JP3683022B2 - Method for producing expandable resin particles - Google Patents

Method for producing expandable resin particles Download PDF

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Publication number
JP3683022B2
JP3683022B2 JP03574096A JP3574096A JP3683022B2 JP 3683022 B2 JP3683022 B2 JP 3683022B2 JP 03574096 A JP03574096 A JP 03574096A JP 3574096 A JP3574096 A JP 3574096A JP 3683022 B2 JP3683022 B2 JP 3683022B2
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Prior art keywords
particles
resin
polystyrene
conjugated diene
die
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JPH09208735A (en
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正道 金子
重成 谷
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Asahi Kasei Life and Living Corp
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Asahi Kasei Life and Living Corp
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C44/00Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
    • B29C44/34Auxiliary operations
    • B29C44/3461Making or treating expandable particles
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29BPREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B9/00Making granules
    • B29B9/02Making granules by dividing preformed material
    • B29B9/06Making granules by dividing preformed material in the form of filamentary material, e.g. combined with extrusion
    • B29B9/065Making granules by dividing preformed material in the form of filamentary material, e.g. combined with extrusion under-water, e.g. underwater pelletizers
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2793/00Shaping techniques involving a cutting or machining operation
    • B29C2793/0027Cutting off
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/001Combinations of extrusion moulding with other shaping operations
    • B29C48/0022Combinations of extrusion moulding with other shaping operations combined with cutting
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/04Particle-shaped
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29KINDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2105/00Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/04Condition, form or state of moulded material or of the material to be shaped cellular or porous

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
  • Compositions Of Macromolecular Compounds (AREA)

Description

【0001】
【発明の属する技術分野】
本発明はポリスチレン系発泡性粒子の製造方法に関し、更に詳しくは、発泡剤含浸工程における生産性が改良された共役ジエン系重合体成分含有ポリスチレン系発泡性粒子の製造方法に関する。
【0002】
【従来の技術】
近年、共役ジエン系重合体成分含有ポリスチレン系樹脂から成る発泡粒子成形体は耐割れ性の優れたポリスチレン系発泡成形体として注目され始めている。共役ジエン系重合体成分含有ポリスチレン系樹脂の発泡粒子にあって、粒子形状がより真球状に近いものは型内への充填性が良好でその結果として成形体の粒子融着性や耐割れ性が優れたものとなる。
【0003】
特開平6−49262号公報、特開平7−90105号公報にはポリブタジエンとスチレン系単量体との重合で得られたハイインパクトポリスチレンを押出機からストランド状に押し出し、カッターで切断して円柱状の樹脂粒子とし、更にこの粒子に水性媒体中で発泡剤を含浸させて得られる発泡性樹脂粒子が開示されている。しかし、この粒子は発泡剤含浸前の粒子形状は円柱状であり、発泡剤含浸工程での樹脂の加熱可塑化により、この円柱状粒子形状を球状に変えるのに長時間がかかるという問題があった。
【0004】
このため含浸前の粒子は円柱状でなく予め球状にしておくことが有利である。スチレン系樹脂を押出機中で加熱溶融させ、ダイノズルより押出すと同時にホットカットして略球状の粒子を製造し、この粒子に水性媒体中で発泡剤を含浸せしめる発泡性スチレン系樹脂粒子の製造方法は、従来から公知である。
【0005】
特公昭58−33889号公報には、ポリスチレンをダイ温度230〜240℃にて押し出し、水中ホットカット方式で概ね球状のポリスチレン粒子を得た後、この粒子をポリビニルアルコールを溶解した水性媒体中に分散させ、シクロヘキサンを含浸させた後n−ペンタンを含浸させる発泡性ポリスチレン粒子の製造方法が開示されている。しかし、ポリスチレンの代わりに共役ジエン系重合体成分含有ポリスチレンを用いると、水中ホットカットで得られた粒子は、発泡剤含浸工程で偏平状になり、球状になりにくいという問題があった。
【0006】
特開平4−325534号公報、及び特開平6−145409号公報には、廃発泡ポリスチレン系樹脂成形体を再生させるため、廃発泡ポリスチレン系樹脂成形体の粉砕品を押し出し機中で加熱溶融し円柱状粒子とした後、再度押し出し機に投入して、ダイノズルより押し出すと同時にホットカット方式にて切断し球状の樹脂粒子を得ており、更にこの粒子に水性媒体中で発泡剤を含浸せしめる発泡性スチレン系樹脂粒子の製造方法が開示されている。しかし、発泡ポリスチレン再生樹脂の代わりに共役ジエン系重合体成分含有ポリスチレン樹脂を用いてホットカットして得られる粒子は形状が不定形となり易く、発泡剤含浸工程で粒子を加熱、可塑化し、形状を球状にさせるのには長い時間がかかるという問題があった。また、含浸時間を短縮するために含浸温度を高めると含浸中に粒子のブロッキングが発生するという問題があった。
【0007】
【発明が解決しようとする課題】
本発明は上記問題を解決するものであり、共役ジエン系重合体成分含有ポリスチレン樹脂粒子に水性媒体中で発泡剤を含浸させつつ、粒子ブロッキング発生を抑え、短時間で粒子を真球形化せしめる発泡性の共役ジエン系重合体成分含有ポリスチレン樹脂粒子の製造方法を提供する。
【0008】
