JP4173580B2

JP4173580B2 - Polystyrene foamed particle molded body and method for producing the same

Info

Publication number: JP4173580B2
Application number: JP16279998A
Authority: JP
Inventors: 正道金子; 信幸小谷
Original assignee: Takashima and Co Ltd
Current assignee: Takashima and Co Ltd
Priority date: 1998-05-28
Filing date: 1998-05-28
Publication date: 2008-10-29
Anticipated expiration: 2018-05-28
Also published as: JPH11333938A

Description

【０００１】
【発明の属する技術分野】
本発明は互いに連通した空隙を有するポリスチレン系発泡粒子成形体及びその製造方法に関し、更に詳しくは、透水性を保有しながら土砂等のフィルター機能に優れ、かつ強度にも優れたポリスチレン系発泡粒子成形体及びその製造方法に関する。
【０００２】
【従来の技術】
連通した空隙を保有する熱可塑性樹脂発泡粒子成形体は、その連通空隙の持つ透水性を利用して暗渠排水材、軽量盛土材等に使われている。
特にポリスチレン系発泡粒子の空隙保有成形体は透水性、耐久性、断熱性、施工性を備えた部材として近年注目されており、土木分野例えば軟弱土壌の暗渠排水材、屋上庭園の土中面状排水材あるいは透水性歩道の凍上防止材等に好適に用いることができ利用され始めている。
【０００３】
かかる空隙を有する熱可塑性樹脂発泡粒子成形体は従来から知られている。
例えば特開平７−１３７０６５号公報には３次元座標の寸法を規定した発泡体を結合してなる発泡成形体が示されており、空隙部の最大径をＬとした場合に、Ｌが２ｍｍ以上の空隙部の全個数に対してＬが２〜１０ｍｍの空隙部の個数の割合が０．９以上である成形体は土砂が詰まりにくいことが開示されている。
また、特開平７−１３７０６８号公報には上記と同様な３次元座標の寸法を規定した発泡体を結合してなる発泡成形体で、透水係数が１．０×１０^-2〜９．０×１０^-2ｃｍ／秒であるものが透水性、強度の観点で好ましいことが記載されている。
【０００４】
また、特開平９−３２４４１０号公報にはＳ字型の合成樹脂発泡部材が互いに溶着された透水性ブロック成形体で土中排水を行うこと及び成形体に窪みや溝等形成させて排水路を形成させることが示されている。
また、特開平１−１６３３３１号公報には軟弱地盤に埋設するコンクリートブロック外壁を透水性発泡スチロールで覆い土中水を排水する構造が開示されている。
更に、空隙を有する熱可塑性樹脂発泡粒子成形体の製法として、特開昭６０−１０４３１８号公報及び特開平５−１７７７２３号公報には異形または非球形のポリスチレン系発泡粒子を金型内で成形する方法が開示されている。
【０００５】
【発明が解決しようとする課題】
しかしながら、特開平７−１３７０６５号公報に記載された発泡粒子成形体では土砂が詰まりにくい替わりに透水性が十分でなく土中排水に時間がかかるという問題があった。
特開平７−１３７０６８号公報に記載の発泡粒子成形体では透水係数が１．０×１０^-2〜９．０×１０^-2ｃｍ／秒のものが開示されているが、該透水係数は細かい砂の透水係数と同等であり、土壌の排水を迅速に行うための排水材としては透水性能が不足していた。また、オレフィン系樹脂を発泡粒子の基材樹脂として使用しているため、圧縮強度や圧縮クリープ耐性に問題があった。
【０００６】
特開平９−３２４４１０号公報にはブロック成形体を構成する粒子の形状が規定されているが、透水性とフィルター機能を両立させにくいものであった。即ち、発泡粒子を互いに溶着させる成形体製造工程において、発泡粒子の加熱膨張を抑えて発泡粒子間空隙を大きくしたものでは透水性能は高まるものの、発泡粒子同士の融着が不十分になりやすく成形体の強度に問題があった。また、発泡粒子のサイズを大きくして粒子間の空隙サイズを大きくすると、フィルター機能が低下して空隙部から土砂が流出しやすいという問題がおこった。逆に、発泡粒子を小さくして粒子間空隙サイズを小さくすると土砂の流出は少なくなるが、空隙に土砂が詰まって透水性が低下しやすく長期の透水性能の維持が難しかった。また、特開平１−１６３３３１号公報の透水性発泡スチロールも透水性とフィルター機能を両立させにくいという問題があった。
【０００７】
特開昭６０−１０４３１８号公報、及び特開平５−１７７７２３号公報に開示される方法では成形体内部の粒子同士の融着が不十分になるという問題があった。即ち、発泡粒子をスチームで加熱成形する際、型の表面部分の発泡粒子から先に膨張融着して粒子間の隙間を塞ぐため金型内部へのスチームの導入が抑えられてしまい成形体表面に比べ成形体内部の発泡粒子同士の融着が不十分になるという問題があった。
本発明は、上記従来技術の欠点を克服し、空隙を有するポリスチレン系発泡粒子成形体であって、透水性とフィルター機能の両方に優れ、かつ強度にも優れた成形体を提供することを目的とする。
【０００８】
【課題を解決するための手段】
本発明者らは上記課題を達成するため鋭意検討した結果、空隙を有する発泡粒子成形体において、透水性能とフィルター機能を兼備するためには成形体中の透水流速のコントロールが重要であることに着目した。
即ち、成形体空隙部のうち透水流速の小さい部分にフィルター機能、大きい部分に透水機能を持たせ両者を混合分散させた構造とすることにより長期使用に耐えるものが得られる。
また、成形体空隙が表面と内部で均一で優れた透水性の発泡粒子成形体を製造するには発泡粒子の形状、発泡膨張力が重要である。本発明はこれらの点に着目してなされたものである。
【０００９】
即ち、本発明の発泡粒子成形体は、複数のポリスチレン系発泡粒子を加熱発泡させて結合してなり、該発泡粒子間に互いに連通する空隙が形成された発泡粒子成形体であって、該成形体断面１００ｃｍ^２当たりに前記発泡粒子が４０〜８０個存在し、前記成形体断面１００ｃｍ^２当たりに最大径が１５〜３０ｍｍである空隙が１〜１０個存在し、該成形体の空隙率が８〜２０％で、透水係数（ｃｍ／秒）が０．１５〜２．００であることを特徴とするポリスチレン系発泡粒子成形体に係わる。
更には、発泡粒子が揮発性発泡剤を樹脂１００重量部当たり２〜４重量部含有し、１粒当たりの体積が２〜６ｃｍ^３で、充填空隙率が４０〜６０％であるポリスチレン系発泡粒子を金型キャビティー内に充填し、水蒸気で加熱して成形する成形体の製造方法に係わる。
