CN115928261A - Easy-to-dye composite elastic fiber and preparation method thereof - Google Patents

Abstract

The invention relates to the technical field of elastic fibers, in particular to a dyeable composite elastic fiber and a preparation method thereof. The composite elastic fiber is prepared by melt spinning of a thermoplastic polyester chip and a modified PBT chip, wherein the thermoplastic polyester chip comprises the following raw materials in parts by weight: 65-80 parts of polytrimethylene terephthalate, 10-25 parts of polyamide copolymer, 2-8 parts of compatibilizer, 0.5-3 parts of lubricant and 0.1-1 part of antioxidant. Wherein, by introducing 1, 4-cyclohexanedimethanol and sulfonic acid groups into a PBT molecular chain, the modified PBT slice which has good mechanical property, high heat resistance, easy dyeing and easy processing is obtained; the dyeable composite elastic fiber prepared by compounding the modified PBT and the thermoplastic polyester and carrying out spinning processing has the characteristics of high comprehensive mechanical property, good heat resistance and good dyeing property.

Description

Easy-to-dye composite elastic fiber and preparation method thereof

Technical Field

The invention relates to the technical field of elastic fiber materials, in particular to a dyeable composite elastic fiber and a preparation method thereof.

Background

Polyester fibers are spinning materials with excellent mechanical properties and strong processability, represented by polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT) and the like, and are widely applied to various textile products. However, the difference between different application fields and use environments has different requirements on the performance of polyester fibers, and the application limitation of single PET, PBT or PTT fibers caused by the characteristics of the materials is inevitable, for example, the PBT has better comprehensive performance but low notch impact strength, poor toughness and difficult dyeing; PET has poor hygroscopicity, stretch recovery, and flammability due to its close molecular arrangement and lack of hydrophilic groups; PTT has excellent stretch resilience and stability, but poor water absorption and heat resistance.

In the aspect of fiber dyeing, PTT has better dyeing performance compared with PBT and PET, and the PTT is usually dyed at medium and high temperature by adopting disperse dyes, while with the alternate development of cationic dyeing technology, the cationic dyeing mode has the advantages of low price, multiple varieties, environmental protection, brighter color and high color fastness, and better meets the requirement of diversification of fiber products in the market. Therefore, in order to further conduct intensive research and development on fiber products, extensive research on dyeing processes of fiber products is also required. Therefore, the present invention is to overcome the defects of single polyester fiber to obtain a composite elastic fiber with strong comprehensive mechanical properties, good dyeing properties and excellent processability, so as to meet the market diversification requirements.

Disclosure of Invention

The invention aims to solve the defects of the prior art and provide the dyeable composite elastic fiber which has good comprehensive mechanical property, heat resistance, processability and dyeing property; and the preparation method of the composite elastic fiber is simple to operate, stable in product quality and suitable for large-scale production.

The purpose of the invention is realized by the following technical scheme: the dyeable composite elastic fiber is prepared by melt spinning of a thermoplastic polyester chip and a modified PBT chip, wherein the thermoplastic polyester chip comprises the following raw materials in parts by weight: 65-80 parts of polytrimethylene terephthalate, 10-25 parts of polyamide copolymer, 2-8 parts of compatibilizer, 0.5-3 parts of lubricant and 0.1-1 part of antioxidant.

Furthermore, sulfonic acid groups are randomly distributed on the molecular chain of the modified PBT slice.

Further, the preparation method of the modified PBT slice comprises the following steps: (1) Putting terephthalic acid, 1, 4-butanediol, 1, 4-cyclohexanedimethanol and tetrabutyl titanate into a reaction kettle, introducing nitrogen into the reaction kettle, and reacting for 2-4 hours at 230-250 ℃ while stirring; (2) Adding dihydroxy ethyl isophthalate-5-sodium sulfonate into a reaction kettle, carrying out pre-polycondensation at the reaction temperature of 230-250 ℃ under the reaction pressure of 20-80Pa for 30-50min, then raising the reaction temperature to 240-260 ℃ under the reaction pressure of 20-60Pa for 2-3h, and after the reaction is finished, cooling the material and slicing to obtain the modified PBT slice.

