JP7650479B2 - Linear resin molding - Google Patents

Description

The present invention relates to a linear resin molding, and in particular to a linear resin molding used as a raw material in modeling devices that construct three-dimensional objects, such as so-called 3D printers.

So-called 3D printers have been attracting attention as a method for forming three-dimensional objects, and it is now possible to easily create three-dimensional objects with complex shapes that were previously difficult to realize. By using a 3D printer, it is possible to process shapes that would be impossible to realize using normal methods by stacking any material, such as resin or metal.

There are several known types of 3D printers, among which the type that extrudes and stacks resin strands (linear resin moldings) (fused deposition modeling) is advantageous in terms of cost and is being developed in various fields (see, for example, Patent Document 1 and Patent Document 2).

For example, in the additive manufacturing system of Patent Document 1, a filament, which is the modeling material, is supplied to an extrusion head, the filament is melted by a liquefier mounted on the extrusion head, and the molten filament is extruded onto a base through a nozzle. The extrusion head and base move relative to each other to form a 3D model, and multiple linear and layered pieces of material are stacked to produce the 3D model.

Patent document 2 discloses a method of constructing a 3D object that includes delivering a modified ABS material to an extrusion head of an extrusion layer-by-layer deposition system, melting the delivered modified ABS material in the extrusion head under conditions that improve the response time of the extrusion head, and depositing the molten thermoplastic material layer-by-layer to form the 3D object.

The basic idea of this type of method is to melt and deposit a resin material, and resin strands (linear resin moldings) are used as the raw material. Patent Documents 3 and 4 disclose the resin strands used as the raw material and the method of supplying them.

US Patent No. 5,399,633 discloses a composition for creating three-dimensional objects, which is fed as flexible filaments to an extrusion head in an extrusion machine that produces the model. The filaments are melted in a liquefier carried by the extrusion head. The liquefier heats the filaments to a temperature slightly above their freezing point, causing them to become molten. The molten material is extruded through an orifice in the liquefier onto a base.

Patent document 4 discloses a filament cassette and a filament cassette receiver for supplying filaments within a three-dimensional deposition modeling machine. Patent document 4 provides a method for engaging and disengaging a filament from the modeling machine in a simple manner, which can be achieved in a manner that protects the filament from moisture in the environment.

Special Publication No. 2009-500194 Special Publication No. 2010-521339 Patent No. 5039549 Patent No. 4107960

In the 3D printer described above, a shape memory polymer can also be used as the resin material for modeling. A shape memory polymer is a resin that can be used to change between a molded shape and a deformed shape by controlling the temperature with heat. A molded body of a shape memory polymer is deformed at a temperature equal to or higher than the glass transition temperature (Tg) of the shape memory polymer and lower than its melting temperature or decomposition temperature, and the deformed shape is fixed by cooling the molded body to a temperature equal to or higher than the glass transition temperature and lower than its melting temperature or decomposition temperature while maintaining the shape. The original molded shape can be restored by heating the molded body to a temperature equal to or higher than the glass transition temperature and lower than its melting temperature or decomposition temperature.

However, it has been found that when such shape-memory polymers are used as filaments in 3D printers, their performance deteriorates due to moisture absorption. Due to their shape change and memory properties, shape-memory polymers are expected to be used, for example, as various supports and orthodontic appliances. However, it has been found that when used in a humid environment (such as orthodontic supports in the mouth), their performance deteriorates if they absorb moisture above a certain level, and improving this is an issue.

For example, Patent Document 4 attempts to protect the filament from moisture in the environment, but does not take into consideration moisture absorption by the molded object.

The present invention was proposed in consideration of the above-mentioned conventional situation, and aims to provide a linear resin molding that can prevent moisture absorption in objects 3D-modeled from shape memory polymers and can maintain its performance even in humid environments, for example.

In order to achieve the above object, the linear resin molding of the present invention is a linear resin molding used in a fusion lamination deposition model 3D printer, characterized in that it has an outer layer made of an ethylene-vinyl alcohol copolymer on the outside of an inner layer material containing a shape memory polymer, or characterized in that it has an outer layer made of a water vapor barrier composition containing an inorganic layered compound and a resin on the outside of an inner layer material containing a shape memory polymer.

By covering the inner layer material made of a shape memory polymer with an outer layer made of a water barrier material, moisture absorption by the inner layer material made of a shape memory polymer is prevented, and deterioration of the performance of the shape memory polymer is suppressed.

