JPH07238155A - Polyester copolymer resin and hollow vessel made therefrom - Google Patents

Abstract

PURPOSE:To obtain a polyester copolymer resin used as a molding material and having transparency, heat resistance and impact resistance. CONSTITUTION:This polyester copolymer resin is one wherein the constituent dicarboxylic acid component comprises 5-70mol% 4-4'-biphenyldicarboxylic acid represented by formula I and the constituent glycol component comprises 5-90mol% compound represented by formula II (wherein p is 1-4; and m and n each is 1-5).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester resin for molding materials having transparency, heat resistance, and impact resistance, and a hollow container using the same.

[0002]

2. Description of the Related Art Currently,
Polyethylene terephthalate (PET) is a material widely used as a transparent packaging material. PET
By stretching, a molded product having excellent impact resistance can be obtained. However, if stretching is not performed, PET
The impact resistance is still insufficient, and when a molding method such as extrusion molding that does not involve stretching is used, the strength of the molded body becomes low. For this reason, PET molding often uses a molding method involving stretching. Molding with stretching,
There was a drawback that the structure and control of the device became complicated. If a sufficiently strong polyester can be obtained without stretching, it is possible to more easily process the polyester having excellent transparency into a molded body.

The same applies to containers, such as polyvinyl chloride,
Polyethylene and other containers are molded by extrusion blow molding,
In the case of PET, the preform is once molded by injection molding,
After that, it is usual to perform container molding by injection biaxial stretch blow molding in which stretch blow is performed, which complicates the structure and control of the equipment and requires running costs such as molds, which is suitable for mass production but a small amount. Not suitable for many varieties. When PET is subjected to extrusion blow molding, there is a problem that the drawdown is large, crystallization occurs, and it is difficult to obtain a uniform transparent container, and the PET container that is not stretched has insufficient impact strength.

Polyvinyl chloride is widely used as a material for packaging materials because it has excellent properties such as moldability and impact resistance. However, in recent years, there is a tendency that there is a problem that polyvinyl chloride containing chlorine atoms may adversely affect the global environment, such as the generation of hydrogen chloride by incineration. It is on the decline. Therefore, if a resin capable of direct blow molding, which has transparency and impact resistance, can be obtained instead of polyvinyl chloride, the capital investment of a molding machine can be dispensed with, and its significance is significant.

As such a polyester resin, a polyester prepared by copolymerizing cyclohexanedimethanol or isophthalic acid has already been known, but a container having a small capacity causes no problem, but a relatively large container having a capacity of 500 ml to 1 liter is resistant. There was a problem that the impact strength was insufficient.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that transparency, heat resistance,
The present invention has been completed by finding a specific copolyester resin having impact resistance, finding that the polyester resin is suitable for extrusion blow molding, and that the resulting hollow container is also excellent in transparency, heat resistance and impact resistance. Came to.

That is, in the present invention, 5 to 70 mol% of the dicarboxylic acid component constituting the polyester is 4,4'-biphenyldicarboxylic acid represented by the following formula (I), and 5 to 90 mol% of the glycol component. Is a compound represented by the following formula (II), and a hollow container using the copolymerized polyester resin.

[0008]

[Chemical 2]

(In the formula, p represents an integer of 1 to 4, m and n each represent an integer of 1 to 5.) 5 to 70 mol% of the dicarboxylic acid component constituting the polyester resin in the present invention is represented by the formula (I 4,4'-biphenyldicarboxylic acid represented by the formula (4), and terephthalic acid is preferably used in addition to the above. Other than terephthalic acid, other dicarboxylic acid components may be contained within the range of less than 20 mol%. Other dicarboxylic acid components include isophthalic acid,
1,5-, 1,6-, 1,7-, 2,6- or 2,
7-naphthalenedicarboxylic acid, phthalic acid, cyclohexanedicarboxylic acid, dibromoisophthalic acid, sodium-
Aromatic dicarboxylic acids such as sulfoisophthalic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, diphenoxyethane dicarboxylic acid, phenylenedioxydiacetic acid, adipic acid, sebacic acid, succinic acid, glutaric acid, piperic acid , Aliphatic acid dicarboxylic acids such as suberic acid, azelaic acid, undecadioic acid, and dodecadioic acid, or a mixture of two or more thereof.

