Degradable plastic bag material and preparation method thereof

Abstract

The invention provides a degradable plastic bag material and a preparation method thereof, and belongs to the field of plastic bag materials. The degradable plastic bag material is prepared from the following chemical components: 40 to 50 parts of polylactic acid, 15 to 25 parts of 3-hydroxybutyrate-co-4-hydroxybutyric acid copolymer, 5 to 15 parts of silane coupling agent modified starch, 3 to 8 parts of acetylated bamboo source nano cellulose, 5 to 15 parts of furan-terminated polylactic acid copolymer, 3 to 8 parts of bismaleimide dodecanedioate, 2 to 6 parts of coffee residue loaded WO3 and TiO2 and 1 to 5 parts of epoxidized soybean oil, the composition comprises the following components in parts by weight: 1-3 parts of sodium alginate microencapsulated lipase, 1-3 parts of quaternary ammonium salt modified hydrophilic kaolin, 0.1-1 part of zinc phenylphosphate and 0.1-0.8 part of polycarbodiimide. According to the application, the balance between the mechanical property and the degradation rate of the plastic bag material is realized through light-enzyme synergistic trigger degradation and dynamic covalent network regulation and control.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of plastic bag materials, and in particular to a degradable plastic bag material and a preparation method thereof. BACKGROUND

[0002] In modern society, plastic bags are widely used in daily life to hold various items due to their high strength, light weight, corrosion resistance, and low price, and have become an indispensable part of people's lives. However, while traditional plastic bags bring convenience, they also cause extremely serious environmental problems. Most of the discarded plastic bags are extremely slow in natural environment, relying on photolysis and biodegradation, and often take hundreds of years to completely disappear. Although they can be disposed of by burying or burning, burying will occupy a large amount of land resources, and long-term residual plastic bags will affect soil structure and fertility; burning may produce harmful gases and pollute the atmosphere.

[0003] To solve this problem, degradable plastics have emerged. Degradable plastics are mainly divided into two categories: photodegradable plastics and biodegradable plastics. At present, although some progress has been made in the research and development of degradable plastic bags, the mechanical properties of degradable plastics depend on stable molecular structures (such as long chains, high crystallinity, and strong interactions), while the degradation rate depends on easily broken molecular structures (such as unstable bonds and hydrophilic groups). There is an inherent contradiction between the two in terms of structural requirements, leading to performance conflicts. For example, Chinese patent CN114479393A discloses an environmentally friendly degradable plastic packaging bag and a preparation process thereof, which is made of components such as polylactic acid, polycaprolactone, and nanocellulose. The patent aims to achieve the degradability of plastic bags, but the plastic packaging bag prepared by this scheme has obvious shortcomings in mechanical properties, with low tensile strength, poor elongation at break, and poor toughness that cannot meet the requirements of daily use, which limits its popularization and application. At the same time, its degradation rate is not ideal, and it cannot quickly and effectively reduce the pressure of plastic garbage on the environment. Therefore, the technical problem to be solved at present is how to ensure that the plastic bag material has good mechanical properties, meets the requirements of daily use strength and toughness, and significantly improves the degradation rate of the plastic bag material, so as to achieve the dual goals of environmental protection and practical application, promote the widespread application of degradable plastic bag materials in the market, and effectively alleviate the problem of white pollution. SUMMARY

[0004] The present application provides a degradable plastic bag material and a preparation method thereof to solve the technical problem of how to improve the degradation rate of the plastic bag material while ensuring the mechanical properties of the plastic bag material.

[0005] In a first aspect, the embodiments of the present application provide a degradable plastic bag material, which is composed of the following chemical components in mass parts: polylactic acid: 40-50 parts, 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer: 15-25 parts, silane coupling agent modified starch: 5-15 parts, acetylated bamboo-derived nanocellulose: 3-8 parts, furan-terminated polylactic acid copolymer: 5-15 parts, dodecanedioic acid bismaleimide ester: 3-8 parts, coffee grounds loaded WO3@TiO2: 2-6 parts, epoxy soybean oil: 1-5 parts, sodium alginate microencapsulated lipase: 1-3 parts, quaternary ammonium salt modified hydrophilic kaolin: 1-3 parts, zinc phenylphosphate: 0.1-1 part, and polycarbodiimide: 0.1-0.8 part. wherein the crystallinity of the polylactic acid is >50%; The number average molecular weight of the furan-terminated polylactic acid copolymer is 7000-9000 g / mol.

[0006] Optionally, the molar amount of 4-hydroxybutyric acid monomer in the 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer is 20-30%, and the number average molecular weight is 80000-120000 g / mol.

[0007] Optionally, the silane grafting rate of the silane coupling agent modified starch is ≥85%.

[0008] Optionally, the diameter of the acetylated bamboo-derived nanocellulose is 20-50 nm, the aspect ratio is >50, and the acetylation substitution degree is 0.8-1.2.

[0009] Optionally, the preparation method of the furan-terminated polylactic acid copolymer comprises: under a nitrogen atmosphere, carrying out copolymerization reaction on polylactic acid oligomer, furan formic acid and tetrabutyl titanate, and then carrying out purification treatment to obtain the furan-terminated polylactic acid copolymer; wherein the molar ratio of the polylactic acid oligomer to the furan formic acid is 1:(1.2-1.5), and the mass of the tetrabutyl titanate is 0.2-1.0% of the mass of the polylactic acid oligomer; The temperature of the copolymerization reaction is 120-150°C, and the reaction time is 4-8 h.

[0010] Optionally, in the quaternary ammonium salt modified hydrophilic kaolin, the quaternary ammonium salt is cetyltrimethylammonium bromide, and the quaternary ammonium salt grafting amount is ≥5 wt%.

[0011] Optionally, the preparation method of the coffee grounds loaded WO3@TiO2 comprises: under a nitrogen atmosphere, carrying out carbonization treatment on coffee grounds to obtain a porous carbonized coffee grounds carrier; adding the porous carbonized coffee residue carrier into a tetrabutyl titanate-ethanol mixed solution, ultrasonic dispersion, then adding dilute nitric acid dropwise to adjust pH to 2-3, stirring and aging, drying, first calcination to obtain coffee residue loaded TiO2; ultrasonic treatment of the coffee residue loaded TiO2 in a sodium tungstate solution, centrifugation, drying, and second calcination to obtain the coffee residue loaded WO3@TiO2; The temperature of the carbonization treatment is 280-320 DEG C, and the time is 2-4 h. The temperature of the first calcination is 400-500 DEG C, and the time is 2-3 h. The temperature of the second calcination is 350-450 DEG C, and the time is 1-2 h. In the coffee residue loaded WO3@TiO2, the loading amount of WO3@TiO2 is 25-35 wt%, and the molar ratio of TiO2 to WO3 is 4:1.

[0012] Optionally, the preparation method of the sodium alginate microencapsulated lipase comprises: At room temperature, lipase with enzyme activity of 8000 U / g is uniformly mixed with a sodium alginate solution, the sodium alginate is used as a coating matrix, the mixed solution is spun into fibrous microcapsules by an electrospinning device, and the spinning product is collected and dried to obtain the sodium alginate microencapsulated lipase. The mass-volume ratio of the lipase to the sodium alginate solution is 1 g:(10-20) mL, and the mass concentration of the sodium alginate solution is 3%-5%. The voltage of the electrospinning is 15-25 kV, the receiving distance is 10-15 cm, and the advancing rate is 0.5-1.5 mL / h. The microcapsule particle size of the sodium alginate microencapsulated lipase is 10-50 mu m.

[0013] In a second aspect, the embodiments of the present application provide a preparation method of the degradable plastic bag material according to any one of the embodiments of the first aspect, and the method comprises: The polylactic acid, the 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer, the silane coupling agent modified starch, the acetylated bamboo-derived nanocellulose, the furan-terminated polylactic acid copolymer, the dodecanedioic acid bismaleimide ester, the coffee residue loaded WO3@TiO2, the epoxidized soybean oil, the quaternary ammonium salt modified hydrophilic kaolin, the zinc phenylphosphate, and the polycarbodiimide are mixed in a preset ratio, and a first blend is obtained through melt blending treatment; Sodium alginate microencapsulated lipase is added to the first blend, and the mixture is uniformly mixed to obtain a second blend. The second blend is blow molded to obtain the degradable plastic bag material.

[0014] Optionally, the temperature of the melt blending is 170-180 DEG C, the rotating speed is 30-50 r / min, and the time is 10-15 min. The mixing temperature after adding the sodium alginate microencapsulated lipase is 80-100 DEG C, and the time is 3-5 min. The temperature of the blow molding is 165-185 DEG C, and the blow ratio is 2-3.

