JP3970191B2 - Self-extinguishing foamable styrenic resin particles, pre-foamed particles, and foamed molded products - Google Patents

Description

【００１４】
（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）で表される難燃助剤１０〜６０重量％とからなり、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発泡性スチレン系樹脂粒子が提供される。
【００１５】
更に、本発明によれば、上記自己消火型発泡性スチレン系樹脂粒子を予備発泡させて得られた予備発泡粒子が提供される。
【００１６】
また、本発明によれば、上記自己消火型スチレン系予備発泡樹脂粒子を発泡成形して得られた発泡成形体が提供される。
【００１７】
【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℃）からなる難燃剤と、下記一般式
【００１８】
【化３】

【００１９】
（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）で表される難燃助剤とからなる。
【００２０】
難燃助剤の具体例としては、Ｒ１〜Ｒ４がメチル基である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℃）、Ｒ１とＲ２がメチル基、Ｒ３とＲ４がエチル基である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。
【００２１】
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等は見い出している。例えば、横軸が複合難燃剤中の難燃助剤ＢＣの割合を、縦軸が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％とからな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。
【００２２】
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。
【００２３】
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％の割合で使用される。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。
【００２４】
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合せは、ＴＤＩＣとＢＣの組合せである。
【００２５】
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、十分な自己消火性が得られない。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。より好ましい含有割合は、１〜５重量部である。
【００２６】
本発明に使用できるスチレン系樹脂粒子としては、スチレン系であれば特に限定されない。例えば、スチレン単独重合体であっても、スチレンとそれと共重合可能な他のモノマーとの共重合体であってもよい。他のモノマーとしては、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が挙げられる。なお、本明細書では、スチレン及びスチレンと共重合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、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が挙げられる。混合の方法としては、押出機での押出ブレンドの他、重合ブレンド（水性媒体中でポリエチレン樹脂粒子等のスチレン系樹脂以外の樹脂粒子にスチレンモノマーを含浸させて重合させる方法）が挙げられる。
【００２７】
自己消火型発泡性スチレン系樹脂粒子に含まれる易揮発性発泡剤としては、プロパン、ブタン、ペンタン、ヘキサン、それらの異性体等の脂肪族炭化水素、シクロブタン、シクロペンタン等の脂環式炭化水素、ジフルオロエタン、テトラフルオロエタン等のフッ化炭化水素等が挙げられる。特に好ましい易揮発性発泡剤は、ノルマルブタンとイソブタンの混合物である。易揮発性発泡剤は、スチレン系樹脂１００重量部に対して、２〜１０重量部含まれていることが好ましい。易揮発性発泡剤の含有量が２重量部未満の場合、成形体の低密度化が困難であるばかりでなく、成形時に二次発泡力を高める効果が得られず成形体の外観が劣る場合があるため好ましくない。１０重量部を超える場合、成形体中に残存する発泡剤量が多くなり、自己消火性が劣る場合があるだけでなく、成形サイクルが長くなる場合があり、生産性の観点からも好ましくない。より好ましい含有量は、３〜８重量部である。
【００２８】
自己消火型発泡性スチレン系樹脂粒子の平均粒径は、用途に応じて適宜選択でき、例えば、０．３〜３ｍｍの平均粒径のものを使用することができる。
より好ましい平均粒径は、０．５〜２ｍｍである。
【００２９】
自己消火型発泡性スチレン系樹脂粒子には、更に添加剤が含まれていてもよい。添加剤としては、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、動植物硬化油等の滑剤、トルエン、シクロヘキサン、ジイソブチルアジペート等の発泡助剤、可塑剤、気泡調整剤、気泡安定剤、充填剤、着色剤、酸化防止剤、紫外線吸収剤等が挙げられる。これら添加剤は、粒子の製造時や、複合難燃剤の含浸又は混練時に粒子に含ませることができる。
【００３０】
自己消火型発泡性スチレン系樹脂粒子の製造方法としては、懸濁重合法や、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法が好ましい。
【００３１】
また、発泡剤の含浸方法としては、懸濁重合時又は懸濁重合とは別に含浸させる方法が挙げられる。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、従来から懸濁重合において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化合物等が挙げられる。難水溶性無機化合物を用いる場合には、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挙げられる。
【００３２】
懸濁重合法において、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。
【００３３】
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、撹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。更に、易揮発性発泡剤及び／又は上記添加剤と同時に含浸させることが好ましい。
【００３４】
含浸をより円滑に行うために、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。
【００３５】
複合難燃剤及び易揮発性発泡剤が含浸された自己消火型発泡性スチレン系樹脂粒子は、必要に応じて水性媒体から取り出される。取り出した粒子は、洗浄及び脱水乾燥させてもよい。
【００３６】
本発明では、上記自己消火型発泡性スチレン系樹脂粒子を予備発泡させた予備発泡粒子も提供される。予備発泡方法は、公知の方法をいずれも使用することができる。例えば、発泡ポリスチレンビーズ用予備発泡機を用いて、通常の条件で、製造することができる。また、発泡性樹脂粒子には適当な表面処理剤による処理がなされていてもよい。表面処理剤には、結合防止剤、帯電防止剤、滑剤、融着促進剤、ハイサイクル剤、離型剤等の公知のものを用いることができる。この他にも紫外線吸収剤、防錆剤、木材用防腐剤、防蟻剤、防黴剤、抗菌剤、香料、着色剤等の公知の添加剤を表面処理剤と併用してもよい。表面処理の方法は、タンブラーミキサー、ナウターミキサー、レディゲミキサー、プロシェアミキサーリボンブレンダー等の混合機を用いた公知の方法を用いることができる。なお、予備発泡粒子の嵩密度は、０．００８〜０．２ｇ／ｃｍ³の範囲であることが好ましい。
【００３７】
更に、本発明では、上記予備発泡粒子を成形した発泡成形体も提供される。成形方法は、公知の方法をいずれも使用することができる。具体的には、予備発泡粒子を成形用金型内に充填し、金型内へ蒸気を吹き込んで予備発泡粒子を加熱する。蒸気との接触によって予備発泡粒子が加熱されると、予備発泡粒子は膨張するが、成形用金型によって発泡できる空間が限定されているので、互いに密着すると共に融着一体化して所望の発泡成形体が得られる。
【００３８】
本発明の発泡成形体は、壁材、床材、天井材等の建築用断熱材の原料、ＥＰＳ土木工法の原料、包装材の原料として好適に使用できる。
【００３９】
上記発泡成形体は、難燃剤の含まれていない一般のポリスチレン発泡成形体と同様に押出機で減容や溶融混練してリサイクルしても、従来の自己消火型発泡性スチレン系樹脂粒子から得られる発泡成形体をリサイクルするよりも樹脂の劣化が少なく、リサイクル性の高い成形体である。
【００４０】
【実施例】
以下、実施例及び比較例により本発明を更に具体的に説明するが、本発明はこれらに限定されるものではない。
【００４１】
まず、スチレン系樹脂粒子、発泡粒子及び発泡成形体の評価方法を以下に示す。
【００４２】
［重合転化率の定量］
重合転化率は以下の式で算出した。
【００４３】
重合転化率（％）＝１００×（Ａ−Ｂ)／Ａ
但し、Ａは未反応の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。ＧＣによるスチレン単量体の定量は、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）を加えて以下の条件で測定した。
【００４４】
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℃
【００４５】
［重量平均分子量］
スチレン樹脂粒子の重量平均分子量（Ｍｗ）は、ＧＰＣ（ゲルパーミエイションクロマトグラフィー）によって、以下の条件で測定した。なお、重量平均分子量の測定に際して、測定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、検量線は、重量平均分子量が２．７４×１０³、１．９１×１０⁴、１．０２×１０⁵、３．５５×１０⁵、２．８９×１０⁶、４．４８×１０⁶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）を用いて以下の条件で作成した。
【００４６】
ＧＰＣ：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
【００４７】
［平均気泡径］
無作為に取り出した発泡粒子をカッターで略二分割し、一方の切断面を走査型電子顕微鏡にて４０倍に拡大して写真撮影した。その写真上に発泡粒子の直径となるように直線を引き、この直線上に掛かる全ての気泡の最大径を測定する。この測定を１０個の発泡粒子に対して行い、求められた該最大径の相加平均値を発泡粒子の平均気泡径とした。
【００４８】
［融着率］
長さ４００ｍｍ、幅３００ｍｍ、厚み３０ｍｍの平板形状の発泡成形体の表面に、一対の長辺の中心同士を結ぶ直線に沿ってカッターナイフで深さ約５ｍｍの切り込み線を入れた後、この切り込み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）と粒子どうしの界面で破断している粒子の数（ｂ）とを数え、式［（ａ）／（（ａ）＋（ｂ））］×１００に代入して得られた値を融着率（％）とした。
【００４９】
［燃焼性］
ＪＩＳ Ａ−９５１１に基づき、自己消火性を測定した。ＪＩＳ規格から、自己消火時間が３．０秒以内であることが望まれ、２．０秒以内が好ましい。なお、成形後に５０℃で２４時間養生した発泡成形体を測定試料とした。
【００５０】
実施例１
撹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を反応器に入れ撹拌し、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。
【００５１】
内容積５リットルの撹拌機付き圧力容器に、水２リットルに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、トルエン２０ｇを懸濁させた懸濁液を入れ、撹拌しながら上記ポリスチレン樹脂粒子２ｋｇと、トリス（２，３−ジブロモプロピル）イソシアヌレート（難燃剤：ＴＤＩＣ）１．５重量％及び２，３−ジメチル−２，３−ジフェニルブタン（難燃助剤：ＢＣ）０．３重量％からなる複合難燃剤を入れて容器を密閉し、引き続き撹拌しながら１００℃まで昇温した後に、１００℃の含浸温度でノルマルブタン９８ｇとイソブタン４２ｇを圧入し３時間保持した。次いで、２５℃まで冷却し、圧力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うことで、自己消火型発泡性ポリスチレン樹脂粒子を得た。
【００５２】
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、以下の条件でＤＴＡ測定することで求めた。
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
【００５３】
この発泡性樹脂粒子を２０℃の恒温室で５日間保持した後に、予備発泡機で発泡し、予備発泡粒子を得た。得られた予備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１に示す。また、予備発泡粒子５００ｇ中、互に結合した粒子の量を測定し、予備発泡時結合量として表１に示す。
【００５４】
この予備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（平板形状：長さ４００ｍｍ、幅３００ｍｍ、厚み３０ｍｍ）。得られた発泡成形体の融着率、外観及びＪＩＳ Ａ９５１１の燃焼試験Ａ法にて燃焼性を測定した結果を表１に示す。
【００５５】
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２．０重量％及び２，３−ジメチル−２，３−ジフェニルブタンを０．４重量％使用すること以外は実施例１と同様にして、自己消火性発泡性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１０３℃であった。
【００５６】
また、実施例１と同様にして予備発泡粒子を得、平均気泡径、嵩発泡倍率及び予備発泡時結合量として表１に示す。
【００５７】
更に、実施例１と同様にして発泡成形体を得、融着率、外観及び燃焼性を測定した結果を表１に示す。
【００５８】
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３．０重量％及び２，３−ジメチル−２，３−ジフェニルブタンを０．４重量％使用すること以外は実施例１と同様にして、自己消火性発泡性ポリスチレン樹脂粒子を得た。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。
【００５９】
また、実施例１と同様にして予備発泡粒子を得、平均気泡径、嵩発泡倍率及び予備発泡時結合量として表１に示す。
【００６０】
更に、実施例１と同様にして発泡成形体を得、融着率、外観及び燃焼性を測定した結果を表１に示す。
【００６１】
実施例４
難燃助剤を３，４−ジメチル−３，４−ジフェニルヘキサン（ＤＤＰＨ）に代えること以外は実施例１と同様にして、自己消火性発泡性ポリスチレン樹脂粒子を得た。また、複合難燃剤（ＤＤＰＨ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。
【００６２】
また、実施例１と同様にして予備発泡粒子を得、平均気泡径、嵩発泡倍率及び予備発泡時結合量として表１に示す。
【００６３】
更に、実施例１と同様にして発泡成形体を得、融着率、外観及び燃焼性を測定した結果を表１に示す。
【００６４】
比較例１
難燃剤及び難燃助剤を使用しないこと以外は実施例１と同様にして、発泡性ポリスチレン樹脂粒子を得た。
【００６５】
また、実施例１と同様にして予備発泡粒子を得、平均気泡径、嵩発泡倍率及び予備発泡時結合量として表１に示す。
【００６６】
更に、実施例１と同様にして発泡成形体を得、融着率、外観及び燃焼性を測定した結果を表１に示す。
【００６７】
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３．０重量％使用し、難燃助剤を使用しないこと以外は実施例１と同様にして、発泡性ポリスチレン樹脂粒子を得た。また、難燃剤（ＢＣ割合０％）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。
【００６８】
また、実施例１と同様にして予備発泡粒子を得、平均気泡径、嵩発泡倍率及び予備発泡時結合量として表１に示す。
【００６９】
更に、実施例１と同様にして発泡成形体を得、融着率、外観及び燃焼性を測定した結果を表１に示す。
【００７０】
比較例３
難燃助剤としてジクミルパーオキサイド（ＤＣＰ）を使用したこと以外は実施例１と同様にして、発泡性ポリスチレン樹脂粒子を得た。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できなかった。
【００７１】
また、実施例１と同様にして予備発泡粒子を得、平均気泡径、嵩発泡倍率及び予備発泡時結合量として表１に示す。
【００７２】
更に、実施例１と同様にして発泡成形体を得、融着率、外観及び燃焼性を測定した結果を表１に示す。
【００７３】
比較例４
難燃剤としてテトラブロモシクロオクタン（ＴＢＣＯ）を使用したこと以外は実施例１と同様にして、発泡性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。
【００７４】
また、実施例１と同様にして予備発泡粒子を得、平均気泡径、嵩発泡倍率及び予備発泡時結合量として表１に示す。
【００７５】
更に、実施例１と同様にして発泡成形体を得、融着率、外観及び燃焼性を測定した結果を表１に示す。
【００７６】
比較例５
難燃剤としてヘキサブロモシクロドデカン（ＨＢＣＤ）を使用したこと以外は実施例１と同様にして、発泡性ポリスチレン樹脂粒子を得た。ただし、圧力容器内には、ヘキサブロモシクロドデカンが樹脂粒子に吸収されずに残っていた。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に由来する融点は１０６℃、ＨＢＣＤに由来する融点は１９０℃であった。
【００７７】
また、実施例１と同様にして予備発泡粒子を得、平均気泡径、嵩発泡倍率及び予備発泡時結合量として表１に示す。
【００７８】
更に、実施例１と同様にして発泡成形体を得、融着率、外観及び燃焼性を測定した結果を表１に示す。
【００７９】
比較例６
難燃剤の添加量を３．０重量％、難燃助剤の添加量を０．６重量％としたこと以外は比較例５と同様にして、発泡性ポリスチレン樹脂粒子を得た。圧力容器内には、比較例５と同様に、ヘキサブロモシクロドデカンが樹脂粒子に吸収されずに残っていた。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に由来する融点は１０６℃、ＨＢＣＤに由来する融点は１９０℃であった。
【００８０】
また、実施例１と同様にして予備発泡粒子を得、平均気泡径、嵩発泡倍率及び予備発泡時結合量として表１に示す。
【００８１】
更に、実施例１と同様にして発泡成形体を得、融着率、外観及び燃焼性を測定した結果を表１に示す。
【００８２】
表１中、ＴＤＩＣはトリス（２，３−ジブロモプロピル）イソシアヌレート、ＴＢＣＯはテトラブロモシクロオクタン、ＨＢＣＤはヘキサブロモシクロドデカン、ＢＣは２，３−ジメチル−２，３−ジフェニルブタン、ＤＤＰＨは３，４−ジメチル−３，４−ジフェニルヘキサン、ＤＣＰはジクミルパーオキサイドを意味する。
【００８３】
【表１】

