Polyester and molded article composed of same

Abstract

This polyester comprises a dicarboxylic acid unit and a diol unit, wherein: the dicarboxylic acid unit includes a structural unit derived from terephthalic acid; the diol unit includes a first diol unit, a second diol unit, and a third diol unit; the first diol unit is a structural unit derived from ethylene glycol; the second diol unit is a structural unit derived from 1,2-propanediol; and the third diol unit is a structural unit derived from a bisphenol A ethylene oxide adduct and / or cyclohexanedimethanol. Said polyester is suitable as a raw material for molding having less influence on the environment, in particular, a raw material for extrusion blow molding, and a molded article having favorable impact resistance is obtained by using said polyester.

Description

Polyester and molded products made from it

[0001] The present invention relates to a polyester suitable as a raw material for extrusion blow molding and a molded article made thereof.

[0002] Polyesters such as polyethylene terephthalate (PET) have excellent properties, including transparency, mechanical properties, gas barrier properties, and flavor barrier properties. Furthermore, polyesters are hygienic and safe, with minimal risk of residual monomers or harmful additives when molded into products. Therefore, taking advantage of these properties, polyesters have been widely used in recent years as a substitute for polyvinyl chloride resin to make hollow containers for juices, soft drinks, seasonings, oils, cosmetics, detergents, and other products.

[0003] One known molding method for producing hollow polyester molded articles is extrusion blow molding, in which molten plasticized resin is extruded through a die orifice to form a cylindrical parison, which is then sandwiched between molds while still softened and then molded by blowing air or other fluid into the parison. This method is simpler than injection blow molding and does not require sophisticated techniques for mold construction and molding, reducing equipment and mold manufacturing costs, making it suitable for high-mix, low-volume production. Another advantage is that it can be used to produce molded articles with complex shapes, such as thin, deep, large, and with handles.

[0004] Patent Document 1 describes polyester pellets obtained by condensation polymerization of terephthalic acid, ethylene glycol, cyclohexanedimethanol or bisphenol A ethylene oxide adduct, and a polyvalent ester. Patent Document 2 describes a polyester containing 15 to 500 ppm of a component derived from 1,2-propanediol. Furthermore, Patent Document 3 discloses a copolymerized polyester in which a compound such as propylene glycol is copolymerized in an amount of 0.5 to 30 mol % relative to the total glycol component in a polyester in which the main acid component is terephthalic acid and the main glycol component is ethylene glycol, and 2 to 30 ppm of an alkali metal compound is also contained.

[0005] International Publication No. 2016 / 104689 International Publication No. 2013 / 35559 Japanese Patent Application Laid-Open No. 2-191626

[0006] The polyester described in Patent Document 1 contains structural units derived from cyclohexanedimethanol or bisphenol A ethylene oxide adduct. When structural units derived from cyclohexanedimethanol or bisphenol A ethylene oxide adduct are included, the physical properties of the polyester, particularly impact resistance, are improved. On the other hand, an increase in the amount of structural units derived from bisphenol A ethylene oxide adduct requires the use of a large amount of bisphenol A, which is a raw material used in synthesizing bisphenol A ethylene oxide adduct. It has been reported that bisphenol A released into the atmosphere or rivers, etc., can adversely affect the nerves, behavior, mammary glands, and prostate gland when ingested by animals. From this perspective, it is desirable to limit the amount of bisphenol A used, and therefore to avoid excessive content of structural units derived from bisphenol A ethylene oxide adduct. Furthermore, an increase in the content of structural units derived from cyclohexanedimethanol results in a relative decrease in the content of structural units derived from ethylene glycol, impairing the properties of PET. In this case, the polyester will fall outside the polyester recycling system and will no longer be eligible for recycling as a recycle mark and identification number "1" or "PET." From this perspective, it is desirable that the structural units derived from cyclohexanedimethanol not be too high. Therefore, there is a need for polyesters that can maintain the same physical properties as polyesters with a higher content of structural units derived from cyclohexanedimethanol or bisphenol A ethylene oxide adducts, even when the content of these units is reduced. Patent Documents 2 and 3 only list 1,2-propanediol and cyclohexanedimethanol among the many examples of copolymerizable monomers, and make no mention of the impact resistance of polyesters.

[0007] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a polyester that has good impact resistance even when the content of structural units derived from cyclohexanedimethanol or bisphenol A ethylene oxide adduct is small.

[0008] As a result of extensive research, the present inventors have found that polyesters containing dicarboxylic acid units and specific diol units are suitable as molding raw materials with low environmental impact, particularly as raw materials for extrusion blow molding, and that the use of such polyesters allows for the production of molded articles with good impact resistance. Based on this finding, the present inventors have conducted further research and arrived at the present invention.

