Acid-dyeable thermoplastic polyurethane fibre for main yarns and process for the preparation thereof

Abstract

The application discloses a thermoplastic polyurethane fiber for acid-dyeing main yarn and a preparation method thereof, and relates to the technical field of new fiber materials.The fiber is prepared from a prepolymer prepared from a polyol and a diisocyanate, and a first chain extender and a second chain extender through step-by-step reaction and melt spinning.The first chain extender contains an amide group, and the second chain extender contains a dialkyl-substituted tertiary amino group.The step-by-step reaction is adopted according to the difference in reactivity of the two chain extenders, so that the ordered construction of the core high-strength hydrogen bond network is ensured.The fiber has high strength, excellent acid-dyeing property and elastic recovery performance, can be used as the main yarn alone, does not need to be covered and blended with polyamide and polyester, and is convenient for closed-loop recycling of waste textiles.

Description

Technical Field

[0001] This invention relates to the field of new fiber materials technology, and in particular to an acid-dyeable thermoplastic polyurethane fiber for main yarn and its preparation method. Background Technology

[0002] Spandex is a type of highly elastic fiber widely used in clothing products such as shapewear, shirts, sportswear, jeans, and casual wear, and is favored by consumers for its excellent elasticity. However, spandex has the disadvantages of low strength and excessive elongation, and cannot be used as a main yarn on its own. It can only be used as an elastic auxiliary yarn in physical blends with high-strength fibers such as nylon and polyester.

[0003] In the textile industry, nylon and polyester have long dominated the main synthetic fiber yarn market due to their high strength, good abrasion resistance, and dimensional stability. However, both have inherent shortcomings: polyester has poor skin-friendliness and weak moisture absorption and wicking ability; while nylon has high strength, its elastic recovery rate and wearing comfort are difficult to match the level of professional elastic fibers. To balance fabric strength and elasticity, the industry often uses nylon and polyester main yarns with spandex to make covered yarns. However, spandex is a polymer with different chemical systems than nylon and polyester, making it difficult to effectively separate waste textiles, which seriously restricts the closed-loop recycling of textile materials.

[0004] Thermoplastic polyurethane (TPU) is a melt-processable elastomer with the theoretical potential to replace traditional nylon and polyester as main yarns. However, three major technological bottlenecks currently hinder its ability to meet the requirements for main yarn use. First, insufficient strength: the breaking strength of conventional TPU fibers is only 1-2 cN / dtex, far lower than nylon (4-9 cN / dtex) and polyester (3-8 cN / dtex), failing to meet the high strength requirements of main yarns. Second, difficulty in balancing dyeing and strength: to impart acidic dyeability to TPU fibers, basic dyeing sites such as tertiary amine groups need to be introduced into the molecular chain. However, these groups disrupt the crucial hydrogen-bonded physical cross-linking network between the hard segments of polyurethane, leading to a significant decrease in material strength, modulus, and elastic recovery rate. The contradiction between introducing dyeing sites and maintaining mechanical properties has long remained unresolved. Third, poor recyclability and reprocessability: some high-performance TPUs introduce chemical cross-links to improve strength, or suffer from insufficient melt strength and thermal stability due to molecular structural defects, making multiple melt-reprocessing difficult and affecting the closed-loop recycling of fiber-textile-fiber.

[0005] In summary, existing elastic fibers and main yarn materials for textiles cannot simultaneously meet the comprehensive requirements of high strength, acid dyeability, good elasticity, and closed-loop recycling. Traditional spandex, nylon, and polyester blends suffer from recycling difficulties, while conventional thermoplastic polyurethane fibers have problems such as low strength and mutual constraints between dyeing and mechanical properties. Therefore, developing a novel thermoplastic polyurethane fiber that can be used directly as a main yarn, possesses both high strength and acid dyeability, and is melt-recyclable has become an urgent technical challenge to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to provide an acid-dyeable thermoplastic polyurethane fiber for use as a main yarn and its preparation method, thereby solving the problems existing in the prior art. The thermoplastic polyurethane fiber of this invention can not only be used alone as a main yarn, but also possesses excellent acid-dyeable properties. Furthermore, the fiber structure is fully thermoplastic, ensuring that it and the covering yarn composed of homologous elastic spandex can achieve efficient melt recycling and reprocessing.

