Low-emission starch-based biodegradable composition and use thereof

Abstract

This invention provides a low-emission starch-based biodegradable composition and its application. By weight, the low-emission starch-based biodegradable composition comprises 40-92 parts of flexible polyester, 2-10 parts of polylactic acid, 5-35 parts of starch, and 1-15 parts of plasticizer; the zero-shear viscosity of the flexible polyester is 1100-10000 Pa·s; in this invention, a flexible polyester with a specific zero-shear viscosity is compounded with polylactic acid, starch, and plasticizer, resulting in a lower content of aldehyde compounds in the products processed from the biodegradable composition.

Description

Technical Field

[0001] This invention belongs to the field of biodegradable polymer materials technology, specifically relating to a low-emission starch-based biodegradable composition and its application. Background Technology

[0002] With the increasing threat of white pollution to the environment, a global wave of plastic bans has begun, and the concepts of global carbon neutrality and carbon peaking have gained widespread acceptance. Bio-based biodegradable materials are developing rapidly, with the film and bag industry being a pioneer. Currently, bio-based biodegradable materials are gradually replacing non-degradable traditional plastics such as PE and PP globally. However, because bio-based monomers inevitably introduce impurities, such as malic acid in bio-based succinic acid and methanol and tetrahydrofuran in bio-based 1,4-butanediol, these impurity acids and alcohols can easily generate aldehydes such as formaldehyde, acetaldehyde, and acrolein during complex melt blending processes. These small molecules are not olfactory and are harmful to the human body.

[0003] Furthermore, to obtain biodegradable materials with superior performance, a composite system of flexible polyester, polylactic acid, and starch is often used. However, this system is more prone to generating aldehydes during processing, such as due to improper starch plasticization leading to increased aldehyde content. This hinders the widespread use of biodegradable materials, particularly in areas like food packaging, such as takeout bags and beverage bags, severely restricting their expansion.

[0004] Therefore, developing a starch-based biodegradable material with low aldehyde content is an urgent problem to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a low-emission starch-based biodegradable composition and its applications. This low-emission starch-based biodegradable composition solves the problem of high aldehyde content in starch-based polyester composite materials in existing technologies.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a low-emission starch-based biodegradable composition, wherein, by weight, the low-emission starch-based biodegradable composition comprises 40-92 parts of flexible polyester, 2-10 parts of polylactic acid, 5-35 parts of starch and 1-15 parts of plasticizer; wherein the zero-shear viscosity of the polyester is 1100-10000 Pa·s.

[0007] In this invention, a flexible polyester with a specific zero-shear viscosity is used, which is beneficial for better plasticization of starch under high shear during blending, thereby reducing the generation and release of aldehyde compounds. If the zero-shear viscosity of the flexible polyester is too low, the plasticization efficiency of starch is low, phase separation is severe, and interface defects can easily lead to the release of aldehyde molecules when heated. If the zero-shear viscosity is too high, over-plasticization occurs, starch molecule chains move, the system viscosity increases, resulting in residual miscellaneous acids and fusel alcohols, which are more likely to generate small aldehyde molecules.

[0008] In this invention, 40 to 92 parts of flexible polyester can be, for example, 42 parts, 45 parts, 48 ​​parts, 50 parts, 52 parts, 55 parts, 58 parts, 60 parts, 62 parts, 64 parts, 66 parts, 68 parts, 70 parts, 72 parts, 74 parts, 76 parts, 78 parts, 80 parts, 82 parts, 84 parts, 86 parts, 88 parts, 90 parts, 92 parts, or any of the above values, and more preferably 51 to 89.5 parts.

[0009] In this invention, the mass percentage of flexible polyester in the low-emission starch-based biodegradable composition is ≥45%, preferably 60~90%.

[0010] In this invention, 2 to 10 parts of polylactic acid can be, for example, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts or any of the above values, preferably 2.1 to 9.6 parts.

