JP3568655B2 - Extruded polycarbonate resin laminated sheet - Google Patents

Description

よって、式（１）、（２）より下記式（３）が求められ、定数ｋの値が１９．２〔ｋｇ／（ｃｍ・ｇ）^１／２〕となる。
Ｐ≦１９．２√ＤＴ^２ ・・・（３）
【０００７】
本発明のポリカーボネート系樹脂押出発泡積層シートは、密度０．０５〜０．４ｇ／ｃｍ^３の範囲のものである。該密度が０．０５ｇ／ｃｍ^３未満のものは強度が小さすぎるし、０．４ｇ／ｃｍ^３を超えると断熱性の低下や、重量増加の上に製造原価も増加してしまう。
【０００８】
又、本発明の積層シートの厚みは、０．８〜１０ｍｍの範囲のもの好ましくは３〜８ｍｍのものである。該厚みが０．８ｍｍ未満のものは強度的に小さすぎるし、１０ｍｍを超えるものは積層後の積層シートの厚みが厚くなりすぎ、加熱形成の際にシート表面と内側の温度が不均一となり、そのために成形不良となる。
【０００９】
次に、本発明のポリカーボネート系樹脂押出発泡積層シートについて詳細に説明する。
本発明の積層シートを構成する各発泡シートは、ポリカーボネート系樹脂押出発泡シートで、密度及び厚みが積層された際に前記範囲内のものとなれば、必ずしも同一のものである必要はなく、また積層構造も２層のみでなく３層以上であってもよい。
【００１０】
本発明における発泡シートの積層方法としては以下の方法が挙げられる。
▲１▼ 接着剤による積層方法。
▲２▼ 表面を熱溶融させた後、圧着積層する方法。
更に熱溶融方法としては、熱板に接触、非接触の輻射熱、熱風による方法等がある。
▲３▼ 溶融させたポリカーボネート樹脂を両発泡シートの間に入れ圧着積層する方法。
▲４▼ 押出直後に得られたチューブ状の発泡体を、バルーンの内面が接着可能な状態にあるうちに押圧ロールでバルーンを挟み込み内面を貼り合わせ積層する方法。
【００１１】
上記▲１▼、▲２▼及び▲３▼の積層方法において、積層させる各シートがサーキュラーダイスより押し出しマンドレル上を通過させた後切り開いて得られる発泡シートである場合、表面状態の良好で平滑性に優れる積層体を得るためには、積層面は、発泡シートのマンドレル面同士を選択する事が好ましい。マンドレル面とスキン面との積層体はカールの発生がみられ、また、スキン面同士の積層体は表面状態があまり良くない。
また上記▲４▼の積層方法においては、バルーン内面を貼り合わせるために、得られるシートの幅が切り開き方式に比べて同一装置では狭くなる。
【００１２】
本発明においては上記どの方法によっても積層体を得ることは可能であるが、特に熱風による方法は熱風排出口とポリカーボネート系樹脂押出発泡シートが直接接触しないので汚れもなく、また、発泡シート貼合せ面近傍の気泡破壊も発生しないため単層の発泡シートの気泡構造が維持されており、製品強度の低下もなく、特に曲げ強さにおいては明らかに優れたものとなり、反り等も無い。又、接着の為の副資材の必要性が無く、広幅の発泡積層シートを得ることが可能であることを考え合わせると、熱風ラミネートの方法が最も好ましい。
【００１３】
以下に熱風ラミネート方式を図１に基づいて詳細に説明する。
積層シート１を得るにあたって、図１に示すように送り出し装置４から送り出された発泡シート２と、他の送り出し装置５から送り出された別の発泡シート３との積層面に、ドライヤー６（熱風発生源）から熱風を局部的に吹き付けて両シートを加熱し、圧着ロール７で押圧しながら積層した後に巻取り装置８に巻き取って連続的に積層一体化することができる。もしくは、圧着ロール７で押圧しながら積層した後、断裁機にて平板にすることも可能である。
上記熱風ラミネートにおいて、ラインスピード、圧着ロールの隙間、熱風発生源から圧着ロールまでの距離、熱風温度、熱風の吹き付け方向等の加工条件は、積層一体化される両発泡シート２、３の厚み、密度等によって適宜選択されるが、通常は１〜４０ｍ／ｍｉｎのラインスピードで発泡シート２、３を送り出し、該発泡シート２、３が発泡シート２、３を単に重ね合わせたときのその厚みの７５〜１００％の隙間に設定された圧着ロールに挟まれる直前に、熱風発生源から０．０２〜０．２５ｍの距離をもって、３００〜８００℃の熱風を発泡シート積層面の局所に吹き付ける事によって行われる。
【００１４】
本発明のポリカーボネート系樹脂押出発泡積層シートを構成する単層の発泡シートの一般的製造方法（押出発泡）を以下に記述する。
▲１▼ 押し出し機内に樹脂と気泡調整剤等の添加剤とを仕込み、該機内で加熱・溶融・混練する。
▲２▼ 混練物に所望量の発泡剤を圧入して混練物に発泡剤を練り込む。
▲３▼ 発泡剤が練り込まれている混練物を、所定温度で押出機先端のサーキュラダイから低圧部に押し出し、これを円柱形状の樹脂冷却装置（マンドレル）の円柱側面上に引取って管状発泡体を形成させてから、押出方向に切り開いてシート状発泡体とする。
上記の方法で発泡シートを製造する場合、ポリスチレン発泡シート等の一般的樹脂発泡シート作製時は、樹脂押出速度より多少高速で管状発泡体が引取られるから、管状発泡体に引取り方向の張力がかかって該発泡体内の押出方向断面の気泡が偏平に形成される。そして、該シートを成形するために成形機内で加熱軟化させると、シート内気泡が偏平状から球状にになろうとしてシートが収縮し、ピンと張った状態となる。その結果、加熱ムラが無く形の良い成形品が得られる、曲げ強度や機械的強度も向上すると考えられる。
【００１５】
一方、ポリカーボネート系樹脂押出発泡シートでは、ダイス出口から押し出される樹脂の伸びが極めて小さいから、該樹脂がダイスから押し出される速度より早い速度でマンドレルに引取るのが困難である。そこで、実際には管状発泡体を多少だぶつかせながらマンドレルに引取っており、気泡が形成されるダイス出口付近では管状発泡体がだぶついているから、形成される気泡が厚み方向に多少縦長の球状になる。このように気泡が形成されているために、該発泡シートを成形機内で加熱軟化させて成形加工する場合には、軟化温度で気泡が真球状になろうとするために発泡シートが伸びてしまう。しかし、成形機内ではシート端部が押さえられているから伸びたシートの逃げ場が無く、成形機内でシートが波打ってあばれて加熱ムラが発生し、その様なシートを成形することによりナキや破れ等の不具合が生じて成型品の品質が低下してしまう。なお、前記したナキは発泡シート表面に形成されるスキン層に亀裂が入っている状態を意味している。
