Polybutylene adipate terephthalate resin composition and method for producing the same

Abstract

The present invention relates to a polybutylene adipate terephthalate resin composition and a method for producing the same.

Description

Technical Field

[0001] Cross-reference of related applications This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0010704 filed on January 25, 2022, and all the contents disclosed in the literature of the Korean patent application are included as part of this specification.

[0002] The present invention relates to a polybutylene adipate terephthalate resin composition and a method for producing the same.

Background Art

[0003] Thermoplastic polymer resins are excellent in mechanical and chemical properties and are used in various fields such as drinking water containers, medical applications, food wrapping papers, food containers, automotive molded products, and agricultural vinyls.

[0004] Among thermoplastic polymer resins, polyethylene films, etc. are excellent in mechanical physical properties and harmless to the human body, but can be continuously deformed when heated, so they are widely used in hot-seal bags for food packaging, agricultural mulching films, etc., and their consumption is increasing annually based on their excellent functions and low prices.

[0005] However, recently, as the interest in the country and social environment has grown, problems such as environmental problems like microplastics, problems of human body safety like environmental hormones, and depletion of natural resources that are raw materials for plastics have emerged.

[0006] In particular, recently, it is known that plastics such as discarded polyethylene films flow into the sea and are crushed into microplastics with extremely small sizes by reflux and sunlight in the sea.

[0007] Currently, it is known that such microplastics are floating in the sea in an uncountable amount from billions to hundreds of billions or more, which flow into the bodies of marine organisms, accumulate within the ecosystem, and affect the entire food chain.

[0008] Therefore, research into alternative materials to previously used thermoplastics is necessary, and among these, there is growing interest in polybutyleneadipate terephthalate (PBAT), a biodegradable polymer with flexible properties.

[0009] PBAT is mostly used in environmentally friendly consumer film applications as a substitute for polyethylene or polyethylene terephthalate, where appearance is particularly important. However, when increasing the molecular weight of polybutylene adipate terephthalate to improve mechanical properties, polymer gels can form, which can impair appearance and reduce mechanical properties such as tensile strength and elongation. [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] This specification provides a polybutylene adipate terephthalate resin composition that suppresses gel formation during the manufacturing process and exhibits excellent mechanical properties and appearance characteristics.

[0011] Furthermore, this specification provides a method for producing a polybutylene adipate terephthalate resin composition. [Means for solving the problem]

[0012]

[0013] This specification provides a polybutylene adipate terephthalate resin composition comprising a polybutylene adipate terephthalate resin, a chain extender, and a gel-reducing agent.

[0014] The chain extender and gel reducer may exist in a dispersed form within the polybutylene adipate terephthalate resin.

[0015] According to one embodiment of the invention, the chain extender may include a diisocyanate compound. Specifically, for example, the chain extender may include one or more compounds selected from the group consisting of hexamethylene diisocyanate, methylenediphenyl diisocyanate, toluene diisocyanate, and isophorone diisocyanate.

[0016] According to one embodiment of the invention, the chain extender is present in an amount of about 0.1 to about 10 parts by weight, or about 0.1 to about 5 parts by weight, most preferably about 0.2 to about 3 parts by weight, per 100 parts by weight of the polybutylene adipate terephthalate.

[0017] According to one embodiment of the invention, the gel-reducing agent may include one or more compounds selected from the group consisting of secondary alcohol compounds having 3 to 10 carbon atoms and tertiary alcohol compounds having 4 to 10 carbon atoms.

[0018] The gel-reducing agent may specifically include, for example, one or more selected from the group consisting of 2,5-dimethyl-2,5-hexanediol, 2-phenyl-2-propanol, 2,3-hexanediol, 2,5-hexanediol, 2-methyl-1-phenyl-2-propanol, 2,4-pentanediol, isosorbide, cyclobutanediol, cyclopentanediol, and cyclohexanediol.

[0019] According to one embodiment of the invention, the gel-reducing agent is present in an amount of 0.01 to 10 parts by weight, or about 0.01 to about 5 parts by weight, most preferably about 0.1 to about 1 part by weight, per 100 parts by weight of the polybutylene adipate terephthalate.

[0020] According to one embodiment of the invention, the weight-average molecular weight of the polybutylene adipate terephthalate resin may be about 50,000 to about 150,000, or about 100,000 to about 150,000, most preferably about 130,000 to about 140,000.

