High-barrier moisture-absorbing packaging film and preparation process thereof

Abstract

The invention relates to the technical field of multifunctional packaging materials, in particular to a high-barrier moisture-absorbing packaging film and a preparation process thereof.The preparation process comprises the steps that a quaternary ammonium salt intercalator containing phenolic hydroxyl functional groups is prepared; the preparation method comprises the following steps: carrying out intercalation modification treatment on Na-montmorillonite by using a quaternary ammonium salt intercalator to prepare intercalation modified montmorillonite; the intercalation modified montmorillonite and the polyvinyl alcohol resin are compounded through hydrogen-bond interaction between a phenolic hydroxyl functional group contained on the surface of the intercalation modified montmorillonite and a hydroxyl functional group of the polyvinyl alcohol resin, and the organic-inorganic composite type barrier moisture absorption agent is prepared. The high-barrier moisture-absorbing packaging film is prepared by adding the organic-inorganic composite barrier moisture-absorbing agent into a polypropylene film and adopting a three-layer co-extrusion blow molding film forming process, and the film has excellent barrier performance and moisture-absorbing performance and can be used for manufacturing barrier moisture-absorbing packaging bags.

Description

Technical Field

[0001] The present invention relates to the technical field of multifunctional packaging materials, and particularly to a high-barrier moisture-absorbing packaging film and a preparation process thereof. Background Art

[0002] During storage and transportation, products are easily damaged due to moisture absorption. High-barrier moisture-absorbing packaging materials can not only prevent external moisture from entering the inner packaging of products, but also absorb the moisture inside the packaging, keeping the products in a dry state, thereby extending the shelf life and quality.

[0003] Moisture-absorbing materials can be divided into inorganic moisture-absorbing materials (silica gel, charcoal, molecular sieve, calcium chloride and montmorillonite) and organic moisture-absorbing materials (polyvinyl alcohol, polypropionic acid, starch and cellulose). Among them, inorganic moisture-absorbing materials have disadvantages such as limited moisture absorption capacity, large dosage and low moisture absorption efficiency, while organic moisture-absorbing materials have high costs and unstable moisture absorption performance. Therefore, organic-inorganic composite moisture-absorbing agents have gradually become the development trend of the moisture-absorbing packaging industry. Summary of the Invention

[0004] The present invention independently develops a new type of organic-inorganic composite barrier moisture-absorbing agent, which is added to a polypropylene film as a modifier to achieve the technical effect of improving the barrier performance and moisture absorption performance of the polypropylene film. The high-barrier moisture-absorbing packaging film prepared therefrom can be used to manufacture barrier moisture-absorbing packaging bags.

[0005] A preparation process of a high-barrier moisture-absorbing packaging film includes the following steps:

[0006] Step 1: Prepare a quaternary ammonium salt intercalating agent containing phenolic hydroxyl functional groups;

[0007] Step 2: Perform an intercalation modification treatment on sodium montmorillonite with the quaternary ammonium salt intercalating agent. After the ammonium cation of the quaternary ammonium salt intercalating agent undergoes an ion exchange reaction with the interlayer sodium cation of sodium montmorillonite, it is adsorbed on the surface of montmorillonite nanosheets through electrostatic interaction to prepare an intercalation-modified montmorillonite;

[0008] Step 3: Composite the intercalation-modified montmorillonite with polyvinyl alcohol resin through the hydrogen bond action between the phenolic hydroxyl functional groups on the surface of the intercalation-modified montmorillonite and the hydroxyl functional groups of the polyvinyl alcohol resin to prepare an organic-inorganic composite barrier moisture-absorbing agent;

[0009] Step 4: Add the organic-inorganic composite barrier moisture-absorbing agent to a polypropylene film and use a three-layer co-extrusion blow molding process to prepare a high-barrier moisture-absorbing packaging film.

[0010] Preferably, the preparation method of the quaternary ammonium salt intercalating agent containing phenolic hydroxyl functional groups is:

[0011] Step S2-1: Based on the Mannich reaction mechanism, a condensation reaction occurs between acetylsyringone containing α-H, syringaldehyde, and dimethylamine to generate a tertiary amine monomer containing a phenolic hydroxyl functional group.

