Aliphatic-aromatic copolyester, preparation method therefor, and application thereof

Abstract

The present application provides an aliphatic-aromatic copolyester, a preparation method therefor, and an application thereof. The aliphatic-aromatic copolyester comprises the following components: a component A, comprising the following acid components: a1) 63-69 mol% of terephthalic acid, or a derivative thereof, or a mixture thereof, based on the total moles of a1) and a2); a2) 31-37 mol% of adipic acid, or a derivative thereof, or a mixture thereof, based on the total moles of a1) and a2); and component B: 1,4-butanediol, in an amount at least equimolar to component A. The aliphatic-aromatic copolyester has a crystallization enthalpy of -20 to -46 J / g. The aliphatic-aromatic copolyester of the present application is used for preparing packaging film, which has a high heat-sealing strength even after prolonged storage, and the impact on the degradation performance of the packaging film is minor.

Description

An aliphatic-aromatic copolyester, its preparation method and application Technical Field

[0001] This application belongs to the field of polyester materials technology, specifically relating to an aliphatic-aromatic copolyester, its preparation method, and its application. Background Technology

[0002] Biodegradable aliphatic-aromatic copolyesters obtained from dicarboxylic acids and diols are known in the literature. In addition to their biodegradability, these polyesters also have good elongation and strong mechanical properties, exhibiting properties similar to low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE). Therefore, they are widely used in packaging bag products such as shopping bags, garbage bags, and express delivery bags.

[0003] To maintain sufficient biodegradability, commercially available aliphatic-aromatic copolyesters typically have an aromatic dicarboxylic acid content of less than 49% in the polyester chain. This is because above this threshold, the biodegradability percentage of such polyesters decreases significantly. According to literature reports, when the terephthalate molar content in polybutylene terephthalate (PBAT) is 42 mol%, the polyester completely biodegrades to form compost after twelve weeks, while when the terephthalate molar content is higher than 51 mol%, the biodegradability percentage is less than 40%.

[0004] Although polymer blends based on aliphatic-aromatic copolyesters with an aromatic dicarboxylic acid molar content of less than 49 mol% exhibit good degradation properties, the packaging bags require heat sealing during manufacturing. However, due to limitations in production workshop layout and the need to maintain production efficiency, manufacturers typically produce pre-made packaging films for bag fabrication. Once a certain quantity of film has accumulated, it is then used for printing and bag making. However, when these stored films are used for bag making, problems such as poor heat sealing and reduced heat seal strength often occur.

[0005] Therefore, developing a polyester material that can improve the heat-sealing strength of packaging films while having a smaller impact on degradation performance is a technical problem that urgently needs to be solved in this field.

[0006] Summary of the Invention

[0007] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0008] This application provides an aliphatic-aromatic copolyester, its preparation method, and its application. The aliphatic-aromatic copolyester provided in this application is used to prepare packaging films, which still have high heat-sealing strength after long-term storage and have little impact on the degradation performance of the packaging film.

[0009] In a first aspect, this application provides an aliphatic-aromatic copolyester, wherein the aliphatic-aromatic copolyester comprises the following components:

[0010] Component A contains the following acid components:

[0011] a1) Based on the total molar percentage of a1) and a2), 63 to 69 mol% of terephthalic acid or its derivatives or mixtures thereof;

[0012] a2) Based on the total molar percentage of a1) and a2), 31–37 mol% of adipic acid or its derivatives or mixtures thereof;

[0013] and,

[0014] Component B: 1,4-Butanediol in at least an equimolar amount as component A.

[0015] The enthalpy of crystallization of the aliphatic-aromatic copolyester is -20 to -46 J / g.

[0016] Heat-sealing strength refers to the adhesive strength between heat-sealing materials under certain temperature and pressure conditions. The essence of heat sealing lies in the fact that when a material is heated, its surface melts; under pressure, the polymer molecules on the surface of the heat-sealing material fuse and entangle; and during cooling, the material recrystallizes internally. The heat-sealing strength of a film is related to its heat-melting properties, physical properties, and heat-sealing conditions, namely heat-sealing temperature, time, and pressure. Under certain conditions, the wider the heat-sealing temperature range, the better the heat-sealing performance, and the easier and more stable the quality control.

[0017] Generally, higher crystallinity and larger grains improve the temperature resistance of the film. However, when the crystallinity exceeds a certain level, the flexibility of the film gradually decreases, resulting in a loss of plasticity. At the same time, the movement of molecular chains slows down, and the entanglement of molecular chains on the film surface weakens during heat sealing, leading to a decrease in heat sealing strength.

[0018] In this application, by controlling the molar content of aromatic dicarboxylic acids in the aliphatic-aromatic copolyester within a specific range, and the crystallization enthalpy of the aliphatic-aromatic copolyester within the aforementioned limited range, the crystallinity of the material can be effectively regulated, resulting in packaging films prepared from the aliphatic-aromatic copolyester having high heat-sealing strength and minimal impact on the degradation performance of the packaging film, as well as good processing performance and low cost.

[0019] In this application, the 63-69 mol% can be, for example, 63 mol%, 63.2 mol%, 63.4 mol%, 63.6 mol%, 63.8 mol%, 64 mol%, 64.2 mol%, 64.4 mol%, 64.6 mol%, 64.8 mol%, 65 mol%, 65.2 mol%, 65.4 mol%, 65.6 mol%, 65.8 mol%, 66 mol%, 66.2 mol%, 66.4 mol%, 66.6 mol%, 66.8 mol%, 67 mol%, 67.2 mol%, 67.4 mol%, 67.6 mol%, 67.8 mol%, 68 mol%, 68.2 mol%, 68.4 mol%, 68.6 mol%, 68.8 mol%, or 69 mol%, etc.

[0020] In this application, the total molar percentage of components a1) and a2) is 100 mol%. In this application, the derivative of terephthalic acid can be a di-C1-C6 alkyl ester of terephthalic acid, exemplarily such as dimethyl ester, diethyl ester, di-n-propyl ester, diisopropyl ester, di-n-butyl ester, diisobutyl ester, di-tert-butyl ester, di-n-pentyl ester, diisopentyl ester, or di-n-hexyl ester. The derivative of terephthalic acid can be used alone or in a mixture of two or more. Particularly preferred are terephthalic acid or derivatives thereof forming esters, such as dimethyl terephthalate.

[0021] In this application, the derivative of adipic acid can be a di-C1-C6 alkyl ester of adipic acid, exemplarily such as dimethyl ester, diethyl ester, di-n-propyl ester, diisopropyl ester, di-n-butyl ester, diisobutyl ester, di-tert-butyl ester, di-n-pentyl ester, diisopentyl ester, or di-n-hexyl ester. The derivative of adipic acid can be used alone or in a mixture of two or more.

[0022] In this application, the enthalpy of crystallization of the aliphatic-aromatic copolyester is -20 to -46 J / g, for example, it can be -45 J / g, -44 J / g, -42 J / g, -40 J / g, -38 J / g, -36 J / g, -34 J / g, -32 J / g, -30 J / g, -28 J / g, -26 J / g, -24 J / g, -22 J / g, or -21 J / g, etc.

[0023] In this application, the enthalpy of crystallization of the aliphatic-aromatic copolyester depends on its monomer composition, monomer ratio, molecular weight and molecular weight distribution, and branching structure. Furthermore, adjustments to the sequence structure of the aliphatic-aromatic copolyester during synthesis will also affect its enthalpy of crystallization. For example, increasing the content of aromatic monomers in the aliphatic-aromatic copolyester can improve the regularity of the polyester material to a certain extent, thereby enhancing its crystallinity and increasing its enthalpy of crystallization. In the molecular chain structure, the more branched structures there are, the greater the steric hindrance, and the weaker the molecular chain mobility, which will also weaken the polyester's crystallinity and reduce its enthalpy of crystallization. The branching structure is related to the monomer composition of the aliphatic-aromatic copolyester, the type of branching agent, and the amount of branching agent added.

