JP6032320B2 - PREFORM, PREFORM MOLD, AND METHOD FOR PRODUCING SYNTHETIC RESIN CONTAINER - Google Patents
PREFORM, PREFORM MOLD, AND METHOD FOR PRODUCING SYNTHETIC RESIN CONTAINER Download PDFInfo
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Description
本発明は、ペットボトルなどの、二軸延伸ブロー成形により成形される合成樹脂製容器の底部軽量化を可能にするプリフォーム、及び、そのプリフォームを成形するプリフォーム成形金型、並びに、このプリフォームを延伸ロッドにより延伸しながらブロー成形する合成樹脂製容器の製造方法に関し、特に、これらを可能にするプリフォーム底部の形状に関する。 The present invention relates to a preform capable of reducing the weight of the bottom of a synthetic resin container formed by biaxial stretch blow molding, such as a PET bottle, a preform molding die for molding the preform, and this The present invention relates to a method for manufacturing a synthetic resin container in which a preform is blow-molded while being stretched by a stretching rod, and particularly relates to a shape of a preform bottom that enables these.
ポリエチレンテレフタレートなどの合成樹脂を二軸延伸ブロー成形などによってボトル状に成形してなるペットボトルなどの合成樹脂製容器が、各種飲料品を内容物とする飲料用容器として普及、浸透している。このような合成樹脂製容器の多くは、射出成形や圧縮成形などによって成形された有底筒状前成形体のプリフォームを加熱、軟化させた状態でブロー成形金型内にセットし、次いで、延伸ロッドを用いて縦方向に延伸しながら高圧のブローエアーによって横方向にも延伸することにより、所定の容器形状にブロー成形される。下記に示す特許文献１には、プリフォームをブロー成形する技術が開示されている。 Synthetic resin containers such as PET bottles formed by forming a synthetic resin such as polyethylene terephthalate into a bottle shape by biaxial stretch blow molding or the like have become widespread and penetrated as beverage containers containing various beverage products. Many of these synthetic resin containers are set in a blow mold in a state where the preform of the bottomed cylindrical preform formed by injection molding or compression molding is heated and softened, The film is blow-molded into a predetermined container shape by stretching in the transverse direction with high-pressure blow air while stretching in the longitudinal direction using a stretching rod. Patent Document 1 shown below discloses a technique for blow-molding a preform.
プリフォームの底部内面及び外面は、縦断面形状は円弧形状の球面部であるのが一般的である。しかし、底部内面及び外面が球面部であるプリフォームは、二軸延伸ブロー成形により底部中心およびその近傍が不要に厚肉の容器となりやすい。
そのため、下記の特許文献２に開示されているプリフォームでは、その底部外面が球面部である一方、内面については、プリフォームの胴部から底部の先端中心に至るまでの湾曲面を縦断面においては曲率半径の異なる２つの円弧である、曲面と球面部で結び、プリフォームの底部の肉厚を底部中心部側の球面部の肉厚が薄くなるように形成している。
Generally, the inner surface and the outer surface of the bottom portion of the preform are spherical portions having a circular cross-sectional shape. However, a preform whose inner surface and outer surface of the bottom portion are spherical portions is likely to be a thick-walled container with the center of the bottom portion and its vicinity unnecessary by biaxial stretch blow molding.
Therefore, in the preform disclosed in Patent Document 2 below, the bottom outer surface is a spherical portion, while the inner surface has a curved surface extending from the preform body portion to the tip center of the bottom portion in a longitudinal section. Are two arcs having different radii of curvature, which are connected by a curved surface and a spherical portion, and are formed so that the thickness of the bottom portion of the preform is thin at the spherical portion on the bottom center side.
二軸延伸ブロー成形の際、高圧ブローエアー供給より前に延伸ロッドの先端がプリフォームの底部に接触し、縦延伸を開始する。
特許文献２のプリフォームのように、内面を曲面と球面部で形成してプリフォームの底部中心およびその近傍の肉厚を薄くすると、延伸ロッド当接部分の肉厚が十分確保しにくい。延伸ロッド当接部分の肉厚が十分確保されないと、二軸延伸ブロー成形する合成樹脂製容器の肉厚調整や耐熱性向上のため、プリフォーム加熱時にプリフォーム底部の温度をより高く設定した際、延伸ロッドでプリフォームの延伸時に過延伸が起こりやすくなり、過延伸白化や、極度の薄肉化による容器の耐熱性不良が起こるおそれがある。さらには、延伸ロッドによるプリフォーム底部突き抜け（突き破り）が生じるおそれがある。底部突き抜けは歩留りを低下させる。また、底部中心から胴部にかけての肉厚を好適に増加させにくく、射出成形機によってプリフォームを形成する際、溶融樹脂が成形孔（キャビティ）を通りにくくなり、溶融樹脂が成形孔全体に行き渡らず、ショートショットが生じる。
本願発明は、このような事情に鑑みてなされたもので、プリフォームの底部中心およびその近傍の肉厚を薄くしても、射出成形性、圧縮成形性に優れ、また、延伸ロッドによるプリフォーム底部延伸成形性が良好なプリフォーム及びプリフォームの成形金型、並びに、合成樹脂製容器の製造方法を提供することを目的とする。
At the time of biaxial stretch blow molding, the tip of the stretch rod comes into contact with the bottom of the preform before the high pressure blow air supply, and longitudinal stretching is started.
As in the preform of Patent Document 2, if the inner surface is formed of a curved surface and a spherical surface portion and the thickness of the bottom center of the preform and the vicinity thereof are reduced, it is difficult to ensure a sufficient thickness at the stretch rod contact portion. If the thickness of the stretch rod contact part is not sufficiently secured, the temperature at the bottom of the preform is set higher when heating the preform in order to adjust the thickness of the synthetic resin container to be biaxially stretch blow molded and to improve heat resistance. When the preform is stretched with the stretching rod, overstretching tends to occur, and there is a possibility that overstretching whitening or poor heat resistance of the container due to extreme thinning may occur. Furthermore, there is a risk that preform bottom portion penetration (breakthrough) may occur due to the stretching rod. Bottom penetration will reduce yield. Also, it is difficult to suitably increase the thickness from the center of the bottom to the body, and when forming a preform by an injection molding machine, the molten resin does not easily pass through the molding hole (cavity), and the molten resin spreads over the entire molding hole. Short shot occurs.
The present invention has been made in view of such circumstances, and is excellent in injection moldability and compression moldability even when the thickness of the center of the bottom of the preform and the vicinity thereof is reduced. It is an object of the present invention to provide a preform having a good bottom stretch moldability, a molding die for the preform, and a method for producing a synthetic resin container.
