JP3391872B2 - Plastic square bottle manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a plastic rectangular bottle.

[0002]

2. Description of the Related Art In recent years, various plastic materials have been used as materials for juice, natural water, tea and other beverage bottles. Among them, saturated polyester resins such as polyethylene terephthalate are transparent, gas barrier, heat resistant and It is widely used because of its excellent mechanical strength.

In order to manufacture a rectangular bottle 1 as shown in FIG. 1 using plastic as a raw material, conventionally, an injection molding machine is used.
A cylindrical preform 2 as shown in Fig. 3 (Fig. 3 shows its cross-sectional shape) is formed, and then the obtained preform 2 is obtained.
The bottles are manufactured by stretch-blowing with a biaxial stretch-blowing molding machine, and the cross-section in the horizontal direction at each height (cross-section)
The variation in the thickness of the bottle was very large, and the ratio between the minimum thickness and the maximum thickness was sometimes doubled, and the mechanical properties of the bottle, particularly the dimensional stability such as deformation, were poor.

[0004]

When the bottle obtained as described above is filled with the liquid heat-sterilized at room temperature or high temperature under normal pressure or pressure, the residual strain is generated when the wall thickness largely varies. It is not constant and causes problems such as bottle deformation, shrinkage, and expansion. Further, from the economical point of view, in order to reduce the weight of the bottle, it is absolutely necessary to reduce the variation in wall thickness.

According to the present invention, the residual strain is constant and the deformation, contraction,
An object of the present invention is to provide a method for producing a plastic rectangular bottle which is excellent in dimensional stability such as expansion and has little variation in wall thickness and is economically excellent.

[0006]

As a result of experiments, the inventors of the present invention have found that the thickness y at each position excluding the bottle cap portion is 0.8x ≦ y ≦ with respect to the average horizontal thickness x at that position. 1.2x
It has been found that the dimensional stability of the bottle is excellent when the relationship of (1) is satisfied. The present inventors have also found that the cause of the lack of dimensional stability such as deformation, shrinkage, and expansion of the plastic rectangular bottle is that the bottle 1 as shown in FIG. When a bottle is manufactured using a conventional cylindrical preform, the stretch ratio is different between the surface 1a on the long side and the surface 1b on the short side at any height of the bottle,
As a result, we thought that the thickness of the cross section of the body in the horizontal direction was not uniform and the residual strain (residual stress) was not constant, and as a result of diligent study, we found that dimensional stability against deformation, shrinkage, expansion, etc. In order to bring about, the horizontal cross-sectional shape of the preform when stretch-blowing from the preform to the bottle should be similar to the horizontal cross-sectional shape of the rectangular bottle, which can reduce the thickness of the horizontal cross-sectional shape of the bottle body. The inventors have found that they can be made uniform and have completed the present invention.

Therefore, in the method for manufacturing a plastic rectangular bottle of the present invention, the thickness of the body up to each height is represented by the following equation.
In the method of manufacturing plastic rectangular bottles,
The horizontal cross section of at least the trunk is substantially the same as that of a rectangular bottle.
Form a preform of similar shape and then draw it.
And wherein the Su Rukoto. 0.8x ≦ y ≦ 1.2x y: Thickness of bottle in horizontal direction at each height x: Average thickness of bottle in horizontal direction at each height In the bottle of the present invention, dimensional stability such as deformation, shrinkage, expansion, etc. It is excellent in cost performance, has less variation in wall thickness, and has less excess meat, so it is economically superior.

In the bottle manufacturing method according to the present invention, a preform having a horizontal cross-sectional shape substantially similar to that of a rectangular bottle is formed at each position except the bottle cap portion, and then the preform is stretched and blown. However , when manufacturing a preform of similar shape, it is advisable to add R to the corner portion of the horizontal cross section. According to the present invention, by using a rectangular bottle and a preform having a similar cross-section, the long side and the short side of the body are stretched at the same stretch ratio during stretching from the preform to the bottle. Therefore, the thickness of the cross section of the body is made uniform, and the crystallization density is made constant, so that it is possible to obtain a bottle having excellent dimensional stability such as deformation, shrinkage, expansion, etc., and weight reduction of the bottle. You can also

The plastic used as the material for the bottle of the present invention is preferably a saturated polyester resin, and examples of the saturated polyester resin include polyethylene terephthalate resin, polyethylene naphthalate resin and the following copolymerized polyester resins (1) to (7). It is illustrated. Hereinafter, these resins will be specifically described.