【課題を解決するための手段】
本発明は、水性媒体中で共役ジエン系重合体成分含有ポリスチレン系樹脂粒子に発泡剤を含浸させてなる平均粒径0.5mm以上、3.0mm以下の球状発泡性ポリスチレン系樹脂粒子の製造方法において、共役ジエン系重合体成分含有ポリスチレン系樹脂の共役ジエン成分含有量が3wt%以上、20wt%以下であり、ポリスチレン系成分相は30℃トルエン中での極限粘度が0.6以上、0.9以下であり、発泡剤含浸前の樹脂粒子が共役ジエン系重合体成分含有ポリスチレン系樹脂を、押し出し時の樹脂温度が220〜260℃で、押出機中で加熱溶融し、ダイランド径が0.5〜2.5mmで、ダイランド部における樹脂のせん断速度が2500(1/秒)以上、10000(1/秒)以下で押出孔より水中に押し出すと同時にダイフェース面で切断して得られる粒子であることを特徴とする発泡性ポリスチレン系樹脂粒子の製造方法、に係わる。
【0010】
本発明が従来技術と相違するところは、共役ジエン系重合体成分含有ポリスチレン系樹脂をダイランド部での樹脂のせん断速度が2500(1/秒)以上、10000(1/秒)以下であり、見かけ粘度が150ポイズ以上、700ポイズ以下で水中ホットカットして得た球状粒子を発泡性粒子となす点にある。
【0011】
図1、及び図2に押出機と水中ホットカット装置の模式説明図を示す。押出機のスクリュウ(8)で混練された加熱溶融樹脂は押出機のダイヘッド(1)に設けられたダイランド(10)を通り、押出孔(12)よりカッターボックス(5)内に押し出される。カッターボックス内には循環水が供給されている。水中ホットカットとは、押出孔より押し出された樹脂を、モーター(4)で高速回転されているカッタ−刃(3)によりダイフェース面(9)で直ちにカットし、カットされた樹脂粒子を循環水と共にカッターボックス(5)より排出する方法である。
【0012】
次に、ダイフェース面での押し出し樹脂のホットカットにより球状粒子が得られるメカニズムを図面により説明する。すなわち、ダイランド(10)内での樹脂の流動においては、壁面によるせん断応力により樹脂の流速分布が生じランド中心部では流速が大きく、ランドの壁面では流速が小さくなっている。従って、ダイフェース面(9)をカッター刃(3)が通り過ぎた(前カット面ができる)後、押出孔から押し出される樹脂は中心部が盛り上がった状態で押し出され、水によりその表層が冷却される。このようにして前カット面は丸みを持つことになる。中心部が盛り上がって押出孔より顔を出している状態の樹脂は、更に次に回転してくるカッター刃により切断され(後カット面ができる)粒子となるが、粒子と成った後、後カット面は樹脂表面張力により中心部が盛り上がり丸みを持つようになる。更に粒子は全表層が冷却されつつ、球状粒子として固化すると考えられる。
【0013】
従って、水中ホットカット粒子を球形化し、粒子内の配向を抑えるには、樹脂の流動特性と共にダイランドにおける樹脂のせん断速度と見かけ粘度が重要な因子となる。また、樹脂特性においてはマトリックス相であるポリスチレン系成分相の粘度特性が重要である。
【0014】
ところが、共役ジエン系重合体成分含有ポリスチレン系樹脂を、ポリスチレン樹脂をホットカットして略球形粒を得るのと同様な条件でホットカットしても粒子形状が球形に成りにくい。これは一つには共役ジエン系重合体成分含有ポリスチレン系樹脂の流動特性がポリスチレン樹脂と異なるためと考えられる。更にはホットカット時の粒子の内部あるいはカット面における残留応力やポリスチレン系成分相の分子配向性、及び加熱によるポリスチレン系成分相の分子配向緩和特性が共役ジエン系重合体成分の影響を受け、ポリスチレン系樹脂単体の場合とは異なるためと考えられる。
【0015】
真球状の共役ジエン系重合体成分含有ポリスチレン系樹脂の発泡性粒子を製造する上で、発泡剤含浸工程での生産性は、必要量の発泡剤を含浸させると同時に、粒子のブロッキングを抑え、いかに短時間で粒子を真球形化できるかにかかっている。本発明は共役ジエン系重合体成分含有ポリスチレン系樹脂を水中ホットカットして得た粒子を用いることで、粒子への発泡剤含浸工程において、加熱可塑化された状態で粒子が表面張力により真球形化する時間を短縮し、生産性を向上させるものである。
【0016】
共役ジエン系重合体成分含有ポリスチレン系樹脂の円柱状粒子に発泡剤を含浸させる場合には、粒子が加熱され、発泡剤が含浸して樹脂が可塑化されるにつれ配向が緩和され、粒子形状がラグビーボール状になり、更に加熱時間の経過とともに偏平状となり、長時間経過後には形状が球形化するという現象が見られる。従って、円柱状粒子の球形化には長時間を必要とし、生産性が良くない。また、含浸時間を短縮するため含浸温度を高くすると粒子のブロッキングが発生し易くなる。
【0017】
本発明においては、ダイランド部における樹脂のせん断速度の好ましい範囲は2500〜10000(1/秒)である。2500(1/秒)以下では粒子形状がいびつな形状になり、発泡剤含浸時に粒子の真球化に長時間を要する。また、10000(1/秒)以上では粒子糸引き、カット不良で粒子同士が付着し易くなる上、ホットカット時の粒子の内部応力やポリスチレン系成分相の分子配向性が大きくなって、発泡剤含浸時に粒子が偏平なラグビーボール状になり、真球化に長時間を要する。また、せん断速度の更に好ましい範囲は3000(1/秒)〜7000(1/秒)である。
【0018】
また見かけ粘度の好ましい範囲は150ポイズ以上、700ポイズ以下である。150ポイズ未満では粒子がカット不良になり粒子同士が付着し易くなり、700ポイズを越えると粒子が球状になりにくい。見かけ粘度の更に好ましい範囲は200ポイズ以上、500ポイズ以下である。
【0019】
加熱溶融樹脂の押し出しホットカットには、水中ホットカット、空中ホットカット、水噴霧ホットカット等があるが、本発明においては粒子形状を真球状にするため押し出された樹脂の表面を冷却する伝熱効率が良い水中ホットカット法を用いる。
【0020】
本発明において共役ジエン系重合体成分含有ポリスチレン系樹脂とは、ポリスチレン樹脂、あるいは、少なくとも50部以上のスチレン単量体と他の重合可能な単量体との共重合体樹脂と、共役ジエン化合物とが重合または共重合して構成されている樹脂である。共重合可能な単量体としてはメチルスチレン、アクリロニトリル、アクリル酸もしくはメタクリル酸と1〜8個の炭素数を有するアルコールとのエステル、マレイン酸、無水マレイン酸等である。
【0021】
本発明における共役ジエン系重合体成分含有ポリスチレン系樹脂中の共役ジエン成分含有量は3wt%以上、20wt%以下が好ましい。3wt%未満では、発泡粒子成形体の耐割れ性が不十分であり、20wt%を越えると発泡粒子成形体の強度が低下する。
【0022】
共役ジエン系重合体成分をポリスチレン系樹脂中に含有させる方法は、(1)スチレン系モノマーに共役ジエン系重合体を溶解させた溶液を重合させ、ポリスチレン系樹脂の連続相中に共役ジエン系重合体を分散相として存在させる方法と、(2)ポリスチレン系樹脂に共役ジエン系重合体成分を機械的に混合する方法、があるが、本発明ではいずれの方法も用いることができる。
【0023】
本発明における共役ジエン系重合体成分含有ポリスチレン系樹脂中のポリスチレン系成分相の30℃トルエン中での極限粘度は0.6以上、0.9以下の範囲であることが好ましい。極限粘度が0.6未満では樹脂の水中ホットカット時に、樹脂の流動性が大きく、押し出し樹脂の前カット面がいびつに変形しやすく丸みを持ちにくい。また、極限粘度が0.9を越えると樹脂の後カット面での表面張力による丸みが生じにくくなり球状の粒子が得られにくくなる。更に、発泡剤含浸工程での樹脂の可塑化が抑制され、粒子が真球状になりにくい。
【0024】
本発明における共役ジエン系重合体成分としては、ポリブタジエン、ポリイソプレン、スチレン−ブタジエン共重合体、スチレン−イソプレン共重合体、アクリロニトリル−ブタジエン共重合体等がある。これらの重合体成分は分子内二重結合を部分的に、あるいは大部分を水素添加したものでもかまわない。特に好ましい重合体成分はポリブタジエン、あるいはスチレン−ブタジエン共重合体である。
【0025】
樹脂には必要に応じて、添加剤、滑剤、難燃剤、帯電防止剤、染顔料、発泡核剤、紫外線安定剤等を添加することができる。
発泡粒子の形状は、発泡粒子を型内成形する際の粒子融着性に影響を及ぼす。真球に近い程、粒子融着性が向上する。これは型内成形時に粒子が等方的に膨張して型内の粒子同士が均一に圧縮しあうためであり、粒子間の空隙のムラが小さく、成形後の粒子間隙間であるボイドが小さくなるためである。本発明においては、得られる発泡性粒子は球状であるが、その球形度は1.0〜1.3の範囲である。
【0026】
