JP2001247686A - Preparation method of polyester molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a preparation method of a polyester molding capable of economically preparing a polyester molding, reducing an energy cost upon its preparation and obtaining the polyester molding having excellent transparency, and further improving mold stain upon the preparation. SOLUTION: The preparation method of a polyester molding comprises (a) a preparation step of a low polymer esterifying or ester interchanging an aromatic dicarboxylic acid or its functional derivative and glycol or its functional derivative, (b) a polycondensation step polycondensing the low polymer obtained in the step (a), (c) a water treatment step contact treating the polyester obtained in the step (b) with water, and (d) a molding step melt molding the treated polyester in the step (c).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a molded product of polyester used for producing a sheet or film for food packaging, or a container such as a bottle, and more particularly to a method for producing a polycondensed polyester. Producing economically advantageous polyester molded products that have excellent transparency, do not easily generate off-flavors and odors, and do not easily generate mold stains during molding by being subjected to contact treatment with water and then directly melt-molded. How to do it.

[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 like, and these oligomers adhere to the inner surface of the mold, the exhaust port of the mold gas, and the exhaust pipe. Dirt was easy to occur.

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, containers made of polyester, mainly 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 reducing the acetaldehyde content of the beverage container alone does not improve the flavor or odor of these contents. I understand.

In addition, for the 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.

In Japanese Patent Application Laid-Open No. H8-238643, a polyethylene terephthalate having an intrinsic viscosity of 0.5 to 0.75 dl / g is reduced to 0.75 to 0.95 dl / g in a post-condensation reactor. A method for forming a preform by increasing the acetaldehyde content while increasing the acetaldehyde content is disclosed. This method is more economical than the conventional method in that a molded body is obtained without passing through the steps of solidification and remelting, but the residence time in the post-condensation reactor is increased in order to increase the intrinsic viscosity. Takes 30 to 60 minutes, which is a problem from the viewpoint of productivity of polycondensation, and the content of cyclic trimers and oligomers is as large as about 1.0% by weight or more. Is not improved, which is also a problem from the viewpoint of molding productivity.

As a method for solving such a problem,
JP-A-3-47830 discloses a polyethylene terephthalate.
(Hereinafter abbreviated as PET) has been proposed.

[0012]

Conventionally, polyester chips from the surface of which water has been removed by draining after the above-mentioned water treatment or, if necessary, water has been further removed are subjected to a sieving step in an air atmosphere or an air flow. After the fines are removed by the fine removing device according to (1), the fines are filled in a container such as a flexible container for transportation, temporarily stored, and then transported to a molding process. Generally, the above-mentioned storage container and transport container are provided with an inner lining or an inner bag made of polyethylene film inside the container, so that when the polyester chip is filled or discharged, the polyethylene comes into contact with the polyester chip. However, at this time, a small amount of polyethylene adheres to the surface of the polyester chip and is mixed.
This polyethylene has the effect of accelerating the crystallization of polyester, and causes problems such as deterioration of the transparency of the molded article and fluctuation of the slipperiness of the molded article.

[0013] Further, during such a complicated process, the shape of the polyester chip changed to a flaky or fine powder due to a prolonged contact or collision between the polyester chip and equipment or piping in various processes. Non-defective products (hereinafter abbreviated as fine) are generated in large quantities. Some of these defective products may have a high melting point, which may appear as an unmelted material in the molded product, and may exhibit the effect of promoting crystallization of polyester even if the melting point is normal. Exists. Also, the effect of crystallization promotion may be imparted to the chip surface, probably because the microstructure of the chip surface changes due to collision with a pipe or the like. The crystallization speed of the molded article obtained through such a complicated process is increased, and the fluctuation is also increased.For example, the transparency of the hollow molded article is deteriorated, and the slipperiness of the film is changed. It becomes a problem. In addition, when a storage container or the like is filled in an air atmosphere and stored for a period of one month or more, the flavor and odor of the contents of the molded body may deteriorate depending on the environment.

An object of the present invention is to solve the above-mentioned problems of the prior art. The molded article is excellent in transparency, the molded article is unlikely to have an unpleasant taste and smell, and the mold is not easily stained during molding. It is an object of the present invention to provide a method for producing a polyester which is economically advantageous and has little adverse effect on the environment.

[0015]

Means for Solving the Problems In order to achieve the above object, a method for producing a polyester molded article according to the present invention comprises esterifying or reacting an aromatic dicarboxylic acid or a functional derivative thereof with glycol or a functional derivative thereof. A low polymer production step (a) for transesterification, a polycondensation step (b) for polycondensation of the low polymer obtained in the low polymer production step, and contact treatment of the polyester obtained in the polycondensation step with water. And a molding step (d) of melt-molding the polyester treated in the water treatment step.

In this case, the polycondensation step (b)
May include a melt polycondensation step or a melt polycondensation step and a solid phase polycondensation step.

In this case, a drying step can be added after the water treatment step. In this case,
A deaeration step is added to the molding step (d), and
And can be degassed under an inert gas flow.

In this case, the difference between the intrinsic viscosity after the water treatment step and the intrinsic viscosity of the molded article can satisfy the following expression. Intrinsic viscosity after the water treatment step (c) -Intrinsic viscosity of the molded body = -0.10 to 0.15 dl / g

In this case, the polyester molded article may have an acetaldehyde content of 30 ppm or less. In this case, the intrinsic viscosity of the polyester from the polycondensation step (b) is 0.55 to 0.90 dl /
g.

In this case, the scrap or the used molded product generated in the molding step (d) is removed from the molding step (d).
Can be added.

In this case, the polyester is polyethylene terephthalate or polyethylene naphthalate.
Can be. In this case, the polyester molded article may be a sheet, a film, a parison, and a tube.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The method for producing a polyester molded article of the present invention comprises a low polymer production step (a) of esterifying or transesterifying an aromatic dicarboxylic acid or a functional derivative thereof with a glycol or a functional derivative thereof, The polycondensation step (b) of polycondensing the low polymer obtained in the production step, the water treatment step (c) of contacting the polyester obtained in the polycondensation step with water, and the water treatment step And a molding step (d) of melt-molding the polyester.

