CN115433393B - Polylactic acid-nanocellulose composite packaging material and preparation method thereof - Google Patents
Polylactic acid-nanocellulose composite packaging material and preparation method thereof Download PDFInfo
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- 229920001046 Nanocellulose Polymers 0.000 title claims abstract description 72
- 239000011091 composite packaging material Substances 0.000 title claims abstract description 34
- 238000002360 preparation method Methods 0.000 title claims abstract description 19
- 229920000747 poly(lactic acid) Polymers 0.000 claims abstract description 73
- 239000004626 polylactic acid Substances 0.000 claims abstract description 73
- 238000010438 heat treatment Methods 0.000 claims abstract description 24
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 claims abstract description 24
- 239000004367 Lipase Substances 0.000 claims abstract description 13
- 102000004882 Lipase Human genes 0.000 claims abstract description 13
- 108090001060 Lipase Proteins 0.000 claims abstract description 13
- 235000019421 lipase Nutrition 0.000 claims abstract description 13
- 239000004310 lactic acid Substances 0.000 claims abstract description 12
- 235000014655 lactic acid Nutrition 0.000 claims abstract description 12
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 42
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 42
- 239000010902 straw Substances 0.000 claims description 41
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 claims description 38
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 31
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 30
- 238000005406 washing Methods 0.000 claims description 25
- 239000000047 product Substances 0.000 claims description 23
- 240000008042 Zea mays Species 0.000 claims description 21
- 235000005824 Zea mays ssp. parviglumis Nutrition 0.000 claims description 21
- 235000002017 Zea mays subsp mays Nutrition 0.000 claims description 21
- 239000007864 aqueous solution Substances 0.000 claims description 21
- 235000005822 corn Nutrition 0.000 claims description 21
- 239000007788 liquid Substances 0.000 claims description 20
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 18
- 238000001914 filtration Methods 0.000 claims description 18
- 238000001746 injection moulding Methods 0.000 claims description 18
- 238000003756 stirring Methods 0.000 claims description 18
- 239000002131 composite material Substances 0.000 claims description 17
- 238000002156 mixing Methods 0.000 claims description 16
- 229910052757 nitrogen Inorganic materials 0.000 claims description 15
- 238000000034 method Methods 0.000 claims description 14
- 230000007935 neutral effect Effects 0.000 claims description 14
- 239000000843 powder Substances 0.000 claims description 14
- UKLNMMHNWFDKNT-UHFFFAOYSA-M sodium chlorite Chemical compound [Na+].[O-]Cl=O UKLNMMHNWFDKNT-UHFFFAOYSA-M 0.000 claims description 14
- 229960002218 sodium chlorite Drugs 0.000 claims description 14
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 claims description 12
- 229910000077 silane Inorganic materials 0.000 claims description 12
- 238000001035 drying Methods 0.000 claims description 11
- 238000006068 polycondensation reaction Methods 0.000 claims description 8
- 238000012545 processing Methods 0.000 claims description 8
- 239000002904 solvent Substances 0.000 claims description 8
- 239000000725 suspension Substances 0.000 claims description 8
- 238000004140 cleaning Methods 0.000 claims description 7
- 238000005520 cutting process Methods 0.000 claims description 7
- 239000012065 filter cake Substances 0.000 claims description 7
- INJVFBCDVXYHGQ-UHFFFAOYSA-N n'-(3-triethoxysilylpropyl)ethane-1,2-diamine Chemical compound CCO[Si](OCC)(OCC)CCCNCCN INJVFBCDVXYHGQ-UHFFFAOYSA-N 0.000 claims description 7
- 238000006116 polymerization reaction Methods 0.000 claims description 7
- 238000007873 sieving Methods 0.000 claims description 7
- 238000002791 soaking Methods 0.000 claims description 7
- 230000002194 synthesizing effect Effects 0.000 claims description 7
- 238000002390 rotary evaporation Methods 0.000 claims description 6
- 239000000243 solution Substances 0.000 claims description 6
- 230000000379 polymerizing effect Effects 0.000 claims description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 4
- 238000007865 diluting Methods 0.000 claims description 4
- IDGUHHHQCWSQLU-UHFFFAOYSA-N ethanol;hydrate Chemical compound O.CCO IDGUHHHQCWSQLU-UHFFFAOYSA-N 0.000 claims description 4
- 238000009210 therapy by ultrasound Methods 0.000 claims description 4
- 239000011259 mixed solution Substances 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 14
- 239000002121 nanofiber Substances 0.000 abstract description 12
- 239000005022 packaging material Substances 0.000 abstract description 11
- 238000007142 ring opening reaction Methods 0.000 abstract description 7
- 230000002255 enzymatic effect Effects 0.000 abstract description 4
- 238000005886 esterification reaction Methods 0.000 abstract description 4
- 229920003023 plastic Polymers 0.000 abstract description 4
- 239000004033 plastic Substances 0.000 abstract description 4
- 238000001125 extrusion Methods 0.000 abstract description 3
- 239000002689 soil Substances 0.000 abstract description 3
- 231100000053 low toxicity Toxicity 0.000 abstract 1
- 238000012360 testing method Methods 0.000 description 21
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 20
- 239000001569 carbon dioxide Substances 0.000 description 10
- 229910002092 carbon dioxide Inorganic materials 0.000 description 10
- 229920002678 cellulose Polymers 0.000 description 10
- 239000001913 cellulose Substances 0.000 description 10
- 238000006065 biodegradation reaction Methods 0.000 description 7
- 238000005452 bending Methods 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 230000015556 catabolic process Effects 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 238000006731 degradation reaction Methods 0.000 description 5
