Biodegradable polymers

Abstract

The present specification relates to a biodegradable polymer that has excellent mechanical properties and a high degree of biodegradability.

Description

[Technical Field]

[0001] The present specification relates to a biodegradable polymer that has excellent mechanical properties and a high degree of biodegradability. [Background technology]

[0002] Polyester resins have excellent mechanical and chemical properties and are used in a wide range of applications, including drinking water containers, medical applications, food packaging paper, food containers, sheets, films, and automotive molded parts.

[0003] Among them, polybutylene adipate terephthalate (PBAT) is a soft polyester that is biodegradable, and is therefore gaining attention as a substitute for polyolefin polymers, which are mainly used in packaging materials and agricultural films, in response to recent environmental regulations.

[0004] However, when soft PBAT is used alone for this purpose, it must be processed into a thin film to ensure biodegradability. However, such a thin thickness often results in film properties that are inferior to the actual resin properties. To ensure film stability, a branching agent is added during polymerization, or PBAT is blended with hard polylactic acid (PLA), or PBAT is used alone and compounded with an organic filler such as carbon black.

[0005] However, adding more than a certain amount of branching agent has the disadvantage of deepening gelation, leading to defects in the outer shape and reduced physical properties. When blended with PLA, the biodegradability of PBAT decreases compared to PBAT alone, necessitating the addition of a compatibilizer. When PBAT is used alone through compounding with organic fillers, mixing using an extruder is used, but this type of physical mixing has limitations in dispersing the organic filler, and in many cases an excess amount is added compared to the actual amount needed, which can reduce the biodegradability or mechanical properties of PBAT. Summary of the Invention [Problem to be solved by the invention]

[0006] The present specification aims to provide a biodegradable polymer that has excellent mechanical properties and a high degree of biodegradability. [Means for solving the problem]

[0007] In one embodiment of the present invention, there is provided a polybutylene adipate terephthalate copolymer comprising a first repeating unit derived from a terephthalic acid-based monomer, a second repeating unit derived from an adipic acid-based monomer, and a third repeating unit derived from a butanediol-based monomer, wherein the second repeating unit comprises at least one of a 2-1 repeating unit derived from adipic acid and a 2-2 repeating unit derived from 3-methyl adipic acid, and the third repeating unit comprises at least one of a 3-1 repeating unit derived from 1,4-butanediol and a 3-2 repeating unit derived from 1,2-butanediol.

[0008] The polybutylene adipate terephthalate copolymer may necessarily contain at least one of the 2-2 repeating unit and the 3-2 repeating unit.

[0009] and the molar ratio of the second repeating unit to the first repeating unit in the polybutylene adipate terephthalate copolymer is about 0.5:1. fromThe ratio of the repeating units derived from the adipic acid-based monomer to the repeating units derived from the terephthalic acid-based monomer may be about 1.5:1. That is, the ratio of the repeating units derived from the adipic acid-based monomer to the repeating units derived from the terephthalic acid-based monomer may be about 50 moles. from Approximately 150 moles, or approximately 80 moles from Approximately 120 guns or approximately 100 moles from It may be present in a molar ratio of about 120.

[0010] The third repeating unit may be contained in the polybutylene adipate terephthalate copolymer at a ratio of about 50 to about 60 mol %.

[0011] In the polybutylene adipate terephthalate copolymer, the second repeating unit may include both a 2-1 repeating unit derived from adipic acid and a 2-2 repeating unit derived from 3-methyladipic acid.

[0012] In this case, the molar ratio of the 2-1 repeating unit to the 2-2 repeating unit in the polybutylene adipate terephthalate copolymer is about 1000:1. from In other words, when the polybutylene adipate terephthalate copolymer contains both repeating units derived from adipic acid and repeating units derived from 3-methyl adipic acid, the repeating units derived from 3-methyl adipic acid may be about 0.1 moles per 100 moles of the repeating units derived from adipic acid. from About 20 moles, or about 0.5 from About 15 moles, or about 0.5 from It may be present in a molar ratio of about 10.

