Biodegradable aliphatic polyester, and preparation method therefor and use thereof

Abstract

A biodegradable aliphatic polyester, and a preparation method therefor and a use thereof. The biodegradable aliphatic polyester contains units derived from at least one aliphatic dicarboxylic acid and at least one aliphatic diol, and satisfies the following conditions: 1.54≤Mw / Mn≤1.98, and Mw / q≥50,000, wherein q is the mass percentage of a low-molecular polymer with the molecular weight of less than or equal to 1,000 Dalton, which is measured by GPC, of the biodegradable aliphatic polyester. By regulating and controlling the molecular weight distribution of the biodegradable aliphatic polyester and the mass percentage of the low-molecular polymer with the molecular weight lower than 1,000 Dalton, the biodegradable aliphatic polyester has good barrier properties and excellent self-adhesiveness.

Description

A biodegradable aliphatic polyester and its preparation method and application Technical Field

[0001] The present invention relates to the technical field of polymer compounds, and more particularly to a biodegradable aliphatic polyester and a preparation method and application thereof. Background Art

[0002] Cling film is a thin plastic packaging product that not only prolongs the storage time of food in the refrigerator but also retains moisture to maintain its freshness. When used for individually wrapped food, it effectively prevents odor transfer between foods. More importantly, when used on opened beverages, fruits, or tableware, it can isolate bacteria, improving hygiene and safety. Therefore, cling film is widely used in household use, supermarkets, and industrial food packaging. However, traditional cling film is mostly made of polyethylene film, biaxially oriented polyester (BOPET), BOPP film, or CPP film. These cling films are non-biodegradable and easily lead to "white pollution" problems after being discarded.

[0003] To alleviate the environmental issues associated with discarded traditional cling film, biodegradable polyester polybutylene terephthalate-co-polybutylene adipate (PBAT) has been used to replace these traditional film materials to improve their degradability. PBAT combines the degradability of aliphatic polyesters with the mechanical properties of aromatic polyesters, offering good ductility and elongation at break. However, cling film made from biodegradable PBAT has poor barrier properties, which can lead to food that requires extended storage becoming perishable during storage, limiting its long-term freshness-preserving properties. Furthermore, cling film must possess good self-adhesive properties to better meet user requirements.

[0004] Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects and shortcomings of the existing biodegradable polyester PBAT, such as poor barrier properties and self-adhesion, and to provide a biodegradable aliphatic polyester.

[0006] Another object of the present invention is to provide a method for preparing biodegradable aliphatic polyester.

[0007] Another object of the present invention is to provide the use of the above-mentioned biodegradable aliphatic polyester in the preparation of food packaging films, industrial packaging films or agricultural mulch films.

[0008] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0009] The present invention protects a biodegradable aliphatic polyester comprising units derived from at least one aliphatic dicarboxylic acid and at least one aliphatic diol and satisfying the following conditions: 1.54≤Mw / Mn≤1.98, Mw / q≥50000;

[0010] Wherein, q is the mass percentage of low molecular weight polymers with a molecular weight of ≤1000 Dalton in the biodegradable aliphatic polyester determined by GPC.

[0011] Preferably, the Mw / Mn is 1.65 to 1.85, and 70000≤Mw / q≤110000.

[0012] The molecular weight and molecular weight distribution (Mw / Mn) of the polymer, as well as the type and content of oligomers are affected by many factors, such as the type of monomer, the ratio of monomers, the type and amount of branching agents and chain extenders added, the branching structure, the polymerization process (continuous or batch process), the reaction temperature, the reaction time and the reaction pressure.

[0013] The number average molecular weight (Mn) of the biodegradable aliphatic polyester of the present invention is 45,000 to 85,000, specifically 45,000, 50,000, 55,000, 60,000, 65,000, 70,000 or 80,000; the weight average molecular weight (Mw) is 87,000 to 132,000, specifically 90,000, 95,000, 100,000, 105,000, 110,000, 115,000, 120,000, 125,000 or 130,000; and the mass percentage (q) of low molecular weight polymers with a molecular weight of ≤1,000 Dalton is less than 1.93%, specifically 1.11%, 1.35%, 1.38%, 1.55%, 1.67%, 1.72% or 1.91%.

[0014] Optionally, the unit derived from an aliphatic dicarboxylic acid is an aliphatic dicarboxylic acid and its esters having 2 to 22 carbon atoms in the main chain. Specifically, the aliphatic dicarboxylic acid is at least one of succinic acid, adipic acid, azelaic acid, sebacic acid, or tridecanedioic acid; preferably succinic acid and / or adipic acid.

[0015] Optionally, the unit derived from an aliphatic diol is an aliphatic diol having 2 to 13 carbon atoms in the main chain. Specifically, the aliphatic diol is at least one of 1,2-ethanediol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, or 1,13-tridecanediol; preferably 1,4-butanediol and / or 1,3-propylene glycol.

[0016] Specifically, the biodegradable aliphatic polyester comprises the following components:

[0017] A) Aliphatic dicarboxylic acid component:

[0018] a1) 65 to 100 mol % of a derivative of succinic acid or its ester, or a mixture thereof, based on the total amount of a1) and a2);

[0019] a2) 0 to 35 mol% of a derivative of adipic acid or its ester, or a mixture thereof, based on the total amount of a1) and a2), wherein the total molar percentages of components a1) and a2) is 100 mol%;

[0020] B) The aliphatic diol component is 1,4-butanediol, and the molar ratio of the aliphatic diol component to the aliphatic dicarboxylic acid component is ≥1.

