Polyester resin and molded article

Abstract

The present invention provides a polyester resin having a structural unit represented by the following general formula (1) and a number average molecular weight of 42,000 to 50,000, and a molded article obtained by molding the polyester resin. [In general formula (1), m represents an integer of 2 to 10, and n represents an integer of 230 to 275. ]

Description

Technical Field

[0001] This invention relates to polyester resin and molded parts. Background Technology

[0002] Polyester resins typically exhibit excellent physical and chemical properties, as well as excellent processability, such as blow molding, extrusion molding, and injection molding. Therefore, polyester resins have a wide range of applications and are widely used as engineering plastics in industrial products. Requirements for industrial products include the ability to be molded in a short time, excellent mechanical properties, long-term stability, and low environmental impact (e.g., carbon footprint). From these perspectives, novel biomass-derived polyester resins have been considered examples. A representative example is polyester resins synthesized using biomass-derived furan dicarboxylic acids (such as polyethylene furanate). Polyethylene furanate, etc., uses raw materials manufactured from biomass cultivated by absorbing carbon dioxide, which enables a reduced carbon footprint and exhibits excellent mechanical properties. However, when such novel polyester resins are molded into industrial products, for example, through injection molding, many aspects of moldability remain unclear, and the properties required for industrial products (such as mechanical properties) may not be fully obtained. This can lead to problems such as the inability to obtain molded parts or insufficient functionality as industrial products. Furthermore, a problem in practical use is that quality may become unstable due to increased degree of polymerization.

[0003] Patent Document 1 addresses the quality instability caused by the increased degree of polymerization of polyethylene furanate, etc., as described above, and discloses a novel polyester resin and its manufacturing method, which aims to produce molded parts exhibiting excellent quality stability (hydrolysis resistance) even with increased degree of polymerization. This is characterized by its molecular structure and number-average molecular weight. It has been found that by having predetermined structural units and a number-average molecular weight of 110,000 to 190,000, polyester resins exhibit stable quality even with increased degree of polymerization.

[0004] Reference List

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2010-280767 Summary of the Invention

[0007] However, while the quality can be stabilized by increasing the degree of polymerization of polyester resin, the molding conditions, mechanical properties, and other aspects remain to be clarified, and it is unknown whether polyester resins with such a structure can be used as industrial products. Furthermore, since the fluidity of resins tends to decrease with increasing degree of polymerization, a number average molecular weight of 110,000 to 190,000 will be accompanied by a decrease in fluidity, which may not be suitable depending on the molding method.

[0008] The present invention was made in view of such problems in the prior art. Furthermore, an object of the present invention is to provide a polyester resin derived from biomass and molded articles using the polyester resin, which exhibits excellent mechanical properties and is suitable for use as industrial products.

[0009] The polyester resin according to one aspect of the invention has structural units represented by the general formula (1) given below and a number-average molecular weight of 42,000 to 50,000.

[0010]

[0011] [In general formula (1), m represents an integer from 2 to 10, and n represents an integer from 230 to 275.]

[0012] Furthermore, according to one aspect of the present invention, the molded part is obtained by molding the aforementioned polyester resin.

[0013] According to the present invention, it is possible to provide a polyester resin derived from biomass and a molded part using the polyester resin, the polyester resin exhibiting excellent mechanical properties and suitable for use as an industrial product. Detailed Implementation

[0014] The polyester resin of this embodiment has a structural unit represented by the following general formula (1) and a number-average molecular weight of 42,000 to 50,000.

[0015]

[0016] [In general formula (1), m represents an integer from 2 to 10, and n represents an integer from 230 to 275.]

[0017] In the polyester resin of this embodiment, the molecular weight and flowability of polyethylene furanate were considered to address problems in the prior art. Generally, the flowability of a resin decreases with increasing molecular weight. In injection molding of resins with high molecular weights, cycle time increases, and defects are more likely to occur. Therefore, an appropriate molecular weight range is set to achieve efficient injection molding. Accordingly, for polyethylene furanate with different degrees of polymerization, the molecular weight was measured by GPC measurement, and the flowability was evaluated by MFR measurement. Based on the results, patterns that satisfy the properties (formability, mechanical properties) required for industrial products obtained by injection molding were discovered.

