Polymers and their uses

Abstract

To provide a polymer that offers superior heat resistance while exhibiting superior biodegradable and mechanical properties, and applications thereof.SOLUTION: A polymer according to the present invention includes a plurality of triblock structures. In the triblock structure, polylactic acid units are linked via ester bonds to both ends of a polycaprolactone unit. The triblock structures are mutually linked via units including urethane bonds.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polymer and its uses. [Background technology]

[0002] Polylactic acid, polycaprolactone, and copolymers thereof have been proposed as biodegradable polymers (e.g., Patent Documents 1 to 6). However, while polylactic acid generally has excellent heat resistance, its high glass transition temperature makes it insufficient in biodegradability. Therefore, there is a problem that it is difficult to decompose in natural environments such as seawater and soil. Furthermore, polycaprolactone generally has insufficient heat resistance, which may limit the applications and versatility of polycaprolactone. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-3262 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-183042 [Patent Document 3] Special Publication No. 2019-505624 [Patent Document 4] Japanese Patent Application Publication No. 8-27256 [Patent Document 5] Japanese Patent Application Publication No. 2022-77948 [Patent Document 6] Japanese Patent Application Laid-Open No. 2016-210894 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the inventors' investigations, the polymers proposed in Patent Documents 1 to 6 have the following problems: The polymers proposed in Patent Documents 1 to 3 have insufficient biodegradability, and the polymer proposed in Patent Document 3 has low elongation at break and insufficient mechanical properties. The polymer of Patent Document 4 has low elongation at break and insufficient mechanical properties. The polymers of Patent Documents 5 and 6 have low modulus of elasticity and insufficient mechanical properties.

[0005] The present invention provides a polymer that has excellent heat resistance, biodegradability, and mechanical properties, and uses thereof. [Means for solving the problem]

[0006] The present invention has the following aspects. [1] A polymer having a plurality of triblock structures in which polylactic acid units are bonded to both ends of a polycaprolactone unit via ester bonds, and the plurality of triblock structures are bonded to each other via units containing urethane bonds. [2] The polymer according to [1], which has a glass transition temperature of 30°C or lower. [3] The polymer according to [1] or [2], wherein when the polymer is molded into a film under the following conditions, the film has a breaking elongation of 200% or more. Film molding conditions: Heat press molding using a 0.1 mm thick mold under conditions of 20 MPa, 10 minutes, and 180°C. [4] The polymer according to any one of [1] to [3], wherein when the polymer is molded into a film under the following conditions, the total light transmittance of the film is 85% or more and the haze of the film is 50% or less. Film molding conditions: Heat press molding using a 0.1 mm thick mold under conditions of 20 MPa, 10 minutes, and 180°C. [5] A molded article comprising the polymer according to any one of [1] to [4]. [Effects of the Invention]

[0007] According to the present invention, there are provided a polymer that has excellent heat resistance, biodegradability and mechanical properties, and uses thereof. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 shows a schematic diagram of an example of the chemical structure of the polymer of the present invention. [Figure 2] FIG. 2 shows a schematic diagram of an example of the chemical structure of a conventional polymer. DETAILED DESCRIPTION OF THE INVENTION

[0009] In this specification, the use of "to" to indicate a range of values ​​means that the values ​​before and after it are included as the lower and upper limits. The lower and upper limits of the ranges disclosed in this specification can be combined in any way to create new ranges.

[0010] <Polymer> The polymer of the present invention has a plurality of triblock structures in which polylactic acid units are bonded to both ends of a polycaprolactone unit via ester bonds, and the plurality of triblock structures are bonded to each other via units containing urethane bonds.

[0011] Figure 1 shows a schematic diagram of an example of the chemical structure of a polymer of the present invention. As shown in Figure 1, polymer 1 has a plurality of triblock structures 4, each of which has a polylactic acid unit 3 bonded to both ends of a polycaprolactone unit 2. These triblock structures 4 are repeatedly bonded together by a unit 5 containing a urethane bond. In contrast, in the conventional polymer 100 shown in Figure 2, polycaprolactone units 2 and polylactic acid units 3 are bonded together via units 5 containing urethane bonds. Furthermore, polycaprolactone units 2 and polylactic acid units 3 are bonded together via units 5 containing urethane bonds.

[0012] As shown in the example of Polymer 1, the polymers of the present invention have triblock structures bonded together by units containing urethane bonds. Polymers of the present invention having such a chemical structure exhibit properties not possible with conventional polymers. Specifically, they can simultaneously achieve excellent heat resistance, biodegradability, and mechanical properties. An example of a polymer of the present invention will be described in detail below. However, the following disclosure is a representative example, and the present invention is not limited to this disclosure.

[0013] (Triblock structure) In the triblock structure, polylactic acid units are bonded to both ends of the polycaprolactone unit, and the polycaprolactone unit and the polylactic acid unit are bonded via ester bonds.

[0014] The polycaprolactone unit is typically a polymer unit obtained by ring-opening polymerization of ε-caprolactone. In a typical example, the polycaprolactone unit has a unit based on ε-caprolactone. However, in one example, instead of or in addition to the unit based on ε-caprolactone, the polycaprolactone unit may have a unit based on a monomer in which an optional side chain, such as an alkyl chain, is bonded to any carbon atom of ε-caprolactone.

