Non-toxic flame retardant filament and manufacturing method thereof

Abstract

The present invention relates to a non-toxic flame retardant filament and a manufacturing method thereof. The non-toxic flame retardant filament according to the present invention comprises a blend composed of polylactic acid (PLA) powder, shell powder, and ammonium polyphosphate (APP) powder. According to an embodiment of the present invention, the three-component mixed filament including shells can provide excellent mechanical properties and flame retardancy.

Description

Non-toxic flame-retardant filament and method for manufacturing the same

[0001] The present invention relates to a non-toxic flame-retardant filament and a method for producing the same. More specifically, it relates to a three-type mixed filament including shells and a method for producing the same, which has excellent mechanical properties and flame-retardant properties.

[0002]

[0003] Non-toxic flame retardant materials are required to prevent large-scale fires in the event of a fire and to prevent combustion from producing toxic gases.

[0004] Meanwhile, shells, with a production volume of approximately 280,000 tons as of 2018, possess excellent mechanical properties and a high calcium carbonate content of approximately 92%. Calcium carbonate decomposes into calcium oxide and carbon dioxide upon thermal decomposition, and the carbon dioxide can extinguish the parent material. However, shells alone lack the binding strength to be utilized as a material, and the amount of carbon dioxide generated during thermal decomposition is insufficient to extinguish the ignited parent material, making them unsuitable for large-scale fires.

[0005] Ammonium polyphosphate (APP), commonly known as APP, exhibits excellent bonding properties with other materials and acts as a flame retardant. Upon thermal decomposition, it decomposes into water, carbon dioxide, and phosphine. The water aids in extinguishing fire through an endothermic reaction, the carbon dioxide slows the combustion rate of the parent material, and the phosphine lowers the ambient oxygen concentration.

[0006] Accordingly, the present invention aims to provide a non-toxic flame retardant material using shells and APP.

[0007] The present invention relates to a technology developed by the Industry-Academic Cooperation Foundation of Changwon National University through the research project "Development of Eco-Friendly Flame-Retardant Hybrid Composite Technology (New Materials Research Center)" funded by the Ministry of Education (Project Unique Number: 1345280847, Project Number: 2018R1A6A1A03024509, Research Period: 2018.06.01 ~ 2027.02.28).

[0008]

[0009] One object of the present invention is to manufacture a filament having improved mechanical properties and flame retardancy compared to existing PLA filaments by using shells.

[0010] Another object of the present invention is to manufacture a non-toxic, environmentally friendly flame-retardant filament that does not exhibit toxicity when burned using shells.

[0011]

[0012] A non-toxic flame-retardant filament according to the present invention comprises a mixture of PLA (polylactic acid) powder, shell powder, and APP (ammonium polyphosphate) powder.

[0013] In one embodiment, the shell powder may be included in an amount of 1% to 10% of the total weight of the formulation, and the APP powder may be included in an amount of 1% to 10% of the total weight of the formulation.

[0014] In one embodiment, the PLA powder contains voids, and the shell powder and APP powder can fill the voids.

[0015] In one embodiment, the particle size of the shell powder may be from 1 μm to 1 mm.

[0016] In some embodiments, the particle size of the APP powder may be from 1 μm to 1 mm.

[0017] In one embodiment, the shell powder may comprise 92% to 95% calcium carbonate (CaCO3).

[0018] A method for manufacturing a non-toxic flame-retardant filament according to the present invention includes a step of preparing PLA powder, shell powder and APP powder by powderizing PLA (polylactic acid), shell and APP (ammonium polyphosphate), a step of preparing a mixture by mixing the shell powder and APP powder with the PLA powder, and a step of manufacturing a filament by injecting the mixture.

[0019] In one embodiment, the shell powder may be mixed in an amount of 1% to 10% based on the total weight of the mixture, and the APP powder may be mixed in an amount of 1% to 10% based on the total weight of the mixture.

[0020] In one embodiment, after the step of powdering PLA, shell, and APP, a step of drying the PLA powder, shell powder, and APP powder to remove moisture may be further included.

[0021] In one embodiment, the step of drying the PLA powder, shell powder and APP powder to remove moisture may be performed at 50°C to 70°C for 6 to 24 hours.

[0022] In one embodiment, the step of preparing the mixture may be performed at 180°C to 240°C for 1 hour to 4 hours.