The linear resin molding of the present invention can prevent moisture absorption in the object when three-dimensionally modeling a shape memory polymer, making it possible to maintain performance even in a humid environment, for example.

FIG. 1 is a diagram illustrating a schematic configuration of a 3D printer. FIG. 2 is a schematic perspective view showing an example of a linear resin molding. 3 is a cross-sectional view of the linear resin molding shown in FIG. 2. FIG. 2 is a diagram showing an example of a production line for a filamentary resin molding.

Below, an embodiment of a linear resin molding to which the present invention is applied will be described with reference to the drawings. However, before describing the linear resin molding of this embodiment, a 3D printer in which the linear resin molding is used will first be described.

The basic mechanism of a 3D printer is to use 3D data created by a computer as a blueprint, and to create a solid object, i.e. a 3D (three-dimensional) object, by layering cross-sectional shapes. Methods for this include, for example, the inkjet method, in which liquid resin is irradiated with ultraviolet light or the like to gradually harden it, the powder adhesion method, in which powdered resin is sprayed with adhesive, and the fused lamination method, in which resin melted by heat is layered little by little. The linear resin molded body according to this embodiment is used in a fused lamination method 3D printer, and is supplied to the 3D printer, for example, wound on a reel.

Figure 1 is a diagram showing an example of a 3D printer. The main components of the 3D printer in this example are a modeling head 2 that is driven in three dimensions by a drive mechanism 1, and a cartridge 4 that supplies a linear resin molding (filament) 10 made of a resin material to the modeling head 2. The linear resin molding 10 wound around the cartridge 4 is guided to the modeling head 2, heated and melted, and extruded from the nozzle 2A of the modeling head 2. This is then piled up and cooled to form a three-dimensional object M on a base 5.

Figures 2 and 3 show the linear resin molding 10 of this embodiment. The linear resin molding 10 of this embodiment has an inner layer material 11 that is covered with an outer layer 12, and is a linear resin molding 10 with a two-layer structure.

Regarding the materials used for each layer of the linear resin molding 10, the inner layer material 11 of the linear resin molding 10 in this embodiment is a shape-memory polymer, which allows the formation of a 3D model that can be easily changed in shape by heating it to above its glass transition temperature after molding, retains its shape by cooling, and returns to its original shape by reheating it to above its glass transition temperature.

A shape memory polymer is a material that has shape memory properties. Shape memory properties mean that the material elastically returns to its original shape when heated to a certain recovery temperature or higher. The recovery temperature is a temperature determined for each material, and is, for example, 0 to 100°C, and preferably 25 to 80°C, and specifically, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100°C, and may be within a range between any two of the values exemplified here.

The recovery temperature of a shape-memory polymer is its glass transition temperature (Tg). When it is shaped into a secondary shape by applying an external force at a temperature equal to or higher than the Tg, and then cooled to a temperature below the Tg while maintaining the external force, the secondary shape is fixed. At temperatures below the Tg, it does not return to its original shape even when the external force is removed. On the other hand, when a shape-memory polymer with a secondary shape is heated to a temperature equal to or higher than the Tg and no external force is applied, it returns to its original shape due to its elasticity. The original shape can be set, for example, by melting the shape-memory polymer and molding it into the desired shape. Examples of shape-memory polymers include polymers with rubber elasticity, such as polynorbornene, trans-polyisoprene, styrene-butadiene copolymer, and polyurethane.

The amount of shape memory polymer in the inner layer material 11 may be 100% by mass, or other materials may be added taking into consideration moldability, etc. If other materials are added, the amount is preferably 40% to 89% by mass, and more preferably 60% to 79% by mass.

When the shape memory polymer is used alone in the inner layer material 11 of the filamentary resin molding 10, the shape is easily distorted due to the effects of heat during deposition, and it may not be possible to increase the molding speed. Therefore, an inorganic filler may be added to the inner layer material 11 in order to improve heat dissipation.

As inorganic fillers, fibrous or powdery materials can be used, and the material can be any, but materials with high thermal conductivity are preferable. Examples include carbon fiber, glass fiber, talc, nanoclay, calcium carbonate, magnesium carbonate, etc., and carbon fiber and glass fiber, which have good thermal conductivity, are preferable. In addition, when using fibrous inorganic fillers, there is also the advantage that the shape can be easily restored after molding.

The amount of inorganic filler added can be set according to the required performance (heat dissipation, etc.), but is preferably 3% to 30% by mass, and more preferably 5% to 20% by mass. If the amount of inorganic filler is less than 3% by mass, the effect of adding the inorganic filler may be insufficient. Conversely, if the amount of inorganic filler is too high, exceeding 30% by mass, the proportion of shape memory polymer becomes relatively too low, which may cause delamination of the molded object and make molding difficult.

As mentioned above, when the inner layer material 11 of the linear resin molding 10 contains a shape memory polymer, the deterioration of performance due to moisture absorption becomes a problem. Therefore, in the linear resin molding 10 of this embodiment, the outer layer 12 is formed by covering the inner layer material 11.

The outer layer 12 may be formed from a water barrier material that prevents the intrusion of water molecules. For example, the outer layer 12 may be formed as an inorganic coating having water vapor barrier properties by vapor deposition of an inorganic material. However, taking into consideration the moldability and fusion properties of the filamentary resin molding 10, it is preferable that the outer layer 12 be a thermoplastic resin with water barrier properties that prevents the intrusion of water molecules.

Here, the thermoplastic resin with water barrier properties that prevents the intrusion of water molecules is a material with low water absorption or a material with water vapor barrier properties. For example, a material with low water absorption is a material with a water absorption rate of 0.1% or less, preferably 0.05% or less, measured according to Japanese Industrial Standards (JIS) K 7209 "Determination of water absorption rate of plastics". Specific examples include polyethylene, polypropylene, liquid crystal polymer, polyphenylene sulfide, fluororesin, etc.

As a thermoplastic resin having water vapor barrier properties, for example, an ethylene-vinyl alcohol copolymer resin is preferably used. The ethylene-vinyl alcohol copolymer resin is made of a saponified ethylene-vinyl acetate copolymer, and any known resin can be used. In the ethylene-vinyl alcohol copolymer resin, the ethylene content is preferably 20 to 70 mol %, and the degree of saponification of vinyl acetate is preferably 95 mol % or more, and more preferably the ethylene content is 25 to 50 mol %, and the degree of saponification of vinyl acetate is 98 mol % or more. If the degree of saponification is low, the water vapor barrier properties may be reduced.

Alternatively, it is also possible to use a water vapor barrier composition containing inorganic particles and a resin. When the water vapor barrier composition is cured by heat treatment, for example by contact with a thermosetting resin, the inorganic particles are regularly arranged, making it difficult for gas to pass through, and the so-called maze effect is what exerts water vapor barrier properties.

Therefore, the inorganic particles are preferably so-called inorganic layered compounds. Inorganic layered compounds are compounds in which unit crystal layers are stacked on top of each other to form a layered structure, and specific examples include graphite, phosphate derivative compounds (zirconium phosphate compounds, etc.), chalcogenides, hydrotalcite compounds, lithium aluminum composite hydroxides, clay minerals, etc. Clay minerals include kaolinite-serpentine clay minerals such as kaolinite, talc-pyrophyllite clay minerals such as talc, smectite clay minerals such as montmorillonite, vermiculite clay minerals, mica clay minerals such as tetrasilylic mica, brittle mica clay minerals such as xanthophyllite, and chlorite clay minerals such as clinochlore.

Examples of resins include polyvinyl alcohol (PVA), ethylene-vinyl alcohol copolymer (EVOH), polyvinylidene chloride, polyacrylonitrile, polysaccharides, polyacrylic acid and its esters, polymethacrylic acid and its esters, amide resins, imide resins, ester resins, resins with two or more types of functional groups in one molecule, urethane resins, epoxy resins, phenolic resins, and melamine resins.

Commercially available water vapor barrier compositions can be used, such as those manufactured by Sumitomo Chemical Co., Ltd. under the trade name EXCEVIER NOH1200 and EXCEVIER NOH2200.

The outer layer 12 may be formed by any method that can form a coating around the inner layer material 11. For example, the inner layer material 11 and the outer layer 12 may be formed simultaneously by co-extrusion. Alternatively, they may be formed by methods such as dipping or coating.

The thickness of the outer layer 12 is also arbitrary, but considering that it provides sufficient moisture absorption prevention effect and does not adversely affect shape memory, it is preferable to make it several μm to several tens of μm.

In addition, when forming the outer layer 12 as described above, if there is concern that the inner layer material 11 and the outer layer 12 may peel off, it is also possible to form an adhesive layer between the inner layer material 11 and the outer layer 12. In this case, the linear resin molding 10 has a three-layer structure.

In addition to the above-mentioned materials, various additives such as colorants can be added to each layer (inner layer material 11 and outer layer 12) of the filamentary resin molding 10 configured as above, depending on the specifications. The number of layers of the filamentary resin molding 10 is not limited to two or three layers, and the number of layers can be increased as necessary. The outer diameter of the filamentary resin molding 10 can also be set appropriately depending on the required specifications, for example, a filament with a diameter of about 1.75 mm. Alternatively, in a structure made of the filamentary resin molding 10, the filamentary resin molding 10 has a flat shape, and the filament has a wire diameter of 0.4 mm and a short diameter of 0.2 mm.

Next, an example of a method (production line) for producing a filamentary resin molding will be described. As shown in FIG. 4, the production line 30 for the filamentary resin molding 10 includes an extruder 31, a mold 32, a sizing device 33, a water tank 37, a fixed roller 41, an outer diameter dimension measuring device 42, and a winding device 43.

The extruder 31 melts and kneads the raw resin composition and continuously supplies it to the mold 32, and is configured with, for example, a cylinder with a built-in screw, a hopper for feeding the raw material, an injection nozzle, etc. The raw resin composition fed from the hopper for feeding the raw material is melted and kneaded by the screw in the cylinder, and is injected into the mold 32 from the injection nozzle.

The die 32 extrudes the molten resin from the extruder 31 in the horizontal direction, and the extruded molten resin is cooled to become the filamentary resin molding 10. The raw resin composition is the shape memory polymer and a thermoplastic resin that has barrier properties against water molecules, and these are co-extruded so that the outer layer is a layer of water-barrier resin.

The water tank 37 is formed in a long box shape along the conveying direction of the linear resin moldings 10 extruded from the extruder 31. The linear resin moldings 10 are introduced into the water tank 37 from the wall at one end of the water tank 37 and discharged from the wall at the other end of the water tank 37. The water tank 37 stores water 37a in which the linear resin moldings 10 are immersed and which cools the linear resin moldings 10.

The sizing device 33 is located inside the wall at one end of the water tank 37, and has the function of making the cross section of the linear resin molding 10 sent from the extruder 31 into the water tank 37 a perfect circle, and of making the outer diameter dimension of the linear resin molding 10 uniform to a predetermined dimension.

The fixed roller 41 stabilizes the position of the linear resin molding 10 in the water tank 37 after passing through the sizing device 33, and transports the linear resin molding 10 toward the winding device 43.

The outer diameter measuring device 42 measures the outer diameter of the linear resin molding 10 cooled in the water tank 37. The winding device 43 includes a pair of upper and lower winding rollers 43a that sandwich and transport the linear resin molding 10 that has passed through the outer diameter measuring device 42 downstream, and a bobbin winding machine 43b that is disposed downstream of the winding rollers 43a and has a winding shaft 43c that winds up the linear resin molding 10.

The manufacturing method of the linear resin molding 10 includes an extrusion process, a sizing process, a cooling process, a dimension measurement process, and a winding process. In the extrusion process, the resin pellets fed from the hopper 31a are melted in the extruder 31, and the molten resin is extruded from the die 32. The outer diameter of the extruded linear resin molding 10 is D1.

In the sizing process, the linear resin molding 10 travels along the conveying passage, and is formed into a uniform outer diameter D2 that matches the inner diameter of the conveying passage. In the cooling process, the linear resin molding 10 is cooled by passing through a water tank 37, and the outer diameter of the linear resin molding 10 is reduced.

In the dimension measurement process, the outer diameter of the filamentary resin molding 10 is measured, and it is determined whether the measured value is appropriate. If the outer diameter of the filamentary resin molding 10 is outside the standard, each manufacturing condition is reviewed so that the outer diameter is within the standard. In the winding process, if the outer diameter of the filamentary resin molding 10 is within the standard, it is sent to the bobbin winder 43b by the winding roller 43a of the winding device 43, and the continuous filamentary resin molding 10 is wound around the winding shaft 43c. Once a predetermined length of the filamentary resin molding 10 has been wound around the winding shaft 43c, the filamentary resin molding 10 is wound around a new winding shaft 43c.

As described above, by forming an outer layer 12 with water barrier properties on the outside of the inner layer material 11 made of a shape memory polymer, performance degradation due to moisture absorption can be reliably suppressed.

Furthermore, by filling the inner layer material 11 with inorganic filler, it is possible to provide a filamentary resin molding with shape memory properties that can impart high rigidity to the molded object and further improve the ability to restore to its original shape. For example, when using filaments that use conventional shape memory polymers to mold 3D models using a 3D printer, it can be difficult to mold some shapes of the model, but filaments that contain glass fiber or carbon fiber have improved moldability and can be molded without problems.

