Inorganic particle-polymer composite materials, their preparation methods and applications

Abstract

This invention relates to inorganic particle-polymer composite materials, their preparation methods, and applications. The inorganic particle-polymer composite material comprises (A) inorganic particles and (B) a hyperbranched polymer containing reactive functional groups, wherein the inorganic particles are dispersed in the hyperbranched polymer, which is formed by an in-situ reaction of a monomer or polymer having two or more reactive functional groups with a chain extender in the presence of the inorganic particles. The inorganic particle-polymer composite material of this invention, acting as a toughening agent, reacts in-situ with the matrix of polylactic acid (PLA) or PLA-based composite materials during melt blending to further improve the structure, thereby increasing interfacial compatibility. Furthermore, the inorganic particles simultaneously form crosslinking sites in situ and act as nucleating agents to accelerate PLA crystallization, thus achieving toughening modification of PLA and obtaining good mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of polylactic acid (PLA) toughening modifiers, and more particularly to an inorganic particle-polymer composite material, its preparation method, its use as a toughening agent, a polylactic acid composition containing the same, and its uses. Background Technology

[0002] Over the past few decades, environmental pollution such as "white pollution" (plastic waste) and the crisis of dwindling oil resources have attracted widespread attention. Currently, scientists are dedicated to developing biodegradable materials derived from biomass to achieve a green alternative to traditional plastics. Among many polymers, polylactic acid (PLA) has excellent biocompatibility, can be completely degraded to produce carbon dioxide and water, is easy to process and mold, and is abundant and renewable. Characterized by low environmental impact and environmental friendliness, and with sustainable development as its core concept, PLA is a green alternative to petroleum-based plastics with broad prospects. It is mainly used in packaging, industrial and agricultural products, medical devices, electronics, and electrical appliances.

[0003] The core problems in the application of polylactic acid (PLA) at present include: poor toughness and brittleness caused by high crystallinity; after toughening, its crystallization rate is slow, its crystallinity is extremely low, and its thermal stability is poor, resulting in low heat resistance; poor melt strength, which cannot meet the requirements of various processes such as thermoforming, foaming, blow molding and fiber spinning; and poor oxidation resistance, which deteriorates under the influence of ultraviolet light.

[0004] The modification methods for addressing the above problems mainly include: (1) preparing polylactic acid blends by solution or melt; (2) introducing plasticizers or obtaining long-chain branched structures in the chemical structure to prepare compatibilizers; (3) using inorganic nanoparticle nucleating agents to heterogeneously nucleate and improve the crystallization performance of polylactic acid; (4) using rare earth ions to chelate and coordinate with carboxyl groups, hydroxyl groups and other coordinating groups to form network and layered structures to achieve toughening modification.

[0005] The toughening and modification of polylactic acid (PLA) has attracted widespread attention from scientists. Melt blending, being economical, convenient, solvent-free, and requiring minimal equipment, has long been an efficient and convenient method for improving the physical properties and overall performance of PLA. Examples include melt blending with polycaprolactone, polybutylene succinate (PBSA), polymethyl methacrylate, and polycarbonate. However, simple melt blending often results in significant phase separation between the two materials, making it difficult to obtain high-performance composites. Small molecule compatibilizers also suffer from poor aging resistance, migrating to the material surface and failing over time.

[0006] Reactive blending is an effective method to address the brittleness of polylactic acid (PLA) and its composites. Typical examples include reactive blending of PLA with various polymers containing epoxy methyl methacrylate reactive units (ACS Appl. Mater. Interfaces, 2012, 4, 3667–3675.)(Polymer, 2012, 53, 272–276.). Currently, there are no reports on obtaining hyperbranched toughening modifiers with reactive functional groups based on in-situ modified inorganic nanoparticles. Summary of the Invention

[0007] To address the aforementioned defects of traditional polylactic acid (PLA) and the problem of phase separation when PLA is combined with other materials, this invention provides an inorganic particle-polymer composite material with reactive functional groups. These inorganic particles act as toughening agents, reacting in situ with the matrix of PLA or PLA-based composite materials during melt blending to further improve the structure, thereby increasing interfacial compatibility. Furthermore, the inorganic particles form crosslinking sites in situ and simultaneously act as nucleating agents to accelerate PLA crystallization, thus achieving toughening modification of PLA and obtaining good mechanical properties. This completes the invention.

[0008] One object of the present invention is to provide an inorganic particle-polymer composite material.

[0009] Another object of the present invention is to provide a method for preparing the inorganic particle-polymer composite material.

[0010] Another object of the present invention is to provide the use of the inorganic particle-polymer composite material as a toughening agent.

[0011] Another object of the present invention is to provide a polylactic acid composition comprising the inorganic particle-polymer composite material.

[0012] Another object of the present invention is to provide a method for preparing the polylactic acid composition.

[0013] Another object of the present invention is to provide the use of the polylactic acid composition as a biodegradable material.

[0014] Another object of the present invention is to provide a biodegradable plastic article comprising the polylactic acid composition.

[0015] One aspect of the present invention relates to an inorganic particle-polymer composite material, which comprises (A) inorganic particles; and (B) a hyperbranched polymer containing reactive functional groups, wherein the inorganic particles are dispersed in the hyperbranched polymer, the hyperbranched polymer being formed by in-situ reaction of a monomer or polymer having two or more reactive functional groups with a modified chain extender in the presence of the inorganic particles.

[0016] The inorganic particles can have a particle size of 50–1000 nanometers, such as 60, 70, 80, 90, 150, 250, 300, 400, and 500 nanometers, preferably 50–200 nanometers, and more preferably 50–100 nanometers. Within the above particle size range, when the inorganic particle-polymer composite material is used as a toughening agent, the nanoparticles can be uniformly dispersed in the matrix. When the nanoparticles are subjected to impact force in the matrix, they generate a large number of microcracks and further absorb a large amount of impact energy. At the same time, due to the mutual interference of the stress fields between the microcracks, many microcracks terminate between adjacent particles, that is, the development of microcracks is restricted to between two adjacent particles, achieving the technical effect of significantly improving the impact toughness of the composite material. If the particle size is too small, the specific surface area is large and the surface energy is high, and the particles are prone to agglomeration and uneven dispersion. If the particle size is too large, the mismatch in the coefficients of thermal expansion between the nanoparticles and the organic polymer is significant, resulting in obvious phase separation and reduced mechanical properties.

