An aliphatic polyester, a polyester composition comprising the same, and applications thereof

Abstract

This invention provides an aliphatic polyester, a polyester composition comprising the same, and their applications, belonging to the technical field of biodegradable polyester materials. The aliphatic polyester comprises diacid residues and diol residues: the diacid residues include the following residues: a1), 61.2–69.1 mol% succinic acid residues based on a1) and a2), based on a total molar percentage of 100 mol% of a1) and a2), and a2), 30.9–38.8 mol% sebacic acid residues based on a1) and a2), based on a total molar percentage of 100 mol% of a1); the diol residues are selected from 1,4-butanediol residues in at least an equimolar amount as the diacid residues; the mass percentage of oligomers with a number average molecular weight <650 in the aliphatic polyester is 1.09–3%; and the molecular weight distribution coefficient of the aliphatic polyester is 1.72–2.83. The aliphatic polyester exhibits good high-speed blown film forming performance, retains excellent opening performance after high-speed blown film forming, and also possesses excellent puncture resistance.

Description

Technical Field

[0001] This invention belongs to the field of biodegradable polyester materials technology, specifically relating to an aliphatic polyester, a polyester composition containing the same, and their applications. Background Technology

[0002] With the mass production and widespread use of plastics, the amount of waste plastics is also increasing dramatically. Plastics account for a large proportion of packaging materials. However, packaging materials, especially lightweight packaging materials, cannot be recycled on a large scale, and therefore cannot be processed through physical or chemical recycling methods; they can essentially be considered disposable consumer goods. Currently, commonly used packaging materials are mainly made of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), and polystyrene (PS). However, these materials have short lifespans and long degradation times, making them a major source of "white pollution." Therefore, developing high-performance biodegradable materials is one of the important and indispensable means to solve "white pollution."

[0003] Currently, in the lightweight packaging field, the most widely used biodegradable polyesters include aliphatic-aromatic polyesters such as polybutylene terephthalate (PBAT) and polybutylene sebacic acid (PBSeT). To meet the degradation performance requirements, commercially available polyesters of these types have a terephthalic acid content of less than 48 mol%, as the biodegradability of these polyesters decreases significantly above this threshold. When the terephthalic acid segment content is higher than 51%, the biodegradability percentage is less than 40%. However, excessively low terephthalic acid content results in a slow crystallization rate for these polyesters, hindering rapid cooling during molding. This limits the high-speed production of polyester compositions based on these polyesters during blow molding; typically, the production speed cannot exceed 45 kg / h, otherwise, the resulting packaging film will have poor opening performance, affecting customer use.

[0004] To address the issue of high-speed production of polyester compositions, the industry has opted for aliphatic polyesters with faster crystallization rates, such as polybutylene succinate (PBS) and polybutylene adipate succinate (PBSA), as base resins. While this can effectively increase the processing speed of blown film forming of polyester compositions, the short chain segments of polyesters such as PBS and PBSA result in rigid materials with poor puncture resistance, making it difficult to effectively meet the requirements for packaging films.

[0005] Therefore, it is necessary to develop a flexible, biodegradable polyester that, while meeting the material performance requirements—namely, good puncture and opening properties—can also ensure the high-speed production of polyester compositions based on this polyester resin. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an aliphatic polyester, a polyester composition comprising the aliphatic polyester, and its applications. The aliphatic polyester exhibits excellent high-speed blown film forming performance, retains excellent opening properties after high-speed blown film forming, and also possesses excellent puncture resistance, thus meeting the requirements for high-speed blown film forming of polyester compositions.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides an aliphatic polyester comprising diacid residues and diol residues: the diacid residues comprising the following residues: a1), 61.2-69.1 mol% succinic acid residues based on a total molar percentage of a1) and a2), based on a total molar percentage of a1) and a2), 30.9-38.8 mol% sebacic acid residues; the diol residues are selected from 1,4-butanediol residues in at least an equimolar amount with the diacid residues; the mass percentage of oligomers with a number average molecular weight <650 in the aliphatic polyester is 1.09-3%; the molecular weight distribution coefficient of the aliphatic polyester is 1.72-2.83.

[0009] In this invention, firstly, by replacing the short-chain succinic acid or adipic acid residues in traditional aliphatic polyesters PBS or PBSA with long-chain sebacic acid residues, the flexibility of the aliphatic polyester chain segments can be effectively improved. Further controlling the content of succinic acid and sebacic acid residues within the aforementioned range allows the resulting aliphatic polyester to possess excellent puncture resistance. A high succinic acid residue content results in rapid crystallization and high crystallinity of the aliphatic polyester, leading to good opening performance of the packaging film prepared by blown film blowing of the polyester composition based on this aliphatic polyester. However, the excessively short chain segment structure and excessively high crystallinity result in poor puncture resistance of the aliphatic polyester. A high sebacic acid residue content makes the aliphatic polyester chain segments more flexible and improves toughness, but the crystallinity of the material decreases with increasing sebacic acid content. Under high-speed blown film molding, the film material cannot cool and solidify in time, resulting in poor opening performance of the prepared packaging film. Simultaneously, excessively high sebacic acid content lowers the melting point of the material, weakening its processing performance. By adjusting the molar ratio of succinic acid residues and sebacic acid residues within a specific range, aliphatic polyesters can exhibit excellent puncture resistance while ensuring good tensile and degradation properties without affecting their processing performance.

[0010] Secondly, when aliphatic polyesters or packaging films made from aliphatic polyester-based resins come into contact with acidic or alcoholic foods, oligomers are prone to migrate and precipitate, posing a food contact risk. For food safety considerations, those skilled in the art often try various methods to reduce the oligomer content in aliphatic polyesters, hoping for the lowest possible oligomer content. However, the inventors unexpectedly discovered that oligomers with a number-average molecular weight <650 in aliphatic polyesters act as nucleating agents. When the content of oligomers with a number-average molecular weight <650 in the aliphatic polyester exceeds a certain range, such as the mass percentage q of oligomers with a number-average molecular weight <650 as described in this invention being 1.09~3%, the aliphatic polyester exhibits good crystallinity. When the polyester composition prepared from the aliphatic polyester-based resin is used in high-speed blown film forming, the film material can cool rapidly, resulting in packaging films with good opening performance. Conversely, if the oligomer content is too low, the high-speed blown film forming performance is poor, resulting in a low opening grade after forming.

