Coffee residue composite polypropylene degradable material and preparation method thereof

Abstract

The present invention relates to the field of biodegradable materials, and discloses a coffee residue composite polypropylene degradable material and a preparation method thereof, the material is prepared from the following components: homo-polypropylene, co-polypropylene, a polyolefin elastomer, coffee residue, bamboo powder, polypropylene grafted maleic anhydride, a reactive coupling agent / modifier (RCM), a PP flow promoter, zinc stearate and an antioxidant, and a degradation agent; the core of the invention is that the adopted RCM can be subjected to an in-situ chemical reaction with active groups on the surfaces of the coffee grounds and the bamboo powder in the melt blending process to form a functional interface so as to improve the compatibility of the filler and a polypropylene matrix and the mechanical properties of the material. The invention further discloses a preparation method of the material. The preparation method comprises the steps of premixing of the filler and the RCM, total mixing, melt blending extrusion and granulation. The material disclosed by the invention has good mechanical properties and excellent biodegradability, waste biomass resources can be effectively utilized, and environmental pollution is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of biodegradable materials, in particular to a coffee grounds composite polypropylene biodegradable material and a preparation method thereof. Background Art

[0002] Polypropylene (PP) is widely used in packaging, automobiles, home appliances, daily necessities and other fields due to its excellent comprehensive performance and low cost. However, traditional polypropylene materials are difficult to degrade, and the "white pollution" problem caused by waste is becoming increasingly serious, posing a huge threat to the ecological environment. To alleviate this problem, researchers have tried to introduce natural biomass fillers, such as wood powder, plant fibers, and agricultural waste (such as coffee grounds, bamboo powder, etc.), into the polypropylene matrix to prepare bio-based composite materials. On the one hand, this method can reduce dependence on petroleum resources and realize the resource utilization of waste. On the other hand, the natural fillers themselves have certain biodegradability, which can theoretically improve the overall environmental friendliness of the composite materials.

[0003] However, in the existing technology, the practical application of this type of polypropylene / biomass composite materials still faces many challenges. A core problem is the poor interfacial compatibility between the hydrophilic biomass filler and the hydrophobic polypropylene matrix. This not only makes it difficult for the mechanical properties of the composite material to meet expectations, affecting its use value, but also the poor interfacial bonding is not conducive to the effective erosion and degradation of the fillers inside the material by microorganisms. Although traditional compatibilizers such as maleic anhydride grafted polypropylene (PP-g-MAH) are usually used to improve the interface conditions, their role is mainly reflected in the physical or limited chemical bonding level, and their contribution to improving the deep and synergistic biodegradation efficiency of the material is limited.

[0004] In addition, even if the biomass filler can be partially degraded, the inertness of the polypropylene matrix itself is still the key bottleneck restricting the complete biodegradation of the composite material. Although the oxidative degradation promoter added in the prior art can accelerate the chain breaking and fragmentation of polypropylene to a certain extent, this is mainly a non-biological oxidation process. The fragments formed are still polypropylene, and the subsequent biomineralization process is very slow. Therefore, relying solely on the degradation of the filler and the initial oxidation of the matrix, the overall degradation rate and degree of the composite material are often unsatisfactory, and it is difficult to meet the requirements of rapid and efficient biological disposal. The existing technology system also pays less attention to how to actively regulate and enhance the activity of degrading microorganisms through the design of material components. In particular, there is a lack of a technical means that can effectively stimulate microorganisms to produce specific degradation enzymes and promote these enzymes to act synergistically on biological fillers and polymer matrices, thereby achieving optimization of the internal degradation microenvironment of the material and a substantial breakthrough in the overall degradation efficiency. Summary of the Invention

[0005] The present invention aims to solve the technical problems that the existing polypropylene composite material has insufficient biodegradability and the interface bonding between the biological filler and the polymer matrix needs to be improved.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: The first aspect of the present invention provides a coffee grounds composite polypropylene biodegradable material. Through the synergistic effect of specific components, in particular the introduction of a reactive coupling agent / modifier (RCM), a microenvironment conducive to subsequent microbial degradation is constructed within the material, thereby increasing the overall biodegradation efficiency of the material and improving its physical properties.

[0007] To achieve the above-mentioned purpose, the technical solution adopted in the first aspect of the present invention is: A coffee grounds composite polypropylene degradation material, comprising, by weight percentage: Homopolymer polypropylene: 34.0-36.0%; Copolymer polypropylene: 19.0-21.0%; Polyolefin elastomer: 7.0-8.0%; Coffee grounds passed through a 200-mesh sieve: 14.5-15.5%; Bamboo powder passing through 60-mesh sieve: 14.5-15.5%; Polypropylene grafted with maleic anhydride: 2.8-3.2%; Reactive coupling agent / modifier (RCM): 0.5-2.0%; Polypropylene flow aid: 1.4-1.8%; Zinc stearate: 0.25-0.35%; Antioxidant 1010: 0.25-0.35%; Antioxidant 168: 0.25-0.35%; and degraders: 1.8-2.2%.

[0008] The key is that the reactive coupling agent / modifier (RCM) has a special dual-functional design.

[0009] First, it contains functional groups that can undergo an in-situ chemical reaction with reactive groups, such as hydroxyl groups, on the surfaces of the coffee grounds and / or bamboo powder. This in-situ reaction is intended to enhance the interfacial bonding strength between the biofiller and the polypropylene matrix, thereby improving the physical and mechanical properties and processing stability of the composite material.

[0010] Secondly, the chemical structure of the RCM, or the specific small molecule fragments released during the initial stages of material degradation (e.g., through hydrolysis), is designed to interact favorably with specific strains within the composite microbial inoculum when the material subsequently enters a degradation environment and is introduced. This interaction is specifically manifested by the ability to induce or enhance the ability of the specific strain to produce active degradative enzymes (e.g., lignocellulase, esterase, or enzymes targeting the initial oxidized polypropylene fragments).

