Method for recycling blended fiber, and regenerated cellulose and regenerated dialkyl phthalates which are manufactured using same

Abstract

The present invention relates to a method for recycling a blended fiber, and regenerated cellulose and regenerated dialkyl phthalates which are obtained using same so as to have excellent yield, purity and color characteristics, the method comprising the steps of: depolymerizing, with a depolymerization solvent, a blended fiber comprising cotton and a synthetic fiber, so as to prepare a depolymerized product; filtering the depolymerized product so as to obtain regenerated cellulose (r-cellulose); and obtaining regenerated dialkyl phthalates from a filtrate.

Description

Method for recycling blended fibers, regenerated cellulose and regenerated dialkyl phthalate produced thereby

[0001] The present invention relates to a method for recycling blended fibers, and to regenerated cellulose and regenerated dialkyl phthalate obtained thereby, which have improved yield, purity, color, etc.

[0002]

[0003] As plastic recycling becomes more important, the scope of plastics or polymer materials utilized as recycled materials is also expanding. Traditional recycling methods for waste plastics include: ① reusing them for the same or similar purpose after simple pretreatment such as washing; or ② mechanical recycling, or mechanical processing such as extrusion, which transforms waste plastics into polymer chips or pellets for other uses. However, true chemical recycling, distinct from pyrolysis, commonly referred to as chemical recycling, has recently emerged. Unlike conventional pyrolysis, chemical recycling involves sorting waste plastics and chemically treating them to recycle their individual raw materials.

[0004] This method is commonly called solvolysis because it uses a solvent to convert polymers into raw materials. Considering that most solvents used in this process are alcohols such as ethylene glycol (EG) and methanol, it is also called alcoholysis. More specifically, it is also called glycolysis or methanolysis based on the chemical names of each alcohol.

[0005] Compared to the aforementioned traditional methods—reuse and mechanical recycling—the advantages of this solvolysis-based chemical recycling method include the quality benefit of being able to regenerate materials to the same quality as new products, and significant environmental benefits in that it reduces the massive amount of carbon emissions that begin with the extraction of raw materials consumed in the production of new plastics.

[0006] Chemical recycling methods are not applicable to all waste plastics. For chemical recycling to be feasible, the recycling process, such as solvolysis, must first be environmentally friendly and economical. For instance, it is problematic if the chemical recycling process (so-called depolymerization) requires at least more energy than the polymerization process. Furthermore, it is advantageous for the recycled materials to be in a form that can be directly fed into the polymerization process for the same plastic. If the material structure or properties of the recycled raw material differ from those of the original material, new facilities are required to feed it into the existing plastic polymerization process, making it difficult to reduce new plastic production through chemical recycling.

[0007] For example, polyurethane is a plastic that is very easy to recycle chemically, so the urethane bonds can be broken even at temperatures that are not very high. However, the material produced by this process is obtained in a form different from the raw material originally introduced into the urethane polymerization process, so it is considered difficult to recycle.

[0008] In contrast, polyester (e.g., PET (Polyethylene terephthalate)) is considered a very suitable raw material for chemical recycling because the chemical recycling process itself is easy and the resulting materials can be obtained in the same form as the raw material.

[0009] However, even for polyethylene terephthalate (PET), it is generally difficult to obtain feedstock consisting solely of 100% pure waste PET. Typically, the raw materials for PET used in chemical recycling are obtained from bottles or textiles. Bottles contain various polyolefin components, such as polyethylene (PE) and polypropylene (PP), originating from items like bottle caps, while textiles contain large amounts of natural polymer materials used for clothing, such as cotton. In particular, regarding the content of materials other than PET, textiles have a significantly higher concentration compared to bottles. For example, in the case of waste clothing, without a separate collection and sorting / screening process, it is highly likely that approximately 30–50% cotton is mixed in.

[0010] The process troubles that arise when materials are not used in isolation are highly diverse. If adhesive materials are mixed in, blockages in filters or piping can lead to various impairments in process economics. Although the nature of the trouble differs slightly, the chemical recycling of waste textiles can also result in very complex issues.

[0011] The only way to prevent these various problems in advance is sorting. Sorting involves selecting only raw materials with extremely high polyethylene terephthalate (PET) content and feeding them into a chemical recycling process. Consequently, a large number of waste materials with low or at least difficult-to-define PET content must inevitably be disposed of using traditional methods such as landfilling or incineration, making it difficult to pursue eco-friendliness.

[0012] To overcome these drawbacks and achieve complete chemical regeneration, it is first necessary to establish a regeneration method that encompasses the entire composition of raw materials composed of polymers with different chemical structures. To this end, it is crucial to first develop regeneration methods for polymers other than polyethylene terephthalate (PET) for which chemical regeneration methods have not been actively developed or are insufficient.

[0013] As mentioned above, representative polymers other than polyethylene terephthalate (PET) that can be discharged mixed with polyethylene terephthalate (PET) include natural fibers, particularly cotton.

[0014] Based on its chemical structure, cotton can generally be classified as cellulose. Depending on its molecular weight, cellulose can serve as a raw material for clothing, industrial applications, clothing rayon, or paper. Generally, cotton has the highest molecular weight, followed by raw materials for paper or pulp, and finally, raw materials for rayon. Recently, there has been a demand for higher molecular weights in rayon to impart mechanical strength, and thanks to the development of suitable solvents, molecular weights exceeding those of paper-grade cellulose are now being utilized. Representative examples of high-molecular-weight rayon include Tencel, Lyocell, Modal, and Polynosic.

[0015] The best method to remove one material from a mixture of polyethylene terephthalate (PET) and cellulose can be by utilizing the difference in solubility. However, since it is impossible to obtain a level of solubility for separation of both polyethylene terephthalate (PET) and cellulose without using extremely polar solvents, and all available solvents are either ultra-expensive ionic liquids or extremely polar substances such as dimethyl sulfoxide (DMSO) and chloroform, which are expensive materials that can cause health problems for users or serious economic issues, separation using existing commercial solvents (so-called selective dissolution or selective solvation) is still difficult to apply due to economic issues.

[0016] Accordingly, there is a need for a progressive recycling method for synthetic fiber and cotton blend fabrics, which have been utilized in various fields such as clothing and industrial materials, moving beyond existing approaches in terms of economic feasibility, process convenience, and user safety. Furthermore, technologies regarding the conditions for the depolymerization of cotton-polyethylene terephthalate (PET) blended fibers and their utilization after recycling are also required.

[0017]

[0018] Accordingly, the present invention aims to provide a method for recycling a blended fiber including cotton and synthetic fibers.

[0019] In addition, the present invention aims to provide regenerated cellulose and regenerated dialkyl phthalate manufactured according to the above recycling method and having improved yield, purity, and color.

[0020]

[0021] An embodiment of the present invention provides a method for recycling blended fibers, comprising the steps of: depolymerizing a blended fiber comprising cotton and synthetic fibers with a depolymerization solvent to produce a depolymer; filtering the depolymer to obtain regenerated cellulose (r-cellulose); and obtaining regenerated dialkyl phthalate from the filtrate.

[0022] In addition, an embodiment of the present invention provides a regenerated dialkyl phthalate manufactured according to the above method.

[0023]

[0024] According to the present invention, a method for recycling blended fibers including cotton and synthetic fibers can be provided, and the regenerated cellulose and regenerated dialkyl phthalate obtained through this recycling method are excellent in terms of yield, purity, and color.

[0025]

[0026] If it is determined that a detailed description of related known configurations or functions in this specification may obscure the essence of the invention, such detailed description is omitted.

[0027] In this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0028] All numbers and expressions indicating the amounts of components, reaction conditions, etc. described in this specification should be understood as being modified by the term "about" in all cases unless otherwise specified.

[0029] In the following description, the statement that one component is formed above or below another component, or is connected or combined with one another, includes both direct formation, connection, or combination between these components and indirect formation, connection, or combination through the interposition of another component.

