A coffee grounds composite polypropylene degradable material and its preparation method

Abstract

The present application relates to the field of biodegradable materials, and discloses a coffee residue composite polypropylene degradable material and a preparation method thereof, which is made of the following components: homopolymer polypropylene, copolymer polypropylene, polyolefin elastomer, coffee residue, bamboo powder, polypropylene grafted maleic anhydride, reactive coupling agent / modifier (RCM), PP flow aid, zinc stearate, antioxidant, and degradable agent; the core of the present application lies in the use of RCM, which can not only react with the active groups on the surface of coffee residue and bamboo powder in situ during melt blending to form a functional interface to improve the compatibility of fillers with the polypropylene matrix and the mechanical properties of the material. The present application also discloses a preparation method of the material, which comprises the steps of pre-mixing of fillers and RCM, total mixing, melt blending extrusion and granulation. The material of the present application has good mechanical properties and excellent biodegradability, and can effectively utilize waste biomass resources and reduce environmental pollution.

Description

Technical Field

[0001] This invention relates to the field of biodegradable materials technology, and in particular to a coffee grounds composite polypropylene biodegradable material and its preparation method. Background Technology

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

[0003] However, the practical application of such polypropylene / biomass composites still faces many challenges in the current technology. A core issue lies in the poor interfacial compatibility between the hydrophilic biomass filler and the hydrophobic polypropylene matrix. This not only leads to the composite material's mechanical properties often failing to meet expectations, affecting its usability, but also hinders the effective erosion and degradation of the filler by microorganisms. Although traditional compatibilizers such as maleic anhydride-grafted polypropylene (PP-g-MAH) are often used to improve the interfacial condition, their effect is mainly reflected at the physical or limited chemical bonding level, contributing little to improving the deep and synergistic biodegradation efficiency of the material.

[0004] Furthermore, even if the biomass filler is partially degradable, the inertness of the polypropylene matrix itself remains a key bottleneck restricting the complete biodegradation of the composite material. While existing oxidative degradation promoters can accelerate the chain breaking and fragmentation of polypropylene to some extent, this is primarily a non-biological oxidation process; the resulting fragments are still polypropylene, and their subsequent biomineralization is very slow. Therefore, relying solely on the degradation of the filler and the initial oxidation of the matrix often results in unsatisfactory overall degradation rates and degrees, failing to meet the requirements for rapid and efficient biological disposal. Existing technologies also pay little 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 techniques to effectively stimulate microorganisms to produce specific degrading enzymes and promote the synergistic action of these enzymes on the biomass filler and polymer matrix, thereby achieving optimization of the internal degradation microenvironment and a substantial breakthrough in overall degradation efficiency. Summary of the Invention

[0005] The present invention aims to solve the technical problems of insufficient biodegradability of existing polypropylene composite materials and the need to improve the interfacial bonding between biological fillers and polymer matrix.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The first aspect of this invention provides a coffee grounds composite polypropylene biodegradable material. Through the synergistic effect of specific components, particularly the introduction of a reactive coupling agent / modifier (RCM), a microenvironment conducive to subsequent microbial degradation is constructed within the material, thereby aiming to improve the overall biodegradability efficiency and physical properties of the material.

[0008] To achieve the above objectives, the technical solution adopted in the first aspect of the present invention is as follows:

[0009] A coffee grounds composite polypropylene biodegradable material, by weight percentage, comprises:

[0010] Homopolymer polypropylene: 34.0-36.0%;

[0011] Copolymer polypropylene: 19.0-21.0%;

[0012] Polyolefin elastomers: 7.0-8.0%;

[0013] Coffee grounds passing through a 200-mesh sieve: 14.5-15.5%;

[0014] Bamboo powder passing through a 60-mesh sieve: 14.5-15.5%;

[0015] Polypropylene grafted with maleic anhydride: 2.8-3.2%;

[0016] Reactive coupling agent / modifier (RCM): 0.5-2.0%;

[0017] Polypropylene flow aid: 1.4-1.8%;

[0018] Zinc stearate: 0.25-0.35%;

[0019] Antioxidant 1010: 0.25-0.35%;

[0020] Antioxidant 168: 0.25-0.35%;

[0021] And degradation agents: 1.8-2.2%.

[0022] The key is that the reactive coupling agent / modifier (RCM) has a special dual-functional design.

[0023] First, it contains functional groups capable of undergoing in-situ chemical reactions with active groups such as hydroxyl groups on the surface of the coffee grounds and / or bamboo powder. This in-situ reaction aims to enhance the interfacial bonding strength between the bio-filler and the polypropylene matrix, thereby improving the physical and mechanical properties and processing stability of the composite material.

[0024] Secondly, the chemical structure of the RCM or specific small molecule fragments released during the initial stages of material degradation (e.g., through hydrolysis) are designed to facilitate beneficial interactions with specific strains in the compound microbial agent when the material subsequently enters the degradation environment and is introduced. Specifically, this interaction manifests as the ability to induce or enhance the ability of the specific strains to produce active degrading enzymes (e.g., lignocellulase, esterase, or enzymes targeting the initial oxidation of polypropylene fragments).

[0025] Thus, a "self-secretory enzyme-catalyzed degradation microenvironment" with high local enzyme activity is formed around the functionalized filler interface, creating favorable conditions for the effective degradation of subsequent biological fillers and polypropylene matrix.

[0026] In some embodiments, the reactive coupling agent / modifier (RCM) may be selected from bio-based oligomers having epoxy, carboxyl, or anhydride groups (e.g., modified vegetable oil derivatives or modified oligolactic acid products), or from at least one synthetic compound containing isocyanate groups, siloxane groups, and linked to specific bioactive fragments. The selection of these specific functional groups is intended to ensure effective chemical bonding or strong interaction with the active groups on the surface of the biofiller.

