Preparation method of renewable high-barrier packaging material
By organically modifying cellulose nanocrystals and blending them with polylactic acid resin, a high-barrier packaging material with excellent barrier and mechanical properties was prepared, which solved the problem of insufficient barrier properties of PLA materials and achieved environmentally friendly and efficient packaging Materials application.
Patent Information
- Application Number
- CN202411400448.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-09
- Publication Date
- 2025-01-10
Smart Images
Figure QLYQS_1 
Figure QLYQS_2 
Figure BDA0005075126280000031
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of research and development of multifunctional packaging materials, and specifically to a method for preparing a renewable high-barrier packaging material. Background Art
[0002] Plastic flexible packaging materials are widely used as packaging materials for food, medicine, cosmetics and daily necessities due to their convenience, high transparency, easy processing and excellent compression resistance. Traditional petroleum-based plastics (polyethylene, polypropylene, polystyrene, etc.) bring convenience to people, but also bring continuous environmental pollution and high carbon emissions. At the same time, fossil resources such as raw materials such as oil and coal are also facing the dilemma of increasing depletion, forcing people to actively explore green and sustainable packaging alternative materials. Bio-based plastics such as polyamino acids, polylactic acid (PLA), starch, etc. are derived from renewable natural biomass resources. They are degradable bio-based polymer materials and have become a strong competitor to petroleum-based plastics.
[0003] PLA has gradually become the most promising packaging material due to its renewable, non-toxic, non-irritating and high strength. However, PLA has poor barrier properties, so it needs to be modified. In the prior art, there have been reports on the use of cellulose nanocrystals (CNC) as nanopolymer fillers to improve the barrier properties of plastic materials. Summary of the invention
[0004] The present invention develops a novel renewable high-barrier packaging material, which has excellent barrier properties and mechanical properties and can be used in the packaging field.
[0005] A method for preparing a renewable high-barrier packaging material comprises the following steps:
[0006] Step 1: Surface modification of cellulose nanocrystals using an organic modifier to obtain organic molecule-modified cellulose nanocrystals;
[0007] Wherein, the organic modifier is organic modifier I and / or organic modifier II;
[0008] Step 2: 5 to 20 parts by weight of polylactic acid resin and 0.5 to 5 parts by weight of organic molecule modified cellulose nanocrystals are first blended, melted and extruded through a twin-screw extruder, then formed into particles with an average particle size of 1 to 5 mm using a pelletizer, and finally cast into a renewable high-barrier packaging material with a film thickness of 50 to 150 μm using a casting machine.
[0009] Preferably, the preparation method of the organic modifier I is:
[0010] Based on the regioselective mechanism of olefin electrophilic addition orientation reaction, the carboxyl functional group of 1 molar equivalent of gallic acid and the alkenyl functional group of (1.01-1.05) molar equivalent of magnolol were catalyzed by a strong acid catalyst to generate alkenyl monomers.
[0011] The organic modifier I is prepared by an addition reaction between the alkenyl functional group of 1 molar equivalent of the alkenyl monomer and the Si-H bond of (1.01 to 1.05) molar equivalent of dimethylethoxysilane.
[0012] Preferably, the preparation method of the organic modifier II is: based on the regioselective mechanism of the electrophilic addition orientation reaction of olefins, a strong acid catalyst catalyzes the addition reaction of (2.01 to 2.05) molar equivalents of the carboxyl functional group of gallic acid with 1 molar equivalent of the alkenyl functional group of magnolol to prepare the organic modifier II.
[0013] Preferably, the strong acid catalyst is one of sulfuric acid, p-toluenesulfonic acid and fluoroboric acid.
[0014] Preferably, the mass ratio of the organic modifier to the cellulose nanocrystals in the organic molecule-modified cellulose nanocrystals is 1:(1-5).
[0015] Preferably, the cellulose nanocrystals have a diameter of 5 to 20 nm and a length of 200 to 500 nm.
[0016] The water vapor permeability of a renewable high barrier packaging material prepared according to the above method is (2.0-4.0) g / (m 2 ·24h), oxygen permeability is (1.5~3.5)cm 3 / (m 2 ·24h·0.1MPa).
