A PE film, preparation process and application in tissue packaging

Abstract

The invention relates to the technical field of degradable PE packaging materials and discloses a PE film, a preparation process and an application in tissue packaging. The method comprises the following steps: using 7-(diethylamino)coumarin-3-carboxylic acid, 2-naphthalenemethanol and epichlorohydrin as raw materials, preparing an epoxidized biodegradable organic photosensitizer through esterification reaction and quaternization reaction; based on the epoxy-hydroxyl ring-opening reaction mechanism, modifying hydroxylated titanium dioxide nanoparticles and polyvinyl alcohol resin using the epoxidized biodegradable organic photosensitizer respectively, and compounding them based on the π-π stacking effect between aromatic rings to prepare an ultraviolet-dependent photo-biodegradable component; adding the ultraviolet-dependent photo-biodegradable component, a compatible component and a composite auxiliary agent into a polyethylene matrix, and blow-molding the PE film. The film product exhibits excellent photo-biodegradable dual degradation performance, has practical use value, and can be applied in the field of tissue packaging.

Description

Technical Field

[0001] The present invention relates to the technical field of degradable PE packaging materials, in particular to a PE film, a preparation process and application in tissue packaging. Background Art

[0002] Polyethylene (PE) film has excellent moisture resistance (its water vapor transmission rate is as low as 5-10g / m 2 d) Due to its low cost (only 12-15 yuan / kg) and mature supply chain (its production, printing, and packaging equipment are highly standardized), it has become one of the mainstream materials for tissue packaging, especially dominating the tissue paper, roll paper, and wet wipes sectors.

[0003] With increasing environmental protection requirements, green packaging has become the development direction of tissue packaging materials, with biodegradable packaging materials being a major development direction. However, bio-based packaging materials have significant disadvantages such as high cost and poor mechanical properties. Therefore, in the short term, traditional plastic packaging materials will continue to be the most used packaging material. As the most representative packaging material, PE film packaging materials degrade extremely slowly after use, becoming a major source of white pollution.

[0004] Currently, the main methods for degrading polyethylene are biodegradation and photodegradation. Biodegradable polyethylene generally refers to adding natural degradable biomaterials (such as starch, cellulose, etc.) and synthetic biodegradable materials (polyvinyl alcohol, polylactic acid, polybutylene succinate, etc.) to a polyethylene matrix. Under the action of microorganisms and enzymes, the biodegradable materials are eroded, causing the polyethylene to disintegrate into small fragments.

[0005] Photodegradable polyethylene refers to polyethylene that is stimulated and induced to degrade under light conditions. It can be divided into synthetic photodegradation and photosensitizer-added photodegradation. Additive photodegradable polyethylene refers to polyethylene that is added with a photosensitizer. Under light conditions, the photosensitizer triggers the degradation of polyethylene. There are many types of photosensitizers, mainly TiO2 and derived semiconductor photosensitizers. The band gap of TiO2 photosensitizer is large, reaching 3.2eV, and it only responds to ultraviolet light with a wavelength less than 387.5nm. The energy of sunlight is mainly distributed in the wavelength range of 400-760nm. Therefore, the photodegradable polyethylene film made by adding TiO2 to polyethylene has an extremely low risk of degradation when used for product packaging, and after use, it can be induced to degrade by ultraviolet light.

[0006] The study found that organic small molecules with large conjugated structures have excellent light absorption properties and can be used as photosensitive materials as additives to plastics to achieve photodegradation of related materials. Among them, naphthalene compounds show strong absorption ability in the ultraviolet light region (240-320nm) and can be used as organic photosensitizers to achieve photodegradation of materials.

[0007] In addition, polyvinyl alcohol is a vinyl polymer that can be used by bacteria as a carbon source and energy source. It can be degraded under the action of bacteria and enzymes and is a biodegradable polymer material. Summary of the Invention

[0008] The present invention uses ultraviolet-dependent organic photosensitizer naphthalene compounds as raw materials to design and synthesize an organic photosensitizer with coupling function and containing biodegradable groups. On the one hand, the organic photosensitizer is grafted onto the surface of inorganic photosensitizer nano-TiO2 to solve the TiO2 agglomeration problem, and on the other hand, it is modified onto the side chain of synthetic biodegradable material polyvinyl alcohol. The grafted TiO2 and modified polyvinyl alcohol are then compounded and added to a PE matrix. The resulting PE film has both photodegradation and biodegradation capabilities.