[0011] As a result, an "autocrine enzymatic degradation microenvironment" with high local enzyme activity is formed around the functionalized filler interface, creating favorable conditions for the subsequent effective degradation of the biofiller and polypropylene matrix.

[0012] In some embodiments, the reactive coupling agent / modifier (RCM) can be selected from bio-based oligomers with epoxy, carboxyl, or anhydride groups (e.g., modified plant oil derivatives or modified oligomeric lactic acid), or synthetic compounds containing isocyanate or siloxane groups and attached with specific bioactive moieties. These specific functional groups are selected to ensure effective chemical bonding or strong interaction with the active groups on the biofiller surface.

[0013] In some embodiments, the polyolefin elastomer is preferably an ethylene-octene copolymer with an octene content in the range of 20-35 wt %, in order to provide the material with good toughness.

[0014] In some embodiments, the maleic anhydride grafting rate of the polypropylene grafted with maleic anhydride is preferably 0.5-1.2 wt % to help improve the compatibility of the polypropylene matrix with the polar biological filler.

[0015] In some embodiments, the chemical structure of the RCM or its initial degradation products act as signal molecules or substrate analogs to induce or enhance the production of active degrading enzymes by specific strains in the composite microbial inoculum. This mechanism enables the microorganisms to more actively and efficiently secrete the required enzymes during the degradation process, thereby accelerating the degradation process.

[0016] A second aspect of the present invention provides a method for preparing the above-mentioned coffee grounds composite polypropylene degradation material. The method ensures that the RCM can effectively react with the biological filler in situ and uniformly disperse the components through specific process steps.

[0017] To achieve the above-mentioned purpose, the technical solution adopted in the second aspect of the present invention is: A method for preparing the coffee grounds composite polypropylene degradation material as described in any one of the above, the method comprising the following steps: (a) Premixing coffee grounds passed through a 200-mesh sieve, bamboo powder passed through a 60-mesh sieve, and the reactive coupling agent / modifier (RCM) to obtain a filler premix; this step helps the RCM to be more evenly distributed on the surface of the biofiller before subsequent melt blending, creating conditions for in situ reaction.

[0018] (b) mixing the filler premix obtained in step (a) with homopolypropylene, copolymerized polypropylene, polyolefin elastomer, polypropylene grafted maleic anhydride, polypropylene flow aid, zinc stearate, antioxidant 1010, antioxidant 168, and a degradation agent to obtain a total mixture; (c) subjecting the total mixture to melt blending and extrusion. During the melt blending and extrusion process, under the action of high temperature and shear, the RCM undergoes an in situ chemical reaction with the active groups on the surface of the coffee grounds and / or bamboo powder to form a functionalized interface. This in situ reaction is one of the key steps in achieving the dual functionality of the RCM.

[0019] (d) cooling and pelletizing the extrudate to obtain the coffee grounds composite polypropylene degradation material.

[0020] In some embodiments, prior to step (a), the method further comprises drying the coffee grounds and bamboo powder at 80-100°C to reduce their moisture content to less than 0.8 wt%. Sufficiently drying the biofiller helps reduce the adverse effects of moisture evaporation on material properties during subsequent high-temperature processing and facilitates the reaction between the RCM and the filler's surface active groups.

[0021] In some embodiments, the premixing in step (a) and / or the mixing in step (b) can be performed in a high-speed mixer, and the rotation speed thereof can range from 600 to 1200 rpm to ensure the initial dispersion uniformity of each component.

[0022] In some embodiments, the melt blending extrusion in step (c) is performed in a twin-screw extruder, with the temperature of each heating zone of the extruder set within a range of 150° C. to 190° C., and the screw speed controlled within a range of 100-200 rpm. These process parameters are selected to ensure sufficient plasticization of the polymer, effective reaction of the RCM with the filler, and avoid excessive degradation of the material.

[0023] More specifically, the in-situ chemical reaction between RCM and coffee grounds and / or bamboo powder in step (c) is designed to form a unique, functionalized interface. This interface not only contributes to improved physical properties during the material's service life, but more importantly, when the material is discarded and exposed to a specific composite microbial inoculum and degradation conditions, this interface, along with the chemical structure of the RCM or its initial degradation products, effectively induces or enhances the production of active degradative enzymes by specific strains in the inoculum, thereby promoting the biodegradation of the entire composite material. This constitutes one of the core technical features of this invention, which distinguishes it from traditional filler modification or simple component blending.

[0024] In summary, the present invention includes at least one of the following beneficial technical effects: 1. The present invention introduces a specific reactive coupling agent / modifier (RCM). This RCM can not only undergo in situ chemical reactions with active groups on the surface of biofillers such as coffee grounds and bamboo powder to enhance interfacial bonding, but more importantly, its chemical structure or initial degradation products can serve as signal molecules or substrate analogs, effectively inducing or enhancing the enzyme production activity of specific strains in the composite microbial inoculant, thereby constructing an "autocrine enzymatic degradation microenvironment" within the material and accelerating the synergistic degradation of the biofiller and the polypropylene matrix.

[0025] 2. The RCM employed in this invention forms a robust, functionalized interface through an in-situ chemical reaction with the biofiller surface during the melt blending process, significantly improving the compatibility and interfacial bonding strength between the inorganic biofiller and the hydrophobic polypropylene matrix. Combined with a specific pre-mixing process, this ensures full interaction between the RCM and the filler, enabling effective stress transfer. This allows the material to maintain or improve its tensile strength, flexural strength, and impact toughness even at high filler loadings.

[0026] 3. The present invention uses cheap and readily available agricultural and forestry waste such as coffee grounds and bamboo powder as the main functional filler, replacing part of the petroleum-based polypropylene. This not only reduces material costs and reduces dependence on fossil resources, but also helps alleviate the "white pollution" problem by improving the biodegradability of the final product, which is in line with the concept of green and sustainable development.

