A ppct df bio-based composite fiber, a preparation method and application thereof

Abstract

The application discloses a kind of PPCTDF bio-based composite fibers and its preparation method and application.PPCTDF (PPCT DuoFiber) fiber is added isocyanate with polypropylene carbonate dihydric alcohol, and the copolymer (PPCT) after small molecule chain extension such as PDO, BDO is important component, with low melting point polymer (such as PLA, PCL) by double screw spinning process, obtain the bicomponent fiber of skin-core structure or parallel structure.PLA / PPCT skin-core structure fiber can be self-adhesive after hot drying, cooling at 120~145 DEG C.PCL / PPCT skin-core structure fiber can be self-adhesive after hot drying, cooling at 55-65 DEG C.The above two kinds of skin-core structure fibers are used to prepare functional non-woven fabric or flake;Parallel structure fiber is used to prepare warm filling material by the permanent three-dimensional crimp of two components shrinkage difference.Fiber product is discarded, and can be recycled and reused by chemical recycling or biodegraded under industrial composting conditions, and the fiber of the application realizes the unity of green environmental protection, high performance and multi-function.

Description

Technical Field

[0001] This invention relates to the field of composite fiber technology, and more specifically, to a PPCTDF bio-based composite fiber, its preparation method, and its application. Background Technology

[0002] With the deepening of the concept of sustainable development, developing bio-based and biodegradable functional fibers is an important direction for iterating traditional petrochemical-based fibers. In existing technologies, while single-component bio-based fibers such as polylactic acid (PLA) are biodegradable, they generally suffer from drawbacks such as poor toughness, insufficient processability, and uncontrollable degradation. Although PLA has a tensile strength of approximately 60 MPa, its elongation at break is only about 6%, and its brittleness is its biggest weakness. Furthermore, single-component fibers have functional limitations.

[0003] Polypropylene carbonate (PPC) is an aliphatic polycarbonate copolymerized from carbon dioxide (CO2) and propylene oxide (PO) under the action of a catalyst, which can fix more than 40 wt% of the total CO2 during the synthesis process. PPC is an amorphous thermoplastic polymer with good barrier properties, biocompatibility, and impact resistance, but it has a low glass transition temperature (Tg) and poor temperature resistance. Blending PPC with PLA can improve the toughness of PLA. Studies have shown that adding hyperbranched polymer (HBP) derivatives can increase the elongation at break of PLA / PPC blends while maintaining essentially the same tensile strength.

[0004] Bicomponent composite fiber technology, such as core-sheath composites and side-by-side composites, can achieve special functions such as self-adhesion and three-dimensional crimping through the synergistic effect between components, significantly expanding the application scenarios of fibers. Companies such as NatureWorks have developed mature processing technologies for PLA bicomponent short fibers. Among known technologies, Far East New Century Company disclosed a thermally bonded bicomponent fiber using PLA with different melting points as the core and sheath (US20080057309A1), but this scheme is entirely based on the PLA system, and its toughness and heat resistance are still limited by the inherent defects of PLA. Other studies have used electrospinning technology to prepare PPC-based fiber membranes, but electrospinning cannot achieve continuous industrial production.

[0005] Currently, research on applying high-performance bio-based materials to bicomponent composite spinning is still lacking, especially the lack of a bio-based composite fiber that can simultaneously meet the requirements of controllable degradation, aging resistance, high performance, and multifunctionality. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing and applying PPCTDF bio-based bicomponent composite fibers, thereby solving the technical problems of low processability and difficulty in achieving both high performance and multifunctionality in existing bio-based fibers.

[0007] The term "PPCTDF" in this invention is an abbreviation for "PPCT DuoFiber," and its name originates as follows: PPCT stands for "Poly (propylene carbonate toughening)," a high-performance toughened polypropylene carbonate matrix material. It is an important component of the fiber in this invention, endowing the fiber with high strength, high toughness, and excellent aging resistance. PPCT is obtained by polymerizing PPC diol (polypropylene carbonate diol) with isocyanate, small molecule chain extender (PDO or BDO), composite catalyst, etc.

[0008] DF stands for "DuoFiber," which is a composite fiber made by spinning two polymers with different properties using a twin-screw composite spinning machine.

