A high barrier moisture-absorbing packaging film and its preparation process

Abstract

This invention relates to the field of multifunctional packaging materials technology, specifically to a high-barrier moisture-absorbing packaging film and its preparation process, comprising: preparing a quaternary ammonium salt intercalating agent containing phenolic hydroxyl functional groups; using the quaternary ammonium salt intercalating agent to perform intercalation modification treatment on sodium-based montmorillonite to prepare intercalated modified montmorillonite; through hydrogen bonding between the phenolic hydroxyl functional groups on the surface of the intercalated modified montmorillonite and the hydroxyl functional groups of polyvinyl alcohol resin, combining the intercalated modified montmorillonite with polyvinyl alcohol resin to prepare an organic-inorganic composite barrier moisture absorber; adding the organic-inorganic composite barrier moisture absorber to a polypropylene film, and using a three-layer co-extrusion blow molding process to prepare a high-barrier moisture-absorbing packaging film. This film has excellent barrier and moisture absorption properties and can be used to manufacture barrier moisture-absorbing packaging bags.

Description

Technical Field

[0001] This invention relates to the field of multifunctional packaging materials technology, specifically to a high-barrier moisture-absorbing packaging film and its preparation process. Background Technology

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

[0003] Moisture-absorbing materials can be divided into inorganic moisture-absorbing materials (silica gel, charcoal, molecular sieves, calcium chloride, and montmorillonite) and organic moisture-absorbing materials (polyvinyl alcohol, polypropylene 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 are expensive and have unstable moisture absorption performance. Therefore, organic-inorganic composite moisture absorbers are gradually becoming the trend in the moisture-absorbing packaging industry. Summary of the Invention

[0004] This invention independently developed a novel organic-inorganic composite barrier moisture absorber, which is added to polypropylene film as a modifier to improve the barrier and moisture absorption properties of polypropylene film. The high barrier moisture-absorbing packaging film prepared in this way can be used to manufacture barrier moisture-absorbing packaging bags.

[0005] A process for preparing 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: Sodium-based montmorillonite is modified by intercalation using a 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-based montmorillonite, it is adsorbed onto the surface of montmorillonite nanosheets through electrostatic interaction, thus preparing intercalated modified montmorillonite.

[0008] Step 3: By using the hydrogen bonding between the phenolic hydroxyl functional groups on the surface of the intercalated modified montmorillonite and the hydroxyl functional groups of polyvinyl alcohol resin, the intercalated modified montmorillonite and polyvinyl alcohol resin are combined to prepare an organic-inorganic composite moisture barrier.

[0009] Step 4: Add an organic-inorganic composite barrier moisture absorber to the 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 as follows:

[0011] Step S2-1: Based on the Mannich reaction mechanism, acetylsyringone containing α-H undergoes a condensation reaction with 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 quaternary ammonium salt intercalating agent containing a phenolic hydroxyl functional group is prepared by quaternization reaction of the tertiary amine group of the tertiary amine monomer containing the phenolic hydroxyl functional group with the bromine functional group of 1-bromo-6-(trimethylammonium)hexyl bromide.

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

[0014] Step S3-1: Set the high-barrier moisture-absorbing packaging film to a three-layer co-extruded film, the film structure of which is as follows:

[0015] First layer: 20-40 parts by weight of polypropylene resin layer prepared from 100wt% polypropylene resin;

[0016] The second layer is a barrier moisture-absorbing layer made of raw materials consisting 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] Third layer: 20-40 parts by weight of polypropylene resin layer prepared from 100wt% polypropylene resin.

[0018] Step S3-2: The raw materials from step S3-1 are fed into the hoppers of the three screw extruders of the three-layer co-extrusion film blow molding unit. After mixing, the molten resin is collected at the die head through the distributor, extruded through the die head, blow molded, cooled, and wound up to obtain a high-barrier moisture-absorbing packaging film.

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

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

[0021] Preferably, the oxygen permeability of the high-barrier moisture-absorbing packaging film is (1.0-1.5) cm³. 3 / (m 2 • 24h • 0.1MPa), water vapor transmission rate is (1.0-2.0) g / (m 2 (24h) Moisture absorption rate is 5-10%.

[0022] Beneficial effects:

[0023] This invention designs and synthesizes a quaternary ammonium salt intercalating agent containing phenolic hydroxyl functional groups. This quaternary ammonium salt intercalating agent modifies sodium montmorillonite through electrostatic interaction and is further compounded with polyvinyl alcohol based on hydrogen bonding to prepare a novel organic-inorganic composite barrier moisture absorber. The organic-inorganic composite barrier moisture absorber is added as a modifier to a polypropylene co-extruded film, and a high-barrier moisture-absorbing packaging film is prepared using a three-layer co-extrusion blow molding process.

[0024] Experiments have shown that, compared with polypropylene film, the high-barrier moisture-absorbing packaging film prepared by this invention can significantly reduce oxygen and water vapor transmission, exhibiting excellent barrier performance.

