Aliphatic-aromatic polyester, and preparation method therefor and use thereof

Abstract

Provided in the present application are an aliphatic-aromatic polyester, and a preparation method therefor and the use thereof. The aliphatic-aromatic polyester has a high whiteness index and a low acid value, and is degradable; and when the aliphatic-aromatic polyester is used for preparing a degradable material, the ageing resistance of the material can be improved, the variation of color values before and after aging is low, and the material still has a relatively high impact strength after aging, thereby avoiding the loss of mechanical properties.

Description

Aliphatic-aromatic polyester and its preparation method and application Technical Field

[0001] The present application belongs to the technical field of polyester synthesis, and specifically relates to an aliphatic-aromatic polyester and a preparation method and application thereof. Background Art

[0002] Polybutylene succinate (PBS) is a thermoplastic biodegradable aliphatic polyester with good biocompatibility. It is highly favored for its good mechanical properties, molding and processing performance, controllable biodegradation rate and high heat resistance, and is widely used in the field of biodegradable straws.

[0003] For biodegradable straws, their application environment includes both hot drink environments (temperature ≥ 50°C) and cold drink environments (ice-water mixture, temperature ≤ 0°C), so high requirements are placed on the performance of straws in cold and hot states. For biodegradable straws based on PBS resin, although PBS has high toughness, PBS crystallizes quickly and has high crystallinity. After crystallization, PBS straws are prone to brittle fracture after cold and hot treatments, which increases the risk of use. In order to further improve the toughness of PBS, a certain amount of aliphatic-aromatic polyester is usually added to PBS straws. However, aliphatic-aromatic polyesters are usually red or yellow, and the addition of aliphatic-aromatic polyesters will affect the color value of the straws. In order to improve the color of aliphatic-aromatic polyesters, the prior art discloses a method for preparing aliphatic-aromatic polyesters. By adding 0.03 wt.% to 0.04 wt.% of a phosphorus compound during the polymerization process (between step ii and step iii), an aliphatic-aromatic polyester with a whiteness index of at least 25 is obtained; however, the acid value of the obtained aliphatic-aromatic polyester is relatively high (1.1 to 1.4 mg KOH / g), which will lead to a decrease in the mechanical properties of the straw, and the whiteness index of the aliphatic-aromatic polyester needs to be further improved.

[0004] Therefore, developing an aliphatic-aromatic polyester with both a high whiteness index and a low acid value, which can reduce the color value change before and after aging of the straw without affecting its mechanical properties, is an urgent problem to be solved in this field.

[0005] Summary of the Invention

[0006] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0007] The present application provides an aliphatic-aromatic polyester having a high whiteness index and a low acid value. The aliphatic-aromatic polyester is used to prepare straws. It can not only improve the anti-aging performance of the material, but also reduce the color value change before and after aging. Moreover, the aliphatic-aromatic polyester still has a high impact strength after aging, thereby avoiding the loss of mechanical properties.

[0008] In a first aspect, the present application provides an aliphatic-aromatic polyester, wherein the aliphatic-aromatic polyester comprises at least the following components:

[0009] Component A, which comprises a dicarboxylic acid component of the following components:

[0010] a1) 43.5 to 52.0 mol % of an aromatic dicarboxylic acid or an ester thereof, or a mixture thereof, based on the total molar amount of a1) and a2);

[0011] a2) 48.0 to 56.5 mol % of an aliphatic dicarboxylic acid or an ester thereof, or a mixture thereof, based on the total molar amount of a1) and a2);

[0012] wherein the total molar percentage of components a1) and a2) is 100%;

[0013] Component B: a dihydroxy compound, wherein the dihydroxy compound comprises a C2-C6 aliphatic alkanediol in an amount at least equimolar to that of component A, or a mixture thereof;

[0014] Component C: 0.01 to 1.3 wt% of a compound containing at least three functional groups, based on the mass of the aliphatic-aromatic polyester.

[0015] The aliphatic-aromatic polyester has an acid value of ≤0.95 mg KOH / g according to DIN EN 12634-1998.

[0016] The 0.01-1.3 wt% can be, for example, 0.01 wt%, 0.02 wt%, 0.04 wt%, 0.06 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%, 1.1 wt%, 1.2 wt% or 1.3 wt%, etc.

[0017] The aliphatic-aromatic polyester has a whiteness index of ≥33 according to standard ASTM E313-73.

[0018] In the present application, the aliphatic-aromatic polyester has a high whiteness index and a low acid value and is degradable. When used to prepare a degradable material, it can not only improve the anti-aging performance of the material, but also has a small change in color value before and after aging, and has high impact strength after aging, thereby avoiding the loss of mechanical properties.

[0019] In the present application, the 43.5-52.0 mol% can be, for example, 44 mol%, 44.2 mol%, 44.5 mol%, 44.8 mol%, 45 mol%, 45.2 mol%, 45.5 mol%, 45.8 mol%, 46 mol%, 46.2 mol%, 46.5 mol%, 46.8 mol%, 47 mol%, 47.2 mol%, 47.5 mol%, 47.8 mol%, 48 mol%, 48.2 mol%, 48.5 mol%, 48.8 mol%, 49 mol%, 49.2 mol%, 49.5 mol%, 49.8 mol%, 50 mol%, 50.2 mol%, 50.5 mol%, 50.8 mol%, 51 mol%, 51.2 mol%, 51.5 mol%, 51.8 mol% or 52 mol%, etc.

[0020] The 48.0-56.5 mol% can be, for example, 48 mol%, 48.2 mol%, 48.4 mol%, 48.6 mol%, 48.8 mol%, 50 mol%, 50.2 mol%, 50.4 mol%, 50.6 mol%, 50.8 mol%, 51 mol%, 51.2 mol%, 51.5 mol%, 51.8 mol%, 52 mol%, 52.2 mol%, 52.5 mol%, 52.8 mol%, 53 mol%, 53.2 mol%, 53.5 mol%, 53.8 mol%, 54 mol%, 54.2 mol%, 54.5 mol%, 54.8 mol%, 55 mol%, 55.2 mol%, 55.5 mol%, 55.8 mol% or 56 mol%, etc.

[0021] In the present application, the total molar amount of the aromatic dicarboxylic acid compound and the aliphatic dicarboxylic acid compound is 100%; the molar percentage of the aromatic dicarboxylic acid compound and the aliphatic dicarboxylic acid compound refers to the molar percentage of the aromatic dicarboxylic acid portion and the aliphatic dicarboxylic acid portion in the final aliphatic-aromatic polyester.

[0022] Preferably, component A comprises a dicarboxylic acid component of the following components:

[0023] a1) 46.3 to 49.5 mol% of an aromatic dicarboxylic acid or an ester thereof, or a mixture thereof, based on the total molar amount of a1) and a2);

[0024] a2) 50.5 to 53.7 mol % of an aliphatic dicarboxylic acid or an ester thereof, or a mixture thereof, based on the total molar amount of a1) and a2);

[0025] The total molar percentage of components a1) and a2) is 100%.

[0026] In the present application, the number of carbon atoms in the aromatic dicarboxylic acid or its ester can be 8 to 20, for example, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20, etc.; preferably 8 to 12.

[0027] In the present application, the aromatic dicarboxylic acid or its ester-forming derivative (component a1) may be used alone or as a mixture of two or more.

[0028] Preferably, the aromatic dicarboxylic acid or its ester includes at least one of terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid or the above aromatic dicarboxylic acid esters, more preferably terephthalic acid and its esters, such as dimethyl terephthalate.