[0013] In the polybutylene adipate terephthalate copolymer, the third repeating unit may include both a 3-1 repeating unit derived from 1,4-butanediol and a 3-2 repeating unit derived from 1,2-butanediol.

[0014] In this case, the molar ratio of the 3-1 repeating unit to the 3-2 repeating unit in the polybutylene adipate terephthalate copolymer is about 1000:1. from That is, when the polybutylene adipate terephthalate copolymer contains both repeating units derived from 1,4-butanediol and repeating units derived from 1,2-butanediol, the repeating units derived from 1,2-butanediol may be about 0.1 moles per 100 moles of the repeating units derived from 1,4-butanediol. from About 5 moles, or about 0.2 from It may be present in a molar ratio of about 3.

[0015] The polybutylene adipate terephthalate copolymer may have a crystallinity value of about 29.0% or less, or about 20 to about 29%, or about 25 to about 28%, as measured using a differential scanning calorimeter.

[0016] The polybutylene adipate terephthalate copolymer may have an MD elongation value measured by ASTM D 882 of about 500% or more, or about 500 to about 700%, or about 500 to about 650%, or about 550 to about 620%.

[0017] The polybutylene adipate terephthalate copolymer may have an elongation value in the TD direction, as measured by ASTM D 882, of about 500% or more, or about 500 to 700%, or about 550 to about 700%.

[0018] The polybutylene adipate terephthalate copolymer may have a weight average molecular weight of about 50,000 to about 100,000, or 50,000 or more, or about 60,000 or more, or about 70,000 or more, and about 100,000 or less, or about 90,000 or less, or about 85,000 or less, or about 80,000 or less.

[0019] In the present invention, terms such as first and second are used to describe various components, and the terms are used only to distinguish one component from another.

[0020] Furthermore, the terms used in this specification are merely used to describe exemplary embodiments and are not intended to limit the present invention.

[0021] The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0022] As used herein, terms such as "comprises," "comprises," or "having" are intended to describe one or more other features, numbers, steps, components, or combinations thereof that may be implemented, but do not exclude the possibility of one or more other features, numbers, steps, components, combinations, or additional features.

[0023] Furthermore, in this specification, when a layer or element is referred to as being formed "on" or "on" another layer or element, it means that the layer or element is formed directly on the layer or element, or that other layers or elements may be additionally formed between the layers, on the object, or on the substrate.

[0024] The present invention can be modified in various ways and can have various forms, and specific examples are shown by way of example and described in detail below, but it should be understood that this is not intended to limit the invention to the particular form disclosed, and that the invention includes all modifications, equivalents, and alternatives falling within the spirit and technical scope of the invention.

[0025] According to one aspect of the present invention, there is provided a polybutylene adipate terephthalate copolymer comprising a first repeating unit derived from a terephthalic acid-based monomer, a second repeating unit derived from an adipic acid-based monomer, and a third repeating unit derived from a butanediol-based monomer, wherein the second repeating unit comprises one or more of a 2-1 repeating unit derived from adipic acid and a 2-2 repeating unit derived from 3-methyladipic acid, and the third repeating unit comprises one or more of a 3-1 repeating unit derived from 1,4-butanediol and a 3-2 repeating unit derived from 1,2-butanediol.

[0026] As mentioned above, PBAT is highly biodegradable, and much research is being conducted to utilize this property. However, it has been difficult to improve the mechanical properties of PBAT while maintaining its excellent biodegradability.

[0027] The inventors of the present invention have found that when a polybutylene adipate terephthalate copolymer is produced by partially adding a monomer other than the monomers commonly used in the past to change the bonding structure of the copolymer, it is possible to maintain high biodegradability and effectively improve its mechanical properties, and have completed the present invention.

