JP2004217875A - Self-extinguishable styrenic resin foamed particle and self-extinguishable foamed molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a self-extinguishable styrenic resin foamed particle excellent in flame retardancy, dimensional stability and recyclability. <P>SOLUTION: This self-extinguishable styrenic resin foamed particle is obtained by expanding a styrenic resin containing a combined flame retardant with an inorganic gas as a foaming agent. The combined flame retardant is composed of 90-40 wt.% flame retardant being tris(2,3-dibromopropyl)isocyanurate and 10-60 wt.% auxiliary flame retardant expressed by the general formula (wherein R1 to R4 are the same or different and each represents a methyl or ethyl group) and contained in an amount of 1-7 pts.wt. to 100 pts.wt. of the styrenic resin particle. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００９】
（式中、Ｒ１〜Ｒ４は、同一又は異なって、メチル又はエチル基である）で表わされる難燃助剤１０〜６０重量％から構成され、スチレン系樹脂粒子１００重量部に対して１〜７重量部含まれる
ことを特徴とする自己消火型スチレン系樹脂発泡粒子が提供される。
更に、本発明によれば、上記自己消火型スチレン系樹脂発泡粒子を型内成形法にて成形して得られた自己消火型発泡成形体が提供される。
【００１０】
【発明の実施の形態】
本発明で使用される複合難燃剤は、トリス（２，３−ジブロモプロピル）イソシアヌレート（以下ＴＤＩＣとも称する。融点１１５℃、分解温度２８５℃）である難燃剤と、下記一般式
【００１１】
【化３】