[0011] Furthermore, both excessively narrow and excessively wide molecular weight distribution coefficients (MFCs) of aliphatic polyesters can affect their puncture and crystallization properties. When the MFC is too wide, the polyester molecular chains are less entangled, making them more mobile and resulting in a faster crystallization rate. This improves the high-speed forming performance of the packaging film and leads to good opening performance after high-speed forming. However, an excessively wide MFC will reduce the puncture resistance of the aliphatic polyester. Conversely, when the MFC is too narrow, the polyester molecular chains are more tightly entangled, resulting in excellent puncture resistance. However, the thermal motion of the molecular chains is hindered, leading to a slower crystallization rate, poorer high-speed forming performance, and poor opening performance after high-speed forming.

[0012] In summary, this invention employs a specific dicarboxylic acid composition and simultaneously controls the content of oligomers with a number average molecular weight <650 in the aliphatic polyester and the molecular weight distribution coefficient of the aliphatic polyester within a specific range, so that the polyester composition prepared based on the aliphatic polyester as the base resin has excellent high-speed blown film forming performance, still has excellent opening performance after high-speed blown film forming, and also has excellent puncture resistance.

[0013] In this invention, the mass percentage of oligomers with a number average molecular weight <650 in the aliphatic polyester is 1.09~3%, for example, it can be 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9% or any range between the above values; preferably 1.6~2.8%, more preferably 2.3~2.7%. For safety reasons, the oligomer content should not be too high.

[0014] In this invention, the molecular weight distribution coefficient of the aliphatic polyester is 1.72 to 2.83, for example, it can be 1.74, 1.76, 1.78, 1.8, 1.82, 1.85, 1.88, 1.9, 1.92, 1.95, 1.98, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8 or any of the above values; more preferably, it is 1.85 to 2.52, and more preferably, it is 1.93 to 2.31.

[0015] In this invention, during the preparation of aliphatic polyester, diacids and diols readily react to generate linear or cyclic oligomers; simultaneously, aliphatic polyesters are prone to thermal decomposition at high temperatures, producing a "biting-back" reaction, which further generates linear or cyclic oligomers.

[0016] In this invention, the oligomers with a number average molecular weight <650 are mainly at least one of linear butyl succinate, cyclic butyl succinate, linear butyl sebacate, and cyclic butyl sebacate, with a degree of polymerization of 1 and 2.

[0017] In this invention, the oligomer content and molecular weight distribution coefficient are affected by a variety of factors, such as the type of monomer, the monomer ratio, the type and amount of branching agent and chain extender, the branching structure, the polymerization process (continuous or batch), the reaction temperature, the reaction time and the reaction pressure, and the post-processing process.

[0018] It should be noted that the term "residue" refers to any organic structure introduced into the polymer molecular chain by the relevant monomer through a polycondensation reaction, that is, an organic structure derived from the relevant monomer; for example, a diacid residue refers to a structure in an aliphatic polyester derived from a diacid monomer.

[0019] In this invention, succinic acid and / or succinic acid derivatives are introduced into the polyester molecular chain through a polymerization reaction to form succinic acid residues; sebacic acid and / or sebacic acid derivatives are introduced into the polyester molecular chain through a polymerization reaction to form sebacic acid residues.

[0020] In this invention, the succinic acid derivative includes alkyl succinic acid esters. Exemplarily, the alkyl succinic acid ester can be at least one of dimethyl succinate, diethyl succinate, di-n-propyl succinate, diisopropyl succinate, di-n-butyl succinate, diisobutyl succinate, di-tert-butyl succinate, di-n-pentyl succinate, diisopentyl succinate, and di-n-hexyl succinate. The alkyl succinic acid ester can be an alkyl ester formed from succinic acid or an alkyl ester formed from succinic anhydride, preferably dimethyl succinate formed from succinic anhydride.

[0021] In this invention, the sebacic acid derivative includes alkyl sebacic acid esters; exemplaryly, the alkyl sebacic acid ester can be at least one of dimethyl sebacic acid ester, diethyl sebacic acid ester, di-n-propyl sebacic acid ester, diisopropyl sebacic acid ester, di-n-butyl sebacic acid ester, diisobutyl sebacic acid ester, di-tert-butyl sebacic acid ester, di-n-pentyl sebacic acid ester, diisopentyl sebacic acid ester, and di-n-hexyl sebacic acid ester; the alkyl sebacic acid ester can be an alkyl ester formed from sebacic acid or an alkyl ester formed from sebacic anhydride.

[0022] Preferably, the dicarboxylic acid residues comprise the following residues: a1), 63.5 to 67.5 mol% succinic acid residues based on a1) and a2), based on a total molar percentage of 100 mol%; a2), 32.5 to 36.5 mol% sebacic acid residues based on a1) and a2), based on a total molar percentage of 100 mol%.

[0023] In this invention, the number average molecular weight (Mn) of the aliphatic polyester is 55,000 to 100,000, for example, it can be 63,000 to 82,000.

[0024] In this invention, the number-average molecular weight can be determined by gel permeation chromatography (GPC), using monodisperse polystyrene as the standard substance.

[0025] In this invention, according to GB / T 32366-2015, the carboxyl content of the aliphatic polyester is <30 mol / t, preferably <20 mol / t, and more preferably 5~15 mol / t.

[0026] In this invention, the aliphatic polyester has a high carboxyl content, resulting in poor hydrolysis resistance and aging resistance; a low carboxyl content results in a low biodegradation rate and high cost. The fewer carboxylic acid termini from unreacted dicarboxylic acid components, the lower the carboxyl content of the aliphatic polyester. Therefore, the carboxyl content can be controlled by adjusting the reaction degree or inhibiting thermal decomposition by changing conditions such as the alkyd-acid ratio, polymerization temperature, and polymerization time. Alternatively, the carboxyl content can also be controlled by inhibiting the types or amounts of impurities in raw materials such as nitrogen compounds and metal ions.

[0027] Preferably, the aliphatic polyester further comprises branching agent residues.

[0028] Preferably, the branching agent residues are derived from branching agents with a functionality ≥3.

[0029] Preferably, based on 100 wt% of the total mass of the aliphatic polyester, the mass percentage of the branching agent residues is 0.20~0.55 wt%, for example, it can be 0.22 wt%, 0.24 wt%, 0.26 wt%, 0.28 wt%, 0.3 wt%, 0.31 wt%, 0.32 wt%, 0.33 wt%, 0.34 wt%, 0.35 wt%, 0.36 wt%, 0.37 wt%, 0.38 wt%, 0.39 wt%, 0.4 wt%, 0.41 wt%, 0.42 wt%, 0.43 wt%, 0.44 wt%, 0.46 wt%, 0.48 wt%, 0.5 wt%, 0.52 wt%, 0.54 wt%, or any range of the above values; more preferably, it is 0.30~0.45 wt%.

[0030] In this invention, the addition of a multifunctional branching agent transforms the structure of aliphatic polyester from linear polyester to branched polyester. By controlling the content of the branching agent, the structure of aliphatic polyester can be further controlled, thereby obtaining aliphatic polyester with better puncture resistance and crystallization properties.

