JP2006137058A - Manufacturing method of plastic bottle container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a plastic bottle container made thin-walled uniformly as a whole by uniformly and sufficiently stretching a preform as a whole by preventing the whitening caused by over-stretching or local stretching at the time of stretch blowing of the preform. <P>SOLUTION: In a stretch blow molding method for forming the plastic bottle container by heating the bottomed cylindrical preform to a predetermined temperature to subject the same to stretch blow molding, blow air is supplied under heating and pressure to hold the preform to a softened state suitable for stretching at a region where the over-stretching or local stretching of the preform in a stretching process is easy to occur and the preform is reasonably stretched to prevent the whitening caused by over-stretching or local stretching to be stretched uniformly and sufficiently as a whole. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, when a preform (parison) made of polyethylene terephthalate or the like is stretch blow molded to produce a plastic bottle container, whitening due to overstretching and local stretching are prevented, and the entire preform is uniform and sufficient. The present invention relates to a method for producing a plastic bottle container, which can be stretched in a uniform manner, whereby the entire bottle container can be uniformly thinned.

In general, 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 subjecting an injection-molded preform (parison) to stretch blow molding (for example, Patent Document 1, Patent Document 2, etc.).
Thus, the plastic bottle container manufactured by the stretch blow molding method has excellent transparency and gas barrier properties, and is widely used as a bottle container for drinking water, mineral water, milk coffee, teas, health drinks, alcoholic beverages, seasonings, etc. in use.

JP 2002-240136 A (page 4, FIG. 4) Japanese Patent Publication No. 3011058 (Page 2)

By the way, in recent years, plastic bottle containers have rapidly spread and penetrated, and with this wide spread, there has been a strong demand for thinner and lighter containers, especially for beverage containers. . For example, a plastic bottle container currently used as a container for a capacity of 2000 ml has an average wall thickness of about 0.35 mm, but there is a demand for further reducing the thickness.
Here, the thickness of the plastic bottle container can be reduced by reducing the resin amount of the preform and performing stretch blow molding at a high stretch ratio.

However, such a method of simply reducing the amount of resin in the preform and increasing the draw ratio has problems such as whitening due to overstretching, rupture and the like, and it is difficult to obtain a bottle with a uniform wall thickness distribution.
In particular, in the rectangular bottle container as described in Patent Document 1 or Patent Document 2, the amount of the preform stretched is relatively large in the corner portion in the circumferential direction, and in the shoulder portion and heel portion in the height direction. For this reason, simply reducing the thickness of the preform or increasing the draw ratio in order to reduce the thickness of the side of the body, which tends to be relatively thick, The stretch ratio is locally increased, and accordingly, the wall thickness is too thin, and problems such as whitening due to overstretching and local stretching become remarkable.

In other words, when the preform is stretched and blown, when looking at the expansion and stretching in the lateral direction by the blow air, the preform is stretched almost concentrically, so when forming a square bottle container, it corresponds to the side of the container After the portion to be stretched has been stretched, the portion corresponding to the corner portion is further stretched. For this reason, the corner part of a square bottle container tends to be highly stretched, and if the diameter and thickness of the preform are designed in consideration of only the distance between the opposing container side surfaces by reducing the thickness of the container, Excessive stretching, especially in the corners, is performed at a low temperature because the preform in the stretching process is cooled by room temperature blow air and solidified to some extent in the later stage of the stretching blow process. It is easy to become overstretched at.
Also, when looking at the longitudinal stretching with blow air and stretch rod, the stretch rod first stretches the part corresponding to the bottom of the nozzle and the heel part first, and then the central part (body part) is stretched by the stretch rod and blow air. Since it is stretched, the bottom of the nozzle and the heel portion are likely to be highly stretched, and local stretching is likely to occur.
For this reason, it is impossible to force a preform that is relatively cold with blow air at room temperature in the diagonal direction of the shoulder portion of the container and the diagonal direction of the heel portion, both of which are likely to be highly stretched in both the horizontal and vertical directions. Since the film is stretched, whitening due to overstretching, local stretching, or the like occurs remarkably.

  The present invention has been proposed in order to solve the problems of the conventional techniques as described above. When the preform is stretch-blown, the preform in the stretching process is maintained in a state suitable for stretching. By making it easy to stretch the preform, it is possible to uniformly and sufficiently stretch the entire preform by preventing whitening due to overstretching and local stretching, thereby making the entire bottle uniform. The purpose is to provide a plastic bottle container that can be made thinner.

