JPH04314520A - Manufacture of bottle made of saturated polyester - Google Patents

Abstract

PURPOSE:To improve stress cracking resistance of a bottle, by immersing only the bottom part of the bottle, which is orientation-blown, into a hot water or an organic solvent. CONSTITUTION:A preform made of saturated polyester is orientation-blown and bottle 1 is molded. Then only the bottom part 5 of the bottle 1 is immersed into a hot water or an organic solvent having a temperature of 20-50 deg.C and stress cracking resistance is improved. With this construction, generation of a crack in the bottom part 5 by an external factor such as the temperature or water or chemicals or a solvent is avoided.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for manufacturing a saturated polyester bottle, and more particularly to a method for manufacturing a saturated polyester bottle with excellent stress crack resistance.

0002

TECHNICAL BACKGROUND OF THE INVENTION In recent years, various plastics have been used as materials for bottles for carbonated drinks such as juice and cola. Among them, saturated polyesters such as polyethylene terephthalate are often used as materials for bottles because of their excellent transparency, gas barrier properties, heat resistance, and mechanical strength.

[0003] A bottle made of saturated polyester is shown in Fig. 1(B).
If the bottle is of the round bottom type shown in Figure 1(A), there will be almost no problems such as cracks occurring at the bottom, but if it is a free-standing bottle like the petaloid bottle shown in Figure 1(A), Since a larger stress than usual is applied to the bottom, there is a risk that cracks may occur in the bottom during the distribution stage from liquid filling to sales.

[0004] Free-standing bottles have more complicated bottom shapes than round-bottomed bottles, and there are parts that are difficult to stretch, so residual stress during molding tends to remain around the boundary between the stretched and unstretched parts. For this reason, it is thought that at the bottom of the bottle, the strength of the material decreases mainly due to external influences, and residual stress is released, causing cracks to occur. Temperature, moisture, chemicals, solvents, etc. can be considered as such external factors.

[0005] The inventors of the present invention conducted extensive studies based on such knowledge and found that the occurrence of cracks as described above can be prevented by improving the crystallinity of the unstretched amorphous portion at the bottom of the bottle. The present invention was completed based on the discovery that this can be done.

[0006]

[Object of the Invention] The present invention aims to solve the problems associated with the conventional technology, and has excellent stress crack resistance and is resistant to external factors such as temperature, moisture, chemicals, and solvents. The purpose of the present invention is to provide a method for manufacturing a saturated polyester bottle that does not cause cracks at the bottom.

[0007]

SUMMARY OF THE INVENTION The method for producing a saturated polyester bottle according to the present invention is to form a bottle by stretch-blowing a saturated polyester preform, and then soak only the bottom part of the bottle in warm water at 20 to 50°C or in an organic solvent. It is characterized by being immersed in it.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The method for producing a saturated polyester bottle according to the present invention will be explained below, but first the saturated polyester resin used in the present invention will be explained.

The saturated polyester resins used in the saturated polyester bottle according to the present invention include polyethylene terephthalate resin, polyethylene naphthalate resin, and the following copolymerized polyester resins (1) to (
7), etc.

Each resin will be explained in more detail below. Polyethylene terephthalate resin The polyethylene terephthalate resin used in the saturated polyester bottle according to the present invention is manufactured from terephthalic acid and ethylene glycol as raw materials.

The polyethylene terephthalate resin may be copolymerized with 20 mol % or less of other dicarboxylic acids and/or other dihydroxy compounds other than terephthalic acid and ethylene glycol. In addition to terephthalic acid, examples of dicarboxylic acids used in copolymerization include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, and diphenoxyethanedicarboxylic acid; adipic acid, sebacic acid, and azelain. Examples include aliphatic dicarboxylic acids such as decanedicarboxylic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. Other than ethylene glycol, dihydroxy compounds used in copolymerization include
Specifically, aliphatic glycols such as trimethylene glycol, propylene glycol, tetramethylene glycol, neopentyl glycol, hexamethylene glycol, and dodecamethylene glycol; alicyclic glycols such as cyclohexanedimethanol; bisphenols;
Examples include aromatic diols such as hydroquinone and 2,2-bis(4-β-hydroxyethoxyphenyl)propane.