【００１６】
以上のほか、従来のポリカーボネート系樹脂押出発泡シートの製造では、シート幅５００ｍｍを超える発泡シート製造が困難なことも欠点の一つである。これは、管状発泡体の伸びが小さいために、サーキュラダイ直径より２５０％程度以上直径が大きいマンドレルでは、押し出された管状発泡体を円滑に引き取るのが難しいために起こる問題である。そして、シート幅が狭いと建築資材用としては作業効率が悪いし大型の成形品製造も困難になる。また、一般に包装用容器等の連続加熱成形機は、作業効率面から最低でも５００ｍｍを超える幅のシートを使うように設計されているから、５００ｍｍ幅以下のシートでは使用可能な成形機の種類が限定される。
これらを解決するために、例えば強引に直径の大きいマンドレルで管状発泡体を引き取る方法を採用しても、この方法ではシートが破れてしまったりシート厚が薄くなったり表面状態が悪くなる等の問題が起こり、高品質の発泡シートを得ることができない。そこで、サーキュラダイの直径を大きくして幅広のシートを得ることも試みられたが、この場合サーキュラダイ直径が大きいから押し出し機先端のダイス圧力を保持するのが難しく、そのためにダイス内部で発泡現象が起こって得られる発泡シートの表面状態や機械的物性等の品質が低下する。
【００１７】
本発明のポリカーボネート系樹脂押出発泡積層シートの気泡の平均径及び形状が下記条件式を満足しているものは、加熱して成形加工する際の寸法安定性が優れ、特に好ましい。
１＜Ｘ／Ｚ≦３
１＜Ｙ／Ｚ≦５
（Ｘ＋Ｙ＋Ｚ）／３≧０．１ｍｍ
〔但し、Ｘはシート幅方向断面の厚み方向と直交する方向の平均気泡径（ｍｍ）を、Ｙはシート押出方向断面の厚み方向と直交する方向の平均気泡径（ｍｍ）を、Ｚはシート断面の厚み方向の平均気泡径（ｍｍ）を表している。〕
【００１８】
本発明の発泡積層シートの気泡の平均径及び形状が前記範囲のものは、加熱下に成形加工する際の寸法安定性が良いからシートが破れたり波打ったりせず、高品質成形品を歩溜り良く製造できる発泡積層シートである。また、幅５００ｍｍを超える優れた発泡積層シートである。そして、Ｘをシート幅方向断面の厚み方向と直交する方向の平均気泡径（ｍｍ）、Ｙをシート押出方向断面の厚み方向と直交する方向の平均気泡径（ｍｍ）を、Ｚをシート断面の厚み方向の平均気泡径（ｍｍ）とした場合、１＜Ｘ／Ｚ≦３、好ましくは１．５＜Ｘ／Ｚ≦３で、１＜Ｙ／Ｚ≦５、好ましくは１．５＜Ｙ／Ｚ≦５の形状を持つ気泡発泡シートである。気泡の大きさは（Ｘ＋Ｙ＋Ｚ）／３≧０．１ｍｍから分かるように平均径０．１ｍｍ以上、好ましくは０．２〜０．５ｍｍに形成されている発泡積層シートである。この押出発泡積層シートを図２に示すが、図２の（ａ）は該発泡積層シートの斜視図、（ｂ）は（ａ）のＡで示される部分の拡大断面図、（ｃ）は（ａ）のＢで示される部分の拡大断面図である。また、図２のｘ、ｙ、ｚはそれぞれシート幅方向、シート押出方向及びシート厚み方向を表し、Ｘ_１、Ｘ_２、Ｙ_１、Ｙ_２、Ｚ_１、Ｚ_２は個々の気泡のそれぞれの方向における径を表している。
前記気泡形状の調整は、発泡積層シートを構成する発泡シート形成時に押出ラインスピード、押出ダイスクリアー等を調節し、あらかじめ調整する方法と、発泡シートを熱風等の加熱手段による積層する際に延伸して調節する積層時に調整する方法が挙げられる。
【００１９】
この発泡積層シートは前記形状の気泡で形成されているために、１７０℃で３０秒間加熱した際の寸法変化が樹脂押出方向で０〜−３０％、特に好ましくは−３〜−３０％の範囲にあり、加熱成形時には多少縮むから、ポリスチレン発泡シート等の成形時と同様に加熱ムラがなく形の良い成形品を得ることができる。また、上記加熱条件における幅方向の寸法変化は、−１〜−１０％、特に−３〜−７％の範囲であることが加熱ムラ防止の点で好ましい。なお、加熱寸法変化の測定は以下のようにして求める。１５０×１５０ｍｍの試験片を作製し、その中央部分に流れ方向（ＭＤ）と幅方向（ＴＤ）に沿って長さ１００ｍｍの直線を十字に引く。この試験片を、１７０±２℃のオーブン内で３０秒間熱処理してから前記直線の長さを測定し、下式によって加熱寸法変化を求める。
加熱寸法変化＝〔（加熱後の長さｍｍ−１００ｍｍ）／１００ｍｍ〕×１００
この試験を３回行って平均値をＭＤ方向及びＴＤ方向の加熱寸法変化とする。
【００２０】
このような本発明の発泡積層シートを構成する好ましいポリカーボネート系樹脂押出発泡シートは、種々の方法で製造することができる。例えば、原料のポリカーボネート系樹脂に粘度平均分子量が２５０００以上で、２５０℃における溶融張力が２．３ｇ以上のものを使うことで達成可能である。このようなポリカーボネート系樹脂としては、三菱ガス化学社製ユーピロンＳ−１０００〔粘度平均分子量２６０００、溶融張力２．４ｇ（２５０℃）〕、ユーピロンＥ−１０００〔粘度平均分子量３２０００、溶融張力６．４ｇ（２５０℃）〕、ユーピロンＥ−２０００〔粘度平均分子量２９０００、溶融張力２．６ｇ（２５０℃）〕等が例示される。このほか、上記以外のポリカーボネート系樹脂と特定の発泡剤とを組み合わせる事によって達成可能な場合もある。
以上に加えて、押出機から出る樹脂温度の制御、或いは管状発泡体の引き取り方法改善等で本発明の好ましい発泡シートが得られる。すなわち、以下の通りである。
【００２１】
一般に押出機のダイス先端から低圧域に押し出された管状発泡体は、内部から空気によって膨らませられながらバルーン（管状発泡体の径がダイス径からマンドレル径まで拡大される部分）を形成した後に、マンドレルの円柱側面上に引き取られる。そして、ポリスチレン系樹脂発泡体やポリエチレン系樹脂発泡体の製造時には、前記の空気として常温のコンプレッサーの空気を使えば良いが、本発明の該発泡シートの基材樹脂はポリカーボネート系樹脂であり、ガラス転移点が１５０℃と高温なために、常温のコンプレッサーの空気ではすぐに管状発泡体が固化して引き取り操作がむずかしくなる。しかし、該空気の温度を５１〜２００℃の範囲内で調整すれば引取り操作を容易にすることができる。更に、バルーン外部から内部と同様に常温空気を吹きつけることにより表面状態が良好となり、加熱空気を吹きつけることにより引取り操作が容易となる。また、引取り操作の際に引取り速度が遅いと、発泡シートを構成する気泡の押出方向への配向が不十分となるから、引きり速度は下記式によって求められる速度より大きくすることが好ましく、この方法によって好ましいポリカーボネート系樹脂押出発泡シートが得られる。
【数３】

