Polyester resin and molded article

Abstract

To provide a biomass-derived polyester resin that offers excellent mechanical properties and is suitably applicable to industrial products, and a molded article obtained by molding the polyester resin.SOLUTION: 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].SELECTED DRAWING: None

Description

[Technical field]

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

[0002] Polyester resins generally have excellent physical and chemical properties, and excellent processing properties for blow molding, extrusion molding, injection molding, and the like. Therefore, they are used in a wide range of applications and are widely used as engineering plastics in industrial products. Conditions that industrial products should have include being moldable in a short time, having excellent mechanical properties, being stable for a long time, and having a low environmental load (carbon footprint, etc.). From these perspectives, new polyester resins derived from biomass have been studied as an example, and polyester resins (polyethylene furanoate, etc.) synthesized using biomass-derived furandicarboxylic acid are representative examples. Polyethylene furanoate, etc., uses raw materials produced from biomass cultivated by absorbing carbon dioxide, so it is possible to aim to reduce the carbon footprint and have excellent mechanical properties. However, when such new polyester resins are made into industrial products by, for example, injection molding, there are many unknowns about their moldability, and the properties (mechanical properties, etc.) required for industrial products are not necessarily obtained sufficiently. Therefore, there are problems such as molded products not being obtained or not functioning sufficiently as industrial products. Furthermore, a problem in practical use is that the quality becomes unstable due to the high degree of polymerization.

[0003] In Patent Document 1, focusing on the quality instability caused by the high polymerization degree of polyethylene furanoate and the like as described above, a new polyester resin and a method for producing the same are described for producing molded products having excellent quality stability (hydrolysis resistance) even at a high polymerization degree. 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 a high polymerization degree. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-280767 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, although it is possible to stabilize the quality by increasing the degree of polymerization of polyester resin, the molding conditions, mechanical properties, etc. are not clear, and it is unclear whether polyester resins with such structures can be used in industrial products. In addition, 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 conventional techniques, 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. [Means for solving the problem]

[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] [ka] [In the 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 another aspect of the present invention is produced by molding the above polyester resin. Effect of the Invention

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

[0011] The polyester resin of the present 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] [ka] [In the general formula (1), m represents an integer of 2 to 10, and n represents an integer of 230 to 275.]

[0013] In the polyester resin of the present embodiment, attention is focused on the molecular weight and fluidity of polyethylene furanoate in order to solve the conventional problems. Generally, the fluidity of a resin decreases with an increase in molecular weight, and in the injection molding of a high molecular weight resin, the cycle time becomes longer and defects are more likely to occur. Therefore, an appropriate molecular weight range is set so that injection molding can be performed efficiently. Therefore, for polyethylene furanoates with different degrees of polymerization, evaluations were performed on the molecular weight by GPC measurement and the fluidity by MFR measurement, and from the results, an embodiment that satisfies the properties (moldability, mechanical properties) required for an injection molded industrial product was found.

[0014] In the 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 article may be deteriorated. m is preferably 2 to 10, and more preferably 2 to 8.

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

[0016] The number average molecular weight of the polyester resin of this embodiment is 42000 to 50000. If it is less than 42000, the tensile strength decreases, and if it exceeds 50000, the fluidity decreases and the suitability for injection molding decreases. The number average molecular weight is preferably 42000 to 50000. The number average molecular weight can be measured as follows. A sample is dissolved in hexafluoroisopropanol (HFIP), and gel permeation chromatography is performed, and polymethyl methacrylate (PMMA) is used as a standard substance to calculate the number average molecular weight.

[0017] The polyester resin of the present embodiment has a number average molecular weight within the above range, so that a molded product obtained by molding the polyester resin has good mechanical properties. Specifically, the tensile strength can be 53 to 91 MPa. Also, the tensile modulus can be 2480 to 3913 MPa.

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

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

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

[0021] In the present embodiment, other dicarboxylic acid components than furandicarboxylic acid may be used as the dicarboxylic acid component 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, undecane diacid, dodecane diacid, 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-norbornene dicarboxylic acid, and tetrahydrophthalic acid.

[0022] The polymerization method for the polyester resin of this embodiment can be, for example, 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 an ester exchange method in which a dimethyl ester of furandicarboxylic acid (containing a methyl ester of another dicarboxylic acid if necessary) is subjected to an ester exchange reaction with ethylene glycol (containing another diol component if necessary).

[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 products> The molded article of this embodiment is formed by molding the polyester resin of this embodiment. As described above, the molded article of this embodiment has good mechanical properties because it is formed by molding the polyester resin of this embodiment. Specifically, the tensile strength can be 53 to 91 MPa. 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 polyester resin of the present embodiment is fed into an extruder together with additives as necessary, melt-kneaded and pelletized, and the pellets are fed into an injection molding machine equipped with a predetermined mold and injection molded to produce the molded article.

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

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

[0028] [Example 1] As raw materials, 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, and the inside of the reaction vessel was made into a nitrogen atmosphere. Next, the reaction vessel was put into an oil bath, stirring was started, and the mixture was heated to 160°C, and the temperature was gradually increased to 210°C, and the mixture was reacted for 6 hours to recover the distillate. Next, the temperature was increased to 220°C, and the pressure was gradually reduced so that the pressure was 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, and a polyester resin (PEF (polyethylene furanoate resin)) was obtained.

[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 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 measuring device GPC-104 (Shoko Scientific Co., Ltd.). Polymethyl methacrylate (PMMA) was used as the standard substance. The measurement results are shown in Table 1.

[0034] <Melt flow rate measurement> 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] [Table 1]

[0036] <Measurement of tensile strength and tensile modulus> The tensile strength and tensile modulus of elasticity of the polyester resin 5A type dumbbell specimens obtained in each of the Examples and Comparative Examples were measured 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 × t2 mm) of the polyester resin obtained in each of the Examples and Comparative Examples 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] [Table 2]

[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, although injection-molded articles were obtained in Comparative Examples 1 and 2, at least one of the evaluations was poor.

[0040] 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 a number average molecular weight of 42,000 to 50,000: 【Chemistry 1】 [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 2480 to 3913 MPa.

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

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