JPH06184286A - Polyethylene terephthalate and hollow vessel and drawn film composed of the resin - Google Patents

Abstract

PURPOSE:To obtain the subject compound free from mold-staining trouble, having excellent reclaimability and useful for film, bottle, sheet, etc., in high efficiency by contacting a polyethylene terephthalate with hot steam after solid- phase polymerization. CONSTITUTION:A polyethylene terephthalate having an intrinsic viscosity of 0.5-1.5dl/g (preferably >=0.70dl/g) and a density of >=1.37g/cm<3> (preferably >=1.39g/cm<3>) and produced by a solid-phase polymerization in a nitrogen atmosphere at 215 deg.C at a polymerization rate of >=0.0060dl/g.hr (preferably >=0.0070dl/g.hr) is made to contact with hot steam of 160-240C for l sec to 5 hr to obtain the objective compound. The polyethylene terephthalate obtained by the solid-phase polymerization has a cyclic trimer content of <=0.50wt.% (preferably <=0.30wt.%) and increment of cyclic trimer of <=0.15wt.% (preferably <=0.06wt.%) after heating at 290 deg.C for 30min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to polyethylene terephthalate used for molding bottles, films, sheets and the like. More specifically, the present invention relates to polyethylene terephthalate (hereinafter referred to as “PET”) which is less likely to cause mold stains during molding and is suitable for recycling, and a molded product made of the same.

[0002]

2. Description of the Related Art PET is excellent in mechanical strength, chemical stability, transparency, hygiene, gas barrier property, etc.
In particular, there has been remarkable growth in recent years as a container for beverages such as carbonated drinks and fruit juice drinks. For example, in the case of a stretched bottle, such a PET is manufactured by molding a preform with an injection molding machine and stretching and blowing the preform in a mold having a predetermined shape. Further, beverage bottles such as fruit juice drinks that require hot filling are generally used after being subjected to heat treatment called heat setting to improve heat resistance.

However, PET usually contains various oligomers, and these oligomers, especially the cyclic trimer which is the main component of the oligomers, have been the cause of mold fouling. Such mold stains cause rough surface of the bottle and whitening. Therefore, conventionally, it has been necessary to frequently clean the mold. Further, in recent years, with respect to PET, environmental problems and waste disposal problems have been screaming loudly, and PET having excellent recyclability has been demanded. The methods of recycling are roughly classified into the following two methods. The first is a method of returning PET bottles to monomers and oligomers such as terephthalic acid, bis (2-hydroxyethyl) terephthalate or dimethyl terephthalate by washing and crushing PET bottles and then depolymerizing. It is a method of melting and using as pellets. Particularly in the latter case, the intrinsic viscosity (hereinafter referred to as “IV”) of PET is unavoidably lowered in the two steps of molding into a bottle and remelting into pellets, resulting in deterioration of physical properties. Therefore, it is necessary to carry out solid phase polymerization again to obtain a predetermined IV. However, if the bottle once filled with the beverage is solid-phase polymerized again during recycling, there is a problem that the solid-phase polymerization rate is slow and the recyclability is deteriorated.

On the other hand, 1 PET having an intrinsic viscosity of 0.50 dl / g or more and a density of 1.37 g / cm ³ or more
A method of treating with water or steam or a steam-containing gas at ˜150 ° C. has also been proposed (JP-A-3-21552).
1) The PET obtained by this method has a slow solid-state polymerization rate in the case of solid-state polymerization, and thus the problem that productivity in the solid-state polymerization step during recycling is inevitable.

[0005]

An object of the present invention is to provide a solid-phase polymerization rate that can maintain sufficient productivity even when solid-phase polymerization is again performed on pellets obtained by remelting a molded article such as a bottle. The purpose of the present invention is to provide a PET suitable for recycling, and further to provide a PET that has a small amount of by-products generated during molding and does not easily cause contamination of a mold or the like during molding.

[0006]

Means for Solving the Problems As a result of intensive studies for achieving the above object, the inventors of the present invention found PET having a specific physical property range and arrived at the present invention. That is, the gist of the present invention is that the intrinsic viscosity is 0.5 to 1.5 dl / g, the density is 1.37 g / cm ³ or more, and 21
The polymerization rate at the time of solid phase polymerization at a temperature of 5 ° C. under a nitrogen atmosphere is 0.0060 dl / g · hour or more, and 29
The present invention relates to PET, which is characterized in that the cyclic trimer increase amount when melted at a temperature of 0 ° C. for 30 minutes is 0.15% by weight or less, and a molded product made of the PET.

The present invention will be described in detail below. The intrinsic viscosity of the PET of the present invention is usually 0.50 dl / g or more, preferably 0.60 dl / g, measured at 30 ° C. in a mixed solvent of phenol / tetrachloroethane (weight ratio 1/1).
The above is more preferable, and more preferable is 0.70 dl / g or more. Below 0.50 dl / g, the obtained P
When ET is used as a molded product, it cannot have sufficient practical strength.

The density of PET of the present invention is carbon tetrachloride / n.
-By means of a density gradient tube with a mixed solvent of heptane, 25
When measured at ° C, it is usually 1.37 g / cm ³ or more, preferably 1.38 g / cm ³ or more, and more preferably 1.39 g / cm ³ or more. Density 1.37g / c
When it is less than m ^3, the amorphous content of PET is high, and the solid phase polymerization and heat treatment are insufficient, so that the amount of cyclic trimers tends to be insufficiently reduced.

The solid-state polymerization of the PET of the present invention at a temperature of 215 ° C. for 20 hours in a nitrogen atmosphere has a polymerization rate of 0.
0060 dl / g · hour or more, preferably 0.0065
dl / g · hour or more, more preferably 0.0070d
l / g · hour or more. When it is less than 0.0060 dl / g · hour, the polymerization rate is low when solid-state polymerization is performed on molten PET for reuse, and the productivity is significantly reduced. The solid phase polymerization rate in the present invention is the difference between the intrinsic viscosities of the resins before and after the solid phase polymerization divided by the solid phase polymerization time of 20 hours.

When the PET of the present invention is melted at a temperature of 290 ° C. for 30 minutes, the amount of cyclic trimer increase is 0.15% by weight or less, preferably 0.10% by weight or less, more preferably 0.08% by weight. % Or less, particularly preferably 0.06% by weight or less. This increase in cyclic trimer was obtained by adding dry PET to a glass tube in a nitrogen atmosphere in an oil bath at 290 ° C.
Obtained as the cyclic trimer increase amount [{cyclic trimer content after melting (wt%)}-{cyclic trimer content before melting (wt%)}] when immersed and melted for 0 minutes To be Since such a PET has few annular trimers at the time of molding, it is supplied to a molding machine such as an injection molding machine to mold a preform for a hollow molded body, and the preform is inserted into a mold and stretch blown. When heat setting is performed after molding to mold a hollow molded container, mold contamination due to the attachment of the annular trimer to the mold is less likely to occur. Regarding the degree of stains on the mold, when the amount of increase of the cyclic trimer was 0.15% by weight or less, almost no stain was found on the mold, and when it was 0.10% by weight or less, the stain on the mold was considerably found. Takes a number of shots.

The content of the cyclic trimer in the PET of the present invention is 0.50% by weight or less, preferably 0.40% by weight or less, more preferably 0.35% by weight or less, particularly preferably 0. It is preferably 30% by weight or less. Generally, the lower the content of the cyclic trimer, the better the contamination of the mold and the like. Content of cyclic trimer is 0.5
When it exceeds 0% by weight, the mold is contaminated remarkably.

In the PET of the present invention, the ratio of the terminal carboxyl groups to the total terminal groups (hereinafter referred to as "AV / TEV").
Is usually 30 to 80 equivalent%, preferably 50 to
It is desirable that the amount is 70 equivalent%, and more preferably 60 to 67 equivalent%. When AV / TEV is in the range, molded articles such as bottles are melted and pelletized again,
Sufficient productivity can be obtained when solid-phase polymerization is performed to obtain a desired IV.

An example of the method for producing PET of the present invention will be specifically described below, but the present invention is not limited to these production methods. The PET of the present invention is produced by using terephthalic acid or its ester-forming derivative and ethylene glycol or its ester-forming derivative as raw materials. This PET usually contains up to 20 mol% of other dicarboxylic acid and / or other dicarboxylic acid. Alternatively, another glycol may be copolymerized.

These dicarboxylic acids or their derivatives include phthalic acid, isophthalic acid, naphthalene dicarboxylic acid, 4,4'-diphenylsulfone dicarboxylic acid, 4,
4'-biphenyldicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-phenylenedioxydiacetic acid,
And production isomers thereof, aliphatic dicarboxylic acids such as malonic acid, succinic acid and adipic acid, and esters of these dicarboxylic acids, oxyacids or derivatives thereof include p-hydroxybenzoic acid and p-hydroxybenzoic acid ester. And glycolic acid. Further, as the diol component, diethylene glycol, 1,2-
Propanediol, 1,3-Propanediol, 1,4
-Butanediol, pentamethylene glycol, hexamethylene glycol, neopentyl glycol and other aliphatic glycols, cyclohexanedimethanol and other alicyclic glycols, and bisphenol A, bisphenol S, and other aromatic dihydroxy compound derivatives You can

A raw material containing terephthalic acid or its ester-forming derivative as described above and ethylene glycol or its ester-forming derivative is subjected to an esterification reaction or a transesterification reaction in the presence of an esterification catalyst or a transesterification catalyst. A bis (β-hydroxyethyl) terephthalate and / or an oligomer thereof is formed, and then melt polycondensation is performed under reduced pressure at high temperature in the presence of a polycondensation catalyst and a stabilizer to produce a prepolymer. Since terephthalic acid is an autocatalyst for the esterification reaction, it is not necessary to use an esterification catalyst, but it is also possible to carry out it in the coexistence of a polycondensation catalyst described later,
Further, a small amount of inorganic acid or the like can be used. As the transesterification catalyst, alkali metal salts such as sodium and lithium, and alkaline earth metal salts such as magnesium and calcium, and metal compounds such as zinc and manganese are preferably used, but manganese compounds are particularly preferable from the viewpoint of transparency. .

As the polycondensation catalyst, a germanium compound,
Compounds soluble in the reaction system such as antimony compounds, titanium compounds, cobalt compounds, and tin compounds are used alone or in combination, and germanium dioxide is particularly preferable in terms of color tone and transparency. As stabilizers, phosphoric acid esters such as trimethyl phosphate, triethyl phosphate, triphenyl phosphate, phosphite esters such as triphenyl phosphite and trisdodecyl phosphate, methyl acid phosphate, dibutyl phosphate, monobutyl phosphate acidic phosphorus Acid esters and phosphorus compounds such as phosphoric acid, phosphorous acid, hypophosphorous acid and polyphosphoric acid are preferred. The proportion of these catalysts or stabilizers used is usually 0.0005 to 0.2% by weight, preferably 0.001 to 0.05% by weight, based on the weight of the metal in the catalyst in the case of the catalyst in the whole polymerization raw material. Used in the range of%. In the case of a stabilizer, the weight of phosphorus atoms in the stabilizer is usually 0.001 to 0.1% by weight, preferably 0.002 to 0.02% by weight. These catalysts and stabilizers can be supplied at the time of preparing the raw material slurry, at any stage of the esterification reaction or transesterification reaction, and further at the initial stage of the polycondensation reaction step.

The prepolymer chips thus obtained are usually 2.0 to 5.5 mm, preferably 2.2 to 5.5 mm.
It is desirable to have an average particle size of 4.0 mm. next,
The prepolymer chips thus obtained by melt polymerization are subjected to solid phase polymerization. The prepolymer chip to be subjected to the solid phase polymerization may be heated in advance when the temperature is lower than the temperature at which the solid phase polymerization is carried out to carry out precrystallization, and then supplied to the solid phase polymerization step. Such a pre-crystallization step can be carried out by heating the prepolymer chips 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 steaming the chips with steam or Normally 120 to 200 ° C under an atmosphere of water vapor-containing inert gas
It can also be carried out by heating at a temperature of 1 minute or more for 1 minute or more, and further, a prepolymer chip conditioned by moisture absorption under an atmosphere of water, steam or a steam-containing inert gas is usually added to 120
It can also be performed by heating to a temperature of up to 200 ° C for 1 minute or more. The humidity of the prepolymer is adjusted so that the water content of the prepolymer is usually 0.01 to 1% by weight, preferably 0.1 to 0.5% by weight. By subjecting the prepolymer chip containing water to the crystallization step or the solid-state polymerization step, it is possible to further reduce the amounts of acetaldehyde and impurities contained in the PET of the present invention in a trace amount.

The solid-phase polymerization step in which the above-mentioned prepolymer chips are supplied comprises at least one stage, and the polymerization temperature is usually 190 to 235 ° C., preferably 195 to 2
The temperature is 30 ° C, and in the case of the inert gas flow method, the pressure is usually 1
kg / cm ² G to 10 mmHg, preferably 0.5 kg
/ Cm ² G to 100 mmHg under the conditions of an inert gas such as nitrogen, argon and carbon dioxide, and in the case of the pressure reduction method, the pressure is usually 0.01 to 300 mmHg, preferably 0.01 to 100 mmHg. It is carried out under the conditions of. The solid phase polymerization time reaches a desired physical property in a shorter time as the temperature is higher, but is usually 1 to 50 hours, preferably 5 to
30 hours, more preferably 10 to 25 hours.

The intrinsic viscosity of the PET thus obtained is usually 0.50 to 1.50 dl / g, preferably 0.
60-1.40 dl / g, more preferably 0.65-
It is preferably 1.30 dl / g. 0.50dl
If less than / g, when the obtained PET is used as a molded product,
It cannot have sufficient practical strength. The density of this PET is usually 1.37 g / cm ³ or more, preferably 1.38 g / cm ^3.
g / cm ³ or more, more preferably 1.39 g / cm ³
That is all.

Usually, solid phase polymerization as described above is carried out.
The novel PET of the present invention can be obtained by treating powder-form PET with hot steam at high temperature. PE here
T powder and granules are chips, pellets, flakes and powdered P
It means ET, but it is preferably a chip or a pellet, and usually 2.0 to 5.5 mm, preferably 2.2.
It is desirable to have an average particle size of 4.0 mm.

The steam used in the present invention is preferably steam heated at 160 ° C. or higher. If the temperature is lower than 160 ° C, it is difficult to realize the effect in a short time. The heated steam may be saturated steam, superheated steam, or steam-containing gas obtained by diluting these steams with air or nitrogen,
If saturated steam is used, water droplets will condense on the surface of the granular material,
There is a risk of blocking the piping due to blocking, etc.
Superheated steam or steam-containing gas is preferred.

The contact between the PET powder and the heated steam is P
It is desirable that ET is performed in heated steam of 160 to 240 ° C. for 1 second to 5 hours, preferably in heated steam of 160 to 180 ° C. for 1 minute to 1 hour. If the temperature is lower than 160 ° C, the solid phase polymerization rate during recycling is slow, which is not preferable.
Further, at a temperature above 240 ° C., PET melts, which is not practical.

The contact treatment with heated steam may be either a continuous method or a batch method. Examples of industrial methods are shown below, but the present invention is not limited thereto. As the batch method, for example, a method of receiving PET powder or granules in a silo type processing device, feeding heated steam in a batch system to perform contact treatment, or putting the PET powder or granules into a double cone type contact treatment device, There is a method in which heated steam is fed while rotating to perform the contact treatment more efficiently.

As a continuous method, there is a method of continuously supplying PET powder or granules from a top to a cylindrical processing apparatus and continuously supplying heated steam in a cocurrent or a countercurrent to perform contact treatment. In addition, these treatments are performed by mechanical stirring with a stirring blade, a torus disk, a screw, etc.
It can be performed more efficiently. The PET powder granules treated with the heated steam can be solid-phase polymerized again if necessary.

By performing the above heating steam treatment,
The PET of the present invention can be obtained. The PET thus obtained can be used for forming films, sheets, containers, and other packaging materials by using a generally used melt molding method. Further, it is possible to improve the mechanical strength by stretching the PET in at least a uniaxial direction.

In producing a stretched film, the stretching temperature may be set between PET and a temperature 70 ° C. higher than that, usually 60 to 170 ° C., preferably 70 to 14 ° C.
It is 0 ° C. The stretching may be uniaxial or biaxial, but biaxial stretching is preferable from the viewpoint of practical physical properties of the film. In the case of uniaxial stretching, the stretching ratio is usually 1.1 to 10 times, preferably 1.5 to 8 times, and in the case of biaxial stretching, it is usually 1 in both the longitudinal direction and the transverse direction. 1-8
Double, preferably 1.5 to 5 times. The longitudinal magnification / lateral magnification is usually 0.5 to 2, preferably 0.7 to 1.3. The obtained stretched film is
Further, heat fixing can be performed to improve heat resistance and mechanical strength. The heat setting is usually carried out under tension at 120 to melting point, preferably 150 to 230 ° C. for usually several seconds to several hours, preferably several tens of seconds to several minutes.

In producing the hollow molded article, a preform molded from the PET of the present invention is stretch blow molded, and an apparatus conventionally used in blow molding of PET can be used. Specifically, for example, a preform is once molded by injection molding or extrusion molding, and as it is, or after processing the plug portion and the bottom portion, it is reheated, and a biaxial method such as a hot parison method or a cold parison method is used. A stretch blow molding method is applied. The molding temperature in this case, specifically, the temperature of each part of the cylinder and the nozzle of the tester is usually in the range of 260 to 300 ° C. The stretching temperature is usually 70 to 120 ° C., preferably 80.
At 110 ° C, the draw ratio is usually 1.5-
It may be performed in a range of 3.5 times and 2 to 5 times in the circumferential direction.

The obtained hollow molded article can be used as it is, but in the case of a content liquid that requires heat filling, such as fruit juice and oolong tea, it is generally further heat-set in a blow mold, Used with heat resistance. Heat fixation is usually 100 to 200 under tension due to compressed air.
C., preferably 120 to 180.degree. C., for a few seconds to a few hours, preferably a few seconds to a few minutes.

[0029]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. (Measurement method) (1) Intrinsic viscosity (hereinafter referred to as "IV") It was measured at 30 ° C in a mixed solvent of phenol / tetrachloroethane (weight ratio 1/1). (2) Density It measured at 25 degreeC using the density gradient tube which used the mixed solvent of carbon tetrachloride / n-heptane.

(3) Content of cyclic trimer (hereinafter referred to as "CT amount")
200 mg of the sample was dissolved in 2 ml of a mixed solution of chloroform / hexafluoroisopropanol (volume ratio 3/2), and 20 ml of chloroform was further added to dilute the mixture. After adding 10 ml of methanol to this and reprecipitating a sample, it filtered and obtained the filtrate. After the filtrate was dried and solidified, a liquid obtained by dissolving the residue in dimethylformamide was analyzed and quantified by liquid chromatography.

(4) Terminal carboxyl group concentration (hereinafter referred to as "A
100 mg of the sample was dissolved in 5 ml of benzyl alcohol by heating, 5 ml of chloroform was added to the sample to dilute it, and titrated with 0.1 N sodium hydroxide / benzyl alcohol solution using phenol red as an indicator for quantification.

(5) Ratio of terminal carboxyl groups to total terminal groups (hereinafter referred to as "AV / TEV") The total terminal groups (hereinafter referred to as "TEV") were calculated using the following formula, and AV was divided by TEV. Was multiplied by 100 and expressed as a percentage. (Unit: equivalent amount%) TEV = {2000000 / (1359 × I
V) ^1.460 } (Unit: eq / ton)

(6) Solid-Phase Polymerization Rate The solid-phase polymerization rate was determined by heating in an oil bath while passing nitrogen as an inert gas in an amount of 3.6 Sl / min in a container containing 100 g of PET chips. Carried out. The temperature was raised from room temperature to 50 ° C. in 30 minutes, then kept at 50 ° C. for 3 hours, then raised from 50 ° C. to 170 ° C. in 30 minutes, then kept at 170 ° C. for 1 hour, and then from 170 ° C. 215 ° C
Up to 30 minutes and then maintained at 215 ° C. for 20 hours to carry out solid phase polymerization. After the solid phase polymerization, the temperature was lowered from 215 ° C. to room temperature, and then the sample was taken out. Solid-state polymerized P
The value obtained by dividing the difference between the IV of ET and the IV of PET before solid phase polymerization by the solid phase polymerization time of 20 hours was defined as the solid phase polymerization rate. (7) Acetaldehyde content (hereinafter referred to as “AA amount”) After extraction with water at 160 ° C. for 2 hours, the content was quantified by gas chromatography.

Example 1 IV of 0.75 dl / g and density of 1.40 g / c
m is ^3, put PET chip 100 kg CT amount of 0.30% by weight in a cylindrical vessel which is covered with an insulating cover of the heater containing the chip temperature under a nitrogen atmosphere 165 ° C.
The heater was heated so that Superheated steam at 165 ° C. was steamed at a rate of 1 kg / hour for 30 minutes from the bottom to the top of the container to treat chips. The IV of this steam-treated chip was 0.72 dl / g and the density was 1.4.
It was 0 g / cm ³ and AV / TEV was 62.6%.

An oligomer by-product experiment was conducted using this steam-treated chip. 5 g of the chips were placed in a glass tube and dried under the conditions of a temperature of 160 ° C. and a pressure of 1 mmHg for 2 hours. Then re-pressurize with nitrogen and put in an oil bath at 290 ° C for 30
After soaking for a minute, the rapidly melted PET was cooled in water and solidified, and the CT content was measured.
0.35% by weight, and the increment of oligomer is 0.05
% By weight. The amount of AA was 8.2 ppm by weight.

The solid-state polymerization rate of this steam-treated chip was also measured. PET chip 10 in a container in an oil bath
0 g was added, and nitrogen was passed as an inert gas at an amount of 3.6 Sl per minute to carry out. The temperature was raised from room temperature to 50 ° C. in 30 minutes, then kept at 50 ° C. for 3 hours, then raised from 50 ° C. to 170 ° C. in 30 minutes, then kept at 170 ° C. for 1 hour, and then from 170 ° C. The temperature was raised to 215 ° C. in 30 minutes, and then the temperature was maintained at 215 ° C. for 20 hours to carry out solid phase polymerization. After the solid phase polymerization, the temperature was lowered from 215 ° C. to room temperature, and then the sample was taken out. IV of PET after solid state polymerization is 0.8
9 dl / g, solid state polymerization rate is 0.0085 dl
/ G · hour.

Example 2 IV is 0.79 dl / g and density is 1.40 g / c
100 kg of PET chips having m ³ and an oligomer content of 0.35% by weight were placed in a cylindrical container covered with a heat insulating cover containing a heater, and the heater was heated so that the chip temperature was 170 ° C. Superheated steam at 170 ° C. was steamed at a rate of 1 kg / hour for 15 minutes from the bottom to the top of the container to treat chips. The IV of this steam-treated chip was 0.73 dl / g and the density was 1.40.
g / cm ³ , and AV / TEV was 52.6%.

When an oligomer by-product experiment was conducted using this steam-treated chip in the same manner as in Example 1, the CT amount was 0.42% by weight, and the increase amount of the oligomer was 0.07.
% By weight. The amount of AA was 7.6 ppm by weight. Further, as a result of measuring the solid phase polymerization rate of the steam-treated chip by the same method as in Example 1, the IV of PET after solid phase polymerization was 0.87 dl / g, and the solid phase polymerization rate was 0.0.
It was 072 dl / g · hour.

Example 3 IV of 0.75 dl / g and density of 1.40 g / c
m is ^3, PET chip 100 oligomer content is polymerized 3 mol% co-isophthalic acid is 0.30 wt%
kg was placed in a cylindrical container covered with a heat insulating cover containing a heater, and the heater was heated so that the chip temperature was 165 ° C. 165 ° C from bottom to top of this container
The superheated steam of was steamed at a rate of 1 kg / hour for 30 minutes to treat the chips. The IV of the steam-treated chip was 0.72 dl / g and the density was 1.40 g / cm ³ ,
AV / TEV was 44.7%.

Using this steam-treated chip, an oligomer by-product experiment was conducted in the same manner as in Example 1. As a result, the CT amount was 0.36% by weight, and the increase amount of the oligomer was 0.06.
% By weight. The amount of AA was 7.8 weight ppm. Further, as a result of measuring the solid phase polymerization rate of the steam-treated chip by the same method as in Example 1, the IV of PET after solid phase polymerization was 0.85 dl / g, and the solid phase polymerization rate was 0.0
It was 065 dl / g · hour.

Comparative Example 1 The raw material PET of Example 1 was dried in the same manner as in Example 1,
When the oligomer content of the melted product was measured,
0.81% by weight, the amount of increase in oligomer is 0.51
% By weight. The amount of AA was 14.5 ppm by weight. Further, the solid-phase polymerization rate was measured by the same method as in Example 1. As a result, IV of PET after solid-phase polymerization was 0.82d.
1 / g, solid-state polymerization rate is 0.0050 dl / g.
It was time.

Comparative Example 2 100 kg of the raw material PET chips of Example 1 were placed in a cylindrical container covered with a heat insulating cover containing a heater, and the heater was heated so that the chip temperature was 95 ° C. The chips were treated by steaming 95 ° C. steam at a rate of 1 kg / h for 4 hours from the bottom to the top of the container. The IV of this steam treatment chip was 0.74 dl / g, and
/ TEV was 28.0%.

Using this steam-treated chip, an oligomer by-product experiment was conducted in the same manner as in Example 1. As a result, the CT amount was 0.48% by weight, and the increase amount of the oligomer was 0.18.
% By weight. The amount of AA was 11.3 weight ppm. In addition, as a result of measuring the solid phase polymerization rate of the steam-treated chip in the same manner as in Example 1, PET after solid phase polymerization was measured.
Has an IV of 0.79 dl / g and a solid-state polymerization rate of 0.
It was 0025 dl / g · hour.

Example 4 The PET chip used in Example 1 was heated and steamed in the same manner as in Example 1, and then, under a nitrogen atmosphere, the temperature of each part of the cylinder and the nozzle head was 280 ° C. and the screw rotation speed was 10 times.
A preform was molded with an injection molding machine IS-60B manufactured by Toshiba Corp., which was set to 0 rpm, an injection time of 10 seconds, and a mold cooling water temperature of 10 ° C. The mouthpiece of this preform was heated and crystallized by an automatic crystallizer, and then molded by a stretch blow molding machine in which the preheating furnace temperature was 90 ° C., the blow pressure was 20 kg / cm ² , and the molding cycle was 10 seconds. Average wall thickness 300 μm,
A bottle having an internal volume of 1.5 liter was prepared, and subsequently, heat-fixed in a mold set at 150 ° C. for 10 seconds under compressed air tension. The bottle was highly transparent, and neither whitening nor clouding was observed, and no bubbles were observed. Further, although 1000 bottles were continuously molded, the injection molding, stretch blow molding, and heat setting molds were not contaminated.

Further, this bottle was crushed with a crusher to form flakes. Approximately 1 of these flakes at 130 ° C under reduced pressure
After drying for 6 hours, each was melted at a temperature of 280 ° C. of each part of the cylinder and the nozzle head using an extruder, and molded into chips. The solid-state polymerization rate of the solid-state polymerization of the PET chip thus obtained in a nitrogen atmosphere was 0.0071 dl.
/ G · hour, which was able to maintain practically sufficient productivity.

Comparative Example 3 The PET used in Example 1 was treated in the same manner as in Example 4 without heating and steaming the same as in Comparative Example 1, and bottle 1 was prepared.
Although 000 bottles were molded, white fogging was observed on the bottle from the 500th bottle. Also, contamination by oligomers was found in the molds for injection molding, stretch blow molding, and heat setting. Further, as in Example 4, the obtained bottle was crushed and the solid-state polymerization rate of PET chips molded by an extruder in a nitrogen atmosphere was 0.0030 dl / g · hour, which was poor in productivity. It was a thing.

[0047]

INDUSTRIAL APPLICABILITY The PET of the present invention is less likely to form an oligomer such as a cyclic trimer which is formed during molding, and therefore, it is possible to prevent the generation of mold stains, and to remold a molded product such as a bottle. It has a solid-state polymerization rate that can maintain sufficient productivity even when the pellets obtained by melting are solid-phase polymerized again.

Therefore, the PET of the present invention is suitable for recycling, and since it is not necessary to wash the mold frequently when manufacturing the molded product, the productivity of the molded product can be improved and obtained. Whitening of the molded product can be prevented. Further, the PET of the present invention has a small increase in acetaldehyde at the time of molding, and further, since impurities contained in the chip in a trace amount are removed, the flavor and aroma of the contents may change due to an offensive odor or offensive odor. There is no.

Claims (6)

[Claims] 1. An intrinsic viscosity of 0.5 to 1.5 dl / g and a density of 1.37 g / cm ³ or more and 21
The polymerization rate at the time of solid phase polymerization at a temperature of 5 ° C. under a nitrogen atmosphere is 0.0060 dl / g · hour or more, and 29
Polyethylene terephthalate, wherein the amount of cyclic trimer increase when melted at a temperature of 0 ° C. for 30 minutes is 0.15% by weight or less. 2. The polyethylene terephthalate according to claim 1, wherein the content of the cyclic trimer is 0.50% by weight or less. 3. The polyethylene terephthalate according to claim 1, wherein the ratio of the terminal carboxyl groups to the total terminal groups is 30 to 80 equivalent%. 4. The method for producing polyethylene terephthalate according to claim 1, wherein the polyethylene terephthalate after the solid phase polymerization is brought into contact with heated steam at 160 to 240 ° C. for 1 second to 5 hours. 5. A hollow container formed by subjecting the polyethylene terephthalate according to claim 1 to a preform by injection molding or extrusion molding and then biaxially stretch blow molding. 6. A stretched film obtained by injection-molding or extrusion-molding the polyethylene terephthalate according to claim 1 and stretching a sheet-like material in at least one direction.