WO2020043065A1 - 一种高立构复合型聚乳酸材料及其制备方法 - Google Patents

一种高立构复合型聚乳酸材料及其制备方法 Download PDF

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WO2020043065A1
WO2020043065A1 PCT/CN2019/102628 CN2019102628W WO2020043065A1 WO 2020043065 A1 WO2020043065 A1 WO 2020043065A1 CN 2019102628 W CN2019102628 W CN 2019102628W WO 2020043065 A1 WO2020043065 A1 WO 2020043065A1
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poly
lactic acid
polylactic acid
irradiated
blending
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French (fr)
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张秀芹
李晓露
王锐
杨博
齐悦
董振峰
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北京服装学院
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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
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/28—Treatment by wave energy or particle radiation
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C08J2367/04—Polyesters derived from hydroxy carboxylic 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
    • 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
    • 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
    • C08L2205/03—Polymer mixtures characterised by other features containing three or more polymers in a blend
    • C08L2205/035—Polymer mixtures characterised by other features containing three or more polymers in a blend containing four or more polymers in a blend

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  • the invention belongs to the technical field of polymer materials, and relates to a method for preparing a polylactic acid material, in particular to a method for preparing a high stereo composite polylactic acid material by irradiation.
  • Polylactic acid is a biodegradable aliphatic polyester. It is manufactured from renewable crops such as corn starch. Polylactic acid can be degraded into CO 2 and H 2 O in the natural environment after use. , No stimulation, green environmental protection and other advantages, is an environmentally friendly green polymer material with great development potential, which has become the focus of research in recent years. In addition, polylactic acid has good biocompatibility and good thermoplastic processing properties, and has been widely used in plastics, clothing, medical and other fields. However, polylactic acid has poor heat resistance and poor mechanical properties, and these shortcomings limit the application range of polylactic acid materials.
  • the monomer lactic acid of polylactic acid is a chiral molecule.
  • the formed polylactic acid has two enantiomers of poly-L-lactic acid (PLLA) and poly-d-lactic acid (PDLA). Blending under certain conditions can form a stereocomplex polylactic acid (sc-PLA) with a special helical structure.
  • PLLA poly-L-lactic acid
  • PDLA poly-d-lactic acid
  • Blending under certain conditions can form a stereocomplex polylactic acid (sc-PLA) with a special helical structure.
  • the sc-PLA has stereocrystalline crystals, and its melting point is about 50 ° C higher than the alpha melting point of polylactic acid homopolymer crystals. It can improve the heat resistance of polylactic acid, and exhibit excellent mechanical properties and hydrolysis resistance, which can greatly expand the application range of polylactic acid.
  • stereocrystals are affected by many factors.
  • the blending ratio, molecular weight, molding method, temperature, etc. will affect the formation of stereocrystals. For example, as the processing temperature increases, The blending ratio of lactic acid is 1: 1, and the content of stereocrystals in the resulting blend gradually decreases.
  • Chinese patent CN105542411A discloses a method for preparing a stereocomplex crystallized polylactic acid material.
  • a new substance polyvinylidene fluoride is added as a promoter to improve the formation of stereocrystals, but the crystallinity of the obtained stereocomplex crystals is less than 17. %;
  • the method of annealing at high temperature can also increase the neutral crystal content of polylactic acid, but polylactic acid is easily degraded at high temperature, which makes the mechanical properties of polylactic acid products decrease. Therefore, how to form polylactic acid with high content of stereocrystals under conventional processing conditions, and the preparation method is easy to realize industrialization has been the research focus.
  • Irradiation technology has the advantages of energy saving, no environmental pollution, easy operation and control, and can trigger various polymerization, crosslinking and grafting of polymers.
  • irradiation is used to prepare a polypropylene material.
  • polylactic acid can be modified by irradiation to obtain polylactic acid with a high stereocrystalline content.
  • poly-L-lactic acid and poly-D-lactic acid were added to poly-L-lactic acid and poly-L-lactic acid, and were blended to obtain a high stereocomplex type.
  • Polylactic acid material which has the characteristics of high stereo crystalline content and good heat resistance, and the method of preparing high stereo composite polylactic acid material by irradiation technology is simple, low cost, green and pollution-free, and the high stereo composite
  • the polylactic acid material can be used to prepare a molded product once, thereby completing the present invention.
  • One aspect of the present invention is to provide a high stereo composite polylactic acid material.
  • the temperature of the melting peak of the polylactic acid material measured by a differential scanning calorimeter is above 210 ° C; the WXRD spectrum of the polylactic acid material is 2 ⁇ at 12 °, There are crystal plane diffraction peaks at 21 ° and 24 °, and the content of stereocrystals of the polylactic acid material is 36% or more.
  • the melting peak temperature of the polylactic acid material is above 220 ° C.
  • the stereocrystalline content of the polylactic acid material is above 40%.
  • the high stereo composite polylactic acid material is prepared by the following method:
  • Step 1 Irradiate poly-L-lactic acid and poly-L-lactic acid separately;
  • Step 2 Blend the irradiated poly-L-lactic acid and the irradiated poly-L-lactic acid with the non-irradiated poly-L-lactic acid and poly-d-lactic acid.
  • the weight-average molecular weight of poly-L-lactic acid is from 1 to 200,000 Da, preferably from 50,000 to 150,000 Da; the molar content of the L optical isomer in poly-L-lactic acid is from 95% to 99%, preferably from 97% to 99%;
  • the weight average molecular weight of poly-d-lactic acid is 1-200,000 Da, preferably 50,000 to 150,000 Da; the molar content of D optical isomers in poly-d-lactic acid is 95% to 99%, preferably 97% to 99%. .
  • Another aspect of the present invention provides a method for preparing the high stereo composite polylactic acid material according to the first aspect of the present invention.
  • the method includes the following steps:
  • Step 1 Irradiate poly-L-lactic acid and poly-L-lactic acid separately;
  • Step 2 Blend the irradiated poly-L-lactic acid and the irradiated poly-L-lactic acid with the non-irradiated poly-L-lactic acid and poly-d-lactic acid.
  • the irradiation dose is 500-700KGy.
  • the weight ratio of the total poly-L-lactic acid to the total poly-d-lactic acid is 2: 8 to 8: 2, preferably 3: 7 to 7: 3, and more preferably 4: 6 to 6: 4. , For example 5: 5;
  • Total poly-L-lactic acid is the sum of poly-L-lactic acid treated with radiation and poly-L-lactic acid not treated with radiation;
  • the total poly-d-lactic acid refers to the sum of poly-d-lactic acid treated with radiation and poly-d-lactic acid not treated with radiation.
  • the weight ratio of the poly (L-lactic acid) treated with radiation and the poly (L-lactic acid) not treated with radiation is 1: 49-10: 40, preferably 1: 49-5: 45, and more preferably 1:49 ⁇ 3: 47, such as 1:49;
  • the weight ratio of the irradiated poly-d-lactic acid and the non-irradiated poly-d-lactic acid is 1:49 to 10:40, preferably 1:49 to 5:45, and more preferably 1:49 to 3 : 47, such as 1:49.
  • step 2 the blending method is melt blending, and the blending equipment is selected from one of a single-screw extruder, a twin-screw extruder or an internal mixer;
  • the blending temperature is 180-250 ° C, preferably 190-230 ° C; the blending time is 5-30 minutes; the rotation speed of the blending is 10-100 rpm, preferably 30-80 rpm.
  • a cross-linking agent is also added during blending, wherein the amount of the cross-linking agent is 0.01% to 3% of the sum of the weight of the total poly-L-lactic acid and the total poly-d-lactic acid.
