JPH04211424A - Polyethylene terephthalate - Google Patents

Abstract

PURPOSE:To obtain the title polymer having specific physical properties, not damaging flavor and fragrance of contents packed into a container in the case of use of the polymer as a material for the container for filling up drink because of a small amount of acetaldehyde increased when it is molded. CONSTITUTION:The objective polymer which is a polyethylene terephthalate having 0.5 or more dl/g intrinsic viscosity and 1.37 or more g/cm<3> density and has W0-W1 of 0-60ppm when acetaldehyde (AA) content of molded article prepared by injection molding the polymer at 290 deg.C is W0ppm and AA content of molded article obtained by injection molding the polymer, which is immersed in hot water at 95 deg.C for 8 hours and dried, as mentioned above, is W1ppm. The polymer is obtained by esterifying a raw material in a slurry, subjecting the esterified substance to liquid-phase polycondensation in the presence of a germanium dioxide compound catalyst and a stabilizer, preliminarily crystallizing the reaction product, subjecting to solid-phase polycondensation and finally bringing the obtained granular polymer into contact with water, steam, etc.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD OF THE INVENTION The present invention relates to polyethylene terephthalate used for bottles, films, sheets, etc., and more particularly to polyethylene terephthalate that causes a small increase in acetaldehyde during molding.

0002

TECHNICAL BACKGROUND OF THE INVENTION Conventionally, various resins have been used as materials for containers for seasonings, oils, beverages, cosmetics, detergents, etc., depending on the type of contents and the purpose of use.

Among these, polyethylene terephthalate has excellent mechanical strength, heat resistance, transparency, and gas barrier properties, and is therefore particularly suitable as a material for containers for filling beverages such as soft drinks and carbonated drinks.

[0004] Such polyethylene terephthalate is supplied to a molding machine such as an injection molding machine to form a preform for a hollow molded object, and this preform is inserted into a mold of a predetermined shape and stretch blow molded to form a hollow molded object. It is molded into a molded container and further heat-treated if necessary.

However, in molded bodies obtained by molding conventional polyethylene terephthalate, the acetaldehyde content increases during molding, and since this acetaldehyde remains in the polyethylene terephthalate molded body, the content filled in the molded body increases. My sense of taste for food sometimes deteriorated significantly.

[0006] The inventors of the present invention have made extensive studies to solve the above-mentioned problems, and have found that if a molded article is manufactured using polyethylene terephthalate that has been subjected to a specific treatment, the content of acetaldehyde will increase during molding. After discovering that it is difficult to do so, we have completed the present invention.

[0007] In addition, JP-A-59-25815 discloses that, prior to solid phase polycondensation of polyethylene terephthalate, polyethylene terephthalate powder and granules are heated with steam at 110°C or higher in order to crystallize the polyethylene terephthalate. A method of processing is disclosed.

[0008] Furthermore, JP-A-59-219328 discloses that the intrinsic viscosity is at least 0.4 dl/g,
A step of conditioning polyester having a density of 1.35 g/cm3 or less and having ethylene terephthalate units as the main repeating unit to a moisture content of at least 0.2% by weight, and pre-crystallizing at a temperature of 140°C or higher. A method for producing a highly polymerized polyester is disclosed, which comprises a step of solid-phase polymerization at a temperature of 180° C. to 240° C. in an inert gas atmosphere or under reduced pressure.

However, with the above method, it has not been possible to reduce the increase in acetaldehyde during molding to a certain amount or less.

0010

OBJECTS OF THE INVENTION The present invention aims to solve the problems associated with the prior art as described above, and aims to provide polyethylene terephthalate in which the amount of acetaldehyde increases little during molding.

[0011]

Summary of the Invention The polyethylene terephthalate according to the present invention is a polyethylene terephthalate having an intrinsic viscosity of 0.50 dl/g or more and a density of 1.37 g/cm3 or more, and which is molded at 290°C. The acetaldehyde content of the molded product obtained by injection molding at a temperature of W0ppm, on the other hand,
The polyethylene terephthalate was immersed in hot water at a temperature of 95°C.
The acetaldehyde content of the molded product obtained by soaking for a time, drying, and then injection molding as described above was determined by W.
It is characterized in that W0-W1 is 0 to 6 ppm when it is 1 ppm.

0012

DETAILED DESCRIPTION OF THE INVENTION The polyethylene terephthalate according to the present invention will be explained in detail below. The polyethylene terephthalate according to the present invention has an intrinsic viscosity of 0.50 d.
l/g or more, preferably 0.54 dl/g or more, more preferably 0.70 dl/g or more, particularly preferably 0.
72 dl/g or more, and the density is 1.37 g/cm
3 or more, preferably 1.38 g/cm3 or more.

[0013] Furthermore, the polyethylene terephthalate according to the present invention is obtained by injection molding the polyethylene terephthalate at a molding temperature of 290°C, and the acetaldehyde content of the molded product obtained is W0 ppm. When the acetaldehyde content of the molded product obtained by immersion in hot water for 8 hours, drying, and then injection molding as described above is W1ppm, W0-W1 is 0 to 6ppm, preferably 0 to 5p.
pm, more preferably 0 to 4 ppm.

