Method for preparing a biodegradable polymer composite and biodegradable polymer composite

Abstract

This disclosure relates to a method for preparing a biodegradable polymer composite with excellent mechanical properties, and a biodegradable polymer composite with excellent mechanical properties.

Description

Technical Field

[0001] Cross-references to related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2020-0139328, filed on October 26, 2020, and Korean Patent Application No. 10-2021-0143059, filed on October 25, 2021, the entire contents of which are incorporated herein by reference.

[0003] This disclosure relates to a method for preparing a biodegradable polymer composite with excellent mechanical properties and a biodegradable polymer composite with excellent mechanical properties. Background Technology

[0004] Polyester resins have excellent mechanical and chemical properties, making them suitable for a variety of applications. For example, they are commonly used in drinking water containers and medical applications, food packaging paper, food containers, sheets, films, and automotive molded products.

[0005] Among them, polybutylene terephthalate (PBAT) is a biodegradable soft polyester, and therefore, due to recent environmental regulations, it has attracted much attention as an alternative to polyolefin polymers mainly used in packaging materials and agricultural films.

[0006] However, since the mechanical properties of PBAT are slightly insufficient when used alone for this purpose, PBAT is mainly used in combination with light polylactic acid (PLA); PBAT is used alone, but in combination with organic fillers such as carbon black.

[0007] However, when mixed with PLA, its biodegradability decreases compared to PBAT alone, and due to the incompatibility of PBAT and PLA, a compatibilizer is required. Furthermore, when PBAT is used alone by mixing with organic fillers, this is done using an extruder. This physical mixing has limitations in dispersing the organic fillers, often resulting in the addition of excessive amounts, and typically the preparation and mixing of masterbatches with high organic filler content. Summary of the Invention

[0008] Technical issues

[0009] One object of this disclosure is to provide a method for preparing a biodegradable polymer composite with excellent mechanical properties, and a biodegradable polymer composite with excellent mechanical properties.

[0010] Technical solution

[0011] In one embodiment of this disclosure, a method for preparing an organic filler and polybutylene terephthalate (PBAT) is provided, comprising the step of preparing a catalyst mixture in the presence of the organic filler and then adding the mixture to a polymerization system.

[0012] In another embodiment of this disclosure, a biodegradable polymer composite is provided, comprising: polybutylene adipate terephthalate; and an organic filler dispersed between the polymer chains of polybutylene adipate terephthalate.

[0013] Beneficial effects

[0014] According to the preparation method of one embodiment, a biodegradable polymer composite with excellent mechanical properties can be provided with high efficiency and low cost, even when used alone without post-treatment.

[0015] Furthermore, since the crystallinity is controlled according to the content of organic filler, the biodegradable polymer composite of one embodiment has excellent biodegradability. Detailed Implementation

[0016] The technical terms used herein are for describing exemplary embodiments only and are not intended to limit the scope of the invention. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” are intended to include the plural forms. It should be understood that the terms “comprising,” “including,” “having,” etc., as used herein are used to specify the presence of the stated features, integers, steps, components, or combinations thereof, but do not exclude the presence or addition of one or more other features, integers, steps, components, or combinations thereof.

[0017] While this disclosure may take many forms and can be modified in various ways, specific examples will be illustrated and explained in detail. However, it is not intended to limit this disclosure to its form, and it should be understood that all modifications, equivalents, or substitutions within the concept and scope of this disclosure are included herein.

[0018] The specific implementation of this disclosure will now be described in more detail.

[0019] Methods for preparing biodegradable polymer complexes

[0020] According to one embodiment of this disclosure, a method for preparing a biodegradable polymer composite is provided, comprising the steps of: preparing a monomer mixture comprising adipic acid and terephthalic acid; mixing an organic filler, 1,4-butanediol and a catalyst to prepare a catalyst mixture; and mixing the monomer mixture with the catalyst mixture and carrying out an esterification reaction.

[0021] According to one embodiment of the preparation method, polybutylene adipate terephthalate can be provided by in-situ polymerization and compounding with organic fillers, which can exhibit sufficient physical properties even when used alone.

[0022] Therefore, according to one embodiment of the preparation method, unlike polybutylene adipate terephthalate polymerized without organic fillers, a biodegradable polymer composite with improved biodegradability can be provided with high efficiency and low cost, while exhibiting sufficient physical properties even when used alone without post-treatment.

[0023] Here, in the biodegradable polymer composite, the organic filler is dispersed and placed between the polymer chains of polybutylene terephthalate, which differs from a blend resin in which a polymer resin composition of liquid or solid polybutylene terephthalate is simply mixed with the organic filler.