[0007] To achieve the above objectives, the present invention provides the following solution: This invention provides a thermoplastic polyurethane fiber, which is obtained by reacting a prepolymer formed of polyol and diisocyanate with a first chain extender, then with a second chain extender, and finally by melt polymerization and spinning after the reaction is completed. The first chain extender is a compound containing at least two hydroxyl groups and at least one amide group (-NH-CO-); The second chain extender is an aliphatic compound containing at least two hydroxyl groups and one tertiary amino group (-NR¹R²), wherein R¹ and R² are each independently C1-C4 alkyl groups.

[0008] Furthermore, the mass ratio of the polyol, diisocyanate, and the first chain extender to the total mass of the second chain extender is 80~100:33~153:26~87.

[0009] Furthermore, the preparation of the prepolymer also includes a catalyst and an antioxidant; the mass ratios are as follows: polyol: diisocyanate: first chain extender and second chain extender total mass: catalyst: antioxidant = 80~100: 33~153: 26~87: 0.01~0.03: 0.4~0.8.

[0010] Further, the catalyst is one or more of the following: triethylenediamine, cyclohexylmethyl tertiary amine, dimethylethanolamine, triethylamine, dibutyltin dilaurate, stannous octoate, potassium isooctanoate, zinc isooctanoate, bismuth isooctanoate, and tetrabutyl titanate. Further, the antioxidant is at least one selected from pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris(2,4-di-tert-butyl)phosphite, and bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite.

[0011] Furthermore, the first chain extender has a structure of general formula (1) or general formula (2): General formula (1): HO-R 3 -NH-CO-CO-NH-R 4 -OH; General formula (2): HO-R 5 -NH-CO-(CH2)m-OH; where R 3 R 4 R 5 It is a C2-C4 alkylene group, where m is an integer from 4 to 6.

[0012] Furthermore, the first chain extender is selected from at least one of N,N-bis(2-hydroxyethyl)oxalamide and 5-hydroxy-N-(2-hydroxyethyl)pentanamide.

[0013] Furthermore, the second chain extender is selected from at least one of N-methyldiethanolamine and N-ethyldiethanolamine.

[0014] Furthermore, the molar ratio of the first chain extender to the second chain extender is 90:10 to 70:30.

[0015] Furthermore, the diisocyanate is selected from one of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate.

[0016] Furthermore, the polyol is selected from at least one of polytetrahydrofuran diol, polybutylene adipate diol, and poly(1,6-hexanediol carbonate) diol.

[0017] Furthermore, a third chain extender may be added; the third chain extender is a small molecule diol or diamine, selected from ethylene glycol, 1,4-butanediol, 1,2-propanediol, neopentyl glycol, methylpropanediol, 1,6-hexanediol, ethylenediamine, and hexamethylenediamine.

[0018] The third chain extender is only an optional additive component and is not a necessary technical component for achieving the high strength, acid dyeability, and main yarn applicability of the present invention. It does not participate in the construction of the core strong and weak hydrogen bond synergistic network of the present invention, nor does it change the functional mechanism of the first and second chain extenders. Its role is only to slightly adjust the performance of polyurethane fibers, and it can be added or omitted according to actual production needs.

[0019] The present invention also provides a method for preparing the above-mentioned thermoplastic polyurethane fiber, comprising the following steps: The polyol and diisocyanate are prepolymerized to obtain a prepolymer; then the prepolymer is reacted with a first chain extender, and after the reaction is completed, a second chain extender is added and reacted. After the reaction is completed, the prepolymer is melt-extruded and pelletized to obtain polyurethane chips. The polyurethane chips are melt-spun, drawn, and heat-set to obtain the thermoplastic polyurethane fiber.

[0020] During the preparation process, the catalyst and antioxidant are added at the initial stage of the prepolymerization of polyol and diisocyanate, and participate in the stepwise chain extension reaction of the first chain extender and the second chain extender along with the prepolymer until the polyurethane chips are formed.

