KR20080032357A - Method of increasing the molecular weight of waste nylon using blocked diisocyanate derivatives as chain extenders - Google Patents

Abstract

The present invention relates to a method of increasing the molecular weight of waste nylon by using a blocked diisocyanate derivative as a chain extender, and more particularly, both terminal isocyanate groups (-NCO) of an aliphatic or aromatic diisocyanate compound are lactam, oxime, The present invention relates to a method of increasing the molecular weight of waste nylon by melt compounding the waste nylon with melt extrusion using a diisocyanate derivative blocked by a blocking agent selected from alcohols, esters, and amine compounds as a chain extender. .

Description

Process for increasing the molecular weight of waste nylon using blocked diisocyanates as chain extender}

1 is an FT-IR spectrum of hexamethylene dicarbamoyl dicaprolactam (HDC).

2 is a DSC-TGA spectrum of hexamethylene dicarbamoyl dicaprolactam (HDC).

3 is an FT-IR spectrum of toylene dicarbamoyl dicaprolactam (TDC).

4 is a DSC-TGA spectrum of toylene dicarbamoyl dicaprolactam (TDC).

5 is a graph showing the intrinsic viscosity after melt compounding waste nylon using three blocked diisocyanate derivatives as chain extenders.

6 is a graph showing the intrinsic viscosity after melt compounding a waste nylon mixture using blocked three diisocyanate derivatives, bisoxazoline compounds, and mixtures thereof as chain extenders.

The present invention relates to a method of increasing the molecular weight of waste nylon by using a blocked diisocyanate derivative as a chain extender, and more particularly, both terminal isocyanate groups (-NCO) of an aliphatic or aromatic diisocyanate compound are lactam, oxime, The present invention relates to a method of increasing the molecular weight of waste nylon by melt compounding the waste nylon with melt extrusion using a diisocyanate derivative blocked by a blocking agent selected from alcohols, esters, and amine compounds as a chain extender. .

According to the recently announced European Union End-of-Life Vehicle Directive 2000/53 / EC, by 2015, 85% recycling rate and 95% recovery rate An automaker that fails to achieve is planning not to sell cars in the EU. Therefore, in the long run, domestic manufacturers have to meet the EU scrap-car guidelines, leading automobile manufacturers to take the lead in dealing with them. Therefore, it is necessary to find ways to increase the recycling rate of nylon collected from scrap cars, which not only saves resources and energy, but also provides a strong environmental and technical foundation for the long-term export of automobiles to Europe. Can be. Since waste nylon is severely deteriorated in molecular weight through hydrolysis, photolysis, pyrolysis, glycol decomposition and the like, the waste nylon cannot be recycled immediately if it cannot be restored to its original molecular weight. It is therefore very important to find a way to restore the molecular weight of waste nylon to its original molecular weight. The least cost-effective way to increase the recycling rate of waste nylon is to mix the waste nylon with the chain extender and melt compound it to recover the original molecular weight.

The method proposed by many researchers to obtain high molecular weight or high intrinsic viscosity of nylon is summarized as follows.

The first method is to synthesize nylon m, n by condensation of a nylon salt obtained from monomers diamine and dicarboxylic acid under high temperature and high pressure conditions, and initially using a ringtam monomer as an initiator to open a ring-opening polymerization reactor. In the polymerization stage or the end, there is a method of synthesizing nylon n through a polycondensation reaction between both ends. In this case, in order to obtain nylon having a high degree of polymerization, water, which is a reaction product, must be effectively removed from the polymerization system. However, since it is not easy to remove water effectively under high viscosity, it is first prepared in the state of nylon chips having a suitable degree of polymerization, and then the molecular weight is increased through solid phase polymerization. This method is disadvantageous in that it takes time and consumes a lot of energy.

The second method is a method of synthesizing high molecular weight nylon in a short time by selecting a chain extender having high reactivity with carboxylic acid and amine groups, which are terminal groups of nylon, and adding them to the polymerization intermediate and terminal groups. Chain extenders are based on the ability to extend the length of the polymer chain by reacting with carboxyl or amine groups, both ends of nylon. Existing chain extenders include bislactams (US Pat. No. 2,682,526) proposed by Flory of the United States, as well as isophthaloyl biscarrolactam (IBC) and adifoil biscaprol as chain extenders. Lactam (ABC), terephthaloyl biscaprolactam (TBC), and the like are known.

