the modeled object layers, thereby manufacturing a three-dimensional object. Note that the manufacturing method of the three-dimensional object may include other steps as necessary, such as a step of preheating the resin composition.

Thin layer formation process (process (1))
In this process, a thin layer containing a particulate resin composition is formed. For example, the resin composition supplied from a powder supply unit of a three-dimensional modeling device is spread evenly on a modeling stage by a recoater. The thin layer may be formed directly on the modeling stage, or may be formed on a powder material that has already been spread or on a modeled object layer that has already been formed. The resin composition may be mixed with a flow agent or a laser absorbent, as described below, as necessary.

The thickness of the thin layer is the same as the thickness of the desired model layer. The thickness of the thin layer can be set arbitrarily depending on the accuracy of the three-dimensional model to be manufactured, but is usually 0.01 mm or more and 0.30 mm or less. By setting the thickness of the thin layer to 0.01 mm or more, it is possible to prevent the resin composition of the lower layer from being melted and bonded by the laser light irradiation for forming the next model layer, and furthermore, it is possible to spread the powder uniformly. In addition, by setting the thickness of the thin layer to 0.30 mm or less, the energy of the laser light can be transmitted to the lower part of the thin layer, and the resin composition constituting the thin layer can be sufficiently melted and bonded throughout the entire thickness direction. From the above viewpoint, it is more preferable that the thickness of the thin layer is 0.01 mm or more and 0.10 mm or less. In addition, from the viewpoint of melting and bonding the resin composition more sufficiently throughout the entire thickness direction of the thin layer and making it less likely to cause cracks in the model layer, it is preferable to set the thickness of the thin layer so that the difference from the beam spot diameter of the laser light described later is within 0.10 mm.

Here, examples of laser absorbents that can be mixed with the resin composition include carbon powder, nylon resin powder, pigments, dyes, etc. The amount of laser absorbent can be appropriately set within a range that facilitates melt bonding of the resin composition. For example, it can be more than 0% by mass and less than 3% by mass with respect to the total mass of the resin composition. Only one type of laser absorbent may be used, or two or more types may be used in combination.

On the other hand, the flow agent that can be mixed with the resin composition may be any material that has a small coefficient of friction and self-lubricating properties. Examples of such flow agents include silicon dioxide and boron nitride. These flow agents may be used alone or in combination of two or more. The amount of the flow agent may be appropriately set within a range that improves the fluidity of the resin composition and sufficiently melts and bonds the resin composition, and may be, for example, more than 0% by mass and less than 2% by mass relative to the total mass of the resin composition.

Laser light irradiation step (step (2))
In this process, a laser beam is selectively applied to a thin layer containing the resin composition at a position where a modeling layer is to be formed, and the resin composition at the irradiated position is melted and bonded. The melted resin composition melts with the adjacent resin composition to form a melt-bonded body, which becomes the modeling layer. At this time, the resin composition that has received the energy of the laser beam is also melted and bonded with the already formed modeling layer, so that adhesion also occurs between adjacent layers.

The wavelength of the laser light may be set within the range of wavelengths absorbed by the resin composition. At this time, it is preferable to make the difference between the wavelength of the laser light and the wavelength at which the resin composition has the highest absorption rate small, but since resins generally absorb light in various wavelength ranges, it is preferable to use a laser light with a wide wavelength range, such as a _CO2 laser. For example, the wavelength of the laser light can be, for example, 0.8 μm or more and 12 μm or less.

The power of the laser light when it is output may be set within a range in which the resin composition is sufficiently melted and bonded at the scanning speed of the laser light described below. Specifically, it may be set to 5.0 W or more and 60 W or less. From the viewpoint of reducing the energy of the laser light, reducing manufacturing costs, and simplifying the configuration of the manufacturing apparatus, it is preferable that the power of the laser light when it is output is 30 W or less, and more preferably 20 W or less.

The scanning speed of the laser light may be set within a range that does not increase the manufacturing cost and does not make the device configuration excessively complicated. Specifically, the scanning speed is preferably 1 m/sec to 10 m/sec, more preferably 2 m/sec to 8 m/sec, and even more preferably 3 m/sec to 7 m/sec.
The beam diameter of the laser light can be appropriately set depending on the precision of the three-dimensional object to be manufactured.

Regarding repetition of steps (1) and (2): When manufacturing a three-dimensional object, the above-described steps (1) and (2) are repeated any number of times. This causes layers of the object to be stacked, thereby obtaining a desired three-dimensional object.

