JP3970188B2 - Self-extinguishing foamable styrenic resin particles, pre-foamed particles and self-extinguishing foam - Google Patents

Description

【００１３】
（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％とから構成され、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発泡性スチレン系樹脂粒子が提供される。
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。
また、本発明によれば、上記予備発泡粒子を発泡成形して得られた自己消火型発泡成形体が提供される。
【００１４】
【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
【００１５】
【化３】

【００１６】
（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。
【００１７】
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。
【００１８】
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℃を越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。
【００１９】
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％を越える場合、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。
【００２０】
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。
【００２１】
次に、本発明では、スチレン系樹脂が、
（１）スチレン系モノマーの含有量がスチレン系樹脂に対して２０００ｐｐｍ以下、
（２）多分散度（Ｍｗ／Ｍｎ）が３．５〜７．０、
（３）メルトフローレート（２００℃、５．０ｋｇ荷重）が０．１〜２．０ｇ／１０分、
（４）メルトフローレート測定時の膨張割合ＳＲ、即ち内径Ｂｍｍのオリフィスから押出された樹脂ストランドの外径をＡｍｍとしたときのＡ／Ｂの値が１．６０〜２．５０
の性質を有している。この性質を有する樹脂を使用することで、少ない易揮発性発泡剤量で高発泡化でき、より自己消火性に優れた発泡性スチレン系樹脂粒子を得ることができる。なお、（１）〜（４）の具体的な測定方法は、実施例の欄に記載する。
【００２２】
（１）本発明では、スチレン系モノマーの含有量を２０００ｐｐｍ以下に抑えているので、シックハウス症候群（室内空気汚染）の発生を抑制することができる。スチレン系モノマーの含有量は、１０００ｐｐｍ以下であることがより好ましい。
（２）において、多分散度が３．５未満の場合は高発泡時の成形性に劣り、外観に優れた成形品とすることが難しい。７．０を超えると成形性には優れるが成形サイクルが長く、コストアップを招く傾向にある。より好ましい多分散度は、３．５〜５．０である。
（３）において、メルトフローレートが０．１ｇ／１０分未満であると発泡成形体の機械的強度は高くなるが、高発泡化しにくくなる。２．０ｇ／１０分を超えると発泡成形体の強度が低下する傾向にある。より好ましいメルトフローレートは、０．５〜１．８ｇ／１０分である。
（４）において、膨張割合（ＳＲ）が１．６０未満であると高発泡化は不十分となり、低密度化によって発泡成形体に収縮が起こり易く、外観に劣ったものとなり易い。この場合、発泡成形体を加熱養生しても収縮は回復しにくい。２．５０を超えると高発泡化効果は飽和となるだけでなく、逆に成形性は低下するので美麗な外観の発泡成形体性は得らにくい傾向にある。より好ましいＳＲは、１．８０〜２．５０である。
【００２３】
本発明のスチレン系樹脂は、上記（１）〜（４）の性質を有する限りどのようなスチレン系樹脂でも使用することができる。例えば、スチレン単独重合体であっても、スチレン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、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が挙げられる。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、スチレン系樹脂は、他樹脂との混合樹脂であってもよい。他の樹脂の例としては、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。
【００２４】
本発明では、スチレンに対して、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などの多官能性モノマー０．００８〜０．０３ｍｏｌ％を共重合して得られたスチレン系樹脂を使用することが好ましい。多官能性モノマーを使用することが好ましい理由は、発泡成形体の気泡に、破れやシワが発生することを抑制し、より低い熱伝導率を得るためである。また、多官能性モノマーの量が０．００８ｍｏｌ％未満の場合は、添加した効果が現れにくいので好ましくなく、０．０３ｍｏｌ％を超える場合は、発泡性が低下し高発泡化できなくなるので好ましくない。より好ましい多官能性モノマーの量は、０．０１〜０．０２４ｍｏｌ％である。
【００２５】
本発明で使用されるスチレン系樹脂粒子の製法は、特に限定されず、公知の方法をいずれも使用することができる。例えば、押出機から押し出されたスチレン系樹脂のストランドをペレタイズし樹脂粒子を得る方法、スチレン系モノマーを水性媒体中に懸濁させて重合させる、いわゆる懸濁重合法、あるいは水性媒体中にスチレン系重合体粒子（種粒子）を分散させ、これにスチレン系モノマーを連続的または断続的に供給して重合開始剤の存在下で重合するいわゆるシード重合法が採用できる。この内、生産効率の観点から懸濁重合法及びシード重合法が好ましい。
【００２６】
懸濁重合法及び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。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、断熱性能が低下する場合がある。
【００２７】
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、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とし、それ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／又はその他の添加剤と同時に含浸させることが好ましい。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。
【００２８】
上記懸濁重合法及びシード重合法において、スチレン系樹脂粒子の重合は、重合開始剤の存在下で通常行われる。重合開始剤としては、当該分野で公知のものをいずれも使用することができる。例えば、ラジカル発生型重合開始剤を用いることができる。具体的には、ベンゾイルパーオキサイド、ラウリルパーオキサイド、ｔ−ブチルパーオキシ−２−エチルヘキサノエート、ジｔ−ブチルパーオキシヘキサハイドロテレフタレート、ｔ−ブチルパーオキサイド、ｔ−ブチルパーオキシピバレート、ｔ−ブチルパーオキシイソプロピルカーボネート、ｔ−ブチルパーオキシアセテート、２，２−ｔ−ブチルパーオキシブタン、ｔ−ブチルパーオキシ−３，３，５−トリメチルヘキサノエート、ｔ−ブチルパーオキシ−２−エチルヘキシルカーボネート等の有機過酸化物やアゾビスイソブチロニトリル、アゾビスジメチルバレロニトリル等のアゾ化合物が挙げられる。これらの重合開始剤は単独または２種以上併用して用いることができる。特に、分子量を調整し残存モノマーを減少させる為に、１０時間の半減期を得るための分解温度が８０〜１２０℃の異なる重合開始剤を併用することが望ましい。
【００２９】
懸濁重合及びシード重合を行う際に、スチレン系単量体の小滴及び種粒子を水性媒体中に分散させるために懸濁安定剤を使用してもよい。懸濁安定剤としては、懸濁重合において一般に使用されている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等が挙げられる。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。
【００３０】
アニオン界面活性剤としては、例えば脂肪酸石鹸、Ｎ−アシルアミノ酸またはその塩、アルキルエーテルカルボン酸塩などのカルボン酸塩，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などのスルホン酸塩；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などの硫酸エステル塩；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などのリン酸エステル塩などがある。
【００３１】
本発明で使用される易揮発性発泡剤としては、一般の熱可塑性樹脂発泡体の製造に使用されている炭素数３〜５の炭化水素、即ちプロパン、ブタン、ペンタン、ヘキサン及びそれらの異性体を用いることができる。特にブタンとイソブタンを併用することが好ましい。
発泡剤の使用割合は、スチレン系樹脂１００重量部に対して２〜１０重量部とすることが好ましい。２重量部未満であると、低密度化が困難であるばかりでなく、成形時の二次発泡力を高める効果が得られない為に成形体の外観が劣る場合があるので好ましくない。一方、１０重量部を超えると、発泡成形体中の残存ガスが多くなるので自己消火性に劣るだけでなく、成形サイクルが長くなり、生産性の観点からも好ましくない。好ましくは、３〜８重量部である。
【００３２】
本発明においては、上記易揮発性発泡剤を水性媒体中でスチレン系樹脂粒子に含浸させる際に、ステアリン酸アミド、１２−ヒドロキシステアリン酸アミド、エチレンビスステアリン酸アミド、エチレンビスオレイン酸アミド、メチレンビスステアリン酸アミドなどの脂肪酸アミドを水性媒体中に添加しておくことが好ましい。これらの添加により、最終的に得られる発泡性スチレン系樹脂粒子の熱安定性が向上する。例えば、夏場の高温雰囲気下での放置や発泡及び成形加工する工場へ輸送する際の熱履歴によって気泡が不均一かつ粗大化する（熱あれ）のを防止することができる。また、該発泡性スチレン系樹脂粒子を予備発泡すると、内部気泡よりも表面気泡が細かくなった発泡粒子が得られ、成形サイクルを短縮させることができる。通常、表面の平均気泡径を内部の平均気泡径の２／３以下とするとその顕著な効果が現れる。
【００３３】
例えば嵩密度０．０２ｇ／ｃｍ³に予備発泡した場合、内部の平均気泡径は１５０〜３００μｍ程度であることが好ましく、表面の平均気泡径は５０〜２００μｍ程度であることが好ましい。
脂肪酸アミドの添加量は、スチレン系樹脂１００重量部に対して通常０．０１〜０．２重量部であることが好ましい。これらの添加時期は、上記のように易揮発性発泡剤を含浸させる時が好ましい。スチレン系モノマーを重合させるときに添加した場合、予備発泡粒子（嵩密度０．０２ｇ／ｃｍ³）の平均気泡径は内部、表面共に１００μｍ以下となり、得られる発泡成形体は断熱性の劣ったものとなる場合がある。
