JP2004066624A - Method for stretching/blow-molding plastic bottle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a plastic bottle of polyethylene terephthalate lightweight while securing suitability for the use with a bender regarding the bottle to be stored inside an automatic vending machine which can be made lightweight as a whole without resistance to deformation under load of the barrel part of the bottle. <P>SOLUTION: This method is characterized by heating a part becoming the shoulder part of the bottle, a center part becoming the barrel part of the bottle and a part becoming the bottom of the bottle to a higher temperature than the other spot, executing blow-molding by one stage blow molding method and orienting the resin at the parts heated to the higher temperature to form a thin-walled part 13a in the central part of the barrel of the bottle. A first and a second thick-walled parts 13b and 13c are formed by allotting a stretching resin to parts connected to the thin-walled parts 13a. Thus, the bottle showing outstanding strength characteristics while being entirely made lightweight is molded. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a stretch blow molding method for forming a plastic bottle container by stretch blow molding a parison made of polyethylene terephthalate or the like.
In particular, the present invention is to heat a predetermined portion such as a central portion and a shoulder portion of a parison body at a higher temperature than other portions, and to stretch-blow mold using a single-stage blow molding method to thereby provide a center portion of a bottle body. Resin located in the part and shoulders is allocated to increase the thickness of the predetermined part, reducing the weight of the resin used and increasing the thickness of the predetermined part of the body to which a load is applied, and the load bearing strength of the container body The present invention relates to a stretch blow molding method for a plastic bottle container which can reduce the weight of the entire bottle container without impairing the quality.
[0002]
[Prior art]
Generally, a plastic bottle container made of polyester such as polyethylene terephthalate, polypropylene, polyamide or the like and formed by stretch blow is known.
This type of plastic bottle container is generally manufactured by stretch blow molding an injection molded parison (preform).
Plastic bottle containers manufactured by the stretch blow molding method have excellent transparency and gas barrier properties and are widely used as bottle containers for beverages such as carbonated beverages such as cola and cider, fruit juice beverages, mineral water, and various teas. ing.
[0003]
[Problems to be solved by the invention]
In recent years, plastic bottle containers have rapidly spread and spread, and with this widespread use, there has been a strong demand for lighter containers, especially for beverage containers. For example, a plastic bottle container currently used as a container for a capacity of 500 ml has a weight of about 32 g, and there is a demand to reduce the weight.
Here, the weight of the plastic bottle container is determined by the weight of the parison before being stretch blow-molded. Therefore, if the parison is reduced in weight, the bottle container is also reduced in weight.
[0004]
However, in this simple method of reducing the weight of the parison, the thickness of the wall of the bottle container, specifically, the thickness of the stretched container body is reduced by the reduced weight, and the load bearing strength is reduced. The problem of being damaged occurred.
In particular, in the case of a bottle container for beverages, it is general that the bottle container is stored in a vending machine, and in the vending machine, a large number of bottle containers arranged horizontally are stored in a vertically stacked state. Then, a load from another stacked container is applied to the body of the container stacked on the bender bar in the vending machine. For this reason, in the case of a container having a thinner body portion for reducing the weight, the load-bearing strength is insufficient, and the container is deformed or crushed, thereby causing a problem that the suitability for bender is lost.
[0005]
As described above, even if an attempt is made to reduce the weight of the bottle container simply by reducing the weight of the parison, the thickness of the container body becomes thinner, and the load-bearing strength of the container becomes insufficient. However, it has not been possible to cope with the reduction in the weight of the beverage bottle container stored in the container.
The present inventor has conducted intensive studies in view of the above circumstances. As a result, the shoulder portion, the central portion of the body portion, and the bottom portion of the bottle container have thicker portions than the amount required to maintain the load-bearing strength of the container. The present inventors have found that there is, and have thought that by improving the thickness distribution at the shoulder and the center of the trunk, it is possible to reduce the weight of the entire container without impairing the strength of the container.
