JP4146303B2

JP4146303B2 - Foamed synthetic resin container, its lid, its manufacturing method, and its molding die

Info

Publication number: JP4146303B2
Application number: JP2003190968A
Authority: JP
Inventors: 和史小澤
Original assignee: ホクト化学工業株式会社
Priority date: 2003-07-03
Filing date: 2003-07-03
Publication date: 2008-09-10
Anticipated expiration: 2023-07-03
Also published as: JP2005022275A

Description

【０００１】
【発明の属する技術分野】
本発明は、魚箱等の発泡成形体からなる容器、その蓋、それの製造方法及びその成形用金型に関する。
【０００２】
【従来の技術】
魚箱等の発泡ポリスチレンの容器は、従来、型内発泡成形方法により製造されてきた（例えば特許文献１を参照）。
【特許文献１】
特開２０００−２１０９６５号公報
【０００３】
魚箱等の発泡合成樹脂製容器の製造方法は次の通りである。コア型とキャビティ型を一対とする金型を準備し、予備発泡ビーズを充填する。発泡成形においては、発泡剤を含浸させた原料ビーズを成形する製品の重量・強度等に合致させるべく予備発泡を行い、その要求発泡倍率に発泡させた予備発泡ビーズを金型に送る。予備発泡ビーズは発泡剤を含んだポリスチレン樹脂であることが多い。そして予備発泡ビーズを充填する方法としては、クラッキング充填法、加圧充填法又は圧縮充填法などが広く採用されている。充填後、金型に配置した水蒸気配管を通過する水蒸気の熱で予備発泡ビーズを加熱して、溶融発泡させて発泡成形体を成形する。そして発泡成形体を冷却固化させ、金型から取り出す。
【０００４】
ここでクラッキング充填法とは、金型を完全に型閉めせずにわずかな隙間（クラッキング隙間）を設けて予備発泡ビーズを充填する方法である。この隙間を設けることにより予備発泡ビーズの供給のために流す搬送空気が抜けやすくなり、型に均一に予備発泡ビーズが行き渡ることとなる。このクラッキング隙間は容器の壁肉厚のおおよそ１０％で、魚箱を成形する場合では約２ｍｍである。
【０００５】
そして、成形された発泡合成樹脂製容器では、底部、壁などいずれの箇所においても均一な発泡倍率であることが望まれる。
【０００６】
【発明が解決しようとする課題】
魚箱の外形大きさは例えば５５０×３５０×１４５ｍｍである。そして必要な強度を得るために底部肉厚は２０ｍｍ、側壁肉厚は２５ｍｍ、蓋の天井部分の肉厚は１８ｍｍとしている。なお、発泡合成樹脂としては発泡ポリスチレンが使用され、その樹脂発泡倍率は約６０％である。
【０００７】
近年輸送の長距離化が望まれており、保冷効果の長時間化が望まれている。魚箱の外形大きさを変えずに内容積を増大させることが出来れば魚等と共に梱包する氷量を増やすことができ、結果として保冷効果の長時間化を実現することができる。
【０００８】
また、内容積を変えずに魚箱の背低化ができれば、運送時に同じ高さでより多くの魚箱が積載できる。
【０００９】
魚箱の内容積を多くするか或いは魚箱を背低化するためには、箱の肉厚、特に底部肉厚を薄くすることが考えられる。しかし、単に底部肉厚を薄くしたのでは１箱あたりで使用する発泡ポリスチレン量を少なくすることが出来るものの、強度低下をきたしてしまう。
【００１０】
そこで魚箱底部の強度を維持しながら、底部肉厚を薄くした魚箱が望まれる。このとき、魚箱を成形する際の予備発泡ビーズ使用量、成形時間など従来と同条件で製造しうる安価な製造方法も望まれる。
【００１１】
一方魚箱は、底部に氷を敷き詰め、その上に魚等の内容物を入れて使用される。魚と氷を入れて魚箱に蓋をしたときに蓋内面に魚が接触する場合がある。蓋内面と魚が接触していると輸送時の振動で魚が痛んでしまう。接触を避けるために氷を減らすことも考えられるが、保温効果の短時間化を招き好ましくない。そこで、氷量を減らさずに魚と接触しにくい内面形状を有する蓋が望まれる。
【００１２】
本発明の目的は、内容積の増大或いは魚箱の背低化を箱の強度低下を招かずに実現した容器とそれを安価で製造できる製造方法及びその成形用金型を提供することである。また、梱包した魚を傷めず且つ強度低下を招かない容器用蓋とそれを安価で製造できる製造方法及びその成形用金型を提供することである。
【００１３】
【課題を解決するための手段】
本発明に係る発泡合成樹脂製容器の製造方法は、箱型の容器の底部肉厚を、該容器の側壁肉厚の２０〜４０％の厚さ分だけ薄肉化した容器状成形体の成形空間を有する型内発泡成形用金型を完全に型閉めせずに、前記薄肉化した肉厚相当分を、薄肉化前の肉厚の６〜１０％に相当するクラッキング隙間に加え該隙間を大きくした状態で予備発泡ビーズを充填した後、前記金型を完全に型閉めして前記予備発泡ビーズを加熱し溶融発泡させて容器状発泡成形体を成形し、該容器状発泡成形体を冷却固化させた後、該容器状発泡成形体を前記金型から取り出すことを特徴とする。使用樹量は従来と同一としつつ、容器の底部肉厚を薄肉化し、且つ薄肉化した部分の強度低下をきたさない為の成形方法を提案するものである。前記箱型の容器は例えば魚箱である。
【００１４】
また、発泡合成樹脂製容器用蓋の製造方法は、箱型の容器用蓋の天井部肉厚を、容器の側壁肉厚の２０〜４０％の厚さ分だけ天井部内面側から薄肉化した蓋状成形体の成形空間を有する型内発泡成形用金型を完全に型閉めせずに、前記薄肉化した肉厚相当分を、薄肉化前の肉厚の６〜１０％に相当するクラッキング隙間に加え該隙間を大きくした状態で予備発泡ビーズを充填した後、前記金型を完全に型閉めして前記予備発泡ビーズを加熱し溶融発泡させて蓋状発泡成形体を成形し、該蓋状発泡成形体を冷却固化させた後、該蓋状発泡成形体を前記金型から取り出すことを特徴とする。使用樹量は従来と同一としつつ、蓋天井部肉厚を薄肉化し、且つ薄肉化した部分の強度低下をきたさない為の成形方法を提案するものである。
【００１６】
本発明に係る発泡合成樹脂製容器の成形用金型は、箱型の容器の底部肉厚を、該容器の側壁肉厚の２０〜４０％の厚さ分だけ薄肉化した容器状成形体の成形空間を有するコア型とキャビティ型を一対とする型内発泡成形用金型であって、前記薄肉化した肉厚相当分を、薄肉化前の肉厚の６〜１０％に相当するクラッキング隙間に加え該隙間を大きくした状態にて予備発泡ビーズをもらさずに型閉めしうる接合構造をコア型外周面とキャビティ型内周面との間に設けたことを特徴とする。
