High-elasticity degradable Pick ball and preparation method thereof

Abstract

The preparation method comprises the following steps: providing an elastic master batch, and carrying out foaming treatment on the elastic master batch and a foaming agent to form a microporous elastic core particle with a closed-pore or semi-closed-pore structure; a biodegradable fiber material is adopted to prepare an annular reinforcing belt through winding or pre-forming processing; the preparation method comprises the following steps: preparing a hemispherical microporous elastic inner shell layer by adopting a first biodegradable material through a rotational molding process; the annular reinforcing belt is positioned at a preset position on the outer surface of the hemispherical microporous elastic inner shell layer, and pre-fixing is achieved in a heating or bonding mode; providing a second biodegradable material, and forming on the outer surfaces of the two hemispherical microporous elastic inner shell layers by adopting a rotational molding process to form a hemispherical compact outer skin layer so as to obtain a hemispherical complex with the inner shell layers, the reinforcing belt and the outer skin layer; and aligning and welding the two hemispherical composites to form the high-elasticity degradable Pick ball, so that the high elasticity and the degradability are both considered.

Description

Technical Field

[0001] This invention relates to the field of pickle technology, and more particularly to a highly elastic biodegradable pickle and its preparation method. Background Technology

[0002] Pickles, as light sports equipment for mass recreation and sports training, are widely used in long-term outdoor or semi-outdoor settings such as community sports fields, school physical education classes, beaches, resorts, and family backyards. These balls require portability, good bounce, safety without sharp edges (especially for children), and the ability to withstand frequent impacts and bending. Meanwhile, with increasing environmental regulations and consumer awareness, the market demand for recyclable, compostable, or biodegradable materials is growing. Therefore, it is desirable for products to guarantee at least 1-2 years of outdoor service life and to be effectively degraded under industrial or household conditions after disposal, avoiding persistent plastic pollution.

[0003] Existing sphere manufacturing technologies mostly employ single-material injection molding or compression molding (such as thermoplastic elastomers / TPR, polyvinyl chloride, or non-degradable TPU) as well as hollow blow molding and foam molding processes. Some high-performance products also improve resilience and impact resistance through multi-layer co-injection, coating, or filling air chambers. To pursue lightweight and elasticity, some solutions use closed-cell or open-cell foam cores paired with dense outer skins; others attempt to use bio-based polymers (such as PLA) or their blends to make outer skins or structural components to improve biodegradability. From the perspective of "material and performance trade-offs," the main shortcomings of existing technologies are: directly using biodegradable polymers (especially PLA-based ones) often leads to brittleness, poor weather resistance, and insufficient impact resistance, resulting in a significant decrease in resilience and fracture resistance under long-term outdoor sunlight, temperature cycling, and impact loads, creating a contradiction of "difficulty in balancing performance and biodegradability." Summary of the Invention

[0004] The purpose of this invention is to provide a high-elasticity biodegradable pick ball and its preparation method, solving the technical problem of the difficulty in balancing high-performance sports balls with environmentally friendly biodegradability.

[0005] To achieve this objective, the present invention adopts the following technical solution: A method for preparing a highly elastic biodegradable pickball includes the following steps: a) Provide elastic masterbatch, and foam it with a foaming agent to form microporous elastic core particles with closed-cell or semi-closed-cell structures; b) Annular reinforcing strips are prepared by winding or preforming biodegradable fiber materials; c) Using a first biodegradable material, a hemispherical microporous elastic inner shell is prepared by rotational molding process; d) Position the annular reinforcing strip at a predetermined position on the outer surface of the hemispherical microporous elastic inner shell, and pre-fix it by heating or bonding. e) Provide a second biodegradable material, which is formed on the outer surface of the two hemispherical microporous elastic inner shells using a rotational molding process to form a hemispherical dense outer skin, thereby obtaining a hemispherical composite with an inner shell, a reinforcing band and an outer skin; f) Align and weld the two hemispherical composites to form a highly elastic biodegradable pickball.

[0006] Optionally, the elastic masterbatch in step a) includes the following components: 40%~90% polylactic acid, 5%~40% polycaprolactone, 0.1%~5% chain extender, 0.1%~10% surface-modified nanofiller, 0.05%~2% heat stabilizer, and 0.1%~5% flow aid.

[0007] Optionally, the chain extender is one or more of the following: a polyfunctional epoxy compound or a polyfunctional isocyanate, a carbodiimide or a maleic anhydride graft copolymer. The surface-modified nanofiller is selected from any one of surface-modified silica, modified nanoclay, graphene oxide, or surface-grafted nanocellulose.