【００１２】
（式中、Ｒは同一又は異なって、メチル又はエチル基である）で表わされる難燃助剤から構成される。
難燃助剤の具体例としては、２，３−ジメチル−２，３−ジフェニルブタン（ビスクミルと呼ばれることから、以下ＢＣとも称する。融点１１３℃、分解温度２０５℃）、３，４−ジメチル−３，４−ジフェニルヘキサン（融点１４２℃、分解温度２３０℃）等が挙げられる。
上記難燃剤と難燃助剤は、融点が比較的近いため、それらを混合した複合難燃剤は、融点がほぼ一つのピークを形成する（この温度を融点ピーク温度と称する）。また、複合難燃剤の融点ピーク温度は、融点降下により難燃剤及び難燃助剤単独の融点より低いことを発明者らは見出している。例えば、横軸に複合難燃剤中の難燃助剤ＢＣの割合を、縦軸に複合難燃剤の融点ピーク温度を表す図１に示すように、ＴＤＩＣ７０重量％とＢＣ３０重量％とから構成される複合難燃剤の場合、示差熱分析（ＤＴＡ）にて測定した融点ピーク温度は約１０１℃であり、ＴＤＩＣとＢＣ単独の融点より１５℃程度低くなっている。複合難燃剤の融点ピーク温度は、含浸温度又は混練温度をより低くすることができるので好ましい。なお、融点ピーク温度は、８０〜１４０℃の範囲にあることが好ましい。融点ピーク温度が８０℃より低いと、含浸時に樹脂粒子同士の合着や混練時に難燃剤がブリードし、予備発泡時に発泡粒子同士の合着を起こすため好ましくない。一方、１４０℃を超えると含浸効率や混練時の分散性が劣る場合があるので好ましくない。より好ましい融点ピーク温度は９０〜１３０℃である。
【００１３】
本発明において難燃剤と難燃助剤は、９０〜４０重量％と１０〜６０重量％割合で使用される。難燃助剤の割合が１０重量％未満の場合、自己消火性の発現には複合難燃剤を多量に使用する必要が生じ、その結果リサイクル性が阻害される。また、融点ピーク温度があまり低下せず、含浸温度又は混練温度を高くしなければならない。一方、６０重量％を超える場合、難燃剤の割合が減るため、自己消火性が劣ることとなる。また、融点ピーク温度があまり低下せず、含浸温度又は混練温度を高くしなければならない。より好ましい難燃剤と難燃助剤の割合は、９０〜６０重量％と１０〜４０重量％である。
なお、本発明において、より好ましい難燃剤と難燃助剤の組み合わせは、ＴＤＩＣとＢＣの組み合わせである。
複合難燃剤の含有割合は、スチレン系樹脂粒子１００重量部に対して、１〜７重量部である。１重量部未満では十分な自己消火性は得られない。一方、７重量部を超える場合、自己消火性効果は飽和し、経済的でない。通常、１〜５重量部で十分である。
【００１４】
本発明のスチレン系樹脂は、スチレンの単独重合体でもよく、スチレンと共重合可能な他のモノマー、例えば、α−メチルスチレン、ビニルトルエン、アクリロニトリル、メチルメタクリレート、グリシジルメタクリレート、ブチルアクリレート、メタクリル酸、ジビニルベンゼン、アルキレングリコールジメタクリレート等とスチレンとの共重合体でもよい。なお、本発明では、スチレン及びスチレンと共重合と可能なモノマーもスチレン系モノマーと称している。
更に、本発明におけるスチレン系樹脂は、他樹脂との混合樹脂であってもよい。他樹脂の例としては、ポリエチレン、ポリプロピレン、ポリフェニレンエーテル及びゴム変性スチレン系樹脂等が挙げられる。
また、スチレン系樹脂中には適当な添加剤が含まれていてもよい。添加剤の例としては、高級脂肪酸アマイド、芳香族ビスアマイド、エチレンビスステアリルアマイド、高級脂肪酸、パラフィン、ワックス、動植物硬化油、ジイソブチルアジペート等が挙げられる。この他にも従来からスチレン系樹脂粒子の製造に使用される添加剤、例えば滑剤、可塑剤、気泡調整剤、気泡安定化剤、充填剤、着色剤、酸化防止剤、紫外線吸収剤等を必要に応じて適宜使用してもよい。
これら添加剤は前もってスチレン系樹脂粒子の重合時に添加されるか、難燃剤の含浸又は混練時に樹脂粒子に含ませることができる。
【００１５】
また、スチレン系モノマーのスチレン系樹脂に対する含有量は、発泡成形体の品質及び低ＶＯＣの観点から５００ｐｐｍ以下とすることが好ましく、更に３００ｐｐｍ以下とすることが好ましい（下限は０ｐｐｍである）。スチレン系モノマーを含む揮発性有機溶剤のスチレン系樹脂に対する含有量は、発泡成形体の品質及び低ＶＯＣの観点から１０００ｐｐｍ以下とすることが好ましく、更に５００ｐｐｍ以下が好ましい（下限は０ｐｐｍである）。
スチレン系樹脂は粒子の形で用いられるが、その粒子の大きさは０．３〜３．０ｍｍであるのが好ましく、更に０．５〜２．０ｍｍであることが好ましい。
自己消火型スチレン系樹脂粒子の製造方法としては、懸濁重合法やシード重合法、押出機でスチレン系樹脂と複合難燃剤とを溶融混練した後、押し出したストランドをペレタイズする方法が挙げられる。この内、生産効率の観点から懸濁重合又はシード重合法が好ましい。懸濁重合又はシード重合法において、複合難燃剤を樹脂粒子に含浸させる方法としては、重合転化率が９９．８％以上の段階又は、重合完了後の水性媒体中に添加して含浸させる方法が挙げられる。重合転化率が９９．８％以上のときに含浸させることで、所定の分子量のスチレン系樹脂粒子を簡便に得ることができるので好ましい。
重合転化率が９９．８％未満の時点で難燃剤が含浸されると、それ以降のスチレン系モノマーの重合が阻害されて、最終的に得られる発泡成形体中にモノマーが多量に残る場合があるので好ましくない。また、該発泡成形体の気泡径が微細化するために熱伝導率が高くなり、断熱性能は低下する場合があるので好ましくない。含浸は、通常、攪拌機を具備した反応器で行われる。
【００１６】
含浸に用いられる水性媒体には、含浸時のスチレン系樹脂粒子同士の結合を防止するために、懸濁安定剤を添加することが好ましい。懸濁安定剤としては、従来から一般に使用されている公知のポリビニルアルコール、メチルセルロース、ポリアクリルアミド、ポリビニルピロリドン等の水溶性高分子や、第三リン酸カルシウム、ハイドロキシアパタイト、ピロリン酸マグネシウム等の難水溶性無機塩が挙げられる。難水溶性無機塩を用いる場合には、通常アニオン界面活性剤が併用される。アニオン界面活性剤としては、例えば脂肪酸石鹸、Ｎ−アシルアミノ酸又はその塩、アルキルエーテルカルボン酸塩等のカルボン酸塩、アルキルベンゼンスルホン酸塩、アルキルナフタレンスルホン酸塩、ジアルキルスルホコハク酸エステル塩、アルキルスルホ酢酸塩、α−オレフィンスルホン酸塩等のスルホン酸塩；高級アルコール硫酸エステル塩、アルキルエーテル硫酸塩、ポリオキシエチレンアルキルフェニルエーテル硫酸塩等の硫酸エステル塩；アルキルエーテルリン酸エステル塩、アルキルリン酸エステル塩等のリン酸エステル塩等がある。
【００１７】
複合難燃剤の添加方法は、例えば、水性媒体中に難燃剤と難燃助剤を別々に又は同時に投入する方法、難燃剤と難燃助剤とをスーパーミキサー等で混合してから粉体状態のままで水性媒体中に投入する方法、攪拌装置を備えた予備分散槽内で均一に分散させた懸濁液を水性媒体に投入する方法が挙げられる。含浸をより円滑に行なうために、水性媒体を加温することが好ましい。具体的には７０〜１２０℃の温度で、１〜６時間加温することが好ましい。
難燃剤及び難燃助剤が含浸されたスチレン系樹脂粒子は反応器から取り出された後、洗浄及び脱水乾燥することで自己消火型スチレン系樹脂粒子となる。
次に、これら自己消火型スチレン系樹脂粒子に、発泡剤である無機ガスを含浸させる。発泡剤の含浸前に、樹脂粒子表面には適当な表面処理がなされていてもよい。表面処理剤の例としては、発泡時の結合防止剤として炭酸カルシウム、タルク、コロイド状シリカ、アルミナ粉末等、帯電防止剤として高級脂肪酸モノグリセライド、ポリエチレングリコール等、この他にも融着促進剤、ハイサイクル剤、離型剤、防蟻剤、防黴剤、防錆剤等が挙げられる。表面処理法は、リボンブレンダー、ナウターミキサー、タンブラーミキサー、レディゲミキサー等を用いて混合する方法が挙げられる。
無機ガスとしては、炭酸ガス、空気、窒素、これらガスの混合ガス等が挙げられる。この内、炭酸ガスを主成分とすることが好ましく、できる限り炭酸ガス単独で用いることが発泡性の点からより好ましい。
【００１８】
無機ガスの含浸は上記樹脂粒子を密閉できる圧力容器に入れ、この容器内に無機ガスを圧入して気相加圧下で行われる。無機ガス含浸を行なう温度は樹脂粒子が軟化して結合しない範囲内の温度、すなわち緩和温度とすることが望ましい。緩和温度は、スチレン系樹脂のビカット軟化点よりも少なくとも１０℃低い温度を意味する。具体的な温度はスチレン系樹脂の組成と無機ガスの種類によって異なる。ガス含浸量と圧力容器の関係から一般的に言えば含浸温度は低いことが望ましく、４０℃以下が好ましい。しかし０℃以下では工業的にエネルギー消費が大きいので好ましくない。工業的に安定して比較的高い倍率に発泡させる含浸温度は０〜４０℃がより好ましく、特に好ましくは５〜３０℃である。
樹脂粒子に無機ガスを含浸させる適当な圧力は１．５ＭＰａ以上が好ましく、より好ましくは２〜５ＭＰａである。
かかる含浸処理により、自己消火型スチレン系樹脂粒子に無機ガスを均一に含浸できる。含浸時間は無機ガスの種類、圧力、樹脂粒子の組成、粒径によって異なるが、少なくとも無機ガスが０．０５モル／ｋｇ（樹脂粒子）以上含浸されるまで行なうこと好ましく、この含浸は通常１〜１０時間の含浸時間で達成できる。
【００１９】
このようにして無機ガスが含浸された自己消火型スチレン系樹脂粒子は、次いで発泡に付される。無機ガスを含浸させた発泡性樹脂粒子は圧力容器から取り出した後、直ちにこれを加熱して発泡させる。この際重要なことは樹脂粒子中の無機ガス含有量の下限が０．１モル／ｋｇ（樹脂粒子）以上の条件で発泡を行なうことである。すなわち無機ガスを含浸した発泡性樹脂粒子は圧力容器から大気中へ取り出すと発泡剤である無機ガスが徐々に大気へ逸散してその含有量が低下し、上記の下限値未満になると発泡性の低下により目標発泡倍数まで発泡することが困難となる。また上限は２．３モル／ｋｇ（樹脂粒子）以下であり、これ以上の量になると発泡性が高過ぎるため均一な発泡倍数の発泡粒子を生産することが困難になる。
従って工業生産上は加圧状態から直接、予熱された発泡機に上記発泡性樹脂粒子を導入し発泡することが好ましい。あるいは除圧して圧力容器から取り出した後、直ちに予熱された発泡機に導入し発泡してもよい。ただし、除圧後に発泡する場合は除圧後３０分以内、特に２分以内に発泡させることが好ましい。
【００２０】
発泡は公知の方法で行うことが可能であるが、優れた発泡成形体を得る上で、より好ましい発泡方法として下記の方法が採用できる。すなわち、発泡工程において発泡性樹脂粒子は、蒸気導入ラインと排気ラインとを備えた発泡機内に投入される。次いで蒸気導入ラインから蒸気を０．０５〜０．５ＭＰａの導入圧力で発泡機内に供給すると共に、排気ラインから蒸気を含む雰囲気ガスを排気し、且つその間、発泡機内の圧力を蒸気の導入圧力より０．００５〜０．２ＭＰａ低く維持しながら発泡される。発泡に要する時間は加圧蒸気の圧力、温度、樹脂粒子の組成、無機ガスの含有量等によって影響され、通常は１０〜１５０秒、好ましくは２０〜９０秒である。
【００２１】
なお、樹脂発泡粒子の製造に使用できる発泡機の一例を図２に示す。図中、２は撹拌モーター、３は撹拌翼、４は邪魔棒、５は発泡槽上面検出器、６は発泡性粒子輸送器、７は発泡性粒子計量槽、８は発泡性粒子投入器、９は蒸気吹込制御弁、１０は蒸気チャンバー、１１は凝縮水排出弁、１２は排気制御弁、１３は発泡粒子排出口、１４は発泡粒子一時受器、１５は空気輸送設備、１６は内圧検出・制御装置、１７は蒸気吹込孔、１８は蒸気導入圧力計、１９は減圧弁、２０は蒸気元圧力計を意味する。
こうして得られた発泡粒子は光沢に優れ、発泡粒子をプレスして得られた発泡粒子板が３０〜６０の表面光沢度を有している。表面光沢度は３５〜５０であることが特に好ましい。この発泡粒子から得られる成形体は長期に渡って寸法が安定し、表面平滑性に優れ、美麗な外観を実現できる。なお、表面光沢度が３０より小さいと、発泡成形体が黒ずんで見え、著しく商品価値が劣ることがある。また、６０より大きいと成形体としたときの内部融着が悪く、十分な機械的強度が得られないことがある。表面光沢度の測定法は、実施例の欄に記載する。
【００２２】
こうして得られた自己消火型スチレン系樹脂発泡粒子は、通常、これを大気中に放置し熟成させる。発泡粒子の熟成時間は発泡により生じた気泡内が発泡後冷却して減圧になるのを大気中の空気が補い常圧に戻ることを基準として定める。その時間はおよそ４時間程であり、これよりも短時間では発泡粒子の気泡内が減圧となっているため、型内成形時に発泡粒子が収縮を起こし良好な発泡成形体が得られない場合がある。また、本発明で得られた発泡粒子には放置時間の上限は特になく、基材樹脂自体が劣化しなければ発泡後１年を経過した発泡粒子でも何ら問題なく使用できる。
発泡粒子を型内成形するのに適した平均気泡径は５０〜５００μｍであり、好ましくは１００〜３００μｍである。平均気泡径が５０μｍよりも小さくなると、加熱により発泡体表面が融けて収縮し良好な発泡成形体が得られない場合があるので好ましくない。また、平均気泡径が５００μｍよりも大きくなると、強度に優れた成形品が得られなくなるので好ましくない。
このようにして得られた自己消火型スチレン系樹脂発泡粒子は公知手法により、いわゆる型内成形に付されて種々の発泡成形体（例えば、建物の壁材、床材、天井材等の建築用断熱材、ＥＰＳ土木工法のような土木用緩衝材、包装材等）を得る材料として用いられる。
【００２３】
【実施例】
以下、本発明を実施例を用いて説明するが、これにより本発明は限定されるものではない。
まず、スチレン系樹脂粒発泡子及び発泡成形体の評価方法を以下に示す。
［重量平均分子量］
重合体の重量平均分子量（Ｍｗ）は、ＧＰＣ（Ｇｅｌ Ｐｅｒｍｅａｔｉｏｎ
Ｃｈｒｏｍａｔｏｇｒａｐｈｙ）によって、以下の条件で測定した。
測定装置：東ソー社製 高速ＧＰＣ装置 ＨＬＣ−８０２０
カラム：積水ファインケミカル社製 ＨＳＧ−６０Ｓ×２本、ＨＳＧ−４０Ｈ×１本、ＨＳＧ−２０Ｈ×１本
カラム温度：４０℃、移動相：ＴＨＦ（テトラヒドロフラン）、
流量：１．０ｍｌ／分、注入量：５００ｍｌ
検出器：東ソー社製 ＲＩＤ−６Ａ
試料の分子量測定：試料の分子量測定に当たっては、該試料の有する分子量分布が、数種の単分散ポリスチレン標準試料により作成された検量線の分子量の対数とカウント数が直線となる範囲内に包含される測定条件を選択した。また、本発明においてポリスチレンの検量線は、重量平均分子量が２．７４×１０^３、１．９１×１０^４、１．０２×１０^５、３．５５×１０^５、２．８９×１０^６、４．４８×１０^６である東ソー社製の６個のポリスチレン標準試料（ＴＳＫスタンダードポリスチレン）を用いて作成した。
【００２４】
［融着率］
長さ４００ｍｍ、幅３００ｍｍ、厚み３０ｍｍの板形状を有する発泡成形体の一方の表面に一対の長辺から長辺まで連続する３００ｍｍ長さの切込みをカッターナイフで深さ約５ｍｍに入れた後、この線に沿って発泡成形体を手で二分割し、その破断面における発泡粒子について、粒子内で破断している粒子の数（ａ）と粒子同士の界面で破断している粒子の数（ｂ）とを数え、下式
融着率（％）＝［（ａ）／｛（ａ）＋（ｂ）｝］×１００
に代入して得られた値を融着率（％）とした。
【００２５】
［燃焼性］
ＪＩＳ Ａ９５１１の燃焼試験Ａ法にて燃焼性を測定した。このＪＩＳ規格では自己消火時間が３．０秒以内である必要がある。なお、２．０秒以内であればより好ましい。
［重合転化率と残存スチレン量の定量］
重合転化率は以下の式で算出した。
重合転化率（重量％）＝１００×（Ａ−Ｂ）／Ａ
また、残存スチレン量は以下の式で算出した。
残存スチレン量（重量％）＝１００×Ｂ／Ａ
但し、Ａは未反応スチレン系単量体を含むスチレン系樹脂粒子の重量（ｇ）であり、Ｂは上記未反応のスチレン系単量体を含む樹脂粒子中の未反応単量体の重量（ｇ）である。Ｂは、例えば、ガスクロマトグラフィー（ＧＣ）等により定量される。ＤＣによるスチレン系単量体の定量は、スチレン系樹脂粒子をＮ，Ｎ−ジメチルホルムアミドに溶解し、内部標準液（シクロペンタノール）を加えて測定した。
ＧＣ：島津製作所社製 ＧＣ−１４Ａ
カラム：ＰＥＧ−２０Ｍ ＰＴ２５％ ６０／８０（２．５ｍ）
カラム温度：１０５℃
検出器（ＦＩＤ）温度：２２０℃
【００２６】
［揮発性有機化合物の含有量］
以下に示す三種類の測定法によって得られた値を合計して求める。
（炭素数５以下の炭化水素化合物の測定）
発泡樹脂粒子又は発泡成形体から切り出した所定量の試料を１８０℃の熱分解炉に入れ、揮発した炭化水素をガスクロマトグラフィーにて測定する。なお、発泡成形体については、実施例にて得られた発泡成形体の長辺及び短辺から１００ｍｍ、上下面から５ｍｍ入った部位から試験片を切り出し測定試料とした。
ガスクロマトグラフィー（ＧＣ）：島津製作所社製 ＧＣ−１４Ｂ
熱分解炉：島津製作所社製 ＰＹＲ−１Ａ
カラム：ポラパックＱ ８０／１００（３ｍｍφ×１．５ｍ）
カラム温度：１００℃
検出器（ＦＩＤ）温度：１２０℃
（炭素数６以上の炭化水素であって、ガスクロマトグラムに現われるスチレンのピークまでの炭化水素の測定）
前記と同様に発泡樹脂粒子又は発泡成形体から切り出した所定量の試料をジメチルホルムアミドに溶解し、内部標準液（シクロペンタノール）を加えてＧＣにより測定する。ただし、特定できないピークについてはトルエンの検出量に換算して定量する。
ＧＣ：島津製作所社製 ＧＣ−１４Ａ
カラム：ＰＥＧ−２０Ｍ ＰＴ２５％ ６０／８０（２．５ｍ）