[0025] The high-barrier moisture-absorbing packaging film prepared by this invention achieves a significant improvement in moisture absorption performance and also slightly improves mechanical properties. Attached Figure Description

[0026] Figure 1 Synthetic routes for quaternary ammonium salt intercalating agents containing phenolic hydroxyl functional groups;

[0027] Figure 2 These are the performance test results of a high-barrier moisture-absorbing packaging film. Detailed Implementation

[0028] This invention combines inorganic montmorillonite with excellent barrier properties and organic polyvinyl alcohol with excellent moisture absorption properties using a newly synthesized quaternary ammonium salt intercalating agent to prepare an organic-inorganic composite barrier and moisture absorber, which is then used to improve the barrier and moisture absorption capacity of polypropylene films.

[0029] Example 1:

[0030] The preparation steps for an organic-inorganic composite barrier moisture absorber are as follows:

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

[0032] Step 2: Sodium-based montmorillonite is modified by intercalation using a 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-based montmorillonite, it is adsorbed onto the surface of montmorillonite nanosheets through electrostatic interaction, thus preparing intercalated modified montmorillonite.

[0033] Step 3: By using the hydrogen bonding between the phenolic hydroxyl functional groups on the surface of the intercalated modified montmorillonite and the hydroxyl functional groups of polyvinyl alcohol resin, the intercalated modified montmorillonite and polyvinyl alcohol resin are combined to prepare an organic-inorganic composite moisture barrier.

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

[0035] (1) Preparation of quaternary ammonium salt intercalating agents containing phenolic hydroxyl functional groups, such as Figure 1 As shown, its preparation process is as follows:

[0036] Preparation of tertiary amine monomers containing phenolic hydroxyl functional groups: Based on the Mannich reaction mechanism, tertiary amine monomers containing phenolic hydroxyl functional groups are generated by the condensation reaction of acetyl syringone containing α-H with syringaldehyde and dimethylamine. The specific experimental steps are as follows: 2.0 g acetyl syringone, 1.8 g syringaldehyde, 0.5 g dimethylamine and 50 mL anhydrous ethanol are added to a three-necked flask. Under nitrogen protection and mechanical stirring, 5 drops of concentrated hydrochloric acid are slowly added to the three-necked flask. The mixture is heated to 85 °C and refluxed for 4 h. After cooling to room temperature, the solvent is removed by rotary evaporation. The mixture is then filtered and dried to obtain tertiary amine monomers containing phenolic hydroxyl functional groups.

[0037] Preparation of quaternary ammonium salt intercalating agent containing phenolic hydroxyl functional group: Based on the nucleophilic substitution mechanism, the tertiary amine group of the tertiary amine monomer containing phenolic hydroxyl functional group undergoes a quaternization reaction with the bromine functional group of 1-bromo-6-(trimethylammonium)hexyl bromide to generate a quaternary ammonium salt intercalating agent containing phenolic hydroxyl functional group. The specific experimental steps are as follows: 2.0 g of tertiary amine monomer containing phenolic hydroxyl functional group and 20 mL of N,N-dimethylformamide are added to a three-necked flask. Under nitrogen protection and mechanical stirring, the mixture is stirred at room temperature until completely dissolved. Then, 10 mL of N,N-dimethylformamide solution containing 1.5 g of 1-bromo-6-(trimethylammonium)hexyl bromide is added to the three-necked flask. The mixture is heated to 40 °C and stirred for 10 h. The solvent is removed by rotary evaporation, and the mixture is dried under vacuum to obtain the quaternary ammonium salt intercalating agent containing phenolic hydroxyl functional group.

[0038] The 1H NMR characterization of quaternary ammonium salt intercalating agents containing phenolic hydroxyl functional groups is as follows: 1 H NMR (CDCl3, 400MHz) 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) Preparation of intercalated modified montmorillonite: 3g sodium-based montmorillonite nanosheets and 100mL ethanol were added to a three-necked flask, sonicated for 30min, heated to 70℃ and stirred for 2h, and then 20mL quaternary ammonium salt intercalating agent solution (prepared by 2g quaternary ammonium salt intercalating agent and 20mL ethanol) were added to the three-necked flask, and the reaction was stirred at 70℃ for 4h. The mixture was filtered while hot, washed with ethanol until no precipitate could be detected in silver nitrate solution, vacuum dried and ground to obtain intercalated modified montmorillonite;

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

[0041] (3) Preparation of organic-inorganic composite barrier moisture absorber: 10g of polyvinyl alcohol resin and 100mL of deionized water were added to a three-necked flask, heated to 90℃ and stirred to dissolve for 2h, cooled to 60℃, and 10mL of deionized water containing 2.5g of intercalated modified montmorillonite was added to the three-necked flask. The mixture was stirred and reacted at 60℃ for 10h. After mixing evenly, the mixture was dried under vacuum to obtain the organic-inorganic composite barrier moisture absorber.