[0015] Compared with the prior art, the above technical solution provided by the embodiments of the present application has the following advantages: The embodiments of the present application provide a degradable plastic bag material, which improves the degradation rate while ensuring the mechanical properties by reasonably designing the chemical composition of the plastic bag material, and the specific mechanism is as follows: On the one hand, polylactic acid with a crystallinity of > 50% is used as a matrix skeleton, which provides basic rigidity and tensile strength by virtue of high crystallinity, and provides structural support for the bag material; 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer improves the brittleness of polylactic acid through flexible segments, and the two form a blend system, which inhibits phase separation through intermolecular interaction, and takes into account rigidity and toughness, avoiding the problem of easy brittle fracture of pure polylactic acid. At the same time, acetylated bamboo-derived nanocellulose forms a three-dimensional network structure at the phase interface of polylactic acid / 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer, which transmits stress through the "fiber bridging" effect and improves the tensile and impact resistance of the material; acetylation can avoid nanofiber agglomeration, ensuring its compatibility with the matrix, enhancing the mechanical properties without hindering subsequent degradation. In addition, furan-terminated polylactic acid copolymer (number average molecular weight 7000-9000 g / mol) and dodecanedioic acid bismaleimide ester form a dynamic covalent network through Diels-Alder reaction, which is stable at room temperature, can ensure the integrity of the bag material structure during use, resist external impact, and maintain mechanical properties.

[0016] On the other hand, coffee residue loaded WO3@TiO2can respond to visible light, generate hydroxyl radicals to randomly cut the polymer main chain, and reduce the molecular weight to facilitate subsequent degradation; sodium alginate microencapsulated lipase is released after the bag material is discarded, and specifically hydrolyzes the ester bond in dodecanedioic acid bismaleimide ester and polylactic acid / 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer, wherein the long-chain ester bond of dodecanedioic acid provides a high-efficiency cutting site for lipase, accelerating material disintegration; the two form a synergistic effect of "photocatalytic main chain breaking-enzymatic crosslinking point cutting", improving the degradation efficiency. At the same time, silane coupling agent modified starch is preferentially eroded at the initial stage of degradation, forming microporous channels to provide diffusion paths for microorganisms and enzymes, making the degradation penetrate from the surface to the inside; quaternary ammonium salt modified hydrophilic kaolin adsorbs negatively charged microorganisms (such as Bacillus) through surface positive charge, promoting the formation of a biofilm, and cooperating with the microporous channels to improve the enrichment rate of microorganisms on the material surface, accelerating biodegradation. In addition, the dynamic covalent network is broken under the action of light and enzymes, making the network disintegrate into small molecular fragments, which are more easily decomposed by microorganisms, avoiding the problem of slow degradation of traditional materials due to stable structure.

[0017] Therefore, the present application guarantees the mechanical properties through rigid-flexible balance, nano-enhancement, dynamic network stabilization, etc., and improves the degradation rate through light-enzyme synergy, microbial infection acceleration, dynamic network disintegration, etc., to achieve the synergistic goal of "durable in use and fast degradation after disposal". BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate an embodiment consistent with the present application and, together with the description, serve to explain the principles of the application.

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor.

[0020] Figure 1 A flowchart of a preparation method of a degradable plastic bag material is provided. DETAILED DESCRIPTION

[0021] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0022] The application embodiment provides a degradable plastic bag material, which is composed of the following chemical components in mass parts: polylactic acid: 40-50 parts, 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer: 15-25 parts, silane coupling agent modified starch: 5-15 parts, acetylated bamboo-derived nanocellulose: 3-8 parts, furan-terminated polylactic acid copolymer: 5-15 parts, dodecanedioic acid bismaleimide ester: 3-8 parts, coffee grounds loaded WO3@TiO2: 2-6 parts, epoxy soybean oil: 1-5 parts, sodium alginate microencapsulated lipase: 1-3 parts, quaternary ammonium salt modified hydrophilic kaolin: 1-3 parts, zinc phenylphosphonate: 0.1-1 part, and polycarbodiimide: 0.1-0.8 part. 2: 2-6 parts, epoxy soybean oil: 1-5 parts, sodium alginate microencapsulated lipase: 1-3 parts, quaternary ammonium salt modified hydrophilic kaolin: 1-3 parts, zinc phenylphosphonate: 0.1-1 part, and polycarbodiimide: 0.1-0.8 part. The crystallinity of the polylactic acid is >50%. The number average molecular weight of the furan-terminated polylactic acid copolymer is 7000-9000 g / mol.

[0023] The application embodiment rationally designs the chemical components of the degradable plastic bag material, takes polylactic acid, 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer and silane coupling agent modified starch as core matrix components to build a basis of high strength and processing stability, takes acetylated bamboo-derived nanocellulose, furan-terminated polylactic acid copolymer and dodecanedioic acid bismaleimide ester as reinforcing and dynamic regulating components to improve mechanical properties and controllable degradation, takes coffee grounds loaded WO3@TiO2, sodium alginate microencapsulated lipase and quaternary ammonium salt modified hydrophilic kaolin as degradation accelerating and functional regulating components to realize "on-demand fast degradation", and takes epoxy soybean oil, zinc phenylphosphonate and polycarbodiimide as auxiliary components to optimize processing and performance stability. Specifically, the functions of each component are as follows: Polylactic acid (PLA, 40-50 parts): as a matrix skeleton, it provides rigidity and tensile strength (support material bearing capacity) with a high crystallinity of >50%, and the ester bond in the molecular chain is the basic site for biodegradation. At the same time, it ensures that the bag material is not easy to break when loaded with heavy objects (such as 5-10 kg of objects), and the initial tensile strength can reach more than 40 MPa.

[0024] 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer (P(3HB-co-4HB), 15-25 parts): the flexible segment of 4-hydroxybutyric acid (20-30% molar amount) improves the brittleness of PLA and improves the material toughness, and itself has excellent biodegradability. At the same time, 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer and PLA form a blending system, which inhibits phase separation through intermolecular chain interaction, and takes into account rigidity and toughness, solving the problem of brittle cracking of pure PLA.

[0025] Silane coupling agent modified starch (5-15 parts): After silane grafting (grafting rate ≥ 85%), the compatibility with PLA / PHA matrix is significantly improved, reducing the cost of the material, and the hydroxyl groups in the starch molecule can be connected to the matrix through hydrogen bonds to enhance the interfacial bonding force; at the same time, starch will preferentially dissolve and erode at the initial stage of degradation, forming microporous channels to accelerate microbial infection; in addition, the microporous channels provide diffusion paths for microorganisms and enzymes, allowing degradation to penetrate from the surface to the interior, shortening the degradation period.

[0026] Acetylated bamboo-derived nanocellulose (3-8 parts): Nanocellulose with a diameter of 20-50 nm and an aspect ratio > 50 is oriented and arranged at the PLA / PHA phase interface, forming a "three-dimensional network reinforcement structure" (similar to "organic steel bars"), which improves the tensile strength, and acetylation treatment avoids the agglomeration of nanofibers. Acetylated bamboo-derived nanocellulose is tightly combined with the matrix polymer through hydrogen bonding, improving the strength while not hindering ester bond hydrolysis, achieving a balance between "high strength and degradability".

[0027] Furan-terminated polylactic acid copolymer (5-15 parts) and dodecanedioic acid bismaleimide ester (5-12 parts): Both form a dynamic covalent network (DCN) through Diels-Alder (D-A) reaction: furan end groups and maleimide groups can reversibly combine, and the network is stable at room temperature (ensuring performance during use), and when degraded, the D-A bond breaks, causing the network to disintegrate. More importantly, the long-chain ester bonds in dodecanedioic acid are specific cutting sites for lipase, improving enzyme efficiency and triggering rapid network disintegration, accelerating the conversion of the material from a "stable structure" to "degradable fragments".

[0028] Coffee grounds loaded WO3@TiO2 (2-6 parts): Coffee grounds form a porous carrier (pore size 50-200 nm) after carbonization, and the loaded WO3@TiO2 composite photocatalyst can respond to visible light (450 nm wavelength), generating hydroxyl radicals to randomly cut the polymer main chain, reducing the molecular weight to promote subsequent biodegradation. At the same time, the coffee grounds loaded WO3@TiO2 and the enzyme system form a "light-enzyme dual trigger" mechanism, with photocatalysis first breaking the main chain (reducing the mechanical properties of the material), and enzyme hydrolysis then precisely cutting the crosslinking points, improving the degradation efficiency. In addition, WO3@TiO2 can synergize with microbial enzymatic degradation mechanisms to maintain degradation efficiency under weak light.

[0029] Sodium alginate microencapsulated lipase (1-3 parts): Microcapsules (particle size 10-50 μm) protect lipase during processing, and after disposal, the microcapsules break to release lipase (enzyme activity ≥ 8000 U / g), which specifically hydrolyzes the ester bonds in dodecanedioic acid bismaleimide ester and PLA / PHA. At the same time, sodium alginate microencapsulated lipase catalyzes the ester bond cleavage directionally.

[0030] Quaternary ammonium salt modified hydrophilic kaolin (1-3 parts): After modification by cetyltrimethylammonium bromide (grafting amount ≥ 5wt%), the surface of kaolin is positively charged, which can adsorb negatively charged microorganisms (such as Bacillus spores) and promote the formation of biofilm, accelerating the decomposition of polymers by microorganisms. At the same time, the quaternary ammonium salt modified hydrophilic kaolin cooperates with the microporous channels formed by starch dissolution to improve the enrichment rate of microorganisms on the material surface and strengthen the biodegradation efficiency.

