JP3399885B2 - Polyester production method - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing polyesters used for forming films and sheets, including bottles. More specifically, the present invention is excellent in transparency and crystallization controllability during molding, The present invention relates to a method for producing polyester in which mold stains are unlikely to occur.

[0002]

BACKGROUND OF THE INVENTION Polyester such as polyethylene terephthalate has a high industrial value because of its excellent mechanical properties and chemical properties, and it has high industrial value.
Widely used as bottles.

As a material for containers such as seasonings, oils, beverages, cosmetics and detergents, various resins have been adopted depending on the type of filling contents and the purpose of use thereof.

Of these, polyester is excellent in mechanical strength, heat resistance, transparency and gas barrier property, and is therefore most suitable as a material for a beverage filling container such as juice, soft drink, carbonated drink and the like.

Such polyester is supplied to a molding machine such as an injection molding machine to mold a preform for a hollow molded body, and the preform is inserted into a mold having a predetermined shape and stretch blow-molded, followed by a body portion of a bottle. Heat treatment (heat set)
It is then generally molded into a hollow molded container, and if necessary, the bottle cap is heat treated (crystallized in the cap). However, conventional polyester contains oligomers such as cyclic trimers, and these oligomers adhere to the inner surface of the mold, the gas exhaust port of the mold, and the exhaust pipe, resulting in mold contamination. It was easy.

Further, the polyester contains acetaldehyde which is a by-product. When the content of acetaldehyde in the polyester is high, the content of acetaldehyde in the material of the container or other packaging molded from this is also high, which affects the flavor and odor of the beverage or the like filled in the container or the like. Therefore, various measures have been conventionally taken to reduce the acetaldehyde content in polyester.

In recent years, polyester containers centered on polyethylene terephthalate have been used for mineral water and water.
It has come to be used as a container for low flavor beverages such as ron tea. In the case of such a beverage, these beverages are generally heat-filled or sterilized by heating after filling, but the flavor and odor of these contents may not be improved only by reducing the acetaldehyde content of the beverage container. I understand.

For the metal can for beverages, a metal plate coated with a polyester film having ethylene terephthalate as a main repeating unit on its inner surface is used for the purpose of process simplification, hygiene and pollution prevention. The method of making cans has come to be adopted. Also in this case, the contents are heat-sterilized at a high temperature after filling, but it has been found that the flavor and odor of the contents are not improved by using a film having a low acetaldehyde content.

As a method of solving such a problem,
Japanese Patent Laid-Open No. 3-47830 discloses polyethylene terephthalate.
A method of treating water with water is disclosed.

However, at the stage of water treatment, fine (resin fine powder) adhering to the polyester chips floats and precipitates in the treated water and adheres to the treatment tank wall and the pipe wall, clogging the pipes and treating the water. Problems such as making cleaning of tanks and piping difficult occur.

Further, the fine particles floating and settled in the treated water and adhering to the wall of the treatment tank or the pipe wall are reattached to the polyester chip, promoting crystallization at the time of molding, resulting in a poorly transparent bottle, and a spout. After the partial crystallization, the size of the plug portion did not meet the standard, resulting in a problem such as capping failure.

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

[0013]

DISCLOSURE OF THE INVENTION The present invention is to solve the above-mentioned problems of the prior art. The transparency of the bottle and the crystallization of the plug portion are good, and the mold stains occur during molding. The purpose is to provide a polyester that is difficult to prevent.

[0014]

In order to achieve the above object, a method for producing a polyester of the present invention is a method in which a polyester chip is treated with water in a treatment layer, then the polyester chip and the treated water are separated , and then , in the method for manufacturing a polyester of drying polyester chips, Po
As water for water treatment of reester chips, particle size from outside the system
Includes 10 to 50,000 particles / 10 cc of 1 to 25 μm
Water is introduced into the treatment tank for water treatment, and the water treatment works
The method for producing polyester is characterized in that the water adhering to the polyester chips sent to the drying step is reduced to 10% by weight or less and then sent to the drying step.

In the present invention, at least a part of the treated water discharged from the treatment tank can be returned to the treatment tank for repeated use. In the present invention, the treated water discharged from the treatment tank can be discharged without returning to the treatment 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 polyester chips can be filled in the treatment layer, and the entire amount of polyester chips can be extracted after the water treatment is completed. 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 treated water containing fines discharged from the separation treatment device is filtered by a belt filter type filtering device to remove fines, and then returned to the treatment tank for repeated use. .

