Polyester resin and molded article

Abstract

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

Description

Polyester resin and moldings

[0001] The present invention relates to a polyester resin and a molded article.

[0002] Polyester resins generally have excellent physical and chemical properties, as well as excellent processing characteristics for blow molding, extrusion molding, injection molding, and other processes. Therefore, they have a wide range of applications and are widely used as engineering plastics in industrial products. Requirements for industrial products include short moldability, excellent mechanical properties, long-term stability, and a low environmental impact (e.g., carbon footprint). From these perspectives, novel biomass-derived polyester resins have been investigated, and representative examples include polyester resins (e.g., polyethylene furanoate) synthesized using biomass-derived furandicarboxylic acid. Polyethylene furanoate and other polyester resins are produced using raw materials produced from biomass grown by absorbing carbon dioxide, which allows for a reduced carbon footprint and excellent mechanical properties. However, when such novel polyester resins are injection-molded into industrial products, for example, their moldability remains unclear, and they do not necessarily achieve the properties (e.g., mechanical properties) required for industrial products. This can lead to problems such as failure to obtain molded products or insufficient functionality as industrial products. Furthermore, a problem that arises when putting the polymer into practical use is that the quality becomes unstable due to the high degree of polymerization.

[0003] Patent Document 1 focuses on the quality instability caused by high polymerization of polyethylene furanoate and the like, and describes a novel polyester resin and a method for producing the same for producing molded articles with excellent quality stability (hydrolysis resistance) even at high polymerization degrees. The characteristics of the polyester resin are its molecular structure and number-average molecular weight. It has been found that by having a predetermined structural unit and a number-average molecular weight of 110,000 to 190,000, the quality is stable even at high polymerization degrees.

[0004] JP 2010-280767 A

[0005] However, although it is possible to stabilize the quality of polyester resins by increasing the degree of polymerization, the molding conditions, mechanical properties, etc. have not been clarified, and it is unclear whether polyester resins with such structures can be used in 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 is accompanied by a decrease in fluidity and is not necessarily suitable for some molding methods.

[0006] The present invention has been made in view of the problems inherent in the prior art, and an object of the present invention is to provide a biomass-derived polyester resin that has good mechanical properties and can be suitably used as an industrial product, and a molded article using the polyester resin.

[0007] The polyester resin according to an embodiment of the present invention has a structural unit represented by the following general formula (1) and has a number average molecular weight of 42,000 to 50,000.

[0008] [In general formula (1), m represents an integer of 2 to 10, and n represents an integer of 230 to 275.]

[0009] A molded article according to an embodiment of the present invention is obtained by molding the polyester resin.

[0010] According to the present invention, it is possible to provide a biomass-derived polyester resin that has good mechanical properties and can be suitably used as an industrial product, and a molded article using the polyester resin.

[0011] The polyester resin of this embodiment has a structural unit represented by the following general formula (1) and has a number average molecular weight of 42,000 to 50,000.

[0012] [In general formula (1), m represents an integer of 2 to 10, and n represents an integer of 230 to 275.]

[0013] In order to solve the conventional problems, the polyester resin of this embodiment focuses on the molecular weight and fluidity of polyethylene furanoate. Generally, the fluidity of a resin decreases as the molecular weight increases, and injection molding of high-molecular-weight resins tends to result in longer cycle times and more defects. Therefore, an appropriate molecular weight range is set to enable efficient injection molding. Therefore, polyethylene furanoates with different degrees of polymerization were evaluated for molecular weight by GPC measurement and fluidity by MFR measurement, and from the results, an embodiment was found that satisfies the properties (moldability, mechanical properties) required for injection-molded industrial products.

[0014] In general formula (1), m represents an integer of 2 to 10. If it is less than 2, the raw material is unstable and the target product cannot be obtained, and if it exceeds 10, the thermal properties of the molded product may be reduced. m is preferably 2 to 10, and more preferably 2 to 8.