  • FIG. 1 shows DSC curves of sc-PLA prepared in Examples 1-3 and Comparative Examples 1-3;
  • FIG. 2 shows a two-dimensional graph test result of WAXD of sc-PLA prepared in Examples 1-3 and Comparative Examples 1-3;
  • FIG. 3 shows the one-dimensional curve test results of the WAXD of sc-PLA prepared in Examples 1-3 and Comparative Examples 1-3.
  • the first aspect of the present invention provides a high stereo composite polylactic acid material.
  • the melting peak temperature of the polylactic acid material measured by a differential scanning calorimeter is above 210 ° C; the WAXD spectrum of the polylactic acid material is 2 ⁇ at 12 ° There are crystal plane diffraction peaks at, 21 °, and 24 °; the content of stereocrystals of the polylactic acid material is more than 36%.
  • the melting peak temperature of the polylactic acid material measured by a differential scanning calorimeter is above 220 ° C., and the polylactic acid material has a stereocrystalline content of more than 40%. .
  • the melting peak temperature of the polylactic acid material measured by a differential scanning calorimeter can reach 230 ° C, and the stereocrystalline content of the polylactic acid material can reach 42%. .
  • the polylactic acid material is prepared by the following method:
  • Step 1 Irradiate poly-L-lactic acid and poly-L-lactic acid separately;
  • the weight-average molecular weight of poly-L-lactic acid is 1 to 200,000 Da, preferably 50,000 to 150,000 Da, and more preferably 100,000 Da.
  • the molar content of the L optical isomer in poly-L-lactic acid (PLLA) is 95% to 99%, preferably 97% to 99%.
  • the weight average molecular weight of poly (d-lactic acid) (PDLA) is from 1 to 200,000 Da, preferably from 50,000 to 150,000 Da, and more preferably from 100,000 Da.
  • the molar content of the D optical isomer in the polyd-lactic acid (PDLA) is 95% to 99%, preferably 97% to 99%.
  • poly-L-lactic acid and poly-L-lactic acid are commercially available products.
  • Poly-L-lactic acid was purchased from Zhejiang Hisun Biological Co., Ltd. under the brand name of REVODE190; poly-L-lactic acid was purchased from Jinan Li Biological Engineering Co., Ltd.
  • Irradiation technology is the use of ionizing radiation to induce physical and chemical changes.It is not only highly efficient, but also has the advantages of energy saving, pollution-free, green environmental protection, simple process and easy control of the operation process. It can process substances in batches, is suitable for industrial production, and has stable and reliable product performance. .
  • Currently applied to the field of polymer materials are mainly synthesis and modification. The application of irradiation technology to the modification of polylactic acid has important practical application value.
  • poly-L-lactic acid and poly-D-lactic acid are modified by irradiation technology, respectively.
  • both PLLA and PDLA molecules can generate free radicals, and the free radicals can cause cross-linking and copolymerization of molecules, and
  • the stereocomplex polylactic acid obtained by blending the irradiated PLLA and PDLA has a higher stereocrystalline content, and its crystallinity can reach 42%, that is, stereocrystalline
  • the mass percentage content i.e., the crystalline content
  • the irradiation treatment of PLLA and PDLA is performed by irradiation means such as 60 Co- ⁇ rays and electron beam irradiation.
  • the irradiation dose can affect the radiation modification effects of PLLA and PDLA.
  • Different radiation doses have different concentrations of free radicals.
  • the degree of molecular cross-linking and copolymerization will be different.
  • the content is different. The lower the radiation dose, the less the cross-linked structure is formed, and the content of the stereocrystals of the polylactic acid material is less. If the radiation dose is too high, the molecular chain breakage becomes the main reaction, and it is difficult to form the cross-linked structure.
  • the irradiation dose is 500-700KGy, preferably 550-650KGy, and more preferably 600KGy.
  • the irradiation dose when the irradiation dose is higher than 700KGy, the molecular chain break of the irradiation-treated PLLA and the irradiation-treated PDLA becomes the main reaction.
  • the irradiation dose is less than 500KGy, under a short period of electron beam irradiation, sufficient free radicals are not formed for subsequent reactions.
  • Step 2 Blend the irradiated poly-L-lactic acid and the irradiated poly-L-lactic acid with the non-irradiated poly-L-lactic acid and poly-d-lactic acid.
  • blending of poly-L-lactic acid PDLA and poly-L-lactic acid PLLA can form a stereocomplex polylactic acid (sc-PLA), which has a stereocomplex crystal (sc) having a melting point higher than that of pure poly-L-lactic acid PLLA or pure D-lactic acid PDLA has a high melting point, which is about 50 ° C higher, and sc-PLA has excellent mechanical properties and heat resistance, has good practical application value, and broadens the application range of polylactic acid.
  • sc-PLA stereocomplex polylactic acid
  • sc-PLA stereocomplex crystal having a melting point higher than that of pure poly-L-lactic acid PLLA or pure D-lactic acid PDLA has a high melting point, which is about 50 ° C higher
  • sc-PLA has excellent mechanical properties and heat resistance, has good practical application value, and broadens the application range of polylactic acid.
  • the crystals of poly-L-lactic acid PLLA and poly-d-lactic acid PDLA are in the ⁇ -type, and the molecular chains are spirally stacked to form a pseudo-orthogonal crystal system, while the crystal of the stereocomplex crystal (sc) is transformed into a triclinic system Or a trigonal crystal system, in this spiral-shaped stacking, the chain stacking is closer, thereby increasing the melting point of the material and improving the heat resistance.
  • step 2 the irradiated PLLA and the irradiated PDLA are blended and modified with the unirradiated PLLA and PDLA to prepare a high stereocomplex polylactic acid.
  • the mass ratio of the total poly-L-lactic acid PLLA and the total poly-L-lactic acid PDLA is 2: 8 to 8: 2, preferably 3: 7 to 7: 3, and more preferably 4: 6 ⁇ 6: 4, for example, 5: 5.
  • the total poly-L-lactic acid refers to the sum of poly-L-lactic acid PLLA after irradiation treatment and poly-L-lactic acid PLLA without irradiation treatment;
  • the total poly-d-lactic acid PDLA refers to the sum of the poly-d-lactic acid PDLA treated and the non-irradiated poly-d-lactic acid PDLA.
  • the present invention in the process of preparing sc-PLA by blending PLLA and PDLA, when the blending ratio of total PLLA and total PDLA is 1: 1, it is easier to form sc-PLA with high stereocrystalline content.
  • the inventors have found that compared to sc-PLA prepared by blending and modifying PLLA and PDLA without irradiation treatment, the PLLA and PDLA after irradiation treatment generate active free radicals due to irradiation.
  • PLLA It is easier to copolymerize and crosslink with PDLA under the action of active free radicals to form block copolymers, promote the formation of stereocrystals in the blend, and form stereocomplex polylactic acid with high stereocrystal content.
  • the weight ratio of the irradiated PLLA to the non-irradiated PLLA is 1: 49-10: 40, preferably 1: 49-5: 45, and more preferably 1:49.
  • ⁇ 3: 47 such as 1:49.
  • the weight ratio of the PDLA after irradiation treatment to the PDLA without irradiation treatment is 1:49 to 10:40, preferably 1:49 to 5:45, and more preferably 1:49.
  • ⁇ 3: 47 such as 1:49.
  • step 2 when the addition ratio of PLLA and PDLA after irradiation treatment is low, PLLA and PDLA are more likely to form a crosslinked structure, and a low content of the crosslinked structure can promote the formation of neutral crystals of the polylactic acid material; If the content of the cross-linked structure is too high, the movement of the molecular segments will be inhibited, and the content of stereocrystals will be reduced.
  • a cross-linking agent may be added during blending to promote the reaction. Proceeding is conducive to the formation of stereocrystals and increase the content of stereocrystals in the blend.