【００１７】
また、本発明に係る発泡合成樹脂製容器用蓋の成形用金型は、箱型の容器用蓋の天井部肉厚を、容器の側壁肉厚の２０〜４０％の厚さ分だけ天井部内面側から薄肉化した蓋状成形体の成形空間を有するコア型とキャビティ型を一対とする型内発泡成形用金型であって、前記薄肉化した肉厚相当分を、薄肉化前の肉厚の６〜１０％に相当するクラッキング隙間に加え該隙間を大きくした状態にて予備発泡ビーズをもらさずに型閉めしうる接合構造をコア型外周面とキャビティ型内周面との間に設けたことを特徴とする。
【００１８】
容器の底部肉厚又は蓋天井部肉厚を薄肉化し、且つ薄肉化した部分の強度低下をきたさない為の専用金型を提案するものである。ここで、蓋の金型の場合、蓋内面を窪ませることで魚との接触を防止することができる蓋状成形体が得られる。
【００１９】
本発明に係る発泡合成樹脂製容器は、本発明の発泡合成樹脂製容器の製造方法に従って製造され、箱型の容器の底部肉厚を、該容器の側壁肉厚の２０〜４０％の厚さ分だけ薄肉化して大容積化或いは背低化した発泡合成樹脂製容器であって、該容器の底部の樹脂発泡倍率を側壁部の樹脂発泡倍率よりも低くしたことを特徴とする。ここで前記容器の中央縦断面の底部形状は、容器内側に凸の円弧形状とすることが好ましい。このような底面形状とすることで、強度の向上が見込めるからである。
【００２０】
本発明に係る発泡合成樹脂製容器用蓋は、本発明の発泡合成樹脂製容器用蓋の製造方法に従って製造され、箱型の容器用蓋の天井部肉厚を、容器の側壁肉厚の２０〜４０％の厚さ分だけ天井部内面側から薄肉化した発泡合成樹脂製容器用蓋であって、該容器用蓋の天井部の樹脂発泡倍率を、前記容器の開口部に嵌着する前記容器用蓋の嵌合部の樹脂発泡倍率よりも低くしたことを特徴とする。
【００２１】
容器の底部又は蓋天井部の樹脂発泡倍率を小さくすることで、当該箇所で使用する樹脂量を薄肉化しない場合と同等のとして強度を確保する。容器の底部を薄肉化した厚さ相当分については内容積の増大若しくは魚箱の背低化の少なくともいずれかに反映できる。また蓋内面を窪ませることで魚との接触を防止することができる。
【００２２】
【発明の実施の形態】
以下、本発明について具体的且つ詳細に説明するが、本発明はこれらの記載に限定して解釈されない。容器が魚箱の場合として説明する。
【００２３】
まず、発泡合成樹脂製容器の成形用金型について説明する。図１に本実施形態に係る成形装置の一形態を示す概略構成図を示した。ここで金型については魚箱（蓋を除く）の成形空間を有する成形用金型とし、縦断面概略図を示した。すなわち、符号１１で示した箇所が成形体である魚箱の底部となる箇所であり、符号１２で示した箇所が側壁となる部分である。図１で示すように本実施形態に係る成形装置は、コア型２とキャビティ型１を一対とする型内発泡成形用の金型３と、接合構造４と、キャビティ型１を移動させて金型３の開閉を行なう金型開閉手段５と、予備発泡ビーズを蓄え且つ熟成するためのホッパー７と、予備発泡ビーズを空気搬送するための予備発泡ビーズ搬送管６と、搬送用の空気供給源８と、空気供給源８に接続された空気配管９と、空気配管９と予備発泡ビーズ搬送管６との接続部１０とを備える。
【００２４】
図２には図１における成形用金型部分の縦断面概略図を示した。ここで（ａ）は従来型の金型で、（ｂ）は本実施形態に係る金型である。従来型の金型は、得られる魚箱の底部と側壁部とが同一の肉厚（たとえば２５ｍｍ）となるようにかたどりされている。一方、本実施形態に係る金型は、魚箱の側壁肉厚よりも底部肉厚を薄肉化するようにコア型をかたどりしている。すなわち、（ａ）の金型よりも（ｂ）の金型のほうがコア型の魚箱深さ方向の厚さが大きく、（ｂ）の金型においてコア型を厚くした分だけ底部肉厚が薄肉化される。（ａ）の金型を使用する際、クラッキング隙間は通常２ｍｍ程度である。しかし、（ｂ）の金型を使用する際には、後述するように薄肉化した肉厚相当分を通常のクラッキング隙間に加えて隙間を大きくする。したがって、（ｂ）の金型においては、薄肉化した肉厚相当分を通常のクラッキング隙間に加えて隙間を大きくした状態において予備発泡ビーズがもれずに型閉めしうる接合構造をコア型外周面とキャビティ型内周面との間に設ける。
【００２５】
金型３は予備発泡ビーズを充填する際にキャビティ型１の移動により、クラッキング隙間を設けた状態から金型３を完全に型閉めした状態との間で遷移する。接合構造４は、充填した予備発泡ビーズを成形空間１３外に漏らさないように、コア型２の外周面とキャビティ型１の内周面との間で設けるものであり、コア型２をクラッキング隙間に相当する距離だけ移動させたときに、その移動している間はコア型２の外周面とキャビティ型１の内周面とをほぼ接面させる。ここで、図３に示すように接合構造４において予備発泡ビーズ搬送時に供給する空気を金型外に排気することが出来るだけの空気隙間１５を設ける。図２の（ａ）の金型よりも（ｂ）の金型のほうがクラッキング隙間を大きくとる為、（ｂ）の接合構造４は、通常よりも少なくともクラッキング隙間を大きくした分だけ従来の金型よりも長くする必要がある。なお、接合構造４はコア型と一体としても良く、別体で接合しても良い。
【００２６】
コア型２の外表面側は魚箱の内壁面を形成し、キャビティ型１の内表面は魚箱の外壁面を形成する。コア型２、キャビティ型１の少なくともいずれか一方の表面近傍には、水蒸気を流しその熱によって予備発泡ビーズを加熱する加熱手段（不図示）が設けられており、成形空間１３内に充填した予備発泡ビーズを加熱し、発泡成形体を形成する。また、コア型２側には金型開閉手段５が接続されており、金型３の開閉を行なうことが出来る。図１では金型開閉手段５をコア型２に接続したが、キャビティ型１に接続しても良い。
【００２７】