[0021] According to one embodiment of the invention, the molecular weight distribution value of the polybutylene adipate terephthalate resin may be about 3 to 5, or about 3 to 4.5, most preferably about 3.5 to 4.

[0022] In addition, this specification provides a method for producing polybutylene adipate terephthalate, which includes a polymerization step of producing a polymer by polycondensing 1,4-butanediol, adipic acid, and terephthalic acid in the presence of a catalyst; a mixing step of adding a chain extender and a gel reducing agent to the polymer to produce a mixture; and a molding step of extruding the mixture.

[0023] At this time, the ratio of the molecular weight after extrusion to the molecular weight before extrusion is about 1 or more, or about 1 to about 2, most preferably about 1.3 to about 1.5, and the molecular weight can be increased by the extrusion process.

[0024] The terms used in this specification are only used to explain exemplary embodiments and are not intended to limit the present invention.

[0025] Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0026] In this specification, terms such as "comprising", "including", or "having" are used to describe implemented features, numbers, steps, components, or combinations thereof, and do not exclude the possibility of one or more other features, numbers, steps, components, combinations thereof or additions.

[0027] In addition, in this specification, when it is mentioned that each layer or element is formed "on" each layer or element, it means that each layer or element is directly formed on each layer or element, or other layers or elements can be additionally formed between each layer, on the object, or on the substrate.

[0028] Although the present invention can be modified in various ways and can have various forms, specific embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to a specific disclosed form, and it should be understood that it includes all modifications, equivalents, or alternatives included in the spirit and technical scope of the present invention.

[0029] In this specification, polybutylene adipate terephthalate resin or polybutylene adipate terephthalate polymer is used to include not only a polymer chain containing repeating units derived from butylene, adipate, and terephthalate, but also all forms in which a chain extender intervenes in the middle of the polymer repeating units and is included in the polymer chain by a chain extension reaction.

[0030] Hereinafter, the present invention will be described in detail.

[0031] As described above, in order to improve the mechanical properties of polybutylene adipate terephthalate, it is necessary to increase the molecular weight of polybutylene adipate terephthalate. However, when increasing the molecular weight of polybutylene adipate terephthalate, problems may occur such as the formation of polymer gels, which harm the appearance and reduce mechanical properties such as tensile strength and elongation.

[0032] Polybutylene adipate terephthalate mostly undergoes a polymerization process and an extrusion molding process for increasing the molecular weight of the polybutylene adipate terephthalate polymer produced in the polymerization process during production.

[0033] The polybutylene adipate terephthalate produced in the polymerization process has a not-so-high molecular weight and a not-high melt viscosity, so by-products such as gels can be easily removed.

[0034] However, the polybutylene adipate terephthalate polymer obtained after the extrusion molding process has a high molecular weight and a greatly increased melt viscosity value, so there is a problem that by-products such as gels contained therein are difficult to easily remove.

[0035] As a result of continuing research to solve the above problems, the inventors of the present invention discovered that the formation of gels within polybutylene adipate terephthalate polymers can be suppressed by a specific combination of compounds, and thus completed the present invention.

[0036] According to one aspect of the present invention, a polybutylene adipate terephthalate resin composition is provided, comprising a polybutylene adipate terephthalate resin, a chain extender, and a gel-reducing agent.

[0037] The chain extender and gel reducer may exist in a dispersed form within the polybutylene adipate terephthalate resin.

[0038] Furthermore, in the polybutylene adipate terephthalate resin composition, the chain extender and gel reducer may also exist in a form in which they react with each other while dispersed in the resin composition, forming two reaction products.

[0039] According to one embodiment of the invention, the chain extender may include a diisocyanate compound. Specifically, for example, the chain extender may include one or more compounds selected from the group consisting of hexamethylene diisocyanate, methylenediphenyl diisocyanate, toluene diisocyanate, and isophorone diisocyanate.

[0040] According to one embodiment of the invention, the chain extender is present in an amount of about 0.1 to about 10 parts by weight, or about 0.1 to about 5 parts by weight, most preferably about 0.2 to about 3 parts by weight, per 100 parts by weight of the polybutylene adipate terephthalate.

[0041] If the content of the chain extender is excessively low, a problem may arise in which the molecular weight of the polybutylene adipate terephthalate resin does not become sufficiently high. Conversely, if the content of the chain extender is excessively high, a problem may arise in which the content of the reaction by-product, polybutylene adipate terephthalate polymer gel, becomes high.

