Method for recycling waste blended fiber and regenerated cellulose obtained therefrom

Abstract

The present invention relates to a method for recycling waste blended fibers and regenerated cellulose obtained therefrom. The recycling method comprises the steps of: pre-treating waste blended fibers including cotton and polyester with a pre-treatment agent; depolymerizing the pre-treated waste blended fibers to obtain regenerated cellulose (R-cellulose) and a depolymerized product; and post-treating the regenerated cellulose with a post-treatment agent.

Description

Recycling method for waste blended fibers and regenerated cellulose obtained therefrom

[0001] The present invention relates to a method for recycling waste blended fibers and a recycled raw material (e.g., recycled cellulose) obtained therefrom.

[0002] As plastic recycling is increasingly emphasized, the range of plastics or polymer raw materials utilized as recycled materials is steadily expanding. Traditional methods of recycling waste plastics included mechanical recycling, where waste plastics were reused for the same or similar purposes after simple pretreatment such as washing, or transformed into polymer chips or pellets through mechanical processing, such as extrusion, for other uses. Meanwhile, chemical recycling, distinct from pyrolysis, has recently been taking place. Unlike pyrolysis, this chemical recycling method involves sorting waste plastics and then chemically treating them to break them down into their respective raw material components for regeneration.

[0003] The above chemical recycling is commonly referred to as solvolysis, based on the method of converting polymers into raw materials using a solvent; it is also called alcoholylysis, considering that most of the solvents used are alcohols such as ethylene glycol (EG) and methanol. Specifically, it is also referred to as glycolysis, methanolysis, etc., based on the chemical names of the respective alcohols.

[0004] The advantages of this solvolysis-based chemical recycling include the quality superiority of being able to regenerate products to the same quality as new ones compared to traditional recycling methods, and significant environmental benefits as it can curb the massive carbon emissions generated during the extraction of raw materials for the production of new plastics.

[0005] The aforementioned chemical recycling cannot be applied 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 undesirable for the depolymerization process required for recycling to demand at least more energy than the polymerization process. Furthermore, it is advantageous for the recycled raw material generated through recycling to be of a quality suitable for direct input into the polymerization process of the same plastic. If the structure or properties of the recycled raw material differ from those of the original material, new facilities become required to input it directly into the polymerization process, making it difficult to reduce waste plastic through chemical recycling.

[0006] For example, polyurethane is a plastic that is very easy to chemically recycle, and its urethane bonds can be broken even at low temperatures. However, the recycled raw material produced by this process is of a different quality from the raw material originally introduced into the urethane polymerization process, and is considered difficult to recycle.

[0007] In contrast, polyester (specifically, polyethylene terephthalate (PET)) is considered a plastic suitable for chemical recycling because it is easy to chemically recycle, and the resulting recycled raw material can be obtained as a substance identical to the original raw material.

[0008] However, it is not easy to obtain feedstock consisting of 100% pure waste polyester. The waste polyester typically used for chemical recycling consists of bottles or textiles. The aforementioned bottles contain polyolefin components such as PE and PP originating from bottle caps, while the aforementioned textiles contain a large amount of natural polymer components such as cotton. In particular, in terms of component content, textiles contain a much higher proportion of non-polyester components than bottles. For example, in the case of waste polyester fibers, without a separate collection and sorting / screening process, it is highly likely that approximately 30–50% cotton is mixed in.

[0009] Various process troubles arise when chemically recycling waste polyester that is not composed of a single component. For example, if adhesive materials are mixed in, clogging of filters or piping can lead to a decrease in process economic efficiency. Although the nature of the troubles differs slightly, complex issues can also occur in the chemical recycling of waste textiles. A method to prevent these process troubles in advance is sorting. Sorting involves selecting only feedstocks with a very high polyester content and feeding them into the chemical recycling process. However, due to sorting, feedstocks with low polyester content or those whose content is difficult to determine must inevitably be landfilled or incinerated, making it difficult to pursue eco-friendliness.

[0010] To improve these shortcomings and achieve complete chemical recycling, a recycling method targeting the entire composition of raw materials, which are a mixture of polymers with different chemical structures, must be established. This requires the development of recycling methods for polymers other than polyester, for which chemical recycling has not been actively pursued or is inadequate. As mentioned above, representative polymers that are often mixed with polyester and discharged include natural fibers, particularly cotton.

[0011] Cotton can be classified as cellulose based on its chemical structure. Depending on its molecular weight, cellulose can be used as a raw material for clothing, industrial materials, or paper. Generally, cotton has the highest molecular weight, followed by paper and pulp, and rayon has the lowest. Rayon has recently seen a demand for higher molecular weight cellulose to impart mechanical strength, and by using appropriate solvents, cellulose used in paper can also be used in the production of rayon. Examples of rayon with high molecular weight cellulose include Tencel, Lyocell, Modal, and Polynosic.

[0012] The best way to remove one material from waste polyester and cotton blended fibers is to exploit the difference in solubility. However, both polyester and cotton cannot achieve a level of solubility that allows separation without using highly polar solvents. Furthermore, these solvents are either extremely expensive or, like chloroform, pose health risks to users. Therefore, exploiting this difference in solubility remains difficult to commercialize.

[0013] The inventors of the present invention have studied various technologies for recycling waste blended fibers used in various fields such as clothing and industrial use in an economical, easy, and user-safe environment, departing from the conventional method, and as a result, have found that waste blended fibers can be effectively recycled through specific pretreatment and posttreatment.

[0014] Therefore, the objective of the present invention is to provide a recycling method that can efficiently recycle waste blended fibers to obtain diverse and high-quality recycled raw materials, such as recycled cellulose.

[0015] In addition, the present invention provides a high-quality recycled product manufactured from the above-mentioned recycled raw material, e.g., recycled cellulose.

[0016] In order to solve the above problem, the present invention provides a method for recycling waste blended fibers, comprising the steps of pretreating waste blended fibers containing cotton and polyester with a pretreatment agent; depolymerizing the pretreated waste blended fibers to obtain regenerated cellulose (r-cellulose) and a depolymerized product; and posttreating the regenerated cellulose with a posttreatment agent.

[0017] In addition, the present invention provides regenerated cellulose obtained from the recycling method of the waste blended fibers, having a Color L of 80 or more.

[0018] The present invention also provides a regenerated product manufactured from a raw material containing the regenerated cellulose.

[0019] The recycling method according to the present invention allows for economical and easy recycling of waste blended fibers by pre-treating, depolymerizing, and then post-treating the waste blended fibers. Furthermore, the recycling method allows for high yields of regenerated cellulose with excellent color characteristics and an optimized degree of polymerization from the waste blended fibers. Accordingly, the present invention can utilize the regenerated cellulose to produce a variety of high-quality regenerated products (e.g., recycled paper, recycled rayon, recycled acetate, recycled cotton, etc.).

[0020] Hereinafter, the present invention will be described in detail. Herein, the present invention is not limited to the contents described below, and may be modified in various forms as long as the gist of the invention is not changed.

[0021] The word "comprising" or "including" in this specification is intended to specify particular features, regions, steps, processes, elements and / or components, and does not exclude the presence or addition of other features, regions, steps, processes, elements and / or components, unless specifically stated to the contrary.

[0022] In this specification, the terms first, second, primary, secondary, etc. are used for the purpose of distinguishing one component from another, and the components are not limited by the terms.