The method for producing a plastic bottle container of the present invention is a method for producing a plastic bottle container by heating a bottomed cylindrical preform at a predetermined temperature and performing stretch blow molding, wherein the preform is stretch blown. Blow air is supplied under heating and pressure so that the preform in the stretching process maintains a softened state suitable for stretching.
By adopting such a configuration, it is possible to maintain a state suitable for stretching even in a region where overstretching and local stretching are likely to occur, and it is possible to perform stretching without difficulty, whitening due to overstretching, Without causing local stretching, it is possible to satisfactorily manufacture a plastic bottle container that is thinned uniformly throughout.

At this time, the blow air is preferably supplied by heating in a temperature range of 70 to 180 ° C. in consideration of the material constituting the preform, the draw ratio when the preform is drawn into a container form, In consideration of the stretching speed, the set temperature of the blow air, etc., it is preferable to pressurize in a pressure range of 2 to 4 MPa.
Moreover, it is preferable that the preform is heated to a temperature of 110 to 120 ° C. prior to stretching blow. By appropriately combining this heating condition and the temperature setting of the blow air, it is possible to reduce the viscosity of the resin, and to suppress whitening due to distortion or overstretching that occurs in stretch molding.

  Further, in the method for manufacturing a plastic bottle container according to the present invention, the stepped portion is formed while reducing the weight of the container bottom by forming a stepped portion between the body portion and the bottom portion of the preform. By extending the bottom part and the bottom part integrally, it is possible to uniformly stretch a predetermined range of the body part and the bottom part of the preform. Further, between the mouth portion and the trunk portion of the preform, a straight portion that is thinner than the trunk portion and a throttle portion that gradually increases the thickness while the diameter is narrowed and connects the straight portion and the trunk portion. By forming the neck lower portion, the neck lower portion is extended integrally with the body portion, so that a predetermined range of the preform body portion and the mouth portion can be uniformly extended. As a result, the entire preform can be stretched uniformly.

  According to the stretch blow molding method of the plastic bottle container of the present invention as described above, the blow air for stretching and blowing the preform is heated and pressurized to maintain the preform in the stretching process in a softened state suitable for stretching. By doing so, it is possible to maintain a state suitable for stretching even in a region where overstretching or local stretching is likely to occur, and to perform stretching without difficulty. Accordingly, the entire bottle can be uniformly thinned without causing whitening due to overstretching or local stretching, and for example, a desired thin-walled bottle having an average wall thickness of about 0.22 mm or less can be obtained.

Hereinafter, a preferred embodiment of a method for producing a plastic bottle container according to the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing a preform used in an embodiment of a method for producing a plastic bottle container according to the present invention. 2A and 2B are enlarged views of the main part of the preform shown in FIG. 1, wherein FIG. 2A is an enlarged view of the vicinity of the lower part of the neck, and FIG. FIG. 3 is a process diagram showing an outline of a production process in an embodiment of the method for producing a plastic bottle container according to the present invention.

[preform]
1. As shown in FIG. 1, a preform 1 used in the present embodiment is a preform for producing a bottle container 10 (see FIG. 4), and is made of a thermoplastic resin and has a cylindrical shape. Body portion 4, a mouth portion 2 that opens to one end side of the body portion 4, and a substantially hemispherical bottom portion 5 that closes the other end side of the body portion 4. ing.
The preform 1 includes a stepped portion 5 a formed in a predetermined shape between the body portion 4 and the bottom portion 5, and a neck lower portion 3 formed in a predetermined shape between the mouth portion 2 and the body portion 4. It has.

The stepped portion 5a is a part (predetermined range) of the preform 1 located between the barrel portion 4 and the bottom portion 5 and is continuous from the barrel portion 4 with substantially the same thickness. Both the inner surface and the outer surface are on the cylinder center side. It is formed so as to continue to the bottom 5 while inclining.
Here, the stepped portion 5a can set the wall thickness, the inclination angle of the inner and outer surfaces, the length, etc. to desired values, depending on the size, shape, wall thickness, etc. of the bottle container to be manufactured. Can be set arbitrarily.

In the present embodiment, the ratio of the thickness Ta of the body 4 shown in FIG. 2 to the thickness Tb of the boundary between the stepped portion 5a and the bottom 5 is 1.0 <Ta / Tb ≦ 1.5. It is set.
Setting such a range makes it difficult to injection-mold the preform 1 so that the thickness of the stepped portion 5a is larger than that of the body portion 4 (Ta / Tb ≦ 1.0). When Ta / Tb exceeds 1.5 (Ta / Tb> 1.5), the difference in thickness between the body 4 and the stepped portion 5a becomes too large, and the local portion is continuously formed between the body 4 and the stepped portion 5a. This is because stretching and overstretching tend to occur. The thickness Tb of the stepped portion 5a refers to the thickness of the boundary portion between the bottom portion 5 and the stepped portion 5a (see FIG. 2B).

