JP2004277673A

JP2004277673A - Styrene-based resin-foamed board and method for producing the same

Info

Publication number: JP2004277673A
Application number: JP2003074957A
Authority: JP
Inventors: Naoyuki Futamura; 直行二村; Shinichi Anami; 伸一阿南
Original assignee: Sekisui Plastics Co Ltd
Current assignee: Sekisui Kasei Co Ltd
Priority date: 2003-03-19
Filing date: 2003-03-19
Publication date: 2004-10-07
Anticipated expiration: 2023-03-19
Also published as: JP4101684B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a styrene-based resin-foamed board excellent in heat-insulating property and flame retardant property, especially in the heat-insulating property, having the excellent heat insulation satisfying class B-3 specified by JIS A9511, and used suitably as the insulation material for construction, etc. <P>SOLUTION: This styrene-based resin-foamed board produced by an extrusion foaming by using a blowing agent consisting of dimethyl ether, butane and water is characterized by having 0.05-0.20 mm mean bubble diameter in thickness direction of the styrene-based resin foamed board in at least one bubble on the surface layer, and 1.45-2.50 folds mean bubble diameter in the thickness direction of the styrene-based resin-foamed board in a bubble at a central layer as compared with the mean bubble diameter in thickness direction of the styrene-based resin foamed board in the bubble in the surface layer, and having an excellent heat insulation and flame retardant property even being produced by using a non-chlorofluorocarbon blowing agent. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、断熱性及び難燃性に優れたスチレン系樹脂発泡板及びその製造方法に関する。
【０００２】
【従来の技術】
従来からスチレン系樹脂発泡板は建築用断熱材に汎用されており、このスチレン系樹脂発泡板は、スチレン系樹脂を押出機に供給して溶融、混練した後、この溶融状態のスチレン系樹脂に発泡剤を圧入した上で押出機から押出発泡させて製造されている。
【０００３】
そして、上記発泡剤としては、ジクロロジフルオロメタン（フロン−１２）等の塩素原子含有ハロゲン化炭化水素（ＣＦＣ）が用いられていたが、オゾン層を破壊するという環境上の問題点があることから、１−モノクロロ−１，１−ジフルオロエタン（フロン−１４２ｂ）等の塩素原子を部分的に水素化した水素原子含有ハロゲン化炭化水素（ＨＣＦＣ）への改善が試みられ、更に、ＨＣＦＣから１、１，１，２−テトラフルオロエタン（フロン−１３４ａ）等のフッ素化炭化水素（ＨＦＣ）への転換が行われている。
【０００４】
加えて、発泡剤のノンフロン化を図るために、塩化メチルや塩化エチル等のハロゲン化炭化水素と、ブタンやプロパン等の炭化水素とを組み合わせた発泡剤の使用も行われているが、塩化メチルや塩化エチル等は塩素原子を含んでいることから、環境上、可能であれば代替されることが好ましいとされている。
【０００５】
そこで、特許文献１には、ジメチルエーテル等のエーテル類及びブタンやプロパン等の炭化水素からなる発泡剤及び水を用いて製造された、大小径気泡が共存するセル構造を有するスチレン系樹脂発泡体が提案されている。
【０００６】
しかしながら、上記スチレン系樹脂発泡体は、ＪＩＳＡ９５１１で規定されたＢ類２種程度の断熱性しか有せず、断熱性に劣るものであって、ノンフロンの発泡剤を用いて製造された断熱性に優れたスチレン系樹脂発泡板が所望されていた。
【０００７】
【特許文献１】
ＷＯ９９／５４３９０（特許請求の範囲）
【０００８】
【発明が解決しようとする課題】
本発明は、断熱性及び難燃性に優れ、特に、断熱性にあっては、ＪＩＳＡ９５１１で規定されたＢ類３種を満たす優れた断熱性を有し、建築用断熱材等に好適に用いることができるスチレン系樹脂発泡板及びその製造方法を提供する。
【０００９】
【課題を解決するための手段】
本発明のスチレン系樹脂発泡板は、ジメチルエーテル、ブタン及び水からなる発泡剤を用いて押出発泡により製造されたスチレン系樹脂発泡板であって、少なくとも一つの表面層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径が０．０５〜０．２０ｍｍであると共に、中心層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径が、上記表面層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径の１．４５〜２．５０倍であることを特徴とする。
【００１０】
上記スチレン系樹脂発泡板の少なくとも一つの表面層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径は、小さいと、中心層の気泡における厚み方向の平均気泡径が小さくなって厚みの厚いスチレン系樹脂発泡板とすることができず、又、大きいと、気泡壁による熱の遮断回数が少なくなってしまってスチレン系樹脂発泡板の断熱性が低下するので、０．０５〜０．２０ｍｍに限定され、０．０８〜０．１５ｍが好ましい。なお、スチレン系樹脂発泡板の二つの表面の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径が、０．０５〜０．２０ｍｍに限定され、０．０８〜０．１５ｍとされるのが好ましい。
【００１１】
又、上記スチレン系樹脂発泡板の中心層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径は、上記表面層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径の１．４５〜２．５０倍に限定され、１．５０〜２．３０倍が好ましく、１．５０〜２．００倍がより好ましい。
【００１２】