Further, in the step (1), the molar ratio of terephthalic acid to 1, 4-butanediol and 1, 4-cyclohexanedimethanol is 1. The adding mass of the tetrabutyl titanate is 0.03 percent of that of the terephthalic acid.

Further, in the step (2), the mass of the sodium bis (hydroxyethyl) isophthalate-5-sulfonate is 5-20% of the mass of the theoretical product.

According to the invention, 1, 4-cyclohexanedimethanol and sulfonic acid groups are introduced into a PBT molecular chain by adopting the technical scheme, so that the modified PBT slice which is good in mechanical property, high in heat resistance, easy to dye and easy to process is obtained. Wherein, 1, 4-cyclohexanedimethanol is added in the step (1), so that the crystallization capacity of the modified PBT is reduced, and the modified PBT slice can be prevented from warping and deforming in the processing process; and the melt viscosity, the strength and the fluidity of the final modified PBT polyester can be increased, so that the strength, the processability and the heat resistance of the modified PBT slice are improved. The dyeing property of the modified PBT slice is remarkably improved by adding the m-phthalic acid dihydroxy ethyl ester-5-sodium sulfonate in the step (2) and properly introducing a sulfonic acid group as an active dyeing site.

Further, the preparation method of the polyamide copolymer specifically comprises the following steps: adding m-phenylenediamine and modified diamine prepolymer into 90-110mL of dimethylacetamide solvent, stirring and dissolving, transferring to a constant-temperature freezing circulating bath at-5-0 ℃ after dissolving, dropwise adding 17.5-19.2g of isophthaloyl dichloride, stirring for 1-2h at 15-25 ℃, adding 7-8g of calcium hydroxide to obtain a viscous polymer, putting the viscous polymer into deionized water for precipitation, washing with water, and drying in an oven to obtain the polyamide copolymer.

Furthermore, the molar ratio of the modified diamine prepolymer to the m-phenylenediamine is 1.5-9.2.

Furthermore, the preparation method of the modified diamine prepolymer specifically comprises the following steps: heating 2, 4-diaminobenzene sulfonic acid and anhydrous calcium chloride to 80-90 ℃, dissolving in 30-40mL of dimethylacetamide, then transferring to a low-temperature circulating freezing bath at-5-0 ℃, slowly adding isophthaloyl dichloride for reacting for 20-25min, raising the temperature to 10-15 ℃ for reacting for 0.5-1h, then adding m-phenylenediamine, raising the reaction temperature to 20-25 ℃, continuously stirring for 1-1.5h, finally putting the obtained viscous polymer in deionized water for precipitation, washing with water, and drying to obtain the modified diamine prepolymer. Wherein the molar ratios of the 2, 4-diaminobenzene sulfonic acid, the anhydrous calcium chloride, the isophthaloyl dichloride and the m-phenylenediamine are respectively 1.

Further, the compatibilizer is at least one of hexadecylamine, phenyl o-hydroxybenzoate, polyethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer and maleic anhydride grafted polyethylene copolymer.

Further, the lubricant is at least one of liquid paraffin, organosilane, oleamide and ethylene bis fatty acid amine.

Further, the oxidant is at least one of alkyl phosphate, trimethyl phosphite, triphenyl phosphate, antioxidant 1010 and antioxidant 168.

Further, the intrinsic viscosity of the polytrimethylene terephthalate is 0.8-1.2dL/g.

By adopting the technical scheme, the strength, the heat resistance and the stability of the polytrimethylene terephthalate can be effectively improved by adding the polyamide copolymer. The polyamide copolymer obtained by the preparation method has the characteristics of good mechanical property and high thermal stability. More preferably, the preparation method of the modified diamine prepolymer is used for introducing 2, 4-diaminobenzene sulfonic acid as a third monomer into copolymerization modification of the polyamide copolymer to be used as an active dyeing site for enhancing the dyeing performance of the thermoplastic polyester chip. Meanwhile, hydrogen bonds are generated among molecular chains due to the introduction of sulfonic acid groups, so that the mechanical property of the thermoplastic polyester chip is improved. According to the invention, the thermoplastic polyester chip obtained by taking polytrimethylene terephthalate and polyamide copolymer as main raw materials and adding the compatibilizer, the lubricant and the oxidant is used for preparing the elastic fiber by spinning, so that the performance defect of a single PBT or thermoplastic polyester material can be made up, and the composite elastic fiber with excellent comprehensive mechanical property and wide application range is obtained.