[0031] In this invention, the branching agent contains at least one of a hydroxyl group, a carboxyl group, or an anhydride in its molecular structure.

[0032] Preferably, the branching agent includes at least one of polyol, polyacid, polyol acid, or polyacid anhydride, and more preferably a polyol.

[0033] Preferably, the polyol includes at least one of trimethylolpropane, trimethylolethane, pentaerythritol, polyether triol, or glycerol.

[0034] Preferably, the polyacid includes at least one of 1,3,5-benzotriic acid, 1,2,4-benzotriic acid, or 1,2,4,5-benzotetraic acid.

[0035] Preferably, the polyol acid includes at least one of tartaric acid, citric acid, or malic acid.

[0036] In this invention, the polyol acid refers to a molecular structure containing at least one hydroxyl group and at least one carboxyl group.

[0037] Preferably, the polybasic acid anhydride includes 1,2,4-benzotriacid anhydride and / or benzotriacid dianhydride.

[0038] In this invention, the preparation method of the aliphatic polyester is not particularly limited, and any method capable of preparing the aliphatic polyester with the specific structure of this invention is acceptable; preferably, the preparation method of the aliphatic polyester includes the following steps:

[0039] (1-1) Succinic acid and / or succinic acid derivatives, 1,4-butanediol and optional branching agents are mixed, and an alkaline compound is added to adjust the pH of the system to 4.0-6.0. The mixture is reacted for 1.9-4.1 h at a temperature of 164-181 °C and a pressure of 0.79-1.11 bar to obtain esterified product A1 with a viscosity of 9.9-17.1 ml / g as determined by GB / T 17931-1999 in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05 °C.

[0040] (1-2) Sebacic acid and / or its derivatives were mixed with 1,4-butanediol, and an alkaline compound was added to adjust the pH of the system to 5.5-6.5. The mixture was reacted at a temperature of 189-201℃ and a pressure of 0.79-1.11 bar for 2.9-4.1 h to obtain esterified product B1 with a viscosity of 9.9-15.1 ml / g as determined by GB / T 17931-1999 in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05℃.

[0041] (2) Esterification product A1 and esterification product B1 are mixed and prepolymerized at a temperature of 234~244℃ and a pressure of 0.51~0.71 bar for 79~101 min to obtain a prepolymer with a viscosity of 39~61 ml / g as determined by GB / T 17931-1999 in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05℃.

[0042] (3) The prepolymer obtained in step (2) is subjected to polycondensation reaction at a temperature of 239~247℃ and a pressure of 0.99~1.21 mbar for 87~111 min to obtain an aliphatic polyester with a viscosity of 160 ml / g or more, as determined by GB / T 17931-1999 in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05℃.

[0043] In this invention, the aliphatic polyester can also be prepared by the following method, the method comprising:

[0044] (S1-1) Succinic acid and / or succinic acid derivatives, 1,4-butanediol and optional branching agents are mixed, and an alkaline compound is added to adjust the pH of the system to 4.0-6.0. The mixture is reacted at a temperature of 155-165℃ and a pressure of 1-1.2 bar for 3-5 h to obtain esterified product A2 with a viscosity of 8-12 ml / g as determined in a phenol / o-dichlorobenzene solution at a weight ratio of 1:1 in a constant temperature water bath at 25±0.05℃, according to GB / T 17931-1999.

[0045] (S1-2) Sebacic acid and / or its derivatives are mixed with 1,4-butanediol, and an alkaline compound is added to adjust the pH of the system to 5.5-6.5. The mixture is reacted at 185-195℃ and 0.7-0.9 bar for 2.5-3.5 h to obtain esterified product B2 with a viscosity of 8-13 ml / g as determined by GB / T 17931-1999 in a phenol / o-dichlorobenzene solution at a weight ratio of 1:1 in a constant temperature water bath at 25±0.05℃.

[0046] (S2) Mix esterification product A2 and esterification product B2, and prepolymerize for 65-75 min at a temperature of 232-238℃ and a pressure of 0.5-0.7 bar to obtain a prepolymer with a viscosity of 32-42 ml / g as determined by GB / T 17931-1999 in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05℃.

[0047] (S3) The prepolymer obtained in step (2) is subjected to polycondensation reaction at a temperature of 235~245℃ and a pressure of 1.05~1.25 mbar for 80~90 min to obtain a polycondensation product with a viscosity of 155~165 ml / g as determined by GB / T 17931-1999 in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05℃.

[0048] (S4) The polycondensation product is mixed with a chain extender and the chain extension reaction is carried out at 205~215℃ for 5~9 min to obtain an aliphatic polyester with a viscosity of 160 ml / g or more as determined by GB / T 17931-1999 in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05℃.

[0049] In this invention, the aliphatic polyester can also be prepared by the following method, the method comprising:

[0050] (I) Succinic acid and / or succinic acid derivatives, sebacic acid and / or sebacic acid derivatives, 1,4-butanediol and optional branching agents are mixed, and an alkaline compound is added to adjust the pH of the system to 4.0~6.5. The mixture is reacted at a temperature of 195~205℃ and a pressure of 1~1.2 bar for 3.5~4.5 h to obtain an esterified product with a viscosity of 18~22 ml / g as determined in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 according to GB / T 17931-1999 in a constant temperature water bath at 25±0.05℃.

[0051] (II) The esterified product is prepolymerized at a temperature of 234~242℃ and a pressure of 0.5~0.7 bar for 85~95 min to obtain a prepolymer with a viscosity of 45~55 ml / g as determined by GB / T 17931-1999 in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05℃.

[0052] (III) The prepolymer product is subjected to polycondensation reaction at a temperature of 239~244℃ and a pressure of 1~1.2mbar for 95~105 min to obtain an aliphatic polyester with a viscosity of 160 ml / g or more, as determined by GB / T 17931-1999 in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05℃.

[0053] In this invention, the source of succinic acid and / or succinic acid derivatives in the aforementioned preparation method is not particularly limited. They can be derived from bio-based succinic acid and / or succinic acid derivatives (i.e., the raw material for preparation is biomass resources) or from petroleum-based succinic acid and / or succinic acid derivatives (i.e., the raw material for preparation is petroleum resources).