[0018] In general formula (1), m represents an integer from 2 to 10. When m is less than 2, the target product cannot be obtained because the raw materials are unstable. When m exceeds 10, the thermal properties of the molded part may decrease. m is preferably 2 to 10, and more preferably 2 to 8.

[0019] Furthermore, in general formula (1), n ​​represents an integer from 230 to 275. When n is less than 230, the tensile strength decreases. When n exceeds 275, the molecular weight increases and the flowability decreases. n is preferably from 230 to 275.

[0020] The number-average molecular weight of the polyester resin in this embodiment is 42,000 to 50,000. When the number-average molecular weight is less than 42,000, the tensile strength decreases. When the number-average molecular weight exceeds 50,000, the flowability decreases, and the suitability for injection molding decreases. The number-average molecular weight is preferably 42,000 to 50,000. Note that the number-average molecular weight can be measured in the following manner: The sample is dissolved in hexafluoroisopropanol (HFIP), and gel permeation chromatography is performed while using polymethyl methacrylate (PMMA) as a standard, and the number-average molecular weight is calculated therefrom.

[0021] When the polyester resin of this embodiment has a number-average molecular weight falling within the above-mentioned range, the molded part obtained by molding the polyester resin exhibits excellent mechanical properties. Specifically, the tensile strength can be from 53 MPa to 91 MPa. Furthermore, the tensile modulus can be from 2,480 MPa to 3,913 MPa.

[0022] The polyester resin of this embodiment can be compounded with various additives such as antioxidants, nucleating agents, fillers, heat stabilizers, hydrolysis inhibitors, flame retardants, antistatic agents, release agents, and ultraviolet absorbers. Examples of antioxidants include, for example, Irganox 1010 (hindered phenolic antioxidant) manufactured by BASF. Examples of nucleating agents include talc, boron nitride, silica, layered silicates, and polyethylene wax.

[0023] The polyester resin of this embodiment can be manufactured as follows. It is obtained by polycondensation of at least one dicarboxylic acid component containing furan dicarboxylic acid or its esterified derivative (furan dicarboxylic acid, acidic halide, etc.) and a diol component containing an alkylene glycol or its esterified derivative (acetylation). Examples of alkylene glycols include aliphatic glycols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,10-decanediol.

[0024] 2,5-Furandicarboxylic acid, as a furan dicarboxylic acid, can be used as a raw material. 2,5-Furandicarboxylic acid can be obtained from biomass such as cellulose, glucose, fructose, or mucilage by known methods. Thus, by using the furan ring, biomass-derived materials can be used as aromatic rings that contribute to heat resistance.

[0025] In this embodiment, dicarboxylic acid components other than furan dicarboxylic acid can be used as dicarboxylic acid components for copolymerization. Examples of such other dicarboxylic acid components include: aliphatic dicarboxylic acids, such as oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, undecanoic acid, dodecanoic acid, octadecanoic acid, fumaric acid, maleic acid, itaconic acid, aconitic acid, citraconic acid, and dimer acids; aromatic dicarboxylic acids, such as terephthalic acid, phthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and 4,4'-biphenyl dicarboxylic acid; and alicyclic dicarboxylic acids, such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 2,5-norbornenedicarboxylic acid, and tetrahydrophthalic acid.

[0026] As a polymerization method for the polyester resin of this embodiment, a direct polymerization method can be used, in which furan dicarboxylic acid and ethylene glycol, as well as other optional dicarboxylic acid components and glycol components, react directly. Alternatively, a transesterification method can be used, in which a dimethyl ester of furan dicarboxylic acid (optionally including methyl esters of other dicarboxylic acids) and ethylene glycol (optionally including other glycol components) undergo a transesterification reaction.

[0027] Meanwhile, the number-average molecular weight of the polyester resin in this embodiment can be adjusted by adjusting the condensation reaction time, changing the type of catalyst, and adjusting the concentration of catalyst added.

[0028] <Molded Parts>

[0029] The molded part of this embodiment is obtained by molding the polyester resin described above. As described above, the molded part of this embodiment is obtained by molding the polyester resin described above, and therefore, excellent mechanical properties are obtained. Specifically, the tensile strength can be from 53 MPa to 91 MPa. Furthermore, the tensile modulus can be from 2,480 MPa to 3,913 MPa.