[0014] The content W of acetaldehyde as described above
A method for manufacturing a measurement sample (stepped rectangular plate-shaped molded product, polyethylene terephthalate molded product) for which 0 and W1 ppm are measured will be described.

First, 2 kg of granular polyethylene terephthalate as a raw material was dried using a tray type dryer at a temperature of 140° C. and a pressure of 10 torr for more than 16 hours to reduce the moisture content of the granular polyethylene terephthalate to 50 pp.
m or less.

Next, the dried granular polyethylene terephthalate was injection molded using an M-70A injection molding machine manufactured by Meiki Seisakusho Co., Ltd. at a cylinder temperature of 290°C and a mold cooling water temperature of 15°C to form a stepped square plate. A shaped body is manufactured.

[0017] This stepped rectangular plate-shaped molded product was weighed for 12 seconds,
The dried granular polyethylene terephthalate is supplied from a hopper to an injection molding machine whose molding conditions are adjusted so that the injection time is 60 seconds. Further, the residence time of the molten resin in the molding machine is approximately 72 seconds. The weight of the resin used per each stepped square plate-shaped molded product was 75 g. As the sample for acetaldehyde measurement, any one of the 11th to 15th samples after the start of injection molding is used.

[0018] The stepped rectangular plate-shaped molded body 1 has a shape as shown in FIG. The thickness of part C is approximately 4mm
It is. In the present invention, the acetaldehyde content of the stepped rectangular plate-shaped molded product is measured using part C of the molded product.

Specifically, the C portion (
The acetaldehyde concentration is measured for a sample (chip) obtained by cutting a portion (4 mm thick) into chips. In other words, the content of acetaldehyde in polyethylene terephthalate can be determined by cooling and crushing 2 g of a sample (chip), returning it to room temperature, collecting 1 g, placing it in a container, adding 2 cc of internal standard solution to the container, and sealing it. Then, acetaldehyde was extracted in an oven at 120°C for 1 hour, cooled on ice, and 5 μl of the supernatant was added to a Shimadzu (Shimadzu)
It is determined by analysis using GC-6A manufactured by Co., Ltd.

In the present invention, the acetaldehyde content as described above includes the acetaldehyde content (W0 ppm) measured on a molded product obtained by injection molding polyethylene terephthalate at a molding temperature of 290°C.
The acetaldehyde content of the molded product obtained by immersing this polyethylene terephthalate in hot water at a temperature of 95° C. for 8 hours, drying it, and then injection molding it as described above is (W1 ppm). In the present invention, the value of W0-W1 is calculated from the above values of W1 and W0.

By using polyethylene terephthalate whose value of W0-W1 calculated as above, that is, the amount of increase in acetaldehyde during molding is 0 to 5 ppm, the amount of increase in acetaldehyde during molding is small. It is possible to obtain a molded product that is less likely to generate bad or unusual odors or change the flavor or aroma of its contents.

The polyethylene terephthalate of the present invention having the above characteristics can be produced, for example, as follows. Polyethylene terephthalate according to the present invention is produced using terephthalic acid or an ester-forming derivative thereof and ethylene glycol or an ester-forming derivative thereof as raw materials. Further, this polyethylene terephthalate may be copolycondensed with 20 mol% or less of other dicarboxylic acids and/or other glycols. Examples of dicarboxylic acids other than terephthalic acid used in copolycondensation include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, and diphenoxyethane dicarboxylic acid, adipic acid, and sebacic acid. , azelaic acid, aliphatic dicarboxylic acids such as decanedicarboxylic acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid.

Examples of glycols other than ethylene glycol used in copolycondensation include aliphatic glycols such as trimethylene glycol, propylene glycol, tetramethylene glycol, neopentyl glycol, hexamethylene glycol, and dodecamethylene glycol, and cyclohexane. Examples include alicyclic glycols such as dimethanol, bisphenols, hydroquinone, and aromatic diols such as 2,2-bis(4-β-hydroxyethoxyphenyl)propane.

[0024] The raw materials containing terephthalic acid or its ester-forming derivative as described above and ethylene glycol or its ester-forming derivative are esterified in the presence of an esterification catalyst (esterification reaction step), and then polymerized. liquid phase polymerization in the presence of a catalyst (liquid phase polycondensation step). In the present invention, the reaction product may be treated with hot water as it is after the polycondensation step as described above, but it is preferably further subjected to solid phase polymerization (solid phase polymerization step).

The method for producing polyethylene terephthalate according to the present invention may be either a batch method or a continuous method. The method for producing polyethylene terephthalate of the present invention will be specifically explained below by showing an example of a preferred production method.

First, a slurry containing terephthalic acid or its ester-forming derivative and ethylene glycol or its ester-forming derivative is prepared, and an esterification reaction is carried out in this slurry.