[0031] Epoxidized soybean oil (1-5 parts): As a bio-based plasticizer, epoxidized soybean oil reduces the melt viscosity and improves the processing fluidity of the material (such as film thickness uniformity during blow molding), and its ester bond can be hydrolyzed by lipase without affecting the degradation performance.

[0032] Zinc phenylphosphate (0.1-1 parts): As a nucleating agent, it improves the crystallization rate of PLA, increases the crystallinity to more than 60%, and enhances the heat resistance to avoid deformation of the bag material when containing high-temperature objects.

[0033] Polycarbodiimide (0.1-0.8 parts): It inhibits ester bond hydrolysis during short-term storage and initial use, ensuring the stability of the bag material performance during the shelf life; as a carbodiimide compound, polycarbodiimide contains carbon-nitrogen double bonds and other sites that can be acted upon by microbial enzymes, so it can be decomposed by microorganisms and does not hinder the later degradation.

[0034] In some embodiments, the 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer has a 4-hydroxybutyric acid monomer molar content of 20-30%, and a number average molecular weight of 80000-120000 g / mol.

[0035] The 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer has a 4-hydroxybutyric acid monomer molar content of 20-30%, and the 4-hydroxybutyric acid is a flexible segment. This ratio can balance the crystallinity and flexibility of the copolymer, improve the elongation at break of the material, and effectively compensate for the brittleness of PLA. The number average molecular weight is limited to 80000-120000 g / mol to ensure the entanglement ability with the PLA molecular chain, avoid mechanical property degradation due to low molecular weight, and ensure processing fluidity and matrix compatibility during melt blending.

[0036] In some embodiments, the silane grafting rate of the silane coupling agent modified starch is ≥ 85%.

[0037] The silane grafting rate is limited to ≥ 85%, and more siloxane groups with good compatibility with PLA / PHA are introduced to the surface of the starch molecules, which can significantly reduce the interface defects between the starch and the matrix, enhance the interface bonding force, and avoid fracture caused by interface separation when the material is stressed.

[0038] In some embodiments, the acetylated bamboo-derived nanocellulose has a diameter of 20-50 nm and an aspect ratio of >50, and an acetylation degree of 0.8-1.2.

[0039] The diameter of the acetylated bamboo-derived nanocellulose is limited to 20-50 nm and the aspect ratio is >50, and the nanoscale and high aspect ratio can maximize the dispersion area thereof in a matrix, transfer stress through a "fiber bridging" effect, and improve the tensile and impact resistance of the material; a diameter that is too large is prone to agglomeration, and a diameter that is too small is difficult to form an effective reinforcing network. The acetylation degree is limited to 0.8-1.2, which can balance the hydrophilicity and hydrophobicity of the nanocellulose, and can ensure uniform dispersion of the nanocellulose at the phase interface of polylactic acid / 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer and the formation of a three-dimensional network.

[0040] The oriented nanocellulose in the embodiments of the present application forms a "mechanical anchor" at the interface between polylactic acid and 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer, prevents phase separation, and simultaneously uniformly transfers external force to the entire material system, thereby improving the tensile strength.

[0041] In some embodiments, the method for preparing the furan-terminated polylactic acid copolymer comprises: The polylactic acid oligomer, furan carboxylic acid, and tetrabutyl titanate are subjected to a copolymerization reaction under a nitrogen atmosphere, and then subjected to a purification treatment to obtain the furan-terminated polylactic acid copolymer; The molar ratio of the polylactic acid oligomer to the furan carboxylic acid is 1:(1.2-1.5), and the mass of the tetrabutyl titanate is 0.2-1.0% of the mass of the polylactic acid oligomer; The copolymerization reaction is performed at a temperature of 120-150°C for 4-8 h.

[0042] The molar ratio of the polylactic acid oligomer to the furan carboxylic acid is limited to 1:(1.2-1.5), and the excess of furan carboxylic acid can ensure that the end groups of the polylactic acid oligomer are fully modified by furan groups, ensure the Diels-Alder reaction efficiency with dodecanedioic acid bismaleimide ester in the subsequent step, and avoid a too-low crosslinking density of the dynamic network due to an insufficient number of furan end groups.

[0043] The amount of tetrabutyl titanate is limited to 0.2-1.0% as a catalyst for esterification, and this amount can efficiently promote the condensation reaction between the hydroxyl groups of the polylactic acid oligomer and the carboxyl groups of the furan carboxylic acid; a too-low amount will result in incomplete reaction, and a too-high amount may cause side reactions (such as excessive crosslinking of molecular chains).

[0044] The copolymerization temperature is limited to 120-150℃, and the time is 4-8h. If the temperature is too low, the reaction rate is slow, and if the time is insufficient, the molecular weight is low. If the temperature is too high or the time is too long, the molecular chain may be degraded. This parameter range can precisely control the number average molecular weight of the product to be 7000-9000g / mol, ensuring compatibility with the matrix.

[0045] In some embodiments, the quaternary ammonium salt in the quaternary ammonium salt modified hydrophilic kaolin is cetyltrimethylammonium bromide, and the amount of quaternary ammonium salt grafting is ≥5wt%.

[0046] The amount of cetyltrimethylammonium bromide grafting in the quaternary ammonium salt modified hydrophilic kaolin is limited to ≥5wt%, which can provide sufficient positive charge on the surface of the kaolin, efficiently adsorb negatively charged microorganisms (such as lipase producing bacteria) in the environment through electrostatic interaction, promote the rapid formation of biofilms on the material surface, and accelerate the degradation efficiency of microorganisms.

[0047] In some embodiments, the preparation method of the coffee grounds loaded WO3@TiO2 comprises: The coffee grounds are subjected to carbonization treatment under a nitrogen atmosphere to obtain a porous carbonized coffee grounds carrier; The porous carbonized coffee grounds carrier is added to a tetrabutyl titanate-ethanol mixed solution, ultrasonically dispersed, and then diluted nitric acid is added dropwise to adjust the pH to 2-3. After stirring and reaction and standing and aging, the coffee grounds loaded TiO2 is obtained by drying and first calcination; The coffee grounds loaded TiO2 is immersed in a sodium tungstate solution and ultrasonically treated. After centrifugation and drying, the coffee grounds loaded WO3@TiO2 is obtained by second calcination; The temperature of the carbonization treatment is 280-320℃, and the time is 2-4h; The temperature of the first calcination is 400-500℃, and the time is 2-3h; The temperature of the second calcination is 350-450℃, and the time is 1-2h; In the coffee grounds loaded WO3@TiO2, the loading amount of WO3@TiO2 is 25-35wt%, and the molar ratio of TiO2 to WO3 is 4:1.

[0048] The temperature of the carbonization treatment is limited to 280-320℃, and the time is 2-4h, which can form a porous structure with a pore size of 50-200nm in the coffee grounds, which not only retains the mechanical strength of the carrier, but also provides a high specific surface area to enhance the loading capacity of WO3@TiO2. If the temperature is too high, the pore structure will collapse, and if the temperature is too low, the porosity will be insufficient.

[0049] The temperature of the first calcination is 400-500℃, and the time is 2-3h, and the temperature of the second calcination is 350-450℃, and the time is 1-2h, the first calcination makes the tetrabutyl titanate completely hydrolyze and crystallize into anatase TiO2 (with the highest photocatalytic activity), and the second calcination promotes the uniform dispersion of WO3 on the surface of TiO2, and forms a stable heterostructure.

[0050] The loading amount of WO3@TiO2 is limited to 25-35wt%, and the molar ratio of TiO2 to WO3 is 4:1, too high loading amount will cause the catalyst to agglomerate, and too low loading amount will result in insufficient photocatalytic efficiency, and the molar ratio of 4:1 can form the best heterojunction, and the light response range is widened to the visible light region of 450nm, and the utilization rate of natural light is improved.

[0051] In some embodiments, the preparation method of the sodium alginate microencapsulated lipase comprises: At room temperature, the lipase with an enzyme activity of ≥8000U / g is uniformly mixed with a sodium alginate solution, the sodium alginate is used as a coating matrix, the mixed solution is spun into fibrous microcapsules by an electrospinning device, and the spinning product is collected and dried to obtain the sodium alginate microencapsulated lipase. The mass-volume ratio of the lipase to the sodium alginate solution is 1g:(10-20)mL, and the mass concentration of the sodium alginate solution is 3%-5%. The voltage of the electrospinning is 15-25kV, the receiving distance is 10-15cm, and the advancing rate is 0.5-1.5mL / h. The microcapsule particle size of the sodium alginate microencapsulated lipase is 10-50μm.

[0052] The ratio of the lipase to the sodium alginate solution is limited to 1g:(10-20)mL, and the concentration of the sodium alginate is limited to 3%-5%, which can ensure that the lipase is uniformly embedded, and too low concentration of the sodium alginate will result in a fragile microcapsule structure, and too high concentration will result in too large viscosity and difficulty in spinning, and finally ensure that the embedding rate is >90%.