[0030] In this specification, when a numerical range with a limited upper limit and a numerical range with a limited lower limit are described to illustrate the size, physical properties, etc. of a component, it should be understood that a numerical range in which these upper and lower limits are combined is also included in the exemplary range of the present invention.

[0031] In this specification, singular expressions should be interpreted to include the singular or plural as interpreted in context unless otherwise specified.

[0032] The present invention is not limited to the contents disclosed below, but can be modified in various forms as long as the essence of the invention is not altered.

[0033]

[0034] Recycling methods for blended fibers

[0035] A method for recycling blended fibers according to an embodiment of the present invention comprises the steps of: preparing a depolymerized product by depolymerizing a blended fiber comprising cotton and synthetic fibers with a depolymerization solvent; obtaining regenerated cellulose (r-cellulose) by filtering the depolymerized product; and obtaining regenerated dialkyl phthalate from the filtrate.

[0036]

[0037] A step of preparing a depolymer by depolymerizing a blend of fibers including cotton and synthetic fibers using a depolymerization solvent.

[0038] A method for recycling a blended fiber according to an embodiment of the present invention comprises the step of producing a depolymerized product by depolymerizing a blended fiber including cotton and synthetic fibers with a depolymerization solvent.

[0039] The above blended fiber includes cotton. The above cotton refers to a fiber drawn from a plant of the Malvaceae family, specifically the genus Cotton (cotton). The above cotton contains 90% to 95% by weight of cellulose, and the cellulose is derived from the cell walls of the cotton. In addition to the cellulose, the above cotton may include other components such as wax, protein, pectin, and fat. In the present invention, the above cotton may include cotton of various colors, such as black, navy, brown, red, and gray.

[0040] The above blended fiber includes synthetic fibers, and the synthetic fibers may include polyethylene terephthalate (PET). In addition, the synthetic fibers may include one or more selected from the group consisting of polyamide, polyurethane, polypropylene, polyethylene, and polyether, in addition to the polyethylene terephthalate. In summary, the synthetic fibers may include one or more selected from the group consisting of polyethylene terephthalate, polyamide, polyurethane, polypropylene, polyethylene, and polyether.

[0041] At this time, the blended fiber may contain 0.1% by weight or more, 1% by weight or more, 2% by weight or more, 3% by weight or more, 4% by weight or more, or 5% by weight or more of the cotton based on the total weight, and may contain 99.9% by weight or less, 99% by weight or less, 98% by weight or less, 97% by weight or less, 96% by weight or less, or 95% by weight or less. For example, the blended fiber may contain 0.1% by weight to 99.9% by weight, 5% by weight to 95% by weight, 20% by weight to 80% by weight, 20% by weight to 60% by weight, 40% by weight to 80% by weight, 20% by weight to 40% by weight, 40% by weight to 60% by weight, or 60% by weight to 80% by weight based on the total weight.

[0042] At this time, the blended fiber may contain the synthetic fiber in an amount of 0.1% or more by weight, 1% or more by weight, 2% or more by weight, 3% or more by weight, 4% or more by weight, or 5% or more by weight based on the total weight, and may contain 99.9% or less by weight, 99% or less by weight, 98% or less by weight, 97% or less by weight, 96% or less by weight, or 95% or less by weight. For example, the blended fiber may contain the synthetic fiber in an amount of 0.1% to 99.9% by weight, 5% to 95% by weight, 20% to 80% by weight, 20% to 60% by weight, 40% to 80% by weight, 20% to 40% by weight, 40% to 60% by weight, or 60% to 80% by weight based on the total weight.

[0043] When a blended fiber in which the cotton and synthetic fiber content is controlled within the corresponding range is depolymerized using a depolymerization solvent, the yield, purity, color, etc. of the final product obtained from the blended fiber can be improved.

[0044] The above depolymerization solvent may be any solvent used in the depolymerization reaction of synthetic fibers, such as glycolysis, hydrolysis, methanolysis, and aminolysis. For example, the depolymerization solvent may include a monoalcohol having 1 to 14 carbon atoms or a polyhydric alcohol having 2 or more carbon atoms. For example, the depolymerization solvent may include a monoalcohol having 1 to 14 carbon atoms, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, 1-unadecanol, 1-dodecanol, 1-tridecanol, and 1-tetradecanol, and may include a polyhydric alcohol having 2 or more carbon atoms, such as ethylene glycol, propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,2-pentanediol, glycerol, erythritol, and sorbitol. More specifically, the depolymerization solvent may be at least one selected from the group consisting of methanol, n-butanol, and ethylene glycol. When the above depolymerization solvent is used, the yield, purity, color, etc. of the final product obtained from the above blended fibers can be improved.

[0045] The total amount of the depolymerization solvent added may be 1, 2, or 3 times the weight of the blended fiber, and may also be 7, 5, or 4 times or less. For example, the amount of the depolymerization solvent added may be 1 to 7 times the weight of the blended fiber, specifically 2 to 5 times, and more specifically 3 to 4 times. When the depolymerization solvent is added in the amount of the added weight, the yield, purity, color, etc. of the final product obtained from the blended fiber may be improved.

[0046] Meanwhile, a depolymerization catalyst may be introduced in the step of preparing the above depolymer. The depolymerization catalyst may be a metal catalyst, for example, a metal salt catalyst or a metallic organic catalyst. Specifically, the depolymerization catalyst may be an acetate, carbonate, oxide, or hydroxide of a metal, and the metal may be an alkali metal, an alkaline earth metal, a transition metal, etc. As a specific example, the depolymerization catalyst includes an acetate of a metal, an anhydride or hydride thereof, and more specifically, it may be one or more selected from the group consisting of zinc acetate, sodium acetate, cobalt acetate, and manganese acetate, or in the form of a hydride or anhydride thereof.

[0047] In addition, the input weight of the catalyst may be 0.01 parts by weight or more, 0.1 parts by weight or more, 0.2 parts by weight or more, or 0.3 parts by weight or more relative to 100 parts by weight of the blended fiber, and may also be 5 parts by weight or less, 1 part by weight or less, 0.7 parts by weight or less, 0.6 parts by weight or less, or 0.5 parts by weight or less. For example, the input weight of the catalyst may be 0.1 to 1 part by weight relative to 100 parts by weight of the blended fiber, and specifically, 0.2 to 0.7 parts by weight. More specifically, the catalyst may be used in an amount of 0.2 to 0.5 parts by weight relative to 100 parts by weight of the blended fiber. By using the catalyst under the corresponding content conditions, the yield, purity, color, etc., of the final product obtained from the blended fiber may be improved.

[0048] The above depolymerization may be performed at a temperature of 180°C or higher, 185°C or higher, 190°C or higher, 195°C or higher, or 200°C or higher, and may be performed at a temperature of 280°C or lower, 270°C or lower, 260°C or lower, 250°C or lower, 240°C or lower, 230°C or lower, or 220°C or lower. For example, the depolymerization may be performed at a temperature of 180°C to 280°C or 200°C to 220°C. By performing the depolymerization under the corresponding temperature conditions, the yield, purity, color, etc. of the final product obtained from the blended fiber may be improved.

[0049] Pretreatment process

[0050] Meanwhile, according to an embodiment of the present invention, prior to performing the step of manufacturing a depolymerized product, a step of pretreating the blended fiber comprising the cotton and synthetic fibers with a pretreatment agent may be further included. In this case, the pretreatment step may be a step of removing impurities including chromophores and polyurethane from the blended fiber.

[0051] The pretreatment agent used for pretreatment of the above-mentioned blended fiber may include at least one selected from the group consisting of an organic solvent, an oxidizing agent, and a reducing agent. Pretreatment may be performed by extracting pigments, dyes, etc. contained in the above-mentioned blended fiber with the organic solvent or decomposing and removing them with the oxidizing agent and / or reducing agent.

