Aliphatic polyester, polyester composition containing aliphatic polyester and application of aliphatic polyester

Abstract

The invention provides aliphatic polyester, a polyester composition containing the aliphatic polyester and application of the aliphatic polyester, the aliphatic polyester comprises binary acid residues and dihydric alcohol residues, and the binary acid residues comprise the following residues: a1) 61.2-69 mol% of succinic acid residues based on 100 mol% of the total mole percentage of a1) and a2); a2), 31 to 38.8 mol% of sebacic acid residues based on 100 mol% of the total mole percentage content of a1) and a2); the dihydric alcohol residues are selected from 1, 4-butanediol residues which are at least equal to the dibasic acid residues in molar weight. According to the invention, the aliphatic polyester has good uniformity in the aspect of longitudinal and transverse tearing properties, is high in tensile strength, has a short biological disintegration period under the condition of household composting, and meets the requirements of household composting.

Description

Technical Field

[0001] The present invention belongs to the technical field of biodegradable polyester materials, and particularly relates to an aliphatic polyester, a polyester composition containing the same, and their applications. Background Art

[0002] Resource and environmental problems are major issues faced by humanity in achieving sustainable development. Among them, environmental pollution is one manifestation of resource and environmental problems. For example, the white pollution caused by general plastics, especially packaging film materials such as shopping bags, garbage bags, agricultural mulch films, etc., seriously affects the land use rate, causes air and water pollution, and is prone to fires, affecting life and health. White pollution is a phenomenon in which plastics are randomly discarded after use and are difficult to degrade, thus causing environmental pollution; therefore, developing biodegradable materials with good performance is one of the important and indispensable means to solve white pollution.

[0003] In biodegradable materials, in order to reduce costs and improve the flexibility of the film, natural source polymers such as starch are usually filled. However, commercially available starch-based biodegradable materials have problems with poor mechanical property uniformity, especially in terms of tear properties in the transverse and longitudinal directions. Such biodegradable materials are prone to transverse tearing and thus cannot withstand a certain limit of weight. In addition, most commercially available starch-based biodegradable materials use aliphatic-aromatic polyesters as the base resin, such as poly(butylene adipate-co-terephthalate) (PBAT), poly(butylene sebacate-co-terephthalate) (PBSeT), etc. Due to the relatively high content of terephthalate chain segments in their molecular structures, aliphatic-aromatic polyesters usually cannot meet the requirements of home composting when the product thickness is relatively thick (>50 μm).

[0004] To solve the problem of mechanical property uniformity of starch-based biodegradable materials, especially the anisotropy problem of tear properties in the longitudinal and transverse directions, CN101522797A discloses a biodegradable composition. By using starch with an average particle size less than 0.25 μm as the dispersed phase, the anisotropy problem of the material is effectively improved. However, the finer the starch particle size, the higher the cost, and the more difficult it is to disperse in a high filling system; furthermore, the composition uses PBAT as the base resin and cannot effectively solve the home composting problem of the material.

[0005] Based on this, developing an aliphatic polyester with good longitudinal and transverse tear property uniformity, high disintegration rate, which can be used to prepare starch-based biodegradable materials and can meet the requirements of home composting, is an urgent problem to be solved in this field. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide an aliphatic polyester, a polyester composition containing the same, and their applications. The aliphatic polyester can be used to prepare starch-based biodegradable materials, solve the problem of anisotropy and poor uniformity of the longitudinal and transverse tear properties of starch-based biodegradable materials, and can meet the requirements of home composting.

[0007] To achieve this purpose, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides an aliphatic polyester, which contains dibasic acid residues and diol residues: the dibasic acid residues include the following residues: a1), based on the total molar percentage content of a1) and a2) being 100 mol%, 61.2 - 69 mol% of succinic acid residues; a2), based on the total molar percentage content of a1) and a2) being 100 mol%, 31 - 38.8 mol% of sebacic acid residues; the diol residues are selected from 1,4-butanediol residues with at least an equimolar amount to the dibasic acid residues. In the present invention, by controlling the contents of succinic acid residues and sebacic acid residues within the above ranges, polybutylene sebacate with uniform longitudinal and transverse tear properties can be obtained; using the polybutylene sebacate as the base resin to prepare starch-based biodegradable materials solves the problems of anisotropy and poor uniformity of the longitudinal and transverse tear properties of starch-based biodegradable materials, and at the same time can ensure that the material has good tensile properties and degradation properties; it can meet the requirements of home composting.

[0009] It should be noted that the "residue" refers to any organic structure introduced into the polymer molecular chain by the polycondensation reaction of the relevant monomer, that is, the organic structure derived from the relevant monomer; for example, the dibasic acid residue refers to the structure derived from the dibasic acid monomer in the aliphatic polyester.

[0010] In the present 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; in the chain segment structure of the aliphatic polyester, when the content of succinic acid residues is high, the crystallization rate of the aliphatic polyester is fast, the crystallinity is high, and the uniformity of the longitudinal and transverse tear properties is poor; when the content of sebacic acid residues is high, the chain segments of the aliphatic polyester become flexible, and the uniformity of the longitudinal and transverse tear properties also becomes poor. Controlling the molar ratio of succinic acid residues and sebacic acid residues within a specific range can enable the aliphatic polyester to have excellent uniformity of longitudinal and transverse tear properties, while ensuring that the material has good tensile properties, degradation properties and does not affect the processing properties of the material.

[0011] In the present invention, the succinic acid derivative includes an alkyl succinate. Exemplarily, the alkyl succinate may be at least one of dimethyl succinate, diethyl succinate, di-n-propyl succinate, di-isopropyl succinate, di-n-butyl succinate, di-isobutyl succinate, di-tert-butyl succinate, di-n-pentyl succinate, di-isopentyl succinate, and di-n-hexyl succinate; the alkyl succinate may be an alkyl ester formed from succinic acid or an alkyl ester formed from succinic anhydride, and preferably dimethyl succinate formed from succinic anhydride is used.

[0012] In the present invention, the sebacic acid derivative includes an alkyl sebacate; Exemplarily, the alkyl sebacate may be at least one of dimethyl sebacate, diethyl sebacate, di-n-propyl sebacate, di-isopropyl sebacate, di-n-butyl sebacate, di-isobutyl sebacate, di-tert-butyl sebacate, di-n-pentyl sebacate, di-isopentyl sebacate, and di-n-hexyl sebacate; the alkyl sebacate may be an alkyl ester formed from sebacic acid or an alkyl ester formed from sebacic anhydride.