[0009] The present invention provides the following items [1] to [6]: [1] A polyester containing dicarboxylic acid units and diol units, wherein the dicarboxylic acid units contain structural units derived from terephthalic acid, and the diol units contain first diol units, second diol units, and third diol units, the first diol units are structural units derived from ethylene glycol, the second diol units are structural units derived from 1,2-propanediol, and the third diol units are structural units derived from a bisphenol A ethylene oxide adduct and / or cyclohexanedimethanol, and when the total amount of diol units contained in the polyester is taken as 100 mol %, the content X (mol %) of the second diol units, the content Y (mol %) of the structural units derived from the bisphenol A ethylene oxide adduct, and the content Z (mol %) of the structural units derived from cyclohexanedimethanol satisfy the following formulas (1) and (2): 0.001≦X≦0.5 (1) 2≦Y+Z≦25 (2) [2] The polyester according to [1], wherein the content X (mol %) of the second diol units, the content Y (mol %) of the structural units derived from the bisphenol A ethylene oxide adduct, and the content Z (mol %) of the structural units derived from the cyclohexanedimethanol satisfy the following formula (3): 5≦(Y+Z) / X≦100 (3) [3] The polyester according to [1] or [2], wherein the content of the first diol units is 75 to 98 mol % when the total of the diol units contained in the polyester is 100 mol %. [4] The polyester according to [1] to [3], wherein the polyester has an intrinsic viscosity of 0.8 to 1.5 dL / g. [5] A molded article containing the polyester according to any one of [1] to [4]. [6] A molded article obtained by extrusion blow molding the polyester according to any one of [1] to [5].

[0010] According to the present invention, a polyester can be obtained which is suitable as a raw material for extrusion blow molding, which has little impact on the environment, and which can be used to produce molded articles having good impact resistance.

[0011] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these.

[0012] The polyester of the present invention is a polyester containing dicarboxylic acid units and diol units, wherein the dicarboxylic acid units contain structural units derived from terephthalic acid, and the diol units contain first diol units, second diol units, and third diol units, wherein the first diol units are structural units derived from ethylene glycol, the second diol units are structural units derived from 1,2-propanediol, and the third diol units are structural units derived from a bisphenol A ethylene oxide adduct and / or cyclohexanedimethanol, and when the total amount of diol units contained in the polyester is taken as 100 mol %, the content X (mol %) of the second diol units, Y (mol %) of the structural units derived from the bisphenol A ethylene oxide adduct, and Z (mol %) of the structural units derived from cyclohexanedimethanol satisfy the following formulas (1) and (2): 0.001≦X≦0.5 (1) and 2≦Y+Z≦25 (2).

[0013] The polyester of the present invention contains, in addition to ethylene glycol as the first diol unit, a structural unit derived from 1,2-propanediol as the second diol unit, and a structural unit derived from either or both of a bisphenol A ethylene oxide adduct and cyclohexanedimethanol as the third diol unit. By including the third diol unit in the polyester, impact resistance is improved. Furthermore, by including the third diol unit in the polyester, the melting point of the polyester can be lowered, and the molding temperature in direct blow molding can also be lowered. From the viewpoint of impact resistance at low temperatures, it is preferable that the polyester contains a structural unit derived from cyclohexanedimethanol as the third diol unit. On the other hand, from the viewpoint of chemical resistance to high-concentration alcohols, it is preferable that the polyester contains a structural unit derived from a bisphenol A ethylene oxide adduct as the third diol unit.

[0014] As described above, the inclusion of third diol units in polyesters improves impact resistance, but from the viewpoints of environmental and biological impacts and recycling, it is desirable that the content of third diol units not be too high. The present inventors have discovered that by including a certain amount of structural units derived from 1,2-propanediol as second diol units in addition to first diol units and third diol units, impact resistance can be improved even when the content of third diol units is low. Furthermore, by including a certain amount or more of 1,2-propanediol-derived components as second diol units in the polyesters of the present invention, amorphousness is further improved, making it easier to obtain transparent, beautiful bottles.

[0015] The content of structural units derived from terephthalic acid in the polyester of the present invention is preferably 80 mol % or more, more preferably 90 mol % or more, and even more preferably 95 mol % or more, when the total amount of dicarboxylic acid units in the polyester is taken as 100 mol %. It is even more preferable that the dicarboxylic acid units in the polyester are substantially only structural units derived from terephthalic acid.

[0016] In the present invention, the first diol unit is a structural unit derived from ethylene glycol. The content of the structural unit derived from ethylene glycol is not particularly limited, but is preferably 75 to 98 mol% when the total amount of diol units contained in the polyester is 100 mol%. The content of the structural unit derived from ethylene glycol is more preferably 78 mol% or more, even more preferably 80 mol% or more, and in some cases, 83 mol% or more, 85 mol% or more, 88 mol% or more, or 90 mol% or more is preferred. The content of the structural unit derived from ethylene glycol is more preferably 97.5 mol% or less, and in some cases, 97 mol% or less, 96 mol% or less, or 95 mol% or less is preferred. The structural unit derived from ethylene glycol may be derived from biomass-derived ethylene glycol.

[0017] In the present invention, the second diol units are structural units derived from 1,2-propanediol, and when the total amount of diol units contained in the polyester is taken as 100 mol %, the content X of the second diol units is 0.001 to 0.5 mol %. If the content X of the second diol units is greater than the above upper limit, the impact resistance of containers and the like made of the polyester will deteriorate. In particular, from the viewpoint of improving the impact resistance of containers and the like, the content X of the second diol units is preferably 0.4 mol % or less, more preferably 0.35 mol % or less, and even more preferably 0.3 mol % or less. On the other hand, the lower limit of the content of the second diol units is preferably 0.01 mol% or more, more preferably 0.05 mol% or more, even more preferably 0.08 mol% or more, and in some cases 0.10 mol% or more, 0.13 mol% or more, 0.137 mol% or more, 0.14 mol% or more, 0.15 mol% or more, 0.16 mol% or more, 0.162 mol% or more, 0.17 mol% or more, 0.18 mol% or more, or 0.189 mol% or more is preferred. If it is less than the lower limit, it is necessary to increase the content of the third diol units in order to improve impact resistance, which is not preferred.