前記目的を達成するために、本発明のプリフォームは、開口部を有する口頸部と、該口頸部に連続する筒状の胴部と、該胴部を閉塞する底部とを有するプリフォームにおいて、前記プリフォームの底部肉厚は、胴部側から底部中心部に向かって漸次薄くなるよう形成され、前記底部の内面は、前記プリフォームの中心軸を含む縦断面上で該中心軸上に長軸を有する楕円弧形状であり、前記底部の外面が、球面部で形成されるか、又は前記底部の外面が、前記プリフォームの中心軸を含む縦断面上で該中心軸上に長軸を有する楕円弧形状であり、前記底部の外面が、球面部で形成され、前記底部の外面が球面部で形成され、底部内面は前記球面部と中心が一致し、前記プリフォームの中心軸上に長軸を備え長球面部で形成され、前記プリフォームの胴部肉厚Ｔが２．００〜５．００ｍｍ、前記底部の外面における、球面部の半径Ｒが７．５０〜１７．００ｍｍであって、前記底部の内面における、長球面部の短半径ａがＲ−Ｔであるときに、前記長球面部の長半径ｂが、
（Ｒ＋１９ａ）／２０≦ｂ≦（７Ｒ＋１３ａ）／２０の範囲にある。
また、前記目的を達成するために、本発明のプリフォームの成形金型は、雄型と、雌型とを備えたプリフォーム成形金型において、前記雄型と前記雌型の型閉時に、雄型先端部と雌型の底部面との間で形成される隙間が底部中心部に向かって漸次狭くなるよう形成され、前記プリフォームの底部内面を形成する前記雄型先端部が前記雄型中心軸を含む縦断面上で該中心軸上に長軸を備える楕円弧形状であり、前記雌型の底部面は、球面部で形成されるか、又は前記雌型の底部面は、前記雌型の中心軸を含む縦断面上で該中心軸上に長軸を有する楕円弧形状であり、前記雌型の底部面は、球面部で形成され、前記雌型の底部面が球面部で形成され、前記雄型の先端部は前記雄型中心軸上に長軸を備える長球面部で形成され、前記雄型と雌型を型閉時に、前記球面部中心と長球面部の中心は一致し、前記プリフォームの胴部を形成する成形金型の隙間Ｔが２．００〜５．００ｍｍ、前記雌型の底部面における、球面部の半径Ｒが７．５０〜１７．００ｍｍであって、前記雄型先端部における、長球面部の短半径ａがＲ−Ｔであるときに、前記長球面部の長半径ｂが、
（Ｒ＋１９ａ）／２０≦ｂ≦（７Ｒ＋１３ａ）／２０の範囲にある。
また、前記目的を達成するために、本発明のプリフォームの合成樹脂製容器の製造方法は、前記プリフォームを延伸ロッドにより二軸延伸ブロー成形する合成樹脂製容器の製造方法において、前記プリフォームは、開口部を有する口頸部と、該口頸部に連続する筒状の胴部と、該胴部を閉塞する底部とを有し、底部肉厚は、胴部側から底部中心部に向かって漸次薄くなるよう形成され、底部の内面は、プリフォームの中心軸を含む縦断面上で中心軸上に長軸を有する楕円弧形状であり、前記延伸ロッドは、プリフォーム底部中心部より厚肉の底部中心外部に最初に当接してプリフォームを延伸する。
In order to achieve the above object, a preform of the present invention is a preform having a mouth and neck having an opening, a cylindrical trunk that is continuous with the mouth and neck, and a bottom that closes the trunk. The bottom wall thickness of the preform is formed so as to gradually decrease from the body side toward the bottom center part, and the inner surface of the bottom part is on the center axis on a longitudinal section including the center axis of the preform. The outer surface of the bottom is formed as a spherical surface, or the outer surface of the bottom is a long axis on the longitudinal axis including the central axis of the preform. elliptic arc shape der with is, the outer surface of the bottom portion is formed by the spherical surface portion, the outer surface of the bottom portion is formed by the spherical surface portion, the inner bottom surface is the spherical surface portion and the center coincides, on the center axis of said preform Formed with a long spherical surface with a long axis, The barrel portion thickness T is 2.00 to 5.00 mm, the radius R of the spherical portion on the outer surface of the bottom portion is 7.50 to 17.00 mm, and the short radius of the major spherical portion on the inner surface of the bottom portion is When a is RT, the major radius b of the major spherical surface portion is
It is in the range of (R + 19a) / 20 ≦ b ≦ (7R + 13a) / 20 .
In order to achieve the above object, a preform mold of the present invention is a preform mold including a male mold and a female mold, and when the male mold and the female mold are closed, The gap formed between the male tip and the bottom surface of the female die is formed so as to gradually narrow toward the center of the bottom, and the male tip that forms the bottom inner surface of the preform is the male die. It is an elliptical arc shape having a long axis on the central axis on a longitudinal section including the central axis, and the bottom surface of the female mold is formed of a spherical surface, or the bottom surface of the female mold is the female mold elliptic arc shape der having a major axis on the central axis on the vertical plane containing the central axis of the is, the bottom surface of the female type, is formed by the spherical surface portion, the bottom surface of the female type is formed by the spherical surface portion The tip of the male mold is formed of an oblong spherical surface having a long axis on the male mold central axis, and the male mold and the female mold are molded. Sometimes, the center of the spherical surface portion coincides with the center of the long spherical surface portion, the gap T of the molding die forming the body of the preform is 2.00 to 5.00 mm, and the spherical surface portion on the bottom surface of the female die When the radius R is 7.50 to 17.00 mm, and the minor radius a of the major spherical surface portion at the male tip is RT, the major radius b of the major spherical portion is
It is in the range of (R + 19a) / 20 ≦ b ≦ (7R + 13a) / 20 .
In order to achieve the above object, a manufacturing method of a synthetic resin container preform of the present invention is a method of manufacturing a synthetic resin container of biaxially stretch blow molding by stretching rod the preform, the preform Has a mouth and neck part having an opening, a cylindrical trunk part continuous to the mouth and neck part, and a bottom part closing the trunk part, and the bottom thickness is from the trunk part side to the center part of the bottom part. The inner surface of the bottom is formed in an elliptical arc shape having a long axis on the central axis on the longitudinal section including the central axis of the preform, and the stretching rod is thicker than the central part of the preform bottom. The preform is stretched by first contacting the outside of the center of the meat.
本発明のプリフォームは、底部の内面がプリフォームの中心軸を含む縦断面上で中心軸上に長軸を有する楕円弧形状であり、前記底部の外面が、球面部で形成されるか、又は前記底部の外面が、前記プリフォームの中心軸を含む縦断面上で該中心軸上に長軸を有する楕円弧形状であるため、底部の中心寄りの箇所を薄肉にし、底部の胴部寄り箇所に向かって連続的に好適に厚肉化できるため、延伸ロッドによる延伸時に延伸ロッドが当接する底部の胴部寄り箇所は十分な肉厚が確保されるので、延伸ロッドによるプリフォームの延伸成形性を良好にし、かつ、底部が軽量化された合成樹脂製容器をブロー成形可能である。
また、本発明のプリフォームの成形金型は、プリフォームの底部内面を形成する雄型先端部が前記雄型中心軸を含む縦断面上で中心軸上に長軸を備える楕円弧形状であり、前記雌型の底部面は、球面部で形成されるか、又は前記雌型の底部面は、前記雌型の中心軸を含む縦断面上で該中心軸上に長軸を有する楕円弧形状であるため、底部の中心寄りの箇所を薄肉にし、底部の胴部寄り箇所に向かって連続的に好適に厚肉化できる成形金型のため、延伸ロッドによる延伸時に延伸ロッドが当接する底部の胴部寄り箇所は十分な肉厚が確保され、延伸ロッドによるプリフォームの延伸成形性を良好にし、かつ、底部が軽量化された合成樹脂製容器をブロー成形可能なプリフォームを成形できる。
また、本発明の合成樹脂製容器の製造方法は、プリフォーム底部の内面がプリフォームの中心軸を含む縦断面上で中心軸上に長軸を有する楕円弧形状であるため、底部の中心寄りの箇所を薄肉にし、底部の胴部寄り箇所に向かって連続的に好適に厚肉化でき、そして、延伸ロッドは、プリフォーム底部中心部より厚肉の底部中心外部に最初に当接してプリフォームを延伸するため、延伸ロッドによるプリフォームの延伸成形性を良好にし、かつ、底部が軽量化された合成樹脂製容器をブロー成形により製造可能である。
The preform of the present invention, or the inner surface of the bottom Ri elliptic shape der having a major axis on the center axis on the vertical plane containing the central axis of the preform, the outer surface of the bottom portion is formed by the spherical surface portion, Or, since the outer surface of the bottom is an elliptical arc shape having a long axis on the longitudinal axis on the longitudinal section including the central axis of the preform , the portion near the center of the bottom is thinned, and the portion near the trunk of the bottom As the thickness can be increased continuously and continuously, a sufficient thickness is secured at the bottom portion of the bottom where the stretching rod abuts when stretching with the stretching rod. It is possible to blow-mold a synthetic resin container having a good bottom and a lightweight bottom.
Further, the molding die of the preform of the present invention, Ri elliptic shape der the male tip forming the bottom inner surface of the preform comprises a long axis on the central axis on the vertical plane containing the male central axis The bottom surface of the female mold is formed as a spherical surface, or the bottom surface of the female mold is in an elliptical arc shape having a long axis on the central axis on a longitudinal section including the central axis of the female mold. some reason, the closer to the center point of the bottom to thin, because of the mold that can be continuously suitably thickening towards the body portion toward part of the bottom cylinder of the bottom stretch rod during stretching by the stretching rod is in contact A sufficient thickness can be secured at the portion near the portion, the preform can be stretch-molded with a stretch rod, and a preform capable of being blow-molded with a synthetic resin container having a lightweight bottom can be formed.
Further, in the method for producing a synthetic resin container according to the present invention, the inner surface of the preform bottom has an elliptical arc shape having a long axis on the central axis on the longitudinal section including the central axis of the preform. The part can be made thin and continuously thickened toward the bottom part near the body part, and the stretch rod first contacts the outside of the thick bottom part center from the preform bottom part. Therefore, it is possible to produce a synthetic resin container having improved preform moldability with a stretch rod and having a light weight bottom by blow molding.