カラム温度：１０５℃
検出器（ＦＩＤ）温度：２２０℃
（ガスクロマトグラムに現われるスチレンの次のピークから炭素数１６（ｎ−ヘキサデカン）までの炭化水素の測定）
【００２７】
前記と同様に発泡樹脂粒子又は発泡成形体から切り出した所定量の試料をクロロホルムに溶解し、ガスクロマトグラフ質量分析計（ＧＣＭＳ）にて測定する。ただし、試験片を溶解しない溶剤のみの空試験を行い、空試験の検出物質量を差し引く。更に、特定できないピークについてはトルエンの検出量に換算して定量する。
ＧＣＭＳ：島津製作所社製 ＱＰ５０００
カラム：Ｊ＆Ｗ Ｓｃｉｅｎｔｉｆｉｃ社製 ＤＢ−１
（１μｍ×６０ｍ ０．２５ｍｍφ）
測定条件：カラム温度
（６０℃で１分保持した後、１０℃／分で３００℃まで昇温）
スプリット比：１０
キャリアガス：Ｈｅ（１ｍｌ／分）
インターフェイス温度：２６０℃
【００２８】
［表面光沢度］
表面光沢度はＪＩＳ Ｋ７１０５（プラスチックの光学的特性試験方法）に準拠し、次のように測定した値を意味する。但し、試験片は発泡粒子をプレスした発泡粒子板を作製し用いた。この平滑面に６０度の角度で光を当てた時の正反射の割合（％）を表面光沢度とする。具体的には、ステンレス製円筒容器（内径７６ｍｍ、深さ１５ｍｍ）に発泡粒子を山盛りにならないように満杯に入れ、この容器の開口部をアルミ箔にて覆い、直径７５ｍｍのステンレス製円盤（表面鏡面仕上げ）を用いてプレス機にて１５ＭＰａの加圧状態で７２時間放置することで、発泡粒子の平滑面を形成する。測定面は円盤側の平滑面を用いる。この平滑面を光沢度測定装置（グロスチェッカ ＩＧ−３３０：株式会社堀場製作所製）を用い、入射角６０度−受光角６０度（６０度計）の光学系により測定することで表面光沢度を得ることができる。但し、測定は暗室で行なう等、外光の影響を受けない条件で行なう。
発泡粒子板の測定はプレス機の加圧状態を開放した後、３０秒以内に測定を行なう。また、試験片には発泡粒子間の境界線が現われるが、測定の際にはこの境界線を含んでいても特に問題はない。
光学測定は、１試験片に対し測定面上の重複しない任意の７箇所で行い、最大値と最小値を除いた５点の平均をその試験片の光沢度とする。この一連の測定を発泡粒子１種類について３回行い、３回の平均値をその発泡粒子の光沢度とする。
【００２９】
［寸法変化率］
長さ４００ｍｍ、幅３００ｍｍ、厚み３０ｍｍの板形状を有する発泡成形体を成形金型から取り出し、温度２３℃、相対湿度５０％の恒温恒湿室（ＪＩＳ Ｋ７１００の標準温湿度状態）に２４時間放置した後、この発泡成形体の中央部から上下面が平行で正方形状の平板（長さ１５０ｍｍ、巾１５０ｍｍ、厚み３０ｍｍ）を切り出し、その中央部に縦及び横方向にそれぞれ互いに平行に３本の直線を５０ｍｍ間隔になるように記入してＪＩＳ Ｋ６７６７に従う試験片とする。この試験片を２３℃に保った乾燥機の中に水平に置き、７２０時間後取り出し、再び恒温恒湿室に１時間放置した。寸法測定はＪＩＳ Ｋ６７６７に準拠して実施し、寸法変化率は次の式にしたがって求める。
寸法変化率（％）＝（Ｌ２−Ｌ１）×１００／Ｌ１
（ただし、Ｌ１は、型内成形後に２３℃、相対湿度５０％で２４時間放置されたスチレン系樹脂発泡成形体から得られた試験片の寸法、Ｌ２は該スチレン系樹脂発泡成形体を２３℃で７２０時間放置した後の試験片の寸法である）
なお、寸法とは、試験片に記入した縦横それぞれ３本の直線の長さの平均値である。
また、上記とは別の試験片を８０℃に保った熱風循環式乾燥機の中に水平に置き、１６８時間加熱試験を行った後に取り出し、再び恒温恒湿室に１時間放置し寸法変化率を求める。この寸法変化率を加熱寸法変化率と称する。
【００３０】
［メルトフローレート（ＭＦＲ）の測定］
ＭＦＲの測定は、ＪＩＳ Ｋ７２１０に基づき下記の条件で行った。
測定装置：東洋精機製作所製 メルトインデクサー
測定温度：２００℃
測定荷重：５．０ｋｇｆ
オリフィス径：２．０９ｍｍ
【００３１】
実施例１
ポリスチレン樹脂粒子は次のように重合したものを用いた。
攪拌機を具備した内容積１００リットルの反応器に、脱イオン水３６リットル、ピロリン酸マグネシウム７５ｇ、ドデシルベンゼンスルホン酸ナトリウム６ｇを入れた後に、重合開始剤としてベンゾイルパーオキサイド１２０ｇとｔ−ブチルパーオキシベンゾエート２９ｇを溶解したスチレン４６ｋｇを反応器に入れ攪拌し、９０℃に昇温してから６時間保持した後１２５℃に昇温し３時間保持して重合を行なった。重合終了時における重合転化率は９９．９８％であった。その後冷却して内容物を取り出し洗浄及び脱水乾燥した後に篩い機に掛け粒子径０．９〜１．２ｍｍのポリスチレン樹脂粒子を得た。このポリスチレン樹脂粒子の重量平均分子量は２８００００であった。
【００３２】
上記ポリスチレン樹脂粒子２ｋｇと、ドデシルベンゼンスルホン酸ナトリウム０．５ｇと、ピロリン酸マグネシウム６ｇと、水２リットル、及びトリス（２，３−ジブロモプロピル）イソシアヌレート３０．０ｇ（１．５重量％）と２，３−ジメチル−２，３−ジフェニルブタン６．０ｇ（０．３重量％）を混合した複合難燃剤を配合して、内容積５リットルの密閉容器内で攪拌しながら１２０℃まで昇温し３時間保持した後に２５℃まで冷却し、密閉容器から樹脂粒子を取り出した後、樹脂粒子の洗浄及び脱水乾燥を行い自己消火型ポリスチレン樹脂粒子を得た。
【００３３】
また、上記複合難燃剤（ＢＣ割合１６．７％）の融点をＤＴＡにて測定したところ、融点ピーク温度は一つであり１０３℃であった。なお、複合難燃剤の融点ピーク温度は、ＪＩＳ Ｋ７１２１に準拠し、ＤＴＡ測定を行うことで求めた。熱分析装置：セイコーインスツルメンツ社製ＴＧ／ＤＴＡ６２００Ｒ
測定試料質量：１０ｍｇ
昇温速度：１０℃／分
この自己消火型ポリスチレン樹脂粒子１ｋｇに対し、発泡時結合防止剤として炭酸カルシウム微粉末１．５ｇと、帯電気防止剤としてステアリン酸モノグリセライド０．５ｇを樹脂粒子表面に均一に付着させた後に圧力容器に入れ密閉し、次いで炭酸ガスを３．０ＭＰａまで圧入し２０℃の雰囲気下で６時間保持した。圧力容器内の内圧を抜いた後、直ちに予熱された発泡機内に投入し加圧蒸気（発泡機への導入圧力０．２ＭＰａ、発泡機内の圧力０．０７ＭＰａ）を用いて加熱発泡し自己消火型ポリスチレン樹脂発泡粒子を得た。得られた発泡粒子を常温常圧下で１日放置し乾燥した後の平均気泡径、嵩発泡倍率、スチレン系モノマーの含有量及び揮発性有機化合物の含有量を表１に示す。この発泡粒子を成形型内に充填し水蒸気にて加熱発泡成形し、長さ４００ｍｍ、幅３００ｍｍ、厚み３０ｍｍの板形状を有する自己消火型発泡成形体を得た。得られた発泡成形体の融着、外観、燃焼性の測定結果を表１に示す。
【００３４】
（実施例２）
トリス（２，３−ジブロモプロピル）イソシアヌレートを４０．０ｇ（２．０重量％）とし、２，３−ジメチル−２，３−ジフェニルブタンを８．０ｇ（０．４重量％）としたこと以外は実施例１と同様にして、自己消火型ポリスチレン樹脂発泡粒子を得た。また、複合難燃剤（ＢＣ割合１６．７％）の融点をＤＴＡにて実施例１と同様に測定したところ、融点ピーク温度は一つであり１０３℃であった。得られた発泡粒子を常温常圧下で１日放置し乾燥した後の平均気泡径、嵩発泡倍率、スチレン系モノマーの含有量及び揮発性有機化合物の含有量を表１に示す。更にこの発泡粒子を実施例１と同様にして自己消火型発泡成形体を得た。得られた発泡成形体の融着、外観及び燃焼性の測定結果を表１に示す。
【００３５】
（実施例３）
トリス（２，３−ジブロモプロピル）イソシアヌレートを６０．０ｇ（３．０重量％）とし、２，３−ジメチル−２，３−ジフェニルブタンを８．０ｇ（０．４重量％）としたこと以外は実施例１と同様にして、自己消火型ポリスチレン樹脂発泡粒子を得た。また、複合難燃剤（ＢＣ割合１１．８％）の融点をＤＴＡにて実施例１と同様に測定したところ、融点ピーク温度は一つであり１０４℃であった。得られた発泡粒子を常温常圧下で１日放置し乾燥した後の平均気泡径、嵩発泡倍率、スチレン系モノマーの含有量及び揮発性有機化合物の含有量を表１に示す。更にこの発泡粒子を実施例１と同様にして自己消火型発泡成形体を得た。得られた発泡成形体の融着、外観及び燃焼性の測定結果を表１に示す。
【００３６】
（実施例４）
２，３−ジメチル−２，３−ジフェニルブタンを３，４−ジメチル−３，４−ジフェニルヘキサン６．０ｇ（０．３重量％）とした以外は実施例１と同様にして、自己消火型ポリスチレン樹脂発泡粒子を得た。また、複合難燃剤（ＢＣ割合１６．７％）の融点をＤＴＡにて実施例１と同様に測定したところ、融点ピーク温度は一つであり１３１℃であった。得られた発泡粒子を常温常圧下で１日放置し乾燥した後の平均気泡径、嵩発泡倍率、スチレン系モノマーの含有量及び揮発性有機化合物の含有量を表１に示す。更にこの発泡粒子を実施例１と同様にして自己消火型発泡成形体を得た。得られた発泡成形体の融着、外観及び燃焼性の測定結果を表１に示す。
【００３７】
（実施例５）
実施例１と同じ方法を用いて、自己消火型ポリスチレン樹脂粒子を得た。この自己消火型ポリスチレン樹脂粒子１ｋｇに対し、発泡時の結合防止剤として炭酸カルシウム微粉末１．５ｇと、帯電防止剤としてステアリン酸モノグリセライド０．５ｇを樹脂粒子表面に均一に付着させた後に圧力容器に入れて密閉し、次いで炭酸ガスを３．０ＭＰａまで圧入し２０℃の雰囲気下で６時間保持した。圧力容器内の内圧を抜いた後、直ちに予熱された発泡機（上記導入ラインと排気弁の開度を電気的に制御しうる排気ラインとを備えた発泡機）内に投入し、０．２ＭＰａの上記を発泡機内に導入した。このときの発泡機内の圧力が０．０７ＭＰａになるように、排気ラインを使って過剰供給分の圧力を外部に逃がした。このように上記を発泡機内に連続的に導入しながら加熱発泡させて自己消火型ポリスチレン樹脂発泡粒子を得た。また、複合難燃剤（ＢＣ割合１６．７％）の融点をＤＴＡにて実施例１と同様に測定したところ、融点ピーク温度は一つであり１０３℃であった。得られた発泡粒子を常温常圧下で１日放置し乾燥した後の平均気泡径、嵩発泡倍率、スチレン系モノマーの含有量及び揮発性有機化合物の含有量を表１に示す。この発泡粒子を成形型内に充填し、水蒸気にて加熱発泡成形し自己消火型発泡成形体を得た。得られた発泡成形体の融着、外観、燃焼性の測定結果を表１に示す。
【００３８】
（比較例１）
実施例１と同じポリスチレン樹脂粒子１ｋｇに対し、発泡時結合防止剤として炭酸カルシウム微粉末１．５ｇと、帯電気防止剤としてステアリン酸モノグリセライド０．５ｇを樹脂粒子表面に均一に付着させた後に圧力容器に入れ密閉し、次いで炭酸ガスを３．０ＭＰａまで圧入し２０℃の雰囲気下で６時間保持した。圧力容器の内圧を抜いた後、直ちに予熱された発泡機内に投入し加熱蒸気を用いて加熱発泡しポリスチレン樹脂発泡粒子を得た。得られた発泡粒子を常温常圧下で１日放置し乾燥した後の平均気泡径、嵩発泡倍率、スチレン系モノマーの含有量及び揮発性有機化合物の含有量を表１に示す。更にこの発泡粒子を実施例１と同様にして発泡成形体を得た。得られた発泡成形体の融着、外観及び燃焼性の測定結果を表１に示す。
【００３９】
（比較例２）
トリス（２，３−ジブロモプロピル）イソシアヌレートを６０ｇ（３．０重量％）とし、２，３−ジメチル−２，３−ジフェニルブタンを使用しないこと以外は実施例１と全く同様にしてポリスチレン樹脂発泡粒子を得た。また、難燃剤の融点をＤＴＡにて実施例１と同様に測定したところ、融点ピーク温度は一つであり１１５℃であった。得られた発泡粒子を常温常圧下で１日放置し乾燥した後の平均気泡径、嵩発泡倍率、スチレン系モノマーの含有量及び揮発性有機化合物の含有量を表１に示す。更にこの発泡粒子を実施例１と同様にして自己消火型発泡成形体を得た。得られた発泡成形体の融着、外観及び燃焼性の測定結果を表１に示す。
【００４０】
（比較例３）
２，３−ジメチル−２，３−ジフェニルブタンをジクミルパーオキサイド６．０ｇ（０．３重量％）としたこと以外は実施例１と同様にして、ポリスチレン樹脂発泡粒子を得た。しかしながら、発泡の際に投入した樹脂粒子１ｋｇに対し１８０ｇの結合が発生した。また、複合難燃剤（ＤＣＰ割合１６．７％）の融点をＤＴＡにて実施例１と同様に測定したところ、測定途中でＤＣＰが分解してしまい測定は不可能であった。得られた発泡粒子を常温常圧下で１日放置し乾燥した後の平均気泡径、嵩発泡倍率、スチレン系モノマーの含有量及び揮発性有機化合物の含有量を表１に示す。この発泡粒子を成形型内に充填し水蒸気にて加熱発泡成形し発泡成形体を得た。得られた発泡成形体は融着が３０％と悪く、外観は収縮し良好な成形体は得られなかった。この発泡成形体の燃焼性の測定結果を表１に併記する。
【００４１】
（比較例４）
トリス（２，３−ジブロモプロピル）イソシアヌレートをテトラブロモシクロオクタン３０．０ｇ（１．５重量％）としたこと以外は実施例１と同様にして、ポリスチレン樹脂粒子を得た。また、複合難燃剤（ＢＣ割合１６．７％）の融点をＤＴＡにて実施例１と同様に測定したところ、融点ピーク温度は一つであり８８℃であった。このポリスチレン樹脂粒子１ｋｇに対し、発泡時結合防止剤として炭酸カルシウム微粉末１．５ｇと、帯電気防止剤としてステアリン酸モノグリセライド０．５ｇを樹脂粒子表面に均一に付着させた後に圧力容器に入れ密閉し、次いで炭酸ガスを３．０ＭＰａまで圧入し２０℃の雰囲気下で６時間保持した。圧力容器内の内圧を抜いた後、直ちに予熱された発泡機内に投入し加圧蒸気を用いて加熱発泡したところ、発泡機内で発泡粒同士が結合し成形可能な発泡粒子を得られなかった。
【００４２】
（比較例５）
トリス（２，３−ジブロモプロピル）イソシアヌレートをテトラブロモシクロオクタン４０．０ｇ（２．０重量％）とし、２，３−ジメチル−２，３−ジフェニルブタンを８．０ｇ（０．４重量％）としたこと以外は実施例１と同様にして、ポリスチレン樹脂粒子を得た。また、複合難燃剤（ＢＣ割合１６．７％）の融点をＤＴＡにて実施例１と同様に測定したところ、融点ピーク温度は一つであり８８℃であった。このポリスチレン樹脂粒子１ｋｇに対し、発泡時結合防止剤として炭酸カルシウム微粉末１．５ｇと、帯電気防止剤としてステアリン酸モノグリセライド０．５ｇを樹脂粒子表面に均一に付着させた後に圧力容器に入れ密閉し、次いで炭酸ガスを３．０ＭＰａまで圧入し２０℃の雰囲気下で６時間保持した。圧力容器内の内圧を抜いた後、直ちに予熱された発泡機内に投入し加圧蒸気を用いて加熱発泡したところ、発泡機内で発泡粒同士が結合し成形可能な発泡粒子を得られなかった。
【００４３】
（比較例６）
トリス（２，３−ジブロモプロピル）イソシアヌレートをヘキサブロモシクロドデカン３０．０ｇ（１．５重量％）としたこと以外は実施例１と同様にしてポリスチレン樹脂粒子を得た。しかしながら、この含浸反応に用いた反応液中には難燃剤が残されており、ポリスチレン樹脂粒子に難燃剤がほとんど含浸されていないことを示していた。また、複合難燃剤（ＢＣ割合１６．７％）の融点をＤＴＡにて実施例１と同様に測定したところ、融点ピーク温度は二つであり、ＢＣの融点は１０６℃、ＨＢＣＤの融点は１９０℃であった。次に、実施例１と同様にしてポリスチレン樹脂発泡粒子を得た。得られた発泡粒子を常温常圧下で１日放置し乾燥した後の平均気泡径、嵩発泡倍率、スチレン系モノマーの含有量及び揮発性有機化合物の含有量を表１に示す。更にこの発泡粒子を実施例１と同様にして発泡成形体を得た。得られた発泡成形体の融着、外観及び燃焼性の測定結果を表１に示す。
【００４４】
（比較例７）
トリス（２，３−ジブロモプロピル）イソシアヌレートをヘキサブロモシクロドデカン４０．０ｇ（２．０重量％）とし、２，３−ジメチル−２，３−ジフェニルブタンを８．０ｇ（０．４重量％）としたこと以外は実施例１と同様にしてポリスチレン樹脂粒子を得た。しかしながら、この含浸反応に用いた反応液中には難燃剤が残されており、ポリスチレン樹脂粒子に難燃剤がほとんど含浸されていないことを示していた。また、複合難燃剤（ＢＣ割合１６．７％）の融点をＤＴＡにて実施例１と同様に測定したところ、融点ピーク温度は二つであり、ＢＣの融点は１０５℃、ＨＢＣＤの融点は１９０℃であった。また、実施例１と同様にしてポリスチレン樹脂発泡粒子を得た。得られた発泡粒子を常温常圧下で１日放置し乾燥した後の平均気泡径、嵩発泡倍率、スチレン系モノマーの含有量及び揮発性有機化合物の含有量を表１に示す。更にこの発泡粒子を実施例１と同様にして発泡成形体を得た。得られた発泡成形体の融着、外観及び燃焼性の測定結果を表１に示す。
【００４５】
（比較例８）
トリス（２，３−ジブロモプロピル）イソシアヌレートをヘキサブロモシクロドデカン６０．０ｇ（３．０重量％）とし、２，３−ジメチル−２，３−ジフェニルブタンを１２．０ｇ（０．６重量％）としたこと以外は実施例１と同様にしてポリスチレン樹脂粒子を得た。しかしながら、この含浸反応に用いた反応液中には難燃剤が残されており、ポリスチレン樹脂粒子に難燃剤がほとんど含浸されていないことを示していた。また、複合難燃剤（ＢＣ割合１６．７％）の融点をＤＴＡにて実施例１と同様に測定したところ、融点ピーク温度は二つであり、ＢＣの融点は１０６℃、ＨＢＣＤの融点は１９０℃であった。また、実施例１と同様にしてポリスチレン樹脂発泡粒子を得た。得られた発泡粒子を常温常圧下で１日放置し乾燥した後の平均気泡径、嵩発泡倍率、スチレン系モノマーの含有量及び揮発性有機化合物の含有量を表１に示す。更にこの発泡粒子を実施例１と同様にして発泡成形体を得た。得られた発泡成形体の融着、外観及び燃焼性の測定結果を表１に示す。
【００４６】
【表１】

