CN113861640A - Method for improving crystallization capacity of polylactic acid copolymer material based on stereo-composition - Google Patents
Method for improving crystallization capacity of polylactic acid copolymer material based on stereo-composition Download PDFInfo
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- 238000002425 crystallisation Methods 0.000 title claims abstract description 31
- 230000008025 crystallization Effects 0.000 title claims abstract description 31
- 229920000747 poly(lactic acid) Polymers 0.000 title claims abstract description 26
- 239000004626 polylactic acid Substances 0.000 title claims abstract description 26
- 239000000463 material Substances 0.000 title claims abstract description 21
- 238000000034 method Methods 0.000 title claims abstract description 19
- 239000000203 mixture Substances 0.000 title claims abstract description 9
- 229920001432 poly(L-lactide) Polymers 0.000 claims abstract description 24
- JVTAAEKCZFNVCJ-REOHCLBHSA-N L-lactic acid Chemical compound C[C@H](O)C(O)=O JVTAAEKCZFNVCJ-REOHCLBHSA-N 0.000 claims abstract description 23
- 238000002156 mixing Methods 0.000 claims abstract description 20
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- RBMHUYBJIYNRLY-UHFFFAOYSA-N 2-[(1-carboxy-1-hydroxyethyl)-hydroxyphosphoryl]-2-hydroxypropanoic acid Chemical compound OC(=O)C(O)(C)P(O)(=O)C(C)(O)C(O)=O RBMHUYBJIYNRLY-UHFFFAOYSA-N 0.000 claims abstract 5
- 229920001434 poly(D-lactide) Polymers 0.000 claims abstract 5
- JJTUDXZGHPGLLC-IMJSIDKUSA-N 4511-42-6 Chemical compound C[C@@H]1OC(=O)[C@H](C)OC1=O JJTUDXZGHPGLLC-IMJSIDKUSA-N 0.000 claims description 22
- 229920001072 poly(l-lactide-co-caprolactone) Polymers 0.000 claims description 7
- 229920001577 copolymer Polymers 0.000 abstract description 25
- 238000002360 preparation method Methods 0.000 abstract description 20
- 238000012986 modification Methods 0.000 abstract description 4
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- 239000002994 raw material Substances 0.000 abstract 1
- 229920005689 PLLA-PGA Polymers 0.000 description 26
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- 230000000052 comparative effect Effects 0.000 description 17
- OZJPLYNZGCXSJM-UHFFFAOYSA-N 5-valerolactone Chemical compound O=C1CCCCO1 OZJPLYNZGCXSJM-UHFFFAOYSA-N 0.000 description 16
- 239000013078 crystal Substances 0.000 description 15
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- -1 cyclic lactone Chemical class 0.000 description 2
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- 238000001938 differential scanning calorimetry curve Methods 0.000 description 2
- 230000004927 fusion Effects 0.000 description 2
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- 239000000178 monomer Substances 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- JVTAAEKCZFNVCJ-UWTATZPHSA-N D-lactic acid Chemical compound C[C@@H](O)C(O)=O JVTAAEKCZFNVCJ-UWTATZPHSA-N 0.000 description 1
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- 230000003993 interaction Effects 0.000 description 1
- 238000010309 melting process Methods 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
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- 238000012545 processing Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
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- 238000003786 synthesis reaction Methods 0.000 description 1
- KSBAEPSJVUENNK-UHFFFAOYSA-L tin(ii) 2-ethylhexanoate Chemical compound [Sn+2].CCCCC(CC)C([O-])=O.CCCCC(CC)C([O-])=O KSBAEPSJVUENNK-UHFFFAOYSA-L 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- 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
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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
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- C08L2201/08—Stabilised against heat, light or radiation or oxydation
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- Compositions Of Macromolecular Compounds (AREA)
Abstract
The invention relates to a polylactic acid copolymer material modification technology, and aims to provide a method for improving the crystallization capacity of a polylactic acid copolymer material based on stereocomplex. The method comprises the following steps: taking a PLLA copolymer and a PDLA copolymer according to the mass ratio of 10-90: 10-90, wherein the sum of the two is 100 parts by mass; blending under the melting condition to obtain a blend, namely the polylactic acid copolymer material. Compared with single-component copolymer, the product of the invention has greatly improved crystallization speed and crystallinity and excellent heat resistance. When the product is prepared, only two copolymers are blended and melted according to a certain proportion, a solvent is not used, and any crystallization nucleating agent and crystallization accelerator are not required to be added; therefore, the preparation process is simple, the commercial cost is low, and large-scale industrial production can be realized. The raw materials are completely compatible, can be blended according to any proportion, does not need to add any compatible auxiliary agent, and has strong operability.