Polyethylene terephthalate resin is produced by using terephthalic acid and ethylene glycol as raw materials.
Up to 0 mol% of other dicarboxylic acids and / or other dihydroxy compounds may be copolymerized. Specific examples of dicarboxylic acids used for copolymerization other than terephthalic acid include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid; adipic acid, sebacic acid, and azelaine. Examples thereof include acids and aliphatic dicarboxylic acids such as decanedicarboxylic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid.

As dihydroxy compounds used for copolymerization other than ethylene glycol, specifically, aliphatic glycols such as trimethylene glycol, propylene glycol, tetramethylene glycol, neopentyl glycol, hexamethylene glycol and dodecamethylene glycol; cyclohexane Alicyclic glycols such as dimethanol; bisphenols; hydroquinone, 2,
Examples thereof include aromatic diols such as 2-bis (4-β-hydroxyethoxyphenyl) propane.

Such a polyethylene terephthalate resin is a polyester which is substantially linear by forming ethylene terephthalate component units alone or by randomly arranging the ethylene terephthalate component units and the dioxyethylene terephthalate component units to form an ester bond. Is forming. The fact that the polyethylene terephthalate resin is substantially linear is confirmed by the fact that the polyethylene terephthalate resin is dissolved in o-chlorophenol.

Such a polyethylene terephthalate resin has an intrinsic viscosity [η] (25 in o-chlorophenol).
The value measured at 0 ° C. is usually 0.6 to 1.5 dl / g, preferably 0.7 to 1.2 dl / g. The melting point measured by a differential scanning calorimeter (DSC) is usually 210 ° C to 265 ° C, preferably 220 ° C to 260 ° C.
℃ is desirable, glass transition temperature is usually 50 ℃
It is desirable that the temperature is 120 ° C to 120 ° C, preferably 60 ° C to 100 ° C.

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

The melting point, glass transition temperature and the like are measured by the following methods. That is, DS manufactured by Perkin Elmer
Approximately 5 mm at approximately 140 ° C using a C-7 scanning calorimeter
Approximately 10 samples taken from the center of polyethylene naphthalate resin chips dried under Hg pressure for about 5 hours or more
A thin slice of mg is enclosed in an aluminum pan for liquid under N ₂ gas atmosphere for measurement. The measurement conditions are as follows: the peak temperature of the exothermic peak detected when the temperature is rapidly raised from room temperature, melted and held at 290 ° C. for 10 minutes, rapidly cooled to room temperature, and then heated at a temperature rising rate of 10 ° C./min. Ask for.

The polyethylene naphthalate resin is 2,6
-It is desirable that the ethylene-2,6-naphthalate unit derived from naphthalenedicarboxylic acid and ethylene glycol is contained in an amount of 60 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more, Constituent units other than ethylene-2,6-naphthalate may be contained in an amount of less than 40 mol%.

As constitutional units other than ethylene-2,6-naphthalate, terephthalic acid, isophthalic acid, 2,7
-Naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, 4,4
Aromatic dicarboxylic acids such as ′ -diphenyl ether dicarboxylic acid, 4,4′-diphenyl sulfone dicarboxylic acid, 4,4′-diphenoxyethane dicarboxylic acid and dibromoterephthalic acid; adipic acid, azelaic acid, sebacic acid, decane dicarboxylic acid Aliphatic dicarboxylic acids such as;
Alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, cyclopropanedicarboxylic acid and hexahydroterephthalic acid; hydroxycarboxylic acids such as glycolic acid, p-hydroxybenzoic acid and p-hydroxyethoxybenzoic acid, and propylene glycol, Trimethylene glycol, diethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol, neopentylene 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-phenylene bi Examples thereof include structural units derived from bis (dimethylsiloxane), glycerin and the like.

Further, the polyethylene naphthalate resin contains a small amount of structural units derived from a polyfunctional compound such as trimesic acid, trimethylolethane, trimethylolpropane, trimethylolmethane, and pentaerythritol, for example, 2 mol% or less. You can leave. Further, the polyethylene naphthalate resin contains a small amount of structural units derived from a monofunctional compound such as benzoylbenzoic acid, diphenylsulfone monocarboxylic acid, stearic acid, methoxypolyethylene glycol and phenoxypolyethylene glycol, for example, 2 mol% or less. You may stay.