As a third method, as proposed in US Pat. No. 3,551,548 and US Pat. No. 3,763,113, a method of increasing the molecular weight effectively by adding a substance such as phosphoric acid under nitrogen at a temperature higher than the melting point of the nylon-based polymer is prevented from thermally decomposing. There is this.

However, most of the techniques known to date focus only on the study of increasing the molecular weight of virgin nylon fibers for improving the strength of virgin nylon fibers and moldings, and the molecular weights of waste nylon and degraded nylon, especially glycol degraded nylon. Very little research has been published on how to improve growth.

In addition, even in the domestic industrial field, research on the reuse of a single thermoplastic resin composite material (polyamide resin) recycled as a raw material resin for vibration damping materials and automotive engine cover used in automobiles and acid hydrolysis of waste carpet There have been studies on the regeneration method for recovering the wastes, and there is no technique for recycling waste nylon products without completely decomposing waste nylons into monomers.

As described above, research on recycling of nylon has been conducted for a long time, but most studies have only been conducted to recover the waste nylon in the form of monomers by acid hydrolysis. The process of recovering nylon as a monomer by chemical reaction is complicated by the recovery process and the energy is high, so it is more economical to use monomer synthesized from petroleum resources than using monomer recovered by recycling waste nylon. From the point of view of cost reduction, nylon recycling is not a good way to recover monomers. Another method is to add a chain extender that can increase the molecular weight when the waste nylon is recycled to the melt compounding process. However, various chain extenders are known to increase the molecular weight of nylon, but the reaction rate is not fast or is limited to the increase in molecular weight of virgin nylon (non-regenerated nylon). Nylon chain extenders known to date are epoxy, organic phosphite ester, bisoxazoline, bisoxazolone, biscaprolactam, acylbislactam, benzoxazine and the like.

Heat, UV, ozone, ethylene glycol (EG), water, and metal chlorides are factors that decompose nylon. To date, nylon recycling research has been focused on research on heat and ultraviolet rays, and thus, automotive cooling water. There is almost no research on the method of increasing the molecular weight of nylon decomposed by ethylene glycol and the decomposition mechanism of nylon used as an engine tank or a bumper of an automobile decomposed by a mixed solution of ethylene glycol / water.

It is an object of the present invention to provide a use of a diisocyanate derivative blocked by a blocking agent selected from lactams, oximes, alcohols, esters, and amine compounds as a chain extender for nylon.

Another object of the present invention is to provide a method of rapidly increasing molecular weight by melt compounding with waste nylon using the blocked diisocyanate derivative as a chain extender.

The present invention relates to a diisocyanate derivative in which a chain extender of nylon is blocked by a blocking agent selected from lactam, oxime, alcohol, ester, and amine compounds with both terminal isocyanate groups (-NCO) of aliphatic or aromatic diisocyanate compounds. It is characterized by that.

The present invention also provides a method for increasing the molecular weight of waste nylon by reacting with a chain extender, the method of increasing the molecular weight of waste nylon using the blocked diisocyanate derivative described above as the chain extender. do.

Referring to the present invention in more detail as follows.

The present invention relates to a novel blocked diisocyanate derivative that is useful as a chain extender of nylon. The chain extender proposed by the present invention is similar to the chemical structure of nylon, and thus, even if the polymer chain of nylon is broken, it is virgin. ) It is not much different from the basic chemical structure of nylon and has properties similar to those of virgin nylon.

In addition, the technique for increasing the molecular weight of the waste nylon proposed by the present invention is effective to increase the molecular weight of the waste nylon glycol-degraded by the mixed solution of ethylene glycol / water used as a component of the waste nylon, especially automotive cooling water. The proposed blocked diisocyanate has the property of rapidly increasing the molecular weight of glycol-decomposed nylon in the melt compounding process much more effectively than the conventional chain extender.

The chain extender characterized by the present invention is a diisocyanate derivative in which isocyanate groups (-NCO) present at both ends of the diisocyanate compound are blocked by a specific blocking agent. The diisocyanate compound can react with these blocking agents to produce a chain extender having thermoreversibility.

