A biodegradable composite film paper material and its preparation method

Abstract

This invention belongs to the field of packaging materials technology, and particularly relates to a biodegradable composite film-paper material and its preparation method. The biodegradable composite film-paper material comprises a polymer layer and a paper layer. The polymer layer, by weight, comprises the following components: 70-80 parts polylactic acid, 20-30 parts polycaprolactone, 1-3 parts synergist, 8-10 parts citrate starch, 0.3-1.0 parts lubricant, and 0.2-0.5 parts antioxidant. Experimental results show that the biodegradable composite film-paper material prepared by this invention has an antibacterial grade of 0, a tensile strength of 30-34 MPa, and an elongation at break of 415-450%.

Description

Technical Field

[0001] This invention belongs to the field of packaging materials technology, and in particular relates to a biodegradable composite film paper material and its preparation method. Background Technology

[0002] Biodegradable film paper, as a new type of green and sustainable packaging material, not only meets the market's urgent demand for environmentally friendly products, but also provides manufacturers, brand owners and consumers with a more environmentally friendly and practical packaging option, which has a profound impact on promoting the green development of society.

[0003] Existing technology CN107902258A discloses a fully degradable paper-plastic composite film and its preparation method. This composite film includes a polylactic acid film layer, an adhesive layer, and a paper layer, and possesses fully biodegradable properties, effectively reducing environmental pollution from petrochemical plastic products. However, its main focus is on improving the mechanical properties of the composite film. CN103538317A discloses a composite film, particularly a high-strength paper-plastic composite film. Although it enhances tensile strength and heat-sealing strength by combining a kraft paper film layer, a polyester film layer, an aluminum foil layer, and a polyethylene film layer, and optimizes the bag's resistance to breakage during drops, its focus is also on improving mechanical properties, without significantly contributing to the improvement of antibacterial properties.

[0004] The shortcomings of existing composite paper films in terms of mechanical and antibacterial properties limit their widespread application in the packaging field. Especially given the current market's increasing demands for food safety and environmental protection, developing a composite paper film that maintains good mechanical properties while possessing excellent antibacterial capabilities is of paramount importance. Such a material could not only reduce or eliminate the use of chemical preservatives but also further enhance food safety and the environmental friendliness of packaging. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, one of the objectives of this invention is to provide a biodegradable composite film paper material with good biodegradability and antibacterial properties.

[0006] One of the objectives of this invention is achieved through the following technical solution:

[0007] A biodegradable composite film-paper material includes a polymer layer and a paper layer. The polymer layer comprises, by weight, the following components: 70-80 parts polylactic acid, 20-30 parts polycaprolactone, 1-3 parts synergist, 8-10 parts citrate starch, 0.3-1.0 parts lubricant, and 0.2-0.5 parts antioxidant; the synergist has the following structure:

[0008]

[0009] Furthermore, the preparation process of the synergist includes the following steps:

[0010]

[0011] (1) Take 1,2-bis(2-iodoethoxy)ethane and 1-methyl-1H-imidazol-4-carboxaldehyde into acetonitrile and react at 85-95℃ for 16-24h. After treatment, intermediate 1 is obtained.

[0012] (2) Take intermediate 1, inorganic base, and S8 into methanol and react at 70-90℃ for 36-48h. After treatment, intermediate 2 is obtained.

[0013] (3) Take intermediate 2 and iodomethane into N,N-dimethylformamide and react at 25-35°C for 16-24 hours. After treatment, intermediate 3 is obtained.

[0014] (4) Take intermediate 3 and phenylethylamine into methanol and react at 25-35℃ for 6-12 hours. After treatment, the synergist is obtained.

[0015] Further, the molar ratio of 1,2-bis(2-iodoethoxy)ethane and 1-methyl-1H-imidazol-4-carboxaldehyde in step (1) is 1:(2-2.5).