[0018] The term "components of structural units derived from 1,2-propanediol" refers to the total amount of 1,2-propanediol detected when the polyester is decomposed and analyzed, and represents the total amount of 1,2-propanediol consisting of a 1,2-propanediol-derived structure copolymerized in the polymer chain and 1,2-propanediol present intermixed between polymers. That is, this 1,2-propanediol may be partially copolymerized in the polyester main chain, or may be contained as 1,2-propanediol alone without being copolymerized.

[0019] In the present invention, the third diol unit is a structural unit derived from a bisphenol A ethylene oxide adduct and / or cyclohexanedimethanol.

[0020] The structural unit derived from the bisphenol A ethylene oxide adduct is formed by adding at least one ethylene oxide to each hydroxyl group of bisphenol A. The amount of ethylene oxide added is usually 2 to 4 mol % per 1 mol of bisphenol A.

[0021] Examples of the cyclohexanedimethanol include 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol. Among these, 1,4-cyclohexanedimethanol is preferred because it is easily available, the polyester can be easily made crystalline, pellets are less likely to stick together during solid-state polymerization, and the impact resistance of the resulting molded article is further improved.

[0022] The structural units derived from the cyclohexanedimethanol contain cis- and trans-isomers, and the ratio thereof is not particularly limited. However, when the cis / trans-isomer ratio of the cyclohexanedimethanol is in the range of 0 / 100 to 50 / 50, the crystallinity of the polyester of the present invention is easily increased, pellets are less likely to stick together during solid-state polymerization, and the impact resistance of the resulting molded article is further improved.

[0023] In the present invention, when the total diol units contained in the polyester is taken as 100 mol%, the sum (Y + Z) of the content Y of structural units derived from bisphenol A ethylene oxide adduct and the content Z of structural units derived from cyclohexanedimethanol is 2 to 25 mol%. If Y + Z is less than 2 mol%, the impact resistance and transparency of the resulting molded article will be reduced. Y + Z is preferably 2.5 mol% or more, more preferably 3 mol% or more, even more preferably 4 mol% or more, and in some cases, 6 mol% or more or 8 mol% or more is preferred. On the other hand, if Y + Z exceeds 25 mol%, it becomes difficult to increase the solid-state polymerization temperature, resulting in reduced productivity and a deterioration in the color tone of the resulting molded article. In some cases, Y + Z is preferably 20 mol% or less, 18 mol% or less, 15 mol% or less, 13 mol% or less, 10 mol% or less, or 8 mol% or less.

[0024] In the present invention, when a bisphenol A ethylene oxide adduct is used as the third diol component, the content Y of structural units derived from the bisphenol A ethylene oxide adduct is 25 mol % or less, preferably 20 mol % or less, more preferably 15 mol % or less, and even more preferably 10 mol % or less, when the total amount of diol units contained in the polyester is taken as 100 mol %, for the reasons described above.

[0025] In the present invention, when cyclohexanedimethanol is used as the third diol component, the content Z of structural units derived from cyclohexanedimethanol, when the total amount of diol units contained in the polyester is taken as 100 mol %, is 25 mol % or less, preferably 20 mol % or less, more preferably 15 mol % or less, and even more preferably 10 mol % or less, for the reasons described above.

[0026] In the present invention, it is preferable that the content X (mol %) of the second diol unit, the content Y (mol %) of the structural unit derived from the bisphenol A ethylene oxide adduct, and the content Z (mol %) of the structural unit derived from the cyclohexanedimethanol satisfy the following formula (3). This makes it possible to further improve impact resistance, particularly when the contents of the structural unit derived from the bisphenol A ethylene oxide adduct and the structural unit derived from cyclohexanedimethanol are low. 5≦(Y+Z) / X≦100 (3)

[0027] The ratio [(Y+Z) / X] of the sum of the content Y (mol%) of structural units derived from the bisphenol A ethylene oxide adduct and the content Z (mol%) of structural units derived from cyclohexanedimethanol to the content X (mol%) of the second diol units is more preferably 10 or more, and even more preferably 12 or more. On the other hand, the ratio [(Y+Z) / X] is more preferably 60 or less, still more preferably 40 or less, and particularly preferably 30 or less. When the ratio [(Y+Z) / X] is equal to or less than the above upper limit, the color tends to be excellent.

[0028] The total content of the first diol unit, second diol unit, and third diol unit contained in the polyester of the present invention is usually preferably 75 mol% or more, more preferably 90 mol% or more, and even more preferably 95 mol% or more, when the total of the diol units in the polyester is 100 mol%. The total content is usually 100 mol% or less. The polyester may contain 1 to 5 mol% of units derived from diethylene glycol, a by-product of the condensation polymerization reaction, relative to 100 mol% of the total of the diol units in the polyester.

[0029] The polyester of the present invention may optionally contain units derived from a polyvalent ester, such as pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 1,3,5-tris[2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoyloxy]ethyl]hexahydro-1,3,5-triazine-2,4,6-trione.