[0012] Such a polyethylene terephthalate resin is a substantially linear polyester formed by ethylene terephthalate component units alone or by randomly arranging the ethylene terephthalate component units and dioxyethylene terephthalate component units to form ester bonds. is forming. The fact that the polyethylene terephthalate resin is substantially linear is confirmed by dissolving the polyethylene terephthalate resin in o-chlorophenol.

[0013] Such polyethylene terephthalate resin has an intrinsic viscosity [η] (25
It is desirable that the value (measured at °C) is usually 0.6 to 1.5 dl/g, preferably 0.7 to 1.2 dl/g. In addition, the melting point is usually 210°C to 265°C, preferably 210°C to 265°C.
It is desirable that the temperature is 20 to 260°C, and the glass transition temperature is usually 50 to 120°C, preferably 60 to 100°C.

Polyethylene naphthalate resin The polyethylene naphthalate resin used in the saturated polyester bottle according to the present invention is produced from 2,6-naphthalene dicarboxylic acid and ethylene glycol.

This polyethylene naphthalate resin contains 4
Less than 0 mol % of other dicarboxylic acids and/or other than 2,6-naphthalenedicarboxylic acid and ethylene glycol
Alternatively, other dihydroxy compounds may be copolymerized.

In addition to 2,6-naphthalene dicarboxylic acid, dicarboxylic acids used in copolymerization include terephthalic acid, isophthalic acid, 2,7-naphthalene dicarboxylic acid, 2,5-naphthalene dicarboxylic acid, and diphenyl- Aromatic dicarboxylic acids such as 4,4'-dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 4,4'-diphenylsulfone dicarboxylic acid, 4,4'-diphenoxyethane dicarboxylic acid, dibromoterephthalic acid; adipine aliphatic dicarboxylic acids such as azelaic acid, sebacic acid, and decanedicarboxylic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, cyclopropanedicarboxylic acid, and hexahydroterephthalic acid; glycolic acid, p-hydroxybenzoic acid Examples include acids, hydroxycarboxylic acids such as p-hydroxyethoxybenzoic acid, and the like.

In addition to ethylene glycol, dihydroxy compounds used in copolymerization include propylene glycol, trimethylene glycol, diethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol, neopentyl glycol, p-xylene glycol, 1,4-cyclohexanedimethanol, bisphenol A, p,p-diphenoxysulfone, 1,4
-bis(β-hydroxyethoxy)benzene, 2,2-
Bis(p-β-hydroxyethoxyphenol)propane, polyalkylene glycol, p-phenylenebis(
(dimethylsiloxane), glycerin, etc.

[0018] The polyethylene naphthalate resin used in the present invention also contains a small amount, for example, 2 mol% or less, of structural units derived from polyfunctional compounds such as trimesic acid, trimethylolethane, trimethylolpropane, trimethylolmethane, and pentaerythritol. It may be included in an amount of

Furthermore, the polyethylene naphthalate resin used in the present invention contains a small amount, for example 2 moles, of a constituent unit derived from a monofunctional compound such as benzoylbenzoic acid, diphenylsulfone monocarboxylic acid, stearic acid, methoxypolyethylene glycol, or phenoxypolyethylene glycol. % or less.

Such polyethylene naphthalate resins are substantially linear, which is confirmed by their dissolution in o-chlorophenol.

The intrinsic viscosity [η] of polyethylene naphthalate resin measured in o-chlorophenol at 25°C is:
0.2-1.1dl/g, preferably 0.3-0.9d
l/g, particularly preferably in the range of 0.4 to 0.8 dl/g.

The intrinsic viscosity [η] of the polyethylene naphthalate resin is measured by the following method. That is, polyethylene naphthalate resin was dissolved in o-chlorophenol at a concentration of 1 g/100 ml, and the solution viscosity was measured using an Ubbelohde capillary viscometer at 25°C.
After that, o-chlorophenol was gradually added, the solution viscosity on the low concentration side was measured, and the concentration was increased to 0%, and the intrinsic viscosity (
[η]).