[0015] In general formula (1), n ​​represents an integer of 230 to 275. If n is less than 230, the tensile strength decreases, and if it exceeds 275, the molecular weight increases and the fluidity decreases. n is preferably 230 to 275.

[0016] The number average molecular weight of the polyester resin of this embodiment is 42,000 to 50,000. If it is less than 42,000, the tensile strength decreases, and if it exceeds 50,000, the fluidity decreases and the suitability for injection molding decreases. The number average molecular weight is preferably 42,000 to 50,000. The number average molecular weight can be measured as follows: A sample is dissolved in hexafluoroisopropanol (HFIP), and gel permeation chromatography is performed. Polymethyl methacrylate (PMMA) is used as a standard substance, and the number average molecular weight is calculated.

[0017] The polyester resin of this embodiment has a number average molecular weight within the above range, so that molded articles made from the polyester resin have good mechanical properties. Specifically, the tensile strength can be 53 to 91 MPa. The tensile modulus can be 2480 to 3913 MPa.

[0018] The polyester resin of this embodiment may contain various additives such as antioxidants, crystal nucleating agents, fillers, heat stabilizers, hydrolysis inhibitors, flame retardants, antistatic agents, mold release agents, and ultraviolet absorbers. Examples of antioxidants include Irganox 1010 (a hindered phenol-based antioxidant) manufactured by BASF. Examples of crystal nucleating agents include talc, boron nitride, silica, layered silicates, and polyethylene wax.

[0019] The polyester resin of this embodiment can be produced as follows. It is obtained by polycondensation of a dicarboxylic acid component containing at least furandicarboxylic acid or an ester-forming derivative thereof (such as furandicarboxylic acid or an acid halide), and a glycol component containing alkylene glycol or an ester-forming derivative thereof (such as an acetylated product). Examples of alkylene glycols include aliphatic glycols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,10-decanediol.

[0020] 2,5-furandicarboxylic acid can be used as a raw material for furandicarboxylic acid. 2,5-Furandicarboxylic acid can be obtained by converting biomass such as cellulose, glucose, fructose, or mucic acid using a known method. Therefore, when a furan ring is used, a biomass-derived material can be used as the aromatic ring that contributes to heat resistance.

[0021] In the present embodiment, a dicarboxylic acid component other than furandicarboxylic acid may be copolymerized as the dicarboxylic acid component. 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, undecanedioic acid, dodecanedioic acid, octadecanedioic acid, fumaric acid, maleic acid, itaconic acid, mesaconic acid, citraconic acid, and dimer acid; aromatic dicarboxylic acids such as terephthalic acid, phthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and 4,4′-dicarboxybiphenyl; 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.

[0022] The polyester resin of this embodiment can be polymerized, for example, by a direct polymerization method in which furandicarboxylic acid is directly reacted with ethylene glycol, and, if necessary, other dicarboxylic acid components and diol components, or by a transesterification method in which a dimethyl ester of furandicarboxylic acid (including, if necessary, a methyl ester of another dicarboxylic acid) is transesterified with ethylene glycol (including, if necessary, other diol components).

[0023] On the other hand, the number average molecular weight of the polyester resin of the present embodiment can be adjusted by controlling the condensation reaction time, changing the catalyst type, adjusting the catalyst addition concentration, and the like.

[0024] <Molded Article> The molded article of this embodiment is obtained by molding the polyester resin of this embodiment. As described above, the molded article of this embodiment is obtained by molding the polyester resin of this embodiment, and therefore has good mechanical properties. Specifically, the tensile strength can be 53 to 91 MPa. Furthermore, the tensile modulus can be 2480 to 3913 MPa.

[0025] The method for producing the molded article of the present embodiment is not particularly limited, and any known method can be used. For example, the molded article can be produced by feeding the polyester resin of the present embodiment, together with optional additives, into an extruder, melt-kneading the mixture, and pelletizing the pellets, and then feeding the pellets into an injection molding machine equipped with a predetermined mold and injection molding the mixture.

[0026] Examples of applications of the molded article of this embodiment include various parts in the electrical and electronic fields and automobiles, films, containers, fibers, and the like.