Further, 5 to 90 mol% of the glycol component constituting the polyester resin in the present invention is composed of the compound represented by the formula (II), and a plurality of compounds represented by the formula (II) are combined. The total amount may be 5 to 90 mol%. In the formula (II), p represents an integer of 1 to 4, preferably 1 or 2. Further, m and n each represent an integer of 1 to 5, and those of 1 to 3 are particularly preferable.
When m and n are more than 5, the glass transition temperature (Tg) of the polyester resin obtained by using them becomes low, and mechanical properties such as elastic modulus and tensile strength are deteriorated, which is not preferable.

Examples of the compound represented by the formula (1I) include 1,4-bis (2-hydroxyethoxy) benzene and 1,4-bis (2-hydroxyethoxyethoxy).
Benzene, 4,4'-bis (2-hydroxyethoxy) biphenyl, 4,4'-bis (2-hydroxyethoxy) terphenyl, 4,4'-bis (2-hydroxyethoxy)
Examples thereof include quarterphenyl and 4,4′-bis (2-hydroxyethoxyethoxy) biphenyl. Among them, those in which p is 1 or 2 are preferable, and 1,4-bis (2-
Hydroxyethoxy) benzene and 4,4′-bis (2-hydroxyethoxy) biphenyl are particularly preferably used.

Examples of the glycol component other than the compound represented by the above formula (II) which constitutes the copolyester resin of the present invention include ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol and octamethylene glycol. Aliphatic glycols such as methylene glycol, decamethylene glycol, propylene glycol, neopentylene glycol, diethylene glycol, polyethylene glycol, alicyclic glycols such as cyclohexanedimethanol, o,
Examples thereof include aromatic glycols such as m, p-xylylene glycol, 2,2-bis (4-hydroxyethoxyphenyl) propane and ethylene oxide and propylene oxide adducts thereof, or a mixture of two or more thereof. Of these, ethylene glycol is preferably used, and the compound represented by the formula (II) and glycols other than ethylene glycol are preferably used within the range of less than 20 mol% of the total glycol component of the copolyester resin.

The copolyester resin of the present invention contains 4,4'-biphenyldicarboxylic acid represented by the above formula (I) in the dicarboxylic acid component in an amount of 5 to 70 mol%, preferably 10 to 4 mol%.
The content is 60 mol%, more preferably 25 to 55 mol%. The glycol component contains the compound represented by the formula (II) in an amount of 5 to 90 mol%, preferably 10 to 80 mol%, and more preferably 20 to 60 mol%. 4,4 ′ represented by the above formula (I) in the dicarboxylic acid component
When both the amount of biphenyldicarboxylic acid and the amount of the compound represented by the formula (II) in the glycol component are out of the above ranges, the resin improving effect is small and only a polyester resin having a low impact strength can be obtained. Further, when either the amount of the compound represented by the formula (I) in the dicarboxylic acid component or the amount of the compound represented by the formula (II) in the glycol component is out of the above range, the impact strength is to some extent. Although improved, the impact strength is still at an insufficient level when, for example, a large container of about 1000 ml is used.

In the copolyester resin of the present invention, hydroxycarboxylic acids such as glycolic acid, hydroxybenzoic acid and hydroxynaphthoic acid, hydroquinone, resorcinol, dihydroxydiphenyl, dihydroxydiphenyl ether and 2,2-bis (4-hydroxyphenyl) are further used. ) Diphenol such as propane may be copolymerized. As a method for synthesizing a polyester using these monomers, any method may be used as long as it is a general polyester synthesizing method such as a direct polycondensation method or a transesterification method.

Intrinsic viscosity of the copolyester resin of the present invention (phenol / tetrachloroethane (weight ratio 6/4)
0.5 dL / g or more is preferable, and 0.6 dL / g or more is more preferable. If it is less than 0.5 dl / g, the mechanical properties of the container obtained from this polyester resin are deteriorated, which is not preferable. The glass transition temperature (Tg) of the copolyester resin of the present invention for bottles is preferably 50 to 180 ° C, more preferably 60 to 150 ° C.

