JP2003160654A - Polyalkylene terephthalate and molding made of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain high quality polyalkylene terephthalate capable of providing resin moldings such as hollow moldings, thermoformed containers, sheets and injection moldings excellent in hygiene, transparency and heat stability by using high purity terephthalic acid recovered from polyester scrap as a raw material. <P>SOLUTION: The polyalkylene terephthalate is obtained by the polycondensation reaction of terephthalic acid with an alkylene glycol in the presence of an antimony catalyst. The terephthalic acid contains 1,000 ppm or less of monomethyl terephthalate and 1 ppm or less in total of 4- carboxybenzaldehyde, para-toluic acid, bezoic acid and dimethyl hydroxyterephthalate. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyalkylene obtained by a polymerization reaction using terephthalic acid obtained by subsequent hydrolysis through dimethyl terephthalate recovered from a packaging material polyalkylene terephthalate. Regarding terephthalate.

[0002]

2. Description of the Related Art Currently, polyalkylene terephthalates,
Above all, polyethylene terephthalate (hereinafter PET)
Sometimes abbreviated. ) Is for fiber, resin, packaging material,
It is widely used in the world as a film and other molded products, but the disposal of used materials, especially PET bottles, has become a big problem in recent years.

[0003] In the past few years, used PET bottles are collected as polyester scraps, then pulverized, separated from other materials, and washed, and then reprocessed into fibers or sheets. A circular loop is created and is starting to work. However, the materials processed by this system have restrictions on reprocessing equipment and conditions, and also have a problem of quality deterioration of reprocessed resin products, and their applications are also restricted.

In recent years, in order to improve the problem of foreign matter and deterioration of quality, many chemical recycling methods have been proposed in which discarded polyester is subjected to a chemical reaction treatment and reused. For example, it is put into the polymerization step again. Method (Japanese Patent Laid-Open No.
000-302849), a method of depolymerizing into a monomer, purifying, and then repolymerizing (JP-A-11-302443).
Japanese Patent Laid-Open No. 2000-169623), and these techniques have significantly improved the quality and expanded the range of reusable applications.

However, the application to the packaging material that is most desired to be reused (in particular, the reuse for bottles) has very severe restrictions from the viewpoint of hygiene and quality, and it is still satisfactory. The current situation is that we have not obtained the quality that can be achieved.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to solve the problems of the prior art described above, to recover high-purity terephthalic acid from polyester scrap, and to use a specific polymerization catalyst based on this raw material. By carrying out a polymerization reaction, hygiene,
To obtain high-quality polyalkylene terephthalate having excellent transparency and thermal stability, and to provide a resin molded product such as a hollow molded product (bottle, container, etc.), a thermoformed container, a sheet, an injection molded product, etc. is there.

[0007]

The present inventor has completed the present invention as a result of extensive studies in view of the above-mentioned conventional techniques.

That is, the object of the present invention is a polyalkylene terephthalate obtained by polycondensing terephthalic acid and alkylene glycol in the presence of an antimony catalyst, wherein the terephthalic acid contains monomethyl terephthalate in an amount of 1000 ppm or less. It can be achieved by polyalkylene terephthalate, characterized in that it contains 4-carboxybenzaldehyde, paratoluic acid, benzoic acid and dimethyl hydroxyterephthalate in a total value of 1 ppm or less.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

The terephthalic acid of the present invention includes 4-carboxybenzaldehyde (hereinafter abbreviated as 4-CBA), paratoluic acid (hereinafter abbreviated as p-TA), and benzoic acid (hereinafter abbreviated as p-TA). , BA may be abbreviated) and hydroxybenzaldehyde (hereinafter, H
It may be abbreviated as DT. ) Is contained so as to be 1 ppm or less in total, and monomethyl terephthalate (hereinafter, M
It may be abbreviated as MT. ) Is contained in 1000 ppm or less, the method for producing this terephthalic acid will be described step by step.

