Moisture absorption packaging composite film and preparation process thereof

Abstract

The invention relates to the technical field of moisture-proof and moisture-absorption packaging material research and development, and discloses a moisture-absorption packaging composite film and a preparation process thereof, and the preparation process comprises the following steps: preparing a tricarboxyl pyridyl s-triazine ligand; the preparation method comprises the following steps: carrying out coordination reaction on a tricarboxyl pyridyl s-triazine type ligand and metal ions to prepare an MOF type moisture absorbent; performing functional modification on low-density polyethylene resin by using an MOF type moisture absorbent to prepare moisture absorption type polyethylene; the moisture-absorbing packaging composite film is prepared by taking moisture-absorbing polyethylene as a raw material to generate the inner layer and adopting a nine-layer co-extrusion blow molding film forming process, and the composite film has excellent moisture-absorbing performance and moisture-proof performance and can be used in the packaging field.

Description

Technical Field

[0001] The invention relates to the technical field of research and development of moisture-proof and hygroscopic packaging materials, in particular to a hygroscopic packaging composite film and a preparation process thereof. Background Art

[0002] At present, most moisture-proof packaging on the market uses desiccant as a moisture absorber, which absorbs moisture inside the package to achieve the purpose of moisture-proof. However, this type of packaging has some problems. For example, the moisture absorber is not only easy to be missed or eaten by mistake during the packaging process, but also occupies a certain amount of packaging space and increases the weight of the product. In addition, the purchase of desiccant is required, which increases the packaging cost. The development and application of packaging materials with moisture-proof and moisture-absorbing functions have solved a series of problems.

[0003] Metal-organic frameworks (MOFs) are a type of porous crystalline material formed by self-assembly of metal ions and organic ligands through coordination bonds. They have the characteristics of large surface area, ultra-high porosity and more than 90% pore space, and have excellent hygroscopic activity. In the prior art, there have been reports on the use of MOF materials as desiccant in food preservation. Summary of the invention

[0004] The present invention independently develops a new type of MOF type desiccant, utilizes the MOF type desiccant to simultaneously improve the hygroscopicity and moisture-proof properties of the nine-layer co-extruded film, and prepares a hygroscopic packaging composite film, which can be used to manufacture packaging materials with moisture-proof and moisture-absorbing functions.

[0005] A preparation process of a hygroscopic packaging composite film comprises the following steps:

[0006] Step 1: preparing tricarboxyl pyridyl s-triazine type ligand;

[0007] Step 2: A MOF-type desiccant is prepared by a coordination reaction between a tricarboxylpyridyl-s-triazine ligand and a metal ion; wherein the metal ion is Ag. + , Cu 2+ , Ca 2+ 、Ti 2+ 、Zn 2+ One of;

[0008] Step 3: Use MOF-type hygroscopic agent to modify the function of low-density polyethylene resin to prepare hygroscopic polyethylene;

[0009] Step 5: Using hygroscopic polyethylene as a raw material to generate an inner layer, and adopting a nine-layer co-extrusion blow molding film-forming process to prepare a hygroscopic packaging composite film.

[0010] Preferably, the preparation method of the tricarboxyl pyridyl s-triazine type ligand is:

[0011] Step S2-1: using 5-(methylamino)nicotinate as a nucleophilic reagent, a secondary amine functional group of 5-(methylamino)nicotinate reacts with a chlorine functional group of cyanuric chloride to generate a triester-pyridyl-s-triazine monomer;

[0012] Step S2-2: In the presence of sodium hydroxide, the ester functional group of the triester pyridyl s-triazine type monomer undergoes a hydrolysis reaction to generate a tricarboxy pyridyl s-triazine type ligand.