[0052] According to the present invention, the organic solvent may include at least one selected from the group consisting of cyclohexanone (CH), ethylene glycol (EG), 1-butanol (1-BD), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAC), dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), benzyl alcohol (BA), toluene, and xylene.

[0053] The organic solvent may have a boiling point of 100°C or higher. Specifically, the organic solvent may have a boiling point of 105°C or higher, 110°C or higher, 115°C or higher, 120°C or higher, 130°C or higher, 150°C or higher, 170°C or higher, 180°C or higher, or 200°C or higher (e.g., 100 to 220°C, 110 to 210°C, 130 to 205°C, 150 to 200°C, or 155 to 190°C).

[0054] According to the present invention, the oxidizing agent may include at least one selected from the group consisting of sodium hypochlorite, potassium hypochlorite, hydrogen peroxide, ozone, and potassium permanganate. Specifically, the oxidizing agent may be sodium hypochlorite.

[0055] Additionally, the reducing agent may include at least one selected from the group consisting of sodium hydrosulfite and thiourea dioxide. Specifically, the reducing agent may be sodium hydrosulfite.

[0056] By pretreating the blended fiber with the above pretreatment agent, the safety of the user can be ensured, damage to the fiber can be prevented, and pigments, dyes, etc. can be efficiently removed.

[0057] The proportion of the pretreatment agent to be added is not particularly limited, but considering process safety, economic feasibility, and foreign substance removal efficiency (decolorization efficiency), it may be added in an amount of 5 to 100 ml per 1 g of the blended fiber. Specifically, it may be 50 to 2,000 parts by weight, 100 to 1,800 parts by weight, 500 to 1,700 parts by weight, 700 to 1,500 parts by weight, 800 to 1,300 parts by weight, or 900 to 1,000 parts by weight, based on 100 parts by weight of the blended fiber.

[0058] According to the present invention, the pretreatment of the blended fiber can be performed at a temperature of 40 to 180°C. Specifically, the pretreatment can be performed at a temperature of 50 to 170°C, 60 to 160°C, 70 to 150°C, 75 to 140°C, or 80 to 135°C. By performing the pretreatment at the above temperature, foreign substances contained in the blended fiber (specifically, cellulose) can be efficiently removed while preventing damage to the blended fiber.

[0059]

[0060] A step of filtering the depolymerized product to obtain regenerated cellulose (r-cellulose).

[0061] A method for recycling a blended fiber according to an embodiment of the present invention includes a step of filtering a depolymerized product to obtain regenerated cellulose (r-cellulose).

[0062] First, the depolymerization product is cooled to a certain temperature. The depolymerization product is cooled to 95°C or lower, 90°C or lower, or 85°C or lower.

[0063] Next, regenerated cellulose is obtained by filtration. Various filtration methods, such as gravity filtration, vacuum filtration, pressure filtration, and membrane filtration, can be applied for the filtration.

[0064] Process for post-processing regenerated cellulose

[0065] Meanwhile, according to an embodiment of the present invention, a process for post-treating the regenerated cellulose obtained by filtration may be included.

[0066] At this time, the post-treatment process can be performed by injecting a post-treatment solvent including a protic or aprotic solvent having a boiling point of 40°C or higher into the regenerated cellulose. As a specific example, the post-treatment solvent can include methanol, ethanol, n-propanol, n-butanol, ethylene glycol, acetone, dimethylformamide, dimethyl sulfoxide, toluene, ethyl acetate, etc. Meanwhile, it is preferable to inject the post-treatment solvent used in the post-treatment process in an amount of 5 to 100 times based on the total weight of the regenerated cellulose.

[0067] Meanwhile, the post-treatment process may be performed at a temperature of 40°C or higher, 50°C or higher, 60°C or higher, 70°C or higher, or 80°C or higher, and may be performed at a temperature of 160°C or lower, 150°C or lower, 140°C or lower, 130°C or lower, or 120°C or lower. For example, the post-treatment process may be performed at a temperature of 40°C to 160°C or at a temperature of 80°C to 120°C. When the post-treatment process is performed under the corresponding temperature conditions, impurities can be separated from the regenerated cellulose, thereby improving the yield, purity, and color of the regenerated cellulose.

[0068] Meanwhile, the post-treatment process may be performed for 1 hour or more, 2 hours or more, 3 hours or more, or 4 hours or more, or 10 hours or less, 9 hours or less, or 8 hours or less. For example, the post-treatment process may be performed for 1 to 10 hours or 4 to 8 hours. When the post-treatment process is performed for the corresponding time, impurities can be separated from the regenerated cellulose, thereby improving the yield, purity, and color of the regenerated cellulose.

[0069] Meanwhile, if the synthetic fiber is polyethylene terephthalate, the post-treatment solvent may be a depolymerization solvent for polyethylene terephthalate. That is, the post-treatment solvent may be the same solvent as the depolymerization solvent used in the step of producing the depolymerized product.

[0070] Process of mercerizing regenerated cellulose

[0071] Meanwhile, according to an embodiment of the present invention, a process for mercerizing the regenerated cellulose may be included. The process for mercerizing the regenerated cellulose comprises immersing the regenerated cellulose in an alkaline solution to mercerize the regenerated cellulose.

[0072] At this time, the alkaline solution may include sodium hydroxide, potassium hydroxide, lithium hydroxide, etc., and the concentration of the alkaline solution may be 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, 10% or more, 11% or more, 12% or more, 13% or more, 14% or more, or 15% or more, and may be 35% or less, 34% or less, 33% or less, 32% or less, 31% or less, 30% or less, 29% or less, 28% or less, 27% or less, 26% or less, or 25% or less. For example, the alkaline solution may include sodium hydroxide, and the concentration of the alkaline solution may be 5% to 35% or 15% to 25%. When an alkaline solution under the corresponding conditions is used, the structure of the regenerated cellulose is rearranged, and the color of the final product may be improved.

[0073] The process of mercerizing the regenerated cellulose may be performed by immersing the regenerated cellulose in an alkaline solution and stirring for 5 minutes or more, 10 minutes or more, 20 minutes or more, 30 minutes or more, or 40 minutes or more, or by stirring for 100 minutes or less, 90 minutes or less, or 80 minutes or less. For example, the process of mercerizing the regenerated cellulose may be performed by immersing the regenerated cellulose in an alkaline solution and stirring for 5 minutes to 100 minutes or 40 minutes to 80 minutes. When the mercerizing process is performed under the above conditions, the structure of the regenerated cellulose is rearranged, so that the color characteristics of the final product, etc., may be improved.

[0074] Step of acetylating regenerated cellulose

[0075] The method for recycling a blended fiber according to an embodiment of the present invention may further include a step of acetylating the regenerated cellulose after performing the step of obtaining the regenerated cellulose.

[0076] The step of acetylating the regenerated cellulose may be performed by immersing the regenerated cellulose in a solution containing acetic acid, acetic anhydride, sulfuric acid, etc., and stirring at a temperature of 20°C to 60°C for 6 to 18 hours. When acetylation is performed under the above conditions, the color of the final product may be improved.

[0077] Step of decolorizing regenerated cellulose with bleach

[0078] The method for recycling a blended fiber according to an embodiment of the present invention may further include a step of decolorizing the regenerated cellulose with a bleaching agent after performing the step of obtaining the regenerated cellulose.

[0079] At this time, the bleaching agent may include at least one selected from the group consisting of hydrogen peroxide, sodium hypochlorite, potassium hypochlorite, potassium permanganate, ozone, and sodium hydrosulfite. The bleaching agent may be in the form of an aqueous solution, and may have a concentration of 1% or more, 2% or more, or 3% or more, and may be 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, or 5% or less. For example, the bleaching agent may be in the form of an aqueous solution, and may have a concentration of 1% to 10%, 3% to 5%, or 8% to 10%. When the bleaching agent has the above concentration, the color characteristics of the final product may be further improved.