[0054] In this invention, in the aforementioned preparation method, the molar ratio of the diol to the diacid is independently (1.2~3):1, for example, it can be 1.2:1, 1.5:1, 1.8:1, 2:1, 2.2:1, 2.5:1, 2.8:1, 3:1 or any range of the above values, more preferably (1.4~2):1; that is, in steps (1-1) and (S1-1), the molar ratio of 1,4-butanediol to succinic acid and / or succinic acid derivatives is independently (1.2~3):1; in steps (1-2) and (S1-2), the molar ratio of 1,4-butanediol to sebacic acid and / or sebacic acid derivatives is independently (1.2~3):1; in step (I), the ratio of the total molar content of butanediol to succinic acid and / or succinic acid derivatives, sebacic acid and / or sebacic acid derivatives is (1.2~3):1.

[0055] In this invention, steps (1-1), (1-2), (S1-1), (S1-2), and (I) can each be carried out independently in a mixing device, where a diacid and a diol are mixed to obtain a slurry, and then the mixture is heated to carry out the reaction.

[0056] In this invention, after the reactions described in steps (1-1), (1-2), (S1-1), (S1-2), and (I), each step independently includes removing excess diol by distillation. The removed diol can be purified by distillation and reused as a raw material. The purity of the purified diol is ≥95%.

[0057] In this invention, in steps (1-1), (1-2), (S1-1), (S1-2), and (I), the alkaline compound includes carbonates and / or hydroxides.

[0058] Optionally, the carbonate includes at least one selected from sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate. Preferably, the carbonate is sodium carbonate.

[0059] Optionally, the hydroxide includes sodium hydroxide and / or potassium hydroxide. Preferably, the hydroxide is sodium hydroxide.

[0060] In this invention, in the aforementioned preparation methods, the prepolymerization reactions can all be carried out in a single prepolymerization reactor.

[0061] In this invention, the polycondensation reaction in the aforementioned preparation method can be carried out in a finishing machine suitable for polycondensation reactions, such as a rotary reactor, a cage reactor, or a horizontal reactor.

[0062] In this invention, the prepolymerization reaction in the aforementioned preparation method is carried out in the presence of a catalyst; the catalyst can be a tin compound, antimony compound, cobalt compound, lead compound, zinc compound, aluminum compound, or titanium compound, more preferably a zinc compound, aluminum compound, or titanium compound, and most preferably a titanium compound; the titanium compound can be tetrabutyl titanate or tetraisopropyl titanate; the titanium compound has lower residual levels and lower toxicity in the product or downstream products compared to other compounds. It is particularly suitable for preparing biodegradable polyesters that can be directly introduced into the environment in the form of compost bags or covering films.

[0063] In this invention, the total mass of the catalyst is 0.001 to 1 wt%, based on a total mass of 100 wt% of the reactants (diacid, diol and optional branching agent).

[0064] In this invention, other additives may be added during the polycondensation reaction according to actual needs in the aforementioned preparation method; the other additives include, but are not limited to, catalyst deactivators, color stabilizers, activators, etc.

[0065] The catalyst passivator includes, but is not limited to, phosphorus compounds; the phosphorus compounds include, but are not limited to, one or more of phosphorous acid and phosphoric acid; based on 100 wt% of the prepolymer product, the mass of the catalyst passivator is 0.001~0.1 wt%, preferably 0.01~0.05 wt%. For example, when a highly active titanium compound is selected as the catalyst, a catalyst passivator can be added, wherein the molar ratio of Ti to P is (1.1~1.5):1, and particularly preferably the molar ratio of Ti to P is (1.1~1.3):1.

[0066] The color stabilizer includes, but is not limited to, phosphorus compounds; the phosphorus compounds include, but are not limited to, one or more of phosphoric acid, phosphorous acid, triphenyl phosphite, triphenyl phosphate, sodium hypophosphite, and sodium phosphite; the use of color stabilizers generally leads to a decrease in the condensation rate. Therefore, triphenyl phosphate, which has no adverse effect on the condensation rate, is preferred as a color stabilizer. The color stabilizer is 0.001 to 1.5 wt%, preferably 0.01 to 1.0 wt%, based on 100 wt% of the prepolymer; when the catalyst is selected from titanium compounds, the molar ratio of Ti to P is 1:(0.3 to 1.0), particularly preferably 1:(0.5 to 1.0).

[0067] The activator includes, but is not limited to, phosphorus compounds; the phosphorus compounds include, but are not limited to, one or more of disodium hydrogen phosphate, calcium hypophosphite, calcium phosphite, calcium phosphate, sodium hypophosphite, sodium phosphite, triphenyl phosphite, triphenyl phosphate, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, and tributyl phosphate. Based on 100 wt% of the prepolymer product, the activator comprises 0.001~1.5 wt%, preferably 0.01~1.0 wt%; when the catalyst is selected from titanium compounds, the molar ratio of Ti to P is (1.0~1.5):1, particularly preferably (1.1~1.3):1.

[0068] More preferably, a combination of color stabilizers and activators is used, for example, a combination of triphenyl phosphate and disodium hydrogen phosphate.

[0069] In this invention, the chain extender includes one or more of isocyanates, peroxides, epoxides, oxazolines, oxazines, caprolactam, or carbodiimides.

[0070] In this invention, the isocyanate can be an aromatic diisocyanate and / or an aliphatic diisocyanate. The aromatic diisocyanate can be toluene 2,4-diisocyanate, toluene 2,6-diisocyanate, diphenylmethane 2,2′-diisocyanate, diphenylmethane 2,4′-diisocyanate, diphenylmethane 4,4′-diisocyanate, naphthalene 1,5-diisocyanate, or xylene diisocyanate; particularly preferred are diphenylmethane 2,2′-diisocyanate, diphenylmethane 2,4′-diisocyanate, or diphenylmethane 4,4′-diisocyanate. The aromatic diisocyanate can also be a polynuclear aromatic diisocyanate, such as tris(4-isocyanate-phenyl)methane with three rings, which can be formed during the production of diisocyanates with one or two rings. The aliphatic diisocyanate may be a straight-chain or branched alkylene diisocyanate containing 2 to 20 carbon atoms or a cycloalkylene diisocyanate containing 3 to 20 carbon atoms; exemplary, the aliphatic diisocyanate includes hexamethylene diisocyanate, pentamethylene diisocyanate, isophorone diisocyanate, or methylene di(4-isocyanate cyclohexane) diisocyanate. Hexamethylene diisocyanate is particularly preferred.

[0071] In this invention, based on the total mass of the polycondensation product, the mass of the isocyanate can be 0.05~2 wt%, particularly preferably 0.1~1.5 wt%.

[0072] In this invention, the peroxide may be one or more of the following: benzoyl peroxide, 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(tert-butylperoxy)methylcyclododecane, n-butyl 4,4-di(butylperoxy)valerate, dicumyl peroxide, tert-butyl peroxybenzoate, dibutyl peroxide, α,α-di(tert-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hex-3-yne, or tert-butylperoxycumene.

