Reaction catalyst, nylon-based thermoplastic elastomer and synthesis, recovery method thereof

Abstract

The application belongs to the technical field of polymer materials, and relates to a reaction type catalyst, a nylon-based thermoplastic elastomer and a synthesis and recovery method thereof. The synthesis method of the reaction type catalyst comprises the following steps: (1) ion exchange is carried out on sodium 5-sulfonated isophthalic acid and a divalent metal ion compound in methanol to obtain a SSIPA-M intermediate which is slightly soluble in methanol; and (2) the SSIPA-M intermediate is reacted with a diatomic amine to obtain the reaction type catalyst. The divalent metal ion of the reaction type catalyst is combined with the carbonyl oxygen of the amide bond to enhance the electrophilicity of the carbonyl carbon, and to promote the nucleophilic attack of the polyether hydroxyl group on the carbonyl carbon of the amide bond. In addition, the divalent metal ion can catalyze the esterification and polycondensation reaction of the isophthalic acid carboxylic acid and the polyether hydroxyl group. Finally, the reaction type catalyst and the diatomic hydroxyl polyether upgrade the waste nylon 6 to the nylon-based thermoplastic elastomer, and the nylon-based thermoplastic elastomer is recovered by self-catalytic hydrolysis in the later period, and no additional catalyst needs to be added for catalytic hydrolysis recovery.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high polymer materials, and particularly relates to a reactive catalyst, a nylon-based thermoplastic elastomer and a synthesis and recovery method thereof. BACKGROUND

[0002] Polyamide 6, commonly known as nylon 6, is a synthetic polymer with a main chain containing repeating amide bonds (-CO-NH-). It has excellent comprehensive performance and is widely used in the fields of fibers, engineering plastics, films, etc. and is widely used in daily life. At present, the recycling rate of waste nylon 6 is less than 3%, and the discarded waste nylon 6 will cause microplastic pollution and release toxic amines (such as caprolactam, etc.), causing serious harm to the ecological environment; and burning emissions will produce pollutants such as hydrogen cyanide, aggravating air pollution. Therefore, how to efficiently solve the recycling problem of waste nylon 6 is imminent.

[0003] At present, the main recycling technologies include physical recycling, chemical recycling, biological recycling, etc.

[0004] Most of the waste is recycled by physical methods, which melt the waste and granulate, and then are sorted, washed, melt-extruded, and processed into recycled products; but the processing process will cause molecular chain breakage and mechanical property degradation, so that only downcycling can be achieved, and some low-end daily necessities such as carpets and ropes can be made; textile products are crushed and regenerated fibers are combed, but the fiber length is shortened and can only be downcycled for use as a filler material, etc., and the mechanical recycling times are limited.

[0005] Chemical recycling mainly includes hydrolysis, ammonolysis and alcoholysis; polyamide is depolymerized into monomers or oligomers, and then re-polymerized into products for use. At present, the chemical recycling of waste polyamide is a "polymer-monomer (prepolymer)-polymer" recycling mode, but these recycling conditions are harsh (such as strong acid, strong base, high pressure, etc.), the monomer purification is complicated, and the cycle from waste polyamide to recycled product is long; although high-value recycling can be achieved, the energy consumption is high and the cost is high; in addition, additional catalysts are needed for the synthesis and recycling of polymers to promote polymerization or depolymerization, which is more costly, and the residual catalysts may cause the polymer to change color or degrade, and heavy metal catalysts are biotoxic, which endangers the ecological environment and human health.

[0006] Biological recycling refers to the use of enzymes / microorganisms to degrade nylon to break the amide bond, but the efficiency is low and far from industrialization. SUMMARY

[0007] Based on the above-mentioned shortcomings and deficiencies existing in the prior art, one of the purposes of the present application is to at least solve one or more of the above-mentioned problems existing in the prior art, in other words, one of the purposes of the present application is to provide a reactive catalyst, a nylon-based thermoplastic elastomer and a synthesis and recovery method thereof which meet one or more of the aforementioned needs.