[0009] This invention relates to a PPCTDF bio-based composite fiber, which is obtained by spinning PPCT material with a low-melting-point polymer. The PPCT material comprises 40-70 parts by weight of polypropylene carbonate diol, 25-55 parts by weight of isocyanate, and 0.2-5 parts by weight of PDO (1,3-propanediol) or BDO (1,4-butanediol); the composite fiber comprises 20-50 parts by weight of PPCT material, 50-80 parts by weight of low-melting-point polymer, and 1-5 parts by weight of toughening modifier; the toughening modifier is selected from one or more of epoxy functionalized chain extenders, hyperbranched polymers, and their derivatives.

[0010] The PPCTDF fiber of this invention comprises the following composite forms: Core-sheath structure: Using PPCT as the core layer and a low-melting-point polymer (such as low-melting-point PLA) as the sheath layer, the resulting fibers can achieve sheath melting through heat treatment, and are used for thermal bonding of nonwoven fabrics or filling wadding. The mass ratio of sheath layer to core layer is 70:30 to 50:50, preferably 60:40.

[0011] Side-by-side structure: PPCT is compounded with another polymer (such as PLA or PCL) in a side-by-side manner, utilizing the shrinkage difference between the two components to obtain fibers with permanent three-dimensional crimp properties. The mass ratio of PPCT to the other polymer is 40:60 to 50:50, preferably 50:50.

[0012] The method for preparing PPCTDF bio-based composite fiber of the present invention includes the following steps: Step 1: Raw material preparation and drying Prepare PPCT particles and low-melting-point polymer particles.

[0013] The low-melting-point polymer is selected from one of the following: Low melting point PLA (D-lactic acid content 8%~12%, melting point 120~140℃, MFI = 15~40 g / 10min, 210℃) is suitable for core-sheath structure thermal bonding fibers. Polycaprolactone (PCL, melting point 55-65℃, Mn=60,000-100,000) is suitable for special low-temperature bonding requirements.

[0014] Step 2: Composite spinning The two raw materials are fed separately into two independent screw systems of the composite spinning machine. The composite spinning machine includes two independent feeding systems, screw extrusion systems, melt filtration systems and melt metering pumps, as well as an integrated spinning assembly and spinneret.

[0015] The process parameters for each system are as follows: 1. For core-skin structure PPCT side (core / A component): Screw type: single screw or twin screw, L / D = 24~36; The temperature of the metering section and spinning box on the PPCT side (core layer or parallel side) is controlled at 165–190℃ (preferably 170–185℃). To avoid thermal degradation caused by prolonged residence of PPC at high temperatures, the extrusion system adopts a short-flow design, and the residence time of the melt in the barrel is controlled within 3–5 minutes.

[0016] The speed of the melt metering pump is adjusted according to the target linear density, with a metering accuracy of ±0.5%. Melt filtration accuracy: 15-25μm stainless steel metal fiber filter screen; Low-melting-point polymer side (skin / component B): Screw type: Single screw, L / D = 24~30; The temperatures of each zone and the spinning box need to be set separately according to the type of low-melting-point polymer selected: When using low melting point PLA: the temperature of each zone is set as follows: 120-135℃ for the feeding section, 130-150℃ for the compression section, and 135-155℃ for the metering section; the temperature of the spinning box is 130-160℃. When using PCL, the temperature of each zone and the spinning box should preferably be controlled around 58-65℃, and can be finely adjusted within the above range according to the specific conditions of the equipment.

[0017] The speed of the melt metering pump is coordinated with that of component A to ensure the predetermined skin-to-core ratio or parallel ratio; Melt filtration accuracy: 20~40μm stainless steel metal fiber filter screen; 2. For parallel structures For PPCT / PLA parallel structure fibers, the PPCT side temperature setting is the same as above; the PLA side temperature can be set according to the grade of low melting point PLA or conventional PLA. When using low-melting-point PLA in parallel processes, the following settings can be used as a reference: feeding section 120~135℃, compression section 130~150℃, metering section 135~155℃, spinning box temperature 130~160℃. If PLA with a higher melting point is selected as the other side, the temperature of the feeding section, compression section, metering section and chamber can be increased to the corresponding range of 165-200℃, and it can be ensured that thermal degradation of the PPCT side is not caused. The quality ratio of parallel products is controlled between 40:60 and 50:50, with 50:50 being preferred.

[0018] All metal parts in contact with the polymer melt are preferably made of 316L stainless steel to prevent corrosion and catalytic degradation by metal ions. The spinning assembly should be preheated to 10–20°C above the spinning temperature before installation to reduce heat loss during installation and ensure stable melt flow.

