CN112522804B

CN112522804B - Physical aging-resistant polylactic acid fiber material, and preparation method and application thereof

Info

Publication number: CN112522804B
Application number: CN202011326243.6A
Authority: CN
Inventors: 黄威; 陈鹏
Original assignee: Ningbo Institute of Material Technology and Engineering of CAS
Current assignee: Ningbo Institute of Material Technology and Engineering of CAS
Priority date: 2020-11-23
Filing date: 2020-11-23
Publication date: 2022-04-26
Anticipated expiration: 2040-11-23
Also published as: CN112522804A

Abstract

The invention discloses a physical aging resistant polylactic acid fiber material, a preparation method and application thereof. The polylactic acid fiber material is in a fibrous form and consists of an amorphous phase; the amorphous phase comprises 5wt% to 95wt% of a metastable phase, and the polylactic acid fiber material further formed therefrom comprises 15wt% to 85wt% of a crystalline phase and 15wt% to 85wt% of an amorphous phase; the amorphous phase comprises 5wt% to 65wt% of metastable phase, and the characteristic peak of the metastable phase in an infrared spectrogram appears at 918cm^‑1To (3). The polylactic acid fiber material has the characteristics of excellent physical aging resistance, small change rate of tensile strength and elongation at break before and after storage, high orientation degree, simple preparation process, contribution to large-scale production and wide application prospect, and can keep the stability of size and performance at the storage logistics stage.

Description

Physical aging-resistant polylactic acid fiber material, and preparation method and application thereof

Technical Field

The invention relates to a polylactic acid material, in particular to a physical aging resistant polylactic acid fiber material, a preparation method and application thereof (surgical suture lines, spunlace, needle punching, spun-bonded non-woven fabrics and the like), and belongs to the technical field of fiber materials.

Background

With the explosive development of the global petroleum industry, a large amount of petroleum-based polyester, nylon and other related resins are made into fibers every year, and are used in the fields of clothing and medical health. In 2017, the yield of the global synthetic fibers (except polyolefin fibers) breaks through 6000 million tons for the first time. Wherein, the output of the polyester filament yarn reaches 3717 ten thousand tons, and the polyester filament yarn is widely applied to the fields of clothes, medical and health products and the like, such as adult clothes, infant clothes, facial masks, medical protective clothing and the like, and the products bring great convenience to the high-quality life of people. However, uncertainty of health safety due to precipitation of the petroleum-based resin itself and related auxiliaries, and "white" pollution of environment due to non-degradability of the petroleum-based resin cover the shadow of the wide application of petroleum-based fibers in the fields of clothing and medical health. Therefore, the development of the bio-based degradable resin fiber is necessary.

Polylactic acid has good biocompatibility and biodegradability, can be degraded into lactic acid in nature, and finally forms carbon dioxide and water through microbial decomposition, and is one of biodegradable polymers certified by the U.S. food and drug administration. Has wide application prospect in the fields of tissue engineering, medical treatment and health, flexible packaging materials and the like. In particular to polylactic acid fiber which can be used for clothes, medical protective clothing, textiles for vehicles and the like. Among these, the fields of clothing, home textiles and textiles for vehicles require polylactic acid fibers with sufficiently high tenacity and sufficiently long retention time of mechanical properties to varying degrees. However, numerous documents (Macromolecules2007, 40, 9664-. Among them, physical aging is a process in which a molecular segment spontaneously changes from a non-equilibrium state to an equilibrium state, and is essentially a reduction in free volume. This makes polylactic acid articles highly susceptible to physical degradation during the warehouse logistics stage leading to sharp embrittlement of the article. However, at present, no report is found on the development of polylactic acid fibers with physical aging resistance through process optimization.

The preparation of polylactic acid fiber has many publications, wherein the main purpose is to improve the strength and functionality of the fiber. For example, CN1814867A reports a method for preparing a polylactic acid fiber filament by a melt spinning method, in which a chip mainly containing L-polylactic acid is melted, spun at a speed of 1000 to 3000 m/min, and subjected to 2 to 3 times of hot drawing to obtain a polylactic acid fiber with a tensile strength of 2.1 to 3.8 cN/dtex. CN1357017A reports polylactic resin and a method for preparing fiber products by melt spinning by mainly taking L-polylactic acid as a raw material, wherein the spinning speed is 3000-5000 m/min, and the fiber has the tensile strength of 3.5-4.5 cN/dtex after hot drawing and heat setting. CN101608345A reports a method for preparing biodegradable polylactic acid fiber with improved fiber strength, which improves spinning kinetics by using liquid phase constant temperature bath, and makes the prepared fiber superior in performance to conventional melt-spun fiber by using higher spinning speed and lower draw ratio. CN105220264A reports a preparation method of modified polylactic acid fiber for improving fiber performance, by adding degradable resin (polytrimethylene terephthalate or/and polyhydroxyalkanoate) with good mechanical property, and the resin has good compatibility with polylactic acid, the service performance of the modified polylactic acid fiber is improved. CN108035013A reports a cool polylactic acid fiber with improved comfort and a preparation method thereof, wherein the cool master batch and polylactic acid are melted, blended, granulated and spun to obtain the polylactic acid fiber with cool temperature reduction, skin friendliness and bacteriostasis.

Although the above known technologies can prepare polylactic acid fibers, under the current technical conditions, the fibers obtained by melt spinning of polylactic acid are amorphous, and crystalline fibers can be obtained only by subsequent drawing and heat setting; the polylactic acid fiber subjected to heat setting is easy to be physically aged in a storage logistics stage to cause rapid embrittlement; therefore, there is a need to develop new polylactic acid fibers with physical aging resistance and a preparation method thereof to meet the high requirements of various applications on the comprehensive properties thereof.

Disclosure of Invention

The invention mainly aims to provide a polylactic acid fiber material with physical aging resistance, a preparation method and application thereof, thereby overcoming the defects in the prior art.

In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:

the embodiment of the invention provides a polylactic acid fiber material (also called polylactic acid amorphous fiber material) with physical aging resistance, which is in a fibrous form, and the polylactic acid fiber material consists of an amorphous phase; the above-mentionedThe amorphous phase contains 5wt% to 95wt% of metastable phase, and the characteristic peak of the metastable phase in an infrared spectrogram appears at 918cm^-1At least one of (1) and (b); more importantly, after the polylactic acid fiber material is stored below the glass transition temperature for enough time, the change rate of tensile strength is lower than 30%, the change rate of elongation at break is lower than 40%, and obvious yield and subsequent plastic deformation zones appear on a stress-strain curve.

Furthermore, the orientation degree of the polylactic acid fiber material (also called polylactic acid amorphous fiber material) is 0.2-0.8.

The embodiment of the invention also provides a polylactic acid fiber material (also called polylactic acid crystalline fiber material) with physical aging resistance, which is in a fibrous form, and the polylactic acid fiber material comprises 15wt% -85 wt% of crystalline phase and 15wt% -85 wt% of amorphous phase; the amorphous phase comprises 5wt% to 65wt% of metastable phase, and the characteristic peak of the metastable phase in an infrared spectrogram appears at 918cm^-1At least one of (1) and (b); more importantly, after the polylactic acid fiber material is stored below the glass transition temperature for enough time, the change rate of tensile strength is lower than 30%, the change rate of elongation at break is lower than 40%, and obvious yield and subsequent plastic deformation zones appear on a stress-strain curve.

Further, the polylactic acid fiber material (also referred to as polylactic acid crystal fiber material) has an orientation degree of 0.35 to 0.99.

Further, after the polylactic acid fiber material is stored below the glass transition temperature for a sufficient time, an endothermic peak with an enthalpy value delta H which is sufficiently large appears in a Differential Scanning Calorimetry (DSC) curve of the polylactic acid fiber material immediately after the glass transition temperature, the enthalpy value of the endothermic peak is not changed along with the change of the temperature rising rate of a DSC test, and the infrared spectrogram of the polylactic acid fiber material is within 918cm^-1The bands show characteristic peaks whose intensity increases with the storage time.

The embodiment of the invention also provides a method for preparing the polylactic acid fiber material (also called polylactic acid amorphous fiber material) with the physical aging resistance, which comprises the following steps:

providing a dry polylactic acid or a dry mixture of polylactic acid;

and extruding and spinning the dried polylactic acid or the dry polylactic acid mixture by a melt spinning device, wherein the spinning temperature is 170-270 ℃, the winding speed is 500-8000 m/min, the polylactic acid fiber material is rapidly quenched to room temperature at the quenching speed of 8-2000 ℃/s, and the quenching time is 0.1-29 s, so that the polylactic acid fiber material (namely the polylactic acid amorphous fiber material) in a fibrous form is prepared.

The embodiment of the present invention also provides another method for preparing the polylactic acid fiber material (also referred to as polylactic acid crystalline fiber material) with physical aging resistance, which comprises:

preparing the polylactic acid amorphous fiber material by adopting the method;

fully preheating the polylactic acid amorphous fiber material, and then carrying out secondary drafting, wherein the drafting temperature is 65-145 ℃, the drafting multiple is 1-6 times, but relaxation heat setting is not carried out, then rapidly quenching to room temperature at the quenching speed of 2-800 ℃/s, and the quenching time is 0.1-59 seconds, so as to prepare the polylactic acid fiber material (namely the polylactic acid crystalline fiber material) in a fibrous form.

The embodiment of the invention also provides another method for preparing the polylactic acid fiber material (namely the polylactic acid crystalline fiber material) with the physical aging resistance, which comprises the following steps:

providing a dry polylactic acid or a dry mixture of polylactic acid;

and extruding and spinning the dried polylactic acid or the dry polylactic acid mixture by a melt spinning device, drafting by a high-speed hot-roll one-step method at the spinning temperature of 170-270 ℃, the drafting temperature of 65-165 ℃, the drafting multiple of 1-5 times and the winding speed of 500-5000 m/min, but not performing relaxation heat setting, and then rapidly quenching to room temperature at the quenching rate of 2.5-800 ℃/s for 0.1-59 s to prepare the fibrous polylactic acid crystalline fiber material.

The embodiment of the invention also provides application of the physical aging resistant polylactic acid fiber material in preparing fiber products.

Further, the embodiment of the invention also provides a fiber product made of the polylactic acid fiber material with the physical aging resistance.

Further, the fiber product includes a thread product, a garment, a home textile product, a nonwoven fabric product, and the like, but is not limited thereto.

Further, the embodiment of the invention also provides a disinfection packaging and storage method of the polylactic acid fiber material with physical aging resistance, which comprises the following steps:

providing a polylactic acid fiber material resistant to physical aging in any of the previous embodiments, and subjecting the polylactic acid fiber material to a temperature T at the glass transition temperature thereof_gThe packaging and storage is sterilized as follows.

Compared with the prior art, the polylactic acid fiber material (including polylactic acid amorphous fiber material, polylactic acid crystalline fiber material and the like) provided by the embodiment of the invention has the characteristic of physical aging resistance, the change rate of the tensile strength before and after storage is smaller, the change rate of the elongation at break is smaller, the orientation degree is higher, and products such as polylactic acid surgical suture lines and the like made of the polylactic acid amorphous fiber material not only have the strength equivalent to or superior to that of the existing polylactic acid surgical suture lines, but also have excellent physical aging resistance and anti-inflammation performance; the products such as clothes, home textile fabrics, needle-punched non-woven fabrics, spunlace non-woven fabrics, spun-bonded non-woven fabrics (including short fibers) and the like made of the polylactic acid crystalline fiber material not only have the strength equivalent to or superior to that of the existing polylactic acid fiber products, but also have excellent physical aging resistance, can keep the stability of size and performance in the storage logistics stage, and meanwhile, the preparation process is simple, is beneficial to large-scale production, and has wide application prospect.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a stress-strain curve of a polylactic acid fiber material resistant to physical aging obtained in example 1 of the present invention;

FIG. 2 is a stress-strain graph of the polylactic acid fiber material obtained in comparative example 1.

Detailed Description

The present invention will be more fully understood from the following detailed description. Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed embodiment.

