JP4111437B2 - Manufacturing method of polystyrene resin extruded foam plate and polystyrene resin extruded foam plate - Google Patents

Description

【００２７】
本発明の押出発泡板は、熱伝導率が０．０３１Ｗ/ｍＫ以下であることが好ましい。熱伝導率が０．０３１Ｗ/ｍＫ以下である発泡板は、ＪＩＳ Ａ ９５１１(１９９５)記載の押出ポリスチレンフォーム保温板３種についての熱伝導率の規格を満足するものであり、断熱板として好適なものである。尚、この熱伝導率は、ＪＩＳ Ａ １４１２(１９９４)記載の平板熱流計法（熱流計２枚方式、平均温度２０℃）にて測定される値である。
【００２８】
本発明の発泡板中における難燃剤の含有量は、難燃性を向上するとともに、機械的物性の低下を最小の物とするうえで、ポリスチレン系樹脂１００重量部当たり１〜１０重量部が好ましく１．５〜７重量部がより好ましく、２〜５重量部が更に好ましい。
【００２９】
本発明において難燃剤としては、ハロゲン系難燃剤が好適であり、中でもヘキサブロモシクロドデカン、臭素化イソシアヌレート、臭素化ビスフェノールの１種又は２種以上を使用することが好ましい。臭素化イソシアヌレートは、下記式（１）に示される、イソシアヌル酸又はイソシアヌル酸誘導体の臭素化物である。該臭素化イソシアヌレートは、構造式中にイソシアヌレート骨格を有することで、難燃効果を発揮する臭化水素を、ポリスチレン系樹脂分解温度において効率的に発生させることが可能となり、燃焼時に該難燃剤から生成する臭化水素が、ポリスチレン系樹脂が分解して生じる活性ラジカルと反応することでその量を下げる効果をもたらし、燃焼を継続させる活性ラジカル生成の連鎖反応を停止させ、また、臭素ガスによる遮蔽効果も作用して優れた難燃性を発揮させることが可能となる。
【００３０】
【化１】

［式中、Ｒ^１，Ｒ^２，Ｒ^３は、水素原子、炭素数１〜８のアルキル基、−Ｙ−Ｘで表される有機基（Ｙは炭素数１〜６のアルキレン基、Ｘはエポキシ基、カルボキシル基、水酸基、アミノ基、フェニル基である）、およびフェニル基の中から選択されるもの、および、これらの原子及び原子団のうち、少なくとも１つの水素原子が臭素原子に置換されているものである。但し、Ｒ^１，Ｒ^２，Ｒ^３のうち少なくとも１つは、前記原子及び原子団のうち少なくとも１つの水素原子が臭素原子に置換されているものとする。尚、Ｒ^１，Ｒ^２，Ｒ^３の原子及び原子団は相互に異なるものであっても同じものであってもよい。］
【００３１】
上記臭素化イソシアヌレートの具体例としては、モノ（２，３−ジブロモプロピル）イソシアヌレート、ジ（２，３−ジブロモプロピル）イソシアヌレート、トリス（２，３−ジブロモプロピル）イソシアヌレート、モノ（２，３，４−トリブロモブチル）イソシアヌレート、ジ（２，３，４−トリブロモブチル）イソシアヌレート、トリス（２，３，４−トリブロモブチル）イソシアヌレート等が挙げられる。また、上記の臭素化イソシアヌレートの中で特に、トリス（２，３−ジブロモプロピル）イソシアヌレートは、ポリスチレン系樹脂との相溶性が良好であり、分解開始温度が２５０〜２６５℃、融点が１００〜１１０℃であるために発泡板製造時における取扱いが容易で、ポリスチレン系樹脂との混練時において分解する可能性も小さく、極めて高い難燃効果が容易に発現されるため好ましい。臭素化イソシアヌレートは、上記式（１）にて示されるもののうち、１種又は２種以上をポリスチレン系樹脂に添加することができる。
【００３２】
臭素化ビスフェノールは下記式（２）で示される、ビスフェノールＡ又はビスフェノールＡ誘導体の臭素化物である。該臭素化ビスフェノールは、構造式中にビスフェノール骨格を有することで、難燃効果を発揮する臭化水素をポリスチレン系樹脂分解温度において、効率的に発生させることが可能となり、燃焼時に該難燃剤から生成する臭化水素が、ポリスチレン系樹脂分解時に発生する活性ラジカルと反応することでその量を下げる効果をもたらし、燃焼を継続させる活性ラジカル生成の連鎖反応を停止させ、また、臭素ガスによる遮蔽効果も作用して優れた難燃性を発揮させることが可能となる。
【００３３】
【化２】