Such polyethylene naphthalate resin is substantially linear, which is confirmed by the dissolution of the polyethylene naphthalate resin in o-chlorophenol. Polyethylene naphthalate resin o
The intrinsic viscosity [η] measured in chlorophenol at 25 ° C. is from 0.2 to 1.1 dl / g, preferably 0.3
To 0.9 dl / g, particularly preferably 0.4 to 0.8 d
It is preferably in the range of 1 / g.

The temperature rising crystallization temperature (Tc) of the polyethylene naphthalate resin when heated with a differential scanning calorimeter (DSC) at a rate of 10 ° C./min is usually 150 ° C. or higher, preferably. It is desirable to be in the range of 160 ° C to 230 ° C, more preferably 170 ° C to 220 ° C. The copolymerized polyester resin (1) is composed of a dicarboxylic acid constituent unit containing a terephthalic acid component unit and an isophthalic acid component unit, and a dihydroxy compound constituent unit containing an ethylene glycol component unit.

The dicarboxylic acid constitutional unit constituting the copolyester resin (1) contains the terephthalic acid component unit in an amount of 85 to 99.5 mol%, preferably 90 to 99.5 mol%, and the isophthalic acid component. It is desirable that the units are present in an amount of 0.5 to 15 mol%, preferably 0.5 to 10 mol%. In the copolymerized polyester resin (1), other than the above-mentioned terephthalic acid as the dicarboxylic acid component, other dicarboxylic acids can be used in a range that does not impair the characteristics of the copolymer polyester resin (1) obtained, for example, 1 mol% or less. Acids can also be used.

Examples of such dicarboxylic acids include phthalic acid, 2-methylterephthalic acid and 2,6-naphthalenedicarboxylic acid. In the copolymerized polyester resin (1), other than the ethylene glycol as described above as a dihydroxy compound, other dihydroxy compounds may be used in a range that does not impair the characteristics of the obtained copolymerized polyester resin (1), for example, 1 mol% or less. Can also be used.

Examples of 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.

The copolyester resin (2) is formed from a dicarboxylic acid constitutional unit containing a terephthalic acid component unit and a 2,6-naphthalene dicarboxylic acid component unit, and a dihydroxy compound constitutional unit containing an ethylene glycol component unit. . The dicarboxylic acid constitutional unit constituting the copolymerized polyester resin (2) has a terephthalic acid component unit of 80 to 99.5 mol%, preferably 90 to 99.5.
The amount of the 2,6-naphthalenedicarboxylic acid component unit is 0.5 to 20 mol%, preferably 0.5 to 10 in an amount of mol%.
It is preferably present in an amount of mol%.

In the copolyester resin (2), the above-mentioned terephthalic acid and 2,2 are used as the dicarboxylic acid component.
In addition to 6-naphthalenedicarboxylic acid, other dicarboxylic acids may be used in a range that does not impair the properties of the resulting copolyester resin (2), for example, 1 mol% or less. Examples of such dicarboxylic acid include isophthalic acid, phthalic acid, and 2-methylterephthalic acid.

Further, in the copolyester resin (2),
As the dihydroxy compound, other than the ethylene glycol as described above, other dihydroxy compounds can be used in a range that does not impair the properties of the resulting copolyester resin (2), for example, 1 mol% or less. Examples of such dihydroxy compounds include 1,3-propanediol, 1,4-butanediol, neopentyl glycol, cyclohexanediol, cyclohexanemethanol, 1,3-bis (2-hydroxyethoxy) benzene and 1,4-bis. Examples of dihydroxy compounds having 3 to 15 carbon atoms such as (2-hydroxyethoxy) benzene, 2,2-bis (4-β-hydroxyethoxyphenyl) propane, and bis (4-β-hydroxyethoxyphenyl) sulfone. You can

The copolyester resin (3) is composed of a dicarboxylic acid constituent unit containing a terephthalic acid component unit and an adipic acid component unit, and a dihydroxy compound constituent unit containing an ethylene glycol component unit. The dicarboxylic acid constitutional unit constituting the copolyester resin (3) contains the terephthalic acid component unit in an amount of 85 to 99.5 mol%, preferably 90 to 99.5 mol%, and the adipic acid component unit is 0. It is desirable to be present in an amount of 0.5 to 15 mol%, preferably 0.5 to 10 mol%.