以下、本発明の実施形態によるプリフォーム及びプリフォームの成形金型、並びに、合成樹脂製容器の製造方法について説明する。なお、プリフォームについては、符号や鎖線の見易さを重視し、断面を示すハッチングを省略している。
［プリフォームの形状］
図１は、本発明に係るプリフォームを示し、プリフォーム１はペットボトルなどの合成樹製容器が二軸延伸ブロー成形される前の形状であり、上部から下部に向かって、口頸部２、胴部３及び底部４を備えている。口頸部２には、容器に成形後、飲料などの充填口、及び、注出口となる開口部６、キャップの雌ネジが螺着される雄ネジ部７、該雄ネジ部７の下部に配置される円環状のネックリング８が形成されている。
Hereinafter, a preform, a molding die for the preform, and a method for manufacturing a synthetic resin container according to an embodiment of the present invention will be described. For the preform, emphasis is placed on the ease of seeing the reference numerals and chain lines, and hatching indicating the cross section is omitted.
[Preform shape]
FIG. 1 shows a preform according to the present invention. The preform 1 has a shape before a synthetic tree container such as a plastic bottle is biaxially stretch blow-molded. The body part 3 and the bottom part 4 are provided. The mouth-and-neck portion 2 is formed into a container and then filled with a beverage or the like, an opening 6 serving as a spout, a male screw portion 7 into which a female screw of a cap is screwed, and a lower portion of the male screw portion 7. An annular neck ring 8 to be arranged is formed.
胴部３は、ネックリング８よりも下部に設けられ、円筒形状である。本実施形態では、胴部３の上端側を除いて胴部３の肉厚をほぼ一定にしている。胴部３と底部４との境界域には、プリフォーム１の縦断面形状が直線から曲線に変化する接続部が設けられ、プリフォーム１の直線状縦断面の胴部３から湾曲状縦断面の底部４に変化する。接続部は、胴部３と底部４の内面側に位置する内接続部１０ｂと外面側に位置する外接続部１０ａとを有する。
プリフォーム１の底部４の形状は、外面が曲率半径Ｒの半球面部４ａで形成される。内面はプリフォーム１の中心軸Ｌ上に長軸を備える楕円の、長軸を回転軸とする回転楕円体である長球（長楕円体，扁長楕円体）の表面（回転楕円面）を、長軸に垂直な面で半裁した半長球面部４ｂ全体、または、その一部で形成される。半長球面部４ｂは、中心軸Ｌを含む縦断面上において、図１Ｂのように中心軸Ｌ上に長軸を有する楕円の一部である楕円弧形状となる。
The trunk portion 3 is provided below the neck ring 8 and has a cylindrical shape. In the present embodiment, the thickness of the body portion 3 is made substantially constant except for the upper end side of the body portion 3. In the boundary area between the body part 3 and the bottom part 4, a connecting part is provided in which the longitudinal cross-sectional shape of the preform 1 changes from a straight line to a curved line. Changes to the bottom 4 of. The connection portion includes an inner connection portion 10b located on the inner surface side of the trunk portion 3 and the bottom portion 4, and an outer connection portion 10a located on the outer surface side.
The shape of the bottom portion 4 of the preform 1 is formed by a hemispherical portion 4a having an outer surface with a radius of curvature R. The inner surface is a surface (spheroid ellipsoid) of an ellipse (long ellipsoid, oblate ellipsoid) which is an ellipse having a major axis on the central axis L of the preform 1 and whose major axis is the rotation axis. The half-spherical spherical surface portion 4b half cut by a plane perpendicular to the long axis is formed by the whole or a part thereof. On the longitudinal section including the central axis L, the semi-long spherical surface portion 4b has an elliptical arc shape that is a part of an ellipse having a long axis on the central axis L as shown in FIG. 1B.
図２のＡ〜Ｃは、プリフォーム１の底部４について、それぞれの半径が等しい半球面部４ａと、それぞれの長径，短径が等しい半長球面部４ｂ、または、その部分で構成され、半球面部４ａの中心Ｃ１と半長球面部４ｂの中心Ｃ２の位置を変更した３つの実施形態である。 2A to 2C, the bottom portion 4 of the preform 1 includes a hemispherical surface portion 4a having the same radius and a hemispherical surface portion 4b having the same major axis and minor axis, or a portion thereof. changing the position of the center C 2 of the center C 1 and Hancho spherical portion 4b of 4a is a three embodiments.
ここで、図２のＡを参照して、プリフォーム１の胴部３の肉厚ｔ１は、胴部３の外面３ａ上の肉厚測定点からの法線の、外面３ａから内面３ｂまでの長さである。
プリフォーム１の底部４の肉厚ｔ２は、底部４の外面（半球面部４ａ）上の肉厚測定点の法線Ｎの、外面（半球面部４ａ）から内面（半長球面部４ｂ）までの長さである。
図２のＡは、底部内面の半長球面部４ｂの中心Ｃ２と底部外面の半球面部４ａの中心Ｃ１を一致させた第１実施形態であり、この場合、胴部３と底部４との境界域としての外接続部１０ａと内接続部１０ｂの位置は同一高さ（同一平面）上にある。そして底部４の肉厚ｔ２は外接続部１０ａ、及び、内接続部１０ｂの高さ位置から中心軸Ｌが通る底部中心Ｏ側に向かって、漸減する。なお、プリフォーム１が後述の射出成形により成形される場合は、溶融樹脂を射出充填した際の跡であるゲート跡が底部中心Ｏに残っていてもよい。
Here, with reference to A of FIG. 2, the thickness t 1 of the barrel 3 of the preform 1, the normal line of the wall thickness measurement point on the outer surface 3a of the body portion 3, from the outer surface 3a to the inner surface 3b Is the length of
Thickness t 2 of the bottom portion 4 of the preform 1, the normal line N of thickness measuring points on the outer surface of the bottom 4 (hemisphere surface 4a), from the outer surface (hemispherical surface portion 4a) to the inner surface (semimajor spherical portion 4b) Is the length of
A of FIG. 2 is a first embodiment to match the center C 1 of the hemisphere surface 4a of the center C 2 and the bottom outer surface of the semimajor spherical portion 4b of the inner bottom surface, in this case, the body portion 3 and the bottom 4 The positions of the outer connecting portion 10a and the inner connecting portion 10b as the boundary area are on the same height (same plane). The thickness t 2 of the bottom 4 is the outer connecting portion 10a, and, towards the bottom center O side through which the central axis L from the height position of the inner connection portion 10b, gradually decreases. When the preform 1 is molded by injection molding described later, a gate mark that is a mark when the molten resin is injected and filled may remain in the bottom center O.
図２のＢは、半球面部４ａの中心Ｃ１よりも半長球面部４ｂの中心Ｃ２が上に位置する第２実施形態であり、外接続部１０ａが内接続部１０ｂよりも低い位置にある。第２実施形態では、外接続部１０ａの高さ位置から底部中心Ｏ側を底部４とする。底部４の内面は、半長球面部４ｂを、半球面部４ａの中心Ｃ１を通り中心軸Ｌに垂直な平面で切断したときの底部中心Ｏ側の長球面の部分とする。このとき、底部４の肉厚は漸減するが、図２のＡに示す第１実施形態よりも漸減の変化は小さく、底部４は厚肉傾向になる。
図２のＣは、半球面部４ａの中心Ｃ１よりも半長球面部４ｂの中心Ｃ２が下に位置する第３実施形態であり、外接続部１０ａが内接続部１０ｂよりも高い位置にある。第３実施形態も第２実施形態同様、外接続部１０ａの高さ位置から底部中心Ｏ側を底部４とする。ことのき、底部４の肉厚は漸減するが、図２のＡに示す第１実施形態よりも、漸減の変化は大きくなり、底部４をより薄くできる。
Of B 2, from the center C 1 of the hemisphere surface portion 4a is a second embodiment where the center C 2 of the semimajor spherical portion 4b is located at the top, at a position lower than the inner connection portion 10b outer connecting portion 10a is there. In the second embodiment, the bottom portion center O side from the height position of the external connection portion 10a is the bottom portion 4. The inner surface of the bottom portion 4 is a hemispherical portion 4b that is a portion of an oblong surface on the bottom portion center O side when the hemispherical portion 4b is cut by a plane that passes through the center C1 of the hemispherical portion 4a and is perpendicular to the central axis L. At this time, the thickness of the bottom portion 4 gradually decreases, but the change of the gradual decrease is smaller than that of the first embodiment shown in FIG. 2A, and the bottom portion 4 tends to be thick.
