JPH091639A - Stretch blow molding preform and molding method using the same - Google Patents

Abstract

PURPOSE: To reduce the using amount of material resin of a plastic bottle and to improve the orientation thickness reduction of the bottom by specifying the ratio of the thickness of a cylindrical and tapered body with a semispherical bottom to that of the bottom and the taper angle of the tapered part. CONSTITUTION: Preform is manufactured by injection molding a thermoplastic resin, and formed of a neck part 1, a body part 2, a closed bottom 3 and a tapered part 4 for connecting the body to the bottom 3. The body 2 is a tapered state in which the diameter is reduced toward the cylindrical bottom as a hole, the body 2 and the bottom 3 are smoothly connected at the inner surface 9 of the preform, and connected via the part 4 in which the outer diameter is reduced toward the bottom at the outer surface of the preform. In this case, the ratio of the thickness 12 d1 of the body 2 to that d2 of the bottom is in the range of 1.0 to 1.5, and the tapered angle θ of the part 4 is in the range of 2 to 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretch blow molding preform and a molding method using the same, and more specifically, it can reduce the amount of raw material resin used in the production of biaxially stretched plastic bottles. The present invention relates to a stretch blow molding preform capable of reducing the weight of a plastic bottle and capable of uniformly stretching and thinning the bottom portion, and a molding method using the same.

[0002]

2. Description of the Related Art Stretch blow-molded plastic bottles, especially polyester bottles, have become common today, and due to their excellent transparency and moderate gas barrier properties, liquid products such as liquid detergents, shampoos, cosmetics, soy sauce, sauces, etc. Besides, it is widely used for carbonated drinks such as beer, cola and cider, and other beverage containers such as fruit juice and mineral water.

In molding a polyester bottle, a bottomed preform whose size is considerably smaller than that of the final container and whose polyester is amorphous is stretched axially in a blow mold at a stretching temperature by injection molding of the polyester. In addition, the method of blow stretching in the circumferential direction is adopted.

The bottomed preform has a mouth-and-neck portion of a bottle, for example, a mouth-and-neck portion composed of an opening end for sealing, a screw for engaging a lid, a support ring and the like, and the overall shape is a test tube. Things are common. However, on the other hand, attempts have been made to improve the shape of this bottomed preform in order to improve the strength, the degree of stretching and the like of the product.

For example, in Japanese Patent Publication No. 62-54696, the wall thickness of the bottle bottom part and the bottle shoulder part is approximately 80% to 80% of the wall thickness of the bottle body part. A method for molding a synthetic resin biaxially stretched bottle is described, which comprises biaxially stretching the following intermediate material so that the stretching ratio of the bottom portion and the shoulder portion becomes larger than that of the body portion. . It is also described that by this method, a biaxially stretched synthetic resin bottle in which the bottom portion and the shoulder portion are sufficiently stretched can be obtained.

Japanese Unexamined Patent Publication (Kokai) No. 2-258214 discloses a bottomed plastic preform having an inner wall surface having a specific shape. Stability can be improved by blow molding the preform. It is described that a plastic bottle excellent in strength and strength can be obtained.

Further, Japanese Patent Laid-Open No. 3-26513 discloses that
A cylindrical preform for biaxial stretch blow molding having a mouth portion, a body portion and a bottom portion, which has at least a thin band-shaped portion in the body portion is described. When this preform is heated, the temperature of the thin band portion decreases more rapidly than that of the other thick portions, and this fact can be utilized to reduce the thickness of a specific part of the product. Have been described.

Furthermore, in Japanese Patent Laid-Open No. 4-366604, an annular step portion is provided between the bottle bottom equivalent portion and the bottle body equivalent portion, whereby the bottle bottom equivalent portion is thickened. There is described a preform for blow molding of a synthetic resin bottle, which is characterized by being thinned or thinned or narrowed down to a diameter smaller than the body. In this way, by making the portion corresponding to the bottom thicker or thinner, or by blow-molding the preform that is narrowed down to a diameter smaller than the body according to the conditions, extreme uneven thickness and local thinning of the bottle bottom can be achieved. It states that it can be prevented.

[0009]

On the other hand, in the field of polyester bottles for beverages, new molding methods, new bottle shapes, etc. have been developed for the purpose of resource saving, cost reduction, product weight reduction and volume reduction. In particular, new preform shapes have been tried by each container manufacturer.