[0008] In order to achieve the above-mentioned purposes of the application, the following technical solutions are adopted in the present application:

[0009] A reactive catalyst, the structural formula of which is:

[0010] ;

[0011] In the formula, R is a hydrocarbon group or an aromatic group, and M is a divalent metal Zn or Mg.

[0012] The present application also provides a synthesis method of the reactive catalyst as described in the above scheme, comprising the following steps:

[0013] (1) ion exchange of sodium 5-sulfoisophthalate and a divalent metal ion compound in methanol to obtain a SSIPA-M intermediate which is slightly soluble in methanol;

[0014] (2) reaction of the SSIPA-M intermediate with a diamine to obtain the reactive catalyst.

[0015] As a preferred scheme, in the step (1), the ion exchange is carried out in a condensation reflux device in an inert gas environment, the reaction temperature is 50-70℃, the stirring speed is 50-150rpm, and the time is 5-10h; after the reaction, the temperature is lowered to 0℃, the precipitate is obtained by cooling, and the SSIPA-M intermediate is obtained by filtration and drying.

[0016] As a preferred scheme, in the step (2), the SSIPA-M intermediate and the diamine are subjected to amidation reaction in DMF, the reaction temperature is 40-60℃, the reaction time is 6-12h, and then the reactive catalyst is separated by fast column chromatography.

[0017] As a preferred scheme, in the step (1), the molar ratio of sodium 5-sulfoisophthalate to the divalent metal ion compound is (1-3):1; and in the step (2), the molar ratio of the SSIPA-M intermediate to the diamine is 1:(1-1.5).

[0018] As a preferred scheme, the divalent metal ion compound is zinc chloride, zinc sulfide, zinc carbonate, magnesium chloride, magnesium sulfide or magnesium carbonate.

[0019] The diamine is ethylenediamine, propylenediamine, butylenediamine, pentanediamine, hexanediamine or octanediamine.

[0020] The application also provides a synthesis method of the nylon-based thermoplastic elastomer, comprising:

[0021] The waste nylon 6, the reactive catalyst as described in the above scheme or the reactive catalyst synthesized by the synthesis method as described in any one of the above schemes, and the dihydroxy polyether are reacted by a one-step method of a melt polycondensation process to obtain the nylon-based thermoplastic elastomer.

[0022] As a preferred scheme, the specific process of the one-step method of the melt polycondensation process comprises:

[0023] The reaction is carried out under an inert gas atmosphere, the reaction temperature is 180-240 DEG C, and the reaction time is 1-4 h; then the polymerization is carried out under a vacuum condition of less than 100 Pa, the reaction temperature is 220-240 DEG C, and the reaction time is 1-5 h.

[0024] As a preferred scheme, the molar ratio of the waste nylon 6, the reactive catalyst, and the dihydroxy polyether is 1: (0.005-0.025): (0.01-0.05).

[0025] The dihydroxy polyether is polyethylene glycol, polypropylene glycol, polytetrahydrofuran, polybutylene glycol, or polytrimethylene glycol.

[0026] The application also provides a recovery method of the nylon-based thermoplastic elastomer synthesized by the synthesis method as described in any one of the above schemes, comprising:

[0027] After 10-40 parts of the thermoplastic elastomer are mixed with 100 parts of water, hydrolysis is carried out in a stainless steel autoclave, the hydrolysis temperature is 150-180 DEG C, the time is 0.5-1 h, the pressure is 0.1-1.0 MPa, and caprolactam, the reactive catalyst, and the dihydroxy polyether are obtained.

[0028] Compared with the prior art, the application has the beneficial effects that:

