CN112406071B - Physical aging-resistant polylactic acid blow molding product, and preparation method and application thereof - Google Patents

Abstract

The invention discloses a polylactic acid blow-molded product with resistance to physical aging, a preparation method and application thereof. The polylactic acid blow-molded product has a closed or open cell structure, and it contains 0wt%-85wt% of a crystalline phase and 15wt%-100wt% of an amorphous phase; the amorphous phase contains 5wt%-75wt% of a metastable phase, The characteristic peak of the metastable phase in the infrared spectrum appears at 918 cm ^-1 . The polylactic acid blow-molded product of the present invention has the characteristics of resistance to physical aging, and the yield strength and elongation at break change rate before and after storage are small. Bottles, medical hanging bottles and other products not only have the strength superior to the existing polylactic acid blow molding products, but also have excellent physical aging resistance, which can maintain the stability of size and performance in the storage and logistics stage, and the preparation process is beneficial to mass production.

Description

Polylactic acid blow molding product resistant to physical aging, its preparation method and application

technical field

The invention relates to a polylactic acid product, in particular to a polylactic acid blow-molded product resistant to physical aging, a preparation method and application thereof (drinking water bucket, milk bucket, beverage bottle, milk bottle, cosmetic packaging bottle, medical hanging bottle, etc.) , belonging to the field of blow molding technology.

Background technique

With the vigorous development of the global oil industry, a large number of petroleum-based polymers are made into barrels, bottles and other containers every year, which are used in industrial, medical and daily life fields. Among them, beverage bottles greatly facilitate people's diet and life because of the convenience of "disposal after use"; medical hanging bottles improve the safety of the medical and health field because of their one-time setting. However, the uncertainty of health and safety caused by the precipitation of petroleum-based resin itself and related additives, as well as the "white" pollution caused by the non-degradability of petroleum-based resins to the environment, have all contributed to the impact of petroleum-based resins in the fields of daily diet and medical care. Wide application casts a shadow. Therefore, the development of bio-based degradable resin blow molding products is particularly necessary.

Polylactic acid has good biocompatibility and biodegradability. It can be degraded into lactic acid in nature. After microbial decomposition, it finally forms carbon dioxide and water. It is one of the biodegradable polymers certified by the U.S. Food and Drug Administration. . It has broad application prospects in many fields such as tissue engineering, medical and health care, and flexible packaging materials. Among them, medical hanging bottles, drinking water bottles, barrels, etc. all require polylactic acid to have a long enough mechanical property retention time (at least to keep the mechanical properties stable during the shelf life). However, numerous literatures (Macromolecules 2007, 40, 9664-9671; Macromolecules 2019, 52, 8878-8894; Polymer 2020, 186, 122014; Macromolecules 2019, 52, 5429-5441; 2244) reported that polylactic acid is a semi-crystalline polymer, and the amorphous phase is prone to physical aging below the glass transition temperature, which makes the material rapidly brittle. Among them, physical aging is the process of spontaneous transition of molecular segments from non-equilibrium state to equilibrium state, and its essence is the reduction of free volume. This makes polylactic acid products prone to physical aging during the warehousing and logistics stage (shelf life), resulting in sharply brittle products. However, the development of physical aging-resistant polylactic acid blow-molded products through process optimization has not yet been reported.

There are many public reports on the preparation of polylactic acid packaging bottles and beverage bottles. For example, CN 103831966 A reports a preparation method of a heat-resistant polylactic acid water bottle. The preform is prepared by injection molding equipment, and the bottle mouth is insulated and crystallized; the water bottle is further prepared by blow molding equipment, and the bottle mouth and bottle body are insulated and crystallized. CN 109111710 A reports a heat-resistant polylactic acid-based degradable plastic bottle. Aiming at the problems of heat resistance and toughness that restrict the application of polylactic acid, plant-derived polycarbonate is used to modify polylactic acid to improve the heat resistance and mechanical properties of polylactic acid. CN 106574104 A reports a stretch-formed bottle resistant to environmental stress cracking. By selecting vinyl resins with similar melt flow properties to PLA and adding them to PLA to stretch plastic bottles (mainly blow molding), the environmental stress crack resistance is improved. CN 108948703 A reports a weather-resistant degradable plastic bottle. Aiming at the slow crystallization, large molding shrinkage, hard and brittle performance of existing polylactic acid products, and a series of aging phenomena such as fading, cracking, and chalking of plastic products that are easily affected by natural factors such as sunlight and temperature, the A weather-resistant degradable plastic bottle and a preparation method thereof. By blending modified attapulgite to graft polymethyl methacrylate, the weather resistance and mechanical properties of polylactic acid are greatly improved.

Although the above known technologies can prepare polylactic acid plastic bottles, under the current technical conditions, polylactic acid plastic bottles do not strictly design and control the process steps from the molecular nature of resistance to physical aging, and are easy to use in the storage and logistics stage (shelf period). ) physical aging leads to rapid embrittlement; therefore, it is necessary to develop new physical aging-resistant polylactic acid blow-molded products and their preparation methods to meet the higher requirements of various applications for their comprehensive properties.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to provide a physical aging-resistant polylactic acid blow-molded product, its preparation method and application, so as to overcome the deficiencies in the prior art.

In order to realize the foregoing invention purpose, the technical scheme adopted in the present invention includes:

The embodiment of the present invention provides a polylactic acid blow-molded product with resistance to physical aging, which has a closed or open-chamber structure and a density equal to or greater than 1.24 g/cm ³ ; and the polylactic acid blow-molded product contains 0wt%～ 85wt% crystalline phase and 15wt%～100wt% amorphous phase; the amorphous phase contains 5wt%～75wt% metastable phase, and the characteristic peak of the metastable phase in the infrared spectrum appears at 918cm ^-1 ; more It is important that after the polylactic acid blow molded product is stored for a sufficient time below the glass transition temperature, the rate of change of yield strength is less than 30%, the rate of change of elongation at break is less than 40%, and the stress-strain curve appears. Significant yielding and subsequent plastic deformation zone.

Further, after the polylactic acid blow-molded product is stored for a sufficient time below the glass transition temperature (T _g ), in the differential scanning calorimetry (DSC) curve of the polylactic acid blow-molded product, after the glass transition temperature (post-T _g ), followed by an endothermic peak with a sufficiently large enthalpy value (ΔH), the enthalpy value (ΔH) of the endothermic peak does not change with the change of the heating rate in the DSC test, and the polylactic acid blowing A characteristic peak appears in the 918cm ^-1 band in the infrared spectrum of the plastic product, and the intensity of the characteristic peak increases with the storage time. Wherein, the storage time is not limited; however, in general, the sufficient time is ≥ 1 hour. The said enthalpy value (ΔH) is also not limited; however, in general, the enthalpy value (ΔH) ≥ 1 J/g.

An embodiment of the present invention also provides a method for preparing the physical aging-resistant polylactic acid blow-molded product, comprising:

(1) Provide dry polylactic acid or polylactic acid dry mixture;

(2) melting and extruding the dried polylactic acid or polylactic acid dry mixture through a screw extrusion equipment to obtain a polylactic acid melt, wherein the screw temperature is 150-270° C.;

(3) Inputting the polylactic acid melt into a split-molding blow molding equipment for blow molding, the blow molding temperature is equal to or greater than the glass transition temperature but lower than the melting point, preferably 65-145° C., blowing along the radial direction The plastic stretching ratio is 1 to 6 times, and then it is rapidly quenched to room temperature at a quenching rate of 2 to 800°C/second, and the quenching time is 0.1 to 59 seconds to obtain a blown polylactic acid with a closed or open cavity structure. plastic products;

(4) Place the polylactic acid blow-molded product with a closed or open chamber structure in a pressurized container (such as a pressure tank) that can be pressurized, temperature-controlled, and pressure-controlled, and subjected to pressurization and constant temperature treatment to increase the blowing rate. Comprehensive performance of plastic products, the pressure in the pressurized container is equal to or greater than 1 standard atmosphere, preferably 1.05 to 1.5 standard atmospheres, and the temperature is equal to or greater than the glass transition temperature (T _g of the blow-molded product in the pressure tank) but low At the cold crystallization temperature, preferably 65 to 95 °C; then firstly drop to room temperature at a selected cooling rate, preferably 10 °C/min; then at a selected pressure relief rate to 1 standard atmosphere, preferably 1 A standard atmospheric pressure/min, a polylactic acid blow-molded product with a closed or open cavity structure and a more stable structure is produced.

Further, the method for preparing the physical aging-resistant polylactic acid blow-molded product provided in another aspect of the embodiments of the present invention may further specifically include:

Provide dry polylactic acid or polylactic acid dry mixture;

Melt extrusion of the dried polylactic acid or polylactic acid dry mixture through screw extrusion equipment;

The melt is directly fed into the split mold for blow molding; or 1) the melt is stretched in the axial direction and then blow molded; or 2) the melt is injected into the blank, which is further preheated and fed into the split mold for blow molding; or 3) The melt injection molding embryo is further preheated and stretched in the axial direction before blow molding;

The polylactic acid blow-molded product is placed in a pressurized container under pressure and constant temperature to obtain a blow-molded product with better comprehensive performance.

The embodiments of the present invention also provide the use of the physical aging-resistant polylactic acid blow-molded product in the preparation of container products.

Further, the container products include bottles, cans, barrels, boxes, boxes or tubes, etc., but are not limited thereto.

Further, an embodiment of the present invention also provides a method for sterilizing, packaging and storing a polylactic acid blow-molded product resistant to physical aging, which includes:

Any of the physical aging-resistant polylactic acid blow-molded products in the foregoing embodiments are provided, and the polylactic acid blow-molded products are sterilized, packaged and stored below their glass transition temperature _Tg .

Compared with the prior art, the polylactic acid blow-molded product provided by the foregoing embodiments of the present invention has the characteristics of resistance to physical aging, the change rate of yield strength before and after storage is small, and the change rate of elongation at break is also small. Drinking water barrels, milk barrels, beverage bottles, milk bottles, cosmetic packaging bottles, medical hanging bottles and other products not only have the strength equivalent to or better than the existing polylactic acid blow molding products, but also have excellent resistance to physical aging. It maintains the stability of size and performance in the stage of warehousing and logistics, and at the same time, its preparation process is conducive to large-scale production and has broad application prospects.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments described in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

1 is a stress-strain curve diagram of a polylactic acid blow-molded product resistant to physical aging obtained in Example 3 of the present invention;

FIG. 2 is a stress-strain curve diagram of the polylactic acid blow molded product obtained in Comparative Example 1. FIG.

