Polyester resin

Abstract

A polyester resin comprising dicarboxylate structural units and diol structural units, wherein the diol structural units include a structural unit A1 derived from a diol having a cyclic acetal backbone and a structural unit A2 derived from 2,2,4,4-tetramethoxy-1,3-cyclobutanediol, and the dicarboxylate structural units include a structural unit B1 derived from 2,6-naphthalene dicarboxylic acid and / or dimethyl 2,6-naphthalene dicarboxylate.

Description

[Technical Field]

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

[0002] Aromatic saturated polyester resins, particularly polyethylene terephthalate (hereinafter sometimes referred to as "PET"), are resins that offer a good balance of mechanical properties, solvent resistance, aroma retention, weather resistance, and recyclability, and are used in large quantities, primarily for applications such as bottles and films.

[0003] However, because PET is highly crystalline, when thick molded bodies or sheets are produced, it suffers from whitening due to crystallization, resulting in a loss of transparency. Furthermore, because PET's glass transition temperature is around 80°C, it cannot be used for applications requiring high heat resistance, such as products used inside automobiles, packaging materials for imports and exports, food packaging materials that are retorted or heated in microwave ovens, and baby bottles and tableware that are heat sterilized.

[0004] Therefore, as a polyester resin that has improved heat resistance while maintaining high transparency, a polyester resin composed of a diol such as spiroglycol or 1,4-cyclohexanedimethanol and a dicarboxylic acid such as terephthalic acid has been disclosed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2012-512936 Summary of the Invention [Problem to be solved by the invention]

[0006] However, although the polyester resin described in Patent Document 1 is colorless and transparent, its glass transition temperature is about 128° C., and there is room for further improvement in terms of heat resistance.

[0007] The present invention has been made in view of the above problems, and an object of the present invention is to provide a polyester resin having excellent transparency and heat resistance. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to solve the above problems, and as a result have found that the above problems can be solved by using a specific diol structural unit and a dicarboxylic acid structural unit, thereby completing the present invention.

[0009] That is, the present invention is as follows. [1] Contains dicarboxylic acid structural units and diol structural units, the diol structural unit includes a structural unit A1 derived from a diol having a cyclic acetal skeleton and a structural unit A2 derived from 2,2,4,4-tetramethoxy-1,3-cyclobutanediol; The dicarboxylic acid structural unit includes a structural unit B1 derived from 2,6-naphthalenedicarboxylic acid and / or dimethyl 2,6-naphthalenedicarboxylate. Polyester resin. [2] The diol structural unit further includes a structural unit A3 derived from ethylene glycol, The polyester resin according to [1]. [3] The diol having a cyclic acetal skeleton includes at least one selected from the group consisting of compounds represented by the following formula (1) and formula (2): The polyester resin according to [1] or [2]. [ka] (In formula (1), R 1 and R2 each independently represents a divalent aliphatic group having 1 to 10 carbon atoms, a divalent alicyclic group having 3 to 10 carbon atoms, or a divalent aromatic group having 6 to 10 carbon atoms. [ka] (In formula (2), R 1 represents a divalent aliphatic group having 1 to 10 carbon atoms, a divalent alicyclic group having 3 to 10 carbon atoms, or a divalent aromatic group having 6 to 10 carbon atoms; R 3 represents a monovalent aliphatic group having 1 to 10 carbon atoms, a monovalent alicyclic group having 3 to 10 carbon atoms, or a monovalent aromatic group having 6 to 10 carbon atoms. [4] The diol having a cyclic acetal skeleton includes 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane. The polyester resin according to any one of [1] to [3]. [Effects of the Invention]

[0010] According to the present invention, a polyester resin having excellent transparency and heat resistance can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0011] Below, we will explain in detail the embodiment of the present invention (hereinafter referred to as the ``present embodiment''), but the present invention is not limited to this and various modifications are possible within the scope of the gist of the present invention.

[0012] 1. Polyester resin The polyester resin of this embodiment contains dicarboxylic acid structural units and diol structural units, the diol structural units containing structural units A1 derived from a diol having a cyclic acetal skeleton and structural units A2 derived from 2,2,4,4-tetramethoxy-1,3-cyclobutanediol, and the dicarboxylic acid structural units containing structural units B1 derived from 2,6-naphthalenedicarboxylic acid and / or dimethyl 2,6-naphthalenedicarboxylate.