[0009] A preparation process for a PE film comprises the following steps:

[0010] Step 1: Synthesis of epoxidation biodegradable organic photosensitizer;

[0011] Step 2: Based on the epoxy-hydroxyl ring-opening reaction mechanism, the epoxidized biodegradable organic photosensitizer is grafted onto the surface of hydroxylated titanium dioxide nanoparticles to obtain a biodegradable photosensitizer, and the epoxidized biodegradable organic photosensitizer is grafted onto the side chain of polyvinyl alcohol to obtain a photosensitive polyvinyl alcohol;

[0012] Step 3: Based on the π-π stacking interaction between aromatic rings, a biodegradable photosensitizer is compounded with a photosensitive polyvinyl alcohol to prepare a UV-dependent photo-biodegradable component;

[0013] Step 4: adding the UV-dependent photo-biodegradable component, the compatible component and the composite additive into the polyethylene matrix, and blow-molding to obtain a PE film.

[0014] Preferably, the preparation method of the epoxidation biodegradable organic photosensitizer is:

[0015] The carboxyl functional group of 7-(diethylamino)coumarin-3-carboxylic acid and the hydroxyl functional group of 2-naphthalenemethanol undergo esterification reaction to generate a coumarin-based naphthyl tertiary amine monomer;

[0016] Based on the nucleophilic substitution reaction mechanism, the tertiary amine functional group of the coumarin-naphthyl tertiary amine monomer and the chlorine functional group of epichlorohydrin undergo quaternization reaction to generate an epoxidized biodegradable organic photosensitizer.

[0017] Preferably, the amount of the UV-dependent photo-biodegradable component in the PE film is 15-40 wt % of the amount of polyethylene.

[0018] Preferably, the mass ratio of the biodegradable photosensitizer to the photosensitive polyvinyl alcohol in the ultraviolet light-dependent photo-biodegradable component is 1:(2-5);

[0019] Preferably, the mass ratio of the epoxidized biodegradable organic photosensitizer to the hydroxylated titanium dioxide nanoparticles in the biodegradable photosensitizer is 1:(3-8);

[0020] Preferably, the mass ratio of the epoxidation biodegradable organic photosensitizer to the polyvinyl alcohol in the photosensitive polyvinyl alcohol is 1:(3-8).

[0021] Preferably, the particle size of the titanium dioxide is 5-10 nm.

[0022] A PE film prepared according to the above process includes the following raw materials in parts by weight:

[0023] 60-70 parts of low-density polyethylene resin;

[0024] 5-12 parts of compatible components;

[0025] 10-30 parts of UV-dependent photo-biodegradable components;

[0026] 1-5 parts of compound additives.

[0027] Preferably, the compatible component is maleic anhydride grafted polyethylene resin or methacrylic acid grafted maleic anhydride high-density polyethylene resin.

[0028] Preferably, the composite auxiliary agent includes 0.5-2 parts by weight of an antioxidant, 0.2-2 parts by weight of an antistatic agent and 0.3-2 parts by weight of an anti-blocking agent.

[0029] Preferably, the thickness of the PE film is 100-150 μm.

[0030] The PE film prepared according to the above process is used in tissue packaging. Beneficial effects

[0031] The invention is based on the mechanism of esterification reaction and quaternization reaction, and uses biodegradable 7-(diethylamino)coumarin-3-carboxylic acid, ultraviolet light-dependent organic photosensitizer 2-naphthalenemethanol and epichlorohydrin as raw materials to synthesize an epoxidized biodegradable organic photosensitizer.

[0032] Based on the epoxy-hydroxyl ring-opening reaction mechanism, on the one hand, the epoxidized biodegradable organic photosensitizer is grafted onto the surface of hydroxylated titanium dioxide nanoparticles to obtain a biodegradable photosensitizer, and on the other hand, the epoxidized biodegradable organic photosensitizer is grafted onto the side chain of polyvinyl alcohol to obtain a photosensitive polyvinyl alcohol.

[0033] Based on the π-π stacking effect between aromatic rings, a biodegradable photosensitizer is compounded with photosensitizing polyvinyl alcohol to prepare a UV-dependent photo-biodegradable component.