発泡剤を含浸させた原料ビーズを成形する製品の重量・強度等に合致させるべく予備発泡を行い、その要求発泡倍率に発泡させた予備発泡ビーズをホッパー７に蓄える。ここに用いる発泡性合成樹脂原料粒子としては、発泡性ポリスチレン系樹脂原料粒子又は発泡性ポリエチレン系樹脂原料粒子、発泡性ポリプロピレン系樹脂原料粒子等の発泡性ポリオレフィン系樹脂原料粒子、その他発泡性共重合系樹脂原料粒子が利用可能である。また原料粒子は予備発泡させないものを用いることもできるが、予備発泡させたものを用いることが好ましい。原料粒子の発泡倍率は用いる樹脂素材によっても若干変動するが、３〜１５０倍の範囲内が好ましい。この発泡倍率は、発泡性ポリスチレン系樹脂原料粒子では３〜１００倍、好ましくは３〜６５倍、又発泡性ポリオレフィン系樹脂原料粒子では３〜６０倍、好ましくは３〜４５倍の範囲内のものがそれぞれ好適に利用可能である。また粒径は用いる樹脂素材によっても若干変動するが、１〜１０ｍｍの範囲内のものが好適に利用できる。予備発泡ビーズ搬送管６はホッパー７に蓄えた予備発泡ビーズを金型３の成形空間１３まで空気搬送するための配管である。空気供給源８から発生した搬送空気は空気配管９を介して接続部１０において予備発泡ビーズ搬送管６に導入する。
【００２８】
次に図４〜６を参照しながら本実施形態に係る金型を用いた成形方法を説明する。ここで、従来の金型を用いた場合と対比しながら説明を行なう。成形装置は図１の成形装置を用いる。なお、理解の容易化のためにクラッキング隙間等の寸法の実例を挙げて説明するが、この寸法に本発明が限定されないことはいうまでもない。図４〜６中の（ａ）は従来金型を用いた場合、（ｂ）は本発明の実施形態に係る金型を用いた場合である。
【００２９】
図４は、予備発泡ビーズの充填工程を示す図である。ホッパーから空気搬送で予備発泡ビーズが送られ、成形空間内に充填される。（ａ）（ｂ）共に成形空間の側壁に相当する厚さを２５ｍｍとしている。成形体の側壁も同じ厚さの２５ｍｍが得られる。ところで、（ａ）ではクラッキング隙間を２ｍｍとし、成形空間の底部に相当する厚さを２７ｍｍとしている。金型を完全に型示したときは図２に示したように成形空間の底部に相当する厚さが２５ｍｍとなるように設計されているため、クラッキング隙間分に相当する厚さを加算したこととなる。通常型内発泡成形法では厚さの６〜１０％程度のクラッキング隙間を設ける。（ａ）の従来例ではクラッキング隙間を底部の厚さに対して８％としている。一方、（ｂ）ではクラッキング隙間を７ｍｍとし、成形空間の底部に相当する厚さを（ａ）と同じく２７ｍｍとしている。（ａ）と同じ２７ｍｍとなるのは図２に示したように成形空間の底部に相当する厚さが２０ｍｍとなるように設計されているためである。本実施例ではクラッキング隙間を底部の厚さに対して３５％としているが、強度維持の観点からクラッキング隙間を底部の厚さに対して２０〜４０％とすることが好ましい。（ａ）（ｂ）共にクラッキング隙間を設けたときに底部空間の厚さは２７ｍｍであるため、成形空間の底部に相当する箇所には同量の予備発泡ビーズが充填される。なお、成形空間内に予備発泡ビーズと共に供給される搬送空気は、接合構造に設けた空気隙間から金型外へ排気される。
【００３０】
図５は予備発泡ビーズを充填した後、金型を完全に型閉めした状態を示す図である。（ａ）（ｂ）共に成形空間の側壁に相当する箇所にある予備発泡ビーズはほとんど圧縮圧力を受けない。しかし、成形空間の底部に相当する箇所にある予備発泡ビーズは圧縮圧力を受ける。（ａ）の場合は、完全に型閉めすることにより体積換算で９２．６％に圧縮され、（ｂ）の場合は同じく７４．１％に圧縮される。なお、金型を完全に型閉めするときには、成形空間内の過剰空気は接合構造に設けた空気隙間から金型外へ排気される。なお、容器側壁の高さを１６０ｍｍとすると、（ａ）の場合の側壁部分の圧縮は、９８．８％、（ｂ）の場合の側壁部分の圧縮は、９５．８％で３％程度の違いしかない。
【００３１】
図６は予備発泡ビーズを加熱し溶融発泡させて発泡成形体を成形する加熱工程を示す図である。コア型の外面近傍若しくはキャビティ型の内面近傍の少なくともいずれかに設けた加熱手段（不図示）に水蒸気を流しその熱によって予備発泡ビーズを加熱する。この加熱によって、予備発泡ビーズの発泡、ビーズ同士の融着が起こり、金型の成形空間に型とられた成形体が得られる。
【００３２】
加熱工程を経て、発泡成形体を冷却固化させ（冷却工程）、発泡成形体を金型から取り出す（離型工程）。
【００３３】
上記の説明は魚箱について説明したが、魚箱の蓋も同様の成形装置を用いて、蓋用のコア型とキャビティ型を一対とする型内発泡成形用金型を用いて成形することが出来る。この場合、金型は、蓋天井部肉厚を天井部内側から薄肉化するようにかたどりされた金型を使用する。特に蓋をしたときの内容積が増大するように蓋内面形状をたとえば５ｍｍ分、凹形状とすることが好ましい。凹形状とすることにより魚と天井部内面との接触を防止できる。また、魚箱の場合と同様に充填工程において薄肉化した肉厚相当分をクラッキング隙間に加えて隙間を大きくした状態として予備発泡ビーズを充填する。薄肉化した肉厚相当分は、容器の側壁肉厚の２０〜４０％とすることが好ましい。これにより、図７（ｂ）（ｃ）に示したように蓋内面形状を（ａ）と比較してより凹形状とした蓋が成形される。
【００３４】
以上により、発泡合成樹脂製容器として魚箱とその蓋を得た。図７に得られた魚箱の蓋をつけたときの縦断面図を示した。（ａ）は従来例であり、（ｂ）は魚箱の外形大きさは従来の魚箱と同じとして内容積を増大させた場合、（ｃ）は従来例と内容積を同じとして高さを低くして背低化した場合を示した。なお、蓋は従来形状の蓋を用いても良いが、（ｂ）（ｃ）のように蓋の天井部肉厚を天井部内側から薄くしたほうが好ましく、内容積の増大はもちろんのこと、魚を輸送時の振動で傷めることもない。
【００３５】
（ａ）において魚箱及びその蓋の発泡倍率はいずれの箇所においても凡そ６０％となる条件下において、（ｂ）（ｃ）の場合、側壁部分２２の発泡倍率は約６０％であり、魚箱の底部２１と蓋の天井部２０は約５０％であった。これは魚箱の底部と蓋の天井部において（ａ）の場合と同量の予備発泡ビーズを充填して且つ肉厚を５ｍｍ薄くしたことによる。なお、発泡倍率はポリスチレンの密度が１．０５ｇ／ｃｍ^３であり、発泡ポリスチレンの密度を測定してこれらを比較することにより算出できる。
【００３６】
図８に図７（ｂ）（ｃ）と同じ蓋の内面の概略図を示した。容器の開口部に嵌着する容器用蓋の嵌合部２３の幅３０は容器の側壁の厚さ２２と同等となる。このとき、容器用蓋の天井部２０の樹脂発泡倍率は約５０％であり、容器の開口部に嵌着する容器用蓋の嵌合部２３（図８中、灰色で示した箇所）の樹脂発泡倍率は６０％となり、天井部２０の樹脂発泡倍率約は嵌合部２３の樹脂発泡倍率よりも低くなる。
【００３７】
このように本実施形態では、魚箱は底部肉厚を薄肉化していて、魚箱の底部の樹脂発泡倍率は側壁部の樹脂発泡倍率よりも低い。また、その蓋は天井部肉厚を薄肉化していて、天井部の樹脂発泡倍率は容器の側壁部に嵌着する嵌合部の樹脂発泡倍率よりも低い。発泡倍率が６０％から５０％にすることで断熱効果が向上し、保冷時間を長くすることができる。