これは、スチレン系樹脂発泡板の中心層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径が、上記表面層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径の１．４５倍を下回ると、中心層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径と、表面層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径との差が小さくなって、スチレン系樹脂発泡板の気泡径が全体的に小さくなり、厚みの厚いスチレン系樹脂発泡板を得ようとすると、気泡がスチレン系樹脂発泡板の厚み方向に長い紡錘形状となり、気泡壁による熱の遮断回数が少なくなってスチレン系樹脂発泡板の断熱性が低下し、或いは、スチレン系樹脂発泡板がその押出方向に収縮するといった問題点が発生するからである。
【００１３】
一方、スチレン系樹脂発泡板の中心層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径が、上記表面層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径の２．５０倍を上回ると、中心層の気泡径が大きくなり、気泡壁による熱の遮断回数が少なくなってスチレン系樹脂発泡板の断熱性が低下するからである。
【００１４】
なお、スチレン系樹脂発泡板の厚み方向とは、スチレン系樹脂発泡板の肉薄方向であって、スチレン系樹脂発泡板の表面に対する法線方向をいう。そして、スチレン系樹脂発泡板の表面層とは、スチレン系樹脂発泡板の表面と、この表面から厚み方向に４ｍｍだけ内側に入った部分との間にある部分をいい、又、スチレン系樹脂発泡板の中心層とは、スチレン系樹脂発泡板から、スチレン系樹脂発泡板の表面と、この表面から厚み方向に１０ｍｍだけ内側に入った部分との間にある部分を除いた残余部分をいう。
【００１５】
ここで、スチレン系樹脂発泡板の表面層又は中心層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径は下記の要領で測定されたものをいう。即ち、スチレン系樹脂発泡板を任意の箇所にて押出方向に直交する面で切断する。そして、スチレン系樹脂発泡板の切断面にて目的とする層、即ち、表面層又は中心層から任意に三点を選択し、この選択された三点のそれぞれについて電子顕微鏡を用いて２０倍の拡大写真を撮影する。
【００１６】
得られた拡大写真上に長さ８０ｍｍの直線を三本、スチレン系樹脂発泡板の厚み方向に任意に描き、各直線上にある気泡の数を数え、各直線毎に下記式に基づいて、スチレン系樹脂発泡板の厚み方向の気泡径を算出する。
【００１７】
そして、９本の直線のそれぞれから算出された、スチレン系樹脂発泡板の厚み方向の気泡径の平均を、表面層又は中心層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径とする。なお、直線上にある気泡の数を数える際、気泡の一部分が僅かでも直線上にある場合は一つとして数えた。
【００１８】
スチレン系樹脂発泡板の厚み方向の気泡径（ｍｍ）＝８０／２０×ｎ（ｎ：直線上にある気泡の数）
【００１９】
上記スチレン系樹脂発泡板の表面層及び中心層における気泡構造としては、各層毎に均一な気泡径を有する気泡構造であっても、大きな気泡径の気泡（大径気泡）と小さな気泡径の気泡（小径気泡）とが同一層内において存在し、大径気泡が小径気泡中に不規則に存在している気泡構造であってもよいが、気泡壁による熱の遮断効果が高く、得られるスチレン系樹脂発泡板の断熱性が高いことから、大小径気泡が同一層内において存在し、大径気泡が小径気泡中に不規則に存在している気泡構造が好ましい。
【００２０】
上記スチレン系樹脂発泡板を構成するスチレン系樹脂としては、特に限定されず、例えば、スチレン、メチルスチレン、エチルスチレン、イソプロピルスチレン、ジメチルスチレン、クロロスチレン、ブロモスチレン等のスチレン系単量体の単独重合体又はこれらスチレン系単量体を２種以上組み合わせた共重合体；アクリル酸、メタクリル酸、アクリル酸メチル、メタクリル酸メチル、アクリロニトリル、無水マレイン酸、ブタジエン等の単量体と上記スチレン系単量体との共重合体等が挙げられる。なお、共重合体は、ブロック共重合体、ランダム共重合体、グラフト共重合体の何れであってもよい。又、上記スチレン系樹脂が５０重量％以上含有しておれば、スチレン系樹脂以外の熱可塑性樹脂を添加させてもよい。
【００２１】
なお、上記スチレン系樹脂発泡板には、その物性を損なわない範囲内において、タルク、炭酸カルシウム、珪酸カルシウム、酸化チタン、グラファイト、ベントナイト等の気泡調整剤；フェノール系抗酸化剤；耐光性安定剤；ヘキサブロモシクロドデカン等の難燃剤、リン系難燃剤等の難燃剤；ステアリン酸モノグリセライド等の帯電防止剤；顔料等の着色剤；ステアリン酸マグネシウム等の高級脂肪酸金属塩等の添加剤が含有されてもよい。なお、難燃剤としてヘキサブロモシクロドデカンを添加する場合には、スチレン系樹脂１００重量部に対して２．０〜４．０重量部が好ましい。
【００２２】
次に、スチレン系樹脂発泡板の製造方法を説明する。このスチレン系樹脂発泡板は、スチレン系樹脂１００重量部、ヘキサブロモシクロドデカン２．０〜４．０重量部及び合成雲母０．３〜３．０重量部を押出機に供給して溶融、混練し、この溶融状態のスチレン系樹脂中にジメチルエーテル６０〜８０重量％及びブタン２０〜４０重量％からなる有機系発泡剤３〜１５重量部及び水０．７〜１．５重量部を圧入した後、押出機に取り付けた金型のリップ先端温度を下記式を満たす温度に保持しつつ、上記金型から押出発泡することにより製造することができる。
押出機から吐出された樹脂温度−４０℃≦
金型のリップ先端温度≦押出機から吐出された樹脂温度−１５℃
【００２３】
そして、上記ヘキサブロモシクロドデカンの添加量は、少ないと、スチレン系樹脂発泡板の難燃性が低下し、又、多いと、表面層及び中心層における気泡を所定大きさに制御することができず、スチレン系樹脂発泡板の機械的強度や、スチレン系樹脂の発泡性が低下するので、スチレン系樹脂１００重量部に対して２．０〜４．０重量部が好ましく、２．５〜３．５重量部がより好ましい。
【００２４】
又、上記合成雲母は、天然の雲母とは異なり、天然の雲母の結晶構造中の全ての−ＯＨ基が−Ｆ基で置換された組成を有する人工的に作られた雲母であり、ＫＭｇ_３ＡｌＳｉ_３Ｏ_１０Ｆ_２を理想組成とするものである。
【００２５】
そして、合成雲母の平均粒径は、小さいと、嵩比重が小さくなり、押出機へ供給する際に凝集して樹脂中への分散が不十分となって、スチレン系樹脂発泡板内に合成雲母の凝集体が発生したり或いは連続気泡率が高くなることがあり、又、大きいと、スチレン系樹脂発泡板の気泡数が減少して平均気泡径が大きくなることがあるので、１〜５０μｍが好ましく、１〜２０μｍがより好ましく、１〜１０μｍが特に好ましい。
【００２６】
なお、上記合成雲母の平均粒径は、レーザー散乱法によって測定されたものをいい、具体的には、島津製作所社から商品名「ＳＡＬＤ−２１００」、日機装社から商品名「マイクロトラック９３２０ＨＲＡ」で市販されている測定装置を用いて湿式法にて測定することができる。
【００２７】
そして、合成雲母の添加量は、少ないと、溶融状態のスチレン系樹脂に圧入した水が合成雲母に吸収されずに溶融状態のスチレン系樹脂から分離して押出機のシリンダ内面に付着し、スチレン系樹脂に対する押出機の推進力が低下して、押出発泡が不安定となり、又、多いと、合成雲母同士が凝集し、表面層及び中心層の気泡径を特定大きさで形成することが困難となってスチレン系樹脂発泡板の断熱性が低下するので、スチレン系樹脂１００重量部に対して０．３〜３．０重量部が好ましく、０．５〜２．０重量部がより好ましく、０．８〜１．５重量部が特に好ましい。
【００２８】
又、有機系発泡剤としては、ジメチルエーテル及びブタンからなるものが用いられる。上記ブタンとしては、イソブタン、ノルマルブタンが挙げられ、単独で用いられても併用されてもよい。
【００２９】
そして、ブタンとしてイソブタンとノルマルブタンとを併用する場合、ブタン中におけるイソブタンの含有量は、少ないと、スチレン系樹脂発泡板の断熱性が低下することがあるので、３０重量％以上が好ましく、５０重量％以上がより好ましい。
【００３０】