[0023] Further, the crystallization temperature (Tc) of polyethylene naphthalate resin when heated at a rate of 10°C/min using a differential scanning calorimeter (DSC) is usually 150°C or higher, and preferably 160-230°C, more preferably 1
It is desirable that the temperature is in the range of 70 to 220°C.

The elevated temperature crystallization temperature (Tc) of polyethylene naphthalate resin is measured by the following method. That is, using a PerkinElmer Model DSC-2 differential calorimeter, about 10 mg of a sample was collected from the center of a polyethylene naphthalate resin chip that had been dried at about 140°C and under a pressure of about 5 mmHg for about 5 hours or more. The flakes are sealed in an aluminum liquid pan under a nitrogen atmosphere and measured. The measurement conditions were as follows: First, the temperature was rapidly raised from room temperature to 290°C for 10
After holding the melt for a minute, it was rapidly cooled to room temperature, and then for 10 minutes.
The apex temperature of the exothermic peak detected when the temperature is raised at a heating rate of °C/min is determined.

Copolymerized polyester resin (1) The copolymerized polyester resin (1) used in the saturated polyester bottle according to the present invention contains a dicarboxylic acid constituent unit containing a terephthalic acid component unit and an isophthalic acid component unit, and an ethylene glycol component. It is formed from dihydroxy compound constituent units containing units.

The dicarboxylic acid constituent units constituting this copolymerized polyester resin (1) include terephthalic acid component units in an amount of 85 to 99.5 mol%, preferably 90 to 99.5 mol%, and isophthalic acid component units. Component unit is 0.5-15
Desirably, it is present in an amount of mol %, preferably 0.5 to 10 mol %.

Copolymerized polyester resin (1) according to the present invention
), in addition to the above-mentioned terephthalic acid and isophthalic acid, the dicarboxylic acid component is used within a range that does not impair the properties of the resulting copolyester resin (1), such as 1
Other dicarboxylic acids can also be used in amounts up to mole percent.

Examples of such dicarboxylic acids include phthalic acid, 2-methylterephthalic acid, and 2,6-naphthalene dicarboxylic acid. In addition, in the copolyester resin (1) according to the present invention, in addition to ethylene glycol as described above, the dihydroxy compound may be added in an amount within a range that does not impair the properties of the resulting copolyester resin (1), for example, 1 mol% or less. Other dihydroxy compounds can also be used.

Such dihydroxy compounds include:
1,3-propanediol, 1,4-butanediol,
Neopentyl glycol, cyclohexanediol, cyclohexanedimethanol, 1,3-bis(2-hydroxyethoxy)benzene, 1,4-bis(2-hydroxyethoxy)benzene, 2,2-bis(4-β-hydroxyethoxyphenyl) ) propane, bis(4-β-hydroxyethoxyphenyl)sulfone, and other dihydroxy compounds having 3 to 15 carbon atoms.

Copolymerized polyester resin (2) The copolymerized polyester resin (2) used in the saturated polyester bottle according to the present invention is a dicarboxylic acid constituent unit containing a terephthalic acid component unit and a 2,6-naphthalene dicarboxylic acid component unit. and a dihydroxy compound structural unit containing an ethylene glycol component unit.

The dicarboxylic acid constituent units constituting this copolymerized polyester resin (2) contain terephthalic acid component units in an amount of 80 to 99.5 mol%, preferably 90 to 99.5 mol%, and 2, It is desirable that the 6-naphthalene dicarboxylic acid component units are present in an amount of 0.5 to 20 mol%, preferably 0.5 to 10 mol%.

Copolymerized polyester resin (2) according to the present invention
), in addition to the above-mentioned terephthalic acid and 2,6-naphthalene dicarboxylic acid, other dicarboxylic acid components are used in an amount that does not impair the properties of the resulting copolyester resin (2), for example, 1 mol% or less. Dicarboxylic acids can also be used.

Examples of such dicarboxylic acids include isophthalic acid, phthalic acid, and 2-methylterephthalic acid. In addition, in the copolymerized polyester resin (2) according to the present invention, in addition to the above-mentioned ethylene glycol, the dihydroxy compound may be added within a range that does not impair the properties of the resulting copolymerized polyester resin (2), for example, 1
Other dihydroxy compounds can also be used in amounts up to mole percent.