[0023] In one embodiment, the particle size of the shell powder may be from 1 μm to 1 mm, and the particle size of the APP powder may be from 1 μm to 1 mm.

[0024]

[0025] According to an embodiment of the present invention, a filament having improved mechanical properties and flame retardancy performance compared to existing PLA filaments can be manufactured using shells.

[0026] According to the present invention, a non-toxic, environmentally friendly flame-retardant filament that does not exhibit toxicity when burned can be manufactured using shells.

[0027]

[0028] Figures 1 to 3 are SEM images of Comparative Example 1 taken at magnifications of 5,000 times, 10,000 times, and 20,000 times, respectively.

[0029] Figures 4 to 6 are SEM images of Comparative Example 3-3 taken at magnifications of 5,000 times, 10,000 times, and 20,000 times, respectively.

[0030] Figures 7 to 9 are SEM images of Example 1-1 taken at magnifications of 5,000 times, 10,000 times, and 20,000 times, respectively.

[0031]

[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings and the contents described in the attached drawings, but the present invention is not limited or restricted by the embodiments.

[0033] The terminology used herein is for the purpose of describing embodiments only and is not intended to limit the present invention. In this specification, the singular also includes the plural unless the context clearly dictates otherwise. As used herein, the terms "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components, steps, operations, and / or elements.

[0034] The terms “embodiment,” “example,” “aspect,” “example,” and the like as used herein are not to be construed as implying that any aspect or design described is better or advantageous over other aspects or designs.

[0035] Also, the term 'or' means 'inclusive or' rather than 'exclusive or'. That is, unless stated otherwise or clear from context, the expression 'x utilizes a or b' means any one of the natural inclusive permutations.

[0036] Additionally, as used in this specification and claims, the singular forms “a” or “an” should generally be construed to mean “one or more” unless otherwise indicated or clear from the context to be in the singular form.

[0037] Additionally, when a part such as a film, layer, area, or component request is said to be "on top" or "over" another part, this includes not only cases where it is directly on top of the other part, but also cases where there are other films, layers, areas, components, etc. intervening therebetween.

[0038]

[0039] In the present invention, a composite material in which PLA (polylactic acid), shell, and APP (ammonium polyphosphate) are mixed at a certain ratio is intended to be used as a non-toxic flame retardant material.

[0040] The non-toxic flame retardant filament according to the present invention comprises a blend of PLA powder, shell powder and APP powder.

[0041] In one embodiment, the shell powder may be included in an amount of 1% to 10% of the total weight of the blend. If the shell powder is included in an amount of less than 1%, the mechanical strength and flame retardancy properties are not improved compared to filaments made with only PLA powder. As the content of the shell powder increases, the mechanical properties and combustion speed of the blended filament decrease, but if the content of the shell powder exceeds 5%, the mechanical properties of the blended filament actually decrease. In addition, since the shell powder sufficiently exhibits flame retardancy properties for use as a flame retardant filament when included in an amount of 1% or more, there is no need to blend in an amount exceeding 10%.

[0042] In one embodiment, the APP powder may be included in an amount of 1% to 10% of the total weight of the blend. As the APP powder content increases, the mechanical strength of the blended filament increases. However, if the APP powder content exceeds 5%, the mechanical strength actually decreases. Furthermore, since the APP powder sufficiently exhibits flame-retardant properties for use as a flame-retardant filament when included in an amount of 1% or more, there is no need to blend in amounts exceeding 10%.

[0043]

[0044] Below, each material that makes up the non-toxic flame retardant filament will be described in detail.

[0045] PLA is the filament material traditionally used in FDM printing. FDM (Fused Deposition Modeling) refers to a method of creating the shape of an output object by melting the material above its melting point, drawing lines of a certain thickness, and then continuously stacking these layers.

[0046]

[0047] A shell is the outer covering of a mollusk, formed by the hardening of calcium carbonate secreted from the mantle. Its main component is calcium carbonate. Shells possess excellent mechanical strength due to their hardness, and contain calcium carbonate, which can undergo combustion by thermal decomposition into calcium oxide and carbon dioxide. In one embodiment, the shell powder may comprise 90% to 95% calcium carbonate (CaCO3).