[0015] The number average molecular weight of the polycaprolactone unit is preferably 300 to 2,000, more preferably 400 to 10,000, and even more preferably 500 to 5,000. When the number-average molecular weight of the polycaprolactone unit is equal to or greater than the lower limit of the above-mentioned range, biodegradability is likely to be improved. When the number-average molecular weight of the polycaprolactone unit is equal to or less than the upper limit of the above-mentioned range, heat resistance and mechanical properties are likely to be improved. In addition, the polymer is easy to synthesize. The number average molecular weight of the polycaprolactone units can be adjusted during the synthesis of the triblock structure.

[0016] The polylactic acid unit is typically a polymer unit obtained by polymerizing lactide. In a typical example, the polylactic acid unit has a unit based on lactide. However, instead of or in addition to the unit based on lactide, the polylactic acid unit may have a unit based on a monomer in which an optional side chain, such as an alkyl chain, is bonded to any carbon atom of lactide. In one example, units based on each monomer are bonded to each other via ester bonds to form a polylactic acid unit.

[0017] The polylactic acid unit is bonded to both ends of the polycaprolactone unit via ester bonds containing oxygen atoms at both ends of the polycaprolactone unit. The repeating numbers and monomer unit compositions of the two polylactic acid units bonded to both ends of the polycaprolactone unit may be different or the same.

[0018] The number average molecular weight of the polylactic acid unit is preferably 300 to 30,000, more preferably 400 to 15,000, and even more preferably 500 to 10,000. When the number-average molecular weight of the polylactic acid unit is equal to or greater than the lower limit of the above-mentioned range, heat resistance is likely to be improved, and polymer synthesis is easy. When the number-average molecular weight of the polylactic acid unit is equal to or less than the upper limit of the above-mentioned range, biodegradability is likely to be improved. The number average molecular weight of the polylactic acid unit can be adjusted during the synthesis of the triblock structure.

[0019] (unit containing urethane bond) In the polymer of the present invention, a plurality of triblock structures are bonded to each other by a unit containing a urethane bond (—NH—CO—). 1 When 1 H NMR measurement is performed, a peak due to the "-NH-" of the urethane bond can be detected around 3.1 ppm. The polymer of the present invention can also be said to be a thermoplastic polyurethane polymer or a copolymer in which a polyol having a triblock structure is one constituent unit and a plurality of such constituent units are bonded together via units containing urethane bonds.

[0020] The unit containing a urethane bond is typically a unit based on an aliphatic diisocyanate, such as tetramethylene diisocyanate, dodecamethylene diisocyanate, hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, and 3-methylpentane-1,5-diisocyanate. However, compounds that can provide units containing urethane bonds are not limited to these examples of aliphatic diisocyanates.

[0021] (chemical structure) An example of the chemical structure of the polymer of the present invention is shown below.

[0022] [ka]

[0023] In the above chemical structural formula, R1 is not particularly limited, but is preferably an aliphatic ether having 2 to 12 carbon atoms derived from an aliphatic diol, or an aliphatic hydrocarbon having 1 to 12 carbon atoms. Examples of aliphatic diols include ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,3-butanediol, 2-methylpropanediol, 1,4-butanediol, neopentyl glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, dodecamethylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, and polyethylene glycol having a molecular weight of 1,000 or less. The aliphatic diols may be used alone or in combination of two or more.

[0024] In the above chemical structural formula, R2 is not particularly limited as long as it is a structure derived from an aliphatic diisocyanate, but is preferably an aliphatic hydrocarbon.

[0025] In the above chemical structural formula, m is 1 or more. m is preferably 1 to 150, more preferably 1 to 70, and even more preferably 1 to 35. When m is equal to or greater than the lower limit of the above numerical range, biodegradability is likely to be improved. When m is equal to or less than the upper limit of the above numerical range, heat resistance and mechanical properties are likely to be improved.

[0026] In the above chemical structural formula, n is 1 or more. n is preferably 4 to 500, more preferably 5 to 300, and even more preferably 6 to 150. When n is equal to or greater than the lower limit of the above numerical range, heat resistance is likely to be improved. When n is equal to or less than the upper limit of the above numerical range, biodegradability is likely to be improved.

[0027] In the above chemical structural formula, l is the number of repetitions of the triblock structure and the isocyanate structure attached thereto. l is preferably 1 to 300, and more preferably 2 to 100. When l is equal to or greater than the lower limit of the above numerical range, mechanical properties tend to be improved.

[0028] (Properties) The number average molecular weight (Mn) of the polymer is preferably from 10,000 to 300,000, more preferably from 20,000 to 200,000, and even more preferably from 30,000 to 100,000. When the Mn of the polymer is equal to or greater than the lower limit of the above-mentioned range, mechanical properties such as toughness tend to be improved.

[0029] The mass average molecular weight (Mw) of the polymer is preferably from 10,000 to 300,000, more preferably from 20,000 to 200,000, and even more preferably from 30,000 to 150,000. When the Mw of the polymer is equal to or greater than the lower limit of the above-mentioned range, mechanical properties such as toughness tend to be improved.