[0027] 4. The technical solution of this invention, through the specific design of the RCM, combines the initial oxidation of polypropylene by a degradation agent with the synergistic degradation of a composite microbial inoculum, to construct a multi-layered, multi-pathway degradation system. The RCM's induction of microbial enzyme production makes the degradation process more targeted and efficient, particularly at the interface between the biofiller and the polymer matrix, creating a localized environment of high enzyme activity and promoting the effective disintegration of the material from the inside out. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below with reference to Examples. It should be noted that the following Examples and their parameters are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention. Any modifications or equivalent replacements made based on the technical concept of the present invention should be included within the scope of protection of the present invention.

[0029] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present invention are commercially available or prepared by conventional methods in the art; the percentages used are by weight unless otherwise specified.

[0030] The raw materials used in the following examples and comparative examples are mainly as follows: Homopolymer polypropylene (hPP): brand T30S, melt index (230°C, 2.16kg) of 3.0-5.0 g / 10 min, purchased from Sinopec.

[0031] Copolymer polypropylene (cPP): brand K8003, ethylene content 3-4 wt%, melt index (230° C., 2.16 kg) 8-12 g / 10 min, purchased from SK Co., Ltd. of South Korea.

[0032] Polyolefin elastomer (POE): brand Engage TM 8150 (Dow Chemical Company), ethylene-octene copolymer, octene content of about 30 wt%, melt index (190°C, 2.16 kg) of about 0.5-1.5 g / 10 min.

[0033] Coffee grounds: The residue after grinding food-grade discarded Arabica coffee beans was washed, dried in an 80°C oven for 12 hours, ground with a grinder, and sieved through a 200-mesh standard sieve.

[0034] Bamboo powder: Moso bamboo is mechanically crushed, dried in an 80°C oven for 12 hours, and then sieved through a 60-mesh standard sieve.

[0035] Polypropylene grafted maleic anhydride (PP-g-MAH): Brand P353 (DuPont), maleic anhydride grafting rate 0.8-1.0wt%, melt index (190°C, 2.16kg) about 100-130g / 10min.

[0036] Reactive coupling agents / modifiers (RCM): RCM-A: Epoxidized Soybean Oil (ESO), industrial grade, epoxy value ≥ 6.0%, purchased from Arkema.

[0037] RCM-B: Homemade maleated polylactic acid oligomer (M-PLAO), prepared as follows: L-lactic acid (content ≥88%) is subjected to a polycondensation reaction at 160-180°C under nitrogen with stirring for 4-6 hours to obtain a polylactic acid oligomer (PLAO) with a number average molecular weight of 1800-2200 Da. PLAO is then reacted with maleic anhydride (mass ratio PLAO:maleic anhydride = 10:1 to 10:1.5) in xylene solvent at 130-140°C for 3-5 hours. After the reaction, the solvent and unreacted maleic anhydride are removed by distillation under reduced pressure to obtain M-PLAO with an acid value of 20-30 mg KOH / g.

[0038] PP flow aid: ethylene bisstearamide (EBS), industrial grade, melting point 140-145°C.

[0039] Zinc stearate: industrial grade, zinc content 10.5-11.5%.

[0040] Antioxidant 1010: Chemical name: Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], industrial grade, purity ≥98%.

[0041] Antioxidant 168: Chemical name: tris(2,4-di-tert-butylphenyl) phosphite, industrial grade, purity ≥98%.

[0042] Degradation agent: Oxidative degradation accelerator masterbatch containing a complex of ferrocene and calcium stearate, trade name Reverte TM , purchased from Wells Plastics Ltd., UK.

[0043] Composite microbial agent: prepared by mixing Trichoderma reesei ATCC 26921, Aspergillus niger ATCC 16404, and Pseudomonas fluorescens ATCC13525 in a ratio of 1:1:1 (w / w / w, based on the weight of lyophilized powder). Resuscitated with sterile water before use and cultured to the logarithmic growth phase to prepare a total viable count of not less than 1×10 9 The bacterial suspension was 1000 CFU / mL. Each strain was purchased from China General Microbiological Culture Collection Center (CGMCC).

[0044] Examples 1 to 4: Example 1: Recipe composition: The weights of the components (unit: gram) and their corresponding weight percentages (%) are as follows: Homopolymer polypropylene (hPP): 350.0 g (35.0%); Copolymerized polypropylene (cPP): 200.0 g (20.0%); Polyolefin elastomer (POE): 75.0 g (7.5%); Coffee grounds (200 mesh): 150.0 g (15.0%); Bamboo powder (60 mesh): 150.0g (15.0%); Polypropylene grafted maleic anhydride (PP-g-MAH): 30.0 g (3.0%); Reactive coupling agent / modifier (RCM-A): 10.0 g (1.0%); PP flow aid (EBS): 16.0 g (1.6%); Zinc stearate: 3.0 g (0.3%); Antioxidant 1010: 3.0 g (0.3%); Antioxidant 168: 3.0 g (0.3%); Degradant: 20.0 g (2.0%).

[0045] The total weight of each component is 1000.0 g.

[0046] Preparation steps: (1) Raw material pretreatment: The weighed coffee grounds and bamboo powder were placed in a forced air drying oven and dried at 90±2°C to reduce the moisture content to below 0.8 wt%.

[0047] (2) Premixing I: Add the coffee grounds and bamboo powder dried in step (1) and the formulated amount of RCM-A into a SHR-25A high-speed mixer and premix at a speed of 800 rpm for 10 minutes.

[0048] (3) Premix II: Add the formulated amounts of homopolypropylene, copolymer polypropylene, polyolefin elastomer, polypropylene grafted maleic anhydride, PP flow aid, zinc stearate, antioxidant 1010, antioxidant 168 and degradation agent to the mixture of step (2), and continue mixing in a high-speed mixer at a speed of 800 rpm for 15 minutes to obtain a uniform total mixture.

[0049] (4) Melt Blending and Extrusion Granulation: The total mixture obtained in step (3) was fed into a co-rotating twin-screw extruder (screw diameter 35.6 mm, aspect ratio L / D = 40) through a feeding device. The temperatures of the extruder sections from the feed port to the die were set as follows: 150°C, 170°C, 175°C, 165°C, 160°C, 150°C, and 190°C (die). The screw speed was set at 150 rpm.