The invention also provides a preparation method of the easy-dyeing composite elastic fiber, which is characterized by comprising the following steps: the method comprises the following steps: respectively placing the thermoplastic polyester chip and the modified PBT chip in a vacuum drying oven at the temperature of 120-140 ℃ and the temperature of 110-120 ℃ for drying for 4-12h; and then placing the dried thermoplastic polyester chip and the modified PBT chip in a double-screw melt spinning machine according to the mass ratio of 30-70, heating and melting, then distributing through a spinneret plate, converging from the outlet of the spinneret plate, cooling through air, cooling through side blowing, drafting, oiling, and winding to obtain the composite elastic fiber.

Specifically, the spinning heating temperature of the modified PBT chip is 265-285 ℃, the spinning heating temperature of the thermoplastic polyester chip is 255-265 ℃, the spinning speed is 2000-3000m/min, the circular blowing temperature is 30 ℃, the drawing ratio is 1.5-4 times, and the drawing temperature is 130-160 ℃.

The invention has the beneficial effects that: the dyeable composite elastic fiber prepared by melt spinning the thermoplastic polyester chip and the modified PBT chip has the characteristics of high comprehensive mechanical property, good heat resistance and good dyeing property. Wherein, the modified PBT slice with good mechanical property, high heat resistance, easy dyeing and easy processing is obtained by introducing 1, 4-cyclohexanedimethanol and sulfonic acid groups on the molecular chain of the PBT. The thermoplastic polyester chip prepared by taking the polytrimethylene terephthalate and the polyamide copolymer as main raw materials has the advantages that the excellent elasticity and the processing performance of the polytrimethylene terephthalate are kept, and the strength, the heat resistance and the dyeing performance of the polytrimethylene terephthalate are enhanced. The composite elastic fiber can be applied to civil and industrial fabrics in the fields of clothing, packaging, automobiles, medical treatment, health, buildings and the like, and has wide market prospect and application potential.

Detailed Description

The present invention will be further described with reference to the following examples for facilitating understanding of those skilled in the art, and the description of the embodiments is not intended to limit the present invention.

Example 1

The dyeable composite elastic fiber is prepared by melt spinning of a thermoplastic polyester chip and a modified PBT chip, wherein the thermoplastic polyester chip comprises the following raw materials in parts by weight: 65 parts of polytrimethylene terephthalate, 10 parts of polyamide copolymer, 2 parts of compatibilizer, 0.5 part of lubricant and 0.1 part of antioxidant.

In this embodiment, the preparation method of the modified PBT slice includes the following steps: (1) Putting terephthalic acid, 1, 4-butanediol, 1, 4-cyclohexanedimethanol and tetrabutyl titanate into a reaction kettle, introducing nitrogen into the reaction kettle, and reacting for 4 hours at 230 ℃ while stirring; (2) Adding dihydroxy ethyl isophthalate-5-sodium sulfonate into a reaction kettle, controlling the reaction temperature at 230 ℃, the reaction pressure at about 60Pa and the reaction time at 30min, carrying out pre-polycondensation, then increasing the reaction temperature to 240 ℃, controlling the reaction pressure at about 20Pa and the reaction time at 2h, cooling the materials after the reaction is finished, and slicing to obtain the modified PBT slice.

In the step (1), the molar ratio of terephthalic acid to 1, 4-butanediol and 1, 4-cyclohexanedimethanol is 1.6, the molar ratio of 1, 4-cyclohexanedimethanol to 1, 4-butanediol is 1.

In step (2), the mass of sodium bis (hydroxyethyl) isophthalate-5-sulfonate was 5% of the mass of the theoretical product.

In this example, the intrinsic viscosity of the poly (trimethylene terephthalate) was 0.9dL/g.

In this embodiment, the preparation method of the polyamide copolymer specifically comprises: adding m-phenylenediamine and modified diamine prepolymer with the molar ratio of 1.