[0011] In this invention, 5 to 35 parts of starch can be, for example, 6 parts, 8 parts, 10 parts, 12 parts, 15 parts, 18 parts, 20 parts, 22 parts, 25 parts, 28 parts, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts or any of the above values, preferably 5.5 to 33.5 parts.

[0012] In this invention, 1 to 15 parts of plasticizer can be, for example, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts or any of the above values, and more preferably 1.2 to 14.2 parts.

[0013] In this invention, the zero-shear viscosity of the flexible polyester is 1100~10000 Pa·s, for example, it can be 1120 Pa·s, 1500 Pa·s, 2000 Pa·s, 2500 Pa·s, 3000 Pa·s, 3500 Pa·s, 4000 Pa·s, 4500 Pa·s, 5000 Pa·s, 5500 Pa·s, 6000 Pa·s, 6500 Pa·s, 7000 Pa·s, 7500 Pa·s, 8000 Pa·s, 8500 Pa·s, 9000 Pa·s, 9500 Pa·s, 10000 Pa·s or any of the above values, more preferably 2000~8500 Pa·s, more preferably 3000~7000 Pa·s.

[0014] In this invention, the molecular weight distribution coefficient (PDI) of the flexible polyester is 1.3 to 3.2, for example, it can be 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2 or any of the above values; more preferably 1.4 to 2.9, and particularly preferably 1.55 to 2.65.

[0015] In this invention, when the molecular weight distribution coefficient (PDI) of the flexible polyester is within the aforementioned range, the resulting product exhibits lower aldehyde emission. Flexible polyesters with a PDI within a certain range possess a suitable branched structure, making it easier for their molecular chains to physically entangle with polylactic acid (PLA) and starch molecular chains. When the PDI is too low, the branching degree of the flexible polyester is low, resulting in excessively long main chain lengths for the same molecular weight. This makes it difficult to untangle the formed physical entanglements, easily leading to stress damage to the PLA chains and excessive plasticization of starch, increasing the system viscosity. This makes it easier for residual acids and alcohols in the flexible polyester to generate small aldehyde molecules. When the PDI is too high, there are too many short or medium-length branches for the same molecular weight, resulting in a weak physical entanglement effect under twin-screw shearing. Short or medium-length branches are easily untangled, leading to weak compatibility with PLA, low plasticization efficiency of starch, severe phase separation of the three components, and interface defects that easily cause aldehyde molecules to be emitted when heated.

[0016] Preferably, the flexible polyester comprises an aliphatic-aromatic polyester.

[0017] In this invention, the flexible polyester comprises diacid residues and diol residues; the diacid residues comprise aromatic diacid residues and / or aliphatic diacid residues, preferably aromatic diacid residues comprise terephthalic acid residues and / or furanyl dicarboxylic acid residues; preferably aliphatic diacid residues comprise at least one of adipic acid residues, succinic acid residues, azelaic acid residues, sebacic acid residues, or brassic acid residues; the diol residues preferably comprise propylene glycol residues and / or butanediol residues. The molar percentage of aromatic diacid residues in the diacid residues is 5-90 mol%, preferably 20-70 mol%, more preferably 41-49.5%.

[0018] In this invention, the term "residue" refers to a structural unit introduced into the polyester molecular chain by a related monomer through a polycondensation reaction. Specifically, aromatic diacids and / or their derivatives are introduced into the polyester molecular chain through a polycondensation reaction to form aromatic diacid residues; aliphatic diacids and / or their derivatives are introduced into the molecular chain through a polycondensation reaction to form aliphatic diacid residues; the aromatic diacids include, but are not limited to, terephthalic acid, furanyl dicarboxylic acid, etc.; the aliphatic diacids include, but are not limited to, adipic acid, azelaic acid, sebacic acid, succinic acid, brassic acid, etc.; the derivatives include esters of aromatic diacids or esters of aliphatic diacids, such as diC1-C10 alkyl esters of aromatic diacids, diC1-C10 alkyl esters of aliphatic diacids, etc., wherein diC1-C10 alkyl esters exemplarily include, but are not limited to, dimethyl ester, diethyl ester, di-n-propyl ester, di-n-butyl ester, di-n-hexyl ester, di-n-decyl ester, etc.