In order to achieve such an object, it is conceivable to reduce the thickness of the body of the preform, but this approach requires bottle performance (for example, strength), moldability, filling line, handling during transportation, etc. There is a limit from the viewpoint, and the wall thickness must be reduced within a range that does not exceed the limit. Further, since there is a standard for the mouth-neck portion of the preform, particularly for the nozzle portion, it is difficult to reduce the weight of the raw material resin and the product by changing the shape of the mouth-neck portion of the preform.

Therefore, an object of the present invention is to reduce the amount of raw material resin used in the production of a biaxially stretched plastic bottle, to reduce the weight of a plastic bottle which is a product, and to further reduce the thickness of stretched bottom plastics. It is an object of the present invention to provide a stretch blow molding preform capable of producing a bottle and a plastic bottle molding method using the preform.

[0012]

Means for Solving the Problems As a result of intensive studies, the inventors of the present invention have made the bottom of a plastic bottle, particularly the top, thin, that is, the bottom equivalent of the preform, especially the top equivalent. It was thought that the above object could be achieved by reducing the wall thickness without affecting the bottle performance of the product, and various shapes of bottomed preforms were investigated. As a result, we succeeded in developing the shape of the preform that brings about a reduction in the amount of the raw material resin that cannot be realized by the above-mentioned prior art, and completed the present invention. .

That is, according to the present invention, there is provided a stretch blow molding preform having a body portion, a mouth / neck portion provided at one end of the body portion, and a closed bottom portion provided at the other end of the body portion. The body has a tubular or tapered shape, and the bottom has a substantially hemispherical shape, and the inner surface is smoothly connected and the outer surface is reduced in outer diameter toward the bottom. are connected via a tapered portion, the ratio of the trunk portion of the thickness (d ₁₎ and the bottom of the thickness _{(d 2) (d 1 /} d 2) is in the range of 1.0 to 1.5, and a tapered portion The stretch blow molding preform is characterized in that the taper angle is in the range of 2 to 12 degrees.

According to the present invention, the preform is heated to a stretching temperature so that the hemisphere portion has a bottom center and the outer diameter reducing taper portion has a bottom outer periphery.
It is stretched and stretched in the axial direction and blow-stretched in the circumferential direction, and then the bottom center is bottomed to make the outer diameter reducing taper part the grounding part and the outer peripheral bottom part, and the hemisphere part more than the grounding part. There is provided a method for molding a plastic stretched bottle, which is characterized in that it is molded on the inner upper base.

[0015]

The present invention relates to the bottom of a stretch blow molding preform.
A tapered part with a specific shape is provided on the body near the connection part.
The character is the character. That is, the preform of the present invention
Is a substantially hemispherical closed bottom and a cylindrical body,
The inner surface is connected smoothly and the outer surface is connected.
In that case, through the taper part whose outer diameter decreases toward the bottom
And the thickness of the body (d₁ ) And the thickness of the bottom (d_Two )
And the ratio is (d₁ / D _Two ) Is 1.0 to 1.5, especially 1.
The taper of the taper portion is in the range of 1 to 1.4
The angle should be between 2 and 12 degrees, especially between 3 and 10
Is a remarkable feature.

In the present invention, the preform is heated to a stretching temperature, and the preform is stretched and stretched in the axial direction so that the hemisphere portion is the center of the bottom and the outer diameter reducing taper portion is the outer periphery of the bottom. Blow stretch in the circumferential direction,
Then, the center of the bottom is bottomed out to form the outer diameter reducing taper portion as a grounding portion and a bottom portion on the outer periphery of the grounding portion, and the hemispherical portion is formed on the upper bottom inside the grounding portion.

In the stretch blow molding preform,
The connecting portion between the body portion and the bottom portion has a taper shape in which the thickness gradually decreases from the body portion to the bottom portion at the taper angle, so when this is stretched, the stress per unit cross-sectional area gradually increases from the body portion to the bottom portion. growing. For this reason, it is possible to sufficiently and evenly stretch and thin the center portion of the bottom, which is difficult to stretch, and to bring about a uniform thinning of the upper bottom portion without lowering the buckling resistance and the like. It is possible to reduce the weight per unit area to half or less than that of the conventional one.

The taper portion is formed so that it is smoothly connected on the inner surface side and the outer diameter is reduced toward the bottom on the outer surface side in terms of formability of the preform. Further, it also brings advantages in terms of stretch formability of the preform. That is, when resin is injection-molded, the resin smoothly flows through the tapered portion into the body portion and further into the mouth portion, so that the injection moldability is good, and the die-release from the injection mold is also good. Is. Further, the taper portion gradually shifts the stretching start point to the body portion, so that the stretching operation can be performed smoothly. Further, the outer mold of the injection mold is generally composed of three parts of a slide insert, a cavity, and a gate pad. However, in the present invention, it is possible to change the gate pad to the one provided with the above-mentioned taper portion, and the predetermined shape is obtained. A shaped preform can be formed.