- 239000003054 catalyst Substances 0.000 description 4
- 238000011161 development Methods 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 230000004888 barrier function Effects 0.000 description 3
- 238000009264 composting Methods 0.000 description 3
- 238000006482 condensation reaction Methods 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 239000000835 fiber Substances 0.000 description 3
- 230000036541 health Effects 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000035484 reaction time Effects 0.000 description 3
- 238000007151 ring opening polymerisation reaction Methods 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- VHYFNPMBLIVWCW-UHFFFAOYSA-N 4-Dimethylaminopyridine Chemical compound CN(C)C1=CC=NC=C1 VHYFNPMBLIVWCW-UHFFFAOYSA-N 0.000 description 2
- 102000004190 Enzymes Human genes 0.000 description 2
- 108090000790 Enzymes Proteins 0.000 description 2
- 206010016654 Fibrosis Diseases 0.000 description 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 2
- 238000002835 absorbance Methods 0.000 description 2
- 150000001412 amines Chemical class 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000004761 fibrosis Effects 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000004806 packaging method and process Methods 0.000 description 2
- 239000002685 polymerization catalyst Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 229910001887 tin oxide Inorganic materials 0.000 description 2
- QHGNHLZPVBIIPX-UHFFFAOYSA-N tin(ii) oxide Chemical class [Sn]=O QHGNHLZPVBIIPX-UHFFFAOYSA-N 0.000 description 2
- 231100000419 toxicity Toxicity 0.000 description 2
- 230000001988 toxicity Effects 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- 239000011701 zinc Substances 0.000 description 2
- OEOIWYCWCDBOPA-UHFFFAOYSA-N 6-methyl-heptanoic acid Chemical compound CC(C)CCCCC(O)=O OEOIWYCWCDBOPA-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229920000858 Cyclodextrin Polymers 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000000862 absorption spectrum Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 239000002041 carbon nanotube Substances 0.000 description 1
- 229910021393 carbon nanotube Inorganic materials 0.000 description 1
- 238000007385 chemical modification Methods 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 230000002939 deleterious effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000032050 esterification Effects 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 235000013305 food Nutrition 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000004442 gravimetric analysis Methods 0.000 description 1
- 238000007731 hot pressing Methods 0.000 description 1
- JJTUDXZGHPGLLC-UHFFFAOYSA-N lactide Chemical compound CC1OC(=O)C(C)OC1=O JJTUDXZGHPGLLC-UHFFFAOYSA-N 0.000 description 1
- 244000005700 microbiome Species 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- RGGFMFZQWTZKDV-UHFFFAOYSA-N n,n-dimethylpyridin-1-ium-4-amine;trifluoromethanesulfonate Chemical compound [O-]S(=O)(=O)C(F)(F)F.CN(C)C1=CC=[NH+]C=C1 RGGFMFZQWTZKDV-UHFFFAOYSA-N 0.000 description 1
- 229910017059 organic montmorillonite Inorganic materials 0.000 description 1
- 239000011846 petroleum-based material Substances 0.000 description 1
- 238000007639 printing Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- HFHDHCJBZVLPGP-UHFFFAOYSA-N schardinger α-dextrin Chemical compound O1C(C(C2O)O)C(CO)OC2OC(C(C2O)O)C(CO)OC2OC(C(C2O)O)C(CO)OC2OC(C(O)C2O)C(CO)OC2OC(C(C2O)O)C(CO)OC2OC2C(O)C(O)C1OC2CO HFHDHCJBZVLPGP-UHFFFAOYSA-N 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- HUAUNKAZQWMVFY-UHFFFAOYSA-M sodium;oxocalcium;hydroxide Chemical compound [OH-].[Na+].[Ca]=O HUAUNKAZQWMVFY-UHFFFAOYSA-M 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- -1 β -aminoethyl Chemical group 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
- C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
- C08L1/08—Cellulose derivatives
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B15/00—Preparation of other cellulose derivatives or modified cellulose, e.g. complexes
- C08B15/05—Derivatives containing elements other than carbon, hydrogen, oxygen, halogens or sulfur
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
- C08L1/02—Cellulose; Modified cellulose
-
- C—CHEMISTRY; METALLURGY
- C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
- C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
- C12P7/00—Preparation of oxygen-containing organic compounds
- C12P7/62—Carboxylic acid esters
- C12P7/625—Polyesters of hydroxy carboxylic acids
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W90/00—Enabling technologies or technologies with a potential or indirect contribution to greenhouse gas [GHG] emissions mitigation
- Y02W90/10—Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Health & Medical Sciences (AREA)
- Engineering & Computer Science (AREA)
- Polymers & Plastics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Medicinal Chemistry (AREA)
- Biochemistry (AREA)
- Wood Science & Technology (AREA)
- Zoology (AREA)
- General Chemical & Material Sciences (AREA)
- Bioinformatics & Cheminformatics (AREA)
- General Engineering & Computer Science (AREA)
- General Health & Medical Sciences (AREA)
- Genetics & Genomics (AREA)
- Microbiology (AREA)
- Biotechnology (AREA)
- Materials Engineering (AREA)
- Biological Depolymerization Polymers (AREA)
Abstract
The invention discloses a polylactic acid-nanocellulose composite packaging material and a preparation method thereof, and belongs to the technical field of plastic preparation. The polylactic acid is prepared by heating and ring-opening lactic acid, and then performing lipase enzymatic esterification reaction, and the metal-free polylactic acid is more easily degraded in soil and has extremely low toxicity. On the basis, the polylactic acid and the nanofiber are compounded to prepare the packaging material, the nanofiber and the polylactic acid can be well dispersed during extrusion, and the mechanical property and the thermal stability of the material can be improved.