[0030] The glass transition temperature (Tg) of the polymer is preferably 30°C or lower, more preferably 5 to 25°C, and even more preferably 5 to 20°C. The lower limit of the Tg of the polymer is not particularly limited, and there is no problem even if it is 0°C or lower. When the Tg of the polymer is within the above numerical range, it is preferable in terms of preventing adhesion during storage of the film and formability. When the Tg of the polymer is equal to or lower than the above upper limit, the biodegradability of the polymer is even better. The Tg of the polymer is a value determined by the method described in the Examples below.

[0031] The melting point (Tm) of the polymer is preferably 130°C or higher, more preferably 140°C or higher, and even more preferably 145°C or higher. When the Tm of the polymer is equal to or higher than the lower limit of the above-mentioned range, the heat resistance of the polymer is further improved. The upper limit of the Tm of the polymer is not particularly limited. The Tm of a polymer is a value determined by the method described in the Examples below.

[0032] The crystallization temperature (Tc) of the polymer is not particularly limited. Tc can be appropriately set taking into consideration the moldability of the polymer. The Tc of the polymer is a value determined by the method described in the examples below.

[0033] The heat resistance of the polymer can be easily maintained by reducing the amount of polycaprolactone units used. For example, the desired heat resistance can be achieved by adjusting the ratio of the amounts or molecular weights of the polylactic acid units and the polycaprolactone units used in the triblock synthesis stage. The PLA ratio (%) is preferably 30-100, more preferably 40-95, and even more preferably 50-90. When the PLA ratio is equal to or greater than the lower limit of the range, the melting point is likely to increase, making it easier to maintain heat resistance. When the PLA ratio is equal to or less than the upper limit of the range, the Tg is likely to decrease. This is therefore advantageous in terms of the biodegradability of the polymer. However, the upper limit of the PLA ratio is not limited in any way in terms of heat resistance. The PLA ratio (%) can be adjusted by the amount charged in the synthesis stage, and can also be calculated by analyzing the oligomer described in the Examples below by NMR or GPC. PLA ratio (%) = (mass of lactide charged (charge value)) / (total charged mass) × 100 = (Molecular weight of PLA in oligomer (NMR analysis value)) / (Total molecular weight of oligomer (GPC analysis value)) × 100

[0034] When the polymer is hot-press molded into a film using a 0.1 mm thick mold at 20 MPa, 10 minutes, and 180°C, the film preferably has a breaking elongation of 200% or more, more preferably 300% or more, and even more preferably 320% or more. When the breaking elongation of the film is equal to or greater than the lower limit, the film has even better mechanical properties such as toughness. The upper limit of the breaking elongation of the film is not particularly limited. The breaking elongation is a value determined by the method described in the Examples below.

[0035] When the polymer is hot-press molded into a film using a 0.1 mm thick mold at 20 MPa for 10 minutes at 180°C, the tensile modulus of the film is preferably 200 MPa or more, more preferably 500 MPa or more, and even more preferably 800 MPa or more. When the tensile modulus of the film is equal to or greater than the lower limit, the mechanical properties are even more excellent. The upper limit of the tensile modulus of the film is not particularly limited. The tensile modulus is a value determined by the method described in the Examples below.

[0036] When the polymer is hot-press molded into a film using a 0.1 mm thick mold at 20 MPa, 10 minutes, and 180°C, the maximum stress of the film is preferably 10 MPa or more, more preferably 20 MPa or more, and even more preferably 28 MPa or more. When the maximum stress of the film is equal to or greater than the lower limit, the mechanical properties are even more excellent. The upper limit of the maximum stress of the film is not particularly limited. The maximum stress is a value determined by the method described in the Examples section below.

[0037] When the polymer was hot-pressed using a 0.1 mm thick mold at 20 MPa for 10 minutes at 180°C to form a film, the toughness of the film was 20 MJ / m 3 More than 40MJ / m is preferable. 3 More than 60MJ / m is more preferable. 3 The above is more preferable. When the toughness of the film is equal to or greater than the above lower limit, the mechanical properties are further improved. The upper limit of the toughness of the film is not particularly limited. The toughness is a value determined by the method described in the Examples below.

[0038] When the polymer is heat-pressed using a 0.1 mm thick mold at 20 MPa, 10 minutes, and 180°C to form a film, it is preferable that the total light transmittance of the film is 85% or more and the haze is 50% or less. The total light transmittance of the film is more preferably 88% or more, and even more preferably 90% or more. When the total light transmittance of the film is equal to or greater than the lower limit, the polymer has excellent transparency and visibility. The upper limit of the total light transmittance of the film is not particularly limited. The haze of the film is more preferably 45% or less, and even more preferably 40% or less. When the haze of the film is equal to or less than the upper limit, the polymer has excellent transparency and visibility. The lower limit of the haze of the film is not particularly limited. The total light transmittance and haze are values ​​determined by the methods described in the examples below.

[0039] When the polymer is heat-pressed using a 0.1 mm thick mold at 20 MPa, 10 minutes, and 180°C to form a film, the crystallinity of the film when treated at 0.1 MPa, 70°C, and 12 hours is preferably 50% or less, more preferably 48% or less, and even more preferably 46% or less. The lower limit of the crystallinity is not particularly limited, but is thought to be, for example, about 1%. The crystallinity is a value determined by X-ray analysis, as described in the Examples below.