[0048] By dissolving oyster shells, converting calcium into an ionic state, filtering out impurities, and extracting only the calcium, the calcium carbonate is reacted with the carbon dioxide generated during the dissolution, resulting in the extraction of 99.5% pure calcium carbonate. Oyster shells yield a greater amount of calcium carbonate than other shells, and their mass ratio also exceeds that of other shells. In other words, compared to general shells, which contain an average of 92% calcium carbonate, oyster shells contain approximately 95% calcium carbonate.

[0049]

[0050] Furthermore, recycling discarded shells has an environmentally friendly effect, reducing marine pollution. However, shells have poor bonding properties, making them difficult to use as filament material. Furthermore, the small amount of carbon dioxide produced by thermal decomposition makes it difficult to extinguish a large fire.

[0051] Furthermore, while shells are typically refined or processed for use, the present invention utilizes raw materials without undergoing such processes. By omitting the refining or processing steps, costs are reduced. Furthermore, calcium carbonate is removed during the refining or processing process, limiting the amount of calcium carbonate ultimately obtained, which can reduce the tensile strength of the filament. However, using the shells as they are allows for the full utilization of the calcium carbonate contained within.

[0052]

[0053] APP possesses excellent bonding properties with other materials, making it useful in the production of composite materials. It decomposes into water, carbon dioxide, and phosphine upon pyrolysis, making it suitable for use as a flame retardant. Water, through its endothermic reaction, can help extinguish fires; carbon dioxide can slow the combustion rate of the ignition source; and phosphine, due to its high reactivity with oxygen, can reduce the surrounding oxygen concentration, thereby preventing the spread of fire and slowing the combustion rate.

[0054] The non-toxic flame-retardant material according to the present invention comprises PLA and shell powder, and has environmentally friendly characteristics, and by adjusting the ratio of the components, the mechanical properties can be enhanced to facilitate use as a filament. In particular, it is intended to manufacture a material that enhances mechanical properties, exhibits excellent flame retardancy, and thereby reduces the combustion speed of fire, thereby preventing a phenomenon that leads to a large-scale fire. The optimal mixing ratio of PLA, shell powder, and APP can be provided. More specifically, the mechanical properties are not deteriorated compared to filaments manufactured from PLA alone during the process of mixing various materials, and in the case of a mixed filament, the phenomenon of breakage due to insufficient bonding between the mixed materials can be prevented. As a result, even when printing for a long time or printing a composite structure, the filament breakage and nozzle clogging are prevented, enabling it to replace existing PLA-only filaments.

[0055]

[0056] In one embodiment, the PLA powder contains voids, and the shell powder and APP powder can fill the voids. That is, the PLA powder contains a large number of voids, and when the shell powder or APP powder is mixed with the PLA powder, the voids of the PLA are filled with these powder grains, thereby producing a filament with improved mechanical properties such as tensile strength. However, when the shell powder or APP powder is mixed beyond a certain ratio, the remaining amount after eliminating the voids of the PLA acts as an impurity, which may actually reduce the mechanical properties of the non-toxic flame-retardant filament. Therefore, in order to improve the mechanical strength, a specific range of mixing ratios must be satisfied.

[0057]

[0058] In one embodiment, the particle size of the shell powder may be 1 μm to 1 mm. Preferably, the particle size of the shell powder may be 20 μm to 40 μm. Most preferably, the particle size of the shell powder may be 40 μm. The shells may be manufactured to have the same diameter as the powder using an air grinder. If the particle size of the shell powder is smaller than 20 μm, the unique properties of the shell are lost. On the other hand, if the particle size of the shell powder exceeds 40 μm, the shell powder is not inserted into the pores of the PLA, and thus the tensile strength of the blended filament cannot be improved compared to the PLA filament alone. In addition, if the particle size of the shell powder is too large, the nozzle may become clogged when injecting the compounding material during the filament manufacturing process.

[0059]

[0060] In one embodiment, the particle size of the APP powder may be 1 μm to 1 mm. Preferably, the particle size of the APP powder may be 20 μm to 40 μm. Most preferably, the particle size of the APP powder may be 40 μm. The APP powder may be manufactured to have the same diameter using an air grinder. If the particle size of the APP powder is less than 20 μm, there is a problem that the original unique properties are lost, similar to shells. On the other hand, if the particle size of the APP powder exceeds 40 μm, the APP powder is not inserted into the pores of the PLA, and thus the tensile strength of the blended filament cannot be improved compared to the PLA filament alone. In addition, if the particle size of the APP powder is too large, the nozzle may become clogged when injecting the compound material during the filament manufacturing process.

