JP3632302B2

JP3632302B2 - Self-supporting container

Info

Publication number: JP3632302B2
Application number: JP16653596A
Authority: JP
Inventors: 正樹三浦
Original assignee: Toyo Seikan Kaisha Ltd
Current assignee: Toyo Seikan Kaisha Ltd
Priority date: 1996-05-24
Filing date: 1996-05-24
Publication date: 2005-03-23
Anticipated expiration: 2016-05-24
Also published as: JPH09315419A

Description

【０００１】
【発明の属する技術分野】
本発明はベースカップを使用しない延伸ブロー形成により成形した自立容器に関する。さらに詳しくはガス含有小容量自立容器や果汁、乳酸等の入ったガス含有自立容器に関する。
【０００２】
【従来の技術】
従来ベースカップを使用しない延伸成形された自立型容器として、特公昭４８−５７０８号公報、特公昭６１−９１７０号公報、特開平１−２６７１４６号公報、特公昭５９−４０６９３号公報等に記載された容器が知られている。
これ等の容器はいずれも容器の底部に脚部を形成して自立出来るようにしたものである。
これ等従来の容器の問題点はこれ等の容器の底部を分割する谷底面と、谷底面を挾む両側壁部即ち脚部側壁との境界線で区画した放射状に周縁に向って広がる谷部、を有する底部は半球殻の一部をなす谷底面により耐内圧性を向上させる効果を期待したものである。
ところがこのような自立容器には経時変化が生ずることがわかった。自立容器にガス含有内容物を収納すると時間の経過とともに底面が変形し、下方に突出して来る傾向が大きく、底部中央部分が膨出して接地し、自立安定性がなくなる場合もある。特に、内容量が１０００ｍｌ以下の小容量自立容器においてこの傾向が顕著に現れる。
小容量容器には脚部の賦形性悪く、耐熱安定性と、耐ＥＳＣ性が悪くクレージングが発生する問題もある。
【０００３】
【発明が解決しようとする課題】
本発明はガスを含有する内容物を収納しても経時的に変形しない底面を有する自立容器を提供するものである。
特に容量２００〜１０００ｍｌの小容量容器は重量のバランスが悪ので脚部の賦形性を良好にして自立安定性を向上する必要がある。
【０００４】
【課題を解決するための手段】
本発明は、
「１．谷底面により等分割された分割底面部を有する自立容器であって、
Ａ．二軸延伸された耐圧容器の底面を等中心角で等分する、底中央部から外側に向かって上昇傾斜した谷底面と、谷底面を挾む脚部側壁とからなる谷部と、
Ｂ．脚部側壁と、谷部によって等中心角で等分され底中央部周縁から延伸された脚部頂面と、谷部により区画された胴下端部で形成された脚部外側壁とからる、四角台形状の脚部と、
Ｃ．複数の脚部項面の外円周部からなる接地部と、
からなる、二軸延伸成形した自立容器であり、
谷底面が、
ａ．底中央部から底部と胴部の結合部に向かって上昇傾斜した、水平面と１５度〜２５度の角度をなす平らな面を有する斜面と、
ｂ．水平面と４５度〜７０度の角度をなす平らな面を有する傾斜面とが、
容器の高さ方向の中心軸線から径方向に容器の半径の５０％〜７５％の位置で、かつ接地面から高さ方向に胴部直径の８％〜２０％の位置で交差して形成された底面である、
ことを特徴とする分割底面部を有する二軸延伸成形した自立容器。
２．谷底面により等分割された分割底面部を有する自立容器であって、
Ａ．二軸延伸された耐圧容器の底面を等中心角で等分する、底中央部から外側に向かって上昇傾斜した谷底面と、谷底面を挾む脚部側壁とからなる谷部と、
Ｂ．脚部側壁と、谷部によって等中心角で等分された底中央部周縁から延伸された脚部頂面と、谷部により区画された胴下端部で形成された脚部外側壁とからる、四角台形状の脚部と、
Ｃ．複数の脚部頂面の外円周部からなる接地部と、
からなる、二軸延伸成形した自立容器であり、
谷底面が、
ａ．原点を容器の高さ方向の中心軸線に対して脚部反対側に有し底中央部周縁から上方に広がり、容器の胴部の直径の５０％〜３００％の半径を有する弧面と、
ｂ．水平面と４５度〜７０度の角度をなす傾斜面とが、
中心軸線から径方向に容器胴部の半径の５０％〜７５％の位置で、かつ接地面から高さ方向に胴部直径の８％〜２０％の位置で交差して形成された底面である、ことを特徴とする分割底面部を有する二軸延伸成形した自立容器。
３．弧面がａ．原点を容器の高さ方向の中心軸線上に有し、容器の胴部の直径の５０〜３００％の半径を有する弧面である、２項に記載された二軸延伸成形した自立容器。
４．脚部頂面の外円周部からなる接地部分を結ぶ円弧の直径が、胴下端部の直径の０．６５〜０．８５倍である、１項ないし３項のいずれか１項に記載された二軸延伸成形された自立容器。