[0029] In the present application, aromatic dicarboxylic acid esters include ester compounds formed from aromatic dicarboxylic acids, including but not limited to di-C1-C6 alkyl esters. Specifically, the C1-C6 alkyl group can be, for example, any one of dimethyl, diethyl, di-n-propyl, diisopropyl, di-n-butyl, diisobutyl, di-tert-butyl, di-n-pentyl, diisopentyl or di-n-hexyl. In the present application, the aromatic dicarboxylic acid esters also include esters formed from anhydride compounds of aromatic dicarboxylic acids. In the present application, the number of carbon atoms in the aliphatic dicarboxylic acid or its ester can be 2 to 40, for example, 2, 4, 6, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38 or 40, etc.; preferably 4 to 14.

[0030] Preferably, the aliphatic dicarboxylic acid or its ester includes at least one of succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, tridecanedioic acid or the above aliphatic dicarboxylic acid esters, more preferably adipic acid and / or sebacic acid and their esters.

[0031] In the present application, aliphatic dicarboxylic acid esters include ester compounds formed from aliphatic dicarboxylic acids, including but not limited to di-C1-C6 alkyl esters. Specifically, the C1-C6 alkyl group can be, for example, any one of dimethyl, diethyl, di-n-propyl, diisopropyl, di-n-butyl, diisobutyl, di-tert-butyl, di-n-pentyl, diisopentyl, or di-n-hexyl. In the present application, the aliphatic dicarboxylic acid esters also include esters formed from anhydride compounds of aliphatic dicarboxylic acids.

[0032] Preferably, the component B, C2-C6 aliphatic alkanediol, can be a branched or straight-chain aliphatic alkanediol having 2-6 carbon atoms; the C2-C6 can be, for example, C2, C3, C4, C5 or C6.

[0033] In the present application, the aliphatic alkanediol includes at least one of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,4-dimethyl-2-ethyl-1,3-hexanediol, 2,2-dimethyl-1,3-propylene glycol or 2-ethyl-2-butyl-1,3-propylene glycol; more preferably at least one of ethylene glycol, 1,3-propylene glycol or 1,4-butanediol.

[0034] Preferably, the functional group of component C includes at least one of a carboxyl group, a hydroxyl group or an acid anhydride group.

[0035] Preferably, based on the mass of the aliphatic-aromatic polyester, the mass percentage of the component C is 0.05 to 1 wt%, more preferably 0.08 to 0.6 wt%.

[0036] In the present application, the component C includes at least one of tartaric acid, citric acid, malic acid, trimethylolpropane, trimethylolethane, pentaerythritol, polyether triol, glycerol, 1,3,5-trisic acid, 1,2,4-trisic acid, 1,2,4-trisic anhydride, 1,2,4,5-pyromellitic acid or pyromellitic dianhydride, further preferably at least one of trimethylolpropane, pentaerythritol or glycerol, and particularly preferably glycerol.

[0037] Preferably, the aliphatic-aromatic polyester further comprises component D, and the component D is a chain extender.

[0038] Preferably, based on the mass of the aliphatic-aromatic polyester, the mass percentage of the chain extender is 0.05-2.5wt%, for example, it can be 0.05wt%, 0.06wt%, 0.08wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt%, 2wt%, 2.1wt%, 2.2wt%, 2.3wt%, 2.4wt% or 2.5wt%, etc.; more preferably, it is 0.1-2wt%, and more preferably, it is 0.3-1.2wt%.

[0039] Preferably, the chain extender comprises a difunctional or low-functionality chain extender.

[0040] Preferably, the chain extender includes at least one of isocyanate compounds, isocyanurate compounds, peroxides, epoxides, oxazoline compounds, oxazine compounds, caprolactam or carbodiimide.

[0041] In the present application, the isocyanate compound includes aromatic diisocyanates and / or aliphatic diisocyanates; the aromatic diisocyanates include, but are not limited to, 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 at least one of diphenylmethane 2,2′-diisocyanate, diphenylmethane 2,4′-diisocyanate, or diphenylmethane 4,4′-diisocyanate. The isocyanate compound may also include tris(4-isocyanato-phenyl)methane having three rings. This polynuclear aromatic diisocyanate can be formed, for example, during the production of a diisocyanate having one or two rings.

[0042] In the present application, the aliphatic diisocyanate includes an aliphatic diisocyanate containing 2 to 20 carbon atoms, preferably an aliphatic diisocyanate containing 3 to 12 carbon atoms, specifically including but not limited to: at least one of hexamethylene-1,6-diisocyanate, isophorone diisocyanate or methylene di(4-isocyanatocyclohexane); preferably hexamethylene-1,6-diisocyanate.

[0043] In the present application, the peroxide specifically includes but is not limited to 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-butyl peroxide cumene.

[0044] In the present application, the epoxide includes but is not limited to: 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, and one or more of a copolymer containing an epoxy group based on styrene, acrylate and / or methacrylate.

[0045] In the present application, the oxazoline compounds and oxazine compounds each independently include a bridging portion that is a single bond, -(CH2) z - or arylene dioxazoline and dioxazine, wherein z = 2, 3 or 4, such as methylene, ethane-1,2-diyl, propane-1,3-diyl or propane-1,2-diyl, etc.; the arylene group includes phenylene.

[0046] Preferably, the dioxazoline comprises 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.

[0047] The dioxazine is preferably at least one of 2,2′-di(2-dioxazine), di(2-dioxazinyl)methane, 1,2-di(2-dioxazinyl)ethane, 1,3-di(2-dioxazinyl)propane, 1,4-di(2-dioxazinyl)butane, 1,4-di(2-dioxazinyl)benzene, 1,2-di(2-dioxazinyl)benzene or 1,3-di(2-dioxazinyl)benzene.

[0048] The carbodiimide may be at least one 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.

[0049] In the present application, the aliphatic-aromatic polyester at least comprising the following components refers to a molecular structure formed by component A, component B, component C and optional component D in the molecular structure of the aliphatic-aromatic polyester.

[0050] Preferably, the whiteness index of the aliphatic-aromatic polyester is 34-54, more preferably 41-47.

[0051] Preferably, the acid value of the aliphatic-aromatic polyester is 0.39 to 0.90 mg KOH / g, more preferably 0.55 to 0.75 mg KOH / g.

[0052] Preferably, according to ISO 1133-2011, at 190°C and 2.16 kg, the melt index of the aliphatic-aromatic polyester is 1.0 to 12.0 g / 10 min, for example, 1 g / 10 min, 1.5 g / 10 min, 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, g / 10min, 10.5 g / 10min, 11 g / 10min, 11.5 g / 10min or 12 g / 10min, etc.; more preferably 3.0 to 8.5 g / 10min.

[0053] Preferably, according to GB / T 17931-1999, the viscosity number of the aliphatic-aromatic polyester is 155 to 210 mL / g, for example, 155 mL / g, 156 mL / g, 158 mL / g, 160 mL / g, 162 mL / g, 164 mL / g, 166 mL / g, 168 mL / g, 170 mL / g, 172 mL / g, 174 mL / g, 176 mL / g, 178 mL / g, 180mL / g, 182mL / g, 184mL / g, 186mL / g, 188mL / g, 190mL / g, 192mL / g, 194mL / g, 196mL / g, 198mL / g, 200mL / g, 202mL / g, 204mL / g, 206mL / g, 208mL / g or 210mL / g, etc.; more preferably 181-187mL / g.