[0008] Optionally, the elastic masterbatch in step a) is a modified elastic masterbatch, and the modified elastic masterbatch is prepared by the following steps: a1) Mix the components of the elastic masterbatch according to the preset ratio, and dehydrate the agent until the moisture content is less than 0.02 wt%; a2) The dehydrated mixture is fed into a twin-screw reactive extruder and reactively extruded at a set temperature and speed. Chain extension / grafting modification is carried out in the molten state, so that the chain extender reacts chemically with polylactic acid and polycaprolactone to form grafts or increase molecular weight. a3) Surface-modified nanofillers are added in a segmented feeding manner during the reactive extrusion process and dispersed in the extrusion section. Modified elastic masterbatch is obtained by melt pelletizing and cooling.

[0009] Optionally, the first biodegradable material in step b) is selected from one or more combinations of the following: polylactic acid monofilament or drawn filament, polyhydroxybutyrate fiber, PLA / PHB blend fiber, PLA / PBAT blend tape, or bio-based thermoplastic tape that has been stretched, oriented and heat-set in sequence. The first biodegradable fiber material has the following performance parameters: linear density in the range of 0.5~5 dtex, tensile strength ≥200MPa, and initial modulus in the range of 1~10GPa.

[0010] Optionally, the annular reinforcing strip described in step b) further includes a surface affinity treatment after molding; The surface affinity treatment includes the following steps: b1) Clean and dehumidify the annular reinforcing belt; b2) The surface of the annular reinforcing strip is activated by an activation treatment, wherein the activation treatment is selected from any one of corona treatment, plasma treatment or chemical oxidation treatment; b3) Coat the surface of the activated annular reinforcing strip with an affinity interface primer, wherein the affinity interface coating is selected from any of the following: maleic anhydride grafted polymer solution, isocyanate-terminated polyurethane prepolymer, epoxy-containing grafted resin or polyfunctional hydroxyl / amine prepolymer; wherein the coating amount of the affinity interface is 1~50μm of dry film thickness. b4) The coated annular reinforcing strip is dried at a constant temperature or cured at a low temperature. The drying / curing temperature is 60~140°C and the time is 1~30 minutes to obtain a surface with high affinity.

[0011] Optionally, the second biodegradable material in step e) is selected from one or more combinations of the following: polylactic acid, polycaprolactone, polybutylene terephthalate, or polyhydroxyalkanoate; The second biodegradable material is in granular or powder form suitable for rotational molding, and its melt flow rate is in the range of 5-50 g / 10 min.

[0012] Optionally, the process may also include a post-forming step d) heat-setting the resulting multilayer composite sphere to stabilize the microporous structure and strengthen the interlayer bonding, followed by surface microtexturing to obtain a highly elastic biodegradable pick ball.

[0013] Optionally, the specific process of the heat setting treatment in step d) includes: The obtained multilayer composite spheres were placed in a temperature-controlled drying oven and heated in the temperature range of 60°C to 120°C for 30 to 180 minutes. This allowed the microporous elastic core to undergo stress relaxation and crystallization / rearrangement under conditions higher than its glass transition temperature and lower than its melting temperature, thereby stabilizing the pore structure and promoting interlayer interface reactions. Afterward, the spheres were slowly cooled to room temperature at a rate of 0.5 to 5°C / min.

[0014] The present invention also provides a highly elastic biodegradable pick ball, which is prepared by the method described above. The highly elastic biodegradable pick ball has a three-layer functionalized structure, which includes a microporous elastic inner shell layer, a ring fiber reinforcing band and a biodegradable outer skin layer in sequence. Each layer is embedded in the mold and partially chemically bonded to form an integral composite. The material used is a biodegradable polymer or a blend thereof.

[0015] Compared with the prior art, the present invention has the following beneficial effects: Pre-made elastic masterbatch is saturated with a foaming agent and microporousized to obtain microporous elastic core particles with closed or semi-closed pore microstructures; simultaneously, biodegradable high-strength fiber materials are used to prepare annular reinforcing strips that match the sphere mold cavity through winding or preforming processing; the annular reinforcing strips are positioned at a designated position in the mold cavity in a mold with mold positioning and dual material injection ports; the melt of the microporous elastic core particles is first injected into the center of the mold cavity to form a core and cover the inner side of the annular strip; then, the melt of the biodegradable outer skin material is injected through the outer skin nozzle; the inner shell, reinforcing strip, and outer skin are interlocked and bonded within the mold using an in-mold bonding process to complete pressure molding, obtaining a sphere with a multi-layered molded body. While maintaining the high resilience and anti-fracture performance of the sphere, the integrated in-mold co-molding process of functionally partitioned microporous core + annular fiber reinforcement + biodegradable dense outer skin achieves a balance between high elasticity and biodegradability. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] The structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0018] Figure 1 This is a schematic diagram of the highly elastic biodegradable pickball in Embodiment Six.

