A bio-based tipping paper based on environmentally degradable materials and a method for its preparation

Abstract

The application discloses a kind of based on environmental degradation material's bio-based cigarette tipping paper and preparation method thereof, belong to tobacco packaging material technical field.The tipping paper includes substrate layer and functional coating coated on its surface, functional coating with molar grafting rate 3%‑12% polycaprolactone grafting glycidyl methacrylate as core film-forming resin, through epoxy group and substrate cellulose hydroxyl group in-situ ring-opening etherification reaction forms covalent bond combination, substrate layer contains 5wt%‑20wt% 2mm‑4mm natural plant short fiber.The application solves the industry pain point that existing degradable tipping paper adhesion is insufficient, degradation behavior is uncontrollable, realizes 0 level highest adhesion and use period stability, ideal mode of fast degradation after disposal, process and existing production line are compatible, adapt to high-speed cigarette production.

Description

Technical Field

[0001] This invention belongs to the technical field of tobacco packaging materials, specifically relating to an environmentally degradable bio-based cigarette tipping paper, and more specifically, to a cigarette tipping paper using epoxy-functionalized polycaprolactone as the core film-forming resin and its preparation method. Background Technology

[0002] Cigarette tipping paper, commonly known as cork paper, is the core packaging material connecting the cigarette filter to the main body of the cigarette. Its performance directly determines the appearance, smoking safety, adaptability to high-speed production, and environmental friendliness throughout the entire life cycle of the cigarette. Traditional cigarette tipping paper often uses a polypropylene plastic film or non-degradable synthetic resin coating on the surface of the base paper to meet the requirements of water resistance, gloss, and printability. However, these products cannot completely degrade in the natural environment after consumption, resulting in persistent microplastic pollution. This is seriously contrary to global "plastic reduction" policies and "dual carbon" development goals, and the industry urgently needs environmentally friendly and degradable alternatives.

[0003] Currently, the mainstream research and development direction of biodegradable tipping paper in the industry mainly focuses on coating systems based on polylactic acid (PLA), polycaprolactone (PCL), and their conventional modifiers. Among them, PLA coatings have the defects of high brittleness, weak adhesion to the paper base, and easy hydrolysis and embrittlement during storage, making them unsuitable for high-speed cigarette production of more than 10,000 cigarettes per minute. Although conventional PCL coatings are more flexible than PLA, they can only form a physical adsorption bond with the paper base, resulting in insufficient adhesion. They are prone to interfacial failure under humid environments and high-speed friction, and the degradation cycle has no clear induction period, failing to achieve the ideal model of "stable during use and rapid degradation after disposal". Existing anhydride grafted modified PCL solutions have improved the bonding force between the coating and the paper base to a certain extent, but they still have problems such as insufficient reactivity, inability to balance coating flexibility and adhesion, and insufficient precision in controlling degradation behavior. They have not yet solved the core contradiction in the industry of biodegradable tipping paper: the inability to simultaneously achieve "high interfacial bonding strength, stable performance during use, and controllable rapid degradation".

[0004] Polycaprolactone-grafted glycidyl methacrylate (PCL-g-GMA), as a known epoxy-functionalized modified polymer material, is currently only used as a reactive compatibilizer in polymer blends and a crosslinking component in adhesive systems. Its application scenarios are limited to improving polymer interfacial compatibility and basic adhesion performance. To date, no existing technology has publicly disclosed or implied its application in the field of cigarette tipping paper, and no related technology has revealed that it can simultaneously achieve high adhesion and controllable degradation performance in the context of cigarette tipping paper. Meanwhile, the development of biodegradable tipping paper in this field has long been path-dependent. Researchers have consistently focused on the technical route of grafting anhydride monomers to modify PCL, generally placing their research emphasis on optimizing the types of anhydride monomers and adjusting the grafting rate. As for epoxy monomer-modified PCL, researchers in this field generally do not consider applying it to the field of cigarette tipping paper. The reason is that, in the conventional understanding of this field, the ring-opening reaction between epoxy groups and cellulose hydroxyl groups requires a special catalyst or a longer reaction time to be fully carried out. However, the coating and drying time of cigarette tipping paper is only tens of seconds, which cannot meet the conventional conditions for epoxy ring-opening reaction. Therefore, there has never been any motivation in this field to introduce epoxy-functionalized polycaprolactone into the research and development system of cigarette tipping paper. Summary of the Invention

[0005] In view of this, the present invention proposes a bio-based cigarette tipping paper based on environmentally degradable materials and its preparation method.

[0006] The technical solution of this invention is implemented as follows:

[0007] In a first aspect, the present invention provides a bio-based cigarette tipping paper based on environmentally degradable materials, comprising a substrate layer and a functional coating coated on at least one side of the substrate layer. The functional coating uses polycaprolactone-grafted glycidyl methacrylate (PCL-g-GMA) as the core film-forming resin, and the content of PCL-g-GMA is 55wt%-75wt% based on the total dry weight of the functional coating. The molar grafting rate of glycidyl methacrylate in PCL-g-GMA is 3%-12%. The functional coating forms covalent bonds with the hydroxyl groups on the surface of the cellulose of the substrate layer through an in-situ ring-opening etherification reaction of the epoxy groups of the side chains of PCL-g-GMA. The substrate layer contains 5wt%-20wt% of natural plant short fibers, and the length of the natural plant short fibers is 2mm-4mm.