The terephthalic acid of the present invention first undergoes a depolymerization reaction of PET with ethylene glycol by the method described in WO01 / 30729 from the collected used packaging material PET, and subsequently, transesterification with methanol. By the reaction, highly pure dimethyl terephthalate (hereinafter sometimes abbreviated as DMT) is obtained. The total value of 4-CBA, p-TA, BA and HDT in this DMT is 1 ppm or less.

Further, the high-purity DMT is hydrolyzed, and this reaction is carried out in the reactor without catalyst or with catalyst. At this time, either a batch system or a continuous system can be adopted without any problem.

In order to obtain terephthalic acid having an MMT content of 1000 ppm or less, the hydrolysis reaction of DMT is carried out at a temperature of 230 to 260 ° C. and a pressure of 3.0 to 4.6 MPa.
(Gauge pressure), preferably 250 to 260 ° C., pressure 4.
It is necessary to react for several hours at 0 to 4.6 MPa (gauge pressure). The methanol produced by the hydrolysis reaction is removed by introducing stripping vapor together with dimethyl ether produced as a by-product.

The terephthalic acid formed by the hydrolysis reaction is suspended or dissolved in water, discharged from the reactor, crystallized in several stages, and solid-liquid separated. The obtained terephthalic acid cake can be dried, pulverized, slurried with EG, esterified and then subjected to a polymerization reaction.
Typically under these reaction conditions, the impurity content remains below 1000 ppm and can be used as a suitable terephthalic acid for PET packaging materials.

The polyalkylene terephthalate of the present invention is a polyalkylene terephthalate obtained by subjecting terephthalic acid and alkylene glycol to polycondensation reaction in the presence of an antimony catalyst.
As mentioned above, 4-CBA, p-TA, BA and HD
It is characterized by being terephthalic acid containing T so as to be 1 ppm or less in total and MMT at 1000 ppm or less.

In ordinary terephthalic acid starting from paraxylene, 4-CBA, p-TA, BA and HD are contained.
Impurities typified by T are contained in the range of tens to hundreds of ppm, which affects the hue and thermal stability of the polyalkylene terephthalate obtained therefrom. As impurities in terephthalic acid of the present application, 4-CBA, p-TA, BA and HD
When T is contained in a total amount of more than 1 ppm, the resulting polyalkylene terephthalate is unfavorably deteriorated in thermal stability such as a decrease in hue, an increase in the amount of acetaldehyde upon remelting, and a decrease in intrinsic viscosity.

Furthermore, the terephthalic acid of the present application contains MMT, and since the glycol end of the polyalkylene terephthalate obtained by polycondensation is blocked, the thermal stability is improved, but the obtained polyalkylene terephthalate is transparent. MMT content is 1000 to reduce
ppm or less is preferable.

The polyalkylene terephthalate of the present invention is a polyalkylene terephthalate composed of a terephthalic acid unit and an alkylene glycol unit, and examples thereof include polyethylene terephthalate, polypropylene terephthalate, polytetramethylene terephthalate and polyhexamethylene terephthalate. The acid component accounts for 85 mol% or more based on the total acid component,
The alkylene glycol component preferably accounts for 85 mol% or more based on the total diol component, and particularly preferably polyethylene terephthalate.

The polyalkylene terephthalate contains, for example, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid in an amount of less than 15 mol% based on the total acid components. Aromatic dicarboxylic acids such as acid, 1,7-naphthalenedicarboxylic acid, other isomers of naphthalenedicarboxylic acid, isophthalic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfonedicarboxylic acid, etc. Acids, alicyclic dicarboxylic acids such as hexahydroterephthalic acid, hexahydroisophthalic acid, etc., aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, etc., p-β-hydroxyethoxybenzoic acid, ε-oxy Bifunctional such as oxyacids such as caproic acid At least one acid component selected from carboxylic acids may be copolymerized.