[0021] Preferably, a1) in the aliphatic dicarboxylic acid component is 73-80 mol% of succinic acid or its ester derivatives, or a mixture thereof; a2) in the aliphatic dicarboxylic acid component is 20-27 mol% of adipic acid or its ester derivatives, or a mixture thereof.

[0022] The water vapor transmission rate of the biodegradable aliphatic polyester is measured according to ASTM F1249-13 standard at a sample thickness of 12±2 μm, 40°C and RH=60%, and is ≤750 g / (d·m 2 ), preferably, the water vapor transmission rate is ≤480g / (d·m 2 ); More preferably, the water vapor transmission rate is ≤330g / (d·m 2 ).

[0023] The biodegradable aliphatic polyester has good self-adhesiveness, which is characterized by shear peel strength. The higher the shear peel strength, the better the self-adhesiveness of the film. According to GB / T 10457-2009 standard, the biodegradable aliphatic polyester has a shear peel strength of ≥0.60N / cm under the condition of a sample thickness of 12±2μm. 2 ; Preferably, shear peel strength ≥ 0.72N / cm 2 More preferably, the shear peel strength is ≥ 0.85N / cm 2 .

[0024] The present invention also protects a method for preparing the above-mentioned biodegradable aliphatic polyester, comprising the following steps:

[0025] Step i): mixing an aliphatic dicarboxylic acid or a derivative thereof (component A) and an aliphatic diol (component B) and performing an esterification reaction or an ester exchange reaction to obtain an esterified product;

[0026] Step ii): subjecting the esterification product in step i) to a pre-condensation reaction to obtain a pre-polymerized product;

[0027] Step iii): subjecting the prepolymerized product in step ii) to a polycondensation reaction until the acid value of the formed polycondensation product measured according to GB / T 32366-2015 standard is 15 to 50 mol / t, thereby obtaining a biodegradable aliphatic polyester;

[0028] The acid value of the esterification product in step i) measured according to GB / T 32366-2015 is 360 to 770 mol / t; the acid value of the prepolymerization product in step ii) measured according to GB / T 32366-2015 is 70 to 110 mol / t.

[0029] The above-mentioned aliphatic dicarboxylic acids or their derivatives can be used alone or as a mixture of two or more. In the present invention, in step i), the molar ratio of component A to component B is 1:(1.2-2.4), wherein the specific values ​​of 1.2-2.4 can be 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, etc.; more preferably, it is 1:(1.4-1.8).

[0030] In step i), when two or more aliphatic dicarboxylic acids or derivatives thereof are present, in addition to the method of blending all aliphatic dicarboxylic acids or derivatives thereof with aliphatic diol (component B) for mixed esterification as described in step i), individual aliphatic dicarboxylic acids or derivatives thereof may also be independently esterified with aliphatic diol (component B), for example, the aliphatic dicarboxylic acid component a1) is subjected to an esterification reaction with the aliphatic diol (component B), and the aliphatic dicarboxylic acid component a2) is subjected to an esterification reaction with the aliphatic diol (component B), and then the esterified products of the two are mixed.

[0031] When using a separate esterification process, the molar ratio of component a1 to component B is 1:(1.1-1.8), specifically 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, or 1:1.7; the molar ratio of component a2 to component B is 1:(1.3-2.0), specifically 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, or 1:1.9. The esterification reaction temperature is 150-200°C, preferably 180-195°C; the pressure is 0.7-1.1 bar, preferably 0.8-1.0 bar, and the reaction time is 2-4 hours. Under the separate esterification conditions, the acid value of the esterified product corresponding to each esterification reaction is 360-770 mol / t, as measured according to GB / T 32366-2015.

[0032] Specifically, the above preparation method comprises the following steps:

[0033] In step i), after the aliphatic dicarboxylic acid or its derivative is mixed with the aliphatic diol, a catalyst may or may not be added. When the catalyst is added, it may be added all at once or in multiple additions. The total mass of the catalyst is 0.001 to 1 wt% of the mass of the aliphatic polyester, for example, 0.001 wt%, 0.002 wt%, 0.005 wt%, 0.008 wt%, 0.01 wt%, 0.02 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, etc.; preferably, it is 0.03 to 0.2 wt%.

[0034] These catalysts typically include zinc compounds, aluminum compounds, and titanium compounds. Titanium compounds, in particular, have an advantage over tin, antimony, cobalt, and lead compounds commonly used in the literature. Titanium catalysts (such as tetrabutyl titanate or tetraisopropyl titanate) have the potential to reduce residual toxicity in the final product or downstream products. This toxicity is particularly important in biodegradable polyesters, as these compounds can enter the environment directly through compost bags or mulch films.

[0035] In step i), based on the total weight of the aliphatic dicarboxylic acid or its derivative and the aliphatic diol, 0 to 3 wt% of a cross-linking agent having at least three functional groups may be further included; preferably 0.01 to 2 wt%, more preferably 0.05 to 1 wt%, and particularly preferably 0.08 to 0.20 wt%.

[0036] The cross-linking agent having at least three functional groups is a compound having 3 to 6 hydroxyl groups. Specifically, it can be at least one of tartaric acid, citric acid, malic acid, trimethylolpropane, trimethylolethane, pentaerythritol, polyether triol, glycerol, trimellitic acid, trimellitic acid, trimellitic anhydride, pyromellitic acid, or pyromellitic dianhydride. It is preferably a polyol such as trimethylolpropane, pentaerythritol, or glycerol, and is particularly preferably glycerol.

