Environment-friendly composite tea bag and preparation method thereof

Abstract

This invention belongs to the field of tea bag packaging technology and discloses an environmentally friendly composite tea bag and its preparation method to solve the problems existing in the current tea bag packaging technology. The tea bag consists of a bag body made of composite roll film, with an expansion and contraction strip inside the bag body. The expansion and contraction strip consists of a strip body and contents sealed within the strip body. The strip body is made of food contact grade water-permeable packaging material. The contents within the strip body can expand after absorbing water, and the strip body is provided with several hard serrations at intervals. This invention uses hard serrations to actively create deterministic and regularly distributed pre-puncture holes during the brewing stage, fundamentally solving the randomness problem of "when and where" cracks will initiate. By pre-setting the macroscopic crack propagation path through a high-water-loss shrinkage warp network, this invention can achieve complete biodegradation in the natural environment within 180 days. The final products are environmentally harmless H2O, CO2, and humus, completely eliminating microplastics and any form of persistent pollution.

Description

Technical Field

[0001] This invention relates to the field of tea bag packaging technology, specifically to an environmentally friendly composite tea bag and its preparation method. Background Technology

[0002] Tea bags have become a widely accepted form of tea consumption in today's fast-paced lifestyle due to their convenience, hygiene, and portability. Traditional tea bags typically use non-woven fabric, nylon, PET, or composite films of these materials with aluminum foil as packaging. These materials maintain their structural integrity during brewing, preventing tea leakage and providing a consistent user experience. However, these materials degrade at extremely slow rates in the natural environment, taking decades or even centuries to completely decompose after disposal, placing a long-term burden on the environment.

[0003] In particular, tea bags are typically discarded along with the tea leaves after use. Existing packaging materials cannot quickly rupture after disposal, leaving the tea leaves sealed and severely limiting their contact with external microorganisms, moisture, and oxygen. This slows down or even inhibits the biodegradation process of the tea leaves. In landfill environments, such packaging easily creates localized anaerobic microenvironments, promoting the growth of sulfate-reducing bacteria and other microorganisms, producing corrosive gases such as hydrogen sulfide. This not only exacerbates the corrosion of landfill equipment but also necessitates additional desulfurization processes, increasing treatment costs. Simultaneously, the incomplete degradation of organic matter in the tea leaves may generate intermediate products such as aldehydes and ketones, and even induce the growth of harmful microorganisms such as Aspergillus flavus and the accumulation of their toxins, posing a potential threat to the ecological environment and human health.

[0004] In recent years, the market has seen the emergence of "biodegradable tea bags" aimed at improving environmental performance. Their technological approaches typically rely on a single biodegradable material (such as pure PLA or starch-based materials) or a physically-induced cracking structure (such as water-soluble fibers or pre-installed weak threads). However, these solutions generally suffer from the following unresolved technical shortcomings in achieving a dynamic balance between "usage strength" and "post-disposal brittleness," particularly in achieving "rapid and controllable post-disposal cracking":

[0005] First, there is a contradiction between the degradation performance and rupture reliability of a single material: pure PLA or starch-based materials degrade slowly in the post-disposal environment, and their shrinkage and rupture behavior is random and unpredictable, making it impossible to guarantee the stable and efficient exposure of tea residue. Experiments show that the coefficient of variation of the rupture area can exceed 30% 24 hours after disposal.

[0006] Secondly, there are challenges to the controllability and production feasibility of physically-induced cracking structures: Solutions with built-in water-soluble fibers or brittle particles are prone to displacement during high-speed encapsulation, and the crack triggering conditions are unstable. Pre-installed laser weak lines may become stress weak points during the brewing stage, or become clogged by tea residue after disposal, thus inhibiting crack propagation.

[0007] Third, there is a lack of macroscopic fracture guidance mechanisms: existing technologies rely on the uniform shrinkage of the material itself, resulting in large fluctuations in the fracture morphology and area. Essentially, there is a lack of guiding structures to guide stress release and crack propagation on a macroscopic scale, which prevents a breakthrough in the key technological bottleneck of shifting fracture behavior from "random" to "directional." Therefore, it is urgent to solve the above-mentioned technical problems. Summary of the Invention

[0008] The purpose of this invention is to solve the problems existing in the existing tea bag packaging technology, and to provide an environmentally friendly composite tea bag that can maintain structural integrity and ease of use during the brewing stage, and can break down quickly after disposal, making the post-disposal breakage behavior highly controllable and predictable, thereby significantly improving the stability and degradation efficiency of tea residue exposure.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] An environmentally friendly composite tea bag, characterized in that it includes a bag body made of composite roll film, and the bag body has at least two expansion and stretch strips inside;

[0011] The composite roll film includes a base film and high-water-loss shrinkage warp embedded in the base film;

[0012] The base film includes a matrix layer and a reinforcing dispersant uniformly dispersed in the matrix layer;

[0013] The matrix layer is composed of food-grade corn starch-based material, polylactic acid, chitosan, and sodium carboxymethyl cellulose; the food-grade corn starch-based material accounts for 40%-60%, polylactic acid accounts for 15%-25%, chitosan accounts for 10%-20%, and sodium carboxymethyl cellulose accounts for 5%-15%.

[0014] The reinforcing dispersant is composed of plant fiber, citric acid and nanocellulose, wherein the plant fiber accounts for 5%-15% of the total weight of the matrix layer, the citric acid accounts for 0.5%-3% of the total weight of the matrix layer, and the nanocellulose accounts for 1%-5% of the total weight of the matrix layer.

[0015] The expandable strip consists of a strip body and contents encapsulated within the strip body. The strip body is made of food-contact grade water-permeable packaging material, and the longitudinal cross-section of the strip body along its length is arc-shaped. The contents within the strip body can expand to 90-100 times their original volume after absorbing water. Furthermore, the strip body is provided with several hard serrations at intervals.