[0021] When a third chain extender is added, the third chain extender and the second chain extender are added together.

[0022] The present invention discloses the following technical effects: This invention creatively combines two complementary chain extenders for synergistic effects: the first chain extender can construct a high-density, high-strength hierarchical hydrogen bond network in the polyurethane molecular backbone, serving as the main physical crosslinking site, effectively solving the technical defects of traditional thermoplastic polyurethane fibers having low strength and being unable to be used alone as main yarn; the second chain extender can introduce effective dyeing sites for acid dyeing into the molecular chain and form a secondary hydrogen bond network with relatively weak strength.

[0023] This invention employs a stepwise reaction approach to accommodate the difference in reactivity between two types of chain extenders: the first chain extender, containing amide groups, has lower reactivity and requires sufficient reaction time to fully construct a well-ordered, high-strength hydrogen-bonded network; the second chain extender, containing tertiary amine groups, has high reactivity and a fast reaction rate. If the two chain extenders are mixed and added at once, the highly reactive second chain extender will preferentially occupy reaction sites, interfering with the orderly construction of the core hydrogen-bonded network of the first chain extender. This invention, through a stepwise, sequential reaction, successfully introduces coloring functional groups while avoiding damage to the main high-strength network structure.

[0024] This invention forms a strong and weak hydrogen bond synergistic crosslinking system. The weak hydrogen bonds constructed by the second chain extender can preferentially break and recombine with the strong hydrogen bonds of the first chain extender, realizing external force dissipation and structural self-recovery, effectively protecting the stability of the main network. At the same time, the dynamic and reversible hydrogen bond structure is more conducive to acid dye molecules approaching and combining with tertiary amino dye seats, greatly improving the acid dyeing performance of fibers.

[0025] The fiber obtained by this invention has excellent mechanical strength, elastic recovery performance and acid dyeability. It can be used directly as the main yarn without blending or covering with nylon or polyester. At the same time, it is conducive to the separation and recycling of waste textiles and meets the closed-loop circular application requirements of textile materials. Detailed Implementation

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0027] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0029] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0030] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0031] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0032] In this embodiment of the invention, 5-hydroxy-N-(2-hydroxyethyl)pentanamide was prepared by the following steps: Under nitrogen protection to prevent oxygen or moisture from interfering with the reaction, toluene was used as a solvent, and δ-valerol (101 g, 1 mol) was added as one of the reactants. Ethanolamine (61 g, 1 mol) was slowly added dropwise, and the reaction was carried out under reflux for 2 hours to allow the reaction to proceed fully. After the reaction was completed, the mixture was cooled to room temperature, and the white solid produced was 5-hydroxy-N-(2-hydroxyethyl)pentanamide.

[0033] Example 1 (1) Preparation of prepolymer: 100 parts of polybutylene adipate diol with a molecular weight of 2000 g / mol and 83.5 parts of diphenylmethane diisocyanate were subjected to a prepolymerization reaction at 70 °C to obtain a prepolymer melt with an NCO mass content of 13%.

[0034] (2) Polymerization and Granulation: A two-stage screw extruder was used for polymerization. 35 parts of N,N-bis(2-hydroxyethyl)oxalamide were reacted with the prepolymer melt in the first stage screw at a reaction temperature of 120°C. 10.2 parts of N-methyldiethanolamine were added in the second stage screw, and the reaction continued at 100°C. The molar ratio of the first chain extender to the second chain extender was 70:30, and the molar ratio of total hydroxyl to NCO in the system was 1:1. During the reaction, 0.014 parts of dibutyltin dilaurate and 0.47 parts of pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid) were added. Polyurethane chips were obtained by melt extrusion and underwater pelletizing.

[0035] (3) Spinning and forming: The obtained polyurethane chips are melt-spun to obtain nascent fibers.

[0036] (4) Stretching and shaping: The nascent fibers are stretched at an ultra-high ratio to achieve molecular chain orientation and shaping, and then subjected to texturing treatment to obtain low-elasticity thermoplastic polyurethane fibers.