[0027] In some embodiments, the polyolefin elastomer is preferably an ethylene-octene copolymer with an octene content ranging from 20 to 35 wt%, in order to provide good toughness to the material.

[0028] 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.

[0029] In some embodiments, the chemical structure of the RCM or its initial degradation products serve as signaling molecules or substrate analogs, thereby inducing or enhancing the production of active degrading enzymes by specific strains in the composite microbial agent. This mechanism enables microorganisms to secrete the required enzymes more actively and efficiently during the degradation process, thereby accelerating the degradation process.

[0030] The second aspect of the present invention provides a method for preparing the above-mentioned coffee grounds composite polypropylene degradable material. The method ensures that RCM can effectively react in situ with the biological filler and that the components are uniformly dispersed through specific process steps.

[0031] To achieve the above objectives, the second aspect of the present invention adopts the following technical solution:

[0032] A method for preparing a coffee grounds composite polypropylene degradable material as described in any of the preceding claims, the method comprising the following steps:

[0033] (a) Coffee grounds that have passed through a 200-mesh sieve, bamboo powder that has passed through a 60-mesh sieve, and the reactive coupling agent / modifier (RCM) are premixed to obtain a filler premix; this step helps the RCM to be more evenly distributed on the surface of the biological filler before subsequent melt blending, creating conditions for in-situ reaction.

[0034] (b) The filler premix obtained in step (a) is mixed with homopolymer polypropylene, copolymer polypropylene, polyolefin elastomer, polypropylene grafted maleic anhydride, polypropylene flow aid, zinc stearate, antioxidant 1010, antioxidant 168 and degradation agent to obtain a total mixture.

[0035] (c) The total mixture is melt-blended and extruded. During the melt-blending and extrusion process, under high temperature and shearing, 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 to achieve the dual function of RCM.

[0036] (d) The extrudate is cooled and pelletized to obtain the coffee grounds composite polypropylene degradation material.

[0037] In some embodiments, prior to step (a), the method further includes drying the coffee grounds and bamboo powder at 80-100°C to reduce their moisture content to below 0.8 wt%. Thorough drying of the bio-filler helps reduce the adverse effects of moisture evaporation during subsequent high-temperature processing on material properties and facilitates the reaction between RCM and the surface-active groups of the filler.

[0038] In some embodiments, the premixing in step (a) and / or the mixing in step (b) can be carried out in a high-speed mixer with a rotation speed range of 600-1200 rpm to ensure the initial uniformity of dispersion of the components.

[0039] In some embodiments, the melt blending extrusion in step (c) is carried out in a twin-screw extruder, with the temperature of each heating zone set in the range of 150°C to 190°C and the screw speed controlled in the range of 100-200 rpm. These process parameters are chosen to ensure adequate plasticization of the polymer, effective reaction between the RCM and the filler, and to avoid excessive degradation of the material.

[0040] More specifically, the in-situ chemical reaction of RCM with coffee grounds and / or bamboo powder in step (c) aims 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 specific composite microbial agents and degradation conditions, this interface, along with the chemical structure of RCM or its initial degradation products, can effectively induce or enhance the production of active degrading enzymes by specific strains in the agent, thereby promoting the biodegradation process of the entire composite material. This constitutes one of the core technical features that distinguish this invention from traditional filler modification or simple component blending.

[0041] In summary, the present invention has at least one of the following beneficial technical effects:

[0042] 1. This invention introduces a specific reactive coupling agent / modifier (RCM). This RCM can not only undergo in-situ chemical reactions with the active groups on the surface of biological fillers such as coffee grounds and bamboo powder to enhance interfacial bonding, but more importantly, its chemical structure or initial degradation products can act as signal molecules or substrate analogs to effectively induce or enhance the enzyme production activity of specific strains in the composite microbial agent, thereby constructing a "self-secreted enzyme-catalyzed degradation microenvironment" inside the material and accelerating the synergistic degradation of the biological filler and the polypropylene matrix.

[0043] 2. The RCM used in this invention forms a stable functionalized interface through an in-situ chemical reaction with the surface of the bio-filler during melt blending, significantly improving the compatibility and interfacial bonding strength between the inorganic bio-filler and the hydrophobic polypropylene matrix. Combined with a specific premixing process, this ensures the full interaction between the RCM and the filler, enabling effective stress transfer and maintaining or improving the tensile strength, flexural strength, and impact toughness of the material even at high filler contents.

[0044] 3. This invention uses inexpensive 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 dependence on fossil resources, but also helps alleviate the problem of "white pollution" by improving the biodegradability of the final product, which is in line with the concept of green and sustainable development.

[0045] 4. The technical solution of this invention, through the specific design of RCM, combined with the initial oxidation of polypropylene by the degrading agent and the synergistic degradation by the composite microbial agent, constructs a multi-level, multi-pathway degradation system. The induction effect of RCM on microbial enzyme production makes the degradation process more targeted and efficient, especially in the interface region between the biological filler and the polymer matrix, forming a local environment with high enzyme activity, which promotes the effective disintegration of the material from the inside out. Detailed Implementation

[0046] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be described in detail below with reference to embodiments. It should be noted that the following embodiments and their parameters are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Any modifications or equivalent substitutions made based on the technical concept of the present invention should be included within the scope of protection of the present invention.