The polyester used in the present invention is a polyester mainly obtained from an aromatic dicarboxylic acid component and a glycol component, preferably a polyester containing an aromatic dicarboxylic acid unit in an amount of at least 85 mol% of the acid component. More preferably, it is a polyester containing an aromatic dicarboxylic acid unit in an amount of 90 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,
Examples thereof include aliphatic glycols such as trimethylene glycol and tetramethylene glycol, and alicyclic glycols such as cyclohexanedimethanol.

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

The glycol component used by copolymerization in the polyester includes aliphatic glycols such as ethylene glycol, trimethylene glycol, tetramethylene glycol, diethylene glycol and neopentyl glycol, bisphenol A and bisphenol A. And alicyclic glycols such as cyclohexanedimethanol, and polyalkylene glycols such as polyethylene glycol and polybutylene glycol.

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

One preferred example of the polyester used in the present invention is a polyester whose main repeating unit is composed of ethylene terephthalate units, more preferably a linear polyester containing at least 85 mol% of ethylene terephthalate units, and particularly preferably. A linear polyester containing at least 90 mol% of ethylene terephthalate units, that is, 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-
Polyesters composed of 2,6-naphthalate units, more preferably linear polyesters containing at least 85 mol% of ethylene-2,6-naphthalate units, particularly preferred are ethylene-2,6-naphthalate units Is a linear polyester containing at least 90 mol% of
It is a polyethylene naphthalate homopolymer or a polyethylene naphthalate copolymer containing ethylene terephthalate units (hereinafter abbreviated as PEN).

Other preferred examples of the polyester used in the present invention include linear polyesters containing 85 mol% or more of propylene terephthalate units, 1,4-
It is a linear polyester containing at least 85 mol% of cyclohexane dimethylene terephthalate units or a linear polyester containing at least 85 mol% of butylene terephthalate units. Examples of a method for producing the polyester used in the present invention include a batch method and a continuous method. Hereinafter, an example of a preferable production method in a continuous method will be described using polyethylene terephthalate as an example.

First, the case where a low polymer is produced by an esterification reaction will be described. A slurry containing ethylene glycol in an amount of 1.02 to 1.5, preferably 1.03 to 1.4 mol per 1 mol of terephthalic acid or its ester derivative is prepared, and this is continuously used in the esterification reaction step. Supply.

The esterification reaction is carried out using a multistage apparatus in which at least two esterification reactors are connected in series, and under conditions where ethylene glycol is refluxed, water or alcohol produced by the reaction is removed outside the system by a rectification column. Perform while removing. The temperature of the first stage esterification reaction is 240 ~
270 ° C, preferably 245-265 ° C, pressure 0.2
３3 kg / cm ² G, preferably 0.5-2 kg / cm ²
G. The temperature of the final esterification reaction is usually 25.
The temperature is 0 to 280 ° C, preferably 255 to 275 ° C, and the pressure is usually 0 to 1.5 kg / cm ² G, preferably 0 to 1.3.
kg / cm ² G. When the reaction is carried out in three or more stages, the reaction conditions for the intermediate stage esterification reaction are the first
This is a condition between the reaction condition of the stage and the reaction condition of the final stage. It is preferable that the increase in the conversion of these esterification reactions is smoothly distributed at each stage. Finally, the esterification reaction rate is 90% or more, preferably 93%.
It is desirable to reach the above. A low-order condensate having a molecular weight of about 500 to 5,000 is obtained by these esterification reactions. When terephthalic acid is used as a raw material, the esterification reaction can be carried out without a catalyst by the catalytic action of terephthalic acid as an acid, but may be carried out in the presence of a polycondensation catalyst.

Tertiary amines such as triethylamine, tri-n-butylamine and benzyldimethylamine;
When a small amount of a quaternary ammonium hydroxide such as tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide and trimethylbenzylammonium hydroxide and a basic compound such as lithium carbonate, sodium carbonate, potassium carbonate and sodium acetate are added, The ratio of the dioxyethylene terephthalate component unit in the main chain of polyethylene terephthalate can be kept at a relatively low level (5 mol% or less based on the total diol component), which is preferable.

Next, when a low polymer is produced by a transesterification reaction, 1.1 to 1.6 mol, preferably 1.2 to 1.5 mol of ethylene glycol is added to 1 mol of dimethyl terephthalate. The contained solution is prepared and fed continuously to the transesterification step.

In the transesterification reaction, methanol produced by the reaction is removed outside the system by a rectification column under the condition that ethylene glycol is distilled back using a device in which one or two transesterification reactors are connected in series. It is implemented while doing. The temperature of the first-stage transesterification reaction is 180 to 250 ° C, preferably 200 to 240 ° C. The temperature of the final transesterification reaction is usually 230 to 270 ° C., preferably 24 to 270 ° C.
0 to 265 ° C., and as a transesterification catalyst, Zn,
Fatty acid salts such as Cd, Mg, Mn, Co, Ca, and Ba;
Carbonate, Pb, Zn, Sb, Ge oxide or the like is used. By these transesterification reactions, the molecular weight is about 200 to 500.
A low degree of condensate is obtained.

Next, the obtained low-order condensate is supplied to a multi-stage liquid phase condensation polymerization step. The polycondensation reaction conditions are as follows: the reaction temperature of the first stage polycondensation is 250 to 290 ° C, preferably 260 to 280 ° C, and the pressure is 500 to 20 Torr.
r, preferably 200 to 30 Torr, and the temperature of the final polycondensation reaction is 265 to 300 ° C, preferably 275
To 295 ° C., and the pressure is 10 to 0.1 Torr, preferably 5 to 0.5 Torr. When the reaction is carried out in three or more stages, the reaction conditions for the polycondensation reaction in the intermediate stage are those between the above-mentioned first-stage reaction conditions and the last-stage reaction conditions. Preferably, the degree of increase in intrinsic viscosity (IV) achieved in each of these polycondensation reaction steps is distributed smoothly. The polycondensation reaction uses a polycondensation catalyst. G
A compound of e, Sb, Ti, or Al is used,
In particular, a Ge compound or a Ti compound, or a Ge compound
It is also convenient to use a compound or a mixture thereof with an Al compound. These compounds are added to the reaction system as a powder, an aqueous solution, an ethylene glycol solution, a slurry of ethylene glycol, and the like.