[0023] In this specification, singular expressions may be interpreted to include singular or plural forms as interpreted in context unless otherwise specified.

[0024] In this specification, when numerical values ​​with limited upper and lower limits are described to illustrate the size, physical properties, etc. of a component, it can 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.

[0025]

[0026] Recycling method of waste blended fibers

[0027] A recycling method for waste blended fibers according to the present invention comprises the steps of: pre-treating waste blended fibers comprising cotton and polyester with a pre-treatment agent; depolymerizing the pre-treated waste blended fibers to obtain regenerated cellulose (r-cellulose) and a depolymerized product; and post-treating the regenerated cellulose with a post-treatment agent.

[0028] The present invention has the technical characteristic of producing regenerated cellulose with significantly improved color characteristics and a high-purity depolymerized product at high yields, even when the waste blended fiber contains various mixed components, by specifically controlling the recycling process of waste blended fibers. A detailed description of this waste blended fiber recycling method is as follows.

[0029]

[0030] 1) Pretreatment of waste mixed fibers

[0031] This step involves pre-treating the waste blended fibers with a pretreatment agent to remove foreign substances, such as impurities (oil, dust, etc.), pigments, and dyes contained in the waste blended fibers. Specifically, the pretreatment may be a step of decolorizing the waste blended fibers.

[0032] The above-mentioned waste blended fibers include cotton and polyester, and are not particularly limited as long as they are used waste fibers. Specifically, the above-mentioned waste blended fibers may refer to discarded waste clothing, factory-manufactured but unsold inventory clothing, or inventory and defective fabrics discarded in their original state without being converted into clothing. Furthermore, the above-mentioned waste blended fibers include fibers used not only for clothing purposes but also for industrial purposes (e.g., industrial materials, nonwoven fabrics, fabrics, etc.).

[0033] According to the present invention, the content of the cotton included in the waste blended fiber may be 1 to 95 weight% based on the total weight of the waste blended fiber. Specifically, the content of the cotton may be 2 to 95 weight%, 5 to 90 weight%, 10 to 85 weight%, 15 to 80 weight%, 20 to 70 weight%, 30 to 60 weight%, 40 to 50 weight%, 50 to 60 weight%, or 70 to 95 weight%.

[0034] In addition, the content of the polyester included in the waste blended fiber may be 5 to 99 weight% based on the total weight of the waste blended fiber. Specifically, the content of the polyester may be 5 to 98 weight%, 10 to 95 weight%, 15 to 90 weight%, 20 to 85 weight%, 30 to 80 weight%, 40 to 70 weight%, 50 to 60 weight%, 40 to 50 weight%, or 5 to 30 weight%.

[0035] These waste blended fibers may be surface-treated or water-repellent treated. The surface treatment may include physical surface treatments such as sanding, calendering, and heat setting; chemical surface treatments such as chlorine treatment, alkali treatment, acid treatment, and hydrophobic / hydrophilic treatment; physical / chemical surface treatments such as plasma treatment and corona treatment; biological surface treatments such as enzyme treatment, or a combination thereof. The water-repellent finishing may include fluorine-based compound treatment, silicone-based compound treatment, wax treatment, paraffin treatment, oil treatment, or a combination thereof.

[0036] For example, the waste blended fiber may be waste polycotton, which is a mixture of cotton and polyethylene terephthalate (PET). Additionally, it may be waste polycotton coated with a polyurethane (PU) component on the surface to impart functionality such as waterproofing to the polycotton, or may be waste polycotton mixed with polyurethane yarn (PU Yarn) to supplement the insufficient elasticity of the polycotton.

[0037] The above-mentioned waste blended fibers generally have a large cross-sectional area due to their intended use, and thus, their specific gravity is generally low. Therefore, to enhance the reactivity of bleaching and depolymerization, as well as the ease of feeding into a depolymerization reactor, the waste blended fibers can be shredded into small pieces through a shredding process, followed by compression or heat treatment to form a bundle. When inducing a bundle through heat treatment, the ratio of cotton to polyester can determine the success of the process. These ratios can promote the formation of various impurities during the purification process after depolymerization, and thus special conditions may be required.

[0038] The pretreatment agent used for pretreatment of the above waste 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 waste blended fiber with the organic solvent or decomposing and removing them with the oxidizing agent and / or reducing agent.

[0039] 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.

[0040] 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).

[0041] 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.

[0042] 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.

[0043] By pretreating the waste mixed 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.

[0044] The input ratio of such pretreatment agent is not particularly limited, but considering process safety, economic efficiency, and foreign substance removal efficiency (bleaching efficiency), it may be input at a ratio of 0.5 to 100 ml per 1 g of waste blended fiber. Specifically, the input ratio of the pretreatment agent relative to the waste blended fiber (L / S, ml / g) may be 0.5 to 50, 0.5 to 20, 1 to 18, 5 to 17, 7 to 15, 8 to 13, or 9 to 10.

[0045] According to the present invention, the pretreatment of the waste blended fiber can be performed at 40 to 180 ℃. Specifically, the pretreatment can be performed at 50 to 170 ℃, 60 to 160 ℃, 70 to 150 ℃, 75 to 140 ℃, or 80 to 135 ℃. By performing the pretreatment at the above temperatures, foreign substances contained in the waste blended fiber can be efficiently removed while preventing damage to the waste blended fiber.

[0046] Waste blended fibers that have undergone such pretreatment may have a relatively high Color L value as foreign substances are efficiently removed. Specifically, the pretreated waste blended fibers may have a Color L of 50 or more, 52 or more, 54 or more, 56 or more, 58 or more, 60 or more, 62 or more, 64 or more, 66 or more, 68 or more, or 70 or more (e.g., 50 to 75, 51 to 73, 53 to 70, or 55 to 69).

[0047]

[0048] 2) Depolymerization of waste blended fibers

[0049] This step involves depolymerizing the pretreated waste blended fibers to obtain regenerated cellulose (r-cellulose) and a depolymerized product.

[0050] The above depolymerization is not particularly limited as long as it is a commonly known chemical depolymerization (e.g., glycolysis, methanolilysis, hydrolysis under water or acid / base conditions, alkaline hydrolysis under basic conditions (NaOH, KOH), etc.). Specifically, according to the present invention, the depolymerization can be carried out through alcoholic decomposition using a solvent comprising a mono-alcohol having 1 to 8 carbon atoms or a di-alcohol having 2 to 4 carbon atoms. The solvent may be, for example, methanol, n-butanol, 2-ethyl-1-hexanol, ethylene glycol, 1,3-propanediol, or 1,4-butanediol. Through such alcoholic decomposition, the desired regenerated cellulose and depolymerized product can be obtained in high yield. For example, through the alcohol decomposition, the cotton contained in the waste blended fiber can be decomposed into regenerated cellulose, and the polyester contained in the waste blended fiber can be decomposed into a depolymer, thereby obtaining regenerated cellulose and a depolymer.

[0051] The input ratio of the solvent during the above alcohol decomposition is not particularly limited, but considering the depolymerization efficiency, it may be input in an amount of 3 to 100 ml per 1 g of pretreated waste blended fiber. Specifically, the input ratio of the solvent (L / S, ml / g) relative to the pretreated waste blended fiber may be 3 to 100, 3 to 70, 4 to 50, 4 to 30, 5 to 20, 5 to 15, or 6 to 10.