[0013] Preferably, the dibasic acid residue contains the following residues: a1), based on the total molar percentage content of a1) and a2) being 100 mol%, 63.5 to 67.5 mol% of succinic acid residue; a2), based on the total molar percentage content of a1) and a2) being 100 mol%, 32.5 to 36.5 mol% of sebacic acid residue.

[0014] Preferably, the number average molecular weight (Mn) of the aliphatic polyester is 30,000 to 150,000, preferably the number average molecular weight is 45,000 to 120,000, and more preferably the number average molecular weight is 58,000 to 79,000.

[0015] In the present invention, the number average molecular weight can be measured by gel permeation chromatography (GPC) using monodisperse polystyrene as the standard substance. If the number average molecular weight is too high or too low, the uniformity of the longitudinal and transverse tearing properties of the aliphatic polyester will be poor.

[0016] In the present invention, the number average molecular weight can be regulated by controlling the polymerization temperature, time, and adding cross-linking agents, chain transfer agents, etc.

[0017] Preferably, according to GB / T 32366-2015, the carboxyl group content of the aliphatic polyester < 35 mol / t, preferably the carboxyl group content < 28 mol / t, and more preferably the carboxyl group content is 5 to 20 mol / t.

[0018] In the present invention, the aliphatic polyester has a high carboxyl content, poor hydrolysis resistance and aging resistance; when the carboxyl content is low, the biodegradation rate is low and the cost is high; the fewer the carboxylic acid terminals from the unreacted dicarboxylic acid components, the lower the carboxyl content of the aliphatic polyester; therefore, the carboxyl content is controlled by adjusting the reaction degree or inhibiting thermal decomposition by changing conditions such as the alcohol-acid ratio, polymerization temperature, and polymerization time; in addition, 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.

[0019] Preferably, according to GB / T 17931-1999, the intrinsic viscosity of the aliphatic polyester is 1.38 to 2.32 dL / g, preferably the intrinsic viscosity is 1.5 to 2.2 dL / g, more preferably the intrinsic viscosity is 1.58 to 2.11 dL / g, still more preferably the intrinsic viscosity is 1.67 to 2.02 dL / g, and particularly preferably the intrinsic viscosity is 1.82 to 1.95 dL / g.

[0020] In the present invention, when the intrinsic viscosity of the aliphatic polyester is within the above range, the aliphatic polyester can have good uniformity in longitudinal and transverse tear properties, and can ensure the mechanical properties of the molded body during molding processing. In addition, it can also prevent the melt viscosity of the polyester during molding processing from imposing an excessive load on molding machines such as extruders and injection machines, thereby ensuring productivity.

[0021] In the present invention, the preparation method of the aliphatic polyester is not particularly limited, as long as it can prepare the aliphatic polyester with a specific structure of the present invention; preferably, the preparation method of the aliphatic polyester includes the following steps:

[0022] (1) React a dicarboxylic acid with a diol to obtain an esterification product;

[0023] (2) Carry out a prepolymerization reaction on the esterification product obtained in step (1) to obtain a prepolymerization product;

[0024] (3) Carry out a polycondensation reaction on the prepolymerization product obtained in step (2) to obtain a polycondensation product, that is, the aliphatic polyester of the present invention.

[0025] In the present invention, the dicarboxylic acid in step (1) is succinic acid and / or succinic acid derivatives, and sebacic acid and / or sebacic acid derivatives; the dicarboxylic acid can be used alone or as a mixture of at least two; the diol is 1,4-butanediol.

[0026] In the present invention, the molar ratio of the diol to the dicarboxylic acid is (1.2 to 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 a range between any of the above values, and more preferably (1.4 to 2):1.

[0027] In the present invention, the source of the succinic acid and / or succinic acid derivative is not particularly limited. It may be a succinic acid and / or succinic acid derivative derived from a bio-based source (i.e., the preparation raw material is a biomass resource), or a succinic acid and / or succinic acid derivative derived from a petroleum-based source (i.e., the preparation raw material is a petroleum resource).

[0028] In the present invention, the raw materials for the reaction in step (1) further include a crosslinking agent; based on the total mass of the aliphatic polyester being 100 wt%, the mass of the crosslinking agent is 0 to 3 wt%; the crosslinking agent includes at least one of a polyol, a polycarboxylic acid, or a polycarboxylic anhydride; exemplarily, the crosslinking agent includes, but is not limited to, tartaric acid, citric acid, malic acid, trimethylolpropane, trimethylolethane, pentaerythritol, polyether triol, glycerol, 1,3,5-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic anhydride, 1,2,4,5-benzenetetracarboxylic acid, pyromellitic dianhydride, etc.

[0029] In the present invention, the reaction in step (1) includes an esterification reaction and / or a transesterification reaction; the temperature of the reaction is 150 to 220 °C, the pressure is 0.7 to 1.3 bar, and the time is 2 to 6 h. Further preferably, the temperature of the reaction is 165 to 210 °C, the pressure is 0.8 to 1.2 bar, and the time is 3 to 5 h.

[0030] In the present invention, step (1) can be carried out in a mixing device. The dibasic acid and the diol are mixed to obtain a slurry, and then the temperature is raised for the reaction.

[0031] In the present invention, the carboxyl content of the esterification product in step (1) is 240 to 570 mol / t, more preferably 300 to 400 mol / t.

[0032] In the present invention, after the reaction in step (1), it further includes a step of removing the excess diol by distillation. The removed diol can be purified by distillation and reused as a raw material, and the purity of the purified diol is ≥95%.

[0033] In the present invention, the temperature of the prepolymerization reaction in step (2) is 230 to 260 °C, the pressure is 0.3 to 0.8 bar, and the time is 70 to 200 min; further preferably, the temperature of the reaction is 240 to 250 °C, the pressure is 0.5 to 0.7 bar, and the time is 90 to 130 min.

[0034] In the present invention, step (2) can be carried out in a prepolymerization reactor.