[0037] After mixing an aliphatic dicarboxylic acid or its derivative with an aliphatic diol, the temperature is then increased. In step i), the reaction system temperature is set to 150-200°C, preferably 165-190°C, and the pressure is set to 0.7-1.1 bar, preferably 0.8-1.0 bar. Step i) can be carried out in a mixing apparatus, with a specific reaction time of 2-4 hours. An esterified product having an acid value of 360-770 mol / t as determined in accordance with GB / T 32366-2015 can be produced.

[0038] The excess diol component in step i) is generally removed by distillation and returned to the loop after distillation purification. The purity of the diol component after distillation purification is ≥95%.

[0039] In step ii), the esterification product from step i) (along with the remaining catalyst if the catalyst was added in multiple portions) is added to a reactor suitable for a precondensation reaction. Suitable reactors for the precondensation reaction include tube bundle reactors, cascade reactors, or bubble columns, particularly downflow cascade reactors, which may be equipped with a degassing unit if appropriate. The reaction temperature is typically set at 230-260°C, preferably 235-245°C; the reaction pressure is typically set at 0.3-0.6 bar, preferably 0.35-0.55 bar; and the reaction time is 70-200 minutes. A prepolymer product having an acid value of 70-110 mol / t, as measured according to GB / T 32366-2015, can be produced. Preferably, the acid value of the prepolymer product is controlled within the range of 82-100 mol / t.

[0040] In the polycondensation step iii), a catalyst deactivator may be mixed with the prepolymer product, depending on actual conditions and needs. Specifically, the deactivator is a phosphorus compound, an organic phosphite (such as phosphorous acid), or phosphoric acid. For example, if a highly active titanium catalyst is used, a deactivator may be added. Based on the amount of polymer after step iii), the deactivator may be added in an amount of 0.001 to 0.1 wt%, preferably 0.01 to 0.05 wt%. The molar ratio of Ti to P is preferably (1.1 to 1.5):1, and particularly preferably (1.1 to 1.3):1.

[0041] Furthermore, depending on actual circumstances and needs, a color stabilizer for the condensation process can be mixed with the prepolymerized product in the polycondensation step iii). Suitable color stabilizers are primarily phosphorus compounds, specifically at least one of phosphoric acid, phosphorous acid, triphenyl phosphite, triphenyl phosphate, sodium hypophosphite, or sodium phosphite. While the use of general color stabilizers typically reduces the condensation rate, triphenyl phosphate is a particularly suitable color stabilizer because it has little adverse effect on the condensation rate.

[0042] The color stabilizer may be added in an amount of 0.001 to 1.5 wt %, preferably 0.01 to 1.0 wt %, based on the amount of polymer after step iii). Preferably, the molar ratio of Ti / P is 1.0:(0.3 to 1.0); more preferably 1.0:(0.5 to 1.0).

[0043] Furthermore, depending on actual conditions and needs, an activator for the condensation process can be mixed with the prepolymerized product in the polycondensation step iii). Optionally, the activator is a phosphorus compound; specifically, it can be at least one of disodium hydrogen phosphate, calcium hypophosphite, calcium phosphite, calcium phosphate, sodium hypophosphite, sodium phosphite, triphenyl phosphite, triphenyl phosphate, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, or tributyl phosphate. Preferably, the activator is disodium hydrogen phosphate and / or sodium phosphite.

[0044] Specifically, based on the amount of polymer after step iii), the amount of the activator added may be 0.001 to 1.5 wt%, preferably 0.01 to 1.0 wt%. Preferably, the molar ratio of Ti / P is (1.0 to 1.5):1; more preferably, the molar ratio of Ti / P is (1.1 to 1.3):1.

[0045] Color stabilizers can also be used in combination with activators, such as using the color stabilizer triphenyl phosphate in combination with the activator disodium hydrogen phosphate.

[0046] The reactor for the polycondensation reaction in step iii) can be a rotary disc reactor or a cage reactor. The reaction temperature is generally 235 to 260° C., preferably 240 to 255° C.; the pressure is generally 0.2 to 5 mbar, preferably 0.5 to 3 mbar; the reaction time is 45 to 110 minutes, preferably 60 to 90 minutes, and a polycondensation product having an acid value of 15 to 50 mol / t as measured according to GB / T 32366-2015 can be produced.

[0047] Specifically, the polycondensation product in step iii) can be added together with a chain extender into an extruder (a continuous kneader (List reactor) or a static mixer) to cause a chain extension reaction.

[0048] Specifically, the static mixer can use an SMR, SMX, or SMXL component, or a combination thereof. The List reactor can be a single-screw DISCOTHERM B or a twin-screw CRP or ORP reactor. The extruder can be a single-screw extruder or a twin-screw extruder. Preferably, the chain extension reaction is carried out in the extruder. After chain extension, the resulting polyester has an acid number of 15 to 50 mol / t as measured according to GB / T 32366-2015.

[0049] Optionally, the chain extender includes at least one of isocyanate, peroxide, epoxide, oxazoline, oxazine, caprolactam or carbodiimide.

[0050] Specifically, the isocyanate may be an aromatic diisocyanate or an aliphatic diisocyanate; for example, the aromatic diisocyanate may be at least one of 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, preferably diphenylmethane 2,2'-diisocyanate, diphenylmethane 2,4'-diisocyanate, or diphenylmethane 4,4'-diisocyanate.

[0051] Isocyanates that can also be used in the present invention include tris(4-isocyanato-phenyl)methane having three rings. This polynuclear aromatic diisocyanate can be formed during the production of diisocyanates having one or two rings.