In the present invention, the treated water containing fines discharged from the separation treatment device is filtered by a bag filter type filtering device to remove fines, and then returned to the treatment tank for repeated use. .

In the present invention, the polyester may be a polyester having an intrinsic viscosity of 0.55 to 1.30 deciliter / gram and ethylene terephthalate as the main repeating unit. . 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 Embodiments of the method for producing a polyester of the present invention will be specifically described below. The polyester used in the present invention is preferably a crystalline polyester obtained mainly from an aromatic dicarboxylic acid component and a glycol component, and more preferably, the aromatic dicarboxylic acid unit contains 85 mol% or more of the acid component. A polyester, particularly preferably a polyester containing an aromatic dicarboxylic acid unit in an amount of 95 mol% or more of the acid component.

As the aromatic dicarboxylic acid component constituting the polyester used in the present invention, terephthalic acid,
2,6-naphthalenedicarboxylic acid, diphenyl-4,
Examples thereof include aromatic dicarboxylic acids such as 4′-dicarboxylic acid and diphenoxyethanedicarboxylic acid, and functional derivatives thereof.

As the glycol component constituting the polyester used in the present invention, ethylene glycol,
Trimethylene glycol, tetramethylene glycol,
Examples thereof include 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 and diphenoxyethanedicarboxylic 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 dicarboxylic acids and functional derivatives thereof, 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. Examples thereof include aromatic glycols such as alkylene oxide adducts of polyethylene glycol, polyalkylene glycols such as polyethylene glycol and polybutylene glycol.

Further, polyfunctional compounds such as trimellitic acid, trimesic acid, pyromellitic acid, tricarballylic acid, glycerin, pentaerythritol, trimethylolpropane and the like are copolymerized within a range where the polyester is substantially linear. Alternatively, a monofunctional compound such as benzoic acid or naphthoic acid may be copolymerized.

A preferable example of the polyester used in the present invention is a polyester whose main repeating unit is ethylene terephthalate, more preferably a linear polyester containing 85 mol% or more of ethylene terephthalate units, and particularly preferable. Linear polyester containing 95 mol% or more of ethylene terephthalate units, that is, polyethylene terephthalate (hereinafter PET)
Is abbreviated).

In another preferred example of the polyester used in the present invention, the main repeating unit is ethylene-
A polyester composed of 2,6-naphthalate, more preferably a linear polyester containing 85 mol% or more of ethylene-2,6-naphthalate units, and particularly preferably 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 in which terephthalic acid, ethylene glycol and optionally other copolymerization components are directly reacted to distill off water to esterify, and then polycondensate 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 distill off methyl alcohol for transesterification and then polycondensation under reduced pressure. Further, solid phase polymerization may be carried out in order to increase the intrinsic viscosity and decrease the acetaldehyde content and the like.

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

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

As the Ge compound, amorphous germanium dioxide, crystalline germanium dioxide powder or a slurry of ethylene glycol, a solution of crystalline germanium dioxide dissolved in water by heating or a solution obtained by adding ethylene glycol to the solution and subjecting it to heat treatment is used. However, in particular, in order to obtain the polyester used in the present invention, it is preferable to use a solution in which germanium dioxide is dissolved in water by heating or a solution in which ethylene glycol is added and heated. These polycondensation catalysts can be added during the esterification process. When a Ge compound is used, the amount used is 10 to 150 ppm, preferably 13 to 100 ppm, and more preferably 15 to 7 as the Ge residual amount 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 their partial hydrolysis. Examples thereof include titanyl oxalate, titanyl ammonium oxalate, sodium titanyl oxalate, potassium titanyl oxalate, titanyl calcium oxalate, titanyl oxalate compounds such as strontium titanyl oxalate, trimellitic acid titanium, titanium sulfate, titanium chloride and the like. The Ti compound is a formed polymer.
It is added so that the remaining amount of Ti in it is in the range of 0.1 to 10 ppm.

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

As the stabilizer, it is preferable to use phosphoric acid, polyphosphoric acid, phosphoric acid 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 produced polymer is in the range of 5 to 100 ppm.