Description
Technical Field
The invention relates to the technical field of modification of polylactic acid copolymer materials, in particular to a method for improving the crystallization capacity of a polylactic acid copolymer material based on stereocomplex.
Background
Polylactic acid is a common biodegradable high polymer material, has good degradability and biocompatibility, can be completely degraded into water and carbon dioxide under natural conditions or in organisms, is non-toxic and harmless, is safe and environment-friendly, and can replace part of petroleum-based non-degradable plastics. Polylactic acid materials are hard and brittle and difficult to process, and usually need to introduce another copolymerization component for adjustment and modification. For example, high molecular weight polylactic acid copolymer materials are generally obtained by ring-opening polymerization of L-lactide (L-LA) or D-lactide (D-LA) monomers and other cyclic lactone monomers, such as Glycolide (GL), Valerolactone (VL), Caprolactone (CL), etc., under catalysis of stannous octoate, and are respectively called poly (L-LA) copolymer or poly (D-LA) copolymer.
However, the introduction of a comonomer causes the deterioration of the regularity of the polylactic acid chain, the deterioration of crystallinity, the reduction of the crystallization rate and crystallinity, and the deterioration of heat resistance. For this reason, a large amount of research work has been carried out by the skilled person. Various methods for improving the crystallization ability of polylactic acid copolymer materials have been reported in the literature. Among them, the method of adding a component (e.g., nucleating agent) capable of promoting crystallization nucleation to the copolymer matrix is more common. In addition, a component capable of promoting crystallization is added to regulate and control the crystal structure and morphology of the copolymer, and meanwhile, the spherulites of the copolymer are refined, so that the heat resistance of the copolymer is improved.
However, most crystallization promoters have high selectivity for promoting the crystallization of polymers, and not all promoters can improve the crystallization ability of polylactic acid copolymers. In addition, the accelerator itself has a problem of uneven dispersibility in the polymer matrix. The crystallization promoter has the problems of long design time, high synthesis cost and poor compatibility. Therefore, the high molecular weight polylactic acid copolymer material has the defects of low crystallinity and poor heat resistance, and the wide application of the high molecular weight polylactic acid copolymer material is limited.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects in the prior art and provides a method for improving the crystallization capacity of a polylactic acid copolymer material based on stereocomplex.
In order to solve the technical problem, the solution of the invention is as follows:
the method for improving the crystallization capacity of the polylactic acid copolymer material based on the stereo-complexation comprises the following steps:
taking a PLLA (poly-L-lactic acid) copolymer and a PDLA (poly-D-lactic acid) copolymer according to a mass ratio of 10-90: 10-90, wherein the sum of the two is 100 parts by mass; blending under the melting condition to obtain a blend, namely the polylactic acid copolymer material.
As a preferable scheme of the invention, the molecular weight ranges of the PLLA copolymer and the PDLA copolymer are both 10-20 ten thousand;
in a preferred embodiment of the present invention, the PLLA copolymer is any one of poly (L-lactide-co-glycolide), poly (L-lactide-co-valerolactone) or poly (L-lactide-co-caprolactone) (i.e., PLLGA, PLLVL or PLLCL).
In a preferred embodiment of the present invention, the PLLA copolymer contains 85 to 95% by mass of L-lactide.