[0053] The voltage of the electrospinning is limited to 15-25kV, the receiving distance is limited to 10-15cm, and the advancing rate is limited to 0.5-1.5mL / h, which can cooperatively control the microcapsule particle size to be 10-50μm, too small particle size will result in low enzyme loading, and too large particle size will result in uneven dispersion in the matrix; the parameters can ensure that the microcapsule structure is complete, and the survival rate of the lipase during bag material processing is >90%.

[0054] The enzyme activity is limited to ≥8000U / g, and high enzyme activity can ensure that after the material is discarded, the lipase rapidly catalyzes the hydrolysis of the ester bond of dodecanedioic acid bismaleimide ester and PLA / PHA, and accelerates the degradation process.

[0055] Figure 1A flowchart of a preparation method of a degradable plastic bag material is provided in the embodiments of the present application.

[0056] Based on a general inventive concept, as Figure 1 As shown in the embodiments of the present application, the preparation method of the degradable plastic bag material is provided, and the method comprises: S1, according to a predetermined ratio, the polylactic acid, the 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer, the silane coupling agent modified starch, the acetylated bamboo-derived nanocellulose, the furan-terminated polylactic acid copolymer, the dodecanedioic acid bismaleimide ester, the coffee grounds loaded WO3@TiO2, the epoxy soybean oil, the quaternary ammonium salt modified hydrophilic kaolin, the zinc phenylphosphate and the polycarbodiimide are mixed, and a first blend is obtained by melt blending treatment; S2, sodium alginate microencapsulated lipase is added to the first blend, and uniform mixing is continued to obtain a second blend; S3, the second blend is blow molded to obtain the degradable plastic bag material.

[0057] In some embodiments, the temperature of the melt blending is 170-180°C, the rotation speed is 30-50 r / min, and the time is 10-15 min.

[0058] The temperature of the melt blending is limited to 170-180°C: this temperature is higher than the melting temperature of PLA (melting point 150-160°C) and PHA (melting point 120-140°C), which can ensure that the base polymer is completely melted, while being lower than its decomposition temperature (≥200°C), avoiding performance degradation caused by molecular chain rupture; high temperature can also promote the preliminary formation of a dynamic covalent network of furan-terminated polylactic acid copolymer and dodecanedioic acid bismaleimide ester. The rotation speed is limited to 30-50 r / min, and moderate shear rate can make each component (such as nanocellulose, coffee grounds loaded WO3@TiO2) uniformly dispersed, avoiding filler agglomeration caused by too high rotation speed or uneven mixing caused by too low rotation speed; at the same time, it reduces the excessive conversion of mechanical energy into heat energy, preventing local temperature from being too high. The time is limited to 10-15 min, which ensures that the polymer is fully melted and mixed uniformly with the additives, and the dynamic covalent network is preliminarily crosslinked and shaped, and the time is too short, which will not be fully mixed, and the time is too long, which may cause the molecular weight to decrease due to thermal oxidation aging.

[0059] In some embodiments, the mixing temperature after adding sodium alginate microencapsulated lipase is 80-100°C, and the time is 3-5 min.

[0060] The temperature of the mixture after adding lipase is limited to 80-100°C, which is significantly lower than the heat tolerance threshold of sodium alginate microcapsules (230°C), so that the high temperature does not cause the inactivation of lipase (the activity of lipase decreases sharply at >140°C), and at the same time, the material has a certain flowability to achieve uniform dispersion. The time is limited to 3-5 minutes, which ensures the uniform dispersion of lipase microcapsules in the first blend under the premise of protecting the activity of the enzyme, and too long time will increase the risk of heat exposure of the enzyme, and too short time may cause uneven dispersion and lead to local degradation rate difference.

[0061] In some embodiments, the temperature of the blow molding is 165-185°C, and the blow ratio is 2-3.

[0062] The temperature of the blow molding is limited to 165-185°C, which can match the melt viscosity of the material, ensure that the melt has good flowability and ductility, and facilitate blow molding; if the temperature is too low, the melt is too thick, which may cause uneven thickness of the film; if the temperature is too high, the polymer may be degraded or the dynamic network may be prematurely disintegrated. The blow ratio is limited to 2-3, which is the transverse stretching multiple of the film. This range can make the polymer molecular chain moderately oriented in the transverse direction, improve the transverse mechanical properties (such as tear resistance) of the film, and at the same time ensure the uniformity of the film thickness (usually 20-50μm), which meets the use requirements of plastic bags; if the blow ratio is too large, the film may be easily broken, and if the blow ratio is too small, the mechanical properties may be insufficient.

[0063] In summary, the present application improves the degradation rate significantly while ensuring the mechanical properties of the plastic bag material through multi-component synergistic design and structure regulation, and the specific path is as follows: I. Mechanism of ensuring mechanical properties (1) Synergistic enhancement of rigidity and toughness: high crystallinity (>50%) polylactic acid (PLA) is used as the base skeleton to provide basic rigidity and tensile strength, ensuring that the bag material has sufficient load-bearing capacity; at the same time, 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer is introduced to optimize and improve the material toughness through flexible segments, making up for the brittleness of PLA, and the two form a blend system to inhibit phase separation through molecular chain entanglement, balancing rigidity and toughness; in addition, silane coupling agent modified starch (grafting rate ≥85%) is combined with the base through hydrogen bonds to enhance the interfacial force, reducing the cost without sacrificing the mechanical properties.

[0064] (2) Nano-scale reinforcing network: acetylated bamboo-derived nanocellulose (diameter 20-50nm, aspect ratio >50) is oriented and arranged at the PLA / PHA phase interface to form a three-dimensional network reinforcing structure, which transmits stress through the "fiber bridging" effect and significantly improves the tensile strength; acetylation balances the hydrophilic and hydrophobic properties, avoids agglomeration, and ensures the reinforcing effect and compatibility with the base.

[0065] (3) Structural stability of the dynamic network: Furan-terminated polylactic acid copolymer and dodecanedioic acid bismaleimide ester form a dynamic covalent network through the Diels-Alder reaction. The network is stable at room temperature, ensuring the structural integrity during use and resisting external force impact.

[0066] 2. Mechanism of increasing degradation rate (1) Light-enzyme dual-triggered degradation system: Coffee grounds loaded with WO3@TiO2 composite photocatalyst can respond to visible light (450nm) to generate hydroxyl radicals to cut the polymer main chain, reducing the molecular weight to promote subsequent degradation; at the same time, sodium alginate microencapsulated lipase (enzyme activity ≥8000U / g) is released after the material is discarded, specifically hydrolyzing the ester bonds in dodecanedioic acid bismaleimide ester and PLA / PHA, among which the long-chain ester bond of dodecanedioic acid serves as the enzyme cleavage site, greatly improving the enzymatic hydrolysis efficiency; the two form a synergistic mechanism of "photocatalysis first breaks the main chain - enzymatic hydrolysis and then cuts the cross-linking point", accelerating the disintegration of the material.

[0067] (2) Accelerated path of microbial infection: Silane coupling agent-modified starch preferentially dissolves in the early stage of degradation, forming microporous channels, which provide diffusion paths for microorganisms and enzymes, allowing degradation to penetrate from the surface to the inside; at the same time, quaternary ammonium salt-modified hydrophilic kaolin (grafting amount ≥5wt%) adsorbs negatively charged microorganisms through surface positive charges, promotes biofilm formation, and synergizes with microporous channels to enhance microbial enrichment and infection rates, thereby accelerating biodegradation.

[0068] (3) Controllable disintegration of dynamic network: The dynamic covalent network formed by furan-terminated polylactic acid copolymer and dodecanedioic acid bismaleimide ester undergoes bond breakage under degradation conditions (light and enzyme action), causing the network to disintegrate into small molecular fragments, which are easier to be decomposed by microorganisms, thus avoiding the problem of incomplete degradation of traditional materials.

[0069] 3. Balance strategy between mechanical properties and degradation rate (1) Polycarbodiimide is used to inhibit the hydrolysis of ester bonds in the short term during storage and the initial stage of use, ensuring that the performance of the bag material is stable during the shelf life. At the same time, it can be decomposed by microorganisms and does not hinder subsequent degradation.

[0070] (2) During the processing, the melt blending and blow molding parameters (such as temperature and rotation speed) are precisely controlled to ensure the uniform dispersion of the components and the formation of a dynamic network, while avoiding the inactivation of lipase or polymer degradation caused by high temperature, and ultimately achieving the synergistic goal of "meeting the mechanical properties during use and rapid degradation after disposal".

[0071] The present application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate but not limit the scope of the present application. The experimental methods in the following examples, if no specific conditions are noted, are generally determined according to the industry standards. If there is no corresponding industry standard, the general international standards, conventional conditions, or the conditions suggested by the manufacturers are followed.