[0028] A polybutylene adipate terephthalate copolymer according to one aspect of the present invention comprises a first repeating unit derived from a terephthalic acid-based monomer, a second repeating unit derived from an adipic acid-based monomer, and a third repeating unit derived from a butanediol-based monomer, wherein the second repeating unit comprises one or more of a 2-1 repeating unit derived from adipic acid and a 2-2 repeating unit derived from 3-methyladipic acid, and the third repeating unit comprises one or more of a 3-1 repeating unit derived from 1,4-butanediol and a 3-2 repeating unit derived from 1,2-butanediol.

[0029] Each monomer used in the polybutylene adipate terephthalate copolymer of the present invention will be explained below.

[0030] First, a polybutylene adipate terephthalate copolymer according to one aspect of the present invention contains a first repeating unit derived from a terephthalic acid monomer.

[0031] In this specification, the first repeating unit refers to a residue remaining in the polymer chain in the reaction of forming a polybutylene adipate terephthalate copolymer by condensation of a terephthalic acid-based monomer.

[0032] That is, when producing the polybutylene adipate terephthalate of the present invention, a terephthalic acid-based monomer is used, and the group derived from the terephthalic acid-based monomer is referred to as the first repeating unit.

[0033] Here, the terephthalic acid monomer means terephthalic acid and its derivatives.

[0034] The polybutylene adipate terephthalate copolymer according to one aspect of the present invention contains a second repeating unit derived from an adipic acid monomer.

[0035] In this specification, the second repeating unit refers to a group that remains in the polymer chain in the reaction in which adipic acid-based monomers are condensed to form a polybutylene adipate terephthalate copolymer.

[0036] That is, when producing the polybutylene adipate terephthalate of the present invention, an adipic acid-based monomer is used, and the residue derived from the adipic acid-based monomer is referred to as the second repeating unit.

[0037] The second repeating unit further includes at least one of a 2-1 repeating unit derived from adipic acid and a 2-2 repeating unit derived from 3-methyladipic acid.

[0038] That is, when producing the polybutylene adipate terephthalate of the present invention, at least one of adipic acid and 3-methyladipic acid must be used, and the polybutylene adipate terephthalate produced thereby must contain at least one of the 2-1 repeating unit and the 2-2 repeating unit.

[0039] In particular, 3-methyladipic acid has a methyl group attached to the side chain of the adipic acid structure, which can increase the frequency of chain entanglement during the production of PBAT, thereby improving the toughness of the produced polymer and the mechanical properties of the polymer.

[0040] The polybutylene adipate terephthalate copolymer according to one aspect of the present invention contains a third repeating unit derived from a butanediol-based monomer.

[0041] In this specification, the third repeating unit refers to a residue remaining in the polymer chain in the reaction of forming a polybutylene adipate terephthalate copolymer by condensation of a butanediol-based monomer.

[0042] That is, when producing the polybutylene adipate terephthalate of the present invention, a butanediol-based monomer is used, and the group derived from the butanediol-based monomer is referred to as the third repeating unit.

[0043] The third repeating unit further includes at least one of a 3-1 repeating unit derived from 1,4-butanediol and a 3-2 repeating unit derived from 1,2-butanediol.

[0044] That is, when producing the polybutylene adipate terephthalate of the present invention, at least one of 1,4-butanediol and 1,2-butanediol must be used, and the polybutylene adipate terephthalate produced thereby must contain at least one of the 3-1 repeating unit and the 3-2 repeating unit.

[0045] In particular, 1,2-butanediol, unlike 1,4-butanediol, has a methyl group linked thereto that can function as a side chain in terms of structure, which can increase the frequency of chain entanglement during the production of PBAT, thereby improving the toughness of the produced polymer and the mechanical properties of the polymer.

[0046] The polybutylene adipate terephthalate copolymer may necessarily contain at least one of the 2-2 repeating unit and the 3-2 repeating unit.