[0080] The decolorization may be performed at a temperature of 15°C or higher, or at a temperature of 100°C or lower, 90°C or lower, 80°C or lower, 70°C or lower, 60°C or lower, or 50°C or lower. In addition, the decolorization may be performed for 1 minute or longer, 5 minutes or longer, 10 minutes or longer, 20 minutes or longer, or 30 minutes or longer, and may be performed for 8 hours or shorter, 7 hours or shorter, 6 hours or shorter, 5 hours or shorter, 4 hours or shorter, 3 hours or shorter, or 2 hours or shorter. For example, the decolorization may be performed at a temperature of 15°C to 100°C or 15°C to 50°C, for 1 minute to 8 hours, or 1 minute to 2 hours. When the decolorization is performed under the above conditions, the color characteristics of the final product are improved.

[0081] When decolorization is complete, it is desirable to filter the solution containing regenerated cellulose to recover the regenerated cellulose, wash it with water, and dry it under vacuum.

[0082]

[0083] Step of obtaining regenerated dialkyl phthalate from the filtrate

[0084] A method for recycling a blended fiber according to an embodiment of the present invention includes a step of obtaining a regenerated dialkyl phthalate from a filtrate.

[0085] The above filtrate may refer to a filtrate obtained by filtering regenerated cellulose in the step of obtaining the regenerated cellulose (r-cellulose).

[0086] In the step of obtaining the above-mentioned regenerated dialkyl phthalate, the filtrate is concentrated using a reduced pressure distiller to remove excess unreacted methanol, and then fractionally distilled to obtain the regenerated dialkyl phthalate.

[0087] The step of obtaining the above-mentioned regenerated dialkyl phthalate may include a process of distillation under reduced pressure using a vacuum distillation unit, wherein moisture or residual solvent in the filtrate can be removed and concentrated through the distillation under reduced pressure. Since unreacted solvents such as methanol, ethanol, and ethylene glycol may remain in the filtrate, it is necessary to remove these from the filtrate prior to the subsequent step.

[0088] The reduced pressure distillation for removing the unreacted solvent can be performed at a known appropriate temperature to improve the purity of the regenerated dialkyl phthalate. For example, the reduced pressure distillation for removing the unreacted solvent can be performed at 190°C or lower, 180°C or lower, or 170°C or lower, and can also be performed at 60°C or higher, 70°C or higher, 80°C or higher, or 90°C or higher. Specifically, the temperature during the reduced pressure distillation for removing the unreacted solvent can be 60°C to 190°C or 80°C to 180°C. As a more specific example, the distillation for removing the unreacted solvent can be performed at a temperature of 90°C to 170°C. The pressure during the reduced pressure distillation for removing the unreacted solvent may be, for example, 0.1 Torr to 760 Torr, 0.1 Torr to 200 Torr, or 0.5 Torr to 30 Torr, and more specifically, the reduced pressure distillation may be performed under stepwise reduced pressure conditions from 760 torr to 0.8 torr.

[0089] Meanwhile, the step of obtaining the regenerated dialkyl phthalate may include a fractional distillation step. The regenerated dialkyl phthalate may be obtained by performing a reduced pressure distillation step and performing a fractional distillation step on the concentrated filtrate. Alternatively, the step of obtaining the regenerated dialkyl phthalate may include a step of adding water and an adsorbent to the concentrated filtrate and performing adsorption. For example, a carbon-based inorganic adsorbent may be used as the adsorbent, and specifically, activated carbon or the like may be used. The adsorption step may be performed under stirring at a temperature of 75°C to 95°C or 80°C to 90°C for 1 to 4 hours or 1 to 3 hours. After performing the adsorption step on the filtrate, the regenerated dialkyl phthalate may be obtained by performing a crystallization step.

[0090]

[0091] According to the method for recycling blended fibers of the present invention, the recovery rate of regenerated cellulose according to the following formula 1 may be 90% or more, 91% or more, 92% or more, 93% or more, or 94% or more, and may be 100% or less. For example, the regenerated cellulose may have a recovery rate of 90% to 100% or 94% to 100% according to the following formula 1.

[0092] [Formula 1]

[0093]

[0094] As the recovery rate of the above regenerated cellulose is within the above range, regenerated cellulose can be provided at a high yield from the blended fiber.

[0095] According to the method for recycling a blended fiber of the present invention, the yield of the regenerated dialkyl phthalate according to the following formula 2 may be 85% or more, 86% or more, 87% or more, 88% or more, 89% or more, or 90% or more, and may be 100% or less, 99% or less, 98% or less, or 97% or less. For example, the regenerated dialkyl phthalate may have a yield of 85% to 100% or 90% to 97% according to the following formula 2.

[0096] [Formula 2]

[0097]

[0098] As the recovery rate of the yield of the above-mentioned regenerated dialkyl phthalate is within the above range, regenerated dialkyl phthalate can be provided at a high yield from the blended fiber.

[0099]

[0100] regenerated cellulose

[0101] According to an embodiment of the present invention, regenerated cellulose is provided through the above recycling method.

[0102] The regenerated cellulose may have a degree of polymerization (DP) according to TAPPI T230 of 200 or more, 300 or more, 400 or more, 410 or more, 420 or more, 430 or more, 440 or more, 450 or more, 460 or more, 470 or more, 480 or more, 490 or more, 500 or more, 510 or more, 520 or more, or 530 or more, or 800 or less, 790 or less, 780 or less, 770 or less, or 760 or less. For example, the regenerated cellulose may have a degree of polymerization (DP) according to TAPPI T230 of 200 to 800 or 530 to 760. When the degree of polymerization of the regenerated cellulose is within the above range, the mechanical properties of the final product, such as paper, manufactured using the regenerated cellulose are excellent.

[0103] The regenerated cellulose may contain a synthetic fiber-derived component containing polyethylene terephthalate (PET) in the regenerated cellulose in an amount of 100 ppm or less and 0 ppm or more. For example, the regenerated cellulose may contain a synthetic fiber-derived component containing polyethylene terephthalate (PET) in the regenerated cellulose in an amount of 0 ppm to 100 ppm. When the content of the synthetic fiber-derived component containing polyethylene terephthalate (PET) in the regenerated cellulose is controlled within the range, the mechanical properties of final products such as paper manufactured using the regenerated cellulose are excellent.

[0104] The above regenerated cellulose has a molecular weight of 4.0×10 4 g / mol or more, 4.5×10 4 g / mol or more, 5.0×10 4 g / mol or more or 5.2×10 4 g / mol or more, and may be 8.0×10 4 g / mol or less, 7.5×10 4 g / mol or less, 7.0×10 4 g / mol or less or 6.7×10 4 g / mol or less. For example, the regenerated cellulose has a molecular weight of 4.0×10 4 g / mol to 8.0×10 4 g / mol or 5.2×10 4 g / mol to 6.7×10 4 g / mol. When the molecular weight of the regenerated cellulose satisfies the range, the mechanical properties of final products, such as paper, manufactured using the regenerated cellulose can be improved.

[0105] The regenerated cellulose may have a Color L value of 70 or more and 99 or less as measured by a colorimeter. The regenerated cellulose may have a Color L value of 70 to 99, 70 to 95, 70 to 75, 75 to 80, 80 to 85, 85 to 90, 90 to 95, 70 to 80, 80 to 90, or 80 to 95 as measured by a colorimeter. As the Color L value of the regenerated cellulose satisfies the above range, the color of the final product, such as paper, manufactured using the regenerated cellulose is appropriate.

[0106]

[0107] Recycled dialkyl phthalate

[0108] According to an embodiment of the present invention, a regenerated dialkyl phthalate is provided through the recycling method.

[0109] The above dialkyl phthalate may refer to dialkyl terephthalate. Specifically, the recycled dialkyl phthalate may include recycled dimethyl terephthalate (r-DMT), recycled dibutyl terephthalate (r-DBTP), recycled bis(2-hydroxyethyl) terephthalate (r-BHET), and the like.

