JPH09296029A - Polyester and hollow vessel prepared therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester having a low ethylene terephthalate cyclic trimer content, which causes only a slight CTET increase when it is molten at a high temp. and which scarcely stains the mold in the course of molding a hollow vessel or the like. SOLUTION: The polyester mainly comprises terephthalic acid as the dicarboxylic acid component and ethylene glycol as the dial component and contains 5×10<-6> to 1×10<-3> mol of germanium atom and 1×10<-4> to 5×10<-3> mol of an alkaline earth metal atom per mol of the whole acid component constituting the polyester.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention has good transparency,
In addition, the present invention relates to a polyester which is less likely to cause mold contamination during molding and a hollow container made of the same.

[0002]

2. Description of the Related Art Polyethylene terephthalate (PET)
Is excellent in mechanical strength, chemical stability, heat resistance, transparency, gas barrier property, etc., and is lightweight and inexpensive, so that it is widely used for bottles, films, sheets, fibers, foams, etc., In particular, carbonated drinks, fruit juice drinks, liquid seasonings,
It is suitable as a material for a container for filling food and drink such as edible oil, liquor and wine.

Such PET is usually obtained by subjecting a terephthalic acid component and an ethylene glycol component to an esterification reaction, followed by melt polycondensation in the presence of a polycondensation reaction catalyst and then solid phase polymerization. Is.

Then, this PET is supplied to a molding machine such as an injection molding machine to mold a preform, and the preform is inserted into a mold having a predetermined shape and stretch blow molded, or further heat treated (heat set). Then, it is a general method to form a hollow container.

However, PET obtained by the above method includes ethylene terephthalate cyclic trimer (hereinafter referred to as “CT”).
ET ”. ) And other oligomers are contained in a considerable amount, and these oligomers adhere to the gas exhaust port, exhaust pipe, etc. of the mold during stretch blow molding, so that mold contamination is likely to occur. Further, since such mold contamination causes the surface roughness and whitening of the obtained bottle, it is necessary to wash the mold frequently, and there is also a problem that productivity is significantly reduced. Therefore, oligomers such as CTET are less likely to be generated during molding, and PET having a small content thereof is desired.

Conventionally, some proposals have been made for PET in which oligomers such as CTET are less likely to be generated even when remelted. For example, in Japanese Patent Laid-Open No. 6-3202082,
A method of copolymerizing a monofunctional component having a hydroxyl group or a carboxyl group with PET has been proposed. However, this method has a problem that the terminal group is blocked by a monofunctional component at the time of melt polycondensation, so that the polycondensation reaction is inhibited and a polyester having a large intrinsic viscosity cannot be obtained.

In producing PET through the melt polycondensation step and the solid phase polymerization step, hot water or steam treatment is performed after the solid phase polymerization step to deactivate the polycondensation catalyst contained in the PET. Has proposed a method of suppressing the generation of oligomers such as CTET during molding (Japanese Patent Application Laid-Open No. 3-174441, Japanese Patent Publication No. 7-37515, etc.). However, these methods require a hydrothermal treatment device or a steam treatment device in addition to the solid-state polymerization device in order to deactivate the polycondensation catalyst, and have a problem that the cost is increased.

Further, there has been proposed a method for solid-state polymerization of a PET type prepolymer containing a specific amount of germanium atoms and alkali metal atoms (JP-A-6-9763).
However, with this method, the effect of suppressing the formation of oligomers such as CTET during remelting was insufficient.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a polyester having a low CTET content, a small increase in CTET when melted at a high temperature, and less likely to cause mold contamination during molding, and a hollow fiber made of the same. It is intended to provide a container.

[0010]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that a specific amount of an alkaline earth metal atom and a specific amount of a germanium atom produced by melt polycondensation are combined. The inventors have found that this object can be achieved by solid-phase polymerizing the contained PET-based polymer, and arrived at the present invention.

That is, the gist of the present invention is as follows. (1) A polyester containing terephthalic acid as a dicarboxylic acid component and ethylene glycol as a diol component as a main component and having an intrinsic viscosity of 0.5 or more and 5 × with respect to 1 mol of all acid components constituting the polyester. 10 ^-6 ~
1 × 10 ^-3 mol germanium atom and 1 × 10 ^{-4 to} 5 × 10 ^-3
A polyester containing a mole of an alkaline earth metal atom. (2) A hollow container formed by stretch blow molding a preform obtained by injection molding or extrusion molding of the above polyester.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

The polyester of the present invention is produced mainly with a terephthalic acid component and an ethylene glycol component.

The intrinsic viscosity of the polyester must be 0.5 or more, and 0.6 to 1.2 is particularly preferable. When the intrinsic viscosity is less than 0.5, the mechanical properties of the molded product deteriorate, which is not preferable.