[0013] Preferably, the preparation method of the hygroscopic packaging composite film is:

[0014] Step S4-1: The hygroscopic packaging composite film is set to be a nine-layer co-extruded film, and the film structure thereof is as follows:

[0015] First layer: low-density polyethylene resin layer, 10 to 25 parts by weight;

[0016] Second layer: low-density polyethylene resin layer, 3 to 10 parts by weight;

[0017] The third layer: low-density polyethylene resin layer, 5 to 15 parts by weight;

[0018] The fourth layer: maleic anhydride grafted low-density polyethylene resin layer, 3 to 8 parts by weight;

[0019] The fifth layer: ethylene-vinyl alcohol copolymer resin layer, 10 to 25 parts by weight;

[0020] The sixth layer: maleic anhydride grafted low-density polyethylene resin layer, 3 to 8 parts by weight;

[0021] Ninth layer: low-density polyethylene resin layer, 5 to 15 parts by weight;

[0022] The eighth layer: low-density polyethylene resin layer, 3 to 10 parts by weight;

[0023] Ninth layer: Hygroscopic polyethylene layer, 10 to 30 parts by weight

[0024] Step S4-2: The raw materials in step S4-1 are respectively put into a nine-layer co-extrusion film blowing unit, melt-extruded, and converged at the mouth of the nine-layer die head through their respective flow channels, and then blown into shape with the blowing ratio controlled at 2.5 to 2.9 to prepare a hygroscopic packaging composite film.

[0025] Preferably, the mass ratio of the MOF type hygroscopic agent to the low-density polyethylene resin in the hygroscopic polyethylene is 1:(3-15).

[0026] The thickness of the moisture-absorbing packaging composite film prepared according to the above process is 50 to 150 μm.

[0027] Preferably, the moisture absorption rate of the hygroscopic packaging composite film is (0.4-0.5)%, and the water vapor permeability is (1.0-1.5) g / (m 2 ·24h).

[0028] Beneficial effects:

[0029] The present invention designs and synthesizes a novel tricarboxyl pyridyl s-triazine ligand, prepares a MOF-type hygroscopic agent based on metal coordination, uses the MOF-type hygroscopic agent to perform functional modification on polyethylene resin to obtain hygroscopic polyethylene, uses the hygroscopic polyethylene as a raw material to generate an inner layer, and adopts a nine-layer co-extrusion blow molding film-forming process to prepare a hygroscopic packaging composite film;

[0030] Through experiments, it is found that the new composite film developed by the present invention has achieved significantly improved technical effects in terms of moisture absorption and moisture resistance, and can be used in the packaging field. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is the chemical structural formula of triester pyridyl s-triazine type monomer;

[0032] Figure 2 is the chemical structural formula of tricarboxylpyridyl-s-triazine type ligand;

[0033] Figure 3 These are the performance test results of the hygroscopic packaging composite film. DETAILED DESCRIPTION

[0034] Embodiment 1:

[0035] The MOF type desiccant is prepared, and the preparation steps are as follows:

[0036] Step 1: preparing tricarboxyl pyridyl s-triazine type ligand;

[0037] Step 2: preparing a MOF-type moisture absorbent by a coordination reaction between a tricarboxylpyridyl-s-triazine-type ligand and a metal ion;

[0038] The metal ion is Ag + , Cu 2+ , Ca 2+ 、Ti 2+ 、Zn 2+ One of them; this embodiment chooses to use Cu 2+ ;

[0039] The specific experimental steps for preparing MOF-type moisture absorbent are as follows:

[0040] (1) Preparation of tricarboxyl pyridyl s-triazine type ligand, the preparation process is as follows:

