JP2001072754A - Preparation of polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester which can give a bottle excellent in transparency and properly crystallized in a mouth portion and hardly causes mold fouling when molded. SOLUTION: In a polyester manufacturing method comprising feeding of polyester chips together with treating water into a treating tank and treating the polyester chips with water, polyester chips are discharged together with the treating water from the treating tank and subsequently the treating water is separated from the polyester chips to decrease water adhered to chips to 10 wt.% or less and then transferred to a drying process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing polyester used for forming bottles, films, sheets and the like, and more particularly, to a molded article having excellent transparency and controllability of crystallization. The present invention relates to a method for producing polyester which is less likely to cause mold contamination.

[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.

[0004] Among them, polyester is excellent in mechanical strength, heat resistance, transparency and gas barrier properties, and is therefore most suitable as a material for containers for filling beverages such as juices, soft drinks and carbonated drinks.

[0005] 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, stretch blow-molded, and then the body of the bottle is formed. 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 oligomers adhere to the inner surface of the mold, the exhaust port of the mold gas, and the exhaust pipe, thereby causing mold contamination. It was easy.

[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. Also in this case, the contents are heat-sterilized at a high temperature after filling, and 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 of 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.

Fines floating and settling in the treated water and adhering to the walls of the treatment tank and pipes adhere to the polyester chip again, which promotes crystallization during molding, resulting in poorly transparent bottles, There was a problem that the size of the plug after the partial crystallization did not meet the standard, resulting in poor capping.

Furthermore, in order to supply the polyester to the next step, it is necessary to dry after water treatment to reduce the water content of the chips to about 0.1% by weight or less. When the moisture adhering to the surface of the chip is large, the crystallization promoting effect is excessively imparted to the polyester in a step such as a drying treatment, so that the transparency of the obtained bottle becomes very poor.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art. The present invention has good transparency of a bottle and excellent crystallization of a plug portion, and generates mold contamination during molding. The purpose is to provide a polyester that is difficult to make.

[0014]

In order to achieve the above object, a method for producing a polyester according to the present invention comprises the steps of treating a polyester chip with water in a treatment layer, separating the polyester chip from treated water, and then treating the polyester chip. Is a method for producing a polyester, characterized in that water attached to polyester chips sent to the drying step is reduced to 10% by weight or less and sent to the drying step.

In the present invention, at least a part of the treatment water discharged from the treatment tank can be returned to the treatment tank and used repeatedly. In the present invention, the processing water discharged from the processing tank can be discharged without returning to the processing tank. In the present invention, the polyester chips can be continuously or intermittently supplied to the treatment tank and extracted.

In the present invention, 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. In the present invention, 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.

In the present invention, the fine water containing fines discharged from the separation processing device is removed by filtering it with a belt filter type filtering device and then returned to the processing tank to be used repeatedly. .

In the present invention, the fine water containing fines discharged from the separation processing device is filtered by a bag filter type filtering device to remove the fines, and then returned to the processing tank to be used repeatedly. .

In the present invention, the polyester may have a limiting viscosity of 0.55 to 1.30 deciliters / gram and the main repeating unit is composed of ethylene terephthalate. . In the present invention, the polyester can be a polyester whose main repeating unit is composed of ethylene naphthalate.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of a method for producing a polyester of the present invention will be specifically described. The polyester used in the present invention is preferably a crystalline polyester obtained mainly from an aromatic dicarboxylic acid component and a glycol component. More preferably, the aromatic dicarboxylic acid unit contains at least 85 mol% of the acid component. It is a polyester, particularly preferably a polyester containing an aromatic dicarboxylic acid unit in an amount of 95 mol% or more of the acid component.

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; Examples of the acid component used by copolymerization in the polyester include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, and 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.

Examples of the glycol component used by copolymerization in the polyester include 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, and trimethylolpropane is copolymerized within a range where 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 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 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, or phosphoric esters such as trimethyl phosphate. 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 addition, DEG copolymerized in polyester
Basic compounds in the esterification step to control the content,
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 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 composed of 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 polyester used in the present invention has an acetaldehyde content of 10 ppm or less, preferably 8 ppm or less.
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 the adhesion of oligomers such as cyclic trimers 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, a method of immersing in water may be mentioned. 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 chips subjected to the water treatment under the above-mentioned conditions are subjected to a water separation treatment by a drainer such as a vibrating sieve or a simmon cutter, and are transferred to a drying step. At the time of this transfer, the polyester chips accompanied by the attached water come into contact with or collide with forced chip transport means such as a transport pipe or a rotary feeder, and are impacted on the chip surface. Also, when drying in a stirring dryer or a rotary dryer,
The polyester chips collide with the walls of the stirrer or dryer and are similarly impacted on the chip surface. In this way, the polyester is transferred with a large amount of attached water or is put into the drying process with a large amount of attached water, and subsequently the polyester that has been dried has a very high crystallization rate. It has been found that the hollow molded container obtained from the polyester has extremely poor transparency.