【００３８】
強度については従来と同量の樹脂量で成形しているので、従来とほぼ同等の強度が得られた。
【００３９】
本実施形態において、図９〜図１１に示すように魚箱の中央縦断面の底部形状を容器内側に凸の円弧形状とすることが好ましい。底部中央を容器内側に凸となる曲面形状とすることで底部の強度向上が図れ、重量物を容器に入れても底が抜ける恐れが少なくなる。また、本実施形態における魚箱では氷が溶けたときに生ずる水を排水するために排水孔３１を設けるが、魚箱の中央縦断面の底部形状を容器内側に凸の円弧形状とすることで溶けた水が効率よく排水孔に導かれ、排水させることができる。
【００４０】
【発明の効果】
本発明により、魚箱の外形大きさを変えずに内容積を増大させることが出来たので、魚等と共に梱包する氷量を増やすことができ、結果として保冷効果の長時間化を実現することができる。これにより輸送の長距離化に対応できる。或いは内容積を変えずに魚箱の背低化ができるので、運送時に同じ高さでより多くの魚箱が積載できる。本発明では魚箱底部の強度を維持しながら上記事項が実現できる。この時、樹脂量を増やすことを必要としない。容器の中央縦断面の底部形状を容器内側に凸の円弧形状とすることで、より強度を確保することができる。
【００４１】
また本発明の蓋は同様に薄肉化することで氷量を減らさずに魚と接触しにくい内面形状を有するので、蓋内面と魚が接触して輸送時の振動で魚を傷めてしまうことがない。氷量を減らさないため保温効果の短時間化を招かない。
【００４２】
本発明は、上記の特性を有する魚箱及びその蓋を、内容積の増大或いは魚箱の背低化を強度低下させずに成形しうる安価な製造方法とその成形用金型を提供することが出来る。
【図面の簡単な説明】
【図１】本実施形態に係る成形装置の一形態を示す概略構成図を示す。
【図２】図１における成形用金型部分の縦断面概略図であり、（ａ）は従来型の金型の概略図で、（ｂ）は本実施形態に係る金型の概略図を示す。
【図３】図２における符号１４で示した部分の拡大概略図である。
【図４】予備発泡ビーズの充填工程を示す図であり、（ａ）は従来例、（ｂ）は本実施形態を示す。
【図５】予備発泡ビーズを充填した後、金型を完全に型閉めした状態を示す図であり、（ａ）は従来例、（ｂ）は本実施形態を示す。
【図６】予備発泡ビーズを加熱し溶融発泡させて発泡成形体を成形する加熱工程を示す図であり、（ａ）は従来例、（ｂ）は本実施形態を示す。
ある。
【図７】本実施形態の蓋をしたときの魚箱の縦断面概略図であり、（ａ）は従来例、（ｂ）は魚箱の外形大きさは従来の魚箱と同じとして内容積を増大させた例、（ｃ）は従来例と内容積を同じとして高さを低くして背低化した例を示した。
【図８】図７（ｂ）（ｃ）と同じ蓋の内面の一形態を示す概略図である。
【図９】本実施形態に係る魚箱を開口部側から内部をみた概略図である。
【図１０】図９のＸ−ＹにおけるＡ−Ａ´断面の概略図である。
【図１１】図９のＸ−ＹにおけるＢ−Ｂ´断面の概略図である。
【符号の説明】
１，キャビティ型
２，コア型
３，金型
４，接合構造
５，金型開閉手段
６，予備発泡ビーズ搬送管
７，ホッパー
８，空気供給源
９，空気配管
１０，接続部
１３，成形空間
１５，空気隙間
２０，天井部
２１，容器底部
２２，側壁部
２３，容器用蓋の嵌合部
３１，排水孔[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a container made of a foam molded body such as a fish box, a lid thereof, a method for producing the same, and a molding die for the same.
[0002]
[Prior art]
Conventionally, foamed polystyrene containers such as fish boxes have been manufactured by an in-mold foam molding method (see, for example, Patent Document 1).
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-210965
A method for producing a foamed synthetic resin container such as a fish box is as follows. A mold having a core mold and a cavity mold as a pair is prepared and filled with pre-expanded beads. In foam molding, pre-foaming is performed to match the weight, strength, etc. of the product to be molded with the raw material beads impregnated with the foaming agent, and the pre-foamed beads foamed to the required foaming ratio are sent to the mold. Pre-expanded beads are often polystyrene resins containing a blowing agent. As a method for filling the pre-expanded beads, a cracking filling method, a pressure filling method, a compression filling method, or the like is widely adopted. After filling, the pre-expanded beads are heated and melt-foamed by the heat of water vapor passing through the water vapor piping arranged in the mold to form a foam molded article. And the foaming molding is solidified by cooling and taken out from the mold.