[0017] Beneficial effects:
[0018] The present invention uses biodegradable, renewable, high-specific-surface-area cellulose nanocrystals as barrier fillers, and uses chemical bonding (reaction of silanol and hydroxyl groups) and / or hydrogen bonding to perform surface modification treatment on cellulose nanocrystals using an organic modifier synthesized from renewable bioactive compounds magnolol and gallic acid extracted from plants, thereby preparing organic molecule-modified cellulose nanocrystals.
[0019] Using fully degradable and renewable polylactic acid resin as film raw material, through the blending-extrusion-casting process, using organic molecule-modified cellulose nanocrystals as modification reagents, a renewable high-barrier packaging material is prepared;
[0020] It is found through experiments that the packaging material prepared by the present invention not only has excellent barrier properties, but is also renewable and recyclable, which is in line with the trend of environmental protection. DETAILED DESCRIPTION
[0021] Experimental Example 1:
[0022] The organic modifier I is prepared as follows:
[0023] The synthesis of olefin monomers is carried out according to the following method: based on the regioselective mechanism of olefin electrophilic addition orientation reaction (Markovnikov rule), a strong acid catalyst is used to catalyze the addition reaction of 1 molar equivalent of gallic acid carboxyl functional group and (1.01-1.05) molar equivalent of magnolol olefin functional group to generate olefin monomers. The specific experimental steps are: 2.7 g magnolol, 1.7 g gallic acid and 50 mL acetone are added to a four-necked bottle under nitrogen protection, and the mixture is stirred at room temperature until all the solvent is removed. Then, 10 mL of acetone solution containing 0.8 g p-toluenesulfonic acid is added dropwise to the four-necked bottle, and the mixture is heated to 60° C. and refluxed for reaction for 4 h. After cooling, the solvent is removed by rotary evaporation, and vacuum drying is performed to obtain an olefin monomer. The chemical structure of the olefin monomer is as follows:
[0024]
[0025] Among them, the strong acid catalyst is selected from sulfuric acid, p-toluenesulfonic acid, and fluoroboric acid; in this experimental example, p-toluenesulfonic acid is preferably used as the catalyst;
[0026] The organic modifier I is synthesized by an addition reaction between the alkenyl functional group of 1 molar equivalent of the alkenyl monomer and the Si-H bond of (1.01 to 1.05) molar equivalent of dimethylethoxysilane to generate the organic modifier I. The specific experimental steps are as follows: 2.1 g of the alkenyl monomer and 50 mL of toluene are added to a four-necked bottle under nitrogen protection, and stirred at room temperature until all dissolved. Then, 10 mL of a toluene solution containing 0.5 g of dimethylethoxysilane is added dropwise to the four-necked bottle, and 4 drops of a Custer catalyst are added dropwise under stirring. The temperature is raised to 80° C. and stirred for 24 hours. The organic modifier I is cooled to room temperature, the solvent is removed by rotary evaporation, and vacuum dried to obtain the organic modifier I. The chemical structure of the organic modifier I is as follows:
[0027]
[0028] The H NMR spectrum of organic modifier I is characterized as follows: 1H NMR (CDCl3, 400MHz) δ: 0.06 (s, 6H), 0.83-0.86 (t, 2H), 1.08-1.12 (t, 3H), 1.37-1.39 (d, 3H), 1.58-1.65 (m , 2H), 2.54-2.58(t, 2H), 2.95-2.97(d, 2H), 3.65-3.71(m, 2H), 5.07-5.16(m, 1H), 6.88-7.17(m, 8H, Ar-H).
[0029] Experimental Example 2:
[0030] The organic modifier II is prepared by a method of: based on the regioselective mechanism of the electrophilic addition orientation reaction of olefins, a strong acid catalyst catalyzes the addition reaction of the carboxyl functional group of (2.01-2.05) molar equivalents of gallic acid and the olefinic functional group of 1 molar equivalent of magnolol to generate an organic modifier II. The specific experimental steps refer to the preparation experiment of the olefinic monomer, and the only difference is that 3.4 g of gallic acid is used to replace 1.7 g of gallic acid to prepare the organic modifier II, and its chemical structure is:
[0031]
[0032] Among them, the strong acid catalyst is selected from sulfuric acid, p-toluenesulfonic acid, and fluoroboric acid; in this experimental example, p-toluenesulfonic acid is preferably used as the catalyst;
[0033] The hydrogen nuclear magnetic resonance spectrum of the organic modifier II is characterized by: 1H NMR (CDCl3, 400 MHz) δ: 1.38-1.39 (d, 6H), 2.95-2.97 (d, 4H), 5.09-5.18 (m, 2H), 6.88-7.12 (m, 10H, Ar-H).
