CN112322011B - Physical aging-resistant polylactic acid pipe and preparation method and application thereof - Google Patents

Physical aging-resistant polylactic acid pipe and preparation method and application thereof Download PDF

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CN112322011B
CN112322011B CN202011326050.0A CN202011326050A CN112322011B CN 112322011 B CN112322011 B CN 112322011B CN 202011326050 A CN202011326050 A CN 202011326050A CN 112322011 B CN112322011 B CN 112322011B
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polylactic acid
acid pipe
pipe
temperature
stretching
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CN112322011A (en
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黄威
陈鹏
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Ningbo Institute of Material Technology and Engineering of CAS
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Ningbo Institute of Material Technology and Engineering of CAS
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
    • C08L67/04—Polyesters derived from hydroxycarboxylic acids, e.g. lactones
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2201/00—Properties
    • C08L2201/08—Stabilised against heat, light or radiation or oxydation
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2203/00—Applications
    • C08L2203/18—Applications used for pipes
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2205/00—Polymer mixtures characterised by other features
    • C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
    • C08L2205/025—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure

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  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Extrusion Moulding Of Plastics Or The Like (AREA)
  • Shaping By String And By Release Of Stress In Plastics And The Like (AREA)

Abstract

The invention discloses a physical aging resistant polylactic acid pipe, a preparation method and application thereof. The polylactic acid pipe is in a hollow tubular shape, and comprises 0wt% -85 wt% of crystalline phase and 15wt% -100 wt% ofwt% amorphous phase; the amorphous phase comprises 5wt% to 75wt% of metastable phase, and the characteristic peak of the metastable phase in an infrared spectrogram appears at 918cm‑1To (3). The polylactic acid pipe has the characteristic of physical aging resistance, the yield strength and the elongation at break change rate before and after storage are small, the orientation degree is high, the obtained disposable suction pipe, medical catheter and the like not only have the strength equivalent to or superior to that of the existing polylactic acid pipe, but also have excellent physical aging resistance, the stability of size and performance can be kept at the stage of storage and logistics, and meanwhile, the preparation process is beneficial to large-scale production and has wide application prospect.

Description

Physical aging-resistant polylactic acid pipe and preparation method and application thereof
Technical Field
The invention relates to a polylactic acid material, in particular to a physical aging resistant polylactic acid pipe, a preparation method and application thereof (a disposable straw, a medical catheter and the like), belonging to the technical field of hollow pipes.
Background
With the vigorous development of the global petroleum industry, a large amount of petroleum-based polymers are made into pipes every year, and the pipes are used in the fields of industry, medical treatment, daily life and the like. The disposable plastic suction tube and the medical catheter are applied, so that the disposable plastic suction tube and the medical catheter are convenient to use and throw away, the eating and drinking life of people is greatly facilitated, and the safety of medical sanitation is improved. However, uncertainty of health safety due to precipitation of the petroleum-based resin and related additives, and "white" pollution of environment due to non-degradability of the petroleum-based resin are shadow on the wide application of the petroleum-based resin in the fields of daily diet and medical health. Therefore, the development of the bio-based degradable resin pipe is particularly necessary.
Polylactic acid has good biocompatibility and biodegradability, can be degraded into lactic acid in nature, and finally forms carbon dioxide and water through microbial decomposition, and is one of biodegradable polymers certified by the U.S. food and drug administration. Has wide application prospect in various fields such as tissue engineering, medical treatment and sanitation, flexible package, disposable suction tube and the like. Among them, medical catheters and disposable pipettes require polylactic acid tubes to have a sufficiently long mechanical property retention time (stability of mechanical properties during shelf life) to various degrees. However, numerous documents (Macromolecules2007, 40, 9664-. Among them, physical aging is a process in which a molecular segment spontaneously changes from a non-equilibrium state to an equilibrium state, and is essentially a reduction in free volume. This makes polylactic acid articles very susceptible to physical degradation during the warehouse logistics stage (shelf life) leading to sharp embrittlement of the article. However, at present, no report is found on the development of a polylactic acid pipe with physical aging resistance through process optimization.
The preparation of polylactic acid tubes has been reported in many publications, and related patents of polylactic acid straws are mainly discussed here. For example, CN 108976731 a reports a method for preparing a polylactic acid transparent straw, which increases the toughness and processability of PLA resin while maintaining high transparency of PLA resin by preferably using a small amount of polyethylene oxide of a specific molecular weight. CN 111040398A reports that aiming at the problems of poor mechanical property, low heat-resistant temperature, easy degradation, easy breeding of harmful microorganisms in the storage process and the like of the existing polylactic acid straw material, a polylactic acid/polyhydroxyalkanoate degradable straw and a preparation method thereof are provided, the patent forms a blending formula with performance advantages by compounding epoxidized soybean oil, bamboo powder and the like, and obtains the straw with excellent performance under the existing straw preparation process (extrusion and traction). CN 111410826A reports that aiming at the problems of non-lasting antibacterial property, hard and brittle performance and the like of the existing polylactic acid product, a degradable antibacterial polylactic acid environment-friendly straw and a preparation method thereof are provided. The patent has the advantages that polycaprolactone is introduced to enhance the heat resistance stability and toughness of the polylactic acid, and nano silver is used for enhancing the antibacterial property of the polylactic acid. TW 169383 048B and US 2020/0253403A 1 report an environment-friendly straw prepared by blending plant fiber powder and polylactic acid (or/and containing polybutylene succinate). Unlike conventional plastic drinking straws, the drinking straw is derived from non-petroleum based raw materials; when buried in soil, it is decomposed by microorganisms.
Although the above known technologies can prepare the polylactic acid straw, under the current technical conditions, the polylactic acid straw is strictly designed and controlled because the preparation process (melt extrusion, traction, cooling and cutting) does not start from the essence of physical aging resistance, and is easy to be physically aged in the storage logistics stage (shelf life) to cause rapid brittleness; therefore, there is a need to develop new physical aging resistant polylactic acid tube materials and methods of making the same to meet the high overall performance requirements imposed on the materials by various applications.
Disclosure of Invention
The invention mainly aims to provide a polylactic acid pipe with physical aging resistance, a preparation method and application thereof, thereby overcoming the defects in the prior art.
In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:
the embodiment of the invention provides a physical aging resistant polylactic acid pipe, which is in a hollow tubular shape, and comprises 0wt% -85 wt% of crystalline phase and 15wt% -100 wt% of amorphous phase; the amorphous phase comprises 5wt% to 75wt% of metastable phase, and the characteristic peak of the metastable phase in an infrared spectrogram appears at 918cm-1At least one of (1) and (b); more importantly, after the polylactic acid pipe is stored below the glass transition temperature for enough time, the change rate of the yield strength is lower than 30%, the change rate of the elongation at break is lower than 40%, and obvious yield and subsequent plastic deformation zones appear on a stress-strain curve.
Furthermore, the orientation degree of the polylactic acid material is 0.35-0.95.
Further, after the polylactic acid pipe is stored below the glass transition temperature for a sufficient time, an endothermic peak with an enthalpy value delta H which is sufficiently large appears in a Differential Scanning Calorimetry (DSC) curve of the polylactic acid pipe after the glass transition temperature, the enthalpy value of the endothermic peak does not change along with the change of the temperature rising rate of a DSC test, and the infrared spectrogram of the polylactic acid pipe is 918cm in length-1The bands show characteristic peaks whose intensity increases with the storage time.