Also, DEG copolymerized in polyester
Basic compound in the esterification process to control the content,
For example, a tertiary amine such as triethylamine or tri-n-butylamine, a quaternary ammonium salt such as tetraethylammonium hydroxide, or the like can be added.

The polyester used in the present invention, in particular,
The intrinsic viscosity of a polyester whose main repeating unit is ethylene terephthalate is 0.50 to 1.30 deciliter / gram, preferably 0.55 to 1.20 deciliter / gram, and more preferably 0.60 to 0.
It is in the range of 90 deciliters / gram. When the intrinsic viscosity is less than 0.50 deciliter / gram, the mechanical properties of the obtained molded product and the like are poor. On the other hand, when it exceeds 1.30 deciliters / gram, the resin temperature becomes high when melted by a molding machine or the like and the thermal decomposition becomes violent, resulting in an increase in free low molecular weight compounds which affect the aroma retention, Will be colored yellow.

Further, 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 deciliter / gram, more preferably 0.
It is in the range of 45-0.90 deciliters / gram. When the intrinsic viscosity is less than 0.40 deciliter / gram, the mechanical properties of the obtained molded product are poor. On the other hand, if it exceeds 1.00 deciliter / gram, the resin temperature becomes high when melted by a molding machine or the like, and thermal decomposition becomes violent, resulting in an increase in free low-molecular-weight compounds that affect aroma retention, or a molded product. Will be colored yellow.

The shape of the polyester chips may be any of cylinder type, square type, flat plate type and the like, and their sizes are usually 1.6 to 3.5 in length, 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, it is practical that the weight of the chip is 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, formaldehyde content is 7 ppm or less, preferably 6 ppm or less,
More preferably, it is 4 ppm or less. The polyester used in the present invention has an acetaldehyde content of 10 ppm.
Hereinafter, the method for reducing the formaldehyde content to 7 ppm or less is not particularly limited. For example, a method of solid-phase polymerizing a low molecular weight polyester under reduced pressure or in an inert gas atmosphere at a temperature of 170 to 230 ° C. is used. I can name it.

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%, based on the glycol component constituting the polyester. Preferably 1.5
Is about 4.0 mol%. The amount of diethylene glycol is 5.
When it exceeds 0 mol%, the thermal stability is deteriorated, the molecular weight is greatly reduced during molding, and the acetaldehyde content and the formaldehyde content are increased, which is not preferable. In addition, the content of diethylene glycol is 1.0 mol%
If it is less than the above range, the transparency of the obtained molded article becomes poor.

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 the following. 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,
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 product is extremely deteriorated.

The polyester is melted in order to prevent contamination of the mold due to oligomers such as cyclic trimers adhering to the inner surface of the mold, the gas exhaust port of the mold, the exhaust pipe, etc. during molding. After polycondensation or solid phase polymerization, contact treatment with water is performed. Examples of the method of contact treatment with water include a method of immersing in water. The time for 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 temperature of water is 20 to 180 ° C., preferably 40 to 150. C., more preferably 50 to 120.degree.

The polyester chips that have been treated with water under the above conditions are separated by a draining device such as a vibrating screener or a simon coater, and transferred to a drying step. At the time of this transfer, the polyester chips accompanied by the adhered water come into contact with or collide with a forced chip transporting means such as a transport pipe or a rotary feeder, and the chip surface is impacted. When drying with a stirring dryer or rotary dryer,
The polyester chips collide with the walls of the stirrer and the dryer, and the chip surface is similarly impacted. In this way, the polyester that has been transferred with a large amount of adhered water, or put into the drying treatment step with a large amount of adhered water and subsequently subjected to the drying treatment has a very high crystallization rate. It was found that the hollow molded container obtained from the polyester had very poor transparency.

According to the present invention, the polyester chips are discharged together with the treated water from the treatment tank, and the treated water is separated from the polyester chips to obtain 10% by weight of the water adhering to the chips.
The above problems are 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 water adhering to the chips after separating 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 water content on the polyester chips after water treatment to 10% by weight or less will be illustrated below, but the method is not limited thereto.

In order to reduce the water adhering to the polyester chips after the water treatment, a device for separating the adhering water is installed at at least one place in the steps up to the drying step. Examples of the device for separating the adhered water include a vibration type sifter, a batch type centrifugal separator, a continuous type centrifugal separator, a batch type centrifugal dehydrator, a continuous type centrifugal dehydrator and a wind type dehydrator.