[0034] The ultraviolet-dependent photo-biodegradable component, the compatible component and other additives are added to the polyethylene matrix, and blow-molded to obtain a PE film product;

[0035] The experimental results show that the PE film product prepared by the present invention not only has barrier properties that meet the technical requirements for paper towel product packaging and can be used for paper towel product packaging, but can also effectively ensure the shelf life of paper towel products. Moreover, when the paper towel product is used up, ultraviolet light can be used to induce photodegradation of the discarded PE film until the appearance no longer changes significantly, and then the discarded film portion that has not undergone ultraviolet light degradation can be further degraded by microorganisms. DETAILED DESCRIPTION Example 1:

[0036] Preparation of epoxidation biodegradable organic photosensitizer, the preparation process is as follows:

[0037] Step 1: The carboxyl functional group of 7-(diethylamino)coumarin-3-carboxylic acid and the hydroxyl functional group of 2-naphthalenemethanol undergo esterification reaction to generate a coumarin-naphthyl tertiary amine monomer, the chemical structure of which is:

[0038] ;

[0039] Step 2: Based on the nucleophilic substitution reaction mechanism, the tertiary amine functional group of the coumarin-naphthyl tertiary amine monomer and the chlorine functional group of epichlorohydrin undergo quaternization reaction to generate an epoxidized biodegradable organic photosensitizer, the chemical structure of which is:

[0040] ;

[0041] The specific experimental steps for preparing epoxidation biodegradable organic photosensitizers are as follows:

[0042] 2.6 g of 7-(diethylamino)coumarin-3-carboxylic acid, 1.6 g of 2-naphthalenemethanol and 50 mL of N,N-dimethylformamide were added to a three-necked flask and stirred at room temperature until all dissolved. Then, 2.5 mL of concentrated sulfuric acid was added dropwise to the three-necked flask, and the temperature was raised to 80° C. and stirred for 6 h. The flask was cooled to room temperature, and the solvent was removed by rotary evaporation. The amine was washed with anhydrous ethanol and dried in vacuo to obtain a coumarin-based naphthyl tertiary amine monomer.

[0043] 2.0 g of coumarin-based naphthyl tertiary amine monomer and 30 mL of acetonitrile were added to a three-necked flask and stirred at room temperature until completely dissolved. Then, 0.4 mL of epichlorohydrin was added to the three-necked flask. Under nitrogen protection and mechanical stirring, the temperature was raised to 50° C. and stirred for 12 h. The mixture was cooled to room temperature and the solvent was removed by rotary evaporation. The mixture was washed with anhydrous ethanol and dried in vacuo to obtain an epoxidized biodegradable organic photosensitizer.

[0044] The nuclear magnetic resonance hydrogen spectrum of the epoxidation biodegradable organic photosensitizer is characterized as follows: 1 H NMR (CDCl3, 400MHz) δ: 1.37-1.41 (t, 6H), 3.62-3.63 (d, 2H), 4.00-4.12 (m, 5H), 4.18-4.20 (d, 2H), 5.24 (s, 2H), 7.37-8.01 (m, 10H, Ar-H), 8.51 (s, 1H). Example 2:

[0045] Preparation of a biodegradable photosensitizer: The epoxy functional groups of the epoxidized biodegradable organic photosensitizer undergo a ring-opening reaction with the hydroxyl functional groups on the surface of hydroxylated titanium dioxide nanoparticles to complete the grafting modification of the epoxidized biodegradable organic photosensitizer on titanium dioxide, thereby obtaining a biodegradable photosensitizer. The specific experimental steps are as follows: 5 g of hydroxylated titanium dioxide nanoparticles and 50 mL of N, N-dimethylformamide are added to a three-necked flask, stirred and dissolved at room temperature for 30 minutes, and ultrasonically dispersed for 1 hour. Under nitrogen protection, 10 mL of an N, N-dimethylformamide solution of 1 g of the epoxidized biodegradable organic photosensitizer and 1.5 mL of triethylamine catalyst are added dropwise to the three-necked flask, the temperature is raised to 70° C., stirred and reacted for 6 hours, cooled to room temperature, the solvent is removed by rotary evaporation, washed with anhydrous ethanol, and vacuum dried to obtain a biodegradable photosensitizer.