【００２２】
上記のような、本発明の発泡積層シートを構成するポリカーボネート系樹脂押出発泡シートを製造する場合の原料樹脂や発泡剤は特に限定されないが、使用可能な原料や発泡剤等の範囲について記述すると以下の通りである。
発泡シート原料として使用されるポリカーボネート系樹脂は、炭酸とグリコール又はビスフェノールから形成されるポリエステルである。そして、分子鎖にジフェニルアルカンを有する芳香族ポリカーボネートは、結晶性が高く高融点の上に、耐熱性、耐候性及び耐酸性に優れているから好適である。このようなポリカーボネート系樹脂としては、２，２−ビス（４−オキシフェニル）プロパン（別名ビスフェノールＡ）、２，２−ビス（４−オキシフェニル）ブタン、１，１−ビス（４−オキシフェニル）シクロヘキサン、１，１−ビス（４−オキシフェニル）イソブタン１，１−ビス（４−オキシフェニル）エタン等のビスフェノールから誘導されるポリカーボネート系樹脂が例示される。
【００２３】
発泡シート製造の際に使われる発泡剤は、無機発泡剤、揮発性発泡剤、分解型発泡剤のいずれも使用可能であるが、押出発泡法の場合は分解型発泡剤を使うと発泡倍率の高い発泡体が得られにくいから、無機発泡剤や揮発性発泡剤を使用するのが好ましい。
無機発泡剤としては、二酸化炭素、空気、窒素等が好ましく用いられる。
揮発性発泡剤としては、プロパン、ｎ−ブタン、ｉ−ブタン、ｎ−ペンタン、ｉ−ペンタン、ヘキサン等の低級脂肪族炭化水素；シクロブタン、シクロペンタン等の低級脂環式炭化水素、；ベンゼン、トルエン、キシレン等の低級芳香族炭化水素；メタノール、エタノール等の脂肪族低級一価アルコール；アセトン、メチルエチルケトン等の低級脂肪族ケトン；１−クロロ−１，１−ジフルオロエタン、ペンタフルオロエタン、１，１，１，２−テトラフルオロエタン、１，１−ジフルオロエタン等の低沸点ハロゲン化炭化水素；等が例示される。
【００２４】
以上に詳記した発泡剤は、単独又は２種以上混合して使用可能であり、例えば無機発泡剤と揮発性発泡剤のように異なった型の発泡剤の併用も可能である。
発泡剤使用量は発泡剤の種類や所望する発泡倍率によっても異なり、発泡倍率によって該発泡シートの密度が定まるから、主に所望する発泡シートの密度で発泡剤の使用量が定まると云える。そして、本発明の発泡積層シートは、前記したように密度０．０５〜０．４ｇ／ｃｍ^３であるから、この範囲もしくは多少密度が小さめとなるように発泡剤を使えばよい。そのために必要な発泡剤量は樹脂１００重量部当たり揮発性発泡剤では０．４〜１２重量部（ブタンを使用した場合）、無機発泡剤では０．２〜１５重量部（二酸化炭素を使用した場合）程度である。
【００２５】
本発明の発泡積層シートを構成する発泡シートは、ポリカーボネート系樹脂を円滑に発泡させるために、樹脂と発泡剤との溶融混練物中に必要に応じて気泡調整剤を添加することができる。この場合の気泡調整剤としては、タルクやシリカ等の無機粉末、多価カルボン酸の酸性塩、多価カルボン酸と炭酸ナトリウム又は重炭酸ナトリウムとの混合物等が好ましい。その添加量は、樹脂１００重量部当たり０．０１〜１．０重量部、好ましくは０．０５〜０．５重量部とするのが良い。
また、発泡シートには、難燃剤、熱安定剤、耐候性向上剤、着色剤等のように、通常の発泡シートに添加される公知の添加剤を添加することができる。
本発明の発泡積層シートは、ポリカーボネート系樹脂からなり、独立気泡率の高い気泡構造が形成されているために、好ましくは酸素透過量が標準状態で２４時間当たり６５００ｃｍ^３／ｍ^２以下の発泡シートである。そして、このように酸素透過量が少ないために、断熱性が良く圧縮強度の低下も少ない上に永久歪みも小さい発泡積層シートである。
【００２６】
酸素透過量の測定は以下のようにして行うことができる。気体が透過しない容器の開口面を該開口面と同寸法の測定用発泡シートで蓋をしてから、エポキシ系接着剤で該発泡シートと該開口面とを接着するとともに発泡シートの切断面を充分にシールする。この容器にはガス置換用の２本の銅パイプが接続されているから、容器内を窒素で充分置換してから一方の銅パイプから窒素を２０ｍｌ／分の速度で供給し、他方の銅パイプから容器内ガスを排出する。このようにして得られた排出ガス中の酸素分を、ＭＯＤＥＲＮ ＣＯＮＴＲＯＬＳ社製ＯＸ−ＴＲＡＮ１００等の酸素検出器で検出し、２４時間当たりの酸素検出量ｘ〔ｃｍ^３／２４ｈｒ〕（２５℃、１ａｔｍ）を求める。この値と空気中の酸素モル分率及び容器開口面積に相当する測定用発泡シート面積Ｓ〔ｍ^２〕から、酸素透過量Ｘ〔ｃｍ^３／ｍ^２・２４ｈｒ〕を下記式により算出する。
Ｘ〔（ＳＴＰ）ｃｍ^３／ｍ^２・２４ｈｒ〕＝（１００・ｘ）／（２１・Ｓ）
【００２７】
本発明の発泡積層シートを構成する発泡シートは、原料樹脂の溶融粘度と粘度平均分子量との関係や、押し出された管状発泡体の引き取り方法等に留意しているために、サーキュラダイ直径より２５０％以上、更には３００〜３５０％の直径をもつマンドレルに管状発泡体を引取ることができる。そして、サーキュラダイ直径より２５０％以上も直径が大きいマンドレルに管状樹脂を引取っても、シート厚が部分的又は全面的に薄くなることがなく、シートの厚みを０．４〜５ｍｍ、特に１〜３．０ｍｍの均一厚にすることができる。なお、発泡シート厚が０．４ｍｍ未満では該シートで形成される成形品の強度が小さく、厚みが５ｍｍを超えると厚みの均一性及びシート物性が不十分となり、良好な発泡シートを得ることが難しい。
前記のように、本発明の発泡積層シートを構成する発泡シートは均一な厚みのシートとして得られるが、厚みをより均質にするためには▲１▼サーキュラダイの開口部付近における樹脂流路幅を狭める；▲２▼サーキュラダイから押し出された管状発泡体をマンドレルに引取って冷却する際に、マンドレル表面及び外側から管状発泡体の内表面及び外表面に冷却空気を吹き付ける；等の方法を１種又は２種以上行えば良い。
【００２８】
本発明の、前記原料のポリカーボネート系樹脂を用い、発泡シートを形成し、該発泡シートを複数枚積層した特定の密度、厚みを有するポリカーボネート系樹脂発泡積層シートは、熱安定性に非常に優れ、例えば、８５℃、２４時間の耐熱評価でも寸法変化を全く起こさない。
このように本発明の発泡積層シートは、耐熱性の要求される種々の用途に好適に使用できる。
例えば、自動車内装材や、自動車天井材は、夏期の自動車内温度が（特に天井近くでは）異常に高くなり、耐熱性が強く要求され、高温や低温の雰囲気下での長期間使用においても変形が生じないことが要求されているが、このような用途にも本発明の発泡積層シートは好適に使用できる。
また、本発明の発泡積層シートの１７０℃、６０秒間の加熱寸法変化をみても、押出方向、幅方向共に±３％以内にあり、加熱成形時にシートが伸びない為、極端なドローダウンやシートの波打ちを起こさず、その為に加熱ムラがない。このことから、本発明の発泡積層シートは、以下に示す熱成形により、自動車内装材、自動車天井材、容器、その他用途に応じ多種多様に賦形することができる。更に、本発明の発泡積層シートの曲げ強度（ｋｇ／ｃｍ^２）を見ても図３に示すように同じ厚みの単層の発泡シートと比較して明らかに優れていることが認められ、特に、自動車天井材として使用される場合は耐熱性の高さとの相乗効果により垂れ下がりの問題が解決され好適である。
【００２９】
本発明の発泡積層シートは以下に示す熱成形により、用途に応じ多種多様に賦形することができる。
１．発泡積層シートをそれが軟化するまで予熱し、モールドに位置決めする工程
２．予熱されたシートをモールド表面に、真空引き及び／又は圧空等により密着させる工程
３．賦型された発泡積層シートを冷却する工程
４．成形品をモールドのキャビテーから取り出す工程
を経ることにより成形される。上記２の工程で示した真空成形、更には圧空成形等の具体的な例示としては、ストレート成形、ドレープ成形、リバースドロー成形、エアスリップ成形、チャンバブロー方式によるエアスリップ成形、プラグアシスト成形、ドレープアンドプラグアシスト成形、プラグアシストリバースドロー成形、エアクッション成形、プラグアシストエアスリップ成形、接触加熱式圧空成形、プレス成形等が挙げられる。
【００３０】
【実施例】
次に、本発明を実施例に基づいて更に具体的に説明するが、本発明はこれらの実施例に限定されるものではない。
【００３１】
実施例１
押出機内でビスフェノールＡよりなるポリカーボネート（粘度平均分子量２９０００）１００重量部と発泡剤としてｎ−ペンタンを１．２重量部を溶融混練した後、溶融混練物を押出機先端に取り付けたサーキュラーダイスの環状リップより押出発泡してチューブ状の発泡体を得、次いでこのチューブを切り開いてシート状として発泡シートを得た。この時得られた発泡シートは、シート厚み１．４ｍｍ、密度０．２７１ｇ／ｃｍ^３、幅６３０ｍｍの物であった。
次に得られた発泡シート同士を熱風ラミネートにより溶融接着して積層一体化した。尚、このときの加工条件は以下のとおりである。
〔熱風ラミネートの加工条件〕
・ラインスピード：２〜３ｍ／ｍｉｎ
・圧着ロール間隔：積層する発泡シートの合計厚みの８５％
・熱風温度 ：５００℃
【００３２】
実施例２
発泡剤量を２．４重量部に変更した以外は、実施例１と同様な方法でシート厚み２．６ｍｍ、密度０．１９４ｇ／ｃｍ^３、幅１３１５ｍｍの発泡シートを得た後、実施例１と同様に熱風ラミネートにより溶融接着して積層体を得た。
【００３３】
実施例３
Ｎ値１．４０の分岐化ＰＣを１００重量部と発泡剤としてｎ−ペンタンを２．４重量部使用した以外は実施例１と同様の方法で、シート厚み３．５ｍｍ、密度０．１６ｇ／ｃｍ^３、幅６３０ｍｍの発泡シートを得た後、実施例１と同様に熱風ラミネートにより溶融接着して積層体を得た。
尚、上記Ｎ値とは構造粘性指数であり、以下の測定方法により求められる。
乾燥したペレットをＪＩＳ Ｋ７２１０に準拠する装置である高架式フローテスターＣＦＴ５００〔島津製作所（株）製〕を使用して、ノズル長さ（ｍｍ）／直径（ｍｍ）＝２０／１、温度３００℃の一定の条件にて加える圧力Ｐ（２０、５０、１００、２００、３００ｋｇ／ｃｍ^２の５点）と夫々の溶融樹脂の流量Ｑ（ｃｃ／ｓｅｃ）を測定し、それぞれの値を両対数グラフにプロットして得られる回帰直線の勾配をＮ値とする。
但し、Ｎ値は上記５点の測定点の示す（ｌｏｇＰ、ｌｏｇＱ）のプロットを基に最小自乗法によって求める。
【００３４】
実施例４
押出機内でビスフェノールＡよりなるポリカーボネート（粘度平均分子量２９０００）１００重量部と発泡剤としてｎ−ペンタン２重量部を溶融混練した後、この溶融混練物を押出機先端に取り付けたサーキュラーダイスの環状リップより押出発泡してチューブ状の発泡体を得た。この時点でチューブ状の発泡体の上部、下部とも密度０．１８５ｇ／ｃｍ^３、厚み２．６ｍｍであった。次いで該発泡体（バルーン）の内側が接着可能な状態にあるうちに押圧ロールでバルーンを挟み込み内面を接着することにより発泡積層シートを得た。この発泡積層シートは、厚み４．８ｍｍ、密度０．２００／ｃｍ^３、幅５００ｍｍの物であった。
【００３５】
実施例５
押出機のサイズを小型化し、発泡剤の量を２．７重量部に変更した以外は実施例４と同様な方法で発泡体を得た。
この時、バルーン状態の上部及び下部の密度は０．１２９ｇ／ｃｍ^３、厚みは２．２ｍｍであった。
又、実施例４と同様にして得られた積層発泡シートは、厚み４．０５ｍｍ、密度０．１４０ｇ／ｃｍ^３、幅３００ｍｍの物であった。
【００３６】
比較例１〜６
実施例１と同様の押出発泡法により、発泡剤量、又は樹脂を表１に示すように変更し、またダイスサイズ等を変更し、各種厚み、密度、幅を持つ単体（単層）のポリカーボネート系樹脂押出発泡シートを得た。
【表１】

