JPH0939934A - Heat-, pressure resistant self-supporting container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the heat-creep at the bottom at the time of thermal sterilization by specifying, relating to a self-supporting container having a bottom part comprising a plurality of troughs positioned on an imaginary curved surface projecting toward the bottom and foot-parts positioned between troughs, the angle of opening between foot-parts which are planes perpendicular to a trough and have the trough in between and the total surface area of the bottom troughs. SOLUTION: A self-supporting container is formed by biaxially stretched blowing molding of resin and has in its bottom part 4 a bottom-center part 5 in the center and in its periphery a plurality of troughs 6 and a plurality of foot-parts 7 alternated with one another. The troughs 6 are positioned on an imaginary curved surface projecting toward the bottom and the foot-parts 7 are positioned between troughs 6 and projecting toward the bottom farther than the troughs. In this instance a plane which is passed across between foot-parts 7 and is perpendicular to the trough forms with another plane an angle θ of 65 deg. or more by which the foot-parts are open and the trough 6 is held in between and an equation S>=0.2.So is satisfied where S represents the total surface area of the troughs included within 80% of the diameter of the drum part, and So, the surface area of the imaginary curved plane included within 80% of the drum part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-standing heat and pressure resistant container formed by biaxial stretch blow molding of a resin and having excellent heat and pressure resistance and self-sustainability.

[0002]

2. Description of the Related Art Polyethylene terephthalate (PET)
The biaxially stretched blow-molded container made of thermoplastic polyester has excellent transparency and surface gloss, and also has the necessary impact resistance, rigidity, and gas barrier properties for bottles. That is, it is used as a bottle.

[0003] Generally, in the production of bottled products, it is necessary to heat-fill the contents or to heat-sterilize or sterilize the contents after filling the contents in order to enhance the preservability of the contents. However, polyester bottles have the disadvantage of poor heat resistance, and cause thermal deformation and shrinkage of volume when hot-filling the contents. Therefore, heat-setting (heat set) after forming a biaxially stretched blow container. Operation has been performed.

[0004] However, in applications where heat-sterilization or sterilization is carried out after filling and sealing the contents having autogenous pressure (heat-resistant pressure bottle), pressure and heat act simultaneously on the bottom of the bottle to cause bulging deformation due to thermal creep. For this reason, the above-mentioned heat fixing is not sufficient, and the bottom of the bottle is rounded, and a separate Hakama part (base cup) is attached to the bottom (Japanese Utility Model Laid-Open No. 55-143433, And JP-B-61-30982).

Further, in such a two-piece type heat resistant pressure bottle, in order to minimize the deformation of the bottom due to heat and pressure, Japanese Patent Publication No. Hei 6-22862 discloses an unstretched or low-stretched bottom center. It is described that heat crystallization is performed by heating, and furthermore, the entire container excluding the heat crystallization part is highly drawn by performing biaxial stretch blow molding of a preform molded body in which the bottom central part and the mouth and neck are thermally crystallized. It is described that the film can be stretched at a magnification, and in particular, the bottom of the hemisphere can be thinned by stretching, except for the center of the bottom.

[0006] A polyester bottle having a one-piece structure and pressure resistance, that is, a petaloid type bottle has already been proposed. For example, Japanese Patent Application Laid-Open No. 4-154535 discloses a method in which a plurality of leg pieces are bulged at equal intervals. A biaxially stretched blow-molded bottle having a petaloid-type bottom with a valley wall formed between the leg pieces, and an unstretched peripheral portion located around a central flat portion including a stretch center point of the bottom. A biaxially stretched blow-molded bottle is described in which a central portion containing is crystallized in a form having a higher density on the outer surface side than on the inner surface side of the wall of the central portion.

[0007]

A container having a hemispherical bottom portion which has been thinned by stretching is excellent in heat and pressure resistance, and is filled with contents such as carbonated beverages to which internal pressure is applied, and hot water is added to the filled product from the top. Heat sterilization treatment (10 ° C at 65 ° C on the law)
Min), but there is the inconvenience that the base cup must be manufactured separately from the container and fixed to the container by adhesion or the like.

A self-supporting container having a petaloid bottom, that is, a foot-integrated bottom has the advantage that the base cup is not required to be manufactured or attached, but its heat resistance, especially the heat resistance and pressure resistance of the bottom is still insufficient. It has the drawback of being That is, in this type of container, there is always an unstretched or low stretched thick portion, and under this condition where heat and pressure act simultaneously, thermal creep deformation occurs,
This impairs the independence of the container.

Further, in molding a self-supporting container having a foot-integrated bottom, when a preform molded body in which the center of the bottom and the mouth and neck are thermally crystallized is biaxially stretch blow molded at one time,
Since the shape of the bottom portion is complicated, it is difficult to reduce the thickness of the entire bottom portion under high stretching, and it is unavoidable that a low stretched portion having a relatively large thickness remains. This low-stretched portion having a relatively large thickness is inferior in heat and pressure resistance, and it becomes difficult to secure the self-supporting property when the contents are filled in such a container and heat sterilized.

Further, since the foot portion which gives the container self-supporting property is formed so as to protrude in the bottom direction from the valley portion located on the hemispherical surface, the wall thickness of the foot portion is inevitably thin, and at the time of blow molding. There is also a problem that the foot part bursts or the pressure resistance of the foot part decreases.

Therefore, an object of the present invention is to prevent the foot from becoming excessively thin while the entire bottom is thinned by stretching, to completely prevent the thermal creep phenomenon of the bottom during heat sterilization, and to have excellent heat resistance. Another object is to provide a biaxially stretched resin container having a combination of pressure resistance, impact resistance and self-supporting property.

[0012]

According to the present invention, the resin
Mouth and neck formed by biaxial stretch blow molding, shoulder,
An imaginary curved surface having a body and a bottom, and the bottom being convex toward the bottom
Located between the valleys located above and between the valleys,
It projects in the bottom direction and extends radially from the center root.
In a free-standing container consisting of a foot with the tip of the
On the plane that crosses between the feet and is perpendicular to the valley.
The opening angle θ between the legs is 65 ° or more, and the body diameter D₀ of
The total surface area of the bottom valleys included in the diameter of 80% is S and
And body diameter D ₀Of the virtual curved surface contained within the diameter of 80% of
Surface area is S₀Then S ≧ 0.2 · S₀To be
A heat resistant and pressure resistant self-supporting container is provided.

In the heat and pressure resistant self-supporting container of the present invention: 1. The foot opening angle θ is in the range of 70 ° to 110 °; 2. The total surface area S of the bottom valley portion is within the range of the formula 0.5 · S ₀ ≧ S ≧ 0.3 · S ₀ . 3. In the virtual curved surface, the total length (L) of the valleys occupying on the circumference of the diameter d ₀ +10 mm of the central root is L ≧ 0.2 · πd. To the radius of curvature R ₁ of the bottom valley of the bottom near the center and 1.05 to 1.6 times the barrel radius _{(D 0/2), 5} . The entire bottom part is stretched at a relatively high draw ratio except for the center part of the bottom, and the thickness of the bottom part is reduced to 1 mm or less except for the center part of the bottom.
5. It is in the range of 15 mm to 0.8 mm. 6. The bottom except the center of the bottom has a crystallinity of 20% or more; Except for the center of the bottom, the bottom is heat-set, and the valleys within the diameter range of 50% of the body diameter (D ₀ ) have a crystallinity of 25 to 55% excluding the center of the bottom. 7. 8. Spherulize the mouth and neck of the container, 10. The diameter D _c of the bottom center portion of the substantially unstretched state is 25% or less of the diameter D ₀ of the body portion, 10. Heat fixing the center of the bottom so as to have a crystallinity of 20 to 45%; It is preferable to provide 5 to 6 bottom feet.

[0014]

In FIG. 1 (partially sectional side view) showing the heat and pressure resistant self-supporting container of the present invention, the container is a mouth / neck part 1, a shoulder part 2, and a body part 3 formed by biaxial stretch blow molding of resin.
And a bottom portion 4, and the bottom portion 4 has a bottom center portion 5 at the center thereof and a plurality of valley portions 6 and a plurality of foot portions 7 alternately on the periphery. The valley 6 is located on a virtual curved surface that is convex in the bottom direction, while the feet 7 located between the valleys are provided so as to protrude in the bottom direction from the valley 6. In the foot portion 7, a tip portion 9 extending in the radial direction from a root portion 8 at the center serves as a grounding portion.