The copolymerized polyester resin of the present invention is PE
It has a higher impact resistance than T and can be molded into a sheet, a film, a bottle, and the like, but is particularly preferable as a polyester resin for extrusion blow molding, because extrusion blow molding is easy. It can be used for hollow containers. Further, various additives such as a colorant, an antioxidant, an ultraviolet absorber, an antistatic agent, a flame retardant and the like can be blended with the polyester resin of the present invention as required.

The hollow container of the present invention can be produced by the usual extrusion blow molding method (direct blow molding method) or biaxial stretch blow molding method using the copolymerized polyester resin of the present invention. The method is preferably used. The hollow container obtained by the present invention is excellent in transparency, heat resistance, and mechanical strength, and thus is useful as a substitute container for a polyvinyl chloride container.

[0018]

The present invention will be described in detail below with reference to examples, but these examples do not limit the present invention. The intrinsic viscosity of the polymer was measured at 25 ° C. using a mixed solvent of phenol / tetrachloroethane (weight ratio 6/4). The glass transition temperature (Tg) was measured using a dynamic viscoelasticity measuring device RSA-2 manufactured by Rheometrics. The glass transition temperature was defined as the peak top of the loss elastic modulus when strain was applied at a cycle of 1 Hz. The impact resistance test is JIS-
According to K7110, using injection-molded specimens with a width of 2.5 mm,
A notched Izod impact test was performed and evaluated.

Further, the evaluation of the hollow container was carried out by the following items. <Moldability> It was evaluated whether or not it could be molded into a bottle shape. <Transparency> Evaluation was made by visual observation in three grades of ◯, Δ, and ×. ○: As transparent as PET △: Slightly hazy ×: Opaque <Impact resistance> Add 1000 ml of ion-exchanged water to the container, cap the container, and leave it at 23 ° C and 65% RH for 1 day. Then 1
It was dropped from the height of m to the concrete surface and indicated by how many times it cracked (n = 10 average). Dropped up to 5 times.

Example 1 90 mol of dimethyl terephthalate (17.48 kg), 10 mol of dimethyl 4,4'-biphenyldicarboxylate (2.70 kg), and 1,4 in a reactor equipped with a stirring blade, a nitrogen inlet and a pressure reducing port. -Bis (2-hydroxyethoxy) benzene (in the formula (II), p =
1, m = 1, n = 1) 20 mol (3.96 kg), ethylene glycol 180 mol (11.17 kg), and 10 g each of zinc acetate and germanium dioxide as catalysts were charged. Under a stream of nitrogen 1
The mixture was heated to 80 ° C. for transesterification, and methanol was distilled off. After 4 hours, the theoretical amount of methanol was distilled off, so the temperature was raised to 270 ° C and the pressure was gradually reduced to 0.1.
Polymerized at ~ 0.3 Torr for 5 hours. The resulting polymer is ¹ H
-As a result of analysis by NMR, 90 mol% of the dicarboxylic acid residues constituting the polyester are terephthalic acid units,
10 mol% is 4,4'-biphenyldicarboxylic acid unit, and 19 mol% of the glycol component is 1,4-bis (2-
Hydroxyethoxy) benzene unit, 81 mol% was ethylene glycol unit. Table 1 shows the physical properties of the resin.
Shown in.

After crushing the obtained polymer with a crusher,
Dry at 80 ° C for 1 day, and use an extrusion blow molding machine manufactured by Tahara Seisakusho, capacity about 1000ml, height about 185mm, body width (maximum value) about 105mm, body depth (maximum value) about 85mm, mouth A flat container (weight: about 60 g) having a diameter of about 23 mm was molded. The cylinder temperature was 200 to 250 ° C and the mold temperature was 10 to 40 ° C.
Moldability, transparency and impact resistance of the obtained container were evaluated. The results are shown in Table 1.

Example 2 A polymer was prepared in the same manner as in Example 1 except that the charged amounts of dimethyl terephthalate and dimethyl 4,4'-biphenyldicarboxylate were 70 mol (13.60 kg) and 30 mol (8.10 kg), respectively. Synthesized. As a result of ¹ H-NMR analysis of the obtained polymer, it was confirmed that the dicarboxylic acid residue constituting the polyester
70 mol% is terephthalic acid unit, 30 mol% is 4,4'-
It was a biphenyldicarboxylic acid unit, 19 mol% of the glycol component was 1,4-bis (2-hydroxyethoxy) benzene unit, and 81 mol% was ethylene glycol unit. Table 1 shows the physical properties of the resin and the physical properties of the container obtained by direct blow molding.