[0019] Step 3: Composite spinning and cooling molding (1) Composite molding: The two molten polymer melts are combined in the spinning assembly according to the preset composite morphology.

[0020] Core-skin composite assembly: Utilizing a concentric circular pipe structure, the outer pipe delivers the skin polymer, while the inner pipe delivers the PPCT core polymer. The two melt streams converge at the front end of the spinneret, forming a composite melt flow where the skin layer encapsulates the core layer.

[0021] Parallel composite component: adopts a "C"-shaped or eccentric parallel pipe structure, in which two streams of melt contact each other in parallel at the front end of the spinneret orifice, forming a two-phase parallel composite melt flow.

[0022] (2) Spinneret parameters: Spinneret diameter: 0.20–0.40 mm, preferably 0.25–0.35 mm; The length-to-diameter ratio of the spinneret orifice L / D is 2:1 to 4:1, preferably 3:1; Spinneret hole count: Depending on the capacity design, short fiber production lines typically have 800 to 3000 holes per plate; Spinneret surface temperature: the same as or within 5°C lower than the chamber temperature.

[0023] (3) Rapid cooling: After the nascent fibers are extruded from the spinneret, they enter the side-blowing (or ring-blowing) cooling zone for rapid cooling. Cooling parameters: Cooling air temperature: 12~20℃, preferably 15℃; Cooling air velocity: 0.3~1.2 m / s, preferably 0.5~0.8 m / s; Cooling distance (from spinneret surface to bundle point): 800–1500 mm; The single-unit suction system has an air velocity of 0.3–1.5 m / s to prevent residual oligomers (such as lactide) from accumulating on the spinneret surface and in the cooling zone.

[0024] (4) Oiling and bundling: The cooled nascent fibers are oiled and bundled through an oil nozzle or oil roller.

[0025] Oil type: Anionic or nonionic spinning oil, which must be compatible with the PLA / PPC system; Oiling rate: 0.3%–0.8% (oil / fiber mass ratio), preferably 0.4%–0.6%; Oiling temperature: 15~25℃.

[0026] (5) Winding and dropping into the spinning drum: The oiled nascent filaments are wound by the guide rollers and dropped into the spinning drum for temporary storage. The temporary storage time in the spinning drum should not exceed 24 hours to prevent fiber aging and uneven crystallization.

[0027] Step 4: Post-processing The nascent fibers undergo the following post-processing steps to obtain the finished PPCTDF bio-based composite fiber: (1) Twisting and Bundling: Multiple filament bundles in the spinning drum are twisted together on a bundling frame to form a large filament bundle (tow) with a bus density of 50,000 to 200,000 dtex. The pretension is controlled at ≤0.2 cN / dtex to prevent the filament bundle from being stretched prematurely before drafting.

[0028] (2) Pre-drawing and impregnation: The large filament bundle is passed through a pre-drawing impregnation tank filled with warm water containing spinning oil. The temperature of the pre-drawing water bath is controlled at 25-40℃. This temperature is lower than the Tg of low-melting-point PLA (approximately 58℃), ensuring that the skin layer or the parallel side has sufficient strength to transfer the drawing force; at the same time, this temperature is close to or slightly higher than the Tg of the PPC component in PPCT (approximately 35℃), so that the PPCT component is in a highly elastic state, which is conducive to the orientation of macromolecular chains without breakage. Meanwhile, the impregnation length is 1.5-3.0m to ensure that the filament bundle is fully impregnated and initially heated.

[0029] (3) Multi-stage stretching: A two-stage drawing process is employed to maximize tensile properties while avoiding stress bleaching. First-stage drawing (main drawing): The drawing ratio is 65%–75% of the total drawing ratio. A hot water immersion bath or steam heating device is provided between the drawing rolls. When the low-melting-point polymer is low-melting-point PLA, the first-stage drawing temperature is 60–70℃; when the low-melting-point polymer is PCL, the first-stage drawing is performed by room temperature cold stretching or by controlling the temperature at 30–40℃. The linear speed of the first-stage drawing rolls is 80–150 m / min.

[0030] Second-stage drawing (supplementary drawing): The drawing ratio is 25% to 35% of the total drawing ratio. When the low-melting-point polymer is low-melting-point PLA, the second-stage drawing temperature is 65 to 80°C; when the low-melting-point polymer is PCL, the second-stage drawing temperature is controlled at 35 to 45°C. The second-stage drawing roll is equipped with a cooling device to prevent the filament bundle from sticking to the roll.