The embodiment of the invention also provides a method for preparing the physical aging resistant polylactic acid pipe, which comprises the following steps:
(1) providing a dry polylactic acid or a dry mixture of polylactic acid;
(2) melting and extruding the dried polylactic acid or the dry polylactic acid mixture through screw extrusion equipment to obtain a polylactic acid melt, wherein the temperature of a screw is 150-270 ℃;
(3) and stretching the polylactic acid melt in the axial direction at the screw port, wherein the stretching temperature is equal to or more than the glass transition temperature but less than the melting point, preferably 65-145 ℃, the stretching multiple is 1-6 times, then rapidly quenching to room temperature at the quenching rate of 2-800 ℃/second, and the quenching time is 0.1-59 seconds, so as to prepare the polylactic acid pipe in the hollow tubular shape.
The embodiment of the invention also provides application of the physical aging resistant polylactic acid pipe in preparing tubular products.
Further, the embodiment of the invention also provides a tubular product made of the polylactic acid pipe resistant to physical aging.
Further, the tubular articles include, but are not limited to, straws, medical catheters, and the like.
Correspondingly, the embodiment of the invention also provides a preparation method of the tubular product, which comprises the following steps:
preparing a polylactic acid pipe material with physical aging resistance by adopting the method;
and carrying out traction and cutting treatment on the polylactic acid pipe material with the physical aging resistance to form a tubular product with required specification.
Further, the embodiment of the invention also provides a disinfection packaging and storage method of the polylactic acid pipe material with physical aging resistance, which comprises the following steps:
providing a polylactic acid pipe resistant to physical aging according to any of the preceding embodiments, and subjecting the polylactic acid pipe to a glass transition temperature TgThe packaging and storage is sterilized as follows.
Compared with the prior art, the polylactic acid pipe provided by the embodiment of the invention has the characteristic of physical aging resistance, the change rate of yield strength before and after storage is small, the change rate of elongation at break is small, and the crystallinity and the orientation degree are high, so that the obtained disposable suction pipe, medical catheter and the like not only have the strength equivalent to or superior to that of the existing polylactic acid pipe, but also have excellent physical aging resistance, can keep the stability of size and performance in the storage logistics stage, and meanwhile, the preparation process is beneficial to large-scale production and has wide application prospect.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a stress-strain curve of a polylactic acid pipe resistant to physical aging obtained in example 11 of the present invention;
FIG. 2 is a stress-strain curve of the polylactic acid pipe obtained in comparative example 1.
Detailed Description
The present invention will be more fully understood from the following detailed description. Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed embodiment.
One aspect of the embodiments of the present invention provides a polylactic acid tube with physical aging resistance, which is in a hollow tubular shape, and has a crystalline phase content of 0wt% to 85wt%, an amorphous phase content of 15wt% to 100wt%, the amorphous phase containing 5wt% to 75wt% of a metastable phase, and a characteristic peak of the metastable phase in an infrared spectrogram of 918cm-1At least one of (1) and (b); more importantly, after the polylactic acid pipe is stored below the glass transition temperature for enough time, the change rate of the yield strength is lower than 30%, the change rate of the elongation at break is lower than 40%, and obvious yield and subsequent plastic deformation zones appear on a stress-strain curve.
In some preferred embodiments, the polylactic acid pipe resistant to physical aging has a crystalline phase content of 20wt% to 70wt% and a metastable phase content of 10wt% to 50wt% in the amorphous phase.
In some more preferred embodiments, the polylactic acid pipe resistant to physical aging has a crystalline phase content of 30wt% to 50wt% and a metastable phase content of 20wt% to 40wt% in the amorphous phase.
Furthermore, the orientation degree of the polylactic acid material is 0.35-0.95, preferably 0.6-0.8.
Further, the polylactic acid pipe resistant to physical aging has the glass transition temperature (T) of polylactic acidg) After storage (shelf life) for a sufficient period of time, as measured by Differential Scanning Calorimetry (DSC), the DSC curve shows the post-glass transition temperature (post-T)g) Then, an endothermic peak having an enthalpy value (Δ H) sufficiently large and having an enthalpy value (Δ H) which does not vary with the temperature increase rate in the DSC test is generated, and the infrared spectrum thereof is within 918cm-1The bands show characteristic peaks whose intensity increases with the storage time. Wherein, the storage time is not limited; however, in general, the sufficient time is 1 hour or more. The enthalpy (Δ H) is also not limited; however, in general, the enthalpy (. DELTA.H) is 1J/g or more.
Further, the physical aging resistant polylactic acid pipe is at TgAfter storage (shelf life) for a sufficient time, 918cm of an infrared spectrum is obtained by detection by means of a Micro-infrared spectrometer (Micro-FTIR)-1Characteristic peaks appear in the bands and the intensity of the characteristic peaks rises with prolonged storage time. Wherein, the storage time is not limited; however, in general, the time is 1 hour or more.
Further, the polylactic acid pipe is at TgAfter a sufficient storage (shelf life) time, yieldThe rate of change of intensity is generally less than 30%; the elongation at break generally has a rate of change of less than 40% and no ductile to brittle transition.
Further, the polylactic acid pipe may further contain any one or a combination of more of a polymer (for example, any one or more of a polyhydroxyalkanoate, polyglycolic acid, polycaprolactone, polybutylene succinate, polybutylene adipate/terephthalate, and other homo-or co-polymer), a plasticizer, a compatibilizer, a transesterification agent, a chain extender, an end-capping agent, a flame retardant, an antioxidant, a lubricant, an antistatic agent, an antifogging agent, a light stabilizer, an ultraviolet absorber, a color masterbatch, an antifungal agent, an antibacterial agent, a foaming agent, and other additive components, within a range not to hinder the achievement of the process object of the present invention, and is not limited thereto. In summary, any method is within the scope of the present invention as long as it does not hinder the achievement of the process object of the present invention (the process optimization and the formulation control are such that the phenomenon of brittleness of the polylactic acid product caused by physical aging does not occur).
Another aspect of the embodiments of the present invention provides a polylactic acid pipe with physical aging resistance, which is obtained by melt extrusion, melt stretching, quenching, drawing, cutting and the like with a screw extrusion device.
Further, another aspect of the embodiments of the present invention provides a method for preparing the physical aging resistant polylactic acid pipe, including:
providing a dry polylactic acid or a dry mixture of polylactic acid;
melt-extruding the dried polylactic acid or the dry polylactic acid mixture through a screw extrusion device;
stretching the obtained polylactic acid melt along the axial direction, and quenching;
and further drawing and cutting the cooled pipe.
In some embodiments, the method of making specifically comprises:
(1) providing a dry polylactic acid or a dry mixture of polylactic acid;
(2) melting and extruding the dried polylactic acid or the dry polylactic acid mixture through screw extrusion equipment to obtain a polylactic acid melt, wherein the temperature of a screw is 150-270 ℃;
(3) and stretching the polylactic acid melt in the axial direction at the screw port, wherein the stretching temperature is equal to or more than the glass transition temperature but less than the melting point, preferably 65-145 ℃, the stretching multiple is 1-6 times, then rapidly quenching to room temperature at the quenching rate of 2-800 ℃/second, and the quenching time is 0.1-59 seconds, so as to prepare the polylactic acid pipe in the hollow tubular shape.
Wherein the dry blend of polylactic acid may comprise one or more of the aforementioned additional ingredients.
In some embodiments, the weight average molecular weight of the polylactic acid in step (1) is 8 to 50 ten thousand, wherein the molar content of the L optical isomer is 85 to 99%.