In FIG. 2 (bottom perspective view) for explaining the details of the arrangement of the bottom valley and the foot and the foot opening angle in this container, the valley 6 is formed on a virtual curved surface which is convex in the bottom direction. However, the foot portion 7, especially the tip portion 9 thereof is located at the inclined portion 1.
It projects downward through 0 (toward the ground). In the present invention, as shown in FIG. 2, one end of the valley portion 6 and the corresponding end of the foot portion 7 are arranged in a plane that crosses between the adjacent foot portions 7, 7 and is perpendicular to the valley portion 6. Connecting line a and valley 6
A ′ connecting the other end of the foot and the corresponding end of the foot 7
And a foot opening angle θ that sandwiches the foot is defined.

In FIG. 3 (enlarged cross-sectional view of an essential part) for explaining various dimensions at the bottom of the container, the body 3 directly above the bottom of the container has a body diameter of D ₀ , and the bottom 4 is D _c. Has a bottom central diameter. The valley 6 has a radius of curvature R ₁ near the center of the bottom and a radius of curvature R ₂ around the bottom. On the other hand, the foot tip 9 has a radius of curvature of r. A foot height H ₀ is maintained between the ground contact surface of the foot tip 9 and the center 5 of the bottom.

In FIG. 4 (enlarged bottom view) for explaining the valley area and other dimensions at the bottom of the container, a circle c having a diameter of 80% of the body diameter D ₀ is drawn from the center of the bottom and within this circle c. Let S ₀ be the surface area of the virtual curved surface included in In addition, the total surface area of the bottom valley portion 6 included in this circle c is S
(Indicated by the dot surface). Also, the base of the foot 8
Let d ₀ be the diameter of the circle containing, and let L be the total length of the valleys occupying the circumference of this diameter d of d ₀ +10 mm.

The inventors of the present invention have studied to secure the self-supporting property of a container by adopting a petaloid bottom shape composed of a plurality of legs and valleys even in a container for heat and pressure resistance. According to the research, when the biaxially stretched blow molding was performed, the entire bottom part except for the center of the bottom was thinned to a relatively high draw ratio.
It was found that a molded product having a bottom having a sufficient yield stress strength in a temperature range of about 0 to 70 ° C can be obtained.

At this time, in order to secure the heat resistance and pressure resistance of the bottom portion, a petaloid type bottom shape is adopted in which the bottom valley portion is a hemispherical surface having the same radius of curvature as the body radius. However, in that case, there arises a problem that the tip portion of the bottom foot portion is locally too thin. In order to secure the thickness of the tip of the bottom foot, it is desirable to shorten the distance between the valley and the tip of the foot, that is, to increase the radius of curvature near the center of the bottom of the valley to form a relatively shallow valley shape. . However, if the radius of curvature of the valley is increased, the heat resistance and pressure resistance performance is usually lowered. Therefore, there has been a demand for an epoch-making means for enhancing the heat and pressure resistance performance while ensuring the thickness of the tip of the foot.

As a result of earnest studies, the present inventors have paid particular attention to the foot opening angle θ that sandwiches the valley reaching the tip of the foot in a plane that crosses between the feet and is perpendicular to the valley. For example, when the container having the above-mentioned foot opening angle θ of 55 ° was filled with the contents of 3 gas volumes, the foot opening angle θ expanded to 58 °. Apply a hot water shower at 70 ° C to the filling,
When heat sterilization is performed at a temperature of 65 ° C. for 15 minutes at the center of the bottom, the bottom deforms and the above-mentioned foot opening angle θ
Obtained results that spread to 90 ° were obtained.

The inventors of the present invention considered that the remarkable expansion of the foot opening angle θ during heat sterilization causes a relatively large deformation of the valley, that is, expansion of the valley. Therefore, if the foot opening angle θ that sandwiches the valley at the foot part reaching the tip of the foot is increased to a certain degree or more in advance, the deformation of the valley during thermal sterilization can be suppressed as a result, and an experiment was performed. Was. As a result of the experiment, it has been found that in the container in which the foot opening angle θ is 65 ° or more, the deformation of the valley during the heat sterilization can be extremely reduced.

Increasing the foot opening angle θ sandwiching the valley makes the direction of the force acting such that the foot pulls up the valley formed of a part of a curved surface such as a spherical surface, closes the direction of the spherical surface. Therefore, the force component that acts perpendicularly to the spherical trough, that is, the force component that deforms the trough, is reduced. As a result, the deformation of the valley can be reduced.

On the other hand, as another force that acts to deform the bottom valley portion, there is a force that acts to spread the spherical surface by the internal pressure, and it is also important to suppress the deformation of the valley portion due to this force. . The present inventors conducted experiments with various changes in the radius of curvature of the valley and the surface area of the valley, and as a result, found that there was a suitable range for them.

Regarding the radius of curvature of the trough, it is preferable that the radius is the same as the radius of the body in terms of strength, but from the viewpoint of molding to secure the wall thickness of the tip of the foot, the trough near the center of the bottom is It is preferable that the radius of curvature R ₁ be made larger than the radius R _{0 of the} body portion and the radius of curvature R ₂ of the valley portion at the peripheral edge of the bottom portion be made small to smoothly connect to the body portion. In reality, the radius of curvature R of the valley
₁ is preferably in the range of 1.1 × R _{0 to} 1.6 × R ₀ . The radius of curvature R ₁ of the valley near the center of the bottom is 1.1 × R
_When it is less than ₀ , the moldability of the foot is poor and it becomes difficult to secure the wall thickness of the tip of the foot. On the other hand, if the radius of curvature R ₁ of the valley exceeds 1.6 × R ₀ , the heat resistant pressure resistance strength of the bottom is lowered, and the deformation of the valley after filling tends to be too large. In this case, the radius of curvature of the bottom central valley inside the foot root where the foot starts from the center of the bottom is a smooth connection with the foot,
It is determined in consideration of the formability of the foot. Specifically, the bottom central valley can be spherical or flat with a radius of curvature greater than the radius of curvature R ₁ of the valley that follows it.

In the present invention, the radius of curvature R ₁ of the valley is made relatively large in order to ensure the formability of the foot. Therefore, in order to secure preferable heat resistance and pressure resistance, it is preferable to increase the foot angle θ that sandwiches the valley portion and to relatively increase the surface area of the valley portion. Specifically, 80 of the body diameter D ₀
% Total surface area S of the bottom valleys included in the diameter of
Preferably the Sokotani portion is 20% or more of the surface area S ₀ of the imaginary spherical surface of the bottom portion and forming a part included in the 80% of the diameter of _0, particularly preferably in the range of 30 to 50% . When the valley surface area ratio S / S ₀ is less than 20%,
The width of the valley becomes too narrow, and it is difficult to ensure sufficient heat resistance and pressure resistance, and the deformation of the valley during heat sterilization becomes large. On the other hand, when the valley surface area ratio S / S ₀ exceeds 50%,
Since the valley width is wide, the moldability of the foot portion is reduced, and it becomes difficult to secure a preferable thickness of the tip portion of the foot portion.

Furthermore, in addition to securing the surface area S of the valley as described above, the foot width near the foot center of the bottom where the foot starts from the center of the bottom is made narrower, and the valley width is made relatively large. It was found that taking them is effective for obtaining sufficient heat resistance and pressure resistance. Specifically, in the virtual bottom valley spherical surface, the ratio of the total length L of the valley portion occupying on the circumference of the diameter d which is the diameter d ₀ +10 mm of the bottom center foot portion is 20% or more, and particularly 30% or more. Preferably. As described above, by making the valley width in the vicinity of the center of the bottom relatively wide, the width of the foot connected to the center of the bottom becomes narrow, and the force transmitted from this foot to the center of the bottom can be reduced. As a result, the deformation of the central portion of the bottom is significantly reduced. In this case, even if the valley width in the vicinity of the foot root portion in the center of the bottom is widened, the formability of the foot tip portion is not adversely affected. That is, the foot tip portion is connected to the bottom valley portion located in a diameter portion of about 45 to 70% of the body diameter D ₀ , and by making the ratio of the valley width of this portion relatively small, Moldability can be secured.