[0052] For the purposes of the present invention, the aliphatic diisocyanate may be any linear or branched alkylene diisocyanate or cycloalkylene diisocyanate containing 2 to 20 carbon atoms, preferably 3 to 12 carbon atoms. For example, it may be hexamethylene diisocyanate, pentamethylene diisocyanate, isophorone diisocyanate, or methylene di(4-isocyanatocyclohexane) diisocyanate; preferably, hexamethylene diisocyanate.

[0053] Based on the total weight of the biodegradable aliphatic polyester, the amount of isocyanate used may be 0.05 to 2 wt%, preferably 0.1 to 1.5 wt%.

[0054] Specifically, the above-mentioned peroxide can be at least one of benzoyl peroxide, 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(tert-butylperoxy)methylcyclododecane, 4,4-di(butylperoxy)butyl 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-butylperoxide cumene.

[0055] Based on the total weight of the biodegradable aliphatic polyester, the amount of peroxide used may be 0.1 to 2 wt%, preferably 0.2 to 1 wt%.

[0056] Specifically, the above-mentioned epoxide can 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, polybutylene glycol diglycidyl ether, or a copolymer containing an epoxy group based on styrene, acrylate and / or methacrylate.

[0057] Based on the total weight of the biodegradable aliphatic polyester, the amount of epoxide used may be 0.1 to 2 wt%, preferably 0.2 to 1 wt%.

[0058] Specifically, the above-mentioned dioxazoline can be at least one of 2,2′-di(2-oxazoline), di(2-oxazolinyl)methane, 1,2-di(2-oxazolinyl)ethane, 1,3-di(2-oxazolinyl)propane or 1,4-di(2-oxazolinyl)butane; preferably at least one of 1,4-di(2-oxazolinyl)benzene, 1,2-di(2-oxazolinyl)benzene or 1,3-di(2-oxazolinyl)benzene.

[0059] Specifically, the above-mentioned dioxazine can be 2,2′-di(2-dioxazine), di(2-dioxazinyl)methane, 1,2-di(2-dioxazinyl)ethane, 1,3-di(2-dioxazinyl)propane or 1,4-di(2-dioxazinyl)butane; in particular, at least one of 1,4-di(2-dioxazinyl)benzene, 1,2-di(2-dioxazinyl)benzene or 1,3-di(2-dioxazinyl)benzene.

[0060] Specifically, the above-mentioned carbodiimide can be 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.

[0061] Based on the total weight of the biodegradable aliphatic polyester, the amount of oxazoline, oxazine, caprolactam or carbodiimide can be 0.1 to 2 wt%, preferably 0.2 to 1 wt%.

[0062] The chain growth reaction is carried out under superatmospheric pressure or atmospheric pressure, with a reaction temperature of 170 to 240° C., preferably 180 to 240° C.; and a reaction time of 2 to 15 minutes, preferably 4 to 10 minutes.

[0063] The biodegradable aliphatic polyester prepared according to the preparation method has a melt flow rate (MFR) of 1.0 to 40.0 g / 10 min, preferably 2.5 to 32.0 g / 10 min, and particularly preferably 3.5 to 22.0 g / 10 min, according to ISO 1133-2-2011 (190° C., 2.16 kg).

[0064] The present invention also protects a biodegradable aliphatic polyester mixture, which contains the above-mentioned biodegradable aliphatic polyester; based on the total weight of the biodegradable aliphatic polyester mixture, the weight content of the biodegradable aliphatic polyester is 50 to 95 wt%, preferably 65 to 90 wt%.

[0065] In addition, the biodegradable aliphatic polyester mixture may further comprise at least one polymer derived from a synthetic or natural source. The polymer derived from a synthetic source may specifically be at least one of polylactic acid (PLA), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polybutylene succinate sebacate (PBSSe), polybutylene sebacate (PBSe), polybutylene terephthalate succinate (PBST), polybutylene terephthalate adipate (PBAT), polybutylene terephthalate sebacate (PBSeT), or polybutylene furandicarboxylate adipate (PBAF). Based on the total weight of the biodegradable aliphatic polyester mixture, the weight content of the polymer derived from a synthetic source is 1 to 20 wt%, preferably 4 to 10 wt%.

[0066] The polymer from natural sources can specifically be at least one of starch, cellulose, chitin, chitosan, alginate, protein (such as gluten, zein or casein), collagen, gelatin, natural rubber, rosin acid and its derivatives or lignin and its derivatives. Preferably, starch or a mixture of starch and other natural polymers. Starch can be used in a modified and gelatinized form or as a filler. The starch can be distributed in a continuous phase, a dispersed phase or in a co-continuous form. Based on the total weight of the biodegradable aliphatic polyester mixture, the mass content of the polymer from natural sources is 1 to 25 wt%, preferably 2 to 10 wt%.

[0067] Specifically, the above-mentioned biodegradable aliphatic polyester or biodegradable aliphatic polyester mixture can be prepared by a reactive extrusion method. The extruder used in the reactive extrusion method can be a single-screw extruder, a twin-screw extruder or a multi-screw extruder, the extrusion temperature is 140-220° C., and the screw speed is 200-500 rpm.

[0068] The use of the above-mentioned biodegradable aliphatic polyester or biodegradable aliphatic polyester mixture in the preparation of food packaging film, industrial packaging film or agricultural mulch film also falls within the scope of protection of the present invention.