【００８４】
表１から、実施例１〜４の予備発泡粒子は、予備発泡時の結合が少なく、取り扱いが良好であった。更に、この予備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。
【００８５】
比較例１の予備発泡粒子及び発泡成形体は、予備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。
【００８６】
比較例２の予備発泡粒子は、難燃助剤を含まないため、得られた発泡成形体の自己消火性が極めて劣っていた。
【００８７】
比較例３の予備発泡粒子は、予備発泡時結合量が比較例２より多く、得られた発泡成形体の融着率は悪く、外観は表面が融け、かつ全体が収縮していた。自己消火性も実施例１〜４より劣っていた。
【００８８】
比較例４の予備発泡粒子は、予備発泡時結合量が比較例３より多く、得られた発泡成形体の融着率は悪く、外観は表面が融け、かつ全体が収縮していた。自己消火性も実施例１〜４より劣っていた。
【００８９】
比較例５と６の予備発泡粒子は、予備発泡時結合量、融着率及び外観は良好であるが、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。
【００９０】
実施例５
この実施例は、懸濁重合によりスチレン樹脂粒子の形成後、懸濁液中に難燃剤及び難燃助剤を添加した例である。
【００９１】
撹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、更に粒子径が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、公知の懸濁重合を行って得た粒子）１１ｋｇを加えて撹拌することで懸濁させた。
【００９２】
次いで、脱イオン水６リットル、ピロリン酸マグネシウム１０ｇ、ドデシルベンゼンスルホン酸ナトリウム２ｇからなる懸濁液を予め用意し、この懸濁液に重合開始剤としてベンゾイルパーオキサイド９０ｇとｔ−ブチルパーオキシベンゾエート８ｇを溶解したスチレン５ｋｇを加え、ホモミキサーで撹拌して懸濁液とし、これを７０℃に保持した上記反応器に添加した。
【００９３】
添加後、ポリスチレン樹脂粒子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、スチレンを連続的に１０ｋｇ／時の速度で３時間供給した。また、スチレン供給終了時に、反応器内の温度が１０５℃になるように徐々に昇温した。引き続き１２０℃に昇温して２時間保持することで、重合転化率を９９．９８％とした。
【００９４】
次いで、水２リットルにドデシルベンゼンスルホン酸ナトリウム２ｇと、ピロリン酸マグネシウム１６ｇと、トルエン４６０ｇと、トリス（２，３−ジブロモプロピル）イソシアヌレート（難燃剤：ＴＤＩＣ）６９０ｇ（１．５重量％）及び２，３−ジメチル−２，３−ジフェニルブタン（難燃助剤：ＢＣ）１３８ｇ（０．３重量％）を懸濁させた懸濁液を予め用意し、この懸濁液を反応器に圧入した後に１００℃に冷却した。次いで、１００℃の含浸温度でノルマルブタン２．２５ｋｇとイソブタン０．９５ｋｇを圧入し３時間保持した。次いで、常温（約２５℃）まで冷却し、圧力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うことで、粒子径が０．９〜１．２ｍｍの自己消火型発泡性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３０００００であった。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。
【００９５】
この発泡性樹脂粒子を２０℃の恒温室で５日間保持した後に、予備発泡機で発泡し、予備発泡粒子を得た。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２に示す。また、予備発泡時結合量も表２に示す。
【００９６】
この予備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の融着率、外観及びＪＩＳ Ａ９５１１の燃焼試験Ａ法にて燃焼性を測定した結果を表２に示す。
【００９７】
【表２】

【００９８】
表２から、実施例５の予備発泡粒子は、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発泡性スチレン樹脂粒子から得られていても、予備発泡時の結合が少なく、取り扱いが良好であった。更に、この予備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。
【００９９】
実施例６
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。
【０１００】
実施例１と２及び比較例１、３と４で得られた発泡性ポリスチレン樹脂粒子のメルトフローレート（ＭＦＲ）を以下の条件で測定した。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３に示す。
【０１０１】
［ＭＦＲの測定］
ＭＦＲの測定は、ＪＩＳ Ｋ７２１０に基づき下記の条件で行った。まず、測定試料は、実施例及び比較例にて得られた発泡性ポリスチレン樹脂粒子を、５０℃のオーブン中で到達圧力１０Ｐａで真空吸引しながら２４時間保持し、樹脂粒子中の揮発性有機化合物を除去したものを用いた。
【０１０２】
測定装置：東洋精機製作所社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
【０１０３】
【表３】

