JP2001081171A - Production of polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the sludge in a treating vessel and piping used when treating a polyester chip, and to produce the polyester hardly causing remaining foreign taste and nasty smell when producing a molded product from the polyester chip. SOLUTION: This method for producing a polyester by treating a polyester chip with water in a treating layer comprises treating the polyester chip while keeping the content of acetaldehyde in the treating water in the treating vessel so as to be <=10 ppm without recycling the treating water discharged from the treating vessel to the treating vessel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing polyester used for molding bottles, films, sheets, and the like. The present invention relates to a method for producing a polyester which is less likely to cause crystallization and has excellent crystallization controllability of a molded article.

[0002]

2. Description of the Related Art Various resins are employed as materials for containers such as seasonings, oils, beverages, cosmetics, detergents, etc., depending on the type of filling content and the purpose of use.

[0003] Among them, polyester is excellent in mechanical strength, heat resistance, transparency and gas barrier properties, and is therefore particularly suitable as a material for containers for filling beverages such as juices, soft drinks and carbonated drinks.

[0004] Such polyester is supplied to a molding machine such as an injection molding machine to form a preform for a hollow molded body, and the preform is inserted into a mold having a predetermined shape and stretch blow-molded. Heat treatment (heat set)
Then, it is general that the plug portion of the bottle is heat-treated (the plug portion is crystallized) if necessary.

However, conventional polyesters contain oligomers such as cyclic trimers and the like, and these oligomers adhere to the inner surface of the mold, the gas exhaust port of the mold, and the exhaust pipe. Dirt was easy to occur. Further, a molded article obtained by molding such a polyester has a residual off-flavor represented by acetaldehyde, and has a problem particularly when used as a container for filling beverages such as juices, soft drinks, and carbonated drinks.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art, and to reduce contamination of a treatment tank and piping during water treatment of polyester chips, and to manufacture molded articles from polyester chips. It is an object of the present invention to provide a polyester with less residual off-flavor and off-flavor even when it is made.

[0007]

Means for Solving the Problems In order to achieve the above object, a method for producing a polyester according to the present invention is a method for producing a polyester in which a polyester chip is treated with water in a treatment layer. A polyester production method characterized in that a polyester chip is treated while maintaining an acetaldehyde content of treated water in a treatment tank at 10 ppm or less without being circulated back to a treatment tank.

In the present invention, a polyester chip is
It can be continuously or intermittently supplied to the treatment tank and extracted. Further, the entire amount of the polyester chips can be filled in the treatment layer, and the entire amount of the polyester chips can be extracted after the water treatment.

In this case, the discharge of the treated water from the treatment tank and the supply of new treated water to the treatment tank can be continued. In this case, the discharge of the treated water from the treatment tank and the supply of new treated water to the treatment tank can be intermittent.

In this case, the treated water in the treatment tank is
Acetaldehyde can be removed by aeration using a gas bubbling type processing device. In this case, the polyester has an intrinsic viscosity of 0.55 to 0.55.
The main repeating unit at 1.30 deciliters / gram can be a polyester composed of ethylene terephthalate. In this case, the polyester may be a polyester having a limiting viscosity of 0.40 to 1.00 deciliter / gram and a main repeating unit composed of ethylene naphthalate. According to the method for producing a polyester of the present invention, it is possible to advantageously produce a polyester which is less likely to have an unpleasant odor when the polyester is formed into a molded product.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester used in the present invention is preferably a crystalline polyester mainly obtained from an aromatic dicarboxylic acid component and a glycol component, and more preferably an aromatic dicarboxylic acid unit having an acid unit. A polyester containing 85 mol% or more of the acid component, and particularly preferably, an aromatic dicarboxylic acid unit containing 95 mol% of the acid component.
It is a polyester containing the above.

The aromatic dicarboxylic acid component constituting the polyester used in the present invention includes terephthalic acid,
2,6-naphthalenedicarboxylic acid, diphenyl-4,
Aromatic dicarboxylic acids such as 4′-dicarboxylic acid and diphenoxyethane dicarboxylic acid, and functional derivatives thereof are exemplified.