[0054] In the present application, the viscosity number of the aliphatic-aromatic polyester is within a specific range, and a polyester with a high whiteness index and a low acid value can be obtained, which is used to prepare degradable materials, such as straws. It can reduce the color value change of the straws before and after aging, and has little loss in its mechanical properties, and has a high strength retention rate after aging.

[0055] In this application, the acid value in aliphatic-aromatic polyesters generally refers to the terminal carboxyl content of the polyester product, which is an important indicator reflecting the quality of aliphatic-aromatic polyester products. In the process of polyester synthesis, unreacted aromatic dicarboxylic acid compounds and aliphatic dicarboxylic acid compound end chains may form terminal carboxyl groups, and thermal degradation during the polymerization process may also generate terminal carboxyl groups. The acid value of polyester is usually affected by many factors, such as the type of aliphatic dicarboxylic acid compound and aromatic dicarboxylic acid compound, the feed ratio of aliphatic dicarboxylic acid compound to aromatic dicarboxylic acid compound, the alcohol-acid ratio (the molar ratio of total aliphatic diols to total dicarboxylic acids), and synthesis process conditions. Whiteness is a property of color perception, and it is judged by this property whether the color of an object is close to perfect white. For aliphatic-aromatic polyesters, the product whiteness index is related to factors such as the type of aliphatic dicarboxylic acid, the type and addition amount of catalyst, catalyst deactivator and color stabilizer, and synthesis process conditions. For example, as disclosed in prior art EP3630869 (B1), in the synthesis process of butylene phthalate-co-butylene adipate (PBAT), by adding 0.03-0.04 wt.% of a phosphorus compound, particularly phosphorous acid, after the prepolymerization reaction and before the polycondensation reaction, the resulting PBAT has a whiteness index of greater than 25. However, the acid value of the product increases to 1.1-1.4 mg KOH / g with the addition of the phosphorus compound.

[0056] In a second aspect, the present application provides a method for preparing the aliphatic-aromatic polyester according to the first aspect, the preparation method comprising the following steps:

[0057] (1) reacting component A, component B, and component C at a temperature of 220-248° C. and a pressure of 68-82 kPa for 2.5-5.5 hours to obtain a first product having a viscosity of 24-33 mL / g;

[0058] (2) subjecting the first product obtained in step (1) to a pre-condensation reaction at a temperature of 235 to 250° C. and a pressure of 900 to 1500 Pa for 2.5 to 4.5 hours to obtain a pre-condensation product having a viscosity of 73 to 86 mL / g;

[0059] (3) subjecting the pre-condensation product obtained in step (2) to a condensation reaction at a temperature of 240 to 249° C. and a pressure of 110 to 200 Pa for 1 to 3 hours to obtain the aliphatic-aromatic polyester.

[0060] In the present application, the viscosity of the product in steps (1) to (3) is controlled so that the final aliphatic-aromatic polyester has a high whiteness index and a low acid value, and is used to prepare straws, so that the color value of the straws changes little before and after aging, and the strength retention rate is high.

[0061] In the present application, the reaction in step (1) includes esterification reaction and / or transesterification reaction.

[0062] Preferably, the molar ratio of component B to component A in step (1) is (1.4-2.2):1, wherein the specific value in (1.4-2.2) can be, for example, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2, 2.1, 2.15 or 2.2, etc.; more preferably, it is (1.5-1.7):1.

[0063] In the present application, the viscosity number is 24 to 33 mL / g, for example, it can be 24 mL / g, 24.5 mL / g, 25 mL / g, 25.5 mL / g, 26 mL / g, 26.5 mL / g, 27 mL / g, 27.5 mL / g, 28 mL / g, 28.5 mL / g, 29 mL / g, 29.5 mL / g, 30 mL / g, 30.5 mL / g, 31 mL / g, 31.5 mL / g, 32 mL / g, 32.5 mL / g or 33 mL / g, and is preferably 27.5 to 30.5 mL / g.

[0064] Preferably, the viscosity number of the first product in step (1) is 27.5 to 30.5 mL / g.

[0065] In the present application, the viscosity number is 73 to 86 mL / g, for example, it can be 73 mL / g, 73.5 mL / g, 74 mL / g, 74.5 mL / g, 75 mL / g, 75.5 mL / g, 76 mL / g, 76.5 mL / g, 77 mL / g, 77.5 mL / g, 78 mL / g, 78.5 mL / g, 79 mL / g, 79.5 mL / g, 80 mL / g, 80.5 mL / g, 81 mL / g, 81.5 mL / g, 82 mL / g, 82.5 mL / g, 83 mL / g, 83.5 mL / g, 84 mL / g, 84.5 mL / g, 85 mL / g, 85.5 mL / g or 86 mL / g.

[0066] Preferably, the viscosity of the pre-condensation product in step (2) is 78.5 to 82.5 mL / g.

[0067] In the present application, step (1) is preferably carried out at 225-245° C. and a pressure of 70-80 kPa for 3-5 h; step (2) is preferably carried out at a temperature of 240-250° C. and a pressure of 1000-1400 Pa for a pre-condensation reaction for 3-4 h; and step (3) is preferably carried out at a temperature of 242-247° C. and a pressure of 122-170 Pa for a condensation reaction for 1-3 h.

[0068] Preferably, after the polycondensation reaction is completed, the process further comprises mixing the polycondensation product with a chain extender to carry out a chain extension reaction.

[0069] Preferably, the chain extension reaction temperature is 185-220°C, the time is 6-10 minutes, and the temperature is more preferably 190-220°C.

[0070] Preferably, the viscosity number of the product obtained by the polycondensation reaction is 122-138 mL / g, for example, it can be 122 mL / g, 123 mL / g, 124 mL / g, 125 mL / g, 126 mL / g, 127 mL / g, 128 mL / g, 129 mL / g, 130 mL / g, 131 mL / g, 132 mL / g, 133 mL / g, 134 mL / g, 135 mL / g, 136 mL / g, 137 mL / g or 138 mL / g, etc.; more preferably, it is 127.5-134.5 mL / g.

[0071] In the present application, when a chain extender is added to carry out a chain extension reaction, the viscosity of the product obtained by the polycondensation reaction is controlled to be 122 to 138 mL / g, and then a chain extension reaction is carried out to obtain an aliphatic-aromatic polyester with a viscosity of 155 to 210 mL / g. If a chain extender is not added to carry out a chain extension reaction, the polycondensation reaction directly obtains an aliphatic-aromatic polyester with a viscosity of 155 to 210 mL / g. In the present application, the viscosity is measured in accordance with GB / T17931-1999 in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05°C.

[0072] In the present application, the reactions in steps (1) to (3) and the chain growth reaction are each independently carried out in the presence of a catalyst, which may be an external catalyst or present in the system; the catalyst comprises at least one of a tin compound, an antimony compound, a cobalt compound, a lead compound, a zinc compound, an aluminum compound, or a titanium compound, preferably at least one of a zinc compound, an aluminum compound, or a titanium compound, and most preferably a titanium compound. The catalysts in steps (1) to (3) and the chain growth reaction may be the same or different.

[0073] Specifically, in step (1), components A, B, and C are mixed with 40-70% of the catalyst (referring to 40-70% of the total catalyst amount) and reacted; during the prepolymerization reaction in step (2), the remaining catalyst is added, and the catalyst required for step (3) and the chain growth reaction is the catalyst present in the system. In this application, the titanium catalyst can be tetrabutyl titanate or tetraisopropyl titanate. Compared with other compounds, the titanium catalyst has low toxicity when left in the product or downstream products. This property is particularly important in biodegradable polyesters because they can directly enter the environment in the form of compost bags or mulch films.