At the bottom of the petaloid mold, the vicinity of the tip of the foot portion is stretched most to be thinned, but the strength is 0.
A plate thickness of 15 mm or more, preferably 0.2 mm or more is required. In order to secure the thickness of the tip of the foot, it is preferable from the viewpoint of molding that the radius of curvature R ₁ of the valley is relatively large and the radius of curvature r of the foot is large in order to bring the distance between the valley and the foot close. . Specifically, the curvature radius r of the tip of the foot is preferably 6 mm or more.

Further, the foot height H _0, which is the height from the center of the bottom to the foot contact portion, is preferably 3 mm to 8 mm. If the foot height H ₀ is less than 3 mm, it is difficult to effectively secure the self-supporting property of the container after filling the contents and heat sterilization, and if the foot height H ₀ is more than 8 mm, from the valley part. The distance to the foot becomes long, and it becomes difficult to secure the thickness of the tip of the foot.

In the conventional pressure resistant container, there is no heat sterilization process, and no decrease in material strength is observed during the heat sterilization process as in the heat resistant pressure resistant container. Therefore, in a pressure-resistant container, the foot opening angle θ is usually about 50 to 60 °, and after the contents are filled, the foot opening angle θ is at most about 60 to 70 °. The influence of θ is small. On the other hand, in the heat resistant and pressure resistant container, the foot opening angle is expanded to about 80 ° to 110 ° or more in the heat sterilization treatment step after filling, and accordingly, the valley portion is also relatively deformed.

In the present invention, the foot opening angle θ that sandwiches the bottom valley extending to the tip of the foot on a plane that crosses between the feet and is perpendicular to the valley is 65 ° or more, particularly preferably 70 ° to 110 °.
Range. In the container in which the foot opening angle θ is smaller than 65 °, the foot opening angle θ after the filling of the contents and the heat sterilization treatment is greatly increased, and the deformation amount of the valley becomes too large. As described above, the foot opening angle θ
However, it is preferable that the foot opening angle θ
If is too large, the width of the foot tip grounding part tends to become narrower. If the foot tip grounding portion becomes too thin, it tends to fall, especially in an empty container before filling, which is not preferable. Therefore, the foot opening angle θ is preferably 110 ° or less.

The number of legs is preferably 5 to 6. When the number of legs is four or less, the leg angle θ is set to be relatively large, so that it is difficult to increase the width of the foot contact portion, which causes a problem that the empty container easily falls.
On the other hand, when the number of feet is 7 or more, it is difficult to keep the foot angle θ and the width of the valley in a preferable range, and further, the width of the feet is reduced, so that the formability of the feet is deteriorated. Become.

The heat resistant and pressure resistant container of the present invention is required to have excellent material strength at the time of high temperature at the bottom. When the bottom portion is relatively thick and is in an unstretched state or a relatively low stretched state, if it is sufficiently heated to a crystallization temperature of about 130 ° C. or higher, it is thermally crystallized into spherulites while whitening occurs. In this case, when the thermal crystallinity is 20% or more, preferably 25% or more, the yield stress in a relatively high temperature state is significantly improved,
Sufficient strength for heat and pressure resistance. However, if the crystallinity of the whitened spherulized portion becomes too high, it becomes relatively brittle, and if the area extends over a relatively wide range of the bottom portion, problems with impact resistance tend to occur, which is not preferable. Therefore, when the whitened spherulite is spread over a relatively wide range,
The crystallinity of the spherulite portion is preferably about 40% or less.

Further, when the bottom portion is relatively thick and the stretched state is relatively low, or the stretch degree is slightly insufficient, the main polyester material constituting the container has a relatively low glass transition point (Tg). It is effective to increase the glass transition temperature of the composite material and increase the material strength at high temperature by making the composite material into which a high organic material is blended. Specifically, ethylene terephthalate-based polyester having a glass transition point of about 70 ° C. is blended with polyethylene naphthalate having a glass transition temperature of about 120 ° C. or polyarylate having a glass transition temperature of about 180 ° C. by about 8 to 25%. Thereby, the material strength at a high temperature of about 60 to 70 ° C. can be increased, and the deformation of the valley portion and the foot portion during the heat sterilization treatment can be relatively reduced. In this case, the strength of the material at high temperature can be further increased by heating and fixing the bottom made of the composite material. Further, by stacking and using a conventional material having a low glass transition point and a material having a high glass transition point as described above, the material strength at high temperature can be similarly increased. in this case,
The laminated portion can be limited to the vicinity of the bottom portion.

As a means for satisfying the material strength characteristics of the bottom portion at high temperature required for the heat and pressure resistant container, in the present invention, the bottom portion except the center portion of the bottom portion is in a relatively high stretched state during biaxial stretch blow molding. It is preferable to reduce the thickness. On the other hand, when the thickness of the bottom portion exceeds 1 mm, the oriented crystallinity degree due to the ordinary stretching process is 10% or less, which is 60 to 70.
It becomes difficult to obtain a preferable yield stress strength in the temperature range of ° C. That is, the thinned bottom portion in the relatively high stretched state is highly oriented and crystallized, and the yield stress strength in the temperature range of about 60 to 70 ° C. is sufficiently high. Therefore,
It can be sufficiently used as a heat-resistant and pressure-resistant container that is heat-sterilized at a temperature of about 65 ° C.

From the above viewpoint, the bottom portion excluding the center portion of the bottom is 1 mm or less, preferably 0.8 by biaxial stretch blow molding.
mm or less and 20% or more, preferably 2% or more.
It is preferable to carry out orientational crystallization to a crystallinity of 5% or more. On the other hand, when the thickness of the bottom portion is more than 1 mm, the oriented crystallinity usually becomes 10% or less in the drawing process, and it becomes difficult to obtain a preferable yield stress strength in the temperature range of 60 to 70 ° C.

Further, in the present invention, the bottom portion thinned and stretched to have a high orientation except for the center portion of the bottom is heated and heat-fixed to proceed with thermal crystallization, whereby the bottom portion, particularly the valley portion near the center of the bottom, is formed. The strength can be increased and the heat and pressure resistance performance can be further improved. At this time, the bottom portion, which has been stretched and thinned to a high orientation, is heat-set at a temperature of about 130 ° C. to 200 ° C. to be thermally crystallized with almost no spherulitic whitening, and therefore, usually has sufficient impact resistance performance. Can have. It is important to increase the crystallinity of the bottom valley spherical surface portion within the diameter range of about 50% of the body diameter by heat fixing the bottom portion, and the crystallinity of that portion is 30 to 55%.
It is preferable that

As a means for obtaining a heat-resistant and pressure-resistant container having a relatively thin stretched bottom portion, a product is obtained by a one-step blow molding method in which the final product shape is obtained by one blow molding, or by double blow molding. A step blow molding method can be adopted.

As the two-step blow molding method, a secondary molded product having a substantially spherical bottom is prepared from a preform molded product by the primary blow molding, and one is formed on the bottom portion of the secondary molded product and the body portion connected to the bottom portion. It is possible to employ a step of heat-shrinking the part to obtain a tertiary molded product, and further subjecting the tertiary molded product to secondary blow molding to obtain a final shape.

In this case, 2 obtained by primary blow molding
It is preferable that the bottom of the next molded product is thinned to a relatively high stretch except for the center. In order to reduce the thickness of the bottom part to a relatively high stretch in the primary blow molding, the center part of the bottom of the preform molded product is sufficiently sandwiched between the stretched rod arranged inside the molded product and the press rod installed outside. It is desirable to perform biaxially stretch blow molding. At this time, the center portion of the bottom sandwiched between the stretch rod and the press rod remains as a thick portion in an almost unstretched state.

It is preferable that the center portion of the bottom having a relatively thick thickness is stopped to have a relatively small diameter in order to maintain the preferable heat resistance and pressure resistance of the bottom portion. Usually, the diameter D _{c of the} center of the bottom is the body diameter D _0.
Of 25% or less, preferably 18% or less.

Further, by heating and fixing the thick portion by heating, the material strength at the time of heat sterilization treatment can be improved. In the above-mentioned two-step blow molding method, when heating the bottom of the secondary molded product, it is possible to heat-fix the thick center portion of the bottom and the highly stretched thin portion at the periphery thereof at the same time. At this time, in order to secure impact resistance, it is preferable that the central portion of the thick bottom has a somewhat lower upper limit of the crystallinity than the thin portion at the periphery thereof. The degree of crystallinity is preferably 20 to 45%, and the degree of crystallinity of the highly stretched thin portion at the periphery thereof is preferably 30 to 55%.