［式中，Ｒ^４，Ｒ^５は、水素原子、炭素数１〜８のアルキル基、−Ｙ−Ｘで表される有機基（Ｙは炭素数１〜６のアルキレン基、Ｘはエポキシ基、カルボキシル基、水酸基、アミノ基、フェニル基である）、およびフェニル基のうちから選ばれるもの、および、これらの原子及び原子団のうち、少なくとも１つの水素原子が臭素原子に置換されているものである。尚、Ｒ^４，Ｒ^５の原子及び原子団は相互に異なるものであっても同じものであってもよい。］
【００３４】
式（２）で示される臭素化ビスフェノールの具体例としては、テトラブロモビスフェノールＡ、テトラブロモビスフェノールＡビス（２，３−ジブロモプロピルエーテル）、テトラブロモビスフェノールＡビス（２−ブロモエチルエーテル）、テトラブロモビスフェノールＡビス（２−ブロモエチルエーテル）オリゴマー、テトラブロモビスフェノールＡビス（１−ブロモプロピルエーテル）、テトラブロモビスフェノールＡビス（アリルエーテル）、テトラブロモビスフェノールＡビス（２−ハイドロキシエチルエーテル）、テトラブロモビスフェノールＡジグリシジルエーテル、テトラブロモビスフェノールＡジグリシジルエーテルのトリブロモフェノール付加物、テトラブロモビスフェノールＡポリカーボネートオリゴマー、テトラブロモビスフェノールＡオリゴマーのエポキシ基付加物等が挙げられる。また、上記の臭素化ビスフェノ−ルの中で特に、テトラブロモビスフェノ−ルＡビス（２，３−ジブロモプロピルエーテル）、テトラブロモビスフェノールＡビス（２−ブロモエチルエーテル）、テトラブロモビスフェノールＡビス（２−ブロモエチルエーテル）オリゴマーが、ポリスチレン系樹脂との相溶性が良く、分解開始温度が２７５〜３１０℃、融点が１０５〜１３０℃であって発泡板製造時における取扱いが容易で、ポリスチレン系樹脂との混練時において分解する可能性も小さく、難燃効果も高く発現し易いため好ましい。臭素化ビスフェノールは、上記式（２）にて示されるもののうち、１種又は２種以上のものであってもよい。
【００３５】
本発明の発泡板は、ＪＩＳ Ａ ９５１１(１９９５年)記載の押出ポリスチレンフォーム保温板を対象とする燃焼性規格を満足する耐燃焼性を有していることが好ましい。即ち、ＪＩＳ Ａ ９５１１(１９９５年)に記載されている４．１３．１「測定方法Ａ」の燃焼性の測定を行なった場合、炎が３秒以内に消え、残じんがなく、燃焼限界指示線を越えて燃焼することがないことである。従ってこのような燃焼特性の発泡板は、着火した場合であっても、火が燃え広がる可能性が小さいので、建材用の押出ポリスチレンフォーム保温板として要求される安全性を備えるものである。このような燃焼特性のポリスチレン系樹脂押出発泡板は、難燃剤として前記したヘキサブロモドデカン、臭素化イソシアヌレート、臭素化ビスフェノールの１種又は２種以上を発泡板中に含有させることにより容易に得ることができる。
【００３６】
本発明のポリスチレン系樹脂押出発泡板は、厚み１０〜１５０ｍｍのものである。厚みが１０ｍｍ未満の場合、イソブタン及び／又はイソペンタンの含有量と、グラファイトの含有量が上記した範囲内であっても、断熱材に要求される断熱性が不十分となり、１５０ｍｍを超えると断熱材としての取扱い性が悪くなる。発泡板の厚みは、好ましくは１５〜１２０ｍｍである。
【００３７】
本発明の発泡板は、見かけ密度２５〜５５ｋｇ／ｍ^３を有する。見かけ密度が２５ｋｇ／ｍ^３未満という低密度の押出発泡体を製造すること自体、かなり困難なものである上に、仮にそのような低密度の発泡体が得られたとしても、断熱板として用いる場合の機械的物性が、従来の発泡断熱板と比較して不充分なものとなるので使用できる用途が限定される。一方、見かけ密度が５５ｋｇ／ｍ^３を超える場合は、発泡板の厚みを必要以上に厚くしない限り、充分な断熱性を発揮させることが難しく、また、軽量性の点において不充分なものとなる虞れがある。特に本発明において、押出発泡板の見掛け密度が２５〜５５ｋｇ／ｍ^３の場合に高い断熱性能を付与し易い上、この種の発泡板に古くから使用されているヘキサブロモシクロドデカンを難燃剤として使用した場合、比較的少量の使用において高い難燃性能を付与することができるという利点がある。
【００３８】
本発明の発泡板は、厚み方向平均気泡径（Ｄ_Ｔ）が０．０５〜０．３０ｍｍである。厚み方向平均気泡径（Ｄ_Ｔ）が０．０５ｍｍ未満となるような場合には、製造時にダイリップを通して押出された発泡途上にある発泡性溶融樹脂混合物（押出後の時間の経過と共に「溶融」状態から「非溶融状態」へと変化するので、厳密には必ずしも「溶融」とは言えない状態をも含む可能性があるが、本明細書では便宜上この表現を採用する）を、後述する賦形装置を使用したとしても板状の発泡体とならなくなる虞れがある。一方、厚み方向平均気泡径（Ｄ_Ｔ）が０．３０ｍｍを超える場合は、イソブタン及び／又はイソペンタンの含有率、グラファイトの含有率が上記範囲内であっても、目的とする断熱性を得ることができない虞れがある。優れた断熱性の発泡体であるために、厚み方向平均気泡径（Ｄ_Ｔ）が０．０６〜０．２５ｍｍであるものが好ましく、０．０８〜０．２０ｍｍであるものがより好ましい。
【００３９】
上記厚み方向平均気泡径（Ｄ_Ｔ）の測定方法は次の通りである。まず、発泡板の押出方向と直交する任意の面で発泡板をきれいに切断する。その切断面における後述する９箇所の各々に対し、顕微鏡で２００倍に拡大した画面上又はその画面を撮影した写真上で、全景が確認できる気泡（画面や写真の端部で気泡の一部が欠落しているものや、画面や写真の端部ではないが気泡壁の一部欠落により隣の気泡等と連通して一体化している気泡は除く）を対象にして無作為に２０個の気泡を選択する。この際、画面上又は顕微鏡写真上で全景が映し出された気泡が２０個に満たない場合には、発泡板の押出方向と直交する任意の他の断面に対する画面又はその顕微鏡写真を付加的に使用すればよい。次に、選択された気泡のそれぞれに対し、気泡壁と接する長方形又は正方形を描く。この際、長方形又は正方形の相対向する一対の辺は発泡板の厚み方向と一致するように、また長方形又は正方形のもう一方の相対向する一対の辺は発泡板の幅方向と一致するように描く。このようにして得られた２０個の長方形又は正方形について、それぞれ、発泡板の厚み方向と一致する辺の長さを測定し、測定値を相加平均することによって各測定部における厚み方向平均気泡径を得ることができる。次に、９箇所の測定結果を相加平均してこれを本発明における厚み方向平均気泡径（Ｄ_Ｔ）とする。尚、測定の対象となる９箇所とは、発泡板の幅方向を４等分する３箇所のそれぞれにおいて、発泡板の厚み方向を４等分する３箇所の計９箇所である。
【００４０】
発泡板の断熱性が更に優れたものとなるとともに、厚み方向における圧縮強度にも優れたものとする上で、前記厚み方向平均気泡径気泡（Ｄ_Ｔ）を、水平方向平均気泡径（Ｄ_Ｈ）で除して求められる気泡変形率が０．７〜２．０であることが好ましい。水平方向平均気泡径（Ｄ_Ｈ）は、幅方向平均気泡径（Ｄ_Ｗ）と押出方向平均気泡径（Ｄ_Ｌ）の相加平均である。幅方向平均気泡径（Ｄ_Ｗ）は、上記厚み方向気泡径を求める際に、発泡板の幅方向垂直断面において選択した気泡の気泡壁と接するように描いた長方形又は正方形の、幅方向と一致する辺の長さを測定して、厚み方向平均気泡径（Ｄ_Ｔ）を求めたと同様にして求めることができる。また押出方向平均気泡径（Ｄ_Ｌ）は、発泡板の押出方向に沿った垂直断面から、同様にして求めた押出方向の気泡径の平均値である。気泡変形率が０．７未満という扁平な気泡構造のものは、厚み方向の圧縮強度が低下する傾向にある。また気泡変形率が２．０を超える縦長の気泡構造のものは、厚み方向の気泡数が少なくなるために断熱性が低下する傾向にある。発泡板中の気泡は、気泡変形率は０．８０〜１．７であることがより好ましく、０．８５〜１．５であることが更に好ましい。平均気泡径の大きさは、主としてグラファイトの添加量と気泡調整剤の添加量で調整され、気泡変形率は主として押出発泡板の製造時における賦形する際の３次元方向の拡大の度合いを制御することにより調整される。
【００４１】
また、本発明の押出発泡板の独立気泡率は９０％以上であることが好ましく、９３％以上であることがより好ましい。独立気泡率が高いほど断熱性能を高く維持できる。
【００４２】
押出発泡板の独立気泡率は、ＡＳＴＭ−Ｄ２８５６−７０の手順Ｃに従って、東芝ベックマン株式会社の空気比較式比重計９３０型を使用して測定（押出発泡板から２５ｍｍ×２５ｍｍ×２０ｍｍのサイズに切断された成形表皮を持たないカットサンプルをサンプルカップ内に収容して測定する。ただし、厚みが薄く厚み方向に２０ｍｍのカットサンプルが切り出せない場合には、例えば、２５ｍｍ×２５ｍｍ×１０ｍｍのサイズのカットサンプルを２枚同時にサンプルカップ内に収容して測定すればよい。）された押出発泡板（カットサンプル）の真の体積Ｖｘを用い、下記（３）式により独立気泡率Ｓ（％）を計算する。尚、一つの押出発泡板に対して３箇所の異なる部分からカットサンプルを切り出して各々のカットサンプルについて上記測定を行ない得られた値の平均値を独立気泡率とする。
【００４３】
【数１】
Ｓ（％）＝（Ｖｘ−Ｗ／ρ）×１００／（Ｖａ−Ｗ／ρ） （３）
【００４４】
Ｖｘ：上記方法で測定されたカットサンプルの真の体積（ｃｍ^３）であり、カットサンプルを構成する樹脂の容積と、カットサンプル内の独立気泡部分の気泡全容積との和に相当する。
Ｖａ：測定に使用されたカットサンプルの外寸から計算されたカットサンプルの見掛け上の体積（ｃｍ^３）。
Ｗ：測定に使用されたカットサンプル全重量（ｇ）。
ρ：押出発泡板を構成する樹脂の密度（ｇ／ｃｍ^３）。
【００４５】
【実施例】
次に、具体的な実施例を挙げて、本発明を更に詳細に説明する。
【００４６】
実施例１
ポリスチレン（東洋スチレン社製Ｇ３３０Ｃ）に、気泡調整剤としてのタルク（松村産業株式会社製：ハイフィラー＃１２）、難燃剤としてヘキサブロモシクロドデカン及びグラファイト（日本黒鉛工業株式会社製の鱗状黒鉛粉末、平均粒径１７μｍ）を、ポリスチレン１００重量部（マスターバッチのポリスチレンを合計した全ポリスチレン）当たりに対して表１に示す量となるように添加した。タルクは上記ポリスチレン６９重量％、タルク３０重量％、ステアリン酸亜鉛１重量％含むタルクマスターバッチを用い、グラファイトは上記ポリスチレン７０重量％、グラファイト３０重量％からなるグラファイトマスターバッチを用い、タルク、グラファイトの割合が表１に示す量となるように、ポリスチレンとマスターバッチとを押出機内で混合して溶融した。ついでこの溶融ポリスチレン組成物に、表１に示す組成の混合発泡剤を、マスターバッチを配合して調整した溶融ポリスチレン組成物に発泡剤を圧入した後の発泡剤の割合が、表１に示す量となるように混合発泡剤を圧入して混練し、発泡性溶融ポリスチレン組成物とした。
【００４７】
押出機としては、口径６５ｍｍの押出機（以下、「第一押出機」という。）と口径９０ｍｍの押出機（以下、「第二押出機」という。）と口径１５０ｍｍ押出機（以下、「第三押出機」という。）とを直列に連結したものを使用した。各押出機のダイリップは、先端に幅１１５ｍｍ、間隙１．５ｍｍ（長方形横断面）の樹脂排出口を備えたものを使用した。ポリスチレン、タルクマスターバッチ、グラファイトマスターバッチは第一押出機に供給し、２２０℃まで加熱して溶融混練した後、上記混合発泡剤を第一押出機の先端付近において溶融樹脂中に圧入混練して発泡性溶融ポリスチレン組成物とした。続く第二押出機、第三押出機において、ダイリップを取り付けたアダプター部での樹脂圧力が３０ｋｇｆ／ｃｍ^２となるように、各押出機内で樹脂温度を調整し、第三押出機に取付けたダイリップより、表２に示す吐出量で押出して発泡させ、ついで賦型装置を通過させて板状に成形した。第三押出機から押出す直前の発泡性溶融ポリスチレン組成物の温度（発泡温度）を表３に示す。
【００４８】
得られた押出発泡板の見掛け密度、厚み、独立気泡率、厚み方向平均気泡径、気泡変形率、熱伝導率、燃焼性、発泡剤残存量を表３に示す。
【００４９】
実施例２
表１に示すようにグラファイトとタルクの添加量が異なる他は、実施例１と同様にして発泡板を得た。得られた発泡板の諸物性を表３に示す。
【００５０】
実施例３
実施例１で用いた平均粒径１７μｍのグラファイトにかえて、平均粒径４０μｍのグラファイト（日本黒鉛工業株式会社製の鱗状黒鉛粉末）を用いた他は実施例１と同様にして発泡板を得た。得られた発泡板の諸物性を表３に示す。
【００５１】
実施例４
実施例１で用いた平均粒径１７μｍのグラファイトにかえて、平均粒径７μｍのグラファイト（日本黒鉛工業株式会社製の土状黒鉛粉末）を用いた他は実施例１と同様にして発泡板を得た。得られた発泡板の諸物性を表３に示す。
【００５２】
実施例５
実施例１で用いた平均粒径１７μｍのグラファイトにかえて、平均粒径２０μｍのグラファイト（日本黒鉛工業株式会社製の人造黒鉛粉末）を用いた他は実施例１と同様にして発泡板を得た。得られた発泡板の諸物性を表３に示す。
【００５３】
実施例６
混合発泡剤をイソブタン、ジメチルエーテル、二酸化炭素の混合物にかえ、表１に示す割合で含有させた他は実施例１と同様にして発泡板を得た。得られた発泡板の諸物性を表４に示す。
【００５４】
実施例７
混合発泡剤をイソブタン、エタノール、二酸化炭素の混合物にかえ、表１に示す割合で含有させた他は実施例１と同様にして発泡板を得た。得られた発泡板の諸物性を表４に示す。
【００５５】
実施例８
実施例１におけるハロゲン系難燃剤としてヘキサブロモシクロドデカンにかえて、トリス（２，３−ジブロモプロピル）イソシアヌレート（鈴裕化学社製の臭素化イソシアヌレート）にかえ、表１に示す割合で添加した他は実施例１と同様にして発泡板を得た。得られた発泡板の諸物性を表４に示す。
【００５６】
実施例９
ポリスチレンを出光石油化学社製のＨＨ３２にかえ、ダイリップとして先端幅６５ｍｍ、間隙３ｍｍのものを用いた他は実施例１と同様にして発泡板を得た。得られた発泡板の諸物性を表４に示す。
【００５７】
比較例１
表２に示すようにグラファイトの添加量が異なる他は、実施例１と同様にして発泡板を得た。得られた発泡板の諸物性を表５に示す。この発泡板は、耐燃焼性は良好であったが、熱伝導率が高く断熱性に問題を有していた。
【００５８】
比較例２
表２に示すようにグラファイトとタルクの添加量が異なる他は、実施例１と同様にして発泡板を得た。得られた発泡板の諸物性を表５に示す。比較例２の発泡板はグラファイトの添加量が多すぎたため押出機の圧力上昇や得られる発泡板の発泡倍率の極端な低下が見られ、また、外観については発泡板の表面に複数の亀裂が発生していた。
【００５９】
比較例３、４
表１に示す混合発泡剤を同表に示す割合で添加した他は、実施例１と同様にして発泡板を得た。得られた発泡板の諸物性を表５に示す。比較例３の発泡板は、耐燃焼性は良好であったが、熱伝導率が高く断熱性に問題を有していた。また比較例４の発泡板は、イソブタンの残存量が多量であったため耐燃焼性（難燃性）に劣るものであった。
【００６０】
参考例
グラファイトのかわりに、カーボンブラック（粒径１７ｎｍ）を用いた他は、実施例１と同様にして発泡板を得た。得られた発泡板の諸物性を表５に示す。参考例の発泡板は、熱伝導率が低く断熱性に優れるものであったが、耐燃焼性に問題を有していた。
【００６１】
【表１】