[0004]
Here, the cracking filling method is a method of filling a pre-expanded bead by providing a slight gap (cracking gap) without completely closing the mold. By providing this gap, the carrier air flowing for supplying the pre-expanded beads can be easily removed, and the pre-expanded beads are uniformly distributed in the mold. This cracking gap is about 10% of the wall thickness of the container, and is about 2 mm when forming a fish box.
[0005]
In the molded synthetic resin container, it is desired that the foaming ratio be uniform at any location such as the bottom and the wall.
[0006]
[Problems to be solved by the invention]
The outer size of the fish box is, for example, 550 × 350 × 145 mm. In order to obtain the required strength, the bottom wall thickness is 20 mm, the side wall wall thickness is 25 mm, and the wall thickness of the lid ceiling is 18 mm. Note that foamed polystyrene is used as the foamed synthetic resin, and the resin foaming ratio is about 60%.
[0007]
In recent years, it has been desired to increase the distance of transportation, and it is desired to increase the cooling effect for a long time. If the internal volume can be increased without changing the outer size of the fish box, the amount of ice to be packed with the fish and the like can be increased, and as a result, a longer cooling effect can be realized.
[0008]
If the height of the fish box can be reduced without changing the internal volume, more fish boxes can be loaded at the same height during transportation.
[0009]
In order to increase the internal volume of the fish box or reduce the height of the fish box, it is conceivable to reduce the thickness of the box, particularly the bottom thickness. However, if the bottom thickness is simply reduced, the amount of expanded polystyrene used per box can be reduced, but the strength is lowered.
[0010]
Therefore, a fish box having a thin bottom thickness while maintaining the strength of the bottom of the fish box is desired. At this time, an inexpensive manufacturing method that can be manufactured under the same conditions as in the prior art, such as the amount of pre-expanded beads used for molding a fish box and the molding time, is also desired.
[0011]
On the other hand, a fish box is used by laying ice on the bottom and putting contents such as fish on it. When the fish box is covered with fish and ice, the fish may come into contact with the inner surface of the lid. If the inner surface of the lid is in contact with the fish, the fish will hurt due to vibration during transportation. Although it is conceivable to reduce ice in order to avoid contact, it is not preferable because the heat retention effect is shortened. Therefore, a lid having an inner surface shape that does not easily contact the fish without reducing the amount of ice is desired.
[0012]
An object of the present invention is to provide a container that realizes an increase in internal volume or a reduction in height of a fish box without causing a reduction in the strength of the box, a manufacturing method that can be manufactured at a low cost, and a mold for the same. . Another object of the present invention is to provide a container lid that does not damage the packaged fish and does not cause a decrease in strength, a manufacturing method that can be manufactured at a low cost, and a molding die for the same.
[0013]
[Means for Solving the Problems]
The method for producing a foamed synthetic resin container according to the present invention includes a container-shaped molded body in which the bottom wall thickness of the box-shaped container is reduced by 20 to 40% of the side wall thickness of the container. without completely mold-closing the mold foam molding mold having a wall thickness equivalent to the above thin, large the gap is added to the cracking gap corresponding 6-10% of the wall thickness before thinning after filling the pre-onset foam beads state, the mold completely mold-closing and the pre-expanded beads were heated to melt foaming the molded containers shaped foam molded article, cooling the container-like foamed molded article After solidifying, the container-like foamed molded product is taken out from the mold. The present invention proposes a molding method in which the amount of trees used is the same as before, and the thickness of the bottom portion of the container is reduced, and the strength of the thinned portion is not reduced. The box-shaped container is, for example, a fish box.
[0014]
Moreover, the manufacturing method of the lid | cover for foam synthetic resin containers reduced the thickness of the ceiling part of the box-shaped container lid from the inner surface side of the ceiling part by the thickness of 20 to 40% of the side wall thickness of the container . Cracking corresponding to 6 to 10% of the thickness before thinning without completely closing the mold for foam molding in the mold having the molding space of the lid-shaped molded body. after filling the pre-onset foam beads while large the gap is added to the gap to mold the lid-like foamed molded completely mold-closing and the pre-expanded beads were heated to melt foaming the mold, the After the lid-like foamed molded product is cooled and solidified, the lid-shaped foamed molded product is taken out from the mold. The present invention proposes a molding method in which the amount of trees used is the same as before, and the thickness of the lid ceiling is reduced and the strength of the reduced thickness is not reduced.
[0016]
A molding die for a foamed synthetic resin container according to the present invention is a container-like molded body in which the bottom wall thickness of a box-shaped container is reduced by a thickness of 20 to 40% of the side wall thickness of the container. A mold for in-mold foam molding in which a core mold having a molding space and a cavity mold are paired, wherein the thickness corresponding to the reduced thickness corresponds to 6 to 10% of the thickness before the thickness reduction. In addition to this, a joining structure capable of closing the mold without obtaining pre-expanded beads in a state where the gap is enlarged is provided between the core mold outer peripheral surface and the cavity mold inner peripheral surface.
[0017]
Further, the molding die for the foamed synthetic resin container lid according to the present invention is such that the ceiling thickness of the box-shaped container lid is 20 to 40% of the wall thickness of the container. A mold for in-mold foam molding in which a core mold and a cavity mold having a molding space of a lid-shaped molded body thinned from the inner surface side are paired, and the thickness equivalent to the thinned thickness In addition to the cracking gap corresponding to 6 to 10% of the thickness, a joint structure is provided between the core mold outer peripheral surface and the cavity mold inner peripheral surface that allows the mold to be closed without obtaining pre-expanded beads in a state in which the gap is enlarged. It is characterized by that.
[0018]
The present invention proposes a dedicated mold for reducing the thickness of the bottom wall of the container or the thickness of the lid ceiling and preventing the strength of the thinned portion from being reduced. Here, in the case of a lid mold, a lid-shaped molded body that can prevent contact with fish is obtained by recessing the inner surface of the lid.
[0019]
The foamed synthetic resin container according to the present invention is manufactured according to the method for producing a foamed synthetic resin container of the present invention, and the bottom wall thickness of the box-shaped container is 20 to 40% of the side wall thickness of the container. amount corresponding to thinned a foamed synthetic resin container obtained by a large volume of or back Tayca, characterized by being lower than the resin expansion ratio of the side wall portion of the resin expansion ratio of the bottom of the vessel. Here, it is preferable that the bottom shape of the central longitudinal section of the container is a circular arc shape convex toward the inside of the container. This is because such a bottom shape can be expected to improve strength.