At the bottom of the final plastic bottle,
The reason for providing the grounding portion on the outer circumference of the bottom and providing the upper bottom located above the grounding portion at the center of the bottom is to prevent the self-sustainability of the bottle from being impaired even if the center of the bottom is slightly deformed. However, it is obvious that the self-supporting property is impaired when the ground contact portion is deformed. Further, if the grounding portion is too thin, this portion may be damaged during blow molding or deformed during heat sterilization. Furthermore, since the blow stretch ratio in the circumferential direction becomes large in the outer peripheral portion of the bottom such as the installation portion, the tendency of thinning is large. In the present invention, the outer diameter reducing taper portion is the grounding portion and the bottom portion on the outer periphery of the grounding portion, so that it is possible to prevent excessive thinning of these portions and enhance the self-sustaining stability of the bottle.

In the present invention, the ratio of the thickness (d ₁ ) of the body of the preform to the thickness (d ₂ ) of the bottom is (d ₁ / d)
It is also important that ₂ ) is in the above range. If this ratio is smaller than the above range, the reduction of the basis weight due to the high stretching and thinning of the upper bottom becomes unsatisfactory. The bulging deformation of the steel sheet becomes large, and the strength also decreases. Further, if the taper angle of the taper portion is smaller than the above range, it becomes difficult to achieve the above thickness ratio, and it becomes unsatisfactory to reduce the basis weight by highly stretching or thinning the upper bottom, while the above range If it is larger than this, the stress concentration in the taper portion becomes excessively large, which makes it difficult to perform a smooth stretching operation.

That is, by making a part of the body part tapered and making the hemispherical bottom part connected to this part thinner, it is possible to reduce the amount of raw material resin used, and at the same time make the bottom part highly stretched and uniformly thin. As a result, a plastic bottle having good bottle performance such as strength can be obtained.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on specific examples shown in the accompanying drawings. 1 and 2 showing an example of the preform of the present invention, this preform is manufactured by injection molding of a thermoplastic resin. For example, it is produced in a substantially amorphous state by injection molding of polyethylene terephthalate and supercooling. This preform is roughly divided into a mouth / neck portion 1, a body portion 2, a closed bottom portion 3, and a taper portion 4 connecting the body portion and the closed bottom portion.

The mouth / neck portion 1 has an opening end 5 for sealing, a screw 6 for engaging a lid, and a support ring 7. The mouth / neck portion 1 may exist in an amorphous state, or may be crystallized (whitened) by heat treatment in order to impart rigidity and heat resistance thereof.

The body 2 has a cylindrical shape as a whole or a taper shape whose diameter decreases toward the bottom, and generally has a small taper angle of about 0.3 to 2 degrees so that the mold can be easily removed. Is desirable. The body portion 3 is smoothly connected to the lower end portion 8 of the mouth / neck portion, and the thickness (outer diameter) gradually increases to a substantially constant thickness d ₁ . The thickness d ₁ is generally in the range of 2.5 to 6 mm, particularly 3 to 4.5 mm, though it varies depending on the volume and shape of the plastic bottle and the use. The length of the body portion 2 depends on the size of the container as a matter of course, but including the tapered portion, it is generally in the range of 60 to 200 mm, particularly 90 to 140 mm.

The closed bottom portion 3 has a substantially hemispherical shape, and its thickness d ₂ is substantially constant over the entire hemisphere. Generally, it is 2.5 to 4 although it varies depending on the volume, shape and use of the plastic bottle. 0.5 mm, especially 3-4 m
m. The inner diameter R of the closed bottom portion 3 is to be smoothly connected to the body portion 2, and although it varies depending on the inner diameter of the body portion 2, a range of generally 6 to 16 mm, particularly 7 to 10 mm is suitable.

The body portion 2 and the closed bottom portion 3 are smoothly connected to each other on the inner surface 9 of the preform, and on the outer surface of the preform, the taper portion 4 whose outer diameter decreases toward the bottom. Connected through. The ratio between the thickness of the body portion 2 (d ₁₎ and the closed bottom of the thickness (d ₂₎ (d ₁ /
d ₂ ) is generally in the range of 1.0 to 1.5, preferably 1.1 to 1.4, and the taper angle (θ) of the tapered portion is generally in the range of 2 to 12 degrees, and particularly It is in the range of 3 to 10 degrees.