[0061]

[0062] At this time, the more similar the particle sizes of the shell powder and APP powder are, the less likely the nozzle will clog when injecting the compounding material during the filament manufacturing process. Therefore, while shell powder and APP powder can be used with different particle sizes, it is preferable to use the same particle size. Shell powder and APP powder can be made to the same particle size using an air-flow mill, etc.

[0063]

[0064] A method for manufacturing a non-toxic flame-retardant filament according to the present invention includes a step of preparing PLA powder, shell powder and APP powder by powderizing PLA (polylactic acid), shell and APP (ammonium polyphosphate), a step of preparing a mixture by mixing the shell powder and APP powder with the PLA powder, and a step of manufacturing a filament by injecting the mixture.

[0065]

[0066] In one embodiment, the shell powder may be mixed in an amount of 1% to 10% based on the total weight of the mixture, and the APP powder may be mixed in an amount of 1% to 10% based on the total weight of the mixture. If the shell powder and the APP powder are mixed in an amount less than or exceeding the above range to produce a mixed filament, the strength will not be improved compared to a PLA single filament, or the maximum strength will not be obtained for a three-part mixed filament including PLA, shell, and APP. In addition, if the shell powder and the APP powder are mixed in an amount less than the above range, the combustion rate in case of fire will be fast, so that it cannot be used as a flame retardant material, and if it is mixed in an amount of 10% or more, even if the mixed filament catches fire, it will be extinguished immediately, so it is difficult to expect better flame retardant properties even if it is mixed in a ratio exceeding this.

[0067]

[0068] In one embodiment, after the step of powdering PLA, shell, and APP, a step of drying the PLA powder, shell powder, and APP powder to remove moisture may be further included. If the drying step is not included, the binding strength of the raw materials during the mixing step may prevent proper mixing with other materials.

[0069]

[0070] In one embodiment, the step of drying the PLA powder, shell powder, and APP powder to remove moisture may be performed at 50°C to 70°C for 6 to 24 hours. If drying is performed at a temperature lower than 50°C, drying is insufficient due to the low temperature. If drying is performed at a temperature higher than 70°C, the inherent properties of the materials deteriorate, making it difficult to obtain proper properties when printing the mixed filament. In addition, if drying is performed for less than 6 hours, drying is insufficient, and if drying is performed for more than 24 hours, drying is already completed, resulting in losses in terms of time and cost.

[0071]

[0072] In one embodiment, the step of preparing the mixture may be performed at 180°C to 240°C for 1 to 4 hours. If the mixing step is performed at a temperature below 180°C, each material may not be completely melted, preventing smooth mixing. If the mixing step is performed at a temperature exceeding 240°C, there is a possibility of the materials burning, which may cause a problem of deterioration in the properties of the mixed material. In addition, if the mixing step is performed for less than 1 hour, mixing is not completed. If the mixing step is performed for more than 4 hours, additional mixing may occur even after mixing is completed, resulting in loss of time and cost.

[0073]

[0074] In one embodiment, the particle size of the shell powder may be 1 μm to 1 mm, and the particle size of the APP powder may be 1 μm to 1 mm. Preferably, the particle size of the shell powder may be 20 μm to 40 μm, and the particle size of the APP powder may be 20 μm to 40 μm. The shell powder may be manufactured to have the same diameter using an air grinder. If the particle size of the shell powder and the APP powder is less than 20 μm, the inherent physical properties of each material may be destroyed, which may cause a problem in obtaining proper results. On the other hand, if the particle size of the shell powder and the APP powder exceeds 40 μm, the shell powder and the APP powder may be too large to be inserted into the pores of the PLA, and thus the tensile strength of the blended filament may not be improved compared to the PLA filament alone. In addition, if the particle size of the shell powder and the APP powder is too large, the nozzle may become clogged when injecting the blended material during the filament manufacturing process.

[0075] At this time, the more similar the particle sizes of the shell powder and APP powder are, the less likely the nozzle will clog when injecting the compounding material during the filament manufacturing process. Therefore, while shell powder and APP powder can be used with different particle sizes, it is preferable to use the same particle size. Shell powder and APP powder can be made to the same particle size using an air-flow mill, etc.