In a more preferred embodiment, the polylactic acid preferably has a weight average molecular weight of 20 to 40 ten thousand and a molar content of the L optical isomer of 92 to 98%.
In some embodiments, the stretching temperature for axially stretching the polylactic acid melt in the step (3) is 65-145 ℃, the stretching multiple is 1-6 times, and the quenching time is 0.1-59 seconds; the preferable stretching temperature of the melt stretching along the axial direction is 85-145 ℃, the stretching multiple is 2-5 times, and the quenching time is 0.1-30 seconds. Wherein:
when the weight average molecular weight of the polylactic acid is 8-15 ten thousand, the stretching temperature for stretching the polylactic acid melt along the axial direction is 65-95 ℃, the stretching multiple is 3-6 times, the quenching rate is 15-800 ℃/s, and the quenching time is 0.1-5 s;
when the weight average molecular weight of the polylactic acid is 15-30 ten thousand, the stretching temperature for stretching the polylactic acid melt along the axial direction is 85-115 ℃, the stretching multiple is 2-4 times, the quenching rate is 3-15 ℃/s, and the quenching time is 5-30 s;
when the weight average molecular weight of the polylactic acid is 30-50 ten thousand, the stretching temperature for stretching the polylactic acid melt along the axial direction is 105-145 ℃, the stretching multiple is 1-3 times, the quenching rate is 2-3 ℃/s, and the quenching time is 30-59 s.
The preparation method provided by the previous embodiment of the invention has the advantages ofSelecting the molecular weight and the optical isomer content of polylactic acid, and preparing the polylactic acid pipe under proper screw temperature and melt stretch ratio, namely the polylactic acid pipe with physical aging resistance. The polylactic acid pipe has better physical aging resistance, and the phenomenon of physical aging and embrittlement can not occur in the shelf life; but forms a metastable phase of polylactic acid, and the DSC curve of the amorphous (or low crystallinity) polylactic acid pipe shows TgThe enthalpy value (delta H) of the nearby endothermic peak does not change along with the change of the temperature rising rate of the DSC test; and the yield strength change rate before and after storage is small, the elongation at break change rate is small, and the crystallinity and the orientation degree are high.
Another aspect of the embodiments of the present invention provides a use of the polylactic acid pipe resistant to physical aging in the field of preparing tubular products.
Further, the tubular articles include, but are not limited to, disposable straws, medical tubes, and the like.
For example, another aspect of an embodiment of the present invention also provides a tubular article made from any of the foregoing physical aging resistant polylactic acid tubing.
Further, the tubular articles include, but are not limited to, disposable straws, medical tubes, and the like.
Accordingly, another aspect of an embodiment of the present invention also provides a method of preparing a tubular article, comprising:
preparing a polylactic acid pipe material with physical aging resistance by adopting the method;
and carrying out traction and cutting treatment on the polylactic acid pipe material with the physical aging resistance to form a tubular product with required specification.
Further, the preparation method comprises the following steps: the cooled polylactic acid pipe is further pulled and cut off to prepare the polylactic acid disposable suction tube, the medical catheter and the like.
Further, another aspect of the embodiments of the present invention provides a method for sterilizing, packaging and storing a polylactic acid tube material with physical aging resistance, which includes:
providing a polylactic acid pipe resistant to physical aging of any of the preceding embodiments, and extruding the polylactic acid pipeLactic acid pipe material at its glass transition temperature TgThe packaging and storage is sterilized as follows.
Further, in the foregoing embodiment, after the polylactic acid tube is prepared, the polylactic acid tube is sterilized and packaged, and enters a warehouse logistics stage; the set temperature of the sterilization packaging and the storage logistics stage (shelf life) is lower than Tg。
Furthermore, the polylactic acid pipe prepared in the embodiment of the invention has a stable structure and no looseness, the mechanical property of the pipe is not inferior to that of the existing polylactic acid pipe, and particularly, the physical aging resistance of the polylactic acid pipe prepared in the embodiment of the invention is remarkably improved by melt stretching in the preparation process and a rapid quenching process carried out after stretching. In addition, the polylactic acid metastable phase formed in the storage logistics stage can obviously reduce the internal stress of the polylactic acid pipe in the embodiment of the invention and improve the stability of the product. Therefore, the polylactic acid pipe disclosed by the embodiment of the invention has excellent physical aging resistance, can keep the stability of size and performance in a warehouse logistics stage, and breaks through the performance bottleneck of the conventional polylactic acid pipe, so that the use requirement is met, and the application field is expanded.
The technical scheme provided by the embodiment of the invention has the advantages that:
the technical scheme of the invention is as follows: (1) different from the traditional pipe preparation process, for example, the stretching treatment can not be carried out after melt extrusion; after the polylactic acid pipe is melted and extruded, the melt is stretched along the axial direction;
(2) different from the traditional pipe preparation process, such as melt extrusion and rapid quenching after traction are avoided; after the melt of the polylactic acid pipe is stretched along the axial direction, the polylactic acid pipe is quickly quenched;
(3) different from the traditional method for improving the performance of the product by annealing crystallization treatment (the pressure is 1 standard atmosphere, and the temperature is near the cold crystallization temperature); the polylactic acid pipe is subjected to heat treatment at a temperature higher than room temperature and lower than the glass transition temperature, so that the structure of the product is further stabilized (the content of metastable phase is improved to different degrees);
the technical effect thus obtained is: (1) through the permutation and combination of the above 3 technical schemes, after the polylactic acid pipe is stored below the glass transition temperature for enough time, the change rate of the yield strength is lower than 30%, the change rate of the elongation at break is lower than 40%, and obvious yield and subsequent plastic deformation zones appear on a stress-strain curve;
(2) the polylactic acid pipe comprises 0wt% -85 wt% of crystalline phase, 15wt% -100 wt% of amorphous phase, 5wt% -75 wt% of metastable phase in the amorphous phase, and a characteristic peak of the metastable phase in an infrared spectrogram of 918cm-1At least one of (1) and (b);
(3) the DSC curve of the polylactic acid amorphous (or low-crystallinity) pipe shows post-glass transition temperature (post-T)g) Then, an endothermic peak having an enthalpy value (Δ H) sufficiently large occurs, and the enthalpy value (Δ H) of the endothermic peak does not change with a change in the temperature increase rate of the DSC test;
the reason is presumed to be: (1) the inventor obtains the technical scheme and the effect through a large number of experiments, and the existing theory cannot explain the technical scheme and the effect, but the inventor conjectures that the possible reason is that the melt is stretched along the axial direction after melt extrusion, so that the orientation degree of a molecular chain in the amorphous region of the polylactic acid is improved;
(2) after the polylactic acid pipe is melted and extruded, a melt is stretched along the axial direction and then is rapidly quenched, so that molecular chains in a polylactic acid amorphous region are prevented from being subjected to de-orientation (or the de-orientation degree is low);
(3) the poly-tube material is processed at a constant temperature above room temperature and below the glass transition temperature, so that the structure of a product is further stable, and simultaneously, the molecular chain in an amorphous region is possibly prevented from being subjected to de-orientation (or the de-orientation degree is lower) in the processing process;
(4) unlike the traditional polylactic acid product which is easy to be physically aged and embrittled (the molecular chain in the amorphous region of the polylactic acid is subjected to disorientation), the polylactic acid foaming material only forms a polylactic acid metastable phase in the conventional storage logistics stage; without forming a condensed and tangled structure, resulting in the occurrence of physical aging and embrittlement.