[0035] In the present invention, the carboxyl content of the prepolymerization product in step (2) is 40 to 90 mol / t, more preferably 55 to 75 mol / t.

[0036] In the present invention, the temperature of the polycondensation reaction in step (3) is 235 - 260 °C, the pressure is 0.2 - 5 mbar, and the time is 40 - 110 min; more preferably, the reaction temperature is 240 - 250 °C, the pressure is 0.5 - 2 mbar, and the time is 70 - 100 min.

[0037] In the present invention, step (3) can be carried out in a finishing machine suitable for polycondensation reaction, such as a rotary reactor, a cage reactor, a horizontal reactor, etc.

[0038] In the present invention, the reaction in step (2) is carried out in the presence of a catalyst; the catalyst can be a tin compound, an antimony compound, a cobalt compound, a lead compound, a zinc compound, an aluminum compound or a titanium compound, more preferably a zinc compound, an aluminum compound or a titanium compound, and most preferably a titanium compound; the titanium compound can be tetrabutyl titanate or tetraisopropyl titanate; the titanium compound has less residue and lower toxicity in the product or downstream products compared to other compounds. It is especially suitable for preparing biodegradable polyesters and can directly enter the environment in the form of compost bags or mulch films.

[0039] In the present invention, based on the total mass of the reaction raw materials (dicarboxylic acid, diol and optional crosslinking agent) being 100 wt%, the total mass of the catalyst is 0.001 - 1 wt%.

[0040] In the present invention, other additives can be added during the reaction in step (3) according to actual needs; the other additives include but are not limited to catalyst passivators, color stabilizers, activators, etc.

[0041] 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 the mass of the prepolymer being 100 wt%, the mass of the catalyst passivator is 0.001 - 0.1 wt%, preferably 0.01 - 0.05 wt%. Exemplarily, when a highly active titanium compound is selected as the catalyst, a catalyst passivator can be added, where 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.

[0042] 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 the color stabilizer generally results in a decrease in the condensation rate. Therefore, triphenyl phosphate, which has no adverse effect on the condensation rate, is preferably used as the color stabilizer. Based on the mass of the prepolymer product being 100 wt%, the mass of the color stabilizer is 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:(0.3 - 1.0), and particularly preferably the molar ratio of Ti to P is 1:(0.5 - 1.0).

[0043] 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 the mass of the prepolymer product being 100 wt%, the mass of the activator is 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, and particularly preferably the molar ratio of Ti to P is (1.1 - 1.3):1.

[0044] More preferably, the color stabilizer and the activator are used in combination, for example, triphenyl phosphate and disodium hydrogen phosphate are used in combination.

[0045] In the present invention, after the polycondensation reaction, a chain growth reaction is further included, that is, the product obtained from the polycondensation reaction (polycondensate) is reacted with a chain extender to obtain the aliphatic polyester.

[0046] In the present invention, the chain extender includes one or several of isocyanates, peroxides, epoxides, oxazolines, oxazines, caprolactam, or carbodiimides.

[0047] In the present invention, the isocyanate may be an aromatic diisocyanate and / or an aliphatic diisocyanate. The aromatic diisocyanate may 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 preferably, diphenylmethane 2,2'-diisocyanate, diphenylmethane 2,4'-diisocyanate or diphenylmethane 4,4'-diisocyanate is used. The aromatic diisocyanate may also be a polynuclear aromatic diisocyanate, such as tris(4-isocyanatophenyl)methane with three rings, which may 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; exemplarily, the aliphatic diisocyanate includes hexamethylene diisocyanate, pentamethylene diisocyanate, isophorone diisocyanate or the diisocyanate of methylene bis(4-isocyanatocyclohexane). Particularly preferred is hexamethylene diisocyanate.

[0048] In the present invention, based on the total mass of the polycondensation product, the mass of the isocyanate may be 0.05 to 2 wt%, particularly preferably 0.1 to 1.5 wt%.

[0049] In the present invention, the peroxide may be one or more of benzoyl peroxide, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-butylperoxy)methylcyclododecane, n-butyl 4,4-bis(butylperoxy)valerate, dicumyl peroxide, tert-butyl peroxybenzoate, dibutyl peroxide, α,α-bis(tert-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hex-3-yne or cumene hydroperoxide.

[0050] In the present invention, based on the total mass of the polycondensation product, the mass of the peroxide may be 0.1 to 2 wt%, particularly preferably 0.2 to 1 wt%.

[0051] In the present invention, the epoxide may be one or more of 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, and copolymers containing epoxy groups based on styrene, acrylate, and / or methacrylate.

[0052] In the present invention, based on the total mass of the polycondensation product, the mass of the epoxide may be 0.1 to 2 wt%, preferably 0.2 to 1 wt%.

[0053] In the present 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.

[0054] In the present invention, based on the total mass of the polycondensation product, the mass of the oxazoline, oxazine, caprolactam, and carbodiimide is independently 0.1 to 2 wt%, preferably 0.2 to 1 wt%.

[0055] In the present invention, the temperature of the chain growth reaction is 170 to 240 °C, more preferably 180 to 220 °C; it is carried out under superatmospheric pressure or atmospheric pressure, which varies with the system used.

[0056] In the present 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 a combination thereof. Examples of List reactors are single-shaft DISCOTHERM B or twin-shaft CRP or ORP reactors. Preferably, the chain growth reaction is carried out in an extruder, and the residence time in the extruder is 2 to 15 min, more preferably 4 to 10 min.

[0057] In the present invention, the aliphatic polyester can also be prepared by the following method: in step (1), succinic acid and / or succinic acid derivatives and sebacic acid and / or sebacic acid derivatives are respectively reacted with 1,4-butanediol to obtain two esterified products, and then the two esterified products are subjected to subsequent prepolymerization reaction, polycondensation reaction, and optional chain growth reaction.

[0058] Exemplarily, the preparation method specifically includes the following steps:

[0059] Step (1-1): React succinic acid and / or succinic acid derivatives, 1,4-butanediol and an optional crosslinking agent at a temperature of 150 to 180 °C and a pressure of 0.7 to 1.1 bar for 2 to 5 h to obtain an esterification product A with a carboxyl content of 450 to 750 mol / t.