The cross-sectional shape of the outer surface of the tapered portion 4 is generally straight (straight line), but it may be curved upwardly convex or upwardly concave. In the latter case, the angle (θ) of the taper portion is the taper angle formed by the line connecting the large-diameter connecting portion 10 between the taper portion and the straight body portion and the small-diameter connecting portion 11 between the taper portion and the closed bottom portion. Means In the former case, the connecting portion 10 and the connecting portion 11 may be provided with a curvature portion having a constant curvature radius (R1). The radius of curvature (R1) is suitably 10 mm or less.

The taper portion 4 and the hemispherical closed bottom portion 3 are
As shown in FIG. 1, it may be directly connected, or as shown in FIG. 2, a straight portion 12 having a constant thickness and a short length may be provided between them. The length of the straight portion 12 is preferably 1 time or less, particularly 0.5 time or less, of the bottom thickness d ₂ .

As the preform-molding plastic of the present invention, any moldable thermoplastic resin can be used. Examples of such resins include thermoplastic polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate; polycarbonates; acrylic-
Butadiene-styrene copolymer (ABS resin); polyacetal resin; nylon 6, nylon 66, nylons such as copolymerized nylon thereof; acrylic resin such as polymethylmethacrylate; isotactic polypropylene; polystyrene and other low -, Medium- or high-density polyethylene, ethylene-propylene copolymer, ethylene-butene-1 copolymer, styrene-butadiene thermoplastic elastomer and the like can be mentioned. These plastics contain various additives such as colorants, UV absorbers, release agents, lubricants, etc. within a range that does not impair the quality of products.
A nucleating agent or the like can be added.

In particular, it is preferable to use polyester as the thermoplastic resin, and in this case, the intrinsic viscosity (η) of the polyester may be a bottle molding grade, which is 0.6.
It is preferably 5 dl / g or more, particularly in the range of 0.70 to 0.90 dl / g, and the content of diethylene glycol unit is in the range of 1.60% by weight or less, particularly 1.50% by weight or less. used.

The preform according to the present invention is manufactured by an injection molding method. In FIG. 3, which shows a mold used for this injection molding, the mold includes a core mold 20 that defines an inner surface of a preform, a slide insert mold 21, a cavity mold 22, and a gate pad that define an outer surface of the preform. It consists of 23. Slide insert mold 21
Mainly molds the mouth and neck of the preform, and inserts and pulls out the core mold 20 while sliding the core mold 20 into the cavity through the mold. The cavity mold 22 forms the body of the preform, and the shapes of the slide insert mold 21 and the cavity mold 22 are known per se.

The gate pad 23 is provided with a gate 24 for forming a taper portion and a closed bottom portion of the preform and for injecting resin into the cavity.

Using the above device, the gate pad 23
It is possible to manufacture a preform for bottle manufacturing in which the weight of the upper bottom is remarkably reduced only by changing the shape to that shown in FIG.

In order to impart heat resistance and rigidity to the mouth of the obtained preform, the mouth and neck may be crystallized by heat treatment at the stage of preform to be whitened, or by the biaxial stretching blow molding described later. After molding the preform into a bottle,
The mouth and neck of the obtained plastic bottle may be crystallized and whitened.

The preform is heated to a stretching temperature, and the preform is stretched and stretched in the axial direction and blow stretched in the circumferential direction so that the hemispherical portion is the center of the bottom and the outer diameter reducing taper portion is the outer periphery of the bottom. Then, the center of the bottom is bottomed to form the outer diameter reducing taper portion as the ground contact portion and the bottom portion on the outer periphery of the ground contact portion, and the hemisphere portion is formed on the upper bottom inside the ground contact portion.

Prior to the stretch blow molding, the preform is preheated to a stretching suitable temperature by means of hot air, an infrared heater, high frequency induction heating or the like. The temperature range is 85
To 120 ° C, particularly 95 to 110 ° C.

This preform is fed into a stretch blow molding machine known per se, set in a mold, stretched axially by pushing a stretch rod, and blown in the circumferential direction by blowing a fluid. Stretching and finally bottoming the bottom with a bottoming die to form the top. At this time, due to the above-mentioned action, the portion to be the upper bottom can be lightened and sufficiently stretched to obtain a desired strength.