[0024] In the following text, in some cases, the term "biodegradable polymer complex" may be simply referred to as "complex".

[0025] Preparation process of catalyst mixture

[0026] In the preparation of the catalyst mixture, 1,4-butanediol and the catalyst are mixed together with organic filler to prepare the catalyst mixture. Through this process, a catalyst mixture in which the organic filler is uniformly dispersed can be supplied to the polymerization system.

[0027] When this organic filler is polymerized with polymers such as PBAT, in order to effectively improve physical properties, the organic filler must be uniformly dispersed between the newly formed polymer chains.

[0028] In one example of the method according to this disclosure, a catalyst mixture is prepared by first reacting an organic filler, such as cellulose, with a catalyst, and then the catalyst mixture prepared therefrom is added to the polymerization reaction. In this case, compared to the case where the polymerization product, polymerization catalyst, and organic filler are added simultaneously, the organic filler can be more uniformly dispersed during the formation of PBAT polymer chains.

[0029] According to an example method of this disclosure, an organic filler and a catalyst material are premixed, thereby distributing the catalyst on the surface of the organic filler. More specifically, an ester exchange reaction occurs between various functional groups contained in the organic filler molecules and the catalyst molecules, and this ester exchange reaction is somewhat restricted due to the steric hindrance of the organic filler molecules, thereby forming a catalyst-organic filler composite in the form of catalyst molecules coating the surface of the organic filler.

[0030] Typically, organic fillers may aggregate intramolecularly due to their functional groups and morphology. According to an example method of this disclosure, as described above, the surface of the organic filler is coated with catalyst molecules, thereby preventing the organic filler molecules from overlapping or aggregating. By this principle, the organic filler molecules are dispersed, thus allowing for more uniform dispersion of the organic filler within the polymer, even during the polymerization process that forms PBAT polymer chains.

[0031] Therefore, during the polymerization reaction, the polymer chains grow around the surface of the organic filler, allowing the organic filler to be uniformly dispersed between the polymer chains, achieving a level where the polymer chains and organic filler do not separate from each other.

[0032] Furthermore, according to this method, organic fillers can be uniformly dispersed between polymer chains, thereby preventing the crystallization of polymer chains and producing polymer composites with low crystallinity.

[0033] Furthermore, in this process, the catalyst cluster is partially destroyed beforehand, which increases the number of reaction sites to prepare a partially activated catalyst. By supplying a partially activated catalyst in this way, the initial reaction rate of the polymerization system can be increased, and the polymerization time can be shortened.

[0034] The step of preparing the catalyst mixture can be carried out for 10 to 120 minutes in a temperature range of 40°C to 240°C.

[0035] Within the aforementioned temperature and time range, a catalyst mixture with uniformly dispersed organic filler can be prepared. Furthermore, the catalyst clusters are disrupted to generate the maximum number of reaction sites, and the catalyst can be coated onto the surface of the organic filler to appropriately mediate the polymerization reaction of the monomer and the prepolymer, as described later.

[0036] However, if the temperature during catalyst mixture preparation is too low, the dispersibility of the organic filler decreases and 1,4-butanediol crystallizes, causing problems with miscibility and / or reactivity. Conversely, if the temperature during catalyst mixture preparation is too high, the thermal stability of the catalyst decreases, resulting in the eventual discoloration of PBAT.

[0037] On the other hand, if the preparation time of the catalyst mixture is too short, insufficient activation will occur; if the preparation time of the catalyst mixture is too long, polymerization of 1,4-butanediol will take place, or the final discoloration of PBAT will occur.

[0038] Taking this trend into account, the temperature during the preparation of the catalyst mixture can be adjusted. For example, the step of preparing the catalyst mixture can be carried out within a temperature range of above 40°C, above 50°C, above 60°C, or above 70°C, and below 240°C, below 200°C, below 140°C, or below 90°C. Furthermore, the step can be carried out within a time range of above 10 minutes, above 15 minutes, above 20 minutes, or above 25 minutes, and below 120 minutes, below 90 minutes, below 60 minutes, and below 40 minutes.

[0039] Based on 100 parts by weight of adipic acid in the monomer mixture, the catalyst content in the catalyst mixture can be from 0.001 parts by weight to 10 parts by weight.

[0040] Within the aforementioned range, the esterification reaction of monomer mixtures and the polymerization reaction of esterification products (i.e., prepolymers) can be appropriately mediated.