[0040] (Polymer production method) The method for producing the polymer of the present invention is not particularly limited as long as it can produce a predetermined chemical structure. For example, the polymer of the present invention can be synthesized by adding polylactic acid units to both ends of a polycaprolactone unit to synthesize a triblock structure, and then carrying out a urethane reaction to bond the triblock structures together using units containing urethane bonds. In this case, after synthesizing the triblock structure, the triblock structure may be purified and recovered before the urethane reaction is carried out.

[0041] The polycaprolactone unit can be synthesized, for example, by polymerizing a monomer component (1) containing ε-caprolactone. Monomer component (1) typically contains ε-caprolactone. However, in one example, monomer component (1) can contain, instead of or in addition to ε-caprolactone, a monomer in which an optional side chain, such as an alkyl chain, is bonded to any carbon atom of ε-caprolactone. Alternatively, commercially available polycaprolactone or commercially available polycaprolactone diol can be used as the polycaprolactone unit. The molecular weight of the polycaprolactone unit may be controlled by the composition of the monomer component (1), the polymerization reaction, and the polymerization conditions. A commercially available product having a molecular weight within the desired range may also be purchased.

[0042] In synthesizing a triblock structure, for example, a lactide-containing monomer component (2) can be addition polymerized to both ends of a polycaprolactone unit. In one example, the monomer undergoes an addition reaction with the hydroxyl groups (-OH) at both ends of the polycaprolactone unit, resulting in the extension of each polylactic acid unit, resulting in the synthesis of a triblock structure.

[0043] Monomer component (2) typically includes lactide. However, in one example, monomer component (2) may include, instead of or in addition to lactide, a monomer in which an optional side chain, such as an alkyl chain, is bonded to any carbon atom of lactide. The molecular weight of the polylactic acid unit can be controlled by the composition of monomer component (2), the polymerization reaction, and the polymerization conditions.

[0044] In a typical example of a urethanization reaction, a triblock structure is reacted with an aliphatic diisocyanate to bond the triblock structures together through units containing urethane bonds, thereby producing a polymer having the chemical structure of the present invention.

[0045] (Mechanism of action) The polymer of the present invention has excellent heat resistance because each of the multiple triblock structures contains a polylactic acid unit. In addition, in each triblock structure, the polylactic acid units are bonded to both ends of the polycaprolactone unit via ester bonds. This allows the glass transition temperature of the polymer to be lowered while maintaining excellent heat resistance. A lower glass transition temperature allows the polymer to have sufficient mobility in the natural environment. Furthermore, the triblock structure, in which the polycaprolactone unit and the polylactic acid unit are linked by ester bonds, provides good biodegradability. As a result, the polymer is more susceptible to hydrolysis, and the polymer chains are more easily cleaved, resulting in a polymer with excellent biodegradability. In the polymer of the present invention, the triblock structures are bonded together by units containing urethane bonds. This provides the polymer with tenacity, i.e., toughness. As a result, the elongation at break and modulus of elasticity are increased, resulting in improved mechanical properties. Therefore, the polymer of the present invention is highly versatile and can be used in a variety of applications.

[0046] <Application> The applications of the polymers of the present invention are not particularly limited. For example, they can be used as materials for various articles such as films, sheets, injection-molded products, fibers, containers, medical products, and toys. Fibers can be applied to textile products such as nonwoven fabrics and woven fabrics. Films and containers can be used in various fields such as the food industry, clothing industry, medical products industry, and pharmaceutical industry. Potential applications in the medical and pharmaceutical fields include sutures, artificial bones, artificial skin, wound dressings, microcapsules and other DDS applications, and scaffolding materials for tissue and organ regeneration. Applications of the polymer of the present invention include, but are not limited to, binders in toners and thermal transfer inks.

[0047] The polymer of the present invention may be used alone or in the form of a composition in combination with additives, etc. The additives are not particularly limited and can be appropriately selected depending on the application and molding method. The polymer of the present invention can be applied to various molding methods. The molding method is not particularly limited. For example, various molding methods such as heat press molding, injection molding, solvent casting, and extrusion molding can be applied. Specific forms of the molded product include, but are not limited to, sheets, films, containers, petri dishes, plates, housings, fibers, and nonwoven fabrics. [Example]

[0048] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following descriptions.

[0049] Example 1 20 g of lactide (molar number: 0.139 mol, Mn: 144.13 g / mol) and 5 g of polycaprolactone diol (molar number: 0.0025 mol, Mn: 2000 g / mol, Sigma-Aldrich Corporation) were placed in a 200 mL three-neck flask and dried under reduced pressure. 20 mg of tin(II) 2-ethylhexanoate (molar number: 0.00005 mol, Mn: 405.12 g / mol) was added dropwise, and the atmosphere in the flask was repeatedly replaced with nitrogen to create a nitrogen atmosphere. The mixture was then stirred at 180°C for 3 hours under a nitrogen atmosphere to synthesize an oligomer with a triblock structure. After taking a sample for analysis, 412 mg of hexamethylene diisocyanate (molar number: 2.45 mmol, Mn: 168.2 g / mol) was added dropwise to the molten oligomer so that the NCO / OH ratio was 1 / 1 (mmol), and the reaction was carried out at 180°C for 30 minutes under a nitrogen atmosphere. The reaction product was then dissolved in chloroform and reprecipitated with methanol to recover the polymer. The recovered polymer was melted at 180°C and pressed at 20 MPa for 10 minutes to obtain a 0.1 mm thick film.