[0016] Further, in step (2), the molar ratio of intermediate 1, inorganic base, and S8 is 1:(2.5-4):(2-2.5); the inorganic base is either potassium carbonate or cesium carbonate.

[0017] Further, the molar ratio of intermediate 2 and iodomethane in step (3) is 1:(5-7).

[0018] Further, the molar ratio of intermediate 3 and phenylethylamine in step (4) is 1:(1.1~1.3).

[0019] Furthermore, the antioxidant is antioxidant 1076, and the lubricant is ethylene bis-stearamide (EBS).

[0020] Furthermore, the polycaprolactone is of specification CAPA6800, and the polylactic acid is of specification 4032D.

[0021] The second objective of this invention is to provide a method for preparing a biodegradable composite film paper material.

[0022] The second objective of this invention is achieved by the following technical solution:

[0023] The preparation method of the above-mentioned biodegradable composite film paper material includes the following steps:

[0024] S1: Add polylactic acid, polycaprolactone, synergist, citrate starch, lubricant, and antioxidant to the casting machine according to the formula, mix for 1-2 hours, and then extrude to form a film to obtain a polymer layer;

[0025] S2: The paper and the polymer are first hot-pressed together by a hot press roller, and then flattened by a cold press roller to obtain a biodegradable composite film paper material.

[0026] Furthermore, the film-forming temperature in step S1 is 60-70°C.

[0027] Further, in step S2, the temperature of the hot pressing roller is 130-170℃ and the pressure is 0.2-0.5MPa; the temperature of the cold pressing roller is 20-25℃ and the pressure is 0.05-0.10MPa.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. This invention provides a biodegradable composite film-paper material, comprising a paper layer and a polymer layer. The polymer layer leverages the biodegradability of polylactic acid (PLA) and polycaprolactone (PCL) in the natural environment, and also incorporates a novel synergist to address the issues of insufficient mechanical properties and poor antibacterial properties in PLA / PCL composite films. Experimental results show that the biodegradable composite film-paper material prepared by this invention has an antibacterial grade of 0, a tensile strength of 30-34 MPa, and an elongation at break of 415-450%.

[0030] 2. Through careful molecular design, the synergist prepared in this invention contains a number of active functional groups, such as quaternary ammonium cations, imine groups, and thioether bonds. Quaternary ammonium cations can adsorb onto negatively charged bacterial cell membranes to achieve antibacterial effects, while imine bonds (C=N) can form hydrogen bonds with carboxyl and hydroxyl groups in PLA molecules, significantly improving intermolecular interaction forces and thus enhancing the mechanical properties of the material. Thioether bonds can chemically react or physically adsorb with hydroxyl groups and other groups on the surface of cellulose paper to form a strong interfacial bond. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating the preparation process of the synergist of the present invention. Detailed Implementation

[0032] The present invention will now be further described with reference to the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, all reagents or instruments used are conventional products obtained through commercial channels.

[0033] Example 1

[0034] A biodegradable composite film paper material, by weight, comprises the following components: 70 parts polylactic acid, 30 parts polycaprolactone, 2 parts synergist, 9 parts citrate starch, 0.6 parts ethylene bis-stearamide, and 0.3 parts antioxidant 1076.

[0035] The preparation process of the synergist is as follows: Figure 1 As shown, it includes the following steps:

[0036] (1) Take 0.1 mol of 1,2-bis(2-iodoethoxy)ethane and 0.22 mol of 1-methyl-1H-imidazol-4-carboxaldehyde into 300 mL of acetonitrile and react at 90 °C for 18 h; after filtering the reaction solution, concentrate the filtrate, dissolve the concentrated crude product in 30 mL of dichloromethane, filter and concentrate to obtain intermediate 1;

[0037] (2) Take intermediate 1 (0.1 mol), potassium carbonate (0.32 mol), and S8 (0.22 mol) into 150 mL of methanol and react at 80 °C for 36 h. After filtering the reaction solution, concentrate the filtrate. Dissolve the concentrated crude product in 30 mL of dichloromethane, filter and concentrate to obtain intermediate 2.