【００３４】
本発明においては、より低密度の発泡成形体を得る目的で可塑剤を使用してもよい。可塑剤としては、ジイソブチルアジペート、ジオクチルアジペート、ジブチルセバケート、グリセリントリステアレート、グリセリントリカプリレート、ヤシ油、パーム油などが挙げられる。可塑剤の使用量は、スチレン系樹脂１００重量部に対して２重量部以内であることが好ましい。２重量％を超える場合は成形時に収縮及び溶けが発生するばかりか、製造コストが高くなり好ましくない。可塑剤はスチレン系樹脂粒子の重合工程、複合難燃剤及び発泡剤を含浸させる工程等で添加される。また、押出機等で造粒する際に添加してスチレン系樹脂粒子に含有させることも可能である。
【００３５】
本発明においては、従来から発泡性スチレン系樹脂粒子の製造に使用される気泡調整剤、気泡安定化剤、充填剤、着色剤等を必要に応じて適宜使用してもよい。得られた自己消火型発泡性スチレン系樹脂粒子は、脱水、乾燥、分級を施し、次いで粒子表面に帯電防止剤や予備発泡時の粒子同士の合着を防ぐために結合防止剤で被覆してもよい。
予備発泡は発泡ポリスチレンビーズ用予備発泡機を用いて行うことができる。得られる予備発泡粒子の嵩密度は、０．００８〜０．１ｇ／ｃｍ³であることが好ましい。
予備発泡粒子を成形機の金型内に充填し、水蒸気等で再加熱して予備発泡粒子同士を熱融着させた後に、冷却することで所望の形の発泡成形体を得ることができる。成形機には、公知の発泡ポリスチレン用成形機を用いることができる。
【００３６】
【実施例】
以下、実施例及び比較例にて、本発明を詳細に述べるが、本発明はこれら実施例に限定されるものではない。
なお、分析及び評価は次に示す方法で行った。
【００３７】
［重合転化率と残留スチレン量の定量］
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。ＧＣ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℃
【００３８】
［平均分子量］
重合体の平均分子量（Ｍｗ及びＭｎ）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：試料の分子量測定条件は、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ド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２．７４×１０³、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）を用いて作成した。
【００３９】
［平均気泡径］
発泡粒子表面及び発泡粒子内部の平均気泡径を求める。
まず、発泡粒子をカッターで略二分割した一方の切断面を、走査型電子顕微鏡にて４０倍に拡大して写真撮影し、その写真上に発泡粒子の直径となるように直線を引く。
発泡粒子表面の平均気泡径として、直線により二分割された発泡粒子断面の内、どちらか一方の半円の最外周（直線に掛かる気泡も含む。また、非発泡のスキン層を有する発泡粒子においては、スキン層の内側を最外周とする）にある全ての気泡の最大径を測定し、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表面の平均気泡径とした。
発泡粒子内部の平均気泡径として、上記直線を四等分した内側二つの線分上に掛かる全ての気泡の最大径を測定し、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内部の平均気泡径とした。
【００４０】
［熱伝導率］
熱伝導率の測定は、ＪＩＳ−Ａ−１４１２−２に基づき行った。試験片は実施例で得られた発泡成形体（長さ４００ｍｍ×幅３００ｍｍ×厚み２０ｍｍ）の中央部から所定の寸法で切り出したものを使用した。
測定装置：英弘精機社製ＡＵＴＯ−Ａ ＨＣ−０７２
試験片：長さ２００ｍｍ×幅２００ｍｍ×厚み２０ｍｍ
測定方法：平板熱流計法
測定温度：２０℃
【００４１】
［燃焼性］
ＪＩＳ Ａ９５１１に基づき自己消火にかかる時間を測定した。ＪＩＳ規格から、自己消火時間が３．０秒以内である必要があり、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。
【００４２】
［メルトフローレート（ＭＦＲ）と膨張割合（ＳＲ）］
上記メルトフローレートと膨張割合（ＳＲ）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℃
荷重重量：５ｋｇｆ
オリフィス径：２．０９ｍｍ（Ｂ）
押出後のストランド径 Ａ ｍｍ（ストランド先端より５ｍｍの間で測定）
膨張割合（ＳＲ）＝Ａ／Ｂ
スチレン系樹脂５ｇを予め２００℃に加熱したメルトインデクサー内に入れ、３分程放置する。次に５ｋｇｆの荷重を加え、オリフィス径２．０９ｍｍよりスチレン系樹脂を押出す。押出されたストランドを取り、先端から５ｍｍの間でストランド径を５個所測定し平均値をＡとする。
【００４３】
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自己消火型発泡性スチレン系樹脂粒子を、５０℃のオーブン中で到達圧力１０Ｐａとして真空吸引しながら２４時間保持し、樹脂粒子中の揮発性有機溶剤を除去したものを用いた。
【００４４】
実施例１
（懸濁重合によるポリスチレン粒子の製造）
内容量１００Ｌの攪拌機付き重合容器に、水４０．０Ｌ、第三リン酸カルシウム１００ｇ及びドデシルベンゼンスルホン酸ソーダ２．０ｇを入れ、続いて攪拌しながらスチレン４０．０ｋｇ、ベンゾイルパーオキサイド１００．０ｇ、ｔ−ブチルパーオキシ−２−エチルヘキシルカーボネート２８．０ｇを添加し、８８℃に昇温して重合温度とした。そしてこの温度で６時間３０分保持し、更に１２５℃に昇温してから２時間後、冷却し球状のポリスチレン粒子（Ａ）を得た。
ポリスチレン粒子（Ａ）の重合転化率は９９．９６重量％であり、Ｍｗは２９．５万、多分散度（Ｍｗ／Ｍｎ）は３．０であり、メルトフローレートは４．２ｇ／１０分、膨張割合ＳＲは１．４２であった。
【００４５】
上記で得られたポリスチレン粒子（Ａ）を篩分けして粒子径０．５〜０．７ｍｍのポリスチレン粒子（Ｂ）を得た。内容量５Ｌの攪拌機付き耐圧容器に、水２．２Ｌ、ポリスチレン粒子（Ｂ）５００ｇ、ピロリン酸マグネシウム６．０ｇ及びドデシルベンゼンスルホン酸ナトリウム０．３ｇを入れ、攪拌しながら７０℃に昇温した。次いでベンゾイルパーオキサイド５．２ｇ、ｔ−ブチルパーオキシ−２−エチルヘキシルカーボネート１．１ｇをスチレン２００ｇに溶解し耐圧容器に入れた。３０分後９０℃に昇温して、予めジビニルベンゼン０．４５ｇを溶解したスチレン１３００ｇを２時間かけてポンプで一定量づつ耐圧容器に供給した。供給を終了してから３０分後に１２５℃まで昇温して２時間保持した。その後、７０℃まで冷却して容器内から一部をサンプリングして球状のポリスチレン粒子を得た。
【００４６】
このポリスチレン粒子の重合転化率は９９．９５重量％であり、Ｍｗは４４．７万、多分散度（Ｍｗ／Ｍｎ）は４．５、メルトフローレートは１．４ｇ／１０分、膨張割合ＳＲは２．１６であった。
次いで攪拌を継続しながら、トリス（２，３−ジブロモプロピル）イソシアヌレート３４．０ｇと２，３−ジメチル−２，３−ジフェニルブタン６．０ｇとを混合した複合難燃剤を投入して混合した。
また、上記複合難燃剤（ＢＣ割合１５．０％）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
【００４７】
続いて、別の容器内でドデシルベンゼンスルホン酸ナトリウム０．１ｇを溶解した水２００ｇにジイソブチルアジペート１０．０ｇとエチレンビスステアリン酸アミド０．８ｇを加えて乳濁液とし、該乳濁液を耐圧容器に入れた。その後、耐圧容器内を１００℃に昇温してから、ノルマルブタン１０５ｇとイソブタン３５ｇを圧入して４時間保持した。
次に、耐圧容器内を３０℃以下まで冷却し自己消火型発泡性ポリスチレン粒子を得た。取り出した発泡性ポリスチレン粒子を乾燥した後、２０℃の恒温室で５日間保存し、次いで予備発泡機で嵩密度０．０２ｇ／ｃｍ³に発泡した。得られた予備発泡粒子の平均気泡径は内部が１８０μｍ、表面が７０μｍであった。
予備発泡粒子を室温（２５℃）で８時間熟成した後、発泡ポリスチレン用成形機（積水工機社製ＡＣＥ−３ＱＳ）で成形し、外観の美麗な板状発泡成形体（長さ４００ｍｍ、幅３００ｍｍ、厚み２０ｍｍ）を得た。この発泡成形体を５０℃の乾燥室で６時間養成した後、ＪＩＳ−Ａ９５１１の燃焼試験を行った。その結果を表１に示す。
【００４８】
実施例２
複合難燃剤をトリス（２，３−ジブロモプロピル）イソシアヌレートを２８．０ｇ、２，３−ジメチル−２，３−ジフェニルブタンを１２．０ｇとした他は実施例１と同様して板状発泡成形体を得た。また、上記複合難燃剤（ＢＣ割合３０．０％）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１０３℃であった。評価結果を表１に示す。
【００４９】
実施例３
複合難燃剤をトリス（２，３−ジブロモプロピル）イソシアヌレートを６８．０ｇ、２，３−ジメチル−２，３−ジフェニルブタンを１２．０ｇとした他は実施例１と同様して板状発泡成形体を得た。また、上記複合難燃剤（ＢＣ割合１５．０％）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１０３℃であった。評価結果を表１に示す。
【００５０】
実施例４
複合難燃剤に使用する難燃助剤の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（ＤＤＰＨ）とした他は実施例１と同様して板状発泡成形体を得た。また、複合難燃剤（ＤＤＰＨ割合１５．０％）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１３１℃であった。評価結果を表１に示す。
【００５１】
実施例５
ｔ−ブチルパーオキシ２−エチルヘキシルカーボネートを１．１ｇを０．０６ｇとした他は実施例１と同様して板状発泡成形体を得た。また、複合難燃剤（ＢＣ割合１５．０％）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１０３℃であった。評価結果を表１に示す。
【００５２】
比較例１
トリス（２，３−ジブロモプロピル）イソシアヌレートを７．０ｇ、２，３−ジメチル−２，３−ジフェニルブタンを３．０ｇとした他は実施例１と同様して板状発泡成形体を得た。また、複合難燃剤（ＢＣ割合３０．０％）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１０３℃であった。評価結果を表１に示す。
【００５３】
比較例２
内容量５Ｌの攪拌機付き耐圧容器に、水２．２Ｌ、実施例１で得られたポリスチレン粒子（Ｂ）５００ｇ、ピロリン酸マグネシウム６．０ｇ及びドデシルベンゼンスルホン酸ナトリウム０．３ｇを入れ、攪拌しながら７０℃に昇温した。次いでベンゾイルパーオキサイド５．２ｇ、ｔ−ブチルパーオキシ２−エチルヘキシルカーボネート１．１ｇをスチレン２００ｇに溶解し耐圧容器に入れた。３０分後９０℃に昇温して、予めジビニルベンゼン０．４５ｇを溶解したスチレン１３００ｇを２時間かけてポンプで一定量づつ耐圧容器に供給した。供給を終了してから３０分後に容器内から一部をサンプリングして球状のポリスチレン粒子を得た。このポリスチレン粒子の重合転化率は９４．２重量％であった。
【００５４】