[0029] The divalent metal ion of the reaction catalyst of the present application is combined with the carbonyl oxygen of the amide bond of nylon 6 to enhance the electrophilicity of the carbonyl carbon, promoting the nucleophilic attack of the polyether hydroxyl group on the carbonyl carbon of the amide bond; in addition, the divalent metal ion can also catalyze the esterification and polycondensation reaction of isophthalic acid carboxylic acid and polyether hydroxyl group, and finally the reaction catalyst, the polyether ester amide elastomer, i.e. the nylon-based thermoplastic elastomer, is upgraded and recycled from waste nylon 6; wherein the metal ion in the elastomer can form ion aggregation physical crosslinking points with sulfonate and ether bond oxygen, thereby improving the strength and elasticity of the elastomer; and the presence of the metal ion also helps the post-catalytic hydrolysis and recovery of the nylon-based thermoplastic elastomer, without the need for additional catalysts to catalyze the hydrolysis and recovery, and the hydrophilicity of the sulfonate and polyether increases the solubility of the elastomer, thereby helping to improve the hydrolysis efficiency in the later stage, and finally hydrolyzing into the reaction catalyst, the dihydroxy polyether, and the amine-based hexanoic acid, which is then cyclized into caprolactam; the synergistic effect of the metal ion, sulfonate and ether bond promotes the post-hydrolysis and recovery of the elastomer, and a self-catalytic depolymerization rate of 95% can be achieved, and the monomer material after depolymerization can be polymerized into nylon 6 and its derivative products. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is the mechanical tensile curve diagram of the nylon-based thermoplastic elastomer of the present application embodiment 7, comparative example 2 and nylon 6;

[0031] Figure 2 is the 4-cycle tensile curve diagram of the nylon-based thermoplastic elastomer of the present application embodiment 7 with a strain of 300%. DETAILED DESCRIPTION

[0032] The reaction catalyst, the nylon-based thermoplastic elastomer and the synthesis and recovery method thereof of the present application are explained and described in detail as follows.

[0033] The reaction catalyst of the present application has the following structural formula:

[0034] ;

[0035] Wherein, R is a hydrocarbon group or an aromatic group, and M is a divalent metal Zn or Mg.

[0036] The two isophthalic acids of the above reaction catalyst share the same divalent metal ion, which can directly participate in the subsequent upgrading and recycling reaction of waste nylon 6.

[0037] The synthesis method of the above reaction catalyst comprises the following steps:

[0038] (1) ion exchange of isophthalic acid-5-sodium sulfonate and divalent metal ion compound in methanol to obtain a slightly soluble SSIPA-M intermediate in methanol;

[0039] The ion exchange is specifically carried out in a condensation reflux device in an inert gas environment, the reaction temperature is 50-70 DEG C, the stirring speed is 50-150 rpm, and the time is 5-10 h; after the reaction, the temperature is lowered to 0 DEG C, the precipitate is obtained by cooling, and the SSIPA-M intermediate is obtained by filtering and drying;

[0040] The divalent metal ion compound is zinc chloride, zinc sulfide, zinc carbonate, magnesium chloride, magnesium sulfide or magnesium carbonate, and can be specifically selected according to actual application requirements.

[0041] (2) the SSIPA-M intermediate is reacted with a diamine to obtain a reaction-type catalyst;

[0042] The SSIPA-M intermediate and the diamine are subjected to amidation reaction in DMF, the reaction temperature is 40-60 DEG C, the reaction time is 6-12 h, and then two isophthalic acid shared divalent metal ion reaction-type catalysts are obtained by rapid column chromatography separation;

[0043] The molar ratio of the isophthalic acid-5-sodium sulfonate and the divalent metal ion compound is (1-3):1; the molar ratio of the SSIPA-M intermediate and the diamine is 1:(1-1.5); and the specific molar ratio can be determined according to actual application requirements.

[0044] The diamine is ethylenediamine, propylenediamine, butylenediamine, pentanediamine, hexanediamine or octanediamine, and can be specifically selected according to actual application requirements.

[0045] In addition, in order to upgrade and recycle waste nylon 6, the waste nylon 6 is upgraded and recycled, and specifically, the synthesis method of the nylon-based thermoplastic elastomer comprises the following steps:

[0046] The waste nylon 6, the reaction-type catalyst and the dihydroxyl polyether are subjected to one-step reaction based on a melt polycondensation process to obtain the nylon-based thermoplastic elastomer.