[0030] When the polyhydric ester-derived unit is a carboxylic acid ester of a trivalent or higher polyol, and the carboxylic acid is derived from a polyhydric ester having a hindered phenol group, the unit may be incorporated into the polyester of the present invention by melt-kneading the polyhydric ester with terephthalic acid, ethylene glycol, and cyclohexanedimethanol and / or a bisphenol A ethylene oxide adduct to cause condensation polymerization. In the condensation polymerization, the polyol unit of the polyhydric ester and the carboxylic acid unit having a hindered phenol group are incorporated into the polyester by transesterification. The polyol unit is incorporated into the main chain, branched chain, or terminal of the polyester. Some of the polyol units serve as crosslinking points and act as a crosslinking agent. Meanwhile, some of the carboxylic acid units having a hindered phenol group are incorporated into the polyester at the terminal, and some are incorporated into the polyester together with the polyol unit in a state bonded to the polyol unit. As described above, it is believed that the incorporation of the polyhydric ester-derived unit into the polyester improves the drawdown resistance of the polyester of the present invention and further improves the color tone of the resulting molded article. The polyvalent ester is preferably a carboxylic acid ester of a trivalent or greater and pentavalent or less polyol.

[0031] When the polyester of the present invention contains the polyvalent ester-derived units, the content thereof is preferably 0.005 to 0.040% by mass. Here, the content of the polyvalent ester-derived components in the polyester is the total amount of the polyvalent ester-derived units incorporated into the polyester chain and the components not incorporated into the polyester chain. It is considered that the polyvalent ester added during melt-kneading is generally contained in the polyester chain. If the content of the polyvalent ester-derived units is less than 0.005% by mass, the drawdown resistance of the polyester may be reduced, or the polyester may be prone to yellowing when heated during polymerization or molding, resulting in a deterioration in the color tone of the resulting molded article. On the other hand, if the content of the polyvalent ester-derived units exceeds 0.040% by mass, crosslinking by the polyvalent ester-derived units may proceed excessively, resulting in an excessively high melt viscosity and a reduction in the impact resistance of the resulting molded article. The content of the polyvalent ester-derived units is more preferably 0.030% by mass or less, and even more preferably 0.020% by mass or less.

[0032] When the polyester of the present invention contains structural units derived from the polyvalent ester, the total content of structural units derived from terephthalic acid, ethylene glycol, cyclohexanedimethanol, bisphenol A ethylene oxide adduct, and polyvalent ester is preferably 75 mol% or more, more preferably 90 mol% or more, and even more preferably 95 mol% or more, based on the total of all structural units in the polyester. When producing a polyester with this total content less than 75 mol%, the resin tends to soften and stick during solid-state polymerization, making it difficult to achieve a high degree of polymerization. The total content is usually 100 mol% or less.

[0033] The polyester of the present invention may optionally contain structural units derived from bifunctional compounds other than the structural units derived from terephthalic acid, the first diol unit, the second diol unit, and the third diol unit. The content of the structural units derived from the bifunctional compounds (the total content when two or more types of units are present) is preferably 20 mol% or less, more preferably 10 mol% or less, and even more preferably 5 mol% or less, when the total of all structural units constituting the polyester is 100 mol%. The bifunctional compounds may be any of dicarboxylic acids, diols, hydroxycarboxylic acids, and esters, and these may be aliphatic, alicyclic aliphatic, or aromatic. Examples include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-biphenyldicarboxylic acid, and ester-forming derivatives thereof; aliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid, adipic acid, sebacic acid, and dimer acid, and ester-forming derivatives thereof; aliphatic diols such as neopentyl glycol, 1,4-butanediol, 1,5-pentamethylenediol, 1,6-hexamethylenediol, diethylene glycol, and dimer diol; and ethylene oxide adducts of bisphenol S.

[0034] The polyester of the present invention may contain structural units derived from polyfunctional compounds, as long as the effects of the present invention are not impaired. The structural units derived from polyfunctional compounds are polyfunctional compounds derived from polyfunctional compounds having three or more carboxyl groups, hydroxyl groups, and / or ester-forming groups thereof. The content of structural units derived from polyfunctional compounds (the total content when two or more types of units are present) is preferably 0.05% by mass or less, and more preferably 0.04% by mass or less, when the total of all structural units of the polyester is taken as 100 mol %. Examples of polyfunctional compound units include polyfunctional compound units derived from 2-[3-(2-hydroxyethyl)-4-(2-hydroxyethoxy)phenyl]-2-[4-(2-hydroxyethoxy)phenyl]propane, trimellitic acid, pyromellitic acid, trimesic acid, trimethylolpropane, and glycerin. On the other hand, when structural units derived from the polyfunctional compounds are contained, the content thereof is preferably 0.01% by mass or more.

[0035] The polyester of the present invention may, if necessary, be capped at its polymerization terminals or branched terminals with a monofunctional compound. Examples of monofunctional compounds include benzoic acid, 2,4,6-trimethoxybenzoic acid, 2-naphthalenecarboxylic acid, stearic acid, stearyl alcohol, monocarboxylic acids other than carboxylic acids having hindered phenol groups, monoalcohols, and their ester-forming derivatives. The monofunctional compound caps the molecular chain terminal groups and / or branched chain terminal groups of the polyester, preventing excessive crosslinking and gel formation in the polyester. When the polyester contains such monofunctional compound units, the content of the monofunctional compound units (the total content when two or more types of units are present) is preferably 1 mol% or less, and more preferably 0.5 mol% or less, when the total of all structural units of the polyester is taken as 100 mol%. If the content of other monofunctional compound units in the polyester exceeds 1 mol%, the polymerization rate during polyester production slows, tending to reduce productivity.

