JP2001081174A - Production of polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the sludge in a treating vessel and piping when treating a polyester chip with water, and to produce a polyester hardly causing the dirt on a mold when molding the polyester and capable of providing a bottle good in transparency and crystallization of a stopper part. SOLUTION: This method for producing a polyester chip by treating the polyester chip with water in a treating layer comprises carrying out the treatment with water by using the polyester chip having <=300 ppm content of fine powder of the resin.

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 having excellent controllability.

[0002]

2. Description of the Related Art Polyesters such as polyethylene terephthalate are excellent in both mechanical properties and chemical properties, and therefore have high industrial value, and include fibers, films, sheets, and the like.
Widely used as bottles.

[0003] As materials for containers such as seasonings, oils, beverages, cosmetics, and detergents, various resins are employed depending on the type of filling content and the purpose of use. Among them, polyester is excellent in mechanical strength, heat resistance, transparency, and gas barrier property, and thus is most 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.

[0006] Further, the polyester contains acetaldehyde which is a by-product. When the content of acetaldehyde in the polyester is large, the content of acetaldehyde in the material of a container or other packaging formed therefrom also increases, which affects the flavor and odor of the beverage or the like filled in the container or the like. Therefore, various measures have conventionally been taken to reduce the acetaldehyde content in the polyester.

In recent years, polyester containers mainly made of polyethylene terephthalate have been used for mineral water and water.
It has been used as a container for low-flavor beverages such as long tea. In the case of such beverages, these beverages are generally heat-filled or sterilized by heating after filling, but the reduction of the acetaldehyde content of the beverage container alone may not improve the flavor and odor of these contents. I understand.

In addition, for a metal can for beverages, a metal plate coated with a polyester film having ethylene terephthalate as a main repeating unit is used for the purpose of simplifying the process, improving hygiene and preventing pollution. The method of making cans has been adopted.

In this case, the contents are filled and sterilized by heating at a high temperature. It has been found that the flavor and odor of the contents are not improved even if a film having a low acetaldehyde content is used.

As a method for solving such a problem,
JP-A-3-47830 discloses a polyethylene terephthalate.
A method for water treatment of wastewater is disclosed.

However, at the stage of water treatment, fines (resin fine powder) adhering to the polyester chips float and precipitate in the treated water and adhere to the treatment tank wall and the pipe wall, causing clogging of the pipe or treatment. Problems such as difficulty in cleaning tanks and pipes have arisen.

Further, fines floating and settling in the treated water and adhering to the walls of the treatment tank and piping adhere to the polyester chips again, which promotes crystallization during molding, resulting in a bottle with poor transparency, There was a problem that the size of the plug after crystallization of the plug did not conform to the standard, resulting in poor capping.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art, and to reduce the contamination of a treatment tank and piping during the water treatment of polyester chips, and to further reduce the mold during molding. It is an object of the present invention to provide a polyester which is less likely to generate stains and further has good transparency of a bottle and crystallization of a plug portion.

[0014]

Means for Solving the Problems To achieve the above object, a method for producing a polyester according to the present invention is a method for producing a polyester, wherein the polyester chip having a fine content of 300 ppm or less is treated in a treated layer with water. And a water treatment.

Further, at least a part of the treatment water discharged from the treatment tank can be returned to the treatment tank and used repeatedly. Further, the processing water discharged from the processing tank can be discharged without returning to the processing tank. Further, the polyester chips 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 completion of the water treatment. Also, the discharge of the treated water from the treatment tank and the return of the discharged treated water to the treatment tank can be continuous or intermittent.

According to the method for producing a polyester of the present invention, contamination of a treatment tank or piping during water treatment can be reduced.
Further, it is possible to advantageously produce a polyester which is less likely to cause mold contamination during molding, and furthermore, has good transparency and good crystallization of a plug portion of a bottle.

[0017]

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 by copolymerization in the polyester includes 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, polyfunctional compounds such as trimellitic acid, trimesic acid, pyromellitic acid, tricarballylic acid, glycerin, pentaerythritol, and trimethylolpropane are copolymerized within a range in which the polyester is substantially linear. Or a monofunctional compound such as benzoic acid or naphthoic acid.