[0072] Example 1 The present example provides a degradable plastic bag material, which consists of the following chemical components in mass parts: polylactic acid (PLA, crystallinity 55%, CAS No. 26100-51-6, Model 4032D, NatureWorks): 45 parts; 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer (4-hydroxybutyric acid monomer molar mass 25%, number average molecular weight 100000 g / mol, CAS No. 80181-31-3, Tianjin Gu Yung Biological): 16 parts; silane coupling agent modified starch (silane grafting rate 88%, silane coupling agent is KH550, starch is corn starch, CAS No. 9005-25-8): 10 parts; acetylated bamboo-derived nanocellulose (average diameter 35 nm, average aspect ratio 60, acetylation degree 1.0, nanocellulose CAS No. 9004-34-6): 5 parts; furan-terminated polylactic acid copolymer (number average molecular weight 8000 g / mol): 8 parts; dodecanedioic acid bismaleimide ester (CAS No. 13676-54-5, Aldrich reagent): 5 parts; coffee grounds loaded WO3@TiO2 (WO3@TiO2 loading 30 wt%, TiO2 to WO3 molar ratio 4:1): 3 parts; epoxy soybean oil (CAS No. 8013-07-8, Model ESO-80, Jiangsu Kainuo Plasticization): 3 parts; sodium alginate microencapsulated lipase (enzyme activity 8500 U / g, microcapsule evaluation particle size 30 μm): 2 parts; quaternary ammonium salt modified hydrophilic kaolin (hexadecyltrimethylammonium bromide grafting amount 5.5 wt%, kaolin CAS No. 1332-58-7): 2 parts; zinc phenylphosphonate (CAS No. 13845-36-8, Aldrich reagent): 0.55 parts; polycarbodiimide (CAS No. 69411-29-0): 0.45 parts.

[0073] The preparation method of the furan-terminated polylactic acid copolymer is as follows: under a nitrogen atmosphere, polylactic acid oligomer (number average molecular weight 4000 g / mol), furan formic acid (CAS No. 88-14-2), and tetrabutyl titanate (CAS No. 5593-70-4) are copolymerized at a molar ratio of 1:1.35, wherein the amount of tetrabutyl titanate is 0.6% of the mass of the polylactic acid oligomer; the reaction temperature is 135°C, and the time is 6h; after the reaction, the target product is obtained by ethanol precipitation, deionized water washing, and vacuum drying.

[0074] The preparation method of the coffee grounds loaded WO3@TiO2 is as follows: under a nitrogen atmosphere, the coffee grounds are carbonized at 300 DEG C for 3 hours to obtain a porous carbonized coffee grounds carrier; the carrier is added into a tetrabutyl titanate-ethanol mixed solution (volume ratio 1:3), ultrasonic dispersion is performed for 45 minutes, dilute nitric acid is added dropwise to adjust the pH to 2.5, stirring is performed for 3 hours, then aging is performed for 18 hours, drying is performed, and then calcination is performed at 450 DEG C for 2.5 hours to obtain coffee grounds loaded TiO2; the coffee grounds loaded TiO2 is immersed into a sodium tungstate solution (concentration 0.1 mol / L) and ultrasonic treatment is performed for 35 minutes, centrifugal separation is performed, drying is performed, and then calcination is performed at 400 DEG C for 1.5 hours to obtain the target product.

[0075] The preparation method of the sodium alginate microencapsulated lipase is as follows: at room temperature, lipase (CAS No. 9001-62-1) and 5% (mass concentration) sodium alginate solution (CAS No. 9005-38-3) are uniformly mixed at a ratio of 1 g:15 mL, sodium alginate is used as a coating matrix, and a microcapsule is spun by an electrostatic spinning device (voltage 20 kV, receiving distance 12.5 cm, and pushing rate 1.0 mL / h), vacuum drying is performed after collection to obtain a product with a particle size of 30 μm.

[0076] The preparation method of the silane coupling agent modified starch is as follows: at 50 DEG C, corn starch (CAS No. 9005-25-8) and deionized water are mixed at a mass ratio of 1:5, and stirring is performed until complete gelatinization; 3% of the mass of the starch of silane coupling agent KH550 (CAS No. 919-30-2) is added, the pH is adjusted to 4.5, and stirring is performed at 60 DEG C for 3 hours; after the reaction is completed, ethanol precipitation and washing are performed, and vacuum drying is performed at 80 DEG C for 4 hours to obtain modified starch with a silane grafting rate of 88%.

[0077] The preparation method of the acetylated bamboo-derived nanocellulose is as follows: bamboo fibers (diameter 50-100 μm) are treated with 10% sodium hydroxide solution at 80 DEG C for 2 hours to obtain cellulose after lignin removal; the cellulose is treated by a high-pressure homogenizer (pressure 60 MPa) for 10 times to obtain bamboo-derived nanocellulose (diameter 20-50 nm); the bamboo-derived nanocellulose is dispersed in a mixed solution of acetic anhydride (CAS No. 108-24-7) and pyridine (volume ratio 1:1), and reaction is performed at 50 DEG C for 4 hours, washing is performed until neutral, and freeze-drying is performed to obtain the product with an acetylated substitution degree of 1.0.

[0078] The preparation method of the quaternary ammonium salt modified hydrophilic kaolin is as follows: kaolin (CAS No. 1332-58-7) is calcined at 800 DEG C for 2 hours, and then mixed with deionized water at a mass ratio of 1:10 and ultrasonic dispersion is performed for 30 minutes; 8% of the mass of the kaolin of cetyltrimethylammonium bromide (CAS No. 57-09-0) is added, and stirring is performed at 70 DEG C for 2 hours; after centrifugal separation, washing is performed with deionized water until there is no bromide ion, and drying is performed at 60 DEG C for 6 hours to obtain modified kaolin with a quaternary ammonium salt grafting amount of 5.5 wt%.

[0079] Based on the above degradable plastic bag material, the embodiment simultaneously provides a preparation method of the degradable plastic bag material, and the method comprises the following steps: S11, according to the above proportion, polylactic acid, 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer, silane coupling agent modified starch, acetylated bamboo source nanocellulose, furan end group poly lactic acid copolymer, dodecanedioic acid bismaleimide ester, coffee residue loaded WO3@TiO2, epoxy soybean oil, quaternary ammonium salt modified hydrophilic kaolin, zinc phenylphosphate and polycarbodiimide are mixed, and melt blending is carried out in a double screw extruder, the temperature is 170℃, the rotating speed is 60r / min, the time is 12.5min, and a first blend is obtained; S21, sodium alginate microcapsulated lipase is added to the first blend, and mixing is continued at 80℃ for 4min to obtain a second blend; S31, the second blend is sent into a blow molding machine, blow molding is carried out at 175℃, the blow ratio is 2.5, and a degradable plastic bag material is obtained.

[0080] Example 2 The embodiment provides a degradable plastic bag material, which is composed of the following chemical components in mass parts: polylactic acid (PLA, crystallinity 51%, CAS number 26100-51-6, model number 4032D, NatureWorks): 48 parts; 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer (4-hydroxybutyric acid monomer molar mass 20%, number average molecular weight 80000 g / mol, CAS number 80181-31-3, Tianjin Guoyun Biology): 18 parts; silane coupling agent modified starch (silane grafting rate 85%, silane coupling agent is KH550, starch is corn starch, CAS number 9005-25-8): 8.5 parts; acetylated bamboo-derived nanocellulose (average diameter 20 nm, average aspect ratio 51, acetylation degree of substitution 0.8, nanocellulose CAS number 9004-34-6): 8 parts; furan-terminated polylactic acid copolymer (number average molecular weight 7000 g / mol): 6 parts; dodecanedioic acid bismaleimide ester (CAS number 13676-54-5, Aldrich reagent): 3 parts; coffee grounds loaded WO3@TiO2 (WO3@TiO2 loading 25wt%, TiO2 to WO3 molar ratio 4:1): 2 parts; epoxy soybean oil (CAS number 8013-07-8, model number ESO-80, Jiangsu Kenno Plasticization): 2 parts; sodium alginate microencapsulated lipase (enzyme activity 8000 U / g, microcapsule average particle size 10 μm): 1.5 parts; quaternary ammonium salt modified hydrophilic kaolin (hexadecyltrimethylammonium bromide grafting amount 5wt%, kaolin CAS number 1332-58-7): 1.5 parts; zinc phenylphosphate (CAS number 13845-36-8, Aldrich reagent): 1 part; polycarbodiimide (CAS number 69411-29-0): 0.5 parts.

[0081] The preparation method of the furan-terminated polylactic acid copolymer is as follows: under a nitrogen atmosphere, polylactic acid oligomer (number average molecular weight 4000 g / mol), furan formic acid (CAS number 88-14-2) and tetrabutyl titanate (CAS number 5593-70-4) are copolymerized in a molar ratio of 1:1.2, wherein the amount of tetrabutyl titanate is 0.2% of the mass of the polylactic acid oligomer; the reaction temperature is 120 DEG C, and the reaction time is 4h; after the reaction, the target product is obtained by ethanol precipitation, deionized water washing and vacuum drying.

[0082] The preparation method of the coffee grounds loaded WO3@TiO2 is as follows: under a nitrogen atmosphere, the coffee grounds are carbonized at 280 DEG C for 2 hours to obtain a porous carbonized coffee grounds carrier; the carrier is added into a tetrabutyl titanate-ethanol mixed solution (volume ratio 1:3), ultrasonic dispersion is performed for 30 minutes, dilute nitric acid is added dropwise to adjust the pH to 2, stirring is performed for 2 hours, then aging is performed for 12 hours, drying is performed, and then calcination is performed at 400 DEG C for 2 hours to obtain coffee grounds loaded TiO2; the coffee grounds loaded TiO2 is immersed into a sodium tungstate solution (concentration 0.05 mol / L) and ultrasonic treatment is performed for 20 minutes, centrifugal separation is performed, drying is performed, and then calcination is performed at 350 DEG C for 1 hour to obtain the target product.