The glycol component constituting the polyester used in the present invention includes ethylene glycol,
Trimethylene glycol, tetramethylene glycol,
Alicyclic glycols such as cyclohexanedimethanol;

The acid component used in the polyester by copolymerization is terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, diphenyl-4,4 '.
-Aromatic dicarboxylic acids such as dicarboxylic acid, diphenoxyethane dicarboxylic acid, oxyacids such as p-oxybenzoic acid and oxycaproic acid and functional derivatives thereof, adipic acid, sebacic acid, succinic acid, glutaric acid, dimer acid And aliphatic derivatives thereof, and functional derivatives thereof, and alicyclic dicarboxylic acids such as hexahydroterephthalic acid, hexahydroisophthalic acid, and cyclohexanedicarboxylic acid, and functional derivatives thereof.

The glycol component used by copolymerization in the polyester includes aliphatic glycols such as ethylene glycol, trimethylene glycol, tetramethylene glycol, diethylene glycol and neopentyl glycol, bisphenol A and bisphenol A. And aromatic glycols such as alkylene oxide adducts of the above, and polyalkylene glycols such as polyethylene glycol and polybutylene glycol.

Further, a polyfunctional compound such as trimellitic acid, trimesic acid, pyromellitic acid, tricarballylic acid, glycerin, pentaerythritol, trimethylolpropane or the like is copolymerized within a range in which the polyester is substantially linear. Or a monofunctional compound such as benzoic acid or naphthoic acid.

One preferred example of the polyester used in the present invention is a polyester whose main repeating unit is composed of ethylene terephthalate, more preferably a linear polyester containing at least 85 mol% of ethylene terephthalate units, and particularly preferably. A linear polyester containing at least 95 mol% of ethylene terephthalate units, ie, polyethylene terephthalate (hereinafter referred to as PET)
Abbreviation).

Another preferred example of the polyester used in the present invention is that the main repeating unit is ethylene-
It is a polyester composed of 2,6-naphthalate, more preferably a linear polyester containing at least 85 mol% of ethylene-2,6-naphthalate units, and particularly preferably a linear polyester containing ethylene-2,6-naphthalate units. It is a linear polyester containing 95 mol% or more, that is, polyethylene naphthalate.

The above polyester can be produced by a conventionally known production method. That is, in the case of PET, a direct esterification method of directly reacting terephthalic acid with ethylene glycol and, if necessary, other copolymerization components to remove water and esterify, followed by polycondensation under reduced pressure,
Alternatively, it is produced by a transesterification method in which dimethyl terephthalate is reacted with ethylene glycol and, if necessary, other copolymerization components to remove methyl alcohol and transesterify, followed by polycondensation under reduced pressure. Solid-state polymerization may be further performed to increase the intrinsic viscosity and decrease the acetaldehyde content and the like.

The melt polycondensation reaction may be performed in a batch reactor or a continuous reactor. In any of these methods, the melt polycondensation reaction may be performed in one step or may be performed in multiple steps.
The solid-state polymerization reaction can be performed in a batch-type apparatus or a continuous-type apparatus as in the melt polycondensation reaction. The melt polycondensation and the solid phase polymerization may be performed continuously or may be performed separately.

In the case of the direct esterification method, compounds of Ge, Sb, and Ti are used as a polycondensation catalyst, and it is particularly convenient to use a Ge compound or a mixture thereof with a Ti compound.

As the Ge compound, amorphous germanium dioxide, crystalline germanium dioxide powder or a slurry of ethylene glycol, a solution obtained by dissolving crystalline germanium dioxide in water, or a solution obtained by adding ethylene glycol to this and heat-treating the same are used. However, to obtain the polyester used in the present invention, it is particularly preferable to use a solution obtained by heating and dissolving germanium dioxide in water or a solution obtained by adding ethylene glycol to the solution and heating. These polycondensation catalysts can be added during the esterification step. When a Ge compound is used, the amount of Ge compound used is 10 to 150 ppm, preferably 13 to 100 ppm, more preferably 15 to 7 ppm as the amount of Ge remaining in the polyester resin.
It is 0 ppm.

Examples of the Ti compound include tetraalkyl titanates such as tetraethyl titanate, tetraisopropyl titanate, tetra-n-propyl titanate and tetra-n-butyl titanate, and partial hydrolysis thereof. Products, titanyl oxalate, titanyl ammonium oxalate, sodium titanyl oxalate, potassium titanyl oxalate, titanyl calcium oxalate, titanyl strontium oxalate, and the like, titanium trimellitate, titanium sulfate, titanium chloride, and the like. The Ti compound is formed polymer
It is added so that the remaining amount of Ti therein is in the range of 0.1 to 10 ppm.