[0047] More specifically, for example, the polybutylene adipate terephthalate copolymer of the present invention may comprise: i) a 1 repeat unit, a 2-1 repeat unit, and a 3-1 repeat unit; ii) a 1 repeat unit, a 2-1 repeat unit, and a 3-2 repeat unit; iii) a 1 repeat unit, a 2-2 repeat unit, and a 3-1 repeat unit; iv) a 1 repeat unit, a 2-2 repeat unit, and a 3-2 repeat unit; or v) comprising a 1-repeat unit, a 2-1-repeat unit, a 2-2-repeat unit, and a 3-1-repeat unit; or vi) comprising a 1-repeat unit, a 2-1-repeat unit, a 3-1-repeat unit, and a 3-2-repeat unit; or vii) It may be in a form including a 1st repeating unit, a 2-1st repeating unit, a 2-2nd repeating unit, a 3-1st repeating unit, and a 3-2nd repeating unit.

[0048] and the molar ratio of the second repeating unit to the first repeating unit in the polybutylene adipate terephthalate copolymer is about 0.5:1. from The ratio of the repeating units derived from the adipic acid-based monomer to the repeating units derived from the terephthalic acid-based monomer may be about 1.5:1. That is, the ratio of the repeating units derived from the adipic acid-based monomer to the repeating units derived from the terephthalic acid-based monomer may be about 50 moles. from Approximately 150 moles, or approximately 80 moles from About 120 or about 100 moles from It may be present in a molar ratio of about 120.

[0049] If the content of terephthalic acid is too high, the biodegradability and processability of the produced polybutylene adipate terephthalate copolymer may be significantly reduced.

[0050] And, in the polybutylene adipate terephthalate copolymer, the third repeating unit is about 50 from It may be contained in a ratio of 60 mol %.

[0051] In the polybutylene adipate terephthalate copolymer, the second repeating unit may include both a 2-1 repeating unit derived from adipic acid and a 2-2 repeating unit derived from 3-methyladipic acid.

[0052] In this case, the molar ratio of the 2-1 repeating unit to the 2-2 repeating unit in the polybutylene adipate terephthalate copolymer is about 1000:1. from In other words, when the polybutylene adipate terephthalate copolymer contains both repeating units derived from adipic acid and repeating units derived from 3-methyl adipic acid, the repeating units derived from 3-methyl adipic acid may be about 0.1 moles per 100 moles of the repeating units derived from adipic acid. from About 20 moles, or about 0.5 from About 15 moles, or about 0.5 from It may be present in a molar ratio of about 10.

[0053] If the content of the repeating unit derived from 3-methyladipic acid, i.e., the 2-2 repeating unit, is too low, the effect of improving mechanical properties will be minimal. If the content of the repeating unit derived from 3-methyladipic acid, i.e., the 2-2 repeating unit, is too high, the degree of entanglement of polymer chains in the produced polybutylene adipate terephthalate copolymer will increase, causing a rapid increase in the melt viscosity of the copolymer, which may result in processing problems such as reduced processability and productivity.

[0054] In the polybutylene adipate terephthalate copolymer, the third repeating unit may include both a 3-1 repeating unit derived from 1,4-butanediol and a 3-2 repeating unit derived from 1,2-butanediol.

[0055] In this case, the molar ratio of the 3-1 repeating unit to the 3-2 repeating unit in the polybutylene adipate terephthalate copolymer is about 1000:1. fromThat is, when the polybutylene adipate terephthalate copolymer contains both repeating units derived from 1,4-butanediol and repeating units derived from 1,2-butanediol, the repeating units derived from 1,2-butanediol may be about 0.1 moles per 100 moles of the repeating units derived from 1,4-butanediol. from About 5 moles, or about 0.2 from It may be present in a molar ratio of about 3.

[0056] If the content of the repeating unit derived from 1,2-butanediol, i.e., the 3-2 repeating unit, is too low, the effect of improving mechanical properties will be minimal. If the content of the repeating unit derived from 1,2-butanediol, i.e., the 3-2 repeating unit, is too high, the degree of entanglement of polymer chains in the produced polybutylene adipate terephthalate copolymer will increase, and the melt viscosity of the copolymer may increase sharply, which may cause problems in processing, such as reduced processability and productivity.