The method for industrially treating water will be illustrated below, but the method is not limited thereto. The treatment 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 water treatment in a batch system, a silo type treatment tank can be used. That is, the polyester chips are received in silos in a batch system and treated with water. Alternatively, it is also possible to receive the polyester chips in a rotating tubular processing tank and perform water treatment while rotating to make the contact with water more efficient. In this case, put the polyester chips into the processing tank,
Filled and filled with treated water, the treated water circulates continuously or intermittently (may be collectively referred to as continuous) if necessary, and continuously or intermittently discharges part of the treated water. Water is additionally treated by supplying new treated water. And
After the water treatment is completed, the polyester chips discharged from the treatment tank together with the treated water are sent to a water separation device, the water adhering to the chips is reduced to 10% by weight or less, and then the polyester chips are dried to solve the above problems.

As a matter of course, the water separated from the polyester chips by the water separation device is sent to a device such as a filter-type filtration device, a centrifuge, an activated carbon adsorption device, an ion exchange device, etc., and is again treated for water treatment. Can be used.

When the polyester chips are continuously treated with water, the polyester chips are continuously or intermittently received from the upper part and continuously supplied with water in a cocurrent or countercurrent for water treatment. You can Then, the above-mentioned problems are solved by sending the polyester chips discharged from the treatment tank after the water treatment to a water separation device, reducing the water attached to the chips to 10% by weight or less, and then drying.

Regardless of whether the water treatment method is continuous or batchwise, if all or most of the treated water discharged from the treatment tank is treated as industrial wastewater, a large amount of new water can be used. Not only that, but there is concern that the increase in the amount of wastewater will have an impact on the environment. That is, by returning at least a part of the treated water discharged from the treatment tank to the water treatment tank and reusing it, it is possible to reduce the necessary amount of water, and it is possible to reduce the effect on the environment due to the increase in the amount of drainage. If the wastewater returned to the water treatment tank maintains a certain temperature,
The heating amount of treated water can be reduced.

However, in the treated water discharged from the treatment tank,
Fines already attached to the polyester chips at the stage of receiving the polyester chips in the treatment tank, and polyester fines generated by friction between the polyester chips or the walls of the treatment tank during water treatment are included. Therefore, when the treated water discharged from the treatment tank is returned to the treatment tank for reuse, the amount of fines contained in the treated water in the treatment tank gradually increases. Therefore, the fines contained in the treated water may adhere to the walls of the treatment tank or the piping wall and clog the piping. Also, the fines contained in the treated water adhere to the polyester chips again, and after this, the fines adhere to the polyester chips due to the electrostatic effect at the stage of drying and removing water, so even if the fines are removed after drying. Difficult to remove. Since this fine has an effect of promoting crystallization, the crystallinity of the polyester is promoted, resulting in a bottle with poor transparency, and the crystallinity at the time of crystallization of the mouth plug portion becomes excessive, resulting in the dimension of the mouth stopper portion. May not meet the standard, resulting in poor capping of the spout.

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

If the fine content exceeds 300 ppm, the fine content in the treated water in the treatment tank will rapidly increase, causing clogging of the pipes, and a large amount of fine content attached to the treated polyester chips. Becomes
Crystallinity is promoted by the influence of this fine, and only a bottle with poor transparency can be obtained.

As a method for 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 process or a fine removing process by an air flow can be mentioned.

In the present invention, in the case of the continuous water treatment method for polyester chips, the fine powder amount of the treated water discharged from the treatment tank together with the polyester chips is 1000 ppm or less, preferably 500 ppm or less, more preferably 3
It is desirable to return a part of the treated water discharged from the treatment tank to the treatment tank and repeatedly use the same while keeping the concentration below 00 ppm. Further, in the case of the batch type water treatment method, at least one of the treated water discharged from the treatment tank so that 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. The part is returned to the treatment tank for repeated use. Here, the amount of fine powder is obtained by the following measuring method.

In order to suppress an increase in the amount of fine powder of treated water in the treatment tank, a device for removing fines is installed at least at 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 precipitation tank, a centrifuge, and a foam entrainment processor. For example, if it is a filter filtration device, the belt filter
Examples of the filter device include a bag filter system, a cartridge filter system, and a centrifugal filtration system. Among them, a belt filter type, a centrifugal filtration type, and a bag filter type filtration device are suitable for continuous operation. Further, in the case of a belt filter type filtering device, examples of the filter material include paper, metal, cloth and the like. Further, in order to remove fines and to flow the treated water efficiently, 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.