In the two-stage blow molding method, by making the primary blow molding free blow molding without using a mold, the entire bottom portion can be stretched and thinned. In the free-blow-molded secondary molded product, the bottom center portion can be thinned while being relatively stretched, and the peripheral edge portion can be thinned to be relatively stretched. The secondary molded product thus obtained is subjected to heat shrinkage of the body and the bottom to form a tertiary molded product that can be fitted in the secondary blow molding die, and the final molded product is subjected to secondary blow molding to obtain the final molded product. Can be a product. In this case, when heating the secondary molded product, the bottom portion is heated to 130 ° C to 200 ° C.
By heat setting at about temperature, the crystallinity of the entire bottom of the final product can be increased to about 30 to 55%.

By preheating the neck and neck and the center of the bottom of the preform molded product to make them spherulite, it is possible to easily increase the degree of thinning of the stretched shoulder and bottom during blow molding. This can be adopted in the one-stage blow molding method, in which case the container bottom taken can be thinned to a relatively high stretch up to the very end of the spherulization part located in the center of the bottom. Further, in the primary blow molding of the two-stage blow molding method, it is effective as a stable means for reducing the wall thickness to a relatively high stretch until the very end of the spherulization portion at the bottom.

The diameter D _c of the spherulized portion located at the center of the bottom is preferably 5 to 25% of the body diameter D ₀ . Further, the crystallinity of the spherulite whitened portion is preferably 25% to 50%. In this way, by limiting the maximum diameter of the spherulized portion at the center of the bottom and limiting the range of crystallinity, a heat and pressure resistant container excellent in heat resistance and pressure resistance and having no problem in impact resistance can be obtained. Obtainable.

As described above, according to the present invention, a biaxially stretched resin container in which the thermal creep phenomenon of the bottom portion during heat sterilization is completely prevented and which has an excellent combination of heat resistance and pressure resistance, impact resistance and self-standing property is provided. It is possible to provide a self-supporting container having a petaloid bottom part that is uniformly and uniformly highly biaxially stretched, that is, a foot-integrated bottom part, with high productivity and with good reproducibility.

[0046]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, any plastic material can be used as long as it can be stretch blow molded and heat crystallized, but thermoplastic polyester, particularly ethylene terephthalate thermoplastic polyester. Is advantageously used. Of course, polycarbonate, arylate resin, or the like can also be used.

The ethylene terephthalate type thermoplastic polyester used in the present invention comprises most of ester repeating units,
In general, the ethylene terephthalate unit accounts for 70 mol% or more, particularly 80 mol% or more, and has a glass transition point (Tg) of 50 to 90 ° C., particularly 55 to 80 ° C., and a melting point (Tm) of 200 to 275 ° C. Especially 220 to 27
Thermoplastic polyesters at 0 ° C. are preferred.

Although homopolyethylene terephthalate is preferable in terms of heat resistance and pressure resistance, a copolymerized polyester containing a small amount of ester units other than ethylene terephthalate units can also be used.

Dibasic acids other than terephthalic acid include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid and naphthalenedicarboxylic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; succinic acid, adipic acid, sebacic acid and dodecane. Aliphatic dicarboxylic acids such as dionic acid; and combinations of two or more thereof. As the diol component other than ethylene glycol, propylene glycol,
1,4-butanediol, diethylene glycol, 1,
One or more of 6-hexylene glycol, cyclohexane dimethanol, an ethylene oxide adduct of bisphenol A and the like can be mentioned.

Further, it is possible to use a composite material in which about 5% to 25% of ethylene terephthalate type thermoplastic polyester is blended with a relatively high glass transition point, for example, polyethylene naphthalate, polycarbonate or polyarylate. The material strength at high temperature can be increased. Further, polyethylene terephthalate and the above-mentioned material having a relatively high glass transition point can be laminated and used.

The ethylene terephthalate type thermoplastic polyester used should have at least a molecular weight sufficient to form a film, and an injection grade or an extrusion grade is used depending on the application. Its intrinsic viscosity (IV) is generally 0.6 to 1.4 dl / g,
In particular, those in the range of 0.63 to 1.3 dl / g are desirable.

According to the method for producing a container of the present invention, first, a tubular preform having a bottom is formed, and the mouth / neck portion or the bottom portion of the preform is heated to locally provide a thermal crystallization portion. .

In FIG. 5 (partially sectional side view) showing an example of a preform used in the present invention, particularly a preform suitable for two-stage blow molding, this preform 20 includes a neck portion 21, a body portion 22 and a closed bottom portion. The neck portion 21 is provided with a lid fastening mechanism 24 such as a screw and a support ring 25 for holding the container, and the like, and the neck portion 21 is thermally crystallized or spherulized over a range of the length K. Has been done. The spherulized neck portion 21 becomes the container neck portion 1 of FIG.

Injection molding can be used to mold the plastic material into the preform 20. That is, plastic is melt-injected into a cooled injection mold to form a supercooled amorphous plastic preform.

An injection machine known per se equipped with an injection plunger or a screw is used, and the polyester is injected into an injection mold through a nozzle, a sprue and a gate. As a result, the polyester or the like flows into the injection mold cavity and is solidified to form a preform for stretch blow molding.

As the injection mold, one having a cavity corresponding to the shape of the container is used, but it is preferable to use a one-gate type or a multi-gate type injection mold. Injection temperature is 270 ~ 310 ℃, pressure is 28 ~ 110kg / c
m ² is preferable.

The spherulization of the neck 21 of the preform 20 is
It can be carried out by selectively heating these parts by means known per se. Since thermal crystallization of polyester or the like remarkably occurs at an intrinsic crystallization temperature, generally, the corresponding portion of the preform may be heated to the crystallization temperature. Heating can be performed by infrared heating, dielectric heating, or the like. Generally, it is preferable to selectively heat the body to be stretched by shielding the body from a heat source with a heat insulating material.

The above spherulization may be carried out simultaneously with the preheating of the preform 20 to the stretching temperature or separately.

The stretching temperature of the preform is generally 85 to 135 ° C., particularly 90 to 130 ° C., and the heating is carried out by means known per se such as infrared heating, hot air heating furnace, dielectric heating and the like. be able to. Also,
Mouth spherification is generally 140-220 ° C. with the preform bottom and mouth thermally insulated from other parts.
In particular, it can be performed by heating to a temperature of 160 to 210 ° C. Crystallinity of preform mouth is 25%
It should be above.

In the stretch blow molding from the preform, a method of utilizing the heat given to the preform molded article to be molded, that is, residual heat, and performing the stretch blow molding subsequent to the preform molding can also be used. However, in general, a method is preferred in which a preformed product in a supercooled state is once produced, and the preform is heated to the above-mentioned drawing temperature to carry out draw blow molding.

According to the two-stage blow molding method, the preform thus preheated for partial thermal crystallization and stretching is biaxially stretch blow molded in a primary blow mold,
A substantially dome-shaped bottom portion was formed, and a portion other than the heat-crystallized portion of the preform was stretched to a high stretch ratio to obtain a secondary molded product (Fig. 6); a bottom portion of this secondary molded product and a cylinder connected to the bottom portion. At least a part of the part is heated to form a tertiary molded product in which the bottom part and a part of the body part are shrunk (FIG. 8); and this tertiary molded product is blow-molded in a secondary blow mold. ,
The final product is composed of a plurality of valleys and feet, and has a bottom thinned by high stretching except for the center of the bottom (Fig. 9).
And FIG. 10).

In the present invention, it is preferable that the bottom portion is thinned to a relatively high stretch in the primary blow molding step. For that purpose, it is important to balance the heating temperature of the bottom portion and the body portion of the preform. That is, by bringing the heating temperature of the bottom portion of the preform close to the heating temperature of the barrel portion, the bottom portion can be thinned to a relatively high stretch as in the barrel portion during blow molding. On the other hand, if the heating temperature of the bottom of the preform is considerably lower than that of the body, the degree of stretching of the bottom during blow molding will be low.

In FIG. 6 showing the primary blow molding process,
The preform 20 has its neck supported by a core mold 31 and is held in a closed split mold 32. On the opposite side of the core mold, a bottom mold 33 that defines the bottom shape of the secondary molded product is also arranged. A stretch rod 34 is inserted into the preform 20, the tip thereof is pressed against the bottom of the preform to pull and stretch the preform 20 in the axial direction, and at the same time, a fluid is blown into the preform 20 so that the preform is circumferentially stretched. It is expanded and stretched. At this time, the press rod 35 is arranged on the side of the bottom mold 33 coaxially with the stretch rod 34, and the bottom portion 23 of the preform is sandwiched by the stretch rod 34 and the press rod 35 at the time of pulling and stretching. The position of the bottom portion 23 is regulated so that it is located at the center of the secondary molded product 36. The bottom mold 33 is for regulating the bottom shape of the secondary molded product 36 to a suitable shape described below in a heat treatment step to be performed subsequently.