[0057] The polybutylene adipate terephthalate copolymer may have a crystallinity value of about 29.0% or less, or about 20 to about 29%, or about 25 to about 28%, as measured using a differential scanning calorimeter.

[0058] The degree of crystallinity can be calculated as the weight fraction of the crystalline portion of the entire resin. In the case of biodegradable polyester resins, it is known that the higher the degree of crystallinity, the lower the degree of biodegradation, and the degree of biodegradation can also be roughly predicted based on the degree of crystallinity.

[0059] The polybutylene adipate terephthalate copolymer of this embodiment contains a monomer with a structure that has not been commonly used in the past, resulting in lower chain symmetry compared to existing PBAT, and therefore lower crystallinity.

[0060] The polybutylene adipate terephthalate copolymer of the present invention has a crystallinity value within the above range, which allows it to maintain excellent biodegradability.

[0061] Here, the crystallinity can be measured using a differential scanning calorimeter (DSC, device name: DSC 2500, manufacturer: TA Instrument). Specifically, a differential scanning calorimeter (DSC, device name: DSC 2500, manufacturer: TA Instrument) is used to sequentially perform primary heating, primary cooling, and secondary heating in the temperature range (-70 to 200°C, 10°C / min), and the crystallinity is calculated using the heat of fusion of the melting transition during the secondary heating (PBAT ΔH). m 0 =114J / g available).

[0062] The polybutylene adipate terephthalate copolymer may have an MD elongation value measured by ASTM D 882 of about 500% or more, or about 500 to about 700%, or about 500 to about 650%, or about 550 to about 620%.

[0063] The polybutylene adipate terephthalate copolymer may have an elongation value in the TD direction, as measured by ASTM D 882, of about 500% or more, or about 500 to 700%, or about 550 to about 700%.

[0064] As described above, the polybutylene adipate terephthalate copolymer according to one example of the present invention can achieve superior mechanical properties compared to conventional copolymers.

[0065] The polybutylene adipate terephthalate copolymer may have a weight average molecular weight of about 50,000 to about 150,000, or 50,000 or more, or about 60,000 or more, or about 70,000 or more, and about 150,000 or less, or about 100,000 or less, or about 90,000 or less, or about 85,000 or less, or about 80,000 or less.

[0066] The polybutylene adipate terephthalate copolymer can be produced by subjecting a monomer mixture containing the above-mentioned monomers to an esterification reaction in the presence of a polymerization catalyst.

[0067] The catalyst is not particularly limited as long as it is widely used as a polyester polymerization catalyst in the technical field to which the present invention pertains.

[0068] Specifically, the catalyst may be at least one selected from the group consisting of titanium methoxide, titanium ethoxide, titanium propoxide, titanium isopropoxide, titanium butoxide, and titanium isobutoxide.

[0069] For example, the catalyst may be titanium butoxide.

[0070] The polymerization reaction may be carried out on a total monomer mixture in which the above-mentioned monomers and catalyst are mixed together, or may be carried out by separately mixing the monomers and catalyst and then individually adding them to a reactor to carry out the polymerization reaction, or may be carried out by first producing a prepolymer and then carrying out the main polymerization reaction.

[0071] When the catalyst mixture is separately prepared, a butanediol-based monomer and a catalyst may be mixed to prepare a catalyst mixture, and a terephthalic acid-based monomer and an adipic acid-based monomer may be prepared as a separate monomer mixture, and then the two may be mixed.

[0072] The catalyst in the catalyst mixture may be included in an amount of 0.001 to 10 parts by weight based on 100 parts by weight of adipic acid in the monomer mixture.

[0073] Within this range, the esterification reaction of the monomer mixture and the polymerization of the esterification reaction product (i.e., prepolymer) can be adequately mediated.