[0041] However, if too little catalyst is added during the preparation of the catalyst mixture, the polymerization time will be longer and the productivity will decrease. Conversely, if too much catalyst is added, the polymerization time will be shorter, but the likelihood of discoloration of the final PBAT will increase. Therefore, the amount of heat stabilizer added must increase proportionally with the amount of catalyst added, which leads to increased manufacturing costs.

[0042] Taking this trend into account, the amount of catalyst added to the catalyst mixture can be adjusted. For example, based on 100 parts by weight of adipic acid in the monomer mixture, the content of catalyst in the catalyst mixture can be more than 0.001 parts by weight, more than 0.005 parts by weight, or more than 0.01 parts by weight, and less than 10 parts by weight, less than 5 parts by weight, or less than 0.1 parts by weight.

[0043] The content of organic filler in the catalyst mixture can be 0.5g to 20g, or 1.0g to 20g, or 1.5g to 17g, or 1.5g to 5g, or 1.5g to 3g per 1mmol catalyst.

[0044] Within the aforementioned range, the reinforcing effect of organic fillers and the reaction-mediating effect of catalysts can be balanced.

[0045] However, if the amount of organic filler added is too low compared to the catalyst, the enhancing effect caused by the interaction between the organic filler and the catalyst will be insufficient, and if the amount of organic filler added is too high, uneven dispersion will occur and the catalyst activity will deteriorate.

[0046] Meanwhile, based on 100 parts by weight of adipic acid in the monomer mixture, the content of 1,4-butanediol in the catalyst mixture can be from 150 parts by weight to 250 parts by weight.

[0047] This is the total amount of 1,4-butanediol required for the synthesis of PBAT. 1,4-Butanediol is a reaction product and can also act as a solvent or dispersant for dispersing the organic filler. Normally, only a portion of the 1,4-butanediol to be reacted is supplied to ensure the homogeneity and stability of the catalyst during polymerization, while the remaining amount is typically supplied in subsequent reactions. However, in a preparation method according to one embodiment of this disclosure, the entire amount of the 1,4-butanediol to be reacted can be supplied to the catalyst mixture to enhance the dispersibility of the organic filler described later.

[0048] From this perspective, based on 100 parts by weight of adipic acid in the monomer mixture, the content of 1,4-butanediol in the catalyst mixture can be from 150 parts by weight to 250 parts by weight.

[0049] For example, based on 100 parts by weight of adipic acid in the monomer mixture, the content of 1,4-butanediol in the catalyst mixture can be from 180 parts by weight to 220 parts by weight.

[0050] There are no particular limitations on organic fillers, as long as they are widely used as polymer-reinforcing materials in the technical field to which this disclosure pertains.

[0051] Specifically, the organic filler may include, for example, cellulose, starch-based compounds, etc. Substances substituted with alkyl, hydroxyl, carboxyl, hydroxyalkyl, or carboxyl groups may also be used as cellulose and starch-based compounds.

[0052] There are no particular limitations on the catalyst, as long as it is widely used as a polyester polymerization catalyst in the technical field to which this disclosure pertains.

[0053] Specifically, the catalyst may be at least one selected from methyl titanate, ethyl titanate, n-propyl titanate, isopropyl titanate, tetra-n-butyl titanate, and tetraisobutyl titanate.

[0054] For example, the catalyst may be tetrabutyl titanate.

[0055] Prepolymer preparation process

[0056] Prepolymers are polymers with a relatively low degree of polymerization in which the polymerization reaction is stopped at an intermediate stage to facilitate molding.

[0057] In one embodiment, the prepolymer corresponds to a polymer with a relatively low degree of polymerization prepared by esterifying a monomer mixture containing adipic acid and terephthalic acid in the presence of a catalyst mixture.

[0058] According to one embodiment of this disclosure, during the formation of the prepolymer, initial polymer chains can be formed around the surface of the organic filler, centered on a catalyst coated on the surface of the organic filler.

[0059] Specifically, based on 100 parts by weight of adipic acid in the monomer mixture, the monomer mixture may contain 50 to 150 parts by weight of terephthalic acid.

[0060] Terephthalic acid, due to its aromatic ring structure, can affect the crystallinity of polymers, and the mechanical properties and biodegradability of polymers prepared within the above-mentioned charge range can be satisfactorily achieved.

[0061] For example, based on 100 parts by weight of adipic acid in the monomer mixture, the monomer mixture may contain 80 to 120 parts by weight of terephthalic acid.

[0062] In the step of preparing the prepolymer, based on 100 parts by weight of adipic acid in the monomer mixture, an esterification reaction can be carried out by adding 0.1 to 1 part by weight of a crosslinking agent or branching agent.

[0063] When an esterification reaction is carried out by adding a crosslinking agent, an internally crosslinked prepolymer can be prepared, and the mechanical properties of the final composite can be improved.