[0024] Preferably, the aliphatic-aromatic copolyester further comprises a crosslinking agent, wherein the crosslinking agent comprises 0.05-1 wt% of 100 wt% of the aliphatic-aromatic copolyester, for example, 0.05 wt%, 0.055 wt%, 0.06 wt%, 0.065 wt%, 0.07 wt%, 0.075 wt%, 0.08 wt%, 0.085 wt%, 0.09 wt%, 0.095 wt%, 0.1 wt%, 0.12 wt%, 0.14 wt%, 0.16 wt%, 0.18 wt%, 0.2 wt%, 0.22 wt%, 0.25 wt%, 0.28 wt%, 0.3 wt%, or 0.32 wt%. The concentrations are 0.12% to 0.48% wt%, 0.42% wt%, 0.45% wt%, 0.48% wt%, 0.5% wt%, 0.52% wt%, 0.55% wt%, 0.58% wt%, 0.6% wt%, 0.62% wt%, 0.65% wt%, 0.68% wt%, 0.7% wt%, 0.72% wt%, 0.75% wt%, 0.78% wt%, 0.8% wt%, 0.82% wt%, 0.85% wt%, 0.88% wt%, 0.9% wt%, 0.92% wt%, 0.95% wt%, 0.98% wt%, or 1% wt%, etc.; preferably 0.12% to 0.48% wt%, more preferably 0.22% to 0.45% wt%.

[0025] Preferably, the crosslinking agent has a functionality of ≥3, for example, it can be 3, 4, 5 or 6, etc.

[0026] In this application, the crosslinking agent contains at least one of hydroxyl, carboxyl, or anhydride groups in its molecular structure; the functionality ≥3 refers to the total functionality of hydroxyl, carboxyl, and anhydride groups in the molecular structure being ≥3; compounds having 3 to 6 hydroxyl groups are particularly preferred.

[0027] Preferably, the crosslinking agent comprises at least one selected from tartaric acid, citric acid, malic acid, trimethylolpropane, trimethylolethane, pentaerythritol, polyether triol, glycerol, 1,3,5-benzotriic acid, 1,2,4-benzotriic acid, 1,2,4-benzotriic anhydride, 1,2,4,5-benzotetraic acid, or benzopyrenic acid dianhydride, more preferably trimethylolpropane, pentaerythritol, or glycerol, and particularly preferably glycerol.

[0028] Preferably, the aliphatic-aromatic copolyester further comprises a chain extender, wherein the chain extender comprises 0.05-1 wt% of 100 wt% of the aliphatic-aromatic copolyester, for example, 0.05 wt%, 0.055 wt%, 0.06 wt%, 0.065 wt%, 0.07 wt%, 0.075 wt%, 0.08 wt%, 0.085 wt%, 0.09 wt%, 0.095 wt%, 0.1 wt%, 0.12 wt%, 0.14 wt%, 0.16 wt%, 0.18 wt%, 0.2 wt%, 0.22 wt%, 0.25 wt%, 0.28 wt%, 0.3 wt%, etc. The concentrations are 0.1% to 0.6% (t%), 0.32 wt%, 0.35 wt%, 0.38 wt%, 0.4 wt%, 0.42 wt%, 0.45 wt%, 0.48 wt%, 0.5 wt%, 0.52 wt%, 0.55 wt%, 0.58 wt%, 0.6 wt%, 0.62 wt%, 0.65 wt%, 0.68 wt%, 0.7 wt%, 0.72 wt%, 0.75 wt%, 0.78 wt%, 0.8 wt%, 0.82 wt%, 0.85 wt%, 0.88 wt%, 0.9 wt%, 0.92 wt%, 0.95 wt%, 0.98 wt%, or 1 wt%, with a particularly preferred concentration of 0.1 to 0.6 wt%.

[0029] Preferably, the chain extender has a functionality of ≥2, for example, 2, 3, 4, 5, etc.

[0030] Preferably, the chain extender comprises at least one of isocyanate compounds, isocyanurate compounds, peroxides, epoxides, oxazoline compounds, oxazine compounds, caprolactam, or carbodiimide, and more preferably isocyanate compounds.

[0031] In this application, the isocyanate compounds may be aromatic diisocyanates and / or aliphatic diisocyanates; wherein, 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. The aliphatic diisocyanate may be any straight-chain or branched alkylene diisocyanate or cycloalkylene diisocyanate containing 2 to 20 carbon atoms, preferably 3 to 12 carbon atoms, for example, hexamethylene diisocyanate, isophorone diisocyanate, or methylene di(4-isocyanate cyclohexane); a particularly preferred aliphatic diisocyanate is hexamethylene diisocyanate.

[0032] In this application, the peroxides include, but are not limited to, benzoyl peroxide, 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(tert-butylperoxy)methylcyclododecane, n-butyl 4,4-di(butylperoxy)valerate, dicumyl peroxide, tert-butyl peroxybenzoate, dibutyl peroxide, α,α-di(tert-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hex-3-yne, or tert-butylperoxycumene.

[0033] The epoxides described in this application include, but are not limited to, hydroquinone, diglycidyl ether, resorcinol diglycidyl ether, 1,6-hexanediol diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, diglycidyl terephthalate, tetrahydrophthalic acid diglycidyl ether, hexahydrophthalic acid diglycidyl ether, dimethyl phthalic acid diglycidyl ether, phenylene diglycidyl ether, ethylene diglycidyl ether, trimethylene diglycidyl ether, tetramethylene diglycidyl ether, and hexamethylene diglycidyl ether. One or more of the following: 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, or polybutylene glycol diglycidyl ether. Preferably, it is a copolymer based on styrene, acrylate, and / or methacrylate containing epoxy groups, wherein the epoxy-containing unit is preferably (meth)acrylate glycidyl ether.

[0034] In this application, the oxazoline compounds and oxazine compounds each independently include a bridging portion consisting of a single bond or -(CH2). z - or arylene dioxazoline and dioxazine, wherein z = 2, 3 or 4, such as methylene, ethyl-1,2-diyl, propion-1,3-diyl, propion-1,2-diyl, etc.; the arylene group includes phenylene.

[0035] In this application, the dioxazoline is preferably at least one 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.

[0036] Dioxazine is preferably at least one 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.

[0037] In this application, the carbodiimide may be at least one of the following: 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.

[0038] Preferably, the melting point of the aliphatic-aromatic copolyester is 153.8 to 182.2°C, for example, it can be 154°C, 155°C, 156°C, 158°C, 160°C, 162°C, 164°C, 166°C, 168°C, 170°C, 172°C, 174°C, 176°C, 178°C, 180°C, or 182°C, etc.; preferably it is 163 to 174°C.

[0039] Preferably, the crystallization temperature of the aliphatic-aromatic copolyester is 92-133°C, for example, it can be 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C, 100°C, 102°C, 104°C, 106°C, 108°C, 110°C, 112°C, 114°C, 116°C, 118°C, 120°C, 122°C, 124°C, 126°C, 128°C, 130°C, 131°C, 132°C, or 133°C, etc.; more preferably, it is 94-130°C; more preferably, it is 102-124°C.

[0040] Preferably, the enthalpy of crystallization of the aliphatic-aromatic copolyester is -28 to -38 J / g.