[0052] The above alcoholysis can be carried out in the presence of a commonly known catalyst. Specifically, the catalyst can include at least one selected from the group consisting of Zn(OAc)2, Co(OAc)2, Mn(OAc)2, Mg(OAc)2, Ca(OAc)2, Ba(OAc)2, LiOAc, NaOAc, KOAc, Zn(OAc)2·2H2O, Co(OAc)2·4H2O, Pb(OAc)2, Mn(OAc)2·4H2O, Mg(OAc)2·4H2O, Pd(OAc)2, Ti(OBu)4, Ti(OiPr)4, GeO2, Al(OiPr)3, Na2CO3, K2CO3, dibutyltin(IV)oxide, tin octoate, titanium phosphate, and terephthalic acid.

[0053] The reaction conditions (specifically, alcohol decomposition conditions) for performing depolymerization of the above-mentioned waste mixed fiber are not particularly limited, but the reaction temperature may be 160 to 280°C, 165 to 260°C, 170 to 250°C, 180 to 230°C, or 190 to 210°C, and the reaction time may be 1 to 10 hours, 2 to 8 hours, 3 to 6 hours, 3 to 4 hours, or 4 to 5 hours.

[0054] The depolymer obtained through the above depolymerization may contain various components. These components may be liquid or solid in nature at high or low temperatures, and their solubility in a reaction solvent or a third solvent may be the same or different from one another.

[0055] Specifically, according to the present invention, the depolymer may include regenerated bis(2-hydroxyethyl)terephthalate (r-BHET), regenerated dimethyl terephthalate (r-DMT), regenerated dibutyl terephthalate (r-DBTP), or a combination thereof.

[0056] These depolymers may have high purity and excellent color characteristics. Specifically, the depolymer may have a purity of 95% or more, 96% or more, 97% or more, 98% or more, or 99% or more (e.g., 95 to 100%, 96.5 to less than 100%, 97.5 to 99.9%, or 98 to 99.5%). In addition, the depolymer may have a Color YID (yellowness index) of less than 5, 4.5 or less, 4 or less, 3.8 or less, 3.5 or less, 3.2 or less, 3 or less, 2.8 or less, or 2.5 or less (e.g., greater than 0 to 4.5, 0.5 to 4, 1 to 3.5, 1.5 to 3).

[0057] The above depolymer may undergo a purification process that is generally known. The purification process may include processes such as decolorization, adsorption, distillation, crystallization, filtration, and extraction.

[0058] The above bleaching can be performed by an oxidizing agent treatment that decomposes the dye components. Chlorine-based or oxygen-based oxidizing agents may be used as the oxidizing agent, and since they exhibit different effects depending on the dye components, they may be used alone or in combination.

[0059] The above adsorption can be performed by using an adsorbent to adsorb dyes and components generated by decomposition onto the surface or pores. The adsorbent may be activated carbon, zeolite, or silica gel, and the choice may depend on the particle size or polarity of the component to be removed. Through this adsorption, impurities such as non-polyester and partially decomposed components can also be removed.

[0060] The distillation described above utilizes the difference in boiling points between two substances and can be performed through reduced pressure and heating. This distillation can efficiently remove intermediates such as dyes, partially decomposed components, and non-polyesters. However, the distillation process is a high-temperature process, which consumes significant energy and limits the separation of substances with low high-temperature stability. Therefore, it may be advantageous to perform this process in combination with other processes rather than applying it alone.

[0061] The above crystallization separates two substances with different solubilities and can be performed by cooling and / or solvent treatment. This crystallization can be applied simultaneously with the solidification of substances present in a dissolved or molten state during high-temperature processes. Therefore, when performed under appropriate solvent or temperature conditions, it can achieve high efficiency and reduced investment costs. However, the above crystallization process requires a separation process between process solvents when a third solvent is used, limiting its use as a primary purification process. Therefore, it may be advantageous to perform it in combination with other processes.

[0062] The above extraction separates various substances with different solubilities and can be performed through solvent treatment. For example, a solvent that does not mix well with substances with high solubility in process solvents such as water or ethylene glycol (EG) but can dissolve other substances can be used to separate various substances. This extraction can be performed alone, but it may be advantageous to perform it in combination with other processes, taking into account the separation, purification, and recovery of the process solvent.

[0063] These depolymers can be converted into regenerative monomers, such as terephthalic acid (TPA), through commonly known hydrolysis.

[0064] The reaction conditions for carrying out the hydrolysis of the above-mentioned depolymer are not particularly limited, but the reaction temperature may be 180 to 250 ℃, 185 to 240 ℃, 190 to 235 ℃, 195 to 230 ℃, or 200 to 210 ℃, and the reaction time may be 3 to 12 hours, 4 to 10 hours, 5 to 9 hours, 6 to 8 hours, or 5 to 6 hours.

[0065] The regenerated monomer (i.e., TPA) obtained through such hydrolysis may have high purity and excellent color characteristics. Specifically, the regenerated monomer may have a purity of 95% or more, 96% or more, 97% or more, 98% or more, or 99% or more (e.g., 95 to 100%, 96.5 to less than 100%, 97.5 to 99.9%, or 98 to 99.5%). In addition, the regenerated monomer may have a Color b of 2 or less, 1.9 or less, 1.8 or less, 1.7 or less, 1.6 or less, 1.5 or less, 1.4 or less, or 1.3 or less (e.g., 0 to 2, 0.5 to 1.9, 1 to 1.8, 1.1 to 1.5).

[0066]

[0067] 3) Post-treatment of regenerated cellulose

[0068] This step involves post-treating the regenerated cellulose with a post-treatment agent to remove foreign substances, such as pigments and dyes, contained in the regenerated cellulose obtained through depolymerization. Specifically, the post-treatment may be a step of decolorizing the regenerated cellulose.

[0069] The post-treatment agent used for the post-treatment of the above-mentioned regenerated cellulose may include one or more selected from the group consisting of oxidizing agents and reducing agents. Post-treatment may be performed by decomposing and removing pigments, dyes, etc. contained in the above-mentioned regenerated cellulose with the oxidizing agent and / or reducing agent.

[0070] 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.

[0071] 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.

[0072] By post-treating the regenerated cellulose with the above post-treatment agent, user safety is ensured, damage to the fiber is prevented, and pigments, dyes, etc. can be efficiently removed.

[0073] The input ratio of such post-treatment agent is not particularly limited, but considering process safety, economic efficiency, and foreign substance removal efficiency (decolorization efficiency), it may be input in an amount of 0.5 to 100 ml per 1 g of regenerated cellulose. Specifically, the input ratio of the post-treatment agent relative to the regenerated cellulose (L / S, ml / g) may be 0.5 to 50, 0.5 to 20, 1 to 18, 3 to 15, 5 to 13, 10 to 12, or 18 to 20.

[0074] According to the present invention, the post-treatment of the regenerated cellulose can be performed at 15 to 130 ℃. Specifically, the post-treatment can be performed at 15 to 100 ℃, 18 to 80 ℃, 20 to 75 ℃, 22 to 65 ℃, 25 to 55 ℃, 27 to 45 ℃, or 30 to 35 ℃. By performing the post-treatment at the above temperatures, foreign substances contained in the regenerated cellulose can be efficiently removed while preventing damage to the regenerated cellulose.

[0075] Meanwhile, the pretreatment agent used for the pretreatment of the waste blended fibers and the posttreatment agent used for the posttreatment of the regenerated cellulose may be the same or different.