The isocyanate compound used for the preparation of the chain extender is a conventional aliphatic or aromatic diisocyanate compound having NCO groups bonded to both terminals, and the present invention does not place any particular limitation on the selection of the diisocyanate compound. Specifically describing the diisocyanate compound, the aliphatic diisocyanate compound may include a straight-chain, crushed or cyclic alkylene diisocyanate compound having 2 to 12 carbon atoms, and more specifically 1,6-hexamethylene diisocyanate (HDI). , 4,4'-diisocyanato dicyclohexylmethane (hydrogenated MDI), and 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethyl-cyclohexane (IPDI) Optional can be used. Aromatic diisocyanate compounds are aromatic diisocyanate compounds are 4,4'- diisocyanato diphenylmethane (4,4'-MDI), 2,4'- diisocyanato diphenylmethane (2,4'-MDI ), 2,2'-diisocyanato diphenylmethane (2,2'-MDI), 2,4-torylene diisocyanate (2,4-TDI), 2,6-torylene diisocyanate (2, 6-TDI), and naphthalene-1,5-diisocyanate (NDI). In the embodiment of the present invention, 1,6-hexamethylene diisocyanate (HDI) is used as the aliphatic diisocyanate compound, and 2,4-torylene diisocyanate (2,4-TDI) is used as the aromatic diisocyanate compound. Although only the example which manufactured the chain extender is described, the effect as a chain extender of the nylon which this invention aims can fully be acquired even if another diisocyanate compound is used.

In addition, a blocking agent used in the manufacture of the chain extender may be selected from lactams, oximes, alcohols, esters, and amine compounds. Specific examples of such blocking agents include lactam compounds including ε-caprolactam, α-pyrrolidone or 1-phenyl-3-methyl-5-pyrazolone; Oxime compounds including oxime or acetone oxime; Alcohol compounds including trihydroxymethylpropane (TMP), 6-hydroxytetraline, pyrocatechol, 6-hydroxybiphenyl, phenol, isooctylphenol, or 2,4-diisobutylphenol; Acetate compounds comprising ethylene malonate, or acetyl acetoacetate; And amine compounds including hydroxyamine, diphenylamine, monomethylaniline, or triazole; You can use it.

Since the blocked diisocyanate chain extender of the present invention is thermoreversible, the resulting diisocyanate is decomposed at the ends of light, heat, and hydrolyzed nylon while the blocking agent is liberated in the melt compounding process with the waste nylon. amine (-NH ₂₎ group or by reaction of ethylene glycol present at the terminal of the decomposition nylon amine (-NH ₂₎ group and a hydroxyethyl (-CH ₂ CH ₂ OH) group and the molecular weight by creating a urea bond and urethane bond Can be increased. In practice, blocked diisocyanates liberate isocyanates at temperatures above the melting point of the waste nylon to react with amine groups (-NH ₂ ) or hydroxyl groups (-OH), which are end groups of the waste nylon, to produce urea and urethane bonds, respectively. Can increase in a short time.

Accordingly, the present invention proposes a method of using the above-mentioned blocked diisocyanate derivative as a chain extender in a method of increasing the molecular weight of waste nylon using a chain extender. Waste nylon used in the present invention is a waste resource in which the molecular weight of nylon is greatly reduced through hydrolysis, photolysis, thermal decomposition, glycol decomposition, and the like. The present invention may be preferred from the viewpoint of environmental protection in that the molecular weight of the waste nylon is restored to the original molecular weight and recycled. Since the glycol decomposed waste nylon has a hydroxyl group (-OH) or an amine group (-NH ₂ ) as the terminal group, the blocked diisocyanate chain extender alone can effectively increase the molecular weight of the waste nylon. However, when the molecular weight of nylon is lowered by heat, light, hydrolysis, etc., rather than glycol degradation, the end groups of the waste nylon have an amine group (-NH ₂ ) and a carboxyl group (-COOH). The chain extender alone cannot effectively advance the chain extension reaction. In the method of maximizing the molecular weight increase of waste nylon decomposed by other than glycol decomposition, when a certain amount of bisoxazolin-based compound is added to the blocked diisocyanate as a chain extender, the molecular weight of waste nylon is more effectively used in the melt compounding process. Can be increased. Therefore, the present invention also includes a method of mixing and using a bisoxazolin-based compound which has been conventionally used together with blocked diisocyanate as a chain extender. Bisoxazolin-based compound is a known chain extender, specifically, it may be represented by the following formula (1).

[Formula 1]

In Formula 1, R represents an aliphatic or aromatic ring group having 1 to 10 carbon atoms, specifically, R is an alkylene group having 1 to 6 carbon atoms, m- or p-phenylene group.

When the bisoxazoline-based chain extender reacts with the waste nylon at a temperature above the melting point of the waste nylon, the ring is opened and condensed with the carboxy group, which is an end group of the waste nylon, to extend the chain.

