JP2014227479A - Hydrolysis inhibiting polyester and production method of polyester composition using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester composition and a production method of the composition, in which foaming is suppressed while a terminal carboxyl group amount is reduced by using oxalic acid.SOLUTION: A hydrolysis inhibiting polyester is provided, in which an acid component includes 10 to 70 mol% of an oxalic acid component and 90 to 30 mol% of an aromatic dicarboxylic acid component, and a glycol component includes 80 mol% or more of an alkylene glycol component having 2 to 4 carbon atoms. The polyester contains Sn by 50 ppm or less and has an intrinsic viscosity of 0.25 to 0.75 dl/g and a melting point of 180 to 250°C. The production method of a polyester composition comprises melting and kneading the above hydrolysis inhibiting polyester and a polyester having an add amount of oxalic acid by 0 mol% or more and less than 0.2 mol% and an Sb content of 50 ppm or less, in such a way that the amount of the added oxalic acid component reaches 0.2 to 5.0 mol% on a molar number basis of the whole acid component.

Description

  The present invention relates to a polyester copolymerized with oxalic acid to improve hydrolysis resistance and a method for producing a polyester composition using the same.

Polyesters, especially polyethylene terephthalate, have been widely used because of their excellent productivity, mechanical properties, thermal properties, electrical properties, chemical properties and dimensional stability. However, when most polyesters are used in a high-temperature and high-humidity environment, there is a problem that the physical performance tends to deteriorate due to hydrolysis and the use period and use conditions are limited.
In recent years, in solar cell applications used in harsh natural environments, it has been demanded to improve long-term reliability. When a polyester film is used as a solar cell protective film, it has excellent hydrolysis resistance. It is necessary to grant.

  Various proposals have conventionally been made to improve the hydrolysis resistance of polyester. Under such circumstances, Patent Documents 1 to 3 propose that copolymerization of oxalic acid can reduce the amount of terminal carboxyl groups of polyester that greatly affects hydrolysis resistance. Specifically, Patent Document 1 describes a method of adding an oxalic acid glycol ester and / or an oxalic acid-based polyester having a polymerization degree of 4 or less. Patent Document 2 describes a method of adding a low-polymerization degree oligomer having oxalic acid glycol ester and / or oxalic acid as an acid component to polybutylene naphthalate. Furthermore, Patent Document 3 proposes adding oxalic acid as it is for the purpose of omitting the glycol ester synthesis step of oxalic acid.

  However, as disclosed in these Patent Documents 1-3, the method of adding a glycol ester of oxalic acid or a low polymer thereof to a polyester reaction system can reduce the amount of terminal carboxyl groups, It has been found that a large amount of bubbles are generated in the produced polyester and the quality is deteriorated.

Japanese Patent Publication No. 48-35953 JP-A-6-263850 JP-A-8-208816

  This invention is providing the manufacturing method of the polyester composition which suppressed generation | occurrence | production of the bubble while reducing the amount of terminal carboxyl groups using the oxalic acid, ie, the problem which the said prior art has.

  As a result of intensive studies to achieve the above object, the inventors of the present invention have an intrinsic viscosity of 0.25 to 25% copolymerized in the absence of an antimony compound so that 10 to 70 mol% of the acid component becomes an oxalic acid component. A polyester having a melting point of 180 to 250 ° C. at 0.75 dl / g (hereinafter referred to as a hydrolysis-inhibiting polyester) was produced in advance, and this was not copolymerized with oxalic acid or copolymerized in a trace amount. The present inventors have found that the amount of terminal carboxyl groups can be reduced while suppressing air bubbles by mixing with a polyester containing almost no antimony compound (hereinafter abbreviated as a diluted polymer).

Thus, according to the present invention, the following 1) to 2) hydrolysis-inhibiting polyesters and the following 3) to 4) polyester composition production methods are provided.
1) From a copolyester in which 10 to 70 mol% of the acid component is an oxalic acid component, 90 to 30 mol% is an aromatic dicarboxylic acid component, and 80 mol% or more of the glycol component is an alkylene glycol component having 2 to 4 carbon atoms The hydrolysis-inhibiting polyester having an antimony element content of 50 ppm or less, an intrinsic viscosity of 0.25 to 0.75 dl / g, and a melting point of 180 to 250 ° C. with respect to the mass of the polyester.
2) The hydrolysis-inhibiting polyester according to 1) above, wherein the polymerization catalyst is a titanium compound.
3) The content of antimony contained in the hydrolysis-inhibiting polyester according to any one of the above-mentioned 1-2 and oxalic acid is 0 mol% or more and less than 0.2 mol% based on the number of moles of all acid components. A method for producing a polyester composition in which 50 ppm or less of polyester is melt-kneaded with respect to the mass of the polyester, wherein the amount of oxalic acid component contained is the number of moles of all acid components of the polyester constituting the polyester composition. A method for producing a polyester composition, which is melt-kneaded so as to be 0.2 to 5.0 mol% as a reference.
4) The method for producing a polyester composition as described in 3) above, wherein a polyester having an oxalic acid content of 0.2 to 5.0 mol% based on the number of moles of all acid components is further melt kneaded.