Description
Technical Field
The invention relates to the technical field of plastic preparation, in particular to a polylactic acid-nanocellulose composite packaging material and a preparation method thereof.
Background
Polylactic acid is one of the most interesting biodegradable materials for research at home and abroad, and medical use, packaging and fiber are three popular application fields. Polylactic acid takes lactic acid from natural sources as a main raw material, has good biodegradability and biocompatibility, has a life cycle which is obviously lower than that of petroleum-based materials and is considered as a green packaging material with the most development prospect.
The packaging aims at protecting the product, facilitating storage and transportation and promoting sales. In the aspect of protecting products, the appearance of the package is required to be complete and not damaged, the strength and weather resistance of the packaging material are required to meet the requirements, the internal quality of the product in the shelf life, such as the barrier property of the packaging material, is required to be protected, the food is ensured not to be oxidized and rancid or to be corroded by microorganisms, and the metal product is not rusted and the like. In the aspect of convenient storage and transportation, the material is required to have excellent mechanical strength and sealing strength so as to ensure that the package is not damaged in the circulation processes of carrying, storage, transportation and the like. The promotion of sales is mainly reflected in structural and decorative design aspects, such as printing adaptability of packaging materials, transparency, glossiness and the like of the packaging materials.
Polylactic acid also has excellent post-processability, gas barrier property, thermal barrier property, biocompatibility, transparency and the like, but at the same time, the single polylactic acid material has some defects in performance, such as high brittleness, poor impact resistance, low heat distortion temperature, poor hydrophilicity and the like. Aiming at the defects of polylactic acid performance, the prior art carries out modification treatment on the polylactic acid packaging material, including chemical modification, physical modification, composite material modification and the like. The preparation of the composite material is the most important way for widening the application of the polylactic acid, and the composite material has better capability than a single polylactic acid material in crystallinity, biocompatibility and hydrophilicity. According to the difference of filling components, the polylactic acid composite material comprises: polylactic acid/carbon nanotube composite material, polylactic acid/cyclodextrin composite material, polylactic acid/cellulose composite material, polylactic acid/organic montmorillonite composite material, and the like.
Chinese patent CN 106893284A discloses a preparation method of polylactic acid/nanocellulose composite material, comprising the following specific steps: 1) Preparing nano cellulose organogel; 2) Immersing the nano cellulose organogel block prepared in the step 1) in a chloroform solution of polylactic acid for 24-48 hours, taking out the gel block from the solution, drying the gel block for 2-5 hours at normal temperature, placing the gel block into a vacuum drying box, drying the gel block in vacuum for 10-15 hours at 50-60 ℃, and hot-pressing the gel block by a hot press to obtain the polylactic acid/nano cellulose composite material.
Chinese patent CN 110730792A discloses a polylactic acid grafted cellulose nanofiber and a method for producing the same, which comprises a grafted cellulose having a graft chain bonded to cellulose constituting the cellulose nanofiber, and is a polylactic acid grafted cellulose nanofiber in which the graft chain is polylactic acid and the ratio of absorbance of c=o derived from polylactic acid to absorbance of O-H derived from cellulose in an infrared absorption spectrum is 0.01 to 1000. The present invention is also a method for producing a polylactic acid grafted cellulose nanofiber, which comprises a step of graft polymerizing lactide onto cellulose constituting the cellulose nanofiber in the presence of an organic polymerization catalyst comprising an amine and a salt obtained by reacting the amine with an acid. As the organic polymerization catalyst, 4-dimethylaminopyridine and 4-dimethylaminopyridinium triflate are preferred.
However, in the existing polylactic acid packaging material, polylactic acid is mostly prepared by ring-opening polymerization and direct condensation reaction, and the ring-opening reaction requires a higher temperature and a longer reaction time. In addition, the condensation process generally uses a metal catalyst, so that health and safety problems are easily caused, and therefore, the development of the polylactic acid composite packaging material with strong mechanical properties and environmental protection is particularly important.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a polylactic acid-nanocellulose composite packaging material and a preparation method thereof.
A preparation method of a polylactic acid-nanocellulose composite packaging material comprises the following steps:
s1, preparing nanocellulose;
s2, synthesizing polylactic acid;
s3, preparing a composite material.