In a preferred embodiment of the present invention, the PDLA copolymer is any one of poly (D-lactide-co-glycolide), poly (D-lactide-co-valerolactone) or poly (D-lactide-co-caprolactone) (i.e., PDLGA, PDLVL or PDLCL).
In a preferred embodiment of the present invention, the mass ratio of D-lactide in the PDLA copolymer is 85 to 95%.
As a preferred embodiment of the present invention, the blending under the melting condition specifically means: and (3) carrying out melt mixing by adopting a double-screw extruder, wherein the mixing time is 3-7 min, and the mixing temperature is 180-230 ℃.
Description of the invention
In the present invention, since the PLLA copolymer and the PDLA copolymer have excellent compatibility, when the two are blended, the PLLA copolymer chain can be sufficiently and uniformly mixed with the PDLA copolymer chain. Because the PLLA copolymer and the PDLA copolymer respectively contain a large number of PLLA and PDLA chain segments and strong hydrogen bond interaction exists between the PLLA and the PDLA chain segments, the PLLA and the PDLA chain segments can be close to each other and folded and crystallized together to form a stereo composite crystal, thereby improving the crystallinity of the blend.
In the prior technical scheme for improving the crystallization capacity of the polylactic acid copolymer material, the crystallization capacity of the polylactic acid copolymer is improved by the aid of a nucleating agent by those skilled in the art, and the invention breaks the inertial thought and improves the crystallization capacity of the polylactic acid copolymer material by means of compatible blending of the PLLA copolymer and the PDLA copolymer.
Compared with the prior art, the invention has the beneficial effects that:
1. compared with single-component PLLA copolymer or PDLA copolymer, the polylactic acid copolymer material prepared by the invention has greatly improved crystallization speed and crystallinity.
2. Compared with single-component PLLA copolymer or PDLA copolymer, the polylactic acid copolymer material prepared by the invention has excellent heat resistance, and can expand the commercial application of the polylactic acid copolymer.
3. The preparation process of the product only needs to blend and melt the PLLA copolymer and the PDLA copolymer according to a certain proportion. In the processing process, no solvent is used, and no crystallization nucleating agent or crystallization promoter is added; therefore, the preparation process is simple, the commercial cost is low, and large-scale industrial production can be realized.
4. In the preparation process, the PLLA copolymer and the PDLA copolymer are completely compatible, can be blended according to any proportion, do not need to add any compatible auxiliary agent, and have strong operability.
Drawings
FIG. 1 is a DSC curve of comparative examples 1, 2 and examples 1-3 during a 10 deg.C/min temperature increase after melting to eliminate the thermal history and quenching.
FIG. 2 is a thermogravimetric plot of comparative example 2 and example 1.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. The following examples are presented to enable those skilled in the art to more fully understand the present invention and are not intended to limit the invention in any way.
The copolymer may be prepared from L-lactide (L-LA), D-lactide (D-LA), Glycolide (GL), Valerolactone (VL), Caprolactone (CL), poly (L-lactide-co-glycolide) (PLLGA), poly (D-lactide-co-glycolide) (PDLGA), poly (L-lactide-co-valerolactone) (PLLVL), poly (D-lactide-co-valerolactone) (PDLVL), poly (L-lactide-co-caprolactone) (PLLCL) or poly (D-lactide-co-caprolactone) (PDLCL), and the specific sources thereof are not particularly limited, and they may be prepared by a known method, or commercial products may be directly purchased.
Example 1: preparation of PLLGA-10w-85/PDLGA-10 w-8550/50 samples
50 parts by mass of PLLGA with the molecular weight of 10 ten thousand and 50 parts by mass of PDLGA with the molecular weight of 10 ten thousand are mixed for 3min at 220 ℃ by a double screw extruder, wherein L-LA accounts for 85 parts by mass, GL accounts for 15 parts by mass in the PLLGA, D-LA accounts for 85 parts by mass, and GL accounts for 15 parts by mass in the PDLGA, and the PLLGA-10w-85/PDLGA-10 w-8550/50 sample is obtained.
