Biodegradable polyester resin, its manufacturing method, and biodegradable polyester film containing the same

Abstract

The present invention provides a polyester resin having excellent physical properties, such as adhesive properties, tensile strength, tear strength, and coefficient of friction, as well as moldability and processability, and a method for producing the same. Furthermore, the present invention provides a biodegradable polyester film using the polyester resin that not only achieves the above-mentioned excellent physical properties but also has excellent biodegradability and hydrodegradability. [Solution] A biodegradable polyester resin and a method for producing the same, in which a first repeating unit containing a first diol residue and a residue of an aromatic dicarboxylic acid and a second repeating unit containing a second diol residue and a residue of an aliphatic dicarboxylic acid have a ratio of the number of repeating units within a specific range, and the flexibility index of the resin satisfies a specific range.

Description

[Technical Field]

[0001] The present invention relates to a biodegradable polyester resin, a method for producing the same, and a biodegradable polyester film containing the same. [Background technology]

[0002] In recent years, growing concerns about environmental issues have led to a demand for solutions to the problem of disposing of various daily necessities, particularly disposable products. Specifically, polymeric materials are inexpensive and have excellent processability and other properties, and are widely used to manufacture a variety of products, such as films, fibers, packaging materials, bottles, and containers. However, when used products reach the end of their lifespan, they release toxic substances when incinerated, and depending on the type, they can take hundreds of years to completely decompose naturally.

[0003] To overcome these limitations, active research is being conducted into biodegradable polymers that degrade more quickly. Biodegradable polymers such as polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), and polybutylene succinate (PBS) are currently used. However, these biodegradable polymers are very sticky and easily stretched when subjected to external forces during blown film production, resulting in poor blown film formability. Furthermore, the film surfaces tend to adhere to each other during winding, reducing processability and productivity, limiting their applications.

[0004] In an attempt to overcome these physical limitations, such as adhesive properties, inorganic substances such as silica and calcium carbonate have been added, but this requires the use of excessive amounts of inorganic substances, which results in the formation of voids during the inflation process, reducing physical properties such as tensile strength and tear strength, and thus reducing moldability. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Korean Patent Publication No. 2012-0103158 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a polyester resin having excellent physical properties such as adhesive properties, tensile strength, tear strength and coefficient of friction, as well as moldability and processability, and a method for producing the same.

[0007] Furthermore, another object of the present invention is to provide a biodegradable polyester film that uses the polyester resin and achieves the above-mentioned excellent physical properties, and also has excellent biodegradability and hydrodegradability. [Means for solving the problem]

[0008] The present invention provides a biodegradable polyester resin comprising a first repeating unit containing a first diol residue and a residue of an aromatic dicarboxylic acid, and a second repeating unit containing a second diol residue and a residue of an aliphatic dicarboxylic acid, wherein the first diol residue and the second diol residue each contain a residue of 1,4-butanediol, 1,2-ethanediol, 1,3-propanediol, or a derivative thereof; the aromatic dicarboxylic acid residue contains a residue of terephthalic acid, dimethyl terephthalate, or a derivative thereof; and the aliphatic dicarboxylic acid residue contains a residue of adipic acid, succinic acid, sebacic acid, or a derivative thereof; the ratio (X / Y) of the number of the first repeating units (X) to the number of the second repeating units (Y) is 0.6 to 1.8; and the biodegradable polyester resin has a softness index (SI) represented by the following formula 1 of 90 to 130.

[0009] [Formula 1] JPEG0007783842000001.jpg869In the above formula 1, Tc and VST are unit-free values ​​measured on a biodegradable polyester film test piece produced from the biodegradable polyester resin, Tc is the crystallization temperature (°C) measured using a differential scanning calorimeter (DSC) in the process of heating from 40°C to 180°C at a rate of 10°C / min and then cooling to -50°C at a rate of 10°C / min. VST (Vicat Softening Temperature) is the temperature (°C) at which the tip of a needle passes through 1 mm of a test piece 5 mm thick and 10 mm wide when the test piece is measured at 50°C / hour and a load of 10 N according to ASTM D1525.

[0010] The present invention also provides a biodegradable polyester resin comprising a first repeating unit containing a first diol residue and a residue of an aromatic dicarboxylic acid, and a second repeating unit containing a second diol residue and a residue of an aliphatic dicarboxylic acid, the first repeating unit containing a first diol residue and a residue of an aromatic dicarboxylic acid, and the second repeating unit containing a second diol residue and a residue of an aliphatic dicarboxylic acid, the third repeating unit being a mixture of the first diol and the aromatic dicarboxylic acid, the second repeating unit being a mixture of the first diol and the aromatic dicarboxylic acid, the second repeating unit being a mixture of the first diol and the aromatic dicarboxylic acid, the second repeating unit being a mixture of the first diol and the aromatic dicarboxylic acid, the third ... third repeating unit being a mixture of the first diol and the aromatic dicarboxylic acid, the second repeating unit being a mixture of the first diol and the aromatic dicarboxylic acid, the third repeating unit being a mixture of the first diol and the aromatic dicarboxylic acid, the The diol residue and the second diol residue each include a residue of 1,4-butanediol, 1,2-ethanediol, 1,3-propanediol, or a derivative thereof; the aromatic dicarboxylic acid residue includes a residue of terephthalic acid, dimethyl terephthalate, or a derivative thereof; and the aliphatic dicarboxylic acid residue includes a residue of adipic acid, succinic acid, sebacic acid, or a derivative thereof; the ratio (X / Y) of the number of the first repeating units (X) to the number of the second repeating units (Y) is 0.6 to 1.8; and the softness index (SI) represented by the formula 1 is 90 to 130.

[0011] The present invention further provides a biodegradable polyester film comprising a biodegradable polyester resin, the biodegradable polyester resin comprising a first repeating unit including a first diol residue and a residue of an aromatic dicarboxylic acid, and a second repeating unit including a second diol residue and a residue of an aliphatic dicarboxylic acid, wherein the first diol residue and the second diol residue each include a residue of 1,4-butanediol, 1,2-ethanediol, 1,3-propanediol, or a derivative thereof, the aromatic dicarboxylic acid residue includes a residue of terephthalic acid, dimethyl terephthalate, or a derivative thereof, and the aliphatic dicarboxylic acid residue includes a residue of adipic acid, succinic acid, sebacic acid, or a derivative thereof, wherein the ratio (X / Y) of the number of the first repeating units (X) to the number of the second repeating units (Y) is 0.6 to 1.8, and the softness index (SI) represented by the above formula 1 is 90 to 130. [Effects of the Invention]

[0012] In one embodiment of the biodegradable polyester resin of the present invention, the first repeating unit containing a first diol residue and a residue of an aromatic dicarboxylic acid and the second repeating unit containing a second diol residue and a residue of an aliphatic dicarboxylic acid have a ratio of the number of repeating units within a specific range, and the flexibility index of the resin satisfies a specific range, thereby simultaneously improving productivity, processability, and moldability.

[0013] Furthermore, the biodegradable polyester resin can provide a biodegradable polyester sheet or film that has excellent physical properties such as excellent tensile strength, tear strength, and a low coefficient of friction, as well as excellent biodegradability and hydrodegradability, and therefore the biodegradable polyester resin can be used in a wider variety of fields and can exhibit excellent properties. [Brief explanation of the drawings]

[0014]

Figure 1

[0015] The present invention will be described in more detail below. In this specification, when a part is said to "comprise" a certain component, this does not mean that it excludes other components, but that it may further include other components, unless otherwise specified.

[0016] Furthermore, all numerical ranges indicating physical properties, dimensions, etc. of components described in this specification should be understood to be modified in all cases by the term "about" unless otherwise specified.

[0017] In this specification, terms such as first, second, primary, and secondary are used to describe various components, and the components are not limited by the terms. The terms are used only to distinguish one component from another.

[0018] In one embodiment of the present invention, there is provided a biodegradable polyester resin comprising a first repeating unit including a first diol residue and a residue of an aromatic dicarboxylic acid, and a second repeating unit including a second diol residue and a residue of an aliphatic dicarboxylic acid, wherein the first diol residue and the second diol residue each include a residue of 1,4-butanediol, 1,2-ethanediol, 1,3-propanediol, or a derivative thereof; the aromatic dicarboxylic acid residue includes a residue of terephthalic acid, dimethyl terephthalate, or a derivative thereof; and the aliphatic dicarboxylic acid residue includes a residue of adipic acid, succinic acid, sebacic acid, or a derivative thereof; the ratio (X / Y) of the number of the first repeating units (X) to the number of the second repeating units (Y) is 0.6 to 1.8; and the biodegradable polyester resin has a softness index (SI) represented by the following formula 1 of 90 to 130.

[0019] [Formula 1] JPEG0007783842000002.jpg869In the above formula 1, Tc and VST are unit-free values ​​measured on a biodegradable polyester film test piece produced from the biodegradable polyester resin, Tc is the crystallization temperature (°C) measured using a differential scanning calorimeter (DSC) in the process of heating from 40°C to 180°C at a rate of 10°C / min and then cooling to -50°C at a rate of 10°C / min. VST is the temperature (°C) at which the tip of a needle passes through 1 mm of a test piece 5 mm thick and 10 mm wide when the test piece is measured at 50°C / hour and a load of 10 N based on ASTM D1525.

[0020] Generally, the blown film process is a very important production process in the production of biodegradable polyester films. That is, during the blown film process, it is necessary to produce a finished product with good bubble formation and without fusion of the film surfaces during winding. For this purpose, it is important to realize appropriate levels of physical properties such as tensile strength, tear strength, and friction coefficient as well as productivity, processability, and moldability of the biodegradable polyester resin.

[0021] Therefore, in order to realize the above-mentioned properties of the biodegradable polyester resin, the structure, softness or adhesive properties, crystallization temperature and softening point temperature of the polyester resin are very important factors.

[0022] In one embodiment of the present invention, the biodegradable polyester resin comprises first repeating units containing a first diol residue and a residue of an aromatic dicarboxylic acid, and second repeating units containing a second diol residue and a residue of an aliphatic dicarboxylic acid. By adjusting the ratio (X / Y) of the number of the first repeating units (X) to the number of the second repeating units (Y) within a specific range and simultaneously controlling the flexibility index of the resin within a specific range, the productivity, processability, and moldability of the polyester resin can be simultaneously improved, and a biodegradable polyester sheet or film can be provided that has excellent physical properties such as excellent tensile strength, tear strength, and a low coefficient of friction, as well as excellent biodegradability and hydrodegradability. Furthermore, the present invention has the technical significance of being extensible to various injection molding applications. The biodegradable polyester resin will be described in more detail below.

[0023] [Biodegradable polyester resin] A biodegradable polyester resin according to one embodiment of the present invention includes a first repeating unit including a first diol residue and a residue of an aromatic dicarboxylic acid, and a second repeating unit including a second diol residue and a residue of an aliphatic dicarboxylic acid.

[0024] The first diol residue and the second diol residue each include a residue of 1,4-butanediol, 1,2-ethanediol, 1,3-propanediol, or a derivative thereof; the aromatic dicarboxylic acid residue includes a residue of terephthalic acid, dimethyl terephthalate, or a derivative thereof; and the aliphatic dicarboxylic acid residue includes a residue of adipic acid, succinic acid, sebacic acid, or a derivative thereof.

[0025] The biodegradable polyester resin having the above structure can improve the biodegradability, hydrolysis and physical properties of the biodegradable polyester sheet, film or molded article obtained using the same.

[0026] The first diol residue and the second diol residue may each include a residue of 1,4-butanediol, 1,2-ethanediol, 1,3-propanediol, or a derivative thereof, specifically a residue of 1,4-butanediol, 1,2-ethanediol, or a derivative thereof, and more specifically a residue of 1,4-butanediol or a derivative thereof. For example, when the diol includes 1,4-butanediol, this may be more advantageous in improving the biodegradability, hydrodegradability, and physical properties of the biodegradable polyester resin or a biodegradable polyester sheet, film, or molded article obtained using the same.