An aspect of the embodiments of the present invention provides a polylactic acid fiber material (polylactic acid amorphous fiber material) with resistance to physical aging, which is in a fibrous form, and consists of 100 wt% of an amorphous phase; the amorphous phase comprises 5wt% to 95wt% of metastable phase, and the characteristic peak of the metastable phase in an infrared spectrogram appears at 918cm^-1At least one of (1) and (b); more importantly, after the polylactic acid fiber material is stored below the glass transition temperature for enough time, the change rate of tensile strength is lower than 30%, the change rate of elongation at break is lower than 40%, and obvious yield and subsequent plastic deformation zones appear on a stress-strain curve.

In some more preferred embodiments, the content of the metastable phase in the amorphous phase of the polylactic acid amorphous fiber material is 20wt% to 70 wt%.

In some more preferred embodiments, the content of the metastable phase in the amorphous phase of the polylactic acid amorphous fiber material is 30-50 wt%.

In some preferred embodiments, the polylactic acid fiber material has an orientation degree of 0.2 to 0.8, preferably 0.4 to 0.6.

Further, the polylactic acid amorphous fiber material has a polylactic acid glass transition temperature (T)_g) Sufficient time for following storage (shelf life)Then, the glass transition temperature is measured by Differential Scanning Calorimetry (DSC), and the DSC curve shows the post-T glass transition temperature_g) Then, an endothermic peak having an enthalpy value (Δ H) sufficiently large and having an enthalpy value (Δ H) which does not vary with the temperature increase rate in the DSC test is generated, and the infrared spectrum thereof is within 918cm^-1The bands show characteristic peaks whose intensity increases with the storage time. Wherein, the storage time is not limited; however, in general, the sufficient time is 1 hour or more. The enthalpy (Δ H) is also not limited; however, in general, the enthalpy (. DELTA.H) is 1J/g or more.

Further, the polylactic acid amorphous fiber material may further contain any one or a combination of more of a polymer (for example, any one or more of a polyhydroxyalkanoate, polyglycolic acid, polycaprolactone, polybutylene succinate, polybutylene adipate/terephthalate, and other homo-or co-polymer), a plasticizer, a compatibilizer, a transesterification agent, a chain extender, a capping agent, a flame retardant, an antioxidant, a lubricant, an antistatic agent, an antifogging agent, a light stabilizer, an ultraviolet absorber, a color masterbatch, an antifungal agent, an antibacterial agent, a foaming agent, and other additive components, within a range not to hinder the achievement of the process object of the present invention, and is not limited thereto. In summary, any method is within the scope of the present invention as long as it does not hinder the achievement of the process object of the present invention (the process optimization and the formulation control are such that the phenomenon of brittleness of the polylactic acid product caused by physical aging does not occur).

In some more preferred embodiments, the monofilament diameter of the polylactic acid amorphous fiber material is 10 to 150 micrometers.

Another aspect of the embodiments of the present invention provides a polylactic acid fiber material (polylactic acid crystalline fiber material) resistant to physical aging, which is in a fibrous form, and which includes 15wt% to 85wt% of a crystalline phase and 15wt% to 85wt% of an amorphous phase; the amorphous phase comprises 5wt% to 65wt% of metastable phase, and the characteristic peak of the metastable phase in an infrared spectrogram appears at 918cm^-1At least one of (1) and (b); more importantly, the polylactic acid fiber material is stored for enough time below the glass transition temperatureThe rate of change of tensile strength is less than 30% and the rate of change of elongation at break is less than 40%, with a distinct yield and subsequent plastic deformation zone on the stress-strain curve.

In some more preferred embodiments, the polylactic acid crystalline fiber material has a crystallinity of 30wt% to 70wt% and a metastable phase content of 15wt% to 55wt% in the amorphous phase.

In some more preferred embodiments, the physical aging resistant polylactic acid fiber material has a crystalline phase content of 40wt% to 60wt% and a metastable phase content of 25wt% to 45wt% in the amorphous phase.

In some preferred embodiments, the polylactic acid fiber material has an orientation degree of 0.35 to 0.99, preferably 0.6 to 0.8.

Further, the polylactic acid crystal fiber material has a polylactic acid glass transition temperature (T)_g) After storage (shelf life) for a sufficient period of time, as measured by Differential Scanning Calorimetry (DSC), the DSC curve shows the post-glass transition temperature (post-T)_g) Then, an endothermic peak having an enthalpy value (Δ H) sufficiently large and having an enthalpy value (Δ H) which does not vary with the temperature increase rate in the DSC test is generated, and the infrared spectrum thereof is within 918cm^-1The bands show characteristic peaks whose intensity increases with the storage time. Wherein, the storage time is not limited; however, in general, the sufficient time is 1 hour or more. The enthalpy (Δ H) is also not limited; however, in general, the enthalpy (. DELTA.H) is 1J/g or more.

Further, the polylactic acid crystalline fiber material with the physical aging resistance has the glass transition temperature (T) of polylactic acid_g) After storage (shelf life) for a sufficient time, 918cm of an infrared spectrum is obtained by detection by means of a Micro-infrared spectrometer (Micro-FTIR)^-1Characteristic peaks appear in the bands and the intensity of the characteristic peaks rises with prolonged storage time. Wherein, the storage time is not limited; however, in general, the time is 1 hour or more.

Further, the polylactic acid crystalline fiber material is in T_gThe rate of change of tensile strength after a sufficient period of storage (shelf life) is generally as followsLess than 30%; the elongation at break generally has a rate of change of less than 40% and no ductile to brittle transition.

Further, the polylactic acid crystalline fiber material may further contain any one or a combination of more of a polymer (for example, any one or more of a polyhydroxyalkanoate, polyglycolic acid, polycaprolactone, polybutylene succinate, polybutylene adipate/terephthalate, and other homo-or co-polymer), a plasticizer, a compatibilizer, a transesterification agent, a chain extender, a capping agent, a flame retardant, an antioxidant, a lubricant, an antistatic agent, an antifogging agent, a light stabilizer, an ultraviolet absorber, a color master batch, an antifungal agent, an antibacterial agent, a foaming agent, and other additive components, within a range not to hinder the achievement of the process object of the present invention, and is not limited thereto. In summary, any method is within the scope of the present invention as long as it does not hinder the achievement of the process object of the present invention (the process optimization and the formulation control are such that the phenomenon of brittleness of the polylactic acid product caused by physical aging does not occur).

In some more preferred embodiments, the polylactic acid crystalline fiber material has a filament diameter of 5 to 80 μm.

Another aspect of the embodiments of the present invention provides a method for preparing a polylactic acid fiber material (polylactic acid amorphous fiber material) with physical aging resistance, including:

providing a dry polylactic acid or a dry mixture of polylactic acid;

and extruding and spinning the dried polylactic acid or the dry polylactic acid mixture by melt spinning equipment to prepare the polylactic acid fiber material (polylactic acid amorphous fiber material).

In some embodiments, the method of making specifically comprises:

providing a dry polylactic acid or a dry mixture of polylactic acid;

and extruding and spinning the dried polylactic acid or the dry polylactic acid mixture by a melt spinning device, wherein the spinning temperature is 170-270 ℃, the winding speed is 500-8000 m/min, the polylactic acid or the dry polylactic acid mixture is rapidly quenched to room temperature at the quenching speed of 8-2000 ℃/s, and the quenching time is 0.1-29 seconds, so that the polylactic acid fiber material (polylactic acid amorphous fiber material) in a fibrous form is prepared.

In some preferred embodiments, the preparation method specifically comprises:

(1) providing a dry polylactic acid or a dry mixture of polylactic acid;

(2) and extruding and spinning the dried polylactic acid (or polylactic acid blend) by melt spinning equipment, wherein the spinning temperature is 200-250 ℃, the winding speed is 1500-5000 m/min, and the quenching time is 0.1-15 seconds, so as to obtain the polylactic acid amorphous fiber material.

Wherein the dry blend of polylactic acid may comprise one or more of the aforementioned additional ingredients.

In some embodiments, the weight average molecular weight of the polylactic acid in step (1) is 8 to 50 ten thousand, wherein the molar content of the L optical isomer is 85 to 99%.

In a more preferred embodiment, the polylactic acid preferably has a weight average molecular weight of 15 to 30 ten thousand and a molar content of the L optical isomer of 92 to 98%.

In some embodiments, the polylactic acid amorphous fiber material in the step (2) has a filament diameter of 10 to 150 μm.

In some embodiments, the spinning temperature used in step (2) is 200 to 250 ℃, the winding speed is 1500 to 5000 m/min, and the quenching time is 0.1 to 15 seconds; wherein:

when the weight-average molecular weight of the polylactic acid is 8-15 ten thousand, the adopted spinning temperature is 170-230 ℃, the winding speed is 3000-8000 m/min, the quenching rate is 50-2000 ℃/s, and the quenching time is 0.1-3 s;

when the weight-average molecular weight of the polylactic acid is 15-30 ten thousand, the spinning temperature is 200-250 ℃, the winding speed is 2000-5000 m/min, the quenching rate is 12-50 ℃/s, and the quenching time is 3-15 s;

when the weight average molecular weight of the polylactic acid is 30-50 ten thousand, the spinning temperature is 220-270 ℃, the winding speed is 500-3000 m/min, the quenching rate is 8-12 ℃/s, and the quenching time is 15-29 s.

The preparation method (two-step method) of the polylactic acid fiber material (polylactic acid crystalline fiber material) with physical aging resistance provided by the embodiment of the invention can be used for melt extrusion and spinning by melt spinning equipment; secondary drawing, quenching and the like.

In some embodiments, the method of making specifically comprises:

providing a dry polylactic acid or a dry mixture of polylactic acid;

extruding and spinning the dried polylactic acid or the dry polylactic acid mixture by a melt spinning device, wherein the spinning temperature is 170-270 ℃, the winding speed is 500-8000 m/min, the polylactic acid or the dry polylactic acid mixture is rapidly quenched to room temperature at the quenching speed of 8-2000 ℃/s, and the quenching time is 0.1-29 seconds, so that the polylactic acid fiber material (polylactic acid amorphous fiber material) in a fibrous form is prepared;

fully preheating the polylactic acid amorphous fiber material, and then carrying out secondary drafting, wherein the drafting temperature is 65-145 ℃, the drafting multiple is 1-6 times, but relaxation heat setting is not carried out, then rapidly quenching to room temperature at the quenching speed of 2-800 ℃/s, and the quenching time is 0.1-59 seconds, so as to prepare the polylactic acid fiber material (polylactic acid crystalline fiber material) in a fibrous form.

In some preferred embodiments, the preparation method specifically comprises:

(1) providing a dry polylactic acid or a dry mixture of polylactic acid;

(2) extruding and spinning the dried polylactic acid (or polylactic acid blend) through a melt spinning device, wherein the spinning temperature is 170-270 ℃, the winding speed is 500-8000 m/min, the polylactic acid blend is rapidly quenched to room temperature at the quenching speed of 8-2000 ℃/s, and the quenching time is 0.1-29 seconds, so as to prepare the polylactic acid amorphous fiber material;

(3) fully preheating the polylactic acid amorphous fiber material, and then carrying out secondary drafting, wherein the drafting temperature is 65-145 ℃, the drafting multiple is 1-6 times, but relaxation heat setting is not carried out, then rapidly quenching to room temperature at the quenching rate of 2-800 ℃/s, and the quenching time is 0.1-59 seconds, so as to obtain the polylactic acid crystalline fiber material.

In some embodiments, the drawing temperature used in step (3) is 65 to 145 ℃, the drawing multiple is 1 to 6 times, and the quenching time is 0.1 to 59 seconds; the preferable drafting temperature is 85-145 ℃, the drafting multiple is 2-5 times, and the quenching time is 0.1-30 seconds. Wherein:

when the weight average molecular weight of the polylactic acid is 8-15 ten thousand, the adopted drafting temperature is 65-95 ℃, the drafting multiple is 3-6 times, the quenching rate is 15-800 ℃/s, and the quenching time is 0.1-5 s;

when the weight-average molecular weight of the polylactic acid is 15-30 ten thousand, the adopted drafting temperature is 85-115 ℃, the drafting multiple is 2-4 times, the quenching rate is 3-15 ℃/s, and the quenching time is 5-30 seconds;

when the weight average molecular weight of the polylactic acid is 30-50 ten thousand, the adopted drafting temperature is 105-145 ℃, the drafting multiple is 1-3 times, the quenching rate is 2-3 ℃/s, and the quenching time is 30-59 s.

In some embodiments, the polylactic acid crystalline fiber material in step (3) has a diameter of 5 to 80 μm.