[0050] (5) Granulation and molding: After the extruded strips were cooled in a water trough, they were cut into pellets with a length of approximately 3 mm by a pelletizer. The pellets were dried in an oven at 100°C for 4 hours and then injection molded into standard tensile, flexural, and impact test specimens using an injection molding machine. The injection molding process parameters were: barrel temperatures of 170 / 175 / 180 / 185°C (from hopper to nozzle) and a mold temperature of 40°C.

[0051] Example 2: Recipe composition: The weights of the components (unit: gram) and their corresponding weight percentages (%) are as follows: Homopolymer polypropylene (hPP): 345.0 g (34.5%); Copolymerized polypropylene (cPP): 200.0 g (20.0%); Polyolefin elastomer (POE): 75.0 g (7.5%); Coffee grounds (200 mesh): 150.0 g (15.0%); Bamboo powder (60 mesh): 150.0g (15.0%); Polypropylene grafted maleic anhydride (PP-g-MAH): 30.0 g (3.0%); Reactive coupling agent / modifier (RCM-B): 15.0 g (1.5%); PP flow aid (EBS): 16.0 g (1.6%); Zinc stearate: 3.0 g (0.3%); Antioxidant 1010: 3.0 g (0.3%); Antioxidant 168: 3.0 g (0.3%); Degradant: 20.0 g (2.0%).

[0052] The total weight of each component is 1000.0 g.

[0053] Preparation steps: The preparation steps were the same as those in Example 1, except that RCM-A was replaced with RCM-B having the same technical effect in the premix I of step (2). All other raw materials, equipment, process parameters and operations were the same as those in Example 1.

[0054] Example 3: Recipe composition: The weights of the components (unit: gram) and their corresponding weight percentages (%) are as follows: Homopolymer polypropylene (hPP): 355.0 g (35.5%); Copolymerized polypropylene (cPP): 200.0 g (20.0%); Polyolefin elastomer (POE): 75.0 g (7.5%); Coffee grounds (200 mesh): 150.0 g (15.0%); Bamboo powder (60 mesh): 150.0g (15.0%); Polypropylene grafted maleic anhydride (PP-g-MAH): 30.0 g (3.0%); Reactive coupling agent / modifier (RCM-A): 5.0 g (0.5%); PP flow aid (EBS): 16.0 g (1.6%); Zinc stearate: 3.0 g (0.3%); Antioxidant 1010: 3.0 g (0.3%); Antioxidant 168: 3.0 g (0.3%); Degradant: 20.0 g (2.0%).

[0055] The total weight of each component is 1000.0 g.

[0056] Preparation steps: The preparation steps were the same as in Example 1, except that in the premix I of step (2), the amount of reactive coupling agent / modifier (RCM-A) was adjusted to 5.0 g, and the amount of homopolypropylene (hPP) was adjusted to 355.0 g. All other raw materials, equipment, process parameters, and operations remained the same as in Example 1.

[0057] Example 4: Recipe composition: The weights of the components (unit: gram) and their corresponding weight percentages (%) are as follows: Homopolymer polypropylene (hPP): 340.0 g (34.0%); Copolymerized polypropylene (cPP): 200.0 g (20.0%); Polyolefin elastomer (POE): 75.0 g (7.5%); Coffee grounds (200 mesh): 150.0 g (15.0%); Bamboo powder (60 mesh): 150.0g (15.0%); Polypropylene grafted maleic anhydride (PP-g-MAH): 30.0 g (3.0%); Reactive coupling agent / modifier (RCM-A): 20.0 g (2.0%); PP flow aid (EBS): 16.0 g (1.6%); Zinc stearate: 3.0 g (0.3%); Antioxidant 1010: 3.0 g (0.3%); Antioxidant 168: 3.0 g (0.3%); Degradant: 20.0 g (2.0%).

[0058] The total weight of each component is 1000.0 g.

[0059] Preparation steps: The preparation steps were the same as in Example 1, except that in the premix I of step (2), the amount of reactive coupling agent / modifier (RCM-A) was adjusted to 20.0 g, and the amount of homopolypropylene (hPP) was adjusted to 340.0 g. All other raw materials, equipment, process parameters, and operations remained the same as in Example 1.

[0060] Comparative Examples 1 to 3: Comparative Example 1: Compared with Example 1, the difference is that the reactive coupling agent / modifier (RCM-A) is not added, and its 10.0 g weight is replaced by 10.0 g of homopolypropylene (hPP), that is, the amount of homopolypropylene (hPP) used is 360.0 g. The types and amounts of the remaining components and all preparation steps are exactly the same as in Example 1.

[0061] Comparative Example 2: Compared to Example 1, the difference is that the reactive coupling agent / modifier (RCM-A) is omitted, and its 10.0 g weight is replaced by 10.0 g of homopolypropylene (hPP), i.e., the amount of homopolypropylene (hPP) used is 360.0 g. In this comparative example, the amount of polypropylene grafted with maleic anhydride (PP-g-MAH) used remains at 30.0 g. The types and amounts of the remaining components, as well as all preparation steps, are identical to those in Example 1.

[0062] Comparative Example 3: The formulation was identical to that of Example 1, except for the premixing method used in the preparation steps: Step (2) "Premixing I" (i.e., the separate premixing step of coffee grounds, bamboo powder, and RCM-A) in Example 1 was omitted. Specifically, the dried coffee grounds, bamboo powder, RCM-A, and all other components listed in Step (3) of Example 1 were added simultaneously to a high-speed mixer and mixed at 800 rpm for 25 minutes to obtain a total mixture. The remaining raw material pretreatment, melt blending, extrusion granulation, and injection molding steps were identical to those of Example 1.

[0063] Test cases 1 to 3: Test Example 1: Mechanical properties test 1. Purpose of the experiment This test example aims to evaluate the mechanical properties of the coffee grounds composite polypropylene degradation material prepared by the methods of the examples and comparative examples, mainly including tensile properties, bending properties and impact properties.

[0064] 2. Experimental equipment and materials Universal materials testing machine.