The slurry used here contains, per mole of terephthalic acid or its ester-forming derivative,
Usually 1.02 to 1.4 mol, preferably 1.03 to 1
．． Three moles of ethylene glycol or its ester-forming derivative are included. This slurry is continuously fed to the esterification reaction step.

The esterification reaction is carried out using an apparatus in which at least two esterification reactors are connected in series, under conditions in which ethylene glycol is refluxed, and water produced by the reaction is removed from the system in a rectification column. Implemented. The reaction conditions for carrying out the esterification reaction are such that the temperature of the first stage esterification reaction is usually 240 to 270°C, preferably 245 to 270°C.
The temperature is 265℃ and the pressure is usually 0.2-3Kg/cm2G
, preferably 0.5 to 2 Kg/cm2G, and the temperature of the final stage esterification reaction is usually 250 to 280
℃, preferably 255-275℃, and the pressure is usually 0
~1.5Kg/cm2G, preferably 0-1.3Kg/
cm2G.

Therefore, when carrying out the esterification reaction in two stages, the reaction conditions are set so that the esterification reaction conditions in the first stage and the second stage are within the above ranges, and If it is to be implemented in more than one stage, the first
The reaction conditions for the first stage and the final stage are set as described above, and the reaction conditions for the esterification reaction from the second stage to one stage before the final stage are the same as the reaction conditions for the first stage and the final stage. The reaction conditions are set to be intermediate between those of the eye.

For example, when the esterification reaction is carried out in three stages, the reaction temperature of the second stage esterification reaction is usually 245 to 275°C, preferably 250 to 270°C.
℃, and the pressure is usually 0 to 2 Kg/cm2G, preferably 0.2 to 1.5 Kg/cm2G. There is no particular restriction on the reaction rate at each stage of these esterification reactions, but the esterification reaction rate must increase at each stage and the reaction rate must be distributed smoothly (the reaction must be ensured so that there is no discontinuity in each stage). It is preferable that the degree of increase in the ratio is distributed almost equally among the stages. Furthermore, reaction conditions are set so that the reaction rate of the esterification reaction product in the final stage usually reaches 90% or more, preferably 93% or more.

A lower condensate is obtained by these esterification reaction steps, and the number average molecular weight of this lower condensate is usually 500 to 5,000. Such an esterification reaction involves components other than terephthalic acid and ethylene glycol (
For example, it is possible to carry out the process without adding any additives (for example, additives), or in the coexistence of a polycondensation catalyst, which will be described later. tertiary amine,
By adding a small amount of quaternary ammonium hydroxide such as tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide, and trimethylbenzylammonium hydroxide, and basic compounds such as lithium carbonate, sodium carbonate, potassium carbonate, and sodium acetate. If carried out, the proportion of dioxyethylene terephthalate component units in the main chain of polyethylene terephthalate can be maintained at a relatively low level, which is preferable.

The lower condensate obtained as above is
Next, it is heated under reduced pressure in the presence of a polycondensation catalyst to a temperature equal to or higher than the melting point of the resulting polyethylene terephthalate. The glycol produced at this time is distilled out of the system, and the lower condensate is supplied to a liquid phase condensation polymerization step for polycondensation.

The polycondensation reaction in such a liquid phase polycondensation step may be carried out in one step or divided into multiple steps. When performing the polycondensation reaction in multiple stages, the polycondensation reaction conditions are such that the reaction temperature for the first stage polycondensation is usually 250 to 290°C, preferably 260 to 280°C, and the pressure is usually 500°C.
-20 torr, preferably 200-30 torr, and the temperature of the final stage polycondensation reaction is usually 265-20 torr.
The temperature is 300°C, preferably 275 to 295°C, and the pressure is usually 10 to 0.1 torr, preferably 5 to 0.5 t.
It is orr.

When the polycondensation reaction is carried out in two stages,
The polycondensation reaction conditions for the first stage and the second stage are within the above ranges, and when the reaction is carried out in three or more stages, the polycondensation reaction conditions for the first stage
The conditions for the first stage and the final stage are set as above, and the reaction conditions for the polycondensation reaction from the second stage to one stage before the final stage are the reaction conditions for the first stage and the reaction conditions for the final stage. The condition is set between .

For example, when the polycondensation reaction is carried out in three stages, the reaction temperature of the second stage polycondensation reaction is usually 260 to 295°C, preferably 270 to 285°C, and the pressure is Usually 50-2 torr, preferably 40-5 torr
torr range. Although there is no particular limit to the intrinsic viscosity (IV) reached in each of these polycondensation reaction steps, it is preferable that the degree of increase in intrinsic viscosity at each stage is smoothly distributed. That is, it is preferable that the degree of increase in intrinsic viscosity is distributed almost equally among the stages so as not to be discontinuous in each stage. The intrinsic viscosity (IV) of polyethylene terephthalate obtained from the final stage polycondensation reactor is usually 0.35 to 1.
．． 00dl/g, preferably 0.45-0.95dl/
The reaction conditions of each stage are set so that the amount of dl/g is more preferably in the range of 0.55 to 0.85 dl/g.