[0031] Total draw ratio: 2.0 to 4.0 times for core-sheath structure fibers, preferably 3.5 times; 2.0 to 3.5 times for parallel structure fibers, preferably 3.0 times.

[0032] (4) Oiling agent replenishment: The drawn fiber bundle is replenished with oiling agent through the second oiling device. The oiling agent should be applied before entering the drying and setting stage, and the oiling rate of the fiber after drawing should be controlled at 0.35% to 0.6%.

[0033] (5) Curling treatment: The drawn filament bundles are mechanically coiled in a filling box type coiling machine.

[0034] Preheating before crimping: Preheat the fibers before they enter the crimping machine. If the low-melting-point polymer is low-melting-point PLA, raise the temperature to 40–55°C; if the low-melting-point polymer is PCL, maintain room temperature (20–25°C) or a slightly warm temperature (not exceeding 35°C) and perform mechanical crimping directly. This makes the fibers soft and flexible, reducing fiber damage during crimping. The temperature must not exceed the softening temperature of the low-melting-point polymer in the cortex.

[0035] Curling machine parameters: filling box flap pressure 0.8~2.0 bar, roller pressure 1.5~2.5 bar; Target curling parameters: 8-14 curls / 25mm, curling degree 12%-20%; For side-by-side fibers, in addition to mechanical crimp, the fibers also possess a potential three-dimensional crimp caused by the shrinkage difference between the two components. This potential crimp can be fully revealed during subsequent relaxation heat treatment.

[0036] (6) Drying and heat setting: The curled filaments enter a hot air through-type dryer for drying and heat setting. The dryer should be equipped with multiple temperature zones and an outlet cooling zone; Core-sheath structure fiber: When the low-melting-point polymer is low-melting-point PLA, the drying and heat setting temperature is 80-100℃; when the low-melting-point polymer is PCL, the drying and heat setting temperature should be controlled at 30-45℃ (preferably 35-40℃), or room temperature dehumidification drying should be used to prevent the fiber surface from melting and sticking; drying time is 4-8 minutes.

[0037] Parallel structure fibers: Drying temperature 100–130℃, drying time 5–10 minutes. Higher setting temperatures help fix the internal crystalline structure of the fibers, improving crimp permanence and dimensional stability; Hot air velocity: 0.5~2.0 m / s; The density of the fiber bundles laid in the dryer is 1.5 to 3.0 kg / m².

[0038] (7) Cut off: After the filament bundle is cooled to room temperature (≤25℃), it enters the cutting process to prevent the curl from being straightened due to tension.

[0039] Type of cutting machine: Rotary cutting machine; The cutting length is set according to the application requirements: 38 mm (for non-woven fabrics), 51 mm (for general spinning), and 64 mm (for filling cotton). The cutting tension is controlled by the tension frame at the front of the cutting machine to ensure uniform cutting; Cutting accuracy: Cutting length deviation within ±5%.

[0040] Furthermore, the application of PPCTDF bio-based composite fiber in the preparation of thermally bonded nonwoven fabric is characterized by the following: the fiber has a core-sheath structure, and self-adhesion between fibers is achieved by the melting of the low-melting-point polymer in the sheath through hot rolling or hot air process; when the sheath is PCL, the thermal bonding temperature is preferably 55-65℃; when the sheath is low-melting-point PLA (melting point 120-140℃), the thermal bonding temperature is preferably 120-145℃.

[0041] Furthermore, the application of PPCTDF bio-based composite fiber in the preparation of three-dimensional crimped fibers or thermal insulation filling materials is characterized by: the fiber having a parallel structure, utilizing the shrinkage difference between the two components to form a permanent three-dimensional crimp; the number of three-dimensional crimps is ≥12 / 25mm.

[0042] By adopting the above technical solution, the beneficial effects of the present invention are as follows: Multifunctional: By changing the composite form (core-sheath type or parallel type), it can perform multiple functions in one machine, producing two types of functional fibers: thermal bonding type and three-dimensional crimp type, with a wide range of applications.

[0043] Superior performance: With high-performance PPCT as the key component, the strength and toughness of the fiber are significantly better than ordinary PLA single-component fiber and PPC / PLA simple blend fiber.

[0044] Green and environmentally friendly: PPC is derived from the copolymerization reaction of CO2 and propylene oxide, and each ton of PPC can fix approximately 430 kg of CO2. The raw materials are renewable, and the product is completely biodegradable.