【００６２】
【表２】

【００６３】
【表３】

【００６４】
【表４】

【００６５】
【表５】

【００６６】
表３、４、５における見掛け密度は、ＪＩＳ Ｋ ７２２２(１９８５年）に基づいて測定された値である。
【００６７】
表３、４、５における厚みは、幅方向を４等分する位置の３箇所で測定し、それらを相加平均した値である。
【００６８】
表３、４、５における厚み方向平均気泡径及び気泡変形率は、前記の方法で測定された値である。
【００６９】
表３、４、５における独立気泡率は、押出発泡板から２５ｍｍ×２５ｍｍ×２０ｍｍのサイズに切断された成形表皮を持たないカットサンプルを使用して上記の方法で測定された値である。
【００７０】
表３、４、５における熱伝導率は、製造後４週間経過した押出発泡板と製造後３ヶ月経過した押出発泡板のそれぞれに対し、縦２０ｃｍ、横２０ｃｍ、押出発泡板厚みの試験片を切り出し、各試験片について、ＪＩＳ Ａ ９５１１(１９９５年)４．７の記載により、英弘精機株式会社製の熱伝導率測定装置「オートΛ ＨＣ-７３型」を使用して、ＪＩＳ Ａ１４１２(１９９４年)記載の平板熱流計法（熱流計２枚方式、平均温度２０℃）に基づいて測定した。
【００７１】
表３、４、５における耐燃焼性は、製造後５日間経過後および製造後２週間経過後の押出発泡板から切り出した試験片を、ＪＩＳ Ａ９５１１（１９９５年）の４．１３．１「測定方法Ａ」に基づいて測定した。尚、該測定は一つの押出発泡板に対して試験片を１０個切り出して下記の評価基準にて評価した。
◎：全ての試験片において３秒以内で消え、且つ、１０個の試験片の平均燃焼時間が２秒以内である。
〇：全ての試験片において３秒以内で消え、且つ、１０個の試験片の平均燃焼時間が２秒を越え３秒以内である。
△：１０個の試験片の平均燃焼時間が３秒以内であるが、１個以上の試験片において３秒以内で消えないものがある。
×：１０個の試験片の平均燃焼時間が３秒を越える。
【００７２】
表３、４、５における発泡剤残存量（発泡板１ｋｇ当たりの発泡剤の含有量)の測定は、株式会社島津製作所製、島津ガスクロマトグラフＧＣ−１４Ｂを使用し、シクロペンタンを内標準物質として、前記方法に基づいて測定した。
【００７３】
表３、４、５における発泡体外観は下記の評価基準にて評価した。
○：表面に亀裂の発生が認められない。
×：表面に亀裂の発生が認められる。
【００７４】
【発明の効果】
本発明方法は、オゾン破壊係数が０であり、地球温暖化係数が小さいイソブタンやイソペンタンを特定の割合で含み、クロロフルオロカーボンやフルオロカーボンを実質的に含まない混合発泡剤を用い、難燃剤と、特定量のグラファイトとを併用してポリスチレン系樹脂押出発泡板を得る方法を採用したため、軽量性、難燃性、断熱性に優れたポリスチレン系樹脂押出発泡板を得ることができるとともに、環境に対する負荷が小さい優れた方法である。グラファイトは気泡調整剤としても作用し、気泡のきめを細かくする効果が得られるため、タルク等の気泡調整剤使用量を低減化でき、種々の添加剤を添加することによる発泡板の機械的物性低下等を生じる虞れがない。またグラファイトとして固定炭素分９０％以上のものを用いると、高濃度のグラファイトを含むマスターバッチを製造する際の作業性が向上され、ポリスチレン系樹脂押出発泡板製造の作業性が向上する。
【００７５】
本発明のポリスチレン系樹脂押出発泡板は、発泡板中に特定量のイソブタンやイソペンタンが残留し、かつ特定量のグラファイトを含有していることにより、断熱性が大きく向上されるとともに、イソブタンやイソペンタン等の可燃性気体が残留しているにもかかわらず、優れた耐燃焼性を有する。また従来は回収した着色ポリスチレン系樹脂発泡体の再使用には大きな制限があったが、本発明発泡板はグラファイトによりグレー又は黒色に着色されるため、発泡板製造時に着色された回収原料を添加混合しても得られる発泡板の色目はさほど影響を受けないので、回収原料の再使用が容易となる等の利点を有する。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a polystyrene resin extruded foam plate used for heat insulating materials such as walls, floors and roofs of buildings, tatami core materials, and the like, and a polystyrene resin extruded foam plate.
[0002]
[Prior art]
Conventionally, polystyrene-based resin foams have been widely used as heat insulating materials because they have excellent heat insulating properties and suitable mechanical strength, and thus are molded into a plate having a constant width. As a method for producing such a foamed plate, extrusion foaming is performed in which a foam regulator is added to a polystyrene-based resin, heated and melt-kneaded, a physical foaming agent is added, and the foamable molten resin composition is extruded from a high pressure region to a low pressure region. The law is known.
[0003]
Conventionally, chlorofluorocarbons (hereinafter referred to as CFC) such as dichlorodifluoromethane have been widely used as the foaming agent used in the production of the foamed plate. However, since CFC has a high risk of destroying the ozone layer, hydrogen atom-containing chlorofluorocarbon (hereinafter referred to as HCFC) having a small ozone depletion coefficient has been used in place of CFC in recent years.
[0004]
However, since the HCFC also has an ozone depletion coefficient that is not zero, there is no risk of destroying the ozone layer. Therefore, it has been studied to use a fluorinated hydrocarbon (hereinafter referred to as HFC) having an ozone depletion coefficient of 0 and having no chlorine atom in the molecule as a foaming agent.
[0005]
However, since this HFC has a large global warming potential, there is room for improvement in terms of protecting the global environment. For this reason, it is desired to produce a polystyrene resin extruded foam plate using an environmentally friendly foaming agent having an ozone depletion coefficient of 0 and a low global warming potential.
[0006]
Isobutane and isopentane are excellent foaming agents from the viewpoint of having an ozone depletion coefficient of 0, a small global warming potential, and being friendly to the global environment. Moreover, since the permeation | transmission rate with respect to a polystyrene is very slower than air, the heat insulation board which uses isobutane and isopentane can maintain the heat insulation at the time of manufacture over a long period of time. However, although isobutane and isopentane have a lower thermal conductivity in the gas state than air, they have a higher thermal conductivity in the gas state than conventional CFCs, HCFCs, and HFCs, and have the same heat insulating properties as HFCs. Is difficult to get. Furthermore, since its own flammability is high, it is extremely difficult to impart flame retardancy to the obtained foam.
[0007]
On the other hand, as means for obtaining a thermoplastic resin foam having excellent heat insulation properties, a method of adding metal powder such as aluminum powder or silver powder or fine powder reflecting infrared rays such as graphite to the resin (Patent Document 1), carbon dioxide Attempts have been made to use water and / or alcohol as a foaming agent and to add graphite (Patent Document 2).
[0008]
However, in the method of adding fine powder reflecting infrared rays described in Patent Document 1, it is difficult to produce a polystyrene foam having high flame retardancy. In the method described in Patent Document 1, no flame retardant is used, but even if a halogen-based flame retardant widely used for polystyrene foam is added, sufficient flame retardancy cannot be imparted. According to the knowledge of the present inventors, in the case of polystyrene foam, when the fine powder or the like that reflects infrared rays is aluminum powder or silver powder, even if a halogen-based flame retardant is added, the effect of improving flame retardancy is hardly recognized. . The reason for this is not clear, but it is thought that aluminum powder or silver powder may inhibit the function of the halogen flame retardant. It has been found that only graphite does not hinder the function of the flame retardant. However, in Patent Document 1, a large amount of a foaming agent composed of a flammable gas such as butane or pentane is used. It was difficult to impart flammability. Addition of a large amount of flame retardant is expected to improve flame retardancy, but it may be difficult to obtain low density foam, which may lead to a decrease in closed cell ratio and mechanical properties of the resulting polystyrene foam. There was a problem of becoming. In Patent Document 1, butane or pentane is used as a foaming agent, but these are relatively slow to escape from the foam with the passage of time, but from the foam much faster than isobutane or isopentane. Since it escaped, it was insufficient for maintaining the long-term heat insulation performance of the foam.
[0009]
On the other hand, in the method described in Patent Document 2, graphite is added when producing a polystyrene foam, but carbon dioxide, water and / or alcohol is used as a foaming agent. It was difficult to impart a high degree of heat insulation.
[0010]
[Patent Document 1]
Japanese Unexamined Patent Publication No. 63-183941
[Patent Document 2]
International Publication No. 01/04191 Pamphlet
[0011]
[Problems to be solved by the invention]
The present invention is a foamed plate manufactured using a foaming agent having an ozone depletion coefficient of 0 and a low global warming coefficient in view of the above-described problems of the prior art, and has excellent flame retardancy and long-term thermal conductivity. An object of the present invention is to provide a small and excellent polystyrene-based resin extruded foam plate.
[0012]
[Means for Solving the Problems]
  In the present invention, (1) a polystyrene resin is heated in an extruder, and a foaming agent, a flame retardant, andGraphiteA foamable molten mixture obtained by kneading together with a polystyrene-based resin extruded foam plate that is extruded and foamed to a low pressure region through a die attached to the tip of the extruder,
SaidThe blowing agent is a mixed blowing agent composed of 70 to 25 mol% of isobutane and / or isopentane and 30 to 75 mol% of another blowing agent (provided that the total amount of these blowing agents is 100 mol%). ),The graphite is graphite having a fixed carbon content of 90% by mass or more,And the graphiteThe polystyrene resin extruded foam plate is configured as a masterbatch blended with polystyrene resin.1 to 5 parts by weight per 100 parts by weight of polystyrene resinTo beA method for producing a polystyrene-based resin extruded foam plate, characterized by comprising: (2)SaidThe main component of graphite is scaly graphite,as well asThe above (which is one kind selected from artificial graphite or a mixture thereof) (1)(3) A method for producing a polystyrene resin extruded foam plate according toSaidOther blowing agents mixed with isobutane and / or isopentane are alkyl chloride, carbon dioxide, dimethyl ether, aliphatic alcohols,as well asSaid (1) which is 1 type, or 2 or more types chosen from waterOr (2)(4) a foaming agent comprising a mixture of a polystyrene resin, isobutane and / or isopentane, and another foaming agent,Graphite is added as a masterbatch blended with polystyrene resinGraphite,AndThickness of 10 to 150 mm obtained by extruding a foamable molten mixture containing a flame retardant from a high pressure region to a low pressure region, and an apparent density of 25 to 55 kg / m³A polystyrene-based extruded foam plate having an average cell diameter in the thickness direction of 0.05 to 0.30 mm,
The residual amount of isobutane and / or isopentane in the foam plate is 0.2 to 0.8 mol per kg of the foam plate,
The graphite is graphite having a fixed carbon content of 90% by mass or more,
Configure the foam plate1 to 5 parts by weight is added to 100 parts by weight of polystyrene resinAnd
And this polystyrene-type resin extrusion foaming board is 0.031W. / It has a thermal conductivity of mK or less and satisfies the flammability standard of 4.13.1 measuring method A described in JIS A9511 (1995).
A polystyrene resin extruded foam board characterized by that.
(5) As a flame retardant, one or more of hexabromocyclododecane, brominated isocyanurate, brominated bisphenol,4And a polystyrene-based resin extruded foam plate as described above.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Examples of polystyrene resins used in the present invention include styrene homopolymers, styrene-acrylic acid copolymers based on styrene, styrene-methacrylic acid copolymers, styrene-maleic anhydride copolymers, styrene- Examples thereof include a butadiene copolymer, a styrene-acrylonitrile copolymer, an acrylonitrile-butadiene-styrene copolymer, and a high impact polystyrene. These may be used alone or in admixture of two or more. In addition, the styrene component content in the styrene-based copolymer is preferably 50 mol% or more, particularly preferably 80 mol% or more.
[0014]
The polystyrene resin used in the present invention has a melt flow rate (MFR) in the range of 0.5 to 30 g / 10 min (however, MFR measured according to test method 8 of method A of JIS K7210 (1976)). Further, it is more preferable to use a material having a content of 1 to 10 g / 10 minutes because the extruded foam plate is excellent in the extrudability when producing the extruded foam plate and the mechanical strength of the obtained extruded foam plate is improved.
In the present invention, a polystyrene resin may be further mixed with another polymer or copolymer such as a polyolefin resin, a styrene elastomer, or a polyphenylene ether resin within a range not impairing the object of the present invention. However, the amount of the other polymer or copolymer used is preferably 50 parts by weight per 100 parts by weight of the polystyrene resin, more preferably 30 parts by weight or less, and still more preferably 10 parts by weight or less. .