[0013] In the polyester resin of this embodiment, by using the structural unit A2 derived from 2,2,4,4-tetramethoxy-1,3-cyclobutanediol in addition to the structural unit A1 derived from a diol having a cyclic acetal skeleton, the glass transition temperature is further improved and high heat resistance can be exhibited.

[0014] Furthermore, the polyester resin of this embodiment uses the structural unit A1 derived from a diol having a cyclic acetal skeleton and the structural unit A2 derived from 2,2,4,4-tetramethoxy-1,3-cyclobutanediol, thereby reducing crystallinity and enabling the resin to exhibit high transparency. Each of the structural components will be described in detail below.

[0015] 1.1. Diol building blocks The diol structural unit includes a structural unit A1 derived from a diol having a cyclic acetal skeleton and a structural unit A2 derived from 2,2,4,4-tetramethoxy-1,3-cyclobutanediol, and may also include a structural unit A3 derived from ethylene glycol or a structural unit A4 derived from other diols, as necessary.

[0016] 1.1.1. Building block A1 The structural unit A1 is a structural unit derived from a diol having a cyclic acetal skeleton. The diol having a cyclic acetal skeleton is not particularly limited, but examples thereof include at least one selected from the group consisting of compounds represented by the following formulas (1) and (2). Use of such a diol tends to further reduce crystallinity and further improve heat resistance. [ka] (In formula (1), R 1 and R 2 each independently represents a divalent aliphatic group having 1 to 10 carbon atoms, a divalent alicyclic group having 3 to 10 carbon atoms, or a divalent aromatic group having 6 to 10 carbon atoms. [ka] (In formula (2), R 1 represents a divalent aliphatic group having 1 to 10 carbon atoms, a divalent alicyclic group having 3 to 10 carbon atoms, or a divalent aromatic group having 6 to 10 carbon atoms; R 3 represents a monovalent aliphatic group having 1 to 10 carbon atoms, a monovalent alicyclic group having 3 to 10 carbon atoms, or a monovalent aromatic group having 6 to 10 carbon atoms.

[0017] R 1 and R 2 The divalent aliphatic group having 1 to 10 carbon atoms represented by the formula (I) is not particularly limited, and examples thereof include straight-chain aliphatic groups such as a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, and a hexylene group; and divalent branched aliphatic groups such as an isopropylene group, an isobutylene group, a tertiary butylene group, a neopentylene group, and a 2-hexylene group.

[0018] R 1 and R 2 The divalent alicyclic group having 3 to 10 carbon atoms represented by the formula (I) is not particularly limited, but examples thereof include a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, and a cyclooctylene group.

[0019] R 1 and R 2 The divalent aromatic group having 6 to 10 carbon atoms represented by the formula is not particularly limited, but examples thereof include a phenylene group and a naphthylene group.

[0020] R 3 The monovalent aliphatic group having 1 to 10 carbon atoms represented by the formula (I) is not particularly limited, and examples thereof include linear aliphatic groups such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group; and divalent branched aliphatic groups such as an isopropyl group, an isobutyl group, a tertiary butyl group, a neopentyl group, and a 2-hexyl group.

[0021] R 3The monovalent alicyclic group having 3 to 10 carbon atoms represented by the formula is not particularly limited, but examples thereof include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and a cyclooctyl group.

[0022] R 3 The monovalent aromatic group having 6 to 10 carbon atoms represented by the formula is not particularly limited, but examples thereof include a phenyl group and a naphthyl group.

[0023] The compounds represented by formula (1) and formula (2) are not particularly limited, but examples thereof include 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane (hereinafter also referred to as "spiroglycol") and 5-methylol-5-ethyl-2-(1,1-dimethyl-2-hydroxyethyl)-1,3-dioxane (hereinafter also referred to as "dioxane glycol"). Among these, spiroglycol is more preferred. By including a structural unit A1 derived from such a diol having a cyclic acetal skeleton, crystallinity tends to be further reduced and heat resistance tends to be further improved. The diol having a cyclic acetal skeleton may be used alone or in combination of two or more.