【０１０４】
まず、押出機で溶融混練し、ストレ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（比較例１）のＭＦＲに近いことが好ましい。この観点から表３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。
【０１０５】
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３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の低下は小さく、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。
【０１０６】
【発明の効果】
本発明の自己消火型発泡性スチレン系樹脂粒子によれば、スチレン系樹脂粒子へ含浸しやすい難燃剤及び難燃助剤を使用しているため、少量の難燃剤及び難燃助剤で所定の自己消火性を発泡成形品に与えることができる。
【０１０７】
また、本発明の自己消火型発泡成形体は、それを熱処理しても重量平均分子量低下が小さいため、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であり、環境にやさしい発泡成形体である。
【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。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a self-extinguishing foamable styrene resin particle, a pre-foamed particle and a foamed molded article containing a composite flame retardant comprising a specific flame retardant and a flame retardant aid. More specifically, the present invention relates to recyclable self-extinguishing foamable styrene resin particles, pre-foamed particles, and foamed molded articles. The self-extinguishing foamable styrene resin particles, pre-expanded particles and foamed molded products of the present invention are used as raw materials for building insulation materials such as wall materials, flooring materials and ceiling materials, as raw materials for EPS civil engineering methods, and as raw materials for packaging materials. It can be used suitably.
[0002]
[Prior art]
In order to impart self-extinguishing properties to styrene-based resins, it is known to use a flame retardant or a composite flame retardant in which a flame retardant and a flame retardant aid are combined. Common flame retardants include halogen-based flame retardants such as tetrabromocyclooctane, hexabromocyclododecane, tetrabromobisphenol A diallyl ether, tris (2,3-dibromopropyl) isocyanurate, and flame retardant aids , Dicumyl peroxide, cumene hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, and the like.
[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 aid. Expandable styrenic resin particles are described.
[0004]
JP-A-9-255879 (Patent Document 2) describes a styrene-based flame retardant resin composition using tris (2,3-dibromopropyl) isocyanurate as a flame retardant.
[0005]
Further, JP-A-11-130898 (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. Are listed.
[0006]
[Patent Document 1]
JP 60-206845 A
[Patent Document 2]
JP-A-9-255879
[Patent Document 3]
JP-A-11-130898
[0007]
[Problems to be solved by the invention]
In order to impart self-extinguishing properties to the expandable styrenic resin particles, the pre-expanded particles obtained therefrom, and the foamed molded product, it is desirable that the flame retardant is uniformly dispersed in the particles and the molded product.
[0008]
From the above point of view, even if the flame retardant has a relatively high melting point and a large molecular weight such as hexabromocyclododecane, it will increase the molecular weight of the styrene resin because it will inhibit the polymerization of the styrene monomer when added during suspension polymerization. Is difficult, and the strength of the resin is reduced. On the other hand, a method of impregnating the particles after polymerization is conceivable. However, in this method, the flame retardant has a high melting point, so the styrene resin particles can hardly be impregnated, and this method can provide self-extinguishing properties. It becomes difficult. Therefore, it is limited to the method of mixing and dispersing the molten resin and the flame retardant as in the extrusion method, and as a result, the manufacturing process becomes complicated.
[0009]
Tris (2,3-dibromopropyl) isocyanurate has a low melting point and can be impregnated into the expandable styrene resin particles relatively uniformly even by the impregnation method. Therefore, self-extinguishing properties are low, and further improvement of self-extinguishing properties is desired.
[0010]
For this purpose, an organic peroxide such as dicumyl peroxide or cumene hydroperoxide is added as a flame retardant aid. As an effect, it is considered that the self-extinguishing property is efficiently imparted to the foamed molded body in a smaller amount by generating radicals during combustion. However, when such organic peroxides are melted and kneaded at the time of recycling, radicals are generated, the radicals decompose the styrene-based resin, leading to a decrease in molecular weight, and the quality such as strength of the recycled resin is improved. There is a problem of making it worse.
[0011]
[Means for Solving the Problems]
The inventors of the present invention have studied combinations of various flame retardants and flame retardant aids. As a result, a composite flame retardant containing a specific ratio of the following types of flame retardants and flame retardant aids is an expandable styrene type. As a flame retardant for resin particles, the present inventors have surprisingly found that the molecular weight is not easily lowered during recycling, can exhibit excellent self-extinguishing properties, and the method for dispersing the resin particles is not limited.
[0012]
Thus, according to the present invention, at least the composite flame retardant comprising the styrene resin particles, the readily volatile foaming agent, and the flame retardant and the flame retardant aid is included, and the composite flame retardant is tris (2,3-dibromopropyl). 90-40% by weight of a flame retardant composed of isocyanurate and the following general formula
[0013]
[Chemical 2]

[0014]
(Wherein, R1 to R4 are the same or different and are methyl or ethyl groups) and represented by 10 to 60% by weight of a flame retardant aid, and 1 to 7 with respect to 100 parts by weight of styrene resin particles. Self-extinguishing foamable styrenic resin particles characterized in that they are contained in parts by weight are provided.
[0015]
Furthermore, according to the present invention, pre-expanded particles obtained by pre-expanding the self-extinguishing foamable styrene resin particles are provided.
[0016]
Moreover, according to this invention, the foaming molding obtained by foam-molding the said self-extinguishing styrene-type pre-expanded resin particle is provided.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The composite flame retardant used in the present invention includes a flame retardant comprising tris (2,3-dibromopropyl) isocyanurate (hereinafter also referred to as TDIC, melting point 115 ° C., decomposition temperature 285 ° C.), and the following general formula:
[0018]
[Chemical 3]