[0050] <Example 2> A polymer was synthesized in the same manner as in Example 1, except that the amount of hexamethylene diisocyanate used was changed so that NCO / OH = 2 / 1 (mmol) when hexamethylene diisocyanate was added dropwise, and a 0.1 mm thick film was obtained.

[0051] Example 3 A polymer was synthesized in the same manner as in Example 2. The recovered polymer was dissolved in chloroform and a film having a thickness of 0.1 mm was obtained by solvent casting.

[0052] Example 4 After synthesizing an oligomer having a triblock structure in Example 1, a step of reprecipitating the reaction product and removing impurities was added before forming urethane bonds between the triblock structures. Specifically, the following operations were performed. 20 g of lactide (molar number: 0.139 mol, Mn: 144.13 g / mol) and 5 g of polycaprolactone diol (molar number: 0.0025 mol, Mn: 2000 g / mol, Sigma-Aldrich) were placed in a 200 mL three-neck flask and dried under reduced pressure. 20 mg of tin(II) 2-ethylhexanoate (molar number: 0.00005 mol, Mn: 405.12 g / mol) was added dropwise, and the atmosphere in the flask was repeatedly replaced with nitrogen to create a nitrogen atmosphere. The mixture was stirred at 180°C for 3 hours under a nitrogen atmosphere to synthesize a triblock structure. The reactant was then dissolved in chloroform and reprecipitated with methanol, and the oligomer with a triblock structure was recovered. 6 g of the recovered oligomer was placed in a separate flask and melted at 180°C. 68 mg of hexamethylene diisocyanate (molar number: 0.40 mmol, Mn: 168.2 g / mol) was added dropwise to the molten triblock structure so that the NCO / OH ratio was 1 / 1 (mmol), and the reaction was carried out at 180°C for 30 minutes under a nitrogen atmosphere. The reactant was then dissolved in chloroform and reprecipitated with methanol to recover the polymer. The recovered polymer was melted at 180°C and pressed at 20 MPa for 10 minutes to obtain a 0.1 mm thick film.

[0053] <Comparative Example 1> 20 g of lactide (molar number: 0.139 mol, Mn: 144.13 g / mol) and 0.106 g of polycaprolactone diol (molar number: 0.002 mol, Mn: 530 g / mol, Sigma-Aldrich) were placed in a 200 mL three-neck flask and dried under reduced pressure. 1.62 mg of tin(II) 2-ethylhexanoate (molar number: 0.00004 mol, Mn: 405.12 g / mol) was added dropwise, and the atmosphere in the flask was repeatedly purged with nitrogen to create a nitrogen atmosphere. The mixture was then stirred at 180°C for 3 hours under a nitrogen atmosphere to synthesize a polymer with a triblock structure. The reactant was then dissolved in chloroform and reprecipitated with methanol to recover the polymer. The recovered polymer was melted at 180°C and pressed at 20 MPa for 10 minutes to obtain a 0.1 mm thick film. In this way, in Comparative Example 1, a polymer having a high molecular weight was synthesized by the ester bond in the triblock structure without carrying out a urethane reaction.

[0054] <Comparative Example 2> A 200 mL three-neck flask was charged with 40 g of lactide (molar number: 0.278 mol, Mn: 144.13 g / mol) and 0.8 g of polycaprolactone diol (molar number: 0.004 mol, Mn: 2000 g / mol, Sigma-Aldrich Corporation), which was then dried under reduced pressure and dehydrated. 3.24 mg of tin(II) 2-ethylhexanoate (molar number: 0.00008 mol, Mn: 405.12 g / mol) was added dropwise, followed by repeated nitrogen substitution to create a nitrogen atmosphere inside the flask. The mixture was then stirred at 180°C for 3 hours under a nitrogen atmosphere to synthesize a polymer with a triblock structure. The reactant was then dissolved in chloroform and reprecipitated with methanol to recover the polymer. The recovered polymer was melted at 180°C and pressed at 20 MPa for 10 minutes to obtain a 0.1 mm thick film. In this way, in Comparative Example 2, a polymer having a high molecular weight was synthesized by the ester bond in the triblock structure without carrying out a urethane reaction.

[0055] <Comparative Example 3> 20 g of lactide (molar number: 0.139 mol, Mn: 144.13 g / mol) and 5 g of polycaprolactone diol (molar number: 0.025 mol, Mn: 2000 g / mol, Sigma-Aldrich) were placed in a 200 mL three-neck flask and dried under reduced pressure. 20 mg of tin(II) 2-ethylhexanoate (molar number: 0.00005 mol, Mn: 405.12 g / mol) was added dropwise, and the atmosphere in the flask was repeatedly purged with nitrogen to create a nitrogen atmosphere. The mixture was then stirred at 180°C for 3 hours under a nitrogen atmosphere to synthesize a polymer with a triblock structure. The reactant was then dissolved in chloroform and reprecipitated with methanol to recover the polymer. The recovered polymer was melted at 180°C and pressed at 20 MPa for 10 minutes to obtain a 0.1 mm thick film. In this way, a polymer with a high molecular weight was synthesized by the ester bond in the triblock structure without performing a urethane reaction in Comparative Example 3. In addition, the polymer was synthesized so that the molecular weight was smaller than those of Comparative Examples 1 and 2.