As described above, in the method for producing a three-dimensional object by the SLS method, a step of preheating the resin composition may be performed. The preheating of the resin composition may be performed after the thin layer formation (step (1)) or before the thin layer formation. Alternatively, the preheating may be performed both after and before the thin layer formation.

The preheating temperature is set to a temperature lower than the melting temperature of the resin composition so that the resin compositions do not melt and bond to each other. The preheating temperature is appropriately selected according to the melting temperature of the resin composition, and can be, for example, 50°C or higher and 300°C or lower, more preferably 100°C or higher and 230°C or lower, and even more preferably 150°C or higher and 190°C or lower.

In this case, the heating time is preferably 1 to 30 seconds, and more preferably 5 to 20 seconds. By preheating at the above temperature for the above period of time, the time it takes for the resin composition to melt when irradiated with laser energy can be shortened, making it possible to produce a three-dimensional object with a small amount of laser energy.

Others In order to prevent the strength of the three-dimensional object from decreasing due to oxidation of the resin composition during melt bonding, it is preferable to carry out at least step (2) under reduced pressure or in an inert gas atmosphere. The pressure at the time of decompression is preferably 10 ⁻² Pa or less, and more preferably 10 ⁻³ Pa or less. Examples of inert gases that can be used at this time include nitrogen gas and rare gases. Among these inert gases, nitrogen (N ₂ ) gas, helium (He) gas, or argon (Ar) gas are preferable in terms of ease of availability. In terms of simplifying the manufacturing process, it is preferable to carry out both steps (1) and (2) under reduced pressure or in an inert gas atmosphere.

2-2. Manufacturing method of a three-dimensional object by FDM method The manufacturing method of a three-dimensional object by FDM method can be a method including (1) a melting step of melting the above-mentioned resin composition, and (2) a thin layer forming step of extruding the molten resin composition into a filament shape to form a thin layer made of the resin composition. Then, the steps (1) and (2) are repeated multiple times to laminate the thin layers, thereby manufacturing a three-dimensional object. Note that the manufacturing method of the three-dimensional object may include other steps as necessary.

Melting step (step (1))
In this process, at least a part of the resin composition is melted. For example, the resin composition is melted by a heat melter of a three-dimensional modeling apparatus equipped with an extrusion head and a heat melter. As long as the resin composition can be extruded in a filament shape from the extrusion head in the thin layer formation process described later, the shape of the resin composition used is not particularly limited, and may be, for example, granular or pellet-shaped. However, it is preferable to use a filament-shaped resin composition from the viewpoint of stably feeding the resin composition to the heat melter.

When supplying a filament-like resin composition to a heating and melting device, it is common to engage the filaments with a driving roll such as a nip roll or gear roll and supply the resin composition while drawing it up.

Heating using a heating melter or the like is preferably performed so that the temperature of the resin composition is equal to or higher than the melting temperature, and more preferably is performed so that the temperature is 10°C or higher than the melting temperature. Specifically, heating to 100 to 300°C is preferable, and heating to 150 to 230°C is more preferable. By setting the temperature of the resin composition to 300°C or lower, it is possible to prevent thermal decomposition of the thermoplastic resin. It also becomes possible to melt the resin composition efficiently. On the other hand, by setting the temperature of the resin composition to 100°C or higher, the resin composition can be sufficiently melted, and the dimensional accuracy of the resulting three-dimensional object is improved.

Thin layer formation process (process (2))
In this process, the molten resin composition is extruded in the form of a filament to form a thin layer of the resin composition. For example, the resin composition molten in the melting process described above is extruded in the form of a filament from a nozzle of an extrusion head of a three-dimensional modeling device onto a modeling stage to form a thin layer in a desired shape.

The diameter of the filament-like resin composition extruded from the extrusion head is preferably 0.01 to 1 mm, and more preferably 0.02 to 0.8 mm. The diameter of the resin composition corresponds to the thickness of the thin layer. Therefore, by setting the thickness of the resin composition within this range, the reproducibility of the resulting three-dimensional object tends to be good.

In addition, the extrusion speed of the resin composition is preferably 20 mm/sec or more, more preferably 30 mm/sec or more, and even more preferably 50 mm/sec or more. On the other hand, the extrusion speed is usually 200 mm/sec or less.

Specific examples of the present invention are described below. Note that the scope of the present invention is not to be construed as being limited by these examples.