【００４７】
表１から実施例１〜５の発泡粒子は、発泡時の結合が少なく、取扱いが良好であった。更に、この発泡粒子から得られた発泡成形体は、融着率及び外観共に良好であり、加えて燃焼試験も３秒以下と優れた自己消火性を示した。
比較例１の発泡粒子及び発泡成形体は、発泡時結合量は少なく、また融着率及び外観は良好であるが、難燃剤及び難燃助剤を含まないため自己消火性が極めて劣っていた。
比較例２の発泡粒子は、発泡時結合量が多く、難燃助剤を含まないため自己消火性が劣っていた。
比較例３の発泡粒子及び発泡成形体は、発泡時の結合が比較例２よりも多く、得られた発泡成形体の融着率は悪く、外観は表面が融け、成形品全体が収縮して外観不良品となった。
比較例４及び５では、発泡時に発泡粒子全体が結合し、成形可能な発泡粒子が得られなかった。
比較例６〜８の発泡粒子及び発泡成形体は、発泡時結合量、融着率及び外観は良好であったが、難燃剤を実質的に含まないため自己消火性が極めて劣っていた。
実施例１〜５の光沢度と寸法変化率の測定結果を表２に示す。
【００４８】
【表２】

【００４９】
表２から、実施例１〜５の発泡成形体の中でも、光沢度の高い実施例５の発泡成形体は特に寸法変化率が極めて小さく、寸法安定性に優れた成形体であった。
【００５０】
（実施例６）
この実施例は、懸濁重合によりスチレン系樹脂の形成後、懸濁液中に難燃剤及び難燃助剤を添加した例である。
攪拌機を具備した内容積１００リットルの反応器に、脱イオン水３０リットル、ピロリン酸マグネシウム１００ｇ、ドデシルベンゼンスルホン酸ナトリウム１５ｇを入れ、粒子径が０．６３〜０．７１ｍｍで重量平均分子量が２８００００のポリスチレン樹脂粒子（スチレンをピロリン酸マグネシウム、ドデシルベンゼンスルホン酸ナトリウムを使用した水性媒体中で、通常の懸濁重合を行なって得たもの）１１ｋｇを加えて攪拌し懸濁させた。
【００５１】
次いで、あらかじめ用意した脱イオン水６リットル、ドデシルベンゼンスルホン酸ナトリウム２ｇ、ピロリン酸マグネシウム１０ｇの懸濁液に、ベンゾイルパーオキサイド９０ｇ、ｔ−ブチルパーオキシベンゾエート８ｇ溶解したスチレン５ｋｇを加え、ホモミキサーで攪拌して懸濁液とし、これを７０℃に保持した反応器に添加した。その後ポリスチレン粒子中にスチレンと重合開始剤が十分に吸収されるように、１時間保持した後に、スチレンを連続的に１０ｋｇ／時の速度で３時間供給しながら、スチレン供給終了時に１０５℃になるように反応器を昇温した後に、引き続き１２０℃に昇温し２時間保持した。重合終了時の重合転化率は９９．９８％であった。
【００５２】
次いで９０℃まで冷却し、あらかじめ用意した脱イオン水２リットル、ドデシルベンゼンスルホン酸ナトリウム２ｇ及び、トリス（２、３−ジブロモプロピル）イソシアヌレート６９０ｇと２，３−ジメチル−２，３−ジフェニルブタン１３８ｇとからなる複合難燃剤の懸濁液を反応器に圧入し１２０℃に昇温し３時間保持した。また、複合難燃剤（ＢＣ割合１６．７％）の融点をＤＴＡにて実施例１と同様に測定したところ、融点ピーク温度は一つであり１０３℃であった。その後、常温まで冷却して内容物を取り出し洗浄及び脱水乾燥して、粒子径が０．９〜１．２ｍｍの自己消火型ポリスチレン樹脂粒子を得た。この樹脂粒子の重量平均分子量は３０００００であった。この自己消火型ポリスチレン樹脂粒子から実施例１と同様にして自己消火型ポリスチレン樹脂発泡粒子を得た。
得られた発泡粒子を常温常圧下で１日放置し乾燥した後の平均気泡径と嵩発泡倍率を表３に示す。更にこの発泡粒子を実施例１と同様にして自己消火型発泡成形体を得た。得られた発泡成形体の融着、外観及び燃焼性の測定結果を表３に示す。
【００５３】
【表３】

【００５４】
表３から実施例６の発泡粒子は、難燃剤及び難燃助剤を重合後の懸濁液に添加して得られたスチレン系樹脂粒子から得られていても、発泡時の結合が少なく、取扱いが良好であった。更にこの発泡粒子から得られた発泡成形体は、融着率及び外観共に良好であり、加えて燃焼試験も３秒以下と優れた自己消火性を示した。
【００５５】
（実施例７）
この実施例は、上記実施例及び比較例の発泡成形体のリサイクル性を評価する例である。
実施例１と２及び比較例１、３と４で得られたポリスチレン樹脂粒子のメルトフローレート（ＭＦＲ）を測定した。また、ＭＦＲ測定前後の樹脂粒子の重量平均分子量も測定した。ＭＦＲ及び重量平均分子量を表４に示す。
【００５６】
【表４】

【００５７】
まず、押出機で溶融混練し、ストランド化することでリサイクルが可能なポリスチレン樹脂のＭＦＲは、２０ｇ／１０分以下、好ましくは１５ｇ／１０分以下、特に難燃剤未添加の場合のＭＦＲに近いことが好ましい。この観点から表４を見ると、実施例１と２の樹脂粒子はいずれも１５ｇ／１０分以下であり、十分リサイクル可能である。これに対して、比較例３と４の樹脂粒子は、ＭＦＲが測定限界の２００ｇ／１０分を超えており、リサイクル困難である。
更に、重量平均分子量は熱処理（ＭＦＲ測定処理）の前後において、できるだけ変化しないことがリサイクルの観点から望まれる。大きく低下すると、押出機で溶融混練した後にストランドとして押し出せない又はストランドの切断が頻繁に起こり、リサイクルが困難である。この観点から表４を見ると、実施例１と２の樹脂粒子は、難燃剤未添加の場合に比べて重量平均分子量が低下は少なく、十分リサイクル可能である。これに対して、比較例３と４の樹脂粒子は、重量平均分子量が大きく低下しており、リサイクルしても強度低下が著しく再利用できない。
【００５８】
【発明の効果】
本発明によれば、生産効率が良く、少量の難燃剤量で自己消火性に優れたスチレン系樹脂発泡成形体が得られる。この発泡成形体は発泡成形体中の残存スチレンモノマー分が少なく、発泡剤も無機ガスであるため低ＶＯＣ材料としての性質を有し、建築用断熱材やＥＰＳ土木工法の用途に好適である。
また、押出機で溶融混練することでリサイクルしても分子量が大きく低下することなく、一般のスチレン系樹脂発泡成形体と共にリサイクル可能な、環境適合性に優れた自己消火型スチレン系樹脂発泡成形体が得られる。
【図面の簡単な説明】
【図１】複合難燃剤の融点を示すグラフである。
【図２】樹脂発泡粒子の製造に使用できる発泡機の一例を示す概略図である。
【符号の説明】
２ 撹拌モーター
３ 撹拌翼
４ 邪魔棒
５ 発泡槽上面検出器
６ 発泡性粒子輸送器
７ 発泡性粒子計量槽
８ 発泡性粒子投入器
９ 蒸気吹込制御弁
１０ 蒸気チャンバー
１１ 凝縮水排出弁
１２ 排気制御弁
１３ 発泡粒子排出口
１４ 発泡粒子一時受器
１５ 空気輸送設備
１６ 内圧検出・制御装置
１７ 蒸気吹込孔
１８ 蒸気導入圧力計
１９ 減圧弁
２０ 蒸気元圧力計[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a self-extinguishing styrene-based resin foam particle and a self-extinguishing foam article. More specifically, the present invention comprises a styrene-based resin particle containing a specific composite flame retardant, which is excellent in self-extinguishing properties with a small amount of flame retardant, has high foaming properties and high heat insulation properties, and has a residual styrene-based The present invention relates to self-extinguishing styrene-based resin foamed particles and a self-extinguishing foamed molded article containing less monomer. INDUSTRIAL APPLICABILITY The self-extinguishing type foam molded article of the present invention can be suitably used as a building insulation material such as a wall material, a floor material, a ceiling material, a cushioning material for civil engineering such as an EPS civil engineering method, a packaging material, and the like.
[0002]
[Prior art]
It is known to use a flame retardant or a composite flame retardant in which a flame retardant and a flame retardant auxiliary are combined in order to impart self-extinguishing properties to a styrene resin. Common flame retardants include halogen-based flame retardants such as tetrabromocyclooctane, hexabromocyclododecane, tetrabromobisphenol A diallyl ether, and tris (2,3-dibromopropyl) isocyanurate. , Dicumyl peroxide, cumene hydroperoxide and 2,3-dimethyl-2,3-diphenylbutane.
[0003]
Specifically, JP-A-60-206845 (Patent Document 1) uses hexabromocyclododecane as a flame retardant and 2,3-dimethyl-2,3-diphenylbutane as a flame retardant auxiliary. Expandable styrenic resin particles are described.
Japanese Patent Application Laid-Open No. 9-255879 (Patent Document 2) describes a styrene-based flame-retardant resin composition using tris (2,3-dibromopropyl) isocyanurate as a flame retardant.
Further, Japanese Patent Application Laid-Open No. H11-13098 (Patent Document 3) discloses expanded polystyrene resin particles using tetrabromobisphenol A diallyl ether as a flame retardant and dicumyl peroxide or cumene hydroperoxide as a flame retardant aid. Has been described.
[0004]
[Patent Document 1]
JP-A-60-206845
[Patent Document 2]
JP-A-9-255879
[Patent Document 3]
JP-A-11-130898
[0005]
[Problems to be solved by the invention]
In order to impart self-extinguishing properties to the expandable styrene-based resin particles, the pre-expanded particles obtained therefrom, and the foamed molded article, it is desired that the flame retardant is uniformly dispersed in the particles and the molded article.
From the above point of view, even a flame retardant with a relatively high melting point and a large molecular weight, such as hexabromocyclododecane, inhibits the polymerization of the styrene monomer when added during suspension polymerization. Is difficult to obtain, and the strength of the resin is reduced. On the other hand, a method of impregnating the particles after polymerization is conceivable, but in this method, the flame retardant can hardly be impregnated because the melting point is higher than that of the styrene resin particles, and in this method, self-extinguishing properties are imparted. It becomes difficult. Therefore, the method is limited to a method of mixing and dispersing a melted resin and a flame retardant, such as an extrusion method. As a result, the manufacturing process becomes complicated.
Further, tris (2,3-dibromopropyl) isocyanurate has a low melting point and can be relatively uniformly impregnated into expandable styrene resin particles by an impregnation method. Low flame retardancy and cannot exhibit self-extinguishing properties.
[0006]
For this purpose, an organic peroxide such as dicumyl peroxide or cumene hydroperoxide is added as a flame retardant aid. It is considered that, by generating radicals at the time of combustion, self-extinguishing property is efficiently imparted to the flame retardant with a smaller amount. However, when such organic peroxides are melt-kneaded at the time of recycling, radicals are generated, and the radicals decompose the styrene-based resin to cause a decrease in molecular weight. There is a problem that it worsens.
Further, in the conventional styrene resin, a hydrocarbon gas is often used as a foaming agent, and since this foaming agent easily remains in the foamed particles and the molded body after foaming, the foamed particles and the molded body are hardly used. The dimensional stability was reduced.
Therefore, it is intended to provide styrene-based resin foamed particles and foamed moldings which retain the original properties of the styrene-based resin foam molded article, such as heat insulation and mechanical strength, and have excellent self-extinguishing properties and excellent dimensional stability. Was desired.
[0007]
[Means for Solving the Problems]
The inventors of the present invention have studied combinations of various flame retardants and flame retardant auxiliaries in order to solve the above-mentioned problems. As a result, a composite flame retardant containing the following types of flame retardants and flame retardant auxiliaries at a specific ratio was obtained. The flame retardant is unlikely to cause a decrease in the molecular weight of the styrenic resin during recycling, retains the inherent properties of the styrenic resin (for example, heat insulation and mechanical strength), exhibits excellent self-extinguishing properties, and is used as a styrenic resin. It was surprisingly found that the method of dispersing is not limited. Further, they have found that dimensional stability can be improved by using an inorganic gas as a foaming agent, and have reached the present invention.
Thus, according to the present invention, a styrene-based resin containing a composite flame retardant is foamed with an inorganic gas as a foaming agent, and the composite flame retardant is tris (2,3-dibromopropyl) isocyanurate. And the following general formula
[0008]
Embedded image