[0074] However, if the amount of catalyst added during the preparation of the catalyst mixture is too small, the polymerization time will be long and productivity will decrease.In contrast, if the amount of catalyst added is too large, the polymerization time will be short, but the possibility of discoloration of the final PBAT will increase, so the amount of heat stabilizer added must be increased in proportion to the amount of catalyst added, which will increase production costs.

[0075] Taking these trends into consideration, the amount of catalyst in the catalyst mixture can be adjusted. For example, the catalyst in the catalyst mixture may be used in an amount of 0.001 parts by weight or more, 0.005 parts by weight or more, or 0.01 parts by weight or more, and 10 parts by weight or less, 5 parts by weight or less, or 0.1 parts by weight or less, based on 100 parts by weight of the adipic acid-based monomer in the monomer mixture.

[0076] On the other hand, a prepolymer refers to a polymer with a relatively low degree of polymerization, in which the polymerization reaction is stopped at the intermediate coating stage in order to facilitate molding.

[0077] When producing a prepolymer, a monomer mixture containing adipic acid and terephthalic acid is subjected to an esterification reaction in the presence of the catalyst mixture to carry out primary polymerization, thereby producing a low-molecular-weight copolymer with a low degree of polymerization.

[0078] When preparing the prepolymer, 0.1 to 1 part by weight of a crosslinking agent or branching agent may be added based on 100 parts by weight of adipic acid in the monomer mixture to carry out the esterification reaction.

[0079] When a crosslinking agent is added and an esterification reaction is carried out, an internally crosslinked prepolymer is produced, which can improve the mechanical properties of the final composite.

[0080] The crosslinking agent is a low molecular weight compound containing three or more hydroxy groups or three or more carboxy groups in the molecule, and may be, for example, an erythritol-based compound, a glycerol-based compound, a citric acid-based compound, etc. For example, the crosslinking agent may be pentaerythritol.

[0081] The step of preparing the prepolymer may be carried out at a temperature ranging from 150 to 350°C.

[0082] Within this temperature range, the prepolymer can be produced while maintaining uniform dispersion of each monomer.

[0083] For example, the step of preparing the prepolymer may be carried out in a temperature range of 150°C or more, 170°C or more, 190°C or more, or 210°C or more, and 350°C or less, 320°C or less, 290°C or less, or 250°C or less.

[0084] Nitrogen gas may be injected during the preparation of the prepolymer. Specifically, by injecting nitrogen gas, water generated as a by-product can be rapidly removed, suppressing reverse reactions caused by water and improving the monomer conversion rate, thereby increasing the molecular weight of the copolymer produced.

[0085] For example, nitrogen gas may be injected at a rate of (0.00)1 ml / min or more, (0.0)1 ml / min or more, (0.02) ml / min or more, or (0.05) ml / min or more, and at a rate of (100) ml / min or less, (50) ml / min or less, (10) ml / min or less, or (5) ml / min or less.

[0086] In the main polymerization reaction for repolymerizing the prepolymer, 0.001 to 10 parts by weight of a catalyst may be added based on 100 parts by weight of adipic acid in the monomer mixture.

[0087] The activity of the catalyst initially added is likely to decrease during the prepolymer production step. For example, titanium, the central metal component of the catalyst, may react with water, a by-product of the esterification reaction, to form titanium oxide, and the monomer or prepolymer components may be substituted at the alkoxide site of the titanium alkoxide.

[0088] Therefore, it is preferable to add an additional catalyst immediately before the reaction.

[0089] For example, the additional catalyst may be used in an amount of 0.001 parts by weight or more, 0.005 parts by weight or more, or 0.01 parts by weight or more, and 10 parts by weight or less, 5 parts by weight or less, or 0.1 parts by weight or less, based on 100 parts by weight of the adipic acid-based monomer in the monomer mixture.

[0090] After adding the catalyst, a heat stabilizer may be added, which can prevent discoloration of the final PBAT.