[0046] Among them, the preparation method of hydroxylated titanium dioxide nanoparticles is: add 10g of nano titanium dioxide powder (particle size of 5-10nm) and 200mL of hydrogen peroxide aqueous solution (40wt%) into a three-necked flask, ultrasonically disperse them for 30 minutes, heat them to 105℃ and reflux them for 6 hours under mechanical stirring, cool them to room temperature, centrifuge them, repeatedly centrifuge and wash them with deionized water, and vacuum dry them to obtain hydroxylated titanium dioxide nanoparticles. Example 3:

[0047] Preparation of photosensitive polyvinyl alcohol: The epoxy functional group of the epoxidation biodegradable organic photosensitizer undergoes a ring-opening reaction with the hydroxyl functional group on the molecular main chain of the polyvinyl alcohol resin, thereby completing the grafting modification of the epoxidation biodegradable organic photosensitizer on the polyvinyl alcohol resin to obtain photosensitive polyvinyl alcohol. The specific experimental steps are as follows: 10g of polyvinyl alcohol resin (brand 28-98) and 100mL of dimethyl sulfoxide are added to a three-necked flask, the temperature is raised to 60°C and stirred until completely dissolved, then the temperature is lowered to 30°C, and 10mL of a dimethyl sulfoxide solution containing 2g of the epoxidation biodegradable organic photosensitizer and 1.8mL of triethylamine catalyst are slowly added to the three-necked flask under nitrogen protection, the temperature is raised to 70°C and stirred for 5h, the reaction is cooled to room temperature, and the solvent is removed by rotary evaporation using a vacuum pump at 50mbar and 45°C, and vacuum drying is performed to obtain photosensitive polyvinyl alcohol. Example 4:

[0048] Preparation of ultraviolet-dependent photo-biodegradable components: The inorganic component titanium dioxide and the organic component polyvinyl alcohol are compounded by π-π stacking of the naphthalene imide and coumarin groups contained on the surface of the biodegradable photosensitizer with the naphthalene imide and coumarin groups contained on the molecular main chain of the photosensitive polyvinyl alcohol, thereby preparing an ultraviolet-dependent photo-biodegradable component. The specific experimental steps are as follows: 6g of photosensitive polyvinyl alcohol and 100mL of dimethyl sulfoxide are added to a beaker, the temperature is raised to 70°C and stirred until completely dissolved, then 2g of biodegradable photosensitizer is added to the beaker, the reaction is maintained at 70°C with stirring for 5h, the reaction is cooled to room temperature, and the solvent is removed by rotary evaporation using a vacuum pump at 50mbar and 45°C, and the reaction is vacuum dried to obtain an ultraviolet-dependent photo-biodegradable component. Embodiment 5:

[0049] A PE film I comprises the following raw materials in parts by weight:

[0050] 65 parts of low-density polyethylene resin (brand LD 150DW);

[0051] 10 parts of maleic anhydride grafted polyethylene resin (brand 4288);

[0052] 18 parts of UV-dependent photo-biodegradable components;

[0053] 2 parts of antioxidant 1010; wherein, the antioxidant may also be antioxidant 168 or antioxidant 1076;

[0054] 1 part of antistatic agent PELESTAT 230; wherein, the antistatic agent may also be antistatic agent PELESTAT 300 or antistatic agent PELESTAT 1251;

[0055] 1 part of octadecyl erucamide; in addition to octadecyl erucamide, oleamide or stearamide can also be used as the opening agent. Example 6:

[0056] A preparation process of PE film I comprises the following steps:

[0057] Step 1: Prepare ingredients according to the formula of PE film I, add all raw materials into a high-speed mixer and mix evenly, extrude and granulate through a twin-screw extruder, and vacuum dry to obtain degradation-modified PE masterbatch I;

[0058] The process parameters of the twin-screw extruder were set as follows: the temperatures of zones 1-6 were 150°C, 160°C, 165°C, 170°C, 180°C, and 185°C, respectively, and the rotation speed was 400 r / min;

[0059] Step 2: Add the degradation-modified PE masterbatch I into a single-screw extruder film blowing machine, and use the upward blowing method to blow the film to obtain a 120 μm PE film I;

[0060] Among them, the process parameters of the single-screw extrusion film blowing machine are set as follows: the temperatures of zones 1-3 are 150°C, 170°C, and 190°C respectively, the rotation speed is 60r / min, the traction speed is 5m / min, the die head diameter of the film blowing machine is 60mm, and the blow-up ratio is 2.6. Embodiment seven:

[0061] A PE film II: Compared with the PE film I, the only difference is that the amount of the ultraviolet light-dependent photo-biodegradable component is 10 parts by weight. Embodiment 8:

[0062] A PE film III: Compared with the PE film I, the only difference is that the amount of the ultraviolet light-dependent photo-biodegradable component is 26 parts by weight.