[0015]
In the present invention, as the foaming agent, a mixed foaming agent of isobutane and / or isopentane and other foaming agents other than isobutane and other than isopentane (hereinafter simply referred to as “other foaming agents”) is used. Isobutane and isopentane remain in the polystyrene resin foam plate for a long time after production, and have a good characteristic in maintaining the heat insulation property of the foam plate for a long time because the gas thermal conductivity is lower than that of air. is doing. However, isobutane is preferable to isopentane because it is easier to handle. Other foaming agents other than isobutane and other than isopentane can be used. The use of chlorofluorocarbons and / or fluorocarbons as other blowing agents is avoided as much as possible. In the present invention, the amount of chlorofluorocarbon or / and fluorocarbon used is 0 to 5 mol%, preferably 0 to 3 mol%, most preferably 0, when the mixed foaming agent is 100 mol%. Also, as other foaming agents, flammable aliphatic hydrocarbons such as propane and normal butane other than isobutane and isopentane have a relatively slow escape rate from polystyrene resin foam plates. Since there is a possibility that the flame retardancy is lowered or the heat insulation property is lowered early, their use amount is 0 to 5 mol%, preferably 0 to 3 mol%, preferably 0 to 2 mol%. Most preferred. On the other hand, among other foaming agents, one or more foaming agents selected from the group consisting of alkyl chloride, carbon dioxide, dimethyl ether, aliphatic alcohol, and water have a high gas permeability to polystyrene, so that they quickly escape from the foam plate. Therefore, it is easy to obtain a low-density foam plate because the foam plate has excellent foaming power and the properties such as heat insulation and flame retardance of the foam plate are stabilized early. Therefore, one or two or more blowing agents selected from the group consisting of alkyl chloride, carbon dioxide, dimethyl ether, aliphatic alcohol and water are used at 90 to 100 mol% when the total amount of other blowing agents is 100 mol%. It is preferable to use at 95 to 100 mol%. Among them, in the present invention, as the other foaming agent, one or two or more foaming agents selected from the group of carbon dioxide, dimethyl ether and aliphatic alcohol, when the total amount of the other foaming agent is 100 mol%, It is preferable to use at -100 mol%, and it is more preferable to use at 95-100 mol%.
[0016]
The ratio of isobutane and / or isopentane to other blowing agents in the mixed blowing agent is 70 to 25 mol% of isobutane and / or isopentane, 30 to 75 mol% of other blowing agent (provided that isobutane and / or isopentane, The total amount of other blowing agents is 100 mol%), but 65 to 30 mol% of isobutane and / or isopentane, 35 to 70 mol% of other blowing agents (provided that isobutane and / or isopentane, etc.) The total amount of the blowing agent is preferably 100 mol%), 60 to 35 mol% of isobutane and / or isopentane, 40 to 65 mol% of the other blowing agent (provided that isobutane and / or isopentane and other blowing agents) The total amount of the agent is 100 mol%). When the proportion of isobutane and / or isopentane in the mixed foaming agent exceeds 70 mol%, it is difficult to obtain a low-density foam plate, and when it is less than 25 mol%, the proportion of isobutane and isopentane remaining in the foam Decreases and the heat insulating property of the foam decreases. The amount of the mixed foaming agent added to the polystyrene resin varies depending on the target foaming ratio and the composition of the mixed foaming agent, but the apparent density is 25 to 55 kg / m.³In order to obtain a foamed plate, addition of 0.5 to 2.5 moles of mixed foaming agent per 1 kg of polystyrene resin is preferred, and addition of 0.7 to 2.0 moles is more preferred.
[0017]
As the graphite, scaly graphite, artificial graphite, earthy graphite, or the like is used, and it is preferable to use one or a mixture of those in which the main component is scaly graphite or artificial graphite. The graphite used in the present invention has good workability when producing a high-concentration masterbatch by adding to a polystyrene-based resin by the masterbatch method, and the heat insulation improvement effect of the foam is excellent. Graphite having a fixed carbon content of 90% or more is preferable. In order to further improve the heat insulating property of the foam, the graphite preferably has a fixed carbon content of 93% or more, more preferably 95% or more. The fixed carbon content of the graphite is a value measured by the method described in JIS M 8511 (1976).
[0018]
As a method of blending graphite and flame retardant into polystyrene resin, a method of supplying a predetermined ratio of graphite and flame retardant together with polystyrene resin to the supply section provided upstream of the extruder and kneading in the extruder. Can be adopted. In addition, a method of supplying graphite or a flame retardant into the molten polystyrene resin from a supply unit provided in the middle of the extruder can also be employed. Specifically, a method of supplying a melt blended graphite, flame retardant and polystyrene resin to an extruder and melt-kneading, a melt-kneaded material obtained by kneading graphite, flame retardant and polystyrene resin with a kneader, etc. To prepare a flame retardant master batch in which high-concentration graphite and flame retardant are blended with polystyrene resin in advance, and supply this to an extruder and melt-knead with polystyrene resin not containing flame retardant, etc. In particular, from the viewpoint of dispersibility, it is preferable to employ a method in which a graphite master batch or a flame retardant master batch is prepared and supplied to an extruder. The graphite masterbatch is preferably adjusted so that the masterbatch contains 10 to 80% by weight of graphite using a polystyrene resin having an MFR of 0.5 to 30 g / 10 min as the base resin. It is more preferable to adjust so that it may contain -70weight%, and it is still more preferable to adjust so that it may contain 30-60weight%. In addition, the flame retardant masterbatch is adjusted so that the flame retardant is contained in the masterbatch in an amount of 10 to 80% by weight using a polystyrene resin having an MFR of 0.5 to 30 g / 10 min as the base resin. It is more preferable to adjust so that it may contain 20 to 70 weight%, and it is still more preferable to adjust so that it may contain 30 to 60 weight%.
[0019]
The foaming agent is press-fitted into a molten polystyrene resin containing graphite and a flame retardant, and then extruded and foamed from an extruder. If necessary, an additive such as a bubble regulator is added to the molten polystyrene resin. be able to. As the air conditioner, inorganic powders such as talc, kaolin, mica, silica, calcium carbonate, barium sulfate, titanium oxide, clay, aluminum oxide, bentonite, and diatomaceous earth can be used. Of these, talc that allows easy adjustment of the bubble diameter and easily reduces the bubble diameter without impairing the flame retardancy is suitable, and the 50% particle size (light transmission centrifugal sedimentation method) is particularly 0.1 to 20 μm. Fine talc is preferable, and fine talc of 0.5 to 15 μm is preferable. The amount of the bubble regulator added varies depending on the type of the regulator, the target bubble diameter, etc., but when talc is used as the bubble regulator, it is preferably 0 to 7 parts by weight per 100 parts by weight of polystyrene resin. -5 parts by weight is more preferable, and 0.05-3 parts by weight is still more preferable.
[0020]
In the method of the present invention, various additives such as a colorant, a heat stabilizer and a filler can be appropriately blended with the polystyrene resin melted in the extruder as long as the purpose is not hindered.
[0021]
Expanding the expandable polystyrene resin composition by extruding a molten expandable polystyrene resin composition containing additives such as graphite, a flame retardant, a foaming agent, and an air conditioner under an atmospheric pressure from an extruder, followed by Then, it can be passed through a shaping device and shaped into a plate shape to obtain a polystyrene-based resin foam plate.
[0022]
The polystyrene-based resin extruded foam plate of the present invention can be obtained by extruding a foamable molten polystyrene-based resin composition from an extruder and molding as described above. The foamed plate of the present invention has a residual amount of isobutane and / or isopentane per 1 kg of foamed plate of 0.2 to 0.8 mol, and graphite in a ratio of 1 to 5 parts by weight per 100 parts by weight of polystyrene resin. By containing in a foamed board, very high heat insulation is expressed.
[0023]
If the remaining amount of isobutane and / or isopentane in 1 kg of foamed board exceeds 0.8 mol, flame retardancy may not be obtained as a building material even if it contains a flame retardant. If a large amount of a flame retardant is added for the purpose of increase, there is a risk of lowering the closed cell ratio and mechanical strength of the foamed plate obtained. Further, when the residual amount of isobutane and / or isopentane in 1 kg of the foamed plate is less than 0.2 mol, the flame retardancy is good, but sufficient heat insulation can be obtained unless graphite is contained in an amount exceeding 5 parts by weight. However, when a large amount of graphite is added, problems such as a decrease in the closed cell ratio and mechanical strength of the foam and difficulty in obtaining a low-density foam arise. The residual amount of isobutane and / or isopentane in the foamed plate is preferably 0.25 to 0.75 mol, more preferably 0.3 to 0.7 mol per kg of the foamed plate.
[0024]
On the other hand, if the amount of graphite added in the foamed plate is less than 1 part by weight per 100 parts by weight of the polystyrene resin, there is a possibility that a sufficient heat insulating effect cannot be obtained, and foaming obtained when the amount exceeds 5 parts by weight. Since the bubble diameter of the plate becomes too fine, it is difficult to obtain a low-density foam, and the mechanical properties of the foam may be reduced. The amount of graphite added is preferably 1.5 to 4 parts by weight, more preferably 2 to 4 parts by weight, per 100 parts by weight of polystyrene resin.
[0025]
The residual amount of isobutane and / or isopentane in the foam plate is measured using a gas chromatograph. Specifically, a sample cut out from the center of the extruded foam plate is placed in a sample bottle with a lid containing toluene, and after the lid is closed, the sample is thoroughly stirred and the foaming agent in the extruded foam plate is added to toluene. The residual amount of isobutane and isopentane contained in the foam plate can be determined by performing gas chromatography analysis on the sample dissolved in the sample. The sample used in this measurement has a width and thickness of 2.5 cm, and the length is such that the weight of the cut sample is 1 g.
[0026]
The measurement conditions for gas chromatographic analysis are as follows.