【００３７】
比較例７
実施例１と同様の樹脂を用いて０．７ｍｍのフィルムを作成し、これを二酸化炭素圧が４０ｋｇ／ｃｍ^２に保たれている圧力容器内に２３℃で６０時間放置後、１６０℃に保たれている油浴で４０秒間加熱して発泡させた。この発泡によって厚みは１．８ｍｍとなり、密度は０．０９５ｇ／ｃｍ^３であった。次に、得られた発泡シート同士を熱風ラミネートにより実施例１と同様の方法により溶融接着を行った。
【００３８】
各実施例及び各比較例により得られた発泡積層シートについて、シート密度、シート厚み、シート幅、最大曲げ強度、及び曲げ強さを測定した結果を表２に示す。 又、１７０℃×６０秒における加熱寸法変化の結果を併せて表２に示す。また８５℃における加熱寸法変化は実施例、比較例共に０％であった。
尚、最大曲げ強度、曲げ強さ、加熱寸法変化の測定方法は、以下のとおりである。

（加熱寸法変化）
▲１▼８５℃における加熱寸法変化
２２０×２２０ｍｍの試験片を作成し、その中央部に流れ方向（ＭＤ）と幅方向（ＴＤ）の長さ１００ｍｍの直線を十字に引く。この試験片を８５±２℃のオーブン内で２４時間処理してから前記直線の長さを測定し、下式によって加熱寸法変化を求める。

この試験を３回行い（ｎ＝３）、その平均値をＭＤ方向及びＴＤ方向の加熱寸法変化とする。
▲２▼１７０℃における加熱寸法変化
１５０×１５０ｍｍの試験片を作成し、その中央部にＭＤ方向とＴＤ方向の長さ１００ｍｍの直線を十字に引く。この試験片を１７０±２℃のオーブン内で６０秒間熱処理してから前記直線の長さを測定し、加熱前後の長さの変化からＭＤ方向及びＴＤ方向の加熱寸法変化を８５℃における加熱寸法の場合と同様にして求める。
（平均気泡径）
発泡積層シート（比較例１〜６については発泡シート）のＭＤ方向及びＴＤ方向断面の顕微鏡拡大図を得、図２（ｂ）、（ｃ）にならってシート両表面から０．１ｍｍ以上内側に存在する１００個以上の気泡について気泡径を測定し、その平均値をもってＸ、Ｙ、Ｚとする。但し、実施例１〜５及び比較例７において、フィルム状になっている発泡シート貼り合わせ面近傍の破壊もしくは微細化した気泡部分は測定せず、図２（ｂ）、（ｃ）のαの範囲内で気泡径を測定する。
【００３９】
【表２】