That is, as shown in FIG. 6, it is also useful to form the diameter of the bottom portion 37 of the secondary molded body in a large diameter portion that is larger than the diameter of the body portion and the bottom portion of the final container.
This is because when the bottom of the secondary molded product is contracted, the bottom having a large diameter acts to form a hemispherical surface by suppressing depression toward the center. It is preferable that the diameter of the bottom portion 37 of the secondary molded body is about 1.05 to 1.3 times the diameter of the body portion and the bottom portion of the final container.

Further, as shown in FIG. 7, if a relatively small recess 38 is provided on the outer surface of the central portion of the bottom portion 37 of the secondary molded body during the primary blow molding, the bottom of the tertiary molded body is subjected to a heat treatment step. The shoulder is prevented from being excessively drawn inward. It is considered that this is because the concave portion 38 has a function of lifting the bottom portion to a hemispherical surface at the time of thermal contraction. The size of the recess 38 is such that the diameter is 15 to 60 of the barrel diameter D ₀ of the final container.
%, And a depth of 0.5 to 5 mm is suitable. The formation of the recess 38 is achieved by forming an inward projection 39 on the inner surface of the central portion of the bottom mold 33. Furthermore, if a partially spherical projection 40 is formed at the tip of the press rod 35, the pinching is ensured by the cooperation with the extending rod at the center of the bottom, and the bottom center of a small size (D _C ) is excluded. Thus, the degree of stretching of the peripheral edge of the center of the bottom can be increased. Further, the center of the bottom can be made relatively thin, and the above-described recess can be formed on the outer surface side of the center of the bottom of the secondary molded product.

The stretching ratio is 2 to 5 in the axial direction.
, Especially 2.2 to 4 times, and the stretching ratio in the circumferential direction is preferably 2.5 to 6.6 times, especially 3 to 6 times. The axial stretching ratio is determined by the axial length of the preform molded article and the stroke length of the stretching rod, while the circumferential stretching ratio is determined by the diameter of the preform and the diameter of the mold cavity. . As the pressure fluid, room temperature or heated air or other gas such as nitrogen, carbon dioxide or water vapor can be used, and the pressure is usually 10 to 40 kg / cm ² gauge, particularly 15 to 30 kg / g. c
It may be in the range of m ² gauge.

In FIG. 8 showing the details of the heat treatment process, 2
The secondary molded product 36 is supported by the core mold 31 and rotates about its axis, and the infrared heating body 41 is provided so as to face at least a part of the bottom portion 37 and the body portion connected to the bottom portion of the secondary molded product. There is. In the secondary molded product 34, at least a part of the bottom portion and the body portion connected to the bottom portion are heated by the infrared rays from the infrared heating body 41, and the bottom portion 42 and the partial body portion 4 are contracted.
A tertiary molded product 44 of 3 is obtained.

It is preferable to heat the bottom portion and a part of the body of the secondary molded product 36 at a temperature of 120 to 200 ° C., whereby heat shrinkage and heat fixing of these portions can be effectively performed. . In the heating from the infrared radiator, since the non-contact heating is used, the bottom part and the part of the body part shrink without restriction, and the infrared rays irradiated on the surface of the secondary molded product are:
A part of it passes through the plate thickness, reaches the inner surface opposite to the irradiation site, and a part of it is further absorbed. Will be

Further, the infrared radiator 41 in the heat treatment step
And one or more infrared radiators disposed on the upper or side surfaces of the passage along the path along which the secondary molded article moves, and the secondary molded article is axially arranged in the infrared radiator. If it is rotated and moved while heating, the heat shrinkage of the secondary molded product and the movement between the steps can be performed at the same time, so that heat treatment can be performed without loss time and productivity can be improved. Infrared radiator is 400-1000
It is advisable to use a combination of those having a planar surface which is heated to about ℃ and has a relatively high radiation efficiency and a relatively large surface area. This makes it possible to irradiate the secondary molded article with infrared rays having a relatively high energy density, thereby enabling short-time heating. In particular, in the present invention, since the heating portion of the secondary molded product is thinned by high drawing, it can be heated to a predetermined temperature in a short time of, for example, 10 seconds or less by the infrared heating body. Specifically, the infrared heater is obtained by burning a solid surface or gas such as a metal surface such as carbon steel or stainless steel, a ceramic surface such as alumina, magnesia or zirconia, or a composite material surface such as ceramic and carbon. Gas surfaces can be used. The surface of the solid-state infrared heater is heated to a predetermined temperature by heating with an embedded electric heater or high-frequency induction heating.

The bottom of the secondary molded product, which has been thinned to a high stretch by the primary blow molding, has a relatively poor moldability, and the temperature of the molding part is 120 to 2 in order to perform the secondary blow molding well.
It is necessary to be 00 ° C. Further, by heating the heated portion of the tertiary molded product to a temperature of 120 to 200 ° C. and performing heat fixing, the crystallinity of the bottom trough of the container can be finally set in the above-described range. In addition to improving the heat-resistant pressure strength by the high stretch orientation at the bottom, the heat-resistant pressure strength can be further increased by this bottom crystallization.

In FIG. 9 showing the details of the secondary blow molding step, the neck of the tertiary molded product 44 is supported by the core mold 31 and is held in the closed split mold 51.
On the opposite side of the core mold, a bottom mold 52 that defines the bottom shape of the final container is also arranged. A fluid is blown into the tertiary molded product 44 to subject the tertiary molded product to secondary blow molding to form a bottom shape of a final container (five legs) 50 having a predetermined valley portion and valley portion. The molded container 50 is opened by the secondary blow mold 5 by a take-out mechanism (not shown) known per se.
It is taken out from 1.

In the secondary blow molding process of the present invention, the molded product (tertiary molded product) in the heat treatment process is blow molded in the secondary blow molding die, and the foot portion and the valley portion are alternately arranged. Mold on the bottom. In the secondary blow molding, the cavity of the secondary blow mold used is naturally larger than that of the tertiary molded product, and conforms to the dimensions and shape of the final molded product including the self-supporting bottom shape. There must be.

Further, in the tertiary molded product, since the elastic modulus increases due to crystallization by heat treatment, it is preferable to use a high fluid pressure, and generally, a pressure of 15 to 45 kg / cm ² is used. preferable.

In the secondary blow molding, the temperature of the mold is
Cooling may be performed immediately after molding while maintaining the temperature at 5 to 135 ° C., or cooling may be performed by flowing cold air or the like into the final molded product.

In FIG. 11 showing the structure of the bottle bottom portion by the two-stage blow molding method, the bottom center portion 5 is in an unstretched and relatively thick state, but its size is limited to a small diameter D _C. Therefore, the body portion 6 and the foot portion 7 are sufficiently thinned by stretching and heat-fixed. Therefore, this container has sufficient heat resistance and pressure resistance and self-supporting property. The container of this example has five legs and is asymmetric with respect to the centerline of the bottom.

The height H ₀ of the ground contact portion at the center of the bottom is preferably 3 mm or more, and particularly 4 to 8 mm in an empty state. As a result, sufficient independence is ensured even during filling heat sterilization.

Another example of the preform used in the present invention, which is a preform suitable for one-step blow molding, is shown in FIG. 12. The preform 20 comprises a neck portion 21, a body portion 22 and a closed bottom portion 23. 21 includes a lid fastening mechanism 24 such as a screw and a support ring 2 for holding the container.
5, the neck portion 21 has a length K, and the bottom center portion 23 is spherulized over a range of a diameter K ₁ . This spherulized neck 21 becomes the container neck 2 of FIG. 1, while the bottom center 23 becomes the spherulized bottom 5 of the bottom center of FIG. The diameter K ₁ substantially corresponds to the diameter D _C in FIG.