When the polyester chips are industrially treated with water, natural water (industrial water) or waste water is often reused because the amount of water used for the treatment is large. Usually, this natural water is taken from river water, groundwater, etc., and is said to have undergone treatment such as sterilization and removal of foreign substances without changing the shape of water (liquid). Further, natural water that is generally used industrially has an origin in natural particles, such as inorganic particles and bacteria such as silicates and aluminosilicates, clay minerals such as aluminosilicates, bacteria, and spoiled plants and animals. It contains a lot of organic particles. When water treatment is performed using these natural waters, particles adhere to and permeate the polyester chips to form crystal nuclei, and the transparency of the hollow molding container using such polyester chips becomes extremely poor.

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

The particles having a particle size of less than 1 μm in the treated water are not particularly specified in the present invention, but the smaller amount is preferable 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 100,000 particles / 10 cc or less, more preferably 50,000 particles / 10 cc or less, and further preferably 200.
00 pieces / 10 cc or less, particularly preferably 10,000 pieces /
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 sizes of 1 to 25 μm used for water treatment below
The method for obtaining water containing 10 to 50,000 particles / 10 cc. The number of particles in water is 50,000 / 10cc
As a method to be described below, an apparatus for removing particles is installed at at least one place in the process until natural water such as industrial water is supplied to the treatment tank. Preferably from the natural water sampling port, to the treatment tank described above, a pipe for returning the water drained from the treatment tank to the treatment tank again, a fine removal device, and the like, to a treatment device including incidental equipment necessary for water treatment A device for removing particles is installed between them, and the content of particles having a particle size of 1 to 25 μm in the water supplied to the processing device is 10 to 50000 particles / 1
It is preferably 0 cc. As the device for removing the particles of the treated water in the treatment tank, the above-mentioned fines removing device in water can be used.

Natural water may contain a large amount of metal ions such as Na, Mg and Ca. When water treatment is performed using such natural water, these adhere to and permeate the polyester chips. Then, it acts as a crystallization accelerator, and the transparency of the hollow molded container using such a polyester chip becomes extremely 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.

Natural water generally used for industrial use contains a large amount of the above-mentioned bacteria, bacteria, etc., organic compounds originating from spoiled plants and animals, and the like. These bacteria, bacteria or organic compounds are oxidized to ammonia, nitrous acid or nitric acid under aerobic conditions. When water treatment is carried out using these natural waters, these nitrogen compounds adhere to the polyester chips, causing off-taste and off-odor, and the flavor and aroma of the contents of the hollow molding container using such polyester chips are 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 system, the ammoniacal nitrogen content of the treated water discharged together with the polyester chips from the treatment tank is maintained at 0.5 mg / liter or less and the nitrate nitrogen content is maintained at 1 mg / liter or less. Also, in the case of the batch method, the above problems can be solved by maintaining the ammoniacal nitrogen content of the treated water in the treatment tank at the end of the water treatment at 0.5 mg / liter or less and the nitrate nitrogen content at 1 mg / liter or less. Solve the point.

Further, 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 0.01 to 1 mg of nitrate nitrogen content
It is also necessary to maintain at / liter.

The method for reducing the contents of ammonia, nitric acid and the like in the treated water in the treatment tank will be exemplified 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. should be provided in the process until the industrial water newly supplied to the treated tank is sent to the treated tank. Install a device to remove. In addition, at least 1 step is required in the process until the treated water discharged from the treatment tank is returned to the treatment tank again.
You may install the apparatus which removes an organic substance, ammonia, nitric acid, etc. in more than one place. Examples of the device for removing organic substances, ammonia, nitric acid, etc. include a deaerator, an ion exchange device, and an activated carbon adsorption device.

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

After the water treatment, the treated water adheres to the polyester chips from which the treated water has been separated, and this treated water contains fine powder, metals derived from the treated water, particles, etc. as described above. However, when the amount of treated water attached increases, the polyester chips after drying inevitably contain these impurities, which causes inferior transparency, off-flavors, and crystallization speed of the mouth plug. It is thought that the bottle will be too early or colored. The method of the present invention can prevent these problems.

