JP4484175B2 - Method for producing multilayer polyethylene-based resin foam molding - Google Patents

Method for producing multilayer polyethylene-based resin foam molding Download PDF

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JP4484175B2
JP4484175B2 JP36755899A JP36755899A JP4484175B2 JP 4484175 B2 JP4484175 B2 JP 4484175B2 JP 36755899 A JP36755899 A JP 36755899A JP 36755899 A JP36755899 A JP 36755899A JP 4484175 B2 JP4484175 B2 JP 4484175B2
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resin
layer
foam
parison
multilayer parison
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JP2001179805A (en
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直親 小暮
誠治 高橋
広行 極楽
大典 今成
卓 北浜
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JSP Corp
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JSP Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/30—Extrusion nozzles or dies
    • B29C48/32—Extrusion nozzles or dies with annular openings, e.g. for forming tubular articles
    • B29C48/335—Multiple annular extrusion nozzles in coaxial arrangement, e.g. for making multi-layered tubular articles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/001—Combinations of extrusion moulding with other shaping operations
    • B29C48/0011—Combinations of extrusion moulding with other shaping operations combined with compression moulding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/09—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/09—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
    • B29C48/10—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels flexible, e.g. blown foils

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a foamed multi-layer polyethylene resin molding which does not need a complex process. SOLUTION: By coextruding a molten expandable resin by melt-kneading a base material resin having a specified storage modulus of elasticity which is a polyethylene resin of 900-940 kg/m3 density and a molten synthetic resin obtained by melting a synthetic resin having a specified melt flow rate, a multi- layer parison 6 having a polyethylene resin layer 3 comprising the molten synthetic resin at least on the outer surface of a foamed polyethylene resin layer 2 is formed. Next, the parison 6 is molded in a molding mold so that at least part of each innermost surface of the parison is fused.

Description

【０００１】
【発明の属する技術分野】
本発明は、ポリエチレン系樹脂層を表皮とし内部にポリエチレン系樹脂発泡層を備える多層ポリエチレン系樹脂発泡成形体に関し、具体的には、床やドア等の軽量断熱パネル、パレット、容器、自動車部材等に用いられる多層ポリエチレン系樹脂発泡成形体に関する。
【０００２】
【従来の技術】
従来から、樹脂発泡層の表面に熱可塑性樹脂層が形成された、種々の形状の多層樹脂発泡成形体が知られている。このような発泡層の表面にソリッド層が形成された構造の多層樹脂発泡成形体は、洗浄可能なリターナブル容器として使用可能であることから、使い捨ての発泡スチロール製魚箱の代替品として従来から使用されてきたが、近年のごみ問題の重要性に鑑み今後は更なる需要が期待されている。
【０００３】
又、上記構造の多層樹脂発泡成形体の魚箱は、冷凍倉庫等の低温雰囲気で使用されることが多く、耐低温衝撃性が多層樹脂発泡成形体の重要な特性として要求される。かかる観点からはポリスチレン系樹脂やポリプロピレン系樹脂を用いた容器は低温での耐衝撃性が不充分であって、低温での使用に適したポリエチレン系樹脂を用いて多層樹脂発泡成形体を製造することが求められている。
【０００４】
【発明が解決しようとする課題】
かかる多層樹脂発泡成形体の製造方法としては、例えば、熱可塑性樹脂にて中空構造の成形体を成形し、その成形体内部の空洞部に、ウレタン樹脂を注入する方法や樹脂発泡粒子などを充填成形する方法が知られている（特公昭５８−１０２１７号公報、特開平６−３３９９７９号公報等）。しかしながら、これらの方法は、表面の樹脂層の成形と内部の発泡層との形成が別工程になるので成形工程が複雑になるという問題や、特殊な成形機を必要としたりするという問題があった。その結果、成形体内部にウレタン樹脂を注入する方法や樹脂発泡粒子などを充填成形する方法では、安価な多層樹脂発泡成形体を提供するのは困難であった。
【０００５】
上記工程上の問題や価格上の問題を解決する方法として、樹脂発泡層の表面に熱可塑性樹脂層を有する中空の多層パリソンを金型で圧縮しながら成形し、該パリソンの対向する内面を融着させた多層樹脂発泡成形体を得る方法が提案されている（特公昭６２−２７９７８号公報、特開平６−３１２４４９号公報等）。
【０００６】
しかしながら、上記の金型で多層パリソンを圧縮しながら成形する方法（特開平６−３１２４４９号公報等）を採用して、密度４００ｋｇ／ｍ3以下という低密度でしかも厚みのあるポリエチレン系樹脂発泡層の表面にポリエチレン系樹脂層を有する多層樹脂発泡成形体を製造しようとすると、発泡層を構成している気泡の破泡や連泡化、発泡層の収縮が起こり易いなどの現象が発生し、低密度で厚みのあるポリエチレン系樹脂発泡層を有する多層樹脂発泡成形体を得ることが困難であった。
【０００７】
本発明は、上記従来技術の欠点に鑑み、発泡層表面の樹脂層となる成形体を製造後、その中に発泡体を注入する等という複雑な工程が不要な多層ポリエチレン系樹脂発泡成形体の製造方法であって、しかも外観が奇麗であり、軽量性、機械的強度、断熱性、緩衝性、防音性、防振性、耐薬品性、リサイクル性、低温衝撃性等にも優れた多層ポリエチレン系樹脂発泡成形体の製造方法を提供することを目的とする。
【０００８】
【課題を解決するための手段】
即ち本発明の多層ポリエチレン系樹脂発泡成形体の製造方法は、主成分が密度９００〜９４０（ｋｇ／ｍ３）のポリエチレン系樹脂であると共に、１９０℃の温度条件下で振動歪みを与える動的粘弾性測定において角周波数ω＝１０−１〜１０１（ｒａｄ／ｓｅｃ）の範囲における貯蔵弾性率Ｇ'（Ｐａ）が下記（１）式を満足する基材樹脂に、物理発泡剤を添加し溶融混練して得られる発泡性溶融樹脂と、２０〜１００重量％のポリエチレン系樹脂を含む合成樹脂であると共に、該合成樹脂のメルトフローレイト：ＭＦＲ１（ｇ／１０分）と上記基材樹脂のメルトフローレイトＭＦＲ２（ｇ／１０分）との比が下記（２）式を満足する合成樹脂を、溶融して得られる溶融合成樹脂とを、共押出することにより、上記発泡性溶融樹脂よりなるポリエチレン系樹脂発泡層の少なくとも外面に上記溶融合成樹脂よりなるポリエチレン系樹脂層を有する多層パリソンを形成し、次いで該パリソン最内面同士の少なくとも一部が融着するように成形型にて成形することによって密度２５〜４００ｋｇ／ｍ ３ のポリエチレン系樹脂発泡層の表面に厚み１００μｍ〜１０ｍｍのポリエチレン系樹脂層を有する発泡成形体を得ることを特徴とする。
【０００９】
【数５】
logＧ'＝αlogω＋β （１）
α＝０．５０〜１．５０
β＝２．０〜５．０
【００１０】
【数６】
ＭＦＲ１／ＭＦＲ２＞１．０ （２）
【００１１】
上記基材樹脂の貯蔵弾性率Ｇ'（Ｐａ）は下記（３）式を満足することが好ましい。
【００１２】
【数７】
logＧ'＝αlogω＋β （３）
α＝０．６０〜１．４０
β＝２．０〜３．８
【００１４】
【発明の実施の形態】
本発明の方法によって得られる多層ポリエチレン系樹脂発泡成形体（以下、「発泡成形体」という。）の具体例を図１に示す。
図１（ａ）に示す発泡成形体は、ポリエチレン系樹脂発泡層の全表面がポリエチレン系樹脂層で覆われた構成を有する。図１（ａ）において、１は発泡成形体を、１２は発泡成形体のポリエチレン系樹脂発泡層（以下、「発泡成形体の発泡層」という。）を、１３は発泡成形体のポリエチレン系樹脂層（以下、「発泡成形体の樹脂層」という。）をそれぞれ示す。
【００１５】
図１（ｂ）に示す発泡成形体１は、図１（ａ）に示す発泡成形体１の表面が更に重合体層で覆われた構成を有する。図１（ｂ）において、１４は発泡成形体１の樹脂層１３の外面に設けられた重合体層（以下、「発泡成形体の重合体層」という。）を示す。
【００１６】
図１（ｃ）に示す発泡成形体１は、ポリエチレン系樹脂の芯層が図１（ａ）に示す発泡成形体１の発泡層１２の中に挟まれている構成を有する。図１（ｃ）において、１５はポリエチレン系樹脂の芯層（以下、「発泡成形体の芯層」という。）を示す。
【００１７】
本発明の製造方法が目的とする上記発泡成形体１は、多層パリソンを金型などの成形型に挟み込んで圧縮成形することで得られる。本発明において多層パリソンとは、吹き込み成形で金型に挟んで成形されるものと同じ又は類似の機能を発揮できるものである。
【００１８】
本発明の製造方法においては、後述する基材樹脂に、発泡剤を添加し溶融混練して得られる発泡性溶融樹脂と、後述する合成樹脂を溶融混練して得られる溶融合成樹脂とを例えば筒状に共押出することにより、上記多層パリソンが形成される。
【００１９】
図２に多層パリソンの一例を示す。図１（ａ）に示す発泡成形体１は図２（ａ）に示す多層パリソンから、図１（ｂ）に示す発泡成形体１は図２（ｂ）に示す多層パリソンから、図１（ｃ）に示す発泡成形体１は図２（ｃ）に示す多層パリソンから、それぞれ後述する方法によってよって得られる。
【００２０】
図２（ａ）の多層パリソンは、ポリエチレン系樹脂の発泡層の外面に、ポリエチレン系樹脂の樹脂層が積層された構成を有する。図２（ａ）において、６は多層パリソンを、２はポリエチレン系樹脂の発泡層（以下、「多層パリソンの発泡層」という。）を、３はポリエチレン系樹脂の樹脂層（以下、「多層パリソンの樹脂層」という。）をそれぞれ示す。
【００２１】
図２（ｂ）に示す多層パリソン６は、図２（ａ）に示す多層パリソンの樹脂層３の表面に重合体層が積層された構成を有する。図２（ｂ）において、４は多層パリソン６の重合体層（以下、「多層パリソンの重合体層」という。）を示し、該多層パリソンの重合体層４は後述するようにポリオレフィン系樹脂等からなり、必要に応じて設けられる。
【００２２】