[0036] This polycondensation reaction is preferably carried out in the presence of a catalyst and a stabilizer. As the catalyst, germanium compounds such as germanium dioxide, germanium tetraethoxide, and germanium tetra-n-butoxide, antimony catalysts such as antimony trioxide, and titanium catalysts such as titanium tetrabutoxide can be used. Among these catalysts, germanium dioxide compounds are preferred because the produced polyethylene terephthalate has excellent hue and transparency. Also,
Stabilizers include phosphoric acid esters such as trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate, and tricresyl phosphate, triphenyl phosphite, trisdodecyl phosphite, and trisnonylphenyl phosphite. Phosphite esters such as methyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, dibutyl phosphate, monobutyl phosphate, dioctyl phosphate, etc., and phosphorus compounds such as phosphoric acid and polyphosphoric acid are used. It will be done. The proportion of these catalysts or stabilizers used is usually 0.0005 to 0.2 in terms of the weight of the metal in the catalyst, based on the weight of the mixture of terephthalic acid and ethylene glycol.
% by weight, preferably in the range of 0.001 to 0.05% by weight, and in the case of a stabilizer, usually 0.001 to 0.1% by weight, preferably 0.001 to 0.1% by weight, as the weight of phosphorus atoms in the stabilizer. It is in the range of 0.002 to 0.02% by weight. These catalysts and stabilizers can be supplied to the first stage reactor of the polycondensation reaction process, or can be supplied at the stage of the esterification reaction process performed before this polycondensation reaction process. can.

The polyethylene terephthalate of the present invention is
As mentioned above, dicarboxylic acids other than terephthalic acid or diols other than ethylene glycol may be contained in an amount of 20 mol % or less, but particularly preferred polyethylene terephthalate in the present invention has the general formula [I]

[0038]

[Chemical formula 1]

The content of the ethylene terephthalate component unit (a) represented by [I] is usually in the range of 95.0 to 99.0 mol%, and the content of the ethylene terephthalate component unit (a) represented by the general formula [II]

[0040]

[Case 2]

... [II] The content of the dioxyethylene terephthalate component unit (b) represented by is usually in the range of 1.0 to 7.0 mol%, preferably 1.0 to 5.0 mol%. Polyethylene terephthalate.

[0042] Polyethylene terephthalate obtained by such a liquid phase polycondensation process is usually molded into granules (chips) by melt extrusion. The granular polyethylene terephthalate thus obtained is usually 2.0
It has an average particle size of ~5.0 mm, preferably 2.2-4.0 mm.

The density of polyethylene terephthalate obtained from the final liquid phase polycondensation reactor is usually 1.33 to 1.33.
It is 35g/cm3. The granular polyethylene terephthalate obtained as described above is usually further fed to a preliminary crystallization step.

[0044] Precrystallization can also be carried out by heating the granular polyethylene terephthalate in a dry state to a temperature of usually 120 to 200°C, preferably 130 to 180°C for 1 minute to 4 hours, or the granular polyethylene terephthalate can be heated to a temperature of 1 minute to 4 hours. Or normally 1 under an inert gas atmosphere containing water vapor.
It can also be carried out by heating to a temperature of 20 to 200°C for 1 minute or more.

[0045] The granular polyethylene terephthalate obtained through the preliminary crystallization step as described above or the granular polyethylene terephthalate obtained without undergoing the above preliminary crystallization step is usually further subjected to a solid phase polymerization step. Supplied.

The solid phase polycondensation step consists of at least one heating step. In this solid phase polymerization, the polycondensation temperature is usually 19
The temperature is 0 to 230°C, preferably 195 to 225°C, and the pressure is usually 1 kg/cm2G to 10 torr, preferably normal pressure to 100 torr, under an inert gas atmosphere such as nitrogen gas, argon gas, carbon dioxide gas, etc. A solid phase polycondensation reaction is carried out. Among these inert gases, nitrogen gas is preferred.

For example, the intrinsic viscosity of polyethylene terephthalate obtained as described above is usually 0.50 dl/
g or more, preferably 0.54 dl/g or more, more preferably 0.70 dl/g or more, particularly preferably 0.72
dl/g or more.

[0048] The density of this polyethylene terephthalate is usually 1.37 g/cm3 or more, preferably 1.37 g/cm3 or more.
38 g/cm3 or more g/cm3 or more. By subjecting the granular polyethylene terephthalate obtained as described above to water treatment, the amount of increase in acetaldehyde in the molded article can be reduced.

This water treatment is carried out by bringing the granular polyethylene terephthalate into contact with water, water vapor, water vapor-containing gas, or the like. The contact between granular polyethylene terephthalate and water is such that polyethylene terephthalate is
In water at 50°C for 1 minute to 100 hours, preferably 5 minutes to 1 hour.
This is done by soaking for 0 hours. Preferably, granular polyethylene terephthalate is added to water at a temperature of 30 to 150°C.
This is done by soaking for 15 minutes to 15 hours. More preferably, the granular polyethylene terephthalate is 40 to 1
This is done by immersing it in water at 10°C for 3 minutes to 12 hours. Particularly preferably, granular polyethylene terephthalate is immersed in water at 50 to 100°C for 5 minutes to 8 hours.