[0063] Performance testing:

[0064] 1. Barrier properties

[0065] The barrier properties of the film samples were tested in accordance with GB / T 1037-2021. The specific test steps are as follows: 30 cm circular samples were placed in a glass desiccator at an ambient temperature of 25°C with anhydrous calcium chloride as a desiccant for 72 hours. The barrier properties of the samples were then tested using a TC-03 water vapor transmission rate tester, and the water vapor transmission rate of the samples was recorded.

[0066] The above experimental results are shown in Table 1 below.

[0067] Table 1 Test results of barrier properties of PE films

[0068]

[0069] The experimental results in Table 1 show that the water vapor permeability of the PE film product prepared by the present invention meets the use requirements of paper towel packaging products;

[0070] 2. Degradation performance

[0071] (1) Initial mechanical properties test: The mechanical properties of the film samples were tested using an Instron 5565 universal tensile testing machine (sampling was performed along the film blowing direction) in accordance with GB / T 1040.3-2006. The longitudinal tensile strength and longitudinal elongation at break of the samples were recorded. The sample size was 100 mm × 20 mm (length × width) and the test speed was 50 mm / min.

[0072] (2) Mechanical property test after 90 days of indoor placement: Place the film sample indoors at room temperature and pressure for 90 days, and perform mechanical property test according to the method in performance test (1). Record the longitudinal tensile strength and longitudinal elongation at break of the sample at this time, and calculate the change rate of longitudinal tensile strength and longitudinal elongation at break of the sample after 90 days of indoor placement. The specific method is as follows:

[0073] Change rate of longitudinal tensile strength = (initial longitudinal tensile strength - longitudinal tensile strength after 90 days of indoor placement) / initial longitudinal tensile strength × 100%;

[0074] Change rate of longitudinal elongation at break = (initial longitudinal elongation at break - longitudinal elongation at break after 90 days of indoor placement) / initial longitudinal elongation at break × 100%;

[0075] (3) Mechanical property test after 5 days of UV irradiation: Place the film sample in a UV aging test chamber (with three 20W UV high-pressure mercury lamps and a wavelength of 313nm) with the vertical distance between the lamp tube and the sample being 14.5cm. Irradiate the film sample at room temperature and pressure for 5 days. Take the film sample out and perform mechanical property test according to the method in performance test (1). Record the longitudinal tensile strength and longitudinal elongation at break of the sample at this time. Calculate the change rate of longitudinal tensile strength and longitudinal elongation at break of the sample after 5 days of UV irradiation according to the method in performance test (2);

[0076] (4) Mechanical property test after 5 days of UV irradiation and 90 days of microbial treatment: The film sample that was irradiated with UV light for 5 days in performance test (3) was buried in soil with the same properties at the same geographical location. The pH of the soil was 6.0 and the burial depth was 30 cm. After 90 days, it was taken out and washed with distilled water and ethanol. After drying, the mechanical property test was performed according to the method in performance test (1). The longitudinal tensile strength and longitudinal elongation at break of the sample were recorded at this time. The change rate of longitudinal tensile strength and longitudinal elongation at break of the sample after 5 days of UV irradiation and 90 days of microbial treatment were calculated according to the method in performance test (2);

[0077] The above experimental results are shown in Table 2 below.

[0078] Table 2 Experimental results of degradation performance of PE film

[0079]

[0080] By comprehensively analyzing the above experimental results, the following conclusions can be drawn:

[0081] Conclusion 1: After 90 days of storage indoors, the mechanical properties of the PE film product prepared by the present invention remained almost unchanged, indicating that the risk of spontaneous degradation under natural conditions is extremely low. This means that the PE film prepared by the present invention can be used for packaging paper towel products and has minimal adverse effects on the shelf life of these products.