次いで攪拌を継続しながら、トリス（２，３−ジブロモプロピル）イソシアヌレート３４．０ｇと２，３−ジメチル−２，３−ジフェニルブタン６．０ｇとからなる複合難燃剤を投入して混合した。また、上記複合難燃剤（ＢＣ割合１５．０％）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１０３℃であった。次いで、１２５℃まで昇温して２時間保持した。その後、７０℃まで冷却して、別の容器内でドデシルベンゼンスルホン酸ナトリウム０．１ｇを溶解した水２００ｇにジイソブチルアジペート１０．０ｇとエチレンビスステアリン酸アミド０．８ｇを加えて乳濁液としたものを入れた。その後、耐圧容器内を１００℃に昇温してから、ノルマルブタン１３０ｇとイソブタン５０ｇを圧入して４時間保持した。
次に、耐圧容器内を３０℃以下まで冷却し自己消火型発泡性ポリスチレン粒子を得た。取り出した発泡性粒子は実施例１と同様の処理を行ってから評価した。その結果を表１に示す。
【００５５】
比較例３
トリス（２，３−ジブロモプロピル）イソシアヌレートを８０．０ｇとし、２，３−ジメチル−２，３−ジフェニルブタンを使用しなかった他は実施例１と同様にした。また、この難燃剤（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、１１５℃であった。その評価結果を表１に示す。
【００５６】
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１６．０ｇとし、２，３−ジメチル−２，３−ジフェニルブタンを６４．０ｇ（８０重量％）とした他は実施例１と同様にした。また、この複合難燃剤（ＢＣ割合８０．０％）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１０４℃であった。評価結果を表１に示す。
【００５７】
比較例５
２，３−ジメチル−２，３−ジフェニルブタンを６．０ｇの替わりにジクミルパーオキサイド（ＤＣＰ）６．０ｇとした他は実施例１と同様にした。また、この複合難燃剤（ＤＣＰ割合１５．０％）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。評価結果を表１に示す。
【００５８】
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３４．０ｇの替わりにヘキサブロモシクロドデカン２８．０ｇ、更に２，３−ジメチル−２，３−ジフェニルブタンを１２．０ｇとした他は実施例１と同様した。しかし、ヘキサブロモシクロドデカンは吸収されずに耐圧容器内に残っていた。また、この複合難燃剤（ＢＣ割合３０．０％）の融点をＤＴＡにて実施例１と同様に測定したところ、融点ピーク温度は二つであり、ＢＣの融点は１０６℃、ＨＢＣＤの融点は１９０℃であった。評価結果を表１に示す。
【００５９】
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３４．０ｇの替わりにテトラブロモシクロオクタン２８．０ｇとし、更に２，３−ジメチル−２，３−ジフェニルブタン６．０ｇの替わりにジクミルパーオキサイド１２．０ｇとした他は実施例１と同様した。また、この複合難燃剤（ＤＣＰ割合３０．０％）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。その評価結果を表１に示す。
【００６０】
【表１】

【００６１】
表１から、実施例１〜５の予備発泡粒子から得られた発泡成形体は断熱性に優れ、加えて燃焼試験も３秒以内と優れた自己消火性を示した。
比較例１の予備発泡粒子から得られた発泡成形体は、断熱性は良好であったが、複合難燃剤の含有量が１．０重量部未満であるため、自己消火性に劣った発泡成形体であった。
比較例２はスチレン系樹脂粒子の重合途中、すなわち重合転化率が低い状態で難燃剤を添加した例であるが、この結果より、ポリスチレン粒子の重合転化率が低い時点で複合難燃剤を添加すると、残留スチレンが多くなるだけでなく、発泡成形体は気泡が微細で断熱性能に劣っていた。
比較例３の予備発泡粒子から得られた発泡成形体は、難燃助剤を含まないため自己消火性に劣っていた。
【００６２】
比較例４の予備発泡粒子から得られた発泡成形体は、実施例１よりも断熱性に劣り、また実質的に難燃剤の含有量が少ないため自己消火性に劣っていた。
比較例５においては、難燃助剤としてジクミルパーオキサイドを使用すると難燃剤の不均一吸収が起こり、その結果気泡の微細な発泡粒子が混在し（内部気泡では６０μｍのものと１７０μｍのものが混在）、成形時に凹凸が発生して外観の良好な発泡成形体は得られなかった。また、断熱性も実施例１より劣っていた。
比較例６の予備発泡粒子から得られた発泡成形体は、難燃剤を実質的に含まないため自己消火性に劣っていた。
比較例７の予備発泡粒子から得られた発泡成形体は、比較例５と同様に気泡の粗密が混在し、外観の良好なものが得られなかった。また、断熱性も実施例１よりも劣っていた。
【００６３】
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。
実施例１と２及び比較例５と７で得られた自己消火型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２に示す。
なお、比較のため、以下のように難燃剤を含まないポリスチレン粒子を作製しＭＦＲの測定を行った。
【００６４】
（難燃剤を含まないポリスチレン粒子の作製）
ポリスチレン粒子（Ａ）を篩分けして粒子径０．５〜０．７ｍｍのポリスチレン粒子（Ｂ）を得た。内容量５Ｌの攪拌機付き耐圧容器に、水２．２Ｌ、ポリスチレン粒子（Ｂ）５００ｇ、ピロリン酸マグネシウム６．０ｇ及びドデシルベンゼンスルホン酸ナトリウム０．３ｇを入れ、攪拌しながら７０℃に昇温した。次いでベンゾイルパーオキサイド５．２ｇ、ｔ−ブチルパーオキシ−２−エチルヘキシルカーボネート１．１ｇをスチレン２００ｇに溶解し耐圧容器に入れた。３０分後９０℃に昇温して、予めジビニルベンゼン０．４５ｇを溶解したスチレン１３００ｇを２時間かけてポンプで一定量づつ耐圧容器に供給した。供給を終了してから３０分後に１２５℃まで昇温して２時間保持した。その後、３０℃まで冷却して容器内から取り出し洗浄及び乾燥して、粒子状のポリスチレン粒子（Ｃ）を得た。
【００６５】
【表２】

表２から以下のことがわかる。
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、すなわち粒子（Ｃ）のＭＦＲに近いことが好ましい。この観点から表２を見ると、実施例１と２の樹脂粒子はいずれも１５ｇ／１０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５と７の樹脂粒子は、ＭＦＲが大きく上昇しており、リサイクル困難である。
【００６６】
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か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２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５と７の樹脂粒子は、重量平均分子量が大きく低下しており、リサイクル困難しても強度低下が著しく再利用できない。
【００６７】
【発明の効果】
本発明によれば、特定の種類の難燃剤と難燃助剤とを特定の比率で含む複合難燃剤を使用するので、リサイクル時にスチレン系樹脂の分子量低下を起こしにくく、スチレン系樹脂のもつ本来の特性（例えば断熱性、機械的強度）を保持し、優れた自己消火性を発揮し、かつスチレン系樹脂への分散方法が限定されない。更に、特定の複合難燃剤を、特定の性質を有するスチレン系樹脂粒子に使用することで、樹脂の特性を阻害することなく自己消火性を付与できる。
【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 self-extinguishing foamable styrene resin particles, pre-expanded particles, and a self-extinguishing foam molded article. More specifically, the present invention includes a specific composite flame retardant in the styrene resin particles, so that it has excellent self-extinguishing properties with a small amount of flame retardant, has high foaming properties and high heat insulation properties, and residual styrene type. The present invention relates to an expandable styrene resin particle, a pre-expanded particle, and a self-extinguishing foamed molded product with a small amount of monomer.
[0002]
[Prior art]
In general, a foam molded article obtained by molding expandable styrene resin particles by an in-mold molding method (bead method) has many features and is used in a wide range of applications. For example, it is used as a heat insulating building material for a house because of its light weight and excellent heat insulation and water resistance. However, this foam molding is one of the volatile organic compounds (VOCs) that are flammable and are a causative substance of sick house syndrome (indoor air pollution) that has become a problem with the recent high airtightness of houses. It has the property that many styrenic monomers are contained.
[0003]
Various methods for imparting self-extinguishing properties to a styrene-based resin foam molded article with a flame retardant have already been studied in order to make the foam molded article difficult to burn.