[0060] Step (1-2): React sebacic acid and / or sebacic acid derivatives with 1,4-butanediol at a temperature of 180 to 210 °C and a pressure of 0.6 to 1.1 bar for 3 to 6 h to obtain an esterification product B with a carboxyl content of 300 to 620 mol / t. Then, the esterification product A and the esterification product B are mixed and subjected to a prepolymerization reaction, a polycondensation reaction, and an optional chain growth reaction; wherein, the conditions of the prepolymerization reaction, the polycondensation reaction, and the optional chain growth reaction are selected from the same ranges as those in step (2), step (3), and the aforementioned chain growth reaction.

[0061] In a second aspect, the present invention provides a polyester composition, which includes polymer A and polymer B; polymer A includes the aliphatic polyester described in the first aspect.

[0062] Preferably, polymer A further includes a second polyester.

[0063] Preferably, the second polyester includes at least one of polylactic acid (PLA), aliphatic-aromatic polyester, or other aliphatic polyesters.

[0064] Preferably, the aliphatic-aromatic polyester includes at least one of poly(butylene succinate terephthalate) (PBST), poly(butylene adipate terephthalate) (PBAT), poly(butylene sebacate terephthalate) (PBSeT), or poly(butylene adipate 2,5-furandicarboxylate) (PBAF).

[0065] Preferably, the other aliphatic polyester includes at least one of poly(butylene succinate) (PBS), poly(butylene succinate adipate) (PBSA), or poly(butylene sebacate) (PBSe).

[0066] In the present invention, the second polyester can be selected according to actual needs, not limited to the polyesters mentioned above only.

[0067] Preferably, the polymer B includes at least one of starch, cellulose, chitin, chitosan, alginate, protein, gelatin, natural rubber, lignin, or derivatives of the foregoing substances.

[0068] In the present invention, the protein includes but is not limited to gluten, zein, casein, collagen, etc.; the lignin includes unpurified lignin, purified hydrolyzed lignin, alkalized lignin, etc. Starch can also be used in the form of allosteric and gelling forms or in the form of a filler. The starch can represent a continuous phase or a dispersed phase, or can be in a co-continuous form.

[0069] Preferably, the polyester composition further includes an auxiliary agent.

[0070] In the present invention, the auxiliary agent can be added according to actual needs, including but not limited to at least one of an antioxidant, a lubricant, a light stabilizer, a mold release agent, or an antistatic agent.

[0071] In the present invention, the types of auxiliary agents are not overly limited, and conventional auxiliary agents can be used. Exemplarily, the antioxidant includes but is not limited to any one of antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant 164, antioxidant DLTP, or antioxidant TPP.

[0072] The light stabilizer includes but is 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.

[0073] The lubricant includes but is not limited to at least one of esters (such as polyethylene glycol esters, polyol esters), lignite salts, ethylene bisstearamide, or polyethylene wax.

[0074] The mold release agent includes, but is not limited to, at least one of inorganic mold release agents (such as talc powder, mica powder, clay, etc.), organic mold release agents (such as fatty acids, paraffin wax, glycerin, petrolatum, etc.), or polymer mold release agents (such as silicone oil, polyethylene glycol, low molecular weight polyethylene, etc.).

[0075] The antistatic agent includes, but is not limited to, at least one of cationic antistatic agents (such as quaternary ammonium salts), anionic antistatic agents (such as alkyl sulfonates, phosphates), amphoteric antistatic agents (such as amphoteric imidazoline compounds), nonionic antistatic agents (such as hydroxyethyl alkylamines, fatty acid amides, polyoxyethylene, polyol esters), or polymer antistatic agents (such as polyethers).

[0076] As a preferred technical solution of the present invention, in parts by weight, the polyester composition includes 50 to 95 parts of aliphatic polyester (for example, it can be 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, 90 parts, 95 parts or the range between any of the above values, preferably 52 to 92 parts, more preferably 56 to 82 parts), 1 to 20 parts of a second polyester (for example, it can be 1 part, 2 parts, 4 parts, 6 parts, 8 parts, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts or the range between any of the above values, preferably 1.5 to 15 parts, more preferably 2.5 to 8.5 parts), 1 to 30 parts of polymer B (for example, it can be 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 the range between any of the above values, preferably 9 to 27 parts, more preferably 21 to 26.5 parts), and 0 to 15 parts of additives (for example, it can be 1 part, 2 parts, 4 parts, 6 parts, 8 parts, 10 parts, 12 parts, 14 parts, 15 parts or the range between any of the above values).

[0077] In the present invention, the preparation method of the polyester composition includes: mixing polymer A, polymer B and optionally additives, and extruding to obtain the polyester composition; the extruder includes a reactive extruder, and the extruder can be a single-screw extruder, a twin-screw extruder or a multi-screw extruder; the extrusion temperature is 140 to 220 °C, and the rotational speed of the screw during extrusion is 200 to 500 rpm.

[0078] In the third aspect, the present invention provides a packaging film, and the packaging film includes the aliphatic polyester described in the first aspect or the polyester composition described in the second aspect.

[0079] In the present invention, other substances can also be added to the packaging film according to actual needs, 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 powder, calcium carbonate, kaolin, etc.

[0080] Preferably, the degree of orientation of the packaging film is 0.7 to 1.6, more preferably 0.8 to 1.4, and still more preferably 0.9 to 1.2.

[0081] In the present invention, the degree of orientation of the packaging film refers to the ratio of the longitudinal tear strength to the transverse tear strength; the higher the degree of orientation, the stronger the longitudinal tear performance and the weaker the transverse tear performance, and during use, transverse rupture is more likely to occur; the lower the degree of orientation, the weaker the longitudinal tear performance and the stronger the transverse tear performance, and during use, longitudinal breakage is more likely to occur; the closer the degree of orientation is to 1, the more uniform the longitudinal and transverse tear properties of the material.

[0082] In the present invention, according to ASTM D1922, the Elmendorf tear strength of the packaging film in the transverse and longitudinal directions is tested, the thickness of the test sample is 55 ± 3 μm, and then the degree of orientation is the ratio of the longitudinal Elmendorf tear strength to the transverse Elmendorf tear strength.

[0083] In the present invention, according to ISO 527-2:2012, the longitudinal tensile strength of the packaging film ≥ 18 MPa, and the transverse tensile strength ≥ 16 MPa; more preferably, the longitudinal tensile strength ≥ 20 MPa, and the transverse tensile strength ≥ 18 MPa.