[0076]

[0077] The recycling method for waste blended fibers according to the present invention may further include a step of manufacturing a recycled product using the recycled cellulose. Specifically, the step of manufacturing the recycled product may include a papermaking process, a viscose process, or an acetylation process.

[0078]

[0079] regenerated cellulose

[0080] The regenerated cellulose according to the present invention is obtained from the recycling method of waste blended fibers described above. Since this regenerated cellulose is obtained from the recycling method of waste blended fibers described above, it has excellent color characteristics and can have a degree of polymerization that allows it to be utilized in the manufacture of various products.

[0081] Specifically, according to the present invention, the regenerated cellulose may have a Color L of 80 or more. More specifically, the regenerated cellulose may have a Color L of 82 or more, 84 or more, 86 or more, 88 or more, 90 or more, 92 or more, 94 or more, 96 or more, or 98 or more (e.g., 80 to 100, 81 to 99, 83 to 98, 85 to 97, 87 to 96, or 89 to 95).

[0082] In addition, the regenerated cellulose may have a degree of polymerization (DP) of 200 or more, 203 or more, 205 or more, 210 or more, 215 or more, 217 or more, 220 or more, 224 or more, 228 or more, or 300 or more (e.g., 200 to 750, 200 to 700, 200 to 350, 203 to 300, 205 to 270, or 210 to 250).

[0083] These recycled celluloses have a high whiteness with a Color L of 80 or higher, so when recycled products are manufactured using them, recycled products with excellent color characteristics can be realized.

[0084]

[0085] recycled products

[0086] The regenerated product according to the present invention is manufactured from a raw material containing the above-described regenerated cellulose.

[0087] For example, the recycled product may be recycled paper, and the recycled paper may include the recycled cellulose and exhibit a brightness of 80 or more. Specifically, the recycled paper may have a brightness of 81 or more, 83 or more, 85 or more, 87 or more, 89 or more, 90 or more, 92 or more, 94 or more, or 95 or more (e.g., 80 to 100, 82 to 98, 84 to 96, 86 to 94, 88 to 93, or 90 to 92) measured according to the ISO-2470-1 standard.

[0088] The content of the recycled cellulose included in the recycled paper may be 5 to 100 weight% based on the total weight of the recycled paper. Specifically, the content of the recycled cellulose may be 10 to 100 weight%, 20 to 100 weight%, 25 to 95 weight%, 30 to 90 weight%, 35 to 85 weight%, 40 to 80 weight%, 50 to 80 weight%, or 30 to 50 weight%. As the content of the recycled cellulose is within the above range, economic efficiency and eco-friendliness can be improved while securing the color characteristics of the recycled paper.

[0089] These recycled papers may include virgin cellulose (virgin pulp) together with the recycled cellulose. The content of the virgin cellulose included in the recycled paper may be 5 to 95 weight%, 10 to 90 weight%, 15 to 80 weight%, 20 to 65 weight%, 20 to 60 weight%, or 20 to 50 weight% based on the total weight of the recycled paper.

[0090] The above-mentioned recycled paper can be manufactured by mixing raw materials containing regenerated cellulose with water, dissolving and refining them, and then forming them into sheets (fibers) using a paper machine.

[0091] Meanwhile, the regenerated product may be regenerated rayon, regenerated acetate, or regenerated cotton, all of which contain the regenerated cellulose.

[0092] The above regenerated rayon can be manufactured through a process of alkalizing and xanthating regenerated cellulose and then spinning it. Such regenerated rayon may refer to viscose, modal, Tencel (lyocell), cupro, etc.

[0093] The above regenerated acetate can be manufactured by reacting regenerated cellulose with acetic acid to form cellulose acetate, and then dissolving and spinning it.

[0094] The above-mentioned recycled cotton refers to the above-mentioned recycled rayon, or can be manufactured through a process of mixing with natural cellulose and then spinning.

[0095] The present invention will be explained in more detail through the following examples. However, the following examples are merely illustrative of the present invention, and the scope of the present invention is not limited thereto.

[0096]

[0097] [Example 1] Pretreatment of waste blended fibers (1st bleaching)

[0098] [Example 1-1]

[0099] 100 g of black waste blended fibers (composition: Cotton 5 wt% / PET 95 wt%) cut into 2 cm × 2 cm pieces and 1,000 ml of dimethyl sulfoxide (DMSO) were placed in a 2 L flask and stirred at 120 ℃ for 1 hour. Next, the stirred solution was cooled to 80 ℃, vacuum filtered, and washed twice each with DMSO and water. Subsequently, a light beige waste blended fiber was obtained by drying in a vacuum oven at 80 ℃ for 6 hours.

[0100]

[0101] [Example 1-2]

[0102] Pretreatment was performed through the same process as in Example 1-1, except that black waste blended fibers with a composition of 20 wt% cotton / 80 wt% PET were used.

[0103]

[0104] [Example 1-3]

[0105] Pretreatment was performed through the same process as in Example 1-1, except that black waste blended fibers with a composition of 50 wt% cotton / 50 wt% PET were used.

[0106]

[0107] [Example 1-4]

[0108] Pretreatment was performed through the same process as in Example 1-1, except that black waste blended fibers with a composition of 80 wt% cotton / 20 wt% PET were used.

[0109]

[0110] [Example 1-5]

[0111] Pretreatment was performed through the same process as in Example 1-1, except that black waste blended fibers with a composition of 95 wt% cotton / 5 wt% PET were used.

[0112]

[0113] [Examples 1-6]

[0114] Pretreatment was performed through the same process as in Examples 1-2, except that cyclohexanone was used instead of dimethyl sulfoxide as the pretreatment agent and washing solution.

[0115]

[0116] [Examples 1-7]

[0117] Pretreatment was performed through the same process as in Examples 1-2, except that benzyl alcohol was used instead of dimethyl sulfoxide as the pretreatment agent and washing solution.

[0118]

[0119] [Examples 1-8]

[0120] Pretreatment was performed through the same process as in Examples 1-2, except that N-methyl-2-pyrrolidone was used instead of dimethyl sulfoxide as the pretreatment agent and washing solution.

[0121]

[0122] [Examples 1-9]

[0123] Pretreatment was performed through the same process as in Examples 1-2, except that dimethylacetamide was used instead of dimethyl sulfoxide as the pretreatment agent and washing solution.

[0124]

[0125] [Example 1-10]

[0126] Pretreatment was performed through the same process as in Examples 1-2, except that toluene was used instead of dimethyl sulfoxide as the pretreatment agent and washing solution.

[0127]

[0128] [Example 1-11]

[0129] Pretreatment was performed through the same process as in Examples 1-2, except that xylene was used instead of dimethyl sulfoxide as the pretreatment agent and washing solution.

[0130]

[0131] [Example 1-12]

[0132] Pretreatment was performed through the same process as in Examples 1-2, except that ethylene glycol was used instead of dimethyl sulfoxide as the pretreatment agent and washing solution.

[0133]

[0134] [Example 1-13]

[0135] Pretreatment was performed through the same process as in Examples 1-2, except that 1-butanol was used instead of dimethyl sulfoxide as the pretreatment agent and washing solution.

[0136]

[0137] [Example 1-14]

[0138] Pretreatment was performed through the same process as in Examples 1-2, except that dimethylformamide was used instead of dimethyl sulfoxide as the pretreatment agent and washing solution.