[0041] In this application, the melting point, crystallization temperature, and crystallization enthalpy of the aliphatic-aromatic copolyester can all be tested by differential scanning calorimetry (DSC).

[0042] Preferably, the viscosity of the aliphatic-aromatic copolyester is 140-270 mL / g, for example, it can be 140 mL / g, 145 mL / g, 150 mL / g, 155 mL / g, 160 mL / g, 165 mL / g, 170 mL / g, 175 mL / g, 180 mL / g, 185 mL / g, 190 mL / g, 195 mL / g, 200 mL / g, 205 mL / g, 210 mL / g, 215 mL / g, 220 mL / g, 225 mL / g, 230 mL / g, 235 mL / g, 240 mL / g, 245 mL / g, 250 mL / g, 255 mL / g, 260 mL / g, 265 mL / g, or 270 mL / g, etc.

[0043] Preferably, the melt flow rate of the aliphatic-aromatic copolyester is 2 to 12 g / 10 min, for example, it can be 2 g / 10 min, 2.5 g / 10 min, 3 g / 10 min, 3.5 g / 10 min, 4 g / 10 min, 4.5 g / 10 min, 5 g / 10 min, 5.5 g / 10 min, 6 g / 10 min, 6.5 g / 10 min, 7 g / 10 min, 7.5 g / 10 min, 8 g / 10 min, 8.5 g / 10 min, 9 g / 10 min, 9.5 g / 10 min, 10 g / 10 min, 10.5 g / 10 min, 11 g / 10 min, 11.5 g / 10 min, or 12 g / 10 min; more preferably, it is 3 to 10 g / 10 min.

[0044] In this application, the melt flow rate of the aliphatic-aromatic copolyester is tested under the following conditions: 190°C, 2.16 kg, according to ISO 1133-2-2011.

[0045] Secondly, this application provides a method for preparing an aliphatic-aromatic copolyester according to the first aspect, the method comprising the following steps:

[0046] (1) Component A and component B are reacted to obtain an esterified product with a viscosity of 11 to 31 mL / g;

[0047] (2) The esterified product obtained in step (1) is subjected to a pre-condensation reaction to obtain a pre-condensation product with a viscosity of 35-70 mL / g.

[0048] (3) The prepolymer obtained in step (2) is subjected to a polycondensation reaction to obtain the aliphatic-aromatic copolyester with a viscosity of 140-270 mL / g.

[0049] Preferably, the raw materials for the reaction in step (1) further include a crosslinking agent.

[0050] Preferably, the reaction in step (1) includes:

[0051] (S1) Mix and react components a1) and a2) with component B and optional crosslinking agent to obtain an esterified product with a viscosity of 11 to 31 mL / g.

[0052] And / or,

[0053] (S2) React component a1) with component B to obtain esterified product 1 with a viscosity of 11 to 31 mL / g; react component a2) with component B and optional crosslinking agent to obtain esterified product 2 with a viscosity of 11 to 31 mL / g; mix esterified product 1 and esterified product 2 to proceed to step (2).

[0054] Preferably, the reaction temperature in step (S1) is 180–260°C, for example, 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C, 225°C, 230°C, 235°C, 240°C, 245°C, 250°C, 255°C, or 260°C; the pressure is 40–120 kPa, for example, 40 kPa, 45 kPa, 50 kPa, 55 kPa, 60 kPa, 65 kPa, etc. The pressure is 70 kPa, 75 kPa, 80 kPa, 85 kPa, 90 kPa, 95 kPa, 100 kPa, 105 kPa, 110 kPa, 115 kPa, or 120 kPa, etc.; the time is 2 to 8 hours, for example, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, or 8 hours, etc.; more preferably, the temperature is 220 to 250°C, the pressure is 60 to 90 kPa, and the time is 3 to 6 hours.

[0055] Preferably, in step (S2), the reaction temperature between component a1) and component B is 235–260°C, for example, 235°C, 240°C, 245°C, 250°C, 255°C, or 260°C; the pressure is 58–120 kPa, for example, 58 kPa, 60 kPa, 65 kPa, 70 kPa, 75 kPa, 80 kPa, 85 kPa, 90 kPa, 95 kPa, 100 kPa, 105 kPa, 110 kPa, or 120 kPa. 15 kPa or 120 kPa, etc.; the time is 2.5 to 8 hours, for example, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, or 8 hours, etc.; the reaction temperature of component a2) with component B is 195 to 260°C, for example, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C, 225°C, 230°C, 235°C, 240°C, 245°C, 250°C, etc. Temperatures range from 255℃ to 260℃; pressure ranges from 80 to 120 kPa, for example, 80 kPa, 85 kPa, 90 kPa, 95 kPa, 100 kPa, 105 kPa, 110 kPa, 115 kPa, or 120 kPa; time ranges from 3.5 to 8 hours, for example, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, or 8 hours.

[0056] In this application, the viscosity number is 11 to 31 mL / g, for example, it can be 11 mL / g, 12 mL / g, 13 mL / g, 14 mL / g, 16 mL / g, 18 mL / g, 20 mL / g, 22 mL / g, 24 mL / g, 26 mL / g, 28 mL / g, 30 mL / g or 31 mL / g, etc.

[0057] In this application, the molar ratio of component A to component B is 1:(1.2 to 2.4), wherein the specific values ​​of (1.2 to 2.4) can be, for example, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3 or 2.4, etc.; more preferably, it is 1:(1.4 to 1.8).

[0058] Preferably, in step (S2), the molar ratio of component a1) to component B is 1:(1.2 to 1.7), and the molar ratio of component a2) to component B is 1:(1.2 to 1.4).

[0059] In this application, the reaction described in step (1) can be carried out in a mixing device, such as a vertical reactor with a stirrer.

[0060] Preferably, the temperature of the pre-condensation reaction in step (2) is 230–270°C, for example, 230°C, 235°C, 240°C, 245°C, 250°C, 255°C, 260°C, 265°C, or 270°C; the pressure is 600–3000 Pa, for example, 600 Pa, 700 Pa, 800 Pa, 900 Pa, 1000 Pa, 1100 Pa, 1200 Pa, 140 Pa, etc. The pressure is 0 Pa, 1600 Pa, 1800 Pa, 2000 Pa, 2200 Pa, 2400 Pa, 2600 Pa, 2800 Pa, or 3000 Pa, etc.; the time is 2 to 6 hours, for example, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, or 6 hours, etc.; more preferably, the temperature is 240 to 260°C, the pressure is 800 to 2100 Pa, and the time is 3 to 5 hours.

[0061] Preferably, the viscosity of the prepolymerized product in step (2) is 35-70 mL / g, for example, it can be 35 mL / g, 36 mL / g, 38 mL / g, 40 mL / g, 42 mL / g, 45 mL / g, 48 mL / g, 50 mL / g, 52 mL / g, 55 mL / g, 58 mL / g, 60 mL / g, 62 mL / g, 65 mL / g, 68 mL / g or 70 mL / g, etc.

[0062] Preferably, the temperature of the polycondensation reaction in step (3) is 230–270°C, for example, 230°C, 235°C, 240°C, 245°C, 250°C, 255°C, 260°C, 265°C, or 270°C; the pressure is 50–600 Pa, for example, 50 Pa, 60 Pa, 80 Pa, 100 Pa, 150 Pa, 200 Pa, 250 Pa, 300 Pa, 350 Pa, 400 Pa, 450 Pa, 500 Pa, 550 Pa, or 600 Pa; the time is 2–6 h, for example, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, or 6 h; more preferably, the temperature is 240–260°C, the pressure is 100–300 Pa, and the time is 3–5 h. In this application, the polycondensation reaction is carried out in a rotary reactor or a cage reactor.