[0036] The polyester of the present invention may contain other additives as long as the effects of the present invention are not impaired, and examples thereof include colorants such as dyes and pigments, stabilizers such as ultraviolet absorbers, antistatic agents, flame retardants, flame retardant assistants, lubricants, plasticizers, inorganic fillers, etc. The content of these additives is preferably 10% by mass or less, more preferably 5% by mass or less.

[0037] The intrinsic viscosity of the polyester of the present invention is not particularly limited, but from the viewpoint of extrusion blow molding, the lower limit of the intrinsic viscosity is preferably 0.8 dL / g or more, more preferably 0.9 dL / g or more, while from the viewpoint of molding, the upper limit of the intrinsic viscosity is preferably 1.5 dL / g or less, more preferably 1.4 dL / g or less.

[0038] The polyester of the present invention can be produced by employing a known production method. Among these, the polyester of the present invention can be efficiently produced by employing a production method for polyester comprising step (A) of esterifying or transesterifying a carboxylic acid and a diol, step (B) of melt polycondensing the polyester oligomer obtained in step (A), and then step (C) of solid-state polymerizing the composition obtained in step (B), wherein the diol contains 0.001 to 0.5 mol % of 1,2-propanediol when the total amount of the diols is taken as 100 mol %.

[0039] In producing the polyester, the above-mentioned carboxylic acid may be used as it is to form a dicarboxylic acid unit, or a carboxylic acid ester may be used. The alcohol portion of the carboxylic acid ester is not particularly limited, and examples thereof include monools such as methanol and ethanol; and polyols such as ethylene glycol, cyclohexanedimethanol, and bisphenol A ethylene oxide adducts, which are structural units of the polyester.

[0040] In the production of polyester, the diol may be used as it is to form a diol unit, or a monoester or diester of the diol may be used. The carboxylic acid moiety of the monoester or diester is not particularly limited, and examples thereof include carboxylic acids such as formic acid, acetic acid, and propionic acid.

[0041] When a polyvalent ester is used, it may be reacted with a dicarboxylic acid and a diol in the step (A) or may be reacted with a polyvalent ester after the polyester oligomer is obtained.

[0042] When a coloration inhibitor is used in the condensation polymerization, for example, a phosphoric acid compound such as phosphorous acid or an ester thereof can be used, and these can be used alone or in combination of two or more. Examples of phosphoric acid compounds include phosphorous acid, phosphite esters, phosphoric acid, trimethyl phosphate, and triphenyl phosphate. The amount of the coloration inhibitor used is preferably within a range of 80 to 1000 ppm based on the total amount of the dicarboxylic acid component and the diester component. Furthermore, in order to suppress coloration due to thermal decomposition of the polyester, it is preferable to add a cobalt compound such as cobalt acetate, and the amount used is more preferably within a range of 100 to 1000 ppm based on the total amount of the dicarboxylic acid component and the diester component.

[0043] The polymerization catalyst used in the melt polycondensation is preferably a compound containing germanium, antimony, or titanium. Examples of compounds containing antimony include antimony trioxide, antimony chloride, and antimony acetate. Examples of compounds containing germanium include germanium dioxide, germanium tetrachloride, and germanium tetraethoxide. Examples of compounds containing titanium include tetraisopropyl titanate and tetrabutyl titanate. Among these, antimony trioxide and germanium dioxide are preferred in terms of polymerization catalyst activity, the physical properties of the resulting polyester, and cost. When a polycondensation catalyst is used, the amount added is preferably within a range of 0.002 to 0.8% by mass based on the mass of the dicarboxylic acid component.

[0044] The above-mentioned esterification reaction or transesterification reaction is preferably carried out by charging the above-mentioned raw materials, polymerization catalyst, and, if necessary, additives such as a coloring inhibitor into a reactor, and under an absolute pressure of about 0.5 MPa or less or under normal pressure at a temperature of 160 to 280°C while distilling off the produced water or alcohol.

[0045] The melt polycondensation following the esterification reaction or transesterification reaction is preferably carried out by adding the above-mentioned raw materials, polycondensation catalyst, and additives such as a color inhibitor to the resulting polyester oligomer as needed, and then performing the reaction at a reduced pressure of 1 kPa or less at a temperature of 260 to 290°C until a polyester with the desired viscosity is obtained. If the reaction temperature of the melt polycondensation reaction is below 260°C, the polymerization activity of the polymerization catalyst may be low, and a polyester with the desired degree of polymerization may not be obtained. On the other hand, if the reaction temperature of the melt polymerization reaction is above 290°C, the decomposition reaction may be more likely to proceed, and as a result, a polyester with the desired degree of polymerization may not be obtained. The melt polycondensation reaction can be carried out using, for example, a tank-type batch polycondensation apparatus or a continuous polycondensation apparatus consisting of a biaxial rotating horizontal reactor.

[0046] The intrinsic viscosity of the polyester obtained by melt polycondensation is preferably 0.4 dL / g or more. This improves handleability and, when the polyester obtained by melt polycondensation is further subjected to solid-phase polymerization, it can be made into a high molecular weight in a short time, thereby improving productivity. The intrinsic viscosity is more preferably 0.55 dL / g or more, and even more preferably 0.65 dL / g or more. On the other hand, in terms of facilitating the removal of the polyester from the reactor and suppressing discoloration due to thermal degradation, the intrinsic viscosity is preferably 0.9 dL / g or less, more preferably 0.85 dL / g or less, and even more preferably 0.8 dL / g or less.