又、有機系発泡剤中におけるジメチルエーテルの含有量は、少ないと、相対的にブタン量が多くなってスチレン系樹脂発泡板の難燃性が低下し、又、多いと、相対的にブタン量が少なくなってスチレン系樹脂発泡板の断熱性が低下するので、６０〜８０重量％が好ましい。同様の理由で、有機系発泡剤中におけるブタンの含有量は、２０〜４０重量％が好ましい。
【００３１】
そして、上記有機系発泡剤の添加量は、少ないと、スチレン系樹脂発泡板の発泡倍率が低下して断熱性や軽量性が低下し、又、多いと、スチレン系樹脂発泡板内部にボイド（大きな空隙部）が生じるので、スチレン系樹脂１００重量部に対して３〜１５重量部が好ましい。
【００３２】
更に、溶融状態のスチレン系樹脂中に圧入される水は、特に限定されないが、不純物の少ないもの、例えば、純水を用いることが好ましい。なお、水の添加量は、スチレン系樹脂１００重量部に対して０．７〜１．５重量部が好ましく、０．９〜１．３重量部がより好ましい。
【００３３】
これは、水の添加量がスチレン系樹脂１００重量部に対して０．７重量部を下回ると、表面層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径と、中心層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径との差が小さくなって、スチレン系樹脂発泡板の気泡径が全体的に小さくなり、厚みの厚いスチレン系樹脂発泡板を得ようとすると、気泡がスチレン系樹脂発泡板の厚み方向に長い紡錘形状となり、厚み方向の気泡数が減少して気泡壁による熱の遮断回数が少なくなってスチレン系樹脂発泡板の断熱性が低下し、或いは、スチレン系樹脂発泡板がその押出方向に収縮するといった問題点が発生する一方、水の添加量がスチレン系樹脂１００重量部に対して１．５重量部を上回ると、押出発泡時に押出変動が発生して良好なスチレン系樹脂発泡板を得ることができないからである。
【００３４】
又、上記有機系発泡剤及び水を溶融状態のスチレン系樹脂中に圧入するタイミングとしては、有機系発泡剤と水とをスチレン系樹脂中に同時に圧入しても別々に圧入してもよいが、有機系発泡剤を先にスチレン系樹脂中に圧入した後に水をスチレン系樹脂中に圧入するのが好ましい。
【００３５】
これは、水は、ヘキサブロモシクロドデカンを分解して難燃剤の効果を損なわせる作用があるため、押出機中における水とヘキサブロモシクロドデカンとの接触時間をできるだけ短くして、水によるヘキサブロモシクロドデカンの分解を最小限にとどめ、スチレン系樹脂発泡板の難燃性を向上させるためである。
【００３６】
そして、押出機に取り付けた金型のリップ先端温度を下記式を満たすように保持しつつ、金型から押出発泡している。
押出機から吐出された樹脂温度−４０℃≦
金型のリップ先端温度≦押出機から吐出された樹脂温度−１５℃
【００３７】
更に、押出機に取り付けた金型のリップ先端温度を下記式を満たすように保持しつつ、金型から押出発泡するのが好ましい。
押出機から吐出された樹脂温度−３５℃≦
金型のリップ先端温度≦押出機から吐出された樹脂温度−２０℃
【００３８】
なお、金型のリップ内に形成された冷却媒体流路には、該リップを冷却させるために、水やオイル等の冷却媒体を連続的に流通させており、この冷却媒体をリップの冷却媒体流路内に供給する時の温度を、金型のリップ先端温度とする。
【００３９】
そして、上記冷却媒体を金型のリップの冷却媒体流路内に流通させる流量は、冷却媒体流路内に流入する時の冷却媒体の温度と、冷却媒体流路から流出する時の冷却媒体の温度との差が、好ましくは５℃未満、より好ましくは３℃未満となるように調整する。
【００４０】
又、押出機樹脂出口部に配設したブレーカプレートの中心部温度を熱電対を用いて測定し、この測定された温度を、押出機から吐出された樹脂温度とする。
【００４１】
これは、金型のリップ先端温度が、押出機から吐出された樹脂温度よりも４０℃を超えて低いと、金型のリップでスチレン系樹脂が固化して押出発泡することができない一方、金型のリップ先端温度と、押出機から吐出された樹脂温度との差が１５℃未満であると、表面層の気泡径が大きくなって、スチレン系樹脂発泡板の厚み方向における気泡の数が少なくなり気泡壁による熱の遮断回数が減少してスチレン系樹脂発泡板の断熱性が低下したり、或いは、突沸が発生して良好なスチレン系樹脂発泡板を得ることができないからである。
【００４２】
ここで、本発明のスチレン系樹脂発泡板の製造方法では、合成雲母及び水を所定割合でスチレン系樹脂に供給すると共に、金型のリップ部分によって所定温度に冷却することによって、難燃剤であるヘキサブロモシクロドデカンの存在にもかかわらず、表面層及び中心層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径を上述のように制御してなるスチレン系樹脂発泡板を得ることができる。
【００４３】
この理由は明確に解明されていないが、合成雲母は層状に形成され、押出機内における剪断応力によって各層が互いに剥離して微細な形状となった上で溶融状態のスチレン系樹脂中に均一に分散すると共に、合成雲母はその表面に水を吸着すればする程、核剤効果を発揮して気泡をより多く発生させる。
【００４４】
しかも、本発明のスチレン系樹脂発泡板の製造方法では、スチレン系樹脂との相溶性が低い水をスチレン系樹脂１００重量部に対して０．７〜１．５重量部と若干、過剰に添加していることから、水は、金型内部の樹脂流路を流通する間に外側（金型壁面側、表面側）に移行し、発泡適性温度に冷却された溶融状態のスチレン系樹脂の表面近傍部における水の濃度が残余のスチレン系樹脂部分よりも高くなっている。
【００４５】
その結果、スチレン系樹脂の表面近傍部に分散した合成雲母は、スチレン系樹脂の内面側（中心部）に分散した合成雲母に比して、水を充分に吸着した状態となっており、この合成雲母の作用によって溶融状態のスチレン系樹脂の表面近傍部に、残余のスチレン系部分に比して、より多くの微細な気泡が発生する。
【００４６】
その上、スチレン系樹脂を金型から押出発泡する際、金型のリップ先端温度を押出機から吐出されたスチレン系樹脂の温度から所定温度だけ低い温度範囲に調整していることも相まって、得られるスチレン系樹脂発泡板は、その表面層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径が小さく形成されている一方、中心層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径が、表面層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径よりも所定倍だけ大きく形成されており、その結果、ＪＩＳＡ９５１１で規定されたＢ類３種を満たす優れた断熱性を有すると共に、押出発泡時におけるスウェル減少の抑制によって厚みの厚いものとすることができる。
【００４７】
そして、上記の如くして得られたスチレン系樹脂発泡板の密度は、低いと、断熱性が低下することがあり、又、高いと、厚みの厚いスチレン系樹脂発泡板とすることが困難となることがあるので、３０〜４５ｋｇ／ｍ^３が好ましい。なお、スチレン系樹脂発泡板の密度は、ＪＩＳＫ７２２２に準拠して測定されたものをいう。
【００４８】
更に、スチレン系樹脂発泡板の熱伝導率は、０．０２８０Ｗ／ｍＫ以下が好ましい。なお、スチレン系樹脂発泡板の熱伝導率は以下の要領で測定されたものをいう。
【００４９】
即ち、押出発泡後３０日が経過したスチレン系樹脂発泡板から、押出方向（ＭＤ方向）に２００ｍｍ、押出方向に直交し且つスチレン系樹脂発泡板の表面に沿った方向（ＴＤ方向）に１５０ｍｍ、厚み方向（ＶＤ方向）に２５ｍｍの寸法でもって試験片を切り出す。なお、試験片の一面全面がスチレン系樹脂発泡板の表面層となるようにする。
【００５０】
しかる後、上記試験片の熱伝導率を、ＪＩＳＡ１４１２：１９９４の「熱絶縁材の熱伝導率及び熱抵抗の測定方法」にて規定された平板熱流計法に基づいて測定する。
【００５１】
又、押出発泡後３０日経過したスチレン系樹脂発泡板に含まれるブタン量は、少ないと、スチレン系樹脂発泡板の断熱性が低下する一方、多いと、スチレン系樹脂発泡板の難燃性が低下するので、１．５重量％以上で且つ３．０重量％未満が好ましく、２重量％以上で且つ２．５重量％未満がより好ましい。