Further, the preparation method of the modified diamine prepolymer comprises the following steps: heating 2, 4-diaminobenzene sulfonic acid and anhydrous calcium chloride to 80 ℃, dissolving in 30mL of dimethylacetamide, then transferring to a low-temperature circulating freezing bath at-5 ℃, slowly adding isophthaloyl dichloride for reacting for 20min, raising the temperature to 10 ℃ for reacting for 0.5h, then adding m-phenylenediamine, raising the reaction temperature to 20 ℃, continuing stirring for 1h, putting the obtained viscous polymer in deionized water for precipitation, washing with water, and drying to obtain the modified diamine prepolymer. Wherein the molar ratio of the 2, 4-diaminobenzene sulfonic acid to the anhydrous calcium chloride to the m-phenylene dichloride to the m-phenylenediamine is 1.

In this embodiment, the compatibilizer is hexadecylamine; the lubricant is oleamide; the oxidant is a mixture prepared by mixing octadecyl phosphate and an antioxidant 1010 according to a mass ratio of 3.

Example 2

The dyeable composite elastic fiber is prepared by melt spinning of a thermoplastic polyester chip and a modified PBT chip, wherein the thermoplastic polyester chip comprises the following raw materials in parts by weight: 72 parts of polytrimethylene terephthalate, 15 parts of polyamide copolymer, 4 parts of compatibilizer, 1 part of lubricant and 0.6 part of antioxidant.

In this embodiment, the preparation method of the modified PBT slice comprises the following steps: (1) Putting terephthalic acid, 1, 4-butanediol, 1, 4-cyclohexanedimethanol and tetrabutyl titanate into a reaction kettle, introducing nitrogen into the reaction kettle, and reacting for 3 hours at the temperature of 240 ℃ while stirring; (2) Adding dihydroxy ethyl isophthalate-5-sodium sulfonate into a reaction kettle, carrying out pre-polycondensation at the reaction temperature of 240 ℃, the reaction pressure of about 60Pa and the reaction time of 40min, then raising the reaction temperature to 250 ℃, controlling the reaction pressure of about 40Pa and the reaction time of 2.5h, and after the reaction is finished, cooling the materials and then slicing to obtain the modified PBT slice.

In the step (1), the molar ratio of terephthalic acid to 1, 4-butanediol and 1, 4-cyclohexanedimethanol is 1.7, the molar ratio of 1, 4-cyclohexanedimethanol to 1, 4-butanediol is 1.

In step (2), the mass of sodium bis (hydroxyethyl) isophthalate-5-sulfonate was 10% of the mass of the theoretical product.

In this example, the intrinsic viscosity of the poly (trimethylene terephthalate) was 0.9dL/g.

In this embodiment, the preparation method of the polyamide copolymer specifically comprises: adding m-phenylenediamine and modified diamine prepolymer with the molar ratio of 1.

Further, the preparation method of the modified diamine prepolymer specifically comprises the following steps: heating 2, 4-diaminobenzene sulfonic acid and anhydrous calcium chloride to 85 ℃, dissolving the mixture in 30mL of dimethylacetamide, then transferring the mixture to a low-temperature circulating freezing bath at about 0 ℃, slowly adding isophthaloyl dichloride to react for 20min, raising the temperature to 15 ℃ to react for 0.5h, then adding m-phenylenediamine, raising the reaction temperature to 20 ℃, continuing stirring for 1h, finally putting the obtained viscous polymer in deionized water to precipitate, and washing and drying the viscous polymer to obtain the modified diamine prepolymer. Wherein the molar ratio of the 2, 4-diaminobenzene sulfonic acid to the anhydrous calcium chloride to the m-phenylene dichloride to the m-phenylenediamine is 1.

In this example, the compatibilizer is phenyl ortho-hydroxybenzoate; the lubricant is liquid paraffin; the oxidant is a mixture prepared by mixing trimethyl phosphate and an antioxidant 1010 according to a mass ratio of 2.5.