[0063] Preferably, after the polycondensation reaction in step (3) is completed, the obtained polycondensation product is mixed with a chain extender to carry out a chain extension reaction.

[0064] Preferably, the temperature of the chain extension reaction is 180–235°C, for example, 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C, 225°C, 230°C, or 235°C; and the time is 3–15 min, for example, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, or 15 min.

[0065] Preferably, the viscosity of the condensation product obtained in step (3) is 140-240 mL / g, for example, it can be 140 mL / g, 145 mL / g, 150 mL / g, 155 mL / g, 160 mL / g, 165 mL / g, 170 mL / g, 175 mL / g, 180 mL / g, 185 mL / g, 190 mL / g, 195 mL / g, 200 mL / g, 205 mL / g, 210 mL / g, 215 mL / g, 220 mL / g, 225 mL / g, 230 mL / g, 235 mL / g or 240 mL / g, etc. Preferably, the viscosity of the product obtained by the chain extension reaction is 160-270 mL / g, for example, it can be 160 mL / g, 165 mL / g, 170 mL / g, 175 mL / g, 180 mL / g, 185 mL / g, 190 mL / g, 195 mL / g, 200 mL / g, 205 mL / g, 210 mL / g, 215 mL / g, 220 mL / g, 225 mL / g, 230 mL / g, 235 mL / g, 240 mL / g, 245 mL / g, 250 mL / g, 255 mL / g, 260 mL / g, 265 mL / g, or 270 mL / g, etc.

[0066] In this application, the chain extension reaction is carried out in a twin-screw extruder or in addition to a static mixer.

[0067] In this application, if no chain extender is added during the reaction, the product obtained by polycondensation is an aliphatic-aromatic copolyester; if a chain extender is added during the reaction, the product obtained by the chain extension reaction is the aliphatic-aromatic copolyester; in order to better control the acid value, it is preferable to add a chain extender to carry out the chain extension reaction to obtain the aliphatic-aromatic copolyester.

[0068] In this application, the viscosity numbers mentioned are all determined according to the method specified in GB / T 17931-1999, in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1, in a constant temperature water bath at 25±0.05℃.

[0069] In this application, steps (1)-(3) and the chain extension reaction are carried out independently in the presence of a catalyst, and the catalysts used in steps (1)-(3) and the chain extension reaction may be the same or different. The catalyst can be an external catalyst or a catalyst present in the system. For example, in the reaction described in step (1), 50-80 wt% of the total mass of the catalyst is added; in the reaction described in step (2), the remaining catalyst is added; and the catalyst required for step (3) and the chain extension reaction is a catalyst present in the system. Controlling the amount of catalyst added can make the subsequent processing more stable. The total mass of the catalyst is 0.001-1 wt% of the mass of the final polymerization product, for example, it can be 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%, or 1 wt%, etc.; preferably 0.03-0.2 wt%.

[0070] In this application, the catalyst may be a tin compound, antimony compound, cobalt compound, lead compound, zinc compound, aluminum compound, or titanium compound, more preferably a zinc compound, aluminum compound, or titanium compound, and most preferably a titanium compound; the titanium compound may be tetrabutyl titanate or tetraisopropyl titanate, which has less residual amount and lower toxicity in the product or downstream product compared to other compounds.

[0071] Thirdly, this application provides a biodegradable composition, which, by weight, comprises 45 to 75 parts of biodegradable polyester (e.g., 45, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, or 75 parts, etc.) and 3 to 10 parts of polylactic acid (e.g., 3, 4, 5, 6, or 7 parts). The aliphatic-aromatic copolyester comprises 8 parts, 9 parts, or 10 parts, etc., 2 to 8 parts (e.g., 2 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts, 3 parts, 3.2 parts, 3.4 parts, 3.6 parts, 3.8 parts, 4 parts, 4.2 parts, 4.4 parts, 4.6 parts, 4.8 parts, 5 parts, 5.2 parts, 5.5 parts, 5.8 parts, 6 parts, 6.2 parts, 6.5 parts, 6.8 parts, 7 parts, 7.2 parts, 7.5 parts, 7.8 parts, or 8 parts, etc.) and 20 to 40 parts (e.g., 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, or 40 parts, etc.); the aliphatic-aromatic copolyester includes the aliphatic-aromatic copolyester described in the first aspect.

[0072] In this application, a specific amount of aliphatic-aromatic copolyester is used to blend with other components such as biodegradable polyester and polylactic acid, so that the composition has both excellent heat-sealing performance and biodegradability.

[0073] Preferably, the biodegradable polyester comprises the following components:

[0074] Acid components:

[0075] i-1) Based on the total molar amount of i-1) and i-2), 45 to 50 mol% (e.g., 45 mol%, 46 mol%, 47 mol%, 48 mol%, 49 mol%, or 50 mol%) of aromatic dicarboxylic acids or their esters, or mixtures thereof;

[0076] i-2) Based on the total molar amount of i-1) and i-2), 50 to 55 mol% (e.g., 50 mol%, 51 mol%, 52 mol%, 53 mol%, 54 mol%, or 55 mol%) of aliphatic dicarboxylic acids or their esters, or mixtures thereof;

[0077] The total molar percentage of components i-1) and i-2) is 100 mol%.

[0078] Dihydroxy compound components

[0079] i-3) is at least equimolar in amount with the acid component a C2-C6 aliphatic alkyl diol (e.g., C2, C3, C4, C5 or C6), or a mixture thereof.

[0080] Preferably, the biodegradable polyester comprises at least one of polybutylene terephthalate, polybutylene adipate, polybutylene sebacate, polypropylene adipate, or polypropylene sebacate.

[0081] Preferably, the inorganic filler includes at least one of calcium carbonate, talc, chalk, calcium oxide, kaolin, silica, titanium dioxide, silicate, mica, or montmorillonite; more preferably, calcium carbonate and / or talc.

[0082] Preferably, the mass ratio of calcium carbonate to talc is (2-4):1, wherein the specific values ​​of (2-4) can be, for example, 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8 or 4.

[0083] Preferably, the biodegradable composition further includes 0.01 to 1 part by weight of a copolymer containing epoxy groups, such as 0.01, 0.02, 0.04, 0.06, 0.08, 0.1, 0.2, 0.4, 0.6, 0.8 or 1 part.

[0084] Preferably, the epoxy-containing copolymer includes at least one of a copolymer of styrene and acrylate, a copolymer of styrene and methacrylate, or a copolymer of styrene, acrylate, and methacrylate.

[0085] In this application, the method for preparing the biodegradable composition includes, but is not limited to, obtaining it via reactive extrusion in an extruder. The reactive extruder may be a single-screw extruder, a twin-screw extruder, or a multi-screw extruder, with an extrusion temperature of 140–220°C and a screw speed of 200–500 rpm.

[0086] The biodegradable compositions, including aliphatic-aromatic copolyesters, mentioned in this application, and the articles prepared therefrom are all biodegradable.

[0087] For the purposes of this application, a substance or mixture of substances is considered "biodegradable" if it exhibits a biodegradability of at least 90% as defined in DIN EN 13432.

[0088] According to DIN EN 13432, during composting, CO2-free air is introduced into the maturing compost, and the compost is subjected to a specific temperature process. Here, biodegradability is defined as the percentage degree of biodegradation expressed as the ratio of the net amount of CO2 released by the sample (minus the amount of CO2 released by compost without the sample) to the maximum amount of CO2 that the sample can release (calculated from the carbon content in the sample). After only a few days of composting, biodegradable polyesters and biodegradable polyester mixtures typically show obvious signs of degradation, such as fungal growth, lysis, and perforation.