[0047] Unless otherwise specified, all raw materials used in the embodiments and comparative examples of this invention are commercially available or prepared by conventional methods in the art; all percentages used, unless otherwise specified, are weight percentages.

[0048] The main raw materials used in the following examples and comparative examples are as follows:

[0049] Homopolymer polypropylene (hPP): Grade T30S, melt index (230℃, 2.16kg) is 3.0-5.0g / 10min, purchased from China Petroleum & Chemical Corporation.

[0050] Copolymer polypropylene (cPP): Grade K8003, ethylene content 3-4wt%, melt index (230℃, 2.16kg) 8-12g / 10min, purchased from SK Corporation, South Korea.

[0051] Polyolefin elastomer (POE): Brand name Engage TM 8150 (Dow Chemical Company), ethylene-octene copolymer, octene content approximately 30 wt%, melt index (190℃, 2.16 kg) approximately 0.5-1.5 g / 10 min.

[0052] Coffee grounds: The residue from grinding food-grade waste Arabica coffee beans, which is washed, dried in an 80℃ oven for 12 hours, ground in a grinder, and then sieved through a 200-mesh standard sieve.

[0053] Bamboo powder: obtained by mechanically crushing moso bamboo, drying it in an oven at 80℃ for 12 hours, and then screening it through a 60-mesh standard sieve.

[0054] Polypropylene grafted with maleic anhydride (PP-g-MAH): Grade P353 (DuPont), maleic anhydride grafting rate 0.8-1.0wt%, melt index (190℃, 2.16kg) approximately 100-130g / 10min.

[0055] Reactive coupling agents / modifiers (RCM):

[0056] RCM-A: Epoxidized Soybean Oil (ESO), industrial grade, epoxy value ≥6.0%, purchased from Arkema.

[0057] RCM-B: Homemade maleic anhydride-modified polylactic acid oligomer (M-PLAO) is prepared as follows: L-lactic acid (content ≥88%) is subjected to a polycondensation reaction at 160-180℃ under nitrogen protection and stirring for 4-6 hours to obtain a polylactic acid oligomer (PLAO) with a number average molecular weight of 1800-2200 Da; then PLAAO is reacted with maleic anhydride (mass ratio PLAAO:maleic anhydride = 10:1 to 10:1.5) in xylene solvent at 130-140℃ for 3-5 hours. After the reaction is completed, the solvent and unreacted maleic anhydride are removed by vacuum distillation to obtain M-PLAO with an acid value of 20-30 mg KOH / g.

[0058] PP flow aid: Ethylene bis-stearamide (EBS), industrial grade, melting point 140-145℃.

[0059] Zinc stearate: Industrial grade, zinc content 10.5-11.5%.

[0060] Antioxidant 1010: Chemical name: Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid], industrial grade, purity ≥98%.

[0061] Antioxidant 168: Chemical name: Tris(2,4-di-tert-butylphenyl) phosphite, industrial grade, purity ≥98%.

[0062] Degrading agent: Oxidative degradation accelerator masterbatch containing a ferrocene and calcium stearate complex, trade name Reverte TM Purchased from Wells Plastics Ltd., UK.

[0063] Compound microbial inoculant: Prepared by uniformly mixing Trichoderma reesei ATCC 26921, Aspergillus niger ATCC 16404, and Pseudomonas fluorescens ATCC 13525 in a 1:1:1 (w / w / w, based on the weight of the lyophilized powder). Before use, resuscitate with sterile water and culture to the logarithmic growth phase to prepare a total viable count of not less than 1×10⁻⁶. 9 CFU / mL bacterial suspensions. All strains were purchased from the China General Microbiological Culture Collection Center (CGMCC).

[0064] Examples 1-4:

[0065] Example 1:

[0066] Formula composition:

[0067] The components, their weights (in grams), and corresponding weight percentages (%) are as follows:

[0068] Homopolymer polypropylene (hPP): 350.0g (35.0%);

[0069] Copolymer polypropylene (cPP): 200.0g (20.0%);

[0070] Polyolefin elastomer (POE): 75.0g (7.5%);

[0071] Coffee grounds (200 mesh): 150.0g (15.0%);

[0072] Bamboo powder (60 mesh): 150.0g (15.0%);

[0073] Polypropylene grafted with maleic anhydride (PP-g-MAH): 30.0g (3.0%);

[0074] Reactive coupling agent / modifier (RCM-A): 10.0g (1.0%);

[0075] PP flow aid (EBS): 16.0g (1.6%);

[0076] Zinc stearate: 3.0g (0.3%);

[0077] Antioxidant 1010: 3.0g (0.3%);

[0078] Antioxidant 168: 3.0g (0.3%);

[0079] Degrading agent: 20.0g (2.0%).

[0080] The total weight of all components is 1000.0g.

[0081] Preparation steps:

[0082] (1) Raw material pretreatment: The weighed coffee grounds and bamboo powder are placed in a forced-air drying oven and dried at 90±2℃ to reduce their moisture content to below 0.8wt%.

[0083] (2) Premix I: Add the dried coffee grounds, bamboo powder and the amount of RCM-A in step (1) to the SHR-25A high-speed mixer and premix for 10 minutes at 800 rpm.

[0084] (3) Premixing II: Add the formulated amounts of homopolymer polypropylene, copolymer polypropylene, polyolefin elastomer, polypropylene grafted maleic anhydride, PP flow aid, zinc stearate, antioxidant 1010, antioxidant 168 and degradation agent to the mixture in step (2), and continue to mix in a high-speed mixer at a speed of 800 rpm for 15 minutes to obtain a uniform total mixture.