[0073] In this invention, based on the total mass of the polycondensation product, the mass of the peroxide can be 0.1 to 2 wt%, particularly preferably 0.2 to 1 wt%.

[0074] In this invention, the epoxide may be one or more of the following: diglycidyl ether, hexamethylene diglycidyl ether, sorbitol diglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and polybutylene glycol diglycidyl ether, or copolymers containing epoxy groups based on styrene, acrylates, and / or methacrylates.

[0075] In this invention, based on the total mass of the polycondensation product, the mass of the epoxide can be 0.1~2 wt%, preferably 0.2~1 wt%.

[0076] In this invention, the oxazoline may be selected from one or more of 2,2′-bis(2-oxazoline), bis(2-oxazolinyl)methane, 1,2-bis(2-oxazolinyl)ethane, 1,3-bis(2-oxazolinyl)propane, 1,4-bis(2-oxazolinyl)butane, 1,4-bis(2-oxazolinyl)benzene, 1,2-bis(2-oxazolinyl)benzene, or 1,3-bis(2-oxazolinyl)benzene. The oxazine may be selected from one or more of 2,2′-bis(2-dioxazine), bis(2-dioxazinyl)methane, 1,2-bis(2-dioxazinyl)ethane, 1,3-bis(2-dioxazinyl)propane, 1,4-bis(2-dioxazinyl)butane, 1,4-bis(2-dioxazinyl)benzene, 1,2-bis(2-dioxazinyl)benzene, or 1,3-bis(2-dioxazinyl)benzene. The carbodiimide may be selected from one or more of N,N′-di-2,6-diisopropylphenylcarbodiimide, N,N′-di-o-tolylcarbodiimide, N,N′-diphenylcarbodiimide, N,N′-dioctyldecylcarbodiimide, N,N′-di-2,6-dimethylphenylcarbodiimide, N-tolyl-N′-cyclohexylcarbodiimide, N,N′-di-2,6-di-tert-butylphenylcarbodiimide, N,N′-di-2,4,6-triisobutylphenylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, tert-butylisopropylcarbodiimide, di-β-naphthylcarbodiimide, or di-tert-butylcarbodiimide.

[0077] In this invention, based on the total mass of the polycondensation product, the mass of each of the oxazoline, oxazine, caprolactam and carbodiimide is independently 0.1 to 2 wt%, preferably 0.2 to 1 wt%.

[0078] In this invention, the chain growth reaction is carried out under ultra-high atmospheric pressure or atmospheric pressure, depending on the system used.

[0079] In this invention, the chain growth reaction can be carried out in an extruder, a continuous kneader (List reactor), or a static mixer. The extruder can be a single-screw extruder or a twin-screw extruder; the static mixer can use SMR, SMX, or SMXL components, or combinations thereof. Examples of List reactors are single-screw DISCOTHERM B, twin-screw CRP, or ORP reactors, with the chain growth reaction preferably carried out in an extruder.

[0080] In this invention, the aliphatic polyester is not limited to the preparation method described above. Based on considerations of industrialization and cost, the preparation method described above is preferred. However, it can also be obtained by other methods, such as by mixing polyesters with different oligomer contents and molecular weight distribution coefficients, followed by melting, extrusion, and granulation.

[0081] In a second aspect, the present invention provides a polyester composition comprising a polymer A and a component B; wherein the polymer A comprises the aliphatic polyester described in the first aspect.

[0082] Preferably, polymer A further includes a second polyester.

[0083] Preferably, the second polyester comprises at least one of polylactic acid (PLA), aliphatic-aromatic polyester, or other aliphatic polyesters.

[0084] Preferably, the aliphatic-aromatic polyester comprises at least one of polybutylene terephthalate (PBST), polybutylene adipate terephthalate (PBAT), polybutylene sebacate terephthalate (PBSeT), or polybutylene adipate furanate (PBAF).

[0085] Preferably, the other aliphatic polyesters include at least one of polybutylene succinate (PBS), polybutylene adipate succinate (PBSA), or polybutylene sebacate (PBSe).

[0086] In this invention, the second polyester can be selected from appropriate polyesters according to actual needs, and is not limited to the polyesters mentioned above.

[0087] Preferably, component B comprises at least one selected from starch compounds, cellulose compounds, chitin compounds, chitosan compounds, alginate compounds, protein compounds, gelatin compounds, natural rubber compounds, and lignin compounds. In this invention, the term "compound class," such as starch compounds, indicates that component B can be starch or a starch derivative.

[0088] In this invention, the protein compounds include, but are not limited to, gluten, zein, casein, and collagen; the lignin compounds include unpurified lignin, purified and hydrolyzed lignin, and alkalized lignin. Starch compounds can also be used in allosteric and gelling forms or as fillers. The starch compounds can represent a continuous phase or a dispersed phase, or they can be in a co-continuous form.

[0089] Preferably, the polyester composition further includes auxiliaries.

[0090] In this invention, the additives can be added as needed, including but not limited to at least one of antioxidants, lubricants, light stabilizers, release agents, or antistatic agents.

[0091] In this invention, the types of additives are not limited too much; conventional additives can be used. For example, the antioxidants include, but are not limited to, any one of antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant 164, antioxidant DLTP, or antioxidant TPP.

[0092] The light stabilizers include, but are not limited to, at least one of hindered amine light stabilizers (such as light stabilizer 770, light stabilizer 622, light stabilizer 944, etc.), benzophenone light stabilizers (such as UV531), or benzotriazole light stabilizers.

[0093] The lubricant includes, but is not limited to, at least one of esters (such as polyethylene glycol esters, polyol esters), lignite salts, ethylene bis-stearamide, or polyethylene wax.

[0094] The release agent includes, but is not limited to, at least one of the following: inorganic release agents (such as talc, mica powder, clay, etc.), organic release agents (such as fatty acids, paraffin wax, glycerin, petrolatum, etc.), or polymeric release agents (such as silicone oil, polyethylene glycol, low molecular weight polyethylene, etc.).

[0095] The antistatic agent includes, but is not limited to, at least one of the following: cationic antistatic agents (such as quaternary ammonium salts), anionic antistatic agents (such as alkyl sulfonates and phosphates), amphoteric antistatic agents (such as amphoteric imidazoline compounds), nonionic antistatic agents (such as hydroxyethylalkylamines, fatty amides, polyoxyethylene compounds, and polyol esters), or polymeric antistatic agents (such as polyethers).