[0074] In the present application, the catalyst content is 0.001 to 1 wt% based on the mass of the aliphatic-aromatic polyester, for example, 0.001 wt%, 0.002 wt%, 0.005 wt%, 0.008 wt%, 0.01 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%, 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, 1 wt%, etc., preferably 0.03 to 0.2 wt%. Controlling the amount of catalyst added can make the subsequent processing more stable.

[0075] In the present application, step (1) can be carried out in a mixing device, such as a vertical reactor with stirring; the polycondensation reaction in step (3) occurs in a rotating disc reactor or a cage reactor; and the chain growth reaction in step (4) is carried out in a static mixer.

[0076] In a preferred embodiment of the present application, the preparation method of the aliphatic-aromatic polyester comprises:

[0077] (1) reacting component A, component B, and component C in the presence of a catalyst at 220-248° C. and 68-82 kPa for 2.5-5.5 hours to obtain a first product having a viscosity number of 24-33 mL / g;

[0078] (2) in the presence of a catalyst, subjecting the first product obtained in step (1) to a pre-condensation reaction at 235-250° C. and 900-1500 Pa for 2.5-4.5 hours to obtain a pre-condensation product having a viscosity of 73-86 mL / g;

[0079] (3) subjecting the pre-condensation product obtained in step (2) to a condensation reaction at 240-249° C. and 110-200 Pa for 1-3 hours to obtain a condensation product having a viscosity of 122-138 mL / g;

[0080] (4) mixing the polycondensation product obtained in step (3) with a chain extender, and performing a chain extension reaction at 185-220° C. for 6-10 minutes to obtain the aliphatic-aromatic polyester having a viscosity of 155-210 mL / g.

[0081] In the present application, the preparation method uses raw materials of specific components, and through the mutual coordination of process parameters in each step, the obtained aliphatic-aromatic polyester has a high whiteness index and a low acid value; when used to prepare degradable materials, it can not only improve the anti-aging performance of the material, but also have little change in color value after aging, and high impact strength after aging, thereby avoiding the loss of mechanical properties.

[0082] It should be further noted that the aliphatic-aromatic polyester having both a high whiteness index and a low acid value described in the present application is not limited to the above-mentioned method and can also be obtained by other process methods. For example, in step (1), an aromatic dicarboxylic acid compound and an aliphatic dicarboxylic acid compound are reacted with an aliphatic diol compound to obtain two esters, which are then mixed and subjected to subsequent prepolymerization, polycondensation, and chain growth reactions.

[0083] Specifically, the method includes:

[0084] Component a2), component B and component C are reacted at a temperature of 185-195° C. and a pressure of 95-105 kPa for 2.5-5.5 hours to obtain an esterification product A having a viscosity of 10-15 mL / g; component a1) and component B are reacted at a temperature of 230-240° C. and a pressure of 75-85 kPa in the presence of a catalyst for 3-5 hours to obtain an esterification product B having a viscosity of 18-25 mL / g; the esterification product A and the esterification product B are then mixed and subjected to a pre-polycondensation reaction, a polycondensation reaction and preferably a chain extension reaction; wherein the conditions for the pre-polycondensation reaction, the polycondensation reaction and preferably the chain extension reaction are selected from the same range as steps (2) to (4).

[0085] In a third aspect, the present application provides a biodegradable polyester composition, which comprises, in parts by weight, 30 to 70 parts of polybutylene succinate (for example, 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, 44 parts, 46 parts, 48 ​​parts, 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, 62 parts, 64 parts, 66 parts, 68 parts or 70 parts), 3 to 15 parts of aliphatic-aromatic polyester (for example, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts or 15 parts), 5 ~35 parts of polylactic acid (for example, it can be 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, 32 parts, 34 parts or 35 parts, etc.) and 10-35 parts of filler (for example, it can be 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, 32 parts, 34 parts or 35 parts, etc.); the aliphatic-aromatic polyester includes the aliphatic-aromatic polyester as described in the first aspect or the aliphatic-aromatic polyester prepared according to the preparation method described in the second aspect.

[0086] In the present application, the filler includes at least one of talc, calcium carbonate, barium sulfate, montmorillonite or kaolin.

[0087] In the present application, 0.5 to 1.5 parts of other additives may be added according to actual needs, for example, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts or 1.5 parts, etc.

[0088] Preferably, the other auxiliary agents include but are not limited to at least one of an antioxidant, a light stabilizer, a lubricant, a release agent or an antistatic agent.

[0089] In the present application, there is no excessive limitation on the types of auxiliary agents, and conventional auxiliary agents can be used. Specifically, the antioxidant includes but is not limited to any one of antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant 164, antioxidant DLTP or antioxidant TPP.

[0090] The light stabilizer includes but is not limited to at least one of a hindered amine light stabilizer (such as light stabilizer 770, light stabilizer 622, light stabilizer 944, etc.), a benzophenone light stabilizer (such as UV531) or a benzotriazole light stabilizer.

[0091] The lubricant includes but is not limited to at least one of esters (such as polyethylene glycol esters, polyol esters), montanate, ethylene bisstearamide or polyethylene wax.

[0092] The release agent includes at least one of an inorganic release agent (such as talc, mica powder, clay, etc.), an organic release agent (such as fatty acid, paraffin, glycerin, vaseline, etc.) or a polymer release agent (such as silicone oil, polyethylene glycol, low molecular weight polyethylene, etc.).

[0093] The antistatic agent includes at least one of a cationic antistatic agent (such as a quaternary ammonium salt), an anionic antistatic agent (such as an alkyl sulfonate, a phosphate), an amphoteric antistatic agent (such as an amphoteric imidazoline compound), a nonionic antistatic agent (such as a hydroxyethyl alkylamine, a fatty amide, a polyoxyethylene, a polyol ester) or a polymer antistatic agent (such as a polyether).

[0094] In a fourth aspect, the present application provides a straw, comprising the biodegradable polyester composition described in the third aspect.

[0095] Preferably, after aging the straws at 60°C and 60% humidity for 48 hours and then at -10°C to 0°C for 72 hours, the color change ΔE of the straws is less than 1, for example, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or 0.98; the notched impact strength retention rate η is ≥ 70%, for example, 70%, 72%, 75%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, or 96%. More preferably, ΔE is less than 0.7, and η is ≥ 75%.

[0096] In this application, the color value change of the straw before and after aging is tested according to CIE 1976 (L*a*b*); the notched impact strength before and after aging is tested according to ISO 180-2000, and the retention rate is calculated.

[0097] In the present application, the aliphatic-aromatic polyester and the polyester composition containing the aliphatic-aromatic polyester are also biodegradable.

[0098] For the purposes of this application, 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%.

[0099] Biodegradation generally refers to the breakdown of a polyester or polyester blend within a reasonable period of time. Degradation can occur via enzymatic, hydrolytic, or oxidative pathways, and / or through exposure to electromagnetic radiation, such as ultraviolet radiation, most commonly through exposure to microorganisms such as bacteria, yeast, fungi, and algae. Biodegradability can be quantified by mixing the polyester with compost and storing it for a specific period of time. For example, 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 degree 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 based on the carbon content of the sample).