[0047] The specific process of the one-step melt polycondensation process comprises the following steps:

[0048] The reaction is carried out in an inert gas atmosphere, the reaction temperature is 180-240 DEG C, the reaction time is 1-4 h; and then polymerization is carried out under a vacuum condition of less than 100 Pa, the reaction temperature is 220-240 DEG C, and the reaction time is 1-5 h;

[0049] The molar ratio of the waste nylon 6, the reaction-type catalyst and the dihydroxyl polyether is 1:(0.005-0.025):(0.01-0.05); and the specific molar ratio can be determined according to actual application requirements.

[0050] The dihydroxy polyether is polyethylene glycol, polypropylene glycol, polytetrahydrofuran, polybutylene oxide glycol or polytrimethylene ether glycol, and can be selected according to actual application requirements.

[0051] The application further provides a recycling method of the nylon-based thermoplastic elastomer synthesized by the synthetic method.

[0052] 10-40 parts of the thermoplastic elastomer is mixed with 100 parts of water, and then added into a stainless steel autoclave for hydrolysis, the temperature of the hydrolysis is 150-180 DEG C, the time is 0.5-1 h, and the pressure is 0.1-1.0 MPa, so that caprolactam, the reactive catalyst and the dihydroxy polyether are obtained.

[0053] For upgrading and recycling of waste nylon 6, the application adopts a "polymer-polymer" recycling mode, combines the advantages of physical recycling and chemical recycling, and develops a reactive catalyst that can participate in the reaction, so that the waste nylon 6 is directly upgraded and recycled into a thermoplastic elastomer, and in the absence of additional catalyst addition, the synergistic effect of the reactive catalyst and the polyether oxygen realizes the hydrolysis recycling of the regenerated elastomer. The "polymer-polymer" recycling mode reduces the process and cost of chemical recycling to purify monomers.

[0054] The recyclable nylon-based thermoplastic elastomer has good mechanical properties, heat resistance and cyclic tensile properties.

[0055] The following further explains and describes the reactive catalyst, the nylon-based thermoplastic elastomer and the synthesis and recycling method thereof by specific examples.

[0056] Example 1:

[0057] The synthesis method of the reactive catalyst of the example specifically includes the following steps:

[0058] According to the molar ratio, 5-sodium sulfonated isophthalic acid: zinc chloride = 3:1, 5-sodium sulfonated isophthalic acid 12.0 g and zinc chloride 2.0 g are added to 50 mL of methanol, and reacted in a condensation reflux device in an inert gas N2 environment at 60 DEG C for 10 h, the magnetic stirring speed is 100 rpm, then the temperature is reduced to 0 DEG C in an ice bath, a white precipitate is generated, the filter residue is dried and filtered to obtain the SSIPA-Zn intermediate;

[0059] Then according to the molar ratio, SSIPA-Zn intermediate: propylene diamine = 1:1, the SSIPA-Zn intermediate 5 g and the propylene diamine 0.66 g are reacted in DMF, the reaction temperature is 50 DEG C, the reaction time is 12 h, and finally the reactive catalyst SSIPA-Zn is separated by flash column chromatography.

[0060] Example 2:

[0061] The synthesis method of the reactive catalyst of the present example is different from that of Example 1 in that:

[0062] Zinc chloride is replaced by zinc sulfate, and the amount of zinc sulfate added is 2.4 g;

[0063] The other steps are the same as those of Example 1.

[0064] Example 3:

[0065] The synthesis method of the reactive catalyst of the present example is different from that of Example 1 in that:

[0066] Propylenediamine is replaced by hexanediamine, and the amount of hexanediamine added is 1 g;

[0067] The other steps are the same as those of Example 1.

[0068] Example 4:

[0069] The synthesis method of the reactive catalyst of the present example comprises the following steps:

[0070] Sodium isophthalic acid-5-sulfonic acid: magnesium chloride = 3: 1 by mole ratio, sodium isophthalic acid-5-sulfonic acid 12.0 g, magnesium chloride 104 g are added to 50 mL of methanol, and reacted in a condensation reflux device in an inert gas N2 environment at 60°C for 10 h, the magnetic stirring speed is 100 rpm, then the temperature is reduced to 0°C in an ice bath, a white precipitate is produced, the filter residue is dried to obtain the SSIPA-Mg intermediate;

[0071] Then SSIPA-Mg 5 g, propylenediamine 0.72 g are reacted in DMF, the reaction temperature is 50°C, the reaction time is 12 h, and finally the reactive catalyst SSIPA-Mg is separated by flash column chromatography.

