A bio-based spandex elastane fiber and a method of making the same

Abstract

The application provides a kind of bio-based spandex elastic fiber and its preparation method, the bio-based spandex is introduced into spandex molecular chain by bio-based polyether polyol, and the bio-based polyether polyol contains bio-based 1,3-propanediol unit structure.The preparation method is that the bio-based spandex is obtained by including bio-based polyurethane prepolymer, mixed amine reaction to obtain the raw material containing polyurethane-urea polymer, and the raw material is used as the spinning solution to obtain by dry spinning.The performance of the spandex product is close to the petrochemical-based spandex product, which can perfectly replace the petrochemical-based spandex product and better promote the transformation and upgrading of the product.The technical problem that the difference in performance between bio-based raw materials and petrochemical-based materials leads to insufficient reaction or instability is solved, the conventional petroleum-based spandex production equipment can be directly used, and industrial production is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of preparation of high molecular bio-based materials, in particular to a bio-based spandex elastic fiber and a preparation method thereof. BACKGROUND

[0002] Spandex, also known as polyurethane elastic fiber, is one of the best elastic fibers in synthetic fibers, with high elasticity, high elongation, low modulus, high hydrolysis resistance, etc. It is widely used in the clothing and textile industry, including high-performance structural composites, swimwear, stockings, diapers, etc. However, with the proposal of the national "double carbon" goal, as a traditional industry, spandex must also accelerate the transformation and upgrading of green new technology and industry, and green and low-carbon bio-based spandex will be the trend of future spandex development.

[0003] At present, most of the spandex is prepared by using petrochemical-based raw materials PTMEG and MDI, and the bio-based carbon content in the prepared spandex fiber is almost zero. There are few reports on the preparation method of bio-based spandex, mainly by adding bio-based polyester diols to replace PTMEG in spandex fibers. For example, patent CN115233331A, a bio-based spandex fiber and a preparation method thereof, selects bio-based polyester diols as raw materials, reacts with diisocyanate to prepare isocyanate-terminated bio-based polyester, then uses bio-based lysine for chain extension, and finally uses bio-based amino acid for end capping to prepare spandex fiber. The bio-based polyester diols used have the following structure: wherein R1 is: -(CH2)8- or -(CH2)9-, or a mixture of the two; R2 is: -(CH2)6-, -(CH2) 10 or -(CH2) 11 , or a mixture of the two; n is a natural number of 3-11. Patent CN114031742A, a biodegradable melt-spun spandex chip and a preparation method and application thereof, selects bio-based polyester polyols and diisocyanate to prepare a biodegradable melt-spun spandex chip for producing melt-spun spandex fibers. The bio-based polyester polyols used are polymerized from bio-based sebacic acid and bio-based isosorbide. Although the above-mentioned patents also prepare bio-based spandex fibers, the bio-based raw materials used are polyester diols. Since the spandex prepared from polyester diols has poor hydrolysis resistance and the mechanical properties of the spandex yarn are also low, it cannot replace conventional spandex for use, and the synthesis of the above-mentioned bio-based polyester polyols is complex and cannot be mass-produced, which cannot be widely used. SUMMARY

[0004] Technical problem: The technical problem to be solved by the present application is to provide a bio-based spandex fiber and a preparation method thereof. The technical problem of insufficient reaction or instability caused by the difference in performance between bio-based raw materials and petrochemical-based materials is solved, and the production equipment for conventional petrochemical-based spandex can be directly used, and industrial production is realized.

[0005] Technical solution: The present application provides a bio-based spandex fiber, wherein the bio-based spandex is introduced into the molecular chain of the spandex by bio-based polyether polyol, and the bio-based polyether polyol contains a bio-based 1,3-propanediol unit structure.

[0006] The preparation method of the bio-based spandex fiber of the present application is to obtain a raw material containing a polyurethane-urea polymer by reacting a bio-based polyurethane prepolymer and a mixed amine, and to obtain the bio-based spandex fiber by dry spinning using the raw material as a spinning solution.