  According to the present invention, it is possible to produce a polyester composition having extremely good hydrolysis resistance with less bubbles. Moreover, if the manufacturing method of the polyester composition of this invention is used, the amount of terminal carboxyl groups can also be adjusted arbitrarily only by adjusting the compounding quantity of a hydrolysis suppression polyester. In addition, if the polyester composition obtained by the production method of the present invention is used, it has excellent hydrolysis resistance but has few bubbles, so that it can be formed into an extremely high-quality molded product such as a film.

  Hereinafter, the hydrolysis-inhibiting polyester, the polyester composition, and the production method thereof of the present invention will be described.

<Hydrolysis-inhibiting polyester>
In the hydrolysis-inhibiting polyester of the present invention, 10 to 70 mol% of the acid component is an oxalic acid component, 90 to 30 mol% is an aromatic dicarboxylic acid component, and 80 mol% or more of the glycol component is an alkylene glycol having 2 to 4 carbon atoms. It consists of copolymerized polyester as a component, has an intrinsic viscosity of 0.25 to 0.75 dl / g, and a melting point of 180 to 250 ° C.

  If the oxalic acid component is less than the lower limit, the effect of reducing the amount of carboxyl groups is small when mixed with the dilute polymer described below, and if the upper limit is exceeded, foaming during the production of the hydrolysis-inhibiting polyester is remarkable and productivity is impaired. It is. The minimum of the copolymerization amount of a preferable oxalic acid component is 20 mol% or more, and an upper limit is 50 mol% or less, The upper limit of the copolymerization amount of a preferable aromatic dicarboxylic acid component is 80 mol% or less, and a minimum is 50 mol% or more.

  Moreover, generation | occurrence | production of a bubble can also be suppressed, reducing the amount of a terminal carboxyl group efficiently, when mixing with the dilution polymer mentioned later because the intrinsic viscosity of the hydrolysis suppression polyester of this invention exists in the said range. The preferable lower limit of the intrinsic viscosity is 0.45 dl / g, and the preferable upper limit is 0.70 dl / g.

  Moreover, generation | occurrence | production of a bubble can also be suppressed, reducing the amount of a terminal carboxyl group efficiently, when mixing with the dilution polymer mentioned later because melting | fusing point of the hydrolysis suppression polyester of this invention exists in the said range. The preferable lower limit of the melting point is 190 ° C., and the preferable upper limit is 240 ° C.

  By the way, although the oxalic acid component in this invention may be used in the state of oxalic acid, it is preferable to use it in the form of an oxalic acid ester. Oxalates include dimethyl oxalate, diethyl oxalate, di-n-propyl oxalate, diisopropyl oxalate, dibutyl oxalate, dipentyl oxalate, dihexyl oxalate, diheptyl oxalate, dioctyl oxalate, dinonyl oxalate, Examples include didecyl oxalate, diundecyl oxalate, didodecyl oxalate, diphenyl oxalate, dinaphthyl oxalate, and the like. Among them, dimethyl oxalate and diethyl oxalate are preferable.

  In addition, examples of the aromatic dicarboxylic acid component in the present invention include a terephthalic acid component, a naphthalenedicarboxylic acid component, an isophthalic acid component, a diphenyl ketone dicarboxylic acid component, and an anthracene dicarboxylic acid component. These aromatic dicarboxylic acid components may be used as they are, or may be used in the form of a derivative such as a lower alkyl ester having 1 to 3 carbon atoms. Among these, from the viewpoint of the effects of the present invention, a terephthalic acid component and a 2,6-naphthalenedicarboxylic acid component are preferable, and a terephthalic acid component is particularly preferable.

  In addition, examples of the glycol component in the present invention include linear, branched, and cyclic aliphatic diols. Specific examples include ethylene glycol, propylene glycol, trimethylene glycol, and 1,2-tetramethylene glycol. 1,3-tetramethylene glycol, 1,4-tetramethylene glycol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecane Examples include diol, 3-methylpentanediol, neopentylene glycol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, tetraethylene glycol, and dipropylene glycol. Among these, ethylene glycol, trimethylene glycol, 1,4-tetramethylene glycol, 1,6-hexanediol, and tetraethylene glycol can be exemplified, and ethylene glycol is particularly preferable from the viewpoint of the effect of the present invention.

  Next, the method for producing the hydrolysis-inhibiting polyester of the present invention will be described with reference to a method of polycondensation via an ester exchange reaction, but the present invention is not limited thereto.