[0083] The preparation method of the sodium alginate microencapsulated lipase is as follows: at room temperature, lipase (CAS No. 9001-62-1) and 3% (mass concentration) sodium alginate solution (CAS No. 9005-38-3) are uniformly mixed at a ratio of 1 g:10 mL, sodium alginate is used as a coating matrix, and a microcapsule is spun by an electrostatic spinning device (voltage 15 kV, receiving distance 10 cm, and pushing rate 0.5 mL / h), vacuum drying is performed after collection to obtain a product with a particle size of 10 μm.

[0084] The preparation method of the silane coupling agent modified starch is as follows: at 40 DEG C, corn starch (CAS No. 9005-25-8) and deionized water are mixed at a mass ratio of 1:4, and stirring is performed until complete gelatinization; 2% of the mass of the starch of silane coupling agent KH550 (CAS No. 919-30-2) is added, the pH is adjusted to 4.0, and stirring is performed at 50 DEG C for 2 hours; after the reaction is completed, ethanol precipitation and washing are performed, and vacuum drying is performed at 70 DEG C for 3 hours to obtain modified starch with a silane grafting rate of 85%.

[0085] The preparation method of the acetylated bamboo source nanocellulose is as follows: bamboo fibers (diameter 50-100 μm) are treated with 8% sodium hydroxide solution at 70 DEG C for 1.5 hours to obtain cellulose after lignin removal; the cellulose is treated by a high-pressure homogenizer (pressure 50 MPa) for 8 times to obtain bamboo source nanocellulose (diameter 20 nm); the bamboo source nanocellulose is dispersed in a mixed solution of acetic anhydride (CAS No. 108-24-7) and pyridine (volume ratio 1:2), and reaction is performed at 40 DEG C for 3 hours, washing is performed until neutral, and freeze drying is performed to obtain the product with an acetylated substitution degree of 0.8.

[0086] The preparation method of the quaternary ammonium salt modified hydrophilic kaolin is as follows: kaolin (CAS No. 1332-58-7) is calcined at 700 DEG C for 1.5 hours, and then mixed with deionized water at a mass ratio of 1:8 and ultrasonic dispersion is performed for 20 minutes; 5% of the mass of the kaolin of cetyltrimethylammonium bromide (CAS No. 57-09-0) is added, and stirring is performed at 60 DEG C for 1.5 hours; after centrifugal separation, washing is performed with deionized water until there is no bromide ion, and drying is performed at 50 DEG C for 5 hours to obtain modified kaolin with a quaternary ammonium salt grafting amount of 5 wt%.

[0087] Based on the above degradable plastic bag material, the embodiment simultaneously provides a preparation method of the degradable plastic bag material, which comprises the following steps: S11, according to the above proportion, polylactic acid, 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer, silane coupling agent modified starch, acetylated bamboo source nanocellulose, furan end group poly lactic acid copolymer, dodecanedioic acid bismaleimide ester, coffee residue loaded WO3@TiO2, epoxy soybean oil, quaternary ammonium salt modified hydrophilic kaolin, zinc phenylphosphate and polycarbodiimide are mixed, and melt blending is carried out in a double screw extruder, the temperature is 170℃, the rotating speed is 30r / min, the time is 10min, and a first blend is obtained; S21, sodium alginate microcapsulated lipase is added to the first blend, and mixing is continued at 80℃ for 3min to obtain a second blend; S31, the second blend is sent into a blow molding machine, blow molding is carried out at 165℃, the blow ratio is 2, and a degradable plastic bag material is obtained.

[0088] Example 3 The embodiment provides a degradable plastic bag material, which is composed of the following chemical components in mass parts: polylactic acid (PLA, crystallinity 60%, CAS number 26100-51-6, model number 4032D, NatureWorks): 40 parts; 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer (4-hydroxybutyric acid monomer molar mass 30%, number average molecular weight 120000 g / mol, CAS number 80181-31-3, Tianjin Guoyun Biology): 25 parts; silane coupling agent modified starch (silane grafting rate 90%, silane coupling agent is KH550, starch is corn starch, CAS number 9005-25-8): 5 parts; acetylated bamboo-derived nanocellulose (average diameter 50 nm, average aspect ratio 60, acetylation degree 1.2, nanocellulose CAS number 9004-34-6): 3 parts; furan-terminated polylactic acid copolymer (number average molecular weight 9000 g / mol): 5 parts; dodecanedioic acid bismaleimide ester (CAS number 13676-54-5, Aldrich reagent): 8 parts; coffee grounds loaded WO3@TiO2 (WO3@TiO2 loading 35wt%, TiO2 to WO3 molar ratio 4:1): 6 parts; epoxy soybean oil (CAS number 8013-07-8, model ESO-80, Jiangsu Kenno Plasticization): 1 part; sodium alginate microencapsulated lipase (enzyme activity 9000 U / g, microcapsule average particle size 50 μm): 3 parts; quaternary ammonium salt modified hydrophilic kaolin (hexadecyltrimethylammonium bromide grafting amount 6wt%, kaolin CAS number 1332-58-7): 3 parts; zinc phenylphosphate (CAS number 13845-36-8, Aldrich reagent): 0.1 part; polycarbodiimide (CAS number 69411-29-0): 0.9 parts.

[0089] The preparation method of the furan-terminated polylactic acid copolymer is as follows: under a nitrogen atmosphere, polylactic acid oligomer (number average molecular weight 4000 g / mol), furan formic acid (CAS number 88-14-2) and tetrabutyl titanate (CAS number 5593-70-4) are copolymerized in a molar ratio of 1:1.5, wherein the amount of tetrabutyl titanate is 1.0% of the mass of the polylactic acid oligomer; the reaction temperature is 150 DEG C, and the reaction time is 8h; after the reaction, the target product is obtained by ethanol precipitation, deionized water washing and vacuum drying.

[0090] The preparation method of the coffee grounds-loaded WO3@TiO2 is as follows: carbonizing the coffee grounds at 320°C for 4 hours under a nitrogen atmosphere to obtain a porous carbonized coffee grounds carrier; adding the carrier to a tetrabutyl titanate-ethanol mixture (volume ratio of 1:3), ultrasonically dispersing the carrier for 60 minutes, dropping dilute nitric acid to adjust the pH to 3, stirring the reaction for 4 hours, standing and aging for 24 hours, drying, and calcining at 500°C for 3 hours to obtain coffee grounds-loaded TiO2; immersing the coffee grounds in a sodium tungstate solution (concentration 0.15 mol / L) and ultrasonically treating the solution for 50 minutes, centrifuging, drying, and calcining at 450°C for 2 hours to obtain the target product.

[0091] The preparation method of the sodium alginate microencapsulated lipase comprises: uniformly mixing the lipase (CAS No. 9001-62-1) and a 5% (mass concentration) sodium alginate solution (CAS No. 9005-38-3) at a ratio of 1 g:20 mL at room temperature, using the sodium alginate as a coating matrix, spinning the microcapsules into microcapsules using an electrospinning device (voltage 25 kV, receiving distance 15 cm, propulsion rate 1.5 mL / h), collecting and vacuum drying to obtain a product with a particle size of 50 μm.

[0092] The preparation method of the silane coupling agent modified starch comprises: mixing corn starch (CAS No. 9005-25-8) and deionized water at a mass ratio of 1:6 at 60° C. and stirring until completely gelatinized; adding silane coupling agent KH550 (CAS No. 919-30-2) at a concentration of 4% by mass of the starch, adjusting the pH to 5.0, and stirring at 70° C. for 4 hours; after the reaction, ethanol precipitation and washing are performed, and vacuum drying is performed at 90° C. for 5 hours to obtain a modified starch with a silane grafting rate of 90%.

[0093] The preparation method of the acetylated bamboo-derived nanocellulose comprises the following steps: treating bamboo fibers (diameter 50-100 μm) with a 12% sodium hydroxide solution at 90°C for 2.5 hours to remove lignin and obtain cellulose; treating the fibers with a high-pressure homogenizer (pressure 70 MPa) 12 times to obtain bamboo-derived nanocellulose (diameter 50 nm); dispersing the fibers in a mixture of acetic anhydride (CAS No. 108-24-7) and pyridine (volume ratio 2:1), reacting the mixture at 60°C for 5 hours, washing the mixture until neutral, and freeze-drying the mixture to obtain a product with an acetylation degree of substitution of 1.2.

[0094] The preparation method of the quaternary ammonium salt-modified hydrophilic kaolin comprises the following steps: calcining kaolin (CAS No. 1332-58-7) at 900° C. for 2.5 hours, cooling, mixing with deionized water at a mass ratio of 1:12, and ultrasonically dispersing for 40 minutes; adding hexadecyltrimethylammonium bromide (CAS No. 57-09-0) at a mass ratio of 10% by mass of the kaolin, stirring and reacting at 80° C. for 2.5 hours; centrifuging, washing with deionized water until bromide ions are removed, and drying at 70° C. for 7 hours to obtain modified kaolin with a quaternary ammonium salt grafting amount of 6% by weight.