In summary, according to the technical scheme provided by the embodiment of the invention, a high shear flow field and a high tensile flow field are provided through melt extrusion and melt stretching to induce the stretching and orientation of the polylactic acid molecular chain, and then the relaxation of the polylactic acid molecular chain is hindered through rapid quenching, so that the amorphous divided molecular chain orientation structure is maintained, and the physical aging resistance of the polylactic acid pipe is improved. The polylactic acid pipe is enabled to form a polylactic acid metastable phase along with the generation of dipole-dipole interaction by providing proper temperature and time in the storage process, so that the internal stress of the polylactic acid pipe is reduced, and the performance stability of the polylactic acid pipe in the shelf life (storage logistics stage) and the use stage is improved.
In conclusion, the polylactic acid pipe material provided by the embodiment of the invention has stable orientation and no looseness, has mechanical properties equivalent to those of the polylactic acid pipe material known at present, particularly has excellent physical aging resistance, can keep the dimensional stability and the performance stability of the polylactic acid pipe material and related products prepared from the polylactic acid pipe material in shelf life (storage logistics stage) and use stage, breaks through the performance bottleneck of the conventional polylactic acid pipe material, fully meets the use requirements, and greatly expands the application field of the polylactic acid pipe material.
The technical solution and effects of the present invention will be further described with reference to the following embodiments and accompanying drawings. Wherein, the glass transition temperature and the melting point are measured by a Differential Scanning Calorimetry (DSC) method; the glass transition temperature is determined by an angle bisection method, and the melting point is the peak temperature; the crystallinity is measured by X-ray diffraction (XRD) method. The method does not adopt a DSC method to calculate the crystallinity, and the measured crystallinity is higher than a true value because the secondary crystallization is caused by heating a sample in the DSC test process as well known. In the following examples of the invention, the formation of the metastable phase of polylactic acid was identified by microscopic infrared (Micro-FTIR); the tensile property of the polylactic acid pipe is measured by a universal material tensile testing machine, the distance between the clamps is 30mm, and the testing speed is 15 mm/min.
Example 1:
taking polylactic acid with the weight-average molecular weight of 15 ten thousand and the molar content of the L optical isomer of 95 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 50 ppm; extruding the dried polylactic acid granules by screw extrusion equipment to obtain a polylactic acid melt, wherein the temperature of a screw is 190 ℃; milk conglomeratesDirectly stretching the acid melt in the axial direction at a screw port at the stretching temperature of 95 ℃ and the stretching multiple of 3 times; quickly entering a quick cooling device to obtain a polylactic acid pipe in a hollow tubular shape, wherein the quenching rate is 15 ℃/s, and the quenching time is 5 s; further drawing and cutting the cooled polylactic acid pipe to prepare a polylactic acid disposable pipe; subsequently subjecting the polylactic acid pipe to a temperature T of glass transitiongSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid pipe before storage is 41 percent, and the orientation degree is 0.7; the crystallinity of the polylactic acid pipe is basically unchanged after the polylactic acid pipe is stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid pipe is 921cm before storage-1The appearance of a crystallization characteristic peak; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ is 918cm-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 39%. The glass transition temperature of the polylactic acid pipe before storage is 55 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ has no obvious endothermic peak near the glass transition temperature. In addition, the yield strength of the polylactic acid pipe before storage is 60MPa, and the elongation at break is 67%; the yield strength of the polylactic acid pipe stored for half a year at the temperature of 30 +/-5 ℃ is 62MPa, and the elongation at break is 65%; the polylactic acid pipe prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.
Example 2:
taking polylactic acid with the weight-average molecular weight of 30 ten thousand and the molar content of the L optical isomer of 95 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 45 ppm; extruding the dried polylactic acid granules by screw extrusion equipment to obtain a polylactic acid melt, wherein the temperature of a screw is 230 ℃; directly stretching the polylactic acid melt in the screw port along the axial direction, wherein the stretching temperature is 115 ℃, and the stretching multiple is 2 times; quickly entering a quick cooling device to obtain a polylactic acid pipe in a hollow tubular shape, wherein the quenching rate is 3 ℃/s, and the quenching time is 30 s; further drawing and cutting the cooled polylactic acid pipe to prepare a polylactic acid disposable pipe; subsequently subjecting the polylactic acid toPipe material at its glass transition temperature TgSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid pipe before storage is 45 percent, and the orientation degree is 0.6; the crystallinity of the polylactic acid pipe is basically unchanged after the polylactic acid pipe is stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid pipe is 921cm before storage-1The appearance of a crystallization characteristic peak; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ is 918cm-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 35%. The glass transition temperature of the polylactic acid pipe before storage is 60 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ has no obvious endothermic peak near the glass transition temperature. In addition, the yield strength of the polylactic acid pipe before storage is 75MPa, and the elongation at break is 51%; the yield strength of the polylactic acid pipe stored for half a year at the temperature of 30 +/-5 ℃ is 77MPa, and the elongation at break is 53 percent; the polylactic acid pipe prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.
Example 3:
taking polylactic acid with the weight-average molecular weight of 8 ten thousand and the molar content of the L optical isomer of 95 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 43 ppm; extruding the dried polylactic acid granules by screw extrusion equipment to obtain a polylactic acid melt, wherein the temperature of a screw is 170 ℃; directly stretching the polylactic acid melt in the screw port along the axial direction at the stretching temperature of 65 ℃ and the stretching multiple of 3 times; quickly entering a quick cooling device to obtain a polylactic acid pipe in a hollow tubular shape, wherein the quenching rate is 500 ℃/s, and the quenching time is 0.1 s; further drawing and cutting the cooled polylactic acid pipe to prepare a polylactic acid disposable pipe; subsequently subjecting the polylactic acid pipe to a temperature T of glass transitiongSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid pipe before storage is 60 percent, and the orientation degree is 0.65; the crystallinity of the polylactic acid pipe is basically unchanged after the polylactic acid pipe is stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid pipe is 921cm before storage-1The appearance of a crystallization characteristic peak; after storage for half a year at 30 + -5 deg.CThe polylactic acid pipe is 918cm-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 15%. The glass transition temperature of the polylactic acid pipe before storage is 54 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ has no obvious endothermic peak near the glass transition temperature. In addition, the yield strength of the polylactic acid pipe before storage is 34MPa, and the elongation at break is 48%; the yield strength of the polylactic acid pipe stored for half a year at the temperature of 30 +/-5 ℃ is 36MPa, and the elongation at break is 47%; the polylactic acid pipe prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.
Example 4:
taking polylactic acid with the weight-average molecular weight of 8 ten thousand and the molar content of L optical isomer of 99 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 52 ppm; extruding the dried polylactic acid granules by screw extrusion equipment to obtain a polylactic acid melt, wherein the screw temperature is 175 ℃; directly stretching the polylactic acid melt in the axial direction at a screw port, wherein the stretching temperature is 95 ℃, and the stretching multiple is 6 times; quickly entering a quick cooling device to obtain a polylactic acid pipe in a hollow tubular shape, wherein the quenching rate is 800 ℃/s, and the quenching time is 0.1 s; further drawing and cutting the cooled polylactic acid pipe to prepare a polylactic acid disposable pipe; subsequently subjecting the polylactic acid pipe to a temperature T of glass transitiongSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid pipe before storage is 85 percent, and the orientation degree is 0.95; the crystallinity of the polylactic acid pipe is basically unchanged after the polylactic acid pipe is stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid pipe is 921cm before storage-1The appearance of a crystallization characteristic peak; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ is 918cm-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 5%. The glass transition temperature of the polylactic acid pipe before storage is 56 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ does not have obvious phenomenon near the glass transition temperatureEndothermic peak. In addition, the yield strength of the polylactic acid pipe before storage is 41MPa, and the elongation at break is 19%; the yield strength of the polylactic acid pipe stored for half a year at the temperature of 30 +/-5 ℃ is 42MPa, and the elongation at break is 23%; the polylactic acid pipe prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.