[0085] (4) Melt blending extrusion granulation: The total mixture obtained in step (3) is fed into a co-rotating twin-screw extruder (screw diameter 35.6 mm, length-to-diameter ratio L / D = 40) via a feeding device. The temperatures of each section of the extruder from the feed port to the die are set sequentially as follows: 150℃, 170℃, 175℃, 165℃, 160℃, 150℃, 190℃ (die). The screw speed is set to 150 rpm.

[0086] (5) Granulation and molding: After being cooled in a water bath, the extruded strips are pelletized into pellets with a length of about 3 mm by a pelletizer. The resulting pellets are dried in an oven at 100°C for 4 hours and then injection molded into standard tensile, bending and impact test specimens using an injection molding machine. The injection molding process parameters are: barrel temperature 170 / 175 / 180 / 185°C (from hopper to nozzle), mold temperature 40°C.

[0087] Example 2:

[0088] Formula composition:

[0089] The components, their weights (in grams), and corresponding weight percentages (%) are as follows:

[0090] Homopolymer polypropylene (hPP): 345.0 g (34.5%);

[0091] Copolymer polypropylene (cPP): 200.0g (20.0%);

[0092] Polyolefin elastomer (POE): 75.0g (7.5%);

[0093] Coffee grounds (200 mesh): 150.0g (15.0%);

[0094] Bamboo powder (60 mesh): 150.0g (15.0%);

[0095] Polypropylene grafted with maleic anhydride (PP-g-MAH): 30.0g (3.0%);

[0096] Reactive coupling agent / modifier (RCM-B): 15.0g (1.5%);

[0097] PP flow aid (EBS): 16.0g (1.6%);

[0098] Zinc stearate: 3.0g (0.3%);

[0099] Antioxidant 1010: 3.0g (0.3%);

[0100] Antioxidant 168: 3.0g (0.3%);

[0101] Degrading agent: 20.0g (2.0%).

[0102] The total weight of all components is 1000.0g.

[0103] Preparation steps:

[0104] The preparation steps are the same as in Example 1, except that in the premixing I step (2), RCM-A is replaced with RCM-B, which has the same technical effect. All other raw materials, equipment, process parameters and operations are consistent with those in Example 1.

[0105] Example 3:

[0106] Formula composition:

[0107] The components, their weights (in grams), and corresponding weight percentages (%) are as follows:

[0108] Homopolymer polypropylene (hPP): 355.0g (35.5%);

[0109] Copolymer polypropylene (cPP): 200.0g (20.0%);

[0110] Polyolefin elastomer (POE): 75.0g (7.5%);

[0111] Coffee grounds (200 mesh): 150.0g (15.0%);

[0112] Bamboo powder (60 mesh): 150.0g (15.0%);

[0113] Polypropylene grafted with maleic anhydride (PP-g-MAH): 30.0g (3.0%);

[0114] Reactive coupling agent / modifier (RCM-A): 5.0g (0.5%);

[0115] PP flow aid (EBS): 16.0g (1.6%);

[0116] Zinc stearate: 3.0g (0.3%);

[0117] Antioxidant 1010: 3.0g (0.3%);

[0118] Antioxidant 168: 3.0g (0.3%);

[0119] Degrading agent: 20.0g (2.0%).

[0120] The total weight of all components is 1000.0g.

[0121] Preparation steps:

[0122] The preparation steps are the same as in Example 1, except that in the premixing I step (2), the amount of reactive coupling agent / modifier (RCM-A) is adjusted to 5.0 g, and correspondingly, the amount of homopolymer polypropylene (hPP) is adjusted to 355.0 g. All other raw materials, equipment, process parameters, and operations are consistent with those in Example 1.

[0123] Example 4:

[0124] Formula composition:

[0125] The components, their weights (in grams), and corresponding weight percentages (%) are as follows:

[0126] Homopolymer polypropylene (hPP): 340.0g (34.0%);

[0127] Copolymer polypropylene (cPP): 200.0g (20.0%);

[0128] Polyolefin elastomer (POE): 75.0g (7.5%);

[0129] Coffee grounds (200 mesh): 150.0g (15.0%);

[0130] Bamboo powder (60 mesh): 150.0g (15.0%);

[0131] Polypropylene grafted with maleic anhydride (PP-g-MAH): 30.0g (3.0%);

[0132] Reactive coupling agent / modifier (RCM-A): 20.0g (2.0%);

[0133] PP flow aid (EBS): 16.0g (1.6%);

[0134] Zinc stearate: 3.0g (0.3%);

[0135] Antioxidant 1010: 3.0g (0.3%);

[0136] Antioxidant 168: 3.0g (0.3%);

[0137] Degrading agent: 20.0g (2.0%).

[0138] The total weight of all components is 1000.0g.

[0139] Preparation steps:

[0140] The preparation steps are the same as in Example 1, except that in the premixing I step (2), the amount of reactive coupling agent / modifier (RCM-A) is adjusted to 20.0 g, and correspondingly, the amount of homopolymer polypropylene (hPP) is adjusted to 340.0 g. All other raw materials, equipment, process parameters, and operations are consistent with those in Example 1.

[0141] Comparative Examples 1-3:

[0142] Comparative Example 1:

[0143] Compared to 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 homopolymer polypropylene (hPP), i.e., the amount of homopolymer polypropylene (hPP) used is 360.0 g. The types and amounts of all other components and all preparation steps are exactly the same as in Example 1.

[0144] Comparative Example 2:

[0145] Compared to 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 homopolymer polypropylene (hPP), i.e., the amount of homopolymer polypropylene (hPP) used is 360.0 g. In this comparative example, the amount of polypropylene grafted with maleic anhydride (PP-g-MAH) remains 30.0 g. The types and amounts of all other components and all preparation steps are exactly the same as in Example 1.