Example 3 Dimethyl terephthalate and dimethyl 4,4'-biphenyldicarboxylate were charged at 50 mol (9.71 kg) and 50 mol, respectively.
A polymer was synthesized in the same manner as in Example 1 except that (13.50 kg) was used. As a result of ¹ H-NMR analysis of the obtained polymer, it was confirmed that the dicarboxylic acid residue constituting the polyester
49 mol% is terephthalic acid unit, 51 mol% is 4,4'-
It was a biphenyldicarboxylic acid unit, 19 mol% of the glycol component was 1,4-bis (2-hydroxyethoxy) benzene unit, and 81 mol% was ethylene glycol unit. Table 1 shows the physical properties of the resin and the physical properties of the container obtained by direct blow molding.

Example 4 Dimethyl terephthalate and dimethyl 4,4'-biphenyldicarboxylate were charged at 40 mol (7.77 kg) and 60 mol, respectively.
A polymer was synthesized in the same manner as in Example 1 except that the weight was changed to (16.20 kg). As a result of ¹ H-NMR analysis of the obtained polymer, it was confirmed that the dicarboxylic acid residue constituting the polyester
40 mol% is terephthalic acid unit, 60 mol% is 4,4'-
It was a biphenyldicarboxylic acid unit, and 18 mol% of the glycol component was a 1,4-bis (2-hydroxyethoxy) benzene unit and 82 mol% was an ethylene glycol unit. Table 1 shows the physical properties of the resin and the physical properties of the container obtained by direct blow molding.

Example 5 Dimethyl terephthalate and dimethyl 4,4'-biphenyldicarboxylate were charged at 50 mol (9.71 kg) and 50 mol, respectively.
(13.50kg), 1,4-bis (2-hydroxyethoxy)
Charge benzene (p = 1, m = 1, n = 1 in formula (II)) and ethylene glycol 50 mol (9.9 kg), 150 mol
A polymer was synthesized in the same manner as in Example 1 except that (9.31 kg) was used. As a result of ¹ H-NMR analysis of the obtained polymer, it was found that the dicarboxylic acid residue of the polyester was 49
Mol% is terephthalic acid unit, 51 mol% is 4,4'-biphenyldicarboxylic acid unit, and 49 mol% of glycol component is 1,4-bis (2-hydroxyethoxy).
The benzene unit and 51 mol% were ethylene glycol units. Table 1 shows the physical properties of the resin and the physical properties of the container obtained by direct blow molding.

Example 6 4,4'-instead of 1,4-bis (2-hydroxyethoxy) benzene (in formula (II) p = 1, m = 1, n = 1)
Bis (2-hydroxyethoxy) biphenyl (Formula (II)
A polymer was synthesized in the same manner as in Example 1 except that 20 mol (4.94 kg) of p = 2, m = 1, n = 1) was used. The obtained polymer was analyzed by ¹ H-NMR. As a result, 90 mol% of the dicarboxylic acid residues constituting the polyester were terephthalic acid units, 10 mol% were 4,4′-biphenyldicarboxylic acid units, and 20 mol% is 4,
4'-bis (2-hydroxyethoxy) biphenyl unit, 80 mol% was ethylene glycol unit.
Table 1 shows the physical properties of the resin and the physical properties of the container obtained by direct blow molding.

Example 7 Instead of 1,4-bis (2-hydroxyethoxy) benzene (p = 1, m = 1, n = 1 in the formula (II)) 4,4'-
Bis (2-hydroxyethoxy) biphenyl (Formula (II)
A polymer was synthesized in the same manner as in Example 2 except that 20 mol (4.94 kg) of p = 2, m = 1, n = 1) was used. As a result of ¹ H-NMR analysis of the obtained polymer, 69 mol% of dicarboxylic acid residues constituting the polyester were terephthalic acid units, 31 mol% were 4,4'-biphenyldicarboxylic acid units, and 20 mol% is 4,
4'-bis (2-hydroxyethoxy) biphenyl unit, 80 mol% was ethylene glycol unit.
Table 1 shows the physical properties of the resin and the physical properties of the container obtained by direct blow molding.