[0034] Such dihydroxy compounds include:
1,3-propanediol, 1,4-butanediol,
Neopentyl glycol, cyclohexanediol, cyclohexanedimethanol, 1,3-bis(2-hydroxyethoxy)benzene, 1,4-bis(2-hydroxyethoxy)benzene, 2,2-bis(4-β-hydroxyethoxyphenyl) ) propane, bis(4-β-hydroxyethoxyphenyl)sulfone, and other dihydroxy compounds having 3 to 15 carbon atoms.

Copolymerized polyester resin (3) The copolymerized polyester resin (3) used in the saturated polyester bottle according to the present invention contains a dicarboxylic acid constituent unit containing a terephthalic acid component unit and an adipic acid component unit,
It is formed from a dihydroxy compound structural unit containing an ethylene glycol component unit.

The dicarboxylic acid constituent units constituting this copolymerized polyester resin (3) include terephthalic acid component units in an amount of 85 to 99.5 mol%, preferably 90 to 99.5 mol%, and adipic acid component units in an amount of 85 to 99.5 mol%, preferably 90 to 99.5 mol%. It is desirable that the component units are present in an amount of 0.5 to 15 mol%, preferably 0.5 to 10 mol%.

Copolymerized polyester resin (3) according to the present invention
), other dicarboxylic acids may be used as the dicarboxylic acid component in addition to the above-mentioned terephthalic acid and adipic acid in an amount that does not impair the properties of the resulting copolyester resin (3), for example, in an amount of 1 mol% or less. You can also do it.

Examples of such dicarboxylic acids include isophthalic acid, phthalic acid, 2-methylterephthalic acid, 2,6-
Examples include naphthalene dicarboxylic acid. Moreover, in the copolymerized polyester resin (3) according to the present invention,
In addition to ethylene glycol as a dihydroxy compound,
Other dihydroxy compounds can also be used in an amount that does not impair the properties of the resulting copolyester resin (3), for example, in an amount of 1 mol % or less.

Such dihydroxy compounds include:
1,3-propanediol, 1,4-butanediol,
Neopentyl glycol, cyclohexanediol, cyclohexanedimethanol, 1,3-bis(2-hydroxyethoxy)benzene, 1,4-bis(2-hydroxyethoxy)benzene, 2,2-bis(4-β-hydroxyethoxyphenyl) ) propane, bis(4-β-hydroxyethoxyphenyl)sulfone, and other dihydroxy compounds having 3 to 15 carbon atoms.

Copolymerized polyester resin (4) The copolymerized polyester resin (4) used in the saturated polyester bottle according to the present invention contains dicarboxylic acid constituent units including terephthalic acid constituent units, ethylene glycol constituent units, and diethylene glycol constituent units. It is formed from a dihydroxy compound constituent unit containing.

The dihydroxy compound constituent units constituting this copolymerized polyester resin (4) contain 93 to 98 mol%, preferably 95 to 98 mol% of ethylene glycol component units.
It is desirable that the diethylene glycol component units are present in an amount of 2 to 7 mol %, preferably 2 to 5 mol %.

Copolymerized polyester resin (4) according to the present invention
), other dicarboxylic acids may be used as the dicarboxylic acid component in addition to the above-mentioned terephthalic acid in an amount that does not impair the properties of the resulting copolyester resin (4), for example, in an amount of 1 mol % or less.

Examples of such dicarboxylic acids include isophthalic acid, phthalic acid, 2-methylterephthalic acid, 2,6-
Examples include naphthalene dicarboxylic acid. Moreover, in the copolymerized polyester resin (4) according to the present invention,
In addition to the above-mentioned ethylene glycol and diethylene glycol, other dihydroxy compounds can also be used in an amount that does not impair the properties of the resulting copolyester resin (4), for example, in an amount of 1 mol% or less.

[0044] Such dihydroxy compounds include:
1,3-propanediol, 1,4-butanediol,
Neopentyl glycol, cyclohexanediol, cyclohexanedimethanol, 1,3-bis(2-hydroxyethoxy)benzene, 1,4-bis(2-hydroxyethoxy)benzene, 2,2-bis(4-β-hydroxyethoxyphenyl) ) Dihydroxy compounds having 3 to 15 carbon atoms such as propane and bis(4-β-hydroxyethoxyphenyl)sulfone are used.