[0146] Comparative Example 3:

[0147] Compared to Example 1, the formulation composition is exactly the same, except for the premixing method 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 is omitted. Specifically, the dried coffee grounds, bamboo powder, RCM-A, and all other components listed in step (3) of Example 1 are added to a high-speed mixer at once and mixed at 800 rpm for 25 minutes to obtain the total mixture. The remaining raw material pretreatment, melt blending, extrusion granulation, and injection molding steps are exactly the same as in Example 1.

[0148] Test Examples 1-3:

[0149] Test Example 1: Mechanical Property Test

[0150] 1. Experimental Objective

[0151] This test case aims to evaluate the mechanical properties of coffee grounds composite polypropylene degradable materials prepared by the methods of the examples and comparative examples, mainly including tensile properties, flexural properties and impact properties.

[0152] 2. Experimental Equipment and Materials

[0153] Universal testing machine.

[0154] Simply supported beam impact testing machine.

[0155] Test samples: standard injection molded specimens obtained from step (5) of the preparation methods of Examples 1-4 and Comparative Examples 1-3.

[0156] 3. Experimental Procedure

[0157] All mechanical property tests were conducted at room temperature (23±2)℃ and relative humidity (50±5)%. Before testing, all specimens were conditioned under the same conditions for at least 24 hours.

[0158] Tensile property test:

[0159] (1) The test shall be conducted in accordance with GB / T 1040.2-2006 "Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics".

[0160] (2) Select standard IBA type dumbbell-shaped spline.

[0161] (3) Install the specimen on the fixture of the universal testing machine and set the test speed to 50 mm / min.

[0162] (4) Start the testing machine, record the maximum tensile load and gauge length elongation when the specimen breaks, and calculate the tensile strength and elongation at break.

[0163] (5) Test at least 5 valid samples for each formulation group and take the arithmetic mean of the results.

[0164] Bending performance test:

[0165] (1) The test was conducted in accordance with GB / T 9341-2008 "Determination of bending properties of plastics".

[0166] (2) Select a long strip with dimensions of 80mm×10mm×4mm.

[0167] (3) Set the test span to 64 mm (16 times the thickness of the strip) and the test speed to 2 mm / min.

[0168] (4) Place the spline on the three-point bending fixture of the testing machine.

[0169] (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.

[0170] (6) At least 5 valid samples were tested for each formulation group, and the results were taken as the arithmetic mean.

[0171] Notched impact strength test of simply supported beam:

[0172] (1) The test was conducted in accordance with GB / T 1043.1-2008 "Determination of impact properties of simply supported plastic beams - Part 1: Non-instrumental impact test".

[0173] (2) Select a long strip with dimensions of 80mm×10mm×4mm and process a type A notch in the center of the strip (comply with the requirements of type 1A specimen in GB / T 1043.1-2008, with a notch depth of 2mm and a notch tip radius of 0.25mm).

[0174] (3) Select a suitable 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 10% to 80% of the nominal energy of the pendulum.

[0175] (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.

[0176] (5) Release the pendulum and record the energy absorbed by the spline during fracture.

[0177] (6) Calculate the notched impact strength of a simply supported beam (unit: kJ / m) 2 The calculation formula is: a cN =(E c / (h·b N ))×10 3 E c is the energy absorbed when the specimen fractures (joules), h is the specimen thickness (millimeters), and b is the energy absorbed when the specimen fractures. N This represents the remaining width (in millimeters) of the specimen at the notch.

[0178] (7) Test at least 5 valid samples for each formulation group and take the arithmetic mean of the results.

[0179] 4. Experimental Data Recording

[0180] Table 1. Mechanical property test results of composite materials in each embodiment and comparative example.

[0181]

[0182] As can be seen from the mechanical property test results in Table 1, the composite materials prepared in Examples 1 to 4 of this invention show a certain degree of improvement in tensile strength, flexural strength, and flexural modulus compared to Comparative Example 1, which does not contain reactive coupling agent / modifier (RCM), and Comparative Example 2, which relies solely on traditional polypropylene grafted with maleic anhydride as a compatibilizer. This is mainly attributed to the introduced RCM component, whose functional groups can undergo in-situ chemical reactions with the surface-active groups of coffee grounds and / or bamboo powder, promoting the enhancement of interfacial bonding between the filler and the polypropylene matrix during melt blending. This enhanced interfacial interaction facilitates the effective transfer of stress between the interfaces, thereby improving the material's ability to resist external loads. Examples 1 and 2 used RCM-A (epoxidized soybean oil) and RCM-B (maleic anhydride-modified polylactic acid oligomer), which have different chemical structures, respectively, and both obtained similar performance improvement trends, indicating that different types of RCM, but possessing the specific reactivity mentioned above, can effectively improve interfacial compatibility, thereby improving the macroscopic mechanical properties of the material.

[0183] Comparing the results of Example 1 and Comparative Example 3, it can be seen that even with the same formulation, the premixing step of RCM and the bio-filler, as well as suitable melt blending conditions, are crucial for achieving the best results from RCM. In Example 1, the premixing of RCM and the filler allows RCM to be more uniformly adsorbed onto the filler surface. During the subsequent melt blending extrusion process, under the set temperature and shear conditions, RCM fully undergoes an in-situ chemical reaction with the active groups on the filler surface, forming a more effective and stable functionalized interface. In Comparative Example 3, due to the omission of the separate premixing step of RCM and the filler, or the use of processing conditions unfavorable to the reaction, RCM may not have been able to interact fully and uniformly with the filler surface. Therefore, its effect on improving interfacial bonding is limited, and the improvement in mechanical properties is not as significant as in Example 1. This highlights the importance of the specific preparation method proposed in this invention for achieving the intended function of RCM.