[0110] The above recycled dialkyl phthalate may have a purity of 90% or more, 95% or more, 96% or more, 97% or more, or 100% or less. For example, the above recycled dialkyl phthalate may have a purity of 90% to 100% or 97% to 100%. As the purity of the above recycled dialkyl phthalate satisfies the corresponding range, a recycled dialkyl phthalate having a high purity can be provided.

[0111] The above-mentioned recycled dialkyl phthalate may have a yellowness index of 1 or more, 2 or more, and 10 or less, 9 or less, 8 or less, 7 or less, or 6 or less as measured by a colorimeter. For example, the above-mentioned recycled dialkyl phthalate may have a yellowness index of 1 to 10, or 2 to 6 as measured by a colorimeter. As the yellowness index of the above-mentioned recycled dialkyl phthalate satisfies the corresponding range, a recycled dialkyl phthalate having an appropriate color can be provided.

[0112] Meanwhile, the above-mentioned regenerated dialkyl phthalate can be used in various ways, such as by hydrolysis and as a raw material for manufacturing regenerated terephthalic acid.

[0113]

[0114] The above contents are explained in more detail with the following examples. However, the following examples are only for illustrating the present invention, and the scope of the examples is not limited to these examples.

[0115]

[0116] Example

[0117] Example 1

[0118] <Example 1-1>

[0119] In a 1 L high-pressure reactor, 100 g of a black cotton 5 wt% / PET 95 wt% blended fiber, 400 ml of methanol, and 100 mg of Zn(OAc)2·2H2O were added and reacted at 200 ° C. for 4 hours. The reaction solution was cooled to 50 ° C. and filtered to obtain brown regenerated cellulose (r-cellulose). The obtained regenerated cellulose (r-cellulose) was washed three times with 100 ml of methanol and dried at 100 ° C. for 6 hours. Meanwhile, the filtrate was concentrated in a reduced pressure distillation unit to remove excess unreacted methanol, and then fractionally distilled to obtain regenerated dimethyl terephthalate (r-DMT).

[0120]

[0121] <Example 1-2>

[0122] Regenerated cellulose (r-cellulose) and regenerated dimethyl terephthalate (r-DMT) were obtained through the same process as Example 1-1, except that a blended fiber of 30 wt% black cotton / 70 wt% PET (cut to about 1×1 cm) was used.

[0123]

[0124] <Example 1-3>

[0125] Regenerated cellulose (r-cellulose) and regenerated dimethyl terephthalate (r-DMT) were obtained through the same process as Example 1-1, except that a blended fiber of 50 wt% black cotton / 50 wt% PET (cut to about 1×1 cm) was used.

[0126]

[0127] <Example 1-4>

[0128] Regenerated cellulose (r-cellulose) and regenerated dimethyl terephthalate (r-DMT) were obtained through the same process as Example 1-1, except that a blended fiber of 70 wt% black cotton / 30 wt% PET (cut to about 1×1 cm) was used.

[0129]

[0130] <Example 1-5>

[0131] Regenerated cellulose (r-cellulose) and regenerated dimethyl terephthalate (r-DMT) were obtained through the same process as Example 1-1, except that a blended fiber of 95 wt% black cotton / 5 wt% PET (cut to about 1×1 cm) was used.

[0132]

[0133] <Example 1-6>

[0134] In a 1 L high-pressure reactor, 100 g of a black cotton 5 wt% / PET 95 wt% blended fiber, 400 ml of n-butanol, and 100 mg of Zn(OAc)2·2H2O were charged and reacted at 220 ° C. for 4 hours. The reaction solution was cooled to room temperature and filtered to obtain brown regenerated cellulose (r-cellulose). The obtained regenerated cellulose (r-cellulose) was washed three times with 100 ml of n-butanol and then dried at 100 ° C. for 6 hours. Meanwhile, the filtrate was concentrated in a reduced pressure distillation unit to remove excess unreacted butanol, and then fractionally distilled to obtain regenerated dibutyl terephthalate (r-DBTP).

[0135]

[0136] <Example 1-7>

[0137] Regenerated cellulose (r-cellulose) and regenerated dibutyl terephthalate (r-DBTP) were obtained through the same process as in Example 1-6, except that a blended fiber of 30 wt% black cotton / 70 wt% PET (cut to about 1×1 cm) was used.

[0138]

[0139] <Example 1-8>

[0140] Regenerated cellulose (r-cellulose) and regenerated dibutyl terephthalate (r-DBTP) were obtained through the same process as in Example 1-6, except that a blended fiber of 50 wt% black cotton / 50 wt% PET (cut to about 1×1 cm) was used.

[0141]

[0142] <Example 1-9>

[0143] Regenerated cellulose (r-cellulose) and regenerated dibutyl terephthalate (r-DBTP) were obtained through the same process as Example 1-6, except that a blended fiber of 70 wt% black cotton / 30 wt% PET (cut to about 1×1 cm) was used.

[0144]

[0145] <Example 1-10>

[0146] Regenerated cellulose (r-cellulose) and regenerated dibutyl terephthalate (r-DBTP) were obtained through the same process as in Example 1-6, except that a blended fiber of 95 wt% black cotton and 5 wt% PET (cut to about 1×1 cm) was used.

[0147]

[0148] <Example 1-11>

[0149] In a 1 L high-pressure reactor, 100 g of a black cotton 5 wt% / PET 95 wt% blended fiber, 400 ml of ethylene glycol, and 100 mg of Zn(OAc)2·2H2O were added and reacted at 200 ° C. for 4 hours. The reaction solution was cooled to 80 ° C. and filtered to obtain brown regenerated cellulose (r-cellulose). The obtained regenerated cellulose (r-cellulose) was washed three times with water and 100 ml of acetone, and then dried at 100 ° C. for 6 hours. Meanwhile, the filtrate was concentrated in a reduced pressure distillation unit to remove excess unreacted ethylene glycol, and then 200 ml of water was added. Activated carbon was added, stirred at 85 ° C. for 2 hours, filtered, and recrystallized to obtain regenerated bis(2-hydroxyethyl) terephthalate (r-BHET).

[0150]

[0151] <Example 1-12>

[0152] Regenerated cellulose (r-cellulose) and regenerated bis(2-hydroxyethyl) terephthalate (r-BHET) were obtained through the same process as Example 1-11, except that a blended fiber of 30 wt% black cotton / 70 wt% PET (cut to about 1×1 cm) was used.

[0153]

[0154] <Example 1-13>

[0155] Regenerated cellulose (r-cellulose) and regenerated bis(2-hydroxyethyl) terephthalate (r-BHET) were obtained through the same process as Example 1-11, except that a blended fiber of 50 wt% black cotton / 50 wt% PET (cut to about 1×1 cm) was used.

[0156]

[0157] <Example 1-14>

[0158] Regenerated cellulose (r-cellulose) and regenerated bis(2-hydroxyethyl) terephthalate (r-BHET) were obtained through the same process as Example 1-11, except that a blended fiber of 70 wt% black cotton / 30 wt% PET (cut to about 1×1 cm) was used.

[0159]

[0160] <Example 1-15>

[0161] Regenerated cellulose (r-cellulose) and regenerated bis(2-hydroxyethyl) terephthalate (r-BHET) were obtained through the same process as Example 1-11, except that a blended fiber of 95 wt% black cotton and 5 wt% PET (cut to about 1×1 cm) was used.

[0162]

[0163] <Examples 1-16 to 1-30>

[0164] Regenerated cellulose (r-cellulose) and dialkyl phthalate were obtained through the same process as in Examples 1-1 to 1-15, except that a navy colored blended fiber instead of a black blended fiber was used.

[0165]

[0166] Example 2

[0167] <Example 2-1>

[0168] 4.0 g of regenerated cellulose (r-cellulose) of Example 1-1 was added to 200 ml of a 20% NaOH aqueous solution and stirred at room temperature for 1 hour. After filtration, the obtained cotton was washed with a filter and water and then vacuum-dried to obtain mercerized regenerated cellulose.