[0009]
(Wherein R1 to R4 are the same or different and each is a methyl or ethyl group) and is composed of 10 to 60% by weight of a flame retardant aid, and 1 to 7 parts by weight based on 100 parts by weight of the styrene resin particles. Parts by weight included
The present invention provides a self-extinguishing styrene-based resin foamed particle characterized by the above.
Further, according to the present invention, there is provided a self-extinguishing foam molded article obtained by molding the above-mentioned foamed self-extinguishing styrene resin particles by an in-mold molding method.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The composite flame retardant used in the present invention is tris (2,3-dibromopropyl) isocyanurate (hereinafter also referred to as TDIC; melting point 115 ° C., decomposition temperature 285 ° C.)
[0011]
Embedded image

[0012]
Wherein R is the same or different and is a methyl or ethyl group.
Specific examples of the flame retardant aid include 2,3-dimethyl-2,3-diphenylbutane (hereinafter referred to as BC because it is called biscumyl; melting point 113 ° C, decomposition temperature 205 ° C), 3,4-dimethyl- 3,4-diphenylhexane (melting point 142 ° C., decomposition temperature 230 ° C.) and the like.
Since the above-mentioned flame retardants and flame retardant auxiliaries have relatively close melting points, the composite flame retardant obtained by mixing them has a melting point with almost one peak (this temperature is referred to as a melting point peak temperature). In addition, the inventors have found that the melting point peak temperature of the composite flame retardant is lower than the melting points of the flame retardant and the flame retardant auxiliary alone due to the melting point drop. For example, the horizontal axis represents the proportion of the flame retardant auxiliary agent BC in the composite flame retardant, and the vertical axis represents the melting point peak temperature of the composite flame retardant, as shown in FIG. In the case of the composite flame retardant, the melting point peak temperature measured by differential thermal analysis (DTA) is about 101 ° C., which is about 15 ° C. lower than the melting points of TDIC and BC alone. The melting point peak temperature of the composite flame retardant is preferable because the impregnation temperature or the kneading temperature can be made lower. The melting point peak temperature is preferably in the range of 80 to 140 ° C. If the melting point peak temperature is lower than 80 ° C., the flame retardant bleeds during coalescence or kneading of the resin particles during the impregnation, and the coalescence of the foamed particles during the prefoaming is not preferable. On the other hand, if the temperature exceeds 140 ° C., the impregnation efficiency and the dispersibility during kneading may be poor, which is not preferable. A more preferable melting point peak temperature is 90 to 130 ° C.
[0013]
In the present invention, the flame retardant and the flame retardant auxiliary are used in 90 to 40% by weight and 10 to 60% by weight. When the proportion of the flame retardant auxiliary is less than 10% by weight, it is necessary to use a large amount of the composite flame retardant in order to exhibit self-extinguishing properties, and as a result, recyclability is impaired. Further, the melting point peak temperature does not decrease so much, and the impregnation temperature or kneading temperature must be increased. On the other hand, when the content exceeds 60% by weight, the proportion of the flame retardant decreases, so that the self-extinguishing property is deteriorated. Further, the melting point peak temperature does not decrease so much, and the impregnation temperature or kneading temperature must be increased. More preferred ratios of the flame retardant and the flame retardant auxiliary are 90 to 60% by weight and 10 to 40% by weight.
In the present invention, a more preferable combination of a flame retardant and a flame retardant auxiliary is a combination of TDIC and BC.
The content ratio of the composite flame retardant is 1 to 7 parts by weight based on 100 parts by weight of the styrene resin particles. If the amount is less than 1 part by weight, sufficient self-extinguishing properties cannot be obtained. On the other hand, if it exceeds 7 parts by weight, the self-extinguishing effect is saturated and is not economical. Usually, 1 to 5 parts by weight is sufficient.
[0014]
The styrene resin of the present invention may be a homopolymer of styrene, and other monomers copolymerizable with styrene, for example, α-methylstyrene, vinyltoluene, acrylonitrile, methyl methacrylate, glycidyl methacrylate, butyl acrylate, methacrylic acid, A copolymer of styrene with divinylbenzene, alkylene glycol dimethacrylate, or the like may be used. In the present invention, styrene and monomers copolymerizable with styrene are also referred to as styrene monomers.
Further, the styrene-based resin in the present invention may be a mixed resin with another resin. Examples of other resins include polyethylene, polypropylene, polyphenylene ether, and rubber-modified styrene resins.
Further, a suitable additive may be contained in the styrene resin. Examples of the additives include higher fatty acid amide, aromatic bisamide, ethylene bisstearyl amide, higher fatty acid, paraffin, wax, hardened animal and vegetable oil, diisobutyl adipate, and the like. In addition, additives conventionally used in the production of styrenic resin particles, such as lubricants, plasticizers, cell regulators, cell stabilizers, fillers, colorants, antioxidants, and ultraviolet absorbers are required. May be used as appropriate.
These additives can be added in advance during the polymerization of the styrene resin particles, or can be included in the resin particles during the impregnation or kneading of the flame retardant.
[0015]
Further, the content of the styrene-based monomer with respect to the styrene-based resin is preferably 500 ppm or less, and more preferably 300 ppm or less (the lower limit is 0 ppm) from the viewpoint of the quality of the foamed molded article and low VOC. The content of the volatile organic solvent containing the styrene-based monomer with respect to the styrene-based resin is preferably 1000 ppm or less, and more preferably 500 ppm or less (the lower limit is 0 ppm) from the viewpoint of the quality of the foamed molded article and low VOC.
The styrene-based resin is used in the form of particles, and the size of the particles is preferably 0.3 to 3.0 mm, and more preferably 0.5 to 2.0 mm.
Examples of the method for producing self-extinguishing styrene resin particles include a suspension polymerization method and a seed polymerization method, and a method in which a styrene resin and a composite flame retardant are melt-kneaded by an extruder, and then the extruded strand is pelletized. Among them, suspension polymerization or seed polymerization is preferred from the viewpoint of production efficiency. In the suspension polymerization or the seed polymerization method, as a method of impregnating the resin particles with the composite flame retardant, a method in which the polymerization conversion rate is 99.8% or more, or a method in which the resin is impregnated by adding it to an aqueous medium after the polymerization is completed. No. Impregnation when the polymerization conversion is 99.8% or more is preferable because styrene resin particles having a predetermined molecular weight can be easily obtained.
If the flame retardant is impregnated when the polymerization conversion rate is less than 99.8%, the polymerization of the styrene-based monomer thereafter is inhibited, and a large amount of the monomer may remain in the finally obtained foamed molded article. Is not preferred. Further, the thermal conductivity is increased due to the finer cell diameter of the foamed molded article, and the heat insulating performance may be reduced, which is not preferable. The impregnation is usually performed in a reactor equipped with a stirrer.
[0016]
It is preferable to add a suspension stabilizer to the aqueous medium used for impregnation in order to prevent the styrene-based resin particles from binding to each other during the impregnation. Examples of the suspension stabilizer include known water-soluble polymers such as commonly used polyvinyl alcohol, methylcellulose, polyacrylamide, and polyvinylpyrrolidone, and poorly water-soluble inorganic materials such as tribasic calcium phosphate, hydroxyapatite, and magnesium pyrophosphate. Salts. When a poorly water-soluble inorganic salt is used, an anionic surfactant is usually used in combination. Examples of the anionic surfactant include fatty acid soap, N-acyl amino acid or a salt thereof, carboxylate such as alkyl ether carboxylate, alkylbenzene sulfonate, alkylnaphthalene sulfonate, dialkyl sulfosuccinate, and alkyl sulfoacetic acid. Sulfonates such as salts and α-olefin sulfonates; sulfates such as higher alcohol sulfates, alkyl ether sulfates and polyoxyethylene alkylphenyl ether sulfates; alkyl ether phosphates and alkyl phosphates Phosphate salts such as salts.
[0017]
The method of adding a composite flame retardant is, for example, a method of separately or simultaneously adding a flame retardant and a flame retardant auxiliary agent into an aqueous medium, a method of mixing the flame retardant and the flame retardant auxiliary agent with a super mixer and the like, and then setting a powder state. A method in which the suspension is poured into an aqueous medium as it is, and a method in which a suspension uniformly dispersed in a preliminary dispersion tank provided with a stirring device is charged into the aqueous medium. In order to perform the impregnation more smoothly, it is preferable to heat the aqueous medium. Specifically, it is preferable to heat at a temperature of 70 to 120 ° C. for 1 to 6 hours.
The styrene-based resin particles impregnated with the flame retardant and the flame-retardant auxiliary are taken out of the reactor, washed and dehydrated and dried to become self-extinguishing styrene-based resin particles.
Next, the self-extinguishing styrene resin particles are impregnated with an inorganic gas as a foaming agent. Before the impregnation with the blowing agent, the surface of the resin particles may be subjected to an appropriate surface treatment. Examples of the surface treatment agent include calcium carbonate, talc, colloidal silica, alumina powder and the like as a binding inhibitor at the time of foaming, higher fatty acid monoglyceride, polyethylene glycol and the like as an antistatic agent. Cycle agents, mold release agents, termiticides, fungicides, rust inhibitors, and the like. Examples of the surface treatment method include a method of mixing using a ribbon blender, a Nauter mixer, a tumbler mixer, a Loedige mixer, or the like.
Examples of the inorganic gas include carbon dioxide, air, nitrogen, and a mixed gas of these gases. Of these, carbon dioxide is preferably used as a main component, and it is more preferable to use carbon dioxide alone as much as possible from the viewpoint of foaming properties.
[0018]
The impregnation of the inorganic gas is carried out in a pressure vessel capable of sealing the resin particles, pressurizing the inorganic gas into the vessel, and performing gas phase pressurization. The temperature at which the inorganic gas is impregnated is desirably a temperature within a range in which the resin particles do not soften and bond, that is, a relaxation temperature. The relaxation temperature means a temperature at least 10 ° C. lower than the Vicat softening point of the styrenic resin. The specific temperature differs depending on the composition of the styrene resin and the type of the inorganic gas. Generally speaking, from the relationship between the gas impregnation amount and the pressure vessel, the impregnation temperature is preferably low, and is preferably 40 ° C. or lower. However, if the temperature is 0 ° C. or lower, energy consumption is industrially large, which is not preferable. The impregnation temperature for industrially stabilizing and foaming at a relatively high magnification is more preferably from 0 to 40 ° C, particularly preferably from 5 to 30 ° C.
An appropriate pressure for impregnating the resin particles with the inorganic gas is preferably 1.5 MPa or more, more preferably 2 to 5 MPa.
By this impregnation treatment, the self-extinguishing styrene resin particles can be uniformly impregnated with the inorganic gas. The impregnation time varies depending on the type of inorganic gas, the pressure, the composition of the resin particles, and the particle size. However, it is preferable to perform the impregnation until at least 0.05 mol / kg (resin particles) of the inorganic gas is impregnated. This can be achieved with an impregnation time of 10 hours.
[0019]
The self-extinguishing styrenic resin particles impregnated with the inorganic gas in this manner are then subjected to foaming. The foamable resin particles impregnated with the inorganic gas are taken out of the pressure vessel and immediately heated to foam. In this case, it is important that foaming is performed under the condition that the lower limit of the inorganic gas content in the resin particles is 0.1 mol / kg (resin particles) or more. In other words, when the expandable resin particles impregnated with the inorganic gas are taken out of the pressure vessel into the atmosphere, the content of the inorganic gas as a foaming agent gradually escapes to the atmosphere, and the content thereof decreases. Makes it difficult to foam to the target multiple. The upper limit is not more than 2.3 mol / kg (resin particles). If the amount is more than 2.3 mol / kg, the foamability is too high, so that it is difficult to produce foamed particles having a uniform expansion ratio.
Therefore, in terms of industrial production, it is preferable that the expandable resin particles are directly introduced from a pressurized state into a preheated foaming machine and foamed. Alternatively, after the pressure is released and taken out of the pressure vessel, it may be immediately introduced into a preheated foaming machine to foam. However, when foaming is performed after depressurization, foaming is preferably performed within 30 minutes after depressurization, particularly within 2 minutes.
[0020]
Foaming can be performed by a known method, but the following method can be adopted as a more preferable foaming method for obtaining an excellent foamed molded article. That is, in the foaming step, the expandable resin particles are charged into a foaming machine having a steam introduction line and an exhaust line. Next, the steam is supplied from the steam introduction line into the foaming machine at an introduction pressure of 0.05 to 0.5 MPa, and the atmosphere gas containing the steam is exhausted from the exhaust line. Foaming is performed while maintaining a low value of 0.005 to 0.2 MPa. The time required for foaming is affected by the pressure and temperature of the pressurized steam, the composition of the resin particles, the content of the inorganic gas, and the like, and is usually 10 to 150 seconds, preferably 20 to 90 seconds.
[0021]
FIG. 2 shows an example of a foaming machine that can be used for producing resin foam particles. In the figure, 2 is a stirring motor, 3 is a stirring blade, 4 is a baffle bar, 5 is a detector for the top of the foaming tank, 6 is an expandable particle transporter, 7 is an expandable particle measuring tank, 8 is an expandable particle injector, 9 is a steam injection control valve, 10 is a steam chamber, 11 is a condensed water discharge valve, 12 is an exhaust control valve, 13 is a foam particle discharge port, 14 is a foam particle temporary receiver, 15 is a pneumatic transport facility, and 16 is an internal pressure detection A control device, 17 is a steam injection hole, 18 is a steam introduction pressure gauge, 19 is a pressure reducing valve, and 20 is a steam source pressure gauge.
The foamed particles thus obtained are excellent in gloss, and the foamed particle plate obtained by pressing the foamed particles has a surface gloss of 30 to 60. The surface glossiness is particularly preferably from 35 to 50. A molded article obtained from the expanded particles has stable dimensions over a long period of time, has excellent surface smoothness, and can achieve a beautiful appearance. If the surface glossiness is smaller than 30, the foamed molded article may appear dark, and the commercial value may be significantly inferior. On the other hand, if it is larger than 60, the internal fusion when formed into a molded product is poor, and sufficient mechanical strength may not be obtained. The method for measuring the surface glossiness is described in the section of Examples.
[0022]
The self-extinguishing styrene-based resin foamed particles thus obtained are usually left to mature in the air. The aging time of the foamed particles is determined based on the fact that the inside of the bubbles generated by the foaming is cooled after the foaming and the pressure is reduced, and the air in the atmosphere compensates to return to the normal pressure. The time is about 4 hours, and in a shorter time, since the pressure inside the cells of the expanded particles is reduced, the expanded particles may shrink during the in-mold molding, and a good expanded molded article may not be obtained. is there. Further, the foamed particles obtained by the present invention have no particular upper limit of the standing time, and foamed particles one year after foaming can be used without any problem as long as the base resin itself does not deteriorate.
The average cell diameter suitable for in-mold molding of the expanded particles is 50 to 500 µm, preferably 100 to 300 µm. If the average cell diameter is less than 50 μm, the foam surface melts and shrinks due to heating, and a good foamed molded product may not be obtained. On the other hand, when the average cell diameter is larger than 500 μm, it is not preferable because a molded article having excellent strength cannot be obtained.
The self-extinguishing styrene-based resin foam particles obtained in this manner are subjected to so-called in-mold molding by a known method to produce various foam molded articles (for example, building materials such as building wall materials, floor materials, and ceiling materials). It is used as a material for obtaining a heat insulating material, a cushioning material for civil engineering such as an EPS civil engineering method, a packaging material, and the like.
[0023]
【Example】
Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited thereto.
First, a method for evaluating a styrene-based resin particle foam and a foam molded article will be described below.
[Weight average molecular weight]
The weight average molecular weight (Mw) of the polymer is determined by GPC (Gel Permeation).
(Chromatography) under the following conditions.
Measuring device: Tosoh high speed GPC device HLC-8020
Column: HSG-60S x 2, HSG-40H x 1, HSG-20H x 1 manufactured by Sekisui Fine Chemical Co., Ltd.
Column temperature: 40 ° C., mobile phase: THF (tetrahydrofuran),
Flow rate: 1.0 ml / min, injection volume: 500 ml
Detector: Tosoh RID-6A
Measurement of molecular weight of sample: In measuring the molecular weight of a sample, the molecular weight distribution of the sample is included in a range in which the logarithm of the molecular weight and the count number of a calibration curve prepared from several types of monodisperse polystyrene standard samples are linear. Measurement conditions were selected. In the present invention, the calibration curve of polystyrene shows that the weight average molecular weight is 2.74 × 10 4 ³ , 1.91 × 10 ⁴ , 1.02 × 10 ⁵ 3.55 × 10 ⁵ , 2.89 × 10 ⁶ , 4.48 × 10 ⁶ Using six standard polystyrene standard samples (TSK standard polystyrene) manufactured by Tosoh Corporation.
[0024]
[Fusing rate]
After making a cut of 300 mm length continuous from a pair of long sides to the long side on one surface of a foam molded article having a plate shape of length 400 mm, width 300 mm, thickness 30 mm with a cutter knife to a depth of about 5 mm, The foam molded article is divided into two by hand along this line, and the number of particles (a) broken in the particles and the number of particles broken at the interface between the particles (a) b) and the following formula
Fusion rate (%) = [(a) / {(a) + (b)}] × 100
The value obtained by substituting into (1) was defined as the fusion rate (%).
[0025]
[Combustion quality]
Flammability was measured by the flammability test A method of JIS A9511. According to this JIS standard, the self-extinguishing time must be within 3.0 seconds. It is more preferable that the time is within 2.0 seconds.
[Polymerization conversion and determination of residual styrene content]
The polymerization conversion was calculated by the following equation.
Polymerization conversion (% by weight) = 100 × (AB) / A
The amount of residual styrene was calculated by the following equation.
Residual styrene amount (% by weight) = 100 × B / A
Here, A is the weight (g) of the styrene resin particles containing the unreacted styrene monomer, and B is the weight of the unreacted monomer in the resin particles containing the unreacted styrene monomer ( g). B is quantified by, for example, gas chromatography (GC). Determination of the styrene-based monomer by DC was performed by dissolving the styrene-based resin particles in N, N-dimethylformamide and adding an internal standard solution (cyclopentanol).
GC: Shimadzu Corporation GC-14A
Column: PEG-20M PT25% 60/80 (2.5m)
Column temperature: 105 ° C
Detector (FID) temperature: 220 ° C
[0026]
[Content of volatile organic compound]
The values obtained by the following three types of measurement methods are summed and determined.
(Measurement of hydrocarbon compounds having 5 or less carbon atoms)
A predetermined amount of a sample cut from the foamed resin particles or the foamed molded article is placed in a pyrolysis furnace at 180 ° C., and the volatile hydrocarbon is measured by gas chromatography. In addition, about a foaming molded object, the test piece was cut out from the site | part which is 100 mm from the long side and the short side obtained from the Example, and 5 mm from the upper and lower surfaces, and was used as the measurement sample.
Gas chromatography (GC): GC-14B manufactured by Shimadzu Corporation