[0076]

[0077] Hereinafter, the present invention will be described in more detail through examples. These examples are intended to explain the present invention more specifically, but the scope of the present invention is not limited by these examples.

[0078]

[0079] [Preparation] Shell powder, APP powder

[0080] Biodegradable PLA (Hisun Co., Ltd. model name: REVODE 190) (25 kg), shells, and APP were each pulverized to a particle size of 40 μm using an air-flow grinder. PLA powder, shell powder, and APP powder were dried at 60°C for 12 hours to remove moisture.

[0081]

[0082] [Comparative Example 1] PLA single filament

[0083] PLA powder was injected into filament manufacturing equipment (3DK-SJ25) to produce a PLA single filament weighing 2 kg, 350 m in length, and 1.75 mm in diameter.

[0084]

[0085] [Comparative Example 2-1] APP 1% mixed filament

[0086] 9.9 kg of PLA powder and 0.1 kg of APP powder were used for preparation, and mixing was performed at 220°C for 2 hours. The mixed PLA and APP powders were injected using filament manufacturing equipment (3DK-SJ25) to manufacture two types of mixed filaments with a total weight of 2 kg, length of 350 m, diameter of 1.75 mm, and APP mixed at 1% of the total weight.

[0087]

[0088] [Comparative Example 2-2] APP 3% mixed filament

[0089] 9.7 kg of PLA powder and 0.3 kg of APP powder were used for preparation, and mixing was performed at 220°C for 2 hours. The mixed PLA and APP powders were injected using filament manufacturing equipment (3DK-SJ25) to manufacture two types of mixed filaments with a total weight of 2 kg, length of 350 m, diameter of 1.75 mm, and APP mixed at 3% of the total weight.

[0090]

[0091] [Comparative Example 2-3] APP 5% mixed filament

[0092] 9.5 kg of PLA powder and 0.5 kg of APP powder were used for preparation, and mixing was performed at 220°C for 2 hours. The mixed PLA and APP powders were injected using filament manufacturing equipment (3DK-SJ25) to manufacture two types of mixed filaments with a total weight of 2 kg, length of 350 m, diameter of 1.75 mm, and APP mixed at 5% of the total weight.

[0093]

[0094] [Comparative Example 2-4] APP 10 wt% mixed filament

[0095] 9.0 kg of PLA powder and 1.0 kg of APP powder were used for mixing at 220°C for 2 hours. The mixed PLA and APP powders were injected using filament manufacturing equipment (3DK-SJ25) to manufacture two types of mixed filaments with a total weight of 2 kg, length of 350 m, diameter of 1.75 mm, and APP mixed at 10 wt% relative to the total weight.

[0096]

[0097] [Comparative Example 3-1] 1% shell mixed filament

[0098] 9.9 kg of PLA powder and 0.1 kg of shell powder were used for preparation, and mixing was performed at 220°C for 2 hours. The mixed PLA and shell powders were injected using filament manufacturing equipment (3DK-SJ25) to manufacture two types of mixed filaments with a total weight of 2 kg, length of 350 m, diameter of 1.75 mm, and shell content of 1% of the total weight.

[0099]

[0100] [Comparative Example 3-2] 3% shell mixed filament

[0101] 9.7 kg of PLA powder and 0.3 kg of shell powder were used for preparation, and mixing was performed at 220°C for 2 hours. The mixed PLA and shell powder were injected using filament manufacturing equipment (3DK-SJ25) to manufacture two types of mixed filaments with a total weight of 2 kg, length of 350 m, diameter of 1.75 mm, and containing 3 wt% of shell powder relative to the total weight.

[0102]

[0103] [Comparative Example 3-3] 5% shell mixed filament

[0104] 9.5 kg of PLA powder and 0.5 kg of shell powder were used for preparation, and mixing was performed at 220°C for 2 hours. The mixed PLA and shell powder were injected using filament manufacturing equipment (3DK-SJ25) to manufacture two types of mixed filaments with a total weight of 2 kg, length of 350 m, diameter of 1.75 mm, and containing 5 wt% of shell powder relative to the total weight.

[0105]

[0106] [Comparative Example 3-4] 10% shell mixed filament

[0107] 9.0 kg of PLA powder and 1.0 kg of shell powder were used for preparation, and mixing was performed at 220°C for 2 hours. The mixed PLA and shell powders were injected using filament manufacturing equipment (3DK-SJ25) to manufacture two types of mixed filaments with a total weight of 2 kg, length of 350 m, diameter of 1.75 mm, and containing 10 wt% of shell powder relative to the total weight.