[0041] Preparation of triester pyridyl s-triazine monomer: 5-(methylamino)nicotinate methyl ester is used as a nucleophilic reagent, and the secondary amine functional group of 5-(methylamino)nicotinate reacts with the chlorine functional group of cyanuric chloride to generate a triester pyridyl s-triazine monomer, whose chemical structure is as follows: Figure 1 As shown, the specific experimental steps are as follows: 1.8g of cyanuric chloride, 0.7g of anhydrous potassium carbonate and 5.0g of 5-(methylamino)nicotinate methyl ester are added to a three-necked flask in sequence, and the mixture is allowed to stand in an ice-water bath for 30 minutes under the protection of nitrogen. Then, 40mL of anhydrous tetrahydrofuran and 20mL of anhydrous 1,4-dioxane are injected into the three-necked flask in sequence, and the mixture is stirred and reacted for 2 hours under the ice-water bath condition. The ice-water bath is removed, and the mixture is stirred and reacted at room temperature for 4 hours. The mixture is heated to 100°C and refluxed for 4 hours. The solvent is removed by reduced pressure distillation, and the mixture is washed with ethanol and deionized water in sequence until it is neutral. The mixture is dried in vacuo to obtain a triester-pyridyl-s-triazine monomer.

[0042] Preparation of tricarboxylpyridyl-s-triazine ligand: In the presence of sodium hydroxide, the ester functional group of the triesterpyridyl-s-triazine monomer undergoes a hydrolysis reaction to generate a tricarboxylpyridyl-s-triazine ligand, the chemical structure of which is as follows: Figure 2 As shown, the specific experimental steps are as follows: 2.9 g of triester pyridyl-s-triazine monomer, 2.0 g of sodium hydroxide, 10 mL of 1,4-dioxane and 40 mL of deionized water are added to a three-necked flask, the temperature is raised to 70° C. and stirred for reaction for 2 h, concentrated hydrochloric acid is used to adjust the solution pH to 2, the solution is cooled to room temperature, the solution is washed with deionized water, and vacuum dried to obtain a tricarboxyl pyridyl-s-triazine ligand;

[0043] The nuclear magnetic resonance hydrogen spectrum of the tricarboxyl pyridyl triazine type ligand is characterized by: 1 H NMR (CDCl3, 400MHz) δ: 3.79 (s, 9H), 7.83 (s, 3H), 8.41 (s, 3H), 8.77 (s, 3H); the active hydrogen in the carboxyl functional group of the tricarboxylpyridyl-s-triazine type ligand has no peak in the CDCl3 solvent;

[0044] (2) Preparation of MOF type desiccant: 5.3 g of tricarboxypyridyl-s-triazine ligand and 4.5 g of copper nitrate were dissolved in 100 mL of N,N-dimethylformamide, and the mixture was sealed in a Teflon-lined stainless steel autoclave after ultrasonic treatment for 30 min. The mixture was heated to 100 °C and kept for 48 h. The mixture was cooled to room temperature and centrifuged at 8000 r / min for 15 min. The mixture was redispersed with N,N-dimethylformamide, centrifuged and dried to obtain the MOF type desiccant.

[0045] Embodiment 2:

[0046] Preparation of hygroscopic polyethylene: 10 g of low-density polyethylene resin and 2 g of MOF-type hygroscopic agent are added into a twin-screw extruder, and the mixture is blended, melted, extruded and pelletized by the twin-screw extruder to obtain hygroscopic polyethylene;

[0047] The process parameters of the twin-screw extruder were set as follows: the temperatures of zones 1-3 were 120°C, 150°C, and 180°C, respectively, and the rotation speed was 40 r / min;

[0048] The low-density polyethylene resin was purchased from CNOOC Shell Petrochemical Co., Ltd., and its specifications are: 2420H, Mn-180000, MFR 2.0-2.5 g / 10 min.