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 Al compound, aluminum formate, aluminum acetate, aluminum propionate,
Carboxylates such as aluminum oxalate, oxides, inorganic salts such as aluminum hydroxide, aluminum chloride, aluminum hydroxide chloride, and aluminum carbonate; aluminum alkoxides such as aluminum methoxide and aluminum ethoxide; and aluminum acetylacetonate. To
Examples thereof include aluminum chelate compounds with aluminum acetyl acetate and the like, organoaluminum compounds such as trimethylaluminum and triethylaluminum, and partially hydrolyzed products thereof. Of these, aluminum acetate, aluminum chloride, aluminum hydroxide, aluminum hydroxide chloride, and aluminum acetylacetonate are particularly preferred. The Al compound is added so that the residual amount of Al in the produced polymer is in the range of 5 to 200 ppm.

In the case of an Al compound, an alkali metal compound or an alkaline earth metal compound may be used in combination. The alkali metal compound or alkaline earth metal compound includes carboxylate such as acetate of these elements, alkoxide and the like, and is added to the reaction system as powder, aqueous solution, ethylene glycol solution and the like. The alkali metal compound or alkaline earth metal compound is added so that the residual amount of these elements in the produced polymer is in the range of 1 to 50 ppm.

Various P compounds can be used as stabilizers. Examples of the P compound used in the present invention include phosphoric acid, phosphorous acid, and derivatives thereof. Specific examples include phosphoric acid, trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, monomethyl phosphate, dimethyl phosphate, monobutyl phosphate, dibutyl phosphate, and dibutyl phosphate. Phosphoric acid, trimethyl phosphite, triethyl phosphite, tributyl phosphite, etc., which may be used alone or in combination of two or more.
The P compound is 1 to 10 as a residual amount of P in the produced polymer.
It can be added at any stage of the polyester production reaction step so as to be in the range of 00 ppm.

When a low acetaldehyde content or a low cyclic trimer content is required, such as in a low-flavor beverage heat-resistant container or a film for the inner surface of a metal can for beverage, etc. The obtained melt-polycondensed polyester is subjected to solid-state polymerization. The polyester is subjected to solid-state polymerization by a conventionally known method. First, the polyester to be subjected to solid-state polymerization is treated under an inert gas or under reduced pressure or under an atmosphere of steam or an inert gas containing steam.
It is pre-crystallized by heating at a temperature of 00 to 210 ° C. for 1 to 5 hours. Then, under an inert gas atmosphere or reduced pressure, 19
The solid state polymerization is carried out at a temperature of 0 to 230 ° C. for 1 to 30 hours.

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 in the range of 1.5 to 4 mm in height, width and height. For example, in the case of a cylinder type, the length is 1.
It is practical that the diameter is about 5 to 4 mm and the diameter is about 1.5 to 4 mm. Further, the weight of the chip is practically in the range of 15 to 30 mg / piece.

The intrinsic viscosity after the above-mentioned polycondensation reaction can be set to a desired intrinsic viscosity depending on the application.
It is preferably 0.90 dl / g. It is more preferably 0.60 to 0.85 dl / g, and still more preferably 0.65 to 0.80 dl / g.

The content 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. More preferably, it is 1.5 to 4.0 mol%. When the content of diethylene glycol exceeds 5.0 mol%, thermal stability deteriorates, the molecular weight decreases during molding, and the acetaldehyde content and the formaldehyde content increase undesirably. When the content of diethylene glycol is less than 1.0 mol%, the transparency of the obtained molded article is deteriorated. The acid value of the polyester used in the present invention is preferably in the range of 5 to 80 equivalents / ton. When the acid value is lower than 5 equivalents / ton, the amount of aldehyde generated by decomposition increases, and the acetaldehyde content of the polyester molded article does not decrease to 30 ppm or less.
On the other hand, if the acid value exceeds 80 equivalents / ton, there is a problem that the reaction rate of the polycondensation is slowed and the residence in the polycondensation reactor until the desired intrinsic viscosity is reached is prolonged. Occurs, or impurities due to polyester decomposition increase.

Although the acetaldehyde content of the polyester obtained by melt polycondensation is as high as about 50 ppm or more, the acetaldehyde content of the polyester obtained by solid-state polymerization is 10 ppm or less, preferably 8 ppm or less, more preferably 5 ppm or less. Formaldehyde content is 7p
pm or less, preferably 6 ppm or less, more preferably 4 ppm or less.

The content of the cyclic trimer of the polyester thus obtained by solid-state polymerization 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 used in the present invention, heat treatment is performed in a heating mold, but the content of the cyclic trimer is 0.5%.
When the content is 0% 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.

Next, polyester is used in order to prevent mold contamination and the like caused by oligomers such as cyclic trimers adhering to the inner surface of the mold, the exhaust port of the mold gas, the exhaust pipe, etc. during molding. After the above-mentioned melt polycondensation or solid phase polymerization, a contact treatment with water is performed.

As a method of the contact treatment with water, a method of immersion 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.

When the polyester chips are to be continuously treated with water, the polyester chips are continuously treated in a tower-type treatment tank, or the polyester chips are intermittently received from above, and water is continuously supplied in parallel or countercurrently to treat the water. Can be done. The treated polyester chips are continuously or intermittently extracted from the lower part of the treatment layer. The water-treated polyester chips are drained by a draining device such as a vibrating sieve or a Simon Carter and separated from the treated water.