As the Sb compound, antimony trioxide,
Antimony acetate, antimony tartrate, antimony potassium tartrate, antimony oxychloride, antimony glycolate
And antimony pentoxide, triphenylantimony and the like. The Sb compound is added so that the residual amount of Sb in the resulting polymer is in the range of 50 to 250 ppm.

As the stabilizer, it is preferable to use phosphoric acid, polyphosphoric acid, phosphate esters such as trimethyl phosphate, and the like. These stabilizers can be added during the esterification reaction step from a slurry preparation tank of terephthalic acid and ethylene glycol. The P compound is added so that the residual amount of P in the resulting polymer is in the range of 5 to 100 ppm.

In order to control the content of diethylene glycol copolymerized in the polyester, a basic compound such as triethylamine, tri-n
-A tertiary amine such as butylamine, and a quaternary ammonium salt such as tetraethylammonium hydroxide can be added.

The polyester used in the present invention, in particular,
The limiting viscosity of the polyester whose main repeating unit is composed of ethylene terephthalate is 0.50 to 1.30 dL / g, preferably 0.55 to 1.20 dL / g, more preferably 0.60 to 0.1 dL / g.
It is in the range of 90 deciliters / gram. If the intrinsic viscosity is less than 0.50 deciliter / gram, the obtained molded article or the like has poor mechanical properties. On the other hand, if it exceeds 1.30 deciliters / gram, the resin temperature rises during melting by a molding machine or the like, and thermal decomposition becomes severe, so that free low-molecular-weight compounds that affect fragrance retention increase, Causes problems such as coloring of yellow.

The intrinsic viscosity of the polyester used in the present invention, particularly the polyester whose main repeating unit is ethylene-2,6-phthalate, is 0.40 to 0.40.
1.00 deciliter / gram, preferably 0.42
0.95 deciliters / gram, more preferably 0.
It is in the range of 45-0.90 deciliter / gram. If the intrinsic viscosity is less than 0.40 deciliter / gram, the obtained molded article or the like has poor mechanical properties. On the other hand, if it exceeds 1.00 deciliters / gram, the resin temperature rises during melting by a molding machine or the like, and thermal decomposition becomes severe, so that free low-molecular-weight compounds that affect fragrance retention increase, Causes problems such as coloring of yellow.

The shape of the polyester chip may be any of a cylinder type, a square type, a flat plate shape and the like, and the size thereof is usually 1.6 to 3.5 in height, width and height, respectively.
mm, preferably in the range of 1.8 to 3.5 mm. For example, in the case of a cylinder type, the length is 1.8 to 3.5 m
It is practical that m and the diameter are about 1.8 to 3.5 mm. Further, the weight of the chip is practically in the range of 15 to 30 mg / piece.

The acetaldehyde content of the polyester used in the present invention is 10 ppm or less, preferably 8 ppm.
ppm or less, more preferably 5 ppm or less, the formaldehyde content is 7 ppm or less, preferably 6 ppm or less,
More preferably, it is 4 ppm or less. The acetaldehyde content of the polyester used in the present invention is 10 ppm
Hereinafter, the method for reducing the formaldehyde content to 7 ppm or less is not particularly limited. For example, a method for solid-phase polymerization of a low-molecular-weight polyester at a temperature of 170 to 230 ° C. under reduced pressure or an inert gas atmosphere is used. Can be mentioned.

The amount of diethylene glycol copolymerized with the polyester used in the present invention is 1.0 to 5.0 mol%, preferably 1.3 to 4.5 mol%, of the glycol component constituting the polyester. Preferably 1.5
~ 4.0 mol%. The amount of diethylene glycol is 5.
If it exceeds 0 mol%, the thermal stability will be poor, the molecular weight will decrease during molding, and the acetaldehyde content and the formaldehyde content will increase undesirably. The diethylene glycol content is 1.0 mol%
If it is less than 1, the transparency of the obtained molded article is deteriorated.

The content of the cyclic trimer of the polyester used in the present invention is 0.50% by weight or less, preferably 0.45% by weight or less, more preferably 0.40% by weight.
It is as follows. When molding a heat-resistant hollow molded article or the like from the polyester of the present invention, heat treatment is performed in a heating mold,
When the content of the cyclic trimer is 0.50% by weight or more, the adhesion of the oligomer to the surface of the heating mold rapidly increases, and the transparency of the obtained hollow molded article or the like is extremely deteriorated.