[0095] Based on the above degradable plastic bag material, the embodiment simultaneously provides a preparation method of the degradable plastic bag material, and the method comprises the following steps: S11, according to the above proportion, polylactic acid, 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer, silane coupling agent modified starch, acetylated bamboo source nanocellulose, furan end group poly lactic acid copolymer, dodecanedioic acid bismaleimide ester, coffee residue loaded WO3@TiO2, epoxy soybean oil, quaternary ammonium salt modified hydrophilic kaolin, zinc phenylphosphate and polycarbodiimide are mixed, and melt blending is carried out in a double screw extruder, the temperature is 180℃, the rotating speed is 50r / min, the time is 15min, and a first blend is obtained; S21, sodium alginate microencapsulated lipase is added to the first blend, and mixing is continued at 100℃ for 5min, to obtain a second blend; S31, the second blend is sent into a blow molding machine, blow molding is carried out at 185℃, the blow ratio is 3, and the degradable plastic bag material is obtained.

[0096] Example 4 Based on the disclosure of example 1, the following modifications are made: The degradable plastic bag material is composed of the following chemical components: polylactic acid: 42 parts; 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer: 15 parts; silane coupling agent modified starch: 15 parts; acetylated bamboo source nanocellulose: 4.5 parts; furan end group poly lactic acid copolymer: 7 parts; dodecanedioic acid bismaleimide ester: 4.5 parts; coffee residue loaded WO3@TiO 2: 3.5 parts; epoxy soybean oil: 3 parts; sodium alginate microencapsulated lipase: 1.2 parts; quaternary ammonium salt modified hydrophilic kaolin: 1.8 parts; zinc phenylphosphate: 0.6 parts; polycarbodiimide: 0.4 parts.

[0097] Example 5 Based on the disclosure of example 1, the following modifications are made: The degradable plastic bag material is composed of the following chemical components: polylactic acid: 42 parts; 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer: 15 parts; silane coupling agent modified starch: 15 parts; acetylated bamboo source nanocellulose: 4.5 parts; furan end group poly lactic acid copolymer: 7 parts; dodecanedioic acid bismaleimide ester: 4.5 parts; coffee residue loaded WO3@TiO 2: 3 parts; epoxy soybean oil: 3 parts; sodium alginate microencapsulated lipase: 1.2 parts; quaternary ammonium salt modified hydrophilic kaolin: 1.8 parts; zinc phenylphosphate: 0.6 parts; polycarbodiimide: 0.4 parts.

[0098] Comparative Example 1 The comparative example is modified as follows based on the disclosure of Example 1: The chemical components of the degradable plastic bag material do not contain 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer.

[0099] Comparative Example 2 The comparative example is modified as follows based on the disclosure of Example 1: The chemical components of the degradable plastic bag material do not contain silane coupling agent modified starch.

[0100] Comparative Example 3 The comparative example is modified as follows based on the disclosure of Example 1: The chemical components of the degradable plastic bag material do not contain acetylated bamboo-derived nanocellulose, furan-terminated poly(lactic acid) copolymer, and dodecanedioic acid bismaleimide ester.

[0101] Comparative Example 4 The comparative example is modified as follows based on the disclosure of Example 1: The chemical components of the degradable plastic bag material do not contain coffee grounds loaded WO3@TiO2.

[0102] Comparative Example 5 The comparative example is modified as follows based on the disclosure of Example 1: The chemical components of the degradable plastic bag material do not contain sodium alginate microencapsulated lipase.

[0103] Comparative Example 6 The comparative example is modified as follows based on the disclosure of Example 1: The chemical components of the degradable plastic bag material do not contain quaternary ammonium salt modified hydrophilic kaolin.

[0104] Comparative Example 7 The comparative example is modified as follows based on the disclosure of Example 1: The chemical components of the degradable plastic bag material do not contain zinc phenylphosphate.

[0105] Comparative Example 8 The comparative example is modified as follows based on the disclosure of Example 1: The chemical components of the degradable plastic bag material do not contain polycarbodiimide.

[0106] Comparative Example 9 The comparative example is modified as follows based on the disclosure of Example 1: The chemical components of the degradable plastic bag material do not contain acetylated bamboo-derived nanocellulose.

[0107] Comparative Example 10 The comparative example is modified as follows based on the disclosure of Example 1: The chemical components of the degradable plastic bag material do not contain furan-terminated polylactic acid copolymer and dodecanedioic acid bismaleimide ester.

[0108] The mechanical properties and degradation properties of the degradable plastic bag materials obtained in Examples 1 to 5 and Comparative Examples 1 to 10 were measured, and the results are shown in Tables 1 and 2. At the same time, the mechanical properties and degradation properties were measured as follows: Mechanical properties test: Tensile strength is tested in accordance with ISO527 standard using a type 5 dumbbell specimen (thickness 0.1mm) at a tensile rate of 50mm / min; elongation at break is tested in accordance with ISO527 standard using a type 5 dumbbell specimen (thickness 0.1mm) with the same gauge length as the tensile strength, and the elongation at break is recorded; notched impact strength is tested in accordance with ISO180 standard using a specimen size of 80×10×0.1mm (V-notch) using an impact testing machine with a pendulum energy of 1J; heat deformation temperature (HDT) is tested in accordance with ISO75 standard using a specimen size of 80×10×0.1mm under a load of 0.45MPa at a heating rate of 120℃ / h; puncture strength is tested in accordance with ASTMD1709 standard using a 100×100×0.1mm film specimen and a 38mm diameter dart.

[0109] Degradation performance test: The 60-day soil degradation rate was tested in accordance with ISO17556. The samples were placed in standard soil at 25°C and 60% humidity, and the degree of degradation was evaluated by weight loss rate and CO2 release. The 30-day seawater degradation rate was tested in accordance with ASTMD6691. The samples were placed in natural seawater at 25°C and cultured under oscillation. The degradation performance was evaluated by disintegration area ratio and molecular weight reduction rate. The light-enzyme synergistic degradation (acceleration) was tested using a customized method under UV / visible light conditions combined with a lipase solution (37°C). The surface erosion depth (μm / 24h) was used as the evaluation index. The UV / visible light intensity was 0.5W / m 2 The concentration of the lipase solution was 5 mg / mL. The molecular weight reduction rate over 60 days was determined according to ISO16014 standard using chloroform as the mobile phase. The changes in number average molecular weight (Mn), weight average molecular weight (Mw) and polydispersity index (PDI) were determined by gel permeation chromatography (GPC) to calculate the reduction rate.

[0110] Table 1 Mechanical properties and degradation properties of the degradable plastic bag materials of Examples 1 to 5 As shown in Table 1, the tensile strength of the degradable plastic bag materials of Examples 1 to 5 is 38.7-58.1 MPa, the elongation at break is 182.7-224.7%, and the notched impact strength is 12.0-18.2 kJ / m 2, the hot deformation temperature was 85.7-98.9℃, the puncture strength was 28.1-42.9N, the soil weight loss rate was 65.2-92.7% in 60 days, the seawater disintegration area ratio was 46.8-81.8% in 30 days, the light-enzyme erosion depth was 12.3-23.5μm / 24h, and the molecular weight reduction rate was 76.7-94.7% in 60 days.

[0111] Table 2 mechanical properties and degradation properties of the degradable plastic bag material of Comparative Example 1-Comparative Example 10 As shown in Table 2, Comparative Example 1 does not contain 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer, and the flexible segment matrix is missing, so the material toughness is insufficient, the tensile strength, elongation at break and impact strength are all lower than the range of the examples, especially the impact strength is significantly reduced, because the rigidity of PLA cannot be balanced by the flexibility of PHA.

[0112] Comparative Example 2 does not contain silane coupling agent modified starch, the interface compatibility of starch and the matrix is reduced, the dispersion is uneven, the mechanical properties are weakened, and the degradation channel is reduced due to the lack of starch, so the soil weight loss rate in 60 days and the seawater disintegration area ratio are reduced.

[0113] Comparative Example 3 does not contain acetylated bamboo-derived nanocellulose, furan-terminated polylactic acid copolymer and dodecanedioic acid bismaleimide ester, and the nanometer reinforcing phase and crosslinking system are missing, so the three-dimensional network structure cannot be formed, the tensile strength and impact strength in the mechanical properties are significantly reduced, and the material is prone to breakage due to insufficient crosslinking.

[0114] Comparative Example 4 does not contain coffee grounds loaded WO3@TiO2, the photocatalytic degradation path is interrupted, the light-enzyme synergistic effect is invalid, the light-enzyme erosion depth is greatly reduced, and the seawater disintegration area ratio in 30 days and the molecular weight reduction rate in 60 days are lower than the range of the examples.