Further, the CTET content of the polyester is preferably 0.50% by weight or less, and particularly preferably 0.40% by weight or less. The content of CTET
If it exceeds 0.50% by weight, mold contamination is likely to occur during molding, which is not preferable.

Further, polyester has a temperature of 280 ° C.
The amount of increase in CTET when melted for minutes is preferably 0.25 wt% or less. If the amount of increase in CTET exceeds 0.25% by weight, contamination of the mold is apt to occur during molding, which is not preferable.

In addition to the above components, the polyester includes phthalic acid, isophthalic acid, 5-sodium sulfoisophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid and the like. Aromatic dicarboxylic acid component, aromatic polycarboxylic acid such as trimellitic acid, pyromellitic acid and its acid anhydride, oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, decanedicarboxylic acid and other aliphatic compounds Dicarboxylic acid component, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol,
Aliphatic diol components such as 1,4-butanediol, 2,3-butanediol, diethylene glycol, 1,5-pentanediol, neopentyl glycol, triethylene glycol, polyethylene glycol, etc. Aliphatic trimethylolpropane, pentaerythritol, etc. Polyhydric alcohol components, alicyclic diol components such as 1,4-cyclohexanedimethanol and 1,4-cyclohexanediethanol, aromatic diol components such as ethylene oxide adducts of bisphenol A and bisphenol S, 4-hydroxybenzoic acid, ε A copolymerization component such as a hydroxycarboxylic acid component such as caprolactone may be contained within a range that does not impair the characteristics of PET.

Next, a method for producing the polyester of the present invention will be described. The polyester of the present invention is first obtained by using an esterification reaction with a terephthalic acid component and an ethylene glycol component as main raw materials to obtain an esterified product. Next, the obtained esterified product is subjected to melt polycondensation in the presence of a specific amount of germanium atom and a specific amount of alkaline earth metal atom, and then solid phase polymerization is performed.

In the present invention, the esterified product is usually bis- (β-hydroxyethyl) terephthalate (hereinafter abbreviated as “BHET”) and / or the same obtained by the esterification reaction of terephthalic acid and ethylene glycol. It can be obtained by adding terephthalic acid and ethylene glycol to the low polymer and performing an esterification reaction at a temperature of 160 to 280 ° C. under nitrogen gas.

Next, the esterified product is 260 to 310 in the presence of a specific amount of germanium atom and a specific amount of alkaline earth metal atom, usually under reduced pressure of about 0.01 to 13.3 hPa.
Melt polycondensation is carried out at a temperature of ℃, preferably 275 to 290 ℃, to obtain a polyester prepolymer (hereinafter referred to as "prepolymer").

At this time, the content of germanium atoms is 5 × 10 5 with respect to 1 mol of all acid components constituting the polyester.
^-6 to 1 x 10 ^-3 mol is required, and 5 x
It is particularly preferable to set it in the range of 10 ⁻⁵ to 8 × 10 ⁻⁴ mol.
When this content is less than 5 × 10 ⁻⁶ mol, a polyester having a large intrinsic viscosity cannot be obtained. On the other hand, this content is 1 × 10
^When it exceeds ^-3 mol, the color tone and transparency of the polyester are deteriorated, and the mold is liable to be contaminated during molding, which is not preferable.

As the compound containing a germanium atom,
Examples thereof include germanium dioxide, germanium butoxide, germanium chloride, germanium hydroxide, and germanium acetate, with germanium dioxide being particularly preferred in terms of color tone and transparency. Further, two or more kinds of these compounds may be used in combination.

Further, the content of the alkaline earth metal atom is based on 1 mol of all the acid components constituting the polyester.
It is necessary to set it in the range of 1 × 10 ^{−4 to} 5 × 10 ⁻³ mol, and it is particularly preferable to set it in the range of 5 × 10 ⁻⁴ to 2 × 10 ⁻³ mol. When this content is less than 1 × 10 ⁻⁴ mol, the effect of suppressing the increase in CTET during remelting is insufficient. On the other hand, if this content exceeds 5 × 10 ^-3 mol, the color tone and transparency of the polyester will deteriorate, which is not preferable.

Examples of the compound containing an alkaline earth metal atom include oxides of magnesium, calcium, strontium, barium and radium, aliphatic carboxylates, aromatic carboxylates, alkoxides, alkyl compounds, hydroxides and halides. Among these, various compounds of magnesium are preferable, and magnesium oxide is particularly preferable.

Further, during the melt polycondensation, it is preferable to add a phosphorus compound such as phosphoric acid, phosphoric acid ester, phosphorous acid, phosphorous acid ester, etc. as a heat stabilizer, but phosphoric acid is particularly preferable. . The content of these phosphorus compounds is preferably in the range of 1 × 10 ⁻⁵ to 1 × 10 ⁻³ mol with respect to 1 mol of all acid components constituting the polyester.