According to the present invention, the polyester chips are discharged together with the treated water from the treatment tank, and then the treated water is separated from the polyester chips to reduce the amount of water adhering to the chips to 10% by weight.
The above problem is solved by reducing the amount to 5% by weight or less, more preferably 3% by weight or less, and sending it to the drying step. If the amount of water adhering to the chips after the separation of the treated water exceeds 10% by weight, the transparency of the obtained hollow molded article becomes extremely poor, and the commercial value is lost.

A method for reducing the amount of water adhering to polyester chips after water treatment to 10% by weight or less will be described below, but the method is not limited thereto.

In order to reduce the amount of water adhering to the polyester chips after the water treatment, an apparatus for separating the adhering water is installed at at least one place in the steps up to the drying step. Examples of a device for separating adhered water include a vibrating sieve, a batch centrifuge, a continuous centrifuge, a batch centrifugal dehydrator, a continuous centrifugal dehydrator, a wind dehydrator, and the like.

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 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, put the polyester chips into the processing tank,
Fill and fill the treated water, the treated water circulates continuously or intermittently (may be collectively referred to as continuous) as necessary, and discharges some of the treated water continuously or intermittently. Water treatment is performed by additionally supplying new treated water. And
After the water treatment is completed, the above problem is solved by sending the polyester chips discharged together with the treated water from the treatment tank to a water separator, reducing the water adhering to the chips to 10% by weight or less, and then drying.

Naturally, the water separated from the polyester chips by the above-mentioned water separator is sent to a filter-type filter, a centrifuge, an activated carbon adsorber, an ion exchanger or the like, and after the treatment, the water is again treated. Can be used.

When the polyester chips are to be continuously treated with water, the polyester chips are continuously treated in a tower-type treatment tank, or intermittently, the polyester chips are received from above, and water is continuously supplied in cocurrent or countercurrent to perform water treatment. Can be. Then, the above problem is solved by sending the polyester chips discharged from the treatment tank after the water treatment to a water separator, reducing the water adhering to the chips to 10% by weight or less, and then drying.

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.

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. Also, fines contained in the treated water adhere to the polyester chips again, and thereafter, the fines adhere to the polyester chips by an electrostatic effect at the stage of drying and removing the moisture. Removal becomes difficult. Since this fine has a crystallization accelerating effect, the crystallinity of the polyester is promoted, resulting in a bottle with poor transparency, and the degree of crystallinity at the time of crystallization of the plug part becomes excessive, and the size of the plug part becomes large. May not meet the standard, resulting in poor capping of the plug.

Therefore, the fine content of the polyester chips supplied or filled into the water treatment layer is about 300 ppm.
Below, it is desirable to limit to 100 ppm or less, more preferably to 50 ppm or less.

When the fine content exceeds 300 ppm, the fine content in the treated water in the treatment tank sharply increases, so that the piping is clogged, and the fine content adhering to the treated polyester chips is large. Become
The crystallinity is promoted by the influence of this fine, and only a bottle 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 can be mentioned.

In the present invention, 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 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 place 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. Further, in order to efficiently remove fines and flow the treated water, the size of the mesh of the filter is 5 to 100 μm, preferably 10 to 70 μm, and 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 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.

A particle size of 1 to 25 μm used for water treatment is described below.
An example of a method for obtaining water containing 10 to 50000 particles / 10 cc is as follows. 50,000 particles / 10cc in water
As a method described below, a device 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 a 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 in between, and the content of particles having a particle size of 1 to 25 μm in water supplied to the treatment device is 10 to 50,000 particles / 1.
It is preferably 0 cc. 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 the polyester chip and penetrate. 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 necessary to reduce these metal ions to about 1.0 mg / liter or less by an ion exchange device or the like.

Further, natural water generally used for industrial purposes contains a large amount of the aforementioned bacteria, bacteria and the like, organic compounds originating from spoiled plants and animals, and the like. These bacteria, bacteria or organic compounds are oxidized to ammonia, nitrous acid and nitric acid under aerobic conditions. When water treatment is performed using these natural waters, these nitrogen compounds adhere to the polyester chips, causing unpleasant taste and odor, and the flavor and aroma of the contents of the hollow molded container using such polyester chips are reduced. It turned out to be very bad. The contents of ammonia and nitric acid in the treated water are measured as the contents of ammonia nitrogen and nitrate nitrogen.