[0027] Furthermore, when the aromatic dicarboxylic acid and the aliphatic dicarboxylic acid each contain the above residue, they can react more uniformly with the diol component in the preparation process of the present invention, thereby increasing the reaction efficiency, which may be more advantageous in preparing a biodegradable polyester resin having the above physical properties.

[0028] Specifically, the first diol residue and the second diol residue may each include a residue of 1,4-butanediol or a derivative thereof, the aromatic dicarboxylic acid residue may include a residue of terephthalic acid or a derivative thereof, and the aliphatic dicarboxylic acid residue may include a residue of adipic acid, succinic acid, or a derivative thereof.

[0029] The biodegradable polyester resin may include a first repeat unit including a residue of 1,4-butanediol or a derivative thereof and a residue of terephthalic acid or a derivative thereof.

[0030] Alternatively, the biodegradable polyester resin may include a first repeat unit including a residue of 1,4-butanediol or a derivative thereof and a residue of dimethyl terephthalate or a derivative thereof.

[0031] The biodegradable polyester resin may include a second repeat unit including residues of 1,4-butanediol or a derivative thereof and residues of adipic acid or a derivative thereof.

[0032] Alternatively, the biodegradable polyester resin may include a second repeat unit that includes residues of 1,4-butanediol or a derivative thereof and residues of succinic acid or a derivative thereof.

[0033] A biodegradable polyester resin according to an embodiment of the present invention may include a first repeat unit comprising a residue of 1,4-butanediol or a derivative thereof and a residue of terephthalic acid or a derivative thereof; and a second repeat unit comprising a residue of 1,4-butanediol or a derivative thereof and a residue of adipic acid or a derivative thereof.

[0034] If the first repeating unit and the second repeating unit satisfy the above structure, it may be more advantageous to provide a biodegradable polyester sheet or film having excellent biodegradability and hydrodegradability.

[0035] On the other hand, in order to provide the biodegradable polyester resin with excellent productivity, processability, and moldability, and to simultaneously improve the biodegradability and hydrodegradability of the biodegradable polyester sheet or film produced using the same, it is very important to adjust the number of the repeating units constituting the biodegradable polyester resin.

[0036] According to an embodiment of the present invention, the ratio (X / Y) of the number of the first repeat units (X) to the number of the second repeat units (Y) may be 0.6 to 1.8. Specifically, the ratio (X / Y) of the number of the first repeat units (X) to the number of the second repeat units (Y) may be 0.7 to 1.8, 0.75 to 1.7, 0.8 to 1.6, 0.8 to 1.5, 0.8 to 1.4, 0.8 to 1.3, 0.8 to 1.2, 0.8 to 1.1, or 0.8 to 1.0.

[0037] If the ratio (X / Y) of the number of the first repeating units (X) to the number of the second repeating units (Y) is less than the above range, the tensile strength, elongation, and tear strength may decrease, and the adhesive properties may increase, resulting in poor processability. In particular, during the inflation film process, the bubble shapes may not be properly aligned, or may stretch to one side, or the bubbles may break, resulting in poor inflation moldability. Furthermore, biodegradable polyester sheets or films using biodegradable polyester resins may show a significant decrease in the rate of decrease in hydrolysis after 3 months, and biodegradability may decrease under seawater or humid conditions.

[0038] Specifically, the number of the first repeating units may be 100 to 900, 300 to 900, 350 to 900, 355 to 900, 360 to 900, 400 to 900, or 450 to 900.

[0039] The number of the second repeating units can be 100 to 1100, 200 to 1100, 250 to 1100, 260 to 1100, 270 to 1100, 300 to 1100, 400 to 1100, 450 to 1100, or 450 to 1080.

[0040] When the number of the first repeating unit and the number of the second repeating unit each satisfy the above range, the processability and physical properties can be improved, and the physical properties, biodegradability, and hydrolysis reduction rate of the biodegradable polyester sheet, film, or molded product produced using the same can be further improved.

[0041] In particular, the second repeating unit containing the second diol residue and the aliphatic dicarboxylic acid residue is a linear chain aliphatic dicarboxylic acid residue, and depending on the aliphatic dicarboxylic acid residue and its content, the degree of softening of the biodegradable polyester resin may change, and the crystallization temperature and Vicat softening point may also change. Therefore, by setting the number of the second repeating units within the above range, the processability of the biodegradable polyester resin can be further improved.

[0042] The biodegradable polyester resin according to one embodiment of the present invention has a softness index (SI) of 90 to 130, as expressed by the following formula 1.

[0043] [Formula 1] JPEG0007783842000003.jpg868In the above formula 1, Tc and VST are unit-free values ​​measured on a biodegradable polyester film test piece produced from the biodegradable polyester resin, Tc is the crystallization temperature (°C) measured using DSC in the process of heating from 40°C to 180°C at a rate of 10°C / min and then cooling to -50°C at a rate of 10°C / min. VST is the temperature (°C) at which the tip of a needle passes through 1 mm of a test piece 5 mm thick and 10 mm wide when the test piece is measured at 50°C / hour and a load of 10 N based on ASTM D1525.

[0044] The softness index (SI) expressed by the above formula 1 is an index showing the degree of softness of a biodegradable polyester resin, and is the sum of the crystallization temperature (Tc) of the biodegradable polyester resin divided by 100 and the Vicat softening point (VST, Vicat A50) of the biodegradable polyester resin.

[0045] The SI may be higher as the adhesive properties are lower, or lower as the adhesive properties are higher. The SI may also be higher as the crystallization temperature (Tc) of the biodegradable polyester resin is higher, or higher as the Vicat softening point (VST, Vicat A50) of the biodegradable polyester resin is higher.

[0046] When the softness index (SI) having such properties satisfies an appropriate range, it can improve not only the physical properties of the biodegradable polyester resin but also the productivity, processability and moldability at the same time.

[0047] Specifically, the Flexibility Index (SI) of the biodegradable polyester resin may be, for example, 90 to 130, 90 to 127, 90 to 126, 90 to 125, 90 to 120, 90 to 116, 90 to 115, 90 to 110, 92 to 110, 93 to 110, 94 to 109, 95 to 109, 97 to 109, 98 to 109, 99 to 109, or 100 to 109. When the Flexibility Index (SI) of the biodegradable polyester resin satisfies the range of 90 to 130, the degree of flexibility is appropriate, which can simultaneously improve the productivity, processability, and moldability of the biodegradable polyester resin, and can provide a biodegradable polyester sheet or film with excellent biodegradability and hydrodegradability.

[0048] If the scalability index (SI) of the biodegradable polyester resin is less than 90, the crystallization temperature (Tc) and / or Vicat softening point (VST, Vicat A50) of the biodegradable polyester resin will be too low, which may adversely affect the productivity, processability, and moldability of the biodegradable polyester resin. In particular, the adhesive properties may be so severe that the film surfaces may stick together during winding, resulting in poor inflation moldability. Furthermore, if the SI of the biodegradable polyester resin is more than 130, physical properties such as tensile strength, tear strength, and elongation may decrease, and inflation moldability may also be poor.

[0049] The crystallization temperature (Tc) of the biodegradable polyester resin was measured using DSC by heating from 40°C to 180°C at a rate of 10°C / min, isothermally removing the thermal history for 5 minutes, and then cooling from 180°C to -50°C at a rate of 10°C / min and isothermally removing the thermal history for 5 minutes.

[0050] The crystallization temperature (Tc) of the biodegradable polyester resin may be 38°C or higher, for example, 38°C to 70°C, for example, 38°C to 65°C, for example, 39°C to 60°C, for example, 40°C to 60°C, for example, 44°C to 60°C, for example, 44°C to 59°C, for example, 44°C to 58°C, for example, 45°C to 58°C, for example, 44°C to 55°C, or for example, 47°C to 58°C.

[0051] When the crystallization temperature (Tc) of the biodegradable polyester resin satisfies the above range, the crystallization rate and degree of crystallization are appropriate, so that cooling crystallization after extrusion during the blown film process is fast, blown film molding is stable, and adhesive properties can be reduced, which is advantageous in terms of bubble stability.

[0052] The Vicat softening point (VST, Vicat A50) of the biodegradable polyester resin is measured based on ASTM D1525 (ISO 306) by measuring a biodegradable polyester chip (test piece) with a thickness of 5 mm and a width of 10 mm at 50°C / hour and a load of 10 N. The Vicat softening point (VST, Vicat A50) of the biodegradable polyester resin is the temperature (°C) at which the tip of a needle passes through 1 mm of the test piece. This can indicate the degree of softening of the biodegradable polyester resin.

[0053] The Vicat softening point (VST, Vicat A50) of the biodegradable polyester resin may be 90°C or higher, for example, 90°C to 130°C, for example, 90°C to 128°C, for example, 90°C to 126°C, for example, 90°C to 125°C, for example, 90°C to 120°C, for example, 90°C to 115°C, for example, 90°C to 114°C, for example, 90°C to 110°C, for example, 92°C to 110°C, for example, 93°C to 110°C, for example, 94°C to 110°C, for example, 95°C to 110°C, for example, 96°C to 109°C, for example, 97°C to 109°C, or for example, 100°C to 108°C.

[0054] When the Vicat softening point (VST, Vicat A50) of the biodegradable polyester resin satisfies the above range, the adhesive properties of the biodegradable polyester resin can be reduced and the inflation moldability can be further improved. For example, when producing a biodegradable polyester film, the polyester pellets are softened and melted by extrusion at high temperatures during extrusion and inflation molding. The higher the Vicat softening point, the higher the melting point and the better the flexibility. Therefore, when the Vicat softening point satisfies the above range, the processability during inflation film molding can be improved.

[0055] On the other hand, in order to further improve the effects of the present invention, the melt crystallization enthalpy ΔHmc of the biodegradable polyester resin may also satisfy a specific range.

[0056] The ΔHmc of the biodegradable polyester resin may be 14 J / g or more. Specifically, the ΔHmc of the biodegradable polyester resin may be, for example, 14 J / g to 30 J / g, for example, 15 J / g to 30 J / g, for example, 15 J / g to 25 J / g, for example, 15 J / g to 22 J / g, for example, 15 J / g to 20 J / g, or for example, 15 J / g to 19 J / g. The ΔHmc of the biodegradable polyester resin is the melt crystallization enthalpy measured using DSC in the same manner as the crystallization temperature (Tc) (°C) of the biodegradable polyester resin.

[0057] When the ΔHmc of the biodegradable polyester resin satisfies the above range, the crystallization rate and degree of crystallization are appropriate, and during the blown film process, cooling crystallization after extrusion is accelerated, blown film molding is performed stably, and adhesive properties can be reduced.

[0058] Meanwhile, the biodegradable polyester resin may have a molding index (FI) of 25 to 53, as expressed by the following formula 2:

[0059] [Formula 2] JPEG0007783842000004.jpg842In the above formula 2, TS and FC are unit-free values ​​measured on a biodegradable polyester sheet test piece produced from the biodegradable polyester resin, TS is JIS K 6251 After preparing a test piece based on the above, the test piece was measured for tear strength (N / cm) using a universal testing machine (UTM), FC is the static friction coefficient measured by bringing one surface of the test piece into contact with stainless steel (SUS) in accordance with ASTM D1894.

[0060] The molding index (FI) expressed by Equation 2 is an index showing the moldability of a biodegradable polyester resin, and the molding index (FI) may affect the inflation moldability or injection moldability, etc. The molding index (FI) of a biodegradable polyester resin indicates the ratio of the tear strength (TS) of a biodegradable polyester sheet produced using the biodegradable polyester resin to the coefficient of static friction (FC) of the biodegradable polyester sheet.

[0061] The forming index (FI) may be higher as the tear strength of the biodegradable polyester sheet is higher, and may be higher as the static friction coefficient of the biodegradable polyester sheet is lower.

[0062] The molding index (FI) of the biodegradable polyester resin may be, for example, 28-53, for example, 29-53, for example, 30-53, for example, 30-52, for example, 35-50, for example, 36-50, for example, 38-50, for example, 50, or for example, 43-48.

[0063] When the molding index (FI) of the biodegradable polyester resin satisfies the range of 25 to 53, the inflation moldability or injection moldability can be further improved, and at the same time, the physical properties of the biodegradable polyester sheet or film can be improved.