[0006]
That is, the present invention has been proposed in order to solve the problems of the conventional technology as described above, and a predetermined portion of the parison corresponding to the shoulder, the center of the body, and the bottom of the bottle container is replaced with another portion. By applying stretch blow molding using a single-stage blow molding method, the resin forming the center and shoulders of the bottle can be allocated to specific parts, and the weight of the resin used can be reduced. It is an object of the present invention to provide a stretch blow molding method for a plastic bottle container that can increase the thickness of a predetermined portion of a body portion to which a load is applied while reducing the load-bearing strength of the container body portion and reduce the weight of the entire bottle container.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the stretch blow molding method for a plastic bottle container according to the present invention comprises heating a bottomed cylindrical preform at a predetermined temperature and stretching blow molding to form a mouth, a shoulder, a trunk, and a body. A stretch blow molding method for forming a plastic bottle container having a bottom portion, wherein at least a predetermined portion of the preform, which corresponds to the center of the body of the bottle container, is heated at a temperature higher than the heating temperature of other portions. The preform is stretch-blow-molded by a single-stage blow molding method to stretch the resin at the high-temperature heating location to form at least one thin portion at the center of the body of the bottle container.
[0008]
Further, a method is provided in which at least two thick portions are formed in the body of the bottle container by stretching the resin at the high-temperature heating portion, thereby allocating the resin to a portion continuous with the thin portion.
Further, in addition to the center of the body of the bottle container of the preform, by heating a predetermined portion of the shoulder and / or bottom of the bottle container at a temperature higher than the heating temperature of the other portion, the thin portion and Alternatively, it is a method of forming a thick portion.
Then, the thick portion is formed at a position where a load of the plastic bottle container is applied.
[0009]
According to the stretch blow molding method for a plastic bottle container of the present invention constituted by such a method, in the stretch blow step in the single-stage blow molding method, a specific portion corresponding to the bottle shoulder, the center, and the bottom of the parison (preform) is specified. The part is heated at a higher temperature than the other parts. By stretching the high-temperature heated portion, the resin in the high-temperature heated portion can be stretched so as to be thinner than the other portions, and the resin in the stretched portion can be allocated to a predetermined portion of the bottle body.
As a result, even when the weight of the resin forming the parison is reduced, the thickness of the predetermined portion of the body to which a load is applied can be increased by controlling the thickness distribution, and the load bearing strength of the body can be increased. Thus, the entire bottle container can be reduced in weight without impairment.
Therefore, even if the bottle container according to the present invention is loaded and stored in a vending machine, deformation and crushing do not occur, and it sufficiently responds to the demand for reducing the weight of bottles for containers of soft drinks without impairing the suitability for vendors. Will be able to
[0010]
And it is preferable that the thickness of the thick part is 0.33 to 0.45 mm, and the thin part is 0.25 to 0.31 mm.
By setting the thick part and the thin part of the torso in such a range, the load-bearing strength of a predetermined part of the torso to which a load is applied is within a range in which the strength of the central part of the torso and the shoulder is not impaired. A good range can be achieved, and the weight of the entire bottle container can be reduced.
[0011]
Further, the plastic bottle container manufactured by the present invention is preferably formed so that at least the body has a crystallinity of 30 to 40% among the mouth, shoulder, body and bottom.
It is preferable to form it.
By setting the crystallinity of the body of the bottle in this range, the heat resistance of the bottle and the impact strength of the snapper can be further improved, which is particularly preferable as a bottle for beverages and the like stored in a vending machine. .
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the stretch blow molding method for a plastic bottle container according to the present invention will be described with reference to FIGS.
FIG. 1 is a cross-sectional view showing an example of a preform (parison) for manufacturing a plastic bottle container by a stretch blow molding method according to an embodiment of the present invention.
FIG. 2 is a partial cross-sectional view showing a plastic bottle container formed by the stretch blow molding method according to the present embodiment.
[0013]
[Method of manufacturing plastic bottle containers]
1. Preform manufacturing
First, a proform is formed.
As the preform, a bottomed cylindrical preform (parison) as shown in FIG. 1 can be manufactured by known injection molding or extrusion molding.