[0008] Secondly, the present invention also provides a method for preparing the above-mentioned bio-based cigarette tipping paper based on environmentally degradable materials, comprising the following steps: (1) Substrate preparation: Food-grade bamboo pulp / sugarcane pulp bio-pulp is dispersed with natural plant short fibers with a length of 2mm-4mm in a certain proportion, and after adding a wet strength agent, it is formed to obtain a basis weight of 40g / m 2 -50g / m 2 The base paper of the substrate layer contains natural plant short fibers accounting for 5wt%-20wt% of the total oven-dry fiber content of the substrate layer; (2) Coating preparation: Polycaprolactone-grafted glycidyl methacrylate, glycidyl methacrylate, nano-calcium carbonate, and environmentally friendly plasticizer are mixed and solvent is added to prepare a uniform functional coating. The polycaprolactone-grafted glycidyl methacrylate accounts for 55wt%-75wt% of the total dry weight of the functional coating, and the molar grafting rate of glycidyl methacrylate in the polycaprolactone-grafted glycidyl methacrylate is 3%-12%. (3) Coating reaction: The functional coating is applied to at least one side of the substrate layer and dried at 100℃-130℃ for 10-60 seconds. Simultaneously, the epoxy groups of polycaprolactone grafted with glycidyl methacrylate and the cellulose hydroxyl groups of the substrate layer are reacted in situ to complete the ring-opening etherification reaction, and the bio-based cigarette tipping paper is obtained.

[0009] In some embodiments, the molar grafting rate of the glycidyl methacrylate is 4%-10%.

[0010] This grafting rate range allows for the formation of epoxy active sites of moderate density on the polycaprolactone (PCL) backbone. This ensures sufficient reactive groups to achieve efficient covalent bonding with the cellulose hydroxyl groups, resulting in the highest level of interfacial adhesion. At the same time, it avoids disrupting the linear structure and inherent flexibility of the PCL backbone due to excessive grafting, perfectly balancing the interfacial bonding strength, bending flexibility, and degradation behavior control of the coating. 3% is the lower limit of the grafting rate; below this value, there are insufficient epoxy reactive sites, making it impossible to achieve Grade 0 adhesion and stable, controllable degradation. 12% is the upper limit of the grafting rate; above this value, the branching degree of the PCL backbone significantly increases, increasing the coating's brittleness and making it unsuitable for the high-frequency bending and friction conditions of high-speed cigarette production, while also making the degradation rate uncontrollable.

[0011] In some embodiments, the content of polycaprolactone-grafted glycidyl methacrylate is 55wt%-75wt% based on the total dry weight of the functional coating.

[0012] This content range ensures that the functional coating forms a continuous and complete resin matrix after film formation, providing sufficient matrix support for the interfacial reaction between epoxy groups and cellulose, while also providing a compatible and stable dispersion carrier for various functional additives. If the content is below this range, the coating will have insufficient film-forming properties and will not be able to form a continuous protective system and a complete interfacial reaction layer. If the content is above this range, the coating will have increased rigidity, insufficient space for the addition of functional additives, and a narrowed range for controlling the degradation rate, making it impossible to balance stability during use and degradation efficiency after disposal.

[0013] In some embodiments, the functional coating further includes stigmast and nano-calcium carbonate; the stigmast content is 10wt%-20wt% and the nano-calcium carbonate content is 15wt%-30wt% based on the total dry weight of the functional coating.

[0014] Bright polysaccharide and polycaprolactone grafted glycidyl methacrylate exhibit excellent compatibility, enabling them to synergistically form a dense film-forming structure with the resin matrix. This also imparts certain antibacterial and moisture-proof properties to the coating, making it suitable for oral contact applications and moisture-proof storage requirements of cigarette tipping paper. Nano-calcium carbonate, as an inorganic functional filler, can precisely adjust the smoothness, whiteness, and air permeability of the coating without disrupting the resin film-forming system. This optimizes the printability of the tipping paper and creates pre-defined channels for microbial erosion within the coating, achieving precise control of degradation behavior in synergy with polycaprolactone grafted glycidyl methacrylate.

[0015] In some embodiments, the bio-slurry of the substrate layer is one or a combination of food-grade bamboo pulp and sugarcane pulp; the natural plant short fiber is one or a combination of kenaf short fiber and sisal short fiber.

[0016] Food-grade bamboo pulp and sugarcane pulp are fully bio-based renewable raw materials that can construct the basic fiber network of the substrate layer, ensuring the biosafety, fiber bonding strength, and basic mechanical properties of the substrate, fully meeting the safety requirements for food contact materials. Kenaf and sisal short fibers are high-modulus, high-strength natural plant fibers. Their 2mm-4mm length specifications can form a uniformly distributed three-dimensional reinforcing skeleton in the substrate fiber network, significantly improving the dry and wet tensile strength of the substrate. This avoids the interfacial failure problem of the paper base breaking first when the high-adhesion coating is subjected to stress, and forms a performance synergy with the high adhesion of the functional coating.

[0017] In some embodiments, one side of the substrate layer is coated with the functional coating, and the other side of the substrate layer is coated with an inner adhesive layer; the inner adhesive layer is based on an aqueous solution of oxidized starch or an aqueous solution of sodium carboxymethyl cellulose, and also contains 5wt%-15wt% of a bio-based aqueous polyurethane dispersion by dry weight of the base material.

[0018] Using oxidized starch or sodium carboxymethyl cellulose as the base material ensures the biocompatibility and basic adhesive performance of the inner adhesive layer. The compounded bio-based waterborne polyurethane dispersion can significantly improve the initial tack and holding power between the inner adhesive layer and the cellulose acetate filter tip, avoiding problems such as delamination and edge curling during high-speed winding. At the same time, the inner adhesive layer and the functional coating are respectively set on both sides of the substrate layer, which can form complementary internal and external properties without interfering with each other's functional realization.