[0012] Step S2-2: Based on the nucleophilic substitution mechanism, a quaternization reaction occurs between the tertiary amine group of the tertiary amine monomer containing a phenolic hydroxyl functional group and the bromo functional group of 1-bromo-6-(trimethylammonium)hexyl bromide to prepare a quaternary ammonium salt intercalating agent containing a phenolic hydroxyl functional group.

[0013] Preferably, the preparation method of the high-barrier moisture-absorbing packaging film is as follows:

[0014] Step S3-1: Set the high-barrier moisture-absorbing packaging film as a three-layer coextruded film, and its film structure is as follows in sequence:

[0015] The first layer: a polypropylene resin layer prepared from 100 wt% polypropylene resin, 20 - 40 parts by weight;

[0016] The second layer: a barrier moisture-absorbing layer prepared from a raw material composed of 60 - 80 wt% polypropylene resin, 20 - 30 wt% organic-inorganic composite barrier moisture-absorbing agent, and 3 - 10 wt% maleic anhydride-grafted polypropylene resin, 30 - 50 parts by weight;

[0017] The third layer: a polypropylene resin layer prepared from 100 wt% polypropylene resin, 20 - 40 parts by weight

[0018] Step S3-2: Respectively put the raw materials in Step S3-1 into the hoppers of three screw extruders of a three-layer coextruded film blowing machine. After stirring and mixing, the molten resins converge at the head through a diverter, and are extruded, blown, cooled, and wound through a die head to obtain a high-barrier moisture-absorbing packaging film.

[0019] Preferably, the mass ratio of the quaternary ammonium salt intercalating agent, sodium-based montmorillonite, and polyvinyl alcohol resin in the organic-inorganic composite barrier moisture-absorbing agent is 1:(0.5 - 5):(5 - 15).

[0020] A high-barrier moisture-absorbing packaging film prepared according to the above process has a thickness of 50 - 150 μm.

[0021] Preferably, the oxygen transmission rate of the high-barrier moisture-absorbing packaging film is (1.0 - 1.5) cm 3 / (m 2 ·24h·0.1MPa), the water vapor transmission rate is (1.0 - 2.0) g / (m 2 ·24h), and the moisture absorption rate is 5 - 10%.

[0022] Beneficial effects:

[0023] The present invention designs and synthesizes a quaternary ammonium salt intercalating agent containing phenolic hydroxyl functional groups. This quaternary ammonium salt intercalating agent is used to intercalate and modify sodium montmorillonite through electrostatic interaction, and is compounded with polyvinyl alcohol based on hydrogen bond interaction to prepare a novel organic-inorganic composite barrier and moisture absorbent. The organic-inorganic composite barrier and moisture absorbent is added as a modifier to a polypropylene coextrusion film, and a high-barrier moisture absorbent packaging film is prepared by a three-layer coextrusion blow molding process.

[0024] Through experiments, it is found that compared with the polypropylene film, the high-barrier moisture absorbent packaging film prepared by the present invention can significantly reduce the oxygen transmission rate and water vapor transmission rate, showing excellent barrier performance.

[0025] The high-barrier moisture absorbent packaging film prepared by the present invention has achieved a significant improvement in the technical effect of moisture absorption performance, and also has a slight improvement in mechanical properties. Brief Description of the Drawings

[0026] Figure 1 It is the synthesis route of the quaternary ammonium salt intercalating agent containing phenolic hydroxyl functional groups.

[0027] Figure 2 It is the performance test result of the high-barrier moisture absorbent packaging film. Detailed Embodiments

[0028] The present invention combines inorganic montmorillonite with excellent barrier performance and organic polyvinyl alcohol with excellent moisture absorption performance through a newly synthesized quaternary ammonium salt intercalating agent to prepare an organic-inorganic composite barrier and moisture absorbent, which is used to improve the barrier and moisture absorption capabilities of polypropylene films.