【００４０】
【発明の効果】
本発明のポリカーボネート系樹脂押出発泡積層シートは、８５℃、２４時間の耐熱評価においては、寸法変化を全く起さず、また、１７０℃、６０秒間の耐熱評価においても寸法変化がほとんどなく、耐熱性の極めて優れたシートである。
また、曲げ強さにおいても単体（単層）の発泡シートと比較して優れたものであり、かつ、厚み及び幅において十分なものが得られ、積層することにより従来の単層のもの課題を解決し、更に物性の向上も達成されたシートである。
更に、本発明の前記特に好ましい気泡の平均径及び形状を有するポリカーボネート系樹脂押出発泡積層シートは、発泡気泡が偏平に成形されているために加熱して形成加工する際に特に安定性が良く、そのために形成の際に発泡シートが破れたり波打ったりすることが少なく、該発泡積層シートから歩留り良く高品質の成形品を得ることができる。
このように本発明の発泡積層シートは耐熱性及び曲げ強さが極めて優れているため、自動車の内装材や、自動車の天井材として好適に用いられ、また熱成形によっても各種用途に応じ多種多様に賦形することができる。
【図面の簡単な説明】
【図１】熱風ラミネート法による発泡積層シートにの成形方法の概略図である。
【図２】本発明の発泡積層シートにおける好ましい気泡形状を説明する図である。
【図３】本発明の発泡積層シート及び発泡単体シートの密度と曲げ強さの関係を説明する図である。
【符号の説明】
１ 発泡積層シート
２ 発泡シート
３ 発泡シート
ｘ シート幅方向
ｙ シート押出方向
ｚ シート厚み方向[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polycarbonate resin extruded foam laminated sheet, and more particularly, to a polycarbonate resin extruded foam laminated sheet having excellent bending strength.
[0002]
[Prior art]
Extruded polycarbonate resin foam has high heat resistance, aging resistance, water resistance, etc., and good electrical and mechanical properties, so it is expected to be used for interior materials for automobiles and buildings, packaging materials, various containers, etc. Expected.
In particular, interior materials for automobiles are required to pass a heat resistance test at 80 ° C. or higher, and furthermore, do not hinder weight reduction and are required to have safe and constant bending strength as interior materials.
Polycarbonate resin is an ideal resin that can satisfy all of the required physical properties, and its foaming has been studied in various ways. In particular, it has been previously proposed by the present applicant to laminate a polycarbonate resin to a foam as a base material for molding an automobile interior material, but a stronger bending strength than that obtained by laminating a film has been required. .
In addition, it was difficult to obtain a thick foam having excellent properties due to the polycarbonate resin.
In addition, although the use of a branched polycarbonate resin was attempted to obtain a thick material, the cost was extremely high and was not practical, and the bending strength of the obtained thick material sheet was difficult to sufficiently bring out the original performance of the resin, and was satisfactory. It was not a good value.
As described above, it has been desired to improve the bending strength of the foam sheet itself.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to provide a polycarbonate resin extruded foam laminated sheet having a sufficient thickness and improved bending strength of the foam sheet.
[0004]
[Means for Solving the Problems]
According to the present invention, a density of 0.05 to 0.4 g / cm obtained by bonding a plurality of extruded polycarbonate resin foam sheets³, A laminated sheet having a thickness of 0.8 to 10 mm and having a strength satisfying the following formula:
(Equation 1)
P> k ・ √D ・ T²
[Where P is the maximum bending strength (kg)
D: Density of foam laminated sheet (g / cm³)
T: Thickness of foam laminated sheet (cm)
k: 19.2 (kg / (cm · g)^1/2)]
Further, according to the present invention, the extruded polycarbonate resin sheet is a foamed sheet obtained by being extruded from a circular die and cut open after passing over a mandrel, and the mandrel surfaces of the sheet are bonded together. The present invention provides a polycarbonate resin extruded foamed laminated sheet characterized by the following.
[0005]
The present inventors first measured the flexural strength of sheets having various magnifications and thicknesses to determine which factor was most effective for improving the flexural strength of the extruded polycarbonate resin foam sheet. I found regularity like an expression.
(Equation 2)
P = k√D ・ T²
[Where P is the maximum bending strength (kg)
D: Foam density (g / cm³)
T: Foam thickness (cm)
k: constant (kg / (cm · g)^1/2)]
According to this equation, it was found that the bending strength of the extruded foam sheet greatly depends on the thickness.
Therefore, as a result of conducting various studies to increase the thickness of the polycarbonate resin extruded foam sheet, a laminate of the polycarbonate resin extruded foam sheets is most effective for obtaining a thickness that could not be obtained by itself, Further, it was found that the bending strength was improved as compared with a simple substance having the same thickness by laminating, that is, the following relational expression was satisfied.
(Equation 1)
P> k ・ √D ・ T²
[Where P is the maximum bending strength (kg)
D: Density of foam laminated sheet (g / cm³)
T: Thickness of foam laminated sheet (cm)
k: 19.2 (kg / (cm · g)^1/2)]
The value of the constant k in polycarbonate is determined by the following method.
[0006]
The bending strength k of the single-layer foamed sheet obtained using various polycarbonate-based resins was measured, and the relationship between the density of the foamed sheet and the bending strength was plotted on a graph. From these plots, the following empirical formula (1) for the density and bending strength of the single-layer foamed sheet was derived.
K ≦ 57.74√D (1)
The calculation formula (2) for the bending strength k defined by JIS is as shown below.