[0184] In Examples 1, 3, and 4, the effect of RCM-A dosage ranging from 0.5% to 2.0% was investigated. The results showed that within this dosage range, the mechanical properties of the materials were superior to the control group without RCM. This indicates that the selected RCM can effectively exert its interfacial enhancement effect within this concentration range. This optimized interface constructed by RCM is not only crucial for the mechanical properties of the material during its use, but also lays the physical foundation for the interaction between the chemical structure of RCM or its initial degradation products and the composite microbial agent to induce or enhance enzyme production activity after the material is discarded. In other words, it creates an interfacial microenvironment that is more conducive to microbial attachment and enzymatic action, thus echoing the core innovative concept of this invention—constructing a self-secreted enzymatic degradation microenvironment and improving the overall biodegradability of the material.

[0185] Test Example 2: Biodegradability Test (Loss of Weight Method)

[0186] 1. Experimental Objective

[0187] This test case aims to evaluate the biodegradability of coffee grounds composite polypropylene degradable materials prepared by the methods of the examples and comparative examples under controlled composting conditions, and the evaluation is carried out by measuring the weight loss rate of the materials.

[0188] 2. Experimental Equipment and Materials

[0189] Thermostatic aerobic composting chamber: The temperature can be controlled at (58±2)℃ and aerobic conditions can be maintained.

[0190] Analytical balance: accuracy 0.1 mg.

[0191] Forced-air drying oven: Used for drying samples.

[0192] Test sample: The injection-molded strips obtained in step (5) of the preparation methods of Examples 1-4 and Comparative Examples 1-3 were cut into sheet-like samples with a size of 25mm×25mm×2mm.

[0193] Composting medium: Mature municipal solid waste compost with an organic matter content >40%, a C / N ratio of 20-30:1, and a pH value of 7.0-8.0. Impurities larger than 10mm are removed by screening. Adjust the moisture content to (55±5)% before use.

[0194] Compound microbial agents: the same as the compound microbial agents listed in the raw materials section above.

[0195] 3. Experimental steps (1) Initial sample treatment: Dry the cut sheet samples in a 60℃ forced-air drying oven to constant weight, accurately weigh the initial dry weight and record it as W0. Prepare at least 3 parallel samples for each formulation group.

[0196] (2) Construction of composting system: Take an appropriate amount of composting medium with adjusted moisture content and mix it evenly with the test sample at a ratio of 10:1 (dry weight of compost: dry weight of sample). At the beginning of composting, inoculate 10 grams (calculated as freeze-dried powder) of compound microbial agent per kilogram of dry composting medium, and evenly spray and mix the bacterial suspension that has been revived and cultured to the logarithmic growth phase into the composting system.

[0197] (3) Composting conditions: The composting system containing the sample was placed in a constant-temperature aerobic composting chamber, and the temperature was set at (58±2)℃. The compost was turned over 1-2 times daily to ensure good aerobic conditions. The moisture content of the compost was checked and adjusted weekly to maintain it at (55±5)%.

[0198] (4) Sampling and processing: Samples were taken from each composting system at 0, 15, 30, 45, 60 and 90 days after the start of composting.

[0199] (5) Post-processing of samples: The removed samples were carefully rinsed with distilled water to remove compost residues adhering to the surface and avoid sample loss. Then, the cleaned samples were placed in a 60°C forced-air drying oven to dry to constant weight, and the dry weight was accurately measured and recorded as W. t .

[0200] (6) Weight loss rate calculation: The weight loss rate of the sample at each time point is calculated using the following formula:

[0201] Weight loss rate (%) = ((W0-W) t ) / W0)×100%((W0-W t ) / W0)×100%;

[0202] 4. Experimental Data Recording

[0203] Table 2. Weight loss (%) of composite materials in each example and comparative example under controlled composting conditions.

[0204] 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

[0205] Table 2 clearly shows that the composite materials prepared in Examples 1 to 4 of this invention exhibit significantly better biodegradability than Comparative Examples 1, 2, and 3 under simulated controlled composting conditions. Specifically, after 90 days of composting, the weight loss rate of the materials in the examples was much higher than that of the comparative examples. This result strongly supports the positive role of the introduced reactive coupling agent / modifier (RCM) in improving the biodegradability of the materials. The presence of RCM not only improves the interfacial bonding between the bio-filler (coffee grounds and bamboo powder) and the polypropylene matrix, as indirectly reflected in 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 bio-filler, which has biodegradability potential, more easily utilized by microorganisms.

[0206] The core technical concept of this 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 bio-filler. Second, and more importantly, the chemical structure of RCM, or the small molecular fragments produced during its initial degradation in a composting environment (e.g., through hydrolysis), is designed to interact with specific strains in the inoculated composite microbial agent, thereby inducing or enhancing the ability of these strains to produce active degrading enzymes (such as cellulase, esterase, etc.). These "activated" or "enhanced" microorganisms and their secreted enzymes can more effectively degrade the bio-filler and, synergistically with the degrading agent (promoting the initial oxidative chain scission of polypropylene), also produce a certain degree of degradation effect on the polypropylene matrix. Comparative Example 1, lacking RCM, exhibited the lowest degradation rate. Although Comparative Example 2 contained the conventional compatibilizer PP-g-MAH, its main function was to improve compatibility and it did not possess the specific function of inducing microbial enzyme production; therefore, its degradation performance improvement was limited. The formulation of Comparative Example 3 was the same as that of Example 1, but an improper premixing process was used. This may have resulted in RCM failing to react sufficiently with the filler in situ or failing to distribute evenly, thereby weakening its subsequent enzyme-inducing effect. Its weight loss rate was between that of Comparative Example 1 / 2 and Example 1, further confirming the importance of a specific preparation method for achieving the expected function of RCM.