[0019] Figure 2 This is a partial cross-sectional schematic diagram of the highly elastic biodegradable pick ball in Embodiment Six. Detailed Implementation

[0020] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] In the description of this invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be a component positioned centrally in the connection.

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1: This invention provides a method for preparing highly elastic biodegradable pickballs, comprising the following steps: a) Provides an elastic masterbatch, which is foamed with a foaming agent to form microporous elastic core particles with closed-cell or semi-closed-cell structures. Through a combination of molecular modification and controllable microporousization, a microporous core with both low density and high resilience and energy absorption capacity, while retaining a biodegradable framework, is obtained. The following are examples: PLA is polylactic acid, PCL is polycaprolactone, PHB is polyhydroxybutyrate, and PBAT is polybutylene terephthalate / butylene adipate.

[0024] Specifically, elastic masterbatch refers to a melt formulation with biodegradable polyester as the main chain (such as a blend or coexistence system of PLA and PCL) and containing chain extenders / grafting agents, surface-modified nanofillers, and necessary additives. After pre-drying, reactive extrusion in a twin-screw reactive extruder can achieve chain elongation / grafting modification to improve melt strength and compatibility, thereby giving the masterbatch good foaming processability and melt viscosity stability. Subsequently, the modified masterbatch is swelled / foamed with a foaming agent (selectively supercritical CO2 saturated or chemical foaming agent), and microporousization is triggered at the extruder head or die by instantaneous decompression or thermal decomposition to form microporous elastic core particles with closed / semi-closed pore microstructures.

[0025] A method for preparing a highly elastic biodegradable pickball includes the following steps: a) Provide elastic masterbatch, and foam it with a foaming agent to form microporous elastic core particles with closed-cell or semi-closed-cell structures; b) Annular reinforcing strips are prepared by winding or preforming biodegradable fiber materials; c) Using a first biodegradable material, a hemispherical microporous elastic inner shell is prepared by rotational molding process; d) Position the annular reinforcing strip at a predetermined position on the outer surface of the hemispherical microporous elastic inner shell, and pre-fix it by heating or bonding. e) Provide a second biodegradable material, which is formed on the outer surface of the two hemispherical microporous elastic inner shells using a rotational molding process to form a hemispherical dense outer skin, thereby obtaining a hemispherical composite with an inner shell, a reinforcing band and an outer skin; f) Align and weld the two hemispherical composites to form a highly elastic biodegradable pickball.

[0026] g) The obtained multilayer composite spheres are subjected to heat setting treatment to stabilize the microporous structure and strengthen the interlayer bonding, and then subjected to surface microtexturing treatment to obtain highly elastic biodegradable pick balls.

[0027] After heat setting, the outer skin is surface micro-textured or textured (this can be achieved by in-mold texture replication or by hot pressing / roll pressing / laser engraving, etc.) to improve the feel, anti-slip and wear resistance. At the same time, it should be ensured that the surface treatment method used does not damage the biodegradability (e.g., avoid a large proportion of non-degradable coatings).

[0028] The working principle of this invention is as follows: Pre-made elastic masterbatch is saturated with a foaming agent and then microporous to obtain microporous elastic core particles with closed or semi-closed pore microstructures; simultaneously, biodegradable high-strength fiber materials are used to prepare annular reinforcing strips that match the sphere mold cavity through winding or preforming; in a mold with mold positioning and dual injection ports, the annular reinforcing strips are positioned at a designated location in the mold cavity; first, the melt of the microporous elastic core particles is injected into the center of the mold cavity to form a core and cover the inner side of the annular strip; then, the melt of the biodegradable outer skin material is injected through the outer skin nozzle; the inner shell, reinforcing strip, and outer skin are interlocked and bonded within the mold using an in-mold bonding process to complete pressure molding, resulting in a sphere with a multi-layered molded body. While maintaining the sphere's high resilience and anti-fracture performance, the integrated in-mold co-molding process of functionally partitioned microporous core + annular fiber reinforcement + biodegradable dense outer skin achieves a balance between high elasticity and biodegradability.

[0029] In this embodiment, the elastic masterbatch in step a) includes the following components: 40%~90% polylactic acid, 5%~40% polycaprolactone, 0.1%~5% chain extender, 0.1%~10% surface-modified nanofiller, 0.05%~2% heat stabilizer, and 0.1%~5% flow aid.

[0030] In elastic masterbatch formulations, polylactic acid (PLA) accounts for 40% to 90% to provide a basic rigid framework and biodegradability, and is the main phase of the masterbatch; polycaprolactone (PCL) accounts for 5% to 40% as a toughening phase and a flexible component that reduces brittleness. Because its melting point and glass transition temperature are lower than those of PLA, it can improve the impact toughness and low-temperature resilience of the material and increase the ductility of the melt, which is beneficial for subsequent microporous formation and foaming nucleation.