本発明において、発泡性粒子径は0.5〜3.0mmの範囲が好ましい。粒径が0.5mm未満では樹脂押し出し時にダイノズルが詰まり易く製造困難であり、3.0mmを越えては含浸時の真球化に温度と時間を要する上、発泡粒子となし型内成形する場合に型内細部への充填性が低下する。更に好ましい粒径は0.6〜2.0mmの範囲である。
【0027】
本発明において共役ジエン系重合体成分含有ポリスチレン系樹脂の押し出し装置としては、ダイランド径は0.5〜2.5mmが好ましく、更に好ましくは0.6〜1.5mmの範囲である。ダイランド長さは短いとスエルが大きくなり、また長いとノズルが詰まり易い。好ましいランド長さは5〜12mmの範囲である。
【0028】
押し出し時の樹脂温度は220〜260℃、樹脂圧力は90〜120kgf/cm2 が好ましい。また樹脂供給速度は大きいと樹脂圧が高くなり、樹脂供給速度が小さいと、ダイノズルへの熱供給が不足してノズルが詰まり易い。
ダイフェース面に供給する水の温度は40〜90℃の範囲が好ましい。40℃未満ではダイフェース面が冷却されすぎて樹脂の詰まりが発生しやすい。また、90℃を越えてた温水は蒸気が発生して扱いにくい。更に好ましい温度50〜70℃の範囲である。
【0029】
ランド部における樹脂のせん断速度、及び見かけ粘度は次のようにして求めた。
ランド部の直径をd(cm)、ランド1本当たりの樹脂供給量をq(gr/秒)、ダイ温度での樹脂密度をn(gr/cm3 )とすると、ランド部の樹脂線速度vは、v=(4・q)/(π・n・d2 )で与えられる。
【0030】
この時、ランド部における樹脂のせん断速度γ(1/秒)は、式
γ=(8v)/d
により算出した。
また、ランド部における見かけ粘度は、予め、各温度での樹脂せん断速度と見かけ粘度との特性を求めておき、ダイランド温度と樹脂せん断速度から見かけ粘度を求めた。
【0031】
本発明において、発泡性樹脂粒子を得る方法は水中懸濁含浸法であれば特に限定されるものではない。すなわち、前記で得られたゴム成分含有ポリスチレン系樹脂粒子を撹拌機付きの耐圧容器に入れ、懸濁安定剤、界面活性剤の存在下に水性媒体中で撹拌の下に分散させ、発泡剤を含浸させる方法で、公知の種々の方法を用いることができる。この時必要なら容器内を加熱することもできる。含浸処理後、常温に冷却し、容器に残留している発泡剤を除いて、常温下に取り出して発泡性粒子とする。
【0032】
本発明で用いられる揮発性発泡剤としては、常圧における沸点が−30〜+100℃の範囲にあるもの、例えばプロパン、ブタン、ペンタン、ヘキサン、ヘプタン、石油エーテル等の脂肪族炭化水素及びシクロペンタン、ジクロルヘキサン等の環状脂肪族炭化水素、及び塩化メチル、塩化エチル、臭化メチル、ジクロロジフルオロメタン、1,2−ジクロロテトラフルオロエタン、モノクロロトリフルオロエタン等のハロゲン化炭化水素類等を挙げることができる。特に好ましい発泡剤はペンタン、ブタンである。
【0033】
水性媒体中には、上記発泡剤の他、ドデシルベンゼンスルホン酸塩類、ラウリルアルコキシスルホン酸塩類等の界面活性剤、炭酸マグネシウム、硫酸マグネシウム、ピロリン酸ナトリウム、炭酸カルシウム、タルク、リン酸三カルシウム等の分散剤、トルエン、キシレン等の溶剤等を混合することができる。
【0034】
発泡剤は樹脂100重量部に対し4〜12重量部の範囲を含浸させるのが好ましい。発泡剤含浸量が4部未満では発泡性粒子を高倍率に発泡させることが難しく、また、12重量部を越えると発泡時に倍率の調整が難しくなる。発泡剤含浸量が多い程粒子の発泡倍率を高くできる。発泡剤含浸量の更に好ましい範囲は5〜11重量部である。
発泡剤含浸時間を短くし、樹脂粒子を真球状にするためには容器内を40〜130℃に加熱することが好ましい。加熱温度は容器の耐圧、樹脂粒子のブロッキング性、含浸時間等を考慮して選択することが好ましい。
【0035】
得られた発泡性粒子から発泡粒子、成形体を得る間の工程は、通常行われている方法を用いることができ、特に限定されない。例えば発泡性樹脂粒子を公知のポリスチレン発泡ビーズ用発泡機でスチームによって発泡させ、かさ倍率5〜100倍の発泡粒子とする。発泡条件は例えば加熱温度を95〜104℃とし、この温度での発泡保持時間を10〜150秒とする。更に該発泡粒子を大気にさらし、空気を発泡粒子内に浸透させる。
このようにして得た発泡樹脂粒子を、公知のポリスチレン発泡ビーズ用自動成形機に内蔵された、小さな孔やスリットが設けられた成形型内でスチーム加熱して融着一体化させ、発泡成形体とする方法、等を用いることができる。
【0036】
【実施例】
以下に実施例等によりさらに詳細に本発明を説明するが、本発明はこれらにより何ら限定されるものではない。
なお、実施例、比較例中の粒子等の性質等は以下のようにして測定し、評価した。
【0037】
(1)粒子の球形度
[測定法]
粒子の投影面を平行な2直線で挟んだ時の最大幅Hを求める。投影方向を変えるとHの値も変化するが、変化するHの値の中で最大値をH1、最小値をH2とする。粒子の球形度Uは次の式より求めた。
U=H1/H2
[評価]
記 号 U値
◎ 1.00以上 1.15未満
○ 1.15以上 1.30未満
△ 1.30以上 1.60未満
× 1.60以上
【0038】
(2)粒子ブロッキング率
[測定法]
発泡剤含浸工程で得られた全粒子重量(W1)及び2粒以上集塊している粒子の重量(W2)を求め、下記の式より粒子ブロッキング率(B)を求めた。
B=(W2/W1)×100
[評価]
記 号 B値
◎ 0.0%以上 0.5%未満
○ 0.5 以上 1.5 未満
△ 1.5 以上 4.0 未満
× 4.0 以上
【0040】
(3)粒径
[測定法]
任意に選んだ100粒から、粒子の1粒当たりの平均重量を求め、樹脂密度で除して体積を算出する。更に粒子形状が真球とした時の球の直径を算出し、粒径とした。
【0041】
(4)ポリスチレン系成分相の極限粘度
[測定法]
樹脂1gをメチルエチルケトン/メタノール=9/1容量比の溶媒20ml中に加え、振とうし、遠心分離する。上澄み液からメタノールで樹脂分を析出させる。このようにして得られた樹脂の0.5g/dlのトルエン溶液の粘度を測定し、30℃における換算粘度ηsp/cを求めた。
【0042】
(5)発泡剤含有量
[測定法]
発泡性粒子を200℃の熱盤上で加熱処理し、重量減少から発泡剤含有量を求めた。
【0043】
(6)発泡粒子の真密度
[測定法]
次の式により発泡粒子の真密度ρ(g/cm3 )を求めた。
【0046】
ρ=W/V
ただし、W :発泡粒子の重量(g)
V :水没法により求めた発泡粒子の体積(cm3
【0044】
(7)発泡粒子成形体のかさ密度
[測定法]
JIS K6767に準拠して次の式により発泡粒子成形体のかさ密度D(g/cm3 )を求めた。
【0047】
D=G/V
ただし、G :発泡粒子成形体の重量(g)
V :発泡粒子成形体の体積(cm3
【0045】
(8)成形体の粒子融着率
[測定法]
成形体破断面に露出した粒子の中で、粒子内部まで破壊している粒子数をN1とし、粒子内部が破壊されず粒子表面が露出している粒子数をN2として、下記の式より成形体の粒子融着率Y(%)を求めた。
Y=〔(N1)/(N1+N2)〕×100
[評価]
記 号 Y値
◎ 90%以上 100%以下
○ 80 以上 90 未満
△ 70 以上 80 未満
× 70 未満
【0046】
(9)成形体の引張破断強度
[測定法]
JIS K6767に準拠して測定した。
[評価]
記 号 引張破断強度値
◎ 3.5kgf/cm2 以上
○ 3.0 以上 3.5kgf/cm2 未満
△ 2.5 以上 3.0 未満
× 2.5 未満
【0047】
(10)成形体の耐割れ落下高さ
[測定法]
厚み20mm、縦、横長さ各70mm、幅60mmのL型成形体を製作した。木製直角三角柱型の直角部を上に向けて置き、直角稜上に成形体の直角部をかぶせるようにして成形体を載せ、更に成形体の上にAフルートダンボールをかぶせた。成形体上高さH(cm)から重さ2.43kgの平板状おもりを落下させ、成形体が稜エッジ部で破断する最小高さHminを測定し、Hminを成形体の耐割れ落下高さT(cm)とした。
[評価]
記 号 T値
◎ 11.0cm以上
○ 9.5 以上 11.0cm未満
△ 8.0 以上 9.5 未満
× 8.0 未満
【0048】
(実施例1)
ブタジエン成分9wt%、ポリスチレン相の極限粘度0.7のゴム成分含有ポリスチレン(旭化成工業製)にエチレンビスステアロアミド0.1部、ステアリン酸アミド0.1部を混合したものを押出機中で240〜250℃で加熱溶融させ溶融混練した。溶融混練した樹脂を直径0.7mmのダイランド、直径0.7mm×60個の押出孔を備えたダイヘッドから循環使用している60℃の水中に押し出すと同時に、ダイス面で回転刃によりカットした。カット粒子を循環水と共に取り出し、遠心脱水、乾燥処理して平均粒径1.1mmの球形粒子を得た。この時のダイランド部の樹脂のせん断速度は4500(1/秒)、見かけ粘度は320ポイズであった。
