CN114181504A - Method for preparing polylactic acid by using modified cellulose nanocrystals - Google Patents
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- CN114181504A CN114181504A CN202111589594.0A CN202111589594A CN114181504A CN 114181504 A CN114181504 A CN 114181504A CN 202111589594 A CN202111589594 A CN 202111589594A CN 114181504 A CN114181504 A CN 114181504A
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- lactic acid
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- 239000004626 polylactic acid Substances 0.000 title claims abstract description 54
- 229920000747 poly(lactic acid) Polymers 0.000 title claims abstract description 53
- 229920002678 cellulose Polymers 0.000 title claims abstract description 50
- 239000001913 cellulose Substances 0.000 title claims abstract description 50
- 239000002159 nanocrystal Substances 0.000 title claims abstract description 44
- 238000000034 method Methods 0.000 title claims abstract description 24
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 claims abstract description 80
- 239000004310 lactic acid Substances 0.000 claims abstract description 40
- 235000014655 lactic acid Nutrition 0.000 claims abstract description 40
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 28
- 239000002202 Polyethylene glycol Substances 0.000 claims abstract description 20
- 229920001223 polyethylene glycol Polymers 0.000 claims abstract description 20
- 229920000742 Cotton Polymers 0.000 claims abstract description 13
- 239000000047 product Substances 0.000 claims description 16
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 12
- 239000000463 material Substances 0.000 claims description 11
- 238000002156 mixing Methods 0.000 claims description 10
- 238000005406 washing Methods 0.000 claims description 10
- 239000006185 dispersion Substances 0.000 claims description 8
- 239000007788 liquid Substances 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- 239000008367 deionised water Substances 0.000 claims description 7
- 229910021641 deionized water Inorganic materials 0.000 claims description 7
- 238000006243 chemical reaction Methods 0.000 claims description 6
- 239000000243 solution Substances 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- 239000006228 supernatant Substances 0.000 claims description 6
- 239000007864 aqueous solution Substances 0.000 claims description 4
- 238000001035 drying Methods 0.000 claims description 4
- 238000004108 freeze drying Methods 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- -1 polytetrafluoroethylene Polymers 0.000 claims description 4
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 4
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 4
- 238000004321 preservation Methods 0.000 claims description 4
- 238000001291 vacuum drying Methods 0.000 claims description 3
- 230000035484 reaction time Effects 0.000 claims description 2
- 238000002425 crystallisation Methods 0.000 abstract description 16
- 230000008025 crystallization Effects 0.000 abstract description 15
- 230000009471 action Effects 0.000 abstract description 3
- 125000002887 hydroxy group Chemical group [H]O* 0.000 abstract description 3
- 238000006482 condensation reaction Methods 0.000 abstract description 2
- 239000002667 nucleating agent Substances 0.000 description 12
- 238000010899 nucleation Methods 0.000 description 9
- 230000006911 nucleation Effects 0.000 description 9
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 238000001816 cooling Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 238000007151 ring opening polymerisation reaction Methods 0.000 description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- 238000001914 filtration Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000006068 polycondensation reaction Methods 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 238000006116 polymerization reaction Methods 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical class O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 1
- 229920003043 Cellulose fiber Polymers 0.000 description 1
- 208000034530 PLAA-associated neurodevelopmental disease Diseases 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000005903 acid hydrolysis reaction Methods 0.000 description 1
- 238000010306 acid treatment Methods 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 229920006038 crystalline resin Polymers 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000000113 differential scanning calorimetry Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 230000009477 glass transition Effects 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000002085 irritant Substances 0.000 description 1
- 231100000021 irritant Toxicity 0.000 description 1
- JJTUDXZGHPGLLC-UHFFFAOYSA-N lactide Chemical compound CC1OC(=O)C(C)OC1=O JJTUDXZGHPGLLC-UHFFFAOYSA-N 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000004060 metabolic process Effects 0.000 description 1
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 239000002114 nanocomposite Substances 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 229910052615 phyllosilicate Inorganic materials 0.000 description 1
- 239000004014 plasticizer Substances 0.000 description 1
- 230000000379 polymerizing effect Effects 0.000 description 1
- 238000005036 potential barrier Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 150000003384 small molecules Chemical class 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- 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
- C08L2205/00—Polymer mixtures characterised by other features
- C08L2205/24—Crystallisation aids
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Processes Of Treating Macromolecular Substances (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Biological Depolymerization Polymers (AREA)
Abstract
The invention relates to a method for preparing polylactic acid by using modified cellulose nanocrystals. The invention firstly carries out acidolysis on cotton fiber in lactic acid and hydrochloric acid, on one hand, disordered and amorphous cellulose in the cotton fiber is dissolved, then partial hydroxyl on the surface of the cellulose nanocrystal is combined with the lactic acid under the combined action of the lactic acid and the hydrochloric acid, and the lactic acid is grafted to the cellulose nanocrystal. And then, by condensation reaction of polyethylene glycol and lactic acid, the polyethylene glycol is further grafted to the cellulose nanocrystal to obtain the cellulose nanocrystal grafted with the lactic acid and the polyethylene glycol together, so that the compatibility of the cellulose nanocrystal and polylactic acid is improved, and the crystallization property and the mechanical property of the polylactic acid are effectively improved.