Detailed ways

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 may 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 for teaching one skilled in the art to vary in virtually any suitable detailed embodiment. The manner adopts the representative basis of the present invention.

One aspect of the embodiments of the present invention provides a polylactic acid blow-molded product with resistance to physical aging, which has a closed or open-chamber structure, and a density ^of 1.24 g/cm or more; and the crystalline phase content of the polylactic acid blow-molded product It is 0wt% to 85wt%, the amorphous phase content is 15wt% to 100wt%, the content of the metastable phase in the amorphous phase is 5wt% to 75wt%, and the characteristic peaks of the metastable phase appear in the infrared spectrum. At 918cm ^-1 ; more importantly, after the polylactic acid blow molding product is stored for a sufficient time below the glass transition temperature, the change rate of yield strength is less than 30%, and the change rate of elongation at break is less than 40% , a pronounced yielding and subsequent plastic deformation zone appears on the stress-strain curve.

In some more preferred embodiments, the content of the crystalline phase of the physical aging-resistant polylactic acid blow molding product is 20wt%-70wt%, and the content of the metastable phase in the amorphous phase is 10wt%-50wt%.

In some more preferred embodiments, the content of the crystalline phase of the physical aging-resistant polylactic acid blow molding product is 30wt% to 50wt%, and the content of the metastable phase in the amorphous phase is 20wt% to 40wt% .

Further, after the physical aging-resistant polylactic acid blow-molded product is stored (shelf life) for a sufficient time below the polylactic acid glass transition temperature (T _g ), it is detected by a differential scanning calorimeter (DSC), and the DSC curve shows After the glass transition temperature (post-T _g ), an endothermic peak with a sufficiently large enthalpy value (ΔH) appears immediately, and the enthalpy value (ΔH) of the endothermic peak does not change with the change of the heating rate in the DSC test, and, A characteristic peak appeared in the 918cm ^-1 band in its infrared spectrum, and the intensity of the characteristic peak increased with the storage time. Wherein, the storage time is not limited; however, in general, the sufficient time is ≥ 1 hour. The said enthalpy value (ΔH) is also not limited; however, in general, the enthalpy value (ΔH) ≥ 1 J/g.

Further, after the physical aging-resistant polylactic acid blow-molded product is stored for a sufficient time below T _g (shelf life), it is detected by a micro-infrared spectrometer (Micro-FTIR), and the 918cm ^-1 band of the infrared spectrum appears characteristic. peaks and the intensity of characteristic peaks increases with storage time. Wherein, the storage time is not limited; however, generally speaking, the time is ≥ 1 hour.

Further, after the polylactic acid blow-molded product is stored for a sufficient time below T _g (shelf life), the rate of change of yield strength before and after storage is generally lower than 30%; the rate of change of elongation at break before and after is generally lower than 40%. There is a transition from ductility to brittleness.

Further, within the scope of not hindering the realization of the technical purpose of the present invention, polymers (such as polyhydroxyalkanoate, polyglycolic acid, polycaprolactone, polysuccinic acid can also be added to the polylactic acid blow-molded product). Butylene glycol ester, polyadipate/butylene terephthalate and other homopolymers or any one or more of copolymers), plasticizers, compatibilizers, transesterifiers, chain extenders, Any of the additives such as end-capping agents, flame retardants, antioxidants, lubricants, antistatic agents, antifogging agents, light stabilizers, ultraviolet absorbers, color masterbatches, antifungal agents, antibacterial agents, and foaming agents A combination of one or more, but not limited thereto. All in all, as long as it does not impede the realization of the technological purpose of the present invention (processing optimization and formula regulation make the phenomenon that the polylactic acid product becomes brittle due to physical aging does not occur), no matter what method is adopted, it is within the protection scope of the present invention.

Another aspect of the embodiments of the present invention provides the physical aging-resistant polylactic acid blow molded product (one-step method), which can be obtained by melt extrusion, (melt stretching), blow molding, quenching and other processes with screw extrusion equipment.

Further, the method for preparing the physical aging-resistant polylactic acid blow-molded product provided by another aspect of the embodiments of the present invention includes:

(1) Provide dry polylactic acid or polylactic acid dry mixture;

(2) melting and extruding the dried polylactic acid or polylactic acid dry mixture through a screw extrusion equipment to obtain a polylactic acid melt, wherein the screw temperature is 150-270° C.;

(3) Inputting the polylactic acid melt into a split-molding blow molding equipment for blow molding, the blow molding temperature is equal to or greater than the glass transition temperature but lower than the melting point, preferably 65-145° C., blowing along the radial direction The plastic stretching ratio is 1 to 6 times, and then it is rapidly quenched to room temperature at a quenching rate of 2 to 800°C/second, and the quenching time is 0.1 to 59 seconds to obtain a blown polylactic acid with a closed or open cavity structure. plastic products;

(4) Place the polylactic acid blow-molded product with a closed or open chamber structure in a pressurized container (such as a pressure tank) that can be pressurized, temperature-controlled, and pressure-controlled, and subjected to pressurization and constant temperature treatment to increase the blowing rate. The overall performance of plastic products, the pressure in the pressurized container (such as a pressure tank) is equal to or greater than 1 standard atmospheric pressure, preferably 1.05 to 1.5 standard atmospheric pressure, and the temperature is equal to or greater than the glass transition temperature (the pressure of the blow molded product in the pressure tank). T _g ) but lower than the cold crystallization temperature, preferably 65 to 95 ° C; then firstly drop to room temperature at a certain cooling rate, preferably 10 ° C/min; It is preferably 1 standard atmosphere per minute, which produces a polylactic acid blow-molded product with a closed or open cell structure and a more stable structure.

In some embodiments, step (3) further comprises: first stretching the polylactic acid melt in the axial direction, and then inputting it into the split-molding blow molding equipment, wherein the stretching temperature in the axial direction is equal to or It is higher than the glass transition temperature but lower than the melting point, preferably 65 to 145° C., and the draw ratio is 1 to 6 times.

In some more specific embodiments, the preparation method specifically includes:

(1) Provide dry polylactic acid or polylactic acid dry mixture;

(2) melt extruding the dried polylactic acid (or polylactic acid blend) through screw extrusion equipment, and the screw temperature is 150-270 °C;

(3) The polylactic acid melt is directly input into the split mold for blow molding (or, the melt is first stretched in the axial direction, the stretching temperature is 65-145° C., and the stretching ratio along the axial direction is 1-6 times). ; Then enter the split-molding blow molding), the blowing (in-mold) temperature is 65-145 °C, the blowing stretch ratio along the radial direction is 1-6 times, and then quenching at 2-800 °C/sec. The cooling rate is rapidly quenched to room temperature, and the quenching time is 0.1 to 59 seconds to obtain a polylactic acid blow molded product;

(4) Place the polylactic acid blow-molded product with a closed or open chamber structure in a pressurized container (such as a pressure tank) that can be pressurized, temperature-controlled, and pressure-controlled, and subjected to pressurization and constant temperature treatment to increase the blowing rate. The overall performance of plastic products, the pressure in the pressurized container (such as a pressure tank) is equal to or greater than 1 standard atmospheric pressure, preferably 1.05 to 1.5 standard atmospheric pressure, and the temperature is equal to or greater than the glass transition temperature (the pressure of the blow molded product in the pressure tank). T _g ) but lower than the cold crystallization temperature, preferably 65 to 95 ° C; then firstly drop to room temperature at a certain cooling rate, preferably 10 ° C/min; It is preferably 1 standard atmosphere per minute, which produces a polylactic acid blow-molded product with a closed or open cell structure and a more stable structure.

Wherein, the polylactic acid dry mixture may contain one or more of the aforementioned additives.

In some embodiments, the polylactic acid in step (1) has a weight average molecular weight of 80,000 to 500,000, wherein the molar content of the L optical isomer is 85% to 99%.

As one of the more preferred embodiments, the weight average molecular weight of the polylactic acid is preferably 200,000 to 400,000, and the molar content of the L optical isomer is 92% to 98%.

In some embodiments, the blowing (in-mold) temperature used in step (3) is 65-145° C., the blowing stretch ratio in the radial direction is 1-6 times, and the quenching time is 0.1-59 seconds; The preferable blow molding (in-mold) temperature is 85 to 145° C., the blowing stretch ratio in the radial direction is 2 to 5 times, and the quenching time is 0.1 to 30 seconds. in:

When the weight-average molecular weight of polylactic acid is 80,000 to 150,000, the blowing (in-mold) temperature used is 65-95°C, the blowing stretch ratio along the radial direction is 3-6 times, and the quenching rate is 15- 800℃/sec, quenching time is 0.1～5sec;

When the weight-average molecular weight of polylactic acid is 150,000 to 300,000, the blowing (in-mold) temperature used is 85-115°C, the blow-moulding stretching ratio along the radial direction is 2-4 times, and the quenching rate is 3- 15℃/second, quenching time is 5～30 seconds;

When the weight-average molecular weight of polylactic acid is 300,000 to 500,000, the blowing (in-mold) temperature used is 105-145°C, the blowing stretch ratio along the radial direction is 1-3 times, and the quenching rate is 2- 3°C/sec, and the quenching time is 30 to 59 seconds.

In some embodiments, the pressure in the pressurized vessel used in step (4) is 1.05-1.5 standard atmospheric pressure, the temperature is 65-95°C, and the treatment time is not limited; the preferred pressure in the pressurized vessel is 1.2-1.4 Standard atmospheric pressure, the temperature is 75 ~ 85 ℃, and the pressure treatment time is more than 5 seconds. in:

When the weight-average molecular weight of the polylactic acid is 80,000 to 150,000, the pressure in the pressurized container used is 1.2 to 1.5 standard atmospheres, and the temperature is 65 to 78°C;

When the weight-average molecular weight of the polylactic acid is 150,000 to 300,000, the pressure in the pressurized container used is 1.1 to 1.3 standard atmospheres, and the temperature is 73 to 87°C;

When the weight average molecular weight of the polylactic acid is 300,000 to 500,000, the pressure in the pressurized container used is 1.05 to 1.15 standard atmospheres, and the temperature is 82 to 95°C.

In addition, specifically, the physical aging-resistant polylactic acid blow-molded product (two-step method) provided by the embodiment of the present invention can be melt-extruded, injection-molded, (melt-stretched), blow-molded, quenched by screw extrusion equipment Wait for the process to get.