[0024] The content of the structural unit A1 is preferably 1 to 60 mol %, more preferably 3 to 45 mol %, and even more preferably 5 to 30 mol %, relative to the total amount of diol structural units. When the content of the structural unit A1 is within the above range, crystallinity tends to be further reduced and heat resistance tends to be further improved.

[0025] 1.1.2. Building block A2 The structural unit A2 is a structural unit derived from 2,2,4,4-tetramethoxy-1,3-cyclobutanediol. By including the structural unit A2, crystallinity is further reduced and heat resistance is further improved.

[0026] The content of the structural unit A2 is preferably 3 to 55 mol %, more preferably 5 to 45 mol %, and even more preferably 10 to 35 mol %, relative to the total amount of diol structural units. When the content of the structural unit A2 is within the above range, crystallinity tends to be further reduced and heat resistance tends to be further improved.

[0027] 1.1.3. Building block A3 The structural unit A3 is a structural unit derived from ethylene glycol. By including the structural unit A3, condensation polymerization during resin synthesis can be more easily carried out, thereby improving production efficiency.

[0028] The content of the structural unit A3 is preferably 1 to 25 mol %, more preferably 3 to 20 mol %, and even more preferably 5 to 15 mol %, relative to the total amount of diol structural units. When the content of the structural unit A3 is within the above range, production efficiency and heat resistance tend to be further improved.

[0029] 1.1.4. Building block A4 The structural unit A4 is a structural unit derived from another diol. The other diol is not particularly limited, but examples thereof include aliphatic diols such as trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, propylene glycol, and neopentyl glycol; polyether diols such as polyethylene glycol, polypropylene glycol, and polybutylene glycol; 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,2-decahydronaphthalenedimethanol, 1,3-decahydronaphthalenedimethanol, 1,4-decahydronaphthalenedimethanol, 1,5-decahydronaphthalenedimethanol, 1,6-decahydronaphthalenedimethanol, and 2,7-decahydronaphthalenedimethanol. Examples of the diols include alicyclic diols such as hydronaphthalenedimethanol, tetralindimethanol, norbornanedimethanol, tricyclodecanedimethanol, and pentacyclododecanedimethanol; bisphenols such as 4,4'-(1-methylethylidene)bisphenol, methylenebisphenol, 4,4'-cyclohexylidenebisphenol, and 4,4'-sulfonylbisphenol; alkylene oxide adducts of the above bisphenols; aromatic dihydroxy compounds such as hydroquinone, resorcinol, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxydiphenyl ether, and 4,4'-dihydroxydiphenylbenzophenone; and alkylene oxide adducts of the above aromatic dihydroxy compounds. The other diols may be used alone or in combination of two or more.

[0030] Among these, alicyclic diols are preferred, and 1,4-cyclohexanedimethanol is more preferred. By including such a structural unit A4, crystallinity tends to be further reduced and heat resistance tends to be further improved.

[0031] When the structural unit A4 is contained, its content relative to the total amount of diol structural units is preferably 25 to 75 mol %, more preferably 35 to 65 mol %, and even more preferably 45 to 55 mol %. When the content of the structural unit A4 is within the above range, crystallinity tends to be further reduced and heat resistance tends to be further improved.

[0032] 1.2. Dicarboxylic acid building blocks The dicarboxylic acid structural units include structural units B1 derived from 2,6-naphthalenedicarboxylic acid and / or dimethyl 2,6-naphthalenedicarboxylate, and may also include structural units B2 derived from other dicarboxylic acids as necessary.

[0033] 1.2.1. Building block B1 The structural unit B1 is a structural unit derived from 2,6-naphthalenedicarboxylic acid and / or dimethyl 2,6-naphthalenedicarboxylate. The presence of the structural unit B1 further reduces crystallinity and improves heat resistance. Note that dimethyl 2,6-naphthalenedicarboxylate is included in the polyester resin as a dicarboxylic acid structural unit that is essentially the same as 2,6-naphthalenedicarboxylic acid through a transesterification reaction.

[0034] The content of the structural unit B1 is preferably 10 to 100 mol %, more preferably 50 to 100 mol %, and even more preferably 80 to 100 mol %, relative to the total amount of dicarboxylic acid structural units. When the content of the structural unit B1 is within the above range, crystallinity tends to be further reduced and heat resistance tends to be further improved.