[0031] Chain extenders (0.1%–5%) react chemically with terminal functional groups (~OH, -COOH, etc.) of polyester during reactive extrusion, performing chain elongation, partial grafting, or mild crosslinking to improve melt strength, melt viscosity stability, and processing window, thereby facilitating controllable microporous formation. Surface-modified nanofillers (0.1%–10%) enhance pore wall strength and overall mechanical properties by strengthening the matrix-phase interface, improving nucleation effects, and providing mechanical reinforcement. Heat stabilizers (0.05%–2%) inhibit thermal degradation during high-temperature processing, ensuring controllable molecular weight loss. Flow aids or nucleating agents (0.1%–5%) improve melt flowability, reduce injection pressure, and act as foaming nucleation sites to regulate pore size distribution.

[0032] The above component ranges were determined with consideration of biodegradability, mechanical / processing properties, and microporous controllability. Exceeding these ranges may lead to adverse deviations in melt properties, foaming behavior, or final degradability (for example, too low PLA content may weaken the overall bio-based properties, while too high PCL content may reduce weather resistance and stiffness).

[0033] In this embodiment, it is further explained that the chain extender is one or more combinations of polyfunctional epoxy compounds or polyfunctional isocyanates, carbodiimides or maleic anhydride graft copolymers; the surface-modified nanofiller is selected from any one of surface-modified silica, modified nanoclay, graphene oxide or surface-grafted nanocellulose.

[0034] To achieve the synergistic effect of chain extension / graft modification and nanofiller, this embodiment preferably uses one or a combination of polyfunctional epoxy compounds, polyfunctional isocyanates, carbodiimides, or maleic anhydride graft copolymers as chain extenders. Specifically, polyfunctional epoxy compounds can extend chain segments and introduce reactive groups by undergoing addition reactions with the terminal hydroxyl or carboxyl groups of the polyester through epoxy ring opening; polyfunctional isocyanates can form urea / carbamate bonds with hydroxyl groups to increase molecular weight and melt strength; carbodiimides can promote the coupling of carboxyl end groups; and maleic anhydride graft copolymers can act as compatibilizers and provide functional groups on the surface for easy interfacial bonding.

[0035] The surface-modified nanofillers are preferably selected from surface-modified silica, organic-group-modified nanoclay, graphene oxide (or reduced form), and surface-grafted nanocellulose, etc. These nanofillers can achieve good dispersion and enhance interfacial adhesion in the polyester matrix through surface functionalization or grafting of organic chains. At the same time, as uniform nucleation centers, they are conducive to the formation of fine and uniform closed / semi-closed pore structures.

[0036] In this embodiment, the elastic masterbatch in step a) is a modified elastic masterbatch, and the modified elastic masterbatch is prepared through the following steps: a1) Mix the components of the elastic masterbatch according to the preset ratio, and dehydrate the agent until the moisture content is less than 0.02wt%; in order to reduce hydrolysis degradation and molecular weight loss during high-temperature melting and processing.

[0037] a2) The dehydrated mixture is fed into a twin-screw reactive extruder and reactively extruded at a set temperature and speed. Chain extension / grafting modification is carried out in the molten state, so that the chain extender reacts chemically with polylactic acid and polycaprolactone to form grafts or increase molecular weight.

[0038] By setting appropriate residence time and shear energy, the added chain extender (such as multifunctional epoxy or maleic anhydride graft) can undergo addition or grafting reactions with the hydroxyl / carboxyl groups at the ends of PLA and PCL chains, resulting in molecular weight increase or slight chain linkage, thereby improving melt strength, melt viscosity and compatibility.

[0039] a3) Surface-modified nanofillers are added in a segmented feeding manner during the reactive extrusion process and dispersed in the extrusion section. Modified elastic masterbatch is obtained by melt pelletizing and cooling.

[0040] In the reactive extrusion process, a segmented feeding strategy is adopted for the surface-modified nanofillers. For example, they are added in the middle or later stages of the extruder via side feeding or branch feeding, and fully dispersed in the high-shear section to obtain a uniform nano-dispersion state. This avoids degradation of the nanofillers or polymer chain breakage during prolonged high-temperature residence. Dispersion optimization can be supplemented by feeding in the form of short-path high-shear mixers or pre-dispersed masterbatches of nanofillers. After the melt completes the reaction and dispersion, it is pelletized through a die (or water-cooled annular pelletizing), and the pellets are cooled, dried, and shaped by air cooling or belt drying to finally obtain modified elastic masterbatch.

[0041] In this embodiment, the biodegradable fiber material in step b) is selected from one or more combinations of the following: polylactic acid monofilament or drawn filament, polyhydroxybutyrate fiber, PLA / PHB blend fiber, PLA / PBAT blend tape, or bio-based thermoplastic tape that has been stretched, oriented and heat-set in sequence.

[0042] Biodegradable fiber materials have the following performance parameters: linear density in the range of 0.5~5dtex, tensile strength ≥200MPa, initial modulus in the range of 1~10GPa, or after winding, the interlayer angle, layer thickness and mold cavity are matched to ensure that the circumferentially reinforced ring has the required circumferential stiffness and crack resistance.

[0043] Optionally, the first biodegradable material in step b) is selected from one or more combinations of the following: polylactic acid monofilament or drawn filament, polyhydroxybutyrate fiber, PLA / PHB blend fiber, PLA / PBAT blend tape, or bio-based thermoplastic tape that has been stretched, oriented and heat-set in sequence. The first biodegradable fiber material has the following performance parameters: linear density in the range of 0.5~5 dtex, tensile strength ≥200MPa, and initial modulus in the range of 1~10GPa.

[0044] In this embodiment, the annular reinforcing strip in step b) further includes a surface affinity treatment after molding; the surface affinity treatment includes the following steps: b1) Clean and dehumidify the annular reinforcing strip; common methods include solvent wiping (e.g., using isopropanol, ethanol or low-residue organic solvents), ultrasonic cleaning or water spray cleaning, followed by dehumidification using hot air or vacuum dryer until the surface and substrate moisture is reduced to a controllable level.

[0045] b2) The surface of the annular reinforcing belt is activated by any one of corona treatment, plasma treatment or chemical oxidation treatment, with the aim of improving the polarity and wettability of the fiber surface.

[0046] To improve the polarity and wettability of the fiber surface, this embodiment performs an activation treatment on the surface of the annular reinforcing tape after cleaning. Preferred methods include corona treatment, low-temperature plasma treatment, or chemical oxidation treatment (e.g., rapid neutralization and rinsing after mild alkaline / oxidizing agent impregnation). The main function of the activation treatment is to introduce hydroxyl, carboxyl, aldehyde, ketone, or other polar groups and remove low surface energy organic layers, thereby significantly reducing the contact angle and improving the wetting, adhesion, and spread of subsequent affinity primers.

[0047] b3) Coat the surface of the activated annular reinforcing strip with an affinity interface primer, wherein the affinity interface coating is selected from any of the following: maleic anhydride grafted polymer solution, isocyanate-terminated polyurethane prepolymer, epoxy-containing grafted resin or polyfunctional hydroxyl / amine prepolymer; wherein the coating amount of the affinity interface is 1~50μm of dry film thickness.

[0048] A homogeneous interfacial primer is uniformly coated onto the surface of the activated annular reinforcing strip to form a transition layer that can mechanically intercalate or chemically bond with the core / outer skin melt. In this embodiment, the coating method can be brushing, dip coating, spraying, or roll-to-roll coating. The coating amount is controlled to a dry film thickness of approximately 1-50 μm to balance interfacial adhesion performance and maintain the flexibility of the fiber strip. This primer grafts or cures with the injected melt within the mold through chemical compatibility or a thermally catalytic reaction, enhancing interlayer adhesion strength and reducing the risk of delamination and peeling.

[0049] b4) The coated annular reinforcing strip is dried at a constant temperature or cured at a low temperature. The drying / curing temperature is 60~140°C and the time is 1~30 minutes to obtain a surface with high affinity.

[0050] The high-affinity surface can mechanically intercalate and / or partially chemically bond with the core melt or skin melt within the mold, allowing the subsequently injected core / skin melt to form interlayer bonds within the mold through thermal grafting or co-curing.

[0051] In this embodiment, in step c), the mold cavity is provided with an annular flow guide structure at the positioning point of the annular reinforcing belt for controlling the melt flow and realizing the semi-embedded positioning of the annular belt.

[0052] The circumferential flow guide structure is a continuous or discontinuous circumferential groove with a groove depth of 5% to 30% of the mold wall thickness and a groove width of 0.5 to 5 mm. The circumferential flow guide structure causes the injected microporous elastic core melt to preferentially gather along the circumferential direction in the mold cavity and form at least one layer of coating on the inner side of the annular reinforcing strip, thereby realizing the interlocking of the inner shell layer and the reinforcing strip and improving the interlayer bonding strength during the in-mold molding process.

[0053] The design of this structure is based on fluid mechanics and mold flow control principles: appropriate groove depth and width can provide preferential flow channels for the melt to ensure the integrity of the coating, without significantly weakening the mold strength or causing local refrigerant retention; intermittent grooves can be used to control the segmented filling of the melt, alleviate capillary retraction, and facilitate gas discharge.

[0054] In this embodiment, the specific process of heat setting in step d) includes: placing the obtained multilayer composite sphere in a temperature-controlled drying oven and heating it at a temperature range of 60°C to 120°C for 30 to 180 minutes, so that the microporous elastic core undergoes stress relaxation and crystallization / rearrangement under conditions higher than its glass transition temperature and lower than its melting temperature to stabilize the pore structure and promote interlayer interface reaction; then slowly cooling it to room temperature at a rate of 0.5 to 5°C / min. The slowly cooled multilayer can be selectively subjected to further aging treatment, which involves maintaining it at 40°C to 70°C and relative humidity of 30% to 90% for 24 to 168 hours to complete interface curing and weather resistance stabilization; the heat setting and / or aging treatment can be carried out under a vacuum or nitrogen protective atmosphere.

[0055] Example 2: This embodiment provides a specific preparation method. The elastic masterbatch provided in step a) consists of the following components: 60 wt% polylactic acid, 30 wt% polycaprolactone, 2 wt% chain extender, 5 wt% surface-modified silica, 1 wt% heat stabilizer, and 2 wt% flow aid. The components are mixed and vacuum dried at 80°C for 6 hours to remove moisture until the moisture content is below 0.02 wt%. The mixture is then fed into a twin-screw reactive extruder and reactive extruded at a zone temperature of 180-200°C and a rotation speed of 200 rpm. After melt pelletizing, the mixture is foamed to obtain microporous elastic core particles with an average pore size of approximately 20 μm.

[0056] In step b), annular reinforcing belts are prepared using PLA / PHB blended fibers with a fiber linear density of approximately 2.0 dtex and a breaking strength of approximately 230 MPa. After being wound and shaped and subjected to plasma activation treatment, a maleic anhydride grafted polymer solution with a dry film thickness of 10 μm is uniformly sprayed onto the surface and dried under hot air at 100°C for 10 min.

[0057] In step c), the treated annular reinforcing strip is positioned in the mold cavity groove, with a groove depth of 10% of the mold wall thickness and a groove width of 1 mm. First, the above-mentioned microporous elastic core melt is injected, the injection temperature is controlled at 185°C, and the pressure is held for 30 seconds to form a continuous coating layer on the inner side of the annular strip. Then, PLA outer skin melt is injected with a thickness of about 0.5 mm to complete the multi-layer composite molding.

[0058] In step d), the obtained spheres are placed in a vacuum drying oven and heat-set at 100°C for 60 minutes, then slowly cooled to room temperature at a rate of 1°C / min. The resulting pickles are lightweight, have high resilience, a rebound rate of over 85%, and maintain stable deformation recovery under simulated outdoor high humidity conditions.

[0059] Example 3: This embodiment provides a second specific preparation method. In step a), the elastic masterbatch components are: PLA 70wt%, PCL 20wt%, maleic anhydride grafted polymer 2wt%, modified nano-clay 6wt%, and flow aid 2wt%. After vacuum drying at 100°C for 4 hours, the mixture is fed into a twin-screw reactive extruder and extruded and granulated at a zone temperature of 190~210°C and a speed of 250 rpm. After melt pelletizing, the mixture is physically foamed to obtain microporous core particles with a closed-cell rate of approximately 75% and a pore size distribution of 10~30 μm.

[0060] In step b), PLA filaments are stretched and oriented to form a linear density of 1.5 dtex and a modulus of about 6 GPa. The fibers are mechanically pre-formed to obtain annular reinforcing belts, which are then subjected to corona discharge treatment. Subsequently, they are impregnated with an epoxy-grafted resin solution to form a coating film with a thickness of about 20 μm, and then dried at 80°C for 20 min.

[0061] In step c), the mold circumferential guide channel is an intermittent channel with a width of 2 mm and a depth of 20% of the wall thickness. During injection, the microporous core melt (195°C) is injected first, and the injection rate is controlled at 50 cm³ / s to allow the melt to preferentially accumulate on the inner side of the ring; then the PLA / PBAT blend outer skin layer is injected, with a skin thickness of approximately 0.6 mm.

[0062] In step d), the resulting composite spheres were heat-set at 90°C for 120 minutes under a nitrogen protective atmosphere, and then slowly cooled to room temperature. The product has uniform pore size and good interfacial bonding. Impact tests showed that the spheres had no obvious interlayer separation and could be completely degraded within 180 days in a composting environment.

[0063] Example 4: This embodiment provides a third specific preparation method. In step a), the elastic masterbatch components are: PLA 50wt%, PCL 40wt%, carbodiimide chain extender 3wt%, surface-grafted nanocellulose 5wt%, heat stabilizer 1wt%, and flow aid 1wt%. The mixture is dehumidified under vacuum at 80°C for 8 hours and then fed into a twin-screw reactive extruder. It is reactive extruded at 200°C, pelletized, and then foamed to obtain semi-closed-cell core particles with an average pore size of approximately 15μm.

[0064] In step b), PLA / PBAT blended fiber tape with a width of 1.0 mm is used. After orientation and heat setting treatment, the initial modulus is approximately 5 GPa. The surface of the ring tape is chemically oxidized and then sprayed with isocyanate-terminated polyurethane prepolymer solution, with a coating thickness of approximately 5 μm, and cured in hot air at 120°C for 15 min.

[0065] In step c), the ring is placed in a continuous circumferential groove with a mold wall thickness of 15%. First, core melt (190°C) is injected to fill and partially embed the inner side of the ring. Then, PLA outer skin melt (0.4 mm thick) is injected to form a three-layer composite sphere.

[0066] In step d), the composite spheres were placed in a vacuum drying oven and heat-set at 70°C for 180 min, then slowly cooled to room temperature at a rate of 2°C / min, and finally subjected to damp heat aging treatment (50°C, 70%RH, 48 h). The resulting spheres showed strong adhesion between the surface and core interfaces, and exhibited no cracking after 50 high-intensity impact tests, demonstrating superior resilience compared to the control product.

[0067] Example 5: This embodiment provides a fourth specific preparation method. In step a), the elastic masterbatch components are: PLA 80wt%, PCL 15wt%, polyfunctional isocyanate chain extender 1wt%, graphene oxide 3wt%, and flow aid 1wt%. After vacuum drying at 85°C for 6 hours, the mixture is react-extruded and pelletized in a twin-screw extruder (zone temperature 185–200°C, speed 220 rpm). Closed-cell microporous core particles with an average pore size of 10 μm are obtained through CO2 physical foaming.

[0068] In step b), PLA monofilament fibers (linear density 1 dtex, tensile strength 220 MPa) are wound to form a ring. After plasma activation, the surface is dip-coated with a multifunctional amine prepolymer, the dry film thickness of the coating is 30 μm, and it is dried at 80°C for 10 min.

[0069] In step c), the mold uses a circumferential discontinuous groove with a groove width of 0.8 mm and a groove depth of 10%. First, inject the microporous core melt (temperature 180°C) and hold the pressure for 20 seconds to ensure that the melt is evenly distributed on the inner side of the ring. Then, inject the PLA outer skin melt with an outer skin thickness of about 0.5 mm to complete the composite molding.

[0070] In step d), the composite spheres were heated at 110°C for 90 minutes under a nitrogen atmosphere, then slowly cooled to room temperature and further aged at 40°C and 50%RH for 72 hours. The resulting peaked balls have a dense structure and strong interlayer bonding. The bouncing height of the balls is comparable to that of traditional petrochemical-based plastic balls, and the degradation rate exceeds 90% within 120 days in an industrial composting environment.

[0071]

[0072] Performance control group comparison table of pickball preparation Example 6: Combination Figure 1 and Figure 2 As shown, the present invention also provides a highly elastic biodegradable pick ball, which is prepared by the method of preparing highly elastic biodegradable pick balls as in Example 1. The highly elastic biodegradable pick ball has a three-layer functionalized structure, which includes a microporous elastic inner shell layer 10, a ring fiber reinforcing band 20 and a biodegradable outer skin layer 30 in sequence. Each layer is embedded in the mold and partially chemically bonded to form an integral composite. The material used is a biodegradable polymer or a blend thereof.

[0073] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a highly elastic biodegradable pickball, characterized in that, Includes the following steps: a) Provide elastic masterbatch, and foam it with a foaming agent to form microporous elastic core particles with closed-cell or semi-closed-cell structures; b) Annular reinforcing strips are prepared by winding or preforming biodegradable fiber materials; c) Using a first biodegradable material, a hemispherical microporous elastic inner shell is prepared by rotational molding process; d) Position the annular reinforcing strip at a predetermined position on the outer surface of the hemispherical microporous elastic inner shell, and pre-fix it by heating or bonding. e) Provide a second biodegradable material, which is formed on the outer surface of the two hemispherical microporous elastic inner shells using a rotational molding process to form a hemispherical dense outer skin, thereby obtaining a hemispherical composite with an inner shell, a reinforcing band and an outer skin; f) Align and weld the two hemispherical composites to form a highly elastic biodegradable pickball.

2. The method for preparing highly elastic biodegradable pickballs according to claim 1, characterized in that, The elastic masterbatch in step a) comprises the following components: 40%~90% polylactic acid, 5%~40% polycaprolactone, 0.1%~5% chain extender, 0.1%~10% surface-modified nanofiller, 0.05%~2% heat stabilizer, and 0.1%~5% flow aid.

3. The method for preparing highly elastic biodegradable pickballs according to claim 2, characterized in that, in, The chain extender is one or more of the following: a polyfunctional epoxy compound, a polyfunctional isocyanate, a carbodiimide, or a maleic anhydride graft copolymer. The surface-modified nanofiller is selected from any one of surface-modified silica, modified nanoclay, graphene oxide, or surface-grafted nanocellulose.

4. The method for preparing highly elastic biodegradable pickballs according to claim 2, characterized in that, The elastic masterbatch mentioned in step a) is a modified elastic masterbatch, and the modified elastic masterbatch is prepared by the following steps: a1) Mix the components of the elastic masterbatch according to the preset ratio, and dehydrate the agent until the moisture content is less than 0.02 wt%; a2) The dehydrated mixture is fed into a twin-screw reactive extruder and reactively extruded at a set temperature and speed. Chain extension / grafting modification is carried out in the molten state, so that the chain extender reacts chemically with polylactic acid and polycaprolactone to form grafts or increase molecular weight. a3) Surface-modified nanofillers are added in a segmented feeding manner during the reactive extrusion process and dispersed in the extrusion section. Modified elastic masterbatch is obtained by melt pelletizing and cooling.

5. The method for preparing highly elastic biodegradable pickballs according to claim 1, characterized in that, The first biodegradable material in step b) is selected from one or more combinations of the following: polylactic acid monofilament or drawn filament, polyhydroxybutyrate fiber, PLA / PHB blend fiber, PLA / PBAT blend tape, or bio-based thermoplastic tape that has been stretched, oriented and heat-set in sequence. The first biodegradable fiber material has the following performance parameters: linear density in the range of 0.5~5 dtex, tensile strength ≥200MPa, and initial modulus in the range of 1~10GPa.

6. The method for preparing highly elastic biodegradable pickballs according to claim 1, characterized in that, The annular reinforcing strip described in step b) also undergoes surface affinity treatment after molding; The surface affinity treatment includes the following steps: b1) Clean and dehumidify the annular reinforcing belt; b2) The surface of the annular reinforcing strip is activated by an activation treatment, wherein the activation treatment is selected from any one of corona treatment, plasma treatment or chemical oxidation treatment; b3) Coat the surface of the activated annular reinforcing strip with an affinity interface primer, wherein the affinity interface coating is selected from any of the following: maleic anhydride grafted polymer solution, isocyanate-terminated polyurethane prepolymer, epoxy-containing grafted resin or polyfunctional hydroxyl / amine prepolymer; wherein the coating amount of the affinity interface is 1~50μm of dry film thickness. b4) The coated annular reinforcing strip is dried at a constant temperature or cured at a low temperature. The drying / curing temperature is 60~140°C and the time is 1~30 minutes to obtain a surface with high affinity.

7. The method for preparing highly elastic biodegradable pickballs according to claim 1, characterized in that, The second biodegradable material in step e) is selected from one or more combinations of the following: polylactic acid, polycaprolactone, polybutylene terephthalate, or polyhydroxyalkanoate; The second biodegradable material is in granular or powder form suitable for rotational molding, and its melt flow rate is in the range of 5-50 g / 10 min.

8. The method for preparing highly elastic biodegradable pickballs according to claim 1, characterized in that, It also includes a post-forming step d) to heat-set the obtained high-elasticity biodegradable pickballs to stabilize the microporous structure and strengthen the interlayer bonding, and then to perform surface micro-texturing treatment to obtain the finished pickballs.

9. The method for preparing highly elastic biodegradable pickballs according to claim 8, characterized in that, The specific process of the heat setting treatment in step d) includes: The obtained multilayer composite spheres were placed in a temperature-controlled drying oven and heated in the temperature range of 60°C to 120°C for 30 to 180 minutes. This allowed the microporous elastic core to undergo stress relaxation and crystallization / rearrangement under conditions higher than its glass transition temperature and lower than its melting temperature, thereby stabilizing the pore structure and promoting interlayer interface reactions. Afterward, the spheres were slowly cooled to room temperature at a rate of 0.5 to 5°C / min.

10. A highly elastic biodegradable pickball, characterized in that, The high-elasticity biodegradable pick ball is prepared by the preparation method of any one of claims 1 to 9. The high-elasticity biodegradable pick ball has a three-layer functionalized structure, which includes a microporous elastic inner shell layer, a ring fiber reinforcing band and a biodegradable outer skin layer in sequence. Each layer is embedded in the mold and partially chemically bonded to form an integral composite. The material used is a biodegradable polymer or a blend thereof.

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