[0016] Under conditions of water loss, the bag shrinks, and under the tension of the expansion strip, the pre-puncture stress of the hard serrations, and the guidance of the high-water-loss shrinkage warp, the bag ruptures.

[0017] Furthermore, the strip satisfies: C2≥1.3×C1; A2≥1.5×A1, where C1 and A1 are the perimeter and cross-sectional area of ​​the strip in the dry state, respectively; C2 and A2 are the perimeter and cross-sectional area of ​​the maximum circumscribed cylinder that the contents of the strip can reach after fully absorbing water, respectively.

[0018] Furthermore, the high water loss shrinkage warp uses monofilament warp with a diameter of 0.05mm-0.15mm; when the high water loss shrinkage warp is arranged parallel to the long axis of the bag, the warp spacing is 5mm-15mm; when the high water loss shrinkage warp is arranged in a grid pattern, the grid line spacing is 8mm-20mm.

[0019] Furthermore, the material of the high-water-loss shrinkage warp is SAP-CMC composite fiber.

[0020] Furthermore, the thickness of the composite roll film is 40μm-200μm, and the moisture permeability is not less than 800g / (m²·24h).

[0021] Furthermore, the contents consist of food-grade superabsorbent resin and a natural polysaccharide compound system, and the ratio of food-grade superabsorbent resin to natural polysaccharide compound system is controlled at 1:(0.5-2).

[0022] Furthermore, the natural polysaccharide complex comprises citrus fiber, sodium alginate, sodium carboxymethyl cellulose, gelatin, and konjac glucomannan, with a weight ratio of 5:2:1:1:1.

[0023] Furthermore, the number of expansion and contraction strips is 2-4; the longitudinal cross-section of the strip along its length is a C-shaped arc, and the transverse cross-section of the strip perpendicular to its length is circular; the height of the hard serrations is 0.3mm-0.8mm, the tooth tip angle is 30°-60°, and the spacing between adjacent serrations is 2mm-5mm.

[0024] Furthermore, the high-water-loss shrinkage warp threads are arranged parallel to each other along the long axis of the bag, or in a grid pattern, or embedded in the base film in a geometric pattern.

[0025] A method for preparing environmentally friendly composite tea bags includes the following steps:

[0026] Step 1: During the manufacturing process of the composite roll film, high water loss and shrinkage warp yarns are embedded into the film body of the base film through hot pressing or co-extrusion casting, with an interfacial bonding strength ≥3N / 15mm.

[0027] Step 2) Fold the composite roll film lengthwise to form the front and back of the bag;

[0028] Step 3) Continuously heat seal the back centerline of the folded composite roll film to form a longitudinal seal. The heat sealing temperature is 120℃-135℃ and the pressure is 0.3-0.6Mpa.

[0029] Step 4) Pack the prepared tea contents and the expansion strip into the inner cavity of the bag formed by the folded composite roll film;

[0030] Step 5) Perform horizontal heat sealing and cut the bag to a preset length of 20-60mm to form a horizontal seal. The heat sealing temperature is 130℃-150℃ and the pressure is 0.4-0.8MPa to obtain individual tea bags.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] The rupture behavior of the bag body in this invention is fully controllable:

[0033] Controllable crack initiation: By actively creating deterministic and regularly distributed pre-puncture holes during the soaking stage with hard serrations, the randomness of crack initiation "when and where" is fundamentally solved.

[0034] Controllable expansion: By pre-setting the macroscopic crack propagation path through a high-water-loss shrinkage meridian network, the crack is "locked" on a predetermined track.

[0035] Anchoring reinforcement: The design of expansion strips with longitudinal C-shaped and transverse circular cross sections introduces a stronger mechanical anchoring effect. Combined with the layout of multiple expansion strips, a new efficient "regional contraction-anchoring tearing" mechanism is formed, making the overall tearing process more synchronous, faster, and more regular.

[0036] The shape can be designed: by changing the layout of the warp lines (grid, parallel, pattern), the tear shape of the discarded packaging (square, strip, fun shape) can be pre-designed, realizing the "programmability" of the tear pattern. The repeatability of the tear area is extremely high, and the standard deviation is reduced by more than 60% compared with traditional random tear schemes.

[0037] The fracture triggering efficiency of this invention has been significantly improved:

[0038] 1) Physical pre-puncture provides an immediate stress concentration point;

[0039] 2) The strong anchoring effect of the expansion and contraction strip with a specific cross-section accelerates the stress concentration at the boundary of the region;

[0040] 3) The strong guiding effect of the warp network, together with the other three, bypasses the long process of material deterioration and cracking caused by changes in environmental humidity.

[0041] This invention maximizes the dissolution and exposure of the mixture within the tea bag:

[0042] The vertically C-shaped and horizontally circular strip structure creates three-dimensional flow channels and expanded space within the bag, making it particularly suitable for mixed solid materials of various forms such as tea leaves, goji berries, longan, and chrysanthemums, promoting uniform wetting and simultaneous, efficient dissolution. The grid-like or patterned cracking creates regular crack boundaries, effectively dividing and fully exposing the mixed material clumps. Sufficient contact with oxygen, moisture, and microorganisms increases the initial degradation rate (mass loss rate in the first 30 days) under composting or soil burial by 35%-45%, significantly shortening the overall degradation cycle.

[0043] The invention achieves temporal and synergistic control and perfect synergy between the mechanical properties of the materials and the structure:

[0044] High toughness in wet conditions: This invention utilizes the base film formulation to achieve a high elongation at break (≥30%) during brewing, making it possible to "puncture without tearing" and ensuring absolute safety during use.