図２（ｃ）に示す多層パリソン６は、図２（ａ）に示す多層パリソン６の内面にポリエチレン系樹脂の樹脂層が積層された構成を有する。図２（ｃ）において、５は多層パリソンの内面に設けられた内面の樹脂層（以下、「多層パリソンの内面樹脂層」という。）を示し、該多層パリソンの内面樹脂層５は必要に応じて設けられる。
【００２３】
上記多層パリソンの発泡層２は図１（ａ）（ｂ）（ｃ）に示す発泡成形体の発泡層１２に対応し、上記、多層パリソンの樹脂層３は図１（ａ）（ｂ）（ｃ）に示す発泡成形体の樹脂層１３に対応し、図２（ｂ）に示す多層パリソンの重合体層４は図１（ｂ）に示す発泡成形体の重合体層１４に対応する。
又、図２（ｃ）に示す多層パリソンの内面樹脂層５は図１(ｃ)に示す発泡成形体の芯層１５に対応し、発泡成形体の芯層１５は、多層パリソンの内面樹脂層５の内面同士の少なくとも一部が融着したものである。
【００２４】
上記多層パリソン６は、多層パリソンの発泡層２を構成するポリエチレン系樹脂に発泡剤を添加して押出機内で溶融混練して調製した発泡性溶融樹脂と、多層パリソンの樹脂層３を構成するポリエチレン系樹脂を別の押出機内で溶融して調製した溶融樹脂（或いは更に多層パリソンの重合体層４や内面樹脂層５を構成する重合体やポリエチレン系樹脂を更に別の押出機内等で溶融して調製したもの）とを、▲１▼共押出用のダイ内にて合流積層させ、該ダイから低圧域に共押出して発泡性樹脂を発泡させる方法、又は▲２▼ダイ内で合流積層することなく、各溶融樹脂ごとに出口が設けられたダイから各溶融樹脂を低圧域に押出した後、好ましくは直後に発泡層２を形成する発泡樹脂と、樹脂層３等を形成する樹脂とを積層する共押出方法により得ることができる。
【００２５】
上記多層パリソンの発泡層２を構成する基材樹脂（以下、「基材樹脂（Ａ）」という）、即ち発泡成形体の発泡層１２を構成する基材樹脂の主成分（５０重量％以上の成分）は、樹脂密度が９００〜９４０ｋｇ／ｍ3のポリエチレン系樹脂である。該樹脂密度は９１０〜９３０ｋｇ／ｍ3であることが好ましい。樹脂密度が９００ｋｇ／ｍ3未満であると結晶化度が低すぎることから、発泡成形体１の強度が低くなる虞がある。密度が９４０ｋｇ／ｍ3を超えると結晶化度が高くなりすぎて、発泡が困難となる虞がある。
【００２６】
上記多層パリソンの発泡層２を構成する基材樹脂（Ａ）は、１９０℃の温度条件下で振動歪みを与える動的粘弾性測定において、角周波数ω＝１０-1〜１０1(ｒａｄ／ｓｅｃ)の範囲における貯蔵弾性率Ｇ'（Ｐａ)が下記（１）式を満足する。
【００２７】
【数９】
logＧ'＝αlogω＋β ‥‥（１）
α＝０．５０〜１．５０
β＝２．０〜５．０
上記（１）式を満足しない基材樹脂を使用すると、高発泡倍率、高厚みの多層パリソンの発泡層２を得ることができず、ひいては高発泡倍率、高厚みの発泡成形体の発泡層１２を有する発泡成形体１を得ることができない。また、更に好ましい基材樹脂（Ａ）は下記（３）式を満足する樹脂であり、（３）式を満足する基材樹脂を使用すると更に高発泡倍率、高厚みのものを得ることができる。
【００２８】
【数１０】
logＧ'＝αlogω＋β ‥‥（３）
α＝０．６〜１．４
β＝２．０〜３．８
【００２９】
上記α及びβは、動的粘弾性測定機（レオメトリックス・サイエンティフィック・エフ・イー社製のダイナミックアナライザーＳＲ２００型）により測定することができる。α及びβは測定用サンプル樹脂板を１９０℃に温度を保持した状態で、線形領域内において角周波数：ωを変化させて動的粘弾性測定を行って得た貯蔵弾性率Ｇ'の対数値を縦軸に、Ｇ'に対応するωの対数値を横軸にプロットした結果により求めることができる。
【００３０】
本明細書における動的粘弾性の測定は、ヒートプレスにより温度２００℃、圧力８０００ｋＰａの条件下で５分間プレス成形することにより得た厚さ２ｍｍの測定用サンプル樹脂板から直径２５ｍｍの円盤サンプルを調製し、このサンプルを動的粘弾性測定機の直径２５ｍｍのパラレルプレート間に挟んで１９０℃に昇温し、約１０分間放置した後、始点の角周波数を１０ｒａｄ／ｓｅｃ、終点の角周波数を１０−１ｒａｄ／ｓｅｃ、５ポイント／ｄｅｃａｄｅ、線径領域内（応力１×１０３Ｐａ）の条件下ωを変化させてωに対応するＧ'の測定を行なうものとする。
【００３１】
本明細書におけるα及びβは、上記のようにして求めたωの値と、そのωに対応するＧ'の値を基に、べき乗回帰計算により、回帰式
logＧ'＝αlogω＋β ・・・・（５）
のα（傾き値）及びβ（切片）として求められる。
【００３２】
上記αが０．５０未満の場合は上記βの値が大きくなる傾向にあり、発泡時の弾性力が大きくなり易く、高倍率の発泡層２を得ることが困難となる虞がある。また、ダイ内における発熱も大きくなって、発泡条件の調整が難しくなる虞がある。一方、αが１．５０を超える場合は、気泡を維持する力が低いため発泡倍率が高く、厚みが厚い良好な発泡層２を得ることができない。また、発泡層２のドローダウンが大きくなるので、大型の発泡成形体を得るには特殊な装置が必要となる。
上記βが２．０未満の場合は、発泡層２を構成している樹脂の歪みに対して抵抗する樹脂の弾性力が小さくなるので破泡が起きやすくなり、高倍率、高厚みの発泡層２を得ることができない。逆にβが５．０を超える場合は、樹脂の弾性力が大きすぎて抵抗力が強くなって高倍率の発泡層２を得ることができない。
【００３３】
上記多層パリソンの樹脂層３、即ち発泡成形体の樹脂層１３は非発泡体あるいは密度４００ｋｇ／ｍ3以上の発泡体又は無機物充填非発泡体として構成することが好ましい。該多層パリソンの樹脂層３（以下、「合成樹脂（Ｂ）」という。）は、２０〜１００重量％のポリエチレン系樹脂を含む合成樹脂によって形成される。ポリエチレン系樹脂の配合が２０重量％未満の場合は、樹脂層３と発泡層２との接着性が不充分となる場合がある。また、他の重合体成分が多く含まれることになるので、リサイクル性の面で好ましくない。
尚、合成樹脂(Ｂ)に含有させ得るポリエチレン系樹脂以外の成分としては、ポリプロピレン系樹脂、ポリエステル系樹脂、熱可塑性エラストマー、ゴム等が挙げられる。
【００３４】
多層パリソンの樹脂層３を構成する合成樹脂（Ｂ）は、合成樹脂（Ｂ）のメルトフローレイト：ＭＦＲ１（ｇ／１０分）と上記基材樹脂（Ａ）のメルトフローレイト：ＭＦＲ２（ｇ／１０分）との比が下記（２）式を満足する樹脂である。
【００３５】
【数１１】
ＭＦＲ１／ＭＦＲ２＞１．０ （２）
【００３６】
上記メルトフローレイト比が小さすぎる場合は、多層パリソンの樹脂層３の流れが多層パリソンの発泡層２よりも極端に悪くなるので、ダイにおける押出温度を高くして多層パリソンの樹脂層３の流れを良くしなければならない。これに対し、多層パリソンの樹脂層３が積層される多層パリソンの発泡層２は発泡に適正な粘度になるまでダイにおける押出温度を下げる必要性があるため、結局、多層パリソンの樹脂層３の熱により多層パリソンの発泡層２の気泡構造が破壊され、高厚み、高倍率の発泡層２を得ることができなくなる。
尚、ＭＦＲ１／ＭＦＲ２の値が大きすぎる場合、樹脂層３の厚みむら、多層パリソン６のドローダウンが大きくなる虞がある。ＭＦＲ１／ＭＦＲ２の上限値は２０以下であることが好ましい。
【００３７】
本発明において多層パリソンの発泡層２、多層パリソンの内面樹脂層５、及び多層パリソンの樹脂層３を構成するポリエチレン系樹脂は、エチレンの単独重合体、エチレンと炭素数が３〜１２個のα−オレフィンとの重合体等が６０重量％以上含有されているものであって、具体的には、高密度ポリエチレン、中密度ポリエチレン、低密度ポリエチレン、直鎖状低密度ポリエチレン、超低密度ポリエチレン、エチレン−酢酸ビニル共重合体、エチレン−アクリル酸共重合体、エチレン−アクリル酸メチル共重合体、エチレン−アクリル酸エチル共重合体、エチレン−メタクリル酸共重合体、エチレン−メタクリル酸メチル共重合体、エチレン−メタクリル酸エチル共重合体、エチレン−無水マレイン酸共重合体、エチレン−スチレン共重合体、エチレン−ブテン共重合体、エチレン−ビニルアルコール、エチレン−グリシジルメタクリレート、エチレン−メタクリル酸共重合体やエチレン−アクリル酸共重合体などのアイオノマー等が挙げられる。
【００３８】
また、上記ポリエチレン系樹脂は、単独で用いるのみならず、２種以上を混合することによって多層パリソンの発泡層２等を構成することもできる。更に、基材樹脂（Ａ）には、ポリエチレン本来の特性、発泡性が損なわれない範囲で、スチレン系樹脂、環状ポリオレフィン、ポリプロピレンなどのオレフィン系樹脂、スチレン系エラストマー、オレフィン系エラストマー等の熱可塑性エラストマー等の他の重合体成分を必要に応じて混合しても良い。ポリエチレン系樹脂に他の樹脂成分を混合して基材樹脂（Ａ）を調製する場合には、好ましくは７０重量％以上、更に好ましくは８０重量％以上の割合でポリエチレン系樹脂が含まれるようにする。
【００３９】
本発明におけるメルトフローレイト：ＭＦＲ（ｇ／１０分）は、ＪＩＳ Ｋ７２１０に記載されている１９０℃、荷重２１．１８Ｎで測定した値を採用するものとする。
【００４０】
動的粘弾性測定における上記（１）式を満足する基材樹脂（Ａ）は、主成分としてのポリエチレン系樹脂として分岐鎖を有するポリエチレン系樹脂を用い、該樹脂の分岐鎖の長さ、主鎖に対する分岐鎖の長さの割合、分子量、分子量分布等を調製することにより得ることができる。該ポリエチレン系樹脂としては、例えば、日本ユニカー社製のＮＵＣ８００８、ＮＵＣ８１６０、ＮＵＣ８００９などの原料が挙げられる。
【００４１】
メルトフローレイト比が上記（２）式で示す関係を有する合成樹脂（Ｂ）は、配合するポリエチレン系樹脂の分子量、分子量分布、滑剤の種類及び添加量等を調製することにより得ることができる。
【００４２】
多層パリソンの発泡層２を形成するために基材樹脂（Ａ）に添加される発泡剤としては、物理発泡剤、分解型発泡剤のいずれも使用可能であるが、発泡倍率の高い発泡層を得るには物理発泡剤を使用する。物理発泡剤としては例えば、プロパン、ノルマルブタン、イソブタン、ノルマルペンタン、イソペンタン、ノルマルヘキサン、イソヘキサン、シクロヘキサン等の脂肪族炭化水素、塩化メチル、塩化エチル等の塩化炭化水素、1,1,1,2-テトラフロロエタン、1,1-ジフロロエタン、ジフロロメタン等のフッ化炭化水素、二酸化炭素、窒素、水、メチルアルコール、エチルアルコール等が挙げられる。分解型発泡剤としては、アゾジカルボンアミド等が挙げられる。上記した発泡剤は、２種以上混合して使用することができ、又、気泡の調整も兼ねて分解型発泡剤を物理発泡剤に添加することもできる。
【００４３】
発泡成形体の樹脂層１３の外面に更に発泡成形体の重合体層１４を有する発泡成形体１を得る際に、多層パリソンの重合体層４を構成するために用いられる熱可塑性重合体としては例えば、低密度ポリエチレン、高密度ポリエチレン、直鎖状低密度ポリエチレン等のポリエチレン系樹脂、ポリプロピレン、プロピレン−エチレンランダム共重合体、プロピレン−1ブテンランダム共重合体、プロピレン−エチレンブロック共重合体、プロピレン−1ブテンブロック共重合体等のポリプロピレン系樹脂、環状ポリオレフィン、ポリカーボネート系樹脂、ポリエステル系樹脂、スチレン系エラストマー、オレフィン系エラストマー、ポリエステル系エラストマー等から選択される一種又は二種以上の混合物等の熱可塑性重合体が挙げられる。尚、これらの樹脂のうちで、多層パリソンの樹脂層３を構成する樹脂と実用的に十分な熱接着性を有さない熱可塑性重合体を用いる場合には、多層パリソンの重合体層４と多層パリソンの樹脂層３との間に接着層を設けると良い。
【００４４】
多層パリソンの重合体層４として、ポリオレフィン系エラストマー、ポリスチレン系エラストマー、耐衝撃性ポリスチレンを用いることが、耐衝撃性に優れた発泡成形体１を得ることができるので好ましく、特にポリプロピレン系エラストマーを用いることが耐衝撃性と共に耐熱性も優れる発泡成形体１を得ることができるので好ましい。また、多層パリソンの重合体層４はフィルム状又はシート状に限らず、不織布、織布等の繊維状の形態のものであっても良く、また単層のものに限らず多層のものであっても良い。
【００４５】
また、多層パリソンの発泡層２、多層パリソンの樹脂層３、多層パリソンの重合体層４及び多層パリソンの内面樹脂層５には、収縮防止剤、耐候剤、紫外線吸収剤、紫外線反射剤、赤外線吸収剤、赤外線反射剤、難燃剤、流動性向上剤、耐候剤、着色剤、熱安定剤、酸化防止剤、結晶核剤、無機充填剤、ゴム等の各種添加剤を必要に応じて適宜配合することができる。
【００４６】
本発明における多層パリソン６は、上記発泡性溶融樹脂よりなる多層パリソンの発泡層２の少なくとも外面に上記溶融合成樹脂よりなる多層パリソンの樹脂層３を有する。かかる構成の多層パリソン６は、上記基材樹脂（Ａ）に発泡剤と、必用に応じて添加するタルク等の気泡調整剤や収縮防止剤等とを押出機にて溶融混練することにより得られる発泡性溶融樹脂と、上記合成樹脂（Ｂ）と必要に応じて添加する各種添加剤と押出機にて溶融混練することにより得られる溶融合成樹脂（Ｂ）とを共押出することによって得られる。
【００４７】