  First, the oxalic acid component is added at the time of producing the hydrolysis-inhibiting polyester of the present invention after the aromatic dicarboxylic acid component and the glycol component substantially complete the esterification reaction or transesterification reaction. preferable. For example, when an oxalic acid component and an aromatic dicarboxylic acid component are charged at the same time and a transesterification reaction proceeds in the presence of a glycol component, a reaction failure tends to occur. Thereafter, a polycondensation reaction is carried out, and the reaction temperature at that time is preferably in the range of a temperature higher by 15 ° C. or more than the boiling point of the glycol component to be used to 260 ° C. If this temperature is lower than the boiling point of the glycol component + 15 ° C., the used glycol component tends to remain in the hydrolysis-inhibiting polyester, the reaction does not proceed, the melting point is lowered, or the melting point itself is not amorphous. On the other hand, when the polycondensation reaction temperature exceeds 260 ° C., the obtained hydrolysis-inhibiting polyester is greatly deteriorated, and the intrinsic viscosity does not increase or bubbles are remarkably generated.

The details will be described below.
Examples of the transesterification reaction catalyst used in the above reaction include those known per se, and preferred examples include calcium compounds, magnesium compounds, manganese compounds, and titanium compounds. Moreover, in order to further reduce the number of carboxylic acid terminal groups of the obtained polyester before the beginning of the transesterification reaction and during the initial reaction, a trace amount of an alkali metal compound such as potassium hydroxide may be added. In order to improve electrostatic application characteristics, a trace amount of a magnesium compound such as magnesium acetate may be added between the end of the transesterification reaction and the beginning of the polycondensation reaction.

The precursor thus obtained through the transesterification reaction is subjected to a polycondensation reaction in a molten state. At this time, the phosphorus compound is preferably added by the initial stage of the polycondensation reaction, preferably after completion of the transesterification reaction. Although it does not specifically limit as a phosphorus compound, Orthophosphoric acid, phosphorous acid, phenylphosphonic acid, a phosphonic acid type compound, a phosphinic acid type compound, a phosphine oxide type compound, a phosphonous acid type compound, a phosphinic acid type compound, a phosphine When one or two or more compounds selected from the group consisting of a series compound are used, the effect of improving the catalytic activity is greatly preferred, and among these, phenylphosphonic acid is particularly preferred.
As the polycondensation reaction catalyst, those known per se can be used, and examples thereof include compounds such as titanium, germanium, zinc, iron, tin, manganese, cobalt, lithium, calcium, and antimony.

  By the way, from the point of the effect of this invention, about the antimony compound, the content is 50 ppm or less with respect to the mass of polyester by the amount of antimony elements, It is preferable that the antimony compound is not added. When the amount of the antimony element exceeds the upper limit, the decomposition reaction of the oxalic acid component is likely to proceed, and bubbles are likely to be generated in the obtained hydrolysis-inhibiting polyester. From such a viewpoint, the polycondensation reaction catalyst is preferably a titanium compound that can be used as a transesterification reaction catalyst and is less prone to decomposition of oxalic acid than an antimony compound.

<Diluted polymer>
The diluted polymer in the present invention is polyester, and the content of oxalic acid is in the range of 0 mol% or more and less than 0.2 mol% based on the number of moles of all acid components. If the content of oxalic acid exceeds the upper limit, the diluted polymer itself contains a large amount of bubbles or the proportion of hydrolysis-inhibiting polyester that can be melt-kneaded decreases, and the effect of reducing the carboxyl group amount when melt-kneaded is poor. Become.

  The polyester constituting the diluted polymer is not particularly limited as long as it is substantially linear and has film-forming properties, particularly film-forming properties by melt molding. Among them, alkylene terephthalate and alkylene naphthalate are used. The main constituents are preferred, particularly polyethylene terephthalate, polyethylene-2,6-naphthalenedicarboxylate, and for example, 80 mol% or more of all dicarboxylic acid components are terephthalic acid or 2,6-naphthalenedicarboxylic acid. Homopolymers and copolymers are preferred. Particularly preferred is a polyester in which 85 mol% or more of the repeating units are ethylene terephthalate.

  The intrinsic viscosity of the polyester constituting the diluted polymer is preferably 0.60 dl / g or more, and the upper limit is preferably 0.85 dl / g or less. By being in such a range, kneading with the above-described hydrolysis-inhibiting polyester can be easily performed uniformly while suppressing the generation of bubbles, while sufficiently expressing the effect of reducing the amount of carboxyl groups. The preferred lower limit of intrinsic viscosity is 0.62 dlg, while the upper limit is 0.75 dl / g.

  When ethylene glycol is selected as the glycol component in the diluted polymer in the present invention, the content of diethylene glycol contained as a by-product is 1.3% by weight or less, further 1.2% by weight or less, particularly 1.0% by weight. The following is preferable. If the amount of diethylene glycol exceeds the upper limit, the reason is not clear, but the durability after film formation may be inferior.