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

In this case, the entire amount of the polyester chips is charged and filled in the treatment tank, and the treated water is filled with the treated water, and the treated water is circulated continuously or intermittently as needed (generally referred to as continuous). In addition, part of the treated water is discharged continuously or intermittently, and new treated water is additionally supplied. After the water treatment, the entire amount of the polyester chips is extracted from the treatment layer. Also in this case, the water-treated polyester chips
Drain with a draining device such as a vibrating sieve machine or Simon Carter,
Separate from treated water.

Regardless of whether the method of water treatment 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 new water is required. In addition to the above, there is a concern that the loss of calorific value of the discharged treated water and the increase in the amount of wastewater will affect the environment.

In order to solve such problems, the treated water discharged from the overflow port of the water treatment tank and the treated water discharged together with the polyester chips from the treatment tank and then separated from the chips are treated. A method is employed in which substantially the entire amount, or about 50% thereof, is reused for water treatment.

Therefore, in order to carry out the water treatment without any problems, it is necessary to compensate for the reduced water amount due to the above-mentioned causes by supplying fresh water from outside the system. The amount of replenishing water from outside the system is about 5 times the amount of circulating water.
0% or less.

As the wastewater from the water treatment tank, there are two kinds of treated water discharged from the water treatment tank together with the polyester chips and treated water discharged from the overflow port of the water treatment tank. By returning substantially all of the treated water discharged from the water treatment tank to the water treatment tank for reuse, or by reusing it for the next batch of water treatment, the amount of newly supplied water required for water treatment can be reduced. If the wastewater returned to the water treatment tank maintains a certain temperature, the heating amount of the treated water can be reduced. The discharged treated water can be returned to the water treatment layer and reused. here,
The treated water discharged from the treatment tank in this way and returned to the treatment tank and reused is referred to as recycled water.

In the treated water discharged from the treatment tank during the water treatment, fine water already attached to the polyester chip at the stage of receiving the polyester chip into the treatment tank,
It contains polyester fines generated by friction between polyester chips or between the processing tank walls during water treatment. 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. In addition, fines contained in the treated water adhere to the polyester chip again, and after this,
Since fines adhere to the polyester chip by an electrostatic effect at the stage of drying and removing the water, the fines content of the polyester becomes very large.

Although fines generated in the polyester production process have a crystallization promoting effect, the crystallization promoting effect of fines generated in the above-described process from the polyester chips subjected to the water treatment process was found to be very high. .
The crystallinity of the polyester is promoted by such fineness, the transparency of the obtained bottle is deteriorated, and the degree of crystallinity at the time of crystallization of the bottle plug portion becomes excessive, and the size of the plug portion becomes standard. It will not be able to enter, which will lead to poor capping of the plug and therefore leakage of contents.

Therefore, 100,000 particles / 10 ml each having a particle size of 1 to 40 μm existing in the recycled water
In the following, it is desirable to return to the treatment tank and maintain repeated use, preferably at 80,000 cells / 10 ml or less, more preferably at 50,000 cells / 10 ml or less, for repeated use.

In order to suppress an increase in the amount of particles in the recycle water, 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, a screen filter system, and a centrifugal filtration system may be used. Of these, a belt filter system, a centrifugal filtration system, a bag filter system, and a screen filter system are suitable for continuous operation. In the case of a filter device of a belt filter type, examples of the filter medium include paper, metal, cloth, and the like. In order to efficiently remove fines and flow treated water, the mesh size of the filter is 5 to 100 μm, preferably 5 to 70 μm, and more preferably 5 to 40 μm.

The polyester chip is made of an aldehyde compound such as acetaldehyde or formaldehyde produced during the production of the polyester, a glycol as a raw material, a monomer or aromatic made up of an aromatic dicarboxylic acid and a glycol as a reaction product. It contains low molecular weight compounds such as dimers composed of dicarboxylic acids and glycols, and these aldehyde compounds, glycols, monomers and dimers composed of aromatic dicarboxylic acids and glycols during water treatment. Elutes in the treated water.

From the economic and environmental viewpoints, in the case of batch type water treatment, treated water is repeatedly used, and in the case of continuous type water treatment, treated water discharged from the water treatment tank is returned to the treatment tank. In each case, the content of acetaldehyde, the content of glycol, the content of monomer composed of aromatic dicarboxylic acid and glycol and the content of dimer in the treatment tank increase with time. I will do it. When the content of these compounds increases, the content of the chips after water treatment and drying increases, and the flavor and aroma of the contents in a hollow molded container or the like using such polyester chips become extremely poor. In addition, the treatment tanks and pipes of the water treatment apparatus become more contaminated.

In the case of the continuous system, the content of the glycol derived from the polyester and the content of the monomer composed of the aromatic dicarboxylic acid and the glycol in the recycled water are 100 ppm or less, preferably 50 ppm or less, respectively. The above-mentioned problems are solved by maintaining the content of acetaldehyde in the recycled water at 10 ppm or less, preferably 5 ppm or less, more preferably 1 ppm or less. In the case of the batch method, the content of the glycol derived from the polyester and the content of the monomer composed of the aromatic dicarboxylic acid and the glycol in the treatment water in the treatment tank at the end of the water treatment are each 100 ppm or less. , Preferably 50 ppm
The above problems are solved by maintaining the content of acetaldehyde in the recycled water at 10 ppm or less, preferably 5 ppm or less, more preferably 1 ppm or less.

When the polyester is polyethylene terephthalate, the glycol is ethylene glycol, and the monomer composed of an aromatic dicarboxylic acid and glycol is monohydroxyethyl terephthalate. Tartrate and bishydroxyethyl terephthalate.

The polyester is polyethylene-2,6
In the case of -naphthalate, the glycol is ethylene glycol, and the monomer composed of aromatic dicarboxylic acid and glycol is 2,6-monohydroxyethylnaphthalate and 2 And 6-bishydroxyethylnaphthalate.