The self-extinguishing property of the styrene resin foam molded article by the bead method is as follows: (1) a method in which a flame retardant is added during suspension polymerization of a styrene monomer, and (2) resin particles (mini Pellets), a method of adding a flame retardant into the molten resin, (3) a method of coating the flame retardant on the surface of the expandable styrene resin particles, and (4) impregnating the styrene resin particles with a volatile foaming agent. There is a method of adding a flame retardant.
[0004]
As flame retardants used in these methods, hexabromocyclododecane, pentabromocyclooctane, tribromophenol, tetrabromobisphenol A, tetrabromobisphenol A diallyl ether and the like are generally known. In addition, it is known to use a flame retardant aid to improve the performance of the flame retardant. As the flame retardant aid, organic peroxides such as dicumyl peroxide and cumene hydroperoxide and 2,3- Dimethyl-2,3-diphenylbutane (biscumyl) is used.
[0005]
Specifically, JP-A-60-206845 (Patent Document 1) discloses hexabromocyclododecane as a flame retardant and 2,3-dimethyl-2,3-diphenyl as a flame retardant aid during suspension polymerization. An expandable styrene resin particle to which butane is added is described (the above method (1)).
JP-A-2000-001563 (Patent Document 2) discloses hexabromocyclododecane as a flame retardant and 2,3-dimethyl-2,3-diphenylbutane as a flame retardant at the time of extrusion of a styrene resin. The added expandable styrenic resin particles are described (the above method (2)).
[0006]
Further, JP-A-5-339416 (Patent Document 3) discloses an expandable styrene in which the surface of expandable styrene resin particles is coated with hexabromocyclododecane as a flame retardant and azodiisobutyronitrile as a flame retardant aid. System resin particles are described (the above method (3)).
Furthermore, in Japanese Patent Application Laid-Open No. 11-130898 (Patent Document 4), when styrene resin particles are impregnated with a volatile foaming agent, tetrabromobisphenol A diallyl ether is used as a flame retardant, and dicumyl is used as a flame retardant aid. An expandable styrene resin particle to which peroxide or cumene hydroperoxide is added is described (the above method (4)).
[0007]
[Patent Document 1]
JP 60-206845 A
[Patent Document 2]
JP 2000-001563 A
[Patent Document 3]
JP-A-5-339416
[Patent Document 4]
JP-A-11-130898
[0008]
[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.
From the above viewpoint, even if a flame retardant having a relatively high melting point and a large molecular weight such as hexabromocyclododecane is added during suspension polymerization, it inhibits the polymerization of the styrenic monomer. It becomes difficult to reduce the strength of the resin. In addition, the residual monomer increases, making it difficult to achieve low VOC. On the other hand, a method of impregnating resin particles after polymerization is conceivable. However, since the above flame retardant has a high melting point, styrene resin particles can hardly be impregnated, and it is difficult to provide self-extinguishing properties by this method. It becomes. Therefore, when using the above-mentioned flame retardant, the method of dispersing the particles and the molded body is limited to the method of kneading and dispersing the molten resin and the flame retardant as in the extrusion method, resulting in a complicated manufacturing process. It becomes.
[0009]
Further, organic peroxides such as dicumyl peroxide and cumene hydroperoxide are known as flame retardant aids. However, such organic peroxides generate radicals when melt-kneaded at the time of recycling, and the radicals decompose the styrene resin, leading to a decrease in molecular weight, and deteriorate the quality such as strength of the recycled resin. There is a problem of making it.
Therefore, the foamed molded product that retains the original properties of the styrene-based resin foamed molding, such as heat insulation and mechanical strength, is excellent in self-extinguishing properties and has little residual styrene-based monomer, and the foamable styrene based material It was desired to provide resin particles.
[0010]
[Means for Solving the Problems]
The inventors of the present invention have studied a combination of various flame retardants and flame retardant aids in order to solve the above problems, and as a result, a composite containing the following types of flame retardants and flame retardant aids in a specific ratio: The flame retardant is unlikely to cause a decrease in the molecular weight of the styrene resin during recycling, retains the original characteristics of the styrene resin (for example, heat insulation and mechanical strength), exhibits excellent self-extinguishing properties, and is a styrene resin. Surprisingly, it was found that the dispersion method is not limited. Furthermore, it has been found that by using this composite flame retardant for styrene resin particles having specific properties, self-extinguishing properties can be imparted without impairing the properties of the resin.