  • a cross-linking agent is further added during blending, and the cross-linking agent is preferably triallyl tricyanate (TAC accelerator).
  • TAC accelerator triallyl tricyanate
  • the amount of the cross-linking agent added is 0.01% to 3%, preferably 0.05% to 2%, and more preferably 0.1% to 1% of the sum of the weight of the total PLLA and the total PDLA. For example 0.5%.
  • the blending method in the preparation of the stereocomplex polylactic acid includes melt blending and solution blending.
  • solution-blending is used to prepare sc-PLA, a large number of toxic solvents such as dichloromethane and chloroform are required, and the preparation process is complicated, time-consuming, and inefficient, which causes environmental pollution and is not suitable for large-scale industrial production.
  • sc-PLA is prepared by melt blending without adding an organic solvent, and has a simple preparation process and high efficiency, which is suitable for large-scale industrial production.
  • the blending method is melt blending.
  • the blending equipment is a device commonly used in the art, and is selected from one of a single-screw extruder, a twin-screw extruder or an internal mixer, preferably an internal mixer.
  • the blending melting temperature has an important effect on the formation of stereocomposite crystals.
  • the blending melting temperature is low, the product obtained is a powdery solid and cannot be molded, that is, a primary molded product cannot be obtained;
  • polylactic acid is easily degraded, which also makes it impossible to obtain stereocomplex polylactic acid material.
  • the blending temperature is 180 to 250 ° C, preferably 190 to 230 ° C, and more preferably 200 to 230 ° C, such as 230 ° C.
  • the length of the blending time also affects the formation of stereocomposite crystals. If the blending time is too long, the copolymerized cross-linked structure of PLLA and PDLA is destroyed, the content of the formed stereocrystals decreases, and the blending efficiency is affected. ; Blending time is too short, unirradiated and irradiated PLLA and PDLA cannot be fully mixed, polylactic acid with high stereocrystalline content cannot be formed, and the technical effect achieved by irradiation cannot be reflected.
  • the blending time is 5 to 30 minutes, preferably 5 to 20 minutes, and more preferably 5 to 10 minutes, such as 5 minutes.
  • step 2 the blending speed is too fast, and the molecular structure of PLLA and PDLA is easily destroyed; the blending speed is too slow, and PLLA and PDLA cannot be fully mixed, and the blending speed is too fast or too slow to form high stereocrystals. Content of sc-PLA.
  • the blending speed is 10 to 100 rpm, preferably 30 to 80 rpm, and more preferably 40 to 70 rpm, such as 60 rpm.
  • a one-time molded product of high stereo composite polylactic acid material can be prepared, the preparation method is simple, the obtained product has a high stereo crystal content, which can be as high as 42% or more, and has excellent heat resistance.
  • the invention also provides another method for preparing a high stereo composite polylactic acid material, which method comprises: blending poly-L-lactic acid and poly-D-lactic acid while performing irradiation treatment.
  • the mass ratio of the total poly-L-lactic acid and the total poly-d-lactic acid is 2: 8 to 8: 2, preferably 7: 3 to 3: 7, and more preferably 4: 6 to 6: 4, for example It's 5: 5.
  • the blending method of poly-L-lactic acid and poly-L-lactic acid is preferably melt blending.
  • the high stereo composite polylactic acid material sc-PLA can also be prepared by melting and blending poly-L-lactic acid PLLA and poly-d-lactic acid PDLA while irradiating.
  • a cross-linking agent can be added to promote the reaction during blending and irradiation, which is beneficial to the formation of stereocrystals and the neutrality of the sc-PLA product. Crystal content.
  • a cross-linking agent is also added during blending, and the cross-linking agent is preferably triallyl tricyanate (TAC accelerator).
  • TAC accelerator triallyl tricyanate
  • the cross-linking agent is added in an amount of 0.01% to 3%, preferably 0.05% to 2%, and more preferably 0.1% to 1%, such as 0.5%, based on the sum of the weights of PLLA and PDLA.
  • the blending equipment is selected from a single-screw extruder, a twin-screw extruder or an internal mixer, preferably an internal mixer.
  • the blending temperature is 180 to 250 ° C, preferably 190 to 240 ° C, and more preferably 200 to 230 ° C, such as 230 ° C.
  • the blending time is 5 to 30 minutes, preferably 5 to 20 minutes, and more preferably 5 to 10 minutes, such as 5 minutes.
  • the blending rotation speed is 40 to 80 rpm, preferably 50 to 70 rpm, and more preferably 55 to 65 rpm, such as 60 rpm.
  • irradiation treatment is performed on poly-L-lactic acid and poly-D-lactic acid using irradiation technology, so that PLLA and PDLA generate free radicals, which can then trigger cross-linking and copolymerization of molecules to form block copolymers, and promote the formation of stereocrystals.
  • PLLA and PDLA generate free radicals, which can then trigger cross-linking and copolymerization of molecules to form block copolymers, and promote the formation of stereocrystals.
  • the generated free radicals will quickly participate in cross-linking copolymerization, thereby forming sc-PLA with a higher content of stereocrystals.
  • PLLA and PDLA are irradiated with an electron beam.
  • the irradiation dose of the irradiation treatment is 5 to 10 kgy, preferably 6 to 9 kgy, and more preferably 7.5 kgy.
  • the irradiation time of polylactic acid is longer, and the molecular chain breakage is prone to occur.
  • a low value is selected. Irradiation dose is performed on polylactic acid.
  • the high stereo composite polylactic acid material provided by the present invention has a high content of stereo crystals, a high melting point, and good heat resistance.
  • a WAXD test is performed on the high stereo composite polylactic acid material to obtain the WAXD of the polylactic acid material.
  • the one-dimensional spectrum has crystalline diffraction peaks at 2 ⁇ at 12 °, 21 °, and 24 °.
  • the polylactic acid material has a crystalline content above 36%, even above 40%, and even reaches 42%. ; Perform DSC test on it, the melting point is above 210 ° C, even above 220 ° C, and even reaches 230 ° C.
  • the high stereo composite polylactic acid material provided by the present invention contains a high content of stereo crystals, and the content of stereo crystals can reach 42%.
  • the melting point of the high stereo composite polylactic acid material provided by the present invention can reach 230 ° C, and the heat resistance is good.
  • the shortcomings of low heat resistance inherent in polylactic acid are overcome, and the application range of polylactic acid is widened.
  • the present invention adopts PLLA and PDLA blending modification to prepare stereocomplex polylactic acid, uses irradiation technology to modify PLLA and PDLA respectively, and then blends and uses irradiation technology to modify the preparation.
  • the method is novel, the operation is simple, it does not cause harmful substances to cause environmental pollution, and the obtained polylactic acid has a high stereocrystalline content.
  • the preparation method of the high stereo composite polylactic acid provided by the present invention is simple, easy to operate and controllable, low in cost, environmentally friendly, and energy-saving, and is suitable for industrialized large-scale production.
  • the method provided by the present invention is advantageous for preparing a disposable molded product of a polylactic acid material with a high stereocrystalline content.
  • the Q2000 type differential scanning calorimeter (DSC) of American TA company was used to perform the melting crystallization process test.
  • the instrument was calibrated with indium before the test, and the test was performed under a nitrogen atmosphere.
  • the sample was heated to 250 ° C at 10 ° C / min, and the temperature rise curve of the sample was recorded.
  • the nitrogen flow rate is 50 mL / min, and the sample amount is 5-10 mg.
  • the German BRUKER company D8DISCOVER was used for the two-dimensional wide-angle X-ray diffraction test.