In the copolyester resin (3), the amount of dicarboxylic acid component other than terephthalic acid and adipic acid as described above, which does not impair the characteristics of the copolyester resin (3), for example, 1 mol% or less. It is also possible to use other dicarboxylic acids. Examples of such a dicarboxylic acid include isophthalic acid, phthalic acid, 2-methylterephthalic acid, and 2,6-naphthalenedicarboxylic acid.

In the copolymerized polyester resin (3), other dihydroxy compounds may be added in a range not impairing the characteristics of the copolymerized polyester resin (3) other than ethylene glycol as the dihydroxy compound, for example, 1 mol% or less. It can also be used. Examples of 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,
Examples thereof include dihydroxy compounds having 3 to 15 carbon atoms such as bis (4-β-hydroxyethoxyphenyl) sulfone.

The copolymerized polyester resin (4) is composed of a dicarboxylic acid constituent unit containing a terephthalic acid constituent unit, and a dihydroxy compound constituent unit containing an ethylene glycol constituent unit and a diethylene glycol constituent unit. The dihydroxy compound constitutional unit which constitutes this copolymerized polyester resin (4) has an ethylene glycol component unit of 93 to 98 mol%, preferably 95 to 98 mol%.
And the diethylene glycol component unit is present in an amount of 2 to 7 mol%, preferably 2 to 5 mol%.

In the copolyester resin (4), in addition to the above-mentioned terephthalic acid as the dicarboxylic acid component,
Other dicarboxylic acids can be used in a range that does not impair the properties of the resulting copolyester resin (4), for example, 1 mol% or less. Examples of such a dicarboxylic acid include isophthalic acid, phthalic acid, 2-methylterephthalic acid, and 2,6-naphthalenedicarboxylic acid.

Further, in the copolyester resin (4),
As the dihydroxy compound, other dihydroxy compounds may be used in a range that does not impair the characteristics of the copolymerized polyester resin (4) other than ethylene glycol and diethylene glycol as described above, for example, 1 mol% or less. As such a dihydroxy compound,
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) ) Hydroxy compounds having 3 to 15 carbon atoms such as propane and bis (4-β-hydroxyethoxyphenyl) sulfone are used.

The copolyester resin (5) is composed of a dicarboxylic acid constituent unit containing a terephthalic acid constituent unit and a dihydroxy compound constituent unit containing an ethylene glycol constituent unit and a neopentyl glycol constituent unit. The dihydroxy compound constitutional unit constituting the copolymerized polyester resin (5) has an ethylene glycol component unit of 85 to 99.5 mol%, preferably 90 to 9
It is desirable that the neopentyl glycol component unit be present in an amount of 9.5 mol% and in an amount of 0.5 to 15 mol%, preferably 0.5 to 10 mol%.

In the copolyester resin (5), other than terephthalic acid as the dicarboxylic acid component, other properties can be obtained within a range not impairing the properties of the copolyester resin (5) obtained, for example, 1 mol% or less. It is also possible to use dicarboxylic acids. Examples of such a dicarboxylic acid include isophthalic acid, phthalic acid, 2-methylterephthalic acid, and 2,6-naphthalenedicarboxylic acid.

In the copolyester resin (5), other than ethylene glycol and neopentyl glycol as the dihydroxy compound, the range of not impairing the characteristics of the copolyester resin (5) obtained,
For example, other dihydroxy compounds can be used in an amount of 1 mol% or less. Examples of such dihydroxy compounds include 1,3-propanediol, 1,4-butanediol, cyclohexanediol, cyclohexanedimethanol, 1,3-bis (2-hydroxyethoxy) benzene, and 1,4-bis (2- Examples thereof include dihydroxy compounds having 3 to 15 carbon atoms such as hydroxyethoxy) benzene, 2,2-bis (4-β-hydroxyethoxyphenyl) propane and bis (4-β-hydroxyethoxyphenyl) sulfone.

The copolyester resin (6) is composed of a dicarboxylic acid constituent unit containing a terephthalic acid constituent unit and a dihydroxy compound constituent unit containing an ethylene glycol constituent unit and a cyclohexanedimethanol constituent unit. The dihydroxy compound constitutional unit constituting the copolyester resin (6) has an ethylene glycol component unit of 85 to 99.5 mol%, preferably 90 to
In an amount of 99.5 mol%, and the cyclohexanedimethanol component unit is 0.5 to 15 mol%, preferably 0.5 to
It is preferably present in an amount of 10 mol%.