[0019]
(Wherein, R1 to R4 are the same or different and are methyl or ethyl groups).
[0020]
Specific examples of flame retardant aids include 2,3-dimethyl-2,3-diphenylbutane (hereinafter referred to as biscumyl, in which R1 to R4 are methyl groups, hereinafter also referred to as BC. Melting point 113 ° C., decomposition temperature 205 ° C. ), 3,4-dimethyl-3,4-diphenylhexane (melting point 142 ° C., decomposition temperature 230 ° C.) in which R 1 and R 2 are methyl groups and R 3 and R 4 are ethyl groups.
[0021]
Since the flame retardant and the flame retardant aid have a relatively close melting point, the composite flame retardant mixed with them forms a peak having almost one melting point (this temperature is referred to as a melting point peak temperature). Further, the inventors have found that the melting point peak temperature of the composite flame retardant is lower than the melting point of the flame retardant and the flame retardant aid alone due to the melting point drop. For example, as shown in FIG. 1 where the horizontal axis represents the ratio of the flame retardant aid BC in the composite flame retardant and the vertical axis represents the melting point peak temperature of the composite flame retardant, the composite flame composed of 70% by weight of TDIC and 30% by weight of BC. In the case of a 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 further lowered.
[0022]
In addition, it is preferable that melting | fusing point peak temperature exists in the range of 80-140 degreeC. When the melting point peak temperature is lower than 80 ° C., it is not preferable because the resin particles coalesce at the time of impregnation or the flame retardant bleeds at the time of kneading, and the foamed particles coalesce at the time of preliminary foaming. On the other hand, if it exceeds 140 ° C., the impregnation efficiency and the dispersibility during kneading may be inferior. A more preferable melting point peak temperature is 90 to 130 ° C.
[0023]
In the present invention, the flame retardant and the flame retardant aid are used in a ratio of 90 to 40% by weight and 10 to 60% by weight. When the ratio of the flame retardant aid is less than 10% by weight, it is necessary to use a large amount of the composite flame retardant for the self-extinguishing property, and as a result, the recyclability is hindered. In addition, 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 it exceeds 60% by weight, the ratio of the flame retardant is reduced, so that the self-extinguishing property is inferior. In addition, the melting point peak temperature does not decrease so much and the impregnation temperature or kneading temperature must be increased. The ratio of a more preferable flame retardant and a flame retardant adjuvant is 90 to 60 weight% and 10 to 40 weight%.
[0024]
In the present invention, a more preferable combination of the flame retardant and the flame retardant aid is a combination of TDIC and BC.
[0025]
The content rate of a composite flame retardant is 1-7 weight part with respect to 100 weight part of styrene resin particles. If it is less than 1 part by weight, sufficient self-extinguishing properties cannot be obtained. On the other hand, when it exceeds 7 parts by weight, the self-extinguishing effect is saturated and is not economical. A more preferable content ratio is 1 to 5 parts by weight.
[0026]
The styrene resin particles that can be used in the present invention are not particularly limited as long as they are styrene. For example, it may be a styrene homopolymer or a copolymer of styrene and another monomer copolymerizable therewith. Examples of other monomers include α-methylstyrene, vinyltoluene, acrylonitrile, methyl methacrylate, glycidyl methacrylate, butyl acrylate, methacrylic acid, divinylbenzene, and alkylene glycol dimethacrylate. In the present specification, styrene and monomers copolymerizable with styrene are also referred to as styrene monomers. Furthermore, the styrene resin may be a mixed resin with other resins. Examples of other resins include polyethylene, polypropylene, polyphenylene ether, and rubber-modified styrene resin. As a mixing method, in addition to extrusion blending in an extruder, polymerization blending (a method in which resin particles other than styrenic resins such as polyethylene resin particles are impregnated with a styrene monomer in an aqueous medium and polymerized) is exemplified.
[0027]
The volatile foaming agents contained in the self-extinguishing foamable styrene resin particles include aliphatic hydrocarbons such as propane, butane, pentane, hexane and isomers thereof, and alicyclic hydrocarbons such as cyclobutane and cyclopentane. Fluorinated hydrocarbons such as difluoroethane and tetrafluoroethane. A particularly preferred readily volatile blowing agent is a mixture of normal butane and isobutane. The readily volatile foaming agent is preferably contained in an amount of 2 to 10 parts by weight with respect to 100 parts by weight of the styrene resin. When the content of the easily volatile foaming agent is less than 2 parts by weight, it is difficult not only to lower the density of the molded body, but also the appearance of the molded body is inferior because the effect of increasing the secondary foaming power cannot be obtained during molding. This is not preferable. When the amount exceeds 10 parts by weight, not only the amount of the foaming agent remaining in the molded product is increased and the self-extinguishing property may be inferior, but the molding cycle may be prolonged, which is not preferable from the viewpoint of productivity. A more preferable content is 3 to 8 parts by weight.
[0028]
The average particle diameter of the self-extinguishing foamable styrene resin particles can be appropriately selected according to the application, and for example, an average particle diameter of 0.3 to 3 mm can be used.
A more preferable average particle diameter is 0.5 to 2 mm.
[0029]
The self-extinguishing foamable styrene resin particles may further contain an additive. Examples of additives include higher fatty acid amides, aromatic bisamides, ethylene bisstearyl amides, higher fatty acids, paraffins, waxes, hardened animal and vegetable oils, foaming aids such as toluene, cyclohexane, diisobutyl adipate, plasticizers, and bubble regulators. , Bubble stabilizers, fillers, colorants, antioxidants, ultraviolet absorbers and the like. These additives can be included in the particles during the production of the particles or during the impregnation or kneading of the composite flame retardant.
[0030]
Examples of the method for producing self-extinguishing foamable styrene resin particles include a suspension polymerization method and a method of pelletizing extruded strands after melt-kneading a styrene resin and a composite flame retardant with an extruder. Among these, the suspension polymerization method is preferable from the viewpoint of production efficiency.
[0031]
Examples of the impregnation method of the foaming agent include a method of impregnation at the time of suspension polymerization or separately from suspension polymerization. It is preferable to add a suspension stabilizer to the aqueous medium used for impregnation in order to prevent bonding of styrene resin particles during impregnation. Examples of the suspension stabilizer include water-soluble polymers such as known polyvinyl alcohol, methyl cellulose, polyacrylamide, and polyvinyl pyrrolidone that are conventionally used in suspension polymerization, and tricalcium phosphate, hydroxyapatite, magnesium pyrophosphate, and the like. Examples include hardly water-soluble inorganic compounds. When using a poorly water-soluble inorganic compound, an anionic surfactant is usually used in combination. Examples of anionic surfactants include fatty acid soaps, N-acyl amino acids or salts thereof, carboxylates such as alkyl ether carboxylates, alkylbenzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinate esters, alkyl sulfoacetic acids. Salts, sulfonates such as α-olefin sulfonates; sulfates such as higher alcohol sulfates, alkyl ether sulfates, polyoxyethylene alkylphenyl ether sulfates; alkyl ether phosphates, alkyl phosphates Examples thereof include phosphate ester salts such as salts.
[0032]
Examples of the method of impregnating the resin particles with the composite flame retardant in the suspension polymerization method include a step where the polymerization conversion rate is 99.8% or more, or a method of adding and impregnating the resin particles in an aqueous medium after the completion of polymerization. It is preferable to impregnate when the polymerization conversion rate is 99.8% or more because styrene resin particles having a predetermined molecular weight can be easily obtained.
[0033]
The method of adding the composite flame retardant is, for example, a method in which the flame retardant and the flame retardant aid are added separately or simultaneously in an aqueous medium, and the powdered state after mixing the flame retardant and the flame retardant aid with a super mixer or the like. Examples thereof include a method of charging into an aqueous medium as it is, and a method of charging a suspension dispersed uniformly in a pre-dispersion tank equipped with a stirring device into the aqueous medium. Furthermore, it is preferable to impregnate simultaneously with a volatile foaming agent and / or the said additive.
[0034]
In order to perform the impregnation more smoothly, it is preferable to warm the aqueous medium. Specifically, it is preferable to heat at a temperature of 70 to 120 ° C. for 1 to 6 hours.
[0035]
The self-extinguishing foamable styrene resin particles impregnated with the composite flame retardant and the readily volatile foaming agent are taken out from the aqueous medium as necessary. The removed particles may be washed and dehydrated and dried.
[0036]
The present invention also provides pre-expanded particles obtained by pre-expanding the self-extinguishing foamable styrene resin particles. Any known method can be used as the pre-foaming method. For example, it can be produced under normal conditions using a pre-foaming machine for expanded polystyrene beads. Further, the foamable resin particles may be treated with a suitable surface treatment agent. As the surface treatment agent, known ones such as a binding inhibitor, an antistatic agent, a lubricant, a fusion accelerator, a high cycle agent, and a release agent can be used. In addition, known additives such as ultraviolet absorbers, rust preventives, wood preservatives, antifungal agents, antifungal agents, antibacterial agents, fragrances, and colorants may be used in combination with the surface treatment agent. As a surface treatment method, a known method using a mixer such as a tumbler mixer, a Nauter mixer, a Redige mixer, a Proshear mixer ribbon blender, or the like can be used. The bulk density of the pre-expanded particles is 0.008 to 0.2 g / cm. ^Three It is preferable that it is the range of these.
[0037]
Furthermore, the present invention also provides a foamed molded product obtained by molding the above pre-expanded particles. As the molding method, any known method can be used. Specifically, the pre-expanded particles are filled into a molding die, and steam is blown into the mold to heat the pre-expanded particles. When pre-expanded particles are heated by contact with steam, the pre-expanded particles expand, but the space that can be expanded by the molding die is limited. The body is obtained.
[0038]
The foamed molded product of the present invention can be suitably used as a raw material for building heat insulating materials such as wall materials, floor materials, ceiling materials, raw materials for EPS civil engineering methods, and raw materials for packaging materials.
[0039]
The above foamed molded product can be obtained from conventional self-extinguishing foamable styrene resin particles even if it is recycled by volume reduction, melting and kneading with an extruder, in the same way as general polystyrene foam molded products not containing a flame retardant. It is a molded product with less resin degradation and higher recyclability than recycling the foamed molded product.
[0040]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to these.
[0041]
First, evaluation methods for styrene resin particles, expanded particles, and expanded molded articles are shown below.
[0042]
[Quantification of polymerization conversion rate]
The polymerization conversion rate was calculated by the following formula.
[0043]
Polymerization conversion rate (%) = 100 × (AB) / A
However, A is the weight (g) of the styrene resin particle containing an unreacted styrene monomer, and B is the weight of the unreacted monomer in the resin particle containing the unreacted styrene monomer. (G). B is quantified by, for example, gas chromatography (GC). The styrene monomer was quantified by GC by measuring styrene resin particles in N, N-dimethylformamide and adding an internal standard solution (cyclopentanol) under the following conditions.
[0044]
GC: Shimadzu Corporation GC-14A
