A biodegradable cigarette packaging film blend material and preparation method thereof

Abstract

A biodegradable cigarette packaging film blend material and its preparation method belong to the technical field of biodegradable materials. It is characterized by the following: the raw materials are composed by weight of 20 to 40 parts of PPCP-T, 20 to 40 parts of PLA, 40 to 60 parts of PBAT, and 0.1 to 0.5 parts of a chain extender, wherein the chain extender is a prepolymer of an aliphatic isocyanate and a dibasic organic acid. The film is formed by a co-extrusion casting and biaxial stretching preparation process. This invention solves the problem of the difficulty of blending PPCP-T with PLA and PBAT without adding multiple additives. This avoids the reduction in strength and barrier properties of the cigarette film due to its small thickness after the addition of additives.

Description

Technical Field

[0001] The invention discloses a biodegradable cigarette packaging film blend material and a preparation method thereof, belonging to the technical field of degradable materials. Background Art

[0002] Cigarette packaging films require excellent dimensional stability, high mechanical strength, good transparency, and a strong water vapor barrier. Traditionally, biaxially oriented polypropylene (BOPP) film is used, but this film is non-degradable. Biodegradable polylactic acid (PLA) biaxially oriented cigarette packaging films are expensive and lack sufficient water and oxygen barrier properties, preventing them from maintaining moisture and flavor for extended periods. Currently, they can only be used for whole carton packaging, while individual packs still rely on traditional BOPP materials.

[0003] To address the water and gas barrier properties of degradable cigarette packaging films, patent CN116021850A proposed a biodegradable cigarette packaging film with barrier properties. This film, which combines a semi-aromatic CO2-based copolymer film with a PLA film, successfully addresses the issue of PLA's poor barrier properties. However, the processing of this composite film is complex, requiring multi-layer co-extrusion casting and biaxial stretching. This results in high equipment costs and difficult process control, necessitating further improvements. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a biodegradable cigarette packaging film blend material with simple production process and good barrier properties and a preparation method thereof.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a biodegradable cigarette packaging film blend material, characterized in that the raw materials are composed by weight of 20 to 40 parts of PPCP-T, 20 to 40 parts of PLA, 40 to 60 parts of PBAT, and 0.1 to 0.5 parts of a chain extender, wherein the chain extender is a prepolymer of an aliphatic isocyanate and a dibasic organic acid.

[0006] Typically, blending PPCP-T with PLA and PBAT is challenging. To improve processing performance, various additives are required for effective blending. However, cigarette film thickness is very thin, while gas barrier properties are demanding. Adding these additives not only reduces film strength but also its barrier properties. To achieve uniform blending of PPCP-T, PLA, and PBAT, this invention utilizes a novel prepolymer chain extender. This enhances uniform mixing and chain extension, resulting in a cigarette film that maintains high strength while exhibiting enhanced barrier properties.

[0007] The raw material composition by weight is preferably 25-35 parts PPCP-T, 25-35 parts PLA, 45-55 parts PBAT, and 0.15-0.3 parts chain extender. This preferred composition by weight allows for optimal performance, resulting in a film with optimal strength and barrier properties.

[0008] Preferably, in the above-mentioned biodegradable cigarette packaging film blend material, the preparation process of the PPCP-T is:

[0009] 1) Propylene oxide, phthalic anhydride, catalyst 1, and solvent are placed in a high-pressure reactor, wherein the molar ratio of propylene oxide to phthalic anhydride is 2.5-4:1; the temperature is raised to a reaction temperature of 35°C-45°C for reaction;

[0010] 2) After the phthalic anhydride is completely reacted, the second catalyst is added, and carbon dioxide is introduced to a reaction pressure of 2.4 MPa to 3.5 MPa. The reaction temperature is maintained and the reaction is continued until the propylene oxide is completely reacted. The temperature is then lowered and the pressure is released.

[0011] 3) Add 10% to 15% of the propylene oxide and phthalic anhydride in step 1) again, add catalyst 3, and heat to the above reaction temperature again for reaction. After the monomer reaction is complete, terminate the reaction to obtain a glue solution; the glue solution is washed and devolatilized to obtain the glue solution.

[0012] PPCP-T is a block terpolymer of propylene oxide, phthalic anhydride, and carbon dioxide. Compared with random PPCP, it has better toughness and dimensional stability. The PPCP-T prepared by the above process has better performance itself and can be better mixed with PLA and PBAT. The toughness and barrier properties of the resulting film are better.