[0065] Simple supported beam impact testing machine.

[0066] Test sample: standard injection molded specimen obtained by step (5) in the preparation method of Examples 1-4 and Comparative Examples 1-3.

[0067] 3. Experimental Procedure All mechanical property tests were conducted at room temperature (23±2)°C and relative humidity (50±5)%. Before testing, all specimens were conditioned under the same conditions for at least 24 hours.

[0068] Tensile properties test: (1) Refer to GB / T 1040.2-2006 “Determination of tensile properties of plastics Part 2: Test conditions for moulding and extruded plastics”.

[0069] (2) Select the standard IBA dumbbell spline.

[0070] (3) Install the specimen on the fixture of the universal material testing machine and set the test speed to 50 mm / min.

[0071] (4) Start the testing machine, record the maximum tensile load and gauge elongation when the specimen breaks, and calculate the tensile strength and elongation at break.

[0072] (5) At least 5 valid samples were tested for each formula group, and the arithmetic mean of the results was taken.

[0073] Bending performance test: (1) Refer to GB / T 9341-2008 “Determination of flexural properties of plastics”.

[0074] (2) Select a long strip spline with a size of 80mm×10mm×4mm.

[0075] (3) Set the test span to 64 mm (16 times the thickness of the specimen) and the test speed to 2 mm / min.

[0076] (4) Place the specimen on the three-point bending fixture of the testing machine.

[0077] (5) Start the testing machine, record the maximum bending load and corresponding deflection when the specimen breaks or reaches the specified deflection, and calculate the bending strength and bending modulus.

[0078] (6) At least 5 valid samples were tested for each formula group, and the arithmetic mean of the results was taken.

[0079] Charpy notched impact strength test: (1) Refer to GB / T 1043.1-2008 “Determination of impact properties of simply supported plastic beams Part 1: Non-instrumented impact test”.

[0080] (2) Select a long strip of spline with a size of 80 mm × 10 mm × 4 mm and machine an A-type notch in the center of the spline (in accordance with the requirements of type 1A specimen in GB / T 1043.1-2008, with a notch depth of 2 mm and a notch tip radius of 0.25 mm).

[0081] (3) Select an appropriate pendulum energy (e.g., a 2J or 4J pendulum) to ensure that the spline breaks after impact and the energy consumed by the pendulum is within the range of 10% to 80% of the nominal energy of the pendulum.

[0082] (4) Place the notched specimen on the simply supported beam support of the impact testing machine with the notch facing away from the impact direction, and ensure that the center line of the specimen is aligned with the center line of the support.

[0083] (5) Release the pendulum and record the energy absorbed by the spline fracture.

[0084] (6) Calculate the notched impact strength of simply supported beam (unit: kJ / m 2 ), the calculation formula is: cN =(E c / (h·b N ))×10 3 , where E c is the energy absorbed when the sample breaks (joules), h is the thickness of the sample (mm), b N is the remaining width of the specimen at the notch (mm).

[0085] (7) At least 5 valid samples were tested for each formula group, and the arithmetic mean of the results was taken.

[0086] 4. Experimental data recording Table 1 Mechanical properties test results of the composite materials of various embodiments and comparative examples From the mechanical property test results in Table 1, it can be seen that the composite materials prepared by Examples 1 to 4 of the present invention show a certain degree of improvement in tensile strength, flexural strength and flexural modulus compared to Comparative Example 1 which does not contain a reactive coupling agent / modifier (RCM) and Comparative Example 2 which relies only on traditional polypropylene grafted maleic anhydride as a compatibilizer. This is mainly attributed to the introduced RCM component, which contains functional groups that can react in situ with the surface active groups of coffee grounds and / or bamboo powder, which promote the enhancement of the interfacial bonding force between the filler and the polypropylene matrix during the melt blending process. This enhanced interfacial interaction is conducive to the effective transfer of stress between the interfaces, thereby improving the ability of the material to resist external loads. Example 1 and Example 2 used RCM-A (epoxidized soybean oil) and RCM-B (maleic anhydride polylactic acid oligomer) with different chemical structures, respectively, and both obtained similar performance improvement trends, indicating that different types of RCMs with the specific reactivity can effectively improve interfacial compatibility, thereby improving the macroscopic mechanical properties of the material.

[0087] Comparing the results of Example 1 and Comparative Example 3, it can be seen that even if the same formula is used, the pre-mixing step of RCM and biological filler in the preparation process and the appropriate melt blending conditions are crucial to achieving the best effect of RCM. In Example 1, the pre-mixing of RCM and filler enables RCM to be more evenly adsorbed on the surface of the filler, and in the subsequent melt blending and extrusion process, it fully undergoes in situ chemical reaction with the active groups on the surface of the filler under the set temperature and shear conditions to form a more effective and stable functionalized interface. In Comparative Example 3, since the separate pre-mixing step of RCM and filler was omitted, or processing conditions that are not conducive to the reaction were used, RCM may not be able to fully and evenly interact with the filler surface, and its effect of improving interfacial bonding is therefore limited, and the improvement in mechanical properties is not as good as in Example 1. This emphasizes the importance of the specific preparation method proposed in the present invention for achieving the expected function of RCM.

[0088] In Example 1, Example 3 and Example 4, the effect of the amount of RCM-A in the range of 0.5% to 2.0% was investigated. The results showed that within this range of addition, the mechanical properties of the materials were better than those of the control group without RCM. This indicates that the selected RCM can effectively exert its interface enhancement effect within this concentration range. This optimized interface constructed by RCM is not only crucial for the mechanical properties of the material during the use phase, but also lays a physical foundation for the subsequent interaction between the chemical structure of RCM or its initial degradation products and the composite microbial agent to induce or enhance enzyme activity after the material is discarded, that is, it creates an interface microenvironment that is more conducive to microbial attachment and enzyme action, thereby echoing the core innovative concept of the present invention - the goal of constructing an autocrine enzymatic degradation microenvironment and improving the overall biodegradability of the material.