The stretching ratio in the final container is suitably 8 to 12 times in area ratio. Among these, the axial stretching ratio is 1.8 to 2.7 and the circumferential stretching ratio is 3.0.
It is better to set the value to 4.5 times. Further, the height of the central portion of the upper bottom from the ground contact portion is appropriately 10 to 18 mm.

FIG. 4 (front view), FIG. 5 (side view), FIG. 6 (plan view), FIG. 7 (bottom view), and FIG. 8 (AA) showing an example of a bottle manufactured by the method of the present invention. Cross-sectional view), FIG.
(BB sectional view), FIG. 10 (CC sectional view), and FIG.
In (D-D cross-sectional view), this bottle is
0, a trapezoidal shoulder portion 31, an upper body portion 32, a lower body portion 33, and a bottom portion 34.

The bottom portion 34 is formed of a grounding portion 35 and an upper bottom 36 which is raised above the grounding portion, and the taper portion (4) for reducing the diameter of the preform serves as the grounding portion 35 to reduce the thickness of the preform. The hemispherical bottom portion (3) serves as the upper bottom 36. It should be understood that this top sole 36 is provided radially with ribs 37 for the purpose of reinforcing the bottom.

The mouth-neck portion 30 of the bottle has the same shape and size as the mouth-neck portion (1) of the preform, and the shoulder portion 31 includes the lower portion of the mouth-neck portion (8) of the preform or an increased thickness portion (8).
a).

In the upper body 32 and the lower body 33 of the bottle,
The panel portion (mirror portion) 38 for absorbing the reduced pressure deformation is the rib 39.
Is formed through. Also, the upper body 32 and the lower body 3
A peripheral concave bead 40 for reinforcement is formed between the peripheral concave bead 40 and the circular concave bead 40.

FIG. 12 (front view), FIG. 13 (side view), and FIG. 14 showing other examples of bottles manufactured by the method of the present invention.
(Plan view), FIG. 15 (bottom view), FIG. 16 (A-A cross-sectional view), and FIG. 17 (B-B cross-sectional view), this bottle has a mouth-neck portion 30, a trapezoidal-shaped shoulder portion 31, The upper body portion 32, the lower body portion 33, and the bottom portion 34 are the same as in the case of FIGS. 4 to 11, but in this example, the upper bottom portion 36 is formed to bulge into a dome shape.

Further, a large number of circumferential concave beads 41 for reinforcement are arranged at small intervals on the upper body portion 32, and a panel portion 38 is provided on the lower body portion 33 via ribs 39. ,
Fine concavo-convex beads 42 are also formed on the panel portion 38.

In any of these examples, the grounding portion 35 is formed from the taper portion (4) for reducing the diameter of the preform, and the upper bottom 36 which is sufficiently stretched from the thinned hemispherical bottom portion (3) of the preform is formed. Since it is formed, the weight of the bottom can be reduced, the material cost can be reduced, and the weight of the container can be reduced while maintaining the strength of the bottom sufficiently high and maintaining the self-sustaining stability of the container.

[0046]

The present invention will be described with reference to the following examples.

Example 1 Using an injection mold similar to that shown in FIG. 3 and injection molding polyethylene terephthalate, the shape shown in FIG.
A preform having the following dimensions was manufactured. Overall length 152 mm Mouth neck opening inner diameter 20 mm Body taper angle 1 ° Body thickness 4.5 mm Bottom thickness 3.6 mm Bottom inner surface radius of curvature 9 mm Distance from opening to start end of thickness reduction taper 128 mm Thickness reduction taper taper Angle 8 ° Preform weight 57g

The above preform was preheated to a temperature of 105 ° C., and stretch blow-molded by a known biaxial stretching blow molding machine at a longitudinal stretching ratio of 2.1 times and a transverse stretching ratio of 4.4 times, as shown in FIGS. It was molded into a bottle having a shape shown in FIG.

For comparison, a similar bottle was molded using a preform having a thickness of 4.5 mm, which is the same as the body thickness, without providing a thickness reducing taper portion.

The upper bottom of the obtained bottle was cut out and its weight was measured.
That of the bottle of this example was 5.5 g, compared to 0.2 g. Also, 45k required for heat resistant bottles
A compressive strength of g or more was obtained, and the self-supporting property was also extremely satisfactory.