【００５２】
なお、押出発泡後３０日経過したスチレン系樹脂発泡板に含まれるブタン量は、下記の要領で測定されたものをいう。即ち、押出発泡後３０日経過したスチレン系樹脂発泡板から、該スチレン系樹脂発泡板の両面と、この両面のそれぞれから厚み方向に内側に４ｍｍだけ入った部分との間にある表層部分を除外し、この表層部分が除外されたスチレン系樹脂発泡板から、押出方向（ＭＤ方向）に３５ｍｍ、スチレン系樹脂発泡板の表面に沿い且つ押出方向に直交する方向（ＴＤ方向）に５ｍｍ、厚み方向（ＶＤ方向）に５ｍｍの大きさを有する直方体形状の試験片を切り出し、この試験片の重量を測定する。
【００５３】
そして、上記試験片を１５０℃の熱分解炉に供給してガスクロマトグラフィーからチャートを得、予め測定しておいたブタンの検量線に基づいて上記チャートから試験片中のブタン量を算出し、以下の式に基づいて求める。
【００５４】
（押出発泡後３０日経過したスチレン系樹脂発泡板に含まれるブタン量）＝１００×試験片中のブタン量／試験片の重量
【００５５】
更に、上記では、発泡剤として、有機系発泡剤及び水をスチレン系樹脂中に圧入しているが、得られるスチレン系樹脂発泡板の物性を損なわない範囲内において、有機系発泡剤及び水以外の発泡剤を添加してもよいが、ハロゲン原子を含む発泡剤は用いないのが好ましい。
【００５６】
このような発泡剤としては、例えば、窒素、塩化メチル、１，１−ジフルオロエタン、１，１，１−トリフルオロエタン、１，１，１，２−テトラフルオロエタン、１，１，１，２，２−ペンタフルオロエタン、二酸化炭素等が挙げられる。
【００５７】
【実施例】
（実施例１〜２、比較例１〜４）
押出機として、第一押出機の先端部に第二押出機を連結させてなるタンデム型押出機を用い、この第一押出機に、表１に示した所定量のポリスチレン（東洋スチレン社製商品名「ＨＲＭ−１８」）、ヘキサブロモシクロドデカン（ＨＢＣＤ）、合成雲母（コープケミカル社製商品名「ＭＥ１００」、平均粒径：３μｍ）及びタルクを供給して溶融、混練した。
【００５８】
そして、上記第一押出機の先端部分に一体的に設けた一の注入口から、表１に示した所定量のジメチルエーテル及びブタン（イソブタン：６０重量％、ノルマルブタン：４０重量％）からなる有機系発泡剤を溶融状態のポリスチレンに圧入した後、第一押出機の他の注入口から表１に示した所定量の水を溶融状態のポリスチレンに圧入して、ポリスチレンと、有機系発泡剤及び水とを混合した。
【００５９】
しかる後、溶融状態のポリスチレンを第一押出機から第二押出機に連続的に供給して、第二押出機にてポリスチレンを発泡に適した樹脂温度に冷却した上で、第二押出機の先端に取り付けた金型から押出発泡した。なお、押出機からのポリスチレンの吐出量を３５ｋｇ／時間とした。
【００６０】
続いて、第二押出機の金型から押出発泡された直後の溶融状態の押出発泡板を、第二押出機の先端部に取り付けられた金型に密接させて配設された、上下方向に３０ｍｍの間隔を存して平行に配設され且つ約３０℃に維持された上下一対の板状体（サイジングプレート）の対向面間に連続的に供給して押出発泡板の両面を冷却してスチレン系樹脂発泡板を得た。なお、金型のリップ先端温度及び押出機から吐出された樹脂温度は表１の通りであった。
【００６１】
なお、比較例３については、押出発泡板の表面に突沸が発生して良好なスチレン系樹脂発泡板を得ることができず、又、比較例４については、全体的に気泡径が小さくなりすぎてスチレン系樹脂発泡板を得ることができなかった。
【００６２】
以上の如くして得られたスチレン系樹脂発泡板の表面層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径（表面層気泡径）、中心層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径（中心層気泡径）、密度、熱伝導率、押出発泡後３０日経過したスチレン系樹脂発泡板に含まれるブタン量（残ブタン量）、難燃性について測定し、その結果を表２に示した。
【００６３】
（難燃性）
ＪＩＳＡ９５１１：１９９５に規定された測定方法Ａの燃焼性試験に基づいて測定した際の消炎時間の平均値を燃焼性とした。なお、押出発泡後１週間経過したスチレン系樹脂発泡板から、該スチレン系樹脂発泡板の両面と、この両面から厚み方向に２ｍｍ以上、内側に入った部分との間にある部分を除去し、このスチレン系樹脂発泡板の残余部分から、押出方向（ＭＤ方向）に２００ｍｍ、押出方向に直交し且つスチレン系樹脂発泡板の表面に沿った方向（ＴＤ方向）に２５ｍｍ、厚み方向（ＶＤ方向）に１０ｍｍの寸法でもって試験片を５個、切り出し、各試験片の消炎時間の平均時間を難燃性とした。
【００６４】
【表１】

【００６５】
【表２】

【００６６】
なお、実施例１で得られたスチレン系樹脂発泡板について、押出方向（ＭＤ方向）に２００ｍｍ、押出方向に直交し且つスチレン系樹脂発泡板の表面に沿った方向（ＴＤ方向）に１５０ｍｍ、厚み方向（ＶＤ方向）に全厚み寸法（２８ｍｍ）でもって試験片を切り出し、この試験片について上述と同様の要領で熱伝導率を測定したところ、０．０２６３Ｗ／ｍＫであった。
【００６７】
【発明の効果】
請求項１に記載のスチレン系樹脂発泡板は、ジメチルエーテル、ブタン及び水からなる発泡剤を用いて押出発泡により製造されたスチレン系樹脂発泡板であって、少なくとも一つの表面層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径が０．０５〜０．２０ｍｍであると共に、中心層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径が、上記表面層の気泡におけるスチレン系樹脂発泡板の厚み方向の平均気泡径の１．４５〜２．５０倍であることを特徴とするので、ノンフロンの発泡剤を用いて製造されたものであるにもかからず優れた断熱性及び難燃性を有し、特に、断熱性は、ＪＩＳＡ９５１１で規定されたＢ類３種を満たす優れた断熱性を有している。
【００６８】
しかも、上記スチレン系樹脂発泡板は、その断熱性及び難燃性を損ねることなく、厚みを厚くすることができ、種々の用途、特に、建築用断熱材等の建築用途に好適に用いることができる。
【００６９】
そして、請求項２に記載のスチレン系樹脂発泡板は、請求項１に記載のスチレン系樹脂発泡板において、密度が３０〜４５ｋｇ／ｍ^３であると共に、熱伝導率が０．０２８０Ｗ／ｍＫ以下であることを特徴とするので、軽量性及び断熱性に優れており、建築用断熱材等の建築用途に用いた場合、優れた取り扱い性を発揮する。
【００７０】
請求項３に記載のスチレン系樹脂発泡板は、請求項１又は請求項２に記載のスチレン系樹脂発泡板において、押出発泡後３０日経過したスチレン系樹脂発泡板に含まれるブタン量が１．５重量％以上で且つ３．０重量％未満であることを特徴とするので、断熱性及び難燃性を両立させつつ両性能を効果的に発揮させることができる。
【００７１】
請求項４に記載のスチレン系樹脂発泡板の製造方法は、スチレン系樹脂１００重量部、ヘキサブロモシクロドデカン２．０〜４．０重量部及び合成雲母０．３〜３．０重量部を押出機に供給して溶融、混練し、この溶融状態のスチレン系樹脂中にジメチルエーテル６０〜８０重量％及びブタン２０〜４０重量％からなる有機系発泡剤３〜１５重量部及び水０．７〜１．５重量部を圧入した後、押出機に取り付けた金型のリップ先端温度を上述した関係を満たす温度に保持しつつ、上記金型から押出発泡することを特徴とするので、地球環境に与える影響を極めて小さくしつつ、断熱性、特に、ＪＩＳＡ９５１１に規定されたＢ類３種を満たす断熱性と、難燃性とに優れていると共に厚みの厚いスチレン系樹脂発泡板を円滑に且つ確実に製造することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a styrene-based resin foam plate excellent in heat insulation and flame retardancy, and a method for producing the same.
[0002]
[Prior art]
Conventionally, styrene resin foam boards have been widely used as heat insulating materials for buildings.The styrene resin foam boards are supplied to an extruder, melted and kneaded, and then mixed with the molten styrene resin. It is manufactured by press-fitting a foaming agent and extruding foam from an extruder.
[0003]
As the foaming agent, a halogen atom-containing halogenated hydrocarbon (CFC) such as dichlorodifluoromethane (CFC-12) has been used. However, there is an environmental problem of destroying the ozone layer. , 1-monochloro-1,1-difluoroethane (Freon-142b) and the like to improve hydrogen atom-containing halogenated hydrocarbons (HCFCs) in which chlorine atoms have been partially hydrogenated. Conversion to fluorinated hydrocarbons (HFCs) such as 1,1,2-tetrafluoroethane (Freon-134a) has been performed.
[0004]
In addition, in order to make the blowing agent non-fluorocarbon, a blowing agent combining a halogenated hydrocarbon such as methyl chloride or ethyl chloride with a hydrocarbon such as butane or propane has been used. Since ethyl chloride and the like contain a chlorine atom, it is said that it is preferable to substitute it if possible in the environment.
[0005]
Therefore, Patent Document 1 discloses a styrene-based resin foam having a cell structure in which large and small-diameter bubbles coexist, which is manufactured by using a blowing agent comprising ethers such as dimethyl ether and a hydrocarbon such as butane and propane, and water. Proposed.
[0006]
However, the above-mentioned styrene resin foam has only about two kinds of heat insulating properties of Class B specified in JIS A9511, is inferior in heat insulating property, and has a heat insulating property produced by using a non-fluorocarbon foaming agent. There has been a demand for a styrene-based resin foam plate having excellent resistance.
[0007]
[Patent Document 1]
WO99 / 54390 (Claims)
[0008]
[Problems to be solved by the invention]
INDUSTRIAL APPLICABILITY The present invention has excellent heat insulating properties and flame retardancy, and particularly, in terms of heat insulating properties, has excellent heat insulating properties satisfying three kinds of Class B specified in JIS A9511, and is suitable for architectural heat insulating materials and the like. Provided are a styrene resin foam plate that can be used and a method for producing the same.
[0009]
[Means for Solving the Problems]
The styrene resin foam board of the present invention is a styrene resin foam board manufactured by extrusion foaming using a foaming agent consisting of dimethyl ether, butane and water, and the styrene resin foam board in at least one surface layer of bubbles. The average cell diameter in the thickness direction is 0.05 to 0.20 mm, and the average cell diameter in the thickness direction of the styrene resin foam plate in the air bubbles in the center layer is the styrene resin foam plate in the air bubbles in the surface layer. It is characterized by being 1.45 to 2.50 times the average cell diameter in the thickness direction.
[0010]
The average cell diameter in the thickness direction of the styrene resin foam plate in the cells of at least one surface layer of the styrene resin foam plate is small, and the average cell diameter in the thickness direction of the cells in the center layer is small and the thickness is large. If the styrene resin foam plate cannot be used, and if it is large, the number of times of heat interruption by the cell walls decreases, and the heat insulating property of the styrene resin foam plate decreases, so that 0.05 to 0.20 mm Is limited to 0.08 to 0.15 m. In addition, the average cell diameter in the thickness direction of the styrene-based resin foam plate in the cells on the two surfaces of the styrene-based resin foam plate is limited to 0.05 to 0.20 mm, and is set to 0.08 to 0.15 m. Is preferred.
[0011]
The average cell diameter in the thickness direction of the styrene resin foam plate in the cells in the center layer of the styrene resin foam plate is 1.45 of the average cell diameter in the thickness direction of the styrene resin foam plate in the cells in the surface layer. The ratio is limited to ~ 2.50 times, preferably 1.50 to 2.30 times, more preferably 1.50 to 2.00 times.
[0012]
This is because the average cell diameter in the thickness direction of the styrene resin foam plate in the cells in the center layer of the styrene resin foam plate is 1.45 of the average cell diameter in the thickness direction of the styrene resin foam plate in the cells in the surface layer. If it is less than twice, the difference between the average cell diameter in the thickness direction of the styrene resin foam plate in the bubbles in the center layer and the average cell diameter in the thickness direction of the styrene resin foam plate in the cells in the surface layer becomes smaller, When trying to obtain a thicker styrene-based resin foam plate with a smaller cell diameter as a whole and a thicker styrene-based resin foam plate, the cells have a spindle shape that is longer in the thickness direction of the styrene-based resin foam plate, and heat is blocked by the cell wall. This is because the number of times is reduced, and the heat insulating property of the styrene resin foam board is reduced, or the styrene resin foam board shrinks in the extrusion direction.
[0013]
On the other hand, the average cell diameter in the thickness direction of the styrene resin foam plate in the bubbles in the center layer of the styrene resin foam plate is 2.50 times the average cell diameter in the thickness direction of the styrene resin foam plate in the cells in the surface layer. If the ratio exceeds the above, the cell diameter of the central layer becomes large, the number of times of heat interruption by the cell walls is reduced, and the heat insulating property of the styrene resin foam plate is reduced.
[0014]
In addition, the thickness direction of the styrene-based resin foam plate refers to a direction in which the thickness of the styrene-based resin foam plate is thin, and a normal direction to the surface of the styrene-based resin foam plate. The surface layer of the styrene-based resin foam board refers to a portion between the surface of the styrene-based resin foam board and a portion inwardly extending 4 mm from the surface in the thickness direction. The central layer of the plate refers to the remaining portion of the styrene-based resin foamed plate except for the portion between the surface of the styrene-based resin foamed plate and a portion inward of the surface by 10 mm in the thickness direction.
[0015]
Here, the average cell diameter in the thickness direction of the styrene-based resin foam plate in the cells in the surface layer or the center layer of the styrene-based resin foam plate refers to one measured in the following manner. That is, the styrene-based resin foam plate is cut at an arbitrary position on a surface orthogonal to the extrusion direction. Then, arbitrarily select three points from the target layer on the cut surface of the styrene-based resin foam plate, that is, the surface layer or the central layer, and use an electron microscope to magnify each of the three selected points by 20 times. Take a magnified photo.
[0016]
On the obtained enlarged photograph, three straight lines having a length of 80 mm are arbitrarily drawn in the thickness direction of the styrene-based resin foam plate, the number of bubbles on each straight line is counted, and for each straight line, based on the following equation, Calculate the cell diameter in the thickness direction of the styrene resin foam plate.
[0017]
Then, the average of the cell diameters in the thickness direction of the styrene-based resin foam plate calculated from each of the nine straight lines is defined as the average cell diameter in the thickness direction of the styrene-based resin foam plate in the bubbles in the surface layer or the center layer. . When counting the number of bubbles on a straight line, even if a part of the bubbles was on a straight line, it was counted as one.
[0018]
Cell diameter (mm) in the thickness direction of the styrene resin foam plate = 80/20 × n (n: number of cells on a straight line)
[0019]
Regarding the cell structure in the surface layer and the center layer of the styrene resin foam plate, even if the cell structure has a uniform cell diameter for each layer, the cells having a large cell diameter (large cells) and the cells having a small cell diameter are used. (Small-diameter bubbles) may be present in the same layer and the large-diameter bubbles may be irregularly present in the small-diameter bubbles. Since the heat insulation of the resin foam plate is high, a bubble structure in which large- and small-diameter bubbles are present in the same layer and large-diameter bubbles are irregularly present in the small-diameter bubbles is preferable.