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

[0043] Example 2:

[0044] The preparation of a high-barrier moisture-absorbing packaging film includes the following steps:

[0045] Step 1: Set the high-barrier moisture-absorbing packaging film as a three-layer co-extruded film, with the following film structure:

[0046] First layer: 30 parts by weight of polypropylene resin layer prepared from 100wt% polypropylene resin;

[0047] Second layer: a barrier moisture-absorbing layer made of raw materials consisting of 70wt% polypropylene resin, 25wt% organic-inorganic composite barrier moisture absorber and 5wt% 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: The raw materials from Step 1 are fed into the hoppers of the three screw extruders of the three-layer co-extrusion film blow molding unit. After mixing, the molten resin is collected at the die head through the distributor, extruded through the die head, blow molded, cooled, and wound up to obtain a high-barrier moisture-absorbing packaging film with a thickness of 100μm.

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

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

[0052] The polypropylene resin was purchased from Shanghai Qiaowei Chemical Technology Co., Ltd., with the grade HJ4012; the maleic anhydride-grafted polypropylene resin was purchased from Keais Chemical Co., Ltd., with the grade B1.

[0053] Comparative example:

[0054] Preparation of polypropylene film: Polypropylene film is prepared by replacing the organic-inorganic composite barrier moisture absorber in the high-barrier moisture-absorbing packaging film with only polypropylene resin, while keeping all other parts the same.

[0055] Performance testing:

[0056] I. Barrier Performance Test:

[0057] (1) The oxygen barrier performance of the sample was tested using a Y110 oxygen permeability tester in accordance with GB / T 1038-2000, and the oxygen permeability of the sample was recorded.

[0058] (2) The water resistance performance of the sample was tested using the TC-03 water vapor transmission rate according to GB / T 1037-2021, and the water vapor transmission rate of the sample was recorded.

[0059] II. Moisture Absorption Performance Test:

[0060] A 60mm × 60mm (length × width) sample was dried in an oven at 55℃ for 4 hours, then weighed and recorded as the initial weight. The dried sample was then completely immersed in distilled water for 24 hours to equilibrate. It was then removed with tweezers and the surface moisture was absorbed with absorbent filter paper before weighing, which was recorded as the weight after moisture absorption. The moisture absorption rate of the sample was calculated using the following method:

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

[0062] III. Mechanical Properties:

[0063] The tensile strength of the sample was tested according to GB / T 13022-1991 "Test Method for Tensile Properties of Plastic Films". The 30mm×5mm sample was fixed on the Instron 5565 universal tensile testing machine and the tensile test was carried out at a tensile rate of 5mm / min. The longitudinal and transverse tensile strengths were recorded respectively.

[0064] The 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] A comprehensive analysis of the above experimental results leads to the following conclusions:

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

[0069] Conclusion 2: The high-barrier moisture-absorbing packaging film prepared by the present invention achieves a significant improvement in moisture absorption performance and also shows a slight improvement in mechanical properties.

Claims

1. A preparation process for a high-barrier moisture-absorbing packaging film, characterized in that, Includes the following steps: Step 1: Prepare a quaternary ammonium salt intercalating agent containing a phenolic hydroxyl functional group, the chemical structural formula of which is: Step 2: Sodium-based montmorillonite is modified by intercalation using a 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-based montmorillonite, it is adsorbed onto the surface of montmorillonite nanosheets through electrostatic interaction, thus preparing intercalated modified montmorillonite. Step 3: By using the hydrogen bonding between the phenolic hydroxyl functional groups on the surface of the intercalated modified montmorillonite and the hydroxyl functional groups of polyvinyl alcohol resin, the intercalated modified montmorillonite and polyvinyl alcohol resin are combined to prepare an organic-inorganic composite moisture barrier. Step 4: Add an organic-inorganic composite barrier moisture absorber to the polypropylene film and use a three-layer co-extrusion blow molding process to prepare a high-barrier moisture-absorbing packaging film.

2. The preparation process of a high-barrier moisture-absorbing packaging film according to claim 1, characterized in that, The preparation method of the quaternary ammonium salt intercalating agent containing phenolic hydroxyl functional groups is as follows: Step S2-1: Based on the Mannich reaction mechanism, acetylsyringone 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, a quaternary ammonium salt intercalating agent containing a phenolic hydroxyl functional group is prepared by quaternization reaction of the tertiary amine group of the tertiary amine monomer containing the phenolic hydroxyl functional group with the bromine functional group of 1-bromo-6-(trimethylammonium)hexyl bromide.

3. The preparation process of 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: Set the high-barrier moisture-absorbing packaging film to a three-layer co-extruded film, the film structure of which is as follows: First layer: 20-40 parts by weight of polypropylene resin layer prepared from 100wt% polypropylene resin; The second layer is a barrier moisture-absorbing layer made of raw materials consisting 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. Third layer: 20-40 parts by weight of polypropylene resin layer prepared from 100wt% polypropylene resin. Step S3-2: The raw materials from step S3-1 are fed into the hoppers of the three screw extruders of the three-layer co-extrusion film blow molding unit. After mixing, the molten resin is collected at the die head through the distributor, extruded through the die head, blow molded, cooled, and wound up to obtain a high-barrier moisture-absorbing packaging film.

4. The preparation process of a high-barrier moisture-absorbing packaging film according to claim 1, characterized in that, The mass ratio of quaternary ammonium salt intercalating agent, sodium montmorillonite and 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 according to any one of claims 1-4, 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) Moisture absorption rate is 5-10%.

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

Images