[0011]
Thus, according to the present invention, it is composed of a styrene resin, a readily volatile foaming agent, and a composite flame retardant,
Styrenic resin
(1) The content of the styrene monomer is 2000 ppm or less with respect to the styrene resin,
(2) Polydispersity (Mw / Mn) is 3.5 to 7.0,
(3) Melt flow rate (200 ° C., 5.0 kg load) is 0.1 to 2.0 g / 10 minutes,
(4) The value of the expansion ratio SR when measuring the melt flow rate is 1.60 to 2.50,
The composite flame retardant is tris (2,3-dibromopropyl) isocyanurate 90 to 40% by weight, and the flame retardant aid is represented by the following general formula:
[0012]
[Chemical 2]

[0013]
(Wherein R1 to R4 are the same or different and are methyl or ethyl groups) and are composed of 10 to 60% by weight of a flame retardant aid represented by 1 to 100 parts by weight of styrene resin particles. 7 parts by weight included
Self-extinguishing foamable styrene resin particles are provided.
Furthermore, according to the present invention, pre-expanded particles obtained by pre-expanding the self-extinguishing foamable styrene resin particles are provided.
Moreover, according to this invention, the self-extinguishing type | mold foaming molding obtained by foam-molding the said pre-expanded particle is provided.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The composite flame retardant used in the present invention is a flame retardant which is tris (2,3-dibromopropyl) isocyanurate (hereinafter also referred to as TDIC, melting point 115 ° C., decomposition temperature 285 ° C.), and the following general formula:
[0015]
[Chemical 3]

[0016]
(Wherein R1 to R4 are the same or different and are methyl or ethyl groups).
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.
[0017]
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 auxiliary alone due to the melting point drop. For example, the horizontal axis represents the ratio of the flame retardant auxiliary 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. 1, it is composed of 70% by weight of TDIC and 30% by weight of BC. In the case of a 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 further lowered.
[0018]
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., the flame retardant bleeds during resin impregnation or kneading at the time of impregnation, and the foam particles adjoin 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.
[0019]
In the present invention, the flame retardant and the flame retardant aid are used in a proportion 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%.
[0020]
In the present invention, a more preferable combination of the flame retardant and the flame retardant aid is a combination of TDIC and BC.
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. Usually 1 to 5 parts by weight is sufficient.
[0021]
Next, in the present invention, the styrene resin is
(1) The content of the styrene monomer is 2000 ppm or less with respect to the styrene resin,
(2) Polydispersity (Mw / Mn) is 3.5 to 7.0,
(3) Melt flow rate (200 ° C., 5.0 kg load) is 0.1 to 2.0 g / 10 minutes,
(4) The expansion ratio SR when measuring the melt flow rate, that is, the A / B value is 1.60 to 2.50, where Amm is the outer diameter of the resin strand extruded from the orifice having the inner diameter Bmm.
It has the properties of By using a resin having this property, it is possible to obtain a foamable styrene resin particle that can be highly foamed with a small amount of a volatile foaming agent and that is more excellent in self-extinguishing properties. In addition, the specific measuring method of (1)-(4) is described in the Example column.
[0022]
(1) In this invention, since content of a styrene-type monomer is restrained to 2000 ppm or less, generation | occurrence | production of sick house syndrome (room air pollution) can be suppressed. The content of the styrene monomer is more preferably 1000 ppm or less.
In (2), when the polydispersity is less than 3.5, the moldability at the time of high foaming is inferior, and it is difficult to obtain a molded product having an excellent appearance. If it exceeds 7.0, the moldability is excellent, but the molding cycle is long and the cost tends to increase. A more preferable polydispersity is 3.5 to 5.0.
In (3), if the melt flow rate is less than 0.1 g / 10 minutes, the mechanical strength of the foamed molded product is increased, but it is difficult to achieve high foaming. If it exceeds 2.0 g / 10 minutes, the strength of the foamed molded product tends to decrease. A more preferable melt flow rate is 0.5 to 1.8 g / 10 min.
In (4), when the expansion ratio (SR) is less than 1.60, high foaming is insufficient, and the foamed molded product tends to shrink due to low density, and the appearance tends to be inferior. In this case, shrinkage is difficult to recover even if the foamed molded body is heat-cured. If it exceeds 2.50, not only the high foaming effect is saturated, but also the moldability is lowered, so that it is difficult to obtain a foamed molded product having a beautiful appearance. More preferable SR is 1.80 to 2.50.
[0023]
Any styrenic resin can be used as the styrenic resin of the present invention as long as it has the properties (1) to (4). For example, it may be a styrene homopolymer or a copolymer with another monomer copolymerizable with styrene. Examples of other monomers include α-methylstyrene, vinyl toluene, acrylonitrile, methyl methacrylate, glycidyl methacrylate, butyl acrylate, methacrylic acid, divinylbenzene, and alkylene glycol dimethacrylate. In the present invention, styrene and monomers capable of copolymerization 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.
[0024]
In this invention, it is preferable to use the styrene resin obtained by copolymerizing 0.008-0.03 mol% of polyfunctional monomers, such as divinylbenzene and alkylene glycol dimethacrylate, with respect to styrene. The reason why it is preferable to use a polyfunctional monomer is to suppress the generation of tears and wrinkles in the bubbles of the foamed molded product and to obtain a lower thermal conductivity. In addition, when the amount of the polyfunctional monomer is less than 0.008 mol%, the added effect is hardly exhibited, which is not preferable. When the amount exceeds 0.03 mol%, the foamability is lowered and high foaming cannot be achieved. . A more preferable amount of the multifunctional monomer is 0.01 to 0.024 mol%.
[0025]
The production method of the styrene resin particles used in the present invention is not particularly limited, and any known method can be used. For example, a method of obtaining resin particles by pelletizing a strand of a styrene resin extruded from an extruder, a so-called suspension polymerization method in which a styrene monomer is suspended in an aqueous medium, or a styrene resin in an aqueous medium. A so-called seed polymerization method in which polymer particles (seed particles) are dispersed, and a styrene monomer is continuously or intermittently supplied to the polymer particles in the presence of a polymerization initiator can be employed. Among these, the suspension polymerization method and the seed polymerization method are preferable from the viewpoint of production efficiency.
[0026]
In the suspension polymerization method and 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 of adding and impregnating into the aqueous medium after the polymerization is completed Is mentioned. 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. If the flame retardant is impregnated when the polymerization conversion rate is less than 99.8%, the subsequent polymerization of the styrenic monomer is inhibited, and a large amount of monomer may remain in the finally obtained foamed molded article. is there. Moreover, since the bubble diameter of the foamed molded product is made finer, the thermal conductivity is increased, and the heat insulation performance may be lowered.
[0027]
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 preparing a suspension uniformly dispersed in a pre-dispersion tank equipped with a stirrer and charging it into an aqueous medium. Furthermore, it is preferable to impregnate simultaneously with a readily volatile foaming agent and / or other additives. 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.
[0028]
In the suspension polymerization method and the seed polymerization method, the polymerization of the styrene resin particles is usually performed in the presence of a polymerization initiator. Any polymerization initiator known in the art can be used. For example, a radical generating polymerization initiator can be used. Specifically, benzoyl peroxide, lauryl peroxide, t-butylperoxy-2-ethylhexanoate, di-t-butylperoxyhexahydroterephthalate, t-butylperoxide, t-butylperoxypivalate, t-butylperoxyisopropyl carbonate, t-butylperoxyacetate, 2,2-t-butylperoxybutane, t-butylperoxy-3,3,5-trimethylhexanoate, t-butylperoxy-2 -Organic peroxides such as ethylhexyl carbonate and azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile. These polymerization initiators can be used alone or in combination of two or more. In particular, in order to adjust the molecular weight and reduce the residual monomer, it is desirable to use together different polymerization initiators having a decomposition temperature of 80 to 120 ° C. in order to obtain a half-life of 10 hours.
[0029]
A suspension stabilizer may be used to disperse styrenic monomer droplets and seed particles in an aqueous medium during suspension polymerization and seed polymerization. Suspension stabilizers include water-soluble polymers such as polyvinyl alcohol, methyl cellulose, polyacrylamide, and polyvinyl pyrrolidone that are commonly used in suspension polymerization, and poorly water-soluble inorganic substances such as tricalcium phosphate, hydroxyapatite, and magnesium pyrophosphate. Examples include salts. When using a poorly water-soluble inorganic salt, an anionic surfactant is usually used in combination.
[0030]
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 There are phosphate ester salts such as salts.
[0031]
As the readily volatile foaming agent used in the present invention, hydrocarbons having 3 to 5 carbon atoms used in the production of general thermoplastic resin foams, that is, propane, butane, pentane, hexane and isomers thereof. Can be used. It is particularly preferable to use butane and isobutane in combination.