The preparation method provided by the previous embodiment of the invention prepares the polylactic acid amorphous fiber material at a proper spinning temperature and winding speed by optimizing the molecular weight and the optical isomer content of the polylactic acid, and further prepares the polylactic acid crystalline fiber material, namely the polylactic acid fiber material resistant to physical aging, by secondary drafting. The polylactic acid fiber material has better physical aging resistance, does not have the phenomenon of physical aging and embrittlement in shelf life, but forms a polylactic acid metastable phase; DSC curve shows T_gThe enthalpy value (delta H) of the nearby endothermic peak does not change along with the change of the temperature rising rate of the DSC test; the tensile strength change rate before and after storage is small, and the product is brokenThe elongation change rate is small, and the orientation degree is high.

In addition, the preparation method (one-step method) of the polylactic acid fiber material (polylactic acid crystalline fiber material) with physical aging resistance provided by another embodiment of the invention can be obtained by melt extrusion, spinning, drawing and other processes of melt spinning equipment.

In some embodiments, the method of making specifically comprises:

providing a dry polylactic acid or a dry mixture of polylactic acid;

and extruding and spinning the dried polylactic acid or the dry polylactic acid mixture by a melt spinning device, drafting by a high-speed hot-roll one-step method at the spinning temperature of 170-270 ℃, the drafting temperature of 65-165 ℃, the drafting multiple of 1-5 times and the winding speed of 500-5000 m/min, but not performing relaxation heat setting, and then rapidly quenching to room temperature at the quenching rate of 2.5-800 ℃/s for 0.1-59 s to prepare the fibrous polylactic acid fiber material.

In some preferred embodiments, the preparation method specifically comprises:

(1) providing a dry polylactic acid or a dry mixture of polylactic acid;

(2) extruding and spinning the dried polylactic acid (or polylactic acid blend) through melt spinning equipment, and drafting by a high-speed hot roll one-step method; the spinning temperature is 170-270 ℃, the drafting temperature is 65-165 ℃, the drafting multiple is 1-5 times, and the winding speed is 500-5000 m/min; but not performing relaxation heat setting, wherein the quenching rate is 2.5-800 ℃/s, and the quenching time is 0.1-59 s, so as to prepare the polylactic acid crystalline fiber material.

In some embodiments, the drawing temperature used in step (2) is 65-165 ℃, the drawing multiple is 1-5 times, and the quenching time is 0.1-59 seconds; the preferable drafting temperature is 85-145 ℃, the drafting multiple is 2-5 times, and the quenching time is 0.1-30 seconds. Wherein:

when the weight-average molecular weight of the polylactic acid is 8-15 ten thousand, the adopted drafting temperature is 65-110 ℃, the drafting multiple is 3-5 times, the quenching rate is 15-800 ℃/s, and the quenching time is 0.1-5 seconds;

when the weight-average molecular weight of the polylactic acid is 15-30 ten thousand, the adopted drafting temperature is 90-135 ℃, the drafting multiple is 2-4 times, the quenching rate is 3-15 ℃/s, and the quenching time is 5-30 seconds;

when the weight average molecular weight of the polylactic acid is 30-50 ten thousand, the adopted drafting temperature is 120-165 ℃, the drafting multiple is 1-3 times, the quenching rate is 2.5-3 ℃/s, and the quenching time is 30-59 seconds.

In some embodiments, the polylactic acid crystalline fiber material in step (2) has a diameter of 5 to 80 μm.

The preparation method provided by the previous embodiment of the invention prepares the polylactic acid crystalline fiber material, namely the polylactic acid fiber with physical aging resistance at proper spinning temperature, drawing temperature and winding speed by optimizing the molecular weight and the optical isomer content of the polylactic acid. The polylactic acid fiber has good physical aging resistance, does not generate physical aging and embrittlement phenomena in shelf life, but forms a polylactic acid metastable phase, and a DSC curve shows T_gThe enthalpy value (delta H) of the nearby endothermic peak does not change along with the change of the temperature rising rate of the DSC test; further, the change rate of tensile strength before and after storage is small, the change rate of elongation at break is also small, and both the crystallinity and the degree of orientation are high.

Another aspect of the embodiments of the present invention provides a use of the polylactic acid fiber material with physical aging resistance in the field of preparing fiber products.

Further, the fiber product includes a thread product, a garment, a home textile, a nonwoven fabric product, and the like, but is not limited thereto.

Further, the fiber product includes, but is not limited to, surgical suture, clothing, home textiles, needle punched non-woven fabrics, spunlaced non-woven fabrics (low temperature air dried) or spun bonded non-woven fabrics (chemical bonding or mechanical reinforcement, including staple fibers), and the like.

For example, another aspect of an embodiment of the present invention also provides a fibrous article made from any of the foregoing polylactic acid fibrous materials that is resistant to physical aging.

Further, another aspect of the embodiments of the present invention provides a method for sterilizing, packaging and storing a polylactic acid fiber material with physical aging resistance, which includes:

providing a polylactic acid fiber material (comprising a polylactic acid amorphous fiber material or a polylactic acid crystalline fiber material) with physical aging resistance in any one of the previous embodiments, and placing the polylactic acid amorphous fiber material or the polylactic acid crystalline fiber material at the glass transition temperature T_gThe packaging and storage is sterilized as follows.

Further, in the foregoing embodiment, after the preparation of the polylactic acid amorphous fiber material or the polylactic acid crystalline fiber material or the corresponding product thereof is completed, the polylactic acid amorphous fiber material or the polylactic acid crystalline fiber material or the corresponding product thereof is sterilized and packaged, and then enters a warehouse logistics stage; the set temperature of the sterilization packaging and the storage logistics stage (shelf life) is lower than T_g。

Further, the polylactic acid amorphous fiber material prepared in the embodiment of the invention has stable molecular chain orientation and is not loosened, so that the physical aging resistance of the polylactic acid amorphous fiber material in the embodiment of the invention is remarkably improved. In addition, the polylactic acid metastable phase formed in the storage logistics stage can obviously reduce the internal stress of the polylactic acid amorphous fiber material in the embodiment of the invention and improve the stability of the product. The polylactic acid surgical suture prepared from the polylactic acid suture has the strength equivalent to or superior to that of the existing polylactic acid surgical suture; meanwhile, by regulating the content of the metastable phase of the polylactic acid, the polylactic acid surgical suture line with adjustable degradation time, adjustable mechanical property, excellent physical aging resistance and anti-inflammation can be prepared.

In addition, the polylactic acid crystalline fiber material prepared in the embodiment of the invention has stable crystallization and orientation without relaxation, and mechanical properties not inferior to those of the existing polylactic acid crystalline fiber, and particularly, the polylactic acid crystalline fiber material prepared in the embodiment of the invention has remarkably improved physical aging resistance due to the rapid quenching process after extrusion spinning and drawing in the preparation process. In addition, the polylactic acid metastable phase formed in the storage logistics stage can obviously reduce the internal stress of the polylactic acid crystalline fiber in the embodiment of the invention and improve the stability of the product. Therefore, the polylactic acid crystalline fiber provided by the embodiment of the invention has excellent physical aging resistance, can keep the stability of size and performance in a warehouse logistics stage, and breaks through the performance bottleneck of the conventional polylactic acid crystalline fiber, thereby meeting the use requirements and expanding the application field.

The technical scheme provided by the embodiment of the invention has the advantages that:

the technical scheme of the invention is as follows: (1) different from the traditional fiber spinning process, for example, after the primary fiber is drafted, the relaxation heat setting is carried out; after the polylactic acid fiber is drafted, the polylactic acid fiber is directly quenched without relaxation and heat setting;

(2) different from the traditional fiber spinning process, for example, the fiber cannot be quenched quickly after melt spinning and drawing; the polylactic acid is rapidly quenched after melt spinning and after drafting to obtain a polylactic acid fiber material;

(3) different from the traditional method for improving the performance of the product by annealing crystallization treatment (the pressure is 1 standard atmosphere, and the temperature is near the cold crystallization temperature); the polylactic acid fiber material is subjected to heat treatment at a temperature higher than room temperature and lower than the glass transition temperature, so that the structure of the product is further stabilized (the content of metastable phase is improved to different degrees);

the technical effect thus obtained is: (1) through the permutation and combination of the above 3 technical schemes, after the polylactic acid fiber material is stored below the glass transition temperature for a sufficient time, the change rate of the yield strength is lower than 30%, the change rate of the elongation at break is lower than 40%, and obvious yield and subsequent plastic deformation zones appear on a stress-strain curve;

(2) the polylactic acid amorphous fiber material consists of an amorphous phase; the amorphous phase comprises 5wt% to 95wt% of metastable phase, and the characteristic peak of the metastable phase in an infrared spectrogram appears at 918cm^-1At least one of (1) and (b); the polylactic acid crystalline fiber material comprises 15wt% -85 wt% of crystalline phase and 15wt% -85 wt% of amorphous phase; the amorphous phase comprises 5wt% to 65wt% of metastable phase, and the characteristic peak of the metastable phase in an infrared spectrogram appears at 918cm^-1To (3).

(3) After the polylactic acid amorphous (or low-crystallinity) fiber material is stored below the glass transition temperature for enough time, a DSC curve shows post-glass transition temperature (post-T)_g) Then, an endothermic peak having an enthalpy value (Δ H) sufficiently large occurs, and the enthalpy value (Δ H) of the endothermic peak does not change with a change in the temperature increase rate of the DSC test;

(4) the polylactic acid amorphous fiber material is prepared by regulating and controlling the heat treatment temperature (T)_gFollowing) and time, a polylactic acid surgical suture line with adjustable metastable phase content, adjustable degradation time, adjustable mechanical property and excellent physical aging resistance can be obtained;

the reason is presumed to be: (1) the inventor obtains the technical scheme and the effect through a large number of experiments, and the existing theory cannot explain, but the inventor conjectures that the possible reason is that the molecular chain in the amorphous region of the polylactic acid is not subjected to relaxation heat setting after being drafted, so that the molecular chain is possibly prevented from being subjected to de-orientation (or the de-orientation degree is lower);

(2) the polylactic acid fiber material is rapidly quenched after melt spinning and drafting, so that molecular chains in a polylactic acid amorphous region are possibly prevented from being subjected to de-orientation (or the de-orientation degree is lower);

(3) the polylactic acid fiber material is processed at a constant temperature above room temperature and below the glass transition temperature, so that the structure of a product is further stable, and the molecular chain in an amorphous region is possibly prevented from being subjected to de-orientation (or the de-orientation degree is lower) in the processing process;

(4) unlike the traditional polylactic acid relaxation heat setting fiber which is easy to generate the phenomenon of physical aging and embrittlement (the molecular chain in the polylactic acid amorphous region is subjected to disorientation), the polylactic acid fiber material only forms a polylactic acid metastable phase in the conventional storage logistics stage; without forming a condensed and tangled structure, resulting in the occurrence of physical aging and embrittlement.

In a word, the technical scheme provided by the embodiment of the invention firstly provides a higher shear flow field and a higher tension flow field through melt extrusion and spinning drafting, induces the stretching and orientation of the polylactic acid molecular chain, and then hinders the relaxation of the polylactic acid molecular chain through rapid quenching, so that the amorphous divided molecular chain orientation structure is maintained, and the physical aging resistance of the polylactic acid fiber material is improved. The polylactic acid fiber is subjected to a storage process to provide proper temperature and time, so that a polylactic acid metastable phase is formed along with the generation of dipole-dipole interaction, the internal stress of the polylactic acid fiber is reduced, and the performance stability of the polylactic acid fiber in the shelf life (storage logistics stage) and the use stage is improved.

In conclusion, the polylactic acid fiber of the embodiment of the invention has stable orientation and no relaxation, has mechanical properties equivalent to those of the polylactic acid fiber known at present, particularly has excellent physical aging resistance, can keep the dimensional stability and the performance stability of the polylactic acid fiber and related products prepared from the polylactic acid fiber in the shelf life (storage logistics stage) and the use stage, breaks through the performance bottleneck of the conventional polylactic acid fiber, fully meets the use requirements, and greatly expands the application field of the polylactic acid fiber.