Column: PEG-20M PT25% 60/80 (2.5 m)
Column temperature: 105 ° C
Detector (FID) temperature: 220 ° C
[0045]
[Weight average molecular weight]
The weight average molecular weight (Mw) of the styrene resin particles was measured by GPC (gel permeation chromatography) under the following conditions. In the measurement of the weight average molecular weight, the molecular weight distribution of the measurement sample is included in a range in which the logarithm of the molecular weight and the count number of the calibration curve prepared by several monodisperse polystyrene standard samples are linear. Selected. The calibration curve has a weight average molecular weight of 2.74 × 10. ^Three 1.91 × 10 ^Four 1.02 × 10 ^Five 3.55 × 10 ^Five 2.89 × 10 ⁶ 4.48 × 10 ⁶ It was created under the following conditions using 6 polystyrene standard samples (TSK standard polystyrene) manufactured by Tosoh Corporation.
[0046]
GPC: Tosoh Corporation high-speed GPC device HLC-8020
Column: manufactured by Sekisui Fine Chemical Co., Ltd. HSG-60S × 2, HSG-40H × 1, HSG-20H × 1
Column temperature: 40 ° C
Mobile phase: THF (tetrahydrofuran)
Flow rate: 1.0 ml / min
Injection volume: 500ml
Detector: RID-6A manufactured by Tosoh Corporation
[0047]
[Average bubble diameter]
Randomly removed foam particles were roughly divided into two by a cutter, and one of the cut surfaces was magnified 40 times with a scanning electron microscope and photographed. A straight line is drawn on the photograph so as to have the diameter of the expanded particles, and the maximum diameter of all the bubbles on the straight line is measured. This measurement was performed on 10 foamed particles, and the arithmetic average value of the maximum diameter thus obtained was defined as the average cell diameter of the foamed particles.
[0048]
[Fusion rate]
After making a cut line with a depth of about 5 mm with a cutter knife along the straight line connecting the centers of a pair of long sides on the surface of a flat foam molded body having a length of 400 mm, a width of 300 mm, and a thickness of 30 mm, this cut The foamed molded body is manually divided into two along the line, and for the foamed particles in the fracture surface, the number of particles broken in the particles (a) and the number of particles broken at the interface between the particles (b ) And the value obtained by substituting it into the formula [(a) / ((a) + (b))] × 100 was defined as the fusion rate (%).
[0049]
[Combustion quality]
Self-extinguishing properties were measured based on JIS A-9511. From the JIS standard, it is desired that the self-extinguishing time is within 3.0 seconds, and preferably within 2.0 seconds. A foamed molded article cured at 50 ° C. for 24 hours after molding was used as a measurement sample.
[0050]
Example 1
A reactor having an internal volume of 100 liters equipped with a stirrer was charged with 36 liters of deionized water, 75 g of magnesium pyrophosphate and 6 g of sodium dodecylbenzenesulfonate, and then 120 g of benzoyl peroxide and t-butylperoxy as a polymerization initiator. 46 kg of styrene in which 29 g of benzoate was dissolved was placed in a reactor and stirred. After the temperature was raised to 90 ° C. and held for 6 hours, the temperature was raised to 125 ° C. and held for 3 hours for polymerization. The polymerization conversion rate at the end of the polymerization was 99.98%. Thereafter, the content was taken out by cooling, washed and dehydrated and dried, and then passed through a sieve to obtain polystyrene resin particles having a particle diameter of 0.9 to 1.2 mm. The polystyrene resin particles had a weight average molecular weight of 280000.
[0051]
In a pressure vessel equipped with a stirrer with an internal volume of 5 liters, a suspension obtained by suspending 0.5 g of sodium dodecylbenzenesulfonate, 6 g of magnesium pyrophosphate and 20 g of toluene in 2 liters of water is stirred and the polystyrene is stirred. 2 kg of resin particles, 1.5% by weight of tris (2,3-dibromopropyl) isocyanurate (flame retardant: TDIC) and 2,3-dimethyl-2,3-diphenylbutane (flame retardant aid: BC) A composite flame retardant consisting of 3% by weight was added, the container was sealed, and the temperature was raised to 100 ° C. with stirring. Then, 98 g of normal butane and 42 g of isobutane were injected at 100 ° C. and held for 3 hours. Subsequently, after cooling to 25 degreeC and taking out the resin particle from a pressure vessel, the self-extinguishing type | mold foaming polystyrene resin particle was obtained by performing washing | cleaning and dehydration drying of the resin particle.
[0052]
Moreover, when the melting point of the said composite flame retardant (BC ratio 16.7%) was measured by DTA, the melting | fusing point peak temperature was one and was 103 degreeC. In addition, melting | fusing point peak temperature of the composite flame retardant was calculated | required by measuring DTA on the following conditions based on JISK7121.
Thermal analyzer: Seiko Instruments TG / DTA6200R
Measurement sample mass: 10 mg
Temperature increase rate: 10 ° C / min
[0053]
The expandable resin particles were held in a thermostatic chamber at 20 ° C. for 5 days, and then expanded with a pre-foaming machine to obtain pre-expanded particles. Table 1 shows the average cell diameter and bulk expansion ratio after the pre-expanded particles obtained were allowed to stand at room temperature and normal pressure for 1 day and dried. In addition, the amount of particles bonded to each other in 500 g of the pre-expanded particles was measured and is shown in Table 1 as the amount of pre-expanded bonds.
[0054]
The pre-expanded particles were filled in a mold and heat-foamed with water vapor to obtain a foamed molded product (flat plate shape: length 400 mm, width 300 mm, thickness 30 mm). Table 1 shows the fusion rate, appearance, and results of measurement of flammability by the combustion test A method of JIS A9511.
[0055]
Example 2
The same procedure as in Example 1 except that 2.0% by weight of tris (2,3-dibromopropyl) isocyanurate and 0.4% by weight of 2,3-dimethyl-2,3-diphenylbutane were used. Fire extinguishing expandable polystyrene resin particles were obtained. Moreover, 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.
[0056]
Further, pre-expanded particles were obtained in the same manner as in Example 1, and are shown in Table 1 as the average cell diameter, bulk expansion ratio, and pre-expanded binding amount.
[0057]
Furthermore, the foamed molded body was obtained in the same manner as in Example 1, and the results of measuring the fusion rate, appearance, and combustibility are shown in Table 1.
[0058]
Example 3
The same procedure as in Example 1 was conducted except that 3.0% by weight of tris (2,3-dibromopropyl) isocyanurate and 0.4% by weight of 2,3-dimethyl-2,3-diphenylbutane were used. Fire extinguishing expandable polystyrene resin particles were obtained. Further, the melting point of the composite flame retardant (BC ratio 11.8%) was measured by DTA in the same manner as in Example 1. As a result, the melting point peak temperature was 1, which was 104 ° C.
[0059]
Further, pre-expanded particles were obtained in the same manner as in Example 1, and are shown in Table 1 as the average cell diameter, bulk expansion ratio, and pre-expanded binding amount.
[0060]
Furthermore, the foamed molded body was obtained in the same manner as in Example 1, and the results of measuring the fusion rate, appearance, and combustibility are shown in Table 1.
[0061]
Example 4
Self-extinguishing expandable polystyrene resin particles were obtained in the same manner as in Example 1 except that the flame retardant aid was replaced with 3,4-dimethyl-3,4-diphenylhexane (DDPH). Moreover, when the melting point of the composite flame retardant (DDPH ratio 16.7%) was measured by DTA in the same manner as in Example 1, the melting point peak temperature was 1, which was 131 ° C.
[0062]
Further, pre-expanded particles were obtained in the same manner as in Example 1, and are shown in Table 1 as the average cell diameter, bulk expansion ratio, and pre-expanded binding amount.
[0063]
Furthermore, the foamed molded body was obtained in the same manner as in Example 1, and the results of measuring the fusion rate, appearance, and combustibility are shown in Table 1.
[0064]
Comparative Example 1
Expandable polystyrene resin particles were obtained in the same manner as in Example 1 except that no flame retardant and flame retardant aid were used.
[0065]
Further, pre-expanded particles were obtained in the same manner as in Example 1, and are shown in Table 1 as the average cell diameter, bulk expansion ratio, and pre-expanded binding amount.
[0066]
Furthermore, the foamed molded body was obtained in the same manner as in Example 1, and the results of measuring the fusion rate, appearance, and combustibility are shown in Table 1.
[0067]
Comparative Example 2
Expandable polystyrene resin particles were obtained in the same manner as in Example 1 except that 3.0% by weight of tris (2,3-dibromopropyl) isocyanurate was used and no flame retardant aid was used. Further, when the melting point of the flame retardant (BC ratio 0%) was measured by DTA in the same manner as in Example 1, the melting point peak temperature was 1, which was 115 ° C.
[0068]
Further, pre-expanded particles were obtained in the same manner as in Example 1, and are shown in Table 1 as the average cell diameter, bulk expansion ratio, and pre-expanded binding amount.
[0069]
Furthermore, the foamed molded body was obtained in the same manner as in Example 1, and the results of measuring the fusion rate, appearance, and combustibility are shown in Table 1.
[0070]
Comparative Example 3
Expandable polystyrene resin particles were obtained in the same manner as in Example 1 except that dicumyl peroxide (DCP) was used as a flame retardant aid. Further, when the melting point of the composite flame retardant (DCP ratio 16.7%) was measured with DTA in the same manner as in Example 1, DCP was decomposed during the measurement and could not be measured.
[0071]
Further, pre-expanded particles were obtained in the same manner as in Example 1, and are shown in Table 1 as the average cell diameter, bulk expansion ratio, and pre-expanded binding amount.
[0072]
Furthermore, the foamed molded body was obtained in the same manner as in Example 1, and the results of measuring the fusion rate, appearance, and combustibility are shown in Table 1.
[0073]
Comparative Example 4
Expandable polystyrene resin particles were obtained in the same manner as in Example 1 except that tetrabromocyclooctane (TBCO) was used as a flame retardant. Moreover, 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 88 ° C.
[0074]
Further, pre-expanded particles were obtained in the same manner as in Example 1, and are shown in Table 1 as the average cell diameter, bulk expansion ratio, and pre-expanded binding amount.
[0075]
Furthermore, the foamed molded body was obtained in the same manner as in Example 1, and the results of measuring the fusion rate, appearance, and combustibility are shown in Table 1.
[0076]
Comparative Example 5
Expandable polystyrene resin particles were obtained in the same manner as in Example 1 except that hexabromocyclododecane (HBCD) was used as a flame retardant. However, hexabromocyclododecane remained in the pressure vessel without being absorbed by the 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 two, the melting point derived from BC was 106 ° C., and derived from HBCD. The melting point was 190 ° C.
[0077]
Further, pre-expanded particles were obtained in the same manner as in Example 1, and are shown in Table 1 as the average cell diameter, bulk expansion ratio, and pre-expanded binding amount.
[0078]
Furthermore, the foamed molded body was obtained in the same manner as in Example 1, and the results of measuring the fusion rate, appearance, and combustibility are shown in Table 1.
[0079]
Comparative Example 6
Expandable polystyrene resin particles were obtained in the same manner as in Comparative Example 5, except that the addition amount of the flame retardant was 3.0 wt% and the addition amount of the flame retardant aid was 0.6 wt%. As in Comparative Example 5, hexabromocyclododecane remained in the pressure vessel without being absorbed by the 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 two, the melting point derived from BC was 106 ° C., and derived from HBCD. The melting point was 190 ° C.
[0080]
Further, pre-expanded particles were obtained in the same manner as in Example 1, and are shown in Table 1 as the average cell diameter, bulk expansion ratio, and pre-expanded binding amount.
[0081]
Furthermore, the foamed molded body was obtained in the same manner as in Example 1, and the results of measuring the fusion rate, appearance, and combustibility are shown in Table 1.
[0082]
In Table 1, TDIC is tris (2,3-dibromopropyl) isocyanurate, TBCO is tetrabromocyclooctane, HBCD is hexabromocyclododecane, BC is 2,3-dimethyl-2,3-diphenylbutane, DDPH is 3 , 4-Dimethyl-3,4-diphenylhexane, DCP means dicumyl peroxide.
[0083]
[Table 1]