[0034] Embodiment 1:
[0035] Preparation of organic molecule modified cellulose nanocrystals I: Based on the coupling reaction of silanol functional groups and hydroxyl functional groups, cellulose nanocrystals (cellulose nanocrystals have hydroxyl functional groups on their surfaces) are modified with organic modifier I to obtain organic molecule modified cellulose nanocrystals I. The specific experimental steps are as follows: 5 g of cellulose nanocrystals, 80 mL of anhydrous ethanol and 20 mL of deionized water are added to a beaker, ultrasonically treated for 10 min, heated to 40°C and stirred for 1 h, then 2 g of organic modifier I is added to the beaker, heated to 60°C and stirred for 8 h, centrifuged, and repeatedly centrifuged and washed with anhydrous ethanol and deionized water, and vacuum dried to obtain organic molecule modified cellulose nanocrystals I;
[0036] Among them, cellulose nanocrystals were purchased from Nanjing Tianlu Nanotechnology Co., Ltd., with specifications of: diameter 5-20nm, length 200-500nm.
[0037] Embodiment 2:
[0038] Preparation of organic molecule modified cellulose nanocrystal II: Based on the coupling reaction of silanol functional groups and hydroxyl functional groups and hydrogen bonding, cellulose nanocrystals are modified together with organic modifiers I and organic modifiers II to obtain organic molecule modified cellulose nanocrystal II. The specific experimental steps are different from those of organic molecule modified cellulose nanocrystal I only in that 2g of organic modifier I is replaced by 1g of organic modifier I and 1g of organic modifier II.
[0039] Embodiment 3:
[0040] Preparation of high barrier packaging material I: 10 g of polylactic acid resin and 1 g of organic molecule modified cellulose nanocrystal I are put into a twin-screw extruder for melting and extrusion, and then cut with a pelletizer to obtain polylactic acid resin particles of 1 to 5 mm, and then directly add the particles to a casting machine preheated to 150° C., cast into a film, and obtain a high barrier packaging material I with a thickness of 100 μm;
[0041] The process parameters of the twin-screw extruder were set as follows: the temperatures of zones 1-7 were 165°C, 170°C, 175°C, 180°C, 190°C, 180°C, and 170°C, respectively, and the rotation speed was 80 r / min;
[0042] The process parameters of the tape casting machine were set as follows: the temperatures of zones 1-7 were 165°C, 170°C, 180°C, 185°C, 190°C, 185°C, and 180°C, respectively, and the speed was 60 r / min;
[0043] Polylactic acid resin was purchased from Hubei Xinyuhong Biopharmaceutical Technology Co., Ltd. with the product number of 26100-51-6.
[0044] Embodiment 4:
[0045] High barrier packaging material II is prepared by using only organic molecule modified cellulose nanocrystal II to replace organic molecule modified cellulose nanocrystal I in high barrier packaging material I, while the rest of the components are the same as those of high barrier packaging material I.
[0046] Comparative Example:
[0047] Preparation of polylactic acid film: 10 g of polylactic acid resin was put into a twin-screw extruder for melting and extrusion, and then cut into polylactic acid resin particles of 1 to 5 mm by a pelletizer, and then directly added into a casting machine preheated to 150° C., cast into a film, and obtained a polylactic acid film with a thickness of 100 μm;
[0048] Among them, the process parameters of the polylactic acid resin, the twin-screw extruder and the casting machine are the same as those in Example 3.
[0049] Performance Testing:
[0050] 1. Barrier performance test:
[0051] (1) Water barrier performance: With reference to the test method of GB / T 1037-2021, the test was conducted using a TC-03 water vapor transmission rate tester. The specific test steps are as follows: first, 15 mL of water was added to a test cup (diameter 4.5 cm, height 3 cm) to keep the humidity at 90%. Then, a 6 cm round sample was fixed to the mouth of the cup with paraffin wax and placed in a glass desiccator (RH = 0%) with an ambient temperature of 25°C and anhydrous calcium chloride as a desiccant. The temperature was maintained for 72 h, and the water vapor transmission rate of the sample was recorded.