[0013] Preferably, in the above-mentioned PPCP-T preparation process, the solvent in step 1) is 2-methyltetrahydrofuran, tetrahydrofuran, or n-butyl ether; the catalyst 1 in step 1) is a composite catalyst comprising tetra-n-butylammonium halide and triethylboron in a molar ratio of 1:1.3-2.7; the catalyst 2 in step 2) is triethylboron; and the catalyst 3 in step 3) is tetra-n-butylammonium chloride. The combination of the preferred solvent and catalyst, combined with the reaction rate and conversion rate controlled by the above-mentioned process conditions, results in the PPCP-T having improved strength and barrier properties, and the resulting film exhibits optimal toughness and barrier properties.

[0014] Preferably, the prepolymer in the biodegradable cigarette packaging film blend has a molecular weight of 1,000 to 8,000, and an NCO content of 12% to 20% by weight. NCO refers to the isocyanate group in a chemical material, and its value refers to the mass of isocyanate (-NCO) groups contained in a 100g sample. Prepolymerizing the isocyanate with a dibasic organic acid adjusts the reactivity of the chain extender, resulting in a more uniform dispersion within the blend and a significant chain extension effect. This improves the toughness of the material after use and prevents yellowing even during high-temperature processing.

[0015] Preferably, in the prepolymer, the aliphatic isocyanate is isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), or methylcyclohexane diisocyanate (HTDI). After prepolymerization, the above aliphatic isocyanates can achieve a good chain extension effect in the present material.

[0016] Preferably, in the biodegradable cigarette packaging film blend material, the dibasic organic acid is oxalic acid, phthalic acid, or isophthalic acid. The prepolymer chain extender obtained by polymerizing the preferred dibasic organic acid with an isocyanate has a more suitable reaction rate and improves the performance of the cigarette packaging film material after mixing.

[0017] Preferably, in the above-mentioned biodegradable cigarette packaging film blend material, the preparation step of the prepolymer includes:

[0018] a) dropping isocyanate into a reaction kettle pre-filled with a dibasic organic acid and a solvent at room temperature to carry out a polymerization reaction;

[0019] b) After the isocyanate is added dropwise according to the ratio, the reaction is continued for 30 minutes to 80 minutes; then the prepolymer generated by the reaction is separated into solid and liquid.

[0020] Isocyanate is added dropwise to the dibasic organic acid to react, and the isocyanate and the dibasic organic acid are prepolymerized at room temperature. The solvent is preferably n-butyl ether, diethyl ether, tetrahydrofuran or methyltetrahydrofuran.

[0021] A preparation process of the above-mentioned biodegradable cigarette packaging film blend material is characterized by:

[0022] Ⅰ) Co-extrusion casting: The materials are placed in a twin-screw extruder, plasticized and melted at high temperature and extruded through the gap between two relatively rotating, horizontally set rollers to form a single-layer sheet;

[0023] II) Biaxial stretching: The single-layer sheet is cut into pieces and placed in a high-temperature double-line film stretching machine. After preheating, it is biaxially stretched in the longitudinal and transverse directions in sequence; cooled and shaped, and then post-processed and slit to form a film.

[0024] Preferably, the melt temperature of the twin-screw extruder in step I) is 160°C to 175°C; in step II) biaxial stretching, the longitudinal and transverse stretching ratios are both 2 to 4 times, the longitudinal and transverse stretching temperatures are both 80°C to 110°C, and the longitudinal and transverse stretching rates are both 60 mm / s to 70 mm / s.

[0025] The biodegradable cigarette packaging film material of the present invention is formed into a sheet after co-extrusion casting and then biaxially stretched to reach a desired thickness. During the biaxial stretching process, the arrangement of the molecular chains is adjusted, further improving the toughness and barrier properties of the film.

[0026] Compared to existing technologies, the biodegradable cigarette packaging film blend material and preparation method of the present invention offer the following advantages: Without the addition of multiple additives, the present invention addresses the difficulty of blending PPCP-T with PLA and PBAT. This also avoids the reduction in strength and barrier properties of the thin cigarette film after the addition of additives. The present invention utilizes a novel prepolymer chain extender to achieve uniform blending of PPCP-T, PLA, and PBAT. The resulting cigarette film maintains high strength while exhibiting enhanced barrier properties. DETAILED DESCRIPTION

[0027] The present invention will be described in detail below by way of examples. Unless otherwise specified, all raw materials used are commercially available.