５．ａ傾斜面またはａ弧面とｂ傾斜面との交差点が、容器胴部の直径の５％〜３０％の小さい半径を有する曲面で連結されている、１項ないし４項のいずれか１項に記載された二軸延伸成形した自立容器。
６．ｂ．傾斜面と胴部下端との間に胴部直径に対し５〜３０％の小径の曲面の連結部を設置した、１項ないし５項のいずれか１項に記載された二軸延伸成形した自立容器。
７．等中心角による底面の分割が奇数等分である、１項ないし６項のいずれか１項に記載された二軸延伸成形した自立容器。
８．等中心角による底面の奇数等分割が、３または５等分割である、１項ないし７項のいずれか１項に記載された二軸延伸成形した自立容器。
９．底中心部を熱結晶化した、１項ないし８項のいずれか１項に記載された二軸延伸成形した自立容器。
１０．容器が容量が２００ｍｌ〜１０００ｍｌの小容量容器である、１項ないし９項のいずれか１項に記載された二軸延伸成形した自立容器。］
に関する。
【０００５】
【発明の実施の形態】
内容量が１０００ｍｌ以下の小容量容器では、特公昭４８−５７０８号公報等に開示された従来の底部形状では熱水殺菌時に底中央部が膨出する等の変形が発生し充分な耐圧性が得られない。
また、果汁や乳酸菌を含むガス含有飲料を冷間充填した容器を熱水殺菌すると、容器内の内圧が高くなると共に容器を構成する材料の剛性が失われて容器の耐熱圧性が低下するが、小容量容器ではこの傾向が著しい。
ここで言う耐熱圧性とは、ガス含有飲料を充填した容器を熱水等で殺菌する場合、これに耐える性能を意味する。
従来用いられている耐熱圧性容器としては、特公平７−３７２６０号公報に記載されているように容器の半球形状の底部にベースカップを装着するものである。
しかしながら、使用済みの容器を資源として再利用するためには容器と材質の異なるベースカップを使用することができないが、自立のため脚部を形成して同一材質の容器とすると谷底面を半球殻の一部としても耐熱圧性は良好とならない。
【０００６】
本発明者は種々研究した結果、容器底面の谷部に直線部分を有さない半球形状や特公昭５９−４０６９３号公報に開示された部分的に直線部分を有する従来の底部形状では小容量容器としたとき耐変形強度が弱く充分な耐圧性が得られないことが判明した。
さらに研究した結果、小容量容器は谷部が半球殻の一部をなす形状では耐熱圧性は良くならないことがわかった。
谷部が弧状部分と直線状部分の組み合わせからなる場合でも、弧状部分の交差する位置が径方向及び高さ方向で特定範囲の位置にないと、耐熱圧性が悪く、経時変化が大きい。
また、弧状部分の半径が容器胴部の直径の５０〜３００％でないと耐熱圧性が悪く、経時変化が発生する。弧状部分の半径は５０％〜３００％、特に５０〜２００％の範囲にあるのが好ましい。弧状部分の半径が５０％未満であれば耐熱圧性が悪く、経時変化も大きい。
【０００７】
本発明は容器の底面を形成する谷底面が、水平面と１５〜２５度の角度をなす平らな面を有するａ傾斜面と、水平面と４５〜７０度の角度をなす平らな面を有するｂ傾斜面とで形成されているところに大きな特徴があるが、それだけでは経時変化を防止することはできない。この二傾斜面を特定の位置で交差して谷底面を形成するところにも重要な特徴がある。
前記二傾斜面は容器の中心軸から径方向に容器胴部の半径の５０％〜７５％高さ方向に容器胴部の直径の８％〜２０％の位置で交差しなければならない。この二傾斜面の傾斜角度は夫々前述の１５度〜２５度、４５〜７０度であり、交差位置が前記の位置にあると、ガス含有内容物を収納して放置したときの経時変化は、ａ傾斜面が容器の外方に膨出し、ｂ傾斜面が容器の内方に膨出するように作用し、変形を防止するが、この両傾斜面の交差点が変形の反点となる。そして、二傾斜面の傾斜角度が重要であり、ａ傾斜面の傾斜角度が１５度未満では底部の変形が大きくなり、２５度を越えても賦形性が悪くなる。またｂ傾斜面の傾斜角度が４５度未満では賦形性が悪くなり、７０度を越えると底部の変形が大きくなる。さらに傾斜した二傾斜面の交差する位置も重要であって、交差点は中心軸線から径方向に容器胴部の半径の５０％〜７５％、接地面から高さ方向に容器胴部の直径の８％〜２０％の位置で交差しなければならない。交差位置が径方向に容器胴部の半径の５０％より小さければ賦形性が悪くなり、７５％より大きければ底部の変形が大きくなり、かつ接地面から高さ方向に容器胴部の直径の８％より小さいと底部の変形が大きくなり、２０％を越えると賦形性が悪くなるからである。
【０００８】
底中央部から底部と胴部の結合部に向って上昇傾斜した水平面と１５度〜２５度の角度をなす平らな面を有するａ傾斜面は中心軸線上に半径の原点をもつ弧面に比べて応力集中点が底中央部側から谷部側に移行するので底部の変形が防止される。
このａ傾斜面に代えて、容器の胴部の直径の５０％〜３００％の半径の弧面を設けることもできる。ｂ傾斜面は前述の通り直線状の斜面である。この弧面とｂ傾斜面との交差位置は同様に容器の径方向に中心軸線から容器胴部の半径の５０％〜７５％の位置で、かつ接地面から高さ方向に容器胴部直径の８％〜２０％の位置で交差しなければならない。
【０００９】