As the preform, a multilayer preform having an oxygen absorbing layer in an intermediate layer as described later can be used. When such a multilayer preform is used, a conventionally known co-injection molding machine is used. The inner and outer layers are made of polyester resin, and one or more oxygen absorbing layers are inserted between the inner and outer layers to obtain a multilayer mold having a bottom and an opening corresponding to the shape of the injection preform mold. Reforms can be manufactured.
[0014]
2. Stretch blow molding
Next, the preform is biaxially stretch blow-molded.
The stretch blow molding method generally includes two methods, a hot parison method (single-stage blow molding method) and a cold parison method (two-stage blow molding method). The hot parison method is a method in which a bottomed preform (parison) formed by injection molding a polyester resin is stretch blow-molded in a softened state without completely cooling, and has excellent productivity.
On the other hand, in the cold parison method, a cooling bottomed preform in which the dimensions are smaller than the final shape and the polyester is amorphous is formed in advance by injection molding a polyester resin. Is pre-heated to a stretching temperature and stretched in a blow molding die, and is excellent in accuracy such as dimensions.
Either method can be used for manufacturing the bottle container 10 according to the present embodiment.
[0015]
For such stretch blow molding, a single-stage blow molding method in which the preform is blown as it is to the size of the final molded product, and an intermediate product in which the preform is once blown so as to be larger than the final molded product. There is a two-stage blow molding method of molding and heat shrinking the intermediate product to obtain a final molded product.
Although the two-stage blow molding is suitable for making the thickness of the container uniform, there is a problem that the number of steps is increased and the productivity is reduced due to complexity.
In the present embodiment, since the bottle container 10 having a desired thickness distribution can be obtained by the single-stage blow molding as described below, a single-stage blow molding method with few steps and excellent productivity can be adopted. It is designed to be compatible with beverage bottle containers that are required to be inexpensive and mass-produced.
[0016]
In the single-stage blow molding method according to the present embodiment, first, the mouth 1a of the preform 1 is crystallized (whitened) by an appropriate means. Then, the preform is heated to a predetermined stretching temperature equal to or higher than the glass transition point (Tg), for example, 85 to 120 ° C., and the heated preform is placed in a mold heated to a predetermined heat treatment (heat set) temperature. Biaxial stretch blow molding.
Specifically, the heated preform is stretched in a longitudinal direction (axial direction) by a stretching rod and is stretched in a lateral direction (circumferential direction) by blow air.
In the present embodiment, as shown in FIG. 1, when the preform 1 is heated at a predetermined stretching temperature, the preform 1 has a portion 2 serving as a bottle shoulder and a portion 3 serving as a bottle trunk. And a predetermined portion of the portion 4 which will be the bottom of the bottle is heated at a higher temperature than the other portions (the black portion in FIG. 1 indicates a high-temperature heating portion).
It is preferable that the high-temperature heating portion be heated so as to be about 2 ° C. to 10 ° C. higher than other portions.
Further, the method of heating the high-temperature heating location can be performed by, for example, disposing a high-temperature heater or the like only at the high-temperature heating location, or disposing heating means such as a heater inside and outside the preform only at the high-temperature heating location.
[0017]
As described above, by heating a predetermined portion of the portion 2 serving as the bottle shoulder portion, the portion 3 serving as the bottle body portion, and the portion 4 serving as the bottle bottom portion of the preform 1 at a higher temperature than other portions, the high temperature can be obtained. The heated part is easily stretched.
Therefore, by the rod stretching and the blow stretching, the high temperature heating portion is stretched to be thinner (thinner) than other portions, and the thin portion (the thinner portion of the bottle container 10) is provided at the central portion corresponding to the bottle body. The part 13a) is formed.
Then, the thickness of the body 3 side continuous to the thin portion is not large (thick) by the resin stretched in the thin portion, but is a thick portion (the first and second thick portions 13b of the bottle container 10). , 13c) will be formed.
At this time, a thin portion and a thick portion can be formed at desired portions of the bottle container 10 by adjusting the position of the high-temperature heating portion on the preform 1, the heating temperature, and the like.