Specifically, the preparation method of the polylactic acid-nanocellulose composite packaging material comprises the following steps:
s1, preparing nanocellulose: cutting off corn straw, cleaning, airing, crushing, sieving to 80-100 meshes to obtain corn straw powder, and soaking in 1-2wt% sodium hydroxide aqueous solution for 20-24 hours, wherein the ratio of the corn straw powder to the sodium hydroxide aqueous solution is 1: 18-20 g/mL, stirring at 600-800 rpm for 15-20 min, filtering, washing filter residues with water, and drying at 60-80 ℃ for 5-7 h to obtain straw residues; taking 5-8 parts by weight of straw residues, adding 120-150 parts by weight of water, 2.5-3.8 parts by weight of sodium chlorite and 1-2 parts by weight of acetic acid, stirring at 300-500 rpm for 30-40 min, heating at 70-80 ℃ for 1-3 h, adding 1.5-2 parts by weight of sodium chlorite and 1-2 parts by weight of acetic acid every 1h, filtering, washing a filter cake to be neutral by water, and airing at normal temperature; adding 3-5 parts by weight of dried straw residues into 200-280 parts by weight of 2-4wt% KOH aqueous solution, standing for 6-8 hours at normal temperature, heating for 2-3 hours at 70-80 ℃, washing with water to be neutral, and airing at normal temperature to obtain nanocellulose;
s2, synthesizing polylactic acid: dehydrating 5-10 parts by weight of lactic acid at 110-120 ℃ under continuous nitrogen flow for 1-2 h, then carrying out polycondensation reaction at 150-160 ℃ under the condition of no nitrogen flow, reacting for 2-3 h, distilling the obtained oligomer at 200-210 ℃ for 2-3 h, collecting distilled liquid, diluting the distilled liquid with toluene at 70-80 ℃ to obtain mixed liquid, adding lipase into the mixed liquid, polymerizing for 20-24 h at 35-40 ℃ to obtain a polymerized product, adding chloroform into the polymerized product, mixing uniformly, and carrying out rotary evaporation at 30-35 ℃ to remove chloroform to obtain the polylactic acid;
s3, preparing a composite material: mixing the polylactic acid prepared in the step S2 with the nanocellulose prepared in the step S1, processing by an extruder, and performing injection molding by an injection molding machine to obtain the polylactic acid-nanocellulose composite packaging material.
Further, in the step S2, the lipase accounts for 8-10wt% of the mixed solution.
Further, the mass ratio of the polymerization product to chloroform in the step S2 is 1:2 to 3.
Further, in the step S3, the mixing ratio of the polylactic acid to the nanocellulose is 1:5 to 10 mass ratio.
Further, the extruder in the step S3 is a twin-screw extruder, and the temperatures of the sections 1 to 6 of the extruder are 170 to 175 ℃, 170 to 177 ℃, 175 to 180 ℃, 180 to 185 ℃ and 185 to 190 ℃ respectively.
Further, the injection molding conditions in the step S3 are as follows: the temperature is 180-185 ℃, the working pressure is 0.4-0.7 MPa, and the heating time is 270-320 s.
Preferably, the nanocellulose is silane modified nanocellulose, and the preparation method is as follows: cutting off corn straw, cleaning, airing, crushing, sieving to 80-100 meshes to obtain corn straw powder, and soaking in 1-2wt% sodium hydroxide aqueous solution for 20-24 hours, wherein the ratio of the corn straw powder to the sodium hydroxide aqueous solution is 1: 18-20 g/mL, stirring at 600-800 rpm for 15-20 min, filtering to obtain filter residue, washing with water, and drying at 60-80 ℃ for 5-7 h to obtain straw residue; taking 5-8 parts by weight of straw residues, adding 120-150 parts by weight of water, 2.5-3.8 parts by weight of sodium chlorite and 1-2 parts by weight of acetic acid, stirring at 300-500 rpm for 30-40 min, heating at 70-80 ℃ for 1-3 h, adding 1.5-2 parts by weight of sodium chlorite and 1-2 parts by weight of acetic acid every 1h, filtering, washing a filter cake to be neutral by water, and airing at normal temperature; adding 3-5 parts by weight of dried straw residues into 200-280 parts by weight of 2-4wt% KOH aqueous solution, standing for 6-8 hours at normal temperature, heating for 2-3 hours at 70-80 ℃, washing with water to be neutral, and drying at normal temperature to obtain nanocellulose; adding 5-7 parts by weight of N- (beta-aminoethyl) -gamma-aminopropyl triethoxysilane into 50-60 parts by weight of 70-85 wt% ethanol water solution, stirring at 40-50 ℃ for 30-50 min to obtain a solvent A, adding nanocellulose into water to form a suspension with the concentration of 1-3 wt%, carrying out ultrasonic treatment on the suspension at 300-400W and 35-40 kHz for 2-3 h, mixing with the solvent A, reacting at 110-120 ℃ for 2-3 h, filtering, and washing with absolute ethanol until the pH value is 7-8 to obtain silane modified nanocellulose.
The invention also provides a polylactic acid-nanocellulose composite packaging material, which is prepared by adopting the method.
Polylactic acid is used as an environment-friendly material, and has the most outstanding characteristic of degradability. The degradation of polylactic acid is based on the breaking of alpha bonds, and under natural environment, the polylactic acid is firstly hydrolyzed, the molecular skeleton is broken, and after components with lower relative molecular weight are formed, the components are further degraded into small molecular products, so that the final biodegradation is realized. And in the natural environment, the degradation speed of polylactic acid is very slow.
The most popular polylactic acid preparation technology at present is ring-opening polymerization and direct condensation reaction, and the ring-opening reaction requires higher temperature and longer reaction time. In addition, the polycondensation process typically uses metal catalysts (zinc and tin oxides) that can raise health and safety concerns. For bio-based routes, enzyme-catalyzed polymerization has many advantages, including mild reaction conditions, selective reactions leading to well-defined structures, substitution of toxic metal catalysts with natural enzymes and no residual metal-containing deleterious products. In the invention, the polylactic acid oligomer is formed by heating and ring-opening lactic acid, and the nitrogen flow is stable so as to eliminate water vapor generated by the reaction. Then, lipase enzymatic esterification is carried out to synthesize biodegradable metal-free polylactic acid, wherein the degree of amorphous state in the polylactic acid is increased, the polylactic acid is easier to degrade in soil, and the toxicity is extremely low; on the basis, the polylactic acid and the nanofiber are compounded to prepare the packaging material, but during extrusion processing, the nanofiber is aggregated due to the development of intermolecular hydrogen bonds, so that caking is formed, and the caking is used as a stress concentration point, so that the mechanical property is reduced, and the nanofiber is further required to be pretreated. The invention uses N- (beta-aminoethyl) -gamma-aminopropyl triethoxy silane to treat the nanocellulose, still maintains a long fiber structure, but the surface becomes smooth, the degree of fibrosis is reduced, the nanocellulose can be well dispersed when the nanocellulose is extruded with polylactic acid, and the mechanical property and the thermal stability of the material can be improved.