[0069] For the purposes of the present invention, a substance or a mixture of substances is characterized as "biodegradable" if it shows a percentage degree of biodegradation as defined in DIN EN 13432 of at least 90%.

[0070] According to DIN EN 13432, during the composting process, CO₂-free air is introduced into the mature compost and the compost is subjected to a specific temperature profile. Biodegradability is defined as the percentage of biodegradation expressed as the ratio of the net amount of CO₂ released by the sample (after subtracting the amount of CO₂ released by the compost without the sample) to the maximum amount of CO₂ that the sample could release (calculated from the carbon content of the sample). Biodegradable polyesters and biodegradable polyester blends often show clear signs of degradation, such as fungal growth, cracking, and perforation, after only a few days of composting. Other methods for determining biodegradability are described, for example, in ASTM D5338 and ASTM D6400.

[0071] Compared with the prior art, the present invention has the following beneficial effects:

[0072] The present invention regulates the molecular weight distribution of the biodegradable aliphatic polyester and the mass percentage of low-molecular polymers with a molecular weight of less than 1000 Dalton, so that the biodegradable aliphatic polyester has both low water vapor permeability and high self-adhesion, thereby giving the film material good barrier properties and excellent self-adhesion. DETAILED DESCRIPTION

[0073] The present invention will be further described below in conjunction with specific embodiments, but the examples do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the examples of the present invention are conventionally purchased raw materials and reagents.

[0074] 1. The molecular weight Mw and Mn of biodegradable aliphatic polyesters were determined by gel permeation chromatography (GPC).

[0075] A chromatography system can be used at 40 ° C with a set of three columns in series (particle diameter 5 μm and porosity and ), were measured using a refractive index detector, chloroform as the eluent (flow rate 1 mL / min) and polystyrene as the reference standard.

[0076] 2. Test of the mass percentage q of low molecular weight polymers ≤1000 Dalton measured by GPC

[0077] The determination method is as follows: a sample (F1) of polyester (approximately 3 to 4 g) is placed in a 200 mL flask along with 30 mL of chloroform. After the polyester is completely dissolved, 100 mL of a 1:1 (v / v) mixed solution of methanol and acetone is added and the mixture is kept under stirring for 2 hours. The mixture is then filtered through a paper filter with a pore size of 8 μm, the polymer remaining on the filter is rinsed with acetone, and the methanol / acetone solution is heated under an air flow at 70°C to completely evaporate the methanol / acetone solution and record the weight of the residual solid component (F2). A sample of the solid component (approximately 10 mg) is dissolved in 10 mL of chloroform and analyzed by GPC according to the above disclosed method. The mass percentage (P1) of low molecular weight polymers with a molecular weight of ≤1000 Dalton is determined based on the molecular weight distribution curve recorded by the GPC instrument. The mass percentage q of polyester oligomers having a molecular weight ≤ 1000 Dalton is calculated according to the following equation: (P1*F2) / F1*100%; the above-mentioned determination of Mn, Mw and q can be carried out on polyester pellets or on films obtained therefrom.

[0078] 3. Water vapor transmission rate test is carried out in accordance with the standard ASTM F1249-13

[0079] Films with a thickness of 12 ± 2 μm were prepared using a film blowing machine with a screw diameter of 40 mm, a film blowing temperature of 120-160° C., a die gap of 1 mm, a flow rate of 25 ± 0.5 kg / h, and a blow-up ratio of 3.0. The water vapor transmission rates of the sample films were measured according to ASTM F-1249.

[0080] 4. Shear peel strength test is carried out in accordance with the standard GB / T 10457-2009

[0081] Cut 10 specimens, each 50mm long and 25mm wide, into groups of two. Place the specimens so that their adhesive surfaces face each other in the longitudinal direction, overlapping end to end. The overlap is 15mm long and 25mm wide. Lay the specimens flat on a smooth surface. Use a rubber roller (40mm diameter, 100mm length, 300g mass) to roll back and forth three times across the overlap, ensuring that no air remains between the two layers of plastic wrap at the overlap. Place the prepared specimens under experimental conditions for 20 minutes before testing.

[0082] Each set of specimens was stretched on a tensile testing machine, and the force required to separate the two specimens was measured. The results were taken as the arithmetic average of the five sets of specimens. The tensile speed used in the test was 250 mm / min ± 50 mm / min.

[0083] Example 1

[0084] A biodegradable aliphatic polyester is prepared by the following preparation method:

[0085] Step i) Physically mixing 350 kg of succinic acid, 143 kg of adipic acid, 500 kg of 1,4-butanediol, and 0.35 kg of glycerol, the mixture was transferred to an esterification reactor. The reaction mixture was esterified at 200°C and 1.1 bar for 3 hours, resulting in an esterified product with an acid value of 438 mol / t.

[0086] Step ii). The esterification product obtained in step i) was transferred to a stirred vertical reactor, 0.32 kg of tetrabutyl titanate was added, and the reaction mixture was pre-polycondensed at 250 ° C and a pressure of 0.60 bar in the reactor for 110 minutes. The acid value of the obtained prepolymer product was 101 mol / t;

[0087] Step iii). The prepolymer obtained in step ii) was transferred to a stirred horizontal reactor and subjected to polycondensation at 245° C. and a pressure of 2.3 mbar for 80 minutes. The resulting biodegradable aliphatic polyester had an acid value of 22.8 mol / t and a melt index of 4.1 g / 10 min (test standard and conditions were ISO 1133-2-2011, 190° C., 2.16 kg).