[0047] The polyester obtained as described above is extruded into a shape such as a strand or a sheet, cooled, and then cut with a strand cutter, a sheet cutter, or the like to produce intermediate pellets having a shape such as a cylindrical, elliptical cylindrical, disk, die, etc. The cooling after extrusion can be carried out by, for example, a water cooling method using a water tank, a method using a cooling drum, or an air cooling method.

[0048] To further increase the degree of polymerization of the intermediate pellets, the intermediate pellets may be subjected to solid-state polymerization. In this case, it is preferable to heat the intermediate pellets prior to solid-state polymerization to partially crystallize the polyester. This prevents the pellets from sticking together during solid-state polymerization. The crystallization temperature is preferably 100 to 180°C. Crystallization may be performed in a vacuum tumbler or by heating in an air-circulating heating device. When heating in an air-circulating heating device, the internal temperature is preferably 100 to 160°C. Heating using an air-circulating heating device has better thermal conductivity than crystallization using a vacuum tumbler, thereby shortening the time required for crystallization and reducing the cost of the device. The time required for crystallization is not particularly limited, but is typically about 30 minutes to 24 hours. It is also preferable to dry the pellets at a temperature below 100°C prior to crystallization.

[0049] The temperature of the solid-state polymerization is preferably 170 to 250°C. If the temperature of the solid-state polymerization is less than 170°C, the solid-state polymerization time may be prolonged, which may result in a decrease in productivity. The temperature of the solid-state polymerization is more preferably 175°C or higher, and even more preferably 180°C or higher. On the other hand, if the temperature of the solid-state polymerization exceeds 250°C, there is a risk of the pellets sticking together. The temperature of the solid-state polymerization is more preferably 240°C or lower, and even more preferably 230°C or lower. The time of the solid-state polymerization is usually about 5 to 70 hours. Furthermore, the catalyst used in the melt polymerization may be present during the solid-state polymerization.

[0050] The solid-state polymerization is preferably carried out under reduced pressure or in an inert gas such as nitrogen gas. To prevent adhesion between pellets, the solid-state polymerization is preferably carried out while moving the pellets by a suitable method such as a rolling method or a gas fluidized bed method. When the solid-state polymerization is carried out under reduced pressure, the pressure is preferably 1 kPa or less.

[0051] The intrinsic viscosity of the polyester obtained by solid-state polymerization varies depending on the type of melt molding method used for the copolymerized polyester. However, when used in melt molding involving melt extrusion, particularly extrusion blow molding, it is preferably 0.8 to 1.5 dL / g. From the perspectives of the mechanical properties, appearance, and productivity of the resulting extrusion blow-molded article, it is more preferably 0.9 to 1.4 dL / g. In particular, when performing extrusion blow molding, if the copolymerized polyester has an intrinsic viscosity of less than 0.8 dL / g, the parison drawdown during extrusion blow molding is likely to be large, resulting in molding defects, and the resulting molded article is likely to have reduced mechanical properties such as tensile strength and impact resistance. On the other hand, if the copolymerized polyester has an intrinsic viscosity greater than 1.5 dL / g, the melt viscosity becomes too high, resulting in poor appearance of the resulting molded article. Furthermore, high torque during extrusion can easily lead to molding problems such as uneven extrusion rates. Furthermore, the time required to extrude a given amount of copolymerized polyester increases, reducing the productivity of molded articles.

[0052] From the viewpoint of further improving the transparency of the resulting molded article, the half-crystallization time at the crystallization peak temperature of the polyester contained in the polyester obtained by solid-state polymerization may be 30 minutes or more. In the present invention, the "peak crystallization temperature" refers to the exothermic peak temperature associated with crystallization, measured using a differential scanning calorimeter (DSC) by heating an amorphous polyester from room temperature (20°C) to a temperature above its melting point (280°C) at a rate of 10°C / min. Furthermore, the "half-crystallization time at the peak crystallization temperature" refers to the time from when the peak crystallization temperature is reached until the amount of heat generated by isothermal crystallization becomes half of the total amount of heat generated, when the polyester is heated to a temperature above its melting point (280°C) using a differential scanning calorimeter (DSC) to melt it, then quenched to the peak crystallization temperature at -50°C / min, and then held at the peak crystallization temperature to perform isothermal crystallization.

[0053] From the viewpoint of preventing the pellets from sticking to the inside of a tumbler during solid-state polymerization, the polyester of the present invention may have a crystalline melting enthalpy of 20 J / g or more. The pellets obtained by solid-state polymerization contain polyester that has been crystallized at high temperatures for a long period of time, and therefore may have such a large crystalline melting enthalpy.

[0054] Various molded articles can be obtained by melt molding the polyester of the present invention. The molding method is not particularly limited, and various melt molding methods, such as extrusion molding and injection molding, can be used. Furthermore, the melt molded article can also be further processed to obtain a molded article. In particular, the polyester of the present invention has a high viscosity during melt molding, making it suitable for extrusion blow molding. The temperature of the resin composition during extrusion molding is preferably within the range of (melting point of polyester + 10°C) to (melting point of polyester + 70°C), and more preferably within the range of (melting point of polyester + 10°C) to (melting point of polyester + 40°C). By extruding at a temperature relatively close to the melting point, drawdown can be suppressed.