Copolymerized polyester resin (5) The copolymerized polyester resin (5) used in the saturated polyester bottle according to the present invention contains dicarboxylic acid constituent units including terephthalic acid constituent units, ethylene glycol constituent units, and neopentyl glycol. It is formed from a dihydroxy compound structural unit containing a component unit.

The dihydroxy compound constituent units constituting this copolymerized polyester resin (5) contain 85 to 99.5 mol% of ethylene glycol component units, preferably 90 to 99.5 mol%.
In an amount of 99.5 mol %, the neopentyl glycol component unit is also 0.5 to 15 mol %, preferably 0.5 to 1
Preferably, it is present in an amount of 0 mol%.

Copolymerized polyester resin (5) according to the present invention
), other dicarboxylic acids can be used as the dicarboxylic acid component in addition to the above-mentioned terephthalic acid in an amount that does not impair the properties of the obtained copolyester resin (5), for example, in an amount of 1 mol % or less.

Examples of such dicarboxylic acids include isophthalic acid, phthalic acid, 2-methylterephthalic acid, 2,6-
Examples include naphthalene dicarboxylic acid. Moreover, in the copolymerized polyester resin (5) according to the present invention,
In addition to the above-mentioned ethylene glycol and neopentyl glycol as the dihydroxy compound, a range that does not impair the properties of the resulting copolyester resin (5),
Other dihydroxy compounds can also be used, for example in amounts up to 1 mole percent.

Such dihydroxy compounds include:
1,3-propanediol, 1,4-butanediol,
Cyclohexanediol, cyclohexanedimethanol, 1,3-bis(2-hydroxyethoxy)benzene,
1,4-bis(2-hydroxyethoxy)benzene, 2
, 2-bis(4-β-hydroxyethoxyphenyl)propane, bis(4-β-hydroxyethoxyphenyl)
Dihydroxy compounds having 3 to 15 carbon atoms such as sulfone can be mentioned.

Copolymerized polyester resin (6) The copolymerized polyester resin (6) used in the saturated polyester bottle according to the present invention contains a dicarboxylic acid constituent unit containing a terephthalic acid component unit, an ethylene glycol component unit, and cyclohexanedimethanol. It is formed from a dihydroxy compound structural unit containing a component unit.

The dihydroxy compound constituent units constituting this copolymerized polyester resin (6) contain 85 to 99.5 mol% of ethylene glycol component units, preferably 90 to 99.5 mol%.
In an amount of 99.5 mol %, the cyclohexanedimethanol component unit is also 0.5 to 15 mol %, preferably 0.5 mol %.
Desirably, it is present in an amount of ~10 mole %.

Copolymerized polyester resin (6) according to the present invention
), other dicarboxylic acids may be used as the dicarboxylic acid component in addition to the above-mentioned terephthalic acid in an amount that does not impair the properties of the obtained copolyester resin (6), for example, in an amount of 1 mol % or less.

Examples of such dicarboxylic acids include isophthalic acid, phthalic acid, 2-methylterephthalic acid, 2,6-
Examples include naphthalene dicarboxylic acid. Moreover, in the copolymerized polyester resin (6) according to the present invention,
In addition to the above-mentioned ethylene glycol and cyclohexanedimethanol as the dihydroxy compound, other dihydroxy compounds can also be used in an amount that does not impair the properties of the resulting copolyester resin (6), for example, 1 mol% or less.

[0054] Such dihydroxy compounds include:
1,3-propanediol, 1,4-butanediol,
Cyclohexanediol, 1,3-bis(2-hydroxyethoxy)benzene, 1,4-bis(2-hydroxyethoxy)benzene, 2,2-bis(4-β-hydroxyethoxyphenyl)propane, bis(4-β) -3 carbon atoms such as hydroxyethoxyphenyl) sulfone
~15 dihydroxy compounds are used.

Copolymerized polyester resin (7) The copolymerized polyester resin (7) used in the saturated polyester bottle according to the present invention contains a dicarboxylic acid constituent unit,
It is formed from a dihydroxy compound structural unit and a polyfunctional hydroxy compound structural unit having at least three hydroxy groups.