A 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 ethylene terephthalate unit in an amount of 85 mol% or more, 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 preferable 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 above-mentioned melt polycondensation reaction may be carried out 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 preferable 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 in water or a solution obtained by adding ethylene glycol to this and heat-treating the solution 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 used is preferably 10 to 150 as the amount of Ge remaining in the polyester resin.
ppm, more preferably 13 to 100 ppm, even more preferably 15 to 70 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 residual amount of Ti therein is preferably 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 amount of Sb remaining in the resulting polymer is preferably 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 amount of P remaining in the resulting polymer is preferably in the range of 5 to 100 ppm.

In order to control the DEG content in the polyester, a basic compound, for example,
Tertiary amines such as triethylamine and tri-n-butylamine, and quaternary ammonium salts 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 preferably 0.50 to 0.50.
1.30 deciliter / gram, more preferably 0.5
The range is 5 to 1.20 deciliters / gram, and more preferably 0.60 to 0.90 deciliters / gram. If the intrinsic viscosity is less than 0.50 deciliter / gram, the obtained molded article or the like has poor mechanical properties. Also, 1.
If it exceeds 30 deciliters / gram, the resin temperature rises during melting by a molding machine or the like, and thermal decomposition becomes severe, free low-molecular-weight compounds that affect fragrance retention increase, or the molded product is colored yellow. Problems occur.

The intrinsic viscosity of the polyester used in the present invention, especially the polyester whose main repeating unit is composed of ethylene-2,6-phthalate, is preferably 0.40 to 1.00 deciliter / gram, more preferably 0 to 1.00 deciliter / gram. .42 to 0.95 deciliter / gram, more preferably 0.45 to 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 preferably 10 ppm or less, more preferably 8 ppm or less, further preferably 5 ppm or less, and the formaldehyde content is preferably 7 ppm or less.
More preferably 6 ppm or less, still more preferably 4 ppm
It is as follows. The method of reducing the acetaldehyde content of the polyester used in the present invention to 10 ppm or less and the formaldehyde content to 7 ppm or less is not particularly limited. For example, a low-molecular-weight polyester may be used under reduced pressure or in an inert gas atmosphere. ~ 230 ° C
Of solid-state polymerization at a temperature of

The amount of diethylene glycol copolymerized in the polyester used in the present invention is preferably from 1.0 to 5% of the glycol component constituting the polyester.
0 mol%, more preferably 1.3 to 4.5 mol%, and still more preferably 1.5 to 4.0 mol%. When the amount of diethylene glycol exceeds 5.0 mol%, the thermal stability deteriorates, the molecular weight decreases during molding, and the acetaldehyde content and the formaldehyde content increase unfavorably. When the diethylene glycol content is less than 1.0 mol%, the transparency of the obtained molded article is deteriorated.

The content of the cyclic trimer of the polyester used in the present invention is preferably 0.50% by weight or less.
More preferably, it is 0.45% by weight or less, further preferably 0.40% by weight or less. When a heat-resistant hollow molded article or the like is molded from the polyester of the present invention, heat treatment is performed in a heating mold. However, when the content of the cyclic trimer is 0.50% by weight or more, the heating mold is used. The adhesion of oligomers to the surface sharply increases, and the transparency of the obtained hollow molded article or the like becomes extremely poor.

Polyester is used for the above-mentioned melting to prevent mold contamination due to the oligomers such as cyclic trimers adhering to the inner surface of the mold, the exhaust port of the mold gas and the exhaust pipe during molding. 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 immersion in water. The time for performing the contact treatment with water is preferably 5 minutes to 2 days, more preferably 10 minutes to
1 day, more preferably 30 minutes to 10 hours, and the temperature of water is 20 to 180 ° C, preferably 40 to 15 ° C.
The temperature is 0 ° C, more preferably 50 to 120 ° C.

Regardless of whether the water treatment method is continuous or batch, if all or most of the treated water discharged from the treatment tank is converted into industrial wastewater, a large amount of fresh water is required. In addition, there is a concern about the impact on the environment due to increased wastewater volume. That is, at least a part of the treated water discharged from the treatment tank is returned to the water treatment tank and reused, thereby reducing the required amount of water and reducing the effect on the environment by increasing the amount of wastewater. If the wastewater returned to the water treatment tank maintains a certain temperature,
The heating amount of the treated water can be reduced.