C of Figure 2, from the center C 1 of the hemisphere face 4a a third embodiment in which the center C 2 of the semimajor spherical portion 4b is located below, at a position higher than the inner connection portion 10b outer connecting portion 10a is there. Similarly to the second embodiment, the third embodiment uses the bottom center O side from the height position of the outer connection portion 10a as the bottom portion 4. At that time, the thickness of the bottom portion 4 gradually decreases, but the change of the gradual decrease becomes larger than in the first embodiment shown in FIG. 2A, and the bottom portion 4 can be made thinner.
このように、外接続部１０ａと内接続部１０ｂの高さが一致したり、上下にずれて位置したりするが、いずれの場合でも本願発明は実施が可能である。
こうして、本願発明は、内接続部１０ｂから底部中心Ｏ側、及び外接続部１０ａから底部中心Ｏ側にわたってなだらかに連続したそれぞれ１つの曲面で結ぶことができる。したがって、異なる曲率半径を有する複数の円弧面同士によって内面または外面を形成した形状よりも曲率変化が滑らかな曲面が得られる。
As described above, the heights of the outer connection portion 10a and the inner connection portion 10b coincide with each other or are displaced from each other up and down, but the present invention can be implemented in any case.
In this manner, the present invention can be connected by one continuous curved surface from the inner connecting portion 10b to the bottom center O side and from the outer connecting portion 10a to the bottom center O side. Therefore, a curved surface having a smoother curvature change than a shape in which an inner surface or an outer surface is formed by a plurality of circular arc surfaces having different radii of curvature can be obtained.
［プリフォームの成形金型］
次に、プリフォーム１を成形するための金型について説明する。
図３はプリフォーム１の射出成形金型を示す。図に示すように、成形金型１１は雄型１２と、雌型本体１８及び割型１４からなる雌型１３で構成され、通常、プリフォーム１を横に寝かせた形状の成形孔１９が形成されている。
[Preform Mold]
Next, a mold for forming the preform 1 will be described.
FIG. 3 shows an injection mold for the preform 1. As shown in the figure, the molding die 11 is composed of a male die 12 and a female die 13 composed of a female die body 18 and a split die 14, and usually a molding hole 19 having a shape in which the preform 1 is laid sideways is formed. Has been.
雄型１２は、図示しない型開閉手段によって、左右に移動が可能であり、左部に基部１５が設けられ、基部１５の右部中央から右方に延びる略円柱形状のコア本体１６が設けられている。このコア本体１６の外面は、プリフォーム１の口部天面及び内面を形成する。そして、コア本体１６がプリフォーム１の口頸部２（図１Ａ参照）の内面を形成するコア口頸部１６ａとコア胴部１６ｂの間にはコア傾斜部１７が形成され、コア傾斜部１７よりも右側は、先端のプリフォーム底部との境界に至るまでのコア胴部１６ｂがほぼ同径に形成されている。コア本体１６の先端部１６ｃは、コア本体１６の中心軸上に長軸を備える楕円の、長軸を回転軸とする回転楕円体である長球の表面を長軸に垂直な面で半裁した半長球面部全体、またはその部分によって形成されている。このコア本体１６の先端部１６ｃは、プリフォーム１の底部内面を形成する部分である。コア本体１６の先端部１６ｃは、コアの中心軸を含む縦断面上において、図３Ｂのように中心軸上に長軸を有する楕円の一部である楕円弧形状となる。 The male mold 12 can be moved left and right by a mold opening / closing means (not shown), a base 15 is provided on the left, and a substantially cylindrical core body 16 extending rightward from the center of the right of the base 15 is provided. ing. The outer surface of the core body 16 forms the mouth top surface and the inner surface of the preform 1. A core inclined part 17 is formed between the core neck part 16a and the core body part 16b in which the core body 16 forms the inner surface of the mouth neck part 2 (see FIG. 1A) of the preform 1, and the core inclined part 17 is formed. On the right side, the core body portion 16b is formed with substantially the same diameter up to the boundary with the preform bottom at the tip. The tip 16c of the core body 16 has an ellipse having a major axis on the central axis of the core body 16, and the surface of a long sphere, which is a spheroid having the major axis as a rotation axis, is half-cut with a plane perpendicular to the major axis It is formed by the whole semi-long spherical surface part or its part. The front end portion 16 c of the core body 16 is a portion that forms the bottom inner surface of the preform 1. The tip 16c of the core body 16 has an elliptical arc shape that is a part of an ellipse having a long axis on the central axis as shown in FIG. 3B on a longitudinal section including the central axis of the core.
雄型１２の基部１５の右側には、プリフォーム１の口頸部２と胴部３の外面の一部を形成する割型１４が配設されている。割型１４は一対の分割金型からなり、各々がコア本体１６に対してほぼ対称の半円環であり、左右および上下に移動可能に構成されている（図３ＡおよびＢ参照）。割型１４の両者が合わせられ一体となった際、割型１４の中央に貫通孔が形成され、雄型１２の基部１５と割型１４を合わせて一体にしたとき、プリフォーム１の口頸部２と胴部３の一部を形成する成形孔１９の一部、および、プリフォーム１の胴部内面３ｂと底部内面４ｂを形成する。 On the right side of the base portion 15 of the male mold 12, a split mold 14 that forms part of the outer surface of the mouth neck portion 2 and the trunk portion 3 of the preform 1 is disposed. The split mold 14 includes a pair of split molds, each of which is a semicircular ring that is substantially symmetrical with respect to the core body 16, and is configured to be movable left and right and up and down (see FIGS. 3A and B). When both of the split molds 14 are combined and integrated, a through hole is formed in the center of the split mold 14, and when the base 15 of the male mold 12 and the split mold 14 are combined and integrated, the mouth and neck of the preform 1 A part of the molding hole 19 that forms part of the part 2 and the body part 3, and the body part inner surface 3 b and the bottom part inner surface 4 b of the preform 1 are formed.
雌型本体１８は、左方に開口する凹部２１が形成されている。凹部２１は底部を除いてほぼ同一径の孔で形成され、プリフォーム１の胴部外面３ａの大半の部分を形成する。凹部２１の底部面２２は半球面が形成され、プリフォーム１の底部外面を形成する。そして、成形金型１１は、閉じ状態にて雄型１２および雌型本体１８、割型１４が組み合わせられ、コア本体１６が割型１４の貫通孔と凹部２１に挿入されると、プリフォーム１と同じ形状の成形孔（キャビティ）１９（図３のＡ）が形成される。
雌型本体１８の底部面２２の中心部には、合成樹脂を混練・溶融・射出する図示しない射出成形機に連通し、溶融樹脂を成形孔１９に供給するための孔径φ１〜φ４ｍｍの射出孔（ゲート）２３が形成されている。プリフォーム１（容器）を構成する合成樹脂は、熱可塑性樹脂であれば任意のものを使用することができ、例えばポリエチレンテレフタレートが使用される。
The female mold body 18 has a recess 21 that opens to the left. The recess 21 is formed with a hole having substantially the same diameter except for the bottom, and forms most of the outer surface 3a of the body portion of the preform 1. The bottom surface 22 of the recess 21 is formed as a hemispherical surface and forms the bottom outer surface of the preform 1. When the molding die 11 is closed, the male die 12, the female die body 18, and the split die 14 are combined, and the core body 16 is inserted into the through hole and the recess 21 of the split die 14. A molding hole (cavity) 19 (A in FIG. 3) having the same shape as that of FIG.
An injection hole having a hole diameter of φ1 to φ4 mm for communicating with an injection molding machine (not shown) for kneading, melting, and injecting synthetic resin and supplying the molten resin to the molding hole 19 is provided at the center of the bottom surface 22 of the female mold body 18. A (gate) 23 is formed. As the synthetic resin constituting the preform 1 (container), any thermoplastic resin can be used. For example, polyethylene terephthalate is used.