[0028] Example 1

[0029] Preparation of PPCP-T: 1) Propylene oxide, phthalic anhydride, catalyst 1, and n-butyl ether were placed in an autoclave; catalyst 1 was a composite catalyst of tetra-n-butylammonium halide and triethylboron in a molar ratio of 1:2.2, and the molar ratio of propylene oxide to phthalic anhydride was 2.8:1; and the reaction was carried out at a reaction temperature of 40°C.

[0030] 2) After the phthalic anhydride is completely reacted, triethylboron is added until the molar ratio of tetra-n-butylammonium halide to triethylboron reaches 1:3.0, carbon dioxide is introduced to a reaction pressure of 3.0 MPa, and the reaction temperature is maintained and the reaction is continued until the propylene oxide is completely reacted, and the temperature is lowered and the pressure is released.

[0031] 3) Adding 12% of the propylene oxide and phthalic anhydride obtained in step 1) again, and adding tetra-n-butylammonium chloride until the molar ratio of tetra-n-butylammonium halide to triethylboron reaches 1:2.8, and heating again to the above reaction temperature for reaction. After the monomer reaction is complete, the reaction is terminated to obtain a latex; the latex is washed and devolatilized to obtain the latex.

[0032] Prepolymer preparation: IPDI was added dropwise to a reactor containing phthalic acid and n-butyl ether at a mass ratio of 16:84 at room temperature for polymerization. After the addition was complete, the reaction was continued for 55 minutes. The resulting prepolymer was then separated into a solid and liquid state. The resulting prepolymer had a molecular weight of 3600 and an NCO content of 15.8 wt%.

[0033] Preparation: 30 parts of the obtained PPCP-T, 30 parts of PLA, 50 parts of PBAT, and 0.2 parts of the obtained prepolymer chain extender.

[0034] Preparation of cigarette film: Ⅰ) Co-extrusion casting: Place all materials in a twin-screw extruder with a melt temperature of 170°C; plasticize and melt extrude the materials and press them into a single-layer sheet through the gap between two relatively rotating, horizontally arranged rollers.

[0035] II) Biaxial stretching: Cut the single-layer sheet into pieces and place them in a high-temperature double-line film stretching machine. After preheating, they are biaxially stretched in the longitudinal and transverse directions in sequence. The longitudinal and transverse stretching ratios are both 3 times, the longitudinal and transverse stretching temperatures are both 95°C, and the longitudinal and transverse stretching rates are both 65 mm / s. Cool and shape, and then process them into films after post-processing and slitting.

[0036] Example 2

[0037] Prepare the following materials: 35 parts of PPCP-T prepared in Example 1, 25 parts of PLA, 45 parts of PBAT, and 0.3 parts of the prepolymer chain extender prepared in Example 1. A cigarette film was prepared using the process of Example 1.

[0038] Example 3

[0039] Prepare the following materials: 25 parts of PPCP-T prepared in Example 1, 35 parts of PLA, 55 parts of PBAT, and 0.15 parts of the prepolymer chain extender prepared in Example 1. A cigarette film was prepared using the process of Example 1.

[0040] Example 4

[0041] The materials, proportions, and preparation process were the same as those in Example 1, except that the preparation process of PPCP-T was as follows: 1) propylene oxide, phthalic anhydride, catalyst 1, and 2-methyltetrahydrofuran were placed in an autoclave; catalyst 1 was a composite catalyst of tetra-n-butylammonium halide and triethylboron in a molar ratio of 1:1.3, and the molar ratio of propylene oxide to phthalic anhydride was 2.5:1; and the reaction was carried out at a reaction temperature of 35°C.

[0042] 2) After the phthalic anhydride is completely reacted, triethylboron is added until the molar ratio of tetra-n-butylammonium halide to triethylboron reaches 1:3.0, carbon dioxide is introduced to a reaction pressure of 3.5 MPa, and the reaction temperature is maintained and the reaction is continued until the propylene oxide is completely reacted, and the temperature is lowered and the pressure is released.

[0043] 3) Add 10% of the propylene oxide and phthalic anhydride in step 1) again, add tetra-n-butylammonium chloride until the molar ratio of tetra-n-butylammonium halide to triethylboron reaches 1:2.8, and heat again to the above reaction temperature for reaction. After the monomer reaction is complete, terminate the reaction to obtain a glue solution; the glue solution is washed and devolatilized to obtain the glue solution.

[0044] Example 5

[0045] The materials, proportions, and preparation process were the same as those in Example 1, except that the preparation process of PPCP-T was as follows: 1) propylene oxide, phthalic anhydride, catalyst 1, and tetrahydrofuran were placed in an autoclave; catalyst 1 was a composite catalyst of tetra-n-butylammonium halide and triethylboron in a molar ratio of 1:2.7, and the molar ratio of propylene oxide to phthalic anhydride was 4:1; and the reaction was carried out at a reaction temperature of 45°C.

[0046] 2) After the phthalic anhydride is completely reacted, triethylboron is added until the molar ratio of tetra-n-butylammonium halide to triethylboron reaches 1:3.0, carbon dioxide is introduced to a reaction pressure of 2.4 MPa, and the reaction temperature is maintained and the reaction is continued until the propylene oxide is completely reacted, and the temperature is lowered and the pressure is released.

[0047] 3) Adding 15% of the propylene oxide and phthalic anhydride in step 1) again, adding tetra-n-butylammonium chloride until the molar ratio of tetra-n-butylammonium halide to triethylboron reaches 1:2.8, and heating again to the above reaction temperature for reaction. After the monomer reaction is complete, the reaction is terminated to obtain a glue solution; the glue solution is washed and devolatilized to obtain the glue solution.

[0048] Example 6

[0049] The materials, proportions, and preparation process were the same as in Example 1, except that the prepolymer chain extender was prepared by dropping HTDI at a mass ratio of 12:88 into a reactor pre-filled with isophthalic acid and n-butyl ether at room temperature to initiate a polymerization reaction. After the isocyanate was added according to the proportion, the reaction was continued for 30 minutes. The resulting prepolymer was then separated from the solid and liquid phases. The resulting prepolymer had a molecular weight of 1000 and an NCO content of 11.9 wt%.

[0050] Example 7

[0051] The materials, proportions, and preparation process were the same as in Example 1, except that the prepolymer chain extender was prepared by adding HDI at a mass ratio of 20:80 to a reactor containing oxalic acid and n-butyl ether at room temperature for polymerization. After the isocyanate was added according to the proportion, the reaction was continued for 80 minutes. The resulting prepolymer was then separated from the solid and liquid phases. The resulting prepolymer had a molecular weight of 8000 and an NCO content of 19.6 wt%.

[0052] Example 8

[0053] Prepare the following materials: 20 parts of PPCP-T prepared in Example 1, 40 parts of PLA, 60 parts of PBAT, and 0.5 parts of the prepolymer chain extender prepared in Example 1. A cigarette film was prepared using the process of Example 1.

[0054] Example 9

[0055] Prepare the following materials: 40 parts of PPCP-T prepared in Example 1, 20 parts of PLA, 40 parts of PBAT, and 0.1 parts of the prepolymer chain extender prepared in Example 1. A cigarette film was prepared using the process of Example 1.

[0056] Comparative Example 1

[0057] The materials, proportions, and preparation process were the same as in Example 1, except that an equal amount of PPCP was used instead of PPCP-T. The preparation process for PPCP was as follows: 1) Propylene oxide, phthalic anhydride, and a catalyst were placed in an autoclave; the catalyst was a composite catalyst of tetra-n-butylammonium halide and triethylboron in a molar ratio of 1:2.2, and the molar ratio of propylene oxide to phthalic anhydride was 2.8:1; carbon dioxide was introduced to a reaction pressure of 3.0 MPa and the temperature was raised to 40°C for reaction until the reaction was complete, followed by cooling and pressure relief to obtain a latex; the latex was then washed and devolatilized to obtain the final product.

[0058] Comparative Example 2

[0059] The materials, proportions and preparation process were the same as those in Example 1, except that the prepolymer chain extender was replaced by an equal amount of IPDI.

[0060] The performance indicators of the embodiments and comparative examples are as follows: the data of the performance tests are measured according to relevant national standards.