[0089] Other methods for determining biodegradability are described, for example, in ASTM D5338 and ASTM D6400.

[0090] Fourthly, this application provides a packaging film comprising an aliphatic-aromatic copolyester as described in the first aspect or a biodegradable composition as described in the second aspect.

[0091] In this application, the packaging film is used to prepare packaging bags, including shopping bags, garbage bags, compost bags, and express delivery bags, etc.

[0092] Preferably, the heat seal strength of the packaging film after 7 days of storage at a temperature of 25±5℃ and a humidity of 55±5% is >9.4N / 20mm.

[0093] The numerical range described in this application includes not only 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, this application will not exhaustively list the specific point values ​​included in the range.

[0094] The system refers to an equipment system, device system, or production device.

[0095] Compared with related technologies, the beneficial effects of this application are as follows:

[0096] The aliphatic-aromatic copolyester provided in this application controls the molar content of aromatic dicarboxylic acids in the aliphatic-aromatic copolyester within a specific range, and at the same time, the crystallization enthalpy of the aliphatic-aromatic copolyester is within a specific range, so that the packaging film prepared by the aliphatic-aromatic copolyester has high heat-sealing strength and has little impact on the degradation performance of the packaging film, with good processing performance and low cost.

[0097] After reading and understanding the detailed description, other aspects can be understood. Detailed Implementation

[0098] The technical solution of this application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely to help understand this application and should not be regarded as specific limitations on this application.

[0099] The materials used in this application are as follows:

[0100] 1,4-Butanediol was purchased from Xinjiang Meike Chemical Co., Ltd.

[0101] Terephthalic acid was purchased from Zhuhai INEOS Chemical Co., Ltd.

[0102] Adipic acid was purchased from Chongqing Huafeng Chemical Group Co., Ltd.

[0103] Glycerin was purchased from Aladdin;

[0104] Tetrabutyl titanate was purchased from Jianyi Chemical Import & Export Co., Ltd.

[0105] Hexamethylene diisocyanate was purchased from Aladdin;

[0106] Polylactic acid, grade FY804, was purchased from Anhui Fengyuan Futailai Polylactic Acid Co., Ltd.

[0107] copolymers based on styrene, acrylates and / or methacrylates and containing epoxy groups: ADR 4368, purchased from BASF Resins BV;

[0108] The biodegradable PBAT resin is a product with the grade KB100 provided by Kingfa Biomaterials Co., Ltd. The product has a molar content of terephthalic acid of 47.8±0.5mol%, a melt flow rate of 3.7±0.3g / 10min (190℃, 2.16kg), and a melting point of 117±3℃.

[0109] In this application, the molar content of aromatic diacids and the molar content of aliphatic diacids in the aliphatic-aromatic copolyester are tested using the following methods:

[0110] 20 mg of aliphatic-aromatic copolyester sample was dissolved in 0.6 mL of deuterated chloroform, and then measured at room temperature using a Bruker AV 500 nuclear magnetic resonance spectrometer. 1 ¹H NMR, the chloroform solvent peak was determined to be around 7.26 ppm.

[0111] References: Chen, X.; Chen, W.; Zhu, G.; Huang, F.; Zhang, J., Synthesis, 1H-NMR characterization, and biodegradation behavior of aliphatic–aromatic random copolyester. J. Appl. Polym. Sci. 2007, 104(4): 2643-2649. It can be seen that for aromatic dicarboxylic acids, such as terephthalic acid, the four hydrogen atoms on the benzene ring in the repeating unit appear around 8.10 ppm; for aliphatic dicarboxylic acids, such as adipic acid, the four hydrogen atoms in the two CH2 units adjacent to the carbonyl group in the repeating unit appear around 2.33 ppm. Thus, the molar content of the dicarboxylic acid component can be determined by the integral area (I0.10) of the peaks at 8.10 ppm and 2.33 ppm. T and I A )express:

[0112] The molar content of aromatic dicarboxylic acids in aliphatic-aromatic copolyesters = I T / (I T +I A )×100%;

[0113] The molar content of aliphatic dicarboxylic acids in aliphatic-aromatic copolyesters = I A / (I T +I A )×100%.

[0114] In this application, the melting point, crystallization temperature, and enthalpy of the aliphatic-aromatic copolyester are determined by DSC testing. The specific method includes: taking 5-10 mg of sample, placing it in a crucible, and testing it using a NETZSCH DSC instrument. The test procedure is as follows: initial temperature: 20℃, heating to 200℃ at a rate of 10 K / min, holding at 200℃ for 5 minutes, cooling to 20℃ at a rate of 10 K / min, holding at 20℃ for 3 minutes, heating to 200℃ at a rate of 10 K / min, holding at 200℃ for 2 minutes, and cooling to 50℃ at a rate of 20 K / min. The entire test is conducted under nitrogen protection.

[0115] In this application, the viscosity of the products was determined in accordance with GB / T 17931-1999 in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05℃.

[0116] Example 1

[0117] This embodiment provides an aliphatic-aromatic copolyester, the preparation method of which includes:

[0118] (1) 470 kg of terephthalic acid, 237 kg of adipic acid, 600 kg of 1,4-butanediol, 2.8 kg of glycerol and 0.350 kg of tetrabutyl titanate were physically mixed at room temperature in an esterification reactor. The resulting mixture was then subjected to an esterification reaction at 240 °C and 80 kPa pressure for 3 h to obtain an esterification product with a viscosity of 13 mL / g.

[0119] (2) The esterification product obtained in step (1) was introduced into a vertical stirred fully mixed reactor. 0.255 kg of tetrabutyl titanate was added to the reactor, heated to 250 °C, and reacted at a pressure of 1500 Pa for 4.5 h. Most of the excess 1,4-butanediol was removed by distillation, and a prepolymer with a viscosity of 36 mL / g was obtained.

[0120] (3) The prepolymer obtained in step (2) is transferred to a final polymerization reactor and polycondensed at a temperature of 252°C and a pressure of 200Pa for 3.5 hours. The excess 1,4-butanediol and other byproducts are removed by distillation. Then, the prepolymer is granulated by an underwater granulator and dried to obtain an aliphatic-aromatic copolyester with a viscosity of 176 mL / g.

[0121] Example 2

[0122] This embodiment provides an aliphatic-aromatic copolyester, the preparation method of which includes:

[0123] (1) 510 kg of terephthalic acid, 237 kg of adipic acid, 610 kg of 1,4-butanediol, 3.00 kg of glycerol and 0.365 kg of tetrabutyl titanate were physically mixed at room temperature in an esterification reactor. The resulting mixture was then subjected to an esterification reaction at 230 °C and 90 kPa pressure for 4 h to obtain an esterification product with a viscosity of 16 mL / g.

[0124] (2) The esterification product obtained in step (1) was introduced into a vertical stirred fully mixed reactor. 0.285 kg of tetrabutyl titanate was added to the reactor, heated to 246 °C, and reacted at a pressure of 1700 Pa for 5 h. Most of the excess 1,4-butanediol was removed by distillation, and a prepolymer with a viscosity of 38 mL / g was obtained.

[0125] (3) The prepolymer obtained in step (2) is transferred to a final polymerization reactor and polycondensed at a temperature of 246°C and a pressure of 140Pa for 4.5 hours. The excess 1,4-butanediol and other byproducts are removed by distillation. Then, the prepolymer is granulated by an underwater granulator and dried to obtain an aliphatic-aromatic copolyester with a viscosity of 192 mL / g.