Furthermore, by reusing the water, the flow rate of the treated water flowing into the water treatment tank can be increased, and the water in the treatment tank can be prevented from becoming uneven. And a resin of stable quality can be obtained. Further, the water treatment also has an effect of washing out fines attached to the polyester chip, but the flow rate can be increased, so that a stable resin with few fines can be obtained.

However, the treated water discharged from the treatment tank includes:
Fines already attached to the polyester chips at the stage of receiving the polyester chips into the processing tank, and polyester fines generated by friction between the polyester chips or the processing tank wall during water treatment are included. Therefore, when the treated water discharged from the treatment tank is returned to the treatment tank and reused, the fine amount contained in the treated water in the treatment tank gradually increases. For this reason, fines contained in the treated water may adhere to the treatment tank wall or the pipe wall, and clog the pipe.

Even when water is not circulated and reused, if the amount of fines is large, the fines once flowing into the water sink into the bottom of the treatment layer, and when the polyester chips are extracted, the fines are extracted together with the chips. Non-uniformity in the batch and no consistent quality polyester chips.

In the method of circulating treated water and removing fines flowing out of the treated water with a filter or the like, the filter is clogged in a short period of time. I have a problem.

Further, the fines contained in the treated water adhere to the polyester chips again, and thereafter, the fines adhere to the polyester chips by the electrostatic effect at the stage of drying and removing the moisture. Even if it is performed, removal becomes difficult. Since this fine has a crystallization promoting effect, the crystallinity of the polyester is promoted,
In some cases, the bottle becomes poorly transparent, or the degree of crystallization at the time of crystallization of the plug becomes excessive, so that the size of the plug does not conform to the standard, resulting in poor capping of the plug.

According to the present invention, the fine content of the polyester chips to be supplied or filled into the water treatment layer is 300 ppm or less, preferably 100 ppm or less, more preferably 5 ppm or less.
The above problem is solved by limiting the content to 0 ppm or less. When the fine content exceeds 300 ppm, the fine content in the treatment water in the treatment tank rapidly increases, and the pipes are clogged, and the fine content attached to the polyester chips after the treatment increases. Crystallinity is promoted by the influence of fine,
Only bottles with poor transparency can be obtained.

As a method of reducing the fine amount of the polyester chips to be put into the water treatment tank, for example, a method of passing the polyester chips after the solid phase polymerization through a sieving step or a fine removing step by an air flow may be mentioned.

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.

In the case of treating the polyester chips with water in a batch system, a silo-type treatment tank may be used. That is, the chips of polyester are received in a silo in a batch system and water treatment is performed. Alternatively, it is also possible to receive a polyester chip in a rotating cylindrical processing tank and perform water treatment while rotating the chip, thereby making contact with water more efficient.

In this case, polyester chips having a fine content of 300 ppm or less are charged and filled in the treatment tank, and the treated water is filled with the treated water. The treated water is continuous or intermittent as required (generally referred to as continuous). And a part of the treated water is discharged continuously or intermittently to supply new treated water.

In the case of continuously treating polyester chips with water, the polyester chips having a fine content of 300 ppm or less are continuously received in a tower-type treatment tank or intermittently, and water is co-currently or countercurrently supplied. Water can be continuously supplied and treated.

In the present invention, in the case of a continuous water treatment method for polyester chips, the amount of 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 3 ppm or less.
It is desirable to return a part of the treatment water discharged from the treatment tank to the treatment tank and maintain repeated use of the treated water while maintaining the concentration at 00 ppm or less, and use it repeatedly. In the case of the batch water treatment method, at least one of the treated water discharged from the treatment tank is adjusted so that the amount of fine powder in the water at the end of the water treatment is 1000 ppm or less, preferably 500 ppm or less, more preferably 300 ppm or less. Return the part to the treatment tank and use it repeatedly. Here, the amount of fine powder is determined by the following measuring method.

In order to suppress an increase in the amount of fine powder of the treated water in the treatment tank, a device for removing fines is installed at at least one or more places in the process until the treated water discharged from the treatment tank is returned to the treatment tank again. . Examples of the device for removing fines include a filter filtration device, a membrane filtration device, a sedimentation tank, a centrifugal separator, and a foam entrainer. For example, if it is a filter filtration device, a belt filter system as a system,
Filtration devices such as a bag filter system, a cartridge filter system, and a centrifugal filtration system may be used. Above all, a belt filter system, a centrifugal filtration system, and a bag filter system are suitable for continuous operation. In the case of a filter device of a belt filter type, examples of the filter medium include paper, metal, cloth, and the like. In addition, in order to efficiently remove fines and flow treated water, the mesh size of the filter is preferably 5 to 100 μm, more preferably 10 to 70 μm.
μm, more preferably 15 to 40 μm.