The amount of carboxyl groups of the diluted polymer in the present invention is preferably 15 eq / t or less, more preferably 13 eq / t or less, from the viewpoint of hydrolysis resistance, in an amount per 10 ⁶ g of the polyester. . Although a minimum in particular is not restrict | limited, From points, such as productivity, it is 5 eq / t or more.

  The diluted polymer in the present invention will be described below by taking polyethylene terephthalate (hereinafter sometimes referred to as PET) as an example. First, a precursor may be produced by esterifying or transesterifying terephthalic acid or an ester-forming derivative thereof and ethylene glycol, and the obtained precursor may be subjected to a polycondensation reaction in the presence of a catalyst. That is, the reaction may be conducted through either a transesterification reaction using an ester-forming derivative of terephthalic acid as a raw material or an esterification reaction using terephthalic acid as a raw material. At that time, as a preferred embodiment of the present invention, solid phase polymerization may be further performed. Examples of ester-forming derivatives of terephthalic acid include lower alkyl esters such as dimethyl ester, diethyl ester, and dipropyl ester of terephthalic acid.

  The conditions and catalyst for the transesterification reaction and esterification reaction are not particularly limited, and a method known per se can be suitably employed. Specific examples of the transesterification reaction catalyst include calcium, magnesium, manganese, and titanium compounds. On the other hand, in the case of passing through the esterification reaction, the conditions for the esterification reaction and the catalyst are not particularly limited, and a method known per se can be suitably employed. The esterification reaction catalyst may or may not be used, but when it is used, those exemplified for the above-mentioned transesterification reaction catalyst are preferable.

  In addition, in order to further reduce the number of carboxylic acid end groups of the obtained PET during the initial to intermediate period of the esterification reaction or before the start of the transesterification reaction, the addition of a trace amount of an alkali metal compound such as potassium hydroxide is added. You may do it. In order to improve electrostatic application characteristics, a trace amount of a magnesium compound such as magnesium acetate may be added from the end of the esterification reaction to the beginning of the polycondensation reaction or before the start of the transesterification reaction.

  The precursor thus obtained through the esterification reaction or transesterification reaction is subjected to a polycondensation reaction in a molten state. At this time, the phosphorus compound is preferably added by the initial stage of the polycondensation reaction, preferably after completion of the esterification reaction or transesterification reaction. Although it does not specifically limit as a phosphorus compound, Orthophosphoric acid, phosphorous acid, phenylphosphonic acid, a phosphonic acid type compound, a phosphinic acid type compound, a phosphine oxide type compound, a phosphonous acid type compound, a phosphinic acid type compound, a phosphine Use of one or two or more compounds selected from the group consisting of a series compound is preferred because the effect of improving the catalytic activity is great. Of these, phenylphosphonic acid is preferred because it does not deactivate the polymerization activity even at low temperatures.

  Next, the precursor obtained via the transesterification or esterification reaction is subjected to a polycondensation reaction in a molten state. In this case, phenylphosphonic acid and the polycondensation reaction catalyst are prepared by the initial stage of the polycondensation reaction, preferably during the polycondensation reaction until the intrinsic viscosity becomes 0.3 dl / g after completion of the transesterification reaction or esterification reaction. It is preferable to add a catalyst such as antimony, germanium, or titanium compound. As the order of addition, it is preferable from the viewpoint of polycondensation reactivity and hydrolysis resistance that the addition interval is 5 minutes or more in the order of phenylphosphonic acid and polycondensation reaction catalyst. Among them, the content of the antimony compound is the amount of antimony element and is 50 ppm or less with respect to the mass of the polyester, and more preferably substantially no addition is preferable. When this value exceeds the upper limit, bubbles tend to be generated when melt-kneaded with the aforementioned hydrolysis-inhibiting polyester.

  In order to make the present invention more effective, the temperature of the polycondensation reaction of the diluted polymer is preferably in the range of the melting point of the obtained polyester to the melting point + 20 ° C., and more preferably in the range of the melting point to the melting point + 10 ° C. For example, polyethylene terephthalate usually undergoes a polycondensation reaction at 280 to 300 ° C., but if phenylphosphonic acid is used, the polycondensation reaction is not deactivated even at low temperatures, so that the polycondensation reaction rate is maintained even at low temperatures. The number of carboxylic acid end groups of the diluted polymer can be reduced. The preferable polycondensation reaction temperature in the case of polyethylene terephthalate is 268 to 275 ° C, and more preferably 269 to 272 ° C.

  Furthermore, in the present invention, it is also preferable to carry out solid phase polymerization to obtain a polyester with a small amount of oligomer. Solid-phase polymerization can be suitably performed by a method known per se, and is not particularly limited. For example, the solid state polyester may be retained and polymerized at a temperature of 150 to 250 ° C. in a vacuum or under a nitrogen stream until a desired intrinsic viscosity is obtained. Examples of the method for retaining the polyester chips under the above-described conditions include, for example, a method for retaining in a rotating sealed reaction vessel, and a method for retaining the chips for an arbitrary time while continuously moving the chips in a reaction tank having a certain volume. Methods.