In the above-mentioned melt polycondensation, the compound containing a germanium atom, the compound containing an alkaline earth metal atom and the phosphorus compound can be added at any stage, but in view of productivity and easy handling, the melt polycondensation is performed. It is preferably added just before condensation.

The prepolymer produced by such liquid phase polycondensation usually has a CTET content of more than 0.50% by weight and a CTET when melted at a temperature of 280 ° C. for 30 minutes.
Is more than 0.25% by weight, and it is very easy to cause mold contamination during molding. Therefore, in the present invention, it is necessary to perform solid phase polymerization next.

The solid phase polymerization is usually carried out by forming the prepolymer obtained by melt polycondensation into chips having a diameter of 2 to 5 mm and a length of 3 to 6 mm, preferably 3 to 4 mm in diameter and 4 to 5 mm in length. It is preferable to carry out at a temperature lower than the melting point of the polyester for 5 hours or more, preferably 10 hours or more under the flow of an inert gas or under reduced pressure. At this time, the temperature of the solid phase polymerization is
It is more preferable that the temperature is lower than the melting point by 10 ° C. or higher and 190 ° C. or higher. If this temperature is lower than 190 ° C., the rate of decrease of the CTET content is slow and solid phase polymerization requires a long time. On the other hand, if the temperature is near the melting point, the chips are naturally fused, which is not preferable.

If the preliminary crystallization is carried out at a temperature lower than the temperature at which the solid phase polymerization is carried out, the solid phase polymerization will proceed efficiently. This pre-crystallization step involves drying the prepolymer chips in a dry state, usually at a temperature of 100-180 ° C.
Heat for 30 minutes to 8 hours.

The polyester obtained by the above method usually has a CTET content of 0.50% by weight or less,
Moreover, the amount of increase in CTET when melted at a temperature of 280 ° C. for 30 minutes is 0.25% by weight or less, and this can be molded into a hollow container.

The method for molding a hollow container using the polyester of the present invention is no different from the stretch blow molding method used in conventional PET. For example, a preform is molded by injection molding and then molded. A hot parison method of axial stretch blow molding, or a cold parison method of molding a preform by injection molding, preheating the plug portion and bottom of the preform, and then biaxially stretch blow molding can be applied.

At this time, the molding temperature at the time of injection molding, specifically, the temperature of each cylinder of the molding machine and the temperature of the nozzle are usually
The temperature should be in the range of 270-300 ℃ The stretching temperature is usually 70
The stretch ratio is preferably 1.5 to 3.5 times in the machine direction and 2 to 5 times in the circumferential direction at 120 to 120 ° C., preferably 80 to 110 ° C.

The obtained hollow container can be used as it is, but in the same blow mold as that used for molding, particularly when it is necessary to heat-fill the content liquid, such as fruit juice drink, It is a general method to heat-set in a separately provided mold to improve heat resistance before use. This heat setting is usually 100 to 200 ° C, preferably 120 to 180 ° C under tension by compressed air or mechanical stretching.
It is usually 2 seconds to 2 hours, preferably 10 seconds to 30 minutes.

[0034]

EXAMPLES Next, the present invention will be described in detail with reference to examples. In the examples, the characteristic values of the prepolymer and the polyester were measured as follows. (a) Intrinsic viscosity [η] Measured at a temperature of 20 ° C. using an equal weight mixture of phenol and ethane tetrachloride as a solvent. (b) Content of CTET Prepolymer and polyester chips are hexafluoroisopropanol / chloroform (1/1, volume ratio)
After dissolving in a mixed solvent of, the polymer component was poured into acetonitrile to precipitate the polymer component, and CTET in the filtrate filtered with a membrane filter was quantified by a high performance liquid chromatograph (manufactured by Waters, 600E). (c) Germanium atom content (hereinafter referred to as "Ge amount") 2.0 g of polyester chips were ashed in the presence of sulfuric acid by a conventional method, completely decomposed, and then distilled to a volume of 100 ml with distilled water to emit light. It was quantified by spectroscopic analysis. The Ge amount was expressed as the number of moles per 1 mole of all the acid components that compose the polyester. (d) Content of alkaline earth metal atoms (hereinafter referred to as "AEM
Quantity. ) A polyester chip melt-molded into a circular plate having a diameter of 4 cm and a thickness of 8 mm was quantified with an X-ray spectrometer (Rigaku Corporation, Model 3270). The AEM amount was expressed as the number of moles per 1 mole of all the acid components constituting the polyester. (e) Plate haze Polyester chips, thickness 5 mm x length 10 cm x width 6 cm
Injection-molded on the plate (molding condition: extrusion temperature 2
The temperature was measured at 85 ° C., mold temperature 20 ° C., cooling time 30 seconds) with a turbidimeter (MODEL 1001DP manufactured by Nippon Denshoku Industries Co., Ltd.). The haze value of air is 0%. The smaller the haze value, the better the transparency, and the haze value of less than 10 can be put to practical use.