[0139]

[0140] [Example 1-15]

[0141] 100 g of black waste blended fibers (composition: 20 wt% cotton / 80 wt% PET) cut into 2 cm × 2 cm pieces and 1,000 ml of 2% sodium hypochlorite were placed in a 2 L flask and stirred at 70 ° C for 2 hours. Next, the stirred solution was cooled to room temperature, vacuum filtered, and washed twice with water. Then, the mixture was dried in a vacuum oven at 80 ° C for 6 hours to obtain light red waste blended fibers.

[0142]

[0143] [Example 1-16]

[0144] 60 g of black waste blended fiber (20 wt% cotton / 80 wt% PET) cut into 2 cm × 2 cm pieces, 6 g of sodium hyposulfite, 6 g of sodium hydroxide, and 600 ml of water were placed in a 1 L autoclave and stirred at 130 ° C. for 2 hours. Next, the stirred solution was cooled to room temperature, vacuum filtered, and washed twice with water. Then, the mixture was dried in a vacuum oven at 80 ° C. for 6 hours to obtain light beige waste blended fiber.

[0145]

[0146] [Comparative Example 1-1]

[0147] Pretreatment was performed through the same process as in Example 1-2, except that acetone was used instead of dimethyl sulfoxide as the pretreatment agent and washing solution, and the pretreatment temperature was set to 50 ℃.

[0148]

[0149] [Comparative Example 1-2]

[0150] Pretreatment was performed through the same process as in Example 1-2, except that methanol was used instead of dimethyl sulfoxide as the pretreatment agent and washing solution, and the pretreatment temperature was set to 65 ℃.

[0151]

[0152] [Example 1]

[0153] The pretreated waste blended fibers were measured using a spectrophotometer (KONICA MINOLTA CM-3600A) to determine the Color L value (whiteness), and the results are shown in Table 1 below.

[0154]

[0155] Distinctive pretreatment agent (bleaching agent) Color L Example 1-1 Dimethyl sulfoxide 69 Example 1-2 Dimethyl sulfoxide 65 Example 1-3 Dimethyl sulfoxide 66 Example 1-4 Dimethyl sulfoxide 69 Example 1-5 Dimethyl sulfoxide 65 Example 1-6 Cyclohexanone 60 Example 1-7 Benzyl alcohol 61 Example 1-8 N-methyl-2-pyrrolidone 68 Example 1-9 Dimethylacetamide 66 Example 1-10 Toluene 60 Example 1-11 Xylene 62 Example 1-12 Ethylene glycol 64 Example 1-13 1-butanol 67 Example 1-14 Dimethylformamide 68 Example 1-15 Sodium hypochlorite 56 Example 1-16 Sodium bisulfite 55 Comparative Example 1-1 Acetone 35 Comparative Example 1-2 Methanol 37

[0156] Referring to Table 1 above, the waste blended fibers pretreated according to the present invention show a Color L value of 50 or higher, confirming that the decolorization was successfully achieved through pretreatment.

[0157]

[0158] [Example 2] Depolymerization of waste blended fibers (alcohol decomposition)

[0159] [Example 2-1]

[0160] 40 g of waste blended fibers pretreated according to Example 1-1, 40 mg of Zn(OAc)2·2H2O, and 160 ml of methanol were added to a 600 ml high-pressure reactor, and the mixture was reacted at 200 ℃ for 4 hours. After the reaction was completed, the reaction solution was cooled to 50 ℃ and filtered to obtain brown cellulose and the filtrate, respectively.

[0161] The above brown cellulose was washed three times with 50 ml of hot methanol and then dried at 80°C for 6 hours to recover regenerated cellulose (r-cellulose).

[0162] The above liquid was concentrated using a vacuum distillation apparatus to remove unreacted methanol, and then fractional distillation was performed to obtain r-DMT.

[0163]

[0164] [Examples 2-2 to 2-16]

[0165] Regenerated cellulose (r-cellulose) and r-DMT were obtained through the same process as in Example 2-1, except that waste blended fibers pretreated in Examples 1-2 to 1-16 were applied instead of the waste blended fibers pretreated in Example 1-1.

[0166]

[0167] [Example 2-17]

[0168] 40 g of waste blended fibers pretreated according to Example 1-2, 40 mg of Zn(OAc)2·2H2O, and 160 ml of 1-butanol were added to a 600 ml high-pressure reactor, and the mixture was reacted at 220 ℃ for 4 hours. After the reaction was completed, the reaction solution was cooled to room temperature (25 ℃) and filtered to obtain brown cellulose and the filtrate, respectively.

[0169] The above brown cellulose was washed three times with 50 ml of 1-butanol and then dried at 80°C for 6 hours to recover regenerated cellulose (r-cellulose).

[0170] The above liquid was concentrated using a vacuum distillation apparatus to remove unreacted 1-butanol, and then fractional distillation was performed to obtain r-DBTP.

[0171]

[0172] [Examples 2-18 to 2-28]

[0173] Regenerated cellulose (r-cellulose) and r-DBTP were obtained through the same process as Example 2-17, except that waste blended fibers that had undergone pretreatment in Examples 1-6 to 1-16 were used instead of waste blended fibers that had undergone pretreatment in Example 1-2.

[0174]

[0175] [Example 2-29]

[0176] 40 g of waste mixed fibers pretreated in Example 1-2, 40 mg of Zn(OAc)2·2H2O, and 400 ml of ethylene glycol were added to a 600 ml high-pressure reactor, and the mixture was reacted at 200°C for 4 hours. After completion of the reaction, the reaction solution was cooled to 80°C and filtered to obtain brown cellulose and a filtrate, respectively.

[0177] The above brown cellulose was washed three times with 50 ml of water and dried at 100°C for 6 hours to recover regenerated cellulose (r-cellulose).

[0178] The above filtrate was concentrated using a reduced pressure distiller to remove unreacted ethylene glycol, and then 200 ml of water was added to the reactor. Next, 0.4 g of activated carbon was added to the reactor, stirred at 100°C for 2 hours, filtered, and recrystallized to obtain r-BHET.

[0179]

[0180] [Examples 2-30 to 2-40]

[0181] Regenerated cellulose (r-cellulose) and r-BHET were obtained through the same process as Example 2-29, except that waste blended fibers that had undergone pretreatment in Examples 1-6 to 1-16 were used instead of waste blended fibers that had undergone pretreatment in Example 1-2.

[0182]

[0183] [Comparative Example 2-1]

[0184] Regenerated cellulose (r-cellulose) and r-DMT were obtained through the same process as in Example 2-1, except that the waste blended fibers pretreated in Comparative Example 1-1 were used instead of the waste blended fibers pretreated in Example 1-1.

[0185]

[0186] [Comparative Example 2-2]

[0187] Regenerated cellulose (r-cellulose) and r-DBTP were obtained through the same process as in Example 2-17, except that the waste blended fibers pretreated in Comparative Example 1-1 were used instead of the waste blended fibers pretreated in Example 1-2.

[0188]

[0189] [Comparative Example 2-3]

[0190] Regenerated cellulose (r-cellulose) and r-BHET were obtained through the same process as in Example 2-29, except that the waste blended fibers pretreated in Comparative Example 1-1 were used instead of the waste blended fibers pretreated in Example 1-2.

[0191]

[0192] [Comparative Example 2-4]

[0193] Regenerated cellulose (r-cellulose) and r-DMT were obtained through the same process as in Example 2-1, except that waste blended fibers pretreated in Comparative Example 1-2 were used instead of waste blended fibers pretreated in Example 1-1.