Detailed Description
Introduction of raw materials in the examples:
lactic acid, CAS:10326-41-7 available from Hubei Long Xin chemical industry Co., ltd;
n- (β -aminoethyl) - γ -aminopropyl triethoxysilane, CAS:5089-72-5, available from Hubei Fangde New Material Co., ltd;
lipase, cat No.: xia Cheng SDG-2426, enzyme activity 10000u/g, available from Xia Cheng Biotechnology development Co., ltd;
stannous isooctanoate, model 301-10-0, available from Wohan Ji Xinyi bang Biotechnology Co.
Example 1
A preparation method of a polylactic acid-nanocellulose composite packaging material comprises the following steps:
s1, preparing nanocellulose: cutting corn straw, cleaning, airing, crushing, sieving to 100 meshes to obtain corn straw powder, and soaking in 2wt% of sodium hydroxide aqueous solution for 24 hours, wherein the ratio of the corn straw powder to the sodium hydroxide aqueous solution is 1:18g/mL, stirring at 800rpm for 20min, filtering, washing filter residues, drying at 70 ℃ for 6h to obtain straw residues, adding 150kg of water, 3.1kg of sodium chlorite and 1kg of acetic acid at 450rpm to 8kg of straw residues, stirring for 40min, heating at 80 ℃ for 3h, adding 1.5kg of sodium chlorite and 1kg of acetic acid every 1h, filtering, washing a filter cake to be neutral by water, airing at normal temperature, adding 250kg of aired straw residues into 250kg of 3wt% KOH aqueous solution, standing at normal temperature for 8h, heating at 70 ℃ for 3h, washing with water to be neutral, airing at normal temperature to obtain nanocellulose;
s2, synthesizing polylactic acid: dehydrating 8kg of lactic acid at 120 ℃ under a continuous nitrogen flow for 2 hours, then carrying out polycondensation reaction at 160 ℃ without nitrogen flow for 3 hours, distilling the obtained oligomer at 210 ℃ for 2 hours, collecting distilled liquid, diluting the distilled liquid with toluene at 75 ℃ to obtain mixed liquid, wherein the mass ratio of the distilled liquid to the toluene is 1:3, adding lipase into the mixed liquid, wherein the lipase accounts for 10 weight percent of the mixed liquid, polymerizing for 24 hours at 40 ℃ to obtain a polymerized product, adding chloroform into the polymerized product, and uniformly mixing, wherein the mass ratio of the polymerized product to the chloroform is 1:2, removing chloroform by rotary evaporation at 35 ℃ to obtain the polylactic acid;
s3, preparing a composite material: mixing the polylactic acid prepared in the step S2 and the nanocellulose prepared in the step S1 according to the mass ratio of 1:8, processing by an extruder, wherein the temperatures of sections 1-6 of the extruder are respectively 170 ℃, 175 ℃, 177 ℃, 180 ℃, 185 ℃ and 190 ℃, performing injection molding by an injection molding machine, wherein the injection molding temperature is 185 ℃, the working pressure is 0.7MPa, and the heating time is 300S, so that the polylactic acid-nanocellulose composite packaging material is obtained.
Example 2
A preparation method of a polylactic acid-nanocellulose composite packaging material comprises the following steps:
s1, preparing silane modified nanocellulose: cutting corn straw, cleaning, airing, crushing, sieving to 100 meshes to obtain corn straw powder, and soaking in 2wt% of sodium hydroxide aqueous solution for 24 hours, wherein the ratio of the corn straw powder to the sodium hydroxide aqueous solution is 1:18g/mL, stirring at 800rpm for 20min, filtering, washing filter residues, drying at 70 ℃ for 6h to obtain straw residues, adding 150kg of water, 3.1kg of sodium chlorite and 1kg of acetic acid at 450rpm to 8kg of straw residues, stirring for 40min, heating at 80 ℃ for 3h, adding 1.5kg of sodium chlorite and 1kg of acetic acid every 1h, filtering, washing a filter cake to be neutral by water, airing at normal temperature, adding 250kg of aired straw residues into 250kg of 3wt% KOH aqueous solution, standing at normal temperature for 8h, heating at 70 ℃ for 3h, washing with water to be neutral, airing at normal temperature to obtain nanocellulose; adding 6kg of N- (beta-aminoethyl) -gamma-aminopropyl triethoxysilane into 60kg of 80wt% ethanol water solution, stirring at 50 ℃ for 50min to obtain a solvent A, adding nanocellulose into water to form 2wt% suspension, carrying out ultrasonic treatment on the suspension at 400W and 35kHz for 3h, mixing with the solvent A, reacting at 120 ℃ for 3h, filtering and washing with absolute ethanol until the pH value is 7 to obtain silane modified nanocellulose;
s2, synthesizing polylactic acid: dehydrating 8kg of lactic acid at 120 ℃ under a continuous nitrogen flow for 2 hours, then carrying out polycondensation reaction at 160 ℃ without nitrogen flow for 3 hours, distilling the obtained oligomer at 210 ℃ for 2 hours, collecting distilled liquid, diluting the distilled liquid with toluene at 75 ℃ to obtain mixed liquid, wherein the mass ratio of the distilled liquid to the toluene is 1:3, adding lipase into the mixed liquid, wherein the lipase accounts for 10 weight percent of the mixed liquid, polymerizing for 24 hours at 40 ℃ to obtain a polymerized product, adding chloroform into the polymerized product, and uniformly mixing, wherein the mass ratio of the polymerized product to the chloroform is 1:2, removing chloroform by rotary evaporation at 35 ℃ to obtain the polylactic acid;
s3, preparing a composite material: mixing the polylactic acid prepared in the step S2 and the silane modified nanocellulose prepared in the step S1 according to the mass ratio of 1:8, processing by an extruder, wherein the temperatures of sections 1-6 of the extruder are 170 ℃, 175 ℃, 177 ℃, 180 ℃, 185 ℃ and 190 ℃, and performing injection molding by an injection molding machine, wherein the injection molding temperature is 185 ℃, the working pressure is 0.7MPa, and the heating time is 300S, so that the polylactic acid-nanocellulose composite packaging material is obtained.