[0064] If the molding index (FI) of the biodegradable polyester resin is less than 25, the physical properties of the biodegradable polyester sheet or film, such as tensile strength, tear strength, or elongation, may decrease, resulting in poor inflation moldability. Furthermore, if the molding index (FI) of the biodegradable polyester resin is more than 53, the productivity, processability, and moldability of the biodegradable polyester resin may be adversely affected. In particular, the adhesive properties may be so severe that the film surfaces may stick together during winding, resulting in poor inflation moldability.

[0065] In the above formula 2, the tear strength (N / cm) indicating TS is calculated by using the biodegradable polyester resin. JIS K 6251After preparing a biodegradable polyester sheet specimen based on the above, a 2 mm notch is made in the center and the specimen is measured using an INSTRON universal testing machine (UTM, 4206-001). The tear strength refers to the ratio of the force (N) applied when tearing to the thickness (cm) of the specimen, i.e., the maximum load until the specimen breaks. The tear strength may refer not only to the specimen using the biodegradable polyester resin, but also to the tear strength of a biodegradable polyester sheet, film, or polyester molded product.

[0066] The tear strength (N / cm) may be 300 N / cm or more, for example, 300 N / cm to 600 N / cm, for example, 300 N / cm to 550 N / cm, for example, 300 N / cm to 500 N / cm, for example, 305 N / cm to 480 N / cm, for example, 310 N / cm to 450 N / cm, for example, 330 N / cm to 450 N / cm, for example, 350 N / cm to 450 N / cm, for example, 360 N / cm to 450 N / cm, or for example, 360 N / cm to 440 N / cm.

[0067] If the tear strength satisfies the above range, it is advantageous to achieve the target moldability index (FI) by implementing the present invention, and therefore the productivity, processability and moldability of the biodegradable polyester resin can be simultaneously satisfied.

[0068] The static friction coefficient (FC) represented by FC in Equation 2 can be measured, for example, using a Qmesys friction coefficient tester (QM110CF), and is the value measured when stainless steel (SUS) and one side of a biodegradable polyester sheet test piece are brought into contact and slide against each other in accordance with ASTM D1894. The static friction coefficient is a coefficient that indicates the magnitude of the force (frictional force) acting between the surfaces of two objects that tries to inhibit movement when one object starts to move along the surface of another object or when the object continues to move, and is not related to the size of the contact area but can be determined by the properties of both surfaces.

[0069] The static friction coefficient is the coefficient of friction when an object starts to slide from a stationary state, i.e., when an external force is applied to an object stationary on a flat surface to cause it to slide, a force in the opposite direction acts on the contact surface to resist. The static friction coefficient (FC) can refer to the static friction coefficient of not only a sheet specimen using the biodegradable polyester resin, but also a biodegradable polyester film or polyester molded product.

[0070] The static friction coefficient (FC) decreases as the adhesive properties of the biodegradable polyester resin decrease, and increases as the adhesive properties of the biodegradable polyester resin increase.

[0071] The static friction coefficient (FC) may be less than 10, for example, 3 or more and less than 10, for example, 3 or more and 9.8 or less, for example, 4 or more and 9.8 or less, for example, 4 or more and 9.5 or less, for example, 5 or more and 9.5 or less, for example, 6 or more and 9.5 or less, for example, 7 or more and 9.5 or less, for example, more than 8.5 and 9.5 or less, for example, 8.6 or more and 9.5 or less, for example, 8.5 or more and 9.4 or less, for example, 8.5 or more and 9.3 or less, for example, 8.6 or more and 9.3 or less, for example, 8.8 or more and 9.3 or less, or for example, 8.9 or more and 9.3 or less.

[0072] When the static friction coefficient (FC) satisfies the above range, the adhesive properties of the biodegradable polyester resin can be reduced, and the inflation moldability can be further improved.

[0073] Meanwhile, the biodegradable polyester resin may have a loss tangent (tan δ) greater than 1, as expressed by the following formula 3:

[0074] [Formula 3] JPEG0007783842000005.jpg851 In the above formula 3, G' is the storage modulus of the biodegradable polyester sheet produced from the biodegradable polyester resin at 240°C and a vibration frequency of 5 rad / s in dynamic viscoelasticity measurement; G'' is the loss modulus of the biodegradable polyester sheet produced from the biodegradable polyester resin at 240°C and a vibration frequency of 5 rad / s in dynamic viscoelasticity measurement.

[0075] The storage modulus and loss modulus of the polyester sheet may refer to the storage modulus and loss modulus of the polyester resin.

[0076] The loss tangent (tanδ) of the biodegradable polyester resin can be calculated using Equation 3 after forming the biodegradable polyester resin into a sheet using a dynamic viscoelasticity tester, RDS (Rheometrics Dynamic Spectrometer, TA Instrument, Discovery HR 30), measuring the storage modulus and loss modulus.

[0077] That is, the loss tangent (tanδ) of the biodegradable polyester resin is the ratio of the loss modulus (G″) of the biodegradable polyester resin to the storage modulus (G′) of the biodegradable polyester resin, and when the value of the loss modulus (G″) of the biodegradable polyester resin is greater than the value of the storage modulus (G′) of the biodegradable polyester resin, that is, the loss tangent (tanδ) of the biodegradable polyester resin expressed by the above formula 3 can exceed 1.

[0078] Specifically, the loss tangent (tan δ) of the biodegradable polyester resin may be, for example, 1.05 to 1.30, for example, 1.05 to 1.25, for example, 1.08 to 1.25, for example, 1.10 to 1.25, for example, 1.10 to 1.20, or for example, 1.15 to 1.19.

[0079] When the loss tangent (tan δ) of the biodegradable polyester resin satisfies the above range, the productivity, processability, and moldability of the biodegradable polyester resin can be improved simultaneously. Furthermore, the biodegradable polyester resin can achieve excellent physical properties such as tensile strength, tear strength, and a low coefficient of friction, and can provide a biodegradable polyester sheet or film with excellent biodegradability and hydrodegradability.

[0080] The storage modulus (G') of the biodegradable polyester resin can be measured after forming a sheet using the biodegradable polyester resin. In this case, it is, for example, 200,000 dyne / cm 2 ~400,000 dyne / cm 2 , e.g., 200,000 dyne / cm 2 ~380,000 dyne / cm 2 , e.g., 200,000 dyne / cm 2 ~360,000 dyne / cm 2 , e.g., 200,000 dyne / cm 2 ~350,000 dyne / cm 2 , or for example 200,000 dyne / cm 2 ~330,000 dyne / cm 2 It could be.

[0081] The loss modulus (G'') of the biodegradable polyester resin can be measured after forming the biodegradable polyester resin into a sheet. In this case, it is, for example, 220,000 dyne / cm 2 ~450,000 dyne / cm 2 , e.g., 220,000 dyne / cm 2 ~400,000 dyne / cm 2 , e.g., 230,000 dyne / cm 2 ~390,000 dyne / cm 2 , e.g., 240,000 dyne / cm 2 ~380,000 dyne / cm 2 , or for example 240,000 dyne / cm 2 ~370,000 dyne / cm 2 It could be.

[0082] When the storage modulus (G') and loss tangent (tanδ) of the biodegradable polyester resin satisfy the above ranges, the processability and physical properties can be improved, and the biodegradability and hydrolysis reduction rate of the biodegradable polyester sheet or film produced using the same can be improved.

[0083] Meanwhile, the biodegradable polyester sheet manufactured using the biodegradable polyester resin may have a tensile strength of 30 MPa or more.

[0084] The tensile strength can be measured by preparing a biodegradable polyester sheet specimen using the biodegradable polyester resin according to ASTM D638V standard, and then testing it at a tensile speed of 100 mm / min using an Instron universal testing machine (UTM, 4206-001) using a program installed in the machine.

[0085] The tensile strength may be, for example, 30Mpa to 50Mpa, for example, 30Mpa to 49Mpa, for example, 30Mpa to 48Mpa, for example, 32Mpa to 48Mpa, for example, 33Mpa to 48Mpa, for example, 34Mpa to 48Mpa, for example, 35Mpa to 49Mpa, for example, 35Mpa to 48Mpa, for example, 35Mpa to 47Mpa, or for example, 35Mpa to 46Mpa.

[0086] When the tensile strength satisfies the above range, the productivity, processability and moldability of the biodegradable polyester resin can be improved at the same time.

[0087] Meanwhile, the biodegradable polyester sheet manufactured using the biodegradable polyester resin may have an elongation of 200% or more.

[0088] The elongation may be, for example, 200% to 900%, for example, 200% to 800%, for example, 200% to 600%, for example, 200% to 500%, or for example, 250% to 400%.

[0089] On the other hand, the biodegradable polyester film containing the biodegradable polyester resin has the following properties: ISO 14855 The biodegradability measured by the amount of carbon dioxide generated based on the above formula may be 90% or more, and the reduction rate of water decomposition expressed by the following formula 4 may be 85% or more.

[0090] [Formula 4] JPEG0007783842000006.jpg13128In the above formula 4, Mn A and Mn B is the number average molecular weight of the biodegradable polyester sheet, which is produced from the biodegradable polyester resin, measured by gel permeation chromatography (GPC) after immersing the biodegradable polyester sheet in water and subjecting it to accelerated water decomposition in a conventional (hot air) oven at 80°C; Mn A is the initial number average molecular weight of the biodegradable polyester sheet, Mn B is the number average molecular weight of the biodegradable polyester sheet 3 months after accelerated hydrolysis.

[0091] The above-mentioned acceleration of hydrolysis means that the biodegradable polyester sheet is immersed in water and hydrolyzed at a temperature of 80°C.

[0092] The rate of decrease in hydrolysis degree can be calculated by measuring the initial number average molecular weight of the biodegradable polyester sheet and the number average molecular weight after 3 months of accelerated hydrolysis. That is, the rate of decrease in hydrolysis degree of the biodegradable polyester sheet is expressed as a percentage of the difference between the initial number average molecular weight and the number average molecular weight after 3 months of accelerated hydrolysis, relative to the initial number average molecular weight of the biodegradable polyester sheet represented by Equation 4 using gel permeation chromatography (GPC).

[0093] The water decomposition reduction rate of the biodegradable polyester sheet may be 85% or more, 86% or more, 87% or more, 88% or more, 89% or more, 90% or more, or 91% or more.

[0094] When the water decomposition rate of the biodegradable polyester sheet satisfies the above range, it may be biodegradable under seawater or humid conditions.

[0095] The initial number average molecular weight (Mn A ) can be 40,000 g / mol or more, 40,000 g / mol to 80,000 g / mol, 40,000 g / mol to 70,000 g / mol, 40,000 g / mol to 65,000 g / mol, or 50,000 g / mol to 60,000 g / mol.

[0096] The biodegradable polyester sheet was immersed in water at 80°C, and the number average molecular weight (Mn B The number average molecular weight (Mn) of the biodegradable polyester sheet may be 5000 g / mol or less, 4900 g / mol or less, 4800 g / mol or less, 4600 g / mol or less, or 4500 g / mol or less. After immersing the biodegradable polyester sheet in water at 80°C, the number average molecular weight (Mn) of the biodegradable polyester sheet after 3 months of accelerated hydrolysis treatment may be measured. B ) can be, for example, 3000 g / mol to 5000 g / mol, 3500 g / mol to 5000 g / mol, 3800 g / mol to 4800 g / mol, or 4000 g / mol to 4600 g / mol.

[0097] The initial number average molecular weight (Mn A ) and the number average molecular weight (Mn B ) respectively satisfy the above ranges, the water decomposition rate reduction rate can be satisfied within the above ranges, and biodegradation may be possible under seawater decomposition or humidified conditions.

[0098] The structure and physical properties of the biodegradable polyester resin according to an embodiment of the present invention can be efficiently achieved by utilizing a method for producing the biodegradable polyester resin according to an embodiment of the present invention.

[0099] The method for producing the biodegradable polyester resin will now be described in detail.