In some embodiments, the preparation method specifically includes:

(1) Provide dry polylactic acid or polylactic acid dry mixture;

(2) Melt and extrude the dried polylactic acid (or polylactic acid blend) through screw extrusion equipment, and further inject into polylactic acid parison, the screw temperature is 150-270°C, and the temperature in the injection mold is 65-145°C , and then rapidly quenched to room temperature at a quenching rate of 2 to 800°C/sec, and the quenching time was 0.1 to 59 seconds;

(3) After fully preheating the polylactic acid parison, it is directly input into the split mold for blow molding (or, the parison is first stretched in the axial direction, the stretching temperature is 65-145 °C, and the stretching ratio is 1-6 times; and then enter the split-molding blow molding), the blowing (in-mold) temperature is 65-145 °C, the blowing stretch ratio along the radial direction is 1-6 times, and then the blow molding temperature is 2-800 °C/sec. The quenching rate is rapidly quenched to room temperature, and the quenching time is 0.1 to 59 seconds to obtain a polylactic acid blow-molded product;

(4) Place the polylactic acid blow-molded product with a closed or open chamber structure in a pressurized container (such as a pressure tank) that can be pressurized, temperature-controlled, and pressure-controlled, and subjected to pressurization and constant temperature treatment to increase the blowing rate. For the comprehensive performance of plastic products, the pressure in the pressurized container (such as a pressure tank) is 1.05 to 1.5 standard atmospheric pressure, and the temperature is 65 to 95 °C; The decompression rate per minute is decompressed to 1 standard atmosphere, and a polylactic acid blow molded product with a closed or open cavity structure and a more stable structure is prepared.

Wherein, the polylactic acid dry mixture may contain one or more of the aforementioned additives.

In some embodiments, the polylactic acid in step (1) has a weight average molecular weight of 80,000 to 500,000, wherein the molar content of the L optical isomer is 85% to 99%.

As one of the more preferred embodiments, the weight average molecular weight of the polylactic acid is preferably 200,000 to 400,000, and the molar content of the L optical isomer is 92% to 98%.

In some embodiments, the temperature of the screw used in step (2) is 150-270°C, the temperature in the injection mold is 65-145°C, and the quenching time is 0.1-59 seconds; the preferred screw temperature is 180-220°C, The temperature in the injection mold is 85-145°C, and the quenching time is 0.1-30 seconds. in:

When the weight-average molecular weight of the polylactic acid is 80,000 to 150,000, the temperature in the injection mold used is 65-95°C, the quenching rate is 15-800°C/sec, and the quenching time is 0.1-5 seconds;

When the weight-average molecular weight of the polylactic acid is 150,000 to 300,000, the temperature in the injection mold used is 85-115°C, the quenching rate is 3-15°C/sec, and the quenching time is 5-30 seconds;

When the weight-average molecular weight of the polylactic acid is 300,000 to 500,000, the temperature in the injection mold used is 105-145° C., the quenching rate is 2-3° C./second, and the quenching time is 30-59 seconds.

In some embodiments, the blowing (in-mold) temperature used in step (3) is 65-145° C., the blowing stretch ratio in the radial direction is 1-6 times, and the quenching time is 0.1-59 seconds; The preferable blow molding (in-mold) temperature is 85 to 145° C., the blowing stretch ratio in the radial direction is 2 to 5 times, and the quenching time is 0.1 to 30 seconds. in:

When the weight-average molecular weight of polylactic acid is 80,000 to 150,000, the blowing (in-mold) temperature used is 65-95°C, the blowing stretch ratio along the radial direction is 3-6 times, and the quenching rate is 15- 800℃/sec, quenching time is 0.1～5sec;

When the weight-average molecular weight of polylactic acid is 150,000 to 300,000, the blowing (in-mold) temperature used is 85-115°C, the blow-moulding stretching ratio along the radial direction is 2-4 times, and the quenching rate is 3- 15℃/second, quenching time is 5～30 seconds;

When the weight-average molecular weight of polylactic acid is 300,000 to 500,000, the blowing (in-mold) temperature used is 105-145°C, the blowing stretch ratio along the radial direction is 1-3 times, and the quenching rate is 2- 3°C/sec, and the quenching time is 30 to 59 seconds.

In some embodiments, the pressure in the pressurized vessel used in step (4) is 1.05-1.5 standard atmospheric pressure, the temperature is 65-95°C, and the treatment time is not limited; the preferred pressure in the pressurized vessel is 1.2-1.4 Standard atmospheric pressure, the temperature is 75 ~ 85 ℃, and the pressure treatment time is more than 5 seconds. in:

When the weight-average molecular weight of the polylactic acid is 80,000 to 150,000, the pressure in the pressurized container used is 1.2 to 1.5 standard atmospheres, and the temperature is 65 to 78°C;

When the weight-average molecular weight of the polylactic acid is 150,000 to 300,000, the pressure in the pressurized container used is 1.1 to 1.3 standard atmospheres, and the temperature is 73 to 87°C;

When the weight average molecular weight of the polylactic acid is 300,000 to 500,000, the pressure in the pressurized container used is 1.05 to 1.15 standard atmospheres, and the temperature is 82 to 95°C.

The preparation method provided by the foregoing embodiments of the present invention is prepared by optimizing the molecular weight and optical isomer content of polylactic acid, blow molding at an appropriate blow molding temperature and blow molding stretch ratio, and further treating it under pressure and constant temperature in a pressure tank. The polylactic acid blow-molded product with more stable structure, namely the polylactic acid blow-molded product with resistance to physical aging. The polylactic acid blow-molded product has good resistance to physical aging, and will not become brittle due to physical aging during the shelf life; instead, it forms a polylactic acid metastable phase, and the DSC curve shows the enthalpy of the endothermic peak near T _g ( ΔH) did not change with the change of heating rate in DSC test; furthermore, the change rate of yield strength before and after storage was small, and the change rate of elongation at break was also small.

Further, another aspect of the embodiments of the present invention provides the use of the physical aging-resistant polylactic acid blow-molded product in the preparation of container products.

Further, the container products include bottles, cans, barrels, boxes, boxes or tubes, etc., but are not limited thereto.

Further, the container products include drinking water buckets, milk buckets, beverage bottles, milk bottles, cosmetic packaging bottles or medical hanging bottles, etc., but are not limited thereto.

Further, another aspect of the embodiments of the present invention also provides a method for sterilizing, packaging and storing a polylactic acid blow-molded product that is resistant to physical aging, including:

Any of the physical aging-resistant polylactic acid blow-molded products in the foregoing embodiments are provided, and the polylactic acid blow-molded products are sterilized, packaged and stored below their glass transition temperature _Tg .

Further, in the foregoing embodiment, after the preparation of the polylactic acid blow-molded product is completed, that is, sterilized packaging, and enters the storage logistics stage; the set temperature of the disinfection packaging and storage logistics stage (shelf life) is lower than T _g .

Further, the polylactic acid blow-molded products prepared in the foregoing embodiments of the present invention are stable in structure and not loose, and their mechanical properties are not inferior to the existing polylactic acid blow-molded products, especially the rapid quenching after injection molding and blow molding in the preparation process. process, so that the physical aging resistance performance of the polylactic acid blow molded product of the embodiment of the present invention is significantly improved. In addition, the polylactic acid metastable phase formed in the storage and logistics stage can significantly reduce the internal stress of the polylactic acid blow-molded product according to the embodiment of the present invention, and improve the stability of the product. Therefore, the polylactic acid blow-molded product of the embodiment of the present invention has excellent resistance to physical aging, can maintain the stability of size and performance in the storage and logistics stage, and breaks through the performance bottleneck of conventional polylactic acid blow-molded products, thereby meeting the requirements for use. Expand the field of application.

The advantages of the technical solutions provided by the embodiments of the present invention are at least as follows:

The technical scheme of the present invention is as follows: (1) different from the traditional blow molding process, after the blow molding is finished, the heat resistance of the product is improved by constant temperature heat setting in the split mold; the present invention does not carry out constant temperature heat setting in the mold, but rapid quenching;

(2) Different from the traditional method of annealing and crystallization (pressure is 1 standard atmospheric pressure, temperature is near the cold crystallization temperature) to improve product performance; the polylactic acid blow molded product of the present invention is pressurized in a pressure tank and kept at a constant temperature (equal to or Greater than the glass transition temperature but lower than the cold crystallization temperature) treatment, the structure of the product is further stabilized (the content of metastable phase is increased to varying degrees);

(3) Different from the traditional pressurization (the higher the molecular weight, the higher the pressure) treatment method, the polylactic acid blow molding product of the present invention is pressurized and thermostatically treated in a pressure tank, and the pressure in the pressure tank is inversely proportional to the molecular weight of the polylactic acid , the temperature is proportional to the molecular weight of PLA;

(4) After the polylactic acid blow-molded product is pressurized in the pressure tank and treated at a constant temperature, the temperature is first lowered to room temperature, and then the pressure is released to 1 standard atmospheric pressure at a slow pressure release rate;

The technical effects obtained from this are: (1) Through the arrangement and combination of the above four technical solutions, after the polylactic acid blow molded product of the present invention is stored for a sufficient time below the glass transition temperature, the change rate of the yield strength is less than 30% , the rate of change of elongation at break is less than 40%, and the stress-strain curve shows obvious yield and subsequent plastic deformation zone;

(2) The content of the crystalline phase of the polylactic acid blow-molded product is 0wt% to 85wt%, the content of the amorphous phase is 15wt% to 100wt%, and the content of the metastable phase in the amorphous phase is 5wt% to 75wt%, The characteristic peak of the metastable phase in the infrared spectrum appears at 918 cm ⁻¹ ;

(3) The DSC curve of the polylactic acid amorphous (or low crystallinity) blow-molded product shows that the glass transition temperature (post-T _g ) is followed by an endothermic peak with a sufficiently large enthalpy value (ΔH), and The enthalpy (ΔH) of the endothermic peak does not change with the change of the heating rate in the DSC test;

It is speculated that the reasons are: (1) The inventors obtained the above technical solutions and effects through a large number of experiments, which cannot be explained by the existing theory, but the inventors speculate that the possible reason is that the rapid quenching after blow molding prevents the polylactic acid amorphous The molecular chain in the region is de-oriented (or the degree of de-orientation is low);

(2) The polylactic acid blow-molded product of the present invention is pressurized and treated at a constant temperature in a pressure tank, so as to further stabilize the structure of the product, and at the same time, it may avoid the de-orientation (or de-orientation) of the molecular chains in the amorphous region during the treatment process. less oriented);

(3) After the polylactic acid blow-molded product of the present invention is pressurized and treated at a constant temperature in a pressure tank, the temperature is first lowered to room temperature, and then the pressure is released to 1 standard atmosphere at a slow pressure release rate. Avoid de-orientation of molecular chains in the amorphous region of polylactic acid (or the degree of de-orientation is low);

(4) Unlike traditional polylactic acid products, which are prone to physical aging and brittleness (the molecular chain in the polylactic acid amorphous region is de-oriented), the polylactic acid blow molding product of the present invention only forms a polylactic acid metastable phase in the conventional storage and logistics stage. ; instead of forming a cohesive entanglement structure, resulting in physical aging and brittleness.