In the range of less than 15 mol% based on the total diol component, for example, ethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, decamethylene glycol, neopentyl. Glycol, diethylene glycol, 1,1-
At least one selected from cyclohexane dimethanol, 1,4-cyclohexane dimethanol, 2,2-bis (4'-β-hydroxyphenyl) propane, bis (4'-β-hydroxyethoxyphenyl) sulfone, etc. One or more diol components may be copolymerized.

In the present invention, the polyalkylene terephthalate may be copolymerized with a compound having a functionality of 3 or more in the range of 2% or less.

Next, a method for producing the polyalkylene terephthalate of the present invention, particularly polyethylene terephthalate will be described.

In the method for producing polyethylene terephthalate of the present invention, a raw material containing terephthalic acid and ethylene glycol is esterified to form bis (β-hydroxyethyl) terephthalate and / or an oligomer thereof, and thereafter, Melt polycondensation is carried out under reduced pressure at high temperature in the presence of a polycondensation catalyst and a stabilizer to obtain a polymer.
It is not necessary to use an esterification catalyst because terephthalic acid serves as an autocatalyst for the esterification reaction. As the polycondensation catalyst, an antimony compound is used, and antimony trioxide is preferable, and the addition amount is 100 to 100 as an antimony element.
It is preferably 400 ppm (based on the acid component), more preferably 150 to 350 ppm, and still more preferably 150 to 300 ppm. Furthermore, for toning, at least one pigment selected from the group consisting of oxide pigments, ferrocyanide pigments, silicate pigments, phosphate pigments, carbon black, condensed polycyclic pigments and phthalocyanine pigments, or cobalt compounds. (Acetate, carbonate, etc.) may be contained.

Examples of the oxide pigment include cobalt blue (cobalt oxide / aluminum oxide complex oxide pigment), and examples of the ferrocyanide pigment include navy blue and phosphoric acid. Examples of salt pigments include manganese violet, examples of condensed polycyclic pigments include anthraquinone pigments, and examples of phthalocyanine pigments include phthalocyanine blue and Fast Sky Blue.
Ultramarine can be illustrated as a silicate pigment.

Further, as a stabilizer added at the time of polymerization,
Trimethyl phosphate, triethyl phosphate, triphenyl phosphate and other phosphoric acid esters, triphenyl phosphate, trisdodecyl phosphate and other phosphorous acid esters, methyl acid phosphate, dibutyl phosphate, monobutyl phosphate acidic phosphate ester, phosphoric acid Phosphorus compounds such as phosphorous acid, hypophosphorous acid and polyphosphoric acid are preferred. The proportion of the stabilizer used is
The weight of phosphorus atom in the stabilizer in all the polymerization raw materials is usually 10 to 1000 ppm, preferably 20 to 500 pp.
m, more preferably 20 to 100 ppm.

The catalyst and the stabilizer can be supplied at any stage of the esterification reaction or transesterification reaction, in addition to the preparation of the raw material slurry. Further, it can be supplied at the beginning of the polycondensation reaction step. The reaction temperature during the esterification reaction or transesterification reaction is usually 240 to 280.
C., and the reaction pressure is atmospheric pressure to 0.3 MPa. The reaction temperature during polycondensation is usually 250 to 300 ° C., and the reaction pressure is usually 60 to 0.1 kPa. Such esterification or transesterification reaction and polycondensation reaction,
It may be carried out in one step or divided into a plurality of steps. The polymer thus obtained has an intrinsic viscosity of usually 0.45.
It is about 0.70, and chips are formed by a conventional method. The average particle size of the polymer chips is usually 2.0 to 5.5 mm, preferably 2.2 to 4.0 mm.