[0084]
From Table 1, the pre-expanded particles of Examples 1 to 4 had few bonds during pre-expansion and were easy to handle. Furthermore, the foamed molded product obtained from the pre-expanded particles had good fusion rate and appearance, and in addition, the combustion test showed excellent self-extinguishing properties of 3 seconds or less.
[0085]
The pre-expanded particles and the foamed molded product of Comparative Example 1 have a low amount of bonding at the time of pre-expansion and good fusion rate and appearance. It was.
[0086]
Since the pre-expanded particles of Comparative Example 2 did not contain a flame retardant aid, the self-extinguishing property of the obtained foamed molded article was extremely inferior.
[0087]
The pre-expanded particles of Comparative Example 3 had a larger amount of pre-expanded bonds than Comparative Example 2, and the resulting foamed molded article had a poor fusion rate, the appearance was melted on the surface, and the whole was contracted. The self-extinguishing property was also inferior to Examples 1-4.
[0088]
The pre-expanded particles of Comparative Example 4 had a larger amount of bonding at the time of pre-expansion than Comparative Example 3, and the obtained foamed molded article had a poor fusion rate, the appearance was melted on the surface, and the whole was contracted. The self-extinguishing property was also inferior to Examples 1-4.
[0089]
The pre-expanded particles of Comparative Examples 5 and 6 had good pre-expanded bonding amount, fusion rate, and appearance, but were substantially inferior in self-extinguishing properties because they contained substantially no flame retardant.
[0090]
Example 5
In this example, after formation of styrene resin particles by suspension polymerization, a flame retardant and a flame retardant aid were added to the suspension.
[0091]
A reactor having a volume of 100 liters equipped with a stirrer is charged with 30 liters of deionized water, 100 g of magnesium pyrophosphate, and 15 g of sodium dodecylbenzenesulfonate, and further has a particle diameter of 0.63 to 0.71 mm and a weight average molecular weight. 118,000 kg of polystyrene resin particles of 280000 (particles obtained by performing known suspension polymerization in an aqueous medium using magnesium pyrophosphate and sodium dodecylbenzenesulfonate) were added and suspended by stirring.
[0092]
Next, a suspension composed of 6 liters of deionized water, 10 g of magnesium pyrophosphate and 2 g of sodium dodecylbenzenesulfonate was prepared in advance, and 90 g of benzoyl peroxide and 8 g of t-butylperoxybenzoate were used as polymerization initiators in this suspension. 5 kg of styrene dissolved was added and stirred with a homomixer to form a suspension, which was added to the reactor maintained at 70 ° C.
[0093]
After the addition, the polystyrene resin particles were held for 1 hour so that the styrene and the polymerization initiator were sufficiently absorbed, and then styrene was continuously supplied at a rate of 10 kg / hour for 3 hours. Further, at the end of the styrene supply, the temperature in the reactor was gradually raised so as to be 105 ° C. Subsequently, the temperature was raised to 120 ° C. and held for 2 hours, so that the polymerization conversion rate was 99.98%.
[0094]
Subsequently, 2 g of water, 2 g of sodium dodecylbenzenesulfonate, 16 g of magnesium pyrophosphate, 460 g of toluene, 690 g (1.5% by weight) of tris (2,3-dibromopropyl) isocyanurate (flame retardant: TDIC) and A suspension in which 138 g (0.3% by weight) of 2,3-dimethyl-2,3-diphenylbutane (flame retardant: BC) is suspended is prepared in advance, and this suspension is press-fitted into the reactor. And then cooled to 100 ° C. Next, 2.25 kg of normal butane and 0.95 kg of isobutane were injected at a temperature of 100 ° C. and maintained for 3 hours. Next, after cooling to room temperature (about 25 ° C.) and taking out the resin particles from the pressure vessel, the resin particles are washed and dehydrated to dry, and self-extinguishing foaming with a particle size of 0.9 to 1.2 mm. Polystyrene resin particles were obtained. The polystyrene resin particles had a weight average molecular weight of 300,000. Moreover, 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.
[0095]
The expandable resin particles were held in a thermostatic chamber at 20 ° C. for 5 days, and then expanded with a pre-foaming machine to obtain pre-expanded particles. Table 2 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. Table 2 also shows the amount of bonds during preliminary foaming.
[0096]
The pre-expanded particles were filled in a mold and subjected to foaming by heating with water vapor to obtain a foamed molded product. Table 2 shows the fusion rate, appearance, and results of measurement of combustibility by the combustion test A method of JIS A9511.
[0097]
[Table 2]

