JP4292918B2 - Preforms for plastic bottle containers - Google Patents

Description

The present invention relates to a preform (parison) made of polyethylene terephthalate or the like, which is a preform of a plastic bottle container.
In particular, by forming a portion corresponding to the bottom heel and shoulder of the bottle in a predetermined shape, the entire preform can be stretched uniformly and sufficiently by preventing local stretching and overstretching. The present invention relates to a preform for a plastic bottle container, which can uniformly reduce the thickness of the entire bottle without whitening, and can produce a bottle container that is capable of high-temperature heat setting and has excellent heat resistance.

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 stretch-blow molding an injection-molded preform (parison) (see, for example, Patent Documents 1-3).
Thus, the plastic bottle container manufactured by the stretch blow molding method is excellent in transparency and gas barrier property, and is used as a bottle container for beverages such as carbonated beverages such as cola and cider, fruit juice beverages, mineral water, and various teas. Widely used.

JP 2002-240136 A (page 4, FIG. 4) Japanese Patent Publication No. 2781810 (5th page, Fig. 2-4) 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 thickness of about 0.35 mm, and there is a demand for further reducing the thickness to about 0.25 mm.
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, in this method of simply reducing the amount of preform resin and increasing the draw ratio, especially in the case of flat bottle containers, stretch distortion occurs, a bottle with a uniform wall thickness distribution cannot be obtained, and whitening occurs. There was a problem that it was easy. In particular, in the diagonal direction of the heel portion of the rectangular bottle container, the stretch ratio is locally high, and problems such as strain, whitening, and deformation due to overstretching are significant.
Further, in a bottle container in which stretch distortion has occurred, if the heat set temperature of the mold is the same as that of a normally thick bottle (for example, about 120 to 135 ° C.), the bottle shrinks when removed from the mold. In particular, so-called sink marks were easily generated in the overstretched portion of the heel portion of the rectangular bottle.

Further, in order to prevent such shrinkage of the bottle, it is necessary to lower the heat set temperature (blow mold temperature) (for example, about 80 ° C.). There was a problem that heat resistance could not be obtained.
A bottle container that does not have heat resistance cannot withstand the hot water sterilization washing temperature (about 65 to 80 ° C.) in an aseptic filling application that does not require relatively high heat resistance. Could not be used as well.

In this way, simply reducing the amount of resin in the preform and increasing the draw ratio to reduce the thickness of the bottle container will result in uneven thickness distribution, whitening of the bottle, and further deterioration in heat resistance. Problems have arisen, and it has not been possible to cope with the thinning of the aseptic bottle, which is particularly desired to be lightweight.
As a result of intensive studies in view of the above circumstances, the present inventor has established a preform in a predetermined shape, thereby preventing local stretching and overstretching, thereby enabling uniform stretch blow molding. The inventor has come up with the idea that the inconvenience of reducing the thickness of the container can be solved.

That is, the present invention has been proposed in order to solve the problems of the conventional techniques as described above, and by forming portions corresponding to the bottom heel portion and shoulder portion of the bottle in a predetermined shape, The entire preform can be stretched uniformly and sufficiently, preventing excessive stretching and overstretching, which enables uniform thinning of the entire bottle without whitening, enabling high-temperature heat setting. The present invention relates to preforms for plastic bottle containers suitable for flat bottles, aseptic bottles and the like, which can produce bottle containers having excellent heat resistance.

In order to achieve the above object, a preform for a plastic bottle container according to the present invention includes a cylindrical body, a mouth opening at one end of the body, and a bottom for closing the other end of the body. A preform that has a bottomed cylindrical shape and becomes a plastic bottle container by stretch blow molding, and is continuous between the barrel and the bottom with almost the same thickness from the barrel, and both the inner and outer surfaces are on the center side of the barrel. The step is provided with a stepped portion that continues to the bottom while inclining.

Further, a plastic bottle preform of the present invention includes a cylindrical body portion, and a mouth that opens on one end side of the body, a bottomed cylindrical shape having a bottom which closes the other end of the body portion None, a preform that becomes a plastic bottle container by stretch blow molding, and has a neck lower part that is continuous from the mouth part and is connected to the body part through a straight part thinner than the body part between the body part and the mouth part. As a configuration.