[0108]

[0109] [Example 1-1] 5% shell + 1% APP mixed filament

[0110] 9.4 kg of PLA powder, 0.5 kg of shell powder, and 0.1 kg of APP powder were used for mixing at 220°C for 2 hours. The mixed PLA, shell, and APP powders were injected using filament manufacturing equipment (3DK-SJ25) to manufacture a three-type mixed filament with a total weight of 2 kg, a length of 350 m, a diameter of 1.75 mm, and a mixture of shell at 5 wt% and APP at 1 wt% relative to the total weight.

[0111]

[0112] [Example 1-2] 5% shell + 5% APP mixed filament

[0113] 9.0 kg of PLA powder, 0.5 kg of shell powder, and 0.5 kg of APP powder were used for mixing at 220°C for 2 hours. The mixed PLA, shell, and APP powders were injected using filament manufacturing equipment (3DK-SJ25) to manufacture a three-type mixed filament with a total weight of 2 kg, a length of 350 m, a diameter of 1.75 mm, and a mixture of 5 wt% of shell and 10 wt% of APP relative to the total weight.

[0114]

[0115] Figures 1 to 3 are SEM images of Comparative Example 1 (PLA 100%) taken at magnifications of 5,000x, 10,000x, and 20,000x, respectively. Referring to Figures 1 to 3, it can be confirmed that numerous pores exist on the surface of the PLA filament.

[0116] Figures 4 to 6 are SEM images of Comparative Example 3-3 (PLA 95% + shell 5%) taken at magnifications of 5,000x, 10,000x, and 20,000x, respectively. The shell powder filled the pores of the PLA, and the two-type mixed filament showed almost no surface pores.

[0117] Figures 7 to 9 are SEM images of Example 1-1 (PLA 94% + shell 5% + APP 1%) taken at magnifications of 5,000x, 10,000x, and 20,000x, respectively. The shell powder and APP powder filled the pores of the PLA, and almost no surface pores were observed in the three-type mixed filament.

[0118]

[0119] [Characteristic Evaluation 1] Evaluation of Mechanical Properties and Flame Retardancy of Two Types (PLA+APP) Blended Filaments

[0120] The mechanical properties of the filaments were evaluated through a tensile test according to the ASTM E8 standard. The evaluation results are summarized in Table 1. Referring to Table 1, the maximum tensile strength of the filaments increased as the APP mixing ratio increased until the APP mixing ratio was 3% (Comparative Example 2-2). However, when the APP mixing ratio exceeded 3%, the maximum tensile strength of the filaments actually decreased. Similar trends to the maximum tensile strength were observed in Young's modulus, yield strength, breaking strength, and elongation.

[0121]

[0122] Classification (Unit) Comparative Example 1 (PLA) Comparative Example 2-1 (APP 1%) Comparative Example 2-2 (APP 3%) Comparative Example 2-3 (APP 5%) Comparative Example 2-4 (APP 10%) Maximum tensile strength [MPa] 32.16 38.27 39.31 35.07 32.13 Young's modulus [%] 11.32 13.25 13.74 12.27 12.46 Yield strength [MPa] 22.29 27.92 29.71 27.72 26.13 Breaking strength [MPa] 17.73 33.5 133.77 33.01 29.30 Elongation [%] 7.49 7.18 8.315.5 16.59

[0123] The flame retardancy grade of the filament was evaluated by conducting a UL-94 HB flame retardancy test, and the results of five measurements are summarized in Table 2. Referring to Table 2, even if APP was mixed at only 1% (Comparative Example 2-1), it was completely extinguished in the UL-94 HB test, confirming that the flame retardancy properties of the filament mixed with APP were excellent.