[0207] In summary, the high weight loss rate exhibited by the materials in the examples is the result of the synergistic effect of multiple factors: including the RCM-reinforced interface making it easier for the bio-filler to contact microorganisms; the initial oxidation of the polypropylene matrix by the degrading agent; and most importantly, the induction and enhancement of the enzyme-producing ability of the composite microbial agent mediated by the structural characteristics of RCM. This "self-secreted enzymatic degradation microenvironment" formed inside the material, especially near the interface between the bio-filler and the polymer matrix, significantly accelerates the biodegradation process of the entire composite material. Examples 1 (RCM-A) and 2 (RCM-B), using RCMs with different chemical structures, both exhibited good degradation performance, indicating that the technical principles of this invention have a certain degree of universality. The changes in the amount of RCM-A in Examples 3 and 4 also reflect the influence of its addition on the final degradation effect; within the tested range, the addition of RCM significantly improved the degradation performance. These results collectively confirm the effectiveness and innovation of the coffee grounds composite polypropylene degradation material and its preparation method provided by this invention in improving the biodegradability of materials.

[0208] Test Example 3: Indirect Indication of RCM Function - Observation of Microbial Growth Promotion

[0209] 1. Experimental Objective

[0210] This test case aims to observe the growth of compound microbial agents in culture media using different material powders as potential carbon sources or stimulants (measured by optical density OD).600 The reactive coupling agent / modifier (RCM) used in this invention or the structure formed in the material can be used to indirectly evaluate the potential promoting effect of the reactive coupling agent / modifier (RCM) on microbial activity, thereby providing evidence for the mechanism by which RCM can induce or enhance microbial enzyme production.

[0211] 2. Experimental Equipment and Materials

[0212] UV-Vis spectrophotometer: capable of measuring absorbance at 600 nm.

[0213] Thermostatic shaking incubator: temperature and oscillation frequency can be controlled.

[0214] High-pressure steam sterilizer.

[0215] Sterile conical flasks, pipettes, and other routine laboratory glassware and consumables.

[0216] Material powder:

[0217] The composite material particles prepared in Example 1 were frozen and embrittled in liquid nitrogen, then ground with a high-speed pulverizer and screened through a 100-mesh sieve to obtain the material powder of Example 1.

[0218] Take the composite material particles prepared in Comparative Example 1 and process them in the same way to obtain the material powder of Comparative Example 1.

[0219] Take the composite material particles prepared in Comparative Example 3 and process them in the same way to obtain the material powder of Comparative Example 3.

[0220] Basic carbon-free liquid culture medium: per liter contains 1.0 g (NH4)2SO4, 0.5 g KH2PO4, 0.5 g K2HPO4, 0.2 g MgSO4·7H2O, and 0.1 g yeast extract. The pH is adjusted to 7.0-7.2 with NaOH. This medium contains extremely low levels of yeast extract, primarily providing trace growth factors; the carbon source mainly depends on the added powdered materials.

[0221] Compound microbial inoculants: The same compound microbial inoculants listed in the raw materials section above, prepared into OD (Oxygen Demand) form before use. 600 A bacterial suspension with a density of approximately 1.0.

[0222] 3. Experimental steps (1) Preparation and dispensing of culture medium: Prepare basic carbon-free liquid culture medium according to the formula, and dispense it into several 250mL Erlenmeyer flasks, 100mL per flask.

[0223] (2) Addition of material powder:

[0224] Group A (Example 1): 0.50g of the material powder from Example 1 was precisely added to several conical flasks.

[0225] Group B (Comparative Example 1): 0.50g of the material powder from Comparative Example 1 was precisely added to several conical flasks.

[0226] Group C (Comparative Example 3): 0.50g of the material powder from Comparative Example 3 was precisely added to several conical flasks.

[0227] Group D (blank control group): No material powder was added, only 100 mL of basic carbon-free liquid culture medium.

[0228] (3) Sterilization: Seal all conical flasks with cotton plugs and sterilize them with high-pressure steam at 121℃ for 20 minutes.

[0229] (4) Microbial inoculation: After the culture medium has cooled to room temperature, under aseptic conditions, 1.0 mL of the pre-prepared compound microbial agent suspension (OD) was inoculated into the three groups of conical flasks containing material powder (A, B, and C) and the blank control bottle (D group). 600 (Approximately 1.0).

[0230] (5) Culture: Place all the inoculated conical flasks in a constant temperature shaker at 30℃ and 150rpm for culture.

[0231] (6) OD value determination: Samples were aseptically taken from each group of conical flasks at 0, 24, 48, and 72 hours after the start of incubation, and the absorbance (OD) of the culture medium at 600 nm was measured using a UV-Vis spectrophotometer. 600 (Value). Three parallel samples were taken from each group at each time point for measurement, and the average value was taken. Before measurement, if the sample was too turbid and affected the reading, a small amount of uninoculated culture medium (containing the corresponding powder) from the same group could be used as a reference for zeroing.

[0232] 4. Experimental Data Recording

[0233] Table 3. Growth of composite microbial agents under different material powder culture conditions (OD) 600 value)

[0234] Incubation 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

[0235] Note: The OD value at 0 hours mainly reflects the amount of bacteria inoculated and the initial turbidity of the material powder itself.