[0045] Dry-state high brittleness: Utilizing citric acid crosslinking and the inherent properties of the material, the membrane that has lost water after disposal can be restored to high strength and high brittleness, ensuring that cracks propagate rapidly once they initiate.

[0046] Intelligent interface: The strength of the warp-base film interface is designed to be "weak after discarding and strong after soaking", perfectly realizing the functional requirements at different stages.

[0047] Structural-functional integration: The longitudinal C-shaped and transverse circular cross-section expansion bars are a model of integrated structural and functional design. The C-shaped longitudinal structure provides excellent longitudinal stiffness, stability, and anchoring capability, while the transverse circular cross-section ensures uniform radial expansion and piercing force, together achieving performance optimization throughout the entire process from positioning, piercing, promoting dissolution to strong anchoring after disposal.

[0048] This invention achieves full-chain green environmental protection and ultimate harmlessness:

[0049] From the base film, warp threads, and expanded strip substrate to the hard serrations, all material components are made of fully biodegradable materials (starch-based, PLA, PBAT / PBS, cellulose, etc.). After completing its entire mission of "packaging-solubilization-pre-puncture-guided rupture," the system can achieve complete biodegradation in the natural environment within 180 days, with the final products being environmentally harmless H2O, CO2, and humus, completely eliminating microplastics and any form of persistent pollution.

[0050] This invention has excellent feasibility for industrial production and market adaptability:

[0051] The warp yarns can be manufactured using mature textile and composite processing technologies, while expansion strips with specific cross-sections can be produced using mature processes such as thermoforming. The key visual positioning integration technology is a secondary development based on mature industrial applications, with controllable costs. The unique longitudinal C-shaped structure of the expansion strip gives it excellent bending resistance and conveying stability, ensuring good compatibility with existing high-speed pillow packaging machines and achieving high-speed, stable production of 80-150 packs per minute. By adjusting parameters (such as warp density, serration parameters, and expansion interference ratio), it can flexibly adapt to the needs of different contents (with varying requirements for soaking time and dissolution characteristics) and different climatic regions. Furthermore, it can be extended to other food and pharmaceutical packaging fields requiring rapid disintegration after disposal, demonstrating strong technological versatility and a broad market prospect. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the structure of the bag body of the present invention;

[0053] Figure 2 This is a schematic diagram of the bag body of the present invention from another direction;

[0054] Figure 3 This is a schematic diagram of the initial state of the expansion and contraction strip of the present invention;

[0055] Figure 4 This is a schematic diagram of the structure of the expansion strip of the present invention after absorbing water;

[0056] Figure 5 This is a schematic diagram showing one state in which the expansion strip of the present invention is inserted into the bag body;

[0057] Figure 6 This is a schematic diagram showing another state in which the expansion and telescopic strip of the present invention is inserted into the bag.

[0058] The meanings of the reference numerals in the attached figures are as follows:

[0059] 1. Bag body; 2. High-shrinkage warp yarn; 3. Expansion strip; 4. Strip body; 5. Hard serrations. Detailed Implementation

[0060] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0061] An environmentally friendly composite tea bag includes a bag body 1 made of composite roll film.

[0062] The composite roll film serves as a rapidly degradable substrate, providing encapsulation functionality, wet flexibility, dry brittleness, and a driving force for shrinkage due to water loss.

[0063] The thickness of the composite roll film is 40μm-200μm, preferably 50±5μm (including the raised portion where the warp threads are embedded). In the warp thread embedding area, the base film can be locally thinned to 35-45μm to promote the interfacial effect. The moisture permeability is ≥800 g / (m²·24h) (tested according to GB / T1037-1988, 38℃, 90%RH). High moisture permeability is a prerequisite for rapid water loss and shrinkage.

[0064] Mechanical properties of the composite roll film: Dry tensile strength ≥25MPa, wet (saturated water absorption) tensile strength ≥8MPa (tested according to GB / T1040.3-2006). Wet elongation at break ≥30%. This indicator is crucial to ensure that the film has sufficient flexibility and extensibility during blistering, and that when punctured by serrations, it undergoes plastic perforation rather than brittle tearing, with the edges of the pores relatively closed to maintain a seal.

[0065] The heat-sealing strength of the composite roll film is ≥15N / 15mm (tested according to GB / T2790-1995), ensuring that the sealing edge is firm under internal pressure.

[0066] The composite roll film includes a base film 11 and high-shrinkage warp threads 12. The high-shrinkage warp threads 12 are arranged parallel to each other along the long axis of the bag body 1, in a grid pattern, or embedded in the base film 11 in a geometric pattern. The high-shrinkage warp threads 12 are monofilament warp threads with a diameter of 0.05mm-0.15mm. When the high-shrinkage warp threads 12 are arranged parallel to each other along the long axis of the bag body 1, the warp thread spacing is 5mm-15mm. When the high-shrinkage warp threads 12 are arranged in a grid pattern, the grid line spacing is 8mm-20mm. The warp threads are embedded in the film body during the base film manufacturing process through hot-pressing or co-extrusion casting, and the interface bonding strength is ≤1.2 N / 15mm. This strength ensures that the interface becomes a relatively weak area to guide cracking during post-disposal dehydration, while also preventing premature debonding during rinsing.

[0067] The high-water-loss shrinkage warp yarn is selected from materials whose degradation period in natural environments (such as soil composting) is comparable to that of the base membrane (complete degradation within 180 days), but whose water-loss shrinkage rate and final shrinkage rate are significantly higher than those of the base membrane. SAP (superabsorbent polymer)-CMC composite fiber is preferred. This fiber is produced by blending and spinning CMC and SAP precursors, with an equilibrium water absorption rate between 30% and 60%, and a linear shrinkage rate ≥8% during water loss (compared to 3-5% for the base membrane). Under medium-temperature composting conditions, the time required to reach a 50% water loss rate is more than 60% shorter than that of the aforementioned base membrane formulation materials. All warp yarn materials must comply with GB4806.6-2016 "National Food Safety Standard for Plastic Resins for Food Contact" and related migration requirements.