[0042] Diisocyanate compounds are typical chain extenders used in polyester polymers such as polybutylene adipate terephthalate, as described in the present invention.

[0043] The isocyanate groups contained in diisocyanate compounds can react with hydroxyl or carboxyl groups at the polyester termini to form urethane bonds. Therefore, in the case of diisocyanate compounds containing two or more isocyanate groups in the molecule, the above-described reaction proceeds at both termini, linking the ends of the polyester polymer, extending the chain, and increasing the molecular weight of the polyester polymer.

[0044] When the urethane group generated in the intermediate stage of the above reaction reacts again with the isocyanate group of the chain extender, an alfarnate compound is formed. Three or more polymer chains are linked to the nitrogen atom of this alfarnate compound, acting as a kind of crosslinking point, and a polymer gel is formed by such crosslinking.

[0045] Furthermore, when the isocyanate group reacts with water, a compound containing the amine group is formed, and when this compound reacts again with a chain extender, a urea bond can be formed. When such a urea group reacts again with a chain extender, a biuret compound is formed, which can also act as a crosslinking site for the formation of polymer gels.

[0046] However, in a resin composition according to one aspect of the present invention, the inclusion of a gel-reducing agent makes it possible to prevent the formation of such a gel during the chain extension process of the polybutylene adipate terephthalate polymer.

[0047] According to one embodiment of the invention, the gel-reducing agent may include one or more compounds selected from the group consisting of secondary alcohol compounds having 3 to 10 carbon atoms and tertiary alcohol compounds having 4 to 10 carbon atoms.

[0048] The gel-reducing agent may specifically include, for example, one or more selected from the group consisting of 2,5-dimethyl-2,5-hexanediol, 2-phenyl-2-propanol, 2,3-hexanediol, 2,5-hexanediol, 2-methyl-1-phenyl-2-propanol, 2,4-pentanediol, isosorbide, cyclobutanediol, cyclopentanediol, and cyclohexanediol.

[0049] The aforementioned secondary and tertiary alcohol compounds contain a hydroxyl group within their molecules and, in terms of their molecular structure, have a suitable degree of reactivity with the isocyanate group. This effectively prevents the formation of the aforementioned alphanate bond without inhibiting the chain extension reaction that extends the chain of the polybutylene adipate terephthalate polymer during the extrusion process.

[0050] According to one embodiment of the invention, the gel-reducing agent is present in an amount of 0.01 to 10 parts by weight, or about 0.01 to about 5 parts by weight, most preferably about 0.1 to about 1 part by weight, per 100 parts by weight of the polybutylene adipate terephthalate.

[0051]

[0052] If the gel-reducing agent content is excessively high, the polymer chain extension reaction of polybutylene adipate terephthalate may be inhibited, resulting in a problem where the molecular weight of polybutylene adipate terephthalate cannot be sufficiently increased. In fact, depolymerization of polybutylene adipate terephthalate may occur, leading to a decrease in the physical properties of the resin composition. If the gel-reducing agent content is excessively low, the gel-reducing effect may not be observed.

[0053] According to one embodiment of the invention, the weight-average molecular weight of the polybutylene adipate terephthalate resin may be about 50,000 to about 150,000, or about 100,000 to about 150,000, most preferably about 130,000 to about 140,000.

[0054] Here, the weight-average molecular weight is the value measured using GPC with polystyrene having molecular weights of 1,000, 10,000, 50,000, 70,000, 100,000, 120,000, 150,000, 170,000, and 200,000, respectively, as a standard substance.

[0055] If the weight-average molecular weight of the polybutylene adipate terephthalate resin is excessively low, problems may arise in that the mechanical properties of the resin composition deteriorate. Conversely, if the weight-average molecular weight of the polybutylene adipate terephthalate resin is excessively high, problems may arise in that the processability of the resin deteriorates.

[0056] Furthermore, according to one embodiment of the invention, the molecular weight distribution value of the polybutylene adipate terephthalate resin may be about 3 to 5, or about 3 to 4.5, most preferably about 3.5 to 4.

[0057] If the molecular weight distribution of polybutylene adipate terephthalate resin is excessively low, it can lead to problems with reduced processability. Conversely, if the molecular weight distribution of polybutylene adipate terephthalate resin is excessively high, it can lead to problems with reduced mechanical properties of the resin composition.