【0049】
得られた球形粒子100gを0.5Lの撹拌機付き耐圧容器中へ水130g、炭酸マグネシウム粉末5g、ドデシルベンゼンスルホン酸ソーダ0.01gと共に仕込み、更に発泡剤であるi−ペンタン/n−ペンタン=50/50(重量比)組成の混合ペンタンを14g添加し、容器を密閉した後、600rpmで撹拌しながら、30分で120℃に昇温し、120℃で6時間保持した。容器を冷却し、発泡性粒子を得た。容器内の粒子のブロッキング発生率は0.4%であった。ブロッキングせずに得られた粒子の球形度は1.11であった。また、得られた粒子中の発泡剤含有量は樹脂100重量部に対し、7.4重量部であった。
【0050】
得られた発泡性粒子をスチーム加熱により発泡させ、真密度0.029g/cm3 の発泡粒子とし、この発泡粒子をスチーム圧0.8kgf/cm2 で型内成形して300×300×50mmの板状成形体を得た。得られた成形体のかさ密度は0.020g/cm3 であり、成形体の粒子融着率は92%、引張破断強度は3.6kgf/cm2 であった。成形体の耐割れ性を耐割れ落下高さで評価した結果は11.0cmであり良好であった。
【0051】
(実施例2)
発泡剤を含浸させる工程での発泡剤仕込量を12部及び17部とする他は実施例1と同様な操作を行って発泡性粒子を得た。得られた粒子中の発泡剤含有量は樹脂100重量部に対し、各々、6.5重量部、9.2重量部であった。得られた発泡性粒子の性状を表1に示す(表中、ゴム成分含有ポリスチレンをHIPSと記す。水中ホットカット条件をUWC条件と記す)。また、実施例1に示された条件と同様の条件で発泡性粒子を発泡成形して得られた成形体の性能を表3に示す。
【0052】
(実施例3)
ブタジエン成分含有ポリスチレンを押し出す工程において、ダイス温度及び樹脂供給速度をコントロールすることにより、ダイランド部におけるせん断速度を2900、6100、8500(1/秒)、見かけ粘度を各々610、220、180ポイズとした他は実施例1と同様な操作を行って発泡性粒子を得た。得られた発泡性粒子の性状を表1に示す。また、実施例1に示された条件と同様の条件で発泡性粒子を発泡成形して得られた成形体の性能を表3に示す。
【0053】
(実施例4)
ダイランド径(押出孔も同じ径)を1.2mm、及び2.0mmとした他は実施例1と同様な操作を行って発泡性粒子を得た。ダイランド部のせん断速度は4000、3500(1/秒)であり、見かけ粘度は各々310、400ポイズであった。得られた発泡性粒子の性状を表1に、成形体の性能を表3に示す。
【0054】
(実施例5)
ブタジエン成分含有ポリスチレン中のブタジエン成分含有量を5重量%、12重量%(旭化成工業製)として他は実施例1と同様な操作を行って発泡性粒子を得た。ダイランド部のせん断速度は4500(1/秒)であり、見かけ粘度は各々290、360ポイズであった。得られた発泡性粒子の性状を表1に、成形体の性能を表3に示す。
【0055】
(比較例1)
ブタジエン成分9%のハイインパクトポリスチレン(旭化成工業製)を用い、ダイランド部の樹脂のせん断速度を2200、11000(1/秒)とし、見かけ粘度を各々750、140ポイズとした他は実施例1と同様な操作を行って発泡性粒子を得た。得られた発泡性粒子の性状を表2に示す。粒子球形度、ブロッキング率とも劣るものであった。実施例1に示されると同様の条件で発泡性粒子を発泡成形して得られた成形体の性能を表4に示す。耐割れ性は実施例1の成形体に比べ劣るものであった。
【0056】
(比較例2)
発泡剤含浸条件を120℃で12時間保持する他は比較例1と同様の操作を行って発泡性粒子を得た。得られた発泡性粒子の性状を表2に示す。比較例1のものに比べ発泡性粒子は球形度は改善されたが、ブロッキング率は大きかった。実施例1に示されると同様の条件で発泡性粒子を発泡成形して得られた成形体の性能を表4に示す。
【0057】
(比較例3)
ダイランド径(押出孔も同じ径)を2.6mm、及び0.4mmとした他は実施例1と同様な操作を行って発泡性粒子を得た。ダイランド部のせん断速度は3200、8500(1/秒)であり、見かけ粘度は各々510、190ポイズであった。
ダイランド径が0.4mmの場合にはダイノズルに詰まりが発生しやすく、樹脂の押し出しを続けることが困難であった。
得られた粒子を実施例1に示される方法と同様の方法で水媒体中に分散させ発泡剤を含浸させた。得られた発泡性粒子の性状を表2に示す。実施例1に示された条件と同様の条件で発泡性粒子を発泡成形して得られた成形体の性能を表4に示す。
【0058】
(比較例4)
ブタジエン成分含有ポリスチレン中のゴム成分含有量が6%、15%であり、極限粘度が各々0.57、0.92のHIPSを用い、表2に示す条件で押し出した他は実施例1と同様に操作で発泡性粒子を得た。得られた発泡性粒子の性状を表2に、成形体の性能を表4示す。
【0059】
(比較例5)
実施例1で用いたHIPS及び添加剤の混合物を押出機から押し出し、直径1.0mm、長さ1.2mmの円柱状ペレットを得た。このペレットを実施例1と同様にして発泡剤含浸容器に仕込み、120℃含浸時間を6時間、12時間として発泡性粒子を得た。この粒子の性状を表2に示す。また、成形体の性能を表4に示す。
【0060】
(比較例6)
ブタジエン成分9%のポリスチレン(旭化成工業製)をポリスチレンでブタジエン濃度を希釈し、ブタジエン成分2%のポリスチレンを調製した。この樹脂を用い、ダイランド部の樹脂のせん断速度を4500、8500(1/秒)とし、見かけ粘度を各々360、190ポイズとした他は実施例1と同様な操作を行って発泡性粒子を得た。得られた発泡性粒子の性状を表2に示す。実施例1に示された条件と同様の条件で発泡性粒子を発泡成形して得られた成形体の性能を表3示す。
【0061】
【表1】

Figure 0003683022
【0062】
【表2】
Figure 0003683022
【0063】
【表3】
Figure 0003683022
【0064】
【表4】
Figure 0003683022
【0065】
【発明の効果】
本発明によれば、共役ジエン系重合体成分含有ポリスチレン樹脂製の真球状の発泡性粒子を短い発泡剤含浸時間でブロッキングを発生させずに生産性良く製造できる。また得られた発泡性樹脂粒子を発泡、成形して得られた成形体は耐割れ性の良好なものである。
【図面の簡単な説明】
【図1】押出機と水中ホットカット装置を示す模式説明図である。
【図2】押し出し機ダイ断面構造を示す模式説明図である。
【符号の説明】
1 ダイヘッド
2 ダイノズル
3 カッター刃
4 モーター
5 カッターボックス
6 水入口
7 水出口
8 押し出し機スクリュウ
9 ダイフェース面
10 ダイランド
11 テーパ部
12 ダイ押出孔[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing polystyrene-based expandable particles, and more particularly to a method for producing conjugated diene-based polymer component-containing polystyrene-based expandable particles having improved productivity in a foaming agent impregnation step.
[0002]
[Prior art]
In recent years, foamed particle molded articles made of polystyrene resin containing a conjugated diene polymer component have begun to attract attention as polystyrene foam molded articles having excellent crack resistance. Foamed particles of polystyrene resin containing a conjugated diene polymer component, and those with a particle shape closer to a true sphere have good filling properties in the mold, and as a result, the particle fusion and crack resistance of the molded product Will be excellent.