[0007] The specific preparation method specifically includes:

[0008] 1) Prepolymerization of a polyisocyanate and a bio-based polyether polyol in the presence of a solvent to obtain a bio-based polyurethane prepolymer solution;

[0009] 2) Reacting the polyurethane prepolymer solution and the mixed amine solution to obtain a polyurethane-urea stock solution;

[0010] 3) Aging the polyurethane-urea stock solution, and obtaining the bio-based spandex fiber by dry spinning technology using the aged polyurethane-urea stock solution as a raw material.

[0011] The bio-based spandex fiber contains more than 25% of bio-based carbon, preferably between 25% and 80%, and more preferably between 35% and 60%.

[0012] The bio-based polyurethane prepolymer is obtained by reacting a bio-based polyether polyol and a polyisocyanate; and the NCO content of the bio-based polyurethane prepolymer is 2.5-3.1 wt%.

[0013] The number average molecular weight of the bio-based polyether polyol is 1500-5000 g / mol.

[0014] The polyisocyanate includes one or more of diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and / or derivatives and / or modified polymers.

[0015] The mixed amine includes a diamine chain extender and a monoamine end-capping agent; the diamine chain extender includes a chain diamine, and the chain diamine includes one or more of ethylenediamine, 1,2-propylenediamine, and 2-methyl-1,5-pentanediamine, preferably ethylenediamine; the monoamine end-capping agent includes one or more of diethylamine, dipropylamine, and n-hexylamine.

[0016] The diamine chain extender includes a mixed amine of a chain diamine and a cyclic diamine, and the cyclic diamine includes one or more of methylcyclohexanediamine, 4,4-diaminodicyclohexylmethane, and 3,3-dimethyl-4,4-diaminodicyclohexylmethane, preferably 3,3-dimethyl-4,4-diaminodicyclohexylmethane.

[0017] The molar ratio of the chain diamine and the cyclic diamine is 3:1 to 10:1.

[0018] The molar ratio of the diamine chain extender and the monoamine end-capping agent is 6.5:1 to 12:1.

[0019] Advantages:

[0020] (1) The biomass carbon content of the bio-based polyurethane elastic fiber of the present application can reach more than 25%, and the carbon dioxide emission is 20-60% lower than that of traditional petrochemical-based spandex products, and 18-48% lower than that of oil gas-based products. From the perspective of non-renewable energy consumption, bio-based spandex is 18-46% lower than oil-based, and 15-40% lower than oil gas-based. (2) The bio-based spandex of the present application contains bio-based 1,3-propanediol unit structure, and the hydrolysis resistance and alkali resistance are significantly better than those of bio-based spandex products prepared by using bio-based polyester polyol, and the performance of the spandex product is close to that of petrochemical-based spandex product, which can perfectly replace petrochemical-based spandex product and better promote the transformation and upgrading of the product. (3) The preparation process of the bio-based spandex of the present application is stable, which solves the technical problems of insufficient or unstable reaction caused by the performance difference between bio-based raw materials and petrochemical-based materials, and can directly use the production equipment of conventional oil-based spandex and realize industrialized production. DETAILED DESCRIPTION

[0021] The bio-based spandex contains bio-based 1,3-propanediol unit structure, and the spandex molecular chain is introduced by bio-based polyether polyol containing bio-based 1,3-propanediol unit structure.

[0022] The bio-based carbon content in the bio-based spandex is more than 25%, preferably between 25% and 80%, and more preferably between 35% and 60%.

[0023] The bio-based 1,3-propanediol is prepared from biological raw materials.

[0024] In the present application, the biological raw material refers to including animal and plant oils and fats, wood, tree bark, crop straw, corn, bamboo, sugarcane residue, etc.;

[0025] As an example, the bio-based 1,3-propanediol is obtained by microbial fermentation process of the sugar extracted from the biological raw material;

[0026] The bio-based polyether polyol is obtained by polymerization of the bio-based 1,3-propanediol;

[0027] In some examples of the present application, the bio-based polyether polyol is the product of Shanghai Huafeng Ruixin Biomaterials Co., Ltd.;

[0028] In the present application, the bio-based carbon content refers to the test result obtained by ASTM6866-22 method B (AMS) TOC.

[0029] Further, the bio-based spandex is obtained by reacting the bio-based polyurethane prepolymer and mixed amine to obtain a raw material containing polyurethane-urea polymer, and by using the raw material as a spinning solution to obtain by dry spinning;

[0030] The bio-based polyurethane prepolymer is obtained by reacting the bio-based polyether polyol and polyisocyanate;

[0031] The number average molecular weight of the bio-based polyether polyol is 1500-5000 g / mol.

