The method for preparing thermal insulation and flame-retardant bio fillers for resin composites, fillers prepared by the method, and polylactic acid-based thermal insulation and flame-retardant resin composites containing the fillers

Abstract

The present invention provides a method for manufacturing an insulating and flame-retardant filler for resin composites, comprising the steps of: preparing orange peel powder (OP); carbonizing the orange peel to prepare orange peel biochar (OPB); and surface modifying the surface of the orange peel biochar by crosslinking it with calcium ions. Furthermore, by including the manufactured filler, the invention provides an environmentally friendly polylactic acid-based insulating and flame-retardant resin composite that exhibits excellent insulating and flame-retardant properties and excellent biodegradability.

Description

Technology Field

[0001] The present invention relates to a technology for manufacturing functional resin composites, and more specifically, to the manufacture of a resin composite based on a biodegradable resin having excellent thermal insulation and flame retardant properties, and to a technology for manufacturing a biofiller to realize the same. Background Technology

[0002] With the recent increase in interest in biodegradable plastics, polylactic acid resin (PLA) is garnering attention as an eco-friendly material. PLA is produced from renewable raw materials such as corn starch and is widely used in packaging and medical materials. However, due to its high flammability, its application is limited in high-temperature environments, such as those in the electronics and automotive industries. To overcome this, research is being conducted on the development of composite materials utilizing various fillers.

[0003] Previous studies have attempted to improve the mechanical and thermal performance of PLA by applying bio-based fillers such as cellulose and lignin, but existing methods had problems such as minimal reduction in thermal conductivity and hindered biodegradability. In addition, there were limitations in reducing fire risk due to insufficient flame retardant performance. As such, although PLA is environmentally friendly, its industrial application remains limited due to low thermal stability and high flammability. Prior art literature

[0005] Korean Registered Patent No. 10-2754202 (2025.01.08) (PLA-based composite plastic and uses thereof) The problem to be solved

[0006] The present invention is an invention sought to overcome the problems and limitations of the prior art described above, and aims to provide a biofiller that can be applied to a biodegradable, eco-friendly polylactic acid composite material to realize excellent thermal insulation and flame retardant properties.

[0007] In addition, the present invention aims to provide a polylactic acid-based resin composite that is biodegradable and has excellent thermal insulation and flame retardant properties by including the above-mentioned filler. means of solving the problem

[0008] A method for manufacturing an insulating and flame-retardant filler for a resin composite according to one embodiment of the present invention comprises the steps of: preparing orange peel powder (OP); carbonizing the orange peel to prepare orange peel biochar (OPB); and surface modifying the surface of the orange peel biochar by crosslinking it with calcium ions.

[0009] The surface modification step may include: a step of surface-treating the orange peel biochar with an ammonium hydroxide solution to introduce amine groups (-NH2) to the surface of the orange peel biochar; a step of coating the surface-treated orange peel biochar with sodium alginate (SA); and a step of forming cross-links by calcium ions on the surface of the coated orange peel biochar.

[0010] An insulating and flame-retardant filler for a resin composite according to one embodiment of the present invention comprises orange peel biochar particles formed by carbonizing an orange peel; and It contains calcium ions cross-linked to the surface of the orange peel biochar particles.

[0011] The surface of the above orange peel biochar particles may be coated with sodium alginate.

[0012] A polylactic acid-based thermal insulation and flame-retardant resin composite according to one embodiment of the present invention comprises: a polylactic acid (PLA) resin as a matrix; and a filler comprising orange peel biochar particles dispersed within the polylactic acid resin and formed by carbonizing orange peels, and calcium ions cross-linked to the surface of the orange peel biochar particles.

[0013] The above filler may be included in the above composite material in an amount of 2 to 6 w%.

[0014] The above resin composite can have a pellet shape by injection molding the above polylactic acid resin and the above filler mixture using a double screw extruder. Effects of the invention

[0016] According to the present invention, calcium-crosslinked orange peel biochar (CC-OPB) can be used as a filler for polylactic acid (PLA) composite materials to improve thermal insulation performance and heat resistance.

[0017] The porous structure of CC-OPB effectively blocks heat transfer pathways to lower thermal conductivity, and thermal insulation performance can be maximized due to the excellent interfacial adhesion between the filler and the matrix.