Description
Technical Field
The invention belongs to the field of polylactic acid, and particularly relates to a method for preparing polylactic acid by using modified cellulose nanocrystals.
Background
Polylactic acid (PLA) is a polymer obtained by polymerizing lactic acid serving as a main raw material, is a non-toxic, non-irritant, biocompatible and biodegradable high-molecular compound, can participate in metabolism of a human body by using metabolites of carbon dioxide, water and lactic acid in the body, and is widely applied to the fields of medical treatment, clothing, industry, food packaging industry and the like.
The preparation method of the polylactic acid mainly comprises a direct polycondensation method and a ring-opening polymerization method, wherein the direct polycondensation method and the ring-opening polymerization method are adopted, the polylactic acid is obtained by directly dehydrating and condensing lactic acid, and the product obtained by the method has lower relative molecular mass, wider molecular weight distribution, easy decomposition and no practical value; the latter depolymerizes the oligomer obtained after lactic acid dehydration condensation under the action of catalyst to obtain lactide, then adds catalyst to make it undergo the process of ring-opening polymerization to obtain polylactic acid with high molecular weight, and because the ring-opening polymerization method has no by-product of small molecule, it can accurately control and raise polymerization reaction degree, and the molecular weight of the obtained polylactic acid product is up to above 10 ten thousand, and its performance index can meet the performance requirements for using as common structural material, so that it is a universal technological process for industrial production of polylactic acid at present.
In theory, PLA belongs to a crystalline polymer, and crystallization occurs in the cooling process of molding processing, but only the properties of semi-crystalline resins can be achieved in actual production, and the degree of crystallization is low and the crystallization speed is slow. If the crystallinity cannot be improved more, the heat resistance and the transparency of the product are affected, for example, the glass transition temperature of low-crystalline PLA is only about 60 ℃, and the crystallization capacity of the PLA can be improved by modifying the PLA, so that the heat resistance temperature, the transparency, the tensile strength, the bending strength and the modulus of the PLA can be improved, the degradation rate is reduced, and the barrier property is improved.
However, the nucleation rate and the crystallization rate of the PLA under the homogeneous nucleation condition are low, the nucleation rate is improved by adding the nucleating agent at present, and the addition of the nucleating agent can reduce the surface free potential barrier required by the nucleation of the PLA and enable the PLA to be nucleated in a heterogeneous mode, so that the crystallization time is shortened, the crystallization rate is improved, and the crystallization of the PLA is promoted. In addition, the nucleation mobility of the molecular chain is increased by adding a plasticizer, thereby improving the crystallization property of the PLA. The nucleating agent of PLA mainly has the functions of improving the nucleation density, shortening the semi-crystallization time and reducing the nucleation induction period, and mainly comprises an inorganic nucleating agent and an organic nucleating agent. The commonly used inorganic nucleating agents at present comprise phyllosilicates, inorganic salts, carbon and the like, and the inorganic nucleating agents have the defects of poor compatibility with PLA, general nucleating effect and low price. The organic nucleating agent has good compatibility and good nucleating effect, but is expensive.