尚、図２（ｂ）に示す多層パリソンの樹脂層３の外面に多層パリソンの重合体層４が設けられた多層パリソン６等の３層以上の異なる層からなる多層パリソンは、層の数に応じた押出機を使用するとともに、多層パリソンの層の数に応じた複数の樹脂を合流積層することができる構造の環状ダイ等を使用することによって得られる。尚、図２（ｃ）に示す多層パリソンの内面樹脂層５が設けられた多層パリソン６等は、多層パリソンの内面樹脂層５が多層パリソンの樹脂層３と同じ合成樹脂で構成される場合には、押出機の数は増やさないで、同一の押出機から供給される溶融合成樹脂を共押出用の環状ダイ内にて分岐した後、各々を発泡性溶融樹脂と積層することによっても得ることができる。
【００４８】
多層パリソン６の大きさは、用途に応じて概ね１．５ｍ3迄の範囲内で選択することができる。
【００４９】
多層パリソンの発泡層２の密度は、２０〜５００ｋｇ／ｍ3が好ましく、さらに好ましくは２５〜４００ｋｇ／ｍ3である。該多層パリソンの発泡層２の密度が５００ｋｇ／ｍ3を超えると、該多層パリソンから得られる発泡成形体１が軽量とは言い難くなる上に、断熱性等の物性が低下する虞がある。また多層パリソンの発泡層２の密度が２０ｋｇ／ｍ3未満の場合は、多層パリソンの発泡層２を構成している気泡膜が薄くなるので成形時に破泡し易くなる等、良好な発泡成形体１を得ることができない虞がある。
【００５０】
多層パリソンの発泡層２の厚みは、１ｍｍ〜１００ｍｍが好ましい。多層パリソンの発泡層２の厚みが１ｍｍ未満になると、該多層パリソンから得られる発泡成形体１の強度、防音性、断熱性等の物性が低下する虞がある。一方、多層パリソンの発泡層２の厚みが１００ｍｍを超えると、発泡や成形が困難になり、良好な発泡成形体１を得ることができない虞がある。
【００５１】
多層パリソンの樹脂層３の厚みは、１００μｍ〜１０ｍｍが好ましく、更に好ましくは１００μｍ〜７ｍｍである。多層パリソンの樹脂層３の厚みが薄くなりすぎると、該多層パリソンから得られる発泡成形体１の表面平滑性が低下するため外観が悪くなる虞がある。一方、多層パリソンの樹脂層３の厚みが厚くなりすぎると、該多層パリソンから得られる発泡成形体１の重量が重くなり、用途によっては軽量とは言い難くなり、また、多層パリソンの発泡層２の独立気泡率が低くなる虞がある。
【００５２】
多層パリソン６に図２（ｂ）に示す多層パリソンの重合体層４を設ける場合、該多層パリソンの重合体層４の厚みは、２０μｍ〜１０ｍｍが好ましく、更に好ましくは５０μｍ〜７ｍｍである。多層パリソンの重合体層４の厚みが薄くなりすぎると、耐衝撃性、耐寒性、耐熱性、耐薬品性、緩衝性、耐候性、難燃性、外観の向上、機械的強度の向上など多層パリソンの重合体層４を設けることにより発泡成形体１に付与される効果が小さくなる可能性がある。一方、多層パリソンの重合体層４の厚みが厚くなりすぎると、該多層パリソンから得られる発泡成形体１の重量が重くなり、用途によっては軽量とは言い難くなる。
【００５３】
多層パリソン６に図２（ｃ）に示す多層パリソンの内面樹脂層５を設ける場合、該多層パリソンの内面樹脂層５の厚みは、１００μｍ〜１０ｍｍが好ましい。多層パリソンの内面樹脂層５の厚みが１００μｍ未満になると、該多層パリソンから得られる発泡成形体における収縮や変形の発生を防止するリブの如き働きが低下し、発泡成形体の形状によっては収縮や変化が発生しやすくなる虞がある。一方、多層パリソンの内面樹脂層５の厚みが厚すぎる場合は発泡成形体の軽量性を損ねる可能性がある。
【００５４】
本発明の発泡成形体１の製造方法においては、上記多層パリソン６を、該パリソン６の最内面同士の少なくとも一部が融着するように成形型にて成形することによって、発泡成形体の発泡層１２の表面に発泡成形体の樹脂層１３を有する発泡成形体１が得られる。
【００５５】
本明細書においては、上記多層パリソン６の最内面同士の融着割合は、融着部面積比（％）で表すものとする。本発明においては、十分な機械的強度、寸法安定性を有する発泡成形体１を得るという観点から、融着部面積比が３０％以上であることが好ましく、４０％以上であることがより好ましく、６０％以上であることが特に好ましい。該融着部面積比の測定方法は以下の通りである。
【００５６】
まず、発泡成形体１を、切断面が発泡成形体１製造時の多層パリソン６の押出方向に直交し、且つ多層パリソン６の金型圧縮方向に平行になるように等間隔で１０等分に切断する。
【００５７】
次に切断された発泡成形体切断片を、発泡成形体１を形成していた順番通りに切断面が左右方向に位置するように置き、各成形体切断片における右側の切断面において多層パリソン最内面同士が融着している部分の長さ（ｍｍ）を求め、これを２倍した値を融着部長さＬ（ｍｍ）とする。又、該右側の切断面において、多層パリソンの最内面同士が融着することなく空隙部を形成している場合、空隙部の内周長さＭ（ｍｍ）を求める。尚、各切断面において前記融着部及び／又は空隙部が複数存在する場合は各々の箇所について、各部分の融着部長さ及び／又は各部分の空隙部の内周長さを求め、各々の合計をＬ又はＭとする。次に、これらの値から下記式により融着部面積比（％）求める。
【００５８】
【数１４】
融着部面積比（％）＝［Ｌ／（Ｌ＋Ｍ）］×１００
【００５９】
本明細書においては、各切断面（但し、最内面融着部自体が存在しない切断面は除く）の融着部面積比の算術平均値をもって発泡成形体の融着部面積比（％）とする。尚、最内面同士が隙間なく融着していて、空隙部がない断面は融着部面積比は１００％となる。
【００６０】
本発明の方法によって得られる発泡成形体の発泡層１２の密度は、２５〜４００ｋｇ／ｍ 3 である。上記したように、多層パリソンの発泡層２を形成することによって、このような密度の発泡成形体の発泡層１２を形成することができる。発泡成形体の発泡層１２の密度が高すぎる場合は、発泡成形体１が軽量とは言い難くなる上に、断熱性等の物性が低下する虞れがある。また発泡成形体の発泡層１２の密度が低すぎる場合は、発泡成形体の発泡層１２を構成している気泡膜が薄く、成形時に破泡し易いものである等、良好な発泡成形体１とはならない虞れがある。
【００６１】
本明細書における発泡成形体の発泡層１２の密度は次のようにして求める。発泡成形体１より発泡成形体の発泡層１２のみを切り出し、切り出したサンプルの重量（ｇ）を、その外形寸法より求められる体積（ｃｍ3）にて割り、得られた数値をｋｇ／ｍ3単位に換算することにより求められる。また各層の厚みは、成形体断面（必要に応じて顕微鏡により拡大し、拡大された投影図を用いる）より求めることができる。尚、発泡成形体１の部分ごとに発泡成形体の発泡層１２の密度が異なる場合があるため、発泡成形体１の底面、側面等の１０箇所以上から発泡成形体の発泡層１２のサンプルを切り出し、各々のサンプルについて密度を測定し、最大値及び最小値を除いた残りの測定値の算術平均をもって発泡成形体の発泡層１２の密度とする。
【００６２】
本発明の方法によって得られる発泡成形体１において、発泡成形体の樹脂層１３の厚みは１００μｍ〜１０ｍｍであり、好ましくは１００μｍ〜７ｍｍである。多層パリソンの樹脂層３を、上記したように形成することによって、このような厚みの発泡成形体の樹脂層１３を得ることができる。発泡成形体の樹脂層１３の厚みが薄くなりすぎると表面平滑性が低下するため、発泡成形体１の外観が悪くなる虞れがある。一方、発泡成形体の樹脂層１３の厚みが厚くなりすぎると、発泡成形体１全体の重量も重くなって、用途によっては、軽量とは言い難くなる上に、発泡成形体の発泡層１２の独立気泡率が低くなる虞がある。
【００６３】
本発明の方法によって得られる発泡成形体１は、発泡成形体の発泡層１２に挟まれた発泡成形体の芯層１５を設け、該発泡成形体の芯層１５にリブの如き働きをさせることによって、発泡成形品１に収縮や変形が発生するのを防止することが好ましい。該発泡成形体の芯層１５の厚みは１００μｍ〜１０ｍｍが好ましく、上記の如く多層パリソンの内面樹脂層５を形成することによって、かかる厚みの発泡成形体の芯層１５を得ることができる。発泡成形体の芯層１５の厚みが１００μｍ未満になると、上記のリブの如き働きが低下し、発泡成形体１の形状によっては収縮や変形が発生しやすくなる虞れがある。一方、発泡成形体の芯層１５が厚すぎる場合は発泡成形体の軽量性を損ねる可能性がある。
【００６４】
発泡成形体の芯層１５は、目的とする厚みに対応して次のように形成することができる。
発泡成形体の芯層１５の厚みが薄い場合は、多層パリソン６から発泡成形体１を成形する際に、成形条件を適宜選択することによって多層パリソン６の内面同士が融着した部分に比較的高密度の薄い発泡成形体の芯層１５を形成することができる。発泡成形体の芯層１５の厚みが厚い場合は、多層パリソン６に上記したような多層パリソンの内面樹脂層５を設けることによって、目的とする発泡成形体の芯層１５を形成することができる。
【００６５】
本発明の方法によって得られる発泡成形体１の全体の密度は、好ましくは２０〜８００ｋｇ／ｍ3であり、更に好ましくは２０〜４００ｋｇ／ｍ3である。該発泡成形体１の全体の密度が８００ｋｇ／ｍ3を超えると軽量性や断熱性が低下する虞れがある。また、発泡成形体１の密度が２０ｋｇ／ｍ3未満の場合は圧縮強度等の機械的物性が低下する虞れがある。
【００６６】
本明細書における発泡成形体１の全体の密度は、発泡成形体１の重量（ｋｇ）を、該発泡成形体１を水没して測定した体積（ｍ3）（但し、発泡成形体内部に空隙部が存在する場合であっても求められる該成形体の体積より空隙部の容積を差し引くことはしない）で除することにより求められる値である。
【００６７】
本発明の方法によって得られる容器の具体例として挙げた図１に示す発泡成形体１は、多層パリソ６ンの最内面同士を隙間なく完全に融着させた構成を採用し、容器空間１６が形成されるように成形することによって得られる。
【００６８】
図１に示すように発泡成形体の用途として容器を選択する場合は、密度が３０〜４００ｋｇ／ｍ3となるように構成すると、より軽量で、断熱性に優れたものとなり、また発泡成形体の樹脂層１３の厚みが２００μｍ〜５ｍｍとなるように構成すると、耐久性、表面平滑性が高く、外観と軽量性のバランスのとれたものとなる上に、成型後の容器の収縮が小さく、外力に対する機械的強度に優れたものとなる。また、発泡成形体の樹脂層１３の表面に発泡成形体の重合体層１４が設けられた多層樹脂発泡成形体製とすると、リターナブル容器として特に好適なものとなる。
【００６９】
本発明の発泡成形体１の製造方法を、図３及び図４に基いて、更に詳しく説明する。
多層パリソン６は、図３に示すように、多層パリソン６の各層を形成する基材樹脂をそれぞれ別々の押出機（図示しない）により溶融混練し、これらをダイ２１内で積層合流させながら低圧域に押し出すことによって得られる。必要に応じて押出機とダイ２１の間もしくはダイ２１内には、アキュームレーターを設置してもよい。
【００７０】
多層パリソン６から発泡成形体１を得る方法は、次の通りである。
まず、多層パリソン６を成形後、図３に示すように、押し出された多層パリソン６を両側面から挟むように分割形式の金型２２ａ、２２ｂを閉鎖する。金型を閉鎖すると、発泡した多層パリソン６が金型内面において圧縮されて、偏平状に変形しながら金型に密着する。次に、図４に示すように金型を閉鎖すると、多層パリソン６の内側表面同士の少なくとも一部が融着して、本発明の発泡成形体１が得られる。尚、図１に示すように、多層パリソン６の最内面同士が完全に密着して、隙間なく一体化した発泡成形体１が、機械的強度、寸法安定性に優れるため好ましい。
【００７１】
また、図３に示すように金型に減圧用配管２３を設けることによって、金型２２ａ、２２ｂの内面と多層パリソン６の外表面との間を減圧可能に形成された金型を用い、減圧しながら金型を閉鎖して成形すると、多層パリソン６の外表面と金型内面とがよく密着し、金型形状を良好に再現した発泡成形体１を得ることができる。しかも、このようにして得られた発泡成形体１は、金型内面に模様を有する金型を使用した場合の発泡成形体表面への金型模様転写が向上し、更に外観に優れたものとなる。
【００７２】
また多層パリソン６を押し出した直後、パリソンピンチにより多層パリソン６を閉鎖し、プリブローを行って膨張させた多層パリソン６を上記と同様にして成形してもよい。
【００７３】
多層パリソン６を深絞り成形する場合には、図５(a)、（ｂ）に示すように、雌型２２ｂの四方の側面部２５が底面部２４を中心に可動可能に雌型２２ｂを構成することによって、雌型２２ｂの型組み、展開を可能にすることが好ましい。このように構成し、雌型２２ｂが展開した状態から、雌型２２ｂの側面部２５を動かして雌型２２ｂを型組みしながら、雄型２２aと雌型２２ｂを閉鎖して成形すると、多層パリソン６の深絞り成形が容易になる。
【００７４】
尚、図３〜５は発泡成形体の製造例を概念的に示す説明図であり、本発明において発泡成形体を製造する具体的な操作手順は図示するものに限定されない。
【００７５】
【実施例】
以下、実施例を挙げて本発明をより詳細に説明する。以下の実施例、比較例において使用したポリエチレン系樹脂のメルトフローレイト：ＭＦＲ（ｇ／１０分）、密度（ｋｇ／ｍ3）、及びα、βの値は表１、表２に示す。