Therefore, the following equation (3) is obtained from the equations (1) and (2), and the value of the constant k is 19.2 [kg / (cm · g)].^1/2].
P ≦ 19.2√DT² ... (3)
[0007]
The polycarbonate resin extruded foam laminated sheet of the present invention has a density of 0.05 to 0.4 g / cm.³Of the range. The density is 0.05 g / cm³If less, the strength is too low and 0.4 g / cm³Exceeding the above will lower the heat insulating properties, increase the weight, and increase the manufacturing cost.
[0008]
The thickness of the laminated sheet of the present invention is in the range of 0.8 to 10 mm, preferably 3 to 8 mm. If the thickness is less than 0.8 mm, the strength is too small, and if it exceeds 10 mm, the thickness of the laminated sheet after lamination becomes too thick, and the temperature of the sheet surface and the inside becomes uneven during heat forming, This results in molding failure.
[0009]
Next, the polycarbonate resin extruded foam laminated sheet of the present invention will be described in detail.
Each foamed sheet constituting the laminated sheet of the present invention is a polycarbonate resin extruded foamed sheet, if the density and thickness are within the above range when laminated, it is not necessarily the same, The laminated structure may be not only two layers but also three or more layers.
[0010]
The method for laminating the foamed sheet in the present invention includes the following methods.
(1) Lamination method using an adhesive.
{Circle around (2)} A method in which the surface is thermally melted and then pressure-bonded and laminated.
Further, as a heat melting method, there is a method using radiant heat in contact with, non-contact with a hot plate, hot air, or the like.
{Circle around (3)} A method in which a molten polycarbonate resin is placed between both foamed sheets and pressure-bonded and laminated.
{Circle around (4)} A method in which the tubular foam obtained immediately after extrusion is sandwiched and laminated by pressing the balloon with a pressing roll while the inner surface of the balloon can be bonded.
[0011]
In the laminating method of the above (1), (2) and (3), when each of the sheets to be laminated is a foamed sheet obtained by extruding from a circular die, passing over a mandrel, and then cutting open, the surface condition is good and smoothness is obtained. In order to obtain a laminate having excellent lamination, it is preferable to select the mandrel surfaces of the foamed sheet from each other as the lamination surface. Curling occurs in the laminate of the mandrel surface and the skin surface, and the surface condition of the laminate of the skin surfaces is not very good.
Further, in the laminating method of the above (4), the width of the obtained sheet is smaller in the same apparatus than in the slit-opening method because the inner surface of the balloon is bonded.
[0012]
In the present invention, it is possible to obtain a laminated body by any of the above methods, but especially in the method using hot air, since the hot air outlet and the polycarbonate resin extruded foam sheet do not directly contact each other, there is no contamination, and the foam sheet is bonded. Since no bubble destruction occurs near the surface, the cell structure of the single-layer foam sheet is maintained, the product strength is not reduced, and the bending strength is clearly excellent, and there is no warpage. Considering that a wide foamed laminated sheet can be obtained without the necessity of an auxiliary material for bonding, a hot air laminating method is most preferable.
[0013]
Hereinafter, the hot air lamination method will be described in detail with reference to FIG.
In order to obtain the laminated sheet 1, as shown in FIG. 1, a dryer 6 (hot air generation) is provided on a laminated surface of the foam sheet 2 sent from the delivery device 4 and another foam sheet 3 delivered from another delivery device 5. A hot air is locally blown from a source) to heat both sheets, and the sheets are laminated while being pressed by a pressure roll 7 and then wound up by a winding device 8 to be continuously laminated and integrated. Alternatively, after laminating while pressing with the pressure roll 7, it is also possible to form a flat plate with a cutting machine.
In the hot air lamination, processing conditions such as line speed, gap between the pressure rolls, the distance from the hot air generation source to the pressure roll, hot air temperature, and the direction of hot air blowing are determined by the thickness of the foamed sheets 2 and 3 to be laminated and integrated. Although it is appropriately selected depending on the density and the like, usually, the foamed sheets 2 and 3 are sent out at a line speed of 1 to 40 m / min, and the thickness of the foamed sheets 2 and 3 when the foamed sheets 2 and 3 are simply overlapped. Immediately before being sandwiched between the pressure rolls set in a gap of 75 to 100%, a hot air of 300 to 800 ° C. is blown to a local portion of the foam sheet laminated surface at a distance of 0.02 to 0.25 m from a hot air generating source. Done.
[0014]
The general manufacturing method (extrusion foaming) of a single-layer foamed sheet constituting the polycarbonate resin extruded foamed laminated sheet of the present invention is described below.
{Circle around (1)} A resin and an additive such as a bubble regulator are charged in an extruder, and heated, melted and kneaded in the extruder.
{Circle around (2)} A desired amount of a foaming agent is pressed into the kneaded material and the foaming agent is kneaded into the kneaded material.
{Circle around (3)} The kneaded material into which the foaming agent is kneaded is extruded at a predetermined temperature from a circular die at the extruder tip into a low-pressure section, which is pulled on a cylindrical side surface of a cylindrical resin cooling device (mandrel) to form a tube. After the foam is formed, it is cut open in the extrusion direction to obtain a sheet-like foam.
When producing a foamed sheet by the above method, when producing a general resin foamed sheet such as a polystyrene foamed sheet, the tubular foam is taken up at a slightly higher speed than the resin extrusion speed, so the tension in the take-up direction is applied to the tubular foam. As a result, cells having a cross section in the extrusion direction in the foam are formed flat. When the sheet is heated and softened in a molding machine in order to form the sheet, the sheet shrinks as the bubbles in the sheet tend to change from a flat shape to a spherical shape, and become tight. As a result, it is considered that a molded article having good shape without heating unevenness is obtained, and the bending strength and the mechanical strength are also improved.
[0015]
On the other hand, in the extruded polycarbonate resin sheet, since the resin extruded from the die outlet has extremely small elongation, it is difficult to pull the resin into the mandrel at a speed higher than the speed at which the resin is extruded from the die. Therefore, in practice, the tubular foam is pulled up to the mandrel while slightly bumping it, and since the tubular foam is sticking near the die exit where the bubbles are formed, the bubbles formed are slightly longer in the thickness direction. Become spherical. When the foamed sheet is heated and softened in a molding machine to form the foamed sheet due to the formation of the bubbles, the foamed sheet tends to become a true sphere at the softening temperature, so that the foamed sheet expands. However, since the sheet edge is held down in the molding machine, there is no place for the stretched sheet to escape, and the sheet undulates in the molding machine, causing uneven heating, and forming such a sheet causes cracks or tears. And the like, the quality of the molded product is degraded. The above-mentioned pear means a state in which a skin layer formed on the surface of the foam sheet has cracks.
[0016]
In addition to the above, one of the drawbacks is that it is difficult to produce a foamed sheet having a sheet width of more than 500 mm in the production of a conventional extruded polycarbonate resin foam sheet. This is a problem that occurs because it is difficult to smoothly pull out the extruded tubular foam in a mandrel whose diameter is about 250% or more larger than the diameter of the circular die because the elongation of the tubular foam is small. If the sheet width is narrow, the working efficiency is poor for building materials, and it is difficult to manufacture large molded products. In general, continuous heating molding machines for packaging containers and the like are designed to use sheets having a width exceeding at least 500 mm from the viewpoint of work efficiency. Limited.
In order to solve these problems, for example, even if a method of forcibly pulling a tubular foam with a large-diameter mandrel is adopted, this method causes problems such as breakage of the sheet, reduction of the sheet thickness, and deterioration of the surface condition. Occurs, and a high quality foam sheet cannot be obtained. Therefore, attempts were made to increase the diameter of the circular die to obtain a wide sheet.However, in this case, it was difficult to maintain the die pressure at the tip of the extruder due to the large diameter of the circular die. The quality of the resulting foamed sheet, such as the surface condition and mechanical properties, is reduced.
[0017]
The polycarbonate resin extruded foamed laminated sheet of the present invention having an average cell diameter and shape satisfying the following conditional expressions is particularly preferable because of excellent dimensional stability when heated and molded.
1 <X / Z ≦ 3
1 <Y / Z ≦ 5
(X + Y + Z) /3≧0.1 mm
[However, X is the average cell diameter (mm) in the direction orthogonal to the thickness direction of the cross section in the sheet width direction, Y is the average cell diameter (mm) in the direction orthogonal to the thickness direction of the cross section in the sheet extrusion direction, and Z is the sheet. The average bubble diameter (mm) in the thickness direction of the cross section is shown. ]
[0018]
The foamed laminated sheet of the present invention in which the average diameter and the shape of the cells are in the above-mentioned range has good dimensional stability when molded under heating, so that the sheet is not broken or wavy, and a high quality molded article can be produced. It is a foam laminated sheet that can be manufactured well. Further, it is an excellent foam laminated sheet having a width exceeding 500 mm. Then, X is the average cell diameter (mm) in the direction orthogonal to the thickness direction of the cross section in the sheet width direction, Y is the average cell diameter (mm) in the direction orthogonal to the thickness direction of the cross section in the sheet extrusion direction, and Z is the average cell diameter in the sheet cross section. When the average cell diameter (mm) in the thickness direction is 1 <X / Z ≦ 3, preferably 1.5 <X / Z ≦ 3, 1 <Y / Z ≦ 5, preferably 1.5 <Y / This is a foamed foam sheet having a shape of Z ≦ 5. As can be seen from (X + Y + Z) /3≧0.1 mm, the bubble size is a foam laminated sheet formed to have an average diameter of 0.1 mm or more, preferably 0.2 to 0.5 mm. FIG. 2 shows this extruded foamed laminated sheet. FIG. 2 (a) is a perspective view of the foamed laminated sheet, FIG. 2 (b) is an enlarged cross-sectional view of a portion indicated by A in FIG. 2 (a), and FIG. It is an expanded sectional view of the part shown by B of a). Further, x, y, and z in FIG. 2 represent a sheet width direction, a sheet extrusion direction, and a sheet thickness direction, respectively.₁, X₂, Y₁, Y₂, Z₁, Z₂Represents the diameter of each bubble in each direction.
The adjustment of the bubble shape is performed by adjusting the extrusion line speed, extrusion die clearance, and the like at the time of forming the foamed sheet constituting the foamed laminated sheet, a method of adjusting in advance, and stretching when the foamed sheet is laminated by heating means such as hot air. Adjusting during lamination.
[0019]
Since the foamed laminated sheet is formed of the above-described foam, the dimensional change when heated at 170 ° C. for 30 seconds is in the range of 0 to −30%, particularly preferably −3 to −30% in the resin extrusion direction. Since it is slightly shrunk at the time of heat molding, it is possible to obtain a molded article having good shape without heat unevenness as at the time of molding a polystyrene foam sheet or the like. The dimensional change in the width direction under the above heating conditions is preferably in the range of -1 to -10%, particularly -3 to -7%, from the viewpoint of preventing uneven heating. The measurement of the heating dimensional change is obtained as follows. A test piece of 150 × 150 mm is prepared, and a straight line having a length of 100 mm is drawn in the center along the flow direction (MD) and the width direction (TD). The test piece is heat-treated in an oven at 170 ± 2 ° C. for 30 seconds, the length of the straight line is measured, and the change in the heating dimension is determined by the following equation.
Heating dimensional change = [(length after heating mm-100 mm) / 100 mm] × 100
This test is performed three times, and the average value is defined as a heating dimension change in the MD and TD directions.
[0020]
Such a preferable polycarbonate resin extruded foam sheet constituting the foam laminated sheet of the present invention can be produced by various methods. For example, this can be achieved by using a polycarbonate resin as a raw material having a viscosity average molecular weight of 25,000 or more and a melt tension at 250 ° C. of 2.3 g or more. Examples of such a polycarbonate resin include Iupilon S-1000 (viscosity average molecular weight 26000, melt tension 2.4 g (250 ° C.)) and Iupilone E-1000 [viscosity average molecular weight 32,000, melt tension 6.4 g, manufactured by Mitsubishi Gas Chemical Company, Ltd.] (250 ° C.)], Iupilone E-2000 [viscosity average molecular weight 29000, melt tension 2.6 g (250 ° C.)] and the like. In addition, it may be achieved by combining a polycarbonate resin other than those described above with a specific foaming agent.
In addition to the above, the preferable foamed sheet of the present invention can be obtained by controlling the temperature of the resin exiting the extruder or improving the method of taking the tubular foam. That is, it is as follows.
[0021]
In general, a tubular foam extruded from a die tip of an extruder to a low pressure region forms a balloon (a portion where the diameter of the tubular foam expands from a die diameter to a mandrel diameter) while being inflated by air from the inside, and then forms a mandrel. Taken on the side of the cylinder. When producing a polystyrene-based resin foam or a polyethylene-based resin foam, air from a compressor at room temperature may be used as the air, but the base resin of the foamed sheet of the present invention is a polycarbonate-based resin, and Since the transition point is as high as 150 ° C., the tubular foam solidifies immediately with air from the compressor at room temperature, and the take-up operation becomes difficult. However, if the temperature of the air is adjusted within the range of 51 to 200 ° C., the take-off operation can be facilitated. Further, the surface condition is improved by blowing normal-temperature air from the outside of the balloon in the same manner as the inside, and the take-up operation is facilitated by blowing the heated air. Further, if the take-up speed is low during the take-up operation, the orientation of the bubbles constituting the foamed sheet in the extrusion direction becomes insufficient. Therefore, it is preferable that the take-up speed be higher than the speed obtained by the following formula. By this method, a preferable extruded polycarbonate resin foam sheet is obtained.
(Equation 3)

[0022]
As described above, the raw material resin and the foaming agent when producing the polycarbonate resin extruded foam sheet constituting the foam laminated sheet of the present invention are not particularly limited, but the following describes the range of usable raw materials and foaming agents. It is as follows.
The polycarbonate resin used as the foam sheet material is a polyester formed from carbonic acid and glycol or bisphenol. An aromatic polycarbonate having diphenylalkane in the molecular chain is preferable because it has high crystallinity, a high melting point, and excellent heat resistance, weather resistance and acid resistance. Examples of such polycarbonate resins include 2,2-bis (4-oxyphenyl) propane (also known as bisphenol A), 2,2-bis (4-oxyphenyl) butane, and 1,1-bis (4-oxyphenyl). A) Polycarbonate resins derived from bisphenols such as cyclohexane and 1,1-bis (4-oxyphenyl) isobutane 1,1-bis (4-oxyphenyl) ethane.
[0023]
The foaming agent used in the production of the foam sheet can be any of an inorganic foaming agent, a volatile foaming agent, and a decomposable foaming agent. Since it is difficult to obtain a high foam, it is preferable to use an inorganic foaming agent or a volatile foaming agent.
As the inorganic foaming agent, carbon dioxide, air, nitrogen and the like are preferably used.
Examples of the volatile foaming agent include lower aliphatic hydrocarbons such as propane, n-butane, i-butane, n-pentane, i-pentane, and hexane; lower alicyclic hydrocarbons such as cyclobutane and cyclopentane; Lower aromatic hydrocarbons such as toluene and xylene; aliphatic lower monohydric alcohols such as methanol and ethanol; lower aliphatic ketones such as acetone and methyl ethyl ketone; 1-chloro-1,1-difluoroethane, pentafluoroethane, 1,1 And low-boiling halogenated hydrocarbons such as 1,1,2-tetrafluoroethane and 1,1-difluoroethane.
[0024]
The blowing agents described above can be used alone or in combination of two or more. For example, different types of blowing agents such as an inorganic blowing agent and a volatile blowing agent can be used in combination.
The amount of the foaming agent used varies depending on the type of the foaming agent and the desired expansion ratio, and since the density of the foamed sheet is determined by the expansion ratio, it can be said that the amount of the foaming agent used is mainly determined by the desired density of the foamed sheet. And the foamed laminated sheet of the present invention has a density of 0.05 to 0.4 g / cm as described above.³Therefore, a foaming agent may be used in this range or in such a way that the density becomes slightly smaller. The amount of the foaming agent required for this is 0.4 to 12 parts by weight (when using butane) for the volatile blowing agent and 0.2 to 15 parts by weight (for using carbon dioxide) for the inorganic blowing agent per 100 parts by weight of the resin. Case) about.
[0025]
In the foamed sheet constituting the foamed laminated sheet of the present invention, a foam adjuster can be added to the melt-kneaded product of the resin and the foaming agent as necessary in order to smoothly foam the polycarbonate-based resin. In this case, as the cell regulator, inorganic powders such as talc and silica, acidic salts of polyvalent carboxylic acids, and mixtures of polyvalent carboxylic acids with sodium carbonate or sodium bicarbonate are preferable. The amount added is preferably from 0.01 to 1.0 part by weight, preferably from 0.05 to 0.5 part by weight, per 100 parts by weight of the resin.
Known additives that are added to ordinary foamed sheets, such as a flame retardant, a heat stabilizer, a weather resistance improver, and a coloring agent, can be added to the foamed sheet.
Since the foamed laminated sheet of the present invention is made of a polycarbonate resin and has a cell structure with a high closed cell rate, the oxygen permeation amount is preferably 6500 cm per 24 hours in a standard state.³/ M²These are the following foam sheets. Since the oxygen permeation amount is small as described above, the foamed laminated sheet has good heat insulating properties, little decrease in compressive strength, and small permanent set.
[0026]
The measurement of the amount of oxygen permeation can be performed as follows. After covering the opening surface of the gas impermeable container with a measuring foam sheet having the same dimensions as the opening surface, the foam sheet and the opening surface are bonded with an epoxy-based adhesive, and the cut surface of the foam sheet is cut. Seal well. Since two copper pipes for gas replacement are connected to this container, the inside of the container is sufficiently replaced with nitrogen, and then nitrogen is supplied from one copper pipe at a rate of 20 ml / min. From the container. The oxygen content in the exhaust gas thus obtained is detected by an oxygen detector such as OX-TRAN100 manufactured by MODERN CONTROLS, and the amount of oxygen detected per 24 hours x [cm³/ 24hr] (25 ° C, 1 atm). This value and the area S [m of the foam sheet for measurement corresponding to the oxygen mole fraction in air and the container opening area²], The oxygen transmission amount X [cm³/ M².24hr] is calculated by the following equation.
X [(STP) cm³/ M².24hr] = (100.x) / (21.S)
[0027]
The foamed sheet constituting the foamed laminated sheet of the present invention has a diameter of 250 ° from the circular die diameter in order to pay attention to the relationship between the melt viscosity and the viscosity average molecular weight of the raw material resin and the method of taking out the extruded tubular foam. % Or even 300 to 350% of the diameter of the tubular foam. Then, even if the tubular resin is drawn into a mandrel having a diameter that is 250% or more larger than the circular die diameter, the sheet thickness does not become thinner partially or entirely, and the sheet thickness becomes 0.4 to 5 mm, especially 1 to 5 mm. A uniform thickness of up to 3.0 mm can be obtained. If the thickness of the foamed sheet is less than 0.4 mm, the strength of the molded article formed from the sheet is small, and if the thickness exceeds 5 mm, the uniformity of the thickness and the physical properties of the sheet become insufficient, and a good foamed sheet may be obtained. difficult.
As described above, the foamed sheet constituting the foamed laminated sheet of the present invention can be obtained as a sheet having a uniform thickness. However, in order to make the thickness more uniform, (1) the width of the resin flow path near the opening of the circular die {Circle around (2)} When the tubular foam extruded from the circular die is taken up by a mandrel and cooled, blowing cooling air from the mandrel surface and the outside to the inner surface and the outer surface of the tubular foam; One or more types may be used.
[0028]
Polycarbonate resin foam laminated sheet of the present invention, having a specific density obtained by forming a foamed sheet using the polycarbonate resin as the raw material, and laminating a plurality of the foamed sheets, having a very high thermal stability, For example, no dimensional change occurs even at a heat resistance of 85 ° C. for 24 hours.
Thus, the foamed laminated sheet of the present invention can be suitably used for various applications requiring heat resistance.
For example, automotive interior materials and automobile ceiling materials have abnormally high temperatures inside the vehicle during the summer (especially near the ceiling), are required to have high heat resistance, and are deformed even when used for a long time in a high or low temperature atmosphere. However, the foamed laminated sheet of the present invention can be suitably used in such applications.
In addition, the heating dimensional change of the foamed laminated sheet of the present invention at 170 ° C. for 60 seconds is within ± 3% in both the extrusion direction and the width direction, and the sheet does not stretch at the time of heat molding. And no unevenness in heating. For this reason, the foamed laminated sheet of the present invention can be variously shaped by the following thermoforming according to an automobile interior material, an automobile ceiling material, a container, and other uses. Furthermore, the bending strength (kg / cm) of the foamed laminated sheet of the present invention²3), as shown in FIG. 3, is clearly superior to a single-layer foam sheet having the same thickness, and particularly when used as an automobile ceiling material, it has a high heat resistance. The problem of sag is solved by the synergistic effect, which is preferable.
[0029]
The foamed laminated sheet of the present invention can be variously shaped according to the use by the following thermoforming.
1. Preheating the foam laminate sheet until it softens and positioning it in the mold
2. The step of bringing the preheated sheet into close contact with the mold surface by evacuation and / or pressure.
3. Step of cooling the shaped foam laminated sheet
4. Step of removing the molded product from the mold cavity
It is molded by going through. Specific examples of the vacuum forming shown in the above two steps, and the pressure forming, etc., include straight forming, drape forming, reverse draw forming, air slip forming, air slip forming by a chamber blow method, plug assist forming, drape. And plug assist molding, plug assist reverse draw molding, air cushion molding, plug assist air slip molding, contact heating type air pressure molding, press molding and the like can be mentioned.
[0030]
【Example】
Next, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples.
[0031]
Example 1
In an extruder, 100 parts by weight of a polycarbonate made of bisphenol A (viscosity average molecular weight: 29000) and 1.2 parts by weight of n-pentane as a foaming agent are melt-kneaded, and then the circular kneaded product is attached to the tip of the extruder. The foam was extruded and foamed from the lip to obtain a tubular foam, and then the tube was cut open to obtain a foamed sheet. The foam sheet obtained at this time had a sheet thickness of 1.4 mm and a density of 0.271 g / cm.³With a width of 630 mm.
Next, the obtained foamed sheets were melt-bonded with each other by hot-air lamination to be laminated and integrated. The processing conditions at this time are as follows.
[Processing conditions of hot air laminating]
・ Line speed: 2-3m / min
・ Crimping roll interval: 85% of the total thickness of the foamed sheet to be laminated
・ Hot air temperature: 500 ℃
[0032]
Example 2
A sheet thickness of 2.6 mm and a density of 0.194 g / cm were obtained in the same manner as in Example 1 except that the amount of the foaming agent was changed to 2.4 parts by weight.³After obtaining a foamed sheet having a width of 1315 mm, the laminate was melt-bonded by hot air lamination in the same manner as in Example 1 to obtain a laminate.
[0033]
Example 3
Except that 100 parts by weight of a branched PC having an N value of 1.40 and 2.4 parts by weight of n-pentane as a foaming agent were used, a sheet thickness of 3.5 mm and a density of 0.16 g / cm³After obtaining a foamed sheet having a width of 630 mm, the laminate was melt-bonded by hot air lamination in the same manner as in Example 1 to obtain a laminate.
Note that the N value is a structural viscosity index, which is determined by the following measurement method.
Nozzle length (mm) / diameter (mm) = 20/1 at a temperature of 300 ° C. using an elevated flow tester CFT500 (manufactured by Shimadzu Corporation), which is an apparatus based on JIS K7210, based on the dried pellets. Pressure P applied under certain conditions (20, 50, 100, 200, 300 kg / cm²5) and the flow rate Q (cc / sec) of each molten resin is measured, and the slope of a regression line obtained by plotting each value on a log-log graph is defined as the N value.
Here, the N value is obtained by the least square method based on the plot of (logP, logQ) indicating the above five measurement points.
[0034]
Example 4
In an extruder, 100 parts by weight of a polycarbonate made of bisphenol A (viscosity average molecular weight 29000) and 2 parts by weight of n-pentane as a foaming agent are melt-kneaded, and the melt-kneaded material is cut from an annular lip of a circular die attached to the tip of the extruder. Extrusion foaming was performed to obtain a tubular foam. At this point, the density of both the upper and lower portions of the tubular foam is 0.185 g / cm.³And the thickness was 2.6 mm. Then, while the inside of the foam (balloon) was in an adhesive state, the balloon was sandwiched by a pressing roll and the inner surface was adhered to obtain a foam laminated sheet. This foam laminated sheet has a thickness of 4.8 mm and a density of 0.200 / cm.³, With a width of 500 mm.
[0035]
Example 5
A foam was obtained in the same manner as in Example 4, except that the size of the extruder was reduced and the amount of the foaming agent was changed to 2.7 parts by weight.
At this time, the density of the upper and lower portions in the balloon state is 0.129 g / cm.³, And the thickness was 2.2 mm.
The laminated foam sheet obtained in the same manner as in Example 4 had a thickness of 4.05 mm and a density of 0.140 g / cm.³, With a width of 300 mm.
[0036]
Comparative Examples 1 to 6
By the same extrusion foaming method as in Example 1, the amount of the foaming agent or the resin was changed as shown in Table 1, and the die size and the like were changed. An extruded resin foam sheet was obtained.
[Table 1]

[0037]
Comparative Example 7
A 0.7 mm film was prepared using the same resin as in Example 1, and the carbon dioxide pressure was set to 40 kg / cm.²Was left in a pressure vessel kept at 23 ° C. for 60 hours, and then heated in an oil bath kept at 160 ° C. for 40 seconds to foam. This foaming has a thickness of 1.8 mm and a density of 0.095 g / cm.³Met. Next, the obtained foamed sheets were melt-bonded by hot air lamination in the same manner as in Example 1.
[0038]
Table 2 shows the results of measuring the sheet density, the sheet thickness, the sheet width, the maximum bending strength, and the bending strength of the foam laminated sheet obtained in each of the examples and the comparative examples. Table 2 also shows the results of changes in the heating dimensions at 170 ° C. for 60 seconds. The change in heating dimension at 85 ° C. was 0% in both the examples and comparative examples.
In addition, the measuring method of the maximum bending strength, bending strength, and heating dimensional change is as follows.

(Heating dimension change)
(1) Change in heating dimensions at 85 ° C
A test piece of 220 × 220 mm is prepared, and a straight line having a length of 100 mm in a flow direction (MD) and a width direction (TD) is drawn crosswise in the center thereof. The test piece is treated in an oven at 85 ± 2 ° C. for 24 hours, and then the length of the straight line is measured, and the change in the heating dimension is determined by the following equation.

This test is performed three times (n = 3), and the average value is defined as a heating dimension change in the MD and TD directions.
(2) Heating dimension change at 170 ° C
A test piece of 150 × 150 mm is prepared, and a straight line having a length of 100 mm in the MD and TD directions is drawn crosswise at the center. This test piece was heat-treated in an oven at 170 ± 2 ° C. for 60 seconds, and then the length of the straight line was measured. Obtain in the same way as in the case of
(Average bubble diameter)
Obtained microscopic enlarged views of cross sections in the MD and TD directions of the foamed laminated sheet (foamed sheets for Comparative Examples 1 to 6). As shown in FIGS. The bubble diameters of 100 or more existing bubbles are measured, and their average values are defined as X, Y, and Z. However, in Examples 1 to 5 and Comparative Example 7, the broken or miniaturized air bubbles in the vicinity of the bonding surface of the foamed sheet in the form of a film were not measured, and α of FIGS. 2B and 2C was not measured. Measure the bubble diameter within the range.
[0039]
[Table 2]

[0040]
【The invention's effect】
The extruded polycarbonate resin foam laminate sheet of the present invention has no dimensional change in the heat resistance evaluation at 85 ° C. for 24 hours, and has almost no dimensional change in the heat resistance evaluation at 170 ° C. for 60 seconds. It is a sheet with extremely excellent properties.
In addition, the bending strength is superior to that of a single-piece (single-layer) foam sheet, and a sufficient thickness and width can be obtained. This is a sheet that has been solved and improved in physical properties.
Further, the polycarbonate resin extruded foam laminated sheet having the average diameter and shape of the particularly preferred cells of the present invention has particularly good stability when heated and formed because the foamed cells are molded flat, Therefore, the foamed sheet is less likely to be broken or wavy at the time of forming, and a high-quality molded product can be obtained from the foamed laminated sheet with good yield.
As described above, since the foamed laminated sheet of the present invention is extremely excellent in heat resistance and bending strength, it is suitably used as an interior material of an automobile or a ceiling material of an automobile. It can be shaped into
[Brief description of the drawings]
FIG. 1 is a schematic view of a method of forming a foam laminated sheet by a hot air lamination method.
FIG. 2 is a diagram illustrating a preferred cell shape in the foam laminated sheet of the present invention.
FIG. 3 is a diagram illustrating the relationship between the density and the bending strength of the foam laminated sheet and the foam single sheet of the present invention.
[Explanation of symbols]
1 foam laminated sheet
2 Foam sheet
3 Foam sheet
x Sheet width direction
y Sheet extrusion direction
z Sheet thickness direction

Claims (2)

A laminated sheet having a density of 0.05 to 0.4 g / cm ³ and a thickness of 0.8 to 10 mm obtained by bonding a plurality of extruded polycarbonate resin foam sheets, and having a strength satisfying the following formula: Extruded resin-based laminated sheet.

The polycarbonate resin extruded foam sheet is a foam sheet obtained by being cut out after being extruded from a circular die and passing over a mandrel, wherein the mandrel surfaces of the sheet are bonded to each other. Item 4. An extruded polycarbonate resin laminated sheet according to Item 1.

Images