[0084] In the present invention, when the biodegradation rate of the packaging film ≥ 90%, the disintegration period ≤ 21 weeks, and more preferably the disintegration period ≤ 15 weeks.

[0085] In the present invention, the biodegradation rate and disintegration period of the packaging film are determined by the following method:

[0086] The initial mass of a packaging film with a length × width of 10 cm × 10 cm and a thickness of 55 ± 3 μm is measured and denoted as m 0 , and according to the standard AS5810, a home composting test is carried out. Samples are taken once a week, screened, and the packaging film with a length × width greater than or equal to 2 cm × 2 cm remaining on the sieve is retained. The residue on the packaging film is washed, dried, and weighed, and the sample mass is recorded and denoted as m n , when the biodegradation rate of the packaging film [(m 0 -m n) / m 0 ≥ 90%, the corresponding disintegration period n is recorded.

[0087] In the present invention, the packaging film includes food packaging films, industrial packaging films, agricultural mulch films, shopping bags, garbage bags, etc.

[0088] The aliphatic polyester, the polyester composition containing the aliphatic polyester, and the packaging film prepared therefrom in the present invention are all biodegradable.

[0089] For the present invention, a substance or a mixture of substances has the characteristic of "biodegradable" if it shows a degree of biodegradation percentage of at least 90%, as defined in DIN EN 13432.

[0090] According to DIN EN 13432, during the composting process, air without CO 2 is introduced into the matured compost, and the compost is subjected to a specific temperature process. Here, biodegradability is defined as: the net amount of CO 2 released by the sample (after subtracting the amount of CO 2 released by the compost without the sample) divided by the maximum amount of CO 2 that the sample can release (calculated from the carbon content in the sample), representing the degree of biodegradation percentage. Usually, after only a few days of composting, biodegradable polyesters and biodegradable polyester compositions generally show obvious signs of degradation, such as fungal growth, cracking, and perforation.

[0091] Other methods for determining biodegradability are also described in ASTM D5338 and ASTM D6400.

[0092] The numerical ranges described in the present invention not only include the point values listed above, but also any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, the specific point values included in the described ranges are not exhaustively listed in the present invention.

[0093] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0094] The aliphatic polyester provided by the present invention can obtain poly(butylene succinate-co-sebacate) with uniform tear properties in both the transverse and longitudinal directions by controlling the contents of succinic acid and sebacic acid within a specific range; using the poly(butylene succinate-co-sebacate) as the base resin to prepare a starch-based biodegradable material solves the problem of anisotropy and poor uniformity of the longitudinal and transverse tear properties of the starch-based biodegradable material, and at the same time ensures that the material has good tensile properties and degradation properties, and can meet the requirements of home composting. Detailed Embodiments

[0095] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the described embodiments are only for helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0096] In the present invention, the materials used can be purchased commercially or prepared by conventional methods. Unless otherwise specified, the materials used in the present invention are as follows.

[0097] 1,4-Butanediol: Purchased from Xinjiang Meike Chemical Industry Co., Ltd.

[0098] Succinic acid: Purchased from Shandong Landian Biotechnology Co., Ltd.

[0099] Sebacic acid: Purchased from Hengshui Jinghua Chemical Co., Ltd.

[0100] Glycerol: Purchased from Aladdin.

[0101] Tetrabutyl titanate: Purchased from Jianyi Chemical Import and Export Co., Ltd.

[0102] Hexamethylene diisocyanate: Purchased from Aladdin.

[0103] Starch: Purchased from Shandong Shouguang Jueneng Golden Corn Development Co., Ltd.

[0104] Polylactic acid: PLA, KB600 NF30, sourced from Zhuhai Jinfa Biomaterials Co., Ltd.

[0105] In the present invention, the testing methods for Mn, intrinsic viscosity, carboxyl content, and the molar contents of succinic acid residues and sebacic acid residues in the aliphatic polyester are as follows.

[0106] 1. Mn is tested using a gel permeation chromatograph (GPC): Using a chromatographic system at 40 °C, with a set of three columns in series (particle diameter 5 μm and porosities of and ) and a refractive index detector, using chloroform as the eluent (elution flow rate 1 mL / min), and polystyrene as the reference standard for determination.

[0107] 2. The testing of intrinsic viscosity is carried out with reference to Standard GB / T 17931-1999, specifically including: adding 0.1250 ± 0.0002 g of the sample to 25 mL of a phenol / o-dichlorobenzene mixed solution with a weight ratio of 1:1, heating until the sample is completely dissolved, and after the sample is completely dissolved, using an Ubbelohde viscometer for testing at a temperature of 25 ± 0.05 °C.

[0108] 3. The testing of carboxyl content is carried out with reference to Standard GB / T 32366-2015, specifically as follows: dissolving 1 g of the sample in 50 mL of a phenol and chloroform mixed solvent with a volume ratio of 2:3; using an ethanol solution of potassium hydroxide with a concentration of 0.01 mol / L as the standard titrant solution and a bromophenol blue solution with a concentration of 0.2% as the indicator; conducting a blank test according to the method for testing the carboxyl content of the above sample; performing two parallel tests on the sample, with the difference between the two test results required to be less than or equal to 2 mol / t, and the final result taking the average of the two test results.

[0109] 4. The molar content can be obtained through 1Tested by the HNMR method; specifically: 20 mg of the aliphatic polyester sample was dissolved in 0.6 mL of deuterated chloroform, and then its 1 HNMR was measured at room temperature using a Bruker AV 500 nuclear magnetic resonance spectrometer; the characteristic peaks of succinic acid residues and sebacic acid residues (the characteristic chemical shift of succinic acid residues is about 2.63 ppm, representing the 4 hydrogens on the two methylene groups -CH 2 -CH 2 - in succinic acid; the characteristic chemical shift of sebacic acid residues is about 1.30 ppm, representing the 8 hydrogens on the four methylene groups -CH 2 -CH 2 -CH 2 -CH 2 - in the middle of sebacic acid) were integrated, and the respective molar contents of succinic acid residues and sebacic acid residues in the aliphatic polyester were obtained through the proportion of the peak areas; it should be noted that the contents of succinic acid residues and sebacic acid residues in the aliphatic polyester in Table 1 are calculated based on the total molar amount of succinic acid residues and sebacic acid residues being 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 the aliphatic polyester is I1 / (I1 + I2)×100%.