The use ratio of the foaming agent is preferably 2 to 10 parts by weight with respect to 100 parts by weight of the styrene resin. If it is less than 2 parts by weight, not only is it difficult to reduce the density, but the effect of increasing the secondary foaming power during molding cannot be obtained, and the appearance of the molded product may be inferior. On the other hand, when the amount exceeds 10 parts by weight, not only is the self-extinguishing property inferior because the residual gas in the foamed molded product increases, but the molding cycle becomes longer, which is not preferable from the viewpoint of productivity. Preferably, it is 3 to 8 parts by weight.
[0032]
In the present invention, when the styrene resin particles are impregnated with the above-mentioned readily volatile foaming agent in an aqueous medium, stearic acid amide, 12-hydroxystearic acid amide, ethylene bisstearic acid amide, ethylene bisoleic acid amide, methylene It is preferable to add a fatty acid amide such as bis stearic acid amide to the aqueous medium. Addition of these improves the thermal stability of the finally obtained expandable styrene resin particles. For example, it is possible to prevent bubbles from becoming uneven and coarse (heating) due to a heat history when left in a high temperature atmosphere in summer or when transported to a foaming and molding factory. Further, when the expandable styrene resin particles are pre-expanded, expanded particles whose surface bubbles are finer than the internal bubbles can be obtained, and the molding cycle can be shortened. Usually, when the average bubble diameter on the surface is 2/3 or less of the average bubble diameter inside, the remarkable effect appears.
[0033]
For example, bulk density 0.02g / cm ^Three In the case of pre-foaming, the inside average bubble diameter is preferably about 150 to 300 μm, and the surface average bubble diameter is preferably about 50 to 200 μm.
The addition amount of the fatty acid amide is preferably 0.01 to 0.2 parts by weight with respect to 100 parts by weight of the styrene resin. These addition times are preferably when impregnated with a readily volatile foaming agent as described above. When added when polymerizing a styrene monomer, pre-expanded particles (bulk density 0.02 g / cm ^Three ) Average cell diameter is 100 μm or less for both the inside and the surface, and the resulting foamed molded product may be inferior in heat insulation.
[0034]
In the present invention, a plasticizer may be used for the purpose of obtaining a foamed product having a lower density. Examples of the plasticizer include diisobutyl adipate, dioctyl adipate, dibutyl sebacate, glycerin tristearate, glycerin tricaprylate, coconut oil, and palm oil. The amount of the plasticizer used is preferably within 2 parts by weight with respect to 100 parts by weight of the styrene resin. If it exceeds 2% by weight, not only shrinkage and melting occur during molding, but also the production cost increases, which is not preferable. The plasticizer is added in a process of polymerizing styrene resin particles, a process of impregnating a composite flame retardant and a foaming agent, and the like. Further, it can be added when granulated by an extruder or the like and contained in styrene resin particles.
[0035]
In the present invention, a bubble regulator, a bubble stabilizer, a filler, a colorant and the like conventionally used in the production of expandable styrene resin particles may be appropriately used as necessary. The obtained self-extinguishing foamable styrenic resin particles may be dehydrated, dried, classified, and then coated with an antistatic agent or a binding inhibitor to prevent coalescence of particles during preliminary foaming on the particle surface. Good.
Pre-foaming can be performed using a pre-foaming machine for expanded polystyrene beads. The bulk density of the pre-expanded particles obtained is 0.008 to 0.1 g / cm. ^Three It is preferable that
Pre-expanded particles are filled in a mold of a molding machine, reheated with water vapor or the like to heat-seal the pre-expanded particles, and then cooled to obtain a foam-molded article having a desired shape. As the molding machine, a known molding machine for expanded polystyrene can be used.
[0036]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention in detail, this invention is not limited to these Examples.
Analysis and evaluation were performed by the following methods.
[0037]
[Quantification of polymerization conversion and residual styrene content]
The polymerization conversion rate was calculated by the following formula.
Polymerization conversion rate (% by weight) = 100 × (A−B) / A
The amount of residual styrene was calculated by the following formula.
Residual styrene content (% by weight) = 100 × B / A
However, A is the weight (g) of the styrene resin particle containing the 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 by GC was measured by dissolving styrene resin particles in N, N-dimethylformamide and adding an internal standard solution (cyclopentanol).
GC: Shimadzu Corporation GC-14A
Column: PEG-20M PT25% 60/80 (2.5 m)
Column temperature: 105 ° C
Detector (FID) temperature: 220 ° C
[0038]
[Average molecular weight]
The average molecular weight (Mw and Mn) of the polymer was measured by GPC (Gel Permeation Chromatography) under the following conditions.
Measuring device: 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: 500 ml
Detector: RID-6A manufactured by Tosoh Corporation
Measurement of the molecular weight of a sample: The molecular weight measurement conditions of a sample include the molecular weight distribution of the sample within a range in which the logarithm of the molecular weight of the calibration curve prepared by several monodisperse polystyrene standard samples and the number of counds are linear. Measurement conditions were selected. In the present invention, the polystyrene 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 These were prepared using 6 polystyrene standard samples (TSK standard polystyrene) manufactured by Tosoh Corporation.
[0039]
[Average bubble diameter]
The average cell diameter inside the foamed particle surface and inside the foamed particle is determined.
First, one cut surface obtained by dividing the expanded particle into approximately two parts by a cutter is magnified 40 times with a scanning electron microscope and photographed, and a straight line is drawn on the photograph so as to have the diameter of the expanded particle.
As the average bubble diameter on the surface of the expanded particle, the outermost periphery of one of the half circles in the expanded particle cross section divided by a straight line (including air bubbles applied to the straight line. In the expanded particle having a non-expanded skin layer) Measure the maximum diameter of all the bubbles in the skin layer as the outermost periphery), perform this measurement on 10 foamed particles, and calculate the arithmetic mean value of the maximum diameter obtained. The average cell diameter on the particle surface was used.
As the average bubble diameter inside the foamed particles, the maximum diameter of all the bubbles on the two inner line segments obtained by dividing the straight line into four equal parts was measured, and this measurement was performed on ten foamed particles. The arithmetic average value of the maximum diameter was defined as the average cell diameter inside the expanded particles.
[0040]
[Thermal conductivity]
The measurement of thermal conductivity was performed based on JIS-A-1412-2. The test piece used was cut out with a predetermined dimension from the center of the foamed molded product (length 400 mm × width 300 mm × thickness 20 mm) obtained in the examples.
Measuring apparatus: AUTO-A HC-072 manufactured by Eihiro Seiki Co., Ltd.
Test piece: length 200 mm x width 200 mm x thickness 20 mm
Measuring method: Plate heat flow meter method
Measurement temperature: 20 ° C
[0041]
[Combustion quality]
The time required for self-extinguishing was measured based on JIS A9511. From the JIS standard, the self-extinguishing time needs to be 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.
[0042]
[Melt flow rate (MFR) and expansion ratio (SR)]
The melt flow rate and the expansion ratio (SR) were measured under the following conditions based on JIS K7210.
Measuring device: Melt indexer manufactured by Toyo Seiki Seisakusho
Measurement temperature: 200 ° C
Load weight: 5kgf
Orifice diameter: 2.09 mm (B)
Strand diameter after extrusion A mm (measured between 5 mm from the strand tip)
Expansion ratio (SR) = A / B
5 g of styrenic resin is placed in a melt indexer heated to 200 ° C. in advance and left for about 3 minutes. Next, a load of 5 kgf is applied, and a styrene resin is extruded from an orifice diameter of 2.09 mm. Take the extruded strand, measure 5 strand diameters between 5 mm from the tip, and let A be the average value.
[0043]
The measurement of MFR was performed under the following conditions based on JIS K7210. First, the measurement sample was held for 24 hours while holding the self-extinguishing foamable styrene resin particles obtained in Examples and Comparative Examples in a 50 ° C. oven under vacuum at a final pressure of 10 Pa. What removed the volatile organic solvent was used.
[0044]
Example 1
(Production of polystyrene particles by suspension polymerization)
In a polymerization vessel equipped with a stirrer having an internal volume of 100 L, 40.0 L of water, 100 g of tricalcium phosphate and 2.0 g of sodium dodecylbenzenesulfonate were added, followed by stirring with 40.0 kg of styrene, 100.0 g of benzoyl peroxide, t- Butyl peroxy-2-ethylhexyl carbonate (28.0 g) was added, and the temperature was raised to 88 ° C. to obtain a polymerization temperature. And it hold | maintained at this temperature for 6 hours and 30 minutes, and also, after heating up to 125 degreeC, after 2 hours, it cooled and obtained the spherical polystyrene particle (A).