ｂ傾斜面と胴下端部の結合部には、小半径の曲面の連結部を設けるが、ｂ傾斜面が平らな面であるので、この連結部を設けることにより結合部に急激な変曲点が発生せず、応力の集中が防止され、経時変形を防ぐことができる。
この連結部は半径は胴部の直径に対して５〜３０％の小径の曲面である。連結部の半径が５％未満では応力集中が生じて変形が起り、３０％を越えても同様な現象が生じる。
脚部頂面の周辺を結ぶ円弧が有効な自立安定効果を奏するが、この円弧の半径が胴部の直径の０．６５〜０．８５倍の範囲にあると自立性が良好となる。この円弧の径が０．６５倍未満では自立安定性に欠け、０．８５を越えると賦形性が悪くなる。
【００１０】
ａ傾斜面またはａ弧面とｂ傾斜面との交差点を容器胴部の直径の５％〜３０％の小さい半径を有する弧面で連結すると応力の集中が防止され、経時変形が防げる。
また、底面は奇数等分に分割すると耐圧性、自立性が良く、特に５等分割することが好ましい。底中央部を熱結晶化すると未延伸ないし低延仲のこの部分の剛性や耐熱性が向上する。
本発明の特別の構成の容器は、内容が２００ｍｌ〜１０００ｍｌの小容量容器において特に優れた効果を奏する。このような小容量容器では経時変形が大きく、底中央部が突出して接地する問題が多かったが、本発明により解決することができた。
本発明で使用する合成樹脂としては、ポリエステル樹脂が挙げられ、特にポリエチレンテレフタレート（ＰＥＴ）、これを主体とする共重合体やブレンド物が好ましい。
二軸延仲成形は通常のブロー成形が用いられる。
【００１１】
【実施例】
図面に基づいて本発明を説明する。
【００１２】
図１は本発明の二軸延伸成形した内容量５００ｍｌの自立容器である。１は容器、２は胴部であり、３は底部である。底部は谷部面、脚部４及び底中央部から形成されており、連結部７で胴下端部と結合している。５は脚部の頂面の外周部であり、接地部である。６は脚部側壁、１２は容器の高さ方向の中心軸線である。
【００１３】
図２は中心軸線１２に沿った底部の断面を示す。８は底中央部であり、延伸されていないので厚肉となっているが、熱結晶化されている。９は底中央部から径方向外方に上昇傾斜した水平面と２０度の角度を有する平らな面を有する傾斜面であって、本発明で言うａ斜面である。１０は水平面と６０度の傾斜角度をなす平らな面を有する傾斜面であって、本発明で言うｂ傾斜面である。ａ傾斜面９とｂ傾斜面１０は、中心軸線１２から径方向に胴部の半径３５ｍｍの７０％である２５ｍｍ、接地面から高さ方向に胴部の直径の約１５％の１０ｍｍの位置の交差点１３で結合し、谷底面を形成している。この交差点は半径１２ｍｍの小さな曲面で形成されている。ｂ傾斜面１０は胴下端部の連続部１１で胴下端部と結合しているが、この連結部１１は小さい半径をもつ曲面になっている。
【００１４】
図３は別の実施例であって、図２のａ傾斜面の代わりに４２ｍｍの半径を有する弧面１１とした以外は図２と同様にした実施例である。
【００１５】
図４は図２の容器の底面１４を示し、ａ傾斜面とｂ傾斜面１０とは交差点１３で結合している。
【００１６】
図５は比較例であり弧面とｂ傾斜面からなる底面を示す。図６は弧面からなる底面を示す比較例である。
次に容器の具体例および比較例との性能の比較試験を示す。
【００１７】
実施例１
ＰＥＴを用いて射出成形した径２２ｍｍ、長さ１０５ｍｍのＰＥＴ製プリフォームを用いて二軸延伸ブロー成形し、図１、図２、図４に示す内容量５００ｍｌの容器を製造した。
ａ傾斜面の角度は２０度であり、ｂ傾斜面は６０度であった。両斜面は中心軸から４８ｍｍの距離で結合している。谷底の巾は４ｍｍである。
【００１８】
実施例２
底中央部周縁から上方に広がる弧面と、胴下端部より絞り込まれるｂ傾斜面の角度は６０度で弧面との交点の位置が、径方向５０ｍｍ、高さ方向１１ｍｍの位置にあり、弧面の半径は４２ｍｍであった。谷底の巾は４ｍｍである。
【００１９】
実施例３
ＰＥＴを用いて射出成形した径２２ｍｍ、長さ１０５ｍｍのＰＥＴ製プリフォームを用いて二軸延伸ブロー成形し、図１、図３、図４に示す内容量５００ｍｌの容器を製造した。
底中央部周縁から上方に広がる弧面と、胴下端部より絞り込まれるｂ傾斜面の角度は６０度で弧面との交点の位置が、径方向４８ｍｍ、高さ方向１０ｍｍの位置にあり、弧面の半径は４６ｍｍであった。谷底の巾は４ｍｍである。
【００２０】
比較例１
図５に示す底面を有する容器であって、底中央部周縁から上方に広がる半径２５ｍｍの弧面と、前記弧面に接し胴下端部まで上方傾斜するｂ傾斜面の角度は６０度であった。谷底の巾は４ｍｍである。弧面の原点は容器高さ方向の中心線より脚部側にある。
【００２１】
比較例２
図６に示される底面を有する容器であって、、底中央部周縁から上方に広がるａ弧面と、前記弧面に接し胴下端部までなだらかに接合するｂ弧面、全体として楕円状になる谷底面の夫々の弧面の半径は、ａ弧面４２ｍｍｂ弧面２２ｍｍである。谷底の巾は４ｍｍである。ｂ傾斜面がない例である。
［評価方法］
各例共１００本に４ＧＶの炭酸水を充填し、３７℃１ＷＥＥＫの底部変化量と０．２％アルカリ浸漬でのストレスクラッキングの発生本数を調べた。結果を表１と表２に示す。
４ＧＶ−３７℃１ＷＥＥＫの底部変化量
【００２２】
【表１】