このように、本実施形態では、プリフォーム１の底部内面を形成するコア本体１６の先端部１６ｃは、長軸がコア本体１６の中心軸上にある半長球形状であり、雌型本体１８の底部面２２は半球面形状を有することによって、底部外面が半球面部４ａで底部内面が半長球面部４ｂのプリフォーム１が、射出成形によって形成される。
射出成形時、溶融樹脂は図示しない射出成形機から射出孔２３を介して、雌型本体１８の底部から射出される。溶融樹脂は射出孔２３からキャビティ底部の曲面に沿って放射方向へ広がり、プリフォーム１の底部４に対応する位置から、先端部側の胴部３、口頸部２にわたって成形孔１９の全体に充填される。
このとき、成形孔１９の底部では、コア本体１６の先端部１６ｃが、長軸をコア本体１６の中心軸上に備える長球面形状であるため、溶融樹脂が長球面に接触して通ると、射出孔２３から胴部に至るまで隙間が、漸次広くなり、溶融樹脂の抵抗を少なくして底部から前方の胴部側を通り抜けることができる。
Thus, in the present embodiment, the tip end portion 16c of the core body 16 that forms the bottom inner surface of the preform 1 has a hemispherical shape in which the long axis is on the central axis of the core body 16, and the female main body 18 Since the bottom surface 22 has a hemispherical shape, a preform 1 having a hemispherical surface portion 4a at the bottom outer surface and a semi-long spherical surface portion 4b at the bottom inner surface is formed by injection molding.
At the time of injection molding, the molten resin is injected from the bottom of the female mold body 18 through an injection hole 23 from an injection molding machine (not shown). The molten resin spreads radially from the injection hole 23 along the curved surface at the bottom of the cavity, and extends from the position corresponding to the bottom 4 of the preform 1 to the entire molding hole 19 from the body 3 on the tip side to the neck 2. Filled.
At this time, since the tip 16c of the core body 16 has a long spherical shape with the long axis on the central axis of the core main body 16 at the bottom of the molding hole 19, when the molten resin passes through the long spherical surface, A gap gradually increases from the injection hole 23 to the body part, and the resistance of the molten resin can be reduced to pass through the body part on the front side from the bottom part.
［ブロー成形］
次に、プリフォーム１の二軸延伸ブロー成形について説明する。
図４のＡに示すように、胴部３および底部４の温度が合成樹脂の軟化温度に調整されたプリフォーム１は、ブロー成形金型３０の成形孔（キャビティ）３２内にセットされ、内部には、外径がφ９〜φ１４ｍｍの棒状で昇降可能な延伸ロッド３１が挿入される。そして、延伸ロッド３１が下降すると、図５の拡大図に示すように、プリフォーム１の底部内面の半長球面部４ｂに接触する。その後、図４のＢに示すように、延伸ロッド３１をさらに下降させてプリフォーム１のブロー成形部（胴部３、底部４）を延伸させる過程でプリフォーム１内に加圧空気等の流体が導入される。そして、プリフォーム１が延伸ブロー成形され、成形孔３２に対応する形状の合成樹脂製容器が形成される。
[Blow molding]
Next, biaxial stretch blow molding of the preform 1 will be described.
As shown in FIG. 4A, the preform 1 in which the temperature of the body portion 3 and the bottom portion 4 is adjusted to the softening temperature of the synthetic resin is set in the molding hole (cavity) 32 of the blow molding die 30, and the inside Is inserted into a rod 31 having an outer diameter of φ9 to φ14 mm that can be raised and lowered. Then, when the stretching rod 31 is lowered, as shown in the enlarged view of FIG. 5, it comes into contact with the semi-long spherical surface portion 4 b on the bottom inner surface of the preform 1. Thereafter, as shown in FIG. 4B, in the process of further lowering the stretching rod 31 and stretching the blow-molded portion (body portion 3 and bottom portion 4) of the preform 1, fluid such as pressurized air in the preform 1 Is introduced. The preform 1 is stretch blow molded to form a synthetic resin container having a shape corresponding to the molding hole 32.
この二軸延伸ブロー成形時において、延伸ロッド３１がプリフォーム１の底部内面に接触するときに、内面が球面形状（半球面部４ａ）の場合と長球形状（長球面部４ｂ）との相違について、以下説明する。
図１のＢ及び図５を参照にして、プリフォーム１の底部４は、上述したように、外面側半球面部４ａが半径Ｒ，内面側半長球面部４ｂは、回転体の元となる楕円の短軸を楕円中心で分けた短半径がａ、長軸を楕円中心で分けた長半径がｂとして形成されている。図５に示す二点鎖線は、内面側半長球面部４ｂの短径の１／２であるａと同じ長さを半径とする円弧面４ｃであり、底部先端の肉厚を一致させている。プリフォーム１の内部に記載されているものは、ブロー成形に用いられる延伸ロッド３１である。
In this biaxial stretch blow molding, when the stretching rod 31 comes into contact with the inner surface of the bottom of the preform 1, the difference between the inner surface having a spherical shape (semispherical surface portion 4a) and the long spherical shape (long spherical surface portion 4b). This will be described below.
Referring to FIGS. 1B and 5, the bottom portion 4 of the preform 1 has an outer surface side semispherical surface portion 4 a having a radius R and an inner surface side semispherical surface portion 4 b is an ellipse from which the rotating body is based. The short radius of the short axis divided by the center of the ellipse is a, and the long radius of the long axis divided by the center of the ellipse is b. The two-dot chain line shown in FIG. 5 is an arcuate surface 4c having the same length as a which is ½ of the short diameter of the inner surface side semi-long spherical surface portion 4b, and the thickness of the bottom end is matched. . What is described inside the preform 1 is a stretch rod 31 used for blow molding.
図５に示すように、半球面部４ｃ及び半長球面部４ｂにおいて、底部先端の肉厚を一致させた場合、二点鎖線で示す半球面部４ｃよりも実線で示す半長球面部４ｂで内面を形成した方が、底部中心を除く全ての底部で肉厚が厚い。よって、延伸ロッド３１がプリフォーム１の底部４に接触する場合は、延伸ロッド３１と半球面部４ｃとの接触部の肉厚よりも、延伸ロッド３１と半長球面部４ｂとの接触部の肉厚の方が、底部の中心を除いて全ての部分で厚くなる。 As shown in FIG. 5, in the hemispherical surface portion 4c and the semispherical spherical surface portion 4b, when the thicknesses of the bottom end portions are matched, the inner surface of the hemispherical surface portion 4b indicated by a solid line is more than the hemispherical surface portion 4c indicated by a two-dot chain line. When formed, all the bottoms except the bottom center are thicker. Therefore, when the stretching rod 31 comes into contact with the bottom 4 of the preform 1, the thickness of the contact portion between the stretching rod 31 and the hemispherical surface portion 4b is larger than the thickness of the contact portion between the stretching rod 31 and the hemispherical surface portion 4c. The thickness is thicker in all parts except the center of the bottom.
具体的には、図５および図６のグラフを参照して説明する。まず、プリフォームの底部外面を半球面部４ａ（半径Ｒ＝１０．７０ｍｍ）とする。そして、底部内面を、中心を外面の半球面部４ａの中心と一致させた半長球面部４ｂの場合と、（短半径ａ＝７．３５ｍｍ，長半径ｂ＝８．１５ｍｍ）、底部内面を、半径ｒ＝７．３５ｍｍで、底部中心Ｏでの肉厚が、内面が半長球面部４ｂに等しくなるよう配置した半球面部４ｃの場合、さらに、底部内面を、半径ｒ＝７．３５ｍｍで、底部中心Ｏでの肉厚が、内面が半長球面部４ｂや半球面部４ｃの場合よりも０．３０ｍｍ厚肉となるよう中心を上側に配置した半球面部４ｃ’の場合のうち、半長球面部４ｂ、および、半球面部４ｃを図５に示す。そして、半長球面部４ｂ、半球面部４ｃ，４ｃ’について、プリフォーム首下距離（ネックリング８の下からの距離）を縦軸にとり、プリフォーム首下から底部４までの肉厚を横軸にとったグラフを図６Ａに示す。図６Ｂは胴部３下方（ネックリング下から６０ｍｍの位置）から底部４までの肉厚を示す、図６Ａの縦軸について拡大した図である。 Specifically, this will be described with reference to the graphs of FIGS. First, the outer surface of the bottom portion of the preform is a hemispherical portion 4a (radius R = 10.70 mm). And, in the case of the semi-long spherical surface portion 4b whose center coincides with the center of the semi-spherical surface portion 4a of the outer surface (short radius a = 7.35 mm, long radius b = 8.15 mm), the bottom inner surface is In the case of the hemispherical surface portion 4c in which the radius r = 7.35 mm and the thickness at the bottom center O is arranged so that the inner surface is equal to the semi-ellipsoidal spherical surface portion 4b, the bottom inner surface is further configured with the radius r = 7.35 mm. Among the cases of the hemispherical surface portion 4c ′ in which the center is arranged on the upper side so that the wall thickness at the bottom center O is 0.30 mm thicker than that of the semispherical surface portion 4b or the semispherical surface portion 4c, the hemispherical surface The part 4b and the hemispherical part 4c are shown in FIG. And, for the semi-spherical spherical surface portion 4b and the semi-spherical surface portions 4c, 4c ′, the preform neck distance (distance from the bottom of the neck ring 8) is taken on the vertical axis, and the wall thickness from the preform neck bottom to the bottom part 4 is plotted on the horizontal axis. The graph taken is shown in FIG. 6A. FIG. 6B is an enlarged view of the vertical axis of FIG. 6A, showing the thickness from the bottom of the trunk 3 (position 60 mm below the neck ring) to the bottom 4.