In the present invention, in the case of the continuous method, the content of ammonia nitrogen in the treated water discharged together with the polyester chips from the treatment tank is maintained at 0.5 mg / liter or less, and the content of nitrate nitrogen is maintained at 1 mg / liter or less. In the case of the batch method, the above problem is caused by maintaining the ammonia nitrogen content of the treated water in the treatment tank at the end of the water treatment at 0.5 mg / l or less and the nitrate nitrogen content at 1 mg / l or less. Solve the point.

In the present invention, the content of ammonia nitrogen in water introduced from outside the system is 0.01 to 0.5 mg /
Liter, and the content of nitrate nitrogen is 0.01 to 1 mg
It is also necessary to maintain the volume per liter.

A method for reducing the content of ammonia, nitric acid and the like in the treated water in the treatment tank is described below, but the method used for producing the polyester of the present invention is not limited to this.

In order to reduce the content of ammonia, nitric acid, etc. in the treated water, at least one or more organic substances, ammonia, nitric acid, etc. must be provided in the process before the industrial water newly supplied to the treating tank is sent to the treating tank. Install a device to remove the water. Further, at least one step is required in the process until the treated water discharged from the treatment tank is returned to the treatment tank or in the treatment tank.
A device for removing organic substances, ammonia, nitric acid, or the like may be provided at more than two locations. Examples of an apparatus for removing organic substances, ammonia, nitric acid, and the like include a deaerator, an ion exchange apparatus, and an activated carbon adsorption apparatus.

The content of ammonia nitrogen and nitrate nitrogen in treated water introduced in large amounts from outside the system was 0.01 mg /
In order to reduce the water content to less than 1 liter, it is necessary to distill the water or repeat filtration with a reverse osmosis membrane, which increases the cost of the water and is not economically favorable.

After the water treatment, treated water is attached to the polyester chips from which the treated water has been separated, and the treated water contains fine powder, metals and particles derived from the treated water as described above. When the amount of treated water increases, these impurities inevitably increase in the dried polyester chips, which causes poor transparency, unpleasant odor, and crystallization rate of the plug. May be too early or colored. These problems can be prevented by the method of the present invention.

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. 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.

[0071]

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) 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 Polyester Cyclic Trimer A sample is dissolved in a mixture 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 the cyclic trimer composed of ethylene terephthalate units was quantified by liquid chromatography.

(4) Fine Content Measurement Using a 36-mesh standard sieve according to JIS-Z8801, a 1000 kg sample is sieved, and the amount of fine that has passed through the sieve is weighed to determine the content.

(5) Amount of water adhering to chips About 10 g of a sample was placed in a glass container and placed in a vacuum drier for about 1 g.
Heat treatment is performed at 05 ° C. for 7 hours, and the weight loss before and after the treatment is determined and calculated.

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

(7) Amount of fine powder in treated water (ppm) 1000 cc of treated water passed through a JIS standard 20 mesh filter was collected from the outlet of treated water in the treatment tank,
After filtration with a 1G1 glass filter manufactured by Iwaki Glass Co., Ltd., 100
After drying at room temperature for 2 hours and cooling at room temperature, the weight is measured and calculated.

(8) Measurement of Particle Size and Number of Particles in Water A light-shielding type particle measuring device HIAC / ROYCO.TM., Manufactured by Pacific Scientific Company. Counter 4
The measurement was performed using a model 100 and a sampler 3000.

(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 The treated water discharged from the outlet (3), the overflow discharge port, and the polyester chip drained from the discharge port at the lower part of the treatment tank (continuous centrifugal separator) (4). Filter material is 30μm made of paper
A pipe (6) for sending again to a water treatment tank via a filtration device (5) which is a belt-type filter, an inlet (7) for these finely-removed treated water, and acetaldehyde and glyco- A polyethylene terephthalate (hereinafter abbreviated as PET) chip was treated with water using a treatment tank shown in FIG. 1 having a capacity of 320 liters and having an adsorption tower (10) for adsorbing water and the like. The content of particles having a particle size of 1 to 25 μm in the water collected at the inlet (8) of the ion-exchanged water of the water treatment apparatus is about 2500 (pieces / 1).
0 cc).

The polyester chips after the solid phase polymerization were passed through a sieving step, and had a fine content of about 10 ppm, an intrinsic viscosity of 0.74 deciliter / gram, a density of 1.399 g / cm 3, and a cyclic triamount. PET chips having a body content of 0.30% by weight were continuously introduced into the water treatment tank controlled at a treatment water temperature of 95 ° C. at a rate of 50 kg / hour from the upper part (1) of the treatment tank. 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 at the speed of time is started, and the treated water that has passed through the continuous centrifugal dewatering device (4) using wind power is returned to the water treatment tank again through the filtration device (5) for repeated use. Started. After 100 hours of continuous operation, the water-treated PET chips are treated with a continuous centrifugal dehydrator (4) to separate the treated water to reduce the amount of water adhering to the chips to about 0.8% by weight. About 1
It was dried with dehumidified air at 30 ° C. The amount of fine powder in the treated water discharged from the treatment tank was about 80 ppm. The above-mentioned PET chip was dried under reduced pressure, and M-100 manufactured by Meiki Seisakusho Co., Ltd.
A preform of the bottle was molded by an injection molding machine. 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, the preformed body 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 to form a container having a capacity of 2000 cc. The stretching temperature was controlled at 100 ° C. The haze of the obtained container shows excellent transparency at 0.8%.