Example 2: preparation of PLLGA-10w-90/PDLGA-10 w-9050/50 samples
50 parts by mass of PLLGA with the molecular weight of 10 ten thousand and 50 parts by mass of PDLGA with the molecular weight of 10 ten thousand are mixed for 3min at 220 ℃ by a double screw extruder, wherein L-LA accounts for 90 parts by mass, GL accounts for 10 parts by mass in the PLLGA, D-LA accounts for 90 parts by mass, and GL accounts for 10 parts by mass in the PDLGA, and the PLLGA-10w-90/PDLGA-10 w-9050/50 sample is obtained.
Example 3: preparation of PLLGA-10w-95/PDLGA-10w-9550/50 samples
50 parts by mass of PLLGA with the molecular weight of 10 ten thousand and 50 parts by mass of PDLGA with the molecular weight of 10 ten thousand are mixed for 3min at 220 ℃ by a double screw extruder, wherein, L-LA accounts for 95 parts by mass and GL accounts for 5 parts by mass in the PLLGA, D-LA accounts for 95 parts by mass and GL accounts for 5 parts by mass in the PDLGA, and the PLLGA-10w-95/PDLGA-10w-9550/50 sample is obtained.
Example 4: preparation of PLLGA-15w-85/PDLGA-15 w-8510/90 samples
Mixing 10 parts by mass of PLLGA with the molecular weight of 15 ten thousand and 90 parts by mass of PDLGA with the molecular weight of 15 ten thousand at 180 ℃ for 7min by using a double-screw extruder, wherein L-LA accounts for 85 parts by mass, GL accounts for 15 parts by mass in the PLLGA, D-LA accounts for 85 parts by mass, and GL accounts for 15 parts by mass in the PDLGA, and thus obtaining a PLLGA-15w-85/PDLGA-15 w-8510/90 sample.
Example 5: preparation of PLLGA-20w-85/PDLGA-20 w-8590/10 samples
And (2) mixing 90 parts by mass of PLLGA with the molecular weight of 20 ten thousand and 10 parts by mass of PDLGA with the molecular weight of 20 ten thousand by using a double-screw extruder at 230 ℃ for 5min, wherein L-LA in the PLLGA accounts for 85 parts by mass, GL accounts for 15 parts by mass, D-LA in the PDLGA accounts for 85 parts by mass, and GL accounts for 15 parts by mass, and thus obtaining a PLLGA-20w-85/PDLGA-20 w-8590/10 sample.
Example 6: preparation of PLLGA-10w-85/PDLGA-10 w-8530/70 samples
30 parts by mass of PLLGA with the molecular weight of 10 ten thousand and 70 parts by mass of PDLGA with the molecular weight of 10 ten thousand are mixed for 3min at 220 ℃ by a double screw extruder, wherein L-LA accounts for 85 parts by mass, GL accounts for 15 parts by mass in the PLLGA, D-LA accounts for 85 parts by mass, and GL accounts for 15 parts by mass in the PDLGA, and the PLLGA-10w-85/PDLGA-10 w-8530/70 sample is obtained.
Example 7: preparation of PLLGA-10w-85/PDLGA-10 w-8570/30 samples
70 parts by mass of PLLGA with the molecular weight of 10 ten thousand and 30 parts by mass of PDLGA with the molecular weight of 10 ten thousand are mixed for 3min at 220 ℃ by a double screw extruder, wherein L-LA accounts for 85 parts by mass, GL accounts for 15 parts by mass in the PLLGA, D-LA accounts for 85 parts by mass, and GL accounts for 15 parts by mass in the PDLGA, and the PLLGA-10w-85/PDLGA-10 w-8570/30 sample is obtained.
Example 8: preparation of PLLGA-10w-85/PDLGA-20 w-8550/50 samples
50 parts by mass of PLLGA with the molecular weight of 10 ten thousand and 50 parts by mass of PDLGA with the molecular weight of 20 ten thousand are mixed for 3min at 220 ℃ by a double screw extruder, wherein L-LA accounts for 85 parts by mass, GL accounts for 15 parts by mass in the PLLGA, D-LA accounts for 85 parts by mass, and GL accounts for 15 parts by mass in the PDLGA, and the PLLGA-10w-85/PDLGA-20 w-8550/50 sample is obtained.