[0020]
Foamed synthetic resin lid for the container according to the present invention is produced according to the production method of the foamed synthetic resin lid for the container of the present invention, the ceiling portion thickness of the box-type container lid of, the sidewall thickness of the container 20 A foamed synthetic resin container lid thinned from the inner surface side of the ceiling by a thickness of ˜40% , wherein the resin foaming ratio of the ceiling of the container lid is fitted into the opening of the container It is characterized by being lower than the resin foaming ratio of the fitting portion of the container lid.
[0021]
By reducing the resin foaming ratio at the bottom of the container or the ceiling of the lid, the strength is ensured to be equivalent to the case where the amount of resin used at the location is not reduced. The portion corresponding to the thickness of the thinned bottom portion of the container can be reflected in at least one of an increase in the internal volume and a reduction in the height of the fish box. Moreover, contact with the fish can be prevented by recessing the inner surface of the lid.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described specifically and in detail, but the present invention is not construed as being limited to these descriptions. A case where the container is a fish box will be described.
[0023]
First, a mold for molding a foamed synthetic resin container will be described. The schematic block diagram which shows one form of the shaping | molding apparatus based on this embodiment in FIG. 1 was shown. Here, the mold is a molding mold having a molding space for a fish box (excluding the lid), and a schematic longitudinal sectional view is shown. That is, the part shown with the code | symbol 11 is a part used as the bottom part of the fish box which is a molded object, and the part shown with the code | symbol 12 is a part used as a side wall. As shown in FIG. 1, the molding apparatus according to this embodiment includes a mold 3 for in-mold foam molding in which a core mold 2 and a cavity mold 1 are paired, a joining structure 4, and a cavity mold 1 that moves the mold. Mold opening / closing means 5 for opening and closing the mold 3, a hopper 7 for storing and aging pre-expanded beads, a pre-expanded bead transport pipe 6 for air transporting the pre-expanded beads, and an air supply source for transport 8, an air pipe 9 connected to the air supply source 8, and a connection part 10 between the air pipe 9 and the pre-expanded bead carrier pipe 6.
[0024]
FIG. 2 shows a schematic longitudinal sectional view of the molding die portion in FIG. Here, (a) is a conventional mold, and (b) is a mold according to the present embodiment. The conventional mold is shaped so that the bottom and side walls of the resulting fish box have the same thickness (for example, 25 mm). On the other hand, the metal mold | die which concerns on this embodiment has modeled the core type | mold so that the bottom part thickness may be made thinner than the side wall thickness of a fish box. That is, the mold of (b) has a larger thickness in the depth direction of the fish box than the mold of (a), and the bottom wall thickness is increased by the thickness of the core mold in the mold of (b). Thinned. When using the mold (a), the cracking gap is usually about 2 mm. However, when the mold (b) is used, the gap is made larger by adding a portion corresponding to the reduced thickness to the normal cracking gap as described later. Therefore, in the mold of (b), a joining structure capable of closing the mold without leaking the pre-foamed beads in a state where the gap is enlarged by adding the thinned portion corresponding to the thickness to the normal cracking gap is provided on the outer peripheral surface of the core mold. And the cavity mold inner peripheral surface.
[0025]
When the mold 3 is filled with pre-expanded beads, the cavity mold 1 moves to change between a state in which a cracking gap is provided and a state in which the mold 3 is completely closed. The joint structure 4 is provided between the outer peripheral surface of the core mold 2 and the inner peripheral surface of the cavity mold 1 so that the filled pre-expanded beads are not leaked out of the molding space 13. Is moved by a distance corresponding to the distance between the outer peripheral surface of the core mold 2 and the inner peripheral surface of the cavity mold 1 while moving. Here, as shown in FIG. 3, an air gap 15 is provided in the joining structure 4 so that the air supplied when the pre-expanded beads are conveyed can be exhausted out of the mold. Since the mold of (b) has a larger cracking gap than the mold of (a) in FIG. 2, the joining structure 4 of (b) has a conventional mold that is at least as large as the cracking gap. Need to be longer. The joining structure 4 may be integrated with the core mold or may be joined separately.
[0026]
The outer surface side of the core mold 2 forms the inner wall surface of the fish box, and the inner surface of the cavity mold 1 forms the outer wall surface of the fish box. Near the surface of at least one of the core mold 2 and the cavity mold 1, a heating means (not shown) is provided for flowing the water vapor and heating the pre-expanded beads by the heat. The foam beads are heated to form a foam molded article. Further, a mold opening / closing means 5 is connected to the core mold 2 side so that the mold 3 can be opened and closed. Although the mold opening / closing means 5 is connected to the core mold 2 in FIG. 1, it may be connected to the cavity mold 1.
[0027]
Pre-foaming is performed so as to match the weight, strength, etc. of the product for molding the raw material beads impregnated with the foaming agent, and the pre-foamed beads foamed to the required foaming ratio are stored in the hopper 7. The expandable synthetic resin material particles used here include expandable polystyrene resin material particles or expandable polyethylene resin material particles, expandable polyolefin resin material particles such as expandable polypropylene resin material particles, and other expandable copolymers. Resin raw material particles can be used. In addition, raw material particles that are not pre-foamed can be used, but pre-foamed particles are preferably used. The expansion ratio of the raw material particles varies slightly depending on the resin material used, but is preferably in the range of 3 to 150 times. The expansion ratio is 3 to 100 times, preferably 3 to 65 times for expandable polystyrene resin material particles, and 3 to 60 times, preferably 3 to 45 times for expandable polyolefin resin material particles. Can be suitably used. Moreover, although a particle size changes a little also with the resin raw material to be used, the thing within the range of 1-10 mm can be utilized suitably. The pre-expanded bead conveyance pipe 6 is a pipe for air-conveying the pre-expanded beads stored in the hopper 7 to the molding space 13 of the mold 3. The carrier air generated from the air supply source 8 is introduced into the pre-expanded bead carrier pipe 6 at the connection portion 10 through the air pipe 9.
[0028]
Next, a molding method using the mold according to the present embodiment will be described with reference to FIGS. Here, the description will be made in comparison with the case where a conventional mold is used. As the molding apparatus, the molding apparatus shown in FIG. 1 is used. For ease of understanding, an example of a dimension such as a cracking gap will be described, but it goes without saying that the present invention is not limited to this dimension. In FIGS. 4 to 6, (a) shows a case where a conventional mold is used, and (b) shows a case where a mold according to an embodiment of the present invention is used.