  • the wavelength of the light source was Collected by the two-dimensional surface detector VANTEC-500, the exposure time is 300s, and the distance from the sample to the detector is 85.6mm.
  • the irradiation dose is 600KGy, to obtain irradiated poly-L-lactic acid and irradiated poly-L-lactic acid;
  • the weight average molecular weight of poly-L-lactic acid is 100,000 Da
  • the molar content of L optical isomers is 99%
  • the weight-average molecular weight of poly-L-lactic acid is 100,000 Da
  • the molar content of D optical isomers is 99%.
  • a WAXD test was performed on the obtained sc-PLA.
  • the obtained WAXD two-dimensional graph test result is shown in FIG. 2, and the WAXD one-dimensional curve test result is shown in FIG. 3.
  • the irradiation dose is 600KGy, to obtain irradiated poly-L-lactic acid and irradiated poly-d-lactic acid;
  • the weight average molecular weight of poly-L-lactic acid is 100,000 Da
  • the molar content of L optical isomers is 99%
  • the weight-average molecular weight of poly-L-lactic acid is 100,000 Da
  • the molar content of D optical isomers is 99%.
  • a WAXD test was performed on the obtained sc-PLA.
  • the obtained WAXD two-dimensional graph test result is shown in FIG. 2, and the WAXD one-dimensional curve test result is shown in FIG. 3.
  • the weight average molecular weight of poly-L-lactic acid is 100,000 Da
  • the molar content of L optical isomers is 99%
  • the weight-average molecular weight of poly-L-lactic acid is 100,000 Da
  • the molar content of D optical isomers is 99%.
  • a WAXD test was performed on the obtained sc-PLA.
  • the obtained WAXD two-dimensional graph test result is shown in FIG. 2, and the WAXD one-dimensional curve test result is shown in FIG. 3.
  • the weight average molecular weight of poly-L-lactic acid is 100,000 Da
  • the molar content of L optical isomers is 99%
  • the weight-average molecular weight of poly-L-lactic acid is 100,000 Da
  • the molar content of D optical isomers is 99%.
  • the stereocomplex polylactic acid obtained had a stereocrystal content of 52.3%, but the stereocomplex polylactic acid was a powdery solid and a primary molded product could not be obtained.
  • a WAXD test was performed on the obtained sc-PLA.
  • the obtained WAXD two-dimensional graph test result is shown in FIG. 2, and the WAXD one-dimensional curve test result is shown in FIG. 3.
  • the weight average molecular weight of poly-L-lactic acid is 100,000 Da
  • the molar content of L optical isomers is 99%
  • the weight-average molecular weight of poly-L-lactic acid is 100,000 Da
  • the molar content of D optical isomers is 99%.
  • a WAXD test was performed on the obtained sc-PLA.
  • the obtained WAXD two-dimensional graph test result is shown in FIG. 2, and the WAXD one-dimensional curve test result is shown in FIG. 3.
  • the weight average molecular weight of poly-L-lactic acid is 100,000 Da
  • the molar content of L optical isomers is 99%
  • the weight-average molecular weight of poly-L-lactic acid is 100,000 Da
  • the molar content of D optical isomers is 99%.
  • a WAXD test was performed on the obtained sc-PLA.
  • the obtained WAXD two-dimensional graph test result is shown in FIG. 2, and the WAXD one-dimensional curve test result is shown in FIG. 3.
  • FIG. 1 is a DSC curve of the first temperature rise of sc-PLA obtained in Examples 1-3 and Comparative Examples 1-3.
  • the melting point of sc-PLA obtained in Example 1-3 is about 230 ° C.
  • the melting point of sc-PLA prepared in Example 1 and Comparative Examples 1-3 about 220 ° C.
  • the melting peak of the ⁇ -crystal of the homopolymer crystal in Example 1-3 was reduced, and the peak area was smaller than that of the ⁇ -crystal of the homopolymer crystal in Comparative Example 1-3.
  • FIG. 2 is a two-dimensional picture of WAXD of sc-PLA prepared in Examples 1-3 and Comparative Examples 1-3.
  • the sc-PLA samples prepared in Examples 1-3 have stereo crystals.
  • the three characteristic crystal planes of the crystal structure have high diffraction intensity, indicating that they contain only stereocrystals, while the crystal plane diffraction peak intensity of the stereocrystals appearing in Comparative Examples 1-3 is weaker than the crystals of the stereocrystals of Example 1-3.
  • Surface scattering peaks, and other crystal plane diffraction peaks (such as crystal plane diffraction peaks of ⁇ crystals) also exist.
  • FIG. 3 is a one-dimensional WAXD spectrum of sc-PLA prepared in Example 1-3 and comparative example 1-3.
  • the one-dimensional WAXD spectrum of sc-PLA prepared in Example 1-3 is only There are crystal plane diffraction peaks at 2 ⁇ of 12 °, 21 °, and 24 °.
  • the diffraction peaks are the crystal plane diffraction peaks of the stereocrystals.
  • the peaks of the sc-PLA obtained in Examples 1-3 are calculated by fitting the peaks.
  • the crystal content was 36.5%, 42%, and 41.5%, respectively.
  • the sc-PLA of Comparative Examples 1-3 had crystal plane diffraction peaks at 2 ⁇ of 12 °, 21 °, and 24 °, but the diffraction peak intensity was weak and still existed.
  • the stereo-crystal content of sc-PLA prepared in Comparative Examples 1-3 was calculated to be 52.3%, 23.4%, and 6.4%, respectively.
  • the content of stereocrystals is high, but its morphology is a powdery solid, and a primary molded product cannot be obtained. It can be known that the sc-PLA prepared by the irradiation treatment can obtain a primary molded product, and the stereo crystal content is high.
  • the cross-linking agent is added to further increase the stereo crystal content.