The method for reducing the content of glycol and the like in the recycled water to 100 ppm or less and the acetolide content to 10 ppm or less will be exemplified below, but the present invention is not limited to these methods.

Further, when the following method is used, trace odor components such as formaldehyde, acetic acid, and formic acid as well as glycol and acetaldehyde in the recycled water can be removed, and these contents in the treated water can be reduced. It can be below a certain value.

The treated water is discharged from the water treatment tank in order to suppress an increase in the content of the monomer or acetaldehyde composed of glycol and aromatic dicarboxylic acid and the glycol in the recycled water supplied to the water treatment tank. Then, a device for removing glycols and the like is installed at at least one place in the process until the circulating water is returned to the water treatment tank again.

As a method for removing glycol and the like, known methods such as a distillation treatment with a distillation apparatus, an activated carbon adsorption treatment, a bubbling treatment of an inert gas into water, and a heating deaeration treatment can be mentioned. Another example is a method of adding new ion-exchanged water or the like to the recycled water.

Further, a device for automatically measuring the number of particles in the recycled water and the concentration of the low molecular weight compound derived from the polyester is installed in a feed pipe of the recycled water or the like, and these concentrations are automatically measured. The filter of the filtration device can be replaced or the adsorbent of the adsorption device can be replaced depending on the concentration value.

Next, a description will be given of water introduced from outside the system mainly to make up for the above-mentioned shortage of recycled water. In the case of industrially treating polyester chips with water, natural water (industrial water) is used due to the large amount of water used for the treatment.
And wastewater are often reused. 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 for industrial purposes includes inorganic particles such as silicates, aluminosilicates and other clay minerals, bacteria, bacteria, etc., which originate in spoiled plants and animals. And many organic particles and organic compounds having the same. These inorganic particles are
It is composed of a metal-containing substance such as sodium, magnesium, calcium, and silicon.

Regardless of whether the water treatment method is a continuous method or a batch method, the number of particles having a particle size of 1 to 25 μm existing in water introduced from outside the system is determined by X. When the content of sodium is N, the content of magnesium is M, the content of calcium C is silicon, and the content of silicon is S, at least one of the following ranges (1) to (5) is satisfied. It is desirable to carry out water treatment using water. 1 ≦ X ≦ 50000 (pieces / 10 ml) (1) 0.001 ≦ N ≦ 1.0 (ppm) (2) 0.001 ≦ M ≦ 0.5 (ppm) (3) 0.001 ≦ C ≦ 0 0.5 (ppm) (4) 0.01 ≤ S ≤ 2.0 (ppm) (5)

By setting any of the number of particles in the water to be introduced into the water treatment tank and the content of sodium, magnesium, calcium and silicon within the above ranges, metal-containing substances such as oxides and hydroxides called scales can be obtained. May float in the treated water, settle, and adhere to the walls of processing tanks and pipes, which adhere to and penetrate the polyester chips, which promotes crystallization during molding, resulting in poorly transparent bottles. Can be prevented.

The particle size used in the water treatment is 1 to 25 μm.
An example of a method for obtaining water containing 1 to 50,000 particles / 10 ml of the above particles will be described. As a method for reducing the number of particles in water to 50,000 particles / 10 ml or less, an apparatus for removing particles is installed at at least one or more places in a process until natural water such as industrial water is supplied to the treatment tank. Preferably, from the natural water sampling port to the processing tank including the above-mentioned processing tank, piping returning the water drained from the processing tank to the processing tank again, a fine removal device, and other auxiliary equipment necessary for water treatment. A device for removing particles is installed between them, and the particle size of
The content of particles of ２５25 μm is 1 to 50,000 particles / 10 m
It is preferably 1. Examples of the device for removing particles 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, a screen filter system, and a centrifugal filtration system may be used. Of these, a belt filter system, a centrifugal filtration system, a bag filter system, and a screen filter system are suitable for continuous operation. In the case of a filter device of a belt filter type, examples of the filter medium include paper, metal, cloth, and the like. In addition, in order to efficiently remove particles and flow treated water, the size of the filter is 5 to 5.
100 μm, preferably 10 to 70 μm, more preferably 15 to 40 μm.

Further, in order to reduce sodium, magnesium, calcium and silicon in water from outside the system, sodium, magnesium, calcium and silicon are removed in at least one place in a process until industrial water is sent to the treatment tank. Install the equipment. In addition, a filter is provided to remove clay minerals such as silicon dioxide and aluminosilicate which have become particulate. Examples of an apparatus for removing sodium, magnesium, calcium, and silicon include an ion exchange apparatus and an ultrafiltration apparatus.

The water introduced from outside the system may be introduced directly into the water treatment tank, or may be introduced into the water treatment tank after being mixed with the recycled water in the recycled water storage tank or the recycled water feed pipe. Is also good.

After the water treatment, the polyester chips drained by the draining device are transported to a storage tank under an atmosphere of dry air or an inert gas or under the air stream.
Stored temporarily under a stream of dry air or dry inert gas.

By transporting the water-treated polyester to the molding step directly connected to the water treatment apparatus, the contamination of polyethylene or the like from the transport container or the like is eliminated, and the chance of dust and the like being exposed to outside air is reduced. For this reason, it is possible to supply a polyester which gives a molded article having excellent transparency and less occurrence of mold contamination to the molding step. After water treatment with treated water at a temperature of about 80 ° C. or more, the drained polyester chips are placed at about 50 ° C. immediately before the molding machine.
The above temperature is maintained, and if a drying step is added after the water treatment step, since the temperature is further maintained,
It is not only more energy-efficient than the case where it is filled in a transport container and molded at another factory, but also a drying step before molding can be omitted. Also, the cost of transporting the polyester to another factory can be reduced.

The molding process directly connected to the water treatment device is a molding process incorporated in a series of lines, and the polyester resin that has passed through the water treatment device is converted into a paper bag, a flexible container bag, A container that is stored in a transport container such as a tank and is not sent to a different location by means of transportation such as a railway, truck, or ship. Therefore, in a series of lines, a drying step, a degassing step, a temporary storage step using a reserve tank, a fine removing step, and the like can be incorporated between the water treatment apparatus and the forming step, as described later. it can.