Pyrolysis furnace: PYR-1A manufactured by Shimadzu Corporation
Column: Polapack Q 80/100 (3mmφ × 1.5m)
Column temperature: 100 ° C
Detector (FID) temperature: 120 ° C
(Measurement of hydrocarbons having 6 or more carbon atoms up to the peak of styrene appearing in the gas chromatogram)
In the same manner as described above, a predetermined amount of a sample cut out from the foamed resin particles or the foamed molded product is dissolved in dimethylformamide, and an internal standard solution (cyclopentanol) is added, followed by measurement by GC. However, peaks that cannot be identified are quantified in terms of the amount of toluene detected.
GC: Shimadzu Corporation GC-14A
Column: PEG-20M PT25% 60/80 (2.5m)
Column temperature: 105 ° C
Detector (FID) temperature: 220 ° C
(Measurement of hydrocarbons having 16 carbon atoms (n-hexadecane) from the next peak of styrene appearing in the gas chromatogram)
[0027]
In the same manner as described above, a predetermined amount of a sample cut out of the foamed resin particles or the foamed molded product is dissolved in chloroform, and measured by a gas chromatograph mass spectrometer (GCMS). However, perform a blank test using only a solvent that does not dissolve the test piece, and subtract the detected substance amount in the blank test. Further, peaks that cannot be identified are quantified by converting them into the detected amount of toluene.
GCMS: QP5000 manufactured by Shimadzu Corporation
Column: DB-1 manufactured by J & W Scientific
(1μm × 60m 0.25mmφ)
Measurement conditions: Column temperature
(After holding at 60 ° C for 1 minute, the temperature is raised to 300 ° C at 10 ° C / min.)
Split ratio: 10
Carrier gas: He (1 ml / min)
Interface temperature: 260 ° C
[0028]
[Surface gloss]
The surface glossiness is a value measured in the following manner in accordance with JIS K7105 (Test method for optical properties of plastics). However, as the test piece, a foamed particle plate prepared by pressing foamed particles was used. The ratio (%) of regular reflection when light is applied to the smooth surface at an angle of 60 degrees is defined as surface glossiness. Specifically, a stainless steel cylindrical container (inner diameter 76 mm, depth 15 mm) is filled with foamed particles so as not to be piled up, the opening of the container is covered with aluminum foil, and a stainless steel disk with a diameter of 75 mm (surface Using a mirror finish), a smooth surface of the foamed particles is formed by leaving a press machine at a pressure of 15 MPa for 72 hours. The measurement surface is a smooth surface on the disk side. The surface gloss is measured by measuring the smooth surface with an optical system having an incident angle of 60 degrees and a light receiving angle of 60 degrees (60 degree meter) using a glossiness measuring device (Gloss Checker IG-330: manufactured by Horiba Ltd.). Obtainable. However, the measurement is performed in a condition not affected by external light, such as in a dark room.
The measurement of the expanded particle plate is performed within 30 seconds after the pressurized state of the press is released. In addition, although a boundary line between the foamed particles appears on the test piece, there is no particular problem even if the boundary line is included in the measurement.
The optical measurement is performed on one test piece at any seven non-overlapping positions on the measurement surface, and the average of the five points excluding the maximum value and the minimum value is defined as the glossiness of the test piece. This series of measurements is performed three times for one type of foamed particles, and the average value of the three times is defined as the gloss of the foamed particles.
[0029]
[Dimension change rate]
A foamed molded article having a plate shape of 400 mm in length, 300 mm in width and 30 mm in thickness is taken out of the molding die and left in a constant temperature and humidity room (23 ° C., 50% relative humidity) (standard temperature and humidity condition of JIS K7100) for 24 hours. After that, a square flat plate (length 150 mm, width 150 mm, thickness 30 mm) whose upper and lower surfaces are parallel is cut out from the center of the foamed molded article, and three pieces are vertically and horizontally parallel to each other at the center. Draw straight lines at 50 mm intervals to make test specimens in accordance with JIS K6767. The test piece was placed horizontally in a drier kept at 23 ° C., taken out after 720 hours, and left again in a thermo-hygrostat for 1 hour. The dimensional measurement is performed in accordance with JIS K6767, and the dimensional change is determined according to the following equation.
Dimensional change rate (%) = (L2−L1) × 100 / L1
(However, L1 is the size of a test piece obtained from the styrene resin foam molded article left at 23 ° C. and 50% relative humidity for 24 hours after in-mold molding, and L2 is the styrene resin foam molded article at 23 ° C.) This is the size of the test piece after leaving for 720 hours at
The dimension is the average of the lengths of three vertical and horizontal straight lines written on the test piece.
Further, another test piece was placed horizontally in a hot air circulating drier kept at 80 ° C., subjected to a heating test for 168 hours, taken out, left again in a constant temperature and humidity chamber for 1 hour, and subjected to dimensional change. Ask for. This dimensional change rate is called a heating dimensional change rate.
[0030]
[Measurement of melt flow rate (MFR)]
MFR was measured under the following conditions based on JIS K7210.
Measuring device: Toyo Seiki Seisakusho Melt Indexer
Measurement temperature: 200 ° C
Measurement load: 5.0kgf
Orifice diameter: 2.09 mm
[0031]
Example 1
The polystyrene resin particles used were polymerized as follows.
After putting 36 l of deionized water, 75 g of magnesium pyrophosphate and 6 g of sodium dodecylbenzenesulfonate into a reactor having an inner volume of 100 l equipped with a stirrer, 120 g of benzoyl peroxide and 120 g of t-butyl peroxybenzoate as polymerization initiators were added. 46 kg of styrene in which 29 g had been dissolved were placed in a reactor, stirred, heated to 90 ° C., maintained for 6 hours, then heated to 125 ° C. and maintained for 3 hours to carry out polymerization. At the end of the polymerization, the polymerization conversion was 99.98%. After cooling, the contents were taken out, washed, dehydrated and dried, and then passed through a sieving machine to obtain polystyrene resin particles having a particle diameter of 0.9 to 1.2 mm. The weight average molecular weight of the polystyrene resin particles was 280000.
[0032]
2 kg of the polystyrene resin particles, 0.5 g of sodium dodecylbenzenesulfonate, 6 g of magnesium pyrophosphate, 2 liters of water, and 30.0 g (1.5% by weight) of tris (2,3-dibromopropyl) isocyanurate. A compound flame retardant mixed with 6.0 g (0.3% by weight) of 2,3-dimethyl-2,3-diphenylbutane is blended, and the temperature is raised to 120 ° C. while stirring in a closed container having an inner volume of 5 liters. After holding for 3 hours, the mixture was cooled to 25 ° C., and the resin particles were taken out from the sealed container. The resin particles were washed and dehydrated and dried to obtain self-extinguishing polystyrene resin particles.
[0033]
When the melting point of the composite flame retardant (BC ratio 16.7%) was measured by DTA, the melting point peak temperature was one and was 103 ° C. The melting point peak temperature of the composite flame retardant was determined by performing DTA measurement in accordance with JIS K7121. Thermal analyzer: TG / DTA6200R manufactured by Seiko Instruments Inc.
Measurement sample mass: 10 mg
Heating rate: 10 ° C / min
To 1 kg of the self-extinguishing polystyrene resin particles, 1.5 g of calcium carbonate fine powder as an anti-bonding agent at the time of foaming and 0.5 g of stearic acid monoglyceride as an antistatic agent were uniformly attached to the surface of the resin particles. Then, carbon dioxide gas was injected under pressure to 3.0 MPa, and the mixture was kept at 20 ° C. for 6 hours. Immediately after the internal pressure in the pressure vessel is released, it is charged into a preheated foaming machine and heated and foamed using pressurized steam (introduction pressure to foaming machine: 0.2 MPa, pressure in foaming machine: 0.07 MPa), and self-extinguishing type Polystyrene resin expanded particles were obtained. Table 1 shows the average cell diameter, bulk expansion ratio, styrene monomer content, and volatile organic compound content after the obtained foamed particles were allowed to stand at room temperature and pressure for one day and dried. The foamed particles were filled in a mold and foamed by heating with steam to obtain a self-extinguishing foam molded body having a plate shape of 400 mm in length, 300 mm in width and 30 mm in thickness. Table 1 shows the measurement results of fusion, appearance, and flammability of the obtained foamed molded article.
[0034]
(Example 2)
Tris (2,3-dibromopropyl) isocyanurate was 40.0 g (2.0% by weight) and 2,3-dimethyl-2,3-diphenylbutane was 8.0 g (0.4% by weight). Except for the above, the self-extinguishing polystyrene resin foamed particles were obtained in the same manner as in Example 1. Further, when the melting point of the composite flame retardant (BC ratio 16.7%) was measured by DTA in the same manner as in Example 1, the melting point peak temperature was one and was 103 ° C. Table 1 shows the average cell diameter, bulk expansion ratio, styrene monomer content, and volatile organic compound content after the obtained foamed particles were allowed to stand at room temperature and pressure for one day and dried. Further, a self-extinguishing foamed molded article was obtained from the foamed particles in the same manner as in Example 1. Table 1 shows the measurement results of the fusion, appearance, and flammability of the obtained foam molded article.
[0035]
(Example 3)
Tris (2,3-dibromopropyl) isocyanurate was 60.0 g (3.0% by weight), and 2,3-dimethyl-2,3-diphenylbutane was 8.0 g (0.4% by weight). Except for the above, the self-extinguishing polystyrene resin foamed particles were obtained in the same manner as in Example 1. When the melting point of the composite flame retardant (BC ratio 11.8%) was measured by DTA in the same manner as in Example 1, the melting point peak temperature was one and was 104 ° C. Table 1 shows the average cell diameter, bulk expansion ratio, styrene monomer content, and volatile organic compound content after the obtained foamed particles were allowed to stand at room temperature and pressure for one day and dried. Further, a self-extinguishing foamed molded article was obtained from the foamed particles in the same manner as in Example 1. Table 1 shows the measurement results of the fusion, appearance, and flammability of the obtained foam molded article.
[0036]
(Example 4)
Self-extinguishing type was carried out in the same manner as in Example 1 except that 2,3-dimethyl-2,3-diphenylbutane was changed to 6.0 g (0.3% by weight) of 3,4-dimethyl-3,4-diphenylhexane. Polystyrene resin expanded particles were obtained. When the melting point of the composite flame retardant (BC ratio 16.7%) was measured by DTA in the same manner as in Example 1, the melting point peak temperature was one and was 131 ° C. Table 1 shows the average cell diameter, bulk expansion ratio, styrene monomer content, and volatile organic compound content after the obtained foamed particles were allowed to stand at room temperature and pressure for one day and dried. Further, a self-extinguishing foamed molded article was obtained from the foamed particles in the same manner as in Example 1. Table 1 shows the measurement results of the fusion, appearance, and flammability of the obtained foam molded article.
[0037]
(Example 5)
Using the same method as in Example 1, self-extinguishing polystyrene resin particles were obtained. To 1 kg of the self-extinguishing type polystyrene resin particles, 1.5 g of calcium carbonate fine powder as a binding inhibitor at the time of foaming and 0.5 g of monoglyceride stearate as an antistatic agent are uniformly adhered to the surface of the resin particles. , And then carbon dioxide gas was injected thereinto up to 3.0 MPa and kept at 20 ° C. for 6 hours. Immediately after the internal pressure in the pressure vessel was released, the pressure was introduced into a preheated foaming machine (a foaming machine provided with the above-mentioned introduction line and an exhaust line capable of electrically controlling the opening of an exhaust valve), and 0.2 MPa Was introduced into a foaming machine. The excess supply pressure was released to the outside using an exhaust line so that the pressure in the foaming machine at this time became 0.07 MPa. In this way, the foam was heated and foamed while being continuously introduced into a foaming machine, to obtain foamed self-extinguishing polystyrene resin particles. Further, when the melting point of the composite flame retardant (BC ratio 16.7%) was measured by DTA in the same manner as in Example 1, the melting point peak temperature was one and was 103 ° C. Table 1 shows the average cell diameter, bulk expansion ratio, styrene monomer content, and volatile organic compound content after the obtained foamed particles were allowed to stand at room temperature and pressure for one day and dried. The foamed particles were filled in a mold, and heated and foamed with steam to obtain a self-extinguishing foamed foam. Table 1 shows the measurement results of fusion, appearance, and flammability of the obtained foamed molded article.
[0038]
(Comparative Example 1)
To 1 kg of the same polystyrene resin particles as in Example 1, 1.5 g of calcium carbonate fine powder as an anti-bonding agent during foaming and 0.5 g of monoglyceride stearate as an antistatic agent were uniformly adhered to the surface of the resin particles. The vessel was closed and sealed, and then carbon dioxide gas was injected thereinto up to 3.0 MPa and kept at 20 ° C. for 6 hours. Immediately after the internal pressure of the pressure vessel was released, the pressure vessel was charged into a preheated foaming machine, and heated and foamed using heated steam to obtain polystyrene resin foamed particles. Table 1 shows the average cell diameter, bulk expansion ratio, styrene monomer content, and volatile organic compound content after the obtained foamed particles were allowed to stand at room temperature and pressure for one day and dried. Further, a foam molded article was obtained from the foamed particles in the same manner as in Example 1. Table 1 shows the measurement results of the fusion, appearance, and flammability of the obtained foam molded article.
[0039]
(Comparative Example 2)
Polystyrene resin was prepared in the same manner as in Example 1 except that tris (2,3-dibromopropyl) isocyanurate was used in an amount of 60 g (3.0% by weight) and 2,3-dimethyl-2,3-diphenylbutane was not used. Expanded particles were obtained. When the melting point of the flame retardant was measured by DTA in the same manner as in Example 1, the melting point peak temperature was one and was 115 ° C. Table 1 shows the average cell diameter, bulk expansion ratio, styrene monomer content, and volatile organic compound content after the obtained foamed particles were allowed to stand at room temperature and pressure for one day and dried. Further, a self-extinguishing foamed molded article was obtained from the foamed particles in the same manner as in Example 1. Table 1 shows the measurement results of the fusion, appearance, and flammability of the obtained foam molded article.
[0040]
(Comparative Example 3)
Expanded polystyrene resin particles were obtained in the same manner as in Example 1 except that 2,3-dimethyl-2,3-diphenylbutane was changed to 6.0 g (0.3% by weight) of dicumyl peroxide. However, 180 g of bonding was generated with respect to 1 kg of the resin particles charged during foaming. When the melting point of the composite flame retardant (DCP ratio: 16.7%) was measured by DTA in the same manner as in Example 1, the measurement was impossible because DCP was decomposed during the measurement. Table 1 shows the average cell diameter, bulk expansion ratio, styrene monomer content, and volatile organic compound content after the obtained foamed particles were allowed to stand at room temperature and pressure for one day and dried. The foamed particles were filled in a molding die and foamed by heating with steam to obtain a foamed molded product. The obtained foamed molded article had a poor fusion of 30%, shrank in appearance, and could not obtain a good molded article. Table 1 also shows the measurement results of the flammability of the foam molded article.
[0041]
(Comparative Example 4)
Polystyrene resin particles were obtained in the same manner as in Example 1 except that tris (2,3-dibromopropyl) isocyanurate was changed to 30.0 g (1.5% by weight) of tetrabromocyclooctane. The melting point of the composite flame retardant (BC ratio 16.7%) was measured by DTA in the same manner as in Example 1. As a result, the melting point peak temperature was one and was 88 ° C. To 1 kg of the polystyrene resin particles, 1.5 g of calcium carbonate fine powder as a bonding inhibitor at the time of foaming and 0.5 g of monoglyceride stearate as an antistatic agent were uniformly adhered to the surface of the resin particles. Then, carbon dioxide gas was injected to 3.0 MPa, and the mixture was kept at 20 ° C. for 6 hours. Immediately after the internal pressure in the pressure vessel was released, the foamed particles were put into a preheated foaming machine and heated and foamed using pressurized steam.
[0042]
(Comparative Example 5)
Tris (2,3-dibromopropyl) isocyanurate was 40.0 g (2.0% by weight) of tetrabromocyclooctane, and 8.0 g (0.4% by weight) of 2,3-dimethyl-2,3-diphenylbutane. ) To obtain polystyrene resin particles in the same manner as in Example 1. The melting point of the composite flame retardant (BC ratio 16.7%) was measured by DTA in the same manner as in Example 1. As a result, the melting point peak temperature was one and was 88 ° C. To 1 kg of the polystyrene resin particles, 1.5 g of calcium carbonate fine powder as a bonding inhibitor at the time of foaming and 0.5 g of monoglyceride stearate as an antistatic agent were uniformly adhered to the surface of the resin particles. Then, carbon dioxide gas was injected to 3.0 MPa, and the mixture was kept at 20 ° C. for 6 hours. Immediately after the internal pressure in the pressure vessel was released, the foamed particles were put into a preheated foaming machine and heated and foamed using pressurized steam.
[0043]
(Comparative Example 6)
Polystyrene resin particles were obtained in the same manner as in Example 1, except that tris (2,3-dibromopropyl) isocyanurate was changed to 30.0 g (1.5% by weight) of hexabromocyclododecane. However, a flame retardant was left in the reaction solution used for the impregnation reaction, indicating that the polystyrene resin particles were hardly impregnated with the flame retardant. When the melting point of the composite flame retardant (BC ratio 16.7%) was measured by DTA in the same manner as in Example 1, the melting point peak temperature was two, the melting point of BC was 106 ° C, and the melting point of HBCD was 190. ° C. Next, expanded polystyrene resin particles were obtained in the same manner as in Example 1. Table 1 shows the average cell diameter, bulk expansion ratio, styrene monomer content, and volatile organic compound content after the obtained foamed particles were allowed to stand at room temperature and pressure for one day and dried. Further, a foam molded article was obtained from the foamed particles in the same manner as in Example 1. Table 1 shows the measurement results of the fusion, appearance, and flammability of the obtained foam molded article.
[0044]
(Comparative Example 7)
Tris (2,3-dibromopropyl) isocyanurate was 40.0 g (2.0% by weight) of hexabromocyclododecane, and 8.0 g (0.4% by weight) of 2,3-dimethyl-2,3-diphenylbutane. ) To obtain polystyrene resin particles in the same manner as in Example 1. However, a flame retardant was left in the reaction solution used for the impregnation reaction, indicating that the polystyrene resin particles were hardly impregnated with the flame retardant. When the melting point of the composite flame retardant (BC ratio 16.7%) was measured by DTA in the same manner as in Example 1, the melting point peak temperature was two, the melting point of BC was 105 ° C., and the melting point of HBCD was 190. ° C. In addition, expanded polystyrene resin particles were obtained in the same manner as in Example 1. Table 1 shows the average cell diameter, bulk expansion ratio, styrene monomer content, and volatile organic compound content after the obtained foamed particles were allowed to stand at room temperature and pressure for one day and dried. Further, a foam molded article was obtained from the foamed particles in the same manner as in Example 1. Table 1 shows the measurement results of the fusion, appearance, and flammability of the obtained foam molded article.
[0045]
(Comparative Example 8)
Tris (2,3-dibromopropyl) isocyanurate was 60.0 g (3.0% by weight) of hexabromocyclododecane, and 12.0 g (0.6% by weight) of 2,3-dimethyl-2,3-diphenylbutane was used. ) To obtain polystyrene resin particles in the same manner as in Example 1. However, a flame retardant was left in the reaction solution used for the impregnation reaction, indicating that the polystyrene resin particles were hardly impregnated with the flame retardant. When the melting point of the composite flame retardant (BC ratio 16.7%) was measured by DTA in the same manner as in Example 1, the melting point peak temperature was two, the melting point of BC was 106 ° C, and the melting point of HBCD was 190. ° C. In addition, expanded polystyrene resin particles were obtained in the same manner as in Example 1. Table 1 shows the average cell diameter, bulk expansion ratio, styrene monomer content, and volatile organic compound content after the obtained foamed particles were allowed to stand at room temperature and pressure for one day and dried. Further, a foam molded article was obtained from the foamed particles in the same manner as in Example 1. Table 1 shows the measurement results of the fusion, appearance, and flammability of the obtained foam molded article.
[0046]
[Table 1]