In a word, the technical solutions provided by the embodiments of the present invention first provide high shear flow field and extension flow field through melt extrusion, stretching and blow molding, and induce the polylactic acid molecular chain to expand in the axial and radial directions respectively. , orientation, and then through rapid quenching, pressure and constant temperature treatment to hinder the relaxation of the polylactic acid molecular chain, so that the molecular chain orientation structure in the amorphous region can be maintained, and the physical aging resistance of polylactic acid blow molding products can be improved. Among them, the appropriate temperature and time are provided during the storage process, so that the polylactic acid blow-molded product is accompanied by the generation of dipole-dipole interaction, further forming the polylactic acid metastable phase, reducing the internal stress of the polylactic acid blow-molded product, and improving the polylactic acid. Performance stability of lactic acid blow molded products during shelf life (warehousing logistics stage) and use stage.

To sum up these factors, the polylactic acid blow-molded product of the embodiment of the present invention is stable in structure without relaxation, and its mechanical properties are comparable to those of the currently known polylactic acid blow-molded products, especially excellent resistance to physical aging, which makes it itself and by itself. The prepared related products can maintain the stability of size and performance during the shelf life (warehousing and logistics stage) and the use stage, breaking through the performance bottleneck of conventional polylactic acid blow molding products, thus fully meeting the use requirements and greatly expanding its application field.

The technical solutions and effects of the present invention will be further described below with reference to the embodiments and the accompanying drawings. Among them, glass transition temperature, cold crystallization temperature and melting point were measured by differential scanning calorimetry (DSC) method; glass transition temperature was determined by angle bisector method, cold crystallization temperature and melting point were taken as peak temperature; crystallinity was determined by X-ray diffraction (XRD) method. The present invention does not use the DSC method to calculate the crystallinity, because it is well known that the sample is heated during the DSC test, thereby causing secondary crystallization, so the measured crystallinity is higher than the actual value. In the following examples of the present invention, the formation of polylactic acid metastable phase was identified by Micro-FTIR; the tensile properties of polylactic acid blow molded products were measured by a universal material tensile tester.

Example 1:

Take polylactic acid with a weight-average molecular weight of 150,000 and a molar content of L optical isomers of 95% for hot air drying, the drying temperature is 95 ± 2 ° C, the drying time is 8 hours, and the water content is 50 ppm; The material is extruded through screw extrusion equipment to obtain polylactic acid melt, and the screw temperature is 190 °C; the polylactic acid melt is directly input into the split mold for blow molding, the blowing temperature is 95 °C, and the blowing stretch ratio is 3 times; Enter the rapid cooling device to obtain a blow-molded product with a closed or open cavity structure, the quenching rate is 15°C/sec, and the quenching time is 5 seconds; further, the polylactic acid blow-molded product is placed in a pressure tank for pressurization and constant temperature. Treatment, the pressure in the pressure tank is 1.2 standard atmospheres, and the temperature is 78°C; then the temperature is lowered to room temperature at a cooling rate of 10°C/min, and then the pressure is relieved at a pressure relief rate of 1 standard atmosphere/minute to 1 standard atmosphere. Under the following conditions, a polylactic acid blow-molded product with a closed or open cavity structure and a more stable structure is produced; then the polylactic acid blow-molded product is sterilized, packaged and stored below its glass transition temperature _Tg . After testing, the crystallinity of the polylactic acid blow-molded product before storage was 40%; the crystallinity of the polylactic acid blow-molded product after storage at 30±5°C for half a year basically did not change. Before storage, the polylactic acid blow-molded product showed a characteristic peak at 921cm ^-1 ; the polylactic acid blow-molded product after storage at 30±5°C for half a year also showed a characteristic peak at 918cm ^-1 , indicating the formation of polylactic acid metastable phase. The stable phase content is 40%. The glass transition temperature of polylactic acid blow-molded products before storage is 55 °C, and there is almost no endothermic peak near the glass transition temperature; the polylactic acid blow molded products stored at 30±5 °C for half a year are near the glass transition temperature. There is also no obvious endothermic peak. In addition, the blowing direction (radial) yield strength of the polylactic acid blow-molded product before storage was 58MPa, and the elongation at break was 73%; the blow-molding direction ( The radial) yield strength is 61MPa, and the elongation at break is 76%; it shows that the polylactic acid blow-molded product prepared in this example has significant resistance to physical aging, and there is no brittle phenomenon caused by physical aging, but the formation of polylactic acid sub- stable phase.

Example 2:

Take polylactic acid with a weight-average molecular weight of 300,000 and a molar content of L optical isomers of 95% and dry it with hot air. The drying temperature is 95±2° C., the drying time is 8 hours, and the water content is 45 ppm; The material is extruded through a screw extrusion equipment to obtain a polylactic acid melt, and the screw temperature is 230 °C; the polylactic acid melt is directly input into the split mold for blow molding, the blowing temperature is 115 °C, and the blowing stretch ratio is 2 times; Enter the rapid cooling device to obtain a blow-molded product with a closed or open cavity structure, the quenching rate is 3°C/second, and the quenching time is 30 seconds; further, the polylactic acid blow-molded product is placed in a pressure tank for pressurization and constant temperature. Treatment, the pressure in the pressure tank is 1.1 standard atmospheres, and the temperature is 87 °C; after that, the temperature is lowered to room temperature at a cooling rate of 10 °C/min, and then the pressure is relieved at a pressure relief rate of 1 standard atmosphere/minute to 1 standard atmosphere. Under the following conditions, a polylactic acid blow-molded product with a closed or open cavity structure and a more stable structure is produced; then the polylactic acid blow-molded product is sterilized, packaged and stored below its glass transition temperature _Tg . After testing, the crystallinity of the polylactic acid blow-molded product before storage was 45%; the crystallinity of the polylactic acid blow-molded product after storage at 30±5°C for half a year basically did not change. Before storage, the polylactic acid blow-molded product showed a characteristic peak at 921cm ^-1 ; the polylactic acid blow-molded product after storage at 30±5°C for half a year also showed a characteristic peak at 918cm ^-1 , indicating the formation of polylactic acid metastable phase. The stable phase content is 35%. The glass transition temperature of polylactic acid blow-molded products before storage is 60°C, and there is almost no endothermic peak near the glass transition temperature; the polylactic acid blow-molded products stored at 30±5°C for half a year are near the glass transition temperature. A clear endothermic peak appeared. In addition, the blowing direction (radial) yield strength of the polylactic acid blow-molded product before storage was 73 MPa, and the elongation at break was 58%; the blow-molding direction ( The radial yield strength is 74MPa, and the elongation at break is 61%; it shows that the polylactic acid blow-molded product prepared in this example has remarkable resistance to physical aging, and there is no brittle phenomenon caused by physical aging, but the formation of polylactic acid sub- stable phase.

Example 3:

Take polylactic acid with a weight-average molecular weight of 80,000 and a molar content of L optical isomers of 95% and dry it with hot air. The drying temperature is 95±2° C., the drying time is 8 hours, and the water content is 43 ppm; The material is extruded through a screw extrusion equipment to obtain a polylactic acid melt, and the screw temperature is 170 ° C; Enter the rapid cooling device to obtain a blow-molded product with a closed or open cavity structure, the quenching rate is 500°C/second, and the quenching time is 0.1 second; further place the polylactic acid blow-molded product in a pressure tank for pressurization and constant temperature. Treatment, the pressure in the pressure tank is 1.5 standard atmospheres, and the temperature is 67°C; then the temperature is lowered to room temperature at a cooling rate of 10°C/min, and then the pressure is relieved at a pressure relief rate of 1 standard atmosphere/minute to 1 standard atmosphere. Under the following conditions, a polylactic acid blow-molded product with a closed or open cavity structure and a more stable structure is produced; then the polylactic acid blow-molded product is sterilized, packaged and stored below its glass transition temperature _Tg . After testing, the crystallinity of the polylactic acid blow-molded product before storage was 60%; the crystallinity of the polylactic acid blow-molded product after storage at 30±5°C for half a year basically did not change. Before storage, the polylactic acid blow-molded product showed a characteristic peak at 921cm ^-1 ; the polylactic acid blow-molded product after storage at 30±5°C for half a year also showed a characteristic peak at 918cm ^-1 , indicating the formation of polylactic acid metastable phase. The stable phase content is 15%. The glass transition temperature of polylactic acid blow-molded products before storage is 54°C, and there is almost no endothermic peak near the glass transition temperature; the polylactic acid blow-molded products stored at 30±5°C for half a year are near the glass transition temperature. A clear endothermic peak appeared. In addition, the blowing direction (radial) yield strength of the PLA blow-molded product before storage was 42 MPa, and the elongation at break was 60%; the blow-molding direction ( The radial) yield strength is 46MPa, and the elongation at break is 56%, as shown in Figure 1; it shows that the polylactic acid blow-molded product prepared in this example has significant resistance to physical aging, and there is no brittleness caused by physical aging. The polylactic acid metastable phase is formed.