[0098]
From Table 2, even if the pre-expanded particles of Example 5 were obtained from expandable styrene resin particles obtained by adding a flame retardant and a flame retardant aid to the suspension after polymerization, There were few bonds and the handling was good. Furthermore, the foamed molded product obtained from the pre-expanded particles had good fusion rate and appearance, and in addition, the combustion test showed excellent self-extinguishing properties of 3 seconds or less.
[0099]
Example 6
This example is an example for evaluating the recyclability of the foamed molded products of the above examples and comparative examples.
[0100]
The melt flow rate (MFR) of the expandable polystyrene resin particles obtained in Examples 1 and 2 and Comparative Examples 1, 3 and 4 was measured under the following conditions. Further, the weight average molecular weight of the resin particles before and after the MFR measurement was also measured. Table 3 shows the MFR and the weight average molecular weight.
[0101]
[Measurement of MFR]
The measurement of MFR was performed under the following conditions based on JIS K7210. First, the measurement sample was obtained by holding the expandable polystyrene resin particles obtained in Examples and Comparative Examples for 24 hours in an oven at 50 ° C. under vacuum at an ultimate pressure of 10 Pa for 24 hours. The product from which was removed was used.
[0102]
Measuring device: Melt indexer manufactured by Toyo Seiki Seisakusho
Measurement temperature: 200 ° C
Measurement load: 5.0kgf
Orifice diameter: 2.09 mm
[0103]
[Table 3]