[0194]

[0195] [Comparative Example 2-5]

[0196] Regenerated cellulose (r-cellulose) and r-DBTP were obtained through the same process as in Example 2-17, except that the waste blended fibers pretreated in Comparative Example 1-2 were used instead of the waste blended fibers pretreated in Example 1-2.

[0197]

[0198] [Comparative Example 2-6]

[0199] Regenerated cellulose (r-cellulose) and r-BHET were obtained through the same process as in Example 2-29, except that the waste blended fibers pretreated in Comparative Example 1-2 were used instead of the waste blended fibers pretreated in Example 1-2.

[0200]

[0201] [Example 2]

[0202] 1) Recovery rate of regenerated cellulose

[0203] The recovery rate (%) of regenerated cellulose was calculated by converting the content of regenerated cellulose obtained (recovered) by depolymerization into a percentage relative to the cotton content in the waste blended fiber before depolymerization, and the results are shown in Table 2 below.

[0204] 2) Degree of polymerization (DP) of regenerated cellulose

[0205] The degree of polymerization of the recovered regenerated cellulose was calculated by measuring the viscosity in CED (Cupriethylenediamine) according to the standard method TAPPI T230, and the results are shown in Table 2 below.

[0206] 3) Yield of depolymerization

[0207] The yield (%) was calculated by converting the number of moles of the depolymerized product (r-BHET / r-DBTP / r-DMT) obtained by depolymerization into a percentage relative to the total number of moles of PET unit molecules in the waste blended fiber before depolymerization, and the results are shown in Table 2 below.

[0208] 4) Purity of the depolymerization

[0209] The depolymer (r-BHET / r-DBTP / r-DMT) was diluted to 1 wt / v% in methanol (MeOH), and the purity (%) was calculated by high-performance liquid chromatography (HPLC) analysis. The results are shown in Table 2 below.

[0210] 5) Color YID of Depolymer

[0211] After diluting the depolymer (r-BHET / r-DBTP / r-DMT) in dimethylformamide to 10 wt / v%, the YID value was calculated by measuring with a colorimeter, and the results are shown in Table 2 below.

[0212]

[0213] Classification Waste Blended Fiber Alcohol Decomposition (Depolymerization) Regenerated Cellulose (Recovery Rate / DP) Depolymerization (Yield / Purity / YID) Example 2-1 Example 1-1 Methanol (r-DMT) 98 / 350 96 / 99.1 / 1.7 Example 2-2 Example 1-2 94 / 430 93 / 99.0 / 2.0 Example 2-3 Example 1-3 98 / 400 95 / 98.6 / 2.1 Example 2-4 Example 1-4 96 / 410 93 / 98.1 / 1.8 Example 2-5 Example 1-5 98 / 380 97 / 97.9 / 2.0 Example 2-6 Example 1-6 94 / 350 94 / 99.0 / 2.2 Example 2-7 Example 1-797 / 43092 / 97.8 / 2.4 Example 2-8 Example 1-895 / 46090 / 98.3 / 2.1 Example 2-9 Example 1-997 / 37092 / 99.0 / 2.4 Example 2-10 Example 1-1094 / 49095 / 98.5 / 2.2 Example 2-11 Example 1-1196 / 47096 / 98.8 / 2.8 Example 2-12 Example 1-1294 / 43091 / 99.3 / 2.9 Example 2-13 Example 1-1397 / 40093 / 99.4 / 2.3 Example 2-14 Example 1-1495 / 49094 / 98.8 / 2.8 Example 2-15 Example 1-1597 / 43096 / 99.1 / 2.1 Example 2-16 Example 1-1695 / 42096 / 98.2 / 2.1 Example 2-17 Example 1-21 -butanol(r-DBTP)96 / 40092 / 98.3 / 1.9 Example 2-18 Example 1-695 / 32097 / 97.9 / 2.4 Example 2-19 Example 1-794 / 39092 / 99.3 / 2.3 Example 2-20 Example 1-895 / 40095 / 99.1 / 2.8 Example 2-21 Example 1-997 / 42095 / 98.6 / 2.2 Example 2-22 Example 1-1096 / 43096 / 98.1 / 2.6 Example 2-23 Example 1-1198 / 36093 / 99.2 / 2.2 Example 2-24 Example 1-1295 / 38094 / 98.4 / 2.7 Example 2-25 Example 1-1397 / 43092 / 99.0 / 2.0 Example 2-26 Example 1-1496 / 37091 / 98.0 / 2.3 Example 2-27 Example 1-1596 / 41094 / 98.6 / 2.8 Example 2-28 Example 1-1694 / 34095 / 99.1 / 2.Example 1 Example 2-29 Example 1-2 Ethylene Glycol (r-BHET) 95 / 400 96 / 98.5 / 2.4 Example 2-30 Example 1-6 95 / 380 96 / 98.5 / 2.4 Example 2-31 Example 1-7 96 / 350 97 / 98.5 / 2.3 Example 2-32 Example 1-8 95 / 360 96 / 99.0 / 2.0 Example 2-33 Example 1-9 95 / 410 97 / 99.3 / 2.1 Example 2-34 Example 1-10 97 / 340 95 / 98.6 / 2.9 Example 2-35 Example 1-11 96 / 410 94 / 98.7 / 2.5 Example 2-36 Example 1-1294 / 40097 / 99.4 / 2.4 Example 2-37 Example 1-1393 / 44095 / 99.1 / 2.8 Example 2-38 Example 1-1497 / 42096 / 98.2 / 3.3 Example 2-39 Example 1-1596 / 39095 / 98.5 / 3.8 Example 2-40 Example 1-1694 / 43097 / 98.4 / 3.1 Comparative Example 2-1 Comparative Example 1-1 Methanol (r-DMT) 97 / 38093 / 98.3 / 5.8 Comparative Example 2-2 Comparative Example 1-11-Butanol (r-DBTP) 95 / 330 95 / 99.0 / 5.1 Comparative Example 2-3 Comparative Example 1-1 Ethylene Glycol (r-BHET) 98 / 370 96 / 98.3 / 4.9 Comparative Example 2-4 Comparative Example 1-2 Methanol (r-DMT) 96 / 350 95 / 97.7 / 4.2 Comparative Example 2-5 Comparative Example 1-2 1-Butanol (r-DBTP) 94 / 400 94 / 98.3 / 5.5 Comparative Example 2-6 Comparative Example 1-2 Ethylene Glycol (r-BHET) 97 / 360 96 / 97.9 / 5.0.

[0214] Referring to Table 2 above, it can be seen that when the depolymerization of waste blended fibers pretreated as in the present invention is carried out, the recovery rate of regenerated cellulose (r-cellulose) is high, and the yield, purity, and color characteristics of the depolymerized product are excellent.

[0215]

[0216] [Example 3] Hydrolysis of depolymerized product

[0217] [Example 3-1]

[0218] 100 g (0.51 mol) of r-DMT obtained in Example 2-2 and 400 ml (22.20 mol) of water were placed in a 1 L high-pressure reactor and reacted at 200 °C for 6 hours. After the reaction was completed, the reaction mixture was cooled to room temperature and filtered to obtain the product. Subsequently, the product was washed with methanol and dried at 100 °C for 6 hours to obtain r-TPA.