Example 2 Using an injection mold similar to that shown in FIG. 3 and injection molding polyethylene terephthalate, the shape shown in FIG.
A preform having the following dimensions was manufactured. Overall length 158mm Mouth neck opening inner diameter 21mm Body taper angle 1.1 ° Body thickness 4.5mm Bottom thickness 3.6mm Bottom inner surface radius of curvature 9mm Distance from opening to start end of thickness reduction taper portion 137mm Thickness reduction taper portion Taper angle of 10 ° Length of straight part under taper part 2mm Preform weight 65g

Only the mouth and neck of the above preform was heated to crystallize the mouth. This preform is 105 ℃
Pre-heated to a temperature of 10 ° C. and stretch blow-molded by a known biaxial stretching blow molding machine at a longitudinal stretching ratio of 2.1 times and a lateral stretching ratio of 4.4 times, and molded into a bottle having a shape shown in FIGS. 4 to 11. .

For comparison, a similar bottle was molded using a preform having a thickness of 4.5 mm, which is the same as the body thickness, without providing a thickness reducing taper portion.

The upper bottom of the obtained bottle was cut out and its weight was measured.
That of the bottle of this example was 5.5 g, compared to 0.2 g. Further, when oolong tea was hot-filled at 85 ° C. and sealed, the bottom of the container did not bulge and deformed and the self-sustaining property was very satisfactory.

[0055]

According to the present invention, a thickness reducing taper portion having a specific dimension is provided in the vicinity of a connecting portion between a body portion and a bottom portion of a preform, and a bottle grounding portion is formed from the preform thickness reducing taper portion. By forming a fully stretched upper bottom from the thinned hemispherical bottom of the preform, the strength of the bottom is kept sufficiently high and the weight of the bottom is reduced while maintaining the self-sustaining stability of the container. The cost can be reduced and the weight of the container can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a preform of the present invention.

FIG. 2 is a cross-sectional view showing another example of the preform of the present invention.

FIG. 3 is a partial cross-sectional view showing an example of a preform injection mold of the present invention.

FIG. 4 is a front view showing an example of a bottle manufactured by the method of the present invention.

5 is a side view of the bottle of FIG. 4. FIG.

FIG. 6 is a plan view of the bottle of FIG.

FIG. 7 is a bottom view of the bottle of FIG.

8 is a cross-sectional view taken along the line AA of the bottle of FIG.

9 is a BB cross-sectional view of the bottle of FIG.

10 is a cross-sectional view taken along the line CC of the bottle of FIG.

11 is a cross-sectional view taken along the line DD of the bottle of FIG.

FIG. 12 is a front view showing another example of the bottle manufactured by the method of the present invention.

FIG. 13 is a side view of the bottle of FIG.

FIG. 14 is a plan view of the bottle of FIG.

FIG. 15 is a bottom view of the bottle of FIG.

16 is a cross-sectional view taken along the line AA of the bottle of FIG.

17 is a cross-sectional view taken along the line BB of the bottle of FIG.

[Explanation of symbols]

 1 Mouth and neck part 2 Body part 3 Closure bottom part 4 Tapered part 5 Sealing open end 6 Screw for lid engagement 7 Support ring 8 Lower end part of mouth and neck part of preform 9 Inner surface of preform 10 Large diameter connection part 11 Small diameter Connection part 12 Straight part 20 Core mold 21 Slide insert mold 22 Cavity mold 23 Gate pad 24 Gate 30 Bottle mouth / neck part 31 Trapezoidal shoulder part 32 Upper body part 33 Lower body part 34 Bottom part 35 Grounding part 36 Upper base 37 Reinforcement rib 38 Panel portion (mirror portion) 39 Rib 40 Circular concave bead 41 Circular concave bead 42 Concavo-convex bead

Claims (2)

[Claims] 1. A stretch blow molding preform comprising a body and a mouth / neck provided at one end of the body, and a closed bottom provided at the other end of the body, wherein the body is tubular or tubular. It has a tapered shape and the bottom portion is substantially hemispherical, and is smoothly connected on the inner surface side and is connected on the outer surface side via a taper portion whose outer diameter decreases toward the bottom. And the thickness of the body (d ₁ )
And wherein the ratio between the thickness (d ₂₎ of the bottom (d ₁ / d ₂₎ is in the range of 1.0 to 1.5, and the taper angle of the tapered portion is in the range of 2 to 12 degrees and Preform for stretch blow molding. 2. The preform according to claim 1 is heated to a stretching temperature, and the preform is stretched and stretched in the axial direction such that the hemisphere portion has a bottom center and the outer diameter reducing taper portion has a bottom outer periphery. Along with that, the outer diameter reduction taper part is used as the grounding part and the bottom part on the outer periphery thereof, and the hemispherical part is formed on the upper bottom inside the grounding part. A method for molding a plastic stretched bottle, comprising: