JP2024043226A - Molding material for 3d printer, 3d print molded article, and manufacturing method of them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding material for a 3D printer for manufacturing a molded article which has biodegradability, low odor, and excellent transparency/surface treatment (smoothing treatment and coating property) property and moldability, and a related technique of the same.

SOLUTION: In a molding material for a 3D printer, 70-80 mass% of cellulose acetate, and 20-30 mass% of a plasticizer are mixed. A manufacturing method of the molding material for the 3D printer includes the steps of: continuously spraying or intermittently inserting the plasticizer while stirring a granular material of cellulose acetate, and forming the plasticizer into a mixture; leaving the mixture at normal temperature for 8 hours or longer; and setting the mixture at a temperature of viscous flowing and kneading the mixture.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2024,JPO&INPIT

Description

TECHNICAL FIELD The present invention relates to a modeling material for a 3D printer using a thermal fusion deposition method, and technology related to this modeling material.

In recent years, 3D printers that can mold modeling materials such as resin into desired three-dimensional shapes have become popular. A 3D printer is a type of rapid prototyping (3D modeling machine) that creates 3D printed products by discharging and layering modeling materials based on 3D data created on a computer such as a PC.

Examples of such 3D printers include a thermal fusion lamination method in which thermoplastic resin is melted at high temperatures and laminated, and a liquid photocurable resin is printed and irradiated with ultraviolet rays to cure and laminate. An inkjet method is known.

The molding materials generally used in the above-mentioned fused deposition modeling method include ABS resin (acrylonitrile-butadiene-styrene copolymer), PLA (polylactic acid resin), etc. In addition to these materials, molding materials can also be resin compositions containing cyclic polyolefins (for example, Patent Document 1) or acrylic polymer compositions (for example, Patent Document 2).

Japanese Patent Application Publication No. 2016-60147 Special Publication No. 2022-527497

However, shaped articles manufactured using the above-mentioned ABS resin as a shaping material have problems such as large thermal deformation during shaping and strong odor. For this reason, in order to suppress warp deformation, a molded article made of ABS resin requires additional measures to suppress warp deformation, such as heating the modeling table. Moreover, shaped articles manufactured using PLA resin as a shaping material are excellent in that they are less likely to warp, but they have problems such as low heat resistance and somewhat difficult paintability.

Furthermore, since ABS resin and PLA resin have low transparency, there is a problem that they cannot be applied to shaped articles that require transparency. Furthermore, since ABS resins and PLA resins do not have biodegradability, they pose a problem in that they pose a large burden when released into the environment.

For shaped articles requiring transparency, it is conceivable to apply a resin composition or an acrylic polymer composition containing the above-mentioned cyclic polyolefin as a shaping material. However, since none of them are biodegradable, there is a problem in that they pose a large burden if released into the environment.

The present invention was made in consideration of these circumstances, and provides a shaped article that is biodegradable, has low odor, and has excellent transparency, surface treatment (smoothing treatment, paintability), and formability. The purpose is to provide modeling materials for 3D printers and related technologies for manufacturing.

The modeling material for 3D printers according to the present invention is characterized in that it contains 70 to 80% by mass of cellulose acetate and 20 to 30% by mass of plasticizer. The manufacturing method for this modeling material for 3D printers is characterized in that it includes the steps of: forming a mixture by continuously spraying or intermittently adding the plasticizer while stirring cellulose acetate granules; leaving the mixture at rest at room temperature for 8 hours or more; and setting the temperature at which the mixture becomes viscous and flowing, and kneading the mixture.

According to the present invention, a modeling material for a 3D printer and a molding material for producing a molded article that is biodegradable, has low odor, and has excellent transparency, surface treatment (smoothing treatment, paintability), and moldability. Related technology is provided.

A table showing Comparative Example 1 and Examples 1-6 in which the effects of the modeling material for a 3D printer according to the embodiment were confirmed using mechanical strength characteristics as an index. The table shows Comparative Examples 2 and 3 and Examples 7 and 8 in which the effects of the 3D printed article according to the embodiment were confirmed using sensory characteristics as an index.

Hereinafter, a modeling material for a 3D printer (hereinafter simply referred to as "modeling material") according to an embodiment of the present invention will be described. The main component, cellulose acetate, accounts for 70-80% by mass of the entire modeling material, the plasticizer is blended in the range of 20-30% by mass, and the remainder is blended with other additives. I decided to do so. If the proportion of cellulose acetate is less than 70% by mass, transparency will decrease. Furthermore, if the proportion of the plasticizer is less than 20% by mass, the mechanical properties during melting and solidification will be inappropriate, resulting in a decrease in the formability of the 3D printed article.

The recommended basic mechanical strength properties of cellulose acetate resin are tensile strength of 10 MPa or higher, flexural modulus of 2.0 GPa or higher, and heat distortion temperature of 50° C. or higher. Cellulose acetate resin itself is a crystalline resin, but by compounding it with a plasticizer, it becomes an amorphous resin and becomes transparent. The glass transition temperature of cellulose acetate resin is 70 to 80°C.

Typical thermal properties of cellulose acetate resin are: thermal conductivity: 4.0 to 8.0×10 ^-4 cal/cmsK, specific heat: 0.3 to 0.42 cal/gK, thermal expansion coefficient: 8 to 18×10 ^{-5K -1} . Cellulose acetate resin has almost the same mechanical strength characteristics and thermal characteristics as PLA resin, which is generally used as a modeling material for hot melt lamination.

In the fused deposition modeling method, it is required that the previously formed layer does not deform due to the heat and pressure from the next layer to be laminated. From this perspective, it is better for the molding material of the present invention to have a relatively high heat distortion temperature, preferably 30°C or higher. The upper limit of the heat distortion temperature is 50 to 60°C, but there is no particular limitation.

In fused deposition modeling 3D printers, the modeling material is in the form of pellets or filaments. Pellet-shaped modeling material is heated in an ultra-small extruder, and the molten material is ejected from a nozzle to create a three-dimensional object. Filament-shaped modeling material is wound around a spool, and the tip of the material is heated, and the molten material is ejected from a nozzle to create a three-dimensional object. The nozzle diameter is in the range of 1 to 6 mm, and modeling is possible at a layering speed of 1 to 5 kg/Hr.

Cellulose acetate, which is the main component of the modeling material, is preferably cellulose diacetate (CDA) with an acetylation degree of 50 to 59%. This CDA is generally dissolved in a solvent to obtain a shaped article such as a film. However, this general process is complicated by problems such as drying of the solvent and recycling of the solvent.

Therefore, in this embodiment, we use a molding material that is manufactured by a compound method that blends a plasticizer with CDA, rather than the general solvent method, and has heat moldability and can be molded with general petroleum resin molding equipment. do.

Cellulose acetate has the property that the higher the degree of acetylation, the harder and more brittle the shaped article becomes. The physical properties of polymeric materials largely depend on their crystallinity, and those with high crystallinity generally have improved strength but reduced flexibility; in other words, they become brittle and have low elongation. The higher the degree of acetylation, the higher the crystallinity of cellulose acetate, but the addition of a plasticizer imparts flexibility to the shaped article.

Although cellulose acetate has excellent transparency, it has the disadvantages of poor resin fluidity, unstable shapes of molded products, and furthermore, that it is hard and brittle. For this reason, cellulose acetate alone is not suitable as a modeling material for 3D printers. However, these drawbacks can be compensated for by high loading of plasticizer, and cellulose acetate has been found to be promising as a modeling material for 3D printers.

A compounding method in which cellulose acetate is used as a base resin and highly filled with a plasticizer is carried out according to the following steps (A) to (C). That is, (A) a mixture is produced by continuously spraying or intermittently adding a plasticizer while stirring the cellulose acetate granules. (B) The produced mixture is allowed to stand at room temperature for 8 hours or more. (C) The mixture is set at a temperature that causes viscous flow and kneaded.

The stirring device for producing the mixture of cellulose acetate granules and plasticizer may be a ribbon blender, tumbler, etc., but a high-speed mixer is preferred. Although the device for heating and kneading this mixture may be compounding equipment such as a heating roll or a Banbury mixer, it is preferable to uniformly mix the mixture using a twin-screw extruder. The kneading temperature to be set is preferably 230° C. or lower from the viewpoint of preventing thermal decomposition of cellulose acetate.

The weight average molecular weight of cellulose acetate is approximately 1×10 ⁴ to 100×10 ⁴ , preferably 5×10 ⁴ to 75×10 ⁴ , more preferably 10×10 ⁴ to 50×10 ⁴ , but there are no particular limitations. You can choose according to your purpose. The degree of acetylation of cellulose acetate can be selected from the range of 52 to 62.5%. A preferable degree of acetylation is about 59% or less (eg, 52.0 to 58.0%), particularly about 54 to 56% (eg, 55%).

The cellulose acetate applied to the embodiment may also be used in combination with cellulose esters (for example, organic acid esters such as cellulose propionate and cellulose butyrate, and inorganic acid esters such as cellulose nitrate, cellulose sulfate, and cellulose phosphate). You may.

As the plasticizer, glycerin ester compounds, polyether ester compounds, and adipic acid ester compounds are preferably used. Examples of the glycerin ester compound include triacetin, monoglyceride, acetylated monoglyceride, and organic acid monoglyceride. Examples of the adipic acid ester compound include an adipic diester compound and an adipic acid polyester compound. Other ester compounds include sebacic acid ester compounds, epoxy esters, benzoic acid esters, trimellitic acid esters, glycol ester compounds, acetic acid esters, dibasic acid ester compounds, phosphoric acid ester compounds, phthalic acid ester compounds, camphor, Examples include citric acid ester, stearic acid ester, metal soap, polyol, polyalkylene oxide, and the like. These plasticizers can be used alone or in combination.

Moreover, various additives may be blended into the modeling material according to the embodiment within a range that does not impair the effects of the present invention. Specifically, heat stabilizers (e.g. hindered phenolic antioxidants, phosphorus heat stabilizers, metal deactivators, sulfur heat stabilizers, etc.), weathering additives (e.g. liquid ultraviolet absorbing agents, triazine-based UV absorbers, benzophenone-based UV absorbers, benzoate-based UV absorbers, hindered amine-based light stabilizers, etc.), dispersants and lubricants (hydrocarbon-based lubricants, fatty acids, higher alcohol-based lubricants, fatty acid amide-based, metals) Examples include soap-based, ester-based, etc.), anti-blocking agents (silica, etc.), and colorants including dyes and pigments.

The modeling material according to the embodiment has a pellet or filament shape. As described above, a method for manufacturing a filament-shaped shaping material involves melting and kneading a mixture of cellulose acetate and a plasticizer using an extruder or the like, and extruding the mixture into a strand from a die/nozzle. The melt extruded into a strand is cooled with a cooling medium such as water or air and spun. If necessary, it is heated and stretched, heat treated, coated with oil, etc., and then wound into a filament. Make it. The cross-sectional shape of the filament is not particularly limited, and examples include circular, elliptical, triangular, quadrangular, hexagonal, and star-shaped.

There are two methods for manufacturing pellet-shaped modeling materials: as described above, the molten material is extruded into strands, cooled in a water tank, etc., and then cut with a pelletizer (strand method), or the molten material is extruded from a die or nozzle. One example is a method in which a rotating blade instantly cuts the resin (hot cut method).

When manufacturing a 3D printed model using the modeling material of the embodiment by a hot-melt lamination method, the nozzle temperature is set to 120 to 250°C, more preferably 180 to 220°C. If the nozzle temperature is raised to a high temperature exceeding 250° C., cellulose acetate will be hydrolyzed, causing problems such as coloring and acetic acid odor. Since the modeling material of the present invention has little thermal deformation, heating of the modeling table may not be necessary in some cases. The stacking pitch is usually 0.05 to 0.5 mm. The stacking pitch is determined by adjusting the nozzle diameter and extrusion conditions.

Cellulose acetate resin has surface decoration properties such as printability, paintability, and dyeability, and improves the added value of 3D printed products.

Next, an example in which the effects of this embodiment were confirmed will be described together with a comparative example. In the Examples and Comparative Examples, the basic physical properties of the cellulose acetate compositions were measured in accordance with the JIS standards applied to ordinary petroleum-based plastics.

FIG. 1 is a table showing Comparative Examples and Examples 1-6 in which the effects of the modeling material for 3D printers according to the embodiment were confirmed using mechanical strength characteristics as an index. Comparative Example 1 and Example 1-2 use triacetin alone as a plasticizer, and Example 3-6 uses a combination of triacetin and adipic acid ester.

In addition, in Comparative Example 1 and Examples 1 and 4, pellets were produced by mixing cellulose acetate and a plasticizer and then inputting the mixture into a kneading machine without allowing any standing time, and producing pellets in accordance with industrial standards. These are test results using test pieces. In Examples 2, 3, 5, and 6, the mixture was put into a kneader after 8 hours of standing time to produce pellets, and the test results were obtained using test pieces prepared in accordance with industrial standards.

Note that FIG. 1 shows data partially extracted from the results of a huge series of tests in which multiple parameters that affect the basic physical properties of cellulose acetate compositions are simultaneously varied to search for optimal conditions. FIG. 1 shows test results in which the parameters of the standing time (8 hours) and the amount of plasticizer (triacetin, adipic acid ester) filled were changed simultaneously.

Here, if we classify the modeling materials (cellulose acetate compositions) into comparative examples and examples based on the superiority or inferiority of the moldability of 3D printed objects, we can see that systematic differences in the basic physical properties of the modeling materials depend on the amount of plasticizer blended. It is found that Furthermore, when focusing on the test results of MFR, which has a high degree of influence on the formability of 3D printed products, it can be said that the presence or absence of a standing time condition brings about a significant difference in the test results of MFR.

(Manufacture of pellets and test pieces)
The cellulose acetate granules used are commercially available products with a degree of acetylation of 55%. A mixture of cellulose acetate particles and a plasticizer was produced by spraying and mixing the plasticizer while stirring the cellulose acetate particles in a high-speed mixer set at 500 rpm/min. Furthermore, additives (antioxidants, etc.) were mixed into the mixture using a ribbon blender, which is a low-speed mixer set at 120 rpm/min. In Examples 2, 3, 5, and 6, the mixture was placed in a tray and allowed to stand at room temperature (25° C.) for 8 hours in an airtight state before being charged into a kneader. In Comparative Examples and Examples 1 and 4, the mixtures were charged into the kneader within 30 minutes after they were produced.

The kneading machine used was CK70HT (screw diameter 70 mm, L/D=44) manufactured by Taiwanese manufacturer CKF. The screw rotation speed was set at 300-600 rpm, and the molding temperature was 200-220°C.

The kneaded body discharged from the kneader is molded into pellets and cooled, then reheated and melted in an injection molding machine, and then injected into a mold to obtain various basic properties (MFR, flexural modulus, tensile strength). , impact strength) were prepared. As shown in Figure 1, increasing the amount of plasticizer significantly increases MFR and tensile elongation, and the measured basic physical properties are almost equivalent to general-purpose petroleum-based plastics such as PP, PE, and PS. The results were obtained. Moreover, the obtained test piece is transparent.

(Manufacture of filament)
The pellets formed with the composition shown in Figure 1 were extruded using a twin-screw extruder OMEGA-30 manufactured by Steer Co., Ltd. under extrusion conditions of C1 140°C, C2-C6 200°C, H 200°C. It was made into a filament shape with a diameter of 1.7 mm and used as a modeling material.

(3D printing modeling)
2 is a table showing Comparative Examples 2 and 3 and Examples 7 and 8, in which the effects of the 3D printed products according to the embodiment were confirmed using sensory characteristics as an index. The 3D printed product produced in Example 7 was produced by setting the filament-shaped modeling material produced with the composition of Example 1 in MothMachS3DP333 manufactured by S Lab Co., Ltd., and producing it according to the product drawing.

The 3D printed product produced in Example 8 was produced by setting the pellet-shaped modeling material produced with the composition of Example 5 in a MothMachGEM800S manufactured by S.Lab Co., Ltd., and following the product drawing. In both Examples 7 and 8, the nozzle temperature was 220°C, the discharge diameter was 0.4 mm, and the layer pitch was 0.1 mm, and the modeling table was not heated.

The 3D printed product produced in Comparative Example 2 was produced using commercially available ABS resin (acrylonitrile-butadiene-styrene copolymer) 3D printer filament (Raise3D Premium ABS). The production conditions for Comparative Example 2 were the same as those for Example 7, except that the modeling table was heated to 110°C to prevent deformation of the model.

The 3D printed article manufactured in Comparative Example 3 uses a commercially available PLA (polylactic acid resin) filament for 3D printers (manufactured by Polymaker, POLY-MAXPLA, white). The manufacturing conditions of Comparative Example 3 were the same as those of Example 8, except that the molding table was heated to 60° C. to prevent deformation of the molded product.

(evaluation)
Regarding the 3D printed model, a sensory evaluation was conducted to determine whether or not odor was generated. Comparative Examples 2 and 3 were rated as ``strong off-odor'' and ``off-odor present,'' while Examples 7 and 8 were both rated as ``waste.''

Next, the interlayer adhesion of the 3D printed article was evaluated. When attempting to manually peel off the layers of the manufactured shaped articles, none of them peeled off, and all were evaluated as "good." Next, the formability of the 3D printed article was evaluated. The shaped article of Comparative Example 2 was largely deformed as a whole, and the wall thickness was also uneven. Although the shaped article of Comparative Example 3 is not as severe as that of Comparative Example 2, there is a small deformation that can be easily recognized. Although the shaped articles of Examples 7 and 8 had deformation, the amount was much smaller than that of Comparative Example 3.

Next, the transparency of the 3D printed products was evaluated. A newspaper was placed on the opposite side of the product and evaluated whether the letters could be read. Comparative Examples 2 and 3 were "opaque" to the extent that the presence of the letters was not discernible. On the other hand, Examples 7 and 8 were "transparent" to the extent that the letters could be read.

As described above, unlike the case where a general ABS resin or PLA resin is used, the modeling material of the present invention does not emit an unpleasant odor in a 3D printed article and has excellent moldability. Both cellulose acetate and plasticizer are scheduled to receive PL certification, and are highly safe for the human body, and can be applied to medical and food applications. Moreover, it can be used for dental materials and the like. Furthermore, since cellulose acetate has excellent transparency, it is also effective for modeling objects that require skeletons or optical members such as lenses.

Claims (7)

Cellulose acetate is 70 to 80% by mass,
A modeling material for 3D printers that contains a plasticizer in the range of 20 to 30% by mass. The modeling material for a 3D printer according to claim 1,
The cellulose acetate is cellulose diacetate with an acetylation degree of 50 to 59%, and is a modeling material for 3D printers. In the modeling material for a 3D printer according to claim 1 or 2,
The plasticizer is a modeling material for a 3D printer, wherein the plasticizer is at least one selected from a glycerin ester compound, a polyether ester compound, and an adipate ester compound. In the modeling material for a 3D printer according to claim 1 or 2,
A modeling material for 3D printers in the form of pellets or filaments. A method for manufacturing a modeling material for a 3D printer according to claim 1 or 2, comprising:
A step of continuously spraying or intermittently adding the plasticizer while stirring the cellulose acetate granules to form a mixture;
a step of leaving the mixture at room temperature for 8 hours or more;
A method for manufacturing a modeling material for a 3D printer, including the step of setting the mixture at a temperature that causes viscous flow and kneading the mixture. A 3D printed product formed using the 3D printer modeling material described in claim 1 or 2. A step of heating the modeling material for a 3D printer according to claim 1 or claim 2 to a temperature of 230° C. or lower to make it into a melt;
A method for manufacturing a 3D printed article, comprising the step of discharging the melt from a nozzle with a diameter in the range of 1 to 6 mm and laminating the melt.

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