[0003]
In JP-A-6-49262 and JP-A-7-90105, high impact polystyrene obtained by polymerization of polybutadiene and a styrene monomer is extruded into a strand form from an extruder, and is cut by a cutter into a cylindrical shape. Further, expandable resin particles obtained by impregnating the particles with a foaming agent in an aqueous medium are disclosed. However, the particle shape before impregnation with the blowing agent is cylindrical, and there is a problem that it takes a long time to change the cylindrical particle shape into a spherical shape due to heat plasticization of the resin in the step of impregnating the blowing agent. It was.
[0004]
For this reason, it is advantageous to pre-impregnate the particles before impregnation, instead of being cylindrical. Production of expandable styrene resin particles in which styrene resin is heated and melted in an extruder, extruded through a die nozzle and hot cut simultaneously to produce substantially spherical particles, and these particles are impregnated with a foaming agent in an aqueous medium. Methods are conventionally known.
[0005]
In Japanese Patent Publication No. 58-33889, polystyrene is extruded at a die temperature of 230 to 240 ° C., and approximately spherical polystyrene particles are obtained by an underwater hot cut method, and then dispersed in an aqueous medium in which polyvinyl alcohol is dissolved. And a method for producing expandable polystyrene particles impregnated with cyclohexane and then impregnated with n-pentane is disclosed. However, when conjugated diene polymer component-containing polystyrene is used instead of polystyrene, there is a problem that particles obtained by hot-cutting in water become flat and difficult to be spherical in the foaming agent impregnation step.
[0006]
In JP-A-4-325534 and JP-A-6-145409, in order to regenerate a waste foamed polystyrene resin molded product, a pulverized product of the waste foamed polystyrene resin molded product is heated and melted in an extruder to obtain a circle. After making columnar particles, they are put into the extruder again, extruded from the die nozzle and cut at the same time as the hot cut method to obtain spherical resin particles, and the foaming properties of impregnating the particles with a foaming agent in an aqueous medium A method for producing styrene resin particles is disclosed. However, particles obtained by hot cutting using a conjugated diene polymer component-containing polystyrene resin instead of expanded polystyrene recycled resin tend to be irregular in shape, and the particles are heated and plasticized in the foaming agent impregnation process. There was a problem that it took a long time to make it spherical. Further, when the impregnation temperature is increased in order to shorten the impregnation time, there is a problem that particle blocking occurs during the impregnation.
[0007]
[Problems to be solved by the invention]
The present invention solves the above-mentioned problem, while impregnating polystyrene resin particles containing a conjugated diene-based polymer component with a foaming agent in an aqueous medium, suppressing the occurrence of particle blocking, and foaming that makes particles spherical in a short time. A method for producing a polystyrene resin particle containing a functional conjugated diene polymer component is provided.
[0008]
[Means for Solving the Problems]
The present invention relates to a method for producing spherical expandable polystyrene resin particles having an average particle size of 0.5 mm or more and 3.0 mm or less obtained by impregnating polystyrene resin particles containing a conjugated diene polymer component in an aqueous medium with a foaming agent. In The conjugated diene polymer component-containing polystyrene resin has a conjugated diene component content of 3 wt% or more and 20 wt% or less, and the polystyrene component phase has an intrinsic viscosity of 0.6 to 0.9 in 30 ° C. toluene. And The resin particles before impregnation with the blowing agent are conjugated diene polymer component-containing polystyrene resin, the resin temperature at the time of extrusion is 220 to 260 ° C., and heated and melted in an extruder, The die land diameter is 0.5-2.5mm, Resin shear rate at the die land is 2500 (1 / second) or more and 10000 (1 / second) or less Press The present invention relates to a method for producing expandable polystyrene resin particles, wherein the particles are obtained by extruding into water from an outlet and simultaneously cutting on a die face surface.
[0010]
The difference between the present invention and the prior art is that the conjugated diene polymer component-containing polystyrene resin has a shear rate of 2500 (1 / second) or more and 10,000 (1 / second) or less at the dieland portion, and is apparent. The spherical particles obtained by hot-cutting in water at a viscosity of 150 poise or more and 700 poise or less are used as foamable particles.
[0011]
The schematic explanatory drawing of an extruder and an underwater hot cut apparatus is shown in FIG.1 and FIG.2. The heated molten resin kneaded by the screw (8) of the extruder passes through the die land (10) provided in the die head (1) of the extruder and is extruded into the cutter box (5) from the extrusion hole (12). Circulating water is supplied into the cutter box. Underwater hot cut means that the resin extruded from the extrusion hole is immediately cut on the die face surface (9) by the cutter blade (3) rotated at high speed by the motor (4), and the cut resin particles are circulated. It is the method of discharging from a cutter box (5) with water.
[0012]
Next, the mechanism by which spherical particles are obtained by hot cutting of extruded resin on the die face surface will be described with reference to the drawings. That is, in the resin flow in the die land (10), the flow velocity distribution of the resin is generated by the shear stress due to the wall surface, and the flow velocity is large at the center of the land, and the flow velocity is small at the wall surface of the land. Therefore, after the cutter blade (3) passes through the die face surface (9) (the front cut surface is formed), the resin extruded from the extrusion hole is extruded with the center portion raised, and the surface layer is cooled by water. The In this way, the front cut surface is rounded. The resin in the state where the center is raised and the face is exposed from the extrusion hole is further cut into particles (making a back cut surface) by the next rotating cutter blade. The surface is raised and rounded at the center due to the resin surface tension. Further, the particles are considered to solidify as spherical particles while the entire surface layer is cooled.
[0013]
Therefore, in order to spheroidize the hot-cut particles in water and suppress the orientation in the particles, the shear rate and the apparent viscosity of the resin in Dyland are important factors as well as the flow characteristics of the resin. Moreover, in the resin characteristic, the viscosity characteristic of the polystyrene-type component phase which is a matrix phase is important.
[0014]
However, even when a conjugated diene polymer component-containing polystyrene resin is hot-cut under the same conditions as when a polystyrene resin is hot-cut to obtain a substantially spherical particle, the particle shape does not easily become spherical. One reason for this is considered that the flow characteristics of the polystyrene resin containing the conjugated diene polymer component are different from those of the polystyrene resin. Furthermore, the residual stress in the particle or the cut surface during hot cutting, the molecular orientation of the polystyrene component phase, and the molecular orientation relaxation properties of the polystyrene component phase due to heating are affected by the conjugated diene polymer component. This is probably because it is different from the case of a single resin.
[0015]
When producing expandable particles of polystyrene resin containing a true spherical conjugated diene polymer component, productivity in the blowing agent impregnation step impregnates the required amount of blowing agent and at the same time suppresses blocking of the particles, It depends on how quickly particles can be made spherical. The present invention uses particles obtained by hot-cutting a polystyrene-based resin containing a conjugated diene polymer component in water, so that in the step of impregnating the particles with a foaming agent, the particles are spherical due to surface tension in the state of being heat plasticized. This shortens the time required for production and improves productivity.
[0016]
When the cylindrical particles of polystyrene resin containing a conjugated diene polymer component are impregnated with a foaming agent, the orientation of the particles is reduced as the particles are heated and impregnated with the foaming agent to plasticize the resin. It becomes a rugby ball shape, becomes flat as the heating time elapses, and a phenomenon that the shape becomes spherical after a long time is observed. Therefore, it takes a long time to spheroidize the cylindrical particles, and the productivity is not good. Further, when the impregnation temperature is increased in order to shorten the impregnation time, particle blocking tends to occur.
[0017]
In the present invention, the preferred range of the shear rate of the resin in the die land part is 2500 to 10,000 (1 / second). Below 2500 (1 / second), the particle shape becomes irregular, and it takes a long time for the particles to become spherical when impregnated with the blowing agent. In addition, when it is 10,000 (1 / second) or more, particle stringing or cutting is likely to cause the particles to adhere to each other, and the internal stress of the particles at the time of hot cutting and the molecular orientation of the polystyrene-based component phase increase, resulting in a foaming agent. When impregnated, the particles become a flat rugby ball, and a long time is required for sphere formation. A more preferable range of the shear rate is 3000 (1 / second) to 7000 (1 / second).
[0018]
A preferred range of the apparent viscosity is 150 poise or more and 700 poise or less. If it is less than 150 poise, the particles are poorly cut and the particles tend to adhere to each other, and if it exceeds 700 poise, the particles are difficult to be spherical. A more preferable range of the apparent viscosity is 200 poise or more and 500 poise or less.