Example 9: preparation of PLLGA-15w-85/PDLGA-10 w-8550/50 samples
50 parts by mass of PLLGA with the molecular weight of 15 ten thousand and 50 parts by mass of PDLGA with the molecular weight of 10 ten thousand are mixed for 3min at 220 ℃ by a double screw extruder, wherein L-LA accounts for 85 parts by mass, GL accounts for 15 parts by mass in the PLLGA, D-LA accounts for 85 parts by mass, and GL accounts for 15 parts by mass in the PDLGA, and the PLLGA-15w-85/PDLGA-15 w-8550/50 sample is obtained.
Example 10: preparation of PLLVL-10w-85/PDLVL-10w-8550/50 samples
And (2) mixing 50 parts by mass of PLLVL with the molecular weight of 10 ten thousand and 50 parts by mass of PDLVL with the molecular weight of 10 ten thousand at 220 ℃ for 3min by using a double-screw extruder, wherein the L-LA accounts for 85 parts by mass, the VL accounts for 15 parts by mass in the PLLVL, the D-LA accounts for 85 parts by mass and the VL accounts for 15 parts by mass in the PDLVL, and thus obtaining a PLLVL-10w-85/PDLVL-10w-8550/50 sample.
Example 11: preparation of PLLCL-10w-85/PDLCL-10w-8550/50 samples
And (2) mixing 50 parts by mass of PLLCL with the molecular weight of 10 ten thousand and 50 parts by mass of PDLCL with the molecular weight of 10 ten thousand at 220 ℃ for 3min by using a double-screw extruder, wherein the L-LA accounts for 85 parts by mass, the CL accounts for 15 parts by mass in the PLLCL, the D-LA accounts for 85 parts by mass, and the CL accounts for 15 parts by mass in the PDLCL, so that a PLLCL-10w-85/PDLCL-10w-8550/50 sample is obtained.
Example 12: preparation of PLLGA-10w-85/PDLVL-10 w-8550/50 samples
50 parts by mass of PLLGA with the molecular weight of 10 ten thousand and 50 parts by mass of PDLVL with the molecular weight of 10 ten thousand are mixed for 3min at 220 ℃ by a double screw extruder, wherein the L-LA accounts for 85 parts by mass, the GA accounts for 15 parts by mass in the PLLGA, the D-LA accounts for 85 parts by mass and the VL accounts for 15 parts by mass in the PDLVL, and then the PLLGA-10w-85/PDLVL-10 w-8550/50 sample is obtained.
Example 13: preparation of PLLGA-10w-85/PDLCL-10 w-8550/50 samples
And (2) mixing 50 parts by mass of PLLGA with the molecular weight of 10 ten thousand and 50 parts by mass of PDLCL with the molecular weight of 10 ten thousand at 220 ℃ for 3min by using a double-screw extruder, wherein the L-LA accounts for 85 parts by mass, the GA accounts for 15 parts by mass in the PLLGA, the D-LA accounts for 85 parts by mass and the CL accounts for 15 parts by mass in the PDLCL, and thus obtaining a PLLGA-10w-85/PDLCL-10 w-8550/50 sample.
Example 14: preparation of PLLVL-10w-85/PDLCL-10w-8550/50 samples
And (2) mixing 50 parts by mass of PLLVL with the molecular weight of 10 ten thousand and 50 parts by mass of PDLCL with the molecular weight of 10 ten thousand at 220 ℃ for 3min by using a double-screw extruder, wherein the L-LA accounts for 85 parts by mass, the VL accounts for 15 parts by mass in the PLLVL, the D-LA accounts for 85 parts by mass and the CL accounts for 15 parts by mass in the PDLCL, and thus obtaining a PLLVL-10w-85/PDLCL-10w-8550/50 sample.