[0056] <Comparative Example 4> 20 g of lactide (molar number: 0.139 mol, Mn: 144.13 g / mol) and 0.225 g of 1,4-butanediol (molar number: 0.0025 mol, Mn: 90.121 g / mol) were placed in a 200 mL three-neck flask and dried under reduced pressure. 20 mg of tin(II) 2-ethylhexanoate (molar number: 0.00005 mol, Mn: 405.12 g / mol) was added dropwise, and the atmosphere in the flask was repeatedly purged with nitrogen to create a nitrogen atmosphere. The mixture was then stirred at 180°C for 3 hours under a nitrogen atmosphere to synthesize polylactic acid diol. The reactant was then dissolved in chloroform and reprecipitated with methanol, and the polylactic acid diol was recovered. 5 g of the recovered polylactic acid diol (molar number: 0.41 mmol) and 0.82 g of polycaprolactone diol (molar number: 0.41 mmol, Mn: 2000 g / mol, Sigma-Aldrich Corporation) were placed in a separate flask and melted at 180 °C. 137.2 mg of hexamethylene diisocyanate (molar number: 0.82 mmol, Mn: 168.2 g / mol) was added dropwise to the molten oligomer so that the NCO / OH ratio was 1 / 1 (mmol). The reaction was carried out at 180 °C for 30 minutes under a nitrogen atmosphere. The reactant was then dissolved in chloroform and reprecipitated with methanol to recover the polymer. The recovered polymer was melted at 180 °C and pressed at 20 MPa for 10 minutes to obtain a 0.1 mm thick film. In this way, in Comparative Example 4, an oligomer having a triblock structure was not synthesized, but a polylactic acid diol was synthesized first, and then the polylactic acid diol and polycaprolactone diol were subjected to a urethane reaction. The polymer obtained in Comparative Example 4 is a copolymer of polylactic acid diol and polycaprolactone diol with a urethane bond. Comparative Example 4 relates to a method of copolymerization without using a triblock structure. Comparative Example 4 was carried out with reference to JP 2006-183042 A.

[0057] <Comparative Example 5> In a 200 mL three-neck flask, 5 g of commercially available polylactic acid (molar number: 1 mmol, Mn: 5000 g / mol, Sigma-Aldrich Corporation) and 1 g of polycaprolactone diol (molar number: 0.5 mmol, Mn: 2000 g / mol, Sigma-Aldrich Corporation) were melted at 180 °C. 168.2 mg of hexamethylene diisocyanate (molar number: 1 mmol, Mn: 168.2 g / mol) was added dropwise to the molten oligomer so that the NCO / OH ratio was 1 / 1 (mmol). The reaction was carried out at 180 °C for 30 minutes under a nitrogen atmosphere. The reactant was then dissolved in chloroform and reprecipitated with methanol to recover the polymer. The recovered polymer was melted at 180 °C and pressed at 20 MPa for 10 minutes to obtain a 0.1 mm thick film. In this way, commercially available polylactic acid and polycaprolactone diol were subjected to a urethane reaction in Comparative Example 5. The polymer obtained in Comparative Example 5 was a copolymer of commercially available polylactic acid and polycaprolactone diol with a urethane bond.

[0058] <Comparative Example 6> In a 200 mL three-neck flask, 4.9 g of commercially available polylactic acid (molar number: 0.49 mmol, Mn: 10,000 g / mol, Sigma-Aldrich) and 0.49 g of polycaprolactone diol (molar number: 0.245 mmol, Mn: 2,000 g / mol, Sigma-Aldrich) were melted at 180 °C. To the molten oligomer, 82.42 mg of hexamethylene diisocyanate (molar number: 0.49 mmol, Mn: 168.2 g / mol) was added dropwise to achieve an NCO / OH ratio of 1 / 1 (mmol). The reaction was carried out at 180 °C for 30 minutes under a nitrogen atmosphere. The reactant was then dissolved in chloroform and reprecipitated with methanol to recover the polymer. The recovered polymer was melted at 180 °C and pressed at 20 MPa for 10 minutes to obtain a 0.1 mm thick film. In this way, commercially available polylactic acid and polycaprolactone diol were subjected to a urethane reaction in Comparative Example 6. The polymer obtained in Comparative Example 6 was a copolymer of commercially available polylactic acid and polycaprolactone diol with a urethane bond.