[0100] 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 limited space and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0101] Compared with the related art, the beneficial effects of this application are:

[0102] The aliphatic-aromatic polyester provided herein has a whiteness index of 33 or greater and an acid value of 0.95 mg KOH / g or less. When added as an additive to materials used to prepare PBS biodegradable straws, it mitigates the yellowing and mechanical property degradation that occurs during aging of PBS straws. Specifically, after aging the straws comprising the aliphatic-aromatic polyester for 48 hours at 60°C and 60% humidity, and then for 72 hours at -10°C to 0°C, the color change (ΔE) was less than 1, and the notched impact strength retention (η) was ≥70%.

[0103] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0104] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0105] The materials used in this application are as follows. Unless otherwise specified, all materials used in this application can be obtained commercially.

[0106] 1,4-Butanediol was purchased from Xinjiang Meike Chemical Co., Ltd.;

[0107] Terephthalic acid was purchased from Zhuhai INEOS Chemical Co., Ltd.;

[0108] Adipic acid was purchased from Chongqing Huafeng Chemical Group Co., Ltd.;

[0109] Glycerin was sourced from Aladdin;

[0110] Tetrabutyl titanate was purchased from Jianyi Chemical Import and Export Co., Ltd.

[0111] Hexamethylene diisocyanate was purchased from Aladdin;

[0112] Polybutylene succinate was selected from ECOPOND A200 of Zhuhai Jinfa Biomaterial Co., Ltd.;

[0113] The polylactic acid is selected from PLA 3001D and PLA 3251D of Natureworks;

[0114] Other additives: Antioxidant 1010.

[0115] Example 1

[0116] This embodiment provides an aliphatic-aromatic polyester, and the preparation method of the aliphatic-aromatic polyester comprises the following steps:

[0117] (1) 452 kg of terephthalic acid, 437 kg of adipic acid, 770 kg of 1,4-butanediol, 3.50 kg of glycerol, and 0.61 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was subjected to an esterification reaction at 245° C. and 70 kPa for 4.5 hours to obtain an esterified product; the esterified product had a viscosity of 32 mL / g when measured in a mixed solution of phenol and o-dichlorobenzene in a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T 17931-1999;

[0118] (2) introducing the esterification product obtained in step (1) into a vertical stirring fully mixed reactor, adding 0.35 kg of tetrabutyl titanate into the reactor, reacting at 248° C. and 1000 Pa for 3.5 hours, and distilling off most of the excess 1,4-butanediol to obtain a reaction mixture, i.e., a prepolymer; the viscosity of the prepolymer measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T 17931-1999 is 85 mL / g;

[0119] (3) transferring the reaction mixture obtained in step (2) into a final polymerization reactor, polycondensing the mixture at a temperature of 244° C. and a pressure of 125 Pa for 2 h, removing the remaining excess 1,4-butanediol and other by-products by distillation, and then granulating and drying the mixture to obtain a final polymerization product; the final polymerization product has a viscosity of 138 mL / g measured in a mixed solution of phenol and o-dichlorobenzene in a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T 17931-1999;

[0120] (4) The final polymerization product obtained in step (3) was added to a static mixer, 5.8 kg of hexamethylene diisocyanate was added thereto, and the mixture was blended and reacted at 190° C. for 7 minutes. Then, the mixture was granulated and dried to obtain the aliphatic-aromatic polyester.

[0121] Example 2

[0122] This embodiment provides an aliphatic-aromatic polyester, and the preparation method of the aliphatic-aromatic polyester comprises the following steps:

[0123] (1) 452 kg of terephthalic acid, 437 kg of adipic acid, 770 kg of 1,4-butanediol, 3.50 kg of glycerol, and 0.45 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was subjected to an esterification reaction at 225° C. and a pressure of 80 kPa for 3.5 hours to obtain an esterified product; the esterified product had a viscosity of 25 mL / g when measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T 17931-1999;

[0124] (2) introducing the esterification product obtained in step (1) into a vertical stirring fully mixed reactor, adding 0.23 kg of tetrabutyl titanate into the reactor, and reacting at 240° C. and a pressure of 1400 Pa for 3 hours, wherein most of the excess 1,4-butanediol is distilled off to obtain a reaction mixture, i.e., a prepolymer. The viscosity of the prepolymer measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T 17931-1999 is 74 mL / g;

[0125] (3) transferring the reaction mixture obtained in step (3) into a final polymerization reactor, polycondensing the mixture at a temperature of 247° C. and a pressure of 160 Pa for 1.5 h, removing the remaining excess 1,4-butanediol and other by-products by distillation, and then granulating and drying the mixture to obtain a final polymerization product, wherein the final polymerization product has a viscosity of 122 mL / g measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T 17931-1999;

[0126] (4) The final polymerization product obtained in step (3) was added to the end of a static mixer, 3.5 kg of hexamethylene diisocyanate was added thereto, and the mixture was blended and reacted at 200° C. for 8 minutes. Then, the mixture was granulated and dried to obtain the aliphatic-aromatic polyester.

[0127] Example 3

[0128] This embodiment provides an aliphatic-aromatic polyester, and the preparation method of the aliphatic-aromatic polyester comprises the following steps:

[0129] (1) 452 kg of terephthalic acid, 437 kg of adipic acid, 770 kg of 1,4-butanediol, 3.50 kg of glycerol, and 0.50 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was subjected to an esterification reaction at 240° C. and a pressure of 75 kPa for 4 hours to obtain an esterified product, wherein the viscosity of the esterified product measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T17931-1999 is 30 mL / g;

[0130] (2) introducing the esterification product obtained in step (1) into a vertical stirring fully mixed reactor, adding 0.24 kg of tetrabutyl titanate into the reactor, and reacting at 245° C. and a pressure of 1100 Pa for 4.5 hours, wherein most of the excess 1,4-butanediol is distilled off to obtain a reaction mixture, i.e., a prepolymer, wherein the viscosity of the prepolymer is 82 mL / g as measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. as specified in GB / T 17931-1999;

[0131] (3) transferring the reaction mixture obtained in step (2) into a final polymerization reactor, polycondensing the mixture at a temperature of 244° C. and a pressure of 140 Pa for 2 h, removing the remaining excess 1,4-butanediol and other by-products by distillation, and then granulating and drying the mixture to obtain a final polymerization product, wherein the final polymerization product has a viscosity of 134 mL / g as measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T 17931-1999;

[0132] (4) The final polymerization product obtained in step (3) was added to a static mixer, 6.5 kg of hexamethylene diisocyanate was added thereto, and the mixture was blended and reacted at 200° C. for 8 minutes. Then, the mixture was granulated and dried to obtain the aliphatic-aromatic polyester.

[0133] Example 4

[0134] This embodiment provides an aliphatic-aromatic polyester, and the preparation method of the aliphatic-aromatic polyester comprises the following steps:

[0135] (1) 452 kg of terephthalic acid, 437 kg of adipic acid, 770 kg of 1,4-butanediol, 3.50 kg of glycerol, and 0.48 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was subjected to an esterification reaction at 230° C. and a pressure of 75 kPa for 3.5 hours to obtain an esterified product, wherein the viscosity of the esterified product measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T 17931-1999 is 28 mL / g;

[0136] (2) introducing the esterification product obtained in step (1) into a vertical stirring fully mixed reactor, adding 0.21 kg of tetrabutyl titanate into the reactor, and reacting at 242° C. and a pressure of 1300 Pa for 4 hours, wherein most of the excess 1,4-butanediol is distilled off to obtain a reaction mixture, i.e., a prepolymer, wherein the viscosity of the prepolymer is 79 mL / g as measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T 17931-1999;

[0137] (3) transferring the reaction mixture obtained in step (3) into a final polymerization reactor, polycondensing the mixture at a temperature of 242° C. and a pressure of 150 Pa for 1.8 h, removing the remaining excess 1,4-butanediol and other by-products by distillation, and then granulating and drying the mixture to obtain a final polymerization product, wherein the final polymerization product has a viscosity of 128 mL / g as measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T 17931-1999;

[0138] (4) The final polymerization product obtained in step (3) was added to a static mixer, and 6.2 kg of hexamethylene diisocyanate was added, and the mixture was mixed and reacted at 200° C. for 9 minutes. Then, the mixture was granulated and dried to obtain the aliphatic-aromatic polyester.