[0027]
The extruded foam plate of the present invention preferably has a thermal conductivity of 0.031 W / mK or less. A foamed plate having a thermal conductivity of 0.031 W / mK or less satisfies the standard of thermal conductivity for three types of extruded polystyrene foam heat insulating plates described in JIS A 9511 (1995), and is suitable as a heat insulating plate. Is. This thermal conductivity is a value measured by a flat plate heat flow meter method (two heat flow meters, average temperature 20 ° C.) described in JIS A 1412 (1994).
[0028]
The content of the flame retardant in the foamed plate of the present invention is preferably 1 to 10 parts by weight per 100 parts by weight of the polystyrene resin in order to improve the flame retardancy and minimize the decrease in mechanical properties. 1.5-7 weight part is more preferable, and 2-5 weight part is still more preferable.
[0029]
In the present invention, a halogen-based flame retardant is suitable as the flame retardant, and among them, it is preferable to use one or more of hexabromocyclododecane, brominated isocyanurate, and brominated bisphenol. Brominated isocyanurate is a brominated product of isocyanuric acid or an isocyanuric acid derivative represented by the following formula (1). Since the brominated isocyanurate has an isocyanurate skeleton in the structural formula, it is possible to efficiently generate hydrogen bromide exhibiting a flame retardant effect at the polystyrene-based resin decomposition temperature. Hydrogen bromide generated from the flame retardant reacts with the active radicals generated by the decomposition of the polystyrene-based resin, reducing the amount thereof, stopping the chain reaction of active radical generation that continues combustion, and bromine gas It also becomes possible to exert excellent flame retardancy due to the effect of shielding by.
[0030]
[Chemical 1]