The technical solution and effects of the present invention will be further described with reference to the following embodiments and accompanying drawings. Wherein, the glass transition temperature and the melting point are measured by a Differential Scanning Calorimetry (DSC) method; the glass transition temperature is determined by an angle bisection method, and the melting point is the peak temperature; the crystallinity is measured by X-ray diffraction (XRD) method. The method does not adopt a DSC method to calculate the crystallinity, and the measured crystallinity is higher than a true value because the secondary crystallization is caused by heating a sample in the DSC test process as well known. In the following examples of the invention, the formation of the metastable phase of polylactic acid was identified by microscopic infrared (Micro-FTIR); the tensile properties of the polylactic acid fibers were measured by a universal material tensile tester.

Example 1:

taking polylactic acid with the weight-average molecular weight of 15 ten thousand and the molar content of the L optical isomer of 95 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 50 ppm; spinning the dried polylactic acid granules by melt spinning equipment to form a polylactic acid amorphous fiber material, wherein the melting temperature is 230 ℃, the winding speed is 3000 m/min, the quenching is rapidly carried out to room temperature at the quenching speed of 70 ℃/s, and the quenching time is 3 s; fully preheating the polylactic acid amorphous fiber material, and then carrying out secondary drafting, wherein the drafting temperature is 90 ℃, and the drafting multiple is 3 times; but not relaxation heat set; then rapidly quenching to room temperature at a quenching rate of 25 ℃/s for 3 seconds to prepare a fibrous polylactic acid crystalline fiber material; the monofilament diameter of the polylactic acid amorphous fiber material is 50 microns; the monofilament diameter of the polylactic acid crystalline fiber material is 25 micrometers; subsequently subjecting the polylactic acid fiber material to a temperature T of glass transition thereof_gSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid amorphous fiber before storage is 0 percent, and the orientation degree is 0.55; the crystallinity of the polylactic acid amorphous fiber is basically unchanged after being stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid amorphous fiber is 921cm before storage^-1No crystallization characteristic peak appears; the polylactic acid amorphous fiber is 918cm after being stored for half a year at the temperature of 30 +/-5 DEG C^-1Characteristic peaks appear, which indicate the formation of metastable phase of polylactic acid, and the content of metastable phase is 40%. The glass transition temperature of the polylactic acid amorphous fiber before storage is 56 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid amorphous fiber stored for half a year at 30 +/-5 ℃ has obvious endothermic peak near the glass transition temperature. In addition, the enthalpy value of the endothermic peak of the polylactic acid amorphous fiber after being stored for half a year at 30 +/-5 ℃ is independent of the DSC temperature rising rate, which shows that the endothermic peak is the structural transformation of the polylactic acid metastable phase and is not the enthalpy relaxation phenomenon which is specific to physical aging. In addition, polylactic acid amorphous fiber before storageThe tensile strength of the fiber is 1.48cN/dtex, and the elongation at break is 104%; the polylactic acid amorphous fiber after being stored for half a year at 30 +/-5 ℃ has the tensile strength of 1.51cN/dtex and the elongation at break of 102 percent, which is shown in figure 1; the polylactic acid amorphous fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase. In addition, the polylactic acid crystalline fiber before storage had a crystallinity of 40% and an orientation degree of 0.95; the crystallinity of the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ is basically unchanged. The polylactic acid crystal fiber is 921cm before storage^-1The appearance of a crystallization characteristic peak; the polylactic acid crystalline fiber stored at 30 +/-5 ℃ for half a year is 918cm^-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 40%. The glass transition temperature of the polylactic acid crystalline fiber before storage is 57 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid crystal fiber stored at 30 +/-5 ℃ for half a year has no obvious endothermic peak near the glass transition temperature. In addition, the polylactic acid crystalline fiber before storage has a tensile strength of 3.48cN/dtex and an elongation at break of 33%; the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ has the tensile strength of 3.62cN/dtex and the elongation at break of 36 percent; the polylactic acid crystalline fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.

Example 2:

taking polylactic acid with the weight-average molecular weight of 30 ten thousand and the molar content of the L optical isomer of 95 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 45 ppm; spinning the dried polylactic acid granules by melt spinning equipment to form a polylactic acid amorphous fiber material, wherein the melting temperature is 250 ℃, the winding speed is 2000 m/min, the quenching speed is 15 ℃/s, and the quenching time is 15 s; fully preheating the polylactic acid amorphous fiber material, and then carrying out secondary drafting, wherein the drafting temperature is 115 ℃, and the drafting multiple is 2 times; but not relaxation heat set; then rapidly quenching to room temperature at a quenching rate of 3 ℃/s for 30 s to prepare the productObtaining a polylactic acid crystalline fiber material in a fibrous shape; the monofilament diameter of the polylactic acid amorphous fiber material is 80 microns; the monofilament diameter of the polylactic acid crystalline fiber material is 40 microns; subsequently subjecting the polylactic acid fiber material to a temperature T of glass transition thereof_gSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid amorphous fiber before storage is 0 percent, and the orientation degree is 0.56; the crystallinity of the polylactic acid amorphous fiber is basically unchanged after being stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid amorphous fiber is 921cm before storage^-1No crystallization characteristic peak appears; the polylactic acid amorphous fiber is 918cm after being stored for half a year at the temperature of 30 +/-5 DEG C^-1A characteristic peak appears, which indicates the formation of the metastable phase of the polylactic acid, and the content of the metastable phase is 35 percent. The glass transition temperature of the polylactic acid amorphous fiber before storage is 58 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid amorphous fiber stored for half a year at 30 +/-5 ℃ has obvious endothermic peak near the glass transition temperature. In addition, the enthalpy value of the endothermic peak of the polylactic acid amorphous fiber after being stored for half a year at 30 +/-5 ℃ is independent of the DSC temperature rising rate, which shows that the endothermic peak is the structural transformation of the polylactic acid metastable phase and is not the enthalpy relaxation phenomenon which is specific to physical aging. In addition, the tensile strength of the polylactic acid amorphous fiber before storage is 1.62cN/dtex, and the elongation at break is 107%; the polylactic acid amorphous fiber stored for half a year at the temperature of 30 +/-5 ℃ has the tensile strength of 1.73cN/dtex and the elongation at break of 105 percent; the polylactic acid amorphous fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase. In addition, the polylactic acid crystalline fiber before storage had a crystallinity of 45% and an orientation degree of 0.95; the crystallinity of the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ is basically unchanged. The polylactic acid crystal fiber is 921cm before storage^-1The appearance of a crystallization characteristic peak; the polylactic acid crystalline fiber stored at 30 +/-5 ℃ for half a year is 918cm^-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 35%. The glass transition temperature of the polylactic acid crystalline fiber before storage is 62 ℃, and almost no endothermic peak appears near the glass transition temperature;the polylactic acid crystal fiber stored at 30 +/-5 ℃ for half a year has no obvious endothermic peak near the glass transition temperature. In addition, the polylactic acid crystalline fiber before storage has a tensile strength of 3.76cN/dtex and an elongation at break of 28%; the polylactic acid crystalline fiber stored at 30 +/-5 ℃ for half a year has the tensile strength of 3.72cN/dtex and the elongation at break of 31%; the polylactic acid crystalline fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.

Example 3:

taking polylactic acid with the weight-average molecular weight of 8 ten thousand and the molar content of the L optical isomer of 95 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 43 ppm; spinning the dried polylactic acid granules by melt spinning equipment to form a polylactic acid amorphous fiber material, wherein the melting temperature is 190 ℃, the winding speed is 8000 m/min, the quenching speed is 1600 ℃/s, the quenching speed is rapidly quenched to the room temperature, and the quenching time is 0.1 s; fully preheating the polylactic acid amorphous fiber material, and then carrying out secondary drafting, wherein the drafting temperature is 65 ℃, and the drafting multiple is 3 times; but not relaxation heat set; then rapidly quenching to room temperature at a quenching rate of 500 ℃/s for 0.1 s to prepare a fibrous polylactic acid crystalline fiber material; the monofilament diameter of the polylactic acid amorphous fiber material is 10 microns; the monofilament diameter of the polylactic acid crystalline fiber material is 5 microns; subsequently subjecting the polylactic acid fiber material to a temperature T of glass transition thereof_gSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid amorphous fiber before storage is 0 percent, and the orientation degree is 0.8; the crystallinity of the polylactic acid amorphous fiber is basically unchanged after being stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid amorphous fiber is 921cm before storage^-1No crystallization characteristic peak appears; the polylactic acid amorphous fiber is 918cm after being stored for half a year at the temperature of 30 +/-5 DEG C^-1Characteristic peaks appear, which indicate the formation of metastable phase of polylactic acid, and the content of metastable phase is 78%. The glass transition temperature of the polylactic acid amorphous fiber before storage is 55 ℃, and almost no endothermic peak appears near the glass transition temperature; polylactic acid amorphous fiber glass stored for half a year at 30 +/-5 DEG CA distinct endothermic peak appears near the transition temperature. In addition, the enthalpy value of the endothermic peak of the polylactic acid amorphous fiber after being stored for half a year at 30 +/-5 ℃ is independent of the DSC temperature rising rate, which shows that the endothermic peak is the structural transformation of the polylactic acid metastable phase and is not the enthalpy relaxation phenomenon which is specific to physical aging. In addition, the tensile strength of the polylactic acid amorphous fiber before storage is 1.21cN/dtex, and the elongation at break is 67%; the polylactic acid amorphous fiber stored for half a year at the temperature of 30 +/-5 ℃ has the tensile strength of 1.25cN/dtex and the elongation at break of 65 percent; the polylactic acid amorphous fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase. In addition, the polylactic acid crystalline fiber before storage had a crystallinity of 60% and an orientation degree of 0.96; the crystallinity of the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ is basically unchanged. The polylactic acid crystal fiber is 921cm before storage^-1The appearance of a crystallization characteristic peak; the polylactic acid crystalline fiber stored at 30 +/-5 ℃ for half a year is 918cm^-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 15%. The glass transition temperature of the polylactic acid crystalline fiber before storage is 56 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid crystal fiber stored at 30 +/-5 ℃ for half a year has no obvious endothermic peak near the glass transition temperature. In addition, the polylactic acid crystalline fiber before storage has a tensile strength of 2.68cN/dtex and an elongation at break of 27%; the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ has the tensile strength of 2.76cN/dtex and the elongation at break of 29 percent; the polylactic acid crystalline fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.

Example 4:

taking polylactic acid with the weight-average molecular weight of 8 ten thousand and the molar content of L optical isomer of 99 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 52 ppm; spinning the dried polylactic acid granules by melt spinning equipment to form the polylactic acid amorphous fiber material, wherein the melting temperature is 195 ℃, and the winding speed is highThe temperature is 6000 m/min, the steel plate is rapidly quenched to room temperature at the quenching rate of 1700 ℃/s, and the quenching time is 0.1 s; fully preheating the polylactic acid amorphous fiber material, and then carrying out secondary drafting, wherein the drafting temperature is 95 ℃, and the drafting multiple is 6 times; but not relaxation heat set; then rapidly quenching to room temperature at a quenching rate of 800 ℃/s for 0.1 s to prepare a fibrous polylactic acid crystalline fiber material; the monofilament diameter of the polylactic acid amorphous fiber material is 50 microns; the monofilament diameter of the polylactic acid crystalline fiber material is 15 microns; subsequently subjecting the polylactic acid fiber material to a temperature T of glass transition thereof_gSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid amorphous fiber before storage is 0 percent, and the orientation degree is 0.8; the crystallinity of the polylactic acid amorphous fiber is basically unchanged after being stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid amorphous fiber is 921cm before storage^-1No crystallization characteristic peak appears; the polylactic acid amorphous fiber is 918cm after being stored for half a year at the temperature of 30 +/-5 DEG C^-1Characteristic peaks appear, which indicate the formation of a metastable phase of polylactic acid, and the content of the metastable phase is 95 percent. The glass transition temperature of the polylactic acid amorphous fiber before storage is 57 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid amorphous fiber stored for half a year at 30 +/-5 ℃ has obvious endothermic peak near the glass transition temperature. In addition, the enthalpy value of the endothermic peak of the polylactic acid amorphous fiber after being stored for half a year at 30 +/-5 ℃ is independent of the DSC temperature rising rate, which shows that the endothermic peak is the structural transformation of the polylactic acid metastable phase and is not the enthalpy relaxation phenomenon which is specific to physical aging. In addition, the tensile strength of the polylactic acid amorphous fiber before storage is 1.12cN/dtex, and the elongation at break is 85%; the polylactic acid amorphous fiber stored for half a year at the temperature of 30 +/-5 ℃ has the tensile strength of 1.08cN/dtex and the elongation at break of 87%; the polylactic acid amorphous fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase. In addition, the crystallinity of the polylactic acid crystalline fiber before storage was 85%, and the degree of orientation was 0.99; the crystallinity of the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ is basically unchanged. Polylactic acid crystalline fibers prior to storage921cm^-1The appearance of a crystallization characteristic peak; the polylactic acid crystalline fiber stored at 30 +/-5 ℃ for half a year is 918cm^-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 5%. The glass transition temperature of the polylactic acid crystalline fiber before storage is 58 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid crystal fiber stored at 30 +/-5 ℃ for half a year has no obvious endothermic peak near the glass transition temperature. In addition, the polylactic acid crystalline fiber before storage has a tensile strength of 2.96cN/dtex and an elongation at break of 18%; the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ has the tensile strength of 2.93cN/dtex and the elongation at break of 22 percent; the polylactic acid crystalline fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.