[0139] Example 5

[0140] This embodiment provides an aliphatic-aromatic polyester, and the preparation method of the aliphatic-aromatic polyester comprises the following steps:

[0141] (1) 390 kg of terephthalic acid, 437 kg of adipic acid, 770 kg of 1,4-butanediol, 3.30 kg of glycerol, and 0.60 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was subjected to an esterification reaction at 238° C. and a pressure of 72 kPa for 4.3 hours to obtain an esterified product, wherein the viscosity of the esterified product measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T 17931-1999 is 31 mL / g;

[0142] (2) introducing the esterification product obtained in step (1) into a vertical stirring fully mixed reactor, adding 0.28 kg of tetrabutyl titanate into the reactor, reacting at 246° C. and a pressure of 1250 Pa for 3.5 hours, and removing most of the excess 1,4-butanediol by distillation to obtain a reaction mixture, i.e., a prepolymer, wherein the viscosity of the prepolymer is 80 mL / g as measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T 17931-1999;

[0143] (3) transferring the reaction mixture obtained in step (2) into a final polymerization reactor, polycondensing the mixture at a temperature of 243° C. and a pressure of 145 Pa for 2.5 hours, removing the remaining excess 1,4-butanediol and other by-products by distillation, and then granulating and drying the mixture to obtain a final polymerization product, wherein the final polymerization product has a viscosity of 133 mL / g as measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T 17931-1999;

[0144] (4) The final polymerization product obtained in step (3) was passed through a static mixer, 5.6 kg of hexamethylene diisocyanate was added, and the mixture was mixed and reacted at 200° C. for 7 minutes. Then, the mixture was granulated and dried to obtain the aliphatic-aromatic polyester.

[0145] Example 6

[0146] This embodiment provides an aliphatic-aromatic polyester. The preparation method of the aliphatic-aromatic polyester differs from that of Example 1 only in that, based on the total molar amount of dicarboxylic acids as 100 mol%, the molar percentage of terephthalic acid in step (1) is 44.5 mol%, adipic acid is replaced by sebacic acid with a molar percentage of 55.5 mol%; 1,4-butanediol is replaced by 1,3-propylene glycol (the molar ratio of 1,3-propylene glycol to component A is 1.45:1); glycerol is replaced by trimethylolpropane (accounting for 0.4% of the total mass of the aliphatic-aromatic polyester); the temperature of the polycondensation reaction in step (3) is 240°C, the pressure is 180 Pa, and the reaction time is 2 h; in step (4), the reaction is carried out at 185°C for 10 min, and the other steps are the same as in Example 1.

[0147] Example 7

[0148] This embodiment provides an aliphatic-aromatic polyester, and the preparation method of the aliphatic-aromatic polyester comprises the following steps:

[0149] (1-1) 437 kg of adipic acid, 370 kg of 1,4-butanediol, and 3.50 kg of glycerol were physically mixed in a first esterification reactor at room temperature, and then the mixture was subjected to an esterification reaction at 190° C. and 101 kPa for 3.0 hours to obtain an esterified product; the esterified product A had a viscosity of 13 mL / g when measured in a mixed solution of phenol and o-dichlorobenzene in a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T 17931-1999;

[0150] (1-2) 452 kg of terephthalic acid, 400 kg of 1,4-butanediol, and 0.70 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and the mixture was then subjected to an esterification reaction at 236° C. and 80 kPa for 4.0 hours to obtain an esterified product T; the esterified product had a viscosity of 21 mL / g when measured in a mixed solution of phenol and o-dichlorobenzene in a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T 17931-1999;

[0151] (2) introducing the esterified product A and the esterified product T obtained in steps (1-1) and (1-2) into a vertical stirred fully mixed reactor, adding 0.38 kg of tetrabutyl titanate into the reactor, reacting at 242° C. and 1300 Pa for 4.0 h, and distilling off most of the excess 1,4-butanediol to obtain a reaction mixture, i.e., a prepolymer; the viscosity of the prepolymer measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T 17931-1999 is 74 mL / g;

[0152] (3) transferring the reaction mixture obtained in step (2) into a final polymerization reactor, polycondensing the mixture at a temperature of 243° C. and a pressure of 110 Pa for 2 h, removing the remaining excess 1,4-butanediol and other by-products by distillation, and then granulating and drying the mixture to obtain a final polymerization product; the final polymerization product has a viscosity of 128 mL / g measured in a mixed solution of phenol and o-dichlorobenzene in a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T 17931-1999;

[0153] (4) The final polymerization product obtained in step (3) was added to a static mixer, 6.2 kg of hexamethylene diisocyanate was added thereto, and the mixture was blended and reacted at 200° C. for 7 minutes. Then, the mixture was granulated and dried to obtain the aliphatic-aromatic polyester.

[0154] Example 8

[0155] This embodiment provides an aliphatic-aromatic polyester. The only difference between this embodiment and Example 1 is that, in the preparation method of the aliphatic-aromatic polyester, the content of terephthalic acid is increased to achieve a molar percentage of terephthalic acid in the aliphatic-aromatic polyester of 50.0 mol%. The total molar amount of terephthalic acid and adipic acid remains unchanged. Other raw materials, amounts, and process parameters are the same as those in Example 1.

[0156] Example 9

[0157] This embodiment provides an aliphatic-aromatic polyester, and the preparation method of the aliphatic-aromatic polyester comprises the following steps:

[0158] (1) 452 kg of terephthalic acid, 437 kg of adipic acid, 770 kg of 1,4-butanediol, 6.50 kg of glycerol, and 0.70 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was subjected to an esterification reaction at 240° C. and 65 kPa for 4.0 h to obtain an esterified product; the esterified product had a viscosity of 31 mL / g when measured in a mixed solution of phenol and o-dichlorobenzene in a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T17931-1999;

[0159] (2) introducing the esterification product obtained in step (1) into a vertical stirring fully mixed reactor, adding 0.38 kg of tetrabutyl titanate into the reactor, reacting at 245° C. and 1200 Pa for 3.0 h, and distilling off most of the excess 1,4-butanediol to obtain a reaction mixture, i.e., a prepolymer; the viscosity of the prepolymer measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T 17931-1999 is 84 mL / g;

[0160] (3) The reaction mixture obtained in step (2) is transferred to a final polymerization reactor, and polycondensed at a temperature of 245° C. and a pressure of 100 Pa for 3 hours, and the remaining excess 1,4-butanediol and other by-products are distilled off. Then, the reaction mixture is granulated and dried to obtain a final polymerization product; the final polymerization product has a viscosity of 162 mL / g measured in a mixed solution of phenol and o-dichlorobenzene in a weight ratio of 1:1 in a constant temperature water bath at 25±0.05° C. according to GB / T 17931-1999.