[0055] When the polyester of the present invention is used to produce a sheet or film by extrusion molding such as a T-die method or an inflation method, high-quality sheets or films can be produced with good productivity without the occurrence of drawdown, neck-in, film vibration, or unmelted particles. When the sheet or film thus obtained is subjected to secondary processing such as thermoforming, when a deep-drawn molded product or a large molded product is molded, the drawdown is small, the degree of crystallization is good, and thickness unevenness and whitening are unlikely to occur in the process of applying external forces such as vacuum suction or compressed air, and the desired molded product can be obtained with good formability.

[0056] Among extrusion molding methods, extrusion blow molding is particularly suitable for use with the polyester of the present invention. The extrusion blow molding method is not particularly limited, and can be carried out in the same manner as conventionally known extrusion blow molding methods. For example, the extrusion blow molding can be carried out by melt-extruding the polyester of the present invention to form a cylindrical parison, and then sandwiching the parison in a blow mold while it is in a softened state and blowing in a gas such as air to expand the parison into a predetermined hollow shape that conforms to the shape of the mold cavity. When the polyester of the present invention is used, the drawdown property of the extruded parison is good, and hollow molded articles can be produced with good productivity.

[0057] The molded articles thus obtained have excellent transparency, good appearance and color tone, and high mechanical strength, especially impact resistance. Moreover, they also have excellent properties such as gas barrier properties, flavor barrier properties, moisture resistance, and chemical resistance, making them suitable for a variety of applications. They can also be used to form molded articles having a laminate structure with other thermoplastic resins. Molded articles obtained using this polyester have particularly excellent transparency. Thus, molded articles containing the polyester are a preferred embodiment of the present invention, molded articles obtained by extrusion molding the polyester are a more preferred embodiment, and molded articles obtained by extrusion blow molding the polyester are a particularly preferred embodiment.

[0058] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The evaluation methods used in the following examples and comparative examples are shown below.

[0059] (1) Ratio of monomer components The ratio of monomer components that make up polyester is １ The amount of 1,2-propanediol was calculated from the integral ratio of the terephthalic acid peak at around 7.9 to 8.5 ppm and the 1,2-propanediol peak at around 5.3 to 5.7 ppm.

[0060] (2) Intrinsic Viscosity The intrinsic viscosity of the copolymerized polyester obtained in each of the Examples and Comparative Examples was measured at 30°C using an Udderohde viscometer (automatic viscosity measuring device "VMC-422" manufactured by Rigo Co., Ltd.) using a mixture of equal masses of phenol and 1,1,2,2-tetrachloroethane as a solvent.

[0061] (3) Glass Transition Temperature (Tg) and Melting Point (Tm) The melting point (Tm) and glass transition temperature (Tg) of the polyester were measured using a differential scanning calorimeter (TA Instruments, Model TA Q2000). The melting point was measured as the melting peak when the temperature was increased from 30°C to 280°C at a heating rate of 10°C / min, and the glass transition temperature (Tg) was calculated from the data obtained when the temperature was increased from 30°C to 280°C at a heating rate of 10°C / min, then rapidly cooled to 30°C at -50°C / min, and then again increased at a heating rate of 10°C / min.

[0062] (4) Resin color (L ＊ a ＊ b ＊ b in color space ＊ value) Polyester color (b ＊ The color value was measured using a colorimeter (HunterLab's "LSXE LabScan XE"). The measurement pellets were packed into a glass cell, and the measurement was carried out five times by changing the position of the glass cell, and the average value was calculated.

[0063] (5) Bottle Molding, Bottle Drop Strength Test Using an extrusion blow molding machine (Tahara Co., Ltd. "MSE-40E / 32M-A (T1) Model"), a maximum cylinder temperature of 280-290 ° C, a die temperature of 240-250 ° C, a screw rotation speed of 24 rpm, an extrusion resin pressure of 19-30 MPa, and a mold temperature of 30 ° C, a transparent bottle with a volume of 220 mL (27.5 g ± 0.5 g) was molded. The molded bottle was conditioned at 23 ° C for 24 hours. For the bottle drop test, the bottle was filled with water conditioned to 23 ° C so that no air bubbles remained in the bottle, sealed with a cap, and then passed through a vertically installed 10 cm diameter cylinder and dropped alternately from a height of 125 cm onto a horizontal concrete surface and a concrete surface inclined at 45 degrees. The bottle was dropped once on a horizontal surface and once on a 45 degree inclined surface, up to 20 times, until cracks or fractures occurred in the bottle and the water inside leaked. For each composition, a drop test was conducted on five bottles, and the average value was taken as the bottle drop strength. After storing the molded bottles in a thermostatic chamber at 50°C for 67 hours, the bottles were again dropped from a height of 50 cm, and the average of the number of times was taken as the accelerated bottle drop strength (equivalent to 3 months at room temperature). The bottle drop strength and the accelerated bottle drop strength were used as indicators of impact resistance, and the higher the number of times, the better the impact resistance was evaluated to be.