Example 5:

taking polylactic acid with the weight-average molecular weight of 8 ten thousand and the molar content of the L optical isomer of 85 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 43 ppm; spinning the dried polylactic acid granules by melt spinning equipment to form a polylactic acid amorphous fiber material, wherein the melting temperature is 170 ℃, the winding speed is 3000 m/min, quenching is rapidly carried out to room temperature at the quenching speed of 1500 ℃/s, and the quenching time is 0.1 s; fully preheating the polylactic acid amorphous fiber material, and then carrying out secondary drafting, wherein the drafting temperature is 85 ℃, and the drafting multiple is 6 times; but not relaxation heat set; then rapidly quenching to room temperature at a quenching rate of 600 ℃/s for 0.1 s to still prepare the polylactic acid amorphous (drawn) fiber material in a fibrous form; the monofilament diameter of the polylactic acid amorphous fiber material is 62 micrometers; the monofilament diameter of the polylactic acid amorphous (drawn) fiber material is 18 microns; subsequently subjecting the polylactic acid fiber material to a temperature T of glass transition thereof_gSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid amorphous fiber before storage is 0 percent, and the orientation degree is 0.58; the crystallinity of the polylactic acid amorphous fiber is basically unchanged after being stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid amorphous fiber is 921cm before storage^-1No occurrence of crystalline characterA peak; the polylactic acid amorphous fiber is 918cm after being stored for half a year at the temperature of 30 +/-5 DEG C^-1Characteristic peaks appear, which indicate the formation of metastable phase of polylactic acid, and the content of metastable phase is 5%. The glass transition temperature of the polylactic acid amorphous fiber before storage is 53 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid amorphous fiber stored for half a year at 30 +/-5 ℃ has obvious endothermic peak near the glass transition temperature. In addition, the enthalpy value of the endothermic peak of the polylactic acid amorphous fiber after being stored for half a year at 30 +/-5 ℃ is independent of the DSC temperature rising rate, which shows that the endothermic peak is the structural transformation of the polylactic acid metastable phase and is not the enthalpy relaxation phenomenon which is specific to physical aging. In addition, the tensile strength of the polylactic acid amorphous fiber before storage is 0.82cN/dtex, and the elongation at break is 216%; the polylactic acid amorphous fiber stored for half a year at the temperature of 30 +/-5 ℃ has the tensile strength of 0.87cN/dtex and the elongation at break of 207 percent; the polylactic acid amorphous fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase. In addition, the polylactic acid amorphous (drawn) fiber before storage had a crystallinity of 0% and an orientation of 0.63; the crystallinity of the polylactic acid amorphous (drawn) fiber after being stored at 30 +/-5 ℃ for half a year is basically unchanged. Polylactic acid amorphous (drawn) fiber 921cm before storage^-1No crystallization characteristic peak appears; the polylactic acid amorphous (drawn) fiber after being stored for half a year at 30 +/-5 ℃ is 918cm^-1A characteristic peak appears, which indicates the formation of the metastable phase of the polylactic acid, and the content of the metastable phase is 8 percent. The glass transition temperature of the polylactic acid amorphous (drawn) fiber before storage is 54 ℃, and an endothermic peak hardly appears near the glass transition temperature; the polylactic acid amorphous (drawn) fiber stored at 30 +/-5 ℃ for half a year has no obvious endothermic peak near the glass transition temperature. In addition, the polylactic acid amorphous (drawn) fiber before storage had a tensile strength of 0.93cN/dtex and an elongation at break of 195%; the polylactic acid amorphous (drawn) fiber after being stored for half a year at 30 +/-5 ℃ has the tensile strength of 0.96cN/dtex and the elongation at break of 203 percent; the polylactic acid amorphous (drawn) fiber prepared in the embodiment has obvious physical aging resistance, and does not become brittle due to physical agingPhenomenon, but the formation of polylactic acid metastable phase.

Example 6:

taking polylactic acid with the weight-average molecular weight of 50 ten thousand and the molar content of L optical isomer of 93 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 43 ppm; spinning the dried polylactic acid granules by melt spinning equipment to form a polylactic acid amorphous fiber material, wherein the melting temperature is 255 ℃, the winding speed is 1000 m/min, the quenching is rapidly carried out to room temperature at the quenching speed of 8 ℃/s, and the quenching time is 29 s; fully preheating the polylactic acid amorphous fiber material, and then carrying out secondary drafting, wherein the drafting temperature is 145 ℃, and the drafting multiple is 3 times; but not relaxation heat set; then rapidly quenching to room temperature at a quenching rate of 2 ℃/s for 59 seconds to prepare the polylactic acid crystalline fiber material in a fibrous form; the monofilament diameter of the polylactic acid amorphous fiber material is 150 microns; the monofilament diameter of the polylactic acid crystalline fiber material is 62 microns; subsequently subjecting the polylactic acid fiber material to a temperature T of glass transition thereof_gSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid amorphous fiber before storage is 0 percent, and the orientation degree is 0.3; the crystallinity of the polylactic acid amorphous fiber is basically unchanged after being stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid amorphous fiber is 921cm before storage^-1No crystallization characteristic peak appears; the polylactic acid amorphous fiber is 918cm after being stored for half a year at the temperature of 30 +/-5 DEG C^-1Characteristic peaks appear, which indicate the formation of metastable phase of polylactic acid, and the content of metastable phase is 15%. The glass transition temperature of the polylactic acid amorphous fiber before storage is 65 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid amorphous fiber stored for half a year at 30 +/-5 ℃ has obvious endothermic peak near the glass transition temperature. In addition, the enthalpy value of the endothermic peak of the polylactic acid amorphous fiber after being stored for half a year at 30 +/-5 ℃ is independent of the DSC temperature rising rate, which shows that the endothermic peak is the structural transformation of the polylactic acid metastable phase and is not the enthalpy relaxation phenomenon which is specific to physical aging. In addition, the tensile strength of the polylactic acid amorphous fiber before storage is 1.75cN/dtex, and the elongation at break is 68%; polylactic acid amorphous fiber stored at 30 +/-5 ℃ for half a yearThe tensile strength of (A) is 1.80cN/dtex, the elongation at break is 65%; the polylactic acid amorphous fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase. In addition, the polylactic acid crystalline fiber before storage had a crystallinity of 35% and an orientation degree of 0.45; the crystallinity of the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ is basically unchanged. The polylactic acid crystal fiber is 921cm before storage^-1The appearance of a crystallization characteristic peak; the polylactic acid crystalline fiber stored at 30 +/-5 ℃ for half a year is 918cm^-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 15%. The glass transition temperature of the polylactic acid crystalline fiber before storage is 67 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid crystal fiber stored at 30 +/-5 ℃ for half a year has no obvious endothermic peak near the glass transition temperature. In addition, the polylactic acid crystalline fiber before storage has a tensile strength of 4.75cN/dtex and an elongation at break of 32%; the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ has the tensile strength of 4.63cN/dtex and the elongation at break of 33 percent; the polylactic acid crystalline fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.

Example 7:

taking polylactic acid with the weight-average molecular weight of 50 ten thousand and the molar content of L optical isomer of 99 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 33 ppm; spinning the dried polylactic acid granules by melt spinning equipment to form a polylactic acid amorphous fiber material, wherein the melting temperature is 270 ℃, the winding speed is 500 m/min, the quenching is rapidly carried out to the room temperature at the quenching speed of 8 ℃/s, and the quenching time is 29 s; fully preheating the polylactic acid amorphous fiber material, and then carrying out secondary drafting, wherein the drafting temperature is 105 ℃, and the drafting multiple is 1 time; but not relaxation heat set; then rapidly quenching to room temperature at a quenching rate of 2 ℃/s for 40 s to prepare a fibrous polylactic acid crystalline fiber material; the monofilament diameter of the polylactic acid amorphous fiber material is 123 micrometers; polylactic acid knotThe monofilament diameter of the crystalline fiber material is 80 microns; subsequently subjecting the polylactic acid fiber material to a temperature T of glass transition thereof_gSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid amorphous fiber before storage is 0 percent, and the orientation degree is 0.2; the crystallinity of the polylactic acid amorphous fiber is basically unchanged after being stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid amorphous fiber is 921cm before storage^-1No crystallization characteristic peak appears; the polylactic acid amorphous fiber is 918cm after being stored for half a year at the temperature of 30 +/-5 DEG C^-1Characteristic peaks appear, which indicate the formation of metastable phase of polylactic acid, and the content of metastable phase is 5%. The glass transition temperature of the polylactic acid amorphous fiber before storage is 62 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid amorphous fiber stored for half a year at 30 +/-5 ℃ has obvious endothermic peak near the glass transition temperature. In addition, the enthalpy value of the endothermic peak of the polylactic acid amorphous fiber after being stored for half a year at 30 +/-5 ℃ is independent of the DSC temperature rising rate, which shows that the endothermic peak is the structural transformation of the polylactic acid metastable phase and is not the enthalpy relaxation phenomenon which is specific to physical aging. In addition, the tensile strength of the polylactic acid amorphous fiber before storage is 1.65cN/dtex, and the elongation at break is 108%; the polylactic acid amorphous fiber stored for half a year at the temperature of 30 +/-5 ℃ has the tensile strength of 1.56cN/dtex and the elongation at break of 105 percent; the polylactic acid amorphous fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase. In addition, the polylactic acid crystalline fiber before storage had a crystallinity of 15% and an orientation degree of 0.35; the crystallinity of the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ is basically unchanged. The polylactic acid crystal fiber is 921cm before storage^-1The appearance of a crystallization characteristic peak; the polylactic acid crystalline fiber stored at 30 +/-5 ℃ for half a year is 918cm^-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 5%. The glass transition temperature of the polylactic acid crystalline fiber before storage is 64 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid crystal fiber stored for half a year at 30 +/-5 ℃ has obvious endothermic peak near the glass transition temperature. In addition, before storage, polyThe tensile strength of the lactic acid crystalline fiber is 3.65cN/dtex, and the elongation at break is 43%; the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ has the tensile strength of 3.72cN/dtex and the elongation at break of 47 percent; the polylactic acid crystalline fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.