[0064] The crosslinking agent is a low-molecular-weight compound containing three or more hydroxyl groups or three or more carboxyl groups in its molecule. For example, glycerol or citric acid can be used. For example, the crosslinking agent can be glycerol.

[0065] The prepolymer preparation process can be carried out at a temperature range of 150°C to 350°C for 10 to 120 minutes.

[0066] Within the above temperature and time range, prepolymers can be prepared while maintaining the uniform dispersion of organic fillers.

[0067] For example, the prepolymer preparation step can be carried out at temperatures above 150°C, 170°C, 190°C, or 210°C, and below 350°C, 320°C, 290°C, or 250°C. Furthermore, it can be carried out over time periods of 10 minutes, 15 minutes, 20 minutes, or 25 minutes, and below 120 minutes, 90 minutes, 60 minutes, or 40 minutes.

[0068] Nitrogen gas can be injected during the prepolymer preparation step. Specifically, by rapidly removing water, which is generated as a byproduct when nitrogen is injected, the reverse reaction caused by water can be suppressed, and the conversion rate and molecular weight of the monomer can be improved.

[0069] For example, nitrogen gas can be injected at a rate of (0.001) ml / min or higher, (0.01) ml / min or higher, (0.02) ml / min or higher, or (0.05) ml / min or higher, and at a rate of (100) ml / min or lower, (50) ml / min or lower, (10) ml / min or lower, or (5) ml / min or lower.

[0070] During the polymerization of the prepolymer, based on 100 parts by weight of adipic acid in the monomer mixture, 0.001 to 10 parts by weight of catalyst may also be added.

[0071] The catalyst added first is likely to cause a decrease in activity during the prepolymer preparation stage. For example, the central metallic component titanium of the catalyst reacts with water, a byproduct of the esterification reaction, to form titanium oxide, and the functional groups present in the aforementioned organic filler molecules can be substituted at the alkoxide moiety of the titanium alkoxide. Therefore, it is preferable to add the catalyst separately before the reaction.

[0072] For example, based on 100 parts by weight of adipic acid in the monomer mixture, the amount of additional catalyst may be more than 0.001 parts by weight, more than 0.005 parts by weight, or more than 0.01 parts by weight, and less than 10 parts by weight, less than 5 parts by weight, or less than 0.1 parts by weight.

[0073] After adding the catalyst, a heat stabilizer can be added. Adding a heat stabilizer can suppress the final discoloration of PBAT.

[0074] Specifically, based on 100 parts by weight of adipic acid in the monomer mixture, 0.001 parts by weight to 1 part by weight of heat stabilizer may be added.

[0075] For example, based on 100 parts by weight of adipic acid in a monomer mixture, the amount of heat stabilizer added can be more than 0.001 parts by weight, more than 0.005 parts by weight, more than 0.08 parts by weight, or more than 0.01 parts by weight, and less than 1 part by weight, less than 0.6 parts by weight, less than 0.3 parts by weight, or less than 0.1 parts by weight.

[0076] The polymerization process of the prepolymer may include the following steps: raising the temperature of the reactor containing the prepolymer to a range of 150°C to 350°C; after raising the temperature, reducing the pressure of the reactor to a range of 0.1 atm to 0.00001 atm; and terminating the reaction after reducing the pressure and temperature while maintaining the pressure and temperature for 2 to 8 hours.

[0077] For example, the temperature of the reactor containing the prepolymer can be increased to a temperature range of above 150°C, above 170°C, above 190°C, or above 210°C, and below 350°C, below 320°C, below 290°C, or below 250°C.

[0078] After reaching the above temperature range, the pressure in the reactor can be reduced to a pressure range of 0.00001 atm or higher, 0.00005 atm or higher, 0.0001 atm or higher, or 0.0002 atm or lower, and below 0.1 atm, 0.05 atm, 0.03 atm or lower.

[0079] After the pressure is reduced, the reaction continues while maintaining the pressure and temperature, and the reaction can be terminated after more than 2 minutes, 2.2 hours, 2.4 hours or 3 hours after the start, and less than 8 hours, 7.5 hours or 7 hours or 6 hours.

[0080] Biodegradable polymer complexes

[0081] In another embodiment of this disclosure, a biodegradable polymer composite is provided, comprising: polybutylene adipate terephthalate, comprising a) repeating units from 1,4-butanediol, b) repeating units from terephthalic acid, and c) repeating units from terephthalic acid; and an organic filler dispersed between the polymer chains of polybutylene adipate terephthalate.