[0115] Comparative Example 5 does not contain sodium alginate microencapsulated lipase, the enzyme catalytic degradation path is missing, the biodegradation rate is slowed down, the soil weight loss rate in 60 days and the seawater disintegration area ratio in 30 days are reduced, and the hydrolysis effect of lipase on polymer chains cannot be exerted.

[0116] Comparative Example 6 does not contain quaternary ammonium salt modified hydrophilic kaolin, the hydrophilicity of the material is reduced, the adhesion and infection ability of microorganisms is weakened, the soil weight loss rate in 60 days is slightly reduced, and the puncture strength is slightly reduced due to the lack of reinforcing effect of kaolin.

[0117] Comparative Example 7 does not contain zinc phenylphosphate, the lack of nucleating agent reduces the crystallinity of PLA, the hot deformation temperature is reduced, the tensile strength and puncture strength in the mechanical properties are slightly weakened, and the structure stability is insufficient due to imperfect crystallization.

[0118] The anti-hydrolysis stability of Comparative Example 8 is reduced, the molecular chain is easily broken during processing, the tensile strength and impact strength are slightly reduced, and the cross-linking auxiliary role of polycarbodiimide is missing, which weakens the overall material integrity.

[0119] In Comparative Example 9, the acetylated bamboo-derived nanocellulose is not contained, the nanoreinforced phase is missing, the mechanical support structure of the material is destroyed, the tensile strength, puncture strength and impact resistance are all significantly reduced, especially the tensile strength is significantly reduced. Because the three-dimensional network structure formed by the nanocellulose at the interface of polylactic acid / PHA is missing, the stress transfer efficiency is reduced, and the "fiber bridging" effect cannot resist external force; at the same time, the slight increase in the light-enzyme erosion depth due to the decrease in the density of the material, but the microbial infection rate is accelerated due to the missing physical barrier effect of nanofiber, and the soil weight loss rate is only slightly reduced.

[0120] In Comparative Example 10, the furan-terminated polylactic acid copolymer and dodecanedioic acid bismaleimide ester are not contained, the dynamic covalent cross-linking network is missing, and the material's toughness and degradation triggering mechanism are both invalid: on the one hand, the Diels-Alder dynamic cross-linking network is missing, leading to a sharp drop in impact strength and a decrease in elongation at break. Because of the lack of reversible cross-linking points between molecular chains at room temperature, the material cannot dissipate impact energy through dynamic networks; on the other hand, the enzyme cutting target of dodecanedioic acid long chain ester bond is missing, and lipase cannot specifically cut the cross-linking point, leading to a collapse of enzymatic efficiency, a decrease in soil weight loss rate, a sharp decrease in molecular weight, and a blockage of the light-enzyme synergistic degradation path.

[0121] The range described herein, such as a numerical range, a ratio range, etc., includes all possible sub-ranges and single values within the range, for example, the range description of "1 to 6" or "1-6" covers all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "include", "contain" and the like used herein mean "including but not limited to"; the relationship terms "first", "second" and the like are only used to distinguish different entities or operations, and do not imply actual sequence or relationship; "and / or" means that multiple cases can exist independently or simultaneously; "at least one", "multiple", "at least one" and the like refer to any combination of the corresponding objects, including single or multiple combinations of objects. The ratio relationship described herein, such as mass ratio, molar ratio, etc., should be understood as the corresponding relationship between the front and the back in the ratio. The raw materials, reagents, instruments and equipment used herein can be purchased or prepared by existing methods.

[0122] The foregoing detailed description of the application has been presented for purposes of illustration and description. Various modifications and changes can be made to these embodiments without departing from the spirit and scope of the application. It is intended that the scope of the application should not be limited by the particular representative embodiments described above.

Claims

1. A degradable plastic bag material, characterized in that: The degradable plastic bag material is composed of the following chemical components, in parts by mass: polylactic acid: 40-50 parts, 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer: 15-25 parts, silane coupling agent modified starch: 5-15 parts, acetylated bamboo-derived nanocellulose: 3-8 parts, furan-terminated polylactic acid copolymer: 5-15 parts, dodecanedioic acid bismaleimide ester: 3-8 parts, coffee grounds-loaded WO3@TiO2: 2-6 parts, epoxidized soybean oil: 1-5 parts, sodium alginate microencapsulated lipase: 1-3 parts, quaternary ammonium salt-modified hydrophilic kaolin: 1-3 parts, phenyl zinc phosphate: 0.1-1 part, and polycarbodiimide: 0.1-0.8 parts. Wherein, the crystallinity of the polylactic acid is greater than 50%; The number average molecular weight of the furan-terminated polylactic acid copolymer is 7000-9000 g / mol.

2. The degradable plastic bag material according to claim 1, characterized in that: The molar amount of the 4-hydroxybutyric acid monomer in the 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer is 20-30%, and the number average molecular weight is 80,000-120,000 g / mol.

3. The degradable plastic bag material according to claim 1, characterized in that: The silane grafting rate of the silane coupling agent modified starch is ≥85%.

4. The degradable plastic bag material according to claim 1, characterized in that: The diameter of the acetylated bamboo-derived nanocellulose is 20-50 nm, the aspect ratio is greater than 50, and the acetylation substitution degree is 0.8-1.

2.

5. The degradable plastic bag material according to claim 1, characterized in that: The preparation method of the furan-terminated polylactic acid copolymer comprises: Under a nitrogen atmosphere, polylactic acid oligomer, furanoic acid and tetrabutyl titanate are copolymerized, and then purified to obtain the furan-terminated polylactic acid copolymer; The molar ratio of the polylactic acid oligomer to the furanic acid is 1:(1.2-1.5), and the mass of the tetrabutyl titanate is 0.2-1.0% of the mass of the polylactic acid oligomer. The temperature of the copolymerization reaction is 120-150° C., and the reaction time is 4-8 hours.

6. The degradable plastic bag material according to claim 1, characterized in that: In the quaternary ammonium salt-modified hydrophilic kaolin, the quaternary ammonium salt is hexadecyltrimethylammonium bromide, and the grafting amount of the quaternary ammonium salt is ≥5wt%.

7. The degradable plastic bag material according to claim 1, characterized in that: The preparation method of coffee grounds loaded WO3@TiO2 comprises: The coffee grounds are carbonized under a nitrogen atmosphere to obtain a porous carbonized coffee grounds carrier; The porous carbonized coffee grounds carrier is added to a tetrabutyl titanate-ethanol mixture, and after ultrasonic dispersion, dilute nitric acid is added dropwise to adjust the pH to 2-3, stirred for reaction, and allowed to stand for aging, followed by drying and a first calcination to obtain coffee grounds-loaded TiO2; The coffee grounds-loaded TiO2 is immersed in a sodium tungstate solution for ultrasonic treatment, centrifuged, dried, and then calcined for a second time to obtain the coffee grounds-loaded WO3@TiO2; The carbonization treatment temperature is 280-320°C and the time is 2-4 hours. The first calcination temperature is 400-500°C and the time is 2-3 hours; The second calcination temperature is 350-450°C and the time is 1-2 hours; In the coffee grounds-loaded WO3@TiO2, the loading amount of WO3@TiO2 is 25-35 wt%, and the molar ratio of TiO2 to WO3 is 4:

1.

8. The degradable plastic bag material according to claim 1, characterized in that: The preparation method of the sodium alginate microencapsulated lipase comprises: At room temperature, lipase with an enzyme activity of ≥8000 U / g is uniformly mixed with a sodium alginate solution, the sodium alginate is used as a coating matrix, and the mixed solution is spun into fibrous microcapsules by an electrospinning device. The spinning product is collected and dried to obtain the sodium alginate microencapsulated lipase; Wherein, the mass volume ratio of the lipase to the sodium alginate solution is 1 g: (10-20) mL, and the mass concentration of the sodium alginate solution is 3%-5%; The electrospinning voltage is 15-25 kV, the receiving distance is 10-15 cm, and the propulsion rate is 0.5-1.5 mL / h; The particle size of the sodium alginate microencapsulated lipase microcapsules is 10 to 50 μm.

9. A method for preparing the degradable plastic bag material according to any one of claims 1 to 8, characterized in that: The method comprises: According to a preset ratio, the polylactic acid, the 3-hydroxybutyric acid-co-4-hydroxybutyric acid copolymer, the silane coupling agent modified starch, the acetylated bamboo-derived nanocellulose, the furan-terminated polylactic acid copolymer, the dodecanedioic acid bismaleimide ester, the coffee grounds-loaded WO3@TiO2, the epoxy soybean oil, the quaternary ammonium salt-modified hydrophilic kaolin, the phenyl zinc phosphate and the polycarbodiimide are mixed, and a first blend is obtained by melt blending. adding sodium alginate microencapsulated lipase to the first blend and continuing to mix uniformly to obtain a second blend; The second blend is blow-molded to obtain the degradable plastic bag material.

10. The method for preparing a degradable plastic bag material according to claim 9, characterized in that: The melt blending temperature is 170-180°C, the rotation speed is 30-50 r / min, and the time is 10-15 min; The mixing temperature after adding the sodium alginate microencapsulated lipase is 80-100°C and the mixing time is 3-5 minutes; The blow molding temperature is 165-185° C., and the blow ratio is 2-3.

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