[0072] Example 5:

[0073] The synthesis method of the reactive catalyst of the present example is different from that of Example 4 in that:

[0074] Zinc chloride is replaced by magnesium sulfate, and the amount of magnesium sulfate added is 0.9 g;

[0075] The other steps are the same as those of Example 1.

[0076] Example 6:

[0077] The synthesis method of the reactive catalyst of the present example is different from that of Example 4 in that:

[0078] Propylenediamine is replaced by octanediamine, and the amount of octanediamine added is 1.4 g;

[0079] Other steps are the same as Example 1.

[0080] Example 7:

[0081] The synthesis method of the recyclable nylon-based thermoplastic elastomer of the present example comprises the following steps:

[0082] According to the molar ratio, nylon 6: SSIPA-Zn: PEG600 = 1:0.01:0.02, 20g of waste nylon 6, 1g of the reactive catalyst SSIPA-Zn of Example 1, and 2.1g of PEG600 were put into a 250mL three-necked flask, argon was introduced to remove the air in the device, and stirred at 220℃ and 150rpm for 3h; then a vacuum device was connected, the pressure was kept below 100Pa, and stirred at 240℃ and 150rpm for 2h to obtain a recyclable nylon-based thermoplastic elastomer;

[0083] The decomposition temperature of the thermoplastic elastomer of the present example is 380℃, and the viscosity average molecular weight is 25kDa, as shown in Figure 1 , the elongation at break reaches 890%, the breaking strength reaches 33.6MPa, as shown in Figure 2 , the strain is 300% for 4 cycles of stretching.

[0084] Comparative Example 1:

[0085] The synthesis method of the nylon-based thermoplastic elastomer of the present comparative example is different from that of Example 7 in that:

[0086] The reactive catalyst SSIPA-Zn of Example 1 was replaced with sodium 5-sulfonate isophthalic acid, and the specific synthesis steps were as follows:

[0087] According to the molar ratio, nylon 6: sodium 5-sulfonate isophthalic acid: PEG600 = 1:0.02:0.02, 20g of waste nylon 6, 0.95g of sodium 5-sulfonate isophthalic acid, and 2.1g of PEG600 were put into a 250mL three-necked flask, no catalyst was added, argon was introduced to remove the air in the device, and stirred at 220℃ and 150rpm for 3h; then a vacuum device was connected, the pressure was kept below 100Pa, and stirred at 240℃ and 150rpm for 2h to 15h, it was found that high molecular weight polymers could not be synthesized.

[0088] Comparative Example 2:

[0089] The synthesis method of the nylon-based thermoplastic elastomer of the present comparative example is different from that of Example 7 in that:

[0090] The reactive catalyst SSIPA-Zn of Example 1 was replaced with sodium 5-sulfonate isophthalic acid and zinc acetate, and the specific synthesis steps were as follows:

[0091] Example 7: 20 g of waste nylon 6, 0.95 g of sodium 5-sulfoisophthalate, 2.1 g of PEG600 were put into a 250 mL three-necked flask, 0.05 g of zinc acetate was added, argon was introduced to replace the air in the device, and stirring was carried out at 220℃ and 150 rpm for 3 h; then a vacuum device was connected, the pressure was kept below 100 Pa, and stirring was carried out at 240℃ and 150 rpm for 12 h to obtain a nylon-based thermoplastic elastomer.

[0092] The decomposition temperature of the elastomer synthesized by adding a zinc acetate catalyst in this comparative example was 370℃, the viscosity average molecular weight was 12 kDa, the elongation at break was 183%, and the breaking strength was 16.1 MPa, as shown in Figure 1 .