For drying the polyester chips, a commonly used drying treatment for polyester chips can be used. As a continuous drying method, a hopper-type aeration dryer in which polyester chips are supplied from the upper part and a dry gas is aerated from the lower part is usually used. As a method for reducing the amount of dry gas and efficiently drying, a rotating disk type continuous dryer is selected, and while supplying a small amount of dry gas, heating steam, heating medium, etc. are supplied to the rotating disk and the outer jacket. The formed granular polyester chips can be dried indirectly.

A double-cone type rotary dryer is used as a dryer for batch-type drying, and it can be dried under vacuum or under vacuum while a small amount of dry gas is passed through. Alternatively, it may be dried under atmospheric pressure while aerating a dry gas. Although atmospheric air may be used as the dry gas, dry nitrogen and dehumidified air are preferable from the viewpoint of preventing a decrease in molecular weight due to hydrolysis or thermal oxidative decomposition of the polyester.

[0071]

EXAMPLES The present invention will now be described in 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 (IV) of polyester 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 Carbon tetrachloride / n-heptane mixed solvent 25 with a density gradient tube
It was measured at ° C.

(3) Content of cyclic trimer of polyester A sample is dissolved in a hexafluoroisopropanol / chloroform mixture, and chloroform is further added to dilute it. Methanol is added to this to precipitate a polymer, which is then filtered. The filtrate was evaporated to dryness, adjusted to a constant volume with dimethylformamide, and the cyclic trimer composed of ethylene terephthalate units was quantified by liquid chromatography.

(4) Determination of Fine Content 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) Approximately 10 g of water content attached to the chip was placed in a glass container, and about 1 g was put in a vacuum dryer.
Heat treatment is performed at 05 ° C. for 7 hours, and the weight reduction amount before and after the treatment is obtained and calculated.

(6) Haze (% haze) A sample was cut from the body (wall thickness of about 4 mm) of the 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 the treated water in the treatment tank.
100% after filtering with 1G1 glass filter manufactured by Iwaki Glass Co., Ltd.
After drying at ℃ for 2 hours and cooling at room temperature, the weight is measured and calculated.

(8) Particle Size and Number of Particles in Water Light-shielding Particle Measuring Device HIAC / ROYCO. Counter 4
The measurement was performed using a 100 type and a sampler 3000 type.

(Example 1) A device for removing particles in water (9), which is a GAF filter bag PE-1P2S (polyester felt, filtration accuracy: 1 μm) manufactured by ISP, is installed, and ion exchange is performed through this device (9). Water inlet (8), raw material chip supply port (1) at the upper part of the treatment tank, overflow outlet (2) located at the upper limit level of the treated water in the treatment tank, discharge of a mixture of polyester chips and treated water at the lower part of the treatment tank The treated water discharged from the outlet (3) and the overflow outlet and the treated water that has passed through the polyester chip drainer (continuous centrifuge) (4) discharged from the outlet at the bottom of the treatment tank are Filter material made of paper 30μm
(6) for sending it again to the water treatment tank via the filtration device (5) which is a belt type filter of No. 6, an inlet (7) for these fine-removed treated water, and acetaldehyde and glyco-in the fine-removed treated water. A polyethylene terephthalate (hereinafter abbreviated as PET) chip was treated with water by using a tower-type treatment tank having an internal capacity of 320 liters equipped with an adsorption tower (10) for adsorbing the like. The content of particles having a particle size of 1 to 25 μm in the water collected at the ion-exchanged water inlet (8) of the water treatment device is about 2500 (pieces / 1
Was 0 cc).

The polyester chips obtained after the solid phase polymerization were passed through a sieving process to obtain a fine content of about 10 ppm, an intrinsic viscosity of 0.74 deciliter / gram, a density of 1.399 g / cm3, and a cyclic 3 amount. PET chips having a body content of 0.30% by weight were continuously introduced into a water treatment tank whose treated water temperature was controlled at 95 ° C. at a rate of 50 kg / hour from the upper part (1) of the treatment tank. After the lapse of 5 hours from the start of the feeding, the PET chips are fed from the lower portion (3) of the water treatment tank (50 kg / kg) while continuing to feed the PET chips into the water treatment tank.
Withdrawal of the treated water together with the treated water is started at the speed of time, and the treated water that has passed through the continuous centrifugal dehydrator (4) that uses wind power is returned to the water treatment tank through the filtration device (5) and reused repeatedly. Started. Water-treated PET chips after 100 hours of continuous operation were separated by a continuous centrifugal dehydrator (4) to reduce the amount of water adhering to the chips to about 0.8% by weight, and then a hopper-type continuous About 1 by the dryer
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 PET chips are dried under reduced pressure and manufactured by Meiki Seisakusho M-100.
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 device for crystallizing the plug part using a near infrared heater to crystallize the plug part. Next, this preform was biaxially stretch-blown at a ratio of about 2.5 times in the longitudinal direction and about 5 times in the circumferential direction with 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 is 0.8%, which shows excellent transparency.