Cellulose nanocrystals, which are a rod-like nanomaterial extracted from cellulose, are usually isolated from the fiber by sulfuric or hydrochloric acid, and during acid treatment, the disordered and semicrystalline portions of cellulose are preferentially hydrolyzed, while the crystalline portion is completely retained because it is more resistant to acid hydrolysis, thus obtaining cellulose nanocrystals. The cellulose nanocrystal has excellent performances of complete biodegradability, low density, high strength and the like, and can be used as a crystallization nucleating agent of PLA. The cellulose nanocrystal and the polylactic acid are compounded to prepare the nanocomposite material to improve the performance of the polylactic acid, so that the application range of the polylactic acid can be effectively expanded. However, the cellulose nanocrystals are easy to aggregate in a solution due to strong hydrogen bonding, and are not easy to disperse, so that the application of the cellulose nanocrystals in polylactic acid materials is limited. On the other hand, the nano particles are obviously hydrophilic, and the compatibility between the cellulose nano crystals and the polylactic acid is not facilitated, so that the combination of the cellulose nano crystals and the polylactic acid is very challenging.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a method for preparing polylactic acid by using modified cellulose nanocrystals, which comprises the steps of firstly carrying out acidolysis on cellulose fibers by using mixed acid of hydrochloric acid and acetic acid to prepare the cellulose nanocrystals with lactic acid grafted on the surfaces, and then further improving the dispersibility of the cellulose nanocrystals by modifying the surfaces by using polyethylene glycol, wherein the modified cellulose nanocrystals are used as nucleating agents to effectively improve the crystallization performance and mechanical property of the polylactic acid.
In order to achieve the above object, the preparation method of polylactic acid according to the present invention specifically comprises the following steps:
(1) uniformly mixing cotton fiber crushed aggregates, 90wt% of lactic acid aqueous solution and 37wt% of concentrated hydrochloric acid, then transferring the mixture into a polytetrafluoroethylene lining reaction kettle, reacting under a closed condition, washing a product with deionized water, centrifuging, taking supernatant, and freeze-drying to obtain lactic acid grafted cellulose nanocrystals;
(2) ultrasonically dispersing the lactic acid grafted cellulose nanocrystal obtained in the step (1) in N, N-dimethylformamide to form stable dispersion liquid, adding polyethylene glycol into the dispersion liquid, reacting for 2-3 days at the temperature of 110-;
(3) mixing the product prepared in the step (2) with polylactic acid according to the mass ratio of 0.1-5: 100 is added into an internal mixer, the temperature is controlled at 150-210 ℃, the rotating speed is 60-150rpm, the heat preservation is carried out for 30min-150min, then the temperature is reduced to 50-70 ℃, the heat preservation is carried out for 1-3h, and then the temperature is reduced to the room temperature, thus obtaining the polylactic acid material.
Further, in the step (1), crushing cotton fibers: 90wt% aqueous lactic acid solution: the mass ratio of 37wt% concentrated hydrochloric acid is 1: 10-15: 0.1-2.
Further, the reaction temperature in the step (1) is 130-160 ℃, and the reaction time is 3-8 h.
Further, in the step (2), the vacuum drying temperature is 90-120 ℃, and the drying time is 6-12 h.
Further, the mass ratio of the lactic acid grafted cellulose nanocrystal to the polyethylene glycol in the step (2) is 100: 1-5.
Further, the stirring speed in the step (2) is 50-100 rpm.
Further, the cooling rate in the step (3) is 5-20 ℃/min.
Compared with the prior art, the invention has the beneficial effects that:
the cellulose contained in the cotton fiber contains a large amount of hydroxyl, the invention firstly carries out acidolysis on the cotton fiber in lactic acid and hydrochloric acid, on one hand, disordered and amorphous cellulose in the cotton fiber is dissolved, then partial hydroxyl on the surface of the cellulose nanocrystal is combined with the lactic acid under the combined action of the lactic acid and the hydrochloric acid, and the lactic acid is grafted on the cellulose nanocrystal. And then, by condensation reaction of polyethylene glycol and lactic acid, the polyethylene glycol is further grafted to the cellulose nanocrystal to obtain the cellulose nanocrystal grafted with the lactic acid and the polyethylene glycol together, so that the compatibility of the cellulose nanocrystal and polylactic acid is improved. The bio-based cellulose nanocrystalline used in the invention has excellent heterogeneous nucleation effect, the polyethylene glycol has excellent processing fluidity, and the lactic acid is utilized to combine the two to be used as a nucleating agent in a synergistic manner, so that the crystallization property and the mechanical property of the polylactic acid are effectively improved. The obtained polylactic acid material has the crystallinity as high as 52.1 percent, the tensile strength reaches 45MPa, and the polylactic acid material shows excellent crystallization property and mechanical property.
Detailed Description
In order to make the purpose and technical solution of the present invention more apparent, the present invention will be described in detail with reference to specific embodiments, illustrative examples and description of the present invention are provided to explain the present invention, and it should be understood that the specific embodiments described herein are not to be construed as limiting the present invention.