[0169] 0.5 g of the above mercerized regenerated cellulose was mixed with 25 mL of acetic acid, 3.0 g of acetic anhydride, and 50 mg of sulfuric acid, and stirred at 40°C for 12 hours. The reaction product was added dropwise to water to obtain a precipitate, which was filtered and washed with water and vacuum-dried to obtain acetylated regenerated cellulose (r-cellulose).

[0170]

[0171] <Examples 2-2 to 2-30>

[0172] Acetylated regenerated cellulose (r-cellulose) was obtained by performing the same procedure as in Example 2-1, except that the regenerated cellulose (r-cellulose) of Examples 1-2 to 1-30 was used instead of the regenerated cellulose (r-cellulose) of Example 1-1.

[0173]

[0174] <Example 1>

[0175] 1) Recovery rate of regenerated cellulose

[0176] The recovery rate of regenerated cellulose of Examples 2-1 to 2-30 was calculated using the following formula using the weight (g) of the cotton introduced into the reaction and the weight (g) of the recovered regenerated cellulose (r-Cellulose).

[0177] [Formula 1]

[0178]

[0179]

[0180] 2) Degree of polymerization (DP) of regenerated cellulose

[0181] The degree of polymerization of the regenerated cellulose of Examples 2-1 to 2-30 was calculated by measuring the viscosity in CED (Cupriethylene diamine) according to TAPPI T230.

[0182]

[0183] 3) PET depolymerization component content in regenerated cellulose (ppm)

[0184] The regenerated cellulose of Examples 2-1 to 2-30 was freeze-pulverized, cut, and diluted in methanol to 1 wt / v%. The filtrate was syringe filtered, and the remaining PET depolymerization component in the surface was quantified after HPLC measurement.

[0185]

[0186] 4) Molecular weight of regenerated cellulose

[0187] The molecular weight of the regenerated cellulose obtained in Examples 2-1 to 2-30 was measured through gel permeation chromatography (GPC, Chloroform / o-CP eluent) using chloroform (CHCl3) as the main solvent and orthochlorophenol (o-CP) added.

[0188]

[0189] 4) Dialkyl phthalate yield

[0190] The yield of the regenerated dialkyl phthalate obtained in Examples 1-1 to 1-30 was calculated using the following formula using the amount (mol) of polyethylene terephthalate (PET) introduced into the reaction and the amount (mol) of the dialkyl phthalate obtained after depolymerization.

[0191] [Formula 2]

[0192]

[0193]

[0194] 5) Dialkyl phthalate purity

[0195] The regenerated dialkyl phthalate obtained in Examples 1-1 to 1-30 was diluted to 1 wt / v% in methanol and then the purity was measured using high-performance liquid chromatography (HPLC).

[0196]

[0197] 6) Yellowness Index (YID)

[0198] The regenerated dialkyl phthalate obtained in Examples 1-1 to 1-30 was diluted to 10 wt% in a solvent and the yellowness index (YID) was measured using a colorimeter.

[0199]

[0200] Alcohol (product) Raw material Fiber color L / a / b Example Regenerated cellulose Example Regenerated dialkyl phthalate Recovery rate (%) DPPET derived depolymerization component (ppm) Molecular weight Mw (g / mol) Yield (%) Purity (%) Color YID Methanol (DMT) Black 33.0 / 2.20 / -0.152-194620 N.D. 6.1Ⅹ10 4 1-19599.23.72-295660N.D.6.3Ⅹ10 4 1-29298.94.52-395750N.D.6.7Ⅹ10 4 1-39598.74.52-497640N.D.6.1Ⅹ10 4 1-49499.14.82-594590N.D.5.9Ⅹ10 4 1-59698.93.5 Butanol (DBTP)2-695550 N.D.5.7Ⅹ10 4 1-69599.23.82-794580N.D.5.4Ⅹ10 4 1-79298.93.62-896500N.D.5.2Ⅹ10 4 1-89598.72.72-997550N.D.5.5Ⅹ10 4 1-99499.13.62-1095590N.D.5.7Ⅹ10 4 1-109698.93.5 Ethylene glycol (BHET) 2-1195710 N.D. 6.3Ⅹ10 4 1-119299.43.32-1294620N.D.6.1Ⅹ10 41-129199.35.82-1396650N.D.6.0Ⅹ10 4 1-139299.14.72-1496580N.D.5.8Ⅹ10 4 1-149299.43.62-1595630N.D.6.1Ⅹ10 4 1-159099.04.5 Methanol (DMT) Navy 33.2 / 0.31 / -5.002-1696640 N.D. 6.1Ⅹ10 4 1-169599.13.22-1797690N.D.5.4Ⅹ10 4 1-179297.94.12-1897720N.D.6.3Ⅹ10 4 1-189499.23.62-1995600N.D.5.7Ⅹ10 4 1-199498.93.52-2096620N.D.6.1Ⅹ10 4 1-209599.24.0 Butanol (DBTP) 2-2196570 N.D. 5.8Ⅹ10 4 1-219598.73.62-2295580N.D.5.8Ⅹ10 4 1-229799.53.22-2394540N.D.5.4Ⅹ10 4 1-239499.22.82-2497550N.D.5.5Ⅹ10 4 1-249599.33.52-2596570N.D.5.8Ⅹ10 4 1-259599.02.9 Ethylene glycol (BHET) 2-2695690 N.D.6.2Ⅹ10 4 1-269299.33.22-2795650N.D.6.0Ⅹ10 4 1-279099.23.62-2897660N.D.6.3Ⅹ10 4 1-289299.04.72-2995570N.D.5.8Ⅹ10 4 1-299299.24.52-3096650N.D.6.0Ⅹ10 4 1-309199.43.9

[0201] Referring to Table 1 above, the recovery rate of regenerated cellulose (r-Cellulose) of Examples 2-1 to 2-30 is 64% to 97%, the degree of polymerization (DP) is 500 to 750, and the molecular weight is 5.2×10 4 g / mol to 6.7×10 4 It was confirmed that the yield of the regenerated dialkyl phthalate of Examples 1-1 to 1-30 was 90% to 97%, the purity was 97.9% to 99.6%, and the yellowness was 2.7 to 5.8.

[0202]

[0203] Example 3

[0204] <Example 3-1> (Neutral)

[0205] In a 1 L high-pressure reactor, 100 g (0.51 mol) of the regenerated dimethyl terephthalate (r-DMT) obtained in Example 1-2 and 400 ml (22.20 mol) of water were added and reacted at 200 ° C. for 6 hours. The reaction solution was cooled to room temperature, filtered, washed with methanol, and dried at 100 ° C. for 6 hours to produce regenerated terephthalic acid (r-TPA). The yield and quality of the obtained regenerated terephthalic acid (r-TPA) are shown in Table 2.

[0206]

[0207] <Example 3-2> (Neutral)

[0208] In a 1 L high-pressure reactor, 100 g (0.36 mol) of the regenerated dibutyl terephthalate (r-DBTP) obtained in Example 1-7 and 400 ml (22.20 mol) of water were charged and reacted at 220 ° C. for 6 hours. The reaction solution was cooled to room temperature, filtered, washed with butanol, and dried at 100 ° C. for 6 hours to produce regenerated terephthalic acid (r-TPA). The yield and quality of the obtained regenerated terephthalic acid (r-TPA) are shown in Table 2.

[0209]

[0210] <Example 3-3> (Neutral)

[0211] In a 1 L high-pressure reactor, 100 g (0.39 mol) of the regenerated bis(2-hydroxyethyl) terephthalate (r-BHET) obtained in Example 1-12 and 400 ml (22.20 mol) of water were added and reacted at 200 ° C. for 6 hours. The reaction solution was cooled to room temperature, filtered, washed with butanol, and dried at 100 ° C. for 6 hours to produce regenerated terephthalic acid (r-TPA). The yield and quality of the obtained regenerated terephthalic acid (r-TPA) are shown in Table 2.