According to the one-step blow molding method, the preform preheated for partial thermal crystallization and stretching as described above is biaxially stretch blow molded in a blow mold,
Consists of a plurality of valleys and feet of a given shape and dimensions,
The final product has a bottom portion which is thinned by high drawing except the center portion of the bottom. At this time, in heating the preform, by bringing the heating temperature of the bottom portion close to the heating temperature of the body portion, the bottom portion of the final product can be thinned to a relatively high stretch except for the center portion of the bottom during blow molding. .

In FIG. 13 showing the one-step blow molding process, the preform 20 has its neck portion supported by the core die 31 and is held in the closed split die 61.
A bottom mold 62 that defines the bottom shape of the final molded product is also arranged on the opposite side of the core mold. A stretch rod 34 is inserted into the preform 20, the tip thereof is pressed against the bottom of the preform to pull and stretch the preform 20 in the axial direction, and at the same time, a fluid is blown into the preform 20 so that the preform is circumferentially stretched. It is expanded and stretched. At this time, the drawing rod 3
4, the press rod 35 is arranged on the side of the bottom mold 62 so that the spherulized bottom portion 23 of the preform is held by the stretch rod 34 and the press rod 35 during the pulling and stretching, and the bottom portion of the preform is The position is regulated so that 23 is formed at the center of the final molded product 60. The bottom die 62 is for forming the bottom valley portion and the foot portion having the shapes and dimensions described above. In this specific example, six legs are formed.

The blow molding conditions in the one-step blow molding process may be in accordance with the above-mentioned primary blow molding conditions of the two-step molding method. In this specific example, the bottom mold is set to 130 ° C. to 160 ° C., and the bottom part is heat-fixed in the mold.

In FIG. 14 showing the structure of the bottle bottom portion by this one-stage blow molding method, the bottom center portion 5 is highly thermally crystallized and is in a relatively thick state, but its size is a small diameter D. _It is limited to _C , and the body 6 and the foot 7 are sufficiently thinned by stretching and heat-set. Therefore, this container has particularly excellent heat resistance and pressure resistance and self-sustainability. In this specific example, the bottom valley portion 6 and the foot portion 7 are present in axial symmetry.

The heat and pressure resistant polyester bottle of the present invention is useful for filling contents having an autogenous pressure and sterilizing by heating or sterilizing, and as a container for filling and storing carbonated drinks, nitrogen filled drinks, seasonings and the like. It is useful. As a container for heat and pressure resistance, the gas capacity can be up to about 3 VOL, and the heat sterilization temperature is suitably from 60 to 80 ° C.

[0083]

【Example】

Comparative Test 1 Using the apparatus shown in FIGS. 6, 8 and 9, the maximum molded body diameter D ₀ of the final molded product was 94 mm, the total height was 306 mm, the volume was 1500 ml, and the bottom had 5 legs and valleys. A container made of polyethylene terephthalate (PET) as shown in FIG.

A bottomed preform was prepared. The preform has a height of 316 mm, as shown in Figure 6.
Then, using a mold in which the diameter of the body part connected to the bottom part is 105 mm, and the center part is a convex bottom mold inward,
Primary blow molding was performed with compressed air of kgf / cm ² to obtain a secondary molded product. The bottom of the obtained secondary molded product has a recess (diameter 30 mm, depth 3 mm) in the center, and is highly stretched to a plate thickness of 0.5 to 0.6 mm except for the center of the bottom. And the crystallinity of the stretched portion was 25 to 35%.

Next, by moving the secondary molded article while rotating it in a tunnel-shaped heat treatment apparatus in which planar infrared heating elements in which an electric heater is incorporated in ceramics are arranged on the top and side surfaces, the secondary molded article is moved. A third molded product was obtained by heat-shrinking the bottom of the molded product and a part of the body connected to the bottom. The temperature of the infrared heating member was 900 ° C. on the top surface and 750 ° C. on the side surface, and the heating time was 6 seconds. The heated part of the obtained tertiary molded body had a shape that was sufficiently contained in the bottom valley curved surface of the final container.

Finally, the heated tertiary molded article was subjected to 40 kgf using a secondary blow mold having a predetermined bottom shape.
The container was obtained by performing secondary blow molding with compressed air of / cm ² . In this case, as a bottom mold of the secondary blow mold, a foot valley θ that sandwiches the valley on a plane that crosses between the feet and is perpendicular to the valley, and a bottom valley included within a diameter of 80% of the body diameter D _0. The ratio S / S ₀ of the total surface area S of the above to the surface area S ₀ of the bottom virtual curved surface included within the diameter of 80% of the body diameter D ₀ , in the bottom virtual curved surface, the diameter d ₀ of the central root part + the diameter d of 10 mm The total length L of the valleys on the circumference and the circumference length π at the diameter d
Five molds were prepared by appropriately combining the ratio L / πd with d and the ratio R ₁ / R ₀ between the radius of curvature R ₁ of the valley bottom near the center of the bottom and the radius R _{0 of the} body.

Table 1 shows the numerical values of the bottom shapes of the five secondary blow molds used in this comparative test. Containers were prepared for each of the five molds and used as Example 1, Example 2 and Example 3, Comparative Example 1 and Comparative Example 2, and the wall thickness and crystallinity of each part of the obtained container were investigated. . In any case, except for the center of the bottom of the obtained container, the thickness of the bottom valley within a radius of 30 mm is 0.3.
5 to 0.5 mm, and the degree of crystallinity in that portion is 30 to 4
2%. In addition, the diameter D _{c of the} center of the bottom, which is relatively thick,
Was about 10 mm, and the ratio D _c / D ₀ of the diameter at the center of the bottom to the diameter of the body was about 0.1. The thickness of the center of the bottom was about 1 mm. Table 1 also shows the minimum thickness t _min of the foot tip of the obtained container.

[0088]

[Table 1]

Comparative Test 2 Using the apparatus shown in FIG. 13, the maximum barrel diameter D of the final molded product was obtained.
₀ is 94 mm, total height is 306 mm, capacity is 1500 m
A container made of polyethylene terephthalate (PET) having a bottom portion composed of 6 legs and a valley portion was prepared.

A bottomed preform was prepared, and the bottom and neck of the preform were spherulized by infrared heating. Next, a test blow mold provided with a bottom mold having a bottom having six legs and a valley was prepared. In the bottom mold of the test blow mold, the foot angle θ that sandwiches the valley portion on the plane that crosses between the foot portions and is perpendicular to the valley portion is 70 °, and the bottom included within the diameter of 80% of the body diameter D _0. 80 of the total surface area S of the valley and the body diameter D ₀
%, The ratio S / S _{0 of the} bottom virtual curved surface to the surface area S ₀ of the bottom virtual curved surface is 0.33, and the bottom virtual curved surface occupies the circumference of the diameter d of the central root part d ₀ +10 mm. The ratio L / πd of the total length L of the valley portion to the circumferential length πd of the diameter d is 0.39, and the curvature radius R ₁ of the valley bottom portion near the center of the bottom and the body radius R ₀ Ratio R ₁ / R ₀
Was 1.49.

The preform heated to the drawing temperature was blow-molded with compressed air of 40 kgf / cm ² using the above-mentioned test blow mold. At that time, the heating temperature distribution of the preform was changed to prepare two levels of self-supporting containers having different stretching degrees in the vicinity of the center of the bottom, which were referred to as Example 4 and Comparative Example 3. In addition, in Example 4, the bottom temperature of the sample blow mold is set to 1
The temperature was set to 50 ° C., and after blow molding, the bottom of the mold was heat-set by allowing it to stand in the mold for 2 seconds. Table 2 shows the molding conditions of each example, the thickness of the portion having a radius of 10 mm from the center of the bottom of the obtained container, and the crystallinity value. In each example, the bottom-centered spherulized portion had a diameter of 15 mm and a thickness of about 1.5 mm.

[0092]

[Table 2]

Performance Test In each example, 10 containers were used with 2.6 gas volumes (G.
V. ) And 3 gas volumes of carbonated water were filled and capped, and then the contents were heat-sterilized by flowing hot water at 70 ° C. from the top of the container for 30 minutes. In the heat sterilization treatment, the temperature at the bottom central thermal crystal part was increased to 68 ° C at maximum. Measure the amount of deformation of the bottom of the cooled container after completion of heat sterilization, and check the number of containers with a low foot height (H), that is, the center of the bottom is below the feet and lack in independence. It was The results are shown in Table 3.

[0094]

[Table 3]

From the above results, it is understood that the container of the present invention is excellent in heat resistance and pressure resistance.