Example 8:

taking polylactic acid with the weight-average molecular weight of 50 ten thousand and the molar content of the L optical isomer of 85 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 43 ppm; spinning the dried polylactic acid granules by melt spinning equipment to form a polylactic acid amorphous fiber material, wherein the melting temperature is 250 ℃, the winding speed is 2000 m/min, the quenching is rapidly carried out to the room temperature at the quenching speed of 8 ℃/s, and the quenching time is 29 seconds; fully preheating the polylactic acid amorphous fiber material, and then carrying out secondary drafting, wherein the drafting temperature is 125 ℃, and the drafting multiple is 2 times; but not relaxation heat set; then rapidly quenching to room temperature at a quenching rate of 3 ℃/s for 30 s to still prepare the polylactic acid amorphous (drawn) fiber material in a fibrous form; the monofilament diameter of the polylactic acid amorphous fiber material is 140 micrometers; the monofilament diameter of the polylactic acid crystalline fiber material is 68 microns; subsequently subjecting the polylactic acid fiber material to a temperature T of glass transition thereof_gSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid amorphous fiber before storage is 0 percent, and the orientation degree is 0.4; the crystallinity of the polylactic acid amorphous fiber is basically unchanged after being stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid amorphous fiber is 921cm before storage^-1No crystallization characteristic peak appears; the polylactic acid amorphous fiber is 918cm after being stored for half a year at the temperature of 30 +/-5 DEG C^-1Characteristic peaks appear, which indicate the formation of metastable phase of polylactic acid, and the content of metastable phase is 5%. The glass transition temperature of the polylactic acid amorphous fiber before storage is 58 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid amorphous fiber stored for half a year at 30 +/-5 ℃ has obvious endothermic peak near the glass transition temperature. In addition, the glass transition of the polylactic acid amorphous fiber is performed after the polylactic acid amorphous fiber is stored for half a year at the temperature of 30 +/-5 DEG CThe enthalpy value of the endothermic peak near the variable temperature does not depend on the DSC temperature rise rate, which shows that the endothermic peak is the structural transformation of the polylactic acid metastable phase and is not the enthalpy relaxation phenomenon which is specific to physical aging. In addition, the tensile strength of the polylactic acid amorphous fiber before storage is 2.05cN/dtex, and the elongation at break is 82%; the polylactic acid amorphous fiber stored for half a year at the temperature of 30 +/-5 ℃ has the tensile strength of 1.98cN/dtex and the elongation at break of 75 percent; the polylactic acid amorphous fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase. In addition, the polylactic acid amorphous (drawn) fiber before storage had a crystallinity of 0% and an orientation of 0.45; the crystallinity of the polylactic acid amorphous (drawn) fiber after being stored at 30 +/-5 ℃ for half a year is basically unchanged. Polylactic acid amorphous (drawn) fiber 921cm before storage^-1No crystallization characteristic peak appears; the polylactic acid amorphous (drawn) fiber after being stored for half a year at 30 +/-5 ℃ is 918cm^-1Characteristic peaks appear, which indicate the formation of the metastable phase of the polylactic acid, and the content of the metastable phase is 7 percent. The glass transition temperature of the polylactic acid amorphous (drawn) fiber before storage is 60 ℃, and an endothermic peak hardly appears near the glass transition temperature; the polylactic acid amorphous (drawn) fiber after being stored for half a year at 30 +/-5 ℃ has obvious endothermic peak near the glass transition temperature. In addition, the enthalpy value of the endothermic peak of the polylactic acid amorphous (drawn) fiber stored at 30 +/-5 ℃ for half a year does not depend on the DSC temperature rise rate, and the endothermic peak is the structural transition of the polylactic acid metastable phase and is not the enthalpy relaxation phenomenon which is specific to physical aging. In addition, the polylactic acid amorphous (drawn) fiber before storage has a tensile strength of 2.15cN/dtex and an elongation at break of 71%; the polylactic acid amorphous (drawn) fiber after being stored for half a year at 30 +/-5 ℃ has the tensile strength of 2.20cN/dtex and the elongation at break of 68 percent; the polylactic acid amorphous (drawn) fiber prepared in the embodiment has obvious physical aging resistance, does not have the phenomenon of embrittlement caused by physical aging, and forms a polylactic acid metastable phase.

Example 9:

taking polylactic acid with weight-average molecular weight of 15 ten thousand and L optical isomer molar content of 93 percent for hot air dryingThe drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 50 ppm; spinning the dried polylactic acid granules by melt spinning equipment to form a polylactic acid amorphous fiber material, wherein the melting temperature is 215 ℃, the winding speed is 3000 m/min, the quenching is rapidly carried out to the room temperature at the quenching speed of 40 ℃/s, and the quenching time is 5 s; fully preheating the polylactic acid amorphous fiber material, and then carrying out secondary drafting, wherein the drafting temperature is 95 ℃, and the drafting multiple is 4 times; but not relaxation heat set; then rapidly quenching to room temperature at a quenching rate of 15 ℃/s for 5 s to prepare a fibrous polylactic acid crystalline fiber material; the monofilament diameter of the polylactic acid amorphous fiber material is 60 micrometers; the monofilament diameter of the polylactic acid crystalline fiber material is 18 microns; subsequently subjecting the polylactic acid fiber material to a temperature T of glass transition thereof_gSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid amorphous fiber before storage is 0 percent, and the orientation degree is 0.45; the crystallinity of the polylactic acid amorphous fiber is basically unchanged after being stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid amorphous fiber is 921cm before storage^-1No crystallization characteristic peak appears; the polylactic acid amorphous fiber is 918cm after being stored for half a year at the temperature of 30 +/-5 DEG C^-1Characteristic peaks appear, which indicate the formation of metastable phase of polylactic acid, and the content of metastable phase is 40%. The glass transition temperature of the polylactic acid amorphous fiber before storage is 54 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid amorphous fiber stored for half a year at 30 +/-5 ℃ has obvious endothermic peak near the glass transition temperature. In addition, the enthalpy value of the endothermic peak of the polylactic acid amorphous fiber after being stored for half a year at 30 +/-5 ℃ is independent of the DSC temperature rising rate, which shows that the endothermic peak is the structural transformation of the polylactic acid metastable phase and is not the enthalpy relaxation phenomenon which is specific to physical aging. In addition, the tensile strength of the polylactic acid amorphous fiber before storage is 1.35cN/dtex, and the elongation at break is 136%; the polylactic acid amorphous fiber stored for half a year at the temperature of 30 +/-5 ℃ has the tensile strength of 1.40cN/dtex and the elongation at break of 138 percent; the polylactic acid amorphous fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.In addition, the polylactic acid crystalline fiber before storage had a crystallinity of 15% and an orientation degree of 0.57; the crystallinity of the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ is basically unchanged. The polylactic acid crystal fiber is 921cm before storage^-1The appearance of a crystallization characteristic peak; the polylactic acid crystalline fiber stored at 30 +/-5 ℃ for half a year is 918cm^-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 65%. The glass transition temperature of the polylactic acid crystalline fiber before storage is 56 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid crystal fiber stored for half a year at 30 +/-5 ℃ has obvious endothermic peak near the glass transition temperature. In addition, the enthalpy value of the endothermic peak of the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ near the glass transition temperature does not depend on the DSC temperature rising rate, which shows that the endothermic peak is the structural transition of the metastable phase of the polylactic acid and is not the enthalpy relaxation phenomenon which is specific to physical aging. In addition, the polylactic acid crystalline fiber before storage has a tensile strength of 3.18cN/dtex and an elongation at break of 78%; the polylactic acid crystalline fiber stored at 30 +/-5 ℃ for half a year has the tensile strength of 3.25cN/dtex and the elongation at break of 76%; the polylactic acid crystalline fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.

Example 10:

taking polylactic acid with weight average molecular weight of 30 ten thousand and L optical isomer molar content of 99 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 44 ppm; spinning the dried polylactic acid granules by melt spinning equipment to form a polylactic acid amorphous fiber material, wherein the melting temperature is 240 ℃, the winding speed is 2000 m/min, the quenching is rapidly carried out to the room temperature at the quenching speed of 70 ℃/s, and the quenching time is 29 s; fully preheating the polylactic acid amorphous fiber material, and then carrying out secondary drafting, wherein the drafting temperature is 115 ℃, and the drafting multiple is 3 times; but not relaxation heat set; then rapidly quenching to room temperature at a quenching rate of 3 ℃/s for 30 s to prepare the polylactic acid crystalline fiber material in a fibrous form; the monofilament diameter of the polylactic acid amorphous fiber materialIs 48 microns; the monofilament diameter of the polylactic acid crystalline fiber material is 18 microns; subsequently subjecting the polylactic acid fiber material to a temperature T of glass transition thereof_gSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid amorphous fiber before storage is 0 percent, and the orientation degree is 0.42; the crystallinity of the polylactic acid amorphous fiber is basically unchanged after being stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid amorphous fiber is 921cm before storage^-1No crystallization characteristic peak appears; the polylactic acid amorphous fiber is 918cm after being stored for half a year at the temperature of 30 +/-5 DEG C^-1Characteristic peaks appear, which indicate the formation of metastable phase of polylactic acid, and the content of metastable phase is 30%. The glass transition temperature of the polylactic acid amorphous fiber before storage is 62 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid amorphous fiber stored for half a year at 30 +/-5 ℃ has obvious endothermic peak near the glass transition temperature. In addition, the enthalpy value of the endothermic peak of the polylactic acid amorphous fiber after being stored for half a year at 30 +/-5 ℃ is independent of the DSC temperature rising rate, which shows that the endothermic peak is the structural transformation of the polylactic acid metastable phase and is not the enthalpy relaxation phenomenon which is specific to physical aging. In addition, the tensile strength of the polylactic acid amorphous fiber before storage is 1.68cN/dtex, and the elongation at break is 103%; the tensile strength of the polylactic acid amorphous fiber after being stored for half a year at 30 +/-5 ℃ is 1.72cN/dtex, and the elongation at break is 98%; the polylactic acid amorphous fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase. In addition, the polylactic acid crystalline fiber before storage had a crystallinity of 60% and an orientation degree of 0.92; the crystallinity of the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ is basically unchanged. The polylactic acid crystal fiber is 921cm before storage^-1The appearance of a crystallization characteristic peak; the polylactic acid crystalline fiber stored at 30 +/-5 ℃ for half a year is 918cm^-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 30%. The glass transition temperature of the polylactic acid crystalline fiber before storage is 64 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid crystal fiber stored at 30 +/-5 ℃ for half a year does not show obvious phenomenon near the glass transition temperatureEndothermic peak. In addition, the polylactic acid crystalline fiber before storage has a tensile strength of 3.85cN/dtex and an elongation at break of 28%; the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ has the tensile strength of 3.90cN/dtex and the elongation at break of 27%; the polylactic acid crystalline fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.

Example 11:

taking polylactic acid with the weight-average molecular weight of 15 ten thousand and the molar content of the L optical isomer of 95 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 50 ppm; extruding and spinning the dried polylactic acid granules by melt spinning equipment, and drafting by a high-speed hot-roll one-step method to form a polylactic acid crystalline fiber material, wherein the melting temperature is 230 ℃, and the winding speed is 3000 m/min; the drafting temperature is 90 ℃, and the drafting multiple is 3 times; but not relaxation heat set; then rapidly quenching to room temperature at a quenching rate of 25 ℃/s for 3 seconds to prepare a fibrous polylactic acid crystalline fiber material; the monofilament diameter of the polylactic acid crystalline fiber material is 25 micrometers; subsequently subjecting the polylactic acid fiber material to a temperature T of glass transition thereof_gSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid crystalline fiber before storage is 38 percent, and the orientation degree is 0.94; the crystallinity of the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ is basically unchanged. The polylactic acid crystal fiber is 921cm before storage^-1The appearance of a crystallization characteristic peak; the polylactic acid crystalline fiber stored at 30 +/-5 ℃ for half a year is 918cm^-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 38%. The glass transition temperature of the polylactic acid crystalline fiber before storage is 57 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid crystal fiber stored at 30 +/-5 ℃ for half a year has no obvious endothermic peak near the glass transition temperature. In addition, the polylactic acid crystalline fiber before storage has a tensile strength of 3.53cN/dtex and an elongation at break of 34%; the polylactic acid crystalline fiber stored at 30 + -5 ℃ for half a year had a tensile strength of 3.59cN/dtex and an elongation at break of35 percent; the polylactic acid crystalline fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.

Example 12:

taking polylactic acid with the weight-average molecular weight of 30 ten thousand and the molar content of the L optical isomer of 95 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 45 ppm; extruding and spinning the dried polylactic acid granules by melt spinning equipment, and drafting by a high-speed hot-roll one-step method to form a polylactic acid crystalline fiber material, wherein the melting temperature is 251 ℃ and the winding speed is 2000 m/min; the drafting temperature is 115 ℃, and the drafting multiple is 2 times; but not relaxation heat set; then rapidly quenching to room temperature at a quenching rate of 3 ℃/s for 30 s to prepare the polylactic acid crystalline fiber material in a fibrous form; the monofilament diameter of the polylactic acid crystalline fiber material is 40 microns; subsequently subjecting the polylactic acid fiber material to a temperature T of glass transition thereof_gSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid crystalline fiber before storage is 45 percent, and the orientation degree is 0.95; the crystallinity of the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ is basically unchanged. The polylactic acid crystal fiber is 921cm before storage^-1The appearance of a crystallization characteristic peak; the polylactic acid crystalline fiber stored at 30 +/-5 ℃ for half a year is 918cm^-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 34%. The glass transition temperature of the polylactic acid crystalline fiber before storage is 63 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid crystal fiber stored at 30 +/-5 ℃ for half a year has no obvious endothermic peak near the glass transition temperature. In addition, the polylactic acid crystalline fiber before storage has a tensile strength of 3.85cN/dtex and an elongation at break of 28%; the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ has the tensile strength of 3.82cN/dtex and the elongation at break of 29 percent; the polylactic acid crystalline fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.