The stretch ratio of the final blow molded product is preferably about 1.2 to 6 times in the longitudinal direction and about 1.2 to 4.5 times in the transverse direction.
[0018]
3. Heat treatment (heat set)
The above-mentioned blow mold is heated to 120 to 230 ° C., preferably 130 to 210 ° C., and heat treatment is performed by bringing the outside of the wall of the blow molded body into contact with the inner surface of the mold for a predetermined time during biaxial stretching blow. After the heat treatment for a predetermined time, the blow fluid is switched to the internal cooling fluid to cool the inside of the blow molded body.
Here, the heat treatment time varies depending on the thickness and temperature of the blow molded body, but is generally 1.5 to 30 seconds, preferably about 2 to 20 seconds. The cooling time also varies depending on the heat treatment temperature and the type of cooling fluid, but is generally about 0.1 to 30 seconds, preferably about 0.2 to 20 seconds.
By this heat treatment, the blow molded body is crystallized.
Therefore, since the crystallinity of the blow molded product depends on conditions such as the thickness, shape, heat setting temperature, and time of the container, the crystallinity of the body 13 of the bottle container 10 can be optimized by optimizing these conditions. Can be set to a preferable range of 30 to 40% described later.
[0019]
Examples of the cooling fluid include room temperature air, various kinds of cooled gas, for example, nitrogen, air, and carbon dioxide at −40 ° C. to + 10 ° C., as well as a chemically inert liquefied gas, for example, liquefied nitrogen. Gas, liquefied carbon dioxide gas, liquefied trichlorofluoromethane gas, liquefied dichlorodifluoromethane gas, other liquefied aliphatic hydrocarbon gases, and the like can be used. A liquefied mist having a large heat of vaporization such as water can coexist in the cooling fluid. By using such a cooling fluid, a remarkable cooling temperature can be obtained.
The blow molded product taken out of the mold is cooled by allowing it to cool or blowing cold air.
As described above, the bottle container 10 according to the present embodiment as shown in FIG. 2 can be obtained.
[0020]
[preform]
1. Preform structure
A preform 1 for manufacturing a bottle container 10 by the stretch blow molding method according to the present embodiment as shown in FIG. 1 is made of a thermoplastic resin, and is formed from a mouth 1 a, a shoulder 2, a body 3, and a bottom 4. It is formed in a bottomed cylindrical shape (test tube shape).
The preform 1 can have an arbitrary shape. In the example shown in FIG. 1, the bottom 4 has a substantially hemispherical shape. However, the present invention is not particularly limited to this shape. The tip of the bottom 4 can also be flattened.
Then, as described above, the plastic bottle container 10 as shown in FIG. 2 is manufactured by heating the preform 1 to a predetermined stretching temperature and performing biaxial stretch blow molding.
[0021]
2. Structural component
Here, as the thermoplastic resin constituting the preform 1 (and the bottle container 10), any resin can be used as long as the resin can be stretch blow molded and thermally crystallized.
Specifically, thermoplastic polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyarylate, and copolymers thereof, and blends thereof with these resins or other resins are particularly preferable. An ethylene terephthalate-based thermoplastic polyester such as polyethylene terephthalate is preferably used.
Also, acrylonitrile resin, polypropylene, propylene-ethylene copolymer, polyethylene and the like can be used.
These resins are blended with various additives such as a colorant, an ultraviolet absorber, a release agent, a lubricant, a nucleating agent, an antioxidant, an antistatic agent and the like within a range not to impair the quality of the molded article. be able to.
[0022]
The ethylene terephthalate-based thermoplastic polyester constituting the preform 1 occupies most of the ester repeating units, generally 70 mol% or more, of ethylene terephthalate units, has a glass transition point (Tg) of 50 to 90 ° C., and has a melting point ( Those having Tm) in the range of 200 to 275 ° C are preferred.