[0029] Example 1:

[0030] Prepare an organic-inorganic composite barrier and moisture absorbent, and its preparation steps are as follows:

[0031] Step 1: Prepare a quaternary ammonium salt intercalating agent containing phenolic hydroxyl functional groups;

[0032] Step 2: Use the quaternary ammonium salt intercalating agent to intercalate and modify sodium montmorillonite. After the ammonium cation of the quaternary ammonium salt intercalating agent undergoes an ion exchange reaction with the interlayer sodium cation of sodium montmorillonite, it is adsorbed on the surface of montmorillonite nanosheets through electrostatic interaction to prepare an intercalation-modified montmorillonite;

[0033] Step 3: Through the hydrogen bond interaction between the phenolic hydroxyl functional groups on the surface of the intercalation-modified montmorillonite and the hydroxyl functional groups of the polyvinyl alcohol resin, the intercalation-modified montmorillonite and the polyvinyl alcohol resin are compounded to prepare an organic-inorganic composite barrier and moisture absorbent;

[0034] The specific experimental steps for preparing the organic-inorganic composite barrier and moisture absorbent are as follows:

[0035] (1) Prepare a quaternary ammonium salt intercalating agent containing phenolic hydroxyl functional groups, such as Figure 1 shown. The preparation process is as follows:

[0036] Prepare a tertiary amine monomer containing phenolic hydroxyl functional groups: Based on the Mannich reaction mechanism, through the condensation reaction of acetylsyringone containing α-H, syringaldehyde and dimethylamine, a tertiary amine monomer containing phenolic hydroxyl functional groups is generated. The specific experimental steps are as follows: Add 2.0 g of acetylsyringone, 1.8 g of syringaldehyde, 0.5 g of dimethylamine and 50 mL of anhydrous ethanol into a three-necked flask. Under the protection of nitrogen and mechanical stirring, slowly add 5 drops of concentrated hydrochloric acid to the three-necked flask, heat up to 85 °C and reflux for 4 h, cool to room temperature, rotary evaporate to remove the solvent, filter by suction and dry to obtain a tertiary amine monomer containing phenolic hydroxyl functional groups;

[0037] Prepare a quaternary ammonium salt intercalating agent containing phenolic hydroxyl functional groups: Based on the nucleophilic substitution mechanism, through the quaternization reaction of the tertiary amine group of the tertiary amine monomer containing phenolic hydroxyl functional groups with the bromine functional group of 1-bromo-6-(trimethylammonium)hexyl bromide, a quaternary ammonium salt intercalating agent containing phenolic hydroxyl functional groups is generated. The specific experimental steps are as follows: Add 2.0 g of the tertiary amine monomer containing phenolic hydroxyl functional groups and 20 mL of N,N-dimethylformamide into a three-necked flask. Under the protection of nitrogen and mechanical stirring, stir at room temperature until completely dissolved. Then add 10 mL of an N,N-dimethylformamide solution containing 1.5 g of 1-bromo-6-(trimethylammonium)hexyl bromide to the three-necked flask, heat up to 40 °C and stir for 10 h, rotary evaporate to remove the solvent, and vacuum dry to obtain a quaternary ammonium salt intercalating agent containing phenolic hydroxyl functional groups;

[0038] 1H NMR characterization of the quaternary ammonium salt intercalating agent containing phenolic hydroxyl functional groups is as follows: 1 H NMR(CDCl3, 400 MHz)δ: 1.44 - 1.78(m, 8H), 3.27 - 3.29(d, 2H), 3.35(s, 6H), 3.43(s, 9H), 3.48 - 3.52(t, 2H), 3.59 - 3.63(t, 2H), 3.81(s, 6H), 3.91(s, 6H), 5.38 - 5.42(t, 1H), 6.67(s, 2H), 7.16(s, 2H).

[0039] (2) Prepare intercalation-modified montmorillonite: Add 3 g of sodium montmorillonite nanosheets and 100 mL of ethanol into a three-necked flask, ultrasonicate for 30 min, heat up to 70 °C and stir for 2 h. Then add 20 mL of a quaternary ammonium salt intercalating agent solution (prepared from 2 g of the quaternary ammonium salt intercalating agent and 20 mL of ethanol) to the three-necked flask, maintain at 70 °C and stir for 4 h, filter while it is hot, wash with ethanol until no precipitate is detected by silver nitrate solution, vacuum dry and grind to obtain intercalation-modified montmorillonite;

[0040] Among them, the sodium-based montmorillonite nanosheets were purchased from Jiangsu Xianfeng Nano Materials Technology Co., Ltd., and its product number is 103635;