Next, the polymer obtained by melt polycondensation as described above is usually subjected to solid phase polymerization. The polymer chip to be subjected to the solid phase polymerization is heated to a temperature lower than the temperature at which the solid phase polymerization is performed in advance to perform pre-crystallization, and then is subjected to the solid phase polymerization. In the pre-crystallization step, the amorphous polymer chips are usually treated at 120 to 200 ° C., preferably 130 to 18 ° C.
At a temperature of 0 ° C., crystallization is performed by always performing at least 15 minutes in one stage or two stages under a fluidized state so as to prevent fusion due to heat generation of chip crystallization. The next solid phase polymerization step consists of at least one step, usually 190-230 ° C,
Preferably at a polymerization temperature of 195 to 225 ° C., 0.05 to
It is carried out under a vacuum of 5 kPa or under a condition of atmospheric pressure to 0.1 MPa under a flow of an inert gas such as nitrogen, argon or carbon dioxide. The solid phase polymerization time may be shorter as the temperature is higher, but is usually 1 to 50 hours, preferably 5 to 30 hours, and more preferably 10 to 25 hours. The intrinsic viscosity of the polymer obtained by solid phase polymerization is usually 0.70 to
The range is 0.90.

In the present invention, the content of diethylene glycol constituting the polyethylene terephthalate resin obtained by the above method is 0.7 to 2.0 wt% with respect to all diol units constituting polyethylene terephthalate.
It is preferably 1.0 to 1.5 wt%. When the amount is too small, the transparency of the bottle body after molding is deteriorated, and when the amount is too large, the heat resistance is lowered and the crystallization promoting effect is further reduced. As a method of adjusting the diethylene glycol content within the above range, in addition to using diethylene glycol as a polymerization raw material, since diethylene glycol is partially by-produced from ethylene glycol used as a main raw material, combined with the reaction conditions, its by-product amount The method of adjusting is mentioned.

Further, in order to control the crystallization rate, the above-mentioned components other than diethylene glycol may be copolymerized, and particularly isophthalic acid, dimethyl 2,6-naphthalenedicarboxylate, 1,4-cyclohexanedimethanol. Is preferred.

Further, the oligomer component contained in the polymer, which becomes a factor of mold fouling at the time of bottle molding, and the acetaldehyde component contained in the polymer, which influences the taste and odor of the bottle filling, should be reduced as much as possible. Is desirable,
The oligomer content is 0.5 wt% or less, particularly preferably 0.4 wt% or less, and the acetaldehyde content is 5 ppm or less, particularly preferably 2 ppm or less.

Since the reduction of the oligomer and acetaldehyde is carried out in the above solid phase polymerization, the target level can be reached by adjusting the IV, the solid phase polymerization time and the temperature time of the polymer after the melt polymerization. . The concentration of the terminal carboxyl group is particularly preferably in the range of 10 to 25 eq / ton. If the concentration of the terminal carboxyl group is less than the above range, the solid phase polymerizability may be poor and it may take a long time to increase the intrinsic viscosity. When used, the effect of reducing oligomers may be small.

The polyethylene terephthalate produced by the method of the present invention can be molded into various molded products. For molding, a general molding method, for example, in the case of a hollow molded body, injection blow molding, orientation blow, extrusion blow, direct blow, injection blow method, etc. are applied, other molding bodies, injection molding method, sheet molding method,
An inflation molding method, a thermoforming method, various multilayer molding methods and the like can be applied.

First, the injection molding is carried out by heating the polyethylene terephthalate to a temperature above the melting temperature to melt it, and then pouring the molten resin into a mold to cool and solidify it. At this time, the mold is heated or cooled to a temperature suitable for the polyethylene terephthalate. Further, the runner portion may be heated (hot runner) or not heated (cold runner) as necessary. The polyethylene terephthalate resin composition of the present invention has good moldability such as fluidity and crystallinity.

Second, the polyethylene terephthalate of the present invention can be molded into a bottle by using a commonly used melt molding method. Specifically, for example, a parison is once molded by injection molding or extrusion molding, and then,
Alternatively, after processing the plug portion and the bottom portion, they are reheated and a stretch blow molding method such as a hot parison method or a cold parison method is applied.