[0030] The method for manufacturing the molded part according to this embodiment is not particularly limited, and known methods can be used. For example, the polyester resin of this embodiment, together with the required additives, is fed into an extruder, melt-kneaded, and granulated. The resulting granules are then fed into an injection molding machine equipped with a predetermined mold and injection molded. In this way, molded parts can be manufactured.

[0031] Examples of applications of the molded parts in this embodiment include various components, films, containers, fibers, etc., used in the electrical and electronic fields and automobiles.

[0032] Example

[0033] The present embodiment is described in further detail below with reference to the embodiments and comparative examples, but the present embodiment is not limited to those embodiments.

[0034] As raw materials, 50 parts by weight of dimethyl furanate, 37 parts by weight of ethylene glycol, and 0.015 parts by weight of tetra(isopropyl) titanate were added to a reaction vessel, and the interior of the reaction vessel was purged with nitrogen. The reaction vessel was then placed in an oil bath, stirred, and the mixture was heated to 160°C. The temperature was gradually increased to 210°C, and the reaction was carried out for 6 hours while collecting the distillate. Subsequently, the temperature was increased to 220°C, while the pressure was gradually decreased to below 50 Pa. After reaching 220°C and below 50 Pa, the reaction was continued for 15 hours to complete the polycondensation reaction. Thus, a polyester resin (polyethylene furanate (PEF) resin) was obtained.

[0035] Polyester resin (polyethylene furanate (PEF) resin) was obtained in a similar manner to Example 1, except that the polycondensation reaction was carried out for 24 hours.

[0036] Polyester resin (polyethylene furanate (PEF) resin) was obtained in a similar manner to Example 1, except that the polycondensation reaction was carried out for 4 hours.

[0037] Polyester resin (polyethylene furanate (PEF) resin) was obtained in a similar manner to Example 1, except that the polycondensation reaction was carried out for 8 hours.

[0038] Polyester resin (polybutylene terephthalate (PBT) resin) manufactured by Sigma-Aldrich (granules, average Mv up to 38,000) was used.

[0039] <<Measurement of Number-Average Molecular Weight>>

[0040] The samples were dissolved in hexafluoroisopropanol (HFIP), and the molecular weight distribution was measured using a GPC-104 (Shoko Science Co., Ltd.). Polymethyl methacrylate (PMMA) was used as a standard. The measurement results are shown in Table 1.

[0041] <<Measuring Melt Flow Rate>>

[0042] Melt flow rate (MFR) was measured according to JIS K 7210-1 using a melt flow index tester No. 120-FWP (YASUDA SEIKI SEISAKUSHO, LTD.). The measurement results are shown in Table 1.

[0043] Table 1

[0044]

[0045] <<Measurement of Tensile Strength and Tensile Modulus>>

[0046] According to JIS K 7161-1 and JIS K 7161-2, the tensile strength and tensile modulus of the polyester resin 5A dumbbell test specimens obtained in each example and comparative example were measured using an Autograph AGX-V apparatus (Shimadzu Corporation). The measurement results are shown in Table 2.

[0047] <<Measurement of Flexural Temperature under Load>>

[0048] According to JIS K 7191, the flexural temperature under load was measured on strip test specimens (80 mm × 10 mm × 12 mm) of polyester resin obtained in each example and comparative example using a heat distortion tester No. 148-HD-PC (YASUDA SEIKISEISAKUSHO, LTD.). The measurement results are shown in Table 2.

[0049] Table 2

[0050]

[0051] As shown in Table 2, excellent results were obtained in each of the following aspects in Examples 1 and 2: tensile strength, tensile modulus of elasticity, and flexural temperature under load. In contrast, although molded parts were obtained in Comparative Examples 1 and 2, at least one evaluation was poor.

[0052] All contents of Japanese Patent Application No. 2023-133267 (filed on August 18, 2023) are incorporated herein by reference.

[0053] The above describes this embodiment. However, this embodiment is not limited thereto, and various modifications can be made within the spirit of this embodiment.

Claims

1. A polyester resin, characterized in that, The polyester resin has structural units represented by the following general formula (1) and a number-average molecular weight of 42,000 to 50,000. [In general formula (1), m represents an integer from 2 to 10, and n represents an integer from 230 to 275].

2. The polyester resin according to claim 1, wherein, The tensile strength is from 53 MPa to 91 MPa, and the tensile modulus of elasticity is from 2,480 MPa to 3,913 MPa.

3. A molded part obtained by molding the polyester resin according to claim 1 or 2.

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