As the ethylene terephthalate-based thermoplastic polyester, polyethylene terephthalate (PET) is particularly excellent in terms of pressure resistance, heat resistance, heat pressure resistance and the like. Copolymerized polyesters containing a small amount of ester units consisting of diols such as propylene glycol can also be used.
[0023]
In addition, the preform 1 of the present embodiment can be constituted by two or more thermoplastic polyester layers in addition to the case where the preform 1 is constituted by a single layer (one layer) of thermoplastic polyester layer.
Furthermore, the preform 1 of the present embodiment can include an intermediate layer enclosed between an inner layer and an outer layer composed of two or more thermoplastic polyester layers, and the intermediate layer can be an oxygen absorbing layer.
By providing the oxygen absorbing layer in this manner, the permeation of oxygen from the outside into the bottle container can be suppressed, and the contents in the bottle container can be prevented from being altered by oxygen from the outside. It is suitable for bottle containers for beverages.
Here, as the oxygen absorbing layer, any material can be used as long as it absorbs oxygen and prevents the permeation of oxygen. However, a combination of an oxidizable organic component and a transition metal catalyst, or substantially no oxidation is performed. It is preferred to use a combination of a gas barrier resin, an oxidizable organic component and a transition metal catalyst.
[0024]
[Bottle container]
1. Composition of bottle container
The bottle container 10 formed by the stretch blow molding method of the present embodiment is a plastic bottle container formed by stretch blow molding the preform 1 described above, and as shown in FIG. It has a shoulder 12, a body 13 and a bottom 14.
The body 13 of the bottle container 10 is provided with a thin portion 13a at a central portion, and a first thick portion 13b on the shoulder side and a second thick portion 13b on the bottom side in the height direction of the bottle sandwiching the thin portion 13a. A second thick portion 13c is provided.
[0025]
2. Thin and thick parts
The central thin portion 13c, the first thick portion 13b, and the second thick portion 13c of the body portion 13 are formed continuously, and are formed by a stretch blow molding method described later. 2, the resin in the central portion of the body portion 3 and the resin in the bottom portion 4 are stretched by heating at a high temperature, and the resin is allocated to a specific portion corresponding to the bottle body portion. And second thick portions 13b and 13c are formed.
Generally, in a bottle container manufactured by stretch blow molding, the thickness of the shoulder part and the lower part of the trunk is thick. In addition, the torso to be stretched, the entire torso is uniformly stretched, and the thickness of the part where the load is applied and the part where the load is not applied are almost the same, and the center of the torso where the load is not applied is more than necessary. Resin is present.
Therefore, in the present embodiment, the resin corresponding to the bottle shoulder portion (see the dotted line portion 12a shown in FIG. 2), the center of the body portion (see the dotted line portion 13a) and the bottom portion (the dotted line portion 14a) of the preform 1 is applied to the body portion. By allocating to a predetermined location, the thickness of a specific portion (refer to dotted line portions 13b and 13c) of the body portion 13 of the molded bottle container is increased, whereby the preform 1 (that is, the bottle container 10) is formed. The bottle container 10 can be formed without reducing the strength of the body portion 13 even by reducing the resin weight of the item (1).
[0026]
Specifically, the first and second thick portions 13a and 13b of the body 13 are formed at positions where a load is applied when the bottle container 10 is in a loaded state, for example, in a vending machine. It has become.
Generally, when a bottle container is used as a beverage container, it is generally stored in a vending machine. When stored in a vending machine, a large number of bottle containers are stacked and stored in a horizontal state. Then, a load from another stacked container is applied to the body of the container stacked on the bender bar in the vending machine.
For this reason, in a bottle container to be loaded, a load from another container or the like is applied to the body, and if the thickness of the body is reduced for weight reduction, the load-bearing strength is insufficient, and the container is deformed or crushed. Etc. had occurred.
[0027]
Therefore, in the present embodiment, when the bottle container 10 is loaded, the first and second thick portions 13a and 13b are formed at predetermined portions of the body 13 to which a load is applied from another container or the like. It is.