[0068] The base film 11 includes a matrix layer and a reinforcing dispersant uniformly dispersed in the matrix layer.

[0069] The matrix layer is composed of food-grade corn starch-based material, polylactic acid (PLA), chitosan, and sodium carboxymethyl cellulose (CMC-Na). The food-grade corn starch-based material accounts for 40%-60%, serving as a continuous phase and providing a rapidly biodegradable framework, good moisture sensitivity, and cost advantages. It exhibits significant volume shrinkage during drying. PLA accounts for 15%-25%, providing necessary mechanical strength, toughness, and excellent heat-sealing performance to ensure the integrity of the bag during the blistering stage. Chitosan accounts for 10%-20%, providing broad-spectrum antibacterial properties. Its amino and hydroxyl groups enhance the material's hydrophilicity and increase the bulk brittleness of the base film after water loss. Sodium carboxymethyl cellulose (CMC-Na) accounts for 5%-15%, acting as a highly efficient hydrophilic agent and thickener, significantly improving the initial water absorption rate and water retention of the base film, and significantly enhancing the dehydration sensitivity of the base film at the warp interface.

[0070] The preferred weight ratio of food-grade corn starch-based material, polylactic acid, chitosan, and sodium carboxymethyl cellulose (CMC-Na) is 5:2:1.5:1.5. This ratio achieved the optimal balance of wet strength, dry brittleness, shrinkage, and degradation rate in experiments.

[0071] The reinforcing dispersant is composed of plant fibers, citric acid, and nanocellulose. The plant fibers account for 5%-15% of the total weight of the matrix layer, and the length of the plant fibers is 0.5-2.0 mm. It can improve tensile strength and provide microscopic pathways for crack propagation within the matrix film. The citric acid accounts for 0.5%-3% of the total weight of the matrix layer, and the nanocellulose accounts for 1%-5% of the total weight of the matrix layer. The nanocellulose has a diameter of 20-100 nm, which can improve the material modulus and promote degradation uniformity.

[0072] The high-water-loss shrinkage warp 12 exhibits a significantly higher rate and magnitude of water loss and shrinkage than the surrounding base film material, acting as a "track" or "fence" for crack propagation during the post-disposal stage. During the post-disposal dehydration stage, it functions as a "shrinkage driver" and "crack guide." Due to its faster and more intense shrinkage, it generates strong radial tensile stress on the surrounding base film, which has already begun to shrink. This stress is highly concentrated at the warp-base film interface. When superimposed with the stress concentration from the pre-punctured holes, it preferentially induces cracks and limits crack propagation along the warp network.

[0073] The bag body 1 contains 2-4 expansion and contraction strips 3 with specific cross-sections and hard serrations. The expansion and contraction strip 3 consists of a strip body 4, contents encapsulated in the strip body 41, and hard serrations 5.

[0074] Strip 4 is made of food-contact grade permeable packaging material PLA nonwoven fabric or cotton / PLA blended mesh, with a basis weight of 40-80 g / m². The longitudinal section (along the length of the strip) of strip 4 is C-shaped, while the transverse section (perpendicular to the length) is circular, with an arc radius R = 2.5 ± 0.5 mm. In the dry state, the perimeter C1 and cross-sectional area A1 of the strip (including serrations) should be significantly smaller than the expanded C2 and A2 (typically C2 / C1 ≥ 1.3, A2 / A1 ≥ 1.5).

[0075] The contents within strip 4 are a mixture of solid powders or granules, encapsulated within the strip. It consists of food-grade superabsorbent polymer (SAP) and a natural polysaccharide complex system (citrus fiber, sodium alginate, sodium carboxymethyl cellulose, gelatin, and konjac glucomannan). The food-grade SAP provides the core swelling power source, requiring a water absorption ratio ≥ 50 g / g (deionized water). The natural polysaccharide complex system is used to regulate the water absorption and swelling dynamics (rate, uniformity) and the final gel strength, preventing the strip from breaking due to excessively rapid water absorption by the SAP. Typical components include: citrus fiber (providing support and slow release), sodium alginate (forming a strong gel), sodium carboxymethyl cellulose (CMC-Na, thickening and water retention), gelatin (for rapid low-temperature gelation), and konjac glucomannan (a highly viscoelastic gel). The total weight ratio of SAP to natural polysaccharides was controlled at 1:(0.5-2), and the weight ratio of citrus fiber, sodium alginate, sodium carboxymethyl cellulose, gelatin and konjac glucomannan was 5:2:1:1:1.

[0076] Hard serrations 43 are concentrated along the length of strip 4 on the outer surface of the top arc region of the C-shaped longitudinal section, which is the area with the greatest contact pressure with the bag wall and the most direct piercing action. Biodegradable polymers are used, such as polybutylene adipate / terephthalate (PBAT), polybutylene succinate (PBS), or high-hardness modified PLA. A hardness (Shore D) ≥ 65 is required to ensure sufficient piercing capability. Serration height: 0.3mm-0.8mm; too high may affect encapsulation or cause excessive damage to the film under wet conditions, while too low will result in poor piercing effect; serration angle: 30°-60°; smaller angles result in sharper piercing but lower strength; larger angles provide greater strength; adjacent serration spacing: 2mm-5mm, determining the density and distribution of piercing holes; bonded with biodegradable hot melt adhesive or integrally molded onto the strip surface during manufacturing with the strip substrate.