[0096] As a preferred embodiment of the present invention, the polyester composition comprises, by weight, 50-95 parts of a first aliphatic polyester (e.g., 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 parts or any range thereof), and 1-20 parts of a second polyester (e.g., 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 parts or any of the above). (Any range of values), 1 to 30 parts of component B (e.g., 1 part, 2 parts, 4 parts, 6 parts, 8 parts, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 25 parts, 26 parts, 28 parts, 30 parts or any range of the above values) and 0 to 15 parts of adjuvant (e.g., 1 part, 2 parts, 4 parts, 6 parts, 8 parts, 10 parts, 12 parts, 14 parts, 15 parts or any range of the above values).

[0097] In this invention, the method for preparing the polyester composition includes: mixing polymer A with component B and optional additives, and extruding to obtain the polyester composition; the extruder includes a reactive extruder, which may be a single-screw extruder, a twin-screw extruder, or a multi-screw extruder; the extrusion temperature is 140~220℃, and the screw speed during extrusion is 200~500 rpm.

[0098] Thirdly, the present invention provides a packaging film, said packaging film being formed from an aliphatic polyester as described in the first aspect or a polyester composition as described in the second aspect.

[0099] In this invention, the packaging film is made by blown film processing using an aliphatic polyester as described in the first aspect or a polyester composition as described in the second aspect.

[0100] In this invention, other substances may be added to the packaging film as needed, such as colorants, pigments, inorganic fillers, etc.; the pigments include, but are not limited to, titanium dioxide, etc.; the inorganic fillers include, but are not limited to, talc, calcium carbonate, kaolin, etc.

[0101] Preferably, under the condition of a blown film speed of 60±2 kg / h, the opening performance grade of the packaging film is ≥2.5.

[0102] In this invention, the packaging film includes food packaging film, industrial packaging film, agricultural mulch film, shopping bags, garbage bags, etc.

[0103] The aliphatic polyester, the polyester composition comprising the aliphatic polyester, and the packaging film prepared therefrom are all biodegradable.

[0104] For the purposes of this invention, a substance or mixture of substances is considered "biodegradable" if it exhibits a biodegradability of at least 90%, as defined in DIN EN 13432.

[0105] According to DIN EN 13432, during composting, CO2-free air is introduced into the maturing compost, and the compost is subjected to a specific temperature process. Here, biodegradability is defined as the percentage degree of biodegradation expressed as the ratio of the net amount of CO2 released by the sample (minus the amount of CO2 released by compost without the sample) to the maximum amount of CO2 that the sample can release (calculated from the carbon content in the sample). After only a few days of composting, biodegradable polyesters and biodegradable polyester compositions typically show obvious signs of degradation, such as fungal growth, lysis, and perforation.

[0106] Other methods for determining biodegradability are also described in ASTM D5338 and ASTM D6400.

[0107] 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.

[0108] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0109] The aliphatic polyester provided by this invention employs a specific dicarboxylic acid composition, while controlling the content of oligomers with a number average molecular weight <650 and the molecular weight distribution coefficient of the aliphatic polyester within a specific range. This results in polyester compositions prepared based on the aliphatic polyester as the base resin exhibiting excellent high-speed blown film molding performance, excellent opening performance after high-speed blown film molding, and excellent puncture resistance, thus meeting the requirements of high-speed molding. Detailed Implementation

[0110] 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.

[0111] In this invention, all materials used can be purchased commercially or prepared using conventional methods. Unless otherwise specified, the materials used in this invention are as follows.

[0112] 1,4-Butanediol: Purchased from Xinjiang Meike Chemical Co., Ltd.

[0113] Succinic acid: purchased from Shandong Landian Biotechnology Co., Ltd.

[0114] Sebacic acid: Purchased from Hengshui Jinghua Chemical Co., Ltd.

[0115] Glycerin: Purchased from Aladdin.

[0116] Tetrabutyl titanate: Purchased from Jianyi Chemical Import & Export Co., Ltd.

[0117] Hexamethylene diisocyanate: purchased from Aladdin.

[0118] Starch: Purchased from Shandong Shouguang Juneng Golden Corn Development Co., Ltd.

[0119] Polylactic acid (PLA), KB600 NF30, sourced from Zhuhai Kingfa Biomaterials Co., Ltd.

[0120] In this invention, the test methods for the molecular weight distribution coefficient (PDI), molar content of succinic acid residues and sebacic acid residues, mass percentage content of branching agent, and mass percentage content (q) of oligomers with number average molecular weight < 650 of the aliphatic polyester are as follows.

[0121] 1. PDI was tested using gel permeation chromatography (GPC): The chromatographic system was set at 40°C using a set of three tandem columns (particle diameter of 5 μm and porosities of 500 Å, 1000 Å, and 10000 Å, respectively) and a refractive index detector, with chloroform as the eluent (elution flow rate of 1 mL / min) and polystyrene as the reference standard. The instrument model was Waters 1515GPC. The sample preparation method was as follows: aliphatic polyester was directly dissolved in chromatographic grade THF to prepare a 1 mg / mL solution for testing. Specifically, PDI was calculated based on the weight-average molecular weight Mw / number-average molecular weight Mn obtained from the test.

[0122] 2. The molar content of succinic acid residues and sebacic acid residues can be determined by... 1 The test was performed using the HNMR method; specifically, 20 mg of the aliphatic polyester sample was dissolved in 0.6 mL of deuterated chloroform, and then its concentration was determined at room temperature using a Bruker AV 500 nuclear magnetic resonance spectrometer. 1¹H NMR was used to integrate the characteristic peaks of succinic acid residues and sebacic acid residues (the characteristic chemical shift of succinic acid residues is approximately 2.63 ppm, representing the four hydrogens on the two methylene groups -CH₂-CH₂- in succinic acid; the characteristic chemical shift of sebacic acid residues is approximately 1.30 ppm, representing the eight hydrogens on the four methylene groups -CH₂-CH₂-CH₂- in sebacic acid). The molar content of succinic acid residues and sebacic acid residues in aliphatic polyesters was obtained by the percentage of peak areas. It should be noted that the contents of succinic acid residues and sebacic acid residues in aliphatic polyesters in Table 1 are based on the total molar amount of succinic acid residues and sebacic acid residues as 100 mol%. For example, if the integrated area of ​​succinic acid residues is I₁ and the integrated area of ​​sebacic acid residues is I₂, then the molar percentage content of succinic acid residues in aliphatic polyesters is I₁ / (I₁+I₂)×100%.

[0123] 3. The mass percentage of the branching agent was tested by liquid chromatography-mass spectrometry (LC-MS). Specifically, 0.5-1.5 g of sample was added to a three-necked flask, and 30 ml of 1 mol / L potassium hydroxide ethanol solution was added. Alkali hydrolysis was carried out under reflux until the aliphatic polyester was completely hydrolyzed. After cooling, the sample was vacuum filtered. The filtrate was adjusted to neutral with concentrated hydrochloric acid, dried with anhydrous sodium sulfate, and then filtered again. The filtrate was subjected to qualitative and quantitative analysis of the branching agent residues by LC-MS.