[0017] The inorganic particles can be one or more selected from silicon dioxide and rare earth oxides, such as lanthanum oxide, samarium oxide, neodymium oxide, praseodymium oxide, cerium oxide, and yttrium oxide. Using these inorganic particles, strong hydrogen bonds can be formed between the hydroxyl groups on the particle surface and the modified chain extender and hyperbranched polymer, and chemical bonds can be formed with monomers and polymers having two or more reactive functional groups through in-situ Michael addition reactions with the modified chain extender. Other inorganic particles, such as calcium carbonate, cannot form chemical bonds.

[0018] In the aforementioned inorganic particle-polymer composite material, the mass ratio of hyperbranched polymer, based on the total mass of the composite material, is less than 20%, for example, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc., preferably 2-15%, more preferably 5-12%, but not limited thereto. Within the above-mentioned proportion range, when the inorganic particle-polymer composite material is used as a toughening agent, it can enhance the bonding and synergistic effect between the toughening agent and the matrix material. If the mass ratio of hyperbranched polymer is too low, inorganic particle agglomeration will occur, which will become stress concentration points in the matrix material when used as a toughening agent, resulting in a reduction in mechanical properties; if the mass ratio is too high, it will cause the hyperbranched polymer to entangle itself, making it difficult to uniformly disperse and effectively entangle in the matrix material when used as a toughening agent.

[0019] In the inorganic particle-polymer composite material, the hyperbranched polymer can reduce the surface energy of the inorganic particles, thereby enabling the inorganic particles to be uniformly dispersed in the PLA matrix material when used as a toughening agent, increasing the effective entanglement with the PLA matrix material, and providing functional sites for reaction with the PLA matrix material.

[0020] In this invention, the hyperbranched polymer is a hyperbranched polymer formed by the in-situ reaction of a monomer or polymer having two or more reactive functional groups with a modified chain extender. The reactive functional groups of the hyperbranched polymer can originate from the monomer or polymer having two or more reactive functional groups, or from the modified chain extender. The reactive functional groups can be, for example, alkyl hydroxyl, amino, mercapto, carboxyl, phenolic hydroxyl, carbonyl groups on quinone rings, etc., but are not limited to these.

[0021] The monomer or polymer having two or more reactive functional groups may be, for example, one or more selected from lysine, polyethyleneimine, polyetheramine, hyperbranched peptide, hyperbranched polyester, and hyperbranched polyesteramide.

[0022] The weight-average molecular weight of polyethyleneimine can be from 100 to 100,000 Da, such as 500, 1,000, 2,000, 5,000, and 10,000 Da, preferably from 200 to 50,000 Da, and more preferably from 300 to 20,000 Da, but is not limited thereto. Within the above molecular weight range, it is possible to achieve the technical effect of promoting uniform dispersion of inorganic nanoparticles and achieving effective entanglement with the polymer matrix material. If the molecular weight is too large, it will cause self-entanglement of the polymer shell material, making it difficult to achieve uniform dispersion and effective entanglement in the matrix material when used as a toughening agent.

[0023] Polyetheramines, also known as polyetheramines, terminal amino polyethers, or polyether polyamines, are a class of polymers with a polyether main chain and amino groups at the ends. Examples include terminal amino polyoxypropylene ethers and terminal amino polyethylene oxide ethers.

[0024] Specifically, the polyetheramine can be one or more selected from D230, D400, D2000, T403, and T5000.

[0025] The weight-average molecular weight of polyetheramine can be from 100 to 10000 Da, such as 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 300, 4000, 5000, 6000, 7000, 8000, 9000, and 10000 Da, preferably 200 to 5000 Da, but not limited to this. Within the above molecular weight range, when the inorganic particle-polymer composite material is used as a toughening agent, it can achieve the technical effect of promoting the uniform dispersion of inorganic nanoparticles and achieving effective entanglement with the polymer matrix material. If the molecular weight is too large, it will cause self-entanglement of the polymer shell material, making it difficult to uniformly disperse and effectively entangle in the matrix material when used as a toughening agent.

[0026] Hyperbranched peptides, also known as hyperbranched polypeptides, refer to polypeptides with highly branched chains in their structure, especially polylysine. In particular, hyperbranched peptides can be selected from polylysine prepared by melt polycondensation using L-lysine as the AB2 monomer.

[0027] The weight-average molecular weight of the hyperbranched peptide can be from 1,000 to 100,000 Da, for example, 2,500, 3,000, 3,500, 4,000, 4,500, 5,000, 6,000, 7,000, 8,000, 9,000, 10,000, 20,000, 30,000, 40,000, 50,000, 60,000, 70,000, 80,000, 90,000, and 95,000 Da, preferably 2,000 to 50,000 Da, and more preferably 10,000 to 20,000 Da. Within the above molecular weight range, when the inorganic particle-polymer composite material is used as a toughening agent, it can achieve the technical effect of promoting the uniform dispersion of inorganic nanoparticles and achieving effective entanglement with the polymer matrix material. If the molecular weight is too large, it will cause self-entanglement of the polymer shell material, making it difficult to uniformly disperse and effectively entangle in the matrix material when used as a toughening agent.

[0028] Hyperbranched polyesters / hyperbranched polyesteramides refer to hyperbranched polymers with repeating structural units such as ester bonds / amide bonds and end groups containing a large number of hydroxyl or amino groups, for example:

[0029]

[0030] In particular, hyperbranched polyesteramides can be selected from polymers with a large number of reactive hydroxyl groups on the surface obtained by in-situ reaction between D,L-alanine and glycerol carbonate.