[0077] The dimensions of bag 1 are: length L = 50 mm, width W = 50 mm. After brewing and expansion, the internal space of the bag is affected by the filling of the contents (tea leaves, goji berries, longan, chrysanthemum, etc.), and the maximum approximate inner diameter (D) bag The thickness is typically 20-30mm (depending on the density of the contents). maxThe diameter of the longitudinal section along the length of the strip 4 after the contents have fully absorbed water and expanded is approximately C-shaped.

[0078] To achieve reliable penetration, the following condition must be met: D max ≥ 1.05 ×D bag This means there is a radial dimensional interference of 5% or more. This interference is the fundamental mechanical guarantee for driving the saw teeth to overcome the resistance of the wet film and penetrate it. In terms of design, it is preferable to make the transverse cross-sectional diameter of the strip in the dry, unexpanded state slightly larger than the estimated value of the maximum inscribed circle diameter of bag body 1, so as to ensure that it can occupy effective space and establish contact in the early stage of expansion.

[0079] Expansion kinetic properties:

[0080] Expansion force: ≥0.8 MPa (under maximum expansion, simulated test in a confined space, refer to the principle of GB / T 27761-2011). This force must be sufficient to drive the sawtooth array to pierce the wet membrane.

[0081] Expansion time constant (τ): The time required for the tea leaves to expand to 90% of their maximum volume in 98℃ hot water should be controlled between 30 and 60 minutes. This ensures that the piercing process is completed early in the brewing process and allows sufficient time for the subsequent extraction of tea leaves.

[0082] This invention also discloses a method for preparing environmentally friendly composite tea bags, comprising the following steps:

[0083] Step 1: During the manufacturing process of the composite roll film, the high water loss shrinkage type warp 12 is embedded into the film body of the base film 11 by hot pressing or co-extrusion casting, and the interface bonding strength is ≥3N / 15mm.

[0084] Step 2) Fold the composite roll film longitudinally to form the front and back of bag 1.

[0085] Step 3) After folding the composite roll film, the back center line is continuously heat-sealed through a high-speed pillow-type back-sealing packaging machine (linear speed 80-150 packs / minute) to form a longitudinal seal. The heat-sealing temperature is 120℃-135℃, the pressure is 0.3-0.6Mpa, and the time is 0.5-1.0s.

[0086] Step 4) Pack the prepared tea contents and the expansion strip 3 into the inner cavity of the bag body 1 formed by the folded composite roll film.

[0087] Step 5) Perform a horizontal heat seal and cut the bag to a preset length of 20-60mm to form a horizontal seal 5. The heat seal temperature is 130℃-150℃, the pressure is 0.4-0.8MPa, and the bag length is 20-60mm, resulting in an individual tea bag. Typical bag dimensions: length L=50±1mm, width W=30±0.5mm.

[0088] Working principle and dynamic response mechanism of this invention:

[0089] The core innovation of this invention lies in constructing a crack control system that precisely couples "active pre-damage guidance" and "passive environmental response guidance" in time and space.

[0090] Phase 1: Brewing Phase - "Physical Pre-Piercing" Mode;

[0091] Immersion and softening of the tea bag: When the composite tea bag is put into hot water, the highly hydrophilic composite film (especially the effect of CMC-Na and chitosan) quickly absorbs water, the polymer molecular chains swell, the glass transition temperature of the material decreases, the film becomes soft and has high ductility (wet elongation at break ≥30%), and the mechanical strength changes from high strength and high brittleness in the dry state to medium strength and high toughness in the wet state.

[0092] Activation and dimensional interference of the expansion strip 3: The contents (SAP and natural polysaccharides) of the expansion strip 3 at a specific cross-section inside the bag rapidly absorb hot water. SAP generates significant expansion stress, while the natural polysaccharide system forms a gel constraint and regulates the expansion rate. Within minutes, the strip 4 expands to its maximum, with its transverse cross-sectional diameter exceeding the inner diameter of the bag due to the expansion of the contents, resulting in the designed radial dimensional interference (≥5%). The longitudinal C-shaped structure of the strip provides excellent bending stiffness during this process, ensuring that the expansion force is uniformly transmitted to the toothed band along its length.

[0093] Directional puncture by hard serrations 5: Driven by a continuous radial expansion force (≥0.8MPa), the hard serrations 5 (hardness ≥65D) on strip 4 begin to compress and pierce the softened inner wall of the composite roll film. Because the film is in a high-moisture toughness state, the puncture process manifests as plastic perforation – the tooth tips squeeze and separate the polymer chains, forming a relatively regular, closed small hole (i.e., a pre-puncture hole), without triggering instantaneous unstable propagation of brittle cracks. The overall bag structure remains intact, the seal is firm, and there is no leakage of contents.

[0094] Synergistic Function: The expanded strip 4, with its unique longitudinal C-shape and transverse circular structure, effectively pierces the membrane while more fully expanding the various shapes of mixed materials such as tea leaves, goji berries, and longan, creating complex and efficient water flow channels. This significantly increases the contact area and efficiency between solid materials and water, thereby promoting the rapid and simultaneous dissolution of various flavor and functional components. At this time, the warp and base membrane interfaces are firmly bonded because both are in a swollen state, jointly bearing the internal pressure.

[0095] Phase Two: Post-Abandonment Phase "Cooperative Guidance Breakdown" Mode:

[0096] Dehydration Initiation and Shrinkage Mismatch: After use, the bag is removed from the water body and exposed to air (even when placed in a wet waste dump, its surface microenvironment changes). The membrane and warp begin to lose water. A key mechanism emerges: the water loss rate and shrinkage rate of high-water-loss shrinkage warp fibers (such as SAP-CMC fibers) are much higher than those of the base membrane. The warp fibers rapidly shrink and become thinner and shorter, generating strong radial compressive stress and axial tensile stress on the surrounding slowly shrinking base membrane. These stresses are highly concentrated in the warp-base membrane interface region.