[0124] 4. The mass percentage of oligomers with a number-average molecular weight < 650 was tested using the following method: Aliphatic polyester was prepared into sheets with a thickness of 25±2μm and a diameter of 10cm×10cm. The mass of the sheet was accurately recorded as m0. The sheet was completely immersed in 200 ml of 95% ethanol aqueous solution and boiled at 70℃ for 6 hours under reflux conditions. The sheet was then removed, and the solution was poured into a clean evaporating dish. The solution was heated to dryness until 5~10 ml of solution remained in the evaporating dish. The evaporating dish was then placed in a forced-air drying oven at 105℃ for 2 hours. The weight of the sample remaining in the evaporating dish was recorded as m1. The proportion η of oligomers with a number-average molecular weight Mn < 650 in the residual sample was determined by gel permeation chromatography (GPC). The specific test method was as follows: A chromatographic system was used at 40℃ with a set of three tandem columns (particle diameter of 5μm and porosities of 500Å, 1000Å, and 10000Å, respectively). The instrument used was a Waters 1515GPC, with an Å) and a refractive index detector. Chloroform was used as the eluent (elution flow rate of 1 mL / min), and polystyrene was used as the reference standard. The sample preparation method was as follows: the residual sample was directly dissolved in chromatographic grade THF to prepare a 1 mg / mL solution for testing. The mass percentage of oligomers with a median number-average molecular weight < 650 in aliphatic polyesters was calculated as q = (m1 × η) / m0 × 100%.

[0125] Example 1

[0126] This embodiment provides an aliphatic polyester, and the molar content of PDI, succinic acid residues and sebacic acid residues, the type and mass percentage of branching agent, and the mass percentage of oligomers with a number average molecular weight <650 of the aliphatic polyester are specifically shown in Table 1.

[0127] This embodiment provides a method for preparing the aliphatic polyester, specifically including the following steps:

[0128] (1-1) 300 kg of succinic acid was physically mixed with 330 kg of 1,4-butanediol and 2.0 kg of glycerol. A 1,4-butanediol solution containing sodium hydroxide (5 wt% sodium hydroxide) was added to adjust the pH of the system to 4.8. The mixture was then transferred to an esterification reactor and esterified for 3 h at a temperature of 170 °C and a pressure of 1.1 bar to obtain esterification product A with a viscosity of 12 ml / g.

[0129] (1-2) 260 kg sebacic acid and 170 kg 1,4-butanediol were physically mixed, and a 1,4-butanediol solution containing sodium hydroxide (sodium hydroxide mass fraction of 5 wt%) was added to adjust the pH of the system to 5.5. The mixture was then transferred to an esterification reactor and esterified for 4 h at a temperature of 190℃ and a pressure of 1.0 bar to obtain esterification product B with a viscosity of 10 ml / g.

[0130] (2) After mixing the esterification products A and B obtained in steps (1-1) and (1-2), the mixture was transferred to a vertical reactor with a stirrer, and 560 g of tetrabutyl titanate was added. The mixture was prepolymerized for 100 min at a temperature of 240℃ and a pressure of 0.6 bar to obtain a prepolymer with a viscosity of 51 ml / g.

[0131] (3) The prepolymer obtained in step (2) is transferred to a horizontal reactor with a stirrer and polycondensed at a temperature of 245°C and a pressure of 1.1 mbar for 95 min to obtain an aliphatic polyester with a viscosity of 188 ml / g.

[0132] Examples 2-14 and Comparative Examples 1-6 each provide an aliphatic polyester. The molar content of PDI, succinic acid residues and sebacic acid residues, the type and mass percentage of branching agents, and the mass percentage of oligomers with a number average molecular weight <650 of the aliphatic polyester are specifically shown in Table 1.

[0133] Unless otherwise specified, the preparation methods of the aliphatic polyesters are the same as those in Example 1, except for the raw material content, type, reaction temperature, pressure, and time; as shown in Table 2 or 3; " / " indicates that this step is not performed.

[0134] Examples 8 and 13 further include chain growth reactions; specific process parameters are shown in Table 2; the epoxide used in Example 13 is ethylene glycol diglycidyl ether.

[0135] Example 10 uses a one-step esterification method, in which 300 kg of succinic acid, 260 kg of sebacic acid, 500 kg of butanediol and 1.7 kg of glycerol are mixed, and a 1,4-butanediol solution containing sodium hydroxide (sodium hydroxide mass fraction of 5 wt%) is added. The pH of the system is adjusted to 6, and the esterification reaction is carried out at 200 °C and 1.1 bar for 4 h to obtain an esterified product with a viscosity of 20 mL / g. The esterified product is then subjected to a prepolymerization reaction and a polycondensation reaction, and the specific process is the same as steps (2) and (3) of Example 1.

[0136] In Comparative Examples 1 and 5 of Table 3, " "Indicates that no alkali compound is added to adjust the pH of the system in the corresponding step.

[0137] Example 14

[0138] This embodiment provides an aliphatic polyester. The aliphatic polyester provided in Comparative Example 1 and the aliphatic polyester provided in Example 13 were melt-mixed at a mass ratio of 1:1 in a twin-screw extruder (length-to-diameter ratio of 48:1; diameter of 40 mm), and then extruded and granulated. The extrusion temperatures were as follows: Zone 1 90℃, Zone 2 100℃, Zones 3 to 9 130℃, Zone 10 120℃, Zone 11 120℃, Die head 140℃, screw speed 200 rpm, and vacuum -0.60 kg / cm². 2 The aliphatic polyester is obtained.

[0139] Application examples

[0140] This application example provides a polyester composition, by weight, comprising 60 parts aliphatic polyester, 2 parts polylactic acid, 30 parts starch, 3 parts glycerol, 3 parts water, and 1 part other auxiliaries (0.5 parts of a compound antioxidant consisting of antioxidant 1010 and antioxidant 168 in a 1:1 mass ratio and 0.5 parts of lubricant ethylene bis-stearamide); the aliphatic polyester is provided in the examples and comparative examples respectively; the preparation method of the polyester composition includes: mixing the components according to the formulation amount and adding them to a twin-screw extruder (length-to-diameter ratio of 48:1; diameter of 40 mm) for melt mixing, extrusion granulation; the extrusion temperatures are sequentially: zone 1 120℃, zone 2 160℃, zones 3 to 9 180℃, zone 10 170℃, zone 11 170℃, die head 190℃, screw speed 380 rpm, vacuum -0.60 kg / cm 2 The polyester composition is obtained.