[Wherein R¹, R², R³Is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an organic group represented by -Y-X (Y is an alkylene group having 1 to 6 carbon atoms, X is an epoxy group, a carboxyl group, a hydroxyl group, an amino group, phenyl Group) and a phenyl group, and among these atoms and atomic groups, at least one hydrogen atom is replaced by a bromine atom. However, R¹, R², R³And at least one of the atoms and atomic groups is substituted with a bromine atom. R¹, R², R³The atoms and atomic groups may be different or the same. ]
[0031]
Specific examples of the brominated isocyanurate include mono (2,3-dibromopropyl) isocyanurate, di (2,3-dibromopropyl) isocyanurate, tris (2,3-dibromopropyl) isocyanurate, mono (2 , 3,4-tribromobutyl) isocyanurate, di (2,3,4-tribromobutyl) isocyanurate, tris (2,3,4-tribromobutyl) isocyanurate and the like. Among the above brominated isocyanurates, tris (2,3-dibromopropyl) isocyanurate has good compatibility with polystyrene resins, has a decomposition initiation temperature of 250 to 265 ° C., and a melting point of 100. Since it is -110 degreeC, the handling at the time of foaming board manufacture is easy, the possibility that it decomposes | disassembles at the time of kneading | mixing with a polystyrene-type resin is small, and an extremely high flame-retardant effect is expressed easily, and it is preferable. Of the brominated isocyanurates, one or more of those represented by the above formula (1) can be added to the polystyrene resin.
[0032]
Brominated bisphenol is a brominated product of bisphenol A or a bisphenol A derivative represented by the following formula (2). Since the brominated bisphenol has a bisphenol skeleton in the structural formula, it is possible to efficiently generate hydrogen bromide that exhibits a flame retardant effect at the polystyrene resin decomposition temperature, and from the flame retardant during combustion. The generated hydrogen bromide reacts with the active radicals generated during the decomposition of the polystyrene-based resin, reducing the amount thereof, stopping the chain reaction of active radical generation that continues combustion, and shielding effect by bromine gas Can also exert excellent flame retardancy.
[0033]
[Chemical 2]