[0212]

[0213] <Example 3-4> (Alkaline)

[0214] In a 1 L flask, 100 g (0.51 mol) of the regenerated dimethyl terephthalate (r-DMT) obtained in Example 1-2, 51 g (1.28 mol) of NaOH, and 400 ml of water were added and reacted at 100 ° C. for 4 hours. The reaction solution was cooled to room temperature and neutralized with hydrochloric acid. After filtering, it was washed three times with water and dried at 100 ° C. for 6 hours to produce regenerated terephthalic acid (r-TPA). The yield and quality of the obtained regenerated terephthalic acid (r-TPA) are shown in Table 2.

[0215]

[0216] <Example 3-5> (Alkaline)

[0217] In a 1 L high-pressure reactor, 100 g (0.36 mol) of the regenerated dibutyl terephthalate (r-DBTP) obtained in Example 1-7, 36 g (0.90 mol) of NaOH, and 400 ml of water were added and reacted at 100 ° C. for 8 hours. The reaction solution was cooled to room temperature and neutralized with hydrochloric acid. After filtering, the solution was washed three times with water and dried at 100 ° C. for 6 hours to produce regenerated terephthalic acid (r-TPA). The yield and quality of the obtained regenerated terephthalic acid (r-TPA) are shown in Table 2.

[0218]

[0219] <Example 3-6> (Alkaline)

[0220] In a 1 L high-pressure reactor, 100 g (0.39 mol) of the regenerated bis(2-hydroxyethyl) terephthalate (r-BHET) obtained in Example 1-12, 39 g (0.98 mol) of NaOH, and 400 ml of water were charged and reacted at 100 ° C. for 4 hours. The reaction solution was cooled to room temperature and neutralized with hydrochloric acid. After filtering, it was washed three times with water and dried at 100 ° C. for 6 hours to produce regenerated terephthalic acid (r-TPA). The yield and quality of the obtained regenerated terephthalic acid (r-TPA) are shown in Table 2.

[0221]

[0222] <Example 3-7> (Neutral)

[0223] In a 1 L high-pressure reactor, 100 g (0.51 mol) of the regenerated dimethyl terephthalate (r-DMT) obtained in Example 1-5 and 400 ml (22.20 mol) of water were charged and reacted at 200 ° C. for 6 hours. The reaction solution was cooled to room temperature, filtered, washed with methanol, and dried at 100 ° C. for 6 hours to produce regenerated terephthalic acid (r-TPA). The yield and quality of the obtained regenerated terephthalic acid (r-TPA) are shown in Table 2.

[0224]

[0225] <Example 3-8> (Neutral)

[0226] In a 1 L high-pressure reactor, 100 g (0.36 mol) of the regenerated dibutyl terephthalate (r-DBTP) obtained in Example 1-10 and 400 ml (22.20 mol) of water were charged and reacted at 220 ° C. for 6 hours. The reaction solution was cooled to room temperature, filtered, washed with butanol, and dried at 100 ° C. for 6 hours to produce regenerated terephthalic acid (r-TPA). The yield and quality of the obtained regenerated terephthalic acid (r-TPA) are shown in Table 2.

[0227]

[0228] <Example 3-9> (Neutral)

[0229] In a 1 L high-pressure reactor, 100 g (0.39 mol) of the regenerated bis(2-hydroxyethyl) terephthalate (r-BHET) obtained in Example 1-15 and 400 ml (22.20 mol) of water were charged and reacted at 200 ° C. for 6 hours. The reaction solution was cooled to room temperature, filtered, washed with butanol, and dried at 100 ° C. for 6 hours to produce regenerated terephthalic acid (r-TPA). The yield and quality of the obtained regenerated terephthalic acid (r-TPA) are shown in Table 2.

[0230]

[0231] <Example 3-10> (Alkaline)

[0232] In a 1 L flask, 100 g (0.51 mol) of the regenerated dimethyl terephthalate (r-DMT) obtained in Example 1-5, 51 g (1.28 mol) of NaOH, and 400 ml of water were added and reacted at 100 ° C. for 4 hours. The reaction solution was cooled to room temperature and neutralized with hydrochloric acid. After filtering, the solution was washed three times with water and dried at 100 ° C. for 6 hours to produce regenerated terephthalic acid (r-TPA). The yield and quality of the obtained regenerated terephthalic acid (r-TPA) are shown in Table 2.

[0233]

[0234] <Example 3-11> (Alkaline)

[0235] In a 1 L high-pressure reactor, 100 g (0.36 mol) of the regenerated dibutyl terephthalate (r-DBTP) obtained in Example 1-10, 36 g (0.90 mol) of NaOH, and 400 ml of water were charged and reacted at 100 ° C. for 8 hours. The reaction solution was cooled to room temperature and neutralized with hydrochloric acid. After filtering, the solution was washed three times with water and dried at 100 ° C. for 6 hours to produce regenerated terephthalic acid (r-TPA). The yield and quality of the obtained regenerated terephthalic acid (r-TPA) are shown in Table 2.

[0236]

[0237] <Example 3-12> (Alkaline)

[0238] In a 1 L high-pressure reactor, 100 g (0.39 mol) of the regenerated bis(2-hydroxyethyl) terephthalate (r-BHET) obtained in Example 1-15, 39 g (0.98 mol) of NaOH, and 400 ml of water were added and reacted at 100 ° C. for 4 hours. The reaction solution was cooled to room temperature and neutralized with hydrochloric acid. After filtering, the solution was washed three times with water and dried at 100 ° C. for 6 hours to produce regenerated terephthalic acid (r-TPA). The yield and quality of the obtained regenerated terephthalic acid (r-TPA) are shown in Table 2.

[0239]

[0240] <Example 2>

[0241] 1) TPA purity

[0242] The purity (%) of the regenerated terephthalic acid (r-TPA) obtained in Examples 3-1 to 3-12 above is confirmed by diluting it in a solvent and measuring it by HPLC.

[0243]

[0244] 2) Color b measurement

[0245] The Color b value of the powder TPA of the regenerated terephthalic acid (r-TPA) obtained in Examples 3-1 to 3-12 was measured using a colorimeter.

[0246]

[0247] Example Yield (%) Purity (%) Color b3-19599.21.73-29099.51.33-39899.41.23-49799.81.43-59899.81.23-69799.51.13-79499.71.43-89599.41.73-99599.31.33-109799.51.63-119899.81.33-129699.41.5

[0248] Referring to Table 3 above, Example 3-1 obtained recycled terephthalic acid with a yield of 95%, purity of 99.2%, and Color-b value of 1.7, Example 3-2 obtained recycled terephthalic acid with a yield of 90%, purity of 99.5%, and Color-b value of 1.3, Example 3-3 obtained recycled terephthalic acid with a yield of 98%, purity of 99.4%, and Color-b value of 1.2, Example 3-4 obtained recycled terephthalic acid with a yield of 97%, purity of 99.8%, and Color-b value of 1.4, Example 3-5 obtained recycled terephthalic acid with a yield of 98%, purity of 99.8%, and Color-b value of 1.2, and Example 3-6 obtained recycled terephthalic acid with a yield of 97%. Terephthalic acid was obtained, the purity was 99.5%, the Color-b value was 1.1, Example 3-7 obtained regenerated terephthalic acid with a yield of 94%, the purity was 99.7%, the Color-b value was 1.4, Example 3-8 obtained regenerated terephthalic acid with a yield of 95%, the purity was 99.4%, the Color-b value was 1.7, Example 3-9 obtained regenerated terephthalic acid with a yield of 95%, the purity was 99.3%, the Color-b value was 1.3, Example 3-10 obtained regenerated terephthalic acid with a yield of 97%, the purity was 99.5%, the Color-b value was 1.6, Example 3-11 obtained regenerated terephthalic acid with a yield of 98%, the purity was 99.8%, the Color-b value was 1.3, and Example 3-12 obtained recycled terephthalic acid with a yield of 96%, purity of 99.5%, and Color-b value of 1.5.