Example 4:

Take polylactic acid with a weight-average molecular weight of 80,000 and a molar content of L optical isomers of 99% for hot air drying, the drying temperature is 95 ± 2 ° C, the drying time is 8 hours, and the water content is 52 ppm; The material is extruded through a screw extrusion equipment to obtain a polylactic acid melt, and the screw temperature is 175 ° C; Enter the rapid cooling device to obtain a blow-molded product with a closed or open cavity structure, the quenching rate is 800°C/second, and the quenching time is 0.1 second; further, the polylactic acid blow-molded product is placed in a pressure tank for pressurization and constant temperature. Treatment, the pressure in the pressure tank is 1.5 standard atmospheres, and the temperature is 65°C; then the temperature is lowered to room temperature at a cooling rate of 10°C/min, and then the pressure is relieved at a pressure relief rate of 1 standard atmosphere/minute to 1 standard atmosphere. Under the following conditions, a polylactic acid blow-molded product with a closed or open cavity structure and a more stable structure is produced; then the polylactic acid blow-molded product is sterilized, packaged and stored below its glass transition temperature _Tg . After testing, the crystallinity of the polylactic acid blow-molded product before storage was 85%; the crystallinity of the polylactic acid blow-molded product after storage at 30±5°C for half a year basically did not change. Before storage, the polylactic acid blow-molded product showed a characteristic peak at 921cm ^-1 ; the polylactic acid blow-molded product after storage at 30±5°C for half a year also showed a characteristic peak at 918cm ^-1 , indicating the formation of polylactic acid metastable phase. The stable phase content is 5%. The glass transition temperature of polylactic acid blow-molded products before storage is 56°C, and there is almost no endothermic peak near the glass transition temperature; the polylactic acid blow-molded products stored at 30±5°C for half a year are near the glass transition temperature. A clear endothermic peak appeared. In addition, the blowing direction (radial) yield strength of the polylactic acid blow-molded product before storage was 42 MPa, and the elongation at break was 18%; the blow-molding direction ( The radial) yield strength is 43MPa, and the elongation at break is 21%; it shows that the polylactic acid blow-molded product prepared in this example has remarkable resistance to physical aging, and there is no brittle phenomenon caused by physical aging, but the formation of polylactic acid sub- stable phase.

Example 5:

Take polylactic acid with a weight-average molecular weight of 80,000 and a molar content of L optical isomers of 85% for hot air drying, the drying temperature is 95 ± 2 ° C, the drying time is 8 hours, and the water content is 43 ppm; The material is extruded through screw extrusion equipment to obtain polylactic acid melt, and the screw temperature is 150 °C; the polylactic acid melt is directly input into the split mold for blow molding, the blowing temperature is 85 °C, and the blowing stretch ratio is 6 times; Enter the rapid cooling device to obtain a blow-molded product with a closed or open cavity structure, the quenching rate is 600°C/second, and the quenching time is 0.1 second; further, the polylactic acid blow-molded product is placed in a pressure tank for pressurization and constant temperature. For treatment, the pressure in the pressure tank is 1.5 standard atmospheres, and the temperature is 70°C; then the temperature is lowered to room temperature at a cooling rate of 10°C/min, and then the pressure is relieved to 1 standard atmosphere at a pressure relief rate of 1 standard atmosphere/minute. Under the following conditions, a polylactic acid blow-molded product with a closed or open cavity structure and a more stable structure is produced; then the polylactic acid blow-molded product is sterilized, packaged and stored below its glass transition temperature _Tg . After testing, the crystallinity of the polylactic acid blow-molded product before storage was 0%; the crystallinity of the polylactic acid blow-molded product after storage at 30±5°C for half a year basically did not change. Before storage, the polylactic acid blow-molded product did not show a characteristic peak of crystallization at 921cm ^-1 ; after storage at 30±5°C for half a year, the polylactic acid blow-molded product showed a characteristic peak at 918cm ^-1 , indicating the formation of polylactic acid metastable phase. The stable phase content is 5%. The glass transition temperature of polylactic acid blow-molded products before storage is 52°C, and there is almost no endothermic peak near the glass transition temperature; the polylactic acid blow-molded products stored at 30±5°C for half a year are near the glass transition temperature. A clear endothermic peak appeared. In addition, the enthalpy of the endothermic peak near the glass transition temperature of the PLA blow-molded product after storage at 30±5 °C for half a year does not depend on the DSC heating rate, indicating that the above endothermic peak is the structural transition of the polylactic acid metastable phase , rather than the enthalpy relaxation phenomenon characteristic of physical aging. In addition, the blowing direction (radial) yield strength of the polylactic acid blow-molded product before storage was 28MPa, and the elongation at break was 195%; the blow-molding direction ( The radial) yield strength is 31MPa, and the elongation at break is 203%; it shows that the polylactic acid blow-molded product prepared in this example has remarkable resistance to physical aging, and there is no brittle phenomenon caused by physical aging, but the formation of polylactic acid sub- stable phase.

Example 6:

Take polylactic acid with a weight-average molecular weight of 500,000 and a molar content of L optical isomers of 93% for hot air drying, the drying temperature is 95 ± 2 ° C, the drying time is 8 hours, and the water content is 43 ppm; The material is extruded through a screw extrusion equipment to obtain a polylactic acid melt, and the screw temperature is 255 °C; the polylactic acid melt is directly input into the split mold for blow molding, the blowing temperature is 145 °C, and the blowing stretch ratio is 3 times; Enter the rapid cooling device to obtain a blow-molded product with a closed or open cavity structure, the quenching rate is 2°C/second, and the quenching time is 59 seconds; further, the polylactic acid blow-molded product is placed in a pressure tank for pressurization and constant temperature. Treatment, the pressure in the pressure tank is 1.05 standard atmospheres, and the temperature is 90 °C; then the temperature is lowered to room temperature at a cooling rate of 10 °C/min, and then the pressure is released at a pressure relief rate of 1 standard atmosphere/minute to 1 standard atmosphere. Under the following conditions, a polylactic acid blow-molded product with a closed or open cavity structure and a more stable structure is produced; then the polylactic acid blow-molded product is sterilized, packaged and stored below its glass transition temperature _Tg . After testing, the crystallinity of the polylactic acid blow-molded product before storage was 35%; the crystallinity of the polylactic acid blow-molded product after storage at 30±5°C for half a year basically did not change. Before storage, the polylactic acid blow-molded product showed a characteristic peak at 921cm ^-1 ; the polylactic acid blow-molded product after storage at 30±5°C for half a year also showed a characteristic peak at 918cm ^-1 , indicating the formation of polylactic acid metastable phase. The stable phase content is 15%. The glass transition temperature of polylactic acid blow-molded products before storage is 65 °C, and there is almost no endothermic peak near the glass transition temperature; the polylactic acid blow molded products stored at 30±5 °C for half a year are near the glass transition temperature. A clear endothermic peak appeared. In addition, the blowing direction (radial) yield strength of the polylactic acid blow-molded product before storage was 94 MPa, and the elongation at break was 55%; the blow-molding direction ( The radial) yield strength is 95MPa, and the elongation at break is 58%; it shows that the polylactic acid blow-molded product prepared in this example has significant resistance to physical aging, and there is no brittle phenomenon caused by physical aging, but the formation of polylactic acid sub- stable phase.

Example 7:

Take polylactic acid with a weight-average molecular weight of 500,000 and a molar content of L optical isomers of 99% for hot air drying, the drying temperature is 95 ± 2 ° C, the drying time is 8 hours, and the water content is 33 ppm; The material is extruded through a screw extrusion equipment to obtain a polylactic acid melt, and the screw temperature is 270 ° C; Enter the rapid cooling device to obtain a blow-molded product with a closed or open cavity structure, the quenching rate is 2°C/second, and the quenching time is 40 seconds; further, the polylactic acid blow-molded product is placed in a pressure tank for pressurization and constant temperature. Treatment, the pressure in the pressure tank is 1.05 standard atmospheres, and the temperature is 88°C; then the temperature is lowered to room temperature at a cooling rate of 10°C/min, and then the pressure is relieved at a pressure relief rate of 1 standard atmosphere/minute to 1 standard atmosphere. Under the following conditions, a polylactic acid blow-molded product with a closed or open cavity structure and a more stable structure is produced; then the polylactic acid blow-molded product is sterilized, packaged and stored below its glass transition temperature _Tg . After testing, the crystallinity of the polylactic acid blow-molded product before storage was 20%; the crystallinity of the polylactic acid blow-molded product after storage at 30±5°C for half a year basically did not change. Before storage, the polylactic acid blow-molded product showed a characteristic peak at 921cm ^-1 ; the polylactic acid blow-molded product after storage at 30±5°C for half a year also showed a characteristic peak at 918cm ^-1 , indicating the formation of polylactic acid metastable phase. The stable phase content is 5%. The glass transition temperature of polylactic acid blow-molded products before storage is 62°C, and there is almost no endothermic peak near the glass transition temperature; the polylactic acid blow-molded products stored at 30±5°C for half a year are near the glass transition temperature. A clear endothermic peak appeared. In addition, the blowing direction (radial) yield strength of the polylactic acid blow-molded product before storage was 83MPa, and the elongation at break was 48%; The radial) yield strength is 75MPa, and the elongation at break is 47%; it shows that the polylactic acid blow-molded product prepared in this example has significant resistance to physical aging, and there is no brittle phenomenon caused by physical aging, but the formation of polylactic acid sub- stable phase.

Example 8:

Take polylactic acid with a weight-average molecular weight of 500,000 and an L optical isomer molar content of 85% and dry it with hot air. The drying temperature is 95±2° C., the drying time is 8 hours, and the water content is 43 ppm; The material is extruded through screw extrusion equipment to obtain polylactic acid melt, and the screw temperature is 250 °C; the polylactic acid melt is directly input into the split mold for blow molding, the blowing temperature is 125 °C, and the blowing stretch ratio is 2 times; Enter the rapid cooling device to obtain a blow-molded product with a closed or open cavity structure, the quenching rate is 3°C/second, and the quenching time is 30 seconds; further, the polylactic acid blow-molded product is placed in a pressure tank for pressurization and constant temperature. Treatment, the pressure in the pressure tank is 1.05 standard atmospheres, and the temperature is 95 °C; after that, the temperature is lowered to room temperature at a cooling rate of 10 °C/min, and then the pressure is relieved at a pressure relief rate of 1 standard atmosphere/minute to 1 standard atmosphere. Under the following conditions, a polylactic acid blow-molded product with a closed or open cavity structure and a more stable structure is produced; then the polylactic acid blow-molded product is sterilized, packaged and stored below its glass transition temperature _Tg . After testing, the crystallinity of the polylactic acid blow-molded product before storage was 0%; the crystallinity of the polylactic acid blow-molded product after storage at 30±5°C for half a year basically did not change. Before storage, the polylactic acid blow-molded product did not show a characteristic peak of crystallization at 921cm ^-1 ; after storage at 30±5°C for half a year, the polylactic acid blow-molded product showed a characteristic peak at 918cm ^-1 , indicating the formation of polylactic acid metastable phase. The stable phase content is 5%. The glass transition temperature of polylactic acid blow-molded products before storage is 59 °C, and there is almost no endothermic peak near the glass transition temperature; the polylactic acid blow molded products stored at 30±5 °C for half a year are near the glass transition temperature. A clear endothermic peak appeared. In addition, the enthalpy of the endothermic peak near the glass transition temperature of the PLA blow-molded product after storage at 30±5 °C for half a year does not depend on the DSC heating rate, indicating that the above endothermic peak is the structural transition of the polylactic acid metastable phase , rather than the enthalpy relaxation phenomenon characteristic of physical aging. In addition, the blowing direction (radial) yield strength of the polylactic acid blow-molded product before storage was 58MPa, and the elongation at break was 122%; the blow-molding direction ( The radial) yield strength is 56MPa, and the elongation at break is 125%; it shows that the polylactic acid blow-molded product prepared in this example has remarkable resistance to physical aging, and there is no brittle phenomenon caused by physical aging, but the formation of polylactic acid sub- stable phase.