After the water treatment, when not passing through the drying step,
A degassing step can be added to reduce the water content of the polyester and reduce the acetaldehyde content or suppress production. As the deaeration step, any apparatus can be used as long as it can rapidly update the surface of the molten polyester, but an injection molding machine with a vent, an extruder with a vent, a rotary disk processor, a deaeration tank, etc. are used. it can.

The vented extruder used in the present invention may be either a single screw extruder or a twin screw extruder.
A twin-screw extruder is preferred in terms of acetaldehyde reduction efficiency or production suppression. The screw of the twin-screw extruder may be any of an engagement type, a non-engagement type, and an incomplete engagement type.

The resin temperature in the vented extruder was 250
C. to 310 C. are preferred. The degree of vacuum of the vented extruder is 50 torr or less, preferably 20 torr or less,
More preferably, the object can be achieved at 10 torr or less. The residence time is preferably 10 minutes or less, more preferably 5 minutes or less, further preferably 4 minutes or less, particularly preferably 3 minutes or less, and most preferably 2 minutes or less.

The deaeration treatment should be performed in as short a time as possible in order to prevent the polyester molded product from being colored. For this purpose, the deaeration treatment should be performed at the above-mentioned temperature, time and reduced pressure. is there. If the pressure at the time of decompression exceeds the above range,
It is difficult to effectively remove or suppress acetaldehyde, and the polyester molded article tends to be colored. Further, when the resin temperature during the treatment exceeds the above range, it is also difficult to effectively remove or suppress acetaldehyde, and the polyester molded article tends to be colored.

In the case of passing through a drying step, the above-described vented injection molding machine, vented extruder, ventless injection molding machine or extruder can be used.

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 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 drying gas, atmospheric air may be used, but a dehumidifying inert gas such as nitrogen or dehumidified air is preferred from the viewpoint of preventing a reduction in molecular weight due to hydrolysis or thermal oxidative decomposition of the polyester.

The resin temperature in the extruder is from 250 ° C. to 310
C is preferred. Depressurization degree of extruder with vent is 50 to
The object can be achieved at rr or less, preferably at 20 torr or less, more preferably at 10 torr or less. The residence time is preferably 10 minutes or less, more preferably 5 minutes or less, further preferably 4 minutes or less, particularly preferably 3 minutes or less, and most preferably 2 minutes or less.

According to the present invention, after a polyester formed by polycondensation is treated with water, a melt obtained by melting with a vented molding machine is mixed with acetaldehyde-containing polyester without substantially decreasing or increasing the intrinsic viscosity of the polyester. The amount can be reduced by degassing or the concentration increase of the acetaldehyde content can be suppressed by degassing.

Further, the deaeration treatment can be carried out while passing an inert gas under conditions such that the intrinsic viscosity of the polyester molded article does not substantially increase. As the inert gas that can be used, carbon dioxide gas, nitrogen and the like are preferable, and among them, carbon dioxide gas is most preferable.

In the molding step of the present invention, the difference between the intrinsic viscosity after the water treatment step and the intrinsic viscosity of the molded product is -0.10 to 0.1.
Molding is preferably performed in the range of 15 dl / g, more preferably in the range of -0.08 to 0.13 dl / g, and still more preferably in the range of -0.05 to 0.10 / g. .

If the difference between the intrinsic viscosity after the water treatment step and the intrinsic viscosity of the molded product is lower than -0.10 dl / g, it is not economical, and sometimes the obtained polyester molded product has insufficient mechanical properties. . Further, when the intrinsic viscosity after the water treatment step and the intrinsic viscosity of the molded body exceed 0.15 / g, not only the productivity is deteriorated due to prolonged residence in the vented extruder, but also the obtained molding Adverse effects such as coloration of the body and increased acetaldehyde content occur.

Next, the molten polyester is sent to an extruder or a molding machine, or an extrusion step or a molding machine installed continuously to the deaeration step, and is molded.

When the molded product is a sheet or an unstretched film, the polyester after the water treatment is melted by an extruder equipped with a vent, extruded from a die onto a cooling roll, cooled and wound up. In the case of a stretched film, the unstretched film is further stretched.

When the molded article is a hollow molded article, the polyester is pre-formed by the above-mentioned injection molding machine with vent.
And then stretch blown.

[0096] In the process of molding these polyesters, a plurality of series can be installed directly connected to the water treatment process. The intrinsic viscosity of the thus obtained polyester molded article of the present invention is from 0.55 dl / g to 0.85 dl.
/ G. Preferably 0.58 dl / g to 0.83 d
1 / g, more preferably 0.60 dl / g to 0.80
dl / g. When the intrinsic viscosity is lower than 0.55 dl / g, the mechanical properties of the obtained polyester resin are not sufficient. On the other hand, when the intrinsic viscosity is 0.85 dl / g or more, the residence time in the melt polymerization machine is prolonged, which causes a problem of coloring and further lowers the productivity.

The acetaldehyde content of the polyester molded article of the present invention is 30 ppm or less, preferably 20 ppm.
Below, more preferably 15 ppm or less, and most preferably 12 ppm or less, it can be used for various applications including low flavor beverage containers.

Further, poor quality polyester scrap and trimmed polyester generated in the molding step of the present invention, used hollow molded products recovered from the market, etc. are crushed, dried if necessary, and vented. It can be melted by an extruder, added to the molding process and recovered. The addition amount is preferably up to 30% by weight, and if it exceeds this, the acetaldehyde content of the obtained molded article is 30% by weight.
ppm or more, and the transparency and color of the molded article are deteriorated, which is a problem. In addition, the polyester used in the present invention may contain a coloring agent, an ultraviolet absorber, an antioxidant, an acetaldehyde generation inhibitor, an antistatic agent, a lubricant, a nucleating agent, a release agent, and the like, if necessary, to impair the purpose of the present invention. Can be added in a range that is not

[0099]

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

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

(2) Polyethylene diethylene glyco
The content was determined by decomposing with methanol and quantifying the DEG content by gas chromatography, and expressed as a ratio (mol%) to the total glycol components.