[0126] Example 3

[0127] This embodiment provides an aliphatic-aromatic copolyester, the preparation method of which includes:

[0128] (1-1) 237 kg adipic acid, 185 kg 1,4-butanediol and 3.3 kg glycerol were physically mixed at room temperature in an esterification reactor. The resulting mixture was then subjected to esterification reaction at 200 °C and 90 kPa pressure for 4 h to obtain an esterification product with a viscosity of 15 mL / g.

[0129] (1-2) 590 kg of terephthalic acid, 495 kg of 1,4-butanediol and 0.420 kg of tetrabutyl titanate were physically mixed at room temperature in an esterification reactor. The resulting mixture was then subjected to an esterification reaction at 242 °C and 60 kPa pressure for 3 h to obtain an esterification product with a viscosity of 18 mL / g.

[0130] (2) The esterification products obtained in steps (1-1) and (1-2) were introduced into a vertical stirred fully mixed reactor and mixed. 0.330 kg of tetrabutyl titanate was added to the reactor and heated to 245 °C. The reaction was carried out at a pressure of 1300 Pa for 4 h. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer with a viscosity of 63 mL / g.

[0131] (3) The prepolymer obtained in step (2) is transferred to a final polymerization reactor and polycondensed at a temperature of 248°C and a pressure of 110Pa for 4 hours. The excess 1,4-butanediol and other byproducts are removed by distillation. Then, the prepolymer is granulated by an underwater granulator and dried to obtain an aliphatic-aromatic copolyester with a viscosity of 188 mL / g.

[0132] Example 4

[0133] This embodiment provides an aliphatic-aromatic copolyester, the preparation method of which includes:

[0134] (1) 510 kg of terephthalic acid, 237 kg of adipic acid, 610 kg of 1,4-butanediol, 4.0 kg of trimethylolpropane and 0.365 kg of tetrabutyl titanate were physically mixed at room temperature in an esterification reactor. The resulting mixture was then subjected to an esterification reaction at 235 °C and 85 kPa pressure for 4.5 h to obtain an esterification product with a viscosity of 21 mL / g.

[0135] (2) The esterification product obtained in step (1) was introduced into a vertical stirred fully mixed reactor. 0.285 kg of tetrabutyl titanate was added to the reactor, heated to 245 °C, and reacted at a pressure of 1500 Pa for 4.5 h. Most of the excess 1,4-butanediol was removed by distillation, and a prepolymer with a viscosity of 42 mL / g was obtained.

[0136] (3) The prepolymer obtained in step (2) is transferred to a final polymerization reactor and polycondensed at a temperature of 247°C and a pressure of 130Pa for 4 hours. The excess 1,4-butanediol and other byproducts are removed by distillation. Then, the prepolymer is granulated by an underwater granulator and dried to obtain an aliphatic-aromatic copolyester with a viscosity of 189 mL / g.

[0137] Example 5

[0138] This embodiment provides an aliphatic-aromatic copolyester, the preparation method of which includes:

[0139] (1) 510 kg of terephthalic acid, 237 kg of adipic acid, 610 kg of 1,4-butanediol, 3.00 kg of glycerol and 0.365 kg of tetrabutyl titanate were physically mixed at room temperature in an esterification reactor. The resulting mixture was then subjected to an esterification reaction at 230 °C and 90 kPa pressure for 4 h to obtain an esterification product with a viscosity of 16 mL / g.

[0140] (2) The esterification product obtained in step (1) was introduced into a vertical stirred fully mixed reactor. 0.285 kg of tetrabutyl titanate was added to the reactor, heated to 246 °C, and reacted at a pressure of 1700 Pa for 5 h. Most of the excess 1,4-butanediol was removed by distillation, and a prepolymer with a viscosity of 38 mL / g was obtained.

[0141] (3) The prepolymer obtained in step (2) was transferred to a final polymerization reactor and polycondensed at a temperature of 242°C and a pressure of 140Pa for 2 hours. The excess 1,4-butanediol and other by-products were removed by distillation to obtain a final polymer with a viscosity of 141 mL / g.

[0142] (4) The final polymer obtained in step (3) is added to a static mixer, and 5.2 kg of hexamethylene diisocyanate is added to it. The mixture is blended at 195 °C for 8 min. Then, it is granulated and dried to obtain an aliphatic-aromatic copolyester with a viscosity of 212 mL / g.

[0143] Example 6

[0144] This embodiment provides an aliphatic-aromatic copolyester, the preparation method of which includes:

[0145] (1) 470 kg of terephthalic acid, 237 kg of adipic acid, 600 kg of 1,4-butanediol, 5.72 kg of glycerol and 0.350 kg of tetrabutyl titanate were physically mixed at room temperature in an esterification reactor. The resulting mixture was then subjected to an esterification reaction at 240 °C and 80 kPa pressure for 3 h to obtain an esterification product with a viscosity of 17 mL / g.

[0146] (2) The esterification product obtained in step (1) was introduced into a vertical stirred fully mixed reactor. 0.255 kg of tetrabutyl titanate was added to the reactor, heated to 250 °C, and reacted at a pressure of 1500 Pa for 4.5 h. Most of the excess 1,4-butanediol was removed by distillation, and a prepolymer with a viscosity of 40 mL / g was obtained.

[0147] (3) The prepolymer obtained in step (2) is transferred to a final polymerization reactor and polycondensed at a temperature of 252°C and a pressure of 200Pa for 3.5 hours. The excess 1,4-butanediol and other byproducts are removed by distillation. Then, the prepolymer is granulated by an underwater granulator and dried to obtain an aliphatic-aromatic copolyester with a viscosity of 183 mL / g.

[0148] Example 7

[0149] This embodiment provides an aliphatic-aromatic copolyester, the preparation method of which includes:

[0150] (1) 470 kg of terephthalic acid, 237 kg of adipic acid, 600 kg of 1,4-butanediol, 0.90 kg of glycerol and 0.370 kg of tetrabutyl titanate were physically mixed at room temperature in an esterification reactor. The resulting mixture was then subjected to an esterification reaction at 220 °C and 100 kPa pressure for 3 h to obtain an esterification product with a viscosity of 12 mL / g.

[0151] (2) The esterification product obtained in step (1) was introduced into a vertical stirred fully mixed reactor. 0.325 kg of tetrabutyl titanate was added to the reactor and heated to 236 °C. The reaction was carried out at a pressure of 2400 Pa for 6 h. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer with a viscosity of 44 mL / g.

[0152] (3) The prepolymer obtained in step (2) is transferred to a final polymerization reactor and polycondensed at a temperature of 240°C and a pressure of 260Pa for 4 hours. The excess 1,4-butanediol and other byproducts are removed by distillation. Then, the prepolymer is granulated by an underwater granulator and dried to obtain an aliphatic-aromatic copolyester with a viscosity of 167 mL / g.

[0153] Example 8

[0154] This embodiment provides an aliphatic-aromatic copolyester, the preparation method of which includes:

[0155] (1) 590 kg of terephthalic acid, 237 kg of adipic acid, 680 kg of 1,4-butanediol, 8.50 kg of glycerol and 0.470 kg of tetrabutyl titanate were physically mixed at room temperature in an esterification reactor. The resulting mixture was then subjected to an esterification reaction at 235 °C and 50 kPa pressure for 2.5 h to obtain an esterification product with a viscosity of 30 mL / g.

[0156] (2) The esterification product obtained in step (1) was introduced into a vertical stirred fully mixed reactor. 0.380 kg of tetrabutyl titanate was added to the reactor, heated to 238 °C, and reacted at a pressure of 2100 Pa for 5 h. Most of the excess 1,4-butanediol was removed by distillation, and a prepolymer with a viscosity of 68 mL / g was obtained.