[0031]

[0032] The weight-average molecular weight of the hyperbranched polyester and hyperbranched polyesteramide can be from 100 to 100,000 Da, for example, 150, 200, 300, 400, 500, 750, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 6000, 7000, 8000, 9000, 10000, 20000, 30000, 40000, 50000, 60000, 70000, 80000, 90000, 95000 Da, etc., preferably from 200 to 50000 Da, and more preferably from 200 to 20000 Da. Within the above molecular weight range, when the inorganic particle-polymer composite material is used as a toughening agent, it can achieve the technical effect of promoting the uniform dispersion of inorganic nanoparticles and achieving effective entanglement with the polymer matrix material. If the molecular weight is too large, it will cause the polymer shell to become entangled with itself, making it difficult to disperse and effectively entangle in the matrix material when used as a toughening agent.

[0033] In the inorganic particle-polymer composite material, the modified chain extender also plays a role in linking the hyperbranched polymer to the surface of the inorganic nanoparticles. It can provide reactive functional groups for grafting hyperbranched polymer molecules onto the surface of inorganic particles, or it can extend the chain structure of hyperbranched polymer molecules as a multifunctional monomer.

[0034] The modified chain extender can be a compound having ortho-phenolic hydroxyl groups in its molecule, such as one or more selected from phosphate ester compounds, L-DOPA, dopamine, caffeic acid, gallocatechin, tannic acid, or lignin. In the presence of ortho-phenolic hydroxyl groups, these compounds can undergo auto-oxidative polymerization, and subsequently undergo Michael addition reactions with monomers or amino or hydroxyl groups in polymers having two or more reactive functional groups to achieve cross-linking, generating hyperbranched polymers.

[0035] Phosphate-based compounds can be selected from phosphate-functionalized polymers obtained via the Kabachnik-Fields reaction, with typical structures shown below:

[0036]

[0037] L-DOPA refers to compounds with the following structure:

[0038]

[0039] Dopamine refers to compounds with the following structure:

[0040]

[0041] Caffeic acid refers to compounds with the following structure:

[0042]

[0043] Galla catechins refer to compounds with the following structure:

[0044]

[0045] Tannic acid refers to compounds with the following structure:

[0046]

[0047] Lignin refers to compounds with the following structure:

[0048]

[0049] In the hyperbranched polymer, the mass ratio of the modified chain extender to the monomer or polymer having two or more reactive functional groups can be from 1:1 to 1:300, for example, 1:2, 1:3, 1:5, 1:10, 1:20, 1:50, 1:75, 1:100, 1:150, 1:200, 1:250, etc., preferably from 1:10 to 1:300, for example, from 1:10 to 1:250, but not limited thereto. In some embodiments, lignin is used as the modified chain extender, and polyetheramine is used as the polymer having two or more reactive functional groups, and the mass ratio of lignin to polyetheramine can be from 1:1 to 1:50, preferably from 1:10 to 1:30. Within the above ratio range, the molecular weight of the hyperbranched polymer can be controlled by controlling the reaction time. If the amount of modified chain extender is too large, gelation may occur when preparing inorganic particle-polymer composite materials. Furthermore, the polymer shell may become entangled with itself, making it difficult to disperse and effectively entangle in the matrix material when used as a toughening agent. If the amount is too small, the polymer chain cannot be effectively extended, resulting in a low grafting amount and aggregation of inorganic nanoparticles.

[0050] Another aspect of the present invention relates to a method for preparing the above-mentioned inorganic particle-polymer composite material, the method comprising mixing inorganic particles, a modified chain extender, a monomer or polymer having two or more reactive functional groups, and obtaining the inorganic particle-polymer composite material through hydrogen bonding interactions and in-situ Michael addition reactions. Furthermore, other reactions may occur in the reactive functional groups during the mixing process, such as condensation reactions like esterification and dehydration.

[0051] There are no special restrictions on the mixing method. The materials can be mixed and dispersed evenly using conventional dispersion methods well known to those skilled in the art. For example, a mixer, homogenizer, or agitator can be used for mixing. Alternatively, the materials can be prepared into dispersions separately and then mixed, or the materials can be dispersed in a solvent simultaneously or sequentially to prepare a dispersion.

[0052] In some embodiments, the reaction can be carried out in bulk. For example, inorganic particles, monomers or polymers having two or more reactive functional groups, and modified chain extenders can be directly mixed to carry out a bulk melt reaction.

[0053] In some embodiments, the reaction is carried out in the presence of a solvent. For example, inorganic particles, monomers or polymers having two or more reactive functional groups, and modified chain extenders are dispersed separately or co-dispersed in a solvent to carry out Michael addition or multi-component in-situ reactions.

[0054] There is no particular limitation on the amount of solvent used, as long as it facilitates the dispersion and mixing of the inorganic particles, hyperbranched polymer, and modified chain extender. In some embodiments, for example, the amount of solvent used relative to 20g of inorganic particles can be 100 to 1000 mL, preferably 200 to 500 mL, and more preferably 400 mL.

[0055] There are no particular restrictions on the type of solvent, as long as it can disperse the inorganic particles, hyperbranched polymer, and modified chain extender to achieve uniform contact for the above reaction.

[0056] In some embodiments, the solvent may be a mixture of water and organic solvent A. The water may be distilled water, deionized water, etc., but is not limited thereto. The organic solvent A is a polar solvent, preferably selected from one or more of tetrahydrofuran, dimethylformamide, ethanol, and methanol, but is not limited thereto.

[0057] In the mixture, the volume ratio of water to organic solvent A can be (500-5):0-1, preferably 40:0-1.