[0236] Table 3 shows that the growth of the composite microbial inoculant differed significantly under 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 almost no or extremely slow microbial growth), all experimental groups (A, B, and C) with added material powders showed some degree of microbial growth, indicating that the biological filler (coffee grounds and bamboo powder) in the material could provide some nutrition for the microorganisms. More importantly, the OD of the culture medium in group A (material powder from Example 1) was significantly lower than that in group D. 600 The values ​​were significantly higher than those of Group B (comparative Example 1 material powder) and Group C (comparative Example 3 material powder) at all detection 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 by an appropriate process, can more effectively promote the growth and proliferation of the inoculated composite microbial agent.

[0237] The difference in the microbial growth-promoting effect indirectly reflects the specific function of RCM in the material. As mentioned earlier, RCM is designed to interact favorably with target microorganisms through its specific chemical structure or the small molecular fragments released during its initial degradation in the environment (such as hydrolysis). This interaction may include providing microorganisms with a more readily available primary carbon source, or more importantly, acting as a signaling molecule or substrate analog, inducing or enhancing the metabolic activity of microorganisms and the expression and secretion of related enzyme systems (especially enzymes related to the degradation of biofillers, such as cellulase, lignin-degrading enzymes, and esterases related to the initial oxidation products of polymers). Group B (Comparative Example 1) does not contain RCM, so the microorganisms mainly rely on the slow degradation of the biofiller to obtain nutrients, resulting in slower growth. Although Group C (Comparative Example 3) contains RCM, the preparation process may not have achieved sufficient in-situ reaction and uniform dispersion of RCM with the filler, resulting in the release of bioactive substances of RCM or its inducing effect not being fully utilized. Therefore, its growth-promoting effect is between that of Group A and Group B.

[0238] The results of this test example are consistent with the trend of weight loss difference observed in Test Example 2, further revealing the advantages of the technical solution of this invention from the perspective of microbial activity. One mechanism by which the material in Example 1 exhibits superior biodegradability (as shown in Test Example 2) is that RCM enhances the overall enzyme production capacity of the microbial community by promoting the growth and activity of microorganisms. This "activated" microbial community forms a highly active "self-secreted enzymatic degradation microenvironment" within the material, particularly at the interface between the RCM-functionalized filler and the polymer matrix. This microenvironment not only accelerates the decomposition of the biofiller but also creates more favorable conditions for the subsequent degradation of the polypropylene matrix (e.g., by generating enzymes that can act on the primary products of polypropylene oxidation, or by improving the hydrophilicity of the local environment). Therefore, the results of this test example strongly support the core technical concept of RCM improving the overall biodegradability efficiency of composite materials by regulating microbial behavior.

[0239] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A coffee grounds composite polypropylene degradable material, characterized by, by weight percentage, comprising: 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 screen: 14.5-15.5%; bamboo powder passed through a 60-mesh screen: 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%; degradation agent: 1.8-2.2%; wherein the reactive coupling agent / modifier is a maleic anhydride oligomer of polylactic acid; In preparing the coffee grounds composite polypropylene degradation material, the coffee grounds passed through a 200-mesh screen, the bamboo powder passed through a 60-mesh screen, and the reactive coupling agent / modifier are first premixed to obtain a filler premix, and then the filler premix is mixed with the homopolymer polypropylene, the copolymer polypropylene, the polyolefin elastomer, the polypropylene grafted maleic anhydride, the polypropylene flow aid, the zinc stearate, the antioxidant 1010, the antioxidant 168, and the degradation agent for co-extrusion.

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

3. The coffee ground composite polypropylene degradable material according to claim 1, characterized in that, The polypropylene grafted maleic anhydride has a maleic anhydride grafting rate of 0.5-1.2 wt%.

4. A process for the preparation of the coffee grounds composite polypropylene degrading material according to any one of claims 1 to 3, characterized in that, comprising the following steps: (a) premixing the coffee grounds passed through a 200-mesh screen, the bamboo powder passed through a 60-mesh screen, and the reactive coupling agent / modifier to obtain a filler premix; (b) mixing the filler premix obtained in step (a) with the homopolymer polypropylene, the copolymer polypropylene, the polyolefin elastomer, the polypropylene grafted maleic anhydride, the polypropylene flow aid, the zinc stearate, the antioxidant 1010, the antioxidant 168, and the degradation agent to obtain a total mixture; (c) melt blending and extruding the total mixture, and in the process of melt blending and extrusion, the reactive coupling agent / modifier reacts in situ with active groups on the surface of the coffee grounds and / or bamboo powder to form a functional interface; (d) cooling and pelletizing the extrudate to obtain the coffee grounds composite polypropylene degradation material.

5. The method for preparing the coffee grounds composite polypropylene degradable material according to claim 4, characterized in that, Before step (a), it further comprises a step of drying the coffee grounds and bamboo powder at 80-100°C to reduce the water content to less than 0.8 wt%.

6. The method for preparing the coffee grounds composite polypropylene degradable material according to claim 4, characterized in that, The premixing in step (a) and / or the mixing in step (b) is carried out in a high-speed mixer at a speed ranging from 600 to 1200 rpm.

7. The method for preparing the coffee grounds composite polypropylene degradable material according to claim 4, characterized in that, The melt blending and extrusion in step (c) are carried out in a twin-screw extruder, and the temperature of each heating zone of the extruder is set to a range of 150-190°C, and the screw speed is controlled to a range of 100-200 rpm.

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