[0029]
FIG. 4 is a diagram showing a pre-expanded bead filling process. Pre-expanded beads are sent from the hopper by air conveyance and filled into the molding space. In both (a) and (b), the thickness corresponding to the side wall of the molding space is 25 mm. The same thickness of 25 mm is obtained for the side wall of the molded body. By the way, in (a), the cracking gap is 2 mm, and the thickness corresponding to the bottom of the molding space is 27 mm. When the mold is completely modeled, as shown in FIG. 2, the thickness corresponding to the bottom of the molding space is designed to be 25 mm, so the thickness corresponding to the cracking gap is added. It becomes. In the in-mold foam molding method, a cracking gap of about 6 to 10% of the thickness is provided. In the conventional example of (a), the cracking gap is 8% with respect to the thickness of the bottom. On the other hand, in (b), the cracking gap is 7 mm, and the thickness corresponding to the bottom of the molding space is 27 mm as in (a). The reason why it is 27 mm, which is the same as (a), is because the thickness corresponding to the bottom of the molding space is designed to be 20 mm as shown in FIG. In this embodiment, the cracking gap is set to 35% with respect to the thickness of the bottom, but it is preferable that the cracking gap is set to 20 to 40% with respect to the thickness of the bottom from the viewpoint of maintaining the strength. (A) (b) Since the thickness of the bottom space is 27 mm when the cracking gap is provided, the same amount of pre-expanded beads is filled in the portion corresponding to the bottom of the molding space. Note that the carrier air supplied together with the pre-expanded beads in the molding space is exhausted out of the mold through an air gap provided in the joining structure.
[0030]
FIG. 5 is a view showing a state in which the mold is completely closed after filling with the pre-expanded beads. In both (a) and (b), the pre-expanded beads in the portion corresponding to the side wall of the molding space are hardly subjected to compression pressure. However, the pre-expanded beads at the location corresponding to the bottom of the molding space are subjected to compression pressure. In the case of (a), it is compressed to 92.6% by volume conversion by completely closing the mold, and in the case of (b), it is also compressed to 74.1%. When the mold is completely closed, excess air in the molding space is exhausted out of the mold through an air gap provided in the joining structure. If the height of the side wall of the container is 160 mm, the compression of the side wall in the case of (a) is 98.8%, and the compression of the side wall in the case of (b) is 95.8%, about 3%. There is only a difference.
[0031]
FIG. 6 is a diagram showing a heating process in which pre-expanded beads are heated and melt-foamed to form a foamed molded article. Water vapor is passed through heating means (not shown) provided near at least one of the outer surface of the core mold and the inner surface of the cavity mold, and the pre-expanded beads are heated by the heat. By this heating, foaming of the pre-expanded beads and fusion of the beads occur, and a molded body formed in the molding space of the mold is obtained.
[0032]
Through the heating process, the foamed molded body is cooled and solidified (cooling process), and the foamed molded body is taken out from the mold (mold releasing process).
[0033]
The above description has been given for a fish box, but the lid of a fish box can also be molded using a mold for in-mold foam molding in which a core mold for a lid and a cavity mold are paired. I can do it. In this case, a mold that is shaped so that the thickness of the lid ceiling part is reduced from the inside of the ceiling part is used. In particular, the inner surface shape of the lid is preferably a concave shape of, for example, 5 mm so that the inner volume when the lid is closed increases. By making the concave shape, contact between the fish and the inner surface of the ceiling can be prevented. Further, as in the case of the fish box, the pre-expanded beads are filled in such a manner that the thickness corresponding to the thickness reduced in the filling step is added to the cracking gap to increase the gap. The thinned portion corresponding to the thickness is preferably 20 to 40% of the side wall thickness of the container. As a result, as shown in FIGS. 7B and 7C, a lid having a more concave shape compared to (a) is formed.
[0034]
Thus, a fish box and its lid were obtained as a foamed synthetic resin container. FIG. 7 shows a longitudinal sectional view when the lid of the fish box obtained is attached. (A) is a conventional example, (b) is the same as the conventional fish box with the same outer size as the conventional fish box, and (c) is the same as the conventional example and the height is increased. The case where the height is lowered by lowering is shown. In addition, although a lid of a conventional shape may be used as the lid, it is preferable to reduce the thickness of the ceiling of the lid from the inside of the ceiling as shown in (b) and (c). Will not be damaged by vibration during transportation.
[0035]
In (a), under the conditions that the expansion ratio of the fish box and its lid is about 60% in any part, in the case of (b) and (c), the expansion ratio of the side wall portion 22 is about 60%. The bottom 21 of the box and the ceiling 20 of the lid were about 50%. This is because the bottom of the fish box and the ceiling of the lid were filled with the same amount of pre-expanded beads as in (a) and the thickness was reduced by 5 mm. The expansion ratio of polystyrene is 1.05 g / cm ³ and can be calculated by measuring the density of expanded polystyrene and comparing them.
[0036]
FIG. 8 shows a schematic diagram of the inner surface of the same lid as in FIGS. 7B and 7C. The width 30 of the fitting portion 23 of the container lid that fits into the opening of the container is equal to the thickness 22 of the side wall of the container. At this time, the resin foaming ratio of the ceiling portion 20 of the container lid is about 50%, and the resin of the fitting portion 23 (portion shown in gray in FIG. 8) of the container lid that fits into the opening of the container. The expansion ratio is 60%, and the resin expansion ratio of the ceiling portion 20 is lower than the resin expansion ratio of the fitting portion 23.
[0037]
Thus, in this embodiment, the fish box has a thin bottom wall, and the resin foaming ratio at the bottom of the fish box is lower than the resin foaming ratio at the side wall. Further, the lid has a thinner wall thickness at the ceiling, and the resin foaming ratio of the ceiling part is lower than the resin foaming ratio of the fitting part fitted to the side wall part of the container. When the expansion ratio is changed from 60% to 50%, the heat insulating effect is improved and the cooling time can be extended.
[0038]
As for the strength, it was molded with the same amount of resin as the conventional one, so the strength almost equal to the conventional one was obtained.
[0039]
In this embodiment, as shown in FIGS. 9-11, it is preferable to make the bottom part shape of the center longitudinal cross-section of a fish box into the circular arc shape convex to the container inner side. By making the center of the bottom part a curved surface that is convex toward the inside of the container, the strength of the bottom part can be improved, and the possibility that the bottom will come out is reduced even if a heavy object is placed in the container. Moreover, in the fish box in this embodiment, although the drain hole 31 is provided in order to drain the water generated when ice melts, by making the bottom part shape of the central longitudinal section of the fish box into a circular arc shape that protrudes inside the container. The dissolved water is efficiently guided to the drain hole and can be drained.