[Where R⁴, R⁵Is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an organic group represented by -Y-X (Y is an alkylene group having 1 to 6 carbon atoms, X is an epoxy group, a carboxyl group, a hydroxyl group, an amino group, phenyl Group) and a phenyl group, and among these atoms and atomic groups, at least one hydrogen atom is substituted with a bromine atom. R⁴, R⁵The atoms and atomic groups may be different or the same. ]
[0034]
Specific examples of the brominated bisphenol represented by the formula (2) include tetrabromobisphenol A, tetrabromobisphenol A bis (2,3-dibromopropyl ether), tetrabromobisphenol A bis (2-bromoethyl ether), tetra Bromobisphenol A bis (2-bromoethyl ether) oligomer, tetrabromobisphenol A bis (1-bromopropyl ether), tetrabromobisphenol A bis (allyl ether), tetrabromobisphenol A bis (2-hydroxyethyl ether), tetra Bromobisphenol A diglycidyl ether, tribromophenol adduct of tetrabromobisphenol A diglycidyl ether, tetrabromobisphenol A polycarbonate oligomer, tetrabutyl Mo epoxy adduct of bisphenol A oligomers and the like. Among the above brominated bisphenols, tetrabromobisphenol A bis (2,3-dibromopropyl ether), tetrabromobisphenol A bis (2-bromoethyl ether), tetrabromobisphenol A bis (2-Bromoethyl ether) oligomer has good compatibility with polystyrene resin, decomposition start temperature is 275-310 ° C., melting point is 105-130 ° C., easy handling at the time of foam plate production, polystyrene type The possibility of decomposing at the time of kneading with the resin is small, and the flame retarding effect is also high and is easy to express. One or two or more brominated bisphenols may be used among those represented by the above formula (2).
[0035]
The foamed board of the present invention preferably has combustion resistance satisfying the flammability standard for the extruded polystyrene foam heat insulating board described in JIS A 9511 (1995). In other words, when the flammability was measured according to 4.13.1 “Measurement Method A” described in JIS A 9511 (1995), the flame disappeared within 3 seconds, there was no residue, and the combustion limit indication There is no burning beyond the line. Therefore, the foamed plate having such combustion characteristics has the safety required as an extruded polystyrene foam heat insulating plate for building materials since the possibility of fire burning is small even when ignited. A polystyrene resin extruded foam plate having such combustion characteristics can be easily obtained by containing one or more of hexabromododecane, brominated isocyanurate and brominated bisphenol as a flame retardant in the foam plate. be able to.
[0036]
The polystyrene resin extruded foam board of the present invention has a thickness of 10 to 150 mm. When the thickness is less than 10 mm, even if the content of isobutane and / or isopentane and the content of graphite are within the above range, the heat insulating properties required for the heat insulating material are insufficient, and when the thickness exceeds 150 mm, the heat insulating material As a result, handling becomes worse. The thickness of the foam plate is preferably 15 to 120 mm.
[0037]
The foamed plate of the present invention has an apparent density of 25 to 55 kg / m.³Have Apparent density is 25kg / m³It is quite difficult to produce an extruded foam with a low density of less than 1, and even if such a low-density foam is obtained, the mechanical properties when used as a heat insulating plate are: Since it becomes inadequate compared with the conventional foam insulation board, the use which can be used is limited. On the other hand, the apparent density is 55 kg / m³In the case of exceeding the thickness, unless the thickness of the foamed plate is increased more than necessary, it is difficult to exert sufficient heat insulation properties, and there is a possibility that it is insufficient in terms of light weight. Particularly in the present invention, the apparent density of the extruded foam plate is 25 to 55 kg / m.³It is easy to give high heat insulation performance in the case of the above, and when using hexabromocyclododecane, which has been used for a long time for this kind of foamed board, as a flame retardant, it should give high flame retardant performance in a relatively small amount of use. There is an advantage that can be.
[0038]
The foamed plate of the present invention has a thickness direction average cell diameter (D_T) Is 0.05 to 0.30 mm. Thickness direction average cell diameter (D_T) Is less than 0.05 mm, the foamable molten resin mixture in the process of foaming extruded through a die lip at the time of manufacture (from the “molten” state to the “non-molten state” with the passage of time after extrusion) However, in the present specification, this expression is used for the sake of convenience), even if a shaping device described later is used, it is a plate-like shape. There is a risk that it will no longer be a foam. On the other hand, the average cell diameter in the thickness direction (D_T) Exceeding 0.30 mm, the desired heat insulation may not be obtained even if the isobutane and / or isopentane content and the graphite content are within the above ranges. Since it is an excellent heat insulating foam, the average cell diameter in the thickness direction (D_T) Is preferably 0.06 to 0.25 mm, and more preferably 0.08 to 0.20 mm.
[0039]
The average cell diameter in the thickness direction (D_T) Is measured as follows. First, a foam board is cut | disconnected neatly in the arbitrary surfaces orthogonal to the extrusion direction of a foam board. For each of the nine locations described later on the cut surface, a bubble that allows a full view to be confirmed on a screen magnified 200 times with a microscope or on a photograph taken of the screen (a part of the bubble at the edge of the screen or photo) Randomly 20 bubbles, except for missing ones and bubbles that are not at the edges of the screen or photo but are part of the bubble wall and are connected and integrated with the neighboring bubbles. Select. At this time, if less than 20 bubbles are projected on the screen or micrograph, the screen for any other cross section orthogonal to the extrusion direction of the foam plate or the micrograph is additionally used. do it. Next, for each selected bubble, a rectangle or square in contact with the bubble wall is drawn. At this time, the pair of opposite sides of the rectangle or square is aligned with the thickness direction of the foam plate, and the other pair of opposite sides of the rectangle or square is matched with the width direction of the foam plate. Draw. For the 20 rectangles or squares thus obtained, the lengths of the sides that coincide with the thickness direction of the foamed plate are measured, and the average value of the measured values is arithmetically averaged to measure the thickness direction average bubbles in each measurement part. The diameter can be obtained. Next, the measurement results at nine locations were arithmetically averaged and this was averaged in the thickness direction in the present invention (D_T). In addition, the nine places to be measured are a total of nine places, ie, three places that divide the thickness direction of the foam plate into four equal portions in each of three places that divide the width direction of the foam plate into four equal portions.
[0040]
In order to further improve the heat insulating properties of the foam plate and to have excellent compressive strength in the thickness direction, the average cell diameter in the thickness direction (D_T) In the horizontal average bubble diameter (D_HIt is preferable that the bubble deformation rate obtained by dividing by a) is 0.7 to 2.0. Horizontal average bubble diameter (D_H) Is the average cell diameter in the width direction (D_W) And average bubble diameter in the extrusion direction (D_L) Arithmetic average. Average cell diameter in the width direction (D_W) When measuring the bubble diameter in the thickness direction, measure the length of the side of the rectangle or square drawn in contact with the bubble wall of the selected bubble in the vertical cross section of the foam plate in the width direction. Thickness direction average bubble diameter (D_T). The average cell diameter in the extrusion direction (D_L) Is the average value of the bubble diameters in the extrusion direction obtained in the same manner from the vertical cross section along the extrusion direction of the foamed plate. Those having a flat cell structure with a cell deformation rate of less than 0.7 tend to decrease the compressive strength in the thickness direction. Moreover, in the case of a vertically long bubble structure having a bubble deformation rate exceeding 2.0, the number of bubbles in the thickness direction is reduced, and thus the heat insulation tends to be lowered. The bubbles in the foam plate have a bubble deformation rate of more preferably 0.80 to 1.7, and still more preferably 0.85 to 1.5. The size of the average cell diameter is mainly adjusted by the addition amount of graphite and the addition amount of the bubble adjusting agent, and the bubble deformation rate mainly controls the degree of expansion in the three-dimensional direction when forming the extruded foam plate. It is adjusted by doing.
[0041]
The closed cell ratio of the extruded foam plate of the present invention is preferably 90% or more, and more preferably 93% or more. The higher the closed cell ratio, the higher the heat insulation performance can be maintained.
[0042]
The closed cell ratio of the extruded foam plate was measured using an air-comparing hydrometer 930 type manufactured by Toshiba Beckman Co., Ltd. according to ASTM-D2856-70 Procedure C (cut from the extruded foam plate to a size of 25 mm × 25 mm × 20 mm) A cut sample without a molded skin is stored in a sample cup and measured, but if a cut sample with a thickness of 20 mm cannot be cut out in the thickness direction, for example, a cut of 25 mm × 25 mm × 10 mm It is sufficient to store two samples in a sample cup at the same time.) Using the true volume Vx of the extruded foamed plate (cut sample), calculate the closed cell ratio S (%) by the following equation (3). To do. In addition, a cut sample is cut out from three different parts with respect to one extruded foam board, the said measurement is performed about each cut sample, and let the average value of the obtained value be an independent cell rate.
[0043]
[Expression 1]
S (%) = (Vx−W / ρ) × 100 / (Va−W / ρ) (3)
[0044]
Vx: the true volume of the cut sample measured by the above method (cm³It corresponds to the sum of the volume of the resin constituting the cut sample and the total volume of bubbles in the closed cell portion in the cut sample.
Va: apparent volume (cm) of cut sample calculated from outer dimensions of cut sample used for measurement³).
W: Total weight (g) of cut sample used for measurement.
ρ: Density of resin constituting the extruded foam plate (g / cm³).
[0045]
【Example】
Next, the present invention will be described in more detail with reference to specific examples.
[0046]
Example 1
Polystyrene (G330C manufactured by Toyo Styrene Co., Ltd.), talc (manufactured by Matsumura Sangyo Co., Ltd .: High Filler # 12) as a foam regulator, hexabromocyclododecane and graphite (flaky graphite powder manufactured by Nippon Graphite Industries Co., Ltd.), An average particle diameter of 17 μm) was added so as to be an amount shown in Table 1 with respect to 100 parts by weight of polystyrene (total polystyrene obtained by summing the masterbatch polystyrene). Talc is a talc masterbatch containing 69% by weight of polystyrene, 30% by weight of talc and 1% by weight of zinc stearate, and graphite is a masterbatch of graphite consisting of 70% by weight of polystyrene and 30% by weight of graphite. Polystyrene and a master batch were mixed and melted in an extruder so that the ratio was the amount shown in Table 1. Next, the ratio of the foaming agent after the foaming agent was press-fitted into the molten polystyrene composition prepared by blending the blended foaming agent having the composition shown in Table 1 into the molten polystyrene composition and the master batch was adjusted. The mixed foaming agent was press-fitted so as to be kneaded to obtain an expandable molten polystyrene composition.
[0047]
As the extruder, an extruder having a diameter of 65 mm (hereinafter referred to as “first extruder”), an extruder having a diameter of 90 mm (hereinafter referred to as “second extruder”), and an extruder having a diameter of 150 mm (hereinafter referred to as “first extruder”). Three extruders ”) connected in series. The die lip of each extruder used what was equipped with the resin discharge port of width 115mm and gap 1.5mm (rectangular cross section) at the front-end | tip. The polystyrene, talc masterbatch, and graphite masterbatch are supplied to the first extruder, heated to 220 ° C. and melt-kneaded, and then the mixed foaming agent is press-kneaded into the molten resin near the tip of the first extruder. A foamable molten polystyrene composition was obtained. In the subsequent second and third extruders, the resin pressure at the adapter part to which the die lip is attached is 30 kgf / cm.²Then, the resin temperature was adjusted in each extruder, and from the die lip attached to the third extruder, the resin was extruded and foamed at the discharge amount shown in Table 2, and then passed through a shaping apparatus and molded into a plate shape. . Table 3 shows the temperature (foaming temperature) of the expandable molten polystyrene composition immediately before extrusion from the third extruder.
[0048]
Table 3 shows the apparent density, thickness, closed cell ratio, thickness direction average cell diameter, bubble deformation rate, thermal conductivity, combustibility, and foaming agent residual amount of the obtained extruded foamed plate.
[0049]
Example 2
As shown in Table 1, a foamed plate was obtained in the same manner as in Example 1 except that the addition amounts of graphite and talc were different. Table 3 shows various physical properties of the obtained foamed board.
[0050]
Example 3
A foamed plate was obtained in the same manner as in Example 1 except that graphite having an average particle diameter of 40 μm (scale graphite powder manufactured by Nippon Graphite Industry Co., Ltd.) was used instead of graphite having an average particle diameter of 17 μm used in Example 1. It was. Table 3 shows various physical properties of the obtained foamed board.
[0051]
Example 4
In place of the graphite having an average particle diameter of 17 μm used in Example 1 and using graphite having a mean particle diameter of 7 μm (soil graphite powder manufactured by Nippon Graphite Industries Co., Ltd.), a foamed plate was obtained in the same manner as in Example 1. Obtained. Table 3 shows various physical properties of the obtained foamed board.
[0052]
Example 5
A foamed plate is obtained in the same manner as in Example 1 except that graphite having an average particle diameter of 20 μm (artificial graphite powder manufactured by Nippon Graphite Industry Co., Ltd.) is used instead of graphite having an average particle diameter of 17 μm used in Example 1. It was. Table 3 shows various physical properties of the obtained foamed board.
[0053]
Example 6
A foamed plate was obtained in the same manner as in Example 1 except that the mixed foaming agent was replaced with a mixture of isobutane, dimethyl ether and carbon dioxide and contained in the proportions shown in Table 1. Table 4 shows various physical properties of the obtained foamed board.
[0054]
Example 7
A foamed plate was obtained in the same manner as in Example 1 except that the mixed foaming agent was changed to a mixture of isobutane, ethanol and carbon dioxide and contained in the proportions shown in Table 1. Table 4 shows various physical properties of the obtained foamed board.
[0055]
Example 8
Instead of hexabromocyclododecane as the halogen-based flame retardant in Example 1, instead of tris (2,3-dibromopropyl) isocyanurate (brominated isocyanurate manufactured by Suzuhiro Chemical Co., Ltd.), added in the ratio shown in Table 1. A foamed plate was obtained in the same manner as in Example 1. Table 4 shows various physical properties of the obtained foamed board.
[0056]
Example 9
A foamed plate was obtained in the same manner as in Example 1 except that polystyrene was replaced with HH32 manufactured by Idemitsu Petrochemical Co., Ltd., and a die lip having a tip width of 65 mm and a gap of 3 mm was used. Table 4 shows various physical properties of the obtained foamed board.
[0057]
Comparative Example 1
As shown in Table 2, a foamed plate was obtained in the same manner as in Example 1 except that the addition amount of graphite was different. Table 5 shows various physical properties of the obtained foamed board. This foamed plate had good combustion resistance, but had a high thermal conductivity and had a problem with heat insulation.
[0058]
Comparative Example 2
As shown in Table 2, a foamed plate was obtained in the same manner as in Example 1 except that the addition amounts of graphite and talc were different. Table 5 shows various physical properties of the obtained foamed board. In the foamed plate of Comparative Example 2, since the amount of graphite added was too large, an increase in the pressure of the extruder and an extreme decrease in the foaming ratio of the resulting foamed plate were observed, and as for the appearance, there were multiple cracks on the surface of the foamed plate. It has occurred.
[0059]
Comparative Examples 3 and 4
A foamed plate was obtained in the same manner as in Example 1 except that the mixed foaming agent shown in Table 1 was added in the ratio shown in the same table. Table 5 shows various physical properties of the obtained foamed board. The foamed plate of Comparative Example 3 had good combustion resistance, but had high thermal conductivity and had a problem with heat insulation. Further, the foamed plate of Comparative Example 4 was inferior in combustion resistance (flame resistance) because of the large amount of isobutane remaining.
[0060]
Reference example
A foamed plate was obtained in the same manner as in Example 1 except that carbon black (particle size: 17 nm) was used instead of graphite. Table 5 shows various physical properties of the obtained foamed board. The foamed board of the reference example had a low thermal conductivity and excellent heat insulation, but had a problem in combustion resistance.
[0061]
[Table 1]