[0082] The composite of one embodiment is prepared by the preparation method of the above embodiment and exhibits sufficient physical properties even when used alone without post-treatment such as mixing with reinforcing materials.

[0083] Furthermore, the composite material can be a composite material in which the crystallinity is controlled according to the content of organic filler and the biodegradability is improved.

[0084] In the case of a biodegradable polymer complex according to one embodiment of this disclosure, the acid value is comparable to that of a biodegradable polymer polymerized in an environment free of organic fillers, and the acid value according to DIN EN 12634 can be between 1.8 mg KOH / g and 3 mg KOH / g. For example, the acid value of the complex according to DIN EN 12634 can be above 1.8 mg KOH / g, and below 3 mg KOH / g, below 2.6 mg KOH / g, or below 2.5 mg KOH / g.

[0085] Acid value is the number of mg of KOH required to neutralize the free fatty acids contained in 1g of oil. RCOOH + KOH → RCOOK + H2O, that is, acid value is used to measure the amount of free fatty acids in which fatty acids do not exist in the form of glycerides.

[0086] In particular, in esterification reactions, acid value is a measure of the degree of reaction and refers to the amount of KOH required to neutralize the carboxyl groups contained in 1g of polymer. The higher the value, the worse the reaction rate.

[0087] Here, the acid value can be measured according to DIN EN 12634. Specifically, the sample is dissolved in a 1:1 mixture of o-cresol and chloroform, and 1 to 2 drops of an aqueous solution containing 0.1% by weight of phenol red are used as an indicator. A 0.1N potassium hydroxide (KOH) / ethanol solution is titrated using a micropipette, and the acid value can be measured according to Equation 1 below.

[0088] [Equation 1] Acid value (mgKOH / g) = (V-V0)*M*F*1000 / W

[0089] V: Volume (mL) of KOH / ethanol solution consumed in the sample titration.

[0090] V0: The volume (mL) of KOH / ethanol solution consumed in the titration of the blank test.

[0091] M: Molar concentration of KOH / ethanol solution (0.1 M / L)

[0092] W: Mass of the sample (g)

[0093] F: Titer of KOH / ethanol solution

[0094] Furthermore, the crystallinity of the biodegradable polymer composite according to one embodiment of this disclosure, as measured using a differential scanning calorimeter, can be between 20% and 27%. Within this range, regardless of the type of organic filler, the crystallinity decreases further and the biodegradability increases with increasing organic filler content.

[0095] Crystallinity can be calculated as the weight fraction of the crystalline portion relative to the total resin. Higher crystallinity (i.e., increasing crystal number) tends to correlate with higher polymer strength, making it a predictor of strength. In particular, in biodegradable polyester resins, higher crystallinity is known to correlate with lower biodegradability, making it a rough predictor of biodegradability.

[0096] In one embodiment of the biodegradable polymer composite, during the crystallization of molten PBAT by cooling, the crystals cannot grow completely due to the steric hindrance of the organic filler, and the crystallinity is low, which is different from PBAT polymerized without organic filler.

[0097] Here, the crystallinity can be measured using a differential scanning calorimeter. Specifically, a differential scanning calorimeter (DSC, device name: DSC2500, manufacturer: TA Instrument) is used to sequentially perform a first heating, a first cooling, and a second heating at a temperature range of -70°C to 200°C, 10°C / min, and the crystallinity can be calculated using the heat of fusion of the melting transformation during the second heating process (using PBATΔHm0 = 114 J / g).

[0098] One embodiment of the biodegradable polymer composite has a tensile strength of 400 kgf / cm² according to ASTM D 882. 2 Up to 550 kgf / cm 2 .

[0099] At this point, the tensile strength of MD is 400 kgf / cm. 2 Up to 450 kgf / cm 2 Specifically, it is 410 kgf / cm². 2 Up to 450 kgf / cm 2 For example, 410 kgf / cm 2 Up to 430 kgf / cm 2 The tensile strength of TD can reach 400 kgf / cm. 2 Up to 550 kgf / cm 2 Specifically, it is 430 kgf / cm². 2 Up to 550 kgf / cm 2 For example, 430 kgf / cm 2 Up to 500 kgf / cm 2 .

[0100] Tensile strength (maximum stress) can be measured according to ASTM D 882 by preparing molded articles containing the biodegradable polymer composite as blown film specimens. Specifically, tensile strength is measured by performing tensile tests on individual film specimens at a tensile rate of 10 mm / min using an Instron Universal Testing Machine (UTM).

[0101] The tensile test conditions used a 10KN load cell with an LE position of 40mm, and the maximum stress value of the SS curve could be measured separately for the longitudinal direction (MD) as MD and the transverse direction (TD) as TD.