[0089] Test Example 2: Biodegradation Performance Test (Weight Loss Method) 1. Purpose of the experiment This test example aims to evaluate the biodegradability of the coffee grounds composite polypropylene degradable material prepared by the methods of the examples and comparative examples under controlled composting conditions, and the evaluation is performed by measuring the weight loss rate of the material.

[0090] 2. Experimental equipment and materials Constant temperature aerobic composting box: can control the temperature at (58±2)℃ and maintain aerobic conditions.

[0091] Analytical balance: precision 0.1 mg.

[0092] Blast drying oven: used for sample drying.

[0093] Test sample: The injection molded strips obtained in step (5) of the preparation method of Examples 1-4 and Comparative Examples 1-3 were cut into sheet samples with a size of 25 mm × 25 mm × 2 mm.

[0094] Composting medium: Mature municipal solid waste compost with an organic matter content greater than 40%, a C / N ratio of 20-30:1, a pH of 7.0-8.0, and sieved to remove impurities larger than 10 mm. Adjust the moisture content to (55 ± 5)% before use.

[0095] Composite microbial agent: the same as the composite microbial agent listed in the above raw materials section.

[0096] 3. Experimental Procedures (1) Initial Sample Treatment: Dry the cut sheet samples in a forced air drying oven at 60°C to a constant weight, and accurately weigh their initial dry weight, which is recorded as W0. Prepare at least three parallel samples for each formulation group.

[0097] (2) Composting system construction: Take an appropriate amount of compost medium with adjusted moisture content and mix it evenly with the test sample at a ratio of 10:1 (compost dry weight: sample dry weight). At the beginning of composting, inoculate 10 grams (freeze-dried powder) of composite microbial inoculant per kilogram of dry compost medium. The bacterial suspension that has been revived and cultured to the logarithmic growth phase is evenly sprayed and mixed into the composting system.

[0098] (3) Composting conditions: Place the compost containing the sample in a constant-temperature aerobic composting bin set at (58 ± 2)°C. Turn the compost 1-2 times daily to ensure good aerobic conditions. Check and adjust the compost moisture content weekly to maintain it at (55 ± 5)%.

[0099] (4) Sampling and processing: Corresponding samples were taken from each composting system at 0 days, 15 days, 30 days, 45 days, 60 days and 90 days after the start of composting.

[0100] (5) Sample post-processing: The sample was carefully rinsed with distilled water to remove the compost residue attached to the surface and avoid loss of the sample itself. The cleaned sample was then placed in a 60°C blast drying oven to dry to a constant weight, and its dry weight was accurately weighed and recorded as W. t .

[0101] (6) Calculation of weight loss rate: Calculate the weight loss rate of the sample at each time point according to the following formula: Weight loss rate (%) = ((W0-W t ) / W0)×100%((W0-W t ) / W0)×100%; 4. Experimental data recording Table 2 Weight loss rate of composite materials of various embodiments and comparative examples under controlled composting conditions (%) sample 15 days 30 days 45 days 60 days 90 days Example 1 4.2 9.5 16.8 25.1 38.7 Example 2 3.9 8.8 15.5 24.3 37.2 Example 3 3.1 7.2 13.4 20.9 32.5 Example 4 4.8 10.3 18.1 27.3 41.1 Comparative Example 1 1.1 2.5 4.3 6.8 10.2 Comparative Example 2 1.5 3.1 5.2 8.1 12.8 Comparative Example 3 2.3 5.4 9.9 15.6 23.9 The weight loss data shown in Table 2 clearly show that the composite materials prepared in Examples 1 to 4 of the present invention have significantly better biodegradability than Comparative Example 1, Comparative Example 2 and Comparative Example 3 under simulated controlled composting conditions. Specifically, after 90 days of composting, the weight loss rate of the example materials is much higher than that of the comparative example materials. This result strongly supports the positive role of the introduced reactive coupling agent / modifier (RCM) in improving the biodegradability of the material. The presence of RCM not only improves the interfacial bonding between the biofiller (coffee grounds and bamboo powder) and the polypropylene matrix, as indirectly reflected by the mechanical property results of Test Example 1, but more importantly, this functionalized interface creates more favorable conditions for subsequent microbial erosion and enzymatic hydrolysis, making the biofiller with biodegradation potential itself more easily utilized by microorganisms.

[0102] The core technical concept of the present invention lies in the dual function of RCM. First, it constructs a stable functionalized interface by reacting in situ with the active groups on the surface of the biological filler. Secondly, more importantly, the chemical structure of RCM or the small molecule fragments produced by its initial degradation in a composting environment (for example, by hydrolysis) are designed to interact with specific strains in the inoculated composite microbial agent, thereby inducing or enhancing the ability of these strains to produce active degradative enzymes (such as cellulases, esterases, etc.). These "activated" or "enhanced" microorganisms and the enzymes they secrete can more effectively degrade the biological filler, and synergize with the action of the degrader (promoting the initial oxidation chain scission of polypropylene) to produce a certain degree of degradation effect on the polypropylene matrix. Comparative Example 1 has the lowest degradation rate due to the lack of RCM. Although Comparative Example 2 contains the conventional compatibilizer PP-g-MAH, its main function is to improve compatibility and does not have the specific function of inducing microbial enzyme production, so its degradation performance improvement is limited. The formula of Comparative Example 3 is the same as that of Example 1, but an improper premixing process is used, which may result in RCM failing to fully react with the filler in situ or failing to be evenly distributed, thereby weakening its subsequent induction of enzyme production effect. Its weight loss rate is between Comparative Example 1 / 2 and Example 1, further confirming the importance of a specific preparation method for achieving the intended function of RCM.