[0047]
From Table 1, the foamed particles of Examples 1 to 5 had little bonding at the time of foaming and were excellent in handling. Further, the foamed molded article obtained from the foamed particles was excellent in both the fusion ratio and the appearance, and also exhibited excellent self-extinguishing properties of 3 seconds or less in a combustion test.
The foamed particles and foamed molded article of Comparative Example 1 had a small amount of bonding at the time of foaming and a good fusion rate and appearance, but had extremely poor self-extinguishing properties because they did not contain a flame retardant or a flame retardant auxiliary. .
The foamed particles of Comparative Example 2 had a large amount of bonding at the time of foaming, and were inferior in self-extinguishing properties because they did not contain a flame retardant aid.
The foamed particles and foamed molded article of Comparative Example 3 had more bonding at the time of foaming than Comparative Example 2, and the obtained foamed molded article had a poor fusion rate, the appearance melted, and the entire molded article shrank. The appearance was poor.
In Comparative Examples 4 and 5, the whole foamed particles were bonded at the time of foaming, and no moldable foamed particles were obtained.
The foamed particles and foamed molded articles of Comparative Examples 6 to 8 were good in the bonding amount at the time of foaming, the fusion ratio and the appearance, but were extremely poor in self-extinguishing properties because they did not substantially contain a flame retardant.
Table 2 shows the measurement results of the gloss and the dimensional change of Examples 1 to 5.
[0048]
[Table 2]