2, the radius Ra from the cylinder center to the thickness center of the barrel portion 4, the radius Rb from the cylinder center to the thickness center at the boundary between the stepped portion 5 a and the bottom portion 5, and the thickness of the barrel portion 4. The thickness Ta is set to satisfy Rb ≦ Ra−Ta / 2.
The range is set so that a step is not formed unless the radius of the stepped portion 5a is at least smaller than the radius of the body portion 4, while the difference in radius is half the thickness Ta of the body portion 4. The following steps are because injection molding becomes difficult.
By setting the values as described above, the stepped portion 5a can be inclined at a desired angle while making the stepped portion 5a substantially the same thickness as the continuous body portion 4.

Furthermore, the angle θ inclined toward the cylinder center side of the stepped portion 5a shown in FIG. 2B can be set in a desired range. By setting the inclination angle of the stepped portion 5a, the extension amount of the stepped portion 5a and the bottom portion 5 and the weight of the bottom portion 5 can be controlled according to the angle.
That is, if the inclination angle θ of the stepped portion 5a is set to be small, the stretch amount of the stepped portion 5a increases, the stretch amount of the bottom portion 5 decreases, and the weight of the bottom portion 5 increases. On the other hand, if the inclination angle θ of the stepped portion 5a is set to be large, the stretch amount of the stepped portion 5a is reduced, the stretch amount of the bottom portion 5 is increased, and the weight of the bottom portion 5 can be reduced. .

  Here, the inclination angle θ of the stepped portion 5a is preferably 7 ° ≦ θ ≦ 45 °, and particularly preferably set in the range of 20 ° ≦ θ ≦ 40 °. If the inclination angle θ of the stepped portion 5a is smaller than 7 ° (θ <7 °), the effect due to the step cannot be obtained, and if it is larger than 45 ° (θ> 45 °), local stretching and overstretching occur. This is because the tendency becomes stronger.

In the example shown in FIG. 2, the inner surface and the outer surface of the stepped portion 5 a are inclined at substantially the same angle, and the thickness of the stepped portion 5 a is set to be substantially the same value from the body portion 4 to the bottom portion 5. However, the inclination angle of the stepped portion 5a may be different between the inner surface and the outer surface. If it does in this way, the stepped part 5a is formed in the taper shape which becomes thin toward the bottom part 5 from the trunk | drum 4 by setting the inclination angle of the outer surface of the stepped part 5a larger than the inclination angle of an inner surface, for example. It is possible to increase the stretch amount by setting a desired thin portion.
And by providing such a stepped part 5a, when the preform 1 is stretch blow-molded by a process described later, the stepped part 5a and the bottom part 5 are stretched uniformly uniformly, and the body part 4 is stretched. The burden is reduced and the weight of the bottom 5 is reduced, and as a result, the entire preform is stretched uniformly.

The neck lower part 3 is a part (predetermined range) of the preform 1 located between the body part 4 and the mouth part 2, and has a straight part 3 a continuous from the mouth part 2 and thinner than the body part 4. Yes. The straight portion 3a is formed so as to be continuous with the body portion 4 through a narrowed portion 3b that gradually increases in thickness while being narrowed in diameter.
Here, the neck lower part 3 including the straight part 3a and the throttle part 3b can be set to a desired thickness, length, etc., and the size, shape, thickness, etc. of the bottle container to be molded It can be set arbitrarily depending on the situation.

In the present embodiment, the ratio of the thickness Ta of the body portion 4 shown in FIG. 2 to the thickness Tc of the straight portion 3a is set to satisfy 1.2 ≦ Ta / Tc ≦ 1.7.
Setting such a range makes it difficult to injection-mold the preform 1 so that the thickness ratio of the body portion 4 and the straight portion 3a is smaller than 1.2 (Ta / Tc <1.2). Yes, if Ta / Tc exceeds 1.7 (Ta / Tc> 1.7), the thickness difference between the body 4 and the straight portion 3a becomes too large, and the straight portion 3a is locally stretched and overstretched. This is because the tendency to occur becomes stronger.

  Further, the ratio of the length La of the straight portion 3a in the longitudinal direction of the tube to the thickness Tc is set to satisfy 3 ≦ La / Tc ≦ 5. If the straight part 3a is too short (La / Tc <3), the tendency of local stretching and overstretching at the lower neck becomes strong, and if the straight part 3a is too long (La / Tc> 5), injection molding is performed. This is because it is difficult for the material to enter during molding.