【００１０】
以下、本発明の内容について詳細に説明する。
まず、本発明の成形体断面の空孔サイズについて図面を用いて説明する。図１は成形体断面の模式図である。図中１は発泡粒子部の断面であり、２は発泡粒子間の空隙を示す。Ａは、成形体断面において観察される各空隙の最大径の寸法を示す。Ａは、各空隙の外形を平行な２直線で挟んだ時の直線間距離の最大径に相当する。
【００１１】
本発明の成形体では、成形体の透水機能及びフィルター機能を両立させる観点から、成形体断面積１００ｃｍ²当たりに存在する最大径Ａが１５〜３０ｍｍである空隙の数（以下Ｎａとする）が１〜１０個であることが必要である。Ａの値が１５ｍｍ未満の空隙は土砂のフィルター機能を保有するが透水機能は小さく、一方Ａの値が３０ｍｍを越える空隙はフィルター機能を有しない。従って本発明ではＡの値が１５〜３０ｍｍの空隙数に着目した。また、Ｎａが１未満では透水機能が小さく、１０を越えると成形体圧縮強度、圧縮クリープ耐性及びフィルター機能が低下する。Ｎａの値の更に好ましい範囲は２〜６である。
【００１２】
本発明の成形体では、成形体断面１００ｃｍ²当たりに存在する発泡粒子の数（以下Ｎｒとする）は粒子間の空隙を適度にし、フィルター機能を確保できる点で、３０〜９０個が好ましい。このＮｒが３０個未満では空隙の数が減り空隙１個当たりのサイズが大きくなってフィルター機能を低下させる要因となる。逆にＮｒが９０個を越えると空隙の数が増え空隙１個当たりのサイズが小さくなって透水機能を低下させる。Ｎｒの値は更に好ましくは５０〜８０個である。
【００１３】
本発明の成形体の空隙率（以下Ｖとする）は成形体の透水性を確保するため８〜３５％である必要がある。Ｖが８％未満では透水性が確保できず、またＶが３５％を越えると発泡粒子同士の融着が不十分となり、成形体の圧縮強度や圧縮クリープ耐性が低下するので好ましくない。Ｖの更に好ましい範囲は１０〜３０％であり、特に好ましい範囲は１０〜２０％である。
上記したように本発明の成形体ではＮａ、Ｎｒ、Ｖの３者を満たすことが成形体の透水機能及びフィルター機能を両立させる点で重要である。
本発明で得られる成形体の空隙は連続したものである。即ち、成形体の一面から裏側の面に空隙が通じており、成形体を水中に没した場合に水が入り込める部分を成形体の空隙という。
【００１４】
次に本発明の発泡粒子成形体の製造方法について説明する。
成形時に金型キャビティーに充填される発泡粒子に含有される発泡剤量は発泡粒子の膨張力を適正にする観点から、１．５〜４重量部が好ましい。即ち、発泡剤量が１．５重量部未満では発泡粒子の膨張力が不足して十分な粒子間の融着を達成できず、成形体が成形後に収縮しやすい。また、発泡剤量が４重量部を越えると発泡粒子の膨張力が高すぎて粒子間の空隙が埋まってしまい、空隙率をコントロールすることが難しい。また、型表面の発泡粒子から膨張融着が起こり型内部へのスチームの導入部が塞がれて内部融着が不十分となる。
本発明において、発泡粒子に発泡剤が１重量部含有されるとは、樹脂１００重量部に対して発泡剤が１重量部含有されているということである。
【００１５】
本発明の成形体製造法では、金型キャビティーに充填される発泡粒子１粒当たりの体積は、成形体空隙のサイズを適正なものにできる観点から２〜６ｃｍ³である。発泡粒子体積１粒当たりの体積が２ｃｍ³に満たないものでは成形体の空隙サイズが小さくなり透水機能を低下させる。逆に１粒当たりの体積が６ｃｍ³を越えるものでは成形体の空隙サイズが大きくなりフィルター効果が低下するので好ましくない。発泡粒子の体積の更に好ましい範囲は２〜５ｃｍ³である。ここでいう発泡粒子の体積は、成形に使用する任意の２０個の発泡粒子の体積の算術平均をいう。
【００１６】
本発明で用いる発泡粒子の充填空隙率は成形体空隙率を大きくできる観点で４０〜６０％である。発泡粒子の充填空隙率とは発泡粒子を容器に充填し、加重０．２ＫＰａをかけた状態での粒子間空隙率をいう。加重０．２ＫＰａをかけるのは粒子の充填状態で空隙率値が変わらないようにするため充填粒子に一定の荷重をかけ空隙率が一定に測れるようにするためである。充填空隙率の値の更に好ましい範囲は４５〜５５％である。充填空隙率が４０〜６０％となるには粒子形状が球、円筒、楕円球等では達成できない。粒子表面に複数個の窪みを有することが必須である。本発明においては充填空隙率が４０〜６０％であれば粒子形状には拘らない。
【００１７】
本発明の成形体の製造方法で金型キャビティーに充填する発泡粒子密度は、成形性の点から０．０１２〜０．１００ｇ／ｃｍ³が好ましい。密度が０．０１２ｇ／ｃｍ³未満では粒子の膨張力が小さくなる。０．１００ｇ／ｃｍ³超えると強度は大きいが重量が増え製造コストも大きくなる。密度の更に好ましい範囲は０．０１５〜０．０５０ｇ／ｃｍ³である。
本発明の成形体の製造方法は上記した発泡粒子を金型キャビティー内に充填し、水蒸気で型内を加熱し成形する工程からなる。成形方法については公知の方法を用いることができる。例えば多数のステーム孔又はスリットを有する金型のキャビティー内に発泡粒子を充填し次いでキャビティー内に９５〜１１０℃のスチームを所定時間導入し更にキャビティー内を冷却して成形体を取り出す方法が一般的である。
【００１８】
本発明で用いるポリスチレン系樹脂としては、ポリスチレン、スチレン系モノマーを５０％以上含有するスチレン系単独あるいは共重合体を用いることができる。スチレン系モノマーとしては、スチレンの外、メチルスチレン、ジメチルスチレン、エチルメチルスチレン等の核アルキル置換スチレン、クロルスチレン等の核ハロゲン化スチレン等であり、単独あるいは２種以上の混合物として用いられる。
スチレン系共重合モノマーとしては、例えばアクリロニトリル、メチルメタクリレート、無水マレイン酸等がある。また、上記スチレン系樹脂中に共役ジエン系重合体を含有するもの、ＡＢＳ等を用いることができる。共役ジエン系重合体とは、例えばハイシスポリブタジエン、ローシスポリブタジエン、スチレン−ブタジエン共重合体（ランダム及びブロック）、イソプレンゴム等である。
【００１９】
これらの中で特に好ましいものは汎用性、発泡剤保持性の点から、ポリスチレン、ハイインパクトポリスチレンである。
樹脂には必要に応じて、滑剤、離型剤、帯電防止剤、発泡核剤、紫外線安定剤等の添加剤を加えることができる。
本発明で用いられる揮発性発泡剤としては、沸点が−８０〜＋１００℃の範囲にあるもの、例えばブタン、ｎペンタン、イソペンタン、ヘキサン、石油エーテル等の脂肪族炭化水素、シクロペンタン等の環状脂肪族炭化水素の外、ハロゲン化炭化水素等を用いることができる。