[0019] Preferably, the flexible polyester comprises at least one of polybutylene adipate terephthalate (PBAT), polybutylene sebacate terephthalate (PBSeT), or polybutylene terephthalate succinate (PBST).

[0020] In this invention, the flexible polyester is a biodegradable polyester; the monomer raw material used in the flexible polyester is at least one selected from bio-based monomers, such as bio-based succinic acid, bio-based propylene glycol, bio-based butylene glycol, etc.

[0021] In this invention, the preparation method of the flexible polyester is not limited in too much, and any method that can prepare the specific flexible polyester of this invention is acceptable; for example, the flexible polyester can be prepared by the following method.

[0022] The first step involves reacting an aromatic diacid with a diol and a first crosslinking agent at a molar ratio of 1:(1.1~1.3) at 188~194℃ for 1.5~2.5h to obtain the first product; the mass of the first crosslinking agent is 0.06~0.35% of the mass of the aromatic diacid; the first crosslinking agent includes, but is not limited to, glycerol, pentaerythritol, etc.

[0023] The second step involves reacting an aliphatic diacid with a diol and a second crosslinking agent at a molar ratio of 1:(1.1~1.3) at 188~194℃ for 1.5~2.5h to obtain a second product. The mass of the second crosslinking agent is 0.06~0.33% of the mass of the aliphatic diacid. The second crosslinking agent includes, but is not limited to, glycerol, pentaerythritol, etc.

[0024] The third step involves reacting the first and second products in the presence of a catalyst at 238–242 °C and 280–320 Pa for 2.5–16 h to obtain the flexible polyester. The catalyst comprises 0.45–1.58% of the total mass of the dicarboxylic acid. By weight, the catalyst consists of 0.17–0.61 parts tetraisopropyl titanate and 0.0055–0.031 parts zinc isooctanoate.

[0025] By way of example, the flexible polyester of the present invention can also be prepared by the following method.

[0026] The first step involves reacting an aromatic dicarboxylic acid with a molar ratio of 1:(1.1~1.3) with a diol and a first chain extender at 193~197°C for 1.5~2.5 h to obtain the first product. The first chain extender is selected from isocyanate chain extenders, preferably diphenylmethane diisocyanate, and the mass of the first chain extender is 0.0045~0.0055% of the mass of the aromatic dicarboxylic acid.

[0027] In the second step, an aliphatic dicarboxylic acid with a molar ratio of 1:(1.01~1.2) is reacted with a diol and a second chain extender at 193~197℃ for 1.5~2.5h to obtain a second product; the second chain extender is selected from isocyanate chain extenders, preferably hexamethylene diisocyanate, and the mass of the second chain extender is 0.009~0.011% of the mass of the aliphatic dicarboxylic acid.

[0028] The third step involves reacting the first and second products at 238–242 °C and 250–270 Pa for 5.5–6.5 h in the presence of a catalyst and a third crosslinking agent to obtain the flexible polyester. The catalyst comprises 0.98–1.1% of the total mass of the diacids. By weight, the catalyst consists of 0.37–0.43 parts tetraisopropyl titanate and 0.025–0.035 parts zinc isooctanoate. The third crosslinking agent is selected from trimethylolpropane, and its mass comprises 0.13–0.17% of the total mass of the diacids.