【００２３】
（註）比較例１、比較例２はロッカーボトムとなった。
ストレスクラッキングの発生本数
【００２４】
【表２】

【００２５】
この試験結果から本発明容器は耐ストレスクラッギング性、耐変形性に優れていることが理解される。
【００２６】
【発明の効果】
本発明は小容量容器であっても脚部の賦形性が良好で耐熱圧性に優れ、耐ＥＳＣ性も良く自立安定性に優れた効果を奏する。
【図面の簡単な説明】
【図１】自立容器の正面図である。
【図２】本発明の実施例の容器の底部の高さ方向の断面図である。
【図３】他の実施例の底部の高さ方向の断面図である。
【図４】底部の説明図である。
【図５】比較例の底部の説明図である。
【図６】他の比較例の底部の説明図である。
【符号の説明】
１容器
２胴部
３底部
４脚部
５接地部
６脚部側壁
７連結部
８底中央部
９ａ傾斜面
１０ｂ傾斜面
１１弧面
１２容器中心軸線
１３交差点
１４底面[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a self-supporting container formed by stretch blow forming without using a base cup. More specifically, the present invention relates to a gas-containing small-capacity self-supporting container and a gas-containing self-supporting container containing fruit juice, lactic acid and the like.
[0002]
[Prior art]
Conventionally stretched self-supporting containers that do not use a base cup are described in JP-B-48-5708, JP-B-61-9170, JP-A-1-267146, JP-B-59-40693, and the like. Containers are known.
All of these containers can be made self-supporting by forming legs on the bottom of the container.
The problems with these conventional containers are that the valleys that divide radially toward the periphery are defined by the boundary between the bottom of the valley that divides the bottom of these containers and the side walls that sandwich the bottom of the valley, that is, the side walls of the legs. The bottom portion having, is expected to improve the internal pressure resistance due to the bottom of the valley forming part of the hemispherical shell.
However, it has been found that such a self-supporting container changes with time. When the gas-containing contents are stored in a self-supporting container, the bottom surface is deformed over time and tends to protrude downward, and the center portion of the bottom swells and comes into contact with the ground, and the self-supporting stability may be lost. This tendency is particularly noticeable in small-capacity self-supporting containers having an internal volume of 1000 ml or less.
Small-capacity containers also have problems of poor leg shapeability, heat stability, and poor ESC resistance and crazing.
[0003]
[Problems to be solved by the invention]
The present invention provides a self-supporting container having a bottom surface that does not deform over time even when contents containing gas are stored.
In particular, a small-capacity container having a capacity of 200 to 1000 ml has a poor weight balance, so that it is necessary to improve the leg shapeability and improve the self-supporting stability.
[0004]
[Means for Solving the Problems]
The present invention
“1. A self-supporting container having a divided bottom surface portion equally divided by a valley bottom surface,
A. Dividing the bottom surface of the biaxially-stretched pressure vessel equally with an equal central angle, a valley bottom portion that is inclined upward from the center of the bottom toward the outside, and a valley portion that includes leg side walls that sandwich the valley bottom surface;
B. It consists of a leg side wall, a leg top surface equally divided by a valley at an equal central angle and extended from the periphery of the bottom central part, and a leg outer wall formed by a trunk lower end section defined by the valley. A square trapezoidal leg,
C. A grounding portion composed of an outer circumferential portion of a plurality of leg sections,
Is a biaxially stretched freestanding container consisting of
The bottom of the valley
a. An inclined surface having a flat surface and an angle of 15 degrees to 25 degrees with a horizontal plane, which is inclined upward from the bottom center portion toward the joint portion of the bottom portion and the trunk portion;
b. An inclined surface having a flat surface and an angle of 45 to 70 degrees with the horizontal plane,
Formed by intersecting at a position of 50% to 75% of the radius of the container in the radial direction from the central axis in the height direction of the container and at a position of 8% to 20% of the trunk diameter in the height direction from the ground surface. The bottom
A self-supporting container biaxially stretch-molded having a divided bottom surface portion.
2. It is a self-supporting container having a divided bottom surface portion equally divided by a valley bottom surface,
A. Dividing the bottom surface of the biaxially-stretched pressure vessel equally with an equal central angle, a valley bottom portion that is inclined upward from the center of the bottom toward the outside, and a valley portion that includes leg side walls that sandwich the valley bottom surface;
B. It consists of a leg side wall, a leg top surface extended from the periphery of the bottom center part equally divided by a valley at an equal central angle, and a leg outer wall formed by a trunk lower end section defined by the valley part. A square trapezoidal leg,
C. A grounding portion composed of an outer circumferential portion of a plurality of leg top surfaces;
Is a biaxially stretched freestanding container consisting of
The bottom of the valley
a. An arc surface having an origin on the opposite side of the leg with respect to the central axis in the height direction of the container and extending upward from the peripheral edge of the bottom center, and having a radius of 50% to 300% of the diameter of the body of the container;
b. An inclined surface that forms an angle of 45 degrees to 70 degrees with the horizontal plane,
It is a bottom surface formed by intersecting at a position of 50% to 75% of the radius of the container body in the radial direction from the central axis and at a position of 8% to 20% of the body diameter in the height direction from the ground surface. A self-supporting container formed by biaxial stretching having a divided bottom surface portion.