【００２０】
本発明で用いるポリスチレン系発泡粒子は公知の方法を用いて製造することができる。例えば、（ａ）押出機内でポリスチレン系樹脂と発泡剤を混合し未発泡状態でダイノズルからストランド状に押し出したものを粒子状にカットし、スチーム等の加熱により発泡粒子とする方法、（ｂ）表面窪みを有する樹脂粒子に発泡剤を含浸させ、スチーム等の加熱により発泡粒子とする方法、（ｃ）押出機内で樹脂と発泡剤を混合し、ダイノズルからストランド状に発泡させながら押し出したものを粒子状にカットする方法、（ｄ）樹脂発泡体の粉砕品を用いる方法等がある。尚、上記（ａ）〜（ｄ）の発泡粒子の製造法の内、作業性等が容易なことから（ａ）の方法が好ましい。（ａ）の場合、ダイノズルの断面形状はＳ字、Ｗ字、あるいはＭ字状等がある。
未発泡粒子あるいは発泡粒子の大きさはダイノズルの大きさを変えることや、ダイノズルから溶融押し出しされるストランドの引き取り速度を加減することにより所望の大きさに調整することができる。
【００２１】
【発明の実施の形態】
以下に実施例によりさらに詳細に本発明を説明するが、本発明はこれらに限定されるものではない。
なお、実施例、比較例中の発泡粒子及び成形体の性質は以下のようにして測定あるいは評価した。
（１）発泡粒子の密度Ｄｒ
発泡粒子をメスシリンダー中で水没させ、水位上昇値を測定して発泡粒子が押しのけた水量を求め、発泡粒子の体積とした。発泡粒子の重量を測定し、重量を体積で除して発泡粒子の密度Ｄｒ（ｇ／ｃｍ³）を求めた。
【００２２】
（２）発泡粒子の充填空隙率
内容積３０ｃｍ×３０ｃｍ×３０ｃｍの木製容器の重量を測定する。次にこの容器に発泡粒子を押さえつけないように入れて、発泡粒子の面上に０．２ＫＰａに相当する静荷重（１．８ｋｇの上蓋）を載せこの時の厚さが３０ｃｍとなる迄、発泡粒子を容器内に満たし、その時の容器の総重量を測定する。
容器の総重量から容器のみの重量を差し引いて発泡粒子の重量を求め、この重量を容器の内容積２７０００ｃｍ³で除して充填状態でのかさ密度Ｄａ（ｇ／ｃｍ³）とする。発泡粒子の充填空隙率は以下の式で与えられる。
充填空隙率（％）＝１００×〔（Ｄｒ−Ｄａ）／Ｄｒ〕
【００２３】
（３）発泡粒子の発泡剤含有率
発泡後充分に熟成乾燥させた発泡粒子を１８０℃熱板でプレスし、発泡粒子中の発泡剤を揮散させた。熱プレス前と熱プレス後の重量変化分をプレス前重量で除して発泡剤含有率とした。
（４）成形体のかさ密度Ｄｓａ
１０ｃｍ立法の成形体の重量を測定し、得られた重量を１０００ｃｍ³で除して成形体のかさ密度Ｄｓａ（ｇ／ｃｍ³）を求めた。
【００２４】
（５）成形体の空隙率Ｖ（％）
１０ｃｍ立法の成形体を石鹸水中に水没させ、成形体空隙部に十分水を浸透させた後の水位の上昇分体積を成形体の実体積Ｕ（ｃｍ³）とした。成形体の見かけの外形体積は１０００ｃｍ³であるので実体積との差が空隙体積となる。
成形体の空隙率Ｖは以下の式で与えられる。
Ｖ（％）＝１００×〔（１０００−Ｕ）／１０００〕
【００２５】
（６）成形体透水係数
ＪＩＳ−Ａ−１２１８の定水位透水性試験法により測定した。下記の記号により透水性を評価した。
記号評価
◎ 透水係数が１ｃｍ／秒以上。
○ ０．１ｃｍ／秒以上〜１ｃｍ／秒未満。
△ ０．０１ｃｍ／秒以上〜０．１ｃｍ／秒未満。
× ０．０１ｃｍ／秒未満。
【００２６】
（７）成形体のフィルター性能
内寸縦横１５ｃｍ×５０ｃｍ、深さ５０ｃｍ、側面底部に排水口を設けた容器に縦横１５×５０ｃｍで厚み１０ｃｍに切り出した成形体を容器底部に設置した。成形体の上に全面にわたって砂土を深さ３０ｃｍに充填した。更にその上から水道水を供給して容器下部の排水口から水を排水させた。水は砂土上に冠水するよう常に補充供給し連続的に給水排水を行った。排水の状況に応じて下記の記号よりフィルター性能を評価した。
記号評価
○ 排水が透明で澄んでいる。
△ 排水が懸濁状に濁っているが固形物の沈殿は見られない。
× 排水に固形物砂土が混入している。
【００２７】
（８）成形体の５％圧縮強度
ＪＩＳ−Ｚ−０２３４のＡ法に基づいて測定した。
評価は以下のように行った。
記号評価
○ ５％圧縮強度が０．０６ＭＰａ以上
△ ０．０３ＭＰａ以上〜０．０６ＭＰａ未満
× ０．０３ＭＰａ未満
【００２８】
（９）成形体の圧縮クリープ
ＪＩＳ−Ｋ−６７６７に基づいて測定した。荷重は０．０１ＭＰａで３０日間荷重をかけ寸法の減少率を以下のように評価した。
記号評価
◎ 圧縮クリープ値が２％未満
○ ２％以上〜５％未満
△ ５％以上〜１０％未満
× １０％以上
【００２９】
【実施例１】
ポリスチレン樹脂（旭化成工業社製商品名「スタイロン６８０」）を押出し機中で加熱溶融させ、更に発泡剤としてノルマルペンタンを押出し機に供給して樹脂に含浸させた。更に、発泡剤含有熱可塑性樹脂をＳ型のダイノズルより発泡を抑えたストランド状に押出し、直ちに水冷した後、回転刃を備えたカッターでストランド押し出し方向と垂直方向に粒子状にカットした。得られた粒子を１００℃のスチームで１８０秒間加熱し、熟成させて密度（Ｄｒ）が０．０３０ｇ／ｃｍ³の発泡粒子とした。発泡粒子の体積は３．０ｃｍ³であり、充填空隙率は４９％であった。得られた発泡粒子の性状を表１に示す。
【００３０】
この発泡粒子は発泡剤含有量が３．２重量部であったが、この粒子を９００ｍｍ×１８００ｍｍ×３００ｍｍの内寸を持ち、大気開放弁を備えた金型キャビティー内に充填した。スチーム（１００℃）をスチーム導入弁より金型キャビティー内に３００秒間導入し、大気開放弁よりスチームを排気しつつ金型キャビティー内を加熱した。次に、大気開放弁を開としたままブロアーにより空気（２０℃）を金型キャビティー内に３０秒間導入した。空気導入終了後直ちに金型を開いて成形体を取り出した。
【００３１】
得られた成形体を５０℃中で２時間乾燥させた。乾燥後の成形体のかさ密度は１３．５ｋｇ／ｍ³であった。成形体断面１００ｃｍ²当たりの発泡粒子数（Ｎｒ）は５８個、成形体断面１００ｃｍ²当たりの最大径１５〜３０ｍｍである空隙の数（Ｎａ）は２個、成形体の空隙率（Ｖ）は１１％であった。粒子の融着状態は成形体表面、内部とも良好であり、成形体の外観も収縮や反りは見られず良好であった。成形体の透水係数は０．１８ｃｍ／秒であった。得られた成形体の性状を表１に示す。
【００３２】