[0096]

According to the present invention, by designing the bottom structure so that the opening angle θ of the foot sandwiching the valley and the area S of the valley are within a specific range, the entire bottom is thinned by stretching. The biaxially stretched resin container that prevents excessive thinning of the feet while completely preventing the thermal creep phenomenon at the bottom during heat sterilization and has a combination of excellent heat resistance and pressure resistance, impact resistance, and self-supporting property. Could be provided.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional side view showing a heat and pressure resistant self-supporting container of the present invention.

FIG. 2 is a bottom perspective view for explaining the details of the arrangement of the bottom valley portion and the foot portion and the foot opening angle in the container of FIG.

FIG. 3 is an enlarged sectional view of an essential part for explaining various dimensions at the bottom of the container.

FIG. 4 is an enlarged bottom view for explaining the valley area and other dimensions at the bottom of the container.

FIG. 5 is a partial cross-sectional side view showing an example of a preform used in the present invention, particularly a preform suitable for two-stage blow molding.

FIG. 6 is an explanatory view showing a primary blow molding process in two-stage blow molding.

FIG. 7 is an enlarged view of the vicinity of the center of the bottom in the primary blow molding process in the two-stage blow molding.

FIG. 8 is an explanatory diagram of a heat shrinking step of the secondary molded product in the two-stage blow molding.

FIG. 9 is an explanatory diagram of a secondary blow molding process in two-stage blow molding.

FIG. 10 is a side view of the final molded product (5 pairs).

FIG. 11 is an enlarged view of the bottom of the final molded product.

FIG. 12 is a partial cross-sectional side view showing another example of the preform used in the present invention, particularly a preform suitable for one-step blow molding.

FIG. 13 is an explanatory diagram showing a blow molding process in single-stage blow molding.

FIG. 14 is an enlarged view of the bottom of the final molded product (6 legs).

[Explanation of symbols]

 1 Mouth / neck 2 Shoulder 3 Body 4 Bottom 5 Bottom center 6 Valley 7 Foot 8 Center root 9 Tip 10 Inclination 20 Preform 21 Neck 22 Body 23 Closure bottom 24 Lid fastening mechanism 25 Support ring 31 Core Mold 32 Split Mold 33 Bottom Mold 34 Stretching Rod 35 Pressing Rod 36 Secondary Molded Product 37 Bottom 38 Recess 39 Groove 40 Protrusion 41 Infrared Heater 42 Shrinked Bottom 43 Shrinked Part Body 44 Third Molding Item 50 Final container 51 Split mold 52 Bottom mold 60 Final container 61 Split mold 62 Bottom mold

[Procedure amendment]

[Submission date] November 2, 1995

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 5

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 12

[Correction method] Change

[Correction contents]

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

A self-supporting container having a petaloid bottom, that is, a foot-integrated bottom has the advantage that the base cup is not required to be manufactured or attached, but its heat resistance, especially the heat resistance and pressure resistance of the bottom is still insufficient. It has the drawback of being That is, in this type of container, there is always an unstretched or low-stretched thick portion, and under this condition where heat and pressure act simultaneously, thermal creep deformation occurs,
This impairs the independence of the container.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

Further, in molding a self-supporting container having a foot-integrated bottom, when a preform molded body in which the center of the bottom and the mouth and neck are thermally crystallized is biaxially stretch blow molded at one time,
Since the shape of the bottom part is complicated, it is difficult to reduce the thickness of the entire bottom part under high stretching, and it is unavoidable that a relatively thin low stretched part remains. This relatively thick low-stretched part is inferior in heat and pressure resistance, and it becomes difficult to secure independence when the contents are filled in such a container and heat-sterilized.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

In the heat and pressure resistant self-supporting container of the present invention: 1. The foot opening angle θ is in the range of 70 ° to 110 °; 2. The total surface area S of the bottom valley portion is within the range of the formula 0.5 · S ₀ ≧ S ≧ 0.3 · S ₀ . 3. In the virtual curved surface, the total length (L) of the valleys occupying on the circumference of the diameter d ₀ +10 mm of the central root is L ≧ 0.2 · πd. To the radius of curvature R ₁ of the bottom valley of the bottom near the center and 1.1 to 1.6 times the barrel radius _{(D 0/2), 5} . The entire bottom part is stretched at a relatively high draw ratio except for the center part of the bottom, and the thickness of the bottom part is reduced to 1 mm or less except for the center part of the bottom.
5. It is in the range of 15 mm to 0.8 mm. 6. The bottom except the center of the bottom has a crystallinity of 20% or more; Except for the center of the bottom, the bottom is heat-set, and the valleys within the diameter range of 50% of the body diameter (D ₀ ) have a crystallinity of 25 to 55% excluding the center of the bottom. 7. 8. Spherulize the mouth and neck of the container, 10. The diameter D _c of the bottom center portion of the substantially unstretched state is 25% or less of the diameter D ₀ of the body portion, 10. Heat fixing the center of the bottom so as to have a crystallinity of 20 to 45%; It is preferable to provide 5 to 6 bottom feet.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

Further , in addition to securing the surface area S of the valley as described above, the foot width near the foot center of the bottom where the foot starts from the center of the bottom is narrowed to make the valley width relatively large. Have been found to be effective in obtaining sufficient heat resistance and pressure resistance. Specifically, in the virtual bottom valley spherical surface, the ratio of the total length L of the valley portion occupying on the circumference of the diameter d which is the diameter d ₀ +10 mm of the bottom center foot portion is 20% or more, and particularly 30% or more. Preferably. As described above, by making the valley width in the vicinity of the center of the bottom relatively wide, the width of the foot connected to the center of the bottom becomes narrow, and the force transmitted from this foot to the center of the bottom can be reduced. As a result, the deformation of the central portion of the bottom is significantly reduced. In this case, even if the valley width in the vicinity of the foot root portion in the center of the bottom is widened, the formability of the foot tip portion is not adversely affected. That is, the foot tip portion is connected to the bottom valley portion located in a diameter portion of about 45 to 70% of the body diameter D ₀ , and by making the ratio of the valley width of this portion relatively small, Moldability can be secured.

[Procedure amendment 7]

[Document name to be amended] Statement

[Name of item to be corrected] 0032

[Correction method] Change

[Correction contents]

In the heat and pressure resistant container of the present invention, when the bottom part is hot
Excellent material strength is required. Bottom is ratio
ComparativeThick meatAnd is in an unstretched state or a relatively low stretched state.
In this case, heat sufficiently to a crystallization temperature of about 130 ° C or higher.
Then, thermal crystallization occurs in a spherulite state while causing whitening. This place
In this case, the thermal crystallinity is 20% or more, preferably 25% or more.
Then, the yield stress in the relatively high temperature state is significantly improved,
Sufficient strength for heat and pressure resistance. But that
If the crystallinity of the whitened spherulite is too high,
It becomes brittle and resists the area over a relatively large area at the bottom.
This is not preferable because it tends to cause impact problems. Obedience
Therefore, when the whitened spherulized part covers a relatively wide range,
The crystallinity of the spherulite portion may be about 40% or less.
preferable.The crystallinity X _C of each part of the container can be measured by a well-known method.
It is measured by a fixed method, that is, the density method, but
The density ρ (g / cm ³ ) was measured with a density gradient tube, and the crystal
Body density ρ _c (1.455 g / cm ³ ) and amorphous density
ρ_a(1.335 g / cm ^Three) Value,
Converted and calculated at. 

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0036

[Correction method] Change

[Correction contents]

Further, in the present invention, the bottom portion thinned and stretched in a high orientation except the center portion of the bottom is heated and heat-fixed to promote crystallization, thereby advancing the crystallization at the bottom portion, particularly near the center of the bottom portion. The strength of the valley can be increased, and the heat and pressure resistance performance can be further improved. At this time, the bottom portion, which has been stretched and thinned to a high orientation, is heat-set at a temperature of about 130 ° C. to 200 ° C. to be crystallized with almost no spherulitic whitening, and therefore, usually sufficient impact resistance performance is obtained. Can have. It is important to increase the crystallinity of the bottom trough spherical surface portion within a diameter range of about 50% of the trunk diameter by heat fixing the bottom portion, and the crystallinity at that portion is set to 30 to 55%. Is preferred.

[Procedure amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction contents]

As the two-stage blow molding method, blow molding
First blow molding using a mold is used to create a secondary molded product with a generally spherical bottom from the preform molded product, and part of the secondary molded product is heated and shrunk to the bottom and the body part connected to the bottom. Three
It is possible to employ a step of forming a secondary molded product and then subjecting the tertiary molded body to secondary blow molding to obtain a final shape.