[0058] The reaction temperature is not particularly limited, as long as the above reaction can be carried out without adversely affecting the reactants and products. In some embodiments, the reaction temperature can be 20–200°C, such as 25°C, 30°C, 40°C, 50°C, 60°C, 70°C, 75°C, 120°C, 170°C, etc., but is not limited thereto.

[0059] The reaction time is not particularly limited, as long as the reaction can be carried out sufficiently to obtain the desired inorganic particle-polymer composite material. In some embodiments, the reaction time can be 30 minutes or more, or 1 hour or more, etc. There is no particular upper limit to the reaction time; for example, it can be less than 72 hours, less than 48 hours, etc.

[0060] The reaction can be carried out in a pH range of 3-12, preferably in a pH range of 4-6 or 7-10, depending on the reaction system. The reaction can be promoted by controlling the pH of the reaction mixture. For example, when using levodopa as a chain extender, by adjusting the pH of the system to a weakly alkaline state, dopamine undergoes an auto-oxidative polymerization reaction and coats the surface of inorganic nanoparticles. Monomers or polymer molecules containing two or more reactive functional groups such as amino and hydroxyl groups in the system can undergo Michael addition with the double bonds on the benzene ring of oxidized dopamine, thereby introducing functional groups such as amino and hydroxyl groups onto the surface of inorganic nanoparticles. These functional groups can then serve as reaction sites, directly anchoring hyperbranched polymer molecules to the surface of the inorganic nanoparticles.

[0061] The method for preparing inorganic particle-polymer composite materials according to the present invention may further include separation, washing and drying steps.

[0062] The separation step can separate the small monomers, polymers, and chain extenders not grafted onto the inorganic particles. In the case of a bulk reaction, the resulting inorganic particle-polymer composite material can be used directly, or it can be diluted with a solvent first, followed by filtration or centrifugation for separation. The solvent used here is the same as described above and will not be repeated. If the reaction is carried out in the presence of a solvent, filtration or centrifugation can be performed after the reaction.

[0063] The washing step is used to further separate the polymer and modified chain extender not grafted onto the inorganic particles. Washing can use the same solvent as in the separation step or a different solvent. Washing can be performed more than once, for example, 1 to 5 times. In some embodiments, washing is performed using a mixture of water and anhydrous ethanol. In some embodiments, the volume ratio of anhydrous ethanol to water is 1:2 to 40, preferably 1:40.

[0064] The drying step is used to remove solvents from the inorganic particle-polymer composite material. The drying process is not particularly limited and can include spray drying, vacuum drying, etc. The drying temperature is not particularly limited, as long as it does not significantly degrade the properties of the composite material; for example, it can be 40-85°C.

[0065] This invention utilizes in-situ reaction to prepare inorganic nanoparticles modified with hyperbranched polymer molecules. This preparation method can be based on bulk and aqueous systems, is environmentally friendly, low-cost, and easily replicated in large quantities, enabling large-scale industrial production.

[0066] When used as a toughening agent, the inorganic particle-polymer composite material of the present invention comprises a hyperbranched polymer with reactive groups that has a long-chain branched structure in its chemical structure. Compatibilizers with reactive groups are obtained by in-situ grafting onto the surface of inorganic particles. These hyperbranched polymer molecules can form entanglement sites through hydrogen bonding, π-π interactions, and in-situ condensation reactions between amino, hydroxyl, and carboxyl groups. Energy dissipation units with random coil structures and intermolecular bond interactions (i.e., weak bond interactions) are constructed in the matrix material. The formation of random coil structures gives the material an invisible length, and the elongation process under mechanical force can dissipate some energy, thereby playing an excellent toughening role.

[0067] The inorganic particle-polymer composite material of the present invention, as a reactive toughening agent, can significantly improve the interfacial bonding performance of two-phase blends. Compared with the ungrafted hyperbranched molecular group, the elongation at break of the material is doubled. The material exhibits obvious yield point and tensile necking phenomenon during the stretching process, demonstrating the properties of a hard and tough plastic material.

[0068] Therefore, another aspect of the present invention relates to the use of the inorganic particle-polymer composite material of the present invention as a toughening agent.

[0069] Another aspect of the invention relates to a polylactic acid composition comprising polylactic acid and an inorganic particle-polymer composite material according to the invention.

[0070] The polylactic acid refers to a polymer having the following repeating structural units:

[0071]

[0072] The weight-average molecular weight of polylactic acid can be 1.0 × 10⁻⁶. 5 -5.0×10 5 Da; preferably 1.0 × 10 5 -3.0×10 5 Within the aforementioned molecular weight range, the addition of toughening agents can achieve the technical effect of materials with good toughness. If the molecular weight is too small, it is difficult to form a film, and even with the addition of toughening agents, it is difficult to obtain high-performance composite materials. Conversely, if the molecular weight is too large, the melting point is too high, and the melt processing temperature is too high, which can cause degradation during polymer processing.

[0073] In the polylactic acid composition of the present invention, based on 100 parts by weight of polylactic acid, the amount of inorganic particle-polymer composite material can be 1 to 30 parts by weight, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12.5, 15, 17.5, 20, 22.5, 25, 27.5, or 30 parts by weight, preferably 3 to 20 parts by weight. Within the above-mentioned amount range, a polylactic acid composite material with significantly improved toughness can be obtained. If the amount of inorganic particle-polymer composite material is too large, aggregation may occur, tending more towards plasticization than toughening. If the amount is too small, the stress fields between microcracks formed around the inorganic nanoparticle matrix cannot interfere with each other, and multiple microcracks will not terminate between adjacent particles, but will become stress concentration points, reducing the mechanical properties of the material.

[0074] Depending on the intended use, the polylactic acid compositions of the present invention may also include other biodegradable polymers.

[0075] Other biodegradable polymers refer to polymers other than polylactic acid that can be biodegraded, such as polyester copolymers, biodegradable polyurethanes, aliphatic polyesters, and polyhydroxy fatty acids.

[0076] The polyester copolymer can be one of those commonly used in the art, such as polybutylene adipate / terephthalate.