Furthermore , the preform for a plastic bottle container according to the present invention has a bottomed cylindrical shape including a cylindrical body, a mouth opening on one end of the body, and a bottom closing the other end of the body. None, a preform that becomes a plastic bottle container by stretch blow molding, and is continuous between the barrel and the bottom with approximately the same thickness from the barrel, while the inner and outer surfaces are both inclined toward the center of the cylinder and In addition to providing a continuous stepped portion, a neck portion is provided between the trunk portion and the mouth portion, the neck portion being continuous from the mouth portion, passing through the straight portion thinner than the trunk portion, and continuing to the trunk portion.

More specifically, the ratio of the thickness (Ta) of the body portion to the thickness (Tb) of the stepped portion is 1.0 ≦ Ta / Tb ≦ 1.5.
Further , the radius (Ra) from the cylinder center to the thickness center of the barrel portion, the radius (Rb) from the cylinder center to the thickness center of the stepped portion, and the thickness (Ta) of the barrel portion are Rb ≦ Ra−Ta. The configuration becomes / 2.

In addition , the ratio of the thickness (Ta) of the body portion to the thickness (Tc) of the straight portion is 1.2 ≦ Ta / Tc ≦ 1.7.
Further , the ratio of the thickness (Tc) of the straight portion to the length (La) in the longitudinal direction of the cylinder is 3 ≦ La / Tc ≦ 5.

According to the plastic bottle container preform of the present invention as described above, the stepped portion is formed in the portion corresponding to the bottom heel portion of the bottle, and the inclination angle and thickness of the stepped portion are set to predetermined values. By this, the stepped portion and the bottom can be stretched integrally, and local stretching and overstretching can be prevented, and the entire body, stepped portion, and bottom can be stretched uniformly and sufficiently. Become.
In addition, a neck lower part having a straight part is formed in a part corresponding to the shoulder part of the bottle, and the length and thickness of the straight part are set to predetermined values, so that the neck lower part including the straight part is integrated with the trunk part. It can be stretched, and local stretching and overstretching can be prevented from occurring in the lower part of the neck.

In this way, in the present invention, the entire preform can be stretched uniformly, and the entire bottle can be uniformly thinned without causing stretching strain or whitening. For example, the average thickness is about 0.25 mm. Desired thin-walled bottles can be obtained.
In addition, a bottle having no stretching strain can be heat-set at high temperature, and can impart heat resistance substantially the same as that of a normal wall-thick bottle while being thin.
As a result, it is possible to realize a preform for a plastic bottle container suitable for a rectangular bottle that tends to be excessively stretched in the bottle heel portion, an aseptic bottle that requires hot water sterilization cleaning, and the like.

Hereinafter, a preferred embodiment of a preform for a plastic bottle container according to the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a preform for a plastic bottle container according to an embodiment of the present invention.
2 is an enlarged view of the main part of the preform shown in FIG. 1, wherein (a) is an overall view of the preform, (b) is an enlarged view of the lower part of the neck, and (c) is an enlarged view of the stepped portion.
FIG. 3 is an enlarged view of the stepped portion of the preform shown in FIG. 1, and shows a mode in which the inclination angle of the stepped portion is changed.

[preform]
1. As shown in FIG. 1, a preform 1 according to this embodiment is a preformed product for producing a bottle container 10 (see FIG. 6), is made of a thermoplastic resin, and has a cylindrical body. It is formed in a bottomed cylindrical shape (test tube) including a 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. .
The preform 1 according to this embodiment includes a stepped portion 5a formed in a predetermined shape between the body portion 4 and the bottom portion 5, and is formed in a predetermined shape between the mouth portion 2 and the body portion 4. The neck lower part 3 is provided.

The stepped portion 5a is a part of the preform 1 located between the trunk portion 4 and the bottom portion 5 and is continuous from the trunk portion with substantially the same thickness. Both the inner surface and the outer surface are inclined toward the center of the cylinder. 5 to be continuous.
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, and can be arbitrarily set according to the size, shape, wall thickness, etc. of the bottle container to be molded. Can be set.

In the present embodiment, the ratio between the thickness (Ta) of the body 4 shown in FIG. 2 and the thickness (Tb) of the stepped portion 5a (and the continuous bottom 4) is 1.0 ≦ Ta / Tb ≦ 1. It is set to be 5. 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 the barrel portion 4 (Ta / Tb <1). When 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 stretched portion locally extends to the continuous portion of the body 4 and the stepped portion 5a. This is because overstretching occurs. Note that the thickness (Tb) of the stepped portion 5a refers to the thickness of the boundary portion between the bottom portion 4 and the stepped portion 5a (see FIG. 2C).
Further, the radius (Ra) from the cylinder center to the wall thickness center of the body portion 4 shown in FIG. 2, the radius (Rb) from the tube center to the wall thickness center of the stepped portion 5a, and the wall thickness (Ta) of the body portion. , 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 the thickness (Ta) of the body portion. This is because a step of less than half makes injection molding 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.

Further, the angle (θ) inclined toward the cylinder center side of the stepped portion 5a shown in FIG. 2 (c) can be set to a desired range, and as shown in FIG. θa) can be set to (θb), and conversely, the inclination angle can be set to be small. 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 of the stepped portion 5a is set to be small, the stretch amount of the stepped portion 5a is increased, the stretch amount of the bottom portion 5 is decreased, and the weight of the bottom portion 5 is increased. On the other hand, if the inclination angle 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 of the stepped portion 5a is set to 7 ° ≦ θ ≦ 45 °, and particularly preferably set in a range of 20 ° ≦ θ ≦ 40 °. If θ 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.

In the example shown in FIGS. 2 and 3, the inner surface and the outer surface of the stepped portion 5a are inclined at substantially the same angle, and the thickness of the stepped portion 5a is substantially the same value from the trunk 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 of the preform 1 located between the body part 4 and the mouth part 2, and has a straight part 3a continuous from the mouth part 2 and thinner than the body part 4, and this straight It is formed so as to continue to the body part 4 through the part 3a.
Here, the neck lower part 3 including the straight part 3a can be set to a desired value for thickness, length, etc., and arbitrarily according to the size, shape, thickness, etc. of the bottle container to be molded It can be set.
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. is there. 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 it occurs.
Further, the ratio between the thickness (Tc) of the straight portion 3a and the length (La) in the longitudinal direction of the cylinder is set to satisfy 3 ≦ La / Tc ≦ 5. If the straight part 3a is too short (La / Tc <3), it will be the same as the normal preform shape, and local stretching and overstretching will occur at the bottom of the neck, and if the straight part 3a is too long (La / Tc>) 5) This is because it is difficult for the material to enter during injection molding, resulting in molding defects.

Specifically, in the case of a preform for a bottle container having a capacity of 2000 ml, the resin weight is set to about 45 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 trunk portion and the thickness (Tc) of the straight portion shown in FIG. 2 is set to be Ta−Tc = 1.3 mm or less.
Furthermore, the length in the cylinder longitudinal direction of the straight portion 3a can be set in a desired range. In the case of the above-described capacity 2000 ml bottle, the length (La) in the cylinder longitudinal direction shown in FIG. Set to be in the range of 9 mm.
By setting to such a value, a bottle container having a capacity of 2000 ml and an average wall thickness of about 0.25 mm can be obtained.

In this way, the straight portion 3a thinner than the body portion 4 is provided in the neck lower portion 3, and the thickness and length can be set as appropriate, so that the neck lower portion 3 including the straight portion 3a can be stretched locally. The entire neck lower part 3 can be uniformly stretched without causing an overstretched portion. When the preform 1 is stretch-blow-molded by a process to be described later, the neck lower part 3 including the straight part 3a is stretched uniformly as a whole, reducing the stretching burden on the body part 4, and consequently the preform. The whole is stretched uniformly.
In the example shown in FIG. 2, the straight portion 3 a is formed so as to have a uniform thickness from the mouth portion 2 to the trunk portion 4. For example, the straight portion 3 a is inclined on the outer surface or the inner surface. It is also possible to change the wall thickness. If it does in this way, the amount of extending | stretching can be varied between a thick part and a thin part, and the amount of extending | stretching can be adjusted.

2. Component As the thermoplastic resin constituting the preform 1 (and the bottle container 10) according to the present embodiment, any resin can be used as long as it is a resin that can be stretch blow molded and thermally crystallized.
Specifically, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyarylate, thermoplastic polyesters such as copolymers thereof, blends of these resins or other resins are particularly suitable. 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 container by stretch blow molding using the plastic bottle container preform according to the present embodiment as described above will be described.
1. Production of Preform The preform 1 can produce a bottomed cylindrical preform (parison) by known injection molding or extrusion molding. The neck lower portion 3 including the stepped portion 5a between the trunk portion 4 and the bottom portion 5 and the straight portion 3a between the mouth portion 3 and the trunk portion 4 is also manufactured in a desired shape and size by known injection molding or the like. Is possible.
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 bottom and an opening corresponding to the shape of the injection preform mold can be produced by inserting one or more oxygen absorbing layers.

2. Stretch Blow Molding Next, the preform 1 is biaxially stretch blow molded.
In the stretch blow molding method according to this 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 the pro molding.

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. 4A to 4B, the heated preform 1 is first set in the mold 103 (see FIG. 4A), and then stretch rod (stretched) (Rod) 104 is extended in the vertical direction (axial direction) and is extended in the horizontal direction (circumferential direction) by blow air (see FIG. 4B).

Here, in the preform 1 of the present embodiment, as illustrated in FIG. 5A, the stepped portion 5 a 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.
As a result, the entire body part 4, the stepped part 5 a and the bottom part 5 are uniformly stretched from the neck lower part 3, and local stretching and overstretching do not occur. As a result, the bottle container 10 having a uniform wall thickness distribution. Is formed (see FIG. 7).
On the other hand, as shown in FIG. 5 (b), in the conventional preform 201, the joint portion of the bottom portion and the trunk portion and the neck portion are locally stretched, while the overall stretch amount is small. Become. For this reason, since the amount of stretching of the lower neck portion and the bottom portion is reduced, the stretching burden on the body portion is increased, and as a result, stretching strain occurs and a bottle container having a nonuniform thickness distribution is formed. (See FIG. 7).

Here, the stretch ratio of the blow molded article in the present embodiment is set to be about 2.4 times or more in the longitudinal direction and about 5.2 times or more in the transverse direction, and about 12.5 times or more in the length × width direction. .
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, since uniform stretching is possible without causing local stretching or overstretching due to the shape of the preform 1, in order to obtain a bottle container as thin as possible with a uniform wall thickness distribution, at least It is preferable to set it as said draw ratio.
When the draw ratio is set to 15 times or more in the vertical and horizontal directions, whitening of the bottle due to overdrawing occurs. Further, when the draw ratio is 12 times or less, the thickness of the preform must be reduced, and not only uniform drawing cannot be performed, but also such a preform itself cannot be injection molded.
Therefore, in order to perform stretching with a uniform wall thickness, it is preferable to set the stretching ratio in the range of about 12 to 15 times in the vertical and horizontal directions.

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. In the case of a normal bottle container, the heat set temperature is about 120 to 135 ° C. However, in a bottle container that has undergone stretching strain to reduce the thickness of the bottle container, if the heat set temperature of the mold is the same as that of a normally thick bottle, the bottle shrinks when removed from the mold. Oops. On the other hand, when the heat set temperature is lower than 105 ° C., the heat resistance of the bottle cannot be obtained.
In the present embodiment, the shape of the preform 1 enables uniform stretching without causing local stretching or overstretching, and stretching distortion does not occur. Therefore, in the case of a normal bottle container as much as possible, You can get closer. Thereby, desired heat resistance can be imparted to the bottle container.

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.

  In addition, as a cooling fluid, in addition to normal temperature air, various cooled gases, for example, nitrogen at −40 ° C. to + 10 ° C., air, carbon dioxide, etc., 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. In this cooling fluid, liquefied mist having a large heat of vaporization such as water can be coexisted. A remarkable cooling temperature can be obtained by using the cooling fluid as described above.

Thereafter, as shown in FIG. 4D, 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.
Through the steps as described above, for example, the bottle container 10 according to this embodiment as shown in FIG. 6 is manufactured.

[Bottle container]
1. Configuration of Bottle Container The bottle container 10 is a plastic bottle container formed by the stretch blow molding of the preform 1 by the manufacturing process described above. For example, a bottle container 10 as shown in FIG. 6 is manufactured.
The bottle container 10 shown in FIG. 6 is formed with a neck portion 11, a shoulder portion 12, a trunk portion (upper) 13, a waist portion 14, a trunk portion (lower) 15, a heel portion 16 and a bottom portion 17, and has a capacity of 2000 ml. The flat bottle has a substantially rectangular cross section.
In such flat bottles, the stretching ratio in the circumferential direction is greatly different in the short side, the long side, and the diagonal direction (for example, the short side direction: 3.7 times, the long side direction 4.4 times, the diagonal direction) Direction: 5.2 times). For this reason, in the conventional preform and stretch blow molding method, so-called sink marks, deformation, and whitening due to overstretching occurred particularly in the diagonal direction with a high stretch ratio.
Here, in the preform 1 of the present embodiment in which the stepped portion 5a described above is formed, the portion corresponding to the heel portion 16 of the bottle container 10 is the bottom portion without causing local stretching due to the action of the stepped portion 5a. 5 and the body 4 can be uniformly stretched integrally, and uniform stretching without distortion is possible.

So, in this embodiment, while using the preform 1 in which the stepped portion 5a is formed, the shape of the bottle container 10 is such that the shape of the heel portion 16 having the highest draw ratio is suppressed as much as possible. By doing so, a flat bottle in which stretching strain does not occur in the diagonal direction of the heel portion can be obtained.
Specifically, as shown in FIG. 6, the shape of the bottle container 10 is rounded in the diagonal direction of the heel portion 16, and the circumferential cross-sectional shape of the waist portion 14 is substantially rectangular (see FIG. (Refer to (d)), the cross-sectional shape gradually becomes closer to the square as the bottom portion 17 is approached, and the ground contact surface of the bottom portion 17 is formed in a cross-sectional shape that is substantially circular (see FIG. 5E). Such a bottle shape can be obtained by setting the mold (see FIG. 4) to a predetermined shape.
Thereby, the draw ratio of the heel part diagonal direction can be made as small as possible, and it became possible to set it as the rectangular bottle which does not generate | occur | produce a stretching distortion.

2. Thickness As shown in FIG. 7A, the bottle container 10 of the present embodiment has a uniform thickness distribution and an average thickness of about 0.25 mm.
On the other hand, as shown in FIG. 7 (b), only the thickness of the conventional preform is changed, and the stretch blow is performed under the same conditions as a normal thickness bottle (average thickness is about 0.35 mm). When molding is performed, the thickness distribution is not uniform, and stretching strain occurs. In particular, the thickness of the shoulder portion and the bottom heel portion of the bottle becomes too thin due to local stretching and overstretching.

3. Heat Resistance As described above, the bottle container 10 of the present embodiment is heat-set at a mold temperature of about 110 ° C. and has heat resistance at a hot water sterilization washing temperature (about 65 to 80 ° C.).
When the bottle container 10 is rinsed at about 75 ° C. for about 30 seconds, the shrinkage rate is about 1%. This is a normal wall thickness (average wall thickness is about 0.35 mm), and the shrinkage rate of a bottle container heat-set at a mold temperature of about 120 ° C. is about 0.8%. It has sex.
In contrast, a bottle container with a heat set of about 80 ° C. to reduce the amount of resin in the conventional preform and prevent the bottle from shrinking has a shrinkage rate of about 31% and a capacity of 30% or more. It shrinks.
Thus, in the bottle container 10 of the present embodiment, the same heat resistance as that of a normal wall thickness bottle can be secured while the average wall thickness is reduced to about 0.25 mm.

Here, the heat resistance of the bottle container according to the present embodiment can be shown by no-load change evaluation by TMA (Thermal Mechanical Analysis).
Usually, the heat resistance of a plastic bottle container can be indicated by the degree of crystallinity, but in the case of oriented crystallinity, the heat resistance may vary greatly even if the value is the same.
TMA is a thermal analysis method in which a sample is heated in a heating furnace and the shape change accompanying a temperature change is measured under a non-vibrating load. A part of the bottle container is cut out as a sample and heated to change the shape. By measuring, the accurate heat resistance of the bottle container can be shown.
A sample having a width of 5 mm is cut out from the waist portion 14 of the bottle container 10 according to the present embodiment in the lateral direction of the bottle, and heated from room temperature at a temperature increase rate of 5 ° C./min under a non-load (0 kgf) condition. When an unweighted change amount evaluation by TMA is performed on a sample having a distance of 20 mm and a width of 5 mm, the change amount is set to 60 μm or less at a heating temperature of 80 ° C. This is almost the same value as a normal 0.35 mm thick bottle. Thereby, in the bottle container of this embodiment, heat resistance is not impaired by thinning, and heat resistance which is not different from a normal wall thickness bottle is obtained.

4). Crystallinity The thermoplastic polyester forming the bottle container 10 of the present embodiment is such that the crystallinity of the barrel is in the range of 30 to 40%. By making the crystallinity within this range, deformation of the bottle container 10 can be prevented.
When the degree of crystallinity is less than 30%, there is no heat resistance and the effect of preventing deformation is not sufficiently obtained. When the degree of crystallinity exceeds 40%, the mold is separated after biaxial stretch blow molding. There is a tendency that moldability is lowered and deformation after mold release is increased.
By setting the crystallinity of the body part within this range, the heat resistance and impact strength of the bottle container 10 can be further improved.

As described above, according to the plastic bottle container preform of the present embodiment, the stepped portion 5a is formed in the portion corresponding to the heel portion 16 of the bottle container 10, and the inclination angle and thickness of the stepped portion 5a are formed. Is set to a predetermined value, the stepped portion 5a and the bottom portion 5 can be integrally stretched, and local stretching and overstretching are prevented to prevent the trunk portion 4, the stepped portion 5a, and the bottom portion 5 from being stretched. The whole can be stretched uniformly and sufficiently.
Moreover, the neck lower part 3 which has the straight part 3a in the part corresponded to the shoulder part 12 of the bottle container 10 is formed, and the neck lower part containing the straight part 3a is set by setting the length and thickness of the straight part 3a to predetermined values. 3 can be stretched integrally with the body portion 4, and local stretching or overstretching can be prevented from occurring in the lower part of the neck.

In this way, since the entire preform 1 can be stretched uniformly, the entire bottle can be uniformly thinned without causing stretching strain or whitening, and a desired thin-walled bottle having an average wall thickness of about 0.25 mm is obtained. be able to.
In addition, a bottle having no stretching strain can be heat-set at high temperature, and can impart heat resistance substantially the same as that of a normal wall-thick bottle while being thin.
Thereby, it is possible to realize a preform for a plastic bottle container suitable for a rectangular bottle that tends to be excessively stretched in the bottle heel portion, an aseptic bottle that requires hot water sterilization cleaning, and the like.

Hereinafter, the specific Example in the case of carrying out stretch blow molding of a bottle container using the preform for plastic bottle containers of this invention is shown.
[Example 1]
Polyethylene terephthalate (PET) was supplied to the extruder to produce a preform weighing 45 g. In the preform, a stepped portion was formed between the trunk portion and the bottom portion, and a lower neck portion having a straight portion between the trunk portion and the mouth portion was formed.
The thickness of the preform was about 3.4 mm for the body, about 2.3 mm for the straight part, and about 2.8 mm for the stepped part and the bottom part. The straight part was about 7 mm long.
This preform is heated to about 120 ° C. above the glass transition point (Tg), set in a mold heated to about 110 ° C., and biaxially stretched by a one-stage blow molding method, and then about 4 MPa. Cooling blow was performed with air supply pressure to obtain a bottle container having an internal volume of about 2000 ml and an average wall thickness of about 0.25 mm.

[Comparative Example 1]
As in Example 1, 45 g of polyethylene terephthalate (PET) is used, there is no stepped part between the body part and the bottom part, and a thin part of about 3 mm between the body part and the mouth part (the straight part of Example 1) A preform with a conventional shape having
The thickness of the preform was about 3.9 mm at the body.
Like the normal bottle, this preform is heated to about 110 ° C. and set in a mold heated to about 80 ° C., which is lower than the normal bottle, and biaxially stretched and blown by a single-stage blow molding method. Thereafter, like an ordinary bottle, cooling blow was performed with an air supply pressure of about 3 MPa to obtain a bottle container having an internal volume of about 2000 ml and an average wall thickness of about 0.25 mm.

[Comparative Example 2]
Similar to Comparative Example 1, a preform without a stepped portion was used, and the thickness of the barrel was set to 3.5 mm. Under the same molding conditions as in Comparative Example 1, the inner volume was about 2000 ml, and the average thickness was about A 0.25 mm bottle container was obtained.

[Comparative Example 3]
Similar to Comparative Example 1, a preform without a stepped portion was used, and the thickness of the barrel was set to 3.3 mm. Under the same molding conditions as in Comparative Example 1, the internal volume was about 2000 ml and the average thickness was about A 0.25 mm bottle container was obtained.

The thickness distribution of the bottle container is shown in FIGS. 7 (a) and (b).
In Example 1, as shown to Fig.7 (a), thickness is substantially uniform over the whole side surface side of a bottle, and especially the shoulder part and heel part of a bottle are the same as that of another site | part. It became the thickness of.
The bottle container of Example 1 was rinsed with hot shower water at about 80 ° C. for about 30 seconds to measure the inner volume of the container. As a result, the inner volume of the container was reduced by 20 ml and the shrinkage rate was about 1%. there were.
When a similar shower warm water rinse was performed on a normal bottle container having an average wall thickness of about 0.35 mm, the inner volume of the container decreased by 17 ml and the shrinkage rate was about 0.8%.

Further, the crystallinity of the bottle container of Example 1 is about 33% in the waist part, and the waist part of a normal bottle container having an average wall thickness of about 0.35 mm is about 34%, which is almost the same. Value.
Therefore, no load change evaluation by TMA was performed. TMA was performed using the model name DMS6100 (manufactured by Seiko Instruments Inc.).
A sample having a width of 5 mm was cut out from the waist portion of the bottle container of Example 1 in the lateral direction of the bottle, heated under normal temperature at a rate of temperature increase of 5 ° C./min. When an unweighted change amount evaluation by TMA was performed on a sample having a width of 5 mm, the change amount was about 30 μm or less at a heating temperature of 80 ° C. This was almost the same value as the amount of change of a normal 0.35 mm thick bottle was about 20 μm.
From the above, it was found that the bottle container of Example 1 had almost the same heat resistance as a conventional thick bottle container.

On the other hand, in Comparative Examples 1 to 3, as shown in FIG. 7B, Comparative Example 1 (PF wall thickness 3.9 mm), Comparative Example 2 (PF wall thickness 3.5 mm), and Comparative Example 3 (PF wall thickness) In 3.3 mm), the wall thickness distribution was not uniform and stretching strain occurred.
In Comparative Example 1, the wall thickness of the bottle shoulder portion was too thin due to local stretching, while the bottle heel portion was too thick due to insufficient stretching.
Comparative Examples 2 and 3 have almost the same thickness distribution, and the thickness of the bottle shoulder and heel is too thin due to local stretching, and the bottle bottom is not stretched and the thickness is excessive. . Particularly in Comparative Example 2, only the heel portion of the bottle was overstretched, and the bottom portion was not stretched at all.
In addition, when the bottle container of Comparative Examples 1 to 3 was rinsed with hot shower water at about 80 ° C., the container volume decreased by 64 ml, the shrinkage rate was about 31%, and the volume could shrink by more than 30%. all right.
Furthermore, the degree of crystallinity of the bottles of Comparative Examples 1 to 3 was about 32% at the waist, which was almost the same as the degree of crystallinity of the bottle of Example 1. Therefore, when the no-load change amount evaluation by TMA was performed under the same conditions as in Example 1, the change amount was about 80 μm at the heating temperature of 80 ° C. The amount of change was about four times that of a thick bottle.

Thus, when Example 1 and Comparative Examples 1 to 3 in which the weight of the preform is the same are compared, in Comparative Examples 1 to 3, stretching strain due to local stretching and overstretching on the shoulder portion and heel portion of the bottle. In Example 1, the thickness distribution of the entire container is uniform, the entire preform is uniformly stretched, and overstretching and local stretching are performed. It can be seen that there is no stretching strain.
Moreover, in Comparative Examples 1-3, since the heat set was lowered for thinning, the heat resistance of the bottle was deteriorated while showing almost the same crystallization degree, and the hot water sterilization washing temperature (about 65-80) In contrast to the fact that the container shrank by 30% or more without being able to withstand (° C.), the heat resistance similar to that of a normal bottle can be obtained in Example 1 even though the average wall thickness of the bottle is reduced. I understood.
As described above, in Example 1, it was found that the wall thickness was made uniform over the entire bottle, the bottle shoulder portion and the heel portion were not locally stretched, and high heat resistance was obtained.

It should be noted that the preform for a plastic bottle container of the present invention is not limited to the above-described 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, the outer shape of the bottle container is a flat rectangular tube having a substantially rectangular cross section, but the outer shape of the bottle container is not particularly limited to a flat rectangular tube.
As shown in FIG. 8, in addition to a bottle container having a rectangular cross section (see FIG. 8A), a cylindrical bottle container having a substantially circular cross section (see FIG. 8B) may be used. Although not specifically illustrated, a bottle container having a substantially square cross section may be used, and even a bottle container combining a square tube and a cylinder does not hinder the application of the present invention.
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 preform for a plastic bottle container of the present invention described above can be used for a preform (parison) made of polyethylene terephthalate or the like which is a preformed product of a plastic bottle container. In particular, plastic bottles that are suitable for flat bottles, aseptic bottles, etc., because the entire bottle can be uniformly thinned without whitening, and high-temperature heat setting is possible, making it possible to produce bottle containers with excellent heat resistance. Can be used for container preforms.

It is sectional drawing which shows one Embodiment of the preform for plastic bottle containers which concerns on this invention. FIG. 2 is an enlarged view of a main part of the preform shown in FIG. 1, (a) is an overall view of the preform, (b) is an enlarged view of the lower part of the neck, and (c) is an enlarged view of a stepped portion. It is an enlarged view of the step part of the preform shown in FIG. 1, and has shown the aspect which changes the inclination angle of a step part. It is explanatory drawing which shows the manufacturing process of the bottle container using the preform for plastic bottle containers which concerns on this invention. It is principal part sectional drawing which shows the extending | stretching state of the preform for plastic bottle containers which concerns on this invention, (a) is preform of this invention, (b) has shown the preform of the conventional product. It is an external view which shows an example of the bottle container manufactured with the preform for plastic bottle containers which concerns on this invention, (a) is a front view, (b) is a side view, (c) is a top view, (d) A- A line sectional view, (e) is a bottom view. It is a graph which shows the thickness distribution of the bottle container manufactured with the preform for plastic bottle containers which concerns on this invention, (a) is the bottle container of this invention, (b) has shown the thing of the bottle product of a conventional product. . It is a front view which shows the external example of the bottle container which can be manufactured with the preform for plastic bottle containers which concerns on this invention, (a) is a rectangular bottle, (b) is a round bottle.

Explanation of symbols

1 Preform (Parison) according to the present invention
2 mouth part 3 neck lower part 3a straight part 4 preform trunk part 5 preform bottom part 5a preform stepped part 10 bottle container 10a rectangular bottle 10b round bottle 11 bottle neck part 12 bottle shoulder part 13 bottle trunk part (upper)
14 Bottle waist 15 Bottle body (bottom)
16 Bottle heel part 17 Bottle bottom part 201 Conventional preform

Claims (3)

A preform that has a cylindrical body, a mouth opening on one end of the body, and a bottom that closes the other end of the body, and becomes a plastic bottle container by stretch blow molding Because
Between the trunk portion and the bottom portion , the inner surface and the outer surface are both provided with a stepped portion that is continuous with the bottom portion while being inclined at θ at which the inclination angle is 7 ° ≦ θ ≦ 45 ° toward the center of the cylinder ,
The ratio of the thickness (Ta) of the barrel portion to the thickness (Tb) of the stepped portion is 1.0 ≦ Ta / Tb ≦ 1.5, and the radius from the cylinder center of the barrel portion to the thickness center the thickness of the trunk portion radius (Rb) of (Ra) and the cylinder center of the stepped portion to the center thickness (Ta) is, plastic bottle container and Rb ≦ Ra-Ta / 2 der wherein Rukoto preform. A preform that has a cylindrical body, a mouth opening on one end of the body, and a bottom that closes the other end of the body, and becomes a plastic bottle container by stretch blow molding Because
Between the torso and the mouth, with a neck lower part that continues from the mouth and continues to the torso through a straight part that is thinner than the torso ,
The ratio of the thickness (Ta) of the trunk portion to the thickness (Tc) of the straight portion is 1.2 ≦ Ta / Tc ≦ 1.7, and the thickness (Tc) of the straight portion and the longitudinal direction of the cylinder are the ratio of the length (La) is, 3 ≦ La / Tc ≦ 5 der Rukoto plastic bottle preform according to claim. A preform that has a cylindrical body, a mouth opening on one end of the body, and a bottom that closes the other end of the body, and becomes a plastic bottle container by stretch blow molding Because
Between the trunk portion and the bottom portion , the inner surface and the outer surface are both provided with a stepped portion that is continuous with the bottom portion while being inclined at θ at which the inclination angle is 7 ° ≦ θ ≦ 45 ° toward the center of the cylinder ,
The ratio of the thickness (Ta) of the barrel portion to the thickness (Tb) of the stepped portion is 1.0 ≦ Ta / Tb ≦ 1.5, and the radius from the cylinder center of the barrel portion to the thickness center the thickness of the trunk portion radius (Rb) of (Ra) and the cylinder center of the stepped portion to the center thickness (Ta) is, Rb ≦ Ra-Ta / 2 der Rutotomoni,
Between the torso and the mouth, with a neck lower part that continues from the mouth and continues to the torso through a straight part that is thinner than the torso ,
The ratio of the thickness (Ta) of the trunk portion to the thickness (Tc) of the straight portion is 1.2 ≦ Ta / Tc ≦ 1.7, and the thickness (Tc) of the straight portion and the longitudinal direction of the cylinder are the ratio of the length (La) is, 3 ≦ La / Tc ≦ 5 der Rukoto plastic bottle preform according to claim.

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