(Example 2) P used in Example 1
The ET was treated in the same manner as in Example 1 under the same conditions, except that the water content adhering to the chips was changed to about 2.3% by weight after changing the dehydration conditions continuously. The haze of the container obtained by the same method and under the same conditions as in Example was 1.
0% shows excellent transparency.

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

(Comparative Example 1) PET chips solid-phase polymerized in the same manner as in Example 1 were treated with water under the same method and conditions as in Example 1. The PET chip after the water treatment was treated with the same continuous centrifuge as in Example 1, and the water content attached to the chip was about 2
After adjusting to 0% by weight, it was dried at about 130 ° C. by a hopper-type continuous dryer. The haze of the container obtained under the same method and under the same conditions as in Example 1 was 8.7%, which was poor.

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, and the amount of water adhering to the chips was adjusted to about 13% by weight, and then the batch type double-cone rotary dryer was operated at about 130 ° C. Dried. The haze of the container obtained under the same method and under the same conditions as in Example 1 was 17.3%, which was extremely poor.

[0086]

INDUSTRIAL APPLICABILITY The present invention is 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, and the polyester chips are discharged together with the treated water from the treatment tank, and the polyester is then discharged. 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 it to the drying step, the transparency of the bottle and the crystallization control property of the mouth part are good, and A polyester that does not easily generate mold stains can be obtained. When the amount of attached water is large, the crystallization rate due to the impact on the chip surface in the chip transportation step and 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 can be improved by reducing the amount of attached water to 10% by weight or less.

[Brief description of drawings]

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

[Explanation of symbols]

1 Raw material chip supply port 2 Overflow outlet 3 Polyester chips and treated water outlet 4 Continuous centrifugal dehydrator 5 Fine removal filtration equipment 6 piping 7 Treated water inlet 8 Ion exchange water inlet 9 Particle remover 10 adsorption tower

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-12698 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29B 9/06 C08G 63/00-63 / 91

Claims (10)

(57) [Claims] The method according to claim 1 polyester chip processing layer after water treatment and separation treatment of the polyester chips and treatment water, and
Then , in the method for producing polyester, in which the polyester chips are dried, the polyester chips are treated with water.
As water to be used, 10
Water containing ~ 50000 pieces / 10 cc of water is introduced into the treatment tank.
A method for producing polyester, which comprises performing treatment and reducing the amount of water adhering to the polyester chips sent from the water treatment step to the drying step to 10% by weight or less and sending the water to the 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 repeatedly used. 3. The method for producing a 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 withdrawn. 5. The method for producing polyester according to claim 1, wherein the treatment layer is filled with the whole amount of the polyester chips and the whole amount of the polyester chips is extracted after the water treatment is completed. 6. The method for producing a polyester according to claim 2, wherein discharge of the treated water from the treatment tank and return of the discharged treated water to the treatment tank are continuous or intermittent. 7. The treatment water containing fines discharged from the separation treatment device is filtered by a belt filter type filtration device to remove fines, and then returned to the treatment tank for repeated use. Claim 1,
The method for producing a polyester according to any one of 2, 3, 4, 5 and 6. 8. The treatment water containing fines discharged from the separation treatment device is filtered by a bag filter type filtration device to remove fines, and then returned to the treatment tank for repeated use. Claim 1,
The method for producing a polyester according to any one of 2, 3, 4, 5 and 6. 9. The polyester has an intrinsic viscosity of 0.55.
A polyester having a main repeating unit of 1.30 deciliters / gram and composed of ethylene terephthalate.
9. The method for producing a polyester according to 7 or 8. 10. The polyester is a polyester whose main repeating unit is ethylene naphthalate, and is characterized in that:
9. The method for producing a polyester according to 7 or 8.