[0064] Example 1 A slurry containing 100.00 parts by weight of terephthalic acid, 42.59 parts by weight of ethylene glycol, 9.49 parts by weight of bisphenol A ethylene oxide adduct, 0.039 parts by weight of 2-[3-(2-hydroxyethyl)-4-(2-hydroxyethoxy)phenyl]-2-[4-(2-hydroxyethoxy)phenyl]propane (hereinafter referred to as "HEPP"), and 0.216 parts by weight of 1,2-propanediol was prepared, to which 0.020 parts by weight of germanium dioxide and 0.015 parts by weight of phosphorous acid were added. This slurry was heated under pressure (absolute pressure 2.5 kg / cm ２) to 250°C, and an esterification reaction was carried out until the esterification rate reached 95%, producing a low polymer. Subsequently, the low polymer was melt-polycondensed at 270°C under a reduced pressure of 1 mmHg to produce a copolymerized polyester prepolymer with an intrinsic viscosity of 0.76 dL / g, which was extruded from a nozzle in the form of a strand and cut into cylindrical chips (diameter 2.5 mm, length 3.5 mm). The copolymerized polyester prepolymer chips obtained above were then pre-dried at 150°C for 5 hours, and then solid-state polymerized at 200°C under a reduced pressure of 0.1 mmHg for 74 hours to obtain a highly molecular weight copolymerized polyester, which was then evaluated as described above in (1) to (5). The results are shown in Tables 1 and 2.

[0065] [Example 2] Polyester was produced and evaluated in the same manner as in Example 1, except that a slurry containing 100.00 parts by weight of terephthalic acid, 43.49 parts by weight of ethylene glycol, 5.64 parts by weight of a bisphenol A ethylene oxide adduct, 0.216 parts by weight of 1,2-propanediol, and 0.089 parts by weight of HEPP was used and the solid-state polymerization time was set as shown in Table 1. The results are shown in Tables 1 and 2.

[0066] [Example 3] Polyesters were produced and evaluated in the same manner as in Example 1, except that a slurry containing 100.00 parts by weight of terephthalic acid, 42.59 parts by weight of ethylene glycol, 9.52 parts by weight of 1,4-cyclohexanedimethanol, 0.216 parts by weight of 1,2-propanediol, and 0.012 parts by weight of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] was used, and the solid-state polymerization time was set as shown in Table 1. The results are shown in Tables 1 and 2.

[0067] [Example 4] Polyester was produced and evaluated in the same manner as in Example 1, except that a slurry containing 100.00 parts by weight of terephthalic acid, 40.69 parts by weight of ethylene glycol, 11.38 parts by weight of a bisphenol A ethylene oxide adduct, 0.133 parts by weight of 1,2-propanediol, and 0.046 parts by weight of HEPP was used and the solid-state polymerization time was set as shown in Table 1. The results are shown in Tables 1 and 2.

[0068] [Example 5] A polyester was produced and evaluated in the same manner as in Example 1, except that a slurry containing 100.00 parts by weight of terephthalic acid, 40.57 parts by weight of ethylene glycol, 11.51 parts by weight of a bisphenol A ethylene oxide adduct, 0.033 parts by weight of 1,2-propanediol, and 0.044 parts by weight of HEPP was used and the solid-state polymerization time was set as shown in Table 1. The results are shown in Tables 1 and 2.

[0069] Comparative Example 1 A polyester was produced and evaluated in the same manner as in Example 1, except that 1,2-propanediol was not added. The results are shown in Tables 1 and 2. Comparative Example 2 A polyester was produced and evaluated in the same manner as in Example 2, except that 1,2-propanediol was not added and the solid-state polymerization time was set as shown in Table 1. The results are shown in Tables 1 and 2. Comparative Example 3 A polyester was produced and evaluated in the same manner as in Example 3, except that 1,2-propanediol was not added and the solid-state polymerization time was set as shown in Table 1. The results are shown in Tables 1 and 2.

[0070] The bottles obtained by molding polyesters (Examples 1 to 5) having first diol units, second diol units, and third diol units and satisfying the above formulas (1) and (2) had good bottle drop strength and accelerated bottle drop strength, despite the low content of the third diol units. On the other hand, the bottles obtained by molding polyesters (Comparative Examples 1 to 3) not containing second diol units had poor bottle drop strength and accelerated bottle drop strength.

[0071]

[0072]

[0073] According to the present invention, a polyester can be obtained which is suitable as a raw material for extrusion blow molding, which has little impact on the environment, and which can be used to produce molded articles having good impact resistance.

Claims

1. A polyester comprising a dicarboxylic acid unit and a diol unit, the dicarboxylic acid unit comprising a structural unit derived from terephthalic acid, the diol unit comprising a first diol unit, a second diol unit, and a third diol unit, the first diol unit being a structural unit derived from ethylene glycol, the second diol unit being a structural unit derived from 1,2-propanediol, and the third diol unit being a structural unit derived from a bisphenol A ethylene oxide adduct and / or a cyclohexane dimethanol, wherein, when the total of the diol units contained in the polyester is taken as 100 mol %, a content X (mol %) of the second diol unit, a content Y (mol %) of the structural unit derived from the bisphenol A ethylene oxide adduct, and a content Z (mol %) of the structural unit derived from the cyclohexane dimethanol satisfy the following formulas (1) and (2): 0.001≦X≦0.5 (1) 2≦Y+Z≦25 (2)

2. 2. The polyester according to claim 1, wherein the content X (mol%) of the second diol unit, the content Y (mol%) of the structural unit derived from the bisphenol A ethylene oxide adduct, and the content Z (mol%) of the structural unit derived from the cyclohexanedimethanol satisfy the following formula (3): 5≦(Y+Z) / X≦100(3)

3. 2. The polyester according to claim 1, wherein the content of the first diol unit is 75 to 98 mol % when the total amount of the diol units contained in the polyester is 100 mol %.

4. 2. The polyester according to claim 1, having an intrinsic viscosity of 0.8 to 1.5 dL / g.

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

6. A molded article obtained by extrusion blow molding the polyester according to any one of claims 1 to 4.