[0059] <Comparative Example 7> In a 200 mL three-neck flask, 8 g of polycaprolactone diol (molar number: 4 mmol, Mn: 2000 g / mol, Sigma-Aldrich product) was melted at 180°C. 672.8 mg of hexamethylene diisocyanate (molar number: 4 mmol, Mn: 168.2 g / mol) was added dropwise to the molten polycaprolactone diol so that the NCO / OH ratio was 1 / 1 (mmol), and the mixture was allowed to react at 180°C for 30 minutes under a nitrogen atmosphere. The reaction product was then dissolved in chloroform and reprecipitated with methanol to recover the polymer. The recovered polymer was melted at 180°C and pressed at 20 MPa for 10 minutes to obtain a 0.1 mm thick film. In this way, in Comparative Example 7, a urethane reaction was carried out using only polycaprolactone diol.

[0060] <Comparative Example 8> 20 g of lactide (molar number: 0.139 mol, Mn: 144.13 g / mol) and 0.225 g of 1,4-butanediol (molar number: 0.0025 mol, Mn: 90.121 g / mol) were placed in a 200 mL three-neck flask and dried under reduced pressure. 20 mg of tin(II) 2-ethylhexanoate (molar number: 0.00005 mol, Mn: 405.12 g / mol) was added dropwise, and the atmosphere in the flask was repeatedly purged with nitrogen to create a nitrogen atmosphere. The mixture was then stirred at 180°C for 3 hours under a nitrogen atmosphere to synthesize polylactic acid diol. The reactant was then dissolved in chloroform and reprecipitated with methanol, and the polylactic acid diol was recovered. 7.5 g (molar number 0.64 mmol) of the recovered polylactic acid diol was placed in another flask and melted at 180°C. 107 mg of hexamethylene diisocyanate (molar number: 0.64 mmol, Mn: 168.2 g / mol) was added dropwise to the molten polylactic acid diol so that NCO / OH = 1 / 1 (mmol), and the mixture was allowed to react at 180°C for 30 minutes under a nitrogen atmosphere. The reaction product was then dissolved in chloroform and reprecipitated with methanol to recover the polymer. The recovered polymer was melted at 180°C and pressed at 20 MPa for 10 minutes to obtain a 0.1 mm thick film. In this way, in Comparative Example 8, a urethane reaction was carried out using only polylactic acid diol.

[0061] <Comparative Example 9> 20 g of lactide (molar number: 0.139 mol, Mn: 144.13 g / mol) and 0.225 g of 1,4-butanediol (molar number: 0.0025 mol, Mn: 90.121 g / mol) were placed in a 200 mL three-neck flask and dried under reduced pressure. 20 mg of tin(II) 2-ethylhexanoate (molar number: 0.00005 mol, Mn: 405.12 g / mol) was added dropwise, and the atmosphere in the flask was repeatedly purged with nitrogen to create a nitrogen atmosphere. The mixture was then stirred at 180°C for 3 hours under a nitrogen atmosphere to synthesize polylactic acid diol. The reactant was then dissolved in chloroform and reprecipitated with methanol, and the polylactic acid diol was recovered. 3 g of the recovered polylactic acid diol (molar number: 0.26 mmol) and 2 g of polycaprolactone diol (molar number: 1 mmol, Mn: 2000 g / mol, Sigma-Aldrich product) were placed in a separate flask and melted at 180°C. 211.3 mg of hexamethylene diisocyanate (molar number: 1.26 mmol, Mn: 168.2 g / mol) was added dropwise to the molten oligomer so that the NCO / OH ratio was 1 / 1 (mmol), and the reaction was carried out at 180°C for 30 minutes under a nitrogen atmosphere. The reaction product was then dissolved in chloroform and reprecipitated with methanol to recover the polymer. The recovered polymer was melted at 180°C and pressed at 20 MPa for 10 minutes to obtain a 0.1 mm thick film. In Comparative Example 9, after the synthesis of polylactic acid diol, a urethane reaction was carried out with polycaprolactone diol. Comparative Example 9 relates to a method of copolymerization without using a triblock structure, similar to Comparative Example 4. Similar to Comparative Example 4, Comparative Example 9 was carried out with reference to JP-A-2006-183042.

[0062] <Comparative Example 10> For comparison, commercially available polycaprolactone (Mn 8,0000) (a product of Sigma-Aldrich) was melted at 180°C and pressed at 20 MPa for 10 minutes to obtain a film with a thickness of 0.1 mm.

[0063] <Comparative Example 11> For comparison, commercially available polylactic acid (Nature Works product "Ingeo Biopolymer 2003D") was melted at 180°C and pressed at 20 MPa for 10 minutes to obtain a film with a thickness of 0.1 mm.

[0064] <Measurement and evaluation> The films of the examples were measured and evaluated as follows.

[0065] (Mw, Mn) The molecular weights (Mw, Mn) of the polymers were measured by gel permeation chromatography (GPC) molecular weight analysis. Specifically, a GPC (HLC-8420, manufactured by Tosoh Corporation) was used, and measurements were performed using an RI detector. The column used was a TSKgel GMHHR-M (manufactured by Tosoh Corporation). The GPC eluent was chloroform (CHCl3). The column temperature was 40°C, and the flow rate was 1.0 ml / min. The standard sample used for the measurements was polystyrene (standard polystyrene kit PStQuick, manufactured by Tosoh Corporation). A calibration curve was created in polystyrene equivalent, and the molecular weights (Mw, Mn) were calculated.