[0097] The stress amplifier effect of pre-puncture: During dehydration, the entire bag 1 undergoes macroscopic shrinkage due to water loss from the base film and contents. The pre-puncture formed earlier, because it disrupts the continuity of the material, becomes a natural and powerful stress concentration point. The stress level at the edge of the hole can be several times higher than that in the defect-free area.

[0098] Synergistic Crack Initiation: In the initial post-abortion phase (within tens of minutes), two stress fields superimpose: one is a concentrated stress field from the edge of the puncture hole, and the other is a shrinkage mismatch stress field from the meridian-base film interface. When the puncture hole is positioned close to the meridian (especially at intersections) as designed, these two stress fields spatially overlap and reinforce each other. The superimposed stress rapidly exceeds the local fracture strength of the base film material, which has become brittle again due to water loss (dry tensile strength ≥25MPa but low fracture toughness). Therefore, microcracks inevitably and preferentially initiate from the edge of the pre-puncture hole, heading towards the nearest meridian. This solves the deterministic problem of "when and where cracks initiate."

[0099] Regionalized shrinkage-anchoring tearing effect: When multiple expansion and contraction strips 3 with specific cross-sections are arranged inside the bag, their puncture and the strong mechanical anchoring effect brought by the C-shaped longitudinal structure divide the bag into multiple relatively independent regions on the plane and firmly anchor the boundaries of each region. During the post-disposal water loss shrinkage process, the base film and warp lines inside each region cannot shrink freely because the boundaries are strongly constrained by the sawtooth anchor points and their supporting structures. This results in extremely significant shear and tensile combined stress concentration at the junction of adjacent regions (near the line connecting the sawtooth puncture holes). This stress, combined with the aforementioned interface mismatch stress and puncture hole stress field, forms a stronger composite driving force, prompting cracks to preferentially connect and penetrate at the regional boundaries, forming an efficient, almost synchronous tearing mode, further accelerating the overall rupture process.

[0100] Path locking and guided propagation of the warp network: Once a microcrack initiates, its propagation path is immediately dominated by a high-water-loss, shrinkage-type warp network. Because the modulus and shrinkage behavior of the warp material differ significantly from those of the base film, the energy release rate required for crack tip propagation is much greater parallel to the warp direction than perpendicular to it. From a fracture mechanics perspective, cracks always choose the path of least resistance for propagation. Therefore, cracks are "guided" or even "locked" at the weak interface between the warp and the base film or within the stress concentration zone created by the warp, strictly propagating along a pre-defined warp network (grid lines, parallel lines, or pattern contours).

[0101] The final stage of the network-like fracturing process involves cracks originating from individual puncture holes, extending, converging, and connecting along a network of warp lines. Under the powerful synergy of the "regional contraction-anchoring tear" effect, the fracturing process is more rapid, synchronous, and thorough. The entire bag is then divided into a series of small, regularly shaped fragments (square, rectangular, or with specific patterns) defined by warp lines. The fracturing area can reach 70%-85%, with extremely high repeatability (standard deviation less than 5%). The mixed solid material is fully fragmented and exposed between these fragments, resulting in a huge specific surface area.

[0102] Ultimate Degradation: After fulfilling its rupture-guiding mission, the broken packaging fragments (including base film, warp remnants, expansion strip substrate, and hard serrations) continue to be degraded by microorganisms in composting or soil environments. All components are fully biodegradable materials, ultimately converting into carbon dioxide, water, and biomass, leaving no residual pollution.

[0103] Example 1: Standard Grid Guided Eco-friendly Tea Bag

[0104] Raw materials and specifications:

[0105] Composite roll film:

[0106] Base film formulation (by weight): Edible corn starch: PLA: chitosan: CMC-Na = 50:20:15:15.

[0107] Reinforcing phase: 8% bamboo fiber (average length 1.2mm), 0.5% citric acid, and 2% nanocellulose are added.

[0108] Processing technology: The above materials are mixed at high speed, granulated by twin-screw extrusion, and cast into a film. The film thickness is 50±2μm.

[0109] Wet performance: The measured wet elongation at break is 35%, which meets the puncture requirements.

[0110] High-water-loss shrinkage warp 2:

[0111] Material: SAP-CMC composite monofilament fiber, diameter 0.12 mm.

[0112] Layout: 10mm × 10mm square grid layout.

[0113] Composite process: While the cast film is in a semi-molten state, the warp mesh is hot-pressed into the film surface using precision guide rollers, resulting in a localized thinning of the base film at the interface to approximately 40 μm. The measured dry-state interfacial peel strength is 1.0 N / 15 mm.

[0114] Expansion strip 3 with a specific cross-section featuring hard serrations:

[0115] Strip substrate: 55 g / m² PLA spunbond nonwoven fabric, which is prepared into a tubular structure with longitudinal C-shape and transverse circular shape by hot pressing process.

[0116] Hard serration 5: Made of PBS, hardness 70D. Serration height h=0.5mm, serration angle α=45°, spacing p=3mm. It is uniformly adhered to the outer arc surface of the C-shaped structure along the length of the strip using biodegradable hot melt adhesive.

[0117] Contents: 12g of food-grade SAP (water absorption rate 60g / g) and 18g of natural polysaccharide compound (citrus fiber: sodium alginate: CMC-Na: gelatin: konjac glucomannan = 5:2:1:1:1) are mixed evenly, filled into the bar, and sealed.