[0038] (3) Take intermediate 2 (0.1 mol) and iodomethane (0.6 mol) into 300 mL of N,N-dimethylformamide and react at 30 °C for 18 h. Concentrate to obtain intermediate 3;

[0039] (4) Take intermediate 3 (0.1 mol) and phenylethylamine (0.12 mol) into 250 mL of methanol and react at 30 °C for 10 h. After filtering the reaction solution, dry the filter cake to obtain the synergist.

[0040] The 1H NMR spectrum results of the synergist: 1 H NMR (C 34 H 46 I2N6O2S2, 400MHz, DMSO-d6): δ8.28 (s, 2H), 7.76 (s, 2H), 7.25-7.17 (m, 10H), 4.40-4 .32(m, 10H), 3.85(t, 4H), 3.52(s, 4H), 2.90(t, 4H), 2.53-2.60(s, 6H), 1.85(t, 4H).

[0041] The preparation process of the biodegradable composite film paper material includes the following steps:

[0042] S1: Polylactic acid and polycaprolactone are dried in an 80℃ drying oven for 24 hours. The dried polylactic acid, polycaprolactone, synergist, citrate starch, ethylene bis-stearamide, and antioxidant 1076 are put into a casting machine according to the formula. After mixing for 1.5 hours, the mixture is extruded through a flat die to form a film. The film forming temperature is 65℃ to obtain a polymer layer.

[0043] S2: The paper and the above polymer are first hot-pressed together by a hot press roller at 150°C and 0.4MPa for 3 seconds, and then flattened by a cold press roller at 22°C and 0.07MPa to obtain a biodegradable composite film paper material.

[0044] Example 2

[0045] A biodegradable composite film paper material, by weight, comprises the following components: 80 parts polylactic acid, 20 parts polycaprolactone, 3 parts synergist, 8 parts citrate starch, 0.3 parts ethylene bis-stearamide, and 0.2 parts antioxidant 1076.

[0046] The preparation process of the synergist includes the following steps:

[0047] (1) Take 0.1 mol of 1,2-bis(2-iodoethoxy)ethane and 0.25 mol of 1-methyl-1H-imidazol-4-carboxaldehyde into 300 mL of acetonitrile and react at 85 °C for 24 h; after filtering the reaction solution, concentrate the filtrate, dissolve the concentrated crude product in 30 mL of dichloromethane, filter and concentrate to obtain intermediate 1;

[0048] (2) Take intermediate 1 (0.1 mol), potassium carbonate (0.4 mol), and S8 (0.22 mol) into 150 mL of methanol and react at 70 °C for 48 h. After filtering the reaction solution, concentrate the filtrate. Dissolve the concentrated crude product in 30 mL of dichloromethane, filter and concentrate to obtain intermediate 2.

[0049] (3) Take intermediate 2 (0.1 mol) and iodomethane (0.7 mol) into 300 mL of N,N-dimethylformamide and react at 25 °C for 24 h. Concentrate to obtain intermediate 3.

[0050] (4) Take intermediate 3 (0.1 mol) and phenylethylamine (0.13 mol) into 250 mL of methanol and react at 25 °C for 12 h. After filtering the reaction solution, dry the filter cake to obtain the synergist. The 1H NMR spectrum of the synergist shows that its structure is consistent with that of Example 1.

[0051] The preparation process of the biodegradable composite film paper material includes the following steps:

[0052] S1: Polylactic acid and polycaprolactone are dried in an 80℃ drying oven for 24 hours. The dried polylactic acid, polycaprolactone, synergist, citrate starch, ethylene bis-stearamide, and antioxidant 1076 are put into a casting machine according to the formula. After mixing for 2 hours, the mixture is extruded through a flat die to form a film. The film forming temperature is 70℃ to obtain a polymer layer.