[0100] [Method for producing biodegradable polyester resin] In another embodiment of the present invention, there is provided a biodegradable polyester resin comprising: a first step of mixing and pretreating a diol component and an aromatic dicarboxylic acid to obtain a slurry; a second step of esterifying a mixture containing the slurry and an aliphatic dicarboxylic acid, or a mixture containing an aliphatic dicarboxylic acid and a reaction product obtained by esterifying the slurry, at least once to obtain a prepolymer; and a third step of polycondensing the prepolymer, the biodegradable polyester resin comprising a first repeating unit containing a first diol residue and a residue of an aromatic dicarboxylic acid, and a second repeating unit containing a second diol residue and a residue of an aliphatic dicarboxylic acid, The first diol residue and the second diol residue each contain a residue of 1,4-butanediol, 1,2-ethanediol, 1,3-propanediol, or a derivative thereof; the aromatic dicarboxylic acid residue contains a residue of terephthalic acid, dimethyl terephthalate, or a derivative thereof; and the aliphatic dicarboxylic acid residue contains a residue of adipic acid, succinic acid, sebacic acid, or a derivative thereof; the ratio (X / Y) of the number of the first repeating units (X) to the number of the second repeating units (Y) is 0.6 to 1.8; and the softness index (SI) represented by the formula 1 is 90 to 130.

[0101] According to an embodiment of the present invention, the method for producing the biodegradable polyester resin involves mixing a diol component and an aromatic dicarboxylic acid, pretreating the resulting slurry, subjecting the slurry to an esterification reaction to obtain a prepolymer, and then subjecting the prepolymer to a condensation polymerization reaction, thereby efficiently achieving the desired structure and physical properties of the biodegradable polyester resin.

[0102] Referring to FIG. 1, the method for producing the biodegradable polyester resin (S100) includes a first step (S110) of mixing and pre-treating a diol component and an aromatic dicarboxylic acid to obtain a slurry.

[0103] That is, the first step is a pretreatment step prior to the esterification reaction, in which a diol component and an aromatic dicarboxylic acid are mixed and slurried.

[0104] By mixing the diol component and the aromatic dicarboxylic acid and pretreating them to form a slurry, the diol component and the aromatic dicarboxylic acid can be reacted uniformly, and the esterification reaction can be accelerated, thereby increasing the reaction efficiency.

[0105] In particular, when the aromatic dicarboxylic acid is completely crystalline and in the form of a powder, such as terephthalic acid, its solubility in the diol is very low, making it difficult to achieve a homogeneous reaction. Therefore, the pretreatment process of forming a slurry plays a very important role in providing biodegradable polyester resins, sheets, and films with excellent physical properties according to embodiments of the present invention and in enhancing reaction efficiency.

[0106] Furthermore, if the diol component and aromatic dicarboxylic acid are mixed together without performing a pretreatment step, and the diol component, aromatic dicarboxylic acid, and aliphatic dicarboxylic acid are all mixed together and an esterification reaction is carried out, the reaction of the diol component and the aliphatic dicarboxylic acid may occur first, which may make it difficult to realize a biodegradable polyester resin that satisfies the ratio of the number of first repeating units to the number of second repeating units targeted by the present invention.

[0107] According to an embodiment of the present invention, when the aromatic dicarboxylic acid is terephthalic acid, terephthalic acid has complete crystallinity and is a white crystal that sublimes at around 300°C under atmospheric pressure without a melting point. Since terephthalic acid has very low solubility in the diol, a homogeneous reaction is difficult to occur. Therefore, if a pretreatment process is performed before the esterification reaction, the surface area for reaction with the diol within the solid matrix of terephthalic acid can be increased, thereby inducing a homogeneous reaction.

[0108] In addition, according to an embodiment of the present invention, when the aromatic dicarboxylic acid is dimethyl terephthalate, the dimethyl terephthalate can be melted at about 142°C to 170°C through the pretreatment process and reacted with the diol, thereby making the esterification reaction faster and more efficient.

[0109] Meanwhile, in the first pretreatment step, the structure and properties of the biodegradable polyester resin may vary depending on the particle size, particle size distribution, pretreatment reaction conditions, etc. of the aromatic dicarboxylic acid.

[0110] For example, the aromatic dicarboxylic acid may include terephthalic acid, and the terephthalic acid may have an average particle size (D50) of 10 μm to 400 μm in particle size distribution (PSD) measured by a particle size analyzer Microtrac® S3500 (Microtrac Inc.), and the standard deviation for the average particle size (D50) may be 100 or less. The standard deviation refers to the square root of the variance.

[0111] The average particle size (D50) of the terephthalic acid may be, for example, 20 μm to 200 μm, for example, 30 μm to 180 μm, for example, 50 μm to 150 μm, or for example, 50 μm to 100 μm. If the average particle size (D50) of the terephthalic acid satisfies the above range, it may be more advantageous in terms of improving the solubility in diol and the reaction rate.

[0112] If the average particle size (D50) of the terephthalic acid is less than 10 μm, the average particle size is too small and may change from single primary particles to aggregated secondary particles, which is undesirable. If the average particle size (D50) of the terephthalic acid is more than 400 μm, the average particle size is too large, which reduces the solubility in diol, slows the reaction rate, and makes it difficult to achieve a homogenized reaction.

[0113] Furthermore, the standard deviation of the average particle size (D50) of the terephthalic acid may be 100 or less, for example, 5 to 90, for example, 5 to 80, for example, 5 to 70, for example, 10 to 70, for example, 15 to 70, or for example, 20 to 70. When the standard deviation of the average particle size (D50) of the terephthalic acid satisfies the above range, it may be more advantageous in terms of improving the solubility in diol and the reaction rate.

[0114] Furthermore, if the average particle size (D50) and standard deviation of the terephthalic acid satisfy the above ranges, the reaction time can be shortened by 1.5 times or more, which is preferable in terms of reaction efficiency.

[0115] When the aromatic dicarboxylic acid is dimethyl terephthalate, it may be used in a molten state or may have an average particle size (D50) and standard deviation in a range similar to those of the terephthalic acid when measured in a particulate state.

[0116] In the first pretreatment step, the diol and the aromatic dicarboxylic acid may be mixed and charged into a slurry mixer (tank).

[0117] According to an embodiment of the present invention, in the first stage pretreatment process, the stirring force until the slurry is formed is very important, so the number and shape of the stirring blades of the stirrer and the conditions of the slurry formation process are extremely important.

[0118] The slurry agitator may be more advantageous in achieving efficient agitation, for example, if the lowest part is an anchor type, the height to the agitator is 20 mm or more, and the agitator is equipped with two or more rotor blades.

[0119] For example, the height of the slurry agitator may be 20 mm or more, i.e., the reactor and the bottom of the agitator may be almost flush with each other, in which case a slurry without precipitation can be obtained. If the shape and number of rotor blades of the agitator do not satisfy the above conditions, the aromatic dicarboxylic acid may settle to the bottom when the diol and aromatic dicarboxylic acid are initially mixed, which may result in phase separation.

[0120] The first pretreatment step may include mixing a diol component and an aromatic dicarboxylic acid and stirring the mixture at 60° C. to 100° C. and 50 rpm to 200 rpm for 10 minutes or more, for example, 10 to 200 minutes. If the pretreatment step satisfies the above temperature, speed, and stirring time, a uniform slurry can be obtained without phase separation, which is advantageous in terms of reaction efficiency and allows the desired physical properties of the biodegradable polyester resin to be obtained efficiently in the present invention.

[0121] The diol component may include 1,4-butanediol, 1,2-ethanediol, 1,3-propanediol, or derivatives thereof.

[0122] Specifically, the diol component may contain 95 mol% or more, 98 mol% or more, 99 mol% or more, or 100 mol% of 1,4-butanediol, 1,2-ethanediol, 1,3-propanediol, or a derivative thereof, based on the total number of moles of the diol component. By including 1,4-butanediol, 1,2-ethanediol, 1,3-propanediol, or a derivative thereof in the diol component within the above ranges, the biodegradability, hydrolysis, and physical properties of the biodegradable polyester resin or a biodegradable polyester sheet, film, or molded product obtained using the same can be improved.

[0123] The diol component may be added at once or in portions, for example, the diol component may be added separately when mixed with the aromatic dicarboxylic acid and when mixed with the aliphatic dicarboxylic acid.

[0124] The aromatic dicarboxylic acid component may include one or more selected from the group consisting of terephthalic acid, dimethyl terephthalate, and derivatives thereof. Specifically, the aromatic dicarboxylic acid component may be terephthalic acid or dimethyl terephthalate.

[0125] Furthermore, the aromatic dicarboxylic acid component may be used in an amount of 40 mol% to 60 mol%, 42 mol% to 58 mol%, 44 mol% to 58 mol%, 44 mol% to 57 mol%, 44 mol% to 55 mol%, 44 mol% to 53 mol%, 46 mol% to 52 mol%, 48 mol% to 52 mol%, or 50 mol% to 52 mol%, based on the total number of moles of the dicarboxylic acid components.

[0126] Controlling the molar ratio of the aromatic dicarboxylic acid within the above range is more advantageous for achieving the effects of the present invention, and the physical properties, biodegradability, and hydrolysis reduction rate of the biodegradable polyester sheet, film, or molded article produced using the same can be improved.

[0127] Referring again to FIG. 1, the method for producing a biodegradable polyester resin (S100) includes a second step (S120) of esterifying a mixture containing the slurry and an aliphatic dicarboxylic acid, or a mixture containing an aliphatic dicarboxylic acid and a reaction product obtained by esterifying the slurry, at least once to obtain a prepolymer.

[0128] The reaction time of the second stage esterification reaction can be shortened by using the slurry obtained in the first stage, for example, by 1.5 times or more. The second stage esterification reaction can be carried out at least once or more times.

[0129] According to one embodiment of the present invention, the esterification reaction may be carried out once by adding an aliphatic dicarboxylic acid, or a diol and an aliphatic dicarboxylic acid, to the slurry.

[0130] The esterification reaction may be carried out at 250°C or lower for 0.5 to 5 hours. Specifically, the esterification reaction may be carried out at 180°C to 250°C, 185°C to 240°C, or 200°C to 240°C under atmospheric pressure or reduced pressure until the by-product water reaches a theoretical 95%. For example, the esterification reaction may be carried out for 0.5 to 4.5 hours, 0.5 to 3.5 hours, or 1 to 3 hours, but is not limited thereto.

[0131] The number average molecular weight of the prepolymer may be 500 g / mol to 10,000 g / mol. For example, the number average molecular weight of the prepolymer may be 500 g / mol to 8,500 g / mol, 500 g / mol to 8,000 g / mol, 500 g / mol to 7,000 g / mol, 500 g / mol to 5,000 g / mol, or 500 g / mol to 2,000 g / mol. When the number average molecular weight of the prepolymer satisfies the above range, the molecular weight of the polymer can be efficiently increased in the condensation polymerization reaction.

[0132] According to another embodiment of the present invention, the esterification reaction may be performed two or more times, including a step of subjecting the slurry to a first esterification reaction and a step of subjecting the reaction product of the first esterification reaction to a second esterification reaction by adding an aliphatic dicarboxylic acid or a diol and an aliphatic dicarboxylic acid to the reaction product.

[0133] Carrying out the esterification reaction two or more times has the advantage that the reaction stability and reaction uniformity can be improved compared to when the esterification reaction is carried out once, and the ratio between the number of first repeating units and the number of second repeating units can be adjusted as desired, thereby efficiently achieving the effects of the embodiments of the present invention.

[0134] The primary esterification reaction and the secondary esterification reaction may each be carried out at 250°C or less for 0.5 to 5 hours. Specifically, the primary esterification reaction and the secondary esterification reaction may each be carried out at 180°C to 250°C, 185°C to 240°C, or 200°C to 240°C, respectively, at atmospheric pressure until the by-product water reaches a theoretical 95%. For example, the primary esterification reaction and the secondary esterification reaction may each be carried out for 0.5 to 4.5 hours, 0.5 to 3.5 hours, or 1 to 3 hours, respectively, but are not limited thereto.

[0135] The number average molecular weight of the prepolymer may be 500 g / mol to 10,000 g / mol. For example, the number average molecular weight of the prepolymer may be 500 g / mol to 8,500 g / mol, 500 g / mol to 7,000 g / mol, 1,000 g / mol to 6,000 g / mol, or 2,500 g / mol to 5,500 g / mol. When the number average molecular weight of the prepolymer satisfies the above range, the molecular weight of the polymer can be efficiently increased in the polycondensation reaction, thereby further improving strength properties.