[0058] Furthermore, this specification provides a method for producing polybutylene adipate terephthalate, comprising: a polymerization step of producing a polymer by condensation polymerization of 1,4-butanediol, adipic acid, and terephthalic acid in the presence of a catalyst; a mixing step of producing a mixture by adding a chain extender and a gel reducer to the polymer; and a molding step of extruding the mixture.

[0059] The catalyst is not particularly limited as long as it is widely used as a polyester polymerization catalyst in the art to which the present invention pertains.

[0060] Specifically, the catalyst may be one or more selected from the group consisting of titanium methoxide, titanium ethoxide, titanium propoxide, titanium isopropoxide, titanium butoxide, and titanium isobutoxide.

[0061] For example, the catalyst may be titanium butoxide.

[0062] The catalyst can be used in an amount of approximately 0.001 parts by weight or more, approximately 0.005 parts by weight or more, or approximately 0.01 parts by weight or more and approximately 10 parts by weight or less, approximately 5 parts by weight or less, or approximately 0.1 parts by weight or less, based on 100 parts by weight of adipic acid in the monomer mixture.

[0063] If the amount of catalyst added is excessively low, the polymerization time will be prolonged, potentially reducing productivity. Conversely, if the amount of catalyst added is excessively high, the polymerization time will be shortened, but the likelihood of discoloration of the resulting polybutylene adipate terephthalate will increase. This can lead to the problem of having to add additional additives, such as heat stabilizers, in proportion to the amount of catalyst added.

[0064] Furthermore, the 1,4-butanediol can be used in an amount of approximately 150 to 250 parts by weight, or approximately 180 to 220 parts by weight, based on 100 parts by weight of adipic acid in the monomer mixture.

[0065] This is the total amount of 1,4-butanediol required for the synthesis of polybutylene adipate terephthalate.

[0066] Polymerization process A prepolymer is a polymer with a relatively low degree of polymerization, created by stopping the polymerization reaction at an intermediate stage to facilitate molding.

[0067] In one embodiment, the prepolymer corresponds to a polymer with a relatively low degree of polymerization, produced by esterifying a monomer mixture containing 1,4-butanediol, adipic acid, and terephthalic acid in the presence of the catalyst.

[0068] According to one embodiment of the present invention, initial polymer chains are formed around the catalyst, with the catalyst at the center.

[0069] Specifically, the monomer mixture may contain about 50 to about 150 parts by weight of terephthalic acid, based on 100 parts by weight of adipic acid in the monomer mixture.

[0070] Terephthalic acid, due to its aromatic ring structure, can affect the crystallinity of polymers, but polymers produced within the aforementioned input range can achieve excellent mechanical properties and biodegradability.

[0071] For example, the monomer mixture may contain about 80 to about 120 parts by weight of terephthalic acid based on 100 parts by weight of adipic acid in the monomer mixture.

[0072] Furthermore, during the process of producing the prepolymer, 0.1 to 1 part by weight of a crosslinking agent or branching agent can be added to 100 parts by weight of adipic acid in the monomer mixture to carry out the esterification reaction.

[0073] When a crosslinking agent is added to carry out an esterification reaction, an internally crosslinked prepolymer is produced, which can improve the mechanical properties of the resin composition.

[0074] The crosslinking agent is a low-molecular-weight compound containing three or more hydroxyl groups or three or more carboxyl groups in its molecule, such as glycerol, pentaerythritol, or citric acid. For example, the crosslinking agent may be pentaerythritol.

[0075] The step of manufacturing the aforementioned prepolymer is carried out at a temperature range of approximately 150 to 350°C for approximately 10 to 120 minutes.

[0076] Within the aforementioned temperature and time range, a uniform dispersion of the organic filler can be maintained, and a prepolymer can be manufactured.

[0077] For example, the step of manufacturing the prepolymer is carried out in a temperature range of approximately 150°C or higher, approximately 170°C or higher, approximately 190°C or higher, or approximately 210°C or higher and approximately 350°C or lower, approximately 320°C or lower, approximately 290°C or lower, or approximately 250°C or lower. It is also carried out in a time range of approximately 10 minutes or higher, approximately 15 minutes or higher, approximately 20 minutes or higher, or approximately 25 minutes or higher and approximately 120 minutes or lower, approximately 90 minutes or lower, approximately 60 minutes or lower, or approximately 40 minutes or lower.