[0050] The contact between the granular polyethylene terephthalate and water vapor, water vapor-containing gas, or water vapor-containing air is usually carried out at a temperature of 1 to 150°C, preferably 50 to 150°C.
, More preferably, water vapor, water vapor-containing gas, or water vapor-containing air at a temperature of 70 to 110° C. is preferably supplied in an amount of 0.5 g or more as water vapor per 1 kg of granular polyethylene terephthalate, or in the presence of the granular polyethylene terephthalate and water vapor. This is done by bringing them into contact.

[0051] The contact between the granular polyethylene terephthalate and water vapor is usually carried out for 1 minute to 1 year, preferably 5 minutes.
It is carried out for 1 minute to 14 days, more preferably for 5 minutes to 10 hours.

[0052] In producing the polyethylene terephthalate of the present invention, the polyethylene terephthalate of the present invention is produced through the esterification reaction step, liquid phase polycondensation step, preliminary crystallization step, solid phase polymerization step, and water treatment step as described above. A granular polyethylene terephthalate according to the invention can be prepared.

The polyethylene terephthalate according to the present invention can also be prepared by passing through an esterification reaction step, a liquid phase polycondensation step, a preliminary crystallization step if necessary, and a water treatment step.

Furthermore, the polyethylene terephthalate according to the present invention can also be prepared through an esterification reaction step, a liquid phase polycondensation step, and further a water treatment step. When the polyethylene terephthalate treated with water was subjected to solid phase polycondensation treatment heated to a temperature of 215°C in an inert gas atmosphere, the polycondensation rate was set to V0. After immersing in water for 8 hours, 2 hours under an inert gas atmosphere in the same manner as above.
If we take the solid polycondensation rate ratio V1/V0, where V1 is the polycondensation rate during solid phase polycondensation treatment heated to a temperature of 15°C, this value is usually 0.2 to 1.0, Preferably 0.22 to 1.0, more preferably 0.25 to 1.0
is within the range of As the solid state polycondensation rate ratio V1/V0 of such polyethylene terephthalate increases, the amount of increase in acetaldehyde during molding tends to decrease.

The polycondensation rate during solid phase polycondensation of polyethylene terephthalate is specifically measured as follows. Granular polyethylene terephthalate 60g
A cylindrical stainless steel container with an inner diameter of 22 mm and a length of 80 mm is filled and sealed. This container is equipped with an inert gas ventilation nozzle at the bottom and a gas discharge nozzle at the top, and the inert gas supplied from the inert gas ventilation nozzle provided at the bottom is supplied. This inert gas is passed through the container and expelled from the gas exhaust nozzle. The solid-state polycondensation reaction for measuring the solid-state polymerization rate was carried out using the above-described method in which granular polyethylene terephthalate was filled in a sand bath (manufactured by Nippon Parkerizing Co., Ltd., sand; aluminum oxide) equipped with a heating device and sealed. This is done by attaching and fixing a stainless steel container.

[0056] At this time, as the inert gas supplied into the stainless steel container, nitrogen gas having a dew point of -50°C or lower and an oxygen concentration of 20 ppm or lower is used. This nitrogen gas is preheated to the same temperature as the sand bath temperature before being supplied to the stainless steel container. Nitrogen gas is 200 per hour
It is supplied in a stainless steel container in an amount of N liters (standard conditions).

When measuring the polycondensation reaction rate, the sand in the sand bath is fluidized with air so that the temperature of the sand bath becomes uniform and no significant temperature distribution occurs within the bath. The sand bath is heated by a heater controlled by a program controller, and its temperature is controlled to a predetermined solid phase polycondensation temperature.

[0058] The solid phase polycondensation rate is measured using the above-mentioned apparatus, and is specifically quantified by the following method. The granular polyethylene terephthalate was filled into a cylindrical stainless steel container as described above, sealed and fixed in a sand bath, and heated from room temperature to 170°C in 30 minutes while blowing nitrogen gas at a rate of 200N liters per minute. After heating and then holding at 170°C for 1 hour, the temperature was raised from 170°C to 215°C over 30 minutes, and further held at 215°C for 4 hours to perform a solid phase polymerization reaction.

After the solid phase polycondensation reaction, the heating was stopped and the temperature of the sand bath was lowered to 70° C. while nitrogen gas was being passed through.Then, the stainless steel container was taken out from the sand bath and the solid phase polycondensation granules were removed. Measure the intrinsic viscosity (dl/g, IV) of polyethylene terephthalate. This IV value is defined as X dl/g.

In the same manner, the intrinsic viscosity (dl/g, IV) of granular polyethylene terephthalate was measured when the holding time at 215° C. was set to 20 hours. Let this IV value be Y dl/g.

The solid phase polycondensation rate V is calculated by the following formula. V=(Y-X)/16 where V is the solid phase polymerization rate (dl/g/hour),
X and Y after 4 hours and 2 hours, respectively, as described above.
This is the IV value (dl/g) after 0 hours.