[0102] Based on 100 parts by weight of repeating units from terephthalic acid, the polybutylene terephthalate in a biodegradable polymer composite of one embodiment may comprise 150 to 250 parts by weight of repeating units from 1,4-butanediol and 50 to 150 parts by weight of repeating units from terephthalic acid.

[0103] If the content of 1,4-butanediol is too high, it is effective in increasing the esterification reaction rate, but limited in increasing the molecular weight of the polymer, and the amount of THF produced by side reactions increases, which is economically inefficient. Furthermore, if the ratio of terephthalic acid to adipic acid is increased, the processability and biodegradability decrease.

[0104] For example, based on 100 parts by weight of repeating units from terephthalic acid, polybutylene terephthalate in a biodegradable polymer composite of one embodiment may comprise 180 to 220 parts by weight of repeating units from 1,4-butanediol and 80 to 120 parts by weight of repeating units from terephthalic acid.

[0105] Furthermore, based on 100 parts by weight of repeating units of bisacrylic acid in polybutylene adipate terephthalate, a biodegradable polymer composite of one embodiment may contain 0.001 parts by weight to 10 parts by weight of organic filler.

[0106] Molded products

[0107] In another embodiment of this disclosure, a molded article comprising the above-described biodegradable polymer composite is provided.

[0108] The molded products of this implementation scheme are not particularly limited in their use, but can be widely used in food packaging paper, bottles, films, sheets and other products that require transparency.

[0109] The present disclosure will now be described in more detail with reference to embodiments thereof. However, these embodiments are provided for illustrative purposes only and the scope of the disclosure is not limited thereto.

[0110] Preparation of catalyst mixture

[0111] Comparative Example 1

[0112] 0.5 mmol of tetrabutyl titanate and 6.77 mol of 1,4-butanediol were mixed and placed at 160 °C for 60 minutes to obtain a catalyst mixture of 0.17 g.

[0113] Example 1

[0114] 0.5 mmol of tetrabutyl titanate, 0.847 g of cellulose and 6.77 mol of 1,4-butanediol were mixed and reacted at 160 °C for 60 minutes to obtain a catalyst mixture in which 1,4-butanediol and organic filler were dispersed.

[0115] Example 2

[0116] 0.5 mmol of tetrabutyl titanate, 8.47 g of cellulose and 6.77 mol of 1,4-butanediol were mixed and reacted at 160 °C for 60 minutes to obtain a catalyst mixture in which 1,4-butanediol and organic filler were dispersed.

[0117] Example 3

[0118] 0.5 mmol of tetrabutyl titanate, 0.847 g of starch and 6.77 mol of 1,4-butanediol were mixed and reacted at 160 °C for 60 minutes to obtain a catalyst mixture in which 1,4-butanediol and organic filler were dispersed.

[0119] Example 4

[0120] 0.5 mmol of tetrabutyl titanate, 8.47 g of starch and 6.77 mol of 1,4-butanediol were mixed and reacted at 160 °C for 60 minutes to obtain a catalyst mixture in which 1,4-butanediol and organic filler were dispersed.

[0121] Preparation of prepolymer

[0122] A monomer mixture containing 303g of adipic acid, 317g of terephthalic acid and 0.88g of glycerol, as well as the catalyst mixtures of the examples and comparative examples, were added to the reactor.

[0123] The temperature of the reactor containing the reactants was maintained at 230°C, and nitrogen gas was then flowed at a flow rate of 2 cc / min for 240 minutes to prepare the prepolymer while removing byproducts.

[0124] Comparative Example 2

[0125] Preparation of prepolymer

[0126] 610 g of 1,4-butanediol, 0.847 g of cellulose, 303 g of adipic acid, 317 g of terephthalic acid, 0.88 g of glycerol, and 0.17 g of tetrabutyl titanate were added to the reactor. The reactor temperature was maintained at 230 °C, and nitrogen gas was then flowed at a flow rate of 2 cc / min for 240 minutes to prepare the prepolymer while removing byproducts.

[0127] Comparative Example 3

[0128] Preparation of prepolymer

[0129] 610 g of 1,4-butanediol, 8.47 g of cellulose, 303 g of adipic acid, 317 g of terephthalic acid, 0.88 g of glycerol, and 0.17 g of tetrabutyl titanate were added to the reactor. The reactor temperature was maintained at 230 °C, and nitrogen gas was then flowed at a flow rate of 2 cc / min for 240 minutes to prepare the prepolymer while removing byproducts.