[0078] Nitrogen gas can be injected during the manufacturing stage of the prepolymer. Specifically, by rapidly removing water generated as a byproduct when nitrogen gas is injected, the reverse reaction caused by water can be suppressed, improving the monomer conversion rate and increasing the molecular weight of the polymer chain.

[0079] For example, nitrogen gas can be injected at a rate of approximately 0.001 ml / min or more, approximately 0.01 ml / min or more, approximately 0.02 ml / min or more, or approximately 0.05 ml / min or more and approximately 100 ml / min or less, approximately 50 ml / min or less, approximately 10 ml / min or less, or approximately 5 ml / min or less.

[0080] During polymerization of the prepolymer, approximately 0.001 to 10 parts by weight of catalyst can be added to the monomer mixture, based on 100 parts by weight of adipic acid.

[0081] The catalyst initially added is likely to lose activity during the prepolymer manufacturing stage. For example, titanium, the central metal component of the catalyst, may react with water, a byproduct of the esterification reaction, to form titanium oxide, and functional groups present in the organic filler molecules may be substituted at the alkoxide sites of titanium alkoxide. Therefore, it is preferable to add the catalyst immediately before the reaction.

[0082] For example, the additional catalyst can be used in an amount of about 0.001 parts by weight or more, about 0.005 parts by weight or more, or about 0.01 parts by weight or more and about 10 parts by weight or less, about 5 parts by weight or less, or about 0.1 parts by weight or less, based on 100 parts by weight of adipic acid in the monomer mixture.

[0083] After adding the catalyst, a heat stabilizer can be added. Adding the heat stabilizer can suppress discoloration of the final PBAT.

[0084] Specifically, based on 100 parts by weight of adipic acid in the monomer mixture, approximately 0.001 to approximately 1 part by weight of a heat stabilizer can be added.

[0085] The polymerization of the prepolymer may include the steps of: raising the temperature of the reactor containing the prepolymer until the temperature reaches a range of about 150 to about 350°C; reducing the pressure of the reactor after the heating until the pressure reaches about 0.1 to about 0.00001 atm; and maintaining the pressure and temperature after the reduction, and terminating the reaction after reaching about 2 to about 8 hours.

[0086] For example, the temperature of the reactor containing the prepolymer can be raised to a temperature range of approximately 150°C or higher, approximately 170°C or higher, approximately 190°C or higher, or approximately 210°C or higher and approximately 350°C or lower, approximately 320°C or lower, approximately 290°C or lower, or approximately 250°C or lower.

[0087] After reaching the aforementioned temperature range, the reactor pressure can be reduced to a pressure range of approximately 0.00001 atm or higher, approximately 0.00005 atm or higher, approximately 0.0001 atm or higher, or approximately 0.0002 atm or higher and approximately 0.1 atm or lower, approximately 0.05 atm or lower, approximately 0.03 atm or lower, or approximately 0.01 atm or lower.

[0088] After the reduction in pressure, the pressure and temperature can be maintained and the reaction can be allowed to proceed. The reaction can then be terminated after approximately 2 hours or more, approximately 2.2 hours or more, approximately 2.4 hours or more, or approximately 3 hours or more and approximately 8 hours or less, approximately 7.5 hours or less, approximately 7 hours or less, or approximately 6 hours, from the start of the reaction.

[0089] Then, a chain extender and a gel-reducing agent are added to the polymer obtained by this method to produce a mixture.

[0090] During the preparation of the mixture, methods such as grinding the obtained polymer and then mixing it with a chain extender and a gel reducer can be used. The mixing method can be a general method used in the art to which the present invention pertains for the production of blending resins, and in particular, a general method used for feeding the polymer obtained by polymerization into an extruder can be used.

[0091] Then, the mixture is extruded.

[0092] The extruder used in this process can take on different forms depending on the conditions, but generally, a twin-screw extruder, which is advantageous for mixed molding, is preferred.

[0093] If the amount of resin composition fed into the extruder is excessively large, or if the molecular weight of the resin is excessively high, the extrusion pressure will increase, causing an overload that not only affects the physical properties of the extruded resin molded product but can also lead to mechanical problems. Therefore, it is preferable to maintain the extrusion pressure as low as possible, taking into account the discharge volume and residence time.

[0094] The diameter and size of the extruder can be determined by the extrusion conditions such as the discharge rate, but a screw length-to-outer diameter ratio (L / D) of approximately 40 or more, or approximately 40 to approximately 60, most preferably approximately 40 to approximately 50, is appropriate.