【００７６】
【表１】

Figure 0004484175
【００７７】
【表２】
Figure 0004484175
【００７８】
実施例１〜４
表３に示す多層パリソンの発泡層形成用樹脂１００重量部と、ポリエチレン１００重量部に対してクエン酸ナトリウム５重量部とタルク１０重量部とを配合したポリエチレンベースの気泡調整剤マスターバッチ６重量部と、ポリエチレン１００重量部に対してステアリン酸モノグリセライドを１２重量部配合したポリエチレンベースの収縮防止剤マスターバッチ１０重量部とを配合した原料を押出機に供給して加熱、混練して溶融樹脂とした後、更に物理発泡剤としてイソブタンを多層パリソンの発泡層形成用樹脂１００重量部対し２．２重量部（但し、実施例４の場合は３．２重量部）の割合で押出機内の溶融樹脂に圧入混練して発泡性溶融樹脂とした。
【００７９】
一方、表３に示す多層パリソンの樹脂層形成用樹脂に着色剤を配合して、押出機に供給し、加熱溶融して非発泡性の溶融合成樹脂とした。次いで、各押出機内で溶融混練された溶融物を各押出機と連結した各アキュームレーターに各々充填した後、発泡性溶融樹脂と溶融合成樹脂とがダイ内で合流積層するように各アキュームレーターから発泡性溶融樹脂と溶融合成樹脂を射出するとともに、ダイから押出し、発泡性溶融樹脂が発泡して形成された多層パリソンの発泡層の外面に溶融合成樹脂からなる多層パリソンの樹脂層が積層された多層パリソンを得た。
【００８０】
次いで、図５に示すように、押出された前記パリソンを挟むようにダイ直下に設置された箱形状の分割式の金型を閉鎖して、金型内面において多層パリソンを偏平状に変形させ、更に金型を閉鎖して、金型内面に多層パリソンを密着させて賦型した後、冷却、離型して、発泡成形体を得た。該発泡成形体は、開口部外形寸法３００ｍｍ×２６０ｍｍ、底面部外形寸法２６０ｍｍ×１８０ｍｍ、高さ１１０ｍｍ、容器肉圧約２０ｍｍの円すい台形の容器である。尚、上記金型には金型内面に梨地加工を施したものを使用した。
【００８１】
上記実施例１〜４において得られた発泡成形体は、いずれも表面平滑性が良く、収縮変形、座屈などが見られない外観良好なものであった。得られた発泡成形体を切断して断面を観察したところ、いずれも発泡成形体の発泡層の表面に、発泡成形体の樹脂層を有し、また多層パリソンの発泡層の内面同士が隙間なく良好に融着している発泡成形体であった。
【００８２】
各実施例において使用した多層パリソンの発泡層形成用樹脂及び多層パリソンの樹脂層形成用樹脂のメルトフローレイト、α、βの値、及びメルトフローレイト比（ＭＦＲ１/ＭＦＲ２）を表３に、また、得られた発泡成形体の発泡層の厚み、発泡成形体の樹脂層の厚み、発泡成形体の発泡層の密度、発泡成形体全体の密度、及び常温と低温（−２０℃）の各々の条件下で行なった落錘衝撃試験の結果を表４に示す。
【００８３】
【表３】
Figure 0004484175
【００８４】
【表４】
Figure 0004484175
※１：発泡層の気泡の破れや収縮が大きく、外観が悪い上に、各物性が測定可能な発泡成形体が得られなかった。
※２：ドローダウンが大きく、発泡層の厚みが薄く、各物性が測定可能な発泡成形体が得られなかった。
【００８５】
外観の評価は、容器状発泡成形体を目視観察して以下の基準で判断した。
○：表面平滑性、金型再現性が良好である
×：収縮による凹凸が見られる
【００８６】
耐衝撃性試験は、ＪＩＳ Ｋ７２１１に準拠して落錘衝撃試験を行った。
具体的には、常温での落錘衝撃試験は、サイズ１００ｍｍ×１００ｍｍの試験片を発泡成形体から切出し、温度２３℃、湿度５５％の恒温恒湿室において試験片を２４時間放置した後、該試験片を使用して温度２３℃、湿度５５％の恒温恒湿室にて、株式会社東洋精機製作所Ｎｏ．６２１落錘衝撃試験機を用いて、ＪＩＳ Ｋ７２１１に規定する呼びなす１型（質量１ｋｇ）のなす形重錘を１．５ｍの高さから自由落下させて、試験片が破壊するか否かを評価した。
尚、表４において、試験片が破壊しなかった場合を○で表した。
【００８７】
低温での落錘衝撃試験は、−２０℃の恒温槽に２４時間放置したこと、及び各試験片を低温槽から取り出してから温度２３℃、湿度５５％の恒温恒湿室における測定までを２秒以内に行なった以外は、常温での落錘衝撃試験と同様に行ない、同様の基準にて評価した。
【００８８】
実施例５
表３に示す多層パリソンの発泡層形成用樹脂、及び多層パリソンの樹脂層形成用樹脂を用い、実施例1と同様に多層パリソンを形成した。次に、実施例１で用いた金型とは別の箱型形状の多分割式の金型を用いた以外は実施例1と同様に成形して発泡成形体を得た。該発泡成形体は直方体形状の容器であって、寸法は、開口部外径寸法３００ｍｍ×２３０ｍｍ、高さ１２０ｍｍ、容器肉厚み約２０ｍｍである。
【００８９】
実施例５において得られた発泡成形体は、表面平滑性が良く、収縮変形、座屈などが見られない外観良好なものであった。得られた発泡成形体を切断して断面を観察したところ、発泡成形体の発泡層の表面に、発泡成形体の樹脂層を有し、また多層パリソンの発泡層の内面同士が隙間なく良好に融着した発泡成形体であった。
【００９０】
実施例６
実施例１と同様にして発泡性溶融樹脂を得た。一方、表３に示す多層パリソンの樹脂層形成用樹脂を押出機に供給し、加熱溶融して非発泡性の溶融合成樹脂とした。次いで各押出機内で溶融混練された溶融物の各々を各押出機と連結した各アキュムレーターに充填した。尚、非発泡性の溶融合成樹脂は樹脂層形成用樹脂と内面樹脂層形成用樹脂に別けられ、各々別々のアキュームレーターに充填した。その後、３台のアキュームレーターより、外側から順に樹脂層形成用の溶融合成樹脂、発泡性溶融樹脂、内面樹脂層形成用の溶融合成樹脂がダイ内で合流積層するように射出すると共に、ダイから押出し、外側から順に樹脂層、発泡層、内面樹脂層が積層された多層パリソンを得た。次いで、実施例１と同様にして発泡成形体を得た。
【００９１】
実施例６において得られた発泡成形体は、いずれも表面平滑性が良く、収縮変形、座屈などが見られない外観良好なものであった。得られた発泡成形体を切断して断面を観察したところ、発泡成形体の発泡層の表面に、発泡成形体の樹脂層を有し、また多層パリソンの内面樹脂層の内面同士が隙間なく良好に融着して厚み０．５ｍｍの発泡成形体の芯層を形成している発泡成形体であった。
【００９２】
比較例１
表３に示す発泡層形成用樹脂を及び樹脂層形成用樹脂を用いて、実施例１と同様にして多層パリソンを得た。該多層パリソンを成形したが、発泡層の収縮が大きく外観良好な低密度の発泡成形体が得られなかった。
【００９３】
比較例２
表３に示す多層パリソンの発泡層形成樹脂及び多層パリソンの樹脂層形成用樹脂を用い、物理発泡剤を多層パリソンの発泡層形成樹脂１００重量部対して２．４重量部添加した以外は実施例１と同様にして多層パリソンを得た。該多層パリソンを成形したが、発泡層の気泡の破れや収縮が大きく外観良好な発泡成形体が得られなかった。
【００９４】
比較例３
表３に示す多層パリソンの発泡層形成樹脂及び多層パリソンの樹脂層形成用樹脂を用い、実施例1と同様に多層パリソンの製造を試みたが、気泡が破泡し発泡層の収縮が激しくほとんど発泡せず、良好な多層パリソンが得られなかった。この多層パリソンを実施例１と同様に成形したが、ドローダウンが大きく発泡層の厚みが薄くなり、良好な発泡成形体は得られなかった。
【００９５】
【発明の効果】
本発明の多層ポリエチレン系樹脂発泡成形体の製造方法は、主成分が密度９００〜９４０（ｋｇ／ｍ3）のポリエチレン系樹脂であると共に、１９０℃の温度条件下で振動歪みを与える動的粘弾性測定において角周波数ω＝１０-1〜１０1(ｒａｄ／ｓｅｃ)の範囲における貯蔵弾性率Ｇ'（Ｐａ)が下記（１）式を満足する基材樹脂に、物理発泡剤を添加し溶融混練して得られる発泡性溶融樹脂と、２０〜１００重量％のポリエチレン系樹脂を含む合成樹脂であると共に、該合成樹脂のメルトフローレイト：ＭＦＲ１（ｇ／１０分）と上記基材樹脂のメルトフローレイト：ＭＦＲ２（ｇ／１０分）との比が下記(２）式を満足する合成樹脂を、溶融して得られる溶融合成樹脂とを、共押出することにより、上記発泡性溶融樹脂よりなるポリエチレン系樹脂発泡層の少なくとも外面に上記溶融合成樹脂よりなるポリエチレン系樹脂層を有する多層パリソンを形成し、次いで該パリソン最内面同士の少なくとも一部が融着するように成形型にて成形することによって密度２５〜４００ｋｇ／ｍ ３ のポリエチレン系樹脂発泡層の表面に厚み１００μｍ〜１０ｍｍのポリエチレン系樹脂層を有する発泡成形体を得るという構成を採用している。
【００９６】
【数１５】
log Ｇ'＝αlogω＋β （１）
α＝０．５０〜１．５０
β＝２．０〜５．０
【数１６】
ＭＦＲ１／ＭＦＲ２＞１．０ （２）
【００９７】
上記構成を採用したことにより、多層パリソンを構成する発泡性溶融樹脂よりなるポリエチレン系樹脂発泡層の少なくとも外面に上記溶融合成樹脂よりなるポリエチレン系樹脂層を有する多層パリソンの厚み、密度を任意に選択または調節することによって、得られる多層ポリエチレン系樹脂発泡成形体を構成するポリエチレン系樹脂発泡層の厚み、密度を広い範囲で任意に選択または調節することができる。従って、本発明の製造方法によれば、高厚み、低密度の発泡層を有する多層ポリエチレン系樹脂発泡成形体を容易に得ることができる。また、本発明の方法によって得られるポリエチレン系樹脂発泡層の表面に形成されたポリエチレン系樹脂層は、厚みが均一で、表面に鱗状の模様、亀裂や穴が発生することがないので、外観が良好である。
【００９８】
本発明の多層ポリエチレン系樹脂発泡成形体の製造方法は、ポリエチレン系樹脂発泡層の少なくとも外面にポリエチレン系樹脂層を有する多層パリソンを形成し、該パリソン最内面同士の少なくとも一部が融着するように成形型にて成形するものである。従って、本発明の製造方法においては、熱可塑性樹脂にて成形した中空構造の成形体を樹脂層とし、該成形体の内部の空洞部にウレタン樹脂を注入する方法や、該内部の空洞部に樹脂発泡粒子などを充填成形する等の従来の方法とは異なり、複雑な製造工程や装置が不要である。
【００９９】
また本発明の製造方法においては、基材樹脂の貯蔵弾性率Ｇ'（Ｐａ）は下記（３）式を満足し、合成樹脂のメルトフローレイト：ＭＦＲ１（ｇ／１０分）と発泡層を形成する上記基材樹脂のメルトフローレイト：ＭＦＲ２（ｇ／１０分）との比が下記（２）式を満足するという構成を採用することにより、多層パリソンのポリエチレン系樹脂発泡層の発泡性、ドローダウン性等を更に改善すると共に、多層パリソンのポリエチレン系樹脂層の外観、該樹脂層の伸び、ドローダウン性等も更に改善され、従来の多層パリソンを成形する方法では得ることが難しかった低密度の多層ポリエチレン系樹脂発泡成形体が生産性良く得ることが可能になった。
【０１００】
【数１７】
log Ｇ'＝αlogω＋β （３）
α＝０．６０〜１．４０
β＝２．０〜３．８
【数１８】
ＭＦＲ１／ＭＦＲ２＞１．０ （２）
【０１０１】
更に本発明の方法によって得られる多層ポリエチレン系樹脂発泡成形体は、軽量性、耐衝撃性、耐寒性、耐熱性、耐薬品性、リサイクル性、断熱性、緩衝性、防音性、防振性、圧縮、引張、曲げ等の機械的強度に優れたものである。また該発泡成形体は、深絞り成形物や大型成形物としても好適なものであり、リターナブル容器等の容器をはじめ床やドアなどの軽量断熱パネル、パレット、ピラーやバンパー、インスツルメントパネルなどの自動車部材、机、いす、フロート、サーフボード、ボディーボード等、特に冷凍倉庫などで使用される低温用容器などに好適に利用される。
【図面の簡単な説明】
【図１】本発明の方法によって得られる多層ポリエチレン系樹脂発泡成形体の一例を示す縦断面図である。
【図２】本発明の多層ポリエチレン系樹脂発泡成形体の製造方法に用いる多層パリソンの一例を示す一部切欠斜視図である。
【図３】本発明の製造方法の一工程を示す説明図である。
【図４】本発明の製造方法の一工程を示す説明図である。
【図５】本発明の製造方法の異なる態様を示す説明図である。
【符号の説明】
１ 発泡成形体
２ 発泡層
３ 樹脂層
６ 多層パリソン
１２ 発泡成形体の発泡層
１３ 発泡成形体の樹脂層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multilayer polyethylene resin foam molded article having a polyethylene resin layer as a skin and a polyethylene resin foam layer inside, and specifically, for lightweight insulation panels such as floors and doors, pallets, containers, automobile members, etc. It is related with the multilayer polyethylene-type resin foaming molding used.