<Polyester composition>
The polyester composition of the present invention is obtained by melt-kneading the aforementioned hydrolysis-inhibiting polyester of the present invention and the aforementioned diluted polymer. The feature of the present invention is that the amount of carboxyl groups can be reduced even when such a hydrolysis-inhibiting polyester is melt-kneaded without being added in the polymerization stage. It has been found that generation can be suppressed.

  In the polyester composition of the present invention, the amount of the oxalic acid component added needs to be in the range of 0.2 to 5.0 mol% based on the number of moles of all acid components of the polyester constituting the polyester composition. It is. When the amount of the added oxalic acid component exceeds the upper limit, the generation of bubbles increases, and when the amount is less than the lower limit, the effect of reducing carboxyl groups becomes poor. From such a viewpoint, the preferable lower limit of the amount of the oxalic acid component is 0.35 mol%, and the upper limit is 2.5 mol%.

In the polyester composition of the present invention, the amount of terminal carboxyl groups is 35 equivalents / 10 ⁶ g or less and 30 eq / 10 ⁶ g or less in terms of hydrolysis resistance in an amount per 10 ⁶ g of polyester. It is preferable that it is 25 eq / 10 ⁶ g or less. The lower limit is not particularly limited, but is 10 eq / 10 ⁶ g from the viewpoint of productivity. Hereinafter, eq / 10 ⁶ g may be simply referred to as “eq / t”.

  The ratio at the time of melt-kneading the above-mentioned hydrolysis-inhibiting polyester of the present invention and the above-mentioned diluted polymer may be adjusted so that the amount of the oxalic acid component in the polyester composition falls within the above range, and is not particularly limited. . However, since it is easy to uniformly disperse the hydrolysis-inhibiting polyester when melt-kneaded, the weight ratio of the diluted polymer to the hydrolysis-inhibiting polyester (diluted polymer: hydrolysis-inhibiting polyester) is 2: 1 to 100: 1. It is preferable that it is the range of 5: 1 to 20: 1.

  By the way, the polyester composition of the present invention melt-kneaded polyester having an addition amount of oxalic acid of 0.2 to 5.0 mol% based on the number of moles of all acid components within a range not impairing the effects of the present invention. It is also preferable to do. Examples of such a polyester include a recovered polyester obtained by recovering a part that has not become a product such as an edge produced when the polyester composition of the present invention is formed into a film. The ratio in the case of melt kneading in combination with this recovered polyester is not particularly limited, but from the viewpoint of the effect of the present invention, it is 70% by weight or less, and further 50% by weight based on the weight of the obtained polyester composition of the present invention. The following is preferred. On the other hand, the lower limit is not particularly limited, but is preferably 10% by weight or more, and more preferably 20% by weight or more from the viewpoint of increasing the use ratio of the recovered polymer. The amount of terminal carboxyl groups of the recovered polyester is not limited, but is preferably 60 eq / t or less, more preferably 50 eq / t or less, and the intrinsic viscosity is 0.40 dl / g or more, more preferably 0.45 dl / g or more.

  Of course, the hydrolysis-inhibiting polyester and polyester composition of the present invention, as well as the diluted polymer and recovered polymer of the present invention, are within the range that does not impair the effects of the present invention, for example, lubricants, pigments, dyes, antioxidants, light Additives such as stabilizers and light-shielding agents (for example, carbon black, titanium oxide, etc.) can be included as required.

<Method for producing polyester composition>
As a method for producing the polyester composition of the present invention, a method known per se can be adopted except that the hydrolysis-inhibiting polyester, the diluted polymer, and, if necessary, the recovered polymer are used. Specifically, the extruder for melt-kneading the hydrolysis-inhibiting polyester and the diluted polymer may be a single-screw extruder or a twin-screw extruder, and a twin-screw extruder is preferable from the viewpoint of quickly performing melt-kneading. From the viewpoint of suppressing deterioration due to heat, a single screw extruder is preferable. Further, a tandem type having a structure in which the first stage kneader and the second stage kneader are connected in series may be used. In order to suppress thermal deterioration, it is also preferable to use an extruder with a vent.

  By the way, the temperature at the time of melt-kneading is obtained from the viewpoint of suppressing the increase of terminal carboxyl groups generated by thermal decomposition during melt-kneading while reducing the amount of terminal carboxyl groups in the obtained polyester composition by the hydrolysis-inhibiting polyester. It is the range of Tm + 10 degreeC to Tm + 60 degreeC with respect to melting | fusing point (Tm: degreeC) of the polyester composition obtained. Moreover, it is preferable to perform the residence time of melt-kneading for 30 to 600 seconds. The preferable melt kneading temperature is in the range of Tm + 20 ° C. to Tm + 45 ° C., and the melt kneading residence time is 60 to 300 seconds.