In order to prevent mold contamination due to oligomers such as cyclic trimers adhering to the inner surface of the mold, the exhaust port of the mold gas, the exhaust pipe, etc. during molding, the polyester is melted as described above. After polycondensation or solid phase polymerization, a contact treatment with water is performed.

As a method of the contact treatment with water, there is a method of immersing in water. The time for performing the contact treatment with water is 5 minutes to 2 days, preferably 10 minutes to 1 day, more preferably 30 minutes to 10 hours, and the water temperature is 20 to 180 ° C, preferably 40 to 150 ° C. ° C, more preferably 50 to 120 ° C.

The polyester chip contains aldehyde compounds such as acetaldehyde and formaldehyde generated by a side reaction during the production of polyester, and these aldehyde compounds are eluted into the treated water during the water treatment.

Therefore, in the case of the treatment for a long time, the acetaldehyde content in the treatment tank increases with time. When the content of acetaldehyde is increased, the content of acetaldehyde in the chips after the water treatment and drying is increased, and the flavor and aroma of the contents in a hollow molded container or the like using such polyester chips are extremely deteriorated.

In the present invention, in the case of the continuous system, the acetaldehyde content in the treated water in the water treatment tank is 10 ppm or less, preferably 5 ppm without circulating the treated water discharged from the treatment tank back to the treatment tank. In the case of a batch method, the content of acetaldehyde in the treated water at the end of the water treatment is 10 ppm or less without circulating the treated water discharged from the treatment tank back to the treatment tank. The above-mentioned problem is solved by maintaining the concentration at 5 ppm or less, more preferably at 1 ppm or less.

The following is an example of a method for industrially performing water treatment, but the method is not limited thereto. The processing method may be either a continuous method or a batch method, but the continuous method is preferable for industrial use.

When the polyester chips are subjected to the water treatment in a batch system, there are an inner tank in which the polyester chips can stay and the treated water can penetrate, and a water tank type treatment tank into which the inner tank can be charged. That is, the polyester chips can be received into the inner tank in a batch system, and the inner tank can be immersed in the processing tank to perform water treatment, and the polyester chips can be taken out of the processing tank together with the inner tank and discharged. Further, the polyester chips can be received in a silo-type treatment tank or a rotating cylinder-type treatment tank to perform water treatment.

In this case, the polyester chips are charged and filled into the treatment tank, and are filled with fresh treated water to perform water treatment. Some of the treated water is discharged continuously or intermittently as necessary, and new treated water is additionally supplied.

In the case of continuously treating the polyester chips with water, a water tank type treatment tank provided with a carry-out device capable of moving the polyester chips in the treatment tank and sequentially moving the polyester chips out of the treatment tank is exemplified. In other words, the polyester chips can be continuously received in the treatment tank and subjected to water treatment, and the polyester chips can be continuously discharged from the treatment tank by the carry-out device.

A method for reducing the acetaldehyde content of the treated water in the treatment tank will be described below, but the present invention is not limited to this.

A drain port for discharging treated water containing acetaldehyde is provided at at least one place in the treatment tank, and a supply port for supplying fresh treated water to at least one place is provided for the treatment tank. By continuously or intermittently discharging the treated water containing acetaldehyde from the discharge port and supplying new treated water from the supply port, the acetaldehyde content in the treated water in the treatment tank is 10 ppm or less, preferably It is set to 5 ppm or less, more preferably 1 ppm or less. That is, by appropriately discharging the treated water and supplying new treated water so that the content of acetaldehyde in the treated water in the treatment tank does not become excessive, the amount of new treated water and wastewater can be reduced, so that the cost is reduced,
The effect on the environment due to the increase in the amount of drainage can also be reduced.

Further, a bubbling device for an inert gas is installed in the treatment tank, and the bubbling treatment is performed during the water treatment, whereby the acetaldehyde content in the treated water in the treatment tank is reduced to 10%.
It can be set to be at most ppm, preferably at most 5 ppm, more preferably at most 1 ppm.