[0035] 1.2.2. Building block B2 The structural unit B1 is a structural unit derived from another dicarboxylic acid. Examples of the other dicarboxylic acid include, but are not limited to, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, cyclohexanedicarboxylic acid, decanedicarboxylic acid, norbornanedicarboxylic acid, tricyclodecanedicarboxylic acid, and pentacyclododecanedicarboxylic acid; and dicarboxylic acid units derived from aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 2-methylterephthalic acid, biphenyldicarboxylic acid, and tetralindicarboxylic acid. The other dicarboxylic acids may be used alone or in combination of two or more.

[0036] The content of the structural unit B1 is preferably 0 to 90 mol %, more preferably 0 to 50 mol %, and even more preferably 0 to 20 mol %, relative to the total amount of dicarboxylic acid structural units. When the content of the structural unit B1 is within the above range, the mechanical properties tend to be further improved.

[0037] 2. Polyester resin manufacturing method The method for producing the polyester resin of this embodiment is not particularly limited, and a conventionally known method can be used, such as a transesterification method or a direct polymerization method.

[0038] The transesterification method includes a transesterification step in which a raw material diol that forms a diol constituent unit, a dicarboxylic acid ester that forms a dicarboxylic acid constituent unit, and a catalyst are heated to a predetermined temperature to cause a transesterification reaction to proceed, and a polycondensation step in which a catalyst and a heat stabilizer are added to the resulting solution, and the solution is further heated and decompressed to cause a polycondensation reaction to proceed.

[0039] In addition, the direct polymerization method may include a method having an esterification reaction step in which a raw material diol that becomes a diol constituent unit, a dicarboxylic acid that becomes a dicarboxylic acid constituent unit, and a catalyst are heated to a predetermined temperature to cause an esterification reaction to proceed, and a polycondensation step in which a catalyst and a heat stabilizer are added to the obtained solution, and the solution is further heated and decompressed to cause a polycondensation reaction to proceed.

[0040] In each of the above methods, the starting diol and dicarboxylic acid may be charged all at once before the start of the reaction, or a portion of them may be charged during the reaction.

[0041] In addition, in each of the above methods, a known catalyst can be used. Examples of known catalysts include, but are not limited to, metallic magnesium, sodium, and magnesium alkoxides; fatty acid salts, carbonates, hydroxides, chlorides, and oxides of zinc, lead, cerium, cadmium, manganese, lithium, sodium, potassium, calcium, nickel, magnesium, vanadium, aluminum, tin, germanium, antimony, and titanium. Among these, compounds of manganese, titanium, antimony, and germanium are preferred, with manganese acetate, titanium tetrabutoxide, antimony trioxide, and germanium dioxide being particularly preferred. These catalysts may be used alone or in combination of two or more.

[0042] In addition, in each of the above methods, known additives may be used as necessary. Examples of known additives include, but are not limited to, various stabilizers such as an etherification inhibitor, a heat stabilizer, and a light stabilizer, a polymerization regulator, an antistatic agent, a lubricant, an antioxidant, a mold release agent, and a basic compound.

[0043] The etherification inhibitor is not particularly limited, but examples thereof include amine compounds.

[0044] The heat stabilizer is not particularly limited, but examples thereof include phosphorus compounds, of which phosphate esters are preferred, with triethyl phosphate being more preferred.

[0045] The basic compound is not particularly limited, but examples thereof include carbonates, hydroxides, carboxylates, oxides, chlorides, and alkoxides of alkali metals such as lithium, sodium, and potassium. Among these, potassium acetate, sodium acetate, and lithium acetate are particularly preferred.

[0046] 3.Resin composition The resin composition of the present embodiment contains the polyester resin described above, and may also contain other additives as necessary.

[0047] The resin composition of this embodiment has excellent heat resistance and transparency, and can be suitably used for food packaging materials that undergo retort processing or microwave heating, containers such as baby bottles and tableware that undergo heat treatment, and other applications that require high heat resistance. [Example]

[0048] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0049] [Glass transition temperature] The glass transition temperature (Tg) of the polyester resin was measured using a differential scanning calorimeter (model: DSC / TA-50WS) manufactured by Shimadzu Corporation. Approximately 10 mg of the sample was placed in an unsealed aluminum container and measured in a nitrogen gas (50 ml / min) stream at a heating rate of 20°C / min. The glass transition temperature was determined as the temperature at which the temperature changed by half the difference in the baseline before and after the transition of the DSC curve.