[0029] The flexible polyester described in this invention can also be obtained by processing commercially available polyester brands; for example, 99.2 to 99.7 parts by weight of KB100 SF (Zhuhai Kingfa Biotechnology) is mixed with 0.3-0.8 parts by weight of a binary composite chain extender. After uniform mixing, the mixture is melt-blended in a twin-screw extruder to achieve in-situ chain extension. The extrusion temperatures are sequentially 80℃, 120℃, 150℃, 180℃, 180℃, 180℃, 180℃, 180℃, and 190℃, with a speed of 245-255 rpm and an extrusion rate of 245-255 kg / h. The product is then drawn into strands, granulated, and dried to obtain the flexible polyester. The binary composite chain extender uses an isocyanate chain extender and an epoxy chain extender in a mass ratio of (6.5-7.5):(2.5-3.5). The isocyanate chain extender includes, but is not limited to, hexamethylene diisocyanate. The epoxy chain extender includes polymers containing epoxy groups, such as ADR4468 from BASF.

[0030] The preparation method of flexible polyester described in this invention is not limited to the above-mentioned method, and will not be described in detail here.

[0031] In this invention, zero-shear viscosity refers to the viscosity of a fluid when its shear rate approaches zero. It is a crucial fundamental parameter in rheology describing the flow behavior of non-Newtonian fluids and a key parameter for the rheological behavior of reactive resins. The zero-shear viscosity and PDI of flexible polyester can be adjusted by changing process parameters (such as temperature and time), the type and amount of crosslinking agent, the catalyst composition, and the type and content of chain extender.

[0032] Preferably, the polylactic acid includes a copolymer of D-lactic acid and L-lactic acid (PLLA / PDLA copolymer).

[0033] In this invention, the D-type molar content of the polylactic acid is 0.1-15% or the D-type molar content of the polylactic acid is 85-99%.

[0034] In this invention, the moisture content of the polylactic acid is ≤0.05wt%.

[0035] In this invention, the method for testing moisture content includes: drying the sample at 60°C until its weight does not change, and obtaining the moisture content of the sample by measuring the mass change before and after drying.

[0036] Preferably, the starch comprises plant starch and / or plant starch derivatives.

[0037] Preferably, the plant starch includes at least one of corn starch, potato starch, rice starch, tapioca starch, or pea starch.

[0038] Preferably, the plant starch derivative includes at least one of esterified derivatives, etherified derivatives, or oxidized derivatives.

[0039] In this invention, the moisture content of the starch is 8-20 wt%, more preferably 10-15 wt%.

[0040] Preferably, the plasticizer comprises a small molecule organic compound and / or water; the small molecule organic compound contains hydroxyl and / or ester groups in its molecular structure.

[0041] Preferably, the small molecule organic compound includes at least one of glycerol, diglycerol, triglycerol, tetraglycerol, epoxidized soybean oil, citrate, acetylsicitrate, sorbitol, ethylene glycol, or polyethylene glycol, more preferably at least one of glycerol, diglycerol, triglycerol, epoxidized soybean oil, ethylene glycol, or sorbitol.

[0042] In some specific embodiments of the present invention, the plasticizer comprises a small molecule organic compound and water, wherein the mass ratio of the small molecule organic compound to water is (0.4~0.7):1, wherein the specific value of (0.4~0.7) can be, for example, 0.4, 0.42, 0.44, 0.46, 0.48, 0.5, 0.52, 0.54, 0.56, 0.58, 0.6, 0.62, 0.64, 0.66, 0.68, 0.7 or any range between the above values.

[0043] Preferably, the low-emission starch-based biodegradable composition further includes 0.1 to 2 parts by weight of an adjuvant, for example, 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.5, 1.8, 2 parts or any range of the above values.

[0044] Preferably, the additives include at least one of the following: opening agent, lubricant, antioxidant, compatibilizer, nucleating agent, colorant, or stabilizer.

[0045] In this invention, the additives can be selected according to actual needs, as long as they can achieve the corresponding function and do not impair the effect of this invention.

[0046] For example, the opening agent includes, but is not limited to, one or more of talc, montmorillonite, zeolite or barium sulfate, preferably talc and / or montmorillonite; the mass percentage of the opening agent in the biodegradable composition can be 0.1-2%.