[0032] The NCO content of the polyurethane prepolymer is 2.5-3.1 wt%;

[0033] Further, in some examples of the present application, the bio-based polyurethane prepolymer is obtained by reacting the bio-based polyether polyol, petroleum-based polyether polyol, and polyisocyanate;

[0034] Further, in some other examples of the present application, the bio-based polyurethane prepolymer is obtained by reacting the bio-based polyether polyol and polyisocyanate, and then reacting with the petroleum-based polyether polyol;

[0035] The petroleum-based polyether polyol includes polytetramethylene ether polyol PTMEG, and the number average molecular weight is 1200-3000 g / mol, preferably 1800-2000 g / mol;

[0036] Further, the mass ratio of the bio-based polyether polyol and the petroleum-based polyether polyol is between 100:0 and 30:70;

[0037] The polyisocyanate includes one or more of diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and / or derivatives and / or modified polymers;

[0038] In some examples of the present application, the polyisocyanate includes diphenylmethane diisocyanate;

[0039] The mixed amine includes a diamine chain extender and a monoamine end capping agent;

[0040] The diamine chain extender includes one or more of ethylenediamine, 1,2-propylenediamine, 2-methyl-1,5-pentanediamine;

[0041] Further, the diamine chain extender includes a mixed amine of a chain diamine and a cyclic diamine, the cyclic diamine including one or more of methylcyclohexanediamine, 4,4-diaminodicyclohexylmethane, 3,3-dimethyl-4,4-diaminodicyclohexylmethane;

[0042] The molar ratio of the chain diamine and the cyclic diamine is 3:1 to 10:1;

[0043] In the present application, the use of chain diamines and cyclic diamines can further improve the performance of bio-based spandex fibers, making the performance of spandex products closer to that of petrochemical-based spandex products.

[0044] The monoamine end capping agent includes one or more of diethylamine, dipropylamine, n-hexylamine.

[0045] The molar ratio of the diamine chain extender and the monoamine end capping agent is between 6.5:1 and 12:1.

[0046] The method for preparing bio-based spandex fibers includes:

[0047] 1) Prepolymerizing the polyisocyanate and the bio-based polyether polyol in the presence of a solvent to obtain a bio-based polyurethane prepolymer solution;

[0048] 2) Reacting the polyurethane prepolymer solution with a mixed amine solution to obtain a polyurethane-urea stock solution;

[0049] 3) Aging the polyurethane-urea stock solution, and obtaining bio-based spandex fibers by dry spinning technology using the aged polyurethane-urea stock solution as raw material.

[0050] In some examples of the present application, the bio-based spandex fibers do not additionally contain petroleum-based polyether polyols, and the method for preparing bio-based spandex fibers includes:

[0051] 1) adding solvent, bio-based polyether polyol, polyisocyanate into a reactor to react to obtain a bio-based polyurethane prepolymer solution;

[0052] 2) adding a mixed amine solution into the polyurethane prepolymer solution to react, and continuing to react to obtain a polyurethane-urea stock solution;

[0053] 3) after maturing the polyurethane-urea stock solution, spitting, stretching, and drying the matured stock solution into filaments by means of a dry spinning system, to obtain bio-based polyurethane elastic fibers.

[0054] In some other examples of the present application, the bio-based spandex fibers are further added with petroleum-based polyether polyols, and the preparation method of the bio-based spandex fibers comprises:

[0055] 1) adding solvent, bio-based polyether polyol, petroleum-based polyether polyol, polyisocyanate into a reactor to react to obtain a bio-based polyurethane prepolymer solution;

[0056] 2) adding a mixed amine solution into the polyurethane prepolymer solution to react, and continuing to react to obtain a polyurethane-urea stock solution;

[0057] 3) after maturing the polyurethane-urea stock solution, spitting, stretching, and drying the matured stock solution into filaments by means of a dry spinning system, to obtain bio-based polyurethane elastic fibers.