[0093] It can be seen from the comparison of Example 7 with Comparative Examples 1 and 2 that Comparative Example 1 cannot synthesize a thermoplastic elastomer without adding a catalyst; Comparative Example 2 can synthesize an elastomer by adding a catalyst zinc acetate, but the reaction time is longer, which needs 15 h, while the addition of the reaction type catalyst SSIPA-Zn in Example 7 can realize the synthesis in a shorter time (5 h) by self-catalyzing nylon 6; in addition, the molecular weight of the elastomer of Example 7 is higher than that of Comparative Example 2, and the thermal stability is better, and the mechanical toughness is about 5 times higher than that of Comparative Example 2, and the breaking strength is more than 17.5 MPa than that of Comparative Example 2.

[0094] Example 8:

[0095] The difference between the synthesis method of the nylon-based thermoplastic elastomer of this example and Example 7 is that:

[0096] PEG600 is replaced by PEG1000, and the addition amount of PEG1000 is changed to 3.5 g;

[0097] The other steps are the same as those in Example 7.

[0098] The decomposition temperature of the thermoplastic elastomer synthesized in this example is 377℃, the viscosity average molecular weight is 26 kDa, the elongation at break is 910%, and the breaking strength is 30.7 MPa.

[0099] Example 9:

[0100] The difference between the synthesis method of the nylon-based thermoplastic elastomer of this example and Example 7 is that:

[0101] PEG600 is replaced by PTMG650, and the addition amount of PTMG650 is changed to 2.3 g;

[0102] The other steps are the same as those in Example 7.

[0103] The thermoplastic elastomer synthesized in this example has a decomposition temperature of 380°C, a viscosity average molecular weight of 27 kDa, an elongation at break of 980%, and a breaking strength of 41 MPa.

[0104] Example 10:

[0105] The difference between the synthesis method of the nylon-based thermoplastic elastomer of this example and that of Example 7 is that:

[0106] The reaction-type catalyst SSIPA-Zn of Example 1 is replaced with the reaction-type catalyst SSIPA-Mg of Example 4, and the amount of SSIPA-Mg added is changed to 0.9 g;

[0107] The other steps are the same as those of Example 7.

[0108] The thermoplastic elastomer synthesized in this example has a decomposition temperature of 375°C, a viscosity average molecular weight of 23 kDa, an elongation at break of 800%, and a breaking strength of 29.2 MPa.

[0109] Example 11:

[0110] The self-catalytic hydrolysis depolymerization recovery method of the nylon-based thermoplastic elastomer of this example includes the following processes:

[0111] Take 20 g of the nylon-based thermoplastic elastomer of Example 7 and mix it with 100 g of deionized water, then add it to a stainless steel autoclave. The depolymerization temperature is 160°C, the time is 0.5 h, and the pressure is 0.5 MPa. Caprolactam and PEG600 are obtained. According to the calculation of the monomers after depolymerization, the hydrolysis recovery rate of the thermoplastic elastomer reaches 95%.

[0112] Comparative Example 3:

[0113] The self-catalytic hydrolysis depolymerization recovery method of the nylon-based thermoplastic elastomer of this example includes the following processes:

[0114] Take 20 g of the thermoplastic elastomer of Comparative Example 2 and mix it with 100 g of deionized water, then add it to a stainless steel autoclave. The depolymerization temperature is 160°C, the time is 5 h, and the pressure is 0.5 MPa. Caprolactam and PEG600 are obtained. According to the calculation of the monomers after depolymerization, the hydrolysis recovery rate of the thermoplastic elastomer reaches 45%.

[0115] As can be seen by comparing Example 11 with Comparative Example 3, the hydrolysis of Example 11 is faster and has a higher hydrolysis depolymerization rate of 95% compared with Comparative Example 3.

[0116] Example 12:

[0117] The self-catalytic hydrolytic depolymerization recovery method of the nylon-based thermoplastic elastomer of the embodiment comprises the following processes:

[0118] 20 g of the nylon-based thermoplastic elastomer of Example 10 is mixed with 100 g of deionized water and then added into a stainless steel autoclave, the depolymerization temperature is 160 DEG C, the time is 0.5 h, the pressure is 0.5 MPa, and monomer caprolactam and PEG600 are obtained; according to the calculation of the monomers after depolymerization, the hydrolysis recovery rate of the thermoplastic elastomer reaches 90%.