[0047] For example, the lubricant can be used to enhance the slip properties (smoothing properties) during the extrusion process and as an additive to prevent the film surfaces from adhering to each other; the lubricant includes, but is not limited to, at least one of erucamide, oleamide, glyceryl monostearate, pentaerythritol stearate, PE wax, ethylene bis-stearamide (EBS) or silicone lubricants; the mass percentage of the lubricant in the biodegradable composition can be 0.1-2%.

[0048] For example, the antioxidant is an additive used to prevent decomposition by ozone or oxygen, to prevent oxidation during storage, and to prevent deterioration of the physical properties of the membrane; the antioxidant includes, but is not limited to, primary antioxidants, such as any one or a combination of at least two of 2,6-di-tert-butyl-p-cresol (BHT), 2,2'-methylene-bis(4-ethyl-6-tert-butylphenol), 2,2'-methylene-bis(4-methyl-6-tert-butylphenol), 2,2'-methylene-bis(4-methyl-6-cyclohexylphenol), 2,2'-methylene-bis(4-methyl-6-nonylphenol), octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 1,1,3-tris(5-tert-butyl-4-hydroxy-2-methylphenyl)butane, and pentaerythritol tetra(3,5-di-tert-butyl-4-hydroxyhydrocinnamate). The composition may contain auxiliary antioxidants, such as tri(nonylphenyl) phosphite and / or dilauryl thiodipropionate; the antioxidant content in the biodegradable composition may be 0.1-2% by mass.

[0049] Exemplarily, the compatibilizer is an additive used to impart compatibility through the multiphase composition of polyester, polylactic acid, and starch. The compatibilizer includes, but is not limited to, at least one of polyvinyl acetate (PVAc), isocyanate, polypropylene carbonate, glycidyl methacrylate, ethylene-vinyl alcohol, polyvinyl alcohol (PVA), ethylene-vinyl acetate, or maleic anhydride; the mass percentage of the compatibilizer in the biodegradable composition can be 0.1% to 2%.

[0050] Exemplarily, the nucleating agent is an additive used to supplement or change the crystalline morphology of the polymer and to increase the crystallization (solidification) rate when the polymer melt is cooled; the nucleating agent includes, but is not limited to, inorganic compounds (such as calcium carbonate, silica, kaolin, talc, barium sulfate), low molecular weight organic compounds (such as myristic acid, palmitic acid, stearic acid, behenic acid, monomethyl terephthalate, isophthalic acid), polymers (such as polyethylene glycol, polypropylene glycol, carboxyl-containing polyethylene, acrylic-styrene copolymer), etc.; the mass percentage of the compatibilizer in the biodegradable composition can be 0.1-2%.

[0051] For example, the stabilizer is an additive used to protect against oxidation and heat and to prevent color changes. The stabilizer includes, but is not limited to, at least one of trimethyl phosphate, triphenyl phosphate, trimethylphosphine, phosphoric acid, and phosphorous acid; the mass percentage of the stabilizer in the biodegradable composition can be 0.1% to 2%.

[0052] In this invention, the colorants include, but are not limited to, anthraquinone pigments, azo pigments, phthalocyanine pigments, carbon black, iron oxide pigments, etc.

[0053] In this invention, the preparation method of the low-emission starch-based biodegradable composition is not excessively limited; it can be prepared by conventional methods, including but not limited to the following methods: Polylactic acid, flexible polyester, starch, plasticizer and optional additives are mixed, melt-extruded and granulated at 150~200°C, cooled and air-dried to obtain the low-emission starch-based biodegradable composition.

[0054] In a second aspect, the present invention provides a biodegradable film or bag, wherein the biodegradable film or bag is prepared using the low-emission starch-based biodegradable composition described in the first aspect.

[0055] Preferably, based on the ISO 12219-2 bag method, the aldehyde emission level of the biodegradable bag is ≤700 µg / m³. 3 More preferably ≤550 µg / m 3 .