Example 3

The dyeable composite elastic fiber is prepared by melt spinning of a thermoplastic polyester chip and a modified PBT chip, wherein the thermoplastic polyester chip comprises the following raw materials in parts by weight: 80 parts of polytrimethylene terephthalate, 25 parts of polyamide copolymer, 8 parts of compatibilizer, 3 parts of lubricant and 1 part of antioxidant.

In this embodiment, the preparation method of the modified PBT slice comprises the following steps: (1) Putting terephthalic acid, 1, 4-butanediol, 1, 4-cyclohexanedimethanol and tetrabutyl titanate into a reaction kettle, introducing nitrogen into the reaction kettle, and reacting for 2.5 hours at the temperature of 250 ℃ while stirring; (2) Adding dihydroxy ethyl isophthalate-5-sodium sulfonate into a reaction kettle, reacting at 250 ℃ under 80Pa for 30min, performing pre-polycondensation, raising the reaction temperature to 260 ℃, under 40Pa for 3h, and after the reaction is finished, cooling the material and slicing to obtain the modified PBT slice.

In the step (1), the molar ratio of terephthalic acid to 1, 4-butanediol and 1, 4-cyclohexanedimethanol is 1.8, the molar ratio of 1, 4-cyclohexanedimethanol to 1, 4-butanediol is 1.

In step (2), the mass of sodium bis (hydroxyethyl) isophthalate-5-sulphonate was 20% of the theoretical product mass.

In this example, the intrinsic viscosity of the poly (trimethylene terephthalate) was 0.9dL/g.

In this embodiment, the preparation method of the polyamide copolymer specifically comprises: adding m-phenylenediamine and modified diamine prepolymer with the molar ratio of 1.

Further, the preparation method of the modified diamine prepolymer specifically comprises the following steps: heating 2, 4-diaminobenzene sulfonic acid and anhydrous calcium chloride to 90 ℃, dissolving in 40mL of dimethylacetamide, then transferring to a low-temperature circulating freezing bath at 0 ℃, slowly adding isophthaloyl dichloride for reacting for 25min, raising the temperature to 15 ℃ for reacting for 1h, then adding m-phenylenediamine, raising the reaction temperature to 25 ℃, continuing stirring for 1.5h, finally putting the obtained viscous polymer in deionized water for precipitation, washing with water, and drying to obtain the modified diamine prepolymer. Wherein the molar ratio of the 2, 4-diaminobenzene sulfonic acid, the anhydrous calcium chloride, the isophthaloyl dichloride and the m-phenylenediamine is respectively 1.

In this example, the compatibilizer is a maleic anhydride grafted polyethylene copolymer; the lubricant is ethylene bis fatty acid amine; the oxidant is a mixture of trimethyl phosphite and an antioxidant 168 according to a mass ratio of 3.

Comparative example 1

This comparative example differs from example 2 in that: the PBT slice prepared by the method replaces the modified PBT in the example 2, and the preparation method of the PBT slice comprises the following steps: (1) Putting terephthalic acid, 1, 4-butanediol and tetrabutyl titanate into a reaction kettle, introducing nitrogen into the reaction kettle, and reacting for 3 hours at the temperature of 240 ℃ while stirring; (2) Adding dihydroxy ethyl isophthalate-5-sodium sulfonate into a reaction kettle, carrying out pre-polycondensation at the reaction temperature of 240 ℃, the reaction pressure of about 60Pa and the reaction time of 40min, then raising the reaction temperature to 240-260 ℃, controlling the reaction pressure of about 40Pa and the reaction time of 2.5h, and after the reaction is finished, cooling the materials and then slicing to obtain the PBT slice.

In step (1), the total molar ratio of terephthalic acid to 1, 4-butanediol is 1.

In step (2), the mass of sodium bis (hydroxyethyl) isophthalate-5-sulfonate was 10% of the mass of the theoretical product.

Comparative example 2

This comparative example differs from example 2 in that: the PBT slice prepared by the method replaces the modified PBT in the example 2, and the preparation method of the PBT slice comprises the following steps: putting terephthalic acid, 1, 4-butanediol, 1, 4-cyclohexanedimethanol and tetrabutyl titanate into a reaction kettle, introducing nitrogen into the reaction kettle, controlling the reaction pressure to be about 60Pa, and reacting for 3.5 hours at 240 ℃ while stirring; and then, raising the reaction temperature to 250 ℃, controlling the reaction pressure to be about 40Pa, controlling the reaction time to be 2.5h, and slicing after the reaction is finished and cooling the materials to obtain the PBT slices.