[0058] In some other examples of the present application, the bio-based spandex fibers are further added with petroleum-based polyether polyols, and the preparation method of the bio-based spandex fibers comprises:

[0059] 1) adding solvent, bio-based polyether polyol, polyisocyanate into a reactor to react, and then adding petroleum-based polyether polyol to continue to react to obtain a bio-based polyurethane prepolymer solution;

[0060] 2) adding a mixed amine solution into the polyurethane prepolymer solution to react, and continuing to react to obtain a polyurethane-urea stock solution;

[0061] 3) after maturing the polyurethane-urea stock solution, spitting, stretching, and drying the matured stock solution into filaments by means of a dry spinning system, to obtain bio-based polyurethane elastic fibers.

[0062] The NCO mass content of the bio-based polyurethane prepolymer is 2.5-3.1 wt%;

[0063] The solvent includes N,N-dimethylacetamide DMAc, N-methyl-2-pyrrolidone NMP, and dimethylformamide DMF; as an example, the solvent is DMAc;

[0064] The mass concentration of the bio-based polyurethane prepolymer solution of step 1) is 30-40%;

[0065] The concentration of the mixed amine solution of step 2) is 3%-10%;

[0066] The molar ratio of the total amine groups of the mixed amine to the isocyanate groups of the polyurethane prepolymer of step 3) is 1.0-1.2, preferably 1.02-1.10.

[0067] Further, other functional additives can be added to the polyurethane-urea stock solution as long as the performance of the product is not deteriorated. For example, one or more of lubricants, antioxidants, ultraviolet light resistant agents, matting agents, dyeing aids, chlorine resistant agents, and lubricants.

[0068] The following examples are used to describe the production process of the present application in detail, but these examples should not be understood as limiting the present application in any sense.

[0069] Example 1:

[0070] 6.0 kg of solvent dimethylacetamide (DMAC) was added to a first reactor (RA1), and stirring was started. Then, 12.0 kg of bio-based poly 1,3-propanediol with a molecular weight of 2000 and 2.585 kg of diphenylmethane diisocyanate were added to RA1, and the mixture was reacted at 45°C for 3 h to obtain a prepolymer PPS. The PPS was transferred to a second reactor (RA2). 15.86 kg of washing DMAC was added to RA1, and the washing DMAC was transferred to RA2. When the temperature of RA2 cooled to about 10°C, a mixed amine solution containing 281 g of ethylenediamine, 112 g of 4,4-diaminodicyclohexyl methane, and 46 g of diethylamine was added dropwise to RA2 to perform chain extension and chain termination reactions, wherein the mass concentration of the mixed amine solution was 5.0%. After the reaction was completed, the obtained polymer was transferred to a D-FETK, and aging was continued for 20 h to obtain a polyurethane-urea spinning stock solution. Bio-based spandex fibers 1 were obtained by dry spinning.

[0071] Example 2:

[0072] Into a first reactor (RA1), 6.0 kg of solvent dimethylacetamide (DMAC) was added, stirring was started, and then 10.0 kg of bio-based poly 1,3-propanediol having a molecular weight of 2000 and 2.683 kg of diphenylmethane diisocyanate were added to RA1, and reacted at 60 °C for 3 h, and then 2.375 kg of PTMEG having a molecular weight of 1900 was added thereto, and reacted at 45 °C for 3 h to obtain a prepolymer PPS, and the PPS was transferred into a second reactor (RA2). Into RA1, 16.486 kg of washing DMAC was added, and the washing DMAC was transferred into RA2, and stirring was started, and when the temperature of RA2 was cooled to about 10 °C, a mixed amine solution containing 244 g of ethylenediamine, 162 g of 3,3-dimethyl-4,4-diaminodicyclohexyl methane, and 43 g of diethylamine was added dropwise to RA2 to perform chain extension and chain termination reactions, and the mixed amine solution had a mass concentration of 5.0%. After the reaction was completed, the obtained polymer was transferred into a D-FETK, and aging was continued for 20 h to obtain a polyurethane-urea spinning dope, and bio-based spandex fibers 2 were obtained by dry spinning.