Example 8 Instead of 1,4-bis (2-hydroxyethoxy) benzene (p = 1, m = 1, n = 1 in formula (II)) 4,4'-
Bis (2-hydroxyethoxy) biphenyl (Formula (II)
A polymer was synthesized in the same manner as in Example 5 except that 50 mol (12.35 kg) of p = 2, m = 1, n = 1) was used. As a result of ¹ H-NMR analysis of the obtained polymer, 49 mol% of dicarboxylic acid residues constituting the polyester were terephthalic acid units, 51 mol% were 4,4′-biphenyldicarboxylic acid units, and 49 mol% was 4,4'-bis (2-hydroxyethoxy) biphenyl unit and 51 mol% was ethylene glycol unit. Table 1 shows the physical properties of the resin and the physical properties of the container obtained by direct blow molding.

Example 9 1,4-bis (2-hydroxyethoxy) benzene (in formula (II) p = 1, m = 1, n = 1) 1,4-bis instead of 20 mol (3.96 kg) (2-hydroxyethoxy) benzene (in the formula (II), p = 1, m = 1, n = 1) 10 mol (1.98 k
g) and 4,4'-bis (2-hydroxyethoxy) biphenyl (p = 2, m = 1, n = 1 in the formula (II)) 10 moles (2.47k
A polymer was synthesized in the same manner as in Example 1 except that the mixture of g) was used. As a result of ¹ H-NMR analysis of the obtained polymer, 90 mol% of dicarboxylic acid residues constituting the polyester were terephthalic acid units and 10 mol% were 4,4 '.
-Biphenyldicarboxylic acid unit, 9 mol% of the glycol component is 1,4-bis (2-hydroxyethoxy) benzene unit, 10 mol% is 4,4'-bis (2-
Hydroxyethoxy) biphenyl unit, 81 mol% was ethylene glycol unit. Table 1 shows the physical properties of the resin and the physical properties of the container obtained by direct blow molding.

Example 10 1,4-bis (2-hydroxyethoxy) benzene (p = 1, m = 1, n = 1 in the formula (II)) Instead of 20 mol (3.96 kg) 1,4-bis (2-hydroxyethoxy) benzene (in the formula (II), p = 1, m = 1, n = 1) 10 mol (1.98 k
g) and 4,4'-bis (2-hydroxyethoxy) biphenyl (p = 2, m = 1, n = 1 in the formula (II)) 10 moles (2.47k
A polymer was synthesized in the same manner as in Example 3 except that the mixture of g) was used. As a result of ¹ H-NMR analysis of the obtained polymer, 50 mol% of dicarboxylic acid residues constituting the polyester were terephthalic acid units and 50 mol% were 4,4 '.
-Biphenyldicarboxylic acid unit, 9 mol% of the glycol component is 1,4-bis (2-hydroxyethoxy) benzene unit, 10 mol% is 4,4'-bis (2-
Hydroxyethoxy) biphenyl unit, 81 mol% was ethylene glycol unit. Table 1 shows the physical properties of the resin and the physical properties of the container obtained by direct blow molding.

Example 11 1,4-bis (2-hydroxyethoxy) benzene (p = 1, m = 1, n = 1 in the formula (II)) 1,4-bis instead of 50 mol (9.9 kg) (2-hydroxyethoxy) benzene (in the formula (II), p = 1, m = 1, n = 1) 25 mol (4.95 k
g) and 4,4'-bis (2-hydroxyethoxy) biphenyl (in the formula (II), p = 2, m = 1, n = 1) 25 mol (6.18 k
A polymer was synthesized in the same manner as in Example 5 except that the mixture of g) was used. As a result of ¹ H-NMR analysis of the obtained polymer, 50 mol% of dicarboxylic acid residues constituting the polyester were terephthalic acid units and 50 mol% were 4,4 '.
-Biphenyldicarboxylic acid unit, 23 mol% of the glycol component is 1,4-bis (2-hydroxyethoxy) benzene unit, and 25 mol% is 4,4'-bis (2-
Hydroxyethoxy) biphenyl unit, 52 mol% was ethylene glycol unit. Table 1 shows the physical properties of the resin and the physical properties of the container obtained by direct blow molding.