[0119] In view of the fact that there are numerous embodiments of the present application, the raw materials and the amounts involved can be selected according to actual needs within the limited range, and the experimental data of each embodiment are numerous and cannot be listed and explained one by one, but the contents to be verified and the final conclusions obtained by each embodiment are close. Therefore, the verification contents of each embodiment are not described one by one.

[0120] The above only describes the preferred embodiments and principles of the present application in detail, and for those skilled in the art, the specific implementation manner can be changed according to the idea provided by the present application, and these changes should also be considered as the protection scope of the present application.

Claims

1. A reactive catalyst characterized in that, The structural formula is: ； Wherein, R is ethyl, propyl, butyl, pentyl, hexyl or octyl, and M is divalent metal Zn.

2. The method for synthesizing the reactive catalyst as described in claim 1, characterized in that, The method comprises the following steps: (1) ion exchange of sodium 5-sulfoisophthalate and divalent metal Zn ion compound in methanol to obtain a slightly soluble SSIPA-M intermediate in methanol; (2) reaction of the SSIPA-M intermediate with a diamine to obtain a reaction-type catalyst; The diamine is ethylenediamine, propylenediamine, butylenediamine, pentanediamine, hexanediamine or octanediamine.

3. The method of synthesis of claim 2, wherein, In the step (1), the ion exchange is carried out in a condensing reflux device in an inert gas environment, the reaction temperature is 50-70 DEG C, the stirring speed is 50-150 rpm, and the time is 5-10 h; after the reaction, the temperature is lowered to 0 DEG C, and the obtained precipitate is cooled, filtered and dried to obtain the SSIPA-M intermediate.

4. The method of synthesis of claim 2, wherein, In the step (2), the SSIPA-M intermediate is subjected to amidation reaction with the diamine in DMF, the reaction temperature is 40-60 DEG C, the reaction time is 6-12 h, and then the reaction-type catalyst is separated by fast column chromatography.

5. The method of synthesis of claim 2, wherein, In the step (1), the molar ratio of sodium 5-sulfoisophthalate to divalent metal Zn ion compound is (1-3):1; and in the step (2), the molar ratio of the SSIPA-M intermediate to the diamine is 1:(1-1.5).

6. The method of synthesis of claim 2, wherein, The divalent metal Zn ion compound is zinc chloride, zinc sulfide or zinc carbonate.

7. A method of synthesizing a nylon-based thermoplastic elastomer, characterized by, The method comprises the following steps: The waste nylon 6, the reaction-type catalyst as claimed in claim 1 or synthesized by the synthesis method as claimed in any one of claims 2-6, and the dihydroxyl polyether are subjected to one-step reaction based on a melt polycondensation process to obtain a nylon-based thermoplastic elastomer.

8. The method of synthesis of claim 7, wherein, The specific process of the one-step melt polycondensation process comprises: The reaction is carried out in an inert gas atmosphere, the reaction temperature is 180-240 DEG C, and the reaction time is 1-4 h; then the polymerization is carried out under vacuum condition of less than 100 Pa, the reaction temperature is 220-240 DEG C, and the reaction time is 1-5 h.

9. The method of synthesis of claim 7, wherein, The molar ratio of the waste nylon 6, the reaction-type catalyst and the dihydroxyl polyether is 1:(0.005-0.025):(0.01-0.05). The dihydroxyl polyether is polyethylene glycol, polypropylene glycol, polytetrahydrofuran, polybutylene oxide glycol or polytrimethylene ether glycol.

10. A process for recycling a nylon-based thermoplastic elastomer synthesized according to the process of any one of claims 7-9, characterized in that, The method comprises the following steps: 10-40 parts of the thermoplastic elastomer are mixed with 100 parts of water, and then the mixture is added into a stainless steel autoclave for hydrolysis, the temperature for the hydrolysis is 150-180 DEG C, the time is 0.5-1 h, the pressure is 0.1-1.0 MPa, and caprolactam, the reaction-type catalyst and the dihydroxyl polyether are obtained.

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