Example 3
A preparation method of a polylactic acid-nanocellulose composite packaging material comprises the following steps:
s1, preparing silane modified nanocellulose: cutting corn straw, cleaning, airing, crushing, sieving to 100 meshes to obtain corn straw powder, and soaking in 2wt% of sodium hydroxide aqueous solution for 24 hours, wherein the ratio of the corn straw powder to the sodium hydroxide aqueous solution is 1:18g/mL, stirring at 800rpm for 20min, filtering, washing filter residues, drying at 70 ℃ for 6h to obtain straw residues, adding 150kg of water, 3.1kg of sodium chlorite and 1kg of acetic acid at 450rpm to 8kg of straw residues, stirring for 40min, heating at 80 ℃ for 3h, adding 1.5kg of sodium chlorite and 1kg of acetic acid every 1h, filtering, washing a filter cake to be neutral by water, airing at normal temperature, adding 250kg of aired straw residues into 250kg of 3wt% KOH aqueous solution, standing at normal temperature for 8h, heating at 70 ℃ for 3h, washing with water to be neutral, airing at normal temperature to obtain nanocellulose; adding 6kg of N- (beta-aminoethyl) -gamma-aminopropyl triethoxysilane into 60kg of 80wt% ethanol water solution, stirring at 50 ℃ for 50min to obtain a solvent A, adding nanocellulose into water to form 2wt% suspension, carrying out ultrasonic treatment on the suspension at 400W and 35kHz for 3h, mixing with the solvent A, reacting at 120 ℃ for 3h, filtering and washing with absolute ethanol until the pH value is 7 to obtain silane modified nanocellulose;
s2, synthesizing polylactic acid: 8kg of lactic acid is dehydrated for 2 hours under a continuous nitrogen flow at 120 ℃, then 0.06kg of stannous iso-octoate is added, and then polycondensation reaction is carried out at 160 ℃ under the protection of nitrogen for 3 hours, the polymerization product is cooled to room temperature and then mixed with chloroform, and the mass ratio of the polymerization product to chloroform is 1:2, removing chloroform by rotary evaporation at 35 ℃ to obtain the polylactic acid;
s3, preparing a composite material: mixing the polylactic acid prepared in the step S2 and the silane modified nanocellulose prepared in the step S1 according to the mass ratio of 1:8, processing by an extruder, wherein the temperatures of sections 1-6 of the extruder are 170 ℃, 175 ℃, 177 ℃, 180 ℃, 185 ℃ and 190 ℃, and performing injection molding by an injection molding machine, wherein the injection molding temperature is 185 ℃, the working pressure is 0.7MPa, and the heating time is 300S, so that the polylactic acid-nanocellulose composite packaging material is obtained.
Comparative example 1
A preparation method of a polylactic acid-nanocellulose composite packaging material comprises the following steps:
s1, preparing nanocellulose: cutting corn straw, cleaning, airing, crushing, sieving to 100 meshes to obtain corn straw powder, and soaking in 2wt% of sodium hydroxide aqueous solution for 24 hours, wherein the ratio of the corn straw powder to the sodium hydroxide aqueous solution is 1:18g/mL, stirring at 800rpm for 20min, filtering, washing filter residues, drying at 70 ℃ for 6h to obtain straw residues, adding 150kg of water, 3.1kg of sodium chlorite and 1kg of acetic acid at 450rpm to 8kg of straw residues, stirring for 40min, heating at 80 ℃ for 3h, adding 1.5kg of sodium chlorite and 1kg of acetic acid every 1h, filtering, washing a filter cake to be neutral by water, airing at normal temperature, adding 250kg of aired straw residues into 250kg of 3wt% KOH aqueous solution, standing at normal temperature for 8h, heating at 70 ℃ for 3h, washing with water to be neutral, airing at normal temperature to obtain nanocellulose;
s2, synthesizing polylactic acid: 8kg of lactic acid is dehydrated for 2 hours under a continuous nitrogen flow at 120 ℃, then 0.06kg of stannous iso-octoate is added, and then polycondensation reaction is carried out at 160 ℃ under the protection of nitrogen for 3 hours, the polymerization product is cooled to room temperature and then mixed with chloroform, and the mass ratio of the polymerization product to chloroform is 1:2, removing chloroform by rotary evaporation at 35 ℃ to obtain the polylactic acid;
s3, preparing a composite material: mixing the polylactic acid prepared in the step S2 and the nanocellulose prepared in the step S1 according to the mass ratio of 1:8, processing by an extruder, wherein the temperatures of sections 1-6 of the extruder are respectively 170 ℃, 175 ℃, 177 ℃, 180 ℃, 185 ℃ and 190 ℃, performing injection molding by an injection molding machine, wherein the injection molding temperature is 185 ℃, the working pressure is 0.7MPa, and the heating time is 300S, so that the polylactic acid-nanocellulose composite packaging material is obtained.