[0141] Performance testing

[0142] The polyester composition was blown into a film to obtain a packaging film; the puncture resistance and opening performance of the packaging film were tested; the specific test results are shown in Table 4.

[0143] The process parameters for blown film processing are as follows: screw length-to-diameter ratio is 32:1, spiral flow channel die head is used, air ring is a double-outlet air ring, blown film processing temperature setting is 140℃, blow-up ratio is 3.5, blown film thickness is 12±2μm, and blown film speed is 60±2kg / h.

[0144] (1) Puncture resistance: Under the conditions of 25±5℃ and 55±5% humidity, according to GB / T 21302-2007 standard, the puncture needle diameter is 1.00±0.05 mm and the puncture speed is 50±5 mm / min, the maximum puncture force of the test sample is measured.

[0145] (2) Opening performance: The packaging film is made into a packaging bag and then stored in an environment with a temperature of 25±5℃ and a humidity of 55±5% for different periods of time. The rating is carried out according to the standard in Table A.

[0146] Table A

[0147]

[0148] Table 1

[0149]

[0150] Table 2

[0151]

[0152] Table 3

[0153]

[0154] Comparative Example 6

[0155] This comparative example provides an aliphatic polyester. The preparation method differs from Example 1 only in that, in steps (1-1) and (1-2), a 1,4-butanediol solution containing sodium hydroxide is not added to adjust the pH, and a step (4) is also included, in which the aliphatic polyester obtained in step (3) is sliced ​​and then subjected to a contact treatment process with a tetrahydrofuran aqueous solution. The mass ratio of aliphatic polyester particles to tetrahydrofuran aqueous solution is 1:5, the mass concentration of tetrahydrofuran aqueous solution is 70%, the contact treatment temperature is 50°C, and the contact treatment time is 14 hours, thereby obtaining the aliphatic polyester.

[0156] Table 4

[0157]

[0158] As shown in Table 4, the aliphatic polyester provided by this invention employs a specific diacid composition, while controlling the content of oligomers with a number-average molecular weight <650 and the molecular weight distribution coefficient of the aliphatic polyester within a specific range. This results in polyester compositions prepared based on the aliphatic polyester as the base resin exhibiting excellent high-speed blown film molding performance, excellent opening performance after high-speed blown film molding, and excellent puncture resistance, meeting the requirements of high-speed molding. The puncture force of the film bag material including the aliphatic polyester is ≥13 N; the opening grade is ≥2.5.

[0159] As shown in Comparative Example 1, the content of oligomers with a number average molecular weight <650 in the aliphatic polyester is low, resulting in poor opening performance of the film bag material after high-speed blown film forming. As shown in Comparative Examples 2 and 5, the PDI of the aliphatic polyester is too narrow, resulting in poor opening performance after high-speed blown film forming; if the PDI is too wide, the puncture resistance deteriorates.

[0160] As can be seen from Comparative Example 6, the aliphatic polyester has a low content of oligomers with a number average molecular weight of <650 and a narrow PDI, resulting in extremely poor opening performance after high-speed blown film forming.

[0161] As can be seen from Comparative Examples 3 and 4, the molar content of the succinic acid residues and sebacic acid residues is not within a specific range, resulting in poor opening performance and / or puncture resistance after high-speed blown film forming.

[0162] 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. An aliphatic polyester, characterized in that, The aliphatic polyester comprises diacid residues and diol residues: The diacid residues include the following residues: a1), based on the total molar percentage of a1) and a2) as 100 mol%, 61.2~69.1 mol% of succinic acid residues; a2), based on the total molar percentage of a1) and a2) as 100 mol%, contains 30.9~38.8 mol% sebacic acid residues; The diol residue is selected from 1,4-butanediol residues in at least an equimolar amount with the dicarboxylic acid residue; The mass percentage of oligomers with a number average molecular weight <650 in the aliphatic polyester is 1.09~3%; The molecular weight distribution coefficient of the aliphatic polyester is 1.72~2.

83.

2. The aliphatic polyester according to claim 1, characterized in that, The mass percentage of oligomers with a number average molecular weight < 650 in the aliphatic polyester is 1.6~2.8%.

3. The aliphatic polyester according to claim 1, characterized in that, The molecular weight distribution coefficient of the aliphatic polyester is 1.85~2.

52.

4. The aliphatic polyester according to claim 1, characterized in that, The diacid residues include the following residues: a1), based on the total molar percentage of a1) and a2) as 100 mol%, 63.5~67.5 mol% of succinic acid residues; a2), based on the total molar percentage of a1) and a2) as 100 mol%, contains 32.5~36.5 mol% sebacic acid residues.

5. The aliphatic polyester according to claim 1, characterized in that, The aliphatic polyester satisfies at least one of the following: (1) The aliphatic polyester further comprises branching agent residues; (2) The aliphatic polyester further comprises branching agent residues, which are derived from branching agents with a functionality ≥3; (3) The aliphatic polyester further contains branching agent residues, and the mass percentage of the branching agent residues is 0.20~0.55 wt% based on the total mass of the aliphatic polyester being 100 wt%.

6. A polyester composition, characterized in that, The polyester composition comprises polymer A and component B; polymer A comprises the aliphatic polyester according to any one of claims 1 to 5.

7. The polyester composition according to claim 6, characterized in that, The polyester composition satisfies at least one of the following: (1) The polymer A further includes a second polyester; the second polyester includes at least one of polylactic acid, aliphatic-aromatic polyester or other aliphatic polyester; (2) Component B includes at least one of starch compounds, cellulose compounds, chitin compounds, chitosan compounds, alginate compounds, protein compounds, gelatin compounds, natural rubber compounds, and lignin compounds; (3) The polyester composition also includes additives.

8. The polyester composition according to claim 7, characterized in that, The polyester composition satisfies at least one of the following: (1) The aliphatic-aromatic polyester includes at least one of polybutylene terephthalate, polybutylene adipate terephthalate, polybutylene sebacic acid terephthalate or polybutylene adipate furanyl terephthalate. (2) The other aliphatic polyesters include at least one of polybutylene succinate, polybutylene adipate succinate or polybutylene sebacate.

9. The polyester composition according to claim 7, characterized in that, The polyester composition comprises, by weight, 50 to 95 parts of the aliphatic polyester according to any one of claims 1 to 5, 1 to 20 parts of the second polyester, 1 to 30 parts of component B and 0 to 8 parts of additives.

10. A packaging film, characterized in that, The packaging film is formed from an aliphatic polyester as described in any one of claims 1 to 5 or a polyester composition as described in any one of claims 6 to 9.

11. The packaging film according to claim 10, characterized in that, Under the condition of a blown film speed of 60±2 kg / h, the opening performance grade of the packaging film is ≥2.5.

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