[0045] Good processability: The twin-screw composite spinning technology is mature, with a wide process window, making it easy to achieve continuous and large-scale production.

[0046] Process controllability: By independently controlling the melting temperature, metering ratio, and spinning component structure of the two components, the cross-sectional shape, linear density, and functional properties of the fiber can be precisely controlled. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the integrated technology route for PPCTDF fibers.

[0048] Figure 2 This is a schematic diagram of a twin-screw composite spinning equipment and its spinning process.

[0049] Figure 3 This is a schematic diagram of the structure of PPCTDF fiber. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0052] The preparation of the material particles of this invention is as follows: (1) Preparation or selection of PPCT particles: First, PPC diol is prepared by copolymerization of CO2 and propylene oxide under the action of zinc-cobalt dicyandiamide (ZnCo-DMC) catalyst or rare earth ternary catalyst at 50-80℃ and CO2 pressure of 2.0-6.0 MPa. Then, PPC diol is mixed with isocyanate, small molecule chain extender, composite catalyst, etc., and subjected to reaction casting, curing and post-curing treatment to obtain high molecular weight PPCT particles. Before use, PPCT particles need to be dried in a vacuum environment (absolute pressure ≤100Pa) at 25-35℃ for 12-24 h, or treated with a room temperature cold air dehumidification dryer to prevent the particles from softening and clumping, and to reduce the moisture content to ≤50 ppm.

[0053] (2) Selection of PLA resin: Extrusion-grade PLA resin with a melt index (MFI) of 3-30 g / 10min (190℃, 2.16 kg), D-lactic acid content ≤4.0%, and number-average molecular weight (Mn) of 80,000-150,000 should be selected. Before use, the PLA resin should be vacuum dried at 80-100℃ for 4-6 h to reduce the moisture content to ≤50 ppm.

[0054] (3) Selection of toughening modifier (optional): Select one or more combinations of the following toughening modifiers: The amount of epoxy functionalized chain extender (such as Joncryl® ADR-4400) added is 0.1 to 1.5 wt% of the total mass of PPCT particles and PLA. Hyperbranched polymers (HBP) and their derivatives, added in amounts of 0.2–3.0 wt%.

[0055] Preparation example: Preparation of PPCT This preparation example aims to synthesize PPCT (polypropylene carbonate-based thermoplastic polyurethane) copolymer particles for subsequent spinning processes.

[0056] 1. Reaction materials and formulation: The formula is as follows, by weight: Polypropylene carbonate diol (PPC diol): 65 parts; Isocyanate (MDI, diphenylmethane diisocyanate): 30 parts; Small molecule chain extender (1,4-butanediol, BDO): 5 parts; Catalyst (dibutyltin dilaurate, DBTDL): 0.02 parts (optional, added to adjust the reaction rate).

[0057] 2. Preparation steps: Dehydration treatment: Add 65 parts of PPC diol to the reaction vessel, heat to 100-110℃, stir and dehydrate for 2 hours under vacuum degree ≤-0.09 MPa until the moisture content is lower than 0.05%, and cool to 60-70℃ for later use.

[0058] Prepolymerization reaction: 30 parts of MDI were added to the dehydrated PPC diol, and the temperature was slowly raised to 80-90°C under nitrogen protection for 1.5-2 hours to obtain the isocyanate-terminated prepolymer.

[0059] Chain extension reaction: 5 parts of 1,4-butanediol (BDO) were preheated to 60°C and then rapidly added to the prepolymer, along with the catalyst DBTDL. High-shear stirring was initiated, and the reaction was allowed to proceed for 5–10 minutes. When the viscosity of the system rapidly increased to the point where stirring was almost impossible, the mixture was quickly discharged.

[0060] Curing and granulation: The discharged polymer is placed in a constant temperature oven at 100-110℃ for 15-20 hours to cure completely. After curing, it is crushed and extruded by a twin-screw extruder to obtain transparent or semi-transparent PPCT copolymer particles.

[0061] Example 1: Preparation of PPCTDF thermally bonded fiber (core-sheath structure) (1) Raw materials: PPCT particles and low-melting-point PLA particles (D-lactic acid content 10%, melting point 130℃, MFI = 25 g / 10 min). The low-melting-point PLA particles were vacuum dried at 45℃ for 8 h.