[0136] The number average molecular weight can be measured using gel permeation chromatography (GPC). Specifically, data obtained by gel permeation chromatography includes various items such as Mn, Mw, and Mp, and the molecular weight can be measured based on the number average molecular weight (Mn).

[0137] The aliphatic dicarboxylic acid component may include adipic acid, succinic acid, sebacic acid, or derivatives thereof. Specifically, the aliphatic dicarboxylic acid component may include adipic acid or succinic acid.

[0138] Furthermore, the aliphatic dicarboxylic acid component may be used in an amount of 40 mol% to 60 mol%, 42 mol% to 58 mol%, 42 mol% to 56 mol%, 43 mol% to 56 mol%, 45 mol% to 56 mol%, 47 mol% to 56 mol%, 48 mol% to 54 mol%, 48 mol% to 52 mol%, or 48 mol% to 50 mol%, based on the total number of moles of the dicarboxylic acid component.

[0139] By controlling the content of the aliphatic dicarboxylic acid within the above range, the productivity, processability, and moldability of the biodegradable polyester resin can be simultaneously improved, and the physical properties, biodegradability, and hydrodegradability of the biodegradable polyester sheet, film, or molded product produced using the same can be improved.

[0140] In particular, the aliphatic dicarboxylic acid component is composed of a linear chain, which can affect the adhesive properties of the biodegradable polyester resin.

[0141] Specifically, if the content of the aliphatic dicarboxylic acid component is too high, the adhesive properties of the biodegradable polyester resin may increase, resulting in a decrease in processability.

[0142] In the second stage, when the esterification reaction is carried out, for example, when the first and second esterification reactions are carried out, nanocellulose may be further added at the first esterification reaction time, the second esterification reaction time, or both.

[0143] Specifically, when the esterification reaction is carried out once, nanocellulose can be further added at the time of the esterification reaction, for example, at the time of adding the aliphatic dicarboxylic acid, or the diol and the aliphatic dicarboxylic acid.

[0144] Furthermore, when the esterification reaction is performed two or more times, nanocellulose can be added at the time of the first esterification reaction, the time of the second esterification reaction, or both. For example, the nanocellulose can be added at the time of the second esterification reaction, i.e., when the aliphatic dicarboxylic acid or the diol and the aliphatic dicarboxylic acid are added, or at the beginning of the esterification reaction. This can be effective for dispersing nanocellulose. In particular, the addition of nanocellulose is advantageous in terms of the physical properties, such as strength, and thermal properties of the biodegradable polyester resin, and can also improve the physical properties, such as strength, and biodegradability of biodegradable polyester sheets, films, or molded products.

[0145] The nanocellulose may be one or more selected from the group consisting of cellulose nanocrystals, cellulose nanofibers, microfibrillated cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, cellulose acetate, methyl cellulose, ethyl cellulose, propyl cellulose, butyl cellulose, pentyl cellulose, hexyl cellulose, and cyclohexyl cellulose.

[0146] The diameter of the nanocellulose can be 1 nm to 200 nm. For example, the diameter of the nanocellulose can be 1 nm to 150 nm, 1 nm to 120 nm, 1 nm to 100 nm, 1 nm to 95 nm, 5 nm to 90 nm, 10 nm to 80 nm, 1 nm to 50 nm, 5 nm to 45 nm, 10 nm to 60 nm, 1 nm to 10 nm, 10 nm to 30 nm, or 15 nm to 50 nm.

[0147] The length of the nanocellulose may be 5 nm to 10 μm. For example, the length of the nanocellulose may be 5 nm to 1 μm, 10 nm to 150 nm, 20 nm to 300 nm, 200 nm to 500 nm, 100 nm to 10 μm, 500 nm to 5 μm, 300 nm to 1 μm, or 1 μm to 10 μm.

[0148] When the diameter and length of the nanocellulose satisfy the above ranges, the biodegradability and physical properties of the biodegradable polyester resin or the biodegradable polyester sheet, film, and molded product obtained using the same can be further improved.

[0149] Furthermore, the nanocellulose may be pretreated by a bead mill or ultrasonic pretreatment. Specifically, the nanocellulose may be water-dispersed nanocellulose that has been pretreated by a bead mill or ultrasonic pretreatment.

[0150] First, the bead mill pretreatment can be performed using a wet milling device, either a vertical mill or a horizontal mill. A horizontal mill is preferred because it can fill a larger amount of beads in the chamber, reduces wear on the machine and beads, and is easier to maintain, but is not limited thereto.

[0151] The bead mill pretreatment may be carried out using one or more beads selected from the group consisting of zirconium, zircon, zirconia, quartz, and aluminum oxide.

[0152] Specifically, the bead mill pretreatment can be performed using beads with a diameter of 0.3 mm to 1 mm. For example, the diameter of the beads can be 0.3 mm to 0.9 mm, 0.4 mm to 0.8 mm, 0.45 mm to 0.7 mm, or 0.45 mm to 0.6 mm. By ensuring that the bead diameter falls within this range, the dispersibility of the nanocellulose can be further improved. If the bead diameter exceeds this range, the average particle size and particle size deviation of the nanocellulose may increase, resulting in poor dispersibility.

[0153] In addition, the bead mill pretreatment preferably uses beads with a higher specific gravity than nanocellulose, as this allows for sufficient energy transfer. For example, the beads may be one or more selected from the group consisting of zirconium, zircon, zirconia, quartz, and aluminum oxide, which have a higher specific gravity than the water-dispersed nanocellulose. Zirconium beads with a specific gravity at least four times higher than that of the water-dispersed nanocellulose are preferred, but are not limited thereto.

[0154] The ultrasonic pretreatment is a method of physically crushing or pulverizing nanoparticles by the vibrations generated by emitting 20 kHz ultrasonic waves into a solution.

[0155] The ultrasonic pretreatment may be performed for less than 30 minutes at an energy dose of 30,000 J or less. For example, the ultrasonic pretreatment may be performed for 25 minutes or less, 20 minutes or less, or 18 minutes or less at an energy dose of 25,000 J or less or 22,000 J or less. By ensuring that the energy dose and duration are within the above ranges, the effect of the ultrasonic pretreatment, i.e., improvement in dispersibility, can be maximized. If the energy dose exceeds the above range, the nanoparticles may re-agglomerate, resulting in poor dispersibility.

[0156] The nanocellulose according to the embodiment may be bead mill pretreated or ultrasonic pretreated. Alternatively, the nanocellulose according to the embodiment may be both bead mill pretreated and ultrasonic pretreated. In this case, ultrasonic pretreatment after bead mill pretreatment is preferable in terms of preventing re-agglomeration and improving dispersibility.

[0157] According to an embodiment, the polydispersity index (PDI) of the biodegradable polyester resin is less than 2.0. For example, the polydispersity index of the biodegradable polyester resin can be less than 2.0, 1.95 or less, or 1.9 or less.

[0158] By adjusting the polydispersity index within this range, heat resistance can be further improved. Specifically, if the polydispersity index exceeds this range, the heat resistance of the biodegradable polyester resin may be reduced. Therefore, in the process of producing a molded product such as a film using the biodegradable polyester resin, the rate of polymer degradation may increase, resulting in reduced processability and productivity. The polydispersity index can be calculated according to the following formula A:

[0159] [Formula A] JPEG0007783842000007.jpg850In the formula A, Mw is the weight average molecular weight (g / mol) of the resin, and Mn is the number average molecular weight (g / mol) of the resin.

[0160] The content of the nanocellulose is, for example, 3000 ppm or less, 2500 ppm or less, 2000 ppm or less, 1800 ppm or less, 1500 ppm, 1000 ppm or less, 900 ppm or less, 800 ppm or less, 700 ppm or less, 600 ppm or less, 500 ppm or less, or 400 ppm or less, based on the total weight of the diol, aromatic dicarboxylic acid, and aliphatic dicarboxylic acid, and may be, for example, 100 ppm or more, 150 ppm or more, 200 ppm or more, 250 ppm or more, 300 ppm or more, 400 ppm or more, 500 ppm or more, 600 ppm or more, 800 ppm or more, or 1000 ppm or more. By satisfying the above range, physical properties such as biodegradability and strength can be further improved.

[0161] Before the second stage esterification reaction, a titanium-based catalyst or a germanium-based catalyst may be further added to the slurry.

[0162] Specifically, when the esterification reaction is carried out once, a titanium-based catalyst or a germanium-based catalyst may be further added to the slurry.

[0163] In addition, when the esterification reaction is carried out two or more times, a titanium-based catalyst or a germanium-based catalyst may be further added to the slurry, the reaction product obtained by subjecting the slurry to a first esterification reaction, or both, before each esterification reaction.

[0164] Specifically, the biodegradable polyester resin may contain one or more titanium-based catalysts selected from the group consisting of titanium isopropoxide, antimony trioxide, dibutyltin oxide, tetrapropyl titanate, tetrabutyl titanate, tetraisopropyl titanate, antimony acetate, calcium acetate, and magnesium acetate, or one or more germanium-based catalysts selected from the group consisting of germanium oxide, germanium methoxide, germanium ethoxide, tetramethylgermanium, tetraethylgermanium, and germanium sulfide.

[0165] The catalyst content may be 100 ppm to 1000 ppm based on the total weight of the diol, aromatic dicarboxylic acid, and aliphatic dicarboxylic acid. For example, the titanium-based catalyst or germanium-based catalyst may be 100 ppm to 800 ppm, 150 ppm to 700 ppm, 200 ppm to 600 ppm, or 250 ppm to 550 ppm. By ensuring that the catalyst content falls within the above range, processability can be further improved.

[0166] A phosphorus-based stabilizer may be added during the second stage esterification reaction, at the end of the esterification reaction, or both.

[0167] Specifically, when the esterification reaction is carried out once, the phosphorus-based stabilizer may be further added during the esterification reaction, at the end of the esterification reaction, or both.

[0168] In addition, when the esterification reaction is carried out two or more times, a phosphorus-based stabilizer may be further added during the first esterification reaction, the second esterification reaction, or both, or at the end of the first esterification reaction or the second esterification reaction.

[0169] Specifically, the biodegradable polyester resin may further contain one or more phosphorus-based stabilizers selected from the group consisting of an amine-based high-temperature heat stabilizer such as tetraethylenepentamine, phosphoric acid, phosphorous acid, polyphosphoric acid, trimethyl phosphate, triethyl phosphate, triethyl phosphonoacetate, trimethyl phosphine, and triphenyl phosphine.

[0170] The content of the phosphorus-based stabilizer may be 3000 ppm or less based on the total weight of the diol, aromatic dicarboxylic acid, and aliphatic dicarboxylic acid. Specifically, the content of the phosphorus-based stabilizer may be, for example, 10 ppm to 3000 ppm, 20 ppm to 2000 ppm, 20 ppm to 1500 ppm, or 20 ppm to 1000 ppm based on the total weight of the diol, aromatic dicarboxylic acid, and aliphatic dicarboxylic acid. When the content of the phosphorus-based stabilizer satisfies the above range, degradation of the polymer due to high temperatures during the reaction process can be controlled, and the number of polymer end groups can be reduced, resulting in improved color.

[0171] After the second-stage esterification reaction is completed, one or more additives selected from the group consisting of silica, potassium, or magnesium, and color correction agents such as cobalt acetate may be added. That is, after the esterification reaction is completed, the additives and / or color correction agents may be added for stabilization, and then the polycondensation reaction may be carried out.

[0172] Referring again to FIG. 1, the method for producing the biodegradable polyester resin (S100) includes a third step (S130) of subjecting the prepolymer to a polycondensation reaction.

[0173] The polycondensation reaction may be carried out at 180°C to 280°C and 1.0 torr or less for 1 to 5 hours. For example, the polycondensation reaction may be carried out at 190°C to 270°C, 210°C to 260°C, or 230°C to 255°C, at 0.9 torr or less, 0.7 torr or less, 0.2 torr to 1.0 torr, 0.3 torr to 0.9 torr, or 0.4 torr to 0.6 torr, for 1.5 to 5 hours, 2 to 5 hours, or 2.5 to 4.5 hours.