[0062] The polyethylene terephthalate according to the present invention has a small increase in acetaldehyde during molding, so that molded products such as bottles, films, and sheets with low acetaldehyde content can be obtained. In addition, when a molded article containing a large amount of acetaldehyde is used as a container for food or drink, it may cause a bad odor or foreign odor, and the flavor and aroma of the contents may change. Furthermore, photographic films made from polyethylene terephthalate containing a large amount of acetaldehyde are prone to fogging.

[0063]

Effects of the Invention The polyethylene terephthalate according to the present invention has an intrinsic viscosity of 0.50 dl/g or more, preferably 0.
．． 54 dl/g or more and a density of 1.37 g/g
cm3 or more, preferably 1.38 g/cm3 or more, and the acetaldehyde content of the molded product obtained by injection molding the polyethylene terephthalate at a molding temperature of 290°C is W0ppm, while the polyethylene terephthalate is molded at a temperature of 95°C. When the acetaldehyde content of the molded product obtained by immersion in hot water at ℃ for 8 hours and then drying and then injection molding as described above is W1 ppm, W0-W1 is 0 to 5 ppm. The increase in acetaldehyde during molding is small, and the amount of acetaldehyde contained in the resulting polyethylene terephthalate molded product is small.

[0064] Therefore, when a molded article as a container for food or drink is manufactured using the polyethylene terephthalate according to the present invention as a raw material for forming a film or sheet such as a bottle, the contents to be filled therein. It does not impair its flavor or aroma.

[0065]

[Examples] The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

In this specification, the intrinsic viscosity and density of polyethylene terephthalate are measured as follows. Measurement of Intrinsic Viscosity Intrinsic viscosity is determined by mixing 1.2 g of sample with 15 o-chlorophenol.
Calculation was made based on the solution viscosity measured at 25° C. after cooling and dissolving in cc.

Determination of Density Density is determined at a temperature of 23° C. using a density gradient tube using a mixed solvent of carbon tetrachloride and heptane.

[0068]

[Example 1] Distillation of 6.5 kg of granular polyethylene terephthalate having an intrinsic viscosity of 0.80 dl/g, a density of 1.40 g/cm3, and an acetaldehyde content of 0.8 ppm in a stainless steel container. immersed in water. Next, the stainless steel container containing polyethylene terephthalate and distilled water was heated from the outside, and the internal temperature was 9.
The temperature was controlled at 5° C., and the temperature was maintained for 4 hours for hot water treatment, followed by dehydration and drying to obtain polyethylene terephthalate according to the present invention.

After drying this granular polyethylene terephthalate, the acetaldehyde content of the square plate obtained by injection molding at a cylinder temperature of 290°C was 7.2p.
It was pm. Let this acetaldehyde content be W0.

Next, the dried polyethylene terephthalate according to the present invention was further subjected to hot water treatment at an internal temperature of 95°C for 8 hours, dehydrated and dried, and then injection molded at a cylinder temperature of 290°C to obtain a square plate. The acetaldehyde content of is 6
．． It was 0 ppm.

When this acetaldehyde content is defined as W1, W0-W1 was 1.2 ppm. The water-treated and dried granular polyethylene terephthalate was subjected to solid-state polycondensation by heating to a temperature of 215° C. under a nitrogen gas atmosphere as previously described herein, and the polycondensation rate was 0.0.
It was 026 dl/g·hour. This solid phase polycondensation rate is defined as V0.

Next, the water-treated and dried granular polyethylene terephthalate was further treated with hot water at an internal temperature of 95°C for 8 hours, dehydrated and dried, and the solid phase polycondensation rate was measured. Polycondensation rate is 0.0012 dl/g・
It was time.

If this solid phase polycondensation rate is V1, then V1
/V0 was 0.46.

[0074]

[Example 2] The procedure of Example 1 was repeated except that the water treatment was carried out using hot water at an internal temperature of 55°C for 4 hours.

[0075] W0 is 9.0 ppm, W1 is 6.2
ppm, so W0-W1 was 2.8 ppm.

[0076]

[Example 3] The procedure of Example 1 was repeated except that the water treatment was carried out at an internal temperature of 55°C for 2 hours.

W0 is 10.2 ppm, W1 is 6.
5ppm, so W0-W1 is 3.7ppm
Met.

[0078]

[Example 4] Same as Example 1 except that granular polyethylene terephthalate having an intrinsic viscosity of 0.78 dl/g, a density of 1.40 g/cm3, and an acetaldehyde content of 0.6 ppm was used. did.

[0079] W0 is 7.5 ppm, W1 is 6.0
ppm, so W0-W1 was 1.5 ppm. The water-treated and dried granular polyethylene terephthalate was subjected to solid-state polycondensation by heating to a temperature of 215° C. under a nitrogen gas atmosphere as previously described herein, and the polycondensation rate was 0.0016 dl/g.・It was time. This solid phase polycondensation rate is defined as V0.