[0091] Specifically, 0.001 to 1 part by weight of a heat stabilizer may be added based on 100 parts by weight of the adipic acid-based monomer in the monomer mixture.

[0092] For example, the heat stabilizer may be added in an amount of 0.001 part by weight or more, 0.005 part by weight or more, 0.08 part by weight or more, or 0.01 part by weight or more, and 1 part by weight or less, 0.6 part by weight or less, 0.3 part by weight or less, or 0.1 part by weight or less, based on 100 parts by weight of adipic acid in the monomer mixture.

[0093] During polymerization of the prepolymer, the method may include the steps of: increasing the temperature of a reactor containing the prepolymer until the temperature reaches a range of 150 to 350°C; reducing the pressure of the reactor after the temperature increase until the pressure reaches 0.1 to 0.00001 atm; and terminating the reaction after 2 to 8 hours by maintaining the reduced pressure and temperature.

[0094] For example, the temperature of the reactor containing the prepolymer may be increased until it reaches a temperature range of 150°C or more, 170°C or more, 190°C or more, or 210°C or more, and 350°C or less, 320°C or less, 290°C or less, or 250°C or less.

[0095] After reaching the temperature range, 1 to 10 minutes later, the pressure in the reactor may be reduced to a pressure range of 0.00001 atm or more, 0.00005 atm or more, 0.0001 atm or more, or 0.0002 atm or more, and 0.1 atm or less, 0.05 atm or less, 0.03 atm or less, or 0.01 atm or less.

[0096] After the pressure reduction, the pressure and temperature are maintained to carry out the reaction, and the reaction may be terminated after 2 hours or more, 2.2 hours or more, 2.4 hours or more, or 3 hours or more and 8 hours or less, 7.5 hours or less, 7 hours or less, or 6 hours or less have elapsed since the start of the reaction. [Effects of the Invention]

[0097] The biodegradable polymer according to the example given in this specification has excellent mechanical properties and can have a high degree of biodegradability. DETAILED DESCRIPTION OF THE INVENTION

[0098] The functions and effects of the present invention will be described in more detail below through specific examples of the present invention. However, these examples are presented only as examples of the present invention and do not define the scope of the invention.

[0099] <Example> The reaction was carried out batchwise, and after preparing a prepolymer, the main polymerization reaction was carried out.

[0100] The monomer components listed in Table 1 below, pentaerythritol, and titanium butoxide (primary, 0.5 mmol) were charged into a reactor, and the reactor was maintained at about 230°C. Nitrogen gas was introduced into the reactor for about 3 hours to remove by-products, and an esterification reaction (prepolymer reaction) was carried out.

[0101] When the prepolymer reaction was completed, titanium butoxide (2nd generation, 0.7 mmol) and triethyl phosphonoacetate (1.3 mmol) as a thermal stabilizer component were added thereto, and the mixture was stirred so that the catalyst component and the thermal stabilizer component were uniformly dispersed in the prepolymer.

[0102] Thereafter, the temperature of the reactor was increased to about 240°C, and 5 minutes after the temperature of the reactor reached about 240°C, the pressure inside the reactor was reduced, and the main polymerization reaction was carried out at a pressure of 3 mbar or less for about 4 hours to obtain a PBAT polymer.

[0103] The reaction conditions for each of the Examples and Comparative Examples are summarized in Table 1 below.

[0104] [Table 1] *Tp: terephthalic acid; Ad: adipic acid; 3Mad: 3-methyladipic acid; 1,4Bd: 1,4-butanediol; 1,2-Bd: 1,2-butanediol

[0105] Physical property evaluation Measurement of weight average molecular weight: The sample was dissolved in chloroform at a concentration of 1 mg / ml, and the solution was then loaded into a gel permeation chromatography (GPC) instrument (PL GPC220, Agilent Technologies) to measure the molecular weight. Polystyrene was used as the standard polymer.