Test example 1
Mechanical property test was performed on the composite packaging materials prepared in examples 1 to 3 and comparative example 1:
tensile properties: determination of tensile Properties of plastics according to GB/T1040.1-2018 section 1: general rule, the composite packaging materials prepared in examples 1 to 3 and comparative example 1 were tested for tensile properties by using a MTS system (China) CMT-4104 microcomputer controlled electronic universal tester, the test temperature was 25℃at a tensile rate of 50mm/min, the gauge length was 60mm, the thickness was 4mm, 6 samples were set, and the temperature was 24℃and the relative humidity was 52℃for at least 24 hours, and the test results were averaged.
Flexural strength: the bending strength refers to the maximum bending stress that the test specimen can withstand before reaching a prescribed deflection value during bending. The test method is that the composite packaging material samples prepared in the examples 1-3 and the comparative example 1 are crushed again, and then are formed by hot press molding through a die on a flat plate hot press, and parameters of hot press are set: temperature: 190 ℃, pressure: 8Mpa, time: 10min, the size of the die is 50mm multiplied by 2mm, the bending test speed is 20mm/min, then the hot-pressed plate is cut into the required sample size, the bending performance is tested according to GB/T9341-2008 'determination of Plastic bending Performance', a group of 6 samples are tested, and the test results are averaged.
The test results are shown in table 1:
table 1: mechanical test result of polylactic acid-nanocellulose composite packaging material
| Tensile Strength (Mpa) | Flexural Strength (Mpa) | |
| Example 1 | 42.6 | 92.3 |
| Example 2 | 47.8 | 101.8 |
| Example 3 | 40.4 | 80.5 |
| Comparative example 1 | 37.2 | 66.9 |
As can be seen from Table 1, the polylactic acid-nanocellulose composite packaging material prepared in example 2 has higher mechanical strength, the polylactic acid oligomer in example 2 is formed by heating and ring-opening lactic acid, and the nitrogen flow is stable so as to eliminate water vapor generated by the reaction. Then carrying out lipase enzymatic esterification reaction to synthesize the metal-free polylactic acid; in example 1, the polylactic acid and the nanofibers were compounded to prepare a packaging material, but during extrusion processing, the nanofibers were aggregated due to the development of intermolecular hydrogen bonds, so that agglomerates were formed, and these agglomerates served as stress concentration points, resulting in a decrease in mechanical properties. In example 2, the long fiber structure is still maintained by using N- (beta-aminoethyl) -gamma-aminopropyl triethoxy silane to treat the nano cellulose, but the surface becomes smooth, the degree of fibrosis is reduced, the nano cellulose can be well dispersed when the nano cellulose is extruded with polylactic acid, and the mechanical property and the thermal stability of the material are improved.
Test example 2
The polylactic acid-nanocellulose composite packaging materials prepared in examples 1-3 and comparative example 1 were subjected to biodegradation tests, and determination of the percent biodegradation was carried out with reference to the national standard GB/T19277.2-2013 "determination of the final aerobic biological decomposition capability of materials under controlled composting conditions" part 2 of the method for determining released carbon dioxide: the specific procedure in the determination of the amount of carbon dioxide released under laboratory conditions was performed by gravimetric analysis. Determination of the biological decomposition Rate of the test Material under the calculation of the composting conditions carbon dioxide was measured by weighing an absorption device equipped with soda lime and sodium TalcThe amount released was measured periodically to calculate the decomposition rate. The composting period is 60d, and the temperature is 58+/-2 ℃. The amount of carbon dioxide released was periodically weighed with an electronic balance, the percent biodegradation of the material was obtained by comparing the amount of carbon dioxide released to the theoretical amount of carbon dioxide released, and the test was ended when the biodegradation reached a plateau. The percent biodegradation D of the test material in each test vessel was calculated from the accumulated amount of carbon dioxide according to the following formula t (％)：
Wherein:
m(ThCO 2 ) The theoretical release of carbon dioxide in grams (g) was produced for each vessel of the test material.
The specific test results are shown in Table 2.
Table 2 table of degradation test results of polylactic acid-nanocellulose composite packaging material
Polylactic acid is used as an environment-friendly material, and has the most outstanding characteristic of degradability. Polylactic acid degradation is based on a bond rupture, and under natural environment, polylactic acid is firstly hydrolyzed, molecular frameworks are ruptured, and components with lower relative molecular weight are further degraded into micromolecular products after being formed, so that final biodegradation is realized. And in the natural environment, the degradation speed of polylactic acid is very slow. The most popular polylactic acid preparation technology at present is ring-opening polymerization and direct condensation reaction, and the ring-opening reaction requires higher temperature and longer reaction time. In addition, the polycondensation process typically uses metal catalysts (zinc and tin oxides) that can raise health and safety concerns. In examples 1 and 2 of the present invention, the polylactic acid oligomer was formed by ring-opening by heating lactic acid, and the flow rate of nitrogen was stabilized to eliminate water vapor generated by the reaction. And then, carrying out lipase enzymatic esterification reaction to synthesize biodegradable metal-free polylactic acid, wherein the degree of amorphous state in the polylactic acid is increased, the polylactic acid is easier to degrade in soil, the toxicity is extremely low, and the environment-friendly performance of the packaging material is improved.