The method of increasing the molecular weight of waste nylon according to the present invention includes a process of melt compounding, specifically, a mixture of waste nylon and a chain extender is more preferably used at temperatures above the melting point of waste nylon. The molecular weight is increased by melt compounding using a melt extruder at a temperature of 10 to 70 ℃ higher than the melting point of. The chain extender is used in the range of 0.01 to 20% by weight relative to the weight of the waste nylon, preferably in the range of 0.01 to 10% by weight. As the chain extender, a blocked diisocyanate and a bisoxazoline-based compound may be mixed, wherein the bisoxazoline-based compound is used within a weight ratio of 1: 0.5 to 2 based on the blocked diisocyanate.

The present invention as described above will be described in more detail based on the following examples, but the present invention is not limited thereto.

Example

In the following Examples 1 and 2, the basic process for the synthesis of blocked diisocyanate derivatives as the nylon chain extender according to the present invention, and the reaction mechanism between the chain extender and the nylon, was used as hexamethylene dicarbamoyl dicaprolactam and toylene dicarca. Bamoyl dicaprolactam is described by way of example.

Example 1. Hexamethylene dicarbamoyl dicaprolactam (HDC)

1) Synthesis and Purification of Hexamethylene Dicarbamoyl Dicaprolactam (HDC)

0.3 mol of hexamethylene diisocyanate (HDI) and 0.73 mol of ε-caprolactam (CPL) were added in a round flask for 75 hours for 6 hours. The reaction was carried out in a nitrogen environment while maintaining the ℃. Thereafter, acetone was added to the obtained reaction product to form an acetone solution, and then slowly dropped into excess distilled water with vigorous stirring to obtain a precipitate of powdery pure reactant HDC. This was filtered using a Buchner funnel and the reaction was washed repeatedly with distilled water to obtain a powdery HDC. This 80 It was dried for 3 days in a vacuum oven at ℃.

2) Confirmation of the thermoreversibility of hexamethylene dicarbamoyl dicaprolactam (HDC)

In order to confirm the thermal reversibility of the synthesized HDC, FT-IR was measured for each elevated temperature, and DSC and TGA were simultaneously measured. 132 according to the FT-IR spectrum according to FIG. 1 It can be seen that the NCO is released from the temperature, and according to the DSC and TGA measurement results according to FIG. It can be seen that ε-caprolactam (CPL) is volatilized while free NCO is generated near < RTI ID = 0.0 > These results confirm that HDC is thermoreversible.

3) Chain extension reaction between HDC and glycol decomposed nylon

The reaction of HDC and waste nylon at a temperature above the melting point of waste nylon raises the temperature to 132 NCO liberated from 0 ° C. condenses and reacts with hydroxyl or amine groups, which are end groups of waste nylon, to form urethane bonds and urea bonds, thereby extending the length of the chain of waste nylon. Here, the reactor that glycol decomposes nylon to produce hydroxyl group and amine group at the end group is "Kap Jin Kim, Manjula D. Dhevi, Jong Soon Lee, Young Dal Cho, Eun Kyung Choe, Polymer Degradation and Stability, 91 , 1545-1555 (2006) ".

① urethane bond formation reaction:

② urea bond formation reaction:

On the other hand, HDC can extend the molecular chain by forming a covalent bond with a hydroxyl group or an amine group, which is a waste nylon end group, at a temperature above the melting point of the waste nylon through a ring-opening reaction as shown below.

Example 2. Toylene Dicarbamoyl Dicaprolactam (TDC)

1) Synthesis and Purification of Toylene Dicarbamoyl Dicaprolactam (TDC)

0.33 mol of toluene diisocyanate (TDI) and 0.73 mol of ε-caprolactam (CPL) were added to a round flask containing 100 mL dry toluene and reacted under nitrogen stream for 8 hours under reflux. The reaction was then concentrated using a rotary evaporator. The concentrated reactant was slowly dropped into distilled water and stirred constantly to obtain a precipitate of powdery pure reactant TDC. This was washed with distilled water several times using a Buchner funnel (Buchner funnel) to obtain a powdery TDC. It was dried for 3 days in a vacuum oven at 80 ° C.