[0050] [Crystalline] The low crystallinity was evaluated by the calorific value of the crystallization peak during cooling. After measuring the glass transition temperature, the sample was held at 280°C for 1 minute, and then cooled at a rate of 10°C / min. The calorific value of the crystallization peak during cooling was measured from the area of ​​the exothermic peak that appeared when the sample was cooled. (Evaluation criteria) ◯: The calorific value of the crystallization peak during cooling is 5 J / g or less. ×: The calorific value of the crystallization peak during cooling exceeds 5 J / g.

[0051] Example 1 A 30 L polyester resin production apparatus equipped with a partial condenser, a total condenser, a cold trap, a stirrer equipped with a torque detector, a heating device, and a nitrogen inlet tube was charged with 7759 g of dimethyl 2,6-naphthalenedicarboxylate, 2753 g of ethylene glycol, 2465 g of spiro glycol, 1152 g of 2,2,4,4-tetramethoxy-1,3-cyclobutanediol, 3265 g of 1,4-cyclohexanedimethanol, 3.400 g of titanium tetrabutoxide, and 0.784 g of potassium acetate, and a transesterification reaction was carried out in a conventional manner while the temperature was raised to 225°C.

[0052] After the amount of methanol distillate produced by the transesterification reaction reached 90% of the theoretical amount, 1.045 g of germanium dioxide and 3.639 g of triethyl phosphate were added to the reaction solution. The reaction solution was then maintained at 225°C and the pressure was reduced to 13.3 kPa over one hour, after which the temperature was raised to 270°C and the pressure was reduced to 130 Pa over one hour, allowing the polycondensation reaction to proceed. The stirring speed was then gradually reduced from 100 rpm, and the reaction was terminated when the stirring speed reached 10 rpm and the stirrer torque reached 100 N·m, yielding approximately 8 kg of polyester resin pellets.

[0053] [Example 2, Comparative Examples 1 to 5] A polyester resin was prepared in the same manner as in Example 1, except that the monomer composition shown in Table 1 was used.

[0054] [Table 1]

[0055] Table 1 shows the amounts (mol %) of structural units A1 to A4 used when the diol structural unit is 100 mol %, and the amounts (mol %) of structural units B1 and B2 used when the dicarboxylic acid structural unit is 100 mol %. [Industrial Applicability]

[0056] The polyester resin of the present invention has industrial applicability as a food contact material having high transparency and heat resistance.

Claims

1. Contains dicarboxylic acid structural units and diol structural units, the diol structural unit includes a structural unit A1 derived from a diol having a cyclic acetal skeleton and a structural unit A2 derived from 2,2,4,4-tetramethoxy-1,3-cyclobutanediol; the dicarboxylic acid structural unit includes a structural unit B1 derived from 2,6-naphthalenedicarboxylic acid and / or dimethyl 2,6-naphthalenedicarboxylate; Polyester resin.

2. The diol structural unit further includes a structural unit A3 derived from ethylene glycol. The polyester resin according to claim 1.

3. The diol having a cyclic acetal skeleton includes at least one selected from the group consisting of compounds represented by the following formula (1) and formula (2): The polyester resin according to claim 1 or 2. 【Chemistry 1】 (In formula (1), R 1 and R 2 each independently represents a divalent aliphatic group having 1 to 10 carbon atoms, a divalent alicyclic group having 3 to 10 carbon atoms, or a divalent aromatic group having 6 to 10 carbon atoms. 【Chemistry 2】 (In formula (2), R 1 represents a divalent aliphatic group having 1 to 10 carbon atoms, a divalent alicyclic group having 3 to 10 carbon atoms, or a divalent aromatic group having 6 to 10 carbon atoms; R 3 represents a monovalent aliphatic group having 1 to 10 carbon atoms, a monovalent alicyclic group having 3 to 10 carbon atoms, or a monovalent aromatic group having 6 to 10 carbon atoms.

4. the diol having a cyclic acetal skeleton includes 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane; The polyester resin according to claim 1 or 2.

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