[0049]
From Table 2, among the foamed molded articles of Examples 1 to 5, the foamed molded article of Example 5 having a high gloss was a molded article having extremely small dimensional change rate and excellent dimensional stability.
[0050]
(Example 6)
This example is an example in which a styrene resin is formed by suspension polymerization and then a flame retardant and a flame retardant auxiliary are added to the suspension.
A reactor having an inner volume of 100 liters equipped with a stirrer was charged with 30 liters of deionized water, 100 g of magnesium pyrophosphate, and 15 g of sodium dodecylbenzenesulfonate, and had a particle diameter of 0.63 to 0.71 mm and a weight average molecular weight of 280000. 11 kg of polystyrene resin particles (obtained by subjecting styrene to ordinary suspension polymerization in an aqueous medium using magnesium pyrophosphate and sodium dodecylbenzenesulfonate) were added, stirred and suspended.
[0051]
Next, 90 g of benzoyl peroxide and 8 kg of styrene dissolved in 8 g of t-butylperoxybenzoate were added to a previously prepared suspension of 6 liters of deionized water, 2 g of sodium dodecylbenzenesulfonate and 10 g of magnesium pyrophosphate, and the mixture was homogenized with a homomixer. Stirred to a suspension which was added to the reactor maintained at 70 ° C. Then, after maintaining for 1 hour so that the styrene and the polymerization initiator are sufficiently absorbed in the polystyrene particles, styrene is continuously supplied at a rate of 10 kg / hour for 3 hours, and the temperature reaches 105 ° C. at the end of the styrene supply. After the reactor was heated as described above, the temperature was continuously raised to 120 ° C. and maintained for 2 hours. The polymerization conversion at the end of the polymerization was 99.98%.
[0052]
Then, the mixture was cooled to 90 ° C., and 2 liters of previously prepared deionized water, 2 g of sodium dodecylbenzenesulfonate, 690 g of tris (2,3-dibromopropyl) isocyanurate and 138 g of 2,3-dimethyl-2,3-diphenylbutane A composite flame retardant suspension consisting of the following was injected into the reactor, heated to 120 ° C., and held for 3 hours. Further, when the melting point of the composite flame retardant (BC ratio 16.7%) was measured by DTA in the same manner as in Example 1, the melting point peak temperature was one and was 103 ° C. Thereafter, the content was cooled to room temperature, the contents were taken out, washed, dehydrated and dried to obtain self-extinguishing polystyrene resin particles having a particle size of 0.9 to 1.2 mm. The weight average molecular weight of the resin particles was 300,000. Self-extinguishing polystyrene resin foam particles were obtained from the self-extinguishing polystyrene resin particles in the same manner as in Example 1.
Table 3 shows the average cell diameter and bulk expansion ratio after the obtained expanded particles were allowed to stand at room temperature and normal pressure for 1 day and dried. Further, a self-extinguishing foamed molded article was obtained from the foamed particles in the same manner as in Example 1. Table 3 shows the measurement results of the fusion, appearance, and flammability of the obtained foam molded article.
[0053]
[Table 3]

[0054]
From Table 3, the foamed particles of Example 6 have little bonding at the time of foaming even if they are obtained from styrene resin particles obtained by adding a flame retardant and a flame retardant auxiliary to the suspension after polymerization. The handling was good. Furthermore, the foamed molded article obtained from the foamed particles was excellent in both the fusion ratio and the appearance, and also exhibited excellent self-extinguishing properties in a combustion test of 3 seconds or less.
[0055]
(Example 7)
This example is an example for evaluating the recyclability of the foamed molded articles of the examples and the comparative examples.
The melt flow rates (MFR) of the polystyrene resin particles obtained in Examples 1 and 2 and Comparative Examples 1, 3 and 4 were measured. Further, the weight average molecular weight of the resin particles before and after the MFR measurement was also measured. Table 4 shows the MFR and the weight average molecular weight.
[0056]
[Table 4]

[0057]
First, the MFR of a polystyrene resin that can be recycled by being melt-kneaded in an extruder and formed into strands is 20 g / 10 min or less, preferably 15 g / 10 min or less, and particularly close to the MFR when no flame retardant is added. Is preferred. Looking at Table 4 from this viewpoint, the resin particles of Examples 1 and 2 are both 15 g / 10 minutes or less, and are sufficiently recyclable. On the other hand, the resin particles of Comparative Examples 3 and 4 have an MFR exceeding the measurement limit of 200 g / 10 minutes, and are difficult to recycle.
Further, it is desired from the viewpoint of recycling that the weight average molecular weight does not change as much as possible before and after the heat treatment (MFR measurement treatment). If it is significantly reduced, it cannot be extruded as a strand after melt-kneading with an extruder, or the strand frequently breaks, making recycling difficult. Looking at Table 4 from this viewpoint, the resin particles of Examples 1 and 2 have a smaller decrease in the weight average molecular weight as compared with the case where no flame retardant is added, and are sufficiently recyclable. On the other hand, the resin particles of Comparative Examples 3 and 4 have significantly reduced weight average molecular weights, so that even if they are recycled, the strength is significantly reduced and cannot be reused.
[0058]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the styrenic resin foam molded body excellent in self-extinguishing property with good production efficiency and a small flame retardant amount is obtained. The foamed molded article has a low residual styrene monomer content in the foamed molded article, and has a property as a low VOC material because the foaming agent is also an inorganic gas, and is suitable for use as a heat insulating material for buildings or an EPS civil engineering method.
In addition, self-extinguishing styrene resin foam with excellent environmental compatibility that can be recycled together with general styrene resin foam without significantly reducing the molecular weight even when recycled by melt-kneading with an extruder. Is obtained.
[Brief description of the drawings]
FIG. 1 is a graph showing the melting point of a composite flame retardant.
FIG. 2 is a schematic view showing an example of a foaming machine that can be used for producing resin foam particles.
[Explanation of symbols]
2 Stirring motor
3 stirring blade
4 Bar stick
5 Foam tank top detector
6 Expandable particle transporter
7 Measuring tank for expandable particles
8 Expandable particle input device
9 Steam injection control valve
10. Steam chamber
11 Condensate discharge valve
12 Exhaust control valve
13 Foam particle outlet
14 Expanded particle temporary receiver
15 Pneumatic transportation equipment
16 Internal pressure detection / control device
17 Steam inlet
18 Steam introduction pressure gauge
19 Pressure reducing valve
20 Steam pressure gauge

Claims (7)

A styrene-based resin containing a composite flame retardant is obtained by foaming with an inorganic gas as a foaming agent, and the composite flame retardant is tris (2,3-dibromopropyl) isocyanurate. General formula [0001]

[0001]
(Wherein, R1 to R4 are the same or different and each is a methyl or ethyl group), and is composed of 10 to 60% by weight of a flame retardant aid, and 1 to 7 parts by weight based on 100 parts by weight of the styrene resin particles. Self-extinguishing styrene-based resin foamed particles characterized by being contained in parts by weight. The self-extinguishing styrene resin foam particles according to claim 1, wherein the pre-expanded particle plate obtained by pressing the self-extinguishing styrene resin foam particles has a surface glossiness of 30 to 60. The self-extinguishing styrene resin expanded particles according to claim 1, wherein the content of the styrene monomer is 500 ppm or less based on the styrene resin. The self-extinguishing styrene resin foam particles according to claim 1, wherein the flame retardant aid is 2,3-dimethyl-2,3-diphenylbutane or 3,4-dimethyl-3,4-diphenylhexane. The self-extinguishing styrene resin foam particles according to claim 1, wherein the inorganic gas is carbon dioxide gas. A self-extinguishing foam molded article obtained by molding the self-extinguishing styrenic resin expanded particles according to any one of claims 1 to 5 by an in-mold molding method. The self-extinguishing foamed article according to claim 6, wherein the content of the volatile organic compound is 1000 ppm or less based on the styrene resin.

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