  Further, the aperture ratio of the aperture portion 3b, that is, the ratio of the outer diameter φy of the body portion 4 to the outer diameter φx of the straight portion 3a is set to satisfy 0.4 ≦ φy / φx ≦ 1.3. If this drawing ratio is too small (φy / φx <0.4), the tendency to cause local stretching or overstretching becomes strong. If it is too large (φy / φx> 1.3), the straight portion 3a and the drawn portion This is because 3b is not sufficiently stretched, and the stepped portion 5a is stretched first, resulting in overstretching.

Specifically, in the case of a bottle container preform having a capacity of 2000 ml as shown in FIG. 4 to be described later, the resin weight is set to about 30 to 40 g, and the thickness of the body portion 4 is set to about 3 to 4 mm. In this case, the difference between the thickness Ta of the body portion shown in FIG. 2 and the thickness Tc of the straight portion is set to be Ta−Tc = 1.6 mm or less.
Furthermore, the straight part 3a and the narrowed part 3b can be set so that the length in the cylinder longitudinal direction can be set to a desired range, and the length La in the cylinder longitudinal direction of the straight part 3a is set to 5 to 9 mm, The length Lb of the throttle part 3b in the cylinder longitudinal direction is set to be 7 to 15 mm. Further, the length Lc of the barrel portion 4 in the longitudinal direction of the cylinder can also be set to a desired range, and is set to be 56 to 86 mm.
By setting to such a value, a bottle container having a capacity of 2000 ml and an average wall thickness of about 0.22 mm can be obtained.

In this way, the neck portion 3 is provided with a straight portion 3a that is thinner than the trunk portion 4, and a throttle portion 3b that gradually increases the thickness while the diameter is narrowed to connect the straight portion 3a and the trunk portion 4. By making it possible to set the thickness and length and the drawing ratio of the drawn portion 3b as appropriate, the entire neck lower portion 3 including the straight portion 3a and the drawn portion 3b can be stretched uniformly.
When the preform 1 is stretch-blow-molded by the process described later, the neck lower portion 3 is stretched uniformly uniformly, reducing the stretching burden on the body 4, and as a result, the entire preform is stretched uniformly. Will come to be.
In the example shown in FIGS. 1 and 2, the straight portion 3a is formed so that the thickness Tc is uniform from the mouth portion 2 to the throttle portion 3a. For example, the outer surface of the straight portion 3a Alternatively, it is possible to change the wall thickness by inclining the inner surface. If it does in this way, the amount of extending | stretching can be varied between a thick part and a thin part, and an extending amount can be adjusted.

2. Component As the thermoplastic resin constituting the preform 1 used in the present embodiment, any resin can be used as long as it can be stretch blow molded and thermally crystallized.

Specifically, thermoplastic polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyarylate, polylactic acid or copolymers thereof, blends of these resins or other resins are suitable. In particular, an ethylene terephthalate thermoplastic polyester such as polyethylene terephthalate is preferably used.
Further, acrylonitrile resin, polypropylene, propylene-ethylene copolymer, polyethylene and the like can also be used.
These resins are blended with various additives such as colorants, ultraviolet absorbers, mold release agents, lubricants, nucleating agents, antioxidants, antistatic agents, etc. within the range that does not impair the quality of the molded product. be able to.

The ethylene terephthalate-based thermoplastic polyester constituting the preform 1 occupies most of the ester repeating units, generally 70 mol% or more of the ethylene terephthalate units, and has a glass transition point (Tg) of 50 to 90 ° C., a melting point ( Those having a Tm) in the range of 200 to 275 ° C are preferred.
As an ethylene terephthalate-based thermoplastic polyester, polyethylene terephthalate (PET) is particularly excellent in terms of pressure resistance, heat resistance, heat pressure resistance, etc. In addition to ethylene terephthalate units, dibasic acids such as isophthalic acid and naphthalenedicarboxylic acid Copolyesters containing a small amount of ester units composed of diols such as propylene glycol can also be used.

Further, the preform 1 of the present embodiment can be composed of two or more thermoplastic polyester layers in addition to the case of being composed of 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 is a barrier layer or an oxygen absorbing layer. Can do.
By providing the barrier layer and the oxygen absorbing layer in this way, it is possible to suppress the permeation of oxygen from the outside into the bottle container, and to prevent the deterioration of the contents in the bottle container due to the oxygen from the outside. Suitable for bottle containers for beverages containing carbon dioxide gas.
Here, as the oxygen absorbing layer, any layer can be used as long as it absorbs oxygen and prevents permeation of oxygen, but a combination of an oxidizable organic component and a transition metal catalyst, or substantially oxidized. It is preferred to use a combination of non-gas barrier resin, oxidizable organic component and transition metal catalyst.