[0053] S2: The paper and the above polymer are first hot-pressed together by a hot press roller at 170°C and 0.5MPa for 4 seconds, and then flattened by a cold press roller at 25°C and 0.10MPa to obtain a biodegradable composite film paper material.

[0054] Example 3

[0055] A biodegradable composite film paper material, by weight, comprises the following components: 75 parts polylactic acid, 25 parts polycaprolactone, 1 part synergist, 10 parts citrate starch, 1.0 part ethylene bis-stearamide, and 0.5 parts antioxidant 1076.

[0056] The preparation process of the synergist includes the following steps:

[0057] (1) Take 0.1 mol of 1,2-bis(2-iodoethoxy)ethane and 0.2 mol of 1-methyl-1H-imidazol-4-carboxaldehyde into 300 mL of acetonitrile and react at 95 °C for 16 h; after filtering the reaction solution, concentrate the filtrate, dissolve the concentrated crude product in 30 mL of dichloromethane, filter and concentrate to obtain intermediate 1;

[0058] (2) Take intermediate 1 (0.1 mol), potassium carbonate (0.25 mol), and S8 (0.2 mol) into 150 mL of methanol and react at 90 °C for 36 h. After filtering the reaction solution, concentrate the filtrate. Dissolve the concentrated crude product in 30 mL of dichloromethane, filter and concentrate to obtain intermediate 2.

[0059] (3) Take intermediate 2 (0.1 mol) and iodomethane (0.5 mol) into 300 mL of N,N-dimethylformamide and react at 35 °C for 16 h. Concentrate to obtain intermediate 3;

[0060] (4) Take intermediate 3 (0.1 mol) and phenylethylamine (0.11 mol) into 250 mL of methanol and react at 35 °C for 6 h. After filtering the reaction solution, dry the filter cake to obtain the synergist. The 1H NMR spectrum of the synergist shows that its structure is consistent with that of Example 1.

[0061] The preparation process of the biodegradable composite film paper material includes the following steps:

[0062] S1: Polylactic acid and polycaprolactone are dried in an 80℃ drying oven for 24 hours. The dried polylactic acid, polycaprolactone, synergist, citrate starch, ethylene bis-stearamide, and antioxidant 1076 are put into a casting machine according to the formula. After mixing for 1 hour, the mixture is extruded through a flat sheet die to form a film. The film forming temperature is 60℃ to obtain a polymer layer.

[0063] S2: The paper and the above polymer are first hot-pressed together by a hot press roller at 130°C and 0.2MPa for 2 seconds, and then flattened by a cold press roller at 20°C and 0.05MPa to obtain a biodegradable composite film paper material.

[0064] Comparative Example 1

[0065] A biodegradable composite film paper material, which differs from Example 1 in that it omits the synergist.

[0066] Test case

[0067] Peel force, mechanical properties, antibacterial properties and barrier properties were tested on the biodegradable composite film paper materials prepared in Examples 1-3 and Comparative Example 1. The results are shown in Table 1.

[0068] The test methods are as follows: peel strength is tested according to GB / T 36392-2018 "Coated Paper and Paperboard for Food Packaging"; tensile strength is tested according to GB / T1040.3-2006 standard at a test rate of 250 mm / min; antibacterial performance is tested according to QB / T2591-2003 "Test Methods and Antibacterial Effects of Antibacterial Plastics"; oxygen permeability of biodegradable composite film paper materials is determined according to GB / T1038-2000 "Test Method for Gas Permeability of Plastic Films and Sheets - Differential Pressure Method" at 23℃ and 0% RH; water vapor permeability of biodegradable composite film paper materials is determined according to national standard GB / T1037-88 "Test Method for Water Vapor Permeability of Plastic Films and Sheets - Cup Method" at 38℃ and 90% RH.

[0069] Table 1. Performance results of the biodegradable composite film paper materials of Examples 1-3 and Comparative Example 1

[0070]

[0071] As shown in Table 1, the biodegradable composite film paper materials prepared in Examples 1-3 of the present invention have excellent mechanical properties, peel strength and barrier properties, and their antibacterial grade can reach the best grade 0.