3. The arc surface is a. The biaxially stretched self-supporting container according to item 2, which is an arc surface having an origin on a central axis in the height direction of the container and having a radius of 50 to 300% of the diameter of the body of the container.
4). 4. The diameter of the arc connecting the ground contact portion composed of the outer circumferential portion of the leg top surface is 0.65 to 0.85 times the diameter of the lower end of the trunk, and is described in any one of items 1 to 3. A biaxially stretched freestanding container.
5. The intersection of the a inclined surface or the a arc surface and the b inclined surface is connected by a curved surface having a small radius of 5% to 30% of the diameter of the container body, The described biaxially stretched free-standing container.
6). b. 6. A biaxially stretched self-supporting device according to any one of items 1 to 5, wherein a connecting portion having a curved surface having a small diameter of 5 to 30% with respect to the diameter of the body portion is installed between the inclined surface and the lower end of the body portion. container.
7). The biaxially stretched free-standing container described in any one of items 1 to 6, wherein the division of the bottom surface by the equal center angle is an odd number of equal parts.
8). The self-supporting container formed by biaxial stretching according to any one of items 1 to 7, wherein odd-numbered equal divisions of the bottom surface by equal center angles are 3 or 5 equal divisions.
9. 9. A self-supporting container that is biaxially stretch-molded according to any one of items 1 to 8, wherein the bottom center is thermally crystallized.
10. 10. The biaxially stretched self-supporting container described in any one of items 1 to 9, wherein the container is a small capacity container having a capacity of 200 ml to 1000 ml. ]
About.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
In a small-capacity container having an inner volume of 1000 ml or less, the conventional bottom shape disclosed in Japanese Examined Patent Publication No. 48-5708 etc. is deformed such that the bottom center portion swells during hot water sterilization and has sufficient pressure resistance. I can't get it.
In addition, when hot-water sterilizing a container cold-filled with a gas-containing beverage containing fruit juice and lactic acid bacteria, the internal pressure in the container increases and the rigidity of the material constituting the container is lost, and the heat and pressure resistance of the container decreases. This tendency is remarkable in small-capacity containers.
The heat and pressure resistance referred to here means the ability to withstand this when a container filled with a gas-containing beverage is sterilized with hot water or the like.
A conventionally used heat and pressure resistant container is one in which a base cup is attached to the hemispherical bottom of a container as described in Japanese Patent Publication No. 7-37260.
However, in order to reuse used containers as resources, it is not possible to use a base cup made of a material different from that of the container. Even as a part of it, the heat and pressure resistance is not good.
[0006]
As a result of various studies, the present inventor has found that a small-capacity container is not used in the hemispherical shape that does not have a straight portion in the valley portion of the bottom of the container or the conventional bottom shape that is partially disclosed in Japanese Examined Patent Publication No. Sho 59-40693 It was found that the deformation resistance was weak and sufficient pressure resistance could not be obtained.
As a result of further research, it was found that the heat resistance and pressure resistance of small-capacity containers does not improve when the valley is part of a hemispherical shell.
Even when the valley portion is formed by a combination of an arc-shaped portion and a linear portion, if the position where the arc-shaped portion intersects is not located in a specific range in the radial direction and the height direction, the heat and pressure resistance is poor and the change with time is large.
In addition, if the radius of the arc-shaped portion is not 50 to 300% of the diameter of the container body, the heat and pressure resistance is poor and a change with time occurs. The radius of the arcuate part is preferably in the range of 50% to 300%, in particular 50 to 200%. If the radius of the arc-shaped portion is less than 50%, the heat and pressure resistance is poor and the change with time is large.
[0007]
In the present invention, the bottom surface of the valley forming the bottom surface of the container has an a inclined surface having a flat surface forming an angle of 15 to 25 degrees with the horizontal plane, and a b inclined surface having a flat surface forming an angle of 45 to 70 degrees with the horizontal surface. There is a great feature in that it is formed with the surface, but it is not possible to prevent changes with time alone. There is also an important feature in forming a valley bottom by intersecting these two inclined surfaces at a specific position.