[0062] (2) Spinning: A composite spinning machine (skin-core composite spinneret, spinneret diameter 0.30 mm, L / D = 3:1, number of holes 1200) is used.

[0063] PPCT side (core layer): feeding section 160℃, compression section 170℃, metering section 180℃, spinning box 180℃.

[0064] Low melting point PLA side (skin): feeding section 125℃, compression section 135℃, metering section 145℃, spinning box 150℃.

[0065] The core-to-skin mass ratio is 60:40, controlled by the speed of the metering pumps on both sides.

[0066] Cooling air temperature: 15℃, air speed: 0.6 m / s.

[0067] Oiling rate: 0.5%.

[0068] (3) Post-processing: Combined to a bus density of 100,000 dtex; Pre-stretching and impregnation: 35℃ warm water, impregnation length 2m; Two-stage drawing: first-stage drawing ratio 2.5 (filament temperature 62℃, hot water bath), second-stage drawing ratio 1.4 (filament temperature 68℃), total drawing ratio 3.5; Oil supplement: 0.45%; Curling: Before curling, steam heat to 45℃, flip plate pressure 1.2 bar, roller pressure 1.8 bar, curling number 10 / 25mm; Drying and heat setting: 90℃, 6 minutes, then cool to 40℃ at the outlet; Cutting options: 38 mm (for non-woven fabrics) and 51 mm (general purpose).

[0069] Table 1. Fiber Properties

[0070] Thermal bonding test: After the above fibers are carded and laid in a 100% ratio, they are processed by hot rollers (roller surface temperature 140℃, linear pressure 40 N / cm, machine speed 15 m / min). The low melting point PLA skin layer melts and bonds the fiber intersections. The resulting nonwoven fabric has a transverse tensile strength of 15 N / 5cm and a longitudinal tensile strength of 28 N / 5cm, and a soft and uniform hand feel.

[0071] Example 2: Preparation of PPCTDF three-dimensional crimped fibers (parallel structure) (1) Raw materials: PPCT particles and low-melting-point PLA particles (D-lactic acid content 10%, melting point 130℃, MFI = 25 g / 10 min). The low-melting-point PLA particles were vacuum dried at 45℃ for 8 h.

[0072] (2) Spinning: A composite spinning machine (parallel composite spinneret, spinneret diameter 0.30 mm, L / D = 3:1, number of holes 1500) is used.

[0073] PPCT side (component A): Feeding section 160℃, compression section 172℃, metering section 182℃, spinning box 185℃; PLA side (component B): Feeding section 125℃, compression section 135℃, metering section 145℃, spinning box 150℃; The quality ratio of parallel products is 50:50; Cooling air temperature: 15℃, air speed: 0.7 m / s; Oiling rate: 0.5%.

[0074] (3) Post-processing: Combined to a bus density of 80,000 dtex; Pre-stretching and impregnation: 40℃ warm water; Two-stage drawing: first-stage drawing ratio 2.0 (filament temperature 62℃), second-stage drawing ratio 1.5 (filament temperature 72℃), total drawing ratio 3.0; Oil supplement: 0.50%; Curling: Before curling, steam heating to 55℃, flipping pressure 1.5 bar, roller pressure 2.0 bar, mechanical curling number 8-14 / 25mm; Drying and heat setting: 120℃ for 8 minutes, then cooling to 40℃ at the outlet. At this temperature, the two components in the parallel structure exhibit full three-dimensional potential curling due to their different shrinkage rates.

[0075] Cut: 64 mm (for filling cotton).

[0076] Table 2. Fiber Properties

[0077] Due to the difference in heat shrinkage rates between the two components PPCT and PLA (PPCT has a heat shrinkage rate of about 8%, while PLA has a heat shrinkage rate of about 15%, and after heat setting at 120℃), this fiber exhibits a permanent three-dimensional spiral crimp shape, resulting in a fluffy feel, good elasticity, and superior resilience compared to traditional polyester crimped staple fibers.

[0078] Example 3: Preparation of PPCTDF thermally bonded fiber (core-sheath structure, PCL sheath) (1) Raw materials: PPCT particles (prepared in the preparation example) and PCL particles (Mn = 80,000, melting point 60℃, MFI = 3 g / 10min, 80℃). The PCL particles were vacuum dried at 40℃ for 4 h.

[0079] (2) Spinning: A composite spinning machine (skin core composite spinneret with 800 holes) is used.