[0082] Conclusion 2: After irradiation with ultraviolet light for 5 days, the mechanical properties of the PE film product prepared by the present invention showed a significant decrease, indicating that it was degraded under the action of ultraviolet light;

[0083] Conclusion 3: Compared with 5 days of UV irradiation only, the mechanical properties of the PE film product decreased more significantly after 5 days of UV irradiation and 90 days of biological treatment. This shows that after being degraded by UV light, it was further biodegraded by microorganisms, showing dual degradation capabilities of UV light and biological treatment.

Claims

1. A process for preparing a PE film, characterized in that: The following steps are involved: Step 1: Synthesize an epoxidation biodegradable organic photosensitizer, the chemical structure of which is: ； Step 2: Based on the epoxy-hydroxyl ring-opening reaction mechanism, the epoxidized biodegradable organic photosensitizer is grafted onto the surface of hydroxylated titanium dioxide nanoparticles to obtain a biodegradable photosensitizer, and the epoxidized biodegradable organic photosensitizer is grafted onto the side chain of polyvinyl alcohol to obtain a photosensitive polyvinyl alcohol; The mass ratio of the epoxidized biodegradable organic photosensitizer to the hydroxylated titanium dioxide nanoparticles in the biodegradable photosensitizer is 1:(3-8); the mass ratio of the epoxidized biodegradable organic photosensitizer to the polyvinyl alcohol in the photosensitive polyvinyl alcohol is 1:(3-8); Step 3: Based on the π-π stacking effect between aromatic rings, a biodegradable photosensitizer and a photosensitive polyvinyl alcohol are compounded to prepare a UV-dependent photo-biodegradable component. The preparation process is as follows: the photosensitive polyvinyl alcohol is dissolved in dimethyl sulfoxide, the temperature is raised to 70°C and stirred until completely dissolved, then the biodegradable photosensitizer is added, the temperature is maintained at 70°C and stirred for 5 hours, the reaction is cooled to room temperature, and the solvent is removed by rotary evaporation to obtain a UV-dependent photo-biodegradable component; The mass ratio of the biodegradable photosensitizer to the photosensitizer polyvinyl alcohol in the ultraviolet light-dependent photo-biodegradable component is 1:(2-5); Step 4: adding the UV-dependent photo-biodegradable component, the compatible component and the composite additive into the polyethylene matrix, and blow-molding to obtain a PE film; The amount of the ultraviolet-dependent photo-biodegradable component is 15-40 wt % of the amount of the polyethylene matrix.

2. The process for preparing a PE film according to claim 1, wherein: The preparation method of the epoxidation biodegradable organic photosensitizer is as follows: The carboxyl functional group of 7-(diethylamino)coumarin-3-carboxylic acid and the hydroxyl functional group of 2-naphthalenemethanol undergo esterification reaction to generate a coumarin-based naphthyl tertiary amine monomer; Based on the nucleophilic substitution reaction mechanism, the tertiary amine functional group of the coumarin-naphthyl tertiary amine monomer and the chlorine functional group of epichlorohydrin undergo quaternization reaction to generate an epoxidized biodegradable organic photosensitizer.

3. The process for preparing a PE film according to claim 1, wherein: The particle size of the titanium dioxide is 5-10 nm.

4. A PE film prepared by the process according to any one of claims 1 to 3, characterized in that: The PE film comprises the following raw materials in parts by weight: 60-70 parts of low-density polyethylene resin; 5-12 parts of compatible components; 10-30 parts of UV-dependent photo-biodegradable components; 1-5 parts of compound additives.

5. A PE film according to claim 4, characterized in that: The compatible component is maleic anhydride grafted polyethylene resin or methacrylic acid grafted maleic anhydride high-density polyethylene resin.

6. A PE film according to claim 4, characterized in that: The composite auxiliary agent comprises 0.5-2 parts by weight of an antioxidant, 0.2-2 parts by weight of an antistatic agent and 0.3-2 parts by weight of an anti-blocking agent.

7. A PE film according to claim 4, characterized in that: The thickness of the PE film is 100-150 μm.

8. Use of a PE film prepared according to the process according to any one of claims 1 to 3 in tissue packaging.

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