(Example 2) P used in Example 1
The ET was treated in the same manner as in Example 1 using the same apparatus as above, except that the water treatment was continuously performed under the same conditions, and then the dehydration conditions were changed so that the amount of water adhering to the chip was about 2.3% by weight. The haze of the container obtained by the same method and under the same conditions as in the example is as follows.
Excellent transparency is shown at 0%.

(Example 3) P used in Example 1
The ET was continuously treated with water by the same apparatus as in Example 1 under the same conditions, the amount of water adhering to the chips was reduced to about 1.0% by weight or less, and then a double-cone rotary dryer of a batch system was used. Dried at about 130 ° C. The haze of the container obtained by the same method and under the same conditions as in the example shows excellent transparency at 1.3%.

Comparative Example 1 A PET chip subjected to solid phase polymerization in the same manner as in Example 1 was treated with water under the same method and conditions as in Example 1. The PET chips after the water treatment were treated with the same continuous centrifuge as in Example 1 to reduce the amount of water adhering to the chips to about 2
After the amount was reduced to 0% by weight, it was dried at about 130 ° C. by a hopper-type continuous dryer. The haze of the container obtained in the same manner and under the same conditions as in Example 1 was as poor as 8.7%.

(Comparative Example 2) P used in Example 1
The ET was continuously treated with water in the same apparatus as in Example 1 under the same conditions, the amount of water adhering to the chips was adjusted to about 13% by weight, and then the mixture was heated at about 130 ° C. using a batch type double cone rotary dryer. Dried. The haze of the container obtained in the same manner and under the same conditions as in Example 1 was very bad at 17.3%.

[0086]

According to the present invention, there is provided a method for producing polyester in which polyester chips and treated water are supplied to a treatment tank to treat the polyester chips with water, and the polyester chips are discharged from the treatment tank together with the treated water. By separating the treated water from the chips to reduce the amount of water adhering to the chips to 10% by weight or less and sending them to the drying step, the transparency of the bottle and the controllability of the crystallization of the plug portion are good, and the A polyester that does not easily cause mold stains can be obtained. If the amount of attached water is large, the crystallization speed due to the impact on the chip surface in the chip transportation step or the drying step after the water separation treatment becomes very fast, and the transparency of the obtained bottle becomes very poor. The transparency of the bottle is improved by reducing the amount of attached water to 10% by weight or less.

[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]

 DESCRIPTION OF SYMBOLS 1 Raw material chip supply port 2 Overflow discharge port 3 Discharge port of polyester chip and treated water 4 Continuous centrifugal dehydrator 5 Fine removal filtration device 6 Pipe 7 Treated water inlet 8 Ion exchange water inlet 9 Particle remover 10 Adsorption tower

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[Procedure amendment]

[Submission date] July 10, 2000 (2007.1.
0)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shutake Kimura 26-21 Akao-cho, Otsu-shi, Shiga F-term (reference) 4J029 AA01 AA03 AB07 AC01 AD01 AE01 BA03 CB06A CC05A KH03 KH08 LB05

Claims (10)

[Claims] In a method for producing a polyester, the polyester chip is subjected to a water treatment in a treatment layer, the polyester chip is separated from treated water, and then the polyester chip is dried. A method for producing a polyester, comprising reducing the amount to 10% by weight or less and sending the reduced amount to a drying step. 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. 7. The method is characterized in that the fine water containing fines discharged from the separation processing device is removed by filtering with a belt filter type filtering device, and then returned to a processing tank for repeated use. Claim 1,
7. The method for producing a polyester according to 2, 3, 4, 5, or 6. 8. The method is characterized in that fine water containing fines discharged from the separation processing device is filtered by a bag filter type filtering device to remove fines, and then returned to a processing tank and used repeatedly. Claim 1,
7. The method for producing a polyester according to 2, 3, 4, 5, or 6. 9. The polyester has an intrinsic viscosity of 0.55 to 0.55.
The polyester according to claim 1, wherein a main repeating unit of 1.30 deciliters / gram is a polyester composed of ethylene terephthalate.
9. The method for producing a polyester according to 7 or 8. 10. The polyester according to claim 1, wherein the main repeating unit is a polyester composed of ethylene naphthalate.
9. The method for producing a polyester according to 7 or 8.