[0061] <![CDATA[Oxygen transmission rate (cm 3 / m 2 ·24h·0.1MPa)]]> <![CDATA[Water vapor transmission rate (g / m 2 ·24h)]]> Tensile strength (MD) MPa Haze% Thermal shrinkage (MD)% Elastic modulus (MD) MPa Example 1 5.3 4.2 146 1.09 5.4 2597 Example 2 5.0 3.9 148 1.08 5.6 2564 Example 3 5.7 4.5 145 1.09 5.2 2606 Example 4 5.5 4.7 143 1.09 5.5 2581 Example 5 5.9 4.6 143 1.07 5.4 2587 Example 6 5.3 4.3 145 1.10 5.6 2534 Example 7 5.4 4.4 147 1.11 5.7 2529 Example 8 6.9 5.4 139 1.10 5.1 2632 Example 9 4.8 3.6 151 1.09 5.8 2521 Comparative Example 1 10.7 7.9 127 1.27 9.8 2239 Comparative Example 2 8.4 6.3 134 1.21 6.8 2308

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. A biodegradable cigarette packaging film blend material, characterized by: The raw material weight composition is 20 to 40 parts of PPCP-T, 20 to 40 parts of PLA, 40 to 60 parts of PBAT, and 0.1 to 0.5 parts of a chain extender, wherein the chain extender is a prepolymer of an isocyanate and a dibasic organic acid; The preparation process of the PPCP-T is as follows: 1) Propylene oxide, phthalic anhydride, catalyst 1, and solvent are placed in a high-pressure reactor, wherein the molar ratio of propylene oxide to phthalic anhydride is 2.5-4:1; the temperature is raised to a reaction temperature of 35°C-45°C for reaction; 2) After the phthalic anhydride is completely reacted, the second catalyst is added, and carbon dioxide is introduced to a reaction pressure of 2.4 MPa to 3.5 MPa. The reaction temperature is maintained and the reaction is continued until the propylene oxide is completely reacted. The temperature is then lowered and the pressure is released. 3) Adding 10% to 15% of the propylene oxide and phthalic anhydride in step 1) again, adding catalyst 3, and heating to the above reaction temperature again for reaction. After the monomer reaction is complete, the reaction is terminated to obtain a glue solution; the glue solution is washed and devolatilized to obtain; The solvent in step 1) is 2-methyltetrahydrofuran, tetrahydrofuran, or n-butyl ether; the catalyst 1 in step 1) is a composite catalyst of tetra-n-butylammonium halide and triethylboron in a molar ratio of 1:1.3 to 2.7; the catalyst 2 in step 2) is triethylboron; and the catalyst 3 in step 3) is tetra-n-butylammonium chloride. The molecular weight of the prepolymer is 1000-8000; the NCO content in the prepolymer is 12wt%-20wt%; The preparation steps of the prepolymer include: a) adding IPDI dropwise to a reactor pre-filled with phthalic acid and n-butyl ether at room temperature for polymerization reaction, wherein the mass ratio of IPDI to phthalic acid is 16:84; b) After the isocyanate is added dropwise according to the ratio, the reaction is continued for 30 minutes to 80 minutes; then the prepolymer generated by the reaction is separated into solid and liquid.

2. The biodegradable cigarette packaging film blend material according to claim 1, characterized in that: The raw materials are composed of 25 to 35 parts of PPCP-T, 25 to 35 parts of PLA, 45 to 55 parts of PBAT, and 0.15 to 0.3 parts of chain extender in parts by weight.

3. A method for preparing the biodegradable cigarette packaging film blend material according to claim 1 or 2, characterized in that: Ⅰ) Co-extrusion casting: The materials are placed in a twin-screw extruder, plasticized and melted at high temperature and extruded through the gap between two relatively rotating, horizontally set rollers to form a single-layer sheet; II) Biaxial stretching: The single-layer sheet is cut into pieces and placed in a high-temperature double-line film stretching machine. After preheating, it is biaxially stretched in the longitudinal and transverse directions in sequence; cooled and shaped, and then post-processed and slit to form a film.

4. The method for preparing a biodegradable cigarette packaging film blend material according to claim 3, characterized in that: In step I), the melt temperature of the twin-screw extruder is 160° C. to 175° C.; in step II), the longitudinal and transverse stretching ratios in the biaxial stretching are both 2 to 4 times, the longitudinal and transverse stretching temperatures are both 80 to 110° C., and the longitudinal and transverse stretching rates are both 60 mm / s to 70 mm / s.