[Plastic bottle container manufacturing method]
Next, a method for producing a plastic bottle container according to the present embodiment using the above preform will be specifically described.
1. Production of Preform The preform 1 can produce a bottomed cylindrical preform (parison) by known injection molding or extrusion molding. For the neck lower part 3 including the stepped part 5a between the body part 4 and the bottom part 5 described above, the straight part 3a between the mouth part 3 and the body part 4 and the throttle part 3b, a desired shape is obtained by known injection molding or the like. Can be manufactured in dimensions.
When a multilayer preform having an oxygen absorbing layer in the intermediate layer is used as the preform 1, the inner and outer layers are made of polyester resin using a conventionally known co-injection molding machine or the like, and between the inner and outer layers. A multilayer preform having a heel portion and an opening corresponding to the shape of the injection preform mold can be manufactured by inserting one or more oxygen absorbing layers.

2. Stretch Blow Molding Next, the preform 1 is biaxially stretch blow molded.
In the present embodiment, first, the preform 1 is heated to a stretching temperature equal to or higher than the glass transition point (Tg). The preform 1 is heated by a known heating means such as a heater 101 as shown in FIG. Further, at the time of this heating, as shown in FIG. 1, the non-crystalline mouth portion 2 is protected by a heating prevention cooling guide 102 so as not to be heated. A preform in which the mouth 2 is crystallized in advance can also be used.

  In this embodiment, the preform 1 is heated at a heating limit temperature of about 120 ° C. When a normal thick bottle container is manufactured, the heating temperature of the preform is about 85 ° C. to 110 ° C. In this embodiment, the temperature of the resin is increased by raising the temperature to around 120 ° C. which is the heating limit. The viscosity is reduced, and the strain generated by stretch molding is reduced. However, heating at a high temperature exceeding 120 ° C. is not preferable because the bottle is whitened (white turbid) after blow molding. In the present embodiment, a preferable preform heating temperature is 110 to 120 degrees.

Next, the heated preform 1 is subjected to biaxial stretch blow molding in a mold heated to a predetermined heat treatment (heat set) temperature.
Specifically, as shown in FIGS. 3A to 3B, first, the heated preform 1 is set in a mold 103 (see FIG. 3A), and then a stretch rod (stretched). (Rod) 104 is stretched in the longitudinal direction (axial direction) by blow air, and is stretched mainly in the lateral direction (circumferential direction) by blow air, and is also stretched in the longitudinal direction when it is shaped by a mold (see FIG. 3 (b)).

At this time, in this embodiment, the blow air is set to 70 to 180 ° C. in consideration of the material constituting the preform 1, the draw ratio when the preform 1 is drawn into a container form, and the shape of the container 1. Set to temperature. Accordingly, heat is constantly applied to the preform 1 in the stretching process, and a softened state suitable for stretching can be maintained in all the stretching processes.
Accordingly, it is possible to effectively avoid whitening due to overstretching, which has conventionally occurred by further stretching a preform that has been solidified to some extent in the later stage of the preform stretching step.

  The blow air is supplied under pressure in order to stretch the preform 1, and the pressure is preferably set to 2 to 4 MPa in consideration of the stretching speed, the set temperature of the blow air, and the like.

Here, in the preform 1 used in the present embodiment, the stepped portion 5a is uniformly stretched as a whole including the continuous bottom portion 5 during stretching. Moreover, the neck lower part 3 is uniformly extended as a whole including the straight part 3a and the throttle part 3b.
As a result, the entire preform 1 is uniformly stretched, and whitening due to overstretching can be effectively avoided by setting the temperature of the blow air, so that local stretching and overstretching do not occur. The bottle container 10 having a uniform wall thickness distribution is formed.

Moreover, the draw ratio of the blow molded product in the present embodiment is 2.4 to 3.1 times in the vertical direction, 4.5 to 6 times in the horizontal direction, and 10.8 to 18.6 times in the vertical and horizontal directions. Set as follows.
In the case of a normal thick bottle container, the stretch ratio of the blow molded product is about 2.2 times in the vertical direction, about 5 times in the horizontal direction, and about 11 times in the vertical and horizontal directions.
In the present embodiment, the entire preform 1 is uniformly stretched by the shape of the preform 1, and whitening due to overstretching can be effectively avoided by setting the temperature of the blow air, and local stretching and overstretching occur. In order to obtain a bottle container that is as thin as possible with a uniform wall thickness distribution, at least the above draw ratio is preferable.