(1) Intrinsic Viscosity Polyester was dissolved in a phenol: trichloroethane mixed solvent having a weight ratio of 6: 4 under an atmosphere of 35 ° C., and measured using an Ostwald viscometer. The unit is indicated by [dl / g].

(2) a carboxylic acid end groups obtained polyester chips, under nitrogen atmosphere, was dissolved in benzyl alcohol at 200 ° C., by the titration method, as the number of equivalents of the mass 10 per 6 ^g of the polyester carboxylic acid end groups ( eq / t).

(3) Melting point (Tm: ° C)
By using a Du Pont Instruments 910 DSC for the obtained polyester chip, a melting peak is obtained at a temperature rising rate of 20 ° C./min. The sample amount is 20 mg.

(4) Antimony content in polymer The polyester and polyester composition obtained were washed and dried twice with distilled acetone, and 0.200 g was collected. Next, it is wet-decomposed with reagent-grade sulfuric acid, nitric acid, etc., and 20 ml of ion-exchanged distilled water is added to obtain a sample solution. The sample solution was subjected to antimony metal quantitative analysis using a high-frequency plasma emission spectroscopic analyzer (manufactured by Jarrel Ash, apparatus name: Atom Comp Series 800).

(5) Hydrolysis resistance After the obtained polyester composition was dried at 160 ° C. for 6 hours in an electric dryer, it was melt-extruded at 298 ° C. using an extruder manufactured by Hitachi, Ltd. (P40-22AB type), and manufactured by Nippon Steel Works. A polyester sheet having a thickness of 500 μm was prepared using a 2-type film manufacturing apparatus (horizontal moving type). Next, this was stretched with a long stretching machine to obtain a film having a thickness of 45 μm. This film was treated for 72 hours under the conditions of a temperature of 110 ° C. and a humidity of 100% RH using a PC-3011 type pressure cooker manufactured by Hirayama Seisakusho Co., Ltd., and the number of carboxylic acid end groups was measured for this sample. Evaluation was based on the increase in the number of carboxyl groups at the front and rear ends. The lower the increase in the number of carboxyl groups at the end, the better the hydrolysis resistance.

(6) Evaluation of bubbles in polymer After the obtained polyester chip was dried at 160 ° C. for 6 hours in an electric dryer, it was melt-extruded at 298 ° C. with an extruder (P40-22AB type) manufactured by Hitachi, Ltd., and manufactured by Nippon Steel Works. A polyester sheet having a thickness of 500 μm was prepared using a 2-type film manufacturing apparatus (horizontal moving type). Next, this was stretched with a long stretching machine to obtain a film having a thickness of 45 μm. This film was observed under polarized light with a microscope, and the number of surface protrusions due to bubbles was evaluated according to the following criteria.
In addition, the number of surface protrusions was picked up protrusions having a major axis of 30 μm or more, and counted with a film area of 25 cm ² (measured number of times, n = 5).
0 ≤ Number of surface protrusions <5 Very good (◎)
5 ≤ Number of surface protrusions <10 Good (○)
10 <number of surface protrusions <15 pieces Slightly poor (×)
15 ≤ number of surface protrusions (XX)

[Example 1] Hydrolysis-inhibiting polyester 1
A transesterification reaction vessel was charged with 12840 parts of dimethyl terephthalate, 8140 parts by weight of ethylene glycol, and 13.5 parts of manganese acetate tetrahydrate, heated to 150 ° C., melted and stirred. The reaction was advanced while the temperature inside the reaction vessel was slowly raised to 240 ° C., and the produced methanol was distilled out of the reaction vessel. When the distillation of methanol was completed, 5200 parts of dimethyl oxalate (corresponding to 40 mol% relative to the acid component) was added thereafter, and the transesterification reaction was continued, and the reaction was terminated when 11100 parts of methanol was distilled. Next, 8.20 parts of phosphorous acid (ethylene glycol solution = 55%) was added, and after 5 minutes, 89 parts of titanium trimellitic acid (at a Ti concentration of 0.59 mass% in the ethylene glycol solution) was added. After heating to 240 ° C. to distill a part of ethylene glycol, the reaction product was transferred to a polycondensation apparatus having a stirring blade inside. The reaction product was subjected to a polycondensation reaction, and the reaction temperature was allowed to reach 220 ° C. over 30 minutes while gradually increasing the degree of vacuum with a vacuum pump. While maintaining this temperature, the degree of vacuum was kept at 35 Pa or less, and the polycondensation reaction was carried out for 220 minutes. Next, after the stirring blade was stopped to perform the polymer discharging operation, the inside of the PN reaction kettle system was pressurized to 0.17 MPa with nitrogen gas, and the polyester was extruded from the die hole into a strand shape. Thereafter, the polyester was cooled with a cooling bath, and then cut with a letterer to obtain a hydrolysis-inhibited polyester chip having a major axis of about 4 mm, a minor axis of about 2 mm, and a length of about 4 mm. The obtained hydrolysis-inhibiting polyester had an intrinsic viscosity of 0.59 dl / g and a melting point of 207 ° C.