[0174] In addition, a titanium-based catalyst or a germanium-based catalyst may be added to the prepolymer before the polycondensation reaction.In addition, in addition, in addition to the prepolymer before the polycondensation reaction, one or more selected from the group consisting of additives such as silica, potassium, or magnesium; amine-based stabilizers such as trimethyl phosphate, triphenyl phosphate, trimethylphosphine, phosphoric acid, phosphorous acid, or tetraethylenepentamine; and polymerization catalysts such as antimony trioxide, antimony trioxide, or tetrabutyl titanate may be added to the prepolymer before the polycondensation reaction.

[0175] The number average molecular weight of the polymer may be 40,000 g / mol or more. For example, the number average molecular weight of the polymer may be 43,000 g / mol or more, 45,000 g / mol or more, or 50,000 g / mol to 70,000 g / mol. When the number average molecular weight of the polymer satisfies the above range, physical properties and processability can be further improved.

[0176] Pellets may then be made from the polymer. Specifically, the polymer may be cooled to 15° C. or less, 10° C. or less, or 6° C. or less, and then the cooled polymer may be cut into pellets.

[0177] The cutting step can be performed using any pellet cutter commonly used in the art, and the pellets can have various shapes. The pellet cutting method can include an underwater cutting method or a strand cutting method.

[0178] [Biodegradable polyester sheet] Meanwhile, in one embodiment of the present invention, a biodegradable polyester sheet can be obtained using the biodegradable polyester resin.

[0179] For example, the biodegradable polyester sheet can be produced using the biodegradable polyester resin or polyester resin pellets.

[0180] Specifically, the prepared polyester resin is placed in, for example, a stainless steel (SUS) frame and held in a hot press at approximately 150°C to 300°C under a pressure of 5 MPa to 20 MPa for 1 to 30 minutes, then removed and immediately cooled in water at 18°C ​​to 25°C for approximately 10 seconds to 5 minutes to produce a biodegradable polyester sheet.

[0181] [Biodegradable polyester film] In one embodiment, the present invention can provide a biodegradable polyester film comprising a biodegradable polyester resin, the biodegradable polyester resin comprising a first repeating unit including a first diol residue and a residue of an aromatic dicarboxylic acid, and a second repeating unit including a second diol residue and a residue of an aliphatic dicarboxylic acid, wherein the first diol residue and the second diol residue each include a residue of 1,4-butanediol or a derivative thereof, the aromatic dicarboxylic acid residue includes a residue of terephthalic acid, dimethyl terephthalate, or a derivative thereof, and the aliphatic dicarboxylic acid residue includes a residue of adipic acid, succinic acid, sebacic acid, or a derivative thereof, wherein the ratio (X / Y) of the number of the first repeating units (X) to the number of the second repeating units (Y) is 0.6 to 1.8, and the softness index (SI) represented by the above formula 1 is 90 to 130.

[0182] The thickness of the biodegradable polyester film may be 5 μm to 200 μm, for example, 5 μm to 180 μm, 5 μm to 160 μm, 10 μm to 150 μm, 15 μm to 130 μm, 20 μm to 100 μm, 25 μm to 80 μm, or 25 μm to 60 μm.

[0183] The physical properties of the biodegradable polyester film, such as tensile strength, elongation, static friction coefficient, and tear strength, can be satisfied within the ranges mentioned for the biodegradable polyester resin.

[0184] The biodegradable polyester film can be produced using the biodegradable polyester resin or polyester resin pellets.

[0185] Specifically, the method for producing the biodegradable polyester film includes a first step of mixing and pretreating a diol component and an aromatic dicarboxylic acid to obtain a slurry; a second step of esterifying a mixture containing the slurry and an aliphatic dicarboxylic acid, or a mixture containing an aliphatic dicarboxylic acid and a reaction product obtained by esterifying the slurry, at least once to obtain a prepolymer; a third step of subjecting the prepolymer to a polycondensation reaction to obtain a polymer; a fourth step of producing pellets from the polymer; and a fifth step of drying and melt-extruding the pellets.

[0186] Stages 1 to 4 are as described above.

[0187] In the fifth step, the drying may be carried out at 60°C to 100°C for 2 to 12 hours. Specifically, the drying may be carried out at 65°C to 95°C, 70°C to 90°C, or 75°C to 85°C for 3 to 12 hours, or 4 to 10 hours. When the pellet drying process conditions satisfy the above ranges, the quality of the produced biodegradable polyester film or molded article can be further improved.

[0188] After drying, the moisture content may be 500 ppm or less, 400 ppm or less, 350 ppm or less, or 300 ppm or less.

[0189] In the fifth step, the melt extrusion may be performed at a temperature of 270° C. or less. For example, the melt extrusion may be performed at a temperature of 265° C. or less, 260° C. or less, 255° C. or less, 150° C. to 270° C., 150° C. to 255° C., or 150° C. to 240° C. The melt extrusion may be performed by a blown film process.

[0190] According to an embodiment of the present invention, the biodegradable polyester film satisfies the specific structure and specific range of physical properties of the biodegradable polyester resin, and therefore, even if inorganic substances and other additives are added in amounts less than those normally used during the production of the biodegradable polyester film, excellent physical properties, biodegradability, and hydrolysis can be achieved.

[0191] For example, when producing the biodegradable polyester film, the inorganic substance may be added in an amount less than the amount typically added, for example, about 20% by weight, but still achieve the same or better physical properties.

[0192] Furthermore, when producing the biodegradable polyester film, the same or better physical properties, biodegradability, and hydrodegradability can be achieved without adding inorganic substances and other additives.

[0193] [Biodegradable polyester molded products] In one embodiment of the present invention, a biodegradable polyester molded article can be produced using the biodegradable polyester resin.

[0194] Specifically, the molded article is manufactured by molding the biodegradable polyester resin by a method known in the art, such as extrusion or injection molding, and the molded article may be, but is not limited to, an injection molded article, an extrusion molded article, a thin film molded article, or an inflation molded article.

[0195] For example, the molded article may be in the form of a film or sheet that can be used as agricultural mulching film, disposable gloves, disposable film, disposable envelopes, food packaging material, garbage bags, etc., or in the form of a fiber that can be used as a woven fabric, knitted fabric, nonwoven fabric, rope, etc., or in the form of a container that can be used as a food packaging container such as a lunch box, etc. The molded article may also be in the form of various shapes such as disposable straws, spoons, plates, forks, etc.

[0196] In particular, the molded article can be formed from the biodegradable polyester resin, which can improve not only strength and processability but also durability, particularly hydrolysis resistance, and therefore can exhibit excellent properties when applied to packaging materials for products stored and transported at low temperatures, automotive interior materials that require durability, or garbage bags, mulching films, and disposable products that require excellent durability and elongation.

[0197] (Example) The present invention will be described in more detail below with reference to the following examples. However, the following examples are for illustrative purposes only and the scope of the present invention is not limited to these examples.

[0198] Example 1 [Preparation of biodegradable polyester resin] <Step 1: Pretreatment to obtain slurry> 1,4-Butanediol (1,4-BDO) and terephthalic acid (TPA) were mixed in a molar ratio (1,4-BDO:TPA) of 1:1 and charged into a slurry tank (the bottom of the slurry tank was anchor type, the height to the agitator was 30 mm, and three rotor blades were installed) in a catalyst-free state. At this time, the D50 of the terephthalic acid (TPA) was 50 μm, and the standard deviation (SD) for the D50 of the terephthalic acid (TPA) was 40.

[0199] The mixture was then pre-treated by stirring at 70° C. and 150 rpm for 30 minutes to obtain a slurry without phase separation.

[0200] <Second step: obtaining prepolymer> The slurry obtained in the first step was introduced into a reactor via a supply line, and 200 ppm of a titanium-based catalyst, tetrabutyl titanate (Tyzor® TnBT, DuPont®), was added thereto. Then, a primary esterification reaction was carried out at 230°C and atmospheric pressure for about 2 hours until 95% of the by-product water was removed.

[0201] To the reaction product, 48 mol% of 1,4-butanediol (1,4-BDO) based on the total moles of the diol components, 48 ​​mol% of adipic acid (AA) based on the total moles of the dicarboxylic acid components, and tetrabutyl titanate (Tyzor TnBT, DuPont) as a titanium catalyst were added in an amount of 150 ppm based on the total weight of the diol, aromatic dicarboxylic acid, and aliphatic dicarboxylic acid. A secondary esterification reaction was carried out at 210°C and atmospheric pressure for approximately 2 hours until 95% of the by-product water was removed, producing a prepolymer with a number average molecular weight of 5000 g / mol.

[0202] <Step 3: Polycondensation reaction step> The prepolymer obtained in the second step was stabilized for approximately 10 minutes with 150 ppm of titanium-based catalyst tetrabutyl titanate (Dupont, Tyzor TnBT) and 500 ppm of triethyl phosphate stabilizer, based on the total weight of the diol, aromatic dicarboxylic acid, and aliphatic dicarboxylic acid. The reaction mixture was then heated to 250°C and subjected to a condensation polymerization reaction at 0.5 torr for 4 hours to produce a polymer with a number-average molecular weight of 50,000 g / mol. The polymer was then cooled to 5°C and cut using a pellet cutter to obtain biodegradable polyester resin pellets.

[0203] [Production of biodegradable polyester sheets] Two Teflon sheets were prepared, and a stainless steel (SUS) frame (12cm x 12cm) was placed on one of the Teflon sheets. Approximately 7g of the polyester resin pellets were placed in the frame (12cm x 12cm), covered with another Teflon sheet, and placed in the center of a hot press (Hot Press, With Lab, WL 1600SA) with a surface area of ​​approximately 25cm x 25cm. This was held at approximately 210°C under a pressure of approximately 10 MPa for approximately 3 minutes, then removed and immediately cooled in water at approximately 20°C for approximately 30 seconds to produce a biodegradable polyester sheet with an area of ​​approximately 10cm x 10cm and a thickness of approximately 300µm.

[0204] [Production of biodegradable polyester film] The biodegradable polyester resin pellets were dried at 80°C for 5 hours and then melt-extruded at 160°C using an inflation film extruder (Blown Film Extrusion Line, YOOJIN ENGINEERING) to produce a biodegradable polyester film with a thickness of 50 μm.

[0205] Example 2 Biodegradable polyester resins, biodegradable polyester sheets, and biodegradable polyester films were produced in the same manner as in Example 1, except that the amounts of 1,4-butanediol (1,4-BDO), terephthalic acid (TPA), and adipic acid (AA) were changed as shown in Table 1 below, a TPA with a standard deviation (SD) of 70 relative to the D50 of the TPA was used, and 2,000 ppm of cellulose nanocrystals (CNC) (particle size 190 nm) treated with a stirrer at 2,000 rpm for 15 minutes were added when adding 1,4-butanediol (1,4-BDO) and adipic acid (AA).

[0206] Example 3 As shown in Table 1 below, a biodegradable polyester resin, a biodegradable polyester sheet, and a biodegradable polyester film were produced in the same manner as in Example 1, except that dimethyl terephthalate (DMT) was used instead of terephthalic acid (TPA) and the content of each raw material was changed.

[0207] Example 4 <Step 1: Pretreatment to obtain slurry> 54 mol% of 1,4-butanediol (1,4-BDO) based on the total number of moles of diol components and 54 mol% of terephthalic acid (TPA) based on the total number of moles of dicarboxylic acid components were mixed and charged in a catalyst-free state into a slurry tank (the bottom of the slurry tank was anchor type, the height to the agitator was 15 mm, and it was equipped with two rotor blades). The D50 of the terephthalic acid (TPA) was 100 μm, and the standard deviation (SD) for the D50 of the terephthalic acid (TPA) was 50.

[0208] The mixture was then pre-treated by stirring at 80° C. and 180 rpm for 15 minutes to obtain a slurry without phase separation.