[0249]

[0250] Example 4

[0251] <Example 4-1>

[0252] In Example 1-2, 4.0 g of regenerated cellulose was recovered, and 40 ml of a 4% sodium hypochlorite aqueous solution was added, and stirred at room temperature for 1 hour to obtain decolorized regenerated cellulose (r-cellulose). The decolorized regenerated cellulose was filtered, washed with water, and vacuum-dried. The color L was measured, and the results are shown in Table 3.

[0253]

[0254] <Example 4-2>

[0255] Decolorized regenerated cellulose (r-cellulose) was obtained through the same process as Example 4-1, except that the regenerated cellulose recovered in Example 1-7 was used.

[0256]

[0257] <Example 4-3>

[0258] Decolorized regenerated cellulose (r-cellulose) was obtained through the same process as Example 4-1, except that the regenerated cellulose recovered in Example 1-12 was used.

[0259]

[0260] <Example 4-4>

[0261] In Example 1-2, 4.0 g of regenerated cellulose recovered was added to 40 ml of a 10% aqueous hydrogen peroxide solution and stirred at 60°C for 1 hour to obtain decolorized regenerated cellulose (r-cellulose). The decolorized regenerated cellulose was filtered, washed with water, and vacuum-dried. The color L was measured, and the results are shown in Table 3.

[0262]

[0263] <Example 4-5>

[0264] Decolorized regenerated cellulose (r-cellulose) was obtained through the same process as Example 4-4, except that the regenerated cellulose recovered in Example 1-7 was used.

[0265]

[0266] <Example 4-6>

[0267] Decolorized regenerated cellulose (r-cellulose) was obtained through the same process as Example 4-4, except that the regenerated cellulose recovered in Example 1-12 was used.

[0268]

[0269] <Example 4-7>

[0270] Decolorized regenerated cellulose (r-cellulose) was obtained through the same process as Example 4-1, except that the regenerated cellulose recovered in Example 1-17 was used.

[0271]

[0272] <Example 4-8>

[0273] Decolorized regenerated cellulose (r-cellulose) was obtained through the same process as Example 4-1, except that the regenerated cellulose recovered in Example 1-22 was used.

[0274]

[0275] <Example 4-9>

[0276] Decolorized regenerated cellulose (r-cellulose) was obtained through the same process as Example 4-1, except that the regenerated cellulose recovered in Example 1-27 was used.

[0277]

[0278] <Example 4-10>

[0279] Decolorized regenerated cellulose (r-cellulose) was obtained through the same process as Example 4-4, except that the regenerated cellulose recovered in Example 1-17 was used.

[0280]

[0281] <Example 4-11>

[0282] Decolorized regenerated cellulose (r-cellulose) was obtained through the same process as Example 4-4, except that the regenerated cellulose recovered in Example 1-22 was used.

[0283]

[0284] <Example 4-12>

[0285] Decolorized regenerated cellulose (r-cellulose) was obtained through the same process as Example 4-4, except that the regenerated cellulose recovered in Example 1-27 was used.

[0286]

[0287] <Example 3>

[0288] 1) Color L measurement

[0289] The Color L value of the decolorized regenerated cellulose in Examples 4-1 to 4-12 above was measured using a colorimeter.

[0290]

[0291] Example Blended Fiber Color L Discolored r-CelluloseColor L4-133.0784-2824-3914-4724-5754-6884-733.2754-8874-9934-10814-11854-1290

[0292] Referring to Table 3 above, the Color-L values ​​of the decolored regenerated cellulose of Examples 4-1, 4-2, 4-3, 4-4, 4-5, and 4-6 manufactured using waste blended fibers having a Color L value of 33.0 were confirmed to be 78, 82, 91, 72, 75, and 88, respectively, and the Color-L values ​​of the decolored regenerated cellulose of Examples 4-7, 4-8, 4-9, 4-10, 4-11, and 4-12 manufactured using waste blended fibers having a Color L value of 33.2 were confirmed to be 75, 87, 93, 81, 85, and 90, respectively, confirming an excellent color improvement effect.

Claims

A step of producing a depolymerized product by depolymerizing a blended fiber including cotton and synthetic fibers with a depolymerization solvent; A step of filtering the above depolymerized product to obtain regenerated cellulose (r-cellulose); and A method for recycling blended fibers, comprising the step of obtaining a regenerated dialkyl phthalate from the filtrate. In the first paragraph, A method for recycling a blended fiber, wherein the synthetic fiber comprises at least one selected from the group consisting of polyethylene terephthalate, polyamide, polyurethane, polypropylene, polyethylene, and polyether. In the first paragraph, A method for recycling a blended fiber, wherein the blended fiber contains 0.1 to 99.9 wt% of cotton based on the total weight. In the first paragraph, A method for recycling a blended fiber, wherein the depolymerization solvent comprises a monoalcohol having 1 to 14 carbon atoms or a polyhydric alcohol having 2 or more carbon atoms, and the depolymerization is performed at a temperature of 180°C to 280°C. In the first paragraph, A process for pretreating the blended fiber with a pretreatment agent prior to the above depolymerization is included. A method for recycling blended fibers, wherein the above pretreatment process is a process for removing impurities including chromophores or polyurethane from the blended fibers. In paragraph 5, A method for recycling mixed fibers, wherein the pretreatment agent comprises at least one selected from the group consisting of an organic solvent, an oxidizing agent, and a reducing agent. In paragraph 6, A method for recycling a blended fiber, wherein the organic solvent comprises at least one selected from the group consisting of cyclohexanone, ethylene glycol, 1-butanol, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, benzyl alcohol, toluene, and xylene. In paragraph 6, A method for recycling blended fibers, wherein the organic solvent has a boiling point of 100°C or higher. In paragraph 6, A method for recycling blended fibers, wherein the oxidizing agent comprises at least one selected from the group consisting of sodium hypochlorite, potassium hypochlorite, hydrogen peroxide, ozone, and potassium permanganate. In paragraph 6, A method for recycling blended fibers, wherein the reducing agent comprises at least one selected from the group consisting of sodium hydrosulfite and thiourea dioxide. In the first paragraph, It includes a process for post-processing the above regenerated cellulose, A method for recycling blended fibers, wherein the above post-treatment process is performed under temperature conditions of 40°C to 160°C by adding a post-treatment solvent containing a protic or aprotic solvent having a boiling point of 40°C or higher to the regenerated cellulose in an amount of 5 to 100 times based on the total weight of the regenerated cellulose. In paragraph 11, A method for recycling blended fibers, wherein the post-treatment solvent is a depolymerization solvent of polyethylene terephthalate when the synthetic fiber is polyethylene terephthalate. In the first paragraph, A method for recycling blended fibers, further comprising a step of acetylating the regenerated cellulose. In the first paragraph, A method for recycling blended fibers, further comprising a step of decolorizing the above regenerated cellulose with a bleaching agent. In paragraph 14, The above bleaching agent comprises at least one selected from the group consisting of hydrogen peroxide, sodium hypochlorite, potassium hypochlorite, potassium permanganate, ozone, and sodium hydrosulfite. A method for recycling blended fibers, wherein the above decolorization is performed at 15°C to 100°C for 1 minute to 8 hours. Regenerated cellulose manufactured according to the method of claim 1. In paragraph 16, Regenerated cellulose having a synthetic fiber-derived component containing polyethylene terephthalate (PET) in the regenerated cellulose of 100 ppm or less. In paragraph 16, Regenerated cellulose having a degree of polymerization (DP) of 200 or more according to TAPPI T230. In paragraph 16, The above regenerated cellulose is regenerated cellulose having a Color L value of 70 or higher as measured by a colorimeter. A regenerated dialkyl phthalate manufactured according to the method of claim 1. In paragraph 20, Recycled dialkyl phthalate having a yellowness of 10 or less as measured by a colorimeter.

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