[0066] ( 1 H NMR analysis) Using a nuclear magnetic resonance spectrometer (JNM-EC400, JEOL Ltd.), 1 H NMR analysis was performed. The number of accumulations was 32, and chloroform-d (CDCl3) was used as the deuterated solvent. The NMR spectrum was observed for the presence or absence of a peak (around 3.1 ppm) due to the "-NH-" of the urethane bond.

[0067] (film molding) The film forming ability was evaluated according to the following criteria. A: Film formation was possible, and physical properties could be measured. B: The film crumbled during molding, making it impossible to measure its physical properties.

[0068] (Tg, Tm, Tc) The Tg (°C), Tm (°C), and Tc (°C) of the polymer were measured using a DSC (high-sensitivity differential scanning calorimeter DMS-6220, Hitachi High-Tech Science Corporation). The measurement temperature range was -80°C to 200°C, and the heating rate was 10°C / min.

[0069] (Tensile test) A dumbbell-shaped tensile test specimen with a balancing part length of 20 mm and width of 4 mm was prepared and measured using a tensile tester (tabletop precision universal testing machine AGS-X, Shimadzu Corporation). The test conditions were in accordance with JIS K7127. The crosshead speed was 10 mm / min, and the distance between the grippers was 20 mm. The tensile modulus (MPa), maximum stress (MPa), elongation at break (%), and toughness (MJ / m 3 ) was measured.

[0070] (Total light transmittance, haze) A haze meter (NDH-4000, Nippon Denshoku Industries Co., Ltd.) was used. Total light transmittance was measured in accordance with JIS K7361-1:1997. Haze was measured in accordance with JIS K7136:2000.

[0071] (crystallinity) An X-ray diffractometer (RINT-Ultimate III, Rigaku Corporation) was used. Measurements were performed at a tube voltage of 40 kW, a tube current of 40 mA, a measurement range of a diffraction angle 2θ = 5 to 30°, and a scan speed of 1.0° / min. The crystallinity (%) was calculated using the following formula. Crystallinity (%) = (crystalline peak area / (crystalline peak area + amorphous peak area)) × 100

[0072] <Result> The measurement results and evaluation results for each example are shown in Tables 1 and 2.

[0073] [Table 1]

[0074] [Table 2]

[0075] [Table 3]

[0076] As shown in Tables 1 and 2, in Examples 1 to 4, polymers were obtained that had sufficiently high Tm, excellent heat resistance, and low Tg. These polymers with low Tg are considered to have excellent biodegradability. Furthermore, in Examples 1 to 4, when formed into films, the elongation at break was high, indicating excellent mechanical properties. In contrast, in Comparative Examples 1 to 11, it was not possible to achieve both a low Tg and good mechanical properties. In Comparative Examples 5 and 7, no Tg was detected.

[0077] In Comparative Examples 3, 5, 6, and 9, the films were too hard and brittle. As a result, the films broke during molding, and the tensile modulus (MPa), maximum stress (MPa), elongation at break (%), and toughness (MJ / m 3 ) could not be measured. In Comparative Example 7, the film was too soft and brittle. Therefore, the film broke during molding, and the tensile modulus (MPa), maximum stress (MPa), elongation at break (%) and toughness (MJ / m 3 ) could not be measured.

[0078] As shown in Table 3, the polymers of the examples exhibited good appearance, transparency and visibility when formed into films. [Industrial Applicability]

[0079] According to the present invention, there are provided a polymer that has excellent heat resistance, biodegradability and mechanical properties, and uses thereof. [Explanation of symbols]

[0080] 1. Polymer 2 polycaprolactone units 3 Polylactic Acid Unit 4 Triblock structure 5 Units containing urethane bonds

Claims

1. A polymer comprising: The polymer has a plurality of triblock structures in which polylactic acid units are bonded to both ends of a polycaprolactone unit via ester bonds, Multiple triblock structures are bonded to each other by units containing urethane bonds, The polymer has a glass transition point of 5 to 20°C, a melting point of 146°C or higher, a number average molecular weight of the polylactic acid unit of 300 to 30,000, a number average molecular weight of the polycaprolactone unit of 300 to 5,000, and a number average molecular weight of the polymer of 10,000 to 300,000.

2. A polymer described in claim 1, represented by the following structural formula: 【Chemistry 1】 (In the above structural formula, R 1 is an aliphatic ether group having 2 to 12 carbon atoms derived from an aliphatic diol or an aliphatic hydrocarbon group having 1 to 12 carbon atoms; R 2 is an aliphatic hydrocarbon group; m is 1 to 150; n is 4 to 500; and l is 1 to 300.)

3. 2. The polymer according to claim 1, wherein when the polymer is formed into a film under the following conditions, the film has an elongation at break of 200% or more. Film molding conditions: Heat press molding was performed using a mold with a thickness of 0.1 mm under conditions of 20 MPa, 10 minutes, and 180°C.

4. 2. The polymer according to claim 1, wherein when the polymer is formed into a film under the following conditions, the total light transmittance of the film is 85% or more and the haze of the film is 50% or less. Film molding conditions: Heat press molding was performed using a mold with a thickness of 0.1 mm under conditions of 20 MPa, 10 minutes, and 180°C.

5. A molded article comprising the polymer according to any one of claims 1 to 4.

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