[0072] Compared to Comparative Example 1 without the added synergist, Examples 1-3 showed significant improvements in antibacterial properties, mechanical strength, and peel strength. This indicates that the synergist synthesized in this invention can improve the insufficient mechanical properties and poor antibacterial properties of PLA / PCL composite film paper. The quaternary ammonium cations in the synergist designed and synthesized in this invention can achieve antibacterial effects by adsorbing onto the negatively charged bacterial cell membrane, while the imine bond (C=N) can form hydrogen bonds with the carboxyl and hydroxyl groups in PLA molecules, thereby enhancing the mechanical properties of the material; the thioether bond can chemically react or physically adsorb with hydroxyl groups and other groups on the surface of cellulose paper to form a strong interfacial bond.

[0073] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A degradable composite film paper material, characterized by, The polymeric layer comprises the following components in parts by weight: 70-80 parts of polylactic acid, 20-30 parts of polycaprolactone, 1-3 parts of synergist, 8-10 parts of citrate starch, 0.3-1.0 parts of lubricant, and 0.2-0.5 parts of antioxidant.

2. The degradable composite paper material of claim 1, wherein, The preparation process of the synergist comprises the following steps: (1) 1,2-bis(2-iodoethoxy)ethane, 1-methyl-1H-imidazole-4-formaldehyde are taken into acetonitrile and reacted at 85-95℃ for 16-24h, and an intermediate 1 is prepared by treatment; (2) intermediate 1, inorganic base, S8 are taken into methanol and reacted at 70-90℃ for 36-48h, and an intermediate 2 is prepared by treatment; (3) intermediate 2, iodomethane are taken into N,N dimethylformamide and reacted at 25-35℃ for 16-24h, and an intermediate 3 is prepared by treatment; (4) intermediate 3, phenethylamine are taken into methanol and reacted at 25-35℃ for 6-12h, and the synergist is prepared by treatment.

3. The degradable composite paper material of claim 2, wherein, The molar ratio of 1,2-bis(2-iodoethoxy)ethane to 1-methyl-1H-imidazole-4-formaldehyde in step (1) is 1:(2-2.5).

4. The degradable composite paper material of claim 2, wherein, The molar ratio of intermediate 1, inorganic base, S8 in step (2) is 1:(2.5-4):(2-2.5); the inorganic base is one of potassium carbonate and cesium carbonate.

5. The degradable composite paper material of claim 2, wherein, The molar ratio of intermediate 2 to iodomethane in step (3) is 1:(5-7).

6. The degradable composite paper material of claim 2, wherein, The molar ratio of intermediate 3 to phenethylamine in step (4) is 1:(1.1-1.3).

7. The degradable composite paper material of claim 1, wherein, The antioxidant is antioxidant 1076, and the lubricant is ethylene bis-stearamide.

8. The method for preparing the biodegradable composite film paper material according to any one of claims 1 to 7, characterized in that, The method comprises the following steps: S1: polylactic acid, polycaprolactone, synergist, citrate starch, lubricant, and antioxidant are added into a casting machine in a predetermined ratio, mixed for 1-2h, and then extruded into a film to obtain a polymeric layer; S2: the paper and the polymeric layer are first hot-pressed by a hot-pressing roller, and then flattened by a cold-pressing roller to obtain a degradable composite film paper material.

9. The method for preparing the biodegradable composite film paper material according to claim 8, characterized in that, The temperature of the film forming in step S1 is 60-70℃.

10. The method for preparing the biodegradable composite film paper material according to claim 8, characterized in that, The temperature of the hot-pressing roller in step S2 is 130-170℃, and the pressure is 0.2-0.5MPa; the temperature of the cold-pressing roller is 20-25℃, and the pressure is 0.05-0.10MPa.

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