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Abstract

本发明公开了一种高立构复合型聚乳酸材料及其制备方法，用差示扫描量热仪测得该聚乳酸材料的熔融峰的温度在210℃以上；该聚乳酸材料的WAXD一维图谱在2θ为12°、21°和24°处存在立构晶的晶面衍射峰；该聚乳酸材料的立构晶含量为36％以上。该高立构复合型聚乳酸材料的制备方法包括以下步骤：步骤1、分别对聚左旋乳酸和聚右旋乳酸进行辐照处理；步骤2、将辐照过的聚左旋乳酸和辐照过的聚右旋乳酸，与未经辐照的聚左旋乳酸和聚右旋乳酸进行共混。由该制备方法制得耐热性能好，立构晶含量高，可一次成型的高立构复合型聚乳酸材料，并且该制备方法简单易控、成本低廉、绿色环保，易于实现大规模工业化生产。

Description

一种高立构复合型聚乳酸材料及其制备方法 技术领域
本发明属于高分子材料技术领域，涉及聚乳酸材料的制备方法，具体涉及一种辐照形成高立构复合型聚乳酸材料的制备方法。
背景技术
聚乳酸(PLA)是一种可生物降解的脂肪族聚酯，由玉米淀粉等可再生作物加工制造而成，聚乳酸使用后在自然环境中可降解成CO 2和H 2O，具有无毒、无刺激、绿色环保等优点，是一种极具发展潜力的环境友好型绿色高分子材料，成为近年来研究的重点。另外，聚乳酸具有良好的生物相容性和较好的热塑性加工性能，已广泛应用于塑料、服装、医疗等领域。但是聚乳酸的耐热性较差、机械性能差，这些缺点限制了聚乳酸材料的应用范围。
聚乳酸的单体乳酸为一种手性分子，形成的聚乳酸具有聚左旋乳酸(PLLA)和聚右旋乳酸(PDLA)两种对映异构体，将聚左旋乳酸与聚右旋乳酸在一定条件下共混可形成具有特殊螺旋结构的立构复合型聚乳酸(sc-PLA)，该sc-PLA具有立构晶晶体，其熔点比聚乳酸均聚物晶体α晶熔点高约50℃，能改善聚乳酸的耐热性能，且表现出优异的机械性能和耐水解性能，能够大大拓宽聚乳酸的应用范围。
但是，立构晶的形成受多方面的影响，共混比例、分子量、成型方法、温度等都会影响立构晶的形成，例如，随着加工温度的升高，即使聚左旋乳酸和聚右旋乳酸的共混比例是1:1，形成的共混物中立构晶的含量逐渐降低。
中国专利CN105542411A公布了一种易立构复合结晶化聚乳酸材料的制备方法，加入新物质聚偏氟乙烯作为促进剂，提高立构晶的形成，但所得立构复合结晶的结晶度低于17％；利用高温退火的方法也可提高聚乳酸中立构晶含量，但在高温下聚乳酸极易发生降解，使得聚乳酸制品的机械性能下降。因此，如何在常规加工条件下形成具有高含量立构晶的聚乳酸，且制备方法易于实现产业化一 直是研究重点。
辐照技术具有节能、无环境污染、易操作可控等优势，能引发高分子的各种聚合、交联和接枝等。例如辐照交联制备聚丙烯材料，同样地，可采用辐照技术对聚乳酸进行改性以获得高立构晶含量的聚乳酸。
因此，开发一种易获得高立构晶含量的、耐热性能好的、可一次成型的，且制备方法简单、绿色节能环保、可工业化规模生产的高立构复合聚乳酸材料及其制备方法。
发明内容
为了解决上述问题，本发明人进行了锐意研究，结果发现：向聚左旋乳酸与聚右旋乳酸中加入经过辐照处理的聚左旋乳酸和聚右旋乳酸，通过共混，制得高立构复合型聚乳酸材料，该聚乳酸材料具有立构晶含量高、耐热性能好的特点，并且采用辐照技术制得高立构复合型聚乳酸材料的方法简单、成本低廉、绿色无污染，由该高立构复合型聚乳酸材料可制备一次成型制品，从而完成本发明。
本发明一方面提供一种高立构复合型聚乳酸材料，用差式扫描量热仪测得该聚乳酸材料的熔融峰的温度在210℃以上；该聚乳酸材料的WXRD图谱在2θ为12°、21°和24°处存在立构晶的晶面衍射峰，该聚乳酸材料的立构晶含量为36％以上。
优选地，用差式扫描量热仪测试时，该聚乳酸材料的熔融峰的温度在220℃以上，该聚乳酸材料的立构晶含量为40％以上。
优选地，该高立构复合型聚乳酸材料由以下方法制得：
步骤1、分别对聚左旋乳酸和聚右旋乳酸进行辐照处理；
步骤2、将辐照过的聚左旋乳酸和辐照过的聚右旋乳酸，与未经辐照的聚左旋乳酸和聚右旋乳酸进行共混。
其中，聚左旋乳酸的重均分子量为1-20万Da，优选为5-15万Da；聚左旋乳酸中L旋光异构体的摩尔含量为95％～99％，优选97％～99％；
聚右旋乳酸的重均分子量为1-20万Da，优选为5-15万Da；聚右旋乳酸中D旋光异构体的摩尔含量为95％～99％，优选为97％～99％。
本发明的另一方面提供一种制备本发明第一方面所述的高立构复合型聚乳酸材料的方法，该方法包括以下步骤：
步骤1、分别对聚左旋乳酸和聚右旋乳酸进行辐照处理；
步骤2、将辐照过的聚左旋乳酸和辐照过的聚右旋乳酸，与未经辐照的聚左旋乳酸和聚右旋乳酸进行共混。
其中，步骤1中，辐照处理时，辐照剂量为500～700KGy。
其中，步骤2中，总的聚左旋乳酸与总的聚右旋乳酸的重量比为2:8～8:2，优选为3:7～7:3，更优选为4:6～6:4，例如为5:5；
总的聚左旋乳酸是指经过辐照处理的聚左旋乳酸和未经过辐照处理的聚左旋乳酸之和；
总的聚右旋乳酸是指经过辐照处理的聚右旋乳酸和未经过辐照处理的聚右旋乳酸之和。
步骤2中，经过辐照处理的聚左旋乳酸和未经过辐照处理的聚左旋乳酸的重量比为1:49～10:40，优选为1:49～5:45，更优选为1:49～3:47，例如1:49；
经过辐照处理的聚右旋乳酸和未经过辐照处理的聚右旋乳酸的重量比为1:49～10:40，优选为1:49～5:45，更优选为1:49～3:47，例如1:49。
步骤2中，所述共混的方式为熔融共混，共混设备选自单螺杆挤出机、双螺杆挤出机或密炼机中的一种；
共混的温度为180～250℃，优选为190～230℃；共混时间为5～30min；共混的转速为10～100rpm，优选为30～80rpm。
其中，步骤2中，共混时还加入交联剂，其中，交联剂的加入量为总的聚左旋乳酸和总的聚右旋乳酸重量之和的0.01％～3％。
附图说明
图1示出实施例1-3与对比例1-3制得的sc-PLA的DSC曲线；
图2示出实施例1-3与对比例1-3制得的sc-PLA的WAXD的二维图测试结果；
图3示出实施例1-3与对比例1-3制得的sc-PLA的WAXD的一维曲线测试结果。
具体实施方式
下面通过对本发明进行详细说明，本发明的特点和优点将随着 这些说明而变得更为清楚、明确。
本发明第一方面提供一种高立构复合型聚乳酸材料，用差示扫描量热仪测得该聚乳酸材料的熔融峰的温度在210℃以上；该聚乳酸材料的WAXD图谱在2θ为12°、21°和24°处存在立构晶的晶面衍射峰；该聚乳酸材料的立构晶含量为36％以上。
根据本发明提供的一种高立构复合型聚乳酸材料，用差示扫描量热仪测得该聚乳酸材料的熔融峰的温度在220℃以上，该聚乳酸材料的立构晶含量为40％以上。
根据本发明提供的一种高立构复合型聚乳酸材料，用差示扫描量热仪测得该聚乳酸材料的熔融峰的温度可达到230℃，该聚乳酸材料的立构晶含量可达到42％。
根据本发明第一方面所述的高立构复合型聚乳酸材料，该聚乳酸材料由下方法制得：
步骤1、分别对聚左旋乳酸和聚右旋乳酸进行辐照处理；