[0077] Biodegradable polyurethanes can be those commonly used in the art, such as polymers having repeating structural units as follows:

[0078]

[0079] The weight-average molecular weight of biodegradable polyurethane can be 1.0 × 10⁻⁶. 5 -10.0×10 5 Da, preferably 2.0 × 10 5 -5.0×10 5 Da.

[0080] Examples of biodegradable polyurethanes may include (1) natural polymers; (2) vegetable oils; and (3) molecular chain designs, such as polyether ester polyurethanes prepared by mixing ε-caprolactone (ε-CL), diisocyanate (HBH) with different amounts of polyethylene glycol and polyether polyols with diisocyanate, and bi-terminated polyurethanes prepared by polybutylene adipate (PBA-1000), toluene-2,4-diisocyanate (TDI) and hydroxyethyl methacrylate (HEMA).

[0081] Aliphatic polyesters can be those commonly used in the art, such as polymers having repeating structural units as follows:

[0082]

[0083] Where x ranges from 1 to 5.

[0084] The weight-average molecular weight of aliphatic polyesters can be 1.0 × 10⁻⁶. 5 -10.0×10 5 Da, preferably 2.0 × 10 5 -5.0×10 5 Da.

[0085] Examples of aliphatic polyesters may include polycaprolactone, etc.

[0086] Polyhydroxy fatty acids can be those commonly used in the art, such as polymers having repeating structural units as follows:

[0087]

[0088] Where R represents hydrogen or a hydrocarbon group, and x is 1 to 3.

[0089] The weight-average molecular weight of polyhydroxy fatty acids can be 1.0 × 10⁻⁶. 5 -10.0×10 5 Da, preferably 2.0 × 10 5 -5.0×10 5 Da.

[0090] Examples of polyhydroxy fatty acids may include polyhydroxybutyrate, polyhydroxybutyrate-hexanoate copolyester, poly(3-hydroxybutyrate / 4-hydroxybutyrate) copolymer, poly(3-hydroxybutyrate / 3-hydroxyhexanoate), etc.

[0091] The purpose of adding other biodegradable polymers is to improve the brittle behavior of materials. For example, based on 100 parts by weight of polylactic acid, by adding 30 parts by weight of polycaprolactone and 10 parts by weight of the inorganic particle-polymer composite material of the present invention, the elongation at break of polylactic acid can be increased from 10% to 150%. But it is not limited thereto.

[0092] Based on 100 parts by weight of polylactic acid, the amount of the other biodegradable polymers can be from 5 to 100 parts by weight, for example, 10, 15, 20, 30, 40, 50, 60, 70, 75, 80, 85, or 90 parts by weight, preferably from 10 to 80 parts by weight, but not limited thereto.

[0093] Depending on the intended use, the polylactic acid composition of the present invention may also include conventional additives, such as antioxidants, UV stabilizers, etc., but is not limited thereto.

[0094] There are no particular limitations on the antioxidant used; any suitable antioxidant used in the field of polylactic acid can be selected. For example, the antioxidant may be one or more selected from tea polyphenols (TP), tocopherols, flavonoids, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tert-butylhydroquinone (TBHQ), etc., but is not limited to these.

[0095] The amount of antioxidant can be easily determined according to actual needs. In some embodiments, based on 100 parts by weight of polylactic acid, the amount of antioxidant can be 0.1-1.0 parts by weight, preferably 0.3-0.5 parts by weight.

[0096] There are no particular limitations on the UV stabilizer used; any suitable UV stabilizer used in the field of polylactic acid can be selected. For example, the UV stabilizer may be one or more selected from benzophenone, 2-hydroxy-4-n-octyloxybenzophenone, and n-hexadecyl 3,5-di-tert-butyl-4-hydroxybenzoate, but is not limited thereto.

[0097] The amount of the UV stabilizer can be easily determined according to actual needs. In some embodiments, based on 100 parts by weight of polylactic acid, the amount of the UV stabilizer can be 1.0-10 parts by weight, preferably 3.0-5.0 parts by weight.

[0098] Polylactic acid composites modified using the inorganic particle-polymer composite material of the present invention as a toughening agent can have elongation at break of 15-1000%, 100-800%, or 150-600%. Here, the elongation at break is measured according to GB / T1040-1992 standard.

[0099] In addition, polylactic acid composites can have a strength of 13-100 kJ / m³. 2 45-100kJ / m 2 or 60-100kJ / m 2 The impact strength is measured according to ASTM D256 standard.

[0100] Another aspect of the present invention relates to a method for preparing the polylactic acid composition, the method comprising the step of melt blending the inorganic particle-polymer composite material of the present invention with polylactic acid.

[0101] The temperature and time of the melt blending are not particularly limited and can be selected through conventional experiments based on the properties of polylactic acid and the desired degree of crosslinking. Specifically, the melt blending temperature can be 150–220°C, preferably 170–195°C. The melt blending time can be 3–15 minutes.

[0102] The melt blending can be carried out in a mixer, extruder (e.g., a twin-screw extruder), kneader, etc., but is not limited thereto. In some embodiments, the melt blending is carried out in a twin-screw extruder at a rotation speed of 20-100 rpm.

[0103] The polylactic acid composition can be used as a biodegradable material to prepare biodegradable plastic products, such as nonwoven fabrics, microcarriers, face masks, toys, pipes, mulch films, and garbage bags.

[0104] Therefore, another aspect of the present invention relates to the use of the polylactic acid composition as a biodegradable material.

[0105] In another aspect, the present invention provides a biodegradable plastic article comprising the polylactic acid composition.

[0106] The biodegradable plastic products can be prepared using existing manufacturing processes without special limitations. For example, biodegradable plastic products can be prepared by compression molding, injection molding, vacuum forming, melt spinning, electrospinning, electrostatic dripping, and 3D printing.