In the above step, the molar ratio of terephthalic acid to the total of 1, 4-butanediol and 1, 4-cyclohexanedimethanol is 1.7, the molar ratio of 1, 4-cyclohexanedimethanol to 1, 4-butanediol is 1.

Comparative example 3

This comparative example differs from that described in example 2 in that: the composite elastic fiber is prepared by melt spinning of a thermoplastic polyester chip and a modified PBT chip, wherein the thermoplastic polyester chip comprises the following raw materials in parts by weight: 65-80 parts of polytrimethylene terephthalate, 2-8 parts of compatibilizer, 0.5-3 parts of lubricant and 0.1-1 part of antioxidant.

Example 4

The preparation method of the easy-to-dye composite elastic fiber is adopted in the above examples 1-3 and comparative examples 1-3, and the specific steps are as follows: respectively placing the thermoplastic polyester chip and the modified PBT chip (or the PBT chip) in a vacuum drying oven at 130 ℃ and 110 ℃ for drying for 6 hours; then according to the following 55:45, respectively putting the dried thermoplastic polyester chip and the dried modified PBT chip into two boxes of a double-screw melt spinning machine for heating and melting, wherein the spinning heating temperature of the modified PBT chip (or the PBT chip) is 280 ℃, the spinning heating temperature of the thermoplastic polyester chip is 260 ℃, the spinning speed is 2600m/min, then distributing the thermoplastic polyester chip and the modified PBT chip through a spinneret plate, converging the thermoplastic polyester chip and the modified PBT chip at the outlet of the spinneret plate, and obtaining the composite elastic fiber through air cooling, side-blowing cooling, drafting, oiling and winding, wherein the circular blowing temperature is 30 ℃, the stretching ratio is 3 times, and the drafting temperature is 140 ℃.

The elastic fibers prepared in the examples 1-3 and the comparative examples 1-3 are selectively subjected to mechanical property tests according to requirements, wherein the breaking strength, the breaking elongation and the modulus are measured by adopting a GB/T14337-2022 standard, and the elastic recovery is measured by adopting an ASTM D3107-2007 standard; the boiling water shrinkage was measured using GB/T6505-2001 standards, and the test results of examples 1-4 and comparative examples 1-3 are shown in Table 1 below.

TABLE 1 tables of Performance test data for examples 1-4 and comparative examples 1-3

Furthermore, in order to verify the dyeing performance of the elastic fibers prepared in example 2 and comparative examples 1 to 3, the elastic fibers prepared in example 2 and comparative examples 1 to 3 were woven into a gray cloth, the gray cloth after boiling was boiled and dyed with 2% cationic red dye (X-GRL) for 60 minutes at normal temperature, and the dyed gray cloth was subjected to a color fastness test, wherein the water fastness was measured according to the GB/T5713-2013 standard, the rubbing fastness was measured according to the GB/T3920-2008 standard, and the perspiration fastness was measured according to the GB/T3922-2013 standard, and the results are shown in table 2 below:

table 2 test results of color fastness to water and rubbing of example 2 and comparative examples 1 to 3

As can be seen from the test results in tables 1 and 2, the composite elastic fiber prepared in example 2 of the present invention has good properties in terms of elongation at break, strength at break, elastic recovery, modulus and boiling water shrinkage, indicating that the composite elastic fiber has good comprehensive mechanical properties. Compared with the comparative examples 1-2 and 2, the PBT modified by the 1, 4-cyclohexanedimethanol and sulfonic acid groups in the example 2 can effectively improve the strength and stability of the PBT, and obviously improve the dyeing activity and color fastness of the PBT on cationic dyes. Compared with example 2 from comparative example 3, example 2 can significantly improve the strength and heat resistance of polytrimethylene terephthalate by adding a polyamide copolymer in the preparation of thermoplastic polyester chips. According to the invention, the thermoplastic polyester chip and the modified PBT chip are adopted for melt spinning, so that the performance defect of a single PBT or thermoplastic polyester material can be made up, and the composite elastic fiber with excellent comprehensive performance and wide application range is obtained.