[0040]
【The invention's effect】
According to the present invention, the inner volume can be increased without changing the outer size of the fish box, so that the amount of ice packed together with the fish can be increased, and as a result, the cooling effect can be prolonged. Can do. As a result, it is possible to cope with the long distance of transportation. Or since the height of the fish box can be reduced without changing the internal volume, more fish boxes can be loaded at the same height during transportation. In the present invention, the above items can be realized while maintaining the strength of the bottom of the fish box. At this time, it is not necessary to increase the amount of resin. Strength can be ensured more by making the bottom part shape of the central longitudinal section of the container into a circular arc shape convex toward the inside of the container.
[0041]
In addition, the lid of the present invention has an inner surface shape that is difficult to contact with fish without reducing the amount of ice by thinning in the same way, so that the inner surface of the lid contacts the fish and the fish may be damaged by vibration during transportation. Absent. Does not reduce the amount of ice, so it does not shorten the heat insulation effect.
[0042]
The present invention provides an inexpensive manufacturing method and a molding die for molding a fish box having the above characteristics and its lid without increasing the internal volume or reducing the height of the fish box without lowering the strength. I can do it.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of a molding apparatus according to the present embodiment.
2 is a schematic longitudinal sectional view of a molding die portion in FIG. 1. FIG. 2 (a) is a schematic view of a conventional mold, and FIG. 2 (b) is a schematic view of a mold according to the present embodiment. .
FIG. 3 is an enlarged schematic view of a portion indicated by reference numeral 14 in FIG.
FIGS. 4A and 4B are diagrams showing a pre-expanded bead filling process, where FIG. 4A shows a conventional example, and FIG. 4B shows this embodiment.
FIGS. 5A and 5B are diagrams showing a state in which the mold is completely closed after filling with pre-expanded beads, in which FIG. 5A shows a conventional example, and FIG. 5B shows the present embodiment.
FIGS. 6A and 6B are diagrams illustrating a heating process in which pre-expanded beads are heated and melt-foamed to form a foamed molded article, where FIG. 6A shows a conventional example and FIG. 6B shows the present embodiment.
is there.
FIGS. 7A and 7B are schematic longitudinal sectional views of a fish box with a lid according to the present embodiment, in which FIG. 7A is a conventional example, and FIG. (C) shows an example in which the inner volume is the same as that of the conventional example and the height is lowered to reduce the height.
FIG. 8 is a schematic view showing one form of the inner surface of the same lid as in FIGS. 7B and 7C.
FIG. 9 is a schematic view of the inside of the fish box according to the present embodiment as viewed from the opening side.
10 is a schematic view of an AA ′ cross section taken along the line XY of FIG. 9. FIG.
11 is a schematic view of a BB ′ cross section taken along the line XY of FIG. 9;
[Explanation of symbols]
1, cavity mold 2, core mold 3, mold 4, joining structure 5, mold opening / closing means 6, pre-foamed bead transport pipe 7, hopper 8, air supply source 9, air pipe 10, connection portion 13, molding space 15 , Air gap 20, ceiling portion 21, container bottom portion 22, side wall portion 23, container lid fitting portion 31, drainage hole

Claims

The mold for in-mold foam molding having a molding space of a container-shaped molded body in which the bottom wall thickness of the box-shaped container is thinned by 20 to 40% of the side wall thickness of the container is completely closed. without, the thickness equivalent to the above thinned, after filling the pre-onset foam beads while large the gap is added to the cracking gap corresponding 6-10% of the wall thickness before thinning, the gold After the mold is completely closed, the pre-expanded beads are heated and melt-foamed to form a container-shaped foam molded body, and the container-shaped foam molded body is cooled and solidified. A method for producing a foamed synthetic resin container, wherein the container is removed from a mold.

The method for manufacturing a foamed synthetic resin container according to claim 1, wherein the box-shaped container is a fish box.

For in -mold foam molding having a molding space for a lid-shaped molded body in which the thickness of the ceiling portion of the box-shaped container lid is reduced from the inner surface side of the ceiling portion by the thickness of 20 to 40% of the side wall thickness of the container . without completely mold-closing the mold, pre-onset foam beads in a state where the thickness equivalent to the above thinned and increased the gap in addition to the cracking gap corresponding 6-10% of the wall thickness before thinning Then, the mold is completely closed, the pre-expanded beads are heated and melt-foamed to form a lid-like foam molded body, and the lid-like foam molded body is cooled and solidified, and then the lid A method for producing a foamed synthetic resin container lid, wherein the foamed molded article is removed from the mold.

In -mold foaming with a core mold and a cavity mold having a molding space of a container-shaped molded body in which the bottom wall thickness of the box-shaped container is thinned by 20 to 40% of the side wall thickness of the container. a mold, the thickness equivalent to the above thinned, without leaking prefoamed beads in a state with a larger the gap in addition to the cracking gap corresponding 6-10% of the wall thickness before thinning A mold for molding a foamed synthetic resin container, characterized in that a joint structure capable of closing the mold is provided between the core mold outer peripheral surface and the cavity mold inner peripheral surface.

A core mold and a cavity mold having a molding space for a lid-shaped molded body in which the thickness of the ceiling of the box-shaped container lid is reduced from the inner side of the ceiling by the thickness of 20 to 40% of the wall thickness of the container. In a mold for in-mold foam molding, a portion corresponding to the thinned thickness is added to a cracking gap corresponding to 6 to 10% of the thickness before thinning, and the gap is enlarged. A molding die for a foamed synthetic resin container lid, wherein a joining structure capable of closing the mold without receiving pre-expanded beads is provided between the outer peripheral surface of the core mold and the inner peripheral surface of the cavity mold.

It is manufactured according to the method for manufacturing a foamed synthetic resin container according to claim 1 or 2, and the bottom wall thickness of the box-shaped container is reduced by a thickness of 20 to 40% of the side wall thickness of the container to increase the volume. A foamed synthetic resin container, wherein the resin foaming ratio at the bottom of the container is lower than the resin foaming ratio at the side wall.

The foamed synthetic resin container according to claim 6, wherein the bottom shape of the central longitudinal section of the container is a circular arc shape convex toward the inside of the container.

It is manufactured in accordance with the method for manufacturing a foamed synthetic resin container lid according to claim 3, and the ceiling thickness of the box-shaped container lid is 20 to 40% of the thickness of the side wall of the container. A foamed synthetic resin container lid thinned from the side, wherein the resin foaming ratio of the ceiling part of the container lid is the resin foaming ratio of the fitting part of the container lid fitted to the opening of the container A lid for a foamed synthetic resin container characterized by being lower than the above.