根据本发明，聚左旋乳酸(PLLA)的重均分子量为1-20万Da，优选为5-15万Da，更优选为10万Da。
根据本发明，聚左旋乳酸(PLLA)中L旋光异构体的摩尔含量为95％～99％，优选为97％～99％。
根据本发明，聚右旋乳酸(PDLA)的重均分子量1-20万Da，优选为5-15万Da，更优选为10万Da。
根据本发明，聚右旋乳酸(PDLA)中D旋光异构体的摩尔含量为95％～99％，优选为97％～99％。
本发明中，聚左旋乳酸和聚右旋乳酸为市售产品。聚左旋乳酸购自浙江海正生物有限公司，牌号为REVODE190；聚右旋乳酸购自济南岱罡生物工程有限公司。
辐照技术是利用电离辐射诱发物理化学变化，不仅效率高而且具有节能、无公害、绿色环保、工艺简单和操作过程容易控制等优点，对物质可以批量处理、适用于工业化生产，产品性能稳定可靠。目前应用到高分子材料领域主要是合成和改性。将辐照技术应用到聚乳酸的改性中，具有重要的实际应用价值。
本发明中，采用辐照技术分别对聚左旋乳酸和聚右旋乳酸进行改性，经过辐照后，PLLA和PDLA分子均可产生自由基，自由基具 有活性可引发分子发生交联共聚，与未经辐照处理的PLLA和PDLA相比，经过辐照的PLLA和PDLA共混后得到的立构复合型聚乳酸的立构晶含量更高，其结晶度可达到42％，即立构晶的质量百分含量(即立构晶含量)可达到42％。
根据本发明，采用 60Co-γ射线、电子束辐照等辐照手段对PLLA和PDLA进行辐照处理。
本发明人发现，辐照剂量可影响PLLA和PDLA的辐照改性效果。不同辐照剂量，产生的自由基的浓度不同，则在后续步骤中与未经辐照的PLLA和PDLA共混时，分子交联共聚程度不同，形成的立构复合聚乳酸材料的立构晶的含量不同。辐照剂量较低则形成的交联结构较少，形成聚乳酸材料的立构晶含量较少；辐照剂量过高，则分子链断链成为主要反应，不易形成交联结构。
根据本发明，步骤1中，辐照剂量为500～700KGy，优选为550～650KGy，更优选为600KGy。
本发明中，当辐照剂量高于700KGy，经辐照处理的PLLA和经辐照处理的PDLA的分子链断裂成为主要反应。当辐照剂量低于500KGy，在短时间的电子束辐照下，未能形成足够的自由基进行后续反应。
步骤2、将辐照过的聚左旋乳酸和辐照过的聚右旋乳酸，与未经辐照的聚左旋乳酸和聚右旋乳酸进行共混。
本发明中，聚右旋乳酸PDLA与聚左旋乳酸PLLA共混能够形成立构复合型聚乳酸(sc-PLA)，其具有的立构复合晶(sc)的熔点比纯聚左旋乳酸PLLA或纯右旋乳酸PDLA的熔点高，高出约50℃，且sc-PLA具有优异的机械性能和耐热性能，具有很好的实际应用价值，拓宽了聚乳酸的应用范围。其中，聚左旋乳酸PLLA和聚右旋乳酸PDLA的晶体为α晶型，其分子链通过螺旋堆积形成一种伪正交晶系，而立构复合晶(sc)的晶体则转变为三斜晶系或三方晶系，在这种螺旋构成的堆积中，链堆积更加紧密，从而提高了材料的熔点，使耐热性能得到提高。
本发明中，步骤2中，将经过辐照处理的PLLA和经过辐照处理的PDLA，与未经辐照的PLLA和PDLA进行共混改性，以制备高立构复合型聚乳酸。
根据本发明，步骤2中，总的聚左旋乳酸PLLA和总的聚右旋乳酸PDLA的质量比为2:8～8:2，优选为3:7～7:3，更优选为4:6～6:4，例如为5:5。
本发明中，总的聚左旋乳酸是PLLA指经过辐照处理的聚左旋乳酸PLLA和未经过辐照处理的聚左旋乳酸PLLA之和；
总的聚右旋乳酸PDLA是指经过辐照处理的聚右旋乳酸PDLA和未经过辐照处理的聚右旋乳酸PDLA之和。
根据本发明，PLLA和PDLA共混制备sc-PLA的过程中，总的PLLA和总的PDLA的共混重量比为1:1时，更易形成高立构晶含量的sc-PLA。
本发明人发现，相比于未经辐照处理的PLLA和PDLA共混改性制备的sc-PLA，经过辐照处理的PLLA和PDLA由于辐照产生了活性自由基，在共混时，PLLA和PDLA更容易在活性自由基的作用下发生共聚交联，生成嵌段共聚物，促进共混物中立构晶的形成，形成立构晶含量高的立构复合型聚乳酸。
根据本发明，步骤2中，经过辐照处理的PLLA与未经过辐照处理的PLLA的重量比为1:49～10:40，优选为1:49～5:45，更优选为1:49～3:47，例如1:49。
根据本发明，步骤2中，经辐照处理的PDLA与未经过辐照处理的PDLA的重量比为1:49～10:40，优选为1:49～5:45，更优选为1:49～3:47，例如1:49。
根据本发明，步骤2中，经辐照处理的PLLA和PDLA的加入比例较低时，PLLA和PDLA更易形成交联结构，且低含量的交联结构能促进聚乳酸材料中立构晶的形成；若交联结构含量过高，则会抑制分子链段的运动，形成立构晶的含量降低。
本发明中，步骤2中，为进一步促进经过辐照处理的PLLA、PDLA与未经辐照的PLLA、PDLA充分反应，生成嵌段共聚物，在共混时可加入交联剂，促进反应的进行，有利于形成立构晶，提高共混物中立构晶的含量。
根据本发明，步骤2中，在共混时还加入交联剂，交联剂优选为三聚氰酸三烯丙酯(TAC促进剂)。在交联剂作用下，经辐照处理的PLLA和辐照处理的PDLA更容易结合形成交联结构。
根据本发明，步骤2中，交联剂的加入量为总的PLLA和总的PDLA的重量之和的0.01％～3％，优选为0.05％～2％，更优选为0.1％～1％，例如0.5％。
立构复合型聚乳酸制备时的共混方法包括熔融共混和溶液共混。溶液共混制备sc-PLA时，需要使用大量的有毒的溶剂，如二氯甲烷、三氯甲烷等，并且制备工艺复杂、耗时长、效率低，造成环境污染，不适于大规模工业化生产。而熔融共混制备sc-PLA，无需添加有机溶剂，制备工艺简单、效率高、适于大规模工业化生产。
根据本发明，步骤2中，共混方式为熔融共混。
根据本发明，步骤2中，共混设备为本领域技术常用设备，选自单螺杆挤出机、双螺杆挤出机或密炼机中的一种，优选为密炼机。
本发明中，步骤2中，共混熔融温度对立构复合晶的形成具有重要的影响，共混熔融温度较低时，所得产物为粉末状固体，无法成型，即无法获得一次成型制品；温度较高时，聚乳酸极易发生降解，也导致无法获得立构复合型聚乳酸材料。
根据本发明，步骤2中，共混的温度为180～250℃，优选为190～230℃，更优选为200～230℃，例如230℃。
本发明中，共混时间的长短也对立构复合晶的形成有影响，共混时间过长，PLLA和PDLA的共聚交联结构被破坏，形成的立构晶的含量下降，并且影响共混效率；共混时间太短，未辐照的和辐照的PLLA和PDLA不能充分混合，无法形成立构晶含量高的聚乳酸，并且辐照所达到的技术效果无法体现出来。
根据本发明，步骤2中，共混的时间为5～30min，优选为5～20min，更优选为5～10min，例如5min。
本发明中，步骤2中，共混速度太快，PLLA和PDLA的分子结构容易被破坏；共混速度太慢，PLLA和PDLA无法充分混合，共混速度太快或太慢均难以形成高立构晶含量的sc-PLA。
根据本发明，步骤2中，共混转速为10～100rpm，优选为30～80rpm，更优选为40～70rpm，例如60rpm。