[0209] <Second step: obtaining prepolymer> The slurry obtained in the first step, 46 mol % of 1,4-butanediol (1,4-BDO) based on the total moles of the diol components, and 46 mol % of adipic acid (AA) based on the total moles of the dicarboxylic acid components were fed into a reactor via a feed line. To this was added tetrabutyl titanate (Tyzor TnBT, DuPont), a titanium catalyst, in an amount of 300 ppm based on the total weight of the diol, aromatic dicarboxylic acid, and aliphatic dicarboxylic acid. An esterification reaction was carried out at 230°C and atmospheric pressure for about 3 hours until 95% of the by-product water was removed, producing a prepolymer with a number average molecular weight of about 4000 g / mol.

[0210] <Step 3: Polycondensation reaction step> The prepolymer obtained in the second step was added with 150 ppm of titanium-based catalyst tetrabutyl titanate (Dupont, Tyzor TnBT) based on the total weight of the diol, aromatic dicarboxylic acid, and aliphatic dicarboxylic acid. The mixture was heated to 255°C and then subjected to a condensation polymerization reaction at 0.5 torr for 4 hours to produce a polymer with a number average molecular weight of approximately 55,000 g / mol. The polymer was then cooled to 5°C and cut using a pellet cutter to obtain biodegradable polyester resin pellets.

[0211] [Production of biodegradable polyester sheets and films] Biodegradable polyester sheets and films were produced in the same manner as in Example 1.

[0212] Example 5 As shown in Table 1 below, the amounts of 1,4-butanediol (1,4-BDO), terephthalic acid (TPA), and adipic acid (AA) were changed; in the second step of Example 4, 1,000 ppm of cellulose nanocrystals (CNC) (particle size 190 nm) treated with a stirrer at 2,000 rpm for 15 minutes were added; and in the third step, 200 ppm of titanium-based catalyst tetrabutyl titanate (Dupont, Tyzor TnBT) was added based on the total weight of the diol, aromatic dicarboxylic acid, and aliphatic dicarboxylic acid, and the mixture was heated to 240°C. The same procedures as in Example 4 were carried out, except that a biodegradable polyester resin, a biodegradable polyester sheet, and a biodegradable polyester film with a number average molecular weight of approximately 58,000 g / mol were produced.

[0213] Example 6 As shown in Table 1 below, the amounts of 1,4-butanediol (1,4-BDO), terephthalic acid (TPA), and adipic acid (AA) were changed, and the same method as in Example 1 was carried out, except that TPA with a standard deviation (SD) of 20 for D50 of the terephthalic acid (TPA) was used, to produce biodegradable polyester resins, biodegradable polyester sheets, and biodegradable polyester films.

[0214] Example 7 As shown in Table 1 below, biodegradable polyester resin, biodegradable polyester sheet, and biodegradable polyester film were produced in the same manner as in Example 6, except that 600 ppm of cellulose nanocrystals (CNC) (particle size 190 nm) treated with a stirrer at 2000 rpm for 15 minutes were added when 1,4-butanediol (1,4-BDO) and adipic acid (AA) were added.

[0215] (Comparative Example 1) As shown in Table 1 below, a biodegradable polyester resin, a biodegradable polyester sheet, and a biodegradable polyester film having a number average molecular weight of approximately 43,000 g / mol were produced in the same manner as in Example 4, except that the first step (pretreatment step) of Example 4 was not performed, the amounts of terephthalic acid (TPA) and adipic acid (AA) were changed, and TPAs ​​with different D50s and standard deviations (SD) were used.

[0216] (Comparative Example 2) As shown in Table 1 below, the same method as in Comparative Example 1 was used, except that the amounts of terephthalic acid (TPA) and adipic acid (AA) were changed and TPA with different D50 and standard deviation (SD) was used. A biodegradable polyester resin having a number average molecular weight of approximately 43,000 g / mol was prepared.

[0217] A biodegradable polyester sheet was produced in the same manner as in Example 1. The biodegradable polyester resin and calcium carbonate were mixed in a ratio of 6:4 and melt-extruded at 190°C using an inflation film extruder (Blown Film Extrusion Line, YOOJIN ENGINEERING) to produce a biodegradable polyester film with a thickness of 50 μm.

[0218] (Comparative Example 3) As shown in Table 1 below, a biodegradable polyester resin, a biodegradable polyester sheet, and a polyester film having a number average molecular weight of approximately 30,000 g / mol were produced in the same manner as in Example 1, except that the first step (pretreatment step) of Example 1 was not performed, the amounts of terephthalic acid (TPA) and adipic acid (AA) were changed, and TPAs ​​with different D50s and standard deviations (SD) were used.

[0219] Comparative Example 4 As shown in Table 1 below, the amounts of terephthalic acid (TPA) and adipic acid (AA) were changed, and TPA with different D50 and standard deviation (SD) was used. Except for this, the same procedures as in Comparative Example 1 were carried out to produce a biodegradable polyester resin, a biodegradable polyester sheet, and a polyester film having a number average molecular weight of approximately 42,000 g / mol.

[0220] [Table 1]

[0221] (Evaluation example) [Evaluation Example 1: Average particle size (D50) and standard deviation] <Average particle size (D50) and standard deviation of aromatic dicarboxylic acid> From the particle size distribution (PSD), the average particle size (D50) and standard deviation (SD) of the aromatic dicarboxylic acid (TPA or DMT) were determined using a particle size analyzer Microtrac S3500 (Microtrac Inc.) under the following conditions.

[0222] -Usage environment- - Temperature: 10℃~35℃, Humidity: 90%RH, non-condensing maximum - The average particle size distribution, D50 and SD, were measured. The standard deviation means the square root of the variance and can be calculated using software.

[0223] <Particle size of nanocellulose> The particle size and particle size deviation of nanocellulose were measured using dynamic light scattering (DLS) at a temperature of 25°C and a measurement angle of 175° using a Zetasizer® Nano ZS (Marven). The peak value derived from the polydispersity index (PdI) within a confidence interval of 0.5 was used as the particle size.

[0224] [Evaluation Example 2: Crystallization temperature (Tc) and ΔHmc] Using a differential scanning calorimeter (DSC), the sample was heated from 40°C to 180°C at a rate of 10°C / min, followed by a 5-minute isothermal cooling step to remove the thermal history. The sample was then cooled from 180°C to -50°C at a rate of 10°C / min, followed by a 5-minute isothermal cooling step. The crystallization temperature (Tc) and ΔHmc (J / g) were determined during the secondary cooling step.

[0225] [Evaluation example 3: Vicat A50 (VST)] According to ASTM D1525 (ISO 306), the temperature (°C) when the tip of a needle passed through 1 mm of the biodegradable polyester chip (test piece) with a thickness of 5 mm and a width of 10 mm produced in the examples and comparative examples was measured at 50°C / hour and a load of 10 N.

[0226] [Evaluation example 4: Friction coefficient] The static friction coefficient of the biodegradable polyester sheet specimens produced in the Examples and Comparative Examples was measured using a friction coefficient tester (QM110CF) manufactured by Qmesys.

[0227] According to ASTM D1894 standard, one side of the biodegradable polyester sheet produced in the examples or comparative examples was brought into contact with stainless steel (SUS), and the static friction coefficient during sliding was measured.

[0228] [Evaluation Example 5: Tensile strength and elongation at break] The biodegradable polyester sheets manufactured in the examples or comparative examples were cut according to the ASTM D638 V-type standard to make test pieces, and then tested at a tensile speed of 100 mm / min using an Instron universal testing machine (UTM, 4206-001). The tensile strength (kgf / mm 2 = 9.8 MPa) and elongation at break (%) were measured.

[0229] [Evaluation Example 6: Tear Strength] JIS K 6251Based on the above, the biodegradable polyester sheets prepared in the Examples or Comparative Examples were cut to prepare test pieces, and then a 2 mm notch was made in the center. The test pieces were then measured using an Instron Universal Testing Machine (UTM, 4206-001), and the tear strength was calculated based on the following Equation 6. [Formula 6] JPEG0007783842000009.jpg876

[0230] [Evaluation Example 7: Softness Index (SI) and Formability Index (FI)] Using the values ​​of Tc and VST measured in Evaluation Examples 2 and 3, the softness index (SI) expressed by the following formula 1 was calculated.

[0231] [Formula 1] JPEG0007783842000010.jpg869In the above formula 1, Tc and VST are unit-free values ​​measured on a biodegradable polyester film test piece produced from the biodegradable polyester resin, Tc is the crystallization temperature (°C) measured using a differential scanning calorimeter (DSC) in the process of heating from 40°C to 180°C at a rate of 10°C / min and then cooling to -50°C at a rate of 10°C / min. VST is the temperature (°C) at which the tip of a needle passes through 1 mm of a test piece 5 mm thick and 10 mm wide when the test piece is measured at 50°C / hour and a load of 10 N based on ASTM D1525.

[0232] Furthermore, using the values ​​of the static friction coefficient and tear strength measured in Evaluation Examples 4 and 6, the formability index (FI) was calculated using the following formula 2.

[0233] [Formula 2] JPEG0007783842000011.jpg842In the above formula 2, TS and FC are unit-free values ​​measured on a biodegradable polyester sheet test piece produced from the biodegradable polyester resin, TS is JIS K 6251After preparing a test piece based on the above, the test piece was measured for tear strength (N / cm) using a universal testing machine (UTM), FC is the static friction coefficient measured by bringing stainless steel (SUS) into contact with one surface of a test piece in accordance with ASTM D1894.

[0234] [Evaluation Example 8: Storage modulus, loss modulus, loss tangent (tanδ)] The storage modulus and loss modulus of the biodegradable polyester sheet specimens prepared in the examples and comparative examples were measured using a dynamic viscoelasticity tester, RDS (Rheometrics Dynamic Spectrometer, TA Instrument, Discovery HR 30).

[0235] Furthermore, the loss tangent (tan δ) expressed by the following formula 3 was calculated using the values ​​of the storage modulus and loss modulus.

[0236] [Formula 3] JPEG0007783842000012.jpg851 In the above formula 3, G' is the storage modulus of the biodegradable polyester sheet produced from the biodegradable polyester resin at 240°C and a vibration frequency of 5 rad / s in dynamic viscoelasticity measurement, G'' is the loss modulus of the biodegradable polyester sheet produced from the biodegradable polyester resin at 240°C and a vibration frequency of 5 rad / s in dynamic viscoelasticity measurement.

[0237] [Evaluation Example 9: Water Decomposition Reduction Rate] The biodegradable polyester sheets produced in the examples and comparative examples were immersed in water (100% RH) at 80°C, and then subjected to an accelerated hydrolysis test.

[0238] Specifically, 5 g of the polyester sheets of the Examples and Comparative Examples were placed in 500 mL of deionized water (DI Water), and the container was sealed with a stopper to prevent the water from evaporating. The accelerated hydrolysis test was then carried out in a convection (hot air) oven at 80°C. The humidity environment for the biodegradable polyester sheets was 100% RH, the same as when they were immersed in water.

[0239] Using gel permeation chromatography (GPC), the number average molecular weight of the biodegradable polyester sheet after 3 months was compared with the initial number average molecular weight represented by the following formula 4.

[0240] [Formula 4] JPEG0007783842000013.jpg13128In the above formula 4, Mn A and Mn B is the number average molecular weight of the biodegradable polyester sheet produced from the biodegradable polyester resin, measured by gel permeation chromatography (GPC) after immersing the biodegradable polyester sheet in water and subjecting it to accelerated hydrolysis at 80°C in a convection oven, Mn A is the initial number average molecular weight of the biodegradable polyester sheet, Mn B is the number average molecular weight of the biodegradable polyester sheet 3 months after accelerated hydrolysis.

[0241] [Evaluation Example 10: Biodegradability] ISO 14855 Based on the above, the degree of biodegradation was measured by measuring the amount of carbon dioxide generated. Specifically, an inoculum container containing only compost produced at a compost factory was prepared, and test containers were prepared by adding test pieces to the compost at a ratio of 5% by weight of the dry weight of the compost. The compost was then cultured for 180 days under conditions of a temperature of 58±2°C, a moisture content of 50%, and an oxygen concentration of 6% or higher. The carbon dioxide generated in each container was collected and titrated with a phenolphthalein solution to measure the amount of carbon dioxide generated in each container. The biodegradation degree was calculated using the measured amount of carbon dioxide generated according to the following equation 5.