3. Heat setting The stretched blow molded article is heat set (heat-set) in a mold.
In the heat setting, the above-described blow mold 103 is heated to a predetermined temperature, and at the time of biaxial stretching blow, the outer wall of the blow molded article is brought into contact with the inner surface of the mold for a predetermined time for heat treatment.
Here, in this embodiment, the mold is heated to a temperature of about 105 to 115 ° C. as the heat set temperature.

Moreover, although the heat processing time (blow time) of heat set changes also with the thickness and temperature of a blow molded object, it is generally 1 to 10 seconds, Preferably it is about 2 to 5 seconds. Further, the subsequent cooling time varies depending on the heat treatment temperature and the type of cooling fluid, but is generally about 0.1 to 10 seconds, preferably about 0.2 to 5 seconds.
By this heat setting, the blow molded product is crystallized.
The crystallinity of the blow molded product depends on conditions such as the thickness, shape, heat set temperature, time, etc. of the container. By optimizing these conditions, the crystallization of the body portion 13 of the bottle container 10 is achieved. The degree can be set to a suitable range of about 30 to 40%, for example.

4). Cooling Blow After the heat treatment for the predetermined time, the inside of the blow molded body is cooled by the internal cooling fluid ejected from the cooling blow rod 105 as shown in FIG.
Here, in this embodiment, the air supply pressure of the cooling blow is about 4 MPa. When a normal thick bottle container is blow-molded, the air supply pressure of the cooling blow is about 3 MPa. However, in this embodiment, by increasing the air supply pressure, the temperature at which the bottle is taken out after blow molding is increased. This is reduced to prevent the occurrence of sink marks.

  The cooling fluid includes normal temperature air, various cooled gases, for example, nitrogen at −40 ° C. to + 10 ° C., air, carbon dioxide gas, etc., and a chemically inert liquefied gas such as liquefied nitrogen. Gas, liquefied carbon dioxide gas, liquefied trichlorofluoromethane gas, liquefied dichlorodifluoromethane gas, other liquefied aliphatic hydrocarbon gas, and the like can be used. In this cooling fluid, a liquid mist having a large heat of vaporization such as water can coexist. By using the cooling fluid as described above, a remarkable cooling temperature can be obtained.

Thereafter, as shown in FIG. 3D, the molded body is taken out from the mold, and the bottle container 10 is obtained. The blow molded body (bottle container 10) taken out from the mold is cooled by cooling or by blowing cold air. This completes the stretch blow molding process.
This embodiment implemented according to the above processes is particularly suitable for manufacturing a bottle container 10 as shown in FIG. 4, for example.

[Bottle container]
FIG. 4 shows an example of a bottle container manufactured according to the present embodiment, FIG. 4 (a) is a front view of the bottle container, and FIGS. 4 (b) and 4 (c) respectively show FIG. 4 (a). It is an AA lateral end view and BB lateral end view. In the drawing, the thickness of the bottle container 10 is exaggerated in FIGS. 4 (b) and 4 (c).

The bottle container 10 shown in FIG. 4 includes a mouth part 20, a body part 30, and a heel part 40, and has a substantially cylindrical container shape. A waist part 50 with a narrowed diameter is formed in the center of the body part 30 in the height direction. The body part 30 is divided into an upper body part 31 and a lower body part 32 with the waist part 50 as a boundary.
Here, the height direction means a direction along a direction perpendicular to the horizontal plane when the bottle container 10 is placed on a horizontal plane with the mouth portion 20 facing up.

In the illustrated example, a plurality of ridge lines 311 extending along the height direction are formed. Each ridgeline 311 is formed along the side surface of the upper body portion 31 and is observed in a straight line when viewed from the front.
Between these ridges 311, when the internal pressure of the bottle container 10 decreases, twelve decompression absorbing surfaces 312 that gently curve inward of the bottle container 1 and absorb the pressure decrease are formed. The cross-sectional shape of the upper body 31 is a regular dodecagon (see FIG. 4B).
In addition, a plurality of ridge lines 321 extending spirally along the height direction are formed on the lower body section 32, and the cross-sectional shape of the lower body section 32 is correct between the ridge lines 321. The sixteen decompression absorbing surfaces 322 are uniformly formed so as to have a dodecagonal shape (see FIG. 4C).