[0219]

[0220] [Examples 3-2 to 3-4]

[0221] r-TPA was obtained through the same process as in Example 3-1, except that the r-DMT obtained in Examples 2-6 to 2-8 was applied instead of the r-DMT obtained in Example 2-2.

[0222]

[0223] [Examples 3-5]

[0224] 100 g (0.36 mol) of r-DBTP obtained in Example 2-21 and 400 ml (22.20 mol) of water were placed in a 1 L high-pressure reactor and reacted at 220 °C for 6 hours. After the reaction was completed, the reaction mixture was cooled to room temperature and filtered to obtain the product. Subsequently, the product was washed with butanol and dried at 100 °C for 6 hours to obtain r-TPA.

[0225]

[0226] [Examples 3-6 to 3-8]

[0227] r-TPA was obtained through the same process as in Example 3-5, except that the r-DBTP obtained in Examples 2-22 to 2-24 was applied instead of the r-DBTP obtained in Example 2-21.

[0228]

[0229] [Example 3-9]

[0230] 100 g (0.39 mol) of r-BHET obtained in Example 2-37 and 400 ml (22.20 mol) of water were placed in a 1 L high-pressure reactor and reacted at 200 °C for 6 hours. After the reaction was completed, the reaction mixture was cooled to room temperature and filtered to obtain the product. Subsequently, the product was washed with ethylene glycol and dried at 100 °C for 6 hours to obtain r-TPA.

[0231]

[0232] [Examples 3-10 to 3-12]

[0233] r-TPA was obtained through the same process as in Example 3-9, except that the r-BHET obtained in Examples 2-38 to 2-40 was applied instead of the r-BHET obtained in Example 2-37.

[0234]

[0235] [Example 3]

[0236] 1) Yield of r-TPA

[0237] The yield (%) of r-TPA was calculated by converting the number of moles of r-TPA obtained by hydrolysis into a percentage relative to the total number of moles of depolymerization before hydrolysis, and the results are shown in Table 3 below.

[0238] 2) Purity of r-TPA

[0239] After diluting r-TPA in methanol (MeOH) to 1 wt / v%, high-performance liquid chromatography (HPLC) analysis was performed to calculate the purity (%) of r-TPA, and the results are shown in Table 3 below.

[0240] 5) Color b of r-TPA

[0241] The Color b value of r-TPA (powder state) was measured using a colorimeter, and the results are shown in Table 3 below.

[0242]

[0243] Classification Polymer r-TPA Yield (%) Purity (%) Color b Example 3-1 Example 2-29 199.01.2 Example 3-2 Example 2-69 399.61.7 Example 3-3 Example 2-79 499.11.5 Example 3-4 Example 2-89 799.21.7 Example 3-5 Example 2-219 599.71.6 Example 3-6 Example 2-229 699.51.3 Example 3-7 Example 2-239 499.51.2 Example 3-8 Example 2-249 499.71.6 Example 3-9 Example 2-379 699.61.8 Example 3-10 2-389299.41.7 Example 3-11 Example 2-399399.31.1 Example 3-12 Example 2-409699.11.3

[0244] Referring to Table 3 above, it can be confirmed that r-TPA with high purity and excellent color characteristics is obtained in high yield as the hydrolysis of the depolymer obtained through the recycling method of the present invention is carried out.

[0245]

[0246] [Example 4] Post-treatment of regenerated cellulose (r-cellulose) (secondary decolorization)

[0247] [Example 4-1]

[0248] 40 ml of a 1% sodium hypochlorite aqueous solution was added to 4 g of regenerated cellulose (r-cellulose) recovered in Example 2-1 and stirred at room temperature for 1 hour. Subsequently, the stirred solution was cooled to room temperature and regenerated cellulose (r-cellulose) was obtained by vacuum filtration. The obtained regenerated cellulose (r-cellulose) was washed twice with water and vacuum dried to obtain post-treated regenerated cellulose (r-cellulose).

[0249]

[0250] [Examples 4-2 to 4-40]

[0251] Post-treated regenerated cellulose (r-cellulose) was obtained through the same process as in Example 4-1, except that the regenerated cellulose (r-cellulose) recovered in Examples 2-2 to 2-40 was applied instead of the regenerated cellulose (r-cellulose) recovered in Example 2-1.

[0252]

[0253] [Example 4-41]

[0254] 0.4 g of sodium bisulfite, 0.4 g of sodium hydroxide, and 40 ml of water were added to 4 g of regenerated cellulose (r-cellulose) recovered in Example 2-1, and the mixture was stirred at 130 °C for 2 hours. Subsequently, the stirred solution was cooled to room temperature and regenerated cellulose (r-cellulose) was obtained by vacuum filtration. The obtained regenerated cellulose (r-cellulose) was washed twice with water and then vacuum dried to obtain post-treated regenerated cellulose (r-cellulose).

[0255]

[0256] [Examples 4-42 to 4-45]

[0257] Post-treated regenerated cellulose (r-cellulose) was obtained through the same process as in Example 4-41, except that the regenerated cellulose (r-cellulose) recovered in Examples 2-2 to 2-5 was applied instead of the regenerated cellulose (r-cellulose) recovered in Example 2-1.

[0258]

[0259] [Comparative Examples 4-1 to 4-6]

[0260] Post-treated regenerated cellulose (r-cellulose) was obtained through the same process as in Example 4-1, except that the regenerated cellulose (r-cellulose) recovered in Comparative Examples 2-1 to 2-6 was applied instead of the regenerated cellulose (r-cellulose) recovered in Example 2-1.

[0261]

[0262] [Comparative Examples 4-7 to 4-12]

[0263] Post-treated regenerated cellulose (r-cellulose) was obtained through the same process as in Example 4-41, except that the regenerated cellulose (r-cellulose) recovered in Comparative Examples 2-1 to 2-6 was applied instead of the regenerated cellulose (r-cellulose) recovered in Example 2-1.

[0264]

[0265] [Test Example 4]

[0266] The Color L value (whiteness) of post-treated regenerated cellulose (r-cellulose) was measured using a spectrophotometer (KONICA MINOLTA CM-3600A), and the results are shown in Table 4 below.

[0267]

[0268] Classification Regeneration Cellulose Post-treatment Agent (Bleaching Agent) Color L Example 4-1 Example 2-1 Sodium Hypochlorite 88 Example 4-2 Example 2-291 Example 4-3 Example 2-387 Example 4-4 Example 2-490 Example 4-5 Example 2-586 Example 4-6 Example 2-688 Example 4-7 Example 2-785 Example 4-8 Example 2-889 Example 4-9 Example 2-984 Example 4-10 Example 2-1088 Example 4-11 Example 2-1186 Example 4-12 Example 2-1287 Example 4-13 Example 2-1389 Example 4-14 Example 2-1492 Example 4-15 Example 2-1587 Example 4-16 Example 2-1686 Example 4-17 Example 2-1785 Example 4-18 Example 2-1888 Example 4-19 Example 2-1987 Example 4-20 Example 2-2089 Example 4-21 Example 2-2190 Example 4-22 Example 2-2289 Example 4-23 Example 2-2391 Example 4-24 Example 2-2487 Example 4-25 Example 2-2586 Example 4-26 Example 2-2684 Example 4-27 Example 2-2787 Example 4-28 Example 2-2890 Example 4-29 Example 2-2992 Example 4-30 Example 2-3088 Example 4-31 Example 2-3184 Example 4-32 Example 2-3285 Example 4-33 Example 2-3387 Example 4-34 Example 2-3488 Example 4-35 Example 2-3586 Example 4-36 Example 2-3684 Example 4-37 Example 2-3787 Example 4-38 Example 2-3889 Example 4-39 Example 2-3991 Example 4-40 Example 2-4088 Example 4-41 Example 2-1st Sodium Sulfite 84 Example 4-42 Example 2-283 Example 4-43 Example 2-386 Example 4-44 Example 2-484 Example 4-45 Example 2-583 Comparative Example 4-1 Comparative Example 2-1st Sodium Hypochlorite 49 Comparative Example 4-2 Comparative Example 2-242 Comparative Example 4-3 Comparative Example 2-343 Comparative Example 4-4 Comparative Example 2-447 Comparative Example 4-5 Comparative Example 2-550 Comparative Example 4-6 Comparative Example 2-646 Comparative Example 4-7 Comparative Example 2-1st Sodium Sulfite 48 Comparative Example 4-8 Comparative Example 2-242 Comparative Example 4-9 Comparative Example 2-348 Comparative Example Comparative example 4-102-446 Comparative Example 4-11 Comparative Example 2-547 Comparative Example 4-12 Comparative Example 2-642