[0018] Furthermore, thermal stability is increased through calcium crosslinking, allowing the structural stability of the composite material to be maintained even in high-temperature environments. Through this, the present invention provides an eco-friendly composite material with excellent thermal insulation performance and heat resistance, enabling its utilization in various fields such as the construction, electronics, and automotive industries. Brief explanation of the drawing

[0019] FIG. 1 is a schematic diagram conceptually illustrating a method for manufacturing a polylactic acid-based thermal insulation and flame-retardant resin composite in the form of a filler according to one embodiment of the present invention. Figure 2 shows scanning electron microscope (FE-SEM) images and energy dispersive X-ray spectroscopy (EDS) analysis images of calcium-crosslinked orange peel biochar (CC-OPB) and precursors. Figure 3 is a graph showing the respective analysis results (c, d) by X-ray diffraction (XRD) (a), thermogravimetric analysis (TGA) (b), and Fourier spectroscopy (FT-IR) to analyze the structural characteristics of calcium-crosslinked orange peel biochar (CC-OPB) and its precursor. FIG. 4 is a scanning electron microscope (FE-SEM) image showing the cross-sectional structure of a polylactic acid-based thermal insulation and flame-retardant resin composite according to one embodiment of the present invention. Figure 5 is a graph showing the thermal conductivity characteristics according to the filler content of a PLA resin composite containing an orange peel biochar-based filler according to one embodiment of the present invention. Figure 6 is a photograph showing the flame retardant properties of a polylactic acid-based thermal insulation and flame retardant resin composite according to one embodiment of the present invention. Figure 7 is a photograph showing the biodegradability of a polylactic acid-based thermal insulation and flame-retardant resin composite according to one embodiment of the present invention. Specific details for implementing the invention

[0020] Hereinafter, a method for manufacturing a polylactic acid-based thermal insulation and flame-retardant resin composite according to an embodiment of the present invention will be described in detail with reference to the attached drawings. In this process, the method for manufacturing a filler to be introduced into the resin composite, and the method for manufacturing the filler and the pellet-shaped resin composite produced thereby, will be sufficiently described. The following descriptions are exemplary descriptions intended to explain the embodied aspects of the technical concept of the present invention, and the technical concept of the present invention is not limited by the following descriptions. The technical concept of the present invention may be interpreted and limited only by the claims set forth below.

[0021] Meanwhile, conventional table of contents such as "Examples" are excluded, and contents corresponding to "Examples" are appropriately included in the explanation without a special format to promote a thorough understanding of the invention.

[0022] FIG. 1 is a schematic diagram conceptually illustrating a method for manufacturing a polylactic acid-based thermal insulation and flame-retardant resin composite in the form of a filler according to one embodiment of the present invention.

[0023] The insulating and flame-retardant filler for resin composites according to the present invention is a bio-based filler, specifically manufactured using orange peel biochar, which is a carbonized product of orange peel, as a starting material.

[0024] Referring to FIG. 1, a method for manufacturing a thermal insulation and flame-retardant filler for a resin composite according to one embodiment of the present invention comprises the steps of: preparing orange peel powder (OP); preparing orange peel biochar (OPB); and modifying the surface of the orange peel biochar.

[0025] First, to prepare orange peel powder, the obtained oranges are freeze-dried, and then only the peels are separated and ground. The particle size of the powder can be designed and modified in various ways, taking into account factors such as dispersibility with the resin being mixed.

[0026] When orange peel powder (OP) is prepared, the orange peel powder is pyrolyzed to produce carbonized orange peel biochar (OPB). The heat treatment is carried out at a temperature of approximately 300°C (±10°C) for about one hour.

[0027] When the orange peel biochar in powder form is prepared, a step of modifying the surface of the orange peel biochar is performed. The surface modification step can be completed by sequentially performing an amine group introduction step, a sodium alginate coating step, and a cross-linking step by calcium ions.

[0028] In the above amine group introduction step, ammonium chloride (NH4OH) is added to the orange peel biochar powder to perform an amination treatment. The orange peel biochar powder (OPB-NH2), in which amine (-NH2) is introduced to the surface through the amination treatment, undergoes a process of coating the surface with sodium alginate by mixing it with sodium alginate (SA). The orange peel biochar powder (SA-OPB) coated with sodium alginate can be used to obtain orange peel biochar powder in which calcium ions are introduced to the surface through cross-linking with calcium ions.

[0029] Ultimately, the insulating and flame-retardant filler for resin composites manufactured by the above method comprises orange peel biochar particles formed by carbonizing orange peels and calcium ions cross-linked to the surface of the orange peel biochar particles.

[0030] In addition, the surface of the cross-linked portion of the above-mentioned filler is coated with sodium alginate as described above.