二点鎖線で示すのは底部内面が半球面部４ｃの場合の底部中心までの肉厚である。破線で示すものは、首下から胴部３までは半球面部４ｃの場合とほとんど同じで、底部４について底部内面が半球面部４ｃ’の場合の底部中心までの肉厚である。実線で示すのは半長球面部４ｂの場合の底部中心までの肉厚である。
図に示すように、プリフォーム１の首下から１０ｍｍまで肉厚が徐々に厚くなり、その後一定の肉厚を維持し、首下約７０ｍｍから外周面が曲面の底部４で形成され徐々に薄肉になっている。図６Ｂに示すように、このプリフォーム１の底部４について、内面が半球面部４ｃの場合、および、半球面部４ｃ’の場合、底部肉厚は、首下距離にほぼ比例して、漸次減少し薄くなっている。
What is indicated by a two-dot chain line is the thickness up to the center of the bottom when the inner surface of the bottom is the hemispherical portion 4c. What is indicated by a broken line is almost the same as in the case of the hemispherical part 4c from the lower neck to the body part 3, and the thickness of the bottom part 4 to the center of the bottom part when the bottom inner surface is the hemispherical part 4c ′. The solid line shows the thickness up to the center of the bottom in the case of the semi-long spherical surface portion 4b.
As shown in the figure, the thickness of the preform 1 gradually increases from the bottom of the neck to 10 mm, and then maintains a constant thickness, and the outer peripheral surface is formed from the curved bottom 4 from about 70 mm below the neck. It has become. As shown in FIG. 6B, regarding the bottom portion 4 of the preform 1, when the inner surface is the hemispherical portion 4c and when the inner surface is the hemispherical portion 4c ′, the bottom thickness gradually decreases in proportion to the neck distance. It is getting thinner.
これに対して半長球面部４ｂでは、底部４の肉厚の減少が最初は少なく、半球面部４ｃ’よりも厚肉である。その後、肉厚はなだらかな曲線を描いて変化し、徐々に底部中心に向かって大きく減少して、最後に底部中心で半球面部４ｃと同じ肉厚（ｔ＝２．５５ｍｍ）となっている。
すなわち、延伸ロッド３１が底部４を延伸する際に、延伸ロッド３１が当接する底部中心から離れた底部中心外部の箇所は必要な肉厚を確保しやすく、かつ、底部中心の肉厚は薄くできるのである。
On the other hand, in the semi-spherical spherical portion 4b, the thickness of the bottom portion 4 is less decreased at the beginning and is thicker than that of the semi-spherical portion 4c ′. Thereafter, the wall thickness changes in a gentle curve, gradually decreases toward the center of the bottom, and finally reaches the same wall thickness (t = 2.55 mm) as the hemispherical surface 4c at the center of the bottom.
That is, when the stretching rod 31 stretches the bottom portion 4, it is easy to secure a necessary thickness at a position outside the center of the bottom portion away from the bottom center where the stretching rod 31 abuts, and the thickness at the bottom center can be reduced. It is.
［半長球面部形状の範囲］
次に、本実施形態において、底部外面が半径Ｒの半球面部の場合の好ましい底部内面の半長球面部形状について説明する。
図１のＢを参照にして、プリフォーム１の胴部肉厚Ｔが２．０〜５．０ｍｍ、底部外面が、半径Ｒが７．５〜１７．０ｍｍの範囲の球面である場合、底部中心の肉厚ｔ（図３Ａ，Ｂにおける射出孔２３により形成されるゲート跡の部分を除いた、半径Ｒの半球面部の外面側と、半長球面部の内面側との間の肉厚）を、ｔ＜（１３・Ｔ／２０）にすると、底部が薄過ぎて、射出成形時の樹脂の流動性に支障を来す。また、ブロー成形の際、延伸ロッドが加熱軟化した底部の樹脂を過延伸するおそれがある。したがって、肉厚ｔは、（１３・Ｔ／２０）≦ｔの条件を満たす必要がある。また、底部中心の肉厚が、ｔ＞（１９・Ｔ／２０）の場合、底部が厚く、底部軽量化の効果が十分に得られない。したがって、肉厚ｔは、ｔ≦（１９・Ｔ／２０）の条件を満たす必要がある。よって、
（１３・Ｔ／２０）≦ｔ≦（１９・Ｔ／２０）・・・・（式１）
の範囲が、二軸延伸ブロー成形性、および、射出成形性に優れるプリフォーム１の底部中心の肉厚ｔの好適範囲である。
[Range of semi-spherical spherical shape]
Next, in the present embodiment, a preferable semi-ellipsoidal shape of the bottom inner surface when the bottom outer surface is a hemispherical portion having a radius R will be described.
Referring to FIG. 1B, when the body thickness T of the preform 1 is 2.0 to 5.0 mm and the outer surface of the bottom is a spherical surface having a radius R of 7.5 to 17.0 mm, Thickness t at the center (thickness between the outer surface side of the hemispherical surface portion having a radius R and the inner surface side of the hemispherical surface portion excluding the gate trace portion formed by the injection hole 23 in FIGS. 3A and 3B) When t <(13 · T / 20), the bottom portion is too thin, which hinders the fluidity of the resin during injection molding. Further, at the time of blow molding, there is a possibility that the stretched rod may overstretch the resin at the bottom that has been softened by heating. Therefore, the wall thickness t needs to satisfy the condition of (13 · T / 20) ≦ t. Further, when the thickness at the center of the bottom portion is t> (19 · T / 20), the bottom portion is thick, and the effect of reducing the weight of the bottom portion cannot be sufficiently obtained. Therefore, the wall thickness t needs to satisfy the condition of t ≦ (19 · T / 20). Therefore,
(13 · T / 20) ≦ t ≦ (19 · T / 20) (Equation 1)
Is a preferred range of the thickness t at the center of the bottom of the preform 1 that is excellent in biaxial stretch blow moldability and injection moldability.
また、図１のＢから、プリフォーム胴部肉厚Ｔ、底部中心肉厚ｔは、外面である半球面部４ａの半径Ｒ、および、内面である半長球面部４ｂの短半径ａ，長半径ｂから以下のようになる。
Ｔ＝Ｒ−ａ ・・・・（式２）
ｔ＝Ｒ−ｂ ・・・・（式３）
式１に式２のＴ＝Ｒ−ａと式３のｔ＝Ｒ−ｂを代入すると、以下の式４が導かれる。
（Ｒ＋１９・ａ）／２０≦ｂ≦（７・Ｒ＋１３・ａ）／２０・・・・（式４）
このような式４の条件を満たすことによって、プリフォーム１の底部４の肉厚が、底部中心Ｏに向かって好適に漸次薄く形成できる。
なお、このとき底部中心の肉厚ｔが１．５０〜４．７５ｍｍの範囲にあると、より溶融樹脂の流動性が良好になる。
なお、半長球面部４ｂ、またはその部分を形成する長球面部の短半径ａと短半径ｂとの比ａ／ｂは０．６５〜０．９８であると、プリフォーム１の成形性（溶融樹脂の流動性）やブロー成形性（延伸ロッド３１による延伸成形性）の点で好ましい。
Further, from FIG. 1B, the preform body thickness T and the bottom center thickness t are the radius R of the hemispherical surface portion 4a which is the outer surface, and the short radius a and the long radius of the hemispherical surface portion 4b which is the inner surface. From b:
T = R−a (Expression 2)
t = R−b (Expression 3)
Substituting T = Ra in Equation 2 and t = Rb in Equation 3 into Equation 1 yields Equation 4 below.
(R + 19 · a) / 20 ≦ b ≦ (7 · R + 13 · a) / 20 (Equation 4)
By satisfying the condition of Equation 4 as described above, the thickness of the bottom portion 4 of the preform 1 can be formed gradually and gradually thinner toward the bottom center O.
At this time, if the thickness t at the center of the bottom is in the range of 1.50 to 4.75 mm, the fluidity of the molten resin is further improved.