The molding temperature in this case (specifically, the temperature of each part of the cylinder of the molding machine and the nozzle) is 260 to 31.
It is 5 degreeC, Preferably it is 275 degreeC-295 degreeC. The stretching temperature is not lower than the glass transition temperature of polyethylene terephthalate and is usually 70 to 130 ° C. The stretching ratio is usually 1 to 4 times in the machine direction and 1 to 5 times in the circumferential direction.

The obtained bottle can be used as it is, but in the case of a content liquid such as a fruit juice drink and oolong tea which requires heat filling, it is generally heat-set in a heated blow mold to further improve heat resistance. Is used. Heat setting
Normally, the mold temperature is 100 to 200 under tension such as compressed air.
It is performed for several seconds to several minutes at ° C. Alternatively, a method of forming a bottle larger than the final shape, crystallizing the body by shrinking by heating, and then blow molding in a mold of the final shape to obtain a product bottle is also adopted.

Thirdly, the packaging material of various shapes by thermoforming can be carried out as follows, for example. First, a polyethylene terephthalate resin composition is extruded by an extruder and drawn into a sheet. Subsequently, by heating at a temperature not lower than the glass transition temperature and forming by pressure or vacuum forming into an appropriate shape such as a tray, a good appearance and transparency can be obtained.

[0038]

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. Each value in the examples was determined according to the following method. 1. Analysis of terephthalic acid: (1) 4-CBA, p-TA, HDT weight concentration: After dissolving the obtained terephthalic acid in 2N-ammonia water,
Shimadzu Liquid Chromatograph System (LC-6
A) and STRφDS-H column were separately measured. (2) MMT weight concentration: high performance liquid chromatography (device: HPLC D-700 manufactured by Hitachi, Ltd.)
0, packed column: RP-18; 2). (3) BA weight concentration: n after esterification with diazomethane
-It was determined by gas chromatography using 10% SE-30 as a separation column with tridecane as an internal standard.

2. Intrinsic viscosity: According to a conventional method, a fixed amount of a sample cut out from a chip and a molded body is weighed and dissolved in o-chlorophenol at a concentration of 0.012 g / ml, and the temperature is 25 ° C.
It was determined from the value measured inside.

3. Haze: 50mm x 5 from the bottle body
A sample cut out to a size of 0 mm was manufactured by Nippon Denshoku Industries Co., Ltd. under the condition of Color and color dif.
erence meter (MODEL1001DP)
It was measured at.

4. Acetaldehyde content: The content of acetaldehyde (hereinafter, may be abbreviated as AA) content is 150 after freeze-grinding a sample and charging it into a vial.
The temperature was maintained at 60 ° C. for 60 minutes, and the value was measured by headspace gas chromatography manufactured by Hitachi, Ltd.

5. Diethylene glycol content: The content of diethylene glycol (hereinafter sometimes abbreviated as DEG) content was measured by gas chromatography according to a conventional method by decomposing a sample with hydrazine.

6. Col-b: A certain volume of the sample was quantified and measured with a CM-7500 type color machine manufactured by Color Machine Co., Ltd.

7. Oligomer (cyclic trimer) content: The sample was quantified in a fixed volume, dissolved in hexafluoroisopropanol / chloroform = 1/1 (volume ratio), diluted with chloroform, and then GPC (gel permeation chromatography). ) And measured.

8. Amount of copolymerization component: A certain volume of the sample is quantified and decomposed with methanol. This solution was diluted with chloroform and then measured by gas chromatography manufactured by Hitachi, Ltd.