内寸縦横１５ｃｍ×５０ｃｍ、深さ５０ｃｍの容器で底部に直径７ｃｍの排水口を設けた容器に、縦横１５×５０ｃｍで厚み１０ｃｍに切り出した成形体を取り付けた。取り付け位置は成形体の縦横方向を容器の縦横方向に合わせ、容器底部から５ｃｍを浮かせ空間となるようにして取り付け、成形体の上に全面にわたって砂土を深さ３０ｃｍに充填した。更にその上から水道水を供給して容器下部の排水口から水を排水させた。水は砂土上に冠水するよう常に補充供給し連続的に給水排水を３０分間行った。排出水は透明で濁りは見られなかった。成形体の性能を表２に示す。
成形体の５％圧縮強度及び圧縮クリープは表２に示されるように良好なものであった。
【００３３】
【実施例２】
ダイス形状をＣ型に変え、実施例１と同様な樹脂、発泡剤を用いて発泡性粒子を作製した。更に、得られた発泡性粒子を１８０秒間スチーム加熱し発泡粒子を得た。得られた発泡粒子を実施例１と同じ成形金型に充填しスチームで３００秒間加熱して成形体を作製した。得られた発泡粒子の性状及び成形体の形状を表１に示す。
成形体の透水係数、フィルター性能、５％圧縮強度、圧縮クリープ性は表２に示されるように良好なものであった。
【００３４】
【実施例３】
実施例１と同様の樹脂、発泡剤を用いて押し出し操作を行い発泡剤を含有した発泡性粒子を得た。発泡性粒子をスチームで１５０秒加熱し、一旦熟成させた後、再度発泡粒子をスチームで１２０秒間加熱し、発泡粒子を得た。得られた発泡粒子を実施例１と同じ成形金型に充填し、スチームで３６０秒間加熱して成形体を得た。得られた発泡粒子、成形体の性状については表１、成形体の透水性能、強度性能については表２に示す。成形体の透水係数は良好であり、土砂のフィルター性は排水に若干の濁りは見られたが固形物の漏出は見られなかった。成形体の強度もほぼ良好であった。
【００３５】
【実施例４】
実施例２より小型のＣ型のダイスでを用いて実施例１と同様な樹脂、発泡剤を用いて押し出し操作を行い発泡剤含有粒子を得た。更にこの粒子をスチームで１５０秒間加熱及び熟成させて表１に示される発泡粒子を得た。
更に実施例１と同じ成形金型に発泡粒子を充填しスチームを２７０秒間加熱して成形を行い表１、表２に示される性状の成形体を得た。
【００３６】
【比較例１】
発泡剤の添加量を大きくする他は実施例１と同様な操作を行い、発泡剤含有量の多い発泡性粒子を得た。得られた発泡性粒子をスチームで１５０秒間加熱して表１に示す発泡粒子を得た。得られた発泡粒子は発泡剤含有量が４．５重量部であった。得られた発泡粒子を実施例１と同じ成形金型に充填してスチームで３００秒間加熱し成形すると発泡膨張力が大きいため金型の表層付近で発泡粒子が膨張融着して成形体内部の加熱は不十分なものとなった。成形体断面の空隙数（Ｎａ）は１２個であったが表面付近の空隙が少なく成っている影響で透水係数は０．０７ｃｍ／秒と小さなものであった。表２に成形体の性能を示す。
【００３７】
【比較例２】
実施例１と同じ発泡剤を３．０重量部含有する表１に示す球状のポリスチレン発泡粒子を準備した。発泡粒子体積が１．５ｃｍ³と小さいため充填空隙率は３５％と比較的小さいものであった。該発泡粒子を用いて実施例１と同様の金型でスチーム加熱３００秒で成形すると得られた成形体の空隙数（Ｎａ）は０個であった。透水係数は０．０３ｃｍ／秒で小さい物であった。
成形体の形状を表１にし、成形体の透水係数、フィルター性能、５％圧縮強度、圧縮クリープ性は表２に示す。
【００３８】
【比較例３】
実施例１のダイスより大きいダイスを用いて実施例１と同様の樹脂、発泡剤を用いて押し出し操作を行い発泡剤を含有した発泡性粒子を得た。発泡性粒子をスチームで１８０秒加熱し、一旦熟成させた後、再度発泡粒子をスチームで１２０秒間加熱し、発泡粒子を得た。得られた発泡粒子を実施例１と同じ成形金型に充填し、スチームで３６０秒間加熱して成形体を得た。得られた発泡粒子、成形体の性状については表１、成形体の透水性能、強度性能については表２に示す。発泡粒子体積が８．０ｃｍ³と大きいため成形体の空隙数（Ｎａ）は１４個と多かった。Ｎｒも２５個と少なかった。透水係数は５．５と大きく良好であったが、成形体から土砂の流出が見られフィルター性能は劣る物であった。また、５％圧縮強度、圧縮クリープ性とも劣る物であった。
【００３９】
【比較例４】
発泡剤の仕込み量を減らすほかは実施例１と同様な操作を行い発泡性粒子を得た。得られた発泡性粒子をスチームで１５０秒間加熱し表１の発泡粒子を得た。発泡剤含有量が１．２重量部と小さいため、発泡粒子の膨張力が不足し実施例１と同様の成形を行っても成形体の発泡粒子同士の融着が十分ではなく、成形体の空隙数（Ｎａ）も１５個と大きかった。従って成形体のフィルター性能測定においては土砂の漏出が見られ、フィルター性能の劣るものであった。
発泡粒子の性状及び成形体の形状を表１にし、成形体の透水係数、フィルター性能、５％圧縮強度、圧縮クリープ性は表２に示す。
【００４０】
【比較例５】
実施例１と同様の操作を行い発泡剤仕込み量を下げて表１の発泡粒子を得た。実施例１と同じ金型に発泡粒子を充填してスチーム加熱したがスチーム加熱時間が２００秒と短かったため発泡粒子の膨張が不十分であり、成形体の空隙率が４０％であった。成形体のフィルター性能及び強度性能は表２に示されるように不十分なものであった。
発泡粒子の性状及び成形体の形状を表１にし、成形体の透水係数、フィルター性能、５％圧縮強度、圧縮クリープ性は表２に示す。
【００４１】
【表１】

【００４２】
【表２】

【００４３】
【発明の効果】
本発明によれば透水性とフィルター機能の両方に優れ、かつ強度にも優れた、空隙を有するポリスチレン系発泡粒子成形体を提供できる。
【図面の簡単な説明】
【図１】発泡粒子成形体断面の模式図である。
【図２】発泡粒子成形体断面空隙部の最大寸法を示す図である。
【符号の説明】
１成形体断面の発泡粒子部
２成形体断面の粒子間の空隙部
Ａ空隙部の最大寸法[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polystyrene-based foamed particle molded body having voids communicated with each other and a method for producing the same, and more specifically, a polystyrene-based foamed particle molded having excellent water filter permeability and excellent filter function such as earth and sand. The present invention relates to a body and a manufacturing method thereof.