Here, the number of the reduced pressure absorption surfaces 312 and 322 formed on the upper body portion 31 and the lower body portion 32 is such that the angle at which the adjacent reduced pressure absorption surfaces 312 and 322 intersect is 135 to 163.7 degrees, preferably 144 to It is set to be 162 degrees.
Specifically, when the maximum diameter φb of the upper mold body 31 is about 95 to 115 mm, the number of decompression absorption surfaces 312 formed on the upper mold body 31 is 8 to 16 surfaces, preferably 10 to 10 surfaces. There are four sides. When the maximum diameter φc of the lower mold body 32 is about 100 to 120 mm, the number of the reduced pressure absorption surfaces 322 formed on the lower body 32 is 10 to 22, preferably 12 to 20. Surface.
In addition, when the cross-sectional shape of the upper trunk portion 31 and the lower trunk portion 32 is formed in a regular polygon shape, the angle at which the adjacent reduced pressure absorption surfaces 312 intersect is 135 degrees for a regular octagon, 144 degrees for a regular decagon, The angle is 162 degrees for the icosahedron and 163.6 degrees for the regular icosahedron.

  Normally, overstretching is likely to occur in the circumferential direction at the corner portion and its vicinity, and becomes more noticeable as the corner portion is sharpened. If the angle formed by the reduced pressure absorbing surfaces 321 and 322 located on both sides of the ridge lines 311 and 321 is a relatively dull angle within the above range, and the ridge lines 311 and 321 are sharpened, the ridge lines 311 and 321 corresponding to the corner portions are formed. In addition, overstretching in the vicinity thereof can be suppressed, and whitening due to overstretching can be avoided more effectively in applying the manufacturing method of the present embodiment.

  By the way, in the example of the bottle container shown in the figure, the reduced pressure absorption surfaces 312 and 322 have the above-described structure because the entire surface along the circumferential direction of the upper barrel portion 31 and the lower barrel portion 32 functions as the reduced pressure absorption surface. This is because the reduced pressure absorption performance of the bottle container 1 is improved. Further, the ridge lines 311 and 321 formed along the height direction function as columnar structural portions, and in particular, improve load resistance strength against a load in the vertical direction. Furthermore, by forming such ridge lines 311 and 321, sink marks during molding can be prevented and the moldability of the container 1 can be improved.

  Therefore, if the number of decompression absorbing surfaces 312 and 322 is less than the above-described range, the angle formed by the decompression absorbing surfaces 312 and 322 located on both sides of the ridge lines 311 and 321 becomes relatively sharp, and the ridge line 311 , 321 and the vicinity thereof, and the number of the ridge lines 311, 321 is also reduced, so that the ridge lines 311, 321 for improving the load resistance strength and preventing the sink are formed as described above. The effect obtained by this will also become inadequate. In addition, since the reduced pressure absorbing surfaces 312 and 322 become large, sink marks after molding occur, or the amount of deformation per surface at the time of absorbing the reduced pressure becomes too large, which adversely affects the appearance of the bottle container 1.

  On the other hand, when the reduced pressure absorbing surfaces 312 and 322 are formed beyond the above range, overstretching hardly occurs at the ridge lines 311 and 321 and the vicinity thereof, and an effect such as sink prevention by the ridge lines 311 and 321 can be obtained. Since the absorption surfaces 312 and 322 become smaller, the amount of reduced pressure absorption per surface during reduced pressure absorption decreases, and sufficient reduced pressure absorption performance cannot be obtained. Furthermore, since the angle formed between the adjacent vacuum absorbing surfaces 312 and 322 becomes too dull, the function of the ridge lines 311 and 321 for maintaining the container shape is impaired, and the load bearing strength is also reduced.

  Thus, in manufacturing the bottle container 10 as shown in FIG. 4, the number of the reduced pressure absorption surfaces 312 and 322 is the balance between the moldability of the bottle container 10, the required load bearing strength and the reduced pressure absorption performance, Although it is appropriately set in consideration of the deformation of the bottle container 10 at the time of absorbing the reduced pressure, the design of the bottle container 10, etc., in this embodiment, while considering these, overstretching in the ridge lines 311 and 321 and the vicinity thereof is performed. In order to suppress, by setting the angle formed by the reduced pressure absorbing surfaces 312 and 322 and the temperature of blow air at the time of stretch blow molding in a well-balanced manner, a bottle container is manufactured with good moldability while preventing whitening due to overstretching. Can do.