Next, the water-treated and dried granular polyethylene terephthalate was further treated with hot water at an internal temperature of 95°C for 8 hours, dehydrated and dried, and the solid phase polycondensation rate was measured. Polycondensation rate is 0.00095 dl/g
・It was time.

If this solid phase polycondensation rate is V1, then V1
/V0 was 0.59.

[0082]

[Example 5] Example 1 except that 5 kg of granular polyethylene terephthalate from Example 1 was filled into a stainless steel container, and steamed at 100°C at a rate of 0.5 kg per hour for 2 hours.
I did the same thing.

W0 is 10.0 ppm, W1 is 6.0 ppm.
5ppm, so W0-W1 is 3.5ppm
Met.

[0084]

[Example 6] 5 kg of granular polyethylene terephthalate from Example 1 was heated at 40°C and 90% relative humidity.
Processed for weeks.

[0085] W0 is 8.6 ppm, W1 is 6.0
ppm, so W0-W1 was 2.6 ppm.

[0086]

[Comparative Example 1] The acetaldehyde content of a square plate obtained by drying the raw material polyethylene terephthalate of Example 1 without water treatment and injection molding at a cylinder temperature of 290°C was 15 ppm. Let this acetaldehyde content be W0.

Next, this granular polyethylene terephthalate was treated with hot water at an internal temperature of 95°C for 8 hours, dehydrated and dried, and then injection molded at a cylinder temperature of 290°C. The acetaldehyde content of the obtained square plate was determined. was 6.5 ppm.

When this acetaldehyde content is defined as W1, W0-W1 was 8.5 ppm. Further, the polycondensation rate when the granular polyethylene terephthalate was heated to a temperature of 215° C. in a nitrogen atmosphere to undergo solid phase polycondensation was 0.
It was 0067 dl/g·hour. This solid phase polycondensation rate is defined as V0.

Next, the granular polyethylene terephthalate was heat-treated at an internal temperature of 95°C for 8 hours, dehydrated and dried, and the solid phase polycondensation rate was measured. As a result, the polycondensation rate was 0.001.
It was 1 dl/g·hour. This solid phase polycondensation rate is V1
Then, V1/V0 was 0.16.

[0090]

[Comparative Example 2] In Comparative Example 1, the intrinsic viscosity was 0.78 dl.
Comparative Example 1 was carried out in the same manner as in Comparative Example 1, except that granular polyethylene terephthalate having a density of 1.40 g/cm and an acetaldehyde content of 0.6 ppm was used.

W0 is 14.2 ppm, W1 is 6.
0 ppm, and W0-W1 was 8.2 ppm. Further, the polycondensation rate of the granular polyethylene terephthalate, which was subjected to solid phase polycondensation treatment by heating to a temperature of 215° C. in a nitrogen atmosphere, was 0.0057 dl/g·hr. This solid phase polycondensation rate is defined as V0.

Next, the granular polyethylene terephthalate was heat-treated at an internal temperature of 95°C for 8 hours, dehydrated and dried, and the solid phase polycondensation rate was measured. As a result, the polycondensation rate was 0.000.
It was 85 dl/g·hr. This solid phase polycondensation rate is V
1, V1/V0 was 0.15. Further, the polycondensation rate of the granular polyethylene terephthalate, which was subjected to solid phase polycondensation treatment by heating to a temperature of 215° C. in a nitrogen atmosphere, was 0.0057 dl/g·hr. This solid phase polycondensation rate is defined as V0.

Next, the granular polyethylene terephthalate was heat-treated at an internal temperature of 95°C for 8 hours, dehydrated and dried, and the solid phase polycondensation rate was measured. As a result, the polycondensation rate was 0.000.
It was 85 dl/g·hr. This solid phase polycondensation rate is V
1, V1/V0 was 0.15.

[0094]

[Comparative Example 3] In Comparative Example 1, the intrinsic viscosity was 0.82 dl.
The procedure was the same as in Comparative Example 1, except that granular polyethylene terephthalate having a density of 1.40 g/cm3, a density of 1.40 g/cm3, and an acetaldehyde content of 0.8 ppm was used.

W0 is 15.0 ppm and W1 is 7.0 ppm.
0 ppm, and W0-W1 was 8.0 ppm.

[0096]

[Example 7] 5 kg of granular polyethylene terephthalate having an intrinsic viscosity of 0.71 dl/g, a density of 1.34 g/cm3, and an acetaldehyde content of 27 ppm was added to 6.5 kg of distilled water in a stainless steel container. Soaked.

Next, the stainless steel container containing the polyethylene terephthalate and distilled water was heated from the outside.
The internal temperature was controlled at 95° C. and hot water treatment was carried out by maintaining this temperature for 4 hours to obtain polyethylene terephthalate having a density of 1.38 g/cm 3 and an acetaldehyde content of 24 ppm.

[0098] This granular polyethylene terephthalate was dried at 140°C for 3 hours under nitrogen gas flow, and the density was 1.38.
A polyethylene terephthalate according to the invention with an acetaldehyde content of 19 ppm in g/cm3 was obtained.