Furthermore, while conventional shape memory polymers have low rigidity and limited applications, the use of filaments containing glass fiber or carbon fiber provides high strength and high recovery, greatly improving functionality. Therefore, by adding inorganic fillers to shape memory polymers, it is possible to manufacture linear resin molded bodies with various functionalities, enabling modeling with more functionality. In other words, the structure formed by molding the linear resin molded body of this embodiment with a 3D printer using the fused deposition modeling method is less susceptible to performance degradation due to moisture absorption, and can be used, for example, for orthodontic appliances.

The above describes an embodiment of the present invention, but it goes without saying that the present invention is not limited to the above-mentioned embodiment, and various modifications can be made without departing from the spirit of the present invention.

(Preparation of linear resin molded body)
Example 1
A polyurethane-based shape-memory polymer (manufactured by SMP Technology, product name MM-5520) was used as a raw material, which was melt-kneaded in an extruder, fed to a die core, and drawn out from a die provided on the die core. At this time, an ethylene-vinyl alcohol copolymer was co-extruded to form a filamentary resin molding having a polyurethane-based shape-memory polymer as an inner layer material and polyethylene as an outer layer.

After the wire diameter and linearity were adjusted to a certain extent using a die to form a filamentary resin molding, a sizing unit was provided at the entrance of the water tank where the resin was cooled and solidified, and the final cross-sectional shape (wire diameter and linearity) of the filamentary resin molding was adjusted in this sizing unit. After the shape was formed in the sizing unit, the resin molding was cooled and solidified in the water tank, and then wound up by a winder. The filamentary resin molding sent out from the winder was then wound up on a bobbin.

Example 2
A filamentous resin molding was prepared in the same manner as in Example 1, except that an ethylene-vinyl alcohol copolymer was used as the outer layer instead of polyethylene.

Comparative Example 1
A single-layer filamentary resin molding was produced using only a polyurethane-based shape memory polymer (manufactured by SMP Technology, product name MM-5520) as a raw material.

Example 3
A water vapor barrier composition (manufactured by Sumitomo Chemical Co., Ltd., product name EXCEVIER NOH1200) was applied to the outer peripheral surface of the single-layer filamentary resin molding produced in Comparative Example 1 to form an outer layer, thereby obtaining a two-layer filamentary resin molding.

(Verification of effectiveness)
The produced filamentous resin molded body was used to print a 3D model using a 3D printer (manufactured by Bonsai Lab, product name BS-01), and the restoring force of the molded object before and after storage in a humid environment was evaluated by measuring the rigidity using a tensile test. Note that the molded object was molded at 215°C.

The strength of the restoring force was measured using a 75 mm long x 10 mm wide x 1 mm thick model created with a 3D printer, using a universal testing machine with a thermostatic chamber (Universal testing machine: Shimadzu Corporation, product name AGS-X 10kN; thermostatic chamber: Shimadzu Corporation, product name TCRIA-200P) in the following procedure. That is, first, the model was clamped with a chuck distance of 50 mm in an atmosphere of 75°C in the thermostatic chamber, and then the crosshead was moved and pulled 5 mm. After that, the temperature inside the thermostatic chamber was raised to 35°C, and the crosshead was lowered until the load became zero, and the temperature inside the thermostatic chamber was raised again to 75°C, and the force applied to the universal testing machine was measured as the restoring force.

As a result, in Examples 1 to 3, which had a water-barrier outer layer, the restoring force was almost unchanged before and after storage in a humid environment, but in Comparative Example 1, which had a single layer of shape-memory polymer, a clear decrease in performance (decrease in restoring force) was observed after storage in a humid environment.

REFERENCE SIGNS LIST 1 Drive mechanism 2 Modeling head 4 Cartridge 5 Base 10 Filamentary resin molding 11 Inner layer material 12 Outer layer 30 Production line 31 Extruder 32 Mold 33 Sizing device 37 Water tank 42 Outer diameter measuring device 43 Winding device

Claims (2)

A filamentary resin molded body used in a fused deposition model 3D printer,
The inner layer material includes a shape memory polymer, and an outer layer is formed of a water vapor barrier composition containing an inorganic layered compound and a resin on the outer side of the inner layer material.
the outer layer is formed of an inorganic layered compound regularly arranged by contacting and curing a thermosetting resin;
The linear resin molding further comprises an adhesive layer between the inner layer material and the outer layer . 2. The linear resin molding according to claim 1 , wherein the outer layer is formed by coating.

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