共混结束后自然条件下冷却至室温，得到高立构复合型聚乳酸。
根据上述制备方法可制备高立构复合型聚乳酸材料的一次成型制品，制备方法简单，所得制品的立构晶含量高，可高达42％以上， 具有优异的耐热性能。
本发明还提供高立构复合型聚乳酸材料的另一种制备方法，该方法包括：将聚左旋乳酸和聚右旋乳酸进行共混的同时进行辐照处理。
根据本发明，总的聚左旋乳酸和总的聚右旋乳酸的质量比为2:8～8:2，优选为7:3～3:7，更优选为4:6～6:4，例如为5:5。
根据本发明一种优选的实施方式，聚左旋乳酸和聚右旋乳酸的共混方式优选为熔融共混。
根据本发明，高立构复合型聚乳酸材料sc-PLA，还可由聚左旋乳酸PLLA和聚右旋乳酸PDLA边熔融共混边辐照制得。
本发明中，为进一步促进PLLA与PDLA充分反应，生成嵌段共聚物，可加入交联剂，从而在共混和辐照时促进反应进行，有利于形成立构晶，提高产物sc-PLA中立构晶的含量。
根据本发明，在共混时还加入交联剂，交联剂优选为三聚氰酸三烯丙酯(TAC促进剂)。
根据本发明，交联剂的加入量为PLLA和PDLA的重量之和的0.01％～3％，优选为0.05％～2％，更优选为0.1％～1％，例如0.5％。
根据本发明，共混设备选自单螺杆挤出机、双螺杆挤出机或密炼机，优选为密炼机。
根据本发明，共混的温度为180～250℃，优选为190～240℃，更优选为200～230℃，例如230℃。
根据本发明，共混的时间为5～30min，优选为5～20min，更优选为5～10min，例如5min。
根据本发明，步骤2中，共混转速为40～80rpm，优选为50～70rpm，更优选为55～65rpm，例如60rpm。
本发明中，采用辐照技术对聚左旋乳酸和聚右旋乳酸进行辐照处理，使得PLLA和PDLA产生自由基，进而可引发分子发生交联共聚生成嵌段共聚物，促进立构晶的形成，提高聚乳酸的立构晶含量。在原位共混的同时进行辐照处理，产生的自由基会迅速参与交联共聚，从而形成具有较高含量立构晶的sc-PLA。
根据本发明，采用电子束对PLLA和PDLA进行辐照处理。
根据本发明，辐照处理的辐照剂量5～10KGy，优选为6～9KGy， 更优选为7.5KGy。采用边熔融共混边辐照的方法即原位共混辐照的方法，聚乳酸的辐照时间较长，易发生分子链的断链，为避免分子链断链成为主要反应，故选用低辐照剂量对聚乳酸进行辐照处理。
本发明所提供的高立构复合型聚乳酸材料，具有高含量的立构晶，较高的熔点，耐热性能好，例如对该高立构复合型聚乳酸材料进行WAXD测试，得到该聚乳酸材料的WAXD一维图谱在2θ为12°、21°和24°处存在立构晶的晶面衍射峰，该聚乳酸材料的立构晶含量在36％以上，甚至在40％以上，更甚至达到42％；对其进行DSC测试，熔点在210℃以上，甚至在220℃以上，更甚至达到230℃。
本发明所具有的有益效果：
(1)本发明所提供的高立构复合型聚乳酸材料含有高含量的立构晶，立构晶含量可达到42％。
(2)本发明所提供的高立构复合型聚乳酸材料的熔点可达到230℃，耐热性能好，克服了聚乳酸固有的低耐热性能的缺陷，拓宽了聚乳酸的应用范围。
(3)本发明采用基于PLLA和PDLA共混改性制备立构复合型聚乳酸，采用辐照技术分别对PLLA和PDLA进行改性，然后再进行共混，采用辐照技术改性处理的制备方法新颖、操作简单，不会产生有害物质对环境造成污染，且所得聚乳酸的立构晶含量高。
(4)本发明所提供的高立构复合型聚乳酸的制备方法简单、易操作可控，成本低、绿色环保、节能，适于工业化大规模生产。
(5)根据本发明所提供的方法有利于制备高立构晶含量聚乳酸材料的一次性成型制品。
实施例
以下通过具体实例进一步描述本发明。不过这些实例仅仅是范例性的，并不对本发明的保护范围构成任何限制。
结晶行为测试：
采用美国TA公司的Q2000型差示扫描量热仪(DSC)进行熔融结晶过程测试，仪器在测试前经过铟校正，测试在氮气氛围下进行。样品以10℃/min升温至250℃，记录样品的升温曲线。氮气流速为 50mL/min，样品用量为5～10mg。
广角X射线衍射(WAXD)测试：
采用德国BRUKER公司D8DISCOVER进行二维广角X射线衍射测试，光源波长为
Figure PCTCN2019102628-appb-000001
通过二维面探测器VANTEC-500收集，曝光时间300s，样品到探测器的距离为85.6mm。
实施例1
称取10g聚左旋乳酸和10g聚右旋乳酸，采用电子束进行辐照处理，辐照剂量为600KGy，得到辐照后的聚左旋乳酸和辐照后的聚右旋乳酸；
称取0.5g辐照后的聚左旋乳酸和0.5g辐照后的聚右旋乳酸，与24.5g未辐照的聚左旋乳酸和24.5g未辐照的聚右旋乳酸，加入到密炼机中进行熔融共混，设定密炼机温度为230℃，转速为60r/min，密炼时间为5min，密炼结束后，自然冷却至室温，得到立构复合型聚乳酸。
其中，聚左旋乳酸的重均分子量为10万Da，L旋光异构体摩尔含量为99％，聚左旋乳酸的重均分子量为10万Da，D旋光异构体摩尔含量为99％。
对所得立构复合型聚乳酸sc-PLA进行DSC测试，所得第一次升温的DSC曲线如图1所示。
对所得sc-PLA进行WAXD测试，所得WAXD二维图测试结果如图2所示，WAXD一维曲线测试结果如图3所示。
实施例2
称取10g聚左旋乳酸和10g聚右旋乳酸，采用电子束射线进行辐照处理，辐照剂量为600KGy，得到辐照后的聚左旋乳酸和辐照后的聚右旋乳酸；
称取0.5g辐照后的聚左旋乳酸和0.5g辐照后的聚右旋乳酸，24.5g未辐照的聚左旋乳酸、24.5g未辐照的聚右旋乳酸以及0.25g三聚氰酸三烯丙酯，加入到密炼机中进行熔融共混，设定密炼机温度为230℃，转速为60r/min，密炼时间为5min，密炼结束后，自然冷却至室温，得到立构复合型聚乳酸。
其中，聚左旋乳酸的重均分子量为10万Da，L旋光异构体摩尔含量为99％，聚左旋乳酸的重均分子量为10万Da，D旋光异构体摩尔含量为99％。
对所得立构复合型聚乳酸sc-PLA进行DSC测试，所得第一次升温的DSC曲线如图1所示。
对所得sc-PLA进行WAXD测试，所得WAXD二维图测试结果如图2所示，WAXD一维曲线测试结果如图3所示。
实施例3
称取24.87g聚左旋乳酸、24.87g聚右旋乳酸以及0.25g三聚氰酸三烯丙酯，加入到密炼机中进行熔融共混同时进行辐照处理，其中，采用电子束进行辐照处理，辐照剂量为7.5KGy；设定密炼机温度为230℃，转速为60r/min，密炼时间为5min，密炼结束后，自然冷却至室温，得到立构复合型聚乳酸。
其中，聚左旋乳酸的重均分子量为10万Da，L旋光异构体摩尔含量为99％，聚左旋乳酸的重均分子量为10万Da，D旋光异构体摩尔含量为99％。
对所得立构复合型聚乳酸sc-PLA进行DSC测试，所得第一次升温的DSC曲线如图1所示。
对所得sc-PLA进行WAXD测试，所得WAXD二维图测试结果如图2所示，WAXD一维曲线测试结果如图3所示。
对比例1