[0110] Examples 1 to 13, Comparative Examples 1, 2

[0111] Examples 1 to 13, Comparative Examples 1, 2 respectively provide an aliphatic polyester, and the molecular structure composition, Mn, acid value and intrinsic viscosity of the aliphatic polyester are shown in Table 1.

[0112] Table 1

[0113]

[0114] The preparation methods of the aliphatic polyesters provided by Examples 1 to 13, Comparative Examples 1, 2 are as follows.

[0115] Example 1

[0116] A preparation method of the aliphatic polyester is provided, specifically including the following steps:

[0117] (1) Physically mix 350 kg of succinic acid, 323 kg of sebacic acid, 575 kg of 1,4-butanediol and 2.76 kg of glycerol. After mixing, transfer the mixture to an esterification reactor and carry out an esterification reaction at a temperature of 200 °C and a pressure of 1.1 bar for 4 h to obtain an esterification product;

[0118] (2) Transfer the esterification product obtained in step (1) to a vertical reactor equipped with a stirrer, add 1.1 kg of tetrabutyl titanate, and carry out a prepolymerization reaction at a temperature of 243 °C and a pressure of 0.6 bar for 110 min to obtain a prepolymer;

[0119] (3) Transfer the prepolymer obtained in step (2) to a horizontal reactor equipped with a stirrer, and carry out a polycondensation reaction at a temperature of 245 °C and a pressure of 1.1 mbar for 80 min to obtain an aliphatic polyester.

[0120] Example 2

[0121] Provide a method for preparing the aliphatic polyester, which specifically includes the following steps:

[0122] (1) Physically mix 373 kg of succinic acid, 300 kg of sebacic acid, 575 kg of 1,4-butanediol and 2.76 kg of glycerol. After mixing, transfer the mixture to an esterification reactor, and carry out an esterification reaction at a temperature of 190 °C and a pressure of 1.1 bar for 4 h to obtain an esterification product;

[0123] (2) Transfer the esterification product obtained in step (1) to a vertical reactor equipped with a stirrer, add 1.1 kg of tetrabutyl titanate, and carry out a prepolymerization reaction at a temperature of 240 °C and a pressure of 0.7 bar for 120 min to obtain a prepolymer;

[0124] (3) Transfer the prepolymer obtained in step (2) to a horizontal reactor equipped with a stirrer, and carry out a polycondensation reaction at a temperature of 245 °C and a pressure of 1.1 mbar for 100 min to obtain an aliphatic polyester.

[0125] Example 3

[0126] Provide a method for preparing the aliphatic polyester, which specifically includes the following steps:

[0127] (1) Physically mix 330 kg of succinic acid, 343 kg of sebacic acid, 575 kg of 1,4-butanediol and 2.76 kg of glycerol. After mixing, transfer the mixture to an esterification reactor, and carry out an esterification reaction at a temperature of 180 °C and a pressure of 0.9 bar for 3.5 h to obtain an esterification product;

[0128] (2) Transfer the esterification product obtained in step (1) to a vertical reactor equipped with a stirrer, add 1.1 kg of tetrabutyl titanate, and carry out a prepolymerization reaction at a temperature of 242 °C and a pressure of 0.6 bar for 100 min to obtain a prepolymer;

[0129] (3) Transfer the prepolymer obtained in step (2) to a horizontal reactor with stirring, and carry out polycondensation reaction at a temperature of 243 °C and a pressure of 1.3 mbar for 85 min to obtain an aliphatic polyester.

[0130] Example 4

[0131] Provide a method for preparing the aliphatic polyester, which is different from Example 1 only in that there is no glycerol in step (1), the polycondensation reaction temperature in step (3) is 243 °C, the polycondensation time is 60 min under the condition of a pressure of 1.1 mbar. In addition, after the polycondensation reaction in step (3), it also includes extruding the obtained polycondensation product and hexamethylene diisocyanate (with a content of 0.3 wt% of the mass of the polycondensation product) in a reactive extruder at a temperature of 200 °C, and the residence time is 8 min. Other raw materials, steps and polymerization processes are the same as those in Example 1.

[0132] Example 5

[0133] Provide a method for preparing the aliphatic polyester, which is different from Example 1 only in that step (1) includes the following steps:

[0134] (1-1) Physically mix 350 kg of succinic acid, 300 kg of 1,4-butanediol and 2.76 kg of glycerol. After mixing, transfer the mixture to an esterification reactor, and carry out esterification reaction at a temperature of 165 °C and a pressure of 1.1 bar for 4 h to obtain an esterification product A;

[0135] (1-2) Physically mix 323 kg of sebacic acid and 275 kg of 1,4-butanediol. After mixing, transfer the mixture to an esterification reactor, and carry out esterification reaction at a temperature of 200 °C and a pressure of 0.9 bar for 3 h to obtain an esterification product B; After mixing esterification product A and esterification product B, carry out step (2) and step (3). Other raw materials, steps and polymerization processes are the same as those in Example 1.

[0136] Example 6

[0137] Provide a method for preparing the aliphatic polyester, which is different from Example 1 in that the prepolymer obtained in step (2) is transferred to a horizontal reactor with stirring, and the polycondensation reaction is carried out at a temperature of 250 °C and a pressure of 1.4 mbar for 70 min. Other raw materials, steps and polymerization processes are the same as those in Example 1.

[0138] Example 7

[0139] A method for preparing the aliphatic polyester is provided, which is different from Example 4 in that after the polycondensation reaction in step (3), the obtained polycondensation product is extruded with hexamethylene diisocyanate (content: 0.46 wt% of the mass of the polycondensation product) in a reactive extruder at a temperature of 210 °C for a residence time of 5 min, and other raw materials, steps and polymerization processes are the same as those in Example 4.

[0140] Example 8

[0141] A method for preparing the aliphatic polyester is provided, which is different from Example 1 in that in step (1), the addition amount of glycerol is 2.45 kg, and at the same time, the esterification temperature is adjusted to 190 °C and the pressure is 1.0 bar for esterification reaction for 3 h to obtain an esterification product. In step (3), the polycondensation reaction is carried out at a temperature of 243 °C and a pressure of 1.0 mbar for 70 min, and other raw materials, steps and polymerization processes are the same as those in Example 1.