[0106] Crystallinity measurement: The biodegradable polymer composites of Examples 1 to 4 and the PBATs of Comparative Examples 1 to 3 were subjected to primary heating, primary cooling, and secondary heating in the temperature range of -70 to 200°C at 10°C / min using a differential scanning calorimeter (DSC, device name: DSC 2500, manufacturer: TA Instrument). The crystallinity of the PBATs was calculated using the heat of fusion of the melting transition during the secondary heating (PBAT ΔH m 0 =114J / g used).

[0107] Elongation: The PBAT copolymers of the examples and comparative examples were blown into blown films at extrusion temperatures of 130°C to 170°C using a short-circuit extruder (SHINWHA Industrial Single Screw Extruder, Blown Film M / C, 50 mm diameter, L / D = 20) to a thickness of about 50 μm. The die gap and blow-up ratio were 2.0 mm and 2.3, respectively.

[0108] Elongation: Tensile tests were performed on each film specimen at a stretching rate of 10 mm / min using an Instron Universal Testing Machine (UTM) according to ASTM D 882, and elongation values were measured. The tensile test conditions were a Load Cell of 10 KN and a LE position of 40 mm, and elongation was measured in both the machine direction (MD) and the transverse direction (TD).

[0109] The measurement results are summarized in Table 2 below. [Table 2] Referring to Table 2, it can be seen that the polybutylene adipate terephthalate copolymer according to one embodiment of the present invention has a degree of polymerization similar to that of the comparative example, even though it further contains a monomer with a specific structure during polymerization.

[0110] In addition, the crystallinity of the polybutylene adipate terephthalate copolymers according to the examples is generally lower than that of the comparative examples. This is believed to be due to the steric hindrance effect of the side chain alkyl groups of the separately added monomers, which inhibits the crystallization of the chains of the polybutylene adipate terephthalate copolymer.

[0111] In addition, it is generally known that as the crystallinity of polybutylene adipate terephthalate copolymer decreases, the mechanical properties also decrease. However, in the case of the polybutylene adipate terephthalate copolymer according to an embodiment of the present invention, it was confirmed that the mechanical properties were improved compared to the comparative example, despite the crystallinity being lower than that of the comparative example. This is believed to be because the side chain alkyl groups in the polymer chain increased chain entanglement, thereby increasing the toughness of the polymer.

Claims

1. a first repeat unit derived from a terephthalic acid-based monomer, a second repeat unit derived from an adipic acid-based monomer, and a third repeat unit derived from a butanediol-based monomer; the second repeating unit comprises a 2-1 repeating unit derived from adipic acid and a 2-2 repeating unit derived from 3-methyladipic acid; the third repeating unit includes at least one of a 3-1 repeating unit derived from 1,4-butanediol and a 3-2 repeating unit derived from 1,2-butanediol; the molar ratio of the 2-1 repeat unit:2-2 repeat unit is 1000:1 to 100:20; Polybutylene adipate terephthalate copolymer.

2. The polymer must contain at least one of a 2-2 repeat unit and a 3-2 repeat unit. The polybutylene adipate terephthalate copolymer of claim 1.

3. the molar ratio of the second repeat unit to the first repeat unit is from 0.5:1 to 1.5:1; The polybutylene adipate terephthalate copolymer of claim 1.

4. The third repeating unit is contained in an amount of 50 to 60 mol %. The polybutylene adipate terephthalate copolymer of claim 1.

5. The third repeating unit includes a 3-1 repeating unit derived from 1,4-butanediol and a 3-2 repeating unit derived from 1,2-butanediol. The polybutylene adipate terephthalate copolymer of claim 1.

6. the molar ratio of the 3-1 repeat unit: the 3-2 repeat unit is 1000:1 to 100:20; The polybutylene adipate terephthalate copolymer of claim 5.

7. The weight average molecular weight is 50,000 to 150,000. The polybutylene adipate terephthalate copolymer of claim 1.

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