[Example 2] Hydrolysis-inhibiting polyester 2
Addition of 89 parts of trimellitic acid titanium (ethylene glycol solution = 0.59%), 69 parts of trimellitic acid titanium (ethylene glycol solution = Ti concentration 0.59%) and 1.3 parts of antimony trioxide The reaction was carried out in the same manner as in Example 1 except that the addition was performed. Table 1 shows the properties of the obtained hydrolysis-inhibiting polyester. The antimony content in the polymer was 29 ppm.

[Example 3] Hydrolysis-inhibiting polyester 3
A hydrolysis-inhibiting polyester was obtained in the same manner as in Example 1 except that 19260 parts of dimethylene terephthalate and 1300 parts of methyl oxalate (corresponding to 10 mol% relative to the acid component) were changed. Table 1 shows the properties of the obtained hydrolysis-inhibiting polyester.

[Example 4] Hydrolysis-inhibiting polyester 4
A hydrolysis-inhibiting polyester was obtained in the same manner as in Example 1 except that dimethylene terephthalate was changed to 6420 parts and methyl oxalate was changed to 9100 parts (corresponding to 70 mol% of acid component). Table 1 shows the properties of the obtained hydrolysis-suppressed polyester.

[Comparative Example 1] Hydrolysis-inhibiting polyester 5
A hydrolysis-inhibiting polyester was obtained in the same manner as in Example 1 except that dimethylene terephthalate was changed to 20330 parts and methyl oxalate was changed to 650 parts (corresponding to 5 mol% relative to the acid component). Table 1 shows the properties of the obtained hydrolysis-inhibiting polyester.

[Comparative Example 2] Hydrolysis-inhibiting polyester 6
A polymer was obtained in the same manner as in Example 1, except that dimethylene terephthalate was changed to 4280 parts and methyl oxalate was changed to 10400 parts (corresponding to acid component, corresponding to 80 mol%). The properties of the obtained polyester are shown in Table 1. Polyester was remarkably rich in bubbles and could not be pelletized into a chip shape due to strand breakage.

[Comparative Example 3] Hydrolysis-inhibiting polyester 7
A polymer was obtained in the same manner as in Example 1, except that dimethylene terephthalate was changed to 6420 parts, methyl oxalate was changed to 9100 parts (corresponding to 70 mol% of acid component), and the polycondensation reaction temperature was 204 ° C. Table 1 shows the properties of the obtained hydrolysis-inhibiting polyester. Due to the low reaction temperature, the melting point was low, and the polymer became amorphous and difficult to be pelletized.

[Comparative Example 4] Hydrolysis inhibition polyester 8
The reaction was conducted in the same manner as in Example 1 except that the addition of 89 parts of trimellitic acid titanium (ethylene glycol solution = 0.59%) was changed to the addition of 13.0 parts of antimony trioxide. The physical properties of the obtained polymer are shown in Table-1. The antimony content in the polymer was 300 ppm. The polymer had many bubbles and was difficult to pelletize.

  ND in Table 1 means not detected.

[Reference Example 1] Diluted polymer 1
A transesterification vessel was charged with 100 parts by weight of dimethyl terephthalate, 60 parts by weight of ethylene glycol, and 0.019 part of manganese acetate tetrahydrate, heated to 150 ° C., melted and stirred. The reaction was advanced while the temperature inside the reaction vessel was slowly raised to 235 ° C., and the methanol produced was distilled out of the reaction vessel. When the distillation of methanol was completed, 0.014 part of phenylphosphonic acid was added as a phosphorus compound to complete the transesterification reaction. Subsequently, 0.015 part of antimony trioxide and 0.005 part of tetrabutoxy titanate were added as a polycondensation catalyst after 5 minutes and heated to 240 ° C. to distill a part of ethylene glycol. It shifted to the polycondensation apparatus which has a stirring blade inside. Next, 95 minutes were required while gradually increasing the degree of vacuum with a vacuum pump, and the reaction temperature was allowed to reach 273 ° C. While maintaining this temperature, the degree of vacuum was maintained at 35 Pa or less, and the polycondensation reaction was carried out for 190 minutes. Next, after the stirring blade was stopped to perform the polymer discharging operation, the inside of the PN reaction kettle system was pressurized to 0.24 MPa with nitrogen gas, and the polyester was extruded from the die hole into a strand shape. Thereafter, the polyester was cooled with a cooling bath, and then cut with a letterer to obtain a polyester chip having a major axis of about 4 mm, a minor axis of about 2 mm, and a length of about 4 mm. The obtained polymer had an intrinsic viscosity of 0.52 dl / g and a carboxylic acid end group number of 14.0 eq / t. Next, the obtained polymer was pre-dried at 160 ° C. for 4 hours, and then charged in a rotary tumbler type solid-phase polymerization reactor, and subjected to solid-phase polymerization at 225 ° C. and a vacuum of 67 Pa or less for 17 hours. Diluted polymer 1 having 0.75 dl / g, carboxylic acid terminal group number of 8.3 eq / t, and antimony element content of 47 ppm was obtained. The properties of the obtained diluted polymer 1 are shown in Table 2.