[0027] Hereinafter, the present embodiment will be described in more detail with reference to examples and comparative examples, but the present embodiment is not limited to these examples.

[0028] [Example 1] 50 parts by mass of dimethyl furandicarboxylate, 37 parts by mass of ethylene glycol, and 0.015 parts by mass of tetraisopropyl orthotitanate were charged into a reaction vessel as raw materials, and a nitrogen atmosphere was created inside the reaction vessel. The reaction vessel was then placed in an oil bath, stirring was initiated, and the mixture was heated to 160°C, then gradually increased to 210°C, and reacted for 6 hours, followed by recovery of the distillate. The mixture was then heated to 220°C, and simultaneously gradually reduced in pressure to 50 Pa or less. After reaching 220°C and 50 Pa or less, the mixture was reacted for 15 hours to complete the polycondensation reaction, yielding a polyester resin (PEF (polyethylene furanoate resin)).

[0029] Example 2 A polyester resin (PEF (polyethylene furanoate resin)) was obtained in the same manner as in Example 1, except that the polycondensation reaction was carried out for 24 hours.

[0030] Comparative Example 1 A polyester resin (PEF (polyethylene furanoate resin)) was obtained in the same manner as in Example 1, except that the polycondensation reaction was carried out for 4 hours.

[0031] Comparative Example 2 A polyester resin (PEF (polyethylene furanoate resin)) was obtained in the same manner as in Example 1, except that the polycondensation reaction was carried out for 8 hours.

[0032] Comparative Example 3 A polyester resin (PBT (polybutylene terephthalate resin)) manufactured by Sigma-Aldrich (pellets, average Mv of 38,000) was used.

[0033] <<Measurement of number average molecular weight>> The sample was dissolved in hexafluoroisopropanol (HFIP), and the molecular weight distribution was measured using a GPC-104 measuring device (Shoko Scientific Co., Ltd.). Polymethyl methacrylate (PMMA) was used as the standard material. The measurement results are shown in Table 1.

[0034] <<Measurement of Melt Flow Rate>> The melt flow rate (MFR) was measured according to JIS K 7210-1 using a melt flow index tester No. 120-FWP (Yasuda Seiki Seisakusho Co., Ltd.). The measurement results are shown in Table 1.

[0035]

[0036] <<Measurement of Tensile Strength and Tensile Modulus>> Tensile strength and tensile modulus were measured for 5A-type dumbbell test pieces of the polyester resins obtained in each Example and Comparative Example using an autograph AGX-V device (Shimadzu Corporation) in accordance with JIS K 7161-1 and -2. The measurement results are shown in Table 2.

[0037] <<Measurement of Deflection Temperature Under Load>> The deflection temperature under load of rectangular test pieces (80 mm × 10 mm × 2 mm thick) of the polyester resin obtained in each Example and Comparative Example was measured using a heat distortion tester No. 148-HD-PC (Yasuda Seiki Seisakusho Co., Ltd.) in accordance with JIS K 7191. The measurement results are shown in Table 2.

[0038]

[0039] As can be seen from Table 2, good results were obtained in all of the tensile strength, tensile modulus, and deflection temperature under load in Examples 1 and 2. In contrast, in Comparative Examples 1 and 2, although injection-molded articles were obtained, at least one of the evaluations was poor.

[0040] The entire contents of Japanese Patent Application No. 2023-133267 (filing date: August 18, 2023) are incorporated herein by reference.

[0041] Although the present embodiment has been described above, the present embodiment is not limited to this, and various modifications are possible within the scope of the gist of the present embodiment.

Claims

1. A polyester resin having a structural unit represented by the following general formula (1) and having a number average molecular weight of 42,000 to 50,000: [In the general formula (1), m represents an integer of 2 to 10, and n represents an integer of 230 to 275.] 2. The polyester resin according to claim 1, having a tensile strength of 53 to 91 MPa and a tensile modulus of elasticity of 2,480 to 3,913 MPa.

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

Images