Example 5:
taking polylactic acid with the weight-average molecular weight of 8 ten thousand and the molar content of the L optical isomer of 85 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 43 ppm; extruding the dried polylactic acid granules by screw extrusion equipment to obtain a polylactic acid melt, wherein the temperature of a screw is 150 ℃; directly stretching the polylactic acid melt in the axial direction at a screw port, wherein the stretching temperature is 85 ℃, and the stretching multiple is 6 times; quickly entering a quick cooling device to obtain a polylactic acid pipe in a hollow tubular shape, wherein the quenching rate is 600 ℃/s, and the quenching time is 0.1 s; further drawing and cutting the cooled polylactic acid pipe to prepare a polylactic acid disposable pipe; subsequently subjecting the polylactic acid pipe to a temperature T of glass transitiongSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid pipe before storage is 0 percent, and the orientation degree is 0.60; the crystallinity of the polylactic acid pipe is basically unchanged after the polylactic acid pipe is stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid pipe is 921cm before storage-1No crystallization characteristic peak appears; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ is 918cm-1Characteristic peaks appear, which indicate the formation of metastable phase of polylactic acid, and the content of metastable phase is 5%. The glass transition temperature of the polylactic acid pipe before storage is 52 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ has obvious endothermic peak near the glass transition temperature. In addition, the enthalpy value of the endothermic peak of the polylactic acid pipe stored for half a year at 30 +/-5 ℃ near the glass transition temperature does not depend on the DSC temperature rise rate, and the endothermic peak is the structural transition of the metastable phase of the polylactic acid and is not the enthalpy relaxation phenomenon which is specific to physical aging. In addition, the yield strength of the polylactic acid pipe before storage is 29MPa, and the elongation at break is 200%(ii) a The yield strength of the polylactic acid pipe stored for half a year at the temperature of 30 +/-5 ℃ is 33MPa, and the elongation at break is 205%; the polylactic acid pipe prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.
Example 6:
taking polylactic acid with the weight-average molecular weight of 50 ten thousand and the molar content of L optical isomer of 93 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 43 ppm; extruding the dried polylactic acid granules by screw extrusion equipment to obtain a polylactic acid melt, wherein the temperature of a screw is 255 ℃; directly stretching the polylactic acid melt in the screw port along the axial direction, wherein the stretching temperature is 145 ℃, and the stretching multiple is 3 times; quickly entering a quick cooling device to obtain a polylactic acid pipe in a hollow tubular shape, wherein the quenching rate is 2 ℃/s, and the quenching time is 59 s; further drawing and cutting the cooled polylactic acid pipe to prepare a polylactic acid disposable pipe; subsequently subjecting the polylactic acid pipe to a temperature T of glass transitiongSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid pipe before storage is 35 percent, and the orientation degree is 0.6; the crystallinity of the polylactic acid pipe is basically unchanged after the polylactic acid pipe is stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid pipe is 921cm before storage-1The appearance of a crystallization characteristic peak; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ is 918cm-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 15%. The glass transition temperature of the polylactic acid pipe before storage is 65 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ has no obvious endothermic peak near the glass transition temperature. In addition, the yield strength of the polylactic acid pipe before storage is 96MPa, and the elongation at break is 37%; the yield strength of the polylactic acid pipe stored for half a year at the temperature of 30 +/-5 ℃ is 98MPa, and the elongation at break is 39%; the polylactic acid pipe prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.
Example 7:
taking polylactic acid with the weight-average molecular weight of 50 ten thousand and the molar content of L optical isomer of 99 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 33 ppm; extruding the dried polylactic acid granules by screw extrusion equipment to obtain a polylactic acid melt, wherein the temperature of a screw is 270 ℃; directly stretching the polylactic acid melt in the screw port along the axial direction, wherein the stretching temperature is 105 ℃, and the stretching ratio is 1 time; quickly entering a quick cooling device to obtain a polylactic acid pipe in a hollow tubular shape, wherein the quenching rate is 2 ℃/s, and the quenching time is 40 s; further drawing and cutting the cooled polylactic acid pipe to prepare a polylactic acid disposable pipe; subsequently subjecting the polylactic acid pipe to a temperature T of glass transitiongSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid pipe before storage is 20 percent, and the orientation degree is 0.35; the crystallinity of the polylactic acid pipe is basically unchanged after the polylactic acid pipe is stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid pipe is 921cm before storage-1The appearance of a crystallization characteristic peak; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ is 918cm-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 5%. The glass transition temperature of the polylactic acid pipe before storage is 62 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ has no obvious endothermic peak near the glass transition temperature. In addition, the yield strength of the polylactic acid pipe before storage is 88MPa, and the elongation at break is 41%; the yield strength of the polylactic acid pipe stored for half a year at the temperature of 30 +/-5 ℃ is 87MPa, and the elongation at break is 43 percent; the polylactic acid pipe prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.
Example 8:
taking polylactic acid with the weight-average molecular weight of 50 ten thousand and the molar content of the L optical isomer of 85 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 43 ppm; extruding the dried polylactic acid granules by screw extrusion equipment to obtain a polylactic acid melt, wherein the temperature of a screw is 250 ℃; the polylactic acid melt is directly axially processed at the screw portStretching at 125 deg.C with a stretching ratio of 2 times; quickly entering a quick cooling device to obtain a polylactic acid pipe in a hollow tubular shape, wherein the quenching rate is 3 ℃/s, and the quenching time is 30 s; further drawing and cutting the cooled polylactic acid pipe to prepare a polylactic acid disposable pipe; subsequently subjecting the polylactic acid pipe to a temperature T of glass transitiongSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid pipe before storage is 0 percent, and the orientation degree is 0.45; the crystallinity of the polylactic acid pipe is basically unchanged after the polylactic acid pipe is stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid pipe is 921cm before storage-1No crystallization characteristic peak appears; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ is 918cm-1Characteristic peaks appear, which indicate the formation of metastable phase of polylactic acid, and the content of metastable phase is 5%. The glass transition temperature of the polylactic acid pipe before storage is 59 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ has obvious endothermic peak near the glass transition temperature. In addition, the enthalpy value of the endothermic peak of the polylactic acid pipe stored for half a year at 30 +/-5 ℃ near the glass transition temperature does not depend on the DSC temperature rise rate, and the endothermic peak is the structural transition of the metastable phase of the polylactic acid and is not the enthalpy relaxation phenomenon which is specific to physical aging. In addition, the yield strength of the polylactic acid pipe before storage is 70MPa, and the elongation at break is 125%; the yield strength of the polylactic acid pipe stored for half a year at the temperature of 30 +/-5 ℃ is 68MPa, and the elongation at break is 128%; the polylactic acid pipe prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.