(3) Density: Measured at 30 ° C. with a density gradient tube of calcium nitrate / water mixed solution.

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

(5) Acetaldehyde content of polyester (hereinafter referred to as “AA content”) Sample / distilled water = 1 g / 2 cc placed in a nitrogen-substituted glass ampoule was sealed and extracted at 160 ° C. for 2 hours. After the treatment and cooling, the acetaldehyde in the extract was measured by high-sensitivity gas chromatography, and the concentration was expressed in ppm.

(6) Measurement of Fine Content About 0.5 kg of resin was placed on a sieve (diameter 30 cm) with a wire mesh having a nominal size of 1.7 mm according to JIS-Z-8801, and 0.1% of An aqueous solution of a cationic surfactant (alkyltrimethylammonium chloride) at 2 L /
Approximately 7c of total amplitude width while applying shower flow
m, 60 reciprocations / 1 minute for 1 minute. This operation was repeated, and the resin was sieved in a total of 10 to 30 kg. Fine sieved together with a surfactant aqueous solution 1G1 manufactured by Iwaki Glass Co., Ltd.
The solution was collected by filtration with a glass filter (pores 100 to 120 μm), and washed with ion-exchanged water. This was dried together with the glass filter in a dryer at 100 ° C. for 2 hours, cooled, and weighed. The same operation of washing and drying with ion-exchanged water was repeated again to confirm that the weight became constant, and the weight of the glass filter was subtracted from this weight to obtain a fine weight.
The fine content is the amount of fine / the weight of the total resin sieved.

(7) Haze (% haze) Samples were cut from the molded articles (thickness: 5 mm) of the examples and comparative examples and the body (thickness: about 0.45 mm) of the hollow molded container. Measured with a haze meter manufactured by Co., Ltd.

(8) Fine content in treated water (pp
m) 1000 cc of treated water passed through a JIS standard 20 mesh filter was collected from the treated water outlet of 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.

(9) Measurement of Particle Diameter and Number of Particles in Introduced Water Light-shielded 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 A slurry of high-purity terephthalic acid and ethyl glycol was continuously supplied to a first esterification reactor containing a reactant in advance, and the slurry was stirred for about 2 hours.
The reaction was carried out at 50 ° C. and 0.5 kg / cm ² G for an average residence time of 3 hours. This reaction product was sent to the second esterification reactor, and reacted at a temperature of about 260 ° C. and 0.05 kg / cm 2 G to a predetermined degree of reaction with stirring. Hexagonal germanium dioxide is dissolved in water by heating, and ethylene glycol
After the addition of the ethylene glycol solution, the ethylene glycol solution from which the water was distilled off by heating after heating, and the ethylene glycol solution of phosphoric acid were separately and continuously supplied to the second esterification reactor. This esterification reaction product is continuously supplied to a first polycondensation reactor,
Under stirring at about 265 ° C. and 25 torr for 1 hour, and then in a second polycondensation reactor at about 265 ° C. and 3 torr at 1 torr.
About 275 ° C. for an additional hour and with stirring in the final polycondensation reactor,
The polycondensation was performed at 0.5 to 1 torr for 1 hour. The polycondensation reaction product is formed into chips, and subsequently, at about 155 ° C. in a nitrogen atmosphere.
And further preheated to about 200 ° C. in a nitrogen atmosphere, and then sent to a continuous solid-state polymerization reactor for about 205 ° C. in a nitrogen atmosphere.
Solid-state polymerization was performed at ℃. After the solid phase polymerization, the fine particles were continuously removed in a sieving step and a fine removing step to remove fines, and stored in a storage tank under a nitrogen stream.

The intrinsic viscosity of the obtained PET was 0.74 deciliter / gram, the content of DEG was 2.8 mol%, the content of the cyclic trimer was 0.30 wt%, and the content of AA was 2.7.
ppm and density was 1.421 g / cm3. I
An apparatus for removing particles in water (9), which is a GAF filter bag PE-1P2S (polyester felt, filtration accuracy: 1 μm) manufactured by SP Company, is installed, and an inlet (8) for ion-exchanged water via this apparatus (9); Raw material chip supply port (1) at the upper part of processing tank, overflow discharge port (2) located at the upper limit level of processing water in processing tank, discharge port (3) of mixture of polyester chip and processing water at lower part of processing tank, overflow discharge port Of the treated water discharged from the tank and the treated water passed through a continuous centrifugal separator (4), which is a device for draining polyester chips discharged from the discharge port at the bottom of the treatment tank, is a 30 μm belt made of paper filter material. A pipe (6) to be sent again to the water treatment tank via a filtration device (5), which is a type filter, an inlet (7) for these finely removed treated water, and a finely removed treated water. Capacity 50 equipped with an adsorption tower (10) for adsorbing acetaldehyde and glycol in the water
The PET chips described above were treated with water using a 0-liter tower-type treatment tank shown in FIG.

Inlet for ion-exchanged water in water treatment equipment (8)
The content of particles having a particle size of 1 to 25 μm in water collected in
500 (piece / 10ml) sodium content is 0.03p
pm, magnesium content 0.02 ppm, calcium content 0.02 ppm, silicon content 0.10 pp
m. PET was continuously introduced into the water treatment tank controlled at a treatment water temperature of 95 ° C. from the upper part (1) of the treatment tank at a rate of 50 kg / hour. Five hours after the start of charging, withdrawal of PET from the lower part (3) of the water treatment tank together with the treated water was started at a rate of 50 kg / hour while continuing to charge the PET into the water treatment tank, and the wind was used. The treated water passed through the continuous centrifugal dehydrator (4) was returned to the water treatment tank again via the filter (5), and repeated use was started. The fine content in the treated water discharged from the treatment tank was about 10 ppm.