[0019] In some embodiments, step (3) employs a gravure coating method with a screen ruling of 140 lines / inch to 180 lines / inch, and the dry coating weight of the functional coating is 6 g / m². 2 -12g / m 2 .

[0020] Gravure coating technology with 140 lines / inch to 180 lines / inch enables micron-level precise control of functional coating thickness, ensuring uniformity and leveling of the coating on the substrate surface, perfectly meeting the high-definition printing requirements of cigarette tipping paper; 6g / m 2 -12g / m 2 The amount of dry coating can balance the protective performance, interfacial bonding strength, flexibility and degradation efficiency of the coating. Too little coating will result in discontinuous coating, insufficient protective performance and adhesion, while too much coating will result in decreased coating flexibility and prolonged degradation cycle, which will fail to meet the requirements of use and environmental protection.

[0021] In some implementations, the drying in step (3) is carried out in a continuous constant temperature drying tunnel for 10 to 60 seconds.

[0022] This drying time range is precisely matched with the process temperature of 100℃-130℃, which ensures that the solvent in the functional coating fully evaporates and the resin matrix completes film formation. It also provides sufficient reaction time for the in-situ ring-opening etherification reaction of epoxy groups and cellulose hydroxyl groups, ensuring the full formation of interfacial covalent bonds. Too short a drying time will result in solvent residue, insufficient film formation, and incomplete interfacial reaction, while too long a drying time will result in yellowing of the paper base and thermal degradation of polycaprolactone resin, affecting the appearance and performance of the tipping paper.

[0023] In some embodiments, prior to step (3), an inner adhesive layer coating is applied to the other side of the substrate layer and dried.

[0024] Applying and drying the inner adhesive layer before the functional coating can prevent the two coatings from interpenetrating and interfering with each other in a wet state. This ensures that the adhesion performance of the inner adhesive layer and the film-forming performance and interfacial reaction process of the functional coating do not affect each other. At the same time, this process sequence is fully compatible with the existing continuous coating production line for cigarette tipping paper, without the need to modify the existing production line, thus lowering the threshold for industrialization.

[0025] In some implementations, after step (3) is completed, the finished product is further subjected to supercalendering, slitting and winding.

[0026] Supercalendering can further improve the smoothness and gloss of the tipping paper surface, optimize its printability and feel, and the slitting and winding process can adjust the finished product to the specifications suitable for cigarette production, achieving seamless integration with existing cigarette production processes.

[0027] In this invention, glycidyl methacrylate (GMA) is used as the grafting monomer instead of other epoxy monomers. The core reason is that the GMA molecule contains both carbon-carbon double bonds that can participate in free radical grafting and epoxy groups that can react with hydroxyl groups. Moreover, its ester side chain structure has excellent compatibility with the PCL backbone, and grafting will not destroy the linear structure and flexibility of the PCL backbone. On the other hand, allyl glycidyl ether (AGE) only contains terminal epoxy groups and carbon-carbon double bonds. After grafting, it is easy to increase the branching degree of the PCL molecular chain, and the coating flexibility will decrease significantly. At the same time, the reactivity of the epoxy groups is lower than that of GMA. Under the same process conditions, the ring-opening reaction conversion rate is less than 60%, and it is impossible to achieve the synergistic effect of grade 0 adhesion and controllable degradation.

[0028] The present invention has the following advantages over the prior art: This invention breaks away from the long-standing reliance on anhydride-modified polycaprolactone (PCV) for developing biodegradable cigarette tipping paper. It pioneeringly applies PCV grafted with glycidyl methacrylate (GMMA) to cigarette tipping paper for the first time. A stable covalent interface is constructed through the in-situ ring-opening etherification reaction of epoxy groups and cellulose hydroxyl groups, fundamentally solving the industry pain points of insufficient coating adhesion and easy peeling during high-speed production in existing biodegradable tipping papers. Simultaneously, through material structure design, a controllable degradation mode is achieved, ensuring stable performance throughout the tipping paper's service life and rapid degradation after disposal, thus resolving the core contradiction in existing technologies where stability and rapid degradability cannot be simultaneously achieved. Compared to existing conventional biodegradable tipping paper solutions, this invention achieves comprehensive improvements in interface bonding stability, mechanical properties, printability, and controllable degradation. The core embodiments show a final biodegradation rate of ≥90% after 180 days, fully complying with national standards for fully biodegradable materials, fundamentally solving the microplastic pollution problem of traditional tipping paper. Furthermore, the overall preparation process of this invention is fully compatible with existing cigarette tipping paper coating production lines, requiring no large-scale equipment modifications. While meeting the performance requirements of the entire cigarette production process, it achieves environmental friendliness throughout the product's entire life cycle, providing a brand-new, industrializable solution for the environmental transformation of tobacco packaging materials. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] Raw materials and equipment description The preparation processes of all examples and comparative examples are completely consistent in terms of raw material specifications, equipment models, and basic process parameters, except for the single variable that is clearly marked, to ensure that the experimental data have parallel control and reproducibility.