[0037] Example 2 (1) Preparation of prepolymer: 100 parts of polybutylene adipate diol with a molecular weight of 3000 g / mol and 119.3 parts of diphenylmethane diisocyanate were subjected to a prepolymerization reaction at 70 °C to obtain a prepolymer melt with an NCO content of 17%.

[0038] (2) Polymerization and Granulation: A two-stage screw extruder was used for the polymerization reaction. 60.8 parts of 5-hydroxy-N-(2-hydroxyethyl)pentanamide were reacted with the prepolymer melt in the first stage screw at a reaction temperature of 120°C. 7.9 parts of N-methyldiethanolamine were added in the second stage screw, and the reaction continued at 100°C. The molar ratio of the first chain extender to the second chain extender was 85:15, and the molar ratio of total hydroxyl to NCO in the system was 1:1. During the reaction, 0.016 parts of dibutyltin dilaurate and 0.53 parts of pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid) were added. Polyurethane chips were obtained by melt extrusion and underwater pelletizing.

[0039] (3) Spinning and forming: The obtained polyurethane chips are melt-spun to obtain nascent fibers.

[0040] (4) Stretching and shaping: The nascent fibers are stretched at an ultra-high ratio to achieve molecular chain orientation and shaping, and then subjected to texturing treatment to obtain low-elasticity thermoplastic polyurethane fibers.

[0041] Example 3 (1) Preparation of prepolymer: 100 parts of polytetrahydrofuran diol with a molecular weight of 1000 g / mol and 70.3 parts of toluene diisocyanate were subjected to a prepolymerization reaction at 70 °C to obtain a prepolymer melt with an NCO mass content of 15%.

[0042] (2) Polymerization and Granulation: A twin-screw extruder was used for polymerization. 42.9 parts of N,N-bis(2-hydroxyethyl)oxalamide were reacted with the prepolymer melt in the first screw section at a reaction temperature of 120℃. 5.4 parts of N-methyldiethanolamine and 1.4 parts of 1,4-butanediol were added in the second screw section, and the reaction continued at 100℃. The molar ratio of the first, second, and third chain extenders was 80:15:5, and the ratio of the total molar amount of hydroxyl groups to the molar amount of NCO in the system was 1:1. During the reaction, 0.013 parts of dibutyltin dilaurate and 0.52 parts of pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid) were added. Polyurethane chips were obtained by melt extrusion and underwater pelletizing.

[0043] (3) Spinning and forming: The obtained polyurethane chips are melt-spun to obtain nascent fibers.

[0044] (4) Stretching and shaping: The nascent fibers are stretched at an ultra-high ratio to achieve molecular chain orientation and shaping, and then subjected to texturing treatment to obtain low-elasticity thermoplastic polyurethane fibers.

[0045] Comparative Example 1 (1) Preparation of prepolymer: 100 parts of polybutylene adipate diol with a molecular weight of 2000 g / mol and 83.5 parts of diphenylmethane diisocyanate were subjected to a prepolymerization reaction at 70 °C to obtain a prepolymer melt with an NCO mass content of 13%.

[0046] (2) Polymerization and Granulation: A two-stage screw extruder was used for polymerization. 50 parts of N,N-bis(2-hydroxyethyl)oxalamide were reacted with the prepolymer melt in the first stage screw at a reaction temperature of 120°C. No second chain extender was added in the second stage screw. The molar ratio of total hydroxyl to NCO in the system was 1:1. During the reaction, 0.014 parts of dibutyltin dilaurate and 0.47 parts of pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid) were added. Polyurethane chips were obtained by melt extrusion and underwater pelletizing.

[0047] (3) Spinning and forming: The obtained polyurethane chips are melt-spun to obtain nascent fibers.

[0048] (4) Stretching and shaping: The nascent fibers are stretched at an ultra-high ratio to achieve molecular chain orientation and shaping, and then subjected to texturing treatment to obtain thermoplastic polyurethane fibers.

[0049] Comparative Example 2 (1) Preparation of prepolymer: 100 parts of polybutylene adipate diol with a molecular weight of 2000 g / mol and 83.5 parts of diphenylmethane diisocyanate were subjected to a prepolymerization reaction at 70 °C to obtain a prepolymer melt with an NCO mass content of 13%.