[0107] The biodegradable plastic products mentioned can be non-woven fabrics, microcarriers, face masks, toys, pipes, mulch films, and garbage bags, but are not limited to these.

[0108] Beneficial effects

[0109] The inorganic particle-polymer composite material prepared by this invention effectively improves the compatibility between the polylactic acid matrix and the toughening agent, facilitates the uniform dispersion of inorganic nanoparticles in the polymer matrix, increases effective entanglement with the composite matrix, and provides functional sites for in-situ reactions with the polymer matrix. These hyperbranched molecules can form entanglement sites through hydrogen bonding, π-π interactions, and in-situ condensation reactions between amino, hydroxyl, and carboxyl groups, constructing energy dissipation units with random coil structures and intermolecular bond interactions (i.e., weak bond interactions) in the matrix material. The formation of random coil structures gives the material an invisible length, and the elongation process under mechanical force can dissipate some energy, thus playing an excellent toughening role. The preparation process of the inorganic particle-polymer composite material provided by this invention can be based on bulk or aqueous systems, is environmentally friendly, low-cost, and easy to repeat in large quantities, enabling large-scale industrial production.

[0110] The polylactic acid composition provided by this invention exhibits significantly improved interfacial bonding of the composite material and good mechanical properties. Detailed Implementation

[0111] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0112] The reagents used in the following examples are as follows:

[0113] Polylactic acid is a commercially available product with a weight-average molecular weight of 1.0 × 10⁻⁶. 5 -5.0×10 5 The product, known by its brand name Natureworks4032D, contains approximately 2.0% D-type lactic acid units.

[0114] Rare earth oxides such as silicon dioxide, lanthanum oxide, samarium oxide, neodymium oxide, praseodymium oxide, cerium oxide, and yttrium oxide are supplied by Ganzhou Lanxin Rare Earth, with a purity greater than 99.0% and a particle size of approximately 50-100 nm.

[0115] Levodopa: Supplier is Aladdin Reagents, purity approximately 99.0%, molecular weight 197 Da.

[0116] Polyetheramine: CAS No. 9046-10-0, purchased from Wengjiang Reagent, D-2000, purity greater than 95.0%.

[0117] Gallic acid: Supplied by Aladdin Reagents, purity approximately 99.0%.

[0118] Phosphate ester compounds: supplied by Aladdin Reagents, with a purity of approximately 98.0%.

[0119] Polyethyleneimine: Purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd., item number Aladdin E107077-100g, MW 600Da.

[0120] Polylysine: As an example of hyperbranched peptides, the synthesis was described in reference Abstr. Pap. Am. Chem. Soc. 2003, 226, U373-U373. Specifically, 2.0 g of L-lysine dihydrochloride, 40 mg of CsOH, and 20 mg of Ti(OnBu)4 catalyst were added to a three-necked round-bottom flask. The polymerization reaction was carried out under vigorous mechanical stirring and reduced pressure using a gradual heating method. First, the temperature was maintained at 100℃ for 2 hours, then at 120℃ for 2 hours. After sufficient prepolymerization, the temperature was increased to 150℃ until the viscosity of the system increased rapidly, at which point the polymerization was stopped. The number-average molecular weight was determined to be 13.7 kDa, and the molecular weight distribution (weight-average molecular weight / number-average molecular weight) was 3.60.

[0121] Unless otherwise stated, all other materials and reagents used are commercially available standard products.

[0122] Measurement and characterization methods:

[0123] Tensile strength was measured as follows: Tensile tests were conducted on an INSTRON 1121 instrument, according to GB / T1040-1992 standard, with a spline clamping distance of 16.0 mm and a testing rate of 1.0 mm / min. The yield strength and elongation at break of the samples were determined by the force-displacement relationship during deformation. Five parallel samples were used in each group, and the mean and variance were statistically analyzed.

[0124] Young's modulus was measured as follows: Tensile tests were conducted on an INSTRON 1121 instrument, according to GB / T1040-1992 standard, with a strip clamping distance of 16.0 mm and a testing rate of 1.0 mm / min. Young's modulus was determined based on the force exerted during the tensile process. Five parallel samples were used in each group, and the average value was calculated.

[0125] Elongation at break was measured as follows: Tensile tests were conducted on an INSTRON 1121 instrument, according to GB / T1040-1992 standard, with a strip clamping distance of 16.0 mm and a testing rate of 1.0 mm / min. The elongation at break was determined by the displacement of the sample during the tensile process. Five parallel samples were used in each group, and the average value was calculated.

[0126] Impact strength is measured as follows: The impact resistance test, i.e., the impact strength test of a simply supported beam, is completed on a JJ-20 (China) type impact strength tester. The impact specimen is cut into a simply supported beam specimen with a rectangular notch.

[0127] Example 1

[0128] Approximately 20.0 g of cerium oxide was added to 400.0 g of water and stirred at 25°C for 3-5 minutes to ensure uniform dispersion. 10.0 mg of levodopa was added, and sodium hydroxide was added to adjust the pH to approximately 8-9. The mixture was stirred overnight. In the presence of oxygen in the air and under alkaline conditions, levodopa underwent an auto-oxidative polymerization reaction and coated the surface of the inorganic nanoparticles. The next day, 2.0 g of polyetheramine (D2000) was added and stirred for 12 hours. During this process, the hyperbranched polyetheramine in the system could undergo Michael addition with the double bonds on the benzene ring of oxidized dopamine, further forming cross-linked branched chains. The mixture was filtered using a Buchner funnel. The filter cake was repeatedly washed with a large amount of primary water and dried in a vacuum oven at 70°C for 8 hours to obtain an inorganic particle-polymer composite material with reactive units such as amino, carboxyl, phenolic hydroxyl, and carbonyl groups on quinone rings.