[0049] Embodiment 3:

[0050] (1) Preparing a hygroscopic packaging composite film comprises the following steps:

[0051] Step 1: The hygroscopic packaging composite film is set to be a nine-layer co-extruded film, and its film structure is as follows:

[0052] First layer: low-density polyethylene resin layer, 20 parts by weight;

[0053] Second layer: low-density polyethylene resin layer, 5 parts by weight;

[0054] The third layer: low-density polyethylene resin layer, 10 parts by weight;

[0055] The fourth layer: maleic anhydride grafted low-density polyethylene resin layer, 5 parts by weight;

[0056] Fifth layer: ethylene-vinyl alcohol copolymer resin layer, 20 parts by weight;

[0057] The sixth layer: maleic anhydride grafted low-density polyethylene resin layer, 5 parts by weight;

[0058] Ninth layer: low-density polyethylene resin layer, 10 parts by weight;

[0059] The eighth layer: low-density polyethylene resin layer, 5 parts by weight;

[0060] Ninth layer: hygroscopic polyethylene layer, 20 parts by weight;

[0061] Step 2: Put the raw materials in step 1 into a nine-layer co-extrusion film blowing unit respectively, melt and extrude, merge at the mouth of the nine-layer die through their respective flow channels, and then undergo inflation molding with the inflation ratio controlled at 2.7, cool and wind up to obtain a hygroscopic packaging composite film with a thickness of 80 μm;

[0062] The process parameters of the screw extruder corresponding to the hygroscopic polyethylene layer and the low-density polyethylene resin layer are set as follows: the temperatures of zones 1-3 are 120°C, 150°C, and 180°C, respectively, the flow channel temperature is 175°C, and the rotation speed is 30r / min;

[0063] The process parameters of the screw extruder corresponding to the maleic anhydride grafted polyethylene resin layer were set as follows: the temperatures of zones 1-3 were 125°C, 150°C, and 165°C, respectively, the flow channel temperature was 160°C, and the rotation speed was 15 r / min;

[0064] The process parameters of the screw extruder corresponding to the ethylene-vinyl alcohol copolymer resin layer are set as follows: the temperatures of zones 1-3 are 180°C, 200°C, and 210°C, respectively, the flow channel temperature is 205°C, and the rotation speed is 40r / min.

[0065] Among them, ethylene-vinyl alcohol copolymer resin was purchased from Dongguan Kaixili Plastic Raw Materials Co., Ltd., with the specifications of E105B, Mn~10000, and ethylene content of 44%; maleic anhydride grafted low-density polyethylene resin was purchased from Dongguan Taotao Plastic Raw Materials Co., Ltd., with the specifications of 4288, Mn~130000, and grafting rate of 4.5%.

[0066] (2) Preparation of composite film: Referring to the preparation steps and experimental conditions of the hygroscopic packaging composite film, the difference between the preparation steps and experimental conditions of the hygroscopic packaging composite film is that low-density polyethylene resin is used to replace the hygroscopic polyethylene to prepare the composite film, which is used as a comparative example.

[0067] Performance Testing:

[0068] (1) Hygroscopic performance test: a 60 mm × 60 mm (length × width) sample was dried in an oven at 55°C for 4 h, then taken out and weighed, which was recorded as the initial weight. The dried sample was completely immersed in distilled water for 24 h, taken out with tweezers and the moisture on the surface of the sample was absorbed with absorbent filter paper and weighed, which was recorded as the weight after moisture absorption. The moisture absorption rate of the sample was calculated as follows:

[0069] Moisture absorption rate (%) = (weight of sample after moisture absorption - initial weight of sample) / initial weight of sample × 100%;

[0070] (2) Moisture resistance test: According to GB / T 1037-2021 "Determination of water vapor transmission properties of plastic films and sheets - Cup weight gain and weight loss method", the water vapor transmission rate of the sample is tested. A 30 cm round sample is placed in a glass desiccator at an ambient temperature of 25°C and anhydrous calcium chloride is used as a desiccant for 72 hours. After that, the moisture resistance is tested using a W3 / 060 water vapor transmission rate tester;

[0071] (3) Mechanical properties test: The tensile strength of the samples was tested in accordance with GB / T 13022-1991 “Test method for tensile properties of plastic films”. The 30 mm × 5 mm samples were fixed on an Instron 5565 universal tensile testing machine and the tensile test was performed at a tensile rate of 5 mm / min. The longitudinal and transverse tensile strengths were recorded respectively.