The dicarboxylic acid constituent units constituting this copolymerized polyester resin (7) include isophthalic acid component units in an amount of 20 to 100 mol%, preferably 50 to 98 mol%, and terephthalic acid component units in an amount of 0 to 100 mol%. Desirably it is present in an amount of ~80 mol%, preferably 0.5-50 mol%.

[0057] In addition, the dihydroxy compound constituent units include dihydroxyethoxy resol component units in an amount of 5 to 90 mol%.
, preferably in an amount of 10 to 85 mol%, and ethylene glycol component units in an amount of 10 to 95 mol%, preferably 1
Preferably, it is present in an amount of 5 to 90 mol%.

[0058] This copolymerized polyester resin (7) contains:
A polyfunctional hydroxy compound unit having at least three hydroxy groups is present. This polyfunctional hydroxy compound structural unit is 0.05 to 1.0 mol part, preferably 0.1 mol part per 100 mol parts of dicarboxylic acid component units.
Preferably, it is present in an amount of ~0.5 mole part.

Such polyfunctional hydroxy compound structural units are derived from compounds such as trimethylolmethane, trimethylolethane, and trimethylolpropane, among which trimethylolpropane is preferred.

Copolyester resin (7) according to the present invention
), in addition to the above-mentioned isophthalic acid and terephthalic acid as the dicarboxylic acid component, a range that does not impair the properties of the resulting copolyester resin (7), such as 1
Other dicarboxylic acids can also be used in amounts up to mole percent.

Examples of such dicarboxylic acids include isophthalic acid, phthalic acid, 2-methylterephthalic acid, 2,6-
Examples include naphthalene dicarboxylic acid. In the copolymerized polyester resin (7) according to the present invention, in addition to the dihydroxy ethoxy resol and ethylene glycol as described above, the dihydroxy compound may be used in a range that does not impair the properties of the copolymerized polyester resin (7) obtained.
Other dihydroxy compounds can also be used, for example in amounts up to 1 mole percent.

[0062] Such dihydroxy compounds include:
1,3-propanediol, 1,4-butanediol,
Neopentyl glycol, cyclohexanediol, cyclohexanedimethanol, 1,3-bis(2-hydroxyethoxy)benzene, 1,4-bis(2-hydroxyethoxy)benzene, 2,2-bis(4-β-hydroxyethoxyphenyl) ) Dihydroxy compounds having 3 to 15 carbon atoms such as propane and bis(4-β-hydroxyethoxyphenyl)sulfone are used.

Note that the above copolymerized polyester resin (1
The molecular weights of ) to (7) are not particularly limited as long as they are within a range that allows various molded articles, such as bottles, to be produced from the resulting saturated polyester resin composition, but usually copolymerized polyester resins in an o-chlorophenol solvent are used. It is desirable that the intrinsic viscosity [η] of is in the range of 0.5 dl/g to 1.5 dl/g or more, preferably 0.6 to 1.2 dl/g.

[0064] Each of the resins constituting the saturated polyester bottle as described above can be manufactured by conventionally known manufacturing methods. In addition, various compounding agents such as cross-linking agents, heat-resistant stabilizers, weather-resistant stabilizers, antistatic agents, lubricants, mold release agents, inorganic fillers, pigment dispersants, pigments, or dyes are added to each of the above resins. It can be added within a range that does not impair the purpose of the present invention.

Next, a method for manufacturing a saturated polyester bottle according to the present invention will be specifically explained. The saturated polyester bottle according to the present invention includes a spout 2, an upper shoulder 3, a body 4, and a bottom 5, as illustrated in FIG. 1(A).

[0066] To manufacture such a bottle, first,
A preform is manufactured from the resin as described above, and the preform can be manufactured by a conventionally known method such as injection molding or extrusion molding. The heating temperature of saturated polyester for preform formation varies depending on the saturated polyester used, but for example, when the saturated polyester resin is polyethylene terephthalate resin, the heating temperature is 9.
It is preferable that it is 0-110 degreeC.