Example 9:
taking polylactic acid with the weight-average molecular weight of 15 ten thousand and the molar content of L optical isomer of 93 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 50 ppm; extruding the dried polylactic acid granules by screw extrusion equipment to obtain a polylactic acid melt, wherein the screw temperature is 205 ℃; directly stretching the polylactic acid melt in the axial direction at a screw port, wherein the stretching temperature is 95 ℃, and the stretching multiple is 4 times; quickly enters a quick cooling device to obtainThe quenching speed of the hollow tubular polylactic acid pipe is 15 ℃/s, and the quenching time is 5 s; further drawing and cutting the cooled polylactic acid pipe to prepare a polylactic acid disposable pipe; subsequently subjecting the polylactic acid pipe to a temperature T of glass transitiongSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid pipe before storage is 15 percent, and the orientation degree is 0.95; the crystallinity of the polylactic acid pipe is basically unchanged after the polylactic acid pipe is stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid pipe is 921cm before storage-1The appearance of a crystallization characteristic peak; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ is 918cm-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 75%. The glass transition temperature of the polylactic acid pipe before storage is 54 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ has obvious endothermic peak near the glass transition temperature. In addition, the enthalpy value of the endothermic peak of the polylactic acid pipe stored for half a year at 30 +/-5 ℃ near the glass transition temperature does not depend on the DSC temperature rise rate, and the endothermic peak is the structural transition of the metastable phase of the polylactic acid and is not the enthalpy relaxation phenomenon which is specific to physical aging. In addition, the yield strength of the polylactic acid pipe before storage is 55MPa, and the elongation at break is 72%; the yield strength of the polylactic acid pipe stored for half a year at the temperature of 30 +/-5 ℃ is 56MPa, and the elongation at break is 75 percent; the polylactic acid pipe prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.
Example 10:
taking polylactic acid with weight average molecular weight of 30 ten thousand and L optical isomer molar content of 99 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 44 ppm; extruding the dried polylactic acid granules by screw extrusion equipment to obtain a polylactic acid melt, wherein the temperature of a screw is 220 ℃; directly stretching the polylactic acid melt in the screw port along the axial direction, wherein the stretching temperature is 115 ℃, and the stretching multiple is 3 times; quickly entering a quick cooling device to obtain a polylactic acid pipe in a hollow tubular shape, wherein the quenching rate is 3 ℃/s, and the quenching time is 30 s; will coolFurther drawing and cutting the polylactic acid pipe to prepare a polylactic acid disposable pipe; subsequently subjecting the polylactic acid pipe to a temperature T of glass transitiongSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid pipe before storage is 60 percent, and the orientation degree is 0.7; the crystallinity of the polylactic acid pipe is basically unchanged after the polylactic acid pipe is stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid pipe is 921cm before storage-1The appearance of a crystallization characteristic peak; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ is 918cm-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 28%. The glass transition temperature of the polylactic acid pipe before storage is 62 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ has no obvious endothermic peak near the glass transition temperature. In addition, the yield strength of the polylactic acid pipe before storage is 75MPa, and the elongation at break is 32%; the yield strength of the polylactic acid pipe stored for half a year at the temperature of 30 +/-5 ℃ is 77MPa, and the elongation at break is 35 percent; the polylactic acid pipe prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.
Example 11:
taking polylactic acid with the weight-average molecular weight of 23 ten thousand and the molar content of the L optical isomer of 95 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 50 ppm; extruding the dried polylactic acid granules by screw extrusion equipment to obtain a polylactic acid melt, wherein the screw temperature is 215 ℃; directly stretching the polylactic acid melt in the screw port along the axial direction, wherein the stretching temperature is 105 ℃, and the stretching multiple is 3 times; quickly entering a quick cooling device to obtain a polylactic acid pipe in a hollow tubular shape, wherein the quenching speed is 3 ℃/s, and the quenching time is 25 s; further drawing and cutting the cooled polylactic acid pipe to prepare a polylactic acid disposable pipe; subsequently subjecting the polylactic acid pipe to a temperature T of glass transitiongSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid pipe before storage is 40 percent, and the orientation degree is 0.65; the crystallinity of the polylactic acid pipe stored for half a year at 30 +/-5 ℃ is basically unchanged. The polylactic acid pipe is 921cm before storage-1The appearance of a crystallization characteristic peak; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ is 918cm-1Characteristic peaks also appear, indicating the formation of a metastable phase of polylactic acid, with a metastable phase content of 36%. The glass transition temperature of the polylactic acid pipe before storage is 56 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ has no obvious endothermic peak near the glass transition temperature. In addition, the yield strength of the polylactic acid pipe before storage is 66MPa, and the elongation at break is 47%; the yield strength of the polylactic acid pipe stored for half a year at the temperature of 30 +/-5 ℃ is 68MPa, and the elongation at break is 55 percent, which is shown in figure 1; the polylactic acid pipe prepared by the embodiment has obvious physical aging resistance, does not have the phenomenon of brittleness caused by physical aging, and forms a polylactic acid metastable phase.
Comparative example 1:
taking polylactic acid with the weight-average molecular weight of 30 ten thousand and the molar content of the L optical isomer of 95 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 45 ppm; extruding the dried polylactic acid granules by screw extrusion equipment to obtain a polylactic acid melt, wherein the temperature of a screw is 230 ℃; drawing the tube into a rapid cooling device to obtain a hollow tubular polylactic acid tube, wherein the quenching rate is 200 ℃/s, and the quenching time is 1 s; further drawing and cutting the cooled polylactic acid pipe to prepare a polylactic acid disposable pipe; subsequently subjecting the polylactic acid pipe to a temperature T of glass transitiongSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid pipe before storage is 0 percent, and the orientation degree is 0; the crystallinity of the polylactic acid pipe is basically unchanged after the polylactic acid pipe is stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid pipe is 921cm before storage-1No crystallization characteristic peak appears; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ is 918cm-1Nor characteristic peaks, indicating that no metastable polylactic acid phase is formed. The glass transition temperature of the polylactic acid pipe before storage is 56 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ has obvious endothermic peak near the glass transition temperature. In addition, the enthalpy value of the endothermic peak of the polylactic acid pipe material stored at 30 +/-5 ℃ for half a year around the glass transition temperature depends on the DSC heating rate, and the endothermic peak is an enthalpy relaxation phenomenon which is specific to physical aging. In addition, the yield strength of the polylactic acid pipe before storage is 65MPa, and the elongation at break is 300%; the yield strength of the polylactic acid pipe after being stored for half a year at 30 +/-5 ℃ is 68MPa, and the elongation at break is 11 percent, which is shown in figure 2; the polylactic acid pipe prepared by the comparative example is proved to have obvious phenomenon of embrittlement caused by physical aging and does not have physical aging resistance.
Comparative example 2:
taking polylactic acid with the weight-average molecular weight of 30 ten thousand and the molar content of the L optical isomer of 95 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 43 ppm; extruding the dried polylactic acid granules by screw extrusion equipment to obtain a polylactic acid melt, wherein the temperature of a screw is 230 ℃; drawing, and then rapidly quenching to room temperature at a quenching speed of 0.5 ℃/second, wherein the quenching time is 120 seconds; further drawing and cutting the cooled polylactic acid pipe to prepare a polylactic acid disposable pipe; subsequently subjecting the polylactic acid pipe to a temperature T of glass transitiongSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid pipe before storage is 35 percent, and the orientation degree is 0; the crystallinity of the polylactic acid pipe is basically unchanged after the polylactic acid pipe is stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid pipe is 921cm before storage-1The appearance of a crystallization characteristic peak; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ is 918cm-1No characteristic peaks were present, indicating that no metastable polylactic acid phase was formed. The glass transition temperature of the polylactic acid pipe before storage is 58 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ has no obvious endothermic peak near the glass transition temperature. In addition, the yield strength of the polylactic acid pipe before storage is 71MPa, and the elongation at break is 58%; the yield strength of the polylactic acid pipe stored for half a year at the temperature of 30 +/-5 ℃ is 73MPa, and the elongation at break is 8%; the polylactic acid pipe prepared by the comparative example is proved to have obvious phenomenon of embrittlement caused by physical aging and does not have physical aging resistance.