Example 1 Polyethylene terephthalate was depolymerized with ethylene glycol, and then dimethyl terephthalate obtained by transesterification with methanol was further hydrolyzed to obtain terephthalic acid (4-CBA, Total of p-TA, BA, HDT is 1p
Below pm, the MMT was 150 ppm terephthalic acid. ) A slurry composed of 39.2 parts and 22 parts of ethylene glycol was supplied to the polycondensation tank, and 275 ° C under normal pressure,
The esterification reaction is carried out for 4 hours, the water produced as a by-product is discharged to the outside of the system, and the esterification reaction rate is allowed to reach 97% to prepare an oligomer having a polymerization degree of 5 to 10, and then isophthalic acid 0.8 Part (slurry of 0.4 part ethylene glycol)
And an ethylene glycol solution of phosphoric acid (phosphorus concentration 5.5
wt%) 0.017 part and an ethylene glycol solution of antimony trioxide (antimony trioxide concentration 2 wt%) 1.1
Part, and 0.2 part of an ethylene glycol solution of cobalt acetate (cobalt acetate concentration 2 wt%) are added to obtain 2000 Pa.
Under reduced pressure of 1 hour, and subsequently under reduced pressure of 133 Pa, 27
Polycondensation was carried out at 7 ° C for 2 hours.

The polymer produced was taken out in a strand form from an outlet provided by being directly connected to the cooling water tank at the bottom of the polycondensation tank, cooled with water, and then cut into chips to obtain polymer chips. Subsequently, the obtained polymer chips were crystallized by a stirring flow type crystallizer, and then under a nitrogen flow, 1
It was dried at 40 ° C. for 3 hours, then transferred to a packed column type solid-state polymerization tower, and solid-state polymerized at 215 ° C. for 22 hours under a nitrogen flow to produce chip-like polyethylene terephthalate. The obtained polyethylene terephthalate resin composition has an intrinsic viscosity of 0.85, DEG1.3 wt%, an isophthalic acid content of 1.9 mol%, AA = 1.5 ppm, and Col-b =-.
It was 2.5 and the oligomer was 0.38 wt%.

The chips were dried in a dryer at 160 ° C. for 5 hours, and then an injection molding machine (“M-1” manufactured by Meiki Seisakusho Co., Ltd.) was used.
00DM ”), cylinder temperature 275 ° C., screw rotation speed 160 rpm, primary pressure time 3.0 seconds, mold temperature 1
Approx. 28 mm outside diameter, 19 inside diameter at 0 ° C for 30 seconds cycle
A cylindrical preform having a size of mm, a length of 136 mm, and a weight of about 56 g was injection-molded.

The obtained preform has an intrinsic viscosity of 0.7.
7. AA content of 10 ppm, moldability and appearance were good. Then, the surface temperature of the preform is about 110 ℃
Preheat with infrared heater to blow pressure 5-40kg /
The stretch-blow molding was carried out by a blow molding machine set to cm ² and a mold temperature of 150 ° C., and a bottle having an average wall thickness of 330 μm and an internal volume of about 1.5 liter was molded. The haze of the obtained bottle was 0.6%, and the moldability and appearance were good.

Example 2 In Example 1, terephthalic acid was obtained by depolymerizing polyethylene terephthalate with ethylene glycol, and then subjecting dimethyl terephthalate obtained by transesterification with methanol to further hydrolysis. Terephthalic acid (4-CBA, p-T
The sum of A, BA, and HDT is 1 ppm or less, and MMT is 8
The same operation was carried out except that (00 ppm terephthalic acid) was used, and the intrinsic viscosity was 0.85, Col-b =-
2.0, DEG = 1.3 wt%, AA = 1.5 ppm,
Polyethylene terephthalate with 0.40 wt% oligomer
Got

The preform thus obtained had an intrinsic viscosity of 0.76 and an AA content of 8.5 ppm, and was excellent in moldability and appearance. Furthermore, when blow molding was performed in the same manner as in Example 1, the haze of the bottle was 0.9%.