[0118] Size Design: Experiments showed that after filling this bag type (50mm×50mm) with 30g of mixed ingredients and allowing it to expand upon rehydration, D... bag Approximately 21mm. The diameter D of the transverse cross-section after the expansion of strip 4 is designed. max The diameter is 23mm, and the interference ratio ε≈11%. The transverse diameter of the drying strip 4 is approximately 2.0mm, slightly larger than 1 / 10 of the estimated maximum inscribed circle of the bag, which facilitates initial positioning.

[0119] Packaging process:

[0120] Equipment: Modified high-speed pillow-type back-sealing packaging machine, with a linear speed set at 100 packs / minute.

[0121] Heat sealing parameters: longitudinal sealing temperature 130℃, pressure 0.4 MPa, time 0.8 s; transverse sealing temperature 145℃, pressure 0.5 MPa.

[0122] Filling: Each bag is filled with a fixed amount of 50g of mixed solid material (Qimen black tea, goji berries, and Hangzhou white chrysanthemum in a 7:2:1 ratio), and the two expansion strips mentioned above are filled in at the same time.

[0123] Final bag dimensions: length L=50 mm, width W=30 mm.

[0124] Performance test results:

[0125] Brewing performance (98±1℃ hot water, 250mL beaker):

[0126] Puncture verification: After immersion for 2 minutes, regular bulges were observed on both sides of bag 1 corresponding to the expansion and contraction strips 3 due to the C-shaped expansion. After 4 minutes, under high-transmittance light observation, two clear rows of tiny puncture holes with a spacing of 3 mm and a diameter of approximately 0.1 mm were visible. There was no leakage of contents or rupture of the bag throughout the entire process.

[0127] Dissolution rate: After soaking for 5 minutes, the tea was removed and the overall dissolution rate of tea polyphenols, wolfberry polysaccharides, and chrysanthemum flavonoids in the tea infusion was measured. The calculated total dissolution rate was 35% higher than that of using traditional non-woven tea bags (without any solubilizing structures), proving that the expansion and turbulence effect of the specific cross-section expansion strips has a significant enhancing effect on the dissolution of the mixture.

[0128] Post-discard fracturing performance (standard test):

[0129] Method: Remove the brewed tea bag from the hot water, gently drain off the excess water, and immediately place it on a constant temperature and humidity test bench at 23℃ and 50% relative humidity.

[0130] Observation: At the 35th minute, fine cracks visible to the naked eye began to appear near the puncture point (the intersection of the meridians).

[0131] Between 50 and 60 minutes, the cracks rapidly expanded and connected along the 10mm × 10mm meridian grid. Simultaneously, due to the "regional anchoring" effect, the boundary of the area where the expansion and contraction strip 3 was located was significantly torn.

[0132] At the 82nd minute, a highly regular grid-like rupture formed, and bag 1 was divided into approximately 15 small square fragments of about 10mm × 10mm. The rupture area was calculated using image analysis software to be 82% ± 2% (n=30).

[0133] Control group: Samples using the same base film but without warp threads and using ordinary non-serrated cylindrical expansion strips. The rupture morphology was completely random, the rupture initiation time was about 150 minutes, and the final rupture area was only 55% ± 9%.

[0134] Degradation performance (simulated soil burial, 25±2℃):

[0135] Due to the ample exposure of solid materials, the area susceptible to microbial invasion was large. After 30 days, the mass loss rate of bag fragments reached 88% ± 3% (compared to 60% in the control group).

[0136] After 180 days, the biodegradation rate was 97% as determined by the carbon dioxide emission method. Microscopic observation showed that the hard serrated 5 and C-shaped strip structures had also completely disintegrated.

[0137] Example 2: High-speed parallel guided production:

[0138] This embodiment is optimized for customers who pursue ultimate production efficiency.

[0139] Structural optimization:

[0140] Warp layout: The high-water-loss shrinkage type warp 2 adopts a parallel layout, with the direction parallel to the long axis of the bag (50mm direction), and the spacing is fixed at 8mm. This layout is easier to align and control during roll-to-roll production.

[0141] The expansion and contraction strip 3 and the hard serration 5 design: To accommodate higher line speeds, the height of the hard serration 5 is slightly reduced to 0.4mm to reduce the risk of material jamming, and the material is still PBS. The strip body still maintains a longitudinal C-shape and a transverse circular cross-section.

[0142] Process improvements: Packaging machine line speed increased to 130 packs / minute. Optimized film feeding and cutting synchronization reduced positioning delay. The longitudinal C-shaped structure of strip 4 ensures a stable straight-line descent trajectory even at high speeds.

[0143] Performance data:

[0144] Brewing performance: Good puncture resistance, no leakage.

[0145] Post-fracture performance: After cracks initiate from the two rows of puncture holes, they mainly extend in the upward and downward parallel meridian directions. Combined with the anchoring and segmentation of the expansion and contraction strips 3, they eventually form parallel strip-shaped fractures with a width of approximately 8 mm. The average fracture time is 55 minutes, and the fracture area remains stable at 75% ± 3%.

[0146] Production qualification rate (based on no leakage and rupture morphology conforming to design criteria): reached 99.5%, proving that the solution is suitable for high-speed production.

[0147] Example 3: Children's Fun Pattern Guidance Type

[0148] This embodiment demonstrates the technology's appearance and expanded educational functions.

[0149] Structural Innovation:

[0150] Warp pattern: Made of colored SAP-CMC composite fibers, pre-woven into a mesh structure containing the outlines of "little stars" and "little dolphins" through jacquard weaving process, and then hot-pressed into a transparent base film.

[0151] Composite roll film: 1% food-grade iron oxide yellow is added to the base film, giving the bag a soft light yellow background and making the colored warp pattern clearly visible.

[0152] The serrated expansion strip 3: The strip body 4 is made of white PLA non-woven fabric, with a longitudinal C-shape and a transverse circular cross-section. The folding and position of the expansion strip inside the bag are carefully designed to ensure that its serrated strip can form puncture holes near the key outlines of the "star" and "dolphin" patterns after expansion.