[0050] (2) Polymerization and Granulation: A two-stage screw extruder was used for the polymerization reaction. No first chain extender was added to the first stage screw. 33.84 parts of N-methyldiethanolamine were added to the reaction in the second stage screw. The reaction temperature was 100℃. The molar ratio of total hydroxyl to NCO in the system was 1:1. During the reaction, 0.014 parts of dibutyltin dilaurate and 0.47 parts of pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) were added. Polyurethane chips were obtained by melt extrusion and underwater pelletizing.

[0051] (3) Spinning and forming: The obtained polyurethane chips are melt-spun to obtain nascent fibers.

[0052] (4) Stretching and shaping: The nascent fibers are stretched at an ultra-high ratio to achieve molecular chain orientation and shaping, and then subjected to texturing treatment to obtain low thermoplastic polyurethane fibers.

[0053] The acid dye uptake rate of the fiber was tested according to the residual absorbance method specified in GB / T 23976.1-2009; the breaking elongation and breaking strength of the fiber were tested according to GB / T 14344 standard, and the performance data obtained are illustrated using 40D specification fiber as an example.

[0054] Table 1 Multiple melt-recycling tests were conducted on the fiber prepared in Example 1, and the results are shown in Table 2. The fiber maintained good spinnability after multiple melt-reprocessing cycles; the mechanical property retention rates after 1, 2, and 3 melt-recycling cycles were 90%, 87%, and 85%, respectively. Even after three recycling cycles, the product still possesses excellent spinnability and mechanical stability, meeting the requirements for closed-loop recycling of textiles.

[0055] Table 2 The embodiments described are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A thermoplastic polyurethane fiber, characterized in that, The prepolymer formed from polyol and diisocyanate is first reacted with a first chain extender, then with a second chain extender, and then obtained by melt polymerization and spinning. The first chain extender is a compound containing at least two hydroxyl groups and at least one amide group; The second chain extender is an aliphatic compound containing at least two hydroxyl groups and one dialkyl-substituted tertiary amino group, wherein each alkyl group is an alkyl group having 1 to 4 carbon atoms.

2. The thermoplastic polyurethane fiber according to claim 1, characterized in that, The mass ratio of the total mass of the polyol, diisocyanate, first chain extender, and second chain extender is 80~100:33~153:26~87.

3. The thermoplastic polyurethane fiber according to claim 1, characterized in that, The first chain extender has a structure of general formula (1) or general formula (2): General formula (1): HO-R 3 -NH-CO-CO-NH-R 4 -OH; General formula (2): HO-R 5 -NH-CO-(CH2)m-OH; where R 3 R 4 R 5 Independently, it is a C2-C4 alkylene group, where m is an integer from 4 to 6.

4. The thermoplastic polyurethane fiber according to claim 1, characterized in that, The first chain extender is selected from at least one of N,N-bis(2-hydroxyethyl)oxalamide and 5-hydroxy-N-(2-hydroxyethyl)pentanamide.

5. The thermoplastic polyurethane fiber according to claim 1, characterized in that, The second chain extender is selected from at least one of N-methyldiethanolamine and N-ethyldiethanolamine.

6. The thermoplastic polyurethane fiber according to claim 1, characterized in that, The molar ratio of the first chain extender to the second chain extender is 90:10 to 70:

30.

7. The thermoplastic polyurethane fiber according to claim 1, characterized in that, The diisocyanate is selected from one of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate.

8. The thermoplastic polyurethane fiber according to claim 1, characterized in that, The polyol is selected from at least one of polytetrahydrofuran diol, polybutylene adipate diol, and poly(1,6-hexanediol carbonate) diol.

9. A method for preparing the thermoplastic polyurethane fiber according to any one of claims 1-8, comprising the following steps: The polyol and diisocyanate are prepolymerized to obtain a prepolymer; then the prepolymer is reacted with the first chain extender, and after the reaction is completed, the second chain extender is added and reacted. After the reaction is completed, the prepolymer is melt-extruded and pelletized to obtain polyurethane chips. The polyurethane chips are melt-spun, drawn, and heat-set to obtain the thermoplastic polyurethane fiber.

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