Comparative example 1: preparation of PDLGA-10w-90 sample
And (3) mixing PDLGA with the molecular weight of 10 ten thousand at 220 ℃ for 3min by using a double-screw extruder, wherein D-LA accounts for 90 parts by mass and GL accounts for 10 parts by mass in the PDLGA, and thus obtaining a PDLGA-10w-90 sample.
Comparative example 2: preparation of PLLGA-10w-85 samples
And (3) mixing PLLGA with the molecular weight of 10 ten thousand with a double-screw extruder at 220 ℃ for 3min, wherein the L-LA accounts for 85 parts by mass and the GL accounts for 15 parts by mass in the PLLGA, and thus obtaining a PLLGA-10w-85 sample.
Samples of each example and comparative example were subjected to thermogravimetric testing and crystallization behavior and thermal performance parameter testing, wherein:
and (3) thermogravimetric testing:
samples were analyzed for heat resistance using a Pyris 1TGA (PerkinElmer, Waltham, MA, USA). Sample is in N2The temperature in the atmosphere is increased from 50 ℃ to 600 ℃ at a temperature increase rate of 10 ℃/min. The mass of the sample is 3 mg.
Testing of crystallization behavior and thermal performance parameter calculation:
test using Differential Scanning Calorimeter (DSC), nitrogen atmosphere. The sample is heated from 0 ℃ to 250 ℃ at a speed of 50 ℃/min, kept for 3min to eliminate the thermal history, then cooled to-50 ℃ at a speed of 100 ℃/min, kept for 5min at-50 ℃, and then heated to 250 ℃ at a speed of 10 ℃/min. Based on the DSC data, the melting temperature (T) of the homogeneous crystals was countedm, homogeneity) Enthalpy of fusion (Δ H)m, homogeneity) And degree of crystallinity (X) of the homogeneous crystalc, homogeneity) Melting temperature (T) of stereocomplex crystalm, vertical structure) Enthalpy of fusion (Δ H)m, vertical structure) And crystallinity (X) of the stereocomplex crystalc, vertical structure). By calculating Δ Hm, homogeneityMelting enthalpy (. DELTA.H) of homogeneous crystallization with 100% crystallinity0 HomogeneityThe ratio of 93.4J/g) was calculated as the crystallinity of the homogeneous crystal, i.e., Xc, homogeneity＝ΔHm, homogeneity/ΔH0 HomogeneityX 100%. By calculating Δ Hm, vertical structureMelting enthalpy (Δ H) of stereocomplex crystals with 100% crystallinity0 Vertical structure142.0J/g) was calculated as the crystallinity of the stereocomplex crystal, i.e., Xc, vertical structure＝ΔHm, vertical structure/ΔH0 Vertical structureX 100%. Total crystallinity Xtotal＝Xc, homogeneity+Xc, vertical structure。
The results are summarized in Table 1.