Example 1
(1) Uniformly mixing cotton fiber crushed aggregates, 90wt% of lactic acid aqueous solution and 37wt% of concentrated hydrochloric acid, then transferring the mixture into a polytetrafluoroethylene lining reaction kettle, reacting for 7 hours at 140 ℃ under a closed condition, washing a product with deionized water, centrifuging the product, taking supernatant, and freeze-drying the supernatant to obtain lactic acid grafted cellulose nanocrystals; wherein the crushed cotton fibers comprise: 90wt% aqueous lactic acid solution: the mass ratio of 37% concentrated hydrochloric acid is 1: 10: 1;
(2) ultrasonically dispersing the lactic acid grafted cellulose nanocrystal obtained in the step (1) in N, N-dimethylformamide to form stable dispersion liquid, adding polyethylene glycol into the dispersion liquid, reacting for 2 days at 130 ℃ under continuous stirring, wherein the stirring speed is 90rpm, washing the obtained product with ethanol, washing with deionized water, filtering and drying in vacuum to obtain the cellulose nanocrystal grafted with lactic acid and polyethylene glycol; wherein the mass ratio of the lactic acid grafted cellulose nanocrystal to the polyethylene glycol is 100: 4.
(3) mixing the product prepared in the step (2) with polylactic acid according to the mass ratio of 2: 100 is added into an internal mixer, the temperature is controlled at 180 ℃, the rotating speed is 90rpm, the temperature is kept for 120min, then the temperature is reduced to 60 ℃ at the cooling rate of 15 ℃/min, the temperature is kept for 3h, and then the temperature is reduced to the room temperature, so that the polylactic acid material is obtained.
Weighing 5mg of sample, placing the sample into a sample crucible, measuring the thermal property of the sample by utilizing Differential Scanning Calorimetry (DSC), heating the sample from 40 ℃ to 200 ℃ at a heating rate of 10 ℃/min, preserving the temperature for 5min at 200 ℃, then reducing the temperature to 40 ℃ at a cooling rate of 10 ℃/min, increasing the temperature to 200 ℃ at a heating rate of 10 ℃/min, and measuring and calculating the crystallinity of the sample. The polylactic acid material was cut into 30mm by 8mm test specimens, stretched at room temperature at a stretching rate of 10 μm/s, and the tensile strength was measured. The test results are shown in table 1.
Example 2
(1) Uniformly mixing cotton fiber crushed aggregates, 90wt% of lactic acid aqueous solution and 37wt% of concentrated hydrochloric acid, then transferring the mixture into a polytetrafluoroethylene lining reaction kettle, reacting for 3 hours at 160 ℃ under a closed condition, washing a product with deionized water, centrifuging the product, taking supernatant, and freeze-drying the supernatant to obtain lactic acid grafted cellulose nanocrystals; wherein the crushed cotton fibers comprise: 90wt% aqueous lactic acid solution: the mass ratio of 37% concentrated hydrochloric acid is 1: 15: 0.2;
(2) ultrasonically dispersing the lactic acid grafted cellulose nanocrystal obtained in the step (1) in N, N-dimethylformamide to form stable dispersion liquid, adding polyethylene glycol into the dispersion liquid, reacting for 3 days at 110 ℃ under continuous stirring, wherein the stirring speed is 70rpm, washing the obtained product with ethanol, washing with deionized water, filtering and drying in vacuum to obtain the cellulose nanocrystal grafted with lactic acid and polyethylene glycol; wherein the mass ratio of the lactic acid grafted cellulose nanocrystal to the polyethylene glycol is 100: 1-2;
(3) mixing the product prepared in the step (2) with polylactic acid according to the mass ratio of 1: 100 is added into an internal mixer, the temperature is controlled at 200 ℃, the rotating speed is 120rpm, the temperature is kept for 90min, then the temperature is reduced to 50 ℃ at the cooling rate of 10 ℃/min, the temperature is kept for 2h, and then the temperature is reduced to the room temperature, so as to obtain the polylactic acid material. The test results are shown in table 1.
Comparative example 1
The method of preparing polylactic acid according to example 1, except that the operation of step (2) is not performed, and the lactic acid-grafted cellulose nanocrystal prepared in step (1) is directly blended with polylactic acid in an internal mixing.
Comparative example 2
The method for preparing polylactic acid according to example 1, except that the lactic acid-grafted cellulose nanocrystal prepared in step (1) is mixed with polyethylene glycol at room temperature according to the mass ratio, and then subjected to ethanol washing, deionized water washing, filtration and vacuum drying, and the obtained product is blended with polylactic acid in an internal mixing process.