[0041] (3) Preparation of organic-inorganic composite barrier moisture absorbent: Add 10 g of polyvinyl alcohol resin and 100 mL of deionized water into a three-necked flask, heat up to 90 °C and stir to dissolve for 2 h, cool to 60 °C, add 10 mL of deionized water solution containing 2.5 g of intercalation-modified montmorillonite to the three-necked flask, keep stirring at 60 °C for 10 h, mix evenly, and dry in vacuum to obtain the organic-inorganic composite barrier moisture absorbent;

[0042] Among them, the polyvinyl alcohol resin was purchased from Dongguan Yingxiang Plastic Raw Materials Co., Ltd., and its model is 22-88.

[0043] Example 2:

[0044] Preparation of a high-barrier moisture-absorbing packaging film, including the following steps:

[0045] Step 1: Set the high-barrier moisture-absorbing packaging film as a three-layer coextruded film, and its film structure is in turn:

[0046] The first layer: a polypropylene resin layer prepared from 100 wt% polypropylene resin, 30 parts by weight;

[0047] The second layer: a barrier moisture-absorbing layer prepared from a raw material composed of 70 wt% polypropylene resin, 25 wt% organic-inorganic composite barrier moisture absorbent and 5 wt% maleic anhydride grafted polypropylene resin, 40 parts by weight;

[0048] The third layer: a polypropylene resin layer prepared from 100 wt% polypropylene resin, 30 parts by weight;

[0049] Step 2: Put the raw materials in Step 1 into the hoppers of the three screw extruders of a three-layer coextruded film blowing machine respectively. After stirring and mixing, the molten resin converges at the head through a diverter, and is extruded and blown, cooled and wound through a die head to obtain a high-barrier moisture-absorbing packaging film with a thickness of 100 μm;

[0050] Among them, the process parameters of the screw extruder corresponding to the polypropylene resin layer are set as follows: the temperatures of zones 1-3 are 120 °C, 140 °C, 165 °C respectively, the runner temperature is 160 °C, and the rotation speed is 30 r / min;

[0051] The process parameters of the screw extruder corresponding to the barrier moisture-absorbing layer are set as follows: the temperatures of zones 1-3 are 140 °C, 170 °C, 190 °C respectively, the runner temperature is 185 °C, and the rotation speed is 40 r / min;

[0052] Among them, polypropylene resin was purchased from Shanghai Qiaowei Chemical Technology Co., Ltd. with the brand name HJ4012; maleic anhydride grafted polypropylene resin was purchased from Coais Chemical Co., Ltd. with the brand name B1.

[0053] Comparative Example:

[0054] Preparation of polypropylene film: only polypropylene resin is used to replace the organic-inorganic composite barrier moisture absorbing agent in the high barrier moisture absorbing packaging film, and the other parts are the same, so as to prepare the polypropylene film.

[0055] Performance Testing:

[0056] 1. Barrier performance test:

[0057] (1) Use a Y110 oxygen permeability tester to test the oxygen barrier properties of the sample in accordance with GB / T 1038-2000 and record the oxygen permeability of the sample;

[0058] (2) Use TC-03 water vapor transmission meter to test the water barrier properties of the sample in accordance with GB / T 1037-2021 and record the water vapor transmission rate of the sample;

[0059] 2. Moisture absorption performance test:

[0060] A 60 mm × 60 mm (length × width) sample was dried in an oven at 55°C for 4 hours and then taken out and weighed, which was recorded as the initial weight. The dried sample was completely immersed in distilled water for 24 hours, and then 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:

[0061] Moisture absorption rate (%) = (weight of sample after moisture absorption - initial weight of sample) / initial weight of sample × 100%;

[0062] 3. Mechanical properties:

[0063] According to GB / T 13022-1991 "Test Method for Tensile Properties of Plastic Films", the tensile strength of the samples was tested. 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.

[0064] The above experimental results are shown in Table 1 and Figure 2 .