称取25g聚左旋乳酸和25g聚右旋乳酸，加入到密炼机中进行熔融共混，设定密炼机温度为190℃，转速为60r/min，密炼时间为5min，密炼结束后，自然冷却至室温，得到立构复合型聚乳酸。
其中，聚左旋乳酸的重均分子量为10万Da，L旋光异构体摩尔含量为99％，聚左旋乳酸的重均分子量为10万Da，D旋光异构体摩尔含量为99％。
结果发现，所得到的立构复合型聚乳酸的立构晶含量为52.3％，但该立构复合型聚乳酸为粉末状固体，无法得到一次成型制品。
对所得立构复合型聚乳酸sc-PLA进行DSC测试，所得第一次升 温的DSC曲线如图1所示。
对所得sc-PLA进行WAXD测试，所得WAXD二维图测试结果如图2所示，WAXD一维曲线测试结果如图3所示。
对比例2
称取25g聚左旋乳酸和25g聚右旋乳酸，加入到密炼机中进行熔融共混，设定密炼机温度为230℃，转速为60r/min，密炼时间为5min，密炼结束后，自然冷却至室温，得到立构复合型聚乳酸。
其中，聚左旋乳酸的重均分子量为10万Da，L旋光异构体摩尔含量为99％，聚左旋乳酸的重均分子量为10万Da，D旋光异构体摩尔含量为99％。
对所得立构复合型聚乳酸sc-PLA进行DSC测试，所得第一次升温的DSC曲线如图1所示。
对所得sc-PLA进行WAXD测试，所得WAXD二维图测试结果如图2所示，WAXD一维曲线测试结果如图3所示。
对比例3
称取24.87g聚左旋乳酸、24.87g聚右旋乳酸和0.25g三聚氰酸三烯丙酯(TAC促进剂)，加入到密炼机中进行熔融共混，设定密炼机温度为230℃，转速为60r/min，密炼时间为5min，密炼结束后，自然冷却至室温，得到立构复合型聚乳酸。
其中，聚左旋乳酸的重均分子量为10万Da，L旋光异构体摩尔含量为99％，聚左旋乳酸的重均分子量为10万Da，D旋光异构体摩尔含量为99％。
对所得立构复合型聚乳酸sc-PLA进行DSC测试，所得第一次升温的DSC曲线如图1所示。
对所得sc-PLA进行WAXD测试，所得WAXD二维图测试结果如图2所示，WAXD一维曲线测试结果如图3所示。
图1为实施例1-3与对比例1-3所得sc-PLA的第一次升温的DSC曲线，从图1中可以看出，实施例1-3所得sc-PLA的熔点约为230℃，高于实施例1和对比例1-3制得的sc-PLA的熔点(约为220℃)。且实 施例1-3中均聚物晶体α晶的熔融峰减小，峰面积小于对比例1-3中均聚物晶体α晶。
图2为实施例1-3和对比例1-3制得的sc-PLA的WAXD二维图，从图中可以看出，实施例1-3制得的sc-PLA样品出现了立构晶的三个特征晶面衍射，且衍射强度高，表明只含有立构晶，而对比例1-3中出现的立构晶的晶面衍射峰强度弱于实施例1-3立构晶的晶面散射峰，且还存在其他晶面衍射峰(如α晶的晶面衍射峰)。
图3为实施例1-3和对比例1-3制得的sc-PLA的WAXD一维图谱，从图中可以看出，实施例1-3制得的sc-PLA的WAXD一维图谱仅在2θ为12°、21°和24°处存在晶面衍射峰，该衍射峰为立构晶的晶面衍射峰，分峰拟合计算实施例1-3制得的sc-PLA的立构晶含量分别为36.5％、42％和41.5％；对比例1-3的sc-PLA在2θ为12°、21°和24°处存在晶面衍射峰，但其衍射峰强度较弱且还存在其他衍射峰(如α晶衍射峰)，计算对比例1-3制得的sc-PLA的立构晶含量分别为52.3％、23.4％和6.4％，尽管对比例1制得的sc-PLA的立构晶含量较高，但其形态为粉末状固体，无法获得一次成型制品。可知，经过辐照处理所制得的sc-PLA能够得到一次成型制品，并且立构晶含量高，加入交联剂后立构晶含量进一步提高。
以上结合具体实施方式和范例性实例对本发明进行了详细说明，不过这些说明并不能理解为对本发明的限制。本领域技术人员理解，在不偏离本发明精神和范围的情况下，可以对本发明技术方案及其实施方式进行多种等价替换、修饰或改进，这些均落入本发明的范围内。本发明的保护范围以所附权利要求为准。

Claims (10)

  1. 一种高立构复合型聚乳酸材料，其特征在于，用差示扫描量热仪测得该聚乳酸材料的熔融峰的温度在210℃以上；该聚乳酸材料的WAXD图谱在2θ为12°、21°和24°处存在立构晶的晶面衍射峰；该聚乳酸材料的立构晶含量为36％以上。
  2. 根据权利要求1所述的聚乳酸材料，其特征在于，用差示扫描量热仪测得该聚乳酸材料的熔融峰的温度在220℃以上；该聚乳酸材料的立构晶含量为40％以上。
  3. 根据权利要求1或2所述的聚乳酸材料，其特征在于，该聚乳酸材料由以下方法制得：
    步骤1、分别对聚左旋乳酸和聚右旋乳酸进行辐照处理；
    步骤2、将辐照过的聚左旋乳酸和辐照过的聚右旋乳酸，与未经辐照的聚左旋乳酸和聚右旋乳酸进行共混。
  4. 根据权利要求1所述的聚乳酸材料，其特征在于，所述聚左旋乳酸的重均分子量为1-20万Da，优选为5-15万Da；聚左旋乳酸中L旋光异构体的摩尔含量为95％～99％，优选97％～99％；
    所述聚右旋乳酸的重均分子量为1-20万Da，优选为5-15万Da；聚右旋乳酸中D旋光异构体的摩尔含量为95％～99％，优选为97％～99％。
  5. 一种制备根据权利要求1至4之一所述的高立构复合型聚乳酸材料的方法，其特征在于，该方法包括以下步骤：
    步骤1、分别对聚左旋乳酸和聚右旋乳酸进行辐照处理；
    步骤2、将辐照过的聚左旋乳酸和辐照过的聚右旋乳酸，与未经辐照的聚左旋乳酸和聚右旋乳酸进行共混。
  6. 根据权利要求5所述的方法，其特征在于，步骤1中，进行辐照处理时，辐照剂量为500～700KGy。
  7. 根据权利要求5或6所述的方法，其特征在于，步骤2中，总的聚左旋乳酸与总的聚右旋乳酸的重量比为2:8～8:2，优选为3:7～7:3，更优选为4:6～6:4，例如为5:5；
    总的聚左旋乳酸是指经过辐照处理的聚左旋乳酸和未经过 辐照处理的聚左旋乳酸之和；
    总的聚右旋乳酸是指经过辐照处理的聚右旋乳酸和未经过辐照处理的聚右旋乳酸之和。
  8. 根据权利要求5或6所述的方法，其特征在于，步骤2中，
    经过辐照处理的聚左旋乳酸和未经过辐照处理的聚左旋乳酸的重量比为1:49～10:40，优选为1:49～5:45，更优选为1:49～3:47，例如1:49；
    经过辐照处理的聚右旋乳酸和未经过辐照处理的聚右旋乳酸的重量比为1:49～10:40，优选为1:49～5:45，更优选为1:49～3:47，例如1:49。
  9. 根据权利要求5至7之一所述的方法，其特征在于，步骤2中，共混的方式为熔融共混，共混设备选自单螺杆挤出机、双螺杆挤出机和密炼机中的一种；
    共混的温度为180～250℃，优选为190～230℃；共混时间为5～30min；共混的转速为10～100rpm，优选为30～80rpm。
  10. 根据权利要求5至8之一所述的方法，其特征在于，步骤2中，共混时还加入交联剂，其中，交联剂的加入量为总的聚左旋乳酸和总的聚右旋乳酸重量之和的0.01％～3％。
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