[0099] This granular polyethylene terephthalate,
After drying, the acetaldehyde content of the square plate obtained by injection molding at a cylinder temperature of 290°C was 20pp.
It was m. Let this acetaldehyde content be W0.

[0100] Next, the dry polyethylene terephthalate according to the present invention was further added to the treatment solution at a temperature of 95°C.
The acetaldehyde content of the square plate obtained by hot water treatment for a period of time, drying, and injection molding at a cylinder temperature of 290° C. was 15 ppm. Letting this acetaldehyde content be W1, W0-W1 was 5 ppm.

[0101]

[Example 8] Granular polyethylene terephthalate having an intrinsic viscosity of 0.71 dl/g, a density of 1.34 g/cm3, and an acetaldehyde content of 27 ppm was pre-crystallized at 170°C for 10 minutes under nitrogen gas flow. , polyethylene terephthalate having a density of 1.38 g/cm3 and an acetaldehyde content of 23 ppm was obtained.

[0102] This granular polyethylene terephthalate was treated with hot water in the same manner as in Example 7, and the density was 1.38 g/c.
Polyethylene terephthalate having an acetaldehyde content of 19 ppm was obtained. This granular polyethylene terephthalate was dried at 140° C. for 3 hours under nitrogen gas flow to obtain polyethylene terephthalate according to the present invention having a density of 1.38 g/cm 3 and an acetaldehyde content of 15 ppm.

[0103] This granular polyethylene terephthalate,
After drying, the acetaldehyde content of the square plate obtained by injection molding at a cylinder temperature of 290°C was 18pp.
It was m. Let this acetaldehyde content be W0.

Next, the polyethylene terephthalate according to the present invention was further treated with hot water at a treatment liquid temperature of 95°C for 8 hours, dried, and then injection molded at a cylinder temperature of 290°C to obtain an acetaldehyde-containing square plate. When the amount was measured, it was 14 ppm.

[0105] When this acetaldehyde content is defined as W1, W0-W1 was 4 ppm.

[0106]

[Comparative Example 4] Granular polyethylene terephthalate having an intrinsic viscosity of 0.71 dl/g, a density of 1.34 g/cm3, and an acetaldehyde content of 27 ppm was dried at 140°C for 3 hours under a nitrogen gas stream, and the density is 1.
38g/cm3 and acetaldehyde content is 18p
A comparative dry polyethylene terephthalate of pm was obtained.

[0107] After drying this granular polyethylene terephthalate, the acetaldehyde content of the square plate obtained by injection molding at a cylinder temperature of 290°C was 45 pp.
It was m. Let this acetaldehyde content be W0.

[0108] Next, dry polyethylene terephthalate for comparison was further treated with hot water at an internal temperature of 95°C for 8 hours, and after drying, the acetaldehyde content of the obtained square plate was measured by injection molding at a cylinder temperature of 290°C. Then 18ppm
Met.

[0109] Letting this acetaldehyde content be W1, W0-W1 was 27 ppm.

[0110]

[Comparative Example 5] Granular polyethylene terephthalate having an intrinsic viscosity of 0.71 dl/g, a density of 1.34 g/cm3, and an acetaldehyde content of 27 ppm was pre-crystallized at 170°C for 10 minutes under a nitrogen gas stream. , polyethylene terephthalate having a density of 1.38 g/cm3 and an acetaldehyde content of 23 ppm was obtained.

[0111] This granular polyethylene terephthalate,
Dry at 140°C for 3 hours under nitrogen gas ventilation until the density is 1.
38g/cm3 and acetaldehyde content is 17p
A comparative dry polyethylene terephthalate of pm was obtained.

[0112] After drying this granular polyethylene terephthalate, the acetaldehyde content of the obtained square plate was measured by injection molding at a cylinder temperature of 290°C and found to be 39 pp.
It was m. Let this acetaldehyde content be W0.

[0113] Next, dry polyethylene terephthalate for comparison was further treated with hot water at an internal temperature of 95°C for 8 hours, and after drying, the acetaldehyde content of the obtained square plate was measured by injection molding at a cylinder temperature of 290°C. Then 15ppm
Met.

[0114] Letting this acetaldehyde content be W1, W0-W1 was 24 ppm.

[0115]

[Brief explanation of the drawing]

[0116]

FIG. 1 is a diagram conceptually showing the shape of a square plate used in the measurement of acetaldehyde in the present invention.

Claims (1)

[Claims] 1. Polyethylene terephthalate having an intrinsic viscosity of 0.50 dl/g or more and a density of 1.37 g/cm3 or more, which is obtained by injection molding the polyethylene terephthalate at a molding temperature of 290°C. The acetaldehyde content of the molded product is W0ppm,
On the other hand, when the acetaldehyde content of the molded product obtained by immersing the polyethylene terephthalate in hot water at a temperature of 95°C for 8 hours, drying it, and then injection molding it as described above is W1ppm, W0-W1 is 0-6pp
Polyethylene terephthalate characterized by m.