[0130] Preparation of biodegradable polymer complexes

[0131] 0.5 mmol of tetrabutyl titanate as a catalyst was added to the reactor in which the prepolymer was prepared, and the mixture was stirred at 60 rpm for 10 minutes.

[0132] After stirring, add 0.09g of heat stabilizer (triethyl phosphoroacetate) and then stir at 60rpm for 10 minutes.

[0133] The reactor temperature was then increased to 240°C. After 5 minutes at 240°C, the pressure was reduced until the internal pressure of the reactor reached 0.001 atm. While maintaining the reduced pressure, stirring was continued at 60 rpm to carry out polymerization. Stirring was stopped 210 minutes after the start of polymerization, and the reactor was disassembled to finally obtain the biodegradable polymer composite.

[0134] Measurement of weight-average molecular weight

[0135] The target substance was dissolved in chloroform at a concentration of 1 mg / ml, and the solution was then added to a gel permeation chromatography (GPC, PLGPC220, Agilent Technologies) instrument to measure its molecular weight. Polystyrene was used as the standard polymer in this case.

[0136] Measuring acid value

[0137] The sample was dissolved in a 1:1 mixture of o-cresol and chloroform, and 1 to 2 drops of an aqueous solution containing 0.1% by weight of phenol red were used as an indicator.

[0138] Titrate a 0.1N potassium hydroxide (KOH) / ethanol solution using a micropipette and measure the acid value according to Equation 1 below.

[0139] [Equation 1] Acid value (mg KOH / g) = (V - V0) * M * F * 1000 / W

[0140] V: Volume (mL) of KOH / ethanol solution consumed in the sample titration.

[0141] V0: The volume (mL) of KOH / ethanol solution consumed in the titration of the blank test.

[0142] M: Molar concentration of KOH / ethanol solution (0.1 M / L)

[0143] W: Mass of the sample (g)

[0144] F: Titer of KOH / ethanol solution

[0145] Acid value is the number of mg of KOH required to neutralize the free fatty acids contained in 1g of oil. RCOOH + KOH → RCOOK + H2O, that is, acid value is used to measure the amount of free fatty acids in which fatty acids do not exist in the form of glycerides.

[0146] In particular, in esterification reactions, acid value is a measure of the degree of reaction and refers to the amount of KOH required to neutralize the carboxyl groups contained in 1g of polymer. It is a factor that indicates a higher acid value and a worse reaction rate.

[0147] [Table 1]

[0148]

[0149] The results show that, in the cases of comparative examples and exemplary examples, the acid value and weight-average molecular weight values ​​that can be used to determine the polymerization trend are almost at the same level.

[0150] Evaluation of crystallinity and mechanical properties

[0151] The crystallinity and mechanical properties of the biodegradable polymer composites according to the above examples and comparative examples were measured, and the results are summarized in the table below.

[0152] Specifically, the method for measuring crystallinity is as follows.

[0153] Crystallinity:

[0154] For the biodegradable polymer composites of Examples 1 to 4 and PBAT of Comparative Examples 1 to 3, a first heating, a first cooling, and a second heating were performed sequentially within a temperature range (-70°C to 200°C, 10°C / min) using a differential scanning calorimeter (DSC, device name: DSC 2500, manufacturer: TA Instrument), and the degree of crystallinity was calculated using the heat of fusion of the melting transition during the second heating process (using PBAT ΔHm0 = 114 J / g).

[0155] Sample preparation:

[0156] Blow-molded films were prepared by blow-molding the biodegradable polymer composites of the examples and comparative examples to a thickness of about 50 μm using a single-screw extruder (Shinhwa Industry Co., Ltd., Blown Film M / C, 50 pie, L / D = 20) at an extrusion temperature of 130°C to 170°C. In this regard, the die gap was 2.0 mm and the blow-up ratio was 2.3.

[0157] Tensile strength (maximum stress):

[0158] According to ASTM D 882, tensile strength was measured by performing tensile tests on individual membrane specimens at a tensile rate of 10 mm / min using an Intstron Universal Testing Machine (UTM). In this case, the tensile test conditions were set with a 10 kN load cell, an LE position of 40 mm, and the maximum stress values ​​of the SS curves were measured for both the longitudinal direction (MD) as the MD and the transverse direction (TD) as the TD.

[0159] [Table 2]

[0160]

[0161] Crystallinity can be calculated as the weight fraction of the crystalline portion relative to the total resin. Higher crystallinity (i.e., increasing crystal number) tends to correlate with higher polymer strength, making it a predictor of strength. In particular, in biodegradable polyester resins, higher crystallinity is known to correlate with lower biodegradability, making it a rough predictor of biodegradability.