Example 9:

Take polylactic acid with a weight-average molecular weight of 150,000 and a molar content of L optical isomers of 93% and dry it with hot air. The drying temperature is 95±2° C., the drying time is 8 hours, and the water content is 50 ppm; The material is extruded through a screw extrusion equipment to obtain a polylactic acid melt, and the screw temperature is 205 °C; the polylactic acid melt is directly input into the split mold for blow molding, the blowing temperature is 95 °C, and the blowing stretch ratio is 4 times; Enter the rapid cooling device to obtain a blow-molded product with a closed or open cavity structure, the quenching rate is 15°C/sec, and the quenching time is 5 seconds; further, the polylactic acid blow-molded product is placed in a pressure tank for pressurization and constant temperature. Treatment, the pressure in the pressure tank is 1.3 standard atmospheres, and the temperature is 73°C; then the temperature is lowered to room temperature at a cooling rate of 10°C/min, and then the pressure is relieved at a pressure relief rate of 1 standard atmosphere/minute to 1 standard atmosphere. Under the following conditions, a polylactic acid blow-molded product with a closed or open cavity structure and a more stable structure is produced; then the polylactic acid blow-molded product is sterilized, packaged and stored below its glass transition temperature _Tg . After testing, the crystallinity of the polylactic acid blow-molded product before storage was 15%; the crystallinity of the polylactic acid blow-molded product after storage at 30±5°C for half a year basically did not change. Before storage, the polylactic acid blow-molded product showed a characteristic peak at 921cm ^-1 ; the polylactic acid blow-molded product after storage at 30±5°C for half a year also showed a characteristic peak at 918cm ^-1 , indicating the formation of polylactic acid metastable phase. The stable phase content is 75%. The glass transition temperature of polylactic acid blow-molded products before storage is 54°C, and there is almost no endothermic peak near the glass transition temperature; the polylactic acid blow-molded products stored at 30±5°C for half a year are near the glass transition temperature. A clear endothermic peak appeared. In addition, the enthalpy of the endothermic peak near the glass transition temperature of the PLA blow-molded product after storage at 30±5 °C for half a year does not depend on the DSC heating rate, indicating that the above endothermic peak is the structural transition of the polylactic acid metastable phase , rather than the enthalpy relaxation phenomenon characteristic of physical aging. In addition, the blowing direction (radial) yield strength of the polylactic acid blow-molded product before storage was 53 MPa, and the elongation at break was 68%; the blow-molding direction ( The radial yield strength is 55MPa, and the elongation at break is 66%; it shows that the polylactic acid blow-molded product prepared in this example has significant resistance to physical aging, and there is no brittle phenomenon caused by physical aging, but the formation of polylactic acid sub- stable phase.

Example 10:

Take polylactic acid with a weight-average molecular weight of 300,000 and a molar content of L optical isomers of 99% for hot air drying, the drying temperature is 95 ± 2 ° C, the drying time is 8 hours, and the water content is 44 ppm; The material is extruded through a screw extrusion equipment to obtain a polylactic acid melt, and the screw temperature is 220 ° C; Enter the rapid cooling device to obtain a blow-molded product with a closed or open cavity structure, the quenching rate is 3°C/second, and the quenching time is 30 seconds; further, the polylactic acid blow-molded product is placed in a pressure tank for pressurization and constant temperature. Treatment, the pressure in the pressure tank is 1.15 standard atmospheres, and the temperature is 82 °C; then the temperature is lowered to room temperature at a cooling rate of 10 °C/min, and then the pressure is released at a pressure relief rate of 1 standard atmosphere/minute to 1 standard atmosphere. Under the following conditions, a polylactic acid blow-molded product with a closed or open cavity structure and a more stable structure is produced; then the polylactic acid blow-molded product is sterilized, packaged and stored below its glass transition temperature _Tg . After testing, the crystallinity of the polylactic acid blow-molded product before storage was 60%; the crystallinity of the polylactic acid blow-molded product after storage at 30±5°C for half a year basically did not change. Before storage, the polylactic acid blow-molded product showed a characteristic peak at 921cm ^-1 ; the polylactic acid blow-molded product after storage at 30±5°C for half a year also showed a characteristic peak at 918cm ^-1 , indicating the formation of polylactic acid metastable phase. The stable phase content is 30%. The glass transition temperature of polylactic acid blow-molded products before storage is 62°C, and there is almost no endothermic peak near the glass transition temperature; the polylactic acid blow-molded products stored at 30±5°C for half a year are near the glass transition temperature. A clear endothermic peak appeared. In addition, the blowing direction (radial) yield strength of the polylactic acid blow-molded product before storage was 77MPa, and the elongation at break was 36%; the blow-molding direction ( The radial yield strength is 80MPa, and the elongation at break is 37%; it shows that the polylactic acid blow-molded product prepared in this example has remarkable resistance to physical aging, and there is no brittle phenomenon caused by physical aging, but the formation of polylactic acid sub- stable phase.

Example 11:

Take polylactic acid with a weight-average molecular weight of 150,000 and a molar content of L optical isomers of 95% for hot air drying, the drying temperature is 95 ± 2 ° C, the drying time is 8 hours, and the water content is 50 ppm; The material is extruded through a screw extrusion equipment to obtain a polylactic acid melt, and the screw temperature is 190 °C; the polylactic acid melt is first stretched axially, the stretching temperature is 95 °C, and the stretching ratio is 3 times; Blow molding, the blowing temperature is 95°C, and the blowing stretch ratio is 3 times; immediately enter the rapid cooling device to obtain a blow-molded product with a closed or open cavity structure, the quenching rate is 15°C/sec, and the quenching time is 5 seconds; the polylactic acid blow-molded product is further placed in a pressure tank for pressurization and constant temperature treatment. The pressure in the pressure tank is 1.3 standard atmospheres and the temperature is 82 °C; At room temperature, the pressure is released to 1 standard atmosphere at a pressure release rate of 1 standard atmosphere per minute to obtain a polylactic acid blow-molded product with a closed or open cavity structure and a more stable structure; then the polylactic acid is blown Plastic products should be sterilized, packaged and stored below their glass transition temperature _Tg . After testing, the crystallinity of the polylactic acid blow-molded product before storage was 56%; the crystallinity of the polylactic acid blow-molded product after storage at 30±5°C for half a year basically did not change. Before storage, the polylactic acid blow-molded product showed a characteristic peak at 921cm ^-1 ; the polylactic acid blow-molded product after storage at 30±5°C for half a year also showed a characteristic peak at 918cm ^-1 , indicating the formation of polylactic acid metastable phase. The stable phase content was 22%. The glass transition temperature of polylactic acid blow-molded products before storage is 57°C, and there is almost no endothermic peak near the glass transition temperature; the polylactic acid blow-molded products stored at 30±5°C for half a year are near the glass transition temperature. A clear endothermic peak appeared. In addition, the blowing direction (radial) yield strength of the PLA blow-molded product before storage was 64MPa, and the elongation at break was 43%; the blow-molding direction ( The radial yield strength is 62MPa, and the elongation at break is 45%; it shows that the polylactic acid blow-molded products prepared in this example have remarkable resistance to physical aging, and there is no brittle phenomenon caused by physical aging, but the formation of polylactic acid sub- stable phase.

Example 12:

Take polylactic acid with a weight-average molecular weight of 150,000 and a molar content of L optical isomers of 95% for hot air drying, the drying temperature is 95 ± 2 ° C, the drying time is 8 hours, and the water content is 50 ppm; The material is extruded through a screw extrusion equipment, and further injection molded into a polylactic acid parison. The screw temperature is 190 °C, and the temperature in the injection mold is 95 °C. After that, it is rapidly quenched to room temperature at a quenching rate of 15 °C/sec. The quenching time is 5 seconds; the polylactic acid preform is fully preheated and directly input into the split mold for blow molding, the blowing temperature is 95 ° C, and the blowing stretch ratio is 3 times; immediately enter the rapid cooling device to obtain a closed or open mold. For blow-molded products with a chamber structure, the quenching rate is 15°C/sec, and the quenching time is 5 seconds; the polylactic acid blow-molded products are further placed in a pressure tank for pressurization and constant temperature treatment, and the pressure in the pressure tank is 1.2 Standard atmospheric pressure, the temperature is 75 ℃; after that, the temperature is lowered to room temperature at a cooling rate of 10 ℃/minute, and then the pressure is released to 1 standard atmosphere at a pressure release rate of 1 standard atmosphere per minute, to obtain a closed or open cavity. Cell structure and polylactic acid blow molding products with more stable structure. ; Then the polylactic acid blow-molded product is sterilized, packaged and stored below its glass transition temperature T _g . After testing, the crystallinity of the polylactic acid blow-molded product before storage was 41%; the crystallinity of the polylactic acid blow-molded product after storage at 30±5°C for half a year basically did not change. Before storage, the polylactic acid blow-molded product showed a characteristic peak at 921cm ^-1 ; the polylactic acid blow-molded product after storage at 30±5°C for half a year also showed a characteristic peak at 918cm ^-1 , indicating the formation of polylactic acid metastable phase. The stable phase content is 38%. The glass transition temperature of polylactic acid blow-molded products before storage is 55 °C, and there is almost no endothermic peak near the glass transition temperature; the polylactic acid blow molded products stored at 30±5 °C for half a year are near the glass transition temperature. A clear endothermic peak appeared. In addition, the blowing direction (radial) yield strength of the PLA blow-molded product before storage was 57MPa, and the elongation at break was 71%; the blow-molding direction ( The radial) yield strength is 59MPa, and the elongation at break is 66%; it shows that the polylactic acid blow-molded product prepared in this example has significant resistance to physical aging, and there is no brittle phenomenon caused by physical aging, but the formation of polylactic acid sub- stable phase.