[0002]
[Prior art]
Thermoplastic resin foamed particle molded bodies having continuous voids are used for underdrainage materials, lightweight embankment materials, etc. by utilizing the water permeability of the communicating voids.
In particular, polystyrene-containing foam void-containing molded products have attracted attention in recent years as members with water permeability, durability, heat insulation, and workability, such as underdrainage materials for soft soil, such as underdrain surfaces of rooftop gardens. It can be suitably used as a drainage material or an anti-freezing material for a water-permeable sidewalk, and has begun to be used.
[0003]
A thermoplastic resin expanded particle molded body having such voids is conventionally known.
For example, Japanese Patent Application Laid-Open No. 7-137065 discloses a foamed molded body formed by combining foams having dimensions of three-dimensional coordinates, where L is 2 mm or more, where L is the maximum diameter of the gap. It is disclosed that the molded body in which the ratio of the number of voids having L of 2 to 10 mm is 0.9 or more with respect to the total number of voids is not easily clogged with earth and sand.
JP-A-7-137068 discloses a foamed molded product obtained by combining foams having the same three-dimensional coordinate dimensions as described above, and has a water permeability coefficient of 1.0 × 10 ^{−2 to} 9.0 ×. It is described that 10 ⁻² cm / sec is preferable in terms of water permeability and strength.
[0004]
Japanese Patent Laid-Open No. 9-324410 discloses drainage in the soil using a water-permeable block molded body in which S-shaped synthetic resin foam members are welded to each other, and forming a depression or groove in the molded body. It is shown to form.
JP-A-1-163331 discloses a structure in which the outer wall of a concrete block embedded in soft ground is covered with water-permeable foamed polystyrene to drain soil water.
Furthermore, as a method for producing a foamed thermoplastic resin foam particle, Japanese Patent Application Laid-Open No. 60-104318 and Japanese Patent Application Laid-Open No. 5-177723 form irregular or non-spherical polystyrene-based expanded particles in a mold. A method is disclosed.
[0005]
[Problems to be solved by the invention]
However, the foamed particle molded body described in JP-A-7-137065 has a problem in that it does not have sufficient water permeability instead of being easily clogged with earth and sand, and it takes time to drain into the soil.
The foamed particle molded body described in JP-A-7-137068 has a water permeability coefficient of 1.0 × 10 ^{−2 to} 9.0 × 10 ⁻² cm / second, but the water permeability coefficient is small. It has the same permeability as that of sand and lacks water permeability as a drainage material for quickly draining soil. Moreover, since the olefin resin is used as the base resin for the expanded particles, there is a problem in compressive strength and compressive creep resistance.
[0006]
Japanese Patent Application Laid-Open No. 9-324410 defines the shape of particles constituting the block molded body, but it is difficult to achieve both water permeability and filter function. That is, in the molded body manufacturing process in which the foam particles are welded to each other, if the expansion between the foam particles is suppressed by suppressing the thermal expansion of the foam particles, the water permeability is improved, but the foam particles are likely to be insufficiently fused. There was a problem with the strength of the body. In addition, when the size of the expanded particles is increased to increase the size of the gap between the particles, the filter function is deteriorated, and there is a problem that earth and sand easily flows out from the gap. On the contrary, when the foamed particles are made smaller and the gap size between the particles is reduced, the outflow of earth and sand is reduced. However, the gap is clogged with earth and sand, the water permeability is likely to be lowered, and it is difficult to maintain the long-term water permeability. Further, the water-permeable foamed polystyrene disclosed in JP-A-1-163331 also has a problem that it is difficult to achieve both water permeability and a filter function.
[0007]
In the methods disclosed in JP-A-60-104318 and JP-A-5-177723, there is a problem that the fusion of particles inside the molded article becomes insufficient. That is, when foamed particles are heat-formed with steam, the surface of the molded body is suppressed by introducing and condensing steam inside the mold because the foamed particles on the surface of the mold are expanded and fused first to close the gaps between the particles. Compared to the above, there was a problem that the fusion of the foamed particles inside the molded body was insufficient.
An object of the present invention is to overcome the above-mentioned drawbacks of the prior art and provide a polystyrene-based foamed particle molded body having voids, which is excellent in both water permeability and filter function, and has excellent strength. And
[0008]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that in the foamed particle molded body having voids, it is important to control the water flow rate in the molded body in order to combine the water permeability and the filter function. Pay attention.
That is, a product that can withstand long-term use can be obtained by providing a filter function in a portion having a low water permeation flow rate and a water permeation function in a large portion and mixing and dispersing both of the formed body voids.
In addition, the shape of the foamed particles and the foam expansion force are important for producing a water-permeable foamed particle molded body having uniform and excellent voids on the surface and inside. The present invention has been made paying attention to these points.
[0009]
That is, the foamed particle molded body of the present invention is a foamed particle molded body in which a plurality of polystyrene-based foamed particles are bonded by heating and foaming, and voids communicating with each other are formed between the foamed particles. body section 100 cm ² the expanded particles per are present 40 to 80 pieces, the maximum diameter in the molded body section 100 cm ² per are present 1 to 10 voids is 15 to 30 mm, porosity of the molded article 8 It relates to a polystyrene-based foamed particle molded body having a water permeability coefficient (cm / second) of 0.15 to 2.00 at 20 %.
Furthermore, the foamed particles contain 2 to 4 parts by weight of a volatile foaming agent per 100 parts by weight of the resin , the polystyrene-based foamed particles have a volume per particle of 2 to 6 cm ³ and a filling porosity of 40 to 60%. The present invention relates to a method for producing a molded body in which a mold cavity is filled and heated with water vapor and molded.
[0010]
Hereinafter, the contents of the present invention will be described in detail.
First, the hole size of the cross section of the molded product of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a cross section of a molded body. In the figure, 1 is a cross section of the expanded particle part, and 2 indicates a space between the expanded particles. A shows the dimension of the maximum diameter of each space | gap observed in a molded object cross section. A corresponds to the maximum diameter of the distance between straight lines when the outer shape of each gap is sandwiched between two parallel straight lines.