[0080] PPCT side (core layer): feeding section 158℃, compression section 168℃, metering section 178℃, spinning box 178℃; PCL side (skin): Feeding section 75℃, compression section 90℃, metering section 100℃, spinning box 95℃; The ratio of leather to core weight is 50:50. Cooling air temperature: 12℃, air speed: 0.5 m / s; Oiling rate: 0.4%.

[0081] (3) Post-processing: Total draw ratio 2.5, two-stage draw (filament temperature 35-45℃); Curling: Do not heat before curling (to avoid softening of PCL), flip plate pressure 0.8 bar, roller pressure 1.5 bar; Drying and heat setting: 45℃ (below the melting point of PCL), 10 minutes; Cut length: 51 mm.

[0082] (4) Fiber properties: linear density 2.5 dtex, tensile strength 2.5 cN / dtex, elongation at break 40%, thermal bonding temperature 55-60℃. This fiber is suitable for special applications with lower thermal bonding temperature requirements, such as bonding of heat-sensitive substrates and medical dressings.

[0083] Comparative Example 1: PPC / PLA blended single-component fibers Using PPCT particles with the same formulation as in the preparation example, single-component fibers were prepared by conventional single-component melt spinning (spinning temperature 185℃, draw ratio 3.0, linear density 2.0 dtex). The resulting fibers had a breaking strength of 2.5 cN / dtex, an elongation at break of 28%, a HDT of 55℃, no thermal bonding function, and no three-dimensional crimping characteristics.

[0084] Comparative Example 2: Pure PLA bicomponent fibers (core-sheath structure) Using low-melting-point PLA (melting point 130℃) as the sheath and ordinary PLA (melting point 170℃) as the core, bicomponent fibers were prepared using the same spinning and post-processing techniques as in Example 1. The resulting fibers had a linear density of 2.0 dtex, a breaking strength of 2.8 cN / dtex, a breaking elongation of 12%, and a HDT of 54℃.

[0085] Table 3. Performance Comparison

[0086] As shown in the table above, compared with Comparative Example 2 (pure PLA core-sheath fiber), the PPCTDF core-sheath fiber of Example 1, while maintaining its thermal bonding function, achieved an increased breaking elongation of 35% (compared to only 12% in Comparative Example 2) and an improved aging resistance retention rate of 85% (compared to only 62% in Comparative Example 2), indicating that the PPCT core layer significantly improves the fiber's toughness and durability. The PPCTDF parallel fibers of Example 2 simultaneously possess three-dimensional crimping function (13 crimps / 25 mm) and good bulkiness (300 mm), functionalities that Comparative Example 1 (single-component PPCT fiber) cannot achieve.

[0087] Application Example 1: Preparation of Nonwoven Fabrics Nonwoven fabric was produced using PPCTDF core-sheath thermally bonded fibers (38 mm cut length) prepared in Example 1, which were then formed into a web by airflow or carding, and finally bonded using a hot air bonding process (hot air temperature 135℃, air velocity 1.5 m / s, processing time 8 seconds). The nonwoven fabric has a basis weight of 30 g / m², a longitudinal tensile strength of 22 N / 5cm, and a transverse tensile strength of 12 N / 5cm. It can be used for disposable medical protective clothing, sanitary napkin surface layers, and baby diaper surface layers, etc.

[0088] Application Example 2: Preparation of Down-like Biodegradable Filling Cotton The PPCTDF parallel three-dimensional crimped fibers (64 mm cut length) prepared in Example 2 were mixed with the core-sheath thermally bonded fibers from Example 1 at a mass ratio of 85:15. The mixture was then carded, web-laid, and hot-air bonded (120°C, 5 s) to produce a filling. The filling achieved a loft of 290 mm, a warmth retention rate of 75%, and a compression resilience of 75%. The three-dimensional crimped fibers provide loft and warmth, while the thermally bonded fibers provide structural support and anti-migration properties. It can be used in down-like thermal clothing, comforters, sleeping bag fillings, etc.

[0089] Application Example 3: Non-woven fabric for biodegradable and environmentally friendly shopping bags High-strength nonwoven fabric was produced using PPCTDF core-sheath thermally bonded fibers (51 mm cut length) prepared in Example 1, through a needle-punching + hot-rolling composite process (needle-punching density 80 needles / cm², hot-rolling temperature 138℃, linear pressure 50 N / cm). The nonwoven fabric has a basis weight of 80 g / m², a longitudinal tensile strength of 85 N / 5cm, and a transverse tensile strength of 45 N / 5cm. It can be used to make biodegradable shopping bags, packaging linings, etc.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any ordinary changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included within the protection scope of the present invention.