[0095] Furthermore, the extrusion temperature may be approximately 160°C to approximately 250°C, preferably approximately 180°C to approximately 220°C. If the extrusion temperature is excessively high, a decrease in molecular weight may occur due to thermal decomposition of the polymer, and if the extrusion temperature is excessively low, the melting efficiency of the polymer may decrease.

[0096] At this time, the ratio of the molecular weight after extrusion to the molecular weight before extrusion is about 1 or more, or about 1 to about 2, most preferably about 1.3 to about 1.5, and the molecular weight can be increased by the extrusion process. [Effects of the Invention]

[0097] A polybutylene adipate terephthalate resin composition according to an example of the present invention suppresses gel formation during the manufacturing process and exhibits excellent mechanical properties and appearance characteristics. [Modes for carrying out the invention]

[0098] The operation and effects of the invention will be described in more detail below through specific embodiments of the invention. However, these embodiments are presented merely as examples of the invention and do not define the scope of the invention's rights.

[0099] <Manufacturing example> 1220 g of 1,4-butanediol, 606 g of adipic acid, 634 g of terephthalic acid, 0.77 g of pentaerythritol, and 1.0 mmol of titanium butoxide were placed in a polymerization reactor, maintained at approximately 230°C, and the reaction was carried out under a nitrogen atmosphere for approximately 4 hours to produce a prepolymer.

[0100] Once the prepolymer was produced, triethyl phosphonoacetate, a heat stabilizer, was added so that the phosphorus (P) atom content in the resulting polymer was approximately 60 ppm. The mixture was then stirred for about 5 minutes to uniformly disperse the heat stabilizer in the polymer.

[0101] Subsequently, approximately 0.5 mmol of titanium butoxide was added to the reactor, and the temperature was raised to approximately 245°C. Once the reactor temperature reached approximately 245°C, polycondensation was carried out while reducing the pressure.

[0102] The reaction was stopped after confirming that the reactor torque value reached approximately 100 Ncm, yielding polybutylene adipate terephthalate polymer. (Mw: 93,600)

[0103] Example 1 The polybutylene adipate terephthalate polymer obtained in the above production example was freeze-dried and pulverized. Then, approximately 0.75 parts by weight of the chain extender hexamethylene diisocyanate and approximately 0.5 equivalents of the gel-reducing agent 2-phenyl-2-propanol were added to 100 parts by weight of polybutylene adipate terephthalate in a small twin-screw extruder, and the extrusion was carried out to obtain a pellet-shaped resin composition.

[0104] Example 2 The polybutylene adipate terephthalate polymer obtained in the above production example was freeze-dried and pulverized. Then, approximately 0.75 parts by weight of the chain extender hexamethylene diisocyanate and approximately 0.2 equivalents of the gel-reducing agent 2,5-dimethyl-2,5-hexanediol were added to 100 parts by weight of polybutylene adipate terephthalate in a small twin-screw extruder, and the extrusion was carried out to obtain a pelletized resin composition.

[0105] Example 3 The polybutylene adipate terephthalate polymer obtained in the above production example was freeze-dried and pulverized. Then, approximately 0.75 parts by weight of the chain extender hexamethylene diisocyanate and approximately 0.2 equivalents of the gel-reducing agent 2,3-hexanediol were added to 100 parts by weight of polybutylene adipate terephthalate in a small twin-screw extruder, and the extrusion was carried out to obtain a pellet-shaped resin composition.

[0106] Reference example The polybutylene adipate terephthalate polymer obtained in the above production example was freeze-dried and pulverized. Then, approximately 0.75 parts by weight of the chain extender hexamethylene diisocyanate and approximately 1.0 equivalent of the gel-reducing agent 2,5-dimethyl-2,5-hexanediol were added to 100 parts by weight of polybutylene adipate terephthalate in a small twin-screw extruder, and the extrusion was carried out to obtain a pellet-shaped resin composition.

[0107] Comparative Example 1 The polybutylene adipate terephthalate polymer obtained in the above production example was freeze-dried and pulverized. Then, approximately 0.75 parts by weight of the chain extender hexamethylene diisocyanate was added to 100 parts by weight of polybutylene adipate terephthalate in a small twin-screw extruder, and the extrusion was carried out to obtain a pellet-shaped resin composition.