[0124]

[0125] Combustion speed (mm / min) Comparative example 1 (PLA) Comparative example 2-1 (APP 1%) Comparative example 2-2 (APP 3%) Comparative example 2-3 (APP 5%) Comparative example 2-4 (APP 10%) 1 time 46.39 Extinguish Extinguish Extinguish Extinguish Extinguish 2 times 41.67 Extinguish Extinguish Extinguish Extinguish Extinguish 3 times 41.67 Extinguish Extinguish Extinguish Extinguish Extinguish 4 times 38.46 Extinguish Extinguish Extinguish Extinguish 5 times 42.06 Extinguish Extinguish Extinguish 5 times Average combustion speed 42.05 Extinguish Extinguish Extinguish HB grade assigned XOOOO

[0126]

[0127] [Characteristic Evaluation 2] Evaluation of Mechanical Properties and Flame Retardancy of Two Types of Blended Filaments (PLA + Shell)

[0128] The mechanical properties of the filaments were evaluated through a tensile test according to the ASTM E8 standard, and the evaluation results are summarized in Table 3. Referring to Table 3, the maximum tensile strength of the filaments increased as the shell mixing ratio increased until the shell mixing ratio was 5% (Comparative Example 3-3), but from the point where it exceeded 5%, the maximum tensile strength of the filaments actually decreased. Similar trends were observed in the Young's modulus and breaking strength as well as the maximum tensile strength.

[0129]

[0130] Classification (Unit) Comparative Example 1 (PLA) Comparative Example 3-1 (Shell 1%) Comparative Example 3-2 (Shell 3%) Comparative Example 3-3 (Shell 5%) Comparative Example 3-4 (Shell 10%) Maximum tensile strength [MPa] 32.16 38.67 44.47 46.61 32.29 Young's modulus [%] 11.32 12.41 13.20 13.75 14.31 Yield strength [MPa] 22.29 28.09 30.09 29.71 26.95 Breaking strength [MPa] 17.73 35.58 40.21 41.50 31.96 Elongation [%] 7.49 6.49 6.47 5.22 518

[0131] The flame retardancy grade of the filament was evaluated by performing the UL-94 HB flame retardancy test, and the results of five measurements are summarized in Table 4. Referring to Table 4, it was confirmed that the filament mixed with shells reduces the combustion speed of the PLA filament, and generally, the combustion speed decreases as the shell ratio increases, and the combustion speed is slowest when the shell mixing ratio is 5% to 10% (Comparative Examples 3-3 and 3-4). In addition, it was confirmed that the HB grade is satisfied when the shell mixing ratio is 1% (Comparative Example 3-1) or higher, and the filament is extinguished when the shell mixing ratio is 10% (Comparative Example 3-4).

[0132]

[0133] Combustion speed (mm / min) Comparative example 1 (PLA) Comparative example 3-1 (shell 1%) Comparative example 3-2 (shell 3%) Comparative example 3-3 (shell 5%) Comparative example 3-4 (shell 10%) 1 time 46.39 37.19 37.19 26.29 Digestion 2 times 41.67 26.89 36.00 36.29 33.58 3 times 41.67 37.19 36.89 36.00 36.29 4 times 38.46 37.19 36.59 34.35 34.88 5 times 42.06 37.19 26.71 32.85 34.09 5 times Average combustion speed 42.05 37.13 36.47 35.16 34.7 1 HB grade assigned XOOOO

[0134]

[0135] [Characteristic Evaluation 3] Evaluation of Mechanical Properties and Flame Retardancy of 3 Types of Blended Filaments (PLA + Shell + APP)

[0136] The optimal blending ratio of PLA, shell, and APP was selected from experimental data of two blended filaments. Shell exhibited the highest mechanical properties at 5%, and APP demonstrated flame retardancy starting at 1%. Therefore, shell was blended at 5%, and APP was blended at 1% or 5%. The mechanical properties of the three blended filaments were evaluated as in Characteristic Evaluation 1 and 2, and the results are summarized in Table 5 below.

[0137] Referring to Table 5, it was confirmed that the Young's modulus and yield strength were higher for the three-type mixed filament (Example 1-1) with 1% APP added than for the two-type mixed filament with 5% shell (Comparative Example 3-3). The maximum tensile strength and breaking strength were confirmed to be lower than for the two-type mixed filament with 5% shell, but higher than for the PLA single filament. On the other hand, the three-type mixed filament with 5% APP added (Example 1-2) showed lower values ​​than for the PLA single filament (Comparative Example 1) in all mechanical properties, including the maximum tensile strength.