Reference Example 1 In Example 1, para-xylene was used as a starting material as terephthalic acid, and DMT was used.
The same except that terephthalic acid (total of 4-CBA, p-TA, BA, HDT was 110 ppm and MMT was 1 ppm or less) according to a conventional general production method which did not go through via the hydrolysis and did not use hydrolysis. When I went to, the intrinsic viscosity 0.85, Col-b = -1.5, DEG = 1.3w
t%, AA = 1.5 ppm, oligomer 0.42 wt%
Polyethylene terephthalate of

The preform thus obtained had an intrinsic viscosity of 0.75 and an acetaldehyde content of 12 ppm, and had good moldability and appearance. Further, when blow molding was performed in the same manner as in Example 1, the haze of the bottle was 0.9%.

Compared to the examples, the hue of the polymer (Co
(Ib is high) was poor and the decrease in intrinsic viscosity during remelting and the increase in the amount of acetaldehyde were large.

[Comparative Example 1] In Example 1, paraxylene was used as a starting material as terephthalic acid, but terephthalic acid (4- (4) was obtained through dimethyl terephthalate under insufficient hydrolysis conditions. CBA, p-TA, B
The total of A and HDT is 50ppm, MMT is 1300p
It was pm. ) Was used, the same operation was performed. Intrinsic viscosity 0.85, Col-b = -0.5,
A polyethylene terephthalate containing DEG = 1.3 wt%, AA = 1.5 ppm, and oligomer 0.44 wt% was obtained.

The preform thus obtained had an intrinsic viscosity of 0.74 and an acetaldehyde content of 11 ppm, and had good moldability and appearance. Furthermore, when blow molding was carried out in the same manner as in Example 1, the haze of the bottle was 1.2%.

Compared to the examples, the hue of the polymer (Co
(Ib is high) was poor, the intrinsic viscosity upon remelting and the increase in the amount of acetaldehyde were large, and the transparency was reduced.

[0058]

INDUSTRIAL APPLICABILITY According to the present invention, dimethyl terephthalate recovered from a used polyethylene terephthalate material product is passed through, and terephthalic acid obtained by subsequent hydrolysis is used as a raw material to carry out a polymerization reaction to obtain a product again. It is possible to provide a polyalkylene terephthalate excellent in quality such as transparency, heat stability, hue and the like, which can be used, and a molded article made of the same.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4F071 AA46 AA80 AA81 AF55 AH04                       AH05 BB05 BB06 BC01 BC04                 4J029 AA03 AB01 AB07 AD01 AD10                       AE01 AE03 BA03 CB06 JF471                       KA02 KA03

Claims (10)

[Claims] 1. A polyalkylene terephthalate obtained by polycondensation of terephthalic acid and alkylene glycol in the presence of an antimony catalyst, wherein the terephthalic acid is monomethyl terephthalate of 1000.
4-carboxybenzaldehyde, containing less than ppm
A polyalkylene terephthalate, characterized in that the total content of paratoluic acid, benzoic acid and dimethyl hydroxyterephthalate is 1 ppm or less. 2. The polyalkylene terephthalate according to claim 1, wherein the terephthalic acid is terephthalic acid obtained by subsequent hydrolysis via dimethyl terephthalate recovered from the packaging material polyester. 3. The polyethylene terephthalate according to claim 1, wherein the alkylene glycol is ethylene glycol. 4. The antimony catalyst is antimony trioxide, which is polycondensed in the presence of 100 to 400 ppm in terms of antimony element based on terephthalic acid.
The polyethylene terephthalate according to claim 3. 5. The polyethylene terephthalate according to claim 4, which has an intrinsic viscosity of 0.70 to 0.90, an oligomer (cyclic trimer) content of 0.50% by weight or less, and an acetaldehyde content of 5 ppm or less. 6. A molded article made of the polyalkylene terephthalate according to claim 1. 7. The molded product according to claim 6, which is a bottle-shaped product. 8. The molded product according to claim 6, wherein the molded product is a sheet-shaped product. 9. The molded article according to claim 6, wherein the molded article is a thermoformed container. 10. The molded article is an injection molded article.
Molded product described.