[Procedure amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0039

[Correction method] Change

[Correction contents]

In this case, 2 obtained by primary blow molding
It is preferable that the bottom of the next molded product is thinned to a relatively high stretch except for the center. In order to reduce the thickness of the bottom part to a relatively high stretch by primary blow molding, the center part of the bottom of the preform molded product is sufficiently sandwiched between the stretch rod arranged inside the molded product and the press rod installed outside. It is desirable to perform biaxially stretch blow molding. At this time, the central portion of the bottom sandwiched between the stretch rod and the press rod remains as a thick portion in an almost unstretched state.

[Procedure amendment 11]

[Document name to be amended] Statement

[Correction target item name] 0040

[Correction method] Change

[Correction contents]

It is preferable that the center portion of the bottom having a relatively thick wall has a relatively small diameter in order to maintain the preferable heat resistance and pressure resistance of the bottom portion. Usually, the diameter D _{c of the} center of the bottom is the body diameter D _0.
Of 25% or less, preferably 18% or less.

[Procedure amendment 12]

[Document name to be amended] Statement

[Correction target item name] 0041

[Correction method] Change

[Correction contents]

Further, by heating and fixing the thick portion by heating, the material strength at the time of heat sterilization treatment can be improved. In the above-described two-step blow molding method, when the bottom of the secondary molded product is heated, the center of the thick bottom and the highly stretched thin portion of the periphery thereof can be heat set at the same time. At this time, in order to secure the impact resistance, the bottom center of the thicker it is preferable to suppress the upper limit of less crystallinity than the thin portion of its periphery, specifically, the bottom center of the thick The degree of crystallinity is preferably 20 to 45%, and the degree of crystallinity of the highly stretched thin portion at the periphery thereof is preferably 30 to 55%.

[Procedure amendment 13]

[Document name to be amended] Statement

[Correction target item name] 0042

[Correction method] Change

[Correction contents]

Further , in the two-stage blow molding method, the primary blow molding is free blow molding without using a mold, whereby the entire bottom portion can be stretched and thinned. In the free-blow-molded secondary molded product, the bottom center portion can be thinned while being relatively stretched, and the peripheral edge portion can be thinned to be relatively stretched. The secondary molded product thus obtained is subjected to heat shrinkage of the body and the bottom to form a tertiary molded product that can be fitted in the secondary blow molding die, and the final molded product is subjected to secondary blow molding to obtain the final molded product. Can be a product.
In this case, when the secondary molded product is heated, the bottom portion is heated to 130 ° C to 20 ° C.
By heat setting at a temperature of about 0 ° C., the crystallinity of the entire bottom of the final product can be increased to about 30 to 55%.

[Procedure Amendment 14]

[Document name to be amended] Statement

[Correction target item name] 0043

[Correction method] Change

[Correction contents]

By preheating the neck and neck and the center of the bottom of the preform molded product to make them spherulite, it is possible to easily increase the degree of thinning of the stretched shoulder and bottom during blow molding. This can be adopted in the one-step blow molding method, in which case the obtained container bottom can be thinned to a relatively high stretch until the very end of the spherulization part located at the center of the bottom. Further, in the primary blow molding of the two-stage blow molding method, it is effective as a stable means for reducing the wall thickness to a relatively high stretch until the very end of the spherulization portion at the bottom.

[Procedure Amendment 15]

[Document name to be amended] Statement

[Correction target item name] 0062

[Correction method] Change

[Correction contents]

In the present invention, it is preferable to thin the bottom portion to a relatively high stretch in the primary blow molding step, but for that purpose, the balance between the heating temperature of the bottom portion of the preform and the heating temperature of the body portion is important. That is, by bringing the heating temperature of the bottom portion of the preform close to the heating temperature of the barrel portion, the bottom portion can be thinned to a relatively high stretch as in the barrel portion during blow molding. On the other hand, if the heating temperature of the bottom of the preform is considerably lower than that of the body, the degree of stretching of the bottom during blow molding will be low.

[Procedure Amendment 16]

[Document name to be amended] Statement

[Correction target item name] 0087

[Correction method] Change

[Correction contents]

Table 1 shows the numerical values of the bottom shapes of the five secondary blow molds used in this comparative test. Containers were prepared for each of the five molds and used as Example 1, Example 2 and Example 3, Comparative Example 1 and Comparative Example 2, and the wall thickness and crystallinity of each part of the obtained container were investigated. . In any case, except for the center of the bottom of the obtained container, the thickness of the bottom valley within a radius of 30 mm is 0.3.
5 to 0.5 mm, and the degree of crystallinity in that portion is 30 to 4
2%. In addition, the diameter D _{c of the} center of the bottom, which is relatively thick ,
Was about 10 mm, and the ratio D _c / D ₀ of the diameter at the center of the bottom to the diameter of the body was about 0.1. The thickness of the center of the bottom was about 1 mm. Table 1 also shows the minimum thickness t _min of the foot tip of the obtained container.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Settsuko Nakamaki 25 Sachigaoka, Asahi-ku, Yokohama-shi, Kanagawa (72) Inventor Kimio Takeuchi 2297-5 Nogawa, Misaki-ku, Kawasaki-shi, Kanagawa (72) Hotaka Fukahori, Kanagawa 2-206 Nishitobe-cho, Nishi-ku, Yokohama (72) Inventor Yoshihisa Maruhashi 6-35-5 Hiyoshihoncho, Kohoku-ku, Yokohama-shi, Kanagawa

Claims (13)

[Claims] 1. Formed by biaxial stretch blow molding of a resin
And a bottom portion of the body
Between valleys located on a virtual curved surface that is convex toward the bottom
Located at the bottom, protruding from the bottom toward the bottom and at the center
And the foot part that extends in the radial direction from the
In a self-supporting container consisting of
The foot opening angle θ that sandwiches the valley in the vertical plane is 65 ° or less.
Above, the diameter D₀Valley included within 80% diameter of
Total surface area of S, and body diameter D₀ Within 80% of the diameter
The surface area of the virtual curved surface₀Then S ≧
0.2 S₀Heat resistant and pressure resistant self-supporting
vessel. 2. The foot opening angle θ is 70 ° to 110.
The heat resistant and pressure resistant self-supporting container according to claim 1, which is in the range of °. 3. The heat resistant and pressure resistant self-supporting container according to claim 1, wherein the total surface area S of the bottom valleys is within the range of the formula 0.5 · S ₀ ≧ S ≧ 0.3 · S ₀ . 4. The total length (L) of the valleys on the circumference of the diameter d of the central root of the virtual curved surface of the diameter d ₀ +10 mm in the virtual curved surface is L ≧ 0.2 · πd. 1. A heat-resistant pressure-resistant free-standing container according to 1. 5. The radius of curvature R of the bottom valley near the center of the bottom
₁ is barrel radius (D _0/2) is 1.05 to 1.6 times the claims 1 heat- and pressure-resistant self-supporting container according. 6. The heat resistance according to claim 1, wherein the entire bottom part is stretched at a relatively high draw ratio except the center part of the bottom, and the thickness of the bottom part except the center part of the bottom is reduced to 1 mm or less. Pressure freestanding container. 7. The thickness of the bottom is 0.15 except for the center of the bottom.
The heat and pressure resistant freestanding container according to claim 1, which is in the range of mm to 0.8 mm. 8. The heat and pressure resistant self-supporting container according to claim 1, wherein the bottom portion except the center portion has a crystallinity of 20% or more. 9. The bottom is heat-fixed except for the center of the bottom, and the valleys within a diameter range of 50% of the body diameter (D ₀ ) are 25 to 55% except for the center of the bottom. The heat resistant and pressure freestanding container according to claim 1, which has a crystallinity of 1. 10. The heat and pressure resistant self-supporting container according to claim 1, wherein the neck of the container is spherulized. 11. The diameter of the center of the bottom in a substantially unstretched state
D_cIs the diameter D of the body ₀25% or less of
Heat resistant and pressure resistant freestanding container. 12. The center of the bottom is heat-fixed,
The heat resistant and pressure resistant self-supporting container according to claim 1, which has a crystallinity of 0 to 45%. 13. The heat and pressure resistant self-supporting container according to claim 1, wherein 5 to 6 bottom legs are provided.