[0129] Example 2

[0130] Approximately 20.0 g of praseodymium oxide was added to 400.0 g of water and 20 mL of ethanol, and mechanically stirred for 3-5 min. Then, 10.0 mg of levodopa and 2.0 g of polyetheramine (D2000) were added, and the pH was adjusted to approximately 8-9 with sodium hydroxide. The mixture was stirred overnight. Under alkaline conditions and in the presence of oxygen in the air, levodopa underwent an auto-oxidative polymerization reaction and coated the surface of the inorganic nanoparticles. Simultaneously, the polyetheramine in the system could undergo Michael addition with the double bonds on the benzene ring of oxidized dopamine, further forming cross-linked branched chains. The mixture was filtered using a Buchner funnel. The filter cake was repeatedly washed with a large amount of primary water and dried in a vacuum oven at 70 °C for 8 hours to obtain an inorganic particle-polymer composite material with reactive units such as amino, carboxyl, and phenolic hydroxyl groups.

[0131] Example 3

[0132] Approximately 20.0 g of neodymium oxide was added to 400.0 g of water and stirred at room temperature for 3-5 minutes to promote uniform dispersion of inorganic nanoparticles. 10.0 mg of gallic acid and 2.0 g of polylysine were added, along with sodium hydroxide to adjust the pH to approximately 8-9. The mixture was stirred overnight. Under alkaline conditions and in the presence of oxygen in the air, gallic acid underwent an auto-oxidative polymerization reaction and coated the surface of the inorganic nanoparticles. The hyperbranched polylysine in the system could undergo Michael addition with the double bonds on the benzene ring of oxidized gallic acid, further forming cross-linked branched chains. The nanoparticles were centrifuged or filtered using a Buchner funnel, repeatedly washed with a large amount of primary water, and dried in a vacuum oven at 70°C for 8 hours to obtain modified inorganic nanoparticles with reactive units such as amino, carboxyl, phenolic hydroxyl, and carbonyl groups on quinone rings.

[0133] Example 4

[0134] Approximately 20.0 g of lanthanum oxide, 2.0 g of hyperbranched polyethyleneimine, and 10.0 mg of phosphate ester-based compound were reacted at 165 °C for 4 hours under molten conditions. 200.0 g of water was added and stirred thoroughly to disperse the mixture evenly. The mixture was stirred overnight, centrifuged, or filtered using a Buchner funnel. The nanoparticles were washed three times with a large amount of primary water and three times with anhydrous ethanol. The nanoparticles were then dried in a vacuum oven at 70 °C for 8 hours to obtain modified inorganic nanoparticles with reactive units such as amino groups, phenolic hydroxyl groups, and carbonyl groups on quinone rings.

[0135] Comparative Example 1

[0136] 7.20g PLA and 4.80g poly(butylene adipate / terephthalate) were melt-blended in a Haake Rheomix 600 (Germany) at a temperature of 185°C for 8 minutes at a speed of 30 rpm.

[0137] The melt-blended product is added to the injection molding machine barrel, the barrel temperature is controlled at 195℃, and it is injected into the mold at this temperature. The holding time is 6s, and a sheet with a thickness of 2mm is obtained.

[0138] Comparative Example 2

[0139] 1.20 g of cerium oxide nanoparticles were added to 7.20 g of PLA and 4.80 g of poly(butylene adipate / terephthalate). The melt blending temperature was 185 °C and the melt blending time was 8 min.

[0140] The melt-blended product is added to the injection molding machine barrel, the barrel temperature is controlled at 190℃, and it is injected into the mold at this temperature. The holding pressure time is 6s, and a sheet with a thickness of 2mm is obtained.

[0141] Example 6

[0142] Except that the inorganic particle-polymer composite material of Example 1 was used instead of cerium oxide nanoparticles, polylactic acid composition sheets were prepared using the same process as in Comparative Example 2.

[0143] Example 6-1

[0144] Except for the inorganic particle-polymer composite material used in Example 2, polylactic acid composition sheets were prepared using the same process as in Example 6.

[0145] Example 7

[0146] Except that the inorganic particle-polymer composite material of Example 3 was used instead of cerium oxide nanoparticles, polylactic acid composition sheets were prepared using the same process as in Comparative Example 2.

[0147] Example 8

[0148] Except that the amount of inorganic particle-polymer composite material used was 1.50 g, polylactic acid composition sheets were prepared using the same process as in Example 6.

[0149] Example 9

[0150] Except that the amount of inorganic particle-polymer composite material used was 0.60 g, polylactic acid composition sheets were prepared using the same process as in Example 6.

[0151] Example 10

[0152] Except that the amount of inorganic particle-polymer composite material used was 0.30 g, polylactic acid composition sheets were prepared using the same process as in Example 6.

[0153] The polylactic acid composition sheet materials obtained in Comparative Examples 1-2 and Examples 6-10 were subjected to performance tests, and the test results are shown in Table 1.

[0154] Table 1. Test results of tensile strength, Young's modulus, elongation at break, and impact strength.

[0155]

[0156] Comparing Examples 6 and 6-1, it can be seen that the resulting polylactic acid compositions are very similar in performance. Examples 1 and 2 use similar raw materials and ratios, differing only in the order of reactant addition, indicating that the method of addition has little impact on the product.

[0157] Furthermore, as shown in Table 1, the inorganic particle-polymer composite material provided by this invention plays a significant toughening role in the modification of polylactic acid. The preferred group exhibits an elongation at break as high as 361% and an impact strength as high as 95 kJ / m. 2 Meanwhile, the material also exhibits high tensile strength. Both its tensile toughness and impact toughness are significantly improved, enabling polylactic acid materials to have a wider range of applications.