In the copolyester resin (6), in addition to the above-mentioned terephthalic acid as the dicarboxylic acid component,
Other dicarboxylic acids can be used in a range that does not impair the properties of the resulting copolyester resin (6), for example, in an amount of 1 mol% or less. Examples of such a dicarboxylic acid include isophthalic acid, phthalic acid, 2-methylterephthalic acid, and 2,6-naphthalenedicarboxylic acid.

In the copolyester resin (6), other than ethylene glycol and cyclohexanedimethanol as the dihydroxy compound as described above, a range not impairing the properties of the copolyester resin (6) obtained, for example, 1 mol% Other dihydroxy compounds can also be used in the following amounts. Examples of such dihydroxy compounds include 1,3-propanediol, 1,4-butanediol, cyclohexanediol, cyclohexanedimethanol, 1,3-bis (2-hydroxyethoxy) benzene, and 1,4-bis (2- Hydroxyethoxy) benzene, 2,2-bis (4-β-hydroxyethoxyphenyl) propane, bis (4-β-hydroxyethoxyphenyl) sulfone and the like have 3 to 15 carbon atoms.
The dihydroxy compound of is used.

The copolyester resin (7) is composed of a dicarboxylic acid constitutional unit, a dihydroxy compound constitutional unit, and a polyfunctional hydroxy compound constitutional unit having at least 3 hydroxy groups. The dicarboxylic acid constitutional unit constituting the copolyester resin resin (7) has an isophthalic acid component unit in an amount of 20 to 100 mol%, preferably 50 to 98 mol%, and a terephthalic acid component unit in an amount of 0 to 80 mol%. %, Preferably 0.5 to 50 mol%.

The dihydroxy compound constitutional unit contains the dihydroxyethoxyresole component unit in an amount of 5 to 90 mol%, preferably 10 to 85 mol%, and the ethylene glycol component unit in an amount of 10 to 95 mol%, preferably 1%.
It is preferably present in an amount of 5 to 90 mol%. This copolymerized polyester resin (7) has a polyfunctional hydroxy compound structural unit having at least 3 hydroxy groups. The polyfunctional hydroxy compound constitutional unit was 0.1.0 with respect to 100 parts by mole of the dicarboxylic acid component unit.
It is desirable to be present in an amount of 05 to 1.0 part by mole, preferably 0.1 to 0.5 part by mole.

Such polyfunctional hydroxy compound constitutional units are derived from compounds such as trimethylolmethane, trimethylolethane and trimethylolpropane, and among them, trimethylolpropane is preferable. In the copolyester resin (7), other than the above-mentioned isophthalic acid and terephthalic acid as the dicarboxylic acid component, other properties can be obtained within a range not impairing the properties of the copolyester resin (7), for example, 1 mol% or less. It is also possible to use dicarboxylic acids.

Examples of such dicarboxylic acid include isophthalic acid, phthalic acid, 2-methylterephthalic acid and 2,6-
Examples thereof include naphthalenedicarboxylic acid. Further, in the copolymerized polyester resin (7), in a range that does not impair the characteristics of the copolymerized polyester resin (7) obtained as a dihydroxy compound other than the above dihydroxyethoxy resole and ethylene glycol, for example, in an amount of 1 mol% or less. Other dihydroxy compounds can also be used.

Examples of 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.

The molecular weight of the above-mentioned copolymerized polyester resins (1) to (7) is not particularly limited as long as it can produce a bottle from the obtained saturated polyester resin composition, but it is usually o-chloro. Intrinsic Viscosity of Copolymerized Polyester Resin in Phenolic Solvent [η]
Is 0.5 dl / g to 1.5 dl / g or more, preferably 0.6 dl / g to 1.2 dl / g.

Each resin constituting the bottle made of the saturated polyester as described above can be manufactured by a conventionally known manufacturing method. Further, in each of the above resins, various compounding agents such as a crosslinking agent, a heat stabilizer, a weather stabilizer, an antistatic agent, a lubricant, a release agent, an inorganic filler, a pigment dispersant, a pigment or a dye, It can be added within a range that does not impair the object of the invention.