[0002]
[Prior art]
Conventionally, multi-layered resin foam molded products having various shapes in which a thermoplastic resin layer is formed on the surface of a resin foam layer are known. A multilayer resin foam molded body having a structure in which a solid layer is formed on the surface of such a foam layer can be used as a returnable container that can be washed. Therefore, it has been conventionally used as an alternative to disposable polystyrene foam fish boxes. However, in view of the importance of the garbage problem in recent years, further demand is expected in the future.
[0003]
Also, the multilayer resin foam molded fish box having the above structure is often used in a low temperature atmosphere such as a freezer warehouse, and low temperature impact resistance is required as an important characteristic of the multilayer resin foam molded product. From this point of view, containers using polystyrene resin or polypropylene resin have insufficient impact resistance at low temperatures, and a multilayer resin foam molded article is manufactured using polyethylene resin suitable for use at low temperatures. It is demanded.
[0004]
[Problems to be solved by the invention]
As a method for producing such a multilayer resin foam molded body, for example, a hollow structure molded body is molded with a thermoplastic resin, and a urethane resin is injected into a cavity inside the molded body or filled with resin foam particles. Methods of molding are known (Japanese Patent Publication No. 58-10217, Japanese Patent Laid-Open No. 6-339979, etc.). However, these methods have the problem that the molding of the resin layer on the surface and the formation of the internal foamed layer are separate processes, so that the molding process becomes complicated and a special molding machine is required. It was. As a result, it has been difficult to provide an inexpensive multilayer resin foam molded article by a method of injecting urethane resin into the molded article or a method of filling and molding resin foam particles.
[0005]
As a method of solving the above-mentioned process problems and price problems, a hollow multilayer parison having a thermoplastic resin layer on the surface of the resin foam layer is molded while being compressed with a mold, and the opposing inner surfaces of the parison are melted. Methods have been proposed for obtaining a multi-layer resin foam molded article (Japanese Patent Publication No. 62-27978, Japanese Patent Laid-Open No. 6-31449, etc.).
[0006]
However, a method of forming a multilayer parison while compressing it with the above mold (Japanese Patent Laid-Open No. 6-31449, etc.) is adopted, and the density is 400 kg / m.ThreeWhen trying to produce a multilayer resin foam molded body having a polyethylene resin layer on the surface of a polyethylene resin foam layer having a low density and thickness as follows, the bubbles constituting the foam layer are broken or open, Phenomena such as the shrinkage of the foam layer easily occur, and it has been difficult to obtain a multilayer resin foam molded article having a low density and thick polyethylene resin foam layer.
[0007]
In view of the above disadvantages of the prior art, the present invention provides a multilayer polyethylene-based resin foam molded article that does not require a complicated process such as injecting a foam into a molded body that becomes a resin layer on the surface of the foamed layer. Multi-layer polyethylene that is a manufacturing method and has a beautiful appearance, and is excellent in lightness, mechanical strength, thermal insulation, shock-absorbing, soundproofing, vibration-proofing, chemical resistance, recyclability, low-temperature impact resistance, etc. An object of the present invention is to provide a method for producing a resin-based resin foam molding.
[0008]
[Means for Solving the Problems]
  That is, in the method for producing a multilayer polyethylene resin foam molded article of the present invention, the main component has a density of 900 to 940 (kg / m3In the dynamic viscoelasticity measurement in which vibration distortion is given under a temperature condition of 190 ° C., the angular frequency ω = 10-1-101In the base resin whose storage elastic modulus G ′ (Pa) in the range of (rad / sec) satisfies the following formula (1):PhysicsA foamable molten resin obtained by adding a foaming agent and melt-kneading, and a synthetic resin containing 20 to 100% by weight of a polyethylene resin, and a melt flow rate of the synthetic resin: MFR1 (g / 10 minutes) The above foam is obtained by co-extruding a synthetic resin obtained by melting a synthetic resin in which the ratio of the base resin to the melt flow rate MFR2 (g / 10 min) satisfies the following formula (2): Forming a multi-layer parison having a polyethylene-based resin layer made of the above-mentioned molten synthetic resin on at least the outer surface of the polyethylene-based resin foam layer made of a soluble molten resin, and then fusing at least a part of the innermost inner surfaces of the parison By molding withDensity 25-400kg / m 3 ofOn the surface of the polyethylene resin foam layer100 μm to 10 mm thickA foam molded article having a polyethylene resin layer is obtained.
[0009]
[Equation 5]
logG '= αlogω + β (1)
α = 0.50-1.50
β = 2.0-5.0
[0010]
[Formula 6]
  MFR1 / MFR2> 1.0 (2)
[0011]
  The storage elastic modulus G ′ (Pa) of the base resin satisfies the following formula (3)It is preferable to do.
[0012]
[Expression 7]
logG '= αlogω + β (3)
α = 0.60-1.40
β = 2.0 to 3.8
[0014]
DETAILED DESCRIPTION OF THE INVENTION
A specific example of a multilayer polyethylene-based resin foam molded article (hereinafter referred to as “foam molded article”) obtained by the method of the present invention is shown in FIG.
The foamed molded body shown in FIG. 1A has a configuration in which the entire surface of the polyethylene resin foam layer is covered with the polyethylene resin layer. In FIG. 1A, 1 is a foam molded article, 12 is a polyethylene resin foam layer of the foam molded article (hereinafter referred to as “foam layer of foam molded article”), and 13 is a polyethylene resin of the foam molded article. Each layer (hereinafter referred to as “resin layer of foamed molded product”) is shown.
[0015]
The foamed molded product 1 shown in FIG. 1 (b) has a configuration in which the surface of the foamed molded product 1 shown in FIG. 1 (a) is further covered with a polymer layer. In FIG. 1B, reference numeral 14 denotes a polymer layer (hereinafter referred to as “a polymer layer of a foam molded body”) provided on the outer surface of the resin layer 13 of the foam molded body 1.
[0016]
A foam molded body 1 shown in FIG. 1C has a configuration in which a polyethylene resin core layer is sandwiched between foam layers 12 of the foam molded body 1 shown in FIG. In FIG.1 (c), 15 shows the core layer of polyethylene resin (henceforth "the core layer of a foaming molding").
[0017]
The foamed molded article 1 intended by the production method of the present invention can be obtained by sandwiching a multilayer parison in a mold such as a mold and compression molding. In the present invention, the multi-layer parison is capable of exhibiting the same or similar function as that formed by blow molding and sandwiched between molds.
[0018]
In the production method of the present invention, for example, a foamable molten resin obtained by adding a foaming agent to a base resin described later and melt-kneading, and a molten synthetic resin obtained by melting and kneading a synthetic resin described later are, for example, cylinders. The multi-layer parison is formed by co-extrusion in the shape.
[0019]
FIG. 2 shows an example of a multilayer parison. The foam molded body 1 shown in FIG. 1 (a) is from the multilayer parison shown in FIG. 2 (a), and the foam molded body 1 shown in FIG. 1 (b) is from the multilayer parison shown in FIG. 2 (b). The foamed molded product 1 shown in FIG. 2 is obtained from the multilayer parison shown in FIG.
[0020]
The multilayer parison of FIG. 2A has a configuration in which a polyethylene resin layer is laminated on the outer surface of a polyethylene resin foam layer. In FIG. 2A, 6 is a multilayer parison, 2 is a polyethylene resin foam layer (hereinafter referred to as “multilayer parison foam layer”), 3 is a polyethylene resin resin layer (hereinafter “multilayer parison”). Of resin layer)).
[0021]
A multilayer parison 6 shown in FIG. 2B has a configuration in which a polymer layer is laminated on the surface of the resin layer 3 of the multilayer parison shown in FIG. In FIG. 2B, 4 indicates a polymer layer of the multilayer parison 6 (hereinafter referred to as “polymer layer of the multilayer parison”), and the polymer layer 4 of the multilayer parison is a polyolefin-based resin or the like as described later. And is provided as needed.
[0022]
A multilayer parison 6 shown in FIG. 2C has a configuration in which a polyethylene resin layer is laminated on the inner surface of the multilayer parison 6 shown in FIG. In FIG. 2 (c), 5 indicates an inner surface resin layer provided on the inner surface of the multilayer parison (hereinafter referred to as "inner surface resin layer of the multilayer parison"), and the inner surface resin layer 5 of the multilayer parison is provided as necessary. Provided.
[0023]
The foamed layer 2 of the multilayer parison corresponds to the foamed layer 12 of the foamed molded body shown in FIGS. 1 (a), (b), and (c), and the resin layer 3 of the multilayer parison shown in FIGS. Corresponding to the resin layer 13 of the foamed molded product shown in c), the polymer layer 4 of the multilayer parison shown in FIG. 2B corresponds to the polymer layer 14 of the foamed molded product shown in FIG. 1B.
Moreover, the inner surface resin layer 5 of the multilayer parison shown in FIG. 2 (c) corresponds to the core layer 15 of the foam molded body shown in FIG. 1 (c), and the core layer 15 of the foam molded body is the inner surface resin layer of the multilayer parison. 5, at least a part of the inner surfaces of the 5 is fused.
[0024]
The multilayer parison 6 includes a foamable molten resin prepared by adding a foaming agent to a polyethylene resin constituting the foamed layer 2 of the multilayer parison and melt-kneading in the extruder, and a polyethylene constituting the resin layer 3 of the multilayer parison. A molten resin prepared by melting an epoxy resin in another extruder (or a polymer constituting the polymer layer 4 or inner resin layer 5 of the multi-layer parison or a polyethylene resin in another extruder, etc.) (1) prepared by co-extrusion in a co-extrusion die and co-extrusion from the die into a low pressure region to foam a foamable resin, or (2) confluence lamination in a die. Rather, after each molten resin is extruded from the die provided with an outlet for each molten resin to the low pressure region, the foamed resin that forms the foamed layer 2 and the resin that forms the resin layer 3 and the like are preferably laminated immediately after To coextrusion method Ri may be obtained.
[0025]
Base resin (hereinafter referred to as “base resin (A)”) constituting the foamed layer 2 of the multilayer parison, that is, the main component (50% by weight or more) of the base resin constituting the foamed layer 12 of the foam molded article Component) has a resin density of 900 to 940 kg / mThreeThis is a polyethylene resin. The resin density is 910 to 930 kg / m.ThreeIt is preferable that Resin density is 900kg / mThreeIf it is less than 1, the crystallinity is too low, and the strength of the foamed molded product 1 may be lowered. Density is 940kg / mThreeIf it exceeds 1, the crystallinity will be too high, and foaming may be difficult.
[0026]
The base resin (A) constituting the foamed layer 2 of the multi-layer parison has an angular frequency ω = 10 in dynamic viscoelasticity measurement that gives vibration strain under a temperature condition of 190 ° C.-1-101The storage elastic modulus G ′ (Pa) in the range of (rad / sec) satisfies the following formula (1).
[0027]
[Equation 9]
logG '= αlogω + β (1)
α = 0.50-1.50
β = 2.0-5.0
If a base resin that does not satisfy the above formula (1) is used, it is not possible to obtain a foam layer 2 having a high foaming ratio and a thick multi-layer parison. It is not possible to obtain a foamed molded article 1 having Further, a more preferable base resin (A) is a resin that satisfies the following formula (3). When a base resin that satisfies the formula (3) is used, a resin having a higher foaming ratio and a higher thickness can be obtained. .
[0028]
[Expression 10]
logG '= αlogω + β (3)
α = 0.6-1.4
β = 2.0 to 3.8
[0029]
The α and β can be measured by a dynamic viscoelasticity measuring machine (dynamic analyzer SR200 manufactured by Rheometrics Scientific F.E.). α and β are logarithmic values of the storage elastic modulus G ′ obtained by performing the dynamic viscoelasticity measurement by changing the angular frequency: ω in the linear region while keeping the temperature of the measurement sample resin plate at 190 ° C. Is plotted on the vertical axis and the logarithmic value of ω corresponding to G ′ is plotted on the horizontal axis.
[0030]
  In this specification, the dynamic viscoelasticity is measured by measuring a disk sample with a diameter of 25 mm from a 2 mm-thickness measuring sample resin plate obtained by press-molding for 5 minutes under the conditions of a temperature of 200 ° C. and a pressure of 8000 kPa. The sample was sandwiched between parallel plates with a diameter of 25 mm of a dynamic viscoelasticity measuring device, heated to 190 ° C. and allowed to stand for about 10 minutes, and then the angular frequency at the start point was 10 rad / sec and the angular frequency at the end point was 10-1rad / sec, 5 points / decade, within the wire diameter region (stress 1 × 103Measuring G 'corresponding to ω by changing ω under the condition of Pa)WhenTo do.