[0011]
In the molded body of the present invention, from the viewpoint of achieving both the water permeability function and the filter function of the molded body, the number of voids (hereinafter referred to as Na) having a maximum diameter A of 15 to 30 mm per 100 cm ^{2 of the} molded body cross-sectional area is 15 to 30 mm. It is necessary to be 1-10. A void having an A value of less than 15 mm retains the filter function of earth and sand but has a small water permeability function, whereas a void having an A value exceeding 30 mm does not have a filter function. Therefore, in the present invention, attention is paid to the number of voids having a value of A of 15 to 30 mm. Further, if Na is less than 1, the water permeability function is small, and if it exceeds 10, the compact compression strength, compression creep resistance and filter function are deteriorated. A more preferable range of the value of Na is 2-6.
[0012]
In the molded article of the present invention, the number of foamed particles (hereinafter referred to as Nr) present per 100 cm ^{2 of} the molded article cross section is preferably 30 to 90 from the viewpoint that the gap between the particles can be moderated and the filter function can be secured. If the Nr is less than 30, the number of voids decreases, the size per void increases, and the filter function is lowered. On the contrary, when Nr exceeds 90, the number of voids increases and the size per void becomes small, and the water permeability function is lowered. More preferably, the value of Nr is 50-80.
[0013]
The porosity (hereinafter referred to as V) of the molded body of the present invention needs to be 8 to 35% in order to ensure the water permeability of the molded body. If V is less than 8%, water permeability cannot be secured, and if V exceeds 35%, fusion between the foamed particles becomes insufficient, and the compression strength and compression creep resistance of the molded product are lowered, which is not preferable. A more preferable range of V is 10 to 30%, and a particularly preferable range is 10 to 20%.
As described above, in the molded article of the present invention, satisfying the three of Na, Nr, and V is important in terms of achieving both the water permeability function and the filter function of the molded article.
The voids of the molded body obtained by the present invention are continuous. That is, a space is formed from one surface of the molded body to the back surface, and a portion where water can enter when the molded body is submerged in water is referred to as a void of the molded body.
[0014]
Next, the manufacturing method of the expanded particle molding of this invention is demonstrated.
The amount of the foaming agent contained in the foamed particles filled in the mold cavity at the time of molding is preferably 1.5 to 4 parts by weight from the viewpoint of optimizing the expansion force of the foamed particles. That is, if the amount of the foaming agent is less than 1.5 parts by weight, the expansion force of the foamed particles is insufficient and sufficient fusion between the particles cannot be achieved, and the molded body tends to shrink after molding. On the other hand, when the amount of the foaming agent exceeds 4 parts by weight, the expansion force of the foamed particles is too high and the voids between the particles are filled, and it is difficult to control the porosity. Further, expansion fusion occurs from the foam particles on the surface of the mold, and the introduction portion of the steam into the mold is blocked, resulting in insufficient internal fusion.
In the present invention, the expression that 1 part by weight of the foaming agent is contained in the expanded particles means that 1 part by weight of the foaming agent is contained with respect to 100 parts by weight of the resin.
[0015]
In the molded product manufacturing method of the present invention, the volume per one expanded particle filled in the mold cavity is 2 to 6 cm ³ from the viewpoint of making the size of the molded product gap appropriate. When the volume per expanded particle volume is less than 2 cm ³ , the void size of the molded body becomes small, and the water permeability function is lowered. On the contrary, if the volume per grain exceeds 6 cm ³ , the void size of the molded body becomes large and the filter effect is lowered, which is not preferable. A more preferable range of the volume of the expanded particles is 2 to 5 cm ³ . The volume of the expanded particles here refers to an arithmetic average of the volumes of any 20 expanded particles used for molding.
[0016]
The filling porosity of the expanded particles used in the present invention is 40 to 60% from the viewpoint of increasing the molded article porosity. The filling porosity of the expanded particles refers to the interparticle porosity in a state where the expanded particles are filled in a container and a weight of 0.2 KPa is applied. The reason why a weight of 0.2 KPa is applied is to allow a constant load to be applied to the packed particles so that the porosity can be measured constant so that the porosity value does not change in the packed state of the particles. A more preferable range of the value of the filling porosity is 45 to 55%. In order to achieve a filling porosity of 40 to 60%, the particle shape cannot be achieved with a sphere, cylinder, ellipsoid or the like. It is essential to have a plurality of depressions on the particle surface. In the present invention, the particle shape is not limited as long as the filling porosity is 40 to 60%.
[0017]
The density of the expanded particles filled in the mold cavity by the method for producing a molded article of the present invention is preferably 0.012 to 0.100 g / cm ³ from the viewpoint of moldability. When the density is less than 0.012 g / cm ³ , the expansion force of the particles becomes small. If it exceeds 0.100 g / cm ³ , the strength is high, but the weight increases and the production cost also increases. A more preferable range of the density is 0.015 to 0.050 g / cm ³ .
The method for producing a molded article of the present invention comprises the steps of filling the above-mentioned foamed particles in a mold cavity and heating the mold with water vapor to mold. A known method can be used as the molding method. For example, a method in which foamed particles are filled into a cavity of a mold having a large number of stem holes or slits, then steam of 95 to 110 ° C. is introduced into the cavity for a predetermined time, and the cavity is cooled to take out the molded body. Is common.
[0018]
As the polystyrene resin used in the present invention, polystyrene or a styrene homopolymer or copolymer containing 50% or more of a styrene monomer can be used. Styrene monomers include, in addition to styrene, nuclear alkyl-substituted styrenes such as methylstyrene, dimethylstyrene, and ethylmethylstyrene, and halogenated styrenes such as chlorostyrene, which are used alone or as a mixture of two or more.
Examples of the styrene copolymer monomer include acrylonitrile, methyl methacrylate, and maleic anhydride. Moreover, what contains a conjugated diene polymer in the said styrene resin, ABS, etc. can be used. Examples of the conjugated diene polymer include high cis polybutadiene, low cis polybutadiene, styrene-butadiene copolymer (random and block), and isoprene rubber.
[0019]
Among these, polystyrene and high impact polystyrene are particularly preferable from the viewpoint of versatility and foaming agent retention.
If necessary, additives such as a lubricant, a release agent, an antistatic agent, a foam nucleating agent, and an ultraviolet stabilizer can be added to the resin.
Examples of the volatile blowing agent used in the present invention include those having a boiling point in the range of −80 to + 100 ° C., for example, aliphatic hydrocarbons such as butane, n-pentane, isopentane, hexane, and petroleum ether, and cyclic fats such as cyclopentane. In addition to group hydrocarbons, halogenated hydrocarbons and the like can be used.