Next, the method for producing a bottle according to the present invention will be specifically described. First, when the rectangular bottle shown in FIG. 1 is produced, the preform shown in FIG. 5 (having a sectional shape shown in FIG. 6) having a sectional shape similar to the sectional shape of the rectangular bottle shown in FIG. 2 is conventionally known. The method is used, for example, injection molding or extrusion molding. The melting temperature of the plastic for forming the preform is 260 ° C. to 31 when the plastic is, for example, polyethylene terephthalate resin.
It is preferably 0 ° C.

A bottle is manufactured from the obtained preform by a conventionally known method. For example, after heating the preform to a proper stretching temperature with a far infrared heating device or a preform heating device heated with oil, biaxial stretch blow molding is performed with pressurized air in a bottle mold. Get a bottle The manufacturing conditions of the bottle vary greatly depending on the type of plastic used, but in the case of polyethylene terephthalate resin, the molded preform shown in FIG. 5 is heated to an appropriate stretching temperature of 90 ° C. to 130 ° C. / Cm ² of pressurized air at room temperature
Biaxially stretch blow molded at 100 ° C. If necessary, the bottle may be heat-set.

The conditions for carrying out the heat setting treatment vary greatly depending on the type of plastic used,
The case of polyethylene terephthalate resin will be described below. Appropriate stretching temperature 85
Heat to ℃ -130 ℃, stretch blow molding in the mold. Then, the bottle is heat-set at a mold temperature of 105 ° C to 200 ° C, preferably 110 ° C to 170 ° C for 1 second or longer, preferably 3 seconds or longer.

By applying heat-setting treatment to the bottle in this way, the density of the body is improved and residual strain is removed, and a bottle having excellent heat resistance can be obtained. The density of the polyethylene terephthalate resin for molding such a bottle is about 1.355 to 1.370 g / cm ³ when heat setting is not performed on the body portion, but when heat setting is performed, 1. 370 to 1.41
It becomes about 0 g / cm ^3, and depending on the temperature, 1.375 to 1.
It is desirable to control to about 400 g / cm ³ .

The bottle molded as described above needs to be cooled and taken out so as not to be deformed or contracted when taken out. The surface temperature of the bottle when taking it out is 1
It is preferable that the temperature is 00 ° C. or less. Similarly, when manufacturing the bottle of FIG. 7 having the cross-sectional shape of FIG.
Using the preform of FIG. 9 having the cross-sectional shape of FIG. 10 having a similar shape, biaxial stretch blow molding is performed using a, a'for A, A'for b, b'for B, B'for c, c '. By performing C 1 and C ′ in such a manner that d 1 and d ′ correspond to D and D ′, the horizontal cross-sectional direction of the body can be made substantially equal in draw ratio. In other words, a bottle that has less variation in thickness in the horizontal direction (cross-sectional direction) at each height of the body portion, can have a uniform thickness, and has excellent dimensional stability such as deformation and mechanical strength such as buckling strength. Can be manufactured.

Further, when the bottle of FIG. 11 having the cross-sectional shape of FIG. 12 is biaxially stretch blow-molded by using the preform of FIG. 13 having the similar cross-sectional shape of FIG. 14, the bottle crosses at each height. The thickness in the plane direction can be made uniform, and a bottle excellent in dimensional stability such as deformation and mechanical strength can be manufactured.

[0052]

【Example】

Example 1 Polyethylene terephthalate [J135 manufactured by Mitsui Pet Resin Co., Ltd.] was molded by an M-100A injection molding machine manufactured by Meiki Seisakusho Co., Ltd. to obtain a preform. The molding temperature at this time was 290 ° C., and a preform having a draw ratio of 9.6 was used. The weight of the preform at this time was 80 g.

Next, the surface temperature of the preform body central part is 100 ° C. to 1 ° C. with the attached infrared heater of the preform.
The mixture was heated to 15 ° C. and stretch-blown with an LB-01 molding machine manufactured by CORPOPLAST to mold a 2 liter square bottle having a height of 306 mm as shown in FIG. At the time of stretching, heat the blow mold to 100 ° C.
Biaxial stretch blow molding was performed by contacting for 2 seconds, and then the bottle was cooled to 100 ° C. or lower and taken out from the mold.