[0088] Example 2

[0089] A biodegradable aliphatic polyester is prepared by the following preparation method:

[0090] Step i) Physically mixing 350 kg of succinic acid, 143 kg of adipic acid, 650 kg of 1,4-butanediol, and 0.85 kg of glycerol, the mixture was transferred to an esterification reactor. The reaction mixture was esterified at 190°C and 1.0 bar for 4 hours, resulting in an esterified product with an acid value of 382 mol / t.

[0091] Step ii). The esterification product obtained in step i) was transferred to a stirred vertical reactor, 0.40 kg of tetrabutyl titanate was added, and the reaction mixture was pre-polycondensed at 250 ° C and a pressure of 0.45 bar in the reactor for 150 minutes. The acid value of the prepolymer product was 78 mol / t;

[0092] Step iii). The prepolymer obtained in step ii) was transferred to a stirred horizontal reactor and subjected to polycondensation at 245° C. and a pressure of 1.6 mbar for 60 minutes. The resulting biodegradable aliphatic polyester had an acid value of 26.3 mol / t and a melt index of 5.4 g / 10 min (test standard and conditions were ISO 1133-2-2011, 190° C., 2.16 kg).

[0093] Example 3

[0094] A biodegradable aliphatic polyester is prepared by the following preparation method:

[0095] Step i) Physically mixing 350 kg of succinic acid, 143 kg of adipic acid, 550 kg of 1,4-butanediol, and 1.2 kg of glycerol, the mixture was transferred to an esterification reactor. The reaction mixture was esterified at 180°C and 0.95 bar for 2.5 hours, resulting in an esterified product having an acid value of 501 mol / t.

[0096] Step ii). The esterification product obtained in step i) was transferred to a stirred vertical reactor, 0.42 kg of tetrabutyl titanate was added, and the reaction mixture was pre-polycondensed at 243 ° C and a pressure of 0.35 bar in the reactor for 90 minutes. The acid value of the prepolymer product was 84 mol / t;

[0097] Step iii). The prepolymer obtained in step ii) was transferred to a stirred horizontal reactor and subjected to polycondensation at 243° C. and a pressure of 1.3 mbar for 70 minutes. The resulting biodegradable aliphatic polyester had an acid value of 20.5 mol / t and a melt index of 4.0 g / 10 min (test standard and conditions were ISO 1133-2-2011, 190° C., 2.16 kg).

[0098] Example 4

[0099] A biodegradable aliphatic polyester is prepared by the following preparation method:

[0100] Step i) Physically mixing 350 kg of succinic acid, 143 kg of adipic acid, 510 kg of 1,4-butanediol, and 1.0 kg of glycerol, the mixture was transferred to an esterification reactor. The reaction mixture was esterified at 170°C and 0.85 bar for 2.5 hours, resulting in an esterified product having an acid value of 570 mol / t.

[0101] Step ii). The esterification product obtained in step i) was transferred to a stirred vertical reactor, 0.38 kg of tetrabutyl titanate was added, and the reaction mixture was pre-polycondensed at 242 ° C and a pressure of 0.40 bar in the reactor for 110 minutes. The acid value of the obtained prepolymer product was 95 mol / t;

[0102] Step iii). The prepolymer obtained in step ii) was transferred to a stirred horizontal reactor and subjected to polycondensation at 248° C. and a pressure of 1.4 mbar for 65 minutes. The resulting biodegradable aliphatic polyester had an acid value of 21.4 mol / t and a melt index of 9.8 g / 10 min (test standard and conditions were ISO 1133-2-2011, 190° C., 2.16 kg).

[0103] Example 5

[0104] A biodegradable aliphatic polyester is prepared by the following preparation method:

[0105] Step i) Physically mixing 215 kg of succinic acid, 143 kg of adipic acid, 480 kg of 1,4-butanediol, and 1.2 kg of glycerol, the mixture was transferred to an esterification reactor. The reaction mixture was esterified at 180°C and 1.10 bar for 4 hours, resulting in an esterified product with an acid value of 361 mol / t.

[0106] Step ii). The esterification product obtained in step i) was transferred to a stirred vertical reactor, 0.35 kg of tetrabutyl titanate was added, and the reaction mixture was pre-polycondensed at 248 ° C and a pressure of 0.58 bar in the reactor for 145 minutes. The acid value of the obtained prepolymer product was 71 mol / t;

[0107] Step iii). The prepolymer obtained in step ii) was transferred to a stirred horizontal reactor and subjected to polycondensation at 255° C. and a pressure of 1.7 mbar for 100 minutes. The resulting biodegradable aliphatic polyester had an acid value of 28.9 mol / t and a melt index of 5.2 g / 10 min (test standard and conditions were ISO 1133-2-2011, 190° C., 2.16 kg).

[0108] Example 6

[0109] A biodegradable aliphatic polyester is prepared by the following preparation method:

[0110] Step i) Physically mixing 350 kg of succinic acid, 350 kg of 1,4-butanediol, and 1.8 kg of glycerol, and transferring the mixture to an esterification reactor. The reaction mixture was esterified at 160° C. and 0.70 bar for 2 hours, resulting in an esterified product having an acid value of 756 mol / t.

[0111] Step ii). The esterification product obtained in step i) was transferred to a stirred vertical reactor, 0.40 kg of tetrabutyl titanate was added, and the reaction mixture was pre-polycondensed at 250 ° C and a pressure of 0.30 bar in the reactor for 85 minutes. The acid value of the prepolymer product was 110 mol / t;

[0112] Step iii). The prepolymer obtained in step ii) was transferred to a stirred horizontal reactor and subjected to polycondensation at 256° C. and a pressure of 2.5 mbar for 110 minutes. The resulting biodegradable aliphatic polyester had an acid value of 33.4 mol / t and a melt index of 12.3 g / 10 min (test standard and conditions were ISO 1133-2-2011, 190° C., 2.16 kg).