[0019]
Extrusion hot cut of heated and melted resin includes underwater hot cut, aerial hot cut, water spray hot cut, etc., but in the present invention, the heat transfer efficiency for cooling the surface of the extruded resin to make the particle shape into a spherical shape Use a good underwater hot cut method.
[0020]
In the present invention, the conjugated diene polymer component-containing polystyrene resin is a polystyrene resin, or a copolymer resin of at least 50 parts of styrene monomer and other polymerizable monomer, and a conjugated diene compound. Is a resin formed by polymerization or copolymerization. Examples of the copolymerizable monomer include esters of methylstyrene, acrylonitrile, acrylic acid or methacrylic acid with an alcohol having 1 to 8 carbon atoms, maleic acid, maleic anhydride and the like.
[0021]
The conjugated diene component content in the conjugated diene polymer component-containing polystyrene resin in the present invention is preferably 3 wt% or more and 20 wt% or less. If it is less than 3 wt%, the crack resistance of the foamed particle molded body is insufficient, and if it exceeds 20 wt%, the strength of the foamed particle molded body is lowered.
[0022]
The method for incorporating a conjugated diene polymer component in a polystyrene resin is as follows: (1) polymerizing a solution in which a conjugated diene polymer is dissolved in a styrene monomer, and then linking the conjugated diene polymer in the continuous phase of the polystyrene resin. There are a method in which a coalescence is present as a dispersed phase and a method (2) in which a conjugated diene polymer component is mechanically mixed with a polystyrene resin, and any method can be used in the present invention.
[0023]
In the present invention, the intrinsic viscosity of the polystyrene component phase in the conjugated diene polymer component-containing polystyrene resin in 30 ° C. toluene is preferably in the range of 0.6 to 0.9. When the intrinsic viscosity is less than 0.6, the resin fluidity is large when the resin is hot-cut in water, and the front cut surface of the extruded resin is easily deformed and is not easily rounded. On the other hand, if the intrinsic viscosity exceeds 0.9, roundness due to the surface tension at the rear cut surface of the resin hardly occurs, and it becomes difficult to obtain spherical particles. Furthermore, plasticization of the resin in the foaming agent impregnation step is suppressed, and the particles are less likely to be spherical.
[0024]
Examples of the conjugated diene polymer component in the present invention include polybutadiene, polyisoprene, styrene-butadiene copolymer, styrene-isoprene copolymer, acrylonitrile-butadiene copolymer, and the like. These polymer components may be partially or partially hydrogenated with intramolecular double bonds. A particularly preferred polymer component is polybutadiene or a styrene-butadiene copolymer.
[0025]
If necessary, an additive, a lubricant, a flame retardant, an antistatic agent, a dye / pigment, a foam nucleating agent, an ultraviolet stabilizer, and the like can be added to the resin.
The shape of the expanded particles affects the particle fusion property when the expanded particles are molded in the mold. The closer to the true sphere, the better the particle fusion property. This is because the particles in the mold are isotropically expanded during molding in the mold, and the particles in the mold are uniformly compressed together, so that the unevenness of the voids between the particles is small, and the void that is the gap between the particles after molding is small. It is to become. In the present invention, the expandable particles obtained are spherical, but the sphericity is in the range of 1.0 to 1.3.
[0026]
In the present invention, the expandable particle diameter is preferably in the range of 0.5 to 3.0 mm. If the particle size is less than 0.5 mm, the die nozzle is clogged easily during resin extrusion, and if it exceeds 3.0 mm, temperature and time are required for spheroidization during impregnation, and foamed particles and none are molded in the mold. In addition, the filling ability to the details in the mold is lowered. A more preferable particle size is in the range of 0.6 to 2.0 mm.
[0027]
In the present invention, the extrusion device for the conjugated diene polymer component-containing polystyrene resin preferably has a die land diameter of 0.5 to 2.5 mm, more preferably 0.6 to 1.5 mm. When the die land length is short, the swell becomes large, and when the die land length is long, the nozzle is easily clogged. The preferred land length is in the range of 5-12 mm.
[0028]
The resin temperature during extrusion is 220 to 260 ° C., and the resin pressure is 90 to 120 kgf / cm. 2 Is preferred. If the resin supply rate is high, the resin pressure increases. If the resin supply rate is low, the heat supply to the die nozzle is insufficient and the nozzle is likely to be clogged.
The temperature of the water supplied to the die face surface is preferably in the range of 40 to 90 ° C. If it is less than 40 ° C., the die face surface is cooled too much and clogging of the resin is likely to occur. In addition, warm water exceeding 90 ° C. is difficult to handle due to the generation of steam. A more preferable temperature range is 50 to 70 ° C.
[0029]
The shear rate and the apparent viscosity of the resin in the land portion were determined as follows.
The land portion diameter is d (cm), the resin supply amount per land is q (gr / sec), and the resin density at the die temperature is n (gr / cm). Three ), The resin linear velocity v of the land portion is v = (4 · q) / (π · n · d 2 ).
[0030]
At this time, the shear rate γ (1 / second) of the resin in the land portion is expressed by the equation
γ = (8v) / d
Calculated by
The apparent viscosity at the land portion was obtained in advance from the characteristics of the resin shear rate and the apparent viscosity at each temperature, and the apparent viscosity was determined from the die land temperature and the resin shear rate.
[0031]
In the present invention, the method for obtaining expandable resin particles is not particularly limited as long as it is an underwater suspension impregnation method. That is, the rubber component-containing polystyrene resin particles obtained above are placed in a pressure vessel equipped with a stirrer, and dispersed under stirring in an aqueous medium in the presence of a suspension stabilizer and a surfactant. As the impregnation method, various known methods can be used. At this time, if necessary, the inside of the container can be heated. After the impregnation treatment, the mixture is cooled to room temperature, the foaming agent remaining in the container is removed, and taken out at room temperature to obtain expandable particles.
[0032]
Examples of the volatile blowing agent used in the present invention include those having a boiling point in the range of −30 to + 100 ° C. at normal pressure, for example, aliphatic hydrocarbons such as propane, butane, pentane, hexane, heptane, petroleum ether, and cyclopentane. And cycloaliphatic hydrocarbons such as dichlorohexane, and halogenated hydrocarbons such as methyl chloride, ethyl chloride, methyl bromide, dichlorodifluoromethane, 1,2-dichlorotetrafluoroethane, and monochlorotrifluoroethane. be able to. Particularly preferred blowing agents are pentane and butane.
[0033]
In the aqueous medium, in addition to the above foaming agent, surfactants such as dodecylbenzenesulfonates and laurylalkoxysulfonates, magnesium carbonate, magnesium sulfate, sodium pyrophosphate, calcium carbonate, talc, tricalcium phosphate, etc. A dispersant, a solvent such as toluene and xylene, and the like can be mixed.
[0034]
The foaming agent is preferably impregnated in the range of 4 to 12 parts by weight with respect to 100 parts by weight of the resin. When the amount of the foaming agent impregnated is less than 4 parts, it is difficult to foam the expandable particles at a high magnification. When the amount exceeds 12 parts by weight, it is difficult to adjust the magnification at the time of foaming. The larger the amount of foaming agent impregnated, the higher the foaming ratio of the particles. A more preferred range of the amount of foaming agent impregnation is 5 to 11 parts by weight.
In order to shorten the foaming agent impregnation time and make the resin particles spherical, it is preferable to heat the inside of the container to 40 to 130 ° C. The heating temperature is preferably selected in consideration of the pressure resistance of the container, the blocking property of the resin particles, the impregnation time, and the like.
[0035]
The process in which the expanded particle and the molded object are obtained from the obtained expandable particle can use the method currently performed normally, and is not specifically limited. For example, foamable resin particles are foamed with steam in a known foaming machine for polystyrene foam beads to obtain foam particles having a bulk magnification of 5 to 100 times. The foaming conditions are, for example, a heating temperature of 95 to 104 ° C., and a foam retention time at this temperature of 10 to 150 seconds. Further, the foamed particles are exposed to the atmosphere, and air is permeated into the foamed particles.