In the treated water in the treatment tank, fine particles already attached to the polyester chip at the stage of receiving the polyester chip into the treatment tank, or friction between the polyester chips or the wall of the treatment tank during water treatment. Includes polyester fines generated. Therefore, if the treatment is continued for a long time, the fine amount contained in the treated water in the treatment tank gradually increases. Therefore, fines contained in the treated water adhere to the polyester chips again,
Thereafter, fines adhere to the polyester chip by an electrostatic effect at the stage of drying and removing the moisture, so that it becomes difficult to remove fines even after drying. For this reason, the crystallinity of the polyester is promoted, resulting in a bottle having poor transparency, or a shrinkage amount at the time of crystallization of the plug portion does not fall within the specified range, resulting in poor capping and leakage of the contents.

In order to prevent an increase in the fineness of the treated water in the treatment tank, supply new water into the treatment tank, discharge a large amount of the treated water in the treatment tank, and use it as industrial wastewater. There is a concern that the impact on the environment due to the increase in the amount of wastewater will not only be used. If the treated water discharged from the treatment tank is returned to the treatment tank and used again, the fine amount of treated water in the treatment tank not only increases gradually, but also accumulates in the circulation path and clogs the piping. There is. In order to prevent this, equipment for removing fines in the treated water is required.

Accordingly, in the case of the continuous water treatment method for polyester chips, the amount of the fine powder of treated water discharged together with the polyester chips from the treatment tank is 1000 ppm or less, preferably 500 ppm or less, more preferably 300 ppm or less.
It is desirable to keep: In the case of the batch type water treatment method, the amount of fine powder in water at the end of the water treatment is 1000.
ppm or less, preferably 500 ppm or less, more preferably 300 ppm or less.

In the case of industrially treating polyester chips with water, natural water (industrial water) and wastewater are often reused because of the large amount of water used for the treatment.
Normally, this natural water is collected from river water, groundwater, or the like, and refers to water that has been subjected to treatment such as sterilization and removal of foreign substances without changing the shape of water (liquid). In addition, natural water generally used industrially includes inorganic particles and bacteria derived from nature, such as silicates and clay minerals such as aluminosilicates,
It contains many organic particles originating from bacteria, spoiled plants and animals. When water treatment is performed using such natural water, particles adhere and permeate into polyester chips to form crystal nuclei, and the transparency of a hollow molded container using such polyester chips becomes extremely poor.

Therefore, as water introduced from outside the system for water treatment of the polyester chips, the particle size is 1 to 25 μm.
It is necessary to use water containing 10 to 50,000 particles / 10 m. Particles having a particle diameter of more than 25 μm in the treated water are not particularly limited, but are preferably 2 μm.
000 pieces / 10cc or less, more preferably 500 pieces / 1
0 cc or less, more preferably 100/10 cc, particularly preferably 10/10 cc or less.

The particles having a particle diameter of less than 1 μm in the treated water are not particularly specified in the present invention, but are preferably smaller in order to obtain a transparent resin or a resin having an appropriate crystallization rate. The number of particles having a particle size of less than 1 μm is preferably 100000 / 10cc or less, more preferably 50,000 / 10cc or less, and further preferably 200 / 10cc or less.
00 pieces / 10cc or less, particularly preferably 10,000 pieces / cc
It is 10 cc or less. As a method for removing and controlling particles having a size of 1 μm or less from water, a microfiltration method or an ultrafiltration method using a membrane such as a ceramic membrane or an organic membrane can be used.

The water-treated polyester chips are drained by a draining device such as a vibrating sieve or a Simon Carter and transferred to a drying step. Naturally, the water separated from the polyester chips by the draining device is sent to the above-mentioned fine removing device, and can be used again for water treatment.

For drying the polyester chips, a commonly used drying treatment of the polyester chips can be used. As a method for continuous drying, a hopper-type through-air dryer that supplies a polyester chip from the upper portion and allows a drying gas to flow from the lower portion is usually used. As a method of reducing the amount of drying gas and drying efficiently, a rotating disk type continuous dryer is selected, and heating steam, heating medium, etc. are supplied to the rotating disk and the outer jacket while passing a small amount of drying gas. Granulated polyester chips can be dried indirectly

As a dryer for drying in a batch system, a double cone type rotary dryer is used, and drying can be performed under vacuum or while passing a small amount of drying gas under vacuum. Alternatively, it may be dried while passing dry gas under atmospheric pressure.