[0065] Table 2 Performance test results of high barrier moisture absorbing packaging film

[0066]

[0067] By comprehensively analyzing the above experimental results, the following conclusions can be drawn:

[0068] Conclusion 1: Compared with the polypropylene film, the high-barrier moisture-absorbing packaging film prepared by the present invention can significantly reduce the oxygen transmission rate and water vapor transmission rate, showing excellent barrier properties;

[0069] Conclusion 2: In terms of moisture absorption performance, the high-barrier moisture-absorbing packaging film prepared by the present invention achieves a significantly improved technical effect, and also has a slight improvement in mechanical properties.

Claims

1. A process for preparing a high barrier moisture absorbing packaging film, characterized in that: The following steps are involved: Step 1: Prepare a quaternary ammonium salt intercalant containing a phenolic hydroxyl functional group, the chemical structure of which is: Step 2: using a quaternary ammonium salt intercalation agent to perform intercalation modification on the sodium-based montmorillonite, wherein the ammonium cations of the quaternary ammonium salt intercalation agent undergo an ion exchange reaction with the interlayer sodium cations of the sodium-based montmorillonite and then adsorb on the surface of the montmorillonite nanosheets through electrostatic action, thereby preparing an intercalation-modified montmorillonite; Step 3: Compounding the intercalated modified montmorillonite with the polyvinyl alcohol resin by hydrogen bonding the phenolic hydroxyl functional groups on the surface of the intercalated modified montmorillonite with the hydroxyl functional groups of the polyvinyl alcohol resin to prepare an organic-inorganic composite barrier moisture absorbent; Step 4: adding an organic-inorganic composite barrier moisture absorbing agent to a polypropylene film, and adopting a three-layer co-extrusion blow molding film forming process to prepare a high barrier moisture absorbing packaging film.

2. The process for preparing a high barrier moisture absorbing packaging film according to claim 1, characterized in that: The preparation method of the quaternary ammonium salt intercalant containing a phenolic hydroxyl functional group is as follows: Step S2-1: Based on the Mannich reaction mechanism, acetosyringone containing α-H undergoes a condensation reaction with syringaldehyde and dimethylamine to generate a tertiary amine monomer containing a phenolic hydroxyl functional group; Step S2-2: Based on the nucleophilic substitution mechanism, the tertiary amine group of the tertiary amine monomer containing a phenolic hydroxyl functional group undergoes a quaternization reaction with the bromine functional group of 1-bromo-6-(trimethylammonium)hexyl bromide to prepare a quaternary ammonium salt intercalant containing a phenolic hydroxyl functional group.

3. The process for preparing a high barrier moisture absorbing packaging film according to claim 1, characterized in that: The preparation method of the high barrier moisture absorbing packaging film is as follows: Step S3-1: The high barrier moisture absorption packaging film is set to be a three-layer co-extruded film, and the film structure thereof is as follows: The first layer: a polypropylene resin layer prepared from 100wt% polypropylene resin as raw material, 20-40 parts by weight; The second layer: 30-50 parts by weight of a barrier moisture absorbing layer made of 60-80wt% polypropylene resin, 20-30wt% organic-inorganic composite barrier moisture absorbing agent and 3-10wt% maleic anhydride grafted polypropylene resin; The third layer: a polypropylene resin layer prepared with 100 wt% polypropylene resin as raw material, 20-40 parts by weight Step S3-2: The raw materials in step S3-1 are respectively put into the hoppers of the three screw extruders of the three-layer co-extrusion film blow molding unit. After stirring and mixing, the molten resin is converged at the head of the machine through a diverter, extruded and blown through a die head, cooled, and wound to obtain a high barrier moisture-absorbing packaging film.

4. The process for preparing a high barrier moisture absorbing packaging film according to claim 1, characterized in that: The mass ratio of the quaternary ammonium salt intercalation agent, the sodium-based montmorillonite and the polyvinyl alcohol resin in the organic-inorganic composite barrier moisture absorber is 1: (0.5-5): (5-15).

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

6. The high barrier moisture absorbing packaging film according to claim 5, characterized in that: The oxygen permeability of the high barrier moisture absorbing packaging film is (1.0-1.5) cm 3 / (m 2 ·24h·0.1MPa), water vapor transmission rate is (1.0-2.0)g / (m 2 ·24h), the moisture absorption rate is 5-10%.

7. Use of a high barrier moisture absorbing packaging film prepared according to the process according to any one of claims 1 to 4 in the field of packaging.

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