Here, the wall thickness of the body 13 is, for example, in the case of a normal beverage bottle container having a capacity of 500 ml or 350 ml, for the first and second thick portions 13a, 13b, 0.33-0. It is preferable that the thickness be in the range of 45 mm and the center thin portion 13c be formed in the range of 0.25 to 0.31 mm.
By setting the thickness of the torso 13 in such a range, the load-bearing capacity of a predetermined portion of the torso 13 to which a loading load or the like is applied within a range where the strength of the central portion of the torso 13 and the shoulder 12 is not impaired. The strength can be set in a favorable range, and the weight of the entire bottle container 10 can be reduced.
[0028]
The first and second thick portions 13b and 13c are formed at a continuous portion of the shoulder portion 12 and the bottom portion 14, respectively. A continuous portion of the portion 12, a continuous portion of the trunk portion 13 and the bottom portion 14, and a peripheral portion thereof are included.
The first and second thick portions 13a and 13b are formed by stretching the high-temperature heating portion of the preform 1 shown in FIG. Is allocated to form a thick wall.
Therefore, these first and second thick portions 13a and 13b are formed in a certain range on a continuous portion of the body portion 13 and the shoulder portion 12 and the body portion 13 and the bottom portion 14 of the bottle container. As long as the part 13 and the shoulder part 12 and the trunk part 13 and the bottom part 14 are formed in a continuous part and its peripheral part, it is included in the “continuous part” in this specification. The thin portion 13c is located between the first and second thick portions 13a and 13b.
[0029]
3. Crystallinity
The thermoplastic polyester forming the bottle container 10 of the present embodiment is configured so that the crystallinity of the body 13 is in the range of 30 to 40%. By setting the crystallinity within this range, the deformation of the bottle container 10 can be prevented, and the barrier property of the body 13 can be improved.
If the degree of crystallinity is less than 30%, the effect of preventing oxygen permeation and deformation cannot be sufficiently obtained, and if the degree of crystallinity exceeds 40%, the releasability of the mold after biaxial stretch blow molding. And the deformation after release tends to increase.
By setting the crystallinity of the body portion 13 within this range, the heat resistance and impact resistance of the bottle container 10 can be further improved, and it is particularly preferable as a bottle container for beverages and the like stored in a vending machine.
[0030]
As described above, according to the bottle container stretch blow molding method of the present embodiment, when the preform 1 is heated at a predetermined stretching temperature by the single-stage blow molding method, a portion that becomes the bottle shoulder portion of the preform 1 2 and a central portion of the portion 3 serving as the bottle body and a predetermined portion of the portion 14 serving as the bottle bottom are heated at a higher temperature than the other portions. The resin corresponding to the shoulder portion 12 and the central portion of the trunk 13 can be allocated to the portion of the trunk 13 where the load is applied.
Thereby, even if the weight of the preform 1 is reduced, the thickness of the predetermined portion of the body 13 can be increased, and the entire bottle container can be reduced in weight without impairing the load-bearing strength of the body 13. it can.
Therefore, even if the bottle container 10 obtained by the stretch blow molding method of the present embodiment is loaded and stored in a vending machine, it is not deformed or crushed, and a container for a soft drink or the like without impairing the suitability for a vendor. Satisfactorily can meet the demand for bottle weight reduction.
[0031]
【Example】
Hereinafter, specific examples of the plastic bottle container of the present invention will be described with reference to FIGS.
[Example 1]
Polyethylene terephthalate (PET) was fed to an extruder to produce a preform weighing 26 g.
The preform is heated to 90 ° C. above the glass transition point (Tg), and a predetermined portion of the preform is defined as a shoulder portion of the bottle, a center portion of the body portion of the bottle, and a bottom portion of the bottle. The part (see ● part in FIG. 1) is heated at 4 ° C. higher than the other parts, and this preform is set in a mold heated to 160 ° C., and biaxially stretch blown by a single-stage blow molding method. Was carried out to obtain a bottle container having a content of 500 ml.