In addition, if the ratio a / b between the short radius a and the short radius b of the semi-long spherical surface portion 4b or the long spherical surface portion forming the portion is 0.65 to 0.98, the moldability of the preform 1 ( It is preferable in terms of fluidity of the molten resin) and blow moldability (stretch moldability by the stretch rod 31).
以上述べたように、本実施形態によれば、プリフォーム１や、プリフォーム１を二軸延伸ブロー成形した合成樹脂製容器の底部を好適に薄くすることができる。この結果、樹脂の使用量が減少し、樹脂材料費と、軽量化に伴う輸送費を節約できる。また、底部中心Ｏを薄くしても、延伸ロッド３１がプリフォーム１の底部４に接触する部位が、底部内面及び外面を球面同士で形成する場合よりも厚肉にできるので、延伸時に延伸ロッド３１がプリフォーム１の底部４を過延伸しにくくなり、二軸延伸ブロー成形性に優れるプリフォーム１になる。そして、このプリフォーム１で二軸延伸ブロー成形する際、プリフォーム１を加熱時に底部４を高温に設定することで、ブロー成形後の合成樹脂製容器の底部残留ひずみを低減させて耐熱性を向上させることができる。
また、射出成形時において、成形孔１９が底部の中央から胴部に向かうにわたって、連続的に徐々に隙間が広くなっているので、樹脂が先端の口頸部まで行き渡る。
さらに、本実施形態は従来の異なる２つの曲率半径を有する円弧の組み合わせによる底部内面よりも、底部内面全体を滑らかな連続した１つの曲面で形成でき、射出成形性、二軸延伸ブロー成形性に優れるプリフォーム１となる。
As described above, according to the present embodiment, the bottom of the preform 1 and the synthetic resin container in which the preform 1 is biaxially stretched blow-molded can be suitably thinned. As a result, the amount of resin used is reduced, and the resin material cost and the transportation cost associated with weight reduction can be saved. Even if the bottom center O is made thin, the portion where the stretching rod 31 contacts the bottom 4 of the preform 1 can be made thicker than when the bottom inner surface and the outer surface are formed of spherical surfaces. No. 31 becomes difficult to overstretch the bottom 4 of the preform 1, and the preform 1 is excellent in biaxial stretch blow moldability. And when biaxially stretching blow-molding with this preform 1, by setting the bottom 4 at a high temperature when the preform 1 is heated, the residual strain at the bottom of the synthetic resin container after blow molding is reduced and heat resistance is improved. Can be improved.
Further, at the time of injection molding, since the gap is gradually widened gradually from the center of the bottom part toward the body part, the resin spreads to the front neck part.
Furthermore, this embodiment can form the entire bottom inner surface with a single continuous curved surface, rather than the conventional inner surface of a combination of circular arcs having two different radii of curvature, and can achieve injection moldability and biaxial stretch blow moldability. An excellent preform 1 is obtained.
次に、本発明の第４実施形態について説明する。
上記第１実施形態では、プリフォーム１の底部外面を半球面部４ａとし底部内面を半長球面部４ｂとしたが、本実施形態では、図７に示すように、底部内面は第１実施形態同様、半長球面部４ｂとするが、底部外面はプリフォーム１の中心軸Ｌ上に長軸を備える楕円の、長軸を回転軸とする回楕円転体である長球の表面を、長軸に垂直な面で半裁した半長球面部４ｄによって形成している。半長球面部４ｄは、中心軸Ｌを含む縦断面上において、図７のように中心軸Ｌ上に長軸を有する楕円の一部である楕円弧形状となる。
底部外面の半長球面部４ｄ長軸と短軸の比（ａ２／ｂ２）よりも底部内面の半長球面部４ｂの長軸と短軸の比（ａ１／ｂ１）が小さい方が、二軸延伸ブロー成形の際、ストレッチロッド３１が当接する部分のプリフォーム底部肉厚が確保しやすいため好ましい。
Next, a fourth embodiment of the present invention will be described.
In the first embodiment, the outer surface of the bottom portion of the preform 1 is the hemispherical surface portion 4a and the inner surface of the bottom portion is the hemispherical spherical surface portion 4b. However, in this embodiment, the inner surface of the bottom portion is the same as that of the first embodiment as shown in FIG. The outer surface of the bottom is an ellipse having a long axis on the central axis L of the preform 1 and the surface of a long sphere that is a spheroid rolling body with the long axis as the rotation axis. It is formed by a semi-ellipsoidal spherical portion 4d half-cut with a surface perpendicular to the surface. The semi-ellipsoidal spherical portion 4d has an elliptic arc shape that is a part of an ellipse having a long axis on the central axis L as shown in FIG.
The smaller the ratio of the major axis to the minor axis (a1 / b1) of the hemispherical surface part 4b on the inner surface of the bottom part than the ratio of the major axis to the minor axis 4d on the outer surface of the bottom part (a2 / b2), the two axes. In the stretch blow molding, it is preferable because the thickness of the preform bottom portion where the stretch rod 31 comes into contact is easily secured.
外面の半長球面部４ｄと内面の半長球面部４ｂは、中心Ｃ１，Ｃ２を一致させてもよいし、底部４の肉厚が底部中心Ｏに向かって漸次薄くなる形態を保つ範囲で相対的に上下にずらして配置してもよい。
本実施形態のように、プリフォーム１の底部外面が半長球面部４ｄである場合、底部４の肉厚は、外面半長球面部４ｄの法線の半長球面部４ｄから底部内面（半長球面部４ｂ）までの長さである。
The outer semispherical spherical surface portion 4d and the inner half semispherical spherical surface portion 4b may have the centers C1 and C2 aligned with each other, and within a range in which the thickness of the bottom portion 4 is maintained to gradually decrease toward the bottom center O. Alternatively, they may be shifted up and down.
When the bottom outer surface of the preform 1 is the semi-ellipsoidal spherical portion 4d as in the present embodiment, the thickness of the bottom 4 is from the normal semi-spherical portion 4d of the outer semispherical spherical portion 4d to the bottom inner surface (semi-spherical portion 4d). The length up to the long spherical surface portion 4b).
このプリフォームを形成する成形金型については、図３において、第１実施形態の雌型本体１８の凹部２１の底部面２２を、半球面部に換えて、凹部２１の中心軸上に長軸を備える楕円の、長軸を回転軸とする回転楕円体である長球の表面を長軸に垂直な面で半裁した半長球面部によって形成する。雄型１２のコア本体１６の先端外面は、第１実施形態同様、半長球面部によって形成する。 With respect to the molding die for forming this preform, in FIG. 3, the bottom surface 22 of the recess 21 of the female mold body 18 of the first embodiment is replaced with a hemispherical portion, and a long axis is formed on the central axis of the recess 21. The surface of an ellipse, which is a spheroid having a major axis as a rotation axis, is formed by a semi-ellipsoidal spherical portion obtained by semi-cutting a surface perpendicular to the major axis. The outer surface of the distal end of the core body 16 of the male mold 12 is formed by a semi-ellipsoidal spherical portion as in the first embodiment.
第４実施形態による効果は、第１〜第３実施形態と同様である。 The effect by 4th Embodiment is the same as that of 1st-3rd Embodiment.
以上、本発明を実施形態に基づいて添付図面を参照しながら詳細に説明したが、本発明は上記実施形態に限定されるものではなく、本発明の範囲を逸脱することなく、更に他の変形あるいは変更が可能である。
上述の実施形態では、プリフォームとして胴部が円筒形状、底部が内面に半長球面部、外面が半球面部または半長球面部で形成された形状からなり、水平断面（中心軸に垂直な断面）は内周および外周とも円形で全周均等肉厚の円環（なお、底部中心近傍の水平断面は中実の円）であるが、これに限らない。プリフォームの内面が、プリフォーム中心軸を含む縦断面上で中心軸上に長軸を有する楕円弧形状であれば、水平断面の内周および外周の少なくとも一方が楕円などの扁平形状であってもよい。水平断面の内周および外周の少なくとも一方が楕円などの扁平形状である場合、扁平合成樹脂製容器用のプリフォームとして有用である。
また、実施形態では底部の外面は半球面部または半長球面部であったが、胴部と好適に接続するため、半長球面や半球面より若干小さい長球面部や球面部であってもよい。
また、胴部と底部の間に段部やテーパー部を設けてもよい。また胴部と底部の間に厚肉部を設けてもよい。
また、実施形態では、プリフォーム成形金型として射出成形用の金型について説明したが、圧縮成形用，射出圧縮成形用の金型であってもよい。なお、圧縮成形用金型の場合、射出孔は塞ぎ、底部中心およびその近傍外面は縦断面が円弧または楕円弧の曲面とする。圧縮成形用金型や射出圧縮成形用金型についても、射出成形用金型と同様、プリフォーム底部の溶融樹脂の流動性は良好となる。
The present invention has been described in detail based on the embodiments with reference to the accompanying drawings. However, the present invention is not limited to the above-described embodiments, and other modifications can be made without departing from the scope of the present invention. Or it can be changed.