The two inclined surfaces should cross from the central axis of the container in a radial direction at a position of 50% to 75% of the radius of the container body and at a position of 8% to 20% of the diameter of the container body. The inclination angles of the two inclined surfaces are 15 to 25 degrees and 45 to 70 degrees, respectively. When the intersecting position is at the above position, the change with time when the gas-containing contents are stored and left is Although the a sloped surface bulges outward from the container and the b sloped surface bulges inward of the container to prevent deformation, the intersection of both slopes is the anti-deformation point. The inclination angle of the two inclined surfaces is important. If the inclination angle of the a inclined surface is less than 15 degrees, the deformation of the bottom portion becomes large, and if it exceeds 25 degrees, the formability deteriorates. Further, if the angle of inclination of the b inclined surface is less than 45 degrees, the formability deteriorates, and if it exceeds 70 degrees, the deformation of the bottom part becomes large. Further, the position where two inclined surfaces intersect is also important, and the intersection is 50% to 75% of the radius of the container body in the radial direction from the central axis, and 8% of the diameter of the container body in the height direction from the ground surface. You must cross at a position between% and 20%. If the crossing position is smaller than 50% of the radius of the container body in the radial direction, the formability is deteriorated. If it is greater than 75%, the deformation of the bottom is increased, and the diameter of the container body is increased in the height direction from the ground plane. This is because if it is less than 8%, the deformation of the bottom increases, and if it exceeds 20%, the formability deteriorates.
[0008]
The a sloped surface with a flat surface that forms an angle of 15 to 25 degrees with the horizontal plane rising upward from the bottom center toward the joint between the bottom and the body is compared to an arc surface having a radius origin on the central axis. The stress concentration point shifts from the bottom center side to the trough side, so that deformation of the bottom is prevented.
In place of the inclined surface a, an arc surface having a radius of 50% to 300% of the diameter of the body portion of the container may be provided. The b inclined surface is a linear inclined surface as described above. Similarly, the crossing position of the arc surface and the b inclined surface is 50% to 75% of the radius of the container body from the central axis in the radial direction of the container, and the diameter of the container body in the height direction from the ground surface. Must cross at 8-20%.
[0009]
The connecting part of the inclined surface of the b and the lower end of the body is provided with a connecting portion having a curved surface with a small radius, but since the inclined surface of the b is a flat surface, a sharp inflection point is formed in the connecting part by providing this connecting part. Does not occur, stress concentration is prevented, and deformation with time can be prevented.
The connecting portion is a curved surface having a small diameter of 5 to 30% with respect to the diameter of the body portion. If the radius of the connecting portion is less than 5%, stress concentration occurs and deformation occurs, and if it exceeds 30%, the same phenomenon occurs.
An arc connecting the periphery of the top surface of the leg portion has an effective self-supporting stability effect. When the radius of this arc is in the range of 0.65 to 0.85 times the diameter of the trunk portion, the self-supporting property is improved. If the diameter of the arc is less than 0.65 times, the self-supporting stability is insufficient, and if it exceeds 0.85, the formability is deteriorated.
[0010]
If the a inclined surface or the intersection of the a arc surface and the b inclined surface is connected by an arc surface having a small radius of 5% to 30% of the diameter of the container body, concentration of stress is prevented, and deformation with time can be prevented.
Further, when the bottom surface is divided into odd-numbered parts, the pressure resistance and the self-supporting property are good, and it is particularly preferable to divide into five parts. When the bottom center portion is thermally crystallized, the rigidity and heat resistance of the unstretched or low-rolled portion are improved.
The container having a special configuration according to the present invention has a particularly excellent effect in a small-capacity container having a content of 200 ml to 1000 ml. In such a small-capacity container, the deformation with time was large, and there were many problems that the bottom center portion protruded and grounded, but this problem could be solved by the present invention.
Examples of the synthetic resin used in the present invention include a polyester resin, and polyethylene terephthalate (PET), and a copolymer or blend mainly composed of this are preferable.
In the biaxial rolling intermediate molding, ordinary blow molding is used.
[0011]
【Example】
The present invention will be described with reference to the drawings.
[0012]
FIG. 1 shows a self-supporting container having an internal volume of 500 ml formed by biaxial stretching according to the present invention. 1 is a container, 2 is a trunk, and 3 is a bottom. The bottom portion is formed from the valley surface, the leg portion 4 and the bottom center portion, and is connected to the lower end portion of the trunk at the connecting portion 7. Reference numeral 5 denotes an outer peripheral portion of the top surface of the leg portion, which is a grounding portion. 6 is a leg side wall, and 12 is a central axis in the height direction of the container.
[0013]
FIG. 2 shows a cross section of the bottom along the central axis 12. 8 is a bottom center part, and since it is not extended | stretched, it is thick, but it is thermally crystallized. Reference numeral 9 denotes an inclined surface having a flat surface having an angle of 20 degrees with a horizontal surface inclined upward and radially outward from the center of the bottom, and is an a slope referred to in the present invention. Reference numeral 10 denotes an inclined surface having a flat surface that forms an inclination angle of 60 degrees with the horizontal plane, and is an inclined surface b referred to in the present invention. The a inclined surface 9 and the b inclined surface 10 are located at 25 mm, which is 70% of the radius of the barrel 35 mm in the radial direction from the