Comparative Example 1 Polyethylene terephthalate was synthesized from only dimethyl terephthalate and ethylene glycol, and a container was formed by direct blow molding in the same manner as in Example 1. Table 1 shows the physical properties of the resin and the physical properties of the container obtained by direct blow molding.

Comparative Example 2 1,4-bis (2-hydroxyethoxy) benzene and ethylene glycol were charged at 3 mol (0.59 kg), respectively.
A polymer was synthesized in the same manner as in Example 1 except that the amount was 197 mol (12.23 kg). The obtained polymer was analyzed by ¹ H-NMR. As a result, 90 mol% of the dicarboxylic acid residues constituting the polyester were terephthalic acid units, 10 mol% were 4,4′-biphenyldicarboxylic acid units, and 3 mol% was 1,4-bis (2-hydroxyethoxy) benzene unit and 97 mol% was ethylene glycol unit. Table 1 shows the physical properties of the resin and the physical properties of the container obtained by direct blow molding.

Comparative Example 3 1,4-bis (2-hydroxyethoxy) benzene and ethylene glycol were charged at 95 mol (18.81 kg) each.
A polymer was synthesized in the same manner as in Example 1 except that the amount was 105 mol (6.51 kg). ¹ H-NMR of the obtained polymer
As a result of analysis, 90 mol% of the dicarboxylic acid residues constituting the polyester are terephthalic acid units and 10 mol%
Was a 4,4′-biphenyldicarboxylic acid unit, 93 mol% of the glycol component was a 1,4-bis (2-hydroxyethoxy) benzene unit, and 7 mol% was an ethylene glycol unit. Table 1 shows the physical properties of the resin and the physical properties of the container obtained by direct blow molding.

Comparative Example 4 Dimethyl 4,4'-biphenyldicarboxylate was not used as the dicarboxylic acid component, and 100 mol of dimethyl terephthalate was used.
(19.42 kg) was used, and the polymer was synthesized in the same manner as in Example 1 except that. As a result of ¹ H-NMR analysis of the obtained polymer, 100 mol% of the dicarboxylic acid residues constituting the polyester were terephthalic acid units, and 20 mol% of the glycol component was 1,4-bis (2-hydroxyethoxy). ) Benzene unit, 80 mol% was ethylene glycol unit. Table 1 shows the physical properties of the resin and the physical properties of the container obtained by direct blow molding. Although this resin has a level of no problem in a container having an impact strength of about 600 ml, it was slightly fragile in a large container such as 1000 ml.

Comparative Example 5 Dimethyl 4,4'-biphenyldicarboxylate was not used as the dicarboxylic acid component, and 100 mol of dimethyl terephthalate was used.
(19.42 kg) was used, and a polymer was synthesized in the same manner as in Example 6 except that. As a result of ¹ H-NMR analysis of the obtained polymer, 100 mol% of the dicarboxylic acid residues constituting the polyester were terephthalic acid units, and 20 mol% of the glycol component was 4,4'-bis (2-hydroxy). Ethoxy) biphenyl unit, 80 mol% was ethylene glycol unit. Table 1 shows the physical properties of the resin and the physical properties of the container obtained by direct blow molding. Although this resin has a level of no problem in a container having an impact strength of about 600 ml, it was slightly fragile in a large container such as 1000 ml.

Comparative Example 6 PETG67, a commercially available resin, manufactured by Eastman Chemical Company
63 (100 mol% of acid component is terephthalic acid unit, about 30 mol% of diol component is cyclohexanedimethanol unit, about 70 mol% is ethylene glycol unit)
Table 1 shows the physical properties of the resin when used with and the physical properties of the container obtained by direct blow molding.

[0038]

[Table 1]

Claims (2)

[Claims] 1. 5-70 mol% of the dicarboxylic acid component constituting the polyester is 4,4′-biphenyldicarboxylic acid represented by the following formula (I), and 5-90 mol of the glycol component.
A copolymerized polyester resin, wherein mol% is a compound represented by the following formula (II). [Chemical 1] (In the formula, p is an integer of 1 to 4, m and n are 1 to 5 respectively.
Indicates an integer. ) 2. A hollow container comprising the copolymerized polyester resin according to claim 1.