The polymerization conversion rate of the polystyrene particles (A) is 99.96% by weight, the Mw is 295,000, the polydispersity (Mw / Mn) is 3.0, and the melt flow rate is 4.2 g / 10 min. The expansion ratio SR was 1.42.
[0045]
The polystyrene particles (A) obtained above were sieved to obtain polystyrene particles (B) having a particle size of 0.5 to 0.7 mm. In a pressure vessel with a stirrer having an internal volume of 5 L, 2.2 L of water, 500 g of polystyrene particles (B), 6.0 g of magnesium pyrophosphate and 0.3 g of sodium dodecylbenzenesulfonate were added and heated to 70 ° C. while stirring. Subsequently, 5.2 g of benzoyl peroxide and 1.1 g of t-butylperoxy-2-ethylhexyl carbonate were dissolved in 200 g of styrene and placed in a pressure resistant container. After 30 minutes, the temperature was raised to 90 ° C., and 1300 g of styrene, in which 0.45 g of divinylbenzene had been dissolved in advance, was supplied to the pressure vessel by a constant amount over a period of 2 hours. 30 minutes after the supply was completed, the temperature was raised to 125 ° C. and held for 2 hours. Then, it cooled to 70 degreeC and sampled a part from the inside of the container, and obtained the spherical polystyrene particle.
[0046]
The polymerization conversion rate of the polystyrene particles is 99.95% by weight, the Mw is 447,000, the polydispersity (Mw / Mn) is 4.5, the melt flow rate is 1.4 g / 10 min, and the expansion ratio SR. Was 2.16.
Next, with continued stirring, a composite flame retardant mixed with 34.0 g of tris (2,3-dibromopropyl) isocyanurate and 6.0 g of 2,3-dimethyl-2,3-diphenylbutane was added and mixed. .
Moreover, when the melting point of the said composite flame retardant (BC ratio 15.0%) 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 performing DTA measurement based on JISK7121.
Thermal analyzer: Seiko Instruments TG / DTA6200R
Measurement sample mass: 10 mg
Temperature increase rate: 10 ° C / min
[0047]
Subsequently, 10.0 g of diisobutyl adipate and 0.8 g of ethylenebisstearic acid amide are added to 200 g of water in which 0.1 g of sodium dodecylbenzenesulfonate is dissolved in another container to form an emulsion. Placed in a container. Then, after raising the temperature in the pressure vessel to 100 ° C., 105 g of normal butane and 35 g of isobutane were injected and held for 4 hours.
Next, the inside of the pressure vessel was cooled to 30 ° C. or lower to obtain self-extinguishing foamable polystyrene particles. The expanded polystyrene particles taken out are dried and then stored in a constant temperature room at 20 ° C. for 5 days. Then, the bulk density is 0.02 g / cm using a preliminary foaming machine. ^Three Foamed. The obtained pre-expanded particles had an average cell diameter of 180 μm inside and 70 μm on the surface.
After pre-expanded particles were aged at room temperature (25 ° C.) for 8 hours, they were molded with a molding machine for expanded polystyrene (ACE-3QS manufactured by Sekisui Koki Co., Ltd.), and a plate-like expanded molded article having a beautiful appearance (length: 400 mm, width) 300 mm, thickness 20 mm). The foamed molded body was trained in a drying room at 50 ° C. for 6 hours, and then subjected to a combustion test of JIS-A9511. The results are shown in Table 1.
[0048]
Example 2
The plate-like foaming was carried out in the same manner as in Example 1 except that the composite flame retardant was 28.0 g of tris (2,3-dibromopropyl) isocyanurate and 12.0 g of 2,3-dimethyl-2,3-diphenylbutane. A molded body was obtained. Moreover, when the melting point of the said composite flame retardant (BC ratio 30.0%) was measured by DTA similarly to Example 1, the melting | fusing point peak temperature was one and was 103 degreeC. The evaluation results are shown in Table 1.
[0049]
Example 3
The plate-like foaming was the same as in Example 1 except that the composite flame retardant was 68.0 g of tris (2,3-dibromopropyl) isocyanurate and 12.0 g of 2,3-dimethyl-2,3-diphenylbutane. A molded body was obtained. Moreover, when the melting point of the said composite flame retardant (BC ratio 15.0%) was measured by DTA similarly to Example 1, the melting | fusing point peak temperature was one and was 103 degreeC. The evaluation results are shown in Table 1.
[0050]
Example 4
Except that the flame retardant auxiliary 2,3-dimethyl-2,3-diphenylbutane used for the composite flame retardant was changed to 3,4-dimethyl-3,4-diphenylhexane (DDPH), the same as in Example 1. A plate-like foamed molded product was obtained. Moreover, when the melting point of the composite flame retardant (DDPH ratio 15.0%) was measured by DTA in the same manner as in Example 1, the melting point peak temperature was one and 131 ° C. The evaluation results are shown in Table 1.
[0051]
Example 5
A plate-like foamed molded article was obtained in the same manner as in Example 1 except that 1.1 g of t-butylperoxy 2-ethylhexyl carbonate was changed to 0.06 g. Further, the melting point of the composite flame retardant (BC ratio 15.0%) was measured by DTA in the same manner as in Example 1. As a result, the melting point peak temperature was one and was 103 ° C. The evaluation results are shown in Table 1.
[0052]
Comparative Example 1
A plate-like foam molded article was obtained in the same manner as in Example 1 except that 7.0 g of tris (2,3-dibromopropyl) isocyanurate and 3.0 g of 2,3-dimethyl-2,3-diphenylbutane were used. It was. Further, when the melting point of the composite flame retardant (BC ratio 30.0%) was measured by DTA in the same manner as in Example 1, the melting point peak temperature was one and was 103 ° C. The evaluation results are shown in Table 1.
[0053]
Comparative Example 2
In a pressure vessel equipped with a stirrer with an internal volume of 5 L, 2.2 L of water, 500 g of the polystyrene particles (B) obtained in Example 1, 6.0 g of magnesium pyrophosphate and 0.3 g of sodium dodecylbenzenesulfonate were added and stirred. The temperature was raised to 70 ° C. Subsequently, 5.2 g of benzoyl peroxide and 1.1 g of t-butylperoxy 2-ethylhexyl carbonate were dissolved in 200 g of styrene and placed in a pressure resistant container. After 30 minutes, the temperature was raised to 90 ° C., and 1300 g of styrene, in which 0.45 g of divinylbenzene had been dissolved in advance, was supplied to the pressure vessel by a constant amount over a period of 2 hours. A portion of the container was sampled 30 minutes after the supply was completed to obtain spherical polystyrene particles. The polymerization conversion rate of the polystyrene particles was 94.2% by weight.
[0054]
Next, with continuing stirring, a composite flame retardant composed of 34.0 g of tris (2,3-dibromopropyl) isocyanurate and 6.0 g of 2,3-dimethyl-2,3-diphenylbutane was added and mixed. Moreover, when the melting point of the said composite flame retardant (BC ratio 15.0%) was measured by DTA similarly to Example 1, the melting | fusing point peak temperature was one and was 103 degreeC. Subsequently, it heated up to 125 degreeC and hold | maintained for 2 hours. Thereafter, the mixture was cooled to 70 ° C. and 10.0 g of diisobutyl adipate and 0.8 g of ethylenebisstearic acid amide were added to 200 g of water in which 0.1 g of sodium dodecylbenzenesulfonate was dissolved in another container to obtain an emulsion. I put things in. Then, after raising the temperature inside the pressure vessel to 100 ° C., 130 g of normal butane and 50 g of isobutane were injected and held for 4 hours.
Next, the inside of the pressure vessel was cooled to 30 ° C. or lower to obtain self-extinguishing foamable polystyrene particles. The expanded particles taken out were evaluated after the same treatment as in Example 1. The results are shown in Table 1.
[0055]
Comparative Example 3
The procedure was the same as Example 1 except that 80.0 g of tris (2,3-dibromopropyl) isocyanurate was used and 2,3-dimethyl-2,3-diphenylbutane was not used. Moreover, it was 115 degreeC when melting | fusing point of this flame retardant (BC ratio 0%) was measured similarly to Example 1 by DTA. The evaluation results are shown in Table 1.