[Reference Example 2] Diluted polymer 2
In a reactor in which 225 parts of the oligomers were previously retained, 179 parts of high-purity terephthalic acid and 95 parts of ethylene glycol were mixed with stirring under a nitrogen atmosphere at 255 ° C. and normal pressure. The prepared slurry was supplied at a constant rate, and the esterification reaction was completed for 4 hours while water and ethylene glycol generated in the reaction were distilled out of the system to complete the reaction. 225 parts of the oligomer obtained by this esterification reaction was transferred to a polycondensation reaction tank, and 0.018 part of tetrabutoxy titanate was added as a polycondensation catalyst. Subsequently, the polycondensation reaction is carried out while the reaction temperature in the system is increased and reduced in steps from 255 ° C. to 280 ° C. and the reaction pressure is increased from normal pressure to 60 Pa, respectively, and water and ethylene glycol generated in the reaction are removed from the system. Went. The progress of the polycondensation reaction was confirmed without monitoring the load on the stirring blades in the system, and the reaction was terminated when the desired degree of polymerization was reached. Thereafter, the reaction product in the system was continuously extruded in a strand form from the discharge part, cooled and cut to obtain a granular pellet of about 3 mm. The polycondensation reaction time at this time was 110 minutes, and the intrinsic viscosity of the obtained polyethylene terephthalate pellets was 0.52 dl / g. Subsequently, the obtained polyethylene terephthalate pellets were subjected to solid phase polymerization at 220 ° C. for 15 hours under vacuum to obtain a diluted polymer 2 having an intrinsic viscosity of 0.74 dl / g and a carboxylic acid terminal group number of 9.0 eq / t. . The properties of the obtained diluted polymer 2 are shown in Table 2.

[Reference Example 3] Diluted polymer 3
The reaction was conducted in the same manner as in Example 1 except that the amount of antimony trioxide added in Example 1 of the dilution polymer was changed to 0.038 parts. Table 2 shows the physical properties of the obtained diluted polymer 3. The antimony content in the polymer was 105 ppm.

[Reference Example 4] Recovered polymer 1
After chopping the polyester sheet having a thickness of 500 μm prepared in Example 5 of film formation to be described later, it is put into a uniaxial extruder without being dried and remelted (resin temperature 298 ° C.), and then continuously in a strand shape. Extrusion, cooling, and cutting were performed to obtain about 3 mm of recovered granular pellets. The recovered pellet had an intrinsic viscosity of 0.51 dl / g and a COOH end of 36.0 eq / t. The properties of the obtained recovered polymer 1 are shown in Table 2.

  ND in Table 2 means not detected.

[Examples 5 to 11 and Comparative Examples 5 to 10]
Hydrolysis-suppressing polyesters 1 to 8, diluted polymers 1 to 3 and recovered polymer 1 were supplied to the uniaxial extruder at the ratios shown in Table 3, melt-kneaded under the conditions shown in Table 3, and pelletized. Table 3 shows characteristics of the obtained polyester composition and characteristics when formed into a film.

  The production method of the polyester and the polyester composition of the present invention can be suitably used for a film that requires hydrolysis resistance, and can be particularly suitably used for a film for a solar battery backsheet.

Claims (4)

10 to 70 mol% of the acid component is an oxalic acid component, 90 to 30 mol% is an aromatic dicarboxylic acid component, and 80 mol% or more of the glycol component is a copolymerized polyester having 2 to 4 carbon atoms of an alkylene glycol component,
A hydrolysis-inhibiting polyester having an antimony element content of 50 ppm or less, an intrinsic viscosity of 0.25 to 0.75 dl / g, and a melting point of 180 to 250 ° C. with respect to the mass of the polyester.   The hydrolysis-inhibiting polyester according to claim 1, wherein the polymerization catalyst is a titanium compound.   The hydrolysis-inhibiting polyester according to claim 1 or 2, and the content of oxalic acid is 0 mol% or more and less than 0.2 mol% based on the number of moles of all acid components, A method for producing a polyester composition in which 50 ppm or less of polyester is melt-kneaded with respect to the mass of the polyester, and the amount of oxalic acid component added is the number of moles of all acid components of the polyester constituting the polyester composition. A method for producing a polyester composition, comprising melting and kneading so as to be 0.2 to 5.0 mol% as a reference.   The method for producing a polyester composition according to claim 3, wherein a polyester having an oxalic acid content of 0.2 to 5.0 mol% based on the number of moles of all acid components is further melt-kneaded.