Claims

1. A PPCTDF bio-based composite fiber, characterized in that: It is made by spinning PPCT material with a low-melting-point polymer; the PPCT is a copolymer of polypropylene carbonate diol with added isocyanate and chain extended by PDO or BDO small molecules; the composite fiber has a core-sheath structure or a side-by-side structure.

2. The PPCTDF bio-based composite fiber according to claim 1, characterized in that: The PPCT material comprises 40-70 parts by weight of polypropylene carbonate diol, 25-55 parts by weight of isocyanate, and 0.2-5 parts by weight of PDO or BDO. The composite fiber comprises 20-50 parts by weight of PPCT material, 50-80 parts by weight of low-melting-point polymer and 1-5 parts by weight of toughening modifier; The toughening modifier is selected from one or more of epoxy functionalized chain extenders, hyperbranched polymers and their derivatives.

3. The PPCTDF bio-based composite fiber according to claim 1 or 2, characterized in that: In the core-skin structure, the core layer is made of PPCT material, and the skin layer is made of a low-melting-point polymer; the low-melting-point polymer is polylactic acid (PLA) with a melting point of 120-140℃ or polycaprolactone (PCL) with a melting point of 55-65℃; the mass ratio of skin layer to core layer is 70:30 to 50:

50.

4. The PPCTDF bio-based composite fiber according to claim 1 or 2, characterized in that: In the parallel structure, one side is the PPCT material and the other side is polylactic acid (PLA) or polycaprolactone (PCL); the mass ratio of PPCT material to polylactic acid (PLA) or polycaprolactone (PCL) is 40:60 to 50:

50.

5. A method for preparing PPCTDF bio-based composite fibers as described in any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Provide PPCT composite material particles and low melting point polymer particles, respectively dried to a moisture content ≤50ppm; (2) The two types of particles are added to the two independent screw systems of the twin-screw composite spinning machine and melted at their respective set temperatures; (3) The two molten polymer melts are combined in the spinning assembly according to the preset composite morphology and extruded from the spinneret into nascent fibers; (4) The nascent fibers are cooled, oiled, multi-stage stretched, crimped, dried, heat-set and cut to obtain PPCTDF fibers.

6. The method according to claim 5, characterized in that: In step (2), the melting temperature of PPCT material is 170-190℃; when the low melting point polymer is PCL, its melting temperature is 58-65℃; when the low melting point polymer is low melting point PLA, its melting temperature is 125-155℃.

7. The method according to claim 5 or 6, characterized in that: The multi-stage drawing in step (4) is a two-stage drawing; the total draw ratio of the core-sheath structure fiber is 2.0 to 4.0 times, and the total draw ratio of the parallel structure fiber is 2.0 to 3.5 times; when the low-melting-point polymer is low-melting-point PLA, the first-stage drawing temperature is 60 to 70°C, and the second-stage drawing temperature is 65 to 80°C; when the low-melting-point polymer is PCL, the first-stage drawing is performed by room temperature cold stretching or the temperature is controlled at 30 to 40°C, and the second-stage drawing temperature is controlled at 35 to 45°C.

8. The method according to claim 5, characterized in that: In step (3), the spinning assembly is a core-sheath composite assembly or a parallel composite assembly; the diameter of the spinneret spinneret hole is 0.20 to 0.40 mm, and the length-to-diameter ratio L / D is 2:1 to 4:

1.

9. The application of the PPCTDF bio-based composite fiber as described in any one of claims 1 to 4 in the preparation of thermally bonded nonwoven fabrics, characterized in that: The fiber has a core-sheath structure and achieves self-adhesion between fibers by hot rolling or hot air process, utilizing the melting of the low-melting-point polymer in the sheath; when the sheath is PCL, the hot bonding temperature is 55-65℃; when the sheath is low-melting-point PLA, the hot bonding temperature is 120-145℃.

10. The application of the PPCTDF bio-based composite fiber as described in any one of claims 1 to 4 in the preparation of three-dimensional crimped fibers or thermal insulation filling materials, characterized in that: The fibers have a parallel structure and utilize the shrinkage difference between the two components to form permanent three-dimensional crimps; the number of three-dimensional crimps is ≥12 / 25mm.

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