[0113] Example 7

[0114] A biodegradable aliphatic polyester is prepared by the following preparation method:

[0115] Step i-1): 350 kg of succinic acid, 330 kg of 1,4-butanediol, and 1.3 kg of glycerol were physically mixed and, after mixing, transferred to an esterification reactor. The reaction mixture was esterified at 180°C and 1.0 bar for 100 minutes, resulting in an esterified product with an acid value of 370 mol / t.

[0116] Step i-2): 143 kg of adipic acid and 150 kg of 1,4-butanediol were physically mixed and transferred to another esterification reactor. The reaction mixture was esterified at 195°C and 0.80 bar for 90 minutes, resulting in an esterified product with an acid value of 721 mol / t.

[0117] Step ii). The esterification products obtained in step i-1) and step i-2) were mixed and transferred to a stirred vertical reactor, 0.45 kg of tetrabutyl titanate was added, and the reaction mixture was pre-polycondensed at 245 ° C and a pressure of 0.40 bar in the reactor for 100 minutes. The acid value of the obtained prepolymer product was 86 mol / t;

[0118] Step iii). The prepolymer obtained in step ii) was transferred to a stirred horizontal reactor and polycondensed at 247°C and a pressure of 1.1 mbar for 45 minutes. The acid value of the polycondensation product was 15.8 mol / t.

[0119] In step iv), the polycondensation product obtained in step iii) is introduced into a static mixer, 1.8 kg of hexamethylene diisocyanate is added, and the mixture is mixed and reacted at 210° C. for 7 minutes. The resulting biodegradable aliphatic polyester has an acid value of 16.7 mol / t and a melt index of 4.0 g / 10 min (test standard and conditions are ISO 1133-2-2011, 190° C., 2.16 kg).

[0120] Comparative Example 1

[0121] A biodegradable aliphatic polyester is prepared by the following preparation method:

[0122] Step i) Physically mixing 350 kg of succinic acid, 143 kg of adipic acid, 900 kg of 1,4-butanediol, and 3.2 kg of glycerol, the mixture was transferred to an esterification reactor. The reaction mixture was esterified at 210°C and 0.65 bar for 3 hours, resulting in an esterified product with an acid value of 221 mol / t.

[0123] Step ii). The esterification product obtained in step i) was transferred to a stirred vertical reactor, 0.48 kg of tetrabutyl titanate was added, and the reaction mixture was pre-polycondensed at 250 ° C and a pressure of 0.20 bar in the reactor for 156 minutes. The acid value of the obtained prepolymer product was 41 mol / t;

[0124] Step iii). The prepolymer obtained in step ii) was transferred to a stirred horizontal reactor and subjected to polycondensation at 252° C. and a pressure of 1.2 mbar for 50 minutes. The resulting biodegradable aliphatic polyester had an acid value of 12.1 mol / t and a melt index of 3.0 g / 10 min (test standard and conditions were ISO 1133-2-2011, 190° C., 2.16 kg).

[0125] Comparative Example 2

[0126] A biodegradable aliphatic polyester is prepared by the following preparation method:

[0127] Step i) Physically mixing 350 kg of succinic acid, 143 kg of adipic acid, and 410 kg of 1,4-butanediol, and transferring the mixture to an esterification reactor. The reaction mixture was esterified at 160°C and 1.2 bar for 2 hours, resulting in an esterified product with an acid value of 841 mol / t.

[0128] Step ii). The esterification product obtained in step i) was transferred to a stirred vertical reactor, 0.44 kg of tetrabutyl titanate was added, and the reaction mixture was pre-polycondensed at 230 ° C and a pressure of 0.70 bar in the reactor for 120 minutes. The acid value of the obtained prepolymer product was 167 mol / t;

[0129] Step iii). The prepolymer obtained in step ii) was transferred to a stirred horizontal reactor and subjected to polycondensation at 245° C. and a pressure of 2.1 mbar for 90 minutes. The resulting biodegradable aliphatic polyester had an acid value of 58.2 mol / t and a melt index of 15.2 g / 10 min (test standard and conditions were ISO 1133-2-2011, 190° C., 2.16 kg).

[0130] Comparative Example 3

[0131] A biodegradable aliphatic polyester is prepared by the following preparation method:

[0132] Step i) Physically mixing 350 kg of succinic acid, 143 kg of adipic acid, 680 kg of 1,4-butanediol, and 1.8 kg of glycerol, the mixture was transferred to an esterification reactor. The reaction mixture was esterified at 210°C and 0.8 bar for 3 hours, resulting in an esterified product having an acid value of 327 mol / t.

[0133] Step ii). The esterification product obtained in step i) was transferred to a stirred vertical reactor, 0.28 kg of tetrabutyl titanate was added, and the reaction mixture was pre-polycondensed at 240 ° C and a pressure of 0.75 bar in the reactor for 80 minutes. The acid value of the obtained prepolymer product was 112 mol / t;

[0134] Step iii). The prepolymer obtained in step ii) was transferred to a stirred horizontal reactor and polycondensed at 250°C and a pressure of 1.4 mbar for 50 minutes. The acid value of the polycondensation product was 21.3 mol / t.