TABLE 1
| Degree of crystallinity | Tensile Strength (MPa) | |
| Example 1 | 52.1％ | 45MPa |
| Example 2 | 49.4％ | 43MPa |
| Comparative example 1 | 38.3％ | 34MPa |
| Comparative example 2 | 42.3％ | 39MPa |
The test results of the above examples 1-2 and comparative examples 1-2 are shown in table 1, and it can be seen that the polylactic acid material prepared by the present invention has a crystallinity as high as 52.1%, and a tensile strength of 45MPa, and the crystallization property and mechanical property of polylactic acid are effectively improved by using the excellent heterogeneous nucleation effect of the bio-based cellulose nanocrystals and the excellent processing fluidity of polyethylene glycol as a nucleating agent.
The above is only a preferred embodiment of the present invention, and it should be noted that the above preferred embodiment should not be considered as limiting the present invention, and the protection scope of the present invention should be subject to the scope defined by the claims. It will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the spirit and scope of the invention, and these modifications and adaptations should be considered within the scope of the invention.
Claims (7)
1. A method for preparing polylactic acid by utilizing modified cellulose nanocrystals is characterized by comprising the following steps:
(1) uniformly mixing cotton fiber crushed aggregates, 90wt% of lactic acid aqueous solution and 37wt% of concentrated hydrochloric acid, then transferring the mixture into a polytetrafluoroethylene lining reaction kettle, reacting under a closed condition, washing a product with deionized water, centrifuging, taking supernatant, and freeze-drying to obtain lactic acid grafted cellulose nanocrystals;
(2) ultrasonically dispersing the lactic acid grafted cellulose nanocrystal obtained in the step (1) in N, N-dimethylformamide to form stable dispersion liquid, adding polyethylene glycol into the dispersion liquid, reacting for 2-3 days at the temperature of 110-;
(3) mixing the product prepared in the step (2) with polylactic acid according to the mass ratio of 0.1-5: 100 is added into an internal mixer, the temperature is controlled at 150-210 ℃, the rotating speed is 60-150rpm, the heat preservation is carried out for 30min-150min, then the temperature is reduced to 50-70 ℃, the heat preservation is carried out for 1-3h, and then the temperature is reduced to the room temperature, thus obtaining the polylactic acid material.
2. The method of claim 1, wherein in step (1) the cotton fiber chaff: 90wt% aqueous lactic acid solution: the mass ratio of 37wt% concentrated hydrochloric acid is 1: 10-15: 0.1-2.
3. The method as claimed in claims 1-2, wherein the reaction temperature in step (1) is 130-160 ℃ and the reaction time is 3-8 h.
4. The method according to claims 1 to 3, wherein the vacuum drying temperature in step (2) is 90 to 120 ℃ and the drying time is 6 to 12 hours.
5. The method according to claims 1 to 5, wherein the mass ratio of the lactic acid grafted cellulose nanocrystals to the polyethylene glycol in step (2) is 100: 1-5.
6. The method according to claim 1, wherein the stirring speed in the step (2) is 50 to 100 rpm.
7. The method according to claim 1, wherein the temperature reduction rate in step (3) is 5-20 ℃/min.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115975361A (en) * | 2023-01-16 | 2023-04-18 | 宁波马菲羊纺织科技有限公司 | Colored polylactic acid composite material for shoe uppers |
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|---|---|---|---|---|
| WO2007136086A1 (en) * | 2006-05-23 | 2007-11-29 | Kyushu University, National University Corporation | Material comprising polylactic acid and cellulose fiber |
| CN105780189A (en) * | 2016-03-28 | 2016-07-20 | 桂林理工大学 | Preparation method of sisal cellulose nano-whisker enhanced polylactic acid/poly(ethylene succinate) biological composite material |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2007136086A1 (en) * | 2006-05-23 | 2007-11-29 | Kyushu University, National University Corporation | Material comprising polylactic acid and cellulose fiber |
| CN105780189A (en) * | 2016-03-28 | 2016-07-20 | 桂林理工大学 | Preparation method of sisal cellulose nano-whisker enhanced polylactic acid/poly(ethylene succinate) biological composite material |
Non-Patent Citations (2)
| Title |
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| 华笋: "纤维素接枝共聚物对聚乳酸结晶性能和拉伸流变性能的影响" * |
| 张春梅: "接枝改性纤维素纳米晶增强聚乳酸" * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115975361A (en) * | 2023-01-16 | 2023-04-18 | 宁波马菲羊纺织科技有限公司 | Colored polylactic acid composite material for shoe uppers |
| CN115975361B (en) * | 2023-01-16 | 2024-05-28 | 宁波马菲羊纺织科技有限公司 | Colored polylactic acid composite material for vamp |
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