[0031] Referring again to FIG. 1, when a filler is prepared, a thermal insulation and flame-retardant resin composite composition according to one embodiment of the present invention can be prepared by mixing the filler with a resin component.

[0032] As a resin component of the above resin composite composition, the present invention comprises polylactic acid (PLA) resin, which is a biodegradable bio-resin.

[0033] Meanwhile, the above filler is included in the resin composite in an amount of 2 to 6 w%, thereby having sufficient dispersibility while maximizing the thermal insulation and flame retardant properties of the composite.

[0034] When the polylactic acid resin composite composition is prepared by mixing a filler and a resin, a polylactic acid-based thermal insulation and flame-retardant resin composite having a predetermined shape can be manufactured by molding the resin composite composition.

[0035] The above molding can be performed in various ways, and in this embodiment, a resin composite (CC-OPB) having a pellet shape was manufactured by injection molding a mixed composition of the polylactic acid resin and the filler using a double screw extruder.

[0036] The polylactic acid-based thermal insulation and flame-retardant resin composite manufactured by the above method comprises a polylactic acid resin as a matrix and a filler dispersed within the polylactic acid resin.

[0037] The resin composite according to the present invention includes a surface-modified filler, thereby providing excellent filler dispersion within the PLA matrix and creating an environment where microorganisms can easily access due to the porous characteristics of the filler, which can accelerate the biodegradation rate of the resin composite.

[0038] Furthermore, by adding CC-OPB to PLA resin, the thermal conductivity of the PLA composite material can be effectively reduced and the biodegradation rate accelerated. Additionally, the composite material incorporating the filler of the present invention is easily microbially decomposed, and its eco-friendliness can be enhanced compared to conventional PLA. Moreover, the porous structure of CC-OPB improves the thermal insulation and flame retardancy of the composite, allowing for its wide application in various industrial fields.

[0039] The present invention will be explained in more detail below through specific embodiments and experimental examples.

[0040] [Manufacturing of CC-OPB and Composite Materials]

[0041] Calcium-crosslinked orange peel biochar (CC-OPB) was used as a filler to improve the thermal insulation and flame retardancy of PLA. OPB is biochar obtained by pyrolyzing orange peels; after undergoing amination treatment using NH4OH, it was mixed with SA (sodium alginate) to induce crosslinking through calcium ions. Subsequently, the prepared CC-OPB was mixed with a PLA matrix to form composite pellets using a double-screw extruder, and the final composite material was produced through injection molding.

[0042] [CC-OPB Surface Characterization Analysis]

[0043] To analyze the surface characteristics of CC-OPB, FT-IR, XPS, XRD, thermogravimetric analysis (TGA), and scanning electron microscopy (FE-SEM) were performed.

[0044] Figure 2 shows scanning electron microscope (FE-SEM) images and energy dispersive X-ray spectroscopy (EDS) analysis images of calcium-crosslinked orange peel biochar (CC-OPB) and its precursor. Figure 3 shows graphs of the respective analysis results (c, d) by X-ray diffraction (XRD) (a), thermogravimetric analysis (TGA) (b), and Fourier spectroscopy (FT-IR) to analyze the structural characteristics of calcium-crosslinked orange peel biochar (CC-OPB) and its precursor.

[0045] Referring to Figure 2, FT-IR and XPS analysis confirmed that SA and calcium crosslinks were formed on the surface of CC-OPB. Referring to Figure 3, XRD analysis indicated that CC-OPB possessed high structural stability, and TGA analysis confirmed that thermal stability was improved up to 800 °C. In addition, SEM and EDS analysis confirmed the uniform distribution of CC-OPB and the formation of Si-O bonds.

[0046] [Composite Material Cross-sectional Analysis]

[0047] A field-effect scanning electron microscope (FE-SEM) was used to analyze the cross-section of the PLA composite material containing CC-OPB.

[0048] Figure 4 shows scanning electron microscope (FE-SEM) images illustrating the cross-sectional structure of a polylactic acid-based thermal insulation and flame-retardant resin composite according to one embodiment of the present invention. Figure 4 is an image of a cross-section of a PLA composite containing calcium-crosslinked orange peel biochar (CC-OPB) taken with a scanning electron microscope (FE-SEM), and the filler distribution and interfacial adhesion characteristics were analyzed by comparing the cross-sectional structures of pure PLA (a, b), a composite containing OPB (c), a composite containing SA-OPB (d), and a composite containing CC-OPB (e, f).