[0135] In step iv), the polycondensation product obtained in step iii) is introduced into a static mixer, 2.0 kg of hexamethylene diisocyanate is added, and the mixture is mixed and reacted at 220° C. for 10 minutes. The resulting biodegradable aliphatic polyester has an acid value of 23.1 mol / t and a melt index of 4.4 g / 10 min (test standard and conditions are ISO 1133-2-2011, 190° C., 2.16 kg).

[0136] The physical parameters and performances of the biodegradable aliphatic polyesters in Examples 1 to 7 and Comparative Examples 1 to 3 are shown in Tables 1 and 2.

[0137] Table 1 Physical properties of biodegradable aliphatic polyesters in various examples and comparative examples

[0138] Table 2 Properties of biodegradable aliphatic polyesters in various examples and comparative examples

[0139] According to the data in Table 2, the water vapor transmission rate of the biodegradable aliphatic polyester in Examples 1 to 7 is less than 750 g / (d·m 2 ), while the shear peel strength reaches 0.60N / cm 2 The above results indicate that the biodegradable aliphatic polyester of the present invention not only has good barrier properties but also has excellent self-adhesive properties.

[0140] The above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications may be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the claims of the present invention.

Claims

1. A biodegradable aliphatic polyester, characterized in that, The biodegradable aliphatic polyester contains units derived from at least one aliphatic dicarboxylic acid and at least one aliphatic diol, and satisfies the following conditions: 1.54 ≤ Mw / Mn ≤ 1.98, Mw / q ≥ 50000; wherein q is the mass percentage of the low molecular weight polymer with a molecular weight ≤ 1000 Dalton of the biodegradable aliphatic polyester determined by GPC.

2. The biodegradable aliphatic polyester according to claim 1, wherein The Mw / Mn is 1.65 - 1.85, and 70000 ≤ Mw / q ≤ 110000.

3. The biodegradable aliphatic polyester according to claim 1, wherein The units derived from the aliphatic dicarboxylic acid are aliphatic dicarboxylic acids having 2 - 22 carbon atoms in the main chain and their esters.

4. The biodegradable aliphatic polyester according to claim 3, wherein The aliphatic dicarboxylic acid is at least one of succinic acid, adipic acid, azelaic acid, sebacic acid or tridecanedioic acid.

5. The biodegradable aliphatic polyester according to claim 1, characterized in that, The units derived from the aliphatic diol are aliphatic diols having 2 - 13 carbon atoms in the main chain.

6. The biodegradable aliphatic polyester according to claim 5, characterized in that, The aliphatic diol is at least one of 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol or 1,13-tridecanediol.

7. The biodegradable aliphatic polyester according to claim 1, characterized in that, The biodegradable aliphatic polyester contains the following components: A) Aliphatic dicarboxylic acid component: a1) 65 - 100 mol% of succinic acid or its ester derivatives, or a mixture thereof, based on the total amount of a1) and a2); a2) 0 - 35 mol% of adipic acid or its ester derivatives, or a mixture thereof, based on the total amount of a1) and a2), wherein the sum of the molar percentages of components a1) and a2) is 100 mol%; B) The aliphatic diol component is 1,4-butanediol, and its molar ratio to the aliphatic dicarboxylic acid component is ≥ 1.

8. The biodegradable aliphatic polyester according to claim 7, wherein a1) in the aliphatic dicarboxylic acid component is 73 - 80 mol% of succinic acid or its ester derivatives, or a mixture thereof; a2) in the aliphatic dicarboxylic acid component is 20 - 27 mol% of adipic acid or its ester derivatives, or a mixture thereof.

9. The biodegradable aliphatic polyester according to any one of claims 1 to 8, characterized in that, The biodegradable aliphatic polyester, according to the ASTM F1249-13 standard, at a sample thickness of 12 ± 2 μm, 40 °C and RH = 60%, has a measured water vapor transmission rate ≤ 750 g / (d·m 2 ); preferably, the water vapor transmission rate ≤ 480 g / (d·m 2 ); more preferably, the water vapor transmission rate ≤ 330 g / (d·m 2 ).

10. The biodegradable aliphatic polyester according to any one of claims 1 to 8, characterized in that, The biodegradable aliphatic polyester, under the condition that the sample thickness is 12 ± 2 μm according to the standard of GB / T 10457-2009, has a shear peel strength ≥ 0.6 N / cm 2 ; Preferably, the shear peel strength ≥ 0.72 N / cm 2 ; More preferably, the shear peel strength ≥ 0.85 N / cm 2 .

11. A method for preparing the biodegradable aliphatic polyester according to any one of claims 1 to 10, characterized in that, Comprising the following steps: Step i): Mix the aliphatic dicarboxylic acid or its derivative with the aliphatic diol and carry out an esterification reaction or a transesterification reaction to obtain an esterification product; Step ii): Carry out a prepolymerization reaction on the esterification product in Step i) to obtain a prepolymer product; Step iii): Carry out a polycondensation reaction on the prepolymer product in Step ii) until the acid value of the formed polycondensation product measured according to the GB / T 32366-2015 standard is 15 - 50 mol / t, thus obtaining the biodegradable aliphatic polyester; wherein the acid value of the esterification product in Step i) measured according to the GB / T 32366-2015 standard is 360 - 770 mol / t; the acid value of the prepolymer product in Step ii) measured according to the GB / T 32366-2015 standard is 70 - 110 mol / t.

12. Use of the biodegradable aliphatic polyester according to any one of claims 1 to 10 in preparing a food packaging film, an industrial packaging film or an agricultural mulch film.

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