Example 13:

Take polylactic acid with a weight-average molecular weight of 150,000 and a molar content of L optical isomers of 95% for hot air drying, the drying temperature is 95 ± 2 ° C, the drying time is 8 hours, and the water content is 50 ppm; The material is extruded through a screw extrusion equipment, and further injection molded into a polylactic acid parison. The screw temperature is 190 °C, and the temperature in the injection mold is 95 °C. After that, it is rapidly quenched to room temperature at a quenching rate of 15 °C/sec. The quenching time is 5 seconds; the polylactic acid parison is first stretched along the axial direction, the stretching temperature is 95 ° C, and the stretching ratio is 3 times; The plastic stretching ratio is 3 times; immediately enter the rapid cooling device to obtain a blow-molded product with a closed or open cavity structure, the quenching rate is 15°C/second, and the quenching time is 5 seconds; further place the polylactic acid blow-molded product into Pressurization and constant temperature treatment are carried out in a pressure tank. The pressure in the pressure tank is 1.2 standard atmospheres and the temperature is 78°C; then the temperature is lowered to room temperature at a cooling rate of 10°C/min, and then discharged at a rate of 1 standard atmosphere/min. The pressure rate is depressurized to 1 standard atmosphere, and a polylactic acid blow-molded product with a closed or open cavity structure and a more stable structure is obtained; then the polylactic acid blow-molded product is sterilized below its glass transition temperature T _g packaging and storage. After testing, the crystallinity of the polylactic acid blow-molded product before storage was 55%; the crystallinity of the polylactic acid blow-molded product after storage at 30±5°C for half a year basically did not change. Before storage, the polylactic acid blow-molded product showed a characteristic peak at 921cm ^-1 ; the polylactic acid blow-molded product after storage at 30±5°C for half a year also showed a characteristic peak at 918cm ^-1 , indicating the formation of polylactic acid metastable phase. The stable phase content was 19%. The glass transition temperature of polylactic acid blow-molded products before storage is 58°C, and there is almost no endothermic peak near the glass transition temperature; the polylactic acid blow-molded products stored at 30±5°C for half a year are near the glass transition temperature. A clear endothermic peak appeared. In addition, the blowing direction (radial) yield strength of the polylactic acid blow-molded product before storage was 62 MPa, and the elongation at break was 49%; the blow-molding direction ( The radial yield strength is 63MPa, and the elongation at break is 46%; it shows that the polylactic acid blow-molded product prepared in this example has remarkable resistance to physical aging, and there is no brittle phenomenon caused by physical aging, but the formation of polylactic acid sub- stable phase.

Comparative Example 1:

Take polylactic acid with a weight-average molecular weight of 150,000 and a molar content of L optical isomers of 95% for hot air drying, the drying temperature is 95 ± 2 ° C, the drying time is 8 hours, and the water content is 50 ppm; The material is extruded through a screw extrusion equipment to obtain a polylactic acid melt, and the screw temperature is 190 °C; the polylactic acid melt is directly input into the split mold for blow molding, the blowing temperature is 95 °C, and the blowing stretch ratio is 3 times; Quickly quenched to room temperature at a quenching rate of 0.5°C/second, and the quenching time was 120 seconds, to obtain a blow-molded product with a closed or open cavity structure; further place the polylactic acid blow-molded product in a pressure tank for pressurization , constant temperature treatment, the pressure in the pressure tank is 1.2 standard atmospheres, and the temperature is 78 °C; after that, the temperature is lowered to room temperature at a cooling rate of 10 °C/minute, and then the pressure is released at a pressure relief rate of 1 standard atmosphere/minute to 1 Under standard atmospheric pressure, polylactic acid blow-molded products with closed or open cell structures and more stable structures are produced; then the polylactic acid blow-molded products are sterilized, packaged and stored below their glass transition temperature _Tg . After testing, the crystallinity of the polylactic acid blow-molded product before storage was 42%; the crystallinity of the polylactic acid blow-molded product after storage at 30±5°C for half a year basically did not change. The polylactic acid blow-molded product before storage showed a characteristic peak at 921cm ^-1 ; the polylactic acid blow-molded product after storage at 30±5°C for half a year also showed a characteristic peak at 918cm ^-1 , indicating the formation of a polylactic acid metastable phase. The glass transition temperature of polylactic acid blow-molded products before storage is 54°C, and there is almost no endothermic peak near the glass transition temperature; the polylactic acid blow-molded products stored at 30±5°C for half a year are near the glass transition temperature. A clear endothermic peak appeared. In addition, the blowing direction (radial) yield strength of the polylactic acid blow-molded product before storage was 48MPa, and the elongation at break was 63%; the blow-molding direction ( The radial yield strength is 52MPa, and the elongation at break is 14%, as shown in Figure 2; it shows that the polylactic acid blow-molded product prepared by this comparative example has obvious physical aging leading to a decrease in toughness, and does not have physical aging resistance.

Comparative Example 2:

Take the polylactic acid with a weight-average molecular weight of 300,000 and an L optical isomer molar content of 95% and dry it with hot air. The drying temperature is 95±2° C., the drying time is 8 hours, and the water content is 43 ppm; The material is extruded through a screw extrusion equipment to obtain a polylactic acid melt, and the screw temperature is 230 °C; the polylactic acid melt is directly input into the split mold for blow molding, the blowing temperature is 115 °C, and the blowing stretch ratio is 2 times; further , release the blowing gas in the split mold, and heat the blow-molded products in the mold at a constant temperature to improve heat resistance; immediately enter the rapid cooling device to obtain blow-molded products with a closed or open cavity structure, and the quenching rate is 3 ℃ / sec , the quenching time is 30 seconds; the polylactic acid blow-molded product is further placed in a pressure tank for pressurization and constant temperature treatment, the pressure in the pressure tank is 1.1 standard atmospheric pressure, and the temperature is 84 ° C; The cooling rate was reduced to room temperature, and then the pressure was relieved to 1 standard atmosphere at a pressure relief rate of 1 standard atmosphere per minute to obtain a polylactic acid blow molded product with a closed or open cavity structure and a more stable structure; The polylactic acid blow-molded product is sterilized, packaged and stored below its glass transition temperature _Tg . After testing, the crystallinity of the polylactic acid blow-molded product before storage was 45%; the crystallinity of the polylactic acid blow-molded product after storage at 30±5°C for half a year basically did not change. The polylactic acid blow-molded product before storage showed a characteristic peak of crystallization at 921cm ^-1 ; the polylactic acid blow-molded product after storage at 30±5°C for half a year had no characteristic peak at 918cm ^-1 , indicating that no polylactic acid metastable phase was formed. The glass transition temperature of polylactic acid blow-molded products before storage is 60°C, and there is almost no endothermic peak near the glass transition temperature; the polylactic acid blow-molded products stored at 30±5°C for half a year are near the glass transition temperature. A clear endothermic peak appeared. In addition, the yield strength of the polylactic acid blow-molded product before storage was 69MPa, and the elongation at break was 55%; the yield strength of the polylactic acid blow-molded product after storage at 30±5°C for half a year was 67MPa, and the elongation at break was 6 %; indicates that the polylactic acid blow-molded product prepared by the comparative example has obvious physical aging leading to embrittlement, and does not have physical aging resistance.

Comparative Example 3:

Take the polylactic acid with a weight-average molecular weight of 80,000 and a molar content of L optical isomers of 90% for hot air drying, the drying temperature is 95 ± 2 ° C, the drying time is 8 hours, and the water content is 52 ppm; The material is extruded through a screw extrusion equipment to obtain a polylactic acid melt, and the screw temperature is 175 ° C; Enter the rapid cooling device to obtain a blow-molded product with a closed or open cavity structure, the quenching rate is 1500°C/second, and the quenching time is 0.1 second; further, the polylactic acid blow-molded product is placed in a pressure tank for pressurization and constant temperature. Treatment, the pressure in the pressure tank is 1.5 standard atmospheres, and the temperature is 65°C; then the temperature is lowered to room temperature at a cooling rate of 10°C/min, and then the pressure is relieved at a pressure relief rate of 1 standard atmosphere/minute to 1 standard atmosphere. Under the following conditions, a polylactic acid blow-molded product with a closed or open cavity structure and a more stable structure is produced; then the polylactic acid blow-molded product is sterilized, packaged and stored below its glass transition temperature _Tg . After testing, the crystallinity of the polylactic acid blow-molded product before storage was 0%; the crystallinity of the polylactic acid blow-molded product after storage at 30±5°C for half a year basically did not change. Before storage, the polylactic acid blow-molded product did not show a characteristic peak of crystallization at 921cm ^-1 ; the polylactic acid blow-molded product after storage at 30±5°C for half a year did not show a characteristic peak at 918cm ^-1 , indicating that no polylactic acid metastable phase was formed. . The glass transition temperature of polylactic acid blow-molded products before storage is 52°C, and there is almost no endothermic peak near the glass transition temperature; the polylactic acid blow-molded products stored at 30±5°C for half a year are near the glass transition temperature. A clear endothermic peak appeared. In addition, the enthalpy value of the endothermic peak near the glass transition temperature of the PLA blow-molded product after storage at 30±5 °C for half a year depends on the DSC heating rate, indicating that the above endothermic peak is a unique enthalpy relaxation phenomenon of physical aging. In addition, the yield strength of the polylactic acid blow-molded product before storage was 41MPa, and the elongation at break was 210%; the yield strength of the polylactic acid blow-molded product after storage at 30±5°C for half a year was 43MPa, and the elongation at break was 6 %; indicates that the polylactic acid blow-molded product prepared by the comparative example has obvious physical aging leading to embrittlement, and does not have physical aging resistance.

In addition, the inventors of the present application have also carried out experiments with other raw materials, technological operations and technological conditions mentioned in this specification with reference to the foregoing examples, and have obtained relatively ideal results.