[0056] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0057] Compared with the prior art, the beneficial effects of the present invention are as follows: The low-emission starch-based biodegradable composition provided by the present invention is a compound of a flexible polyester with a specific zero-shear viscosity, polylactic acid, starch and plasticizer. The products processed from the low-emission starch-based biodegradable composition have a low content of aldehyde compounds. Detailed Implementation

[0058] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0059] In this invention, the zero-shear viscosity of the flexible polyester was obtained by rotational rheometer (Discovery's HR-2 rheometer). The specific steps include: drying the biodegradable composition granules at 80°C for 10 hours to ensure a moisture content of <500 ppm; then placing an appropriate amount of the biodegradable composition granules into a 100mm×100mm×2mm frame mold, separating the top and bottom with PET film; using a flat vulcanizing apparatus, heating to 150°C within 2 minutes, pressing for 3 minutes, releasing the gas once, pressing for 0.5 minutes, releasing the gas once more, pressing for 2 minutes, and finally cooling on a cooling plate at 30±5°C for 5 minutes; peeling off the PET film to obtain a 100mm×100mm×2mm sheet; cutting the obtained sheet into 10mm×10mm×2mm small sample pieces, placing them in the rotational rheometer, and equilibrating at 150°C for 5 minutes. The test temperature was also set to 150℃, and a strain scanning experiment was performed with a strain of 1.0%. Viscosity was measured at low shear frequencies (0.001~0.1 rad / s) to obtain a complex viscosity-frequency curve (η*-ω). The zero-shear viscosity η0 was then extrapolated from the complex viscosity-frequency curve. The derived equation is as follows: Where ω is the cutoff frequency.

[0060] In this invention, the molecular weight distribution index (PDI) of the flexible polyester was tested using gel permeation chromatography (GPC). GPC was performed using a Waters ACQUITY APC™ instrument at a test temperature of 40°C, using XT45, XT200, and XT459 columns; solvent: tetrahydrofuran; mobile phase flow rate: 0.5 mL / min. Polystyrene standards were used as reference samples to obtain the weight-average molecular weight Mw and number-average molecular weight Mn. PDI = Mw / Mn, and the result was the average of three values.

[0061] All materials used in this invention can be purchased commercially or prepared using conventional methods. Unless otherwise specified, the materials used in this invention are as follows.

[0062] Table 1 Polylactic acid PLA-1: PLA FY804, Anhui Fengyuan Biotechnology Co., Ltd.

[0063] PLA-2: KB600 NF30, Zhuhai Kingfa Biomaterials Co., Ltd.

[0064] Starch 1: Henan Jindan, edible corn starch.

[0065] Starch 2: Potato starch, Beidahuang Group.

[0066] Plasticizers, opening agents, and lubricants are sourced from commercially available products.

[0067] Examples 1-21 and Comparative Examples 1-5 each provide a low-emission starch-based biodegradable composition. The formulations of the low-emission starch-based biodegradable compositions are shown in Tables 2-4, by weight. Unless otherwise specified, all values ​​in Tables 2-4 refer to parts by weight. The preparation method of the low-emission starch-based biodegradable composition includes: mixing flexible polyester, polylactic acid, starch, plasticizer, and optionally an opening agent and lubricant, and extruding at 180°C to obtain the biodegradable composition.

[0068] Table 2 Table 3 Table 4 Performance testing The biodegradable compositions provided in the examples and comparative examples were blown into films with a thickness of 12±1 μm using a blown film machine, and then bagged using a bag-cutting machine. The specific process was as follows: the blown film temperature was 150°C, and the blown film speed was 20 kg / h. The resulting biodegradable films were subjected to the following performance tests.

[0069] Referring to ISO 12219-2-2012 standard, 20 g of film was cut and placed into a 10 L sampling bag. A suitable amount of high-purity nitrogen was introduced and then extracted, repeating this process three times to replace the air in the bag. Subsequently, the bag was accurately filled with 50% high-purity nitrogen, and then placed in an oven, heated to 65±2℃ and maintained for 2 h±10 min. The target odor was then collected using a DNPH tube at a constant flow rate. The collection parameters are shown in Table 5. After adsorption and elution using the DNPH tube, the total emission of the three aldehydes (formaldehyde, acetaldehyde, and acrolein) was measured using high-performance liquid chromatography.