[0062]
[Table 2]

[0063]
[Table 3]

[0064]
[Table 4]

[0065]
[Table 5]

[0066]
The apparent densities in Tables 3, 4, and 5 are values measured based on JIS K 7222 (1985).
[0067]
The thicknesses in Tables 3, 4, and 5 are values obtained by measuring at three locations where the width direction is equally divided into four, and arithmetically averaging them.
[0068]
The thickness direction average bubble diameter and bubble deformation rate in Tables 3, 4, and 5 are values measured by the above methods.
[0069]
The closed cell ratio in Tables 3, 4, and 5 is a value measured by the above method using a cut sample that does not have a molded skin cut to a size of 25 mm × 25 mm × 20 mm from the extruded foam plate.
[0070]
The thermal conductivity in Tables 3, 4 and 5 shows the test pieces of 20 cm in length, 20 cm in width, and the thickness of the extruded foam plate for each of the extruded foam plate that passed 4 weeks after production and the extruded foam plate that passed 3 months after production. For each test piece, according to the description of JIS A 9511 (1995) 4.7, a thermal conductivity measuring device “Auto Λ HC-73” manufactured by Eihiro Seiki Co., Ltd. was used, and JIS A1412 (1994). ) Described in the flat plate heat flow meter method (two heat flow meter method, average temperature 20 ° C.).
[0071]
The flame resistance in Tables 3, 4 and 5 is measured according to 4.13.1 “Measurement” of JIS A9511 (1995) for test pieces cut out from an extruded foamed plate after 5 days from manufacture and after 2 weeks from manufacture. Measurement was performed based on “Method A”. In addition, this measurement cut out 10 test pieces with respect to one extrusion foamed board, and evaluated it on the following evaluation criteria.
A: All specimens disappear within 3 seconds, and the average burning time of 10 specimens is within 2 seconds.
◯: All specimens disappear within 3 seconds, and the average burning time of 10 specimens exceeds 2 seconds and is within 3 seconds.
Δ: The average burning time of 10 test pieces is within 3 seconds, but one or more test pieces do not disappear within 3 seconds.
X: The average burning time of 10 test pieces exceeds 3 seconds.
[0072]
The amount of foaming agent remaining in Tables 3, 4 and 5 (content of foaming agent per kg of foam plate) was measured using Shimadzu Corporation, Shimadzu Gas Chromatograph GC-14B, with cyclopentane as the internal standard substance. , Measured based on the method.
[0073]
The foam appearance in Tables 3, 4, and 5 was evaluated according to the following evaluation criteria.
○: Cracks are not observed on the surface.
X: Cracks are observed on the surface.
[0074]
【The invention's effect】
The method of the present invention uses a mixed foaming agent having an ozone depletion coefficient of 0, a low global warming potential and a small proportion of isobutane and isopentane, and substantially free of chlorofluorocarbons and fluorocarbons. Adopting a method to obtain polystyrene resin extruded foam plates in combination with an amount of graphite, it is possible to obtain polystyrene resin extruded foam plates with excellent lightness, flame retardancy, and heat insulation properties, as well as environmental impact. Small and excellent method. Graphite also acts as a foam regulator, and the effect of reducing the fineness of the foam is obtained, so the amount of foam regulator used, such as talc, can be reduced, and the mechanical properties of the foam plate by adding various additives There is no risk of lowering. When graphite having a fixed carbon content of 90% or more is used, the workability when producing a masterbatch containing a high concentration of graphite is improved, and the workability of producing a polystyrene resin extruded foam plate is improved.
[0075]
The polystyrene-based resin extruded foam plate of the present invention has a specific amount of isobutane and isopentane remaining in the foam plate and contains a specific amount of graphite. In spite of the remaining flammable gas, etc., it has excellent combustion resistance. In addition, there has been a great restriction on the reuse of collected colored polystyrene resin foam in the past, but since the foamed plate of the present invention is colored gray or black by graphite, the recovered raw material colored during the production of the foamed plate is added. Since the color of the foamed plate obtained by mixing is not so affected, there is an advantage that the recovered raw material can be easily reused.

Claims (5)

In a extruder, a polystyrene resin that heats a polystyrene resin and extrudes and foams a foamable molten mixture obtained by kneading together with a foaming agent, a flame retardant, and graphite into a low pressure region through a die attached to the tip of the extruder. A method for producing an extruded foam board, comprising:
The blowing agent is a mixed blowing agent composed of 70 to 25 mol% of isobutane and / or isopentane and 30 to 75 mol% of another blowing agent (provided that the total amount of these blowing agents is 100 mol%) ),
The graphite is graphite having a fixed carbon content of 90% by mass or more,
And, as a master batch blended with polystyrene resin, the graphite is added so as to be 1 to 5 parts by weight with respect to 100 parts by weight of polystyrene resin constituting the polystyrene resin extruded foam plate. A method for producing a polystyrene resin extruded foam board. The main component of the graphite, scaly graphite, and one or method according to claim 1 extruded polystyrene resin foam plate according mixtures thereof are selected from artificial graphite. The polystyrene system according to claim 1 or 2, wherein the other blowing agent mixed with isobutane and / or isopentane is one or more selected from alkyl chloride, carbon dioxide, dimethyl ether, aliphatic alcohol, and water. Manufacturing method of resin extrusion foam board. Polystyrene-based resin, and isobutane and / or isopentane blowing agent consisting of a mixture with other blowing agents, graphite graphite is added as a masterbatch compounded in polystyrene resin, and a flame retardant, foaming molten mixture This is a polystyrene-based extruded foam plate having a thickness of 10 to 150 mm, an apparent density of 25 to 55 kg / m ³ , and an average cell diameter in the thickness direction of 0.05 to 0.30 mm. And
The residual amount of isobutane and / or isopentane in the foam plate is 0.2 to 0.8 mol per kg of the foam plate,
The graphite is graphite having a fixed carbon content of 90% by mass or more,
1 to 5 parts by weight are added to 100 parts by weight of the polystyrene resin constituting the foamed plate ,
The polystyrene-based resin extruded foam plate has a thermal conductivity of 0.031 W / mK or less, and satisfies the flammability standard of 4.13.1 measuring method A described in JIS A9511 (1995) < A polystyrene resin extruded foam board characterized by the above. The polystyrene-based resin extruded foam board according to claim 4 , comprising one or more of hexabromocyclododecane, brominated isocyanurate, and brominated bisphenol as a flame retardant.