[0242] [Formula 5] JPEG0007783842000014.jpg11146

[0243] [Evaluation Example 11: Inflation moldability and adhesive properties] Air was blown into the film from below at 160°C using an inflation molding machine, and bubble formation was observed, and inflation moldability was evaluated as follows. ○: The bubble shape is good, with no deviation to one side or breakage. ×: If the bubble is not properly shaped, stretched to one side, or broken, the moldability is NG.

[0244] Meanwhile, during the production of the biodegradable polyester film, the degree of adhesion between the surfaces when the film was wound up was observed, and the adhesive properties were evaluated as follows. ○: When winding, the surfaces stick together and cannot be separated △: When winding, the surfaces stick together slightly, but can be easily peeled off ×: When the surfaces do not stick together during winding

[0245] [Table 2]

[0246] As shown in Table 2, in the case of the polyester resins of the examples in which the biodegradable polyester resins satisfy the specific ranges for the ratio of the number of first repeating units to the number of second repeating units (X / Y) and the ranges for the softness index, both physical properties and processability are excellent overall, and the biodegradability and the rate of decrease in hydrolysis after 3 months are also excellent.

[0247] Specifically, when the biodegradable polyester resins of Examples 1 to 7 were used, the crystallization temperature (Tc), ΔHmc, and Vicat A50 all satisfied the ranges required for improving moldability, and not only were the static friction coefficient, strength, elongation, and tear strength improved, but inflation moldability and adhesive properties were also improved, resulting in excellent processability. Furthermore, the biodegradability of the biodegradable polyester sheets or films obtained using these biodegradable polyester resins was 90% or higher, and the reduction in hydrolysis rate after 3 months was 86% or higher.

[0248] On the other hand, when the biodegradable polyester resins of Comparative Examples 1 to 4 were used, the crystallization temperature (Tc), ΔHmc, Vicat A50, static friction coefficient, strength, elongation, and tear strength were lower than when the biodegradable polyester resins of Examples 1 to 7 were used. In particular, when the biodegradable polyester resin of Comparative Example 4 was used, the softness index was excessively high, the rate of decrease in hydrolysis after 3 months was very low at 70%, and the inflation moldability and adhesive properties were poor.

[0249] Furthermore, when the biodegradable polyester resin of Comparative Example 3 or 4 was used, which did not satisfy the ratio of the number of first repeating units containing a first diol residue and an aromatic dicarboxylic acid residue to the number of second repeating units containing a second diol residue and an aliphatic dicarboxylic acid residue, the flexibility index and moldability index did not satisfy the appropriate range, and the strength, inflation moldability, and adhesive properties were poor.

[0250] In particular, when the biodegradable polyester resins of Examples 1 to 5, in which the ratio of the number of the first repeating unit to the second repeating unit (X / Y) is about 0.8 to 1.3, are used, the softness index is very appropriate at 90 to 110, compared to the biodegradable polyester resins of Examples 6 and 8, in which the ratio of the number of the first repeating unit to the second repeating unit (X / Y) exceeds 1.3, and it can be confirmed that the rate of decrease in hydrolysis degree after 3 months is somewhat improved.

[0251] On the other hand, it was confirmed that the addition of nanocellulose changes the physical properties of biodegradable polyester resin or biodegradable polyester sheets or films made from it.

[0252] Specifically, in the cases of Examples 2, 5, and 7 in which nanocellulose was added, it was found that the physical properties of elongation, tensile strength, and tear strength were improved.

[0253] Meanwhile, it was confirmed that the physical properties of the biodegradable polyester resin or the biodegradable polyester sheet or film using the same change depending on the processing conditions of the biodegradable polyester resin.

[0254] Specifically, it was confirmed that the use of the biodegradable polyester resins of Examples 1 to 3, which were prepared by performing primary and secondary esterification reactions, was more advantageous in achieving a softness index and moldability index within the appropriate range than the use of the biodegradable polyester resins of Examples 4 and 5, which were prepared by performing only the primary esterification reaction, and that not only the physical properties but also the rate of decrease in hydrolysis degree after 3 months were improved.

[0255] In addition, when the biodegradable polyester resin of Comparative Example 3, which underwent primary and secondary esterification but did not undergo slurry pretreatment, was used, the flexibility index was 79.31, which was very low, and the moldability index was 53.03, which was excessively high, compared to the biodegradable polyester resin of the Example, which underwent slurry pretreatment. Furthermore, the tensile strength was 22 MPa, which was very low, and the static friction coefficient was 13.2, which was excessively high, and the inflation moldability and adhesive properties were significantly poor.

Claims

1. a first repeat unit comprising a first diol residue and a residue of an aromatic dicarboxylic acid; a second repeat unit comprising a second diol residue and a residue of an aliphatic dicarboxylic acid, the first diol residue and the second diol residue each comprise a residue of 1,4-butanediol, 1,2-ethanediol, 1,3-propanediol, or a derivative thereof; the aromatic dicarboxylic acid residue comprises a residue of terephthalic acid, dimethyl terephthalate, or a derivative thereof; The aliphatic dicarboxylic acid residues include residues of adipic acid, succinic acid, sebacic acid, or derivatives thereof; the number of the first repeating units (X) is 100 to 900; the number of the second repeating units (Y) is 100 to 1100; The forming index (FI) represented by the following formula 2 is 25 to 53, A biodegradable polyester resin having a loss tangent (tanδ) represented by the following formula 3 of greater than 1: [Formula 2] [Formula 3] In the formula 2, TS and FC are unit-free values ​​measured on a biodegradable polyester sheet test piece produced from the biodegradable polyester resin, TS is the tear strength (N / cm) measured on a test piece prepared in accordance with JIS K 6251 using a universal testing machine (UTM); FC is the static friction coefficient measured by contacting one side of a test piece with stainless steel (SUS) in accordance with ASTM D1894, In the formula 3, G' is the storage modulus of the biodegradable polyester sheet produced from the biodegradable polyester resin at 240°C and a vibration frequency of 5 rad / s in dynamic viscoelasticity measurement; G'' is the loss modulus of the biodegradable polyester sheet produced from the biodegradable polyester resin at 240°C and a vibration frequency of 5 rad / s in dynamic viscoelasticity measurement.

2. the FC is less than 10; The biodegradable polyester resin according to claim 1, wherein the TS is 300 N / cm or more.

3. The biodegradable polyester resin is A biodegradable polyester film specimen prepared from the biodegradable polyester resin is heated from 40°C to 180°C at a rate of 10°C / min using a differential scanning calorimeter (DSC) and then cooled to -50°C at a rate of 10°C / min. The crystallization temperature measured during this process is 38°C or higher, 2. The biodegradable polyester resin according to claim 1, wherein when a biodegradable polyester film test piece produced from the biodegradable polyester resin and having a thickness of 5 mm and a width of 10 mm is measured at 50°C / hour and a load of 10 N according to ASTM D1525, the temperature (°C) when the end of a needle passes through 1 mm of the test piece is 90°C or higher.

4. The biodegradable polyester film containing the biodegradable polyester resin has a biodegradability of 90% or more as measured by the amount of carbon dioxide generated in accordance with ISO 14855; The biodegradable polyester resin according to claim 1, wherein the water decomposition rate reduction rate represented by the following formula 4 is 85% or more: [Formula 4] In the formula 4, Mn Ａ and Mn Ｂ is the number average molecular weight of the biodegradable polyester sheet produced from the biodegradable polyester resin, measured by gel permeation chromatography (GPC) after immersing the biodegradable polyester sheet in water and subjecting it to accelerated hydrolysis at 80°C in a convection oven, Mn Ａ is the initial number average molecular weight of the biodegradable polyester sheet, Mn Ｂ is the number average molecular weight of the biodegradable polyester sheet 3 months after accelerated hydrolysis.

5. The biodegradable polyester resin is 10. The biodegradable polyester resin of claim 1, further comprising one or more nanocelluloses selected from the group consisting of cellulose nanocrystals, cellulose nanofibers, microfibrillated cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, cellulose acetate, methyl cellulose, ethyl cellulose, propyl cellulose, butyl cellulose, pentyl cellulose, hexyl cellulose, and cyclohexyl cellulose.

6. A first stage of mixing and pretreating a diol component and an aromatic dicarboxylic acid to obtain a slurry; a second step of performing an esterification reaction at least once using a mixture containing the slurry and an aliphatic dicarboxylic acid, or a mixture containing a reaction product obtained by esterifying the slurry and an aliphatic dicarboxylic acid, to obtain a prepolymer; a third step of subjecting the prepolymer to a polycondensation reaction; The first pretreatment step includes mixing a diol component and an aromatic dicarboxylic acid and stirring the mixture at 60°C to 100°C and 50 rpm to 200 rpm; A method for producing a biodegradable polyester resin comprising a first repeating unit containing a first diol residue and a residue of an aromatic dicarboxylic acid, and a second repeating unit containing a second diol residue and a residue of an aliphatic dicarboxylic acid, wherein the first diol residue and the second diol residue each contain a residue of 1,4-butanediol, 1,2-ethanediol, 1,3-propanediol, or a derivative thereof, the aromatic dicarboxylic acid residue contains a residue of terephthalic acid, dimethyl terephthalate, or a derivative thereof, and the aliphatic dicarboxylic acid residue contains a residue of adipic acid, succinic acid, sebacic acid, or a derivative thereof, the number of the first repeating units (X) is 100 to 900, the number of the second repeating units (Y) is 100 to 1100, the molding index (FI) represented by the following formula 2 is 25 to 53, and the loss tangent (tan δ) represented by the following formula 3 is greater than 1: [Formula 2] [Formula 3] In the formula 2, TS and FC are unit-free values ​​measured on a biodegradable polyester sheet test piece produced from the biodegradable polyester resin, TS is the tear strength (N / cm) measured on a test piece prepared in accordance with JIS K 6251 using a universal testing machine (UTM); FC is the static friction coefficient measured by contacting one side of a test piece with stainless steel (SUS) in accordance with ASTM D1894, In the formula 3, G' is the storage modulus of the biodegradable polyester sheet produced from the biodegradable polyester resin at 240°C and a vibration frequency of 5 rad / s in dynamic viscoelasticity measurement; G'' is the loss modulus of the biodegradable polyester sheet produced from the biodegradable polyester resin at 240°C and a vibration frequency of 5 rad / s in dynamic viscoelasticity measurement.

7. Contains biodegradable polyester resin, The biodegradable polyester resin is a first repeat unit comprising a first diol residue and a residue of an aromatic dicarboxylic acid; a second repeat unit comprising a second diol residue and a residue of an aliphatic dicarboxylic acid, the first diol residue and the second diol residue each comprise a residue of 1,4-butanediol, 1,2-ethanediol, 1,3-propanediol, or a derivative thereof; the aromatic dicarboxylic acid residue comprises a residue of terephthalic acid, dimethyl terephthalate, or a derivative thereof; The aliphatic dicarboxylic acid residues include residues of adipic acid, succinic acid, sebacic acid, or derivatives thereof; the number of the first repeating units (X) is 100 to 900; the number of the second repeating units (Y) is 100 to 1100; The forming index (FI) represented by the following formula 2 is 25 to 53, A biodegradable polyester film having a loss tangent (tanδ) represented by the following formula 3 of greater than 1: [Formula 2] [Formula 3] In the formula 2, TS and FC are unit-free values ​​measured on a biodegradable polyester sheet test piece produced from the biodegradable polyester resin, TS is the tear strength (N / cm) measured on a test piece prepared in accordance with JIS K 6251 using a universal testing machine (UTM); FC is the static friction coefficient measured by contacting one side of a test piece with stainless steel (SUS) in accordance with ASTM D1894, In the formula 3, G' is the storage modulus of the biodegradable polyester sheet produced from the biodegradable polyester resin at 240°C and a vibration frequency of 5 rad / s in dynamic viscoelasticity measurement; G'' is the loss modulus of the biodegradable polyester sheet produced from the biodegradable polyester resin at 240°C and a vibration frequency of 5 rad / s in dynamic viscoelasticity measurement.

Images