[0020]
The polystyrene-based expanded particles used in the present invention can be produced using a known method. For example, (a) a method in which a polystyrene resin and a foaming agent are mixed in an extruder and extruded in a strand form from a die nozzle in an unfoamed state, cut into particles and heated to steam or the like to form expanded particles, (b) A method of impregnating a resin particle having a surface depression with a foaming agent and heating it with steam or the like to form a foamed particle. (C) A resin and a foaming agent are mixed in an extruder and extruded from a die nozzle while foaming in a strand shape. There are a method of cutting into particles, a method (d) of using a pulverized resin foam, and the like. Of the methods for producing the expanded particles (a) to (d), the method (a) is preferable because workability and the like are easy. In the case of (a), the die nozzle has an S-shaped, W-shaped or M-shaped cross section.
The size of unexpanded particles or expanded particles can be adjusted to a desired size by changing the size of the die nozzle or by adjusting the take-up speed of the strand melt-extruded from the die nozzle.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.
In addition, the property of the expanded particle and the molded object in an Example and a comparative example was measured or evaluated as follows.
(1) Density of expanded particles Dr
The foamed particles were submerged in a graduated cylinder, and the water level rise value was measured to determine the amount of water displaced by the foamed particles. The weight of the expanded particles was measured, and the density Dr (g / cm ³ ) of the expanded particles was determined by dividing the weight by the volume.
[0022]
(2) The weight of the wooden container having a filling void volume internal volume of 30 cm × 30 cm × 30 cm of the expanded particles is measured. Next, the foamed particles are put into this container so as not to be pressed, and a static load (1.8 kg upper lid) corresponding to 0.2 KPa is placed on the surface of the foamed particles until the thickness at this time becomes 30 cm. Fill the container with the particles and measure the total weight of the container at that time.
Calculated on the weight of the foamed particles from the total weight of the container by subtracting the weight of only the container, the bulk density Da (g / cm ³⁾ in the filling state by dividing the weight by the internal volume 27000Cm ³ of the container. The filling porosity of the expanded particles is given by the following formula.
Filling porosity (%) = 100 × [(Dr−Da) / Dr]
[0023]
(3) Foaming agent content rate of the foamed particles The foamed particles sufficiently aged and dried after foaming were pressed with a hot plate at 180 ° C. to volatilize the foaming agent in the foamed particles. The change in weight before and after hot pressing was divided by the weight before pressing to obtain the foaming agent content.
(4) Bulk density Dsa of the molded body
The weight of the 10 cm cubic compact was measured, and the obtained weight was divided by 1000 cm ³ to obtain the bulk density Dsa (g / cm ³ ) of the compact.
[0024]
(5) Porosity V (%) of the molded body
A 10 cm cubic compact was submerged in soapy water, and the volume of the water level that had risen after sufficient water penetration into the voids of the compact was taken as the actual volume U (cm ³ ) of the compact. Since the apparent outer volume of the molded body is 1000 cm ³ , the difference from the actual volume is the void volume.
The porosity V of the molded body is given by the following formula.
V (%) = 100 × [(1000−U) / 1000]
[0025]
(6) Molded body permeability coefficient Measured by the constant water level permeability test method of JIS-A-1218. Water permeability was evaluated by the following symbols.
Symbol Evaluation ◎ Permeability coefficient is 1 cm / second or more.
○ From 0.1 cm / second to less than 1 cm / second.
Δ: 0.01 cm / second or more and less than 0.1 cm / second.
X Less than 0.01 cm / second.
[0026]
(7) Filter performance of the molded body A molded body cut into a size of 15 cm in length and width of 10 cm and a thickness of 10 cm was placed in the bottom of the container in a container having an inner dimension of 15 cm x 50 cm in depth and a depth of 50 cm and having a drain outlet in the bottom of the side. A sand soil was filled to a depth of 30 cm over the entire surface of the molded body. Further, tap water was supplied from above to drain water from the drain outlet at the bottom of the container. The water was always replenished and supplied and drained continuously to flood the sand. Filter performance was evaluated from the following symbols according to the state of drainage.
Symbol Evaluation ○ Drainage is clear and clear.
△ Drainage is cloudy in suspension but no solid precipitate is observed.
× Solid sand soil is mixed in the waste water.
[0027]
(8) 5% compressive strength of the molded body It was measured based on the method A of JIS-Z-0234.
Evaluation was performed as follows.
Symbol Evaluation ○ 5% compression strength is 0.06 MPa or more Δ 0.03 MPa or more to less than 0.06 MPa × less than 0.03 MPa
(9) Compressive creep of the molded body Measured based on JIS-K-6767. The load was applied at 0.01 MPa for 30 days, and the dimensional reduction rate was evaluated as follows.
Symbol Evaluation ◎ Compression creep value is less than 2% ○ 2% to less than 5% △ 5% to less than 10% × 10% or more [0029]
[Example 1]
Polystyrene resin (trade name “Styron 680” manufactured by Asahi Kasei Kogyo Co., Ltd.) was heated and melted in an extruder, and normal pentane as a foaming agent was supplied to the extruder to impregnate the resin. Further, the foaming agent-containing thermoplastic resin was extruded into a strand shape in which foaming was suppressed from an S-shaped die nozzle, immediately cooled with water, and then cut into particles in a direction perpendicular to the strand extrusion direction with a cutter equipped with a rotary blade. The obtained particles were heated with 100 ° C. steam for 180 seconds and aged to obtain expanded particles having a density (Dr) of 0.030 g / cm ³ . The volume of the expanded particles was 3.0 cm ³ and the filling porosity was 49%. Table 1 shows the properties of the obtained expanded particles.
[0030]
The foamed particles had a foaming agent content of 3.2 parts by weight, and the particles were filled into a mold cavity having an internal size of 900 mm × 1800 mm × 300 mm and equipped with an air release valve. Steam (100 ° C.) was introduced into the mold cavity for 300 seconds from the steam introduction valve, and the inside of the mold cavity was heated while exhausting the steam from the air release valve. Next, air (20 ° C.) was introduced into the mold cavity for 30 seconds by a blower while the air release valve was opened. Immediately after the introduction of air, the mold was opened and the molded body was taken out.
[0031]
The obtained molded body was dried at 50 ° C. for 2 hours. The bulk density of the molded body after drying was 13.5 kg / m ³ . The number of expanded particles per 100 cm ^{2 of the} molded body cross section (Nr) is 58, the number of voids (Na) having a maximum diameter of 15 to 30 mm per 100 cm ^{2 of} the molded body cross section is 2, and the porosity (V) of the molded body is 11%. The fused state of the particles was good both on the surface and inside of the compact, and the appearance of the compact was also good without any shrinkage or warping. The water permeability of the molded body was 0.18 cm / second. Table 1 shows the properties of the obtained molded body.
[0032]
A molded body cut out to a thickness of 15 cm × 50 cm and a thickness of 10 cm was attached to a container having an inner dimension of 15 cm × 50 cm and a depth of 50 cm and a drain outlet having a diameter of 7 cm at the bottom. The mounting position was set so that the vertical and horizontal directions of the molded body were aligned with the vertical and horizontal directions of the container, and 5 cm was lifted from the bottom of the container to form a space, and the entire surface of the molded body was filled with sand and soil to a depth of 30 cm. Further, tap water was supplied from above to drain water from the drain outlet at the bottom of the container. The water was always replenished and supplied so as to be flooded onto the sandy soil, and the water supply and drainage were continuously performed for 30 minutes. The discharged water was clear and not turbid. Table 2 shows the performance of the compact.