2) Check the thermal reversibility of the TDC

FT-IR spectrum measured at elevated temperature (FIG. 2- (a)) shows 126 It can be seen that glass-NCO was released from ℃, and it was also found in Figure 2- (b) obtained by simultaneous DSC and TGA measurements. Melt peak appears at ℃ and immediately 140 It can be seen that CPL is volatilized while free-NCO is generated near < RTI ID = 0.0 > From these results, it was confirmed that the TDC was thermally reversible.

3) Chain extension reaction between TDC and glycol decomposed nylon

The reaction of TDC and waste nylon at a temperature above the melting point of waste nylon raises the temperature to 126 Free-NCO released from ℃ condensation reaction of hydroxyl group or amine group which is end group of waste nylon to generate urethane bond and urea bond to extend waste nylon chain.

① urethane bond formation reaction:

② urea bond formation reaction:

In Example 3 below, the same thermoreversible phenol-blocked diisocyanate such as HDC and TDC shown in Examples 1 and 2 will be described as an example.

Example 3. Phenol-Blocked TDI (p-TDI)

Dissolve 1 mole of TDI and 2.4 mole of phenol in 500 mL of dry toluene in a round flask, and reflux for 3 hours under nitrogen stream to add a synthesized phenol-blocked TDI solution in a small amount of water dropwise and stir to white powdery phenol. Blocked TDI was obtained which was filtered, washed and vacuum dried at 80 ° C. for 24 hours. As a result of checking the thermal reversibility of the phenol-blocked TDI by the method used in Examples 1 and 2, TDI and phenol began to be released at 130 ° C. or higher. Therefore, it can be seen that phenol-blocked TDI can also increase the molecular weight through the melt compounding process of the molecular weight of hydrolyzed and glycol-decomposed nylon having amine groups and hydroxyl groups as shown in Examples 1 and 2 above.

In Examples 4 and 5 below, a method of increasing the molecular weight of nylon using a thermally reversible blocked diisocyanate-based chain extender will be described as an example.

Example 4 Method for Increasing Molecular Weight of Glycolyzed Nylon

Nylon glycol decomposed by ethylene glycol / water (50/50 v / v) has a hydroxyl group (-OH) and an amine group (-NH ₂ ) at both ends. The following experiments were carried out with an emphasis on increasing the molecular weight of nylon, which had been degraded due to glycol degradation, by re-linking these waste nylons and chain extenders again to 80% or more of virgin nylon.

Under the reflux condition, the chain extender was mixed to 3% by weight of waste nylon (nylon 66) decomposed by EG / water (50/50 v / v), and then 280 was prepared using an internal-mixer. The reaction was carried out at 5 ° C for 5 minutes. The resulting mixture was dissolved in formic acid to give 25 The intrinsic viscosity was determined by measuring the solution flow time at ℃, and the results are shown in FIG. As can be seen in Figure 5 when the glycol-decomposed nylon (used nylon) and the chain extender (TDC, HDC, p-TDI) is reacted, the intrinsic viscosity is increased compared to the used nylon (used nylon) virgin nylon before glycol decomposition It can be seen that up to 95% of the intrinsic viscosity of (new nylon) is restored.

Example 5 Method for Increasing Molecular Weight of Nylon Decomposed by Heat, Light and Hydrolysis

Waste nylon decomposed by heat, light, and hydrolysis has an amine group and a carboxyl group at the terminal, and the terminal having an amine group reacts with a blocked diisocyanate chain extender, but the terminal having a carboxyl group does not react. The reaction rate with the blocked diisocyanate chain extender is lower than the reaction rate with the glycol-decomposed waste nylon. Therefore, in order to maximize the molecular weight increase of the waste nylon decomposed by the cause other than glycol degradation, the chain extender was mixed with the waste nylon at a concentration of 3% by weight, and as the chain extender, a blocked diisocyanate chain extender (HDC) was used. , TDC, p-TDI) was used by mixing a bisoxazoline chain extender (R is m-phenylene) in a 1: 1 weight ratio. Reaction conditions were 280 using an internal-mixer as in Example 3 The reaction was carried out at 5 ° C for 5 minutes.