[0049] Referring to Figure 4, it was confirmed that CC-OPB is uniformly distributed in the PLA matrix and that interfacial adhesion between the filler and the matrix is ​​improved. In particular, it was found that structural stability increased in the 6% CC-OPB / PLA composite material through strong interactions between the fillers.

[0050] [Thermal Conductivity of Composite Materials]

[0051] A field-effect scanning electron microscope (FE-SEM) was used to analyze the cross-section of the PLA composite material containing CC-OPB.

[0052] Figure 5 is a graph showing the thermal conductivity characteristics according to the filler content of a PLA resin composite containing an orange peel biochar-based filler according to one embodiment of the present invention.

[0053] Referring to Figure 5, the experimental results showed that as the proportion of CC-OPB increased, the thermal diffusivity and thermal conductivity decreased, and the lowest thermal conductivity (0.081 W / mK) was recorded in the 6% CC-OPB / PLA composite material. This is attributed to the porous structure of CC-OPB and the improved filler-matrix interfacial adhesion.

[0054] [Composite Material Flame Retardancy Evaluation]

[0055] Figure 6 is a photograph showing the flame retardant properties of a polylactic acid-based thermal insulation and flame retardant resin composite according to one embodiment of the present invention.

[0056] Referring to Figure 6, the flame retardancy was evaluated through a UL94 vertical combustion test, and the 6% CC-OPB / PLA composite material obtained a V-0 grade. This is analyzed to be because flame propagation is delayed and the residue after combustion forms a protective layer, thereby improving flame retardancy. On the other hand, the 4% CC-OPB / PLA composite material obtained a V-1 grade, confirming that the CC-OPB content plays an important role in flame retardancy.

[0057] [Evaluation of Tensile Strength and Strain]

[0058] As a result of evaluating tensile strength and strain, the 6% CC-OPB / PLA composite material exhibited the highest mechanical properties, showing a tensile strength of 52.6 MPa. This is attributed to the strong bonding and uniform distribution between the CC-OPB and PLA matrix. On the other hand, the composite material containing only OPB (4% OPB / PLA) recorded a low tensile strength of 10.3 MPa.

[0059] [Composite Material Biodegradability Evaluation]

[0060] Figure 7 is a photograph showing the biodegradability of a polylactic acid-based thermal insulation and flame-retardant resin composite according to one embodiment of the present invention.

[0061] Referring to Figure 7, a degradation experiment was conducted for 20 days to evaluate the biodegradability of PLA composite materials, and the 6% CC-OPB / PLA composite material showed the highest weight loss rate of 25.1%. This is attributed to the fact that the porous structure of CC-OPB increased microbial accessibility, and the SA and calcium crosslinking promoted biodegradability. On the other hand, pure PLA showed a low weight loss rate of 2.1%, confirming that its biodegradability was limited.

Claims

Claim 1 A method for manufacturing an insulating and flame-retardant filler for resin composites, comprising the steps of: preparing orange peel powder (OP); carbonizing the orange peel to prepare orange peel biochar (OPB); and surface modifying the surface of the orange peel biochar by crosslinking it with calcium ions. Claim 2 A method for manufacturing a thermal insulation and flame-retardant filler for resin composites, wherein, in claim 1, the surface modification step comprises: a step of surface-treating the orange peel biochar with an ammonium hydroxide solution to introduce amine groups (-NH2) to the surface of the orange peel biochar; a step of coating the surface-treated orange peel biochar with sodium alginate (SA); and a step of forming cross-links by calcium ions on the surface of the coated orange peel biochar. Claim 3 An insulating and flame-retardant filler for resin composites comprising orange peel biochar particles formed by carbonizing orange peels; and calcium ions cross-linked to the surface of the orange peel biochar particles. Claim 4 In paragraph 3, the insulating and flame-retardant filler for resin composites is characterized in that the surface of the orange peel biochar particles is coated with sodium alginate. Claim 5 A polylactic acid-based thermal insulation and flame-retardant resin composite comprising: a polylactic acid (PLA) resin as a matrix; and a filler comprising orange peel biochar particles dispersed within the polylactic acid resin and formed by carbonizing orange peels, and calcium ions cross-linked to the surface of the orange peel biochar particles. Claim 6 A polylactic acid-based thermal insulation and flame-retardant resin composite according to claim 5, characterized in that the filler is included in the composite in an amount of 2 to 6 w%. Claim 7 A polylactic acid-based thermal insulation and flame-retardant resin composite according to claim 5, characterized in that the polylactic acid resin and the filler mixture are injection molded using a double screw extruder to form a pellet shape.

Images