[0032]
[Comparative Example 1]
This is a conventional non-lightened bottle container that uses polyethylene terephthalate (PET) weighing 32 g and has a content of 500 ml by a conventional biaxial stretch blow molding that does not perform high-temperature heating of a specific portion of the preform in Example 1. A bottle container was obtained.
[0033]
[Comparative Example 2]
Under the same molding conditions as in Comparative Example 1, the weight of polyethylene terephthalate (PET) was reduced to 26 g to obtain a bottle container having an inner capacity of 500 ml.
[0034]
The wall thickness distribution of the shoulder, body and bottom of these bottle containers is shown in FIGS. In Example 1, the minimum thickness of the thin portion of the body portion was 0.269 mm (the measurement point 100 mm), and the maximum thickness of the first thickness portion was 0.361 mm (the measurement point 120 mm). The maximum thickness of the second thick part of the body was 0.371 mm (measuring point 20 mm). In addition, the minimum thickness of the shoulder was 0.268 mm (at a measurement point of 165 mm), and the minimum thickness of the bottom was 0.318 mm (at a measurement point of 0 mm).
Thus, in Example 1, the first and second thick portions are sufficiently thicker than the thin portion at the center of the body portion, and the thickness of the portion where the loading load of the bottle container is applied is large. It was found that a bottle container having a small thickness at a portion where no load was applied was obtained.
[0035]
On the other hand, in Comparative Example 1, the thickness at the measurement point 100 mm corresponding to the thin part at the center of the body part of Example 1 was 0.400 mm, and the thickness at the measurement point 120 mm corresponding to the first thick part was 0.4 mm. 413 mm, the thickness at the measurement point 20 mm corresponding to the second thickness part is 0.501 mm, whereas the thickness at the shoulder measurement point 165 mm is 0.364 mm, and the thickness at the bottom measurement point 0 mm is It was 0.520 mm.
In Comparative Example 1, the thickness of the portion of the body portion where the load is applied and the other portions are substantially uniform, and the thickness of the thin portion and the portion corresponding to the first thick portion in Example 1 are equal. Furthermore, the thickness 0.520 mm at the measurement point 0 mm corresponding to the minimum thickness part at the bottom of Example 1 is larger than the thickness 0.501 mm (the measurement point 20 mm) at the maximum thickness part of the body part in Example 1. Has also grown.
[0036]
In Comparative Example 2, the thickness of the measuring portion 100 mm corresponding to the thin portion at the center of the body portion of Example 1 was 0.333 mm, and the thickness of the measuring portion 120 mm corresponding to the first thick portion was 0.316 mm. The thickness at the measurement point 20 mm corresponding to the second thick part is 0.304 mm, the thickness at the measurement point 165 mm at the shoulder is 0.310 mm, and the thickness at the measurement point 0 mm at the bottom is 0. 323 mm.
In Comparative Example 2, as in Comparative Example 1, the thickness of the portion of the body portion where the load is applied and the other portions are substantially uniform, and the first thick portion, thin portion, and shoulder of Example 1 are formed. The part corresponding to the part had almost the same thickness.
Moreover, in Comparative Example 2, the thickness of the portion (measuring point 20 mm) corresponding to the second thick portion of Example 1 where the loading load is applied is 0.304 mm, which is the minimum thickness in the trunk portion. Was.
[0037]
Comparing Example 1 and Comparative Example 2 in which the weight of the preform is the same, first, in Comparative Example 2, the thickness of the entire container is made uniform, and the thickness of the center of the trunk and the thickness of the shoulder where no load is applied. While the thickness of the body edge, which is the portion where the load is applied, is rather small.
On the other hand, in the first embodiment, the thickness of the shoulder, the center, and the bottom where no load is applied is reduced, and the resin corresponding to the thickness is allocated to the first and second thick portions where the load is applied. Thus, the maximum thickness of the first thick portion is 0.361 mm, and the maximum thickness of the second thick portion is sufficiently large, 0.371 mm.