Example 14

The physical aging-resistant polylactic acid blow molded products obtained in the above Examples 1-13 of the present invention can be processed into desired container products according to the needs of practical applications and in a manner known in the art. E.g:

The physical aging-resistant polylactic acid blow-molded products obtained in the above Examples 1-13 can be processed into drinking water buckets, milk buckets, beverage bottles, milk bottles, cosmetic packaging bottles or medical hanging bottles, etc. The strength of the existing polylactic acid blow molding products has excellent physical aging resistance at the same time, and can maintain the stability of size and performance in the storage and logistics stage.

The aspects, embodiments, features, and examples of the present invention are to be considered in all respects illustrative and not intended to limit 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 sections in this application is not meant to limit the invention; each section is applicable to any aspect, embodiment or feature of the invention.

Throughout this specification, where a composition is described as having, comprising or including particular components, or where a process is described as having, comprising or including particular process steps, it is contemplated that the compositions of the present teachings will also be substantially The above consists of or consists of the recited components, and the processes taught herein also consist essentially of, or consist of, the recited process steps.

The use of the terms "include, includes, including," "have, has, or having" should generally be understood to be open-ended and not limiting unless specifically stated otherwise.

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

Although the present invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions and/or additions and the like may be made without departing from the spirit and scope of the invention Effects replace elements of the described embodiments. 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 not intended herein to limit the invention to the particular embodiments disclosed for carrying out the invention, but it is intended that this invention include all embodiments falling within the scope of the appended claims. Furthermore, unless specifically stated, any use of the terms first, second, etc. does not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.

Claims (23)

1. A polylactic acid blow-molded product with resistance to physical aging, characterized in that: the polylactic acid blow-molded product has a closed or open-chamber structure, the density is above 1.24 g/cm ³ , and the polylactic acid blow-molded product is The product contains 0wt%-85wt% crystalline phase and 15wt%-100wt% amorphous phase; the amorphous phase contains 5wt%-75wt% metastable phase, and the characteristic peak of the metastable phase in the infrared spectrum appears at 918 cm ⁻¹ , after the polylactic acid blow-molded product is stored below the glass transition temperature for a sufficient time, the differential scanning calorimetry DSC curve of the polylactic acid blow-molded product shows an enthalpy immediately after the glass transition temperature. The endothermic peak with a sufficiently large value ΔH , the enthalpy value of the endothermic peak does not change with the change of the heating rate in the DSC test, and the infrared spectrum of the polylactic acid blow-molded product appears in the 918 cm ^-1 band Characteristic peak, the intensity of the characteristic peak increases with the prolongation of storage time, and the rate of change of the yield strength of the polylactic acid blow-molded product is lower than 30%, the rate of change of the elongation at break is lower than 40%, and the stress- Obvious yielding and subsequent plastic deformation zone appear on the strain curve; the sufficient time is ≥ 1 hour, and the ΔH is ≥ 1J/g; The preparation method of the physical aging-resistant polylactic acid blow-molded product includes: (1) providing dry polylactic acid or polylactic acid dry mixture, the polylactic acid has a weight-average molecular weight of 80,000 to 500,000, and the molar content of the L optical isomer is 85% to 99%; (2) melting and extruding the dried polylactic acid or polylactic acid dry mixture through a screw extrusion equipment to obtain a polylactic acid melt, wherein the screw temperature is 150-270 °C; (3) Input the polylactic acid melt into the split-molding blow molding equipment for blow molding, the blowing temperature is equal to or greater than the glass transition temperature but lower than the melting point, and the blowing stretch ratio in the radial direction is 1-6 times, and then rapidly quenched to room temperature at a quenching rate of 2 to 800°C/second, and the quenching time was 0.1 to 59 seconds, to obtain a polylactic acid blow-molded product with a closed or open cavity structure; (4) Place the polylactic acid blow-molded product with a closed or open chamber structure obtained in step (3) in a pressurized container, and perform pressurization and constant temperature treatment. The pressure in the pressurized container is above 1 standard atmosphere, and the temperature is Above the glass transition temperature but below the cold crystallization temperature, and then at a selected cooling rate to room temperature, and then at a selected pressure relief rate to 1 standard atmosphere, a closed or open chamber is prepared. Structure and polylactic acid blow molding products with more stable structure. 2 . The polylactic acid blow-molded product with resistance to physical aging according to claim 1 , wherein the crystalline phase content of the polylactic acid blow-molded product is 20wt% to 70wt%, and the amorphous phase is metastable. 3 . The content of the phase is 10 wt % to 50 wt %. 3 . The polylactic acid blow-molded product with resistance to physical aging according to claim 2 , wherein the crystalline phase content of the polylactic acid blow-molded product is 30wt% to 50wt%, and the amorphous phase is metastable. 4 . The content of the phase is 20 wt % to 40 wt %. 4. The physical aging-resistant polylactic acid blow-molded product according to claim 1, wherein the polylactic acid blow-molded product further comprises a polymer, a plasticizer, a compatibilizer, a transesterifier, and a chain extender , any one or two or more of end-capping agents, flame retardants, antioxidants, lubricants, antistatic agents, antifogging agents, light stabilizers, color masterbatches, antifungal agents, antibacterial agents, and foaming agents The combination. 5 . The polylactic acid blow-molded product with resistance to physical aging according to claim 1 , wherein the polylactic acid in step (1) has a weight average molecular weight of 200,000 to 400,000, wherein the mole of L optical isomer is 200,000 to 400,000. 6 . The content is 92% to 98%. 6 . The physical aging-resistant polylactic acid blow-molded product according to claim 1 , wherein the temperature of the screw in step (2) is 180-220° C. 7 . 7 . The physical aging-resistant polylactic acid blow molded product according to claim 1 , wherein step (3) further comprises: first stretching the polylactic acid melt in the axial direction, and then feeding the halved polylactic acid melt. 8 . Mold blow molding, in which the stretching temperature in the axial direction is equal to or greater than the glass transition temperature but lower than the melting point, and the stretching ratio is 1 to 6 times. 8 . The physical aging-resistant polylactic acid blow molding product according to claim 7 , wherein the stretching temperature along the axial direction is 65-145° C. 9 . 9 . The polylactic acid blow-molded product with resistance to physical aging according to claim 1 , wherein step (3) further comprises: injecting the polylactic acid melt into a polylactic acid parison, preheating and feeding into a split Mold blow molding equipment. 10 . The physical aging-resistant polylactic acid blow-molded product according to claim 9 , wherein step (3) further comprises: injecting the polylactic acid melt into a polylactic acid parison, preheating and axially extending the polylactic acid preform. 11 . It is stretched and then fed into a split-mold blow-molding machine. 11 . The physical aging-resistant polylactic acid blow-molded product according to claim 1 , wherein in step (3), the blowing temperature is 65-145° C., and the blow-molding stretch ratio in the radial direction is 2-5. 11 . times, the quenching time is 0.1 to 30 seconds. 12 . The physical aging-resistant polylactic acid blow-molded product according to claim 11 , wherein the blow-molding temperature in step (3) is 85-145° C. 13 . 13. The physical aging-resistant polylactic acid blow-molded product according to claim 1, wherein step (3) specifically includes: when the weight-average molecular weight of the polylactic acid is 80,000 to 150,000, the blowing temperature used is At 65-95°C, the blowing stretch ratio along the radial direction is 3-6 times, the quenching rate is 15-800°C/sec, and the quenching time is 0.1-5 seconds. 14. The physical aging-resistant polylactic acid blow-molded product according to claim 1, wherein step (3) specifically comprises: when the weight-average molecular weight of the polylactic acid is 150,000 to 300,000, the blowing temperature used is At 85-115°C, the blowing stretch ratio along the radial direction is 2-4 times, the quenching rate is 3-15°C/sec, and the quenching time is 5-30 seconds. 15. The physical aging-resistant polylactic acid blow-molded product according to claim 1, wherein step (3) specifically includes: when the weight-average molecular weight of polylactic acid is 300,000 to 500,000, the blowing temperature used is At 105-145°C, the blowing stretch ratio along the radial direction is 1-3 times, the quenching rate is 2-3°C/sec, and the quenching time is 30-59 seconds. 16 . The physical aging-resistant polylactic acid blow-molded product according to claim 1 , wherein the pressure in the pressurized container used in step (4) is 1.05-1.5 standard atmospheric pressure, and the temperature is 65-95° C. 17 . 17 . The physical aging-resistant polylactic acid blow-molded product according to claim 16 , wherein the pressure in the pressurized container used in step (4) is 1.2-1.4 standard atmospheric pressure, and the temperature is 75-85° C. 17 . The pressure treatment time is more than 5 seconds; wherein: when the weight average molecular weight of the polylactic acid is 80,000 to 150,000, the pressure in the pressurized container used is 1.2 to 1.5 standard atmospheric pressure, and the temperature is 65 to 78°C. 18 . The physical aging-resistant polylactic acid blow-molded product according to claim 16 , wherein the pressure in the pressurized container used in step (4) is 1.2-1.4 standard atmospheres, and the temperature is 75-85° C. 18 . The pressure treatment time is more than 5 seconds; wherein: when the weight-average molecular weight of the polylactic acid is 150,000 to 300,000, the pressure in the pressurized container used is 1.1 to 1.3 standard atmospheres, and the temperature is 73 to 87 ° C. 19 . The physical aging-resistant polylactic acid blow-molded product according to claim 16 , wherein the pressure in the pressurized container used in step (4) is 1.2-1.4 standard atmospheres, and the temperature is 75-85° C. 19 . The pressure treatment time is more than 5 seconds; wherein: when the weight-average molecular weight of the polylactic acid is 300,000 to 500,000, the pressure in the pressurized container used is 1.05 to 1.15 standard atmospheric pressure, and the temperature is 82 to 95 ° C. 20. The use of the physical aging-resistant polylactic acid blow-molded product according to any one of claims 1 to 19 in the preparation of container products. 21. The use of claim 20, wherein the container-like product comprises a bottle, can, barrel, box, box or tube. 22. The use according to claim 21, wherein the container products include drinking water buckets, milk buckets, beverage bottles, milk bottles, cosmetic packaging bottles or medical hanging bottles. 23. A method for sterilizing, packaging and storing a polylactic acid blow-molded product resistant to physical aging, characterized by comprising: providing the polylactic acid blow-molded product resistant to physical aging according to any one of claims 1 to 19, The polylactic acid blow-molded product is sterilized, packaged and stored below its glass transition temperature.

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