[0031]
In the present specification, α and β are regression equations by power regression calculation based on the value of ω obtained as described above and the value of G ′ corresponding to ω.
logG '= αlogω + β (5)
Α (slope value) and β (intercept).
[0032]
When α is less than 0.50, the value of β tends to increase, the elastic force at the time of foaming tends to increase, and it may be difficult to obtain a high-magnification foam layer 2. In addition, heat generation in the die increases, and it may be difficult to adjust the foaming conditions. On the other hand, when α exceeds 1.50, since the force for maintaining the bubbles is low, the foaming ratio is high and a good foam layer 2 with a large thickness cannot be obtained. Moreover, since the drawdown of the foam layer 2 becomes large, a special apparatus is required to obtain a large foam molded article.
When β is less than 2.0, the elastic force of the resin that resists the distortion of the resin constituting the foam layer 2 becomes small, so that foam breakage easily occurs, and the foam layer with a high magnification and thickness is high. Cannot get 2. On the other hand, when β exceeds 5.0, the elastic force of the resin is too large and the resistance is so strong that the high-magnification foam layer 2 cannot be obtained.
[0033]
The resin layer 3 of the multi-layer parison, that is, the resin layer 13 of the foam molded product is a non-foamed material or a density of 400 kg / m.ThreeIt is preferable to configure as the above foam or inorganic-filled non-foam. The resin layer 3 (hereinafter referred to as “synthetic resin (B)”) of the multilayer parison is formed of a synthetic resin containing 20 to 100% by weight of a polyethylene resin. When the blend of the polyethylene resin is less than 20% by weight, the adhesion between the resin layer 3 and the foamed layer 2 may be insufficient. Moreover, since many other polymer components are contained, it is not preferable in terms of recyclability.
Examples of components other than the polyethylene resin that can be contained in the synthetic resin (B) include polypropylene resins, polyester resins, thermoplastic elastomers, and rubbers.
[0034]
  The synthetic resin (B) constituting the resin layer 3 of the multilayer parison is composed of a melt flow rate of the synthetic resin (B): MFR1 (g / 10 minutes) and a melt flow rate of the base resin (A): MFR2 (g / 10 minutes)It is a resin that satisfies the following formula (2).
[0035]
## EQU11 ##
    MFR1 / MFR2> 1.0 (2)
[0036]
  The melt flow rate ratio istoo smallIn this case, the flow of the resin layer 3 of the multilayer parison becomes extremely worse than that of the foamed layer 2 of the multilayer parison, so the extrusion temperature in the die must be increased to improve the flow of the resin layer 3 of the multilayer parison. On the other hand, the foam layer 2 of the multilayer parison on which the resin layer 3 of the multilayer parison is laminated needs to lower the extrusion temperature in the die until the viscosity becomes appropriate for foaming. The cell structure of the foam layer 2 of the multilayer parison is destroyed by heat, and the foam layer 2 having a high thickness and a high magnification is obtained.TheYou can't get it.
In addition, when the value of MFR1 / MFR2 is too large, the thickness unevenness of the resin layer 3 and the drawdown of the multilayer parison 6 may be increased. The upper limit value of MFR1 / MFR2 is preferably 20 or less.
[0037]
In the present invention, the polyethylene resin constituting the foamed layer 2 of the multilayer parison, the inner surface resin layer 5 of the multilayer parison, and the resin layer 3 of the multilayer parison is an ethylene homopolymer, an α having 3 to 12 carbon atoms and ethylene. -Polymers with olefins and the like are contained at 60 wt% or more, specifically, high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, ultra low density polyethylene, Ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer , Ethylene-ethyl methacrylate copolymer, ethylene-maleic anhydride copolymer, ethylene-styrene copolymer Ethylene - butene copolymer, ethylene - vinyl alcohol, ethylene - glycidyl methacrylate, ethylene - methacrylic acid copolymer, ethylene - include ionomers such as acrylic acid copolymer.
[0038]
Moreover, the said polyethylene-type resin can not only be used independently but can comprise the foaming layer 2 of a multilayer parison, etc. by mixing 2 or more types. Furthermore, the base resin (A) has thermoplastic properties such as styrene resins, cyclic polyolefins, olefin resins such as polypropylene, styrene elastomers, and olefin elastomers as long as the original properties and foamability of polyethylene are not impaired. You may mix other polymer components, such as an elastomer, as needed. When the base resin (A) is prepared by mixing other resin components with the polyethylene resin, the polyethylene resin is preferably contained in a proportion of 70% by weight or more, more preferably 80% by weight or more. To do.
[0039]
As the melt flow rate: MFR (g / 10 min) in the present invention, a value measured at 190 ° C. and a load of 21.18 N described in JIS K7210 is adopted.
[0040]
The base resin (A) that satisfies the above formula (1) in the dynamic viscoelasticity measurement uses a polyethylene resin having a branched chain as the polyethylene resin as a main component, and the length of the branched chain of the resin, It can be obtained by adjusting the ratio of the length of the branched chain to the chain, the molecular weight, the molecular weight distribution, and the like. Examples of the polyethylene resin include raw materials such as NUC8008, NUC8160, and NUC8009 manufactured by Nippon Unicar Company.
[0041]
The synthetic resin (B) having a melt flow rate ratio represented by the above formula (2) can be obtained by adjusting the molecular weight, molecular weight distribution, type of lubricant, addition amount, and the like of the polyethylene resin to be blended.
[0042]
  As the foaming agent added to the base resin (A) in order to form the foamed layer 2 of the multilayer parison, either a physical foaming agent or a decomposable foaming agent can be used. Use physical foaming agent to getTo do.Examples of physical foaming agents include propane, normal butane, isobutane, normal pentane, isopentane, normal hexane, isohexane, cyclohexane, and other aliphatic hydrocarbons, methyl chloride, ethyl chloride, and other chlorinated hydrocarbons, 1,1,1,2 -Fluorinated hydrocarbons such as tetrafluoroethane, 1,1-difluoroethane, difluoromethane, carbon dioxide, nitrogen, water, methyl alcohol, ethyl alcohol and the like. Examples of the decomposable foaming agent include azodicarbonamide. Two or more kinds of the above-mentioned foaming agents can be mixed and used, and a decomposable foaming agent can also be added to the physical foaming agent in order to adjust bubbles.
[0043]
As the thermoplastic polymer used for forming the polymer layer 4 of the multilayer parison when obtaining the foam molded body 1 further having the polymer layer 14 of the foam molded body on the outer surface of the resin layer 13 of the foam molded body, For example, polyethylene resins such as low density polyethylene, high density polyethylene, linear low density polyethylene, polypropylene, propylene-ethylene random copolymer, propylene-1 butene random copolymer, propylene-ethylene block copolymer, propylene -Heat of one or a mixture of two or more selected from polypropylene resins such as butene block copolymers, cyclic polyolefins, polycarbonate resins, polyester resins, styrene elastomers, olefin elastomers, polyester elastomers, etc. A plastic polymer is mentioned. Of these resins, when using a resin constituting the resin layer 3 of the multilayer parison and a thermoplastic polymer having no practically sufficient thermal adhesiveness, the polymer layer 4 of the multilayer parison and An adhesive layer may be provided between the resin layer 3 of the multilayer parison.
[0044]
As the polymer layer 4 of the multilayer parison, it is preferable to use a polyolefin-based elastomer, a polystyrene-based elastomer, or an impact-resistant polystyrene because a foamed molded article 1 having excellent impact resistance can be obtained, and in particular, a polypropylene-based elastomer is used. Is preferable because it is possible to obtain a foamed molded article 1 having excellent impact resistance and heat resistance. Further, the polymer layer 4 of the multilayer parison is not limited to a film or sheet, but may be a fibrous form such as a nonwoven fabric or a woven fabric, and is not limited to a single layer but a multilayer. May be.
[0045]
The multilayer parison foam layer 2, multilayer parison resin layer 3, multilayer parison polymer layer 4, and multilayer parison inner surface resin layer 5 include an anti-shrink agent, a weather resistance agent, an ultraviolet absorber, an ultraviolet reflector, and an infrared ray. Various additives such as absorbers, infrared reflectors, flame retardants, fluidity improvers, weathering agents, colorants, heat stabilizers, antioxidants, crystal nucleating agents, inorganic fillers, rubbers, etc. are blended as necessary. can do.
[0046]
The multilayer parison 6 in the present invention has the resin layer 3 of the multilayer parison made of the molten synthetic resin on at least the outer surface of the foamed layer 2 of the multilayer parison made of the foamable molten resin. The multilayer parison 6 having such a structure can be obtained by melt-kneading a foaming agent and an air conditioner such as talc, an anti-shrinkage agent, or the like added to the base resin (A) with an extruder. It can be obtained by co-extrusion of the foamable molten resin, the synthetic resin (B), various additives added as necessary, and the molten synthetic resin (B) obtained by melt-kneading with an extruder.
[0047]
In addition, the multilayer parison which consists of three or more different layers such as the multilayer parison 6 in which the polymer layer 4 of the multilayer parison is provided on the outer surface of the resin layer 3 of the multilayer parison shown in FIG. A suitable extruder is used, and an annular die having a structure capable of merging and laminating a plurality of resins according to the number of layers of the multilayer parison is used. The multilayer parison 6 or the like provided with the inner surface resin layer 5 of the multilayer parison shown in FIG. 2C is used when the inner surface resin layer 5 of the multilayer parison is made of the same synthetic resin as the resin layer 3 of the multilayer parison. Can be obtained by branching the melted synthetic resin supplied from the same extruder in an annular die for coextrusion and then laminating each with a foamable molten resin without increasing the number of extruders. Can do.
[0048]
The size of the multilayer parison 6 is approximately 1.5m depending on the application.ThreeIt is possible to select within the range up to.
[0049]
The density of the foam layer 2 of the multilayer parison is 20 to 500 kg / m.ThreeIs more preferable, and more preferably 25 to 400 kg / m.ThreeIt is. The density of the foam layer 2 of the multilayer parison is 500 kg / mThreeExceeding this makes it difficult to say that the foamed molded article 1 obtained from the multi-layer parison is lightweight, and there is a risk that physical properties such as heat insulation will be reduced. The density of the foam layer 2 of the multilayer parison is 20 kg / mThreeIf it is less than the range, the foam film 2 constituting the foamed layer 2 of the multilayer parison becomes thin, so that it is difficult to obtain a good foamed molded article 1 such that bubbles are easily broken during molding.
[0050]
The thickness of the foamed layer 2 of the multilayer parison is preferably 1 mm to 100 mm. If the thickness of the foamed layer 2 of the multilayer parison is less than 1 mm, physical properties such as strength, soundproofing and heat insulation of the foamed molded product 1 obtained from the multilayer parison may be lowered. On the other hand, if the thickness of the foamed layer 2 of the multilayer parison exceeds 100 mm, foaming or molding becomes difficult, and there is a possibility that a good foamed molded product 1 cannot be obtained.
[0051]
The thickness of the resin layer 3 of the multilayer parison is preferably 100 μm to 10 mm, more preferably 100 μm to 7 mm. If the thickness of the resin layer 3 of the multi-layer parison becomes too thin, the surface smoothness of the foamed molded article 1 obtained from the multi-layer parison is lowered, and the appearance may be deteriorated. On the other hand, when the thickness of the resin layer 3 of the multilayer parison becomes too thick, the foamed molded body 1 obtained from the multilayer parison becomes heavy, and it is difficult to say that it is lightweight depending on the application. There is a possibility that the closed cell ratio of the material becomes low.
[0052]
When the multilayer parison 6 is provided with the polymer layer 4 of the multilayer parison shown in FIG. 2B, the thickness of the polymer layer 4 of the multilayer parison is preferably 20 μm to 10 mm, more preferably 50 μm to 7 mm. If the thickness of the polymer layer 4 of the multi-layer parison becomes too thin, the multi-layer such as impact resistance, cold resistance, heat resistance, chemical resistance, buffering, weather resistance, flame resistance, appearance improvement, mechanical strength, etc. By providing the parison polymer layer 4, the effect imparted to the foam molded article 1 may be reduced. On the other hand, when the thickness of the polymer layer 4 of the multilayer parison becomes too thick, the foamed molded body 1 obtained from the multilayer parison becomes heavy, and it is difficult to say that it is lightweight depending on the application.
[0053]
When the inner surface resin layer 5 of the multilayer parison shown in FIG. 2C is provided in the multilayer parison 6, the thickness of the inner surface resin layer 5 of the multilayer parison is preferably 100 μm to 10 mm. When the thickness of the inner surface resin layer 5 of the multilayer parison is less than 100 μm, the function of a rib for preventing the occurrence of shrinkage and deformation in the foam molded body obtained from the multilayer parison is lowered. Changes are likely to occur. On the other hand, when the thickness of the inner surface resin layer 5 of the multilayer parison is too thick, there is a possibility that the lightweight property of the foamed molded product is impaired.
[0054]
In the method for producing the foam molded body 1 of the present invention, the multilayer parison 6 is molded with a molding die so that at least a part of the innermost surfaces of the parison 6 is fused, thereby foaming the foam molded body. The foam molded body 1 having the resin layer 13 of the foam molded body on the surface of the layer 12 is obtained.