[Example 1]
A resin composition was obtained by kneading 100 parts by mass of polypropylene with 10 parts by mass of basic magnesium sulfate (average major axis: 15 μm, average minor axis: 0.5 μm) and 0.3 parts by mass of magnesium stearate. Half of the resin composition was processed into filaments with a diameter of 1.8 mm by extrusion molding. The remaining half was mechanically pulverized into spherical particles with an average particle diameter of 60 μm.

[Example 2]
A resin composition was obtained by kneading 100 parts by mass of polypropylene with 10 parts by mass of magnesium hydroxide (average major axis: 20 μm, average minor axis: 1 μm) and 0.3 parts by mass of magnesium stearate. The resin composition was processed into filament-like and spherical particles in the same manner as in Example 1.

[Example 3]
A resin composition was obtained by kneading 100 parts by mass of nylon 12 with 10 parts by mass of basic magnesium sulfate (average major axis: 15 μm, average minor axis: 0.5 μm) and 0.3 parts by mass of magnesium stearate. The resin composition was processed into filament-like and spherical particles in the same manner as in Example 1.

[Comparative Example 1]
Only polypropylene was used and processed into filament-like and spherical particles in the same manner as in Example 1.

[Comparative Example 2]
Only nylon 12 was used and processed into filamentary and spherical particles in the same manner as in Example 1.

[Comparative Example 3]
Filamentous and spherical particles were produced in the same manner as in Example 1, except that basic magnesium sulfate (average major axis: 0.5 μm, average minor axis: 0.5 μm) was used.

[Comparative Example 4]
Filamentous and spherical particles were produced in the same manner as in Example 1, except that magnesium hydroxide (average major axis: 1 μm, average minor axis: 1 μm) was used.

[Comparative Example 5]
A resin composition was obtained by kneading 100 parts by mass of polypropylene with 10 parts by mass of carbon fiber (average major axis: 15 μm, average minor axis: 0.5 μm) and 0.3 parts by mass of magnesium stearate. The resin composition was processed into filament-like and spherical particles in the same manner as in Example 1.

[Comparative Example 6]
A resin composition was obtained by kneading 100 parts by mass of polypropylene with 10 parts by mass of talc (average particle size: 10 μm) and 0.3 parts by mass of magnesium stearate. The resin composition was processed into filament-like and spherical particles in the same manner as in Example 1.

[Comparative Example 7]
A resin composition was obtained by kneading 100 parts by mass of polypropylene with 10 parts by mass of alum (average particle size: 5 μm) and 0.3 parts by mass of magnesium stearate. The resin composition was processed into filament-like and spherical particles in the same manner as in Example 1.

[Comparative Example 8]
A resin composition was obtained by kneading 100 parts by mass of nylon 12 with 10 parts by mass of carbon fiber (average fiber major axis: 15 μm, average fiber minor axis: 0.5 μm) and 0.3 parts by mass of magnesium stearate. The resin composition was processed into filament-like and spherical particles in the same manner as in Example 1.

[evaluation]
Three-dimensional objects were produced by the FDM method and the SLS method described below. The metal salts or metal complexes contained in the obtained three-dimensional objects were confirmed to be soluble in water. Furthermore, the breaking elongation and elastic modulus of the obtained three-dimensional objects were evaluated as follows. The results are shown in Table 1.
- Manufacturing of a three-dimensional object by FDM method The filament-shaped resin compositions prepared in the examples and comparative examples were set in a three-dimensional modeling device (M200, manufactured by Zortrax). The resin composition containing polypropylene was melted at 180°C, and the resin composition containing nylon 12 was melted at 200°C, and extruded from a nozzle in the form of filaments. This was repeatedly laminated to obtain a three-dimensional object.

- Manufacturing of a three-dimensional object by the SLS method Using a three-dimensional modeling device sPro140 (manufactured by 3D Systems), the particulate resin composition prepared in the above-mentioned Examples and Comparative Examples was spread on the modeling stage at a predetermined recoating speed (100 mm/s) to form a thin layer with a thickness of 0.1 mm. This thin layer was irradiated with laser light from a _CO2 laser equipped with a YAG wavelength galvanometer scanner in a range of 15 mm long x 20 mm wide under the following conditions to produce a modeled layer. Thereafter, a powder material was further spread on the modeled layer, and the modeled layer was laminated by irradiating it with laser light. These steps were repeated to produce a three-dimensional object (a laminate of modeled layers).