[0072] The above experimental results are shown in Table 1 and Figure 1 .

[0073] Table 1 Performance test results of hygroscopic packaging composite film

[0074]

[0075] By comprehensively analyzing the above experimental results, the following conclusions can be drawn:

[0076] The novel composite membrane developed by the present invention achieves significantly improved technical effects in terms of moisture absorption and moisture resistance.

Claims

1. A process for preparing a hygroscopic packaging composite film, characterized in that: The following steps are involved: Step 1: Prepare a tricarboxylpyridyl-s-triazine ligand, the chemical structure of which is: ； Step 2: A MOF-type desiccant is prepared by a coordination reaction between a tricarboxylpyridyl-s-triazine ligand and a metal ion; wherein the metal ion is Ag. + , Cu 2+ , Ca 2+ 、Ti 2+ 、Zn 2+ One of; Step 3: Use MOF-type hygroscopic agent to modify the function of low-density polyethylene resin to prepare hygroscopic polyethylene; Step 5: Using hygroscopic polyethylene as a raw material to generate an inner layer, and adopting a nine-layer co-extrusion blow molding film-forming process to prepare a hygroscopic packaging composite film.

2. The process for preparing a hygroscopic packaging composite film according to claim 1, characterized in that: The preparation method of the tricarboxyl pyridyl s-triazine type ligand is as follows: Step S2-1: using 5-(methylamino)nicotinate as a nucleophilic reagent, a secondary amine functional group of 5-(methylamino)nicotinate reacts with a chlorine functional group of cyanuric chloride to generate a triester-pyridyl-s-triazine monomer; Step S2-2: In the presence of sodium hydroxide, the ester functional group of the triester pyridyl s-triazine type monomer undergoes a hydrolysis reaction to generate a tricarboxy pyridyl s-triazine type ligand.

3. The process for preparing a hygroscopic packaging composite film according to claim 1, characterized in that: The preparation method of the hygroscopic packaging composite film is: Step S4-1: The hygroscopic packaging composite film is set to be a nine-layer co-extruded film, and the film structure thereof is as follows: First layer: low-density polyethylene resin layer, 10-25 parts by weight; Second layer: low-density polyethylene resin layer, 3-10 parts by weight; The third layer: low-density polyethylene resin layer, 5-15 parts by weight; The fourth layer: maleic anhydride grafted low-density polyethylene resin layer, 3-8 parts by weight; The fifth layer: ethylene-vinyl alcohol copolymer resin layer, 10-25 parts by weight; The sixth layer: maleic anhydride grafted low-density polyethylene resin layer, 3-8 parts by weight; Ninth layer: low-density polyethylene resin layer, 5-15 parts by weight; The eighth layer: low-density polyethylene resin layer, 3-10 parts by weight; Ninth layer: Hygroscopic polyethylene layer, 10-30 parts by weight Step S4-2: The raw materials in step S4-1 are respectively put into a nine-layer co-extrusion film blowing unit, melt-extruded, and converged at the mouth of the nine-layer die head through their respective flow channels, and then blown into shape with the blowing ratio controlled at 2.5~2.9 to prepare a hygroscopic packaging composite film.

4. The process for preparing a hygroscopic packaging composite film according to claim 3, characterized in that: The mass ratio of the MOF type hygroscopic agent to the low-density polyethylene resin in the hygroscopic polyethylene is 1:(3-15).

5. A hygroscopic packaging composite film prepared by the process according to any one of claims 1 to 4, characterized in that: The thickness of the hygroscopic packaging composite film is 50-150 μm.

6. A hygroscopic packaging composite film according to claim 5, characterized in that: The moisture absorption rate of the hygroscopic packaging composite film is (0.4-0.5)%, and the water vapor permeability is (1.0-1.5) g / (m 2 •24h).

7. A hygroscopic packaging composite film prepared by the process according to any one of claims 1 to 4, characterized in that: Application of the hygroscopic packaging composite film in the packaging field.

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