Therefore, in the container of Example 1 according to the present invention, the weight (32 g) of the conventional bottle container of Comparative Example 1 can be reduced by 6 g, and at the same time, compared with the container of Comparative Example 2 in which the resin weight is simply reduced. Thus, the portion of the body to which the load is applied can be made thicker, and the load-bearing strength of the bottle container can be increased.
[0038]
In addition, the stretch blow molding method of the plastic bottle container of the present invention is not limited to the above embodiment, and it goes without saying that various modifications can be made within the scope of the present invention.
For example, in the above embodiment, as shown in FIG. 2, the outer shape is a substantially cylindrical bottle container. However, the outer shape of the bottle container is not particularly limited to a cylindrical shape, and may be a rectangular cylindrical shape. Even a bottle container or a combination of a square tube and a cylinder does not prevent the application of the present invention.
The thin portion provided on the body of the bottle container may be formed in at least one of the places where the loading load is not applied, and may be two or more. For example, if a thick part is formed at a place where a load is applied to a bottle container, a thin part can be formed at any number of places other than the thick part, and two places are formed between three thick parts. It can be set arbitrarily, for example, by providing a thin portion.
[0039]
【The invention's effect】
As described above, according to the stretch blow molding method for a plastic bottle container of the present invention, a predetermined portion of the parison corresponding to the shoulder, the center of the body, and the bottom of the bottle is heated at a higher temperature than other portions. By stretching blow molding using a single-stage blow molding method, the resin that forms the center and shoulders of the body of the bottle can be allocated to specific parts, and the weight of the used body can be reduced while reducing the weight of the resin used. By increasing the thickness of the predetermined portion, the weight of the entire bottle container can be reduced without impairing the load-bearing strength of the container body.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an example of a preform (parison) for producing a plastic bottle container by a stretch blow molding method according to an embodiment of the present invention.
FIG. 2 is a partial cross-sectional view showing a plastic bottle container formed by a stretch blow molding method according to one embodiment of the present invention.
FIG. 3 is a graph showing a wall thickness distribution of a bottle container formed by one embodiment of the stretch blow molding method of the present invention.
FIG. 4 is a table showing a thickness distribution of a bottle container formed by one embodiment of the stretch blow molding method of the present invention.
[Explanation of symbols]
1 Preform (Parison)
1a mouth
2 Shoulder of bottle
3 The part that becomes the body of the bottle
4 The bottom part of the bottle
10 bottle containers
11 mouth
12 Shoulder
13 torso
14 bottom

Claims (6)

A stretch blow molding method for forming a plastic bottle container having a mouth, a shoulder, a body, and a bottom by heating a bottomed cylindrical preform at a predetermined temperature and performing stretch blow molding,
By heating the preform, at least a predetermined portion corresponding to the center of the body of the bottle container, at a temperature higher than the heating temperature of the other portions, and stretch-blow molding the preform by a single-stage blow molding method,
A stretch blow molding method for a plastic bottle container, characterized in that the resin at the high-temperature heating location is stretched to form at least one thin portion at the center of the body of the bottle container. 2. The plastic bottle according to claim 1, wherein by stretching the resin at the high-temperature heating portion, the resin is allocated to a portion that is continuous with the thin portion, and at least two thick portions are formed on the body of the bottle container. 3. Stretch blow molding method for containers. By heating a predetermined portion of the preform, in addition to the center of the body of the bottle container, at the shoulder and / or bottom of the bottle container at a temperature higher than the heating temperature of the other portions, the thin portion and / or the meat The stretch blow molding method for a plastic bottle container according to claim 1 or 2, wherein the thick portion is formed. The stretch blow molding method for a plastic bottle container according to claim 1, 2 or 3, wherein the thick portion is formed at a position where a load of the plastic bottle container is applied. The thickness of the thick portion is 0.33 to 0.45 mm,
The stretch blow molding method for a plastic bottle container according to claim 2, 3 or 4, wherein the thin portion has a thickness of 0.25 to 0.31 mm. 6. The stretch blow molding method for a plastic bottle container according to claim 1, wherein at least the body has a crystallinity of 30 to 40% among the mouth, the shoulder, the body and the bottom.

Images