[0070] Table 5 The specific test results are shown in Table 6.

[0071] Table 6 As shown in Table 6, the low-emission starch-based biodegradable composition provided by this invention is a compound of a flexible polyester with a specific zero-shear viscosity, polylactic acid, starch, and plasticizer. The products processed from this biodegradable composition have a low aldehyde content and an emission rate ≤700 µg / m³. 3 .

[0072] As can be seen from Examples 1, 15-20, the PDI of the flexible polyester within a certain range is beneficial to further reduce the emission of aldehyde compounds in the product.

[0073] As can be seen from Examples 1, 7-12 and Comparative Examples 1-5, when the zero-shear viscosity of the flexible polyester is within the specific range of the present invention, the emission of aldehyde compounds in the product is low; when the zero-shear viscosity is too high or too low, the emission of aldehyde compounds will be high.

[0074] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-emission starch-based biodegradable composition, characterized in that, By weight, the low-emission starch-based biodegradable composition comprises 40-92 parts flexible polyester, 2-10 parts polylactic acid, 5-35 parts starch and 1-15 parts plasticizer; The zero-shear viscosity of the flexible polyester is 1100~10000 Pa·s.

2. The low-emission starch-based biodegradable composition according to claim 1, characterized in that, The zero-shear viscosity of the flexible polyester is 2000~8500 Pa•s, more preferably 3000~7000 Pa•s.

3. The low-emission starch-based biodegradable composition according to claim 1, characterized in that, The molecular weight distribution coefficient of the flexible polyester is 1.3~3.2, more preferably 1.4~2.9, and particularly preferably 1.55~2.

65.

4. The low-emission starch-based biodegradable composition according to claim 1, characterized in that, The flexible polyester includes aliphatic-aromatic polyesters; Preferably, the flexible polyester comprises at least one of polybutylene adipate terephthalate, polybutylene sebacate terephthalate, or polybutylene succinate terephthalate.

5. The low-emission starch-based biodegradable composition according to claim 1, characterized in that, The polylactic acid includes a copolymer of D-lactic acid and L-lactic acid.

6. The low-emission starch-based biodegradable composition according to claim 1, characterized in that, The starch includes plant starch and / or plant starch derivatives; Preferably, the plant starch includes at least one of corn starch, potato starch, rice starch, tapioca starch, or pea starch; Preferably, the plant starch derivative includes at least one of esterified derivatives, etherified derivatives, or oxidized derivatives.

7. The low-emission starch-based biodegradable composition according to claim 1, characterized in that, The plasticizer comprises a small molecule organic compound and / or water; the small molecule organic compound contains hydroxyl and / or ester groups in its molecular structure; Preferably, the small molecule organic compound includes at least one of glycerol, diglycerol, triglycerol, tetraglycerol, epoxidized soybean oil, citrate, acetylsicitrate, sorbitol, ethylene glycol, or polyethylene glycol, more preferably at least one of glycerol, diglycerol, triglycerol, epoxidized soybean oil, ethylene glycol, or sorbitol.

8. The low-emission starch-based biodegradable composition according to claim 1, characterized in that, The low-emission starch-based biodegradable composition further includes 0.1 to 2 parts by weight of adjuvants; Preferably, the additives include at least one of the following: opening agent, lubricant, antioxidant, compatibilizer, nucleating agent, colorant, or stabilizer.

9. A biodegradable film or bag, characterized in that, The biodegradable film or bag is prepared using the low-emission starch-based biodegradable composition according to any one of claims 1 to 8.

10. The biodegradable film or bag according to claim 9, characterized in that, Based on the ISO 12219-2 bag method, the aldehyde emission from the biodegradable bag is ≤700 µg / m³. 3 More preferably ≤550 µg / m 3 .

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