As the dry gas, atmospheric air may be used, but dry nitrogen and dehumidified air are preferred from the viewpoint of preventing molecular weight reduction due to hydrolysis or thermal oxidative decomposition of polyester.

[0055]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. In addition, the measuring method of the main characteristic value in this specification is demonstrated below.

(1) Intrinsic viscosity of polyester (IV) It was determined from the solution viscosity at 30 ° C. in a 1,1,2,2-tetrachloroethane / phenol (2: 3 weight ratio) mixed solvent.

(2) Density: 25 using a density gradient tube of carbon tetrachloride / n-heptane mixed solvent.
Measured in ° C.

(3) Content of cyclic trimer of polyester A sample is dissolved in a mixed solution of hexafluoroisopropanol / chloroform, and further diluted with chloroform. After adding methanol to precipitate a polymer, the mixture is filtered. The filtrate was evaporated to dryness, made up to a constant volume with dimethylformamide, and a cyclic trimer composed of ethylene terephthalate units was quantified by liquid chromatography.

(4) Acetaldehyde content of polyester chip (hereinafter referred to as “AA content in chip”) Chip sample / distilled water = 1 gram / 2 cc placed in a glass ampoule substituted with nitrogen and sealed at 160 ° C. After performing extraction for 2 hours, after cooling, acetaldehyde in the extract was measured by high-sensitivity gas chromatography, and the concentration was measured in ppm.
Displayed with.

(5) Acetaldehyde content in treated water (hereinafter referred to as "AA content in water") Acetaldehyde in a treated water sample was measured by high-sensitivity gas chromatography, and the concentration was indicated in ppm.

(6) Fine content measurement About 0.5 kg of resin is placed on a sieve (diameter 30 cm) equipped with a wire mesh having a nominal size of 1.7 mm according to JIS-Z8801, and 0.1% of a cationic A surfactant (alkyltrimethylammonium chloride) aqueous solution was sieved for 1 minute at a total amplitude of about 7 cm and 60 reciprocations / 1 minute while showering water at a flow rate of 2 L / min. This operation was repeated, and the resin was sieved in a total of 10 to 30 kg. The fines removed by filtration were collected by filtration with a 1G1 glass filter manufactured by Iwaki Glass Co., Ltd. together with a surfactant aqueous solution, and washed with ion-exchanged water. Put this together with the glass filter in a dryer for 1
After drying at 00 ° C. for 2 hours, the mixture was cooled and weighed. The same operation of washing and drying with ion-exchanged water was repeated again to confirm that the weight became constant, and the weight of the glass filter was subtracted from this weight to obtain a fine weight. Fine content is the fine amount / the total resin weight sieved.

(7) Haze (% haze) A sample was cut from the body (thickness: about 4 mm) of a hollow molded container and measured with a haze meter manufactured by Toyo Seisakusho.

(8) Amount of fine powder in treated water (ppm) 1000 ml of treated water passed through a sieve having a nominal size of 850 μm according to JIS-Z8801 from an outlet of treated water in a treatment tank.
The cc was collected, filtered through a 1G1 glass filter manufactured by Iwaki Glass Co., Ltd., dried at 100 ° C. for 2 hours, cooled at room temperature, and then weighed to calculate.

(9) Organoleptic test Distilled water at 70 ° C. was placed in a biaxially stretched blow-molded hollow container, sealed, kept for 30 minutes, cooled to room temperature, allowed to stand at room temperature for one month, opened, flavored, smelled, etc. Was tested. Distilled water was used as a blank for comparison. The sensory test was carried out by 10 panelists according to the following criteria and compared with the average value. (Evaluation criteria) 0: No off-taste or smell is felt 1: A slight difference from the blank is sensed 2: A difference from the blank is sensed 3: A considerable difference from the blank is sensed 4: A very large difference from the blank is sensed feel