Comparative example 3:
taking polylactic acid with the weight-average molecular weight of 8 ten thousand and the molar content of the L optical isomer of 97 percent for hot air drying, wherein the drying temperature is 95 +/-2 ℃, the drying time is 8 hours, and the water content is 52 ppm; extruding the dried polylactic acid granules by screw extrusion equipment to obtain a polylactic acid melt, wherein the screw temperature is 175 ℃; directly stretching the polylactic acid melt in the axial direction at a screw port, wherein the stretching temperature is 95 ℃, and the stretching multiple is 5 times; drawing, and then rapidly quenching to room temperature at a quenching rate of 0.5 ℃/second for 120 seconds to obtain a polylactic acid pipe in a hollow tubular shape; further drawing and cutting the cooled polylactic acid pipe to prepare a polylactic acid disposable pipe; subsequently subjecting the polylactic acid pipe to a temperature T of glass transitiongSterile packaging and storage follows. Through detection: the crystallinity of the polylactic acid pipe before storage is 68 percent, and the orientation degree is 0.91; the crystallinity of the polylactic acid pipe is basically unchanged after the polylactic acid pipe is stored for half a year at the temperature of 30 +/-5 ℃. The polylactic acid pipe is 921cm before storage-1The appearance of a crystallization characteristic peak; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ is 918cm-1No characteristic peaks were present, indicating that no metastable polylactic acid phase was formed. The glass transition temperature of the polylactic acid pipe before storage is 56 ℃, and almost no endothermic peak appears near the glass transition temperature; the polylactic acid pipe stored for half a year at 30 +/-5 ℃ has no obvious endothermic peak near the glass transition temperature. In addition, the yield strength of the polylactic acid pipe before storage is 43MPa, and the elongation at break is 34%; the yield strength of the polylactic acid pipe stored for half a year at the temperature of 30 +/-5 ℃ is 48MPa, and the elongation at break is 3%; the polylactic acid pipe prepared by the comparative example is proved to have obvious phenomenon of embrittlement caused by physical aging and does not have physical aging resistance.
In addition, the inventors of the present invention have also made experiments with other materials, process operations, and process conditions described in the present specification with reference to the above examples, and have obtained preferable results.
Example 12
The physical aging resistant polylactic acid pipes obtained in the above examples 1-11 can be processed into the required tubular products according to the requirements of practical application and in the manner known in the art. For example:
the physical aging resistant polylactic acid pipes obtained in the above examples 1 to 11 can be processed into tubular products, such as straws or medical catheters, which not only have the strength equivalent to or superior to that of the existing polylactic acid pipes, but also have excellent physical aging resistance, and can maintain the stability of size and performance in the stage of warehouse logistics.
The aspects, embodiments, features and examples of the present invention should be considered as illustrative in all respects and not intended to be limiting of the invention, the scope of which is defined only by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.
The use of headings and chapters in this disclosure is not meant to limit the disclosure; each section may apply to any aspect, embodiment, or feature of the disclosure.
Throughout this specification, where a composition is described as having, containing, or comprising specific components or where a process is described as having, containing, or comprising specific process steps, it is contemplated that the composition of the present teachings also consist essentially of, or consist of, the recited components, and the process of the present teachings also consist essentially of, or consist of, the recited process steps.
Unless specifically stated otherwise, use of the terms "comprising", "including", "having" or "having" is generally to be understood as open-ended and not limiting.
It should be understood that the order of steps or the order in which particular actions are performed is not critical, so long as the teachings of the invention remain operable. Further, two or more steps or actions may be performed simultaneously.
While the invention has been described with reference to illustrative embodiments, it will be understood by those skilled in the art that various other changes, omissions and/or additions may be made and substantial equivalents may be substituted for elements thereof without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated any use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.

Claims (19)

1.一种耐物理老化的聚乳酸管材的制备方法，其特征在于包括：1. a preparation method of a polylactic acid pipe material resistant to physical aging, is characterized in that comprising: （1）提供干燥的聚乳酸或聚乳酸干态混合物；(1) Provide dry polylactic acid or polylactic acid dry mixture; （2）将所述干燥的聚乳酸或聚乳酸干态混合物通过螺杆挤出设备熔融挤出，得到聚乳酸熔体，其中螺杆温度为150～270℃；(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）将所述聚乳酸熔体沿轴向方向进行拉伸，拉伸温度等于或大于玻璃化转变温度但低于熔点，拉伸倍数为1~6倍，之后以2～800℃/秒的淬冷速率迅速淬冷至室温，淬冷时间为0.1～59秒，制得呈中空管状形态的聚乳酸管材；(3) The polylactic acid melt is stretched in the axial direction, the stretching temperature is equal to or higher than the glass transition temperature but lower than the melting point, and the stretching ratio is 1 to 6 times, and then the stretching temperature is 2 to 800°C/sec. The quenching rate was rapidly quenched to room temperature, and the quenching time was 0.1 to 59 seconds, and the polylactic acid pipe in the form of a hollow tube was obtained; 所述聚乳酸管材是中空管状形态的，并且，所述聚乳酸管材包含0wt%～85wt%结晶相和15wt%～100wt%非晶相；所述非晶相包含5wt%～75wt%亚稳相，所述亚稳相于红外光谱图内的特征峰出现于918 cm-1处，并且，所述聚乳酸管材于玻璃化转变温度以下存储足够时间后，屈服强度的变化率低于30%、断裂伸长率的变化率低于40%，应力-应变曲线上出现明显的屈服以及后续的塑形变形区，所述的足够时间≥1小时。The polylactic acid pipe is in the form of a hollow tube, and the polylactic acid pipe contains 0wt%-85wt% crystalline phase and 15wt%-100wt% amorphous phase; the amorphous phase contains 5wt%-75wt% metastable phase , the characteristic peak of the metastable phase in the infrared spectrum appears at 918 cm -1 , and after the polylactic acid pipe 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 yielding and subsequent plastic deformation zone, and the sufficient time is ≥ 1 hour. 2.根据权利要求1所述的制备方法，其特征在于：所述聚乳酸管材的结晶相含量为20wt%～70wt%，并且所述非晶相中亚稳相的含量为10wt%～50wt%。