[0153] Performance and features:

[0154] During the brewing process: Children can observe that the white C-shaped expansion strip inside the bag absorbs water and becomes larger, and the colored pattern area on the bag body will faintly show a dot matrix.

[0155] Post-disposal stage (key highlight): After the bag dries, the tearing does not occur randomly, but rather unfolds precisely along the edges of the "stars" and "dolphins" outlined by the colored warp lines. The strong anchoring effect of the C-shaped expansion strips ensures that the tearing occurs precisely along the pattern boundaries. Ultimately, the packaging breaks into several complete "star" and "dolphin" shaped fragments, creating a visually surprising and fun effect.

Claims

1. An environmentally friendly composite tea bag, characterized by: Includes a bag body (1) made of composite roll film, and the bag body (1) has at least two expansion and stretch strips (3) inside. The composite roll film includes a base film and a high-water-loss shrinkage warp (2) embedded in the base film. The base film includes a matrix layer and a reinforcing dispersant uniformly dispersed in the matrix layer; The matrix layer is composed of food-grade corn starch-based material, polylactic acid, chitosan, and sodium carboxymethyl cellulose; the food-grade corn starch-based material accounts for 40%-60%, polylactic acid accounts for 15%-25%, chitosan accounts for 10%-20%, and sodium carboxymethyl cellulose accounts for 5%-15%. The reinforcing dispersant is composed of plant fiber, citric acid and nanocellulose, wherein the plant fiber accounts for 5%-15% of the total weight of the matrix layer, the citric acid accounts for 0.5%-3% of the total weight of the matrix layer, and the nanocellulose accounts for 1%-5% of the total weight of the matrix layer. The expansion and telescopic strip (3) consists of a strip body (4) and contents encapsulated within the strip body (4). The strip body (4) is made of food-contact grade water-permeable packaging material, and the cross-section of the strip body (4) is arc-shaped. The contents inside the strip body (4) can expand after absorbing water, and the strip body (4) is provided with several hard serrations (5) at intervals. Under dehydration conditions, the bag body (1) shrinks and, under the tension of the expansion strip (3), the pre-puncture stress of the hard serrations (5), and the guidance of the high dehydration shrinkage warp (2), the bag body (1) ruptures.

2. The environmentally friendly composite tea bag according to claim 1, characterized in that: The strip (4) satisfies: C2≥1.3×C1; A2≥1.5×A1, where C1 and A1 are the perimeter and cross-sectional area of ​​the strip (4) in the dry state, respectively; C2 and A2 are the perimeter and cross-sectional area of ​​the maximum circumscribed cylinder that the contents of the strip (4) can reach after fully absorbing water.

3. The environmentally friendly composite tea bag according to claim 2, characterized in that: The high water loss shrinkage warp (2) is made of monofilament warp, and the diameter of the monofilament warp is 0.05mm-0.15mm; when the high water loss shrinkage warp (2) is arranged parallel to the long axis of the bag body (1), the warp spacing is 5mm-15mm; when the high water loss shrinkage warp (2) is arranged in a grid pattern, the grid line spacing is 8mm-20mm.

4. The environmentally friendly composite tea bag according to claim 3, characterized in that: The material of the high-water-loss shrinkage warp (2) is SAP-CMC composite fiber.

5. The environmentally friendly composite tea bag according to claim 1, characterized in that: The thickness of the composite roll film is 40μm-200μm, and the moisture permeability is not less than 800g / (m²·24h).

6. The environmentally friendly composite tea bag according to claim 1, characterized in that: The contents consist of a food-grade superabsorbent resin and a natural polysaccharide compound system, and the ratio of the food-grade superabsorbent resin to the natural polysaccharide compound system is controlled at 1:(0.5-2).

7. The environmentally friendly composite tea bag according to claim 6, characterized in that: The natural polysaccharide complex comprises citrus fiber, sodium alginate, sodium carboxymethyl cellulose, gelatin, and konjac glucomannan, with a weight ratio of 5:2:1:1:

1.

8. The environmentally friendly composite tea bag according to claim 1, characterized in that: The number of expansion and contraction strips (3) is 2-4; the longitudinal section of the strip body (4) along the length direction of the strip body is a C-shaped arc, and the transverse section of the strip body (4) perpendicular to the length direction is circular; the height of the hard serrations (5) is 0.3mm-0.8mm, the tooth tip angle is 30°-60°, and the distance between adjacent serrations is 2mm-5mm.

9. The environmentally friendly composite tea bag according to claim 1, characterized in that: The high-water-loss shrinkage warp (2) is arranged parallel to the long axis of the bag body (1) at intervals, in a grid pattern, or embedded in the base film in a geometric pattern.

10. A method for preparing the environmentally friendly composite tea bag according to any one of claims 1-9, characterized in that, Includes the following steps: Step 1: During the manufacturing process of the composite roll film, the high water loss shrinkage warp (2) is embedded into the film body of the base film by hot pressing or co-extrusion casting, and the interface bonding strength is ≥3N / 15mm; Step 2): The composite roll film is folded in half along the longitudinal direction to form the front and back of the bag body (1); Step 3) Continuously heat seal the back centerline of the folded composite roll film to form a longitudinal seal. The heat sealing temperature is 120℃-135℃ and the pressure is 0.3-0.6Mpa. Step 4) Pack the prepared tea contents and the expansion strip (3) into the inner cavity of the bag (1) formed by the folded composite roll film; Step 5) Perform horizontal heat sealing and cut the bag to a preset length of 20-60mm to form a horizontal seal. The heat sealing temperature is 130℃-150℃ and the pressure is 0.4-0.8MPa to obtain individual tea bags.

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