[0020]
The styrene-based resin constituting the styrene-based resin foam board is not particularly limited. For example, styrene-based monomers such as styrene, methylstyrene, ethylstyrene, isopropylstyrene, dimethylstyrene, chlorostyrene, and bromostyrene alone may be used. A polymer or a copolymer obtained by combining two or more of these styrene monomers; monomers such as acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, acrylonitrile, maleic anhydride, butadiene and the above styrene monomer; And a copolymer with a monomer. In addition, the copolymer may be any of a block copolymer, a random copolymer, and a graft copolymer. If the styrene resin is contained in an amount of 50% by weight or more, a thermoplastic resin other than the styrene resin may be added.
[0021]
The foamed styrene-based resin board may have a bubble regulator such as talc, calcium carbonate, calcium silicate, titanium oxide, graphite, bentonite, etc., a phenolic antioxidant; A flame retardant such as hexabromocyclododecane, a flame retardant such as a phosphorus-based flame retardant; an antistatic agent such as monoglyceride stearate; a coloring agent such as a pigment; an additive such as a metal salt of a higher fatty acid such as magnesium stearate; You may. In addition, when hexabromocyclododecane is added as a flame retardant, 2.0 to 4.0 parts by weight is preferable based on 100 parts by weight of the styrene resin.
[0022]
Next, a method for producing a styrene resin foam board will be described. This styrene-based resin foam plate is supplied with 100 parts by weight of a styrene-based resin, 2.0 to 4.0 parts by weight of hexabromocyclododecane, and 0.3 to 3.0 parts by weight of synthetic mica to an extruder to be melted and kneaded. Then, 3 to 15 parts by weight of an organic blowing agent composed of 60 to 80% by weight of dimethyl ether and 20 to 40% by weight of butane and 0.7 to 1.5 parts by weight of water are injected into the molten styrene resin. It can be manufactured by extruding and foaming from the mold while maintaining the lip tip temperature of the mold attached to the extruder at a temperature satisfying the following formula.
Temperature of resin discharged from the extruder −40 ° C. ≦
Mold lip tip temperature ≤ resin temperature discharged from the extruder -15 ° C
[0023]
When the amount of the hexabromocyclododecane is small, the flame retardancy of the styrene-based resin foam plate is reduced, and when it is large, the bubbles in the surface layer and the central layer can be controlled to a predetermined size. However, since the mechanical strength of the styrene-based resin foam plate and the foamability of the styrene-based resin are reduced, 2.0 to 4.0 parts by weight is preferable for 100 parts by weight of the styrene-based resin, and 2.5 to 3 parts by weight. 0.5 parts by weight is more preferred.
[0024]
Further, the synthetic mica is different from the natural mica is mica all -OH groups in the crystal structure of natural mica is artificially created having a composition which is substituted by -F group, KMg ₃ AlSi ₃ O ₁₀ F ₂ has an ideal composition.
[0025]
When the average particle size of the synthetic mica is small, the bulk specific gravity becomes small, and when supplied to an extruder, the aggregates are aggregated and insufficiently dispersed in the resin. Agglomerates may occur or the open cell rate may increase, and if it is large, the number of cells in the styrene-based resin foam plate may decrease and the average cell diameter may increase. Preferably, it is 1-20 μm, more preferably 1-10 μm.
[0026]
The average particle size of the synthetic mica refers to that measured by a laser scattering method. Specifically, Shimadzu Corporation has a trade name of “SALD-2100”, and Nikkiso Co., Ltd. has a trade name of “Microtrack 9320HRA”. It can be measured by a wet method using a commercially available measuring device.
[0027]
If the amount of synthetic mica added is small, water injected into the molten styrene-based resin is separated from the molten styrene-based resin without being absorbed by the synthetic mica and adheres to the inner surface of the extruder cylinder. The extrusion force of the extruder for the base resin decreases, and extrusion foaming becomes unstable. If too much, synthetic mica aggregates and it is difficult to form the cell diameter of the surface layer and the central layer with a specific size. Since the heat insulation of the styrene-based resin foam plate is reduced, the amount is preferably 0.3 to 3.0 parts by weight, more preferably 0.5 to 2.0 parts by weight, based on 100 parts by weight of the styrene-based resin. 0.8 to 1.5 parts by weight is particularly preferred.
[0028]
Further, as the organic foaming agent, one composed of dimethyl ether and butane is used. Examples of the butane include isobutane and normal butane, which may be used alone or in combination.
[0029]
When isobutane and normal butane are used in combination as butane, if the content of isobutane in butane is small, the heat insulating property of the styrene-based resin foam plate may be reduced. % By weight or more is more preferable.
[0030]
Also, when the content of dimethyl ether in the organic foaming agent is small, the butane content is relatively large and the flame retardancy of the styrene-based resin foam board is reduced, and when the content is large, the butane content is relatively large. The content is preferably 60 to 80% by weight, since the heat-insulating property of the styrene-based resin foam plate is reduced. For the same reason, the content of butane in the organic blowing agent is preferably 20 to 40% by weight.
[0031]
If the amount of the organic foaming agent is small, the expansion ratio of the styrene-based resin foam plate is reduced, and the heat insulating property and the lightness are reduced. 3 to 15 parts by weight with respect to 100 parts by weight of the styrene-based resin.
[0032]
Further, the water injected into the molten styrene-based resin is not particularly limited, but it is preferable to use water having a small amount of impurities, for example, pure water. In addition, the addition amount of water is preferably 0.7 to 1.5 parts by weight, more preferably 0.9 to 1.3 parts by weight, based on 100 parts by weight of the styrene resin.
[0033]
This is because when the amount of water added is less than 0.7 parts by weight with respect to 100 parts by weight of the styrene resin, the average cell diameter in the thickness direction of the styrene resin foam plate in the cells of the surface layer and the cell in the center layer are reduced. When the difference from the average cell diameter in the thickness direction of the styrene resin foam board becomes smaller, the cell diameter of the styrene resin foam board becomes smaller overall, and when trying to obtain a thicker styrene resin foam board, bubbles Has a spindle shape that is long in the thickness direction of the styrene resin foam board, the number of cells in the thickness direction decreases, the number of times of heat interruption by the cell walls decreases, and the heat insulation of the styrene resin foam board decreases, or styrene On the other hand, when the amount of water exceeds 1.5 parts by weight with respect to 100 parts by weight of the styrene resin, extrusion fluctuation occurs during extrusion foaming. It is not possible to obtain a good styrene resin foam plate.
[0034]
The timing of injecting the organic blowing agent and water into the styrene resin in a molten state may be such that the organic blowing agent and water may be simultaneously or separately injected into the styrene resin. It is preferable to first press the organic blowing agent into the styrene resin, and then press water into the styrene resin.
[0035]
This is because water has the effect of decomposing hexabromocyclododecane and impairing the effect of the flame retardant, so that the contact time between water and hexabromocyclododecane in the extruder is reduced as much as possible, This is because the decomposition of cyclododecane is minimized and the flame retardancy of the styrene resin foam board is improved.
[0036]
Then, while the lip tip temperature of the mold attached to the extruder is maintained so as to satisfy the following equation, the foam is extruded and foamed from the mold.
Temperature of resin discharged from the extruder −40 ° C. ≦
Mold lip tip temperature ≤ resin temperature discharged from the extruder -15 ° C
[0037]
Further, it is preferable to extrude and foam from the mold while maintaining the lip tip temperature of the mold attached to the extruder so as to satisfy the following equation.