[0031] General raw materials Polycaprolactone (PCL, number average molecular weight Mn=80000, industrial grade); Glycidyl methacrylate (GMA, analytical grade); Maleic anhydride (MAH, analytical grade); Itaconic anhydride (IA, analytical grade); Allyl glycidyl ether (AGE, analytical grade); Dicumyl peroxide (DCP, analytical grade, initiator); Food-grade bamboo pulp board; Kenaf short fiber, sisal short fiber (2-4mm in length, papermaking grade); Polyamide epichlorohydrin resin (PAE, wet strength agent, paper grade); Leucoglucan (degree of deacetylation ≥90%, food grade); Nano-sized calcium carbonate (80nm particle size, industrial grade); Triethyl citrate (analytical grade, plasticizer); Oxidized starch (food grade); Bio-based waterborne polyurethane dispersion (30% solids content, industrial grade); Ethyl acetate (analytical grade, solvent).

[0032] General equipment Twin-screw extruder; Pilot-scale equipment for long-wire paper machine; High-speed disperser; Sand mill; Gravure coating machine; Constant temperature and humidity drying tunnel; Supercalender; Universal material testing machine; Cross-cut adhesion tester; Printing abrasion resistance tester; Simulated composting test chamber.

[0033] Core parameter measurement methods 1. Method for determining the molar grafting rate of glycidyl methacrylate The grafting rate was determined using acid-base titration. The specific steps are as follows: (1) Accurately weigh 2g of the PCL-g-GMA resin particles to be tested, dissolve them in 40mL of hot xylene, cool to room temperature after complete dissolution, and dilute with 25mL of anhydrous ethanol. (2) Add 25 mL of 0.1 mol / L potassium hydroxide-ethanol standard solution to the solution and reflux in a 60°C constant temperature water bath for 2 hours to completely neutralize the anhydride groups; (3) Using phenolphthalein-ethanol solution as an indicator, titrate excess potassium hydroxide with 0.1 mol / L hydrochloric acid-isopropanol standard solution until the red color of the solution completely disappears as the titration endpoint, and record the volume of hydrochloric acid standard solution consumed. (4) Perform a blank control experiment simultaneously and calculate the molar grafting rate using the following formula: Grafting rate (%) = [(V0-V1)×C×M_GMA×10] -3 / m]×100% In the formula: V0 is the volume of hydrochloric acid standard solution consumed in the blank test (mL); V1 is the volume of hydrochloric acid standard solution consumed in the sample titration (mL); C is the concentration of hydrochloric acid standard solution (mol / L); M_GMA is the molar mass of glycidyl methacrylate (g / mol); m is the mass of the sample to be tested (g).

[0034] 2. Method for determining the molar grafting rate of allyl glycidyl ether The same acid-base titration method as the above-mentioned GMA grafting rate was used for determination, except that M_GMA in the formula was replaced with the molar mass of allyl glycidyl ether, and the rest of the test steps were completely the same.

[0035] 3. Verification and Conversion Rate Determination Methods for Interfacial Covalent Bonding Reactions The in-situ ring-opening etherification reaction was verified using Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The conversion rate of the ring-opening reaction was calculated by the change in the peak area of ​​the characteristic peak of the epoxy group in the infrared spectrum. The specific method is as follows: (1) Infrared spectroscopy test: Pure PCL-g-GMA resin, uncoated substrate paper, and coated tipping paper samples were tested respectively, with a wavenumber range of 4000 cm⁻¹. -1 -400cm -1 ; with 2940cm -1 The characteristic peak of the PCL methylene group at 910 cm⁻¹ was used as an internal standard. -1The change in peak area of ​​the characteristic absorption peak of the epoxy group is used to calculate the ring-opening reaction conversion rate of the epoxy group; (2) XPS test: The C1s and O1s high-resolution scans of the sample surface before and after the coating reaction were performed. The formation of interfacial covalent bonds was further verified by the change in the peak area of ​​the COC ether bond characteristic combined with the energy peak at 286.3eV.

[0036] 4. Final biodegradation rate test method Test Standard: GB / T19277.1-2011 "Determination of Final Aerobic Biodegradability of Materials under Controlled Composting Conditions - Method for Measuring Released Carbon Dioxide" Test steps: (1) Cut the sample into 1cm×1cm fragments, accurately weigh 100g of sample and put it into the test bottle for inoculation composting, and set up blank control bottle and reference sample bottle; (2) Control the composting environment temperature to 58±2℃, relative humidity ≥80%, and oxygen concentration ≥18%, and regularly measure the cumulative amount of carbon dioxide released in the test bottle; (3) The test period is 180 days. The final biodegradation rate of the sample is calculated based on the cumulative carbon dioxide release. Three groups are tested in parallel, and the average value of the results is taken.

[0037] Example 1 Step 1: Preparation of modified resin: Take 100 parts by weight of PCL granules, 8 parts by weight of GMA monomer, and 0.6 parts by weight of DCP initiator, and premix them in a high-speed mixer at room temperature for 10 minutes to obtain a uniform premix. Feed the premix into a twin-screw extruder, and under a nitrogen protective atmosphere, control the extrusion temperature at 160℃, the screw speed at 300rpm, and the material residence time at 3 minutes to complete the melt grafting reaction. After water cooling and pelletizing, epoxy functionalized polycaprolactone PCL-g-GMA resin granules with a molar grafting rate of 6% are obtained and sealed for later use.

[0038] Step 2: Preparation of the base paper: Take 85 parts by weight of food-grade bamboo pulp board and 15 parts by weight of 3mm long kenaf short fibers, add them to water for dispersing and prepare a pulp with a concentration of 3.5%; add 0.5 parts by weight of PAE wet strength agent to the pulp, stir evenly, and then form it on a fourdrinier paper machine, press and dewater it, and dry it in a multi-cylinder drying oven to obtain a basis weight of 45g / m². 2 The base paper is stored in a constant temperature and humidity environment for later use.

[0039] Step 3: Preparation of functional coating: On a dry weight basis, take 70 parts by weight of the PCL-g-GMA resin prepared in Step 1, 15 parts by weight of bright polysaccharide, 12 parts by weight of nano calcium carbonate, 3 parts by weight of triethyl citrate, and 0.5 parts by weight of ammonium polyacrylate dispersant, add them to ethyl acetate solvent, disperse them in a high-speed disperser for 30 minutes, grind them twice in a sand mill, and adjust them to a uniform functional coating with a solid content of 25%. Seal and set aside for later use.

[0040] Step 4: Coating and In-situ Reaction: Using a 160 lines / inch gravure coating machine, the functional coating prepared in Step 3 is uniformly coated onto the first side of the substrate paper prepared in Step 2. Immediately after coating, the paper is placed in a constant temperature and humidity drying tunnel. The tunnel temperature is controlled at 120°C and the drying time is 30 seconds. Simultaneously, the coating dries and forms a film, and the in-situ ring-opening etherification reaction between the PCL-g-GMA side chain epoxy groups and the cellulose hydroxyl groups of the substrate layer is completed. The dry coating amount is controlled at 8 g / m². 2 .

[0041] Step 5 Post-processing: The coated paper is fed into a supercalender and calendered at a temperature of 60℃ and a linear pressure of 120N / mm. Finally, it is slit and wound to obtain the finished tipping paper.

[0042] Example 2 Step 1: Preparation of modified resin: Take 100 parts by weight of PCL particles, 12 parts by weight of GMA monomer, and 0.9 parts by weight of DCP initiator, and prepare PCL-g-GMA resin particles with a molar grafting rate of 8% by following the same process as in Step 1 of Example 1.

[0043] Step 2: Preparation of the base paper: Take 90 parts by weight of food-grade bamboo pulp board and 10 parts by weight of sisal short fibers with a length of 3 mm, and process them according to the same procedure as in Step 2 of Example 1 to obtain a paper with a basis weight of 45 g / m³. 2 The base paper of the substrate layer.

[0044] Step 3: Preparation of functional coating: Based on dry weight, take 65 parts by weight of the PCL-g-GMA resin prepared in Step 1, 18 parts by weight of bright polysaccharide, 15 parts by weight of nano calcium carbonate, and 2 parts by weight of triethyl citrate, and prepare a functional coating with a solid content of 25% by the same process as in Step 3 of Example 1.

[0045] Step 4: Coating and In-situ Reaction: Coating was performed using a 160 lines / inch gravure coater, with the oven temperature controlled at 125°C and the drying time at 30 seconds. The dry coating weight of the functional coating was 10 g / m². 2 The remaining processes are the same as step 4 of Example 1.

[0046] Step 5 Post-processing: Same as step 5 of Example 1, to obtain the finished splicing paper.

[0047] Example 3 In step 1, the amount of GMA monomer was adjusted to 4 parts by weight and the amount of DCP was adjusted to 0.3 parts by weight to prepare PCL-g-GMA resin particles with a molar grafting rate of 3%. All other preparation steps, process parameters, and raw material ratios were completely consistent with those in Example 1, and the finished tipping paper was obtained.

[0048] Example 4 In step 1, the amount of GMA monomer was adjusted to 16 parts by weight and the amount of DCP was 1.0 parts by weight to prepare PCL-g-GMA resin particles with a molar grafting rate of 12%. All other preparation steps, process parameters, and raw material ratios were completely consistent with those in Example 1 to obtain the finished tipping paper.

[0049] Example 5 Only two parameters were adjusted: in step 2, the amount of kenaf short fiber in the preparation of the base paper was adjusted to 5 parts by weight and the amount of bamboo pulp board was adjusted to 95 parts by weight; in step 4, the coating and in-situ reaction, the drying tunnel temperature was adjusted to 100℃; all other preparation steps, process parameters, and raw material ratios were completely consistent with those in Example 1, and the finished tipping paper was obtained.

[0050] Example 6 Only two parameters were adjusted: in step 2, the amount of kenaf short fiber in the preparation of the base paper was adjusted to 20 parts by weight and the amount of bamboo pulp board was adjusted to 80 parts by weight; in step 4, the coating and in-situ reaction, the drying tunnel temperature was adjusted to 130℃; all other preparation steps, process parameters, and raw material ratios were completely consistent with those in Example 1, and the finished tipping paper was obtained.

[0051] Example 7 Only three parameters were adjusted: In step 1, the modified resin preparation, PCL-g-GMA resin particles with a molar grafting rate of 4% were prepared; in step 2, the base paper preparation, the amount of kenaf short fibers was adjusted to 10 parts by weight; in step 4, coating and in-situ reaction, the dry coating amount of the functional coating was adjusted to 6 g / m². 2 All other preparation steps, process parameters, and raw material ratios are completely consistent with those in Example 1, resulting in the finished tipping paper.

[0052] Example 8 Steps 1-3 are the same as the preparation process in Example 2; Step 4: Inner Adhesive Layer Coating: Using a metering rod coater, the inner adhesive layer coating is evenly coated onto the second side of the base paper. The coating formulation is an aqueous solution of oxidized starch (15% solid content), with 10% (by dry weight of oxidized starch) of a bio-based aqueous polyurethane dispersion added. After coating, the paper is dried in a 110℃ oven, with a dry coating weight of 3 g / m². 2 ; Step 5: Coating of the outer functional layer and in-situ reaction: The process is the same as in step 4 of Example 2. The functional coating is coated on the first side of the substrate layer and the in-situ reaction is completed. Step 6 Post-processing: Same as step 5 in Example 1, to obtain the finished splicing paper.

[0053] Example 9 In step 1, the modified resin preparation was carried out by replacing GMA monomer with an equal part by weight of allyl glycidyl ether (AGE) to prepare AGE-grafted PCL resin particles with a molar grafting rate of 6%. All other preparation steps, process parameters, and raw material ratios were completely consistent with those in Example 1, and the finished tipping paper was obtained.

[0054] Example 10 In step 3, the functional coating preparation was carried out by replacing ethyl acetate solvent with deionized water to prepare PCL-g-GMA into an aqueous dispersion with a solid content of 40%. This dispersion was then mixed with the remaining raw materials to prepare an aqueous functional coating with a solid content of 28%. All other preparation steps, process parameters, and raw material ratios were completely consistent with those in Example 1, resulting in the finished tipping paper.

[0055] specific: Step 3: Preparation of Functional Coating: Based on dry weight, take 70 parts by weight of the PCL-g-GMA resin prepared in Example 1, 15 parts by weight of stigmosaccharide, 12 parts by weight of nano-calcium carbonate, 3 parts by weight of triethyl citrate, 0.5 parts by weight of ammonium polyacrylate dispersant, and 2 parts by weight of Tween 80 emulsifier. First, dissolve the PCL-g-GMA resin in ethyl acetate, add the emulsifier, and stir at high speed for 30 minutes to form an oil phase. Then, slowly add deionized water to the oil phase, emulsify at high speed for 20 minutes, and remove the ethyl acetate by vacuum distillation to obtain a PCL-g-GMA aqueous dispersion with a solid content of 40%. Mix the aqueous dispersion with the remaining raw materials, disperse at high speed, and mill to prepare a uniform aqueous functional coating with a solid content of 28%. Seal and store for later use. Comparative Example 1 In step 1, the modified resin preparation was carried out by replacing GMA monomer with an equal part by weight of maleic anhydride (MAH) to prepare PCL-g-MAH resin particles with a molar grafting rate of 8%. All other preparation steps, process parameters, and raw material ratios were completely consistent with those in Example 1, and a control sample was obtained.

[0056] Comparative Example 2 In step 1, the modified resin preparation was carried out by replacing GMA monomer with an equal part by weight of itaconic anhydride (IA) to prepare PCL-g-IA resin particles with a molar grafting rate of 7%. All other preparation steps, process parameters, and raw material ratios were completely consistent with those in Example 1, and a control sample was obtained.

[0057] Comparative Example 3 In step 3, the preparation of the functional coating was carried out by replacing PCL-g-GMA resin with an equal weight of unmodified PCL resin. All other preparation steps, process parameters, and raw material ratios were completely consistent with those in Example 1, resulting in a control sample.

[0058] Comparative Example 4 In step 3, the preparation of the functional coating was carried out by replacing PCL-g-GMA resin with an equal weight of polylactic acid PLA resin; in step 4, the coating and in-situ reaction were carried out by adjusting the oven temperature to 140°C; all other preparation steps and raw material ratios were completely consistent with those in Example 1, and a control sample was obtained.

[0059] Comparative Example 5 In step 1, the amount of GMA monomer was adjusted to 2 parts by weight and the amount of DCP was adjusted to 0.2 parts by weight to prepare PCL-g-GMA resin particles with a molar grafting rate of 2%. All other preparation steps, process parameters, and raw material ratios were completely consistent with those in Example 1, and a control sample was obtained.

[0060] Comparative Example 6 In step 1, the amount of GMA monomer was adjusted to 20 parts by weight and the amount of DCP was adjusted to 1.2 parts by weight to prepare PCL-g-GMA resin particles with a molar grafting rate of 15%. All other preparation steps, process parameters, and raw material ratios were completely consistent with those in Example 1, and a control sample was obtained.

[0061] Comparative Example 7 Only in step 4, coating and in-situ reaction, the oven temperature was adjusted to 90°C. All other preparation steps, process parameters, and raw material ratios were completely consistent with those in Example 1, resulting in a control sample.

[0062] Comparative Example 8 Only in step 4, coating and in-situ reaction, the oven temperature was adjusted to 140°C. All other preparation steps, process parameters, and raw material ratios were completely consistent with those in Example 1, resulting in a control sample.

[0063] Comparative Example 9 In step 2, the base paper preparation used 100% food-grade bamboo pulp board without adding kenaf short fibers. All other preparation steps, process parameters, and raw material ratios were completely consistent with those in Example 1, resulting in a control sample.

[0064] Comparative Example 10 In step 4, the coating and in-situ reaction were modified only by adjusting the oven temperature to 90°C and the drying time to 10 seconds to ensure that the epoxy groups did not undergo ring-opening etherification. All other preparation steps, process parameters, and raw material ratios were completely consistent with those in Example 1, resulting in a control sample.

[0065] Comparative Example 11 In step 3, the functional coating formulation was carried out without adding bright polysaccharide and nano calcium carbonate. Only 70 parts by weight of PCL-g-GMA resin, 3 parts by weight of triethyl citrate, and 0.5 parts by weight of dispersant were retained. All other preparation steps and process parameters were completely consistent with those in Example 1, and a control sample was obtained.

[0066] Comparative Example 12 In step 3, the preparation of the functional coating was carried out by replacing PCL-g-GMA resin with an equal part by weight of epoxy-modified acrylic resin. All other preparation steps, process parameters, and raw material ratios were completely consistent with those in Example 1, resulting in a control sample.

[0067] Comparative Example 13 The preparation was carried out entirely according to the conventional combination of existing technologies: Step 1 used PCL-g-GMA (molar grafting rate of 2%) as an adhesive disclosed in Comparative Document 2; Step 2 used pure bamboo pulp base paper disclosed in Comparative Document 1 without adding natural reinforcing fibers; Step 3 used the conventional biodegradable coating formulation disclosed in Comparative Document 1 without adding bright polysaccharides; Step 4 used the 100℃ drying process disclosed in Comparative Document 1 without controlling the in-situ ring-opening reaction; the remaining basic processes were the same as in Example 1, and a control sample was obtained.

[0068] Performance verification All samples from the examples and comparative examples were placed in a constant temperature and humidity environment of 23°C and 50% relative humidity for 24 hours before the following performance tests were conducted. All tests were performed in parallel three times, and the average value of the results was taken.

[0069] 1. Coating adhesion test Test standard: GB / T 9286-1998 "Cross-cut test for paint and varnish film".

[0070] Test procedure: Using a cross-cut adhesion tester, a 6×6 grid is cut on the sample coating surface with a grid spacing of 1mm, and the cutting depth penetrates the coating to the substrate layer; use a soft brush to sweep back and forth 5 times along the diagonal direction of the grid, apply standard test tape and quickly peel it off, observe the coating peeling, and determine the adhesion level according to the standard (level 0 is the best, no coating peeling; level 5 is the worst, large area of ​​coating peeling).

[0071] 2. Wet tensile strength test Test standard: GB / T 465.2-2008 Determination of tensile strength of paper and paperboard after immersion in water.

[0072] Test procedure: Cut the sample into standard specimens of 15mm×180mm and immerse them completely in deionized water at 23℃ for 60 seconds; remove the specimens and use filter paper to absorb the surface water, and immediately use a universal testing machine to test the transverse tensile strength of the specimens at a tensile speed of 20mm / min. Record the maximum tensile strength when the specimen breaks and calculate the wet tensile strength in kN / m.

[0073] 3. Controlled degradation performance test Test standard: ISO 14855-1:2012 "Determination of the final aerobic biodegradability of plastic materials under controlled composting conditions".

[0074] Test procedure: Cut the sample into 1cm×1cm fragments, weigh them accurately, and place them in the test bottle containing compost. The composting environment is controlled at a temperature of 58±2℃ and a relative humidity of ≥80%. Samples are taken on days 0, 30, 60, and 90 of the experiment. The surface of the samples is cleaned to remove compost residues. After vacuum drying to constant weight, the samples are weighed accurately, and the weight loss rate is calculated. At the same time, the degradation state of the samples is observed, and the degradation behavior characteristics are summarized.

[0075] 4. Abrasion resistance test of printing ink Test standard: GB / T 7706-2008 "Relief Printing of Decorative Matter".

[0076] Test procedure: Print standard test color patches on the sample coating surface using an offset printing machine. The dry film thickness of the ink is 2μm, and the sample is left to stand for 24 hours. Use a printing abrasion tester with an ink density of 80g / m². 2 Standard offset paper was used as the friction medium, with a load of 20N, a friction speed of 43 times / minute, and 200 friction cycles. The density change of the color block before and after friction was tested, the density retention rate was calculated, and the abrasion resistance level was determined according to the standard (≥4.5 is the best, ≤3.0 is unqualified).

[0077] 5. Verification of interfacial covalent bonding reaction The occurrence of the in-situ ring-opening etherification reaction was verified using Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The specific methods are as follows: (1) Infrared spectroscopy test: Pure PCL-g-GMA resin, uncoated substrate paper, and coated tipping paper samples were tested respectively, with a wavenumber range of 4000 cm⁻¹. -1 -400cm -1 The coated sample was placed at 1100 cm⁻¹. -1 The characteristic absorption peak of the aliphatic ether bond formed by the ring opening of cellulose and epoxy appears at 910 cm⁻¹, while the epoxy group shows a peak at 910 cm⁻¹. -1 The characteristic absorption peak at the point of absorption is significantly weakened, indicating that the epoxy group and the cellulose hydroxyl group have undergone a ring-opening etherification reaction.

[0078] (2) XPS test: C1s and O1s high-resolution scans were performed on the sample surface before and after the coating reaction. The sample after the reaction showed the characteristic binding energy peak of COC ether bond at 286.3eV, and the peak area ratio was significantly increased, further proving the formation of interfacial covalent bonds.

[0079] Meanwhile, reaction conversion data is added after step 4 of Example 1: According to the above method, the ring-opening reaction conversion rate of epoxy groups in this example is ≥85%, and the interfacial covalent bonding is sufficient.

[0080] 6. Final biodegradation rate test Test Standard: GB / T 19277.1-2011 "Determination of Final Aerobic Biodegradability of Materials under Controlled Composting Conditions—A Method for Measuring Released Carbon Dioxide" Test results: The samples in Examples 1-8 all had a final biodegradation rate of ≥90% within a 180-day composting period, which meets the national standard requirements for fully biodegradable materials; while the epoxy-modified acrylic resin sample in Comparative Example 12 had a biodegradation rate of <15% after 180 days and did not have biodegradability.

[0081] Performance test results

[0082]

[0083] The test results of the above embodiments and comparative examples show that, by using polycaprolactone grafted with glycidyl methacrylate at a molar grafting rate of 3%-12% as the core film-forming resin, combined with the in-situ ring-opening etherification reaction of epoxy groups and cellulose hydroxyl groups, and the design of a natural plant short fiber reinforced substrate, this invention can stably achieve the highest adhesion grade 0, excellent wet tensile strength, and printable abrasion resistance of the coating within the full parameter range defined in the claims. Simultaneously, it exhibits an ideal controllable degradation mode of 30-day induced stabilization period followed by rapid degradation, completely solving the core technical problems proposed in this invention. The final biodegradation rate of all core embodiments within 180 days is ≥90%, fully complying with the national standard for fully biodegradable materials, fundamentally solving the industry pain points of microplastic residues and incomplete degradation existing in traditional tipping paper and current biodegradable solutions. Compared with existing technologies such as anhydride-grafted modified PCL, unmodified PCL, and PLA, this invention achieves qualitative improvements in interfacial bonding stability, controllable degradation behavior, and final biodegradation rate. Control schemes that deviate from the parameter range of this invention and lack core essential technical features fail to simultaneously meet the core performance requirements and the requirement for full biodegradability, fully demonstrating the clear technical necessity and irreplaceability of the parameter limitations and combination of technical features of this invention. The overall preparation process of this invention is fully compatible with existing cigarette tipping paper coating production lines, and its comprehensive performance fully meets the requirements of high-speed cigarette production, possessing excellent feasibility and industrialization value.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A bio-based cigarette tipping paper based on environmentally degradable materials, comprising a substrate layer and a functional coating applied to at least one side of the substrate layer, characterized in that, The functional coating uses polycaprolactone-grafted glycidyl methacrylate as the core film-forming resin. Based on the total dry weight of the functional coating, the content of polycaprolactone-grafted glycidyl methacrylate is 55wt%-75wt%. The molar grafting rate of glycidyl methacrylate in the polycaprolactone-grafted glycidyl methacrylate is 3%-12%. The functional coating forms covalent bonds with the hydroxyl groups on the surface of the cellulose substrate layer through an in-situ ring-opening etherification reaction of the epoxy groups on the side chains of the polycaprolactone-grafted glycidyl methacrylate. The substrate layer contains 5wt%-20wt% of natural plant short fibers, with a length of 2mm-4mm.

2. The bio-based cigarette tipping paper according to claim 1, characterized in that, The molar grafting rate of the glycidyl methacrylate is 4%-10%.

3. The bio-based cigarette tipping paper according to claim 1, characterized in that, The functional coating also includes stigmas and nano-calcium carbonate; based on the total dry weight of the functional coating, the stigmas content is 10wt%-20wt% and the nano-calcium carbonate content is 15wt%-30wt%.

4. The bio-based cigarette tipping paper according to claim 1, characterized in that, The bio-pulp of the substrate layer is one or a combination of two of food-grade bamboo pulp and sugarcane pulp; the natural plant short fiber is one or a combination of two of kenaf short fiber and sisal short fiber.

5. The bio-based cigarette tipping paper according to claim 1, characterized in that, One side of the substrate layer is coated with the functional coating, and the other side of the substrate layer is coated with an inner adhesive layer; the inner adhesive layer uses oxidized starch aqueous solution or carboxymethyl cellulose sodium aqueous solution as the base material, and also adds 5wt%-15wt% of bio-based waterborne polyurethane dispersion by dry weight of the base material.

6. A method for preparing bio-based cigarette tipping paper based on environmentally degradable materials as described in any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Substrate preparation: Food-grade bamboo pulp or sugarcane pulp bio-pulp is dispersed with natural plant short fibers with a length of 2mm-4mm in a certain proportion, and after adding a wet strength agent, it is formed into a sheet with a basis weight of 40g / m 2 -50g / m 2 The base paper of the substrate layer contains natural plant short fibers accounting for 5wt%-20wt% of the total oven-dry fiber content of the substrate layer; (2) Coating preparation: Polycaprolactone-grafted glycidyl methacrylate, glycidyl methacrylate, nano-calcium carbonate, and environmentally friendly plasticizer are mixed and solvent is added to prepare a uniform functional coating. The polycaprolactone-grafted glycidyl methacrylate accounts for 55wt%-75wt% of the total dry weight of the functional coating, and the molar grafting rate of glycidyl methacrylate in the polycaprolactone-grafted glycidyl methacrylate is 3%-12%. (3) Coating reaction: The functional coating is applied to at least one side of the substrate layer and dried at 100℃-130℃ for 10-60 seconds. Simultaneously, the epoxy groups of polycaprolactone grafted with glycidyl methacrylate and the cellulose hydroxyl groups of the substrate layer are reacted in situ to complete the ring-opening etherification reaction, and the bio-based cigarette tipping paper is obtained.

7. The preparation method according to claim 6, characterized in that, In step (3), a gravure coating method with a screen ruling of 140 lines / inch to 180 lines / inch is used for coating, and the dry coating weight of the functional coating is 6 g / m². 2 -12g / m 2 .

8. The preparation method according to claim 6, characterized in that, In step (3), the drying is carried out in a continuous constant temperature drying tunnel for 20-40 seconds.

9. The preparation method according to claim 6, characterized in that, Before step (3), the process also includes coating the other side of the substrate layer with an inner adhesive layer coating and drying it. The inner adhesive layer coating is based on an aqueous solution of oxidized starch or an aqueous solution of sodium carboxymethyl cellulose, and contains 5wt%-15wt% of a bio-based aqueous polyurethane dispersion by dry weight of the base material.

10. The preparation method according to claim 6, characterized in that, After step (3) is completed, the process also includes supercalendering, slitting and rewinding of the finished product.

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