The above specific examples are further illustrative of the technical solutions and advantages of the present invention, and are not intended to limit the embodiments. It will be apparent to those skilled in the art that any obvious alternative is within the scope of the invention without departing from the inventive concept.

Claims (10)

1. The easy-dyeing composite elastic fiber is characterized in that: the composite elastic fiber is prepared by melt spinning of a thermoplastic polyester chip and a modified PBT chip, wherein the thermoplastic polyester chip comprises the following raw materials in parts by weight: 65-80 parts of polytrimethylene terephthalate, 10-25 parts of polyamide copolymer, 2-8 parts of compatibilizer, 0.5-3 parts of lubricant and 0.1-1 part of antioxidant.

2. The dyeable composite elastic fiber of claim 1, wherein: sulfonic acid groups are randomly distributed on the molecular chain of the modified PBT slice.

3. A dyeable composite elastic fiber according to claim 2, wherein: the preparation method of the modified PBT slice comprises the following steps: (1) Putting terephthalic acid, 1, 4-butanediol, 1, 4-cyclohexanedimethanol and tetrabutyl titanate into a reaction kettle, introducing nitrogen into the reaction kettle, and reacting for 2-4 hours at 230-250 ℃ while stirring; (2) Adding dihydroxy ethyl isophthalate-5-sodium sulfonate into a reaction kettle, carrying out pre-polycondensation at the reaction temperature of 230-250 ℃ and the reaction pressure of 20-80Pa for 30-50min, then raising the reaction temperature to 240-260 ℃ and the reaction pressure of 20-60Pa for 2-3h, and after the reaction is finished, cooling the materials and slicing to obtain the modified PBT slice.

4. A dyeable composite elastic fiber according to claim 3, wherein: in step (1), the molar ratio of terephthalic acid to the total of 1, 4-butanediol and 1, 4-cyclohexanedimethanol is 1.6 to 1.8, the molar ratio of 1, 4-cyclohexanedimethanol to 1, 4-butanediol is 1.

5. A dyeable composite elastic fiber according to claim 3, wherein: in the step (2), the mass of the m-phthalic acid dihydroxy ethyl ester-5-sodium sulfonate is 5-20% of the mass of a theoretical product.

6. The dyeable composite elastic fiber of claim 1, wherein: the preparation method of the polyamide copolymer specifically comprises the following steps: adding m-phenylenediamine and modified diamine prepolymer into 90-110mL of dimethylacetamide solvent, stirring and dissolving, transferring to a constant-temperature freezing circulating bath at-5-0 ℃ after dissolving, dropwise adding 17.5-19.2g of isophthaloyl dichloride, stirring for 1-2h at 15-25 ℃, adding 7-8g of calcium hydroxide to obtain a viscous polymer, putting the viscous polymer into deionized water for precipitation, washing with water, and drying in an oven to obtain the polyamide copolymer.

7. The dyeable composite elastic fiber of claim 6, wherein: the molar ratio of the modified diamine prepolymer to the m-phenylenediamine is 1.

8. The dyeable composite elastic fiber of claim 1, wherein: the compatibilizer is at least one of hexadecylamine, phenyl o-hydroxybenzoate, polyethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer and maleic anhydride grafted polyethylene copolymer.

9. The dyeable composite elastic fiber of claim 1, wherein: the lubricant is at least one of liquid paraffin, organosilane, oleamide and ethylene bis fatty acid amine.

10. A process for preparing the dyeable composite elastic fiber of claim 1, comprising: the method comprises the following steps: respectively placing the thermoplastic polyester chip and the modified PBT chip in a vacuum drying oven at the temperature of 120-140 ℃ and the temperature of 110-120 ℃ for drying for 4-12h; and then placing the dried thermoplastic polyester chip and the modified PBT chip in a double-screw melt spinning machine according to the mass ratio of 30-70, heating and melting, then distributing through a spinneret plate, converging from the outlet of the spinneret plate, cooling through air, cooling through side blowing, drafting, oiling, and winding to obtain the composite elastic fiber.