As shown in Table 2, the 5% compressive strength and compressive creep of the molded product were good.
[0033]
[Example 2]
The dice shape was changed to C type, and expandable particles were produced using the same resin and foaming agent as in Example 1. Furthermore, the obtained expandable particles were steam-heated for 180 seconds to obtain expanded particles. The obtained foamed particles were filled in the same molding die as in Example 1 and heated with steam for 300 seconds to produce a molded body. Table 1 shows the properties of the obtained foamed particles and the shape of the molded body.
As shown in Table 2, the water permeability, filter performance, 5% compressive strength, and compressive creep property of the molded product were good.
[0034]
[Example 3]
Extrusion operation was performed using the same resin and foaming agent as in Example 1 to obtain foaming particles containing the foaming agent. The foamable particles were heated with steam for 150 seconds and once aged, and then the foamed particles were again heated with steam for 120 seconds to obtain foamed particles. The obtained foamed particles were filled in the same molding die as in Example 1, and heated with steam for 360 seconds to obtain a molded body. Table 1 shows the properties of the obtained expanded particles and the molded product, and Table 2 shows the water permeability performance and strength performance of the molded product. The water permeability of the molded product was good, and the filterability of the earth and sand showed some turbidity in the drainage, but no solids leaked out. The strength of the molded body was almost good.
[0035]
[Example 4]
Extrusion operation was performed using the same resin and foaming agent as in Example 1 using a smaller C-shaped die than in Example 2 to obtain foaming agent-containing particles. Further, the particles were heated and aged with steam for 150 seconds to obtain expanded particles shown in Table 1.
Furthermore, the same molding die as in Example 1 was filled with foamed particles, and steam was heated for 270 seconds to perform molding, and molded articles having properties shown in Tables 1 and 2 were obtained.
[0036]
[Comparative Example 1]
Except for increasing the addition amount of the foaming agent, the same operation as in Example 1 was performed to obtain expandable particles having a high foaming agent content. The obtained expandable particles were heated with steam for 150 seconds to obtain expanded particles shown in Table 1. The obtained foamed particles had a foaming agent content of 4.5 parts by weight. When the obtained foamed particles are filled in the same molding die as in Example 1 and heated and molded with steam for 300 seconds, the foaming expansion force is large. Heating was inadequate. Although the number of voids (Na) in the cross section of the molded body was 12, the water permeability coefficient was as small as 0.07 cm / second due to the small number of voids near the surface. Table 2 shows the performance of the molded body.
[0037]
[Comparative Example 2]
Spherical polystyrene foam particles shown in Table 1 containing 3.0 parts by weight of the same foaming agent as in Example 1 were prepared. Since the expanded particle volume was as small as 1.5 cm ³ , the filling porosity was relatively small at 35%. The number of voids (Na) of the molded product obtained by molding the foamed particles in the same mold as in Example 1 with steam heating for 300 seconds was zero. The water permeability was 0.03 cm / second and was a small thing.
Table 1 shows the shape of the molded body, and Table 2 shows the water permeability coefficient, filter performance, 5% compressive strength, and compression creep property of the molded body.
[0038]
[Comparative Example 3]
Using a die larger than the die of Example 1, an extrusion operation was performed using the same resin and foaming agent as in Example 1 to obtain expandable particles containing the foaming agent. The foamable particles were heated with steam for 180 seconds and once aged, and then the foamed particles were again heated with steam for 120 seconds to obtain foamed particles. The obtained foamed particles were filled in the same molding die as in Example 1, and heated with steam for 360 seconds to obtain a molded body. Table 1 shows the properties of the obtained expanded particles and the molded product, and Table 2 shows the water permeability performance and strength performance of the molded product. Since the volume of the expanded particles was as large as 8.0 cm ³ , the number of voids (Na) in the molded product was as large as 14. Nr was also as small as 25. The water permeability was 5.5 and good, but the sediment performance was inferior and the filter performance was inferior. Moreover, it was a thing inferior to 5% compressive strength and compression creep property.
[0039]
[Comparative Example 4]
Except for reducing the charging amount of the foaming agent, the same operation as in Example 1 was performed to obtain expandable particles. The obtained expandable particles were heated with steam for 150 seconds to obtain expanded particles shown in Table 1. Since the foaming agent content is as small as 1.2 parts by weight, the expansion force of the expanded particles is insufficient, and even if the same molding as in Example 1 is performed, the fusion of the expanded particles of the molded body is not sufficient, The number of voids (Na) was as large as 15. Therefore, in the measurement of the filter performance of the molded product, leakage of earth and sand was observed, and the filter performance was inferior.
The properties of the expanded particles and the shape of the molded body are shown in Table 1, and the water permeability, filter performance, 5% compressive strength, and compression creep property of the molded body are shown in Table 2.
[0040]
[Comparative Example 5]
The same operation as in Example 1 was performed to reduce the amount of foaming agent charged, and foamed particles shown in Table 1 were obtained. The same mold as in Example 1 was filled with foamed particles and heated with steam. However, the steam heating time was as short as 200 seconds, so the expansion of the foamed particles was insufficient, and the porosity of the molded product was 40%. The filter performance and strength performance of the molded body were insufficient as shown in Table 2.
The properties of the expanded particles and the shape of the molded body are shown in Table 1, and the water permeability, filter performance, 5% compressive strength, and compression creep property of the molded body are shown in Table 2.
[0041]
[Table 1]

[0042]
[Table 2]

[0043]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the polystyrene-type expanded particle molded object which has the space | gap which was excellent in both water permeability and a filter function, and was excellent in intensity | strength can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic view of a cross section of a foamed particle molded body.
FIG. 2 is a diagram showing a maximum dimension of a void portion in a cross section of a foamed particle molded body.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Foamed particle part of a cross section of a molded body 2 Void A between particles of a cross section of a molded body A Maximum dimension of a void

Claims

Becomes bonded by heating and foaming a plurality of polystyrene foam particles, a foamed bead molded article which voids are formed to communicate with each other between the expanded beads, the expanded particles in the molded body section 100 cm ² per 40 80 pieces exists, the space maximum diameter is 15~30mm the molded body section 100 cm ² per are present 1 to 10, in porosity 8-20% of the molded product, permeability (cm / sec ) Is 0.15 to 2.00 .

Foamed particles contain 2-4 parts by weight of volatile foaming agent per 100 parts by weight of resin , polystyrene-based foamed particles having a volume of 2-6 cm ³ per grain and a filling porosity of 40-60% are molded. The method for producing a molded body according to claim 1, wherein the molded body is filled in a cavity and heated and molded with water vapor.