[0157] (3) The prepolymer obtained in step (2) was transferred to a final polymerization reactor and polycondensed at a temperature of 245°C and a pressure of 110Pa for 4 hours. The excess 1,4-butanediol and other by-products were removed by distillation to obtain a final polymer with a viscosity of 152 mL / g.

[0158] (4) The final polymer obtained in step (3) is added to a static mixer, and 7.5 kg of hexamethylene diisocyanate is added to it. The mixture is blended at 200 °C for 10 min. Then, it is granulated and dried to obtain an aliphatic-aromatic copolyester with a viscosity of 235 mL / g.

[0159] Comparative Example 1

[0160] This comparative example provides an aliphatic-aromatic copolyester, the preparation method of which includes:

[0161] (1) 400 kg of terephthalic acid, 400 kg of adipic acid, 780 kg of 1,4-butanediol, 3.8 kg of glycerol and 0.330 kg of tetrabutyl titanate were physically mixed at room temperature in an esterification reactor. The resulting mixture was then subjected to an esterification reaction at 235 °C and 90 kPa pressure for 5 h to obtain an esterification product with a viscosity of 10 mL / g.

[0162] (2) The esterification product obtained in step (1) was introduced into a vertical stirred fully mixed reactor. 0.265 kg of tetrabutyl titanate was added to the reactor, heated to 240 °C, and reacted at a pressure of 1600 Pa for 5 h. Most of the excess 1,4-butanediol was removed by distillation, and a prepolymer with a viscosity of 31 mL / g was obtained.

[0163] (3) The prepolymer obtained in step (2) is transferred to a final polymerization reactor and polycondensed at a temperature of 248°C and a pressure of 125Pa for 7 hours. The excess 1,4-butanediol and other byproducts are removed by distillation. Then, the prepolymer is granulated by an underwater granulator and dried to obtain an aliphatic-aromatic copolyester with a viscosity of 183 mL / g.

[0164] Comparative Example 2

[0165] This comparative example provides an aliphatic-aromatic copolyester, the preparation method of which includes:

[0166] (1) 720 kg of terephthalic acid, 237 kg of adipic acid, 760 kg of 1,4-butanediol, 3.8 kg of glycerol and 0.520 kg of tetrabutyl titanate were physically mixed at room temperature in an esterification reactor. The resulting mixture was then subjected to an esterification reaction at 245 °C and 70 kPa pressure for 5 h to obtain an esterification product with a viscosity of 34 mL / g.

[0167] (2) The esterification product obtained in step (1) was introduced into a vertical stirred fully mixed reactor. 0.410 kg of tetrabutyl titanate was added to the reactor, heated to 248°C, and reacted at a pressure of 1200 Pa for 4 h. Most of the excess 1,4-butanediol was removed by distillation, and a prepolymer with a viscosity of 77 mL / g was obtained.

[0168] (3) The prepolymer obtained in step (2) is transferred to a final polymerization reactor and polycondensed at 250°C and 122 Pa for 4.5 h. The excess 1,4-butanediol and other byproducts are removed by distillation. Then, the prepolymer is granulated by an underwater granulator and dried to obtain an aliphatic-aromatic copolyester with a viscosity of 207 mL / g.

[0169] Comparative Example 3

[0170] This comparative example provides an aliphatic-aromatic copolyester, the preparation method of which includes:

[0171] (1-1) 237 kg adipic acid, 210 kg 1,4-butanediol and 10.8 kg glycerol were physically mixed at room temperature in an esterification reactor. The resulting mixture was then subjected to an esterification reaction at 190 °C and 100 kPa pressure for 3 h to obtain an esterification product with a viscosity of 7 mL / g.

[0172] (1-2) 470 kg of terephthalic acid, 450 kg of 1,4-butanediol and 0.250 kg of tetrabutyl titanate were physically mixed at room temperature in an esterification reactor. The resulting mixture was then subjected to an esterification reaction at 230 °C and 55 kPa pressure for 2 h to obtain an esterification product with a viscosity of 9 mL / g.

[0173] (2) The esterification products obtained in steps (1-1) and (1-2) were introduced into a vertical stirred fully mixed reactor. 0.455 kg of tetrabutyl titanate was added to the reactor, heated to 252 °C, and reacted at a pressure of 1400 Pa for 5 h. Most of the excess 1,4-butanediol was removed by distillation, and a prepolymer with a viscosity of 33 mL / g was obtained.

[0174] (3) The prepolymer obtained in step (2) is transferred to a final polymerization reactor and polycondensed at 250°C and 180Pa for 3.5 hours. The excess 1,4-butanediol and other byproducts are removed by distillation. Then, the prepolymer is granulated by an underwater granulator and dried to obtain an aliphatic-aromatic copolyester with a viscosity of 174 mL / g.

[0175] Comparative Example 4

[0176] This comparative example provides an aliphatic-aromatic copolyester, the preparation method of which includes:

[0177] (1) 520 kg of terephthalic acid, 350 kg of adipic acid, 780 kg of 1,4-butanediol, 1.8 kg of glycerol and 0.430 kg of tetrabutyl titanate were physically mixed at room temperature in an esterification reactor. The resulting mixture was then subjected to an esterification reaction at 240 °C and 70 kPa pressure for 4.5 h to obtain an esterification product with a viscosity of 14 mL / g.

[0178] (2) The esterification product obtained in step (1) was introduced into a vertical stirred fully mixed reactor. 0.365 kg of tetrabutyl titanate was added to the reactor, heated to 245 °C, and reacted at a pressure of 1200 Pa for 5 h. Most of the excess 1,4-butanediol was removed by distillation, and a prepolymer with a viscosity of 38 mL / g was obtained.

[0179] (3) The prepolymer obtained in step (2) is transferred to a final polymerization reactor and polycondensed at a temperature of 245°C and a pressure of 110Pa for 4 hours. The excess 1,4-butanediol and other byproducts are removed by distillation. Then, the prepolymer is granulated using an underwater granulator and dried to obtain an aliphatic-aromatic copolyester with a viscosity of 177 mL / g.

[0180] The relevant parameters of the aliphatic-aromatic copolyesters provided in Examples 1-8 and Comparative Examples 1-4 of this application are shown in Table 1.

[0181] Table 1

[0182] Application Examples 1-13, Comparative Application Examples 1-5

[0183] Application Examples 1-13 and Comparative Application Examples 1-5 each provide a biodegradable composition, the formulation of which is shown in Table 2 by weight. Specifically, in the biodegradable compositions provided in Application Examples 1-8 and Comparative Application Examples 1-4, the aliphatic-aromatic copolyester is the aliphatic-aromatic copolyester provided in Examples 1-8 and Comparative Examples 1-4, respectively; in the biodegradable compositions provided in Application Examples 9-13, the aliphatic-aromatic copolyester is the aliphatic-aromatic copolyester provided in Example 2.

[0184] Table 2

[0185] Performance testing

[0186] Application Examples 1-13 and Comparative Application Examples 1-5 were respectively provided with a biodegradable composition and blown film processing was carried out under the following conditions;

[0187] The screw length-to-diameter ratio is 30–32:1, a spiral flow channel die head is used, the air ring is a double- or multi-port air ring, the blown film processing temperature is set at 115–150℃, the blow-up ratio is 3.5–4.0, and the blown film thickness is 20±2μm. After the packaging film is stored at 25±5℃ and 55±5% humidity for 7 days, the heat seal strength is tested according to QB / T2358-1998 standard, and the results are shown in Table 3.