[0162] The crystallinity of the comparative example PBAT was about 29% to about 34%, and compared with the comparative example, the crystallinity of the biodegradable polymer composites of Examples 1 to 4 containing organic fillers tended to be slightly lower.

[0163] The reason why the crystallinity value of the embodiments of this disclosure is slightly lower than that of the comparative examples is that the crystals cannot grow completely due to the steric hindrance of the organic filler during the crystallization process of molten PBAT by cooling.

[0164] Furthermore, a slight decrease in crystallinity also implies a slight increase in biodegradability. It can be confirmed that in Examples 1 to 4, which contain organic fillers, regardless of the type of organic filler, crystallinity further decreases with increasing organic filler content. This demonstrates that crystallinity and biodegradability can be controlled by adjusting the content of the organic filler.

[0165] Furthermore, compared to the comparative example PBAT, the biodegradable polymer composites of Examples 1 to 4 containing organic fillers exhibited significantly increased horizontal tensile strength and TD tensile strength.

[0166] In particular, in Examples 1 to 4, regardless of the type of organic filler, the horizontal tensile strength and TD tensile strength showed a trend of increasing with the increase of organic filler content.

[0167] This trend is thought to be due to the relative increase in amorphous components as crystallinity decreases.

[0168] Overview

[0169] By adjusting the content of organic filler according to the trends in Examples 1 to 4, the biodegradability and mechanical properties of the biodegradable polymer composite can be adjusted to the desired range.

[0170] However, this is just one example. Unlike polybutylene adipate terephthalate polymerized without organic fillers, biodegradable polymer composites with improved biodegradability can be provided even when used alone without post-treatment, provided that the above series of processes are employed, while exhibiting sufficient physical properties with high efficiency and low cost.

Claims

1. A method for preparing a biodegradable polymer composite, comprising the following steps: Prepare a monomer mixture containing adipic acid and terephthalic acid; Organic filler, 1,4-butanediol and catalyst were mixed to prepare a catalyst mixture; and The monomer mixture and the catalyst mixture are mixed and subjected to an esterification reaction. in, The step of preparing the catalyst mixture is carried out at a temperature range of 40°C to 240°C for 10 to 120 minutes. Based on 100 parts by weight of adipic acid in the monomer mixture, the content of the catalyst in the catalyst mixture is from 0.001 parts by weight to 10 parts by weight. The organic filler content in the catalyst mixture is from 0.5 g to 20 g of organic filler per 1 mmol of catalyst. The catalyst is selected from at least one of methyl titanate, ethyl titanate, n-propyl titanate, isopropyl titanate, tetra-n-butyl titanate, and tetraisobutyl titanate. The organic filler is at least one selected from cellulose and starch-based compounds.

2. The method for preparing a biodegradable polymer composite according to claim 1, wherein, Based on 100 parts by weight of adipic acid in the monomer mixture, the content of 1,4-butanediol in the catalyst mixture is 150 to 250 parts by weight.

3. The method for preparing a biodegradable polymer composite according to claim 1, wherein, Based on 100 parts by weight of adipic acid in the monomer mixture, the content of the organic filler in the catalyst mixture is from 0.01 parts by weight to 10 parts by weight.

4. The method for preparing a biodegradable polymer composite according to claim 1, wherein, Based on 100 parts by weight of adipic acid in the monomer mixture, the monomer mixture contains 50 to 150 parts by weight of terephthalic acid.

5. The method for preparing a biodegradable polymer composite according to claim 1, wherein, The steps for carrying out the esterification reaction include: Preparation of prepolymers; and The prepolymer is polymerized to obtain a biodegradable polymer complex.

6. The method for preparing a biodegradable polymer composite according to claim 5, wherein, During the polymerization of the prepolymer, based on 100 parts by weight of adipic acid in the monomer mixture, 0.001 to 10 parts by weight of catalyst are further added.

7. A biodegradable polymer composite prepared by the method according to claim 1, comprising: Polybutylene adipate terephthalate, comprising a) repeating units from 1,4-butanediol, b) repeating units from terephthalic acid, and c) repeating units from terephthalic acid; and Organic filler dispersed between polymer chains of polybutylene terephthalate (PET).

8. The biodegradable polymer complex according to claim 7, wherein, The crystallinity, as measured using differential scanning calorimetry, ranged from 20% to 27%.

9. The biodegradable polymer complex according to claim 7, wherein, The tensile strength, measured according to ASTM D 882, is 400 kgf / cm². 2 Up to 550 kgf / cm 2 .

10. A molded article comprising the biodegradable polymer composite as described in claim 7.

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