[0055]
In the present specification, the fusion rate between the innermost surfaces of the multilayer parison 6 is represented by the fusion part area ratio (%). In the present invention, from the viewpoint of obtaining a foamed molded article 1 having sufficient mechanical strength and dimensional stability, the fused portion area ratio is preferably 30% or more, more preferably 40% or more. 60% or more is particularly preferable. The method for measuring the area ratio of the fused part is as follows.
[0056]
First, the foam molded body 1 is divided into 10 equal parts at equal intervals so that the cut surface is orthogonal to the extrusion direction of the multilayer parison 6 at the time of manufacturing the foam molded body 1 and parallel to the mold compression direction of the multilayer parison 6. Disconnect.
[0057]
Next, the cut pieces of the foamed molded product are placed so that the cut surfaces are positioned in the left and right directions in the order in which the foamed molded product 1 was formed. The length (mm) of the portion where the inner surfaces are fused is obtained, and a value obtained by doubling the length is defined as a fused portion length L (mm). In addition, when the innermost surface of the multi-layer parison forms a gap without being fused on the right cut surface, the inner circumferential length M (mm) of the gap is obtained. In addition, when there are a plurality of the fusion parts and / or gaps on each cut surface, for each part, obtain the fusion part length of each part and / or the inner peripheral length of the gap part of each part, Let L or M be the sum of. Next, a fusion part area ratio (%) is obtained from these values by the following formula.
[0058]
[Expression 14]
Fusion part area ratio (%) = [L / (L + M)] × 100
[0059]
In the present specification, the fused portion area ratio (%) of the foamed molded product has an arithmetic average value of the fused portion area ratio of each cut surface (excluding the cut surface where the innermost fused portion itself does not exist). To do. In the cross section where the innermost surfaces are fused without a gap and there is no gap, the area ratio of the fused portion is 100%.
[0060]
  The density of the foam layer 12 of the foam molded article obtained by the method of the present invention is25-400kg / m Three It is.As described above, by forming the foamed layer 2 of the multilayer parison, the foamed layer 12 of the foam molded body having such a density can be formed. The density of the foam layer 12 of the foam molded product istoo highIn this case, it is difficult to say that the foamed molded article 1 is lightweight, and physical properties such as heat insulation may be deteriorated. Moreover, the density of the foam layer 12 of the foam molded product isToo lowIn such a case, there is a possibility that the foamed molded body 1 may not be a good foamed molded body 1 because the foam film constituting the foamed layer 12 of the foamed molded body is thin and easily foams during molding.
[0061]
The density of the foamed layer 12 of the foamed molded product in this specification is determined as follows. Only the foam layer 12 of the foam-molded body is cut out from the foam-molded body 1, and the weight (g) of the cut-out sample is determined by the volume (cmThree), And the obtained value is kg / mThreeIt is obtained by converting to a unit. Moreover, the thickness of each layer can be calculated | required from a molded object cross section (it expands with a microscope as needed and uses the enlarged projection figure). In addition, since the density of the foamed layer 12 of the foamed molded product 1 may be different for each part of the foamed molded product 1, samples of the foamed layer 12 of the foamed molded product from 10 or more locations such as the bottom and side surfaces of the foamed molded product 1 are used. Cut out, measure the density of each sample, and use the arithmetic average of the remaining measured values excluding the maximum and minimum values as the density of the foamed layer 12 of the foam molded article.
[0062]
  In the foam molded article 1 obtained by the method of the present invention, the thickness of the resin layer 13 of the foam molded article is 100 μm to 10 mm.And preferably100 μm to 7 mm. By forming the resin layer 3 of the multilayer parison as described above, the resin layer 13 of the foam molded body having such a thickness can be obtained. If the thickness of the resin layer 13 of the foamed molded product becomes too thin, the surface smoothness is lowered, so that the appearance of the foamed molded product 1 may be deteriorated. On the other hand, if the thickness of the resin layer 13 of the foam molded body becomes too thick, the weight of the entire foam molded body 1 becomes heavy. There is a possibility that the closed cell ratio is lowered.
[0063]
The foam molded body 1 obtained by the method of the present invention is provided with a core layer 15 of a foam molded body sandwiched between foam layers 12 of the foam molded body, and causes the core layer 15 of the foam molded body to act like a rib. Therefore, it is preferable to prevent shrinkage and deformation from occurring in the foam molded article 1. The thickness of the core layer 15 of the foam molded article is preferably 100 μm to 10 mm. By forming the inner surface resin layer 5 of the multilayer parison as described above, the core layer 15 of the foam molded article having such a thickness can be obtained. If the thickness of the core layer 15 of the foamed molded product is less than 100 μm, the function of the ribs is lowered, and depending on the shape of the foamed molded product 1, shrinkage or deformation may easily occur. On the other hand, if the core layer 15 of the foamed molded product is too thick, the lightweight property of the foamed molded product may be impaired.
[0064]
The core layer 15 of the foam molded article can be formed as follows corresponding to the target thickness.
In the case where the thickness of the core layer 15 of the foam molded body is thin, when molding the foam molded body 1 from the multilayer parison 6, the inner surface of the multilayer parison 6 is relatively fused to the portion where the inner surfaces of the multilayer parison 6 are fused. The core layer 15 of a high-density thin foam-molded product can be formed. When the thickness of the core layer 15 of the foam molded body is thick, the core layer 15 of the target foam molded body can be formed by providing the multilayer parison 6 with the inner surface resin layer 5 of the multilayer parison as described above. .
[0065]
The overall density of the foamed molded article 1 obtained by the method of the present invention is preferably 20 to 800 kg / m.ThreeAnd more preferably 20 to 400 kg / mThreeIt is. The overall density of the foam molded body 1 is 800 kg / m.ThreeIf it exceeds 1, there is a possibility that the lightness and the heat insulating property are lowered. The density of the foam molded body 1 is 20 kg / m.ThreeIf it is less than 1, mechanical properties such as compressive strength may be lowered.
[0066]
The total density of the foamed molded product 1 in this specification is the volume (m) measured by submerging the foamed molded product 1 in weight (kg).Three(However, the volume of the void portion is not subtracted from the volume of the molded body that is obtained even when a void portion is present inside the foamed molded product).
[0067]
The foamed molded product 1 shown in FIG. 1 given as a specific example of the container obtained by the method of the present invention adopts a configuration in which the innermost surfaces of the multilayer parison 6 are completely fused together without any gap, and the container space 16 is formed. It is obtained by molding to form.
[0068]
As shown in FIG. 1, when a container is selected as an application of a foam molded article, the density is 30 to 400 kg / m.ThreeWhen it is configured to be lighter, it is superior in heat insulation, and when it is configured such that the thickness of the resin layer 13 of the foamed molded product is 200 μm to 5 mm, the durability and surface smoothness are high, and the appearance In addition to a balance between lightness and lightness, the shrinkage of the container after molding is small, and the mechanical strength against external force is excellent. Further, when the product is made of a multilayer resin foam molded article in which the foam molded article polymer layer 14 is provided on the surface of the foam molded article resin layer 13, it is particularly suitable as a returnable container.
[0069]
The manufacturing method of the foaming molding 1 of this invention is demonstrated in more detail based on FIG.3 and FIG.4.
As shown in FIG. 3, the multi-layer parison 6 is prepared by melt-kneading the base resin forming each layer of the multi-layer parison 6 with separate extruders (not shown), and laminating and merging them in a die 21. Obtained by extruding to. If necessary, an accumulator may be installed between the extruder and the die 21 or in the die 21.
[0070]
A method of obtaining the foam molded body 1 from the multilayer parison 6 is as follows.
First, after forming the multilayer parison 6, as shown in FIG. 3, the divided molds 22a and 22b are closed so as to sandwich the extruded multilayer parison 6 from both side surfaces. When the mold is closed, the foamed multilayer parison 6 is compressed on the inner surface of the mold and is brought into close contact with the mold while being deformed into a flat shape. Next, when the mold is closed as shown in FIG. 4, at least a part of the inner surfaces of the multilayer parison 6 is fused to obtain the foamed molded article 1 of the present invention. As shown in FIG. 1, the foam molded body 1 in which the innermost surfaces of the multilayer parison 6 are completely in close contact with each other and integrated without a gap is preferable because of excellent mechanical strength and dimensional stability.
[0071]
  In addition, as shown in FIG. 3, by providing the mold with a decompression pipe 23, the mold22a, 22b and the outer surface of the multilayer parison 6 are used so that the pressure can be reduced, and the mold is closed while being decompressed to form the outer surface of the multilayer parison 6 and the inner surface of the mold. It is possible to obtain a foamed molded article 1 that adheres well and reproduces the mold shape well. Moreover, the foam molded body 1 obtained in this way has improved mold pattern transfer to the surface of the foam molded body when a mold having a pattern on the inner surface of the mold is used, and has an excellent appearance. Become.
[0072]
Alternatively, immediately after the multi-layer parison 6 is extruded, the multi-layer parison 6 may be closed by a parison pinch and expanded by pre-blowing in the same manner as described above.
[0073]
When the multi-layer parison 6 is formed by deep drawing, as shown in FIGS. 5A and 5B, the four side surfaces 25 of the female mold 22b are configured to be movable around the bottom surface 24. By doing so, it is preferable that the female die 22b can be assembled and expanded. When the female mold 22b is unfolded and the female mold 22b is assembled by moving the side surface 25 of the female mold 22b and closing the male mold 22a and the female mold 22b, the multilayer parison is formed. 6 deep drawing molding becomes easy.
[0074]
3-5 is explanatory drawing which shows the example of manufacture of a foaming molding notionally, The specific operation procedure which manufactures a foaming molding in this invention is not limited to what is illustrated.
[0075]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. Melt flow rate of polyethylene resin used in the following examples and comparative examples: MFR (g / 10 min), density (kg / mThree) And α and β are shown in Tables 1 and 2.
[0076]
[Table 1]
Figure 0004484175
[0077]
[Table 2]
Figure 0004484175
[0078]
Examples 1-4
6 parts by weight of a polyethylene-based cell regulator masterbatch in which 100 parts by weight of the foamed layer forming resin of the multilayer parison shown in Table 3 and 5 parts by weight of sodium citrate and 10 parts by weight of talc are blended with 100 parts by weight of polyethylene And a raw material blended with 10 parts by weight of a polyethylene-based anti-shrinkage agent masterbatch blended with 12 parts by weight of monoglyceride stearic acid with respect to 100 parts by weight of polyethylene is heated and kneaded to obtain a molten resin. Thereafter, isobutane as a physical foaming agent was added to the molten resin in the extruder at a ratio of 2.2 parts by weight (in the case of Example 4, 3.2 parts by weight) with respect to 100 parts by weight of the foam layer forming resin of the multilayer parison. It was press-kneaded to obtain a foamable molten resin.
[0079]
On the other hand, a colorant was blended with the resin for forming a resin layer of the multilayer parison shown in Table 3, and supplied to an extruder, and melted by heating to obtain a non-foaming molten synthetic resin. Next, each accumulator connected to each extruder is filled with the melt melt-kneaded in each extruder, and then the foamable molten resin and the molten synthetic resin are joined and laminated in the die from each accumulator. A foamed molten resin and a molten synthetic resin were injected, extruded from a die, and a multilayered parison resin layer made of a molten synthetic resin was laminated on the outer surface of the foamed layer of the multilayered parison formed by foaming the foamable molten resin. A multilayer parison was obtained.
[0080]
Next, as shown in FIG. 5, the box-shaped split mold placed directly under the die so as to sandwich the extruded parison is closed, and the multilayer parison is deformed into a flat shape on the mold inner surface, Further, the mold was closed, the multilayer parison was brought into close contact with the inner surface of the mold and molded, and then cooled and released to obtain a foamed molded product. The foamed molded body is a truncated trapezoidal container having an opening outer dimension of 300 mm × 260 mm, a bottom surface outer dimension of 260 mm × 180 mm, a height of 110 mm, and a container meat pressure of about 20 mm. In addition, the said metal mold | die used what gave the satin finish to the inner surface of the metal mold | die.
[0081]
The foamed molded products obtained in Examples 1 to 4 each had good surface smoothness and good appearance with no shrink deformation or buckling. When the obtained foamed molded product was cut and the cross section was observed, both had a foamed resin layer on the surface of the foamed layer of the foamed molded product, and the inner surfaces of the foamed layers of the multilayer parison had no gaps. The foamed molded product was well fused.
[0082]
Table 3 shows the melt flow rate, α, β values, and melt flow rate ratios (MFR1 / MFR2) of the resin for forming the foam layer of the multilayer parison and the resin for forming the resin layer of the multilayer parison used in each example. The thickness of the foam layer of the obtained foam molded body, the thickness of the resin layer of the foam molded body, the density of the foam layer of the foam molded body, the density of the entire foam molded body, and each of normal temperature and low temperature (−20 ° C.) Table 4 shows the results of the drop weight impact test performed under the conditions.
[0083]
[Table 3]
Figure 0004484175
[0084]
[Table 4]
Figure 0004484175
* 1: Bubbles in the foamed layer were greatly broken and contracted, and the appearance was poor, and a foamed molded product with various physical properties could not be obtained.
* 2: A foamed molded article with large drawdown, thin foam layer, and measurable physical properties could not be obtained.
[0085]
Appearance was evaluated based on the following criteria by visually observing the container-like foamed molded article.