[0067] Next, the molded preform is heated to an appropriate temperature for stretching and stretch blow molding is performed to produce a petaloid bottle. Only the bottom of the bottle thus obtained is immersed in warm water or an organic solvent. Organic solvents used in this case include acetone, methyl alcohol, ethyl alcohol, benzene, toluene, xylene,
Carbon tetrachloride, ethyl acetate, tetrachloroethane, methyl ethyl ketone, etc. can be used, with acetone being particularly preferred.

The temperature and time during immersion vary depending on the saturated polyester used and whether the saturated polyester resin is immersed in warm water or an organic solvent. The temperature of hot water is usually 20-50℃
, preferably 30 to 40°C, and the immersion time is usually 1
~5 hours, preferably 2 to 5 hours. Further, when the saturated polyester resin is a polyethylene terephthalate resin and acetone is used as a solvent, the temperature of the acetone is usually 15 to 30°C, preferably 1
The temperature is 5 to 25°C, and the immersion time is usually 1 to 10 hours, preferably 2 to 7 hours.

By immersing only the bottom of the bottle in hot water or an organic solvent as described above, the degree of crystallinity of the surface layer of the bottom of the bottle, which is insufficiently crystallized, increases, resulting in a bottle with excellent stress crack resistance. Obtainable.

[0070] The density of the polyethylene terephthalate resin forming the bottle varies depending on the degree of stretching even in the bottom part, and when no dipping treatment is performed, the density is 1.33.
Although it is about 5 to 1.337 g/cm3, it is preferable to control it to 1.338 g/cm3 or more by performing a dipping treatment.

[0071]

Effects of the Invention The method for producing a saturated polyester bottle according to the present invention involves stretching and blow-molding a saturated polyester preform to form a bottle, and then immersing only the bottom of the bottle in warm water or an organic solvent. As a result, the resulting bottle has excellent stress crack resistance and does not develop cracks at the bottom due to external factors such as temperature, moisture, chemicals, and solvents.

[0072]

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

[0073] In this specification, the stress crack resistance of the bottle is evaluated as follows. [Evaluation of stress crack resistance] 1480ml in bottle
After filling with water, this water is converted to C by the citric acid-baking soda method.
The O2 concentration was adjusted to 4 gas volume. Thereafter, the bottle was left in an oven at 40° C. and 90% relative humidity, and cracks occurring at the bottom of the bottle were visually observed every 1 day, 3 days, 7 days, and 30 days.

[0074]

[Example 1] Polyethylene terephthalate [J135 manufactured by Mitsui Pet Resin Co., Ltd.] was added to M-70 manufactured by Meiki Seisakusho Co., Ltd.
B A preform was obtained by molding with an injection molding machine. The molding temperature at this time was 290°C.

Next, the preform is heated to a surface temperature of 90 to 100 at the center of the preform body using the attached infrared heater.
CORPOPLAST manufactured by heating to ℃.
A petaloid bottle as shown in FIG. 1 was molded by stretch blowing using an LB-01 molding machine.

[0076] Only the bottom of the obtained bottle was immersed in warm water at 40°C for 2 hours. The bottles thus obtained were evaluated for stress crack resistance as defined in the specification. The results are shown in Table 1.

[0077]

[Example 2] Only the bottom of a bottle molded in the same manner as in Example 1 was immersed in acetone at 23°C for 7 hours.

Regarding the bottle thus obtained,
The stress crack resistance defined in the specification was evaluated. The results are shown in Table 1.

[0079]

[Comparative Example 1] A bottle was prepared in the same manner as in Example 1 except that the bottle was not immersed in hot water.

[0080] This bottle was evaluated for stress crack resistance as defined in the specification in the same manner as in Example 1. The results are shown in Table 1.

[0081]

[Table 1]

[Brief explanation of the drawing]

FIG. 1 (A) is a schematic explanatory diagram of a petaloid bottle. (B) is a schematic explanatory diagram of a round bottom bottle.

[Explanation of symbols]

1 bottle 2. Spout part 3 Upper shoulder 4 Torso 5 Bottom

Claims (1)

[Claims] 1. A saturated polyester bottle characterized in that after a saturated polyester preform is stretch-blown to form a bottle, only the bottom of the bottle is immersed in warm water or an organic solvent at 20 to 50°C. manufacturing method.