[0161] Comparative Example 1

[0162] This comparative example provides an aliphatic-aromatic polyester, which differs from Example 1 only in that the whiteness index of the aliphatic-aromatic polyester is 40.12 and the acid value is 1.68 mg KOH / g. In the preparation method, the reaction temperature in step (1) is 215°C, the reaction pressure is 100 kPa, and the reaction time is 2 h; the reaction temperature in step (3) is 250°C, the reaction pressure is 110 Pa, and the reaction time is 3 h. Other raw materials and amounts are the same as those in Example 1.

[0163] Comparative Example 2

[0164] This comparative example provides an aliphatic-aromatic polyester, which differs from Example 1 only in that the whiteness index of the aliphatic-aromatic polyester is 27.32 and the acid value is 0.71 mg KOH / g. In the preparation method, the reaction temperature in step (1) is 250°C, the reaction pressure is 60 kPa, and the reaction time is 5 h; the reaction temperature in step (3) is 250°C, the reaction pressure is 100 Pa, and the reaction time is 2.5 h. Other raw materials and amounts are the same as those in Example 1.

[0165] Comparative Example 3

[0166] This comparative example provides an aliphatic-aromatic polyester, which differs from Example 1 only in that the aliphatic-aromatic polyester has a whiteness index of 30.17 and an acid value of 1.45 mg KOH / g. In the preparation method, the reaction temperature in step (2) is 240°C, the reaction pressure is 3000 Pa, and the reaction time is 6 h. In step (4), the reaction is carried out at 210°C for 13 min. Other raw materials and amounts are the same as those in Example 1.

[0167] Comparative Example 4

[0168] This comparative example provides an aliphatic-aromatic polyester, which differs from Example 1 only in that the whiteness index of the aliphatic-aromatic polyester is 34.23 and the acid value is 1.27 mg KOH / g. In the preparation method, the reaction temperature in step (2) is 260°C, the reaction pressure is 4000 Pa, and the reaction time is 4.5 h. Other raw materials and amounts are the same as those in Example 1.

[0169] Comparative Example 5

[0170] This comparative example provides an aliphatic-aromatic polyester, which differs from Example 1 only in that, in the preparation method, the feeding amount of terephthalic acid in step (1) is adjusted to 360 kg, and the feeding amount of 1,4-butanediol is adjusted to 700 kg, and the other raw materials, amounts and reaction conditions are the same as those in Example 1.

[0171] Comparative Example 6

[0172] This comparative example provides an aliphatic-aromatic polyester, which differs from Example 1 only in that, in the preparation method of the aliphatic-aromatic polyester, the content of terephthalic acid is increased to achieve a molar percentage of terephthalic acid in the aliphatic-aromatic polyester of 55.0 mol%. The total molar amount of terephthalic acid and adipic acid remains unchanged. Other raw materials, amounts, and process parameters are the same as those in Comparative Example 1.

[0173] The following tests were performed on the aliphatic-aromatic polyesters provided in Examples 1 to 9 and Comparative Examples 1 to 6:

[0174] (1) Testing the molar content of aromatic dicarboxylic acid and aliphatic dicarboxylic acid in aliphatic-aromatic polyester. The specific testing method is as follows:

[0175] 20 mg of aliphatic-aromatic polyester sample was dissolved in 0.6 mL of deuterated chloroform and then measured at room temperature using a Bruker AV 500 NMR spectrometer. 1 H NMR, calibrated to the chloroform solvent peak at around 7.26 ppm.

[0176] Reference: 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 diacid component can be expressed by the integrated areas (IT and IA) of the two peaks at 8.10 ppm and 2.33 ppm:

[0177] Aromatic dicarboxylic acid molar content in aliphatic-aromatic polyester = IT / (IT+IA)×100%;

[0178] The molar content of aliphatic dicarboxylic acid in the aliphatic-aromatic polyester = IA / (IT+IA) x 100%.

[0179] (2) Viscosity number of aliphatic-aromatic polyesters: According to GB / T 17931-1999, the viscosity number was measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25±0.05°C. The sample concentration was 5 mg / mL.

[0180] (3) Melt index: tested in accordance with ISO 1133-2011, test conditions: 190°C, 2.16 kg.

[0181] (4) Acid value of aliphatic-aromatic polyesters: The acid value AN (mg KOH / g) of the sample was determined according to DIN EN 12634, October 1998.

[0182] The solvent mixture used includes: 1 part by volume of dimethyl sulfoxide, 8 parts by volume of isopropyl alcohol and 7 parts by volume of toluene, and the volume of the solvent mixture is 150 mL.

[0183] According to DIN EN 12634, pre-titrate the sample to determine the appropriate sample mass and ensure a volume of 2-3 mL of titrant consumed. Add the sample to the solvent mixture and heat to 70-85°C to dissolve the sample into a clear solution. Maintain the solution temperature between 65-75°C during the titration to prevent sample precipitation. If appropriate, use tetrabutylammonium hydroxide as the titrant, avoiding the highly toxic tetramethylammonium hydroxide. To prevent the solvent mixture from absorbing CO₂ from the air and affecting the volume of the blank solvent consumed, pre-treat the blank solvent using the same pretreatment procedure as the sample test, such as heating the blank solvent for the same time and temperature, before titrating the blank solvent.

[0184] (5) Whiteness Index: The whiteness index of aliphatic-aromatic polyester granules having a particle size of 1.2 to 5.4 g / 100 particles was determined using a Minolta CM-5 spectrophotometer in accordance with ASTM E313-73. Three replicate measurements were performed to determine the average value. A glass cuvette (from Minolta) was filled with the granular material to be analyzed (filling height of at least 3 cm). The granular material was compacted using pressure from the measuring head of the Minolta instrument.

[0185] The specific test results are shown in Table 1:

[0186] Table 1

[0187] In addition, in the preparation methods of aliphatic-aromatic polyesters provided in Examples 1 to 9 and Comparative Examples 1 to 6, the viscosity (mL / g) of the products obtained in steps (1) to (3) is shown in Table 2.

[0188] Table 2

[0189] As can be seen from Tables 1 and 2, the aliphatic-aromatic polyester provided in the present application can obtain polyesters having a high whiteness index and a low acid value by controlling the viscosity of the product of each step within a specific range. As can be seen from the comparison of the examples and the comparative examples, when the viscosity of the product of each step is not within the specific range, the obtained polyester cannot have both a high whiteness index and a low acid value.

[0190] Application Examples 1-7, Comparative Application Examples 1-2

[0191] Application Examples 1-7 and Comparative Application Examples 1-2 respectively provide a biodegradable polyester composition, the formula of which is shown in Table 3 (in parts by weight); the preparation method of the polyester composition comprises: mixing the components and adding them to a twin-screw extruder (L / D = 48; diameter 40 mm), performing melt mixing and extrusion granulation, the temperature of the twin-screw extruder in different intervals is 140-155-160-170-170-180-180-180-190-200 ° C, the screw speed is 300 rpm, and the vacuum is -0.50 kg / cm 2 , to obtain a biodegradable mixture.

[0192] Table 3

[0193] Application Examples 8, 9, and 10, and Comparative Application Examples 3 to 6

[0194] Application Examples 8, 9, and 10, and Comparative Application Examples 3 to 6 respectively provide a biodegradable polyester composition, which differs from Application Example 1 only in that the aliphatic-aromatic polyesters are the aliphatic-aromatic polyesters provided in Examples 7, 8, and 9, and Comparative Examples 3 to 6, respectively, and the other components and dosage agent preparation methods are the same as those in Application Example 1.