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 general, natural water used industrially is derived from nature, inorganic particles and bacteria represented by clay minerals such as silicates and aluminosilicates, bacteria, etc., and has origins in spoiled plants and animals. Contains a lot of organic particles. 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 polyester chips, particles having a particle size of
It is preferable to use water containing 000 pieces / 10 cc.
Particles having a particle size of more than 25 μm in the treated water are not particularly limited, but are preferably 2000 particles / 10 cc or less, more preferably 500 particles / 10 cc or less, still more preferably 100 particles / 10 cc, and particularly preferably 10 particles / cc.
It is 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 small 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. Particle size 1 to 25μ used for water treatment below
An example of a method for obtaining water containing 10 to 50,000 particles / 10 m of m particles will be described.

As a method for reducing the number of particles in water to 50000 particles / 10 cc or less, an apparatus for removing particles is installed at at least one or more places in a process until natural water such as industrial water is supplied to the treatment tank. Preferably, from the natural water sampling port to the processing tank including the above-mentioned processing tank, piping returning the water drained from the processing tank to the processing tank again, a fine removal device, and other auxiliary equipment necessary for water treatment. A device for removing particles is installed between them, and the particle size of
The content of particles of ２５25 μm is 10 to 50,000 particles / 10
cc is preferred. As the device for removing particles of the treated water in the treatment tank, the above-described underwater fine removing device can be used.

In some cases, natural water contains a large amount of metal ions such as Na, Mg, Ca and the like. When water treatment is performed using such natural water, these adhere to and penetrate polyester chips. Then, it acts as a crystallization accelerator, and the transparency of the hollow molded container using such a polyester chip becomes very poor. Therefore, when using natural water for water treatment, it is preferable to reduce these metal ions to about 1.0 mg / liter or less by an ion exchange device or the like.

The polyester chips subjected to the water treatment 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 drainer is a filter-type filter,
It is sent to a fine removal device such as a centrifuge and can be used again for water treatment.

The polyester chips can be dried by a commonly used polyester chip drying treatment. 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. The dried granular polyester chips can be dried indirectly.

As a dryer for drying in a batch system, a double cone type rotary dryer is used, and the drying can be performed under vacuum or while passing a small amount of drying gas under vacuum. Alternatively, the drying may be performed while passing a drying 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 a reduction in molecular weight due to hydrolysis or thermal oxidative decomposition of the polyester.

[0062]

EXAMPLES The present invention will be described below in more detail 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 a mixed solvent of carbon tetrachloride / n-heptane.
Measured in ° C.

(3) Content of Cyclic Trimer of Polyester A sample is dissolved in a mixed solution of hexafluoroisopropanol / chloroform, and further diluted by adding 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 the cyclic trimer composed of ethylene terephthalate units was quantified by liquid chromatography.

(4) Measurement of Fine Content About 0.5 kg of resin was placed on a sieve (diameter 30 cm) 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.

(5) 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.

(6) Amount of fine powder in treated water (ppm) 1000 cc of treated water passed through a filter having a nominal size of 850 μm according to JIS-Z8801 was collected from the outlet of the treated water in the treatment tank, and filtered with a 1G1 glass filter manufactured by Iwaki Glass Co., Ltd. After filtration, drying at 100 ° C. for 2 hours and cooling at room temperature, the weight is measured and calculated.

(Example 1) An apparatus for removing particles in water (9), which is a GAF filter bag PE-1P2S (polyester felt, filtration accuracy: 1 μm) manufactured by ISP, was installed, and ion exchange was performed via this apparatus (9). Water inlet (8), raw material chip supply port (1) at the top of the processing tank, overflow discharge port (2) located at the upper limit level of the processing water in the processing tank, drainage of the mixture of polyester chips and processing water at the bottom of the processing tank Outlet (3), treated water discharged from the overflow discharge port, and treated water discharged through the drainage device (4) for polyester chips discharged from the discharge port at the bottom of the treatment tank, a 30 μm belt type filter medium made of paper A pipe (6) for sending again to the water treatment tank via a filtration device (5) which is a filter, an inlet (7) for these finely treated water, and a finely treated water. A polyethylene terephthalate (hereinafter referred to as PE) is prepared by using a treatment tank shown in FIG. 1 having a 320-liter capacity and having an adsorption tower (10) for adsorbing acetaldehyde, glycol, and the like therein.
The chips were treated with water.