[0158] The above description of the embodiments is merely to aid in understanding the method and core ideas of the present invention. Those skilled in the art to which this invention pertains can make various modifications or additions to the specific embodiments described, or substitute them with similar methods, without departing from the spirit of the invention or exceeding the scope defined by the appended claims. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An inorganic particle-polymer composite material, comprising (A) inorganic particles; and (B) a hyperbranched polymer containing reactive functional groups, wherein, The inorganic particles are dispersed in the hyperbranched polymer, which is formed by a polymer having two or more reactive functional groups and a modified chain extender in the presence of the inorganic particles through hydrogen bonding and in-situ Michael addition reaction. The modified chain extender undergoes an auto-oxidative polymerization reaction and coats the surface of the inorganic particles. The inorganic particles are selected from one or more rare earth oxides; The polymer having two or more reactive functional groups is selected from one or more of polyetheramines and hyperbranched peptides; The weight-average molecular weight of polyetheramines ranges from 100 to 10,000 Da; The hyperbranched peptides were selected from polylysine prepared by melt polycondensation using L-lysine as the AB2 monomer; the weight-average molecular weight was 1,000 to 100,000 Da. The modified chain extender is selected from one or more of L-DOPA, dopamine, caffeic acid, gallocatechin, tannic acid and lignin; The mass ratio of the modified chain extender to the polymer having two or more reactive functional groups is 1:1 to 1:300; In the inorganic particle-polymer composite material, the mass ratio of hyperbranched polymer is 2-15% based on the total mass of the composite material.

2. The inorganic particle-polymer composite material according to claim 1, wherein, The inorganic particles have a particle size of 50–1000 nanometers; and / or The rare earth oxide is selected from one or more of lanthanum oxide, samarium oxide, neodymium oxide, praseodymium oxide, cerium oxide, and yttrium oxide; and / or In the inorganic particle-polymer composite material, the mass ratio of hyperbranched polymer is 5-12% based on the total mass of the composite material; and / or The mass ratio of the modified chain extender to the polymer having two or more reactive functional groups is from 1:10 to 1:

250.

3. The inorganic particle-polymer composite of claim 1, wherein, The inorganic particles have a particle size of 50–200 nanometers.

4. The inorganic particle-polymer composite of claim 1, wherein, The inorganic particles have a particle size of 50–100 nanometers.

5. A method for preparing the inorganic particle-polymer composite material according to any one of claims 1-4, the method comprising mixing inorganic particles, a modified chain extender, and a polymer having two or more reactive functional groups, followed by hydrogen bonding interactions and an in-situ Michael addition reaction to obtain the inorganic particle-polymer composite material, wherein, The modified chain extender undergoes an auto-oxidative polymerization reaction and coats the surface of the inorganic particles.

6. The method of claim 5, wherein, The reaction is carried out either in the bulk or in the presence of a solvent; and / or The reaction temperature of the reaction is 20-200 o C; and / or The reaction time is more than 30 minutes; and / or The reaction was carried out in a pH range of 7-10.

7. The method of claim 6, wherein, The solvent is a mixture of water and organic solvent A, wherein organic solvent A is one or more selected from tetrahydrofuran, dimethylformamide, ethanol, and methanol; the volume ratio of water to organic solvent A is (500~5):0-1; and / or The reaction time is more than 1 hour; and / or The reaction was carried out in a pH range of 8-9.

8. The method of claim 7, wherein, The volume ratio of water to organic solvent A is 40:0-1.

9. Use of the inorganic particle-polymer composite material according to any one of claims 1-4 as a toughening agent for polylactic acid.

10. A polylactic acid composition comprising polylactic acid and the inorganic particle-polymer composite material according to any one of claims 1-4.

11. The polylactic acid composition according to claim 10, wherein, The weight-average molecular weight of polylactic acid is 1.0 × 10⁻⁶. 5 -5.0×10 5 Da; and / or The amount of inorganic particle-polymer composite material is 1 to 30 parts by weight, based on 100 parts by weight of polylactic acid.

12. The polylactic acid composition according to claim 10, wherein, The weight-average molecular weight of polylactic acid is 1.0 × 10⁻⁶. 5 -3.0×10 5 Da; and / or Based on 100 parts by weight of polylactic acid, the amount of inorganic particle-polymer composite material is 3 to 20 parts by weight.

13. The polylactic acid composition according to any one of claims 10-12, wherein, The polylactic acid composition also includes other biodegradable polymers, which are one or more selected from polyester copolymers, biodegradable polyurethanes, and aliphatic polyesters.

14. The polylactic acid composition according to claim 13, wherein, The polyester copolymer is poly(butylene adipate / terephthalate); The biodegradable polyurethane is selected from polyether ester type polyurethane prepared from polyether polyol and diisocyanate, and bi-terminated polyurethane prepared from polybutylene adipate, toluene-2,4-diisocyanate and hydroxyethyl methacrylate. The aliphatic polyester is selected from polycaprolactone and polyhydroxyalkanoates; and / or Based on 100 parts by weight of polylactic acid, the amount of the other biodegradable polymers is 5 to 100 parts by weight.

15. The polylactic acid composition of claim 14, wherein, Based on 100 parts by weight of polylactic acid, the amount of the other biodegradable polymers is 10 to 80 parts by weight.

16. The polylactic acid composition of claim 14, wherein, The polyhydroxy fatty acid ester is polyhydroxybutyrate.

17. The polylactic acid composition of claim 14, wherein, The polyhydroxy fatty acid ester is a polyhydroxybutyrate-hexanoate copolyester.

18. The polylactic acid composition of claim 14, wherein, The polyhydroxy fatty acid ester is selected from one or more of poly(3-hydroxybutyrate / 4-hydroxybutyrate copolymer) and poly(3-hydroxybutyrate / 3-hydroxyhexanoate copolymer).

19. A method for preparing the polylactic acid composition according to any one of claims 10-12, comprising the step of melt blending the inorganic particle-polymer composite material according to any one of claims 1-4 with polylactic acid.

20. Use of the polylactic acid composition according to any one of claims 10-18 as a biodegradable material.

21. A biodegradable plastic article comprising the polylactic acid composition according to any one of claims 10-18.

22. The biodegradable plastic product of claim 21, wherein the product is selected from nonwoven fabrics, microcarriers, face masks, toys, pipes, mulch films and garbage bags.

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