Hereinafter, the specific Example in the case of manufacturing a bottle container by the manufacturing method of the plastic bottle container which concerns on this invention is shown.
[Example]
Polyethylene terephthalate (PET) was supplied to an extruder to produce a preform 1 having a weight of 35 g. In the preform 1, a stepped portion 5 a is formed between the body portion 4 and the bottom portion 5, and a neck lower portion 3 having a straight portion 3 a and a narrowed portion 3 b is formed between the body portion 4 and the mouth portion 2. .
The thickness of the preform 1 was set such that the thickness Ta of the body portion 4 was about 3.5 mm, the thickness Tc of the straight portion 3a was about 2 mm, and the thickness Tb of the stepped portion 5a and the bottom portion 5 was about 3 mm. The inclination angle θ of the stepped portion 5a was about 13 °. The straight portion 3a has a length La of about 7 mm, the throttling portion 3b has a length Lb of about 10 mm, and the throttling portion 3b has a throttling ratio φy / φx of 0.9. The length Lc of the body part 4 was 70 mm.

This preform 1 is heated to about 115 ° C. above the glass transition point (Tg), set in a mold heated to about 110 ° C., and blow air heated to a temperature of about 120 ° C. is pressurized to about 3 MPa. Then, biaxial stretching blow was performed by a single-stage blow molding method, and then cooling blow was performed at an air supply pressure of about 4 MPa to obtain a bottle container having an internal capacity of about 2000 ml as shown in FIG.
The dimensions of the container 1 are: the height H is 310 mm, the opening diameter φa of the mouth portion 2 is 26 mm, the maximum diameter φb of the upper body portion 31 is 107 mm, the maximum diameter φc of the lower body portion 32 is 110 mm, The small diameter φd was 72 mm. Moreover, the average thickness of the trunk | drum 2 was about 0.22 mm.

  In the bottle container thus obtained, whitening due to overstretching was not observed. Moreover, the uneven thickness by local extending | stretching was not observed, but it formed with the uniform thickness as a whole.

  Although the present invention has been described with reference to the preferred embodiment, it is needless to say that the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention. .

For example, as the bottle container suitably manufactured according to the above embodiment, a substantially cylindrical one is illustrated, but the plastic bottle container manufactured according to the present invention is not limited to a cylindrical one. For example, even if it is a square bottle container, it can implement by rounding a corner part or using chamfering together as needed.
Moreover, in the said embodiment, although the capacity | capacitance of a 2000 ml bottle container was shown, in the application of this invention, the capacity | capacitance of a bottle container is not specifically limited. Therefore, for example, even a bottle container with a capacity of 1000 ml or a bottle container with a capacity of 1500 ml does not hinder the application of the present invention.

  The present invention described above can be used in a stretch blow molding method for manufacturing a plastic bottle container by stretch blow molding a preform (parison) made of polyethylene terephthalate or the like, which is a preformed product.

It is sectional drawing which shows the outline of the preform used in one Embodiment of the manufacturing method of the plastic bottle container which concerns on this invention. FIG. 2 is an enlarged view of a main part of the preform shown in FIG. It is process drawing which shows the outline of the manufacturing process in one Embodiment of the manufacturing method of the plastic bottle container which concerns on this invention. An example of the bottle container manufactured by one Embodiment of the manufacturing method of the plastic bottle container which concerns on this invention is shown, (a) is a front view of a bottle container, (b), (c) is (a), respectively. A-A horizontal end face and BB horizontal end face are shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Preform 2 Mouth part 3 Neck lower part 3a Straight part 3b Restriction part 4 Preform trunk | drum 5 Preform bottom part 5a Preform step part 10 Bottle container

Claims (6)

A method of manufacturing a plastic bottle container by heating a bottomed cylindrical preform at a predetermined temperature and performing stretch blow molding,
A method for producing a plastic bottle container, characterized in that blow air for stretching and blowing the preform is heated and pressurized so that the preform in the stretching process maintains a softened state suitable for stretching.   The method for producing a plastic bottle container according to claim 1, wherein the blow air is heated and supplied in a temperature range of 70 to 180 ° C.   The method for producing a plastic bottle container according to claim 1 or 2, wherein the blow air is pressurized and supplied in a pressure range of 2 to 4 MPa.   The method for producing a plastic bottle container according to claim 1, wherein the preform is stretched and blown after being heated in a temperature range of 110 to 120 ° C.   The manufacturing method of the plastic bottle container of Claims 1-4 which extended | stretched the said step part and the said bottom part integrally by forming a step part between the trunk | drum and bottom part of the said preform. .   A neck having a straight part that is thinner than the trunk part and a throttle part that gradually increases the thickness while the diameter is narrowed and connects the straight part and the trunk part between the mouth part and the trunk part of the preform. The method for producing a plastic bottle container according to claim 1, wherein the lower part of the neck is extended integrally with the body part by forming a lower part.

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