[0103] Overall, the high weight loss rate exhibited by the example materials is the result of the synergistic effect of multiple factors: including the RCM-enhanced interface that makes the biofiller more accessible to microorganisms; the initial oxidation of the polypropylene matrix by the degradation agent; and most critically, the induction and enhancement of the enzyme production capacity of the composite microbial agent mediated by the structural characteristics of the RCM. This "autocrine enzymatic degradation microenvironment" formed within the material, especially near the interface between the biofiller and the polymer matrix, significantly accelerates the biodegradation process of the entire composite material. Example 1 (RCM-A) and Example 2 (RCM-B) use RCMs with different chemical structures and both exhibit good degradation performance, indicating that the technical principles of the present invention have a certain degree of universality. The changes in the amount of RCM-A used in Examples 3 and 4 also reflect the impact of its addition amount on the final degradation effect. Within the tested range, the addition of RCM brought about a significant improvement in degradation performance. These results collectively confirm the effectiveness and innovation of the coffee grounds composite polypropylene degradation material and its preparation method provided by the present invention in improving the biodegradability of the material.

[0104] Test Example 3: Indirect Indication of RCM Function - Observation of Microbial Growth Promotion 1. Purpose of the experiment This test case aims to observe the growth of composite microbial agents in culture medium with different material powders as potential carbon sources or stimulants (measured in optical density OD 600The reactive coupling agent / modifier (RCM) or the structure formed by the reactive coupling agent / modifier in the material is indirectly evaluated to indirectly evaluate the potential promoting effect of the reactive coupling agent / modifier (RCM) used in the present invention on the activity of microorganisms, thereby providing evidence for the mechanism by which RCM can induce or enhance the enzyme production of microorganisms.

[0105] 2. Experimental equipment and materials UV-Vis spectrophotometer: capable of measuring absorbance at 600nm.

[0106] Constant temperature shaker incubator: can control temperature and shaking frequency.

[0107] High pressure steam sterilizer.

[0108] Sterile conical flasks, pipettes and other common laboratory glassware and consumables.

[0109] Material powder: The composite material particles prepared in Example 1 were frozen and embrittled in liquid nitrogen, then ground with a high-speed grinder, and sieved through a 100-mesh sieve to obtain the material powder of Example 1.

[0110] The composite material particles prepared in Comparative Example 1 were treated in the same manner to obtain the material powder of Comparative Example 1.

[0111] The composite material particles prepared in Comparative Example 3 were treated in the same manner to obtain the material powder of Comparative Example 3.

[0112] Basic carbon-free liquid medium: Contains (NH₄)₂SO₄ 1.0g, KH₂PO₄ 0.5g, K₂HPO₄ 0.5g, MgSO₄·7H₂O 0.2g, and yeast extract 0.1g per liter. Adjust pH to 7.0-7.2 with NaOH. This medium contains minimal yeast extract, primarily providing trace growth factors. The carbon source is primarily derived from the added powdered materials.

[0113] Composite microbial agent: the same composite microbial agent as listed in the raw materials section above, prepared into OD 600 A bacterial suspension of approximately 1.0.

[0114] 3. Experimental steps (1) Culture medium preparation and packaging: Prepare the basic carbon-free liquid culture medium according to the formula and distribute it into several 250 mL conical flasks, with 100 mL in each bottle.

[0115] (2) Material powder addition: Group A (Example 1 Group): 0.50 g of Example 1 material powder was accurately added to several conical flasks.

[0116] Group B (Comparative Example 1): 0.50 g of the powder of the material of Comparative Example 1 was accurately added to several conical flasks.

[0117] Group C (Comparative Example 3): 0.50 g of the powder of the material of Comparative Example 3 was accurately added to several conical flasks.

[0118] Group D (blank control group): No material powder was added, only 100 mL of basic carbon-free liquid culture medium.

[0119] (3) Sterilization: Seal all conical flasks with cotton plugs and sterilize them by high-pressure steam at 121°C for 20 minutes.

[0120] (4) Microbial inoculation: After the culture medium has cooled to room temperature, 1.0 mL of the pre-prepared composite microbial suspension (OD 600 is approximately 1.0).

[0121] (5) Cultivation: All the inoculated conical flasks were placed in a constant temperature shaker at 30°C and 150 rpm for cultivation.

[0122] (6) OD value determination: After 0 hours, 24 hours, 48 hours and 72 hours of culture, samples were taken from each group of conical flasks aseptically and the absorbance of the culture solution at 600 nm (OD) was measured using a UV-visible spectrophotometer. 600 Values were obtained. Three replicate samples were taken from each group at each time point and the results were averaged. Before measurement, if the sample is too turbid to affect the reading, a small amount of uninoculated culture medium from the same group (containing the corresponding powder) can be used as a reference to adjust the zero.

[0123] 4. Experimental data recording Table 3 Growth of composite microbial agents under different material powder culture conditions (OD 600 value) Culture time (h) Group A (Example 1) Group B (Comparative Example 1) Group C (Comparative Example 3) Group D (blank control) 0 0.052 0.051 0.053 0.049 24 0.283 0.102 0.157 0.065 48 0.615 0.188 0.321 0.073 72 0.927 0.253 0.488 0.081 Note: The OD value at 0 hours mainly reflects the amount of inoculated bacteria and the initial turbidity caused by the material powder itself.

[0124] The data in Table 3 show that there are significant differences in the growth of composite microbial inoculants under the culture conditions with different material powders as the main carbon source or stimulant. Compared with the blank control group D (containing only a very small amount of yeast extract, with little or no microbial growth or very slow growth), all experimental groups (A, B, and C) with added material powders were observed to have a certain degree of microbial growth, indicating that the biological fillers (coffee grounds and bamboo powder) in the materials can provide some nutrition for the microorganisms. More importantly, the OD value of the culture medium of Group A (material powder of Example 1) was 0.04477 W / m. 600The values were significantly higher than those of Group B (powdered material of Comparative Example 1) and Group C (powdered material of Comparative Example 3) at all test time points. This indicates that the material of Example 1, which contains the specific reactive coupling agent / modifier (RCM) of the present invention and is prepared through appropriate processes, can more effectively promote the growth and proliferation of the inoculated composite microbial inoculum.