[0138]

[0139] Classification (Unit) Comparative Example 1 (PLA) Comparative Example 3-3 (Shell 5%) Example 1-1 (Shell 5% + APP 1%) Example 1-2 (Shell 5% + APP 5%) Maximum tensile strength [MPa] 32.16 46.6 141.28 25.25 Young's modulus [%] 11.32 13.75 14.0 19.89 Yield strength [MPa] 22.29 29.7 130.25 19.49 Breaking strength [MPa] 17.73 41.50 28.6 0 6.12 Elongation [%] 7.49 5.2 26.5 7 6.65

[0140] Flame retardancy properties were evaluated using three types of mixed filaments as in Characteristic Evaluations 1 and 2, and the results are summarized in Table 6 below. Referring to Table 6, in the case of the three types of mixed filament (Example 1) with 1% APP added, the combustion rate was reduced compared to the two types of mixed filament (Comparative Example 3-3) with only 5% shell added, and in the case of the three types of mixed filament (Example 1-2) with 5% APP added, it was confirmed that it was extinguished all five times.

[0141]

[0142] Combustion speed (mm / min) Comparative example 1 (PLA) Comparative example 3-3 (Shell 5%) Example 1-1 (Shell 5% + APP 1%) Example 1-2 (Shell 5% + APP 5%) 1 time 46.39 36.29 29.80 Digestion 2 times 41.67 36.29 33.09 Digestion 3 times 41.67 36.00 33.09 Digestion 4 times 38.46 34.35 33.33 Digestion 5 times 42.06 32.85 33.33 Digestion 5 times Average combustion speed 42.05 35.16 32.53 Digestion HB grade assigned XOOO

[0143] [Characteristic Evaluation 4] Output Characteristics

[0144] Using the blended powder form of Example 1-1, a honeycomb structure was printed using a honeycomb structure manufacturing equipment (C600+). The printing took 7 hours and 20 minutes, and continuous printing was possible without interruption. Therefore, the three-type mixed filament is a suitable replacement for conventional PLA single filament.

[0145]

[0146] The invention is not limited to the above-described embodiments, and those skilled in the art will appreciate that various modifications and variations can be made based on this disclosure. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the claims set forth below but also by equivalents thereof.

Claims

1. PLA (Polylactic acid) powder; shell powder; and A non-toxic flame retardant filament comprising a compound composed of APP (Ammonium polyphosphate) powder.

2. In paragraph 1, The above shell powder is included in an amount of 1% to 10% of the total weight of the above mixture, A non-toxic flame retardant filament characterized in that the APP powder is included in an amount of 1% to 10% of the total weight of the mixture.

3. In paragraph 1, The above PLA powder contains voids, A non-toxic flame retardant filament characterized in that the above shell powder and the above APP powder are filled in the above void.

4. In paragraph 1, A non-toxic flame retardant filament characterized in that the particle size of the above shell powder is 1 μm to 1 mm.

5. In paragraph 1, A non-toxic flame retardant filament characterized in that the particle size of the APP powder is 1 μm to 1 mm.

6. In paragraph 1, A non-toxic flame retardant filament characterized in that the above shell powder contains 92% to 95% of calcium carbonate (CaCO3).

7. A step of preparing PLA powder, shell powder and APP powder by powdering PLA (Polylactic acid), shell and APP (Ammonium polyphosphate); A step of preparing a mixture by mixing the shell powder and the APP powder into the PLA powder; and A method for producing a non-toxic flame-retardant filament, comprising a step of producing a filament by injecting the above mixture.

8. In paragraph 7, The above shell powder is mixed in an amount of 1% to 10% based on the total weight of the above mixture, A method for producing a non-toxic flame-retardant filament, characterized in that the APP powder is mixed in an amount of 1% to 10% based on the total weight of the mixture.

9. In paragraph 7, A method for manufacturing a non-toxic flame-retardant filament, characterized in that after the step of powdering the PLA, shell, and APP, the method further comprises the step of drying the PLA powder, the shell powder, and the APP powder to remove moisture.

10. In paragraph 9, A method for manufacturing a non-toxic flame-retardant filament, characterized in that the step of drying the PLA powder, the shell powder, and the APP powder to remove moisture is performed at 50°C to 70°C for 6 to 24 hours.

11. In paragraph 7, A method for producing a non-toxic flame-retardant filament, characterized in that the step of producing the above mixture is performed at 180°C to 240°C for 1 to 4 hours.

12. In paragraph 7, The particle size of the above shell powder is 1 μm to 1 mm, A method for manufacturing a non-toxic flame-retardant filament, characterized in that the particle size of the APP powder is 1 μm to 1 mm.

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