The polyester chips after the solid phase polymerization were passed through a sieving step, and had a fine content of about 40 ppm, an intrinsic viscosity of 0.75 deciliter / gram, a density of 1.400 g / cm ³ , and a cyclic 3 PET chips having a monomer content of 0.33% by weight were continuously charged into the water treatment tank controlled at a treatment water temperature of 95 ° C. from the upper part (1) of the treatment tank at a rate of 50 kg / hour. After 5 hours from the start of the charging, the PET chips are continuously fed into the water treatment tank and 50 kg / PET chips are fed from the lower part (3) of the water treatment tank.
Withdrawal of the treated water was started at the speed of time, and the treated water that had passed through the draining device (4) was returned to the water treatment tank again through the filtration device (5), and repeated use was started. 1
The fine content of the treated PET chips after the continuous operation for 00 hours was 30 ppm, and the amount of fine powder in the treatment tank discharged together with the chips was about 200 ppm.

The above PET chips were dried under reduced pressure, and preforms of bottles were molded using an M-100 injection molding machine manufactured by Meiki Seisakusho. The injection molding temperature was 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. Next, this preform was used as LB-01 manufactured by COPOPLAST.
The container was biaxially stretched and blown at a magnification of about 2.5 times in a vertical direction and about 5 times in a circumferential direction by an E-forming machine to form a container having a capacity of 1000 cc. The stretching temperature was controlled at 100 ° C. The haze of the obtained container shows excellent transparency at 0.8%.

(Comparative Example 1) PET chips solid-phase polymerized in the same manner as in Example 1 were not subjected to the sieving step, and were treated with water in the same manner as in Example 1 while keeping the fine content at about 750 ppm. The fine content of the PET chips obtained after 100 hours of continuous operation was about 670 ppm, and the haze of the container obtained by the same method as in Example 1 was as bad as 8.1%.

[0073]

According to the present invention, there is provided a method for producing a polyester in which polyester chips and treated water are supplied to a treatment tank to treat the polyester chips with water.
0 ppm or less of polyester chips are supplied to the treatment tank for water treatment, so that dirt on piping during water treatment is reduced, and mold dirt is less likely to occur at the time of molding. A polyester having good partial crystallization is obtained.

[Brief description of the drawings]

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

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Raw material chip supply port 2 Overflow discharge port 3 Polyester chip and treated water discharge port 4 Drainer 5 Fine remover 6 Pipe 7 Treated water inlet 8 Ion-exchanged water inlet 9 Particle remover 10 Adsorption tower

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshitaka Eto 20F term of 248 Takajo, Shiga-cho, Shiga-gun, Shiga Prefecture (reference) 4F201 AA24 AC01 AG01 AH55 BA02 BA04 BC01 BC12 BC19 BL43 BL47 BN22 BN45 BQ04 BQ05 BQ53 4J029 AA03 AB07 AC01 AE01 BA03 CB06A KH08

Claims (6)

[Claims] 1. A method for producing polyester in which polyester chips are water-treated in a treatment layer, wherein the polyester chips having a fine content of 300 ppm or less are treated with water. 2. The method for producing a polyester according to claim 1, wherein at least a part of the treated water discharged from the treatment tank is returned to the treatment tank and used repeatedly. 3. The method for producing polyester according to claim 1, wherein the treated water discharged from the treatment tank is discharged without returning to the treatment tank. 4. The method for producing polyester according to claim 1, wherein the polyester chips are continuously or intermittently supplied to the treatment tank and extracted. 5. The method for producing a polyester according to claim 1, wherein the entire amount of the polyester chips is filled in the treatment layer, and the entire amount of the polyester chips is extracted after the water treatment. 6. The method for producing a polyester according to claim 2, wherein the discharge of the treated water from the treatment tank and the return of the discharged treated water to the treatment tank are continuous or intermittent.