Resin temperature discharged from the extruder-35 ° C ≤
Mold lip tip temperature ≤ resin temperature discharged from the extruder-20 ° C
[0038]
In order to cool the lip, a cooling medium such as water or oil is continuously passed through a cooling medium flow path formed in the lip of the mold. The temperature at the time of supply into the flow path is defined as the lip tip temperature of the mold.
[0039]
The flow rate of the cooling medium flowing through the cooling medium flow path of the mold lip is determined by the temperature of the cooling medium flowing into the cooling medium flow path and the cooling medium flowing out of the cooling medium flow path. It is adjusted so that the difference from the temperature is preferably less than 5 ° C, more preferably less than 3 ° C.
[0040]
The temperature of the central portion of the breaker plate provided at the resin outlet of the extruder is measured using a thermocouple, and the measured temperature is defined as the temperature of the resin discharged from the extruder.
[0041]
This is because if the temperature of the lip tip of the mold is lower than the temperature of the resin discharged from the extruder by more than 40 ° C., the styrene-based resin cannot be solidified by the mold lip and foamed by extrusion. If the difference between the lip tip temperature of the mold and the temperature of the resin discharged from the extruder is less than 15 ° C., the cell diameter of the surface layer becomes large, and the number of cells in the thickness direction of the styrene resin foam plate becomes small. This is because the number of times the heat is cut off by the cell walls is reduced, and the heat insulating property of the styrene-based resin foam board is reduced, or bumping occurs, and a good styrene-based resin foam board cannot be obtained.
[0042]
Here, in the method for producing a styrene-based resin foam plate of the present invention, the synthetic mica and water are supplied to the styrene-based resin at a predetermined ratio, and are cooled to a predetermined temperature by a lip portion of a mold, thereby being a flame retardant. Despite the presence of hexabromocyclododecane, it is possible to obtain a styrene-based resin foam plate obtained by controlling the average cell diameter in the thickness direction of the styrene-based resin foam plate in the cells of the surface layer and the center layer as described above. .
[0043]
Although the reason for this has not been clearly elucidated, the synthetic mica is formed in layers, and the layers are exfoliated from each other by the shear stress in the extruder to form a fine shape, and then uniformly dispersed in the molten styrene resin. At the same time, the more water is adsorbed on the surface of the synthetic mica, the more effective the nucleating agent is and the more bubbles are generated.
[0044]
Moreover, in the method for producing a styrene-based resin foam board of the present invention, water having low compatibility with the styrene-based resin is slightly excessively added to 0.7 to 1.5 parts by weight based on 100 parts by weight of the styrene-based resin. As a result, water moves to the outside (mold wall side, surface side) while flowing through the resin flow path inside the mold, and the surface of the molten styrene resin cooled to a suitable temperature for foaming. The concentration of water in the vicinity is higher than that of the remaining styrene resin portion.
[0045]
As a result, the synthetic mica dispersed in the vicinity of the surface of the styrenic resin adsorbed water more sufficiently than the synthetic mica dispersed on the inner surface side (center portion) of the styrenic resin. Due to the action of the synthetic mica, more fine bubbles are generated in the vicinity of the surface of the styrene-based resin in a molten state than in the remaining styrene-based portion.
[0046]
In addition, when the styrene resin is extruded and foamed from the mold, the temperature of the lip tip of the mold is adjusted to a temperature lower than the temperature of the styrene resin discharged from the extruder by a predetermined temperature. The styrene-based resin foam plate is formed such that the average cell diameter in the thickness direction of the styrene-based resin foam plate in the bubbles in the surface layer is formed to be small, while the average bubble in the thickness direction of the styrene-based resin foam plate in the bubbles in the center layer is formed. The diameter is formed to be a predetermined time larger than the average cell diameter in the thickness direction of the styrene resin foam plate in the cells of the surface layer, and as a result, excellent heat insulating properties satisfying three kinds of Class B specified in JIS A9511 And the thickness can be increased by suppressing swell reduction during extrusion foaming.
[0047]
When the density of the styrene-based resin foam board obtained as described above is low, the heat insulating property may be reduced, and when the density is high, it is difficult to obtain a thick styrene-based resin foam board. Therefore, 30 to 45 kg / m ³ is preferable. In addition, the density of the styrene-based resin foam board refers to the density measured according to JIS K7222.
[0048]
Further, the thermal conductivity of the styrene resin foam plate is preferably 0.0280 W / mK or less. In addition, the thermal conductivity of the styrene-based resin foam plate refers to a value measured in the following manner.
[0049]
That is, from the styrene-based resin foam plate 30 days after extrusion foaming, 200 mm in the extrusion direction (MD direction), 150 mm in the direction perpendicular to the extrusion direction and along the surface of the styrene-based resin foam plate (TD direction), A test piece is cut out with a size of 25 mm in the thickness direction (VD direction). The entire surface of the test piece is made to be the surface layer of the foamed styrene resin plate.
[0050]
Thereafter, the thermal conductivity of the test piece is measured based on the flat plate heat flow meter method specified in JIS A1412: 1994 “Method of measuring thermal conductivity and thermal resistance of thermal insulating material”.
[0051]
In addition, when the amount of butane contained in the styrene resin foam board after 30 days from extrusion foaming is small, the heat insulating property of the styrene resin foam board is reduced, and when it is large, the flame retardancy of the styrene resin foam board is reduced. Therefore, the content is preferably 1.5% by weight or more and less than 3.0% by weight, more preferably 2% by weight or more and less than 2.5% by weight.
[0052]
The amount of butane contained in the styrene-based resin foam plate after 30 days from the extrusion foaming is measured in the following manner. That is, from the styrene resin foam plate 30 days after extrusion foaming, a surface layer portion between both sides of the styrene resin foam plate and a portion 4 mm inward in the thickness direction from each of the both surfaces is excluded. Then, from the styrene resin foam plate from which the surface layer was excluded, 35 mm in the extrusion direction (MD direction), 5 mm along the surface of the styrene resin foam plate and perpendicular to the extrusion direction (TD direction), and the thickness direction. A rectangular parallelepiped test piece having a size of 5 mm in the (VD direction) is cut out, and the weight of the test piece is measured.
[0053]
Then, the test piece is supplied to a pyrolysis furnace at 150 ° C. to obtain a chart from gas chromatography, and the amount of butane in the test piece is calculated from the chart based on a calibration curve of butane measured in advance, It is calculated based on the following equation.
[0054]
(Amount of butane contained in styrene resin foam plate after 30 days from extrusion foaming) = 100 × Amount of butane in test piece / Weight of test piece
Further, in the above, an organic foaming agent and water are pressed into the styrene resin as a foaming agent, but other than the organic foaming agent and water as long as the physical properties of the obtained styrene resin foam board are not impaired. May be added, but it is preferable not to use a blowing agent containing a halogen atom.
[0056]
Examples of such a foaming agent include nitrogen, methyl chloride, 1,1-difluoroethane, 1,1,1-trifluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,1,2. , 2-pentafluoroethane, carbon dioxide and the like.
[0057]
【Example】
(Examples 1-2, Comparative Examples 1-4)
As the extruder, a tandem type extruder in which a second extruder is connected to the tip of a first extruder was used, and a predetermined amount of polystyrene (a product of Toyo Styrene Co., Ltd.) shown in Table 1 was added to the first extruder. (“HRM-18”), hexabromocyclododecane (HBCD), synthetic mica (trade name “ME100” manufactured by Corp Chemical Co., average particle size: 3 μm), and talc were supplied and melted and kneaded.