Water-treated PET after continuous operation for 100 hours
Is sent to a directly connected storage tank, stored under a dehumidified nitrogen stream heated to about 110 ° C., and then supplied to an extruder part of a twin-screw extruder / injection molding machine equipped with a vent.
℃, vent vacuum degree 3 torr, residence time 2 min, and then directly supplied to the injection molding machine part, molding temperature 28
At 0 ° C. and a molding cycle of 50 seconds, a stepped molded plate was molded.
The resulting stepped plates were 2, 3, 4, 5, 6, 7, 8,
A plate of about 3 cm x about 5 cm square with a thickness of 9, 10 and 11 mm is provided in a stepwise manner, and the weight of one piece is about 146
g. The haze of the molded plate having a thickness of 5 mm was 3.8%, which was a problem-free value. The fine content in PET before molding was about 2 ppm. Further, a 2L bottle preform mold was attached to the molding machine, and the extrusion temperature was 280.
℃, vent vacuum degree 3 torr, residence time 1.5 min, and then directly fed to the injection molding machine part, molding temperature 2
The preform was molded at 80 ° C. and a molding cycle of 55 seconds. Then, the plug part of this preform was heated by a home-made plug crystallizer of a near-infrared heater type to crystallize the plug part. Next, this preform is called COPOPLA
LB-01E molding machine manufactured by ST, about 2.5 times the vertical method,
It was biaxially stretched and blown at a magnification of about 5 times in the circumferential direction, and then heat-set for about 10 seconds in a mold set at about 150 ° C. to form a container having a capacity of 2000 cc. Stretching temperature is 100 ° C
Was controlled. The haze of the obtained container is 0.3%
Shows excellent transparency. Further, after continuous stretch blow molding for 3 days, the transparency of the hollow molded article was hardly changed. In the above-described PET manufacturing process, as a means for transporting the PET chip to the next step, a plug transport method in which high-pressure nitrogen was used for transport at a low speed was used.

(Comparative Example 1) Under the same equipment and conditions as in Example 1, a PET chip subjected to melt polycondensation, solid-phase polymerization and water treatment was sent to a storage tank and dehumidified by heating to about 110 ° C. After being stored under a nitrogen stream, it was stored in another storage silo at room temperature. From this silo, a 1 ton capacity flexible container with polyethylene inner bag
Was charged. The intrinsic viscosity of the obtained PET is 0.74 deciliter / gram, the content of DEG is 2.8 mol%, the content of cyclic trimer is 0.30 wt%, and the content of AA is 2.7.
ppm and density was 1.420 g / cm ³ . After storing this PET for about one month, it was transported to a molding factory, and the PET was discharged from the flexible container and was sent to the storage tank of the dryer by air. Fine content in PET is about 70pp
m. Using the same molding machine as in Example 1, a stepped molded plate was molded under the same conditions. The haze of the molded plate having a thickness of 5 mm is as high as 28.6%, which is a problem. A preform was molded using the same molding machine as in Example 1 under the same conditions, and a 2 L hollow molded container was stretch blow-molded in the same manner. The haze of the obtained container was very bad at 9.1%. In the manufacturing process of the comparative example, the PE
As a means of transporting T chips, a blower is used to generate wind,
A low-density transport method of transporting by this air flow was adopted.

[0114]

According to the method for producing a polyester molded article of the present invention, a polyester molded article can be economically produced, the energy cost during production can be reduced, and a polyester molded article excellent in transparency can be obtained. It is also possible to improve mold contamination during the production of a molded article.

[Brief description of the drawings]

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

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) // B29K 67:00 B29K 67:00 B29L 22:00 B29L 22:00 C08L 67:02 C08L 67:02 ( 72) Inventor Yoshitaka Eto 20F term of 248 No. 248 Takashiro, Shiga-machi, Shiga-gun, Shiga Pref. 4J029 BA02 BA03 BA05 BD07A CB06A CC06A CG08X KE02 KE12 KH05 KH06 KJ02

Claims (10)

[Claims] 1. A low-polymer production step (a) in which an aromatic dicarboxylic acid or a functional derivative thereof is esterified or transesterified with a glycol or a functional derivative thereof, and the low-polymer production step is obtained. A polycondensation step (b) of polycondensing the low polymer, a water treatment step (c) of subjecting the polyester obtained in the polycondensation step to contact treatment with water, and melt molding of the polyester treated in the water treatment step A method for producing a polyester molded article, comprising the step (d). 2. The method for producing a polyester molded article according to claim 1, wherein the polycondensation step (b) includes a melt polycondensation step or a melt polycondensation step and a solid phase polycondensation step. 3. The method according to claim 1, wherein a drying step is added after the water treatment step. 4. A degassing step is added to the molding step (d),
The method for producing a polyester molded article according to any one of claims 1 to 3, wherein the degassing is performed under reduced pressure or / and under an inert gas flow. 5. The polyester molded article according to claim 1, wherein a difference between the intrinsic viscosity after the water treatment step and the intrinsic viscosity of the molded article satisfies the following expression. Production method. Intrinsic viscosity after the water treatment step (c) -Intrinsic viscosity of the molded body = -0.10 to 0.15 dl / g 6. The method for producing a polyester molded article according to claim 1, wherein the acetaldehyde content of the polyester molded article is 30 ppm or less. 7. The polyester molded article has an intrinsic viscosity of 0.1.
The method for producing a polyester molded article according to any one of claims 1 to 6, wherein the rate is 55 to 0.85 dl / g. 8. The method for producing a polyester molded article according to claim 1, wherein the scrap or used molded article generated in the molding step (d) is added to the molding step (d). . 9. The method according to claim 1, wherein the polyester is polyethylene terephthalate or polyethylene naphthalate. 10. The method for producing a polyester molded article according to claim 1, wherein said polyester molded article is a sheet, film, parison, or tube.