TABLE 1 thermal Performance parameters and thermal degradation temperatures during temperature ramp for samples prepared in comparative examples 1 and 2 and examples 1-12
FIG. 1 is a DSC curve of comparative examples 1, 2 and examples 1-3 during a 10 deg.C/min temperature increase after elimination of the thermal history and quenching, and the thermal performance parameters calculated from FIG. 1 are shown in Table 1. As can be seen from fig. 1 and table 1, comparative example 2 has no distinct melting peak during the temperature rise, indicating that its crystallization rate is very slow, does not crystallize during the temperature rise, and exists in an amorphous state. However, when equal amounts of PLLGA-10 w-15% and PDLGA-10 w-15% were blended in example 1, the prepared PLLGA-10 w-15%/PDLGA-10 w-15% blend showed a distinct crystallization peak during the temperature increase, indicating that crystallization occurred during the temperature increase and only stereocomplex crystals were formed. This phenomenon shows that example 1 has a stronger crystallization ability than comparative example 2. In FIG. 1, the melting peak range of example 3 is two, namely 160-175 ℃ and 200-220 ℃: the melting peak at lower temperature corresponds to the melting of the homogeneous crystal, and the melting peak at higher temperature corresponds to the melting of the stereocomplex crystal; while example 1 and example 2 had only one melting peak of the stereocomplex crystal at a higher temperature during the melting process. As can be seen by comparing the overall crystallinity of comparative example 1 and example 2 in Table 1, the crystallinity of PLLGA-10w-90/PDLGA-10w-90 samples was significantly higher than that of PLLGA-10w-90 alone, which is consistent with the results of comparison of comparative example 2 and example 3. Comparing comparative examples 1, 2 and examples 1-14, it can be seen that the heat resistance of the PLLA copolymer/PDLA copolymer blend samples is significantly better than that of the PLLA copolymer or PDLA copolymer alone, since the stereocomplex crystals can be formed. FIG. 2 is a thermogravimetric plot of comparative example 2 and example 1 during a 10 deg.C/min ramp. Thermal degradation temperature (T) from FIG. 2de) Are listed in table 1. As shown in fig. 2 and table 1, the temperature at which comparative example 2 starts to degrade was 228 ℃, whereas the temperature at which example 1 starts to degrade was 270 ℃, which was higher than comparative example 2 by 40 ℃ or more, and showed more excellent heat resistance. Similarly, comparative example 2 is compared to examples 4 and 5, although the PLLA copolymer/PDLA copolymer ratios in examples 4 and 5, respectively10: 90 and 90: 10, which are non-equivalent blends with large differences in the amounts, but as can be seen from Table 1, stereocomplex crystals were formed in examples 4 and 5, and the heat-resistant temperature was increased by about 15 ℃ as compared with comparative example 2.
Finally, it should be noted that the above-mentioned list is only a specific embodiment of the present invention. It is obvious that the present invention is not limited to the above embodiments, but many variations are possible. All modifications which can be derived or suggested by a person skilled in the art from the disclosure of the present invention are to be considered within the scope of the invention.
Claims (7)
1. A method for improving the crystallization capacity of a polylactic acid copolymer material based on stereocomplex is characterized by comprising the following steps:
taking a PLLA copolymer and a PDLA copolymer according to the mass ratio of 10-90: 10-90, wherein the sum of the two is 100 parts by mass; blending under the melting condition to obtain a blend, namely the polylactic acid copolymer material.
2. The method of claim 1, wherein the molecular weight ranges of both the PLLA copolymer and the PDLA copolymer are from 10 to 20 ten thousand.
3. The method of claim 1, wherein the PLLA copolymer is any one of poly (L-lactide-co-glycolide), poly (L-lactide-co-valerolactone), or poly (L-lactide-co-caprolactone).
4. The method of claim 3, wherein the mass fraction of L-lactide in the PLLA copolymer is 85-95%.
5. The method of claim 1, wherein the PDLA copolymer is any one of poly (D-lactide-co-glycolide), poly (D-lactide-co-valerolactone), or poly (D-lactide-co-caprolactone).
6. The method according to claim 5, wherein the mass ratio of D-lactide in the PDLA copolymer is 85-95%.
7. The process according to any one of claims 1 to 6, characterized in that said blending under melting conditions is in particular: and (3) carrying out melt mixing by adopting a double-screw extruder, wherein the mixing time is 3-7 min, and the mixing temperature is 180-230 ℃.
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| CN114479024A (en) * | 2022-03-01 | 2022-05-13 | 上海东庚化工技术有限公司 | Lactic acid/valeric acid copolymer, preparation method and stereocomplex thereof |
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| CN101663355A (en) * | 2007-02-09 | 2010-03-03 | 帝人株式会社 | Method for producing polylactic acid |
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| CN114479024A (en) * | 2022-03-01 | 2022-05-13 | 上海东庚化工技术有限公司 | Lactic acid/valeric acid copolymer, preparation method and stereocomplex thereof |
| WO2023165120A1 (en) * | 2022-03-01 | 2023-09-07 | 上海东庚化工技术有限公司 | Lactic acid/pentanoic acid copolymer, preparation method and stereocomplex thereof |
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