central axis

12, and 10 mm, which is approximately 15% of the diameter of the barrel in the height direction from the ground plane. They are joined at an intersection 13 to form a valley bottom. This intersection is formed by a small curved surface having a radius of 12 mm. b The inclined surface 10 is connected to the lower end of the cylinder at a continuous part 11 at the lower end of the cylinder, but the connecting part 11 is a curved surface having a small radius.
[0014]
FIG. 3 shows another embodiment, which is an embodiment similar to FIG. 2 except that the arc surface 11 having a radius of 42 mm is used instead of the inclined surface a in FIG.
[0015]
FIG. 4 shows the bottom surface 14 of the container of FIG. 2, where the a inclined surface and the b inclined surface 10 are joined at an intersection 13.
[0016]
FIG. 5 is a comparative example and shows a bottom surface composed of an arc surface and a b inclined surface. FIG. 6 is a comparative example showing a bottom surface made of an arc surface.
Next, performance comparison tests with specific examples of containers and comparative examples are shown.
[0017]
Example 1
Biaxial stretch blow molding was performed using a PET preform having a diameter of 22 mm and a length of 105 mm, which was injection-molded using PET, to produce a container having an internal volume of 500 ml shown in FIGS. 1, 2, and 4.
The angle of the inclined surface a was 20 degrees, and the inclined surface b was 60 degrees. Both slopes are joined at a distance of 48 mm from the central axis. The width of the valley bottom is 4 mm.
[0018]
Example 2
The angle of the arc surface spreading upward from the periphery of the bottom center portion and the b inclined surface narrowed down from the lower end of the trunk is 60 degrees, and the position of the intersection with the arc surface is at a position of 50 mm in the radial direction and 11 mm in the height direction. The radius of the surface was 42 mm. The width of the valley bottom is 4 mm.
[0019]
Example 3
Biaxial stretch blow molding was performed using a PET preform having a diameter of 22 mm and a length of 105 mm, which was injection-molded using PET, to produce a container having an internal volume of 500 ml as shown in FIGS.
The angle of the arc surface spreading upward from the periphery of the bottom center portion and the b inclined surface narrowed down from the lower end of the trunk is 60 degrees, and the position of the intersection with the arc surface is 48 mm in the radial direction and 10 mm in the height direction. The radius of the surface was 46 mm. The width of the valley bottom is 4 mm.
[0020]
Comparative Example 1
In the container having the bottom surface shown in FIG. 5, the angle between the arc surface having a radius of 25 mm that spreads upward from the periphery of the bottom center portion and the b inclined surface that is in contact with the arc surface and is inclined upward to the lower end of the trunk was 60 degrees. . The width of the valley bottom is 4 mm. The origin of the arc surface is on the leg side from the center line in the container height direction.
[0021]
Comparative Example 2
6 is a container having a bottom surface shown in FIG. 6, wherein an a arc surface extending upward from the peripheral edge of the bottom center portion and a b arc surface that is in contact with the arc surface and gently joins to the lower end of the trunk, are elliptical as a whole. The radius of each arc surface of the valley bottom is a arc surface 42 mm b arc surface 22 mm. The width of the valley bottom is 4 mm. In this example, there is no b inclined surface.
[Evaluation methods]
In each case, 100 pieces were filled with 4 GV of carbonated water, and the amount of occurrence of stress cracking at 37 ° C. and 1 WEEK bottom change and 0.2% alkali immersion was examined. The results are shown in Tables 1 and 2.
4GV-37 ° C 1WEEK bottom change [0022]
[Table 1]

[0023]
(Ii) Comparative Examples 1 and 2 were rocker bottoms.
Number of stress cracking occurrences [0024]
[Table 2]