[0269] Referring to Table 4 above, it can be confirmed that the Color L value of the regenerated cellulose (r-cellulose) obtained through pretreatment and depolymerization of waste mixed fibers as in the present invention is 80 or higher when post-treated, thereby obtaining high-quality (excellent color characteristics) regenerated cellulose (r-cellulose).

[0270]

[0271] [Example 5] Manufacturing of recycled paper

[0272] [Example 5-1]

[0273] Regenerated fiber pulp was prepared by fibrillating the post-treated regenerated cellulose (r-cellulose) from Example 4-2 using a grinder to a particle size of 100 μm or less. Subsequently, bleached chemical wood pulp (softwood kraft pulp) and the regenerated fiber pulp were mixed in a weight ratio of 50:50, and then mixed with water to perform dissociation and refining. Next, a calcium carbonate filler was added to the mixed pulp at a weight of 15% to form a slurry-type pulp. The formed pulp was weighed using a paper machine to a basis weight of 100 g / m² 2 Recycled paper was manufactured by forming it into paper and drying it at 100°C using a cylinder and hot air.

[0274]

[0275] [Examples 5-2 to 5-12]

[0276] Recycled paper was manufactured through the same process as Example 5-1, except that post-treated regenerated cellulose (r-cellulose) was used in each of Examples 4-6 to 4-8, 4-21 to 4-24, and 4-37 to 4-40 instead of the post-treated regenerated cellulose (r-cellulose) of Example 4-2.

[0277]

[0278] [Comparative Examples 5-1 to 5-6]

[0279] Recycled paper was prepared through the same process as in Example 5-1, except that the post-treated regenerated cellulose (r-cellulose) from Comparative Examples 4-1 to 4-6 was applied instead of the post-treated regenerated cellulose (r-cellulose) from Example 4-2.

[0280]

[0281] [Example 5]

[0282] The brightness of recycled paper was measured according to the ISO-2470-1 standard, and the results are shown in Table 5 below.

[0283]

[0284] Separated Post-treated Regenerated Cellulose Brightness (%) Example 5-1 Example 4-291 Example 5-2 Example 4-689 Example 5-3 Example 4-787 Example 5-4 Example 4-890 Example 5-5 Example 4-2192 Example 5-6 Example 4-2291 Example 5-7 Example 4-2388 Example 5-8 Example 4-2487 Example 5-9 Example 4-3786 Example 5-10 Example 4-3890 Example 5-11 Example 4-3992 Example 5-12 Example 4-4088 Comparative Example 5-1 Comparative Example 4-157 Comparative Example 5-2 Comparative Example 4-258 Comparative Example 5-3 Comparative Example 4-355 Comparative Example 5-4 Comparative Example 4-457 Comparative Example 5-5 Comparative Example 4-553 Comparative Example 5-6 Comparative Example 4-659

[0285] Referring to Table 5 above, it can be confirmed that the recycled paper obtained through the recycling process according to the present invention has excellent color characteristics (whiteness) with a brightness of 80 or higher.

Claims

1. A step of pretreating waste blended fibers containing cotton and polyester with a pretreatment agent; A step of depolymerizing the above-mentioned pretreated waste mixed fiber to obtain regenerated cellulose (r-cellulose) and a depolymerized product; and A method for recycling waste blended fibers, comprising a step of post-treating the above regenerated cellulose with a post-treatment agent.

2. In paragraph 1, The above pretreatment agent comprises at least one selected from the group consisting of an organic solvent, an oxidizing agent, and a reducing agent, A method for recycling waste blended fibers, wherein the post-treatment agent comprises at least one selected from the group consisting of an oxidizing agent and a reducing agent.

3. In paragraph 2, A method for recycling waste blended fibers, 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.

4. In paragraph 2, A method for recycling waste blended fibers, wherein the organic solvent has a boiling point of 100°C or higher.

5. In paragraph 2, A method for recycling waste 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.

6. In paragraph 2, A method for recycling waste blended fibers, wherein the reducing agent comprises at least one selected from the group consisting of sodium hydrosulfite and thiourea dioxide.

7. In paragraph 1, A method for recycling waste blended fibers, wherein the content of the cotton contained in the waste blended fibers is 1 to 95 wt% based on the total weight of the waste blended fibers.

8. In paragraph 1, A method for recycling waste blended fibers, wherein the pretreatment of the waste blended fibers is performed at 40 to 180°C.

9. In paragraph 1, A method for recycling waste blended fibers, wherein the ratio (L / S, ml / g) of the pretreatment agent to the waste blended fibers is 0.5 to 100.

10. In paragraph 1, A method for recycling waste blended fibers, wherein depolymerization of the above pretreated waste blended fibers is performed through alcoholysis using a solvent containing a mono-alcohol having 1 to 8 carbon atoms or a di-alcohol having 2 to 4 carbon atoms.

11. In paragraph 10, A method for recycling waste blended fibers, wherein the ratio (L / S, ml / g) of the solvent input to the pretreated waste blended fibers is 3 to 100.

12. In paragraph 1, A method for recycling waste blended fibers, wherein depolymerization of the above pretreated waste blended fibers is performed at 160 to 280°C.

13. In paragraph 1, A method for recycling waste blended fibers, wherein the post-treatment of the above-mentioned regenerated cellulose is performed at 15 to 130°C.

14. In paragraph 1, A method for recycling waste mixed fibers, wherein the input ratio (L / S, ml / g) of the post-treatment agent to the regenerated cellulose is 0.5 to 100.

15. In paragraph 1, A method for recycling waste blended fibers, wherein the depolymerized material comprises recycled bis(2-hydroxyethyl)terephthalate, recycled dimethyl terephthalate, recycled dibutyl terephthalate, or a combination thereof.

16. Obtained from the method for recycling waste mixed fibers according to Article 1, Regenerated cellulose with a Color L of 80 or higher.

17. A regenerated product manufactured from a raw material containing regenerated cellulose according to Article 16.

18. In paragraph 17, The above recycled product is recycled paper, The above recycled paper is a recycled product with a brightness of 80 or higher.

19. In paragraph 17, The above recycled product is a recycled product made of recycled rayon, recycled acetate, or recycled cotton.