[0058]
Then, a predetermined amount of dimethyl ether and butane (isobutane: 60% by weight, normal butane: 40% by weight) shown in Table 1 were passed through one injection port provided integrally at the tip of the first extruder. After the system foaming agent is pressed into the molten polystyrene, a predetermined amount of water shown in Table 1 is pressed into the molten polystyrene from another injection port of the first extruder, and the polystyrene, the organic foaming agent and Mix with water.
[0059]
Thereafter, the polystyrene in a molten state is continuously supplied from the first extruder to the second extruder, and after the polystyrene is cooled to a resin temperature suitable for foaming by the second extruder, the second extruder is used. It was extruded and foamed from a mold attached to the tip. The amount of polystyrene discharged from the extruder was 35 kg / hour.
[0060]
Subsequently, the extruded foam plate in the molten state immediately after being extruded and foamed from the mold of the second extruder is disposed in close contact with the mold attached to the tip of the second extruder, and is arranged in a vertical direction. A pair of upper and lower plate bodies (sizing plates) arranged in parallel with an interval of 30 mm and maintained at about 30 ° C. are continuously supplied to cool both surfaces of the extruded foam plate. A styrene resin foam plate was obtained. Table 1 shows the lip tip temperature of the mold and the temperature of the resin discharged from the extruder.
[0061]
In Comparative Example 3, bumping occurred on the surface of the extruded foamed plate, and a good styrene-based resin foamed plate could not be obtained. In Comparative Example 4, the overall bubble diameter was too small. As a result, a styrene resin foam plate could not be obtained.
[0062]
Average cell diameter (surface layer cell diameter) in the thickness direction of the styrene resin foam board in the cells of the surface layer of the styrene resin foam board obtained as described above, and thickness of the styrene resin foam board in the cells of the center layer The average cell diameter in the direction (central layer cell diameter), density, thermal conductivity, the amount of butane (remaining butane) contained in the styrene resin foam plate 30 days after extrusion foaming, and the flame retardancy were measured. Are shown in Table 2.
[0063]
(Flame retardance)
The average value of the quenching time when measured based on the flammability test of the measurement method A specified in JIS A9511: 1995 was defined as flammability. In addition, from the styrene-based resin foamed board one week after extrusion foaming, the portion between the both sides of the styrene-based resin foamed board and 2 mm or more in the thickness direction from both sides, the portion inside, was removed. From the remaining portion of the styrene resin foam board, 200 mm in the extrusion direction (MD direction), 25 mm perpendicular to the extrusion direction and along the surface of the styrene resin foam board (TD direction), and the thickness direction (VD direction). Then, five test pieces having a size of 10 mm were cut out, and the average flame extinction time of each test piece was defined as flame retardancy.
[0064]
[Table 1]

[0065]
[Table 2]

[0066]
The styrene resin foam plate obtained in Example 1 was 200 mm in the extrusion direction (MD direction), 150 mm perpendicular to the extrusion direction and along the surface of the styrene resin foam plate (TD direction), and had a thickness of 150 mm. A test piece was cut out in the direction (VD direction) along the entire thickness (28 mm), and the thermal conductivity of this test piece was measured in the same manner as described above. As a result, it was 0.0263 W / mK.
[0067]
【The invention's effect】
The styrene-based resin foam board according to claim 1, wherein the styrene-based resin foam board is manufactured by extrusion foaming using a foaming agent consisting of dimethyl ether, butane, and water, and the styrene-based foam in at least one surface layer of the foam. The average cell diameter in the thickness direction of the resin foam plate is 0.05 to 0.20 mm, and the average cell diameter in the thickness direction of the styrene resin foam plate in the bubbles in the center layer is the styrene resin in the cells in the surface layer. Since it is characterized by being 1.45 to 2.50 times the average cell diameter in the thickness direction of the foam plate, it has excellent heat insulating properties despite being manufactured using a non-fluorocarbon foaming agent. It has flame-retardant properties, and particularly has excellent heat-insulating properties that satisfy three types of Class B specified in JIS A9511.
[0068]
Moreover, the styrene-based resin foam plate can be thickened without impairing its heat insulating properties and flame retardancy, and can be suitably used for various applications, particularly, architectural applications such as a heat insulating material for architectural use. it can.
[0069]
The foamed styrene resin sheet according to claim 2 is the foamed styrene resin sheet according to claim 1, having a density of 30 to 45 kg / m ³ and a thermal conductivity of 0.0280 W / mK or less. Therefore, it is excellent in lightness and heat insulation, and exhibits excellent handling properties when used for architectural applications such as a heat insulating material for buildings.
[0070]
The styrene resin foam board according to claim 3 is the styrene resin foam board according to claim 1 or 2, wherein the amount of butane contained in the styrene resin foam board after 30 days from extrusion foaming is 1. Since it is characterized by being at least 5% by weight and less than 3.0% by weight, it is possible to effectively exhibit both properties while achieving both heat insulation and flame retardancy.
[0071]
The method for producing a styrene-based resin foam board according to claim 4 extrudes 100 parts by weight of a styrene-based resin, 2.0 to 4.0 parts by weight of hexabromocyclododecane, and 0.3 to 3.0 parts by weight of synthetic mica. The mixture is melted and kneaded in a styrene-based resin, and 3 to 15 parts by weight of an organic blowing agent comprising 60 to 80% by weight of dimethyl ether and 20 to 40% by weight of butane in the styrene resin in the molten state; After pressurizing 0.5 parts by weight, while extruding and foaming from the mold while maintaining the temperature of the lip tip of the mold attached to the extruder at a temperature satisfying the above relationship, the method is applied to the global environment. It is possible to smoothly and reliably form a thick styrene-based resin foam plate which is excellent in heat insulation properties, in particular, heat insulation properties satisfying three kinds of Class B stipulated in JIS A9511 and flame retardance while minimizing the influence. To manufacture Can be

Claims

A styrene-based resin foam plate manufactured by extrusion foaming using a foaming agent composed of dimethyl ether, butane and water, wherein the average cell diameter in the thickness direction of the styrene-based resin foam plate in at least one surface layer is 0.1 mm. The average cell diameter in the thickness direction of the styrene-based resin foam plate in the bubbles in the center layer is 1.45 of the average cell diameter in the thickness direction of the styrene-based resin foam plate in the cells in the surface layer. A styrene-based resin foam plate characterized by a factor of up to 2.50.

With density of 30~45kg / ^{m 3,} a styrene resin foam plate according to claim 1, thermal conductivity equal to or less than 0.0280W / mK.

The styrene according to claim 1 or 2, wherein the amount of butane contained in the styrene-based resin foam plate after 30 days from extrusion foaming is not less than 1.5% by weight and less than 3.0% by weight. Resin foam board.

100 parts by weight of a styrene resin, 2.0 to 4.0 parts by weight of hexabromocyclododecane, and 0.3 to 3.0 parts by weight of synthetic mica are supplied to an extruder and melted and kneaded. After press-fitting 3 to 15 parts by weight of an organic blowing agent comprising 60 to 80% by weight of dimethyl ether and 20 to 40% by weight of butane and 0.7 to 1.5 parts by weight of water into a resin, a mold attached to an extruder A method for producing a foamed styrene-based resin plate, comprising: extruding and foaming from the above-mentioned mold while maintaining the lip tip temperature at a temperature satisfying the following formula.
Temperature of resin discharged from the extruder −40 ° C. ≦
Mold lip tip temperature ≤ resin temperature discharged from the extruder -15 ° C