[0125] This difference in the effect of promoting microbial growth indirectly reflects the specific function of RCM in the material. As mentioned above, the design of RCM is intended to interact favorably with the target microorganisms through its specific chemical structure or the small molecule fragments released by its initial degradation (such as hydrolysis) in the environment. This interaction may include providing a more readily available primary carbon source for the microorganism, or more importantly, as a signal molecule or substrate analog, inducing or enhancing the expression and secretion of microbial metabolic activity and related enzyme systems (especially enzymes related to the degradation of biological fillers, such as cellulases, lignin degrading enzymes, and esterases related to the initial oxidation products of polymers). Since Group B (Comparative Example 1) does not contain RCM, the microorganisms mainly rely on the slow degradation of the biological filler to obtain nutrients, so they grow relatively slowly. Although Group C (Comparative Example 3) contains RCM, since the RCM and the filler may not be fully reacted in situ and evenly dispersed during its preparation process, the release of bioactive substances of RCM or its inductive effect cannot be fully exerted, so its effect on promoting microbial growth is between Group A and Group B.

[0126] The results of this test example are consistent with the trend of the difference in weight loss rate observed in Test Example 2, which further reveals the advantages of the technical solution of the present invention from the perspective of microbial activity. One of the mechanisms why the material of Example 1 shows better biodegradation performance (as shown in Test Example 2) is that RCM promotes the growth and activity of microorganisms, thereby enhancing the enzyme production capacity of the microbial community as a whole. This "activated" microbial community forms an "autocrine enzymatic degradation microenvironment" with high enzyme activity inside the material, especially at the interface between the RCM functionalized filler and the polymer matrix. This microenvironment not only accelerates the decomposition of the biological filler, but also creates more favorable conditions for the subsequent degradation of the polypropylene matrix (for example, by producing enzymes that can act on the primary oxidation products of polypropylene, or by improving the hydrophilicity of the local environment, etc.). Therefore, the results of this test example strongly support the core technical concept of RCM to improve the overall biodegradation efficiency of composite materials by regulating the behavior of microorganisms.

[0127] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A coffee grounds composite polypropylene degradation material, characterized in that: Measured by weight percentage, it comprises: Homopolymer polypropylene: 34.0-36.0%; Copolymer polypropylene: 19.0-21.0%; Polyolefin elastomer: 7.0-8.0%; Coffee grounds passed through a 200-mesh sieve: 14.5-15.5%; Bamboo powder passing through 60-mesh sieve: 14.5-15.5%; Polypropylene grafted maleic anhydride: 2.8-3.2%; Reactive coupling agent / modifier: 0.5-2.0%; Polypropylene flow aid: 1.4-1.8%; Zinc stearate: 0.25-0.35%; Antioxidant 1010: 0.25-0.35%; Antioxidant 168: 0.25-0.35%; Degradants: 1.8-2.2%; The reactive coupling agent / modifier contains a functional group capable of undergoing an in-situ chemical reaction with active groups on the surface of the coffee grounds and / or bamboo powder, and the chemical structure of the reactive coupling agent / modifier or its initial degradation product is suitable for interacting with a specific strain in a subsequently introduced composite microbial inoculant during degradation of the material, thereby inducing or enhancing the production of active degradative enzymes by the strain.

2. The coffee grounds composite polypropylene degradation material according to claim 1, characterized in that: The reactive coupling agent / modifier is selected from at least one of a bio-based oligomer having an epoxy group, a carboxyl group or an anhydride group, or a synthetic compound containing an isocyanate group, a siloxane group and connected with a specific biologically active fragment.

3. The coffee grounds composite polypropylene degradable material according to claim 1, characterized in that: The polyolefin elastomer is an ethylene-octene copolymer, and its octene content ranges from 20 to 35 wt%.

4. The coffee grounds composite polypropylene degradation material according to claim 1, characterized in that: The maleic anhydride grafting rate of the polypropylene grafted with maleic anhydride is 0.5 to 1.2 wt %.

5. The coffee grounds composite polypropylene degradable material according to claim 1, characterized in that: The chemical structure of the reactive coupling agent / modifier or its initial degradation product can serve as a signal molecule or substrate analog to induce or enhance the production of active degradation enzymes by specific strains in the composite microbial agent.

6. A method for preparing the coffee grounds composite polypropylene degradable material according to any one of claims 1 to 5, characterized in that: The following steps are involved: (a) premixing coffee grounds passed through a 200-mesh sieve, bamboo powder passed through a 60-mesh sieve, and the reactive coupling agent / modifier to obtain a filler premix; (b) mixing the filler premix obtained in step (a) with homopolypropylene, copolymer polypropylene, polyolefin elastomer, polypropylene grafted maleic anhydride, polypropylene flow aid, zinc stearate, antioxidant 1010, antioxidant 168, and a degradation agent to obtain a total mixture; (c) subjecting the total mixture to melt blending and extrusion, wherein during the melt blending and extrusion process, the reactive coupling agent / modifier reacts in situ with the active groups on the surface of the coffee grounds and / or bamboo powder to form a functionalized interface; (d) cooling and pelletizing the extrudate to obtain the coffee grounds composite polypropylene degradation material.

7. The preparation method according to claim 6, characterized in that Before step (a), the method further includes drying the coffee grounds and bamboo powder at 80-100° C. to reduce the moisture content of the coffee grounds and bamboo powder to less than 0.8 wt %.

8. The preparation method according to claim 6, characterized in that The premixing in step (a) and / or the mixing in step (b) are performed in a high-speed mixer at a rotation speed ranging from 600 to 1200 rpm.

9. The preparation method according to claim 6, characterized in that The melt blending extrusion in step (c) is carried out in a twin-screw extruder, the temperature of each heating zone of the extruder is set in the range of 150° C. to 190° C., and the screw speed is controlled in the range of 100 to 200 rpm.

10. The preparation method according to claim 6, characterized in that The in situ chemical reaction of the reactive coupling agent / modifier with the coffee grounds and / or bamboo powder in step (c) is intended to form a functionalized interface that, when the material is subsequently exposed to a composite microbial inoculum and degradation conditions, is conducive to the chemical structure of the RCM or its initial degradation products inducing or enhancing the production of active degrading enzymes by specific strains in the inoculum.

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