With respect to the bottles produced as described above, at points A to H in FIG. 16 at l, m and n of heights of 40 mm, 100 mm and 220 mm from the bottom shown in FIG.
The wall thickness was measured to evaluate the dimensional stability (deformability) such as deformation. The results are shown in Tables 1 and 2. Here, the deformability was evaluated by aging the bottle at 40 ° C. × 90% RH for 1 week, filling it with hot water, and visually comparing the deformations. In other words, it was evaluated that the deformation of the bottle was improved when the deformation was small.

Example 2 A bottle was prepared in the same manner as in Example 1 except that the mold temperature was changed to 150 ° C. Table 2 shows the results of the above-mentioned evaluation of heat resistance of the prepared bottle. Example 3 A bottle was prepared in the same manner as in Example 1 except that the preform weight was 72 g and the mold temperature was 150 ° C.

Comparative Example 1 In Example 1, the preform was cylindrical, and the stretching ratio was 6.5 times on the long side, 7.8 times on the short side, and 8.
8x preform (preform weight 80g)
A bottle was prepared in the same manner as in Example 1 except that was used. Table 2 shows the results of evaluation of heat resistance of this bottle in the same manner as in Example 1.

Comparative Example 2 A bottle was prepared in the same manner as in Comparative Example 1 except that the weight of the cylindrical preform was 72 g in Comparative Example 1. Table 2 shows the results of evaluation of heat resistance of this bottle in the same manner as in Example 1.

[0058]

[Table 1]

[0059]

[Table 2]

[0060]

[0061]

According to the method for producing a plastic bottle of the present invention, when a plastic preform is stretch blow-molded to form a bottle, a preform having a shape similar to that of the bottle is used. The long side and the short side can be stretched at the same stretch ratio, and the thickness in the cross-sectional direction can be made uniform to obtain a bottle excellent in dimensional stability such as deformation and mechanical strength such as buckling strength.
You can

[Brief description of drawings]

FIG. 1 is a perspective view of a rectangular bottle.

FIG. 2 is a cross-sectional view of a rectangular bottle.

FIG. 3 is a perspective view of a cylindrical preform.

FIG. 4 is a cross-sectional view of a cylindrical preform.

FIG. 5 is a perspective view of a rectangular preform.

FIG. 6 is a cross-sectional view of a rectangular preform.

FIG. 7 is a perspective view of a rectangular (8-sided) bottle.

FIG. 8 is a cross-sectional view of a rectangular (8-sided) bottle.

FIG. 9 is a perspective view of an eight-sided preform.

FIG. 10 is a cross-sectional view of an 8-sided preform.

FIG. 11 is a perspective view of a bellows type bottle.

FIG. 12 is a cross-sectional view of a bellows type bottle.

FIG. 13 is a perspective view of a bellows type preform.

FIG. 14 is a cross-sectional view of a bellows type preform.

FIG. 15 is a front view of a rectangular bottle showing a wall thickness measurement position.

FIG. 16 is a plan view of the rectangular bottle showing a wall thickness measurement position.

[Explanation of symbols]

1 ... Square bottle 2, 5 ... Preform

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunio Tomita 6-1-2, Waki, Waki-cho, Kuga-gun, Yamaguchi Mitsui Petrochemical Industry Co., Ltd. (56) Reference JP-A-5-309725 (JP, A) ) JP-A-57-72826 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B29C 49/00-49/80 B29B 11/08 B29B 11/14

Claims (6)

(57) [Claims] 1. A method for producing a plastic rectangular bottle thickness at each height of the body is represented by the following formula, at least
The horizontal cross-section of the body is similar to a rectangular bottle.
A method for producing a plastic rectangular bottle , which comprises molding the preform and then stretch-blowing it . 0.8x ≦ y ≦ 1.2x y: Wall thickness in the bottle horizontal direction at each height x: Average wall thickness in the bottle horizontal direction at each height 2. A heat-set after stretching blow claim 1
A method for manufacturing the plastic square bottle described. 3. A process for producing a plastic rectangular bottle according to claim 1, wherein the manufactured rectangular bottle saturated polyester resin. 4. The method for producing a plastic rectangular bottle according to claim 3, wherein the saturated polyester resin is polyethylene terephthalate resin. 5. The method for producing a plastic rectangular bottle according to claim 3, wherein the saturated polyester resin is polyethylene naphthalate resin. 6. The method for producing a plastic rectangular bottle according to claim 3, wherein the saturated polyester resin is a copolyester resin.