○: Surface smoothness and mold reproducibility are good
X: Concavities and convexities due to shrinkage are seen
[0086]
  The impact resistance test isIn accordance with JIS K7211Drop weight impact testWent.
  Specifically, in the drop weight impact test at room temperature, a test piece having a size of 100 mm × 100 mm was cut out from the foamed molded article, and the test piece was left for 24 hours in a constant temperature and humidity chamber at a temperature of 23 ° C. and a humidity of 55%. Using this test piece, in a constant temperature and humidity chamber at a temperature of 23 ° C. and a humidity of 55%, Toyo Seiki Co., Ltd. Using a 621 falling weight impact tester, whether or not the test piece breaks by dropping the shaped weight of the nominal type 1 (mass 1 kg) defined in JIS K7211 from a height of 1.5 m. evaluated.
In Table 4, the case where the test piece did not break was indicated by ◯.
[0087]
The drop weight impact test at a low temperature was conducted by leaving the test piece in a -20 ° C. constant temperature bath for 24 hours and measuring each test piece in the constant temperature and humidity chamber at a temperature of 23 ° C. and a humidity of 55%. Except for being performed within seconds, the test was performed in the same manner as the drop weight impact test at room temperature, and evaluation was performed according to the same criteria.
[0088]
Example 5
A multilayer parison was formed in the same manner as in Example 1, using the resin for forming the foamed layer of the multilayer parison shown in Table 3 and the resin for forming the resin layer of the multilayer parison. Next, a foamed molded article was obtained by molding in the same manner as in Example 1 except that a multi-divided mold having a box shape different from the mold used in Example 1 was used. The foamed molded body is a rectangular parallelepiped container, and the dimensions are an opening outer diameter dimension of 300 mm × 230 mm, a height of 120 mm, and a container wall thickness of about 20 mm.
[0089]
The foamed molded product obtained in Example 5 had good surface smoothness and good appearance with no shrink deformation or buckling. When the obtained foamed molded article was cut and the cross section was observed, it had a resin layer of the foamed molded article on the surface of the foamed layer of the foamed molded article, and the inner surfaces of the foamed layers of the multilayer parison were good without gaps. It was a foamed molded product fused.
[0090]
Example 6
In the same manner as in Example 1, a foamable molten resin was obtained. On the other hand, the resin for forming the resin layer of the multilayer parison shown in Table 3 was supplied to an extruder and melted by heating to obtain a non-foaming molten synthetic resin. Next, each melt melt-kneaded in each extruder was filled in each accumulator connected to each extruder. The non-foaming molten synthetic resin was divided into a resin layer forming resin and an inner surface resin layer forming resin, and each was filled in a separate accumulator. After that, from the three accumulators, the molten synthetic resin for forming the resin layer, the foamable molten resin, and the molten synthetic resin for forming the inner surface resin layer are injected from the die in order from the outside. Extrusion was performed to obtain a multilayer parison in which a resin layer, a foam layer, and an inner surface resin layer were laminated in order from the outside. Next, a foamed molded product was obtained in the same manner as in Example 1.
[0091]
The foamed moldings obtained in Example 6 all had good surface smoothness and good appearance with no shrink deformation or buckling. When the obtained foamed molded product was cut and the cross section was observed, the foamed molded product had a resin layer of the foamed molded product on the surface of the foamed molded product, and the inner surfaces of the inner surface resin layers of the multilayer parison were good without gaps. To form a core layer of a foam molded body having a thickness of 0.5 mm.
[0092]
Comparative Example 1
A multilayer parison was obtained in the same manner as in Example 1 by using the foam layer forming resin and the resin layer forming resin shown in Table 3. Although the multilayer parison was molded, a low-density foam molded article having a large shrinkage of the foamed layer and good appearance could not be obtained.
[0093]
Comparative Example 2
Example except that the foaming layer forming resin of the multilayer parison and the resin for forming the resin layer of the multilayer parison shown in Table 3 were used, and the physical foaming agent was added by 2.4 parts by weight with respect to 100 parts by weight of the foaming layer forming resin of the multilayer parison. A multilayer parison was obtained in the same manner as in Example 1. Although the multilayer parison was molded, a foamed molded article having a good appearance with large tearing and shrinkage of bubbles in the foamed layer could not be obtained.
[0094]
Comparative Example 3
Using the multilayered parison foam layer forming resin and the multilayer parison resin layer forming resin shown in Table 3, production of the multilayer parison was attempted in the same manner as in Example 1. It did not foam and a good multilayer parison was not obtained. This multilayer parison was molded in the same manner as in Example 1, but the drawdown was large and the thickness of the foamed layer was thin, and a good foamed molded product could not be obtained.
[0095]
【The invention's effect】
In the method for producing a multilayer polyethylene resin foam molded article of the present invention, the main component has a density of 900 to 940 (kg / mThreeIn the dynamic viscoelasticity measurement in which vibration distortion is given under a temperature condition of 190 ° C., the angular frequency ω = 10-1-101In the base resin whose storage elastic modulus G ′ (Pa) in the range of (rad / sec) satisfies the following formula (1):PhysicsA foamable molten resin obtained by adding a foaming agent and melt-kneading, and a synthetic resin containing 20 to 100% by weight of a polyethylene resin, and a melt flow rate of the synthetic resin: MFR1 (g / 10 minutes) The above-mentioned base resin melt flow rate: MFR2 (g / 10 min) ratio by co-extrusion with a synthetic resin obtained by melting a synthetic resin satisfying the following formula (2): Form a multi-layer parison having a polyethylene-based resin layer made of the above-mentioned molten synthetic resin on at least the outer surface of a polyethylene-based resin foam layer made of a foamable molten resin, and then molding so that at least a part of the innermost surfaces of the parison are fused together By molding with moldDensity 25-400kg / m 3 ofOn the surface of the polyethylene resin foam layer100 μm to 10 mm thickA configuration is adopted in which a foamed molded product having a polyethylene resin layer is obtained.
[0096]
[Expression 15]
    log G '= αlogω + β (1)
            α = 0.50-1.50
            β = 2.0-5.0
[Expression 16]
    MFR1 / MFR2> 1.0 (2)
[0097]
By adopting the above configuration, the thickness and density of the multilayer parison having the polyethylene resin layer made of the molten synthetic resin on at least the outer surface of the polyethylene resin foam layer made of the foamable molten resin constituting the multilayer parison can be arbitrarily selected. Alternatively, by adjusting, the thickness and density of the polyethylene resin foam layer constituting the obtained multilayer polyethylene resin foam molded article can be arbitrarily selected or adjusted within a wide range. Therefore, according to the production method of the present invention, it is possible to easily obtain a multilayer polyethylene resin foam molded article having a high-thickness and low-density foam layer. In addition, the polyethylene resin layer formed on the surface of the polyethylene resin foam layer obtained by the method of the present invention has a uniform thickness and does not generate scale-like patterns, cracks or holes on the surface. It is good.
[0098]
  Of the present inventionManyA method for producing a layered polyethylene resin foam molded article is a method in which a multilayer parison having a polyethylene resin layer is formed on at least an outer surface of a polyethylene resin foam layer, and at least a part of the innermost inner surfaces of the parison is fused. Is formed by Accordingly, in the manufacturing method of the present invention, a hollow structure molded body molded from a thermoplastic resin is used as a resin layer, and urethane resin is injected into the cavity inside the molded body. Unlike conventional methods such as filling and molding resin foam particles and the like, complicated manufacturing processes and apparatuses are not required.
[0099]
  In the production method of the present invention, the storage elastic modulus G ′ (Pa) of the base resin satisfies the following formula (3), and a melt flow rate of synthetic resin: MFR1 (g / 10 min) and a foamed layer are formed. The ratio of melt flow rate of the base resin to MFR2 (g / 10 min) is as follows:(2)By adopting a configuration that satisfies the formula, the foamability of the polyethylene resin foam layer of the multilayer parison, the drawdown property and the like are further improved, and the appearance of the polyethylene resin layer of the multilayer parison, the elongation of the resin layer, The drawdown property and the like are further improved, and it has become possible to obtain a low-density multilayer polyethylene-based resin foam molded article that is difficult to obtain by a conventional method for molding a multilayer parison with high productivity.
[0100]
[Expression 17]
  log G '= αlogω + β (3)
            α = 0.60-1.40
            β = 2.0 to 3.8
[Expression 18]
  MFR1 / MFR2> 1.0 (2)
[0101]
Furthermore, the multilayer polyethylene-based resin foam molded article obtained by the method of the present invention is lightweight, impact resistant, cold resistant, heat resistant, chemical resistant, recyclable, heat insulating, buffered, soundproof, vibration proof, Excellent mechanical strength such as compression, tension and bending. The foam molded article is also suitable as a deep-drawn molded article or a large molded article, such as containers such as returnable containers, lightweight insulation panels such as floors and doors, pallets, pillars, bumpers, and instrument panels. It is suitably used for low temperature containers used in automobile parts, desks, chairs, floats, surfboards, bodyboards, etc., particularly in refrigerated warehouses.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an example of a multilayer polyethylene resin foam molded article obtained by the method of the present invention.
FIG. 2 is a partially cutaway perspective view showing an example of a multilayer parison used in the method for producing a multilayer polyethylene resin foam molded article of the present invention.
FIG. 3 is an explanatory view showing one step of the production method of the present invention.
FIG. 4 is an explanatory view showing one step of the production method of the present invention.
FIG. 5 is an explanatory view showing a different aspect of the production method of the present invention.
[Explanation of symbols]
1 Foam molding
2 Foam layer
3 Resin layer
6 Multi-layer parison
12 Foamed layer of foamed molding
13 Resin layer of foam molding

Claims (2)

主成分が密度９００〜９４０（ｋｇ／ｍ３）のポリエチレン系樹脂であると共に、１９０℃の温度条件下で振動歪みを与える動的粘弾性測定において角周波数ω＝１０−１〜１０１（ｒａｄ／ｓｅｃ）の範囲における貯蔵弾性率Ｇ'（Ｐａ）が下記（１）式を満足する基材樹脂に、物理発泡剤を添加し溶融混練して得られる発泡性溶融樹脂と、２０〜１００重量％のポリエチレン系樹脂を含む合成樹脂であると共に、該合成樹脂のメルトフローレイト：ＭＦＲ１（ｇ／１０分）と上記基材樹脂のメルトフローレイトＭＦＲ２（ｇ／１０分）との比が下記（２）式を満足する合成樹脂を、溶融して得られる溶融合成樹脂とを、共押出することにより、上記発泡性溶融樹脂よりなるポリエチレン系樹脂発泡層の少なくとも外面に上記溶融合成樹脂よりなるポリエチレン系樹脂層を有する多層パリソンを形成し、次いで該パリソン最内面同士の少なくとも一部が融着するように成形型にて成形することによって密度２５〜４００ｋｇ／ｍ ３ のポリエチレン系樹脂発泡層の表面に厚み１００μｍ〜１０ｍｍのポリエチレン系樹脂層を有する発泡成形体を得ることを特徴とする多層ポリエチレン系樹脂発泡成形体の製造方法。
【数１】 log Ｇ'＝αlogω＋β （１）
α＝０．５０〜１．５０
β＝２．０〜５．０
【数２】 ＭＦＲ１／ＭＦＲ２＞１．０ （２）The main component is a polyethylene resin having a density of 900 to 940 (kg / m 3 ), and an angular frequency ω = 10 −1 to 10 1 (rad) in a dynamic viscoelasticity measurement that gives vibration distortion under a temperature condition of 190 ° C. / Sec), a foamable molten resin obtained by adding a physical foaming agent to a base resin having a storage elastic modulus G ′ (Pa) satisfying the following formula (1) and melt-kneading: 20 to 100 weight % Of the synthetic resin containing polyethylene resin, and the ratio of the melt flow rate of the synthetic resin: MFR1 (g / 10 minutes) to the melt flow rate MFR2 (g / 10 minutes) of the base resin is as follows ( 2) A molten synthetic resin obtained by melting a synthetic resin satisfying the formula is coextruded to form at least the outer surface of the polyethylene-based resin foam layer made of the foamable molten resin. Forming a multilayer parison having become more polyethylene resin layer, and then a polyethylene resin foamed density 25~400kg / m 3 by at least a part of each other the parison innermost surface is molded by the mold to fuse A method for producing a multilayer polyethylene resin foam molded article, comprising obtaining a foam molded article having a polyethylene resin layer having a thickness of 100 μm to 10 mm on the surface of the layer.
## EQU1 ## log G ′ = αlogω + β (1)
α = 0.50-1.50
β = 2.0-5.0
## EQU2 ## MFR1 / MFR2> 1.0 (2) 前記請求項１において基材樹脂の貯蔵弾性率Ｇ'（Ｐａ）が下記（３）式を満足することを特徴とする多層ポリエチレン系樹脂発泡成形体の製造方法。
【数３】 log Ｇ'＝αlogω＋β （３）
α＝０．６０〜１．４０
β＝２．０〜３．８ In Claim 1, the storage elastic modulus G '(Pa) of the base resin satisfies the following formula (3) :
Log G ′ = αlogω + β (3)
α = 0.60-1.40
β = 2.0 to 3.8
JP36755899A 1999-12-24 1999-12-24 Method for producing multilayer polyethylene-based resin foam molding Expired - Fee Related JP4484175B2 (en)

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