The foamed resin particles obtained in this manner are fused and integrated by steam heating in a molding die provided with a small hole or slit incorporated in a known automatic molding machine for polystyrene foam beads. Or the like can be used.
[0036]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples and the like, but the present invention is not limited thereto.
The properties of the particles and the like in the examples and comparative examples were measured and evaluated as follows.
[0037]
(1) Particle sphericity
[Measurement method]
The maximum width H when the particle projection plane is sandwiched between two parallel straight lines is obtained. When the projection direction is changed, the value of H also changes. Among the changing values of H, the maximum value is H1, and the minimum value is H2. The sphericity U of the particles was obtained from the following formula.
U = H1 / H2
[Evaluation]
Symbol U value
◎ 1.00 or more and less than 1.15
○ 1.15 or more and less than 1.30
△ 1.30 or more and less than 1.60
× 1.60 or more
[0038]
(2) Particle blocking rate
[Measurement method]
The total particle weight (W1) obtained in the foaming agent impregnation step and the weight (W2) of two or more agglomerated particles were determined, and the particle blocking rate (B) was determined from the following formula.
B = (W2 / W1) × 100
[Evaluation]
Symbol B value
◎ 0.0% or more and less than 0.5%
○ 0.5 or more and less than 1.5
△ 1.5 or more and less than 4.0
× 4.0 or higher
[0040]
(3) Particle size
[Measurement method]
From 100 grains arbitrarily selected, the average weight per grain is obtained, and the volume is calculated by dividing by the resin density. Furthermore, the diameter of the sphere when the particle shape was a true sphere was calculated and used as the particle size.
[0041]
(4) Intrinsic viscosity of polystyrene component phase
[Measurement method]
1 g of resin is added to 20 ml of a solvent having a volume ratio of methyl ethyl ketone / methanol = 9/1, shaken and centrifuged. The resin content is precipitated from the supernatant with methanol. The viscosity of a 0.5 g / dl toluene solution of the resin thus obtained was measured, and the converted viscosity ηsp / c at 30 ° C. was determined.
[0042]
(5) Foaming agent content
[Measurement method]
The expandable particles were heat-treated on a hot plate at 200 ° C., and the foaming agent content was determined from the weight reduction.
[0043]
(6) True density of expanded particles
[Measurement method]
The true density ρ (g / cm Three )
[0046]
ρ = W / V
W: Weight of expanded particles (g)
V: Volume of expanded particles (cm Three )
[0044]
(7) Bulk density of foamed particle compact
[Measurement method]
In accordance with JIS K6767, the bulk density D (g / cm) Three )
[0047]
D = G / V
G: Weight of the foamed particle molded body (g)
V: Volume of foamed particle molded body (cm Three )
[0045]
(8) Particle fusion rate of the compact
[Measurement method]
Of the particles exposed on the fracture surface of the molded product, the number of particles destroyed to the inside of the particles is N1, and the number of particles whose particle surfaces are exposed without being destroyed is N2. The particle fusion rate Y (%) was determined.
Y = [(N1) / (N1 + N2)] × 100
[Evaluation]
Symbol Y value
◎ 90% or more and 100% or less
○ 80 or more and less than 90
△ 70 or more but less than 80
× Less than 70
[0046]
(9) Tensile breaking strength of the molded product
[Measurement method]
The measurement was performed according to JIS K6767.
[Evaluation]
Symbol Tensile strength at break
◎ 3.5kgf / cm 2 that's all
○ 3.0 or more 3.5kgf / cm 2 Less than
△ 2.5 or more and less than 3.0
× Less than 2.5
[0047]
(10) Crack-resistant drop height of the compact
[Measurement method]
An L-shaped molded body having a thickness of 20 mm, a length and a length of 70 mm each, and a width of 60 mm was manufactured. The right angle part of the wooden right triangular prism type was placed facing upward, the molded body was placed on the right angle ridge so that the right angle part of the molded body was covered, and the A flute cardboard was further covered on the molded body. A flat weight having a weight of 2.43 kg is dropped from the height H (cm) on the molded body, the minimum height Hmin at which the molded body breaks at the ridge edge portion is measured, and Hmin is the crack-resistant drop height of the molded body. T (cm).
[Evaluation]
Symbol T value
◎ More than 11.0cm
○ 9.5 or more and less than 11.0cm
△ 8.0 or more and less than 9.5
× Less than 8.0
[0048]
(Example 1)
A mixture of 9 parts by weight of butadiene component and 0.1 parts of ethylene bisstearamide and 0.1 part of stearamide in a rubber component-containing polystyrene (manufactured by Asahi Kasei Kogyo Co., Ltd.) having a polystyrene phase intrinsic viscosity of 0.7 in an extruder. It was heated and melted at 240 to 250 ° C. and melted and kneaded. The melt-kneaded resin was extruded from a die head having a 0.7 mm diameter die land and a 0.7 mm diameter extrusion hole into circulating water at 60 ° C., and simultaneously cut with a rotary blade on the die surface. The cut particles were taken out together with the circulating water, centrifuged and dehydrated, and dried to obtain spherical particles having an average particle diameter of 1.1 mm. At this time, the shear rate of the resin in the die land part was 4500 (1 / second), and the apparent viscosity was 320 poise.
[0049]
100 g of the obtained spherical particles were charged into a 0.5 L pressure vessel equipped with a stirrer together with 130 g of water, 5 g of magnesium carbonate powder, 0.01 g of sodium dodecylbenzenesulfonate, and i-pentane / n-pentane = foaming agent = After adding 14 g of mixed pentane having a 50/50 (weight ratio) composition and sealing the container, the temperature was raised to 120 ° C. in 30 minutes and held at 120 ° C. for 6 hours while stirring at 600 rpm. The container was cooled to obtain expandable particles. The blocking occurrence rate of particles in the container was 0.4%. The sphericity of the particles obtained without blocking was 1.11. The foaming agent content in the obtained particles was 7.4 parts by weight with respect to 100 parts by weight of the resin.
[0050]
The obtained expandable particles were foamed by steam heating, and the true density was 0.029 g / cm. Three The foamed particles are made into a steam pressure of 0.8 kgf / cm. 2 Was molded in-mold to obtain a plate-like molded body of 300 × 300 × 50 mm. The bulk density of the obtained molded body was 0.020 g / cm. Three The molded product has a particle fusion rate of 92% and a tensile strength at break of 3.6 kgf / cm. 2 Met. The result of evaluating the crack resistance of the molded article by the crack-resistant drop height was 11.0 cm, which was good.
[0051]
(Example 2)
Expandable particles were obtained by performing the same operation as in Example 1 except that the amount of foaming agent charged in the step of impregnating the foaming agent was 12 parts and 17 parts. The foaming agent content in the obtained particles was 6.5 parts by weight and 9.2 parts by weight, respectively, with respect to 100 parts by weight of the resin. Properties of the obtained expandable particles are shown in Table 1 (in the table, the rubber component-containing polystyrene is referred to as HIPS. Underwater hot cut conditions are referred to as UWC conditions). Table 3 shows the performance of a molded product obtained by foaming the expandable particles under the same conditions as those shown in Example 1.
[0052]
(Example 3)
In the process of extruding butadiene component-containing polystyrene, by controlling the die temperature and the resin feed rate, the shear rate in the die land part was 2900, 6100, 8500 (1 / second), and the apparent viscosity was 610, 220, 180 poise, respectively. Otherwise, the same operation as in Example 1 was performed to obtain expandable particles. Table 1 shows the properties of the obtained expandable particles. Table 3 shows the performance of a molded product obtained by foaming the expandable particles under the same conditions as those shown in Example 1.
[0053]
(Example 4)
Expandable particles were obtained by performing the same operation as in Example 1 except that the die land diameter (the same diameter for the extrusion holes) was 1.2 mm and 2.0 mm. The shear rate of the die land part was 4000, 3500 (1 / second), and the apparent viscosity was 310, 400 poise, respectively. The properties of the obtained expandable particles are shown in Table 1, and the performance of the molded product is shown in Table 3.