That is, virgin nylon (N-nylon; nylon 66), waste nylon (U-nylon; waste nylon 66), mixture of waste nylon / hexamethylene dicarbamoyl dicaprolactam (HDC), waste nylon / torylene dicarbamoyl Mixture of dicaprolactam (TDC), mixture of waste nylon / bisoxazoline chain extenders (OX), mixture of waste nylon / bisoxazoline chain extenders / hexamethylene dicarbamoyl dicaprolactam (OX / HDC ), A mixture of waste nylon / bisoxazoline chain extenders / torylene dicarbamoyl dicaprolactam (OX / TDC), a mixture of waste nylon / bisoxazoline chain extenders / phenol-blocked TDI (OX / Intrinsic viscosity was measured by dissolving each of p-TDI) in formic acid. The results are shown in FIG. As shown in FIG. 6, the intrinsic viscosity of the virgin nylon (N-nylon) when a bisoxazolin-based compound is simultaneously used together with a blocked diisocyate chain extender (HDC, TDC, p-TDI) It increased to the intrinsic viscosity. Therefore, the increase in molecular weight can be known from the results of intrinsic viscosity, and the simultaneous use of a blocked diisocyanate chain extender and a bisoxazoline chain extender can increase the waste nylon molecular weight increase more significantly. Could confirm.

As described above, waste nylon having a reduced molecular weight through decomposition of the nylon-based polymer by heat, ultraviolet rays, ozone, ethylene glycol (EG), water, and the like has a hydroxyl group (-OH) and an amine group (-NH _2). Or a carboxyl group (-COOH), and in the present invention, a thermoreversible blocked diisocyanate chain extender that reacts with these terminal groups is synthesized, and the compound is melt-compounded with waste nylon to be used to shorten the molecular weight within a short time. It is a technology that dramatically increases the recycling rate of waste nylon by increasing.

Therefore, the present invention is of great industrial utility as an invention for recycling waste resources.

Claims (12)

The chain of nylon, characterized in that both terminal isocyanate groups (-NCO) of the aliphatic or aromatic diisocyanate compound are diisocyanate derivatives blocked by a blocking agent selected from lactams, oximes, alcohols, esters, and amine compounds. Extender. The chain extender according to claim 1, wherein the aliphatic diisocyanate compound is a C2-C12 linear, pulverized or cyclic alkylene diisocyanate compound. The method of claim 2, wherein the aliphatic diisocyanate compound is 1,6-hexamethylene diisocyanate (HDI), 4,4'-diisocyanato dicyclohexylmethane (hydrogenated MDI), and 1-isocyanato A chain extender, characterized in that selected from -3-isocyanatomethyl-3,5,5-trimethyl-cyclohexane (IPDI). The method of claim 1, wherein the aromatic diisocyanate compound is 4,4'-diisosia neito diphenylmethane (4,4'-MDI), 2,4'-diisocyanato diphenylmethane (2,4 ' -MDI), 2,2'-diisocyanato diphenylmethane (2,2'-MDI), 2,4-torylene diisocyanate (2,4-TDI), 2,6-torylene diisocyanate ( 2,6-TDI), and naphthalene-1,5-diisocyanate (NDI). The method of claim 1, wherein the blocking agent (blocking agent) is a lactam compound comprising ε-caprolactam, a-pyrrolidone or 1-phenyl-3-methyl-5-pyrazolone; Oxime compounds including oxime or acetone oxime; Alcohol compounds including trihydroxymethylpropane (TMP), 6-hydroxytetraline, pyrocatechol, 6-hydroxybiphenyl, phenol, isooctylphenol, or 2,4-diisobutylphenol; Acetate compounds comprising ethylene malonate, or acetyl acetoacetate; And amine compounds including hydroxyamine, diphenylamine, monomethylaniline, or triazole; Chain extender, characterized in that selected from. In a method of increasing the molecular weight of waste nylon by reacting with a chain extender, The chain extender is characterized in that it comprises a blocked diisocyanate derivative selected from claims 1 to 5. 7. The method of claim 6, wherein the waste nylon is pyrolyzed, photolyzed, hydrolyzed or glycolyzed. 7. The method according to claim 6, wherein the chain extender is used in the range of 0.01 to 20% by weight based on the waste nylon. 7. The method of claim 6, wherein the chain extender further comprises a bisoxazolin-based compound. The method of claim 9, wherein the bisoxazolin-based compound is selected from compounds represented by the following formula (1). [Formula 1]

In Formula 1, R represents an aliphatic or aromatic ring group having 1 to 10 carbon atoms. The method of claim 9, wherein the bisoxazoline-based compound is used in a weight ratio of 1: 0.5 to 2 based on the blocked diisocyanate derivative. 7. The method of claim 6, wherein the molecular weight is increased by melt compounding the mixture of the waste nylon and the chain extender using a melt extruder at a temperature of 10 to 70 DEG C above the melting point of the waste nylon.

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