[0142] Example 9

[0143] A method for preparing the aliphatic polyester is provided, which is different from Example 1 in that in step (3), the prepolymer product obtained in step (2) is transferred to a horizontal reactor with stirring, and the polycondensation reaction is carried out at a temperature of 248 °C and a pressure of 1.2 mbar for 50 min. In step (4), the polycondensation product obtained in step (3) is extruded with hexamethylene diisocyanate (content: 0.25 wt% of the mass of the polycondensation product) in a reactive extruder at a temperature of 220 °C for a residence time of 10 min, and other raw materials, steps and polymerization processes are the same as those in Example 1.

[0144] Example 10

[0145] A method for preparing the aliphatic polyester is provided, which is different from Example 1 in that there is no glycerol in step (1), and at the same time, the esterification temperature is adjusted to 180 °C and the pressure is 1.1 bar for esterification reaction for 3 h to obtain an esterification product. In step (3), the polycondensation reaction is carried out at a temperature of 245 °C and a pressure of 1.5 mbar for 75 min, and other raw materials, steps and polymerization processes are the same as those in Example 1.

[0146] Example 11

[0147] A method for preparing the aliphatic polyester is provided, which is different from Example 1 in that in step (3), the prepolymer obtained in step (2) is transferred to a horizontal reactor with stirring, and polycondensation reaction is carried out at a temperature of 242 °C and a pressure of 1.4 mbar for 45 min. In step (4), the polycondensate obtained in step (3) and hexamethylene diisocyanate (with a content of 0.70 wt% of the mass of the polycondensate) are extruded in a reactive extruder at a temperature of 220 °C, and the residence time is 13 min. Other raw materials, steps and polymerization processes are the same as those in Example 1.

[0148] Example 12

[0149] A method for preparing the aliphatic polyester is provided, which specifically includes the following steps:

[0150] (1) Physically mix 350 kg of succinic acid, 323 kg of sebacic acid, 575 kg of 1,4-butanediol and 12.0 kg of glycerol. After mixing is completed, transfer the mixture to an esterification reactor, and carry out esterification reaction at a temperature of 180 °C and a pressure of 1.1 bar for 2 h to obtain an esterification product;

[0151] (2) Transfer the esterification product obtained in step (1) to a vertical reactor with stirring, add 0.8 kg of tetrabutyl titanate, and carry out prepolymerization reaction at a temperature of 235 °C and a pressure of 0.5 bar for 120 min to obtain a prepolymer;

[0152] (3) Transfer the prepolymer obtained in step (2) to a horizontal reactor with stirring, and carry out polycondensation reaction at a temperature of 244 °C and a pressure of 0.9 mbar for 70 min to obtain an aliphatic polyester.

[0153] Example 13

[0154] A method for preparing the aliphatic polyester is provided, which specifically includes the following steps:

[0155] (1-1) Physically mix 350 kg of succinic acid with 300 kg of 1,4-butanediol and 0.5 kg of pentaerythritol. After mixing is completed, transfer the mixture to an esterification reactor, and carry out esterification reaction at a temperature of 160 °C and a pressure of 1.1 bar for 3 h to obtain an esterification product A;

[0156] (1-2) Physically mix 323 kg of sebacic acid with 275 kg of 1,4-butanediol. After mixing is completed, transfer the mixture to an esterification reactor, and carry out esterification reaction at a temperature of 190 °C and a pressure of 1.0 bar for 4 h to obtain an esterification product B.

[0157] (2) Mix the esterification product A obtained in step (1-1) with the esterification product B obtained in step (1-2), then transfer the mixture to a vertical reactor equipped with a stirrer. Add 1.0 kg of tetrabutyl titanate and carry out a prepolymerization reaction at a temperature of 240 °C and a pressure of 0.7 bar for 105 min to obtain a prepolymer product;

[0158] (3) Transfer the prepolymer product obtained in step (2) to a horizontal reactor equipped with a stirrer. Carry out a polycondensation reaction at a temperature of 242 °C and a pressure of 1.1 mbar for 70 min to obtain a polycondensation product; (4) Extrude the polycondensation product obtained in step (3) with hexamethylene diisocyanate (the content is 0.57 wt% of the mass of the polycondensation product) in a reactive extruder at a temperature of 180 °C, with a residence time of 11 min. Other raw materials, steps and polymerization processes are the same as those in Example 1.

[0159] Comparative Example 1

[0160] Provide a method for preparing the aliphatic polyester, which specifically includes the following steps:

[0161] (1) Physically mix 350 kg of succinic acid, 245 kg of sebacic acid, 534 kg of 1,4-butanediol and 2.46 kg of glycerol. After mixing is completed, transfer the mixture to an esterification reactor and carry out an esterification reaction at a temperature of 200 °C and a pressure of 1.1 bar for 3.5 h to obtain an esterification product;

[0162] (2) Transfer the esterification product obtained in step (1) to a vertical reactor equipped with a stirrer. Add 0.92 kg of tetrabutyl titanate and carry out a prepolymerization reaction at a temperature of 245 °C and a pressure of 0.52 bar for 120 min to obtain a prepolymer product;

[0163] (3) Transfer the prepolymer product obtained in step (2) to a horizontal reactor equipped with a stirrer. Carry out a polycondensation reaction at a temperature of 246 °C and a pressure of 1.3 mbar for 90 min to obtain an aliphatic polyester.

[0164] Comparative Example 2

[0165] Provide a method for preparing the aliphatic polyester, which specifically includes the following steps:

[0166] (1) Physically mix 250 kg of succinic acid, 345 kg of sebacic acid, 480 kg of 1,4-butanediol and 2.46 kg of glycerol. After mixing is completed, transfer the mixture to an esterification reactor and carry out an esterification reaction at a temperature of 190 °C and a pressure of 1.1 bar for 4 h to obtain an esterification product;

[0167] (2) Transfer the esterification product obtained in step (1) to a vertical reactor with stirring, add 0.92 kg of tetrabutyl titanate, and carry out a prepolymerization reaction at a temperature of 243 °C and a pressure of 0.52 bar for 130 min to obtain a prepolymer product;

[0168] (3) Transfer the prepolycondensation product obtained in step (2) to a horizontal reactor with stirring, and carry out a polycondensation reaction at a temperature of 246 °C and a pressure of 1.2 mbar for 80 min to obtain an aliphatic polyester.