[0188] Table 3

[0189] As shown in Table 3, the aliphatic-aromatic copolyester provided in this application, by controlling the molar content of aromatic dicarboxylic acids within a specific range and using aliphatic-aromatic copolyesters with specific crystallization temperatures, enthalpies of crystallization, and melting points, results in packaging films with high heat-sealing strength, good processing performance, and low cost. The packaging film, after being stored for 7 days at a temperature of 25±5℃ and a humidity of 55±5%, exhibits a heat-sealing strength >9.4 N / 20 mm.

[0190] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An aliphatic-aromatic copolyester comprising the following components: Component A, which comprises an acidic component including the following components: a1) Based on the total molar percentage of a1) and a2), 63 to 69 mol% of terephthalic acid or its derivatives or mixtures thereof; a2) 31–37 mol% adipic acid or its derivatives, or mixtures thereof, based on the total molar percentage of a1) and a2); and, Component B: 1,4-Butanediol in at least an equimolar amount as component A; The enthalpy of crystallization of the aliphatic-aromatic copolyester is -20 to -46 J / g.

2. The aliphatic-aromatic copolyester according to claim 1, wherein, The aliphatic-aromatic copolyester further comprises a crosslinking agent; based on 100 wt% of the aliphatic-aromatic copolyester, the mass percentage of the crosslinking agent is 0.05-1 wt%, preferably 0.12-0.48 wt%, and more preferably 0.22-0.45 wt%.

3. The aliphatic-aromatic copolyester according to claim 2, characterized in that, The crosslinking agent has a functionality of ≥3; Preferably, the crosslinking agent comprises at least one selected from tartaric acid, citric acid, malic acid, trimethylolpropane, trimethylolethane, pentaerythritol, polyether triol, glycerol, 1,3,5-benzotriic acid, 1,2,4-benzotriic acid, 1,2,4-benzotriic anhydride, 1,2,4,5-benzotetraic acid, or benzopyrenic acid dianhydride, more preferably trimethylolpropane, pentaerythritol, or glycerol, and particularly preferably glycerol.

4. The aliphatic-aromatic copolyester according to any one of claims 1 to 3, wherein, The aliphatic-aromatic copolyester further comprises a chain extender, wherein the chain extender has a mass percentage of 0.05 to 1 wt% based on 100 wt% of the aliphatic-aromatic copolyester. Preferably, the functionality of the chain extender is ≥2; Preferably, the chain extender includes isocyanate compounds, peroxides, epoxides, and oxazoles. At least one of porphyrin compounds, oxazine compounds, caprolactam or carbodiimide, and more preferably isocyanate compounds.

5. The aliphatic-aromatic copolyester according to any one of claims 1 to 4, wherein, The melting point of the aliphatic-aromatic copolyester is 153.8–182.2°C, preferably 163–174°C; Preferably, the crystallization temperature of the aliphatic-aromatic copolyester is 92-133°C, more preferably 94-130°C, and even more preferably 102-124°C; Preferably, the enthalpy of crystallization of the aliphatic-aromatic copolyester is -28 to -38 J / g; Preferably, the viscosity of the aliphatic-aromatic copolyester is 140-270 mL / g.

6. A method for preparing an aliphatic-aromatic copolyester according to any one of claims 1 to 5, comprising the following steps: (1) Component A and component B are reacted to obtain an esterified product with a viscosity of 11 to 31 mL / g; (2) The esterified product obtained in step (1) is subjected to a pre-condensation reaction to obtain a pre-condensation product with a viscosity of 35-70 mL / g. (3) The prepolymer obtained in step (2) is subjected to a polycondensation reaction to obtain the aliphatic-aromatic copolyester with a viscosity of 140-270 mL / g.

7. The preparation method according to claim 6, wherein, The raw materials for the reaction in step (1) also include a crosslinking agent; Preferably, the reaction in step (1) includes: (S1) Mix and react components a1 and a2 with component B and optional crosslinking agent to obtain an esterified product with a viscosity of 11 to 31 mL / g. And / or, (S2) React component a1) with component B to obtain esterified product 1 with a viscosity of 11–31 mL / g; react component a2) with component B and an optional crosslinking agent to obtain esterified product 1 with a viscosity of 11–31 mL / g. Object 2; Preferably, the reaction in step (S1) is carried out at a temperature of 180–260°C, a pressure of 40–120 kPa, and a time of 2–8 h; more preferably, the temperature is 220–250°C, the pressure is 60–90 kPa, and the time is 3–6 h. Preferably, in step (S2), the reaction temperature of component a1) with component B is 235–260°C, the pressure is 58–120 kPa, and the time is 2.5–8 h; the reaction temperature of component a2) with component B is 195–260°C, the pressure is 80–120 kPa, and the time is 3.5–8 h.

8. The preparation method according to claim 6 or 7, wherein, The temperature of the pre-condensation reaction in step (2) is 230-270℃, the pressure is 600-3000Pa, and the time is 2-6h. More preferably, the temperature is 240-260℃, the pressure is 800-2100Pa, and the time is 3-5h.

9. The preparation method according to any one of claims 6 to 8, wherein, The polycondensation reaction in step (3) is carried out at a temperature of 230-270°C, a pressure of 50-600 Pa, and a time of 2-6 h, and more preferably at a temperature of 240-260°C, a pressure of 100-300 Pa, and a time of 3-5 h. Preferably, after the polycondensation reaction in step (3) is completed, the obtained polycondensation product is mixed with a chain extender to carry out a chain extension reaction; Preferably, the chain extension reaction is carried out at a temperature of 180–235°C for a time of 3–15 min. Preferably, the viscosity of the polycondensation product obtained in step (3) is 140-240 mL / g; Preferably, the viscosity of the product obtained by the chain extension reaction is 160-270 mL / g.

10. A biodegradable composition, comprising, by weight, 45-75 parts of biodegradable polyester, 3-10 parts of polylactic acid, 2-8 parts of aliphatic-aromatic copolyester and 20-40 parts of inorganic filler; The aliphatic-aromatic copolyester includes the aliphatic-aromatic copolyester according to any one of claims 1 to 5.

11. The biodegradable composition according to claim 10, wherein, The biodegradable polyester comprises the following components: Acid components: i-1) Based on the total molar percentage of i-1) and i-2), 45-50 mol% of aromatic dicarboxylic acids or their esters, or mixtures thereof; i-2) Based on the total molar percentage of i-1) and i-2), 50-55 mol% of aliphatic dicarboxylic acids or their esters, or mixtures thereof; Dihydroxy compound components: i-3) at least in equimolar amounts with the acid component a C2-C6 aliphatic alkanediol, or a mixture thereof; Preferably, the biodegradable polyester comprises at least one of polybutylene terephthalate, polybutylene adipate, polybutylene sebacate, polypropylene adipate, or polypropylene sebacate.

12. The biodegradable composition according to claim 10 or 11, wherein, The inorganic filler includes at least one of calcium carbonate, talc, chalk, calcium oxide, kaolin, silica, titanium dioxide, silicate, mica, or montmorillonite; more preferably, calcium carbonate and / or talc. Preferably, the mass ratio of calcium carbonate to talc is (2-4):

1.

13. The biodegradable composition according to any one of claims 10 to 12, wherein, by weight, the biodegradable composition further comprises 0 to 1 part of an epoxy group-containing copolymer; Preferably, the epoxy-containing copolymer includes at least one of a copolymer of styrene and acrylate, a copolymer of styrene and methacrylate, or a copolymer of styrene, acrylate and methacrylate.

14. A packaging film comprising an aliphatic-aromatic copolyester as described in any one of claims 1 to 5 or a biodegradable composition as described in any one of claims 10 to 13; Preferably, the heat seal strength of the packaging film after 7 days of storage at a temperature of 25±5℃ and a humidity of 55±5% is >9.4N / 20mm.

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