In the above-described embodiment, the preform has a cylindrical shape, the bottom is a semi-spherical surface on the inner surface, and the outer surface is a semi-spherical surface or a semi-spherical surface. ) Is a circular ring whose inner and outer peripheries are circular and have a uniform thickness on the entire periphery (the horizontal cross section in the vicinity of the center of the bottom is a solid circle), but is not limited thereto. If the inner surface of the preform is an elliptical arc shape having a longitudinal axis on the longitudinal section including the preform central axis and having a major axis on the central axis, even if at least one of the inner circumference and the outer circumference of the horizontal section is a flat shape such as an ellipse Good. When at least one of the inner periphery and the outer periphery of the horizontal cross section is a flat shape such as an ellipse, it is useful as a preform for a flat synthetic resin container.
In the embodiment, the outer surface of the bottom portion is a hemispherical surface portion or a semi-spherical spherical surface portion, but may be an oblong spherical surface portion or a spherical surface portion that is slightly smaller than the hemispherical surface or the hemispherical surface in order to connect with the body portion. .
Moreover, you may provide a step part and a taper part between a trunk | drum and a bottom part. Moreover, you may provide a thick part between a trunk | drum and a bottom part.
In the embodiment, the injection molding mold is described as the preform molding mold. However, it may be a compression molding mold or an injection compression molding mold. In the case of a compression molding die, the injection hole is closed, and the center of the bottom and the outer surface in the vicinity thereof are curved surfaces having a longitudinal section of an arc or an elliptical arc. The compression molding mold and injection compression molding mold also have good fluidity of the molten resin at the bottom of the preform, similar to the injection molding mold.
１ プリフォーム
２ 口頸部
３ 胴部
４ 底部
４ａ 半球面部（底部外面）
４ｂ 半長球面部（長球面部，底部内面）
４ｄ 半長球面部（底部外面）
１１ 成形金型
１２ 雄型
１３ 雌型
１４ 割型
１６ コア本体
１８ 雌型本体
１９ 成形孔
２２ 底面
３０ ブロー成形金型
３１ 延伸ロッド
DESCRIPTION OF SYMBOLS 1 Preform 2 Mouth neck part 3 Torso part 4 Bottom part 4a A hemispherical part (bottom part outer surface)
4b Semi-long spherical surface (long spherical surface, bottom inner surface)
4d semi-long spherical surface (bottom outer surface)
DESCRIPTION OF SYMBOLS 11 Mold 12 Male mold 13 Female 14 Split mold 16 Core main body 18 Female mold main body 19 Molding hole 22 Bottom face 30 Blow molding mold 31 Stretching rod
Claims (10)
前記プリフォームの底部肉厚は、胴部側から底部中心部に向かって漸次薄くなるよう形成され、
前記底部の内面は、前記プリフォームの中心軸を含む縦断面上で該中心軸上に長軸を有する楕円弧形状であり、
前記底部の外面が、球面部で形成され、
前記底部内面は前記球面部と中心が一致し、前記プリフォームの中心軸上に長軸を備え長球面部で形成され、前記プリフォームの胴部肉厚Ｔが２．００〜５．００ｍｍ、前記底部の外面における、球面部の半径Ｒが７．５０〜１７．００ｍｍであって、前記底部の内面における、長球面部の短半径ａがＲ−Ｔであるときに、前記長球面部の長半径ｂが、
（Ｒ＋１９ａ）／２０≦ｂ≦（７Ｒ＋１３ａ）／２０
の範囲にあることを特徴とするプリフォーム。 In a preform having a mouth and neck having an opening, a cylindrical trunk continuous to the mouth and neck, and a bottom for closing the trunk,
The bottom thickness of the preform is formed so as to gradually become thinner from the trunk side toward the center of the bottom,
The inner surface of the bottom has an elliptical arc shape having a long axis on the central axis on a longitudinal section including the central axis of the preform,
The outer surface of the bottom is formed by a spherical portion ;
The inner surface of the bottom portion coincides with the center of the spherical portion, is formed of a long spherical portion having a long axis on the central axis of the preform, and the body thickness T of the preform is 2.00 to 5.00 mm, When the radius R of the spherical portion on the outer surface of the bottom portion is 7.50 to 17.00 mm and the short radius a of the major spherical portion on the inner surface of the bottom portion is R−T, The major radius b is
(R + 19a) / 20 ≦ b ≦ (7R + 13a) / 20
Preform and wherein the range near Rukoto of.
前記雄型と前記雌型の型閉時に、雄型先端部と雌型の底部面との間で形成される隙間が底部中心部に向かって漸次狭くなるよう形成され、
前記プリフォームの底部内面を形成する前記雄型先端部が前記雄型中心軸を含む縦断面上で該中心軸上に長軸を備える楕円弧形状であり、
前記雌型の底部面は、球面部で形成され、
前記雄型の先端部は前記雄型中心軸上に長軸を備える長球面部で形成され、前記雄型と雌型を型閉時に、前記球面部中心と長球面部の中心は一致し、前記プリフォームの胴部を形成する成形金型の隙間Ｔが２．００〜５．００ｍｍ、前記雌型の底部面における、球面部の半径Ｒが７．５０〜１７．００ｍｍであって、前記雄型先端部における、長球面部の短半径ａがＲ−Ｔであるときに、前記長球面部の長半径ｂが、
（Ｒ＋１９ａ）／２０≦ｂ≦（７Ｒ＋１３ａ）／２０
の範囲にあることを特徴とするプリフォーム成形金型。 In a preform mold having a male mold and a female mold,
When the male mold and the female mold are closed, a gap formed between the male tip and the bottom surface of the female mold is formed so as to gradually narrow toward the center of the bottom,
Ri elliptic arc shape der having a major axis on the central axis on the longitudinal section the male tip forming the bottom inner surface of the preform comprises the male central axis,
The bottom surface of the female mold is formed of a spherical portion,
The tip of the male mold is formed as an oblong spherical section having a long axis on the male mold central axis, and when the male mold and the female mold are closed, the center of the spherical section coincides with the center of the oblong spherical section, The gap T of the molding die forming the body portion of the preform is 2.00 to 5.00 mm, and the radius R of the spherical surface portion on the bottom surface of the female die is 7.50 to 17.00 mm, When the minor radius a of the major spherical surface portion at the male tip is RT, the major radius b of the major spherical portion is
(R + 19a) / 20 ≦ b ≦ (7R + 13a) / 20
Preform mold, wherein the range near Rukoto of.
前記プリフォームは、開口部を有する口頸部と、該口頸部に連続する筒状の胴部と、該胴部を閉塞する底部とを有し、底部肉厚は、胴部側から底部中心部に向かって漸次薄くなるよう形成され、底部の内面は、プリフォームの中心軸を含む縦断面上で中心軸上に長軸を有する楕円弧形状であり、
前記延伸ロッドは、プリフォーム底部中心部より厚肉の底部中心外部に最初に当接してプリフォームを延伸することを特徴とする、合成樹脂製容器の製造方法。 In the method for producing a synthetic resin container in which the preform according to any one of claims 1 to 4 is biaxially stretch blow molded with a stretch rod,
The preform includes an opening / closing portion of the mouth / neck portion, a cylindrical body portion continuous to the mouth / neck portion, and a bottom portion that closes the body portion, and the bottom wall thickness is from the body portion side to the bottom portion. The inner surface of the bottom is formed in an elliptical arc shape having a long axis on the central axis on the longitudinal section including the central axis of the preform,
The method of manufacturing a synthetic resin container, characterized in that the stretching rod first comes into contact with the outside of the center of the bottom of the thick wall from the center of the bottom of the preform to stretch the preform.
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| PCT/JP2016/056749 WO2016152456A1 (en) | 2015-03-25 | 2016-03-04 | Preform, preform molding die, and method for manufacturing synthetic resin container |
| CN201680018191.1A CN107405819B (en) | 2015-03-25 | 2016-03-04 | The manufacturing method of prefabrication, prefabrication molding die and synthetic resin container |
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