[0108] Comparative Example 2 The polybutylene adipate terephthalate polymer obtained in the above production example was freeze-dried and pulverized. Then, approximately 0.5 parts by weight of the chain extender hexamethylene diisocyanate was added to 100 parts by weight of polybutylene adipate terephthalate in a small twin-screw extruder, and the extrusion was carried out to obtain a pellet-shaped resin composition.

[0109] Comparative Example 3 The polybutylene adipate terephthalate polymer obtained in the above production example was freeze-dried and pulverized. Then, approximately 0.75 parts by weight of the chain extender hexamethylene diisocyanate and approximately 0.2 equivalents of glycerol were added to 100 parts by weight of polybutylene adipate terephthalate in a small twin-screw extruder, and the extrusion was carried out to obtain a pelletized resin composition.

[0110] Measurement of molecular weight and molecular weight distribution Molecular weight and molecular weight distribution were measured using gel permeation chromatography (GPC, Waters PL-GPC220). The measurement conditions were as follows, and the measured values ​​are summarized in the table below. Column used: Polymer Laboratories PLgel MIX-B 300mm Evaluation temperature: 160℃ Solvent: 1,2,4-Trichlorobenzene Flow rate: 1mL / min Sample: 200 μl supplied at a concentration of 10 mg / 10 mL. Test curve: Use of polystyrene standards (9 types: molecular weight: 2,000 / 10,000 / 30,000 / 70,000 / 200,000 / 700,000 / 2,000,000 / 4,000,000 / 10,000,000)

[0111] Measurement of gel content The pelletized resin compositions produced in the above-mentioned examples, reference examples, and comparative examples were placed into a blow extrusion machine, and blow molding was carried out at a temperature of 160°C and under BUR1.7 conditions.

[0112] A film approximately 50 μm thick was prepared, and then cut into pieces approximately 5 cm in length and width to create measurement samples. The number of gels present in the film was then measured using a CCD camera. The gels exhibited a round shape, and their size was generally distributed between 20 and 500 μm. The measured number of gels was calculated as a ratio to Comparative Example 1, and the results are summarized in the table below. [Table 1]

[0113] Referring to the table above, it can be clearly confirmed that the resin composition according to one embodiment of the present invention shows no significant change in molecular weight compared to the comparative example, and at the same time, the generation of gel during extrusion molding is significantly reduced.

[0114] Therefore, the polybutylene adipate terephthalate resin composition according to one example of the present invention is considered to have excellent mechanical properties and appearance characteristics when applied to applications such as environmentally friendly consumer film.

Claims

1. Polybutylene adipate terephthalate resin, Chain extenders containing diisocyanate compounds, and The gel-reducing agent comprises one or more compounds selected from the group consisting of secondary alcohol compounds having 3 to 10 carbon atoms and tertiary alcohol compounds having 4 to 10 carbon atoms. The chain extender is contained in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the polybutylene adipate terephthalate. The gel-reducing agent is present in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the polybutylene adipate terephthalate. Polybutylene adipate terephthalate resin composition.

2. The polybutylene adipate terephthalate resin composition according to claim 1, wherein the gel-reducing agent comprises one or more selected from the group consisting of 2,5-dimethyl-2,5-hexanediol, 2-phenyl-2-propanol, 2,3-hexanediol, 2,5-hexanediol, 2-methyl-1-phenyl-2-propanol, 2,4-pentanediol, isosorbide, cyclobutanediol, cyclopentanediol, and cyclohexanediol.

3. The polybutylene adipate terephthalate resin composition according to claim 1, wherein the weight-average molecular weight of the polybutylene adipate terephthalate resin is 50,000 to 150,000.

4. The polybutylene adipate terephthalate resin composition according to claim 1, wherein the molecular weight distribution value of the polybutylene adipate terephthalate resin is 3 to 5.

5. A polymerization step to produce a polymer by condensation polymerization of 1,4-butanediol, adipic acid, and terephthalic acid in the presence of a catalyst; A mixing step in which a chain extender and a gel reducer are added to the polymer to produce a mixture; and The molding step includes extruding the mixture, In a method for producing polybutylene adipate terephthalate, The chain extender comprises a diisocyanate compound and is present in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the polybutylene adipate terephthalate. The gel-reducing agent comprises one or more compounds selected from the group consisting of secondary alcohol compounds having 3 to 10 carbon atoms and tertiary alcohol compounds having 4 to 10 carbon atoms, and is present in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the polybutylene adipate terephthalate. A method for producing polybutylene adipate terephthalate.

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