(Example 1) An inner tank (1) in which polyester chips can be retained and treated water can penetrate, and a water tank type treatment tank (2) in which the inner tank (1) can be immersed are prepared. A polyethylene terephthalate (hereinafter abbreviated as PET) chip is prepared by using a device provided with a discharge port (3) for discharging treated water containing 6 fines and a supply port (4) for supplying fresh treated water in (2). Water treated. The discharge of the treated water from the discharge port (3) of the water treatment tank (2) controlled at the treated water temperature of 95 ° C and the supply of fresh treated water from the supply port (4) were started. The intrinsic viscosity is 0.75 deciliter / gram and the density is 1.400 g / c.
m ³ , AA content is 5.0 ppm, and cyclic trimer content is 0.5 ppm.
PET with 33% by weight and fine content of about 15ppm
50 kg of chips are put into the inner tank (1), and the inner tank (1)
Is immersed in a water treatment tank (2), and after 5 hours, PET chips are taken out of the treatment tank (2) together with the inner tank (1),
Further, the PET chips are discharged from the inner tank (1), and the PE chips are discharged.
T chips and treated water in the treatment tank were sampled. Thereafter, feeding, discharging, and sampling of the PET chip were repeated in a batch system.

The sampled PET chips were dried under reduced pressure, and preformed bottles were molded using an M-100 injection molding machine manufactured by Meiki Seisakusho. Injection molding temperature is 295
° C. Next, the plug part of this preform was heated by a home-made plug crystallizer of a near-infrared heater type to crystallize the plug part. This preform was biaxially stretched and blown at a magnification of about 2.5 times in the vertical direction and about 5 times in the circumferential direction using an LB-01E molding machine manufactured by COPOPLAST, and the capacity was 1500 c.
The container of c was molded. The stretching temperature was controlled at 100 ° C. The AA content in water and the amount of fine powder contained in the treated water sampled above were determined. Table 1 shows the properties of the polyester container obtained in Example 1, the AA content in the treated water, and the amount of fine powder together with Comparative Examples.

[0067]

[Table 1]

As is clear from Table 1, when the AA content in the treatment water of the treatment tank of the present invention is set to 10 ppm or less,
The obtained molded product showed excellent sensory test results, and also had good transparency and capping, and did not leak contents.

(Comparative Example 1) The procedure of Example 1 was repeated except that the outlet for treated water and the supply port for fresh treated water provided in the treatment tank used in Example 1 were closed. As shown in Table 1, the AA content of the treated water continued to increase, and the sensory test results of the molded product obtained by the treatment gradually deteriorated, the transparency also deteriorated, and the contents were leaked due to poor capping. Was.

[0070]

According to the present invention, the polyester chips are supplied to the water treatment tank, and at least a part of the treatment water discharged from the treatment tank is not circulated back to the treatment tank. Water treatment is carried out while maintaining the content at 10 ppm or less, so that dirt in the treatment tank and piping during water treatment is reduced, and it is difficult to cause mold dirt during molding, and furthermore, molding from polyester chips. An excellent polyester with little residual off-flavor and off-flavor is obtained even when a product is manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus used for a method for producing a polyester of the present invention.

[Explanation of symbols]

 Reference Signs List 1 inner tank 2 treatment tank 3 treated water outlet 4 ion-exchanged water inlet 5 inner tank hanging jig 6 inner tank moving device

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yoshitaka Eto 20F term of 248 Takagi, Shiga-cho, Shiga-gun, Shiga Prefecture (reference) 4J029 AA01 AB04 AB05 AC01 AD10 AE01 BA03 BA04 BA05 BC07A CB05A CB06A CB10A CC05A CC06A CF15 JA081 JA091 JA111 JF321 JF361 JF471 KE02 KE03 KE08 KE12 KF04 KH05 KH08 LA04 LA05

Claims (6)

[Claims] 1. A process for producing polyester in which a polyester chip is water-treated in a treatment layer, wherein acetaldehyde content of treated water in the treatment tank without circulating treated water discharged from the treatment tank back to the treatment tank. A polyester chip, while maintaining the content at 10 ppm or less. 2. The method for producing a polyester according to claim 1, wherein the polyester chips are continuously or intermittently supplied to the treatment tank and extracted. 3. The method for producing polyester according to claim 1, wherein the whole amount of the polyester chips is filled in the treatment layer, and the whole amount of the polyester chips is extracted after the completion of the water treatment. 4. The polyester production method according to claim 1, wherein discharge of treated water from the treatment tank and supply of new treated water to the treatment tank are continuous. 5. The polyester production method according to claim 1, wherein discharge of the treated water from the treatment tank and supply of new treated water to the treatment tank are intermittent. 6. The process for producing a polyester according to claim 1, wherein the acetaldehyde is removed by aerating the treated water in the treatment tank with a gas bubbling type treatment device. .