[Laser light emission conditions]
Laser output: 12W
Laser light wavelength: 10.6 μm
Beam diameter: 170 μm at the thin layer surface
[Laser light scanning conditions]
Scanning speed: 2000 mm/sec
Number of lines: 1 line

Confirmation of solubility of metal salt or metal complex in water 100 g of a cubic three-dimensional object (90 g of resin, 10 g of metal complex) obtained by the above-mentioned method was immersed in 1000 ml of pure water and left for one day while being vibrated by an ultrasonic homogenizer (product name: US-1200, manufactured by Nippon Kikai Co., Ltd.). Thereafter, the solubility of the metal salt or metal complex in water was confirmed. Specifically, the amount of metal ions in the water was detected using an inductively coupled plasma optical emission spectrometry spectrometer (product name: SPS3520UV, manufactured by SII Nano Technology Co., Ltd.) and evaluated as follows. Note that none of the objects had an amount of metal ions exceeding 10 mg/l.
○: Metal ion amount is 0.001 mg/l to 10 mg/l (soluble in water)
×: Metal ion amount is less than 0.001 mg/l (not necessary for water)

Evaluation of Breaking Elongation Breaking elongation was measured using a Tensilon universal material testing machine RTC-1250 (A&D Co., Ltd.). The measurement conditions were set as follows. The breaking distance was taken as the breaking elongation.
Tensile test specimen: Shape conforming to JIS K7161 Tensile speed: 50 mm/s
Chuck distance: 115 mm
Gauge length: 100 mm

Evaluation of Elastic Modulus Elastic modulus was measured using a Tensilon universal material testing machine RTC-1250 (A&D Co., Ltd.). The measurement conditions were set as follows. The elastic modulus was determined by linear regression between strains of 0.05 and 0.25%.
Tensile test specimen: Shape conforming to JIS K7161 Tensile speed: 1 mm/s
Chuck distance: 115 mm
Gauge length: 100 mm

As shown in Table 1 above, the resin compositions of Examples 1 to 3, which contain a thermoplastic resin and a metal salt and/or metal complex that is soluble in water and has an average minor axis and aspect ratio within a specified range, had a high elastic modulus and also a high elongation at break. It is presumed that the addition of the metal salt and/or metal complex suppressed local melting and softening of the thermoplastic resin. Similar results were obtained with both the FDM method and the SLS method.

In contrast, when no filler was included, the breaking elongation was excellent but the elastic modulus was low (Comparative Examples 1 and 2). On the other hand, even when a filler was included, when the filler was carbon fiber or talc that was not soluble in water, the breaking elongation of the resulting three-dimensional object was low (Comparative Examples 5, 6, and 8). In addition, when a compound that was soluble in water but had a small aspect ratio was used, the breaking elongation was also small (Comparative Examples 3, 4, and 7).

This application claims priority from Japanese Patent Application No. 2019-021606, filed February 8, 2019. The entire contents of said application are incorporated herein by reference.

The resin composition according to the present invention makes it possible to form a three-dimensional object with high precision by either the FDM method or the SLS method. Therefore, the present invention is expected to contribute to the further spread of three-dimensional modeling methods.

Claims (6)

A resin composition for use in a three-dimensional modeling method, which comprises repeatedly forming a thin layer containing a particulate resin composition and selectively irradiating the thin layer with energy, or laminating a molten filament-like resin composition,
A thermoplastic resin and a water-soluble metal salt and/or metal complex,
the metal salt and/or the metal complex are non-spherical, have an average minor axis of 0.1 to 10 μm, and have a ratio of the average major axis to the average minor axis of 10 to 100;
The metal salt and/or the metal complex is contained in the resin composition in an amount of 5 to 60 mass %.
Resin composition. The metal salt and/or the metal complex has water of hydration in the molecule.
The resin composition according to claim 1. It is particulate,
The resin composition according to claim 1 or 2. Filamentous,
The resin composition according to claim 1 or 2. A thin layer forming step of forming a thin layer containing the resin composition according to claim 3;
a laser light irradiation step of selectively irradiating the thin layer with a laser light to form a modeled object layer in which a plurality of the resin compositions are melt-bonded;
Including,
the thin layer forming step and the laser light irradiating step are repeated a number of times to stack the object layers, thereby forming a three-dimensional object.
A method for manufacturing a three-dimensional object. A melting step of melting the resin composition according to claim 4;
a thin layer forming step of extruding the molten resin composition into a filament shape to form a thin layer made of the resin composition;
Including,
The melting step and the thin layer forming step are repeated a number of times to laminate the thin layers to form a three-dimensional object.
A method for manufacturing a three-dimensional object.