Example 1 In an esterification reactor containing BHET and its low polymer, terephthalic acid (TPA) and ethylene glycol (E) were added.
G) slurry with a molar ratio of 1 / 1.6 is continuously fed,
The reaction was carried out under conditions of a temperature of 250 ° C. and a pressure of 50 hPaG, and an esterified product having an average degree of polymerization of 7 was continuously obtained with a residence time of 8 hours. 60 kg of this esterified product is transferred to a polycondensation reactor, and T
2.5 x 10 ^-4 mol of germanium dioxide, 9.3 x 10 ^-4 mol of magnesium oxide and 3 x per mol of PA component
After adding 10 ⁻⁴ mol of phosphoric acid, the pressure inside the polycondensation reactor was gradually reduced, and finally melt polycondensation was carried out at a pressure of 0.67 hPa and a temperature of 280 ° C. for 2 hours. When the melt polycondensation was completed, a prepolymer of [η] 0.62 was discharged from the polycondensation reactor to obtain a prepolymer chip having a diameter of 3 mm and a length of 4 mm. Next, this chip was placed in a rotary solid-state polymerization apparatus, pre-dried under reduced pressure of 1.33 hPa at 70 ° C. for 2 hours, and then heated at 130 ° C. for 6 hours for crystallization. continue,
While flowing nitrogen gas, raise the temperature to 230 ° C and operate at this temperature for 10
Solid-state polymerization was carried out for a period of time to obtain polyester. The Ge amount and AEM amount in this polyester were 1.2 × 10 ⁻⁴ mol and 9.3 × 10 ⁻⁴ mol, respectively, relative to 1 mol of the TPA component. Using the polyester obtained by the above method, each cylinder part and nozzle temperature 280 ℃, screw rotation speed 100 rpm, injection time 8 seconds, cooling time 10 seconds, mold temperature
Injection molding machine set to 20 ° C (Nissei ASB, AS
(B-50HT type). Then
The preform is blown at a pressure of 2 M
Stretch-blow molding was performed at Pa to produce a hollow container having an average body thickness of 300 μm and an internal volume of 1 liter. Further, 2,000 hollow containers were continuously molded under the above conditions, but no contamination of the mold was observed in any of injection molding, stretch blow molding and heat setting. The characteristic values of the obtained prepolymer and polyester are shown in Table 1.

Examples 2 to 6 and Comparative Examples 1 to 5 Except that the kind and the addition amount of the compound containing an alkaline earth metal atom (hereinafter referred to as "AEM compound") were changed as shown in Table 1. Polyester was obtained in the same manner as in Example 1. The Ge content in these polyesters is TPA
The amount of AEM was 1.2 × 10 ^-4 mol per mol of the component, and the amount of AEM was the same as the charging ratio per mol of the TPA component. Next, when a hollow container was produced using these polyesters, in Comparative Example 4, [η] of the polyester was small, and molding was impossible. The characteristic values of the obtained prepolymer and polyester are shown in Table 1.

Comparative Example 6 In place of 2.5 × 10 ^-4 mol germanium dioxide, 2.0
A polyester was produced in the same manner as in Example 1 except that x10 ^-4 mol of antimony trioxide was used, and a hollow container was produced using the polyester. Antimony (S
Both the amount b) and the amount of AEM were the same as the charging ratio with respect to 1 mol of the TPA component. The characteristic values of the obtained prepolymer and polyester are shown in Table 1.

[0038]

[Table 1]

[0039]

According to the present invention, it is possible to obtain a polyester having a low CTET content, a small increase in CTET when melted at a high temperature, and less likely to cause mold contamination during molding of a hollow container or the like. it can.

Claims (4)

[Claims] 1. A terephthalic acid as a dicarboxylic acid component,
A polyester containing ethylene glycol as a main component as a diol component, having an intrinsic viscosity of 0.5 or more, and 1 mol of all acid components constituting the polyester,
5 × 10 ^-6 〜 1 × 10 ^-3 mol of germanium atom and 1 × 10 ^-4
A polyester containing up to 5 × 10 ⁻³ mol of an alkaline earth metal atom. 2. The ethylene terephthalate cyclic trimer content is 0.50% by weight or less, and the increase of the ethylene terephthalate cyclic trimer when melted at a temperature of 280 ° C. for 30 minutes is 0.25% by weight or less. Item 1. The polyester according to item 1. 3. The polyester according to claim 1, wherein the polyester is produced through melt polycondensation and solid phase polymerization. 4. A hollow container obtained by stretch blow molding a preform obtained by injection molding or extrusion molding of the polyester according to claim 1, 2 or 3.