Claims (8)
1. The preparation method of the polylactic acid-nanocellulose composite packaging material is characterized by comprising the following steps of:
s1, preparing silane modified nanocellulose: cutting off corn straw, cleaning, airing, crushing, sieving to 80-100 meshes to obtain corn straw powder, soaking in 1-2wt% sodium hydroxide aqueous solution for 20-24 hours, stirring at 600-800 rpm for 15-20 minutes, filtering, washing filter residues with water, and drying at 60-80 ℃ for 5-7 hours to obtain straw residues; taking 5-8 parts by weight of straw residues, adding 120-150 parts by weight of water, 2.5-3.8 parts by weight of sodium chlorite and 1-2 parts by weight of acetic acid, stirring at 300-500 rpm for 30-40 min, heating at 70-80 ℃ for 1-3 h, adding 1.5-2 parts by weight of sodium chlorite and 1-2 parts by weight of acetic acid every 1h, filtering, washing a filter cake to be neutral by water, and airing at normal temperature; adding 3-5 parts by weight of dried straw residues into 200-280 parts by weight of 2-4wt% KOH aqueous solution, standing for 6-8 hours at normal temperature, heating for 2-3 hours at 70-80 ℃, washing with water to be neutral, and drying at normal temperature to obtain nanocellulose; adding 5-7 parts by weight of N- (beta-aminoethyl) -gamma-aminopropyl triethoxysilane into 50-60 parts by weight of 70-85 wt% ethanol water solution, stirring at 40-50 ℃ for 30-50 min to obtain a solvent A, adding nanocellulose into water to form a suspension with the concentration of 1-3 wt%, carrying out ultrasonic treatment on the suspension at 300-400W and 35-40 kHz for 2-3 h, mixing with the solvent A, reacting at 110-120 ℃ for 2-3 h, filtering, and washing with absolute ethanol until the pH value is 7-8 to obtain silane modified nanocellulose;
s2, synthesizing polylactic acid: dehydrating 5-10 parts by weight of lactic acid at 110-120 ℃ under continuous nitrogen flow for 1-2 h, then carrying out polycondensation reaction at 150-160 ℃ under the condition of no nitrogen flow, reacting for 2-3 h, distilling the obtained oligomer at 200-210 ℃ for 2-3 h, collecting distilled liquid, diluting the distilled liquid with toluene at 70-80 ℃ to obtain mixed liquid, adding lipase into the mixed liquid, polymerizing for 20-24 h at 35-40 ℃ to obtain a polymerized product, adding chloroform into the polymerized product, mixing uniformly, and carrying out rotary evaporation at 30-35 ℃ to remove chloroform to obtain the polylactic acid;
s3, preparing a composite material: mixing the polylactic acid prepared in the step S2 with the silane modified nanocellulose prepared in the step S1, processing by an extruder, and performing injection molding by an injection molding machine to obtain the polylactic acid-nanocellulose composite packaging material.
2. The method for preparing the polylactic acid-nanocellulose composite packaging material as claimed in claim 1, wherein: the ratio of the corn stalk powder to the sodium hydroxide aqueous solution is 1: 18-20 g/mL.
3. The method for preparing the polylactic acid-nanocellulose composite packaging material as claimed in claim 1, wherein: in the step S2, the lipase accounts for 8-10wt% of the mixed solution.
4. The method for preparing the polylactic acid-nanocellulose composite packaging material as claimed in claim 1, wherein: the mass ratio of the polymerization product to chloroform in the step S2 is 1:2 to 3.
5. The method for preparing the polylactic acid-nanocellulose composite packaging material as claimed in claim 1, wherein: the mixing ratio of polylactic acid to silane modified nanocellulose in the step S3 is 1:5 to 10 mass ratio.
6. The method for preparing the polylactic acid-nanocellulose composite packaging material as claimed in claim 1, wherein: the extruder in the step S3 is a double-screw extruder, and the temperatures of the sections 1 to 6 of the extruder are 170 ℃ to 175 ℃, 170 ℃ to 177 ℃, 175 ℃ to 180 ℃, 180 ℃ to 185 ℃ and 185 ℃ to 190 ℃ respectively.
7. The method for preparing the polylactic acid-nanocellulose composite packaging material as claimed in claim 1, wherein the injection molding conditions in the step S3 are as follows: the temperature is 180-185 ℃, the working pressure is 0.4-0.7 MPa, and the heating time is 270-320 s.
8. A polylactic acid-nanocellulose composite packaging material, characterized in that it is prepared by the method according to any one of claims 1 to 7.
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Denomination of invention: A polylactic acid nanocellulose composite packaging material and its preparation method Effective date of registration: 20231212 Granted publication date: 20230502 Pledgee: Agricultural Bank of China Limited Longgang sub branch Pledgor: ZHEJIANG TANGFENG HANDICRAFT Co.,Ltd. Registration number: Y2023330003001 |