[0054]
(Example 5)
Butadiene component content in polystyrene containing butadiene component is 5 weight% , 12 weight% Except for (Asahi Kasei Kogyo Co., Ltd.), the same operation as in Example 1 was performed to obtain expandable particles. The shear rate of the die land part was 4500 (1 / second), and the apparent viscosities were 290 and 360 poise, respectively. The properties of the obtained expandable particles are shown in Table 1, and the performance of the molded product is shown in Table 3.
[0055]
(Comparative Example 1)
Example 1 except that high impact polystyrene (made by Asahi Kasei Kogyo Co., Ltd.) with a butadiene component of 9% was used, the shear rate of the resin in the die land part was 2200, 11000 (1 / second), and the apparent viscosity was 750, 140 poise, respectively. The same operation was performed to obtain expandable particles. Table 2 shows the properties of the obtained expandable particles. Both the particle sphericity and the blocking rate were inferior. Table 4 shows the performance of the molded product obtained by foam-molding the expandable particles under the same conditions as shown in Example 1. The crack resistance was inferior to that of the molded product of Example 1.
[0056]
(Comparative Example 2)
The same procedure as in Comparative Example 1 was performed except that the blowing agent impregnation condition was maintained at 120 ° C. for 12 hours to obtain expandable particles. Table 2 shows the properties of the obtained expandable particles. Compared with that of Comparative Example 1, the expandable particles had improved sphericity, but had a higher blocking rate. Table 4 shows the performance of the molded product obtained by foam-molding the expandable particles under the same conditions as shown in Example 1.
[0057]
(Comparative Example 3)
Expandable particles were obtained in the same manner as in Example 1 except that the die land diameter (extruded holes were the same diameter) was 2.6 mm and 0.4 mm. The shear rate of the die land part was 3200 and 8500 (1 / second), and the apparent viscosities were 510 and 190 poise, respectively.
When the die land diameter was 0.4 mm, the die nozzle was easily clogged, and it was difficult to continue the extrusion of the resin.
The obtained particles were dispersed in an aqueous medium by the same method as shown in Example 1 and impregnated with a foaming agent. Table 2 shows the properties of the obtained expandable particles. Table 4 shows the performance of the molded product obtained by foam-molding the expandable particles under the same conditions as those shown in Example 1.
[0058]
(Comparative Example 4)
Similar to Example 1 except that the rubber component content in the butadiene component-containing polystyrene was 6% and 15%, HIPS having intrinsic viscosities of 0.57 and 0.92, respectively, was extruded under the conditions shown in Table 2. Expandable particles were obtained by the operation. Table 2 shows the properties of the obtained expandable particles, and Table 4 shows the performance of the molded body.
[0059]
(Comparative Example 5)
The mixture of HIPS and additive used in Example 1 was extruded from an extruder to obtain cylindrical pellets having a diameter of 1.0 mm and a length of 1.2 mm. The pellets were charged into a foaming agent-impregnated container in the same manner as in Example 1, and expandable particles were obtained with a 120 ° C. impregnation time of 6 hours and 12 hours. Table 2 shows the properties of the particles. Table 4 shows the performance of the molded body.
[0060]
(Comparative Example 6)
Polystyrene having a butadiene component of 9% (manufactured by Asahi Kasei Kogyo Co., Ltd.) was diluted with polystyrene to prepare a polystyrene having a butadiene component of 2%. Using this resin, expandable particles were obtained in the same manner as in Example 1 except that the shear rate of the resin in the die land part was 4500 and 8500 (1 / second) and the apparent viscosity was 360 and 190 poise, respectively. It was. Table 2 shows the properties of the obtained expandable particles. Table 3 shows the performance of the molded product obtained by foam-molding the expandable particles under the same conditions as those shown in Example 1.
[0061]
[Table 1]
Figure 0003683022
[0062]
[Table 2]
Figure 0003683022
[0063]
[Table 3]
Figure 0003683022
[0064]
[Table 4]
Figure 0003683022
[0065]
【The invention's effect】
According to the present invention, true spherical expandable particles made of polystyrene resin containing a conjugated diene polymer component can be produced with high productivity without causing blocking in a short foaming agent impregnation time. In addition, a molded product obtained by foaming and molding the obtained expandable resin particles has good crack resistance.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view showing an extruder and an underwater hot cut device.
FIG. 2 is a schematic explanatory view showing a cross-sectional structure of an extruder die.
[Explanation of symbols]
1 Die head
2 Die nozzle
3 Cutter blade
4 Motor
5 Cutter box
6 Water inlet
7 Water outlet
8 Extruder screw
9 Die face surface
10 Dailand
11 Taper
12 Die extrusion hole

Claims (1)

水性媒体中で共役ジエン系重合体成分含有ポリスチレン系樹脂粒子に発泡剤を含浸させてなる平均粒径0.5mm以上、3.0mm以下の球状発泡性ポリスチレン系樹脂粒子の製造方法において、共役ジエン系重合体成分含有ポリスチレン系樹脂の共役ジエン成分含有量が3wt%以上、20wt%以下であり、ポリスチレン系成分相は30℃トルエン中での極限粘度が0.6以上、0.9以下であり、発泡剤含浸前の樹脂粒子が共役ジエン系重合体成分含有ポリスチレン系樹脂を、押し出し時の樹脂温度が220〜260℃で、押出機中で加熱溶融し、ダイランド径が0.5〜2.5mmで、ダイランド部における樹脂のせん断速度が2500(1/秒)以上、10000(1/秒)以下で押出孔より水中に押し出すと同時にダイフェース面で切断して得られる粒子であることを特徴とする発泡性ポリスチレン系樹脂粒子の製造方法。In an aqueous medium in the conjugated diene polymer component-containing polystyrene resin particles formed by impregnating a foaming agent average particle size 0.5mm or more, the following method for manufacturing a spherical expandable polystyrene resin particles 3.0 mm, conjugated diene The conjugated diene component content of the polystyrene-based resin containing the polystyrene-based polymer component is 3 wt% or more and 20 wt% or less, and the polystyrene component phase has an intrinsic viscosity of 0.6 or more and 0.9 or less in 30 ° C. toluene. The resin particles before impregnation with the blowing agent are conjugated diene polymer component-containing polystyrene resins, the resin temperature during extrusion is 220 to 260 ° C., and heated and melted in an extruder, and the die land diameter is 0.5 to 2. in 5 mm, shear rate of the resin in the die land part is 2500 (1 / sec) or higher, 10000 (1 / sec) at the same time the die face when extruding from pressing Deana in water below Method for producing expandable polystyrene resin particles, characterized in that in a particle obtained by cutting.
JP03574096A 1996-01-31 1996-01-31 Method for producing expandable resin particles Expired - Lifetime JP3683022B2 (en)

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JP03574096A JP3683022B2 (en) 1996-01-31 1996-01-31 Method for producing expandable resin particles

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JPH09208735A JPH09208735A (en) 1997-08-12
JP3683022B2 true JP3683022B2 (en) 2005-08-17

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DE10226749B4 (en) 2002-06-14 2014-09-04 Basf Se Process for producing expandable polystyrene
WO2004080678A1 (en) 2003-03-12 2004-09-23 Sekisui Plastics Co., Ltd. Granulation die, granulation apparatus and process for producing expandable thermoplastic resin granule
EP1666222B1 (en) * 2003-09-17 2015-02-25 Sekisui Plastics Co., Ltd. Method of manufacturing thermoplastic resin foam particle
JP2006240726A (en) * 2005-03-07 2006-09-14 Jsp Corp Thermally insulated container
JP5086900B2 (en) * 2008-06-04 2012-11-28 積水化成品工業株式会社 Method for producing foamable thermoplastic resin particles, method for producing thermoplastic resin foamed particles, and method for producing thermoplastic resin foam molded article
JP6535629B2 (en) * 2016-03-30 2019-06-26 積水化成品工業株式会社 Method of producing resin particles
WO2024070596A1 (en) * 2022-09-28 2024-04-04 Zsエラストマー株式会社 Method for producing elastomer pellets
WO2024070594A1 (en) * 2022-09-28 2024-04-04 Zsエラストマー株式会社 Method for producing elastomer pellets

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