2 . The preparation method according to claim 1 , wherein the content of the crystalline phase of the polylactic acid pipe is 20wt% to 70wt%, and the content of the metastable phase in the amorphous phase is 10wt% to 50wt%. 3 . . 3.根据权利要求2所述的制备方法，其特征在于：所述聚乳酸管材的结晶相含量为30wt%～50wt%。3 . The preparation method according to claim 2 , wherein the crystalline phase content of the polylactic acid pipe material is 30 wt % to 50 wt %. 4 . 4.根据权利要求2所述的制备方法，其特征在于：所述非晶相中亚稳相的含量为20wt%～40wt%。4 . The preparation method according to claim 2 , wherein the content of the metastable phase in the amorphous phase is 20wt% to 40wt%. 5 . 5.根据权利要求1所述的制备方法，其特征在于：所述聚乳酸管材的取向度为0.35～0.95。5 . The preparation method according to claim 1 , wherein the degree of orientation of the polylactic acid pipe material is 0.35-0.95. 6 . 6.根据权利要求5所述的制备方法，其特征在于：所述聚乳酸管材的取向度为0.6～0.8。6 . The preparation method according to claim 5 , wherein the orientation degree of the polylactic acid pipe material is 0.6-0.8. 7 . 7. 根据权利要求1所述的制备方法，其特征在于：在所述聚乳酸管材于玻璃化转变温度以下存储足够时间后，所述聚乳酸管材的差式扫描量热DSC曲线中于玻璃化转变温度后，紧接着出现焓值ΔH足够大的吸热峰，所述吸热峰的焓值不随DSC测试升温速率的变化而变化，以及，所述聚乳酸管材的红外光谱图内于918 cm-1谱带出现特征峰，所述特征峰的强度随储存时间延长而上升，并且，所述聚乳酸管材的屈服强度的变化率低于30%、断裂伸长率的变化率低于40%，所述的ΔH≥1J/g。7. The preparation method according to claim 1, wherein after the polylactic acid pipe material is stored for a sufficient time below the glass transition temperature, the differential scanning calorimetry DSC curve of the polylactic acid pipe material is in the glass transition temperature. Immediately after the transition temperature, an endothermic peak with a sufficiently large enthalpy ΔH appears, the enthalpy 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 pipe is within 918. A characteristic peak appears in the cm -1 band, and the intensity of the characteristic peak increases with the storage time, and the change rate of the yield strength of the polylactic acid pipe is less than 30%, and the change rate of the elongation at break is less than 40%. %, the ΔH≥1J /g. 8.根据权利要求1所述的制备方法，其特征在于：所述聚乳酸管材还包含聚合物、增塑剂、增容剂、酯交换剂、扩链剂、封端剂、阻燃剂、抗氧化剂、润滑剂、抗静电剂、防雾剂、光稳定剂、色母粒、防霉剂、抗菌剂、发泡剂中的任意一种或两种以上的组合。8 . The preparation method according to claim 1 , wherein the polylactic acid pipe material further comprises polymers, plasticizers, compatibilizers, transesterifiers, chain extenders, end capping agents, flame retardants, Any one or a combination of two or more of antioxidants, lubricants, antistatic agents, antifogging agents, light stabilizers, color masterbatches, antifungal agents, antibacterial agents, and foaming agents. 9.如权利要求1所述的制备方法，其特征在于，步骤（1）中所述聚乳酸的重均分子量为8～50万，其中L旋光异构体的摩尔含量为85%～99%。9 . The preparation method according to claim 1 , wherein the weight average molecular weight of the polylactic acid in step (1) is 80,000 to 500,000, and the molar content of the L optical isomer is 85% to 99%. 10 . . 10.如权利要求9所述的制备方法，其特征在于，步骤（1）中所述聚乳酸的重均分子量为20～40万，其中L旋光异构体的摩尔含量为92%～98%。10 . The preparation method according to claim 9 , wherein the weight average molecular weight of the polylactic acid in step (1) is 200,000 to 400,000, and the molar content of the L optical isomer is 92% to 98%. 11 . . 11.如权利要求1所述的制备方法，其特征在于：步骤（3）中沿轴向对聚乳酸熔体进行拉伸的拉伸温度为65～145℃，拉伸倍数为2～5倍，淬冷时间为0.1～30秒。11 . The preparation method according to claim 1 , wherein the stretching temperature for stretching the polylactic acid melt in the axial direction in step (3) is 65-145° C., and the stretching ratio is 2-5 times. 12 . , the quenching time is 0.1 to 30 seconds. 12.如权利要求11所述的制备方法，其特征在于：步骤（3）中沿轴向对聚乳酸熔体进行拉伸的拉伸温度为85～145℃。12 . The preparation method according to claim 11 , wherein the stretching temperature for stretching the polylactic acid melt in the axial direction in step (3) is 85-145° C. 13 . 13.如权利要求1所述的制备方法，其特征在于，步骤（3）具体包括：13. The preparation method of claim 1, wherein step (3) specifically comprises: 当聚乳酸的重均分子量为8～15万时，沿轴向对聚乳酸熔体进行拉伸的拉伸温度为65～95℃、拉伸倍数为3～6倍，淬冷速率为15～800 ℃/秒，淬冷时间为0.1～5秒；When the weight-average molecular weight of the polylactic acid is 80,000 to 150,000, the stretching temperature for stretching the polylactic acid melt in the axial direction is 65-95° C., the stretching ratio is 3-6 times, and the quenching rate is 15- 800 ℃/second, quenching time is 0.1 to 5 seconds; 当聚乳酸的重均分子量为15～30万时，沿轴向对聚乳酸熔体进行拉伸的拉伸温度为85～115℃、拉伸倍数为2～4倍，淬冷速率为3～15℃/秒，淬冷时间为5～30秒；When the weight-average molecular weight of the polylactic acid is 150,000 to 300,000, the stretching temperature for stretching the polylactic acid melt in the axial direction is 85-115°C, the stretching ratio is 2-4 times, and the quenching rate is 3- 15℃/second, quenching time is 5～30 seconds; 当聚乳酸的重均分子量为30～50万时，沿轴向对聚乳酸熔体进行拉伸的拉伸温度为105～145℃、拉伸倍数为1～3倍，淬冷速率为2～3℃/秒，淬冷时间为30～59秒。When the weight-average molecular weight of polylactic acid is 300,000 to 500,000, the stretching temperature for stretching the polylactic acid melt in the axial direction is 105-145°C, the stretching ratio is 1-3 times, and the quenching rate is 2- 3°C/sec, and the quenching time is 30 to 59 seconds. 14.由权利要求1-13中任一项所述方法制备的耐物理老化的聚乳酸管材于制备管状制品中的用途。14. Use of the physical aging-resistant polylactic acid pipe prepared by the method of any one of claims 1-13 in the preparation of tubular products. 15.根据权利要求14所述的用途，其特征在于：所述管状制品包括吸管或医用导管。15. The use according to claim 14, wherein the tubular article comprises a drinking straw or a medical catheter. 16.由权利要求1-13中任一项所述方法制备的耐物理老化的聚乳酸管材制成的管状制品。16. A tubular article made of the physical aging-resistant polylactic acid pipe prepared by the method of any one of claims 1-13. 17.根据权利要求16所述的管状制品，其特征在于：所述管状制品包括吸管或医用导管。17. The tubular article of claim 16, wherein the tubular article comprises a drinking straw or a medical catheter. 18.一种管状制品的制备方法，其特征在于包括：18. A method for preparing a tubular product, characterized in that it comprises: 采用权利要求1-13中任一项所述方法制备耐物理老化的聚乳酸管材；Using the method described in any one of claims 1-13 to prepare a polylactic acid pipe material resistant to physical aging; 对所述耐物理老化的聚乳酸管材进行牵引、切断处理，形成所需规格的管状制品。The physical aging-resistant polylactic acid pipe is pulled and cut to form a pipe product of the required specification. 19.一种耐物理老化的聚乳酸管材的消毒封装及存储方法，其特征在于包括：提供由权利要求1-13中任一项所述方法制备的耐物理老化的聚乳酸管材，并将所述聚乳酸管材于其玻璃化转变温度以下消毒封装及存储。19. A method for sterilizing, packaging and storing a polylactic acid pipe material resistant to physical aging, characterized by comprising: providing the polylactic acid pipe material resistant to physical aging prepared by the method according to any one of claims 1-13, and placing the The polylactic acid pipe is sterilized, packaged and stored below its glass transition temperature.
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