[0073] Example 3:

[0074] Into a first reactor (RA1), 6.0 kg of solvent dimethylacetamide (DMAC) was added, stirring was started, and then 10.0 kg of bio-based poly 1,3-propanediol having a molecular weight of 2000 and 2.683 kg of diphenylmethane diisocyanate were added to RA1, and reacted at 60 °C for 3 h, and then 2.375 kg of PTMEG having a molecular weight of 1900 was added thereto, and reacted at 45 °C for 3 h to obtain a prepolymer PPS, and the PPS was transferred into a second reactor (RA2). Into RA1, 16.486 kg of washing DMAC was added, and the washing DMAC was transferred into RA2, and stirring was started, and when the temperature of RA2 was cooled to about 10 °C, a mixed amine solution containing 244 g of ethylenediamine, 162 g of 3,3-dimethyl-4,4-diaminodicyclohexyl methane, and 43 g of diethylamine was added dropwise to RA2 to perform chain extension and chain termination reactions, and the mixed amine solution had a mass concentration of 5.0%. After the reaction was completed, the obtained polymer was transferred into a D-FETK, and aging was continued for 20 h to obtain a polyurethane-urea spinning dope, and bio-based spandex fibers 2 were obtained by dry spinning.

[0075] Example 4:

[0076] Into a first reactor (RA1), 6.0 kg of solvent dimethylacetamide (DMAC) was added, stirring was started, and then 10.0 kg of bio-based poly 1,3-propanediol with a molecular weight of 2000, 2.375 kg of PTMEG with a molecular weight of 1900, and 2.683 kg of diphenylmethane diisocyanate were added, and a prepolymer PPS was obtained by reacting at 60 °C for 3 h. The PPS was transferred into a second reactor (RA2). Into RA1, 16.486 kg of washing DMAC was added, and the washing DMAC was transferred into RA2. When the temperature of RA2 cooled to about 10 °C, a mixed amine solution containing 244 g of ethylenediamine, 162 g of 3,3-dimethyl-4,4-diaminodicyclohexyl methane, and 43 g of diethylamine was added dropwise into RA2 to perform chain extension and chain termination reactions, wherein the mass concentration of the mixed amine solution was 5.0%. After the reaction was completed, the obtained polymer was transferred into a D-FETK, and the reaction was aged for 20 h to obtain a polymeric spinning dope, and a bio-based polyurethane elastic fiber was obtained by dry spinning.

[0077] Example 5:

[0078] The difference from Example 1 is that an equimolar amount of ethylenediamine is used to replace 4,4-diaminodicyclohexyl methane.

[0079] Example 6:

[0080] The difference from Example 1 is that an equimolar amount of 4,4-diaminodicyclohexyl methane is used to replace ethylenediamine.

[0081] Comparative Example 1:

[0082] The difference from Example 1 is that an equimolar amount of petroleum-based PTMEG is used to replace bio-based poly 1,3-propanediol, and an equimolar amount of ethylenediamine is used to replace 4,4-diaminodicyclohexyl methane.

[0083] Comparative Example 2:

[0084] The difference from Example 1 is that an equimolar amount of petroleum-based PTMEG is used to replace bio-based poly 1,3-propanediol.

[0085] Comparative Example 3:

[0086] The difference from Example 1 is that an equimolar amount of bio-based polyester polyol (polycondensation of bio-based succinic acid and bio-based 1,4-butanediol) is used to replace bio-based poly 1,3-propanediol.

[0087] Comparative Example 4:

[0088] The difference from Example 1 is that an equimolar amount of bio-based polyethylene glycol polyol is used to replace bio-based poly 1,3-propanediol.

[0089] The polyurethane elastic fibers in the above examples and comparative examples were respectively subjected to tensile property test, alkali resistance test and bio-based carbon content test, and the data are shown in the following table:

[0090] Table 1: Performance test data of different polyurethane elastic fibers

[0091]

[0092]

[0093] SS300 represents the tension when the spandex is stretched by 300%, DS represents the maximum tension when the spandex is stretched to break, DE represents the maximum stretch when the spandex is stretched to break, alkali resistance represents the retention rate of breaking tension (DS) of the spandex after treatment in 10% sodium hydroxide concentration at 100°C for 60 minutes. Bio-based carbon content represents the mass fraction of bio-based carbon in the total carbon in the spandex. Bio-based carbon content represents the mass fraction of bio-based carbon in the total carbon in the spandex.

[0094] SS300, DS, DE test method: Under the condition of 20°C and 70% humidity, using an isometric tensile testing machine, the spandex yarn with a length of 50mm was stretched to break at a speed of 10mm / s, and the elongation stress SS300, breaking strength DS and breaking elongation DE were recorded.