[0104]
First, the MFR of polystyrene resin that can be recycled by melt kneading with an extruder and trending is 20 g / 10 min or less, preferably 15 g / 10 min or less, particularly when no flame retardant is added (Comparative Example 1). It is preferable that it is close to MFR. Looking at Table 3 from this point of view, the resin particles of Examples 1 and 2 are both 15 g / 10 min or less and can be sufficiently recycled. On the other hand, the resin particles of Comparative Examples 3 and 4 have an MFR exceeding the measurement limit of 200 g / 10 min, and are difficult to recycle.
[0105]
Furthermore, it is desirable 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 process). If greatly reduced, it cannot be extruded as a strand after being melt-kneaded by an extruder, or the strand is frequently cut and recycling is difficult. Looking at Table 3 from this point of view, the resin particles of Examples 1 and 2 have a small decrease in 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 a greatly reduced weight average molecular weight, and even after recycling, the strength is not significantly reduced and cannot be reused.
[0106]
【The invention's effect】
According to the self-extinguishing foamable styrene resin particles of the present invention, since a flame retardant and a flame retardant aid that are easily impregnated into the styrene resin particles are used, a small amount of flame retardant and flame retardant aid are used. Self-extinguishing properties can be imparted to foamed molded articles.
[0107]
In addition, the self-extinguishing foam molded article of the present invention is an environment-friendly foam molded article that can be recycled together with a general styrene resin foam molded article because the decrease in weight average molecular weight is small even when heat-treated.
[Brief description of the drawings]
FIG. 1 is a graph showing the melting point of a composite flame retardant.

Claims (5)

A flame retardant 90 comprising at least a styrene resin particle, a readily volatile foaming agent, and a composite flame retardant comprising a flame retardant and a flame retardant aid, wherein the composite flame retardant comprises tris (2,3-dibromopropyl) isocyanurate. ~ 40 wt% and the following general formula

(Wherein, R1 to R4 are the same or different and are methyl or ethyl groups) and represented by 10 to 60% by weight of a flame retardant aid, and 1 to 7 with respect to 100 parts by weight of styrene resin particles. Self-extinguishing foamable styrenic resin particles characterized by containing parts by weight. The self-extinguishing foamable styrene-based resin particle 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 foamable styrene resin particles according to claim 1 or 2, wherein the styrene resin particles are particles obtained by a suspension polymerization method. Pre-expanded particles obtained by pre-expanding the self-extinguishing foamable styrene resin particles according to any one of claims 1 to 3. A self-extinguishing foamable styrene resin foam molded article obtained by foam molding of the pre-foamed resin particles according to claim 4.

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