Example 13:

taking polylactic acid with the weight-average molecular weight of 8 ten thousand and the molar content of the L optical isomer of 95 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 43 ppm; extruding and spinning the dried polylactic acid granules by melt spinning equipment, and drafting by a high-speed hot-roll one-step method to form a polylactic acid crystalline fiber material, wherein the melting temperature is 190 ℃, and the winding speed is 5000 m/min; the drafting temperature is 65 ℃, and the drafting multiple is 3 times; but not relaxation heat set; then rapidly quenching to room temperature at a quenching rate of 500 ℃/s for 0.1 s to prepare a fibrous polylactic acid crystalline fiber material; the monofilament diameter of the polylactic acid crystalline fiber material is 5 microns; subsequently subjecting the polylactic acid fiber product to a temperature T of glass transition_gSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid crystalline fiber before storage is 62 percent, and the orientation degree is 0.96; the crystallinity of the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ is basically unchanged. The polylactic acid crystal fiber is 921cm before storage^-1The appearance of a crystallization characteristic peak; the polylactic acid crystalline fiber stored at 30 +/-5 ℃ for half a year is 918cm^-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 15%. The glass transition temperature of the polylactic acid crystalline fiber before storage is 56 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid crystal fiber stored at 30 +/-5 ℃ for half a year has no obvious endothermic peak near the glass transition temperature. In addition, the polylactic acid crystalline fiber before storage has a tensile strength of 2.65cN/dtex and an elongation at break of 27%; the polylactic acid crystalline fiber stored at 30 +/-5 ℃ for half a year has the tensile strength of 2.72cN/dtex and the elongation at break of 25%; the polylactic acid crystalline fiber prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.

Comparative example 1:

taking polylactic acid with the weight-average molecular weight of 15 ten thousand and the molar content of the L optical isomer of 95 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 50 ppm;spinning the dried polylactic acid granules by melt spinning equipment to form a polylactic acid amorphous fiber material, wherein the melting temperature is 232 ℃, the winding speed is 1000 m/min, the quenching is rapidly carried out to the room temperature at the quenching speed of 2 ℃/s, and the quenching time is 100 seconds; fully preheating the polylactic acid amorphous fiber material, and then carrying out secondary drafting, wherein the drafting temperature is 90 ℃, and the drafting multiple is 3 times; but not relaxation heat set; then rapidly quenching to room temperature at a quenching rate of 0.5 ℃/s for 120 seconds to prepare a fibrous polylactic acid crystalline fiber material; the monofilament diameter of the polylactic acid amorphous fiber material is 50 microns; the monofilament diameter of the polylactic acid crystalline fiber material is 25 micrometers; subsequently subjecting the polylactic acid fiber material to a temperature T of glass transition thereof_gSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid amorphous fiber before storage is 0 percent, and the orientation degree is 0.18; the crystallinity of the polylactic acid amorphous fiber is basically unchanged after being stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid amorphous fiber is 921cm before storage^-1No crystallization characteristic peak appears; the polylactic acid amorphous fiber is 918cm after being stored for half a year at the temperature of 30 +/-5 DEG C^-1Characteristic peaks appear, which indicate the formation of a metastable phase of polylactic acid, and the content of the metastable phase is 12%. The glass transition temperature of the polylactic acid amorphous fiber before storage is 54 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid amorphous fiber stored for half a year at 30 +/-5 ℃ has obvious endothermic peak near the glass transition temperature. In addition, the enthalpy value of the endothermic peak of the polylactic acid amorphous fiber after being stored for half a year at 30 +/-5 ℃ in the vicinity of the glass transition temperature depends on the DSC temperature rising rate, which shows that the endothermic peak is not only the structural transition of the metastable phase of the polylactic acid, but also the enthalpy relaxation phenomenon which is specific to physical aging. In addition, the tensile strength of the polylactic acid amorphous fiber before storage is 1.01cN/dtex, and the elongation at break is 201%; the polylactic acid amorphous fiber after being stored for half a year at 30 +/-5 ℃ has the tensile strength of 0.68cN/dtex and the elongation at break of 5 percent, which is shown in figure 2; the polylactic acid amorphous fiber prepared by the comparative example has no physical aging resistance, and has a phenomenon of brittleness caused by physical aging; it is known that the slow cooling rate causes reorientation of the polylactic acid molecular chains that have already been oriented, resulting in physical agingThe phenomenon of chemical embrittlement occurs. In addition, the polylactic acid crystalline fiber before storage had a crystallinity of 40% and an orientation degree of 0.85; the crystallinity of the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ is basically unchanged. The polylactic acid crystal fiber is 921cm before storage^-1The appearance of a crystallization characteristic peak; the polylactic acid crystalline fiber stored at 30 +/-5 ℃ for half a year is 918cm^-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 21%. The glass transition temperature of the polylactic acid crystalline fiber before storage is 56 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid crystal fiber stored at 30 +/-5 ℃ for half a year has no obvious endothermic peak near the glass transition temperature. In addition, the polylactic acid crystalline fiber before storage has a tensile strength of 3.58cN/dtex and an elongation at break of 33%; the polylactic acid crystalline fiber stored at 30 +/-5 ℃ for half a year has the tensile strength of 3.62cN/dtex and the elongation at break of 5%; the polylactic acid crystalline fiber prepared by the comparative example has no physical aging resistance, and has a phenomenon of brittleness caused by physical aging; it is known that the slow cooling rate causes the oriented polylactic acid amorphous phase to reorient the daughter chains, resulting in the occurrence of physical aging embrittlement.

Comparative example 2:

taking polylactic acid with the weight-average molecular weight of 30 ten thousand and the molar content of the L optical isomer of 95 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 45 ppm; spinning the dried polylactic acid granules by melt spinning equipment to form a polylactic acid amorphous fiber material, wherein the melting temperature is 250 ℃, the winding speed is 2000 m/min, the quenching speed is 15 ℃/s, and the quenching time is 15 s; fully preheating the polylactic acid amorphous fiber material, and then carrying out secondary drafting, wherein the drafting temperature is 115 ℃, and the drafting multiple is 2 times; performing relaxation heat setting; then rapidly quenching to room temperature at a quenching rate of 3 ℃/s for 30 s to prepare the polylactic acid crystalline fiber material in a fibrous form; the monofilament diameter of the polylactic acid amorphous fiber material is 80 microns; the monofilament diameter of the polylactic acid crystalline fiber material is 40 microns; subsequently converting the polylactic acid fiber material into glass transition stateTemperature T_gSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid amorphous fiber before storage is 0 percent, and the orientation degree is 0.56; the crystallinity of the polylactic acid amorphous fiber is basically unchanged after being stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid amorphous fiber is 921cm before storage^-1No crystallization characteristic peak appears; the polylactic acid amorphous fiber is 918cm after being stored for half a year at the temperature of 30 +/-5 DEG C^-1A characteristic peak appears, which indicates the formation of the metastable phase of the polylactic acid, and the content of the metastable phase is 35 percent. The glass transition temperature of the polylactic acid amorphous fiber before storage is 58 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid amorphous fiber stored for half a year at 30 +/-5 ℃ has obvious endothermic peak near the glass transition temperature. In addition, the enthalpy value of the endothermic peak of the polylactic acid amorphous fiber after being stored for half a year at 30 +/-5 ℃ is independent of the DSC temperature rising rate, which shows that the endothermic peak is the structural transformation of the polylactic acid metastable phase and is not the enthalpy relaxation phenomenon which is specific to physical aging. In addition, the tensile strength of the polylactic acid amorphous fiber before storage is 1.62cN/dtex, and the elongation at break is 107%; the polylactic acid amorphous fiber stored for half a year at the temperature of 30 +/-5 ℃ has the tensile strength of 1.73cN/dtex and the elongation at break of 105 percent; the polylactic acid amorphous fiber prepared by the comparative example has obvious physical aging resistance, does not have the phenomenon of embrittlement caused by physical aging, and forms a polylactic acid metastable phase. In addition, the polylactic acid crystalline fiber before storage had a crystallinity of 45% and an orientation degree of 0.82; the crystallinity of the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ is basically unchanged. The polylactic acid crystal fiber is 921cm before storage^-1The appearance of a crystallization characteristic peak; the polylactic acid crystalline fiber stored at 30 +/-5 ℃ for half a year is 918cm^-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 18%. The glass transition temperature of the polylactic acid crystalline fiber before storage is 61 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid crystal fiber stored at 30 +/-5 ℃ for half a year has no obvious endothermic peak near the glass transition temperature. In addition, the polylactic acid crystalline fiber before storage has a tensile strength of 3.74cN/dtex and an elongation at break of 29%; storing at 30 +/-5 deg.CThe polylactic acid crystal fiber after half a year storage has the tensile strength of 3.85cN/dtex and the elongation at break of 4 percent; the polylactic acid crystalline fiber prepared by the comparative example has no physical aging resistance, and has a phenomenon of brittleness caused by physical aging; from this, it is known that relaxation heat setting after drawing causes reorientation of the strand of the oriented polylactic acid amorphous domains, leading to the occurrence of a phenomenon of physical aging and embrittlement.

Comparative example 3:

taking polylactic acid with the weight-average molecular weight of 8 ten thousand and the molar content of the L optical isomer of 95 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 43 ppm; spinning the dried polylactic acid granules by melt spinning equipment to form a polylactic acid amorphous fiber material, wherein the melting temperature is 190 ℃, the winding speed is 8000 m/min, the quenching speed is 1600 ℃/s, the quenching speed is rapidly quenched to the room temperature, and the quenching time is 0.1 s; fully preheating the polylactic acid amorphous fiber material, and then carrying out secondary drafting, wherein the drafting temperature is 165 ℃, and the drafting multiple is 3 times; but not relaxation heat set; then rapidly quenching to room temperature at a quenching rate of 500 ℃/s for 0.1 s to prepare a fibrous polylactic acid crystalline fiber material; the monofilament diameter of the polylactic acid amorphous fiber material is 10 microns; the monofilament diameter of the polylactic acid crystalline fiber material is 5 microns; subsequently subjecting the polylactic acid fiber material to a temperature T of glass transition thereof_gSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid amorphous fiber before storage is 0 percent, and the orientation degree is 0.8; the crystallinity of the polylactic acid amorphous fiber is basically unchanged after being stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid amorphous fiber is 921cm before storage^-1No crystallization characteristic peak appears; the polylactic acid amorphous fiber is 918cm after being stored for half a year at the temperature of 30 +/-5 DEG C^-1Characteristic peaks appear, which indicate the formation of metastable phase of polylactic acid, and the content of metastable phase is 78%. The glass transition temperature of the polylactic acid amorphous fiber before storage is 55 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid amorphous fiber stored for half a year at 30 +/-5 ℃ has obvious endothermic peak near the glass transition temperature. In addition, the polylactic acid amorphous fiber is vitrified after being stored for half a year at 30 +/-5 DEG CThe enthalpy value of the endothermic peak near the transition temperature does not depend on the DSC heating rate, which shows that the endothermic peak is the structural transition of the polylactic acid metastable phase and is not the enthalpy relaxation phenomenon which is specific to physical aging. In addition, the tensile strength of the polylactic acid amorphous fiber before storage is 1.21cN/dtex, and the elongation at break is 67%; the polylactic acid amorphous fiber stored for half a year at the temperature of 30 +/-5 ℃ has the tensile strength of 1.25cN/dtex and the elongation at break of 65 percent; the polylactic acid amorphous fiber prepared by the comparative example has obvious physical aging resistance, does not have the phenomenon of embrittlement caused by physical aging, and forms a polylactic acid metastable phase. In addition, the polylactic acid crystalline fiber before storage had a crystallinity of 38% and an orientation degree of 0.86; the crystallinity of the polylactic acid crystalline fiber after being stored for half a year at 30 +/-5 ℃ is basically unchanged. The polylactic acid crystal fiber is 921cm before storage^-1The appearance of a crystallization characteristic peak; the polylactic acid crystalline fiber stored at 30 +/-5 ℃ for half a year is 918cm^-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 12%. The glass transition temperature of the polylactic acid crystalline fiber before storage is 55 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid crystal fiber stored at 30 +/-5 ℃ for half a year has no obvious endothermic peak near the glass transition temperature. In addition, the polylactic acid crystalline fiber before storage has a tensile strength of 2.56cN/dtex and an elongation at break of 47%; the polylactic acid crystalline fiber stored at 30 +/-5 ℃ for half a year has the tensile strength of 2.72cN/dtex and the elongation at break of 4%; the polylactic acid crystalline fiber prepared by the comparative example has no physical aging resistance, and has a phenomenon of brittleness caused by physical aging; it is known from this that an excessively high drawing temperature causes a de-orientation process to occur while drawing and orienting polylactic acid molecular chains, which reduces the degree of overall orientation of the crystalline fibers, resulting in the occurrence of a phenomenon of physical aging and embrittlement.