[0025]
From this test result, it is understood that the container of the present invention is excellent in stress cragging resistance and deformation resistance.
[0026]
【The invention's effect】
Even if the present invention is a small-capacity container, the leg shape is good, the heat and pressure resistance is excellent, the ESC resistance is good, and the self-standing stability is excellent.
[Brief description of the drawings]
FIG. 1 is a front view of a self-supporting container.
FIG. 2 is a sectional view in the height direction of the bottom of the container according to the embodiment of the present invention.
FIG. 3 is a cross-sectional view in the height direction of the bottom of another embodiment.
FIG. 4 is an explanatory diagram of a bottom portion.
FIG. 5 is an explanatory diagram of a bottom portion of a comparative example.
FIG. 6 is an explanatory view of the bottom of another comparative example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Container 2 trunk | drum 3 bottom part 4 leg part 5 grounding part 6 leg part side wall 7 connection part 8 bottom center part 9 a inclined surface 10 b inclined surface 11 arc surface 12 container center axis 13 intersection 14 bottom surface

Claims

It is a self-supporting container having a divided bottom part equally divided by a valley bottom,
A. Dividing the bottom surface of the biaxially-stretched pressure vessel equally with an equal central angle, a valley bottom portion that is inclined upward from the center of the bottom toward the outside, and a valley portion that includes leg side walls that sandwich the valley bottom surface;
B. It consists of a leg side wall, a leg top surface equally divided by a valley at an equal central angle and extended from the periphery of the bottom center part, and a leg outer wall formed by a trunk lower end defined by the valley. A square trapezoidal leg,
C. A grounding portion composed of an outer circumferential portion of a plurality of leg top surfaces;
Is a biaxially stretched freestanding container consisting of
The bottom of the valley
a. An inclined surface having a flat surface and an angle of 15 degrees to 25 degrees with a horizontal plane, which is inclined upward from the bottom center portion toward the joint portion of the bottom portion and the trunk portion;
b. An inclined surface having a flat surface and an angle of 45 degrees to 70 degrees with the horizontal plane,
Formed by intersecting at a position of 50% to 75% of the radius of the container in the radial direction from the central axis in the height direction of the container and at a position of 8% to 20% of the trunk diameter in the height direction from the ground surface. The bottom
A self-supporting container biaxially stretch-molded having a divided bottom surface portion.

It is a self-supporting container having a divided bottom part equally divided by a valley bottom,
A. Dividing the bottom surface of the biaxially-stretched pressure vessel equally with an equal central angle, a valley bottom portion that rises and slopes outward from the bottom center portion, and a leg portion sidewall that sandwiches the valley bottom surface;
B. It consists of a leg side wall, a leg top surface extended from the periphery of the bottom center part equally divided by an equal central angle by a valley part, and a leg outer wall formed by a trunk lower end part defined by the valley part. A square trapezoidal leg,
C. A grounding portion composed of an outer circumferential portion of a plurality of leg top surfaces;
Is a biaxially stretched freestanding container consisting of
The bottom of the valley
a. An arc surface having an origin on the opposite side of the leg with respect to the central axis in the height direction of the container and extending upward from the periphery of the center of the bottom and having a radius of 50% to 300% of the diameter of the body of the container; b . An inclined surface that forms an angle of 45 degrees to 70 degrees with the horizontal plane,
It is a bottom surface formed by intersecting at a position of 50% to 75% of the radius of the container body in the radial direction from the central axis and at a position of 8% to 20% of the body diameter in the height direction from the ground plane. A self-supporting container biaxially stretch-molded having a divided bottom surface portion.

The arc surface is a. The self-supporting container biaxially stretch-molded according to claim 2, wherein the self-supporting container has an origin on a central axis in the height direction of the container and is an arc surface having a radius of 50 to 300% of the diameter of the body of the container.

The diameter of the circular arc connecting the ground contact portion formed by the outer circumferential portion of the top surface of the leg portion is 0.65 to 0.85 times the diameter of the lower end portion of the trunk, and is described in any one of claims 1 to 3. Biaxially stretched free-standing container.

The intersection of the a inclined surface or the a arc surface and the b inclined surface is connected by a curved surface having a small radius of 5% to 30% of the diameter of the container body. The biaxially stretched self-supporting container described.

b. 6. A biaxially stretched self-supporting body according to any one of claims 1 to 5, wherein a curved connecting portion having a small diameter of 5 to 30% with respect to the body diameter is installed between the inclined surface and the lower end of the body. container.

The self-supporting container formed by biaxial stretching according to any one of claims 1 to 6, wherein the division of the bottom surface by the equal central angle is an odd number of equal parts.

The biaxially stretched self-supporting container according to any one of claims 1 to 7, wherein odd-numbered equal divisions of the bottom surface with equal central angles are 3 or 5 equal divisions.

The self-supporting container biaxially stretch-molded according to any one of claims 1 to 8, wherein the bottom center portion is thermally crystallized.

The self-supporting container biaxially stretch-molded according to any one of claims 1 to 9, wherein the container is a small-capacity container having a capacity of 200 to 1000 ml.