[0052] (2) Oxygen barrier performance: With reference to the GB / T 1038-2000 test method, the test was conducted using a VAC-V1 oxygen transmission rate tester. The specific test steps are as follows: a 9.7 cm round sample was placed in the tester at 25°C and 50% RH for 2 hours. The test area was 38.46 cm 2 , the test time is 8h, and the oxygen pressure is 0.5MPa;
[0053] 2. Mechanical properties test:
[0054] The mechanical properties of the samples were tested using a TA-XT plus texture analyzer. The A / TG tensile mode was selected and calibrated with a 5 kg weight. The initial distance of the gripper was set to 50 mm, the test speed was fixed to 1 mm / s, the sample size was 10 mm × 150 mm, and the tensile strength of the samples was recorded.
[0055] The above experimental results are shown in Table 1 below.
[0056] Table 1 Performance test results of high barrier packaging materials
[0057]
[0058] Through comprehensive analysis of the above experimental results, the following conclusions can be drawn:
[0059] Cellulose nanocrystals are introduced into the polylactic acid film after surface modification by organic modifier I and / or organic modifier II, and the packaging material prepared thereby significantly improves the barrier properties and also improves the mechanical properties;
[0060] Among them, the simultaneous modification of cellulose nanocrystals by organic modifiers I and II has the best effect on improving the barrier properties and mechanical properties of packaging materials.
Claims
1. A method for preparing a renewable high barrier packaging material, characterized in that: The steps include: Step 1: Surface modification of cellulose nanocrystals using an organic modifier to obtain organic molecule-modified cellulose nanocrystals; Wherein, the organic modifier is organic modifier I and / or organic modifier II; The chemical structural formula of the organic modifier I is: ； The chemical structural formula of the organic modifier II is: ； Step 2: 5-20 parts by weight of polylactic acid resin and 0.5-5 parts by weight of organic molecule modified cellulose nanocrystals are first blended, melted and extruded through a twin-screw extruder, then formed into particles with an average particle size of 1-5 mm using a pelletizer, and finally cast into a renewable high-barrier packaging material with a film thickness of 50-150 μm using a casting machine.
2. The method for preparing a renewable high barrier packaging material according to claim 1, characterized in that: The preparation method of the organic modifier I is: Based on the regioselective mechanism of olefin electrophilic addition orientation reaction, the carboxyl functional group of 1 molar equivalent of gallic acid and the alkenyl functional group of (1.01-1.05) molar equivalent of magnolol were catalyzed by a strong acid catalyst to generate alkenyl monomers. The organic modifier I is prepared by an addition reaction between the alkenyl functional group of 1 molar equivalent of the alkenyl monomer and the Si-H bond of (1.01-1.05) molar equivalent of dimethylethoxysilane.
3. The method for preparing a renewable high barrier packaging material according to claim 1, characterized in that: The preparation method of the organic modifier II is as follows: based on the regioselective mechanism of the electrophilic addition orientation reaction of olefins, a strong acid catalyst catalyzes the addition reaction of (2.01-2.05) molar equivalents of the carboxyl functional group of gallic acid and 1 molar equivalent of the alkenyl functional group of magnolol to prepare the organic modifier II.
4. The method for preparing a renewable high barrier packaging material according to claim 2 or 3, characterized in that: The strong acid catalyst is one of sulfuric acid, p-toluenesulfonic acid and fluoroboric acid.
5. The method for preparing a renewable high barrier packaging material according to claim 1, characterized in that: The mass ratio of the organic modifier to the cellulose nanocrystals in the organic molecule modified cellulose nanocrystals is 1:(1-5).
6. The method for preparing a renewable high barrier packaging material according to claim 5, characterized in that: The cellulose nanocrystals have a diameter of 5-20 nm and a length of 200-500 nm.
7. A renewable high barrier packaging material prepared by the method according to any one of claims 1 to 3, characterized in that: The water vapor permeability of the renewable high barrier packaging material is (2.0-4.0) g / (m 2 •24h), oxygen permeability is (1.5~3.5)cm 3 / (m 2 •24h•0.1MPa).
8. Use of a renewable high barrier packaging material prepared according to the method according to any one of claims 1 to 3 in the field of packaging.