[0095] Bio-based carbon content was tested by ASTM6866-22 method B (AMS) TOC.

[0096] As can be seen from the table, different contents of bio-based polyether polyol can be added according to the requirements to prepare bio-based spandex with different bio-based carbon contents. The performance indicators of the bio-based spandex prepared in the preferred examples are close to those of the ordinary conventional petroleum-based spandex (comparative sample 1), and no obvious performance degradation problem occurs, meeting the performance requirements of bio-based spandex in various fields. On the basis of conventional petroleum-based spandex, if the diamine is a mixture of chain diamine and cyclic diamine, even if SS300 and DS are improved, DE decreases significantly (comparative sample 2). The elongation performance and alkali resistance of the bio-based spandex product prepared by adding bio-based polyester polyol (comparative example 3) are far inferior to those of the bio-based spandex product in example 1 and the ordinary spandex product (comparative sample 1). The mechanical properties of the bio-based spandex product prepared by adding other bio-based polyether polyol (comparative example 4) are also inferior to those of the bio-based spandex product in example 1 and the ordinary spandex product (comparative sample 1). In summary, the performance of the bio-based spandex product prepared by the present application can reach the level of ordinary spandex products, and no obvious performance degradation problem occurs, which can perfectly replace petrochemical-based spandex products and better promote the transformation and upgrading of products.

Claims

1. A biobased spandex fiber, characterized in that, The bio-based spandex is introduced into the spandex molecular chain by bio-based polyether polyol containing bio-based 1,3-propanediol unit structure; The bio-based spandex is obtained by dry spinning including the raw material containing polyurethane-urea polymer prepared by bio-based polyurethane prepolymer and mixed amine reaction, and the spinning solution including the raw material is used for dry spinning; The specific preparation method specifically includes: 1) Prepolymerization of polyisocyanate and bio-based polyether polyol in the presence of a solvent to prepare a bio-based polyurethane prepolymer solution; 2) Reaction of the polyurethane prepolymer solution and the mixed amine solution to prepare a polyurethane-urea stock solution; 3) Curing of the polyurethane-urea stock solution, and bio-based spandex fiber is obtained by dry spinning technology using the cured polyurethane-urea stock solution as the raw material; The mixed amine includes a diamine chain extender and a monoamine end-capping agent; The diamine chain extender includes a chain diamine and a cyclic diamine; The diamine chain extender includes a chain diamine, and the chain diamine includes one or more of ethylenediamine, 1,2-propanediamine, and 2-methyl-1,5-pentanediamine; and the monoamine end-capping agent includes one or more of diethylamine, dipropylamine, and n-hexylamine; The diamine chain extender includes a chain diamine and a cyclic diamine, and the cyclic diamine includes one or more of methylcyclohexanediamine, 4,4-diaminodicyclohexylmethane, and 3,3-dimethyl-4,4-diaminodicyclohexylmethane.

2. The bio-based spandex fiber according to claim 1, characterized in that, The bio-based spandex fiber has a bio-based carbon content of 25% or more.

3. The bio-based spandex fiber according to claim 2, wherein, The bio-based spandex fiber has a bio-based carbon content of 25% to 80%.

4. The bio-based spandex fiber according to claim 3, characterized in that, The bio-based spandex fiber has a bio-based carbon content of 35% to 60%.

5. The method of producing a bio-based spandex fiber according to claim 1, characterized in that, The bio-based polyurethane prepolymer is prepared by reaction of bio-based polyether polyol and polyisocyanate; and the NCO content of the bio-based polyurethane prepolymer is 2.5-3.1 wt%.

6. The method of producing a bio-based spandex fiber according to claim 5, characterized in that, The bio-based polyether polyol has a number average molecular weight of 1500-5000 g / mol. The polyisocyanate includes one or more of diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate.

7. The method of producing a bio-based spandex fiber according to claim 1, characterized in that, The molar ratio of the chain diamine to the cyclic diamine is 3:1 to 10:

1.

8. The method of producing a bio-based spandex fiber according to claim 1, characterized in that, The molar ratio of the diamine chain extender to the monoamine end-capping agent is 6.5:1 to 12:1.

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