[0169] Application Examples 1-13, Comparative Application Examples 1, 2

[0170] Application Examples 1-13, Comparative Application Examples 1, 2 respectively provide a polyester composition. By weight, the polyester composition comprises 63 parts of aliphatic polyester, 2 parts of polylactic acid, 27 parts of starch, 4 parts of glycerol, 3 parts of water and 1 part of other additives (0.5 part of a compound antioxidant composed of antioxidant 1010 and antioxidant 168 with a mass ratio of 1:1 and 0.5 part of lubricant ethylene bisstearamide); the aliphatic polyesters are respectively provided by Examples 1-13 and Comparative Examples 1-2; the preparation method of the polyester composition includes: according to the formula amount, mix each component and add it to a twin-screw extruder (length-diameter ratio is 48:1; diameter is 40 mm), carry out melt mixing, and extrude and pelletize; the extrusion temperatures are successively: zone 1 at 120 °C, zone 2 at 160 °C, zones 3 to 9 at 180 °C, zone 10 at 170 °C, zone 11 at 170 °C, die head at 190 °C, screw speed 380 rpm, vacuum -0.60 kg / cm 2 , to obtain the polyester composition.

[0171] Performance testing

[0172] Carry out blown film processing on the polyester compositions provided by Application Examples 1-13 and Comparative Application Examples 1-2 to obtain packaging films; test the tear resistance uniformity, disintegration period and tensile strength of the packaging films; the specific test results are shown in Table 2.

[0173] Among them, the process parameters of the blown film processing are: the screw length-diameter ratio is 32:1, use a spiral flow channel die head, the air ring is a double-port air ring, the set value of the blown film processing temperature is 140 °C, the blow-up ratio is 3.5, the blown film thickness is 55 ± 3 μm, and then test the tear resistance uniformity, disintegration period and tensile strength.

[0174] (1) Tear resistance uniformity: At 25 ± 5 °C and 55 ± 5% humidity, according to the ASTM D1922-2015 standard, test the Elmendorf tear strength of the sample in the transverse direction (ε TD ) and longitudinal direction (ε MD ), and calculate the degree of orientation; degree of orientation = ε MD / εTD 。

[0175] (2) Disintegration period:

[0176] Weigh the sample. The aliphatic polyester is molded into a product with dimensions of 10 cm × 10 cm to obtain the initial mass of the sample, denoted as m 0 , conduct a home composting test according to standard AS5810. Take samples once a week, perform sieving, retain the packaging film with a length × width greater than or equal to 2 cm × 2 cm remaining on the sieve, wash the residue on the packaging film, dry it and then weigh it, record the sample mass, denoted as m n , when the biodegradation rate of the sample [(m 0 -m n) / m 0 ≥ 90%, record the corresponding disintegration period n.

[0177] (3) Tensile strength: Test according to ISO 527-2:2012.

[0178] Table 2

[0179]

[0180] As can be seen from Table 2, for the aliphatic polyester provided by the present invention, by controlling the molar contents of succinic acid and sebacic acid within a specific range, the aliphatic polyester has excellent uniformity in terms of longitudinal and transverse tear properties, and the degree of orientation is close to 1; at the same time, it also has good tensile properties and under home composting conditions, has a high biodegradation rate, a short disintegration period, and meets the requirements of home composting.

[0181] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An aliphatic polyester, characterized in that The aliphatic polyester comprises a dibasic acid residue and a diol residue: The dibasic acid residues include the following residues: a1) 61.2 to 69 mol % of succinic acid residues, based on the total molar percentage of a1) and a2) being 100 mol %; a2) 31 to 38.8 mol % of sebacic acid residues, based on the total molar percentage of a1) and a2) being 100 mol %; The diol residues are selected from 1,4-butanediol residues in at least an equimolar amount to the dibasic acid residues.

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

3. The aliphatic polyester according to claim 1 or 2, characterized in that The number average molecular weight of the aliphatic polyester is 30,000 to 150,000, preferably 45,000 to 120,000, and more preferably 58,000 to 79,000.

4. The aliphatic polyester according to any one of claims 1 to 3, characterized in that According to GB / T32366-2015, the carboxyl content of the aliphatic polyester is less than 35 mol / t, preferably less than 28 mol / t, and more preferably 5 to 20 mol / t.

5. The aliphatic polyester according to any one of claims 1 to 4, characterized in that According to GB / T17931-1999, the intrinsic viscosity of the aliphatic polyester is 1.38 to 2.32 dL / g, preferably 1.5 to 2.2 dL / g.

6. A polyester composition, characterized in that The polyester composition comprises polymer A and polymer B; the 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 polymer A also includes a second polyester; Preferably, the second polyester comprises at least one of polylactic acid, aliphatic-aromatic polyester or other aliphatic polyester; Preferably, the aliphatic-aromatic polyester comprises at least one of polybutylene terephthalate succinate, polybutylene terephthalate adipate, polybutylene terephthalate sebacate or polybutylene furandicarboxylate adipate; Preferably, the other aliphatic polyester comprises at least one of polybutylene succinate, polybutylene succinate adipate or polybutylene sebacate; Preferably, the polymer B comprises at least one of starch, cellulose, chitin, chitosan, alginate, protein, gelatin, natural rubber, lignin or derivatives thereof; Preferably, the polyester composition further comprises an auxiliary agent.

8. The polyester composition according to claim 6 or 7, characterized in that In parts by weight, the polyester composition comprises 50 to 95 parts of aliphatic polyester, 1 to 20 parts of second polyester, 1 to 30 parts of polymer B and 0 to 15 parts of auxiliary agent.

9. A packaging film, characterized in that: The packaging film comprises the aliphatic polyester according to any one of claims 1 to 5 or the polyester composition according to any one of claims 6 to 8.

10. The packaging film according to claim 9, characterized in that: The packaging film has an orientation degree of 0.7 to 1.6, more preferably 0.8 to 1.4, and even more preferably 0.9 to 1.2.

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