[0056]
Comparative Example 4
The same procedure as in Example 1 was repeated except that 16.0 g of tris (2,3-dibromopropyl) isocyanurate and 64.0 g (80% by weight) of 2,3-dimethyl-2,3-diphenylbutane were used. Moreover, when the melting point of this composite flame retardant (BC ratio 80.0%) was measured by DTA in the same manner as in Example 1, the melting point peak temperature was one and was 104 ° C. The evaluation results are shown in Table 1.
[0057]
Comparative Example 5
The same procedure as in Example 1 was conducted except that 6.0 g of 2,3-dimethyl-2,3-diphenylbutane was used instead of 6.0 g of dicumyl peroxide (DCP). Further, when the melting point of the composite flame retardant (DCP ratio 15.0%) was measured by DTA in the same manner as in Example 1, DCP was decomposed during the measurement and could not be measured. The evaluation results are shown in Table 1.
[0058]
Comparative Example 6
Example 3 except that 38.0 g of tris (2,3-dibromopropyl) isocyanurate was replaced with 28.0 g of hexabromocyclododecane and 12.0 g of 2,3-dimethyl-2,3-diphenylbutane. Same. However, hexabromocyclododecane was not absorbed and remained in the pressure vessel. Further, when the melting point of this composite flame retardant (BC ratio 30.0%) 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. The evaluation results are shown in Table 1.
[0059]
Comparative Example 7
Instead of 34.0 g of tris (2,3-dibromopropyl) isocyanurate, 28.0 g of tetrabromocyclooctane was used, and dicumyl peroxide 12 instead of 6.0 g of 2,3-dimethyl-2,3-diphenylbutane. 0.0 g, but the same as Example 1. Further, when the melting point of this composite flame retardant (DCP ratio 30.0%) was measured with DTA in the same manner as in Example 1, DCP was decomposed during the measurement and could not be measured. The evaluation results are shown in Table 1.
[0060]
[Table 1]

[0061]
From Table 1, the foamed moldings obtained from the pre-expanded particles of Examples 1 to 5 were excellent in heat insulating properties, and in addition, the combustion test showed excellent self-extinguishing properties within 3 seconds.
The foam molded product obtained from the pre-expanded particles of Comparative Example 1 had good heat insulation, but the content of the composite flame retardant was less than 1.0 part by weight, so the foam molded product was inferior in self-extinguishing properties. It was a body.
Comparative Example 2 is an example in which a flame retardant is added during the polymerization of styrene resin particles, that is, in a state where the polymerization conversion rate is low. From this result, when a composite flame retardant is added at a time when the polymerization conversion rate of polystyrene particles is low In addition to an increase in residual styrene, the foamed molded product had fine bubbles and poor heat insulation performance.
The foamed molded article obtained from the pre-expanded particles of Comparative Example 3 was inferior in self-extinguishing properties because it did not contain a flame retardant aid.
[0062]
The foamed molded product obtained from the pre-expanded particles of Comparative Example 4 was inferior in heat insulating properties to that in Example 1, and was inferior in self-extinguishing properties because it contained substantially less flame retardant.
In Comparative Example 5, when dicumyl peroxide is used as a flame retardant aid, non-uniform absorption of the flame retardant occurs, and as a result, fine foam particles of bubbles are mixed (internal bubbles of 60 μm and 170 μm Mixed), irregularities occurred during molding, and a foamed molded article having a good appearance could not be obtained. Moreover, the heat insulation was also inferior to Example 1.
The foamed molded article obtained from the pre-expanded particles of Comparative Example 6 was inferior in self-extinguishing properties because it did not substantially contain a flame retardant.
The foamed molded product obtained from the pre-expanded particles of Comparative Example 7 had a mixture of bubbles in the same manner as Comparative Example 5, and a product with good appearance could not be obtained. Further, the heat insulating property was inferior to that of Example 1.
[0063]
Example 6
This example is an example for evaluating the recyclability of the foamed molded products of the above examples and comparative examples.
The melt flow rate (MFR) of the self-extinguishing foamable polystyrene resin particles obtained in Examples 1 and 2 and Comparative Examples 5 and 7 was measured. Further, the weight average molecular weight of the resin particles before and after the MFR measurement was also measured. Table 2 shows the MFR and the weight average molecular weight.
For comparison, MFR was measured by preparing polystyrene particles containing no flame retardant as follows.
[0064]
(Production of polystyrene particles that do not contain flame retardants)
The polystyrene particles (A) were sieved to obtain polystyrene particles (B) having a particle diameter of 0.5 to 0.7 mm. In a pressure vessel with a stirrer having an internal volume of 5 L, 2.2 L of water, 500 g of polystyrene particles (B), 6.0 g of magnesium pyrophosphate and 0.3 g of sodium dodecylbenzenesulfonate were added and heated to 70 ° C. while stirring. Subsequently, 5.2 g of benzoyl peroxide and 1.1 g of t-butylperoxy-2-ethylhexyl carbonate were dissolved in 200 g of styrene and placed in a pressure resistant container. After 30 minutes, the temperature was raised to 90 ° C., and 1300 g of styrene, in which 0.45 g of divinylbenzene had been dissolved in advance, was supplied to the pressure vessel by a constant amount over a period of 2 hours. 30 minutes after the supply was completed, the temperature was raised to 125 ° C. and held for 2 hours. Then, it cooled to 30 degreeC, took out from the inside of a container, and wash | cleaned and dried, and the particulate polystyrene particle (C) was obtained.
[0065]
[Table 2]

Table 2 shows the following.
First, the MFR of polystyrene resin that can be recycled by melt-kneading with an extruder and forming a strand is 20 g / 10 min or less, preferably 15 g / 10 min or less, particularly when no flame retardant is added, that is, particles (C It is preferable that it is close to MFR. Looking at Table 2 from this point of view, the resin particles of Examples 1 and 2 are both 15 g / 10 or less and can be sufficiently recycled. In contrast, the resin particles of Comparative Examples 5 and 7 have a significantly increased MFR and are difficult to recycle.
[0066]
Furthermore, 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 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 difficult to recycle. Looking at Table 2 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 5 and 7 have a greatly reduced weight average molecular weight, and even if it is difficult to recycle, the strength is not remarkably reduced.
[0067]
【The invention's effect】
According to the present invention, since a composite flame retardant containing a specific kind of flame retardant and a flame retardant aid in a specific ratio is used, the molecular weight of the styrene resin is hardly lowered during recycling, and the inherent property of the styrene resin is These properties (for example, heat insulation and mechanical strength) are maintained, excellent self-extinguishing properties are exhibited, and the method for dispersing in styrene resin is not limited. Furthermore, by using a specific composite flame retardant for styrene resin particles having specific properties, self-extinguishing properties can be imparted without impairing the properties of the resin.
[Brief description of the drawings]
FIG. 1 is a graph showing the melting point of a composite flame retardant.

Claims (6)

Consists of styrenic resin, readily volatile foaming agent, composite flame retardant,
Styrenic resin
(1) The content of the styrene monomer is 2000 ppm or less with respect to the styrene resin,
(2) Polydispersity (Mw / Mn) is 3.5 to 7.0,
(3) Melt flow rate (200 ° C., 5.0 kg load) is 0.1 to 2.0 g / 10 minutes,
(4) The value of the expansion ratio SR when measuring the melt flow rate is 1.60 to 2.50,
The composite flame retardant is tris (2,3-dibromopropyl) isocyanurate 90 to 40% by weight, and the flame retardant aid is represented by the following general formula:

(Wherein R1 to R4 are the same or different and are methyl or ethyl groups) and are composed of 10 to 60% by weight of a flame retardant aid represented by 1 to 100 parts by weight of styrene resin particles. 7 parts by weight of self-extinguishing foamable styrenic resin particles. The self-extinguishing foamable styrene resin particle according to claim 1, wherein the styrene resin is a copolymer obtained by copolymerizing 0.008 to 0.03 mol% of a polyfunctional monomer with respect to the styrene monomer. 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, wherein the content of the styrene monomer is 1000 ppm or less with respect to the styrene resin. Pre-expanded particles obtained by pre-expanding the self-extinguishing foamable styrene resin particles according to any one of claims 1 to 4. A self-extinguishing foam molded article obtained by foam molding of the pre-expanded particles according to claim 5.

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