[0195] The biodegradable polyester compositions provided in Application Examples 1 to 10 and Comparative Application Examples 1 to 6 were injection molded into straws and subjected to the following tests:

[0196] (1) Notched impact strength test:

[0197] The notched impact strength of straws before and after aging was tested according to ISO 180-2000. The specific steps included crushing the straws before and after aging and then injection molding them into test strips at 160-180°C. Five strips were tested for each sample, and the average value was taken. The notched impact strength retention rate (η) after aging was calculated using the formula: notched impact strength after aging / notched impact strength before aging × 100%.

[0198] (2) Color value change △E test:

[0199] The color values ​​(L*a*b*) of straws before and after aging were tested according to CIE 1976 (L*a*b*). Specifically, the straws were broken into pieces of approximately 5 mm x 5 mm before and after aging. The color values ​​of the samples were tested according to CIE 1976 (L*a*b*), and the ΔE value was calculated using the following formula.

[0200] Among them, △L represents the difference in L value before and after aging, △a represents the difference in a value before and after aging, and △b represents the difference in b value before and after aging.

[0201] In the present application, the aging conditions are: aging at 60° C. and 60% humidity for 48 hours, and then aging at -10° C. to 0° C. for 72 hours.

[0202] The specific test results are shown in Table 4:

[0203] Table 4

[0204] As can be seen from Table 4, the aliphatic-aromatic polyester provided in the present application has a high whiteness index and a low acid value. When used to prepare straws, it can improve the aging resistance of the straws. After aging, it still has high notched impact strength, and the color value changes little before and after aging. The straws prepared from the biodegradable polyester composition containing the aliphatic-aromatic polyester are aged at 60°C and 60% humidity for 48 hours, and then aged at -10°C to 0°C for 72 hours. The notched impact strength retention rate η is ≥70%, and the color value change ΔE of the product after aging is <1.

[0205] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of this application. It should be understood that the above is only a specific embodiment of this application and is not intended to limit this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application should be included in the scope of protection of this application.

Claims

1. An aliphatic-aromatic polyester comprising at least the following components: Component A, which comprises a dicarboxylic acid component of the following components: a1) 43.5 to 52.0 mol % of an aromatic dicarboxylic acid or an ester thereof, or a mixture thereof, based on the total molar amount of a1) and a2); a2) 48.0 to 56.5 mol % of an aliphatic dicarboxylic acid or an ester thereof, or a mixture thereof, based on the total molar amount of a1) and a2); in, The total molar percentage of components a1) and a2) is 100%; Component B: a dihydroxy compound, wherein the dihydroxy compound comprises a C2-C6 aliphatic alkanediol in an amount at least equimolar to that of component A, or a mixture thereof; Component C: 0.01 to 1.3 wt% of a compound containing at least three functional groups, based on the mass of the aliphatic-aromatic polyester; The aliphatic-aromatic polyester has an acid value of ≤0.95 mg KOH / g according to standard DIN EN 12634-1998; The aliphatic-aromatic polyester has a whiteness index of ≥33 according to standard ASTM E313-73.

2. The aliphatic-aromatic polyester according to claim 1, wherein Component A comprises a dicarboxylic acid component of the following composition: a1) 46.3 to 49.5 mol % of an aromatic dicarboxylic acid or an ester thereof, or a mixture thereof, based on the total molar amount of a1) and a2); a2) 50.5 to 53.7 mol % of an aliphatic dicarboxylic acid or an ester thereof, or a mixture thereof, based on the total molar amount of a1) and a2); The total molar percentage of components a1) and a2) is 100%.

3. The aliphatic-aromatic polyester according to claim 1 or 2, wherein The functional group of component C includes at least one of a carboxyl group, a hydroxyl group or an anhydride group; Preferably, based on the mass of the aliphatic-aromatic polyester, the mass percentage of component C is 0.05 to 1 wt %, and more preferably 0.08 to 0.6 wt %.

4. The aliphatic-aromatic polyester according to any one of claims 1 to 3, wherein The aliphatic-aromatic polyester further comprises a component D, wherein the component D is a chain extender; Preferably, based on the mass of the aliphatic-aromatic polyester, the mass percentage of the chain extender is 0.05 to 2.5 wt %, more preferably 0.1 to 2 wt %, and even more preferably 0.3 to 1.2 wt %.

5. The aliphatic-aromatic polyester according to any one of claims 4, wherein The chain extender includes a difunctional or low-functional chain extender; Preferably, the chain extender includes at least one of isocyanate compounds, isocyanurate compounds, peroxides, epoxides, oxazoline compounds, oxazine compounds, caprolactam or carbodiimide.

6. The aliphatic-aromatic polyester according to any one of claims 1 to 5, wherein The whiteness index of the aliphatic-aromatic polyester is 34 to 54, more preferably 41 to 47; Preferably, the acid value of the aliphatic-aromatic polyester is 0.39 to 0.90 mg KOH / g, more preferably 0.55 to 0.75 mg KOH / g.

7. The aliphatic-aromatic polyester according to any one of claims 1 to 6, wherein According to ISO 1133-2011, at 190°C and 2.16 kg, the melt index of the aliphatic-aromatic polyester is 1.0 to 12.0 g / 10 min, more preferably 3.0 to 8.5 g / 10 min; Preferably, according to GB / T 17931-1999, the viscosity of the aliphatic-aromatic polyester is 155 to 210 mL / g, more preferably 181 to 187 mL / g.

8. A method for preparing an aliphatic-aromatic polyester according to any one of claims 1 to 7, comprising the following steps: (1) Component A, component B and component C are mixed at a temperature of 220-248°C and a pressure of 68-82 kPa. The reaction was carried out for 2.5 to 5.5 hours under the above conditions to obtain a first product having a viscosity of 24 to 33 mL / g; (2) subjecting the first product obtained in step (1) to a pre-condensation reaction at a temperature of 235 to 250° C. and a pressure of 900 to 1500 Pa for 2.5 to 4.5 hours to obtain a pre-condensation product having a viscosity of 73 to 86 mL / g; (3) subjecting the pre-polycondensation product obtained in step (2) to a polycondensation reaction at a temperature of 240 to 249° C. and a pressure of 110 to 200 Pa for 1 to 3 hours to obtain the aliphatic-aromatic polyester.

9. The preparation method according to claim 8, wherein: The viscosity number of the first product in step (1) is 27.5 to 30.5 mL / g; Preferably, the viscosity of the pre-condensation product in step (2) is 78.5 to 82.5 mL / g.

10. The preparation method according to claim 8 or 9, wherein: After the polycondensation reaction is completed, the product obtained by the polycondensation reaction is mixed with a chain extender to perform a chain extension reaction; Preferably, the chain growth reaction temperature is 185-220°C and the time is 6-10 min; Preferably, the viscosity of the product obtained by the polycondensation reaction is 122 to 138 mL / g, more preferably 127.5 to 134.5 mL / g.

11. A biodegradable polyester composition, comprising, by weight, 30 to 70 parts of polybutylene succinate, 3 to 15 parts of aliphatic-aromatic polyester, 5 to 35 parts of polylactic acid and 10 to 35 parts of filler; The aliphatic-aromatic polyester includes the aliphatic-aromatic polyester according to any one of claims 1 to 7.

12. A drinking straw comprising the biodegradable polyester composition according to claim 11; Preferably, after aging the straw at 60°C and 60% humidity for 48 hours and then at -10°C to 0°C for 72 hours, the color value change of the straw is ΔE<1, and the notched impact strength retention rate η≥70%, and more preferably ΔE<0.7, η≥75%.

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