In addition, the inventors of the present invention have also made experiments with other materials, process operations, and process conditions described in the present specification with reference to the above examples, and have obtained preferable results.

Example 14

The physical aging resistant polylactic acid fiber material obtained in the above examples 1-13 can be processed into the desired fiber product according to the actual application requirement and in the manner known in the art. For example:

the physical aging resistant polylactic acid fiber materials obtained in the above examples 1 to 13 can be processed into linear products, garments, home textile products or non-woven fabric products, such as surgical sutures, garments, home textile products, needle punched non-woven fabrics, spunlace non-woven fabrics or spun bonded non-woven fabrics, which not only have strength equivalent to or superior to that of the existing polylactic acid fiber products, but also have excellent physical aging resistance, and can maintain the stability of size and performance in the logistics stage of storage.

It is to be understood that the above-described embodiments are part of the present invention, and not all embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. In addition, the polylactic acid material system provided by the invention is added with one or more additives such as biodegradable polymers (polyhydroxyalkanoate, polyglycolic acid, chitosan, chitin, polycaprolactone and the like), metal alloy materials (such as magnesium alloy, wherein the magnesium alloy is composed of one of magnesium-aluminum alloy, magnesium-manganese alloy, magnesium-zinc alloy, magnesium-zirconium alloy, magnesium-rare earth alloy, magnesium-lithium alloy, magnesium-calcium alloy or magnesium-silver alloy or ternary or multi-element magnesium alloy formed by combining the systems), antibacterial agents (silver, copper, acyclouridine and the like), essential elements for tissue growth (magnesium phosphate, calcium phosphate, sodium alginate and the like), vitamin K3 and the like, and is also protected by the invention.

The aspects, embodiments, features and examples of the present invention should be considered as illustrative in all respects and not intended to be limiting of the invention, the scope of which is defined only by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.

The use of headings and chapters in this disclosure is not meant to limit the disclosure; each section may apply to any aspect, embodiment, or feature of the disclosure.

Throughout this specification, where a composition is described as having, containing, or comprising specific components or where a process is described as having, containing, or comprising specific process steps, it is contemplated that the composition of the present teachings also consist essentially of, or consist of, the recited components, and the process of the present teachings also consist essentially of, or consist of, the recited process steps.

Unless specifically stated otherwise, use of the terms "comprising", "including", "having" or "having" is generally to be understood as open-ended and not limiting.

It should be understood that the order of steps or the order in which particular actions are performed is not critical, so long as the teachings of the invention remain operable. Further, two or more steps or actions may be performed simultaneously.

While the invention has been described with reference to illustrative embodiments, it will be understood by those skilled in the art that various other changes, omissions and/or additions may be made and substantial equivalents may be substituted for elements thereof without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated any use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.

Claims

1. A polylactic acid fiber material with physical aging resistance is characterized in that: the polylactic acid fiber material is in a fibrous form, and the polylactic acid fiber material is composed ofAmorphous phase composition; the amorphous phase comprises 5wt% to 95wt% of metastable phase, and the characteristic peak of the metastable phase in an infrared spectrogram appears at 918cm^-1Wherein the orientation degree of the polylactic acid fiber material is 0.2-0.8, and after the polylactic acid fiber material is stored below the glass transition temperature for enough time, an endothermic peak with enough enthalpy value delta H appears after the glass transition temperature in a Differential Scanning Calorimetry (DSC) curve of the polylactic acid fiber material, the enthalpy value of the endothermic peak is not changed along with the change of the temperature rising rate of DSC test, and the infrared spectrogram of the polylactic acid fiber material is within 918cm^-1A characteristic peak appears in a spectral band, the strength of the characteristic peak rises along with the prolonging of storage time, the change rate of the tensile strength of the polylactic acid fiber material is lower than 30%, the change rate of the elongation at break is lower than 40%, obvious yield and a subsequent plastic deformation area appear on a stress-strain curve, the enough time is more than or equal to 1 hour, and the delta H is more than or equal to 1J/g;

the preparation method of the polylactic acid fiber material with the physical aging resistance comprises the following steps:

providing a dry polylactic acid or a dry mixture of polylactic acid; the weight average molecular weight of the polylactic acid is 8-50 ten thousand, wherein the molar content of the L optical isomer is 85% -99%;

and extruding and spinning the dried polylactic acid or the dry polylactic acid mixture by a melt spinning device, wherein the spinning temperature is 170-270 ℃, the winding speed is 500-8000 m/min, the polylactic acid fiber material is rapidly quenched to room temperature at the quenching speed of 8-2000 ℃/s, and the quenching time is 0.1-29 s, so that the fibrous polylactic acid fiber material is prepared.

2. The physical aging resistant polylactic acid fiber material according to claim 1, wherein: the content of the metastable phase in the amorphous phase of the physical aging resistant polylactic acid fiber material is 20 to 70 weight percent.

3. The physical aging resistant polylactic acid fiber material according to claim 2, wherein: the content of metastable phase in amorphous phase of the physical aging resistant polylactic acid fiber material is 30-50 wt%.

4. The physical aging resistant polylactic acid fiber material according to claim 1, wherein: the orientation degree of the polylactic acid fiber material is 0.4-0.6.

5. The physical aging resistant polylactic acid fiber material according to claim 1, wherein: the polylactic acid fiber material also comprises any one or the combination of more than two of polymer, plasticizer, compatibilizer, ester exchanger, chain extender, end-capping reagent, flame retardant, antioxidant, lubricant, antistatic agent, antifogging agent, light stabilizer, color master batch, mildewproof agent, antibacterial agent and foaming agent.

6. The physical aging resistant polylactic acid fiber material according to claim 1, wherein: the monofilament diameter of the polylactic acid fiber material is 10-150 microns.

7. The physical aging resistant polylactic acid fiber material according to claim 1, wherein: the weight average molecular weight of the polylactic acid is 15-30 ten thousand, wherein the molar content of the L optical isomer is 92-98%.

8. The physical aging resistant polylactic acid fiber material according to claim 1, wherein: the spinning temperature is 200-250 ℃, the winding speed is 1500-5000 m/min, and the quenching time is 0.1-15 seconds.

9. The physical aging resistant polylactic acid fiber material according to claim 1, wherein: when the weight-average molecular weight of the polylactic acid is 8-15 ten thousand, the adopted spinning temperature is 170-230 ℃, the winding speed is 3000-8000 m/min, the quenching rate is 50-2000 ℃/s, and the quenching time is 0.1-3 s;

10. A polylactic acid fiber material with physical aging resistance is characterized in that: the polylactic acid fiber material is in a fibrous form, and comprises 15wt% -85 wt% of crystalline phase and 15wt% -85 wt% of amorphous phase; the amorphous phase comprises 5wt% to 65wt% of metastable phase, and the characteristic peak of the metastable phase in an infrared spectrogram appears at 918cm^-1At least one of (1) and (b); the orientation degree of the polylactic acid fiber material is 0.35-0.99, an endothermic peak with enough enthalpy value delta H appears after the glass transition temperature in a Differential Scanning Calorimetry (DSC) curve of the polylactic acid fiber material after the polylactic acid fiber material is stored for enough time below the glass transition temperature, the enthalpy value of the endothermic peak does not change along with the change of the temperature rising rate of DSC test, and the infrared spectrogram of the polylactic acid fiber material is within 918cm^-1A characteristic peak appears in a spectral band, the strength of the characteristic peak rises along with the prolonging of storage time, the change rate of the tensile strength of the polylactic acid fiber material is lower than 30%, the change rate of the elongation at break is lower than 40%, obvious yield and a subsequent plastic deformation area appear on a stress-strain curve, the enough time is more than or equal to 1 hour, and the delta H is more than or equal to 1J/g;

and extruding and spinning the dried polylactic acid or the dry polylactic acid mixture by a melt spinning device, drafting by a high-speed hot-roll one-step method at the spinning temperature of 170-270 ℃, the drafting temperature of 65-165 ℃, the drafting multiple of 1-5 times and the winding speed of 500-5000 m/min, rapidly quenching to room temperature at the quenching rate of 2.5-800 ℃/sec for 0.1-59 sec to prepare the fibrous polylactic acid fiber material.

11. The physical aging resistant polylactic acid fiber material according to claim 10, wherein: the crystallinity of the polylactic acid fiber material is 30wt% -70 wt%, and the content of the metastable phase in the amorphous phase is 15wt% -55 wt%.

12. The physical aging resistant polylactic acid fiber material according to claim 11, wherein: the crystallinity of the polylactic acid fiber material is 40wt% -60 wt%, and the content of the metastable phase in the amorphous phase is 25wt% -45 wt%.

13. The physical aging resistant polylactic acid fiber material according to claim 10, wherein: the orientation degree of the polylactic acid fiber material is 0.6-0.8.

14. The physical aging resistant polylactic acid fiber material according to claim 10, wherein: the polylactic acid fiber material also comprises any one or the combination of more than two of polymer, plasticizer, compatibilizer, ester exchanger, chain extender, end-capping reagent, flame retardant, antioxidant, lubricant, antistatic agent, antifogging agent, light stabilizer, color master batch, mildewproof agent, antibacterial agent and foaming agent.

15. The physical aging resistant polylactic acid fiber material according to claim 10, wherein: the monofilament diameter of the polylactic acid fiber material is 5-80 microns.

16. The physical aging resistant polylactic acid fiber material according to claim 10, wherein: the weight average molecular weight of the polylactic acid is 15-30 ten thousand, wherein the molar content of the L optical isomer is 92-98%.

17. The physical aging resistant polylactic acid fiber material according to claim 10, wherein: the drafting temperature is 85-145 ℃, the drafting multiple is 2-5 times, and the quenching time is 0.1-30 seconds.

18. The physical aging resistant polylactic acid fiber material according to claim 10, wherein: when the weight-average molecular weight of the polylactic acid is 8-15 ten thousand, the adopted drafting temperature is 65-110 ℃, the drafting multiple is 3-5 times, the quenching rate is 15-800 ℃/s, and the quenching time is 0.1-5 seconds;

19. Use of a polylactic acid fiber material resistant to physical aging according to any one of claims 1 to 18 for the production of a fiber product.

20. Use according to claim 19, characterized in that: the fiber product comprises a linear product, a garment, a home textile product or a non-woven fabric product.

21. Use according to claim 20, characterized in that: the fiber product comprises surgical suture, clothing, home textile, needle punched non-woven fabric, spunlace non-woven fabric or spun-bonded non-woven fabric.

22. A fibrous article made from the physical aging resistant polylactic acid fibrous material of any of claims 1 to 18.

23. A fibrous article according to claim 22, wherein: the fiber product comprises a linear product, a garment, a home textile product or a non-woven fabric product.

24. A fibrous article according to claim 23, wherein: the fiber product comprises surgical suture, clothing, home textile, needle punched non-woven fabric, spunlace non-woven fabric or spun-bonded non-woven fabric.

25. A disinfection packaging and storage method of polylactic acid fiber material with physical aging resistance is characterized by comprising the following steps: providing the polylactic acid fiber material with physical aging resistance of any one of claims 1 to 18, and sterilizing, packaging and storing the polylactic acid fiber material below the glass transition temperature of the polylactic acid fiber material.